Hamid Latif Siddiqui

Synthesis and spectroscopic studies of new Schiff bases.

Five novel Schiff bases have been prepared from o-formylphenoxyacetic acid and a series of aminothiazoles to form a number of potentially biologically active compounds. The structures of these Schiff bases have been characterized using IR and (1)H-and (13)C-NMR spectroscopy.

Anti-oxidant, anti-fungal and anti-leishmanial activities of novel 3-[4-(1H-imidazol-1-yl) phenyl]prop-2-en-1-ones.

A series of new 3-[4-(1H-imidazol-1-yl) phenyl]prop-2-en-1-ones were synthesized by the condensation of various acetophenones with 4-(1H-imidazol-1-yl) benzaldehyde which was itself prepared by the N-arylation of imidazole using hexadecyltrimethylammonium bromide as catalyst for the first time. All the synthesized compounds were subjected to preliminary evaluation for their anti-leishmanial, anti-oxidant and anti-fungal activities. Few of the synthesized compounds showed significant activities.

Facile One‐Pot Synthesis of 4‐Hydroxy‐2‐methyl‐(2H)‐1,2‐benzothiazine‐3‐sulfonic Acid 1,1‐Dioxide

Abstract We report a convenient synthesis of 4‐hydroxy‐2‐methyl‐(2H)‐1,2‐benzothiazine‐3‐sulfonic acid‐1,1‐dioxide (6a) prepared in a novel one‐pot reaction. The synthesis involves two transformations starting from 2‐methyl‐2H‐1,2‐benzothiazin‐4‐(3H)‐one 1,1‐dioxide (7) with an overall yield better than that from the stepwise process, as well as the alternate procedure starting from saccharin (1). One‐pot synthesis of an important intermediate, saccharin‐N‐methane sulfonic acid (4), is also described.

Antifungal activity of flavonoids isolated from mango (Mangifera indica L.) leaves

Five flavonoids, namely (−)-epicatechin-3-O-β-glucopyranoside (1), 5-hydroxy-3-(4-hydroxylphenyl)pyrano[3,2-g]chromene-4(8H)-one (2), 6-(p-hydroxybenzyl)taxifolin-7-O-β-D-glucoside (tricuspid) (3), quercetin-3-O-α-glucopyranosyl-(1 → 2)-β-D-glucopyranoside (4) and (–)-epicatechin(2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol (5), were isolated from the leaves of mango (Mangifera indica L.). Antifungal activity of these compounds was evaluated against five fungal species, namely Alternaria alternata (Fr.) Keissler, Aspergillus fumigatus Fresenius, Aspergillus niger van Tieghem, Macrophomina phaseolina (Tassi) Goid. and Penicillium citrii. Six concentrations, namely 100, 300, 500, 700, 900 and 1000 ppm of each of the five flavonoids were employed by means of the poisoned medium technique. All concentrations of the five test flavonoids significantly suppressed fungal growth. However, the specificity of different test compounds was evident against different fungal species. In general, antifungal activity of the flavonoids was gradually increased by increasing their concentrations. The highest concentration (of 1000 ppm) of compounds 1–5 reduced the growth of different target fungal species by 63–97%, 56–96%, 76–99%, 76–98% and 82–96%, respectively.

Synthesis, Characterization and Antibacterial Activity of Azomethine Derivatives Derived from 2-Formylphenoxyacetic Acid

A series of eight new azomethine derivatives were synthesized by reacting 2-formylphenoxyacetic acid with aromatic amines. The chemical structures of these compounds were confirmed by means of 1H-NMR, 13C-NMR, MS and elemental analysis. The compounds were assayed by the disc diffusion method for antibacterial against Staphylococcus aureus and Escherichia coli. Among the compounds tested, 2a, 2b, 2e, 2g and 2h exhibited good antibacterial activity, almost equal to that of Ciprofloxacin used as standard.

Anti-HIV-1 and cytotoxicity studies of piperidyl-thienyl chalcones and their 2-pyrazoline derivatives

A series of 12 new pyrazoline derivatives was prepared from piperidyl chalcones, which in turn were synthesized by condensing 4-piperidin-1-ylbenzaldehyde with diverse acetylthiophenes. The target compounds were characterized by spectroscopic techniques (NMR, IR, MS) and elemental analysis. All the compounds were screened for cytotoxic and anti-HIV-1 activities. Compounds 1c, 1g, 1j, 2a, 2c, 2e, 2g, and 2k demonstrated potential anti-HIV activity but were cytotoxic except for 2e and 2k, which displayed no cytotoxicity in primary human cells. Bioassay results show that the type and positions of the substituents seem to be critical for their cytotoxic and anti-HIV-1 activities.

N-(X-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide (with X = 2 and 4).

The structures of N-(2-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide and N-(4-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide, both C16H13ClN2O4S, are stabilized by extensive intramolecular hydrogen bonds. The 4-chloro derivative forms dimeric pairs of molecules lying about inversion centres as a result of intermolecular N-H...O hydrogen bonds, forming 14-membered rings representing an R2(2)(14) motif; the 2-chloro derivative is devoid of any such intermolecular hydrogen bonds. The heterocyclic thiazine rings in both structures adopt half-chair conformations.

Discovery and molecular docking of quinolyl-thienyl chalcones as anti-angiogenic agents targeting VEGFR-2 tyrosine kinase.

Vascular endothelial growth factor Receptor-2 (VEGFR-2) kinase inhibition is one of the well established strategies to promptly tackle tumor growth by suppression of angiogenesis. In the current study, structure-based virtual screening methodology of a series of quinolyl-thienyl chalcones indicated their strong potential as VEGFR-2 kinase inhibitors. In vitro VEGFR-2 kinase inhibitory activity was found to be significant (compound 19, IC(50): 73.41nM). All compounds showed significant inhibition of human umbilical vein endothelial cells (HUVEC) proliferation (compound 19, IC(50): 21.78nM). Molecular interactions of the compounds were studied using molecular docking studies.

Novel quinolyl-thienyl chalcones and their 2-pyrazoline derivatives with diverse substitution pattern as antileishmanial agents against Leishmania major

A series of twenty-two new pyrazoline derivatives was prepared from quinoline-based chalcones which in turn were synthesized by condensing formylquinolines with diverse acetylthiophenes. The titled compounds were characterized by spectroscopic techniques (NMR, IR and MS) and elemental analysis. All the compounds were screened for antileishmanial activities. Compounds 1e, 1f, 2a, 2c, 2d, 2g, 2k, and 4a were found potentially active antileishmanial agents. Bioassay results show that the type and positions of the substituents seem to be critical for their antileishmanial activities.

Synthesis and antioxidant studies of novel N-substituted benzyl/phenyl-2-(3,4-dimethyl-5,5-dioxidopyrazolo[4,3-c][1,2]benzothiazin-2(4H) -yl)acetamides

Two new series of twenty-two N-substituted benzyl/phenyl-2-(3,4-dimethyl-5,5-dioxidopyrazolo[4,3-c][1,2]benzothiazin-2(4H)-yl)acetamides were synthesized by synergism of the dihydropyrazolo[4,3-c][1,2]benzothiazine 5,5-dioxide moiety with side chain of carboxamides. The routes of formation for these products have been discussed. All the compounds were characterized by NMR, mass and elemental analysis. Structures of compounds 6d and 6l have been elucidated by X-ray crystallography. The synthesized compounds were screened to the preliminary evaluation for their anti-oxidant activities and most of the compounds were found to possess moderate to significant radical scavenging activity. Furthermore, these compounds could be useful as a template for future development through modification or derivatization to design more potent biologically active compounds.Graphical Abstract[Two series of novel carboxamides based upon pyrazolobenzothiazine ring system have been synthesized and evaluated for antioxidant activity. Many compounds were found to be good scavengers of superoxide anion radical. Moreover, the compounds may also possess the bioactivities of parent ring system and thus, are useful as template for further development of new bioactive molecules.]