New Methods for the Synthesis of Oxygenated Carotenoids

Six keto carotenoids (4, 5, 6, 11, 12, and 22) were synthesized from intermediates which were prepared from the condensation products of mesityl oxide and acetoacetic ester. Compounds 4 and 22 can serve as precursors for zeaxanthin, while 5 can be used as an intermediate for xanthophyll. Echinenone and canthaxanthin were prepared by a new approach from vitamin A. Two new types of keto carotenoids with the keto functions incorporated into the unsaturated chain were prepared.