Report - Synthesis of new antibacterial agents encompassing tosyl, piperidine, propanamide and 1,3,4-oxadiazole functionalities.

A series of propanamide compounds 6a-l was derived by N-substitution reactions, encompassing tosyl, piperidine and 1,3,4-oxadiazole moieties. The intended array of compounds 6a-l was afforded by a series of five steps reaction scheme. 1-Tosylpiperidin-4-carboxylate (1) was synthesized by the reaction of tosyl chloride (a) with ethyl isonipecotate (b) under mild basic conditions. Compound 1 was subjected to nucleophillic substitution by hydrazine to synthesize 1-tosylpiperidin-4-carbohydrazide (2). The compound, 5-(1-tosylpiperidin-4-yl)-1,3,4-oxadiazole-2-thiol (3) was synthesized by intermolecular cyclization of compound 2 by CS2 under strong basic conditions. The target compounds, 6a-l, were finally synthesized from 3 by reacting with different electrophiles, 5a-l, in an aprotic polar solvent with sodium hydride as an activator. The different propanamoyl electrophiles, 5a-l, were synthesized by the reaction of different aromatic and aliphatic amines, 4a-l, with 3-bromopropionyl chloride under mild basic conditions. The structural elucidation was carried out using modern spectroscopic techniques including IR, 1H-NMR and EI-MS. The antibacterial potential of synthesized compounds was assessed against five bacterial strains. Compounds 6a, 6c, 6d, 6e and 6f were found to be potent antibacterial agents.

2-Alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones as potent and selective inhibitors of ectonucleotidases.

A facile method for the modulation of 2-alkoxy side chain of 3-formylchromone enamines has been exploited for the synthesis of a series of 2-alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones. This modulation was achieved by simply changing the alcoholic reaction media from methanol to ethanol, iso-propanol and n-butanol while reacting various 3-formylchromones with aminobenzenesulfonamides. Alcohols are sufficiently nucleophilic and add into the C2-C3 olefinic bond of 3-formylchromones without causing any ring cleavage. The resulting 2-alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones were found to be potent and selective inhibitors of ecto-5'-nucleotidase and alkaline phosphatases (TNAP and IAP). Detailed enzyme kinetics studies revealed competitive inhibition against alkaline phosphatases and un-competitive inhibition against rat and human ecto-5'-nucleotidase. The most active TNAP inhibitor 23 (Ki = 0.078 ± 0.001 µM), exhibited 28 times more selectivity for TNAP over IAP (Ki = 2.18 ± 0.12 µM). Compound 9 was most active IAP inhibitor (Ki = 0.24 ± 0.01 µM), and was 300 times more selective towards IAP than TNAP (Ki = 72.9 ± 1.68 µM). Compound 40 was most active human ecto-5'-nucleotidase inhibitor exhibiting inhibition in low nanomolar range (Ki = 14 nM).

Synthesis and antibacterial screening of S-substituted derivatives of 5-(3,4-methylenedioxyphenyl)-1,3,4-oxadiazol-2-thiol.

The most emerging class among the heterocyclic compounds is 1,3,4-oxadiazoles for their diverse biological activities. In the present research work, piperonylic acid (1) was converted consecutively into corresponding ester (2), hydrazide (3) and 1,3,4-oxadiazole (4) through intermolecular cyclization. The synthesized compound 4 was subjected further to S-alkylation/aralkylation, using alkyl/aralkyl halides (5a-m) and S-substituted-1,3,4-oxadiazole derivatives were synthesized (6a-m). The structure elucidation of the synthesized molecules was processed through (1)H-NMR, IR and mass spectral data. The antibacterial activity showed these molecules moderately good inhibitors of gram-negative and gram-positive bacteria.

Synthesis of some novel enzyme inhibitors and antibacterial agents derived from 5-(1-(4-tosyl)piperidin-4-yl)-1, 3, 4-oxadiazol-2-thiol

ABSTRACT Keeping in mind the pharmacological importance of the 1,3,4-oxadiazole moiety, a series of new S-substituted derivatives, 5a-h, of 5-(1-(4-tosyl)piperidin-4-yl)-1,3,4-oxadiazol-2-thiol (3) were synthesized. The reaction of p-toluenesulfonyl chloride (a) and ethyl isonipecotate (b) produced ethyl 1-(4-tosyl)piperidin-4-carboxylate (1) which was further transformed into 1-(4-tosyl)piperidin-4-carbohydrazide (2) by hydrazine hydrate in methanol. Compound 2 was refluxed with CS2 in the presence of KOH to synthesize 5-(1-(4-tosyl)piperidin-4-yl)-1,3,4-oxadiazol-2-thiol (3). The desired compounds, 5a-h, were synthesized by stirring 3 with aralkyl halides, 4a-h, in DMF using NaH as an activator. The structures of synthesized compounds were elucidated by 1H-NMR, IR and EI-MS spectral studies. These compounds were further evaluated for enzyme inhibitory activity against lipoxygenase and alpha-glucosidase, along with antibacterial activity against Gram-negative and Gram-positive bacteria.

RESUMO Tendo em vista a importância farmacológica da porção 1,3,4-oxadiazol, sintetizou-se uma série de novos derivados S-substituídos, 5a-h, de 5-(1-(4-tosi)piperidin-4-il)-1,3,4-oxadiazol-2-tiol (3). A reação do cloreto de p-toluenossulfonila (a), com isonipecotato de (b) etila forneceu 1-(4-tosil)piperidin-4-carboxilato de metila (1), que foi, em seguida, transformado em 1-(4-tosil)piperidin-4-carbo-hidrazida (2) por reação com hidrato de hidrazina em metanol. O composto 2 foi submetido a refluxo com CS2 na presença de KOH para se obter 5-(1-(4-tosil)piperidin-4-il)-1,3,4-oxadiazol-2-tiol (3). Os compostos desejados, 5a-h, foram obtidos por agitação de 3 com haletos de aralquila, 4a-h, em DMF, na presença de NaH. As estruturas dos compostos sintetizados foram elucidadas através de análise dos espectros de 1H-MNR, IR e EI-MS. Estes compostos foram, ainda, avaliados quanto à inibição das enzimas lipoxigenase e alfa-glucosidase, juntamente com a atividade antibacteriana contra bactérias Gram positivas e Gram negativas.

N-Benzyl-N-(2-meth-oxy-phen-yl)benzene-sulfonamide.

In the title mol-ecule, C(20)H(19)NO(3)S, the dihedral angle between the phenyl rings is 48.93 (18)°, and they make dihedral angles of 38.37 (17) and 86.50 (19)° with the benzene ring. A weak intra-molecular C-H⋯O inter-action might stabilize the mol-ecular conformation. In the crystal, weak π-π stacking inter-actions between the benzene rings [centroid-centroid distance = 3.774 (2) Å] may help to establish the packing.