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 [(1S)-1-(4-oxo-3H-quinazolin-2-yl)ethyl] 3-[(3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydroisoindol-2-yl]propanoate ?
user
C21H21N3O5
assistant