HETEROCYCLIC SYSTEMS CONTAINING BRIDGE HEAD NITROGEN ATOM: REACTION OF 5-MERCAPTO-4H-IMIDAZO[4,5-e]- [2,1,3]BENZOTHIADIAZOLES AND 5,6-DIAMINO[2,1,3]BENZOTHIAZOLE WITH 3-(2-BROMOACETYL)COUMARINS

Condensation of 5-mercapto-4H-imidazo[4,5-e][2,1,3]benzothiadiazole (I) with various 3-(2-bromoacetyl)coumarins, followed by PPA cyclization of the intermediate ketones II, yielded 3-(2,8-dithia 1,3,5b, 9-tetraaza cyclopenta(b)-as-indacen-6-yl)chromen-2-ones III. Reaction of 5,6-diamino[2,1,3]benzothiadiazole with 3-(2-bromoacetyl)- coumarin in anhydrous ethanol containing fused sodium acetate gave the corresponding 2-coumarinyl 3,4-dihydro-1,4-pyrazino[5,6-e][2,1,3]benzothiadiazoles IV.     

Polymerization of Acrylonitrile: Kinetics of the Reaction Initiated by the Mn3+-Cyclohexanol Redox System

The vinyl polymerization of acrylonitrile initiated by the redox system Mn³⁺-cyclohexanol was investigated in aqueous sulfuric acid in the temperature range of 30–45° C. The rate of polymerization R_p and the rate of Mn³⁺ ion disappearance were measured. The effects of certain water-miscible organic solvents and certain anionic, cationic, and nonionic surfactants on the rate of polymerization were investigated. Based on the results obtained, a suitable reaction mechanism involving the formation of a complex between Mn³⁺ and the alcohol, whose decomposition yields the initiating free radical with the polymer chain being terminated by the mutual combination of growing chains is suggested.     

Synthesis of Novel 2-Amino-N-hydroxybenzamide Antimicrobials

New 2-amino-N-hydroxybenzamide derivatives (3a–j) have been synthesized in good to excellent yields from the reaction of isatoic anhydride with different hydroxamic acids. All the compounds of the series were screened against both Gram-positive and Gram-negative bacteria and fungi, and some of them have antibacterial and antifungal activities compared to the standard drugs.     

Spectroscopic and electrochemical study for evaluating DNA interaction activity of 4‐(3‐halophenyl)‐6‐(pyridin‐2‐yl)pyrimidin‐2‐amine based piano stool Cp* Rh (III) and Ir (III) complexes

Six novel organometallic half sandwich complexes [(η5‐C₅Me₅)M(L^1–3)Cl]Cl.2H₂O were synthesized using [{(η⁵‐C₅Me₅)M(μ‐Cl)Cl₂], where M = Ir (III)/Rh (III) and L^1–3 = three pyridyl pyrimidine based ligands; and characterized by NMR, Infra‐red spectroscopy, conductance, elemental and thermal analysis. The complex‐DNA binding mode and/or strength evaluated using absorption titration, electrochemical studies and hydrodynamic measurement proposed intercalative binding mode, which was also confirmed by molecular docking study. Differential pulse voltammetry and cyclic voltammetry studies indicated an alteration in oxidation and reduction potentials of complexes (M⁺⁴/M⁺³) in presence of CT‐DNA. The metal complexes can cleave plasmid DNA as proposed in gel electrophoretic analysis. The LC₅₀ values of complexes evaluated on brine shrimp suggested their potent cytotoxic nature.     

Kinetics and spectral properties of electron and •OH adducts of dimethylpyridines: a pulse radiolysis study

The reactions of e_aq ^-, OH, O^- and SO^- ₄ with 2,4-, 2,6- and 3,5-dimethylpyridines have been investigated in aqueous solution by pulse radiolysis with optical detection. Both e_aq ^- and OH radicals have high reactivity toward these compounds with k = (4-8) × 10⁹ dm³ mol^-1 s^-1. The rates of O^- and SO₄ ^- reactions ((1-3) × 10⁹ dm³ mol^-1 s^-1) were lower compared to the rate observed with the OH radical. The transient absorption spectra obtained in the reaction of e_aq ^- with three isomers exhibited a weak broad band around 340-410 nm. The absorption maxima of the intermediates formed in the OH and SO₄ ^- reactions were centred around 320-330 nm ( = 2450-3500 dm³ mol^-1 cm^-1) with an additional broad peak in the range 460-520 nm which are attributed to the corresponding OH adducts. The spectra in the O^- reaction have absorption maxima between 300 and 320 nm and it reacts both by addition and H-abstraction from the CH₃ group. A reaction mechanism consistent with the observed results is proposed.     

Synthesis of 2‐Oxazolines and 2‐Thiazolines using Lanthanide Amino Alkoxide

New 2‐oxazolines and 2‐thiazolines are prepared from phenacysulfonylacetic acid methyl ester using lanthanide amino alkoxide.     

DNA interaction,free radical scavenging and in‐vitro antibacterial activity of drug‐based copper(II) complexes

The Cu(II) complexes of type [Cu(cpf)(Aⁿ)Cl] (Aⁿ = terpyridines, cpf = ciprofloxacin) were synthesized and characterized using IR, mass and reflectance spectra. The free ligands and their complexes were evaluated for their in‐vitro antimicrobial activity against a panel of Gram‐positive and Gram‐negative bacteria. The complexes exhibit better or equal inhibition in comparison to free fluoroquinolones. Binding interactions of the complexes with calf thymus (CT DNA) were investigated by absorption titration, viscosity studies and DNA melting temperature experiment. The cleavage reaction on pUC19 DNA was monitored by agarose gel electrophoresis. The lower concentration of the complexes was catalysed the dismutation of superoxide radical at biological pH, which indicates that the complexes can act as a possible model for superoxide dismutase. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of modified uracil and cytosine nucleobases using a microwave-assisted method

Modified nucleobases and nucleic acids have found many biological and pharmaceutical applications. Here we report a microwave-directed synthesis of a variety of modified uracil and cytosine nucleobases with high yields under solvent-free conditions. The reaction yields were further improved by addition of Lewis acid. The crystal structures of 5-isopropyl-6-methyluracil and 6-phenyluracil were also determined.     

New cholinesterase inhibiting steroidal alkaloids from the leaves of Sarcococca coriacea of Nepalese origin

From the leaves of Sarcococca coriacea two new steroidal alkaloids, epoxynepapakistamine-A [(20S)-20-(N-methylamino)-3beta-(tigloylamino)-5alpha-pregna-16alpha,17alpha-epoxy-2beta,4beta-di-O-acetate] (1), and epoxysarcovagenine-D [(20S)-20-(N-methylamino)-3beta-(tigloylamino)-5alpha-pregna-2-en-16alpha,17alpha-epoxy-4-one] (2), and two known compounds funtumafrine C [(20S)-20-(N,N-dimethylamino)-5alpha-pregna-3-one] (3) and N-methylfuntumine (4) were isolated. Their structures were elucidated on the basis of their spectral properties. The compounds 1, 3 and 4 were found to have cholinesterase inhibitory activity when tested for the inhibition of electric eel acetylcholinesterase and horse serum butyrylcholinesterase. They inhibited both enzymes in a concentration dependent fashion.