Synthetic studies of the HIV-1 protease inhibitive didemnaketals: precise and stereocontrolled synthesis of the key mother spiroketal

The precise and stereocontrolled synthesis of the C9–C23 portion, the key mother spiroketal of the HIV-1 protease inhibitive didemnaketals from the ascidian Didemnum sp., has been carried out through multisteps starting from (R)-pulegone as the chiral template. This approach involved the distereoselective construction of eight chiral centers by intramolecular chiral inducement and the coupling of two fragments by Julia reaction.