Synthesis of “glycospirostanes”—Steroid sapogenins with a sugar-like ring F

The synthesis of two “glycospirostanes” from 23-oxotigogenin acetate is described. (23S,24S,25R)-5α-Spirostane-3β,23,24,25-tetraol was obtained by dehydrogenation followed by stereoselective reduction of the 23-oxo group and OsO4 dihydroxylation of the C24–C25 double bond. Allylic hydroxylation with SeO2 of 3β-acetoxy-5α-spirost-23-ene obtained from 23-oxotigogenin acetate followed by OsO4 dihydroxylation of the C23–C24 double bond afforded (23R,24S,25R)-5α-spirostane-3β,23,24,25-tetraol.