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PubMed1980

Studies on cardiovascular agents. 6. Synthesis and coronary vasodilating and antihypertensive activities of 1,2,4-triazolo[1,5-a]pyrimidines fused to heterocyclic systems.

The synthesis and coronary vasodilating and antihypertensive activities of 1,2,4-triazolo[1,5-a]pyrimidines fused to pyrrole, thiophene, pyran, pyridine, and pyridazine are described. Among these compounds, 8-tert-butyl-7,8-dihydro-5-methyl-6H-pyrrolo[3,2-e][1,2,4]triazolo[1,5-a]pyrimidine (23) was found to be the most promising potential cardiovascular agent, having been shown to be more potent in coronary vasodilating activity than trapidil [7-diethylamino)-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine] and approximately equipotent to guanethidine sulfate in antihypertensive activity.

Animals↗

PubMed1979

Synthesis of 3,4-dihydro-4-oxothieno[2,3-d]pyrimidine-2-carboxylates, a new series of orally active antiallergy agents.

A series of novel 3,4-dihydro-4-oxothieno[2,3-d]pyrimidine-2-carboxylic acid derivatives has been prepared and tested for antiallergenic activity. Members of the series, including both carboxylic acid salts and esters, have been found to exhibit oral activity in the rat passive cutaneous anaphylaxis (PCA) test. Activity is optimized by H or CH3 substitution at the 5 position and lower alkyl groups at the 6 position. Ethyl 6-ethyl-3,4-dihydro-4-oxothieno-[2,3-d]pyrimidine-2-carboxylate and 3,4-dihydro-5-methyl-6-(2-methylpropyl)-4-oxothieno[2,3-d]pyrimidine-2-carboxylic acid dipotassium salt were the most potent of the esters and salts, respectively. Such compounds have been shown to have a duration of action of up to 4 h in the PCA test and to inhibit both histamine release from rat peritoneal mast cells in vitro and allergen-induced bronchospasm in the rat lung.

Administration, Oral↗

PubMed1982

2-(Alkylthio)-1,2,4-triazolo[1,5-a]pyrimidines as adenosine cyclic 3',5'-monophosphate phosphodiesterase inhibitors with potential as new cardiovascular agents.

A series of new 2-(alkylthio)-5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidines have been prepared as inhibitors of cAMP phosphodiesterase from various tissues. These derivatives were prepared via ring closure of various requisite 3-amino-1,2,4-triazole intermediates. 2-(Benzylthio)-5-methyl-7-(dimethylamino)-1,2,4-triazolo[1,5-a]pyrimidine (15a) is 6.3 times as potent as theophylline in inhibiting cAMP PDE isolated from rabbit heart. Treatment of dogs intravenously with 5 (mg/kg)/h of 15a gave a cardiac output increase of 69%, which was largely sustained for a 2-h period after administration of drug had ceased. There was no significant increase in heart rate upon administration of 15a. Related studies with 5,7-di-n-propyl-2-(benzylthio)-1,2,4-triazolo[1,5-a]pyrimidine (22a) in five dogs showed a 31.5% increase in cardiac output with an increase in stroke volume of 34.4% with no increase in heart rate. The specificity of action of these PDE inhibitors could be due to selective binding at a certain cAMP PDE site in the cardiovascular system. Several of these compounds are candidates for further studies with a view to clinical evaluation.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1983

2-Phenylpyrazolo[1,5-a]pyrimidin-7-ones. A new class of nonsteroidal antiinflammatory drugs devoid of ulcerogenic activity.

Syntheses of some pyrazolo[1,5-a]pyrimidines were performed in order to study the relationship between structural modifications on the parent 4,7-dihydro-2-phenylpyrazolo[1,5-a]pyrimidin-7-one (1) and their antiinflammatory properties. The modifications carried out were introduction and functionalization of a longer side chain at the 4-position, substitution of the hydrogen atom at the 3-position, and replacement of the phenyl group with a 4-methylphenyl, methyl, or hydrogen substituent. 4-Ethyl-4,7-dihydro-2-phenylpyrazolo [1,5-a]pyrimidin-7-one (3) showed the highest activity and a better therapeutic index than phenylbutazone and indomethacin, used as reference drugs. All other changes at the 3-, 5-, and 6-positions, as well as the replacement of the phenyl group at position 2, caused a marked decrease of activity. Compound 3 was found devoid of ulcerogenic activity and was probably endowed with antiulcerogenic properties.

Animals↗

PubMed2002

Inhibition of Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium dihydrofolate reductases by 2,4-diamino-5-[2-methoxy-5-(omega-carboxyalkyloxy)benzyl]pyrimidines: marked improvement in potency relative to trimethoprim and species selectivity relative to piritrexim.

A series of previously undescribed 2,4-diamino-5-[2-methoxy-5-alkoxybenzyl]pyrimidines (3a-e) and 2,4-diamino-5-[2-methoxy-5-(omega-carboxyalkyloxy)benzyl]pyrimidines (3f-k) with up to eight CH2 groups in the alkoxy or omega-carboxyalkyloxy side chain were synthesized and tested for the ability to inhibit partially purified dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), Mycobacterium avium (Ma), and rat liver in comparison with two standard inhibitors, trimethoprim (1) and piritrexim (2). The latter drug is known to be extremely potent but shows a marked preference for binding to mammalian DHFR, whereas the former is very selective for the parasite enzymes but is a much weaker inhibitor. The underlying strategy for the synthesis of compounds 3a-k was that a hybrid structure embodying some features of both 1 and 2 might possess a more favorable combination of potency and selectivity than either parent drug. The choice of analogues 3f-k was based on the idea that the acidic omega-carboxyl group might interact preferentially with a basic center in the active site of DHFR from any of the parasite species relative to the active site of mammalian DHFR. In addition, the omega-carboxyl group was expected to improve water solubility relative to 1 or 2. In standardized spectrophotometric assays with dihydrofolate as the substrate and NADPH as the cofactor, 2,4-diamino-5-[(2-methoxy-4-carboxybutyloxy)benzyl]pyrimidine (3g) inhibited Pc DHFR with an IC(50) of 0.049 microM and rat DHFR with IC(50) of 3.9 microM. Its potency against Pc DHFR was 140-fold greater than that of 1 and close to that of 2, and its selectivity index, defined as the ratio IC(50)(rat liver)/IC(50)(P. carinii), was 8-fold higher than that of 1 and >10(4)-fold higher than that of 2. Although it was less potent and less selective against Tg than Pc DHFR, it was very potent as well as highly selective against Ma DHFR, with an IC(50) of 0.0058 microM and an IC(50)(rat liver)/IC(50)(M. avium) ratio of >600. Because of this favorable combination of potency and selectivity relative to 1 and 2, compound 3g may be viewed as a promising lead in the search for new antifolates with potential clinical activity against P. carinii and other opportunistic pathogens in patients with AIDS.

Animals↗

PubMed2002

Design and synthesis of novel 5-substituted acyclic pyrimidine nucleosides as potent and selective inhibitors of hepatitis B virus.

A novel class of 5-substituted acyclic pyrimidine nucleosides, 1-[(2-hydroxyethoxy)methyl]-5-(1-azidovinyl)uracil (9a), 1-[(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl]-5-(1-azidovinyl)uracil (9b), and 1-[4-hydroxy-3-(hydroxymethyl)-1-butyl]-5-(1-azidovinyl)uracil (9c), were synthesized by regiospecific addition of bromine azide to the 5-vinyl substituent of the respective 5-vinyluracils (2a-c) followed by treatment of the obtained 5-(1-azido-2-bromoethyl) compounds (3a-c) with t-BuOK, to affect the base-catalyzed elimination of HBr. Thermal decomposition of 9b and 9c at 110 degrees C in dioxane yielded corresponding 5-[2-(1-azirinyl)]uracil analogues (10b,c). The 5-(1-azidovinyl)uracil derivatives 9a-c were found to exhibit potent and selective in vitro anti-HBV activity against duck hepatitis B virus (DHBV) infected primary duck hepatocytes at low concentrations (EC(50) = 0.01-0.1 microg/mL range). The most active anti-DHBV agent (9c), possessing a [4-hydroxy-3-(hydroxymethyl)-1-butyl] substituent at N-1, exhibited an activity (EC(50) of 0.01-0.05 microg/mL) comparable to that of reference compound (-)-beta-L-2',3'-dideoxy-3'-thiacytidine (3-TC) (EC(50) = 0.01-0.05 microg/mL). In contrast, related 5-[2-(1-azirinyl)]uracil analogues (10b,c) were devoid of anti-DHBV activity, indicating that an acyclic side chain at C-5 position of the pyrimidine ring is essential for anti-HBV activity. The pyrimidine nucleosides (9a-c, 10b,c) exhibited no cytotoxic activity against a panel of 60 human cancer cell lines. All of the compounds investigated did not show any detectable toxicity to several stationary and proliferating host cell lines or to mitogen stimulated proliferating human T lymphocytes, up to the highest concentration tested.

Animals↗

PubMed2002

Synthesis of N-[4-[1-ethyl-2-(2,4-diaminofuro[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid as an antifolate.

N-[4-[1-Ethyl-2-(2,4-diaminofuro[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid 3 was designed and synthesized to investigate the effect of homologation of a C9-methyl to an ethyl on dihydrofolate reductase (DHFR) inhibition and on antitumor activity. Compound 3 was obtained via a concise seven step synthesis starting from palladium-catalyzed carbonylation of 4-propionylphenol, followed by a Wittig reaction with 2,4-diamino-5-(chloromethyl)furo[2,3-d]pyrimidine (6), catalytic hydrogenation, hydrolysis, and standard peptide coupling with diethyl L-glutamate. The biological results indicated that extending the C9-methyl group to an ethyl on the C8-C9 bridge region (analogue 3) doubled the inhibitory potency against recombinant human (rh) DHFR (IC(50) = 0.21 microM) as compared to the C9-methyl analogue 1 and was 4-fold more potent than the C9-H analogue 2. As compared to 1, compound 3 demonstrated increased growth inhibitory potency against several human tumor cell lines in culture with GI(50) values < 1.0 x 10(-8) M. Compound 3 was also a weak inhibitor of rh thymidylate synthase. Compounds 1 and 3 were efficient substrates of human folylpolyglutamate synthetase (FPGS). Further evaluation of the cytotoxicity of 3 in methotrexate-resistant CCRF-CEM cell sublines and metabolite protection studies implicated DHFR as the primary intracelluar target. Thus, alkylation of the C9 position in the C8-C9 bridge of the classical 5-substituted 2,4-diaminofuro[2,3-d]pyrimidine is highly conducive to DHFR and tumor inhibitory activity as well as FPGS substrate efficiency.

Antineoplastic Agents↗

PubMed2003

Design, synthesis, and biological activities of classical N-[4-[2-(2-amino-4-ethylpyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid and its 6-methyl derivative as potential dual inhibitors of thymidylate synthase and dihydrofolate reductase and as potential antitumor agents.

Two novel analogues, N-[2-amino-4-ethyl[(pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid (2) and N-[2-amino-4-ethyl-6-methyl[(pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid (4), were designed and synthesized as potent dual inhibitors of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) and as antitumor agents. Compound 2 had inhibitory potency against human DHFR similar to N-[4-[2-(amino-3,4-dihydro-4-oxo-7H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid (LY231514) and 1, whereas 4 was inactive against human DHFR. Both 2 and 4 were more potent than LY231514 against E. coliTS. Against human TS, 2 was 7-fold less potent than LY231514 and 4 showed similar inhibitory activity as LY231514. In contrast to 2, which was an efficient substrate of human folypolyglutamate synthetase (FPGS), 4 was a poor substrate of FPGS. Compound 2 showed GI50 values in the nanomolar range against more than 18 human tumor cell lines in the standard NCI preclinical in vitro screen.

Antineoplastic Agents↗

PubMed2003

Synthesis and biological evaluation of 2,4-diamino-6-(arylaminomethyl)pyrido[2,3-d]pyrimidines as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase and as antiopportunistic infection and antitumor agents.

A series of 2,4-diamino-6-(arylaminomethyl)pyrido[2,3-d]pyrimidines were synthesized and evaluated as inhibitors of Pneumocystis carinii (pc), Toxoplasma gondii (tg), and rat liver (rl) dihydrofolate reductase (DHFR) and as inhibitors of the growth of tumor cell lines in culture. Compounds 4-15 were designed as part of a continuing effort to examine the effects of substitutions at the 5-position, in the two-atom bridge, and in the side chain phenyl ring on structure-activity/selectivity relationships of 2,4-diaminopyrido[2,3-d]pyrimidines against a variety of DHFRs. Reductive amination of the common intermediate 2,4-diaminopyrido[2,3-d]pyrimidine-6-carbonitrile 16 with the appropriate anilines afforded the target compounds 4-12. Nucleophilic substitution or reductive methylation afforded the N10-methyl target compounds 13-15. As predicted, compounds 4-15 were, in general, less potent against all three DHFRs compared to the corresponding 2,4-diamino-5-methyl analogues previously reported; however, the greater decrease in potency against rlDHFR compared to pcDHFR and tgDHFR resulted in appreciable selectivity toward pathogenic DHFRs from different pathogens. The 2',5'-dichloro analogue 8 showed selectivity ratios (IC(50) against rlDHFR/IC(50) against pcDHFR or tgDHFR) of 15.7 and 23 for pcDHFR and tgDHFR, respectively. Thus, the selectivity of 8 for pcDHFR is higher than the first line clinical agent trimethoprim (TMP). In a P. carinii cell culture study, analogue 8 exhibited 88% cell growth inhibition at a concentration of 10 muM and afforded marginal effects in an in vivo study in the T. gondii mouse model. Selected compounds were evaluated in the National Cancer Institute (NCI) in vitro preclinical antitumor screening program and inhibited the growth of tumor cells in culture at micromolar to submicromolar concentrations and were selected for evaluation in a NCI in vivo hollow fiber assay.

Animals↗

PubMed2004

Benzoyl ring halogenated classical 2-amino-6-methyl-3,4-dihydro-4-oxo-5-substituted thiobenzoyl-7H-pyrrolo[2,3-d]pyrimidine antifolates as inhibitors of thymidylate synthase and as antitumor agents.

In an attempt to circumvent resistance to and toxicity of clinically used folate-based thymidylate synthase (TS) inhibitors that require folylpoly-gamma-glutamate synthetase (FPGS) for their antitumor activity, we designed and synthesized two classical 6-5 ring-fused analogues, N-[4-[(2-amino-6-methyl-3,4-dihydro-4-oxo-7H-pyrrolo[2,3-d]pyrimidin-5-yl)thio]-2'-fluorobenzoyl]-l-glutamic acid (4) and N-[4-[(2-amino-6-methyl-3,4-dihydro-4-oxo-7H-pyrrolo[2,3-d]pyrimidin-5-yl)thio]-2'-chlorobenzoyl]-l-glutamic acid (5), as TS inhibitors and antitumor agents. The key intermediates in the synthesis of these classical analogues were the mercaptans 10 and 11, which were obtained from the corresponding nitro compounds 6 and 7 respectively, by reduction of the nitro groups followed by diazotization of the amines. The syntheses of analogues 4 and 5 were achieved via the oxidative addition of the sodium salt of ethyl 2-halo-substituted-4-mercaptobenzoate (16 or 17) to 2-amino-6-methyl-3,4-dihydro-4-oxo-7H-pyrrolo[2,3-d]pyrimidine (18) in the presence of iodine. The esters obtained from the reaction were deprotected and coupled with diethyl-l-glutamate followed by saponification. Compounds 4 and 5 were both more potent inhibitors of human TS (IC(50) values of 54 and 51 nM, respectively) than were PDDF and the clinically used ZD1694 and LY231514. Compounds 4 and 5 were not substrates for human FPGS up to 250 muM. In addition, 4 and 5 were growth inhibitory against CCRF-CEM cells as well as a number of other tumor cell lines in culture, and protection studies established TS as the principal target of these analogues.

Antineoplastic Agents↗

PubMed2004

Pyrazolo[1,5-a]pyrimidines: estrogen receptor ligands possessing estrogen receptor beta antagonist activity.

In our search for novel subtype-selective estrogen receptor (ER) ligands, we have examined various heterocyclic units as core structural elements. Here, we have investigated the fused, bicyclic pyrazolo[1,5-a]pyrimidine core, which is a system that allows for analogues to be readily assembled in a library-like fashion. This series of pyrazolo[1,5-a]pyrimidine ER ligands provided us with a new pharmacological profile for an ER ligand: compounds that are passive on both ERs, with a distinct potency selectivity in favor of ERbeta. The most distinctive ligand in this series, 2-phenyl-3-(4-hydroxyphenyl)-5,7-bis(trifluoromethyl)-pyrazolo[1,5-a]pyrimidine, was 36-fold selective for ERbeta in binding. Curiously, on the basis of molecular modeling, the ERbeta binding selectivity of compounds in this series appears to be derived from differing orientations that they adapt in the ligand binding pockets of ERalpha vs ERbeta. In transcription assays this pyrazolopyrimidine was fully effective as an ERbeta antagonist while exhibiting no significant activity on ERalpha. Thus, this ligand functions as a potency- and efficacy-selective ERbeta antagonist that would abrogate estrogen action through ERbeta with minimal effects on its activity through ERalpha; as such, it could be used to study the biological function of ERbeta.

Binding, Competitive↗

PubMed2006

Synthesis and biological evaluation of 6-(alkyn-1-yl)furo[2,3-d]pyrimidin-2(3H)-one base and nucleoside derivatives.

Derivatives of the 2'-deoxynucleoside of furo[2,3-d]pyrimidin-2(3H)-one with long-chain alkyl (or 4-alkylphenyl) substituents at C6 exhibit remarkable anti-VZV (varicella-zoster virus) potency and selectivity, and analogous 2',3'-dideoxynucleoside derivatives show anti-HCMV (human cytomegalovirus) activity. We now report a synthetic approach that enables the preparation of long-chain 6-(alkyn-1-yl)furo[2,3-d]pyrimidin-2(3H)-ones in which the rodlike acetylene spacer replaces the 4-substituted-phenyl ring at C6. Analogues with methyl, beta-d-ribofuranosyl, beta-d-arabinofuranosyl, and 2-deoxy-beta-d-erythro-pentofuranosyl substituents at N3 have been prepared. Long-chain derivatives at C6 in the 2'-deoxynucleoside series showed virus-encoded nucleoside kinase-sensitive anti-VZV activity. Surprisingly, 3-methyl-6-(octyn-1-yl)furo[2,3-d]pyrimidin-2(3H)-one (prepared as a negative anti-VZV test control) exhibited anti-HCMV activity, which supports the possibility of development of non-nucleoside anti-HCMV agents originating from uncomplicated derivatives of such bicyclic ring systems.

Antiviral Agents↗

PubMed2006

Tyrosine kinase inhibitors. 19. 6-Alkynamides of 4-anilinoquinazolines and 4-anilinopyrido[3,4-d]pyrimidines as irreversible inhibitors of the erbB family of tyrosine kinase receptors.

Structure-activity relationships for inhibition of erbB1, erbB2, and erbB4 were determined for a series of alkynamide analogues of quinazoline- and pyrido[3,4-d]pyrimidine-based compounds. The compounds were prepared by coupling the appropriate 6-aminoquinazolines or 6-aminopyrido[3,4-d]pyrimidines with alkynoic acids, using EDCI.HCl in pyridine. The compounds showed pan-erbB enzyme inhibition but were on average about 10-fold more potent against erbB1 than against erbB2 and erbB4. For cellular inhibition, the nature of the alkylating side chains was an important determinant, with 5-dialkylamino-2-pentynamide type Michael acceptors providing the highest potency. This is suggested to be due to an improved ability of the amine to participate in an autocatalysis of the Michael reaction with enzyme cysteine residues. Pyrido[3,4-d]pyrimidine analogue 39 was selected for in vivo evaluation and achieved tumor regressions at 10 mg/kg in the A431 human epidermoid carcinoma and at 40 mg/kg for the SF767 human glioblastoma and the SKOV3 human ovarian carcinoma. Complete stasis was observed at 40 mg/kg in the BXPC3 human pancreatic carcinoma as well as in the H125 human non-small-cell lung carcinoma.

Alkynes↗

PubMed2006

Inhibition of hepatitis B virus (HBV) replication by pyrimidines bearing an acyclic moiety: effect on wild-type and mutant HBV.

Chronic hepatitis B virus (HBV) infection remains a major health problem worldwide. The main clinical limitation of a current antiviral drug for HBV, lamivudine, is the emergence of drug-resistant viral strains upon prolonged therapy. A group of 5-, 6-, or 5,6-substituted acyclic pyrimidine nucleosides with a 1-[(2-hydroxyethoxy)methyl] moiety were synthesized and evaluated for antiviral activities. The target compounds were prepared by the reaction of silylated uracils possessing a variety of substituents at the C-5 or C-6 positions or both with 1,3-dioxolane in the presence of potassium iodide and chlorotrimethylsilane by a convenient and single-step synthesis. Among the compounds tested, 5-chloro and 5-bromo analogues possessing an acyclic glycosyl moiety were the most effective and selective antiviral agents in the in vitro assays against wild-type duck HBV (EC50=0.4-2.2 and 3.7-18.5 microM, respectively) and human HBV-containing 2.2.15 cells (EC50=4.5-45.4 and 18.5-37.7 microM, respectively). These compounds were also found to retain sensitivity against lamivudine-resistant HBV containing a single mutation (M204I) and double mutations (L180M/M204V). The compounds investigated did not show cytotoxicity to host HepG2 and Vero cells, up to the highest concentration tested. The results presented here confirm and accentuate the potential of acyclic pyrimidine nucleosides as anti-HBV agents and extend our previous observations. We herein report the capability of acyclic pyrimidine nucleosides to inhibit the replication of both wild-type and drug-resistant mutant HBV.

Animals↗

PubMed2006

Effect of various pyrimidines possessing the 1-[(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl] moiety, able to mimic natural 2'-deoxyribose, on wild-type and mutant hepatitis B virus replication.

Hepatitis B virus (HBV) is the most common cause of chronic liver disease worldwide. Development of drug resistance against clinical anti-HBV drug lamivudine due to long-term use and rebound of viral DNA after cessation of treatment has been a major setback of the current therapy. We have synthesized a series of pyrimidine nucleosides possessing a variety of substituents at the C-5 position, and a 1-[(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl] flexible acyclic glycosyl moiety at the N-1 position, that have the ability to mimic the natural 2'-deoxyribosyl moiety. Some of these potential antiviral compounds included variations at both C-5 and C-6 positions of the uracil base. Other variations of the uracil derivatives were the 6-aza congeners. 4-Amino and 4-methoxy pyrimidine derivatives were also made. Compounds in which the base moiety was substituted by 5-chloro- (25), 5-(2-bromovinyl)- (32), or 5-bromo-6-methyl- (37) groups possess significant activity against duck-HBV, wild-type human HBV (2.2.15 cells), and lamivudine-resistant HBV containing single and double mutations. No cytotoxicity was seen in host HepG2 and Vero cells, up to the highest concentration tested. The anti-HBV activity exhibited by compounds 25, 32, and 37 was superior for human HBV and comparable for DHBV to that of the corresponding purine nucleoside, ganciclovir. Further, they were only 10-15-fold less inhibitory against human HBV in 2.2.15 cells than the reference drug, lamivudine. Other compounds in the series were moderately inhibitory against DHBV and wild-type human HBV. The size of the halogen and the electronegativity of the substituents at the 5- and 6-positions are important for antiviral activity toward HBV. These compounds were also evaluated for their antiviral activity for West Nile virus, respiratory syncytial virus, SARS-coronavirus, and hepatitis C virus. They were generally inactive in these antiviral assay systems (at concentrations up to 100 microg/mL). 1-[(2-Hydroxy-1-(hydroxymethyl) ethoxy)methyl]-5-fluorocytosine (34) showed some inhibitory activity against hepatitis C virus. Taken together, these data support our previous observations that the 5-substituted pyrimidine nucleosides containing acyclic glycosyl moieties have potential to serve as a new generation of potent, selective, and nontoxic anti-HBV agents for wild-type and lamivudine-resistant mutant HBV.

Animals↗

PubMed1996

2,4-diamino-5-deaza-6-substituted pyrido[2,3-d]pyrimidine antifolates as potent and selective nonclassical inhibitors of dihydrofolate reductases.

Fifteen novel nonclassical and two classical 2,4-diamino-6-(benzylamino)pyrido[2,3-d]pyrimidine antifolates were synthesized as potential inhibitors of Pneumocystis carinii, (pc) Toxoplasma gondii, (tg) rat liver (rl), and human (h) recombinant dihydrofolate reductases (DHFR). These analogues lack a 5-methyl substitution which has been shown to be important for increased hDHFR inhibitory activity. In addition, they contain a reversal of the C9-N10 bridge present in folates and most antifolates. The synthesis of the compounds involved the reaction of 2,4,6-triaminopyrimidine with the sodium salt of nitromalonaldehyde to afford the key intermediate 2,4-diamino-6-nitropyrido[2,3-d]pyrimidine (7), in a single step. Reduction of 7 to the 2,4,6-triaminopyrido[2,3-d]pyrimidine (8), followed by reductive amination with the appropriate benzaldehydes or phenylacetaldehydes afforded the target compounds. N9 methylation of these analogues was carried out using formaldehyde and sodium cyanoborohydride. The analogues demonstrated significant inhibition of pcDHFR and tgDHFR. N9 methylation significantly increased DHFR inhibitory potency. Compound 11, the 3'4'5'-trimethoxy-substituted analogue with a selectivity ratio of 9.4 for tgDHFR (compared to rlDHFR) was the most selective analogue of the nonclassical series. Compound 22, the N9 methyl 2'5'-dimethoxy-substituted analogue was the most potent analogue against tgDHFR (IC 50 = 6.3 nM) and was the second most selective analogue for tgDHFR (compared to rlDHFR) in the nonclassical series. The naphthyl-substituted analogues 23-25 were generally more potent against rlDHFR than against pcDHFR and tgDHFR. Selected analogues were also evaluated against Streptococcus faecium (sf) DHFR, Escherichia coli (ec) DHFR, Lactobacillus casei (lc) DHFR and tgDHFR with hDHFR as the mammalian reference, under slightly different assay conditions than those employed for rlDHFR. Analogues 11 and 22 had selectivity ratios of greater than 100 for tgDHFR (compared to hDHFR). Analogue 22 in particular, was the most selective analogue of the nonclassical series against tgDHFR (selectivity ratio = 303.5) with excellent potency (28 nM). Analogue 11, also displayed significant selectivity for sfDHFR (selectivity ratio = 4902). Compound 22 was evaluated in vivo for the inhibition of the growth of T.gondii trophozoites in mice, where at 50 mg/kg orally, it demonstrated distinct prolongation of survival without toxicity. Compounds 11, 12 and 21-23 were evaluated as antitumor agents in the National Cancer Institutes preclinical in vitro screening program. Compounds 12, 22, and 23 showed GI50s for tumor growth inhibition in the 10 -6 - 10 -7 M range.

Animals↗

PubMed1996

Synthesis and biological evaluation of new imidazole, pyrimidine, and purine derivatives and analogs as inhibitors of xanthine oxidase.

Several derivatives of 4,5-disubstituted imidazole, 2,4,5-trisubstituted pyrimidine, 2-substituted purine, thiazolo[3,2-alpha]purine, [1,3]thiazino[3,2-alpha]purine, thiazolo[2,3-i]purine, [1,3]thiazino-[2,3-i]purine, and 6-substituted pyrazolo[3,4-d]pyrimidine were synthesized and tested as inhibitors of the xanthine oxidase enzyme. Of those, some 4-(acylamino)-5-carbamoylimidazoles and 2-thioalkyl-substituted purines exhibited very good inhibitory activity, being at least 500 times more effective than allopurinol. The ineffectiveness of 6-n-alkylpyrazolo[3,4-d]pyrimidines is imputable to the alkyl chain which could hinder the coordination with molybdenum according to the known mechanism for the binding of the inhibitor allopurinol; the effectiveness of imidazole derivatives, by contrast with the ineffectiveness of 4,5-diamino-2-(thioalkyl)-6-hydroxypyrimidines, indicates the relative importance of the five-membered ring in the interaction with the enzyme. Moreover, the marked effectiveness of the angularly-cyclized [1,3]thiazino[2,3-i]purinones, which constitute an interesting new class of inhibitors, together with the weak activity of linearly-cyclized derivatives, allowed us to characterize more precisely the lipophilic region of the enzyme facing the N(1)-C(2) positions of the substrate hypoxanthine.

Allopurinol↗

PubMed1997

Synthesis and biological evaluation of nonclassical 2,4-diamino-5-methylpyrido[2,3-d]pyrimidines with novel side chain substituents as potential inhibitors of dihydrofolate reductases.

Nine novel 2,4-diamino-5-methyl-6-substituted-pyrido[2,3-d]pyrimidines, 2-10, were synthesized as potential inhibitors of Pneumocystis carinii dihydrofolate reductase (pcDHFR) and Toxoplasma gondii dihydrofolate reductase (tgDHFR). Compounds 2-5 were designed as conformationally restricted analogues of trimetrexate (TMQ), in which rotation around tau 3 was constrained by incorporation of the side chain nitrogen as part of an indoline or an indole ring. Analogue 6, which has an extra atom between the side chain nitrogen and the phenyl ring, has its nitrogen as part of a tetrahydroisoquinoline ring. Analogues 7-9 are epiroprim (Ro 11-8958) analogues and contain a pyrrole ring as part of the side chain substitution on the phenyl ring similar to epiroprim. These analogues were designed to investigate the role of the pyrrole substitution on the phenyl ring of 2,4-diamino-5-methyl-6-(anilinomethyl)pyrido[2,3-d]pyrimidines. Molecular modeling indicated that a pyrrole substituent in the ortho position of the side chain phenyl ring was most likely to interact with pcDHFR in a manner similar to the pyrrole moiety of epiroprim. Analogue 10, in which a phenyl ring replaced a methoxy group, was synthesized to determine the contribution of a phenyl ring on selectivity, lipophilicity, and cell penetration. The synthesis of analogues 2-4 was achieved via reductive amination of 2,4-diamino-5-methyl 6-carboxaldehyde with the appropriately substituted indolines. The indolines were obtained from the corresponding indoles via NaCNBH3 reductions. Analogues 5-10 were synthesized by nucleophilic displacement of 2,4-diamino-5-methyl-6-(bromomethyl)-pyrido[2,3-d]pyrimidine with the 5-methoxyindolyl anion, 6,7-dimethoxytetrahydroisoquinoline, the appropriately substituted pyrroloaniline or 2-methoxy-5-phenylaniline. The pyrroloanilines were synthesized in two steps by treating the substituted nitroanilines with 2,5-dimethoxy-tetrahydrofuran to afford the nitropyrrole intermediates, followed by reduction of the nitro group with Raney Ni. The analogues were more potent than trimethoprim and epiroprim and more selective than TMQ and piritrexim against pcDHFR and tgDHFR. Compounds 5 and 10 had IC50 values of 1 and 0.64 microM, respectively, for the inhibition of the growth of T. gondii cells in culture, and showed excellent culture IC50/enzyme IC50 ratios, which were correlated with their calculated log P values, indicating a direct relationship between calculated lipophilicity and cell penetration.

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