Structural effects on the N-nitrosation of amino acids

The relative importance of three different routes for the N- nitrosation of amino acids (nitrosation by N₂O₃, by NO⁺/NO₂H₂⁺ and by intramolecular migration of the nitroso group from the initially nitrosated carboxylate group) was investigated for methylaminobutyric acid, methylaminoisobutyric acid, azetidine-2-carboxylic acid, azetidine-3-carboxylic acid, indoline carboxylic acid, and phenylaminoacetic acid. Reaction kinetics were determined by the initial rate and Guggenheim methods, by spectrophotometric monitoring of the formation of nitroso amino acid. Kinetic parameters were calculated using a nonlinear optimization algorithm based on Marquardt's method. In the experimental rate equation the dominant term corresponds to nitrosation by dinitrogen trioxide, which experiments at various temperatures show to take place via an ordered transition state. Nitrosation by intramolecular migration is significant for substrates facilitating the formation of a transition state structure with a 5- or 6-membered ring. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 495–504, 1997.