Pathways and populations: stereoelectronic insights into the exocyclic torsion of 5-(hydroxymethyl)tetrahydropyran.
High level ab initio computations in vacuum and with the IEFPCM implicit solvent model are carried out on 5-(hydroxymethyl)tetrahydropyran to investigate the effects of water on the exocyclic torsional surface. Rotamer populations evaluated from the omega(C-C-C-O), theta(C-C-C-O) solvent surface agree almost quantitatively with experimental values for the closely related methyl 4-deoxy-alpha-D-xylohexopyranoside. Potentials of mean force obtained from the two surfaces show substantial solvent stabilization of the TG (omega = 180 +/- 60 degrees) rotamer and the barriers at omega= 120 and 240 degrees but solvent destabilization at the cis barrier (omega = 0 degrees). Natural bond orbital analyses indicate that energetics of these effects are largely explained by overstabilization of the vacuum GT (omega= 60 +/- 60 degrees) and GG (omega = 300 +/- 60 degrees) rotamers. Solvent stabilization of theta conformations provides entropic stabilization.
Woodcock
H Lee
HL
Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA. hlwood@nih.gov
Brooks
Bernard R
BR
Pastor
Richard W
RW
D006027:Glycosides / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011714:Pyrans / Q000737:chemistry*; D013237:Stereoisomerism; D013499:Surface Properties; D013816:Thermodynamics; D014618:Vacuum; D014867:Water / Q000737:chemistry
D006027:Glycosides; D011714:Pyrans; D014867:Water