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:
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:
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:
Alkyl .gamma.-halotiglates of the general formula I ##STR1## where X is Cl or Br and R.sup.2 is alkyl of 1 to 3 carbon atoms, having a high E isomer content, are prepared by a process in which(a) the corresponding 2-methyl-but-3-enoate of the general formula II ##STR2## is reacted with chlorine or bromine in the absence of a solvent and (b) the resulting 2-methyl-3,4-dihalobutyrate of the general formula III ##STR3## is dehydrohalogenated by reaction with a solution of an alkali metal hydroxide in an alcohol R.sup.2 OH, where R.sup.2 has the stated meaning, or in a mixture of water and an alcohol R.sup.2 OH, and the products are further processed to give O,O-dialkyl-.gamma.-phosphonotiglates of the general formula IV ##STR4## where R.sup.1 is alkyl of 1 to 4 carbon atoms and R.sup.2 is alkyl of 1 to 3 carbon atoms, preferably ethyl, by reaction with a trialkyl phosphite and thermal isomerization. The process gives C.sub.5 building blocks which are extremely interesting for polyene chemistry, the said building blocks being obtained in good yields and essentially in the form of the required E isomers.
摘要:
N-(D)-ribitylxylidine (I) is prepared by reacting (D)-ribose (II) with 3,4-dimethylaniline (III) or 3,4-dimethyl-1-nitrobenzene (IV) in aqueous or aqueous/organic solution or in solution in a water-soluble organic solvent under an elevated hydrogen pressure and in the presence of a hydrogenation catalyst and of a boric acid compound,(a) using the boric acid compound in a catalytic amount of from about 6 to 35 mmol, preferably from 6 to 20 mmol, per mol of ribose,(b) carrying out the reaction under a hydrogen pressure of from 1 to 20, preferably from 2 to 9, bar and(c) carrying out the hydrogenation at from 40.degree. to 80.degree. C. over Raney nickel as hydrogenation catalyst.
摘要:
.alpha.-(o-Chlorophenyl)-aminomethylene-.beta.-formylaminopropionitrile, process for its preparation by reacting a metal salt of .alpha.-formyl-.beta.-formylaminopropionitrile with a salt of o-chloroaniline in an aqueous medium, and use of the product to prepare the compound of the formula ##STR1## by reaction with acetamidine. The pyrimidine thus obtained is an intermediate for the preparation of vitamin B.sub.1.
摘要:
An improved process for the preparation of riboflavin by condensation of a 4,5-dimethyl-N-(D)-ribityl-2-phenylazoaniline derivative with barbituric acid in the presence of an acidic condensing agent in an organic solvent, wherein a 4,5-dimethyl-N-(D)-ribityl-2-(o-alkoxyphenylazo)-aniline of the formula IIa ##STR1## where R is alkyl of 1 to 4 carbon atoms, in particular methyl, is reacted with barbituric acid, as well as the novel intermediates of the formula IIa.
摘要:
Novel optically active chroman derivatives of the general formulae Ia and Ib ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen or alkyl and X is --OH, --O--CO-alkyl, --O-alkyl, --O-tosyl, --O-mesyl, --O-benzenesulfonyl, Cl, Br or I, are prepared by a process in which(a) the racemate of the formula I' ##STR2## is esterified in the side chain with a carboxylic acid and then acylated with an optically active carboxylic acid halide of the general formula III ##STR3## or with the corresponding carboxylic anhydride, to give a chroman derivative IV ##STR4## or (b) the racemate I' is esterified in the side chain with the carboxylic acid from which III is derived, and, if required, the resulting ester is acylated with a carboxylic acid halide to give IV' ##STR5## the resulting mixture IV or IV', which consists of two diastereomers, is resolved by fractional crystallization, the diastereomers are hydrolyzed to the alcohols Ia and Ib and, if desired, these are converted to the other compounds Ia and Ib in a conventional manner.Useful optically active chroman derivatives Ia and Ib and diastereomeric chromanyl esters IV and IV' are also claimed.