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Total synthesis of pyrano[3,2-e]indole alkaloid fontanesine B by a double cyclization strategy
- Itoh, Tomoki, Chiba, Yuusuke, Kawaguchi, Shunsuke, Koitaya, Yuki, Yoneta, Yuuma, Yamada, Koji, Abe, Takumi
- RSC advances 2019 v.9 no.18 pp. 10420-10424
- cyclization reactions, indole alkaloids, regioselectivity
- The regioselective synthesis of pyrano[3,2-e]indole alkaloid fontanesine B by two different cyclizations is described. The complete regioselectivity is controlled by the C4 Pictet–Spengler cyclization, in which an iminium ion acts as a transient directing (TDG) group. Furthermore, carbolines were constructed by a new Bischler–Napieralski-type cyclization, in which an unprecedented trichloromethyl carbamate serves as a reactive group.