Novel
antifolates with a 6-5 fused ring system, 6,7-dihydrocyclopenta [d]
pyrimidine, (3a,b and 4a,b) were synthesized on the basis of combined modification of the heterocycle and bridge regions of the
folate molecule. The synthetic method involves (1) synthesis of key intermediates of tert-butyl 4-[omega-(2-substituted-3-oxocyclopentanyl) alkyl]
benzoates (8a,b and 9a,b) by a
carbon-
carbon radical coupling of tert-butyl 4-(omega-iodoalkyl)benzoates (7a,b) with 2-substituted-2-cyclopenten-1-ones (5 and 6) utilizing
tributyltin hydride, (2) cyclization of either the methyl enol-
ethers derived from the 2-cyanocyclopentanones (8a,b) or the 2-(methoxycarbonyl)cyclopentanones (9a,b) themselves by treatment with
guanidine which leads to 6,7-dihydrocyclopenta [d]
pyrimidines with a 4-(tert-butoxycarbonyl)phenylalkyl group (11a,b and 14a,
b), (3) deprotection to the corresponding
carboxylic acids (12a,b and 15a,b), and (4) amidation with diethyl
glutamate and deesterification. Potent
dihydrofolate reductase inhibition and highly potent cell growth inhibition were found with 2,4-diaminopyrimidine-fused
cyclopentene compounds containing the
trimethylene (3a) or
ethylene bridge (3b) but not with the corresponding 2-amino-4-hydroxy analogs (4a,b). Compounds 3a and 3b were more growth inhibitory to several tumor cell lines (P388, colon 26, colon 38, and KB) than was
methotrexate, with 3a being the most potent. Both 3a and 3b gave increases in the lifespan of P388 leukemic mice comparable to that observed with MTX. Both compounds were therapeutic against colon 26
colorectal carcinoma in mice. Compound 3a was highly effective against
LC-6 non-small cell lung carcinoma in nude mice.