DE3707291A1 - Packing for separating optical isomers - Google Patents

Abstract

The invention relates to a packing for separating optical isomers, with a packing component having a hydrophobic surface and an optically active lipophilic crown compound which is adsorbed thereon. By means of the packing amino acids, for example, in the form of aqueous solutions, can be separated in a column.

Description

The invention relates to a new filler for separation an optical isomer and in particular a filler, with which optical isomers are separated from one another by a column Process can separate.

For separating an optical isomer, for example an amino acid, various methods are known, for example Process with formation of diastereomers, Crystal seeding methods, enzymatic methods, Process with insulation films or film insulation and column Method. Of these known methods, it can Column process for a complete optical separation of optical isomers. The column process offers the further advantage that continuous operation is possible if it is combined with the Sarex technology becomes. With most optical column separation processes, which have been proposed for amino acid separation, however, a ligand exchange process is used as the separation principle at. So you have an eluent with a content on metal ions, for example on copper ions, or a  Eluent containing another optical Apply active amino acid as soon as circumstances allow require. These procedures are accordingly unsuitable for the separation of optical isomers.

On the other hand, as a column process in which the ligand exchange principle not applied, only one procedure using a column filler which has been obtained by polystyrene or silicon dioxide gel with an optically active crown connection has been chemically (covalently) linked; J. Am. Chem. Soc., 97 (1975) 1259 and loc. cit. 101 (1979) 3035. However, this method has the disadvantage that not only the number of theoretical floors small, but also separating the filler is problematic and costly is. Another disadvantage is that an organic Solvents can be used as eluents must, so that the process does not involve an aqueous solution of a sample to be separated.

The present invention is based on the foregoing Disadvantages of the prior art.

Accordingly, it is an object of the invention to provide a column filler to provide for the separation of an optical isomer is usable and easy and cheap to manufacture can.

It is also an object of the invention to provide a column filler to provide for the separation of an optical isomer is suitable in which pure water or a volatile, dilute acid as eluent after the adsorption treatment used so that, for example, an aqueous solution an amino acid can be used for separation.  

Other objects, features and advantages of the invention will be apparent derive from the following description.

According to the invention, a column filler is used for the separation proposed an optical isomer, which is characterized is that an optically active, lipophilic crown connection (Crown ether) on a filler component is adsorbed with a hydrophobic surface.

The optically active crown connection which can be used according to the invention essentially comprises all types of crown connections with any optically active group. A crown compound which can be used particularly advantageously according to the invention can be represented by the following general formula (I): where Ar is an optically active, divalent aromatic group which can be represented, for example, by the following general formula (II): wherein A and B each represent a hydrogen atom, an alkyl group (preferably having 1 to 3 carbon atoms), for example a methyl group, or an aryl group, for example a phenyl group.

Furthermore, in the general formula (I), R denotes a hydrogen atom or an alkyl group, in particular a long-chain alkyl group having about 6 to 16 carbon atoms and n an integer from 1 to 2.

The crown compound of the general formula (I) can be prepared, for example, by using an optically active aromatic derivative of the following general formula (III): (in which Ar has the meaning given above and M is an alkali metal) with an alkyl derivative of a 1, omega-substituted penta- or hexaethylene glycol of the following general formula (IV): (wherein X is chlorine, iodine or a tosyloxy group and R and n have the meanings given above) in an equimolar amount in an organic solvent, for example tetrahydrofuran, dioxane or N, N'-dimethylformamide, under inert gas.

The optically active crown connection, the invention  An optical isomer can be used either be in the R-shape or in the S-shape. If, for example the R-form of the optical isomer can be used a column filler can be obtained with the help of which the D form of an isomer after elution of the L form of the Isomer is eluted; if, however, the S form of the isomer a column filler can be obtained with the help of the L-form of an isomer after the D-form is eluted.

According to the invention, the filler component, which carries the optically active crown compound adsorptively, has a hydrophobic surface (reverse phase adsorbent). Such a filler component with a hydrophobic surface can be produced by modifying the surface of a filler material with a hydrophobic compound according to any suitable conventional method. For this purpose, the filler material can be selected from the group consisting of, for example, silicon dioxide, aluminum oxide, magnesium oxide or silicon dioxide / aluminum oxide. The hydrophobic compound can be selected, for example, from the group of
Compounds with any hydrocarbon chains including lower or higher alkyl groups, preferably C _8-18 alkyl groups, for example octyl, dodecyl or octadecyl groups (also including C _1-5 lower alkyl groups, for example methyl, propyl or butyl groups and alkyl groups with more can be used as 18 carbon atoms) and aryl groups, for example phenyl groups, or alkylphenyl groups, or
Select compounds with haloalkyl groups that contain, for example, fluorine or chlorine. The modification of the surface of the filler material with the hydrophobic compound can be carried out by any suitable conventional method, for example by physical adsorption or by chemical bonding, but is not limited to these methods. Also, according to the invention, any commercially available inorganic or organic filler material with a hydrophobic surface can be used as a filler component with a hydrophobic surface without modification.

The filler for separating an optical isomer according to the invention is produced by applying the optically active lipophilic crown compound to the filler component with a hydrophobic surface by physical adsorption. The amount of the crown compound which is adsorptively carried by the filler component having a hydrophobic surface is not particularly limited. For example, you can use 10 ^-15 moles or more per ml of the filler component with a hydrophobic surface. However, there is no upper limit on the amount. It is preferable to use 10 ^-3 mol per ml of the filler component with a hydrophobic surface.

The crown connection is on the filler component preferably adsorptive according to the following procedure applied. So the filler component becomes more hydrophobic Surface placed in a column, after which a solution an optically active fat-soluble crown connection in a mixed solvent of an organic solvent and water of predetermined composition by the Pumps the column in the circuit. To the extent that this How the crown connection works on the filler component adsorptively applied with a hydrophobic surface the concentration of the crown connection in the circulated solution. So it is necessary add additional water to the solution at a timed rate, to the solubility of the crown connection in the  Circuit solution and lower it in the circuit through the pillar. You repeat the way you work, to obtain a filler according to the invention which the filler component with a hydrophobic surface and the crown compound adsorbed thereon. The said organic solvents can be selected from the group consisting of alcohols, such as methanol, ethanol or propanol, acetonitrile or Tetrahydrofuran be chosen.

The column loaded with the filler according to the invention can be used to separate different optical Isomers can be used. For example, it can be useful for the optical separation of an amino compound use, for example an amino acid or an amine. It is particularly suitable for the optical separation of a Compound in which the amino group is attached to an asymmetric Carbon atom is bound, for example for optical Separation of racemic phenylglycine, methionine, leucine, Glutamic acid, phenylalanine, cysteine, tyrosine, alanine or Phenylethylamine. You can also use a column with the Filler according to the invention is loaded for separation optically active organic ions using the Use ion interaction.

As an eluent for the column, which according to the filler the invention is loaded, you can pure water and the dilute aqueous solution of a salt or an acid use. A dilute acid solution is preferably used, because it shows an increased separation effect.

The invention is explained in more detail below by examples.

example 1 A: Column for separating an optical isomer

There was an optically active crown compound of the R form of the above general formula (I), in which Ar is 3,3'-diphenyl-1,1'-binaphthyl-2,2'-diyl, R is a hydrogen atom and n = 1, in an amount of 58 mg in about 80 percent. aqueous methanol solution dissolved; the solution was circulated for 24 hours through a column (ODS column; diameter 4 mm, length 125 mm) using a filler component with commercially available octadecyl silicon dioxide (ODS; particle size 5 µm) with a hydrophobic surface using a pump . Water was added during the circulation to gradually reduce the amount of methanol in the recycle solution so that the recycle solution eventually contained about 40% methanol. As a result, the crown connection was almost completely adsorbed on the ODS feed to the column. The amount of the crown compound on the ODS was 5.8 × 10 ^-5 mol / ml ODS.

B: Separation of an optical isomer

It became a high performance liquid chromatography device with a pump (DIP-1 type from Nippon Bunko Co.), a UV detector (S-3101A type from Sohma Kohgaku Co.) and was provided with a Rheodyne sample injector, with a separation column for optical isomers connected according to the above Working method had been manufactured according to which one different racemic amino acids and amines separated. The results are shown in Table 1.

In the separation process, 10 ^-2 M HClO _{4 was used} as the eluent; the process was carried out at a temperature of 18 ° C and 2 ° C, respectively. The amount of each sample was 10 ^-8 mol. The amino compounds were determined by measuring the UV adsorption at 200 and 254 nm.

Table 1: Optical separation of racemates

Table 1 shows that the L-form before the D-form was eluted at each amino acid while the D form was eluted before the L form in phenylethylamine. The degree of separation was increased or improved when looking at the column temperature lowered. Leave at the column temperature of 2 ° C 14 amino acids, namely alanine, leucine, isoleucine, Allo-isoleucine, glutamic acid, phenylalanine, methionine, Threonine, valine, tyrosine, cyctein, lysine, arginine and Divide phenylglycine completely into its enantiomers. In particular, a degree of separation of Reach 9.

Commercially available DL isoleucine is generally a mixture of four stereoisomers, namely the D, L, D-Allo and L-Allo shape. It was found that these isomers with the column with the column filler according to the invention let separate. So these four isomers could be broken down into three Separate peaks that the L-form / L-Allo-Form, the D-Allo- Form and the D-shape corresponded. In this case it was on a column connection of the column filler used R-form adsorbed. When using a column filler with S-shaped crown compound adsorbed thereon (below Example 2) the L-Form / L-Allo-Form isomer mixture completely separate into the two isomer components.

The separation effects of various eluents are shown in Table 2. Methionine (10 ^-7 mol) was used as the sample to be separated at a column temperature of 18 ° C. When an aqueous solution of perchloric acid (HClO ₄ ) was used as the eluent, the retention time of the methionine gradually decreased with decreasing concentration of the eluent, so that the methionine was eluted more rapidly. For the other dilute acid solutions, this phenomenon occurred when a more hydrophilic acid was used. However, the degree of separation was practically not changed in the tests. The fact that the optical resolution remained practically the same when pure water was used as the eluent shows that the resolution can be carried out extremely practically.

Table 2: Influence of the eluent on the optical separation of methionine

Example 2

Example 1 was essentially repeated to prepare an ODS column, with the exception that 39 mg of an optically active S-form crown compound of the above general formula (I) were used, in which Ar 3,3'-diphenyl-1,1 '-binaphthyl-2,2'-diyl, R is a hydrogen atom and n = 1. The amount of the crown compound on the filler component with the hydrophobic surface was 3.9 × 10 ^-5 mol / ml. The amino acids were subjected to an optical separation treatment with the modified ODS column. The results are shown in Table 3. The column temperature was 2 ° C, using HClO ₄ (10 ^-2 m) as the eluent and each sample in an amount of 10 ^-8 mol.

In this example, the amino acids were preformed to the D form the amino acids of the L-form differing from Example 1.

Compared to Example 1, the degree of separation (alpha) was everyone Sample according to a decreasing amount on ODS adsorbed crown connection.

Table 3: Optical separation of amino acids when using an S-type crown connection

Example 3

It became an optically active crown compound of the R form of the above general formula (I), in which Ar is 3,3'-diphenyl-1,1'-binaphthyl-2,2'-diyl, RC ₁₄ H ₂₉ and n = 1 , in amounts of 58 mg in about 90 percent. Methanol solution dissolved in water according to Example 1. The proportion of water in the solution was gradually increased until the methanol content finally reached approximately 70%, so that the crown compound was adsorbed on an ODS column (diameter 4 mm, length 125 mm). The amount of the crown compound adsorbed was 4.4 × 10 ^-5 mol / ml. The results of the separation of various racemic amino acids into the respective optical isomers using the column mentioned are explained in Table 4. A column temperature of 2 ° C and 10 ^-2 M HClO _{4 were used} as the eluent, the amount of each sample being 10 ^-7 mol. In this example, the L-form of the respective amino acid was eluted before the D-form of the amino acid as in Example 1, so that the D-form of the respective amino acid was separated from the L-form of the amino acid. A precise determination of the respective amino acid was also carried out. The peak in the chromatogram increased linearly with the amino acid concentration, the measurement error being less than 1%. Table 5 shows the temperature dependence of the DL degree of separation alpha for phenylglycine. The degree of separation alpha increased with falling column temperature as in Example 1.

Table 4: DL degree of separation for amino acids

Table 5: Temperature dependence of the DL degree of separation for phenylglycine

From the above examples it follows that the Produce filler according to the invention easily and cheaply leaves and very suitable for the separation of optical isomers is. For a column made with the filler according to the invention is fed, you can use pure water and diluted Use acid as the eluent so that the amino acid solution for a separation in the form of a aqueous solution can be prepared. You can also do that Filler according to the invention not only in a small one Pillar for chemical analysis, but also in technical Use a scale for technical processes.

The revelation also includes the corresponding English Text.

Claims (6)

1. filler for separating an optical isomer with a filler component with a hydrophobic surface and an optically active, lipophilic crown connection the filler component. 2. filler for separating an optical isomer after Claim 1, characterized in that the optically active, lipophilic crown connection on the Filler component adsorbed with a hydrophobic surface is. 3. Filler for separating an optical isomer according to claim 1 or 2, characterized by a lipophilic crown compound of the following formula: wherein Ar represents an optically active divalent aromatic group, R represents a hydrogen atom or an alkyl group and n is an integer from 1 to 2. 4. filler for separating an optical isomer according to claim 3, characterized in that Ar in the formula means an optically active divalent aromatic group of the following formula: wherein A and B each represent a hydrogen atom, an alkyl group or an aryl group. 5. filler for separating an optical isomer after one of the preceding claims, characterized in that the filler component with hydrophobic Surface comprises a filler material, the Surface modified with a hydrophobic compound is. 6. filler for separating an optical isomer according to claim 1, characterized in that the amount of the optically active crown compound on the filler component with a hydrophobic surface is 10 ^-5 mol or more per ml of the filler component.