Synthesis of MTX-Capped Octasacchride & Metal-Free Activation of Carbonate Donor

Abstract

Title: Synthesis of MTX-Capped Octasaccharide & Metal-Free Activation of Carbonate Donor Kingdom of life on the earth contains four types of macromolecules: proteins, lipids, nucleic acid, and carbohydrates. Carbohydrate based polymers are called glycans. However, when it is conjugated to any aglycone residue is called glycoconjugate. Glycans and their glycoconjugates are present in every cell of the kingdom of life and mammals, are involved in a myriad of biological functions, these functions are broadly categorized into three categories mainly: (i) structural and modulatory functions, (ii) specific recognition by other molecules, and (iii) molecular mimicry of host glycans. However, extraction of homogenous glycans and glycoconjugate from nature is a daunting task. Hence, chemical glycosylation is one of the best alternate approaches to obtain these glycans and glycoconjugates. In this regard, our laboratory has developed an alkyne carbonate-based donor which was activated by gold and silver salt (B. Mishra, M. Neralkar, S. Hotha, Angew. Chem. Int. Ed. 2016, 55, 7786.), which was stable and high yielding glycosylation method. In this thesis, I have explored alkyne carbonate-based donor for the chemical synthesis of methylthioxylose (MTX) octasaccharide capping motif of lipoarabinomannan (LAM) present in Mycobacterium tuberculosis exploiting [2+(4+2)] coupling strategy. Moreover, metal-free activation of alkyne carbonate donor and its utility in the synthesis of O-glycoside, nucleosides, and synthesis of pentasaccharide Repeating Unit of Klebsiella Pneumoniae (O-3-Antigen) is discussed.