Allenic carotenoids

The allenic carotenoid fucoxanthin (Fig. 22-5), which is absent in higher plants, predominates in brown algae, where it occurs in light-harvesting complexes along with Chi a and Chi c.306 307... 

Fig. 10. Fluorescence emission and excitation (or absorption) spectra in CSj of p-carotene (A) and fucoxanthin (B). See text for details. Figure source (A) Glllbro and Cogdell (1989) Carotenoid fluorescence. Chem Phys Lett. 158 313. (B) Katoh, Nagashima, and Mimuro (1991) Fluorescence properties of the allenic carotenoid fucoxanthin impiication for energy transfer in photosynthetic pigment systems. Photosynthesis Res 27 223.

Katoh T, Nagashima U and Mimuro M (1991) Fluorescence properties ofthe allenic carotenoid fucoxanthin Implication for energy transfer in photosyntheticpigmentsy stems. Photosyn... 

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). ... 

Miyashita, K. and Hosokawa, M. (2009). Anti-obesity Effect of Allenic Carotenoid, Fucoxanthin. Nutrigenomics and Proteomics in Health and Disease Impact of Food Factors-Gene Interactions. Wiley-Blackwell Publisher, Ames, lA, pp. 145-160. 

Miyashita, K., Nishikawa, S., Beppu, F., Tsukui, T., Abe, M., and Hosokawa, M. (2011). The allenic carotenoid fucoxanthin, a novel marine nutraceutical from brown seaweeds. /. Sci. Food Agric. 91,1166-1174. 

The acetylenic diphosphonate 73 is easily obtained by reaction of dibromide 4 with two equivalents of triethylphosphite under Arbusov conditions [5]. The specific advantages of the diphosphonate 13 have been demonstrated in the field of the synthesis of allenic carotenoids [10]. 

A representative allenic carotenoid is mimulaxanthin (202), a symmetrical structure with allenic end groups. For the total synthesis of mimulaxanthin (202), the most suitable candidate starting compound is the grasshopper ketone (11a) which has been synthesized by several groups [7-13]. 

No allenic carotenoids have yet been prepared by total synthesis, but the allenic ketones (55) and (56) have been synthesized as racemates (92). In a recent preliminary note the total synthesis of optically inactive 2,6-trans-2, 6 -trans decaprenoxanthin has been outlined. Natural deca-prenoxanthin (8) has 2/ ,6R,2 R,6 7 -configuration (11) with the 2,6(2, 6 )-substituents in a cis relationship. 

Johansen, J. E., and S. Liaaen-Jensen Chemical reactions of allenic carotenoids. Acta Chem. Scand. B 28,949 (1974). 

Allenic carotenoids are very limited in algae (Table 106.2). From their chemical structures, all-trani-neoxanthin 18 might be converted to fucoxanthin 75, dinoxanthin 74, peridinin 72, vaucheriaxanthin 69, and diadinoxanthin 67, but the pathways and enzymes remain unknown (Fig. 106.3) [6]. 

Although allenic carotenoids, for example, fucoxanthin (Isler, 1977) which occurs in many brown and freshwater algae, have long been known, and fucoxanthin itself is the most commonly encountered carotenoid, specific syntheses of retinoids with allenic structural elements have only been reported very recently. 

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