Investigation of structure and motional behavior of 1,6:3,4-dianhydro-2-O-tosyl-β-D-galactopyranose in solution by means of multiple-field NMR spectroscopy

In this paper H-1 NMR, density functional theory gauge invariant atomic orbital (DFT GIAO) calculation of proton shielding NMR parameters and multi-field, carbon-13 relaxation data for 1,6:3,4-dianhydro-2-O-tosyl-beta -D-galactopyranose (1) are reported. From 1H NMR measurements, carried out in three solvents (chloroform, benzene and dimethylosulfoxide), it is apparent that the observed shifting of H-1 resonances, among the other factors, is caused by an aromatic ring current effect related to different orientations of the tosyl group with respect to the sugar ring. DFT GIRO calculations are applied for analyzing the changes of H-1 shielding parameters in relation to geometry of the compound 1. The relaxation of the quaternary carbons of tosyl group which relax via CSA mechanism is used to establish the mode of local motion. In the complementary approach, employing the H-1 chemical shift, dynamic parameters analysis, as well as results from theoretical calculations, the changes of the geometry of 1 in different environments are deduced. (C) 2001 Elsevier Science B.V. All rights reserved.