Fig. 2. (A) Schematic diagram of a β-turn structure. (B) Overlay of a potential mode of β-turn mimicry with a tetra-substituted hexahydro-4H-pyrazino[2,1-c][1,2,4]triazine-4,7(6H)-dione. (C) Distance between substituents in the energy-minimized conformer of its tetra-substituted representative analog 7 containing 4-methylphenyl, benzyl, butyl, and 4-chlorophenyl at the R1–R4 positions, respectively. (D) Alignment of an energy-minimized structure of representative compound 7 with the peptide backbone structure of phospholipase A2 β-turn motif (PDB: ; 4BP2).
