Configurational assignment of sugar erythro-1,2-diols from their electronic circular dichroism spectra with dimolybdenum tetraacetate

An extension of the dimolybdenum circular dlichroism methodology for the determination of absolute configuration of erythro-vic-diols is presented. This straightforward, simple, and reliable approach consists of mixing a non-racemic transparent vic-diol with dimolybdenum tetraacetate acting as an auxiliary chromophore. Generally, the application of the helicity rule relating the sign of the O-C-C-O torsional angle with the sign of the Cotton effects arising in the 300-400 nm spectral range allows an unequivocal assignment of the stereostructure of the investigated diols. For erythro vic-diols, however, an additional assumption regarding the preferred conformation of the diol unit in its complexed form had to be made. The molecular modeling calculations provide adequate support to resolve this issue. (C) 2008 Published by Elsevier Ltd.