Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• Abhijit Sau Anup Kumar Misra Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata-700054, India; FAX: +91-33-2355 3886 10.3762/bjoc.8.230 Abstract A tetrasaccharide repeating unit corresponding to the cell-wall lipopolysaccharide of E. coli O40 was synthesized by

• using a convergent block glycosylation strategy. A disaccharide donor was coupled to a disaccharide acceptor by a stereoselective glycosylation. A 2-aminoethyl linker was chosen as the anomeric protecting group at the reducing end of the tetrasaccharide. All glycosylation steps are significantly high

• yielding and stereoselective. Keywords: Escherichia coli; glycosylation; lipopolysaccharide; O-antigen; tetrasaccharide; Introduction Infantile diarrhoea is one of the major causes of morbidity and mortality in infancy in developing countries [1]. Among several factors, Escherichia coli (E. coli

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• affect glycosylation yields. Working in a solid-phase environment could, in principle, additionally reduce the accessibility of a sterically hindered nucleophile. Thus, the possibility of accessing branched structures was explored on the solid support [5]. Sialyl LewisX tetrasaccharide 27 (Scheme 5), has

• optimized conditions, the branched tetrasaccharide 26 was isolated in 51% overall yield after TCA reduction, cleavage, ester saponification and HPLC purification. Finally, solution-phase hydrogenolysis gave tetrasaccharide 27. Automated synthesis of linear α–(2→6) sialosides α-(2→6) Sialylated

• oligosaccharides have been identified in humans as a recurring constituent of the upper respiratory epithelial glycocalix [29]. For instance, tetrasaccharide 30 has been reported to bind to haemagglutinins isolated from different H1N1 human viral strains, and was chosen as a target to showcase the solid-phase

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• ). The products from the conversion of the tetrasaccharide 1b and LacDiNAc 2 could be assigned according to their molecular mass as the corresponding aldehydes 3b and 4, the corresponding α,β-unsaturated aldehyde products 7b and 8, and the galacturonic acid products 5b and 6, as depicted in Table S1 in

• production of a tetrasaccharide that shows an internal and a terminal 6-aldehyde group (11a, see Scheme 2C, Table S1 and Figure S13 in Supporting Information File 1). These results open a range of new possibilities to synthesise poly-LacNAc glycans with internally and/or terminally modified galactose

• reduced with Na[BH3(CN)] to the corresponding hydrazines (15a–c and 16a). B: Elongation of biotinylated LacNAc (15a) and biotinylated tetrasaccharide (15b) by β3-N-acetylglucosaminyltransferase (β3GlcNAc-transferase) leads to an internally modified trisaccharide 16a as the enzymatic elongation of the

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• Abhishek Santra Anup Kumar Misra Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata-700054, India; Fax: 91-33-2355 3886 10.3762/bjoc.7.137 Abstract A convenient synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9 has been

• achieved in excellent yield using a [2 + 2] block glycosylation strategy. TEMPO-mediated selective oxidation of the primary alcohol of the tetrasaccharide derivative 8 to the carboxylic group followed by deprotection of the functional groups furnished target tetrasaccharide 1 as its 4-methoxyphenyl

• the presence of acidic constituents (e.g., uronic acid, pseudaminic acid etc. or lactic acid, pyruvic acid etc.) in their structures [6][7]. Recently, L’vov et al. reported the structure of the O-antigen of Shigella boydii type 9, which is a tetrasaccharide repeating unit containing a D-glucuronic

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• tetrasaccharide 74, which demonstrated its versatility and efficacy. Another study [43] showed that 1,6-anhydro sugars 76 and 78 could be synthesized by utilizing salient features of gold-catalyzed glycosidations. 2.2 Aldehydes and ketones as nucleophiles Different oxygen heterocycles can be obtained from the

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• -containing lactose derivative a suitably protected lacto-N-neotetraose tetrasaccharide structure was constructed through subsequential couplings with two thioglycoside donors, a glucosamine residue followed by a galactose derivative, using NIS/AgOTf as promoter. Removal of a silyl protecting group at the

• group patterns to improve the reactivity [20][21]. Here, however, NIS/AgOTf-promoted glycosylation of acceptor 13 with donor 3 proceeded without difficulties to produce the tetrasaccharide 14 in high yield (77%, Scheme 3). Before the introduction of the azido-galactose residue, the spacer azido function

• was reduced to an amino group, which was protected as a benzyl carbamate (→ 15, 91%). Removal of the TBDMS group with TBAF then gave the tetrasaccharide acceptor 16 (89%). To obtain complete α-selectivity with 2-azido-galactose donors is not trivial. A 4,6-silyl acetal has been suggested as one way to

Convergent syntheses of Le^X analogues

• An Wang,
• Jenifer Hendel and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2010, 6, No. 17, doi:10.3762/bjoc.6.17

• ][33][34][35][36] or chemoenzymatic [37][38] preparation of Lex analogues as well as that of Lex intermediate building blocks to be further converted into the Sialyl Lex tetrasaccharide. The chemical syntheses usually follow one of three synthetic schemes: 1. a stepwise approach involving the