Strategic positioning of a silyl group on the diene unit of a diene-ene substrate allows rigorous regio-and stereocontrol to be exerted during metathesis-based macrocyclization reactions. The versatility of this concise approach to E,Z-configured 1,3-dienes of ring sizes of 12 or larger is demonstrated by an application to the total synthesis of lactimidomycin, a potent translation and cell-migration inhibitor.