Synthesis of locked half-chair and boat δ-lactones from the sesquiterpenoid drimenol

Abstract

The half-chair δ-lactone 4α,6β,10,10-tetramethyl-1αH-3-oxabicyclo[4,4,0]decan-2-one (1)[(5)] and the epimeric boat δ-lactone 4β,6β,10,10-tetramethyl-1αH-3-oxabicyclo[4,4,0]decan-2-one (2)[(6)] have been synthesised from the sesquiterpenoid drimenol via the intermediates 1α-(1-acetoxymethylacetonyl)-2β-methoxycarbonylmethyl-1 β,3,3-trimethylcyclohexane (7), 1α-acetonyl-2β-methoxycarbonylmethyl-1 β,3,3-trimethylcyclohexane (9), 2β-carboxy-1α-[(2R)-2-hydroxypropyl]-1β,3,3-trimethylcyclohexane (13), and 2β-carboxy-1α-[(2S)-2-hydroxypropyl]-1β,3,3-trimethylcyclohexane (26).