Synthesis of some westphalen-type cardenolide analogs

Abstract

Synthesis of the lactone II and thiazole XXIII as models of compounds with cardiotonic activity is described. The key steps in the synthesis of the lactone II are Westphalen rearrangement (XII - XIII), construction of unsaturated lactone ring by intramolecular Witting reaction (XV XIX) and removal of the halogen from 6β-position by reduction with tributyltin hydride. XXIII was obtained from the bromo ketone XXII by treatment with ethyl thioxamate.