518975-22-9Relevant academic research and scientific papers
A general method for the synthesis of oligosaccharides consisting of α-(1→2)- and α-(1→3)-linked rhamnan backbones and GlcNAc side chains
Zhang, Jianjun,Kong, Fanzuo
, p. 1429 - 1441 (2007/10/03)
A general method has been developed for the synthesis of oligosaccharides consisting of (1→2)- and (1→3)-linked rhamnans with GlcNAc side chains. As examples, highly effective and convergent syntheses of two decasaccharides in the O polysaccharide moiety of the lipopolysaccharide of the phytopathogenic bacterium Pseudomonas syringae pv. ribicola NCPPB 1010 were achieved. The two decasaccharides consist of O polysaccharide repeating units I+II and II+I, respectively. Allyl 3-O-acetyl-4-O-benzoyl-α-L-rhamnopyranoside, allyl 2-O-benzoyl-3-O-chloroacetyl-α-L-rhamnopyranoside, 2,4-di-O-benzoyl-3-O-chloroacetyl-α-L-rhamnopyranosyl trichloroacetimidate, and 3-O-acetyl-2,4-di-O-benzoyl-α-L-rhamnopyranosyl trichloroacetimidate, which were obtained by highly regioselective 3-O-acylations, were used as the key synthons to obtain the required α-(1→2)- and α-(1→3)-linked rhamnoocta saccharide acceptors with 33- and 37-free hydroxyl groups. Therefore, several disaccharides were synthesized, from which tetrasaccharides and hexasaccharides were then synthesized. Coupling of the hexasaccharide donors with the disaccharide acceptors gave the octasaccharide acceptors. Finally, the coupling of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl trichloroacetimidate with the octasaccharide acceptors, followed by deprotection, afforded the two target decasaccharides. A repeating hexasaccharide unit of the cell wall polysaccharide of β-hemolytic Streptococci Group A was also synthesized in a similar way.
Synthesis of β-D-Glcp-(1→2)-[β-D-Ribf-(1→3)-]α-L-Rhap- (1→3)-α-L-Rhap-(1→2)-α-L-Rhap, the repeating unit of the lipopolysaccharide of Acetobacter diazotrophicus PAL 5
Zhang, Jianjun,Kong, Fanzuo
, p. 579 - 589 (2007/10/03)
A pentasaccharide, the major repeating unit of the lipopolysaccharide (LPS) of the nitrogen fixing bacterium Acetobacter diazotrophicus PAL 5 was efficiently synthesized as its allyl glycoside using a regio- and stereoselective strategy. The key acceptor, allyl 3-O-acetyl-4-O-benzoyl-α-L-rhamnopyranoside (3), was prepared by selective 3-O-acetylation of allyl 4-O-benzoyl-α-L-rhamnopyranoside. Condensation of 3 with 2,3,4,6-tetra-O-benzoyl-α-D-glucopyranosyl trichloroacetimidate furnished the disaccharide 5. Deallylation and subsequent trichloroacetimidation of 5 afforded 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl-(1→2)-3-O-acetyl-4-O- benzoyl-α-L-rhamnopyranosyl trichloroacetimidate (10). Selective 3-O-glycosylation of allyl α-L-rhamnopyranoside (1) with 10 followed by benzoylation gave trisaccharide (12), which could be conveniently converted to a donor (14). Condensation of 14 with allyl 3,4-di-O-benzoyl-α-L-rhamnopyranoside (15) gave tetrasaccharide 16. Selective deacetylation of 16 gave the acceptor 17 which was ribosylated to furnish the protected pentasaccharide, and finally deprotection led to the title compound.
