SignificanceThe development of selective antagonists for muscarinic acetylcholine receptors is challenging due to high homology in orthosteric binding sites among subtypes. Starting from a single amino acid difference in the orthosteric pockets in M2 muscarinic acetylcholine receptor (M2R) and M3R, we developed an M3R-selective antagonist using molecular docking and structure-based design. The resulting M3R antagonist showed up to 100-fold selectivity over the M2R in affinity and 1,000-fold selectivity in vivo. The docking-predicted geometry was further confirmed by a 3.1 Å crystal structure of M3R in complex with the selective antagonist. The potential of structure-based design to develop selective drugs with reduced off-target effects is supported by this study.

Substituted 2-aminobiphenyls have been prepared from arylhydrazine hydrochlorides and anilines in biphasic radical arylation reactions with dioxygen from air as a most simple and readily available oxidant. Under optimized conditions, the free amino functionality of the aniline leads to high ortho:meta regioselectivities, now even for anilines bearing a donor substituent in the para position. Finally, the mild and metal-free new access to aminobiphenyls was shown to be applicable on a gram scale.

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Although general interest in radical arylation reactions has grown rapidly in recent years, poor regioselectivities and the need to use a large excess of the radical-accepting arene have hindered their application to substituted benzenes. We now describe experimental and computational investigations into the substituent effects that lead to regioselective addition based on the recent discovery of anilines as outstanding substrates for radical arylations.

The diazotization of anilines in aqueous solution has been found to be highly useful as a key reaction step to achieve the denitrification of lowconcentrated nitrogen dioxide in air. The diazonium salt from the wet scrubberalthough obtained in highly diluted aqueous solutionwas shown to be directly applicable in a radical Gomberg-Bachmann aryl−aryl coupling and a Sandmeyer iodination reaction.