The authors considered the possibility that the ligand was actually imine 2 (Figure ), whose planar sp 2 benzylic carbon would resolve this problem, but this was not detected in mass spectra of the crystallization mixture . In a preprint, I proposed an alternative: a revised structure for BU72 with the phenyl group in the opposite (R) configuration (1b, Figure ) . Revised structure 1b fits in a low-energy conformation, eliminating the geometric outliers and unexplained density around the phenyl group, and yielding superior validation metrics (Figure ) . The similar binding affinities of BU72 and imine 2 provide further support to structure 1b: the equatorial phenyl group in 1b is approximately planar, as in imine 2, which also fits the density in a low-energy conformation, unlike 1a (see Extended Data Fig. in ).