Synthesis of Bixin and Three Minor Carotenoids from Annatto (Bixa orellana)

The three apocarotenoids methyl (9Z)-8′-oxo-6,8′-diapocaroten-6-oate ( 2 ), methyl (9Z)-10′-oxo-6,10′-diapocaroten-6-oate ( 4 ), and methyl (9Z)-14′-oxo-6,14′-diapocaroten-6-oate ( 5 ), recently isolated from annatto, were synthesized. The key step of all three syntheses was the Wittig reaction of the (Z)-terminus 6 with the phosphonium salts 15 , 18 , and 24 , carrying the polyene chain. Bixin ( 1 ) was synthesized from 2 in a Horner-Emmons reaction.