A general geometrical model for pseudorotation simulation in five-membered rings

Abstract

A geometrical model for simulation of pseudorotation in five-membered rings, based on the assumption hat during pseudorotational changes the bond lengths and position of geometrical centre of the ring remain constant, is presented. The significance of the ‘planar reference conformation’ is discussed and the method of calculation of this conformation from the knowledge of the ring bond lengths is described. The ‘planar reference conformations’ of cyclopentane, tetrahydrofuran, and 1,3-dioxolane molecules calculated in this way are in a fair agreement with the corresponding ab initio results. The geometries of 183 β-D-furanoside fragments are reconstructed in the frame of our model and also those of Kilpatrick et al., Adams et al., and Altona and his co-workers. The results obtained within our model are the closest to the crystallographic ones. A special version of our model, parametrized for the furanose ring, is also presented.