Ulrich Burkert

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.