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Paper | Special issue | Vol 97, No. 2, 2018, pp.1028-1049
Published online, 4th June, 2018
DOI: 10.3987/COM-18-S(T)85
Synthetic Studies toward Isoschizogamine: Construction of Pentacyclic Core Structure

Kenji Sugimoto, Hiroaki Fujiwara, Akihiro Takada, Dong-Gil Kim, Hirofumi Ueda, and Hidetoshi Tokuyama*

*Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan

Abstract

Development of a concise construction of the pentacyclic core skeleton of isoschizogamine was described. Tetracyclic A,B,D,F-rings structure was assembled by intramolecular aza-Diels–Alder reaction via an ortho-iminoquinone methide intermediate. The C-ring was formed by oxidation of the benzylic position with a combination of Cr(CO)6 and t-BuO2H, followed by the introduction of an aminoethyl side chain, C–H oxidation of the lactam ring with CrO3 and n-Bu4NI, and final cyclization to construct the cyclic aminal moiety.