Configurations and conformations of some 3-acetoxy-cis-hexahydro-2(3H)-benzofuranones

Catalytic hydrogenation of some 2-ethoxalylcyclohexanones afforded a mixture of isomeric 3-hydroxy-cis-hexahydro-2(3H)-benzofuranones. Three 5-t-butyl substituted diastereomers and two 5-unsubstituted epimers were separated and identified as acetates. The configurations were determined by 350 MHz ¹H-nmr analysis. The conformations of these fused-compounds are discussed.     

Separation of caffeoylquinic acids and flavonoids from Asteris souliei by high‐performance counter‐current chromatography and their anti‐inflammatory activity in vitro

Eleven compounds were successfully separated from Asteris souliei by using a two‐step high‐performance counter‐current chromatography method. The first step involved a reversed phase isocratic counter‐current chromatography separation using hexane/ethyl acetate/methanol/water (1:0.8:1:1 v/v/v/v), which produced three fractions, the first two of which were mixtures. The second step used step‐gradient reversed‐phase counter‐current chromatography with hexane/butanol/ethyl acetate/methanol/water (1:0.5:3.5:1:4 v/v/v/v/v) initially followed by hexane/ethyl acetate/methanol/water (1:2:1:2 v/v/v/v) to separate Fraction 1 into seven compounds; and hexane/ethyl acetate/methanol/water (1:1:1:1.2 v/v/v/v) to separate Fraction 2 into three further compounds. The chemical structures of the separated compounds were identified by ESI‐MS and NMR spectroscopy (¹H and ¹³C). Baicalin ( 5 ), eriodictyol ( 7 ), apigenin‐7‐glycoside ( 8 ), quercetin ( 9 ), luteolin ( 10 ), and apigenin ( 11 ) showed obvious inhibitory effects on lipopolysaccharide‐induced nitric oxide production in RAW264.7 cells at a concentration of 10 μg/mL.     

Prediction of Excess Volumes and Excess Surface Tensions from Experimental Refractive Indices

Abstract

Refractive indices for the binary liquid mixtures: {hexane or heptane + ethanol}, {o-xylene + benzene} and {cyclohexane + benzene, toluene or hexane} were measured at 298.15 K. Excess refractive indices were calculated and fitted to a Redlich-Kister function. Using some mixture rules (Lorentz-Lorenz, Dale -Gladstone, Eykman, Oster, Arago-Biot and Newton), predictions for v^E have been made and compared with experimental data taken from the literature. Furthermore the Sugden equation has been used in two different ways for predicting excess surface tensions: the first one starting from densities and the other one from refractive indices. Results are plotted together with the literature data.     

Interconvertible Eudesmanolides Containing a 6,12‐Hemiketal Function from Salvia castanea Diels f. tomentosa Stib.

Two new eudesmanolide sesquiterpenoids containing a hemiacetal function, castanins G and H ( 1 and 2 ), were obtained as a pair of interconvertible isomers from the aerial parts of Salvia castanea Diels f. tomentosa Stib. , and separated as their uninterconvertible acetates 3 and 4 . Their structures were elucidated by unequivocal interpretation and comparative analysis of the NMR and MS data of the mixture 1 / 2 and of their acetates 3 and 4 , respectively. The inhibitory activity of 3 and 4 toward MCF‐7, HeLa, and HepG2 cell lines was also evaluated.     

Separation of flavonoids from Millettia griffithii with high‐performance counter‐current chromatography guided by anti‐inflammatory activity

Millettia griffithii is a unique Chinese plant located in the southern part of Yunnan Province. Up to now, there is no report about its phytochemical or related bioactivity research. In our previous study, the n‐hexane crude extract of Millettia griffithii revealed significant anti‐inflammatory activity at 100 μg/mL, inspiring us to explore the anti‐inflammatory constituents. Four fractions (I, II, III, and A) were fractionated from n‐hexane crude extract by high‐performance counter‐current chromatography with solvent system composed of n‐hexane/ethyl acetate/methanol/water (8:9:8:9, v/v) and then were investigated for the potent anti‐inflammatory activity. Fraction A, with the most potent inhibitory activity was further separated to give another four fractions (IV, V, VI, and B) with solvent system composed of n‐hexane/ethyl acetate/methanol/water (8:4:8:4, v/v). Compound V and fraction B exhibited remarkable anti‐inflammatory activity with nitric oxide inhibitory rate of 80 and 65%, which was worth further fractionation. Then, three fractions (VII, VIII, and IX) were separated from fraction B with a solvent system composed of n‐hexane/ethyl acetate/methanol/water (8:1:8:1, v/v), with compound VIII demonstrating the most potent inhibitory activity (80%). Finally, the IC₅₀ values of compound V and VIII were tested as 38.2 and 14.9 μM. The structures were identified by electrospray ionization mass spectrometry and¹H and ¹³C NMR spectroscopy.     

Simple One-Pot Synthesis of New Derivatives of the Macrocyclic Aminal 1,3,7,9,13,15,19,21-Octaazapentacyclo-[19.3.1.13,7.19,13.115,19]octacosane (OAPO)

A series of 2,2′-(dihydropyrimidine-1,3(2H,4H)-diyldimethanediyl)bis(substituted-phenols) was synthesized using a Mannich-type reaction between the macrocyclic aminal 1,3,7,9,13,15,19,21-octaazapentacyclo[19.3.1.1^3,7.1^9,13.1^15,19]octacosane (OAPO) (1) and substituted phenols in basic media. These previously unreported compounds were separated from the reaction mixture by column chromatography in highly pure form with 25–75% yields. The most stable conformer was predicted using AM1-type semiempirical quantum chemical calculations.     

Use of High Pressure Liquid Chromatography and Thin Layer Chromatography for the Separation and Detection of Testosterone and its Metabolites from in vitro Incubation Mixtures

Abstract

Testosterone and its 6β-, 7α-, and 16α-hydroxylated metabolites were resolved by high pressure liquid chromatography and thin layer chromatography. Separation by HPLC was achieved in less than 45 min on a microparticulate silica gel column using isocratic elution with isopro-panol:tetrahydrofuran:hexane (5:15:80) as the mobile phase. TLC systems utilizing silica gel on glass and plastic plates, and polysilicic acid on glass fiber sheets are presented. The monohydroxylated metabolites of testosterone formed during incubation of (¹⁴C)-testosterone with liver postmitochondrial preparations from adult male rats pre-treated with phenobarbital or Aroclor 1254 were separated and quantitated by both HPLC and TLC. The results using both techniques are compared with those obtained by paper chromatography.     

A simplified method for the determination of fenpropathrin residues in fruits

Summary A simple and efficient method is described for the determination of fenpropathrin in oranges, pears, apples and strawberries. The procedure is based on the extraction of each homogenized fruit sample with hexane:acetone (1∶1, v/v) mixture, followed by a cleanup technique on a column packed with florisil, using a hexane:ethyl ether (7∶3, v/v) mixture, and gas chromatographic analysis with electron capture detection (ECD). The fortification levels (0.5;1.0;2.0 mg kg⁻¹) were selected according to the maximum residue limits (MRLs) established for fenpropathrin by Brazilian legislation. Mean recoveries from five replicates of fortified fruit samples ranged from 83 % to 98%, with coefficients of variation from 1.4 to 13.5 and detection limits varying from 0.1 to 0.2 mg kg⁻¹.     

Separation of R(+)-and S(-)-Benzyl-3-Tetrahydrofuroates Using Two Different Chiral Columns

Abstract

A chiral separation of N(+)-and S(-)-benzyl-3-tetrahydrofuroate (I) and p-nitrobenzyl-3-tetrahydrofuroate (II) using a Chiralcel OB^© (cellulose tribenzoate) column with a hexane/2-propanol (60:40 v/v) mobile phase is described. Enantiomeric purity of R(+)-I was evaluated using the same chromatographic conditions. I was also separated using a Chiralspher^© (polyamides bonded to silica gel) column with an ethanol/distilled water (50:50 v/v) mobile phase.     

Rapid Assay of Hypothalamic Aromatase Using High Performance Liquid Chromatography

Abstract

A rapid assay for hypothalamic aromatase has been developed using HPLC. Each assay tube contained rat anterior hypothalamus homogenized in Na phosphate buffer (pH 7.0), NADPH regenerating system, unlabelled estradiol and estrone, and 10 μCi of ³H-androstenedione. After agitation at 37°C for 3 hours, the reaction mixture was extracted with CH₂Cl₂, partitioned between 90% methanol and hexane, and the methanol layer chromatographed on a Waters 10μ C-18 Radial-PAK column using acetonitrile/water (70:30). The estrogens were collected together and rechromatographed with THF/water (35:65). The estrone peak was collected, and the ³H-estrone produced was determined by liquid scintillation. The estrone collected from the second chromatographic step was found to be at least 95% pure by methylation and rechromatography. Using the HPLC procedure, enzymatic ³H-estrone formation was found to be linear in a time and protein dependant manner.     

2-Phenyl-1-boraadamantane complexes. Synthesis and intramolecular dynamics

The reaction of triallylborane with 3-phenylprop-1-yne at 135–140 °C followed by treatment of the reaction mixture with MeOH afforded 7-benzyl-3-methoxy-3-borabicyclo[3.3.1]non-6-ene (1) in 81% yield. Hydroboration of compound1 with a solution of BH₃ in THF yielded the tetrahydrofuran complex of 2-phenyl-1-boraadamantane (2). The reactions of trimethylamine or pyridine with compound2 afforded the trimethylamine (3) or pyridine (4) complexes of 2-phenyl-1-boraadamantane. respectively. Hindered rotation about the C(2)−Ph bond in adduct3 was observed by¹H and¹³C NMR spectroscopy. The activation energy of this process is 58.6 kJ mol⁻¹ (determined by 2D¹H−¹H EXSY spectroscopy).     

Isolation and identification of a new neo-clerodane diterpenoid from Teucrium chamaedrys L.

Teucrium chamaedrys L. is an aromatic and medicinal plant used as traditional medicine. Aerial parts of the plant material were dried and extracted with hexane–dichloromethane (extract 1), ethyl acetate–dichloromethane (extract 2) and methanol–dichloromethane (extract 3) in a ratio of 1:1 at rt successively. The solvents were evaporated to give crude extracts. Extract 1 was suspended in water at 60°C then partitioned successively with hexane and ethyl acetate to give hexane and ethyl acetate portions. After the column chromatography (silica gel) of ethyl acetate extract, one new and four known compounds were isolated. The new compound was named as 1(12S,18R)-15,16-epoxy-2β,6β-dihydroxy-neo-cleroda-13(16),14-dien-20,l2-olide-l8,l9-hemiacetal (teuchamaedryn D) (4). The known compounds were teucrin A (1), dihydroteugin (2), teucroxide (3), syspirensin A (5). The chromatographic methods were also applied for extract 3 to isolate verbascoside (6) and teucrioside (7). The structure of isolated compounds was elucidated by spectroscopic methods including LC-TOF/MS, 1D NMR and 2D NMR.     

The photochemistry of a potential diphenylsilylene precursor. Time-resolved spectroscopic studies of the reactivity of a transient vinylsilirane

The photochemistry of 3,4-dimethyl-1,1-diphenylsilacyclopent-3-ene (2), a potential precursor to diphenylsilylene (SiPh₂), has been studied in hydrocarbon and methanol solution by steady state and laser flash photolysis techniques. The results are consistent with the formation of three major photoproducts: SiPh₂ (ca. 20%), 2,3-dimethyl-1,3-butadiene (DMB; ca. 20%), and 2-methyl-2-(methylethenyl)-1,1-diphenylsilirane (9; ca. 75%), the product of formal photochemical (1,3)-sigmatropic rearrangement of 2. Attempts to detect the silylene by laser flash photolysis were unsuccessful, but the vinylsilirane could be easily detected as a long-lived transient exhibiting λ_max=285 nm and lifetime τ=1.3 s in hexane at 25 ^{^}C. The same spectrum is observed in neat methanol solution, where the lifetime of the species is shortened to τ=36 ms and it is quenched by sodium methoxide and methanesulfonic acid with absolute rate constants of k _MeO-=2.0×10⁶ M⁻¹ s⁻¹ and k_H+ =2.6×10³ M⁻¹ s ⁻¹, respectively. The photochemistry of 2 is compared to that of the corresponding germanium homologue (1), whose photolysis in solution has been previously shown to afford diphenylgermylene and DMB cleanly and in high yields. The corresponding vinylgermirane (11a), though not detectable as a primary photoproduct from 1 in solution, is the exclusive product of photolysis of 1 in a 3-methylpentane glass at 78 K, where it exhibits an essentially identical UV/vis spectrum to that of 9. The rate constant for its unimolecular thermal isomerization to regenerate 1 is three orders of magnitude larger than that of the corresponding process in the homologous vinylsilirane (9) in hydrocarbon solution at 25 ^C.     

Assay of N-Propylajmaline in Blood Plasma by Ion-Pair Liquid-Liquid Chromatography

Abstract

A sensitive method for assay of N-propylajmaline (prajmaline) in human plasma is described. The quaternary ammonium compound exists as a pair of stereoisomers, which are isolated and separated by ion-pair liquid-liquid chromatography on microporous silica particles. An aqueous solution containing perchloric acid and sodium perchlorate is used as stationary phase and a mixture of butanol, dichloroethane and hexane as mobile phase. The procedure involves ion-pair extraction from plasma and evaporation prior to the chromatographic separation. Selective detection is achieved by using a fluorescence detector. The method allows assay of concentrations down to 10 pmol of the two forms of prajmaline in 1 ml of plasma with a relative standard deviation below 5 %.     

Determination of total PCB and dioxin by activation analysis

The analysis of PCB's and dioxins in water by activation with high energy photons is described. The substances were traced by heterochlorine. PCB and dioxins were separated selectively in the presence of a biphenyl-dibenzofurane mixture as a collector by extraction with hexane. Polar compounds were rinsed out, and chloroalkyles were evaporated. After exposure of the collector to 30 MeV bremsstrahlung it was decomposed following the Schöniger procedure. The chemical yield was measured through activity counting of¹¹C separated as¹¹CO₂ from the collecting agent, in comparison with a reference material. The chlorine yield was determined gravimetrically using a stoichiometrically well-determined reference material. A few nanograms of chlorine per millilitre are detectable whereby primary samples of 1 l or more may be treated. The described procedure can be recommended as a reference technique for analyses via chromatography/mass spectrometry. Simultaneous analyses of other halogens are planned.     

Solid Phase Extraction and Subsequent Identification by Gas-Chromatography-Mass Spectrometry of a Germination Cue Present in Smoky Water

ABSTRACT

Aqueous extracts of plant-derived smoke (smoky water) are a complex mixture of thousands of components. Solid phase extraction (SPE) cartridges of varying polarity were trialed for their effectiveness in cleaning up smoky water, prior to subsequent analysis. The most effective SPE cartridge used was normal phase silica bonded with aminopropyl (NH₂) with hexane/dichloromethane/methanol mixtures as eluting solvents. This system retained all the active components and permitted elution of two active fractions, separated by an inactive fraction. Other cartridges tested either did not retain all active components or eluted active fractions successively, with more overlap between compositions. Active fractions, as identified by germination tests, were examined by GC-MS and were found to be sufficiently simplified to allow the identification of a new germination cue, 1, 8-cineole.     

Studies on Steroids. CLXXXIL. Determination of 6β-Hydroxycortisol in Urine by High-Performance Liquid Chromatography with Fluorescence Detection

Abstract

A new sensitive method for the determination of 6β-hydroxycortisol in urine by high-performance liquid chromatography with fluorescence detection has been developed. 6β-Hydroxycortisol and its C-6 epimer (internal standard) were transformed quantitatively into the 21-(9-anthroyl) derivatives when treated with 9-anthroyl nitrile in the presence of triethylamine in acetonitrile. The resulting fluorescent esters were readily separated on a Cosmosil SSL column using ethyl acetate/hexane (2:1) as a mobile phase with a detection limit of 25 pg. The efficient clean-up was achieved by the combined use of Bond Elut and Clin Elut cartridges. The present method is applicable to the quantification of 6β-hydroxycortiol in human urine with satisfactory accuracy and precision.     

Evaluation and interlaboratory validation of a GC-MS method for analysis of pesticide residues in teas

A method was described for simultaneous determination of nine organic heterocyclic pesticide residues by gas chromatography-mass spectrometry-selected ion monitoring. Atrazine, vinclozolin, procymidone, triflumizole, imazalil, buprofezin, propiconazole, fenarimol, and pyridaben were clearly separated from each other, extracted with acetone—hexane mixture, purified with graphitized carbon black cartridge and neutral Al₂O₃ cartridge, eluted with acetone—hexane mixture, simultaneously determined by GC-MS, and then quantified with an external standard method. Recoveries of pesticides ranged from 73 % to 116 % at the spiked level of 0.01–30 mg kg⁻¹, while the relative standard deviation was between 3 % and 27 %. In addition, the limits of determination (0.01 mg kg⁻¹ to 5.0 mg kg⁻¹) and linearity (0.02–40 μg mL⁻¹) revealed that simultaneous determination of multi-residues in Chinese teas (like Oolong tea, green tea, red tea, etc.) was possible. Furthermore, an interlaboratory study among 5 labs was conducted to further validate the method, and the results were satisfactory.     

Separation of nine compounds from Salvia plebeia R.Br. using two‐step high‐speed counter‐current chromatography with different elution modes

Nine compounds were successfully separated from Salvia plebeia R.Br. using two‐step high‐speed counter‐current chromatography with three elution modes. Elution–extrusion counter‐current chromatography was applied in the first step, while classical counter‐current chromatography and recycling counter‐current chromatography were used in the second step. Three solvent systems, n‐hexane/ethyl acetate/ethanol/water (4:6.5:3:7, v/v), methyl tert‐butyl ether/ethyl acetate/n‐butanol/methanol/water (6:4:1:2:8, v/v) and n‐hexane/ethyl acetate/methanol/water (5:5.5:5:5, v/v) were screened and optimized for the two‐step separation. The separation yielded nine compounds, including caffeic acid ( 1 ), 6‐hydroxyluteuolin‐7‐glucoside ( 2 ), 5,7,3′,4′‐tetrahydroxy‐6‐methoxyflavanone‐7‐glucoside ( 3 ), nepitrin ( 4 ), rosmarinic acid ( 5 ), homoplantaginin ( 6 ), nepetin ( 7 ), hispidulin ( 8 ), and 5,6,7,4′‐tertrahydroxyflavone ( 9 ). To the best of our knowledge, 5,7,3′,4′‐tetrahydroxy‐6‐methoxyflavanone‐7‐glucoside and 5,6,7,4′‐tertrahydroxyflavone have been separated from Salvia plebeia R.Br. for the first time. The purities and structures of these compounds were identified by high‐performance liquid chromatography, electrospray ionization mass spectrometry, ¹H and ¹³C NMR spectroscopy. This study demonstrates that high‐speed counter‐current chromatography is a useful and flexible tool for the separation of components from a complex sample.     

Formation of polycyclic hydrocarbons containing a spiropentane or methylenecyclobutane moiety upon thermal decomposition of cyclopropane-containing 1-pyrazolines

1-Pyrazolines1 and2 obtained by 1,3-dipolar cycloaddition of diazocyclopropane to norbornene or deltacyclene undergo dediazotization at 410–450°C to give a mixture of strained hydrocarbons, namely, spirocyclopropane-1,3'-tricyclo[3.2.1.0^2,4]octane (4) or spiro{cyclopropane-1,4'-pentacyclo[4.4.0.0^2,8.0^3,5.0^7,9]decane} (6) and isomeric tricyclo[5.2.1.0^2,5]dec-5-enes (5) or pentacyclo[6.4.0.0^2,10.0^3,6.0^9,11]dec-6-enes (7) in a 30–70% overall yield. An increase in temperature favors the isomerization of spiro hydrocarbons4 and6 to the respective unsaturated hydrocarbons5 and7. The latter undergo cyclopropanation with diazomethane in the presence of Pd(acac)₂ or (PhO)₃P · CuCl to afford polycyclanes9a,b or10a,b containing a spiro[2.3]hexane moiety condensed at thecis-1,4 position. Unsaturated 1-pyrazoline3 obtained from diazocyclopropane and norbornadiene decomposes at 330–370°C with elimination of cyclopentadiene to give 3(5)-vinylpyrazole in a yield up to 75%.Some of the results reported in this paper have been presented at the VIIIth European Symposium on organic chemistry (Barcelona, August–September 1993),cf. Ref. 1.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 662–667, April, 1994.This study was financially supported by the Russian Fund for Fundamental Research (grant 94-03-08902).