Die bevorzugten Konformationen der in N-Glycoproteinen vorkomrnenden OligosaccharidSequenzen ( [P-D-Gd(l + 4 ) P -~-G l c N A c ( l -+ 2)n-o-Man(l+ 3)] P-D-Gal(i-, 4)P-o-GlcNAc-(1 + 2)a-o-Manfl -+ 6))P-~-Man(l+ 4)- The oligosaccharide sequences4, and P -~-G a l ( l + 4)P-~-GlcNAc(l+ 2)a-~-ManOMe (S), found in N-glycoproteins, were investigated by means of HSEA calculations with the program GESA to reveal the preferred solution conformations of these compounds. Experimental evidence of the calculated conformations was given by ' H and I3C NMR studies like NOE experiments, spin-lattice relaxation-time measurements and observation of special deshielding effects. NMR spectra analysis required application of 2-D-NMR techniques. As a conclusion of the experimantal and theoretical results the common sequences in the saccharides 2, 3, 4, and 5 exhibit very similar conformations. The pentasaccharide 4 takes up a linear conformation whereas 5 shows a bent arrangement of the pyranose rings ("gt conformation") which results in a relatively close contact between the a-D-Man unit and the reducing D-GIcNAc unit. Analogously, both conformations, the linear and the bent one, occur in the octasaccharide 2.

Von den Sacchariden α‐D‐Man(1 → 3)‐β‐D‐Man(1 → 4)‐D=‐GICNAc (1), α‐D‐Man(1 → 6)‐β‐D‐Man(1 → 4)‐D‐GIcNAc(2) und α‐D‐Man(1 → 3)[α‐D‐Man(1 → 6)]‐β‐D‐Man(1 → 4)‐D‐GlcNAc(3), die als Core‐Struktur in N‐Glycoproteinen vorkommen, wurden durch HSEA‐Berechnungen (HSEA: Hard‐Sphere Exo‐Anomeric) mit dem neuen GESA‐Programm (GESA: Geometry of Saccharides) die bevorzugten Konformationen bestimmt. Mit Hilfe von 1H‐NMR‐Experimenten, nämlich NOE‐Experimenten, Spin‐Gitter‐Relaxationszeitmessungen und der Beobachtung selektiver Entschirmungen, ließen sich diese Konformationen in Lösung bestätigen. (1 → 3)‐ und (1 → 4)‐glycosidische Bindungen weisen eine stark bevorzugte Konformation auf. Die weitaus größere Flexibilität der (1 → 6)‐glycosidischen Bindung wird besonders diskutiert. Zur Analyse der Spektren wurden verschiedene 2‐D‐NMR‐Techniken angewandt.

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Building Units of Oligosaccharides, XLVll 'I. -Synthesis of Tri-and Tetrrsaccharide Sequences of N-Glycoproteins Including a P-o-Mannosidic LinkageThe trisaccharides a-

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