Asymmetric Total Syntheses of Sarglamides A, C, and E.

The asymmetric total syntheses of sarglamides A, C, and E in concise and protecting group free fashion is disclosed. Key steps involve an -selective Diels-Alder reaction to construct the bicyclo[2.2.2]nonane framework, a nucleophilic addition and an intramolecular -Michael addition to install the pyrrolidine ring, and a final cinnamoylation reaction. Sarglamide C is biomimetically transformed into E through a Brønsted acid mediated oxy-cyclization. Sarglamide D is also accessible from C based on Yue's research. This work provides an efficient asymmetric approach to the syntheses of sarglamides and also provides insights into understand the plausible biogenetic pathway of these monoterpenoid-indolidinoid hybrid structures.