title: Total Syntheses of Juglorescein and Juglocombins A and B.
abstract: Total syntheses of juglorescein and juglocombins A and B are reported. The highly oxygenated 6/6/5/6/6-fused pentacyclic ring system of these natural products was constructed through a bioinspired dimerization of 1,4-naphthoquinone. Notably, five new stereogenic centers were constructed in a single step by the dimerization reaction. The epoxide intermediate obtained from the dimerization was successfully converted into juglocombins A and B through photoinduced reduction of the epoxide, dehydration, and conversion of the resultant quinone into a hydroquinone derivative. The same epoxide intermediate was also converted into a dicarboxylic acid, which was transformed into juglorescein through intramolecular lactonization, hydrolysis of the resulting lactone, and removal of the protecting groups. Furthermore, the relative and absolute configurations of juglorescein and juglocombins A and B were determined.
authors.affiliation: Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hanki-cho, Sakyo-ku, Kyoto, 606-8522, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Kamo
authors.affiliation: Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hanki-cho, Sakyo-ku, Kyoto, 606-8522, Japan.
authors.forename: Kai
authors.initials: K
authors.lastname: Yoshioka
authors.affiliation: Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hanki-cho, Sakyo-ku, Kyoto, 606-8522, Japan. kuramoch@kpu.ac.jp, kuramoch@rs.tus.ac.jp.|Present address: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan. kuramoch@kpu.ac.jp, kuramoch@rs.tus.ac.jp.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kuramochi
authors.affiliation: Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hanki-cho, Sakyo-ku, Kyoto, 606-8522, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Tsubaki
keywords: 1,4-naphthoquinone; biomimetic synthesis; dimerization; fused-ring systems; total synthesis