C45 und C50‐Carotinoide. 6. Mitteilung. Synthese eines optisch aktiven cyclischen C20‐Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐ϵ, ϵ‐carotin)

C45‐ and C50‐Carotenoids: Synthesis of an Optically Active Cyclic C20‐Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐ϵ, ϵ‐carotene) The synthesis of the optically active cyclic C20‐building block (R, R)‐15 and of the optically active C50‐carotenoid (2R, 6R, 2′R, 6′R)‐decaprenoxanthin (1) starting from (‐)‐β‐pinene ((S)‐2) is reported.