Band 21, Heft 6

An efficient synthetic protocol for the polysubstituted cyclopropyl 2,5-dihydrofuran-3-carboxylate was developed by the triphenylphosphine catalyzed domino reaction of dialkyl acetylenedicarboxylate with 3-aryl-2-benzoylcyclopropane-1,1-dicarbonitrile at room temperature. A special feature of the reaction is the retention of the cyclopropane ring.

A short synthesis of colletotrichumine A, an oxindole-pyrazine alkaloid isolated from the pathogenic fungus Colletotrichum capsici , is described.

The spiroacetal [C(9)–C(20)] fragments of spirofungins A and B, antibiotics isolated from Streptomyces violaceusniger Tü 4113, were prepared from a known bromo alcohol derived from ( S )-citronellal, using thermodynamically controlled iodolactonization and spiroacetalization as the key steps.

An efficient method for the preparation of strobilurin analogues containing benzofuro[3,2- d ]-1,2,4-triazolo[1,5- a ]pyrimidinone side chains were reported. This method is based on the reaction of functionalized iminophosphoranes with carbon disulfide via aza-Wittig reaction. The preliminary investigations on the biological activities show that the majority of compounds synthesized have moderate fungicidal activities against six kinds of fungi at a concentration of 50 mg/L.

Reductive cyclization of 2-{ N -[(2-amino-4,6-dichloropyrimidin-5-yl)methyl]- N -phenethylamino}acetonitrile ( 5 ) with Raney nickel and hydrogen gave the chloropyrimido[4,5- e ][1,4]diazepine 3 which could not be converted to 2 via an attempted nucleophilic aromatic substitution with hydroxide. The title compound ( 2 ) was prepared, however, by the reductive cyclization of 2-{ N -[(2-amino-4-chloro-6-methoxypyrimidin-5-yl)methyl]- N -phenethylamino}acetonitrile ( 13 ) followed by treatment with trimethyliodosilane.

A new cascade reaction provides a direct transformation of pyrazolin-5-ones and benzylidene-malononitriles by the action of bromine into substituted spirocyclopropylpyrazolones in 60–88% yields. This process can be realized in two variants, namely, (1) by treatment with bromine in the presence of base and (2) by treatment with bromine only with heating. These facile and efficient one-step cascade processes lead to the spirocyclopropylpyrazolone framework, which is present in a perspective class of compounds with prominent pharmacological and physiological activity.

A series of novel 6-( sec -butyl)-3-methyl-1-(substituted phenyl)-5,6- dihydropyrrolo[3,4- c ]pyrazol-4-(1 H )ones 5a–h were synthesized using L-isoleucine methyl ester hydrochloride as the starting material. Their structures were characterized by 1 H NMR, FT-IR, EI-MS and elemental analysis. Compound 5f was further analyzed by single-crystal X-ray diffraction. The bioassay results indicate that most of the compounds exhibit inhibitory activity against four plant pathogenic fungi Fusarium graminearum , Botrytis cinerea , Rhizoctonia cerealis and Colletotrichum capsici .

New pyrazoles have been synthesized and evaluated as breast cancer cell growth inhibitors. Condensation of the substituted pyrazole-4-carbaldehyde 1 with acetophenone and chloroacetophenone afforded α, β-unsaturated ketones 2 and 3 , respectively. Compounds 2 and 3 were subjected to different reactions using hydrazine hydrate, substituted hydrazine hydrate, hydroxylamine, o- phenylenediamine, malononitrile under different conditions affording 4-substituted pyrazole derivatives 4–28 . Structure elucidation of these compounds was conducted using IR, 1 H NMR, 13 C NMR, mass spectral data and elemental analysis. Antitumor activity of target compounds was tested against MCF-7 cell line (human breast cancer). Compounds 4 , 10 and 20 show significant antitumor activity against breast cancer. Docking was performed with protein 1UYK to study the binding mode of the designed compounds.

A three-component reaction of an aromatic aldehyde, 1 H -benzo[ d ][1,2,3]triazol-5-amine and tert -butyl 2,4-dioxopiperidine-1-carboxylate in refluxing EtOH under catalyst-free conditions furnishes the title compounds in high yields.

The conversion of arylaldehydes to 1,7-diaryl-5-hydroxyhepta-1,4,6-trien-3-ones (curcuminoids) and the mechanochemical cyclization of these products to 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines using BF 3 -Et 2 O are described. Investigation of the cyanide ion sensing ability of the 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines, in relation to the substituent groups on the aryl ring, showed that a hydroxy susbstituent is required, preferably para to the intervening carbon bridge.

A practical and unified strategy has been described for the construction of trichloromethylated oxindoles via a visible light-promoted aryltrichloromethylation reaction of N -arylacrylamides with tetrachloromethane. These reactions are carried out at room temperature in good to excellent chemical yields with good functional group tolerance.

A stereolibrary of conformationally restricted oxazole-containing amino acids, namely all isomers of 5–pyrrolydinyl- and 5-piperidinyloxazole-4-carboxylic acids, were designed and synthesized in three steps by the reaction of the corresponding N -Boc-protected amino acids and ethyl isocyanoacetate. These natural products-inspired amino acids are valuable building blocks for the synthesis of peptidomimetics and potential lead compounds for drug discovery.

A convenient procedure for the regioselective preparation of [1,3]thiazolo[3,2- b ][1,2,4]triazol-7-ium 10 and [1,2,4]triazolo[5,1- b ][1,3]thiazin-4-ium salts 9 via regioselective electrophilic cyclization of 3-[(2-alken-1-yl)sulfanyl]-4 H -1,2,4-triazoles 3 is reported. Direction of electrophilic heterocyclization strongly depends on nature of the alkenyl substitutent.