New digitalis steroids. Synthesis of 17α-amino 5β,14β-steroids by thermolysis of 17β-azidocarbonyloxymethyl derivatives
Abstract
An efficient procedure for the synthesis of otherwise difficult to access 17α-amino derivatives of the digitalis series is described. The key reaction is the stereospecific thermocyclisation of 3β-acetoxy-l7β-azidocarbonyloxymethyl-5β-androstan-14β-ol 3b to (17R)-3β-acetixy-14β-hydroxyspiro[5β-androstane-17,4′-oxazolidin]-2′-one 4.