摘要:
A new highly diastereoselective and practical route to the lactone 6a which is used as a key building block for the total synthesis of the microtubule-stabilizing anticancer agent discodermolide is reported. This exploits the chiral auxiliary (4R)4-isopropyl-5,5-diphenyloxazolidin-2-one (7) which conveys crystallinity to the synthetic intermediates throughout the entire process. Purifications can thus be performed by recrystallization, avoiding chromatography to afford the final product in high enantiomeric purity. The overall efficiency is augmented by the facile recovery of the auxiliary by precipitation at the end of the sequence.