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 C-45- and C-50-carotenoids (all-E,2S,2'S)-bacterioruberin (1), (all-E,2S,2'S)-monoanhydrobacterioruberin (2), (all-E,2S,2'S)-bisanhydrobactarioruberin (3), (all-E,2R,2'R)-3,4,3',4'-tetrahydrobisanhydrobacterioruberin (5), and (all-E,S)-2-isopentenyl-3,4-dehydrorhododopin (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.