A method for determination of the absolute configuration of chiral glycerol residues in natural products using TEMPO oxidation and characterization of the glyceric acids formed.

A method has been developed for determination of the absolute configuration of glycerol residues in natural products. It is required that the glycerol moiety contain a primary nonsubstituted hydroxymethyl group or that such a group can be obtained by modification without racemization. The method employs TEMPO oxidation of the primary hydroxyl group, hydrolysis, butanolysis with chiral 2-butanol, and acetylation. The acetylated (+)-2-butyl esters of the glyceric acid formed by oxidation are analyzed by gas-liquid chromatography. The esterification can also be performed with other chiral alcohols, e.g., (-)-2-octanol. The method is general and applicable to both primary and secondary substituted glycerols. It has recently been used for determination of the chiral glycerol-1-phosphate residue of the Escherichia coli O28 O-antigen, and now we report the absolute configurations of the glycerol moieties in Streptococcus pneumoniae type 18A and Streptococcus agalactaie type III. All studied glycerol residues were found to have the D-configuration.