You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule methyl (2R)-2-[5-(3,4-dimethylphenyl)-3-methyl-4-oxothieno[2,3-d]pyrimidin-2-yl]sulfanylpropanoate .
user
C19H20N2O3S2
assistant