| Zdroj: |
Bülow, A, Meyer, T, Olszewski, T K & Bols, M 2004, ' The C-4 Configuration as a Probe for the Study of Glycosidation Reactions ', Eur. J. Org. Chem., vol. 2004, pp. 323-329 . |
| Popis: |
The difference in the electron-withdrawing powers of axial and equatorial OBn was used as a probe to investigate the glycosidation reaction. The reactivity of perbenzylated glucosyl and galactosyl donors were compared under a range of glycosidation conditions that involved variations in catalyst, solvent, and glycosyl acceptor. Generally, the galactosyl donor had a reactivity four to five times higher than the glucosyl donor, which is in accord with the transition state having positive character. In certain cases, however, particularly when triflate was present, equal reactivity of glucosyl and galactosyl donors were found. The results are explained in terms of changes in the rate-determining steps. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) |
