Synthesis of Vaniprevir (MK-7009): Lactamization To Prepare a 22-Membered Macrocycle

Development of a practical synthesis of MK-7009, a 22-membered macrocycle, is described. A variety of ring-closing strategies were evaluated, including ring-closing metathesis, intermolecular palladium-catalyzed cross-couplings, and macrolactamization. Ring closure via macrolactamization was found to give the highest yields under relatively high reaction concentrations. Optimization of the ring formation step and the synthesis of key intermediates en route to MK-7009 are reported.