Studies on the Syntheses of Sesquiterpene Lactones. III. Improved Synthesis of Vulgarin

Abstract

Abstract An improved synthesis of vulgarin is described. Epoxidation of 1-oxo-5αH,6β,11βH-eudesm-3-en-6,13-olide and successive treatment of the resulting epoxide with silica gel gave vulgarin. Oxidation of 1-oxo-5αH,6β,11βH-eudesm-3-en-6,13-olide with air or oxygen gas gave 4α-hydroperoxy-1-oxo-5αH,6β,11βH-eudesm-2-en-6,13-olide and 4β-hydroperoxy-1-oxo-5αH,6β,11βH-eudesm-2-en-6,13-olide, which were transformed into vulgarin and C4-epivulgarin, respectively.