- Boronic acid-catalyzed final-stage site-selective acylation for the total syntheses of O-3′-acyl bisabolol β-D-fucopyranoside natural products and their analogues
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The first concise total syntheses of O-3′-senecioyl α-bisabolol β-D-fucopyranoside (4a) and O-3′isovaleroyl α-bisabolol β-D-fucopyranoside (4b) were achieved through final-stage site-selective acylation via the activation of cis-vicinal diols by imidazole
- Nakamura, Yuki,Ochiai, Takayuki,Makino, Kazuishi,Shimada, Naoyuki
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p. 281 - 285
(2021/03/08)
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- Sterically Hindered 2,4,6-Tri- tert-butylpyridinium Salts as Single Hydrogen Bond Donors for Highly Stereoselective Glycosylation Reactions of Glycals
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We demonstrate here that the strained and bulky protonated 2,4,6-tri-tert-butylpyridine salts serve as efficient catalysts for highly stereoselective glycosylations of various glycals. Moreover, the mechanism of action involves an interesting single hydrogen bond mediated protonation of glycals and not via the generally conceived Br?nsted acid pathway. The counteranions also play a role in the outcome of the reaction.
- Ghosh, Titli,Mukherji, Ananya,Kancharla, Pavan K.
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p. 3490 - 3495
(2019/05/24)
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- Solasodine-3-O-β-D-glucopyranoside kills Candida albicans by disrupting the intracellular vacuole
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The increasing incidence of fungal infections and emergence of drug resistance underlie the constant search for new antifungal agents and exploration of their modes of action. The present study aimed to investigate the antifungal mechanisms of solasodine-3-O-β-D-glucopyranoside (SG) isolated from the medicinal plant Solanum nigrum L. In vitro, SG displayed potent fungicidal activity against both azole-sensitive and azole-resistant Candida albicans strains in Spider medium with its MICs of 32 μg/ml. Analysis of structure and bioactivity revealed that both the glucosyl residue and NH group were required for SG activity. Quantum dot (QD) assays demonstrated that the glucosyl moiety was critical for SG uptake into Candida cells, as further confirmed by glucose rescue experiments. Measurement of the fluorescence intensity of 2′,7'-dichlorofluorescin diacetate (DCFHDA) by flow cytometry indicated that SG even at 64 μg/ml just caused a moderate increase of reactive oxygen species (ROS) generation by 58% in C. albicans cells. Observation of vacuole staining by confocal microscopy demonstrated that SG alkalized the intracellular vacuole of C. albicans and caused hyper-permeability of the vacuole membrane, resulting in cell death. These results support the potential application of SG in fighting fungal infections and reveal a novel fungicidal mechanism.
- Chang, Wenqiang,Li, Ying,Zhang, Ming,Zheng, Sha,Li, Yan,Lou, Hongxiang
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p. 139 - 146
(2017/06/05)
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- Stereoselective Epimerizations of Glycosyl Thiols
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Glycosyl thiols are widely used in stereoselective S-glycoside synthesis. Their epimerization from 1,2-trans to 1,2-cis thiols (e.g., equatorial to axial epimerization in thioglucopyranose) was attained using TiCl4, while SnCl4 promoted their axial-to-equatorial epimerization. The method included application for stereoselective β-d-manno- and β-l-rhamnopyranosyl thiol formation. Complex formation explains the equatorial preference when using SnCl4, whereas TiCl4 can shift the equilibrium toward the 1,2-cis thiol via 1,3-oxathiolane formation.
- Doyle, Lisa M.,O'Sullivan, Shane,Di Salvo, Claudia,McKinney, Michelle,McArdle, Patrick,Murphy, Paul V.
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p. 5802 - 5805
(2017/11/10)
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- Synthesis of a chlorogenin glycoside library using an orthogonal protecting group strategy
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Naturally occurring spirostanol saponins bear a chacotriose, α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→4)] -β-d-glucopyranose residue as the oligosaccharide moiety which is believed to be important for biological activity. Herein the development of a concise, combinatorial method for the synthesis of two series of glycan variants at the 2′ and/or 4′ positions of chacotriose is described and the structure-activity relationships of the glycone part at 3-OH of chlorogenin investigated. These compounds were found to be weakly-cytotoxic toward leukemia cell lines CCRF and HL-20, indicating that the chacotriose moiety is important for anticancer activity.
- Wang, Ying-Hsin,Yeh, Hsien-Wei,Wang, Hsiao-Wen,Yu, Chia-Chun,Guh, Jih-Hwa,Liu, Der-Zen,Liang, Pi-Hui
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p. 118 - 135
(2013/07/27)
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- Studies on the conformational flexibility of α-l-rhamnose-containing oligosaccharides using 13C-site-specific labeling, NMR spectroscopy and molecular simulations: Implications for the three-dimensional structure of bacterial rhamnan polysaccha
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Bacterial polysaccharides are comprised of a variety of monosaccharides, l-rhamnose (6-deoxy-l-mannose) being one of them. This sugar is often part of α-(1 → 2)- and/or α-(1 → 3)-linkages and we have therefore studied the disaccharide α-l-Rhap-(1 → 2)-α-l
- Jonsson, K. Hanna M.,Saewen, Elin,Widmalm, Goeran
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p. 2453 - 2463
(2012/04/23)
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- Total synthesis of ouabagenin and ouabain
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A full account of the total synthesis of ouabagenin and ouabain is described. A highly stereocontrolled anionic cycloaddition for the rapid construction of the basic steroid skeleton is a pivotal conversion for the whole strategy. A careful study was need
- Reddy, Maddi Sridhar,Zhang, Hongxing,Phoenix, Serge,Deslongchamps, Pierre
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supporting information; experimental part
p. 725 - 741
(2011/06/25)
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- Total synthesis of ouabagenin and ouabain
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(Chemical Equation Presented) The highly oxygenated steroid ouabagenin (1b) and its glycoside ouabain (1a) were prepared by a strategy based on a polyanionic cyclization. Starting building blocks A and B were combined to give the key intermediate C and transformed into 1b in 27 steps. Finally, ouabagenin (1b) was converted into ouabain (1a) in six steps (see scheme).
- Zhang, Hongxing,Sridhar Reddy, Maddi,Phoenix, Serge,Deslongchamps, Pierre
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p. 1272 - 1275
(2008/12/22)
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- TRITERPENES DERIVATIVES AND USES THEREOF AS ANTITUMOR AGENTS OR ANTI-INFLAMMATORY AGENTS
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A compound of formula (1): wherein R1 is selected from the group consisting of H, α-L-Rhamnopyranose, α-D-Mannopyranose, β-D-Xylopyranose, β-D-Glucopyranose, and α-D-Arabinopyranose; R2 is selected from CH3, COOH, CH2OH, COOCH3 and CH2O-α-D-Arabinopyranose; with the proviso that the compound of formula (I) is not a compound of formula (I) wherein R1 is β-D-Glucopyranose and R2 is COOH; wherein R1 is α-L-Rhamnopyranose and R2 is CH3; wherein R1 is β-D-Glucopyranose and R2 is CH2OH; wherein R1 is β-D-Xylopyranose and R2 is CH2OH; wherein R1 is α-L-Rhamnopyranose and R2 is COOCH3, wherein R1 is H and R2 is CH3; wherein R1 is H and R2 is CH2OH; wherein R1 is H and R2 is COOH; or wherein R1 is H and R2 is COOCH3, or a pharmaceutically acceptable salt thereof.
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Page/Page column 14
(2008/12/06)
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- Glycosidation of lupane-type triterpenoids as potent in vitro cytotoxic agents
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The weak hydrosolubility of betulinic acid (3) hampers the clinical development of this natural anticancer agent. In order to circumvent this problem and to enhance the pharmacological properties of betulinic acid (3) and the lupane-type triterpenes lupeol (1), betulin (2), and methyl betulinate (7), glycosides (β-d-glucosides, α-l-rhamnosides, and α-d-arabinosides) were synthesized and in vitro tested for cytotoxicity against three cancerous (A-549, DLD-1, and B16-F1) and one healthy (WS1) cell lines. The addition of a sugar moiety at the C-3 or C-28 position of betulin (2) resulted in a loss of cytotoxicity. In contrast, the 3-O-β-d-glucosidation of lupeol (1) improved the activity by 7- to 12-fold (IC50 14-15.0 μM). Moreover, the results showed that cancer cell lines are 8- to 12-fold more sensitive to the 3-O-α-l-rhamnopyranoside derivative of betulinic acid (IC50 2.6-3.9 μM, 22) than the healthy cells (IC50 31 μM). Thus, this study indicates that 3-O-glycosides of lupane-type triterpenoids represent an interesting class of potent in vitro cytotoxic agents.
- Gauthier, Charles,Legault, Jean,Lebrun, Maxime,Dufour, Philippe,Pichette, Andre
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p. 6713 - 6725
(2007/10/03)
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- Synthesis of Oligosaccharides Corresponding to the Common Polysaccharide Antigen of Group B Streptococci
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To facilitate mapping of the immunodominant region of the common polysaccharide antigen of group B streptococci, tetrasaccharide 1-O--α-rhamnopyranosyl>-D-glucitol (2) was synthesized in a stepwise fasion
- Pozsgay, Vince,Jennings, Harold J.
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p. 4042 - 4052
(2007/10/02)
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- SYNTHESIS OF THE O-SPECIFIC POLYSACCHARIDE OF SHIGELLA FLEXNERI
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A regular heteropolysaccharide built of tetrasaccharide repeating units is synthesised by means of regio- and stereospecific polycondensation of tritylated cyanoethylidene derivative.The polysaccharide obtained is identical with the O-antigenic polysaccharides of Shigella flexneri serotypes 3b, 3c, and variant Y.It also represents the basic chain of O-antigenic polysaccharides of all serotypes of this bacterium.
- Kotchekov, N. K.,Byramova, N. E.,Tsvetkov, Yu. E.,Backinowsky, L. V.
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p. 3363 - 3375
(2007/10/02)
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