Combining cross-metathesis and activity-based protein profiling: new β-lactone motifs for targeting serine hydrolases.

β-Lactones are a privileged structural motif as enzyme inhibitors and chemical probes, particularly for the inhibition of enzymes from the serine hydrolase class. Herein, we demonstrate that cross-metathesis (CM) of α-methylene-β-lactones offers rapid access to structurally diverse, previously unexplored β-lactones. Combining this approach with competitive activity-based protein profiling (ABPP) identified lead β-lactone inhibitors/probes for several serine hydrolases, including disease-associated enzymes and enzymes of uncharacterized function. The structural diversity afforded by the α-methylene-β-lactone scaffold thus expands the landscape of serine hydrolases that can be targeted by small-molecule inhibitors and should further the functional characterization of enzymes from this class through the optimization of target-selective probes.