“Zipped Synthesis” by Cross-Metathesis Provides a Cystathionine β‑Synthase Inhibitor that Attenuates Cellular H₂S Levels and Reduces Neuronal Infarction in a Rat Ischemic Stroke Model

The gaseous neuromodulator H₂S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H₂S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a “zipped” approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-<i>C</i>₂-symmetric CBS product (l,l)-cystathionine. The “zipped” concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with hydrazine-imine interchange as opposed to the usual imine–imine interchange. It is demonstrated that the most potent “zipped” inhibitor <b>6S</b> reduces H₂S production in SH-SY5Y cells overexpressing CBS, thereby reducing cell death. Most importantly, CBS inhibitor <b>6S</b> dramatically reduces infarct volume (1 h post-stroke treatment; ∼70% reduction) in a rat transient middle cerebral artery occlusion model for ischemia