Given the importance of the chosen representation, the search for descriptive parameters has always been a cornerstone in this field. While Taft and Charton describe steric properties as singular substituent values, Harper et al. showed that a singular value is insufficient to represent steric substituent properties. Instead, the authors used Sterimol parameters as steric descriptors (Figure in their investigation of a peptide-catalysed atroposelective bromination (Figure ). The authors found that the peptidic catalysts can broadly be defined in two categories of βturns: a type I' pre-helical and type II' β-hairpin. Even though the latter was consistently lower in ground state energy (up to 6 kcal/mol for some catalysts), predictive models for enantioselectivity were found for both catalyst conformers in separate MLR models.