- 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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- Acceleration and deceleration factors on the hydrolysis reaction of 4,6-O-benzylidene acetal group
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The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS? were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both Ea/ΔH? and A/ΔS? were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.
- Maki, Yuta,Kajihara, Yasuhiro,Nomura, Kota,Okamoto, Ryo,Izumi, Masayuki,Mizutani, Yasuhisa
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p. 15849 - 15856
(2021/01/18)
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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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- 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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- Ceric ammonium nitrate/acetic anhydride: A tunable system for the O-acetylation and mononitration of diversely protected carbohydrates
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Esterification of a wide range of partially protected carbohydrate derivatives was achieved using acetic anhydride and a catalytic amount of ceric ammonium nitrate (CAN). Compatibility with the commonly used protecting groups was demonstrated, with the es
- Seepersaud, Mohindra,Seecharan, Savita,Lalgee, Lorale J.,Jalsa, Nigel Kevin
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supporting information
p. 853 - 871
(2017/04/27)
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- Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids
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Direct oxidation of the 4,6-O-benzylidene acetal protecting group to C-6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3-NaIO4-mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six-carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.
- Banerjee, Amit,Senthilkumar, Soundararasu,Baskaran, Sundarababu
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supporting information
p. 902 - 906
(2016/01/16)
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- Three Solvent-Free Catalytic Approaches to the Acetal Functionalization of Carbohydrates and Their Applicability to One-Pot Generation of Orthogonally Protected Building Blocks
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Three alternative protocols were developed to carry out the selective installation of acetal groups on carbohydrates and polyols under mildly acidic, solvent-free conditions. One protocol is based on a diol/aldehyde condensation at room temperature, with an acetolysis process serving for the activation of the carbonyl component. A second approach is based on an orthoester-mediated activation of the carbonyl component at high temperature. The third protocol is instead entailing a transacetalation mechanism. Combination of these methods allows a wide set of acetal-protected building blocks to be accessed in short times under very simple experimental conditions working under air. The scope of the latter two approaches was also extended to unusual one-pot synthetic sequences leading to concomitant Fischer glycosidation/acetal protection of reducing sugars.
- Traboni, Serena,Bedini, Emiliano,Giordano, Maddalena,Iadonisi, Alfonso
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p. 3562 - 3572
(2016/01/25)
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- 2,4,6-Trichloro-1,3,5-triazine (TCT) mediated one-pot sequential functionalisation of glycosides for the generation of orthogonally protected monosaccharide building blocks
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Orthogonally protected monosaccharide building blocks have been prepared using TCT in a one-pot multicomponent transformation. The process involves successive steps of arylidene acetalation, esterification and regioselective reductive acetal cleavage. High regioselectivity, scope for using a broad range of substrates, functional group tolerance, mild reaction conditions, easy handling process and wide application range are a few advantages of the current process.
- Tatina, Madhubabu,Yousuf, Syed Khalid,Mukherjee, Debaraj
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supporting information; experimental part
p. 5357 - 5360
(2012/07/30)
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- Exciton chirality method in vibrational circular dichroism
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The interaction of two IR chromophores yields a strong vibrational circular dichroism couplet whose sign reflects the absolute configuration of the molecule. We present a method to determine absolute configuration of a chiral molecule based on this couplet without need of theoretical calculation. Not only can this method analyze various molecules whose absolute configuration is difficult to determine by other spectroscopic methods, but also it can significantly enhance VCD signals.
- Taniguchi, Tohru,Monde, Kenji
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supporting information; scheme or table
p. 3695 - 3698
(2012/04/11)
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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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supporting information; scheme or table
p. 5370 - 5372
(2012/06/18)
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- Tandem one-pot acetalation-acetylation for direct access to differentially protected thioglycosides and O-glycosides with p-toluenesulfonic acid
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A new tandem one-pot acetalation-acetylation procedure is reported which streamlines routine protecting-group manipulation of carbohydrate molecules in production of differentially protected O- and thioglycosides. This new procedure eliminates the use of
- Mong, Kwok-Kong Tony,Chao, Chin-Sheng,Chen, Min-Chun,Lin, Chun-Wei
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body text
p. 603 - 606
(2009/07/01)
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- Fe2(SO4)3·xH2O-catalyzed per-O-acetylation of sugars compatible with acid-labile protecting groups adopted in carbohydrate chemistry
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Fully acetylated saccharides are inexpensive and very useful starting materials for the synthesis of many naturally occurring glycosides, oligosaccharides, and glycoconjugates. Ferric sulfate hydrate (Fe2(SO4)3·xH2O) was found to be a valuable Lewis acid promoter in the per-O-acetylation reaction of saccharides with acetic anhydride in 100% of conversion rate and 88-99% yields. Interestingly, the procedure is perfectly compatible with the presence of a variety of acid-labile protecting groups, such as isopropylidene, benzylidene, trityl, and TBDMS groups. The reactions were simply performed by stirring the mixture of a sugar with a slight excessive acetic anhydride in the presence of 2.0 mol % of Fe2(SO4)3·xH2O at rt and the pure products were obtained by a simple dilution of the reaction mixture with dichloromethane and washings with aqueous Na2CO3.
- Shi, Lei,Zhang, Guisheng,Pan, Feng
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p. 2572 - 2575
(2008/09/19)
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- Synthesis of S-linked carbohydrate analogues via a Ferrier reaction
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In this work, the synthetic utility of the Ferrier reaction to access S-linked disaccharides and S-linked glycoamino acids has been probed. Significantly, entry to a range of 1,4- and 1,6-S-linked disaccharides has been achieved using glycals derived from glucose and galactose, and sulfur containing coupling partners derived from methyl α-d-glucopyranoside. Access to S-linked glycoamino acids and glycopeptides has also been achieved using protected cysteine and homocysteine coupling partners within the Ferrier reaction. Functionalisation of the Ferrier products, for example, via dihydroxylation using OsO4 or amino acid coupling, and deprotection of the targets have also been achieved. In this way, entry to materials of interest as mimics of biologically interesting disaccharides and glycopeptides has been realised, including targets derived from rare sugars such as talopyranose and gulopyranose.
- Ellis, David,Norman, Sarah E.,Osborn, Helen M.I.
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p. 2832 - 2854
(2008/09/19)
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- Indium triflate catalyzed peracetylation of carbohydrates
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Peracetylation is a very common protection strategy that is widely implemented in carbohydrate synthesis. Here, a method for the peracetylation of carbohydrates using catalytic In(OTf)3 in neat acetic anhydride is reported. In(OTf)3 has low toxicity and is mild and water tolerant, and the reactions are high yielding and efficient. Details regarding the scope and mechanism of the reaction are briefly discussed.
- Bizier, Nicholas P.,Atkins, Shannon R.,Helland, Luke C.,Colvin, Shane F.,Twitchell, Joseph R.,Cloninger, Mary J.
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p. 1814 - 1818
(2008/12/21)
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- Synthesis and biophysical characterization of G-rich oligonucleotides conjugated with sugar-phosphate tails
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A number of 5′-and 3′-glycoconjugates of the oligonucleotide 5′d(TGGGAG)3′ have been synthesized, exploiting fully automated, online phosphoramidite-based solid phase strategy, as potential anti-HIV-1 agents. The thermodynamic stability of the resulting quadruplexes has been investigated by thermal denaturation studies, via a detailed CD Q1 analysis. Copyright Taylor & Francis Group, LLC.
- D'Onofrio,Erra,Di Fabio,Iadonisi,Petraccone,De Napoli,Barone,Balzarini,Giancola,Montesarchio
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p. 1225 - 1229
(2008/09/20)
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- An efficient stereoselective dihydroxylation of glycals using a bimetallic system, RuCl3/CeCl3/NaIO4
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A catalytic dihydroxylation reaction on glycals has been developed using a bimetallic oxidizing system to furnish sugar 1,2-diols in a highly setroselective manner.
- Tiwari, Pallavi,Misra, Anup Kumar
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p. 2911 - 2913
(2007/10/03)
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- InCl3 as a powerful catalyst for the acetylation of carbohydrate alcohols under microwave irradiation
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Indium(III) chloride catalyzed microwave assisted acetylation of different carbohydrates is an efficient synthesis of per-O-acetyl derivatives and provides the products in good to excellent yields.
- Das, Saibal Kumar,Reddy, K. Anantha,Krovvidi, V. L. Narasimha Rao,Mukkanti
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p. 1387 - 1392
(2007/10/03)
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- One-pot acetalation-acetylation of sugar derivatives employing perchloric acid immobilised on silica
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Perchloric acid immobilised on silica gel has been used as an efficient promoter for per-O-acetylation, and acetalation and subsequent O-acetylation of glycosides and thioglycosides in one-pot using stoichiometric reagents.
- Mukhopadhyay, Balaram,Russell, David A.,Field, Robert A.
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p. 1075 - 1080
(2007/10/03)
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- Mild and efficient method for the cleavage of benzylidene acetals by using erbium (III) triflate
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Er(OTf)3 is proposed as new efficient Lewis acid catalyst in a mild deprotection protocol of benzylidene derivatives. In a modified procedure, where acetic anhydride is used as the reaction solvent, the simultaneous cleavage of the benzylidene acetal and the peracetylation of the substrates is obtained in quantitative yields and very short reaction times. The Royal Society of Chemistry 2005.
- Procopio, Antonio,Dalpozzo, Renato,De Nino, Antonio,Maiuolo, Loredana,Nardi, Monica,Romeo, Giovanni
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p. 4129 - 4133
(2007/10/03)
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- A rapid and facile preparation of methyl 4,6-O-benzylidene-α-D-glucopyranoside and some related compounds
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A simple and rapid benzylidenation procedure for preparing the title compound and other related derivatives using tin(II) triflate and other triflate salts as catalysts is described.
- Joseph, Cosam C.,Zwanenburg, Binne,Chittenden, Gordon J. F.
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p. 493 - 497
(2007/10/03)
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- An easy approach for the acetylation of saccharidic alcohols. Applicability for regioselective protections
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Cheap 4 ? molecular sieves can promote acetylation of carbohydrate hydroxyl functions with Ac2O in absence of any co-reagent. The procedure is compatible with the presence of a variety of acid labile protecting groups and can be exploited for regioselective protections.
- Adinolfi, Matteo,Barone, Gaspare,Iadonisi, Alfonso,Schiattarella, Marialuisa
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p. 4661 - 4663
(2007/10/03)
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- Solid phase synthesis of oligonucleotides tethered to oligo-glucose phosphate tails
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Oligonucleotides conjugated at both 3′ and 5′-ends with glucose residues, 4,6-linked through a phosphodiester bridge, have been synthesized by sequential addition of a 6-O-DMT-glucose-4-phosphoramidite building block following a standard automated ODN ass
- Adinolfi, Matteo,De Napoli, Lorenzo,Di Fabio, Giovanni,Iadonisi, Alfonso,Montesarchio, Daniela,Piccialli, Gennaro
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p. 6697 - 6704
(2007/10/03)
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- Preparation of cyclic peptide antifungal agents
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The present invention provides phosphonylating agents and phosphonylation conditions that are compatible with the acid- and base-sensitive compounds and which promote a regioselective and reproducible conversion to a phosphonate compound. Also provided are intermediates that may be used to prepare phosphonate derivatives of cyclic peptides antifungal agent and a process for converting the phosphonates to the desired phosphonic acid prodrugs.
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- Use of controlled pore glass in solid phase oligosaccharide synthesis. Application to the semiautomated synthesis of a glyconucleotide conjugate
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Three polymetric supports (polystyrene. Tentagel and controlled pore glass) have been tested for solid phase synthesis of oligosaccharides based on the trichlorocctimidate methodology. Controlled pore glass has been found to yield satisfactory results wit
- Adinolfi, Matteo,Barone, Gaspare,De Napoli, Lorenzo,Iadonisi, Alfonso,Piccialli, Gennaro
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p. 1953 - 1956
(2007/10/03)
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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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