- Discriminating non-ylidic carbon-sulfur bond cleavages of sulfonium ylides for alkylation and arylation reactions
-
A sulfonium ylide participated alkylation and arylation under transition-metal free conditions is described. The disparate reaction pattern allowed the separate activation of non-ylidic S-alkyl and S-aryl bond. Under acidic conditions, sulfonium ylides serve as alkyl cation precursors which facilitate the alkylations. While under alkaline conditions, cleavage of non-ylidic S-aryl bond produces O-arylated compounds efficiently. The robustness of the protocols were established by the excellent compatibility of wide variety of substrates including carbohydrates.
- Fang, Jing,Li, Ting,Ma, Xiang,Sun, Jiuchang,Cai, Lei,Chen, Qi,Liao, Zhiwen,Meng, Lingkui,Zeng, Jing,Wan, Qian
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supporting information
p. 288 - 292
(2021/07/25)
-
- A Unified Strategy to Access 2- And 4-Deoxygenated Sugars Enabled by Manganese-Promoted 1,2-Radical Migration
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The selective manipulation of carbohydrate scaffolds is challenging due to the presence of multiple, nearly chemically indistinguishable O-H and C-H bonds. As a result, protecting-group-based synthetic strategies are typically necessary for carbohydrate modification. Here we report a concise semisynthetic strategy to access diverse 2- and 4-deoxygenated carbohydrates without relying on the exhaustive use of protecting groups to achieve site-selective reaction outcomes. Our approach leverages a Mn2+-promoted redox isomerization step, which proceeds via sugar radical intermediates accessed by neutral hydrogen atom abstraction under visible light-mediated photoredox conditions. The resulting deoxyketopyranosides feature chemically distinguishable functional groups and are readily transformed into diverse carbohydrate structures. To showcase the versatility of this method, we report expedient syntheses of the rare sugars l-ristosamine, l-olivose, l-mycarose, and l-digitoxose from commercial l-rhamnose. The findings presented here validate the potential for radical intermediates to facilitate the selective transformation of carbohydrates and showcase the step and efficiency advantages attendant to synthetic strategies that minimize a reliance upon protecting groups.
- Carder, Hayden M.,Suh, Carolyn E.,Wendlandt, Alison E.
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supporting information
p. 13798 - 13805
(2021/09/07)
-
- Catalytic Site-Selective Carbamoylation of Pyranosides
-
Carbamate-bearing carbohydrates contribute to the pharmacological properties of various natural glycosides. The catalytic site-selective carbamoylation of minimally protected pyranosides was achieved for the first time to bypass protection/deprotection sequences. 1-Carbamoylimidazoles were used as the carbamoylation reagents to circumvent the harmful and unstable phosgene and isocyanates. This borinic acid catalyzed transformation granted an expedient access to the tumor cell-binding carbamoylmannoside moiety of bleomycins and analogs in yields of 56% to 89%.
- Alsarraf, Jér?me,Petitpoisson, Lucas,Pichette, André
-
supporting information
p. 6052 - 6056
(2021/08/03)
-
- Synthesis and biological evaluation of 1,6-bis-triazole-2,3,4-tri-O-benzyl-α-D-glucopyranosides as a novel α-glucosidase inhibitor in the treatment of Type 2 diabetes
-
A novel series of 1,6-bis-triazole-benzyl-α-glucoside derivatives (7a-7ee) were designed, synthesized and evaluated for inhibitory activity against α-glucosidase. Most of the synthesized compounds exhibited good activity with IC50 ranging from
- Chaidam, Suksamran,Saehlim, Natthiya,Athipornchai, Anan,Sirion, Uthaiwan,Saeeng, Rungnapha
-
supporting information
(2021/08/27)
-
- Addressing the biochemical foundations of a glucose-based "trojan horse"-strategy to boron neutron capture therapy: From chemical synthesis to in vitro assessment
-
Boron neutron capture therapy (BNCT) for cancer is on the rise worldwide due to recent developments of in-hospital neutron accelerators which are expected to revolutionize patient treatments. There is an urgent need for improved boron delivery agents, and herein we have focused on studying the biochemical foundations upon which a successful GLUT1-targeting strategy to BNCT could be based. By combining synthesis and molecular modeling with affinity and cytotoxicity studies, we unravel the mechanisms behind the considerable potential of appropriately designed glucoconjugates as boron delivery agents for BNCT. In addition to addressing the biochemical premises of the approach in detail, we report on a hit glucoconjugate which displays good cytocompatibility, aqueous solubility, high transporter affinity, and, crucially, an exceptional boron delivery capacity in the in vitro assessment thereby pointing toward the significant potential embedded in this approach.
- Ekholm, Filip S.,Matovic, Jelena,Jarvinen, Juulia,Bland, Helena C.,Sokka, Iris K.,Imlimthan, Surachet,Huttunen, Kristiina M.,Timonen, Juri,Peraniemi, Sirpa,Aitio, Olli,Airaksinen, Anu J.,Sarparanta, Mirkka,Johansson, Mikael P.,Rautio, Jarkko
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p. 3885 - 3899
(2020/11/12)
-
- Using DMF as Both a Catalyst and Cosolvent for the Regioselective Silylation of Polyols and Diols
-
Highly regioselective silylation of primary hydroxyl groups of unprotected polyols and diols was obtained by the use of a mixed solvent of MeCN/DMF (10:1) in this study. DMF was discovered to be a good catalyst in this reaction, although the silylation us
- Lv, Jian,Luo, Tao,Zou, Dapeng,Dong, Hai
-
p. 6383 - 6395
(2019/11/05)
-
- Intercepted dehomologation of aldoses by N-heterocyclic carbene catalysis-a novel transformation in carbohydrate chemistry
-
The development of an N-heterocyclic carbene (NHC) catalysed intercepted dehomologation of aldoses is reported. The unique selectivity of NHCs for aldehydes is exploited in the complex context of reducing sugars. Examples of strong substrate governance for either intercepted dehomologation or a subsequent redox-lactonisation were identified and mechanistically understood. More importantly, it was shown that catalyst design allowed the tuning of the selectivity of the reaction with structurally unbiased starting materials towards either of the two scenarios.
- Draskovits, Markus,Kalaus, Hubert,Stanetty, Christian,Mihovilovic, Marko D.
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p. 12144 - 12147
(2019/10/21)
-
- Site-Selective and Stereoselective C-H Alkylations of Carbohydrates via Combined Diarylborinic Acid and Photoredox Catalysis
-
Diphenylborinic acid serves as a cocatalyst for site- and stereoselective C-H alkylation reactions of carbohydrates under photoredox conditions using quinuclidine as the hydrogen atom transfer mediator. Products arising from selective abstraction of the equatorial hydrogens of cis-1,2-diol moieties, followed by C-C bond formation with net retention of configuration, are obtained. Computational modeling supports a mechanism involving formation of a tetracoordinate borinic ester, which accelerates hydrogen atom transfer with the quinuclidine-derived radical cation through polarity-matching and/or ion-pairing effects.
- Dimakos, Victoria,Su, Hsin Y.,Garrett, Graham E.,Taylor, Mark S.
-
supporting information
p. 5149 - 5153
(2019/03/29)
-
- Chiron approach to the total synthesis of Amaryllidaceae alkaloid (+)-lycoricidine
-
A highly stereoselective total synthesis of Amaryllidaceae alkaloid starting from α-D-galactopyranoside has been described. The salient features of this total synthesis are Ferrier carbocyclization reaction for the synthesis of ring A and Suzuki Miyaura c
- Saidhareddy, Puli,Shaw, Arun K.
-
p. 6773 - 6779
(2017/10/30)
-
- Structure–Activity Studies of N-Butyl-1-deoxynojirimycin (NB-DNJ) Analogues: Discovery of Potent and Selective Aminocyclopentitol Inhibitors of GBA1 and GBA2
-
Analogues of N-butyl-1-deoxynojirimycin (NB-DNJ) were prepared and assayed for inhibition of ceramide-specific glucosyltransferase (CGT), non-lysosomal β-glucosidase 2 (GBA2) and the lysosomal β-glucosidase 1 (GBA1). Compounds 5 a–6 f, which carry sterically demanding nitrogen substituents, and compound 13, devoid of the C3 and C5 hydroxy groups present in DNJ/NB-DGJ (N-butyldeoxygalactojirimycin) showed no inhibitory activity for CGT or GBA2. Inversion of stereochemistry at C4 of N-(n-butyl)- and N-(n-nonyl)-DGJ (compounds 24) also led to a loss of activity in these assays. The aminocyclopentitols N-(n-butyl)- (35 a), N-(n-nonyl)-4-amino-5-(hydroxymethyl)cyclopentane- (35 b), and N-(1-(pentyloxy)methyl)adamantan-1-yl)-1,2,3-triol (35 f), were found to be selective inhibitors of GBA1 and GBA2 that did not inhibit CGT (>1 mm), with the exception of 35 f, which inhibited CGT with an IC50 value of 1 mm. The N-butyl analogue 35 a was 100-fold selective for inhibiting GBA1 over GBA2 (Ki values of 32 nm and 3.3 μm for GBA1 and GBA2, respectively). The N-nonyl analogue 35 b displayed a Ki value of ?14 nm for GBA1 inhibition and a Ki of 43 nm for GBA2. The N-(1-(pentyloxy)methyl)adamantan-1-yl) derivative 35 f had Ki values of ≈16 and 14 nm for GBA1 and GBA2, respectively. The related N-bis-substituted aminocyclopentitols were found to be significantly less potent inhibitors than their mono-substituted analogues. The aminocyclopentitol scaffold should hold promise for further inhibitor development.
- Gu, Xingxian,Gupta, Vijayalaxmi,Yang, Yan,Zhu, Jin-Yi,Carlson, Erick J.,Kingsley, Carolyn,Tash, Joseph S.,Sch?nbrunn, Ernst,Hawkinson, Jon,Georg, Gunda I.
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p. 1977 - 1984
(2017/11/30)
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- 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)
-
- Biomimetic Total Synthesis of Angiopterlactone B and Other Potential Natural Products
-
A one-pot biomimetic synthesis of (-)-angiopterlactone B and its enantiomer (+)-angiopterlactone B has been accomplished via TBAF-catalyzed tandem ring contraction followed by oxa-Michael/Michael addition sequence. Comparison of specific optical rotations
- Kotammagari, Tharun K.,Gonnade, Rajesh G.,Bhattacharya, Asish K.
-
supporting information
p. 3564 - 3567
(2017/07/17)
-
- Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations
-
tert-Butyldimethylsilyl (TBDMS) and tert-butyldiphenylsilyl (TBDPS) are alcohol protecting groups widely employed in organic synthesis in view of their compatibility with a wide range of conditions. Their regioselective installation on polyols generally r
- Traboni, Serena,Bedini, Emiliano,Iadonisi, Alfonso
-
supporting information
p. 2748 - 2756
(2017/01/09)
-
- 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)
-
- Synthesis and Applications of Silyl 2-Methylprop-2-ene-1-sulfinates in Preparative Silylation and GC-Derivatization Reactions of Polyols and Carbohydrates
-
Trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, and triisopropylsilyl 2-methylprop-2-ene-1-sulfinates were prepared through (CuOTf)2C6H6-catalyzed sila-ene reactions of the corresponding methallylsilanes with SO2 at 50 °C. Sterically hindered, epimerizable, and base-sensitive alcohols gave the corresponding silyl ethers in high yields and purities at room temperature and under neutral conditions. As the byproducts of the silylation reaction (SO2+isobutylene) are volatile, the workup was simplified to solvent evaporation. The developed method can be employed for the chemo- and regioselective semiprotection of polyols and glycosides and for the silylation of unstable aldols. The high reactivity of the developed reagents is shown by the synthesis of sterically hindered per-O-tert-butyldimethylsilyl-α-d-glucopyranose, the X-ray crystallographic analysis of which is the first for a per-O-silylated hexopyranose. The per-O-silylation of polyols, hydroxy carboxylic acids, and carbohydrates with trimethylsilyl 2-methylprop-2-ene-1-sulfinate was coupled with the GC analysis of nonvolatile polyhydroxy compounds both qualitatively and quantitatively. Regio- and chemoselective silylation of polyols and carbohydrates has been achieved by employing silyl sulfinates (see the picture; TBS=tert-butyldimethylsilyl, TES=triethylsilyl, TIPS=triisopropylsilyl, TMS=trimethylsilyl). The silylation reactions proceed in high yield because the reactions are mild and fast and produce only volatile byproducts. Furthermore, the silyl sulfinates are used as new derivatization reagents for the GC analysis of nonvolatile polyhydroxy compounds.
- Markovic, Dean,Tchawou, Wandji Augustin,Novosjolova, Irina,Laclef, Sylvain,Stepanovs, Dmitrijs,Turks, Maris,Vogel, Pierre
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p. 4196 - 4205
(2016/03/16)
-
- Carbohydrate based hyper-crosslinked organic polymers with -OH functional groups for CO2 separation
-
Recently, microporous organic polymers, especially those hyper-crosslinked from functionalized aromatic monomers, have been shown to be effective for CO2 capture and storage with considerable capacity and selectivity. Herein, a class of novel m
- Li, Haiying,Meng, Bo,Mahurin, Shannon M.,Chai, Song-Hai,Nelson, Kimberly M.,Baker, David C.,Liu, Honglai,Dai, Sheng
-
supporting information
p. 20913 - 20918
(2015/11/03)
-
- Crystal structure analysis of 2,3,4-Tri-O-acetyl-α-methyl-D-glucopyranoside
-
2,3,4-Tri-O-acetyl-α-methyl-D-glucopyranoside (F.W. 319.28) was synthesized, characterized by 1H NMR, confirmed by X-ray crystal structure analysis. This compound crystallizes in monoclinic class under the space group orthorhombic P2(1)2(1)2(1) with cell parameters a = 9.0312(18) A?, b = 11.731(2) A?, c = 15.139(3) A?; Z = 4. The structure exhibits inter-molecular hydrogen bonds of the type O-H - O, C-H - O.
- Zhen, Xiao-Li,Zhou, Zhen,Han, Jian-Rong,Tian, Xia,Liu, Shouxin
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p. 552 - 554
(2015/01/30)
-
- Iodine monochloride (ICl) as a highly efficient, green oxidant for the oxidation of alcohols to corresponding carbonyl compounds
-
Iodine monochloride (ICl) was discovered to be a highly efficient, green oxidant, which can oxidize aldose hemiacetals, diarylmethanols, arylalkylmethanols, anddialkylmethanols to the corresponding aldose lactones, diarylmethanones, arylalkylmethanones, and dialkylmethanones, respectively, in high yields. ICl as a green, metal-free oxidant is characterized by mild reaction condition, short reaction time, good yield, and broad scope.
- Wei, Peng,Zhang, Datong,Gao, Zhigang,Cai, Wenqing,Xu, Weiren,Tang, Lida,Zhao, Guilong
-
supporting information
p. 1457 - 1470
(2015/05/20)
-
- Molybdopterin biosynthesis: Trapping an unusual purine ribose adduct in the MoaA-catalyzed reaction
-
MoaA/MoaC catalyze a remarkable rearrangement reaction in which guanosine-5′-triphosphate (GTP) is converted to cyclic pyranopterin monophosphate (cPMP). In this reaction, the C8 of GTP is inserted between the C2′ and the C3′ carbons of the GTP ribose. Previous experiments with GTP isotopomers demonstrated that the ribose C3′ hydrogen atom is abstracted by the adenosyl radical. This led to a novel mechanistic proposal involving an intermediate with a bond between the C8 of guanine and C3′ of the ribose. This paper describes the use of 2′,3′-dideoxyGTP to trap this intermediate.
- Mehta, Angad P.,Abdelwahed, Sameh H.,Begley, Tadhg P.
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supporting information
p. 10883 - 10885
(2013/08/23)
-
- Supermolecular chiral mesogenic tripedes
-
A novel series of chiral liquid crystalline tripedes Glucoside and Mannoside derivatives Gn and Mn (n=1-3) have been synthesised. The inner cores consist of methyl α-D-Glucoside G or methyl α-D-Mannoside M, regioselectively functiona
- Belaissaoui, Abdelhak,Saez, Isabel M.,Cowling, Stephen J.,Zeng, Xiangbing,Goodby, John W.
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supporting information; experimental part
p. 2366 - 2373
(2012/03/27)
-
- Construction of the octose 8-phosphate intermediate in lincomycin A biosynthesis: Characterization of the reactions catalyzed by LmbR and LmbN
-
Lincomycin A is a potent antimicrobial agent noted for its unusual C1 methylmercapto-substituted 8-carbon sugar. Despite its long clinical history for the treatment of Gram-positive infections, the biosynthesis of the C 8-sugar, methylthiolincosamide (MTL), is poorly understood. Here, we report our studies of the two initial enzymatic steps in the MTL biosynthetic pathway leading to the identification of d-erythro-d-gluco-octose 8-phosphate as a key intermediate. Our experiments demonstrate that this intermediate is formed via a transaldol reaction catalyzed by LmbR using d-fructose 6-phosphate or d-sedoheptulose 7-phosphate as the C3 donor and d-ribose 5-phosphate as the C5 acceptor. Subsequent 1,2-isomerization catalyzed by LmbN converts the resulting 2-keto C8-sugar (octulose 8-phosphate) to octose 8-phosphate. These results provide, for the first time, in vitro evidence for the biosynthetic origin of the C8 backbone of MTL.
- Sasaki, Eita,Lin, Chia-I,Lin, Ke-Yi,Liu, Hung-Wen
-
supporting information
p. 17432 - 17435
(2013/01/15)
-
- Synthesis and evaluation of eight- and four-membered iminosugar analogues as inhibitors of testicular ceramide-specific glucosyltransferase, testicular β-glucosidase 2, and other glycosidases
-
Eight- and four-membered analogues of N-butyldeoxynojirimycin (NB-DNJ), a reversible male contraceptive in mice, were prepared and tested. A chiral pool approach was used for the synthesis of the target compounds. Key steps for the synthesis of the eight-membered analogues involve ring-closing metathesis and Sharpless asymmetric dihydroxylation and for the four-membered analogues Sharpless epoxidation, epoxide ring-opening (azide), and Mitsunobu reaction to form the four-membered ring. (3S,4R,5S,6R,7R)-1-Nonylazocane-3,4,5,6,7-pentaol (6) was moderately active against rat-derived ceramide-specific glucosyltransferase, and four of the other eight-membered analogues were weakly active against rat-derived β-glucosidase 2. Among the four-membered analogues, ((2R,3S,4S)-3-hydroxy-1-nonylazetidine-2,4-diyl)dimethanol (25) displayed selective inhibitory activity against mouse-derived ceramide-specific glucosyltransferase and was about half as potent as NB-DNJ against the rat-derived enzyme. ((2S,4S)-3-Hydroxy-1-nonylazetidine-2,4-diyl)dimethanol (27) was found to be a selective inhibitor of β-glucosidase 2, with potency similar to NB-DNJ. Additional glycosidase assays were performed to identify potential other therapeutic applications. The eight-membered iminosugars exhibited specificity for almond-derived β-glucosidase, and the 1-nonylazetidine 25 inhibited α-glucosidase (Saccharomyces cerevisiae) with an IC50 of 600 nM and β-glucosidase (almond) with an IC50 of 20 μM. Only N-nonyl derivatives were active, emphasizing the importance of a long lipophilic side chain for inhibitory activity of the analogues studied.
- Lee, Jae Chul,Francis, Subhashree,Dutta, Dinah,Gupta, Vijayalaxmi,Yang, Yan,Zhu, Jin-Yi,Tash, Joseph S.,Schoenbrunn, Ernst,Georg, Gunda I.
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experimental part
p. 3082 - 3098
(2012/05/31)
-
- Borinic acid-catalyzed regioselective acylation of carbohydrate derivatives
-
Reversible covalent interactions of organoboron compounds are exploited as the basis for regioselective borinic acid-catalyzed acylations of polyols. This catalytic protocol enables differentiation of the secondary OH groups of a wide range of carbohydrat
- Lee, Doris,Taylor, Mark S.
-
supporting information; experimental part
p. 3724 - 3727
(2011/05/14)
-
- DABCO: An efficient promoter for the acetylation of carbohydrates and other substances under solvent-free conditions
-
A simple, mild and efficient solvent-free method for the acetylation of carbohydrates, and their partially protected derivatives, as well as non-carbohydrate substances in excellent yields in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) is described with the advantage of tolerance to various functional groups, short reaction time and ease of product isolation.
- Ch, Ratnasekhar,Tyagi, Mohit,Patil, Premanand Ramrao,Kartha, K.P. Ravindranathan
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scheme or table
p. 5841 - 5846
(2011/12/03)
-
- Rapid, simple, and efficient deprotection of benzyl/benzylidene protected carbohydrates by utilization of flow chemistry
-
A rapid, simple, and efficient deprotection procedure for the deprotection of benzyl- and/or benzylidene protected carbohydrates is described utilizing a continuous flow hydrogenation reactor. The method tolerates both acid- and base sensitive functional groups. The high efficiency, simple work-up, and short reaction time should make this method appealing to researchers working in the fields of carbohydrate chemistry and total synthesis.
- Ekholm, Filip S.,Mándity, István M.,Fül?p, Ferenc,Leino, Reko
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experimental part
p. 1839 - 1841
(2011/04/25)
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- Iodine-promoted silylation of alcohols with silyl chlorides. Synthetic and mechanistic studies
-
An efficient silylating system for 1°, 2°, and 3° alcohols, consisting of a silyl chloride/N-methylimidazole/iodine, was developed. Synthetic and mechanistic aspects of this new reagent system, and particularly the role of iodine were investigated in detail using 1H NMR spectroscopy.
- Bartoszewicz, Agnieszka,Kalek, Marcin,Stawinski, Jacek
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p. 8843 - 8850
(2008/12/21)
-
- Synthesis of S-linked carbohydrate analogues via a Ferrier reaction
-
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)
-
- Application of ball milling technology to carbohydrate reactions: I. Regioselective primary hydroxyl protection of hexosides and nucleoside by planetary ball milling
-
Dry ball milling of hexosides with trityl chloride in the presence of DABCO or Na2CO3 has been found to result in their complete conversion to the respective 6-O-trityl ethers. Further wet grinding of the reaction mixture with Ac2O in the presence of DMAP led to the respective fully protected hexosides in good to excellent yields after isolation. It has been found to be an effective one-pot two-step synthesis under solvent-free condition. The speed of homogenization has been shown to highly influence the rate and outcome of the reaction, and commercially available planetary ball mill has been proved to be very convenient for carrying out the reaction under standardized and reproducible conditions.
- Patil, Premanand Ramrao,Kartha, K.P. Ravindranathan
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p. 279 - 293
(2008/12/21)
-
- Mechanistic studies on the stereoselective formation of β-mannosides from mannosyl iodides using α-deuterium kinetic isotope effects
-
(Chemical Equation Presented) Stereoselective synthesis of β-mannosides is one of the most challenging linkages to achieve in carbohydrate chemistry. Both the anomeric effect and the C2 axial substituent favor the formation of the axial glycoside (α-produ
- El-Badri, Mohamed H.,Willenbring, Dan,Tantillo, Dean J.,Gervay-Hague, Jacquelyn
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p. 4663 - 4672
(2008/02/10)
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- A facile, one-step conversion of 6-O-trityl and 6-O-TBDMS monosaccharides into the corresponding formate esters
-
A convenient method has been developed for a facile and high-yield conversion of 6-O-tert-butyldimethylsilyl and 6-O-trityl protected monosaccharides to their formate esters, which may serve as useful intermediates for the replacement of the primary hydro
- Komiotis, Dimitri,Agelis, George,Manta, Stella,Tzioumaki, Niki,Tsoukala, Evangelia,Antonakis, Kostas
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p. 441 - 450
(2007/10/03)
-
- ACID ADDITION SALT OF CARBASUGAR AMINE DERIVATIVE
-
An acid addition salt of a carba-sugar amine derivative represented by the following formula (1): wherein R1 and R2 each independently represents a hydrogen atom, or an alkyl group, an alkenyl group, an alkynyl group, an acyl group,
- -
-
Page/Page column 9
(2008/06/13)
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- Directing-protecting groups for carbohydrates. Design, conformational study, synthesis and application to regioselective functionalization
-
A novel concept of regioselective transformation of secondary hydroxyl groups in carbohydrates is presented. First, the relative reactivity of the free hydroxyl groups of onoprotected d-glucose derivatives was assessed using acetylation as a model reactio
- Moitessier, Nicolas,Englebienne, Pablo,Chapleur, Yves
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p. 6839 - 6853
(2007/10/03)
-
- Synthesis and evaluation of a mechanism-based inhibitor of KDO8P synthase
-
The enzyme 3-deoxy-D-manno-2-octulosonate-8-phosphate (KDO8P) synthase catalyzes the condensation reaction between phosphoenolpyruvate (PEP) and D-arabinose 5-phosphate (A5P) to produce KDO8P and inorganic phosphate. In attempts to investigate the lack of
- Belakhov, Valery,Dovgolevsky, Ekaterina,Rabkin, Emilia,Shulami, Smadar,Shoham, Yuval,Baasov, Timor
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p. 385 - 392
(2007/10/03)
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- Selective Removal of Benzyl Carbonate Used as a Protecting Group in Carbohydrate Chemistry
-
It has been demonstrated that benzyl carbonate protecting group is orthogonal with tert-butyldimethylsilyl and (4-methoxy)trityl ethers. Moreover, benzyl carbonates can be selectively cleaved using aminolysis conditions.
- Mouffouk, Fouzi,Morere, Alain,Vidal, Sebastien,Leydet, Alain,Montero, Jean-Louis
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p. 303 - 307
(2007/10/03)
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- Regioselective silylation of sugars through palladium nanoparticle-catalyzed silane alcoholysis
-
Palladium (0)-catalyzed silane alcoholysis was applied to sugars for the first time using tertbutyldimethylsilane (TBDMS-H) and Ph3SiH as the silanes. The catalyst is a colloidal solution of Pd(0) generated in situ from PdX2 (X = Cl-, OAc-) and TBDMS-H in N,N-dimethylacetamide. The colloid has been characterized by dynamic light scattering and transmission electron microscopy and consists of catalytically highly active nanoparticles of ~2 nm diameter. The silane alcoholysis reaction is an effective method for the regioselective silylation of methyl and phenyl glycosides and generates hydrogen gas as the only side product. For many of the sugar substrates investigated, the distribution of regioisomers obtained is complementary to that of the traditional R3SiCl/base (base = pyridine, imidazole) methodology and gives convenient access to the 3,6- rather than the 2,6-silylated pyranosides, obtained as the main product by the silyl chloride method. The method also allows a selective axial silylation of levoglucosan and 1,3,5-O-methylidene-myo-inositol. In an attempt to rationalize the observed regioselectivities, ab initio predictions (HF/3-21G*) have been made on the relative energies of some of the silylated products. They suggest that the observed regioselectivities do not reflect a kinetic vs thermodynamic product distribution but are induced by the silylation agent employed. Models for the possible origin of the observed regioselectivity in both silylation methods (silane- and silyl chloride-based) are discussed.
- Chung, Mee-Kyung,Orlova, Galina,Goddard, John D.,Schlaf, Marcel,Harris, Robert,Beveridge, Terrance J.,White, Gisele,Hallett, F. Ross
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p. 10508 - 10518
(2007/10/03)
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- Cerium-mediated deprotection of substituted allyl ethers
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Substituted allyl protecting groups can be removed from alcohols using the CeCl3·7 H2O/NaI system in refluxing nitromethane in the presence of a scavenger for the allyl iodide. In contrast to this, deprotection of the allyl group proceeds barely in acetonitrile.
- Bartoli,Cupone,Dalpozzo,De Nino,Maiuolo,Marcantoni,Procopio
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p. 1897 - 1900
(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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- Effect of solvation on the rotation of hydroxymethyl groups in carbohydrates
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The solvent dependences of the populations of the hydroxymethyl rotamers of methyl 2,3,4,6-tetra-O-[2H3]-α-D-glucopyranoside (2a) and methyl 2,3,4- tri-O-[2H3]-α-D-glucopyranoside (6) in 10 and 8 solvents, respectively, have been determined by analysis of 3J(H5,H6R) and 3J(H5,H6S) values and by consideration of evidence for hydrogen bonding through infrared spectroscopy and 3J(H,OH) values. The methods used to determine coupling constants in individual hydroxymethyl rotamers were reexamined, and an improved protocol was developed. When 0-6 is methylated (2a), the populations of the hydroxymethyl rotamers are largely independent of solvent polarity at ratios of about 61:38:0 gg:gt:tg, except that a small population (4%) of the tg rotamer appears in the most polar solvents at the expense of the gg rotamer. When 0-6 is unsubstituted (6), there are substantial changes in rotamer population as solvent polarity increases due to loss of intramolecular hydrogen bonding and stabilization of the more polar rotamers. The rotamer populations for 6 return to those adopted by the permethylated derivative (2a) in the most polar solvents. It was concluded that hydrogen bond donation from OH-6 to water is not important in determining hydroxymethyl rotational preferences. The well-known 'reversed' chemical shift order of the two C6 protons of peracetylated glucopyranose derivatives was shown to also occur for permethylated derivatives and is ascribed to solvent effects in addition to anisotropy. The solvent effect on the chemical shift difference is attributed to the fact that one of the two protons stays on the same side of the pyranose ring in the two more populated rotamers while the other proton exchanges environments.
- Rockwell, Glen D.,Grindley, T. Bruce
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p. 10953 - 10963
(2007/10/03)
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- Synthesis and biological evaluation of N-acetylneuraminic acid-based rotavirus inhibitors
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Rotavirus can cause severe gastrointestinal disease, especially in infants and young children, and is particularly prevalent in Third-World countries. Therefore, the development of potential inhibitors of this virus is of great interest. The present study describes the synthesis and in vitro biological evaluation of a number of N-acetylneuraminic acid-based compounds as potential rotavirus inhibitors. Our data suggests that it is indeed possible to inhibit adhesion of the virus, and hence in vitro replication, with carbohydrate-based molecules, although this inhibition does appear to be strain dependent.
- Kiefel, Milton J.,Beisner, Birgit,Bennett, Simon,Holmes, Ian D.,Von Itzstein, Mark
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p. 1314 - 1320
(2007/10/03)
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- Efficient method for the t-butyldimethylsilylation of alcohols with N,O-bis(t-butyldimethylsilyl)acetamide
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The efficient t-butyldimethylsilylation of alcohols - including tertiary and sterically hindered secondary alcohols - can be achieved using N,O-bis(t-butyldimethylsilyl)acetamide (BTBSA) in the presence of catalytic amounts (0.01-0.05 equiv) of tetrabutyl
- Johnson, David A.,Taubner, Lara M.
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p. 605 - 608
(2007/10/02)
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- Asymmetric Pauson-Khand reaction. Cobalt-mediated cycloisomerization of 1,6-enynes in carbohydrate templates: Synthesis of bis-heteroannulated pyranosides
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The Pauson-Khand reaction on the carbohydrate derived precursors 1-6 is reported. We have described for the first time the cobalt-mediated cyclization of some O-branched chain 1,6-enynes in carbohydrate templates. The resulting bis-heteroannulated pyranosides 17-22 have been obtained in diastereomerically pure form, in moderate to good yield, and in one, simple synthetic operation. These enantiomerically pure, densely functionalized carbocycles are attractive advanced intermediates for the synthesis of complex natural products.
- Marco-Contelles, Jose
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p. 7666 - 7670
(2007/10/03)
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- Synthesis of mono- and dimannoside phosphoramidite derivatives for solid-phase conjugation to oligonucleotides
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Mannose and dimannose derivatives have been prepared with an anomerically-linked hydrophobic spacer, and converted to phoshoramidite derivatives suitable for conjugation to oligoribodeoxynucleotides on a DNA/RNA synthesizer. Synthesis of a monomannoside-linked 15-mer oligoribodeoxynucleotide is reported.
- Akhtar,Akhtar, Saghir,Routledge,Routledge, Anne,Patel,Patel, Ramila,Gardiner,Gardiner, John M.
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p. 7333 - 7336
(2007/10/02)
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- Some Mechanistic Aspects of Carbohydrate Electrochemistry
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The electroreductive conversion of carbohydrates leads to anions the reactions of which with alkylating or acylating reagents results in the formation of ether or ester derivatives.The obtained substitution patterns are influenced by the acidity of the di
- Hamann, Carl Heinz,Fischer, Susanne,Polligkeit, Herbert,Schleif, Daniela,Wolf, Peter
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- Reactions of N-trimethylsilyl- or N-tert-butyldimethylsilylphthalimide with Carbohydrate Derivatives
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The utility of N-trimethylsilyl- and N-tert-butyldimethylsilyl-phthalimide for the selective silylation of primary hydroxyl groups in carbohydrates has been examined. Key words: Selective silylation, carbohydrates.
- Zamojski, A.,Szarek, W.A.
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p. 1261 - 1265
(2007/10/02)
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- Synthesis of a Methyl Heptaglucoside: Analogue of the Phytoalexin Elicitor from Phytophtora Megasperma
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The ethylthio-laminaribioside 29, prepared by regiospecific glycosylation of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (9) with 2,3,4,6-tetra-O-benzoyl-D-glucopyranosyl imidate 17 and subsequent benzoylation, could be elongated in a step-wise fas
- Verduyn, R.,Douwes, M.,Klein, P.A.M. van der,Moesinger, E.M.,Marel, G.A. van der,Boom, J.H. van
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p. 7301 - 7316
(2007/10/02)
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- Stereoselective routes to the C10-C19 fragment of FK-506
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D-Galactose was used as a starting material to reach the titled system. The key elements of one of the syntheses involved directed homogeneous hydrogenation and diastereoselective lactonization reactions (see 26 → 6 and 6 → 7). In another synthetic route directed catalytic hydrogenation was used to fashion 34 where the end groups were already differentiated.
- Villalobos,Danishefsky
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p. 2776 - 2786
(2007/10/02)
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- STUDIES OF THE SELECTIVE SILYLATION OF METHYL α- AND β-D-ALDOHEXOPYRANOSIDES: STABILITY OF THE PARTIALLY PROTECTED DERIVATIVES IN POLAR SOLVENTS
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Treatment of methyl α- (1) and β-D-glucopyranosides, methyl α- (3) and β-D-galactopyranosides, and methyl α-D-mannopyranoside (5) with 2,3, or 4 mol.equiv. of tert-butyldimethylsilyl (TBDMS) chloride under two conditions afforded mixtures of TBDMS ethers which were identified.The following compounds were isolated in synthetically useful yields, the 2,6-di-TBDMS ether of 1 (70percent), the 2,6-di- and 2,3,6-tri-TBDMS ethers of 3 (84percent and 57percent, respectively), and the 2,6-di and 3,6-di-TBDMS ethers of 5 (50percent and 80percent, respectively).In dipolar solvents, no migration of the TBDMS groups was detected between partially silyated hydroxyl groups, but the addition of a base (triethylamine or imidazole) caused migration to vicinal cis positions.
- Halmos, Therese,Montserret, Roland,Filippi, Jean,Antonakis, Kostas
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- Structural Modification on Partially Silylated Carbohydrates by Means of Triphenylphosphane/Diethylazodicarboxylate. IV. Transformations on Mannose and Galactose
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Reaction of methyl β-D-galactopyranoside (1) with two equivalents of t-butyldimethylchlorosilane yields methyl 2,6-bis-O-(t-BDMSi)-β-D-galactopyranoside (1b), methyl 3,6-bis-O-(tBDMSi)-β-D-galactopyranoside (1c) and methyl 4,6-bis-O-(tBDMSi)-β-D-galactopy
- Mark, Edgar,Zbiral, Erich,Brandstetter, Hannelore H.
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p. 289 - 307
(2007/10/02)
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