6.7‐Dimethyl‐ und 1.3.6.7‐Tetramethyl‐alloxazin

Mechanochemical N-alkylation of imides

“…For instance in the reaction of uracil ( 17 ) or 7,8-dimethylalloxazine ( 36 ). The required substrate 36 was prepared by mechanochemical condensation [35] of alloxane ( 34 ) and 4,5-dimethyl-1,2-phenylenediamine ( 35 ) in the presence of p -toluenesulfonic acid [36–37] (Scheme 3). The α-dione/α-diamine reaction proceeds in a similar manner and yield to the condensation reaction carried out under classical reaction conditions (1 M HCl, 60 °C, 30 min) [38].…”

Mechanism of riboflavin-catalyzed oxidations

“…The spectrum of the heat degradation product obtained after 3 days at 95 to 100°, is presented in Figure 12 This product is undoubtedly l,2-dihydro-6,7-dimethyl-2-keto-1-(1'-D-ribityl)-3-quinoxaline-carboxylic acid. This is the same compound as the one obtained from the alkaline degrada tion (246,247). The spectrum of the latter compound is given in the insert in Figure 12.…”

“…The products obtained from this degradation are large in number, with the side chain isomers being investi gated most thoroughly. The degradation compounds most often studied are lumiflavin (6,7*9™trimethylisoalloxazine) (6, 13, ll|, 1$ ) > lumichrome (6,7-dimethylalloxazine ) ( 16,17), 1'carboxyme thy Hum if lavin (18), 1 1 -carboxy lumif lavin (19,20,21,22), and 1 1 -methyllumiflavin (23) with the by-products formaldehyde, formic acid, glycolic acid, and a four carbon sugar (2I4, 25 ). The structures of the flavins are shown in Figure 1.…”

Mechanism of riboflavin-catalyzed oxidations

“…(0.2 ionic strength) 1[0 ( a M235 = 2.55 x lo4, &M310 a 9.3 X lo3, a M355 « 9*45 x 10 3 ).This product is undoubtedly l,2-dihydro-6,7-dimethyl-2-keto-1-(1'-D-ribityl)-3-quinoxaline-carboxylic acid. This is the same compound as the one obtained from the alkaline degrada tion(246,247). The spectrum of the latter compound is given in the insert inFigure 12.Light stabilityUnder strong irradiation, riboflavin is converted, aerobically, into many degradative products with modified side chains on the 9 position.…”