2(1H)-Pyrazinones from acyclic building blocks: methods of synthesis and further derivatizations

Pyrazinones (2(1H)-pyrazinones) are found as components of a range of natural substances and are involved in the preparation of a great number of bioactive molecules. Synthesis of such compounds, and analogues, requires knowledge of the heterocyclic properties of pyrazinones and, in particular, methods for their ring construction. This review deals with the strategies that have been developed for the synthesis of pyrazinones from acyclic precursors, especially α-amino acid-derived units, from the first examples in 1905 up to the most recent in 2021.

Design, synthesis, and evaluation of new α-aminonitrile-based benzimidazole biomolecules as potent antimicrobial and antitubercular agents

The study explores the one-pot synthesis of novel α-aminonitriles by reacting 4-[(1H-benzimidazol-2-yl)methoxy]benzaldehyde, substituted anilines and sodium cyanide using a catalytic amount of copper dipyridine dichloride (CuPy₂ Cl₂ ) and employing the Strecker reaction under mild conditions. All the synthesized compounds were screened for antimicrobial and antitubercular activity. The promising lead compounds 4d and 4e were identified, with MIC values ranging between 3.9 and 7.8 µg/mL against different bacterial strains. Compounds 4c-e and 4g also showed good antifungal activities against the tested fungal strain. Among those tested, compound 4e exhibited excellent antitubercular activity (MIC 0.05 μg/mL) with a low level of cytotoxicity, suggesting that compound 4e is a promising lead for subsequent investigations in search for new antitubercular agents.

Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues

This review describes the formation of six-membered heterocyclic compounds and their fused analogues under microwave activation using modern organic transformations including cyclocondensation, cycloaddition, multicomponents and other modular reactions. The review is divided according to the main heterocycle types in order of increasing complexity, starting with heterocyclic systems containing one, two and three heteroatoms and their fused analogues. Recent microwave applications are reviewed, with special focus on the chemistry of bioactive compounds. Selected examples from the 2006 to 2015 literature are discussed.

Achiral pyrazinone-based inhibitors of the hepatitis C virus NS3 protease and drug-resistant variants with elongated substituents directed toward the S2 pocket

Herein we describe the design, synthesis, inhibitory potency, and pharmacokinetic properties of a novel class of achiral peptidomimetic HCV NS3 protease inhibitors. The compounds are based on a dipeptidomimetic pyrazinone glycine P3P2 building block in combination with an aromatic acyl sulfonamide in the P1P1' position. Structure-activity relationship data and molecular modeling support occupancy of the S2 pocket from elongated R(6) substituents on the 2(1H)-pyrazinone core and several inhibitors with improved inhibitory potency down to Ki = 0.11 μM were identified. A major goal with the design was to produce inhibitors structurally dissimilar to the di- and tripeptide-based HCV protease inhibitors in advanced stages of development for which cross-resistance might be an issue. Therefore, the retained and improved inhibitory potency against the drug-resistant variants A156T, D168V, and R155K further strengthen the potential of this class of inhibitors. A number of the inhibitors were tested in in vitro preclinical profiling assays to evaluate their apparent pharmacokinetic properties. The various R(6) substituents were found to have a major influence on solubility, metabolic stability, and cell permeability.

Microwave-assisted synthesis of small molecules targeting the infectious diseases tuberculosis, HIV/AIDS, malaria and hepatitis C

The unique properties of microwave in situ heating offer unparalleled opportunities for medicinal chemists to speed up lead optimisation processes in early drug discovery. The technology is ideal for small-scale discovery chemistry because it allows full reaction control, short reaction times, high safety and rapid feedback. To illustrate these advantages, we herein describe applications and approaches in the synthesis of small molecules to combat four of the most prevalent infectious diseases; tuberculosis, HIV/AIDS, malaria and hepatitis C, using dedicated microwave instrumentation.

Microwave multicomponent synthesis

In the manner that very important research is often performed by multidisciplinary research teams, the applications of multicomponent reactions involving the combination of multiple starting materials with different functional groups leading to the higher efficiency and environmentally friendly construction of multifunctional/complex target molecules is growing in importance. This review will explore the advances and advantages in microwave multicomponent synthesis (MMS) that have been achieved over the last five years.