- Experimental and theoretical study of the O3/O4 regioselectivity of glycosylation reactions of glucopyranosyl acceptors
-
The knowledge of the regioselectivity between different hydroxyl groups of glycosyl acceptors is valuable in planning simple strategies for the synthesis of oligosaccharides, minimizing the use of protecting groups. With the aim of obtaining deeper knowle
- Del Vigo, Enrique A.,Stortz, Carlos A.,Marino, Carla
-
-
- Regioselectivity of glycosylation reactions of galactose acceptors: An experimental and theoretical study
-
Regioselective glycosylations allow planning simpler strategies for the synthesis of oligosaccharides, and thus reducing the need of using protecting groups. With the idea of gaining further understanding of such regioselectivity, we analyzed the relative
- Del Vigo, Enrique A.,Stortz, Carlos A.,Marino, Carla
-
supporting information
p. 2982 - 2989
(2020/01/09)
-
- A novel O-fucosylation strategy preactivated by (p-Tol)2SO/Tf2O and its application for the synthesis of Lewis blood group antigen Lewisa
-
Based on a preactivation strategy using (p-Tol)2SO/Tf2O, a new O-fucosylation method with thioglycoside as donor under mild conditions was reported. High yields and excellent α-stereoselectivities of the fucosylation were obtained wi
- Li, Cui-yun,Liu, Guang-jian,Du, Wei,Zhang, Yuan,Xing, Guo-wen
-
supporting information
p. 2109 - 2112
(2017/05/09)
-
- A green and convenient method for regioselective mono and multiple benzoylation of diols and polyols
-
An efficient method for regioselective benzoylation of diols and polyols was developed. The benzoylation is catalyzed by only 0.2 equiv of benzoate anion in acetonitrile with the addition of a stoichiometric amount of benzoic anhydride under very mild condition, leading to high yields. Compared with all other methods, this method shows particular advantage in regioselective multiple benzoylation of polyols, and in avoiding the use of any metal-based catalysts and any amine bases, which is more environment-friendly.
- Zhang, Xiaoling,Ren, Bo,Ge, Jiantao,Pei, Zhichao,Dong, Hai
-
supporting information
p. 1005 - 1010
(2016/02/03)
-
- Tin-mediated regioselective benzylation and allylation of polyols: Applicability of a catalytic approach under solvent-free conditions
-
The first catalytic version of the stannylene-mediated benzylation and allylation of polyols is reported. The methodology is based on a simple solvent-free protocol that significantly advances, in terms of both experimental ease and synthetic scope, the a
- Giordano, Maddalena,Iadonisi, Alfonso
-
p. 213 - 222
(2014/01/17)
-
- A tin-free regioselective radical de-o-benzylation by an intramolecular hydrogen atom transfer on carbohydrate templates
-
Radically selective: A remarkable 1,7-hydrogen atom transfer of a benzylic hydrogen atom to an O-silylmethylene radical initiates a regioselective de-O-benzylation of benzylated saccharides. The reaction terminates by an ionic mechanism and is general for hydroxy benzylated substrates having a variety of functional groups. Copyright
- Attouche, Angie,Urban, Dominique,Beau, Jean-Marie
-
p. 9572 - 9575
(2013/09/23)
-
- Halide promoted organotin-mediated carbohydrate benzylation: Mechanism and application
-
In the present study, the mechanistic origin of the promoted organotin-mediated carbohydrate benzylation by halides was explored by the comparison of the activation ability of halides on benzylation of methyl β-d-galactoside. It was demonstrated that the
- Zhou, Yixuan,Li, Jinyang,Zhan, Yingjie,Pei, Zhichao,Dong, Hai
-
p. 2693 - 2700
(2013/03/28)
-
- Synthesis and glycosidase inhibitory profiles of functionalised morpholines and oxazepanes
-
In this work libraries of morpholines and oxazepanes have been prepared via the reductive amination reaction between dialdehydes, derived from carbohydrates, and a range of amines. In this way, functionalised morpholines and oxazepanes have been prepared
- Burland, Peter A.,Osborn, Helen M.I.,Turkson, Andrea
-
experimental part
p. 5679 - 5692
(2011/10/31)
-
- Some observations on the reductive ring opening of 4,6-O-benzylidene acetals of hexopyranosides with the borane trimethylamine-aluminium chloride reagent
-
Reductive ring openings of 3-O-benzoyl-4,6-O-benzylidene-d-glucopyranosides with BH3·NMe3-AlCl3 are accompanied by side reactions, such as debenzoylation and reduction of the benzoate to benzyl ether. This phenomenon was r
- Daragics, Katalin,Szabó, Pál,Fügedi, Péter
-
experimental part
p. 1633 - 1637
(2011/09/14)
-
- Reductive openings of benzylidene acetals revisited: A mechanistic scheme for regio- and stereoselectivity
-
Despite the importance of regioselective reductive openings of cyclic acetals, mechanistic details are scarce. In this study 4,6-O-benzylidene acetals were used as model compounds for deciphering the mechanism of regioselective openings using a variety of
- Johnsson, Richard,Ohlin, Markus,Ellervik, Ulf
-
supporting information; experimental part
p. 8003 - 8011
(2011/03/18)
-
- Direct selective and controlled protection of multiple hydroxyl groups in polyols via iterative regeneration of stannylene acetals
-
A direct selective protection (O-benzylation) of two or more hydroxyl groups in polyols displaying diverse structural patterns was made possible by the establishment of conditions that enable an efficient turnover for the Bu2Sn group, initially
- Simas, Alessandro B.C.,da Silva, Angelo A.T.,dos Santos Filho, Tarcizio J.,Barroso, Pedro T.W.
-
supporting information; experimental part
p. 2744 - 2746
(2009/09/25)
-
- Direct and convenient method of regioselective benzylation of methyl α-D-glucopyranoside
-
A facile and convenient method for the direct preparation of methyl 2,3,6-tri-O-benzyl-α-D-glucopyranoside (2) by the regioselective benzylation of methyl α-D-glucopyranoside (1) with benzyl bromide in the presence of mild bases K2CO3 and KOH (1:1) withou
- Li, Xiaoliu,Li, Zhiwei,Zhang, Pingzhu,Chen, Hua,Ikegami, Shiro
-
p. 2195 - 2202
(2008/02/05)
-
- SmI2/water/amine mediates cleavage of allyl ether protected alcohols: application in carbohydrate synthesis and mechanistic considerations.
-
[reaction: see text]. SmI2/H2O/amine provides selective cleavage of unsubstituted allyl ethers in good to excellent yields. This method is therefore useful in deprotection of alcohols and carbohydrates.
- Dahlen, Anders,Sundgren, Andreas,Lahmann, Martina,Oscarson, Stefan,Hilmersson, Goeran
-
p. 4085 - 4088
(2007/10/03)
-
- A new method for the deprotection of benzyl ethers or the selective protection of alcohols
-
A new selective method for the deprotection of benzyl ethers situated next to alcohols in the α, β, or γ position is presented which uses either NIS or DIB/I2 as a reagent. After initial formation of a hypoiodite intermediate, the reaction is b
- Madsen, Jacob,Viuf, Christel,Bols, Mikael
-
p. 1140 - 1146
(2007/10/03)
-
- A new intramolecular reaction for the regioselective debenzylation or protection of alcohols
-
Strained benzylidene acetals such as 1 can be prepared with a new intramolecular reaction that allows the selective removal of benzyl protecting groups neighboring free OH groups, without attacking other benzyl groups. The mechanism of this reaction, which is useful for carbohydrate synthesis, probably proceeds via ionic intermediates with neighboring group participation.
- Madsen, Jacob,Bols, Mikael
-
p. 3177 - 3178
(2007/10/03)
-
- REGIOSELECTIVE FORMATION OF DI-O-BENZYL-SUBSTITUTED HEXOPYRANOSIDES VIA STANNYLENE ACETAL INTERMEDIATES
-
The reactions of dibutylstannylene acetals derived from several methyl hexopyranosides with benzyl bromide have been investigated.These reactions occur readily in benzyl bromide at 85 deg C.At reaction times of one to two days, the major products are di-O-benzyl derivatives.In several cases, single di-O-benzyl derivatives are the predominant products: methyl α-D-glucopyranoside and methyl β-D-galactopyranoside gave the 2,6- and 3,6-di-O-benzyl ethers in 82 and 70percent yields, respectively.The species present in these reactions and the reaction pathway are discussed.
- Qin, Huiping,Grindley, T. Bruce
-
p. 475 - 490
(2007/10/02)
-
- Regioselective Monoalkylation of Non-protected Glycopyranosides by the Dibutyltin Oxide Method
-
Regioselective monoalkylation of some pento- and hexopyranosides (Me β-L-Ara, Ph α-L-Ara, Me α-D-Xyl, Me β-D-Xyl, Me α-D-Glc, Me β-D-Glc, Me α-D-Gal, Me β-D-Gal, and Me α-D-Man) was examined by using the dibutyltin oxide method without protecting the hydroxyl groups.By this method, alkylation proceeds more or less in the same fashion as reported for acylation (through the formation of cyclic tin intermediates) and selectively activates an equatorial hydroxyl group which has an oxygenated function (OH or OMe) in a cis relationship at an adjacent position, even in the presence of a more reactive primary hydroxyl group.However, in some instances the position of activation is different.Various monoalkyl ethers thus prepared were identified by analyses of their carbon-13 nuclear magnetic resonance spectra.Keywords-regioselective monoalkylation; glycopyranoside; dibutyltin oxide; cis-vicinal glycol; benzylation; allylation; methoxymethylation; methylation;13C-NMR
- Haque, Mohammed Ekramul,Kikuchi, Tohru,Yoshimoto, Kimihiro,Tsuda, Yoshisuke
-
p. 2243 - 2255
(2007/10/02)
-
- ENTWICKLUNG EINES SYNTHESEBLOCKS DER 3-O-β-D-GALACTOPYRANOSYL-D-GALACTOPYRANOSE
-
In the presence of trimethylsilyl triflate, 1,2,3,4,6-penta-O-acetyl-β-D-galactopyranose reacted with benzyl 4-O-acetyl-2,6-di-O-benzyl-β-D-galactopyranoside to give benzyl 2,6-di-O-benzyl-3-O-β-D-galactopyranosyl-β-D-galactopyranoside further converted i
- Paulsen, Hans,Hasenkamp, Thomas,Paal, Michael
-
-
- Partial Benzylation of Methyl α- and β-D-Galactopyranosides
-
Partial benzylation of methyl α-D-galactopyranoside with benzyl chloride and LiOH selectively gave the 2,3,6-tribenzyl ether, while that using KOH or RbOH gave the 2,4,6-isomer as the main product.Methyl β-D-galactopyranoside afforded the 3,4,6-tribenzyl ether predominantly, irrespective of the alkali used.
- Morishima, Naohiko,Koto, Shinkiti,Oshima, Megumi,Sugimoto, Akiko,Zen, Shonosuke
-
p. 2849 - 2850
(2007/10/02)
-
- REGIOSELECTIVE ALKYLATION via TRIALKYLSTANNYLATION: METHYL α-D-GLUCOPYRANOSIDE
-
Partial stannylation of methyl α-D-glucopyranoside with (Bu3Sn)2O, and subsequent alkylation with benzyl bromide, allyl bromide, and trityl chloride, afforded the 2,6-disubstituted derivative as one of major products in each case.
- Ogawa, Tomoya,Takahashi, Yukio,Matsui, Masanao
-
p. 207 - 216
(2007/10/02)
-
- PROPERTIES OF (13)C-N.M.R. SPECTRA OF O-(1-CARBOXYETHYLIDENE) DERIVATIVES OF METHYL β-D-GALACTOPYRANOSIDE: MODELS FOR DETERMINATION OF PYRUVIC ACID ACETAL STRUCTURES IN POLYSACCHARIDES
-
(13)C-N.m.r. spectra were recorded of compounds containing O-(1-carboxyethylidene) groups linked to galactopyranose and fucopyranose derivatives.These compounds are useful as aids in determination of the positions and configurations of pyruvic acid acetal substituents in polysaccharides.Chemical shifts of non-protonated acetal carbons depend on whether the acetal ring is 5-membered (δc 107-109.5) or 6-membered (δc 100.5-102.4).The C-3 signals of 3,4-(1-carboxyethylidene) acetals are typical, being at ca. δc 81 and in the case of the barium salt of the methyl β-D-galactopyranoside derivative.The exact value depends on the configuration, whether it is an in 6 (δc 81.1) or 5 (δc 80.4).The CH3 signals of proton-n.m.r. spectra are also diagnostically useful, falling at δ 1.97 and 2.07 respectively. (The foregoing shift-values are pH dependent).The pyruvylated galactan from the snail, Pomacea lineata, was shown to contain some residues that could be assigned a structure corresponding, in the position of acetal substitution and acetal configuration, to structure 6.Compound 6 (barium salt) is of interest as its (13)C-n.m.r. spectrum lacks non-protonated carbonyl and acetal carbon resonances, when obtained by the usual procedures.While this is principally because of long T1 values, the non-protonated acetal carbon signals are comparatively broad, possibly through slow conformational interchange.In the case of the carbonyl resonance, the lack of sensitivity is because of a low n.O.e. value of 1.4, approximately one half that of other carbon atoms in the molecule.
- Gorin, Philip A. J.,Mazurek, Mytosk,Duarte, Helena S.,Iacomini, Marcello,Duarte, Jose H.
-
-