Figure 1.

Structural formula of avanafil. In order to bind effectively to the catalytic site of the PDE5, a selective inhibitor has to comprise three major structural principles: a guanine-like base, a ribose- or desoxyribose-like system and, finally, a phosphate diester-like bond. In the avanafil molecule, the central structure is formed by a nitrogen derivative of a pyrimidine carboxamide where the nitrogen atom of the amide is bound to a pyrimidinylmethyl group. It seems likely that the ribose (sugar)-phosphate component is represented by a cyclic chloromethoxybenzylamino structure; in this case, the Cl-atom and the methoxy ligand resemble the phosphate group seen in, for example, sildenafil and vardenafil.