Overlapping Anomeric Effects in a Sucrose Analog
by French, A. D.; Schafer, L.; Newton, S. Q.
Previous calculations with the molecular mechanics program MM3 gave unusually high energies (as much as 5.5 kcal/mol) for sucrosyl geometries found in single-crystal diffraction studies of oligosaccharides. Comparable MM3 energies for observed interresidue linkage conformations of disaccharides such as maltose and cellobiose are all within 2.8 kcal/mol. These results suggest that some energies calculated by MM3 for the linkage between anomeric centers of a pyranose ring and a furanose ring are too high. In the present paper, ab initio calculations at the 4-21G level and MM3 were used to study the conformational energies and geometry of a sucrose analogue, tetrahydro-2-[(tetrahydro-2-furanyl)oxy]-2H-pyran. The range of energies of the observed structures was substantially reduced (to 2.4 kcal/mol) with the 4-21G calculations for the analogue despite an increase for the analogue (to 7.5 kcal/mol) based on new MM3 calculations. Besides the improved energy values, the 4-21G calculations also reproduced the observed variations in the endocyclic C-O bond lengths better than did MM3.
- Journal
- Carbohydrate Research
- Volume
- 239
- Year
- 1993
- Start Page
- 51-60
- URL
- https://dx.doi.org/10.1016/0008-6215(93)84202-h
- ISBN/ISSN
- 1873-426X; 0008-6215
- DOI
- 10.1016/0008-6215(93)84202-h