13C NMR-based empirical rules to determine the configuration of fatty acid butanolides. Novel ç-dilactones from Pterogorgia spp

Abstract

Diastereomeric ç-dilactones isolated from Pterogorgia spp allowed the establishment of 13C NMR-based empirical rules to determine the relative stereochemistry of 3-alkyl-4-hydroxy-5-methyl-2(5 H)-dihydrofuranones, ç-lactone moieties ubiquitous in many bioactive synthetic and natural products. An NMR-based method using Pirkle's reagent at low temperature allowed the absolute configuration of the naturally occurring dibutenolides to be unambiguously determined. A biogenetic pathway that involves oxidation of long-chain (C16:0 and C18:0) fatty acids is proposed.