- Site-Selective Acylation of Pyranosides with Oligopeptide Catalysts
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Herein, we report the oligopeptide-catalyzed site-selective acylation of partially protected monosaccharides. We identified catalysts that invert site-selectivity compared to N-methylimidazole, which was used to determine the intrinsic reactivity, for 4,6
- Seitz, Alexander,Wende, Raffael C.,Roesner, Emily,Niedek, Dominik,Topp, Christopher,Colgan, Avene C.,McGarrigle, Eoghan M.,Schreiner, Peter R.
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p. 3907 - 3922
(2021/03/09)
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- In Situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azopeptide Catalysts
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We present a novel concept for the in situ control of site-selectivity of catalytic acetylations of partially protected sugars using light as external stimulus and oligopeptide catalysts equipped with an azobenzene moiety. The isomerizable azobenzene-peptide backbone defines the size and shape of the catalytic pocket, while the π-methyl-l-histidine (Pmh) moiety transfers the electrophile. Photoisomerization of the E- to the Z-azobenzene catalyst (monitored via NMR) with an LED (λ = 365 nm) drastically changes the chemical environment around the catalytically active Pmh moiety, so that the light-induced change in the catalyst shape alters site-selectivity. As a proof of principle, we employed (4,6-O-benzylidene)methyl-α-d-pyranosides, which provide a change in regioselectivity from 2:1 (E) to 1:5 (Z) for the monoacetylated products at room temperature. The validity of this new catalyst-design concept is further demonstrated with the regioselective acetylation of the natural product quercetin. In situ irradiation NMR spectroscopy was used to quantify photostationary states under continuous irradiation with UV light.
- Eckhardt, André K.,Erb, Frederik R.,Herold, Dominik,Kind, Jonas,Niedek, Dominik,Schreiner, Peter R.,Seitz, Alexander,Thiele, Christina M.,Topp, Christopher,Wende, Raffael C.
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supporting information
(2020/02/04)
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- DBN-Catalyzed Regioselective Acylation of Carbohydrates and Diols in Ethyl Acetate
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The 1,5-diazabicyclo[4.3.0]non-5-ene (DBN)-catalyzed regioselective acylation of carbohydrates and diols in ethyl acetate has been developed. The hydroxyl groups can be selectively acylated by the corresponding anhydride in EtOAc in the presence of a catalytic amount (as low as 0.1 equiv.) of DBN at room temperature to 40 °C. This method avoids metal catalysts and toxic solvents, which makes it comparatively green and mild, and it uses less organic base compared with other selective acylation methods. Mechanism studies indicated that DBN could catalyze the selective acylation of hydroxyl moieties through a dual H-bonding interaction.
- Ren, Bo,Zhang, Mengyao,Xu, Shijie,Gan, Lu,Zhang, Li,Tang, Lin
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supporting information
p. 4757 - 4762
(2019/07/31)
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- Diisopropylethylamine-triggered, highly efficient, self-catalyzed regioselective acylation of carbohydrates and diols
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A diisopropylethylamine (DIPEA)-triggered, self-catalyzed, regioselective acylation of carbohydrates and diols is presented. The hydroxyl groups can be acylated by the corresponding anhydride in MeCN in the presence of a catalytic amount of DIPEA. This method is comparatively green and mild as it uses less organic base compared with other selective acylation methods. Mechanistic studies indicate that DIPEA reacts with the anhydride to form a carboxylate ion, and then the carboxylate ion could catalyze the selective acylation through a dual H-bonding interaction.
- Ren, Bo,Gan, Lu,Zhang, Li,Yan, Ningning,Dong, Hai
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supporting information
p. 5591 - 5597
(2018/08/17)
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- Enhanced site-selectivity in acylation reactions with substrate-optimized catalysts on solid supports
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A concept for site selective acylation of poly-hydroxylated substrates is presented where polymer-supported catalysts are employed: catalytically active DMAP units were combined with a library of small molecule peptides attached to the solid phase with the goal to identify substrate-optimized catalysts through library screening. For selected examples, we demonstrate how the optimized catalysts can convert “their” substrate with a markedly enhanced site-selectivity, compared to only DMAP. Due to the solid support, product purification is significantly simplified, and the peptidic catalysts can be easily reused in multiple cycles while conserving its efficiency.
- Tong, My Linh,Huber, Florian,Taghuo Kaptouom, Estelle S.,Cellnik, Torsten,Kirsch, Stefan F.
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supporting information
p. 3086 - 3089
(2017/03/17)
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- Enhanced basicity of Ag2O by coordination to soft anions
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In Ag2O-mediated benzylation, the addition of a catalytic amount of KI can greatly improve reactivity. This is usually attributed to the formation of a more reactive iodo-substituted electrophile. However, our studies show this to be due to the enhanced basicity of Ag2O through coordination of soft iodide anions to the silver atom, and show KI to be an initiator. A catalytic amount of Ag2O and NaBr can catalyze transesterification reactions, indicating the enhanced basicity of Ag2O by bromide. We believe that this is a general effect for metal oxides and soft anions, applicable to a wider range of organic reaction systems. All your base belongs to us: In Ag2O-mediated benzylation, the addition of a catalytic amount of KI can greatly improve reactivity. Our studies show this to be attributable to the enhanced basicity of Ag2O through coordination of soft iodide anions to the silver atom, and show KI to be an initiator. Thus, NaBr as an initiator combined with Ag2O has been successfully used to catalyze transesterification reactions.
- Ren, Bo,Wang, Meiyan,Liu, Jingyao,Ge, Jiantao,Dong, Hai
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p. 761 - 765
(2015/03/04)
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- Monoacetylation of carbohydrate diols via transesterification with ethyl acetate
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Monoacetylation of secondary diols in protected monosaccharides was achieved with ethyl acetate as acyl donor and sodium tert-butoxide as a base. The regioseletivity of the reaction varied depending on the substrate. This new method provides a simple, fast, and efficient method to access selectively acetylated carbohydrates that is compatible with acid-sensitive protecting groups. CSIRO 2014.
- Liu, Xuyu,Becker, Bernd,Cooper, Matthew A.
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p. 679 - 683
(2014/05/06)
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- Chiral copper(II) complex-catalyzed reactions of partially protected carbohydrates
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Catalyst-controlled regioselective functionalization of partially protected saccharide molecules is a highly important yet under-developed area of carbohydrate chemistry. Such reactions allow for the reduction of protecting group manipulation steps required in syntheses involving sugars. Herein, an approach to these processes using enantiopure copper-bis(oxazoline) catalysts to control couplings of electrophiles to various partially protected sugars is reported. In a number of cases, divergent regioselectivity was observed as a function of the enantiomer of catalyst that is used.
- Allen, C. Liana,Miller, Scott J.
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supporting information
p. 6178 - 6181
(2014/01/17)
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- H-bonding activation in highly regioselective acetylation of diols
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H-bonding activation in the regioselective acetylation of vicinal and 1,3-diols is presented. Herein, the acetylation of the hydroxyl group with acetic anhydride can be activated by the formation of H-bonds between the hydroxyl group and anions. The reaction exhibits high regioselectivity when a catalytic amount of tetrabutylammonium acetate is employed. Mechanistic studies indicated that acetate anion forms dual H-bonding complexes with the diol, which facilitates the subsequent regioselective monoacetylation.
- Zhou, Yixuan,Rahm, Martin,Wu, Bin,Zhang, Xiaoling,Ren, Bo,Dong, Hai
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supporting information
p. 11618 - 11622
(2013/12/04)
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- Organosilicon-mediated regioselective acetylation of carbohydrates
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Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-c
- Zhou, Yixuan,Ramstroem, Olof,Dong, Hai
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p. 5370 - 5372
(2012/06/18)
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- A selective and operationally simple approach for removal of methoxy-, allyloxy-, and benzyloxycarbonyl groups from carbinols
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LiI in refluxing pyridine can remove within a few hours methoxy-, allyloxy-, and benzyloxycarbonyl groups from saccharidic carbinols under conditions compatible with the maintenance of acyl groups. Addition of a stoichiometric excess of acetic acid to the
- Adinolfi, Matteo,Iadonisi, Alfonso,Pastore, Antonello
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experimental part
p. 7051 - 7054
(2010/02/28)
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- METHOD FOR PREPARING HEXOSE DERIVATIVES
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A method for preparing hexose derivatives comprises the steps of providing a silylated hexose, treating the silylated hexose with a first carbonyl compound in the presence of a catalyst to form an ketalized hexose, treating the ketalized hexose with a second carbonyl compound followed by treating with a first reductant to form an etherized hexose, and converting the etherized hexose into a target hexose derivative, which can be 2-alcohol hexose, 3-alcohol hexose, 4-alcohol hexose, or a 6-alcohol hexose. In particular, the present invention can prepare the hexose derivatives with highly regioselective scheme to protect individual hydroxyls of monosaccharide units and install an orthogonal protecting group pattern in a one-pot manner
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Page/Page column 2; 5; 7; Sheet 6/9
(2009/05/29)
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- Directing-protecting groups for carbohydrates. Design, conformational study, synthesis and application to regioselective functionalization
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A novel concept of regioselective transformation of secondary hydroxyl groups in carbohydrates is presented. First, the relative reactivity of the free hydroxyl groups of onoprotected d-glucose derivatives was assessed using acetylation as a model reactio
- Moitessier, Nicolas,Englebienne, Pablo,Chapleur, Yves
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p. 6839 - 6853
(2007/10/03)
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- Silver(I) oxide mediated selective monoprotection of diols in pyranosides
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The reaction of 4,6-O-benzylidene-D-pyranosides with a stoichiometric amount of TsCl, AcCl, and BzCl in the presence of silver(I) oxide and a catalytic amount of potassium iodide led to monosubstituted derivatives in high regioselectivity and in good yiel
- Wang, Haisheng,She, Ji,Zhang, Li-He,Ye, Xin-Shan
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p. 5774 - 5777
(2007/10/03)
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- Regioselective esterification of various D-glucopyranosides: Synthesis of a fully protected disaccharide unit of hyaluronic acid
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A highly regioselective esterification of various D-glucopyranosides with triethylamine and acid anhydrides in excellent yields is described here. Its application toward the synthesis of a fully protected disaccharide unit of hyaluronic acid is also highlighted.
- Lu, Xin-An,Chou, Chien-Hung,Wang, Cheng-Chung,Hung, Shang-Cheng
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p. 1364 - 1366
(2007/10/03)
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- Application of Site-Directed Lipase Mutants on Regioselective Acylation of Monosaccharides
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Mutants F344V and F345V of Candida rugosa lipasel (CRL1) were tested in acylation reactions of monosaccharide derivatives 1-8, in order to study the regioselectivity, and the substrate specificity of lipase variants towards unnatural substrates, such as carbohydrates. Mutant F344V showed a better reaction kinetics and/or regioselectivity then the wild type enzyme with several substrates while mutant F345V was inefficient in most cases. With the aim of correlating experimental data with the structural features of the enzyme and substrates, the interaction of substrates methyl 4,6-O-benzylidene-α- D-glucopyranoside (5a) and 4,6-O-benzylidene-α-D-galactopyranoside (6a) with the wild type enzyme and the mutant F344V was investigated, using a molecular modelling approach.
- Cipolla, Laura,Lotti, Marina,De Gioia, Luca,Nicotra, Francesco
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p. 631 - 644
(2007/10/03)
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- Efficient activation of armed glycosyl trichloroacetimidates with Sm(OTf)3 in the stereoselective glycosidation of saccharidic acceptors
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Catalytic amounts of Sm(OTf)3 activate armed glycosyl trichloroacetimidates under very mild conditions. This reagent proved effective in promoting the glucosylation of saccharidic acceptors 2, 3, 4, and 5, possessing primary or secondary hydroxyls, with the model donor 1. The stereoselectivity of these glycosidations can be controlled by a suitable choice of solvent. (C) 2000 Elsevier Science Ltd.
- Adinolfi,Barone,Guariniello,Iadonisi
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p. 9005 - 9008
(2007/10/03)
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- Tetrabutylammonium nitrite - acetic anhydride system, tetrabutylammonium nitrite, tetrabutylammonium acetate, and cesium acetate - 18-crown-6 for efficient unmasking of alkyl N-phenylcarbamates
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Novel unmasking procedures for alkyl N-phenylcarbamates are established by the use of a tetrabutylammonium nitrite (Bu4NNO2) - acetic anhydride system, Bu4NNO2, Bu4NOAc, and CsOAc 18-crown-6 towards variously functionalized sugar derivatives.
- Akai, Shoji,Nishino, Noriaki,Iwata, Yukihiro,Hiyama, Jun-Ichi,Kawashima, Etsuko,Sato, Ken-Ichi,Ishido, Yoshiharu
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p. 5583 - 5586
(2007/10/03)
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- Investigation of the Regioselectivity of Some Esterifications Involving Methyl 4,6-O-Benzylidene D-Pyranosides and Pseudomonas fluorescens Lipase
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Using Pseudomonas fluorescens lipase in vinyl acetate, the methyl 4,6-O-benzylidene-α-D-pyranosides 1 and 6 - 8 have been esterified with very high selectivity to afford the C-2 acetates 3 and 10 - 12, respectively.In contrast the methyl 4,6-O-benzylidene
- Iacazio, Gilles,Roberts, Stanley M.
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p. 1099 - 1102
(2007/10/02)
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- Novel methods for the preparation of partially acetylated carbohydrates
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The selective acetylation of methyl α-D-hexopyranosides in the presence of zinc chloride shows unusual reactivity patterns compared to control experiments.Hydroperoxide ion is a mild and selective deacetylation reagent which does not attack primary acetates.
- Hanessian, Stephen,Kagotani, Masahiro
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- Selective acylation of 6-deoxyglycals.
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L-Rhamnal was acylated under a variety of conditions with various acylating reagents. Substitution of the hydroxyl group in the allylic position was favored when acetyl chloride, N-acetylimidazole, benzoyl chloride, and N-benzoylimidazole were used (40-60% net yields), whereas the homoallylic group of L-rhamnal was selectively protected when acetic anhydride-pyridine was employed for the acylation. The monoacetates of L-fucal underwent O-3----O-4 migration of the acetyl group, and selective acylation of this glycal could not be achieved.
- Horton,Priebe,Varela
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p. 317 - 324
(2007/10/02)
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- Regioselective alkylation and acylation of carbohydrates engaged in metal complexes.
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Substituted carbohydrate derivatives (D-gluco, D-manno, and D-galacto) having two free hydroxyl groups were converted into their metal chelates by reaction with sodium hydride and a metal chloride (cupric or mercuric) in either oxolane or 1,2-dimethoxyeth
- Eby,Webster,Schuerch
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p. 111 - 120
(2007/10/02)
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- SYNTHESE DES L-FUCOSE ET L-(3-(2)H)FUCOSE A PARTIR DU D-MANNOSE
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Oxidation with the dimethyl sulfoxide-acetic anhydride reagent of methyl 2-O-acetyl-4,6-O-benzylidene-α-D-mannopyranoside, obtained in quantitative yield from the corresponding 4,6-benzylidene acetal by stereoselective opening of a 2,3-orthoester, led in good yield to methyl 2-O-acetyl-4,6-O-benzylidene-α-D-arabino-hexopyranosid-3-ulose, which was reduced with either sodium borohydride or sodium borodeuteride into a methyl 4,6-O-benzylidene-α-D-altopyranoside or its 3-(2)H derivative.A sequence involving a C-6 halogenation-dehydrohalogenation followed by catalytic hydrogenation of the resulting methyl 6-deoxy-α-D-arabino-hex-5-enopyranoside gave methyl 6-deoxy-β-L-galactopyranoside (methyl β-L-fucopyranoside) and then α-L-fucose, with an overall yield of 24percent with respect to the starting methyl α-D-mannopyranoside.
- Defaye, Jacques,Gadelle, Andree,Wong, Chuan C.
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p. 131 - 142
(2007/10/02)
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