- Reactivity–Stereoselectivity Mapping for the Assembly of Mycobacterium marinum Lipooligosaccharides
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The assembly of complex bacterial glycans presenting rare structural motifs and cis-glycosidic linkages is significantly obstructed by the lack of knowledge of the reactivity of the constituting building blocks and the stereoselectivity of the reactions i
- Hansen, Thomas,Ofman, Tim P.,Vlaming, Joey G. C.,Gagarinov, Ivan A.,van Beek, Jessey,Goté, Tessa A.,Tichem, Jacoba M.,Ruijgrok, Gijs,Overkleeft, Herman S.,Filippov, Dmitri V.,van der Marel, Gijsbert A.,Codée, Jeroen D. C.
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supporting information
p. 937 - 945
(2020/12/09)
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- Reagent controlled stereoselective synthesis of teichoic acid α-(1,2)-glucans
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The stereoselective construction of 1,2-cis-glycosidic linkages is key in the assembly of biologically relevant glycans, but remains a synthetic challenge. Reagent-controlled glycosylation methodologies, in which external nucleophiles are employed to modu
- Berni, Francesca,Enotarpi, Jacopo,Overkleeft, Hermen S.,Van Der Marel, Gijs,Wang, Liming,Codée, Jeroen D. C.
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p. 2038 - 2050
(2020/03/27)
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- Conformationally Switchable Glycosyl Donors
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Glycosyl donors functionalized with 2,2′-bipyridine moieties on the 3-OH and 6-OH or the 2-OH and 4-OH undergo a conformational change when forming 1:1 complexes with Zn2+ ions. The pyranoside ring of the zinc complexes adopted axial-rich skew boat conformations. The reactivities of the two glycosyl donors were investigated by performing a series of glycosylations in the presence or absence of Zn2+ ions. These glycosylations suggested a decrease in reactivity when binding Zn2+. The conformational effect of binding Zn2+ was therefore studied using a third glycosyl donor, unable to undergo conformational changes when binding Zn2+. From competition experiments, it was observed that the binding-induced conformational change increased the reactivity slightly compared to the glycosyl donor unable to undergo a conformational change.
- Holmstr?m, Thomas,Pedersen, Christian Marcus
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p. 13242 - 13251
(2019/11/03)
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- Glycosyl Fluorides as Intermediates in BF3·OEt2-Promoted Glycosylation with Trichloroacetimidates
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Glycosyl fluorides have been found to be important intermediates in glycosylations with trichloroacetimidate donors and BF3·OEt2 activation (0.2–1 equiv.). Low-temperature NMR spectroscopy experiments revealed that the α-trichloroacetimidate was transformed into the glycosyl fluoride with inversion of stereochemistry, whereas the β anomer was not. A concerted mechanism was suggested for the stereospecific formation of glycosyl fluorides, which is not accounted for in the classic mechanism.
- Nielsen, Michael M.,Stougaard, Bolette A.,Bols, Mikael,Glibstrup, Emil,Pedersen, Christian M.
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supporting information
p. 1281 - 1284
(2017/03/17)
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- Borinic Acid Catalyzed Stereo- and Regioselective Couplings of Glycosyl Methanesulfonates
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In the presence of a diarylborinic acid catalyst, glycosyl methanesulfonates engage in regio- and stereoselective couplings with partially protected pyranoside and furanoside acceptors. The methanesulfonate donors are prepared in situ from glycosyl hemiacetals, and are coupled under mild, operationally simple conditions (amine base, organoboron catalyst, room temperature). The borinic acid catalyst not only influences site-selectivity via activation of 1,2- or 1,3-diol motifs, but also has a pronounced effect on the stereochemical outcome: 1,2-trans-linked disaccharides are obtained selectively in the absence of neighboring group participation. Reaction progress kinetic analysis was used to obtain insight into the mechanism of glycosylation, both in the presence of catalyst and in its absence, while rates of interconversion of methanesulfonate anomers were determined by NMR exchange spectroscopy (EXSY). Together, the results suggest that although the uncatalyzed and catalyzed reactions give rise to opposite stereochemical outcomes, both proceed by associative mechanisms.
- D'Angelo, Kyan A.,Taylor, Mark S.
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supporting information
p. 11058 - 11066
(2016/09/12)
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- Directing effect by remote electron-withdrawing protecting groups at O-3 or O-4 position of donors in glucosylations and galactosylations
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Glucosylations and galactosylations of various acceptors with donors possessing an electron-withdrawing benzylsulfonyl, benzoyl, or acetyl group at the O-3 or O-4 position were performed. A β-directing effect by the benzylsulfonyl group at O-3 of the glucosyl donors and by the benzylsulfonyl and acyl groups at O-4 of the glucosyl donors was observed. In contrast, acyl groups at O-3 of the glucosyl donors and acyl groups at O-3 and O-4 of the galactosyl donors exhibited an α-directing effect. The α-directing effect is partly considered to remote participation of the acyl groups, whereas the β-directing effect is somewhat attributed to the SN2-like reaction of the acceptor with the glycosyl triflate or the contact ion pair, which is stabilized by remote electron-withdrawing groups. Further evidence for the stability of the α-glycosyl triflates was determined by a low-temperature NMR study.
- Baek, Ju Yuel,Kwon, Hea-Won,Myung, Se Jin,Park, Jung Jun,Kim, Mi Young,Rathwell, Dominea C.K.,Jeon, Heung Bae,Seeberger, Peter H.,Kim, Kwan Soo
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supporting information
p. 5315 - 5320
(2015/07/15)
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- Synthesis and reactivity of 4'-deoxypentenosyl disaccharides
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4-Deoxypentenosides (4-DPs) are versatile synthons for rare or higher-order pyranosides, and they provide an entry for structural diversification at the C5 position. Previous studies have shown that 4-DPs undergo stereocontrolled DMDO oxidation; subsequent epoxide ring-openings with various nucleophiles can proceed with both anti or syn selectivity. Here, we report the synthesis of α- and β-linked 4'-deoxypentenosyl (4'-DP) disaccharides, and we investigate their post-glycosylational C5' additions using the DMDO oxidation/ring-opening sequence. The α-linked 4'-DP disaccharides were synthesized by coupling thiophenyl 4-DP donors with glycosyl acceptors using BSP/Tf2O activation, whereas β-linked 4'-DP disaccharides were generated by the decarboxylative elimination of glucuronyl disaccharides under microwave conditions. Both α- and β-linked 4'-DP disaccharides could be epoxidized with high stereoselectivity using DMDO. In some cases, the α-epoxypentenosides could be successfully converted into terminal l-iduronic acids via the syn addition of 2-furylzinc bromide. These studies support a novel approach to oligosaccharide synthesis, in which the stereochemical configuration of the terminal 4'-DP unit is established at a post-glycosylative stage.
- Padungros, Panuwat,Fan, Ren-Hua,Casselman, Matthew D.,Cheng, Gang,Khatri, Hari R.,Wei, Alexander
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p. 4878 - 4891
(2014/06/23)
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- A convergent ring-closing metathesis approach to carbohydrate-based macrolides with potential antibiotic activity
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An efficient convergent approach has been developed for the construction of novel, non-natural, carbohydrate-based macrolides. The key step in the synthesis is the formation of the macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been screened for biological activity against Gram-positive and Gram-negative bacteria, including resistant strains, yeasts, and molds.
- Blom, Petra,Ruttens, Bart,Van Hoof, Steven,Hubrecht, Idzi,Van Der Eycken, Johan,Sas, Benedikt,Van Hemel, Johan,Vandenkerckhove, Jan
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p. 10109 - 10112
(2007/10/03)
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- Chemistry of 4,6-O-benzylidene-D-glycopyranosyl triflates: Contrasting behavior between the gluco and manno series
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Activation of either anomer of S-phenyl 2,3-di-O-benzyl-4,6-O- benzylidene-1-deoxy-1-thia-D-glucopyranoside with triflic anhydride in dichloromethane at -78 °C in the presence of 2,6-di-tert-butyl-4- methylpyridine affords a highly active glycosylating species which, on addition of alcohols, provides α-glucosides with high selectivity. This selectivity stands in stark contrast to the analogous mannopyranoside series, which affords the β-mannosides with excellent selectivity under the same conditions. Low-temperature NMR experiments support the notion that a glucosyl triflate is formed in the initial activation step. Possible reasons for the diverging stereoselectivity in the gluco and manno series are discussed.
- Crich, David,Cai, Weiling
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p. 4926 - 4930
(2007/10/03)
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- Capsular polysaccharide of Streptococcus pneumoniae type 19F: Synthesis of the repeating unit
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A new and more versatile synthesis of β-d-ManpNAc-(1→4)-α-d-Glcp-(1→2)-α-l-Rhap, the trisaccharide repeating unit of the Streptococcus pneumoniae type 19F capsular polysaccharide, is described. The present approach allows a simple access to different fragments containing the trisaccharide and the conjugation of the product(s) to a protein through the selective manipulation of the anomeric position at the reducing end and of the HO-4 function at the nonreducing end. The synthetic scheme shows an efficient application of the sulfoxide method for the stereoselective and high yielding formation of the glycosidic linkages. Copyright (C) 1998 Elsevier Science Ltd. A new and more versatile synthesis of β-D-ManpNAc-(1→4)-α-D-Glcp-(1→2)-α-L-Rhap, the trisaccharide repeating unit of the Streptococcus pneumoniae type 19F capsular polysaccharide, is described. The present approach allows a simple access to different fragments containing the trisaccharide and the conjugation of the product(s) to a protein through the selective manipulation of the anomeric position at the reducing end and of the HO-4 function at the nonreducing end. The synthetic scheme shows an efficient application of the sulfoxide method for the stereoselective and high yielding formation of the glycosidic linkages.
- Bousquet, Ennio,Khitri, Malika,Lay, Luigi,Nicotra, Francesco,Panza, Luigi,Russo, Giovanni
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p. 171 - 181
(2007/10/03)
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- Chemical synthesis of 6'-α-maltosyl-maltotriose, a branched oligosaccharide representing the branch point of starch
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Chemical synthesis of the branched pentasaccharide 6'-α-maltosyl-maltotriose (15) is reported, based on the use of one synthon as a glycosyl acceptor and another synthon as a glycosyl donor. The synthon used as glycosyl acceptor was phenyl 2,3,6-tri-O-benzyl-1-thio-β-D-glucopyranoside (7) and was synthesized from D-glucose with phenyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside and phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside as key intermediates. The synthon used as glycosyl donor was O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-benzylα-D-glucopyranosyl)-(1 → 4)]-2,3-di-O-benzyl-α,β-D-glucopyranosyl trichloroacetimidate (12) and was synthesized from phenyl O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)(1 → 4)]-2,3-di-O-acetyl-1-thio-β-D-glucopyranoside with O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)]-2,3-di-O-benzyl-D-glucopyranose as an intermediate. Condensation of compounds 7 and 12 followed by removal of the phenylthio group and debenzylation provided the branched pentasaccharide 15. Alternatively, the branched pentasaccharide was produced from amylopectin by consecutive alpha- and beta-amylase treatments and purified by chromatography. The identity of the products obtained by chemical synthesis and enzymatic hydrolysis is documented by 1H and 13C NMR spectra.
- Motawia,Olsen,Enevoldsen,Marcussen,Moller
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p. 109 - 123
(2007/10/02)
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- Practical synthesis of oligosaccharides. Partial synthesis of avermectin B(1a)
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A practical synthesis of oligosaccharides from phenylthio sugars via glycosyl fluorides is described. The new technology is applied to the synthesis of hexasaccharide 9 from a glucose derivative and avermectin B1a(11) from an avermectin B1
- Nicolaou,Dolle,Papahatjis,Randall,Dolle
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p. 4189 - 4192
(2007/10/02)
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- HYDROGENOLYSIS OF THE BENZYLIDENE ACETALS OF THIOGLYCOSIDES WITH THE LiAlH4-AlCl3 REAGENT. SYNTHESIS OF PARTIALLY BENZYLATED THIOGLYCOSIDE DERIVATIVES
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Reductive hydrogenolysis of phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-gluco- (4) and -galactopyranoside (8) and phenyl 2,3,6,2',3'-penta-O-benzyl-4',6'-O-benzylidene-1-thio-β-cellobioside (15) with the LiAlH4-AlCl3 reagent resulted in the corres
- Liptak, A.,Jodal, I.,Harangi, J.,Nanasi, P.
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p. 415 - 422
(2007/10/02)
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