Cyclized dipeptide model for a beta-bend.

Abstract
A cyclic dipeptide in which L-Ala-Gly was cyclized with .epsilon.-aminocaproic acid was synthesized as a model for a .beta.-bend. Its conformational properties were examined using conformational energy calculations and NMR, IR, Raman and circular dichroism spectroscopy in various solvents. A type II .beta.-bend apparently exists in the Ala-Gly moiety, with an NH.cntdot..cntdot..cntdot.O.dbd.C H-bond in the .epsilon.-aminocaproic acid portion of the molecule; the molecule adopts a unique conformation in solution. An open-chain analog of this compound exists in solution as an ensemble of conformations but with a significant amount of a type II .beta.-bend structure in the ensemble.

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