Ene approach for concurrent control over the chiral centres at C-20 and C-22 of steroid side chains: a highly stereocontrolled synthesis of (20S,22R)-(erythro-)22-hydroxy-23,24-acetylenic steroid side chains

Abstract

The ene reactions of a (Z)-Δ¹⁷⁽²⁰⁾-steroidal olefin with acetylenic aldehydes in the presence of Me₂AlCl produce (20S,22R)-(erythro)-22-hydroxy-23,24-acetylenic steroid side chains with high diastereoselectivity and diastereofacial selectivity.