Transformation of the steroidal sapogenin side chain. Part II. A new method for the preparation of 16-alkylated-pregn-16-en-20-ones

Abstract

The addition of Grignard reagents to some sapogenoic acid derivatives occurred at position 16α. The methyl esters gave 16α,26,26-trialkylspirostans which, by enol acetylation, oxidation, and saponification gave the corresponding 16-alkylpregn-16-en-20-one. Direct oxidation afforded 16α-alkylbisnorcholanic 22 → 16β-lactones (γ-lactones). Sapogenoic acids gave 16α-alkyl-20-oxospirostans (δ-lactones) and the amides the corresponding δ-lactams. Base-catalysed autoxidation of the γ- and δ-lactones gave the corresponding 16-alkylpregn-16-en-20-one directly.