Folic acid analogs. Modifications in the benzene-ring region. 5. 2′,6′-diazafolic acid

The synthesis of 2′,6′-diazafolic acid was accomplished by the condensation of 2-acetylamino-4(3H)pteridinone-6-earboxaldehyde (XIV) with diethyl N-(5-amino-2-pyrimidinyl)carbonyl]-L-glutamate (XIII) followed by reduction of the anil double bond and alkaline hydrolylic cleavage of the N²-acetyl and ethyl ester protecting groups. Intermediate XIII was prepared by starling with 5-nitro-2-styrylpyrimidine (VI) and proceeding via 5-arnino-2-styrylpyrimidine (IX). The henzyloxycarbonyl derivative of IX was prepared and oxidized to the corresponding 5-benzyloxycarbonylaminopyrimidine-2-carboxylic acid (XI). The coupling of XI with diethyl L-glutamate followed by hydrogenolysis of the henzyloxycarbonyl function afforded the desired intermediate XIII. 2′,6′-Diazafolic acid was a potent inhibitor of Streptococcus faecium and displayed marginal activity against leukemia 1,1210 in mice.