Determination of Long Range Proton Carbon Coupling Constants by Modified Semi-Selective Two-Dimensional Inept: An Application in Stereochemical Analysis of Saccharides

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Abstract
Long-range proton-carbon coupling constants are useful in the assignment of 13C NMR spectra and in stereochemical analysis. The measurement of vicinal coupling constants, 3JC-H, and their interpretation based on appropriate Karplus-type relationships (e.g. for 3JH-C-C-C or 3JH-C-O-C)1–3 provide valuable information in conformational studies of carbohydrates. Nevertheless, the use of 3JC-H in carbohydrate studies is rather rare because their measurement is time consuming and analysis of 1H-coupled 13C NMR spectra is complicated. However, 2D NMR methods 4–6 that allow precise measurement of long-range couplings in a reasonable time have become available recently.