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Anomeric effect in phosphate moieties of carbohydrates: An Ab initio study
Author(s) -
Kaliannan P.,
Vishveshwara S.,
Rao V. S. R.
Publication year - 1985
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560270209
Subject(s) - anomer , moiety , chemistry , ab initio , anomeric effect , phosphate , crystallography , bond length , ab initio quantum chemistry methods , computational chemistry , stereochemistry , organic chemistry , molecule , crystal structure
Ab initio SCF MO calculations at the STO ‐3G level have been carried out on CH 2 OHOPO 3 − H and CH 2 OHOPO 3 2− , which have been considered as model systems for the Cl‐phosphate moiety of sugars. The results predict higher anomeric energy for the phosphate moiety at Cl atom of pyranosides. Also a trans arrangement of the exocyclic O—P bond is preferred rather than a gauche arrangement, thus exhibiting a reverse exo‐anomeric effect. A complete potential energy map has been constructed for CH 3 OPO 3 − H, a model system for C6‐phosphate moiety. It is seen that the bond angle optimization brings down the relative energies of various conformations. The effect of the phosphate group on the preferred conformation of phosphate containing polysaccharides is also discussed.