High-performance liquid chromatography/electrospray ionization mass spectrometric characterization of new products formed by the reaction between flavanols and malvidin 3-glucoside in the presence of acetaldehyde

Monomer and polymer flavan-3-ols and anthocyanins are the two major groups of phenolic compounds in red wine and one of the most important reactions during red wine ageing is the condensation reaction, either direct or indirect, between these two classes of compounds. In this work, the reaction of (+)-catechin, (-)-epicatechin and dimer procyanidin B2 with malvidin 3-glucoside, in the presence of acetaldehyde, was carried out in wine model solutions at pH 1.7 and 3.2. Identification of the reaction products was carried out by high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) and MS(n) analysis. Various reaction products were detected. The structures of three condensation products - malvidin-3-glucoside-ethyl-(epi)catechin-1'-hydroxyethyl, malvidin-3-glucoside-ethyl-dimer-vinyl and malvidin-3-glucoside-ethyl-dimer-1'-hydroxyethyl - were identified in a model solution for the first time. Moreover, in the reaction solution containing dimer B2 at pH 3.2, monomer epicatechin, trimer and tetramer procyanidins were also detected indicating that, under these conditions, dimer procyanidins can either be hydrolyzed to monomers or polymerized to higher oligomer or polymers.     

Analysis of European oak bark beetle (Scolytus intricatus) extracts using hyphenated and chiral chromatography techniques

Two bioactive compounds, viz. 4-methylheptan-3-ol (I) and 4-methylheptan-3-one (II) have been identified in European oak bark beetle (Scolytus intricatus) extracts by gas chromatography coupled with mass spectrometric and electroantennographic detector systems. Further examination of these compounds using gas chromatography on chiral stationary phases, as well as a comparison with optically active standards proved the absolute configuration of the identified compounds to be (3R,4S)-I and (S)-II. The discovery of (3R,4S)-I and (S)-II as insect-produced compounds in both sexes of S. intricatus constitutes the first reported occurrence in this species.     

Photochemistry of 3H-furo[3,4-c]pyrazoles and 3H-thieno[3,4-c]pyrazoles

The first examples of 3H-furo[3,4-c]pyrazoles and 3H-thieno[3,4-c]pyrazoles were prepared in an attempt to isolate examples of cyclopropane-fused thiophenes and furans. Adducts of acetylenic ketones and 2-diazopropane were reacted with 10-camphorsulfonic acid or phosphorus pentasulfide to produce the title compounds. Photolysis of these compounds did not give the cyclopropane-fused products rather an unreported photochemical fragmentation was observed.     

Nitrogenous sesquiterpenes from the Thai marine sponge Halichondria sp.

Five nitrogenous sesquiterpenes having an isonitrile [(−)-axisonitrile-3], a formamide [(+)-axamide-3, axamide-2 and (3S^*,5R^*,6R^*,9R^*)-3-formamido-1(10)-cadinene], and an amine [(−)-halichamine] functionality were isolated from the Thai marine sponge Halichondria sp., together with two steroids, ergosterol and ergosterol peroxide. (−)-Axisonitrile-3 was isolated from the natural source for the first time, while (+)-axamide-3 and (−)-halichamine were new metabolites. The structures of these compounds were elucidated on the basis of their spectroscopic data and by chemical transformations. All sesquiterpenes were tested for their cytotoxic activity against six cancer cell lines (HeLa, HuCCA-1, A549, MOLT-3, HepG2, MDA-MB231). Only (−)-axisonitrile-3 showed strong activity to the HepG2 cell line with an IC₅₀ value of 1.3 μM.     

Iridium-catalyzed asymmetric hydrogenation of 3-substituted unsaturated oxindoles to prepare C3-mono substituted oxindoles

An efficient and enantioselective hydrogenation of 3-substituted unsaturated oxindoles has been developed by an iridium complex of tropos phosphine-oxazoline ligands. It is the first example to prepare chiral C3-mono substituted oxindoles via asymmetric catalysis. And the reaction provides instant access to this kind of compounds with excellent conversion and enantioselectivities (up to 93% ee).     

New opinions on the amidoalkylation of hydrophosphorylic compounds

A new and milder version of the procedure for the synthesis of N-protected α-aminoalkylphosphorylic compounds by reaction of alkyl carbamates, aldehydes and hydrophosphorylic compounds in acetic anhydride/acetyl chloride and a new mechanism for this type of reaction are described. The isolation, for the first time, of N,N′-benzylidene- and N,N′-alkylidenebiscarbamates as intermediates from the reaction medium and studies of the direct reaction of pre-obtained biscarbamates and hydrophosphorylic compounds in acetic anhydride are reported. A new version of the mechanism for this reaction which includes an Arbuzov-type reaction is proposed.     

A single chalcone and additional rotenoids from Lonchocarpus nicou

The lipophile extract of Lonchocarpusnicou roots afforded the new pyranochalcone 3-O-methylabyssinone A as well as the new rotenoids 7′-hydroxytephrosin, and 7′-nor-6′-oxo-2′,3′-dehydrorotenone, both compounds occurring with the known 7′-hydroxydeguelin and 7′-nor-6′-oxo-2′,3′-dehydro-12aβ-hydroxyrotenone. Furthermore, two rotenoid epoxides previously reported as resulting from the direct oxidative conversion of rotenone and 12aβ-hydroxyrotenone, respectively, were isolated for the first time from a plant source. All the structures were established on the basis of UV, MS, and NMR data.     

Effects of residual metal compounds and chain-end structure on thermal degradation of poly(3-hydroxybutyric acid)

Thermal degradation behaviours of poly(3-hydroxybutyric acid) (P(3HB); bacterial poly[(R)-3-hydroxybutyric acid] and synthetic poly[(R,S)-3-hydroxybutyric acid] samples, were examined under both isothermal and non-isothermal conditions. The inverse of number-average degree of polymerisation for all P(3HB) samples decreased linearly with degradation time during the initial stage of isothermal degradation at a temperature ranging from 170-190 °C. In addition, crotonyl unit was detected in the residual polymer samples as main ω-chain-end. These results indicate that the dominant thermal degradation reaction for P(3HB) is a random chain scission via cis-elimination reaction of P(3HB) molecules. It was found that the presence of either Ca or Mg ions enhances the depolymerisation of P(3HB) molecules, while that Zn ions hardly catalyse the reaction. As a result, a shift of thermogravimetric curves toward the lower temperature regions was observed for the P(3HB) samples containing high amounts of Ca and Mg compounds.     

Identification of shikonin and its ester derivatives from the roots of Echium italicum L.

Nine shikonin pigments: shikonin (S), acetylshikonin (AS), propionylshikonin (PS), isobutyrylshikonin (IBS), tiglylshikonin (TS), 3,3-dimethylacrylshikonin (DAS), angelylshikonin (ANS), 2-methyl-n-butyrylshikonin (MBS) and isovalerylshikonin (IVS) were identified in the root epidermis of Echium italicum L. for the first time. A new thin-layer chromatographic (TLC) method for the separation of enantiomers alkannin and shikonin proved only shikonin after saponification of the root extract, and was afterwards esterified with the corresponding acyl chloride to acquire seven standard compounds (all except ANS). The developed isocratic high-peformance liquid chromatographic (HPLC) methods with VIS and mass spectrometry (MS) detection, allowed for the first time simultaneous separation of all nine compounds with similar structures including positional and geometric isomers in a short time. Structures of the main five compounds (AS, IBS, ANS, MBS, IVS) isolated from the extract by a new semi-preparative HPLC on C18 have additionally been confirmed by ¹H and ¹³C nuclear magnetic resonance spectra, which were reported for AS and MBS for the first time.     

Ultrasound extracted flavonoids from four varieties of Portuguese red grape skins determined by reverse-phase high-performance liquid chromatography with electrochemical detection

Several flavonoids present in red grape skins from four varieties of Portuguese grapes were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) with electrochemical detection (ECD). Extraction of flavonoids from red grape skins was performed by ultrasonication, and hydrochloric acid in methanol was used as extraction solvent. The developed RP-HPLC method used combined isocratic and gradient elution with amperometric detection with a glassy carbon-working electrode. Good peak resolution was obtained following direct injection of a sample of red grape extract in a pH 2.20 mobile phase. Eleven different flavonoids: cyanidin-3-O-glucoside (kuromanin), delphinidin-3-O-glucoside (myrtillin), petunidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside (oenin), (+)-catechin, rutin, fisetin, myricetin, morin and quercetin, can be separated in a single run by direct injection of sample solution. The limit of detection obtained for these compounds by ECD was 20-90 pg/L, 1000 times lower when compared with photodiode array (PDA) limit of detection of 12-55 ng/L. RP-HPLC-ECD was characterized by an excellent sensitivity and selectivity, and appropriate for the simultaneous determination of these electroactive phenolic compounds present in red grape skins.     

[H2en]2{La2M(SO4)6(H2O)2} (M=Co, Ni): First organically templated 3d-4f mixed metal sulfates

The first organically templated 3d-4f mixed metal sulfates, [H₂en]₂{La₂M(SO₄)₆(H₂O)₂} (M=Co 1, Ni 2) have been synthesized and structurally determined from non-merohedrally twinned crystals. The two compounds are isostructural and their structures feature a three-dimensional anionic network formed by the lanthanum(III) and nickel(II) ions bridged by sulfate anions. The La(III) ions in both compounds are 10-coordinated by four sulfate anions in bidentate chelating fashion, and two sulfate anions in a unidentate fashion. The transition metal(II) ion is octahedrally coordinated by six oxygens from four sulfate anions and two aqua ligands. The doubly protonated enthylenediamine cations are located at the tunnels formed by 8-membered rings (four La and four sulfate anions).     

Insights into the reaction of trans-diarylethenes with thionyl chloride: a practical synthesis of chlorobenzo[b]thiophenes

The reactivity of a variety of trans-1,2-diarylethenes with thionyl chloride has been investigated. All the substrates could readily afford 3-chlorobenzo[b]thiophenes in moderate yields and a pair of threo- and erythro-1,2-dichloro-1,2-diarylethanes as the minor products under mild condition. The diastereoisomers of 1,2-dichloro-1,2-diarylethanes with a methoxy group on the benzene ring were found for the first time to be also converted into cholobenzo[b]thiophenes under treatment of thionyl chloride. The chemical transformations have been mechanistically rationalized and successfully applied to a one-pot synthesis of novel fluorescent liquid crystalline compounds containing benzo[b]thiophene and 1,3,4-oxadiazole units. Their spectroscopic and mesogenic behaviours are also described.     

A new approach to the synthesis of 4-(N-aryl)carbamoylmethyl-4,5-dihydropyridazin-3(2H)-ones

Reaction of N-aryl substituted maleimides with aliphatic ketazines leads to the formation of 4,5-dihydropyridazin-3(2H)-ones in moderate yields. The reaction proceeds through 1,4-addition of an azine to the maleimide double bond, as confirmed by separation of the corresponding adducts in some cases, which are then converted into 4,5-dihydropyridazin-3(2H)-ones. In addition, the solid-state synthesis of 4,5-dihydropyridazin-3(2H)-ones is demonstrated for the first time.     

A xanthone and a polyketide derivative from the leaves of Cassia obtusifolia (Leguminosae)

A new xanthone, 1,8-dihydroxy-3-methoxy-6-methylxantone and a new polyketide derivative, (4R^∗,5S^∗,6E,8Z)-ethyl-4-((E)-but-1-enyl)-5-hydroxypentdeca-6,8-dienoate, together with 20 known secondary metabolites, including 2 steroids, 4 xanthones, 10 anthraquinones, 2 triterpenoids, 1 fatty ester, and (E)-eicos-14-enoic acid, were isolated from the leaves of Cassia obtusifolia. To the best of our knowledge, the last compound was isolated from a natural source for the first time. The structures of all the compounds were elucidated on the basis of 1D and 2D NMR experiments. Some of the compounds were tested against Salmonella typhi, Staphylococcus aureus, Candida albicans ATCC 9002, and Candida tropicalis, they did not show any activity.     

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond was investigated and a series of N3-ethoxymethylated heterocyclic compounds were synthesized. A mechanism in which diethyl phosphite acts as an efficient surrogate of ethanol was proposed and supported by several evidences.     

Determination of eighty-one volatile organic compounds in dietary Rumexinduratus leaves by GC/IT-MS, using different extractive techniques

The volatile compounds of Rumexinduratus leaves were studied for the first time. In order to achieve the most complete volatile profile four different extractive techniques (hydrodistillation, solid-phase microextraction, Soxhlet system and direct solvent extraction) were applied. The different extracts were analysed by gas chromatography/ion trap-mass spectrometry (GC/IT-MS) which allowed the identification of 81 compounds, distributed by several chemical classes: esters, terpenes, aldehydes, acids, norisoprenoids, ketones, naphthalene derivatives, steroids derivatives and alcohols, among others. The different techniques lead to different compounds' extraction. Using hexane and dichloromethane, 9 and 4 compounds were extracted, respectively. Hydrodistillation, solid-phase microextraction and Soxhlet extraction allowed the extraction of 43, 24 and 29 compounds, respectively. Hydrodistillation was revealed to be the most effective technique, allowing the extraction of a higher number of compounds, both in the hydrolat (20 compounds) and essential oil (34 compounds), having 11 compounds in common.     

Vinylogous N,N-dimethylaminomethylenation of 3-[(1-substituted)ethylidene]-oxindoles with N,N-dimethylformamide dimethylacetal

An efficient stereoselective synthesis of various 3-(3-dimethylaminoprop-2-enylidene)oxindoles has been disclosed. The compounds were synthesized via a vinylogous N,N-dimethylaminomethylenation at the γ-position of 3-[(1-substituted)ethylidene]oxindoles with DMF-DMA.     

Rapid access of 2,3,4-trisubstituted-2,3,4,9-tetrahydrothiopyrano[2,3-b]indole derivatives via one-pot three component reaction using organocatalysis

A simple, green, and efficient one-pot three component strategy for the synthesis of 2-aryl-3-nitro-4-hydroxy-2,3,4,9-tetrahydrothiopyrano[2,3-b]indole derivatives has been achieved by the combination of N-protected-2-chloro-3-formylindoles, sodium hydrosulfide with β-nitrostyrenes at room temperature in ethanol using DABCO as a catalyst. Furthermore, high enantio- and diastereoselectives’ syntheses of title compounds have been achieved for the first time using cupreidine (5 mol %) as catalyst, providing good to excellent yields.     

Isoaurones: synthesis and stereochemical assignments of geometrical isomers

A series of isoaurones have been synthesized for the first time from substituted acetophenones via benzo-2(3H)-furanone in three steps. Geometrical isomers of the isoaurones were separated. The differences in the proton and carbon NMR spectra of the E- and Z-isoaurones afford a useful method for distinguishing between the two isomers. Marginalin, a metabolite of Dytiscus marginalis has been synthesized and the spectral data of the synthetic E-isomer were in good agreement with those of the natural product. The antioxidant activity of isoaurones was determined by superoxide free radical (NBT) method and isoaurones 12 and 13 displayed excellent antioxidant activity.