Total Synthesis of (R)-Dihydroactinidiolide and (R)-Actinidiolide Using Asymmetric Catalytic Hetero-Diels-Alder Methodology.

The total synthesis of the naturally occurring bicyclic lactones (R)-dihydroactinidiolide and (R)-actinidiolide is presented. The key step in the syntheses is the copper(II)-bisoxazoline-catalyzed hetero-Diels-Alder reaction of a cyclic diene with ethyl glyoxylate giving the hetero-Diels-Alder product in high yield and with very high regio-, diastereo-, and enantioselectivity. The total syntheses proceed via an intermediate, which also has the potential for a series of other natural products. The structure of the key intermediate is confirmed by X-ray analysis.