57793-67-6

Upstream product

• 25394-27-8 isocryptoxanthin 
• 13312-52-2 9-cis-β-carotene 
• 83601-92-7 7-cis-β-carotene 
• 432-68-8 echinenone 
• 7235-40-7 beta-carotene 

Relevant academic research and scientific papers

Nucleophilic reactions of charge delocalised carotenoid mono- and dications

In the present study insight was gained on the larger complexity of cationic mixtures of diaryl (φ,φcarotene, isorenieratene) and aliphatic (Φ,Φ-carotene, lycopene) carotenes, prepared by reaction with BF 3-etherate, compared with β,β-carotene. Chemical reactions of the mono- and dications prepared in situ from the allylic carotenols β,β-caroten-4-ol (isocryptoxanthin) and β,β-carotene-4,4'- diol (isozeaxanthin), and from isorenieratene and lycopene were investigated using selected O, N and S nucleophiles; water, methanol, azide and thioacetate. In total 22, including 18 new, neutral carotenoid products were isolated and identified by VIS, MS and NMR (in part) spectroscopy. Their structures were compatible with the structures of the cationic intermediates. The formal addition of hydride to the various dications, required to rationalise minor reaction products, is discussed in terms of more likely hydrogen radical or proton transfer in cationic reactions. Extensive E/Z isomerisation was observed for all quenching products. The potential use of carotenoid cations for the synthesis of 4,(4')-substituted β,β-carotenes and 7-oxabicycloheptane derivatives is discussed.

Simultaneous Electrochemical and Electron Paramagnetic Resonance Studies of Carotenoids: Effect of Electron Donating and Accepting Substituents

A series of substituted phenyl-7'-apocarotenoids with varying electron donating and accepting substituents was examined by cyclic voltammogram (CV) and simultaneous electrochemical electron paramagnetic resonance (SEEPR).Carotinoids substituted with electron donating groups are more easily oxidized than those with electron accepting substituents.Comproportionation constants for the dication and the neutral species were measured by SEEPR techniques and by simulation of the CVs.The ΔHpp of the SEEPR spectrum of the cation radicals varies from 13.2 to 15.6 G, and the g factors are 2.0027 +/- 0.0002.These EPR parameters suggest a polyene-?-cation radical structure.The CVs are calculated using DigiSim, a CV simulation program, and the proposed mechanism involves three electrode reactions and two homogeneous reactions.

Triplet-Sensitized and Thermal Isomerization of All-Trans, 7-Cis, 9-cis, 13-Cis, and 15-Cis Isomers of β-Carotene: Configurational dependence of the Quantum Yield of Isomerization via the T1 State

The products of triplet-sensitized photoisomerization (excitation at 337 nm of the sensitizer, anthracene) and thermal isomerization of β-carotene in n-hexane, starting from the all-trans, 7-cis, 9-cis, 13-cis, and 15-cis isomers, were analyzed by HPLC.Direct photoisomerization (excitation at 488 and 337 nm) was also examined for comparison.Three different isomerization patterns were found in both triplet-sensitized and thermal isomerization: pattern A, cis to trans isomerization around each cis bond; pattern B, trans to cis isomerization in the central part of the conjugated chain; and pattern C, cis to another cis isomerization.In the T1 state, the pattern A isomerization was predominant even for the peripheral-cis (7-cis and 9-cis) isomers and its efficiency was extremly high for the central-cis (13-cis and 15-cis) isomers.In the S0 state, the pattern B isomerization, instead, was predominant for the peripheral-cis isomers, and the pattern A isomerization was predominant only for the central-cis isomers.The quantum yields of triplet-sensitized isomerization (decrease of the starting isomer per triplet species generated) were determined to be as follows: all-trans, 0.04; 7-cis, 0.12; 9-cis, 0.15; 13-cis, 0.87; and 15-cis, 0.98.In direct photoisomerization, the quantum yield of isomerization at 488-nnm (337 nm) excitation was 4 (3) orders of magnitude lower than the above values, the relative values among the isomers being similar to the above.Further, the overall isomerization patterns of direct photoexcitation were similar to those of triplet-sensitized isomerization, supporting the idea that isomerization takes place via the T1 state even in the case of direct photoexcitation.Carbon-carbon ? bond orders of model polyenes in the T1 and S0 states were calculated by using the Pariser-Parr-Pople CI theorie; bond lengths were optimized by using a bond order-bond length relationship.Isomerization characteristics in the T1 and S0 states observed were discussed based on the results of the calculations.

Simultaneous Electrochemical and Electron Paramagnetic Resonance Studies of Carotenoid Cation Radicals and Dications

Comproportionation equilibrium constants have been determined from simultaneous electrochemical and EPR measurements for the carotenoid cation radicals (CAR.+) and dications (CAR2+) of β-carotene (I), β-apo-8'-carotenal (II), and canthaxanthin (III).K(I)com = 2.4x10-2, Kcom(II) = 1.8x10-2, Kcom(III) = 2.1x103.These indicated that, upon oxidation of III, 96percent CAR.+ would be formed while 99.7percent CAR2+ would be formed for I and II if the oxidation potential was 100 mV anodic of the first observed voltammetric wave.This explains the reason for the strong EPR spectrum observed for III and the weak EPR spectra observed for I and II.Rotating disk experiments confirm that oxidation of carotenoids occurs by an EE rather than by a ECE mechanism and are highly quasireversible systems.The second oxidation peak in the CV spectrum of II has been shown not to be due to a dication analogous to the CV of III but to a radical apparently from the oxidation of a decay product of the dication from II.