Circular dichroism of 1,3-dioxane-type (2′-naphthyl)methylene acetals of glycosides

The CD spectra are reported for a series of 1,3-dioxane-type 4,6-O-(2′-naphthyl)methylene acetals of carbohydrates with and without interacting aromatic protective groups on the C-1, C-2, and C-3 hydroxy groups. In the absence of interacting chromophores, the signs of the 1B transitions are not sensitive to the configuration of C-4, while the signs of the weak 1La bands are opposite in the galacto and gluco derivatives. The equatorial parallel conformation is found to be the preferred conformation of the 2-naphthyl group in the solid state by X-ray diffraction. The intense 1Ba and 1Bb transitions of the naphthalene chromophore allowed a safe configurational assignment by exciton coupled interaction with the aromatic protective groups in para-methoxyphenyl-β-D-glycosides. The origin of the observed CEs were deduced and the additivity of the interactions was studied. The direction of the hydrogenolytic cleavage of 4,6-O-(2′-naphthyl)methylene acetal of carbohydrates could also be detected by the 1Bb transition of the 2-naphthyl chromophore. Chirality 16:244–250, 2004. © 2004 Wiley-Liss, Inc.