1,3‐Dibenzoylimidazolidine‐2‐thione and 1,3‐dibenzo­yl‐3,4,5,6‐tetra­hydro­pyrimidine‐2(1H)‐thione

The title compounds, 1,3‐dibenzo­ylimidazolidine‐2‐thione, C₁₇H₁₄N₂O₂S, (I), and 1,3‐dibenzo­yl‐3,4,5,6‐tetra­hydro­pyrimidine‐2(1H)‐thione, C₁₈H₁₆N₂O₂S, (II), were obtained from the reactions of imidazolidine‐2‐thione and 1,4,5,6‐tetra­hydro­pyrimidine‐2‐thiol, respectively, with benzoyl chloride. Compounds (I) and (II) contain, respectively, imidazolidinethione [C=S = 1.6509 (14) Å] and ­pyrimidinethione [C=S = 1.6918 (19) Å] moieties bonded to two benzoyl rings. The mol­ecules of (I) exhibit C₂ symmetry, the C=S bond lying along the twofold rotation axis, while the mol­ecules of (II) have mirror symmetry (C_s). The imida­zolidine ring in (I) is essentially planar, while the pyrimidine ring in (II) adopts a boat conformation. Mol­ecules of (I) are linked by weak inter­molecular C—H⋯O inter­actions, while mol­ecules of (II) are held together by van der Waals inter­actions.     

Preparation of perinones via a novel multicomponent synthesis of isoindole scaffold

A convenient procedure for the preparation of isoindole derivatives is described. The method is based on the multicomponent reaction of heterocyclic ketene aminals with dialkyl acetylenedicarboxylates in presence of DMAP. The reaction is very simple from an experimental point of view and allows the creation of a fused isoindole moiety with concomitant formation of benzene and pyrrole ring in a single operation.     

Electrochemistry of Novel Phthalocyanines Bearing 1,2,4 Triazole Groups

The phthalonitrile (3) and triazole substituted metallo phthalocyanines (MPc) (4–7) were prepared. The novel compounds were characterized with spectroscopic data. Electrochemical analyses of metallophthalocyanines (4–7) bearing triazole substituents were performed to investigate redox activity of phthalocyanines (Pcs) ring. While incorporation of Ni²⁺ and Cu²⁺ cations in the Pc core only influenced peak positions of Pc ring processes, Co²⁺ and Cl^1?Fe³⁺ cations of CoPc and FePc gave extra redox couples to the Pc based ones. Releasing the axial Cl^1? anion on Fe³⁺ cation of FePc during the reduction reactions complicated the redox responses. Redox reactions of Co²⁺ and Fe³⁺ metal centers also considerable influenced spectral and color responses of these complexes.     

Positional isomeric effect on the crystallization of chlorine‐substituted N‐phenyl‐2‐phthalimidoethanesulfonamide derivatives

The ortho‐, para‐ and meta‐chloro‐substituted N‐chlorophenyl‐2‐phthalimidoethanesulfonamide derivatives, C₁₆H₁₃ClN₂O₄S, have been structurally characterized by single‐crystal X‐ray crystallography. N‐(2‐Chlorophenyl)‐2‐phthalimidoethanesulfonamide, (I), has orthorhombic (P2₁2₁2₁) symmetry, N‐(4‐chlorophenyl)‐2‐phthalimidoethanesulfonamide, (II), has triclinic (P) symmetry and N‐(3‐chlorophenyl)‐2‐phthalimidoethanesulfonamide, (III), has monoclinic (P2₁/c) symmetry. The molecules of (I)–(III) are regioisomers which have crystallized in different space groups as a result of the differing intra‐ and intermolecular hydrogen‐bond interactions which are present in each structure. Compounds (I) and (II) are stabilized by N—H...O and C—H...O hydrogen bonds, while (III) is stabilized by N—H...O, C—H...O and C—H...Cl hydrogen‐bond interactions. The structure of (II) also displays π–π stacking interactions between the isoindole and benzene rings. All three structures are of interest with respect to their biological activities and have been studied as part of a programme to develop anticonvulsant drugs for the treatment of epilepsy.     

Cosolvent‐promoted electrophilic amination of organozinc reagents

In this study, we aimed to develop a simple and efficient method for the electrophilic amination of organozinc reagents. For this reason, 12 cosolvents were screened in the electrophilic amination of ordinary organozinc reagents. By the use of a cosolvent, an easily applicable and high‐yielding method for the preparation of arylamines by electrophilic amination of arylzinc reagents was developed. Copyright © 2009 John Wiley & Sons, Ltd.     

Highly efficient catalytic system for electrophilic amination of arylzinc reagents

The effect of catalyst on the yield of amine in the amination of three classes of arylzinc reagents with acetone oxime O‐tosylate was investigated. Since they allowed the preparation of arylamines in excellent yields in the presence of a minimum amount of copper (I) or copper (II) compounds, the catalytic systems using copper (I) or copper (II) combined with a P‐, N‐ or S‐donor ligand were revealed to be the best catalysts for the electrophilic amination of arylzinc reagents with acetone oxime O‐tosylate in the presence of DMPU. Copyright © 2009 John Wiley & Sons, Ltd.     

Mobility of the active site bound paraoxon and sarin in zinc-phosphotriesterase by molecular dynamics simulation and quantum chemical calculation.

The kinetic data published on phosphotriesterase (PTE), with various complexed metals, clearly indicates that the P=O and P=S bonds of phosphotriester and thiophosphotriester substrates, respectively, are strongly polarized by one or both of the active site complexed metal ions. However, this observation is not consistent with the three-dimensional X-ray crystal structure of zinc-substituted PTE with active site bound substrate analogue diethyl 4-methylbenzylphosphonate. In this structure, the distance between the phosphoryl oxygen and the nearest zinc is 3.4 A, a distance too large to afford strong polarization. In the present paper, the geometry and mobility of various PTE active site-substrate complexes are examined by performing both molecular dynamics (MD) simulations and quantum mechanical calculations. Two known substrates are considered, paraoxon and sarin, although their turnover rates vary about 100-fold. The results indicate that PTE forms a complex with either substrate in which the phosphoryl oxygen becomes strongly coordinated with the less buried zinc atom. It is shown that the geometry of the active site is changed when the protein is immersed in a water bath and relaxed by MD. The most substantial conformational change is the opening of the gateway in a pocket where the location of the leaving group is expected. The opening is observed for the pure enzyme as well as for the enzyme/substrate complexes and it ranges from 11 to 18 A. It is also shown that the pockets, in which the substrate substituents are localized, exhibit different flexibility and interact with the substrate with coordinated conformational adjustments.     

The natural phenolic compounds and their antioxidant and anticholinesterase potential of herb Leiotulus dasyanthus (K. Koch) Pimenov & Ostr.

Abstract

The presented work reports anticholinesterase and antioxidant activities of extracts, fractions from aerial parts, fruits, flowers, roots and isolated compounds of roots from Leiotulus dasyanthus (bergapten, pimpinellin, umbelliferone, quercetin, rutin and kaempferol). Phenolic contents, antioxidant activities of samples were carried out by Folin-Ciocalteu, DPPH, TBA methods. Anticholinesterase activity was evaluated by Ellman’s method. The highest and lowest total phenolic content were detected in root MeOH extract (88.6?mg GAE g^?1 DW) and aerial part (51.83?mg GAE g^?1 DW), respectively. The highest antioxidant activity among isolated secondary metabolites got coumarins umbelliferone, bergapten and pimpinellin. Pimpinellin (66.55%) and umbelliferone (61.09%) demonstrated strong inhibition towards acetylcholinesterase and butyrylcholinesterase, respectively. Dichloromethane fraction of root demonstrated significant inhibition against AChE (49.66%) and BuChE (92.21%) at 20 µg/mL. Dichloromethane fractions of roots had a notableness antioxidant and anticholinesterase activities. The further studies on roots will be important for development use of this plant for pharmaceutical and food research needs.

     

Synthesis, Characterization, and Electrochemical Properties of a Novel Macrocylic Ligand and its Transition Metal Complexes

 2,3-Dibromo-6,7,13,14,15,16,22,23-octahydro-14,15-bis-(hydroxyimino)-tribenzo [e,k,q][1,4,7,10,13,16]tetraoxadiazacyclohexadecine (LH₄) was prepared by condensation of 1,2-bis-(2′-aminophenoxyethoxy)-4,5-dibromobenzene with cyanogen-di-N-oxide. Mono-, di-, and trinuclear transition metal complexes of this ligand ((LH₃)₂Ni, (LH₃)₂Zn, (LH₃)₂Co, (LH₃)₂Cu, (LH₃)₂Fe, (LH₃)₂(UO₂)₂(OH)₂, (LH)₂Cu₃, (LH)₂Co₃) were synthesized under basic conditions. The electrochemical properties of the mono- and dinuclear complexes were studied by cyclic voltammetry in DMSO solution containing TBAP. The results showed that all redox processes are based on the metal center and the oxime ligands stabilize the Ni(III), Fe(III), Co(III), and Cu(III) species formed during oxidation. The Fe(II) and U(VI)O₂ complexes displayed a different behaviour: a reduction peak with the corresponding anodic signal during the reverse scan was observed. The oxime moiety also stabilizes U(V)O₂ which forms during the reduction process of the uranyl complex. Cu(II) was adsorbed on the electrode surface upon scanning cathodically.