• R R Joshi

      Articles written in Journal of Chemical Sciences

    • Organo-lithiation and halogen metal exchange reactions in organic synthesis-an anomolous aromatic substitution via halogen-metal exchange

      N S Narasimhan R R Joshi

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      Synthesis via organo-lithium compounds is reviewed. An anomalous aromatic substitution via halogen-metal exchange is described. Here, the substitution does not occur at the position where the halogen was present; but at an alternate position. A mechanism is advanced, in which the halogen-metal exchange is proposed as being faster than the hydrogen(acidic)-metal exchange.

    • Metallodesferals as a new class of DNA cleavers: Specificity, mechanism and targetting of DNA scission reactions

      R R Joshi K N Ganesh

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      Interaction of metal complexes with nucleic acids is currently attracting wide attention due to their potential utility as drugs, regulators of gene expression and tools for molecular biology. Many metal complexes exhibit nucleolytic activity, the most important examples being Cu(II)-OP, Fe(H)-BLM, Fe(II)-EDTA, metalloporphyrins, Ru and Co complexes of 4,7-diphenyl-l,10-phenanthroline and more recently by Ni(II) complexes. Desferal, a well known siderophore and a highly effective drug in chelation therapy of iron overload diseases, forms a stable octahedral co-ordination Fe(III) complex Eerrioxamine B. We have been interested in the DNA damaging properties of metallodesferals and this paper describes the DNA cleaving ability of metallodesferals, metal-dependent base selectively in DNA scission reactions, mechanistic studies on DNA cleavage by CuDFO and targetting of DNA cutting by covalent MDFO conjugates. This paper reports the synthesis of Cu(II), Co (III) and Ni(II) complexes of a siderophore chelating drug desferal, the studies on cleavage of plasmid DNA, the sequence preference of cleavage reactions, and C1’ as the primary site of hydroxyl radical attack in the reactions. Oligonucleotides covalently linked with this molecular scissor can direct the cleavage of either single or double strand DNA’s, mediated by duplex or triple helix structures respectively. Such targetting of DNA cleavage reactions, mediated by oligonucleotide-Cu(II)/Co(III) desferal conjugates has demonstrated reasonable site specificity and efficiency

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