Synthesis of (±)-Chokol A by a Tandem Michael-Addition/Dieckmann Cyclization

A total synthesis of (±)-chokol A (rac-12) was accomplished in five steps by starting from the α,β-unsaturated ester (E)-2 in an overall yield of 24%. The key step of this synthesis is the tandem conjugate addition/Dieckmann cyclization of the cuprate derived from vinyl bromide 9 with the α,β-unsaturated ester (E)-2.