Allenic carotenoids isolation

Acetylenic and Allenic Carotenoids.—The apo-acetylenic carotenoid hopkinsi-oxanthin (40), identified by McBeth" in the Nudibranch Hopkinsia rosacea, was also isolated from its food, the Bryozoan Eurystomella bilabiata. Other Nudi-branchs contain the related carotenoid triophaxanthin (41). ... 

By using the same method, Katsumura and coworkers isolated the enantiomerically pure allene segment in 97a and 97b (Scheme 26)". The one-step singlet oxygen ene reaction pathway, to produce the allene moiety from the twisted l,3,3-trimethylcyclohexenyl-2-vinyl derivatives, was considered as a possible biomimetic route towards the synthesis of carotenoids. 

Neoxanthin, a precursor of the plant hormone abscisic acid, is an allenic xantho-phyll recognized as the last product of carotenoid synthesis in green plants. A cDNA for neoxanthin synthase (NSY) was isolated from tomato cv. Philippino using a molecular approach based on the mechanistic and structural similarities of NSY to two other closely related carotenogenic enzymes, lycopene cyclase (LCY) and capsanthin-capsorubin synthase (CCS) (Bouvier et al., 2000). 

Bicyclic Carotenoids. Re-investigation of the carotenoids of Anacystis nidulans has confirmed the presence of /3,)8-carotene-2,3,3 -triol (6), and the previously unknown )8,j8-carotene -2,3,2, 3 -tetrol (7) was also isolated. These compounds are considered to be identical with caloxanthin and nostoxanthin, for which allenic structures have previously been suggested. The main carotenoid of Coccolithus... 

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