Synthesen in der Carotinoid‐Reihe. 3. Mitteilung. Die Synthese von 3,4; 3′,4′‐Bisdehydro‐β‐carotin und 3,4‐Monodehydro‐β‐carotin

Abstract 3,4;3′,4′‐Bisdehydro‐β‐carotene and 3,4‐monodehydro‐β‐carotene are synthesized by building up the C 40 skeleton following the scheme C 19 + C 2 + C 19 = C 40 . The synthesis of the symmetrical 3,4;3′,4′‐bisdehydro‐β‐carotene is based on the use of two units of dehydro‐β‐C 19 ‐aldehyde. The asymmetrical 3,4‐monodehydro‐β‐carotene is formed from one unit each of dehydro‐β‐C 19 ‐aldehyde and β‐C 19 ‐aldehyde. 3,4;3′,4′‐Bisdehydro‐β‐carotene forms brighter red solutions than 3,4‐monodehydro‐β‐carotene. In the growth test the former showed 38% and the latter 75% of the activity of β‐carotene.