摘要:
A process for preparing polyenecarbonyl compounds having a high all-E content and their acetals or ketals by aldol condensation or Horner-Emmons reaction comprises carrying out the reaction, for the purposes of the preferred formation of a double bond of E configuration and in order to maintain the E configuration of the double bonds in the stating compounds as completely as possible, in the presence of oxygen or an oxygen-inert gas mixture or nitric oxide or a nitric oxide-inert gas mixture and/or in the presence of specific stable radicals and/or in the presence of quinones or quinone derivatives.
摘要:
A process for the preparation of alkyl esters of 0,0-dialkyl-4-phosphono-2-methyl-2-butenoic acid containing a high percentage of E isomers, wherein the corresponding alkyl esters of 2-hydroxy-2-methyl-3-butenoic acid are caused to react with PBr.sub.3 or PCl.sub.3 at temperatures ranging from 0.degree. to 80.degree. C. in the absence of pyridine and, if desired, the resulting mixture comprising predominantly alkyl esters of 4-halo-2-methyl-2-butenoic acid is caused to react with trialkyl esters of phosphorous acid at temperatures ranging from 70.degree. to 140.degree. C. The end products are desirable C.sub.5 building blocks for polyene syntheses or preceding stages.
摘要:
Compounds of the formula I ##STR1## where R.sup.1 is H or C.sub.1 -C.sub.4 -alkyl,R.sup.2 is C.sub.1 -C.sub.4 -alkyl and R.sup.3 is an ether, silyl ether or acetal protective group which can be converted into a hydroxyl group by hydrolysis, in particular one of the radicals ##STR2## and a process for preparing these compounds by reacting an alkenyne of the formula II ##STR3## in an inert solvent in the presence of lithium amide with a cyclohexenone of the formula III ##STR4## and the use of the compounds of the formula I for preparing astaxanthin, are described.
摘要:
Abstract of the Disclosure: Compounds of the formula I ##STR1## where R.sup.1 is H or C.sub.1 -C.sub.4 -alkyl, R.sup.2 is C.sub.1 -C.sub.4 -alkyl and R.sup.3 is an ether, silyl ether or acetal protective group which can be converted into a hydroxyl group by hydrolysis, in particular one of the radicals ##STR2## and a process for preparing these compounds by reacting an alkenyne of the formula II ##STR3## in an inert solvent in the presence of lithium amide with a cyclohexenone of the formula III ##STR4## and the use of the compounds of the formula I for preparing astaxanthin, are described.
摘要:
Pentoses and hexoses are epimerized by heating sugar dissolved in a solvent in the presence of a molybdenum(VI) compound, by an improved process in which, for the preparation of a sugar having cis OH groups in the 2- or 3-position, of the formula Ia or Ib ##STR1## where R is one of the radicals ##STR2## a homogeneous solution of the corresponding sugar of the formula IIa or IIb ##STR3## is heated to 75.degree.-100.degree. C. in the presence of from 30 to 200 mol %, based on sugar used, of a metal salt of the formula (III)MeX.sub.2 (III)where Me is Mg, Ca, Sr, Ba or Zn and X is Cl or Br, which may or may not contain water of crystallization, and in the presence of from 2 to 20 mol %, based on the sugar used, of a molybdenum(VI) compound.The process is particularly important for the preparation of D-ribose, which is required as an intermediate for vitamin B.sub.2.
摘要:
An improved process for preparing cyclic acetals of 3-formyl-2-butenyltriphenylphosphonium chloride by acetalization of 3-formyl-2-butenyl acetate with an aliphatic 1,3-diol, conversion of the resulting 4-acetoxy acetal into the corresponding 4-hydroxy acetal, Vilsmeier chlorination to give the corresponding 4-chloro acetal and subsequent reaction with triphenylphosphine entails carrying out the first 3 steps in an aliphatic or cycloaliphatic hydrocarbon or mixture of hydrocarbons with 6-8 carbons and the reaction with triphenylphosphine in an alkanol with 1-3 carbons and/or in aliphatic or cycloaliphatic hydrocarbon with 6-8 carbons or a corresponding mixture of hydrocarbons. The process is particularly advantageous when conversion of the 4-acetoxy acetal into the 4-hydroxy acetal is carried out with an aqueous alkali metal hydroxide solution in the presence of phase-transfer catalysts, and the first three, or all four, reaction stages are carried out in the same C.sub.6 -C.sub.8 -hydrocarbon.
摘要:
Ascorbic acid 2-phosphate is prepared by reacting ascorbic acid or an ascorbic acid derivative with POCl.sub.3 in the presence of a tertiary amine in a suitable aqueous solvent at from -10.degree. to 25.degree. C. while maintaining a pH of about 8-13.5 with KOH during the entire phosphorylation reaction and then isolating the ascorbic acid 2-phosphate, by a process in which an aqueous solution of a magnesium compound is added to the reaction mixture obtained in the phosphorylation, without prior treatment with an ion exchanger, until the formation of crystalline KMg PO.sub.4 is complete, the KMgPO.sub.4 which is crystallized out is separated off, the resulting filtrate is evaporated down at a pH of from 6 to 11 and/or from 0.1 to 5 times the amount, based on the evaporated filtrate, of a lower primary alkanol or acetone is added and the stirred mixture is cooled until KCl has completely crystallized out, and the ascorbic acid phosphate is isolated in a conventional manner from the reaction solution obtained by separating off KCl and substantially freed from inorganic salts. It is particularly advantageous if the ascorbic acid 2-phosphate is isolated in the form of the novel potassium magnesium ascorbate 2-phosphate, which is also claimed.The process is particularly advantageous if the ascorbic acid derivative used is 5,6-isopropylideneascorbic acid which has been obtained by reacting ascorbic acid with acetone in the presence of oleum. The process is particularly important for the preparation of L-ascorbic acid 2-phosphate.
摘要:
Potassium magnesium L-ascorbate 2-phosphate is prepared from an aqueous solution of potassium L-ascorbate 2-phosphate which is highly contaminated with KCl, as is produced in the phosphorylation of 5,6-isopropylidene-L-ascorbic acid, by adding to the solution about 1 equivalent of magnesium ions per equivalent of L-ascorbate 2-phosphate, and subsequently removing the KCl by electrodialysis. The product of this process is a novel salt of L-ascorbic acid 2-phosphate and has very advantageous handling properties.
摘要:
Higher &agr;,&bgr;-unsaturated alcohols are prepared by monoethynylation of a ketone by the NH3/KOH method, if desired hydrogenation of the acetylene alcohol in the presence of hydrogen over a Pd-containing thin layer catalyst, purifying distillation of the hydrogenation product, preferably in a dividing wall column with recirculation of the unreacted ketone to the ethynylation step, and, if desired, preparation of higher alcohols having in each case 5 more carbon atoms in the chain by reacting the alcohols prepared by monoethynylation and, if desired, partial hydrogenation with alkyl acetoacetates diketene in a Carroll reaction to form ketones and using these as starting materials for the steps ethynylation, optional hydrogenation and fractional distillation.