Hemisynthesis and odour properties of δ-hydroxy-γ-lactones and precursors derived from linalool

摘要

γ-Lactones are aromatic molecules which constitute the aroma or flavour of many natural products. Func-tionalized y-lactones have attracted attention in recent years due to their synthetic importance as building blocks in bioactive natural product synthesis. Furthermore the δ-hydroxy-γ-lactone motif is the core structure of bioactive natural products. To synthesise lactones, an attractive method consists of subjecting β,γ- or γ,δ-unsaturated ester to a Sharpless asymmetric dihydroxylation. Hemisynthesis of such lactones was here realised in two steps from a monoterpenic alcohol, linalool. First, the allylic terpenol was submitted to a Johnson-Claisen rearrangement to produce γ,δ-unsaturated esters. These γ,δ-unsaturated esters were then subjected to an asymmetric dihydroxylation to give the corresponding γ,δ-unsaturated dihydroxyesters which can directly cyclise to the δ-hydroxy-y-lactones. Five new products were isolated and characterised by 1D- and 2D-NMR. The odour evaluation of lactones and their precursors revealed interesting properties.