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.