REACTION OF L-TRYPTOPHAN WITH TRICHLOROMETHYLPEROXYL RADICAL (CCL3OO.) AND SINGLET OXYGEN (O-1(2)) - FORMATION OF DIFFERENT PAIRS OF ISOMERIC HYDROPEROXIDES

Radiolytic formation of the trichloromethylperoxy radical, in an oxyge nated aqueous solution containing L-tryptophan, results in the formati on of two new hydroperoxides which were identified as the epimeric hyd roperoxyoxindolylalanines 6 underbar and 7 underbar. These hydroperoxi des are suggested to be formed via addition of the CCl3OO. radical ont o the C(2) of the indole ring followed by addition of molecular oxygen onto the resulting carbon centered radical and subsequent decompositi on of the trichloromethylperoxy adduct. Thermal decomposition of the p rimary hydroperoxides 6 underbar and 7 underbar gives a series of know n L-tryptophan degradation products including N-formylkynurenine (10 u nderbar), L-kynurenine (9 underbar), and the corresponding epimeric al cohols 5 underbar and 8 underbar. Trichloromethylperoxy addition onto the C(2) or C(3) of L-tryptophan following rearrangement to yield an i ntermediate 2,3-epoxide derivative, may explain the formation of oxind olylalanine (11 underbar) and the epimeric hydroxypyrroloindoles 1 und erbar and 3 underbar via epoxide hydrolysis. The hydroperoxides 6 and 7 are distinctly different from those observed upon singlet oxygen oxi dation of L-tryptophan and together with their degradation and rearran gement products, these hydroperoxides could serve as probes to study m echanisms of the oxidative degradation of proteins.