Collect. Czech. Chem. Commun. 1985, 50, 2457-2470

Reaction of 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestane derivatives with reducing agents

Helena Velgová and Jaroslav Zajíček

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


Reaction of all stereoisomeric 3-acetoxy-4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestan-4a-ols I-IV with lithium aluminium hydride and reduction of 3-acetoxy-4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestan-4a-ones XXII and XXIII with sodium borohydride were studied. It was found that reductive opening of the 5β,6β-epoxide ring occured only in the case of the derivatives III and IV due to 5(O)n participation of the 3α-oxygen-containing substituent under formation of the transannular 3α,5α-epoxides VIII and IX, resp. On reduction of the 4a-keto epoxides XXII and XXIII with sodium borohydride the trans-epoxy alcohols III and I were formed. On the basis of 1H NMR data the conformation of the A-ring in the epoxides I-IV, XXII, and XXIII is also discussed.