Abstract:
The present invention relates to 2,3-position modified epothilone derivatives, methods of preparation of the derivatives, and intermediates therefor. The compounds of the invention as 16-membered macrolides having the general structure,                            
     which have microtubule-stabilizing effects and cytotoxic activity against rapidly proliferating cells, such as, tumor cells or other hyperproliferative cellular disease.

Description:
This application claims priority from U.S. Provisional application No. 60/082,562, filed Apr. 21, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to epothilone derivatives, methods for the preparation of the derivatives and intermediates therefor. 
     BACKGROUND OF THE INVENTION 
     Epothilones are macrolide compounds which find utility in the pharmaceutical field. For example, Epothilones A and B having the structures:                           
     have been found to exert microtubule-stabilizing effects similar to TAXOL and hence cytotoxic activity against rapidly proliferating cells, such as, tumor cells or other hyperproliferative cellular disease, see  Angew. Chem. Int. Ed. Engl.,  1996, Vol. 35, No. 13/14, p.p. 1567-1569. 
     SUMMARY OF THE INVENTION 
     The present invention relates to compounds of the formula                           
     Q is selected from the group consisting of                           
     G is selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, heterocyclo,                           
     W is O or NR 12 ; 
     X is O, S, or H, H; 
     Y is selected from the group consisting of O; H, OR 13 ; OR 14 , OR 14 ; NOR 15 ; H, NOR 16 ; H, NR 17 R 18 ; H, H; or CHR 19 ; OR 14  OR 14  can be a cyclic ketal; 
     B is selected from the group consisting of H, OR 20 , or OCOR 21 , and NR 22 R 23 ; 
     D is selected from the group consisting of NR 24 R 25  or saturated heterocycle (such as piperidinyl, pyrrolidinyl, and the like); 
     R 1 , R 2 , R 3 , and R 4  are selected from H or lower alkyl; 
     R 15 , R 16 , R 17 , R 18 , and R 19  are selected from the group H, alkyl, substituted alkyl, or aryl; 
     R 6 , R 7 , R 13 , R 14 , R 20 , and R 21  are selected from the group H, alkyl, or substituted alkyl; 
     R 5 , R 8 , R 9 , R 10 , R 11 , R 22 , R 24 , R 26 , and R 27  are selected from the group consisting of H, alkyl, substituted alkyl, aryl, heteroaryl, cycloalkyl, or heterocyclo; 
     R 12 , R 23 , and R 25  are selected from the group consisting of H, alkyl, substituted alkyl, aryl, heteroaryl, cycloalkyl, heterocyclo, R 26 C═O, R 27 SO 2 , hydroxy, O-alkyl or O-substituted alkyl; 
     and any salts, solvates or hydrates thereof 
     Proviso 
     The present invention does not include compounds of formula I wherein 
     W and X are both O; and 
     R 1 , R 2 , R 3 , R 4  are methyl; and 
     R 5  is H or methyl; and 
     G is 1-methyl-2-(2-methyl-4-thiazolyl)ethenyl; and 
     Q is                           
     DETAILED DESCRIPTION OF THE INVENTION 
     Listed below are definitions of various terms used to describe this invention. These definitions apply to the terms as they are used throughout this specification, unless otherwise limited in specific instances, either individually or as part of a larger group. 
     The term “alkyl” refers to straight or branched chain unsubstituted hydrocarbon groups of 1 to 20 carbon atoms, preferably 1 to 7 carbon atoms. The expression “lower alkyl” refers to unsubstituted alkyl groups of 1 to 4 carbon atoms. 
     The term “substituted alkyl” refers to an alkyl group substituted by, for example, one to four substituents, such as, halo, trifluoromethyl, trifluoromethoxy, hydroxy, alkoxy, cycloalkyoxy, heterocylooxy, oxo, alkanoyl, aryloxy, alkanoyloxy, amino, alkylamino, arylamino, aralkylamino, cycloalkylamino, heterocycloamino, disubstituted amines in which the 2 amino substituents are selected from alkyl, aryl or aralkyl, alkanoylamino, aroylamino, aralkanoylamino, substituted alkanoylamino, substituted arylamino, substituted aralkanoylamino, thiol, alkylthio, arylthio, aralkylthio, cycloalkylthio, heterocyclothio, alkylthiono, arylthiono, aralkylthiono, alkylsulfonyl, arylsulfonyl, aralkylsulfonyl, sulfonamido (e.g. SO 2 NH 2 ), substituted sulfonamido, nitro, cyano, carboxy, carbamyl (e.g. CONH 2 ), substituted carbamyl (e.g. CONH alkyl, CONH aryl, CONH aralkyl or cases where there are two substituents on the nitrogen selected from alkyl, aryl or aralkyl), alkoxyearbonyl, aryl, substituted aryl, guanidino and heterocyclos, such as, indolyl, imidazolyl, furyl, thienyl, thiazolyl, pyrrolidyl, pyridyl, pyrimidyl and the like. Where noted above where the substituent is further substituted it will be with halogen, alkyl, alkoxy, aryl or aralkyl. 
     The term “halogen” or “halo” refers to fluorine, chlorine, bromine and iodine. 
     The term “aryl” refers to monocyclic or bicyclic aromatic hydrocarbon groups having 6 to 12 carbon atoms in the ring portion, such as phenyl, naphthyl, biphenyl and diphenyl groups, each of which may be substituted. 
     The term “aralkyl” refers to an aryl group bonded directly through an alkyl group, such as benzyl. 
     The term “substituted aryl” refers to an aryl group substituted by, for example, one to four substituents such as alkyl; substituted alkyl, phenyl, substituted phenyl, heterocyclo, halo, trifluoromethoxy, trifluoromethyl, hydroxy, alkoxy, cycloalkyloxy, heterocyclooxy, alkanoyl, alkanoyloxy, amino, alkylamino, aralkylamino, cycloalkylamino, heterocycloamino, dialkylamino, alkanoylamino, thiol, alkylthio, cycloalkylthio, heterocyclothio, ureido, nitro, cyano, carboxy, carboxyalkyl, carbamyl, alkoxycarbonyl, alkylthiono, arylthiono, alkysulfonyl, sulfonamido, aryloxy. The substituent may be further substituted by halo, hydroxy, alkyl, alkoxy, aryl, substituted aryl, substituted alkyl or aralkyl. 
     The term “cycloalkyl” refers to optionally substituted, saturated cyclic hydrocarbon ring systems, preferably containing 1 to 3 rings and 3 to 7 carbons per ring which may be further fused with an unsaturated C 3 -C 7  carbocyclic ring. Exemplary groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, cyclododecyl, and adamantyl. Exemplary substituents include one or more alkyl groups as described above, or one or more groups described above as alkyl substituents. 
     The terms “heterocycle”, “heterocyclic” and “heterocyclo” refer to an optionally substituted, fully saturated or unsaturated, aromatic or nonaromatic cyclic group, for example, which is a 4 to 7 membered monocyclic, 7 to 11 membered bicyclic, or 10 to 15 membered tricyclic ring system, which has at least one heteroatom in at least one carbon atom-containing ring. Each ring of the heterocyclic group containing a heteroatom may have 1, 2 or 3 heteroatoms selected from nitrogen atoms, oxygen atoms and sulfur atoms, where the nitrogen and sulfur heteroatoms may also optionally be oxidized and the nitrogen heteroatoms may also optionally be quaternized. The heterocyclic group may be attached at any heteroatom or carbon atom. 
     Exemplary monocyclic heterocyclic groups include pyrrolidinyl, pyrrolyl, indolyl, pyrazolyl, oxetanyl, pyrazolinyl, imidazolyl, imidazolinyl, imidazolidinyl, oxazolyl, oxazolidinyl, isoxazolinyl, isoxazolyl, thiazolyl, thiadiazolyl, thiazolidinyl, isothiazolyl, isothiazolidinyl, furyl, tetrahydrofuryl, thienyl, oxadiazolyl, piperidinyl, piperazinyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, 2-oxazepinyl, azepinyl, 4-piperidonyl, pyridyl, N-oxo-pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, tetrahydropyranyl, tetrahydrothiopyranyl, tetrahydrothiopyranyl sulfone, morpholinyl, thiomorpholinyl, thiomorpholinyl sulfoxide, thiomorpholinyl sulfone, 1,3-dioxolane and tetrahydro-1,1-dioxothienyl, dioxanyl, isothiazolidinyl, thietanyl, thiiranyl, triazinyl, and triazolyl, 
     Exemplary bicyclic heterocyclic groups include benzothiazolyl, benzoxazolyl, benzothienyl, quinuclidinyl, quinolinyl, quinolinyl-N-oxide, tetrahydroisoquinolinyl, isoquinolinyl, benzimidazolyl, benzopyranyl, indolizinyl, benzofuryl, chromonyl, coumarinyl, cinnolinyl, quinoxalinyl, indazolyl, pyrrolopyridyl, furopyridinyl (such as furo[2,3-c]pyridinyl, furo[3,1-b]pyridinyl] or furo[2,3-b]pyridinyl), dihydroisoindolyl, dihydroquinazolinyl (such as 3,4-dihydro-4-oxo-quinazolinyl), benzisothiazolyl, benzisoxazolyl, benzodiazinyl, benzofurazanyl, benzothiopyranyl, benzotriazolyl, benzpyrazolyl, dihydrobenzofuryl, dihydrobenzothienyl, dihydrobenzothiopyranyl, dihydrobenzothiopyranyl sulfone, dihydrobenzopyranyl, indolinyl, isochromanyl, isoindolinyl, naphthyridinyl, phthalazinyl, piperonyl, purinyl, pyridopyridyl, quinazolinyl, tetrahydroquinolinyl, thienofuryl, thienopyridyl, thienothienyl. 
     Exemplary substituents include one or more alkyl groups as described above or one or more groups described above as alkyl substituents. Also included are smaller heterocyclos, such as, epoxides and aziridines. 
     The term “heteroatoms” shall include oxygen, sulfur and nitrogen. 
     The compounds of formula I may form salts with alkali metals such as sodium, potassium and lithium, with alkaline earth metals such as calcium and magnesium, with organic bases such as dicyclohexylamine, tributylamine, pyridine and amino acids such as arginine, lysine and the like. Such salts can be obtained, for example, by exchanging the carboxylic acid protons, if they contain a carboxylic acid, in compounds of formula I with the desired ion in a medium in which the salt precipitates or in an aqueous medium followed by evaporation. Other salts can be formed as known to those skilled in the art. 
     The compounds for formula I form salts with a variety of organic and inorganic acids. Such salts include those formed with hydrogen chloride, hydrogen bromide, methanesulfonic acid, hydroxyethanesulfonic acid, sulfuric acid, acetic acid, trifluoroacetic acid, maleic acid, benzenesulfonic acid, toluenesulfonic acid and various others (e.g., nitrates, phosphates, borates, tartrates, citrates, succinates, benzoates, ascorbates, salicylates and the like). Such salts are formed by reacting a compound of formula V in an equivalent amount of the acid in a medium in which the salt precipitates or in an aqueous medium followed by evaporation. 
     In addition, zwitterions (“inner salts”) are formed. 
     Compounds of the formula I may also have prodrug forms. Any compound that will be converted in vivo to provide the bioactive agent (i.e., the compound for formula I) is a prodrug within the scope and spirit of the invention. 
     For example compounds of the formula I may form a carboxylate ester moiety. The carboxylate esters are conveniently formed by esterifying any of the carboxylic acid functionalities found on the disclosed ring structure(s). 
     Various forms of prodrugs are well known in the art. For examples of such prodrug derivatives, see: 
     a)  Design of Prodrugs,  edited by H. Bundgaard, (Elsevier, 1985) and  Methods in Enzymology,  Vol.42, p. 309-396, edited by K. Widder, et al. (Acamedic Press, 1985); 
     b)  A Textbook of Drug Design and Development,  edited by Krosgaard-Larsen and H. Bundgaard, Chapter 5, “Design and Application of Prodrugs,” by H. Bundgaard, p. 113-191 (1991); 
     c) H. Bundgaard,  Advanced Drug Delivery Reviews,  8, 1-38 (1992); 
     d) H. Bundgaard, et al.,  Journal of Pharmaceutical Sciences,  77, 285 (1988); and 
     e) N. Kakeya, et al.,  Chem Phar Bull,  32, 692 (1984). 
     It should further be understood that solvates (e.g., hydrates) of the compounds of formula I are also within the scope of the present invention. Methods of salvation are generally known in the art. 
     Use and Utility 
     The compounds of formula I are microtubule-stabilizing agents. They are thus useful in the treatment of a variety of cancers or other abnormal proliferative diseases, including (but not limited to) the following; 
     carcinoma, including that of the bladder, breast, colon, kidney, liver, lung, ovary, pancreas, stomach, cervix, thyroid and skin; including squamous cell carcinoma; 
     hematopoietic tumors of lymphoid lineage, including leukemia, acute lymphocytic leukemia, acute lymphoblastic leukemia, B-cell lymphoma, T-cell lymphoma, Hodgkins lymphoma, non-Hodgkins lymphoma, hairy cell lymphoma and Burketts lymphoma; 
     hematopoietic tumors of myeloid lineage, including acute and chronic myelogenous leukemias and promyelocytic leukemia; 
     tumors of mesenchymal origin, including fibrosarcoma and rhabdomyoscarcoma; 
     other tumors, including melanoma, seminoma, tetratocarcinoma, neuroblastoma and glioma; 
     tumors of the central and peripheral nervous system, including astrocytoma, neuroblastoma, glioma, and schwannomas; 
     tumors of mesenchymal origin, including fibrosarcoma, rhabdomyoscaroma, and osteosarcoma; and 
     other tumors, including melanoma, xenoderma pigmentosum, keratoactanthoma, seminoma, thyroid follicular cancer and teratocarcinoma. 
     Compounds of formula I may also inhibit tumor angiogenesis, thereby affecting abnormal cellular proliferation. Such anti-angiogenesis properties of the compounds of formula I may also be useful in the treatment of certain forms of blindness related to retinal vascularization, arthritis, especially inflammatory arthritis, multiple sclerosis, restinosis and psoriasis. 
     Compounds of formula I may induce or inhibit apoptosis, a physiological cell death process critical for normal development and homeostasis. Alterations of apoptotic pathways contribute to the pathogenesis of a variety of human diseases. Compounds of formula I, as modulators of apoptosis, will be useful in the treatment of a variety of human diseases with aberrations in apoptosis including cancer (particularly, but not limited to follicular lymphomas, carcinomas with p53 mutations, hormone dependent tumors of the breast, prostrate and ovary, and precancerous lesions such as familial adenomatous polyposis), viral infections (including but not limited to herpesvirus, poxvirus, Epstein-Barr virus, Sindbis virus and adenovirus), autoimmune diseases (including but not limited to systemic lupus erythematosus, immune mediated glomerulonephritis, rheumatoid arthritis, psoriasis, inflammatory bowel diseases and autoimmune diabetes mellitus), neurodegenerative disorders (including but not limited to Alzheimer&#39;s disease, AIDS-related dementia, Parkinson&#39;s disease, amyotrophic lateral sclerosis, retinitis pigmentosa, spinal muscular atrophy and cerebellar degeneration), AIDS, myelodysplastic syndromes, aplastic anemia, ischemic injury associated myocardial infarctions, stroke and reperfusion injury, arrhythmia, atherosclerosis, toxin-induced or alcohol induced liver diseases, hematological diseases (including but not limited to chronic anemia and aplastic anemia), degenerative diseases of the musculoskeletal system (including but not limited to osteoporosis and arthritis), aspirin-sensitive rhinosinusitis, cystic fibrosis, multiple sclerosis, kidney diseases, and cancer pain. 
     The compounds of this invention are also useful in combination with known anti-cancer and cytotoxic agents and treatments, including radiation. If formulated as a fixed dose, such combination products employ the compounds of this invention within the dosage range described below and the other pharmaceutically active agent within its approved dosage range. Compounds of formula I can be used sequentially with known anticancer or cytotoxic agents and treatment, including radiation when a combination formulation is inappropriate. Especially useful are cytotoxic drug combinations wherein the second drug chosen acts in a different phase of the cell cycle, e.g. S phase, than the present compounds of formula I which exert their effects at the G 2 -M phase. 
     The present compounds may exist as multiple optical, geometric, and stereoisomers. Included within the present invention are all such isomers and mixtures thereof. 
     The compounds of this invention can be formulated with a pharmaceutical vehicle or diluent for oral, intravenous or subcutaneous administration. The pharmaceutical composition can be formulated in a classical manner using solid or liquid vehicles, diluents and additives appropriate to the desired mode of administration. Orally, the compounds can be administered in the form of tablets, capsules, granules, powders and the like. The compounds are administered in a dosage range of about 0.05 to 200 mg/kg/day, preferably less than 100 mg/kg/day, in a single dose or in 2 to 4 divided doses. 
     Method of Preparation 
     A compound of formula I can be prepared as shown in Scheme 1, using procedures described in PCT/EP96/05080. A compound of formula 1. A can be esterified using, for example, a mixture of formic acid and acetic anhydride to give a corresponding diformate 1.B. A compound of formula 1.C can be prepared from a compound of formula 1.B using a base such as DBU. A compound of formula I can be prepared from a compound of formula 1.C by treatment with methanolic ammonia.                           
     Compounds of formula I where X is O, W is NH, and Q is an oxiranyl group can be prepared as shown in Scheme 2. A compound of formula 2.A can be esterified using, for example, a mixture of formic acid and acetic anhydride to give a corresponding diformate 2.B. A compound of formula 2.C can be prepared from a compound of formula 2.B by treatment with a base such as DBU. A compound of formula 2.D can be prepared from a compound of formula 2.C using for example methane sulfonyl chloride and triethylamine, or Burgess&#39; reagent. Treatment of a compound of formula 2.D with methanolic ammonia affords a compound of formula I where X is NH and Q is an oxiranyl group.                           
     A compound of formula 2.A where G is —CR 9 ═CR 8 H can be prepared as shown in Scheme 3. A compound of formula 3.B can be prepared from a compound of formula 3.A (an epothilone or epothilone-related natural product) by formation of pi-allylpalladium complex using, for example, palladium tetrakistriphenylphosphine followed by treatment with sodium azide (see, for example: Murahashi, S.-I.; et. al.,  J. Org. Chem.  1989, 54, 3292). Subsequent reduction of a compound of formula 3.B with a reducing agent such as triphenylphosphine provides a compound of formula 3.C. A compound of formula 3.D (or 2.A where G is —CR 9 ═CR 8 H) can be prepared from a compound of formula 3.C by macrolactamization using, for example, diphenylphosphoryl azide (DPPA) or bromotripyrrolidinophosphonium hexafluorophosphate (PyBroP).                           
     A compound of formula I where W is O and X is H,H can be prepared as shown in Scheme 4. The alcohol moiety of a compound of formula I where both W and X are O can be protected using methods in the art to give a compound of formula 4.A, where P 1  is a suitable O-protecting group such as triethylsilyl. Hydrolysis of a compound of formula 4.A, using for example lithium hydroxide monohydrate, provides a compound of formula 4.B. Esterification of a compound of formula 4.B, using for example trimethylsilyl diazomethane, provides a compound of formula 4.C. Selective dihydroxylation of the α,β-unsaturated ester moiety of a compound of formula 4.C by known methods (see Sharpless, K. B. et al.,  J. Org. Chem.  (1992) 57, 2768) provides a compound of formula 4.D. Oxidative cleavage of the diol of a compound of formula 4.D, using for example lead tetraacetate provides a compound of formula 4.E. A compound of formula 4.F can be prepared from a compound of formula 4.E using an allylating agent such as ally bromide and a silver salt such as silver oxide. A compound of formula 4.G can be prepared from a compound of formula 4.F using an olefinating agent such as methyltriphenylphosphonium bromide and a base such as sodium hexamethyldisilazide. A compound of formula 4.H can be prepared from a compound of formula 4.G by ring-closing metathesis using either the Grubbs (RuCl 2  (═CHPh)(PCY 3 ) 2 ; see Grubbs, R. H., et al.,  Angew. Chem. Int. Ed. Engl.;  (1995) 34, 2039) or Schrock catalysts (see Schrock, R. R., et al.,  J. Am. Chem. Soc.,  (1990) 112, 3875). A compound of formula I where W is O and X is H,H can be prepared from a compound of formula 4.H by removal of the protecting group using for example acetic acid/THF/water mixtures.                         
                           
     Alternatively, compounds of formula I where X is H,H can be prepared as shown is Scheme 5. A compound of formula I where X is S can be prepared from a compound of formula I where X is O using, for example, Lawesson&#39;s reagent [2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide]. A compound of formula I where X is H,H can be prepared from a compound of formula I where X is S by reduction with reducing agents such as tri-n-butyltin hydride, Raney nickel, or nickel boride. In Scheme 5, the hydroxyl group can be optionally protected using, for example, a triethylsily group which can be removed ultimately by treatment with hydrogen fluoride-pyridine or acetic acid/THF/water mixtures.                           
     Compounds of formula I where Q is an olefinic group or the corresponding saturated derivative can be prepared as shown in Scheme 6. Compounds of formula I where Q is an oxiranyl group (i.e., compound 6.A) can be reduced using reagents such as reactive titanocene or tungsten chloride and butyllithium to provide compounds of formula I where Q is an olefinic group (i.e., compound 6.B). Further reduction using, for example, diimide provides compounds of formula I where Q is a saturated alkyl chain (i.e., compound 6.C).                           
     In Schemes 1, 3, 4, and 5, the starting material can be obtained from fermentation of  Sorangium cellulosum  as previously described (see  Angew. Chem. Int. Ed. Engl.,  1996, 35, No. 13/14.). In these fermentation products G is usually, but not exclusively, selected from the following:                           
     In cases where G is not selected from the preceding list or obtained from fermentation, synthetic methods can be used. For example, total synthesis routes have been described (See, for example: Danishefsky, S. J., et. al.,  J. Am. Chem. Soc.,  (1997) 119, 10073), and these methods can be used to provide compounds of formula 1.A where G is, for example, alkyl, substituted alkyl, aryl, substituted aryl, heterocyclo, and —CR 9 ═CR 8 H. In addition, semi-synthesis which utilizes degradation of natural epothilones can be employed. For example, epothilones (i.e., 7.A) can be protected and then degraded to a compound of formula 7.B (see PCT/EP96/05080). Subsequent, olefination and deprotection provides compounds of formula 1.A where is —CCH 3 ═CR 8 H (i.e., compound 7.C). Alternatively, 7.B can be treated with an alkyl or arylmagnesium halide to provide a tertiary alcohol which can be dehydrated using, for example, Burgess reagent to provide a compound of formula 1.A where is —CCH 3 ═CR 8 H (i.e., compound 7.C).                           
     Furthermore, starting compounds of formula 1.A where G is —C(O)NR 10 R 11  can be prepared from a compound of formula 7.B as shown in Scheme 8. A compound of formula 8.A where P is a trialkylsilyl group can be prepared from a compound of formula 7.B using for example t-butyldimethylsilyl chloride and triethylamine. Oxidative cleavage of a compound of formula 8.A using for example ozone provides a compound of formula 8.B. Amide coupling of a compound of formula 8.B using methods well known in the art followed by deprotection provides a compound of 1.A where G is —C(O)NR 10 R 11  (i.e., compound 8.C).                           
     The in vitro assessment of biological activity of the compounds of formula I was performed as follows: 
     In vitro Tubulin Polymerization. Twice cycled (2X) calf brain tubulin was prepared following the procedure of Williams and Lee (see Williams, R. C., Jr., and Lee, J. C. Preparation of tubulin from brain. Methods in Enzymology 85, Pt. D: 376-385, 1982) and stored in liquid nitrogen before use. Quantification of tubulin polymerization potency is accomplished following a modified procedure of Swindell, et al., (see Swindell, C. S., Krauss, N. E., Horwitz, S. B., and Ringel, I. Biologically active taxol analogues with deleted A-ring side chain substituents and variable C-2′ configurations. J. Med. Chem. 34: 1176-1184, 1991). These modifications, in part, result in the expression of tubulin polymerization potency as an effective concentration for any given compound. For this method, different concentrations of compound in polymerization buffer (0.1M MES, 1 mM EGTA, 0.5 mM MgCl 2 , pH 6.6) are added to tubulin in polymerization buffer at 37° in microcuvette wells of a Beckman (Beckman Instruments) Model DU 7400 UV spectrophotometer. A final microtubule protein concentration of 1.0 mg/ml and compound concentration of generally 2.5, 5.0, and 10 μM are used. Initial slopes of OD change measured every 10 seconds were calculated by the program accompanying the instrument after initial and final times of the linear region encompussing at least 3 time points were manually defined. Under these conditions linear variances were generally &lt;10 −6 , slopes ranged from 0.03 to 0.002 absorbance unit/minute, and maximum absorbance was 0.15 absorbance units. Effective concentration (EC 0.01 ) is defined as the interpolated concentration capable of inducing an initial slope of 0.01 OD/minute rate and is calculated using the formula: EC 0.01 =concentration/slope. EC 0.01  values are expressed as the mean with standard deviation obtained from 3 different concentrations. EC 0.01  values for the compounds in this invention fall in the range 0.01-1000 μM. 
     Cytoxicity (In-Vitro) 
     Cytoxicity was assessed in HCT-116 human colon carcinoma cells by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphenyl)-2H-tetrazolium, inner salt) assay as reported in T. L. Riss, et. al., “Comparison of MTT, XTT, and a novel tetrazolium compound MTS for in vitro proliferation and chemosensitivity assays.,”  Mol. Biol. Cell  3 (Suppl.):184a, 1992. Cells were plated at 4,000 cell/well in 96 well microtiter plates and 24 hours later drugs were added and serial diluted. The cells were incubated at 37° form 72 hours at which time the tetrazolium dye, MTS at 333 μg/ml (final concentration), in combination with the electron coupling agent phenazine methosulfate at 25 μM (final concentration) was added. A dehydrogenase enzyme in live cells reduces the MTS to a form that absorbs light at 492 nM which can be quantitated spectrophotometrically. The greater the absorbance the greater the number of live cells. The results are expressed as an IC 50 , which is the drug concentration required to inhibit cell proliferation (i.e. absorbance at 450 nM) to 50% of that of untreated control cells. The IC 50  values for compounds of this invention fall in the range 0.01-1000 nM. 
     Preferred Compounds 
     As preferred compounds of the present invention are compounds of formula I wherein 
     Q is selected from the group consisting of                           
      and y is oxygen. 
    
    
     EXAMPLE 1 
     
       
                 
         
             
             
         
      
     
     [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-11-Hydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-hydroxymethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadec-6(E)-ene-5,9-dione 
     
       
                 
         
             
             
         
      
     
     A. [1S-[1R*,3R*(E),7R*,10R*,11S*,12R*,16S*]]-7,11-Dihydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-methyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadecane-5,9-dione, N-oxide 
     A solution of epothilone B (2.0 g, 3.9 mmol) in CH 2 Cl 2  (30 mL) was treated with 3-chloroperoxybenzoic acid (1.0 g, 5.9 mmol) at 25° C., under Ar for 2 h. An additional 0.5 g (3.0 mmol) of 3-chloroperoxybenzoic acid was added and the reaction mixture was then stirred for 2 h. The reaction mixture was filtered and the filtrate was concentrated in vacuo. The residue was dissolved in EtOAc (100 mL), washed with saturated aqueous NaHCO 3  (75 mL), 5% aqueous Na 2 SO 3  (75 mL), H 2 O (75 mL), dried (Na 2 SO 4 ) and concentrated in vacuo. The residue was purified by flash chromatography (SiO 2 , 4.5×30 cm, 2-10% MeOH—CHCl 3  gradient elution) to afford Compound A (1.04 g, 50%) as a white solid. MS (ESI + ): 524.3 (M+H) + ; MS (ESI − ): 522.5 (M−H) − .                           
     B. [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-7,11-Dihydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-aectoxymethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadecane-5,9-dione 
     To a resealable Kontes vial was added compound A (0.20 g, 0.38 mmol) and acetic anhydride (2 mL) under Ar. The reaction vessel was sealed under Ar and heated to 75° C. for 4 min. Acetic acid (0.4 mL) was then introduced into the reaction vessel and the reaction mixture was heated for an additional 30 min at 75° C. After the Kontes vial was cooled to 25° C., the volatiles were removed in vacuo and the residue was purified by flash chromatography (SiO 2 , 3.0×15 cm, 45:45:10 hexane/tert-butyl methyl ether/MeOH) to afford Compound B (0.15 g, 68%) as a colorless oil. MS (ESI + ): 566.2 (M+H) + , 1131.5 (2M+H) + ; MS (ESI−): 564.4 (M−H) − , 1129.7 (2M−H) − .                           
     C. [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-7,11-Dihydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-acetoxymethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadecane-5,9-dione, 7,11 diformate 
     A solution of compound B (0.15 g, 0.27 mmol) in CH 2 Cl 2  (5 mL) was treated with 4-N,N-dimethylaminopyridine (71 mg, 58 mmol), triethylamine (0.37 mL, 2.6 mmol), and formic acid (50 mL, 1.3 mmol) at 25° C., under Ar. The reaction mixture was cooled to −15° C. and acetic anhydride (0.12 mL, 1.3 mmol) was added over 3 min. The reaction mixture was stirred at −15° C. (15 min), warmed to 25° C. (15 min), quenched with pH 7.0 phosphate buffer and extracted with EtOAc (3×30 mL). The combined organic extracts were washed with aqueous 1 N HCl (50 mL), 10% aqueous NaHCO 3  solution (50 mL), brine (50 mL), dried (Na 2 SO 4 ), and concentrated in vacuo. The residue was purified by flash chromatography (SiO 2 , 1.5×10 cm, 10% acetone-CH 2 Cl 2 ) to afford Compound C (0.134 g, 84%) as a glass. MS (ESI + ): 622.2 (M+H) + .                           
     D. [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-11-Hydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-acetoxymethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadec-6(E)-ene-5,9-dione, 11-formate 
     A solution of compound C (0.13 g, 0.21 mmol) in CH 2 Cl 2  (2.2 mL) was treated with 1,8-diazabicyclo[5.4.0]undec-7-ene (0.31 mL, 2.1 mmol) at 25° C., under Ar. The reaction mixture was stirred at 25° C., for 2 h, quenched by the addition of pH 4.0 phosphate buffer, and extracted with EtOAc (3×20 mL). The combined organic extracts were washed with saturated aqueous NaHCO 3  solution (30 mL), brine (30 mL), dried (Na 2 SO 4 ), and concentrated in vacuo. The residue was purified by flash chromatography (SiO 2 , 1.5×10 cm, 25-50% EtOAc-hexane gradient elution) to afford Compound D (0.11 g, 92%) as a foam. MS (ESI + ): 576.2 (M+H) + .                           
     E. [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-11-Hydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-hydroxymethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadec-6(E)-ene-5,9-dione 
     A solution of compound D (0.11 g, 0.19 mmol) in MeOH (1.0 mL) was treated with 2 M ammonia in methanol (1.0 mL) at 25° C., under Ar. The reaction mixture was warmed to 45° C. for 1 h and concentrated in vacuo. The residue was purified by flash chromatography (SiO 2 , 1.5×10 cm, 2-5% MeOH—CHCl 3  gradient elution) to afford the title compound (95 mg, 98%) as a white foam. MS (ESI + ): 506.2 (M+H) + , 1011.3 (2M+H) + ; MS (ESI − ): 504.5 (M−H) − . 
     EXAMPLE 2 
     
       
                 
         
             
             
         
      
     
     [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-11-Hydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-azidomethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadec-6(E)-ene-5,9-dione 
     To a stirred solution of Compound 1E (3.0 mg, 0.0059 mmol) in 0.5 mL THF at 0 C. was added a 0.2M solution of diphenylphosphoryl azide (DPPA) in THF (35 μl, 0.0071 mmol, 1.2 eq) followed by addition of a 0.2M solution of DBU in THF (30 μL, 0.0060 mmol, 1 eq). The mixture was allowed to stir at 0 C. for 3.5 h. An additional 15 μL of DPPA solution (0.0030 mmol, 0.5 eq) and 30 μL of DBU solution (0.0060 mmole, 1 eq) were added, and the mixture was allowed to stir at 0 C. for an additional 20 min. The solution was then warmed to 25 C. and allowed to stir for 15 h. The mixture was diluted with 60 mL ethyl acetate then washed with 10 mL water and dried over Na2SO4. The organic layer was concentrated in vacuo and purified by silica gel chromatography using 2.5% MeOH in CHCl3 to afford 2 mg of a clear film (65%). M+H=531.2 add name to claims: 
     [1S-[1R*,3R*(E),7R*,10S*,11R*,12R*,16S*]]-11-Hydroxy-8,8,10,12,16-pentamethyl-3-[1-methyl-2-(2-aminomethyl-4-thiazolyl)ethenyl]-4,17-dioxabicyclo[14.1.0]heptadec-6(E)-ene-5,9-dione