The reactions of N-acyl-L-tryptophans, (1) and (2), with O2- afforded their corresponding 2,3-bond cleavage compounds, (5) and (7), as the major products. On the other hand, the reactions of N-acyl-L-tryptophan alkylamides, (3) and (4), with O2- afforded their corresponding dioxindoles, (8) and (9), as the major products. A similar reactivity difference was observed for tryptophan-containing dipeptides, (10) and (11).