Total Synthesis of (−)-Chiloscyphone, Sesquiterpenoid Isolated from the Liverwort. Absolute Configuration of (−)-Chiloscyphone and (+)-Chiloscypholone

Abstract

Abstract The absolute configurations of (−)-chiloscyphone and (+)-chiloscypholone isolated from the liverwort Chiloscyphus polyanthos and C. pallescens respectively, have been determined by the total synthesis of the optically active compound. The 1,4-addition of vinylmagnesium bromide to 3,4-dimethyl-2-cyclohexenone in the presence of copper(I) bromide-dimethyl sulfide complex and the subsequent aldol condensation of the ketoaldehyde derived in several steps afforded the hydrindenone derivative. The key intermediate alcohol has been resolved by the use of (1S)-(−)-camphanic chloride. The optically active hydroxy ester has been converted to (−)-chiloscyphone.