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. 2021 Dec 12;22(24):13353. doi: 10.3390/ijms222413353

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© 2021 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

PMC Copyright notice

Design of selected morphine-based opioid compounds. We use the morphine molecule (a) to introduce the overall numbering and ring labels. In parantheses, “an” indicates an MOR antagonist; all other opioid drug molecules are agonists. Circles highlight the addition or substitution of moieties. The structure of (b) heroin, (c) oxymorphone, (d) oxycodone, (e) N-phenethylnormorphine, (f) the antagonist naloxone, (g) the antagonist naltrexone, (h) levorphanol, (i) metazocine, (j) fentanyl, (k) metadone, (l) pethidine, (m) NFEPP. (n) Oliceridine is an agonist unrelated to morphine. Chemical structures were drawn using MarvinSketch 19.4, developed by ChemAxon and assembled using Inkscape 1.0.