Fused carbazoles by tandem Aza Wittig/electrocyclic ring closure. Preparation of 6H-pyrido[4,3-b] carbazole, 11H-pyrido[4,3-a]carbazole and 11H-pyrido[3,4-a]carbazole derivatives

Substituted Carbazoles – A New Class of Anthelmintic Agent

A series of novel carbazoles were synthesized based on structural modifications to lead carbazole 1 (EC100 = 2.5 μM against Haemonchus contortus in vitro), which was revealed in a small molecule screening program as a potentially promising platform for the development of new anthelmintic drugs. Subsequently, analogues 19, 21, 41, 42 (EC100 = 1.25 μM, all), and 39 (EC100 = 0.625 μM) were demonstrated to exhibit enhanced in vitro anthelmintic activity over the lead structure, with compound 39 also being shown to be active in vivo against Heligmosomoides polygyrus.

5-membered cyclic hydroxamic acids as HDAC inhibitors

The new histone deacylases inhibitors (HDACi) were synthesized in the class of 5-membered cyclic hydroxamic acids (5-CHA), showing medium size CHA as a new Zn-binding group. New reaction sequence was proposed for the synthesis of 5-membered alkylidene-cyclic-hydroxamic acids starting from butyrolactone. Compound 10c showed low µM activity on HeLa cell extracts. From these results, cyclic hydroxamic acids will be further investigated to find more potent compounds.

Palladium-catalyzed synthesis of natural and unnatural 2-, 5-, and 7-oxygenated carbazole alkaloids from N-arylcyclohexane enaminones

A palladium-catalyzed synthesis of the carbazole framework is described, including the preparation of 2-, 5-, and 7-oxygenated natural and unnatural carbazole alkaloids. A series of N-arylcyclohexane enaminones, generated by condensation of cyclohexane-1,3-dione with diverse anilines, were aromatized by a Pd(0)-catalyzed thermal treatment to afford the corresponding diarylamines. The latter were submitted to a Pd(II)-catalyzed cyclization and methylation processes to provide the desired carbazoles, including clausine V. Following an inverse strategy, a new and short total synthesis of glycoborine is also reported.

Synthesis, proton and 13C NMR and reaction mechanism studies of novel isoindolones derivatives, obtained through TAWERS procedure

A series of novel isoindolone derivatives (13-18) were prepared in goods yields by applying the TAWERS methodology. A general approach for formation of isoindolones from the aza-Wittig reaction of iminophosphoranes with dialdehydes under neutral and mild conditions was realized. Using 1D NMR a [1,3]-hydride migration was detected. The assignment of the structures and conformation behavior of the derivatives was achieved using 1D and 2D NMR (NOESY, DEPT, HMQC, and HMBC).

Phototoxicity associated with diclofenac: a photophysical, photochemical, and photobiological study on the drug and its photoproducts

Diclofenac (1) is a photosensitizing nonsteroidal antiinflammatory drug. Its photodecomposition gives rise to chlorocarbazole 2a. This product undergoes photodehalogenation to 3a in a subsequent step. When the photobiological activities of 1, 2a, and 3a are compared by means of the photohemolysis test, it is clearly observed that chlorocarbazole 2a causes cell lysis with a markedly higher efficiency than the parent drug or the secondary photoproduct 3a. Laser flash photolysis studies suggest that photodehalogenation of 2a occurs from its excited triplet state via quenching by ground-state 2a and formation of an excimer. As a consequence, an aryl radical plus an N-centered carbazolyl radical are formed. These radical intermediates appear to be responsible for the observed photobiological effects of diclofenac, via hydrogen abstraction from the target biomolecules, which initiates a type-I photodynamic effect. The efficient peroxidation of model lipids, such as linoleic acid, photosensitized by 2a are in favor of this proposal. Thus, the photosensitizing properties of diclofenac appear to be associated with the photochemical and photobiological activity of its major photoproduct.