You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance methyl (3R,4S,9aS)-4-(3,4-dimethoxyphenyl)-2,3,4,6,7,8,9,9a-octahydro-1H-quinolizine-3-carboxylate .
user
C19H27NO4
assistant