Experimental observations on the regioselectivity of glycosylation of a 4,6-diol system in the β-d-mannopyranosyl unit of a N-glycan pentasaccharide core structure

Synthesis and Microarray-Assisted Binding Studies of Core Xylose and Fucose Containing N-Glycans

“…As an additional constraint we found that the presence of a core xylose ( Figure In addition, the pauci-mannosidic compounds G35-G39 were accessible from G3, G4 and G6 by incubation with a β-N-acetyl-glucosaminidase and further derivatization with recombinant glycosyltransferases (see Supporting Information for experimental details). This collection of core-xylosylated compounds was complemented by a library of non-xylosylated Nglycans obtained from the core structures G40-G57 16,19,22,28 Binding studies with plant lectins and DC-SIGN We then studied the influence of N-glycan core modifications (β-1,2-xylose, α-1,3 and α-1,6-fucose) on binding to selected plant lectins ( Figure 5), to a C-type lectin receptor (CLR) involved in pathogen recognition by dendritic cells (DC-SIGN) ( Figure 6) and to antibodies in human Schistosoma mansoni infection sera ( Figure 7). Plant lectins have been defined as proteins that possess at least one non-catalytic domain that binds reversibly to a mono-or oligosaccharide.…”

“…Coupling of O-6 acceptor 9 with glycosyl donor 5 provided the pentasaccharide 17 in 52% yield. This route was preferred to the regioselective glycosylation in O-6 of the corresponding diol as initial attempts had led also to the formation of the undesired O-4 regioisomer, presumably via an orthoester intermediate. , The N-glycan precursors 11 , 13 , and 14 – 17 were deprotected toward the target glycans G1 – G6 either in a three or four step sequence, starting in both cases with the aminolysis of phtalimide groups followed by reacetylation of the intermediate amines. Birch reduction readily removed acetates and benzyl groups and reduced the linker azide to an amine in a single step for the glycans G2 (69%) and G4 (56%).…”

Fucosyltransferases as Synthetic Tools: Glycan Array Based Substrate Selection and Core Fucosylation of Synthetic N-Glycans

“…Compounds A1-A17 used in this study (Figure ) were prepared by a modular synthetic strategy described previously, , and details for the synthesis of compounds A13 and A18 are given in the Supporting Information. All synthetic ligands were spotted by a robotic noncontact printer at 50 μM concentration on NHS-activated glass slides according to the array design detailed in the Supporting Information and similar to published procedures …”

Convergent Synthesis of Sialyl LewisX-O-Core-1 Threonine

“…Despite the evaluation of alternate reaction conditions, a significant improvement was not observed and attempts to conduct the reaction below −20 °C were unsuccessful. This limitation of regioselectivity involving a donor with a participating group and the 4,6-diol system has been previously reported by other groups. ,, While it is unexpected for the axial 4-OH to react, as proposed by Baumann, it is possible that the 6-OH reacts with the intermediate oxazolinium ion via the exocyclic carbon and, upon intramolecular rearrangement, forms the 1→4 linked product (Figure ). To circumvent this limitation, we postulated that a thioglycoside donor would enable glycosylation at a much lower temperature, which would potentially improve regioselectivity.…”