Band 21, Heft 2

Regioselective ring-opening reactions of phenyloxirane by protected cysteine are described, which enable the synthesis of pure regioisomeric cysteine adducts required for bioanalytical studies on adducts of protein with styrene. The reaction catalyzed by tris(pentafluorophenyl)borane proceeds regioselectively and stereospecifically to give protected S -(2-hydroxy-1-phenylethyl)cysteine (α-adduct) with the inversion of configuration at the α-carbon. By contrast, when the same reaction is catalyzed by tetraalkylammonium fluorides, S -(2-hydroxy-2-phenylethyl)cysteine (β-adduct) is formed predominantly, and a compete racemization is observed.

A series of dihydroxytryptanthrins was prepared by the reaction of a suitably substituted isatoic anhydride and isatin as possible metabolites of tryptanthrin. A high-performance liquid chromatography analysis of the synthetic compounds confirmed that 8,9-dihydroxytryptanthrin is the metabolite isolated from rat liver cytosolic metabolites. Although tryptanthrin shows strong cytotoxicity against human cancer cell lines, none of the hydroxylated tryptanthrins exhibit any significant cytotoxicity against selected human cancer cell lines up to 50 μ m .

The reaction of benzil, an aromatic aldehyde, and ammonium acetate in ethanol at reflux in the presence of tributylhexadecylphosphonium bromide as catalyst affords a 2,4,5-trisubstituted imidazole. The present methodology offers several advantages over the literature methods, including excellent yields, shorter reaction times, environmentally benign milder reaction conditions, cost-effectiveness of catalyst, easy workup, and purification of products by nonchromatographic methods.

A series of novel nitroxyl radical hindered-amine light stabilizer monomers were designed and synthesized from 2,2,6,6-tetramethylpiperidine- N -oxyl-4-ol, cyanuric chloride, allylamine, and 2-hydroxyphenylbenzotriazole derivatives. Structures of the new stabilizers were confirmed by 1 H NMR, 13 C NMR, FT-IR, ESI-HRMS, and element analysis. The synthesized compounds 5a–f were evaluated for their antioxidant and antiaging properties, and a significant stabilizing effect against photodegradation was found.

The photochemical oxidation of N , N -Bis-( tert -butoxycarbonyl)-1,4-dihydropyrazines was investigated by irradiation using a medium-pressure mercury lamp. The main products were isolated, and their structures were determined by spectral methods and single crystal X-ray diffraction analysis. Photooxygenation is suggested to be a [2+2] cycloaddition reaction of oxygen to the double bond.

This report provides a description of an efficient and environmentally benign procedure for the synthesis of bis(indole) derivatives via reaction of indole with electron-deficient alkenes. The remarkable advantages of this method for obtaining bis(indoles) are the simplicity of the experimental procedure, short reaction times, and high yields with the green aspects by avoiding toxic catalysts and solvents.

Polysubstituted pyridines 4 bearing methoxyphenyl groups at different positions of the ring have been prepared by the alkylation of 6-thioxo-1,6-dihydropyridines 1 or by the oxidation of 1,4-dihydropyridine 6 with manganese triacetate. The multidrug resistance–modulating (P-glycoprotein inhibition) activity of pyridine derivatives 4 comparable with that of verapamil has been revealed.

Catalyst-free tandem Knoevenagel-Michael reaction of aryl aldehydes and two equivalents of 3-methyl-1-phenyl-2-pyrazolin-5-one results in fast (5 min) formation of medicinally relevant 4,4′-(arylmethylene)bis(1 H -pyrazol-5-ol)s in excellent 93%–99% yield.

An efficient and green methodology for the synthesis of 1,2,3-triazoles substituted with a 4 H -pyran-4-one moiety was developed by treatment of 2-(4-azidomethylphenyl)-6-phenyl-4 H -pyran-4-one with alkynes in water. The yields are good to excellent. The reactions of the terminal alkynes occur in the presence of Cu(I) as catalyst and lead to the formation of 1,4-disubstituted 1,2,3-triazoles. Also, bis-1,2,3-triazoles containing 4 H -pyran-4-one moiety were synthesized by the reaction of 2,6-bis[4-(azidomethyl)phenyl]-4 H -pyran-4-one with internal alkynes in 51–84% yields.

Synthesis, characterization, and investigation of antimicrobial activities of nine novel imidazolylthiazoles are presented. Their structures were determined using 1 H NMR, 13 C NMR, and elemental analysis. Compounds 3e and 3i show very strong or strong bacteriostatic or bactericidal activity [minimal bactericidal concentration/minimal inhibitory concentration (MIC)=2–64] against Staphylococcus spp. (MIC=7.81–15.62 μg/mL), Micrococcus luteus ATCC 10240 (MIC=1.95–3.91 μg/mL), and Bacillus spp. (MIC=3.91–15.62 μg/mL). Compounds 3e and 3i also show the highest fungicidal effect (minimal fungicidal concentration/MIC=2–4) against reference strains of fungi belonging to Candida spp. with MIC ranging from 3.91 to 31.25 μg/mL.