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 identified by 3,4,5-trihydroxy-6-[(2R,4R)-1-[(2R)-2-methyl-3-sulfanylpropanoyl]-4-phenylsulfanylpyrrolidine-2-carbonyl]oxyoxane-2-carboxylic acid ?
user
C21H27NO9S2
assistant