You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2S)-1-(3,4-dihydro-1H-isoquinolin-2-yl)-1-oxopropan-2-yl] 4-amino-5-chloro-2-methoxybenzoate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H21ClN2O4
assistant