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 endo-selective Diels–Alder reaction to
construct the bicyclo[2.2.2]nonane framework, a nucleophilic addition
and an intramolecular aza-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.