Biosynthesis of plant sterols—IV. : An investigation of a possible mode of 14β-hydroxylation in digitoxigenin

Abstract

Hypothetical biosynthetic routes for the introduction of 14β-hydroxyls into C/D trans (14α-H) steroids are discussed. Several theoretical possibilities based on established chemical processes, which are susceptible to experimental evaluation, are forwarded. In the light of these hypotheses the role of 14α-hydroxy progesterone, one of the theoretically possible intermediates in the biosynthesis of cardenolides, was explored. It was shown that under the experimental conditions employed the 1- 3H-14α-hydroxy progesterone was not incorporated into digitoxigenin in Digitalis lanata. The synthesis of the tritiated precursor is described and it was proved that ca. 80 per cent of the tritium had the 1α-stereochemistry and a minimum of ca. 15 per cent had the 1β-stereochemistry.