- A facile chemoselective deacetylation in the presence of benzoyl and p-bromobenzoyl groups using p-toluenesulfonic acid
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The acetyl group was chemoselectively cleaved in the presence of p-toluenesulfonic acid (p-TsOH) in CH2Cl2/MeOH without affecting the benzoyl (benzoate and p-bromobenzoate) groups and no transesterification product was observed. The treatment of protected carbohydrates with p-TsOH·H2O at room temperature usually required a longer reaction time than at 40°C. Other types of sulfonic acid such as 10-camphorsulfonic (CSA) led to similar results.
- González, Antonio G,Brouard, Ignacio,León, Francisco,Padrón, Juan I,Bermejo, Jaime
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- Mild and chemoselective deacetylation method using a catalytic amount of acetyl chloride in methanol
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Efficient deacetylation of alcohol acetates under mild acidic conditions was accomplished with a catalytic amount of acetyl chloride in methanol. Acetates of various primary, secondary, aromatic and sugar alcohols were successfully deprotected. Highly chemoselective removal of acetyl groups in presence of other commonly employed esters was also achieved in excellent yields. The reactivity of this transesterification-mediated deacetylation was found to be directly dependent upon the electronic and steric nature of the acetates. Georg Thieme Verlag Stuttgart.
- Yeom, Chang-Eun,Lee, So Young,Kim, Young Jong,Kim, B. Moon
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Read Online
- Triethylamine-methanol mediated selective removal of oxophenylacetyl ester in saccharides
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A highly selective, mild, and efficient method for the cleavage of oxophenylacetyl ester protected saccharides was developed using triethylamine in methanol at room temperature. The reagent proved successful against different labile groups like acetal, ketal, and PMB and also generated good yields of the desired saccharides bearing lipid esters. Further, we also observed DBU in methanol as an alternative reagent for the deprotection of acetyl, benzoyl, and oxophenylacetyl ester groups. This journal is
- Rasool, Javeed Ur,Kumar, Atul,Ali, Asif,Ahmed, Qazi Naveed
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p. 338 - 347
(2021/01/29)
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- Noncatalytic selective 6-O-acetylation of methyl 2,3-di-O-benzoyl-α-d-glucopyranoside with acetic acid and acetic anhydride
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Noncatalytic acetylation of methyl 2,3-di-O-benzoyl-α-d-glucopyranoside with acetic acid or acetic anhydride proceeds regioselectively at the primary hydroxyl group and affords methyl 6-O-acetyl-2,3-di-O-benzoyl-α-d-glucopyranoside in good yield. The possibility of 6-O-acetylation should be taken into account when removing a 4,6-O-benzylidene protecting group with aqueous acetic acid at elevated temperature.
- Gening, M. L.,Nifantiev, N. E.,Tsvetkov, Y. E.
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p. 2228 - 2230
(2020/12/07)
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- Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity
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The reactivity of both coupling partners—the glycosyl donor and acceptor—is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting-group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure–reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis-glucosylations.
- van der Vorm, Stefan,van Hengst, Jacob M. A.,Bakker, Marloes,Overkleeft, Herman S.,van der Marel, Gijsbert A.,Codée, Jeroen D. C.
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supporting information
p. 8240 - 8244
(2018/05/03)
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- Highly Regioselective Monoacylation of Unprotected Glucopyranoside Using Transient Directing-Protecting Groups
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The regioselective functionalization of monosaccharides is notoriously achieved using metal catalysis, lengthy synthetic strategies requiring protection/deprotection, various enzymes, or other methods that target cis-diols (and thus cannot be used with glucopyranose derivatives), In this paper, we report a new method using selected boronic acids as temporary protecting groups, and describe its application to the regioselective functionalization of methyl α-d-glucopyranoside, the most difficult monosaccharide to functionalize regioselectively. Generally, reactions of glucopyranosides may lead to a plethora of mono- and polyfunctionalized derivatives, yet our method gave the 3-O-acetylated, 2-O-benzoylated, and 2-O-pivaloylated derivatives of methyl α-d-glucopyranoside as major products. We focused on the use of recyclable and green temporary protecting groups (in a one-pot reaction) and on the modulation of the intramolecular hydrogen-bonding network using selected arylboronic acids. A complete scalable procedure leading to a single regioisomer from unprotected methyl α-d-glucopyranoside is presented.
- Rocheleau, Sylvain,Pottel, Joshua,Huski?, Igor,Moitessier, Nicolas
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p. 646 - 656
(2017/02/05)
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- Boronic esters as protective groups in carbohydrate chemistry: processes for acylation, silylation and alkylation of glycoside-derived boronates
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Procedures for selective installation of acyl, silyl ether and para-methoxybenzyl (PMB) ether groups to glycoside substrates have been developed, employing phenylboronic esters as protected intermediates. The sequence of boronic ester formation, functiona
- Mancini, Ross S.,Lee, Jessica B.,Taylor, Mark S.
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p. 132 - 143
(2016/12/27)
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- Cleavage of 4,6- O -benzylidene acetal using sodium hydrogen sulfate monohydrate
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The use of protecting groups is an important protocol in carbohydrate synthesis. Among protecting groups, benzylidene acetals are generally more stable than other acetals; therefore, strong conditions are often required for deprotection. We report the deprotection of 4,6-O-benzylidene derivatives using sodium hydrogen sulfate monohydrate under mild conditions. Georg Thieme Verlag Stuttgart New York.
- Michigami, Kyosuke,Terauchi, Manami,Hayashi, Masahiko
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p. 1519 - 1523
(2013/06/27)
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- Removal of benzylidene acetal and benzyl ether in carbohydrate derivatives using triethylsilane and Pd/C
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Clean deprotection of carbohydrate derivatives containing benzylidene acetals and benzyl ethers was achieved under catalytic transfer hydrogenation conditions by using a combination of triethylsilane and 10% Pd/C in CH 3OH at room temperature. A variety of carbohydrate diol derivatives were prepared from their benzylidene derivatives in excellent yield.
- Santra, Abhishek,Ghosh, Tamashree,Misra, Anup Kumar
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- Enantioselective alkylation of aldehydes using dialkylzincs catalyzed by simple chiral diols derived from naturally occurring monosaccharides
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Enantioselective alkylation of aldehydes was achieved in up to 84% ee using dialkylzincs catalyzed by simple diols derived from naturally occurring monosaccharides.
- Michigami, Kyosuke,Hayashi, Masahiko
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supporting information
p. 4221 - 4225
(2013/06/27)
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- H2SO4-silica-promoted 'on-column' removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups
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H2SO4-silica-promoted removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups from sugar derivatives was accomplished by following an 'on-column' protocol in a virtually waste-free condition.
- Roy, Bimalendu,Verma, Priya,Mukhopadhyay, Balaram
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experimental part
p. 145 - 148
(2011/02/27)
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- Efficient formation and cleavage of benzylidene acetals by sodium hydrogen sulfate supported on silica gel
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NaHSO4SiO2 was used as an efficient heterogeneous catalyst for both the formation and the cleavage of benzylidene acetals. This catalyst is compatible with many functional or protective groups. Under different solvent systems, either the formation or the cleavage of benzylidene acetals was carried out smoothly in excellent yields and with good chemoselectivity. Georg Thieme Verlag Stuttgart.
- Niu, Youhong,Wang, Ning,Cao, Xiaoping,Ye, Xin-Shan
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p. 2116 - 2120
(2008/02/09)
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- Mild and efficient method for the cleavage of benzylidene acetals using HClO4-SiO2 and direct conversion of acetals to acetates
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HClO4-SiO2 has been used successfully for the deprotection of benzylidene acetals and the direct conversion of benzylidene acetals to the corresponding di-O-acetates. The reactions are very fast and yields are excellent.
- Agnihotri, Geetanjali,Misra, Anup Kumar
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p. 3653 - 3658
(2007/10/03)
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- Highly regio- and stereo-selective alkyl substitution with copper reagents for the construction of chiral trifluoromethylated quaternary carbon centres
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A new route for the asymmetric construction of quaternary carbon centres containing a trifluoromethyl group has been established using a highly regio- and stereo-selective SN2′ reaction of organocopper and organocuprate reagents with allylic mesylates 4 and 8.
- Hiraoka, Shuichi,Yamazaki, Takashi,Kitazume, Tomoya
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p. 1497 - 1498
(2007/10/03)
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- A convenient method for highly selective deprotection of benzylidene acetals from sugars
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A new procedure for cleavage of benzylidene acetals from glycopyranosides using tin (II) chloroide is described which does not affect other protecting groups such as benzoyl, acetyl, benzyl, and acetonide.
- Xia, Jie,Hui, Yongzheng
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p. 881 - 886
(2007/10/03)
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- Syntheses and NMR Studies of Pyruvic Acid 4,6-Acetals of some Methyl Hexopyranosides
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The pyruvic acid 4,6-acetals of the methyl glycosides of α- and β-D-glucose, α- and β-D-mannose, and α- and β-D-galactose which correspond to naturally occurring residues in polysaccharides, have been synthesized and their 1H and 13C NMR spectra fully ass
- Jansson, Per-Erik,Lindberg, Johan,Widmalm, Goeran
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p. 711 - 715
(2007/10/02)
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- The Synthesis of Active-Site Directed Inhibitors of Some β-Glucan Hydrolases
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The 2,3-epoxypropyl, 3,4-epoxybutyl and 4,5-epoxypentyl β-glycosides of D-glucose, cellobiose and laminaribiose have been prepared.As well, the 4,5-epoxypentyl β-glycosides of cellotriose, laminaritriose and two other trisaccharides have been synthesized. 3,4-Epoxybutyl β-cellobioside has also been prepared with a 14C-label in the cellobiose residue.
- Rodriguez, Evelyn B.,Stick, Robert V.
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p. 665 - 679
(2007/10/02)
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- The Reaction of Diols with Triphenylphosphine and Di-isopropyl Azodicarboxylate. Part 1. Formation of Cyclic Phosphoranes from 1,3- and 1,4-Diols
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Triphenylphosphine and di-isopropyl azodicarboxylate react with propane-1,3-diol and butane-1,4-diol in tetrahydrofuran at 0 deg C to give cyclic dioxytriphenylphosphoranes that appear to be oligomeric.Under conditions of high-dilution, however, the expected six- and seven-membered-ring phosphoranes are formed.Contrary to a previous report, propane-1,3-diol does not undergo cyclodehydration to give oxetane, but gives instead a pyrazolidine derivative, Substituted, and conformationally restricted, 1,3- and 1,4-diols form the expected six- and seven-membered-ring cyclic phosphoranes without recourse to high-dilution techniques.A 13C n.m.r. method for disthinguishing apical from equatorial phenyl groups in phosphoranes is reported: dialkoxytriphenylphosphoranes bearing an apical phenyl group exhibit much smaller one-bond coupling constants (1JP-C 120 Hz) than those containing only equatorial phenyl groups (1JP-C > 170 Hz).
- von Itzstein, Mark,Jenkins, Ian D.
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p. 437 - 446
(2007/10/02)
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- A New Borylation Method for Alkylbenzene and Polystyrene
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The borylation of alkylbenzenes by Hal2BH (Hal = F, Cl, Br) gives H2 and a mixture of m- and p-alkyl(dihaloboryl)benzenes.In the case of bulky alkyl groups, such as isopropyl, tert-butyl, these are partially split off as R - H and RBHal2.The phenyl groups in polystyrene-divinylbenzene copolymers undergo borylation with Br2BH in a 55percent yield.
- Paetzold, Peter,Hoffmann, Juergen
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p. 3724 - 3733
(2007/10/02)
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