Carotenoids stereochemistry

Resonance Raman Spectroscopy and Carotenoid Stereochemistry Resonance Raman Spectroscopy of Excited States of Carotenoids Resonance Raman of Carotenoid Molecules In Vivo Light-Hanresting Proteins... 

Hubbard, R. and Wald, G. Pauling and Carotenoid Stereochemistry. In Structured Chemistry and Molecular Biology Rich A., Davidson N., Eds. W. H. Freeman San Francisco, 1968. 

Zinc acetylides, prepared in situ by the treatment of lithium acetylides with ZnCF, are widely used. The zinc acetylide 311, prepared in situ, reacts with (Z)-3-iodo-2-buten-l-ol (312) with nearly complete retention of stereochemistry to afford an important intermediate 313 for carotenoid synthesis[227]. 

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

WEEDON B c L and MOSS G (1995) Structure, stereochemistry and nomenclature , in Britton G, Pfander H and Liaaen-Jensen S, Carotenoids, vol. la, Basel, Birkhauser 27—44. 

Scotter, M.J., Characterization of the coloured thermal degradation products of bixin from annatto and a revised mechanism for their formation, Food Chem., 53, 111, 1995. Zechmeister, L., Cis-trans isomerization and stereochemistry of carotenoids and diphenylpolyenes, Chem. Rev., 34, 267, 1944. 

Robert, B. 1999. The electronic structure, stereochemistry and resonance Raman spectroscopy of carotenoids. In The photochemistry of carotenoids, eds. H.A. Frank, A.J. Young, G. Britton, and R.J. Cogdell, pp. 189-201. Dordrecht, the Netherlands Kluwer Academic Publishers. 

Zechmeister, L. 1944. Cis-trans isomerization and stereochemistry of carotenoids and diphenylpolyenes. Chem. Rev. 34 267-344. 

Bone, RA, Landrum, JT, Hime, GW, Cains, A, and Zamor, J, 1993. Stereochemistry of the human macular carotenoids. Invest Ophthalmol Vis Sci 34, 2033-2040. 

Biosynthesis and Metabolism.—Pathways and Reactions. Two reviews of carotenoid biosynthesis discuss, respectively, the early steps and the later reactions." The former paper deals with the mechanism of formation of phytoene and the series of desaturation reactions by which phytoene is converted into lycopene, and also describes in detail the biosynthesis of bacterial C30 carotenoids. The second paper" presents details of the mechanism and stereochemistry of cyclization and the other reactions that involve the carotenoid C-1 —C-2 double bond and the later modifications, especially the introduction of oxygen functions. 

The system of conjugated double bonds responsible for carotenoid colors also helps to impart specific shapes to these largely hydrophobic molecules and ensures that they occupy the appropriate niches in the macromolecular complexes with which they associate. Information on stereochemistry is provided in a short review by Britton.138... 

Stereochemistry.—Carotenoids. The absolute configuration of astaxanthin [3,3 -dihydroxy-/3,/3-carotene-4,4 -dione (33)] has been determined21 as (3S,3 S) by c.d. correlation of the tetrol (34) obtained by LiAlH4 reduction of astaxanthin diester (from lobster) with (37 ,3. R)-zeaxanthin (7). The astaxanthin thus cannot exist in vivo as a bis-dianion, e.g. (35), bound to protein, since chirality could not be introduced by solvent extraction. Actinioerythrin [3,3 -dihydroxy-2,2 -dinor-/3,/3-carotene-4,4 -dione 3,3 -diacylate (36)] is also optically active, with the two end-groups having the same (undetermined) chirality. The (3S,3 S) chirality has also been demonstrated for astaxanthin from the spider mite Schizonobia sycophanta.22... 

New Structures and Stereochemistry.—New Carotenoid Structures. A mutant strain of Rhizobium lupini contains a new nor-carotenoid, 2, 3 -trans-dihydroxy-2-nor-/3,/3-carotene-3,4-dione (1)." The wild-type R. lupini, when cultured in the presence of the cyclization inhibitors nicotine or CPTA, produced three new monocyclic carotenoids, 2,3-h-ans-dihydroxy-/3,-caroten-4-one (2), 3-hydroxy-/3,(/ -caroten-4-one (3), and p,tf/-carotene-2,3-trans-dio (4)," which were characterized by m.s. and n.m.r. The light absorption and mass spectra of a carotenoid from Rhodopseudomonas capsulata allowed its identification" as demethylspheroidenone [l-hydroxy-3,4-didehydro-l,2,7, 8 -tetrahydro- /f,(/f-caroten-2-one (5)]. 

Stereochemistry. "C-Labelling has been used for the first time in the carotenoid field to study the stereochemical course of the cyclization reaction."" When [2- "C]mevalonate was incubated with a Flavobacterium species, grown in the presence of the cyclization inhibitor nicotine, "C n.m.r. spectroscopy showed that... 

Full details have been published of the C and incorporation studies on the stereochemistry of formation of the C50 carotenoid decaprenoxan-thin [(2i ,6i ,2 i ,6 / )-2,2 -bis-(4-hydroxy-3-methylbut-2-enyl)-e,e-carotene (195)] (Scheme 4). Both the stereochemistry of the initial electrophilic attack at C-2 and that of the hydrogen loss from C-4 are opposite to those in the C40 series. ... 

Degraded Carotenoids Physical Methods Separation and Assay N.M.R. Spectroscopy Mass Spectrometry Chiroptical Methods Electronic Absorption Spectroscopy Infrared and Resonance Raman Spectroscopy Other Spectroscopic Techniques Miscellaneous Physical Chemistry Photoreceptor Pigments Biosynthesis and Metabolism Stereochemistry Enzyme Systems Inhibition and Regulation... 

The acidic carotenoid, torularhodin (113), was studied " using [1- C]-and [2- " C,2- H2]-mevalonate. Torularhodin retained nine-elevenths of the tritium of torulene (112) and the car boxy-group contained Hence the acid function was derived from C-2 of mevalonate and has retained its trans stereochemistry. 

New Structures and Stereochemistry.—Carotenoids. Of the few new carotenoid structures that have been reported, all but one are from marine animals. Lac-tucaxanthin, a major xanthophyll in chloroplasts of lettuce (Lactuca sativa) and... 

The absolute stereochemistry of carotenoids is largely based on the correlation of their o.r.d. curves. So far, all samples of any one carotenoid from a wide range of sources have proved to have the same chirality. Furthermore, the... 

Bicyclic Carotenoids.— The absolute stereochemistry of a-carotene (4) has been determined by Eugster and co-workers by relating a-ionone to derivatives of manool and ambrein. Natural (-t- )-a-carotene (4) was synthesised from (-I- )-a-ionone and related by o.r.d. to several other carotenoids with this chiral centre, " ... 

Yokoyama et al. have isolated a series of seco-carotenoids from Rutaceae. Semi-a-carotenone (3) was shown by c.d. studies to have the same absolute stereochemistry as a-carotene. The other examples isolated were semi-j -carotenone (33), jS-carotenone (34) and triphasiaxanthin (35). ... 

Several bacterial species produce C45 and C50 carotenoids which contain one or two extra isoprenyl groups. Although their biosynthesis has not been studied, it is probable that instead of proton-initiated cyclisation at the polyene termini, attack by dimethyl allyl pyrophosphate results in substances such as the symmetrical decaprenoxanthin (P439) (68). The stereochemistry of the isolated acyclic double bond was shown to be trans by the n.m.r. spectrum of the corresponding aldehyde. Other carotenoids present in Flavobacterium... 

---