In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

Synthesis, radiosynthesis, and biological evaluation of carbon-11 labeled 2beta-carbomethoxy-3beta-(3'-((Z)-2-haloethenyl)phenyl)nortropanes: candidate radioligands for in vivo imaging of the serotonin transporter with positron emission tomography.
serotonin