Preparation of kaurenolide and its 5α,6α(H)-isomer

Abstract

In the preparation of kaurenolide, essentially by the literature method, the formation of ent-6-oxokaur-16-en-19-oic acid from the toluene-p-sulphonate of 7β-hydroxykaurenolide was found to be dependent on the quality of the lithium iodide monohydrate used. ent-6-Hydroxykaura-6,16-dien-19-oic acid 19,6-lactone, prepared from the toluene-p-sulphonate of 7β-hydroxykaurenolide, zinc dust, and sodium iodide in refluxing 2-methoxyethanol, was found to be hydrolysed by base to ent-6-oxo-5β-kaur-16-en-19-oic acid, which gave the 5α,6α(H) isomer of kaurenolide upon reduction.