A new strategy applicable to the synthesis of indoloquinolizine natural products has been developed. A cyanide-catalyzed intramolecular imino-Stetter reaction of aldimines, derived from 2-aminocinnamic acid derivatives and 2-pyridinecarboxaldehydes, provided indole-3-acetic acid derivatives bearing a pyridyl ring at the 2-position. Reduction of the carboxylic acid moiety to an alcohol followed by activation of the resulting alcohol with Tf2O or TsCl generated indoloquinolizinium salts, which were utilized as precursors for indoloquinolizine natural products. The advantage of this protocol was successfully demonstrated in the total syntheses of arborescidine A and nauclefidine.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean Government (NRF-2015R1D1A1A01057200, NRF-2017M2A8A4018045, and NRF-20100020209). C.-H. C. thanks the financial support from an NRF grant funded by the Korean Government (NRF-2014-011165, Center for New Directions in Organic Synthesis).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry