Efficient syntheses of C20-carotene and crocetin (descrocetin) esters promoted by an acidic ionic liquid

Abstract Efficient syntheses of C 20 -carotene and crocetin or descrocetin esters from fumaraldehyde bis-dimethylacetal are described. The key steps of these syntheses are the reactions of fumaraldehyde and (2 E ,4 E ,6 E )-octa-2,4,6-trienedial bis-dimethylacetals with alkyl vinyl or alkyl propenyl ethers promoted by the acidic ionic liquid, [emim][HSO 4 ].