An efficient synthesis of the CD rings model for merrilactone A

A synthetic route to the CD rings of merrilactone A was explored by using the model system 9a, which was easily converted from 7,7-dibromohepta-2,6-dienoic acid ethyl ester (8) by the successive Stille–Mizoroki–Heck reaction. The D ring 14 was constructed by applying the intramolecular Tsuji–Trost reaction to the formation of a γ-lactone, whereas the formation of the C ring 18 was effectively accomplished in one step by methylation and conjugate addition toward 1,1-dibromo-1-alkene 17 using Miyashita’s protocol.