- Z -isomerization of retinoids through combination of monochromatic photoisomerization and metal catalysis
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Catalytic Z-isomerization of retinoids to their thermodynamically less stable Z-isomer remains a challenge. In this report, we present a photochemical approach for the catalytic Z-isomerization of retinoids using monochromatic wavelength UV irradiation treatment. We have developed a straightforward approach for the synthesis of Z-retinoids in high yield, overcoming common obstacles normally associated with their synthesis. Calculations based on density functional theory (DFT) have allowed us to correlate the experimentally observed Z-isomer distribution of retinoids with the energies of chemically important intermediates, which include ground- and excited-state potential energy surfaces. We also demonstrate the application of the current method by synthesizing gram-scale quantities of 9-cis-retinyl acetate 9Z-a. Operational simplicity and gram-scale ability make this chemistry a very practical solution to the problem of Z-isomer retinoid synthesis.
- Kahremany, Shirin,Sander, Christopher Lane,Tochtrop, Gregory P.,Kubas, Adam,Palczewski, Krzysztof
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supporting information
p. 8125 - 8139
(2019/09/19)
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- Catalytic synthesis of 9-cis-retinoids: Mechanistic insights
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The regioselective Z-isomerization of thermodynamically stable all-trans retinoids remains challenging, and ultimately limits the availability of much needed therapeutics for the treatment of human diseases. We present here a novel, straightforward approach for the catalytic Z-isomerization of retinoids using conventional heat treatment or microwave irradiation. A screen of 20 transition metal-based catalysts identified an optimal approach for the regioselective production of Z-retinoids. The most effective catalytic system was comprised of a palladium complex with labile ligands. Several mechanistic studies, including isotopic H/D exchange and state-of-the-art quantum chemical calculations using coupled cluster methods indicate that the isomerization is initiated by catalyst dimerization followed by the formation of a cyclic, six-membered chloropalladate catalyst-substrate adduct, which eventually opens to produce the desired Z-isomer. The synthetic development described here, combined with thorough mechanistic analysis of the underlying chemistry, highlights the use of readily available transition metal-based catalysts in straightforward formats for gram-scale drug synthesis.
- Kahremany, Shirin,Kubas, Adam,Tochtrop, Gregory P.,Palczewski, Krzysztof
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supporting information
p. 10581 - 10595
(2019/07/22)
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- METHOD FOR SYNTHESIS OF 9-CIS-BETA-CAROTENE AND FORMULATIONS THEREOF
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The present invention relates to a method for total chemical synthesis of 9-cis-β-carotene (9CBC), and further provides stable formulations thereof.
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- Substrate specificity and subcellular localization of the aldehyde-Alcohol redox-Coupling reaction in carp cones
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Our previous study suggested the presence of a novel conespecific redox reaction that generates 11-cis-retinal from 11-cisretinol in the carp retina. This reaction is unique in that 1) both 11-cis-retinol and all-trans-retinal were required to produce 11-cis-retinal; 2) together with 11-cis-retinal, all-trans-retinol was produced at a 1:1 ratio; and 3) the addition of enzyme cofactors such as NADP(H) was not necessary. This reaction is probably part of the reactions in a cone-specific retinoid cycle required for cone visual pigment regeneration with the use of 11-cis-retinol supplied from Mueller cells. In this study, using purified carp cone membrane preparations, we first confirmed that the reaction is a redox-coupling reaction between retinals and retinols. We further examined the substrate specificity, reaction mechanism, and subcellular localization of this reaction. Oxidation was specific for 11-cis-retinol and 9-cis-retinol. In contrast, reduction showed low specificity: many aldehydes, including all-trans-, 9-cis-, 11-cis-, and 13-cis-retinals and even benzaldehyde, supported the reaction. On the basis of kinetic studies of this reaction (aldehyde-alcohol redox-coupling reaction), we found that formation of a ternary complex of a retinol, an aldehyde, and a postulated enzyme seemed to be necessary, which suggested the presence of both the retinol- and aldehydebinding sites in this enzyme. A subcellular fractionation study showed that the activity is present almost exclusively in the cone inner segment. These results suggest the presence of an effective production mechanism of 11-cis-retinal in the cone inner segment to regenerate visual pigment.
- Sato, Shinya,Fukagawa, Takashi,Tachibanaki, Shuji,Yamano, Yumiko,Wada, Akimori,Kawamura, Satoru
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p. 36589 - 36597
(2014/01/17)
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- Cross-coupling reactions of organosilicon compounds in the stereocontrolled synthesis of retinoids
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This paper presents a full account of the use of Hiyama cross-coupling reactions in a highly convergent approach to retinoids in which the key step is construction of the central C10-C11 bond. Representatives of two families of oxygen-activated dienyl silanes (ethoxysilanes and silanols) and of all reported families of "safety-catch" silanols (siletanes, silyl hydrides, allyl-, benzyl-, aryl-, 2-pyridyl- and 2-thienylsilanes) were regio- and stereoselectively prepared and stereospecifically coupled to an appropriate electrophile by treatment with a palladium catalyst and a nucleophilic activator. Both all-trans and 11-cis-retinoids, and their chain-demethylated analogues, were obtained in good yields regardless of the geometry (E/Z) and of the steric congestion in each fragment. This comprehensive study conclusively establishes the Hiyama cross-coupling reaction, with its mild reaction conditions and stable, easily prepared, ecologically advantageous silicon-based coupling partners, as the most effective route to retinoids reported to date.
- Bergueiro, Julian,Montenegro, Javier,Cambeiro, Fermin,Saa, Carlos,Lopez, Susana
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p. 4401 - 4410
(2012/06/01)
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- Synthesis of 11-cis-retinoids by hydrosilylation-protodesilylation of an 11,12-didehydro precursor: Easy access to 11- and 12-mono- and 11,12-dideuteroretinoids
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An expeditious, highly efficient approach to 11-cis-retinoids was achieved by semihydrogenation of a readily available 11-yne precursor through a hydrosilylation-protodesilylation protocol. The complete chemo-, regio-, and syn-stereoselectivity of the method also allowed direct access to 11- and 12-monodeutero-, and 11,12-dideutero-11-cis-retinoids. The analogous trans series was not accessible by this route, and was synthesized by means of Hiyama coupling. Copyright
- Bergueiro, Julián,Montenegro, Javier,Saá, Carlos,López, Susana
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supporting information
p. 14100 - 14107
(2013/01/15)
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- Laser flash photolysis study on the retinol radical cation in polar solvents
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Laser flash photolysis (LFP) of retinol in argon-saturated methanol gives rise to a transient at 580 nm (transient A). Formation of transient A is accompanied by a transient growth at 370 nm. The rate of this growth is retinol concentration-dependent. The transient growth at 370 nm was removed in the presence of N2O, which is known to scavenge solvated electrons. These results can be interpreted by formation of retinol+ (λmax = 580 nm) and solvated electrons following LFP of retinol. Subsequently, the solvated electrons are rapidly scavenged by retinol to form retinol- (λmax = 370 nm in methanol). On the other hand, transient A is not ascribed to the retinyl cation, as was previously proposed, because the retinyl cation, generated from LFP of retinyl acetate, and transient A show different reactivities towards halide ions (e.g. kBr = 1.7 × 109 and 1.51 × 1010 M-1 s-1 respectively, in acetonitrile). After demonstrating the identity of transient A as retinol+, its reactions with carotenoids were examined in air-saturated polar solvents. In the presence of carotenoids, an enhancement in the decay of retinol+ was observed and was accompanied by formation of the corresponding carotenoid radical cations via electron transfer from carotenoids to retinol+. Furthermore, the reactivity of retinol+ towards pyridine derivatives was investigated in air-saturated polar solvents. It was found that the decay of retinol + was accelerated with concomitant formation, with the same rate, of a transient at 370 nm. Similar observations were obtained with increasing pH of air-saturated aqueous 2% Triton X-100 of retinol+. The 370 nm (or 380 nm in the case of Triton X-100) transient is attributed to the base adducts or deprotonated neutral radicals. On the basis of these results, the reactivities of the retinyl cation and retinol+ are compared and the consequences of retinol+ formation within biological environments are discussed.
- El-Agamey, Ali,Fukuzumi, Shunichi
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scheme or table
p. 6437 - 6446
(2011/10/10)
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- Syntheses of 13C2-labelled 11Z-retinals
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To enable solid-state NMR investigations of the rhodopsin chromophore and its photointermediates, a series of 11Z-retinal isotopomers have been synthesised containing pairs of adjacent 13C labels at C9/C10, C10/C11 or C11/C12, respectively. The C9 labelled carbon atom was introduced through the Heck reaction of a 13C-labelled Weinreb acrylamide derivative, and the label at the C12 position derived from a 13C-containing ethoxy Bestmann-Ohira reagent. The 13C labels at C10 and C11 were introduced through the reaction of β-ionone with labelled triethyl phosphonoacetate.
- McLean, Neville J.,Gansmuller, Axel,Concistre, Maria,Brown, Lynda J.,Levitt, Malcom H.,Brown, Richard C.D.
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supporting information; experimental part
p. 8404 - 8410
(2011/11/12)
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- Hiyama cross-coupling reaction in the stereospecific synthesis of retinoids
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The first application of the Hiyama reaction to the synthesis of retinoids is reported. A range of organosilicon moieties (siloxanes, silanols and three kinds of "safety-catch" silanols) were successfully coupled, under activation, to obtain trans-retinol or 11-cis-retinol with high yield and stereoselectivity. The advantageous properties of the silicon-based coupling partners and the mild reaction conditions firmly establish the Hiyama reaction as a viable (even superior) alternative to the traditional Suzuki and Stille couplings in the retinoid field.
- Montenegro, Javier,Bergueiro, Julian,Saa, Carlos,Lopez, Susana
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body text
p. 141 - 144
(2009/07/04)
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- Highly convergent, stereospecific synthesis of 11-cis-retinoids by metal-catalyzed cross-coupling reactions of (Z)-1-alkenylmetals
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(Chemical Equation Presented) A stereospecific synthesis of 11-cis-retinoids has as its key step the hitherto unexplored palladium-catalyzed cross-coupling of trans-tnenyl electrophiles and (1Z,3E)-penta-1,3-dienyl boronates (a Suzuki-Miyaura reaction) or
- Lopez, Susana,Montenegro, Javier,Saa, Carlos
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p. 9572 - 9581
(2008/04/05)
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- Accurate measurements of 13C-13C J-couplings in the rhodopsin chromophore by double-quantum solid-state NMR spectroscopy
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A new double-quantum solid-state NMR pulse sequence is presented and used to measure one-bond 13C-13C J-couplings in a set of 13C2-labeled rhodopsin isotopomers. The measured J-couplings reveal a perturbation of the electronic structure at the terminus of the conjugated chain but show no evidence for protein-induced electronic perturbation near the C11-C12 isomerization site. This work establishes NMR methodology for measuring accurate 1JCC values in noncrystalline macromolecules and shows that the measured J-couplings may reveal local electronic perturbations of mechanistic significance. Copyright
- Lai, Wai Cheu,McLean, Neville,Gansmueller, Axel,Verhoeven, Michiel A.,Antonioli, Gian Carlo,Carravetta, Marina,Duma, Luminita,Bovee-Geurts, Petra H. M.,Johannessen, Ole G.,De Groot, Huub J. M.,Lugtenburg, Johan,Emsley, Lyndon,Brown, Steven P.,Brown, Richard C. D.,DeGrip, Willem J.,Levitt, Malcolm H.
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p. 3878 - 3879
(2007/10/03)
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- A pericyclic cascade to the stereocontrolled synthesis of 9-cis- retinoids
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A domino reaction that is pericyclic in nature is thought to be triggered upon treatment of alkenynol 10 with arylsulfenyl chlorides. The process comprises an ordered sequence of sigmatropic rearrangements: a reversible [2,3]-allyl sulfenate to allyl sulfoxide shift, followed by a [2,3]-propargyl sulfenate to allenyl sulfoxide rearrangement, and last a stereodifferentiating [1,5]-sigmatropic hydrogen migration leading to polyene 13. The occurrence of the C7 to C11 hydrogen migration has been demonstrated by labeling experiments. The double diastereoselection of the [1,5]- sigmatropic hydrogen shift to afford a single isomer of the final polyene 13 is thought to arise from a combination of the electronic effect of the sulfoxide at one terminus, and the steric effect imparted by the bulky trimethylcyclohexenyl substituent at the other terminus. The overall process thus constitutes a stereoselective synthesis of an E,Z,Z-triene fragment from an alkenynol and, in particular, a retinoid with the 7E,9Z,11Z,13E configuration on the conjugated polyenic side chain. Application of this method to the synthesis of retinoids, including labeled analogues, is straightforward.
- Iglesias, Beatriz,Torrado, Alicia,De Lera, Angel R.,Lopez, Susana
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p. 2696 - 2705
(2007/10/03)
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- Efficient synthesis of 11-cis-retinoids
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The light sensitivity and unstable nature of 11-cis-retinoids makes them ideal visual chromophores in nature. The synthesis of 11-cis-retinal analogues is of paramount importance in bioorganic studies of rhodopsin, the photoreceptor of the visual transduction pathway, but the instability of 11- cis-retinoids complicates their synthesis and there is no general synthetic route. Common strategies to the cis geometry have failed in the case of 11- cis-retinoids, and most often low yields and complex isomeric mixtures are obtained. Herein we report an efficient, general, and mild preparation of 11- cis-retinoids by semi-hydrogenation of 11-yne-retinoid precursors with Cu/Ag- activated zinc dust.
- Borhan, Babak,Souto, Maria L.,Um, Joann M.,Zhou, Bishan,Nakanishi, Koji
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p. 1172 - 1175
(2007/10/03)
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- Process for the synthesis of vitamin A and certain ones of derivatives
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According to this process, one effects a stereospecific reduction of the two hydroxyl groups of an ether-diol by a mixture (titanium trichloride, lithium aluminum hydride) at a temperature between 5° C. and about 40° C. and that optionally, one converts the resulting ether into vitamin A, retinol or retinoic acid.Application to the synthesis of all-trans compounds selected from the group consisting of vitamin A and its ethers, retinol and retinoic acid, and their 13-cis isomers.
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- Base-catalyzed isomerization of retinoic acid. Synthesis and differentiation-inducing activities of 14-alkylated all-trans-, 13-cis-, and 20,14-retro-retinoic acids
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Retinoic acid (1) is isomerized regioselectively by excess amounts of lithium diisopropylamide (LDA) to give 20,14-retro-retinoic acid (3). Alkylation of the intermediate dianion of retinoic acid gave 14-alkylated derivatives of 3. By isomerization of the alkylated retro isomers under basic conditions, several 14-alkyl-all-trans- and -13-cis-retinoic acids were synthesized. The retinoidal activities of these derivatives were examined, based on the ability to induce differentiation of human promyelocytic leukemia cell line HL-60. 20,14-retro-Retinoic acid (3) is 1/50 as active as retinoic acid (1). Although 14-methyl-20,14-retro-retinoic acid (4) is as active as 3, the introduction of a 14-methyl group into all-trans- and 13- cis-retinoic acid resulted in decreased activity. Introduction of bulkier alkyl groups at the C-14 position caused the disappearance of the activity.
- Tanaka,Kagechika,Kawachi,Fukasawa,Hashimoto,Shudo
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p. 567 - 572
(2007/10/02)
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- Process for the preparation of vitamin A
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Vitamin A containing practically no 2-cis or 6-cis isomer is prepared by hydrogenation of the aldehyde of vitamin A, optionally in the form of a complex with hydroquinone, in the presence of a ruthenium hydride catalyst.
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- THE HIGHLY STEREOSELECTIVE SYNTHESIS OF ALL-TRANS AND 13-CIS VITAMIN A VIA DOUBLE ELIMINATION REACTION
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Stereocontrolled convergent synthesis of vitamin A was achieved by the double elimination method employing the C10 sulfone and the C10 aldehydes as starting materials.Thus the all-trans and 13-cis isomers were obtained with the stereochemical purity of 95percent and 90percent, respectively.
- Otera, Junzo,Misawa, Hiromitsu,Mandai, Tadakatsu,Onishi, Takashi,Suzuki, Shigeaki,Fujita, Yoshiji
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p. 1883 - 1886
(2007/10/02)
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- Thermal Sigmatropic Rearrangements of Vinylallenes Leading to 11-cis-Retinoids and the Novel Properties of 9-cis,11-cis,13-cis-Retinal and 11-cis,13-cis-Retinal
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The thermally induced sigmatropic hydrogen shift of vinylallene 5 provided a route to highly hindered 11-cis-retinoids.The coupling ot the hetero cuprate 14 with the propargyl benzoate 13b gave the vinylallene 5, which upon heating (69 deg C, 2 h) gave three geometrically isomeric retinoids: 11-sis (8), 11-cis,13-cis (9), and 9-cis,11-cis,13-cis (11).The fourth possible geometric isomer, 9-cis,11-cis (10), was unstable to the conditions of thermolysis and underwent further electrocyclizations to the tricyclic compound 22.The thermal rearramgement of 9,10-allene 5, though highly specific for the formation of 11-cis-retinoids, exhibits no selectivity in the formation of Δ9 and Δ13 double bonds.The highly hindered 11-cis,13-cis- and 9-cis,11-cis,13-cis-retinals, 9b and 11b, exhibit extraordinary electronic absorption spectra in that they exhibit their main maxima (302 nm) actually to the blue of the corresponding alcohols.The retinals 9b and 11b were thermally unstable and underwent clean isomerization to 13-cis-retinal and 9-cis,13-cis-retinal, respectively.
- Knudsen, Christopher G.,Chandraratna, Roshantha A. S.,Walkeapaeae, Leslie P.,Chauhan, Yeshpal S.,Carey, Stephen C.,et al.
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p. 1626 - 1631
(2007/10/02)
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- Transient Phenomena in the Pulse Radiolysis of Retinyl Polyenes. 1. Radical Anions
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The spectra and kinetics of formation and decay of radical anions of a number of retinyl polyenes have been studied in methanol and 2-propanol at room temperature, using pulse radiolysis and kinetic spectrophotometry.The bimolecular rate constants for the attachment of solvated electrons, e-MeOH, to the retinyl polyenes are in the diffusion-controlled limit (8.6 x 109-1.6 x 1010 M-1 s-1).The radical anions of retinol and retinol acetate have their spectral maxima at 370-390 nm, and undergo decay very slowly with second-order kinetics.On the other hand, the radical anions of retinal, retinal n-butylamine Schiff base, and retinoic acid/ester have spectral maxima at 430-510 nm, and decay by first-order kinetics in methanol with rate constants in the range 1 x 104-1 x 106 s-1.The decay rates of radical anions of retinal and retinoic acid/ester become considerably longer on going from methanol to less acidic alcohol, 2-propanol, suggesting that protonation by solvent is the major mode of their decay in protic media.In the case of retinal Schiff base, an additional slow process with bimolecular rate constant 9.0 x 107 M-1 s-1 im methanol is observed for the formation of radical anion and is ascribed to the electron-transfer reaction from the methanol radical, .CH2OH.
- Raghavan, N.V.,Das, P.K.,Bobrowski, K.
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p. 4569 - 4573
(2007/10/02)
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