C45- and C50-Carotenoids Part7 Total synthesis of (all-E,2R,6R,2′R,6′R)- and (all-E,2R,6S,2′R,6′S)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-γ,γ-carotene (sarcinaxanthin) |
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Authors: | Marc Lanz Birgit Bartels Hanspeter Pfander |
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Abstract: | The synthesis of sarcinaxanthin ((2R,6R,2′R,6′R)- 1 ), a symmetrical C50-carotenoid with two γ-end groups, isolated from Sarcina lutea and from Cellulomonas biazotea as major pigment, was based on the strategy C20 + C10 + C20 = C50 using camphoric acid as starting material for the C20-end group 3. The key step of the synthesis is a ring enlargement of the cyclopentane derivative 10 with 2,4,4,6-tetrabromocyclohexa-2,5-dien-1-one (TBCO) to give the cyclohexane derivative 11 (Scheme 1). The spectroscopic data of the synthetic compound are in full agreement with the data of the isolated product and give the final proof for the (2R,6R,2′R,6′R) chirality of natural sarcinaxanthin. |
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