Reactions of 2-(methoxyimino)benzen-1-ones with α-alkylethoxycarbonylmethylene(triphenyl)phosphoranes

Imidazoles and Oxazoles from Lapachones and Phenanthrene-9,10-dione: A Journey through their Synthesis, Biological Studies, and Optical Applications

Diverse structural frameworks are found in natural compounds and are well known for their chemical and biological properties; such compounds include the imidazoles and oxazoles. Researchers worldwide are continually working on the development of methods for synthesizing new molecules bearing these basic moiety and evaluating their properties and applications. To expand the knowledge related to azoles, this review summarizes important examples of imidazole and oxazole derivatives from 1,2-dicarbonyl compounds, such as lapachones and phenanthrene-9,10-diones, not only regarding their synthesis and biological applications but also their photophysical properties and uses. The data concerning the latter are particularly scarce in the literature, which leads to underestimation of the potential applications that can be envisaged for these compounds.

Iodine-Catalyzed Functionalization of Primary Aliphatic Amines to Oxazoles, 1,4-Oxazines, and Oxazinones

Unprecedented I₂-catalyzed α,α-C(sp³)-H, decarboxylative α-C(sp³)-H, lactonized α-C(sp³)-H, and α,β-C(sp³)-H functionalized 5- and 6-annulation as well as α-C(sp³)-H activated 6-lactonization of primary aliphatic amines are devised under aerobic conditions. The metal-free sustainable strategy was employed for the diverse construction of valuable five-and six-membered polycyclic N,O-heteroaromatics such as oxazoles, 1,4-oxazines, and oxazin-2-one with a rapid reaction rate and high yield. The viability of this mild nonmetallic catalysis is successfully verified through syntheses of labile chiral heterocyclic analogues. In contrast to the common practice, this method is not limited to use of prefunctionalized amines, directing groups (DGs) and/or transient DGs, metal catalysts, and traditional oxidants. The possible mechanistic pathway of the annulation reaction is investigated by control experiments and ESI-MS data collected for a reaction mixture of the ongoing reaction. The synthesized new compounds are potent organic nanobuilding blocks to achieve valuable organic nanomaterials of different sizes, shapes, and dimensions, which are under investigation for the discovery of high-tech devices of innovative organic nanoelectronics and photophysical properties.

Synthesis of quinones with highlighted biological applications: A critical update on the strategies towards bioactive compounds with emphasis on lapachones

Naphthoquinones are of key importance in organic synthesis and medicinal chemistry. In the last few years, various synthetic routes have been developed to prepare bioactive compounds derived or based on lapachones. In this sense, this review is mainly focused on the synthetic aspects and strategies used for the design of these compounds on the basis of their biological activities for the development of drugs against the neglected diseases leishmaniases and Chagas disease and also cancer. Three strategies used to develop bioactive quinones are discussed and categorized: (i) C-ring modification, (ii) redox centre modification and (iii) A-ring modification. Framed within these strategies for the development of naphthoquinoidal compounds against T. cruzi. Leishmania and cancer, reactions including copper-catalyzed azide-alkyne cycloaddition (click chemistry), palladium-catalysed cross couplings, C-H activation reactions, Ullmann couplings and heterocyclisations reported up to July 2019 will be discussed. The aim of derivatisation is the generation of novel molecules that can potentially inhibit cellular organelles/processes, generate reactive oxygen species and increase lipophilicity to enhance penetration through the plasma membrane. Modified lapachones have emerged as promising prototypes for the development of drugs against leishmaniases, Chagas disease and cancer.

Pyridine and p-Nitrophenyl Oxime Esters with Possible Photochemotherapeutic Activity: Synthesis, DNA Photocleavage and DNA Binding Studies

Compared to standard treatments for various diseases, photochemotherapy and photo-dynamic therapy are less invasive approaches, in which DNA photocleavers represent promising tools for novel “on demand” chemotherapeutics. A series of p-nitrobenzoyl and p-pyridoyl ester conjugated aldoximes, amidoximes and ethanone oximes were subjected to UV irradiation at 312 nm with supercoiled circular plasmid DNA. The compounds which possessed appropriate properties were additionally subjected to UVA irradiation at 365 nm. The ability of most of the compounds to photocleave DNA was high at 312 nm, whereas higher concentrations were required at 365 nm as a result of their lower UV absorption. The affinity of selected compounds to calf-thymus (CT) DNA was studied by UV spectroscopy, viscosity experiments and competitive studies with ethidium bromide (EB) revealing that all compounds interacted with CT DNA. The fluorescence emission spectra of the pre-treated EB-DNA exhibited a moderate to significant quenching in the presence of the compounds indicating the binding of the compounds to CT DNA via intercalation as concluded also by DNA-viscosity experiments. For the oxime esters the DNA photocleavage and affinity studies aimed to clarify the role of the oxime nature (aldoxime, ketoxime, amidoxime) and the role of the pyridine and p-nitrophenyl moieties both as oxime substituents and ester conjugates.

O-Benzoyl pyridine aldoxime and amidoxime derivatives: novel efficient DNA photo-cleavage agents

Pyridine oxime esters are effective DNA photocleavers, causing single-/double-stranded DNA cleavage at concentrations as low as 1 μM.

Synthesis of quinoidal molecules: strategies towards bioactive compounds with an emphasis on lapachones

Naphthoquinoidal compounds are of great interest in medicinal chemistry. In recent years, several synthetic routes have been developed to obtain bioactive molecules derived from lapachones. In this mini-review, we focus on the synthetic aspects and strategies used to design these compounds and on the biological activities of these substances for the development of drugs against the neglected diseases leishmaniasis and Chagas disease as well as malaria, tuberculosis and cancer. Three strategies used to develop bioactive naphthoquinoidal compounds are discussed: (i) C-ring modification, (ii) redox centre modification and (iii) A-ring modification. Among these strategies, reactions such as copper-catalysed azide-alkyne cycloaddition (click chemistry), palladium-catalysed cross couplings, and heterocyclisations will be discussed for the development of naphthoquinoidal compounds against Trypanosoma cruzi, Leishmania and cancer. The aim of derivatisation is the generation of novel molecules that inhibit cellular organelles/processes, generate reactive oxygen species (ROS) and increase lipophilicity to enhance penetration through the plasma membrane. Modified lapachones have emerged as promising prototypes for the development of drugs against neglected diseases and cancer.

Synthesis and biological evaluation of novel angular fused Pyrrolocoumarins

Angular pyrrolocoumarins were synthesized from the reaction of 4-hydroxyindole or 5-hydroxyindole with DMAD and PPh(3) and were tested for anti-inflammatory and antioxidant activity. These compounds significantly inhibited the carrageenin-induced paw edema (60.5%-73.4%) and have important scavenging activity. Although their interaction with the free stable radical DPPH is not high, compound 9 is the most potent (73.4%) in the in vivo experiment. Compound 7 seems to be a potent LOX inhibitor. An attempt was made to correlate the biological results with their structural characteristics and physicochemical parameters.