Synthesis of Enantiopure Isosteres of Amino Acids Containing a Quaternary Stereocenter: Experimental and Computational Evaluation of a Novel Class of Atropisomers

Electrophilic amination of diastereomeric 4-methoxycarbonyl pyrrolidin-2-ones allowed to prepare both diastereomers of an amino acid bearing a quaternary chiral center, a key intermediate to antibiotic 8-methoxyquinolone carboxylic acid. Within this synthesis, novel atropisomers, exceedingly stable at room temperature, were isolated and characterized, which were subsequently converted into the desired products by a novel reductive N–N bond cleavage reaction.