Synthesis of some 2,3- and 5,6-unsaturated 19-homosteroids bearing an oxygen containing group at the position 19a

Abstract

A synthesis of 5,6- and 2,3-unsaturated 19a-methoxy-19a-homocholestane derivatives XVII and XXI is reported. The key steps in the synthesis of the former compound is protecting the 3β-hydroxyl group and 5,6-double bond by conversion to a cyclosteroid (IX → VI, selective hydroboration of the protected steroid followed by methylation (VI → X → XI) and reductive removal of the 3β-substituent (XVI → XVII). The 2,3-unsaturated methyl ether XXI was obtained by elimination from the mesylate XX prepared from the 5,6-unsaturated derivative XV in three steps.