Oxidative and reductive transformations of epothilone A

The C7 hydroxy group of cytotoxic epothilone A was selectively oxidized using PDC. A selective oxidation of the C3 hydroxy group was accomplished with Me2S/(PhCO2)2 after in situ protection of C7 OH. Reduction of epothilone A or of a C5, C7 dioxo derivative with NaBH4 proceeded at the C5 carbonyl group. Oxidation and hydrogenation of the C16 C17 double bond proved to be difficult but it was easily cleaved with ozone and the resulting keto derivative was transformed to epothilone analogs with different side chains.