Volume 73, Issue 2

An efficient aldol condensation/click reaction sequence is employed for the synthesis of chalcone-triazole-based derivatives in moderate to good yields. The ability of target compounds to inhibit 15-lipoxygenase enzyme was investigated and moderate to low inhibitory activities were observed for the synthesized compounds.

The investigation of the supramolecular interactions between the lithium isothiocyanate salt and 18-crown-6 (18C-6) in commercial tetrahydrofuran leads to the formation of a lithium compound, LiNCS(H 2 O)(18C-6) ( 1 ). In the crystal structure the asymmetric unit contains two similar LiNCS(H 2 O)(18C-6) molecules. Solid-state photoluminescence experiments have shown that compound 1 emits violet luminescence, and its possible emission mechanism was investigated in detail based on theoretical calculations.

Fifteen new 28-amide derivatives of madecassic acid, isolated from the tropical medicinal herb Centella asiatica (Apiaceae), have been synthesised, and their cytotoxicity on three cancer cell lines, KB (carcinoma cancer), HepG2 (liver cancer) and Lu-1 (lung cancer), was evaluated. The results showed that acetylation of the 2,3,23-hydroxyl group and/or amidation of the 28-COOH group strongly increased the cytotoxicity of the synthesised compounds.

Motivated by the medical interest in methylene blue as potential anti-Alzheimer agent, the charge densities of three salt structures containing the methylene blue cation with nitrate (as dihydrate), chloride (as pentahydrate) and thiocyanate counter-ions were generated by application of the invariom formalism and examined. The so-obtained charge density distributions were analyzed using the QTAIM formalism to yield bond topological and atomic properties. The atomic charges on the methylene blue cation indicate a delocalized charge distribution; only a small positive charge on the sulfur atom was found. Electrostatic potentials mapped onto iso-surfaces of electron density for the cations, and for the methylene blue cations with anions, were compared. The effect of hydrogen disorder on the molecular electrostatic potential was investigated for the thiocyanate structure.

A facile synthesis of some methyl 5-(arylamino)-4-oxothieno[2,3- b ]thiopyran-6-carboxylates 6a–g is achieved via direct reaction of deprotonated methyl 3-(2,5-dichlorothien-3-yl)-3-oxopropanoate with aryl isothiocyanates in anhydrous tetrahydrofuran (THF) under reflux. Upon saponification of 6a,b , the ester group is eliminated, most logically via decarboxylation of the presumably-formed carboxyl group. Structures of the new compounds 6a–g and 7a,b are supported by microanalytical and spectral [NMR, MS electron impact (EI) and HRMS] data.

Reaction of Cd(NCS) 2 and Zn(NCS) 2 with 3-ethylpyridine leads to the formation of compounds of compositions M(NCS) 2 (3-ethylpyridine) 4 (M=Cd, 1-Cd ; Zn, 1-Zn ) and M(NCS) 2 (3-ethylpyridine) 2 (M=Cd, 2-Cd ; Zn, 2-Zn ). 1-Cd and 1-Zn are isotypic and form discrete complexes in which the metal cations are octahedrally coordinated by two trans -coordinating N-bonded thiocyanate anions and four 3-ethylpyridine co-ligands. In 2-Cd the cations are also octahedrally coordinated but linked into chains by pairs of μ -1,3-bridging anionic ligands. 2-Zn is built up of discrete complexes, in which the Zn cation is tetrahedrally coordinated by two N-bonded thiocyanate anions and two 3-ethylpyridine co-ligands. Compounds 1-Cd , 2-Cd and 2-Zn can be prepared in a pure state, whereas 1-Zn is unstable and transforms on storage into 2-Zn . If 1-Cd and 1-Zn are heated, a transformation into 2-Cd , respectively 2-Zn is observed. Luminescence measurements reveal that 1-Cd , 2-Cd and 2-Zn emit light in the blue spectral range with maxima at, respectively, 21724, 21654 and 22055 cm −1 , assigned to ligand-based luminescence.

The reaction of (tht)AuCl (tht=tetrahydrothiophene) with KSCN leads to a mixture of gold(I) thiocyanate AuSCN and [(tht) 2 Au] + [Au(SCN) 2 ] − 1 . The compounds were separated and the X-ray structure of 1 confirmed as an alternating chain of anions and cations linked by aurophilic contacts. Either pure AuSCN or the mixture was used to synthesize further derivatives of AuSCN, all of which were investigated by X-ray methods. Most products were of limited stability when removed from their mother liquor. The dimethyl sulfide derivative 2 is molecular, (Me 2 S)AuSCN; the ammonia derivative 3 is ionic, [(NH 3 ) 2 Au] + [Au(SCN) 2 ] − . The reaction with 2,2-bipyridyl leads (presumably by involvement of the solvent or of atmospheric moisture) to [bipy-H] + [Au(SCN) 2 ] − 13 . All other products involve amines or azaaromatics as ligands L. The primary amine tert -butylamine forms an ionic product [L 2 Au] + (SCN) − 4 . The secondary amines piperidine and dibenzylamine lead to molecular structures LAuSCN ( 5 and 6 ), whereas pyridine-based azaaromatics lead to ionic products [L 2 Au] + [Au(SCN) 2 ] − with L=2-, 3- or 4-picoline ( 7–9 ), 2,4-, 3,4- or 3,5-lutidine ( 10–12 ). The 3,4-lutidine derivative 11 forms two polymorphs that tend to form mixed crystals. The dominant features of the crystal packing for 7–12 are short aurophilic interactions.