Synthesis and properties of 7-methyl-5-oxo-1,5-dihydro-8-[1,2,4]-triazolo [4,3-c]pyrimidinecarboxylic acid derivatives

The synthesis of the new triazolo[4,3-c]pyrimidines is described, starting from derivatives of 5-carboxy-2-hydroxy-4-hydrazino-6-methylpyrimidine. The 4-methyl-2,3-dihydropyrazolo[3,4-d]pyrimidine-3,6-dione was also obtained. Some of triazolo[4,3-c]pyrimidines tested for biological activity were found inactive.     

Synthesis, isomerization, and antimicrobial evaluation of some pyrazolopyranotriazolopyrimidine derivatives

6-Amino-5-imino-pyrazolo[4',3':5,6]pyrano[2,3-d]pyrimidine derivative 4 and pyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-5-ylhydrazine derivative 5 were prepared starting from 6-amino-3-methyl-4-(p-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile 1. The synthesis and structure characterization of 9,11-dihydropyrazolo[4',3':5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine derivatives 7 and 9 and their isomerization to 9,11-dihydropyrazolo[4',3':5,6]pyrano[3,2-e] [1,2,4]triazolo[1,5-c]pyrimidine derivatives 6 and 8, respectively, under different suitable reaction conditions are reported. Moreover, the synthesis of 9,11-dihydropyrazolo[4',3':5,6]pyrano[3,2-e] tetrazolo[1,5-c]pyrimidine derivative 14 and N(9)-acyclic nucleoside 15 are described. Some of the prepared products showed potent antimicrobial activity.     

Synthesis and evaluation of pharmacological and pharmacokinetic properties of 11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepin-3(2H)-ones

A series of 2,3-benzodiazepine derivatives has been previously described as noncompetitive AMPA-type glutamate receptor antagonists potentially useful for treatment of epilepsy. To further explore the structure-activity relationships of AMPA antagonists, a series of 11H-[1,2,4]triazolo[4,5-c][2,3]benzodiazepin-3(2H)-ones (6) was synthesized starting from the corresponding bicyclic 1-aryl-3, 5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-ones (2, CFM). The new compounds were found to possess anticonvulsant effects against seizures induced both by means of auditory stimulation in DBA/2 mice and by pentylenetetrazole or maximal electroshock in Swiss mice. In addition, they antagonize the AMPA-induced seizures, and their anticonvulsant activity is reversed by pretreatment with aniracetam, thus suggesting the involvement of AMPA receptors. The pharmacological studies revealed that the 11H-[1,2,4]triazolo[4, 5-c][2,3]benzodiazepin-3(2H)-ones (6) herein reported show anticonvulsant activity comparable to that of their bicyclic precursors. Furthermore, an HPLC study put in evidence that these tricyclic derivatives 6 were converted in vivo into the corresponding 2, the agents likely to be mainly responsible for the anticonvulsant properties observed.     

Synthesis of certain substituted quinoxalines as antimicrobial agents (part II)

Several fused triazolo and ditriazoloquinoxaline derivatives such as 1-aryl-4-chloro-[1,2,4]triazolo[4,3-a]quinoxalines (3a-d), 4-alkoxy[1,2,4]triazolo[4,3-a]quinoxalines (4a,b), 4-substituted-amino-[1,2,4] triazolo[4,3-a]quinoxalines (5a-h), 1-(aryl)-[1,2,4]triazolo[4,3-a]quinoxalin-4(5H)-thione (6), 4-(arylidenehydrazino)1-phenyl-[1,2,4]triazolo[4,3-a]quinoxalines (10a-e) and [1,2,4]ditriazolo[4,3-a:3',4'-c]quinoxaline derivatives (11-13) have been synthesized and some of these derivatives were evaluated for antimicrobial and antifungal activity in vitro. It was found that compounds 3a and 9b possess potent antibacterial activity compared to the standard tetracycline.     

Synthesis and biological evaluation of new thiazolopyrimidines

In this study, a series of 4-amino-5-cyano-3-substituted-2,3-dihydrothiazol-2-thiones (1a-c), as well as their triazolo and triazinopyrimidine derivatives such as 8-substituted-3-benzyl-5-methylthiazolo[5,4-e][1,2,4] triazolo[1,5-c]pyrimidin-2-thiones (4-6, 10) and 3-benzyl-5-methyl thiazolo[5,4-e]pyrimidino[3,4-b][1,2,4]triazin-2-thiones (7a-b) were prepared as potential antimicrobial and antitumor agents. Some of the tested compounds showed promising antimicrobial activity and non of them showed any appreciable antitumor activity.     

Synthesis and benzodiazepine binding activity of a series of novel [1,2,4]triazolo[1,5-c]quinazolin-5(6H)-ones.

Investigation of tricyclic heterocycles related to the 2-arylpyrazolo[4,3-c]quinolin-3(5H)-ones, structures with high affinity for the benzodiazepine (BZ) receptor, led to the synthesis of 2-phenyl-[1,2,4]triazolo[1,5-c]quinazolin-5(6H)-one, a compound with 4 nM binding affinity to the BZ receptor. Analogues were prepared to assess the importance of the 2-substituent and ring substitution in modifying activity. Several novel synthetic routes were designed to prepare the target compounds, including a two-step synthesis beginning with an anthranilonitrile and a hydrazide. Of the 34 compounds screened in this series, three compounds were found to be potent BZ antagonists in rat models. The leading compound, 9-chloro-2-(2-fluorophenyl) [1,2,4]triazolo[1,5- c]quinazolin-5(6H)-one (CGS 16228), showed activity comparable to that of CGS 8216 from the pyrazolo[4,3-c]quinoline series.     

Synthesis and biological activity of new heterocyclic structures: [1,3]thiazino[2,3-i]purine, thiazolo[3,2-c] [1,2,3]triazolo[4,5-e]pyrimidine and [1,2,3]triazolo [4', 5': 4,5] pyrimido[6,1-b][1,3]thiazine.

Some derivatives of thiazolo[3,2-c]pyrimidine, pyrimido[6,1-b][1,3]thiazine, thiazolo[2,3-i]purine, [1,3]thiazino[2,3-i]purine, thiazolo[3,2-c][1,2,3]triazolo[4,5-e]pyrimidine and [1,2,3]triazolo[4',5':4,5]pyrimido[6,1-b][1,3]thiazine were prepared. The compounds were tested for antimicrobial and antimycotic activity on a number of strains, namely, Escherichia coli, Proteus vulgaris, P. mirabilis, Pseudomonas aeruginosa, Salmonella sp., Staphylococcus aureus, Streptococcus faecalis, Bacillus subtilis, Sarcina lutea, Candida albicans, Aspergillus sp., and for antiviral activity on Herpes simplex virus, Type 1 (HSV-1), Vesicular stomatitis virus (VSV) and Coxsackievirus B5 (CoxB5). The compounds proved to be devoid of activity against viruses, mycetes and gram-negative bacteria, while some of them exhibited a modest activity against gram-positive bacterial strains.     

Synthesis and antimicrobial evaluation of naphtho[2,1-b]pyrano[2,3-d]pyrimidine and pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives

Several novel naphtho[2,1-b]pyrano[2,3-d]pyrimidines, pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidines and their coumarin-3-yl derivatives were synthesized. Some of these derivatives exhibited pronounced antimicrobial activities.     

1,5-Benzodiazepine tricyclic derivatives exerting anti-inflammatory effects in mice by inhibiting interleukin-6 and prostaglandinE(2)production.

The 1,4- and the 1,5-benzodiazepines (BDZ) are commonly used as anxiolytic and anticonvulsive drugs. It has been suggested that they influence, particularly through stimulation of peripheral BDZ receptors, some immune cell properties such as pro-inflammatory cytokine production. The availability of a new class of [1,2,4]triazolo[4,3-a][1,5]benzodiazepine derivatives (compounds IV), endowed with anti-inflammatory and/or analgesic properties but no anti-pentylenetetrazole activity, prompted us to investigate in more detail the anti-inflammatory properties of three selected compounds IV (N,N-dimethyl-1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benz- odiazepin-5-amine; N,N-dibutyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine; 1-methyl-N,N-dimethyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine) and one structurally related compound (1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5(6H)-one). These BDZ derivatives have lost their affinity for the central and peripheral BDZ receptors. The in vivo effect on leukocyte migration of these compounds was investigated by using the mouse air-pouch model of local inflammation. Compounds A and B, significantly inhibited the carrageenan-induced leukocyte recruitment in a dose-dependent manner starting from the dose of 50 mgkg(-1), whereas compound C was effective only at the higher dose of 100 mgkg(-1). Compound D did not exert such effects at any of the doses considered. The effect of compounds A, B and C on leukocyte recruitment was paralleled by a significant inhibition of interleukin-6 and prostaglandin E(2)production in the exudate, similarly to indomethacin, and by a partial reduction of vascular permeability. These features may be relevant for the design and development of innovative anti-inflammatory molecules among the 4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine derivatives.     

Synthesis of new hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT1A and 5-HT2A receptors. Part III

The preparation of new 4-aryl-hexahydropyridol 1,2-c]pyrimidine derivatives III-XXVI with an arylpiperazinylbutyl moiety in N-2 position has been described. Multi-stage synthesis techniques were used to obtain 4-arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine-1,3-dione Ia-f derivatives, being the starting compounds for further modification. N-alkylation of the imide group in compounds Ia-f followed, using 1,4-dibromobutane to yield bromobutyl derivatives IIa-f. The final products III-XXVI were obtained by condensation of aryl- or heteroaryl- piperazine with the bromobutyl derivatives IIa-f. Compounds XII, XIV, XIX, XX, XXIV-XXVI will be submitted to a pharmacological investigation for their affinity towards 5-HT1A, 5-HT2A and alpha1 adrenergic receptor, using radioligand binding assay.     

Synthesis of 6-(Ethoxymethylenimino)-1,2,4-triazolo[3′,4′:5,1]-[1,2,4]triazolo[4,3-a]quinazolin-7(6H)-one

As a progressive continuation of our study in the condensed quinazolinone series^{1, 2)}, we recently described the synthesis and antihypertensive activity of some 4-amino[1,2,4]triazolo[4,3-a]quinazolin-5(4H)-one derivatives ( 1a-c , R=H, OH, SH). Now, we wish to report the conversion of one of these derivatives, namely 4-amino-1-mercapto-[1,2,4]-triazolo[4,3-a]quinazolin-5(4H)-one (1c) into a more complicate condensed quinazolinone system.     

Piperazine derivatives of [1,2,4]triazolo[1,5-a][1,3,5]triazine as potent and selective adenosine A2a receptor antagonists

The [1,2,4]triazolo[1,5-a]triazine derivative 3, more commonly known in the field of adenosine research as ZM-241385, has previously been demonstrated to be a potent and selective adenosine A2a receptor antagonist, although with limited oral bioavailability. This [1,2,4]triazolo[1,5-a]triazine core structure has now been improved by incorporating various piperazine derivatives. With some preliminary optimization, the A2a binding affinity of some of the best piperazine derivatives is almost as good as that of compound 3. The selectivity level over the adenosine A1 receptor subtype for some of the more active analogues is also fairly high, > 400-fold in some cases. Many compounds within this piperazine series of [1,2,4]triazolo[1,5-a]triazine have now been shown to have good oral bioavailability in the rat, with some as high as 89% (compound 35). More significantly, some piperazines derivatives of [1,2,4]triazolo[1,5-a]triazine also possessed good oral efficacy in rodent models of Parkinson's disease. For instance, compound 34 was orally active in the rat catalepsy model at 3 mg/kg. In the 6-hydroxydopamine-lesioned rat model, this compound was also quite effective, with a minimum effective dose of 3 mg/kg po.     

Synthesis and anticonvulsant activities of some triazolothiadiazole derivatives

The present study describes the synthesis and anticonvulsant activity evaluation of 6-substituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives (4a-4x) and their partially dehydrogenated products 5,6-dihydro-6-substituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives (5a-5n). The bioevaluation demonstrated that most compounds in the series of 4a-4x exhibited potent anticonvulsant activity in the maximal electroshock test. Among which, 6-(4-chlorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (4h) emerged as the most promising candidate on the basis of its favorable ED(50) value of 23.7 mg/kg and PI value of 10.8. In addition, the potency of compound 4h against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline in the chemical-induced seizure tests suggested that compound 4h displayed broad-spectrum activity in several models, and it may exert its anticonvulsant activity through affecting the GABAergic system.     

1,2,4-Triazolo[5,1-i]purine derivatives as highly potent and selective human adenosine A(3) receptor ligands

A series of triazolopurines showed structural similarity to human adenosine A(3) receptor antagonist, 9-chloro-2-(2-furanyl)-5-[(phenylacetyl)amino][1,2,4]triazolo[1,5-c]quinazoline (MRS 1220, 1). In this study, we found novel 1,2,4-triazolo[5,1-i]purine derivatives (2) showing human adenosine A(3) receptor affinities. The compounds were obtained in two steps from 5-amino-4-cyanoimidazole (33). The affinity was determined in radioligand binding assays for the cloned human adenosine A(1), A(2A), A(2B), and A(3) receptors. After the structure-activity relationship was analyzed, we determined that there was a mild parabolic relationship between the length of alkyl groups at the 5-position and the affinities at the A(3) receptor and positive correlation between the length of the substituents on phenyl groups at the 8-position and the affinities at the A(2A) receptor. These investigations led to potent and selective human adenosine A(3) receptor ligands. The most potent A(3) receptor ligand (5-n-butyl-8-(4-methoxyphenyl)-3H-[1,2,4]triazolo[5,1-i]purine (27, K(i) = 0.18 nM) and the most selective A(3) receptor ligand against A(1), A(2A), and A(2B) receptors, (5-n-butyl-8-(4-n-propoxyphenyl)-3H-[1,2,4]triazolo[5,1-i]purine (29, >19 600), were discovered.     

Pyrazolo(4.3-c)pyridines (author's transl)

Pyrazolo[4.3-c]pyridine A new process for the synthesis of pyrazolo[4.3-c]pyridine-7-carboxylic-acid derivatives is described. The compounds bear various substituents in 4-position, especially amino- or alkoxygroups.     

SAR of a series of 5,6-dihydro-(9H)-pyrazolo[3,4-c]-1,2,4-triazolo[4,3-alpha]pyridines as potent inhibitors of human eosinophil phosphodiesterase

The potency and physical properties of a previously reported 7-oxo-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine series of human eosinophil phosphodiesterase inhibitors were improved by tying the lactam moiety into a triazolo ring. The resulting 5,6-dihydro-(9H)-pyrazolo[3,4-c]-1,2,4-triazolo[4,3-alpha]pyridine series provided nonionizable analogs with melting point properties suitable for micronization. Substitution at the 3-position of the 5,6-dihydro-(9H)-pyrazolo[3,4-c]-1,2,4-triazolo[4,3-alpha]pyridine tricycle led to a 2-thienyl analog, 19 (tofimilast), a potent PDE4 inhibitor with low oral bioavailability and no emesis-associated behaviors in ferrets at plasma concentrations up to 152 ng/mL.     

Anxiolytic properties of certain annelated [1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-ones.

Modification of the benzodiazepine (BZ) receptor binding template 2-aryl[1,2,4]triazolo[1,5-c]quinazolin-5(6H)-one by replacement of the annelated benzene ring with various alicyclic and heterocyclic moieties led to novel structures with potent BZ receptor binding affinity. High affinity was found in some cycloalkyl-annelated [1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-ones and in some 7,8,9,10-tetrahydropyrido[3,4-e][1,2,4]triazolo[1,5-c]pyrimidin- 5(6H)-ones, in which the degree of activity was strongly dependent on the N-substituent in the 9-position. Nine compounds with BZ receptor IC50 binding affinity values equal or superior to diazepam were evaluated in secondary screening. One of these, 9-benzyl-2-phenyl-7,8,9,10-tetrahydropyrido[3,4-e] [1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-one, showed good activity in rats as a potential anxiolytic agent without sedative liability. However, it increased the rotorod deficit produced by ethanol at anxiolytic doses, an indication of alcohol interaction. Thus, none of the compounds showed an advantage over CGS 9896 (Yokoyama et al. J. Med. Chem. 1982, 25, 337-339), which is free of sedative and alcohol interaction potential as measured by the test procedures described.     

A comparison of the antiserotonin, antihistamine, and anticholinergic activity of cyproheptadine with analogues having furan nuclei fused to the 10,11-vinylene bridge.

A series of cyproheptadine derivatives having furan nuclei fused to the 10,11-vinylene bridge has been prepared. None of the compounds retain the potent antiserotonin and antihistaminic actions of cyproheptadine. 1-methyl-4-(1-methyl-8H-dibenzo[a,e]furo[3,4-c]cyclohepten-8-ylidene)piperidine (7), 1-methyl-4-(1,3-dihydro-1-oxo-8H-[3,4:6,7]cycloheptal[1,2-c]furan-8-ylidene)piperidine (10), and its reduction product 11 retained the peripheral anticholinergic activity of cyproheptadine.     

Synthesis of new hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT(1A) and 5-HT(2A) receptors, Part 2

The synthesis of new of 4-aryl-hexahydro- (11-16) and (R,R)(S,S)4-aryl-octahydropyrido[1,2-c]pyrimidine (23-27) derivatives bearing a aryl- or heteroarylpiperazinyl moiety in position 2 is described. The derivatives of 4-aryl-hexahydro- (1-5) and (R,R)(S,S)4-aryl-octahydropyrido[1,2-c]pyrimidin-1,3-dion (17-19) served as starting compounds for further synteses. The N-alkylation of the imide moiety in compounds 1-5 and 17-19 by 1,4-dibromobutane gave the respective monbromobutyl derivatives 6-10 and 20-22. The final derivatives 11-16 and 23-27 have been produced by condensation of the obtained bromoderivatives with selected 1-aryl and 1-heteroarylpiperazines. Compounds 11-16 and 23-27 were tested for their affinity towards 5-HT(1A), 5-HT(2A) and alpha1 receptors, using a radioligand binding assay.     

Inotropic activities of imidazopyridines

A series of 2-substituted 1H-imidazo[4,5-b]pyridines and the isomeric 1H-imidazo[4,5-c]pyridine derivatives has been prepared and evaluated as inotropic agents. The 1H-imidazo-[4,5-b] derivatives were found to be consistently more potent than their isomers in the [4,5-c] series in isolated guinea pig papillary muscle preparations. Structure-activity relationships and the species-dependence of inotropic potencies are discussed.