Synthesis and Biological Activity of 4-Amino-7-oxo-Substituted Analogues of 5-Deaza-5,6,7,8-tetrahydrofolic Acid and 5,10-Dideaza-5,6,7,8-tetrahydrofolic Acid

The 4-amino-7-oxo-substituted analogues of 5-deaza-5,6,7,8-tetrahydrofolic acid (5-DATHF) and 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (DDATHF) were synthesized as potential antifolates. Treatment of the α,β-unsaturated esters 11a − c, obtained in one synthetic step from commercially available para-substituted methyl benzoates (9a − c) and methyl 2-(bromomethyl)acrylate (10), with malononitrile in NaOMe/MeOH afforded the corresponding pyridones 12a − c. Formation of the pyrido[2,3-d]pyrimidines 13a − c was accomplished upon treatment of 12a − c with guanidine in methanol. After the hydrolysis of the ester group present in 13a − c, the resulting carboxylic acids 14a − c were treated with diethyl cyanophosphonate in Et3N/DMF and coupled with l-glutamic acid dimethyl ester to give 15a − c. Finally, the basic hydrolysis of 15a − c yielded the desired 4-amino-7-oxo-substituted analogues 16a − c in 20−27% overall yield. Compounds 16a − c were tested in vitro against CCRF-CEM leukemia cells. The results obtained indicated that our 4-amino-7-oxo analogues are completely devoid of any activity, the IC50 being higher than 20 μg/mL for all cases except 14c for which a value of 6.7 μg/mL was obtained. These results seem to indicate that 16a − c are inactive precisely due to the presence of the carbonyl group in position C7, the distinctive feature of our synthetic methodology.