Large-scale isolation of flavan-3-ol phloroglucinol adducts by high-speed counter-current chromatography

Flavan-3-ol phloroglucinol adducts were synthesised through acid catalysed degradation of a procyanidins-rich grape seed extract in the presence of phloroglucinol. The reaction mixture (3.3 g) was fractionated without further sample preparation using the all-liquid chromatographic technique of high-speed counter-current chromatography (HSCCC). Selected solvent systems were hexane-ethyl acetate-methanol-water (0.1:5:0.1:5, v/v/v/v) and (1.5:10:1.5:10, v/v/v/v). The fractions obtained were found to contain almost pure compounds, in some cases final purification was achieved by preparative HPLC. The so-obtained pure standards of (+)catechin-(4alpha-->2)-phloroglucinol, (-)epicatechin-(4beta-->2)-phloroglucinol, (+)catechine, (-)epicatechin-3-O-galloyl-(4beta-->2)-phloroglucinol, (-)epicatechin, and (-)epicatechin gallate are required for quantification of acid-catalysed phloroglucinol degradation products of procyanidins.     

(-)-Catechin in cocoa and chocolate: occurrence and analysis of an atypical flavan-3-ol enantiomer

Cocoa contains high levels of different flavonoids. In the present study, the enantioseparation of catechin and epicatechin in cocoa and cocoa products by chiral capillary electrophoresis (CCE) was performed. A baseline separation of the catechin and epicatechin enantiomers was achieved by using 0.1 mol x L(-1) borate buffer (pH 8.5) with 12 mmol x L(-1) (2-hydroxypropyl)-gamma-cyclodextrin as chiral selector, a fused-silica capillary with 50 cm effective length (75 microm I.D.), +18 kV applied voltage, a temperature of 20 degrees C and direct UV detection at 280 nm. To avoid comigration or coelution of other similar substances, the flavan-3-ols were isolated and purified using polyamide-solid-phase-extraction and LC-MS analysis. As expected, we found (-)-epicatechin and (+)-catechin in unfermented, dried, unroasted cocoa beans. In contrast, roasted cocoa beans and cocoa products additionally contained the atypical flavan-3-ol (-)-catechin. This is generally formed during the manufacturing process by an epimerization which converts (-)-epicatechin to its epimer (-)-catechin. High temperatures during the cocoa bean roasting process and particularly the alkalization of the cocoa powder are the main factors inducing the epimerization reaction. In addition to the analysis of cocoa and cocoa products, peak ratios were calculated for a better differentiation of the cocoa products.     

Secolridoids Glycosides from Jasminum amplexicaule

In addition to jaslanceosides B ( 1 ) and E ( 2 ), and jasminoside ( 3 ), a new secoiridoid glucoside, isojasminoside ( 4 ) was isolated from the leaves of Jasminum amplexicaule (Oleaceace). The structure of 4 was determined on the basis of spectral analysis and chemical reactions. Chemotaxonomy for some selected plants in Jasminum is also discussed.     

CO2 laser-induced decomposition of propan-2-ol,butan-2-ol,pentan-2-ol,pentan-3-ol,and hexan-2-ol

The pulsed CO₂ laser-induced decompositions of propan-2-ol, butan-2-ol, pentan-2-ol, pentan-3-ol, and hexan-2-ol in the gas phase have been investigated. Like ethanol which we examined previously [1] the absorption cross section of propan-2-ol for pulsed 9R14 radiation increases with pressure at low pressures, an effect attributed to rotational hole-filling. In contrast the absorption cross section of butan-2-ol (10R24) has only a small pressure dependence and those of pentan-2-ol (9R26), pentan-3-ol (10R14), and hexan-2-ol (9P20) show little or no variation with pressure in the range 0.1–5.0 torr. Decomposition products have been investigated at low pressure where the excitation of the alkanols was essentially collision free. The observed products for all the alkanols can be rationalized on the basis of primary dehydration and C? C fission channels, with minor contributions from other molecular eliminations. © 1994 John Wiley & Sons, Inc.     

Syntheses of tetrahydropyridin-3-ol and tetrahydroazepin-3-ol from a chiral aziridine-2-carboxylate

A method for the stereoselective preparation of 1,2,3,6-tetrahydropyridin-3-ols and 2,3,4,7-tetrahydro-1H-azepin-3-ols, potentially versatile intermediates in the asymmetric synthesis of various piperidine alkaloids and azasugars, has been developed. The routes start with a readily available optically pure aziridine-2-carboxylate. The design strategy relies on four key transformations involving (1) stereoselective reduction of an acyl-aziridine intermediate derived from the aziridine-2-carboxylate, (2) regioselective aziridine ring opening, (3) N-allylation, and (4) ring-closing metathesis. The method developed in this investigation provides ready access to stereochemically defined and highly functionalized 3-hydroxy-substituted tetrahydropyridines and tetrahydroazepines.     

Viscosity of aqueous solutions of 2-propyne-1-ol, 2-methyl-3-butyne-2-ol and 3-butene-2-ol

Viscosities of aqueous solutions of 2-propyne-1-ol (propargyl alcohol), 2-methyl-3-butyne-2-ol and 3-butene-2-ol have been measured at temperatures 308.15, 313.15, 318.15, 323.15 and 328.15?K over the entire composition range. Viscosity of the aqueous solutions of 2-methyl-3-butyne-2-ol and 3-butene-2-ol increases up to a maximum value and then starts decreasing almost linearly as the mole fraction of alcohol increases. 2-Methyl-3-butyne-2-ol + water and 3-butene-2-ol + water systems exhibit maxima around 0.5 and 0.2 mole fraction, respectively. Conversely, 2-propyne-1-ol + water system shows a rapid initial increase in viscosity up to 0.3 mole fraction followed by a slow steady increase as the mole fraction of alcohol increases to its pure state. Plots of excess viscosities against mole fraction of organic solutes for all the systems exhibit a sharp increase in η ^E to reach a well defined maxima, after which the curves show a descending trend. The variations of viscosity and excess viscosity with the composition of the mixtures have been interpreted in terms of hydrophobic and hydrophilic interactions between the species forming the mixtures.     

A New Flavan-3-ol Glucoside from Daphniphyllum oldhami

A new flavan-3-ol glucoside, (-)-afzelechin-7-O-β-D-glucopyranoside (1), has been isolated from the stem of Daphniphyllum oldhami. The structure of the new compound was elucidated on the basis of detailed spectroscopie analysis and comparison with related compounds.     

One-pot synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol

An efficient method for the synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol under copper catalyst conditions has been developed through a one-step one-pot sequence. This method provides a concise and efficient pathway to synthesize 1-monosubstituted-1, 2, 3-triazole derivatives in good to excellent yields.     

Facile and regioselective synthesis of phenylpropanoid-substituted flavan-3-ols

[reaction: see text] A highly efficient, facile, one-pot regioselective synthesis of a series of phenylpropanoid-substituted flavan-3-ols is described. The mechanism involves dienone-phenol rearrangement followed by a Michael-type reaction.     

Constituents from Polygonum cuspidatum

Two lignan sulfates, a stilbene derivative and a phenol sulfate, together with 10 known compounds, were isolated from an aqueous extract of the root of Polygonum cuspidatum. The new compounds were elucidated based on chemical evidence and spectroscopic techniques including two-dimensional NMR methods. They exhibited no inhibition of lipid peroxidation and no cytotoxic and DNA cleavage activities.     

Peroxy and alkoxy radicals from 2-methyl-3-buten-2-ol

Quantum mechanical calculations were used to determine the structure and energetics of peroxy radicals (P1 and P2) and alkoxy radicals (A1-A3) formed in the atmospheric degradation of 2-methyl-3-buten-2-ol. At the level of theory employed (B3LYP/6-31G(d,p)) low energy conformers were identified with zero, one, or two hydrogen bonds. The beta C-C scission (decomposition) reactions are computed to occur with low barriers, and the 1,5 H-shift (isomerization) reaction of A2 is computed to be of negligible importance. Scission 2 of A2 is computed to be about 93% of the fate of A2, with the balance being scission 1. The new BB1K functional of Truhlar was employed to investigate activation barriers for single intramolecular H-atom transfers across the OH...O* hydrogen bonds, but the barriers to these reactions appear to be too high for these reactions to be important. Extensive searches for transition states for simultaneous double intramolecular H-atom transfer across OH...OH...O* hydrogen bond pairs were unsuccessful.     

Extraction of flavan-3-ols from grape seed and skin into wine using simulated maceration

Simulated maceration assays were carried out in wine model systems using increasing ethanol percentages from 0 to 12.5%, in order to study the extraction of flavan-3-ol monomers and oligomers from grape skins and seeds. The amount of flavan-3-ols transferred to the solutions improves with the increase in the alcohol percentage, although flavanols were much more readily released from grape skins than from seeds. Maximum release of flavanols from the skins is reached after 24 h of maceration in 12.5% ethanol, whereas long maceration and higher ethanol percentages were required for extraction from the seeds, from which maximum flavanol extraction was observed after 2-3 weeks of maceration. Thus, the length of the maceration not only had an influence in the total levels of flavanols reached in the wines, but also in their qualitative composition. The contribution of the seeds to the flavanol composition of the model wines was found to range from about 40% at 24 h of maceration in 12.5% ethanol to as high as 90% after 3 weeks. Gallocatechin was the major flavanol contributed by the skins and catechin by the seeds of the grape variety used (Vitis vinifera cv. Viura). Flavanol extraction was also followed during winemaking of commercial red wines, reaching similar conclusions to that obtained from the model assays.     

Anthocyanins and flavan-3-ols from grapes and wines of Vitis vinifera cv. Cesanese d'Affile

The objective of the present study was to evaluate the amount of some potential health-promoting phenols in the grape of Vitis vinifera cv. Cesanese d'Affile and in wines made from these grapes. The analyses were performed using HPLC/DAD/MS. The accumulation of anthocyanins in the skin and flavan-3-ols in the seed was determined at different stages of ripening of the grape (i.e. green, veraison, middle stage of ripening, and complete ripening). Thirteen anthocyanins were identified in the skin at all stages of ripening, except the green stage. With regard to flavan-3-ols, (+)-catechin, (-)-epicatechin, and (-)-epicatechin gallate were detected in all of the seed samples. The highest (+)-catechin content was found in the seeds of the green grape (2 mg g(-1) DW), whereas in the seeds from the completely ripe grape the content was more than ten times lower. The highest catechin content in the seed was correlated with the lowest anthocyanin content in the skin. The wines produced in the years 2004 and 2005 showed, at wavelengths of 520 and 280 nm, almost identical quali-quantitative chromatographic profiles, with high concentrations of anthocyanin 3-O-glucosides, low concentrations of acylated anthocyanins, and trace amounts of (+)-catechin and (-)-epicatechin.     

Thermodynamic interactions in binary mixtures of anisole with ethanol, propan-1-ol, propan-2-ol, butan-1-ol, pentan-1-ol, and 3-methylbutan-1-ol at T = (298.15, 303.15, and 308.15) K

In this paper, excess thermodynamic functions have been computed from the measured values of density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K, ultrasonic velocity at T = 298.15 K over the entire mixture composition range of (anisole with ethanol, propan-1-ol, propan-2-ol, butan-1-ol, pentan-1-ol, or 3-methyl butan-1-ol). Excess molar volume, V^E has been calculated from densities, whereas deviations in viscosity, Δη, were computed from the measured viscosities. From ultrasonic velocities, isentropic compressibilities were calculated, from which deviations in isentropic compressibility, Δk_s have been computed. Lorenz-Lorentz mixture rule was used to compute molar refractivity, R from refractivity index data and from these data, deviations in molar refractivity, ΔR have been computed. Computed thermodynamic quantities have been fitted to Redlich and Kister polynomial equation to derive the coefficients and standard errors between experimental and predicted quantities. Intermolecular interactions between anisole and alkanols have been studied based on the computed excess thermodynamic quantities.     

Unexpected selective monoadduct formation from 2-methyl-3-butyn-2-ol and α,ω-diiodoperfluorobutane

Radical chain addition of α,ω-diiodoperfluorobutane to 2-methyl-3-buten-2-ol and 2-methyl-3-butyn-2-ol has been studied. The Huang sulfinatodehalogenation system, used as initiator, gave satisfactory conversion yields of the starting diiodide when compared to more classical initiators (AIBN, Fe, triethylborane). Addition to the alkenol yields classically the bis-adduct with variable amounts of the monoadduct. On the contrary the alkynol leads exclusively to the monoadduct formation, in high yield. Some considerations are proposed for interpreting this result. The monoadduct selectively obtained constitutes a powerful intermediate for synthesis.     

2,2,4-三甲基-3-戊醇的合成

以氮代叔丁烷和异丁醛为原料，通过格氏试剂法合成了2，2，4-三甲基-3-戊醇，研究了溶剂种类与用量、滴加时间、反应时间等因素对收率的影响及其规律，提出了较佳的合成条件。     

Heterolytische Anlagerungen an Acetylen-Verbindungen, 2. Mitt.: Einwirkung von N-Bromsuccinimid auf 4-Phenyl-3-butin-1-ol oder 3-Phenyl-2-propin-1-ol in Essigsäure

Zusammenfassung Im Gegensatz zu anderen Acetylen-Verbindungen reagiert 4-Phenyl-3-butin-1-ol mit N-Bromsuccinimid in Eisessig bei Raumtemp. zu einem Gleichgewichts-Gemisch von 3,3-Dibrom-3-benzoylpropanol und dessen cyclischem Tautomeren (2-Phenyl-2-hydroxy-3,3-dibrom-tetrahydrofuran), das auch durch Anlagerung von unterbromiger Säure an denselben Acetylen-Alkohol herzustellen ist. Es wird vermutet, daß das entsprechende Dibrom-diacetoxy-derivat als Zwischenprodukt entsteht. 3-Phenyl-2-propin-1-ol reagiert mit N-Bromsuccinimid in Essigsäure nur in Gegenwart von Wasser zu 2,2-Dibrom-2-benzoyläthanol. Die Umsetzung von Acetylen-Verbindungen mit N-Bromsuccinimid in Essigsäure ist eine bequeme Methode zur Herstellung von ,-Dibromketonen, wobei vorhandene OH-Gruppen nicht angegriffen werden.

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Unlike many other acetylenic compounds, 4-phenyl-3-butin-1-ol reacts at room temperature with N-bromosuccinimide in anhydrous acetic acid, yielding an equilibrium mixture of 3,3-dibromo-3-benzoyl-propanol and its cyclic tautomere, 2-phenyl-2-hydroxy-3,3-dibromo-tetrahydrofuran. The same product is obtained also by addition of HOBr to the acetylenic alcohol mentioned above. An assumption is made that the corresponding dibromodiacetoxy derivative is involved as an intermediate in the reaction with N-bromosuccinimide. 3-Phenyl-2-propin-1-ol interacts with N-bromosuccinimide and acetic acid in presence of water only, giving 2,2-dibromo-2-benzoyl-ethanol. The reaction with N-bromosuccinimide is a convenient method for synthesis of ,-dibromo-ketones from acetylenic compounds, preserving unchanged the hydroxyl groups.

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Mit 2 Abbildungen

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Siehe Internationales Symposium über Konstitution und Reaktions-fähigkeit organischer Verbindungen, Sofia, 21. bis 24. Juni 1966.