β-1,4-Galactosyltransferase-catalyzed Synthesis of the Branched Tetrasaccharide Repeating Unit of Streptococcus pneumoniae Type 14

Abstract

AbstractÐA chemoenzymatic approach is described towards the branched tetrasaccharide repeating unit, was synthesized by coupling of peracetylated lactosyl trichloroacetimidate to a suitably protected glucosamine building block and subsequent deprotection steps. The obtained derivative was found to be a good acceptor for bovine milk b-1,4-galactosyltransferase, and the resulting branched tetrasaccharide b-allyl glycoside was isolated and characterized by NMR spectroscopy and FAB mass spectrometry. Reaction of the anomeric allyl function with cysteamine under UVirradiation gave the b-aminoethylthio-extended glycoside suitable for further coupling of the tetrasaccharide to protein carriers. #

Donor Substrate Regeneration for Efficient Synthesis of Globotetraose and Isoglobotetraose

“…Biocatalytic approaches in which isolated enzymes, especially Leloir glycosyltransferases, are used are powerful and complementary alternatives to chemical synthesis of carbohydrates and glycoconjugates (18,19,27). So far, a large number of mammalian glycosyltransferases have been cloned and employed in oligosaccharide synthesis; these enzymes include bovine ␤-1,4-galactosyltransferase (7,24,28) and ␣-1,3-galactosyltransferase (7, 10) and human ␣-2,3-sialyltransferase (31), ␣-1,3-fucosyltransferase (2), and blood group A/B glycosyltransferases (32). However, the utility of these enzymes in large-scale synthesis of glycoconjugates is partially limited by the high cost of eukaryotic cell culture and by the low level of protein expression.…”

Immunogenicity in a Mouse Model of a Conjugate Vaccine Made with a Synthetic Single Repeating Unit of Type 14 Pneumococcal Polysaccharide Coupled to CRM197

“…OSs used for inhibition studies were obtained by either chemoenzymic synthesis as allyl glycosides (OSs 1a to 3a) as previously described (26,27) or by chemical Pn14PS degradation (OSs 4a and 5a) (Fig. 2).…”

“…2). Synthetic OSs 1a to 3a were prepared by a chemoenzymatic approach, as previously described (26,27). Linear OS acceptors and alkyl-bridged OS mimics of fragments of the Pn14PS were synthesized chemically and subsequently galactosylated to the branched OS structures using ␤-1,4-galactosyltransferase.…”

“…The poor immunogenicity of the Pn14PS compared to other PnPSs (18) may be due to structural similarities between antigenic determinants of the Pn14PS and human OS structures (e.g., human milk OSs and blood group carbohydrate structures). To avoid cross-reactivity with human tissue and the induction of autoreactive antibodies (6), we have been investigating the synthesis of well-defined OS fragments (26,27) corresponding to the Pn14PS to enable specific protective epitopes to be defined. Inhibition studies were performed both with synthetic OS structures and fragments from PS degradation to determine optimal OSs for conjugation.…”

Synthesis of oligosaccharide fragments of the Streptococcus pneumoniae type 14 capsular polysaccharide and their neoglycoconjugates with bovine serum albumin

“…Com pound 11 (118 mg, 86%) was isolated by column chromatogra phy (light petroleum-ethyl acetate, 4 : 1) as a foam, [] D +64. 1   D glucopyrano side (12). A 40% aqueous HF (100 L) was added to a solution of monohydroxy derivative 10 (288 mg, 0.36 mmol) in acetonitrile (2 mL).…”