Epothilones A and B (2a and 2b, Scheme 1) are naturally occurring cytotoxic macrolides that were isolated from a cellulose degrading mycobacterium, Sorangium cellulosum (Höfle et al. Angew. Chem., Int. Ed. Engl. 1996, 35, 1567 and J. Antibiot. 1996, 49, 560; each of which is incorporated herein by reference). Despite their vastly different structures, epothilones A and B share the same mechanism of action as paclitaxel (Taxol®) which involves growth inhibition, of tumor cells by tubulin polymerization and stabilization of microtubule assemblies (Bollag et al. Cancer Res. 1995, 55, 2325; incorporated by reference). In spite of its unquestioned clinical value as a front-line chemotherapeutic agent, Taxol® is far from an ideal drug. Its marginal water solubility necessitates recourse to formulation vehicles such as Cremophores that pose their own risks and management issues (Essayan et al. J. Allergy Clin. Immunol. 1996, 97, 42; incorporated herein by reference). Moreover, Taxol® is vulnerable to deactivation through multiple drug resistance (MDR) (Giannakakou et al. J. Biol. Chem. 1997, 272, 17118; incorporated herein by reference). However, it has also been demonstrated that epothilones A and B retain remarkable potency against MDR tumor cells (Kowalski et al. Mol. Biol. Cell 1995, 6, 2137; incorporated herein by reference). Additionally, the increased water solubility in comparison to paclitaxel may be useful for the formulability of epothilones. While the naturally occurring compound, epothilone B (2b, EpoB, in Scheme 1), is a potent member of the epothilone family of natural products, it unfortunately possesses, at least in xenograft mice, a worrisomely narrow therapeutic index (Su et al. Angew. Chem. Int. Ed. Engl. 1997, 36, 1093; Harris et al. J. Org. Chem. 1999, 64, 8434; each of which is incorporated herein by reference).

Given the limited therapeutic index of EpoB, other epothilone analogues, in particular the 12,13-desoxyepothilones, were investigated for their ability to provide an improved therapeutic profile (see, U.S. Pat. Nos. 6,242,469, 6,284,781, 6,300,355, 6,369,234, 6,204,388, 6,316,630; each of which is incorporated herein by reference). In vivo experiments conducted on various mouse models demonstrated that 12,13-desoxyepothilone B (3b, dEpoB in Scheme 2) possesses therapeutic potential against various sensitive and resistant human tumors in mice xenografts (Chouet al. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 9642 and 15798; incorporated herein by reference). Recently, the therapeutic superiority of these desoxyepothilones over other anticancer agents has been conclusively demonstrated by thorough comparative studies (Chou et al. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 8113; incorporated herein by reference). Due to its impressive in vivo profile, dEpoB has been advanced through toxicology evaluations in dogs, and is now2 in human trials as an anticancer drug.

In light of the promising therapeutic utility of the 12,13-desoxyepothilones, it would be desirable to investigate additional analogues as well as additional synthetic methodologies for the synthesis of existing epothilones, desoxyepothilones, and analogues thereof, as well as novel analogues thereof. In particular, given the interest in the therapeutic utility of this class of compounds, it would also be desirable to develop methodologies capable of providing significant quantities of any epothilones or desoxyepothilones previously described, or those described herein, for clinical trials and for large-scale preparation.