You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the compound with this IUPAC name ethyl 2-[(2R,4R)-2-tert-butyl-4-hydroxy-1-oxa-9-azaspiro[5.5]undecan-9-yl]pyridine-3-carboxylate ?
user
C21H32N2O4
assistant