Synthesis of C-8 Deuterated Glycosides of 3-Deoxy-D-manno-oct-2-ulosonic Acid (Kdo) related to Chlamydial Lipolysaccharides

Methyl glycosides of Kdo and a 2 ! 8)-linked Kdo disaccharide were prepared which contain a deuterium label at C-8 of the reducing unit. The label was introduced in fair dias- tereoselectivity upon reduction of an aldehyde group using a chiral borane complex derived from N- benzyloxycarbonyl- S )-proline which produced the 8- S )-deuterated derivative as the major isomer. Further coupling with a Kdo bromide gave the -2 ! 8)-linked disaccharide in good yield. The deprotected disaccharide serves as a model for NMR spectroscopic studies on the side chain con- formation of a carbohydrate epitope from the bacterial pathogen Chlamydia .