stereocontrol. The yield for the 29-step longest linear sequence from Roche ester was 1.53 %. The final key steps to this unnatural product were the vinylzincate C10-C26 addition to aldehydeC1-C9 (leading surprisingly to a complete stereoselectivity for the 9R-epimer), followed by Yamaguchi macrolactonization and global deprotection.