Figure 1.
Selected literature reported chemical structures of PDE9 inhibitors [18]. Compound 1 (BAY73-6691), Compound 2 (28r and 28s), Compound 3 (3r and 3s), Compound 4 (PF-04447943), Compound 5 (PF-4181366), and Compound 6 (4r). The chiral carbon that makes two enantiomers were marked with symbol (*). Common substructure included separately with numbering.
