Structural characterization and identification of oleanane-type triterpene saponins in Glycyrrhiza uralensis Fischer by rapid-resolution liquid chromatography coupled with time-of-flight mass spectrometry

Oleanane‐type triterpene saponins (OTS) are major active ingredients in Glycyrrhiza uralensis. In this work, a rapid‐resolution liquid chromatography with time‐of‐flight mass spectrometry (RRLC/TOF‐MS) method has been developed to characterize and identify OTS from G. uralensis. The major diagnostic ions and fragmentation pathways from thirteen OTS have been characterized for the first time. At a low fragmentor voltage of 120 V in positive ion mode, the precursor ion [M + H]⁺ or/and [M + Na]⁺ was obtained for accurate determination of molecular formula. When the fragmentor voltage was increased to 425 V, abundant characteristic fragment ions were observed for structural characterization. Neutral losses of sugar moieties, such as glucuronic acid (GlcA, 176 Da), glucose (Glc, 162 Da) and rhamnose (Rha, 146 Da), were commonly observed in the MS spectra for prediction of the sugar number and sequences. Other typical losses included AcOH (60 Da), CH₂O (30 Da), 2 × H₂O (2 × 18 Da) and HCOOH (46 Da) from [Aglycone + H–H₂O]⁺ (named [B]⁺), corresponding to the presence of a C₂₂‐acetyl group, C₂₄‐hydroxyl group, C₂₂‐hydroxyl group or C₃₀‐carboxyl group on the aglycone moiety, respectively. In particular, characteristic ring cleavages of the aglycone moieties on A‐ and B‐rings were observed. Based on the fragmentation patterns of reference compounds, nineteen OTS have been identified in an extract of G. uralensis, thirteen of which were unambiguously identified and the other six were tentatively assigned. Copyright © 2010 John Wiley & Sons, Ltd.     

Three sterically hindered 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate derivatives

In the title compounds, 2‐methoxyethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₄, (II), isopropyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₃, (III), and ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₀H₁₈N₂O₃, (IV), the heterocyclic pyran ring adopts a flattened boat conformation. In (II) and (III), the carbonyl group and a double bond of the heterocyclic ring are mutually anti, but in (IV) they are mutually syn. The ester O atoms in (II) and (III) and the carbonyl O atom in (IV) participate in intramolecular C—H...O contacts to form six‐membered rings. The dihedral angles between the naphthalene substituent and the closest four atoms of the heterocyclic ring are 73.3 (1), 71.0 (1) and 74.3 (1)° for (II)–(IV), respectively. In all three structures, only one H atom of the NH₂ group takes part in N—H...O [in (II) and (III)] or N—H...N [in (IV)] intermolecular hydrogen bonds, and chains [in (II) and (III)] or dimers [in (IV)] are formed. In (II), weak intermolecular C—H...O and C—H...N hydrogen bonds, and in (III) intermolecular C—H...O hydrogen bonds link the chains into ladders along the a axis.     

Structural characterization and identification of iridoid glycosides,saponins, phenolic acids and flavonoids in Flos Lonicerae Japonicae by a fast liquid chromatography method with diode‐array detection and time‐of‐flight mass spectrometry

A fast liquid chromatography method with diode‐array detection (DAD) and time‐of‐flight mass spectrometry (TOF‐MS) has been developed for analysis of constituents in Flos Lonicerae Japonicae (FLJ), a traditional Chinese medicine derived from the flower bud of Lonicera japonica. The chromatographic analytical time decreased to 25 min without sacrificing resolution using a column packed with 1.8‐µm porous particles (4.6 × 50 mm), three times faster than the performance of conventional 5.0‐µm columns (4.6 × 150 mm). Four major groups of compounds previously isolated from FLJ were structurally characterized by DAD‐TOF‐MS: iridoid glycosides showed maximum UV absorption at 240 nm; phenolic acids at 217, 242, and 326 nm; flavonoids at 255 and 355 nm; while saponins had no absorption. In electrospray ionization (ESI)‐TOF‐MS experiments, elimination of a glucose unit (162 Da), and successive losses of H₂O, CH₃OH and CO, were generally observed in iridoid glycosides; saponins were characterized by a series of identical aglycone ions; phenolic acids typically generated a base peak at [M–H–caffeoyl]^? by loss of a caffeic acid unit (162 Da) and several marked quinic acid moiety ions; cleavage of the glycosidic bond (loss of 162 or 308 Da), subsequent losses of H₂O, CO, RDA and C‐ring fragmentation were the most possible fragmentation pathways for flavonoids. By accurate mass measurements within 4 ppm error for each molecular ion and subsequent fragment ions, as well as the ‘full mass spectral’ information of TOF‐MS, a total of 41 compounds including 13 iridoid glycosides, 11 phenolic acids, 7 saponins, and 10 flavonoids were identified in a methanolic extract of FLJ. Copyright © 2009 John Wiley & Sons, Ltd.     

Cationic,neutral and anionic metal(II) complexes derived from 4‐oxo‐4H‐pyran‐2,6‐dicarboxylic acid (chelidonic acid)

The structures of five metal complexes containing the 4‐oxo‐4H‐pyran‐2,6‐dicarboxylate dianion illustrate the remarkable coordinating versatility of this ligand and the great structural diversity of its complexes. In tetraaquaberyllium 4‐oxo‐4H‐pyran‐2,6‐dicarboxylate, [Be(H₂O)₄](C₇H₂O₆), (I), the ions are linked by eight independent O—H...O hydrogen bonds to form a three‐dimensional hydrogen‐bonded framework structure. Each of the ions in hydrazinium(2+) diaqua(4‐oxo‐4H‐pyran‐2,6‐dicarboxylato)calcate, (N₂H₆)[Ca(C₇H₂O₆)₂(H₂O)₂], (II), lies on a twofold rotation axis in the space group P2/c; the anions form hydrogen‐bonded sheets which are linked into a three‐dimensional framework by the cations. In bis(μ‐4‐oxo‐4H‐pyran‐2,6‐dicarboxylato)bis[tetraaquamanganese(II)] tetrahydrate, [Mn₂(C₇H₂O₆)₂(H₂O)₈]·4H₂O, (III), the metal ions and the organic ligands form a cyclic centrosymmetric Mn₂(C₇H₂O₆)₂ unit, and these units are linked into a complex three‐dimensional framework structure containing 12 independent O—H...O hydrogen bonds. There are two independent Cu^II ions in tetraaqua(4‐oxo‐4H‐pyran‐2,6‐dicarboxylato)copper(II), [Cu(C₇H₂O₆)(H₂O)₄], (IV), and both lie on centres of inversion in the space group P; the metal ions and the organic ligands form a one‐dimensional coordination polymer, and the polymer chains are linked into a three‐dimensional framework containing eight independent O—H...O hydrogen bonds. Diaqua(4‐oxo‐4H‐pyran‐2,6‐dicarboxylato)cadmium monohydrate, [Cd(C₇H₂O₆)(H₂O)₂]·H₂O, (V), forms a three‐dimensional coordination polymer in which the organic ligand is coordinated to four different Cd sites, and this polymer is interwoven with a complex three‐dimensional framework built from O—H...O hydrogen bonds.     

2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.     

Synthesis and Spectroscopic Study of Some New Phosphoramidates,Crystal Structures of N‐Benzoyl‐N′,N″‐bis(azetidinyl)phosphoric Triamide and N‐Benzoyl‐N′,N″‐bis(hexamethylenyl)phosphoric Triamide

Some new N‐carbonyl, phosphoramidates with formula C₆H₅C(O)N(H)P(O)R₂ (R = NC₃H₆ ( 1 ), NC₆H₁₂ ( 2 ), NHCH₂CH=CH₂ ( 3 ), N(C₃H₇)₂ ( 4 )) and CCl₃C(O)N(H)P(O)R′₂ (R′ = NC₃H₆ ( 5 ), NHCH₂CH=CH₂ ( 6 )) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR and IR spectroscopy and elemental analysis. The structures were determined for compounds 1 and 2 . Compound 1 exists as two crystallographically independent molecules in crystal lattice. Both compounds 1 and 2 produced dimeric aggregates via intermolecular ‐P=O…H‐N‐ hydrogen bonds, which in compound 2 is a centrosymmetric dimer. In compounds with four‐membered ring amine groups, ³J(P,C)>²J(P,C), in agreement with our previous studies about five‐membered ring amine groups. Also, ³J(P,C) values in compounds 1 and 5 are greater than in compounds with five‐, six‐ and seven‐membered ring amine groups.     

5‐Acetyl‐2‐amino‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile and 2‐amino‐5‐benzoyl‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile acetonitrile solvate

The syntheses, X‐ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C₁₅H₁₄N₂O₂, (II), and C₂₀H₁₆N₂O₂·C₂H₃N, (III), respectively. In both mol­ecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo‐axial phenyl substituent and the flat part of the pyran ring are 92.7 (1) and 93.2 (1)° in (II) and (III), respectively. In the crystal structure of (II), inter­molecular N—H⋯N and N—H⋯O hydrogen bonds link the mol­ecules into a sheet along the (103) plane, while in (III), they link the mol­ecules into ribbons along the a axis.     

Gas‐phase fragmentation reactions of protonated benzofuran‐ and dihydrobenzofuran‐type neolignans investigated by accurate‐mass electrospray ionization tandem mass spectrometry

We have investigated gas‐phase fragmentation reactions of protonated benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by accurate‐mass electrospray ionization tandem and multiple‐stage (MSⁿ) mass spectrometry combined with thermochemical data estimated by Computational Chemistry. Most of the protonated compounds fragment into product ions B ([M + H–MeOH]⁺), C ([ B –MeOH]⁺), D ([ C –CO]⁺), and E ([ D –CO]⁺) upon collision‐induced dissociation (CID). However, we identified a series of diagnostic ions and associated them with specific structural features. In the case of compounds displaying an acetoxy group at C‐4, product ion C produces diagnostic ions K ([ C –C₂H₂O]⁺), L ([ K –CO]⁺), and P ([ L –CO]⁺). Formation of product ions H ([ D –H₂O]⁺) and M ([ H –CO]⁺) is associated with the hydroxyl group at C‐3 and C‐3′, whereas product ions N ([ D –MeOH]⁺) and O ([ N –MeOH]⁺) indicate a methoxyl group at the same positions. Finally, product ions F ([ A –C₂H₂O]⁺), Q ([ A –C₃H₆O₂]⁺), I ([ A –C₆H₆O]⁺), and J ([ I –MeOH]⁺) for DBNs and product ion G ([ B –C₂H₂O]⁺) for BNs diagnose a saturated bond between C‐7′ and C‐8′. We used these structure‐fragmentation relationships in combination with deuterium exchange experiments, MSⁿ data, and Computational Chemistry to elucidate the gas‐phase fragmentation pathways of these compounds. These results could help to elucidate DBN and BN metabolites in in vivo and in vitro studies on the basis of electrospray ionization ESI‐CID‐MS/MS data only.     

Fragmentation of 2‐aroylbenzofuran derivatives by electrospray ionization tandem mass spectrometry

We investigated the gas‐phase fragmentation reactions of a series of 2‐aroylbenzofuran derivatives by electrospray ionization tandem mass spectrometry (ESI‐MS/MS). The most intense fragment ions were the acylium ions m/z 105 and [M+H–C₆H₆]⁺, which originated directly from the precursor ion as a result of 2 competitive hydrogen rearrangements. Eliminations of CO and CO₂ from [M+H–C₆H₆]⁺ were also common fragmentation processes to all the analyzed compounds. In addition, eliminations of the radicals •Br and •Cl were diagnostic for halogen atoms at aromatic ring A, whereas eliminations of •CH₃ and CH₂O were useful to identify the methoxyl group attached to this same ring. We used thermochemical data, obtained at the B3LYP/6‐31+G(d) level of theory, to rationalize the fragmentation pathways and to elucidate the formation of E , which involved simultaneous elimination of 2 CO molecules from B .     

Methyl 2‐benzamido‐4‐(3,4‐dimethoxyphenyl)‐5‐methylbenzoate and N‐{5‐benzoyl‐2‐[(Z)‐2‐methoxyethenyl]‐4‐methylphenyl}benzamide

Methyl 2‐benzamido‐4‐(3,4‐dimethoxyphenyl)‐5‐methylbenzoate, C₂₄H₂₃NO₅, (Ia), and N‐{5‐benzoyl‐2‐[(Z)‐2‐methoxyethenyl]‐4‐methylphenyl}benzamide, C₂₄H₂₁NO₃, (IIa), were formed via a Diels–Alder reaction of appropriately substituted 2H‐pyran‐2‐ones and methyl propiolate or (Z)‐1‐methoxybut‐1‐en‐3‐yne, respectively. Each of these cycloadditions might yield two different regioisomers, but just one was obtained in each case. In (Ia), an intramolecular N—H...O hydrogen bond closes a six‐membered ring. A chain is formed due to aromatic π–π interactions, and a three‐dimensional framework structure is formed by a combination of C—H...O and C—H...π(arene) hydrogen bonds. Compound (IIa) was formed not only regioselectively but also chemoselectively, with just the triple bond reacting and the double bond remaining unchanged. Compound (IIa) crystallizes as N—H...O hydrogen‐bonded dimers stabilized by aromatic π–π interactions. Dimers of (IIa) are connected into a chain by weak C—H...π(arene) interactions.     

Thermotropic Liquid Crystals Based on Extended 2,5‐Disubstituted‐1,3,4‐Oxadiazoles: Structure–Property Relationships,Variable‐Temperature Powder X‐ray Diffraction,and Small‐Angle X‐ray Scattering Studies

A class of extended 2,5‐disubstituted‐1,3,4‐oxadiazoles R¹‐C₆H₄‐{OC₂N₂}‐C₆H₄‐R² (R¹=R²=C₁₀H₂₁O 1 a , p‐C₁₀H₂₁O‐C₆H₄‐C?C 3 a , p‐CH₃O‐C₆H₄‐C?C 3 b ; R¹=C₁₀H₂₁O, R²=CH₃O 1 b , (CH₃)₂N 1 c ; F 1 d ; R¹=C₁₀H₂₁O‐C₆H₄‐C?C, R²=C₁₀H₂₁O 2 a , CH₃O 2 b , (CH₃)₂N 2 c , F 2 d ) were prepared, and their liquid‐crystalline properties were examined. In CH₂Cl₂ solution, these compounds displayed a room‐temperature emission with λ_max at 340–471 nm and quantum yields of 0.73–0.97. Compounds 1 d , 2 a – 2 d , and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized‐light optical microscopy and differential scanning calorimetry. Structure determination by a direct‐space approach using simulated annealing or parallel tempering of the powder X‐ray diffraction data revealed distinctive crystal‐packing arrangements for mesogenic molecules 2 b and 3 a , leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200–210 °C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable‐temperature X‐ray diffractometry. Nondestructive phase transitions (crystal‐to‐crystal, crystal‐to‐mesophase, mesophase‐to‐liquid) were observed in the diffractograms of 1 b, 1 d , 2 b, 2 d , and 3 a measured at 25–200 °C. Powder X‐ray diffraction and small‐angle X‐ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure–property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions.     

2J(P,C) and 3J(P,C) Coupling Constants in Some New Phosphoramidates. Crystal Structures of CF3C(O)N(H)P(O)[N(CH3)(CH2C6H5)]2 and 4‐NO2‐C6H4N(H)P(O)[4‐CH3‐NC5H9]2

Some new phosphoramidates were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR spectroscopy and elemental analysis. The structures of CF₃C(O)N(H)P(O)[N(CH₃)(CH₂C₆H₅)]₂ ( 1 ) and 4‐NO₂‐C₆H₄N(H)P(O)[4‐CH₃‐NC₅H₉]₂ ( 6 ) were confirmed by X‐ray single crystal determination. Compound 1 forms a centrosymmetric dimer and compound 6 forms a polymeric zigzag chain, both via ‐N‐H…O=P‐ intermolecular hydrogen bonds. Also, weak C‐H…F and C‐H…O hydrogen bonds were observed in compounds 1 and 6 , respectively. ¹³C NMR spectra were used for study of ²J(P,C) and ³J(P,C) coupling constants that were showed in the molecules containing N(C₂H₅)₂ and N(C₂H₅)(CH₂C₆H₅) moieties, ²J(P,C)>³J(P,C). A contrast result was obtained for the compounds involving a five‐membered ring aliphatic amine group, NC₄H₈. ²J(P,C) for N(C₂H₅)₂ moiety and in NC₄H₈ are nearly the same, but ³J(P, C) values are larger than those in molecules with a pyrrolidinyl ring. This comparison was done for compounds with six and seven‐membered ring amine groups. In compounds with formula XP(O)[N(CH₂R)(CH₂C₆H₅)]₂, ²J(P,CH₂)_benzylic>²J(P,CH₂)_aliphatic, in an agreement with our previous study.     

(M)‐ and (P)‐8‐[(1S,2R)‐2‐hydroxy‐1‐methyl‐2‐phenylethyl]‐8‐methyl‐8,9‐dihydro‐7H‐dinaphth[2,1‐c:1′,2′‐e]azepinium bromide solvates

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C₃₂H₃₀NO⁺·Br^?·3C₃H₆O, while the P isomer crystallizes as a (1/1) di­chloro­methane solvate, C₃₂H₃₀NO⁺·Br^?·CH₂Cl₂. In each structure, O—H?Br hydrogen bonds link the cations and anions to give ion pairs. The seven‐membered azepinium ring adopts the usual twisted‐boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

Catharanthinol and di­hydro­catha­ranth­inol: two Iboga‐class alkaloids

The title compounds are indole alkaloids of the Iboga class. In both compounds, viz. catharanthinol methanol solvate, C₂₀H₂₄N₂O·CH₄O, (I), and di­hydro­catharanthinol mono­hydrate, C₂₀H₂₆N₂O·H₂O, (II), a nitrogen‐containing seven‐membered ring is fused to the indole system and shares two sides with a tricyclic isoquinuclidine group. The main difference between (I) and (II) is the presence of a C=C bond in the isoquinuclidine ring in (I). The presence of amine and hydroxy groups in these mol­ecules and of methanol [in (I)] or water [in (II)] solvent mol­ecules results in intra‐ and/or intermolecular hydrogen bonding.     

7‐Hydroxy‐5‐methoxy‐6,8‐dimethylflavanone: a natural flavonoid

The title flavonoid [systematic name: (2S)‐7‐hydroxy‐5‐methoxy‐6,8‐dimethyl‐2‐phenyl‐3,4‐dihydrochromen‐4(2H)‐one], C₁₈H₁₈O₄, displays statistical conformational disorder, with three conformations of the molecule involving three orientations of the phenyl ring and two orientations of the fused heterocyclic ring. The conformational disorder is correlated with the isomerization equilibrium between the flavanone and chalcone forms. The conformational behaviour has a potential impact on the biological activity of this class of compounds. Moreover, π stacking interactions at van der Waals distances are present between the aromatic rings of chroman‐4‐one groups of symmetry‐related molecules. Apart from these π–π interactions, molecules are linked by strong O—H...O hydrogen bonds between hydroxy and carbonyl groups.     

N—H...O and N—H...N interactions in three pyran derivatives

The three pyran structures 6‐methylamino‐5‐nitro‐2,4‐diphenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₅N₃O₃, (I), 4‐(3‐fluorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄FN₃O₃, (II), and 4‐(4‐chlorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄ClN₃O₃, (III), differ in the nature of the aryl group at the 4‐position. The heterocyclic ring in all three structures adopts a flattened boat conformation. The dihedral angle between the pseudo‐axial phenyl substituent and the flat part of the pyran ring is 89.97 (1)° in (I), 80.11 (1)° in (II) and 87.77 (1)° in (III). In all three crystal structures, a strong intramolecular N—H...O hydrogen bond links the flat conjugated H—N—C=C—N—O fragment into a six‐membered ring. In (II), molecules are linked into dimeric aggregates by N—H... O(nitro) hydrogen bonds, generating an R₂²(12) graph‐set motif. In (III), intermolecular N—H...N and C—H...N hydrogen bonds link the molecules into a linear chain pattern generating C(8) and C(9) graph‐set motifs, respectively.     

Characterization of polyphenol compounds from the roots and stems of Parthenocissus laetevirens by high‐performance liquid chromatography/tandem mass spectrometry

A facile method based on high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC/(–)ESI‐MSⁿ) has been established for the analyses of polyphenol compounds in the root and stems of Parthenocissus laetevirens. Two characteristic fragments [C₃O₂ (68 Da) and C₂H₂O (42 Da)] were utilized for the structural identification of polyphenols. Based on the reference standards, the fragment C₃O₂ was presented when the compound possessed a 2,3‐dihydro‐1H‐indene‐4, 6‐diol moiety. Meanwhile, the C₂H₂O fragment (42 Da) yielded from the resorcinol ring was confirmed by resveratrol and three synthesized compounds identified as (E)‐5‐styrylbenzene‐1,3‐diol, (E)‐4‐styrylphenol and (E)‐4‐(3,4,5‐trimethoxystyryl)phenol. FTICR‐MSⁿ was performed to further confirm the structures of the fragments. Overall, 15 polyphenol compounds were characterized. Three polyphenol compounds were initially and tentatively characterized from P. laetevirens for the first time, and one was proposed as a novel compound. Furthermore, a pair of stereoisomers was readily distinguished by breakdown curves, and the trans‐, cis‐isomers could be identified by HPLC/DAD‐UV spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

6‐Hydroxy‐2,2‐di­methyl‐3,4‐di­hydro‐2H‐benzo[b]pyran

The title compound, 2,2‐di­methyl­chroman‐6‐ol, C₁₁H₁₄O₂, has been identified as a side product from the condensation of hydro­quinone with 2‐methyl­but‐3‐en‐2‐ol. The pyran ring has a half‐chair conformation. The hydroxyl groups are involved in intermolecular hydrogen bonding which generates infinite spiral chains around the fourfold screw axes; the O?O hydrogen‐bonded distances are 2.661 (1) Å.