44826-45-1

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We have studied the reaction of 2,3-dihydro-4H-[1,3]thiazino[3,2-a] benzimidazol-4-one and 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4- ones with amines, alkylating reagents, and hydrogen peroxide. We have shown that the presence of an aryl substituent at the 2 position of [1,3-thiazino[3,2-a] benzimidazol-4-ones has a substantial effect on the direction of the reactions. 2006 Springer Science+Business Media, Inc.

Radioactivity from 14C>formate, from D-14C>-, D-14C>-, and D-3H,6-14C>glucose, from D-14C>fructose and from 14C>- and 14C>glycerol is incorporated nonrandomly into the pyrimidine moiety of thiamin in Saccharomyces cerevisiae.The observed incorporation pattern, established by a new chemical degradation, leads to the inference that there are two biosynthetic pathways to the pyrimidine moiety of thiamin in yeast.In the major pathway, formate is the precursor of C-4 of the pyrimidine nucleus, while hexose metabolites serve as the source of the remaining five carbon atoms of the pyrimidine unit.In the minor pathway, it is C-2 and not C-4 of the pyrimidine nucleus which is derived from formate, while C-4,-5 orginates from carbohydrate.The source of C-2', C-5', and C-6 of the pyrimidine unit in this minor pathway remains unknown.Activity from 14C>citrulline and 14C>urea is not incorporated into thiamin.