Synthesis of Electrophilic Cyclopent‐2‐enone Conjugates With Modulatory Effects on Inflammatory Responses Mediated by Nrf2/Keap1, NF‐κB and IL‐6

Abstract

Cyclopent‐2‐enone bearing natural products possess anti‐inflammatory, cytotoxic, antiproliferative, and antimicrobial activities attributed to the presence of a Michael acceptor enone group acting as a bait for protein targets. To explore the biological activity of synthetic small molecules bearing the cyclopent‐2‐enone moiety, a collection of 4‐substituted cyclopent‐2‐enones (3 a–3 i) was prepared synthetically using Lewis acid‐catalyzed Mukaiyama‐Michael reaction (MMR) in modest to high yields. These derivatives were screened for their effect on inflammatory response mediators, namely Nrf2, NF‐κB, and IL‐6 through cell‐based reporter assays. The results show that 5‐(4‐oxocyclopent‐2‐en‐1‐yl)furan‐2(5H)‐one (3 g) is a potent Nrf2 activator in HaCaT cells. The mechanism of Nrf2 activation by 3 g was investigated through an MS/MS‐directed proteomic analysis and have shown the formation of a Michael adduct via cysteine‐613 on Keap1, an inhibitor of Nrf2. Density functional theory calculations show favorable Michael adduct formation between 3 g and the truncated Keap1 tripeptide Pro‐Cys613‐Ala at the β‐carbon of the cyclopent‐2‐enone moiety. On the other hand, the derivative 4‐(2‐oxo‐2‐phenylethyl)cyclopent‐2‐en‐1‐one (3 a) exhibited selective Nrf2 inhibition in the cancer cell line Huh7, and inhibitory activity along with 3 g against NF‐κB, and IL‐6 in RAW 264.7 cells. This points to the cyclopent‐2‐enone group being an effective scaffold for anti‐inflammatory drug designs.