- Method for high selectivity acylation protection on hydroxyl through catalyzing by stannous chloride
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The invention belongs to the technical field of chemical synthesis of fine chemicals and sugar, and discloses a method for high selectivity acylation protection on hydroxyl through catalyzing by stannous chloride. The method comprises the steps of dissolv
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Paragraph 0056-0067
(2020/09/16)
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- Stannous chloride as a low toxicity and extremely cheap catalyst for regio-/site-selective acylation with unusually broad substrate scope
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This work reports stannous chloride (SnCl2)-catalyzed regio-/site-selective acylation with unusually broad substrate scope. In addition to 1,2- and 1,3-diols and glycosides containing cis-vicinal diol, the substrate scope also includes glycosides without cis-vicinal diol. For such a substrate scope, usually, only methods using stoichiometric amounts of organotin reagents can lead to the same protection pattern with high selectivities and highly isolated yields (84-97% in most cases). Therefore, SnCl2, as a low toxicity and extremely cheap reagent, should be the best catalyst for regio-/site-selective acylation compared with any previously reported reagents. This journal is
- Dong, Hai,Feng, Guang-Jing,Luo, Tao,Lv, Jian,Yu, Jian-Cheng
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supporting information
p. 6936 - 6942
(2020/11/09)
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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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- 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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- Highly Efficient Selective Benzylation of Carbohydrates Catalyzed by Iron(III) with Silver Oxide and Bromide Anion as Co-catalysts
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A highly efficient, green, and regioselective method for the benzylation of diols and polyols was developed. With the use of Ag2O (0.6 equiv.) and tetrabutylammonium bromide (0.1 equiv.) as co-catalysts, the iron(III)-catalyzed benzylation reaction proceeded to completion at 40 °C within 2–3 h and gave the products in high yields with high regioselectivities. A mechanism involving the principle of enhanced basicity of Ag2O by soft anions was proposed.
- Ren, Bo,Lv, Jian,Zhang, Yu,Tian, Jun,Dong, Hai
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p. 950 - 953
(2017/03/27)
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- A green and convenient method for regioselective mono and multiple benzoylation of diols and polyols
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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
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p. 1005 - 1010
(2016/02/03)
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- Site-Selective Acylations with Tailor-Made Catalysts
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The acylation of alcohols catalyzed by N,N-dimethylamino pyridine (DMAP) is, despite its widespread use, sometimes confronted with substrate-specific problems: For example, target compounds with multiple hydroxy groups may show insufficient selectivity for one hydroxyl, and the resulting product mixtures are hardly separable. Here we describe a concept that aims at tailor-made catalysts for the site-specific acylation. To this end, we introduce a catalyst library where each entry is constructed by connecting a variable and readily tuned peptide scaffold with a catalytically active unit based on DMAP. For selected examples, we demonstrate how library screening leads to the identification of optimized catalysts, and the substrates of interest can be converted with a markedly enhanced site-selectivity compared with only DMAP. Furthermore, substrate-optimized catalysts of this type can be used to selectively convert "their" substrate in the presence of structurally similar compounds, an important requisite for reactions with mixtures of substances. Substrate-optimized catalysts: Site- selective acylations were achieved using substrate-optimized catalysts (see scheme) as identified from a library screening. The catalysts are composed of low-molecular-weight peptides that are readily tuned through variation of the amino acid sequence, and one amino acid was connected to DMAP to ensure catalytic activity. These substrate-optimized catalysts were also applied to selectively convert one substrate in the presence of a structurally similar compound.
- Huber, Florian,Kirsch, Stefan F.
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supporting information
p. 5914 - 5918
(2016/04/26)
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- Regioselective acylation of diols and triols: The cyanide effect
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Central topics of carbohydrate chemistry embrace structural modifications of carbohydrates and oligosaccharide synthesis. Both require regioselectively protected building blocks that are mainly available via indirect multistep procedures. Hence, direct pr
- Peng, Peng,Linseis, Michael,Winter, Rainer F.,Schmidt, Richard R.
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supporting information
p. 6002 - 6009
(2016/06/09)
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- Investigation of benzoyloximes as benzoylating reagents: Benzoyl-Oxyma as a selective benzoylating reagent
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Hydroxybenzotriazole (HOBt) and HOBt-derived reagents have been classified as Class I explosives, with restrictions on their transportation and storage. We explored a range of benzoylated oxime-based reagents as alternatives to benzoyloxybenzotriazole (BBTZ) for the selective benzoylation of carbohydrate polyols. Benzoylated oximes derived from 2-hydroximino-malononitrile, ethyl 2-hydroximino-2-cyanoacetate (Oxyma), and tert-butyl 2-hydroximino-2-cyanoacetate were most effective for benzoylation of a simple primary alcohol, with yields approaching that obtained for BBTZ. When applied to carbohydrate diols, the most effective reagent was identified as benzoyl-Oxyma. Benzoyl-Oxyma is a highly crystalline, readily prepared alternative to BBTZ, useful in the selective benzoylation of carbohydrate polyols.
- Burugupalli, Satvika,Shah, Sayali,Van Der Peet, Phillip L.,Arora, Seep,White, Jonathan M.,Williams, Spencer J.
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- Regioselective Benzoylation of 4,6-O-Benzylidene Acetals of Glycopyranosides in the Presence of Transition Metals
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Benzoylation of 4,6-O-benzylidene acetals of glycopyranosides by benzoic anhydride in acetonitrile in the presence of Cu(CF3COO)2 as a promoter gave 2-benzoates for α-D-glucopyranosides and α-D-mannopyranosides and 3-benzoates for β-D-galactopyranosides in good yields with high regioselectivity. Benzoylation of 4,6-O-benzylidene acetals of glycopyranosides of D-galactose and D-mannose by benzoyl chloride in the presence of MoO2(acac)2 as a catalyst in all studied cases led to regioselective 3-substitution.
- Evtushenko, Evgeny V.
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- Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins' Bicyclic Sugar Moiety
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2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.
- Cachatra, Vasco,Almeida, Andreia,Sardinha, Jo?o,Lucas, Susana D.,Gomes, Ana,Vaz, Pedro D.,Florêncio, M. Helena,Nunes, Rafael,Vila-Vi?osa, Diogo,Calhorda, Maria José,Rauter, Amélia P.
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p. 5622 - 5625
(2015/12/01)
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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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- Recognition and site-selective transformation of monosaccharides by using copper(II) catalysis
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We demonstrate copper(II)-catalyzed acylation and tosylation of monosaccharides. Various carbohydrate derivatives, including glucopyranosides and ribofuranosides, are obtained in high yields and regioselectivities. Using this versatile strategy, the site
- Chen, I-Hon,Kou, Kevin G. M.,Le, Diane N.,Rathbun, Colin M.,Dong, Vy M.
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supporting information
p. 5013 - 5018
(2014/05/06)
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- Modular hydroxyamide and thioamide pyranoside-based ligand library from the sugar pool: New class of ligands for asymmetric transfer hydrogenation of ketones
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A large library of pyranoside-based hydroxyamide and thioamide ligands has been synthesized for asymmetric transfer hydrogenation in an attempt to expand the scope of the substrates to cover a broader range of challenging heteroaromatic and aryl/fluoroalkyl ketones. These ligands have the advantage that they are prepared from commercial D-glucose, D-glucosamine and α-amino acids, inexpensive natural chiral feedstocks. By carefully selecting the ligand components (substituents/configurations at the amide/thioamide moiety, the position of amide/thioamide group and the configuration at C-2), we found that pyranoside-based thioamide ligands provided excellent enantioselectivities (in the best cases, ees of >99% were achieved) in a broad range of ketones, including the less studied heteroaromatics and challenging aryl/fluoroalkyls. Note that both enantiomers of the reduction products can be obtained with excellent enantioselectivities by simply changing the absolute configuration of the thioamide substituent.
- Coll, Mercè,Pàmies, Oscar,Diéguez, Montserrat
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supporting information
p. 2293 - 2302
(2014/07/21)
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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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- TMSOTf-catalyzed silylation: Streamlined regioselective one-pot protection and acetylation of carbohydrates
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A highly efficient TMSOTf-catalyzed HMDS silylation of sugars, which can easily be integrated with subsequent reactions in one-pot fashion, has been developed. Its usefulness was demonstrated by applications to streamlined regioselective one-pot protection and nonenzymatic acetylation of unprotected sugars. Monosaccharide and trehalose building blocks with orthogonally well-differentiated hydroxy groups were efficiently prepared starting with free sugars in one-pot fashion without the need for prior per-O-silylation. Regioselectively protected and acetylated building blocks were prepared directly from unprotected sugars in a one-pot manner involving up to five TMSOTf-catalyzed reactions, including a new TMSOTf-catalyzed silylation of carbohydrates. Copyright
- Joseph, A. Abragam,Verma, Ved Prakash,Liu, Xin-Yi,Wu, Chia-Hui,Dhurandhare, Vijay M.,Wang, Cheng-Chung
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p. 744 - 753
(2012/03/11)
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- Noteworthy observations accompanying synthesis of the apoptolidin disaccharide
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A stereoselective synthesis of the apoptolidin disaccharide is reported. The key chemistry features a new transformation utilizing a highly selective tetramethylalkoxyalanate[v]-directed syn-methylation of a vinylogous ester, isolation of a hydrate of a 2-keto sugar, an eco-friendly radical cleavage of a bromomethyl group, and an efficient preparation of a fluorodisaccharide via the use of XtalFluor-E.
- Srinivasarao, Madduri,Park, Taesik,Chen, Yuzhong,Fuchs, Philip L.
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p. 5858 - 5860
(2011/07/08)
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- Selective mono-acylation of 1,2- and 1,3-diols using (α,α- difluoroalkyl)amines
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In the reaction of N,N-diethyl-α,α-difluorobenzylamine (DFBA) with 1,2- or 1,3-diols, selective mono-benzoylation occurs to afford mono-esters of the diols in good yield. The reaction is completed under mild conditions in a short reaction time. Further, prim-, sec-, and tert-diols and catechol can be converted to the corresponding mono-benzoates. DFBA is used for the protection of the hydroxy group in sugars. The selective mono-nicotinylation, formylation and pivaloylation of diols are also performed by using the corresponding difluoroalkylamines.
- Wakita, Natsumi,Hara, Shoji
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experimental part
p. 7939 - 7945
(2010/10/19)
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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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- Synthesis and structural analysis of a series of d-glucose derivatives as low molecular weight gelators
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Low molecular weight gelators are an interesting new type of compounds that are important in supramolecular chemistry and advanced materials. Previously, we had synthesized several acyl derivatives of methyl 4,6-O-benzylidene-α-d-glucopyranoside and found
- Cheuk, Sherwin,Stevens, Edwin D.,Wang, Guijun
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experimental part
p. 417 - 425
(2009/05/27)
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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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- Regioselective esterification of vicinal diols on monosaccharide derivatives via Mitsunobu reactions
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(Chemical Equation Presented) We have carried out a series of esterification reactions of secondary alcohols derived from D-glucose, D-mannose, and D-galaclose via the Mitsunobu reaction. The benzoylation reaction of vicinal diols derived from monosacchar
- Wang, Guijun,Ella-Menye, Jean-Rene,St. Martin, Michael,Yang, Hao,Williams, Kristopher
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supporting information; experimental part
p. 4203 - 4206
(2009/05/30)
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- Stereoselective synthesis of (-)-ara-cyclohexenyl-adenine
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A stereoselective synthesis leading to (-)-ara-cyclohexenyl-adenine is described. The synthesis starts from methyl-α-d-glucopyranose and involves an isomerization step, selective protection/deprotection chemistry, a Ferrier rearrangement and a Mitsunobu r
- Horváth, András,Ruttens, Bart,Herdewijn, Piet
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p. 3621 - 3623
(2008/02/02)
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- Galactose-phosphonates as mimetics of the sialyltransfer by trypanosomal sialidases
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In an attempt to find competitive inhibitors of the trans-sialidase of the pathogen Trypanosoma cruzi, we have synthesized conjugates of carbocyclic sialylmimetics (e.g., cyclohexenephosphonates) and galactose derivatives. A trans-sialidase inhibition ass
- Busse, Heike,Hakoda, Mitsuru,Stanley, Matthew,Streicher, Hansjoerg
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p. 159 - 194
(2008/02/11)
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- 2-(Prenyloxymethyl)benzoyl (POMB) group: a new temporary protecting group removable by intramolecular cyclization
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2-(Prenyloxymethyl)benzoates can be prepared from alcohols and readily available 2-(prenyloxymethyl)benzoic acid by standard acylation techniques or by Mitsunobu reaction with inversion of configuration. The POMB group can be cleaved first by oxidative removal of the prenyl group with DDQ followed by lactonization with expulsion of the alcohol catalyzed by Yb(OTf)3. These reaction conditions are compatible with the presence of a large number of common protecting groups.
- Vatèle, Jean-Michel
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p. 10921 - 10929
(2008/02/12)
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- Scalable synthesis of a mycosamine donor. Overcoming difficult reactivity in allose systems
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Mycosamine is a dideoxyaminosugar found in medicinally relevant macrolides, including amphotericin B and nystatin. Herein we report a reliable, high yielding, scalable synthesis of a mycosamine donor. A major goal of our approach was to minimize purificat
- Manthorpe, Jeffrey M.,Szpilman, Alex M.,Carreira, Erick M.
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p. 3380 - 3388
(2007/10/03)
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- 2-(Prenyloxymethyl)benzoyl (POMB) as a new temporary protecting group for alcohols
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The 2-(prenyloxymethyl)benzoyl (POMB) group was introduced in high yields to hydroxyl functions using the crystalline reagent, 2-(prenyloxymethyl)benzoic acid, in the presence of dicyclohexylcarbodiimide (DCC) and 4- dimethylaminopyridine (DMAP). 2-(Prenyloxymethyl)benzoic acid is readily available, in two steps, from phthalide in 65% overall yield. The POMB group can be cleaved, in two steps, by treatment with 2,3-dichloro-5,6-dicyanoquinone (DDQ) followed by intramolecular lactonisation of the resulting hydroxy ester induced by a catalytic amount of Yb(OTf)3·H2O. The reaction conditions are compatible with the presence of a number of protecting groups such as isopropylidene, benzyl, acetyl, chloroacetyl, benzoyl, levulinoyl, Fmoc and Boc groups.
- Vatèle, Jean-Michel
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p. 2299 - 2301
(2007/10/03)
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- Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols
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Synthesis of 10-membered bislactones by PCC oxidation of methyl 2,6-di-O-pivaloyl-α-D-glucopyranoside and methyl 4,6-O-benzylidene- α-D-glucopyranoside is described, with emphasis on their structure elucidation using the information gained by combination
- Rauter, Amelia P.,Piedade, Fatima,Almeida, Tania,Ramalho, Rui,Ferreira, Maria J.,Resende, Ricardo,Amado, Joana,Pereira, Helena,Justino, Jorge,Neves, Ana,Silva, Filipa V. M.,Canda, Tana
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p. 1889 - 1897
(2007/10/03)
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- Nickel(II) chloride-mediated regioselective benzylation and benzoylation of diequatorial vicinal diols
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Ni(II)-chelates of monosaccharide vicinal diols were found to be useful intermediates in regioselective monobenzylation and monobenzoylation. It was observed that the substitution occurs exclusively at the position adjacent to the axially oriented substit
- Gangadharmath, Umesh B.,Demchenko, Alexei V.
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p. 2191 - 2193
(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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- Tin-mediated equilibration of the benzoate esters of methyl 4,6-O- benzylidene-α-D-glucopyranoside
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The selective dibutyltin oxide-mediated benzoylation of methyl 4,6-O- benzylidene-α-D-glucopyranoside at position 2 is not a post-acylation phenomenon as is the case with the equivalent benzoylation of phenylethyleneglycol. 1H NMR temperature s
- Bredenkamp, Martin W.,Spies, Hendrik S. C.
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p. 543 - 546
(2007/10/03)
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- Chemo- and stereoselective monobenzoylation of 1,2-diols catalyzed by organotin compounds
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A new facile method for monoacylation of diols has been developed. A variety of cyclic and acyclic diols, in particular 1,2-diols, were selectively monobenzoylated in good yields by the reaction with benzoyl chloride in the presence of a catalytic amount of dimethyltin dichloride and inorganic bases such as potassium carbonate. Furthermore, the method was successfully applied to a kinetic resolution of racemic 1-phenyl-1,2- ethanediol using a chiral organotin catalyst. The ee was dependent on the kind of base, water as an additive, and the reaction temperature.
- Iwasaki, Fumiaki,Maki, Toshihide,Onomura, Osamu,Nakashima, Waka,Matsumura, Yoshihiro
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p. 996 - 1002
(2007/10/03)
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- Synthesis and nmr characterisation of methyl mono- and DI-0-α-L-rhamnopyranosyl-α-d-glucopyranosiduronic acids
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The synthesis and NMR characterisation of methyl mono- and di-O-α-L-rhamnopyranosyl-α-D-glucopyranosiduronic acids 1-6 are described. Two commercial starting products were used: methyl α-D-glucopyranoside 7 for the preparation of 1 and 2, and methyl (R)-4,6-O-benzylidene-α-D-glucopyranoside 8 for 3-6. Oxidation reaction of the hydroxymethyl group of glucose to a carboxylic acid group was performed by sodium hypochlorite 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated procedure after the coupling reaction. Glycosylation was carried out using the trichloroacetimidate approach with trimethylsilyl trifluoromethanesulfonate (TMSOTf) as promoter, resulting in a completely stereoselective formation of the a glycosyl linkage.
- Battistelli, Chiara Laura,De Castro, Cristina,Iadonisi, Alfonso,Lanzetta, Rosa,Mangoni, Lorenzo,Parrilli, Michelangelo
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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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- Synthesis of benzoyl and dodecanoyl derivatives from protected carbohydrates under focused microwave irradiation
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A microwave assisted phase transfer transesterification in basic medium with methyl benzoate was studied for several carbohydrates. Small amounts of DMF were necessary to provide good yields (96-76%) within 15 minutes. This method was extended to the synt
- Limousin, Corinne,Cleophax, Jeannine,Loupy, Andre,Petit, Alain
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p. 13567 - 13578
(2007/10/03)
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- Highly stereoselective route to aldol products incorporating fluorine containing methyl groups starting from a single D-glucose-derived intermediate
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Chiral aldol structures with fluorine modifications on a methyl group have been realized by utilization of the relatively rigid cyclic intermediates from the very common chiral pool compound, D-glucose, leading to attainment of the high diastereoselectivi
- Yamazaki, Takashi,Hiraoka, Shuichi,Kitazume, Tomoya
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p. 1157 - 1160
(2007/10/03)
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- Chiral liquid crystalline compounds from D-(+)-glucose
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D-(+)-Glucose was used as a starting material to prepare four potentially useful chiral liquid crystalline molecules 2, 3, 4 and 5 having multiple chiral centers in their rigid cores. It is clear that 2 indeed incorporates properties essential for ferroelectric liquid crystals, i.e., a chiral smectic C phase with an induced spontaneous polarization of about 23 nC/cm2. Compound 3, on the other hand, shows only a nematic phase, while 4 merely shows a sharp melting point and 5 is an oil.
- Ho,Ho, Wai Ming,Wong,Wong, Henry N. C.,Navailles,Navailles, Laurence,Destrade,Destrade, Christian,Nguyen,Nguyen, Huu Tinh,Isaert,Isaert, Noel
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p. 7373 - 7388
(2007/10/02)
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- On the selectivity of stannylene-mediated alkylation and esterification of methyl 4,6-O-benzylidene α-D-glucopyranoside
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Keywords: Methyl 4,6-O-benzylidene-α-D-glucopyranoside; Regiospecificity; Alkylation; Esterification; Stannylene
- Jenkins, David J.,Potter, Barry V. L.
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p. 145 - 150
(2007/10/02)
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- SELECTIVE LIPASE-CATALYZED ACYLATION OF 4,6-O-BENZYLIDENE-D-GLUCOPYRANOSIDES TO SYNTHETICALLY USEFUL ESTERS
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Simple and regioselective lipase-catalyzed acylation of compounds 1 and 4 with synthetically useful esters such as benzoates, chloroacetates, pivaloates and levulinates is described.
- Panza, Luigi,Brasca, Sara,Riva, Sergio,Russo, Giovanni
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p. 931 - 932
(2007/10/02)
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- Regioselective acylation of carbohydrates with 1-acyloxy-1H-benzotriazoles
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Acylation of representative carbohydrate derivatives was accomplished with in situ generated 1-acyloxy-1H-benzotriazoles. The observed high regioselectivity, mild reaction conditions and convenient work-up make the presented one-pot procedure generally applicable and more advantageous than acylations with previously introduced reagents, including N-acylimidazoles.
- Pelyvas,Lindhorst,Streicher,Thiem
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p. 1015 - 1018
(2007/10/02)
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- PREPARATION AND DIELS-ALDER REACTIONS OF A PYRANOID VINYL GLYCAL: MODEL STUDIES FOR ANTHRAQUINONE AGLYCONE AND CARBOHYDRATE SYNTHESES
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The preparation of a conjugated pyranoid vinyl glycal is reported, along with several of its thermal cycloaddition reactions with a variety of dienophiles.Applications to the anthraquinone antitumor agents are discussed.
- Lipshutz, Bruce H.,Nguyen, Sam L.,Elworthy, Todd R.
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p. 3355 - 3364
(2007/10/02)
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- Arylazo-glycenosides. Part 8. Synthesis and Reactions of Some 2- and 3-Arylazo-derivatives of Methyl 4,6-O-Benzylidene-2,3-dideoxy-D-threo-hex-2-enopyranosides
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Preparations are described of the α- and β-anomers of methyl 4,6-O-benzylidene-2,3-dideoxy-2-phenylazo-D-threo-hex-2-enopyranoside and of methyl 4,6-O-benzyliden-2,3-dideoxy-3-phenylazo-α-D-threo-hex-2-enopyranoside using D-galactose as the initial materi
- Dang, Neeta,Munasinghe, Ranjith N.,Overend, W. George
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p. 257 - 264
(2007/10/02)
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- REGIOSELECTIVE O-DEACYLATION OF FULLY ACYLATED GLYCOSIDES AND 1,2-O-ISOPORPYLIDENEALDOFURANOSE DERIVATIVES WITH HYDRAZINE HYDRATE
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On hydrazinolyis in 1:4 acetic acid-pyridine, and in pyridine, partisl O-deacylation of fully acylated methyl glycosides and some other glycosyl compounds ( 23 compounds ) was found to be induced, to give, in good yields, products bearing one free hydroxy
- Ishido, Yoshiharu,Sakairi, Nobuo,Sekiya, Masao,Nakazaki, Nobuo
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