Synthesis and biological evaluation of 6-bromo-6-substituted penicillanic acid derivatives as beta-lactamase inhibitors.

The synthesis of a selected set of 6-bromopenicillanic acid derivatives with an additional C6 substituent is reported. All these substances were tested as inhibitors of class A and C beta-lactamase enzymes derived from Escherichia coli (TEM-1) and E. cloacae (P99). As 6-(1-hydroxyethyl) derivatives 4c and 6c were found to be weak beta-lactamase inhibitors, they were further investigated in combination with amoxicillin against a series of beta-lactamase-producing bacterial strains. Some structure-activity relationships are discussed.

Synthesis of new C-6 alkyliden penicillin derivatives as beta-lactamase inhibitors.

New penicillin, penicillin sulfone and sulfoxide derivatives bearing a C-6-alkyliden substituent were prepared. Their chemical synthesis, in vitro antibacterial activity and inhibition properties against two selected enzymes representing Class A and C beta-lactamases are reported. Compounds 3a-c, 7a-c were able to inhibit either TEM-1 (a Class A enzyme, from Escherichia coli) or P-99 (a Class C enzyme, from E. cloacae), or both enzymes, when tested in competition experiments using nitrocefin as the reporter substrate. However, when tested in combination with amoxicillin, the same compounds did not show synergistic effects against E. coli and E. cloacae strains producing TEM-1 and P99 enzymes, respectively. This finding is most likely related to poor penetration through the bacterial cell wall, as shown by using a more permeable isogenic E. coli strain. Interestingly, a synergistic effect against a strain of S. aureus which produces PC1-enzyme (a Class A beta-lactamase) was observed for compound 3a when used in combination with amoxicillin.

2-N-acylaminoalkylindoles: design and quantitative structure-activity relationship studies leading to MT2-selective melatonin antagonists.

Several indole analogues of melatonin (MLT) were obtained by moving the MLT side chain from C(3) to C(2) of the indole ring. Binding and in vitro functional assays were performed on cloned human MT1 and MT2 receptors, stably transfected in NIH3T3 cells. Quantitative structure-activity relationship studies showed that 4-methoxy-2-(N-acylaminomethyl)indoles, with a benzyl group in position 1, were selective MT2 antagonists and, in particular, N-[(1-p-chlorobenzyl-4-methoxy-1H-indol-2-yl)methyl]propanamide (12) behaved as a pure antagonist at MT1 and MT2 receptors, with a 148-fold selectivity for MT2. We present a topographical model that suggests a lipophilic group, located out of the plane of the indole ring of MLT, as the key feature of the MT2 selective antagonists.

A new melatonin receptor ligand with mt1-agonist and MT2-antagonist properties.

It has been difficult, so far, to obtain melatonin analogs possessing high selectivity for the respective melatonin receptors, mt1 and MT2. In the present work, we report the synthesis and pharmacological characterization of a new compound N-¿2-[5-(2-hydroxyethoxy)-1H-indol-3-yl)] ethyl¿ acetamide or 5-hydroxyethoxy-N-acetyltryptamine (5-HEAT). To assess the activity of the compound, the following tests were performed: affinity determination for the high- and low-affinity receptor states (2-[125I]iodomelatonin binding), potency and intrinsic activity in inducing G protein activation ([35S]GTPgammaS binding assay). 5-HEAT showed little selectivity for the mt1 receptor, with pKi values of 7.77 for mt1 and 7.12 for the MT2 receptors, respectively. 5-HEAT was able to differentiate between the high- and the low-affinity receptor states in the mt1 but not in the MT2 receptor. 5-HEAT induced a high level of G protein activation when acting through the mt1 receptor, with a relative intrinsic activity of 0.92. On the contrary, it elicited only minimal MT2 receptor-mediated G protein activation, with a relative intrinsic activity of 0.16, and was also able to inhibit the melatonin-induced MT2 receptor-mediated G protein activation, with a pKB value of 7.4. In conclusion, it appears that 5-HEAT possesses very different efficacies at the two melatonin receptors, behaving as a full melatonin receptor agonist at the mt1 and as an antagonist/weak partial agonist at the MT2 receptor. Therefore, it is a promising ligand for use in functional studies aimed at distinguishing between the effects mediated by the different melatonin receptors in the human.

3-(2-Carbamoylvinyl)-4,5-dimethylpyrrole-2-carboxylic acids as ligands at the NMDA glycine-binding site: a study on the 2-carbamoylvinyl chain modification.

Twenty 4,5-dimethylpyrrole-2-carboxylic acids (5a-t) with different 2-carbamoylvinyl chains in position 3 were prepared to further investigate the relationships between structure and in vitro affinity for the strychnine-insensitive glycine-binding site. None of these compounds was superior to (E)-3-(N-phenyl-2-carbamoylvinyl)-4,5-dimethylpyrrole-2-carb oxylic acid III (pKi = 6.70), which was taken as a reference standard, but overall the results obtained indicate that the N-phenyl-2-carbamoylvinyl substituent of III may be replaced with the N-(1-adamantyl)-2-carbamoylvinyl group as in 5h (pKi = 6.20) without considerable loss of affinity. This finding adds to previous knowledge.

Melatonin receptor ligands: synthesis of new melatonin derivatives and comprehensive comparative molecular field analysis (CoMFA) study.

The CoMFA methodology was applied to melatonin receptor ligands in order to establish quantitative structure-affinity relationships. One hundred thirty-three compounds were considered: they were either collected from literature or newly synthesized in order to gain information about the less explored positions. To this end, various melatonin derivatives were prepared and their affinity for quail optic tecta melatonin receptor was tested. Compounds were aligned on the putative active conformation of melatonin proposed by our previously reported pharmacophore search, and their relative affinities were calculated from the displacement of 2-[125I]-iodomelatonin on different tissues expressing aMT receptors. Compounds were grouped into three sets according to their topology. Subset A: melatonin-like compounds; subset B: N-acyl-2-amino-8-methoxytetralins and related compounds; subset C:N-acyl-phenylalkylamines and related compounds. CoMFA models were derived for each set, using the steric, electrostatic, and lipophilic fields as structural descriptors; the PLS analyses were characterized by good statistical parameters, taking into account the heterogeneity of the binding data, obtained with different experimental protocols. From the CoMFA model for the melatonin-like compounds, besides the well-known positive effect of 2-substitution, a low steric tolerance for substituents in 1, 6, and 7, and a negative effect of electron-rich 4-substituents were observed; the information provided by the newly synthesized compounds was essential for these results. Moreover, a comprehensive model for the 133 compounds, accounting for a common alignment and a common mode of interaction at the melatonin receptor, was derived (Q2 = 0.769, R2 = 0.905). This model validates our previously reported pharmacophore search and offers a clear depiction of the structure-affinity relationships for the melatonin receptor ligands.

2-[N-Acylamino(C1-C3)alkyl]indoles as MT1 melatonin receptor partial agonists, antagonists, and putative inverse agonists.

The synthesis of several novel indole melatonin analogues substituted at the 2-position with acylaminomethyl (8-11), acylaminoethyl (5a-k), or acylaminopropyl (13) side chains is reported. On the basis of a novel in vitro functional assay (specific binding of [35S]GTPgammaS), which can discriminate agonist from partial agonist, antagonist, and inverse agonist ligands, 5a,g, h,j and 13 were shown to be partial agonists, 5d,e and 8-11 competitive antagonists, and 5b,c,k putative inverse agonists. Binding and functional assays were performed on cloned human MT1 receptor. Structure-activity relationship considerations indicate that N-[1-aryl-2-(4-methoxy-1H-indol-2-yl)(C1-C2)alkyl]alkanamides represent a lead structure for this type of ligands.

1-Aminocylopropane-1-carboxylic acid derivatives as ligands at the glycine-binding site of the N-methyl-D-aspartate receptor.

Several 1-aminocyclopropane-1-carboxylic acid derivatives were prepared and tested for activity at the glycine-binding site of the N-methyl-D-aspartate (NMDA) receptor complex. Structural modifications involved the amino group, the carboxylic function or position 2 of the ring. When tested in a [3H]-MK-801 binding assay in the presence of glutamic acid, some of the compounds were able to activate the receptor. Two of them (3e and 6) are selective ligands for the glycine site of the NMDA receptor.

(E)-3-(2-(N-phenylcarbamoyl)vinyl)pyrrole-2-carboxylic acid derivatives. A novel class of glycine site antagonists.

The synthesis and preliminary biological evaluation of novel (E)-3-(2-(N-phenylcarbamoyl)-vinyl)pyrrole-2-carboxylic acids bearing alkyl, acyl, alkoxy, phenyl, and halo substituents at the 4- and 5-positions of the pyrrole ring are reported. These compounds were studied for their in vitro affinity at the strychnine-insensitive glycine-binding site of the N-methyl-D-aspartate (NMDA) receptor complex. In the [3H]glycine binding assay (E)-4,5-dibromo-3-(2-(N-phenylcarbamoyl)vinyl)pyrrole-2-carboxylic acid 6w (pKi = 7.95 +/- 0.01) and the 4-bromo-5-methyl 6j (pKi = 7.24 +/- 0.01) and 4,5-dimethyl 6g (pKi = 6.70 +/- 0.03) analogues were the most active compounds of the series. Qualitative structure-activity analysis points to a negative correlation between bulk of the C-4 and C-5 substituents and affinity which is enhanced by halo-substituents. QSAR analysis by the Hansch descriptors F, R, pi, and MR, on a subset of compounds with pKi > or = 4, indicates that electron-withdrawing groups at C-4 and C-5 enhance the affinity. Bulk and lipophilicity are also relevant for the substituents at these positions. 6g was found to be a full antagonist (alpha = 0; enhancement of the [3H]TCP binding). The in vivo potency of 6g, 6j, and 6w was evaluated by the inhibition of NMDA-induced convulsions in mice by both the i.v. and po routes; 6w was the most active compound (ED50 = 3 x 10(-3) (0.8-10) g/kg, i.v. and 30 x 10(-3) (4.5-61) g/kg, p.o.). The results of this study indicate that the 3,4-disubstitutedpyrrole-2-carboxylate represents a novel template for the design of new glycine antagonists.

Conformationally restrained melatonin analogues: synthesis, binding affinity for the melatonin receptor, evaluation of the biological activity, and molecular modeling study.

The design, synthesis, and biological profile of several indole melatonin analogues with a conformationally restricted C3 amidoethane side chain are presented. Examination of the accessible conformations of the melatonin side chain led us to explore some of its fully or partially restricted analogues, 2-12, the binding affinity values of which were utilized to gain further insight on the melatonin binding site. Two pharmacophoric models have been devised for melatonin and the active compounds by conformational analysis and superimposition performed using the DISCO program. In these models, the melatonin side chain can adopt a gauche/anti conformation out of the indole plane. Another contribution of this study regards the observation of a possible binding point interaction around the C2 position of the indole, as suggested by the remarkably increased binding affinity observed in the C2-substituted analogues 6 and 9 and especially in the more rigid analogue 5. The biological activity and the efficacy of the new compounds were tested by measuring the inhibition of the forskolin-stimulated cAMP accumulation and the GTP gamma S index. Both analyses demonstrated that all of the compounds were full agonists with the exception of 4 and 9, which showed a slight reduction in efficacy and would seem to be partial agonists.

1-Aminocyclopropane-1-carboxylic acid derivatives: a new, general synthesis and NMDA receptor complex binding affinity study.

A new synthesis of 1-aminocyclopropane-1-carboxylic acid and of its (E)- and (Z)-2-substituted analogues (R = CH3;i-Pr;C6H5) has been performed by means of the "diazo-addition" method, starting from N-(diphenylmethylene)-2,3-dehydro-1-amino-1-carboxylate precursors. The (E)- and (Z)-2-phenyl and the (Z)-2-methylcyclopropaneamino acids have been obtained with high diastereospecificity. All the cyclopropaneamino acids prepared were tested for their affinity for some glutamate receptors and resulted inactive, with the exception of compounds (E)-1b and (Z)-1c which showed a shallow displacement of [3H]-glycine binding.

Methyl N-(diphenylmethyl)-D,L-tryptophanates: synthesis and benzodiazepine receptor affinity.

Several Methyl N-(diphenylmethyl)-D,L-tryptophanates were synthetized and the affinity for the central benzodiazepine receptor was measured. Disappointingly, none of the tested compounds showed to be active, even at the high concentration examined.

Structural requirements for inhibitors of poly(ADP-ribose) polymerase.

The purpose of this study was to examine the structure/activity relationships of a series of substituted benzamides as poly(ADP-ribose) polymerase inhibitors. The experimental approach has involved the use of in vitro and in vivo assays in order to gather information either on the intrinsic activity of the benzamides or on the effect of various pharmacodynamic parameters on the activity in vivo. Although some discrepancies between the data obtained in vivo and in vitro were found in this study, results seem to indicate that most powerful inhibitors were characterized by acylation of the -NH2 function in the 3 position or by substitution in this same position with hydroxy or methoxy groups. The best inhibitors were not cytotoxic under these experimental conditions. Computed calculations of molecular electrostatic potential of these molecules were also performed and a good correlation was found between the similarity index and the experimental inhibitory activity.

N-benzhydryl-tryptamines and 1,1-diphenyl-tetrahydro-beta-carbolines: synthesis, X-ray crystal structure and benzodiazepine receptor affinity.

Several N-benzhydryl-tryptamines and 1,1-diphenyl-tetrahydro-beta-carbolines were synthetized and the requisites for their formation were established. Crystallographic and conformational analyses were carried out on selected compounds and the affinity for the central benzodiazepine receptors was measured.

Analogues of benzamide containing a sulfur atom as poly(ADP-ribose) transferase inhibitors.

Structural analogues of benzamide (BA) containing a sulfur atom were tested for their ability to inhibit the enzyme poly(ADP-ribose)transferase (ADPRT) in cultured Chinese Hamster Ovary (CHO) cells. These compounds were benzene sulfonamide (BSA), thiobenzamide (TB) and 3-thiophene carboxamide (TCA) and their activity was compared with that of benzamide in a number of experimental systems. Results have shown that substitution of the carboxamide function with a sulfonamide group produces an almost complete loss of the enzyme inhibiting activity. Also inactive was TB which however was found to display inhibition of the DNA damaging effect of hydrogen peroxide, thus suggesting a hydroxyl radical scavenging effect of TB. TCA, an isostere of BA, produced some inhibition of ADPRT, although its activity was markedly lower than that of the parental drug. Therefore, these results indicate that: 1) ADPRT inhibiting activity is inverse function of dipole moments, hydrogen bonding strength and steric hindrance of the amide functional group and 2) substitution of benzene with thiophene results in a substantial reduction of the enzyme inhibiting activity.

[Synthesis and antimicrobial activity of 3-nitroisoxazole derivatives]. / Sintesi ed attività' antimicrobica in vitro di derivati 3-nitroisossazolici.

Some azomethine type compounds from 3-nitroisoxazole-5-carboxy-aldehyde were synthesized; among these the most active, oxime (III a), shows bacteriostatic activity in vitro against gram--comparable to that of nitrofurantoin.

[Aryloxy- and arylthioalkylamine hypolipidemic agents]. / Arilossi e ariltioalchilamine ipolipidemizzanti.

Aryloxy and arylthioalkylamines related respectively to clofibrate and 2-(3,5-di-t-butyl-4-hydroxyphenylthio)hexanoic acid, a derivative of an active probucol metabolite, were prepared and pharmacologically screened as hypolipidemic substances. Some of them showed interesting antilipemic activity but also, unfortunately, high acute toxicity.

[Theophylline 7-substitutes. III. Arylderivatives]. / Teofilline 7-sostituite parte III - arilderivati.

Some 7-aryltheophyllines were prepared and pharmacologically screened. They showed low toxicity, sedative properties and, in some cases, anticonvulsant activity.