Lipase Ps-C Catalysed Hydrolysis Of Aryl Deesters: A New Route To The Synthesis Of Achiral Half Esters

Pseudomonas cepacia lipase supported on ceramic particles (PS-C) offers a simple alternative route for the synthesis of achiral half esters, with very high yields, easy work up and remarkable substrate selectivity, as it cleaves only phenolic esters having a phenyl group (i.e. C₆H₅-O-CO-C₆H₅).     

FT-IR and FT-Raman study of Nasicon type phosphates, ASnFe(PO4)3 [A=Na2, Ca, Cd

FT-Raman and FT-IR spectra of ASnFe(PO4)3 [A=Na2, Ca, Cd] were recorded and analyzed. The bands were assigned in terms of the vibrational group frequencies of SnO6 octahedral and PO4 tetrahedral. The spectral analysis shows that the symmetry of corner shared octahedral (SnO6) and the tetrahedral (PO4) are lowered from their free ion symmetry state. The presence of Fe3+ ions disrupts the S-N-O-S-N chain in the structure. This causes distortion of SnO6 and PO4 in the structure of all the compounds. Also it is seen that there are two distinct PO4 tetrahedra of different P-O bond lengths. One of these tetrahedra is linearly distorted in all the title compounds. The PO4 frequencies and bond lengths are calculated theoretically and are in agreement with the experimental values. The presence of PO4 polyanion in the structure can reduce the redox energy and hence reduce the metal oxygen covalency strength in the structure.     

FT-IR, FT-Raman and quantum chemical calculations of (E)-N-carbamimidoyl-4-((3,4-dimethoxybenzylidene) amino) benzenesulfonamide

FT-IR and FT-Raman spectra of (E)-N-carbamimidoyl-4-((3,4-dimethoxybenzylidene) amino) benzenesulfonamide were recorded and analyzed. The vibrational wavenumbers were computed using HF/6-31G*, B3PW91/6-31G* and B3LYP/6-31G* basis. The data obtained from vibrational wavenumber calculations are used to assign vibrational bands obtained experimentally. The results indicate that the B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and structural parameters. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non-linear optics. The geometrical parameters of the title compound are in agreement with that of similar derivatives.     

Oxidation of substituted triazines by sulfate radical anion (SO) in aqueous medium: a laser flash photolysis and steady state radiolysis study

Laser flash photolysis has been used to determine the bimolecular rate constants and the spectral nature of the intermediates obtained by the reaction of sulfate radical anion (SO) with 1,3,5‐triazine (T), 2,4,6‐trimethoxy‐1,3,5‐triazine (TMT), 2,4‐dioxohexahydro‐1,3,5‐triazine (DHT), and 6‐chloro N‐ethyl N'‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine (atrazine, AT). The rate constants determined were in the range 4.6 × 10⁷–3 × 10⁹ dm³ mol^?1 s^?1 at pH 6. The transient absorption spectra obtained from the reaction of SO with T, TMT, DHT and AT has an absorption maximum in the region 320–350 nm and was found to undergo second‐order decay. The intermediate species is assigned to N‐yl C(OH) radical of T (TOH^?), carbon centered neutral radical of TMT, an OH‐adduct of AT and an N‐centered radical in the case of DHT. The interpretations on the experimental results obtained from TMT are supported by DFT calculation using Gaussian 03. Steady state radiolysis technique has also been used to investigate the degradation of AT induced by SO. The degradation profile indicated that about 99% of AT has been decomposed after an absorbed gamma‐radiation dose of 7.5 kGy. The degradation yield of AT (expressed as G(‐AT)) was found to be 0.26 µ mol J^?1. The degradation reactions initiated by SO may thus be employed as a potential alternative for ^?OH‐induced degradation of triazines. Copyright © 2007 John Wiley & Sons, Ltd.     

Immobilized Lipase PS‐C Catalyzed Resolution of Racemic Aromas by Transesterification

Pseudomonas cepacia lipase immobilized on ceramic particles (PS‐C) enantioselectively acylate racemic aroma alcohols with vinyl acetate inorganic solvent. It is observed that laevo isomer under goes enzymatic transesterification enantioselectively.     

A Facile Fabrication of Poly-ethionine Film on Glassy Carbon Electrode for Simultaneous and Sensitive Detection of Dopamine and Paracetamol

An electrochemical sensor based on poly-ethionine (Poly-ET) film modified glassy carbon electrode was developed for sensitive and simultaneous sensing of dopamine (DA) and paracetamol (PA). The electropolymerization of ethionine monomer was carried out to modify the electrode. The modified electrode was characterized by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The Poly-ET/GCE exhibited excellent electrocatalysis towards the sensing of DA and PA. Poly-ET/GCE showed a linear increase of current response with increase concentration of DA and PA ranging from 0.1 μM–60 μM and 0.1 μM–180 μM, respectively. The LODs were found to be 7 nM and 18 nM (S/N=3) for DA and PA, respectively. This electrochemical sensor was successfully utilized for the detection of DA and PA in pharmaceutical samples.     

N-heterocyclic carbene catalyzed reaction of enals and 1,2-dicarbonyl compounds: stereoselective synthesis of spiro gamma-butyrolactones

[reaction: see text]. Nucleophilic heterocyclic carbene (NHC) catalyzed annulation of enals and cyclic 1,2-dicarbonyl compounds, opening a route to gamma-spirolactones, has been observed for the first time. The strategy works well with isatins, leading to spiroannulated oxindole derivatives. It is conceivable that the spiroannulation protocol reported herein will be applicable to the synthesis of important natural products that are endowed with a spiro gamma-butyrolactone motif, especially oxindoles and norsesquiterpenoids.     

Theoretical studies on hydroquinone-benzene clusters

High-level ab initio calculations were carried out to evaluate the interaction between the hydroquinone and benzene molecules. The intermolecular interaction energy was calculated using the M?ller-Plesset second-order perturbation theory at the complete basis set limit and also at the coupled cluster theory with single, double, and perturbatively triple excitations. The calculated binding energy is larger than the benzene dimer interaction energy. The T-shaped cluster (T-a) and the parallel conformation (P-a) are calculated to be nearly isoenergetic. Owing to the large energy gain in the attraction by electron correlation, the dispersion interaction is important for the attraction.     

Methyl-2-arylidene hydrazinecarbodithioates: synthesis and biological activity

Methyl-2-arylidene hydrazine-carbodithioate has not been of particular interest to researchers even though its metal complexes are extensively reported on due to their biological activity. This study examined the cytostatic and antiviral activity of twelve methyl-2-arylidene hydrazinecarbodithioates reported by many researchers as intermediates for the synthesis of thiosemicarbazides and the preparation of their metal complexes. Compounds IIc, IIi, and IIl with tridentate ligand features were found to have the lowest IC₅₀ value (6.5 μM, ≈ 1 μM, and 0.8 μM, respectively) against HL60 human promyelocytic leukemia cells. They were also most inhibitory to human embryonic lung (HEL) fibroblast proliferation (5.3 μM, 17 μM, and 2.6 μM). Compound IIc and IIl show antiviral activity against wild-type herpes simplex virus (HSV), varicella zoster virus (VZV), and acyclovirresistant HSV; however, these activities were observed at concentrations at which the compounds also markedly inhibit HL60 and HEL cell proliferation.