Oligosaccharide microanalysis by c.d. spectroscopy. Reference curves for D-mannose derivatives

This study completes the spectroscopic basis for a novel oligosaccharide microanalytical method, wherein a derivatization sequence provides monosaccharide subunits bearing two types of exciton-coupling chromophore groups ("bichromophoric") for circular dichroic spectroscopy, namely 4-bromobenzoate (lambda max 245 nm) and 4-methoxycinnamate (lambda max 311 nm). The 24 possible derivatives of methyl alpha-D-mannopyranoside bearing two chromophore and two acetate groups have been prepared and their c.d. spectra recorded. These spectra have been used to calculate the c.d. curves of the 14 possible tetrachromophic derivatives according to the pairwise additivity rule. The accuracy of these calculations has been demonstrated for six representative derivatives. The c.d. curves obtained here, together with curves of the corresponding D-glucose and D-galactose derivatives, comprise a set of 42 unique and distinctive spectra which can be utilized to identify sugars and their linkage patterns, and thus represent the basis for an alternative to methylation analysis which does not rely upon synthetic standards.