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 tert-butyl 5-oxospiro[6,7,8,8a-tetrahydro-3H-[1,3]oxazolo[3,2-a]pyrazine-2,4'-piperidine]-1'-carboxylate .
user
C15H25N3O4
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