ISSN:
0030-4921
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The acidity constants of both Z and E conformational isomers of five N-nitroso-N-alkyl-α-amino acids, ON—N(R1)—CH(R2)—COOH, are determined by the observation of selected pH titrated 1H NMR signals. For two glycine derivatives (1, R1=CH3, R2=H, ON—Sar; 2, R1=C2H5, R2=H, ON—EtGly) and two alanine derivatives (3, R1=CH3, R2=CH3, ON—MeAla; 4, R1=C2H5, R2=CH3, ON—EtAla) the E isomers appear to be stronger acids than the Z while for the third alanine derivative (5, R1=n-C3H7, R2=CH3, ON—PrAla) the opposite is observed. These results, also including anisotropy effects associated with the N—NO group, are discussed in terms of conformations. A 7-membered ring conformation with an —NO…HOOC— intramolecular hydrogen bond is proposed to be statistically important in the Z isomers of 1, 2, 3 and, to a lesser extent, 4.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1270180306
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