You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-2-[[3-methyl-3-[(2-methylpropan-2-yl)oxycarbonylamino]butanoyl]amino]-4-phenylbutanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H30N2O5
assistant