You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
tert-butyl N-[(2S)-1-[[(1S,2R,3S,4R)-4-(6-aminopurin-9-yl)-2,3-dihydroxycyclopentyl]amino]-1-oxopropan-2-yl]carbamate is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H27N7O5
assistant