- Preparation method of vitamin A acetate intermediate C15 and vitamin A acetate
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The invention provides a preparation method of a vitamin A acetate intermediate C15 and vitamin A acetate. The method comprises the following steps: taking 1-halogenated-2-methyl-4-acetoxy-2-butene asa raw material, preparing a corresponding Wittig reagent through a substitution reaction with triphenylphosphine or triester phosphite, then carrying out a Wittig reaction with beta-cyclocitral, hydrolyzing an ester group under an alkaline condition, acidifying to obtain a corresponding halide, and carrying out a substitution reaction with triphenylphosphine or triester phosphite again to prepareC15. The vitamin A acetate can be prepared by carrying out a Wittig reaction on the obtained C15 and 2-methyl-4-acetoxy-2-butenal under an alkaline condition. The method has the advantages of singlereaction type, easy operation and realization of reaction conditions, safe and environment-friendly operation, simple post-treatment and low cost; and the reaction activity is strong, the reaction selectivity is high, the atom economy is high, and the target product yield and purity are high.
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- Preparation method of vitamin A ester intermediate C15 and vitamin A ester
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The invention provides a preparation method of a vitamin A ester intermediate C15 and vitamin A ester. The method comprises the following steps: carrying out a halogenation reaction and a cyclizationreaction on 3, 7-dimethyl-3-hydroxy-1, 6-octadiene as an initial raw material, carrying out a substitution reaction on the obtained product and triphenylphosphine or triester phosphite to prepare a corresponding Wittig reagent, carrying out a Wittig reaction on the Wittig reagent and 2-methyl-4-acetoxy-2-butenal, performing acidifying, hydrolyzing and acidifying the obtained product, and carryingout a substitution reaction on the hydrolyzed and acidified product and triphenylphosphine or triester phosphite to prepare C15. The vitamin A ester can be prepared by carrying out a Wittig reaction on the obtained C15 and 2-methyl-4-R3 substituent carbonyloxy-2-butenal. The method has the advantages of single reaction type, easy operation and realization of reaction conditions, safe and environment-friendly operation, simple post-treatment and low cost; and the reaction activity is strong, the reaction selectivity is high, the atom economy is high, and the target product yield and purity arehigh.
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- PROCESS FOR PREPARATION OF HIGHLY PURE ISOTRETINOIN
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The present invention relates to a process for preparation of isotretinoin and more specifically, to a purification process for obtaining highly pure isotretinoin that is useful as a keratolytic agent, particularly useful for the treatment of acne. The process involves treating isotretinoin containing metal contamination and/or other impurities with a base in a suitable solvent to form a solution of isotretinoin, followed by adsorption, precipiation, and filtration or centrifugation
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Page/Page column 4
(2008/12/08)
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- Process for the preparation of 13-cis-retinoic acid
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A process for the preparation of 13-cis-retinoic acid (I) from 3-methyl-5-(2,6,6-trimethyl-1-cyclohexan-1-yl)-2,4-pentadienyl)-triphenylphosphonium chloride (IIa) and 5-hydroxy-4-methyl-2(5H)-furanone (III) is herein disclosed. Compounds (IIa) and (III) are reacted in ethanol as the solvent and KOH as the base at a temperature ranging from -5 to 0°C to give a mixture of retinoic acids which is isomerised to (I) by treatment with a palladium complex.
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- Retinoids and Carotenoids, V.- Synthesis of Modified Retinals
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The syntheses of 13-demethyl-13-ethyl-, 13-demethyl-13-propyl-, 13-demethyl-, 13-demethyl-14-methyl-, and 14-methylretinal are described.The UV spectra of some geometric isomers of these compounds are discussed.
- Bestmann, Hans Juergen,Ermann, Peter,Rueppel, Hartmann,Sperling, Walter
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p. 479 - 498
(2007/10/02)
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- Electro-organic Reactions. Part 16. The Preparative-scale Cathodic Hydrogenolysis and Coupling of Benzyl-, Allyl-, Cinnamyl-, and Polyenylphosphonium salts
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An investigation of the cathodic reduction of benzyltriphenylphosphonium nitrate confirms that optimum yields of the product of coupling (bibenzyl) are formed at an aluminium cathode using high current densities and in dimethylformamide or hexamethylphosphoramide solution.The cathodic reduction of allylphosphonium salts gives mainly cleavage; e.g. α-farnesene (5) is obtained in 32percent yield from the corresponding farnesylphosphonium salt.Moderately efficient coupling (ca. 30percent) is observed for the electro-reduction of trans-cinnamyltriphenylphosphonium nitrate (6) and a C15 polyenylphosphonium salt (7).The products of coupling have been fully characterised; the relative proportions of positional isomers are apparently dictated by steric factors.
- Utley, James H. P.,Webber, Andrew
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p. 1154 - 1160
(2007/10/02)
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