You are a chemist. Now you are given a description of a molecule. Please generate a molecule that meets the description.
system
Generate a molecule that fulfills the requirement: The molecule is a phosphodiesterase inhibitor.
user
CCn1ncc2c(NC3CC(C(=O)O)(C(C)(C)C)C3)c(C3=NOC4(CCC4)C3)cnc21
assistant