[{"from": "human", "value": "Provide a brief overview of this molecule. [C][C][C][=Branch1][C][=O][N][Branch1][=Branch2][C][=C][C][=C][C][=C][Ring1][=Branch1][C][Branch2][Ring1][Ring2][C][C][N][Branch1][Branch1][C][C][Ring1][=Branch1][C][C][C][=C][C][=C][C][=C][Ring1][=Branch1][C][O][C]"}, {"from": "gpt", "value": "The molecule is an opioid related to carfentanil used as an animal tranquilizer. It was first synthesized by Janssen Pharmaceutica as part of a structure-activity relationship study of fentanly and its derivatives. R-30490 was found to be the most selective agonist for the mu opioid receptor out of all the fentanyl analogues tested, but it has never been introduced for medical use in humans, although the closely related drug sufentanil is widely used for analgesia and anesthesia during major surgery."}]