Efficient syntheses of C20-carotene and crocetin or descrocetin esters from fumaraldehyde bis-dimethylacetal are described. The key steps of these syntheses are the reactions of fumaraldehyde and (2E, 4E, 6E)-octa-2, 4, 6-trienedial bis-dimethylacetals with alkyl vinyl or alkyl propenyl ethers promoted by the acidic ionic liquid,[emim][HSO4].
