Fig. 5.

a Representative 3-substituted L-Pro analogs discussed in this article (see Table S3 for structural details). The substituents are labeled according to the stereochemistry of the prochiral hydrogen atom. b Representative 3-substituted D-Pro analogs discussed in this article (see Table S3 for structural details). c Schematic showing the differential effect of 3R substitution (bulky steric group versus electron-withdrawing group). d Schematic showing the differential effect of 3S substitution (bulky steric group versus electron-withdrawing group). e Ramachandran plot for 3-substituted L-Pro analogs (triangle trans; circle cis; open symbols exo; filled symbols endo)