Abstract
Difamilast (also known as OPA-15406 or MM36) is a non-steroidal, highly selective inhibitor of phosphodiesterase 4 (PDE4). Its chemical name is N-[[2-[4-(difluoromethoxy)-3-propan-2-yloxyphenyl]-1,3-oxazol-4-yl]methyl]-2-ethoxybenzamide. The compound has a molecular formula of C(23)H(24)F(2)N(2)O(5) and a molecular weight of 446.44 g/mol. In appearance, difamilast occurs as white crystals or crystalline powder. The compound is highly soluble in N-methylpyrrolidone, freely soluble in methanol and ethanol, and practically insoluble in water.