Unidirectional Dieckmann Cyclizations on a Solid Phase and in Solution

Article abstract of DOI:10.1021/jo01304a015

Dieckmann cyclization of 2percent divinylbenzene-copolystyrene resin alkyl pimelates and analogous benzyl alkyl pimelates is reported.The use of uniquely single-labeled dioate esters has allowed analysis of the direction of closure via decarboxylation of the keto ester products.The influence of steric factors on the competition between enolate condensation and transesterification and upon the direction of closure of the cyclization has been evaluated, and the conditions for achieving >99percent regioselective closure are described.Modifications in the conditions of solid-phase peptide synthesis required for successful high-temperature enolate cyclization have been developed and the results are compared to solution reactions of benzyl alkyl esters under similar conditions.The resin attachment afforded a clear benefit over the benzyl models and greatly simplified isolation and purification of the resulting β-keto esters.