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

In this paper H-1 NMR, density functional theory gauge invariant atomic orb ital (DFT GIAO) calculation of proton shielding NMR parameters and multi-fi eld, carbon-13 relaxation data for 1,6:3,4-dianhydro-2-O-tosyl-beta -D-gala ctopyranose (1) are reported. From 1H NMR measurements, carried out in thre e solvents (chloroform, benzene and dimethylosulfoxide), it is apparent tha t the observed shifting of H-1 resonances, among the other factors, is caus ed by an aromatic ring current effect related to different orientations of the tosyl group with respect to the sugar ring. DFT GIRO calculations are a pplied for analyzing the changes of H-1 shielding parameters in relation to geometry of the compound 1. The relaxation of the quaternary carbons of to syl group which relax via CSA mechanism is used to establish the mode of lo cal motion. In the complementary approach, employing the H-1 chemical shift , dynamic parameters analysis, as well as results from theoretical calculat ions, the changes of the geometry of 1 in different environments are deduce d. (C) 2001 Elsevier Science B.V. All rights reserved.