title: CGTase-catalysed cis-glucosylation of L-rhamnosides for the preparation of Shigella flexneri 2a and 3a haptens.
abstract: We report the enzymatic synthesis of α-D-glucopyranosyl-(1→4)-α-L-rhamnopyranoside and α-D-glucopyranosyl-(1→3)-α-L-rhamnopyranoside by using a wild-type transglucosidase in combination with glucoamylase and glucose oxidase. It was shown that Bacillus circulans 251 cyclodextrin glucanotransferase (CGTase, EC 2.1.4.19) can efficiently couple an α-L-rhamnosyl acceptor to a maltodextrin molecule with an α-(1→4) linkage, albeit in mixture with the α-(1→3) regioisomer, thus giving two glucosylated acceptors in a single reaction. Optimisation of the CGTase coupling reaction with β-cyclodextrin as the donor substrate and methyl or allyl α-L-rhamnopyranoside as acceptors resulted in good conversion yields (42-70%) with adjustable glycosylation regioselectivity. Moreover, the efficient chemical conversion of the products of CGTase-mediated cis-glucosylation into protected building blocks (previously used in the synthesis of O-antigen fragments of several Shigella flexneri serotypes) was substantiated. These novel chemoenzymatic strategies towards useful, convenient intermediates in the synthesis of S. flexneri serotypes 2a and 3a oligosaccharides might find applications in developments towards synthetic carbohydrate-based vaccine candidates against bacillary dysentery.
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), Affiliated with Grenoble University and the Institut de Chimie Moléculaire de Grenoble, Domaine Universitaire de Grenoble, 601 rue de la Chimie, B. P. 53, 38041 Grenoble cedex 9 (France).
authors.forename: Carole
authors.initials: C
authors.lastname: Urbach
authors.forename: Sami
authors.initials: S
authors.lastname: Halila
authors.forename: Catherine
authors.initials: C
authors.lastname: Guerreiro
authors.forename: Hugues
authors.initials: H
authors.lastname: Driguez
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Mulard
authors.forename: Sylvie
authors.initials: S
authors.lastname: Armand
mesh_terms: D001407:Bacillus / Q000201:enzymology; D055162:Biocatalysis; D002240:Carbohydrate Sequence; D004795:Enzyme Stability; D005964:Glucosyltransferases / Q000378:metabolism*; D006031:Glycosylation; D006241:Haptens / Q000737:chemistry*; D007700:Kinetics; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D012763:Shigella flexneri; D013696:Temperature; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D006241:Haptens; D009844:Oligosaccharides; D047392:beta-Cyclodextrins; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase
keywords: Shigella flexneri; biocatalysis; carbohydrates; cis-glycosylation; cyclodextrin glucanotransferase