A New Synthesis Of Podophyllum Lignans By Weitz' Aminium Salt-Induced Free Radical Cycloaddition Reaction Of A Doubly Unsaturated Ester

Abstract

(±)-Isopodophyllotoxin (le) and related lactones 12, 13, 14 were synthesized by a biomimetic procedure from the doubly unsaturated esters 11a and lib by means of an oxidative free radical cycloaddition reaction utilizing a stable cation radical salt, Weitz' aminium salt, in one step. (+)-Isopicropodophyllin (lg), the trans-fused lactones, 12, 13, and 16, and thec cis-fused lactone 17 were also synthesized from the esters 11c and lid by the reaction with the same reagent. © 1995, The Pharmaceutical Society of Japan. All rights reserved.