Abstract
| - A palladium(II)-catalyzed hydroxycyclization−carbonylation−lactonization sequence with appropriate pent-4-ene-1,3-diols provides efficient access to the bicyclic γ-lactones, 5-n-butyl- and 5-n-hexyltetrahydrofuro-[3,2-b]furan-2(3H)-ones (3) and (4), respectively, in both racemic and enantiomeric forms. Some of the substrate pent-4-ene-1,3-diols of high enantiomeric excess (ee) havebeen derived from racemic terminal epoxides by hydrolytic kinetic resolution (HKR) using cobalt(III)−salen complexes. (9Z,12R)-(+)-Ricinoleic acid also serves as a “chiral pool” source of otherpent-4-ene-1,3-diols. These syntheses and enantioselective gas chromatography confirm thestructures and absolute stereochemistry of the lactones in some species of parasitic wasps(Hymenoptera: Braconidae). The highly abundant 5-n-hexyltetrahydrofuro-[3,2-b]furan-2(3H)-one(4) in Diachasmimorpha kraussii and D. longicaudata is of high ee (>99%) with (3aR,5R,6aR)stereochemistry.
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