Development of Guanidine-Bisurea Bifunctional Organocatalyst Bearing Chirality at the Inner and Outer Sides of the Urea Groups, and Application to Enantioselective α-Hydroxylation of Pyranoindolizine Intermediate for Camptothecin Synthesis. - Minami Odagi; Tatsuya Watanabe; Kazuo Nagasawa (Symmetry, 2015)