A Novel Conversion of 2, 4‐Diaryl‐2, 3‐dihydro‐1 H‐1, 5‐benzodiazepines into 2, 4‐Diaryl‐3 H‐1, 5‐benzodiazepines

A novel conversion of 2, 4‐diaryl‐2, 3‐dihydro‐1 H‐1, 5‐benzodiazepins into 2, 4‐diaryl‐3 H‐1, 5‐benzodiazepines by the reaction with m‐chloroperbenzoic acid (MCPBA) was reported.     

Electrostatic Layer‐by‐Layer Assembly of Polycation and DNA Multilayer Films by Real‐time Surface Plasmon Resonance Technique

The assembly of alternating DNA and positively charged poly‐(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer‐by‐layer adsorption has been studied. Real time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. The results indicate that the uniform multilayer can be obtained on the poly‐(ethylenimine) (PEI) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by real‐time BIAcore technique, and the observed rate constant was calculated using a Langmuir model (k_obs = (1.28 ± 0.08) × 10^?2s^?1).     

Synthesis and Magnetic Studies of Copper (II)‐Manganese (II) Heterobinuclear Complexes with an Oxamido Bridge

Four new copper (II)‐manganese (II) heterobinuclear complexes bridged byN, N'‐bis[2‐(dimethylamino)ethyl)]oxamido dianion (dmoxæ) and end‐capped with 1, 10‐phenanthroline (phen), 5‐methyl‐1, 10‐phenanthroline (Mephen), diaminoethane (en) or 1,3‐di‐aminopropane (pn). respectively, namely, [Cu(dmoxae)MnL₂] (CIO₄)₂ (L=phen, Mephen, en, pn), have been synthesized and characterized by elemental analyses, IR, electronic spectral studies, and molar conductivity measurements. The electronic reflectance spectrum indicates the presence of spin exchange‐coupling interaction between bridged copper(II) and manganese (II) ions. The cryomagnetic measurements (4.2‐300 K) of [Cu(dmoxae)Mn(phen)₂](CIO₄)₂ (1) and [Cu(dmoxae)Mn(Mephen)₂](CIO₄)₂(2) complexes demonstrated an antiferromagnetic interaction between the adjacent manganese(II) and copper (II) ions through the oxamido‐bridge within each molecule. On the basis of spin Hamiltonian, H= ‐ 2JS₁. S₂. the magnetic analysis was carried out for the two complexes and the spin‐coupling constant (J) was evaluated as ?35.9 cm^?1 for 1 and ‐ 32.6 cm^?1 for 2. The influence of methyl substitutions in the amine groups of the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.     

Engineering Chiral Catalysts through Asymmetric Activation and Super High Throughput Screening (SHTS)

A conceptually new strategy for asymmetric catalysis, namely asymmetric activation, in which a chiral activator selectively activates one enantiomer of a racemic chiral catalyst, and a highly efficient screening system for finding the most effective catalysts, namely super high throughput screening (SHTS), by which the reaction can be conducted in parallel and the ee% of the product is allowed to determine within minutes, are summarized in the present account. It is reasonable to believe that SHTS technique combined with asymmetric activation or deactivation principle will provide a very powerful methodology for finding the new catalysts and the best catalyst tuning for asymmetric reactions.     

Reductive Cyclodimerization of α, β‐ Unsaturated Ketones Promoted by AlCl3/Sm System: A Facile Synthesis of 2‐Aroyl‐1,3,4‐triaryl Cyclopentanol Derivatives

Promoted by AlCl₃/Sm bimetallic system, α, β‐unsaturated ketones underwent reductive cyclodimerization to afford cyclopentanol derivatives under mild conditions. The reaction is stereocontrolled and regioselective over the competitive carbon‐carbon double bond reduction.     

Evaluation of a Combined Quantum Chemical Method Used in Calculating O?H Bond Dissociation Enthalpy

O? H bond dissociation enthalpies (BDE) for a variety of substituted phenols were calculated using a combined quantum chemical method. It is found that the calculated O? H BDE correlated well with the recommended values, except for ortho‐tert‐butyl substituted phenols. For the electron‐donating group substituted phenols the calculated O? H BDE are slightly higher than the recommended values, however, for the electron‐withdrawing group substituted phenols the calculated O? H BDE are slightly lower than the recommended values.     

Microwave Induced Synthesis of 3‐Aryl‐6‐(6‐/8‐substituted 4‐chloroquinoline‐3‐yl) ‐ s ‐triazolo [3,4‐b] −1,3,4‐thiadiazoles

The condensation of 4‐amino‐3‐aryl‐5‐mercapto‐1, 2, 4‐triazoles (1a‐f) with 6‐/8‐substituted 1,4‐dihydro‐4‐oxo‐quinoline‐3‐carboxylic adds (2a‐d) in the presence of phosphorus oxychloride on refluxng or under microwave irradiation gave twenty four novel 3‐aryl‐6‐ (6‐/8‐substituted 4‐chloroquinoline‐3‐yl)‐s‐triazolo[3,4‐b]‐1, 3,4‐thiadiazoles (4a‐x), Considerable increase in the reaction rate has been observed with improved yields under microwave irradiation. The structures of the compounds synthesized were determined by elemental analyses, IR, ¹H NMR and MS spectra. Their spectral properties and the reaction mechanism were also discussed. The preliminary biological test showed that some of compounds bad moderate antibacterial activities.     

Synthesis and Photophysical Properties of C60‐carbazole Adducts

Three C₆₀‐carbazole adducts have been synthesized by 1, 3‐dipolar cycloaddition reaction. Intramolecular energy/electron transfer from carbazole to C₆₀ was observed by steady‐state absorption and fluorescence spectra. The fluorescence spectra of these adducts were similar to each other and dependent on the excitation wavelength and solvent.     

Ethylene Oligomerization Catalyzed by MCl2(PPh3)2 Complex‐es/Ethylaluminoxane

The catalytic properties of MCl₂ (PPh₃)₂ (M = Fe, A; Co, B; Ni, C) in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization have been investigated. Treatment of the MCl₂ (PPh₃)₂ complexes with EAO in toluene generated active catalysts in situ that are capable of oligomerizating ethylene to low‐carbon olefins. The catalytic activity and product distribution were affected by reaction condition, such as reaction temperature, the ratios of Al/M and the reaction time. The activity of 1.70 × 10⁵ g oligomers/ (mol Co. h) for the catalytic system of CoCl₂(PPh₃)₂ with EAO at 200°C was observed, with the selectivity of 91.1% to C_4–10 olefins and 70.7% to C_4–10 linear α‐olefins.     

Multicanonical parallel simulations of proteins with continuous potentials

The determination of the three‐dimensional (3D) structure of a protein or peptide is a very important research problem in biological and medical sciences. Anfinsen's experiments (Science 1973, 181, 223) on renaturation of denatured proteins have shown that the native 3D structure of a (small) protein at low (room) temperatures is uniquely determined by its amino acid sequence, which suggests that it might be possible to determine the 3D structure of a protein from its amino acid sequence by pure computations. As a step toward that goal, in this article we present a simple approach for parallelization of multicanonical Monte Carlo simulations of proteins with continuous potentials. Our method is based on the parallel calculation of the protein energy function. The algorithm is tested by simulated annealing and multicanonical simulations of two small peptides, and known results are reproduced accurately. An acceptable degree of parallelization can be achieved in the simulation of Protein L using up to 30 PCs. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1287–1296, 2001