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Review | Special issue | Vol 97, No. 1, 2018, pp.107-140
Published online, 12th April, 2018
DOI: 10.3987/REV-18-SR(T)2
Construction of Cyclic Ether-Fused Tricyclic Naphthoquinone Derivatives by Intramolecular Cyclization Reaction

Tokutaro Ogata* and Tetsutaro Kimachi*

*Faculty of Pharmaceutical Sciences, Hokuriku University, 3-Ho, Kanagawa machi, Kanazawa 920-1181, Japan

Abstract

Cyclic ether-fused tricyclic naphthoquinones are major pharmacophores because they have attractive biological activities represented by antitumor and antibacterial properties. An enormous number of related compounds have been synthesized especially in the last two decades. The methodology for the construction of its skeleton is roughly classified into two types: 1) intermolecular cyclization of naphthoquinones and alkenes, 2) intramolecular cyclization of functionalized naphthoquinones. From the viewpoint of the reagents, a wide range of them from classical Brønsted acids to Lewis acids including fifth period elements have been applied to construct skeletons. The choice of appropriate reagent and reaction conditions against the substrate is the key to accomplishing the regio- and/or stereo-selective synthesis of these compounds, though it seems difficult at first glance to decide how because numerous numbers of actual examples have been presented. Therefore, in this review, we have decided to summarize the methods of constructing the tricyclic naphthoquinones limited by type 2 reactions while systematically classifying the substrates and reagents.