- Iridoid glycosides from the leaves of Sambucus ebulus
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Six new iridoid glycosides (1-6) of the "Valeriana type" were isolated from leaves of Sambucus ebulus. The structures were elucidated by 1D- and 2D-NMR spectroscopy, mass spectrometry, and chemical degradation methods as 10-O-acetylpatrinoside-aglycone-11-O-[4″-O-acetyl-α-L- rhamnopyranosyl-(1→2)-β-D-ribohexo-3-ulopyranoside] (1), 7-O-acetylpatrinoside-aglycone-11-O-[4″-O-acetyl-α-L- rhamnopyranosyl-(1→2)-β-D-ribohexo-3-ulopyranoside] (2), 10-O-acetylpatrinoside-aglycone-11-O-[α-L-rhamnopyranosyl-(1→2) -β-D-ribohexo-3-ulopyranoside] (3), patrinoside-aglycone-11-O-[4″-O- acetyl-α-L-rhamnopyranosyl-(1→2)-β-D-ribohexo-3-ulopyranoside] (4), 10-O-acetylpatrinoside-aglycone-11-O-[4″-O-acetyl-α-L- rhamnopyranosyl-(1→2)-β-D-glucopyranoside] (5), and patrinoside-aglycone-11-O-2′-deoxy-β-D-glucopyranoside (6). Compounds 1-4 represent the first examples of acylated iridoid diglycosides bearing the uncommon D-ribohexo-3-ulopyranosyl sugar moiety. Compound 6 is the first iridoid glycoside with a 2-deoxy-D-glucopyranosyl sugar moiety.
- Pieri, Valerio,Schwaiger, Stefan,Ellmerer, Ernst P.,Stuppner, Hermann
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- Harnessing the reactivity of poly(methylhydrosiloxane) for the reduction and cyclization of biomass to high-value products
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Poly(methylhydrosiloxane) (PMHS) has been examined for its ability to reduce and subsequently cyclize carbohydrate substrates using catalytic tris(pentafluorophenyl)borane (BCF). The work herein is the first reported example of the direct conversion of monosaccharides to 1,4-anhydro and 2,5-anhydro products utilizing a hydrosiloxane reducing agent. PMHS is produced from waste products of the silicone industry, making it a green alternative to traditional hydrosilane reducing agents. This work thus contributes to the goal of utilizing renewable feedstocks in the production of fine-chemicals.
- Hein, Nicholas M.,Seo, Youngran,Lee, Stephen J.,Gagné, Michel R.
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p. 2662 - 2669
(2019/06/13)
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- Highly atom economical uncatalysed and I2-catalysed silylation of phenols, alcohols and carbohydrates, using HMDS under solvent-free reaction conditions (SFRC)
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An uncatalysed silylation of phenols, regardless on the aggregate state and nature of the substituents with 0.55 equiv of HMDS under solvent-free reaction conditions (SFRC) at room temperature is reported. Sterically hindered phenols, carbohydrates and most of the alcohols additionally required a catalytic amount (up to 2 mol %) of iodine. The reaction protocol is very simple; obtaining a pure product, particularly of uncatalysed reactions, was frequently a completely solvent-free process.
- Jereb, Marjan
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experimental part
p. 3861 - 3867
(2012/06/30)
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- Time-dependent profiling of metabolites from Snf1 mutant and wild type yeast cells
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The effect of sampling time in the context of growth conditions on a dynamic metabolic system was investigated in order to assess to what extent a single sampling time may be sufficient for general application, as well as to determine if useful kinetic information could be obtained. A wild type yeast strain (W) was compared to a snf1Δ mutant yeast strain (S) grown in high-glucose medium (R) and in low-glucose medium containing ethanol (DR). Under these growth conditions, different metabolic pathways for utilizing the different carbon sources are expected to be active. Thus, changes in metabolite levels relating to the carbon source in the growth medium were anticipated. Furthermore, the Snf1 protein kinase complex is required to adapt cellular metabolism from fermentative R conditions to oxidative DR conditions. So, differences in intracellular metabolite levels between the W and S yeast strains were also anticipated. Cell extracts were collected at four time points (0.5, 2, 4, 6 h) after shifting half of the cells from R to DR conditions, resulting in 16 sample classes (WR, WDR, SR, SDR) x (0.5, 2, 4, 6 h). The experimental design provided time course data, so temporal dependencies could be monitored in addition to carbon source and strain dependencies. Comprehensive two-dimensional (2D) gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS) was used with discovery-based data mining algorithms (Anal. Chem. 2006, 78, 5068-5075 (ref 1); J. Chromatogr., A 2008, 1186, 401-411 (ref 2)) to locate regions within the 2D chromatograms (i.e., metabolites) that provided chemical selectivity between the 16 sample classes. These regions were mathematically resolved using parallel factor analysis to positively identify the metabolites and to acquire quantitative results. With these tools, 51 unique metabolites were identified and quantified. Various time course patterns emerged from these data, and principal component analysis (PCA) was utilized as a comparison tool to determine the sources of variance between these 51 metabolites. The effect of sampling time was investigated with separate PCA analyses using various subsets of the data. PCA utilizing all of the time course data, averaged time course data, and each individual time point data set independently were performed to discern the differences. For the yeast strains examined in the current study, data collection at either 4 or 6 h provided information comparable to averaged time course data, albeit with a few metabolites missing using a single sampling time point.
- Humston, Elizabeth M.,Dombek, Kenneth M.,Hoggard, Jamin C.,Young, Elton T.,Synovec, Robert E.
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experimental part
p. 8002 - 8011
(2009/04/06)
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- Capillary gas-chromatographic analysis of monosaccharides: Improvements and comparisons using trifluoroacetylation and trimethylsilylation of sugar O-benzyl- and O-methyl-oximes
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Two new procedures for the gas-chromatographic analysis of monosaccharides are reported. One involves derivatization of the sugars by reaction with O-benzylhydroxylamine followed by trifluoroacetylation with N-methylbis(trifluoroacetamide) and chromatography on a DB-1701 capillary column. This technique probably provides the best resolution achieved to date of the C3-C6 aldoses, as well as of the corresponding alditols. Ketoses can be qualitatively analyzed by this method, but complications interfere with their quantitative analysis. The second procedure also involves initial derivatization as the O-benzyloxime, but is followed by trimethylsilylation with 1-trimethylsilylimidazole, and chromatography on a DB-17 column. This technique is particularly useful for C5 sugars, C6 ketoses, and mixtures of sugars, alditols, and/or lactones. A number of additional, critical, observations on the derivatization and capillary gas-chromatographic analysis of monosaccharides are described.
- Andrews, Mark A.
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