Characterization of methyl glycosides at the pico- to nano-gram level

We describe a general method that permits characterization of 100-pg to 1-ng quantities of sugars. Thus, oligosaccharides are subjected to methanolysis, followed by per-p-bromobenzoylation or pernaphthoylation, and the methyl glycoside peresters are separated by high-pressure liquid chromatography. The method is also applicable to amino and acetamido sugars. If required, the separated sugar derivatives may be unequivocally identified by the characteristic quasi-M+ peaks of bromobenzoates and extrema of exciton-split circular-dichroism (c.d.) curves. Furthermore, as the c.d. extrema of polybenzoates are predictable from extrema of component dibenzoate units, the c.d. data yield information on the unknown spatial disposition of -OH, -NH2 and -NHAc groups of glycopyranoses. Application of the method is demonstrated with viridopentaose C, a pentasaccharide obtained from the antibiotic sporaviridin.