Molecular-mechanics calculations for cyclic acetals of pentofuranoses, related pentitols, and C-glycosides

Abstract

Molecular-mechanics calculations are reported for the geometries and energies of 2,3- and 3,5-O-isopropylidene-α- and -β-D-ribo- and -L-lyxo-furanoses, and for the 2,3- and 3,5-O-methylene derivatives of 1,4-anhydro-D-ribitol and -L-lyxitol and the related O-isopropylidene derivatives. Calculations were also performed for model compounds of C-glycosides, where the hydroxyl group of the ribo- and lyxo-furanose derivatives was replaced by a methyl group. The results are discussed in terms of conformational equilibria, constitutional equilibria of 2,3- and 3,5-O-alkylidene derivatives, and configurational equilibria (anomeric and C-4-epimeric). The predictions are generally in good agreement with the available experimental data. © 1980, All rights reserved.