Conformational study of the intramolecular Diels-Alder reaction of a pentadienyl acrylate. Theoretical evaluation of kinetic and thermodynamic control

[GRAPHICS] Acrylate 4, prepared from diacetylrhamnal, underwent intramolecular Diels-A lder cycloaddition to give the thermodynamically disfavored trans-fused gam ma-lactone 15 as the major product, along with two stereoisomeric cycloaddu cts. A computational analysis of each of the four transition states arising from 4 and the corresponding cycloadducts permits an understanding of the contrasting requirements for kinetic versus thermodynamic control of the re action.