• Satish Kumar

      Articles written in Journal of Chemical Sciences

    • Chemistry of selected cyclic P(III) compounds possessing a P-Cl bond

      K C Kumaraswamy Sudha Kumaraswamy Praveen Kommana N Satish Kumar K Senthil Kumar

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      The compounds [CH2(6-t-Bu-4-Me-C6H2O)2]PCl (1), (OCH2CMe2CH2O)-PCl (2), and [ClPN(t-Bu)]2 (3) have been utilized as precursors in the synthesis of (i) new pentacoordinate phosphorus compounds [e.g. CH2(6-t-Bu-4-Me-C6H2O)2 P(NRR′)(O2C6C14), CH2(6-t-Bu-4-Me-C6H2O)2PX[OC(O-i-Pr)N=N(C(O)O-i-Pr)],(ii) cyclic phosphates and their complexes [e.g. imidazolium+CH2(6-t-Bu-4-Me-C6H2O)2PO2-.MeOH], (iii) new cycloaddition products [e.g. CH2(6-t-Bu-4-Me-C6H2O)2PC(CO2Me)C(CO2Me)C(O)N, (iv) macrocyclic compounds [e.g. [(t-BuN)P]2[-OCH2CMe2CH2O-]h2] and (v) phosphonates [e.g. (OCH2CMe2CH2O)P (O)CH2C(CN)=CHC5H4FeC5H5]. The synthetic and structural aspects of these new products are discussed.

    • Unusual products in the reactions of phosphorus(III) compounds with N=N, C≡C or conjugated double-bonded systems

      K C Kumara Swamy E Balaraman M Phani Pavan N N Bhuvan Kumar K Praveen Kumar N Satish Kumar

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      The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction.

    • Employing the fluorescence anisotropy and quenching kinetics of tryptophan to hunt for residual structures in denatured proteins

      Satish Kumar Rajaram Swaminathan

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      Residual structures in denatured proteins have acquired importance in recent years owing to their role as protein-folding initiation sites. Locating these structures in proteins has proved quite formidable, requiring techniques like NMR. Here in this report, we take advantage of the ubiquitous presence of tryptophan residues in residual structures to hunt for their presence using steady-state fluorescence spectroscopy. The surface accessibility and rotational dynamics of tryptophan in putative residual structures among ten different proteins, namely glucagon, melittin, subtilisin carlsberg, myelin basic protein, ribonuclease T1, human serum albumin, barstar mutant, bovine serum albumin, lysozyme and Trp-Met-Asp-Phe-NH2 peptide, was studied using steady state fluorescence quenching and anisotropy, respectively. Five proteins, namely ribonuclease T1, bovine serum albumin, melittin, barstar and hen egg white lysozyme appear likely to possess tryptophan(s) in hydrophobic clusters based on their reduced bimolecular quenching rates and higher steady-state anisotropy in proportion to their chain length. We also show that the fluorescence emission maximum of tryptophan is insensitive to the presence of residual structures.

    • An efficient solvent-free synthesis of 3-methyl-4-nitro-5-styrylisoxazoles using solid nano-titania

      KARTIKEY DHAR DWIVEDI SAMEER REDDY MARRI SATISH KUMAR NANDIGAMA RAJU L CHOWHAN

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      An efficient and solvent-free procedure for the synthesis of 3-methyl-4-nitro-5-styrylisoxazoles using nano-titania as solid support and recyclable catalyst is presented. This method provides clean, simple, solvent-free and useful alternative to synthesize styrylisoxazoles. The use of nano-titania provides excellent yield, leading to an easy separation and reuse of the catalyst up to four times without loss of yield. Also, the green matrices calculation shows low environment impact. The green chemistry matrices atom economy,reaction mass efficiency (RME), process mass intensity and E-factor are also calculated which show that this methodology is green and eco-friendly. The catalytic efficiency of heterogeneous TiO2 NPs was successfully demonstrated by recyclability experiment (up to 4 cycles). The sustainability of the catalyst was tested by performing recyclability experiment up to 4 cycles. Calculated turn over frequency (TOF) for each cycle indicates the protocol as sustainable.

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