Band 19, Heft 4

In this review, we discuss the synthesis and photochromism of aryl(heteroaryl)- and diheteroarylethenes, containing pyrane ring of coumarin as part of the photosensitive hexatriene system or bearing a coumarin unit as a substituent outside of hexatriene. Coumarinylethenes with noncyclic double bond as well as coumarinyl(thienyl)thiazoles, coumarinyl(thienyl)maleic anhydride (or maleimide) derivatives, and 3,4-bis(thiazolyl)coumarins possess both photochromism and fluorescence switching properties upon UV/vis irradiation.

The natural product oleanolic acid (OA) was functionalized and labeled with the non-aggregated fluorescent dye BOPIM (boron 2-(2′-pyridyl)imidazole complex) using ‘click’ chemistry, yielding a highly fluorescent probe. The pharmacological activity of the probe is comparable to that of unmodified OA, making it suitable for studying the therapeutic mechanisms of OA derivatives in vitro .

The treatment of 2-(trifluoromethyl)aniline with 2,6-dimethylphenylmagnesium bromide yields 1-methyl-9-(2,6-dimethylphenyl)acridine by the formal reaction of one equivalent of the aniline and two equivalents of the Grignard reagent. Interestingly, one of the methyl groups is eliminated during the reaction, and the product contains three methyl groups only. In a similar way, the reaction of 2-(trifluoromethyl)aniline with 2-ethylphenylmagnesium bromide furnishes 9-(2-ethylphenyl)acridine devoid of one ethyl group. The mechanism is discussed.

New triazolethione Schiff base derivatives 3a–f were synthesized. The structures of the products were characterized by elemental analysis, 1 H NMR, 13 C NMR, IR and MS. Their complexation properties to different heavy and transition metal ions were studied by UV-Vis and fluorescence spectroscopy. Compound 3a shows selective recognition of Fe 3+ with a 1:1 stoichiometric complex formation.

A series of new thienylazothiophenes were prepared by coupling reactions of diazotized thienocoumarins with their corresponding free amines. The structures of the products 3–7 were assigned on the basis of their elemental and spectroscopic data. The HMBC and HSQC techniques were used in some cases to ascertain the structural assignments. The antimicrobial screenings of compounds 3–7 along with substituted 2-aminothiophenes 1a,b were performed against three bacteria and three fungal species and their activities compared to those of nystatin, gentamycin and ciprofloxacin used as reference drugs. It was found that the antimicrobial activities of the tested new hybrid compounds were in some cases equal or better than those of the reference drugs.

Selected 6- and 7-carboxyflavins activate H 2 O 2 , oxidizing thioanisole to its sulfoxide. The greater reactivity of the 6-carboxyflavin derivatives are ascribed to the intramolecular hydrogen bonding between N(5) and the carboxyl group of the flavin system.

An efficient synthesis of novel bis-1,2,4-triazole and bis-1,3,4-thiadiazole derivatives starting from terephthaloyl and isophthaloyl chlorides is described. Terephthaloyl or isophthaloyl chloride was allowed to react with hydrazine hydrate in refluxing ethanol to give a corresponding bis-hydrazide derivative. Further reaction of these compounds with isothiocyanates gave bis-thiosemicarbazide derivatives, which then underwent cyclization to bis-1,3,4-thiadiazoles in the presence of sulfuric acid. The cyclization of these compounds in the presence of sodium hydroxide resulted in the formation of bis-1,2,4-triazole-3-thioles. The structure of these compounds was characterized by IR, NMR, and elemental analysis.

Phosphorus ylides have been prepared in excellent yields by the three-component reaction of activated electron-deficient acetylenic esters (dimethyl and diethyl acetylenedicarboxylate) and thiourea derivatives in the presence of triphenylphosphine. In some cases, these ylides were cyclized to dihydropyrimidothiazine, thioxoimidazolidine, and thioxotetrahydropyrimidine derivatives.

2-Arylsulfonylimino-3,4-dimethyl-2,3-dihydrothiazole-5-carboxylic acid hydrazides 2 were obtained from corresponding 2-arylsulfonylimino-4-methyl-2,3-dihydrothiazole-5-carboxylic acid ethyl esters 1 in a two-step synthesis. Heterocyclization of the hydrazide moiety yielded 2-arylsulfonylimino-3,4-dimethyl-5-(5-thioxo-4,5-dihydro-[1,3,4]oxadiazol-2-yl)-2,3-dihydro-thiazoles 3 . Treatment of compounds 3 with various alkyl halides gave corresponding S -substituted derivatives 4–6 . The plant growth stimulant activities of synthesized compounds were compared with those of similar [1,2,4]triazol- and [1,3,4,]thiadiazol-2-yl-thiazoles.

In the search for new antimicrobial and anticancer agents, a series of (aryl/heteroaryl-piperazino-alkyl)-substituted derivatives of benzo[ b ]furans were prepared. All compounds were characterized by 1 H NMR, 13 C NMR, ESI-MS spectra and elemental analyses. Most of the investigated compounds had no antimicrobial activity (MIC > 512 mg/L) except for 2l , 2m and 2o , which showed activity against Candida albicans . None of the tested compounds showed significant anticancer activity in K562 and HeLa cells.

In the search for biological agents, a series of new N -substituted ethyl 11-ethyl-7-methyl-3,5,10-trioxo-4-azatricyclo[5.2.2.0 2,6 ]undecane-8-carboxylates 3 , 9-methyl-3,5,8-trioxo-4-azatricyclo[5.2.1.0 2,6 ]dec-1-yl acetates 6 and 1,3-dioxo-4,5,6,7-tetraphenyl-2,3,3a,4,5,7a-hexahydro-1 H -isoindole-4-carboxylic acids 9 were prepared. All compounds were characterized by 1 H NMR, ESI-MS, and elemental analyses. Moreover, for intermediate products 2 , 5 , and 8 , X-ray structural analyses were conducted. Compounds 3a–e , 6a, 6b , 9a–e were tested for their cytotoxic properties in K562 and HeLa cells.