Studies on steroidal plant-growth regulator 25. Concise stereoselective construction of sidechain of brassinosteroid from the intact sidechain of hyodeoxycholic acid: Formal syntheses of brassinolide, 25-methylbrassinolide, 26, 27-bisnorbrassinolide and their related compounds

Article abstract of DOI:10.1016/S0040-4020(01)88509-4

A concise stereoselective construction of sidechain of brassinolide (1), 25-methylbrassinolide (3) and 26, 27-bisnorbrassinolide (4), which involves β-alkylative 1,3- carbonyl transposition of the α,gb-unsaturated ketones 11 and 34 and α, β-unsaturated methyl ester 26, using the intact sidechain of hyodeoxycholic acid (2) as starting material, is described. The formal syntheses of 1, 3 and 4 were accomplished. In the mean time, 25-methylcastasterone (21), 26,27-bisnortyphasterol(6) and the new 25-methyltyphasterol (5) were also synthesized.