Synthesis of Structures Related to Antifreeze Glycoproteins

Abstract: In this thesis, 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 thereof. 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.