Synthesis of (2R,3S,22S,23S)-2,3,22,23-tetrahydroxy-B-homo-7-aza-5α-stigmastan-6-one, an aza-analogue of homobrassinolide

Abstract

(2R,3S,22S,23S)-2,3,22,23-Tetrahydroxy-B-homo-7-aza-5α-stigmastan-6-one, an aza-analogue of homobrassinolide, has been synthesized starting with 5α-stigmasta-2,22-dien-6-one. Osmylation of the trimethylsilyl enol ether of this dienone afforded (2R,3S,7S,22S,23S)-2,3,7,22,23-pentahydroxy-5α-stigmastan-6-one, which by oxidation of the acyloin group, after protection of the glycolic systems, afforded (by esterification) an aldehydo ester, which is the key intermediate for the production of the final compound by reductive amination.