bluuebunny/crossref_metadata_2025 huggingface dataset:
HIV-1 integrase inhibitors that block HIV-1 replication in infected cells. Planning synthetic derivatives from natural products
Authors: Di Santo Roberto , Costi Roberta , Artico Marino , Tramontano E. , Colla P. La , Pani A.
Published: October 2007

Combination therapy using reverse transcriptase (RT) and protease (PR) inhibitors is currently the best clinical approach in combatting acquired immunodeficiency syndrome (AIDS), caused by infection from the human immunodeficiency virus type 1 (HIV-1). However, the emergence of resistant strains calls urgently for research on inhibitors of further viral targets such as integrase (IN), the enzyme that catalyzes the integration of the proviral DNA into the host chromosomes. Recently, we started studies on new IN inhibitors as analogs of natural products, characterized by one or two 3,4-dihydroxycinnamoyl moieties, which were proven to be IN inhibitors in vitro. Then, we designed and synthesized a number of derivatives sharing 3,4 dihydroxycinnamoyl groups, obtaining potent IN inhibitors active at submicromolar concentrations. Unfortunately, these derivatives lacked antiretroviral activity, probably owing to their high cytotoxicity. So we designed a number of 3,4,5-trihydroxycinnamoyl derivatives as less-cytotoxic IN inhibitors, which were proven to be antiretrovirals in cell-based assays. Finally, we designed and synthesized a number of aryldiketohexenoic acids, strictly related to the aryldiketo acid series recently reported by Merck Company, which were shown to be potent antiretroviral agents endowed with anti-IN activities either in 3' processing or in strand transfer steps.
New and old challenges in total synthesis. From concept to practice
Authors: Hanessian S. , Margarita Roberto , Hall Adrian , Johnstone Shawn , Tremblay M. , Parlanti L.
Published: October 2007

The total synthesis of dysinosin A, a novel member of the aeruginosin group of marine natural products is discussed. The stereocontrolled synthesis also confirms the proposed structure and absolute stereochemistry of the natural product.
Chemoenzymatic methods for the enantioselective preparation of sesquiterpenoid natural products from aromatic precursors
Authors: Banwell M. G. , Edwards A. J. , Harfoot G. J. , Jolliffe K. A. , McLeod M. D. , McRae K. J. , Stewart S. G. , Vögtle M.
Published: October 2007

The enantiomerically pure cis-1,2-dihydrocatechols 2, which are generated by enzymatic dihydroxylation of the corresponding aromatic, engage in regio- and stereo-controlled Diels-Alder cycloaddition reactions to give a range of synthetically useful bicyclo[2.2.2]octenes. Certain examples of the latter type of compound have been used as starting materials in the synthesis of the sesquiterpenoids (−)-patchoulenone and (−)-hirsutene.
Total synthesis of (­)-clavukerin A
Authors: Grimm E. L. , Methot J.-L. , Shamji M.
Published: October 2007

(−)-Clavukerin A has been synthesized via intramolecular Julia coupling and intramolecular sulfone ester cyclization starting from (+)-limonene oxide.
Progress in fumagillin synthesis
Authors: Picoul W. , Bedel O. , Haudrechy A. , Langlois Y.
Published: October 2007

After a brief account of the syntheses previously described in literature, several approaches of the antiangiogenic sesquiterpene fumagillin are described. Particularly, a Claisen–Ireland ring-closing metathesis strategy allowed the stereoselective preparation of several advanced intermediates in the fumagillin synthesis.
Total syntheses of 11-deoxytetrodotoxin and 8,11-dideoxytetrodotoxin
Authors: Nishikawa T. , Urabe D. , Yoshida K. , Iwabuchi Tomoko , Asai Masanori , Isobe M.
Published: October 2007

11-Deoxytetrodotoxin and 8,11-dideoxytetrodotoxin were synthesized from the same intermediate in the enantiomerically pure form.
Biomimetic approach toward the stereoselective synthesis of acetogenins
Authors: Orru R. V. A. , Groenendaal Bas , van Heyst J. , Hunting Mark , Wesseling C. , Schmitz R. F. , Mayer S. F. , Faber K.
Published: October 2007

Acetogenins isolated from the Annonaceae family of tropical trees have drawn considerable attention owing to their broad spectrum of biological activities. They are structurally characterized by the presence of one to three tetrahydrofuran rings in the center of a long (partly hydroxylated) hydrocarbon chain that ends in a (functionalized) butenolide moiety. Here we describe some of our results toward the first asymmetric total synthesis of cis-gigantrionenin, a principal acetogenin. In this approach, an enzyme-catalyzed epoxide hydrolysis and an enzyme-triggered double cyclization are crucial and give stereoselective access to essential chiral building blocks.
Microencapsulated methylrhenium trioxide (MTO)/H2O2 systems for the oxidation of cardanol derivatives
Authors: Saladino R. , Mincione E. , Attanasi O. A. , Filippone Paolino
Published: October 2007

A convenient and efficient application of microencapsulated/methylrhenium trioxide (MTO) and MTO/pyridine systems for the selective oxidation of cardanol derivatives is reported. Environmentally friendly and low-cost H2O2 was used as the oxygen atom donor. The catalysts were stable systems for at least five recycling experiments. In the oxidation of C2 alkyl-substituted cardanol derivatives, high conversion and yields of the corresponding para-benzoquinones were obtained. By contrast, in the absence of the C2 substituent, an unprecedented oxidative degradation to di-γ-lactone derivative was observed.
Enantioselective synthesis and biological evaluation of a-hydroxylated lactone lignans
Authors: Sefkow M. , Raschke M. , Steiner C.
Published: October 2007

A short and efficient synthesis of enantiomerically pure α-hydroxylated lactone lignans starting from commercially available diisopropyl malate is presented. Stereoselective alkylation with various benzyl bromides and saponification yielded the corresponding succinic acids. Acetalization afforded the dioxolanones, which were stereoselectively alkylated. Reduction (and deprotection, where required) yielded the lactone lignans in up to 30 % overall yield. The inhibition of the proliferation of HT29 colon cancer cells was investigated. One lignane, bis-2,4,6 trimethylbenzyllactone lignan, was active (IC50 = 35 μM), whereas all other tested lignans were inactive within the investigated concentration range.
Stereocontrolled construction of conformationally constrained and rigid bis(a-amino acid) derivatives
Authors: Undheim K. , Efskind Jon , Hoven G. B.
Published: October 2007

Cystine is regarded as a four-atom bridged bis(α-amino acid). The bridge between the two glycine moieties in cystine has been replaced with all-carbon C4-bridges between the α-carbon of the glycines. The products are dicarba analogs of cystine. Conformational constraints have been conferred on these molecules by insertion of cis- and trans- double bonds in the bridge, by alkylidene substituents, by insertion of a triple bond, by insertion of aromatic or heteroaromatic rings, or otherwise by ring formation. Particularly rigidified dicarba analogs of cystine have been prepared where the α-amino acid carbon is quaternary and part of tricyclic ring structures. Ru(II)-catalyzed ring-closing metathesis (RCM) reactions have been widely used in the preparation of cyclic amino acids. Conformational constraints in acyclic structures result from substitution by simple alkyl, alkenyl, or alkynyl groups at the α-amino acid carbon in the formation of α-quaternary amino acid derivatives.
Stereochemical analysis of natural products. Approaches relying on the combination of NMR spectroscopy and computational methods
Authors: Riccio R. , Bifulco Giuseppe , Cimino Paola , Bassarello Carla , Gomez-Paloma Luigi
Published: October 2007

The stereochemical study of flexible stereogenic carbon chains, such as those of many novel natural products, is a particularly challenging task. Recent applications of our group on the so-called "J-based approach", a methodology relying on a detailed analysis of homonuclear (H-H) and heteronuclear (C-H) 2,3
J couplings, include the study of the sphinxolide family of antitumor macrolides, a group of molecules characterized by a flexible macrocyclic framework bearing a number of oxygenated and methylated undetermined stereocenters, and of ascaulitoxin, a nitrogen-containing phytotoxin with herbicidal activity produced by a phytopathogenic fungus. An extension of the original procedure, relying on a Hartree-Fock (HF) ab initio calculation of conformational equilibrium and an estimate of the Boltzmann averaged 2,3
JHH and 2,3
JCH couplings, has been applied to the stereochemical study of sapinofuranone A, where the conformational equilibrium among existing rotamers had initially led to controversial results. 13C NMR chemical shifts are additional useful parameters in the study of complex organic molecules. Along these lines, we have lately proposed the use of Hartree–Fock gauge including atomic orbitals (GIAO) calculated 13C NMR chemical shift values as a supporting tool for the validation of the structure of new natural products and the determination of the relative stereochemistry of diastereomeric flexible compounds that are characterized by multiple conformer equilibria.
Exploitation of proteomics strategies in protein structure-function studies
Authors: Marino Gennaro , Pucci P. , Birolo Leila , Ruoppolo M.
Published: October 2007

Mass spectrometry plays a central role in structural proteomics, particularly in highly intensive structural genomics projects. This review paper reports some examples taken from recent work from the authors' laboratory and is aimed at showing that modern proteomics strategies are instrumental in the integration of structural genomic projects in fields such as: (i) protein–protein interactions, (ii) protein-DNA interactions, (iii) protein–ligand interactions, and (iv) protein-folding intermediates.
Prion protein allotype profiling by mass spectrometry
Authors: Schininà M. E. , Maras Bruno , Cardone Franco , Mancone Carmine , Principe S. , Di Bari M. A. , Parchi P. , Pocchiari M.
Published: October 2007

Prion diseases or transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative pathologies characterized by the formation in the central nervous system of the amyloid protein PrPSc, which derives from a cellular precursor called PrPc. Epidemiological and laboratory studies have shown that in species where the PrPc gene is polymorphic, the genotype composition is an important factor for the development of the disease. Identification of PrPSc allotypes accumulated in the brain during the disease proved valuable to investigate whether these polymorphisms are critical for the pathological conversion. These analyses are complicated by the heterogeneity and the insolubility of the prion amyloid extracted from affected brains, which have been obviated by extensive digestion of extracted fractions and analysis of peptide fragment composition. We have developed an optimized protocol of liquid chromatography/mass spectrometry (LC/MS) that can reliably map PrP peptides in digested fractions with a low PrPSc/contaminants ratio. This approach has been successfully applied to the analysis of amyloidogenesis in experimentally infected PrP-heterozygous laboratory animals.
Toxins from Adriatic blue mussels. A decade of studies
Authors: Ciminiello Patrizia , Dell'Aversano Carmela , Fattorusso Ernesto , Forino Martino , Magno Silvana
Published: October 2007

A research program was initiated in 1990 to carefully examine the toxin profiles in mussels from the northern Adriatic Sea. Since then, a number of polyether toxins have been isolated and characterized, some of which represent new additions to the diarrhetic shellfish poisoning (DSP) class of biotoxins and seem to be peculiar to the Adriatic Sea. During our investigation of toxic Adriatic mussels, we also isolated a new type of toxin, whose structure was elucidated by extensive use of 1D and 2D NMR techniques. Some of them could represent a further alarm for public health owing to their cytotoxic activity. The recent application of liquid chromatography/mass spectrometry (LC/MS) methods for detection of Adriatic marine biotoxins allowed us to hasten the analysis of toxic samples and to advance effective structural hypothesis even when full structure elucidation of new toxins by NMR spectroscopy is hampered by the limited amount of available material.
Bioactive macrolides and polyketides from marine dinoflagellates
Authors: Kobayashi J. , Shimbo K. , Kubota Takaaki , Tsuda M.
Published: October 2007

Absolute stereochemistry of amphidinolides G and H, potent cytotoxic 27- and 26-membered macrolides, respectively, isolated from a marine dinoflagellate Amphidinium sp., was determined by X-ray diffraction analysis, synthesis of a degradation product, and chemical interconversion. Six new macrolides, amphidinolides H2~H5, G2, G3, and W, have been isolated from a marine dinoflagellate Amphidinium sp. (strain Y-42), and the structures were elucidated by 2D NMR data and chemical means. The structure-activity relationship of amphidinolide H-type macrolides for cytotoxicity was examined. The biosynthetic origins of amphidinolides B, C, H, J, T1, and W were investigated on the basis of 13C NMR data of 13C-enriched samples obtained by feeding experiments with [1-13C], [2-13C], and [1,2-13C2] sodium acetates in cultures of the dinoflagellates. Five novel long-chain polyhydroxyl compounds, colopsinols A~E, were obtained from the Amphidinium sp. (strain Y-5).
Detection of pharmacologically active natural products using ecology. Selected examples from Indopacific marine invertebrates and sponge-derived fungi
Authors: Proksch P. , Ebel R. , Edrada R. A. , Schupp P. , Lin W. H. , Sudarsono  , Wray V. , Steube K.
Published: October 2007

This review article presents our group's recent research findings with regard to bioactive natural products from marine sponges and tunicates, as well as from sponge derived fungi. The organisms discussed originate in the Indopacific region, which has an exceptionally rich marine biodiversity. Major topics that are covered in our review include the chemical ecology of sponges, focusing on defense against fishes, as well as the isolation and identification of new bioactive constituents from sponges and tunicates. Sponge derived fungi are introduced as an emerging source for new bioactive metabolites, reflecting the currently growing interest in natural products from marine microorganisms.
Chemical studies on plant leaf movement controlled by a biological clock
Authors: Ueda M. , Sugimoto T. , Sawai Y. , Ohnuki T. , Yamamura Shosuke
Published: October 2007

Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning according to the circadian rhythm controlled by a biological clock. Extensive studies on nyctinastic plants led to the isolation of a variety of leaf-closing and -opening substances. And we found that the biological clock regulates the balance of concentration between leaf-opening and -closing substances in the plant body during the day.
Structural flexibility of hyaluronan oligomers as probed by molecular modelling
Authors: Tafi A. , Manetti Fabrizio , Corelli Federico , Alcaro Stefano , Botta Maurizio
Published: October 2007

In the last few years, molecular modeling studies have been published that are devoted to a better understanding of the structural flexibility of hyaluronan (HA). Further conformational investigations, however, are needed on this polysaccharide, such as the application of statistical methods to perform enhanced one-step conformational analyses of its subunits. Moreover, the adjustment of assisted model building and energy refinement (AMBER) force field could provide the appropriate computational tool to study the interactions of HA and its derivatives with proteins. The present paper reports a combined Monte Carlo (MC) and molecular dynamics (MD) approach applied to the conformational study of HA, using an adjusted version of AMBER force field and the generalized Born solvent-accessible surface area (GB/SA) continuum solvation model. The MC approach turned out to be extremely effective to outline a conformational survey of the disaccharides constituting HA. Complete sets of conformations of the monomers were provided for the first time, some of which had never been predicted. MD technique, integrating the MC results, correctly reproduced the unusual stiffness of HA and predicted the existence of a minor skew-boat conformation of the β-d-glucuronic moiety. The computational approach, as a whole, improved the comprehension of the dynamic behavior of HA and offered a clear causal explanation of the relative dynamics of the glycosidic linkages.
Functional genomics approach to the study of triterpene biosynthesis
Authors: Ebizuka Yutaka , Katsube Yuji , Tsutsumi T. , Kushiro Tetsuo , Shibuya M.
Published: October 2007

The Arabidopsis thaliana genome-sequencing project has identified the presence of 13 oxidosqualene cyclase homologs in this plant. In addition to the already identified clones, namely, CAS1 cycloartenol synthase, LUP1 lupeol synthase, and YUP8H12R.43 multifunctional triterpene synthase, two new cDNAs of the putative oxidosqualene cyclase genes, F1019.4 and T30F21.16, were obtained by polymerase chain reaction (PCR) and functionally expressed in yeast. Liquid chromatography/mass spectrometry (LC/MS) analysis led to the identification of some of their reaction products. Interestingly, except for CAS1 for sterol biosynthesis of primary metabolism, so-far-obtained all triterpene synthases of this plant are multifunctional, producing more than one cyclization product. A feeding experiment of 13C-labeled acetate with LUP1 lupeol synthase transformant demonstrated the stereospecific water addition to lupenyl cation intermediate, yielding 3β,20 dihydroxylupane, which accounts for the multiproduct nature of this synthase.
Mevalonate-independent methylerythritol phosphate pathway for isoprenoid biosynthesis. Elucidation and distribution
Authors: Rohmer M.
Published: October 2007

A long-overlooked metabolic pathway for isoprenoid biosynthesis, the mevalonate-independent methylerythritol phosphate (MEP) pathway, is present in many bacteria and in the chloroplasts of all phototrophic organisms. It represents an alternative to the well known mevalonate pathway, which is present in animals, fungi, plant cytoplasm, archaebacteria, and some eubacteria. This contribution summarizes key steps of its elucidation and the state-of-the-art knowledge of this biosynthetic pathway, which represents a novel target for antibacterial and antiparasitic drugs.
Biotransformation of triptonide by cell suspension cultures of Platycodon grandiflorum
Authors: Ning L. , Guo Hongzhu , Jiang Xiaomei , Bi Kaishun , Guo Dean
Published: October 2007

The biotransformation of triptonide by cell suspension cultures of Platycodon grandiflorum was investigated. After six days of incubation, five products were obtained. On the basis of chemical and spectral evidence, their structures were elucidated as epitriptolide-14-O-β-d-glucoside, 5α-hydroxytriptonide, triptolide, triptodiolide, and 2β-hydroxytriptonide, among which epitriptolide-14-O-β-d-glucoside and 5α-hydroxytriptonide are new compounds.
The deoxyxylulose phosphate pathway of isoprenoid biosynthesis. Discovery and function of the ispDEFGH genes and their cognate enzymes
Authors: Rohdich F. , Hecht Stefan , Bacher Adelbert , Eisenreich Wolfgang
Published: October 2007

Isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) serve as the universal precursors for the biosynthesis of terpenes. Besides the well-known mevalonate pathway, a second biosynthetic pathway conducive to IPP and DMAPP via 1-deoxy-d-xylulose-5-phosphate and 2C-methyl-d-erythritol-4-phosphate has been discovered recently in plants and certain eubacteria. 2C-Methyl-d-erythritol-4-phosphate, the first committed intermediate of the deoxyxylulose phosphate pathway, is converted into 2C-methyl-d-erythritol 2,4-cyclodiphosphate by the catalytic action of three enzymes specified by the ispDEF genes. The cyclic diphosphate is reductively opened by the IspG protein affording 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate. This compound can be converted into IPP as well as DMAPP by the catalytic action of IspH protein. The enzymes of this pathway are potential targets for novel antibacterial, antimalarial, and herbicide agents.
Natural and totally synthetic receptors in the innovative design of HPLC chiral stationary phases
Authors: Gasparrini Francesco , D'Acquarica Ilaria , Misiti D. , Pierini M. , Villani C.
Published: October 2007

An overview is presented of the experimental results obtained by our group in the design, realization, and applications of high-performance liquid chromatography (HPLC) enantioselective stationary phases based on surface-linked macrocyclic receptors. Macrocyclic synthetic receptors and macrocyclic glycopeptide receptors have been grafted on silica particles, and the resulting chiral stationary phases are used to monitor differential associations of the enantiomers of selected chiral guests with the immobilized hosts. Practical implications of the chiral phases in enantioselective analysis and in the study of recognition events are highlighted.
Combination of enzymatic procedures with multicomponent condensations
Authors: Ostaszewski R. , Portlock D. E. , Fryszkowska Anna , Jeziorska Katarzyna
Published: October 2007

A new synthetic method based on combination of enzymatic desymmetrization of 3-phenylglutaric anhydrides with multicomponent condensation is outlined. Enzymatic monoesterification of glutaric anhydrides was performed, and the derived monoacids were used as substrates for subsequent Ugi and Passerini multicomponent condensations. Both reactions were combined as two-step, one-pot processes. The choice of solvent and enzyme type has an appreciable effect on the course of reactions.
Synthesis of coumarins by ring-closing metathesis
Authors: Chatterjee A. K. , Toste F. D. , Goldberg S. D. , Grubbs Robert H.
Published: October 2007

Investigations into olefin ring-closing metathesis (RCM) have led to a general method for the synthesis of coumarins. Catalysts with higher activity, such as the second-generation ruthenium catalyst, promote the intramolecular reaction between two-electron deficient olefins. This method allows for convenient access to a variety of coumarins substituted at both the 3- and 4-positions, as well as a tetrasubstituted example.
Bucky ferrocene. Hybrid of ferrocene and fullerene
Authors: Nakamura E.
Published: October 2007

The idea of “bucky ferrocene” intrigues chemists owing to its aesthetic beauty and to its polarized, extended conjugated system, but the idea has remained hypothetical. The synthesis of close analogs of Fe(C60Me5)Cp and Fe(C70Me3)Cp was achieved in two steps from [60] and [70]fullerenes, relying on an oxidative C–H bond activation starting with an iron(I) complex and the corresponding cyclopentadienyl precursors, respectively. The molecules can be regarded as members of a new organometallic conjugated system connected to a graphitic system. Numerous synthetic transformations and self-organization procedures that are known for the parent ferrocenes and fullerenes are expected to be employable toward productive use of the ferrocene/fullerene hybrid molecules in chemistry and materials sciences.
Carbenes. Pincers, chelates, and abnormal binding modes
Authors: Crabtree Robert H.
Published: October 2007

Routes to pincer and chelate carbene complexes of Pd, Rh, and Ir include double geminal CH activation, metallation, and CH activation. Abnormal binding via imidazole C5 can occur, and ion pairing can strongly influence C2 vs. C5 binding. Prior ligand binding via pyridine N before metallation is not essential. Computational methods are used extensively, for example, to compare N vs. C binding in imidazole. The possibility of C binding by histidine in metalloenzymes is discussed.
Challenging metal-based transformations. From single-bond activation to catalysis and metallaquinonoids
Authors: Milstein D.
Published: October 2007

Catalytic reactions resulting from our C–X (X = H, C, O, N, halide) bond activation studies are described. Aryl chlorides can react with aluminum alkyls in preference to bromides. Using PCP-type Pd catalysts, Heck reaction with aryl iodides and bromides can proceed without involvement of Pd(0). Ru-catalyzed oxidative coupling of arenes with alkenes using O2 was accomplished.

Using specifically designed systems, the scope and mechanisms of C–C activation in solution was studied and compared to C–H activation. C–C activation by Rh(I), Ir(I), Ni(II),Pt(II), Ru(II), and Os(II) was observed. Metal insertion into a strong C–C bond can be kinetically and thermodynamically more favorable than the competing C–H activation. Selective, single-step oxidative addition of a strong C–C bond to a metal was observed and kinetically evaluated. Catalytic C–C hydrogenolysis was demonstrated. A combination of C–C activation and C–R formation (R = aryl, silyl) resulted in unusual methylene transfer chemistry. Selective activation of aryl–O and Me–O bonds was observed. New types of interactions between metals and arenes and unusual quinonoid complexes, including quinone methides, xylylenes, methylene arenium, and a metallaquinone, were discovered. C–H and C–C agostic complexes of cationic metals, proposed as intermediates in bond activation, were isolated. Stabilization and controlled release of biologically relevant, extremely unstable, simple quinone methides, was accomplished.
Organometallic chemistry at the nanoscale. Dendrimers for redox processes and catalysis
Authors: Astruc D.
Published: October 2007

An overview of the metal-mediated synthesis and use of nanosized metallodendrimers is given with emphasis on electron-transfer processes (molecular batteries consisting in dendrimers decorated with a large number of equivalent redox-active centers) and catalytic reactions (electron-transfer-chain catalytic synthesis of dendrimers decorated with ruthenium carbonyl clusters, redox catalysis of nitrate and nitrite electroreduction in water by star-shape hexanuclear catalysts).
Strategies in the cyclopentadienyl chemistry of p-block elements
Authors: Jutzi P.
Published: October 2007

Synthetic strategies in the cyclopentadienyl (Cp) chemistry of the groups 13–15 elements, are based on the following phenomena: (1) low barriers for haptotropic and dyotropic shifts, for sigmatropic rearrangements, and for other types of Cp migration; (2) stabilization of elements in their low-oxidation state by π-complexation; (3) tuning of steric andelectronic effects by suitable ring substituents; and (4) easy homolytic and heterolytic cleavage of El-C(Cp) bonds. These strategies are applied to: (a) the formation of a Si2Me4 doubly bridged dicyclopentadienyl cobalt complex, (b) the chemistry of half-sandwich [Me5C5Ga] and sandwich [(Me5C5)2Si] complexes, (c) the formation of P6, (d) the deposition of Al, Ga, Si, Ge, and As from respective Cp-El precursor molecules, and (d) the “dynamic covalent chemistry” in ferrocenylgallium(III) compounds.
Critical evaluation of stability constants for alpha-hydroxycarboxylic acid complexes with protons and metal ions and the accompanying enthalpy changes. Part II. Aliphatic 2-hydroxycarboxylic acids (IUPAC Technical Report)
Authors: Portanova R. , Lajunen L. H. J. , Tolazzi M. , Piispanen J.
Published: October 2007

Stability constants for different aliphatic 2-hydroxycarboxylic acid complexes in aqueous solutions with protons and metal ions published between 1960 and the end of 1994 have been critically evaluated.
Light-powered molecular-scale machines
Authors: Balzani Vincenzo , Credi Alberto , Venturi M.
Published: October 2007

The macroscopic concepts of a machine can be extended to the molecular level. Molecular-level machines are constructed by the molecule-by-molecule bottom-up approach following the guidelines of supramolecular chemistry. Like macroscopic machines, molecular machines are characterized by (i) the kind of energy supplied to make them work, (ii) the kind of movement performed by their components, (iii) the way in which their operation can be controlled and monitored, (iv) the possibility to repeat the operation, (v) the time needed to complete a cycle of operation, and (vi) the function performed. The most convenient way to supply energy to a molecular machine is through photochemical energy inputs. Photochemical techniques offer, indeed, several advantages: (i) photons can make a machine work without formation of waste products, (ii) light can be switched on/off easily and rapidly, (iii) lasers provide the opportunity of working in very small space and very short time domains, (iv) photons can be used to “read” the state of the system and to monitor the operation of the machine. The extension of the concepts of a machine to the molecular level is of interest not only for basic research, but also for the growth of nanoscience and the development of nanotechnology.
New structurally interesting cyclopropane derivatives. A world of wonders and surprises
Authors: de Meijere Armin , Kozhushkov S. I. , Fokin A. A. , Emme I. , Redlich S. , Schreiner P. R.
Published: October 2007

The structurally intriguing [4]- and [5]triangulanes have been prepared in enantiomerically pure form. Their surprisingly high specific rotations are well reproduced by DFT/SCI computations and stem from the fact that these hydrocarbons essentially are σ-helicenes (i.e., rigidly held helical arrangements of σ-bonds). Some light is shed on the properties of radical cations derived from [3]- and [4]rotanes. While the former adopts Cs or C2v symmetry, the latter retains the D4h symmetry of the neutral hydrocarbon, according to highlevel computations. Experimental and computational evidence is also presented that the antiaromatic cyclopentadienyl cation is stabilized as a singlet ground state by five cyclopropyl substituents. Yet, the three cyclopropyl groups in tricyclopropylamine do not favor the formation of its radical cation, because they are not in the proper orientation. When this amine radical cation is generated by cobalt γ-irradiation in a Freon matrix, evidence for a significant conformational change is obtained by EPR spectroscopy. Finally, the conformational dynamics of the newly prepared crowded molecules tetracyclopropyl- and tetraisopropylmethane are discussed.
In control of switching, motion, and organization
Authors: Feringa Ben L. , van Delden R. A. , ter Wiel M. K. J.
Published: October 2007

Nature’s solutions to control organization, switching, and linear and rotary motion are not only extremely elegant, but fascinating if one considers the design and synthesis of artificial molecular systems with such functions in order to add components to the nanotoolbox. The synthesis of chiroptical molecular switches and their application in the control of the organization of liquid crystalline materials is outlined. The first light-driven unidirectional molecular motor is described, and the second-generation motor as well as approaches to control the speed of the rotary motion are discussed.
Catalytic control of electron-transfer processes
Authors: Fukuzumi Shunichi
Published: October 2007

Catalytic control of electron-transfer processes is described for a number of photoinduced and thermal electron-transfer reactions, including back electron transfer in the charge-separated state of artificial photosynthetic compounds. The intermolecular and intramolecular electron-transfer processes are accelerated by complexation of radical anions, produced in the electron transfer, with metal ions that act as Lewis acids. Quantitative measures to determine the Lewis acidity of a variety of metal ions are given in relation with the promoting effects of metal ions in the electron-transfer reactions. The mechanistic viability of metal ion catalysis in electron-transfer reactions is demonstrated by a variety of examples of both thermal and photochemical reactions that involve metal ion-promoted electron-transfer processes as the rate-determining steps, which are made possible to proceed by complexation of radical anions with metal ions.
Salt effects on the conformational behavior of 5-substituted 1,3-dioxanes
Authors: Juaristi Eusebio , Rosquete-Pina G. A. , Vázquez-Hernández M. , Mota A. J.
Published: October 2007

Since their introduction by E. L. Eliel nearly four decades ago, derivatives of 1,3-dioxane have proved useful in conformational analysis. Examples are discussed, where 5-polar substituents permit the evaluation of fundamental phenomena such as attractive and repulsive gauche effects, electrostatic interactions, and stereoelectronic effects. By the same token, 2-substituted 1,3-dioxanes, 1,3-dithianes, and 1,3-oxathianes are useful frameworks for the study of the anomeric effect and the associated structural and spectroscopic manifestations, such as the so-called Perlin effects. In view of the varied and essential involvement of metal ions and inorganic salts in biological processes, 5-substituted 1,3-dioxanes are presently being examined in the presence of Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, and other cations, with the aim to increase the understanding of biomolecular properties in vivo.
Dynamic barriers and tunneling. New views of hydrogen transfer in enzyme reactions
Authors: Klinman J. P.
Published: October 2007

Hydrogen-transfer processes are expected to show appreciable quantum mechanical behavior. Intensive investigations of enzymes under their physiological conditions show this to be true in practically every example investigated. Initially, tunneling was treated either as a tunneling correction [cf. Bell, The Tunnel Effect in Chemistry, Chapman & Hall, New York, (l980)], or as corner-cutting [Truhlar et al., J. Chem. Phys. 100, 12771 (l996)]. This worked well as long as the observed properties could be explained by “corrections” to transition-state theory. However, over the past several years, enzymatic behaviors have been observed that are so deviant as to lie outside of transition-state theory. This phenomenon is discussed in the context of the enzyme, soybean lipoxygenase. An environmentally coupled hydrogen-tunneling model is presented that derives from the treatments of Kuznetsov and Ullstrup [Can. J. Chem. 77, 689 (l999)], and includes heavy-atom reorganization (temperature-dependent and largely isotope-independent), together with heavy-atom gating (temperature- and isotope-dependent). This treatment can explain a wide range of behaviors and leads to a new view of the origin of kinetic isotope effects in hydrogen-transfer reactions. These properties link enzyme fluctuations to the hydrogen-transfer reaction coordinate, making a quantum view of H-transfer necessarily a dynamic view of catalysis.
Toward replicatable, multifunctional, nanoscaffolded machines. A chemical manifesto
Authors: von Kiedrowski G. , Eckardt L.-H. , Naumann K. , Pankau W. M. , Reimold M. , Rein M.
Published: October 2007

Self-replicating nanorobots were foreseen in technological dreams and visions whose scientific ground found solid criticism from chemical and physical reasoning. If one, however, views such constructs as three-dimensionally defined noncovalent nanoscaffolding of a multitude of modular functions whose array is replicatable in a nonautonomous way, many pieces of technology needed for their implementation became recently available. Gold cluster-labeled molecules were remotely controlled by GHz radio frequency causing local and selective inductive heating, and monoconjugable thermostable gold clusters will become commercially available soon. Charged molecules were electrophoretically steered and manipulated on the surface of microelectrode array chips. Surface-promoted replication and exponential amplification of DNA analogs (SPREAD) may find particular applications for the cloning and copying of informational nanostructures on the surface of such chips. Synthetic trisoligonucleotidyl junctions were reported as covalent building blocks for noncovalent DNA nanostructures, and it was shown that kinetic control during noncovalent synthesis favors small and defined nanostructures instead of polymeric networks. Very recently, it was demonstrated that functionalized DNA nanoscaffolds with stiff tensegrity such as tetrahedra self-assemble from maximally instructed sets of 3- or [3+1]-arm junctions, and that the connectivity information in such nanoscaffolds can be copied. The implications of these developments are discussed with respect to a possible implementation scheme for the issue of the title.
Millimeter-scale self-assembly and its applications
Authors: Boncheva Mila , Bruzewicz D. A. , Whitesides G. M.
Published: October 2007

Self-assembly is a concept familiar to chemists. In the molecular and nanoscale regimes, it is often used as a strategy in fabricating regular 3D structures—that is, crystals. Self-assembly of components with sizes in the µm-to-mm range is less familiar to chemists; this type of self-assembly may, however, become technologically important in the future. In this size range, self-assembly offers methods to form regular 3D structures from components too small or too numerous to be manipulated by other means, and methods to incorporate function into these structures; it also offers simplicity and economy.

This paper focuses on the use of self-assembly to build functional systems of components with sizes in the range from microns to millimeters. It compares the principles of selfassembly at the molecular and millimeter scales, reviews the possible applications of mesoscale, self-assembled systems, and outlines some of the most important issues in the use of self-assembly to build functional systems.
Endocrine disruptors in the environment (IUPAC Technical Report)
Authors: Lintelmann J. , Katayama A. , Kurihara N. , Shore L. , Wenzel A.
Published: October 2007

Many chemical substances of natural or anthropogenic origin are suspected or known to be endocrine disruptors, which can influence the endocrine system of life. This observation has led to increased interest on the part of the public and the media, as well as to a steep rise of research activities in the scientific community. New papers and results are presented so fast that it is impossible to give a complete review of this emerging research field. Therefore, this paper tries to give insight into some topics of the great scope of endocrine disruptors in the environment. To get a general idea of the biochemical and biological background, some parts of the endocrine systems of mammalians and nonmammalians are explained. The sections that follow describe important mechanisms of endocrine disruption such as interactions with hormone receptors. Test strategies for anthropogenic chemicals on various organisms are critically reviewed with respect to their problems and gaps concerning endocrine disruptors. The main emphasis of the paper is on the chemical substances suspected or known to be endocrine disruptors. To get a better comprehension of their behavior in the environment, physicochemical data such as water solubility or Kow, as well as information about their use and/or function are reviewed and compared. The main routes of exposure for most chemicals are shortly described, and data about concentrations in the environment (soil/sediment, water) are detailed.
Atomic weights of the elements. Review 2000 (IUPAC Technical Report)
Authors: de Laeter John R. , Böhlke John Karl , De Bièvre P. , Hidaka H. , Peiser H. S. , Rosman K. J. R. , Taylor P. D. P.
Published: October 2007

A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 ×10−7 . Isotope abundances for an increasing number of elements can be measured to better than 1 ×10−3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample-specific atomic weights. These relative comparisons can often be made with a smaller uncertainty than is achieved in the best calibrated “absolute ” (=SI-traceable) atomic-weight determinations. Accurate determinations of the atomic weights of certain elements also influence the values of fundamental constants such as the Avogadro, Faraday, and universal gas constants. This review is in two parts: the first summarizes the development of the science of atomic-weight determinations during the 20th century; the second summarizes the changes and variations that have been recognized in the values and uncertainties of atomic weights, on an element-by-element basis, in the latter part of the 20th century.
Critical review of analytical applications of Mössbauer spectroscopy illustrated by mineralogical and geological examples (IUPAC Technical Report)
Authors: Kuzmann E. , Nagy S. , Vértes A.
Published: October 2007

We have developed a new terminology for Mössbauer pattern analysis in order to enhance the performance of qualitative analysis by Mössbauer spectroscopy. In this approach, Mössbauer parameters are considered as a function of a number of externally adjusted experimental parameters at which the spectrum has been recorded. The basis of analytical classification is the microenvironment, which is determined by an assembly of atoms causing the same hyperfine interactions at one particular class of the Mössbauer probe atoms.Since Mössbauer spectroscopy measures hyperfine interactions very sensitively, the microenvironment presents itself as a fundamental concept for analytical purposes. Our approach can also help to systematize the Mössbauer data for the identification of individual physicochemical species from the corresponding patterns present in the spectrum.
Molecular thermodynamics for some applications in biotechnology
Authors: Prausnitz J. M.
Published: October 2007

As biotechnology sweeps the world, it is appropriate to remember that the great virtue of thermodynamics is its broad range of applicability. As a result, there is a growing literature describing how chemical thermodynamics can be used to inform processes for old and new biochemical products for industry and medicine.A particular application of molecular thermodynamics concerns separation of aqueous proteins by selective precipitation. For this purpose, we need phase diagrams; for constructing such diagrams, we need to understand not only the qualitative nature of phase equilibria of aqueous proteins, but also the quantitative intermolecular forces between proteins in solution. Some examples are given to show how aqueous protein-protein forces can be calculated or measured to yield a potential of mean force and how that potential is then used along with a statistical-thermodynamic model to establish liquid -liquid and liquid -crystal equilibria. Such equilibria are useful not only for separation processes, but also for understanding diseases like Alzheimer’s, eye cataracts, and sickle-cell anemia that appear to be caused by protein agglomeration.
Potential of group contribution methods for the prediction of phase equilibria and excess properties of complex mixtures
Authors: Gmehling Jürgen
Published: October 2007

Reliable knowledge of the thermophysical properties of pure compounds and their mixtures in the whole composition and a wide temperature and pressure range is a vital prerequisite for computer-aided synthesis, design, and optimization of chemical processes. Knowledge of the various phase equilibria is most important for the development of thermal separation processes (but also for other applications,such as the design of multiphase reactors, the prediction of the fate of a chemical in the environment,etc.).

Whereas 25 years ago, the main interest was directed to the development of predictive tools for vapor–liquid equilibria of subcritical compounds of similar size (ASOG, UNIFAC), 15 years later a proper description of the temperature dependence (excess enthalpies), the activity coefficients at infinite dilution, and solid–liquid equilibria of eutectic mixtures (including strong asymmetric systems) was achieved. After the combination with cubic equations of state [Soave–Redlich–Kwong (SRK), Peng–Robinson (PR)], the group contribution concept was extended to supercritical compounds [predictive SRK (PSRK)]. With the development of an adequate electrolyte model (LIFAC), the equation-of-state approach can even be used for systems with strong electrolytes. With the revision of the group interaction parameters, the extension of the parameter matrix (introduction of new structural groups, filling of parameter gaps), and the help of a large database (Dortmund Data Bank), the predicted results of group contribution methods were significantly improved and the range of applicability greatly extended. Furthermore, still-existing problems with the group contribution approach (proximity effects,etc.) were reduced.

With the help of a volume-translated PR equation of state and application of temperature-dependent and improved mixing rules, the remaining weaknesses of group contribution equations of state (such as poor results for liquid densities, excess enthalpies, and the problems with asymmetric systems) were minimized.
Materials in thermodynamic potential gradients
Authors: Martin M.
Published: October 2007

In materials that are exposed to thermodynamic potential gradients (i.e., gradients of chemical potentials, electrical potential, temperature, or pressure), transport processes of the mobile components occur. These transport processes and the coupling between different processes are not only of fundamental interest, but are also the origin of degradation processes, such as kinetic demixing and decomposition and changes in the morphology of the material, all of which are of great practical relevance.Two classes of materials will be considered: semi-and ion-conducting oxides and ion-conducting halides. In oxides, kinetic demixing of the cations in a multicomponent oxide and kinetic decomposition of the oxide under the influence of an applied thermodynamic potential gradient will be considered for homovalent oxide solid solutions and for heterovalently doped oxides. In ion-conducting halides, the morphological stability of solid/solid interfaces, which are driven by an external electrical potential gradient, is studied. Monte Carlo simulations show that the morphological stability of the interface is determined by the difference in the ionic conductivities of the two crystals.