Furanose ring conformation: the application of ab initio molecular orbital calculations to the structure and dynamics of erythrofuranose and threofuranose rings

Abstract

Ab initiao molecular orbital calculations have been conducted on four tetrofuranose anomers, ..cap alpha..- and ..beta..-D-erythrofuranose and ..cap alpha..- and ..beta..-D-threofuranose, to study the effect of ring conformation on molecular parameters (bond lengths, bond angles, bond torsions) and on total energies. Geometric optimizations of envelope and planar conformers were conducted using the STO-3G basis set; single-point calculations were also performed with the 3-21G basis set. Preferred solution conformations deduced from previous NMR studies are in good agreement with those predicted by calculation, indicating that the intrinsic structures of these furanoses dictate their preferred geometries, and that solvation by water (/sup 2/H/sub 2/O) does not appear to be a major conformational determinant. The ..beta..-D-erythro configuration, which is structurally related to the ..beta..-D-ribo configuration found in RNA, was found to have significantly different conformational behavior from the other three configurations.