- 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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- Process for preparation of allyl sulfone derivatives and intermediates for the preparation
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The present invention relates to a process for producing an allyl sulfone derivative represented by the formula (3): wherein Ar is an optionally substituted aryl group, and the corrugated line means either one of E/Z geometrical isomers, or a mixture thereof, which is an intermediate for producing vitamin A, which process is characterized by reacting an aryl sulfinic acid or a salt thereof represented by the formula (2): ArSO2M (2) wherein Ar is as defined above, and M is hydrogen atom, sodium atom or potassium atom, with an allyl halide derivative represented by the formula (1): wherein X is a halogen atom, and Ar and the corrugated line are as defined above.
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- Process for producing retinol and intermediate compounds for producing the same
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There are disclosed a disulfone compound of formula (1): wherein Ar denotes an aryl group that may have a substituent, R1 denotes a hydrogen atom or a protective group of a hydroxyl group and the wavy ine means that the disulfone compound is an E or Z geometrical isomer or i mixture thereof,a method for producing the same,intermediate compounds therefore anda process for producing retinol through the disulfone compound.
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- P(CH3NCH2CH2)3N as a dehydrobromination reagent: Synthesis of vitamin A derivatives revisited
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Although P(CH3NCH2CH2)3N (1) was found to be less effective than 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in the removal of hydrogen bromide from vitamin A intermediates 13-cis-10-bromo-9,10-dihydroretinyl acetates (6) and 14-bromo-9,14-dihydroretinyl acetate (11) when the reaction was carried out in refluxing benzene, in acetonitrile at room temperature it was superior to DBN and DBU. A 31P NMR study of this reaction suggests that the carbanion generated from acetonitrile-d3 in the presence of 1 is the basic species that initiates the elimination step. Diastereoselectivity of the nucleophilic addition of (Z)-HC≡ C(CH3)=CHCH20H to the carbonyl group of (E)-2-methyl-4-(2′,6′,6′-trimethyl-1′-cyclohexen- 1′-yl)-3-butenal (2) was only moderate (20%), and (9R*, 10S*)-13-cis-11,12 -didehydro-9,10-dihydro-10-hydroxyretinol (3b) predominated. The LiAlH4 reduction of the C≡C bond in the diastereoisomeric diols 3 afforded 13-cis-9,10-dihydro-10-hydroxyretinols 4a and 4b as major products together with 11-cis-13-cis-isomers and the deoxygenated compound (3EZ,5EZ,8E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)- 1,3,5,8-nonatetraene (9). Reaction of 15-acetates of the pure diastereoisomeric allylic alcohols 4a and 4b with PBr3 occurred with significant but not identical retention of configuration, and with concomitant formation of the rearranged bromide 11.
- Wroblewski, Andrzej E.,Verkade, John G.
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p. 420 - 425
(2007/10/03)
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- Preparation of (7Z) - and (7Z,11Z) - Vitamin A
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An efficient access to (7Z)- and (7Z,11Z)-vitamin A is described. Following the addition of a C6-acetylenic building block to 2,6,6-trimethylcyclohexanone (2), dehydration of the tert. alcohol 3 and formation of the C15-Wittig salt, the (7Z)-geometry was introduced by partial hydrogenation of the triple bond over Raney-nickel. Following Wittig reaction with (E)-2-methyl-4-acetoxy-2-butenal gave a mixture of the title compounds 8 and 9 which could easily be separated.
- Soukup,Widmer
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p. 4117 - 4118
(2007/10/02)
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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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- Electro-organic Reactions. Part 20. Electrogenerated Bases, Ylide Formation, and Wittig Alkene Synthesis
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Dicyano(fluoren-9-ylidene)methane (1a), dicyano(2,7-dibromofluoren-9-ylidene)methane (1b), and ethyl 2-cyano-2-fluoren-9-ylideneacetate (1c) may be cathodically reduced in N,N-dimethylforamide to give dianions which efficiently convert phosphonium salts into ylides.The potentials required are sufficiently modest to allow the electrogeneration of the bases in the presence of several phosphonium salts and of several aldehydes to give a convenient method of carrying out the Wittig alkene synthesis.This method has been explored for the synthesis of stilbene, 1,4-diphenylbutadiene, and vitamin A acetate.The basicity of the dianions varies according to the choice of electrolyte cation (Bu4N+ or Li+).The cations also have a marked effect on the stereochemical course of the reaction and, in particular, mixtures of alkenes are obtained in which the cis-isomer predominates in the presence of lithium ion; in the vitamin A acetate synthesis, the 11-cis-isomer constitutes 76percent of the product.The results are consistent with recent hypotheses concerning the mecahnism of the Wittig reaction.
- Mehta, Raj R.,Pardini, Vera L.,Utley, James H. P.
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p. 2921 - 2926
(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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