Patent Publication Number: US-11648324-B2

Title: Lipids and lipid nanoparticle formulations for delivery of nucleic acids

Description:
BACKGROUND 
     Technical Field 
     The present invention generally relates to novel cationic lipids that can be used in combination with other lipid components, such as neutral lipids, cholesterol and polymer conjugated lipids, to form lipid nanoparticles with oligonucleotides, to facilitate the intracellular delivery of therapeutic nucleic acids (e.g. oligonucleotides, messenger RNA) both in vitro and in vivo. 
     Description of the Related Art 
     There are many challenges associated with the delivery of nucleic acids to affect a desired response in a biological system. Nucleic acid based therapeutics have enormous potential but there remains a need for more effective delivery of nucleic acids to appropriate sites within a cell or organism in order to realize this potential. Therapeutic nucleic acids include, e.g., messenger RNA (mRNA), antisense oligonucleotides, ribozymes, DNAzymes, plasmids, immune stimulating nucleic acids, antagomir, antimir, mimic, supermir, and aptamers. Some nucleic acids, such as mRNA or plasmids, can be used to effect expression of specific cellular products as would be useful in the treatment of, for example, diseases related to a deficiency of a protein or enzyme. The therapeutic applications of translatable nucleotide delivery are extremely broad as constructs can be synthesized to produce any chosen protein sequence, whether or not indigenous to the system. The expression products of the nucleic acid can augment existing levels of protein, replace missing or non-functional versions of a protein, or introduce new protein and associated functionality in a cell or organism. 
     Some nucleic acids, such as miRNA inhibitors, can be used to effect expression of specific cellular products that are regulated by miRNA as would be useful in the treatment of, for example, diseases related to deficiency of protein or enzyme. The therapeutic applications of miRNA inhibition are extremely broad as constructs can be synthesized to inhibit one or more miRNA that would in turn regulate the expression of mRNA products. The inhibition of endogenous miRNA can augment its downstream target endogenous protein expression and restore proper function in a cell or organism as a means to treat disease associated to a specific miRNA or a group of miRNA. 
     Other nucleic acids can down-regulate intracellular levels of specific mRNA and, as a result, down-regulate the synthesis of the corresponding proteins through processes such as RNA interference (RNAi) or complementary binding of antisense RNA. The therapeutic applications of antisense oligonucleotide and RNAi are also extremely broad, since oligonucleotide constructs can be synthesized with any nucleotide sequence directed against a target mRNA. Targets may include mRNAs from normal cells, mRNAs associated with disease-states, such as cancer, and mRNAs of infectious agents, such as viruses. To date, antisense oligonucleotide constructs have shown the ability to specifically down-regulate target proteins through degradation of the cognate mRNA in both in vitro and in vivo models. In addition, antisense oligonucleotide constructs are currently being evaluated in clinical studies. 
     However, two problems currently face the use of oligonucleotides in therapeutic contexts. First, free RNAs are susceptible to nuclease digestion in plasma. Second, free RNAs have limited ability to gain access to the intracellular compartment where the relevant translation machinery resides. Lipid nanoparticles formed from cationic lipids with other lipid components, such as neutral lipids, cholesterol, PEG, PEGylated lipids, and oligonucleotides have been used to block degradation of the RNAs in plasma and facilitate the cellular uptake of the oligonucleotides. 
     There remains a need for improved cationic lipids and lipid nanoparticles for the delivery of oligonucleotides. Preferably, these lipid nanoparticles would provide optimal drug:lipid ratios, protect the nucleic acid from degradation and clearance in serum, be suitable for systemic or local delivery, and provide intracellular delivery of the nucleic acid. In addition, these lipid-nucleic acid particles should be well-tolerated and provide an adequate therapeutic index, such that patient treatment at an effective dose of the nucleic acid is not associated with unacceptable toxicity and/or risk to the patient. The present invention provides these and related advantages. 
     BRIEF SUMMARY 
     In brief, the present invention provides lipid compounds, including stereoisomers, pharmaceutically acceptable salts or tautomers thereof, which can be used alone or in combination with other lipid components such as neutral lipids, charged lipids, steroids (including for example, all sterols) and/or their analogs, and/or polymer conjugated lipids to form lipid nanoparticles for the delivery of therapeutic agents. In some instances, the lipid nanoparticles are used to deliver nucleic acids such as antisense and/or messenger RNA. Methods for use of such lipid nanoparticles for treatment of various diseases or conditions, such as those caused by infectious entities and/or insufficiency of a protein, are also provided. 
     In one embodiment, compounds having the following structure (I) are provided: 
                         
or a pharmaceutically acceptable salt, tautomer or stereoisomer thereof, wherein R 1 , R 2 , R 3 , L 1 , L 2 , G 1 , G 2 , and G 3  are as defined herein.
 
     Pharmaceutical compositions comprising one or more of the foregoing compounds of structure (I) and a therapeutic agent are also provided. In some embodiments, the pharmaceutical compositions further comprise one or more components selected from neutral lipids, charged lipids, steroids and polymer conjugated lipids. Such compositions are useful for formation of lipid nanoparticles for the delivery of the therapeutic agent. 
     In other embodiments, the present invention provides a method for administering a therapeutic agent to a patient in need thereof, the method comprising preparing a composition of lipid nanoparticles comprising the compound of structure (I) and a therapeutic agent and delivering the composition to the patient. 
     These and other aspects of the invention will be apparent upon reference to the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the figures, identical reference numbers identify similar elements. The sizes and relative positions of elements in the figures are not necessarily drawn to scale and some of these elements are arbitrarily enlarged and positioned to improve figure legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the figures. 
         FIG.  1    shows time course of luciferase expression in mouse liver. 
         FIG.  2    illustrates the calculation of pKa for MC3 as a representative example relevant to the disclosed lipids. 
         FIG.  3    provides comparative luciferase activity data for selected lipids. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. 
     The present invention is based, in part, upon the discovery of novel cationic (amino) lipids that provide advantages when used in lipid nanoparticles for the in vivo delivery of an active or therapeutic agent such as a nucleic acid into a cell of a mammal. In particular, embodiments of the present invention provide nucleic acid-lipid nanoparticle compositions comprising one or more of the novel cationic lipids described herein that provide increased activity of the nucleic acid and improved tolerability of the compositions in vivo, resulting in a significant increase in the therapeutic index as compared to nucleic acid-lipid nanoparticle compositions previously described. 
     In particular embodiments, the present invention provides novel cationic lipids that enable the formulation of improved compositions for the in vitro and in vivo delivery of mRNA and/or other oligonucleotides. In some embodiments, these improved lipid nanoparticle compositions are useful for expression of protein encoded by mRNA. In other embodiments, these improved lipid nanoparticles compositions are useful for upregulation of endogenous protein expression by delivering miRNA inhibitors targeting one specific miRNA or a group of miRNA regulating one target mRNA or several mRNA. In other embodiments, these improved lipid nanoparticle compositions are useful for down-regulating (e.g., silencing) the protein levels and/or mRNA levels of target genes. In some other embodiments, the lipid nanoparticles are also useful for delivery of mRNA and plasmids for expression of transgenes. In yet other embodiments, the lipid nanoparticle compositions are useful for inducing a pharmacological effect resulting from expression of a protein, e.g., increased production of red blood cells through the delivery of a suitable erythropoietin mRNA, or protection against infection through delivery of mRNA encoding for a suitable antigen or antibody. 
     The lipid nanoparticles and compositions of the present invention may be used for a variety of purposes, including the delivery of encapsulated or associated (e.g., complexed) therapeutic agents such as nucleic acids to cells, both in vitro and in vivo. Accordingly, embodiments of the present invention provide methods of treating or preventing diseases or disorders in a subject in need thereof by contacting the subject with a lipid nanoparticle that encapsulates or is associated with a suitable therapeutic agent, wherein the lipid nanoparticle comprises one or more of the novel cationic lipids described herein. 
     As described herein, embodiments of the lipid nanoparticles of the present invention are particularly useful for the delivery of nucleic acids, including, e.g., mRNA, antisense oligonucleotide, plasmid DNA, microRNA (miRNA), miRNA inhibitors (antagomirs/antimirs), messenger-RNA-interfering complementary RNA (micRNA), DNA, multivalent RNA, dicer substrate RNA, complementary DNA (cDNA), etc. Therefore, the lipid nanoparticles and compositions of the present invention may be used to induce expression of a desired protein both in vitro and in vivo by contacting cells with a lipid nanoparticle comprising one or more novel cationic lipids described herein, wherein the lipid nanoparticle encapsulates or is associated with a nucleic acid that is expressed to produce the desired protein (e.g., a messenger RNA or plasmid encoding the desired protein) or inhibit processes that terminate expression of mRNA (e.g., miRNA inhibitors). Alternatively, the lipid nanoparticles and compositions of the present invention may be used to decrease the expression of target genes and proteins both in vitro and in vivo by contacting cells with a lipid nanoparticle comprising one or more novel cationic lipids described herein, wherein the lipid nanoparticle encapsulates or is associated with a nucleic acid that reduces target gene expression (e.g., an antisense oligonucleotide or small interfering RNA (siRNA)). The lipid nanoparticles and compositions of the present invention may also be used for co-delivery of different nucleic acids (e.g. mRNA and plasmid DNA) separately or in combination, such as may be useful to provide an effect requiring colocalization of different nucleic acids (e.g. mRNA encoding for a suitable gene modifying enzyme and DNA segment(s) for incorporation into the host genome). 
     Nucleic acids for use with this invention may be prepared according to any available technique. For mRNA, the primary methodology of preparation is, but not limited to, enzymatic synthesis (also termed in vitro transcription) which currently represents the most efficient method to produce long sequence-specific mRNA. In vitro transcription describes a process of template-directed synthesis of RNA molecules from an engineered DNA template comprised of an upstream bacteriophage promoter sequence (e.g. including but not limited to that from the T7, T3 and SP6 coliphage) linked to a downstream sequence encoding the gene of interest. Template DNA can be prepared for in vitro transcription from a number of sources with appropriate techniques which are well known in the art including, but not limited to, plasmid DNA and polymerase chain reaction amplification (see Linpinsel, J. L and Conn, G. L., General protocols for preparation of plasmid DNA template and Bowman, J. C., Azizi, B., Lenz, T. K., Ray, P., and Williams, L. D. in RNA in vitro transcription and RNA purification by denaturing PAGE in Recombinant and in vitro RNA syntheses Methods v. 941 Conn G. L. (ed), New York, N.Y. Humana Press, 2012) 
     Transcription of the RNA occurs in vitro using the linearized DNA template in the presence of the corresponding RNA polymerase and adenosine, guanosine, uridine and cytidine ribonucleoside triphosphates (rNTPs) under conditions that support polymerase activity while minimizing potential degradation of the resultant mRNA transcripts. In vitro transcription can be performed using a variety of commercially available kits including, but not limited to RiboMax Large Scale RNA Production System (Promega), MegaScript Transcription kits (Life Technologies) as well as with commercially available reagents including RNA polymerases and rNTPs. The methodology for in vitro transcription of mRNA is well known in the art. (see, e.g. Losick, R., 1972, In vitro transcription, Ann Rev Biochem v.41 409-46; Kamakaka, R. T. and Kraus, W. L. 2001. In Vitro Transcription. Current Protocols in Cell Biology. 2:11.6:11.6.1-11.6.17; Beckert, B. And Masquida, B., (2010) Synthesis of RNA by In Vitro Transcription in RNA in Methods in Molecular Biology v. 703 (Neilson, H. Ed), New York, N.Y. Humana Press, 2010; Brunelle, J. L. and Green, R., 2013, Chapter Five—In vitro transcription from plasmid or PCR-amplified DNA, Methods in Enzymology v. 530, 101-114; all of which are incorporated herein by reference). 
     The desired in vitro transcribed mRNA is then purified from the undesired components of the transcription or associated reactions (including unincorporated rNTPs, protein enzyme, salts, short RNA oligos, etc.). Techniques for the isolation of the mRNA transcripts are well known in the art. Well known procedures include phenol/chloroform extraction or precipitation with either alcohol (ethanol, isopropanol) in the presence of monovalent cations or lithium chloride. Additional, non-limiting examples of purification procedures which can be used include size exclusion chromatography (Lukaysky, P. J. and Puglisi, J. D., 2004, Large-scale preparation and purification of polyacrylamide-free RNA oligonucleotides, RNA v.10, 889-893), silica-based affinity chromatography and polyacrylamide gel electrophoresis (Bowman, J. C., Azizi, B., Lenz, T. K., Ray, P., and Williams, L. D. in RNA in vitro transcription and RNA purification by denaturing PAGE in Recombinant and in vitro RNA syntheses Methods v. 941 Conn G. L. (ed), New York, N.Y. Humana Press, 2012). Purification can be performed using a variety of commercially available kits including, but not limited to SV Total Isolation System (Promega) and In Vitro Transcription Cleanup and Concentration Kit (Norgen Biotek). 
     Furthermore, while reverse transcription can yield large quantities of mRNA, the products can contain a number of aberrant RNA impurities associated with undesired polymerase activity which may need to be removed from the full-length mRNA preparation. These include short RNAs that result from abortive transcription initiation as well as double-stranded RNA (dsRNA) generated by RNA-dependent RNA polymerase activity, RNA-primed transcription from RNA templates and self-complementary 3′ extension. It has been demonstrated that these contaminants with dsRNA structures can lead to undesired immunostimulatory activity through interaction with various innate immune sensors in eukaryotic cells that function to recognize specific nucleic acid structures and induce potent immune responses. This in turn, can dramatically reduce mRNA translation since protein synthesis is reduced during the innate cellular immune response. Therefore, additional techniques to remove these dsRNA contaminants have been developed and are known in the art including but not limited to scaleable HPLC purification (see e.g. Kariko, K., Muramatsu, H., Ludwig, J. And Weissman, D., 2011, Generating the optimal mRNA for therapy: HPLC purification eliminates immune activation and improves translation of nucleoside-modified, protein-encoding mRNA, Nucl Acid Res, v. 39 e142; Weissman, D., Pardi, N., Muramatsu, H., and Kariko, K., HPLC Purification of in vitro transcribed long RNA in Synthetic Messenger RNA and Cell Metabolism Modulation in Methods in Molecular Biology v.969 (Rabinovich, P. H. Ed), 2013). HPLC purified mRNA has been reported to be translated at much greater levels, particularly in primary cells and in vivo. 
     A significant variety of modifications have been described in the art which are used to alter specific properties of in vitro transcribed mRNA, and improve its utility. These include, but are not limited to modifications to the 5′ and 3′ termini of the mRNA. Endogenous eukaryotic mRNA typically contain a cap structure on the 5′-end of a mature molecule which plays an important role in mediating binding of the mRNA Cap Binding Protein (CBP), which is in turn responsible for enhancing mRNA stability in the cell and efficiency of mRNA translation. Therefore, highest levels of protein expression are achieved with capped mRNA transcripts. The 5′-cap contains a 5′-5′-triphosphate linkage between the 5′-most nucleotide and guanine nucleotide. The conjugated guanine nucleotide is methylated at the N7 position. Additional modifications include methylation of the ultimate and penultimate most 5′-nucleotides on the 2′-hydroxyl group. 
     Multiple distinct cap structures can be used to generate the 5′-cap of in vitro transcribed synthetic mRNA. 5′-capping of synthetic mRNA can be performed co-transcriptionally with chemical cap analogs (i.e. capping during in vitro transcription). For example, the Anti-Reverse Cap Analog (ARCA) cap contains a 5′-5′-triphosphate guanine-guanine linkage where one guanine contains an N7 methyl group as well as a 3′-O-methyl group. However, up to 20% of transcripts remain uncapped during this co-transcriptional process and the synthetic cap analog is not identical to the 5′-cap structure of an authentic cellular mRNA, potentially reducing translatability and cellular stability. Alternatively, synthetic mRNA molecules may also be enzymatically capped post-transcriptionally. These may generate a more authentic 5′-cap structure that more closely mimics, either structurally or functionally, the endogenous 5′-cap which have enhanced binding of cap binding proteins, increased half-life, reduced susceptibility to 5′ endonucleases and/or reduced 5′ decapping. Numerous synthetic 5′-cap analogs have been developed and are known in the art to enhance mRNA stability and translatability (see eg. Grudzien-Nogalska, E., Kowalska, J., Su, W., Kuhn, A. N., Slepenkov, S. V., Darynkiewicz, E., Sahin, U., Jemielity, J., and Rhoads, R. E., Synthetic mRNAs with superior translation and stability properties in Synthetic Messenger RNA and Cell Metabolism Modulation in Methods in Molecular Biology v.969 (Rabinovich, P. H. Ed), 2013). 
     On the 3′-terminus, a long chain of adenine nucleotides (poly-A tail) is normally added to mRNA molecules during RNA processing. Immediately after transcription, the 3′ end of the transcript is cleaved to free a 3′ hydroxyl to which poly-A polymerase adds a chain of adenine nucleotides to the RNA in a process called polyadenylation. The poly-A tail has been extensively shown to enhance both translational efficiency and stability of mRNA (see Bernstein, P. and Ross, J., 1989, Poly (A), poly (A) binding protein and the regulation of mRNA stability, Trends Bio Sci v. 14 373-377; Guhaniyogi, J. And Brewer, G., 2001, Regulation of mRNA stability in mammalian cells, Gene, v. 265, 11-23; Dreyfus, M. And Regnier, P., 2002, The poly (A) tail of mRNAs: Bodyguard in eukaryotes, scavenger in bacteria, Cell, v.111, 611-613). 
     Poly (A) tailing of in vitro transcribed mRNA can be achieved using various approaches including, but not limited to, cloning of a poly (T) tract into the DNA template or by post-transcriptional addition using Poly (A) polymerase. The first case allows in vitro transcription of mRNA with poly (A) tails of defined length, depending on the size of the poly (T) tract, but requires additional manipulation of the template. The latter case involves the enzymatic addition of a poly (A) tail to in vitro transcribed mRNA using poly (A) polymerase which catalyzes the incorporation of adenine residues onto the 3′termini of RNA, requiring no additional manipulation of the DNA template, but results in mRNA with poly(A) tails of heterogeneous length. 5′-capping and 3′-poly (A) tailing can be performed using a variety of commercially available kits including, but not limited to Poly (A) Polymerase Tailing kit (EpiCenter), mMESSAGE mMACHINE T7 Ultra kit and Poly (A) Tailing kit (Life Technologies) as well as with commercially available reagents, various ARCA caps, Poly (A) polymerase, etc. 
     In addition to 5′ cap and 3′ poly adenylation, other modifications of the in vitro transcripts have been reported to provide benefits as related to efficiency of translation and stability. It is well known in the art that pathogenic DNA and RNA can be recognized by a variety of sensors within eukaryotes and trigger potent innate immune responses. The ability to discriminate between pathogenic and self DNA and RNA has been shown to be based, at least in part, on structure and nucleoside modifications since most nucleic acids from natural sources contain modified nucleosides In contrast, in vitro synthesized RNA lacks these modifications, thus rendering it immunostimulatory which in turn can inhibit effective mRNA translation as outlined above. The introduction of modified nucleosides into in vitro transcribed mRNA can be used to prevent recognition and activation of RNA sensors, thus mitigating this undesired immunostimulatory activity and enhancing translation capacity (see e.g. Kariko, K. And Weissman, D. 2007, Naturally occurring nucleoside modifications suppress the immunostimulatory activity of RNA: implication for therapeutic RNA development, Curr Opin Drug Discov Devel, v.10 523-532; Pardi, N., Muramatsu, H., Weissman, D., Kariko, K., In vitro transcription of long RNA containing modified nucleosides in Synthetic Messenger RNA and Cell Metabolism Modulation in Methods in Molecular Biology v.969 (Rabinovich, P. H. Ed), 2013); Kariko, K., Muramatsu, H., Welsh, F. A., Ludwig, J., Kato, H., Akira, S., Weissman, D., 2008, Incorporation of Pseudouridine Into mRNA Yields Superior Nonimmunogenic Vector With Increased Translational Capacity and Biological Stability, Mol Ther v.16, 1833-1840. The modified nucleosides and nucleotides used in the synthesis of modified RNAs can be prepared monitored and utilized using general methods and procedures known in the art. A large variety of nucleoside modifications are available that may be incorporated alone or in combination with other modified nucleosides to some extent into the in vitro transcribed mRNA (see e.g. US2012/0251618). In vitro synthesis of nucleoside-modified mRNA have been reported to have reduced ability to activate immune sensors with a concomitant enhanced translational capacity. 
     Other components of mRNA which can be modified to provide benefit in terms of translatability and stability include the 5′ and 3′ untranslated regions (UTR). Optimization of the UTRs (favorable 5′ and 3′ UTRs can be obtained from cellular or viral RNAs), either both or independently, have been shown to increase mRNA stability and translational efficiency of in vitro transcribed mRNA (see e.g. Pardi, N., Muramatsu, H., Weissman, D., Kariko, K., In vitro transcription of long RNA containing modified nucleosides in Synthetic Messenger RNA and Cell Metabolism Modulation in Methods in Molecular Biology v.969 (Rabinovich, P. H. Ed), 2013). 
     In addition to mRNA, other nucleic acid payloads may be used for this invention. For oligonucleotides, methods of preparation include but are not limited to chemical synthesis and enzymatic, chemical cleavage of a longer precursor, in vitro transcription as described above, etc. Methods of synthesizing DNA and RNA nucleotides are widely used and well known in the art (see, e.g. Gait, M. J. (ed.) Oligonucleotide synthesis: a practical approach, Oxford [Oxfordshire], Washington, D.C.: IRL Press, 1984; and Herdewijn, P. (ed.) Oligonucleotide synthesis: methods and applications, Methods in Molecular Biology, v. 288 (Clifton, N.J.) Totowa, N.J.: Humana Press, 2005; both of which are incorporated herein by reference). 
     For plasmid DNA, preparation for use with this invention commonly utilizes but is not limited to expansion and isolation of the plasmid DNA in vitro in a liquid culture of bacteria containing the plasmid of interest. The presence of a gene in the plasmid of interest that encodes resistance to a particular antibiotic (penicillin, kanamycin, etc.) allows those bacteria containing the plasmid of interest to selectively grow in antibiotic-containing cultures. Methods of isolating plasmid DNA are widely used and well known in the art (see, e.g. Heilig, J., Elbing, K. L. and Brent, R (2001) Large-Scale Preparation of Plasmid DNA. Current Protocols in Molecular Biology. 41:11:1.7:1.7.1-1.7.16; Rozkov, A., Larsson, B., Gillstrom, S., Björnestedt, R. and Schmidt, S. R. (2008), Large-scale production of endotoxin-free plasmids for transient expression in mammalian cell culture. Biotechnol. Bioeng., 99: 557-566; and U.S. Pat. No. 6,197,553B 1). Plasmid isolation can be performed using a variety of commercially available kits including, but not limited to Plasmid Plus (Qiagen), GenJET plasmid MaxiPrep (Thermo) and PureYield MaxiPrep (Promega) kits as well as with commercially available reagents. 
     Various exemplary embodiments of the cationic lipids of the present invention, lipid nanoparticles and compositions comprising the same, and their use to deliver active (e.g. therapeutic agents), such as nucleic acids, to modulate gene and protein expression, are described in further detail below. 
     As used herein, the following terms have the meanings ascribed to them unless specified otherwise. 
     Unless the context requires otherwise, throughout the present specification and claims, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open and inclusive sense, that is, as “including, but not limited to”. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. As used in the specification and claims, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. 
     The phrase “induce expression of a desired protein” refers to the ability of a nucleic acid to increase expression of the desired protein. To examine the extent of protein expression, a test sample (e.g. a sample of cells in culture expressing the desired protein) or a test mammal (e.g. a mammal such as a human or an animal model such as a rodent (e.g. mouse) or a non-human primate (e.g., monkey) model) is contacted with a nucleic acid (e.g. nucleic acid in combination with a lipid of the present invention). Expression of the desired protein in the test sample or test animal is compared to expression of the desired protein in a control sample (e.g. a sample of cells in culture expressing the desired protein) or a control mammal (e.g., a mammal such as a human or an animal model such as a rodent (e.g. mouse) or non-human primate (e.g. monkey) model) that is not contacted with or administered the nucleic acid. When the desired protein is present in a control sample or a control mammal, the expression of a desired protein in a control sample or a control mammal may be assigned a value of 1.0. In particular embodiments, inducing expression of a desired protein is achieved when the ratio of desired protein expression in the test sample or the test mammal to the level of desired protein expression in the control sample or the control mammal is greater than 1, for example, about 1.1, 1.5, 2.0. 5.0 or 10.0. When a desired protein is not present in a control sample or a control mammal, inducing expression of a desired protein is achieved when any measurable level of the desired protein in the test sample or the test mammal is detected. One of ordinary skill in the art will understand appropriate assays to determine the level of protein expression in a sample, for example dot blots, northern blots, in situ hybridization, ELISA, immunoprecipitation, enzyme function, and phenotypic assays, or assays based on reporter proteins that can produce fluorescence or luminescence under appropriate conditions. 
     The phrase “inhibiting expression of a target gene” refers to the ability of a nucleic acid to silence, reduce, or inhibit the expression of a target gene. To examine the extent of gene silencing, a test sample (e.g. a sample of cells in culture expressing the target gene) or a test mammal (e.g. a mammal such as a human or an animal model such as a rodent (e.g. mouse) or a non-human primate (e.g. monkey) model) is contacted with a nucleic acid that silences, reduces, or inhibits expression of the target gene. Expression of the target gene in the test sample or test animal is compared to expression of the target gene in a control sample (e.g. a sample of cells in culture expressing the target gene) or a control mammal (e.g. a mammal such as a human or an animal model such as a rodent (e.g. mouse) or non-human primate (e.g. monkey) model) that is not contacted with or administered the nucleic acid. The expression of the target gene in a control sample or a control mammal may be assigned a value of 100%. In particular embodiments, silencing, inhibition, or reduction of expression of a target gene is achieved when the level of target gene expression in the test sample or the test mammal relative to the level of target gene expression in the control sample or the control mammal is about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 0%. In other words, the nucleic acids are capable of silencing, reducing, or inhibiting the expression of a target gene by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% in a test sample or a test mammal relative to the level of target gene expression in a control sample or a control mammal not contacted with or administered the nucleic acid. Suitable assays for determining the level of target gene expression include, without limitation, examination of protein or mRNA levels using techniques known to those of skill in the art, such as, e.g., dot blots, northern blots, in situ hybridization, ELISA, immunoprecipitation, enzyme function, as well as phenotypic assays known to those of skill in the art. 
     An “effective amount” or “therapeutically effective amount” of an active agent or therapeutic agent such as a therapeutic nucleic acid is an amount sufficient to produce the desired effect, e.g. an increase or inhibition of expression of a target sequence in comparison to the normal expression level detected in the absence of the nucleic acid. An increase in expression of a target sequence is achieved when any measurable level is detected in the case of an expression product that is not present in the absence of the nucleic acid. In the case where the expression product is present at some level prior to contact with the nucleic acid, an in increase in expression is achieved when the fold increase in value obtained with a nucleic acid such as mRNA relative to control is about 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 75, 100, 250, 500, 750, 1000, 5000, 10000 or greater. Inhibition of expression of a target gene or target sequence is achieved when the value obtained with a nucleic acid such as antisense oligonucleotide relative to the control is about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 0%. Suitable assays for measuring expression of a target gene or target sequence include, e.g., examination of protein or RNA levels using techniques known to those of skill in the art such as dot blots, northern blots, in situ hybridization, ELISA, immunoprecipitation, enzyme function, fluorescence or luminescence of suitable reporter proteins, as well as phenotypic assays known to those of skill in the art. 
     The term “nucleic acid” as used herein refers to a polymer containing at least two deoxyribonucleotides or ribonucleotides in either single- or double-stranded form and includes DNA, RNA, and hybrids thereof. DNA may be in the form of antisense molecules, plasmid DNA, cDNA, PCR products, or vectors. RNA may be in the form of small hairpin RNA (shRNA), messenger RNA (mRNA), antisense RNA, miRNA, micRNA, multivalent RNA, dicer substrate RNA or viral RNA (vRNA), and combinations thereof. Nucleic acids include nucleic acids containing known nucleotide analogs or modified backbone residues or linkages, which are synthetic, naturally occurring, and non-naturally occurring, and which have similar binding properties as the reference nucleic acid. Examples of such analogs include, without limitation, phosphorothioates, phosphoramidates, methyl phosphonates, chiral-methyl phosphonates, 2′-O-methyl ribonucleotides, and peptide-nucleic acids (PNAs). Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions), alleles, orthologs, single nucleotide polymorphisms, and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al., Nucleic Acid Res., 19:5081 (1991); Ohtsuka et al., J. Biol. Chem., 260:2605-2608 (1985); Rossolini et al., Mol. Cell. Probes, 8:91-98 (1994)). “Nucleotides” contain a sugar deoxyribose (DNA) or ribose (RNA), a base, and a phosphate group. Nucleotides are linked together through the phosphate groups. “Bases” include purines and pyrimidines, which further include natural compounds adenine, thymine, guanine, cytosine, uracil, inosine, and natural analogs, and synthetic derivatives of purines and pyrimidines, which include, but are not limited to, modifications which place new reactive groups such as, but not limited to, amines, alcohols, thiols, carboxylates, and alkylhalides. 
     The term “gene” refers to a nucleic acid (e.g., DNA or RNA) sequence that comprises partial length or entire length coding sequences necessary for the production of a polypeptide or precursor polypeptide. 
     “Gene product,” as used herein, refers to a product of a gene such as an RNA transcript or a polypeptide. 
     The term “lipid” refers to a group of organic compounds that include, but are not limited to, esters of fatty acids and are generally characterized by being poorly soluble in water, but soluble in many organic solvents. They are usually divided into at least three classes: (1) “simple lipids,” which include fats and oils as well as waxes; (2) “compound lipids,” which include phospholipids and glycolipids; and (3) “derived lipids” such as steroids. 
     A “steroid” is a compound comprising the following carbon skeleton: 
                         
Non-limiting examples of steroids include cholesterol, and the like.
 
     A “cationic lipid” refers to a lipid capable of being positively charged. Exemplary cationic lipids include one or more amine group(s) which bear the positive charge. Preferred cationic lipids are ionizable such that they can exist in a positively charged or neutral form depending on pH. The ionization of the cationic lipid affects the surface charge of the lipid nanoparticle under different pH conditions. This charge state can influence plasma protein absorption, blood clearance and tissue distribution (Semple, S. C., et al., Adv. Drug Deliv Rev 32:3-17 (1998)) as well as the ability to form endosomolytic non-bilayer structures (Hafez, L M., et al., Gene Ther 8:1188-1196 (2001)) critical to the intracellular delivery of nucleic acids. 
     The term “polymer conjugated lipid” refers to a molecule comprising both a lipid portion and a polymer portion. An example of a polymer conjugated lipid is a pegylated lipid. The term “pegylated lipid” refers to a molecule comprising both a lipid portion and a polyethylene glycol portion. Pegylated lipids are known in the art and include 1-(monomethoxy-polyethyleneglycol)-2,3-dimyristoylglycerol (PEG-DMG) and the like. 
     The term “neutral lipid” refers to any of a number of lipid species that exist either in an uncharged or neutral zwitterionic form at a selected pH. At physiological pH, such lipids include, but are not limited to, phosphotidylcholines such as 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), phophatidylethanolamines such as 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), sphingomyelins (SM), ceramides, steroids such as sterols and their derivatives. Neutral lipids may be synthetic or naturally derived. 
     The term “charged lipid” refers to any of a number of lipid species that exist in either a positively charged or negatively charged form independent of the pH within a useful physiological range e.g. pH ˜3 to pH ˜9. Charged lipids may be synthetic or naturally derived. Examples of charged lipids include phosphatidylserines, phosphatidic acids, phosphatidylglycerols, phosphatidylinositols, sterol hemisuccinates, dialkyl trimethylammonium-propanes, (e.g. DOTAP, DOTMA), dialkyl dimethylaminopropanes, ethyl phosphocholines, dimethylaminoethane carbamoyl sterols (e.g. DC-Chol). 
     The term “lipid nanoparticle” refers to particles having at least one dimension on the order of nanometers (e.g., 1-1,000 nm) which include one or more of the compounds of structure (I) or other specified cationic lipids. In some embodiments, lipid nanoparticles are included in a formulation that can be used to deliver an active agent or therapeutic agent, such as a nucleic acid (e.g., mRNA) to a target site of interest (e.g., cell, tissue, organ, tumor, and the like). In some embodiments, the lipid nanoparticles of the invention comprise a nucleic acid. Such lipid nanoparticles typically comprise a compound of structure (I) and one or more excipient selected from neutral lipids, charged lipids, steroids and polymer conjugated lipids. In some embodiments, the active agent or therapeutic agent, such as a nucleic acid, may be encapsulated in the lipid portion of the lipid nanoparticle or an aqueous space enveloped by some or all of the lipid portion of the lipid nanoparticle, thereby protecting it from enzymatic degradation or other undesirable effects induced by the mechanisms of the host organism or cells e.g. an adverse immune response. 
     In various embodiments, the lipid nanoparticles have a mean diameter of from about 30 nm to about 150 nm, from about 40 nm to about 150 nm, from about 50 nm to about 150 nm, from about 60 nm to about 130 nm, from about 70 nm to about 110 nm, from about 70 nm to about 100 nm, from about 80 nm to about 100 nm, from about 90 nm to about 100 nm, from about 70 to about 90 nm, from about 80 nm to about 90 nm, from about 70 nm to about 80 nm, or about 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, or 150 nm, and are substantially non-toxic. In certain embodiments, nucleic acids, when present in the lipid nanoparticles, are resistant in aqueous solution to degradation with a nuclease. Lipid nanoparticles comprising nucleic acids and their method of preparation are disclosed in, e.g., U.S. Patent Publication Nos. 2004/0142025, 2007/0042031 and PCT Pub. Nos. WO 2013/016058 and WO 2013/086373, the full disclosures of which are herein incorporated by reference in their entirety for all purposes. 
     As used herein, “lipid encapsulated” refers to a lipid nanoparticle that provides an active agent or therapeutic agent, such as a nucleic acid (e.g., mRNA), with full encapsulation, partial encapsulation, or both. In an embodiment, the nucleic acid (e.g., mRNA) is fully encapsulated in the lipid nanoparticle. 
     As used herein, the term “aqueous solution” refers to a composition comprising water. 
     “Serum-stable” in relation to nucleic acid-lipid nanoparticles means that the nucleotide is not significantly degraded after exposure to a serum or nuclease assay that would significantly degrade free DNA or RNA. Suitable assays include, for example, a standard serum assay, a DNAse assay, or an RNAse assay. 
     “Systemic delivery,” as used herein, refers to delivery of a therapeutic product that can result in a broad exposure of an active agent within an organism. Some techniques of administration can lead to the systemic delivery of certain agents, but not others. Systemic delivery means that a useful, preferably therapeutic, amount of an agent is exposed to most parts of the body. Systemic delivery of lipid nanoparticles can be by any means known in the art including, for example, intravenous, intraarterial, subcutaneous, and intraperitoneal delivery. In some embodiments, systemic delivery of lipid nanoparticles is by intravenous delivery. 
     “Local delivery,” as used herein, refers to delivery of an active agent directly to a target site within an organism. For example, an agent can be locally delivered by direct injection into a disease site such as a tumor, other target site such as a site of inflammation, or a target organ such as the liver, heart, pancreas, kidney, and the like. Local delivery can also include topical applications or localized injection techniques such as intramuscular, subcutaneous or intradermal injection. Local delivery does not preclude a systemic pharmacological effect. 
     “Alkyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, which is saturated or unsaturated (i.e., contains one or more double (alkenyl) and/or triple bonds (alkynyl)), having, for example, from one to twenty-four carbon atoms (C 1 -C 24  alkyl), four to twenty carbon atoms (C 4 -C 20  alkyl), six to sixteen carbon atoms (C 6 -C 16  alkyl), six to nine carbon atoms (C 6 -C 9  alkyl), one to fifteen carbon atoms (C 1 -C 15  alkyl), one to twelve carbon atoms (C 1 -C 12  alkyl), one to eight carbon atoms (C 1 -C 8  alkyl) or one to six carbon atoms (C 1 -C 6  alkyl) and which is attached to the rest of the molecule by a single bond, e.g., methyl, ethyl, n propyl, 1 methylethyl (iso propyl), n butyl, n pentyl, 1,1-dimethylethyl (t butyl), 3-methylhexyl, 2-methylhexyl, ethenyl, prop-1-enyl, but-1-enyl, pent-1-enyl, penta-1,4-dienyl, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like. Unless stated otherwise specifically in the specification, an alkyl group is optionally substituted. 
     “Alkylene” or “alkylene chain” refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, which is saturated or unsaturated (i.e., contains one or more double (alkenylene) and/or triple bonds (alkynylene)), and having, for example, from one to twenty-four carbon atoms (C 1 -C 24  alkylene), one to fifteen carbon atoms (C 1 -C 15  alkylene), one to twelve carbon atoms (C 1 -C 12  alkylene), one to eight carbon atoms (C 1 -C 8  alkylene), one to six carbon atoms (C 1 -C 6  alkylene), two to four carbon atoms (C 2 -C 4  alkylene), one to two carbon atoms (C 1 -C 2  alkylene), e.g., methylene, ethylene, propylene, n-butylene, ethenylene, propenylene, n-butenylene, propynylene, n-butynylene, and the like. The alkylene chain is attached to the rest of the molecule through a single or double bond and to the radical group through a single or double bond. The points of attachment of the alkylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, an alkylene chain may be optionally substituted. 
     “Cycloalkyl” or “carbocyclic ring” refers to a stable non-aromatic monocyclic or polycyclic hydrocarbon radical consisting solely of carbon and hydrogen atoms, which may include fused or bridged ring systems, having from three to fifteen carbon atoms, preferably having from three to ten carbon atoms, and which is saturated or unsaturated and attached to the rest of the molecule by a single bond. Monocyclic radicals include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Polycyclic radicals include, for example, adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl, and the like. Unless otherwise stated specifically in the specification, a cycloalkyl group may be optionally substituted. 
     “Cycloalkylene” is a divalent cycloalkyl group. Unless otherwise stated specifically in the specification, a cycloalkylene group may be optionally substituted. 
     The term “substituted” used herein means any of the above groups (e.g. alkyl, alkylene, cycloalkyl or cycloalkylene) wherein at least one hydrogen atom is replaced by a bond to a non-hydrogen atom such as, but not limited to: a halogen atom such as F, Cl, Br, or I; oxo groups (═O); hydroxyl groups (—OH); C 1 -C 12  alkyl groups; cycloalkyl groups; —(C═O)OR; —O(C═O)R; —C(═O)R′; —OR′; —S(O) x R′; —S—SR′; —C(═O)SR′; —SC(═O)R′; —NR′R′; —NR′C(═O)R′; —C(═O)NR′R′; —NR′C(═O)NR′R′; —OC(═O)NR′R′; —NR′C(═O)OR; —NR S(O)XNR′R; —NR&#39;S(O) x R; and —S(O) x NR′R, wherein: R is, at each occurrence, independently H, C 1 -C 15  alkyl or cycloalkyl, and x is 0, 1 or 2. In some embodiments the substituent is a C 1 -C 12  alkyl group. In other embodiments, the substituent is a cycloalkyl group. In other embodiments, the substituent is a halo group, such as fluoro. In other embodiments, the substituent is an oxo group. In other embodiments, the substituent is a hydroxyl group. In other embodiments, the substituent is an alkoxy group (—OR′). In other embodiments, the substituent is a carboxyl group. In other embodiments, the substituent is an amine group(—NR′R′). 
     “Optional” or “optionally” (e.g., optionally substituted) means that the subsequently described event of circumstances may or may not occur, and that the description includes instances where said event or circumstance occurs and instances in which it does not. For example, “optionally substituted alkyl” means that the alkyl radical may or may not be substituted and that the description includes both substituted alkyl radicals and alkyl radicals having no substitution. 
     “Prodrug” is meant to indicate a compound that may be converted under physiological conditions or by solvolysis to a biologically active compound of the invention. Thus, the term “prodrug” refers to a metabolic precursor of a compound of the invention that is pharmaceutically acceptable. A prodrug may be inactive when administered to a subject in need thereof, but is converted in vivo to an active compound of the invention. Prodrugs are typically rapidly transformed in vivo to yield the parent compound of the invention, for example, by hydrolysis in blood. The prodrug compound often offers advantages of solubility, tissue compatibility or delayed release in a mammalian organism (see, Bundgard, H., Design of Prodrugs (1985), pp. 7-9, 21-24 (Elsevier, Amsterdam)). A discussion of prodrugs is provided in Higuchi, T., et al., A.C.S. Symposium Series, Vol. 14, and in Bioreversible Carriers in Drug Design, Ed. Edward B. Roche, American Pharmaceutical Association and Pergamon Press, 1987. 
     The term “prodrug” is also meant to include any covalently bonded carriers, which release the active compound of the invention in vivo when such prodrug is administered to a mammalian subject. Prodrugs of a compound of the invention may be prepared by modifying functional groups present in the compound of the invention in such a way that the modifications are cleaved, either in routine manipulation or in vivo, to the parent compound of the invention. Prodrugs include compounds of the invention wherein a hydroxy, amino or mercapto group is bonded to any group that, when the prodrug of the compound of the invention is administered to a mammalian subject, cleaves to form a free hydroxy, free amino or free mercapto group, respectively. Examples of prodrugs include, but are not limited to, acetate, formate and benzoate derivatives of alcohol or amide derivatives of amine functional groups in the compounds of the invention and the like. 
     The invention disclosed herein is also meant to encompass all pharmaceutically acceptable compounds of the compound of structure (I) being isotopically-labelled by having one or more atoms replaced by an atom having a different atomic mass or mass number. Examples of isotopes that can be incorporated into the disclosed compounds include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, chlorine, and iodine, such as  2 H,  3 H,  11 C,  13 C,  14 C,  13 N,  15 N,  15 O,  17 O,  18 O,  31 P,  32 P,  35 S,  18 F,  36 Cl,  123 I and  125 I, respectively. These radiolabeled compounds could be useful to help determine or measure the effectiveness of the compounds, by characterizing, for example, the site or mode of action, or binding affinity to pharmacologically important site of action. Certain isotopically-labelled compounds of structure (I) or (II), for example, those incorporating a radioactive isotope, are useful in drug and/or substrate tissue distribution studies. The radioactive isotopes tritium, i.e.,  3 H, and carbon-14, i.e.,  14 C, are particularly useful for this purpose in view of their ease of incorporation and ready means of detection. 
     Substitution with heavier isotopes such as deuterium, i.e.,  2 H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements, and hence may be preferred in some circumstances. 
     Substitution with positron emitting isotopes, such as  11 C,  18 F,  15 O and  13 N, can be useful in Positron Emission Topography (PET) studies for examining substrate receptor occupancy. Isotopically-labeled compounds of structure (I) can generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described in the Preparations and Examples as set out below using an appropriate isotopically-labeled reagent in place of the non-labeled reagent previously employed. 
     The invention disclosed herein is also meant to encompass the in vivo metabolic products of the disclosed compounds. Such products may result from, for example, the oxidation, reduction, hydrolysis, amidation, esterification, and the like of the administered compound, primarily due to enzymatic processes. Accordingly, the invention includes compounds produced by a process comprising administering a compound of this invention to a mammal for a period of time sufficient to yield a metabolic product thereof. Such products are typically identified by administering a radiolabeled compound of the invention in a detectable dose to an animal, such as rat, mouse, guinea pig, monkey, or to human, allowing sufficient time for metabolism to occur, and isolating its conversion products from the urine, blood or other biological samples. 
     “Stable compound” and “stable structure” are meant to indicate a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into an efficacious therapeutic agent. 
     “Mammal” includes humans and both domestic animals such as laboratory animals and household pets (e.g., cats, dogs, swine, cattle, sheep, goats, horses, rabbits), and non-domestic animals such as wildlife and the like. 
     “Pharmaceutically acceptable carrier, diluent or excipient” includes without limitation any adjuvant, carrier, excipient, glidant, sweetening agent, diluent, preservative, dye/colorant, flavor enhancer, surfactant, wetting agent, dispersing agent, suspending agent, stabilizer, isotonic agent, solvent, or emulsifier which has been approved by the United States Food and Drug Administration as being acceptable for use in humans or domestic animals. 
     “Pharmaceutically acceptable salt” includes both acid and base addition salts. 
     “Pharmaceutically acceptable acid addition salt” refers to those salts which retain the biological effectiveness and properties of the free bases, which are not biologically or otherwise undesirable, and which are formed with inorganic acids such as, but are not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as, but not limited to, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, 4-acetamidobenzoic acid, camphoric acid, camphor-10-sulfonic acid, capric acid, caproic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid, fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid, gluconic acid, glucuronic acid, glutamic acid, glutaric acid, 2-oxo-glutaric acid, glycerophosphoric acid, glycolic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, mucic acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid, propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid, thiocyanic acid, p-toluenesulfonic acid, trifluoroacetic acid, undecylenic acid, and the like. 
     “Pharmaceutically acceptable base addition salt” refers to those salts which retain the biological effectiveness and properties of the free acids, which are not biologically or otherwise undesirable. These salts are prepared from addition of an inorganic base or an organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Preferred inorganic salts are the ammonium, sodium, potassium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as ammonia, isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, deanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, benethamine, benzathine, ethylenediamine, glucosamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline and caffeine. 
     Often crystallizations produce a solvate of the compound of the invention. As used herein, the term “solvate” refers to an aggregate that comprises one or more molecules of a compound of the invention with one or more molecules of solvent. The solvent may be water, in which case the solvate may be a hydrate. Alternatively, the solvent may be an organic solvent. Thus, the compounds of the present invention may exist as a hydrate, including a monohydrate, dihydrate, hemihydrate, sesquihydrate, trihydrate, tetrahydrate and the like, as well as the corresponding solvated forms. The compound of the invention may be true solvates, while in other cases, the compound of the invention may merely retain adventitious water or be a mixture of water plus some adventitious solvent. 
     A “pharmaceutical composition” refers to a formulation of a compound of the invention and a medium generally accepted in the art for the delivery of the biologically active compound to mammals, e.g., humans. Such a medium includes all pharmaceutically acceptable carriers, diluents or excipients therefor. 
     “Effective amount” or “therapeutically effective amount” refers to that amount of a compound of the invention which, when administered to a mammal, preferably a human, is sufficient to effect treatment in the mammal, preferably a human. The amount of a lipid nanoparticle of the invention which constitutes a “therapeutically effective amount” will vary depending on the compound, the condition and its severity, the manner of administration, and the age of the mammal to be treated, but can be determined routinely by one of ordinary skill in the art having regard to his own knowledge and to this disclosure. 
     “Treating” or “treatment” as used herein covers the treatment of the disease or condition of interest in a mammal, preferably a human, having the disease or condition of interest, and includes: 
     (i) preventing the disease or condition from occurring in a mammal, in particular, when such mammal is predisposed to the condition but has not yet been diagnosed as having it; 
     (ii) inhibiting the disease or condition, i.e., arresting its development; 
     (iii) relieving the disease or condition, i.e., causing regression of the disease or condition; or 
     (iv) relieving the symptoms resulting from the disease or condition, i.e., relieving pain without addressing the underlying disease or condition. As used herein, the terms “disease” and “condition” may be used interchangeably or may be different in that the particular malady or condition may not have a known causative agent (so that etiology has not yet been worked out) and it is therefore not yet recognized as a disease but only as an undesirable condition or syndrome, wherein a more or less specific set of symptoms have been identified by clinicians. 
     The compounds of the invention, or their pharmaceutically acceptable salts may contain one or more asymmetric centers and may thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)- or (S)- or, as (D)- or (L)- for amino acids. The present invention is meant to include all such possible isomers, as well as their racemic and optically pure forms. Optically active (+) and (−), (R)- and (S)-, or (D)- and (L)-isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques, for example, chromatography and fractional crystallization. Conventional techniques for the preparation/isolation of individual enantiomers include chiral synthesis from a suitable optically pure precursor or resolution of the racemate (or the racemate of a salt or derivative) using, for example, chiral high pressure liquid chromatography (HPLC). When the compounds described herein contain olefinic double bonds or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers. Likewise, all tautomeric forms are also intended to be included. 
     A “stereoisomer” refers to a compound made up of the same atoms bonded by the same bonds but having different three-dimensional structures, which are not interchangeable. The present invention contemplates various stereoisomers and mixtures thereof and includes “enantiomers”, which refers to two stereoisomers whose molecules are nonsuperimposeable mirror images of one another. 
     A “tautomer” refers to a proton shift from one atom of a molecule to another atom of the same molecule. The present invention includes tautomers of any said compounds. 
     Compounds 
     In an aspect, the invention provides novel lipid compounds which are capable of combining with other lipid components such as neutral lipids, charged lipids, steroids and/or polymer conjugated-lipids to form lipid nanoparticles with oligonucleotides. Without wishing to be bound by theory, it is thought that these lipid nanoparticles shield oligonucleotides from degradation in the serum and provide for effective delivery of oligonucleotides to cells in vitro and in vivo. 
     In one embodiment, the compounds have the following structure (I): 
                         
or a pharmaceutically acceptable salt, tautomer, prodrug or stereoisomer thereof, wherein:
 
     one of L 1  or L 2  is —O(C═O)—, —(C═O)O—, —C(═O)—, —O—, —S(O) x —, —S—S—, —C(═O)S—, SC(═O)—, —NR a C(═O)—, —C(═O)NR a —, NR a C(═O)NR a —, —OC(═O)NR a — or —NR a C(═O)O—, and the other of L 1  or L 2  is —O(C═O)—, —(C═O)O—, —C(═O)—, —O—, —S(O) x —, —S—S—, —C(═O)S—, SC(═O)—, —NR a C(═O)—, —C(═O)NR a —, NR a C(═O)NR a —, —OC(═O)NR a — or —NR a C(═O)O— or a direct bond; 
     G 1  and G 2  are each independently unsubstituted C 1 -C 12  alkylene or C 1 -C 12  alkenylene; 
     G 3  is C 1 -C 24  alkylene, C 1 -C 24  alkenylene, C 3 -C 8  cycloalkylene, C 3 -C 8  cycloalkenylene; 
     R a  is H or C 1 -C 12  alkyl; 
     R 1  and R 2  are each independently C 6 -C 24  alkyl or C 6 -C 24  alkenyl; 
     R 3  is H, OR 5 , CN, —C(═O)OR 4 , —OC(═O)R 4  or —NR 5 C(═O)R 4 ; 
     R 4  is C 1 -C 12  alkyl; 
     R 5  is H or C 1 -C 6  alkyl; and 
     x is 0, 1 or 2. 
     In some of the foregoing embodiments, the compound has one of the following structures (IA) or (TB): 
                         
wherein:
 
     A is a 3 to 8-membered cycloalkyl or cycloalkylene ring; 
     R 6  is, at each occurrence, independently H, OH or C 1 -C 24  alkyl; 
     n is an integer ranging from 1 to 15. 
     In some of the foregoing embodiments, the compound has structure (IA), and in other embodiments, the compound has structure (IB). 
     In other embodiments of the foregoing, the compound has one of the following structured (IC) or (ID): 
                         
wherein y and z are each independently integers ranging from 1 to 12.
 
     In any of the foregoing embodiments, one of L 1  or L 2  is —O(C═O)—. For example, in some embodiments each of L 1  and L 2  are —O(C═O)—. In some different embodiments of any of the foregoing, L 1  and L 2  are each independently —(C═O)O— or —O(C═O)—. For example, in some embodiments each of L 1  and L 2  is —(C═O)O—. 
     In some different embodiments of the foregoing, the compound has one of the following structures (IE) or (IF): 
     
       
         
         
             
             
         
       
     
     In some of the foregoing embodiments, the compound has one of the following structures (IG), (IH), (II), or (IJ): 
     
       
         
         
             
             
         
       
     
     In some of the foregoing embodiments, n is an integer ranging from 2 to 12, for example from 2 to 8 or from 2 to 4. For example, in some embodiments, n is 3, 4, 5 or 6. In some embodiments, n is 3. In some embodiments, n is 4. In some embodiments, n is 5. In some embodiments, n is 6. 
     In some other of the foregoing embodiments, y and z are each independently an integer ranging from 2 to 10. For example, in some embodiments, y and z are each independently an integer ranging from 4 to 9 or from 4 to 6. 
     In some of the foregoing embodiments, R 6  is H. In other of the foregoing embodiments, R 6  is C 1 -C 24  alkyl. In other embodiments, R 6  is OH. 
     In some embodiments, G 3  is unsubstituted. In other embodiments, G3 is substituted. In various different embodiments, G 3  is linear C 1 -C 24  alkylene or linear C 1 -C 24  alkenylene. 
     In some other foregoing embodiments, R 1  or R 2 , or both, is C 6 -C 24  alkenyl. For example, in some embodiments, R 1  and R 2  each, independently have the following structure: 
                         
wherein
 
     R 7a  and R 7b  are, at each occurrence, independently H or C 1 -C 12  alkyl; and 
     a is an integer from 2 to 12, 
     wherein R 7a , R 7b  and a are each selected such that R 1  and R 2  each independently comprise from 6 to 20 carbon atoms. For example, in some embodiments a is an integer ranging from 5 to 9 or from 8 to 12. 
     In some of the foregoing embodiments, at least one occurrence of R 7a  is H. For example, in some embodiments, R 7a  is H at each occurrence. In other different embodiments of the foregoing, at least one occurrence of R 7b  is C 1 -C 8  alkyl. For example, in some embodiments, C 1 -C 8  alkyl is methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-hexyl or n-octyl. 
     In different embodiments, R 1  or R 2 , or both, has one of the following structures: 
     
       
         
         
             
             
         
       
     
     In some of the foregoing embodiments, R 3  is OH, CN, —C(═O)OR 4 , —OC(═O)R 4  or —NHC(═O)R 4 . In some embodiments, R 4  is methyl or ethyl. 
     In various different embodiments, the compound has one of the structures set forth in Table 1 below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Representative Compounds 
               
            
           
           
               
               
            
               
                 No. 
                 Structure 
               
               
                   
               
            
           
           
               
               
            
               
                 1 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 2 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 3 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 4 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 5 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 6 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 7 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 8 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 9 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 10 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 11 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 12 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 13 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 14 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 15 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 16 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 17 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 18 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 19 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 20 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 21 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 22 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
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                 24 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 25 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 26 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 27 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 28 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 29 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 30 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 31 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 32 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 33 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 34 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 35 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 36 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 37 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 38 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 39 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 40 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 41 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 42 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 43 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 44 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 45 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 46 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 47 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 48 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 49 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     It is understood that any embodiment of the compounds of structure (I), as set forth above, and any specific substituent and/or variable in the compound structure (I), as set forth above, may be independently combined with other embodiments and/or substituents and/or variables of compounds of structure (I) to form embodiments of the inventions not specifically set forth above. In addition, in the event that a list of substituents and/or variables is listed for any particular R group, L group, G group, A group, or variables a, n, x, y, or z in a particular embodiment and/or claim, it is understood that each individual substituent and/or variable may be deleted from the particular embodiment and/or claim and that the remaining list of substituents and/or variables will be considered to be within the scope of the invention. 
     It is understood that in the present description, combinations of substituents and/or variables of the depicted formulae are permissible only if such contributions result in stable compounds. 
     In some embodiments, compositions comprising any one or more of the compounds of structure (I) and a therapeutic agent are provided. For example, in some embodiments, the compositions comprise any of the compounds of structure (I) and a therapeutic agent and one or more excipient selected from neutral lipids, steroids and polymer conjugated lipids. Other pharmaceutically acceptable excipients and/or carriers are also included in various embodiments of the compositions. 
     In some embodiments, the neutral lipid is selected from DSPC, DPPC, DMPC, DOPC, POPC, DOPE and SM. In some embodiments, the neutral lipid is DSPC. 
     In various embodiments, the molar ratio of the compound to the neutral lipid ranges from about 2:1 to about 8:1. 
     In various embodiments, the compositions further comprise a steroid or steroid analogue. In certain embodiments, the steroid or steroid analogue is cholesterol. In some of these embodiments, the molar ratio of the compound to cholesterol ranges from about 5:1 to 1:1. 
     In various embodiments, the polymer conjugated lipid is a pegylated lipid. For example, some embodiments include a pegylated diacylglycerol (PEG-DAG) such as 1-(monomethoxy-polyethyleneglycol)-2,3-dimyristoylglycerol (PEG-DMG), a pegylated phosphatidylethanoloamine (PEG-PE), a PEG succinate diacylglycerol (PEG-S-DAG) such as 4-O-(2′,3′-di(tetradecanoyloxy)propyl-1-O-(ω-methoxy(polyethoxy)ethyl)butanedioate (PEG-S-DMG), a pegylated ceramide (PEG-cer), or a PEG dialkoxypropylcarbamate such as ω-methoxy(polyethoxy)ethyl-N-(2,3-di(tetradecanoxy)propyl)carbamate or 2,3-di(tetradecanoxy)propyl-N-(ω-methoxy(polyethoxy)ethyl)carbamate. In various embodiments, the molar ratio of the compound to the pegylated lipid ranges from about 100:1 to about 20:1. 
     In some embodiments, the composition comprises a pegylated lipid having the following structure (II): 
                         
or a pharmaceutically acceptable salt, tautomer or stereoisomer thereof, wherein:
 
     R 8  and R 9  are each independently a straight or branched, saturated or unsaturated alkyl chain containing from 10 to 30 carbon atoms, wherein the alkyl chain is optionally interrupted by one or more ester bonds; and 
     w has a mean value ranging from 30 to 60. 
     In some embodiments, R 8  and R 9  are each independently straight, saturated alkyl chains containing from 12 to 16 carbon atoms. In some embodiments, w has a mean value ranging from 43 to 53. In other embodiments, the average w is about 45. In other different embodiments, the average w is about 49. 
     In some embodiments of the foregoing composition, the therapeutic agent comprises a nucleic acid. For example, in some embodiments, the nucleic acid is selected from antisense and messenger RNA. 
     In other different embodiments, the invention is directed to a method for administering a therapeutic agent to a patient in need thereof, the method comprising preparing or providing any of the foregoing compositions and administering the composition to the patient 
     For the purposes of administration, the compounds of the present invention (typically in the form of lipid nanoparticles in combination with a therapeutic agent) may be administered as a raw chemical or may be formulated as pharmaceutical compositions. Pharmaceutical compositions of the present invention comprise a compound of structure (I) and one or more pharmaceutically acceptable carrier, diluent or excipient. The compound of structure (I) is present in the composition in an amount which is effective to form a lipid nanoparticle and deliver the therapeutic agent, e.g., for treating a particular disease or condition of interest. Appropriate concentrations and dosages can be readily determined by one skilled in the art. 
     Administration of the compositions of the invention can be carried out via any of the accepted modes of administration of agents for serving similar utilities. The pharmaceutical compositions of the invention may be formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suspensions, suppositories, injections, inhalants, gels, microspheres, and aerosols. Typical routes of administering such pharmaceutical compositions include, without limitation, oral, topical, transdermal, inhalation, parenteral, sublingual, buccal, rectal, vaginal, and intranasal. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intradermal, intrasternal injection or infusion techniques. Pharmaceutical compositions of the invention are formulated so as to allow the active ingredients contained therein to be bioavailable upon administration of the composition to a patient. Compositions that will be administered to a subject or patient take the form of one or more dosage units, where for example, a tablet may be a single dosage unit, and a container of a compound of the invention in aerosol form may hold a plurality of dosage units. Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in this art; for example, see  Remington: The Science and Practice of Pharmacy,  20th Edition (Philadelphia College of Pharmacy and Science, 2000). The composition to be administered will, in any event, contain a therapeutically effective amount of a compound of the invention, or a pharmaceutically acceptable salt thereof, for treatment of a disease or condition of interest in accordance with the teachings of this invention. 
     A pharmaceutical composition of the invention may be in the form of a solid or liquid. In one aspect, the carrier(s) are particulate, so that the compositions are, for example, in tablet or powder form. The carrier(s) may be liquid, with the compositions being, for example, an oral syrup, injectable liquid or an aerosol, which is useful in, for example, inhalatory administration. 
     When intended for oral administration, the pharmaceutical composition is preferably in either solid or liquid form, where semi-solid, semi-liquid, suspension and gel forms are included within the forms considered herein as either solid or liquid. 
     As a solid composition for oral administration, the pharmaceutical composition may be formulated into a powder, granule, compressed tablet, pill, capsule, chewing gum, wafer or the like form. Such a solid composition will typically contain one or more inert diluents or edible carriers. In addition, one or more of the following may be present: binders such as carboxymethylcellulose, ethyl cellulose, microcrystalline cellulose, gum tragacanth or gelatin; excipients such as starch, lactose or dextrins, disintegrating agents such as alginic acid, sodium alginate, Primogel, corn starch and the like; lubricants such as magnesium stearate or Sterotex; glidants such as colloidal silicon dioxide; sweetening agents such as sucrose or saccharin; a flavoring agent such as peppermint, methyl salicylate or orange flavoring; and a coloring agent. 
     When the pharmaceutical composition is in the form of a capsule, for example, a gelatin capsule, it may contain, in addition to materials of the above type, a liquid carrier such as polyethylene glycol or oil. 
     The pharmaceutical composition may be in the form of a liquid, for example, an elixir, syrup, solution, emulsion or suspension. The liquid may be for oral administration or for delivery by injection, as two examples. When intended for oral administration, preferred composition contain, in addition to the present compounds, one or more of a sweetening agent, preservatives, dye/colorant and flavor enhancer. In a composition intended to be administered by injection, one or more of a surfactant, preservative, wetting agent, dispersing agent, suspending agent, buffer, stabilizer and isotonic agent may be included. 
     The liquid pharmaceutical compositions of the invention, whether they be solutions, suspensions or other like form, may include one or more of the following adjuvants: sterile diluents such as water for injection, saline solution, preferably physiological saline, Ringer&#39;s solution, isotonic sodium chloride, fixed oils such as synthetic mono or diglycerides which may serve as the solvent or suspending medium, polyethylene glycols, glycerin, propylene glycol or other solvents; antibacterial agents such as benzyl alcohol or methyl paraben; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose; agents to act as cryoprotectants such as sucrose or trehalose. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. Physiological saline is a preferred adjuvant. An injectable pharmaceutical composition is preferably sterile. 
     A liquid pharmaceutical composition of the invention intended for either parenteral or oral administration should contain an amount of a compound of the invention such that a suitable dosage will be obtained. 
     The pharmaceutical composition of the invention may be intended for topical administration, in which case the carrier may suitably comprise a solution, emulsion, ointment or gel base. The base, for example, may comprise one or more of the following: petrolatum, lanolin, polyethylene glycols, bee wax, mineral oil, diluents such as water and alcohol, and emulsifiers and stabilizers. Thickening agents may be present in a pharmaceutical composition for topical administration. If intended for transdermal administration, the composition may include a transdermal patch or iontophoresis device. 
     The pharmaceutical composition of the invention may be intended for rectal administration, in the form, for example, of a suppository, which will melt in the rectum and release the drug. The composition for rectal administration may contain an oleaginous base as a suitable nonirritating excipient. Such bases include, without limitation, lanolin, cocoa butter and polyethylene glycol. 
     The pharmaceutical composition of the invention may include various materials, which modify the physical form of a solid or liquid dosage unit. For example, the composition may include materials that form a coating shell around the active ingredients. The materials that form the coating shell are typically inert, and may be selected from, for example, sugar, shellac, and other enteric coating agents. Alternatively, the active ingredients may be encased in a gelatin capsule. 
     The pharmaceutical composition of the invention in solid or liquid form may include an agent that binds to the compound of the invention and thereby assists in the delivery of the compound. Suitable agents that may act in this capacity include a monoclonal or polyclonal antibody, or a protein. 
     The pharmaceutical composition of the invention may consist of dosage units that can be administered as an aerosol. The term aerosol is used to denote a variety of systems ranging from those of colloidal nature to systems consisting of pressurized packages. Delivery may be by a liquefied or compressed gas or by a suitable pump system that dispenses the active ingredients. Aerosols of compounds of the invention may be delivered in single phase, bi-phasic, or tri-phasic systems in order to deliver the active ingredient(s). Delivery of the aerosol includes the necessary container, activators, valves, subcontainers, and the like, which together may form a kit. One skilled in the art, without undue experimentation may determine preferred aerosols. 
     The pharmaceutical compositions of the invention may be prepared by methodology well known in the pharmaceutical art. For example, a pharmaceutical composition intended to be administered by injection can be prepared by combining the lipid nanoparticles of the invention with sterile, distilled water or other carrier so as to form a solution. A surfactant may be added to facilitate the formation of a homogeneous solution or suspension. Surfactants are compounds that non-covalently interact with the compound of the invention so as to facilitate dissolution or homogeneous suspension of the compound in the aqueous delivery system. 
     The compositions of the invention, or their pharmaceutically acceptable salts, are administered in a therapeutically effective amount, which will vary depending upon a variety of factors including the activity of the specific therapeutic agent employed; the metabolic stability and length of action of the therapeutic agent; the age, body weight, general health, sex, and diet of the patient; the mode and time of administration; the rate of excretion; the drug combination; the severity of the particular disorder or condition; and the subject undergoing therapy. 
     Compositions of the invention may also be administered simultaneously with, prior to, or after administration of one or more other therapeutic agents. Such combination therapy includes administration of a single pharmaceutical dosage formulation of a composition of the invention and one or more additional active agents, as well as administration of the composition of the invention and each active agent in its own separate pharmaceutical dosage formulation. For example, a composition of the invention and the other active agent can be administered to the patient together in a single oral dosage composition such as a tablet or capsule, or each agent administered in separate oral dosage formulations. Where separate dosage formulations are used, the compounds of the invention and one or more additional active agents can be administered at essentially the same time, i.e., concurrently, or at separately staggered times, i.e., sequentially; combination therapy is understood to include all these regimens. 
     Preparation methods for the above compounds and compositions are described herein below and/or known in the art. 
     It will be appreciated by those skilled in the art that in the process described herein the functional groups of intermediate compounds may need to be protected by suitable protecting groups. Such functional groups include hydroxy, amino, mercapto and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl or diarylalkylsilyl (for example, t-butyldimethylsilyl, t-butyldiphenylsilyl or trimethylsilyl), tetrahydropyranyl, benzyl, and the like. Suitable protecting groups for amino, amidino and guanidino include t-butoxycarbonyl, benzyloxycarbonyl, and the like. Suitable protecting groups for mercapto include —C(O)—R″ (where R″ is alkyl, aryl or arylalkyl), p-methoxybenzyl, trityl and the like. Suitable protecting groups for carboxylic acid include alkyl, aryl or arylalkyl esters. Protecting groups may be added or removed in accordance with standard techniques, which are known to one skilled in the art and as described herein. The use of protecting groups is described in detail in Green, T. W. and P. G. M. Wutz,  Protective Groups in Organic Synthesis  (1999), 3rd Ed., Wiley. As one of skill in the art would appreciate, the protecting group may also be a polymer resin such as a Wang resin, Rink resin or a 2-chlorotrityl-chloride resin. 
     It will also be appreciated by those skilled in the art, although such protected derivatives of compounds of this invention may not possess pharmacological activity as such, they may be administered to a mammal and thereafter metabolized in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as “prodrugs”. All prodrugs of compounds of this invention are included within the scope of the invention. 
     Furthermore, all compounds of the invention which exist in free base or acid form can be converted to their pharmaceutically acceptable salts by treatment with the appropriate inorganic or organic base or acid by methods known to one skilled in the art. Salts of the compounds of the invention can be converted to their free base or acid form by standard techniques. 
     The following General Reaction Scheme 1 illustrates methods to make compounds of this invention, i.e., compounds of structure (I): 
                         
or a pharmaceutically acceptable salt, tautomer or stereoisomer thereof, wherein R 1 , R 2 , R 3 , L 1 , L 2 , G 1 , G 2 , and G 3  are as defined herein. It is understood that one skilled in the art may be able to make these compounds by similar methods or by combining other methods known to one skilled in the art. It is also understood that one skilled in the art would be able to make, in a similar manner as described below, other compounds of structure (I) not specifically illustrated below by using the appropriate starting components and modifying the parameters of the synthesis as needed. In general, starting components may be obtained from sources such as Sigma Aldrich, Lancaster Synthesis, Inc., Maybridge, Matrix Scientific, TCI, and Fluorochem USA, etc. or synthesized according to sources known to those skilled in the art (see, for example, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 5th edition (Wiley, December 2000)) or prepared as described in this invention.
 
     
       
         
         
             
             
         
       
     
     General Reaction Scheme I provides an exemplary method for preparation of compounds of structure (I). G 1 , G 3 , R 1  and R 3  in General reaction Scheme 1 are as defined herein, and G1′ refers to a one-carbon shorter homologue of G1. Compounds of structure A-1 are purchased or prepared according to methods known in the art. Reaction of A-1 with diol A-2 under appropriate condensation conditions (e.g., DCC) yields ester/alcohol A-3, which can then be oxidized (e.g., PCC) to aldehyde A-4. Reaction of A 4 with amine A-4 under reductive amination conditions yields a compound of structure (I). 
     It should be noted that various alternative strategies for preparation of compounds of structure (I) are available to those of ordinary skill in the art. For example, other compounds of structure (I) wherein L 1  and L 2  are other than ester can be prepared according to analogous methods using the appropriate starting material. Further, General Reaction Scheme 1 depicts preparation of a compound of structure (I), wherein G 1  and G 2  are the same; however, this is not a required aspect of the invention and modifications to the above reaction scheme are possible to yield compounds wherein G 1  and G 2  are different. The use of protecting groups as needed and other modification to the above General Reaction Scheme will be readily apparent to one of ordinary skill in the art. 
     The following examples are provided for purpose of illustration and not limitation. 
     Example 1 
     Luciferase mRNA In Vivo Evaluation Using the Lipid Nanoparticle Compositions 
     Cationic lipid, DSPC, cholesterol and PEG-lipid were solubilized in ethanol at a molar ratio of 50:10:38.5:1.5 or 47.5:10:40.8:1.7. Lipid nanoparticles (LNP) were prepared at a total lipid to mRNA weight ratio of approximately 10:1 to 30:1. Briefly, the mRNA was diluted to 0.2 mg/mL in 10 to 50 mM citrate buffer, pH 4. Syringe pumps were used to mix the ethanolic lipid solution with the mRNA aqueous solution at a ratio of about 1:5 to 1:3 (vol/vol) with total flow rates above 15 ml/min. The ethanol was then removed and the external buffer replaced with PBS by dialysis. Finally, the lipid nanoparticles were filtered through a 0.2 μm pore sterile filter. Lipid nanoparticle particle size was approximately 55-95 nm diameter, and in some instances approximately 70-90 nm diameter as determined by quasi-elastic light scattering using a Malvern Zetasizer Nano ZS (Malvern, UK). 
     Studies were performed in 6-8 week old female C 57 BL/6 mice (Charles River) 8-10 week old CD-1 (Harlan) mice (Charles River) according to guidelines established by an institutional animal care committee (ACC) and the Canadian Council on Animal Care (CCAC). Varying doses of mRNA-lipid nanoparticle were systemically administered by tail vein injection and animals euthanized at a specific time point (e.g 4 hrs) post-administration. Liver and spleen were collected in pre-weighed tubes, weights determined, immediately snap frozen in liquid nitrogen and stored at −80° C. until processing for analysis. 
     For liver, approximately 50 mg was dissected for analyses in a 2 mL FastPrep tubes (MP Biomedicals, Solon Ohio). ¼″ ceramic sphere (MP Biomedicals) was added to each tube and 500 μL of Glo Lysis Buffer—GLB (Promega, Madison Wis.) equilibrated to room temperature was added to liver tissue. Liver tissues were homogenized with the FastPrep24 instrument (MP Biomedicals) at 2×6.0 m/s for 15 seconds. Homogenate was incubated at room temperature for 5 minutes prior to a 1:4 dilution in GLB and assessed using SteadyGlo Luciferase assay system (Promega). Specifically, 50 μL of diluted tissue homogenate was reacted with 50 μL of SteadyGlo substrate, shaken for 10 seconds followed by 5 minute incubation and then quantitated using a CentroXS 3  LB 960 luminometer (Berthold Technologies, Germany). The amount of protein assayed was determined by using the BCA protein assay kit (Pierce, Rockford Ill.). Relative luminescence units (RLU) were then normalized to total ug protein assayed. To convert RLU to ng luciferase a standard curve was generated with QuantiLum Recombinant Luciferase (Promega). Based in the data provided in  FIG.  1   , the four-hour time point was chosen for efficacy evaluation of the lipid formulations. 
     The FLuc mRNA (L-6107) from Trilink Biotechnologies will express a luciferase protein, originally isolated from the firefly, Photinus pyralis. FLuc is commonly used in mammalian cell culture to measure both gene expression and cell viability. It emits bioluminescence in the presence of the substrate, luciferin. This capped and polyadenylated mRNA is fully substituted with 5-methylcytidine and pseudouridine. 
     Example 2 
     Determination of Pka of Formulated Lipids 
     As described elsewhere, the pKa of formulated cationic lipids is correlated with the effectiveness of LNPs for delivery of nucleic acids (see Jayaraman et al, Angewandte Chemie, International Edition (2012), 51(34), 8529-8533; Semple et al, Nature Biotechnology 28, 172-176 (2010)). The preferred range of pKa is ˜5 to ˜7. The pKa of each cationic lipid was determined in lipid nanoparticles using an assay based on fluorescence of 2-(p-toluidino)-6-napthalene sulfonic acid (TNS). Lipid nanoparticles comprising of cationic lipid/DSPC/cholesterol/PEG-lipid (50/10/38.5/1.5 mol %) in PBS at a concentration of 0.4 mM total lipid are prepared using the in-line process as described in Example 1. TNS was prepared as a 100 μM stock solution in distilled water. Vesicles were diluted to 24 μM lipid in 2 mL of buffered solutions containing, 10 mM HEPES, 10 mM MES, 10 mM ammonium acetate, 130 mM NaCl, where the pH ranged from 2.5 to 11. An aliquot of the TNS solution was added to give a final concentration of 1 μM and following vortex mixing fluorescence intensity was measured at room temperature in a SLM Aminco Series 2 Luminescence Spectrophotometer using excitation and emission wavelengths of 321 nm and 445 nm. A sigmoidal best fit analysis was applied to the fluorescence data and the pKa was measured as the pH giving rise to half-maximal fluorescence intensity (see  FIG.  2   ). 
     Example 3 
     Determination of Efficacy of Lipid Nanoparticle Formulations Containing Various Cationic Lipids Using an In Vivo Luciferase mRNA Expression Rodent Model 
     The cationic lipids shown in Table 2 have previously been tested with nucleic acids. For comparative purposes, these lipids were also used to formulate lipid nanoparticles containing the FLuc mRNA (L-6107) using an in line mixing method, as described in Example 1 and in PCT/US 10/22614, which is hereby incorporated by reference in its entirety. Lipid nanoparticles were formulated using the following molar ratio: 50% Cationic lipid/10% distearoylphosphatidylcholine (DSPC)/38.5% Cholesterol/1.5% PEG lipid (“PEG-DMG”, i.e., (1-(monomethoxy-polyethyleneglycol)-2,3-dimyristoylglycerol, with an average PEG molecular weight of 2000). Relative activity was determined by measuring luciferase expression in the liver 4 hours following administration via tail vein injection as described in Example 1. The activity was compared at a dose of 0.3 and 1.0 mg mRNA/kg and expressed as ng luciferase/g liver measured 4 hours after administration, as described in Example 1. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Comparator Lipids showing activity with mRNA 
               
            
           
           
               
               
               
               
            
               
                   
                 Liver Luc 
                 Liver Luc 
                   
               
               
                   
                 @ 0.3  
                 @ 1.0  
                   
               
               
                   
                 mg/kg 
                 mg/kg 
                   
               
               
                 Compound 
                 dose 
                 dose 
                 Structure 
               
               
                   
               
               
                 MC2 
                  4 ± 1 
                 N/D 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 DLinDMA 
                  13 ± 3 
                  67 ± 20 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 MC4 
                  41 ± 10 
                 N/D 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 XTC2 
                  80 ± 28 
                 237 ± 99 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 MC3 
                 198 ± 126 
                 757 ± 528 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 319 (2% PEG) 
                 258 ± 67 
                 681 ± 203 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 137 
                 281 ± 203 
                 588 ± 303 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     Representative compounds of the invention shown in Table 3 were formulated using the following molar ratio: A) 50% cationic lipid/10% distearoylphosphatidylcholine (DSPC)/38.5% Cholesterol/1.5% PEG lipid (“PEG-DMA” 2-[2-(ω-methoxy(polyethyleneglycol 2000 )ethoxy]-N,N-ditetradecylacetamide) or B) 47.5% cationic lipid/10% DSPC/40.8% Cholesterol/1.7% PEG lipid. Relative activity was determined by measuring luciferase expression in the liver 4 hours following administration via tail vein injection as described in Example 1. The activity was compared at a dose of 0.3 and 1.0 mg mRNA/kg and expressed as ng luciferase/g liver measured 4 hours after administration, as described in Example 1. A plot of selected data is given in  FIG.  3    (from top to bottom: triangle=compound 3; circle=compound 2; cross=compound 1; square=MC3). 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Novel Cationic lipids and Associated Activity 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 Liver Luc 
                 Liver Luc 
                   
                   
               
               
                   
                   
                 @ 0.3 mg/kg 
                 @ 1.0 mg/kg 
                   
                   
               
               
                 No. 
                 pK a   
                 (ng luc/g liver) 
                 (ng luc/g liver) 
                 Structure 
                 Lipid Ratio 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 5.89 
                  467 ± 72 
                  3780 ± 210 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 2 
                 6.05 
                 1195 ± 245 
                 10059 ± 3833 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 3 
                 6.09 
                 1275 ± 410 
                 10643 ± 1858 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 4 
                 5.60 
                  378 ± 82 
                  1952 ± 940 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 5 
                 5.59 
                  183 ± 45 
                  713 ± 298 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 6 
                 5.42 
                  122 ± 49 
                  520 ± 365 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 7 
                 6.11 
                 1158 ± 136 
                  8406 ± 2335 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 8 
                 5.84 
                 1467 ± 943 
                  7230 ± 2290 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 15 
                 6.14 
                  247 ± 25 
                  1633 ± 449 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 16 
                 6.31 
                  344 ± 133 
                  2633 ± 1140 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 17 
                 6.28 
                  275 ± 139 
                  1554 ± 761 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 20 
                 6.36 
                  691 ± 150 
                  4279 ± 2226 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 B 
               
               
                   
               
               
                 22 
                 6.10 
                  660 ± 184 
                  7533 ± 4499 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 23 
                 5.98 
                  137 ± 51 
                  487 ± 209 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 25 
                 6.22 
                 1648 ± 534 
                 13880 ± 5083 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 26 
                 5.84 
                 1143 ± 782 
                  1238 ± 1686 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 27 
                 5.77 
                  110 ± 42 
                  1088 ± 802 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 30 
                 6.09 
                  49 ± 17 
                  297 ± 92 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 37 
                 5.89 
                 1244 ± 907 
                  2035 ± 498 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 38 
                 6.10 
                  60 ± 5 
                  365 ± 181 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 A 
               
               
                   
               
               
                 44 
                 5.79 
                  23 ± 11 
                  342 ± 229 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 B 
               
               
                   
               
               
                 45 
                 6.25 
                 1026 ± 199 
                  8806 ± 2836 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 B 
               
               
                   
               
               
                 46 
                 6.06 
                   4 ± 2 
                   5 ± 3 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 B 
               
               
                   
               
            
           
         
       
     
     Example 4 
     Synthesis of 6-(2′-hexyldecanoyloxy)hexan-1-al 
     A solution of hexan-1,6-diol (27.6 g) in methylene chloride (475 mL) was treated with 2-hexyldecanoic acid (19.8 g), DCC (18.2 g) and DMAP (11.3 g). The solution was stirred for three days. The reaction mixture was filtered and hexane (500 mL) added to the filtrate. The mixture was stirred and the precipitates allowed to settle out. The supernatant was decanted and washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed, yielding 30 g of crude product. 
     The crude product dissolved in methylene chloride (200 mL) and treated with pyridinium chlorochromate (15 g) for two hours. Diethyl ether (600 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel plug and the solvent removed. The residue was passed down a silica gel column (80 g) using hexane, followed by methylene chloride, as the eluent. 6-(2′-hexyldecanoyloxy)hexan-1-al (24 g) was obtained as a colorless oil. 
     Example 5 
     Synthesis of 4-(2′-hexyldecanoyloxy)butan-1-al 
     A solution of butan-1,4-diol (12.5 g) in methylene chloride (200 mL) was treated with 2-hexyldecanoic acid (9.2 g), DCC (8.8 g) and DMAP (4.9 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was dissolved in methylene chloride and washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. 
     The crude product was dissolved in methylene chloride (150 mL) and treated with pyridinium chlorochromate (6 g) for one hour. Diethyl ether (450 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 4-(2′-hexyldecanoyloxy)butan-1-al (11 g) was obtained as a colorless oil. 
     Example 6 
     Synthesis of Compound 1 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (3.0 g), acetic acid (0.21 g) and ethanolamine (0.14 g) in methylene chloride (50 mL) was treated with sodium triacetoxyborohydride (1.4 g) overnight. The solution was washed with dilute aqueous sodium hydroxide solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 1 as a colorless oil (0.63 g). 
     Example 7 
     Synthesis of Compound 2 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (3.0 g), acetic acid (0.33 g) and 3-aminopropan-1-ol (0.17 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for one hour. The solution was washed with dilute aqueous sodium hydroxide solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 2 as a colorless oil (1.1 g). 
     Example 8 
     Synthesis of Compound 3 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.33 g) and 4-aminobutan-1-ol (0.23 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for two hours. The solution was washed with aqueous sodium bicarbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 3 as a colorless oil (0.4 g). 
     Example 9 
     Synthesis of Compound 4 
     A solution of 4-(2′-hexyldecanoyloxy)butan-1-al (2.4 g), acetic acid (0.30 g) and 4-aminobutan-1-ol (0.22 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for two hours. The solution was washed with dilute aqueous sodium hydroxide solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient. Partially purified fractions were passed down a second column using an acetic acid/methanol/methylene chloride (2-0/0-10/98-90%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 4 as a colorless oil (0.9 g) 
     Example 10 
     Synthesis of Compound 5 
     A solution of 4-(2′-hexyldecanoyloxy)butan-1-al (2.4 g), acetic acid (0.31 g) and 3-aminopropan-1-ol (0.17 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.4 g) for one hour. The solution was washed with aqueous sodium bicarbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient. Partially purified fractions were passed down a second column using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 5 as a colorless oil (0.57 g). 
     Example 11 
     Synthesis of Compound 6 
     A solution of 4-(2′-hexyldecanoyloxy)butan-1-al (2.4 g), acetic acid (0.30 g) and ethanolamine (0.14 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for two hours. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-10/100-90%) gradient. Partially purified fractions were passed down a second column using an acetic acid/methanol/methylene chloride (2-0/0-9/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 6 as a colorless oil (0.2 g). 
     Example 12 
     Synthesis of Compound 7 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.14 g) and 5-aminopentan-1-ol (0.24 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for two hours. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 7 as a colorless oil (0.5 g) 
     Example 13 
     Synthesis of Compound 8 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.17 g) and 6-aminohexan-1-ol (0.26 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) for two hours. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 8 as a colorless oil (0.5 g) 
     Example 14 
     Synthesis of Compound 9 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g) and trans-2-aminocyclohexanol hydrochloride (0.35 g) in methylene chloride (10 mL)/tetrahydrofuran (10 mL) was treated with sodium triacetoxyborohydride (1.3 g) for 1.5 hours. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a methanol/methylene chloride (0-8/100-92%) gradient, yielding compound 9 as a colorless oil (0.6 g). 
     Example 15 
     Synthesis of Compound 10 
     To a solution of 2-aminoethanol (106 mg, 1.75 mmol) in anhy THF (15 mL), 2-octyldodecyl 6-bromohexanoate (2 eq, 1.66 g, 3.5 mmol), potassium carbonate (2 eq, 3.5 mmol, 477 mg,) and cesium carbonate (0.3 eq, 0.525 mmol, 171 mg,) were added and was heated at 63 C (oil bath) for 16 h. Trace of tetrabutylammonium iodide was added to the mixture and the mixture was heated to reflux for another 4 days. The solvent was evaporated under reduced pressure and the residue was taken in a mixture of hexanes and ethyl acetate (ca 9:1) and washed with water and brine. The organic layer was separated and dried over anhydrous sodium sulphate, filtered and evaporated under reduced to obtain an oil (1.6 g). The residue (1.6 g) was purified by column chromatography on silica gel (MeOH in chloroform, 0 to 4%). This gave compound 10 as colorless oil (700 mg, 0.82 mmol, 47%). 
     Example 16 
     Synthesis of Compound 11 
     To a solution of 2-aminoethanol (116 mg, 1.9 mmol, 115 uL) in 15 ml of anhydrous THF, 2-hexyldecyl 6-bromohexanoate (1.9 eq, 1.52 g, 3.62 mmol), potassium carbonate (1.9 eq, 3.62 mmol, 500 mg), cesium carbonate (0.3 eq, 0.57 mmol, 186 mg,) and sodium iodide (10 mg) were added and was heated to reflux for 6 days under Ar. The solvent was evaporated under reduced pressure and the residue was taken up in hexanes and washed with water and brine. The organic layer was separated, dried over anhydrous sodium sulphate, filtered and evaporated under reduced pressure to obtain a colorless oil. The crude product was purified by flash column chromatography on silica gel (MeOH in chloroform, 0 to 4%) to yield compound 11 as a colorless oil (936 mg, 1.27 mmol, 70%). 
     Example 17 
     Synthesis of Compound 12 
     Compound 12 was prepared in a manner analogous to the procedure for Compound 11 to yield 538 mg of colorless oil, 0.86 mmol, 57%. 
     Example 18 
     Synthesis of Compound 13 
     To a solution of 2-aminoethanol (171 mg, 2.81 mmol, 169 uL) in anhy THF (30 mL), 2-octyldodecyl 4-bromobutyrate (1.9 eq, 2.386 g, 5.33 mmol), potassium carbonate (1.9 eq, 5.33 mmol, 736 mg), cesium carbonate (0.3 eq, 0.84 mmol, 275 mg) and sodium iodide (10 mg) were added and was heated to reflux for 16 h under Ar. TLC (Hexane/Ethyl acetate=9:1, CHCl 3 /MeOH=19:1) showed that significant amount of 2-octyl-1-dodecanol was produced. The mixture was cooled and filtered. The filtrate was concentrated and the residue was dissolved in 2-octyl-1-dodecanol (2.1 g). A few beads of 4 A molecular sieves and N,N-diisopropylethylamine (1.9 equiv., 5.33 mmol, 683 mg, 0.92 mL) was added. The mixture was sealed and heated at 62 C for another 4 days. The reaction mixture was cooled. Hexane was added. The hexane solution was decanted and concentrated to dryness. The residue was purified by by column chromatography on silica gel (MeOH in chloroform, 0 to 4%) to yield compound 13 as a colorless oil (282 mg, 0.35 mmol, 13%). 
     Example 19 
     Synthesis of Compound 14 
     To a solution of heptadecan-9-yl 6-bromohexanoate (2 eq, 1.13 g, 2.61 mmol) in anhy THF (15 mL), was added 2-aminoethanol (1 eq. 1.31 mmol, 79.7 mg), potassium carbonate (2 eq, 2.61 mmol, 361 mg,), cesium carbonate (0.3 eq, 0.39 mmol, 128 mg) and sodium iodide (6 mg). The mixture was heated to reflux for 7 days under Ar. The solvent was evaporated under reduced pressure and the residue was taken in hexanes/ethyl acetate (ca 10%) and washed with water and brine. The organic layer was separated and dried over anhydrous sodium sulphate, filtered and evaporated under reduced to obtain an oil (1 g). The residue (1 g) was purified by gravity column chromatography on silica gel (MeOH in DCM, 0 to 4%). This gave compound 14 as a colorless oil (757 mg 0.99 mmol, 76%). 
     Example 20 
     Synthesis of Compound 15 
     To a solution of 2-hexyldecyl 5-bromopentanoate (2 eq, 1.22 g, 3 mmol) in 15 ml of anhy THF (opened for 2 month), was added 4-amino-1-butanol (1 eq. 1.5 mmol, 0.134 mg, 139 uL), potassium carbonate (2 eq, 3 mmol, 415 mg), cesium carbonate (0.3 eq, 0.45 mmol, 146 mg) and sodium iodide (6 mg). The mixture was heated to reflux for 6 days under Ar. The solvent was evaporated under reduced pressure and the residue was taken up in a mixture of hexanes and ethyl acetate (ca 10%) and washed with water and brine. The organic layer was separated and dried over anhydrous sodium sulphate, filtered and evaporated under reduced to obtain an oil (1.12 g). The residue was purified by column chromatography on silica gel (MeOH in chloroform, 0 to 5%). This gave compound 15 as colorless oil (487 mg, 0.66 mmol, 44%).  1 HNMR (400 MHz, CDCl3) δ: 5.99 (s, 1H), 3.98 (d, 5.8 Hz, 4H), 3.56 (t-like, 4.8 Hz, 2H), 2.48-2.41 (m, 6H), 2.33 (t, 7.4 Hz, 4H), 1.70-1.57 (m, 10H), 1.55-1.47 (m, 4H), 1.35-1.21 (48H), 0.89 (t-like, 6.8 Hz, 12H). 
     Example 21 
     Synthesis of Compound 16 
     To a solution of 3-amino-1-propanol (0.37 mmol, 28 mg) in anhydrous acetonitrile (15 mL), 2-hexyldecyl 6-bromohexanoate (1.9 eq, 294 mg, 0.7 mmol), N,N-diisopropylethylamine (2 equiv., 0.74 mmol, 96 m) and sodium iodide (5 mg) were added and the mixture (two layers) was heated to for 3 days in a pressure flask at 59° C. (oil bath). The mixture was concentrated and the residue was taken up in a mixture of hexane and ethyl acetate (ca 5:1, 100 mL), washed with water, brine, dried over sodium sulfate, filtered and concentrated. A slightly yellow oil was obtained (ca 300 mg). The crude product (300 mg) was purified by flash column chromatography on silica gel (MeOH in chloroform, 0 to 4.4%). This gave compound 16 as colorless oil (95 mg, 0.13 mmol, 36%).  1 HNMR (400 MHz, CDCl3) δ: 5.61-5.44 (br. s, 1H), 3.97 (d, 5.8 Hz, 4H), 3.80 (t-like, 5.1 Hz, 2H), 2.63 (t-like, 5.6 Hz, 2H), 2.43-2.39 (m, 4H), 2.32 (t, 7.5 Hz, 4H), 1.70-1.59 (m, 8H), 1.55-1.45 (m, 4H), 1.36-1.21 (52H), 0.89 (t-like, 6.8 Hz, 12H). 
     Example 22 
     Synthesis of Compound 17 
     To a solution of 2-hexyldecyl 6-bromohexanoate (2 eq, 1.32 g, 3.14 mmol) in 15 ml of anhydrous THF, were added 4-amino-1-butanol (1 eq. 1.57 mmol, 140 mg, 145 uL), potassium carbonate (2 eq, 3.14 mmol, 434 mg), cesium carbonate (0.3 eq, 0.47 mmol, 153 mg) and sodium iodide (6 mg). The mixture was heated in a pressure round-bottom flask under Ar at 75° C. (oil bath) for 6 days. The reaction mixture was cooled and concentrated. The residue was taken up in a mixture of hexane and ethyl acetate (ca 9:1), washed with water, brine, dried over sodium sulfate, filtered and concentrated to dryness (1.28 g colorless oil). The crude product was purified by flash column chromatography on silica gel (MeOH in chloroform, 0 to 5%). This gave compound 17 as colorless oil (581 mg, 0.76 mmol, 48%).  1 HNMR (400 MHz, CDCl3) δ: 6.43-6.17 (br. s, 1H), 3.97 (d, 5.8 Hz, 4H), 3.55 (t-like, 4.7 Hz, 2H), 2.46-2.40 (m, 6H), 2.31 (t, 7.5 Hz, 4H), 1.70-1.59 (m, 10H), 1.55-1.45 (m, 4H), 1.36-1.21 (52H), 0.89 (t-like, 6.7 Hz, 12H). 
     Example 23 
     Synthesis of Compound 20 
     To a solution of 2-hexyldecyl 8-bromooctanoate (2 eq, 3.09 g, 6.9 mmol) in 30 ml of anhydrous THF, were added 4-amino-1-butanol (1 eq. 3.45 mmol, 308 mg), potassium carbonate (2 eq, 6.9 mmol, 954 mg), cesium carbonate (0.3 eq, 1.04 mmol, 337 mg) and sodium iodide (10 mg). The mixture in a pressure round-bottom flask under Ar was heated at 64-70° C. (oil bath) for 6 days. The mixture was cooled and concentrated. The residue was taken up in a mixture of hexane and ethyl acetate (9:1), washed with water, brine, dried over sodium sulfate, filtered and concentrated to dryness (colorless oil). The crude product was purified flash dry column chromatography on silica gel (MeOH in chloroform, 0 to 4.2%). This gave compound 20 as a colorless oil (1.28 g, 1.56 mmol, 45%).  1 HNMR (400 MHz, CDCl3) δ: 6.64-6.45 (br. s, 1H), 3.97 (d, 5.8 Hz, 4H), 3.62-3.51 (br. 2H), 3.07-2.34 (br. 6H), 2.30 (t, 7.5 Hz, 4H), 1.71-1.40 (m, 14H), 1.39-1.19 (m, 60H), 0.89 (t-like, 6.8 Hz, 12H). 
     Example 24 
     Synthesis of 9-(2′-ethylhexanoyloxy)nonan-1-al 
     A solution of nonan-1,9-diol (10.1 g) in methylene chloride (150 mL) was treated with 2-ethylhexanoic acid (9.0 g), DCC (14.3 g) and DMAP (9.1 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using a methanol/methylene chloride (0-8%) gradient, to produce 9-(2′-ethylhexanoyloxy)nonan-1-ol (7.2 g) as an oil. 
     The 9-(2′-ethylhexanoyloxy)nonan-1-ol was dissolved in methylene chloride (100 mL) and treated with pyridinium chlorochromate (7.5 g) for one hour. Hexane (400 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 9-(2′-ethylhexanoyloxy)nonan-1-al (6 g) was obtained as a colorless oil. 
     Example 25 
     Synthesis of 9-(2′-butyloctanoyloxy)nonan-1-al 
     A solution of nonan-1,9-diol (12.0 g) in methylene chloride (150 mL) was treated with 2-butyloctanoic acid (5.0 g), DCC (7.7 g) and DMAP (4.5 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using a methanol/methylene chloride (0-4%) gradient, to produce 9-(2′-butyloctanoyloxy)nonan-1-ol (6 g) as an oil. 
     The 9-(2′-butyloctanoyloxy)nonan-1-ol was dissolved in methylene chloride (100 mL) and treated with pyridinium chlorochromate (3.8 g) overnight. Hexane (300 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 9-(2′-butyloctanoyloxy)nonan-1-al (3.1 g) was obtained as a colorless oil. 
     Example 26 
     Synthesis of 6-(2′-butyloctanoyloxy)hexan-1-al 
     A solution of hexan-1,6-diol (9.4 g) in methylene chloride (150 mL) was treated with 2-butyloctanoic acid (5.0 g), DCC (7.6 g) and DMAP (4.8 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using a methanol/methylene chloride (0-4%) gradient, to produce 6-(2′-butyloctanoyloxy) hexan-1-ol (4.5 g) as an oil. 
     The 6-(2′-butyloctanoyloxy)hexan-1-ol was dissolved in methylene chloride (100 mL) and treated with pyridinium chlorochromate (4.8 g) for two hours. Hexane (300 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 6-(2′-butyloctanoyloxy)hexan-1-al (3.9 g) was obtained as a colorless oil. 
     Example 27 
     Synthesis of 6-(2′-octyldodecanoyloxy)hexan-1-al 
     A solution of hexan-1,6-diol (11.5 g) in methylene chloride (150 mL)/THF (20 mL) was treated with 2-octyldodecanoic acid (9.9 g), DCC (7.5 g) and DMAP (4.7 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using a methanol/methylene chloride (0-4%) gradient, to produce 6-(2′-octyldodecanoyloxy)hexan-1-ol (7.4 g) as an oil. 
     The 6-(2′-octyldodecanoyloxy)hexan-1-ol was dissolved in methylene chloride (100 mL) and treated with pyridinium chlorochromate (4.0 g) for two hours. Diethyl ether (300 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 6-(2′-octyldodecanoyloxy)hexan-1-al (5.3 g) was obtained as a colorless oil. 
     Example 28 
     Synthesis of 6-(2′-decyltetradecanoyloxy)hexan-1-al 
     A solution of hexan-1,6-diol (9.6 g) in methylene chloride (150 mL) was treated with 2-decyltetradecanoic acid (6.1 g), DCC (4.9 g) and DMAP (3.1 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using a methanol/methylene chloride (0-4%) gradient, to produce 6-(2′-decyltetradecanoyloxy)hexan-1-ol (4.6 g). 
     The 6-(2′-decyltetradecanoyloxy)hexan-1-ol was dissolved in methylene chloride (100 mL) and treated with pyridinium chlorochromate (3.2 g) for two hours. Hexane (300 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant product dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 6-(2′-decyltetradecanoyloxy) hexan-1-al (4.2 g). 
     Example 29 
     Synthesis of 12-(2′-hexyldecanoyloxy)dodecan-1-al 
     A solution of dodecan-1,12-diol (25.0 g) in methylene chloride (300 mL)/THF (100 mL) was treated with 2-hexyldecanoic acid (10.6 g), DCC (10.2 g) and DMAP (7.5 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with water. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using hexane followed by methylene chloride, to produce 12-(2′-hexyldecanoyloxy)dodecan-1-ol (7.9 g) as an oil. 
     The 12-(2′-hexyldecanoyloxy)dodecan-1-ol was dissolved in methylene chloride (150 mL) and treated with pyridinium chlorochromate (4.0 g) for three hours. Hexane (300 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 12-(2′-hexyldecanoyloxy)dodecan-1-al (3.9 g) was obtained as a colorless oil. 
     Example 30 
     Synthesis of 9-(2′-hexyldecanoyloxy)nonan-1-al 
     A solution of nonan-1,9-diol (46.8 g) in methylene chloride (600 mL) was treated with 2-hexyldecanoic acid (25.0 g), DCC (22.0 g) and DMAP (15.0 g). The solution was stirred overnight. The reaction mixture was filtered and the solvent removed. The residue was suspended in hexane and filtered. The filtrate was washed with dilute hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate, filtered through a silica gel bed, and the solvent removed. The crude product was passed down a silica gel column using hexane followed by a methanol/methylene chloride (0-8%) gradient, to produce 9-(2′-hexyldecanoyloxy)nonan-1-ol (22 g) as an oil. 
     9-(2′-Hexyldecanoyloxy)nonan-1-ol (5.0 g) was dissolved in methylene chloride (50 mL) and treated with pyridinium chlorochromate (2.7 g) for one hour. Hexane (200 mL) was added and the supernatant filtered through a silica gel bed. The solvent was removed from the filtrate and resultant oil dissolved in hexane. The suspension was filtered through a silica gel bed and the solvent removed, yielding 9-(2′-hexyldecanoyloxy)nonan-1-al (3.6 g) was obtained as a colorless oil. 
     Example 31 
     Synthesis of Compound 22 
     A solution of 9-(2′-hexyldecanoyloxy)nonan-1-al (2.2 g), acetic acid (0.15 g) and 4-aminobutan-1-ol (0.20 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.30 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 22 as a colorless oil (0.93 g). 
     Example 32 
     Synthesis of Compound 23 
     A solution of 12-(2′-hexyldecanoyloxy)dodecan-1-al (2.0 g), acetic acid (0.09 g) and 4-aminobutan-1-ol (0.14 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (0.71 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 23 as a colorless oil (1.0 g). 
     Example 33 
     Synthesis of Compound 24 
     A solution of 9-(2′-ethylhexanoyloxy)nonan-1-al (3.0 g), acetic acid (0.11 g) and 4-aminobutan-1-ol (0.17 g) in methylene chloride (50 mL) was treated with sodium triacetoxyborohydride (0.89 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-10/98-90%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 24 as a colorless oil (0.69 g). 
     Example 34 
     Synthesis of Compound 25 
     A solution of 9-(2′-butyloctanoyloxy)nonan-1-al (2.6 g), acetic acid (0.20 g) and 4-aminobutan-1-ol (0.26 g) in methylene chloride (50 mL) was treated with sodium triacetoxyborohydride (1.42 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 25 as a colorless oil (0.82 g). 
     Example 35 
     Synthesis of Compound 26 
     A solution of 6-(2′-octyldodecanoyloxy)hexan-1-al (2.7 g), acetic acid (0.20 g) and 4-aminobutan-1-ol (0.20 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.30 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 26 as a colorless oil (0.21 g). 
     Example 36 
     Synthesis of Compound 27 
     A solution of 6-(2′-decyltetradecanoyloxy)hexan-1-al (2.1 g), acetic acid (0.11 g) and 4-aminobutan-1-ol (0.13 g) in methylene chloride (30 mL) was treated with sodium triacetoxyborohydride (0.70 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 27 as a colorless oil (0.90 g). 
     Example 37 
     Synthesis of Compound 28 
     A solution of 6-(2′-butyloctanoyloxy)hexan-1-al (2.0 g), acetic acid (0.13 g) and 3-aminopropan-1-ol (0.13 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.0 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 28 as a colorless oil (0.77 g). 
     Example 38 
     Synthesis of Compound 30 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.15 g) and 3-aminopropan-1,2-diol (0.21 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.76 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 30 as a colorless oil (0.60 g). 
     Example 39 
     Synthesis of Compound 31 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.15 g) and 2-aminobutan-1-ol (0.20 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.1 g) for two hours. The solution was washed with dilute aqueous sodium hydroxide solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-4/98-96%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 31 as a colorless oil (0.31 g). 
     Example 40 
     Synthesis of Compound 37 
     A solution of 6-(2′-octyldodecanoyloxy)hexan-1-al (2.7 g), acetic acid (0.20 g) and 3-aminopropan-1-ol (0.17 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.3 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-12/98-88%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 37 as a colorless oil (0.22 g). 
     Example 41 
     Synthesis of Compound 38 
     A solution of 12-(2′-hexyldecanoyloxy)dodecan-1-al (1.8 g), acetic acid (0.08 g) and 3-aminopropan-1-ol (0.11 g) in methylene chloride (10 mL) was treated with sodium triacetoxyborohydride (0.64 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-10/98-90%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 38 as a colorless oil (0.83 g). 
     Example 42 
     Synthesis of Compound 39 
     A mixture (two layers) of ethyl 4-aminobutyrate hydrochloride salt (1.28 mmol, 214 mg), 2-hexyldecyl 6-bromohexanoate (1.9 eq, 2.43 mmol, 1.02 g), N,N-diisopropylethylamine (3.5 equiv., 4.48 mmol, 579 mg) and sodium iodide (5 mg) in anhydrous acetonitrile (15 mL) was heated at 60° C. for 2 days in a pressure flask. The mixture was cooled and concentrated. The residue was taken up in a mixture of hexane and ethyl acetate (ca 5:1, 100 mL), washed with water, brine, dried over sodium sulfate, filtered and concentrated. A brown oil was obtained (ca 1.04 g). The crude product was purified by flash column chromatography on silica gel (MeOH in DCM, 0 to 3.5%). This gave compound 39 as a colorless oil (334 mg, 0.41 mmol, 43%).  1 HNMR (400 MHz, CDCl3) δ: 4.13 (q, 7.1 Hz, 2H), 3.97 (d, 5.8 Hz, 4H), 2.43-2.34 (m, 6H), 2.33-2.28 (m, 6H), 1.73 (quintet, 7.3 Hz, 2H), 1.68-1.58 (m, 6H), 1.47-1.37 (m, 4H), 1.36-1.20 (54H), 0.89 (t-like, 6.8 Hz, 12H). 
     Example 43 
     Synthesis of Compound 40 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.15 g) and 1-aminobutan-2-ol (0.10 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.8 g) for two hours. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 40 as a colorless oil (0.85 g). 
     Example 44 
     Synthesis of Compound 41 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (2.4 g), acetic acid (0.19 g) and 3-methoxypropylamine (0.21 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.8 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 41 as a colorless oil (0.77 g). 
     Example 45 
     Synthesis of Compound 42 
     A solution of 6-(2′-butyloctanoyloxy)hexan-1-al (2.0 g), acetic acid (0.13 g) and 4-aminobutan-1-ol (0.20 g) in methylene chloride (20 mL) was treated with sodium triacetoxyborohydride (1.03 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 42 as a colorless oil (0.54 g). 
     Example 46 
     Synthesis of Compound 43 
     A solution of 9-(2′-ethylhexanoyloxy)nonan-1-al (3.0 g), acetic acid (0.11 g) and 3-aminopropan-1-ol (0.14 g) in methylene chloride (50 mL) was treated with sodium triacetoxyborohydride (0.91 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-6/98-94%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 43 as a colorless oil (1.01 g). 
     Example 47 
     Synthesis of Compound 44 
     A solution of 6-(2′-decyltetradecanoyloxy)hexan-1-al (2.1 g), acetic acid (0.11 g) and 3-aminopropan-1-ol (0.11 g) in methylene chloride (30 mL) was treated with sodium triacetoxyborohydride (0.71 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-96%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 44 as a colorless oil (1.07 g). 
     Example 48 
     Synthesis of Compound 45 
     A solution of 9-(2′-butyloctanoyloxy)nonan-1-al (2.6 g), acetic acid (0.17 g) and 3-aminopropan-1-ol (0.21 g) in methylene chloride (50 mL) was treated with sodium triacetoxyborohydride (1.34 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-96%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 45 as a colorless oil (1.1 g). 
     Example 49 
     Synthesis of Compound 46 
     To a solution of 2-aminoethanol (96.5 mg, 1.58 mmol, 95.4 uL, MW 61.08, d 1.012) in 15 ml of 2-propanol, 2-hexyldecyl 8-bromooctanoate (1.8 eq, 1.27 g, 2.84 mmol), potassium carbonate (1.9 eq, 3 mmol, 414 mg), cesium carbonate (0.3 eq, 0.47 mmol, 154 mg) and sodium iodide (10 mg) were added and was heated for 3 days (oil bath 60° C.). The mixture was concentrated and the residue was taken up in THF (10 mL). To this mixture more aminoethanol (80 mg, 1.3 mmol) was added. Heating was continued at 70° C. for another 3 days. After total 6 days, the reaction mixture was cooled and filtered and concentrated. The residue was purified flash dry column chromatography on silica gel (methanol in chloroform, 1 to 4.2%). This gave compound 46 as a colorless oil (334 mg, 0.42 mmol, 30%).  1 HNMR (400 MHz, CDCl3) δ: 4.09-4.06 (m, 2H), 3.97 (d, 5.8 Hz, 4H), 3.39-3.36 (m, 2H), 3.31-3.23 (m, 4H), 2.31 (t, 7.5 Hz, 4H), 1.88-1.56 (m, 12H), 1.43-1.19 (59H), 0.89 (t-like, 6.8 Hz, 12H). 
     Example 50 
     Synthesis of Compound 47 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (3.0 g), acetic acid (0.20 g) and 3-aminopropionitrile (0.21 g) in methylene chloride (30 mL) was treated with sodium triacetoxyborohydride (1.3 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-6/98-94%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 47 as a colorless oil (0.29 g). 
     Example 51 
     Synthesis of Compound 48 
     A solution of 6-(2′-hexyldecanoyloxy)hexan-1-al (3.0 g) and ethyl 4-aminobutyrate hydrochloride (0.46 g) in methylene chloride (30 mL) was treated with sodium triacetoxyborohydride (1.4 g) overnight. The solution was washed with aqueous sodium hydrogen carbonate solution. The organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent removed. The residue was passed down a silica gel column using a using an acetic acid/methanol/methylene chloride (2-0/0-8/98-92%) gradient. Pure fractions were washed with aqueous sodium bicarbonate solution, yielding compound 48 as a colorless oil (0.80 g). 
     Example 52 
     Synthesis of Compound 49 
     To a solution of 2-butyloctyl 8-bromooctanoate (2 eq, 1.877 g, 4.8 mmol) in 20 ml of anhydrous THF, were added 4-amino-1-butanol (1 eq. 2.4 mmol, 214 mg, 221 ul), potassium carbonate (2 eq, 4.8 mmol, 664 mg), cesium carbonate (0.3 eq, 0.72 mmol, 234 mg) and sodium iodide (ca 5 mg). The mixture in a pressure round-bottom flask was heated (oil bath, 80° C.) for 6 days. The reaction mixture was cooled and concentrated. The residue was taken up in a mixture of hexane and ethyl acetate (ca 5:1), washed with water, brine, dried over sodium sulfate, filtered and concentrated. The residue was purified flash column chromatography on silica gel (methanol in chloroform, 1 to 4%). This gave compound 49 as a colorless oil (857 mg, 1.21 mmol, 50%).  1 HNMR (400 MHz, CDCl3) δ: 6.55 (br. s, 1H), 3.97 (d, 5.8 Hz, 4H), 3.55 (not well resolved triplet, 2H), 2.45-2.40 (m. 6H), 2.30 (t, 7.5 Hz, 4H), 1.71-1.58 (m, 10H), 1.51-1.42 (m, 4H), 1.39-1.19 (m, 44H), 0.93-0.87 (m, 12H). 
     The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.