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 (3R,6S,9S,15S,18S,21S)-3,15-diamino-6-(2-aminoethyl)-9,18-dimethyl-21-(methylamino)-1,4,7,10,13,16,19-heptazacyclotricosane-2,5,8,11,14,17,20-heptone .
user
C21H39N11O7
assistant