Abstract
Oxidation of 1a with DMSO-acetic or trifluoroacetic anhydride led to the formation of a mixture of epimeric gem-diols 2 and 3 in the ratios of ≍3:1 and ≍7:1, respectively. Reduction of this mixture with NaBH4 followed by benzoylation and chromatography afforded 4a and 5a.