The conformations of the Lewis blood group determinants, sucrose and kanamycin A

The main purpose is to illustrate the potential, in terms of structure and conformational analysis in the general area of carbohydrate chemistry, presented by the new generation of high frequency FT nuclear magnetic resonance spectrometers based in the highly stable magnetic fields generated by superconducting solenoids. In the case of the LEWIS human blood group antigenic determinants, specific interunit deshielding effects on 1H-chemical shifts and specific interunit nuclear OVERHAUSER enhancements of 1H-signals allowed specific assignments of overall conformations for these branched oligosaccharides. Furthermore, these conformations are shown to be well anticipated by way of simple hard-sphere calculations but taking into consideration important contributions by the exo-anomeric effect in the assignment of conformational preferences at the glycosidic bonds. The presence of an intramolecular hydrogen bond between OH-2g and OH-1f for sucrose dissolved in dimethylsulfoxide-d6(DMSO-d6) is demonstrated by examining the spectrum of a solution which has near 50% of the OH groups in the OD form. The 1H-signals in the structural unit Clf-O-H comes from O(C2g)-H comes from DMSO-d6 are shown to be deuterium shifted by 0.005-0.007 ppm when in the forms Clf-O-H comes from O(C2g)-D comes from DMSO-d6 (deshielded) and Clf-O-D comes from O(C2g)-H comes from DMSO-d6 (shielded). These small shifts were readily discerned at 400 MHz. The (1H)(400 MHz) and 13C (100 MHz) spectra of kanamycin A both as the free amine and the sulfate salt are presented to illustrate how modern nuclear magnetic resonance spectroscopy together with interpretations based in conformational analysis may allow the elucidation of the structures (except for the absolute configuration) of such substances. It is demonstrated that the effect on 13C chemical shifts of the protonation of the amino groups can provide useful clues as to their relative dispositions in three-dimensional space.