In this thesis, the syntheses of oligosaccharides for interaction studies with various lectins are described. The first section reports the syntheses of tetra, tri- and disaccharides corresponding to truncated versions of the glucosylated arm of Glc1Man9(GlcNAc)2, found in the biosynthesis of N-glycans. The thermodynamic parameters of their interaction with calreticulin, a lectin assisting and promoting the correct folding of newly synthesised glycoproteins, were established by isothermal titration calorimetry. In the second section, a new synthetic pathway leading to the same tetra- and trisaccharides is discussed. Adoption of a convergent strategy and of a different protecting group pattern resulted in significantly increased yields of the target structures. The third section describes the syntheses of a number of monodeoxy-trisaccharides related to the above trisaccharide Glc-α-(1→3)-Man-α-(1→2)-Man-α-OMe. Differentsynthetic approaches were explored and the choice of early introduction of the deoxy functionality proved the most beneficial. In the last section, the synthesis of spacer-linked LacNAc dimers as substrates for the lectins galectin-1 and -3 is presented. This synthesis was realized by glycosidation of a number diols with peracetylated LacNAc-oxazoline. Pyridinium triflate was tested as a new promoter, affording the target dimers in high yields. This promoter in combination with microwave irradiation gave even higher yields and also shortened the reaction times.
Part of urn:nbn:se:su:diva-459
The title compound as its methyl glycoside was efficiently synthesized using a block synthesis approach. Halide-assisted glycosidations between 6-O-acetyl-2,3,4-tri-O-benzyl-α-d-glucopyranosyl iodide and ethyl 2-O-acetyl-4,6-di-O-benzyl-1-thio-α-d-mannopyranoside using triphenylphosphine oxide as promoter yielded, with complete α-selectivity, a disaccharide building block in high yield. The perbenzylated derivative of this proved to be an excellent donor affording 88% of the protected target tetrasaccharide in an NIS/AgOTf-promoted coupling to a known methyl dimannoside acceptor. Deprotection through catalytic hydrogenolysis then gave the target compound in 47% overall yield.