Enantioselective Aza-Diels-Alder Reaction Catalyzed by a Chiral Brønsted Acid: Effect of the Additive on the Enantioselectivity - Akiyama, Takahiko; Tamura, Yukio; Itoh, Junji; Morita, Hisashi; Fuchibe, Kohei (Synlett, 2006)