Microporous organic polymers (MOPs) and silver oxide (Ag 2 O) hybrid composites do show good antimicrobial capabilities, making them flexible for a variety of applications.
24 November 2021 in The Journal of Organic Chemistry
Imine reductases (IREDs) are important biocatalysts in the asymmetric synthesis of chiral amines. However, a detailed understanding of the stereocontrol mechanism of IRED remains incomplete, making the design of IRED for producing the desired amine enantiomers challenging. In this study, we investigated the stereoselective catalytic mechanism and designed an (R)-stereoselective IRED from Paenibacillus mucilaginosus (PmIR) using pharmaceutically relevant 2-aryl-substituted pyrrolines as substrates. A putative mechanism for controlling stereoselectivity was proposed based on the crucial role of electrostatic interactions in controlling iminium cation orientation and employed to achieve complete inversion of stereoselectivity in PmIR using computational design. The variant PmIR-Re (Q138M/P140M/Y187E/Q190A/D250M/R251N) exhibited opposite (S)-stereoselectivity, with >96% enantiomeric excess (ee) towards tested 2-aryl-substituted pyrrolines. Computational tools were employed to identify stabilizing mutations at the interface between the two subunits. The variant PmIR-6P (P140A/Q190S/R251N/Q217E/A257R/T277M) showed a nearly 5-fold increase in activity and a 12 °C increase in melting temperature. The PmIR-6P successfully produced (R)-2-(2,5-difluorophenyl)-pyrrolidine, a key chiral pharmaceutical intermediate, at a concentration of 400 mM with an ee exceeding 99%. This study provides insight into the stereocontrol elements of IREDs and demonstrates the potential of computational design for tailored stereoselectivity and thermal stability.
1 December 2021 in Bioorganic & Medicinal Chemistry Letters
Cyclopropane fragments, which widely exist in marketed drugs and natural products, can confer special pharmacological properties to small‐molecule drugs. Therefore, developing methods to construct cyclopropanes is of great significance. Nevertheless, the introduction of cyclopropane primarily relies on already‐formed cyclopropyl groups, which significantly restricts the diversity of cyclopropane skeletons. Late‐stage direct cyclopropanation is still a challenging task. Herein, a photo‐induced intermolecular deoxycyclopropanation reaction that employs alcohols as substrates, and 1 mol.% of 2,3,5,6‐tetrakis(carbazol‐9‐yl)‐1,4‐dicyanobenzene (4CzTPN) as organophotocatalyst is reported. This method proceeds with high transformation efficiency (up to 98% yield) and exhibits broad functional group tolerance, such as primary, secondary, and tertiary alcohols as well as various activated β‐halogenated alkenes. This process is mild, easy to operate, and has low equipment requirements. The power of this technology is demonstrated by the late‐stage functionalization of five marketed drugs and five natural products.
Non-small cell lung cancer (NSCLC) presents persistent challenges in immunotherapy, as the clinical benefit of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors is frequently constrained by intrinsic and acquired resistance. Central contributors include impaired antigen presentation, T cell exclusion, and the accumulation of immunosuppressive populations that collectively establish a “cold” tumor microenvironment (TME). These mechanisms dampen cytotoxic CD8+ T cell function and limit the durability of PD-1/PD-L1 blockade. Our single-cell RNA-seq reanalysis further supports that exhausted CD8+ T cells and regulatory T cells (Tregs) are enriched in non-responsive NSCLC, accompanied by compensatory upregulation of alternative checkpoints.