cyclorphan cyclorphan cyclorphan is an opioid analgesic of the morphinan family that was never marketed. it acts as a μ-opioid receptor (mor) weak partial agonist or antagonist, κ-opioid receptor (kor) full agonist, and, to a much lesser extent, δ-opioid receptor (dor) agonist (75-fold lower affinity relative to the kor). the drug was first synthesized in 1964 by scientists at research corporation.: 232 in clinical trials, it had relatively long duration, good absorption, and provided strong pain relief but produced psychotomimetic effects via kor activation, so its development was not continued.: 232, 237 cyclorphanidentifiers iupac name (−)-3-hydroxy-n-cyclopropylmethylmorphinan cas number4163-15-9pubchem cid5359966chemspider4514407uniiu6z73n36v0chemblchembl49269comptox dashboard (epa)dtxsid50878519 echa infocard100.021.825 chemical and physical dataformulac20h27nomolar mass297.442 g·mol−13d model (jsmol)interactive imagedensity1.19 g/cm3melting point188 °c (370 °f)boiling point458.4 °c (857.1 °f) smiles oc1ccc4c(c1)25((n(cc2)cc3cc3)c4)cccc5