The Folic Acid Activity and Antagonism of Two Structurally Related Derivatives of Benzimidazole

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Abstract
In a search for molecules having folic acid activity or antagonism, 2 compds. which show interesting relationships of structure to biological action were synthesized. The compds. were assayed for effects on growth of Streptococcus faecalis by the method of Mitchell and Snell (1941). The close structural similarity of benzimidazole to purine and its competitive action with amino purines led to the use of this nucleus. Compd. I, in which the pyrimido-(4,5)-pyrazine (or pterin) nucleus of pteroylglutamic acid was substituted by the benzimidazole nucleus, retained a certain degree of growth-promoting ac-activity. Compd. II, differing only in the substitution of a sulfonyl for a carbonyl group in the p-aminobenzoic acid moiety of the molecule, reversed its biologic activity and became a metabolic antagonist. This reversal throws doubt on the specificity of the pteridin nucleus for the folic acid system.