Efficient Multikilogram Synthesis of a VLA‑4 Antagonist via a Povarov Reaction

Herein we describe the practical synthesis of a novel VLA-4 antagonist 1 as a potential treatment for multiple sclerosis. The key step is based on the Povarov reaction of an imine with an alkene to access a tetrahydroquinoline intermediate, leading to the corresponding quinoline core after an oxidative aromatization step. The development of the synthesis of 1 led to decreased complexity and the elimination of chromatographic purifications. These improvements were demonstrated at scale by the production of 32 kg of 1 in high yield with excellent purity.