Design, Synthesis,and Characterization of GluN2ANegative Allosteric Modulators Suitable for In Vivo Exploration

<i>N</i>-Methyl-d-aspartate receptors are ionotropic glutamate receptors that mediate fast excitatory neurotransmission in the central nervous system. These receptors play essential roles in synaptic plasticity, learning, and memory and are implicated in various neuropathological and psychiatric disorders. Selective modulation of NMDAR subtypes, particularly GluN2A, has proven challenging. The <b>TCN-201</b> derivatives <b>MPX-004</b> and <b>MPX-007</b> are potent and selective for GluN2A receptors, yet their physical properties limit their in vivo utility. In this study, we optimized the <b>MPX-004</b>/<b>MPX-007</b> scaffold by modifying the linker region between the distal halogenated aromatic ring and the central pyrazine nucleus, resulting in the identification of potent and selective compounds with improved drug-like properties. Notably, compound <b>1</b> was used to develop the first GluN2A NAM-based radioligand, and compound <b>11</b> showed improved pharmacokinetics and dose-dependent receptor occupancy in vivo. Thus, we provide an array of powerful new tools for the study of GluN2A receptors.