Expeditious and efficient synthesis of Strecker’s α-aminonitriles catalyzed by sulfated polyborate

A straightforward, mild, efficient, and environmentally benign protocol for a three-component Strecker reaction of aldehydes or ketones, amines, and trimethylsilyl cyanide catalyzed by sulfated polyborate has been described to afford α-aminonitriles under solvent-free reaction conditions. The major advantages of the present method are excellent yields, shorter reaction time, simple experimental procedure, easy workup procedure, recyclability of the catalyst, solvent-free reaction conditions and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.     

Gold-Catalyzed 1,2-Diarylation of Alkenes

Herein, we disclose the gold-catalyzed 1,2-diarylation of alkenes through the interplay of ligand-enabled Au^I/Au^III catalysis with the idiosyncratic π-activation mode of gold complexes. Unlike the classical migratory-insertion-based approach to 1,2-diarylation, the present approach not only circumvents the formation of direct Ar−Ar′ coupling and Heck-type side products but more intriguingly demonstrates reactivity and selectivity complementary to those of previously known metal catalysis (Pd, Ni, or Cu). Detailed investigations to underpin the mechanistic scenario revealed oxidative addition of aryl iodides to an Au^I complex to be the rate-limiting step owing to the non-innocent nature of the aryl alkene.     

Discovering New Classes of <Emphasis Type="Italic">Brugia malayi</Emphasis> Asparaginyl-tRNA Synthetase Inhibitors and Relating Specificity to Conformational Change

SLIDE software, which models the flexibility of protein and ligand side chains while docking, was used to screen several large databases to identify inhibitors of Brugia malayi asparaginyl-tRNA synthetase (AsnRS), a target for anti-parasitic drug design. Seven classes of compounds identified by SLIDE were confirmed as micromolar inhibitors of the enzyme. Analogs of one of these classes of inhibitors, the long side-chain variolins, cannot bind to the adenosyl pocket of the closed conformation of AsnRS due to steric clashes, though the short side-chain variolins identified by SLIDE␣apparently bind isosterically with adenosine. We hypothesized that an open conformation of the motif 2 loop also permits the long side-chain variolins to bind in the adenosine pocket and that their selectivity for Brugia relative to human AsnRS can be explained by differences in the sequence and conformation of this loop. Loop flexibility sampling using Rigidity Optimized Conformational Kinetics (ROCK) confirms this possibility, while scoring of the relative affinities of the different ligands by SLIDE correlates well with the compounds’ ranks in inhibition assays. Combining ROCK and SLIDE provides a promising approach for exploiting conformational flexibility in structure-based screening and design of species selective inhibitors.     

Thermodynamics and the structural aspects of the ternary complexes of Am(III), Cm(III) and Eu(III) with Ox and EDTA + Ox

The stability constants and the associated thermodynamic parameters of formation of the binary and the ternary complexes of Am(3+), Cm(3+) and Eu(3+) were determined by a solvent extraction to measure the variation in the distribution coefficient with temperature (0-60 degrees C) for aqueous solutions of I = 6.60 m (NaClO(4)). The formation of ternary complexes is favored by both the enthalpy (exothermic) and the entropy (endothermic) values. (13) C NMR, TRLFS and EXAFS spectral data was used to study the coordination modes of the ternary complexes. In the formation of the complex M(EDTA)(Ox)(3-), the EDTA retained all its coordination sites with Ox binding via two carboxylates and with one water of hydration remaining attached to the M(3+). In the complex M(EDTA)(Ox)(2)(5-), one carboxylate, either from EDTA or Ox, is not bounded to M(3+) and there were no water of hydration attached to these cations.     

The Young Julian Schwinger. IV. During the Second World War

In this series of articles the early life and work of the young Julian Schwinger are explored. In the present article, Schwinger's work at the MIT Radiation Laboratory during the Second World War is described.     

Surface pressure dependence of phospholipase A2 activity in lipid monolayers is linked to interfacial water activity

The specific activity of pancreatic phospholipase A2 (PLA2) was studied in two disparate systems, one involving phosphatidylcholine monolayer at various surface pressures at the air-water interface and the other involving a solid-state system exposed to various equilibrium relative humidity (ERH). The results were examined in terms of thermodynamic activity of water in the interfacial region (aws*) and in the hydrated solid phase (aw). In both these physically different systems, the specific activity versus aw and aws* profiles of PLA2 were remarkably similar. In both cases, the specific activity exhibited a maximum at aw (or aws*) approximately 0.3. These results suggested that the mechanism of control of PLA2 activity at the lipid-water interface might involve modulation of the hydration state of the enzyme through control of the thermodynamic activity of water in the interfacial region. Extension of these results to biomembranes suggests that one of the functions of lipid bilayer might be the control of local water activity at the lipid-water interface. In biological membranes, localized subtle changes in interfacial water activity may occur as a result of local stretching or compression of the membrane facilitated by conformational changes in membrane-bound receptor proteins.     

Antimony(III) complexes of bifunctional tridentateSchiff bases

Several newSchiff base derivatives of antimony(III) have been synthesized by the reaction of antimony(III) isopropoxide with theSchiff bases having the donor system, O–N–O. The reactions in 1:1 and 2:3 molar ratios [Sb(O-i-C₃H₇)₃: :Schiff base] have yielded Sb(O-i-C₃H₇) (SB) and Sb₂ (SB)₃ type of derivatives (whereSB represents the anion of theSchiff base andSBH₂=o-hydroxyacetophenone-2-hydroxy-1-propylimine, o-hydroxycetophenone-3-hydroxy-1-propylimine, salicylidene-2-hydroxyethylamine, salicylidene-2-hydroxy-1-propylamine and 2-hydroxy-1-naphthylidene-2-hydroxyethylamine) resp. In the resultingSchiff base derivatives, the central antimony atom appears to be tetracoordinated as indicated by their monomeric state determined ebullioscopically. The infrared spectra of the resulting complexes have been recorded and tentative structures indicated. The thermogravimetric analysis of antimony-monoisopropoxysalicylidene-2-hydroxy-1-propylamine has also been carried out.With 1 Figure