Synthesis of (22S, 23S)-homobrassinolide and brassinolide from stigmasterol

Facile Syntheses of Brassinosteroids: Brassinolide, Castasterone, Teasterone and Typhasterol

“…The acetonide 8b was converted into brassinolide (la) in a similar manner to that described from tetraacetylcastasterone. 5 ) The cydoketone 2b was converted into a 3f3-acetate (10) in a similar manner to that described for 3f3-acetoxy-5oc-ergost-22-en-6-one. 6 ) A small amount -of a 3f3-alcohol compound was produced in the reaction, so the product was acetylated and then purified.…”

Synthesis of Brassinolide Analogs with or without the Steroidal Side Chain

“…aroused much interest among synthetic chemists.!) We have already reported the synthesis of brassinolide 1,2,3) (22R,23R)-homobrassinolide 2,4) (22S,23S)-homobrassinolide 3,3,5) and (22S,23S)-28-norbrassinolide 4 6 ) ( Fig. 1).…”

“…For the synthesis of 6 and 7, a known aldehyde 15 was employed as the starting material, which in tum was prepared from stigmastero1. 3 ) Addition of isoamylmagnesium bromide to 15 afforded 16. The (S)-configuration tentatively assigned to the newly generated hydroxyl group at C-22 was based on the assumption that Cram's rule was applicable in this particular case as it was in others.…”

Short-step Syntheses of Homodolicholide and Homodolichosterone

“…ll ) This reaction proceeded quite easily owing to the assistance of the neighboring hydroxyl group. An olefinic ketone 8--which was an intermediate in our syntheses of brassinolide 5,[6][7][8] castasterone 6 7 ,8) and dolicholide 3 9 ) from 7-was treated with m-chloroperbenzoic acid in dichloromethane at room temperature for 8 days to give the two 7-oxa lactonic epoxides 9 (7.0% yield) and 10 (25.3% yield), along with the keto epoxides 16 (3.5% yield) described below and a 6-oxa lactonic epoxide 11 (8.7% yield), after chromatographic separation. Epoxide ring-opening of 10 with a phenylselenyl anion prepared from diphenyl diselenide and sodium borohydride 10 ) yielded a regioisomeric mixture containing 12.…”