28874-44-4Relevant academic research and scientific papers
Olefin metathesis in carotenoid synthesis
Kajikawa, Takayuki,Iguchi, Naoko,Katsumura, Shigeo
supporting information; experimental part, p. 4586 - 4589 (2009/12/08)
Olefin metathesis is a powerful and widely applicable synthetic method for carbon-carbon double bond formation. However, its application to the synthesis of conjugating polyene chains has been very limited because of possible undesired side reactions. We attempted to apply this method to the synthesis of symmetrical carotenoids. In this paper, the syntheses of violaxanthin and mimulaxanthin are described using the olefin metathesis protocol.
Total synthesis of cucurbitaxanthin A, cycloviolaxanthin and capsanthin 3,6-epoxide by applying a regioselective ring opening of tetrasubstituted epoxides
Yamano, Yumiko,Ito, Masayoshi,Wada, Akimori
supporting information; experimental part, p. 3421 - 3427 (2009/02/05)
The synthesis of 3,6-epoxy carotenoids cucurbitaxanthin A 1, cycloviolaxanthin 2 and capsanthin 3,6-epoxide 3, was accomplished via the C15-3,6-epoxides 20e and 20f, prepared by the regioselective ring opening of the 3-hydroxy-5,6-epoxides 10e
(6R,9'Z)-Neoxanthin: Synthesis, physical properties, spectra, and calculations of its conformation in solution
Baumeler,Zerbe,Kunz,Eugster
, p. 909 - 930 (2007/10/02)
The synthesis of pure and crystalline (9'Z)-neoxanthin (6) is described. MnO2 Oxidation of (9Z)-C15-alcohol 7 at room temperature produces a mixture 8/9 of (9Z)- and (9E)-aldehydes. Predominant formation of the required (9Z)-aldehyde 8 is achieved by performing the oxidation at -10°. Condensation of 8 with the mono-Li salt of the symmetrical C10-diphosphonate 10 gave the (9Z)-C25-monophosphonate 11. The Wittig-Horner condensation of 10 with the allenic C15-aldehyde 1b, under selected conditions allows the preparation of pure and crystalline (9'Z)-15,15'-didehydroneoxanthin (12) and, after subsequent semireduction, of crystalline (15Z,9'Z)-neoxanthin (13). Thermal isomerisation of a AcOEt solution of 13 at 95° yields preferentially (9'Z)-neoxanthin (6). Our crystalline sample shows the highest ε-values in the UV/VIS spectra ever recorded. The CD spectra display a pronounced similarity with those of corresponding violaxanthin isomers. In contrast to the (all-E)-isomer 5, (9'Z)-neoxanthin undergoes very little isomerisation when heated to its melting point. For comparison purposes, a crystalline probe of 6 is also isolated from lawn mowings. Extensive 1H- and 13C-NMR investigations at 600 MHz of a (D6)benzene solution using 2D-experiments such as COSY, TOCSY, ROESY, HMBC, and HMQC techniques permit the unambiguous assignment of all signals. Force-field calculations of a model system of 6 indicate the presence of several interconverting conformers of the violaxanthin end group, 66% of which possess a pseudoequatorial and 34% a pseudoaxial OH-C(3'). The torsion angle (ω1) around the C(6')-C(7') bond, known to be of prime importance for the shape of the CD spectra, varies with values of 87° for 55% and 263° for 45% of the molecules. Therefore, the molecules clearly display a preference for the 'syn'-position of the C(7') = C(8') bond and the epoxy group. Unexpectedly, the double bonds of C(7') = C(8') and C(9') = C(10') are not coplanar. The deviation amounts to ± 20°, both in the 'syn'- and the 'anti'-conformation.
CAROTENOID METABOLISM AND THE BIOSYNTHESIS OF ABSCISIC ACID
Parry, Andrew D.,Horgan, Roger
, p. 815 - 821 (2007/10/02)
The conversion of all-trans-violaxanthin to 9'-cis-neoxanthin was shown to occur in fluridone-treated etiolated Lycopersicon and Phaseolus seedlings, following exposure to light.The results of deuterium oxide labelling experiments supported this precursor/product relationship, and provided further evidence for the origin of abscisic acid.Several apo-carotenoids, putative by-products of abscisic acid biosynthesis, were synthesised by chemical oxidation but were not detected in plant extracts.In vitro, lipoxygenase cleaved neoxanthin and violaxanthin down to small (/=C13) fragments.It may be that in vivo any apo-carotenoids formed by the specific cleavage of 9'-cis-neoxanthin, during abscisic acid biosynthesis, are rapidly metabolized by lipoxygenase or similar enzymes.
Syntheses of Enantiomerically Pure Violaxanthins and Related Compounds
Acemoglu, Murat,Uebelhart, Peter,Rey, Max,Eugster, Conrad Hans
, p. 931 - 956 (2007/10/02)
The epoxides 16 and ent-16, prepared by Sharpless-Katsuki oxidation of 15 in excellent yield and very high enantiomeric purity, were used as synthons for the preparation of (+)-(S)-didehydrovomifoliol (45), (+)-(6S,7E,9E)-abscisic ester 46, (+)-(6S,7E,9Z)-abscisic ester 47, (-)-(3S,7E,9E)-xanthoxin (49), (-)-(3R,7E,9E)-xanthoxin (50), (3S,5R,6S,3'S,5'R,6'S,all-E)-violaxanthin (1), (3R,5R,6S,3'R,5'R,6'S,all-E)-violaxanthin (55) and their (9Z) (see 53, 57), (13Z) (see 54, 58), and (15Z) (see 60) isomers.The novel violadione (61) was prepared from 1 by oxidation with DMSO/Ac2O.By base treatment, 61 was converted into violadienedione (62), a potential precursor of carotenoids with phenolic end groups.
210. Synthesis of Enantiomerically Pure Apoviolaxanthinoic Acids, Apoviolaxanthinols, and Apoviolaxanthinals (Including Persicaxanthin, Sinensiaxanthin, and β-Citraurin Epoxide
Uebelhart, Peter,Eugster, Conrad Hans
, p. 1983 - 1998 (2007/10/02)
Starting from (1'S,2'R,4'S,2E,4E)-5-(1',2'-epoxy-4'-hydroxy-2',6',6'-trimethylcyclohexyl)-3-methyl-2,4-pentadienal (3), a recently described synthon , a full range of C20-, C25-, C27-, and C30-polyenic acids, alcohols, and aldehydes and their (8R)- and (8S)-diastereomeric furanoid rearrangement products was prepared.The synthetic C25-alcohols proved to be identical with persicaxanthin (= 12'-apoviolaxanthin-12'-ol) and persicachromes (= 12'-apoauroxanthin-12'-ols) and the C27-alcohols analogously with sinensiaxanthin and sinensiachromes.A correlation between the sign of the Cotton effects in the CD spectra of 5,6- and 5,8-epoxides and their configuration at C(6) and C(8), respectively, was established.
