A ring closing metathesis approach to the indole alkaloid mitralactonine

An efficient utilisation of RCM leading to a convenient synthesis of a pentacyclic indole alkaloid is described.     

PTSA–catalyzed functionalization of hydroquinones with benzhydryl alcohols in water

An intriguing and operationally simple direct benzylation of hydroquinones with benzhydryl alcohols has been developed using PTSA in water, affording functionalized hydroquinones in good to excellent yields. The advantages of being environmentally benign, metal-free, base-free, easy workup and having a wide substrate scope make it a promising process for the synthesis of symmetrically and unsymmetrically benzylated hydroquinones as well as for industrial applications.     

Biosynthetic Approaches towards the Design of Artificial Hydrogen-Evolution Catalysts

Hydrogen is a clean and sustainable form of fuel that can minimize our heavy dependence on fossil fuels as the primary energy source. The need of finding greener ways to generate H₂ gas has ignited interest in the research community to synthesize catalysts that can produce H₂ by the reduction of H⁺. The natural H₂ producing enzymes hydrogenases have served as an inspiration to produce catalytic metal centers akin to these native enzymes. In this article we describe recent advances in the design of a unique class of artificial hydrogen evolving catalysts that combine the features of the active site metal(s) surrounded by a polypeptide component. The examples of these biosynthetic catalysts discussed here include i) assemblies of synthetic cofactors with native proteins; ii) peptide-appended synthetic complexes; iii) substitution of native cofactors with non-native cofactors; iv) metal substitution from rubredoxin; and v) a reengineered Cu storage protein into a Ni binding protein. Aspects of key design considerations in the construction of these artificial biocatalysts and insights gained into their chemical reactivity are discussed.     

Development and validation of a novel high-performance thin-layer chromatography method for the quantitative estimation of neohesperidin from Citrus aurantium peel extract

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography method was developed for the estimation of neohesperidin from Citrus aurantium peel....     

Hydrolytic degradation of polyisobutylene and poly‐L‐lactide–based multiblock copolymers

The hydrolytic degradation of a series of poly‐L ‐lactide (PLLA)‐polyisobutylene (PIB) multiblock copolymers was studied in phosphate buffer solution (pH = 7.4) at 37 °C. The multiblock copolymers were synthesized by chain extension of PLLA‐b‐PIB‐b‐PLLA triblock copolymers, which were obtained by ring‐opening polymerization of L ‐lactide initiated by hydroxyallyl telechelic PIB. The degradation strongly depended on the PLLA segment length. At constant PIB segment length, the multiblock copolymer with the shortest PLLA segment length (DPn = 10), showed significant weight loss after 8 weeks, whereas weight loss for DPn = 36 was only observed after 24 weeks. The gel‐permeation chromatographic analysis showed a similar decrease in the number‐average molecular weight (M_n) with time further supporting the weight loss data. Dynamic mechanical analysis showed a decrease in ultimate stress and modulus with time. The crystallinity of multiblock copolymers changed significantly with degradation time as indicated from differential scanning calorimetric analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3767–3774, 2010     

Investigate oxoazolidine-2,4-dione based eutectic mixture via DFT calculations and SAR

In this work, DFT calculations for the designed eutectic mixtures (EMs) using oxoazolidine 2,4-dione (OZD) and zinc chloride (ZnCl2) are done. The interaction between the hydrogen bond donor and hydrogen bond acceptor at atomic level to get EMs are studied using DFT calculations. At room temperature, the stability of these various systems have been investigated using thermodynamic values or parameters such as enthalpy, free energy and others. DFT calculations is used to investigate the possibility of forming the systems (EMs). Further, the impact of varying the temperature on each system was also investigated (323K, 348K). Various other thermodynamic parameters are studied like dipole moment, hardness, chemical potential of the systems (individual molecules and EMs) at different temperatures. The results of the calculations showed that O1Z4 and O4Z1 have maximum dipole moment having values 8.1291, 9.8801 respectively, indicating maximum polarizability. Change in free energy for O1Z4 is least and was found to be ?37.2496 kcal/ mol. Further on changing the temperature, the parameters do not show much variation. Additionally, we have analyzed structure activity relationship (SAR) method to understand the physico-chemical properties of designed EMs and predict their regression and correlation to optimized energy. From the calculated values of pOE model, the value of r² is 0.9995 confirms the validity of the equation obtained. The results of this study suggest a link between the structures that have been utilized to describe the intermolecular interaction between the hydrogen bond donor and acceptor, as well as the stability of the EMs.     

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g⁻¹ for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g⁻¹ fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h⁻¹ recorded initial deposits of 5.20 and 10.05 μg g⁻¹ and 0.33 and 0.48 μg g⁻¹ for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.     

Gene Cloning,Expression, and Characterization of Recombinant Aerolysin from <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Aerolysin is a significant virulent toxin protein secreted by Aeromonas hydrophila; it produces deep wound infections and hemorrhagic septicemia. The complete aerolysin gene (1,482 bp) was amplified from A. hydrophila. Furthermore, it was cloned and expressed into Escherichia coli BL21(DE3) codon plus RP cells using 0.5 mM IPTG for induction. The protein size was 54 kDa as estimated by SDS-PAGE, and it was purified by Ni–NTA affinity chromatography. Anti-His antibodies were used to characterize the expressed aerolysin by Western blotting and showed hemolytic activity with fish red blood cells. Aerolysin may be used as immunoassays for earlier control of A. hydrophila and is also compatible for vaccination.     

Crystal structures of 2,6- and 3,5-dichlorobenzoic acids: nonbonded Cl ⋅ ⋅ ⋅ Cl contacts

The crystal structures of 2,6-dichlorobenzoic acid (1) and 3,5-dichlorobenzoic acid (2) were obtained by single-crystal X-ray diffraction. Crystallization of 1 occurred in the centrosymmetric triclinic space group P1 (No. 2) with a = 7.2678(9), b = 9.8543(8), and c = 11.8290(11) Å = 95.000(7), = 104.262(10), and = 102.128(8); and Z = 4. Crystallization of 2 occurred in the monoclinic centrosymmetric space group P2₁/n (No. 14) with a = 3.7812(3), b = 13.996(2), and c = 14.514(2) Å = 95.183(8); and Z = 4. Chlorine substituents of four dimeric molecules of 2 formed square channels, ca. 3.54 Å on a side, which run parallel to the crystallographic a axis. Monomers of 1 and 2 formed centrosymmetric dimers via near-linear hydrogen bonds. Details of the structures and spectroscopic results are presented and discussed.