A three-step and enantioselective synthesis of (−)-(S)- or (+)-(R)-2-(furan-3-yl)-3,6-dihydro-2H-pyrans

Enantiomerically enriched (3-furyl)-2-pyran derivatives, key-intermediates in the synthesis of the pharmacophoric pyranofuranone system of the bioactive natural products manoalide and cacospongionolide B, are easily accessible by a rapid sequence involving a chiral allylation and a ring closing metathesis reaction.