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Cyclorphan structure.svg
Systematic (IUPAC) name
CAS Registry Number 4163-15-9
PubChem CID: 5359966
ChemSpider 4514407
Chemical data
Formula C20H27NO
Molecular mass 297.434 g/mol
Physical data
Density 1.19 g/cm3
Melting point 188 °C (370 °F)
Boiling point 458.4 °C (857.1 °F)

Cyclorphan is an opioid compound that is a δ-opioid receptor agonist, a κ-opioid receptor agonist, and a μ-opioid receptor antagonist.[1] Chemically, it is a morphinan and is related to levorphanol.[1]

It was first synthesized in 1964 by scientists at Research Corporation.[2][3]:232 In clinical trials, it had relatively long duration, good absorption, and provided strong pain relief but caused symptoms of psychosis, so its development was not continued.[3]:232, 237


  1. ^ a b Aldrich JV & Vigil-Cruz SC, Narcotic Analgesics (doi 10.1002/0471266949.bmc100), pp 331-482 in Burger's Medicinal Chemistry and Drug Discovery, 7th Edition. 2003. ISBN 9780471266945
  2. ^ Cyclorphan page at Drug Leads, which cites US Patent 3,285,922
  3. ^ a b Varghese V & Hudlicky T. A Short History of the Discovery and Development of Naltrexone and Other Morphine Derivatives. Chapter 6 in Natural Products in Medicinal Chemistry, Volume 60 of Methods and Principles in Medicinal Chemistry. Ed. Stephen Hanessian. John Wiley & Sons, 2013. ISBN 9783527676552