Figure : Phenyl group geometric outliers and unexplained electron density for original (1a) and revised (1b) structures of BU72. Colors: fitted structures (black); ideal structures (grey); geometric outliers in the phenyl group (Z scores, red); 2Fo-Fc density (2.5σ, violet); Fo-Fc omit density (2σ, green). Adapted from The original proposed configuration of 1a was based on unpublished nuclear Overhauser effect (nOe) data, and the basis for the necessary NMR assignments was not stated . Thus, no published data support the original assignment, and the structure of BU72 should be revised to 1b. The authors of the crystal structure, including the lead author of the original synthesis, accepted this revision in a correction notice . However, the revised structure was not shown. Protein Data Bank entry Figure ) should also be revised, since they differ only in the N-substituent ; their synthetic routes diverge after establishment of the phenyl configuration, and the benzylic hydrogen is not exchangeable.