Stereoselective Synthesis of Highly Substituted γ-Lactones and Butenolides by Intramolecular Michael Addition of Enantiomerically Enriched γ-oxy α,β-Unsaturated Esters

Article abstract of DOI:10.1021/jo00095a022

The synthesis of polysubstituted γ-lactones by the base-induced cyclization of enantiomerically enriched γ-<(phenylthio)acyl>oxy α,β-unsaturated esters obtained from 2,3-epoxy alcohols is described.The procedure is highly stereoselective and compatible with a wide range of functionalities (ester, tetrahydropyranyl ether, silyl ether, etc.).Varying degrees of substitution, including quaternary centers, in the final γ-lactone were synthesized with excellent stereoselectivity.Useful functional interconversions were successfully demonstrated, in particular those resulting in butenolides.By the use of AM1 it was concluded that the intramolecular Michael reaction can be described as a kinetically controlled reaction in which the relative stability of the transition states for all possible final configurations led to geometries in agreement with the experimental results.