Palladium(0) catalyzed Suzuki cross-coupling reaction of 2,5-dibromo-3-methylthiophene: selectivity, characterization, DFT studies and their biological evaluations.

Thiophene derivatives have shown versatile pharmacological activities. The Suzuki reaction proved a convenient method for C-C bond formations in organic molecules. In the present research work novel derivatives of 2,5-dibromo-3-methylthiophene (3a-k and 3l-p) has been synthesized, via Suzuki coupling reaction in low to moderate yields. A wide range of functional groups were well tolerated in reaction. Density functional theory investigations on all synthesized derivatives (3a-3p) were performed in order to explore the structural properties. The pharmaceutical potential of synthesized compounds was investigated through various bioassays (antioxidant, antibacterial, antiurease activities). The compounds 3l, 3g, 3j, showed excellent antioxidant activity (86.0, 82.0, 81.3%), respectively by scavenging DPPH. Synthesized compounds showed promising antibacterial activity against tested strains. 3b, 3k, 3a, 3d and 3j showed potential antiurease activity with 67.7, 64.2, 58.8, 54.7 and 52.1% inhibition at 50 µg/ml. Results indicated that synthesized molecules could be a potential source of pharmaceutical agents.

Biotransformation of monoterpenoids and their antimicrobial activities.

Biotransformation is an economically and ecologically viable technology which has been used extensively to modify the structures of many classes of biologically active products. The discovery of novel antimicrobial metabolites from biotransformation is an important alternative to overcome the increasing levels of drug resistance by plant and human pathogens. Monoterpenes, the main constituents of essential oils, are known for their antimicrobial activities. In 2004, Farooq, Atta-Ur-Rahman and Choudhary published a review on fungal transformation of monoterpenes which covers papers published up to 2002. The present review not only updates the previous one but also discusses the antimicrobial activities (antibacterial, antifungal and antiviral) of biotransformed compounds.

Characterisation of hydrazides and hydrazine derivatives as novel aspartic protease inhibitors.

Virtual screening of an in-house virtual library of synthetic compounds using FlexX, followed by enzyme inhibition, identified hydrazide and hydrazine derivatives as novel aspartic protease inhibitors. These compounds inhibited human cathepsin D and Plasmodium falciparum plasmepsin-II with low micromolar concentrations (IC(50) = 1-2.5 microM). Modelling studies with plasmepsin-II predicted binding of ligands at the centre of the extended substrate-binding cleft, where hydrazide/hydrazine parts of the inhibitors acted as the transition state mimic by forming electrostatic interactions with catalytic aspartates.

An expeditious and environmentally friendly synthesis of 3-substituted isocoumarins using microwave irradiation.

A microwave-assisted, environmentally friendly, high-yielding, time-saving synthesis of medicinally important 3-substituted isocoumarins was carried out in a single step by direct condensation of homophthalic acid with aryol and acyl chlorides under solvent-free conditions without any solid support. The synthesised isocoumarins were structurally characterised by microanalysis, 1H NMR, EI, IR and UV.

In vitro leishmanicidal activity of 3-substituted isocoumarins: synthesis and structure activity relationship.

Twenty-five 3-substituted isocoumarins were synthesized using cutting edge microwave-assisted technology in high yields. The syntheses of different isocoumarins were carried out in a single step by the direct condensation of homophthalic acid with aryol and acyl chlorides under the solvent-free conditions without any solid support. The structures of all the synthesized compounds were characterized using different spectroscopic techniques including UV, IR, (1)HNMR and EIMS and purity was confirmed by CHN analysis. All the synthesized compounds were tested for in vitro leishmanicidal activity. Compounds 3a, 3b, 3g, 3l, 3m, 3r, 3t, 3w, 3x, and 3y displayed potential in vitro leishmanicidal activity with IC(50) values in the range of 0.56-84.38 microg/ml, whereas standard inhibitors amphotericine B have IC(50) = 0.24 microg/ml. The compounds 3b, 3g, 3m, 3t, 3w, 3x, and 3y having IC(50) values 27.86, 28.88, 36.49, 34.37, 28.68, 0.89 and 0.56 microg/ml, respectively, were most active among the present series while remaining others were found less active. The compound 3x and 3y can act as potential lead molecules for further development of isocoumarin-based new drugs for the treatment of leishmaniasis.

Structure-activity relationships of tyrosinase inhibitory combinatorial library of 2,5-disubstituted-1,3,4-oxadiazole analogues.

Here the tyrosinase inhibition studies of library of 2,5-disubstituted-1,3,4-oxadiazoles have been reported and their structure-activity relationship (SAR) also have been discussed. The library of the oxadiazoles was synthesized under the microwave irradiation and was structures of these were characterized by different spectral techniques. From this study it could be concluded that for a better inhibition of tyrosinase, electronegative substitution is essential as most probably the active site of the enzyme contain some hydrophobic site and position is also very important for the inhibition purposes due to the conformational space. The electronegativity of the compounds is somewhat proportional to the inhibitory activity. The compound 3e (3'-[5-(4'-bromophenyl)-1,3,4-oxadiazol-2-yl]pyridine) exhibited most potent (IC50 = 2.18 microM) inhibition against the enzyme tyrosinase which is more potent than the standard potent inhibitor L-mimosine (IC50 = 3.68 microM). This molecule can be the best candidate as a lead compound for further development of drug for the treatments of several skin disorders.