Total synthesis of cucurbitaxanthin A, cycloviolaxanthin and capsanthin 3,6-epoxide by applying a regioselective ring opening of tetrasubstituted epoxides.

The synthesis of 3,6-epoxy carotenoids cucurbitaxanthin A 1, cycloviolaxanthin 2 and capsanthin 3,6-epoxide 3, was accomplished via the C(15)-3,6-epoxides 20e and 20f, prepared by the regioselective ring opening of the 3-hydroxy-5,6-epoxides 10e and 10f.