You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule 3-[7-[(5-oxa-2-azaspiro[3.4]octan-6-ylmethylamino)methyl]-3-oxo-1H-isoindol-2-yl]piperidine-2,6-dione ?
user
C21H26N4O4
assistant