Photooxidation ring-opening reactions

The ring opening reaction was also supported by the studies of photooxidation of low molecular model compounds of polystyrene, e.g. 2-phenyl butane (5.85) [1360, 1361] ... 

The photochemical reactivity of alkenes is also of great interest [1,2]. Studies in this area have led to an expansion of the synthetic utility of these substances. Typical photochemical reactions include cis-trans isomeriza-tions, inter- and intramolecular cycloadditions, photooxidations, and electrocyclic ring opening and closing of conjugated dienes and polyenes. Many of these photoreactions have thermal counterparts. In contrast,... 

In the light of these considerations, the results of Jori et al. are questionable and should be considered with utmost caution. All available literature clearly shows that formylkynurenine is not the only product formed upon photooxidation of tryptophan, although seemingly it represents the major reaction pathway. Initial attack by oxygen at indole C-3 is implicated in all current interpretation of indole oxidations, and decomposition of the resulting hydroperoxide usually leads to opening of the indole ring (see also previous Section III. 1.1.). One reason for the lower yields of products obtained from free tryptophan than from a derivative is the occurrence of deamination in the case of the former. 

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