Bentley compounds
The Bentley compounds are a class of semi-synthetic opioids that were first synthesized by K. W. Bentley by Diels-Alder reaction of thebaine with various dienophiles. The compounds are also known as thevinols, orvinols, or bridged oripavine derivatives, due to the characteristic 6,14-endo-ethano- or etheno-bridge and substitution at the 7α position. Buprenorphine and etorphine are perhaps the best known of the family, which was the first series of extremely potent μ-opioid agonists, with some compounds in the series having over many thousands of times the analgesic potency of morphine. See also
 Oripavine#Bridged derivatives

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Semisynthetic opioids