8-Hydroxy-alloxazines

Oxidation with the anion of hydrogen peroxide (HO — O ) converts isoalloxazine-8-sulfonic acids (2) into 8-hydroxy-alloxazines (3). This reaction, which has been described recently by Smith et al. (168) is typical for electron deficient sulfonic acids (178) and apparently does not occur at the less activated position 6. 

The orange chromophore exhibited light sensitivity similar to that of FMN and was degraded to a pale yellow lumichrome analog, which turned orange-red upon deprotonation (pK 6.6). This compound was compared with synthetic 7-methyl-8-hydroxy-alloxazine (17), which in turn was obtained by straightforward condensation of violuric acid with 4-aminocresol in the presence of borate and indeed found to be identical. 

Quinoxaline hydroxy-JV-oxides (l-hydroxyquinoxalin-2-ones) have been prepared by alkaline hydrolysis of alloxazine N-oxides (Scheme... 

Polyakova, N. A., L. S. Tul chinskaya, L. G. Zapesochnaya, and V. M. Bere-zovsKir. Alloxazines and Isoalloxazines XXXI. Synthesis of Hydroxy Analogs of Natural Flavines. Zhur. Obsh. Khim. 42, 465 (1972). 

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