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 identified by (2S)-N-[(2R)-2-amino-3,3-dimethylbutanoyl]-N-[[2-(aminomethyl)-5-chlorophenyl]methyl]-2-methylpyrrolidine-2-carboxamide ?
user
C20H31ClN4O2
assistant