Abstract
In the present study, identification of the compounds produced by the reaction of FMN with H_3PO_4 or AMP in the presence of carbodiimide was attempted by means of paper chromatography, paper electrophoresis, absorption spectrum, phosphate content, potentiometric titration, and others. U_1,U_2 and U_5 were ascertained to be riboflavin-4', 5'-cyclic monophosphate and U_6 to be FAD. Both U_4 and U_8 were probably P^1,P^2-di-(riboflavin-4', 5'-cyclic)-pyrophosphate. U_3 and U_6,which were produced by the reaction of FMN with H_3PO_4 and of FMN with AMP are thought to be P^1-(riboflavin-4', 5'-cyclic)-pyrophosphate and P^1-(riboflavin-4', 5'-cyclic)-P^2-(adenosine-5')-pyrophosphate. The above results suggest that the cyclization is predominant to the formation of pyrophosphate linkage in case of FMN. Consequently, it seems favorable to cover the hydroxyl group at 4'-position of FMN with a suitable protective group for synthesis of pyrophosphate ester such as FAD.
