Circular dichroism spectra of bichromophorically derivatized methyl-d-galactopyranosides, calculable by pairwise additivity, provide a basis for novel microanalysis of oligosaccharides

The spectroscopic basis for a novel alternative to methylation microanalysis for linkage determination is presented. The complex c.d. spectra of "bichromophoric" D-galactopyranoside derivatives, i.e., containing two types of exciton-coupling chromophore, namely, p-bromobenzoate (lambda max 245 nm) and p-methoxycinnamate (lambda max 311 nm), are highly characteristic at nanomolar levels, indicative of the sugar, the substitution pattern, and the D or L configuration. That these spectra are due to a recently demonstrated pairwise additivity is confirmed. Work directed towards an oligosaccharide derivatization-sequence, resulting in the easily identifiable tetrachromophoric monosaccharide residues, is described. Such an analysis can simultaneously accomplish identification of sugar components, linkage pattern, and determination of absolute configuration at the nanomolar level.