Addressing the Opioids Lipophilicity Challenge via a Straightforward and Simultaneous 1 H NMR-Based log P / D Determination, Both Separately and in Mixtures.

A systematic study of trends in the lipophilicity of prominent representatives of the opioid family, including natural, semisynthetic, synthetic, and endogenous neuropeptide opioids, is described. This was enabled by a straightforward 1 H NMR-based log P / D determination method developed for compounds holding at least one aromatic hydrogen atom. Moreover, the new method enables a direct simultaneous log D determination of opioid mixtures, overcoming the high sensitivity of this family to the measurement conditions, which is critical when a determination of the exact Δlog D values of matched pairs is required. Interpretation of the experimental Δlog D 7.4 values of selected matched pairs, focusing inter alia on the 3-OMe and 14-OMe motifs in morphinan opioids, is suggested with the aid of DFT calculations and may be useful for the discovery of new opioid therapeutics.