Stereocontrolled synthesis of the ABCDE ring moiety of ciguatoxin CTX3C

The ABCDE ring moiety of ciguatoxin CTX3C, a major causative agent of ciguatera poisoning, was stereoselectively synthesized. The key transformations are a chiral auxiliary-based asymmetric alkylation and an asymmetric aldol condensation, which controlled the formation of the C11 and C21-stereocenters, respectively. A highly practical and efficient route to the ABCD ring fragment, a common precursor for the divergent synthesis of the left wings of ciguatoxins, was also established.