Clerici Francesca, Gelmi Maria Luisa, Pellegrino Sara, Pilati Tullio
Istituto di Chimica Organica A. Marchesini, Facoltà di Farmacia, Università di Milano, Via Venezian 21, I-20133 Milano, Italy.
J Org Chem. 2003 Jun 27;68(13):5286-91. doi: 10.1021/jo030085x.
A new synthetic approach to diastereomeric cyclopent-3-enylglycines 19/20, functionalized on the ring with a formyl group, and to cyclopentylglycine, substituted with a carboxy group (compounds 21/22), was devised by applying retro-aldol and retro-Claisen reactions, respectively, to diastereomeric 2-amino-3-ethoxycarbonyloxynorbornene-2-carboxylic acid derivatives 5, 6 and to diastereomeric 2-amino-3-oxo-norbornane-2-carboxylic acid derivatives 17, 18. The goal of controlling the cis stereochemistry of the cyclopentyl substituents was reached using compounds 17, 18. A partial control of the stereochemistry of the amino acidic carbon was achieved starting from 17 and using sodium hydrogen carbonate in acetone/DMF. From exo-17, the acid 22 was obtained as the major diastereomer.
