Functionalization of the A ring of pyridoacridine as a route toward greater structural diversity. Synthesis of an octacyclic analogue of eilatin

Emerging pharmaceutical therapies of Ascidian-derived natural products and derivatives

In a growing multidrug-resistant environment, the identification of potential new drug candidates with an acceptable safety profile is a substantial crux in pharmaceutical discovery. This review discusses several aspects and properties of approved marine natural products derived from ascidian sources (phylum Chordata, subphylum Tunicata) and/or their deduced analogues including their biosynthetic origin, (bio)chemical preclinical assessments and known efficacy-safety profiles, clinical status in trials, but also translational developments, opportunities and final conclusions. The review also describes the preclinical assessments of a large number of other ascidian compounds that have not been involved in clinical trials yet. Finally, the emerging research on the connectivity of the ascidian hosts and their independent or obligate symbiotic guests is discussed. The review covers the latest information on the topic of ascidian-derived marine natural products over the last two decades including 2022, with the majority of publications published in the last decade.

Cascade intramolecular imidoylation and C–H activation/annulation of benzimidoyl chlorides with alkynes: one-pot synthesis of 7H-dibenzo[de,h]quinoline analogues

Described herein is a cascade Lewis acid-promoted intramolecular Friedel–Crafts-type imidoylation and Rh(iii)-catalyzed C–H activation/annulation of benzimidoyl chlorides and alkynes, providing a divergent synthetic shortcut to 7H-dibenzo[de,h]quinoline analogues.

Synthesis of three series of ruthenium tris-diimine complexes containing acridine-based π-extended ligands using an efficient “chemistry on the complex” approach

Novel multi-step chemistry on the complex strategy.

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

This review focuses on pyridoacridine-related metabolites as one biologically interesting group of alkaloids identified from marine sources. They are produced by marine sponges, ascidians and tunicates, and they are structurally comprised of four to eight fused rings including heterocycles. Acridine, acridone, dihydroacridine, and quinolone cores are features regularly found in these alkaloid skeletons. The lack of hydrogen atoms next to quaternary carbon atoms for two or three rings makes the chemical shift assignment a difficult task. In this regard, one of the aims of this review is the compilation of previously reported, pyridoacridine (13)C NMR data. Observations have been made on the delocalization of electrons and the presence of some functional groups that lead to changes in the chemical shift of some carbon resonances. The lack of mass spectra information for these alkaloids due to the compactness of their structures is further discussed. Moreover, the biosynthetic pathways of some of these metabolites have been shown since they could inspire biomimetic synthesis. The synthesis routes used to prepare members of these marine alkaloids (as well as their analogues), which are synthesized for biological purposes are also discussed. Pyridoacridines were found to have a large spectrum of bioactivity and this review highlights and compares the pharmacophores that are responsible for the observed bioactivity.

Electrochemical transduction of DNA hybridization at modified electrodes by using an electroactive pyridoacridone intercalator

A synthetic redox probe structurally related to natural pyridoacridones was designed and electrochemically characterised. These heterocycles behave as DNA intercalators due to their extended planar structure that promotes stacking in between nucleic acid base pairs. Electrochemical characterization by cyclic voltammetry revealed a quasi-reversible electrochemical behaviour occurring at a mild negative potential in aqueous solution. The study of the mechanism showed that the iminoquinone redox moiety acts similarly to quinone involving a two-electron reduction coupled with proton transfer. The easily accessible potential region with respect to aqueous electro-inactive window makes the pyridoacridone ring suitable for the indirect electrochemical detection of chemically unlabelled DNA. Its usefulness as electrochemical hybridization indicator was assessed on immobilised DNA and compared to doxorubicin. The voltamperometric response of the intercalator acts as an indicator of the presence of double-stranded DNA at the electrode surface and allows the selective transduction of immobilised oligonucleotide hybridization at both macro- and microscale electrodes.

Electrochemistry and bioactivity relationship of 6-substituted-4H-pyrido[4,3,2-kl]acridin-4-one antitumor drug candidates

We report here the electrochemical characterization of eight synthetic DNA intercalators based on the 4H-pyrido[4,3,2-kl]acridin-4-one structure. We found that the electrochemical behavior of these redox active drugs is strongly influenced by the nature of the solvent. A single two-electron reduction is observed in an aqueous phosphate buffer (PB) whereas two successive one-electron reductions are observed in aprotic solution (acetonitrile). The influence of the molecular structure on the potential values is addressed along with a comparison between the DNA binding constant (K(DNA)) and the cytotoxic activity against HT29 cells (IC(50)). For typical DNA intercalators, one could expect that toxicity will be roughly proportional to the DNA binding constant. Yet, a structure/activity comparison solely based on the DNA affinity was not conclusive. In contrast, a direct relationship was evidenced for the first time between the decimal logarithm of the in vitro bioactivity and the reduction potential of pyridoacridones recorded in PB at pH 7.0. Moreover, most of the bio/electrochemical relationships previously described for quinone-based drugs were reported with electrochemical characterization in aprotic solvents (typically acetonitrile, dimethylformamide or dimethylsulfoxide). But aqueous solution electrochemistry is definitely the most bio-relevant because the redox mechanism of quinone or iminoquinone reduction directly depends on the protic nature of the solvent.

Diving for drugs: tunicate anticancer compounds

The marine biosphere boasts tremendous biodiversity replete with structurally unique, active and selective secondary metabolites. Bioprospecting for antitumor compounds has been rewarding, and tunicates have been especially successful in yielding prospective cancer therapies. These compounds are now subjected to clinical trials in Europe and the USA. With the ongoing search for potent and specific anticancer drugs, in this article we discuss the unique perspectives, compounds and opportunities afforded by this rich source of potential pharmaceuticals. We discuss marine-derived antitumor drugs, their structures, and their various types and levels of antitumor activities in bench and bedside efforts.