- Mild selective hydrolysis of acetals in carbohydrates
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A simple and inexpensive methodology for the selective hydrolysis of acetals using hydrogen chloride as catalyst is described.
- Gomes Cioletti, Alessandra,Alves, Ricardo José,De Souza Filho, José Dias,Gomes Chaves, Josiano,Fontes Prado, Maria Auxiliadora
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Read Online
- Regioselective Reductive Ring Opening of 4-Methoxybenzylidene Acetals of Hexopyranosides. Access to a Novel Protective Group Strategy
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Reduction of fully protected 4,6-O-(4-methoxybenzylidene)hexopyranosides with sodium cyanoborohydride-trifluoroacetic acid in N,N-dimethylformamide, or with trimethylsilyl chloride in acetonitrile, gives the 6- and 4-O-(4-methoxybenzyl) ethers, respectively, in good yields and with good regioselectivity; the 4-methoxybenzyl ether linkage in products containing benzyl ethers or other protective groups is selectively cleaved upon treatment with cerium(IV) ammonium nitrate in aqueous acetonitrile.
- Johansson, Rolf,Samuelsson, Bertil
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Read Online
- Unexpected reaction using methanol dried over molecular sieves
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The absolute methanol dried over 3A molecular sieves cleaves the O-acetyl group due to the existence of methoxy species generated by the 3A molecular sieves.
- Mizuno, Mamoru,Kobayashi, Katsuaki,Nakajima, Hitoshi,Koya, Masahiko,Inazu, Toshiyuki
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Read Online
- Synthesis of methyl 4,6-di-o-ethyl-α-d-glucopyranoside-based azacrown ethers and their effects in asymmetric reactions
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Carbohydrate-based crown ethers have been reported to be able to generate asymmetric induction in certain reactions. Previously, it was proved that the monosaccharide unit, the anomeric substituent, and the sidearm could influence the catalytic activity of the monoaza-15-crown-5 macrocycles derived from sugars. In order to gain information about the effect of the flexibility, 4,6-di-O-ethyl-glucoside-based crown compounds were synthesized, and their efficiency was compared to the 4,6-O-benzylidene analogues. It was found that the absence of the two-ring annulation has a negative effect on the enantioselectivity in liquid-liquid two-phase reactions: in the Darzens condensation of 2-chloroacetophenone and in the epoxidation of chalcone. The same trend was observed in the solid-liquid phase Michael addition of diethyl acetamidomalonate. Surprisingly, in the solid-liquid phase cyclopropanation of benzylidenemalononitrile, one of the new catalysts was highly enantioselective (99% ee).
- Bagi, Péter,Bakó, Péter,Heged?s, László,Orbán, István,Rapi, Zsolt,Varga, Bertalan
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- Triethylamine-methanol mediated selective removal of oxophenylacetyl ester in saccharides
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A highly selective, mild, and efficient method for the cleavage of oxophenylacetyl ester protected saccharides was developed using triethylamine in methanol at room temperature. The reagent proved successful against different labile groups like acetal, ketal, and PMB and also generated good yields of the desired saccharides bearing lipid esters. Further, we also observed DBU in methanol as an alternative reagent for the deprotection of acetyl, benzoyl, and oxophenylacetyl ester groups. This journal is
- Rasool, Javeed Ur,Kumar, Atul,Ali, Asif,Ahmed, Qazi Naveed
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supporting information
p. 338 - 347
(2021/01/29)
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- Systematic Study of Regioselective Reductive Ring-Opening Reactions of 4,6- O-Halobenzylidene Acetals of Glucopyranosides
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Reductive openings of cyclic acetals are widely used in modern synthetic organic chemistry for the regioselective introduction of protecting groups. A systematic study was performed on the applicability and efficacy of various hydride donor and protic or Lewis acid reagent combinations in the reductive ring opening of glucosidic 4,6-halobenzylidene acetals bearing an ortho-, meta-, and para-chloro- or -bromo substituent on the benzene ring. Most of the reagent combinations tested cleaved the 4,6-O-halobenzylidene acetal rings at O4 or O6 efficiently and with the expected regioselectivity. The LiAlH4-AlCl3 and the BH3·THF-TMSOTf combinations produced the 4-O-halobenzyl ether/6-OH products with complete regioselectivity and high yields. The use of Me3N·BH3-AlCl3 reagent system in toluene was also effective in cleaving the acetal ring at O6 but was accompanied by Al-chelation-assisted debenzylation side reactions. The NaCNBH3-HCl and the Et3SiH-BF3·Et2O combinations were highly effective in yielding the 6-halobenzyl ether/4-OH derivatives. Et3SiH, in combination with TfOH, produced the 6-O-ether/4-OH products in rapid reactions but also triggered silylation and reductive halobenzylation as secondary transformations. Reductive opening of the 1,3-dioxane ring of pyranosidic 4,6-O-halobenzylidene acetals by the proper reagent combination was found to be an efficient method for the regioselective introduction of versatile halobenzyl protecting groups onto the pyranose ring.
- Mez?, Erika,Herczeg, Mihály,Demeter, Fruzsina,Bereczki, Ilona,Csávás, Magdolna,Borbás, Anikó
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p. 12973 - 12987
(2021/09/18)
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- Introducing Oxo-Phenylacetyl (OPAc) as a Protecting Group for Carbohydrates
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A series of oxo-phenylacetyl (OPAc)-protected saccharides, with divergent base sensitivity profiles against benzoyl (Bz) and acetyl (Ac) were synthesized, and KHSO5/AcCl in methanol was identified as an easy, mild, selective, and efficient deprotecting reagent for their removal in the perspective of carbohydrate synthesis. Timely monitoring of AcCl reagent was supportive in both sequential and simultaneous deprotecting of OPAc, Bz, and Ac. The salient feature of our method is the orthogonal stability against different groups, its ease to generate different valuable acceptors using designed monosaccharides, and use of OPAc as a glycosyl donar.
- Kumar, Atul,Gannedi, Veeranjaneyulu,Rather, Suhail A.,Vishwakarma, Ram A.,Ahmed, Qazi Naveed
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p. 4131 - 4138
(2019/04/30)
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- The 2,2-Dimethyl-2-(ortho-nitrophenyl)acetyl (DMNPA) Group: A Novel Protecting Group in Carbohydrate Chemistry
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The 2,2-dimethyl-2-(ortho-nitrophenyl)acetyl (DMNPA) group was introduced to synthetic carbohydrate chemistry as a protecting group (PG) for the first time. Benefiting from a unique chemical structure and novel deprotection conditions, the DMNPA group can be cleaved rapidly and mutually orthogonal to other PGs. Orchestrated application of the DMNPA group with other PGs led to the highly efficient synthesis of the glycan of thornasterside A.
- Liu, Hui,Zhou, Si-Yu,Wen, Guo-En,Liu, Xu-Xue,Liu, De-Yong,Zhang, Qing-Ju,Schmidt, Richard R.,Sun, Jian-Song
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supporting information
p. 8049 - 8052
(2019/10/11)
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- Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity
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The reactivity of both coupling partners—the glycosyl donor and acceptor—is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting-group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure–reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis-glucosylations.
- van der Vorm, Stefan,van Hengst, Jacob M. A.,Bakker, Marloes,Overkleeft, Herman S.,van der Marel, Gijsbert A.,Codée, Jeroen D. C.
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supporting information
p. 8240 - 8244
(2018/05/03)
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- Synthesis and mass spectrometric analysis of disaccharides from methanolysis of heparan sulfate
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The quantification of heparan sulfate (HS) in biological matrices, e.g., urine, cerebrospinal fluid, tissue samples etc., is of great importance for the diagnosis and prognosis of several of the mucopolysaccharidosis (MPS) disorders, which are lysosomal storage diseases of impaired glycosaminoglycan metabolism. The development of suitable assays for this purpose is challenging due to the high molecular weight and complexity of HS. Recent efforts towards this goal include the acid catalysed methanolysis of HS, which desulfates the polymer and results in the formation of disaccharide cleavage products which can be detected and quantified by LC-MS/MS. We have synthesized a library of 12 HS-derived disaccharides as methanolysis standards via the stereoselective 1,2-cis glycosylation of suitably protected GlcA and IdoA acceptors with a 2-deoxy-2-azido thioglucoside donor. This facilitated identification of the major peaks in the LC-MS/MS chromatograms, and potentially will allow the monitoring of specific metabolites as surrogate markers for genotype. This work also paves the way towards a fully quantitative LC-MS/MS assay for HS via the preparation of a suitably labelled derivative.
- He, Qi Qi,Trim, Paul J.,Snel, Marten F.,Hopwood, John J.,Ferro, Vito
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p. 8791 - 8803
(2018/11/30)
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- Approaches to Pyranuronic β-Sugar Amino Acid Building Blocks of Peptidosaccharide Foldamers
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Pyranuronic β-sugar amino acids (β-SAAs) are biocompatible and tuneable building blocks of foldamers and chimera-peptides. The scalable and economical total synthesis of two building blocks is described here. These C-4 epimers, Fmoc-GlcAPU(Me)-OH (7) and
- Goldschmidt G?z, Viktória,Pintér, István,Harmat, Veronika,Perczel, András
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p. 355 - 361
(2018/01/27)
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- Synthesis of MeON-neoglycosides of digoxigenin with 6-deoxy- and 2,6-dideoxy-D-glucose derivatives and their anticancer activity
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Cardiac glycosides show anticancer activities and their deoxy-sugar chains are vital for their anticancer effects. In order to study the structure-activity relationship (SAR) of cardiac glycosides toward cancers and get more potent anticancer agents, a series of MeON-neoglycosides of digoxigenin was synthesized and evaluated. First, ten 6-deoxy- and 2,6-dideoxy-D-glucopyranosyl donors were synthesized starting from methyl α-D-glucopyranoside and 2-deoxy-D-glucose. Meanwhile, the digoxigenin was obtained by acidic hydrolysis of commercially available digoxin as glycosyl acceptor. Then, a 22-member MeON-neoglycoside library of digoxigenin was successfully synthesized by neoglycosylation method. Finally, the induction of Nur77 expression and its translocation from the nucleus to cytoplasm together with cytotoxicity of these MeON-neoglycosides were evaluated. The SAR analysis revealed that C3 glycosylation is required for their induction of Nur77 expression. Moreover, some MeON-neoglycosides (2b and 8b) could significant induce the expression of Nur77 and its translocation from the nucleus to cytoplasm. However, these compounds showed no inhibitory effects on the proliferation of cancer cells, suggesting that they may not induce apoptosis of NIH-H460 cancer cells and their underlying potential and application toward cancer cells deserves future study.
- Wang, Dong-dong,Li, Xiao-san,Bao, Yu-zhou,Liu, Jie,Zhang, Xiao-kun,Yao, Xin-sheng,Sun, Xue-Long,Tang, Jin-Shan
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supporting information
p. 3359 - 3364
(2017/07/07)
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- Binding pattern of intermediate UDP-4-keto-xylose to human UDP-xylose synthase: Synthesis and STD NMR of model keto-saccharides
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Human UDP-xylose synthase (hUXS1) exclusively converts UDP-glucuronic acid to UDP-xylose via intermediate UDP-4-keto-xylose (UDP-Xyl-4O). Synthesis of model compounds like methyl-4-keto-xylose (Me-Xyl-4O) is reported to investigate the binding pattern thereof to hUXS1. Hence, selective oxidation of the desired hydroxyl function required employment of protecting group chemistry. Solution behavior of synthesized keto-saccharides was studied without enzyme via1H and13C NMR spectroscopy with respect to existent forms in deuterated potassium phosphate buffer. Keto-enol tautomerism was observed for all investigated keto-saccharides, while gem-diol hydrate forms were only observed for 4-keto-xylose derivatives. Saturation transfer difference (STD) NMR was used to study binding of synthesized keto-gylcosides to wild type hUXS1. Resulting epitope maps were correlated to earlier published molecular modeling studies of UDP-Xyl-4O. STD NMR results of Me-Xyl-4O are in good agreement with simulations of the intermediate UDP-Xyl-4O indicating a strong interaction of proton H3 with the enzyme, potentially caused by active site residue Ala79. In contrast, pyranoside binding pattern studies of methyl uronic acids showed some differences compared to previously published STD NMR results of UDP-glycosides. In general, obtained results can contribute to a better understanding in binding of UDP-glycosides to other UXS enzyme family members, which have high structural similarities in the active site.
- Puchner, Claudia,Eixelsberger, Thomas,Nidetzky, Bernd,Brecker, Lothar
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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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supporting information
p. 1005 - 1010
(2016/02/03)
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- Regioselective mono and multiple alkylation of diols and polyols catalyzed by organotin and its applications on the synthesis of value-added carbohydrate intermediates
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A catalytic amount of dibutyltin dichloride was used to develop regioselective alkylation of diols and multiple alkylation of polyols. Alkyl groups, including allyl, alkynyl and long-chain alkyl groups, were successfully introduced to one or two hydroxyl
- Xu, Hengfu,Ren, Bo,Zhao, Wei,Xin, Xiaoting,Lu, Yuchao,Pei, Yuxin,Dong, Hai,Pei, Zhichao
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p. 3490 - 3499
(2016/06/06)
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- Saccharide conjugates
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The invention provides a series of novel Lipid A analogs that are structually simple, synthetically accessible, and capable of blocking the cellular receptor within the signal transduction pathway. The novel Lipid A analogs can include a monosaccharide co
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Page/Page column 17; 18
(2015/10/05)
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- The synthesis and antitumor activity of twelve galloyl glucosides
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Twelve galloyl glucosides 1-12, showing diverse substitution patterns with two or three galloyl groups, were synthesized using commercially available, low-cost D-glucose and gallic acid as starting materials. Among them, three compounds, methyl 3,6-di-O-galloyl-?±-D-glucopyranoside (9), ethyl 2,3-di-O-galloyl-?±-D-glucopyranoside (11) and ethyl 2,3-di-O-galloyl-?2-D-glucopyranoside (12), are new compounds and other six, 1,6-di-O-galloyl-?2-D-glucopyranose (1), 1,4,6-tri-O-galloyl-?2-D-glucopyranose (2), 1,2-di-O-galloyl-?2-D-glucopyranose (3), 1,3-di-O-galloyl-?2-D-glucopyranose (4), 1,2,3-tri- O-galloyl-?±-D-glucopyranose (6) and methyl 3,4,6-tri-O-galloyl-?±-D-glucopyranoside (10), were synthesized for the first time in the present study. In in vitro MTT assay, 1-12 inhibited human cancer K562, HL-60 and HeLa cells with inhibition rates ranging from 64.2% to 92.9% at 100 ??g/mL, and their IC50 values were determined to be varied in 17.2-124.7 ??M on the tested three human cancer cell lines. In addition, compounds 1-12 inhibited murine sarcoma S180 cells with inhibition rates ranging from 38.7% to 52.8% at 100 ??g/mL in the in vitro MTT assay, and in vivo antitumor activity of 1 and 2 was also detected in murine sarcoma S180 tumor-bearing Kunming mice using taxol as positive control.
- Li, Chang-Wei,Dong, Hua-Jin,Cui, Cheng-Bin
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p. 2034 - 2060
(2015/03/05)
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- Click chemistry route to tricyclic monosaccharide triazole hybrids: Design and synthesis of substituted hexahydro-4H-pyrano[2,3-f][1,2,3]triazolo[5,1-c][1,4]oxazepines
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A click chemistry approach to novel tricyclic monosaccharide triazole hybrids, namely, aryl substituted hexahydro-4H-pyrano[2,3-f][1,2,3]triazolo[5,1-c][1,4]oxazepine derivatives from an intramolecular 1,3-dipolar cycloaddition of 6-azido-4-O-propargyl glycopyranosides has been reported.
- Konda, Saidulu,Rao, Pallavi,Oruganti, Srinivas
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p. 63962 - 63965
(2015/02/19)
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- HClO4-silica-catalysed regioselective opening of benzylidene acetals and its application towards regioselective HO-4 glycosylation of benzylidene acetals in one-pot
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Here we report a high-yielding method for the regioselective reductive ring opening of 4,6-O-benzylidene acetals of hexapyranosides using inexpensive and robust HClO4-SiO2 as the acidic catalyst and triethylsilane as the hydride dono
- Dara, Saidulu,Saikam, Varma,Yadav, Mahipal,Singh, Parvinder Pal,Vishwakarma, Ram A.
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supporting information
p. 93 - 96
(2014/05/20)
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- Selective 4,6-O-benzylidene formation of methyl α-d-mannopyranoside using 2,6-dimethylbenzaldehyde
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While methyl α-d-glucopyranosides and α-d-galactopyranosides selectively form 4,6-O-benzylidenes when reacted with excess benzaldehyde in the presence of acid catalyst methyl α-d-mannopyranosides does not exhibit the same selectivity because of the cis-ar
- Liotta, Louis J.,Chalmers, Jennifer F.,Falco Marshall, Jessica N.,Ferreira, Timothy E.,Mullen, Hannah E.,Pace, Nicholas J.
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- Synthesis of an α-amylase inhibitor: Highly stereoselective glycosidation and regioselective manipulations of hydroxyl groups in carbohydrate derivatives
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Here, we describe the efficient synthesis of α-amylase inhibitor 1. To introduce the most expensive C ring unit at a late stage in the synthesis, we developed 1,2-cis-O-glycosidation of AB and C ring intermediates. Taking advantage of the effect of non-neighboring protecting groups, reaction solvents, and temperature for the glycosidation led to high stereoselectivity and high yield of the 1,2-cis-glycoside product bearing the API skeleton. We also explored protection and deprotection methods for regioselective manipulation of hydroxyl groups in A and B ring intermediates. One-pot benzylation of the 2,3-hydroxyl groups of d-glucose under phase-transfer conditions and regioselective anomeric deacetylation with N-methylpiperazine were developed for the syntheses of A, B, and AB ring intermediates. Thus, the efficiency of the process was dramatically improved. The raw material cost of API was reduced to approximately one-third that of the original route, and the total process was decreased by six steps.
- Ueda, Tsuyoshi,Hayashi, Masaki,Ikeuchi, Yutaka,Nakajima, Takumi,Numagami, Eiji,Kobayashi, Satoshi
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p. 1728 - 1739
(2015/02/05)
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- Linearization of carbohydrate derived polycyclic frameworks
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We report easy access to carbohydrate derived diverse tricyclic skeletons which could be beneficial for exploring polyfunctionalized chiral alicycles. The key reaction to assemble a sugar fused tricyclic core is intermolecular tandem esterification and 1,3-dipolar cycloaddition. The framework was elaborated using amide forming reactions, opening of isoxazolidine rings followed by N and O-acylations. The sequences provide distinct, spatially separated and encoded chemical entities that may pave the way to investigate cell functions.
- Singh, Priyanka,Panda, Gautam
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p. 31892 - 31903
(2014/08/18)
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- Cleavage of 4,6- O -benzylidene acetal using sodium hydrogen sulfate monohydrate
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The use of protecting groups is an important protocol in carbohydrate synthesis. Among protecting groups, benzylidene acetals are generally more stable than other acetals; therefore, strong conditions are often required for deprotection. We report the deprotection of 4,6-O-benzylidene derivatives using sodium hydrogen sulfate monohydrate under mild conditions. Georg Thieme Verlag Stuttgart New York.
- Michigami, Kyosuke,Terauchi, Manami,Hayashi, Masahiko
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p. 1519 - 1523
(2013/06/27)
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- Hafnium(IV) tetratriflate in selective reductive carbohydrate benzylidene acetal opening reaction and direct silylation reaction
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Hafnium(IV) tetratriflate was shown to be an effective catalyst for the regioselective reductive benzylidene ring opening with concurrent silylation reaction. The synthetic conditions were optimized, and the scope and limitations were identified. In addit
- Manabe, Shino,Ito, Yukishige
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p. 6838 - 6840
(2019/04/10)
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- TANNIN INHIBITORS OF HIV
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The invention provides a method to prevent or treat HIV-infection with synthetic tannins, and pharmaceutical compositions comprising synthetic tannins.
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Paragraph 0029; 0033
(2013/10/07)
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- Enantioselective alkylation of aldehydes using dialkylzincs catalyzed by simple chiral diols derived from naturally occurring monosaccharides
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Enantioselective alkylation of aldehydes was achieved in up to 84% ee using dialkylzincs catalyzed by simple diols derived from naturally occurring monosaccharides.
- Michigami, Kyosuke,Hayashi, Masahiko
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supporting information
p. 4221 - 4225
(2013/06/27)
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- Halide promoted organotin-mediated carbohydrate benzylation: Mechanism and application
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In the present study, the mechanistic origin of the promoted organotin-mediated carbohydrate benzylation by halides was explored by the comparison of the activation ability of halides on benzylation of methyl β-d-galactoside. It was demonstrated that the
- Zhou, Yixuan,Li, Jinyang,Zhan, Yingjie,Pei, Zhichao,Dong, Hai
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supporting information
p. 2693 - 2700
(2013/03/28)
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- A tin-free regioselective radical de-o-benzylation by an intramolecular hydrogen atom transfer on carbohydrate templates
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Radically selective: A remarkable 1,7-hydrogen atom transfer of a benzylic hydrogen atom to an O-silylmethylene radical initiates a regioselective de-O-benzylation of benzylated saccharides. The reaction terminates by an ionic mechanism and is general for hydroxy benzylated substrates having a variety of functional groups. Copyright
- Attouche, Angie,Urban, Dominique,Beau, Jean-Marie
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p. 9572 - 9575
(2013/09/23)
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- α-Selective organocatalytic synthesis of 2-deoxygalactosides
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Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety (see scheme). The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. Copyright
- Balmond, Edward I.,Coe, Diane M.,Galan, M. Carmen,McGarrigle, Eoghan M.
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supporting information
p. 9152 - 9155
(2012/10/29)
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- Construction of triazolyl bidentate glycoligands (TBGs) by grafting of 3-azidocoumarin to epimeric pyranoglycosides via a fluorogenic dual click reaction
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Glycoligands, which feature a glycoside as the central template incorporating Lewis bases as metal chelation sites and various fluorophores as the chemical reporter, represent a range of interesting scaffolds for development of chemosensors. Here, new typ
- Xue, Jia-Lu,He, Xiao-Peng,Yang, Jin-Wei,Shi, De-Tai,Cheng, Chao-Ying,Xie, Juan,Chen, Guo-Rong,Chen, Kaixian
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- Carbohydrate-derived PSE acetals: Controlled base-induced ring cleavage
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Retro-Michael type reactions applied to PSE acetals protecting monosaccharides led either to complete removal or to ring-cleavage. In protic medium, application of standard basic conditions resulted in acetal deprotection, while the use of butyl lithium in aprotic medium allowed controlled ring-cleavage. A regio- and stereoselective C- over O-alkylation was observed during the process. Furthermore, depending on the substrates and the reaction conditions involved, new carbohydrate-derived β-alkoxyvinyl sulfones were obtained with varying regioselectivity.
- Chéry, Florence,Cabianca, Elena,Tatibou?t, Arnaud,De Lucchi, Ottorino,Rollin, Patrick
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experimental part
p. 544 - 551
(2012/01/14)
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- Intramolecular base-free sonogashira reaction for the synthesis of benzannulated chiral macrocycles embedded in carbohydrate templates
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A base-free, intramolecular Sonogashira reaction-based general approach has been established for the diversity-oriented synthesis (DOS) of fused bi- and tricyclic systems containing benzannulated, 10- to 13-membered chiral macrocycles embedded in carbohydrate templates. Macrocycles with different ring sizes have been prepared by pre-designing the chiral building blocks. Base-sensitive groups like acetyl and TBDPS survived the reaction conditions. Copyright
- Hussain, Altaf,Yousuf, Syed Khalid,Kumar, Deepak,Lambu, Malikharjunarao,Singh, Baldev,Maity, Sudip,Mukherjee, Debaraj
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p. 1933 - 1940
(2012/09/22)
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- Defining oxyanion reactivities in base-promoted glycosylations
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Saccharide oxyanions obtained by base treatment could be employed in glycosylation to give oligosaccharides with high stereo- and regioselectivities.
- Matwiejuk, Martin,Thiem, Joachim
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supporting information; experimental part
p. 8379 - 8381
(2011/09/14)
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- The UDP-Galp mutase catalyzed isomerization: Synthesis and evaluation of 1,4-anhydro-β-d-galactopyranose and its [2.2.2] methylene homologue
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The synthesis of 1,4-anhydro-β-d-galactopyranose (1,5-anhydro-α- d-galactofuranose), a proposed intermediate in the ring contraction isomerisation catalyzed by UDP-galactopyranose mutase, together with its [2.2.2] bicyclic methylene homologue, synthesised as a possible competitive inhibitor or alternative substrate, are reported. Neither compound was found to be an inhibitor or substrate for UDP-galactopyranose mutase from Klebsiella pneumoniae.
- Sadeghi-Khomami, Ali,Forcada, Tatiana J.,Wilson, Claire,Sanders, David A. R.,Thomas, Neil R.
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supporting information; experimental part
p. 1596 - 1602
(2010/07/04)
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- Metal trifluoromethanesulfonate-catalyzed regioselective reductive ring opening of benzylidene acetals
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A systematic study of various metal trifluoromethanesulfonates as efficient catalysts in the regioselective reductive ring opening of benzylidene acetals is described, including the effects of solvents, reducing agents, and temperature. These catalysts are found to be effective in cleaving the 4,6-O-acetal rings of hexopyranosides at either O4 or O6, respectively. When used in conjunction with a 1 M solution of BH3.THF in THF without extra addition of any solvent, it affects the ring fission at the O6 position to generate the corresponding primary alcohols, whereas O4-opening takes place in acetonitrile in the presence of dimethylethylsilane as the reductant leading to the secondary hydroxyl derivatives in high selectivity and yields. These methodologies can be applied to a wide range of substrates containing various functional groups.
- Shie, Chi-Rung,Tzeng, Zheng-Hao,Wang, Cheng-Chung,Hung, Shang-Cheng
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experimental part
p. 510 - 523
(2010/06/16)
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- Diphenylphosphinoylethylidene (DPE) acetals: an alternative protective strategy in glycochemistry
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Diphenylphoshinoylethyne reacts with diols under basic conditions to produce cycloacetalic phosphine oxides. The reaction appears to be general and particularly effective with carbohydrate derivatives. The 2-(diphenylphoshinoyl)ethylidene (DPE) acetals produced are stable in acidic media while they can be cleaved under reductive and/or basic conditions: base-catalyzed transacetalization is a method of choice for their mild and effective deprotection.
- Pellizzaro, Leonardo,Tatibou?t, Arnaud,Fabris, Fabrizio,Rollin, Patrick,Lucchi, Ottorino De
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body text
p. 101 - 103
(2009/04/14)
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- Truly catalytic and chemoselective cleavage of benzylidene acetal with phosphomolybdic acid supported on silica gel
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Phosphomolybdic acid supported on silica gel provides a truly catalytic method for the chemoselective cleavage of benzylidene acetals having sensitive functional groups under mild conditions. It is easy to perform on large scale owing to minimal catalyst loading (0.5 mol-%). Several sensitive functional groups such as TBDPS ether, -OMs, -OAc, allyl ether, N-Boc, N-Fmoc and N-Cbz are stable under the reaction conditions. In addition, benzylidene acetal is selectively cleaved in the presence of isopropylidene ketal. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Kumar, Ponminor Senthil,Kumar, Gaddale Devanna Kishore,Baskaran, Sundarababu
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supporting information; scheme or table
p. 6063 - 6067
(2009/05/27)
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- Synthesis of novel photolabile glycosides from methyl 4,6-O-(o-nitro)benzylidene-α-d-glycopyranosides
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Novel photolabile sugar derivatives bearing a 4- or 6-O-(o-nitro)benzyl group have been prepared from the corresponding methyl 4,6-O-(o-nitro)benzylidene α-d-glycopyranosides. Regioselective cleavage with BF3·Et2O/Et3SiH led to the methyl 6-O-(o-nitro)benzyl gluco- and manno-α-d-glycopyranosides 3 and 6. Inversion of configuration at 4-OH position of gluco and manno derivatives offered the otherwise inaccessible methyl 6-O-(o-nitro)benzyl galacto- and talo-α-d-glycopyranosides 4, 5, and 7. Careful reaction with PhBCl2/Et3SiH (3 equiv of reagents, 10 min at -78 °C) led to the desired methyl 4-O-(o-nitro)benzyl gluco- and manno-α-d-glycopyranosides 8 and 9 in very good yield. However, prolonged reaction with 6 equiv of PhBCl2/Et3SiH transformed the methyl 4,6-O-(o-nitro)benzylidene α-d-glucopyranoside 11 into the reduced d-glucitol derivative 15. Oxidative cleavage of 5,6-diol function of 15 gave the corresponding photolabile l-xylose 17. The photolabile glucosides 3 and 8 have been further transformed into the photolabile α-C-allyl d-glucopyranosides 20 and 22.
- Zhu, Chen-Jiang,Yi, Hua,Chen, Guo-Rong,Xie, Juan
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p. 10687 - 10693
(2008/12/23)
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- Efficient formation and cleavage of benzylidene acetals by sodium hydrogen sulfate supported on silica gel
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NaHSO4SiO2 was used as an efficient heterogeneous catalyst for both the formation and the cleavage of benzylidene acetals. This catalyst is compatible with many functional or protective groups. Under different solvent systems, either the formation or the cleavage of benzylidene acetals was carried out smoothly in excellent yields and with good chemoselectivity. Georg Thieme Verlag Stuttgart.
- Niu, Youhong,Wang, Ning,Cao, Xiaoping,Ye, Xin-Shan
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p. 2116 - 2120
(2008/02/09)
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- Synthesis of a pentasaccharide repeating unit of the extracellular polysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus 291
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A pentasaccharide methyl glycoside has been synthesized efficiently using a modified glycosylation strategy. This pentasaccharide is a repeating unit of the exopolysaccharides produced by Lactobacillus delbrueckii subsp. bulgaricus 291.
- Tiwari, Pallavi,Misra, Anup Kumar
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p. 239 - 248
(2008/02/12)
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- An iodocyclization approach toward diastereoselective synthesis of highly functionalized tetrasubstituted tetrahydrofurans with 2,5-trans and 2,5-cis relationships from pyranoside derived acyclic oximes
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An efficient method to obtain novel tetrasubstituted tetrahydrofurans with C2 and C5 substitution in trans- and cis-relative configurations has been reported.
- Kumar, Vikas,Gauniyal, Harsh Mohan,Shaw, Arun K.
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p. 2069 - 2078
(2008/02/11)
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- Stereoselective mannich-like reactions of ester enolates generated on sugar templates: A novel access to a key intermediate for 1β-methylcarbapenem synthesis
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The Mannich-like reactions of the enolates generated from 2,3-di-O-protected 6-deoxy-4-O-propionyl-α-D-glucopyranosides with (3R,4R)-4-acetoxy-3-((R)-1-(t-butyldimethylsilyloxy)ethyl ]azetidin-2-one were investigated. The corresponding 2,3-di-O-methyl derivative provided the Mannich adduct in good to excellent stereoselectivity. From the major adduct, the azetidin-2-one incorporating an α-methyl acetic acid side chain at the C-4 position with ?-configuration was obtained by alkaline hydrolysis. This product, (3S,4S)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl 1-4-1(R)-1-carboxyethylJazetidin-2-one, is a useful intermediate for the 1 ?-methylcarbapenem synthesis.
- Sasaki, Daisuke,Sawamoto, Daisuke,Takao, Ken-ichi,Tadano, Kin-ichi,Okue, Masayuki,Ajito, Keiichi
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p. 103 - 110
(2008/02/13)
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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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- A flexible stereospecific synthesis of polyhydroxylated pyrrolizidines from commercially available pyranosides
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Nitrogen-containing sugar analogues, known as azasugars or iminosugars, such as polyhydroxylated piperdines, pyrrolidines, pyrrolizidines, and indolizidines, have the potential to become important therapeutic agents due to their ability to inhibit glycosi
- Sletten, Ellen M.,Liotta, Louis J.
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p. 1335 - 1343
(2007/10/03)
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- Sonochemistry: A powerful way of enhancing the efficiency of carbohydrate synthesis
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Using sonication as a means of facilitating organic reactions in carbohydrate chemistry was explored under the conditions used for traditional organic synthesis. An array of representative reactions, including hydroxy group manipulation (acylation, protection/deprotection, acyl group migration), thioglycoside synthesis, azidoglycoside synthesis, 1,3-dipolar cycloaddition and reductive cleavage of benzylidene, commonly used in the synthesis of carbohydrate derivatives was examined. A series of glycosylation reactions that employ thioglycosides, glycosyl trichloroacetimidate, glycosyl bromide and glycosyl acetate as the glycosyl donors was also examined. Our results demonstrate that sonication can significantly shorten the reaction time, enhance the reactivity of reactant and lead to superior yield and excellent stereoselectivity. More importantly, a general protocol of glycosylation may finally be developed. Sonication is compatible to the conditions used for traditional organic synthesis. We believe that sonication can also be applied to other areas of synthetic processes.
- Deng, Shenglou,Gangadharmath, Umesh,Chang, Cheng-Wei Tom
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p. 5179 - 5185
(2007/10/03)
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- Mild and efficient method for the cleavage of benzylidene acetals using HClO4-SiO2 and direct conversion of acetals to acetates
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HClO4-SiO2 has been used successfully for the deprotection of benzylidene acetals and the direct conversion of benzylidene acetals to the corresponding di-O-acetates. The reactions are very fast and yields are excellent.
- Agnihotri, Geetanjali,Misra, Anup Kumar
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p. 3653 - 3658
(2007/10/03)
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- Nafion-H mediated selective deprotection of terminal isopropylidene acetals and trityl ethers. Application in the synthesis of a substituted piperidone
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A facile chemoselective hydrolysis of terminal isopropylidene acetals has been achieved in good to excellent yields within 2-4 h using Nafion-H in methanol at ambient temperature. This procedure has been employed to synthesize a substituted piperidone der
- Rawal, Girish K.,Rani, Shikha,Kumar, Amit,Vankar, Yashwant D.
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p. 9117 - 9120
(2007/10/03)
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- Bicyclic carbohydrate-derived scaffolds for combinatorial libraries
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A bicyclic scaffold derived from the natural monosaccharide d-glucose, and possessing several diversity sites, was linked to various resins through the primary (C-6) hydroxyl and decorated on the solid phase: the hydroxyl group at C-4 was functionalized a
- Cervi, Giovanni,Peri, Francesco,Battistini, Carlo,Gennari, Cesare,Nicotra, Francesco
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p. 3349 - 3367
(2007/10/03)
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- Selective deprotection of terminal isopropylidene acetals and trityl ethers using HClO4 supported on silica gel
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Terminal isopropylidene acetals are selectively cleaved to the corresponding 1,2-diols in good to excellent yields in 6-24 h at room temperature by using the 'HClO4?SiO2' reagent system. Likewise, trityl ethers are readily cleaved to the corresponding alcohols in good to excellent yields within 2-3 h at room temperature. Work-up involves merely filtration of the reagent followed by purification of the crude product.
- Agarwal, Aditi,Vankar, Yashwant D.
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p. 1661 - 1667
(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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- An investigation into the synthesis of some molecules related to methyl acarviosin
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Methyl acarviosin is an impressive inhibitor of some glycoside hydrolases that process substrates containing α-D-glucosidic linkages. In an attempt to provide putative inhibitors for enzymes that process β-D-glucosidic linkages, we report an improved synthesis of a hydroxylated 'methyl β-acarviosin' and our efforts towards various deoxygenated versions of methyl β-acarviosin. As well, the synthesis of a 1,3-linked variant of methyl β-acarviosin is reported, together with an unsuccessful 'tether' approach to construct the crucial nitrogen linkage in the acarviosins.
- McDonough, Matthew J.,Stick, Robert V.,Tilbrook, D. Matthew G.,Watts, Andrew G.
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p. 233 - 241
(2007/10/03)
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- Application of the Synthetic Aminosugars for Glycodiversification: Synthesis and Antimicrobial Studies of Pyranmycin
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A divergent approach was employed for the synthesis of aminosugars, from which a novel library of aminoglycoside antibiotics (pyranmycins) was synthesized. Pyranmycins have comparable antibacterial activity as neomycin, a clinically used aminoglycoside antibiotic, against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Mycobacterium smegmatis. In addition, pyranmycins, like streptomycin, are bacteriocidal while isoniazid (INH) is bacteriostatic. Therefore, pyranmycins may provide new therapeutic options in the treatment against tuberculosis. Several members of pyranmycins also manifest modest anti-Tat and anti-Rev activities, which may aid in the development of new anti-HIV agents. Although the antibacterial activity of pyranmycins against aminoglycoside resistant bacteria is less than expected, the synthetic methodologies of utilizing a library of aminosugars can be a model for future studies of glycodiversification or glycorandomization.
- Elchert, Bryan,Li, Jie,Wang, Jinhua,Hui, Yu,Rai, Ravi,Ptak, Roger,Ward, Priscilla,Takemoto, Jon Y.,Bensaci, Mekki,Chang, Cheng-Wei Tom
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p. 1513 - 1523
(2007/10/03)
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- Binding equilibrium isotope effects for glucose at the catalytic domain of human brain hexokinase
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We have utilized tritium isotope effects to probe the in vitro binding equilibrium between glucose and human brain hexokinase (E.C.2.7.1.1). Replacing a backbone hydrogen atom in glucose with tritium can significantly increase or decrease the equilibrium association constant. Specifically, the equilibrium tritium isotope effects are 1.027 ± 0.002, 0.927 ± 0.0003, 1.027 ± 0.004, 1.051 ± 0.001, 0.988 ± 0.001, and 1.065 ± 0.003 for [1-t]-, [2-t]-, [3-t]-, [4-t]-, [5-t]-, and [6,6-t2]glucose, respectively. We have shown that the existence of prebinding equilibrium isotope effects can contribute to binding isotope effect studies but that this effect is insignificant for glucose binding to hexokinase. The binding isotope effects are interpreted in the context of structural studies of hexokinase - glucose complexes. Ab initio calculations on 2-propanol with or without a hydrogen bonding partner, in steric collision with formaldehyde or methane, and on ethanol, cyclohexanol and 1-hydroxymethyl-tetrahydropyran are presented to clarify the magnitude of isotope effects possible in such interactions and the accompanying changes in free energy. Position-specific binding isotope effects provide direct evidence of the partial deprotonation and activation of O6 by Asp657, of other hydrogen bonding interactions with ionic residues, and of the steric compression of CH2 by the backbone carbonyl of Ser603.
- Lewis, Brett E.,Schramm, Vern L.
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p. 4785 - 4798
(2007/10/03)
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