Swapping boron acids for carbon acids Carbon-bound boronic acids and their esters are widely used as coupling partners to make carbon-carbon bonds. More recently, these chemicals have garnered pharmaceutical interest in their own right. Li et al. report a versatile nickel-catalyzed process to replace carboxylic acids with boronate esters by using a phthalimide activator. The reaction is well suited to late-stage modification of complex molecules. The authors used the approach to produce a potent in vitro inhibitor of human neutrophil elastase, a target of interest in treating inflammatory lung diseases. Science , this issue p. eaam7355