An efficient synthesis of procyanidins using equimolar condensation of catechin and/or epicatechin catalyzed by ytterbium triflate. - Mohri,Y.; Sagehashi,M.; Yamada,T.; Hattori,Y.; Morimura,K.; Hamauzu,Y.; Kamo,T.; Hirota,M.; Makabe,H. (Heterocycles, 2009)