- SnCl2-Catalyzed Acetalation/Selective Benzoylation Sequence for the Synthesis of Orthogonally Protected Glycosyl Acceptors
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Based on SnCl2-catalyzed acetalation and selective benzoylation, a one-pot strategy to efficiently synthesize orthogonally protected glycosyl acceptors with 2-OH/3-OH was developed. Consequently, 2-OBz or 3-OBz 4,6-O-benzylidene galactosides and glucosides were efficiently prepared in moderate to high yields starting from free galactosides and glucosides, and were used as valuable glycosyl acceptors for the synthesis of blood group antigens O and B analogues in this study.
- Dong, Hai,Feng, Guang-Jing,Guo, Yang-Fan,Liu, Chun-Yang,Lv, Jian
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supporting information
(2022/04/03)
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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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- 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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- 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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- 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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- 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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- 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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- 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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- Synthesis and antibacterial activity of novel modified 5-O-desosamine ketolides
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A series of novel modified 5-O-desosamine-ketolides were synthesized. The 5-O-desosamine fragment was removed from ketolide by an efficient and mild manipulation. 4-O-substituted desosamine was introduced into the ketolide aglycon and various coupling methods were essayed for the glycosylation. Three novel ketolides were tested for in vitro antibacterial activity against a panel of susceptible and resistant pathogens. Compound 26 showed potent activity against all the methicillin-sensitivity and resistant pathogens.
- Chen, Xiaozhuo,Xu, Peng,Xu, Yanpeng,Liu, Lu,Liu, Yi,Zhu, Di,Lei, Pingsheng
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supporting information
p. 7402 - 7405
(2013/02/23)
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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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- FeCl3 mediated arylidenation of carbohydrates
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Glycosides and thioglycosides based on monosaccharides in reaction with benzaldehyde dimethylacetal or p-methoxybenzaldehyde dimethyl acetal undergo FeCl3-catalyzed (20 mol %) regioselective 4,6-O-arylidenation producing the corresponding acetals in high yields. FeCl3 also mediates acetalation of glycosides and thioglycosides of cellobiose, maltose, and lactose affording the corresponding 4′,6′-O-benzylidene acetals, which were isolated after their acetylation in situ with acetic anhydride and pyridine. The combined yields (two steps) of these final products are also high (61-84%). The procedure is applicable to a wide variety of functional groups including -OBn.
- Basu, Nabamita,Maity, Sajal K.,Roy, Soumik,Singha, Shuvendu,Ghosh, Rina
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experimental part
p. 534 - 539
(2011/04/27)
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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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- 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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- 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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- Oligosaccharide glycosides having mammalian immunosuppresive and tolerogenic properties
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Disclosed are novel oligosaccharide glycosides having mammalian immunosuppressive and tolerogenic properties, pharmaceutical compositions containing such oligosaccharide glycosides and to methods of using such oligosaccharide glycosides to modulate cell-m
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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 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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- 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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- Phyllanthoside-Phyllanthostatin Synthetic Studies. 9. Total Syntheses of (-)-Phyllanthostatin 1, (+)-Phyllanthostatin 2, and (+)-Phyllanthostatin 3
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Phyllanthostatins 1, 2, and 3 (2-4) have been synthesized for the first time. The unusual 1′→2β glycosidic linkages of the disaccharide moieties were constructed via anchimerically-assisted Koenigs-Knorr reactions. The novel β-glycosyl esters were then ge
- Smith III, Amos B.,Hale, Karl J.,Vaccaro, Henry A.,Rivero, Ralph A.
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p. 2112 - 2122
(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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- Acetalation studies. Part VI. Concerning the effects of ultrasound on the benzylidenation of some alkyl D-glycopyranosides
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The effects of ultrasound on conventional Freudenberg-type benzylidenation reactions of some alkyl D-glycopyranosides is described.A considerable enhancement in the rates of formation of the expected acetals was observed.The pure products were obtained in good yields.Some of the crude air-dried products were suitable for direct derivatisation.
- Chittenden, Gordon J. F.
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p. 607 - 609
(2007/10/02)
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- Synthesis of p-nitrophenyl 6(5)-O-benzyl-alpha-maltopentaoside, a substrate for alpha amylases.
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p-Nitrophenyl alpha-maltopentaoside, having a benzyl group on O-6 of the terminal (nonreducing) D-glucosyl group was prepared by use of a reductive ring-opening reaction. Highly regioselective reduction of p-nitrophenyl O-(2,3-di-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranosyl)-(1----4)- tris[O-(2,3,6-tri-O-benzoyl-alpha-D-glucopyranosyl)-(1----4)]-2,3,6-tri- O- benzoyl-alpha-D-glucopyranoside by dimethylamine-borane and p-toluenesulfonic acid, followed by debenzoylation, gave p-nitrophenyl O-(6-O-benzyl-alpha-D-glucopyranosyl)-(1----4)-tris[O-alpha-D-glucopyran osyl- (1----4)]-alpha-D-glucopyranoside. An experiment was done on the mode of action of human pancreatic and salivary alpha amylases on this derivative. The compound is suitable as a substrate for the assay of alpha amylase when used with glucoamylase and alpha-D-glucosidase as coupling enzymes.
- Satomura,Iwata,Sakata,Omichi,Ikenaka
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p. 107 - 115
(2007/10/02)
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- Reactions of Relevance to the Chemistry of Aminoglycoside Antibiotics. Part 13. A Novel Synthesis of Benzyl Ethers
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Benzyl ethers were prepared from alcohols by reaction with chloro(phenylmethyl)dimethylammonium chloride and sodium hydrogen telluride in sequence.The salt (1) 1)OR2Cl-; R1=H, R2=cholest-5-en-3β-yl> and sodium borohydride gave the borane complex of 3β-dimethylaminomethoxycholest-5-ene.Salt (1; R1=Ph, R2=cholest-5-en-3β-yl or 5α-cholestan-3β-yl) and ammonia or hydrazine gave the steroidal benzimidates or benzhydrazonate.
- Barrett, Anthony G. M.,Read, Roger W.,Barton, Derek H. R.
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p. 2184 - 2190
(2007/10/02)
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