Assignment of carbonyl carbon and acetyl methyl proton resonances of acetylated saccharides by the use of two‐dimensional NMR techniques

Abstract

AbstractCarbonyl carbons in peracetylated saccharides are coupled via three‐ and two‐bond couplings with ring protons and acetyl methyl protons, respectively. Using their mean values, the optimum setting for 2D heterocorrelated experiments (Freeman–Morris and COLOC sequences) designed for the assignment of carbonyl carbon and acetyl methyl proton resonances is presented. Selective inversion of the methyl proton resonances in the middle of the refocusing period is introduced. This modification eliminates the effect of 2J(CO,CH3) on the intensity of the carbonyl carbon‐ring proton cross‐peaks, which is essential in the assignment procedure. The carbonyl carbon, acetyl methyl and ring proton resonances can be used for the determination of the primary structure of complex saccharides.