Diastereoselective Allylation in the Divergent Total Syntheses of Guaianolides (+)-Ligustrin and (+)-Grosheimin and the Formal Synthesis of (−)-Eupalinilide E

An efficient diastereoselective allylation of aldehydes with functionalized allyl bromolactone paved an excellent path toward the protecting-group-free divergent total synthesis of various guaianolides (+)-ligustrin, (+)-8-epi-ligustrin, and (+)-grosheimin and the formal synthesis of (−)-eupalinilide E. The key steps include diastereoselective allylation, efficient translactonization, and aldehyde–ene reaction. From the common intermediate molecule (+)-ligustrin, the first asymmetric total synthesis of (+)-grosheimin has been achieved.