which are bioactive marine diterpenes containing a serrulatane or amphilectane skeleton, was elaborated. The chirogenic step, i.e. a Cu(I)-catalyzed allylic alkylation of a cinnamyl chloride with methylmagnesiumbromide, proceeded with virtually complete enantioselectivity (99% ee) in the presence of a chiral phosphine-phosphite ligand. The other stereocenters were diastereoselectively established through