Amelie L. Bartuschat

Drugs that treat chronic obstructive pulmonary disease by antagonizing the M3 muscarinic acetylcholine receptor (M3R) have had a significant effect on health, but can suffer from their lack of selectivity against the M2R subtype, which modulates heart rate. Beginning with the crystal structures of M2R and M3R, we exploited a single amino acid difference in their orthosteric binding pockets using molecular docking and structure-based design. The resulting M3R antagonists had up to 100-fold selectivity over M2R in affinity and over 1,000-fold selectivity in vivo. The crystal structure of the M3R-selective antagonist in complex with M3R corresponded closely to the docking-predicted geometry, providing a template for further optimization.

First electrophile, then radical: 4-Substituted tert-butyl phenylazocarboxylates 1 are versatile synthetic equivalents of the para-phenyl radical cation 2. The tert-butyloxycarbonylazo group enables nucleophilic substitutions to proceed under mild conditions and can later be employed for the generation of aryl radicals.

Tertiary amides, which usually occur as cis/trans mixtures, can be effectively shifted to the cis conformation by placing a positive charge in close proximity to the amide carbonyl. This effect was used to prepare cis-configured prolyl amides and to facilitate a strongly rotamer-dependent radical cyclization.

Introduction of [(18) F]fluoride ion into the aromatic core of phenylazocarboxylic esters was achieved in only 30 seconds, with radiochemical yields of up to 95 % (85(±10) %). For labeling purposes, the resulting (18) F-substituted azoester can be further converted in radical-arylation reactions to give biaryls, or in substitutions at its carbonyl unit to produce azocarboxamides.

Erst Elektrophil, dann Radikal: 4-Substituierte Phenylazocarbonsäure-tert-butylester 1 können als vielseitige Synthesebausteine im Sinne des para-Phenylradikalkations 2 eingesetzt werden. Die tert-Butyloxycarbonylazogruppe ermöglicht nucleophile Substitutionen unter milden Bedingungen und kann anschließend zur Erzeugung von Arylradikalen dienen.