Synthesis and cytotoxic activity of imidazo[1,2-a]-1,3,5-triazine analogues of 6-mercaptopurine

A series of 2-substituted imidazo[1,2-a]-1,3,5-triazines with various aliphatic and aromatic amines has been prepared and characterized by IR,1H-NMR, and elemental analysis. The initial in-vitro cytotoxicity studies with five human cancer cell lines showed that all but one of the compounds are without cytotoxic activity. The one active compound, 2-(indolin-1-yl)-7,8-dihydroimidazo[1,2-a]-1,3,5-triazine-4(6H)-thione 12, was tested on 12 human cancer cell lines. Of these, two lines, RT-4 and MCF-7, were the most sensitive to the compound, with IC50 values of 6.98 microM and 8.43 microM, respectively. When compared with the reference anticancer drug 6-mercaptopurine, only the RT-4 urinary bladder and KYSE-70 oesophagus cancer cell lines were more sensitive to the new compound. The antimetabolite thioguanine was more cytotoxic than 12 for all common cell lines tested.     

Reactions with cyanothioacetamide derivatives: Synthesis of several new pyridine and annelated pyridine derivatives

Several new pyridine, pyridinethione, pyrazole[3,4-b]-pyridine, pyrido [1,2-a]-1,3-thiazine and pyrido[1,2-a]pyridine thione derivatives have be synthesised via the reactions of 2-methyl-3-ethoxycarbonyl-4-phenyl-5-cyano-1,4,5,6-tetrahydro-pyridine-6-one 2 with different reagents. The structures of the newly synthesised derivatives were established on the basis of elemental analyses and spectal data studies.     

Benzimidazole condensed ring systems: New synthesis and antineoplastic activity of substituted 3,4-dihydro- and 1,2,3,4-tetrahydro-benzo [4,5]imidazo[1,2-a]pyrinnidine derivatives

As part of an ongoing effort to develop new antineoplastic agents, a series of substituted 3,4-dihydro- and 1,2,3,4-tetrahydro-benzo[4,5]imidazo[1,2-a]pyrimidine derivatives (5-19) were synthesized. 1,2,3,4-Tetrahydrobenzo[4,5]imidazo[1,2-a]pyrimidine-2-one derivatives (5-7) were prepared via one-pot two-component thermal cyclization reaction of 2-aminobenzimidazole 1 and P-substituted methyl cinnamates (2-4). Vilsmir-Haack formylation of these derivatives (5-7) afforded the 2-chloro-3-carboxaldehyde targets (8-10) followed by nucleophilic displacement of the chloro atom in the 3-carboxaldehyde compounds (8-10) to yield the remaining final targets (11-19). The structures of the synthesized derivatives (5-19) were confirmed by means of IR, 1H NMR, MS and elemental analyses. The synthesized derivatives (5-19) were subjected to the National Cancer Institute (NCI) in vitro disease human cell screening panel assay. 2-Chloro-4-phenyl-3,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxyaldehyde (8, NCI 722731) and 4-(4-methoxyphenyl)-2-(4-methylpiperazin-1-yl)-3,4-dihydrobenzo[4,5]imidazo [1,2-a]pyrimidine-3-carboxaldehyde (18, NCI 722739) showed a variable degree of antineoplastic activity against some of the cell lines tested. 2-Chloro-4-(4-nitrophenyl)-3,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxyaldehyde (10, NCI 722743) exhibited good in vitro antineoplastic activity with subpanel disease selectivity against all the cell lines tested with log10 G150 (M), the concentration that inhibits 50% of cell growth, values ranging from -5.08 to < -8.00.     

Synthesis, structural characterization and biological evaluation of novel [1,2,4]triazolo [1,5-b][1,2,4]benzothiadiazine-benzothiazole conjugates as potential anticancer agents

Two series of 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b][1,2,4]benzothiadiazine 2-methyl/ethyl sulfanyl benzothiazole derivatives (5a-d) and 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b][1,2,4] benzothiadiazine 2-phenoxy benzothiazole derivatives (16a-c) were synthesized and their structures confirmed by NMR, MS, IR and X-ray crystallography. These compounds were evaluated for their cytotoxicity against 60 human tumour cell lines. One of the synthesized compounds (5b) exhibited significant inhibitory activity against most of the cell lines and has been further evaluated for the five-dose screening.     

Analytical studies on the hydrolysis of Chinoin-102 and Chinoin-127, candidate compounds for stability studies

The isolation and structural elucidation of some products of hydrolytic studies with two drugs, Chinoin-102 and Chinoin-127, are described. CH-127 is 1,6(ax)-dimethyl-4-oxo-1,6,7,8,9,9a-hexahydro-4H-pyrido-[1,2-a]-pyrimidine-3-carboxamide. CH-102 is 8,9-dimethoxy-3-imino-5,6-dihydro-3H-thiazolo-[4,3-a]-isoquinoline-1-carbonitrile. Degradation of the active compounds was studied by hydrolysing them in acidic, neutral and alkaline media. The isolated degradation products were identified by MS and IR techniques. The products identified were: for CH-127, 1,6-dimethyl-4-oxo-1,6,7,8-tetrahydro-4H-pyrido-[1,2-a]-pyrimidin-3-carboxamide; for CH-102, acid amide and acid derivatives. For the selective determination of the drugs and their degradation products, UV spectrophotometric and densitometric methods were applied.     

1,2-Cyclisierungsreaktionen an Indolderivaten, 5. Mitt. Synthese von 3H-Pyrrolo[1,2,-a] indol-3-onen

Synthesis of 3H-Pyrrolo[1,2-a]indole-3-ones The reaction of some 3-substituted indoles with diketene leads to the 1-acetoacetyl-indoles 1b – f . These and 1-acetoacetyl-indole ( 1a ) cyclize with polyphosphoric acid (PPA), forming the 3H-pyrrolo-[1,2-a]indole-3-ones 2a – f .     

Benzimidazole condensed ring systems. XII. Synthesis and anticancer evaluation of certain pyrido[1,2-a]benzimidazole derivatives.

Previously, we have evaluated several pyrido[1,2-a]benzimidazoles (PBIs) as potential antineoplastic agents. Among them, NSC 649900 and NSC 682011 revealed good antineoplastic activity against some cell lines of clinically isolated human tumors. For further structure-activity relationship (SAR) studies we report here the synthesis and antineoplastic evaluation of related series of PBIs with similar haloarylamino (13-18, 23-28), haloarylaminomethylene (29-34) and haloarylazo (35-38) moieties at position 1 or 2. Some of these derivatives revealed notable activity against some tumor cell lines; the highest activity was recorded for the p-fluorophenylamino-3-phenyl-PBI (23, NSC 699944) and its p-chlorophenyl analog (24, NSC 699948). These compounds were selected by the NCI for further testing in a new in vivo anticancer hollow fiber assay.     

Structure-activity studies of antitumor agents based on pyrrolo[1,2-a]benzimidazoles: new reductive alkylating DNA cleaving agents

Described herein are structure-activity studies of new antitumor agents based on the pyrrolo[1,2-a]benzimidazole (PBI) ring system. These compounds were designed as new DNA cross-linkers mimicking the mitomycin antitumor agents. Actually, the PBI derivatives were found to have anthracycline-like features: (i) shared cross resistance with doxorubicin in a human myeloma line, (ii) cardiotoxicity, and (iii) excellent DNA strand cleaving capability. The DNA strand cleavage is thought to result from reductive alkylation of DNA followed by the generation of reactive oxygen radicals. The best antitumor agent studied is 6-N-aziridinyl-3-hydroxy-7-methyl-2,3-dihydro-1H-pyrrolo- [1,2-a]benzimidazole-5,8-dione 3-acetate (PBI-A), which possesses nanomolar IC50 values against various human ovarian and colon cancer cell lines.     

Synthesis and antiviral activity of fluorinated pyrido[1,2-a]benzimidazoles

Methods for the synthesis of fluorinated pyrido[1,2-a]benzimidazoles have been developed, and a series of such compounds has been obtained and studied for biological activity. In particular, 5,6-difluoro-2-cyanobenzimidazole (II) was synthesized for the first time using the reaction of 1,2-diamino-4,5-difluorobenzole (I) with cyanoacetic ether. Pyrido[1,2-a]benzimidazoles (III, IV) were obtained via condensation of benzimidazole II with diethylethoxymethylene malonate and ethyl acetoacetate. The synthesized pyrido[1,2-a]benzimidazoles (III–XIII) were subjected to screening on a culture of Vero cells for antiviral activity and cytotoxicity with respect to ortho-poxviruses that are pathogenic for humans. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 11, pp. 12–16, November, 2005.     

Synthesis and antitumor cytotoxicity evaluation of pyrido[4,3,2-de]quinolines and isoquinolino[6,5,4,3-cde]quinolines

A series of novel pyrido[4,3,2-de]quinoline and isoquinolino[6,5,4,3-cde] quinoline compounds was synthesized and evaluated for cytotoxicity in the National Cancer Institute developmental therapeutics program. The tricyclic compound 7 was synthesized by the cyclization of 3,4-diamino-1,2dimethoxybenzene with diethyl 1,3-acetonedicarboxylate. Oxidation of monochloropyrido[4,3,2-de]quinoline 8 selectively produced 2,3-diketopyrido[4,3,2-de]quinoline 9 as deep violet crystals. Compound 9, when treated with acetone or acetophenone, affords the tetracyclic isoquinolino[6,5,4,3-cde]quinolines 13 and 14, respectively. 2,3-Diketopyrido[4,3,2-de]quinolines 9 and 10 exhibit higher cytotoxic potency than isoquinolino[6,5,4,3-cdelquinolines 13, 14, 15 and 16. Compound 9 selectively affects the cell growth against leukemia CCRF-CEM and HL-60 cell lines, the non-small cell lung cancer HOP-92 cell line, and breast cancer MDA-MB231/ ATCC and MDA-MB- 435 cell lines with GI(50) values of <2.0 microM. Modification of compound 9 with an ester group at the N-1 position afforded compound 10, which exhibits a wide spectrum of anticancer activities with a mean graph midpoint value of 1.8 microM against the 60 cancer cell lines.     

Synthesis and reactivity of debenzorutaecarpine derivatives]

A series of 7,12-dihydropyrimido[1',2';1,2]pyrido[3,4-b]indol-4(6H)-ones was prepared by Fischer indolization of 9-arylhydrazono-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one s. Quantumchemical calculations (ab initio and AM1) indicate that position 3 of 7,12-dihydro-pyrimido[1',2';1,2]pyrido[3,4-b]indol-4(6H)-one can be involved in electrophilic substitutions, while position 2 is sensitive towards nucleophilic attack. Bromination of 6-methyl-7,12-dihydropyrimido[1',2';1,2]pyrido[3,4-b]indol-4(6H)-o ne (16) with bromine afforded 3-bromo derivative (25), which was reacted with cyclic amines to give 2-amino-7,12-dihydro-pyrimido[1',2';1,2]pyrido[3,4-b]indol-4(6H)-ones (26-30) in an addition-elimination reaction. Vielsmeier-Haack formylation of compound (16) give 12-formyl (31) and 3,12-diformyl (32) derivatives (an N-formyl-1-aza derivative of nauclefidine alkaloid (34) at 60 degrees C and 100 degrees C, respectively. 3,12-dformyl compound (32) was oxidized to 3-carboxyl derivative (33). The quaternary salt (35), obtained from compound (16) with dimethyl sulphate, suffered a ring opening on the action of aqueous sodium hydroxide. The new compounds have been characterized by elemental analyses uv, 1H nmr and in some cases by 13C ruler, CD spectra and X-ray investigations.     

1-Methyl-3H-pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-ones. Design, synthesis, and biological activity of new antitumor agents

1-Methylpyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-ones 4, synthesized in good to excellent yields, were designed as novel alkylating agents because of their peculiar chemical behavior. All derivatives showed antiproliferative activity against more than 50 types of tumor cell lines with GI(50) reaching sub-micromolar values. SAR studies revealed that the presence of a chlorine atom is well-tolerated in both positions 8 and 9, whereas in the case of the methyl group, switching from the 8 to the 9 position gives rise to the most active compound of the series, 4g, either for the number of cell lines inhibited and for selectivity against leukaemia and renal cancer subpanels. COMPARE and 3D-MIND computations indicate, for compounds 4, an activity profile analogous to rifamycins and cytidine analogues.     

Synthesis and antiproliferative activity in vitro of new derivatives of 3-aminopyrazolo[3,4-b]pyridine. Part 1. Reaction of 3-aminopyrazolo[3,4-b]pyridine with 1,3-, 1,4-diketones and alpha,beta-unsaturated ketones

The synthesis of several new pyrazolo[3,4-b]pyridine, pyrido[2',3':3,4]-pyrazolo[1,5-a]pyrimidine and imidazo[1',2':1,5]pyrazolo[3,4-b]pyridine derivatives is described. The obtained compounds were tested for their antiproliferative activity in vitro. One of them, 4-phenyl-2-(3,4,5-trimethoxy-beta-styrylo)pyrido- [2',3':3,4]pyrazolo[1,5-a]pyrimidine (9), revealed cytotoxic properties against the cells of all three human cancer cell lines applied. Another one, 2,4-dimethyl-pyrido[2',3':3,4]pyrazolo[1,5-a]-pyrimidine (2), revealed weak cytotoxic activity only against the cells of human bladder cancer cell line HCV29T. All other compounds tested did not reveal any cytotoxic activity.     

Synthesis and antiinflammatory activity of novel indazolones

In this study, a series of new N2 substituted 1,2-dihydro-3H-indazol-3-ones (3a-d) as well as their condensed pyrazolo, pyridazino derivatives such as pyridazino[1,2-a]indazole-6,9,11-triones (4a-h) and 3,9-dioxo-3H,9H-pyrazolo[1,2-a]indazole (7) were synthesized. The antiinflammatory activity of some synthesized compounds was determined by carrageenan-induced rat paw edema technique using diclofenac as reference drug. The pharmacological data showed that most of the tested compounds exhibited a significant long lasting antiinflammatory activity, which in the case of compound 3b was superior to that of diclofenac.     

Octahydropyrazino[2',3':3,4]pyrido[1,2-a]indoles. A new class of potent antihypertensive agents

Simplifications and modifications of the vincamine molecule led to the discovery of antihypertensive 1,2,3,4,4a,5,6,12b-octahydro-12-methylpyrazino[2',3':3,4]pyr ido[1,2-a] indoles. Stereoselective syntheses of both 4a,12b-cis and 4a,12b-trans isomers represent new annulation strategies for the construction of fused piperazines. Compounds of the trans series were at least 10 times more potent than the corresponding cis isomers. Antihypertensive activity and alpha 1-adrenoceptor blocking properties peaked with a simultaneous introduction of 4-methylethyl and 1-alkyl substituents. Compound 15j (AY-28,228; atiprosin), (4a, 12b-trans)-1-ethyl-1,2,3,4,4a,5,6, 12b-octahydro-12-methyl-4-(1-methylethyl)pyrazino[2',3':3,4]pyrido [1,2-a]indole, was chosen for a detailed preclinical evaluation.     

Convenient synthesis of fused heterocyclic 1,3,5-triazines from some N-acyl imidates and heterocyclic amines as anticancer and antioxidant agents

N-Acyl imidates (2), reacting with 5-amino pyrazole (3), 2-aminobenzimidazole (4), 3-amino-1,2,4-triazole (5), 3,5-diamino-1,2,4-triazole (6), and 5-aminotetrazole (7) give pyrazolo[1,5-a][1,3,5]triazine (8), benzo[4,5]imidazo[1,2-a][1,3,5]triazine (9), [1,2,4]triazolo [2,3-a][1,3,5]triazine (10), [1,2,4]tri azolo[2,3-a][1,3,5]triazin-5-ylamine (12), and tetrazolo-[1,5-a][1,3,5]triazine (14) derivatives, respectively. The synthesized compounds were characterized on the basis of IR, (1)H-NMR, (13)C-NMR, and mass spectral data and elemental analyses results. Five of the newly synthesized compounds, 8a, 9a, 10a, 12a, and 14a, were selected by National Cancer Institute and screened for their anticancer activity against three cancer cell lines MCF7, NCI-H460, and SF-268, where 12a exhibited moderate anti-proliferation potential. 12a was, thus, further tested for anticancer activity against 60 human cancer cell lines and showed moderate growth inhibition potency. 12a showed a high growth inhibitory activity against A498 renal cancer cell line. All of the newly synthesized compounds 8-10, 12 and 14 were tested for their antioxidant capacity where they exhibited very high activity, even higher than the widely used reference antioxidants butylated hydroxytoluene and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). Compound 12a also showed the highest antioxidant activity.     

Benzimidazole condensed ring systems. 8 (1). Synthesis of some substituted 1-oxo-1H,5H-pyrido[1,2-a] benzimidazole-4-carbonitriles with anticipated antimicrobial activity.

As a part of research project on the syntheses of a number of pyrido[1,2-a]benzimidazole derivatives with possible antimicrobial activity, some 3-(chloro or morpholino)-acetyloxy (2,3), 3-(N,N-dimethylcarbamoyloxy) (4,5) and 3-tosyloxy-1-oxo-1H,5H-pyrido[1,2a]benzimidazole-4-carbonitrile s (6) were prepared and evaluated for such activity. Many compounds exhibited in vitro antimicrobial activity and structure-activity relationship is discussed.     

Synthesis of carboline alkaloid analogues

Hybrid compounds were synthesized combining the structural features of two isomer natural indolalkaloids rutaecarpine (1) and nauclefine (2). These aza-bioisosteric analogues are the first representatives of a new heterocyclic ring system. Two alternative reaction routes were developed for the synthesis of pentacyclic compounds (4, 5) in which the key step is the Fischer indolization of the 6-phenylhydrazono-dipyrido[1,2-a;4,3-d]pirimidine-11-ones. In the case of E-ring substituted derivatives the synthesis was carried out via preparation and chemical transformation of pyrido[1,2-a]pirimidine-4-ones (14, 15) to 2-substituted-3-aza-rutaecarpines (17-20). Finally, the nucleophilic displacement of the chlorine atom of 2-chloro-3-aza-rutaecarpine (18) by dialkylaminoethylamine provided the 2-amino-substituted derivative (20) having improved physico-chemical properties and increased antitumour activity. The new compounds are characterized by UV, IR, 1H, 13C NMR spectroscopy.     

Synthesis of new 2-(aminomethyl)-4-phenylpyrrolo[1,2-a]-quinoxalines and their preliminary in-vivo central dopamine antagonist activity evaluation in mice

In the search for antipsychotic agents that are not associated with extrapyramidal side effects, efforts have been focused on finding selective D4-receptor antagonists and investigating their pharmacology. Our laboratory has developed a synthesis program for new pyrroloquinoxalines with therapeutic potential. We have described the synthesis of some new pyrroloquinoxalines with substituted arylpiperazino or aryltetrahydropyrido chain at position 3 of the quinoxaline ring (2-(4-phenylpiperazin-1-ylmethyl)-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3a), 2-[4-(2-methoxyphenyl)piperazin-1-ylmethyl]-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3b), 2-[4-(3-trifluoromethylphenyl)piperazin-1-ylmethyl]-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3c), 2-[4-(4-chlorophenyl)piperazin-1-ylmethyl]-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3d), 2-(4-pyridin-2-ylpiperazin-1-ylmethyl)-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3e), and 2-(4-phenyl1,2,3,6-tetrahydropyridin-1-ylmethyl)-4-phenylpyrrolo[1,2-a]quinoxalinium oxalate (3f)). A preliminary pharmacological study of these products was conducted using climbing behaviour induced by apomorphine (2.5 mg kg(-1), s.c.) in mice. The derivatives were administered intraperitoneally 30 min before apomorphine. Haloperidol, chlorpromazine and clozapine were used as references. Among this series, 3b, 3c and 3f revealed a central dopamine antagonist activity. The most active derivative was 3b, which exhibited a profile relatively close to clozapine.