Abstract
The reaction of thiamine free base (I) with isocyanate derivatives in polar solvent such as dimethylformamide afforded 2- (7-methyl-3, 4-dihydropyrimido [4, 5-d] pyrimidin-3-yl) -2-methyltetrahydrofuran-3-yl alkyl (aryl) carbamthiolate (V), which then reacted with another isocyanate molecule to give N-carbamoylthiamine free base (II). The reaction mechanism is discussed kinetically. The reaction of I with isocyanate derivatives in less polar solvent such as chloroform afforded only II-analogues. The reaction of II with N, N-disubstituted carbamoylchlorides afforded 2- [N-formyl-N- (2-methyl-4-aminopyrimidin-5-yl) methyl] amino-2-methyltetrahydrofuran-3-yl disubstituted carbamthiolates (VIIa-c).
