The synthesis of (–)-sandaracopimaradiene from androstane derivatives

Abstract

The conversion of testosterone and 3β-hydroxyandrost-5-en-17-one into the diterpene sandaracopimaradiene is described. 4,4-Dimethyl-5α-androst-14-ene and its 17β-hydroxy-derivative were prepared by acid-catalysed isomerisation of the 5,7-dienes, hydrogenation, and further isomerisation of the resulting 8(14)-olefins. Cleavage of ring D by reduction of the ozonide and selective oxidation of the seco-diol or triol with manganese dioxide yielded ring-D homo-lactones, which were converted by way of the β-keto-lactone into (–)-sandaracopimaradiene.