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Published August 1, 1978 | public
Journal Article

Nitrogen-15 Nuclear Magnetic Resonance Spectroscopy. A Simple Procedure for Determination of the Rates of N-H Proton Exchange of cis- and trans-1-Aza-2-cyclononanone

Abstract

Several investigations have been made to determine the relative rates of N-H proton exchange in cis and trans isomers of peptide bonds. N-Methylacetamide and medium-ring lactams have been traditional models for the cis and trans isomers, respectively. Klotz and Feidelseit have reported that base-catalyzed N-H proton exchange of 1-aza-2-cyclopentanone is much faster than that of N-methylacetamide. However, Chen and Swenson4 subsequently found that amide protons of 1-aza-2-cycloheptanone exchange more slowly than those of N-methylacetamide in deuterium oxide solution. The nine-membered ring lactam, 1-aza-2-cyclononanone (l), is well established, to exist in several solvents as a nearly 1:l mixture of the cis and trans isomers and, as such, is well suited as a model for both the cis- and trans-amide bonds. We present here the results of a ^(15)N NMR study of base-catalyzed N-H proton-exchange reactions of 1 at the natural-abundance level of the isotope in dimethyl sulfoxide and in 80% aqueous ethanol.

Additional Information

© 1978 American Chemical Society. Received March 31, 1978. Supported by the National Science Foundation and by the Public Health Service, Research Grant No. GM-11072, from the Division of General Medical Sciences.

Additional details

Created:
August 19, 2023
Modified:
October 24, 2023