EXCHANGE OF AMIDE PROTONS - EFFECT OF INTRAMOLECULAR HYDROGEN-BONDING

Kinetics of the exchange of the NH protons of a primary amide with intramolecularly hydrogen bonded protons has been studied by NMR saturation transfer methods. The base-catalyzed exchange is retarded ca. 30-fold by the hydrogen bonding. The exchange is considered to proceed by direct abstraction of the proton from the hydrogen bond. The acid-catalyzed exchange proceeds by the N-protonation mechanism, but there is no retardation due to hydrogen bonding. The significance of these results for NH proton exchange in peptides and proteins is discussed. © 1990, American Chemical Society. All rights reserved.