Tashfeen Akhtar

In vitro antitumor and antiviral activities of new benzothiazole and 1,3,4-oxadiazole-2-thione derivatives.

In vitro antitumor and antiviral activities of new benzothiazole and 1,3,4-oxadiazole-2-thione derivatives A series of new benzothiazole derivatives 6a-h have been synthesized, in five steps, from substituted phenols via the 1,3,4-oxadiazole-2-thiones 5a-h. The in vitro antitumor activity of the compounds obtained was investigated and the benzothiazol derivatives 6d and 6e showed strong effects on leukaemia cell lines CCRF-CEM (CC50 = 12 ± 2 μmol L-1, 8 ± 1 μmol L-1, respectively). These compounds are leading candidates for further development. The title compounds were tested against representatives of several virus families containing single stranded RNA genomes, either positive-sense (ssRNA+), or negativesense (RNA-), and against double-stranded RNA genomes (dsRNA), as well as some Flaviviridae viruses. In vitro antitumorsko i antivirusno djelovanje novih benzotiazola i 1,3,4-oksadiazol-2-tion derivata U pet reakcijskih koraka sintetizirana je serija novih derivata benzotiazola 6a-h polazeći iz supstituiranih fenola preko 1,3,4-oksadiazol-2-tiona 5a-h. Sintetizirani spojevi ispitani su na antitumorsko djelovanje. Benzotiazol derivati 6d i 6e pokazali su jak učinak na staničnu liniju leukemije CCRF-CEM (CC50 = 12 ± 2, odnosno 8 ± 1 μmol L-1). Ti su spojevi predvodni spojevi za daljnji razvoj. Nadalje, novi su spojevi testirani na djelovanje na nekoliko tipova virusa koji sadrže bilo pozitivni (ssRNA+) bilo negativni (RNA-) jednolančani RNA genom ili dvolančani RNA genom (dsRNA), te na neke Flaviviridae viruse.

Design, synthesis, and urease inhibition studies of some 1,3,4-oxadiazoles and 1,2,4-triazoles derived from mandelic acid

Some new structural type inhibitors of urease, i.e. 2,5-disubstituted-1,3,4-oxadiazoles (4a–e) and 4,5-disubstituted-1,2,4-triazole-3-thiones (5a–e) were synthesized in two steps from mandelic acid hydrazides (2a–e) and aryl isothiocyantes. The hydrazides in turn were synthesized from mandelic acid via esterification. Compounds 4a–e and 5a–e were evaluated against jack bean urease. Compounds 4d, 5b, and 5d were found to be more potent, with IC50 values of 16.1 ± 0.12 µM, 18.9 ± 0.188 µM, and 16.7 ± 0.178 µM, respectively, when compared to the standard (thiourea; IC50 = 21.0 ± 0.011 µM). These compounds may be subjected to further investigations for the development of antiulcer drugs.

Syntheses, urease inhibition, and antimicrobial studies of some chiral 3-substituted-4-amino-5-thioxo-1H,4H-1,2,4-triazoles.

Chiral 3-substituted-4-amino-5-thioxo-1H,4H-1,2,4-triazoles (5a-i) were synthesized. The target molecules were prepared by cyclization of the corresponding dithiocarbazinic acids, obtained from hydrazides, in the presence of hydrazine hydrate. The chiral hydrazides were in turn synthesized form L-amino acids. The structures of all the compounds were confirmed by modern spectroscopic techniques and purity ascertained by elemental analysis. The synthesized compounds 5a-i were evaluated for urease inhibition and found to exhibit varying degrees of urease inhibition activity showing IC(50) values ranging from 22.0 +/- 0.5 to 43.8 +/- 0.3 microM. Compound 5b was found to be the most active, exhibiting IC(50) = 22.0 +/- 0.5 microM comparable to the standard, thiourea (IC(50) = 21.0 +/- 0.1 microM). Triazoles 5a-i were also screened for their antimicrobial properties and promising antibacterial activities were observed against five pathogenic bacteria. However, all the compounds were devoid of any antifungal activity.

Synthesis, Crystal Structure and Anti-HIV Activity of 2- Adamantyl/adamantylmethyl-5-aryl-1,3,4-oxadiazoles

Two series of 2-adamantyl/adamantylmethyl-5-aryl-1,3,4-oxadiazoles (4a-l and 5a-l) were synthesized by cyclodehydration of adamantan-1-carboxylic acid/adamantylacetic acid with various aryl hydrazides (3a-l) in the presence of POCl3. The synthesis was supported by spectroanalytical techniques and verified further by crystal structure determination of compounds 4e and 5k. The synthesized compounds were screened for their inhibitory activity against HIV-1 and HIV-2 in MT-4 cells. Compound 5b exhibited a moderate activity in vitro for the replication of both virus types, suggesting for further structural modification as a new lead in the development of an antiviral agent.

A Facile One‐Pot Synthesis of 2‐Arylamino‐5‐Aryloxylalkyl‐1,3,4‐Oxadiazoles and Their Urease Inhibition Studies

A one‐pot method for the synthesis of structural type urease inhibitors, 2‐amino‐1,3,4‐oxadiazoles, was developed. The structures of the compounds were established using spectroanalytical techniques and unambiguously confirmed by single‐crystal X‐ray analysis of compound 3o. The synthesized compounds were tested against jack beans urease, and most of the compounds (3c, 3g, 3j, 3k, 3n, 3r–3v) were found more active than the standard. The most potent compound (3u) had an IC50 value of 6.03 ± 0.02 μm as compared to the IC50 value of the standard (thiourea; 22.0 ± 1.2 μm). The prominent urease inhibition activity of these compounds may serve as an important finding in the development of less toxic and more potent antiulcer drugs. The compounds were also investigated against four bacterial strains, and some of the compounds (3g and 3r) were found more potent than the standard drug (ciprofloxacin) against all the tested strains. The MIC value for compound 3g was 0.156 μmol/mL against the tested bacterial strains.

Synthesis, QSAR and anti-HIV activity of new 5-benzylthio-1,3,4-oxadiazoles derived from α-amino acids

2-(1-[(4-Chloro/methylphenylsulfonylamino)alkyl]-5-thioxo-4,5-dihydro-1,3,4-oxadiazoles (4a–e) were synthesized, in four steps, via the sulfonyl derivatives of l-amino acids (l-alanine, l-methionine and l-phenylalanine) 1a–e, the esters 2a–e, the hydrazides 3a–e and finally the cyclization to 4a–e. Alkylation of 4a–e with 1.0 mole eq. of substituted benzyl halides furnished S-benzyl derivatives 5a–t, while 1.1 mole eq. yielded major 5a–t and minor amount of 6a–d. Alternatively, treatment of 4a–e with 2.0 mole eq. of substituted benzyl halides furnished 6a–d only. The structures of 5b and 5l were further confirmed by single crystal X-ray analysis. Compounds 5a–t and 6a–d showed no selective inhibition against HIV-1 and HIV-2 replication in MT-4 cells. However, 5f and 5j–5q exhibited some inhibitory activity against both types with EC50 values (>11.50 − >13.00 µg/mL). These results suggest that the structural modifications of these compounds might lead to the development of new antiviral agents. The quantum structure-activity relationship of these novel structural congeners is discussed.

New Aryl-1,3-thiazole-4-carbohydrazides, Their 1,3,4-Oxadiazole-2- thione, 1,2,4-Triazole, Isatin-3-ylidene and Carboxamide Derivatives. Synthesis and Anti-HIV Activity

A series of isatin-3-ylidene (6a-i) and arylthiazolyl-1,3,4-oxadiazole-2-thione derivatives 7a-i derived from arylthiazolyl carbohydrazide analogs 4a-i were synthesized. Analogously, coupling of 4f with various amino acid methyl esters in the presence of HOBt/DCC reagents afforded the carboxamide derivatives 9a-d. The newly synthesized compounds were assayed against HIV-1 and HIV-2 in MT-4 cells. All compounds are inactive, except compounds 9b and 9c which showed inhibition of HIV-1 with EC50 = 2:34 μg mL-1, and 1.12 μg mL-1 with therapeutic indexes (SI) of 9 and <1, respectively. Graphical Abstract New Aryl-1,3-thiazole-4-carbohydrazides, Their 1,3,4-Oxadiazole-2- thione, 1,2,4-Triazole, Isatin-3-ylidene and Carboxamide Derivatives. Synthesis and Anti-HIV Activity

Synthesis, crystal structure, anti-HIV, and antiproliferative activity of new oxadiazole and thiazole analogs

A series of 2-adamantyl-5-arylthiazolyl-1,3,4-oxadiazoles 7a–x together with thiazoles 13 and 14 were synthesized. Compounds 7a–l, 13, and 14 were tested in vitro with the aim of identifying novel lead compounds active against human immunodeficiency virus type-1 and human immunodeficiency virus type-2 activity in MT-4 cells. Title compounds were also tested against representatives of Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Salmonella spp.), various mycobacterial strains (Mycobacterium fortuitum and Mycobacterium smegmatis), yeast (Candida albicans), and mold (Aspergillus fumigatus). None of the compounds showed antiviral or antimicrobial activity, except compounds 13 and 14 exhibited anti-human immunodeficiency virus-1 activity with EC50 values of 1.79 and 2.39 μM with Selectivity index = 18 and 4, respectively. On the other hand, compounds 7a and 7j showed a marked cytotoxicity against the human CD4+ lymphocytes (MT-4). Therefore, 7a and 7j were evaluated for their antiproliferative activity against two solid tumor-derived cell lines, which exhibited IC50 values of 8.1 ± 0.10 µM and 4.8 ± 0.08 µM against Hep-G2 cell lines, respectively.

Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays.

Summary Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated-4-alcohols gave the 4-amino-pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium-catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino-pseudodisaccharide as the major product, along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4–6)Glc and Man(N4–6)Man diglycosides. The amine-linked diglycosides were found to show weak glycosidase inhibitory activity.

5-[1-(3,4-Dichloro-phen-oxy)eth-yl]-1,3,4-oxadiazole-2(3H)-thione hemihydrate.

In the title compound, C10H8Cl2N2O2S·0.5H2O, the atoms in the oxadiazole ring are essentially coplanar (r.m.s. deviation 0.010 Å). The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds involving the water molecule, which is situated on an a twofold rotation axis, and two organic molecules, leading to a thione tautomer in the solid state. The C atom attached to the oxadiazole ring adopts a typical sp3 hybridization. The dihedral angle between the mean plane of the benzene ring of the dichlorophenyl group and the mean plane of the oxadiazole ring is 74.18 (4)°. The crystal structure is stabilized by intermolecular N—H⋯O and O—H⋯S hydrogen bonds.