ABSTRACT
Described is the synthesis of 8-azidooctyl glycoside derivatives of the Escherichia coli serotype O9a O-chain tetrasaccharide repeating unit and the terminal tetrasaccharide motif in this polysaccharide, which contains a methyl group on O-3 of the distal mannopyranose residue. The assembly of these compounds involved the sequential addition of monosaccharide residues from the reducing to the nonreducing end of the molecule using glycosyl trichloroacetimidate donors. Both compounds were initially prepared as p-methoxyphenyl glycosides, which were converted to the corresponding 8-azidooctyl derivatives at a late stage in the synthesis.
Subject(s)
Azides/chemical synthesis , Escherichia coli/chemistry , Methylglycosides/chemical synthesis , O Antigens/chemistry , Oligosaccharides/chemical synthesis , Carbohydrate Sequence , Escherichia coli/immunologyABSTRACT
Described is the synthesis of the trisaccharide alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-beta-D-GlcpNAcO(CH2)8N3, the glycan portion of which corresponds to the 'adaptor-primer' moiety linking the O-chain and core oligosaccharide in the lipopolysaccharide of several Escherichia coli and Klebsiella pneumoniae serotypes. This report represents the first synthesis of this trisaccharide motif, and in the route involved, a key step is a [2+1] coupling of a protected Manp-(1-->3)-alpha-D-Manp glycosyl donor with a GlcpNAc acceptor. The azido group was included in the target to facilitate future preparation of neoglycoconjugates.
Subject(s)
Escherichia coli/chemistry , O Antigens/chemistry , Trisaccharides/chemical synthesis , Carbohydrate Sequence , Klebsiella pneumoniae/chemistry , Molecular Sequence Data , Trisaccharides/chemistryABSTRACT
1H-[1,2,3]-Triazol-1-yl mannosides have been synthesized as inhibitors for the beta-galactoside-binding family of galectin proteins. Easier synthetic access to C1 in mannose, as compared to C3 in galactose, for attachment of affinity-enhancing triazoles rendered a synthetic advantage. The best mannose-derived inhibitor for galectin-9N, 4-benzylaminocarbonyl-1H-[1,2,3]-triazol-1-yl beta-D-mannopyranoside, had a Kd value of 540 microM, which compares favorably with its galactoside counterpart (Kd=670 microM) and with LacNAc (Kd=500 microM).
