structure of the flavin: flavins which have either a long alkyl group or a carboxy-group gave rate constants greater by 103–104 fold than unmodified flavin, and the rate constant for flavin (5) which has both groups was further enhanced (> 106fold). On the other hand, the oxidation of (8) was less affected by the change in the flavin structure. The reactivity order for the oxidation of (7) was (1)(unmodified
Hydrolysis of flavin (I) with Triton B gave the 4a-spirohydantoin (II) as the main product along with III, showing that a main nucleophilic attack of hydroxide ion was initiated on the 10a position of I.
Isoalloxazines (2) were prepared easily by heating of the corresponding 5-anilino-6-(alkyl or aryl amino)pyrimidine-2,4(1H,3H)-diones (1) in dimethylformamide under oxygen.