A seven-step asymmetric total synthesis of gymnothelignan N is detailed in the current report. The approach is based on an early-stage one-carbon homologative lactonization reaction, which we recently revisited and modified to construct the core γ-butyrolactone motif with the requisite β,γ-vicinal stereogenic centers. By design, the utilization of the same chiral γ-butyrolactone intermediate permitted the rapid and effective divergent assembly of optically active eupomatilones 1, 3, 4, and 7 in five or six steps from commercially available materials. This represents one of the shortest and highest-yielding syntheses reported to date.

The first total synthesis of tetrahydrofuran dilignan gymnothelignan K is disclosed. The approach is based on implementing an early stage one-carbon homologative lactonization, which we recently disclosed, for constructing the γ-butyrolactone scaffold with the requisite β,γ-trans-vicinal stereocenters. Other salient features of the synthesis include the acid-promoted dimerization and the Suzuki–Miyaura cross-coupling reaction to install the challenging diaryl skeleton that permits the effective assembly of the optically active gymnothelignan K in 8 steps from commercially available materials.