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 [(3R,4R)-3-(6-aminopurin-9-yl)-4-hydroxy-4-methyl-1-oxa-9-azaspiro[5.5]undecan-9-yl]-[(3S)-piperidin-3-yl]methanone .
user
C21H31N7O3
assistant