4,4 -diapocarotene

Apocarotenoids. A new C30 diapocarotenoid has been isolated from the bacterium Pseudomonas rhodos and identified by m.s. and H n.m.r. as 4,4 -diapocarotene-4,4 -dioic acid (13). It occurs as mono- and di-glucosyl esters, and with the glucose residues esterified with fatty acids. °... 

The Heliobacteriaceae only have Cj acyclic carotenes, 4,4"-diapocarotenes, instead of the usual carotenoids (Fig. 11 Takaichi et al., 1997b). 4,4"-Diaponeurosporene is the major carotene, and diapophytoene, diapophytofluene, diapo-C-carotene and diapolycopene are also found as minor components. Two genes encoding enzymes in the early steps of diapocarotene biosynthesis have been... 

All the Heliobacteriaceae only have Cj carotenes, 4,4"-diapocarotenes (Tables 1 and 8). 4,4"-Diapo-neurosporene is the dominant pigment and trace amounts of C30 diapocarotenes are also present. Eurthermore, the esterifying alcohol of BChl g is famesol (C,j) instead of the usual phytol (Cj ) of BChls a and b. Both phytoene and phytol are produced from geranylgeraniol (C20). It is thus likely that the Heliobacteriaceae are unable to produce geranylgeraniol from famesol (Eig. 11). 

See Table 1 Acid carotenoic acid C3Q 4,4 -diapocarotene derivatives Erb-type carotenoid sulfate(s), )3-carotene and its hydroxyl derivatives, y-carotene and its cross-conjugated aldehyde, and spirilloxanthin type. 

Examples of carotenoid carboxylic acids are also found within the so-called diapocarotenoids (C30) [7], exemplified by 4 -p-D-glucopyranosyl 4-hydrogen-7, 8 -dihydro-4,4 -diapocarotene-4,4 -dioate (34) [5],... 

A similar system, but with a more hindered porphyrin (tetramesitylporphyrin = tetraphenylporphyrin bearing three methyl substituents in ortho and para positions on each phenyl group), was tested for P-carotene oxidation by molecular oxygen. This system was chosen to slow the oxidation process and thus make it possible to identify possible intermediates by HPLC-DAD-MS analysis. The system yielded the same product families as with lycopene, i.e., (Z)-isomers, epoxides, and P-apo-carotenals, together with new products tentatively attributed to diapocarotene-dials and 5,6- and/or 5,8-epoxides of P-apo-carotenals. The oxidation mechanism appeared more complex in this set-up. 

Gao, G., A. S. Jeevarajan et al. (1996). Cyclic voltammetry and spectroelectrochemical studies of cation radical and dication adsorption behavior for 7,7 -diphenyl-7,7 -diapocarotene. J. Electroanal. Chem. 411 51-56. 

Gao, G., Y. Wurm et al. (1997). Electrochemical quartz crystal microbalance, voltammetry, spectroelectrochemical, and microscopic studies of adsorption behavior for (7E,7 Z)-diphenyl-7,7 -diapocarotene electrochemical oxidation product. J. Phys. Chem. B 101 2038-2045. 

Linear Dichroism. A linear dichroism study of the orientation of j8-carotene molecules in lamellar liquid-crystalline lipid systems has been reported/ Linear dichroic spectra of the cross-conjugated carotenals renierapurpurin-20-al (169), 20-(2,3,4-trimethylbenzal)renierapurpurin (170), and 8, 8 -diapocarotene-8,20,8 -trial (171) have been recorded/ The results support the assignment of the 13 -cis configuration to (169) and (170). 

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. 

Condensation of 15,15 -didehydro-8 -apo-p-caroten-8 -al (52) and of 8,8 -diapocarotene-8,8 -dial (54) with butylamine in the presence of triisobutyl borate gives the Schiff bases 53 and 55, respectively. These react with the boron oxide complex of acetylacetone to give the polyene P-diketones 56 and 57. 

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