Total Synthesis of the Repeating Units of -Specific Polysaccharide of subsp. UCM B-306 via One-Pot Glycosylation.

Herein we report the first total syntheses of the trisaccharide-repeating units of subsp. UCM B-306 via a one-pot assembly of the core trisaccharide structure. The rare-sugar-containing trisaccharide-repeating units are comprised of d-bacillosamine, 2-amino-2-deoxy-d-galacturonic acid or amide, and d-rhamnose units linked through three consecutive α-linkages. The total syntheses of two repeating units were completed starting from d-mannose via a longest-linear sequence of 27 steps in 5.8% and 4.4% overall yields, respectively.