Evaluation of Larger Side‐Group Functionalities and the Side/End‐Group Interplay in Ritonavir‐Like Inhibitors of CYP3A4

ABSTRACT A new series of 13 ritonavir‐like inhibitors of human drug‐metabolizing CYP3A4 was rationally designed to study the R 2 side‐group and R 3 end‐group interplay when the R 1 side‐group is represented by phenyl. Spectral, functional, and structural characterization showed no improvement in the binding affinity and inhibitory potency of R 1 /R 2 ‐phenyl inhibitors upon elongation and/or fluorination of R 3 ‐Boc (tert‐butyloxycarbonyl) or its replacement with benzenesulfonyl. When R 3 is pyridine, the impact of R 2 ‐phenyl‐to‐indole/naphthalene substitution was multidirectional and highly dependent on side‐group stereo configuration. Overall, the R 2 ‐naphthalene/R 3 ‐pyridine containing 2f ( R / S ) was the series lead compound and one of the strongest binders/inhibitors designed thus far ( K s = 0.009 μM; IC 50 = 0.10 μM). Introduction of a larger biphenyl or fluorene as R 2 did not lead to any improvements. Contrarily, fluorene‐containing 13 was the series weakest binder and inhibitor ( K s = 0.734 μM; IC 50 = 1.32 μM), implying that the fluorene moiety is too large to allow unrestricted access to the active site. The R 2 ‐biphenyl, however, can switch positions with R 3 ‐Boc to enable heme ligation. Thus, for small and chemically simple end‐groups such as Boc and pyridine, the R 2 /R 3 interplay could lead to conformational rearrangement that would be difficult to foresee without structural information.