Ma. Abdallah et al., 1,3-DIPOLAR CYCLOADDITION OF BENZONITRILIUM N-PHENYLIMIDE TO DIDEHYDROPEPTIDES, Journal of chemical research. Synopses, (5), 1993, pp. 182-183
N-Benzoyl-alpha,beta-didehydrophenylalanylglycine ethyl esters 3a-f ad
d benzonitrilium N-phenylimide 2 regioselectively to yield the pyrazol
ylaminocarboxylic acid peptides 6a-f.