[Conformational analysis of the double pentasaccharide sequence of the "bisected" structure ov N-glycoproteins]

In the conformational analysis of the pentasaccharide alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D- Manp-(1----6)]-beta-D-Manp-(1----4)-D-GlcNAc, which represents the essential core structure within the bisected type of N-glycoproteins, n.m.r. experiments and GESA calculations indicated that a gg conformation is preferred for the (1----6)-glycosidic linkage. This is in contrast to the results obtained for the tetrasaccharide alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D- Manp-(1----4)- D-GlcNAc, which indicated that a gt conformation with the (1----6)-linked alpha-D-mannose group folded back is preferred. The conformations of the remaining glycosidic linkages in the tetra- and penta-saccharide are similar.