Revised (β-phenyl) stereochemistry of ultrapotent μ opioid BU72

Abstract

In its crystal structure in complex with the opioid receptor (OR), the opioid BU72 exhibits extreme deviations from the expected geometry.1 Three of these involve the phenyl group. There is also unexplained electron density next to the benzylic carbon. Here I show that inverting the benzylic configuration fills this unexplained density and eliminates the phenyl group outliers, along with all but one of the others. I propose that this is the correct structure of BU72.