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Fourteen out of 21 quinoxaline derivatives described in the present paper were selected at NCI for evaluation of their in vitro anticancer activity. Preliminary screening showed that some derivatives exhibited a moderate to strong growth inhibition activity on various tumor panel cell lines between 10(-5) and 10(-4) M concentrations. Interesting selectivities were also recorded between 10(-8) and 10(-6) M for the compounds 9 and 13.

Since most of the reported adenosine receptor antagonists are 2-(hetero)aryl-substituted tricyclic heteroaromatic derivatives, in the present study we report the synthesis and the biological evaluation of a new set of 4-amino-1,2,4-triazolo[1,5-a]quinoxalines containing at position-2 an ethyl carboxylate group or a hydrogen atom. The structure-activity relationships on these compounds were in accordance with those of a previously reported series of analogous size and shape, thus suggesting a similar A(1)-binding mode. In particular, the binding data indicate that alkylation of the 4-amino group of these derivatives lead to potent A(1)-receptor antagonists. Moreover, as new results, this study has pointed out that the ethyl 2-carboxylate group can advantageously replace the 2-(hetero)aryl ring of previously reported triazoloquinoxaline derivatives, affording an ameliorated interaction with the A(1)-receptor subtype.

A new series of 3-alkyl-, 3-trifluoromethyl-, 3-carboxyethyl- and 3-bromomethylquinoxaline-2-ones and 2,3-bis(bromomethyl)quinoxalines bearing Cl, CF3, morpholine on the benzo-moiety, were synthesised and submitted to a preliminary in vitro evaluation for antibacterial and anticandida activities. Results of the screening showed that compounds 9b, 14b and 19b (MIC=62.5 microg/ml) and 10b (MIC=15.6 microg/ml) were the most active against Vibrio alginolyticus.

Twenty eight pyrrolo[1,2-a]quinoxalines bearing at position 4 various substituents related to the moieties present in classical and non classical antifolic agents were prepared and evaluated in vitro for antiproliferative activity. In an in vitro screening performed at NCI, several compounds emerged as potent antiproliferative agents at concentrations ranging between 10 and 100 microM. Interestingly, some of these compounds proved active also against bovine and murine DHFR (Farmaco 53 (1998) 480). More recently, a compound of classical antifolate type has been reported to be a potent inhibitor of hDHFR in vitro (Farmaco 58 (2003) 51). We then synthesized new derivatives that, in our hands, were endowed with in vitro antiproliferative activities as low as 3.4 microM against a panel of cell lines derived from hematological and solid tumours. In addition, a complete screening of cytotoxicity, antiretroviral HIV-1 and antimicrobial activity has been carried out.

A series of quinazoline derivatives, 2-20, structurally related to the racemic alpha(1)-adrenoceptor antagonist cyclazosin (1), were synthesized and evaluated for their functional antagonism at alpha(1)- and alpha(2)-adrenoceptors and for their binding affinity at human cloned alpha(1a)-, alpha(1b)- and alpha(1d)-adrenoceptor subtypes. They displayed, like 1, preferential antagonism and selectivity for alpha(1) versus alpha(2)-adrenoceptors. Compounds 10, 13, and 18 showed high potency at alpha(1)-adrenoceptors similar to that of 1 (pK(B) values 8.47-8.89 versus 8.67), whereas 13 and 15 were endowed with the highest alpha(1)-adrenoceptor selectivity, only 3- to 4-fold lower than that of 1. In binding experiments, all of the compounds displayed an affinity practically similar to that found for 1, with the exception of 19 and 20 that were definitely less potent. The s-triazine analogue 18 was the most potent of the series with pK(i) values of 10.15 (alpha(1a)), 10.22 (alpha(1b)) and 10.40 (alpha(1d)), resulting 77-fold more potent than 1 at alpha(1a)-adrenoceptors. In addition, the majority of compounds, like prototype 1, showed the same trend of preferential affinity for alpha(1d)- and alpha(1b)-adrenoceptors that alpha(1a)-subtype. In conclusion, we identified compounds 2-5, 10, 12 and 13, bearing either an aliphatic- or an arylalkyl- or aryloxyalkyl-acyl function, with an interesting subtype-selectivity profile, which makes them suitable candidates for their resolution as enantiomers structurally related to (+)-cyclazosin.

Among a new series of 26 4-(3-substituted-2-quinoxalylamino)phenylacetates and 4-(3-substituted-2-quinoxalylamino)-phenylacetyl-L-glutamates, eight were selected at NCI for evaluation of their in vitro anticancer activity. The results obtained in comparison with the corresponding nor-compounds series seem to indicate that this type of homologation is not helpful.

A new series of 3-isopropyl-, 3-trifluoromethyl- and 3-bromomethylquinoxaline-2-ones variously substituted on the benzo-moiety were synthesized and submitted to a preliminary in vitro evaluation for antibacterial, antifungal and anti-HIV activities. Furthermore, all compounds were also tested for cytotoxicity. Results of the screening showed that compound 10 exhibits moderate antimicrobial activity against Staphylococcus aureus (MIC = 33 microM), and that 25 and 26 showed interesting cytotoxicity versus mock-infected MT-4 cells. All the other compounds were inactive.

A series of twelve novel pyrido[2,3-g]quinoxalinones (3-14), variously substituted at the C-3 position, was synthesized, structurally determined and submitted to a preliminary in vitro evaluation for antibacterial, anticandida and anticancer activities. Results of the antimicrobial screening showed that all compounds, with the exception of 6, 11 and 12, exhibited interesting activity against all strains tested; while compound 10 was found to have encouraging in vitro anticancer activity at a concentration of l0(-4) M.

Among a new series of 28 3-carboxy or carbethoxy quinoxalines bearing a substituted benzylamino or N-[4-(aminomethyl)benzoyl]glutamate group on position 2 of the ring and various substituents at C-6, 7 positions, 21 were selected at the National Cancer Institute for evaluation of their in vitro anticancer activity. The results obtained seem to confirm that the carboxy or carbethoxy group on position 3 is not helpful, with a few exceptions, for the anticancer activity.

A new series of quinoxalinones 6/7-trifluoromethyl or nitro- and 6,7-difluoro substituted bearing various side-chains (alkyl, halogenoalkyl, benzyl and phenyl groups) at C-3 of the ring system was synthesized and submitted to preliminary in vitro evaluation for antibacterial, antifungal, antimycobacterial, anticancer and anti-HIV activities. Results of these screenings showed that compounds 23-28 exhibited a good inhibition activity against various strains of Candida. Compound 24 showed also an interesting in vitro anticancer activity.

A new set of 35 3-alkyl and 3-ethoxycarbonylalkyl 6- and/or 7-substituted-2-quinoxalinones was prepared and submitted to a preliminary in vitro investigation of their antimicrobial, anticancer and anti-HIV activities. Results are referred.

Tuberculosis, an ancient disease undergoing recent control by public hygiene and drug therapy, has experienced a recrudescence throughout the world. New and effective therapies are rapidly needed to combat infections caused by these strains. Some new 2-quinoxalinecarbonitriles have been synthesized and tested as antituberculosis agents and interesting results have been obtained from the first screening.

Thirty quinoxalines bearing a substituted phenoxy or hydroxybenzoylglutamate group on position 2, a carboethoxy or carboxy group on position 3 and a trifluoromethyl group on position 6 or 7 of the heterocycle were prepared in order to evaluate the in vitro anticancer activity. Screening over 21 compounds selected at the National Cancer Institute (Bethesda, MD) showed that only few derivatives exhibited a moderate growth inhibition activity on various tumor panel cell lines at 10(-4) molar concentration. The acid derivatives showed no growth inhibition activity. The results obtained in this series seem to indicate that in general carboxy or carboethoxy groups close to O-link with phenyl or benzoyl glutamates on position 2 are detrimental for anticancer activity.

Twenty-four out of twenty-nine quinoxalines were selected at the National Cancer Institute, Bethesda, Md, USA, for in vitro anticancer screening. Among these, 10 derivatives exhibited high values of percent tumor growth inhibition at a concentration of 10(-4) M in all cancer cell lines. Four of these compounds maintained these values at 10(-5) M, whereas a certain number exhibited significant values of percent inhibition at the most diluted concentrations (10(-8)-10(-6) M). Inhibitory activity against dihydrofolate reductase (DHFR) (bovine and rat liver) was determined for the most active compounds. This test showed that this type of quinoxaline exhibited an appreciable activity in comparison with the previously described aza analogues. In the other test (Lactobacillus casei, thymidylate synthase (TS), human HTS) no or poor activity was detected in both series of compounds.

A series of variously substituted quinoxalin-3-ones bearing an ethoxycarbonyl or carboxy group in the C-2 position has been prepared and their structures proved by 1H NMR spectroscopy. The obtained compounds were investigated in vitro for antimicrobial and anticancer activities. Preliminary results showed a moderate activity against a few strains of bacteria but no significant anticancer and anti-HIV activity.

Eighteen quinoxalines bearing a methyleneanilino or methyleneaminobenzoylglutamate group on position 6 of the ring and various lipophilic substituents on positions 2 and 3 were prepared in order to discover if their structural analogy with both trimetrexate (TMQ) and 10-propargyl-5,8-dideazafolic acid (CB 3717) might display in vitro anticancer activity. Among these, 12 compounds were selected at the National Cancer Institute, Bethesda, MD, USA; they exhibited moderate (4b,d,i,l,m and 8) to strong (4f,h and 5a,e) cell-growth inhibition at a concentration of 10(-4) M. Interesting selectivities were also recorded between 10(-8) and 10(-6) M. These analogues proved to be less potent inhibitors of tumor cells than other classical and non-classical antifolate analogues previously described by us.

Among twenty-eight novel compounds (twenty-two 2,3-disubstituted-6-[(substituted-phenoxy)methyl-quinoxalines and six 4-[(2,3-disubstituted-quinoxalin-6-yl)methoxy]benzoylglutamates ) only thirteen were selected at NCI for evaluation of their in vitro anticancer activity. The results have shown that compounds 3l,c,b,e and 4b were endowed with significantly high values of percent tumor growth inhibition on several tumor cell lines at 10(-4) M, while compound 3t was characterized by a high selectivity, being still strongly inhibiting on three cell lines at 10(-5) M. Comparison of the presently observed activity with that of the previously described aza-analogues confirms that the effected isosteric substitution is highly valuable in some cases.

Thirty quinoxalines bearing a substituted anilino group on position 2, a carboethoxy or carboxy group on position 3 and a trifluoromethyl group on position 6 or 7 of the heterocycle were prepared in order to evaluate in vitro anticancer activity. Preliminary screening performed at NCI showed that most derivatives exhibited a moderate to strong growth inhibition activity on various tumor panel cell lines between 10(-5) and 10(-4) molar concentrations. Interesting selectivities were also recorded between 10(-8) and 10(-6) M for a few compounds. One single compound exhibited good activity against Candida albicans.

Thirty-one quinoxalines bearing a substituted benzylamino group on position 2 and various substituents on position 3,6,7 and 8 of the heterocycle were prepared in order to evaluate in vitro anticancer activity. Preliminary screening performed at NCI on twenty-two compounds showed that most derivatives exhibited a moderate to strong growth inhibition activity on various tumor panel cell lines between 10(-5) and 10(-4) molar concentrations. Interesting selectivities were also recorded between 10(-8) and 10(-5) M.

Thirty compounds possessing quinoxaline structure bearing either substituted arylmethylmercapto-, arylmethylsulfinyl group or a piperazinyl moiety in position 2 were prepared in order to evaluate an antiulcer and gastroprotective activity in rat pylorus ligature, in comparison with omeprazole and ranitidine at the dose of 100 mg/kg after oral administration. Among the compounds of the first group one third showed a moderate activity being about half potent as omeprazole whereas in the second group compound 5b exibited an activity superior to that of ranitidine accompanied with the lowest incidence of lesions and mortality and another compound (5i) was equiactive as ranitidine.

Thirty-five quinoxalines bearing a substituted aniline group on position 2 and various substituents on positions 3,6,7 and 8 were prepared in order to evaluate in vitro anticancer activity. Structural elucidation of some isomeric quinoxalinones formed by ring closure of 4-substituted-1,2-diaminobenzenes with dicarbonyl compounds was achieved by comparison with one isomer coming from an unambiguous independent route. Preliminary in vitro screening at NCI showed that many compounds exhibited a moderate to strong growth inhibition activity on various cell lines between 10(-5) and 10(-4) molar concentrations.

A series of substituted [1]benzothieno [2,3-b]pyrazines, structurally related to caroverine, was synthesized. Some of these compounds showed an appreciable inhibition towards KCl induced contractions on isolated rat aortic rings, and a lower potency towards negative inotropic activity tested on isolated guinea pig atrium.

Applying a reaction formerly studied by the Authors between acenaphthenequinone and N1-(2-amino)phenyl-N2-acylhydrazines, a group of N-[(N-alpha- and beta- halogenoacyl)imino]acenaphthenequinoxalines were obtained. On account of the reactivity of the halogen atom, they are potentially interesting as antitumoral agents. In contrast with the beta-chloropropionyl derivative, the alpha-halogenoacyl derivatives were formed in low yields and with the simultaneous loss of the whole halogenoacylimino group. Thus, an alternative synthetic route was set up, consisting in the N-imination of acenaphthenequinoxalines by means of O-mesitylenesulfonylhydroxylamine, followed by acylation of the intermediate N-iminoacenaphthenequinoxalines. The National Cancer Institute of Bethesda evaluated the activity against lymphocytic leukemia P 388 on some of the numerous compounds now described. Only the N-chloroacetyliminoacenaphthenequinoxaline exhibited, at the dose of 50 mg/Kg i.p., 35% increase of the average survival time of treated mice. All the remaining compounds were inactive.

The synthesis and the benzodiazepine receptor activity of some pyrazolo[1,5-a]quinoxalines bearing various substituents on the tricyclic heteroaromatic system are reported. Only one of the tested compounds showed some receptor affinity.

The synthesis, the benzodiazepine binding activity and the "in vitro" biological effect of some 1,2,4-triazolo[1,5-a]quinoxalines, 3-aza-analogues of some previously reported pyrazolo[1,5-a]quinoxalines, are described. Molecular modelling is used to define the structural requirements of the benzodiazepine recognition site which influence the affinity and different efficacy of these rigid ligands.

Tert-aminoalkylderivatives of quinoxalin-2-ones, aza- and diazaquinoxalin-2-ones bearing in position 3 a benzyl group were assayed to evaluate the antispasmodic activity. The tested compounds exhibited moderate aspecific antispastic properties that do not warrant further investigation.

Replacement of the oxygen atom at 1-position in the hexahydronaphthoxazines (4, PHNO) with a sulfur or nitrogen atom leads to the hexahydronaphthiazines (6, PHNT) and octahydro-benzoquinoxalines (5, POBQ) respectively and the 9-OH-PHNT shows to have a high affinity towards D-2 dopamine receptors in the binding assays; the racemic 9-OH-PHNT was then resolved and its absolute configuration was determined by CD. Inactivity on D-2 receptors of (+)-9-OCH3-PHNT 12 confirms the validity of the McDermed receptor model.