Synthesis, structure and Hirshfeld surface analysis of 2-oxo-2H-chromen-4-yl penta-noate.

In the title compound, C14H14O4, the dihedral angle between the coumarin ring system (r.m.s deviation = 0.016 Å) and the penta-noate ring is 36.26 (8)°. A short intra-molecular C-H⋯O contact of 2.40 Šis observed. Hirshfeld surface analysis reveals that 46.1% of the inter-molecular inter-actions are from H⋯H contacts, 28.6% are from H⋯O/O⋯H contacts and 14.7% are from H⋯C/C⋯H.

2-Oxo-2H-chromen-4-yl 3,3-di-methyl-butano-ate.

In the crystal of the title compound, C15H16O4, the mol-ecules are connected through C-H⋯O hydrogen bonds, generating [100] chains, which are crosslinked by weak π-π stacking inter-actions.

Preformulation study for the selection of a suitable polymer for the development of ellagic acid-based solid dispersion using hot-melt extrusion.

Ellagic acid is one of the most studied polyphenolic compounds due to its numerous promising therapeutic properties. However, this therapeutic potential remains difficult to exploit owing to its low solubility and low permeability, resulting in low oral bioavailability. In order to allow an effective therapeutic application of EA, it is therefore necessary to develop strategies that sufficiently enhance its solubility, dissolution rate and bioavailability. For this purpose, solid dispersions based on pre-selected polymers such as Eudragit® EPO, Soluplus® and Kollidon® VA 64, with 5% w/w ellagic acid loading were prepared by hot extrusion and characterized by X-ray diffraction, FTIR spectroscopy and in vitro dissolution tests in order to select the most suitable polymer for future investigations. The results showed that Eudragit® EPO was the most promising polymer for ellagic acid solid dispersions development because its extrudates allowed to obtain a solution supersaturated in ellagic acid that was stable for at least 90 min. Moreover, the resulting apparent solubility was 20 times higher than the actual solubility of ellagic acid. The extrudates also showed a high dissolution rate of ellagic acid (96.25% in 15 min), compared to the corresponding physical mixture (6.52% in 15 min) or the pure drug (1.56% in 15 min). Furthermore, increasing the loading rate of ellagic acid up to 12% in extrudates based on this polymer did not negatively influence its release profile through dissolution tests.

The Metabolomic study of Calotropis procera Ait. from Burkina Faso, based on chemical functional groups profiling using FTIR.

Background C. procera is an important wild medicinal plant used in different area of Burkina Faso for the neuropsychiatric disorders treatment. It was reported to possess many pharmacological properties because of its phytochemical diversity. This study was carried out to identify possible specific chemical characteristics form C. procera leaves and root-bark samples, harvested in two regions of Burkina Faso, for a better selective use of specimens in traditional medicine. Methods Plant materials (leaves and root-bark) were collected from five sites in each region. Samples powders and extracts were mixed with potassium bromide for the Fourier Transform Infrared Spectroscopy (FTIR) analysis. A multivariate data analysis was performed to highlight differences in the FTIR spectral profile of samples. Therefore, phytochemical contents such as phenolics, flavonoids and terpenoids were evaluated with aqueous and methanolic extracts, using UV/visible light spectrophotometer method. Results Results of principal component analysis (PCA) showed a significant difference between leaves and root-bark spectral profile, independently to the region of collection. These profiles possess characteristic signals which could be exploited as biomarkers for plant organ discrimination. The phytochemical contents evaluation showed that C. procera leaves contain more significant phenolics, and root-bark possess more terpenoid compounds. This study of C. procera Ait. based on FTIR spectral characteristic and phytochemical content, suggest that terpenoids, notably cardenolide-type could be a good biomarkers for C. procera samples characterization and to explain root-bark therapeutic potential.

Crystal structure of 2-oxo-2H-chromen-7-yl 4-fluoro-benzoate.

In the title compound, C16H9FO4, (I), the benzene ring is oriented at an acute angle of 59.03 (15)° relative to the coumarin plane (r.m.s deviation = 0.009 Å). This conformation of (I) is stabilized by an intra-molecular C-H⋯O hydrogen bond, which closes a five-membering ring. In the crystal, mol-ecules of (I) form infinite zigzag chains along the b-axis direction, linked by C-H⋯O hydrogen bonds. Furthermore, the crystal structure is supported by π-π stacking inter-actions between neighbouring pyrone and benzene or coumarin rings [centroid-centroid distances in the range 3.5758 (18)-3.6115 (16) Å], as well as C=O⋯π inter-actions [O⋯centroid distances in the range 3.266 (3)-3.567 (3) Å]. The theoretical data for (I) obtained from quantum chemical calculations are in good agreement with the observed structure, although the calculated C-O-C-C torsion angle between the coumarin fragment and the benzene ring (73.7°) is somewhat larger than the experimental value [63.4 (4)°]. Hirshfeld surface analysis has been used to confirm and qu-antify the supra-molecular inter-actions.

2-Oxo-2H-chromen-7-yl 4-tert-butyl-benzoate.

In the title compound, C20H18O4, the benzoate ring is oriented at an acute angle of 33.10 (12)° with respect to the planar (r.m.s deviation = 0.016 Å) coumarin ring system. An intra-molecular C-H⋯O hydrogen bond closes an S(6) ring motif. In the crystal, C-H⋯O contacts generate infinite C(6) chains along the b-axis direction. Also present are π-π stacking inter-actions between neighbouring pyrone and benzene rings [centroid-centroid distance = 3.7034 (18) Å] and C=O⋯π inter-actions [O⋯centroid = 3.760 (3) Å]. The data obtained from quantum chemical calculations performed on the title compound are in good agreement with the observed structure, although the calculated C-O-C-C torsion angle between the coumarin ring system and the benzoate ring (129.1°) is somewhat lower than the observed value [141.3 (3)°]. Hirshfeld surface analysis has been used to confirm and qu-antify the supra-molecular inter-actions.

Crystal structure of 2-oxo-2H-chromen-3-yl 4-chloro-benzoate and Hirshfeld surface analysis.

In the title compound, C16H9ClO4 the dihedral angle between the coumarin ring system [maximum deviation = 0.023 (1) Å] and the benzene ring is 73.95 (8)°. In the crystal, π-π inter-actions link the dimers into a three-dimensional framework. A quantum chemical calculation is in generally good agreement with the observed structure, although the calculated dihedral angle between the ring systems (85.7%) is somewhat larger than the observed value [73.95 (8)°]. Hirshfeld surface analysis has been used to confirm and qu-antify the supra-molecular inter-actions.

Fluorescence Quenching of Two Coumarin-3-carboxylic Acids by Trivalent Lanthanide Ions.

The effects of various trivalent lanthanide ions (acetates of Ce3+, Er3+, Eu3+, Nd3+) on the electronic absorption and fluorescence spectra of un-substituted coumarin-3-carboxylic acid (CCA) and 7-N,N-diethylamino-coumarin-3-carboxylic acid (DECCA) have been investigated in dimethylsulfoxide (DMSO) at room temperature. Depending on the lanthanide ion nature and concentration, significant spectral changes of absorption bands occurred for both coumarin derivatives. These spectral changes were attributed to the formation of ground-state complexes between the coumarin carboxylate derivatives and lanthanide ions. The fluorescence quenching of CCA and DECCA upon increasing the lanthanide ion concentration was studied. Different quantitative treatments, including the Stern-Volmer equation, the Perrin equation and a polynomial equation, were applied and compared in order to determine the nature of the quenching mechanisms for both coumarin derivatives. The results suggested the contribution of both dynamic and static quenching. Significant differences of CCA and DECCA fluorescence quenching efficiency were also observed, depending on the lanthanide ion. DECCA fluorescence lifetime measurements, performed in the absence and in the presence of Ln3+, confirmed a contribution of static quenching.

Crystal structure of 2-oxo-2H-chromen-3-yl propano-ate.

In the title compound, C12H10O4, the dihedral angle between the coumarin ring system [maximum deviation = 0.033 (8) Å] and the propionate side chain is 78.48 (8)°. In the crystal, weak C-H⋯O hydrogen bonds generate inversion dimers and and C-H⋯π and π-π inter-actions link the dimers into a three-dimensional network. A quantum chemical calculation is in good agreement with the observed structure.

2-Oxo-2H-chromen-4-yl 4-methyl-benzoate.

The asymmetric unit of the title compound, C17H12O4, consists of two independent mol-ecules. The chromen-2-one ring and the 4-methyl-benzoate side chain are inclined to one another at a dihedral angle of 64.79 (10)° in one mol-ecule and 88.3 (1)° in the other. In the crystal, mol-ecules form R 2 (2)(8) centrosymmetric dimers via C-H⋯O hydrogen bonds. These dimers are stacked by C-H⋯O hydrogen bonds, resulting in R 2 (2)(18) and R 3 (2)(16) ring motifs. π-π stacking inter-actions between two parallel chromen-2-one rings, with centroid-centroid distances of 3.743 (1) and 3.771 (1) Å, are also present.

2-Oxo-2H-chromen-4-yl propionate.

In the title compound, C12H10O4, the atoms of the 2-oxo-2H-chromene ring system and the non-H atoms of the 4-substituent all lie on a crystallographic mirror plane. The mol-ecular structure exhibits an intra-molecular C-H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, mol-ecules form R 3 (2)(12) trimeric units via C-H⋯O inter-actions which propagate into layers parallel to the ac plane. These layers are linked by weak C-H⋯O inter-actions along the [010] direction, generating a three-dimensional network.

2-Oxo-2H-chromen-4-yl 4-tert-butyl-benzoate.

In the title mol-ecule, C(20)H(18)O(4), the three methyl groups of the tert-butyl substituent show rotational disorder. Each methyl group is split over three positions, with refined site-occupation factors of 0.711 (4), 0.146 (3) and 0.144 (4). The benzene ring of the benzoate group is oriented at a dihedral angle of 60.70 (7)° with respect to the planar chromene ring [maximum deviation = 0.046 (2) Å]. The crystal structure features centrosymmetric R(2) (2)(8) dimers formed via C-H⋯O inter-actions, and these dimeric aggregates are connected by C-H⋯π inter-actions.

4-[(Hy-droxy)(4-methyl-phen-yl)methyl-idene]isochroman-1,3-dione.

In the title compound, C(17)H(12)O(4), the six-membered heterocyclic ring adopts a distorted screw-boat conformation. The mol-ecular structure exhibits an S(6) ring motif, owing to an intra-molecular O-H⋯O hydrogen bond. In the crystal, weak C-H⋯O contacts generate an infinite chain along the c axis. There are also π-π stacking inter-actions between neighbouring isochromanedione benzene rings, with a centroid-centroid distance of 3.755 (1) Å, and C-O⋯π inter-actions with an O⋯centroid distance of 3.964 (2) Å.

2-Oxo-2H-chromen-4-yl 4-meth-oxy-benzoate.

In the title mol-ecule, C17H12O5, the chromen-2-one ring and the 4-meth-oxy-benzoate side chain are inclined to one another at a dihedral angle of 69.82 (9)°. The crystal structure features parallel sheets of centrosymmetric R2(2)(6) dimers joined by a C(7) chain, resulting in centrosymetric tetra-mers of hydrogen-bonded mol-ecules with graph-set motif R4(4)(40). These centrosymetric tetra-mers are connected by a pair of hydrogen bonds described by an R2(2)(8) ring motif and a C(7) chain via C-H⋯O inter-actions. In the structure, there are also π-π stacking inter-actions between chromene benzene and the six-membered heterocyclic rings [centroid-centroid distance = 3.691 (2) Å] and weak C=O⋯π inter-actions [O⋯(ring centroid) distance = 3.357 (3) Å].

4-[(4-Chloro-phen-yl)(hy-droxy)methyl-idene]isochromane-1,3-dione.

In the title compound, C(16)H(9)ClO(4), the six-membered heterocyclic ring adopts a screw-boat conformation. The benzene rings are oriented to each other at a dihedral angle of 59.26 (9)°. The mol-ecular structure exhibits a ring motif, viz. S(6), owing to an intra-molecular O-H⋯O hydrogen bond. The presence of C-H⋯O contacts generates an infinite chain along [001]. Also present are π-π stacking inter-actions between neighbouring isochromanedione benzene rings [centroid-centroid distance = 3.746 (1) Å], and C-O⋯π inter-actions [O⋯centroid = 3.934 (2) Å].

2-Oxochromen-4-yl 4-(dimethyl-amino)-benzoate.

In the title mol-ecule, C(18)H(15)NO(4), the benzoate ring is oriented at a dihedral angle of 43.43 (6)° with respect to the planar [maximum deviation = 0.038 (2) Å] chromene ring. The crystal structure features R(2) (2)(12) centrosymetric dimers formed via C-H⋯O inter-actions and these dimeric aggregates are connected by C-H⋯π inter-actions.

Revisiting the photophysical properties and excited singlet-state dipole moments of several coumarin derivatives.

The solvent effects on the electronic absorption and fluorescence emission spectra of several coumarins derivatives, containing amino, N,N-dimethyl-amino, N,N-diethyl-amino, hydroxyl, methyl, carboxyl, or halogen substituents at the positions 7, 4, or 3, were investigated in eight solvents with various polarities. The first excited singlet-state dipole moments of these coumarins were determined by various solvatochromic methods, using the theoretical ground-state dipole moments which were calculated by the AM1 method. The first excited singlet-state dipole moment values were obtained by the Bakhshiev, Kawski-Chamma-Viallet, Lippert-Mataga, and Reichardt-Dimroth equations, and were compared to the ground-state dipole moments. In all cases, the dipole moments were found to be higher in the excited singlet-state than in the ground state because of the different electron densities in both states. The red-shifts of the absorption and fluorescence emission bands, observed for most compounds upon increasing the solvent polarity, indicated that the electronic transitions were of π-π* nature.