Indolenine hydroperoxide

Asquith and Rivett (72) irradiated tryptophan in oxygenated aqueous solution with a medium pressure mercury lamp under neutral, acidic and basic conditions and identified several degradation products including formylkynurenine, kynurenine, aspartic acid, serine, glycine, alanine and (3-alanine. They suggest that the main degradative pathway of tryptophan is conversion to kynurenine via the indolenine hydroperoxide (see Section III. 1.1). The formation of amino acids could arise from further degradation of kynurenine as shown below. 

Indole chemiluminescence (J> p. 112, I80,i8ia)j can a]so be regarded as a special type of Schiff s base chemiluminescence, for the indole compounds very probably react via a hydroperoxide derived from the respective indolenine form. 

Autoxidation occurs readily with alkyl-indoles, thus, for example, 2,3-diethylindole gives an isolable 3-hydroperoxy-3//-indole. Generally, such processes give more complex product mixtures resulting from further breakdown of the initial hydroperoxide singlet oxygen also produces hydroperoxides, but by a different mechanism. If the indole carries a side-chain capable of trapping the indolenine by intramolecular nucleophilic addition, then tricyclic hydroperoxides can be isolated. ... 

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