Attempted Prediction of the Crystal Structures of Six Monosaccharides

摘要

A method is reported to generate possible crystal struc-vires of the six hexopyranoses where comparison with in X-ray determination is possible. In these molecules, Oternal degrees of freedom are all-important. Using essentially only the information that the space group is P212121 with one molecule in the asymmetric unit, a jystematic search was made for all low-energy crystal jtructures of these substances. The energies were mini-nized with respect to nine lattice and rigid-body parameters and six intramolecular dihedral angles. The number of possible structures within the range 10kcal mol-1 is of the order 1000. In all cases, the experimental jtructure was among them, and in four cases this was either the structure with the lowest energy or only a few enths of a kcal mol-1 higher. However, in the two other cases the relative energy of the experimental structure A'as over 5 kcal mol-1. Such calculations can provide a sensitive test for force fields.