The stereochemical properties ofN-acyl-5H-dibenzo[b,d]azepin-7(6H)-ones (2a–c), which inhibit potassium channels in T cells, were examined by freezing their conformational change due to 4-methyl substitution.N-Acyl-5H-dibenzo[b,d]azepin-7(6H)-ones exist as pairs of enantiomers [(a1R, a2R), (a1S, a2S)], and each atropisomer is separable at room temperature. An alternate procedure for preparing 5H-dibenzo[b,d]azepin-7(6H)-ones involves the intramolecular Friedel–Crafts cyclization ofN-benzyloxycarbonylated biaryl amino acids. Consequently, theN-benzyloxy group was removed during the cyclization reaction to produce 5H-dibenzo[b,d]azepin-7(6H)-ones suitable for the subsequentN-acylation reaction.