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

Acrylate 4, prepared from diacetylrhamnal, underwent intramolecular Diels-Alder cycloaddition to give the thermodynamically disfavored trans-fused gamma-lactone 15 as the major product, along with two stereoisomeric cycloadducts. 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 reaction.

Synthesis of ring D modified morphinan systems via ring expansion of a key codeine intermediate

Ring expansion and ring fragmentation products were synthesized from pentacyclic ketones 3 and 4 via Baeyer-Villiger oxidation. Oxidation of 3 with m-chloroperbenzoic acid afforded delta-lactone 9 which was transformed to enone 12 en route to the C6 inverted ether 14. Analogous oxidation of 4 gave delta-lactone 18. Opening of the lactone ring of 14 and 18 led to seco structures which, in the case of 19, underwent reannulation with incorporation of nitrogen to yield the hydroxylactam 21.