Synthesis of a selectively protected trisaccharide building block that is part of xylose-containing carbohydrate chains from N-glycoproteins
作者:János Kerékgyártó、Jos G.M. van der Ven、Johannis P. Kamerling、András Lipták、Johannes F.G. Vliegenthart
DOI:10.1016/0008-6215(93)87009-h
日期:1993.1
The synthesis is reported of ethyl 4-O-[3-O-allyl-4,6-O-isopropylidene-2-O-(2,3,4-tri-O-acetyl-beta-D- xylopyranosyl)-beta-D-mannopyranosyl]-3,6-di-O-benzyl-2-deoxy-2-phthalim ido-1 - thio-beta-D-glucopyranoside (16), a key intermediate in the synthesis of xylose-containingcarbohydratechainsfromN-glycoproteins. Condensation of ethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-beta-D- glucopyranoside
Comparative evaluation of the manno/gluco ratios obtained in the conventional reductions of beta -D-glucoside-2-uloses (1-4, 13 and 14) reveals the influence of the substitution pattern: the presence of a 4,6-O-acetal function results in lower stereoselectivity in the monosaccharide-uloside cases and low stereoselectivity in the disaccharide-uloside cases, while the absence of a 4,6-O-acetal group provides distinctly higher stereoselectivity. The 3-O-benzyl and 3-O-allyl ethers vicinal to the carbonyl to be reduced have a similar influence on the steric outcome of the carbonyl reduction. A peculiar effect of acetoxydimethylsulfonium acetate ("activated" DMSO) was observed. In all cases, its presence strongly increased the manno-selectivity of the reduction. A simple, preparatively expedient, commonly suitable protocol has been elaborated for achieving high manno-selectivities and, hence, satisfactory yields.
Synthesis of four structural elements of xylose-containing carbohydrate chains from N-glycoproteins
作者:János Kerékgyártó、Johannis P. Kamerling、Jan B. Bouwstra、Johannes F.G. Vliegenthart、András Lipták
DOI:10.1016/0008-6215(89)84004-2
日期:1989.2
promoter, afforded the trisaccharide-glycoside derivative 13, which was transformed into the acetylated trisaccharide-glycoside 16. The disaccharide derivative 10, obtained from 8, and the trisaccharide derivative 15, obtained from 13, were glycosylated at position 3 with O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)trichloroacetimidate (19), using trimethylsilyl triflate as a promoter, giving rise