Volume 22, Issue 6

New heterocyclic compounds with expected biological activity have been prepared by reactions of 6-phenyl-2-thioxo-2,3-dihydropyrimidine-4(5 H )-one ( 4 ) and 7- amino-5-(4-chlorophenyl)-4-phenyl-2-thioxo-2,5-dihydro-1 H -pyrano[2,3- d ]pyrimidine-6-carbonitrile ( 8b ) in the presence of an electrophilic or a nucleophilic reagent.

Regioselective introduction and transformation of substituents at the C 1 carbon of N - tert -butoxycarbonyl-5- syn - tert -butyldimethylsilyloxymethyl-2-azabicyclo[2.1.1]hexane ( 7 ) is described. These azabicycles are precursors to conformationally constrained β-amino acids with potential to form oligomers with definite secondary structures. Selected examples of these precursors are converted into their corresponding amino acid derivatives.

Hetero-crown ethers (ligands I–IV ) containing 1,3,4-thiadiazole-2,5-dithiol (bismuthiol) were synthesized and fully characterized. The ligands were prepared by a nucleophilic substitution (S N 2) reaction of the appropriate ethylene glycol dihalide derivatives with 1,3,4-thiadiazole-2,5-dithiol dipotassium salt under highly diluted conditions, and subsequent ring closure. Complexation constants and selectivity factors for these heterocyclic ligands in dichloromethane or chloroform were determined by ion-pair extraction from an aqueous solution containing Ag + , Ca 2+ , Zn 2+ , Fe 3+ , Cr 3+ , Co 2+ , Cd 2+ , Mg 2+ , Pb 2+ , Ni 2+ , Cu 2+ , Mn 2+ , Na + and K + . These ligands could be applied as metal sensors and used to separate metals from various mixtures.

2-Aminopyridine-3-sulfonyl chlorides undergo a reaction with tertiary amines in the presence of air to produce sulfonylethenamines. The 2-aminopyridine-3-sulfonyl chloride apparently plays a dual role in the process promoting the aerobic oxidation of the amine and electrophilically trapping the resulting enamine.

BODIPY-based chromophores, in which an electron withdrawing difluoro-boraindacene fragment is connected via position 8 to different donor fragments, were synthesized. Their electrochemical and photophysical properties were studied. All compounds exhibit a quasi-reversible oxidation corresponding to the formation of a BODIPY π-radical cation at around 0.8 V vs. FeCp 2 + /FeCp 2 that is slightly sensitive to the nature of the electron donating group. A reversible reduction is observed around−1.6 V vs. FeCp 2 + /FeCp 2 corresponding to the formation of the BODIPY π-radical anion. Cyclic voltammetry analysis of a γ-methylenepyran substituted BODIPY indicates the formation of redox bistable system with high bistability. In dichloromethane solution, the chromophores exhibit an intense absorption band around 502 nm and an emission in the 516–528 nm range. A significant emission quench is observed in case of amino and γ-methylenepyran substituents.

Electrophilic heterocyclization of 5,6-disubstituted 3-alkenyl-2-thioxothieno[2,3- d ]pyrimidin-4-ones by treatment with p -alkoxyphenyltellurium trichlorides leads to annulation of the thiazoline moiety with the formation of 6,7-disubstituted-2-[dichloro-( p -alkoxyphenyl)telluromethyl]-2,3-dihydro-5 Н -[1,3]thiazolo[3,2- а ]thieno[2,3- d ]pyrimidin-5-one hydrochlorides.

4-(2′,4′-Difluorobiphenyl-4-yl)-6-arylpyrimidin-2-amines 5a–g were synthesized and evaluated for their ability to inhibit various bacterial and fungal strains. The cytotoxicity of the compounds was investigated by a 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay against the Hep-2 cell line. Molecular docking studies were also conducted to locate the binding interaction with the target protein 4LRH.

Due to increasing infections caused by microbes, there is an urgent need for the development of new effective antimicrobial agents. Silver- N -heterocyclic carbene (silver-NHC) complexes are a new class of antimicrobial agents. In this study, we aimed to synthesize highly lipophilic silver-NHC complexes. Four new complexes were synthesized by the reaction of the corresponding benzimidazolium salts and Ag 2 O in dichloromethane at room temperature. The synthesized compounds were characterized by 1 H NMR, 13 C NMR, IR and elemental analysis. The antimicrobial performances of benzimidazolium salts and silver complexes were tested against the standard bacterial strains Enterococcus faecalis , Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis . Minimum inhibitory concentrations (MICs) of all compounds were determined. The obtained data demonstrate that all benzimidazolium salts and silver complexes inhibit the growth of bacteria and fungi. Silver complexes are more active than the corresponding benzimidazolium salts (MIC: 6.25 μg/mL for Gram-positive bacteria and fungi).

A series of novel chroman-4-one fused benzofurans were synthesized by cyclization of the corresponding chalcones under microwave irradiation. All new compounds were characterized by IR, 1 H NMR, 13 C NMR and mass spectral data and were evaluated for their in vitro antimicrobial and antioxidant activities.