Zur Struktur von Tris(1,3-dimethyl-2-indolyl)-methan: Ein chiraler C3-Propeller aus der Trishetarylmethan-Reihe / The Structure of Tris(1,3-dim ethyl-2-indolyl)m ethane: a Chiral C3-Propeller in the Trishetarylmethane Series

The structure of tris(1,3-dim ethyl-2-indolyl)methane (1) as a model compound for C3-skeleton symmetric trishetaryl-methanes is elucidated by X-ray diffraction and temperature dependant 1H NMR spectroscopy. The results demonstrate, that 1 adopts a chiral C3-propeller conformation (P/M-helix) as well in crystal as in solution.

The structures of indoiyl(alkoxy)carbenium tetrafluoroborates: a new class of highly stabilized carbenium ions

The conformations of and charge distributions in indolyl(alkoxy)carbenium tetrafluoroborates 2, a new class of highly stabilized carbenium ions, were investigated by 1H and 13C NMR spectroscopy and the crystal structure of indol-3-yl(methoxy)phenylcarbenium tetrafluoroborate (2e) was determined by X-ray diffraction methods. The phenyl-substituted cation of 2e exhibits axial chirality in the crystalline state

New Diels-Alder Reactions of (–)-Thebaine and First X-Ray Crystallographic Structure Analyses of the Cycloadducts

Diels-Alder reactions of (-)-thebaine (1) as an electron-rich diene system with acceptorsubstituted ethenes gave rise to the cycloadducts 2, 3, and 4 in high regio- and stereoselectivities. Structural analyses were performed by high resolution NMR spectroscopy and, for the first time in the thebaine cycloadduct series, by X-ray crystallographic structural analyses of the compounds 2, 3a, and 3b. In the reaction of (-)-thebaine (1) with an in situ generated aryne, the anellated azocine derivative 5 was formed.

Photochemical electrocyclisation of 3-vinylindoles to pyrido[2,3-a]-, pyrido[4,3-a]- and thieno[2,3-a]-carbazoles: design, synthesis, DNA binding and antitumor cell cytotoxicity

In the context of the design and synthesis of DNA ligands, some new hetarene annelated carbazoles were synthesized. As lead structure the intercalating tetracyclic systems pyrido[2,3-a]- and pyrido[4,3-a]-carbazoles and in one case a thieno[2,3-a]-carbazole were taken into account. A dialkyl amino amidic chain was introduced to the planar chromophoric system with the intent to generate minor groove binding properties. The cytotoxicity of some compounds was examined by the NCI antitumor screening. Furthermore, biophysical as well as biochemical studies were performed in order to get some information about the DNA-binding properties and inhibition of DNA related functional enzymes of this new series of molecules.

Design, synthesis and biological evaluation of new oligopyrrole carboxamides linked with tricyclic DNA-intercalators as potential DNA ligands or topoisomerase inhibitors

In the context of the design and synthesis of minor groove binding and intercalating DNA ligands some new oligopyrrole carboxamides were synthesized. These hybrid molecules (combilexins) possess a variable and conformatively flexible spacer at the N-terminal end. As intercalating tricyclic systems acridone, acridine, anthraquinones and in a special case iminostilbene terminate the N-terminal end of the pyrrole chain. The cytotoxicity was examined by the NCI antitumor screening, furthermore, biophysical as well as biochemical studies were performed in order to get some information about the DNA binding properties and topoisomerase inhibition effect of this new series of molecules.

Oligopyrrole carboxamides linked with a nucleobase as potential DNA minor groove binding ligands: synthesis, DNA binding and biological evaluation

The synthesis of a series of new oligopyrrole carboxamides closely related to netropsin and distamycin A, linked with a nucleobase is reported. The new compounds possess similar structure elements as the known peptide nucleic acids which are interesting sequence reading DNA ligands. Cytotoxicity in vitro, the DNA binding characteristics and the inhibition of topoisomerase I were studied. Four of the compounds, 27, 31, 33 and 37 bind to DNA probably at AT sequences like netropsin or distamycin A in the minor groove. Surprisingly, no cytotoxicity and no inhibition of topoisomerase I was found.

Advances in DNA-Ligands with Groove Binding, Intercalating and/or Alkylating Activity: Chemistry, DNA-Binding and Biology

It is known that DNA is a well-characterized intracellular target but its size and sequential characteristics make it an elusive target for selective drug action. Binding of low molecular weight ligands to DNA causes a variety of significant biological responses. In this context the main consideration is given to recent developments in DNA sequence selective binding agents bearing conjugated effectors because of their potential application in treatment of cancers, in diagnosis as well as in molecular biology. In the present review recent results about analogues of netropsins, distamycin A and of some lexitropsins and combilexins or related hybrid molecules with sequence reading, intercalating or alkylating activity are described and evaluated for prospective applications. Furthermore there exists DNA minor groove binder with different basic structures which does not possess the typical polyamide chain, including dimeric intercalating chromophores. Finally new results about peptide nucleic acids and related nucleic acid bases linked with polyamides are reported. In pronounced examples the structural chemistry, synthesis, DNA binding with several biophysical methods, molecular aspects, structure activity relationship, topoisomerase inhibition, antitumour and antibacterial effects are discussed in detail.

Chemistry and biology of new marine alkaloids from the indole and annelated indole series

Chemistry and biology of marine natural products from the indole and annelated indole series have become an attractive research field for development of new pharmacological lead substances. In the past years some of the isolated natural organic compounds were synthesized by chemists and evaluated with great enthusiasm to find new lead natural compounds against different diseases. In this review the latest results for new compounds including isolation, biological evaluation, synthetic pathways and some retrosynthetic analyses are summarized.

New propylamine oligopyrrole carboxamides linked to a heterocyclic or anthraquinone system: synthesis, DNA binding, topoisomerase I inhibition and cytotoxicity

Continuing our studies on combilexines, compounds consisting of a DNA intercalator linked to a minor groove ligand, new results are presented. The synthesis of a series of new propylamine oligopyrrole carboxamides closely related to netropsin and distamycin A, linked to a heterocyclic or anthraquinone system is reported. The cytotoxic activity in vitro, the DNA binding characteristics and the inhibition of the topoisomerase I of the compounds were studied in order to explain the biological mechanism of action of these new potential combilexines. Some of the synthesised compounds showed cytotoxic activity against human tumour cell lines, as well as DNA binding and topoisomerase I inhibiting properties.

Design, synthesis, DNA-binding and cytotoxicity evaluation of new potential combilexines

Combilexines, compounds in which a DNA intercalator is linked to a minor groove binding component, interact with the DNA in a sequence specific manner to yield in most cases compounds with anticancer activity. A series of new compounds closely related to netropsin in which the two components were linked by an amide group was synthesised as potential combilexines. As some of these compounds showed cytotoxic activity in vitro, an attempt was made to rationalise their mechanism of action. The DNA binding characteristics of the carboxamides were evaluated by thermal denaturation experiments and by ethidium bromide displacement assay. Their ability to inhibit the topoisomerase I was also determined. It was concluded that the new compounds were only weak DNA ligands although able in some cases to inhibit topoisomerase I.

New indolocarbazoles as antitumour active compounds: evaluation of the target by experimental and theoretical studies

A series of indolocarbazoles was synthesized as congeners of the natural lead compounds rebeccamycin (1) and staurosporine (2) which reduce cell growth by inhibiting topoisomerase I and protein kinase C respectively. Two of the carbazoles (3 and 4) screened at the National Cancer Institute (NCI, USA) showed an interesting cytotoxic activity and were therefore further analysed. The mechanism of action of these two compounds was studied experimentally using different assay to determine the B-DNA binding ability and the inhibition of topoisomerase I and of protein kinase C. Theoretical molecular modelling studies were also performed to describe the possible interactions with protein kinase C and DNA.

Advances in marine natural products of the indole and annelated indole series: chemical and biological aspects

Marine natural products, form a field of scientific endeavour, that has recently grown considerably. The isolation, biological evaluation, chemical properties and synthetic elaborations of products of marine organisms have attracted the attention of organic chemists, medicinal chemists, biologists and pharmacists. In this context a structurally and biologically highly interesting class is represented by the marine natural products containing an indole moiety in a pure substituted form or in an anellated form. The present review summarizes primarily the actual results concerning these products as new pharmacologically attractive lead compounds for drug design. The chemistry, biological evaluation and synthetic aspects are discussed. The spectrum of compounds represented comprises simply substituted indoles, peptidic products, dimeric indoles, anellated indoles and a variety of carbazoles. Most of them exhibit significant cytotoxicities.

Functionalized and [a]-anellated carbazoles as potential B-DNA ligands: experimental studies of DNA binding and molecular modeling of intercalation complexes

Three synthetically available carbazole derivatives 3-5 were investigated for DNA binding (ethidium bromide displacement assay, DNA unwinding assay), for inhibition of topoisomerase I and for cell cytotoxicity (antitumour cell lines). In addition molecular modeling studies of DNA complexes were performed by semiempirical quantum chemistry, force field calculations and molecular dynamics calculations. In summary, combining the results from experiments and molecular modeling, the naphthoquinone anellated carbazole 4 emerges as a promising antitumour active candidate for further drug design studies in carbazole chemistry.

A molecular modeling study of B-DNA-intercalation complexes with amsacrine and related 9-anilino-acridines

Computer molecular modeling studies of some complexes of amsacrine-derivatives with B-DNA-hexanucleotides were performed to shed new light on the DNA-binding mode of these drugs. The studies are based on routine methods, as are the semiempirical calculations, conformational analyses of the ligands, interaction field analyses, force field and molecular dynamics simulations of ligand/base paired DNA-complexes. The predictions suggest that the tested 9-anilino-acridines 1, 3 and 4 bind by intercalation to the base-paired oligonucleotides. Depending on the substitution pattern of the tested 9-anilino-acridine-series compounds, some distinct binding modes and base sequence selectivities were observed.

Advances in indolo[2,3-a]carbazole chemistry: design and synthesis of protein kinase C and topoisomerase I inhibitors

Indolo[2,3-a]carbazoles, their pyrrolo[3,4-c]anellated variants and structurally closely related bisindolylmaleimides represent a biologically highly interesting class of natural compounds which are potential anticancer agents. According to the ongoing literature new and efficient synthetic methods yield a great variety of these compounds which have been reported in detail. The biological activities and the inhibitory activities against the target enzymes protein kinase C and topoisomerase I are also discussed including structure activity relationships. A molecular binding model of the protein kinase C inhibitors with the target enzyme at the atomic level is presented and supported by X-ray crystallographic structures and by molecular modelling studies.

Advances in lndolo[2,3-a]carbazole Chemistry: Design and Synthesis of Protein Kinase C and Topoisomerase I Inhibitors

Abstract:

lndolo[2,3-a]carbazoles, their pyrrolo[3,4-c]anellated variants and structurally closely related bisindolylmaleimides represent a biologically highly interesting class of natural compounds which are potential anticancer agents. According to the ongoing literature new and efficient synthetic methods yield a great variety of these compounds which have been reported in detail. The biological activities and the inhibitory activities against the target enzymes protein kinase C and topoisomerase I are also discussed including structure activity relationships. A molecular binding model of the protein kinase C inhibitors with the target enzyme at the atomic level is presented and supported by X-ray crystallographic structures and by molecular modelling studies.

Antitumour drug design: DNA-binding ligands, which inhibit the topoisomerase I

DNA-enzymes, which are overexpressed in special tumour cells represent in general interesting targets for an antitumour drug design. In this context a survey about the function and the biochemical mechanistic aspects of topoisomerases is given. In the last years detailed studies in medicinal chemistry (structure activity relationships) revealed that first of all topoisomerase I inhibitor will become an attractive class of promising and perhaps more selective drugs in cancer chemotherapy. Thus, in the present review actual aspects about drug design developments of topoisomerase I inhibitors are presented. Moreover some recent results about new lead substances, some structure activity relationships and some clinical aspects are discussed.