Synthetic studies of an 18-membered antitumor macrolide, tedanolide. 5. Stereoselective synthesis of the C13-C23 part via condensation of two fragments, C13-C17 and C18-C21, by taking advantage of the 3,4-dimethoxybenzyl protecting group.

An efficient and stereoselective synthesis of the C13-C23 part (8) was achieved starting from methyl (R)- and (S)-3-hydroxy-2-methylpropionates (9) via coupling of the C13-C17 aldehyde (6), prepared by Evans asymmetric aldol reaction, with the C18-C21 iodoalkene (5b) by taking advantage of the 3,4-dimethoxybenzyl protecting group.