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 methyl (5R,6S)-4-benzoyloxy-2-butoxy-6-hydroxy-7-oxo-5,6-dihydropyrrolo[1,2-b]oxazine-5-carboxylate ?
user
C20H21NO8
assistant