A chain extension method for apocarotenoids; lycopene and lycophyll syntheses

Choi, Jeongae; Oh, Eun-Taek; Koo, Sangho

doi:10.1016/j.abb.2014.12.028

Cited by 5 publications

(9 citation statements)

References 38 publications

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“…Allylic phenyl sulfone 7 now became the key building block, which would couple with dialdehyde 3 . Diacetal 6 was also planned to be synthesized by the “one‐pot” Julia–Kocienski olefination between allylic benzothiazolyl (BT) sulfone 8 and 2,7‐diphenyl‐2,4,6‐octatrienedial ( 9 ) . These newly devised building blocks 7 , 8 , and 9 were all planned to be synthesized from the common intermediate, 4‐chloro‐2‐phenylbut‐2‐enal ( 10 ), which was proposed to be prepared by CuCl 2 ‐mediated oxidative opening reaction of vinyl epoxide 11 with phenyl substitution.…”

Section: Resultsmentioning

confidence: 99%

Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

et al. 2020

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The synthetic method of tetraphenyl‐substituted all‐E‐carotenes 1 with improved properties of antioxidant and molecular electronic conductance was developed through the formation of tetraphenyl‐substituted all‐E‐apocarotenedial 4. The synthesis highlighted the preparation of novel subunits containing phenyl substituent(s) with E‐configuration starting from the key (E)‐4‐chloro‐2‐phenylbut‐2‐enal (10), utilizing conjugation effect with formyl group or easy recrystallization of sulfone compounds. Sulfone‐mediated coupling methods of Julia and modified Julia–Kocienski olefinations utilizing the subunits were demonstrated to produce tetraphenyl‐substituted apocarotenedials 4. The major all‐E‐forms (73–85 % selectivity) were easily purified by SiO2 chromatography and trituration with Et2O due to the presence of the polar formyl groups. The olefination of all‐E‐apocarotenedials 4 and Wittig salt 5 provided all‐E‐9,9',13,13'‐tetraphenylcarotenes 1.

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Section: Resultsmentioning

confidence: 99%

Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

et al. 2020

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“…2-(4-Chlorobut-2-en-2-yl)-5,5-dimethyl-1,3-dioxane ( 4 ) [ 32 ]: Following the previously published procedure, ( E )-4-chloro-2-methylbut-2-enal (30.1 g, 0.25 mol) was prepared in an 86% overall yield from isoprene (50 mL, 0.50 mol) and N -bromosuccinimide (70.0 g, 0.39 mol) through 1-bromo-2-methylbut-3-en-2-ol and isoprene monoxide in 3 steps [ 32 ]. The protection of aldehyde (10.0 g, 84 mmol) was performed by the reaction with neopentyl glycol (9.7 g, 92 mmol) and p -TsOH (800 mg, 4.2 mmol) in toluene under reflux with a Dean–Stark trap for 3 h to give 4 (8.63 g, 39 mmol) in 66% yield as a 10:1 mixture of E / Z -isomers with light-yellow oil.…”

Section: Methodsmentioning

confidence: 99%

“…(2 E ,4 E ,6 E ,8 E ,10 E ,12 E ,14 E )-2,6,11,15-Tetramethylhexadeca-2,4,6,8,10,12,14-heptaenedial ( 2 ) [ 32 , 36 ]: To a stirred solution of phosphonate 5 (24.63 g, 80.39 mmol) in a 1:1 mixture of THF/ t -BuOH (80 mL), we slowly added t -BuOK (12.30 g, 0.110 mol) at 0 °C. While stirring for 5 min at 25 °C, a solution of aldehyde 1 (6.00 g, 36.54 mmol) in THF (20 mL) was added to the above mixture.…”

Section: Methodsmentioning

confidence: 99%

Oxo-Carotenoids as Efficient Superoxide Radical Scavengers

2022

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Oxo-carotenoids containing conjugated carbonyl groups in their chains were designed to be more efficient superoxide radical scavengers than natural carotenoids, β-carotene and canthaxanthin. A practical chain-extension method for polyene dials (e.g., crocetin dial) was also proposed based on Horner–Wadsworth–Emmons olefination. Double aldol condensation between polyene dials and acetophenones with ring substituents produced oxo-carotenoids with substituted benzene rings. The antioxidant activity of oxo-carotenoids was measured using DPPH (radical) and ABTS (cationic radical) scavenging assays and compared with the analysis with the superoxide (anionic radical) probe. An effective conjugation length by carbon–carbon double bonds is important to provide superior antioxidant activity for oxo-carotenoids, regardless of the type of radical probe used in the assay. Increasing electron density is favorable to strong antioxidant activity in DPPH, and the phenol group is favored in ABTS, whereas electron deficient oxo-carotenoids are very potent in the superoxide radical assay. All oxo-carotenoids exhibited 105~151% better superoxide radical scavenging activity compared to beta-carotene (100%), whereas 38~155% in DPPH and 16~96% in ABTS radical scavenging activities were observed.

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“…The organic synthesis of norbixin ethyl ester 2 was reported by the Wittig olefination of C 20 crocetin dialdehyde 4 with phosphorus ylide 3 (79% yield), derived from ethyl bromoacetate ( 5c ) (Figure ). However, preparation of the fully conjugated crocetin dialdehyde 4 was even more challenging, and the best yield so far was only 21–24% from furan . We demonstrated that C 20 dialdehyde 6 , which can be succinctly prepared by double allylic oxidation of the coupling product between geranyl sulfone and geranyl bromide (54% yield in five steps from geraniol), is an excellent substitute for the fully conjugated version 4 in the sulfone olefination protocol .…”

Section: Introductionmentioning

confidence: 99%

Bromoacetate Olefination Protocol for Norbixin and Julia–Kocienski Olefination for Its Ester Syntheses

et al. 2019

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A new olefination protocol utilizing ethyl bromoacetate was highlighted, in which magnesium enolate of the ester coupled with C 20 dialdehyde 6 , and double eliminations of the protected hydroxyl groups and bromine atoms of the coupling bromohydrin product, efficiently produced norbixin 1 after concomitant hydrolysis of the ester. A new (C 7 + C 10 + C 7 ) disconnection approach was demonstrated for the synthesis of norbixin ethyl ester 2 by the Julia–Kocienski olefination of novel C 7 benzothiazolyl-sulfone 11 and C 10 2,7-dimethyl-2,4,6-octatrienedial ( 12 ).

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A chain extension method for apocarotenoids; lycopene and lycophyll syntheses

Cited by 5 publications

References 38 publications

Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

Oxo-Carotenoids as Efficient Superoxide Radical Scavengers

Bromoacetate Olefination Protocol for Norbixin and Julia–Kocienski Olefination for Its Ester Syntheses

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