Stereoselective synthesis of the 20-hydroxyecdysone side chain
Abstract
A new procedure for the construction of the 20-hydroxyecdysone-type side chain starting from 20-oxopregnane is described. The stereoselective reduction of the lactone (15) as a key reaction to give the δ-lactone (17) and the γ-lactone (18), under various conditions has also been investigated. A stereoselective synthesis of (20R,22R)-5α-cholestane-3β,20,22,25-tetraol (20) is described.