You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-O-tert-butyl 1-O-[(19S)-19-ethyl-14,18-dioxo-17-oxa-3,13-diazapentacyclo[11.8.0.02,11.04,9.015,20]henicosa-1(21),2,4,6,8,10,15(20)-heptaen-19-yl] (2R)-2-[(2-methylpropan-2-yl)oxycarbonylamino]butanedioate is the IUPAC name of a molecule. Please give its molecular formula.
user
C33H37N3O9
assistant