Title : Diversity to Discovery – A Serendipitous ‘Golden’ Odyssey into Glycochemistry.
Speaker : Professor Srinivas Hotha, Department of Chemistry, IISER Pune.
Date : 13/10/2017, Seminar Hall, First Floor.
Gold and sugar allured mankind for many centuries and continue to impact economics even now. A series of serendipitous observations during 2005-06 by my group culminated into the discovery of a glycosylation protocol by amalgamating the elegancies of the chemistry of gold with that of saccharides. Thus, identified procedure has undergone several modifications over the last decade to make it versatile. The latest protocol of alkynyl carbonate donors from the group has opened a new vista of opportunities for the synthesis of giant oligosaccharides which are otherwise quite challenging to accomplish.
To exemplify, the glycocalyx of Mycobacterium tuberculosis comprising xenobiotic arabinose and galactose in furanosyl form was targeted. Two major structural constituents of the cell wall of M. tuberculosis are identified as Lipoarabinomannan and Arabinogalactan. Combining the bioinspired stereoselective synthesis of 1,2-cis and trans furanosides and the new glycosidation method, the synthesis of a heneicosasaccharide containing 19 Araf residues and 2 Galf residues, and a pentacosasaccharide containing 23 Araf residues and 2 Araf residues was accomplished. The synthesis of highly branched, complex and challenging hencontapentasaccharide of Lipoarabinomannan is currently underway in the group.
The path to the discovery, development of the protocol for glycosidation and its applications will be discussed during the seminar.