Short Approach toward the Nonracemic A,B,E Tricyclic Core of Calyciphylline B-Type Alkaloids [component]

A suitably functionalized tricyclic adduct containing the common A,B,E rings found in calyciphylline B-type alkaloids was obtained in nine linear steps. The key transformation features an efficient one-pot sequence of intramolecular Vilsmeier−Haack cyclization and azomethine ylide 1,3-dipolar cycloaddition in which three cycles, three new carbon−carbon bonds, and three stereocenters are formed, one being fully substituted. This work also demonstrates the first use of a chiral, nonracemic cyclic
more » ... , nonracemic cyclic enol ether as an internal carbon nucleophile. Letter
doi:10.1021/acs.orglett.7b01566.s002 fatcat:3kqlswoe5zblbmiympf7n4tieq