A New Antagonist of Thiamine

4-AMINO-5-hydroxymethyl-2-methylthiopyrim-idine 1,2 (I) is an inhibitory antagonist of the pyrimidine moiety of vitamin B 1 (II) 3 . However, a thiamine-requiring mutant of Escherichia coli (strain M 70–17) which can use II for growth will grow in the presence of I if the thiazole moiety of thiamine is also supplied. One possible explanation of this is that, under these conditions, the pyrimidine I is being converted to a functional thiamine-like compound. Consequently, it was decided to synthesize the thiamine analogue derived from I, which would differ from thiamine only in the nature of the 2-substituent, and which, on the basis of a recently proposed mechanism of thiamine action 4 , might be expected to have thiamine activity.