The synthesis of vinylogous amidine heterocycles.

We report herein a convenient synthetic methodology for the conversion of meta-dinitro heterocyclic rings to iminoquinones with vinylogous amidine functionality. These structures are found in nature, particularly in marine organisms, and may be important for the pigments and biological activity observed with such marine secondary metabolites. Using benzimidazole and indole ring systems we show the versatility of these vinylogous amidines for organic synthesis, including the following: transamination substitution reactions with virtually any primary amine, regional control of the substitution with substituents between the vinylogous amidine, and hydrolytic properties that can be controlled or optimized based on the properties of the chosen ring system.

Triple molecular target approach to selective melanoma cytotoxicity.

Phenylalanine-linked pyrrolo[1,2-a]benzimidazoles were successfully designed to target melanoma cells in vitro. Our design utilised three molecular targets: a phenylalanine pump, the reducing enzyme DT-diaphorase, and IMP dehydrogenase. We describe the synthesis of these compounds as well as the results of in vitro, in vivo, and QSAR studies.

Quinone methide chemistry of prekinamycins: 13C-labeling, spectral global fitting and in vitro studies.

In this article, we address the presence of the prekinamycin quinone methide using the techniques of spectral global fitting and the 13C-labeling of the reactive centre. Two-electron reduction of a prekinamycin affords a long-lived quinone methide species that was characterised spectrally. A correlation was made between the calculated DeltaE (kcal/mol) values for quinone methide tautomerisation and cytostatic activity to support the postulate that the quinone methide plays a role in prekinamycin biological activity.

Synthesis and in vitro evaluation of imidazole-based wakayin analogues.

Analogues of wakayin based on diimidazo[1,5,4-de, 1,5,4-h]-quinoxaline have been prepared and evaluated with respect to cytostatic and cytotoxic activity. Assays in a 60-cell-line human cancer panel revealed selective activity against cells with the VEGF (Flt-1) receptor.

Discovery of quinolinediones exhibiting a heat shock response and angiogenesis inhibition.

A series of substituted quinoline-5,8-diones were synthesized and evaluated as inhibitors of the chaperone protein Hsp90 using two assays: competition for binding to C-terminal ATP-binding site and competition for binding to N-terminal ATP-binding site. In addition, the ability of the compounds to induce the heat shock response was determined using a reporter fibroblast cell line. Of all the compounds assayed, only 6-aziridinyl-2-biphenylquinoline-5,8-dione induced a heat shock response and did so without interacting at the ATP binding sites of Hsp90.

Chemistry of pyrrolo[1,2-a]indole- and pyrido[1,2-a]indole-based quinone methides. Mechanistic explanations for differences in cytostatic/cytotoxic properties.

In the present study we investigate pyrido[1,2-a]indole- and pyrrolo[1,2-a]indole-based quinones capable of forming quinone methide and vinyl quinone species upon reduction and leaving group elimination. Our goals were to determine the influence of the 6-membered pyrido and the 5-membered pyrrolo fused rings on quinone methide and vinyl quinone formation and fate as well as on cytostatic and cytotoxic activity. We used the technique of Spectral Global Fitting to study the fleeting quinone methide intermediate directly.

Synthesis and biological evaluation of imidazoquinoxalinones, imidazole analogues of pyrroloiminoquinone marine natural products.

This report describes the synthesis and biological activity of imidazoquinoxalines, benzimidazole-based analogues of indole-based pyrroloiminoquinone marine natural products. Our analogues consist of series 1, which possesses the ethylene tether and extended amidine feature found in the pyrroloiminoquinone natural products, and series 2, which also has the ethylene tether but with an electrostatically stabilized iminoquinone rather than a resonance stabilized iminoquinone (i.e.

Design of a cyclopropyl quinone methide reductive alkylating agent. 2.

A cyclopropyl quinone methide is formed by elimination of a leaving group from an appropriately functionalized hydroquinone. The presence of a carbon spacer results in the formation of a fused ring rather than the classic methide species. Discussed herein is cyclopropyl quinone methide formation from a pyrido[1,2-a]indole ring system.

Solution kinetics of CC-1065 A-ring opening: substituent effects and general acid/base catalysis.

pH-rate studies were carried out on 2-substituted derivatives of the CC 1065 A-ring over the range of pH 5 to 0. The goals were to document the presence of general-acid-catalyzed cyclopropyl ring opening near neutrality and to assess the role of the 2-substituent on the rate of nucleophile trapping by the cyclopropyl ring. Our studies show that the cyclopropyl group undergoes reversible general-acid/base-catalyzed trapping of chloride nucleophiles above pH 4.

Synthesis of imidazo[1,5,4-de]quinoxalin-9-ones, benzimidazole analogues of pyrroloiminoquinone marine natural products.

The imidazoquinoxalinones 1 and 2 are benzimidazole analogues of indole-based marine natural products called makaluvamins. The stabilized cation 1 and the zwitterion 2 were prepared in approximately 9 steps from readily available starting materials. Compound 1 is more cytostatic and cytotoxic than 2 and also shows activity in the hollow fiber assay.

Pyrrolobenzimidazoles linked to heterocycles and peptides. Design of DNA base pair specific phosphate hydrolyzing agents and novel cytotoxic agents.

Work in this laboratory has been involved with the design of aziridinyl quinone-based cancer drugs (PBIs) capable of both recognizing the DNA major groove and cleaving the phosphate backbone upon reduction to the hydroquinone. The hydroquinone species recognizes the major groove of DNA at single base pairs by Hoogsteen-type hydrogen bonding. The present study extends recognition beyond a single base pair by adding amino acid residues to the 3-amino center of the PBI system.

Design of quinolinedione-based geldanamycin analogues.

Quinoline-5,8-dione-based compounds were designed from the structure of the geldanamycin-bound Hsp-90 active site. The active site model predicted that aromatic substituents should be present at the 2-position, to take advantage of a hydrophobic pocket, and amino substituents should be present at the 6- or 7-position. COMPARE analysis revealed that the LC(50) profile of 2-phenyl-6-(2-chloroethylamino)quinoline-5,8-dione has the highest geldanamycin-like activity (0.

Pyrimidoquinazoline-based antitumor agents. Design of topoisomerase II to DNA cross-linkers with activity against protein kinases.

A series of pyrimidoquinazoline analogues, possessing either 4,5-g or 5,4-g fusion, were studied with respect to cytotoxicity, topoisomerase II inhibitory activity, in vivo activity, and DNA cleavage and DNA-protein cross-linking properties. These analogues were designed as electron-deficient anthraquinones with dual alkylating centers to cross-link DNA with topoisomerase II. Our studies verified the presence of DNA-protein cross-linking in vitro as well as topoisomerase II poisoning by pyrimidoquinazoline analogues.

A comprehensive study of the active site residues of DT-diaphorase: rational design of benzimidazolediones as DT-diaphorase substrates.

A series of quinone substrates were modeled into the active site of human DT-diaphorase and minimized. Correlation of these models with the substrate specificity k(cat)/K(m) provided insights into the structural requirements of quinone substrates. The W105, F106, and H194 residues can influence the position of the quinone substrate in the active site resulting in formation of one of the two possible Michael anions resulting from hydride transfer from FADH(2).