You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as (1R,3S,4R,7R,8S,12S,13S)-3,4,7-trihydroxy-13-(2-hydroxy-3,4-dimethoxyphenyl)-17-methyl-9-oxa-14,15-dithia-10,17-diazatetracyclo[10.3.2.01,10.03,8]heptadecane-11,16-dione using the IUPAC nomenclature.
user
C21H26N2O9S2
assistant