Synthesis and conformational and NMR studies of α-d-mannopyranosyl and α-d-mannopyranosyl-(1 → 2)-α-d-mannopyranosyl linked to l-serine and l-threonine

α-d-Mannopyranosyl and α-d-mannopyranosyl-(1 → 2)-α-d-mannopyranosyl linked to l-serine and l-threonine have been synthesised as model substances for the linkage region in certain O-linked glycoproteins. Metropolis Monte Carlo simulations were performed with a modified version of the GESA program, to yield theoretical NOEs and interatomic distances as ensemble-average values, and these were compared with results from steady-state NOE experiments. The NOEs were determined as ensemble-average and as global minimum values. NMR chemical shift differences, obtained for signals of the glycopeptides relative to those of the respective monomers, were interpreted in terms of short inter-residue atomic distances as found within the global minima, and on the basis of averaged distances derived from Monte Carlo simulations.