MXPA01001664A - Enzyme-catalyzed racemic cleavage of primary amines - Google Patents

Abstract

The invention relates to a method for the racemic cleavage of alkoxy-substituted primary amines by reaction with an ester in the presence of a lipase and subsequent separation of the resulting optically active amide from the optically active unreacted amine. This is possibly followed by hydrolysis of the optically active amide, separation of the resulting optically active amine from the acid at the origin of the ester, racemization and recirculation of the undesirable enantiomer of the amine and esterification and recirculation of the acid.

Description

RACEMIC DISSOCIATION OF PRIMARY AMINES CATALYZED BY ENZYMES The present invention relates to a process for resolving racemates of primary amines substituted with alkoxy by reaction with an ester in the presence of a lipase and subsequently separating the optically active amide which is formed from the unreacted, optically active amine. This is followed, as appropriate by hydrolysis of the optically active amide, the separation of the thus produced amine from the acid from which the ester comes, the racemisation and recycling of the unwanted enantiomer of the amine, and the esterification and recycling of the amine. acid. WO 95/08636 describes a process for resolving racemes of primary and secondary amines by reaction with an ester in the presence of hydrolases, especially lipases. Preferred amines are primary arylalkylamines. WO 96/23894 describes a process for resolving racemates of primary and secondary amines substituted with heteroatoms by reaction with an ester in the presence of hydrolases, especially lipases. Preferred amines are O-protected amino alcohols. The preferred esters mentioned in both applications are the C 1 -C 4 alkyl esters of C 1 -C 4 alkoxyacetic acids.

DE 196 03 575 and DE 196 37 336 describe a process for the preparation of optically active amines by reacting the corresponding racemates with an ester in the presence of lipase from Antarctic Candida. Preferred amines are alkylamines substituted with alkoxy, especially 2-amino-1-methoxypropane, and substituted phenylethylamines, especially 4-chlorophenylethylamine. Preferred esters are Ci-Ce alkanoic esters and Ci-Cβ alkoxyalkane esters, especially methyl methoxyacetate. Finally DE 196 21 686 describes a process for the preparation of optically active amines by reacting the corresponding racemates with an ester in the presence of hydrolases, in which substituted phenylethylamines, especially 4-chlorophenylethylamine and haloalkane esters of C? C, especially ethyl chloroacetate. It has now been found, surprisingly, that the process described in the principle can be carried out in a particularly advantageous manner if esters with long chain alcohol residues are used. The process for resolving amine racemates takes place in a particularly advantageous manner if an ester of the general formula I: in which m is O or 1, R 1 is branched or unbranched C 6 -C 2 alkyl or heteroalkyl having from 6 to 20 atoms in the skeleton, R2 is Ci-Cs alkyl or phenyl, R3 is H or C? -C alkyl, is reacted with a primary amine substituted with alkoxy or benzyloxy of the general formula 2. wherein n is 0 or 1, R4, R5 are, independently of each other H, Ci-Cß alkyl or phenyl, R6 is C?-C6 alkyl or benzyl, in the presence of a lipase, giving rise to the amides of the general formula 3: wherein: n, m, R1, R2, R3, R4, R5 and R6 have the meanings stated above, which contains an excess of an optical isomer of the amide. Preferably, there is formation of an amide (R) and particularly preferably enantioselective acylation with a high enantiomeric excess of more than 50% ee, in particular, more than 80% ee, especially more than 90% ee. The unreacted amine comprises an excess of amine (S), preferably more than 50% ee, in particular more than 90% ee, especially more than 99% ee. (R) amide or (R) amine means the optically active amides or amines having the (R) configuration at the carbon of the amino group. A similar statement applies to the amine (S) or amide (S). In addition, it has been found that it is convenient to dry the raw materials. This can, in principle, take place in any manner known to the skilled worker, for example, by azeotropic drying or through desiccants such as sodium sulfate, magnesium sulfate, KOH, phosphorus pentoxide, molecular sieves, silica gel or alumina. .

In addition, it has also been found that it is convenient to use raw materials without acid. The acids can, in principle, be removed in any manner known to the skilled worker, for example, by extraction or distillation, as appropriate, after previous neutralization with alkali metal or alkaline earth metal hydroxides such as sodium, potassium or hydroxide. calcium, with amines such as triethylamine, tributylamine, triethanolamine, pyridine or N, N-dimethylaniline, with carbonates such as sodium, potassium or calcium carbonate or with ion exchangers. It is possible to use a large number of lipases in the process according to the invention. Preferred are microbial lipases from bacteria such as lipases of the genus Bacillus or Pseudomonas, for example, Amano P or the lipase from Pseudomonas spec. DSM 8246, or fungi such as Aspergillus, or yeasts such as Candida. Other preferred lipases are, for example, the lipases SP 523, SP 524, SP 525, SP 526 and Novozym® 435, which are obtained from fungi such as Humicola, Mucor, or Candida Antarctica and which are commercially available. Novo Nordisk It is also possible to use the Chirazyme lipases Ll, L2, L3, L4, L5, L6, L7 and L8 which are available commercially from Boehpnger Mannheim. Lipases can be used naturally or immobilized. The immobilized lipases can be microencapsulated, emulsified with prepolymers and polymerized, crosslinked with bifunctional substances (oligomers, aldehydes, etc.) or linked to inorganic or organic carrier materials such as Celites, Lewatit, zeolites, polysaccharides, polyamides or polystyrene resins. Particularly preferred lipases are Novozym® 435 and Chirazyme L2. The resolution of the enzyme-catalyzed racemate can be carried out in protic or aprotic solvents and without solvent. Examples of suitable solvents are hydrocarbons such as hexane, cyclohexane or toluene, ethers such as diethyl ether, dioxane, methyl tertiary butyl ether, teramyl methyl ether or THF, nitriles such as acetonitrile, butyronitrile, alcohols such as tert-butanol, 3-methyl-3- pentanol and halogenated hydrocarbons such as methylene chloride. The reaction with lipase generally takes place under atmospheric pressure, as appropriate, under inert gas such as nitrogen or argon. However, it can also be done under high pressure. The temperature for the reaction of the ester with the racemic amine substituted alkoxy is usually from 0 to 90 ° C, preferably from 10 to 60 ° C, particularly preferably from 20 to 50 ° C. From 0.5 to 2.0 mol, preferably 0.5 to 1.0 mol of ester is used per mole of racemic amine. The amount of the enzyme required depends on the activity of the preparation of the enzyme and the reactivity of the amine and can be easily established by preliminary tests. As a general rule, from 0.1 to 10% by weight, preferably from 1 to 5% by weight of the preparation of the immobilized enzyme (based on the racemic amine) is used. Novozym® has an activity of approximately 7,000 U / g in the esterification of lauric acid with 1-propanol. The course of the reaction can be easily followed by traditional methods such as GC or HPLC. When the desired conversion is achieved, the reaction of preference is interrupted by removing the catalyst, for example, by filtering the enzyme (attached to the carrier). The reaction can also be interrupted, for example, by adding substances that break down the enzyme such as acids or alkalis or by heating. In a continuous process, the conversion can be controlled through the loading of the enzyme, that is, the amount of amine pumped through the enzyme reactor per unit time. The preference process can be carried out continuously, but it can also be done in batches or semi-continuously. The resolution of the enzyme-catalyzed racemate finally gives rise to a mixture of the acylated amine enantiomer, the unreacted amine enantiomer, the alcohol released from the ester during acylation and, possibly, the ester used in excess. The distillation and extraction processes are particularly convenient for separating this mixture. Thus, the low-boiling amines can be distilled from the reaction mixture directly. The amide may subsequently be separated from the alcohol and, as appropriate, the ester by distillation or extraction and then it may be hydrolyzed in a traditional manner with an acid or base, for example by boiling with sulfuric acid or sodium or potassium hydroxide in solution , with racemization or even without racemization. The hydrolysis can be carried out under atmospheric pressure and, as appropriate, also at elevated temperature under increased pressure to accelerate the reaction. The enantiomer of the secondary amine formed in the hydrolysis can be isolated by distillation or extraction, as appropriate, after being released from the ammonium salt. The acid formed in the hydrolysis can be recovered, as appropriate, after acidification of the hydrolysis solution and preferably by extraction. The acid can be esterified by traditional processes, for example, azeotropically or by extraction, and returned to the racemate solution process. If only one enantiomer of the amine is required, it is possible to racemize the others and return the racemate to the process. It is possible in this form to theoretically convert all the racemate into the required enantiomer. Such racemizations can be carried out, for example, under the same conditions as for preparing amines from alcohols or ketones ("reductive amination"). The esters of formula 1: Suitable for the process according to the invention are those in which: m is 0 or 1, preferably 0 R 1 is branched or unbranched C 1 -C 2 alkyl or heteroalkyl having from 6 to 20 carbon atoms, it being possible for the alkyl or heteroalkyl radical is substituted, independently of one another, by 1 to 5 halogen atoms, preferably F or Cl, and / or an oxo group. Heteroalkyl means that 1, 2 or 3 non-adjacent -CH2- groups are substituted by -O-, -S-, -NH- or 1 or 2 non-adjacent CH groups are substituted by N. The substitution of 1 or 2 CH groups is preferred The preferred heteroatom is O. Examples of R1 are 1-hexyl, 2-hexyl, 3-hexyl, P-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl -3-pentyl, 2-ethyl-1-butyl, 1-heptyl, 2-heptyl-, 3-heptyl-, 2-methyl-1-hexyl, 3-methyl-1-hexyl, 2-ethyl-1-hexyl , 3-ethyl-1-hexyl, 2-methyl-1-heptyl, 3-methyl-1-heptyl, 1-octyl, 1-octyl- [sic], 2-O-tyl- [sic], 3-octyl- [sic], 1-nonyl, 2-nonyl- [sic], 3-nonyl, 1-decyl, 2-decyl, 3,7-dimethyl-1-octyl, 1-undecyl, 1-dodecyl, 1-tridecyl, 1-tetradecyl, 1-pentadecyl, 1-hexadecyl, 1-heptadecyl and 1-octadecyl, 2-methoxyacetoxyethyl, 2-methoxyacetoxybutyl, 2-methoxyacetoxyhexyl, 2-methoxyacetoxidecyl, chloroacetoxybutyl, chloroacetoxyhexyl, chloroacetoxydecyl, trichloroacetoxybutyl, trichloroacetaxyhexyl, trichloroacetoxidecyl, giving preference C C-is alkyl, branched or unbranched or heteroalkyl having 6 to 18 atoms in the main chain, e.g. ex. , 1-hexyl, 1-heptyl, 2-ethyl-1-hexyl, 1-octyl, 1-decyl, 1-dodecyl, 1-tetradecyl, 1-hexadecyl and 1-octadecyl, 2-methoxyacetoxyethyl, 2-methoxyacetoxybutyl, 2 -methoxyacetoxyhexyl, 2-methoxyacetoxidecyl, clear acetoxybutyl, chloroacetoxyhexyl, chloroacetoxy-dexyl, and particular prediction of C6-C alkyl? , linear or branched or heteroalkyl having from 6 to 14 atoms in the main chain, e.g. ex. : 1-hexyl, 2-ethyl-1-hexyl, 1-octyl, 1-decyl and 1-tetradecyl, 2-methoxyacetoxyethyl, 2-methoxyacetoxybutyl, 2-methoxyacetoxyhexyl, 2-methoxyaceto-decylcyl.

R 2 is C 1 -C 8 alkyl, such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 1-pentyl, 2-pentyl, 1-hexyl, 2-hexyl, 1-hepty. 2-ethylhexyl and 1-octyl, preferably methyl, ethyl, 1-propyl, 2-propyl and 1-butyl, particularly preferably methyl and ethyl or phenyl R3 is H, C? -C alkyl, as methyl, ethyl, 1-propyl, 2-propyl and 1-butyl, H, methyl and ethyl are preferred.

Examples of the esters of formula 1 mentioned are the following preferred compounds: 0 / ° r The process according to the invention is convenient for resolving racemates of primary amines substituted with alkoxy of the general formula 2: wherein n is O or 1, preferably O R 4, R 5 are, independently of each other, H, C 1 -C 8 alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 1- pentyl, 2-pentyl, 1-hexyl, 2-hexyl, 1-heptyl, 2-ethylhexyl and 1-octyl. or phenyl, preferably H, C? -C4 alkyl such as methyl, ethyl, 1-propyl, 2-propyl, and 1-butyl, particularly preferably H, methyl and ethyl, Rd is C? -C6 alkyl as methyl , ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 1-pentyl, 2-pentyl, 1-hexyl and 2-hexyl. or benzyl, preferably methyl, ethyl and benzyl. The following compound is mentioned as a preferred example of the amines of the formula 2: NH, Example 1 A mixture of one molar equivalent of 2-amino-1-methoxypropane and one molar equivalent (0.5 mole for diesters) of the particular methoxyacetic ester is mixed with 5% by weight (based on the amine) of Novozym® 435 and stir at room temperature for 24 hours. The conversions were determined by gas chromatography and are compiled in Table 1: Table 1: Comparison of acylation rates of 2-amino-l-methoxypropane with different methoxyacetic esters Example 2 2 g of Novozym® 435 were introduced as a suspension in the particular ester in a glass tube, (internal diameter 1 cm) heated to 60 ° C. An equimolar mixture, which had been dried on molecular sieves (4 Á), of 2-amino-methoxypropane and the particular ester was then pumped at a constant velocity through the enzyme bed. The conversions achieved by this means, and the enantiomeric excesses of the slower reaction enantiomer [(S) -l-amino-2-methoxypropane] are compiled in Table 2: Table 2: Comparison of enantiomeric conversions and excesses in the resolution of racemic l-amino-2-methoxypropane with different methoxyacetic esters (The charge corresponds to the amount of the amine / ester mixture pumped through the enzyme bed per gram of Novozym® 435 and hour).

Claims (1)

1. CLAIMS A process for preparing optically active primary amines by: a) reacting the primary amines with an ester of the formula 1: wherein m = 0 or 1, R1 is branched or unbranched C6-Coalkyl or heteroalkyl having 6 to 20 atoms in the backbone, it being possible for the alkyl or heteroaryl radical to be substituted, independent of each other, by 1 to 5 halogen atoms, and / or an oxo group. R 2 is C 1 -C 8 alkyl or phenyl, R 3 is H or C 1 -C 4 alkyl, in the presence of a lipase, and subsequently separating the enantioselectively acylated amine and the unreacted amine. A process for acylating primary amines of formula 2: wherein n = 0 or 1, R4, R5 = independently of each other H, C? -C8 alkyl or phenyl, R6 is Ci-C? alkyl or benzyl, by reaction of the primary amines with an ester of the formula 1: wherein m = 0 or 1, R1 is branched or unbranched Cd-2o alkyl or heteroalkyl having from 6 to 20 atoms in the backbone, it being possible for the alkyl or heteroaryl radical to be substituted, independent of each other, by 1 to 5 halogen atoms and / or an oxo group. R is C? -C8 alkyl or phenyl, R is H or C? -C4 alkyl, in the presence of a lipase. The process as claimed in claim 1, wherein: a) a primary amine of the formula 2: wherein n = O or 1, R4, R5 are, independently of each other H, Ci-Cs alkyl or phenyl, R6 is C6-C6 alkyl or benzyl, is acylated enantioselectively with an ester of formula 1, as set forth in claim 1, in the presence of a lipase. b) the mixture of the enantioselectively acylated amine and the unreacted, optically active amine are separated, and c) where appropriate, the other enantiomer of the amine is obtained by hydrolyzing the acylated amine. The process as claimed in any of claims 1 or 3, wherein step b) or c) is followed by the undesired enantiomer being racemized or hydrolyzed with racemization and returned to the process. The process as claimed in any of claims 1, 3 or 4, wherein the acid substituted with alkoxy or phenoxy resulting from the hydrolysis of the acylated amine is esterified with the alcohol R 10 H, where R 1 has the meaning set forth in claim 1 , and you go back to the process. The process as claimed in any of claims 1 to 5, wherein R 1 is a branched or unbranched C 1 -C 4 alkyl or heteroalkyl having from 6 to 14 atoms in the backbone, it being possible for the alkyl or heteroalkyl radical to be substituted by an oxo group. The process as claimed in any of claims 1 to 6, wherein the ester is selected from the group consisting of: Jb ^ t &? Tí ^? SS ^ ti? S ^ A *. The process as claimed in any of claims 1 to 7, wherein the primary amine is 2-amino-methoxypropane. The process as claimed in any of claims 1 to 7, wherein the acylated amine has the configuration (R) and the unreacted amine has the (S) configuration at the amino carbon. The process as claimed in any of claims 1 to 9, wherein the raw materials are in an anhydrous and acid-free form.