You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3R,4R)-1-[2-(4-ethoxyphenyl)acetyl]-4-hydroxy-3-(3-methylbutyl)piperidine-3-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H31NO5
assistant