FURTHER EVALUATION OF 5-ALKYL-5-DEAZA ANTIFOLATES - 5-PROPYL-5-DEAZA AND 5-BUTYL-5-DEAZA ANALOGS OF AMINOPTERIN AND METHOTREXATE

5-Propyl-5-deaza and 5-butyl-5-deaza analogues of classical antifolate s were synthesized by extensions of a previously reported general rout e which proceeds through mino-5-alkylpyrido[2,3-d]pyrimidine-6-carboni trile intermediates followed by reductive condensation with diethyl N- 4-(aminobenzoyl)-L-glutamate to give diethyl esters of 5-alkyl-5-deaza aminopterin types. N-10-Methyl derivatives, i.e., derivatives of 5-alk yl-5-deazamethotexate, were also prepared by reductive methylation of the N-10-H compounds. 5-Ethyl-5-deazamethotexate was prepared using an alternative route through 6-(bromomethyl)-2,4-diamino-5 -ethylpyrido [2,3-d]pyrimidine. These antifolates were evaluated for inhibition of dihydrofolate reductase (DHFR) from L1210 cells, their effect on L1210 and S180 tumor cell growth in culture, and carrier-mediated transport through L1210 cell membranes. Inhibitory effect on DHFR was lowered r elative to methotrexate in 5-propyl-5-deazaaminopterin and 5-propyl-5- deazamethotrexate by 2- to 3-fold (K-i = 9.3 and 11.7 pM, respectively , vs. 4.3 pM for methotrexate) and by 17- to 18-fold in 5-butyl-5-deaz aaminopterin and 5-butyl-5-deazamethotrexate (K-i = 74 and 78 pM, resp ectively). Molecular modeling using graphics derived from human DHFR s how the propyl and butyl compounds interacting with the enzyme in conf ormations that account for these slight decreases in binding.