Orally active 4-amino-5-diarylurea-furo[2,3-d]pyrimidine derivatives as anti-angiogenic agent inhibiting VEGFR2 and Tie-2

During our effort to develop dual VEGFR2 and Tie-2 inhibitors as anti-angiogenic agents for cancer therapy, we discovered 4-amino-5-(4-((2-fluoro-5-(trifluoromethyl)phenyl)- aminocarbonylamino)phenyl)furo[2,3-d]pyrimidine (8a) possessing strong inhibitory activity at both the enzyme and cellular level against VEGFR2 and Tie-2. Compound 8a demonstrated high pharmacokinetic exposure through oral administration, and showed marked tumor growth inhibition and anti-angiogenic activity in mouse HT-29 xenograft model via once-daily oral administration.     

An efficient alternative route to 3,6-disubstituted-furo[2,3-d]pyrimidin-2-one analogues

Copper(I)-catalyzed 5-endo-dig cyclizations of 5-(alkyn-1-yl)uracil derivatives had given poor yields of substituted furo[2,3-d]pyrimidin-2-ones unless the uracil ring was substituted at N1 with alkyl or glycosyl groups. This limited flexibility for the synthesis of analogues with varied substituents at N3 and/or C6 of the furo[2,3-d]pyrimidin-2-one core has been overcome with 5-(3-hydroxyalkyn-1-yl)uracil compounds with no substituent at N1. Manipulation of the side-chain hydroxyl group gives access to additional furo[2,3-d]pyrinmidin-2-one analogues.     

Synthesis and evaluation of a classical 2,4-diamino-5-substituted-furo[2,3-d]pyrimidine and a 2-amino-4-oxo-6-substituted-pyrrolo[2,3-d]pyrimidine as antifolates

Two classical antifolates, a 2,4-diamino-5-substituted furo[2,3-d]pyrimidine and a 2-amino-4-oxo-6-substituted pyrrolo[2,3-d]pyrimidine, were synthesized as potential inhibitors of dihydrofolate reductase (DHFR) and thymidylate synthase (TS). The syntheses were accomplished by condensation of 2,6-diamino-3(H)-4-oxo-pyrimidine with alpha-chloro-ketone 21 to afford two key intermediates 23 and 24, followed by hydrolysis, coupling with l-glutamate diethyl ester and saponification of the diethyl ester to afford the classical antifolates 13 and 14. Compounds 13 and 14 with a single carbon atom bridge are both substrates for folylpoly-gamma-glutamate synthetase (FPGS), the enzyme responsible for forming critical poly-gamma-glutamate antifolate metabolites with increased potency and/or increased cell retention. Compound 14 is a highly efficient FPGS substrate demonstrating that 2,4-diamino-5-substituted furo[2,3-d]pyrimidines are important lead structures for the design of antifolates with FPGS substrate activity. It retains inhibitory potency for DHFR and TS compared to the two atom bridged analog 5. Compound 13 is a poor inhibitor of purified DHFR and TS, and both 13 and 14 are poor inhibitors of the growth of CCRF-CEM human leukemia cells in culture, indicating that single carbon bridged compounds in these series though conducive to FPGS substrate activity were not potent inhibitors.     

Synthesis, cytotoxicity, and anti-inflammatory evaluation of 2-(furan-2-yl)-4-(phenoxy)quinoline derivatives. Part 4

A number of 2-(furan-2-yl)-4-phenoxyquinoline derivatives have been synthesized and evaluated for anti-inflammatory evaluation. 4-[(2-Furan-2-yl)quinolin-4-yloxy]benzaldehyde (8), with an IC(50) value of 5.0 microM against beta-glucuronidase release, was more potent than its tricyclic furo[2,3-b]quinoline isomer 3a (>30 microM), its 4'-COMe counterpart 7 (7.5 microM), and its oxime derivative 13a (11.4 microM) and methyloxime derivative 13b (>30 microM). For the inhibition of lysozyme release, however, oxime derivative 12a (8.9 microM) and methyloxime derivative 12b (10.4 microM) are more potent than their ketone precursor 7 and their respective tricyclic furo[2,3-b]quinoline counterparts 4a and 4b. Among them, 4-[4-[(2-furan-2-yl)-quinolin-4-yloxy]phenyl]but-3-en-2-one (10) is the most active against lysozyme release with an IC(50) value of 4.6 microM, while 8 is the most active against beta-glucuronidase release with an IC(50) value of 5.0 microM. (E)-1-[3-[(2-Furan-2-yl)quinolin-4-yloxy]phenyl] ethanone oxime (11a) is capable of inhibiting both lysozyme and beta-glucuronidase release with IC(50) values of 7.1 and 9.5 microM, respectively. For the inhibition of TNF-alpha formation, 1-[3-[(2-furan-2-yl)quinolin-4-yloxy]phenyl]ethanone (6) is the most potent with an IC(50) value of 2.3 microM which is more potent than genistein (9.1 microM). For the inhibitory activity of fMLP-induced superoxide anion generation, 11a (2.7 microM), 11b (2.8 microM), and 13b (2.2 microM) are three of the most active. None of above compounds exhibited significant cytotoxicity.     

A novel oxazine ring closure reaction affording (Z)-((E)-2-styrylbenzo[b]furo[3,2-d][1,3]oxazin-4-ylideno)acetaldehydes and their anti-osteoclastic bone resorption activity

A novel oxazine ring formation method was established using the reaction of 2-acetyl-(E)-3-styrylcarbonylaminobenzo[b]furans (4) with Vilsmeier-Haack-Arnold reagent to afford (E and Z)-((E)-2-styrylbenzo[b]furo[3,2-d][1,3]oxazin-4-ylideno)acetaldehydes (5). (Z)-4-(8-Bromo-(E)-2-styrylbenzo[b]furo[3,2-d][1,3]oxazin-4-ylideno)but-(E)-2-enoic acid ethyl ester (6b), derived from (Z)-5a, showed significantly potent anti-osteoclastic bone resorption activity comparable to 17beta-estradiol (E2).     

Correlation of antibacterial activity of some N-[5-(2-furanyl)-2-methyl-4-oxo-4H-thieno[2,3-d]pyrimidin-3-yl]-carboxamide and 3-substituted-5-(2-furanyl)-2-methyl-3H-thieno[2,3-d]pyrimidin-4-ones with topological indices using Hansch analysis

The antimicrobial activity of the N-[5-(2-furanyl)-2-methyl-4-oxo-4H-theino[2,3-d]pyrimidin-3-y1]-carboxamides and 3-substituted-5-(2-furanyl)-2-methyl-3H-thieno[2,3-d]pyrimidin-4-ones was correlated with different topological indices using Hansch analysis. Good correlations were obtained through a simple regression equation with third order molecular connectivity index (3chi). The developed QSAR models were crossvalidated by leave-one-out technique.     

Synthesis of 5-chloroformycin A, 5-chloro-2''-deoxyformycin A and certain related 5,7-disubstituted 3-beta-D-ribofuranosylpyrazolo[4,3-d] pyrimidines from formycin A.

A facile synthesis of 7-amino-5-chloro-3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine (5-chloroformycin A, 6), 7-amino-5-chloro-3-(2-deoxy-beta-D-erythro-pentofuranosyl) pyrazolo [4,3-d]-pyrimidine (5-chloro-2'-deoxyformycin A, 13) and certain related 5,7-disubstituted pyrazolo[4,3-d]pyrimidine ribonucleosides is described starting with formycin A. Thiation of tri-O-acetyloxoformycin B (4b) with phosphorus pentasulfide, followed 3-beta-D-ribofuranosyl-7-thioxopyrazolo[4,3-d] pyrimidin-5(1H,4H,6H)-one (3b) in excellent yield. Chlorination of 4b with either phosphorus oxychloride or phenyl phosphonicdichloride furnished the key intermediate 5,7-dichloro-3-(2,3, 5-tri-O-acetyl-beta-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (5a), which on deacetylation afforded 5,7-dichloro-3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine (5b). Ammonolysis of 5a with liquid ammonia gave 6, whereas with MeOH/NH3, a mixture of 6 and 7-methoxy-5-chloro-3-beta-D-ribofuranosylpyrazolo[4,3-d]pyrimidine (7) was obtained. Reaction of 6 with lithium azide and subsequent hydrogenation afforded 5-aminoformycin A (10). Treatment of 5a with thiourea gave 5-chloro-3-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl) pyrazolo[4,3-d]pyrimidine-7(1H,6H)-thione (8a), which on further reaction with sodium hydrosulfide furnished 3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine-5,7(1H,4H,6H)-dithione (11). The four-step deoxygenation procedure using phenoxythiocarbonylation of the 2'-hydroxy group of the 3', 5'-protected 6 gave 5-chloro-2'-deoxyformycin A (13).     

Synthesis and anticonvulsant evaluation of some new 2-substituted-3-arylpyrido[2,3-d]pyrimidinones

A series of 2-substituted-3-arylpyrido[2,3-d]pyrimidinones was prepared for evaluation as potential anticonvulsants. In murine screening, compounds 4a-c having a 2-oxo-2-(4-pyridyl)ethyl group in the 2-position and a 2-substituted phenyl moiety at the 3-position of the pyridopyrimidinone system displayed the most potent anti-seizure activity in both the maximal electroshock (MES) and pentylenetetrazol (scPTZ) tests at doses in the 3-10mg/kg range. Compound 4c showed no agonist activity at the GABA(A) receptor and was unable to block presynaptic sodium and calcium channels in vitro.     

4-Acylamino-6-arylfuro[2,3-d]pyrimidines: potent and selective glycogen synthase kinase-3 inhibitors

Modeling studies of a furo[2,3-d]pyrimidine GSK-3 hit compound 1 superimposed onto the X-ray crystal structure of a legacy pyrazolo[3,4-c]pyridazine GSK-3 inhibitor 2 led to the identification of 4-acylamino-6-arylfuro[2,3-d]pyrimidine template 3. Synthesis of analogues based on template 3 has resulted in a number of potent and selective GSK-3beta inhibitors. The most potent and selective compound was the m-pyridyl analogue 24.     

Pyrrolo[2,3-d]pyrimidines containing an extended 5-substituent as potent and selective inhibitors of lck II

Pyrrolo[2,3-d]pyrimidines containing a 5-(4-phenoxyphenyl) substituent are novel, potent and selective inhibitors of lck in vitro. Exploration of C-6 position of the pyrrolo[2,3-d]pyrimidine and the terminal phenyl group structure-activity relationship (SAR) is detailed. Compound 1 is orally active in animal models.     

Synthesis and anti-HIV-1 activity of 4-substituted-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine analogues

Three novel 4-subsituted-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine analogues were designed, synthesized, and tested for their anti-HIV-1 activity. Initial biological studies indicated that among these pyrrolo[2,3-d]pyrimidine ribonucleoside analogues, 4-amino-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine 10 exhibited the most potent anti-HIV-1 activity (EC(50)=0.5±0.3 μM), while 4-hydroxy-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d] pyrimidine 9 and 4-amino-5-fluoro-7-(2'-deoxy-2'-fluoro-4'-azido-β-D-ribofuranosyl)pyrrolo[2,3-d] pyrimidine 11 showed moderate activity (EC(50)=13±8 and 5.4±0.3 μM, respectively). The cytotoxicity of these compounds has also been assessed. No significant cytotoxicities were found for any of these compounds with concentrations up to 25 μM.     

Synthesis and cytotoxic evaluation of certain 4-(phenylamino)furo[2,3-b]quinoline and 2-(furan-2-yl)-4-(phenylamino)quinoline derivatives

Certain 4-(phenylamino)furo[2,3-b]quinoline and 2-(furan-2-yl)-4-(phenylamino)quinoline derivatives were synthesized and evaluated in vitro against the full panel of NCIs 60 cancer cell lines. The preliminary results indicated these tricyclic 4-(phenylamino)furo[2,3-b]quinolines were more cytotoxic than their corresponding 2-(furan-2-yl)-4-(phenylamino)quinoline isomers. For the 4-(phenylamino)furo[2,3-b]quinolines, compounds 2a and 3d are two of the most potent with a mean GI50 value of 0.025 microM in each case. Inactivity of 2b and 2c (positional isomers of 2a) indicated that both electronic environment, and the distance between intercalating pharmacophore and H-bond-donating MeO group are important. For the 2-(furan-2-yl)-4-(phenylamino)quinoline isomers, compound 12 (a mean GI50 of 4.36 microM), which bears a para-COMe substituent, is more active than its meta-substituted counterpart 13 (10.5 microM). However, the electron-donating MeO substituent is preferred at the meta-position, and the cytotoxicity for the meta-substituted derivatives decreased in the order: MeO derivative 14b (3.05 microM) > oxime 16 (6.85 microM) > ketone 13 (10.5 microM) > methyl oxime 18 (20.6 microM).     

Novel 2-N,N-dimethylaminomethyl-2,3,3a,12b-tetrahydrodibenzo[b,f]furo[2,3-d]oxepin derivatives displaying combined norepinephrine reuptake inhibition and 5-HT2A/2C receptor antagonism

A novel series of cis-fused 2-N,N-dimethylaminomethyl-2,3,3a,12b-tetrahydrodibenzo[b,f]furo[2,3-d]oxepin derivatives modified at position C-11 was prepared and evaluated for its potential antidepressant/anxiolytic properties. In vitro affinities for the norepinephrine transporter and for 5-HT(2A) and 5-HT(2C) receptors, as well as the ED(50) values obtained in some in vivo assays predictive for antidepressant and anxiolytic potential are reported.     

Discovery of 7-arylsulfonyl-1,2,3,4, 4a,9a-hexahydro-benzo[4,5]furo[2,3-c]pyridines: identification of a potent and selective 5-HT₆ receptor antagonist showing activity in rat social recognition test

Serotoninergic neurotransmission has been implicated in modulation of learning and memory. It has been demonstrated that 5-hydroxytryptamine(6) (5-HT(6)) receptor antagonists show beneficial effect on cognition in several animal models. Based on a pharmacophore model reported in the literature, we have designed and successfully identified a 7-benzenesulfonyl-1,2,3,4-tetrahydro-benzo[4,5]furo[2,3-c]pyridine (3a) scaffold as a novel class of 5-HT(6) receptor antagonists. Despite good activity against 5-HT(6) receptor, 3a exhibited poor liver microsome stability in mouse, rat and dog. It was demonstrated that the saturation of the double bond of the tetrahydropyridine ring of 3a enhanced metabolic stability. However the resulting compound, 4a (7-phenylsulfonyl-1,2,3,4,4a,9a-hexahydro-benzo[4,5]furo[2,3-c] pyridine-HCl salt) exhibited ～30-fold loss in potency along with introduction of two chiral centers. In our optimization process for this series, we found that substituents at the 2 or 3 positions on the distal aryl group are important for enhancing activity against 5-HT(6). Separation of enantiomers and subsequent optimization and SAR with bis substituted phenyl sulfone provided potent 5-HT(6) antagonists with improved PK profiles in rat. A potent, selective 5-HT(6)R antagonist (15k) was identified from this study which showed good oral bioavailability (F=39%) in rat with brain penetration (B/P=2.76) and in vivo activity in a rat social recognition test.     

Synthesis and optimization of substituted furo[2,3-d]-pyrimidin-4-amines and 7H-pyrrolo[2,3-d]pyrimidin-4-amines as ACK1 inhibitors

Two classes of ACK1 inhibitors, 4,5,6-trisubstituted furo[2,3-d]pyrimidin4-amines and 4,5,6-trisubstituted 7H-pyrrolo[2,3-d]pyrimidin-4-amines, were discovered and evaluated as ACK1 inhibitors. Further structural refinement led to the identification of potent and selective dithiolane inhibitor 37.     

Synthesis and biological activity of 5-fluorotubercidin

The electrophilic fluorination of 4-chloropyrrolo[2,3-d]pyrimidine (1) was studied culminating a 59% conversion of compound 1 to 4-chloro-5-fluoropyrrolo[2,3-d]pyrimidine (2) using Selectfluor. This transformation proceeded via the 4-chloro-5,6-dihydro-5-fluoro-6-hydroxypyrrolo[2,3-d]pyrimidine (3) in a 9:1 trans:cis ratio. The trans isomer of compound 3 was studied by 1H NMR and 19F NMR, and the 5-H tautomer (4) was observed as another intermediate. A modified Vorbruggen procedure of compound 2 and tetra-O-acetylribose gave 4-chloro-5-fluoro-7-(2,3,5,-tri-O-benzoyl-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (6) in a 65% yield. Treatment of compound 6 with ammonia (l) in dioxane gave 5-fluorotubercidin (7). No antibacterial activity was observed. An MTT assay (Promega) against Huh-7 liver cells, normal mouse spleen cells stimulated with Con A (a T-cell mitogen), and normal mouse spleen stimulated with LPS (a B-cell mitogen) showed no significant toxicity. Increased activity of 7 over tubercidin was observed against L-1210 cells and toxicity in fibroblast cells was reduced.     

Discovery of novel c-Met kinase inhibitors bearing a thieno[2,3-d]pyrimidine or furo[2,3-d]pyrimidine scaffold

A series of thieno[2,3-d]pyrimidines and furo[2,3-d]pyrimidines were synthesized and evaluated for the c-Met inhibition. Thieno[2,3-d]pyrimidine 6b stood out as the most potent showing an IC(50) of 35.7 nM. This compound displayed high inhibitory effect on cell proliferation in BaF3-TPR-Met cells and showed high selectivity for c-Met family against other 14 tested kinases. However, compound 6b was found ineffective in the c-Met-dependent U-87MG human gliobastoma xenograft model that may be relevant to its poor PK profile.     

Synthesis of 7-Glycopyranosyl-5-oxq-pyrrolo[2,3-d]Pyrimidine and 4-Glyco Pyranosylamino-Furo[2,3-d]Pyrimidine Derivatives

Abstract

The synthesis of some glycosyl derivatives of furo[2,3-d] and pyrrolo[2,3-d]pyrimidines is described.     

Nucleosides,III1 Synthesis and Properties of 2-Trifluoromethyl-Naphthimidazole-Ribonucleoside

Abstract

The fusion reaction between 2-trifluoromethylnaphth[2,3-d]imidazole (1) and 1-0-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (2) leads to 2,3′,5′-tri-O-benzoyl-1-β-D-ribofuranosylnaphth[2,3-d]imidazole (3). Debenzoylation of (3) gives the corresponding nucleoside 1-β-D-ribofuranosyl -2-trifluoromethylnaphth[2,3-d]imidazole (4). Structural proofs are based on elementary analysis, UV-and ¹H-NMR spectra.     

Furoquinoline alkaloids from the southern African Rutaceae Teclea natalensis

The chloroform and ethyl acetate extracts of the leaves of Teclea natalensis have yielded two furoquinoline alkaloids, 6-[(2,3-epoxy-3-methylbutyl)oxy]-4,7-dimethoxyfuro[2,3-b]quinoline and 4,7-dimethoxy-6-[(3-methyl-2-butenyl)oxy]furo[2,3-b]quinoline, and the known alkaloids 4,7-dimethoxy-8-[(3-methyl-2-butenyl)oxy]furo[2,3-b]quinoline, flindersiamine and dictamnine.