Abstract
Syntheses of dialkyl 2-{3-(2-methyl-4-aminopyrimidin-5-yl) methyl-3a-methylperhydrofuro-[2, 3-d]-thiazole} phosphonates (Va-f), and their thermal isomerization affording dialkyl 7-[2, 9a-dimethyl-9-(2-hydroxyethyl)-5, 6, 7, 9, 9a, 10-hexahydropyrimido [4, 5-d]-thiazolo [3, 4-a] pyrimidine] phosphonates (VIIa-f) are described. Transesterification was occurred in the reaction of thiamine (B1) with diphenyl hydrogen phosphite in methanol. Regeneration of V from VII was also detected. O-allyl 7-[2, 9a-dimethyl-9-(2-hydroxyethyl)-5, 6, 7, 9, 9a, 10-hexahydropyrimido [4, 5-d] thiazolo [3, 4-a] pyrimidine] phosphinic acid (IX), O-allyl 2-[3-(2-methyl-4-aminopyrimidin-5-yl) methyl-4-methyl-5-(2-hydroxyethyl) thiazoline (4)] phosphinic acid (X), methyl and ethyl 2-[3-(2-methyl-4-aminopyrimidin-5-yl) methyl-3 a-methylperhydrofuro [2, 3-d] thiazole] phenylphosphonate (XIIa-b) were obtained. Brief reaction mechanisms are discussed.
