Synthesis and antitumor activities of novel 6-5 fused ring heterocycle antifolates: N-[4-[omega-(2-amino-4-substituted-6,7-dihydrocyclopenta [d]pyrimidin-5-yl)alkyl]benzoyl]-L-glutamic acids

Effect of C9-methyl substitution and C8-C9 conformational restriction on antifolate and antitumor activity of classical 5-substituted 2,4-diaminofuro[2,3-d]pyrimidines

N-[4-[1-methyl-2-(2,4-diaminofuro[2, 3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid (5) and its C8-C9 conformationally restricted E- and Z-isomers (6 and 7) were designed and synthesized in order to investigate the effect of incorporating a methyl group at the C9 position and of conformational restriction at the C8-C9 bridge of N-[4-[2-(2,4-diaminofuro[2, 3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid (1) with respect to dihydrofolate reductase (DHFR) inhibitory activity as well as antitumor activity. The compounds were synthesized by a Wittig reaction of 2,4-diamino-5-(chloromethyl)furo[2,3-d]pyrimidine with ethyl 4-acetylbenzoate followed by catalytic reduction, hydrolysis, and standard peptide coupling with diethyl L-glutamate. The biological results indicated that the addition of a 9-methyl group to the C8-C9 bridge, as in 5, increased recombinant human (rh) DHFR inhibitory potency (IC(50) = 0.42 microM) as well as the potency against the growth inhibition of tumor cells in culture (CCRF-CEM EC(50) = 29 nM, A253 EC(50) = 28.5 nM, and FaDu EC(50) = 17.5 nM) compared with the 9-desmethyl analogue 1. However, the conformationally restricted 4:1 Z/E mixture of 7 and 6 was less potent than 5 in both assays, and the pure E-isomer 6 was essentially inactive. These three classical analogues were also evaluated as inhibitors of Lactobacillus casei, Escherichia coli, and rat and rh thymidylate synthase (TS) and were found to be weak inhibitors. All three analogues 5-7 were good substrates for human folylpolyglutamate synthetase (FPGS). These data suggested that FPGS is relatively tolerant to different conformations in the bridge region. Further evaluation of the cytotoxicity of 5 and 7 in methotrexate (MTX)-resistant CCRF-CEM cell sublines suggested that polyglutamylation was crucial for their mechanism of action. Metabolite protection studies of 5 implicated DHFR as the primary intracellular target. Compound 5 showed GI(50) values in 10(-9)-10(-7) M range against more than 30 tumor cell lines in culture.

Unsaturated Nitriles: Precursors for a Domino Ozonolysis-Aldol Synthesis of Oxonitriles

Cyclic five-, six-, and seven-membered oxonitriles are prepared by a tandem ozonolysis-aldol sequence. Cyclopentenylacetonitrile (4) and cyclohexenylacetonitrile (12) afford the ring-expanded oxonitriles 3 (98%) and 17 (58%), respectively, in highly efficient one-pot syntheses. Homologous five-membered oxonitriles 22a-c are prepared by analogous ozonolysis-aldol cyclizations employing omega-alkenyl beta-ketonitriles. The method tolerates various substitution patterns and allows for the synthesis of beta,beta-disubstituted oxonitriles (22c). The reaction conditions are essentially neutral providing the beta-hydroxyoxonitriles 22d and 22e with only trace amounts of the aromatic dehydration product.

2,4-Diamino-6,7-dihydro-5H-cyclopenta[d]pyrimidine analogues of trimethoprim as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase

Three previously unreported (R,S)-2,4-diamino-5-[(3,4,5-trimethoxyphenyl) alkyl]-6,7-dihydro-5H-cyclopenta[d]pyrimidines 15a-c were synthesized as analogues of trimethoprim (TMP) and were tested as inhibitors of Pneumocystis carinii, Toxoplasma gondii, and rat liver dihydrofolate reductase (DHFR). The length of the alkyl bridge between the cyclopenta[d]pyrimidine and trimethoxyphenyl moiety ranged from one in 15a to three carbons in 15c. The products were tested as competitive inhibitors of the reduction of dihydrofolate by Pneumocystis carinii, Toxoplasma gondii, and rat liver DHFR. Compounds 15a-c had IC50 values of > 32, 1.8 and 1.3 microM, respectively, against P. carinii DHFR, as compared to 12 microM for TMP. Against the T. gondii enzyme, 15a-c had IC50 values of 21, 0.14 and 0.14 microM, respectively, as compared to 2.7 microM for TMP. Inhibitors 15b and 15c with two- and three-carbon bridges were significantly more potent than 15a against all three enzymes. Unlike TMP, 15b and 15c were better inhibitors of the rat liver enzyme than of the microbial enzymes. The potency of 15b and 15c against rat liver DHFR was less than has been reported for the corresponding 6,7-dihydro-5H-cyclopenta[d]pyrimidines with a classical p-aminobenzoyl-L-glutamate side chain as inhibitors of bovine, murine, and human DHFR.

2,4-Diaminothieno[2,3-d]pyrimidine lipophilic antifolates as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase

Ten previously unreported 2,4-diaminothieno[2,3-d]pyrimidine lipophilic dihydrofolate reductase inhibitors were synthesized as potential inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase. Pivaloylation of 2,4-diamino-5-methylthieno[2,3-d]pyrimidine followed by dibromination with N-bromosuccinimide in the presence of benzoyl peroxide gave 2,4-bis(pivaloylamino)-6-bromo-5-(bromomethyl)thieno[2,3-d]pyrimid ine, which after condensation with substituted anilines or N-methylanilines and deprotection with base yielded 2,4-diamino-6-bromo-5-[(substituted anilino)methyl]thieno[2,3-d]pyrimidines. Removal of the 6-bromo substituent was accomplished with sodium borohydride and palladium chloride. The reaction yields were generally good to excellent. The products were tested as inhibitors of dihydrofolate reductase (DHFR) from P. carinii, T. gondii, and rat liver. Although the IC50 could not be reached for the 6-unsubstituted compounds because of their extremely poor solubility, three of the five 6-bromo derivatives were soluble enough to allow the IC50 to be determined against all three enzymes. 2,4-Diamino-5-[3,5-dichloro-4-(1-pyrrolo)anilino]methyl]- 6-bromothieno[2,3-d]pyrimidine was the most active of the 6-bromo derivatives, with an IC50 of 7.5 microM against P. carinii DHFR, but showed no selectivity for either P. carinii or T. gondii DHFR relative to the enzyme from rat liver.