Use of the Anomeric Carbon-13 Proton One Bond Scalar Coupling Constant as a Tool for Detecting 1,2-Orthoester Formation in Oligosaccharide Synthesis

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Abstract
The anomeric 1JC,J value has for some time been successfully used for structural elucidation of oligosaccharides. The first recorded spectra on unenriched carbohydrates were published by Bock et al. in 1973 and pointed out that the anomeric 1JC,J value could be used for assignment of the anomeric configuration since pyranoses with an axial H-1 have a 1JC,J value which is approximately 10 Hz lower than the corresponding value in compounds with an equatorial H-1.1–3 Their method recording non decoupled 13C NMR spectra had the disadvantage of being insensitive and thereby time-consuming. Introduction of INEPT4 followed by technical developments, has overcome this disadvantage. Nowadays, with reverse detection techniques, technical skill instead of sensitivity is a limiting factor. In this communication I would like to emphasize that the anomeric 1JC,J value can be used for detecting 1,2-orthoester formation as well as for establishing a- or P-configuration.