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 methyl 2-(8a-ethyl-3-oxo-1,5,6,8-tetrahydro-[1,3]oxazolo[3,4-a]pyrazin-7-yl)-3-ethylimidazo[4,5-b]pyridine-6-carboxylate using the IUPAC nomenclature.
user
C18H23N5O4
assistant