KR19980701914A - Method for Separating Heteroatomic Substituted Primary and Secondary Amine Racemates by Enzyme Catalyzed Acylation Reaction - Google Patents

Abstract

The process for preparing optically active hetero atom substituted primary and secondary amines from racemates thereof

a) Heteroatom-substituted racemic amines are optionally acylated with enantiomers in the presence of a hydrolase using esters in which the acid component contains fluorine, nitrogen, phosphorus, oxygen or sulfur atoms in the vicinity of carbonyl carbons; ,

b) separating a mixture of an optically active heteroatom substituted amine and an optically active heteroatom substituted acylated amine to obtain one enantiomer of the heteroatom substituted amine,

c) if desired, isolating other enantiomers of the heteroatom-substituted amines from the heteroatom-substituted and acylated amines by the amide separation process.

Description

Method for Separating Heteroatomic Substituted Primary and Secondary Amine Racemates by Enzyme Catalyzed Acylation Reaction

The present invention is carried out by reacting a hetero atom substituted amine with an ester in the presence of a hydrolase, and then separating the hetero atom substituted and enantiomer optionally acylated amine from other unreacted enantiomers of the hetero atom substituted amine. And a novel process for separating racemates of heteroatom-substituted primary and secondary amines.

International Publication No. 95/08636 describes a process for separating racemates of primary and secondary amines by reaction with esters in the presence of a hydrolase.

The inventors have surprisingly found that the method described at the outset functions particularly advantageously when the hetero atom substituted amine used is an amine of the formula (I).

In the above formula,

n is 0, 1, 2, 3,

Y is O, S, NH, NR ⁵ ,

R ¹ , R ² are each independently H, alkyl or aryl, or R ¹ and R ² or R ² and R ³ , or R ¹ and R ⁴ together with adjacent carbon atoms form a ring,

R ⁴ is alkyl or arylalkyl,

R ³ , R ⁵ are independently of each other H, alkyl or arylalkyl.

In addition, the present inventors acylation by reacting a hetero atom-substituted amine with an ester whose acid component contains fluorine, nitrogen, phosphorus, oxygen or sulfur atoms in the vicinity of carbonyl carbon by a specific catalytic reaction by a hydrolytic enzyme. It has been found how to prepare primary and secondary amines.

Suitable esters for the process according to the invention are those in which the acid component comprises an electron-rich hetero atom near the carbonyl carbon or one or more acceptor substituents in the form of one or more hetero atoms are arranged near the carbonyl carbon of the acid component.

Heteroatoms should have at least one free electron pair. The hetero atom may be a fluorine, nitrogen, phosphorus, oxygen or sulfur atom.

Heteroatoms should be placed near the carbonyl carbon. This means that the hetero atom is bonded to the carbon at the alpha, beta or gamma position relative to the carbonyl carbon. In addition, heteroatoms may be multiplely bonded to carbon as in cyano groups. Preferred acid components in the ester are those wherein the hetero atom is bonded to an alpha carbon atom. Oxygen is preferred as the hetero atom.

Heteroatoms can also be bonded to other groups, for example alkyl groups. If the hetero atom is for example oxygen, then ether residues are present.

Particularly suitable esters are the following formulae esters.

In the above formula,

R ¹ is C ₁ -C ₁₀ -alkyl,

R ² is C ₁ -C ₁₀ -alkyl, H,

Phenyl substituted by alkoxy or halogen, - R ³ is H, C ₁ -C ₁₀ - alkyl, or unsubstituted or _{NH 2, OH, C 1 -} 4

X is O, S, NR ⁴ ,

Phenyl substituted by alkoxy or halogen, - R ⁴ is H, C ₁ -C ₁₀ - alkyl, or unsubstituted or _{NH 2, OH, C 1 -} 4

n is 0, 1 or 2.

Of these, C _1, such as ethyl methoxyacetate - are preferred alkyl ester-C ₁ of alkoxy acetic _acid-44.

In the process according to the invention a number of enzymes can be used as hydrolase. Proteases and especially lipases are preferably used. In particular, suitable lipases are microbial lipases that can be isolated, for example, from yeast or bacteria. Specifically, suitable lipases are Pseudomonas, for example lipases from Amano P or lipases from Pseudomonas species DSM 8246. More specifically suitable hydrolase are enzymes commercially available from Novo Nordisk (Enzyme Toolbox), in particular lipases SP 523, SP 524, SP 525 and Novozym ^(R ) 435. These enzymes are microbial lipases that can be prepared from yeasts such as Candida antarctica.

In addition, the method according to the invention permits the use of commercially available lipase Chirazyme L1 to L8 (Boehringer Mannheim).

Enzymes can be used in natural or immobilized form. Immobilized enzyme novozyme ^(R) 435 is particularly suitable.

The process according to the invention can be carried out in the presence or absence of a solvent.

In general, organic solvents are suitable as solvents. The reaction is carried out particularly well in ether, for example MTBE, 1,4-dioxane or THF or in hydrocarbons such as hexane, cyclohexane, toluene or halogenated hydrocarbons such as methylene chloride.

The reaction of the ester with the heteroatom-substituted racemic amine by enzymatic catalysis is usually carried out at room temperature. The reaction time is 1 to 48 hours depending on the substrate. Heteroatom substituted secondary amines typically require longer reaction times than heteroatom substituted primary amines. In addition, the low reactivity of the heteroatom-substituted secondary amines can be supplemented by increasing the amount of catalyst compared to the heteroatom-substituted primary amines.

0.5 to 3 moles of ester are added per mole of amine to be reacted. When racemic substrates are used, 0.5 to 3 moles, preferably 0.5 to 1.0 moles, of esters are added.

The amount of enzyme to be added depends on the nature of the hydrolysis catalyst and the activity of the enzyme preparation method. The optimal amount of enzyme for the reaction can be easily determined by simple preliminary tests. As a rule, 1000 units of lipase are added per millimolar of hetero atom substituted amines.

The progress of the reaction can be easily tracked by conventional methods, for example gas chromatography. For racemic separation, it is wise to terminate the reaction after 50% of the hetero atom substituted racemic amine has reacted. This is usually done by removing the catalyst from the reaction mixture, for example by filtration removal of the enzyme.

The selective reaction of the racemic substrate with the ester and the enantiomer results in the corresponding acylated product (amide) from one enantiomer, while the other enantiomer remains unchanged. The resulting mixture of hetero atom substituted amines and amides can be easily separated by conventional methods. For example, extraction or distillation methods are very suitable for separating mixtures of amines and amides.

The process according to the invention is particularly advantageously suitable for the acylation of hetero atom substituted amines of the formula (I). It is also possible to separate the racemates of substantially all hetero atom substituted primary and secondary amines using the process according to the invention. This is particularly well accomplished with primary amino alcohols, in particular aminoalcohols in which R ⁴ is arylalkyl, in particular benzyl or alkyl, in particular methyl.

Another preferred compound of formula I is that R ¹ and R ² together with adjacent carbon atoms in particular (Cis and trance), Compounds forming the ring system of (cis and trans), or R ² and R ³ are particularly , Compounds which are part of the ring system of, or R ¹ and R ⁴ in particular , It is a compound that is part of the ring system.

Surprisingly, the reaction of heteroatom-substituted amines of formula (I) is carried out with an optical yield much higher than the analogous reaction of heteroatom-unsubstituted amines or amines substituted differently to formula (I).

Furthermore, as a result of the high selectivity and reactivity of the process according to the invention only a slight or not excess amount of acylating agent is required, which greatly facilitates subsequent separation and purification reactions.

In addition, the present invention

a) Heteroatom-substituted racemic amines are optionally acylated with enantiomers in the presence of a hydrolase using esters in which the acid component contains fluorine, nitrogen, phosphorus, oxygen or sulfur atoms in the vicinity of carbonyl carbons; ,

b) separating a mixture of an optically active heteroatom substituted amine and an optically active heteroatom substituted acylated amine to obtain one enantiomer of the heteroatom substituted amine,

c) if necessary, isolating other enantiomers of heteroatom-substituted amines from heteroatom-substituted and acylated amines by the amide separation method, thereby converting optically active heteroatom-substituted primary and secondary amines to their racemates. Suitable for manufacturing from

The process according to the invention can be even more economical if the necessary enantiomers are removed after the necessary enantiomers have been removed and racemated once again in the process. By reusing in this way, a total of at least 50% of the required enantiomers can be obtained from the hetero atom substituted racemic amines.

The process according to the invention is suitable not only for the preparation of optically active hetero atom substituted primary and secondary amines but also can form part of complex multistage chemical synthesis, for example in the preparation of pharmaceuticals or crop protectants.

The following examples illustrate the invention.

Example 1

General method of lipase catalyzed acylation of hetero atom substituted amines

10 mmol of heteroatom-substituted primary or secondary amines were dissolved in MTBE (methyl tert-butyl ether, solution at a concentration of about 10%). 11 mmol of ethyl methoxyacetate was added to this solution, and 100 mg of lipase (Pseudomonas species DSM 8246, about 1000 U / mg) was added to initiate the reaction. After the reaction was terminated (12 to 48 hours depending on the hetero atom substituted amine), the enzyme was filtered off and the solution was concentrated under reduced pressure. Methoxyacetamide was obtained in a yield of at least 90%.

Example 2

General Method of Lassimisome Separation

Heteroatom substituted primary or secondary amines were dissolved in MTBE (about 10% by weight). 1 mol of ethyl methoxyacetate per mol of heteroatom substituted racemic amine was added followed by 1 mol of Pseudomonas lipase (DSM 8246) and the suspension was stirred at room temperature. About 10,000 units (10 mg) of lipase were added per mmol of hetero atom substituted amine. After 50% reaction took place (checked by gas chromatography), which took 1 to 48 hours depending on the hetero atom substituted amine, the enzyme was filtered off. A mixture of hetero atom substituted amines and hetero atom substituted and acylated amines (amides) was separated by distillation or extraction.

Example 3

Racemic Separation Method Including Solvent

5 g (49.5 mmol) of trans-2-aminocyclopentanol are dissolved in 20 ml of 1,4-dioxane, 3.3 g (25 mmol) of isopropyl methoxyacetate is added, and 0.1 g of Novozyme 435 ^(R) After addition was shaken at room temperature. After 12 hours, ¹ H-NMR showed a 50% reaction of the amine, the enzyme was filtered off, the filtrate was concentrated and the unreacted amine was removed from the amide by distillation.

Yield: 2.35 g (94%); [a] _D + 9.1 ° (c = 1.74, EtOH); ee = 25%.

Yield: 4.1 g (95%); Ee = 25% by HPLC.

Example 4

Racemic separation method without solvent

5 g (2 mmol) of trans-2-benzoyloxy-1-cyclopentylamine and 1.8 g (13.4 mmol) of isopropyl methoxyacetate are mixed, 0.1 g of Novozyme 435 ^(R) is added and the mixture is allowed to come to room temperature. Shaken. After 120 hours ¹ H-NMR showed a 50% reaction of the amine. The enzyme was filtered off and the 'amine' was removed from the 'amide' by extraction with 10% concentration of hydrochloric acid.

Yield: 2.2 g (88%); [α] _D + 45.6 ° (c = 1, dioxane); Ee = 99.5% by HPLC.

Yield: 4.9 g (92%); [α] _D + 6.0 ° (c = 1, dioxane); Ee = 93% by HPLC.

Example 5

Another racemate separation method

The following reactions (see table) were carried out in the same manner as in Example 3 or 4.

table

Starting material Example of the same manufacturing method % Conversion Amine amides Rotation ^* ee Rotation ^* ee 3 50 -1.5 ° (c = 1, ethanol) 24% - 26% (HPLC) 3 50 + 4.9 ° (HCl adduct) (c = 1, CHCl ₃ ) 95% (HPLC) + 28 ° (c = 1, dioxane) 99.5% (HPLC) 4 50 + 4.8 ° (HCl adduct) (c = 1, CHCl ₃ ) 95% (HPLC) + 27.5 ° (c = 1, dioxane) 99.5% (HPLC) + 9.8 ° (c = 1, dioxane) 4 42 70% - 99.5% (HPLC) *: Rotation was measured using a Na-D line at room temperature.

The table in Example 5 shows that much higher optical purity can be obtained when oxygen atoms are used, for example using 'protected' amino alcohols adjacent to benzyl or methyl groups than when using unprotected amino alcohols.

Claims (8)

Heteroatom-substituted and acylated primary and secondary by reaction of a heteroatom-substituted amine with an acid component in the presence of a hydrolytic enzyme reacting an ester containing fluorine, nitrogen, phosphorus, oxygen or sulfur atoms in the vicinity of carbonyl carbon Process for preparing amines. The heteroatom-substituted amine and the acid component react with an ester containing a fluorine, nitrogen, phosphorus, oxygen or sulfur atom in the vicinity of the carbonyl carbon in the presence of a hydrolase, followed by a heteroatom-substituted and enantiomer selective acylation. Separating the racemates of the hetero atom substituted primary and secondary amines by separating the amines from other unreacted enantiomers of the hetero atom substituted amines. a) Heteroatom-substituted racemic amines are optionally acylated with enantiomers in the presence of a hydrolase using esters in which the acid component contains fluorine, nitrogen, phosphorus, oxygen or sulfur atoms in the vicinity of carbonyl carbons; , b) separating a mixture of an optically active heteroatom substituted amine and an optically active heteroatom substituted acylated amine to obtain one enantiomer of the heteroatom substituted amine, c) a process for preparing optically active hetero atom substituted primary and secondary amines from their racemates, if desired by isolating other enantiomers of the amine from hetero atom substituted and acylated amines by amide separation methods. . 4. The process according to claim 3, wherein in another step after step b) or c) the unwanted enantiomer is racemized and returned to the racemate separation step. A method for preparing an optically active compound, wherein at least one step comprises the method as claimed in claim 2. The process according to claim 2 or 3, wherein the hetero atom substituted primary or secondary amines used are amines of formula (I). Formula I In the above formula, n is 0, 1, 2, 3, Y is O, S, NH, NR ⁵ , R ¹ , R ² are each independently H, alkyl or aryl, or R ¹ and R ² or R ² and R ³ , or R ¹ and R ⁴ together with adjacent carbon atoms form a ring, R ⁴ is alkyl or arylalkyl, R ³ , R ⁵ are independently of each other H, alkyl or arylalkyl. The method of claim 6, wherein a compound of formula (I) wherein Y is O is used. The method of claim 6, wherein R ⁴ is methyl or benzyl.