Studies on gibberellin synthesis. Preparation of advanced intermediates based on 1 H-2,10a-ethanophenanthrene

Abstract

The phenanthrenone (6) was converted into 1H-2,10a-ethanophenanthrene (16) by means of an acid-induced cyclization of α-diazoketone (14). Protection and hydrogenation of (16), followed by reductive methylation of the resulting tetracyclic ester (20) gave the corresponding dihydro derivatives(22) or (23), potential precursors to gibberellic acid (8).