Determination of the absolute configuration of monosaccharides by 1H NMR spectroscopy of their per-O-(S)-2-methylbutyrate derivatives

An empirical method was developed to determine the absolute configuration of monosaccharides, based on high-field 1H NMR spectroscopy of their per- O-(S)-2-methylbutyrate (SMB) derivatives. The SMB derivatives of the D and L forms of a given monosaccharide are diastereomers, allowing them to be distinguished on the basis of differences in their 1H NMR chemical shifts. The reproducibility of these chemical shift differences may allow the absolute configuration of a wide range of monosaccharides to be routinely determined by comparing the spectra of their SMB derivatives to standard spectra in a data base, making it unnecessary to prepare and analyze new standards for each analysis. The derivatization procedure uses inexpensive, easy-to-handle reagents and is virtually complete. Application of the method to three complex glycans provided an unambiguous determination of the absolute configurations of their constituent monosaccharides. The enantiomeric forms of several monosaccharides are distinguishable by high-field 1H NMR spectroscopy of their per-O-(S)-2-methylbutyrate derivatives.