Studies on a steroidal plant-growth regulator. Part 26. Stereoselective construction of the brassinolide side-chain: new practical syntheses of brassinolide analogues from hyodeoxycholic acid
Abstract
High stereoselectivity in an osmium tetroxide-catalysed asymmetric dihydroxylation of the 5β-cholan-22-en-24-oate 1b has been achieved and the (22R,23S)-22,23-dihydroxycholanoate 2b has been used as the key intermediate for syntheses of brassinolide analogues.