Synthesis and Biological Evaluation of O6C-Salvinorin Alkyne Probes

The authors report an optimized, scalable synthetic route for salvinorin-based probes that target the kappa-opioid receptor. Methodological improvements include substituting a Grignard reagent with an organozinc protocol and enhancing a samarium-mediated reaction with LiBr. These advances enabled the synthesis of two active positive-control probes and three negative-control probes. A screen of over 300 GPCRs confirmed the exceptional KOR selectivity of a novel alkyne probe, establishing it as a tool for validating target-specific engagement in situ.

Study at a glance

Abstract

The salvinorins represent a unique class of polyoxygenated, non-nitrogenous diterpenes that potently and selectively modulate the kappa-opioid receptor (KOR). We recently disclosed a de novo asymmetric synthesis of this scaffold that enabled the discovery of highly potent, biased analogs, including C11-alkynes designed for the CATCH (Clearing-Assisted Tissue Click Chemistry) assay. Here, we report an optimized, scalable synthetic route that substitutes a problematic 1,4-conjugate addition of a Grignard reagent with a robust organozinc protocol in DMA, and improves a samarium-mediated Reformatsky reaction via the addition of LiBr. These methodological improvements facilitated the scalable synthesis of two highly active positive-control probes and three tailored negativecontrol probes, including functionally silent and cross-linking deficient analogs. A screen of >300 GPCRs confirmed the exceptional KOR selectivity of the novel alkyne probe, establishing it as a critical tool to validate target-specific engagement in situ.