Ashfaq Mahmood Qureshi

Removal of methylene blue from aqueous solution using acid/base treated rice husk as an adsorbent

Abstract An agricultural waste, cheap and easily available rice husk is chemically modified with acid/base and used as an adsorbent for the removal of methylene blue (MB) (one of the industrially important dye) from aqueous media. The adsorption data were evaluated by Freundlich, Langmuir and Dubinin–Radushkevich isotherm models. Langmuir model showed best fit to the data indicating the formation of monolayer. The adsorption capacity (q m) of the chemically modified rice husk was found to be 93.5 mg/g at a temperature of 298 K which is higher than that reported earlier in the literature which suggests that the treated rice husk can be efficiently used for the removal of MB. The adsorption kinetics was investigated by pseudo-first-, pseudo-second-order kinetic and intra-particle diffusion models. The q e value calculated from pseudo-second-order kinetic model is in agreement with the experimental value with higher correlation coefficient (0.9988). The non-linearity of intra-particle diffusion model is an i...

Synthesis, characterization, and urease inhibition of 5-substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-diones

Abstract5-Substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione and its anilines, amino pyridines and hydrazides derivatives were prepared in a good to excellent yields. In the first step 8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione (1) was prepared by reacting 4-methyl-2-aminopyridine, with diethylmalonate. Compounds substituted pyrido[1,2-a]pyrimidine-2,4(3H)-diones (PPMDO) (2)–(17) were prepared by condensing 8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione in the presence of triethylorthoformte (TEF) and dimethylformamide (DMF), with respective amino components viz. 2-aminoacetophenone, 3-aminoacetophenone, 4-aminoacetophenone, 2,4,6-trimethylaniline, 2-fluoroaniline, 3-fluoroaniline, 4-fluoroaniline, 2-aminothiophenol, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-5-nitropyridine, Benzoic hydrazide, 4-nitrobenzoic hydrazide, 4-bromobenzoic hydrazide, 4-chlorobenzoic hydrazide and 4-hydroxybenzoic hydrazide, respectively. The chemical structures of all the compounds were elucidated by IR, 1H-NMR, 13C-NMR and elemental analysis data. The synthesized compounds were screened for their in vitro urease inhibition activity, by the phenol hypochlorite method. These compounds were found to exhibit either no or low to moderate or significant activity. The compounds (9) and (14) showed comparatively much higher activity. However, the compound (9) was found to be the most active one.Graphical abstractOf the synthesized compounds (2)–(17), two compounds (9) and (14) were found to be significantly more potent inhibitors of urease activity than the starting compound (1). The same two compounds also exhibited anti-urease activity comparable to thiourea, a standard urease inhibitor used in this study as a reference.

New barbiturates and thiobarbiturates as potential enzyme inhibitors

Abstract A series of 27 new barbiturates and thiobarbiturates have been synthesized by a convenient multi-component reaction in overall excellent yields (87–96%). All the synthesized compounds were characterized by 1H, 13C NMR, EIMS and elemental analysis (C, H, N and S). Furthermore, all compounds were screened for in vitro antioxidant (DPPH radical scavenging), lipoxygenase, chymotrypsin, α-glucosidase and anti-urease activities. Out of the series, 23 in DPPH, 14 in lipoxygenase, 2 in chymotrypsin have shown appreciable IC50 values.

(±)-4,12,15,18,26-Penta­hydroxy-13,17-dioxahepta­cyclo­[14.10.0.03,14.04,12.06,11.018,26.019,24]hexa­cosa-1,3(14),6(11),7,9,15,19,21,23-nona­ene-5,25-dione monohydrate

The title compound, C24H14O9·H2O, displays a cup-shaped form. The water molecule is disordered over two set of sites with an occupancy ratio of 0.78:0.22. The molecule of the compound has four stereocenters and corresponds to the SSRR/RRSS diastereoisomer. In the molecule, the maximum dihedral angle between the planar benzene rings is 80.40 (4)°. The H atoms of the hydroxy groups are engaged in hydrogen bonding, forming infinite chains parallel to the a axis. These chains are interlinked through water molecules, resulting in the formation of a two-dimensional network parallel to the (001) plane. Futhermore C—H⋯O, C—H⋯π and slipped π–π interactions result in the formation of a three-dimensional network.

Synthesis, biological evaluation and molecular docking studies of Mannich bases derived from 1, 3, 4-oxadiazole- 2-thiones as potential urease inhibitors

Purpose : To design and synthesize a series of new structural motifs of urease inhibitors, 3- [{(substituted phenyl) amino} methyl]-5-(3, 4, 5-trimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones and 3- {[(pyridin-2-yl)amino]methyl}-5-(3,4,5-trimethoxy phenyl)-1,3,4-oxadiazole-2(3H)-thiones from 1, 3, 4- oxadiazole-2-thione. Methods : Targeted Mannich base derivatives were synthesized by the reaction of 1, 3, 4-oxadiazole-2- thione with formaldehyde and respective aromatic amines. These structural motifs were subjected to 1 H–NMR, 13 C–NMR and mass spectrometric analysis. Compound 4, i.e., 1,3,4-oxadiazole-2-thione and its corresponding Mannich bases (5-17) were subjected to in silico screening as urease inhibitors, using crystal structure of urease (Protein Data Bank ID: 5FSE) as a model enzyme. Furthermore, the targeted compounds were evaluated for their in vitro urease inhibition and anti-oxidant activities using thiourea and propyl gallate as standards, respectively. Results : The docking score of targeted compounds predicted that they are promising urease inhibitors. Subsequently, in vitro studies on Jack bean urease supported the results from virtual screening, and found compounds 4, 5, 9,10,12, 13, 14 and 15 very potent urease inhibitors with half-maximal inhibitory concentration (IC 50 ) values in the range of 5.93 ± 0.13 to 9.76 ± 0.11, relative to thiourea (IC 50 = 21.25 ± 0.15). Compounds 4 – 6, and compounds 12 - 17 also exhibited higher antioxidant activities than propyl gallate. Conclusion : In view of their potent urease inhibition and antioxidant activities, these structural motifs have potentials as new candidates for the development of anti-ulcer drugs. Keywords : 1, 3, 4-Oxadiazole-2-thiones, Antioxidant, Molecular docking, Urease inhibition, Anti-ulcer

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

The synthesis of various 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones was realized following a simple three-step process. The protocol utilized the photodecarboxylative addition of readily available carboxylates to N-(bromoalkyl)phthalimides as a versatile and efficient key step. The initially obtained hydroxyphthalimidines were readily converted to the desired N-diaminoalkylated 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones via acid-catalyzed dehydration and subsequent nucleophilic substitution with the corresponding secondary amines. The procedure was successfully applied to the synthesis of known local anesthetics (AL-12, AL-12B and AL-5) in their neutral forms.

4-{2-[(Z)-(5-Methyl-2-fur-yl)methyl-idene-amino]-eth-yl}benzene-sulfonamide.

In the title compound, C14H16N2O3S, the dihedral angle between the phenyl and 5-methylfuran groups is 54.89 (14)° and the C=N bond assumes a trans conformation. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) ring motifs. The dimers are interlinked by N—H⋯N hydrogen bonds, resulting in the formation of infinite chains extending along the b axis. The packing is consolidated by weak C—H⋯π interactions.

(4-Fluoro­phen­yl)[6-(2-fur­yl)-7-nitro-2,3,4,6,7,8-hexa­hydro-1H-pyrido[1,2-a]pyrimidin-9-yl]methanone

In the title compound, C19H18FN3O4, the fused pyridine and pyrimidine rings adopt half-chair conformations. The structure displays intramolecular N—H⋯O and intermolecular N—H⋯F hydrogen bonding.

[5-(2-Fur­yl)-6-nitro-1,2,3,5,6,7-hexa­hydro­imidazo[1,2-a]pyridin-8-yl](phen­yl)methanone

In the title compound, C18H17N3O4, the furyl and phenyl rings are inclined at almost right angles [85.77 (7) and 63.25 (7)°, respectively] to the central imidazo[1,2-a]pyridinyl unit. The structure displays both inter- and intramolecular N—H⋯O hydrogen bonding.