A project report on design, synthesis and nmr studies of structures related to antifreeze glycoproteins

Antifreeze glycoproteins are essential for the surviving of many marine teleost fishes in polar and subpolar seawaters, where the temperature consistently are below the freezing point of physiological solutions. In this work, synthesis of structures related to antifreeze glycoproteins (AFGPs) are presented. Synthetic routes to a protected carbohydrate derivative, 2,3,4,6-tetra-O-benzyl- β – galactopyranosyl - (1→3) – 2 – deoxy – 2 – azido - 4, 6 – di – O – benzyl – β – D -thio-1-galactopyranoside, and a tBu-Ala-Thr-Ala-Fmoc tripeptide, are described. These compounds are meant to be used in the assembly of AFGPs and analogues. A Gal-GlcN disaccharide was synthesized via glycosylation between the donor, bromo-2-O-benzoyl-3,4,6-tri-O-benzyl-α-Dgalactopyranoside, and acceptor, ethyl 4,6-O-benzylidene-2-deoxy-2-N-phthalimido-β-D-1- thio-glucopyranoside, using silver triflate activation. Subsequent epimerization to a Gal-GalN disaccharide was achieved using Moffatt oxidation followed by L-selectride reduction. The tripeptide was synthesized in a short and convenient manner using solid phase peptide synthesis with immobilized Fmoc-Ala on Wang resins as starting point.