Publications (26) View all
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Article: Synthesis and biological evaluation of a novel anti-malarial lead
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ABSTRACT: AbstractMalaria is re-emerging in many tropical areas of the world and is often fatal due to drug resistance, leading to about a million deaths each year. Multiple drug resistance has required new efforts in drug discovery and development. Thus, the search for new drugs operating by novel mechanisms of action is receiving increased attention. Herein we report the synthesis and biological evaluation of a novel anti-malarial with micromolar activity against resistant strains of the parasite. Graphical Abstract KeywordsMalaria–Plasmodium–Diamine–ImidazoleMedicinal Chemistry Research 05/2012; 20(4):401-407. · 1.27 Impact Factor -
Article: Monomeric Sn(II) and Ge(II) hydrides supported by a tridentate pincer-based ligand.
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ABSTRACT: Herein we report the syntheses of terminal Sn(II) (3) and Ge(II) (4) hydrides from the corresponding chloride precursors [{2,6-iPr(2)C(6)H(3)NCMe}(2)C(6)H(3)MCl] (M = Sn (1), Ge (2)) using [K{B(sec-Bu)(3)}H] as a hydrogenating agent. Combination of steric shielding and intramolecular N → M interactions resulted in the protection of M(II)-H bonds.Chemical Communications 04/2012; 48(40):4890-2. · 6.17 Impact Factor -
Article: Activation of phosphorus by group 14 elements in low oxidation states.
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ABSTRACT: The activation of phosphorus remains a popular and competitive area of research driven by the dual goals of finding ways to avoid the environmentally questionable P-Cl compounds applied in many industrial processes and the target of catalytic functionalization of P(4). In recent years the activation, degradation, fragmentation, and functionalization of white phosphorus by compounds with heavier main group elements have become a fertile area of research. The isolation of various carbenes and functionalized silylenes has prompted chemists to investigate their reactions with white phosphorus. The most intriguing fact in these reactions is the subtle change in the substituents may afford strikingly different compounds. For example, from the reaction of P(4) with PhC(NtBu)(2)SiCl a cyclic Si(2)P(2) derivative is obtained, whereas the analogous reaction with PhC(NtBu)(2)SiN(SiMe(3))(2) resulted in an acyclic Si(2)P(4) framework. Similar phenomena have also been observed in the carbene mediated P(4) activation. Apart from these, a new entry point into phosphorus chemistry is the gentle activation of P(4) by an alkyne analogue of tin. In this feature article we have covered the activation of phosphorus by compounds with low valent group 14 elements with special concern to the recent developments in this topic.Chemical Communications 02/2012; 48(16):2169-79. · 6.17 Impact Factor -
Article: Interconnected bis-silylenes: a new dimension in organosilicon chemistry.
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ABSTRACT: The past two decades have brought remarkable advances in organosilicon chemistry with the isolation of stable silylenes, persila-allene, and disilynes. The extension of this list gives an impression that it will continue to flourish. The judicous employment of sterically appropriate ligands has enabled the synthesis and isolation of compounds with low-valent silicon. Recently, for example, interconnected bis-silylenes were isolated where the two Si atoms are connected by a σ-bond and each Si atom is possessing a lone pair of electrons. The formal oxidation state of each Si atom in the interconnected bis-silylene is +1, so bis-silylenes can be considered as the valence isomers of disilynes. In this Account, we describe the synthesis of interconnected bis-silylenes and assess their potential as a new building block in organosilicon chemistry. In 2009, we reported the isolation of a bis-silylene ((PhC(NtBu)(2))(2)Si(2)) stabilized by a sterically bulky benz-amidinato ligand with tBu substituents on the nitrogen atoms. Prior to our work, Robinson and co-workers described the synthesis of a N-heterocyclic carbene stabilized bis-silylene. In following years, just two more interconnected bis-silylenes have been reported. Density functional theory calculations to establish the geometric and electronic structures of the reported bis-silylenes have shown that the Wiberg bond index (WBI) for all the reported bis-silylenes is ~1. The synthesis of stable (PhC(NtBu)(2))(2)Si(2) prompted explorations of its reactivity. An important facet of silylene chemistry involves oxidative addition at the Si(II) center with unsaturated substrates, a reaction also available for bis-silylenes. Due to the three reaction sites (two lone pairs of electrons and a labile Si(I)-Si(I) single bond) in the interconnected bis-silylenes, we expect novel product formation. A labile Si-Si bond facilitates the reactions of (PhC(NtBu)(2))(2)Si(2) with diphenyl alkyne or adamantyl phosphaalkyne which afforded 1,4- disilabenzene and 1,3-disilacarbaphosphide (CSi(2)P) derivatives, respectively. The former is a noteworthy addition to the silicon analogues of benzene, and the latter serves as a heavy cyclobutadiene. With white phosphorus, a cyclic Si(2)P(2) derivative, an analogue of cyclobutadiene was obtained. The most predominant structural feature of these heavy cyclobutadienes is the presence of two-coordinate P atoms.Accounts of Chemical Research 01/2012; 45(4):578-87. · 21.64 Impact Factor -
Article: Evaluation of the immunomodulatory properties in mice and in vitro anti-inflammatory activity of cycloartane type saponins from Astragalus species.
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ABSTRACT: Astragalus roots are used to treat leukemia and for their wound healing properties in Southeast Anatolia-Turkey. In vivo studies to investigate the effects of two Astragalus saponins were carried out on the immune response cytokines by using six to eight weeks old male Swiss albino mice. The production of IL-1β, TGF-1β, TNF-α, IL-2, IL-4 and IFN-γ cytokines was determined by ELISA. The spleen and lymph nodes, isolated from the mice subjects, were analyzed to realize induction of the surface antigen productions for IL-2Rα (CD25) and CD69. In addition, their effects on the targets of inflammation such as NF κB, iNOS and NAG-1 were investigated in cell-based assays. The results suggested that AST VII and Mac B had positive effect on Th1 cytokine release (IL-2 and IFN-γ), and suppression on Th2 cytokine production (IL-4). The immunohistochemical results exhibited induction of both IL-Rα (CD25) and CD69 surface receptors justifying the Th1 cytokine release. The compounds did not affect NF-κB or NAG-1 activity but iNOS activity was inhibited by Mac B with an IC(50) of 156 μg/ml. The results show that Ast VII and Mac B create powerful immunoregulatory effects without the stimulation of inflammatory cytokines in mice, and have no significant effect on the inflammatory cellular targets in vitro.Journal of ethnopharmacology 12/2011; 139(2):574-81. · 2.32 Impact Factor
