Übersetzung für "Stereospezifisch" in Englisch

This treatise relates to the synthesis of stereospecific functionalised derivatives of the bicyclo[2.2.1]heptene system.

Moreover, it is stereospecific, which is not ensured in a chemical total synthesis.

This hydroxylation proceeds regio- and stereospecifically in many cases.

Furthermore, hydrogenation of the salt of formula (XIII) gives, in a reaction which proceeds stereo-specifically, only the desired gluco-compounds.

Polypropylene is an isotactic, syndiotactic or atactic polypropylene prepared using stereospecifically acting catalysts.

The addition of BH3 (from B2H6) to an alkyne is a stereospecific cis addition and...

In addition, the processes known hitherto for the preparation of the compound of formula (I) in which R denotes hydrogen, in each case require expensive purification steps, such as extraction, column chromatography or chromatography on exchangers, which are partly also necessary because the hydrogenation of the free bases does not proceed stereospecifically.

It is to be described as exceptionally surprising that the compounds of formula (I) are obtained in excellent yields and as stereospecifically pure compounds by the reaction according to the invention, because according to the state of the art it had to be expected that the deblocking of the compounds of formula (X) with mineral acids would only lead to pyridine derivatives and that the hydrogenation of the free bases obtained by deblocking compounds of formula (XI) would lead to mixtures of gluco-compounds and ido-compounds (see Paulsen, Sangster and Heyns, supra.)

In this case, it is especially desirable that such processes lead stereospecifically to the exclusively or predominantly biologically active E-form.

The addition of methylene to the olefinic double bond of the maleimide of the formula IV according to process (c) proceeds in general stereospecifically (cis-addition).

Yeasts of the genus cryptococcus, preferably of the species C. Laurentii, form, in the presence of aminoacids, an L-aminoacid oxidase which stereospecifically converts L-aminoacids and their derivatives into the corresponding a-ketoacids.

However, the disadvantage of the known processes is that no optically active oxiranes are thereby available in a stereospecific manner.

The reactive compound corresponding to the organic radical Ra generally attacks the substrate stereospecifically.

The subsequent exchange of the trialkyl(or phenyl) stannyl group for bromine or iodine occurs stereospecifically as in the E-configured series.

It has been found that the allyl esters of formula II defined below, wherein the allylic OR8 group is in the 15-position of the molecule, can be converted by reaction with trialkylaluminium compounds of the formula Al(R)3 into the compounds of formula I such that the substituent R to be introduced occupies the 13?-position of the molecule stereospecifically and affords only small amounts of by-products, which are substituted in the 15-position.

This (6R)- or (6S)-pyrandione is tben oxidized, e.g., in acetone by means of Jones' reagent at a temperature below 25° C., to the corresponding pyrandione and the latter is stereo specifically hydrogenated, e.g., in ethyl acetate in the presence of platinum oxide, to the (3S,4S,6R)- or (3R 4R,6S)-pyrandione of Formula V-A in which L' is hydrogen.

This process comprises stereospecifically reducing 1-(5-oxohexyl)-3-methyl-7-propylxanthine using the yeast strain Rhodotorula rubra (which was deposited in the German Collection of Microorganisms and Cell Cultures on 10.7.1989 under the number DSM 5436), S-(+)-1-(5-hydroxyhexyl)-3-methyl-7-propylxanthine being formed, which is then subjected to an inversion of configuration.

This synthesis did stereospecifically yield the desired threo configuration, but it is complicated and the total yield is small.

Another main object of the invention is to provide a process for the production of 4-alkoxy-5-(arylhydroxymethyl)-2(5H)-furanones, which stereospecifically yields in high yield the threo configuration as much as possible in one stage, starting from commercially available materials, as well as without using lithium-organic reagents.

The starting materials used for this synthesis are alkyl iodobenzenes which react with acetylene in the presence of Pd catalysts to yield di(alkylaryl)acetylenes which are subsequently stereo specifically hydrogenated to Z-stilbenes.

In accordance with one aspect of the process, the compound of formula III is converted stereospecifically to the intermediate ##STR4##

The carriers used according to the present invention are suitable for many of the conventional bio-conversion processes, for example for the production of citric acid from starch, for the hydrolysis of Penicillin G by means of acylases to produce 6-aminopenicillic acid, for the production of stereo-specific biologically active compounds, or for the fermentation of sugar-containing waters in the sugar beet industry.

This (6R)- or (6S)-pyranolone is then oxidized, e.g. in acetone by means of Jones' reagent at a temperature below 25° C., to the corresponding pyran-2,4-dione and the latter is stereospecifically hydrogenated, e.g. in ethyl acetate in the presence of platinum oxide, to the (3S,4S,6R)- or (3R,4R,6S)-pyranolone of formula V--A in which L' is hydrogen.

The action of the electrophilic agent that introduces the radical (R1,R2)CH-- on the substrate generally takes place stereospecifically.

However, subsequent work along these lines has likewise shown that the etherification disclosed in the prior art definitely does not proceed stereospecifically when it is scaled up to a commercial scale.