Stereocontrolled Synthesis of Highly Oxygenated Acyclic Systems via the Enolate Claisen Rearrangement of O-Protected Allylic Glycolates

Enolate Claisen rearrangement of E- and Z-allylic glycolates yields the syn- and anti-2-alkoxy-3-alkyl 4-enoates, respectively, in good yields (60-90%) and with high internal diastereoselectivity. Incorporation of the glycolate Claisen procedure into an iterative sequence consisting of Claisen rearrangement and homologation by addition of vinyl nucleophiles results in the efficient, stereocontrolled generation of remotely functionalized, highly oxygenated acyclic systems. This strategy is demonstrated in stereoselective syntheses of pine sawfly pheromone 42 and tocopherol side-chain intermediate 30.