An efficient strategy for rapid assembly of the complex substituted cyclohexene core
that is present in several cyclic imine marine toxins is presented. Several of these
toxins, including pinnatoxin A and recently discovered portimine A, have been the
focus of much attention due to their fascinating biological activities. We demonstrate
that the substituted cyclohexene-diene motif, which is a challenging feature to access
synthetically, can be prepared through a stepwise Ireland–Claisen rearrangement/enyne
metathesis procedure beginning from chiral esters. This approach enables a divergent
strategy that can be implemented in syntheses of cyclic imines or derivatives thereof.
Key words
enyne metathesis - Ireland–Claisen - cyclic imine - portimine - pinnatoxin - kabirimine