35 Plants are vital for the wellbeing of humankind in a variety of ways. Some plant extracts contain 36 antimicrobial properties that can treat different pathogens. Most of the world's population relies 37 on medicinal plants and natural products for their primary health care needs. Therefore, there is a 38 growing interest in natural products, medicinal plants, and traditional medicine along with a 39 desire to design and develop novel plant-based pharmaceuticals. These plant-based 40 pharmaceuticals may address the concerns of reduced efficacy of synthetic antibiotics due to the 41 emergence of drug-resistant pathogens. In this regard, some plant extracts from black pepper 42 (Piper nigrum) with antimicrobial properties, including piperine, have the potential to be used as 43 natural dietary supplements together with modern therapeutic approaches. This review highlights 44 possible applications of piperine as the active compound in the fields of rational drug design and 45 discovery, pharmaceutical chemistry, and biomedicine. We discuss different extraction methods 46 and pharmacological effects of the analyzed substance to pave the way for further research 47 strategies and perspectives towards the development of novel herbal products for better 48 healthcare solutions.49 50

Considering the synthetic relevance of heteroarenes in various areas ranging from organic synthesis to medicinal chemistry, developing practically simple approaches to access functionalized heteroarenes is of significant value. Described herein is an efficient approach for C-H silylation and hydroxymethylation of pyridines and related heterocycles by the 2 combination of silanes or methanol with readily available N-methoxypyridinium ions with a low catalyst loading (2 mol%) under blue light irradiation. The synthetic importance of the developed reactions is illustrated by the synthesis of biologically relevant compounds. EPR spectroscopy, quantum yield measurements and DFT calculations allowed to understand reaction mechanisms of both photocatalytic reactions.

We report herein a visible light-mediated C−H alkylation of pyridine derivatives that proceeds by simple combination of a large variety of N-alkoxypyridinium ions with alkanes in the presence of 2 mol% of fac-Ir(ppy)3 under blue illumination. The mild reaction conditions together with the high group functional tolerance make of this process a useful synthetic platform for the construction of structurally strained heterocycles. Detailed mechanistic investigations, including Density Functional Theory (DFT) calculations and quantum yield measurement, allowed to understand factors controlling the reactivity and the selectivity of the reaction.Alkylated heteroarenes are ubiquitous chemical motifs present in pharmaceuticals, natural products, and ligand scaffolds. 1,2 While access to such molecules can be achieved with different synthetic methodologies, the oxidative cross-coupling between two C−H compounds is evidently one of the most elegant approaches as it provides a direct construction of the C−C bond in a step-and atom-economical fashion. 3 -7 For instance, the generation of an alkyl radical through a hydrogen atom transfer (HAT) event and its subsequent addition to a heteroarene ring followed by a formal hydrogen atom loss can provide a rapid and direct method for heterocycle C−H alkylation. This approach, known as the Minisci reaction, 8 -11 gained much attention during the last decade with the spectacular renaissance of the field of photoredox catalysis that provides very mild conditions for the generation of alkyl radicals. 12 -19 While various elegant photoredox Minisci reactions employing HAT strategy for the generation of the alkyl radical have been developed, there is in most cases need to use an external oxidant and stoichiometric amounts of Brønsted acids to activate the heteroarene ring towards radical addition. 20 -27 Scheme 1. (A) Reported Approaches for C−H Alkylation of Heteroarenes. (B) Current work. HAT denotes Hydrogen Atom Transfer.

The interest in expanded-ring N-heterocyclic carbenes (ER-NHCs) has been recently given a noticeable attention, especially with the Au(I)-catalyzed activation of alkynes. Herein, we report density functional theory (DFT) investigations on...