Synthetic studies on C14 cembranoids: synthesis of C4–12 fragment of sarcophytonolides E–G and L and C5–11 fragment of sarcophytonolide L

An efficient stereoselective synthesis of C4–12 fragment of the cembranoids, sarcophytonolides E–G and L and C5–11 fragment of sarcophytonolide L is described. The C4–12 building block is efficiently assembled starting from chiral pool material (R)-carvone employing the Baeyer–Villiger oxidation, modified Knoevenagel condensation and asymmetric dihydroxylation as the key steps. The synthesis of C5–11 fragment is based on orthoester Johnson–Claisen rearrangement as the key step.