To solution of epothilone C (100 mg, 0.21 mmol) in CH3CN (2.5 mL) and 0.0004 M Na2EDTA (1.5 ml) at 0° C. were added excess CF3COCH3 (1 mL) followed by 2 KHSO5.KHSO4.K2SO4 (potassium peroxymonosulfate) (325 mg, 0.53 mmol) and NaHCO3 (75 mg, 0.89 mmol). The reaction mixture was stirred for 35 min then treated with dimethylsulfide (0.50 mL) and water (3.75 mL). The reaction mixture was warmed to room temperature, extracted with EtOAc (4×10 mL), dried over MgSO4, filtered, and concentrated. The residue was chromatographed with 55% EtOAc/hexanes to give epothilone A (59 mg, 57%) and compound A (30 mg, 29%) as a white solid. m/z: 494(M+H)+.
