Synthesis of a Spore Surface Pentasaccharide of Bacillus anthracis

An analogue 2 of the pentasaccharide 1 found on the spore surface protein BclA of Bacillus anthracis was synthesized by a (3+2) glycosylation approach. A robust building block for 3‐linked α‐rhamnose is presented. Benzoate groups were used to ensure α‐selectivity for the rhamnose units. A radical‐initiated reduction with tributyltin hydride was shown to be able to convert the NHTCA group into an acetylated amine as well as an azido group into a free amine on one strike. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)