[摘要]:The first intramol. version of Gassman's cationic [2 + 2] cycloaddn. employing vinyl acetals tethered to an unactivated olefin and its application in the formal syntheses of raikovenal and epi-raikovenal are described. The two intermediates I and II for the total synthesis of raikovenal and epi-raikovenal were prepd.