Synthesis of Carotenoids in the Gliding Bacteria Taxeobacter : (all‐ E ,2′ R )‐3‐deoxy‐2′‐hydroxyflexixanthin

The c 40 ‐carotenoid (all‐ E , 2′ R )‐deoxy‐2′‐hydroxyflexixanthin (=1′,2′‐dihydroxy‐3′,4′‐didehydro‐1′,2′‐dihydro‐β,ψ‐caroten‐4‐one;(2′ R )‐ 2 ) was synthesized according to a C 15 + C 10 + C 10 = C 40 strategy. The chiral centre was introduced into the C 10 ‐end group by the enantioselective Sharpless dihydroxylation. The four building blocks were coupled by applying four consecutive Witting reactions. By comparison of the CD spectra of the synthetic (2′ R )‐ 2 with those of 2 isolated from the gliding bacteria Taxeobacter , the configuration of natural 2 was determined as (2′ R ).