1. Metal-free, Phosphoric Acid-catalyzed Regioselective 1,6-Hydroarylation of para-Quinone Methides with Indoles in Water
Biquan Xiong, Lulu Si, Yu Liu, Weifeng Xu, Tao Jiang, Fan Cao, Ke-Wen Tang, Wai-Yeung Wong Chem Asian J. 2022 May 2;17(9):e202200042. doi: 10.1002/asia.202200042. Epub 2022 Mar 24.
An efficient, cheap and green protocol for the highly regioselective 1,6-hydroarylation of para-quinone methides (p-QMs) with indoles at the C-3 position has been established by phosphoric acid catalysis in water under transition-metal-free reaction conditions. A wide range of indole derivatives and para-quinone methides (p-QMs) are compatible for the reaction, affording the corresponding 1,6-hydroarylation products with good to excellent yields. The possible mechanism of the reaction has been explored through step-by-step control experiments. The protocol is convenient for practical applications, leading to a safe, green and feasible way for the formation of C-3 diarylmethyl functionalized indole derivatives.
2. Sub-picomolar Inhibition of HIV-1 Protease with a Boronic Acid
Ian W Windsor, Michael J Palte, John C Lukesh 3rd, Brian Gold, Katrina T Forest, Ronald T Raines J Am Chem Soc. 2018 Oct 31;140(43):14015-14018. doi: 10.1021/jacs.8b07366. Epub 2018 Oct 22.
Boronic acids have been typecast as moieties for covalent complexation and are employed only rarely as agents for non-covalent recognition. By exploiting the profuse ability of a boronic acid group to form hydrogen bonds, we have developed an inhibitor of HIV-1 protease with extraordinary affinity. Specifically, we find that replacing an aniline moiety in darunavir with a phenylboronic acid leads to 20-fold greater affinity for the protease. X-ray crystallography demonstrates that the boronic acid group participates in three hydrogen bonds, more than the amino group of darunavir or any other analog. Importantly, the boronic acid maintains its hydrogen bonds and its affinity for the drug-resistant D30N variant of HIV-1 protease. The BOH···OC hydrogen bonds between the boronic acid hydroxy group and Asp30 (or Asn30) of the protease are short ( rO···O = 2.2 Å), and density functional theory analysis reveals a high degree of covalency. These data highlight the utility of boronic acids as versatile functional groups in the design of small-molecule ligands.
3. Chiral Phosphoric Acid Catalyzed Enantioselective Desymmetrization of 1,4-Dihydropyridines by C(sp3 )-H Bromination
Min Han, Shi-Qi Zhang, Xin Cui, Qi-Wei Wang, Guang-Xun Li, Zhuo Tang Angew Chem Int Ed Engl. 2022 May 23;61(22):e202201418. doi: 10.1002/anie.202201418. Epub 2022 Mar 31.
Described herein is the enantioselective synthesis of Hantzsch-type 1,4-dihydropyridines (DHPs), which are frequently contained in pharmaceuticals. Readily available symmetrical 1,4-DHPs were used as substrates, and the methyl group at the 2- or 6-position of the 1,4-DHP was selectively monobrominated by desymmetrizing enantioselective bromination. The inert C-H bond was converted into a versatile C-Br bond, which guaranteed the modification of the chiral 1,4-DHP derivatives with high efficiency. Furthermore, axially chiral 4-aryl pyridines were accessible by central-to-axial chirality conversion.
