Mara Jure

Synthesis and Antiradical Properties of 4-Aryl-3,4-Dihydroquinolin-2-(1H)-Ones, Aza Analogs of Neoflavonoids

A convenient one-pot method is proposed for the synthesis of 4-aryl-3,4-dihydroquinolin-2(1H)-ones from the monoanilides of malonic acid and aromatic aldehydes. The antiradical activity of the synthesized 4-aryl-3,4-dihydroquinolin-2(1H)-ones was examined (tests on the inhibition of 2,2-di-phenyl-1-picrylhydrazyl and galvinoxyl). It was found that the highest antiradical activity is exhibited by derivatives of syringaldehyde; the activity of the other compounds is moderate or low, however in the 2,2-diphenyl-1-picrylhydrazyl inhibition test it is comparable with or higher than for the widely used antioxidant Ionol.

Crystal structures and physicochemical properties of diltiazem base and its acetylsalicylate, nicotinate and L-malate salts

Diltiazem is a drug used as a calcium channel blocker in the treatment of cardiovascular disorders. Because of the poor aqueous solubility of the drug, its hydrochloride salt has been marketed. Due to the short elimination half-life of diltiazem, extended-release formulations were developed. In the present work, the crystal engineering approach has been employed to obtain diltiazem forms with lower water solubility by treating with carboxylic acids. Three molecular salts of diltiazem with aspirin, niacin and L-malic acid were synthesized and characterized by single crystal and powder XRD, DTA, solid state CP-MAS, NMR and UV/vis techniques. The single crystal structure determination allowed us to study the supramolecular structures and proton transfer interactions from the carboxylic acids to diltiazem in the solid state, while the NMR studies showed the interactions in solution. In the crystal, the N,N-(dimethyl)ethylamine fragment of the drug molecule interacts with the carboxylic groups of the acids to form heterosynthons. The maximum 40-fold decrease of the aqueous solubility is achieved for diltiazem acetylsalicylate hydrate in comparison with the solubility of diltiazem hydrochloride.

Molecular salts of propranolol with dicarboxylic acids: diversity of stoichiometry, supramolecular structures and physicochemical properties

Crystallization of the drug propranolol with dicarboxylic acids yielded stable crystalline molecular salts with oxalic and fumaric acids in molar ratios of 1 : 1 and 2 : 1, and with maleic acid in a molar ratio of 1 : 1 only. The melting points of the salts obtained were roughly twice the melting point of pure propranolol, while their aqueous solubility was significantly higher in comparison to that of the propranolol base.

Zwitterionic and free forms of arylmethyl Meldrum's acids

C-Alkyl (including C-arylmethyl) derivatives of Meldrums acids are attractive building blocks in organic synthesis, mainly due to the unusually high acidity of the resulting compounds. Three examples, namely 5-[4-(diethylamino)benzyl]-2,2-dimethyl-1,3-dioxane-4,6-dione, C17H23NO4, (I), 2,2-dimethyl-5-(2,4,6-trimethoxybenzyl)-1,3-dioxane-4,6-dione, C16H20O7, (II), and 5-(4-hydroxy-3,5-dimethoxybenzyl)-2,2-dimethyl-1,3-dioxane-4,6-dione, C15H18O7, (III), have been synthesized, characterized by NMR and IR spectroscopy, and studied by single-crystal X-ray structure analysis. The nature of the different substituents resulted in remarkable differences in both the molecular conformations and the crystal packing arrangements. The presence of a substituent with a basic centre in compound (I) leads to the formation of an inner salt accompanied by drastic changes in the conformation of the 1,3-dioxane-4,6-dione fragment. By virtue of strong N-H···O hydrogen bonds, the residues are assembled into infinite chains with the graph-set descriptor C(10). Compound (II) contains methoxy groups in both the ortho- and para-positions of the arylmethyl fragment. Because of the absence of classical hydrogen-bond donors in this structure, the crystal packing is controlled by van der Waals forces and weak C-H···O interactions. Compound (III) contains methoxy groups in both meta-positions and a hydroxy group in the para-position. Supramolecular tetrameric synthons which comprise hydrogen-bonded dimers associated into tetramers through π-π interactions of overlapping benzene rings were observed.

Extracts of Peppermint, Chamomile and Lavender as Antioxidants

This paper is devoted to the studies of total polyphenol content and antiradical activity of peppermint, chamomile and lavender grown in local backyard gardens of Latvia. Different solvents (96, 70 and 40% ethanol) and extraction methods (maceration at room temperature at dark or under day-light irradiation, as well as reflux) were tested. All extracts were analyzed for total polyphenol content (Folin–Ciocalteu method), as well as for antiradical activity (DPPH and GO assays). It was found out that local peppermint and chamomile is as good source of polyphenols as those plants grown in southern countries; however, the total polyphenol content of lavender is lower than that mentioned in literature. The highest polyphenol content for all plant materials was achieved, when 70% ethanol was used for extraction. Peppermint extracts were found as most powerful free radical scavengers among all tested plant materials. 96% Ethanol extract of peppermint and chamomile demonstrated the highest antiradical activity, while 70% ethanol was the most suitable for preparation of lavender extract with optimal free radical scavenging activity.

Crystal structure of 3-hy­droxy-2-(4-hy­droxy-3-meth­oxy­phenyl­methyl)-5,5-di­methyl­cyclo­hex-2-enone

In the title dimedone derivative, the 4-hydroxy-3-methoxybenzyl substituent adopts a sofa conformation. In the crystal, molecules are assembled into a sheet structure parallel to the ab plane via O—H⋯O hydrogen bonds.

Crystal structure of 3-(4-hydroxy-3-methoxyphenyl)-N-phenylpropanamide, C16H17NO3

Abstract C16H17NO3, orthorhombic, P212121 (no. 19), a = 7.9882 (2) Å, b = 11.4053 (3) Å, c = 16.2381 (5) Å, V = 1479.42 (7) Å3, Z = 4, Rgt(F) = 0.0480, wRref(F2) = 0.0991, T = 173 K.

Crystal structure of 3-(4-hy-droxy-phen-yl)-2-[(E)-2-phenyl-ethen-yl]quinazolin-4(3H)-one.

The title compound consists of a substituted 2-[(E)-2-arylethenyl]-3-arylquinazolin-4(3H)-one skeleton. The substituents at the ethylene fragment are located in trans positions. In the crystal, molecules are connected via O—H⋯O hydrogen bonds forming a 21 helix propagating along the a-axis direction.

Crystal structure of 5-[4-(di-ethyl-amino)-benzyl-idene]-2,2-dimethyl-1,3-dioxane-4,6-dione.

The title compound, 5-[4-(diethylamino)phenylmethylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione, have been synthesized and its crystal structure determined. Due to the absence of hydrogen-bond donors in the structure, the crystal packing is controlled by van der Waals forces and weak C—H⋯O interactions, which associate the molecules in dimers.