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Convergent synthesis of tetra- and penta-saccharide fragments of dimeric Lewis X.

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Title: Convergent synthesis of tetra- and penta-saccharide fragments of dimeric Lewis X.
Authors: Forman, Adam1 (AUTHOR), Hendel, Jenifer1 (AUTHOR), Auzanneau, France-Isabelle1 (AUTHOR) fauzanne@uoguelph.ca
Source: Carbohydrate Research. Aug2019, Vol. 482, pN.PAG-N.PAG. 1p.
Subjects: Thiourea, Glycosylation, Epitopes, Fucosylation, Metals, Immunoglobulins
Abstract: The convergent synthesis of tetra- and penta-saccharide fragments of the TACA dimeric Lex is described. The synthetic strategy relied on the preparation of a protected GlcNTCA-(1,3)-Gal-(1,4)-GlcNAc trisaccharide diol free at O-3 of both glucosamine residues. Key steps in the preparation of this diol involved glycosylation at O-4 of N -acetylglucosamine using activation of a trichloroacetimidate with BF 3 · Et 2 O at 40 °C, removal of the non-reducing end O-3' chloroacetate with thiourea, and glycosylation with a N -trichloroacetamido glucosamine trichloroacetimidate donor. After conversion to the diol acceptor, the trisaccharide was selectively fucosylated at the nonreducing end under NIS/TMSOTf activation, or di-fucosylated under CuBr 2 /Bu 4 NBr activation. The protected tetra- and pentasaccharides were then efficiently deprotected under dissolving metal conditions and the nonreducing end glucosamine residues were N- acetylated during the reaction work up. The deprotected compounds will be used as soluble competitors to characterize the epitopes recognized by anti-polymeric Lex antibodies. Image 1 • Synthesis of tetra- and penta-saccharide fragments of dimeric Lex is described. • A trisaccharide diol free at O-3 of both glucosamine residues was prepared. • The trisaccharide diol was mono-fucosylated under NIS/TMSOTf activation. • The trisaccharide diol was di-fucosylated under CuBr 2 /Bu 4 NBr activation. • Tetra- and pentasaccharides were deprotected under dissolving metal conditions. [ABSTRACT FROM AUTHOR]
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Description
Abstract:The convergent synthesis of tetra- and penta-saccharide fragments of the TACA dimeric Lex is described. The synthetic strategy relied on the preparation of a protected GlcNTCA-(1,3)-Gal-(1,4)-GlcNAc trisaccharide diol free at O-3 of both glucosamine residues. Key steps in the preparation of this diol involved glycosylation at O-4 of N -acetylglucosamine using activation of a trichloroacetimidate with BF 3 · Et 2 O at 40 °C, removal of the non-reducing end O-3' chloroacetate with thiourea, and glycosylation with a N -trichloroacetamido glucosamine trichloroacetimidate donor. After conversion to the diol acceptor, the trisaccharide was selectively fucosylated at the nonreducing end under NIS/TMSOTf activation, or di-fucosylated under CuBr 2 /Bu 4 NBr activation. The protected tetra- and pentasaccharides were then efficiently deprotected under dissolving metal conditions and the nonreducing end glucosamine residues were N- acetylated during the reaction work up. The deprotected compounds will be used as soluble competitors to characterize the epitopes recognized by anti-polymeric Lex antibodies. Image 1 • Synthesis of tetra- and penta-saccharide fragments of dimeric Lex is described. • A trisaccharide diol free at O-3 of both glucosamine residues was prepared. • The trisaccharide diol was mono-fucosylated under NIS/TMSOTf activation. • The trisaccharide diol was di-fucosylated under CuBr 2 /Bu 4 NBr activation. • Tetra- and pentasaccharides were deprotected under dissolving metal conditions. [ABSTRACT FROM AUTHOR]
ISSN:00086215
DOI:10.1016/j.carres.2019.06.009