(1-C-13)ALDITOLS - ELIMINATION OF MAGNETIC EQUIVALENCE IN H-1-NMR AND C-13-NMR SPECTRA OF SYMMETRICAL COMPOUNDS THROUGH (C-13)-SUBSTITUTION

(1-13C)Glycerol, d-(1-13C)arabinitol, d-(1-13C)ribitol, d-(1-13C)xylitol, d-(1-13C)glucitol, d-(1-13C) mannitol, and d-(1-13C)talitol have been prepared by NaBH4 reduction of the corresponding (1-13C)aldoses. A comparison of the 1H- (300 and 620 MHz) and 13C (75 MHz) n.m.r. spectra of natural and (1-13C)-substituted dissymmetric alditols has permitted the unequivocal assignments of their hydroxymethyl proton and carbon signals and the measurement of several 13C1H and 13C13C spin-coupling constants. Similar spectra of (1-13C)-substituted symmetric alditols, however, are more difficult to interpret since they are composed of overlapping 13C-coupled and 13C-noncoupled subspectra. In some cases, 1H difference spectra and 1H-coupled 13C spectra may be used to extract the 13C1H and 13C13C spin couplings from the 13C-coupled component. These couplings have been examined in light of conformational models previously proposed, permitting a preliminary evaluation of standard 3JCH and 3JCC values for specific coupling pathways in these compounds. © 1990.