The enantioselective desymnitrization of carboxylic acids by chiral Bronsted base-catalysis is reported, leading to bridged bicyclic lactones with up to 94% ee. Crystallographic analysis of a substrate-catalyst complex suggests an origin of stereocontrol, retniniscent of functional Bronsted bases in biological Settings, and enabled reaction optimization. The products contain an all-carbon qiiaternary stereocenter and can be-derivatized to functionalized cyclopentanes.