A water-tolerant Lewis acid catalystrecently used in one-pot syntheses ofβ-lactams,and in stereocontrolled radicaland nucleophilicaddition reactions. Catalyzes the synthesis of deoxypenostatin A in a novel, stereoselective, intramolecular Diels-Alder reaction.Lewis acid catalyst used with a silylated chinchona alkaloid in an asymmetric synthesis of substituted β-lactams from an acid chloride and aryl imine.Also used to catalyze an aldehyde-ene reaction in a synthesis of the guaiane skeleton.An important Lewis acid catalyst for a variety of synthetic reactions, including allylborations.