Hydrolysis of isoalloxazines (flavins) in the ground and excited states

Abstract

The hydrolysis of 10-alkyl-3-methylisoalloxazines (flavins) and their 5-oxides with benzyltrimethylammonium hydroxide in dimethylformamide or alcoholic potassium hydroxide in the dark gave the corresponding spirohydantoins, while the same reaction under irradiation brought about the elimination of the 10-alkyl group ( in the case of lower alkyls) to give 3-methylalloxazine; treatment of the spirohydantoins with concentrated sulphuric acid caused intramolecular dehydration to give the original isoalloxazines.