STRUCTURAL ELUCIDATION OF THE CAPSULAR POLYSACCHARIDE EXPRESSED BY ESCHERICHIA-COLI O20-K83-H26 BY HIGH-RESOLUTION NMR-SPECTROSCOPY

The structure of the capsular polysaccharide produced by Escherichia c oli O20:K83:H26 was investigated by one- and two-dimensional H-1 and C -13 NMR spectroscopy, and by glycose and methylation analysis. The cap sular polysaccharide was shown to be comprised of linear pentasacchari de repeating units with the structure: [GRAPHICS] ), 1,4-dideoxy-1,4-i mino-D-arabinitol (5), 1,4-imino-(2-O-beta-D-glucopyranosyl)-D-arabini tol (6), and 1 alpha,2 beta,3 alpha,4 beta-tetrahydroxy-nor-tropane (7 ), designated nortropanoline. The isolation of 2 is the first report o f its natural occurrence. Compounds 3 and 6 are the first naturally oc curring glycosides of 1 and 5, respectively. Natural alkaloidal glycos idase inhibitors are classified into five structural types: namely pol yhydroxylated piperidines, pyrrolidines, pyrrolines, indolizidines, an d pyrrolizidines. Nortropanoline is a novel tropane alkaloid and a new type of polyhydroxylated alkaloid.