کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5217483 | 1383297 | 2013 | 14 صفحه PDF | دانلود رایگان |

Shigella flexneri serotypes 6 and 6a are closely related bacteria causing shigellosis in humans. Their O-antigens are {â4)-β-d-GalpA-(1â3)-β-d-GalpNAc-(1â2)-[3Ac/4Ac]-α-l-Rhap-(1â2)-α-l-Rhap-(1â}n acidic polysaccharides ({ABAcCD}n), which only differ in the degree of O-acetylation. A concise synthesis of two disaccharides (BC, BAcC) and four trisaccharides, representing portions and/or analogs of the O-antigens, is described. A protected intermediate compatible with late stage 3C-O-acetylation, and/or galactosyl (A°) to galacturonic acid (A) conversion, was designed and assembled from trichloroacetimidate and thioglycoside donors tuned for high yielding glycosylation and excellent stereocontrol. The galacturonic moiety was efficiently introduced from galactose using a TEMPO/NaOCl/NaClO2-based oxidation protocol optimized for full compatibility with sensitive moieties, such as allyl ethers and acetates. Final Pd/C-mediated deprotection provided the targets, including the propyl glycoside ABAcC, its non O-acetylated counterpart ABC, and the non acidic analogs A°BAcC and A°BC. The BC and ABC oligosaccharides are also portions of the O-antigen from Escherichia coli O147, which causes diarrhea in pigs.
Journal: Tetrahedron - Volume 69, Issue 48, 2 December 2013, Pages 10337-10350