CHEMICAL CONVERSION OF (4S, 5S)-(+)-GERMACRONE 4, 5-EPOXIDE, A PLAUSIBLE BIOGENETIC INTERMEDIATE FOUND IN THE ESSENTIAL OIL OF ZEDOARIAE RHIZOMA FROM YAKUSHIMA, JAPAN

Abstract

The biogenetic-type chemical conversion of (4S, 5S)-(+)-germacrone 4, 5-epoxide (2___∼) was examined. It was found that acidic treatment of 2___∼ furnished three guaiane-sesquiterpenoids : GU-1 (3___∼), GU-2 (4___∼), and GU-3 (5___∼), while alkaline treatment of 2___∼ provided an eudesmane-sesquiterpenoid EU-1 (6___∼) as respective major reaction products. The structures of these conversion products were determined on the basis of their spectral data. GU-2 (4___∼) was further analyzed by X-ray crystallography. The GU-1 (3___∼) and GU-2 (4___∼) were found in minor quantities in Zedoariae Rhizoma from Yakushima, Japan. THe previously proposed structure of procurcumenol is revised as 3___∼.