Studies on the Synthesis of Steroidal Plant-Growth Hormones; XVIII. A Convenient Route to 26,27-Bisnorbrassinolide

Abstract

(22R,23R)-22,23-Isopropylidenedioxy-6-oxo-24-nor-5α-cholest-2-ene (10), a precursor of 26,27-bisnorbrassinolide (2), is synthesized from the α, β-unsaturated (22R,23R)-γ-lactone 4 by a six-step sequence: hydrogenation, reduction, oxidation, decarbonylation, and reductive elimination. The overall yield is 29% from 4 to 10.