Synthesis and resolution of 4,4,6,6-tetramethyl-4H,6H-pyrrolo[1,2-a][4,1]benzoxazepine-1,10-dicarboxylic acid

Optimized consecutive regioselective dimetallation and carboxylation of 4,4,6,6-tetramethyl-4H,6H-pyrrolo[1,2-a][4,1]benzoxazepine provided the corresponding dicarboxylic acid as a new, structurally rigid member of the atropisomeric 1-arylpyrrole family. Resolution of the new racemate was accomplished with several chiral bases and the absolute configurations of the pure enantiomers were determined by the combined application of ECD spectroscopy and quantum chemical calculations.