A practical, enantiospecific synthesis of (S)-trans-γ- monocyclofarnesol

Abstract

An expedient and concise synthesis of (S)-trans-γ-monocyclofarnesol is here described. The aforementioned sesquiterpene was prepared starting from enantioenriched (S)-γ-dihydroionone, which was in turn obtained from racemic α-ionone through the combined use of two previously developed processes. Key steps of the presented synthesis are the stereoselective Horner-Wadsworth-Emmons reaction between triethyl phosphonoacetate and γ-dihydroionone and the effective fractional crystallization of the γ-monocyclofarnesol-3,5-dinitrobenzoate esters. By these means the target compound was obtained in good yield and with very high stereoisomeric purity.