C45‐ and C50‐Carotehoids. Part 8. Synthesis of (all‐E,2S,2′S)‐bacterioruberin, (all‐E,2S,2′S)‐monoanhydrobacterioruberin, (all‐E,2S,2′S)‐bisanhydrobacterioruberin, (all‐ E,2R,2′R)‐3,4,3′,4′‐tetrahydrobisanhydro‐ bacterioruberin, and (all‐E,S)‐2‐isopentenyl‐3,4‐dehydrorhodopin

Starting from (R)‐3‐hydroxybutyric acid ((R)‐10) the C45‐ and C50‐carotenoids (all‐E,2S,2′S)‐bacterioruberm (1), (all‐E,2S,2′S)‐monoanhydrobacterioruberin (2), (all‐E,2S,2′S)‐bisanhydrobacterioruberin (3), (all‐E,2R,2′R)‐3,4,3′,4′‐tetrahydrobisanhydrobacterioruberin (5), and (all‐E,S)‐2‐isopentenyl‐3,4‐dehydrorhodopin (6) were synthesized. By comparison of the chiroptical data of the natural and the synthetic compounds, the (2S)‐ and (2′S)‐configuration of the natural products 1–3 and 6 was established.