Divergent Total Syntheses of 2, 6-Dioxabicyclo[3.3.1]nonan-3-one Styryllactones: (-)-Goniopypyrone, (+)-Goniochelienlactone and (+)-7-Acetylgoniochelienlactone

Stereoselective total syntheses of (+)-goniochelienlactone, (+)-7-acetylgoniochelienlactone and (-)-goniopypyrone were accomplished by divergent strategies starting from readily available chiral pool methyl & alpha;-D-mannopyranoside. The present work provided an efficient strategy for the stereoselective construction of highly functionalized dioxabicyclo[3.3.1]nonan-3-one ring system through a sequential Bernet-Vasella-type reductive elimination/nucleophilic addition and a sequential cross-metathesis/intramolecular oxa-Michael addition in a one-pot process. The stereoselective syntheses of three 2,6-dioxabicyclo[3.3.1]nonan-3-one styryllactones, goniopypyrone, goniochelienlactone and 7-acetylgoniochelienlactone, has been accomplished based on chiron approach. In particular, (+)-goniochelienlactone and (+)-7-acetylgoniochelienlactone, which are the first total syntheses so far, were achieved in 5 steps (longest linear sequence) with a 28.3 % overall yield and in 8 steps (longest linear sequence) with a 22.2 % overall yield, respectively. The feature of this work involved a sequential reaction of Bernet-Vasella-type reductive elimination and nucleophilic addition by a one-pot sequence, sequential crossing metathesis (CM)/intramolecular oxa-Michael addition, and one-pot tandem deprotection/lactonization.image