摘要:
2,5-bis(1,1-dialkoxy-2-propyl)-2,5-dihydrofurans of the formula I ##STR1## where R.sup.1 and R.sup.2 can be identical or different and can be alkyl of 1 to 4 carbons, the preparation thereof by reaction of 2,5-dialkoxy-2,5-dihydrofurans of the formula II ##STR2## In the presence of protic acids or Lewis acids with an alkyl propenyl ether of the formula III ##STR3## and the use thereof for preparing 2,7-dimethyl-2,4,6-octatrienedial and symmetric C.sub.40 -carotenoids such as .beta.-carotene, canthaxanthin and astaxanthin, are described.
摘要:
Phosphoric acid is separated from aqueous solutions of thiamine phosphates which are obtained in the phosphorylation of thiamine, with or without subsequent partial hydrolysis, by a process in which the phosphoric acid is converted with a virtually water-insoluble or only slightly water-soluble tertiary amine into the corresponding salt and the latter is extracted with a virtually water-immiscible or only slightly water-miscible solvent of moderate polarity. In a particularly advantageous procedure, the phosphoric acid is extracted with a mixture of a virtually water-insoluble or only slightly water-soluble tertiary amine and a virtually water-immiscible or only slightly water-miscible solvent of moderate polarity.
摘要:
Substituted hexatriene derivatives of the formula I ##STR1## where R.sup.1 has the meaning given in the description, and their preparation, are described. The compounds may be used to treat acne and psoriasis.
摘要:
2-Amino-3,5-di-(halomethyl)-pyrazines of the general formula I ##STR1## where X is either chlorine or bromine, m and n may each be 0, 1, 2 or 3 and R.sup.1 and R.sup.2 are each hydrogen or a protective group or may furthermore be bonded to one another, in particular those compounds of the formula I in which m is 1 and n is 2 and/or R.sup.1 and R.sup.2 together form a phthaloyl radical, are useful intermediates for the pteridine building block of folic acid or folic acid analogs.They are obtained by a method in which a 2-amino-3,5-dimethylpyrazine of the general formula II ##STR2## is treated with a chlorinating or brominating agent and, where R.sup.1 and/or R.sup.2 are protective groups, these are, if desired, eliminated when the chlorination or bromination is complete.
摘要:
2-Alkyl-4,4-diacyloxybut-2-enals of the formula ##STR1## where R.sup.1 is alkyl and R.sup.2 is hydrogen or an aliphatic, cycloaliphatic or aromatic radical, are prepared by a process in which a 2-alkyl-1,4-diacyloxy-1,3-butadiene of the formula ##STR2## is reacted with oxygen or an oxygen donor in the presence of an acidic ion exchanger.
摘要:
The invention relates to intermediate compounds having the general formula I ##STR1## in which R.sup.1 is H, an alkyl, arylalkyl or an aliphatic acyl radical, preferably a benzyl or acetyl group and wherein X and Y together span an additional bond between the X and Y carrying C atoms (Ia) or in which Y is OH and X is H (Ib) and in which the dotted line can represent an additional bond particularly[2R,1'Z,3'E,7'E]-6-benzyloxy-2,5,7,8-tetramethyl-2-(4',8',12'-trimethyl-trideca-1',3',7'-trien-1'-yl)chroman and6-benzyloxy-2,5,7,8-tetramethyl-2-(1'-hydroxy-4',8',12'-trimethyl-trideca-3',7'-diene-1'-yl)chroman, as well as compounds and methods of preparing compounds having the general formula II ##STR2## in which Z is one of the groups ##STR3## wherein R.sup.2 is an alkyl group with 1 to 4 carbon atoms preferably CH.sub.3 or C.sub.2 H.sub.5particularly (3,7,11-trimethyl-trideca-2,6,10-trien-1-yl)triphenylphosphonium chloride and (3,7,11-trimethyl-trideca-2,6,10-trien-1-yl) phosphoric acid dimethylester as well as methods for the preparation of (2R,4'RS,8'Rs)-.alpha.-tocopherol and (all-rac)-.alpha.-tocopherol via the new intermediate product.
摘要:
3-Hydroxy-.alpha.-cyclocitral derivatives of the general formula I ##STR1## where R.sup.1 is ##STR2## wherein R.sup.2 and R.sup.3 can be identical or different and are each straight-chain or branched alkyl of 1 to 6 carbon atoms, or R.sup.2 and R.sup.3 together form an ethylene or propylene group which can be substituted by methyl or ethyl, processes for their preparation and their use for the preparation of safranal and 3-hydroxy-.beta.-cyclocitral, as well as optically active - cyclocitral derivatives of the general formulae A and B ##STR3## where R.sup.1 is ##STR4## if X is hydrogen and Y is OH, but is otherwise ##STR5## where R.sup.2 and R.sup.3 have the above meanings, and X and Y together are oxygen, or X is hydrogen if Y is OH, and a process for the preparation of optically active 3-oxo-.alpha.-cyclocitral acetals, wherein a mixture of the corresponding racemic 3-oxo-.alpha.-cyclocitral acetals is separated into the optically active compounds by chromatography over a suitable chiral adsorbent. The novel compounds open up a novel advantageous route to optically active 3-hydroxy-.beta.-cyclocitrals, which are desirable because they are important intermediates for carotinoids identical to the natural products.
摘要:
Riboflavin of the formula I ##STR1## is prepared by condensing a 4,5-dimethyl-N-(D)-ribityl-2-phenylazoaniline of the formula II ##STR2## where R is H or --Cl, --NO.sub.2 or --CH.sub.3 in the o- or p-position, with barbituric acid of the formula III ##STR3## in the presence of an acid as the condensing agent, by an improved process in which the acidic condensing agent used is an aliphatic or cycloaliphatic/aliphatic tertiary carboxylic acid of the general formula IV ##STR4## where R.sup.1, R.sup.2 and R.sup.3 are each a lower alkyl group, R.sup.1, R.sup.2 and R.sup.3 together containing 3 to 20, preferably 3 to 10, carbon atoms, or R.sup.1 is a lower alkyl group, in particular methyl, and R.sup.2 and R.sup.3 together form a tetramethylene or pentamethylene group.The process can be particularly advantageously carried out using trimethylacetic acid or a commercial mixture of saturated tertiary carboxylic acids, e.g. Versatic .sup.R 10-acid.
摘要:
.omega.,.omega.-Diacyloxy-2,6-dimethyl-octatrienoates and -octatrienals, as novel bifunctional asymmetric C.sub.10 building blocks for terpene syntheses, which possess a formyl or alkoxycarbonyl group at one chain end and 2 geminal acyloxy groups at the other, and a process for their preparation from readily obtainable industrial C.sub.5 building blocks and their use for the synthesis of terpene compounds by carbonyl olefination under conventional conditions.
摘要:
2-alkyl-4,4-diacyloxybut-2-enals of the formula ##STR1## where R.sup.1 is alkyl and R.sup.2 and R.sup.3 are each hydrogen or an aliphatic, cycloaliphatic or aromatic radical, are prepared by a process wherein a 2-alkyl-2,4-diacyloxybut-3-enal of the formula ##STR2## is treated with an aliphatic carboxylic acid.