Synthetic plant growth regulators. II. The preparation of tricyclic helminthosporic acid analogues with gibberellin-like properties

Abstract

Cyclopropyl ketone (13), prepared by the copper-catalysed decomposition of diazoketone (12), underwent specific cyclopropyl bond fission on reduction with lithium in liquid ammonia. Oxidation of the reaction product mixture followed by catalytic hydrogenation gave ketone (7) whose stereo-chemistry was established by degradation to trans-decalyl- 9-acetic acid (18), an authentic sample of which was prepared from trans-decalin-9-carboxylic acid. Ketone (7) was converted via its methylene derivative (21) to the pyrrolidinium salt (24) which underwent base induced [2,3]sigmatropic rearrangement, followed by hydrolysis, to give aldehyde (26). Acid (5) was formed by simple oxidation and converted by base catalysed isomerization of its methyl ester, then hydrolysis, into acid (6).