Das, Suman Kalyan2017-12-112023-10-192017-12-112023-10-192017ROLL No. 11612228https://gyan.iitg.ac.in/handle/123456789/885Supervisor: Subhendu Sekhar BagIn short Chapter 1 is a review on the synthesis of unnatural C-nucleosides. Chapter 2 deals with the cobalt catalyzed conversion of 1'-α-ethynyl sugar to 1'-β-ethynyl sugar followed by the synthesis of C-triazolyl-β-nucleosides cTBDo/Ac and their photophysical study. In Chapter 3, the synthesis of an angularly expanded compact hydrophobic Fused triazolyl phenanthrene unnatural nucleoside FTPhen and its photophysical properties are described. In addition, its DNA duplex stabilization within a trimeric DNA duplex against all the natural nucleobases was explored theoretically. Chapter 4 explains the synthesis of an angularly expanded fused triaozalyl nucleoside FTQuon which retains a donor and an acceptor face to make hydrogen bonds with cytosine and thymine. Theoretical calculation suggested that this angularly expanded fused triazolyl nucleoside can act as a complementary nucleoside against cytosine and thymine. Chapter 5 illustrates FRET event within a chimeric DNA duplex involving triazolyl phenanthrene labelled unnatural nucleoside TPhenBDo as a FRET donor and oxopyrene OxoPyU or perylene PerU labelled natural nucleoside as a FRET acceptor.enCHEMISTRYThesis