Synthesis of a series of diaminobenzo[f]- and diaminobenzo[h]pyrimido[4,5-b]quinolines as 5-deaza tetracyclic nonclassical antifolates

A series of diaminobenzo[f]- and diaminobenzo[h]pyrimido[4,5-b]quinolines 1–11 were designed as 5-deaza tetracyclic nonclassical, lipophilic antifolates. The compounds were designed as conformationally semi-rigid and rigid analogs of 2,4-diamino-6-phenyl- 12 and 2,4-diamino-7-phenylpyrido[2,3-d]pyrimidines 13 and 14 . The target compounds were synthesized by cyclocondensation of chlorovinyl aldehydes obtained from appropriately substituted 1- or 2-tetralone, with 2,4,6-friaminopyrimidine. Compounds 1–11 were evaluated as inhibitors of P. carinii and T. gondii dihydrofolate reductases. These pathogens cause fatal opportunistic infections in AIDS patients. In addition, the selectivity of these agents was evaluated using rat liver dihydrofolate reductase as the mammalian source. In general the benzo[f]pyrimido[4,5-b]quinolines 1–5 were more potent than the corresponding benzo[h]pyrimido[4,5-b]quinoline analogues 6–11 against P. carinii and rat liver dihydrofolate reductase and were equipotent against T. gondii dihydrofolate reductase. Compounds 6–11 were moderately selective towards T. gondii dihydrofolate reductase with IC₅₀S in the 10⁻⁷ M range. In contrast analogues 1–5 lacked selectivity against P. carinii or T. gondii dihydrofolate reductase and were, in general, potent inhibitors of rat liver dihydrofolate reductase with IC₅₀S in the 10⁻⁸ M range. Analogues 1 and 4 were evaluated against a series of tumor cell lines in vitro and were found to have moderate antitumor activity (IC50 10⁻⁶ M). The structure activity/selectivity relationships suggest that benzo[f]pyrimido analogues 1–5 with the phenyl ring substitution in the “upper” portion of the tetracyclic ring are better accommodated within the rat liver (mammalian) dihydrofolate reductase and P. carinii dihydrofolate reductase active sites compared to the benzo[h]pyrimido analogues 6–11 which have the phenyl ring substitution in the “lower” portion of the tetracyclic ring. In contrast T. gondii dihydrofolate reductase does not discriminate between the isomers and binds to both series of compounds with similar affinities.     

Synthesis and antifolate activity of 2,4-diamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine analogues of trimetrexate and piritrexim

2,4-Diamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidines with di- and trimethoxyaralkyl substitution at the 6-position were synthesized from the N⁶-unsubstituted compound and appropriate aralkyl bromides in N,N-dimethylformamide solution containing a catalytic amount of sodium iodide. An improved method of preparation of 2,4-diamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine from 2-amino-6-benzyl-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4(3H)-one was also developed, in which N² was protected by reaction with pivalic anhydride and the resulting product was subjected consecutively to reaction with 4-chlorophenylphosphorodichloridate and 1,2,4-triazole, ammonolysis to replace the 4-imidazolido group and remove the N²-pivaloyl group, and catalytic hydrogenolysis to remove the 6-benzyl group. In assays of the ability of the products to inhibit dihydrofolate reductase from Pneumocystis carinii, and Toxoplasma gondii, and rat liver the most active of the compounds tested was 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine. The concentration of this compound needed to inhibit enzyme activity by 50% was 0.51 μM against the P. carinii enzyme, 0.09 μM against the T. gondii enzyme, and 0.35 μM against the rat enzyme. Thus, there was selectivity of binding to T. gondii enzyme, but not P. carinii enzyme, relative to rat enzyme. 2′,5′-Dimethoxybenzyl analogues were less active than the corresponding 3′,4′,5′-trimethoxybenzyl analogues, and compounds with a CH₂CH₂ or CH₂CH₂CH₂ bridge were less active than those with a CH₂ bridge. 2,4-Diamino-6-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine showed greater selectivity than trimetrexate or piritrexim for the P. carinii and T. gondii enzyme, but was less selective than trimethoprim or pyrimethamine. However its molar potency against both enzymes was greater than that of trimethoprim, the antifolate most commonly used, in combination with sulfamethoxazole, for initial treatment of opportunistic P. carinii and T. gondii infections in patients with AIDS and other disorders of the immune system.     

Conformationally restricted tricyclic analogues of lipophilic pyrido[2,3‐d]pyrimidine antifolates

The effect of conformational restriction of the C9‐N10 bridge on inhibitory potency and selectivity of trimetrexate against dihydrofolate reductase, was studied. Specifically three nonclassical tricyclic 1,3‐diamino‐8‐(3′,4′,5′‐trimethoxybenzyl)‐7,9‐dihydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidin‐6(5H,8H)‐one ( 4 ), 1,3‐diamino‐8‐(3′,4′,5′‐trimethoxybenzyl)‐9‐hydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidin‐6‐(8H)‐one ( 5 ) and 1,3‐diamino‐(8H)‐(3′,4′,5′‐trimethoxybenzyl)‐7,9‐dihydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidine ( 7 ) antifolates were synthesized. The tricyclic analogues 4 and 5 were obtained via the regiospecific cyclo‐condensation of the β‐keto ester 17 with 2,4,6‐triaminopyrimidine. The analogue 7 was obtained via reduction of the lactam 4 with borane in tetrahydrofuran. Compounds 4, 5 and 7 were evaluated as inhibitors of dihydrofolate reductase from Pneumocystis carinii, Toxoplasma gondii and rat liver. All three compounds were more selective than trimetrexate against Pneumocystis carinii dihydrofolate reductase and significantly more selective than trimetrexate against Toxoplasma gondii dihydrofolate reductase compared with rat liver dihydrofolate reductase.     

The synthesis of new 2,4‐diaminofuro[2,3‐d]pyrimidines with 5‐biphenyl,phenoxyphenyl and tricyclic substitutions as dihydrofolate reductase inhibitors

Nonclassical 2,4‐diamino‐5‐substituted furo[2,3‐d]pyrimidines 4a‐i, 5a‐b and 7a‐f were synthesized as extended aromatic ring appended analogs of previously reported antifolates 1a‐b. The extended aromatic system was designed to better interact with a phenylalanine residue (Phe69) of dihydrofolate reductase from the opportunistic pathogen Pneumocystis carinii to afford potent and selective inhibitors of Pneumocystis carinii dihydrofolate reductase. The target compounds were synthesized by nucleophilic displacement of 2,4‐diamino‐5‐(chloromethyl)furo[2,3‐d]pyrimidine 3 with the appropriate aromatic amine or thiol. The compounds were evaluated as inhibitors of dihydrofolate reductase from Pneumocystis carinii and Toxoplasma gondii, and their selectivity was determined using rat liver dihydrofolate reductase as the mammalian reference. In the C8‐N9 bridged series, compound 4e , with a 3‐(2‐methoxydibenzofuran)‐ side chain, exhibited greatest potency and was more than 3 times as selective for Pneumocystis carinii dihydrofolate reductase compared to rat liver dihydrofolate reductase. Compounds 4b and 4c also exhibited selectivity. Compounds in the C8‐S9 bridged series showed comparable potencies, and each showed higher selectivity for Pneumocystis carinii dihydrofolate reductase compared to rat liver dihydrofolate reductase.     

Brominated trimetrexate analogues as inhibitors of pneumocystis carinii and toxoplasma gondii dihydrofolate reductase

Five previously undescribed trimetrexate analogues with bulky 2′-bromo substitution on the phenyl ring were synthesized in order to assess the effect of this structure modification on dihydrofolate reductase inhibition. Condensation of 2-[2-(2-bromo-3,4,5-trimethoxyphenyl)ethyl]-1,l-dicyanopropene with sulfur in the presence of N,N-diethylamine afforded 2-amino-5-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-4-methyl-thiophene-3-carbonitrile ( 15 ) and 2-amino-4-[2-(2′-bromo-3′,4′,5′-trimethoxyphenyl)ethyl]thiophene-3-car-bonitrile ( 16 ). Further reaction with chloroformamidine hydrochloride converted 15 and 16 into 2,4-diamino-5-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-4-methylthieno[2,3-d]pyrimidine ( 8a ) and 2,4-diamino-4-[2-(2′-bromo-3′,4′,5′-trimethoxyphenyl)ethylthieno[2,3-d]pyrimidine ( 12 ) respectively. Other analogues, obtained by reductive coupling of the appropriate 2,4-diaminoquinazoline-6(or 5)-carbonitriles with 2-bromo-3,4,5-trimethoxyaniline, were 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)-5-chloro-quinazoline ( 9a ), 2,4-diamino-5-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)quinazoline ( 10 ), and 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)quinazoline ( 11 ). Enzyme inhibition assays revealed that space-filling 2′-bromo substitution in this limited series of dicyclic 2,4-diaminopyrimidines with a 3′,4′,5′-trimethoxyphenyl side chain and a CH₂, CH₂CH₂, or CH₂NH bridge failed to improve species selectivity against either P. carinii or T. gondii dihydrofolate reductase relative to rat liver dihydrofolate reductase.     

Products of ozone oxidation of some saturated cyclic hydrocarbons

Low-temperature ozone oxidation of a series of saturated carbocyclic hydrocarbons afforded the corresponding alcohols and/or ketones in high yield through intermediate trioxidanes. exo,endo-Tetracyclo-[6.2.1.0^3,5]undecane-2,7-dione and exo,endo,endo-hexacyclo[9.3.1.0^3,8.0^4,6.0^5,9.0^12,14]pentadecane-2,10-dione were isolated, and exo,endo,exo-pentacyclo[6.3.1.0^2,7.0^3,5.0^9,11]dodecyl-, exo,exo,exo-heptacyclo-[9.3.1.0^2,10.0^3,8.0^4,6.0^5,9.0^12,14]pentadecyl, and 1-methylcyclohexyltrioxidanes were identified and characterized for the first time.     

Densazalin,a New Cytotoxic Diazatricyclic Alkaloid from the Marine Sponge Haliclona densaspicula

Densazalin, a polycyclic alkaloid, was isolated from the marine sponge Haliclona densaspicula collected in Korea. The complete structure of the compound was determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance techniques, high-resolution mass spectrometry, and comparison of the calculated and measured electronic circular dichroism spectra. Densazalin possesses a unique 5,11-diazatricyclo[7.3.1.0^2,7]tridecan-2,4,6-triene moiety, which is connected by two linear carbon chains. This compound was derived from the biogenetic precursor bis-1,3-dialkylpyridnium. Densazalin exhibited cytotoxic activity on two human tumor cell lines (AGS and HepG2) in the Cell Counting Kit-8 (CCK-8) bioassay, with IC₅₀ values ranging from 15.5 to 18.4 μM.     

An unexpected pathway of the reaction of lithiated 1,1-dimethylallene with isopropyl isothiocyanate

The reaction of lithiated 1,1-dimethylallene with isopropyl isothiocyanate gives 3a,4,5,5a-tetrahydro-4,4,5a-trimethyl-2-methylthio-3H-cyclobuta[b]pyrrole resulting from cyclization of the intermediate 2,7-dimethyl-4-methylthio-3-azaocta-2,4,6-triene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 865–867, April, 1997.     

Derivation of a diazabicyclo[3.2.0]heptadiene from a diazatricyclo [4.1.0.02,7] heptene.

Trifluoromethylated 3,5-diazatricyclo[4.1.0.0^2,7]hept-3-ene was converted thermally or photochemically to 2,4-diazabicyclo[3.2.0]hepta-2,6-diene compound. The latter was photolyzed to an imidazole compound.     

Reaction of 2,2,3,3-tetracyanocyclopropyl ketones with water

3-Benzoylcyclopropane-1,1,2,2-tetracarbonitrile reacted with water to give 2-benzoyl-1,3-dicyanocyclopropane-1-carboxamide as a result of hydrolysis of the cyano group in the trans position with respect to the carbonyl group and subsequent decarboxylation. The reaction of 3-benzoyl-3-methylcyclopropane-1,1,2,2-tetracarbonitrile with water involved heterocyclization with participation of the carbonyl group and cis-cyano groups, leading to 8-methyl-3,6-dioxo-1-phenyl-2,7-diazatricyclo[3.2.1.0^4,8]octane-4,5-dicarbonitrile. Hydrolysis of 3-alkylcyclopropane-1,1,2,2-tetracarbonitrile followed both reaction paths to produce mixtures of products, including 7-alkyl-4-amino-7-hydroxy-1,9-dioxo-3,8-diazatricyclo[4.3.0.0^1,5]non-3-ene-5-carbonitriles. In all cases, the three-membered ring was retained.     

Studies on the Synthesis of New 3-(3,5-Diamino-1-substituted-pyrazol-4-yl)azo-thieno[2,3-b]pyridines and 3-(2-Amino-5,7-disubstituted-pyrazolo[1,5-a]pyrimidine-3-yl)azothieno[2,3-b]pyridines

Coupling the diazonium salt of 3-amino-2-cyano-4,6-dimethylthieno[2,3-b]pyridine 1 with malononitrile 2 gave 2-cyano-3-(hydrazonomalononitrile)-4,6-dimethylthieno[2,3-b]pyridine 3 which then reacted with hydrazine compounds 4a-4h to yield corresponding 2-cyano-3-(3,5-diamino-1-substituted-pyrazol-4-yl)azo-4,6-dimethylthieno[2,3-b]pyridines 5a-5h. The 2-cyano-3-(2-amino-5,7-disubstituted-pyrazolo-[1,5-a]pyrimidine-3-yl)azo-4,6-dimethylthieno[2,3-b]pyridines 7a-7f were obtained in good yield by the cyclocondensation reaction of 2-cyano-3-(3,5-diamino-pyrazol-4-yl)azo-4,6-dimethylthieno[2,3-b]pyridine 5a with the appropriate 1,3-diketones 6a-6f under acidic condition.     

H6P2W18O62-18H2O,a Green and Reusable Catalyst for the Three-Component,One-Pot Synthesis of 4,6-Diarylpyrimidin-2(1H)-ones Under Solvent-Free Conditions

Three-component, one-pot synthesis of 4,6-diarylpyrimidin-2(1H)-ones and 9-phenyl-8-oxa-10,12-diaza-tricyclo[7.3.1.0^2,7]trideca-2(7),3,5-trien-11-one by condensing acetophenone derivatives, aldehydes, and urea in the presence of trimethylsilyl chloride using a catalytic amount of H₆P₂W₁₈O₆₂-18H₂O under solvent-free conditions is reported.     

Photolysis of the Insensitive Explosive 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB)

The explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is of particular interest due to its extreme insensitivity to impact, shock and heat, while providing a good detonation velocity. To determine its fate under environmental conditions, TATB powder was irradiated with simulated sunlight and, in water, under UV light at 254 nm. The hydrolysis of particles submerged in neutral and alkaline solutions was also examined. We found that, by changing experimental conditions (e.g., light source, and mass and physical state of TATB), the intermediates and final products were slightly different. Mono-benzofurazan was the major transformation product in both irradiation systems. Two minor transformation products, the aci-nitro form of TATB and 3,5-diamino-2,4,6-trinitrophenol, were detected under solar light, while 1,3,5-triamino-2-nitroso-4,6-dinitrobenzene, 1,3,5-triamino-2,4-dinitrobenzene and mono-benzofuroxan were produced under UV light. The product identified as 3,5-diamino-2,4,6-trinitrophenol was identical to the one formed in the dark under alkaline conditions (pH 13) and in water incubated at either 50 °C or aged at ambient conditions. Interestingly, when only a few milligrams of TATB were irradiated with simulated sunlight, the aci-isomer and mono-benzofurazan derivative were detected; however, the hydrolysis product 3,5-diamino-2,4,6-trinitrophenol formed only much later in the absence of light. This suggests that the water released from TATB to form mono-benzofurazan was trapped in the interstitial space between the TATB layers and slowly hydrolyzed the relatively stable aci-nitro intermediate to 3,5-diamino-2,4,6-trinitrophenol. This environmentally relevant discovery provides data on the fate of TATB in surface environments exposed to sunlight, which can transform the insoluble substrate into more soluble and corrosive derivatives, such as 3,5-diamino-2,4,6-trinitrophenol, and that some hydrolytic transformation can continue even without light.     

Unusual dihydrazone formation in the fischer-indole cyclization. The synthesis of novel nonclassical annulated 2,4-Diamino-pyrrolo[2,3-d]pyrimidine antifolates

The synthesis of seven novel tetracyclic 2,4-diaminopyrrolo[2,3-d]pyrimidines as conformationally restricted nonclassical antifolates was achieved via an unusual Fischer-indole cyclization of dihydrazones. An attempted synthesis of 2,4-diamino-6-hydrazinopyrimidine afforded 2-amino-4,6-dihydrazinopyrimidine which when reacted with appropriate ketones gave the dihydrazones. The dihydrazones in turn under Fischer-indole cyclization conditions afforded target conformationally restricted tetracyclic products.     

Pyrolysis of tetradecafluorotricyclo [6,2,2,0]dodeca-2,6,9-triene and related compounds. Thermal isomerizations involving fluorine shifts

The vacuum pyrolysis of tetradecafluorotricyclo-[6,2,2,0^2,7]dodeca-2,6,9-triene (6) results in initial isomerization to perfluorotricyclo[8,2,0,0^2,7]dodeca-2,6,8-triene (7) followed by elimination of tetrafluoroethylene and formation of perfluoro-1,2-dihydronaphthalene (8), perfluoro-1,4-dihydronaphthalene (9), perfluoroindene (10) and perfluoro-(2 3)-methylindene (11); the expected primary product of elimination of tetrafluoroethylene from (6) or (7), namely perfluoro-2,3-dihydronaphthalene, was not detected. The formation of the observed products can be accounted for in terms of fluorine migrations, further examples of such migrations are described.     

Synthesis of N-aryl- and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethyl-9-methyl-11-sulfanylidene-8-oxa-10,12-diazatricyclo[7.3.1.0<Superscript>2,7</Superscript>]trideca-2,4,6-triene-13-carboxamides

Three-component condensation of N-aryl- and N,N-diethyl-3-oxobutanamides with salicylaldehyde and thiourea in ethanol in the presence of sodium hydrogen sulfate afforded N-aryl- and N,N-diethyl-9-methyl-11-sulfanylidene-8-oxa-10,12-diazatricyclo[7.3.1.0^2,7]trideca-2,4,6-triene-13-carboxamides. Reaction of the same compounds in the absence of a catalyst under solvent-free conditions gave N-aryl-6-(2-hydroxyphenyl)-4-methyl-2-sulfanylidene-1,2,3,6-tetrahydropyrimidine-5-carboxamides.     

Pyrolysis of tetradecafluorotricyclo [6,2,2,02,7]dodeca-2,6,9-triene and related compounds. Thermal isomerizations involving fluorine shifts

The vacuum pyrolysis of tetradecafluorotricyclo-[6,2,2,0^2,7]dodeca-2,6,9-triene (6) results in initial isomerization to perfluorotricyclo[8,2,0,0^2,7]dodeca-2,6,8-triene (7) followed by elimination of tetrafluoroethylene and formation of perfluoro-1,2-dihydronaphthalene (8), perfluoro-1,4-dihydronaphthalene (9), perfluoroindene (10) and perfluoro-(2 $\text{or}$ 3)-methylindene (11); the expected primary product of elimination of tetrafluoroethylene from (6) or (7), namely perfluoro-2,3-dihydronaphthalene, was not detected. The formation of the observed products can be accounted for in terms of fluorine migrations, further examples of such migrations are described.     

Reaction of 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide with electrophilic reagents: Bromine and nitric acid

Reactions of 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide with bromine and nitric acid lead to the electrophilic substitution of the hydrogen atom in the meta-position with respect to the nitro group. At thebromination the primarily formed 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide when kept in the solution loses an oxygen atom forming 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1-oxide and an isomerization product, 8-bromo-6-nitrospiro[3H-[2,1,4]benzoxadiazine-3,1′-cyclohexane] 4-oxide. The latter exposed to light turns into 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide. The reaction of the initial 1,3-dioxide with nitric acid afforded 4,6-dinitrospiro[benzimidazole-2,1′-cyclohexan]-7-ol 1-oxide whose heating in o-dichlorobenzene resulted in 3,5-dinitro-1,8-diazatricyclo[7.5.0.0^2,7] tetradeca-2(7),3,5,8-tetraen-6-ol.     

Synthesis of substituted dihydrobenzo[f]pyrimido[4,5-b]-quinolines as tetracyclic 5-deaza nonclassical folates

Cyclocondensation of 2,4,6-triaminopyrimidine ( 10 ) with chlorovinyl aldehyde 7 afforded the linear regioisomer 9,1 1-diamino-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 1 ) while the cyclocondensation of 2,6-diamino-4-hydroxypyrimidine ( 11 ) or 6-amino-2,4-dihydroxypyrimidine ( 12 ) with chlorovinyl aldehyde 7 was regiospecific affording the linear regioisomers 9-amino-11-oxo-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 2 ) and 9,11-dioxo-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 3 ) respectively. The linear structures of these compounds were established by ¹H nmr and ¹³C nmr spectral data.     

Reaktionen vonN-Sulfinylverbindungen mit dem 1,2,4-Trithia-3,5-diborolan-Ringsystem und Substitutionsreaktionen am 1,2,4-Trithia-3,5-diborolan und 1,2-Dithia-4-aza-3,5-diborolidin

The reaction of trimethylsilyl- and pentafluorophenyl-N-sulfinylamine respectively with 3,5-dihalogeno-1,2,4-trithia-3,5-diborolanes yields the 1,2-dithia-4-aza-3,5-diborolidines1-3.Tert-butyl-N-sulfinylamine and 3,5-dimethyl-1,2,4-trithia-3,5-diborolane react analogous. OtherN-sulfinylamines however split the disulfane bridge in 3,5-dimethyl-1,2,4-trithia-3,5-diborolane and the 1,4-dithia-2-aza-3,5-diborolidines5A-7(A) are formed. Besides of boroxines, cyclo-2,4,6-trimethyl-1,3-dioxa-5-aza-2,4,6-triboranes and cyclo-2,4,6-trimethyl-1-oxa-3,5-diaza-2,4,6-triboranes are formed as byproducts,8–10 have been isolated. In 1,2,4-trithia-3,5-diborolanes and 1,2-dithia-4-aza-3,5-diborolidines the bromo-atoms can be substituted by alkyl (13, 14), by amino (15–20) and by isothiocyanato groups. The compounds were characterised analytically and spectroscopically (MS; NMR:¹H,¹¹B,¹⁹F,²⁹Si; IR).