Subsequent Enzymatic Galactosylation and Sialylation Towards Sialylated Thomsen–Friedenreich Antigen Components

Abstract

Sialyloligosaccharides of the type Neu5 Aca2-3Galb1-3GalNAc and a range of corresponding motifs play an important role in nature and are found in gangliosides, Lewis type I structures and the sialyl-Thomsen-Friedenreich antigen occurring in higher animals, viruses, bacteria, protozoa and pathogenic fungi. There is considerable interest to evaluate the significant functionalities of these glycostructures, and here we present a chemoenzymatic approach by a facile synthesis of such motifs. Employing chemoenzymatic methods, several modified Galb1-3GalNAc derivatives were synthesized. Modifications were introduced at the stage of the monomeric building blocks prior to formation of the disaccharides by means of four different b-galactosidases from bovine testes, Bacillus circulans and Xanthomonas manihotis as well as the phosphorylase from Bifidobacterium bifidum. Finally, the modified disaccharide derivatives could be efficiently sialylated using the recombinant trans-sialidase from Trypanosoma cruzi.

Synthesis of Amino‐Bridged Oligosaccharide Mimetics

“…Allyl 2-acetamido-2-deoxy-3,6-di-O-pivaloyl-α--glucopyranoside [22] (1.52 g, 3.50 mmol) was dissolved in dry dichloromethane (15 mL) and Dess-Martin periodinane (1.81 g, 4.20 mmol) dissolved in dichloromethane (20 mL) added. The reaction mixture was treated according to general procedure 1b.…”

“…Compound 33 [22] (1.50 g, 4.28 mmol) was dissolved under argon in dry dichloromethane (35 mL) and dry pyridine (2.0 mL). Trifluoromethane sulfuric acid anhydride (0.85 mL, 5.1 mmol) was slowly added at -35°C and the reaction was stirred for 4 h at 0°C.…”

“…NaCNBH 3 , HCl, THF, room temp., 30 min.The partially protected saccharides could be oxidized in good to very good yields. Treatment of glycosides 5 [20] and 11 [21] with pivaloyl chloride gave the partially protected glycosides [22,23] which could be oxidized with Dess-Martin periodinane in dichloromethane to give 4-keto sugars 13 and 14 in 87 and 85 % yield, respectively. En route to the 3keto sugars 17 and 18, AllGlcNAc 5 and 1,5-anhydro-glucitol 12 [24] were transformed into the corresponding benzylidene-protected sugars which were oxidized with Dess-Martin periodinane in dichloromethane in 95 % and 59 % yield.…”

Synthesis of PEGylated lactose analogs for inhibition studies on T.cruzi trans-sialidase

“…Oligosaccharides of the mucins have been synthesized and their acceptor and inhibitory properties were studied [20,21]. Recombinant TcTS has also been used for the preparation of sialylated oligosaccharides [22]. Sialic acid on the surface of the parasite is involved in host cell invasion and in protection of the parasite against complement [23] and from killing by anti α-galactosyl antibodies [24].…”

GM3, GM2 and GM1 mimics designed for biosensing: chemoenzymatic synthesis, target affinities and 900MHz NMR analysis

“…44 Recently, the synthesis of a variety of biologically relevant sialyl oligosaccharides was facilitated by a number of chemoenzymatic strategies using bacterial glycosyltransferases. [45][46][47][48][49][50][51] Thus, several glycosyltransferase genes from C. jejuni have been expressed in E. coli and methods for the efficient synthesis of 2-azidoethyl glycosides corresponding to the oligosaccharides of GD3, GT3, GM2, GD2, GT2, GM1 and GD1a were developed with a water-soluble 2-azidoethyl lactoside as starting compound. 52,53 For the application of such materials into sensing devices, attachment of other than highly water-soluble chains would, however, be a big step forward.…”