Development of a Scalable Synthesis of Mevidalen (LY3154207), an Orally Available Positive Allosteric Modulator of the Human Dopamine D1 Receptor

The evolution from early medicinal chemistry to large-scale production of the chemical synthesis of Lilly D1-positive allosteric modulator (PAM) mevidalen (LY3154207) and its hydroxybenzoate co-crystal is outlined. The issues and steps taken to resolve them are outlined across several generations of synthesis, including unexpected issues that arose during cryogenic addition of MeLi to a key imine intermediate and the use of flow chemistry to enable large-scale production. Ultimately, a process that was used to deliver >100 kg of API to support ongoing clinical trials is described.