You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
6,7-dimethoxy-2-[(3S)-1-(7H-purin-6-yl)piperidin-3-yl]-3,4-dihydro-1H-isoquinoline The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H26N6O2
assistant