Isorenieratene

The synthetic principle of olefinating an a,co-bisfunctional synthon A, representing the later molecular centre of the carotenoid, with two reaction partners B, the future molecular ends, can easily be described by the equation A + 2B -> B—A—B. This method was used by Mayer et al.265> in the synthesis of rhodoxanthin 550, a ketonic carotenoid, which was isolated for the first time from the red berrys of the yew-tree Taxus baccata. The authors describe the conversion of two equivalents of the stable phosphorane 548 with one equivalent of the C12-dialdehyde 549 265) (Scheme 93). The analogous reaction of crocetindial 552 with substituted benzylidenephospho-ranes such as 551 gives carotenoids such as isorenieratene 553266,267) and related compounds 266> (Scheme 93). Condensation of the phosphoranes 554 and 555 with the Cjo-dialdehyde 539 yields carotenoids of the dihydro type 556 268) and such like 557 269), respectively (Scheme 93). 

The intermediate 4-(t-butylthio)-but-3-en-2-one has been used in a new synthesis of isorenieratene [0,0-carotene(69)]. Electroreduction of retinal (70) in the presence of diethyl malonate or diethyl ethylmalonate gave the pinacol 15,15 -dihydro-/S,/8- carotene-15,15 -diol (71)... 

The reagent has been used for synthesis of the natural carotenoid isorenieratene (2) (equation I). ... 

MQ. oxoMQ, Cyts b and c BChl a. BChl c, d or e Plasma membrane chlorosome Chlorobactene, isorenieratene, 7-carotenc... 

Koopmans M. P., Koester J., van Kaam-Peters H. M. E., Kenig F., Schouten S., Hartgers W. A., de Leeuw J. W., and Sinninghe Damste J. S. (1996) Diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia. Geochim. Cosmochim. Acta 60, 4467-4496. 

G. (1999) Functional analysis of genes from Streptomyces griseus involved in the synthesis of isorenieratene, a carotenoid with aromatic end groups, revealed a novel type of carotenoid desaturase. Biochim. Biophys. Acta 1439, 57-64. 

Putschew A., Schaeffer P., Schaeffer-Reiss C., and Maxwell J. R. (1998) Carbon isotope characteristic of the diaromatic carotenoid, isorenieratene (intact and sulfide bound) and a novel isomer in sediments. Org. Geochem. 28, 1849—1856. 

The intermolecular McMurry reaction has proven a particularly valuable route to alkenic hydrocarbons. This is especially true for polyenes and sterically hindered kenes. For example, -carotene (37 equation 78) can be prepared in 85% yield by reductive dimerization of retinal. Isorenieratene (38 equation 78) is similarly synthesized in 96% yield, and the aldehyde (39 equation 79) has been ela-... 

Sinninghe DamsteJ.S., Schouten S., van Duin A.C.T. (2001) Isorenieratene derivatives in sediments possible controls on their distribution. Geochim. Cosmochim.Acta 65, 1557—71. 

Certain bacteria are able to rearrange the normal carbon skeleton to give aromatic carotenoids. Phenolic examples were isolated from Streptomyces mediolani. As well as the hydrocarbon isorenieratene (43), 3-hydroxy- (44), and 3,3 -dihydroxy-isorenieratene (45) were present and their structures confirmed by synthesis. In Thiothece gelatinosa the major carotenoid was okenone... 

The Rhodospirillaceae and Chromatiaceae have the spirilloxanthin or the okenone pathway depending on the genus or species. All of the Ectothiorhodospiraceae have the spirilloxanthin pathway. The isorenieratene, the y-and -carotene, and the diapocarotene pathways are found specifically in the Chlorobiaceae, Chloroflexaceae, and Heliobacteriaceae, respectively. Aerobic photosynthetic bacteria mostly have the spirilloxanthin pathway, further most of these species have unusual carotenoids including non-photosynthetic carotenoids, such as carotenoid sulfates and carotenoic acids, which have no photosynthetic functions. 

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