Substituted hydroxamic acids and uses thereof

This invention provides compounds of formula (I):

FIELD OF THE INVENTION

The invention relates to compounds and methods for the selective inhibition of HDAC6. The present invention relates to compounds useful as HDAC6 inhibitors. The invention also provides pharmaceutical compositions comprising the compounds of the invention and methods of using the compositions in the treatment of various diseases.

BACKGROUND OF THE INVENTION

Histone deacetylase 6 (HDAC6) is a member of a family of amidohydrolases commonly referred as histone or lysine deacetylases (HDACs or KDACs) as they catalyze the removal of acetyl groups from the s-amino group of lysine residues from proteins. The family includes 18 enzymes which can be divided in 3 main classes based on their sequence homology to yeast enzymes Rpd3 (Class I), Hda1 (Class II) and Sir2 (Class III). A fourth class was defined with the finding of a distinct mammalian enzyme—HDAC 11 (reviewed in Yang, et al.,Nature Rev. Mol. Cell. Biol.2008, 9:206-218 and in Saunders and Verdin,Oncogene2007, 26(37):5489-5504). Biochemically, Class I (HDAC1, 2, 3, 8) and Class II (HDAC4, 5, 6, 7, 9, 10) and Class IV (HDAC11) are Zn2+-dependent enzymes, while Class III (SIRT1-7) are dependent on nicotinamide adenine dinucleotide (NAD+) for activity. Unlike all other HDACs, HDAC6 resides primarily in the cytosol. It has 2 functional catalytic domains and a carboxy-terminal Zn2+-finger ubiquitin binding domain that binds ubiquitinated misfolded proteins (Kawaguchi et al.,Cell2003, 115(6):727-738), ubiquitin (Boyaullt et al.,EMBO J.2006, 25(14): 3357-3366), as well as ubiquitin-like FAT10 modifier (Kalveram et al.,J. Cell Sci.2008, 121(24):4079-4088). Known substrates of HDAC6 include cytoskeletal proteins α-tubulin and cortactin; β-catenin which forms part of adherens junctions and anchors the actin cytoskeleton; the chaperone Hsp90; and the redox regulatory proteins peroxiredoxin (Prx) I and Prx II (reviewed in Boyault et al.,Oncogene2007, 26(37):5468-5476; Matthias et al.,Cell Cycle2008, 7(1):7-10; Li et al.,J Biol. Chem.2008, 283(19):12686-12690; Parmigiani et al.,Proc. Natl. Acad. Sci. USA2009, 105(28):9633-9638). Thus, HDAC6 mediates a wide range of cellular functions including microtubule-dependent trafficking and signaling, membrane remodeling and chemotactic motility, involvement in control of cellular adhesion, ubiquitin level sensing, regulation of chaperone levels and activity, and responses to oxidative stress. All of these functions may be important in tumorigenesis, tumor growth and survival as well as metastasis (Simms-Waldrip et al.,Mol. Genet. Metabolism2008, 94(3):283-286; Rodriguez-Gonzalez et al.,Cancer Res.2008, 68(8):2557-2560; Kapoor,Int. J. Cancer2009, 124:509; Lee et al.,Cancer Res.2008, 68(18):7561-7569). Recent studies have shown HDAC6 to be important in autophagy, an alternative pathway for protein degradation that compensates for deficiencies in the activity of the ubiquitin proteasome system or expression of proteins prone to form aggregates and can be activated following treatment with a proteasome inhibitor (Kawaguchi et al.,Cell2003, 115(6):727-738; Iwata et al.,J. Biol. Chem.2005, 280(48): 40282-40292; Ding et al.,Am. J. Pathol.2007, 171:513-524, Pandey et al.,Nature2007, 447(7146):860-864). Although the molecular mechanistic details are not completely understood, HDAC6 binds ubiquitinated or ubiquitin-like conjugated misfolded proteins which would otherwise induce proteotoxic stress and then serves as an adaptor protein to traffic the ubiquitinated cargo to the microtubule organizing center using the microtubule network via its known association with dynein motor protein. The resulting perinuclear aggregates, known as aggresomes, are then degraded by fusion with lysosomes in an HDAC6- and cortactin-dependent process which induces remodeling of the actin cytoskeleton proximal to aggresomes (Lee et al.,EMBO J.2010, 29:969-980). In addition, HDAC6 regulates a variety of biological processes dependent on its association with the microtubular network including cellular adhesion (Tran et al.,J. Cell Sci.2007, 120(8):1469-1479) and migration (Zhang et al.,Mol. Cell.2007, 27(2):197-213; reviewed in Valenzuela-Fernandez et al.,Trends Cell. Biol.2008, 18(6):291-297), epithelial to mesenchymal transition (Shan et al.,J. Biol. Chem.2008, 283(30):21065-21073), resistance to anoikis (Lee et al.,Cancer Res.2008, 68(18):7561-7569), epithelial growth factor-mediated Wnt signaling via β-catenin deacetylation (Li et al.,J. Biol. Chem.2008, 283(19):12686-12690) and epithelial growth factor receptor stabilization by endocytic trafficking (Lissanu Deribe et al.,Sci. Signal.2009, 2(102): ra84; Gao et al.,J. Biol. Chem.2010, 285:11219-11226); all events that promote oncogenesis and metastasis (Lee et al.,Cancer Res.2008, 68(18):7561-7569). HDAC6 activity is known to be upregulated by Aurora A kinase in cilia formation (Pugacheva et al.,Cell2007, 129(7):1351-1363) and indirectly by farnesyl transferase with which HDAC6 forms a complex with microtubules (Zhou et al.,J. Biol. Chem.2009, 284(15): 9648-9655). Also, HDAC6 is negatively regulated by tau protein (Perez et al.,J. Neurochem.2009, 109(6):1756-1766).

Inhibition of HDAC6 may also have a role in cardiovascular disease, i.e. cardiovascular stress, including pressure overload, chronic ischemia, and infarction-reperfusion injury (Tannous et al.,Circulation2008, 117(24):3070-3078); bacterial infection, including those caused by uropathogenicEscherichia coli(Dhakal and Mulve,J. Biol. Chem.2008, 284(1):446-454); neurological diseases caused by accumulation of intracellular protein aggregates such as Huntington's disease (reviewed in Kazantsev et al.,Nat. Rev. Drug Disc.2008, 7(10):854-868; see also Dompierre et al.,J. Neurosci.2007, 27(13):3571-3583; Kozikowski et al.,J. Med. Chem.2007, 50:3054-3061) or central nervous system trauma caused by tissue injury, oxidative-stress induced neuronal or axomal degeneration (Rivieccio et al.,Proc. Natl. Acad. Sci. USA2009, 106(46):19599-195604); and inflammation, including reduction of pro-inflammatory cytokine IL-1β (Carta et al.,Blood2006, 108(5):1618-1626), increased expression of the FOXP3 transcription factor, which induces immunosuppressive function of regulatory T-cells resulting in benefits in chronic diseases such as rheumatoid arthritis, psoriasis, multiple sclerosis, lupus and organ transplant rejection (reviewed in Wang et al.,Nat. Rev. Drug Disc.2009, 8(12):969-981).

Clearly, it would be beneficial to provide novel HDAC6 inhibitors that possess good therapeutic properties, especially for the treatment of proliferative diseases or disorders.

DETAILED DESCRIPTION OF THE INVENTION

1. General Description of Compounds of the Invention

The present invention provides compounds that are effective inhibitors of HDAC6. These compounds are useful for inhibiting HDAC6 activity in vitro and in vivo, and are especially useful for the treatment of various cell proliferative diseases or disorders. The compounds of the invention are represented by formula (I):

or a pharmaceutically acceptable salt thereof;

n is 1-2;

G is —R3, —V1—R3, —V1-L1-R3, -L2-V1—R3, -L2-V2—R3, or -L1-R3; or when R1aand R1bare taken together to form an oxo group, G is —R3, or -L1-R3;

each occurrence of RAis independently hydrogen, fluoro, or unsubstituted or substituted C1-4aliphatic; and

each occurrence of R4ais independently hydrogen, or unsubstituted or substituted C1-4aliphatic;

provided that the compound of formula (I) is other thaw

N-hydroxy-5-(4-methoxybenzyl)-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamide; or

2. Compounds and Definitions

Compounds of this invention include those described generally for formula (I) above, and are further illustrated by the classes, subclasses, and species disclosed herein. As used herein, the following definitions shall apply unless otherwise indicated.

As described herein, compounds of the invention may be optionally substituted with one or more substituents, such as are illustrated generally above, or as exemplified by particular classes, subclasses, and species of the invention. It will be appreciated that the phrase “optionally substituted” is used interchangeably with the phrase “substituted or unsubstituted.” In general, the term “substituted”, whether preceded by the term “optionally” or not, means that a hydrogen radical of the designated moiety is replaced with the radical of a specified substituent, provided that the substitution results in a stable or chemically feasible compound. The term “substitutable”, when used in reference to a designated atom, means that attached to the atom is a hydrogen radical, which hydrogen atom can be replaced with the radical of a suitable substituent. Unless otherwise indicated, an “optionally substituted” group may have a substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds.

A stable compound or chemically feasible compound is one in which the chemical structure is not substantially altered when kept at a temperature from about −80° C. to about +40° C., in the absence of moisture or other chemically reactive conditions, for at least a week, or a compound which maintains its integrity long enough to be useful for therapeutic or prophylactic administration to a patient.

The phrase “one or more substituents”, as used herein, refers to a number of substituents that equals from one to the maximum number of substituents possible based on the number of available bonding sites, provided that the above conditions of stability and chemical feasibility are met.

As used herein, the term “independently selected” means that the same or different values may be selected for multiple instances of a given variable in a single compound.

As used herein, the term “aromatic” includes aryl and heteroaryl groups as described generally below and herein.

The term “aliphatic” or “aliphatic group”, as used herein, means an optionally substituted straight-chain or branched C1-12hydrocarbon. For example, suitable aliphatic groups include optionally substituted linear, branched or cyclic alkyl, alkenyl, alkynyl groups and hybrids thereof. Unless otherwise specified, in various embodiments, aliphatic groups have 1-12, 1-10, 1-8, 1-6, 1-4, 1-3, or 1-2 carbon atoms.

The term “alkyl”, used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having 1-12, 1-10, 1-8, 1-6, 1-4, 1-3, or 1-2 carbon atoms.

The term “alkenyl”, used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having at least one double bond and having 2-12, 2-10, 2-8, 2-6, 2-4, or 2-3 carbon atoms.

The term “alkynyl”, used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having at least one triple bond and having 2-12, 2-10, 2-8, 2-6, 2-4, or 2-3 carbon atoms.

The terms “cycloaliphatic”, “carbocycle”, “carbocyclyl”, “carbocyclo”, or “carbocyclic”, used alone or as part of a larger moiety, refer to an optionally substituted saturated or partially unsaturated cyclic aliphatic ring system having from 3 to about 14 ring carbon atoms. In some embodiments, the cycloaliphatic group is an optionally substituted monocyclic hydrocarbon having 3-10, 3-8 or 3-6 ring carbon atoms. Cycloaliphatic groups include, without limitation, optionally substituted cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cycloheptenyl, cyclooctyl, cyclooctenyl, or cyclooctadienyl. The terms “cycloaliphatic”, “carbocycle”, “carbocyclyl”, “carbocyclo”, or “carbocyclic” also include optionally substituted bridged or fused bicyclic rings having 6-12, 6-10, or 6-8 ring carbon atoms, wherein any individual ring in the bicyclic system has 3-8 ring carbon atoms.

The term “cycloalkyl” refers to an, optionally substituted saturated ring system of about 3 to about 10 ring carbon atoms. Exemplary monocyclic cycloalkyl rings include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl.

The term “cycloalkenyl” refers to an optionally substituted non-aromatic monocyclic or multicyclic ring system containing at least one carbon-carbon double bond and having about 3 to about 10 carbon atoms. Exemplary monocyclic cycloalkenyl rings include cyclopentyl, cyclohexenyl, and cycloheptenyl.

The terms “haloaliphatic”, “haloalkyl”, “haloalkenyl” and “haloalkoxy” refer to an aliphatic, alkyl, alkenyl or alkoxy group, as the case may be, which is substituted with one or more halogen atoms. As used herein, the term “halogen” or “halo” means F, Cl, Br, or I. The term “fluoroaliphatic” refers to a haloaliphatic wherein the halogen is fluoro, including perfluorinated aliphatic groups. Examples of fluoroaliphatic groups include, without limitation, fluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, 1,1,2-trifluoroethyl, 1,2,2-trifluoroethyl, and pentafluoroethyl.

The terms “aryl” and “ar-”, used alone or as part of a larger moiety, e.g., “aralkyl”, “aralkoxy”, or “aryloxyalkyl”, refer to an optionally substituted C6-14aromatic hydrocarbon moiety comprising one to three aromatic rings. Preferably, the aryl group is a C6-10aryl group. Aryl groups include, without limitation, optionally substituted phenyl, naphthyl, or anthracenyl. The terms “aryl” and “ar-”, as used herein, also include groups in which an aryl ring is fused to one or more cycloaliphatic rings to form an optionally substituted cyclic structure such as a tetrahydronaphthyl, indenyl, or indanyl ring. The term “aryl” may be used interchangeably with the terms “aryl group”, “aryl ring”, and “aromatic ring”.

An “aralkyl” or “arylalkyl” group comprises an aryl group covalently attached to an alkyl group, either of which independently is optionally substituted. Preferably, the aralkyl group is C6-10arylC1-6alkyl, including, without limitation, benzyl, phenethyl, and naphthylmethyl.

The terms “heteroaryl” and “heteroar-”, used alone or as part of a larger moiety, e.g., “heteroaralkyl”, or “heteroaralkoxy”, refer to groups having 5 to 14 ring atoms, preferably 5, 6, 9, or 10 ring atoms; having 6, 10, or 14 π electrons shared in a cyclic array; and having, in addition to carbon atoms, from one to five heteroatoms. In some embodiments, the heteroaryl group has 5-10 ring atoms, having, in addition to carbon atoms, from one to five heteroatoms. A heteroaryl group may be mono-, bi-, tri-, or polycyclic, preferably mono-, bi-, or tricyclic, more preferably mono- or bicyclic. The term “heteroatom” refers to nitrogen, oxygen, or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quaternized form of a basic nitrogen. For example, a nitrogen atom of a heteroaryl may be a basic nitrogen atom and may also be optionally oxidized to the corresponding N-oxide. When a heteroaryl is substituted by a hydroxy group, it also includes its corresponding tautomer. The terms “heteroaryl” and “heteroar-”, as used herein, also include groups in which a heteroaromatic ring is fused to one or more aryl, cycloaliphatic, or heterocycloaliphatic rings. Nonlimiting examples of heteroaryl groups include thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, pteridinyl, indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one. The term “heteroaryl” may be used interchangeably with the terms “heteroaryl ring”, “heteroaryl group”, or “heteroaromatic”, any of which terms include rings that are optionally substituted. The term “heteroaralkyl” refers to an alkyl group substituted by a heteroaryl, wherein the alkyl and heteroaryl portions independently are optionally substituted.

A heterocyclic ring can be attached to its pendant group at any heteroatom or carbon atom that results in a stable structure and any of the ring atoms can be optionally substituted. Examples of such saturated or partially unsaturated heterocyclic radicals include, without limitation, tetrahydrofuranyl, tetrahydrothienyl, piperidinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and thiomorpholinyl. A heterocyclyl group may be mono-, bi-, tri-, or polycyclic, preferably mono-, bi-, or tricyclic, more preferably mono- or bicyclic. The term “heterocyclylalkyl” refers to an alkyl group substituted by a heterocyclyl, wherein the alkyl and heterocyclyl portions independently are optionally substituted. Additionally, a heterocyclic ring also includes groups in which the heterocyclic ring is fused to one or more aryl rings.

As used herein, the term “partially unsaturated” refers to a ring moiety that includes at least one double or triple bond between ring atoms. The term “partially unsaturated” is intended to encompass rings having multiple sites of unsaturation, but is not intended to include aromatic (e.g., aryl or heteroaryl) moieties, as herein defined.

The term “alkylene” refers to a bivalent alkyl group. An “alkylene chain” is a polymethylene group, i.e., —(CH2)n′—, wherein n′ is a positive integer, preferably from 1 to 6, from 1 to 4, from 1 to 3, from 1 to 2, or from 2 to 3. An optionally substituted alkylene chain is a polymethylene group in which one or more methylene hydrogen atoms is optionally replaced with a substituent. Suitable substituents include those described below for a substituted aliphatic group and also include those described in the specification herein. It will be appreciated that two substituents of the alkylene group may be taken together to form a ring system. In certain embodiments, two substituents can be taken together to form a 3-7-membered ring. The substituents can be on the same or different atoms.

An alkylene chain also can be optionally interrupted by a functional group. An alkylene chain is “interrupted” by a functional group when an internal methylene unit is interrupted by the functional group. Examples of suitable “interrupting functional groups” are described in the specification and claims herein.

For purposes of clarity, all bivalent groups described herein, including, e.g., the alkylene chain linkers described above, are intended to be read from left to right, with a corresponding left-to-right reading of the formula or structure in which the variable appears.

An aliphatic or heteroaliphatic group, or a non-aromatic carbycyclic or heterocyclic ring may contain one or more substituents and thus may be “optionally substituted”. Unless otherwise defined above and herein, suitable substituents on the saturated carbon of an aliphatic or heteroaliphatic group, or of a non-aromatic carbocyclic or heterocyclic ring are selected from those listed above for the unsaturated carbon of an aryl or heteroaryl group and additionally include the following: ═O, ═S, ═C(R*)2, ═N—N(R*)2, ═N—OR*, ═N—NHC(O)R*, ═N—NHCO2Ro═N—NHSO2Roor ═N—R* where Rois defined above, and each R* is independently selected from hydrogen or an optionally substituted C1-6aliphatic group.

In addition to the substituents defined above and herein, optional substituents on the nitrogen of a non-aromatic heterocyclic ring also include and are generally selected from —R+, —N(R+)2, —C(O)R+, —C(O)OR+, —C(O)C(O)R+, —C(O)CH2C(O)R+, —S(O)2R+, —S(O)2N(R+)2, —C(S)N(R+)2, —C(═NH)—N(R+)2, or —N(R+)S(O)2R+; wherein each R+is defined above. A ring nitrogen atom of a heteroaryl or non-aromatic heterocyclic ring also may be oxidized to form the corresponding N-hydroxy or N-oxide compound. A nonlimiting example of such a heteroaryl having an oxidized ring nitrogen atom is N-oxidopyridyl.

As detailed above, in some embodiments, two independent occurrences of R+(or any other variable similarly defined in the specification and claims herein), are taken together with their intervening atom(s) to form a monocyclic or bicyclic ring selected from 3-13-membered cycloaliphatic, 3-12-membered heterocyclyl having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, 6-10-membered aryl, or 5-10-membered heteroaryl having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Exemplary rings that are formed when two independent occurrences of R+(or any other variable similarly defined in the specification and claims herein), are taken together with their intervening atom(s) include, but are not limited to the following: a) two independent occurrences of R+(or any other variable similarly defined in the specification or claims herein) that are bound to the same atom and are taken together with that atom to form a ring, for example, N(R+)2, where both occurrences of R+are taken together with the nitrogen atom to form a piperidin-1-yl, piperazin-1-yl, or morpholin-4-yl group; and b) two independent occurrences of R+(or any other variable similarly defined in the specification or claims herein) that are bound to different atoms and are taken together with both of those atoms to form a ring, for example where a phenyl group is substituted with two occurrences of OR+

these two occurrences of R+are taken together with the oxygen atoms to which they are bound to form a fused 6-membered oxygen containing ring:

It will be appreciated that a variety of other rings (e.g., spiro and bridged rings) can be formed when two independent occurrences of R+ (or any other variable similarly defined in the specification and claims herein) are taken together with their intervening atom(s) and that the examples detailed above are not intended to be limiting.

The terms “stereoisomer”, “enantiomer”, “diastereomer”, “epimer”, and “chiral center”, are used herein in accordance with the meaning each is given in ordinary usage by those of ordinary skill in the art. Thus, stereoisomers are compounds that have the same atomic connectivity, but differ in the spatial arrangement of the atoms. Enantiomers are stereoisomers that have a mirror image relationship, that is, the stereochemical configuration at all corresponding chiral centers is opposite. Diastereomers are stereoisomers having more than one chiral center, which differ from one another in that the stereochemical configuration of at least one, but not all, of the corresponding chiral centers is opposite. Epimers are diastereomers that differ in stereochemical configuration at only one chiral center.

It is to be understood that, when a disclosed compound has at least one chiral center, the present invention encompasses one enantiomer of the compound, substantially free from the corresponding optical isomer, a racemic mixture of both optical isomers of the compound, and mixtures enriched in one enantiomer relative to its corresponding optical isomer. When a mixture is enriched in one enantiomer relative to its optical isomer, the mixture contains, for example, an enantiomeric excess of at least 50%, 75%, 90%, 95%, 99%, or 99.5%.

The enantiomers of the present invention may be resolved by methods known to those skilled in the art, for example by formation of diastereoisomeric salts which may be separated, for example, by crystallization; formation of diastereoisomeric derivatives or complexes which may be separated, for example, by crystallization, gas-liquid or liquid chromatography; selective reaction of one enantiomer with an enantiomer-specific reagent, for example enzymatic esterification; or gas-liquid or liquid chromatography in a chiral environment, for example on a chiral support for example silica with a bound chiral ligand or in the presence of a chiral solvent. Where the desired enantiomer is converted into another chemical entity by one of the separation procedures described above, a further step is required to liberate the desired enantiomeric form. Alternatively, specific enantiomers may be synthesized by asymmetric synthesis using optically active reagents, substrates, catalysts or solvents, or by converting one enantiomer into the other by asymmetric transformation.

When a disclosed compound has at least two chiral centers, the present invention encompasses a diastereomer substantially free of other diastereomers, an enantiomeric pair of diastereomers substantially free of other stereoisomers, mixtures of diastereomers, mixtures of enantiomeric pairs of diastereomers, mixtures of diastereomers in which one diastereomer is enriched relative to the other diastereomer(s), and mixtures of enantiomeric pairs of diastereomers in which one enantiomeric pair of diastereomers is enriched relative to the other stereoisomers. When a mixture is enriched in one diastereomer or enantiomeric pair of diastereomers pairs relative to the other stereoisomers, the mixture is enriched with the depicted or referenced diastereomer or enantiomeric pair of diastereomers relative to other stereoisomers for the compound, for example, by a molar excess of at least 50%, 75%, 90%, 95%, 99%, or 99.5%.

As used herein, the term “diastereomeric ratio” refers to the ratio between diastereomers which differ in the stereochemical configuration at one chiral center, relative to a second chiral center in the same molecule. By way of example, a chemical structure with two chiral centers provides four possible stereoisomers: R*R, R*S, S*R, and S*S, wherein the asterisk denotes the corresponding chiral center in each stereoisomer. The diastereomeric ratio for such a mixture of stereoisomers is the ratio of one diastereomer and its enantiomer to the other diastereomer and its enantiomer ═(R*R+S*S):(R*S+S*R).

One of ordinary skill in the art will recognize that additional stereoisomers are possible when the molecule has more than two chiral centers. For purposes of the present invention, the term “diastereomeric ratio” has identical meaning in reference to compounds with multiple chiral centers as it does in reference to compounds having two chiral centers. Thus, the term “diastereomeric ratio” refers to the ratio of all compounds having R*R or S*S configuration at the specified chiral centers to all compounds having R*S or S*R configuration at the specified chiral centers. For convenience, this ratio is referred to herein as the diastereomeric ratio at the asterisked carbon, relative to the second specified chiral center.

The diastereomeric ratio can be measured by any analytical method suitable for distinguishing between diastereomeric compounds having different relative stereochemical configurations at the specified chiral centers. Such methods include, without limitation, nuclear magnetic resonance (NMR), gas chromatography (GC), and high performance liquid chromatography (HPLC) methods.

The diastereoisomeric pairs may be separated by methods known to those skilled in the art, for example chromatography or crystallization and the individual enantiomers within each pair may be separated as described above. Specific procedures for chromatographically separating diastereomeric pairs of precursors used in the preparation of compounds disclosed herein are provided the examples herein.

3. Description of Exemplary Compounds

In some embodiments, the compound of formula (I) is represented by:

wherein R1a, R1b, R1c, R1d, and G have the values described herein. In certain embodiments, the compound of formula (I) is represented by formulas (I-a), (I-b), (I-c), or (I-l), wherein R1a, R1b, R1c, R1d, and G have the values described herein.

In some embodiments, the compound of formula (I) is represented by formula (II-i):

wherein X1, X2, n, and G have the values described herein.

In some embodiments, the compound of formula (II-i) is represented by:

wherein G has the values described herein. In certain embodiments, the compound of formula (II-i) is represented by formulas (II-i-a), (II-i-b), or (II-i-c), wherein G has the values described herein.

In some embodiments, the compound of formula (I) is represented by formula (II-ii):

wherein X1, X2, n, and G have the values described herein.

In some embodiments, the compound of formula (II-ii) is represented by:

wherein G has the values described herein. In certain embodiments, the compound of formula (II-ii) is represented by formula (II-ii-b) wherein G has the values described herein.

In some embodiments, the compound of formula (I) is represented by formula (III-a), (III-b), or (III-c):

In some embodiments, the compound of formula (I) is represented by formula (IV-a), (IV-b), or (IV-c):

wherein X1, X2, n, and R3have the values described herein. In certain embodiments, the compound of formula (IV) is represented by formula (IV-a) wherein X1, X2, n, and R3have the values described herein. In certain embodiments, the compound of formula (IV) is represented by formula (IV-b) wherein X1, X2, n, and R3have the values described herein. In certain embodiments, the compound of formula (IV) is represented by formula (IV-c) wherein X1, X2, n, and R3have the values described herein.

The values described below for each variable are with respect to any of formulas (I), (II), (III), (IV), or their sub-formulas as described above.

The variable X1is CH or N. The variable X2is CH or N. In some embodiments, at least one of X1and X2is CH. In certain embodiments, X1is CH and X2is CH. In certain embodiments, X1is CH and X2is N. In certain embodiments, X1is N and X2is CH. In certain embodiments, X1is N and X2is N.

In some embodiments, R1aand R1bare taken together to form an oxo group.

Each occurrence of the variable R1cis independently hydrogen, fluoro, C1-4alkyl, or C1-3fluoroalkyl. In some embodiments, each occurrence of R1cis independently hydrogen, fluoro, or methyl. In certain embodiments, each occurrence of R1cis independently hydrogen or methyl. In certain embodiments, R1cis hydrogen.

The variable n is 1-2. In some embodiments, n is 1.

When R1aand R1bare not taken together to form an oxo group, the variable G is —R3, —V1—R3, —V1-L1-R3, -L2-V1—R3, -L2-V2—R3, or -L1-R3, wherein L1, L2, V1, V2, and R3have the values described herein. In some such embodiments, G is —V1—R3, or —V1-L1-R3, wherein L1, V1, and R3have the values described herein. In certain such embodiments, G is —V1—R3, wherein V1, and R3have the values described herein.

When R1aand R1bare taken together to form an oxo group, G is —R3, or -L1-R3, wherein L1, and R3have the values described herein. In some such embodiments, G is —R3, wherein R3has the values described herein.

The variable L2is an unsubstituted or substituted C2-3alkylene chain. In some embodiments, L2is —CH2CH2— or —CH2CH2CH2—.

Each occurrence of the variable RAis independently hydrogen, halo, or an optionally substituted C1-4aliphatic group. In some embodiments, each occurrence of RAis independently hydrogen, fluoro or methyl. In certain embodiments, RAis hydrogen.

Each occurrence of the variable R4ais independently hydrogen, or unsubstituted or substituted C1-4aliphatic. In certain embodiments, R4ais hydrogen.

In some embodiments, R3is unsubstituted or substituted C1-6aliphatic, unsubstituted or substituted 3-10-membered cycloaliphatic, unsubstituted or substituted 4-10-membered heterocyclyl having 1-5 heteroatoms independently selected from nitrogen, oxygen, and sulfur, unsubstituted or substituted 6-10-membered aryl, or unsubstituted or substituted 5-10-membered heteroaryl having 1-5 heteroatoms independently selected from nitrogen, oxygen, and sulfur; whereineach substitutable carbon chain atom in R3is unsubstituted or substituted with 1-2 occurrences of —R5dd;each substitutable saturated ring carbon atom in R3is unsubstituted or substituted with ═O, ═S, ═C(R5)2, ═N—R5or —R5a;each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a;each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;wherein R5dd, R5, R5a, and R9bhave the values described herein.

In certain embodiments, R3is unsubstituted or substituted C1-6aliphatic, unsubstituted or substituted 3-10-membered cycloaliphatic, unsubstituted or substituted 4-10-membered heterocyclyl having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, unsubstituted or substituted 6-10-membered aryl, or unsubstituted or substituted 5-10-membered heteroaryl having 1-5 heteroatoms independently selected from nitrogen, oxygen, and sulfur; wherein:each substitutable carbon chain atom in R3is unsubstituted or substituted with 1-2 occurrences of —R5dd;each substitutable saturated ring carbon atom in R3is unsubstituted or substituted with —R5a;each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a;the total number of R5asubstituents is p; andeach substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;wherein R5dd, R5a, R9band p have the values described herein.

Each R4is independently hydrogen, unsubstituted or substituted C1-6aliphatic, unsubstituted or substituted 3-10-membered cycloaliphatic, unsubstituted or substituted 4-10-membered heterocyclyl having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, unsubstituted or substituted 6-10-membered aryl, or unsubstituted or substituted 5-10-membered heteroaryl having 1-5 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or two R4on the same nitrogen atom, taken together with the nitrogen atom, form an unsubstituted or substituted 5- to 6-membered heteroaryl or an unsubstituted or substituted 4- to 8-membered heterocyclyl having, in addition to the nitrogen atom, 0-2 ring heteroatoms selected from nitrogen, oxygen, and sulfur.

Each R6is independently unsubstituted or substituted C1-6aliphatic, or unsubstituted or substituted 6-10-membered aryl.

The variable p is 1-2. In some embodiments, p is 1.

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a; and

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;

each substitutable saturated ring carbon atom in R3is unsubstituted or substituted with ═O, ═S, ═C(R5)2, ═N—R5or —R5a;

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a;

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;

wherein R5, R5a, and R9bhave the values described herein.

In certain embodiments, R3is unsubstituted or substituted 3-10-membered cycloaliphatic, unsubstituted or substituted 4-10-membered heterocyclyl having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, unsubstituted or substituted 6-10-membered aryl, or unsubstituted or substituted 5-10-membered heteroaryl having 1-5 heteroatoms independently selected from nitrogen, oxygen, and sulfur, wherein:each substitutable saturated ring carbon atom in R3is unsubstituted or substituted with —R5a;each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a;the total number of R5asubstituents is p; andeach substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;wherein R5a, R9band p have the values described herein.

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a; and

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;

each substitutable saturated ring carbon atom in R3is unsubstituted or substituted with ═O, ═S, ═C(R5)2, ═N—R5or —R5a;

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with —R5a;

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b;

wherein R5aand R9bhave the values described herein.

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with 1-2 occurrences of —R5a;

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b; and

each substitutable unsaturated ring carbon atom in R3is unsubstituted or is substituted with 1-2 occurrences of —R5a;

each substitutable ring nitrogen atom in R3is unsubstituted or substituted with —R9b; and

In some embodiments, when R1aand R1bare not taken together to form an oxo group, G is:

wherein X and Ring C have the values described herein.

In certain such embodiments, G is:

wherein Ring C has the values described herein.

The variable X is —C(O)— or -L2a-R3aa—V2a—, wherein L2a, R3aa, and V2ahave the values described herein. In some embodiments, X is —C(O)—. In some embodiments, X is -L2a-R3aa—V2a—, wherein L2a, R3aa, and V2ahave the values described herein. In some embodiments, X is —C(O)—,

wherein V2aand t have the values described herein.

In certain embodiments, X is —C(O)—,

Ring C is a 4-7 membered heterocyclic ring containing one nitrogen atom, wherein the nitrogen atom is not the atom bound to X, and wherein the nitrogen atom in Ring C is substituted with R9bband Ring C is unsubstituted or substituted by 1-4 occurrences of R5b; wherein R9bb, X, and R5bhave the values described herein. In some embodiments, Ring C is a 4-7 membered heterocyclic ring containing one nitrogen atom, wherein the nitrogen atom is not the atom bound to X, and wherein the nitrogen atom in Ring C is substituted with R9bband Ring C is unsubstituted or substituted by 1-2 occurrences of R5b; wherein R9bb, X, and R5bhave the values described herein.

In certain embodiments, Ring C is:

wherein Ring C is unsubstituted or substituted with 1 occurrence of R5b, wherein R9bband R5bhave the values described herein. In certain embodiments, Ring C is:

wherein R9bb, z and R5bbhave the values described herein.

The variable V2ais a bond, —NH—C(O)—, —NH—S(O)2—, or —NH—C(O)—NH—. In some embodiments, V2ais a bond or —NH—C(O)—. In certain embodiments, V2ais a bond. In certain embodiments, V2ais —NH—C(O)—.

The variable t is 0-2. In some embodiments, t is 0-1. In certain embodiments, t is 0. In certain embodiments, t is 1. In certain embodiments, t is 2.

The variable L2ais a bond or unsubstituted or substituted C1-3alkylene chain. In some embodiments, L2ais a bond, —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain embodiments, L2ais a bond. In certain embodiments, L2ais —CH2—. In certain embodiments, L2ais —CH2CH2—.

The variable R3aais a 6-membered aromatic ring containing 0-2 nitrogen atoms which is unsubstituted or substituted with 1-2 independent occurrences of R4c, wherein R4chas the values described herein. In some embodiments, R3aais phenyl or pyridyl, each of which is unsubstituted or substituted with 1-2 independent occurrences of R4c, wherein R4chas the values described herein. In some embodiments, R3aais:

wherein each ring is unsubstituted or substituted with 1-2 independent occurrences of R4c.

The variable z is 0-1. In some embodiments, z is 0. In some embodiments, z is 1.

Each occurrence of the variable R5bis independently chloro, fluoro, hydroxy, methyl, ethyl, methoxy, ethoxy, trifluoromethyl, trifluoromethoxy, —C(O)NH2, or —CO2H. In some embodiments, each occurrence of the variable R5bis independently chloro, fluoro, hydroxy, methyl, or ethyl. In certain embodiments, each occurrence of the variable R5bis methyl.

The variable R5bbis hydrogen or methyl. In some embodiments, R5bbis hydrogen. In some embodiments, R5bbis methyl.

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1cis independently hydrogen, fluoro, or methyl; and

wherein G has the values described herein.

In such embodiments, when R1aand R1bare not taken together to form an oxo group;

G is —V1—R3, or —V1-L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein R3has the values described herein.

In such embodiments, where R1aand R1bare taken together to form an oxo group;

G is —R3, or -L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein L1and R3have the values described herein.

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1cis independently hydrogen, fluoro, or methyl; and

wherein G has the values described herein.

In such embodiments, when R1aand R1bare not taken together to form an oxo group;

G is —V1—R3, or —V1-L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein R3has the values described herein.

In such embodiments, where R1aand R1bare taken together to form an oxo group;

G is —R3, or -L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein L1and R3have the values described herein.

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1cis independently hydrogen, fluoro, or methyl; and

wherein G has the values described herein.

In such embodiments, when R1aand R1bare not taken together to form an oxo group;

G is —V1—R3, or —V1-L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein R3has the values described herein.

In such embodiments, where R1aand R1bare taken together to form an oxo group;

G is —R3, or -L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein L1and R3have the values described herein.

In certain embodiments, the compound of formula (I) is represented by:

n is 1-2;

each occurrence of R1dis independently hydrogen, fluoro, or methyl; and

wherein Ring C and X have the values described herein.

In such embodiments:

n is 1;

In certain embodiments, the compound of formula (I) is represented by:

n is 1-2;

Ring C is unsubstituted or substituted with one occurrence of R5b; and

In certain such embodiments,

n is 1; and

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

R5bbis hydrogen or methyl; and

z has the values described herein.

In certain such embodiments,

z is 1.

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

R5bbis hydrogen or methyl; and

z has the values described herein.

In certain such embodiments,

z is 1.

In certain embodiments, the compound of formula (I) is represented by:

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

R5bbis hydrogen or methyl; and

z has the values described herein.

In certain such embodiments,

z is 1.

In certain embodiments, the compound of formula (I) is represented by:

G is —V1—R3, or —V1-L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein R3has the values described herein.

In certain such embodiments, the compound of formula (I) is represented by formula (I-a). In certain such embodiments, the compound of formula (I) is represented by formula (I-b). In certain such embodiments, the compound of formula (I) is represented by formula (I-c). In certain such embodiments, the compound of formula (I) is represented by formula (I-d). In certain such embodiments, the compound of formula (I) is represented by formula (I-e). In certain such embodiments, the compound of formula (I) is represented by formula (I-f). In certain such embodiments, the compound of formula (I) is represented by formula (I-g). In certain such embodiments, the compound of formula (I) is represented by formula (I-h).

In certain such embodiments, the compound of formula (I) is represented by formula (I-a), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-b), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-c), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-d), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-e), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-f), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-g), wherein R1bis hydrogen, and R1dis hydrogen. In certain such embodiments, the compound of formula (I) is represented by formula (I-h), wherein R1bis hydrogen, and R1dis hydrogen.

In certain such embodiments, the compound of formula (I) is represented by:

G is —R3, or -L1-R3;

each occurrence of R1dis independently hydrogen, fluoro, or methyl;

wherein L1and R3have the values described herein.

In certain such embodiments, the compound of formula (I) is represented by formula (I-i). In certain such embodiments, the compound of formula (I) is represented by formula (I-j). In certain such embodiments, the compound of formula (I) is represented by formula (I-k). In certain such embodiments, the compound of formula (I) is represented by formula (I-l). In certain such embodiments, the compound of formula (I) is represented by formula (I-m). In certain such embodiments, the compound of formula (I) is represented by formula (I-n). In certain such embodiments, the compound of formula (I) is represented by formula (I-o). In certain such embodiments, the compound of formula (I) is represented by formula (I-p).

In certain such embodiments, the compound of formula (I) is represented by formula (I-i), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-j), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-k), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-l), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-m), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-n), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-o), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—. In certain such embodiments, the compound of formula (I) is represented by formula (I-p), wherein R1dis hydrogen; and L1is —CH2—, —CH2CH2—, or —CH2CH2CH2—.

Representative examples of compounds of formula (I) are shown in Table 1:

The compounds in Table 1 above may also be identified by the following chemical names:

I-12-(4-tert-butylbenzoyl)-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-27-(biphenyl-4-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-3N-hydroxy-2-(imidazo[1,2-a]pyridin-2-ylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-42-(2,5-dimethyl-3-furoyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-5N-hydroxy-2-({4-methyl-2-[4-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrol-5-yl}carbonyl)-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-6N-hydroxy-5-[(1-methylcyclohexyl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-7N-hydroxy-2-[(5-methyl-1-phenyl-1H-pyrazol-4-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-8N-hydroxy-5-{[1-(trifluoromethyl)cyclopropyl]carbonyl}-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-9N-hydroxy-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-102-(1-benzothien-3-ylcarbonyl)-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-115-[(4,5-dichloro-1-methyl-1H-pyrrol-2-yl)carbonyl]-N-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-125-(4-fluorobenzyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-13N-hydroxy-7-(4-methoxybenzoyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-14N-hydroxy-7-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-152-[(4-acetyl-3,5-dimethyl-1H-pyrrol-2-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-165-(1-adamantylcarbonyl)-N-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-175-[4-(benzyloxy)benzoyl]-N-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-182-(4-tert-butylbenzoyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-192-(cyclopentylcarbonyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-20N-hydroxy-2-[(1-methyl-1H-indol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-217-(1-benzofuran-2-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-22N-hydroxy-2-[(5-methyl-1H-indol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-232-benzyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-245-(cyclohexylmethyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-25N-hydroxy-2-(quinolin-4-ylcarbonyl)-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-26N-hydroxy-7-[(1-methylcyclohexyl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-277-[1-adamantylcarbonyl]-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-282-[(3,5-dimethyl-1H-indol-2-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-29N-hydroxy-2-(1H-indol-2-ylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-30N-hydroxy-2-(2-thienylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-31N-hydroxy-5-[(1-methyl-1H-indol-2-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-32N-hydroxy-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-33N-hydroxy-2-[4-(trifluoromethyl)benzoyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-342-{[1-(4-chlorophenyl)cyclopropyl]carbonyl}-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-352-{[2,5-dimethyl-1-(2-thienylmethyl)-1H-pyrrol-3-yl]carbonyl}-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-365-(2,2-dimethylpropanoyl)-N-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-375-[2-(4-chlorophenyl)-2-methylpropanoyl]-N-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-382-[1-adamantylcarbonyl]-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-39N-hydroxy-2-[(1-methyl-1H-pyrazol-3-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-402-[(3,5-dimethyl-1H-pyrrol-2-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-417-(2,2-dimethylpropanoyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-422-benzyl-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-43N-hydroxy-2-(4-methylbenzoyl)-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-447-(1-benzothien-2-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-457-(4-tert-butylbenzoyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-46N-hydroxy-5-isopropyl-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-472-{[5-(aminosulfonyl)-1-methyl-1H-pyrrol-2-yl]carbonyl}-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-48N-hydroxy-4-oxo-5-(2-phenoxyethyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-492-benzyl-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-50N-hydroxy-5-(4-methylpentyl)-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-512-(biphenyl-4-ylcarbonyl)-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-522-[(1,5-dimethyl-1H-pyrazol-3-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-53N-hydroxy-5-(4-methoxybenzoyl)-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-54N-hydroxy-2-[3-(methylsulfonyl)benzoyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-55N-hydroxy-7-[(2-methyl-1,3-thiazol-4-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-562-(4-chlorobenzoyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-577-(4-chlorobenzoyl)-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-58N-hydroxy-2-[(1-methyl-1H-indol-3-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-592-(3,3-dimethylbutanoyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-607-[(3-chloro-1-benzothien-2-yl)carbonyl]-N-hydroxy-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-612-[(3,5-dimethylisoxazol-4-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-622-[1-adamantylcarbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-632-[(3-tert-butyl-1-methyl-1H-pyrazol-5-yl)carbonyl]-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-64N-hydroxy-2-{[1-phenyl-5-(trifluoromethyl)-1H-pyrazol-4-yl]carbonyl}-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-65N-hydroxy-4-oxo-5-(3-phenylpropyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-66N-hydroxy-2-[(2-methyl-4,5,6,7-tetrahydro-2H-indazol-3-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-675-(4-tert-butylbenzyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-68N-hydroxy-2-(4-methoxybenzoyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-69N-hydroxy-2-[(5-methyl-2-thienyl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo [1,2-a][1,4]diazepine-8-carboxamideI-70N-hydroxy-5-[(5-pyridin-2-yl-2-thienyl)carbonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-71N-hydroxy-5-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-725-(1-adamantylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-73N-hydroxy-2-[(2-methyl-1,3-thiazol-4-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-74N-hydroxy-2-[(1-methylcyclohexyl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-75N-hydroxy-2-(1H-indol-3-ylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-76N-hydroxy-5-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-77N-hydroxy-5-(3-methylbutyl)-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-78N-hydroxy-2-[(2-methyl-1,3-thiazol-4-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-792-(2,6-dichlorobenzoyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-80N-hydroxy-2-[(4′-methylbiphenyl-4-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-815-benzyl-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-82N-hydroxy-2-[(5-methyl-2-phenyl-1,3-oxazol-4-yl)acetyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-835-(cyclopropylmethyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-84N-hydroxy-2-(pyrazolo[1,5-a]pyrimidin-3-ylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-852-(2,5-dimethyl-3-furoyl)-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-862-butyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-87N-hydroxy-2-[(2-methyl-1,5-diphenyl-1H-pyrrol-3-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-885-(2-ethoxyethyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-89N-hydroxy-2-[(1-methyl-1H-indol-5-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-90N-hydroxy-5-[(2-methyl-1,3-thiazol-4-yl)acetyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-912-[(4,5-dichloro-1-methyl-1H-pyrrol-2-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-9212-(cyclohexylcarbonyl)-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-93N-hydroxy-5-[(5-methyl-1H-indol-3-yl)acetyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-942-[(2,5-dimethyl-1H-pyrrol-3-yl)carbonyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-952-[(3-ethyl-1-methyl-1H-pyrazol-5-yl)carbonyl]-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-962-(1-benzothien-3-ylcarbonyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-97N-hydroxy-5-[(3-methyl-1-benzothien-2-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-985-(1-benzothien-2-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-99N-hydroxy-2-[(5-methyl-1-phenyl-1H-pyrazol-4-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-100N-hydroxy-5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-101N-hydroxy-7-[(4-methyl-2-pyridin-2-yl-1,3-thiazol-5-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-102N-hydroxy-5-(1H-indol-3-ylacetyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-103N-hydroxy-4-oxo-5-[3-(trifluoromethyl)benzyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-1042-[(4,5-dichloro-1-methyl-1H-pyrrol-2-yl)carbonyl]-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-105N-hydroxy-5-[(1-methyl-1H-indol-2-yl)carbonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-106N-hydroxy-5-(3-phenylpropanoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-107N-hydroxy-5-(quinolin-8-ylcarbonyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-108N-hydroxy-5-[(3-methyl-1-benzofuran-2-yl)carbonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamideI-109N-hydroxy-4-oxo-5-[3-(1H-pyrrol-1-yl)propyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-1105-(3-chlorobenzyl)-N-hydroxy-4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-1112-(cyclohexylcarbonyl)-N-hydroxy-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-112N7-(2-tert-butylphenyl)-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-113N7-[1-adamantyl]-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-114N7-biphenyl-2-yl-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-115N7-(2,6-diethylphenyl)-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-116N2-hydroxy-N7-phenyl-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-117N2-hydroxy-N7-(2-methylphenyl)-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-118N7-(sec-butyl)-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-119N7-(tert-butyl)-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-120N2-hydroxy-N7-(2-phenylethyl)-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-121N7-cyclohexyl-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-122N2-hydroxy-N7-(5-methyl-3-phenylisoxazol-4-yl)-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-123N7-benzyl-N2-hydroxy-5,6-dihydroimidazo[1,2-a]pyrazine-2,7(8H)-dicarboxamideI-124N-hydroxy-1-oxo-2-[4-(trifluoromethyl)benzyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1252-(1-benzothien-2-ylcarbonyl)-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-126N-hydroxy-1-oxo-2-[3-(trifluoromethoxy)benzyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1271-ethyl-N-hydroxy-2-[(1-methylpiperidin-4-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-128N-hydroxy-3-methyl-2-[(1-methylpiperidin-4-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1291-ethyl-N-hydroxy-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-130N-hydroxy-1-isopropyl-2-{[4-(trifluoromethyl)phenyl]sulfonyl}-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-131N-hydroxy-1-methyl-2-[(1-methylpiperidin-4-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-132N2-1-adamantyl-N7-hydroxy-1-methyl-3,4-dihydropyrrolo[1,2-a]pyrazine-2,7(1H)-dicarboxamideI-1332-cyclopropyl-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-134N-hydroxy-1-methyl-2-[(1-methyl-1H-indol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1355-(1-adamantylcarbonyl)-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-136N-hydroxy-4,4-dimethyl-2-[(1-methyl-1H-indol-2-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1372-(2,2-dimethylpropanoyl)-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1382-(3-cyanobenzyl)-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1397-[(dimethylamino)acetyl]-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1405-(1-benzothien-2-ylcarbonyl)-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-141N-hydroxy-7-[(1-methyl-1H-indol-2-yl)carbonyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-142N5-cyclohexyl-N2-hydroxy-4-methyl-6,7-dihydropyrazolo[1,5-a]pyrazine-2,5(4H)-dicarboxamideI-143N-hydroxy-3-methyl-1-oxo-2-[4-(1H-pyrazol-1-yl)benzyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1442-(4-tert-butylbenzyl)-N-hydroxy-4,4-dimethyl-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-145N-hydroxy-4,4-dimethyl-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1462-(4-fluorobenzyl)-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-147N-hydroxy-4,4-dimethyl-2-[(1-methylpiperidin-4-yl)carbonyl]-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1485-(2,2-dimethylpropanoyl)-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-1492-(1-adamantylcarbonyl)-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1502-[(dimethylamino)acetyl]-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1517-[(dimethylamino)acetyl]-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1522-[(5-chloro-1-benzothien-3-yl)methyl]-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-153N2-(tert-butyl)-1-ethyl-N7-hydroxy-3,4-dihydropyrrolo[1,2-a]pyrazine-2,7(1H)-dicarboxamideI-154N-hydroxy-1-oxo-2-[4-(trifluoromethyl)benzyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1552-(cyclopentylacetyl)-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1561-ethyl-N-hydroxy-2-[(1-methyl-1H-indol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-157N-hydroxy-7-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-1582-(biphenyl-4-ylcarbonyl)-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1592-(3-cyanobenzyl)-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-160N-hydroxy-8-methyl-7-[(1-methylpiperidin-4-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1612-(1-adamantylcarbonyl)-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1622-(1-benzothien-2-ylcarbonyl)-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-163N-hydroxy-1-oxo-2-[3-(trifluoromethoxy)benzyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1641-ethyl-N-hydroxy-2-(propylsulfonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1652-(1-adamantylcarbonyl)-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-166N-hydroxy-8-methyl-7-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1677-(biphenyl-4-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-1682-(cyclopentylacetyl)-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-169N-hydroxy-8-isopropyl-7-[(1-methylpiperidin-4-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1707-(biphenyl-4-ylcarbonyl)-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-171N-hydroxy-3-methyl-1-oxo-2-[3-(trifluoromethyl)benzyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-172N-hydroxy-8-isopropyl-7-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1737-(1-benzothien-2-ylcarbonyl)-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-174N-hydroxy-4-methyl-5-[(1-methylpiperidin-4-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-1752-(4-fluorobenzyl)-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-176N-hydroxy-8-isopropyl-7-{[4-(trifluoromethyl)phenyl]sulfonyl}-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1777-(1-adamantylcarbonyl)-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-178N-hydroxy-1-oxo-2-(quinolin-8-ylmethyl)-2,3,4,5-tetrahydro-1H-pynolo[1,2-a][1,4]diazepine-8-carboxamideI-1797-(cyclopentylacetyl)-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-180N-hydroxy-4,4-dimethyl-2-[(5-methyl-3-phenylisoxazol-4-yl)methyl]-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1817-(1-adamantylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-1822-(1-benzothien-2-ylcarbonyl)-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-183N-hydroxy-1-oxo-2-(quinolin-8-ylmethyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-184N-hydroxy-3-methyl-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1852-(biphenyl-4-ylcarbonyl)-N-hydroxy-4,4-dimethyl-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1862-(3-chlorobenzyl)-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-187N2-1-adamantyl-N8-hydroxy-4,4-dimethyl-4,5-dihydro-1H-pyrrolo[1,2-a][1,4]diazepine-2,8(3H)-dicarboxamideI-1882-[(dimethylamino)acetyl]-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1892-[3-(4-fluorophenoxy)benzyl]-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1907-(1-benzothien-2-ylcarbonyl)-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1912-(biphenyl-2-ylmethyl)-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1927-(2,2-dimethylpropanoyl)-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-1932-[3-(4-fluorophenoxy)benzyl]-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-1947-(2,2-dimethylpropanoyl)-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-195N-hydroxy-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-3-phenyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1967-(cyclopentylacetyl)-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-197N-hydroxy-2-[(5-methyl-3-phenylisoxazol-4-yl)methyl]-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1982-(cyclopropylmethyl)-N-hydroxy-3-methyl-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-1997-[(dimethylamino)acetyl]-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2002-ethyl-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-2012-(2,2-dimethylpropanoyl)-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-202N-hydroxy-4-methyl-5-[(1-methyl-1H-indol-2-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-2032-(2,2-dimethylpropanoyl)-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-204N-hydroxy-7-[(1-methylpiperidin-4-yl)carbonyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2052-[(dimethylamino)acetyl]-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2067-(2,2-dimethylpropanoyl)-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-2072-cyclopropyl-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-208N-hydroxy-8-isopropyl-7-[(1-methyl-1H-indol-2-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-2092-ethyl-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2102-[(5-chloro-1-benzothien-3-yl)methyl]-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-211N-hydroxy-8-methyl-7-[(1-methyl-1H-indol-2-yl)carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-212N-hydroxy-4,4-dimethyl-2-(3-methylbutyl)-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-213N-hydroxy-7-{[4-(trifluoromethyl)phenyl]sulfonyl}-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2145-(cyclopentylacetyl)-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-2152-(3-chlorobenzyl)-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-216N-hydroxy-1-methyl-2-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-217N-hydroxy-7-(propylsulfonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2182-(1-adamantylcarbonyl)-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-219N-hydroxy-4-methyl-5-[(1-methyl-1H-pyrrol-2-yl)carbonyl]-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-2202-(biphenyl-2-ylmethyl)-N-hydroxy-1-oxo-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxamideI-2217-(cyclopentylacetyl)-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2222-(cyclopentylacetyl)-N-hydroxy-3-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2232-(1-benzothien-2-ylcarbonyl)-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-224N-hydroxy-3-methyl-2-[(1-methyl-1H-indol-2-yl)carbonyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2252-(cyclopentylacetyl)-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2262-(biphenyl-4-ylcarbonyl)-1-ethyl-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2277-(1-adamantylcarbonyl)-N-hydroxy-8-isopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-2282-[(dimethylamino)acetyl]-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2295-(biphenyl-4-ylcarbonyl)-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-2307-(1-benzothien-2-ylcarbonyl)-N-hydroxy-5,6,7,8-tetrahydro[1,2,4]triazolo[1,5-a]pyrazine-2-carboxamideI-2315-[(dimethylamino)acetyl]-N-hydroxy-4-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamideI-2322-(biphenyl-4-ylcarbonyl)-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2332-(2,2-dimethylpropanoyl)-N-hydroxy-1-methyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2347-(biphenyl-4-ylcarbonyl)-N-hydroxy-8-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-235N-hydroxy-7-{-3-[(pyrrolidin-3-ylamino)carbonyl]benzyl}-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-236N-hydroxy-2-[(1-isopropylpiperidin-4-yl)methyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-237N-hydroxy-7-[(2-{[(4-methylpiperidin-4-yl)carbonyl]amino}pyridin-4-yl)methyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamideI-238N-hydroxy-2-(4-{[(1-methylpiperidin-4-yl)carbonyl]amino}benzyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2392-[(1-ethylpiperidin-4-yl)methyl]-N-hydroxy-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-240N-hydroxy-1-oxo-2-[4-(trifluoromethl)benzyl]-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamideI-2412-(cyclopropylmethyl)-N-hydroxy-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxamide
3. General Synthetic Methods and Intermediates

The compounds of the present invention can be prepared by methods known to one of ordinary skill in the art and/or by reference to the schemes shown below and the synthetic examples. Exemplary synthetic routes are set forth in Schemes below, and in the Examples.

Scheme 1 shows a general route for preparing compounds represented by formula vi. Starting from one of the following: diethyl 1H-pyrrole-2,4-dicarboxylate (prepared as described by Bhattacharya et al.,Tetrahedron Lett.2006, 47(31):5481-5484); 1H-1,2,4-triazole-3,5-dicarboxylic acid, 3,5-diethyl ester (commercially available); diethyl 3,5-pyrazoledicarboxylate (commercially available); or diethyl 5-amino-1H-imidazole-2,4-dicarboxylate (commercially available) compounds of formula v can be prepared in a sequence analogous to that described by Askew et al.,Bioorg. Med. Chem. Lett.1995, 5(5):475.

Treatment of azole i with a dihaloalkane such as dibromoethane in the presence of a base with heating (Method A; see also Pratt, et al.,Bioorg. Med. Chem. Lett.2000, 10:2749) provides access to ii. Displacement of the pendant halide of ii with sodium azide (Method B, see Colombano et al.,J. Med. Chem.2010, 53: 616-623) affords iii which upon application of reducing conditions such as a palladium metal catalyst in a hydrogen atmosphere (Method C) provides access to the corresponding primary amine iv. Primary amine iv can be cyclized with heating in the presence of base (Method D) to generate lactam v. Removal of the amide carbonyl is accomplished via reduction in the presence of a suitable hydride delivery agent such as BH3.THF (Method E) as described by Di Fabio et al.,J. Med. Chem.2009, 52:3238-3247.

Scheme 2 shows a general route for preparing compounds represented by formula xii. Sulfonamide viii can be prepared from the reaction of propargyl amine with o-nitrobenzene sulfonyl chloride (Method F). Alkylation of the sulfonamide can be effected upon treatment with a dihaloalkane such as 1-bromo-2-chloroethane in the presence of a base such as cesium carbonate with heating (Method G). A 3+2 sigmatropic cyclization of the terminal acetylene with ethyl diazoacetate in a solvent such as benzene using a sealed tube with heating results in the construction of the pyrazole ring in compounds of formula x (Method H) in a fashion similar as described by Zrinski et al.,Heterocycles2006, 68(9):1961. An intramolecular cyclization onto the pendant aliphatic chlorine with a pyrazole nitrogen can be achieved through additional heating in the presence of a base such as cesium carbonate (Method I). Removal of the o-nitro sulfonamide protecting group is achieved by treatment with thiophenol as described by Fukuyama et al.,Tetrahedron Lett.1995, 36(36):6373 (Method J). This route can also be employed using substituted propargyl amines (racemic or optically pure) and substituted dihaloalkenes.

Scheme 3 shows a general route for the preparation of compounds of the type represented by formula xviii. Racemic or optically pure isonitriles (xiii) prepared from the corresponding β-amino acids (Sureshbabu et al.,J. Org. Chem.2009, 74:153) can be reacted with ethyl propiolate (xiv) to construct the pyrrole ring of xv through a 3+2 cycloaddition (Method K). Treatment of xv with a dihaloalkane such as dibromoethane in the presence of a base with heating (Method A) affords xvi. Formation of the tetrahydropyrrolopyrazine ring system of xvii can be carried out though the deprotonation of the carbamate nitrogen with sodium hydride, LDA or Cs2CO3followed by cyclization onto the pendent bromide (Method L; Yamaguchi et al.,Chemistry Lett.1996, 8:621). Removal of the Fmoc protecting group using piperidine (Method M) provides compounds of formula xviii.

Scheme 4 shows a general route for the preparation of substituted compounds of the type represented by formula xx. Racemic or optically pure substituted 2-(aminomethyl)-1H-imidazole-4-carboxylate esters depicted by xix (prepared as described by You et al.,Organic Letters2004, 6:1681, can be converted to the tetrahydroimidazopyrazine xx (Methods A, L and M) in a fashion analogous to that depicted in Scheme 3.

Scheme 5 shows a general route for the preparation of compounds of the type represented by formula xxii. The Boc protecting group on 7-tert-butyl 2-ethyl 5,6-dihydro-[1,2,4]triazolo[1,5-a]pyrazine-2,7(8H)-dicarboxylate (xxi) (prepared as described by Carling et al., WO 00/023449) can be removed upon treatment with an acid such as HCl or TFA (Method N).

Scheme 6 shows a route for the preparation of substituted azole compounds of formula xxv. Reaction of the secondary amines represented by compounds of formula xxiii with carboxylic acids (R3—CO2H) employing coupling agents such as HBTU or HATU leads to the formation of the corresponding amide xiv (Method O). Conversion of the ethyl ester in xxiv to a hydroxamate is conducted by reaction with the potassium salt of hydroxylamine (Method P; Huang et al.,J. Med. Chem.2009, 52(21):6757) leading to the formation of compounds of formula xxv.

Scheme 7 shows a route for the preparation of substituted azole compounds of formula xxvii. Reaction of the secondary amine in compounds represented by xxiii with sulfonyl chlorides (Method Q) leads to the formation of the corresponding sulfonamide xxvi. Conversion of xxvi to the corresponding hydroxamate is carried out in an analogous fashion as shown in Scheme 6 (Method P) leading to the formation of compounds of formula xxvii.

Scheme 8 shows a route for the preparation of substituted azole compounds of formula xxix. The reaction of the compounds of formula xxiii with the isocyanates (R3—NCO; Method R) leads to the formation of the corresponding ureas of formula xxviii. Conversion of xxviii to the corresponding hydroxamate is carried out in an analogous fashion as shown in Scheme 6 (Method P) leading to the formation of compounds of formula xxix.

Scheme 9 shows a route for the preparation of substituted azole compounds of formula xxxi. Treatment of amine xxiii with either an aldehyde under standard reductive amination conditions, (i.e. in the presence of a borohydride such as sodium cyanoborohydride, Method S) or an alkyl halide in an SN2 fashion (Method T) affords the tertiary amine xxx. The secondary amine xxiii may also be arylated using standard nucleophilic aromatic substitution of a suitable eletrophile such as 2-chloro-nitropyridine, in the presence of suitable base, such as DIPEA at elevated temperatures (Method U). Amine xxiii may also be N-arylated through a copper(II)-acetate mediated coupling with a suitable arylboronic acid (Method V; Chan et al.Tetrahedron Lett.1998, 39(19):2933). Conversion of xxx to the corresponding hydroxamate is carried out in an analogous fashion as shown in Scheme 6 (Method P) leading to the formation of compounds of formula xxxi.

4. Uses, Formulation and Administration

As discussed above, the present invention provides compounds and pharmaceutical compositions that are useful as inhibitors of HDAC enzymes, particularly HDAC6, and thus the present compounds are useful for treating proliferative, inflammatory, infectious, neurological or cardiovascular disorders.

The compounds and pharmaceutical compositions of the invention are particularly useful for the treatment of cancer. As used herein, the term “cancer” refers to a cellular disorder characterized by uncontrolled or disregulated cell proliferation, decreased cellular differentiation, inappropriate ability to invade surrounding tissue, and/or ability to establish new growth at ectopic sites. The term “cancer” includes, but is not limited to, solid tumors and bloodborne tumors. The term “cancer” encompasses diseases of skin, tissues, organs, bone, cartilage, blood, and vessels. The term “cancer” further encompasses primary and metastatic cancers.

In some embodiments, therefore, the invention provides the compound of formula (I), or a pharmaceutically acceptable salt thereof, for use in treating cancer. In some embodiments, the invention provides a pharmaceutical composition (as described herein) for the treatment of cancer comprising the compound of formula (I), or a pharmaceutically acceptable salt thereof. In some embodiments, the invention provides the use of the compound of formula (I), or a pharmaceutically acceptable salt thereof, for the preparation of a pharmaceutical composition (as described herein) for the treatment of cancer. In some embodiments, the invention provides the use of an effective amount of the compound of formula (I), or a pharmaceutically acceptable salt thereof, for the treatment of cancer.

Non-limiting examples of hematologic malignancies that can be treated with the disclosed inhibitors include acute myeloid leukemia (AML); chronic myelogenous leukemia (CML), including accelerated CML and CML blast phase (CML-BP); acute lymphoblastic leukemia (ALL); chronic lymphocytic leukemia (CLL); Hodgkin's disease (HD); non-Hodgkin's lymphoma (NHL), including follicular lymphoma and mantle cell lymphoma; B-cell lymphoma; T-cell lymphoma; multiple myeloma (MM); Waldenstrom's macroglobulinemia; myelodysplastic syndromes (MDS), including refractory anemia (RA), refractory anemia with ringed siderblasts (RARS), (refractory anemia with excess blasts (RAEB), and RAEB in transformation (RAEB-T); and myeloproliferative syndromes.

In some embodiments, compounds of the invention are suitable for the treatment of breast cancer, lung cancer, ovarian cancer, multiple myeloma, acute myeloid leukemia or acute lymphoblastic leukemia.

In other embodiments, compounds of the invention are suitable for the treatment of inflammatory and cardiovascular disorders including, but not limited to, allergies/anaphylaxis, acute and chronic inflammation, rheumatoid arthritis; autoimmunity disorders, thrombosis, hypertension, cardiac hypertrophy, and heart failure.

Accordingly, in another aspect of the present invention, pharmaceutical compositions are provided, wherein these compositions comprise any of the compounds as described herein, and optionally comprise a pharmaceutically acceptable carrier, adjuvant or vehicle. In certain embodiments, these compositions optionally further comprise one or more additional therapeutic agents.

It will also be appreciated that certain of the compounds of present invention can exist in free form for treatment, or where appropriate, as a pharmaceutically acceptable derivative thereof. According to the present invention, a pharmaceutically acceptable derivative includes, but is not limited to, pharmaceutically acceptable prodrugs, salts, esters, salts of such esters, or any other adduct or derivative which upon administration to a patient in need is capable of providing, directly or indirectly, a compound as otherwise described herein, or a metabolite or residue thereof.

As used herein, the term “pharmaceutically acceptable salt” refers to those salts which are, within the scope of sound medical judgement, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. A “pharmaceutically acceptable salt” means any non-toxic salt or salt of an ester of a compound of this invention that, upon administration to a recipient, is capable of providing, either directly or indirectly, a compound of this invention or an inhibitorily active metabolite or residue thereof. As used herein, the term “inhibitorily active metabolite or residue thereof” means that a metabolite or residue thereof is also an inhibitor of HDAC6.

In yet another aspect, a method for treating a proliferative, inflammatory, infectious, neurological or cardiovascular disorder is provided comprising administering an effective amount of a compound, or a pharmaceutical composition to a subject in need thereof. In certain embodiments of the present invention an “effective amount” of the compound or pharmaceutical composition is that amount effective for treating a proliferative, inflammatory, infectious, neurological or cardiovascular disorder, or is that amount effective for treating cancer. In other embodiments, an “effective amount” of a compound is an amount which inhibits binding of HDAC6, and thereby blocks the resulting signaling cascades that lead to the abnormal activity of growth factors, receptor tyrosine kinases, protein serine/threonine kinases, G protein coupled receptors and phospholipid kinases and phosphatases.

In some embodiments, a compound of formula (I) or a pharmaceutical composition thereof is administered in conjunction with an anticancer agent. As used herein, the term “anticancer agent” refers to any agent that is administered to a subject with cancer for purposes of treating the cancer. Combination therapy includes administration of the therapeutic agents concurrently or sequentially. Alternatively, the therapeutic agents can be combined into one composition which is administered to the patient.

Chemotherapeutic agents that disrupt cell replication include: paclitaxel, docetaxel, and related analogs; vincristine, vinblastin, and related analogs; thalidomide, lenalidomide, and related analogs (e.g., CC-5013 and CC-4047); protein tyrosine kinase inhibitors (e.g., imatinib mesylate and gefitinib); proteasome inhibitors (e.g., bortezomib); NF-κB inhibitors, including inhibitors of IκB kinase; antibodies which bind to proteins overexpressed in cancers and thereby downregulate cell replication (e.g., trastuzumab, rituximab, cetuximab, and bevacizumab); and other inhibitors of proteins or enzymes known to be upregulated, over-expressed or activated in cancers, the inhibition of which down-regulates cell replication. In certain embodiments, a compound of the invention is administered in conjunction with a proteasome inhibitor.

Another aspect of the invention relates to inhibiting HDAC6, activity in a biological sample or a patient, which method comprises administering to the patient, or contacting said biological sample with a compound of formula (I), or a composition comprising said compound. The term “biological sample”, as used herein, generally includes in vivo, in vitro, and ex vivo materials, and also includes, without limitation, cell cultures or extracts thereof; biopsied material obtained from a mammal or extracts thereof; and blood, saliva, urine, feces, semen, tears, or other body fluids or extracts thereof.

Still another aspect of this invention is to provide a kit comprising separate containers in a single package, wherein the inventive pharmaceutical compounds, compositions and/or salts thereof are used in combination with pharmaceutically acceptable carriers to treat disorders, symptoms and diseases where HDAC6 plays a role.

5. Preparation of Exemplary Compounds

EXPERIMENTAL PROCEDURES

Analytical Methods

NMR:1H NMR spectra are run on a 400 MHz Bruker unless otherwise stated.

LCMS: LC-MS spectra are run using an Agilent 1100 LC interfaced to a micromass Waters® Micromass® Zspray™ Mass Detector (ZMD).

HPLC: Preparative HPLC are conducted using 18×150 mm Sunfire C-18 columns eluting with water-MeCN gradients using a Gilson instrument operated by 322 pumps with the UV/visible 155 detector triggered fraction collection set to between 200 nm and 400 nm. Mass gated fraction collection is conducted on an Agilent 1100 LC/MSD instrument.

To a microwave vial containing 1-adamantanecarboxylic acid (0.05 g, 0.283 mmol) was added HATU (0.11 g, 0.283 mmol), triethylamine (0.11 mL, 0.772 mmol) and DMF (1.5 mL). The solution was allowed to stir at rt for 30 minutes before ethyl 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate Intermediate 5 (0.05 g, 0.257 mmol) was added to the solution. The solution was then allowed to stir at rt overnight and then evaporated. To the resulting residue was added DCE (3 mL) and water (1 mL). After separation, the aqueous phase was extracted with DCE (2×3 mL). The combined organic phases were concentrated to give a crude ethyl 2-(1-adamantylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate as a solid.

The following compounds were prepared in an analogous fashion to that described in Example 3 starting from the intermediates which were prepared as described above and the corresponding carboxylic acids.

The title compound was prepared in an analogous fashion to that described in Example 5 starting from the appropriate starting materials. Yield: 61%. LC-MS (FA): ES+272.

To a vial charged with ethyl 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate (0.0298 g, 0.143 mmol) was added cesium carbonate (0.061 g, 0.186 mmol), benzyl bromide (0.037 g, 0.2145 mmol), and acetonitrile (1 mL). The vial was capped and was shaken at 70° C. overnight. The solids were removed by filtration and the solution was concentrated to give crude ethyl 2-benzyl-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate Intermediate 12.

To a vial containing N-methylpyrrole-2-carboxylic acid (0.025 g, 0.2 mmol) was added HATU (0.076 g, 0.2 mmol), DCM (2 mL), and triethylamine (0.112 mL, 0.8 mmol). The solution was stirred at rt for 30 min then ethyl 2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxylate 2,2,2-trifluoroacetate (0.0644 g, 0.2 mmol) in DMF (0.5 mL) was added. The mixture was stirred at rt for 2 h. The reaction was quenched by addition of DCM (1 mL), sat. NaHCO3solution (0.5 mL), and water (1 mL). After separation, the aqueous layer was extracted with DCE (2×3 mL). The combined organic layers were concentrated to give crude ethyl 2-(1-methyl-1H-pyrrole-2-carbonyl)-2,3,4,5-tetrahydro-1H-pyrrolo[1,2-a][1,4]diazepine-8-carboxylate.

The following compounds were prepared in an analogous fashion to that described in Example 9 starting from the intermediates which were prepared as described above and the corresponding carboxylic acids.

Ethyl 5-[(2-nitrophenyl)sulfonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxylate (0.143 g, 0.362 mmol) was dissolved in a mixture of THF (4 mL) and methanol (1 mL) and to the solution was added 1.0 M of lithium hydroxide in water (1.5 mL, 1.5 mmol). The resulting mixture was stirred at room temperature for 2 hours. The mixture was concentrated, and the residue was dissolved in water (5 mL) and neutralized with 1.0 M hydrochloric acid in water (1.5 mL, 1.5 mmol). The resulting precipitate was collected via vacuum filtration to afford Intermediate 20 as a white solid (0.1166 g, 88%). LC-MS: (FA) ES+395.

To a solution of 5-[(2-nitrophenyl)sulfonyl]-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxylic acid (0.116 g, 0.316 mmol) and O-(tetrahydropyran-2-yl)hydroxylamine (0.0407 g, 0.347 mmol) in methylene chloride (2.5 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.144 g, 0.379 mmol) and N-methylmorpholine (0.1 mL, 0.9 mmol). The resulting reaction mixture was stirred at room temperature overnight. The solvent was evaporated and the residue obtained purified via silica chromatography (80-100% EtOAc/hexane) to afford Intermediate 21 as a clear colorless oil (0.152 g, 100%). LC-MS: (FA) ES+466.

To a mixture of ethyl 4,5,6,7-tetrandropyrazolo[1,5-a]pyrazine-2-carboxylate (0.029 g, 0.15 mmol) and 3-methylbenzo[b]thiophene-2-carboxylic acid (0.0314 g, 0.163 mmol) in methylene chloride (1.5 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.0678 g, 0.178 mmol) and N-methylmorpholine (0.05 mL, 0.446 mmol). The reaction mixture was stirred at room temperature overnight. The reaction was diluted with additional methylene chloride (1.5 mL) and was washed with aqueous NaHCO3(2 mL). The layers were separated and the aqueous layer was extracted with additional methylene chloride (3 mL) and the combined organic layers evaporated to dryness to give crude ethyl 5-(3-methylbenzo[b]thiophene-2-carbonyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate Intermediate 23.

The ethyl 5-(3-methylbenzo[b]thiophene-2-carbonyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate obtained in the previous step was dissolved in a mixture of tetrahydrofuran (1.8 mL) and methanol (0.3 mL). To the resulting solution was added 1M aqueous sodium hydroxide (0.4 mL, 0.4 mmol). The solution was stirred at room temperature for 4 hours whereupon the reaction was neutralized with the addition of 1M aqueous hydrochloric acid (0.4 mL). The solvents were evaporated under reduced pressure to afford crude Intermediate 24 as a white solid.

To a mixture of 5-(3-methylbenzo[b]thiophene-2-carbonyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylic acid obtained in the previous step and 0-(tetrahydropyran-2-yl)hydroxylamine (0.035 g, 0.3 mmol) in methylene chloride (1.5 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.085 g, 0.22 mmol) and N-methylmorpholine (0.05 mL, 0.44 mmol). The resulting mixture was stirred overnight at room temperature. The reaction was then diluted with additional methylene chloride (1.5 mL) and washed with aqueous NaHCO3(2 mL). The separated aqueous layer was extracted with methylene chloride (3 mL) and the combined organic layers were concentrated to afford crude Intermediate 25.

The following compounds were prepared in an analogous fashion to that described in Example 13 starting from the intermediates which were prepared as described above and the corresponding carboxylic acids.

To a mixture of ethyl 4,5,6,7-tetrandropyrazolo[1,5-a]pyrazine-2-carboxylate (0.02 g, 0.1 mmol) and indole-3-acetic acid (0.019 g, 0.11 mmol) in methylene chloride (1.5 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.046 g, 0.12 mmol) and N-methylmorpholine (0.02 mL, 0.2 mmol). The reaction mixture was stirred at room temperature overnight. The reaction was diluted with additional methylene chloride (1.5 mL) and washed with aqueous NaHCO3(2 mL). The layers were separated and the aqueous layer was extracted with additional methylene chloride (3 mL) and the combined organic layers evaporated to dryness to give crude ethyl 5-(2-(1H-indol-3-yl)acetyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate.

To a solution of ethyl 5-(2-(1H-indol-3-yl)acetyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate obtained in the previous step in methanol (0.5 mL) was added 1.7 M hydroxylamine potassium salt in methanol (0.5 mL, 0.85 mmol; prepared as described inJournal of Medicinal Chemistry2009, 52(21):6757). The reaction mixture was stirred at room temperature for 1 hour. Upon evaporation of the solvent, the resulting residue was dissolved in DMSO (1 mL) and purified using an Agilent 1100 LC/MSD instrument to afford the title compound as a white solid (11.0 mg, 32%). LC-MS: (FA) ES+340.

The following compounds were prepared in an analogous fashion to that described in Example 15 starting from the intermediates which were prepared as described above and the corresponding carboxylic acids.

To a solution of 4-methoxybenzoic acid (0.187 g, 1.23 mmol) dissolved in N,N-dimethylformamide (5 mL) and triethylamine (0.428 mL, 3.07 mmol) was added tetramethylfluoroformamidinium hexafluorophosphate (0.406 g, 1.54 mmol) and the reaction mixture was stirred for 15 minutes. Ethyl 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate (0.2 g, 1.02 mmol) was added and the reaction continued to stir at room temperature for 5 hours. The reaction mixture was diluted with water and extracted with EtOAc (3×). The combined organic layers were washed with water, brine, dried over anhydrous Na2SO4, filtered and concentrated. The residue was purified via silica gel chromatography (0-90% EtOAc/hexane) to afford ethyl 5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate Intermediate 27 (0.359 g, 100%). LC-MS: (FA) ES+330.

To a solution of ethyl 5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate (0.359 g, 1.09 mmol) obtained in the previous step dissolved in tetrahydrofuran (5 mL), ethanol (5 mL) and water (3 mL) was added lithium hydroxide (0.039 g, 1.64 mmol) and the reaction was stirred at room temperature for 2 hours. The solvent was then concentrated and the remaining aqueous solution was acidified with 1M aqueous hydrochloric acid to pH=1 resulting in the formation of a solid precipitate. EtOAc was added to dissolve the precipitate and the organic layer was separated and the aqueous layer was re-extracted with EtOAc (2×). The combined organic layers were then washed with water, brine, dried over Na2SO4, filtered and concentrated to afford 5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylic acid Intermediate 28 (0.205 g, 62%). LC-MS: (FA) ES+302.

To a solution of 5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylic acid obtained in the previous step (0.205 g, 0.68 mmol) dissolved in N,N-dimethylformamide (5 mL) and triethylamine (0.284 mL, 2.04 mmol) was added tetramethylfluoroformamidinium hexafluorophosphate (0.216 g, 0.816 mmol) and the reaction mixture was stirred for 15 minutes. Solid O-(tetrahydropyran-2-yl)hydroxylamine (0.096 g, 0.816 mmol) was added and the reaction continued to stir at room temperature for 4 hours. The reaction mixture was then diluted with water and extracted with EtOAc (3×). The combined organic layers were then washed with water, brine, dried using anhydrous Na2SO4, filtered and concentrated. The residue was purified via silica gel chromatography (0-10% MeOH/DCM) to afford 5-(4-methoxybenzoyl)-N-(tetrahydro-2H-pyran-2-yloxy)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamide (0.167 g, 61%). LC-MS: (FA) ES+401.

To a solution of 5-(4-methoxybenzoyl)-N-(tetrahydro-2H-pyran-2-yloxy)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamide (0.167 g, 0.417 mmol) obtained in the previous step dissolved in methanol (4 mL) was added 4.0 M of hydrochloric acid in 1,4-dioxane (0.021 mL, 0.083 mmol) and the reaction was stirred at room temperature for 3 hours. The solvent was then concentrated to dryness and the residue was purified on a BioCAD 700E HPLC instrument using a Phenomenex (C18) Luna (21.2 mm×250 mm) column to afford N-hydroxy-5-(4-methoxybenzoyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamide (0.018 g, 14%). LC-MS: (AA) ES+317.

The following compound was prepared in an analogous fashion to that described in Example 17 starting from the intermediates which were prepared as described above and the corresponding carboxylic acid.

To a mixture of N-(tetrahydro-2H-pyran-2-yloxy)-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxamide (0.0283 g, 0.101 mmol) and 4-methoxybenzoic acid (0.016 g, 0.105 mmol) in methylene chloride (1 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.0434 g, 0.114 mmol) and N-methylmorpholine (0.0333 mL, 0.303 mmol). The reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with methylene chloride (2 mL) and washed with aqueous NaHCO3(2 mL). The aqueous layer was extracted with additional methylene chloride (3 mL) and the combined organic layers concentrated to afford Intermediate 30 as a white solid.

To a mixture of ethyl 5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepine-2-carboxylate (0.033 g, 0.16 mmol) and 5-(2-pyridyl)thiophene-2-carboxylic acid (0.036 g, 0.18 mmol) in methylene chloride (1 mL) was added N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (0.07 g, 0.184 mmol) and N-methylmorpholine (0.053 mL, 0.48 mmol). The reaction was stirred overnight at room temperature. The reaction was diluted with methylene chloride (3 mL) and washed with saturated aqueous NaHCO3(2 mL). The aqueous layer was extracted with additional methylene chloride (3 mL). The combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated to dryness to afford Intermediate 31.

The following compounds were prepared in an analogous fashion to that described in Example 20 starting from the intermediates which were prepared as described above and the corresponding carboxylic acids.

To a solution of ethyl 4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate (30 mg, 0.143 mmol) in acetonitrile (1 mL) was added cesium carbonate (93.4 mg, 0.287 mmol) and benzyl bromide (25.6 μL, 0.215 mmol). The reaction mixture was stirred overnight at 70° C. Upon cooling to room temperature, the cesium carbonate was removed by filtration and the solvent evaporated under reduced pressure to afford crude Intermediate 32. LC-MS: (AA) ES+300.

To a solution of the material obtained in the previous step in methanol (3 mL) was added solid potassium hydroxide (100 mg, 2 mmol) and hydroxylamine hydrochloride (50 mg, 0.72 mmol). The reaction mixture was heated at 80° C. for 30 minutes. Upon cooling to room temperature all solids were removed via filtration and the solvent evaporated to dryness. The residue was dissolved in DMSO (1 mL) and purified on an Agilent 1100 LC/MSD instrument to afford the title compound as a white solid (9.1 mg, 21%).1H NMR (400 MHz, MeOD) δ 7.39-7.26 (m, 5H), 7.23 (s, 1H), 4.76 (s, 2H), 4.42-4.38 (m, 2H), 3.77 (dd, J=6.9, 5.5 Hz, 2H); LC-MS: (AA) ES+287.

To a solution of cyclopropylmethyl bromide (0.101 g, 0.75 mmol) and ethyl 4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate (31.4 mg, 0.150 mmol) in acetonitrile (2 mL) was added cesium carbonate (147 mg, 0.45 mmol). The reaction mixture was heated overnight at 70° C. Upon cooling to room temperature, the insolubles were removed by filtration and the solvent evaporated to dryness to afford crude Intermediate 33.

To a solution of the material obtained in the previous step in methanol (1 mL) was added 1.7 M hydroxylamine potassium salt in methanol (1 mL, 1.7 mmol; prepared as described inJournal of Medicinal Chemistry2009, 52(21):6757). The reaction mixture was stirred at room temperature for 1 hour. Upon evaporation of the solvent the residue was dissolved in DMSO (1 mL) and purified on a Agilent 1100 LC/MSD instrument to afford the title compound as a white solid (8.4 mg, 22%). LC-MS: (FA) ES+251.

The following compounds were prepared in an analogous fashion to that described in Example 23 starting from the intermediates which were prepared as described above and the corresponding starting materials.

To a solution of ethyl 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate (29.8 mg, 0.143 mmol) in acetonitrile (1 mL) was added cesium carbonate (60.6 mg, 0.186 mmol) and benzyl bromide (36.7 mg, 0.215 mmol). The reaction mixture was heated at 70° C. overnight. Upon cooling to room temperature all insolubles were removed by filtration and the solvent evaporated to dryness to afforde crude Intermediate 34.

A mixture of potassium hydroxide (100 mg, 2 mmol) and hydroxylamine hydrochloride (49.7 mg, 0.715 mmol) in dimethyl sulfoxide (1 mL) was sonicated until the hydroxylamine hydrochloride had gone into solution. After removal of insolubles, the solution was added to Intermediate 34 obtained in the previous step and the solution stirred at room temperature overnight. The solution was purified directly on an Agilent 1100 LC/MSD instrument to afford the title compound as a white solid (4.9 mg, 12%).1H NMR (400 MHz, MeOD) δ 7.42-7.24 (m, 6H), 7.15 (s, 1H), 4.74 (s, 2H), 4.18 (dd, J=12.2, 6.1 Hz, 2H), 3.64 (dd, J=6.7, 5.1 Hz, 2H). LC-MS: (FA) ES+286.

The following compound was prepared in an analogous fashion to that described in Example 25 starting from the intermediates which were prepared as described above and the corresponding starting material.

To a vial was added 1-methyl-1-cyclohexanecarboxylic acid (0.024 g, 0.168 mmol), HATU (0.064 g, 0.168 mmol), triethylamine (0.134 mL, 0.96 mmol), DCM (2 mL), and DMF (0.2 mL). After shaking for 30 min, ethyl 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate (0.031 g, 0.16 mmol) was added. The mixture was shaken at rt for 16 h. To the vial was added water (1 mL) and DCE (1 mL). After separation, the aqueous layer was extracted with DCE twice (3 mL). The combined organic layers were concentrated to give crude ethyl 7-(1-methylcyclohexanecarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate as a solid.

Preparation of NH2OK solution (1.76 M in methanol): A suspension of hydroxylamine hydrochloride (9.4 g, 135 mmol) in methanol (48 mL) was heated at 68° C. under argon until a clear solution was obtained. To this solution was added a solution of potassium hydroxide (13.4 g, 239 mmol) in methanol (28 mL). After refluxing at 80° C. for 30 min, the mixture was cooled to room temperature and the upper clear solution (approximately 1.76 M NH2OH in methanol) was used directly in further reactions.

The following compounds were prepared in an analogous fashion to that described in Example 27 using the corresponding starting materials.

The following compounds were prepared in an analogous fashion to that described in Example 29 using the corresponding starting materials.

To measure the inhibition of HDAC6 activity, purified human HDAC6 (BPS Bioscience; Cat. No. 5006) is incubated with substrate Ac-Arg-Gly-Lys(Ac)-AMC peptide (Bachem Biosciences; Cat. No. I-1925) for 1 hour at 30° C. in the presence of test compounds or vehicle DMSO control. The reaction is stopped with the HDAC inhibitor trichostatin A (Sigma; Cat. No. T8552) and the amount of Arg-Gly-Lys-AMC generated is quantitated by digestion with trypsin (Sigma; Cat. No. T1426) and subsequent measurement of the amount of AMC released using a fluorescent plate reader (Pherastar; BMG Technologies) set at Ex 340 nm and Em 460 nm. Concentration response curves are generated by calculating the fluorescence increase in test compound-treated samples relative to DMSO-treated controls, and enzyme inhibition (IC50) values are determined from those curves.

Nuclear Extract HDAC Assay

As a screen against Class I HDAC enzymes, HeLa nuclear extract (BIOMOL; Cat. No. KI-140) is incubated with Ac-Arg-Gly-Lys(Ac)-AMC peptide (Bachem Biosciences; Cat. No. 1-1925) in the presence of test compounds or vehicle DMSO control. The HeLa nuclear extract is enriched for Class I enzymes HDAC1, -2 and -3. The reaction is stopped with the HDAC inhibitor Trichostatin A (Sigma; Cat. No. T8552) and the amount of Arg-Gly-Lys-AMC generated is quantitated by digestion with trypsin (Sigma; Cat. No. T1426) and subsequent measurement of the amount of AMC released using a fluorescent plate reader (Pherastar; BMG Technologies) set at Ex 340 nm and Em 460 nm. Concentration response curves are generated by calculating the fluorescence increase in test compound-treated samples relative to DMSO-treated controls, and enzyme inhibition (IC50) values are determined from those curves.

Western Blot and Immunofluorescence Assays

Cellular potency and selectivity of compounds are determined using a published assay (Haggarty et al.,Proc. Natl. Acad. Sci. USA2003, 100 (8): 4389-4394) using Hela cells (ATCC cat#CCL-2™) which are maintained in MEM medium (Invitrogen) supplemented with 10% FBS; or multiple myeloma cells RPMI-8226 (ATCC cat#CCL-155™) which are maintained in RPMI 1640 medium (Invitrogen) supplemented with 10% FBS. Briefly, cells are treated with inhibitors for 6 or 24 h and either lysed for Western blotting, or fixed for immunofluorescence analyses. HDAC6 potency is determined by measuring K40 hyperacetylation of alpha-tubulin with an acetylation selective monoclonal antibody (Sigma cat#T7451) in IC50 experiments. Selectivity against Class I HDAC activity is determined similarly using an antibody that recognizes hyperacetylation of histone H4 (Upstate cat#06-866) in the Western blotting assay or nuclear acetylation (Abeam cat#ab21623) in the immunofluorescence assay.

In vivo Tumor Efficacy Model

Female NCr-Nude mice (age 6-8 weeks, Charles River Labs) are aseptically injected into the subcutaneous space in the right dorsal flank with 1.0−5.0×106cells (SKOV-3, HCT-116, BxPC3) in 100 μL of a 1:1 ratio of serum-free culture media (Sigma Aldrich) and BD Matrigel™ (BD Biosciences) using a 1 mL 26⅜ gauge needle (Becton Dickinson Ref#309625). Alternatively, some xenograft models require the use of more immunocompromised strains of mice such as CB-17 SCID (Charles River Labs) or NOD-SCID (Jackson Laboratory). Furthermore, some xenograft models require serial passaging of tumor fragments in which small fragments of tumor tissue (approximately 1 mm3) are implanted subcutaneously in the right dorsal flank of anesthetized (3-5% isoflourane/oxygen mixture) NCr-Nude, CB-17 SCID or NOD-SCID mice (age 5-8 weeks, Charles River Labs or Jackson Laboratory) via a 13-ga trocar needle (Popper & Sons 7927). Tumor volume is monitored twice weekly with Vernier calipers. The mean tumor volume is calculated using the formula V=W2×L/2. When the mean tumor volume is approximately 200 mm3, the animals are randomized into treatment groups of ten animals each. Drug treatment typically includes the test compound as a single agent, and may include combinations of the test compound and other anticancer agents. Dosing and schedules are determined for each experiment based on previous results obtained from pharmacokinetic/pharmacodynamic and maximum tolerated dose studies. The control group will receive vehicle without any drug. Typically, test compound (100-200 μL) is administered via intravenous (27-ga needle), oral (20-ga gavage needle) or subcutaneous (27-ga needle) routes at various doses and schedules. Tumor size and body weight are measured twice a week and the study is terminated when the control tumors reach approximately 2000 mm3, and/or if tumor volume exceeds 10% of the animal body weight or if the body weight loss exceeds 20%.

The differences in tumor growth trends over time between pairs of treatment groups are assessed using linear mixed effects regression models. These models account for the fact that each animal is measured at multiple time points. A separate model is fit for each comparison, and the areas under the curve (AUC) for each treatment group are calculated using the predicted values from the model. The percent decrease in AUC (dAUC) relative to the reference group is then calculated. A statistically significant P value suggests that the trends over time for the two treatment groups are different.

The tumor measurements observed on a date pre-specified by the researcher (typically the last day of treatment) are analyzed to assess tumor growth inhibition. For this analysis, a T/C ratio is calculated for each animal by dividing the tumor measurement for the given animal by the mean tumor measurement across all control animals. The T/C ratios across a treatment group are compared to the T/C ratios of the control group using a two-tailed Welch's t-test. To adjust for multiplicity, a False Discovery Rate (FDR) is calculated for each comparison using the approach described by Benjamini and Hochberg,J.R. Stat. Soc. B1995, 57:289-300.

As detailed above, compounds of the invention are selective for HDAC6 over other Class I HDAC enzymes. In certain embodiments, the ratio of HDAC IC50 (as obtained in the nuclear extract assay described above) to HDAC6 IC50 is less than 5 (HDAC IC50/HDAC6 IC50). In certain embodiments, the ratio of HDAC IC50to HDAC6 IC50is between 5 and 10. In certain embodiments, the ratio of HDAC IC50to HDAC6 IC50is between 10 and 100.