Basiliolides and transtaganolides are structurally related natural products isolated independently by two different groups from plants of Thapsia genus in 2005,and have been shown to be potent inhibitors against sacroendoplasmic reticulum Ca2+-ATPases(Schem 1).Recently we have already accomplished the total synthesis of Basiliolide B(Schem 2).A similar strategy was used to achieve the total synthesis of Basiliolide A1,A2,C and transtaganolide E,F.The synthesis featured a cyclopropanation/ring opening strategy for establishing the stereogenic centers at C8 and C9,a biomimetic 2-pyrone Diels-Alder cycloaddition for the synthesis of the ABD ring system,and finally a highly efficient biomimetic intramolecular O-acylation for the seven-membered acyl ketene acetal moiety formation(C ring).We have also developed the asymmetric cyclopropanation,studied the stereochemistry of cyclopropane ring opening and prepared a seies of derivatives for biological assays.