|  | This article may be too technical for most readers to understand.(March 2021) | 
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| Formula | C28H32N2O2 | 
| Molar mass | 428.576 g·mol−1 | 
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BU72 is an extremely potent opioid used in pharmacological research.
BU72 is an agonist for the μ-opioid receptor with exceptionally high binding affinity and potency, comparable to carfentanil. [1] It also has extremely high efficacy, giving a stronger maximal effect than the standard full agonist DAMGO. [2] In animal studies, it was found to be a potent analgesic (giving pain relief at very low doses), with a slow onset and long duration of action. [3] [4]
BU72 was used to produce the first crystal structure of the active μ-opioid receptor, [1] and is now widely used to model the activation process. [5] [6] [7] In the crystal structure, BU72 appears to bond to the receptor covalently, [8] [9] but this seems to be an experimental artifact, since the compound binds reversibly, and preventing bond formation has no effect on affinity. [1]
 
 BU72 is synthesized in several steps from thebaine. [10] Its stereochemistry has recently been revised, with the phenyl group in the (R) configuration. [11] [12]