Peter Kutschy

Spirocyclization strategy toward indole phytoalexins. The first synthesis of (′)-1-methoxyspirobrassinin, (′)-1-methoxyspirobrassinol, and (′)-1-methoxyspirobrassinol methyl ether

Abstract The first syntheses of cruciferous indole phytoalexins (±)-1-methoxyspirobrassinin, (±)-1-methoxyspirobrassinol, (±)-1-methoxyspirobrassinol methyl ether as well as a new syntheses of phytoalexins (±)-spirobrassinin and cyclobrassinin were achieved by dioxane dibromide (DDB)-mediated spirocyclization of brassinin and its 1-substituted derivatives.

NEW SYNTHESES OF INDOLE PHYTOALEXINS AND RELATED COMPOUNDS

Abstract Synthesis of indole phytoalexins brassinin, brassitin, cyclobrassinin and related compounds via 3-aminomethylindole and its 1-substituted derivatives obtained by nickel boride catalyzed reduction of corresponding aldoximes with sodium borohydride and via [1-( t -butoxycarbonyl)-indol-3-yl]methyl isothiocyanate, the first stable derivative of indol-3-ylmethyl isothiocyanate is described. Antifungal activity of the prepared compounds was examined by using the fungus Bipolaris leersiae by t.l.c. bioassay and quantitative screening was carried out with the selected compounds.

2-(Substituted phenyl)amino analogs of 1-methoxyspirobrassinol methyl ether: Synthesis and anticancer activity

New analogs of indole phytoalexin 1-methoxyspirobrassinol methyl ether have been designed by replacement of its 2-methoxy group with 2-(substituted phenyl)amino group. Synthesized by spirocyclization methodology, trans- and cis-diastereoisomers of target compounds were isolated and evaluated as potential anticancer and antimicrobial agents. Their molecular geometries were refined by ab initio minimizations. Pharmacophore modeling and QSAR studies were performed in order to correlate their molecular structure and biological activity.

Camalexin induces apoptosis in T-leukemia Jurkat cells by increased concentration of reactive oxygen species and activation of caspase-8 and caspase-9

Camalexin, a major indole phytoalexin of Arabidopsis thaliana, accumulates in various cruciferous plants in response to environmental stress and reportedly displays antimicrobial activities against various plant pathogens. However, its cytotoxicity against eukaryotic cells and potential as a prospective drug for human diseases has been examined only in a limited context. Our data demonstrate the time- and concentration-dependent cytotoxicity of camalexin on human T-leukemia Jurkat cells in the micromolar range, and the lower potency of cytotoxic effects on human lymphoblasts and primary fibroblasts. Cytotoxicity of camalexin is enhanced by the glutathione-depleting agent buthionine sulfoximine and completely blocked by pan-caspase inhibitor Z-VAD-FMK. Treatment of Jurkat cells with camalexin resulted in activation of caspase-8, caspase-9, caspases-3/7, and apoptosis that was detected by the presence of a sub-G1 population of cells, externalization of phosphatidyl serine and decreased mitochondrial membrane potential. Staining with 2′,7′-dichlorodihydrofluorescein diacetate and dihydroethidium bromide displayed increased concentration of reactive oxygen species (ROS) early in camalexin-treated Jurkat cells, prior to the onset of apoptosis, while staining with MitoSOX™ dye identified mitochondria as a source of increased ROS. Our data suggest that this phytochemical, which has a wide range of predicted pharmacological activities, induces apoptosis in Jurkat leukemia cells through increased ROS followed by dissipation of mitochondrial membrane potential and execution of caspase-9- and caspase-8-initiated apoptosis. This is, to the best of our knowledge, the first report on antileukemic activity and mode of action of this unique indole phytoalexin.

Trypanosoma cruzi: Antiproliferative effect of indole phytoalexins on intracellular amastigotes in vitro

American trypanosomiasis (Chagas disease) continues to be a significant public health problem, and the therapeutic potential of current antichagasic agents (nifurtimox and benznidazole) is rather limited. Here we report on the antitrypanosomal effect of 1-methoxyspirobrassinol and other indole phytoalexins--secondary metabolites produced by Cruciferous plants. These compounds, that previously demonstrated antimicrobial and anticancer properties, displayed significant antiproliferative effects on intracellular amastigotes of Trypanosoma cruzi and may be prospective candidates for antichagasic drug design and development.

Anticancer Properties of 2-Piperidyl Analogues of the Natural Indole Phytoalexin 1-Methoxyspirobrassinol

Background: Several indole phytoalexins exhibit antiproliferative and/or cancer chemopreventive properties in vitro. However, the potency and selectivity of their anticancer effects were reported to be relatively weak. In order to improve the anticancer activity of the natural phytoalexin 1-methoxyspirobrassinol, its new 2-amino analogues were synthesized and evaluated. Methods:Cis-1-Boc-, trans-1-Boc-, cis-1-methoxy- and trans-1-methoxy-2-deoxy-2-(1-piperidyl)spirobrassinols (compounds 4–7) were synthesized by spirocyclization reaction and their potency evaluated by SRB assay on the NCI60 panel of human cancer cells. The COMPARE program was employed to analyze patterns of activity of compounds 4–7 against the NCI60 panel for prediction of their probable targets and mode of action. Cellular glutathione, a predicted target, was quantified by DTNB assay. Results: Compounds 4–7 exhibit growth inhibitory effects across the NCI60 panel and, consistent with COMPARE prediction, a glutathione-depleting effect on MCF-7 cells. Conclusion: Considering their remarkable glutathione-depleting effects, compounds 4–7 could be developed as radio- and/or chemosensitizing agents for combination cancer chemotherapy.

Preparation and characterization of the complexes Cu(PTU)2Cl, Cu(ETU)2Cl and Cu(BTU)2Cl (PTU: R=phenyl, ETU: R=ethyl, BTU: R=benzyl in CH3CH=CHCONHCSNHR); crystal structure of the Cu(PTU)2Cl complex

Abstract The complexes Cu(PTU) 2 Cl, Cu(ETU) 2 Cl and Cu(BTU) 2 Cl (PTU: R=phenyl, ETU: R=ethyl, BTU: R=benzyl in CH 3 CHCHCONHCSNHR) were prepared by the reaction of CuCl 2 with the corresponding derivates of 2-propenoyl thiourea. The complexes were investigated by the methods of CHN analysis, infrared spectroscopy, 1 H and· 13 C NMR spectroscopy. The crystal structure of Cu(PTU) 2 Cl was determined by X-ray analysis: triclinic space group P 1 , a =15.538(1), b =14.296(2), c =12.016(2) A, α=102.72(1), β=105.95(1), λ=94.31(1)°, D m =1.44(1), D c =1.44 g cm -3 , Z =4, R =0.066. The unit cell of Cu(PTU) 2 Cl contains two centrosymmetrical dimer molecules of the complex (denoted as A and B) with a different coordination sphere of the Cu(I) atoms. In molecule A two atoms of Cu(I) with coordination number 4 are bridged through chloride bridges (CuCl 2.318(2) and CuCl′ 2.762(2) A) and two molecules of PTU are terminally coordinated through the S atoms. In molecule B the bridges are formed by the atoms of S of one PTU molecule (CuS 2.235(2) and CuS′ 2.904(2) A). The other PTU molecule as well as the Cl − anion are terminally bonded. The results of infrared and NMR spectroscopy indicate that the complexes containing ETU or BTU exhibit analogous structure.

A new approach to the synthesis of rare thiazino[6,5-b]indol-4-one derivatives. First total synthesis of the indole phytoalexin cyclobrassinon

Abstract The first synthesis of the indole phytoalexin cyclobrassinon and some of its analogues, possessing a thiazino[6,5- b ]indol-4-one tricyclic ring system was performed starting from 1-substitued 2-chloroindole-3-carboxaldehydes. The route employed the intramolecular Et 3 N-mediated or photochemical nucleophilic substitution of a chlorine atom in the 2-position of the indole ring with a sulfur atom as a key step. Examination of biological activity against the selected tumor cell lines, bacteria and fungi revealed no expressive activity of synthesized compounds.

A new photocyclization approach to the rare 1,3-thiazino[6,5-b]indol-4-one derivatives

The analogs of indole phytoalexin cyclobrassinon have been prepared in four steps from corresponding 1-substituted 2-chloroindole-3-carboxylic acids, employing a hitherto unknown photochemical cyclization of new indolyl thiocarbamates to 1,3-thiazino[6,5-b]indole-4-one derivatives as a key step.

1,3-Thiazino[6,5-b]indol-4-one derivatives. The first synthesis of indole phytoalexin cyclobrassinon

Abstract The first synthesis of indole phytoalexin cyclobrassinon in six steps, in 12% overall yield and some of its analogues, possessing a 1,3-thiazino[6,5- b ]indol-4-one tricyclic ring system was performed, starting from 2-chloroindole-3-carboxaldehyde and employing the intramolecular Et 3 N-mediated nucleophilic substitution of a chlorine atom in the 2-position of an indole ring with sulfur as a key step.