JPH0543483A - Separating agent for liquid chromatography - Google Patents

Abstract

PURPOSE:To obtain a separating agent useful for optical resolution of beta-amino- alcohol, stably and simply usable, having excellently separating ability, readily producible, having excellent durability by coating a specific complex with a reversed phase-based carrier. CONSTITUTION:A complex of a Schiff base shown by formula I (R1 is lower alkyl, monocyclic aryl lower alkyl, etc.; R2 is monocyclic aryl containing lower alkoxy or monocyclic aryl lower alkoxy as a substituent group; X1 and X2 are H, halogen, etc.) and copper (II) is coated with a reversed phase-based carrier to give the objective separating agent. The complex is obtained by reacting an asymmetric primary amine shown by formula II with a salicylaldehyde derivative shown by formula III to give a Schiff base shown by formula I, reacting the base with a copper (II) salt such as copper acetate and further treating with an alkali. Silica gel subjected to surface treatment with 3-18C alkylsilane is preferable as the reversed-phase carrier.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a new use of a specific asymmetric Schiff base type copper complex. The new use is as a chirality discriminating agent, that is, a mixture of enantiomers of a compound having chirality such as β-amino alcohol in liquid chromatography.
It is used as a separating agent for performing resolution of (for example, racemate).

[0002]

2. Description of the Related Art Separation agents for optical resolution in which a silica gel carrier for reversed phase is coated with an amino acid derivative are already known.
[(1) Chromatographia, Vol. 13, page 677 (1980), (2) JP-A-58-96062.
No. 3, (3) JP-A 64-26523]. Above (1) and
The separating agent described in (2) uses an N-alkyl derivative of proline or hydroxyproline as an amino acid to be supported, and the separating agent described in (3) uses serine as an amino acid to be supported. , N, N-dialkyl derivatives of alanine or norvaline are used.

Further, a separating agent for optical resolution in which a silica gel carrier for reverse phase is coated with an oxyacid derivative is already known [(4) Journal of Liquid Chromatography No. 9]. Vol. 551 (1986)]. The separating agent described in (4) above uses L-tartaric acid mono-n-octylamide as the oxyacid to be carried. Further, it is also known that an asymmetric Schiff base type copper complex (the same as that used in the present invention) is applied to the inner surface of a gas chromatography tube and used [(5) Analytical Chemistry Vol. 29, p. 156]. ..

[0004]

Problems to be Solved by the Invention (1), (2) and
The packing material using the amino acid derivative of (3) shows excellent separability for specific amino acids, but there is no report confirming the separability for β-amino alcohols. the above
The filler using (4) L-tartaric acid mono-n-octylamide shows not only excellent separation ability for amino acids but also for some β-amino alcohols.
Although it shows a slight resolution, it has the disadvantage that the carrier compound must always be contained in the mobile phase in order for it to flow out of the column. In addition,
The technique of gas chromatography (5) is completely different from that of liquid chromatography.

The present invention is particularly suitable for use in the optical resolution of β-aminoalcohols, and is stable, easy to use, and excellent in separability without the above-mentioned drawbacks. The present invention is intended to provide a separating agent for liquid chromatography.

[0006]

That is, the present invention has the general formula (I)

[Chemical 2] [In the formula, * represents an asymmetric carbon. R ₁ represents a lower alkyl group, a monocyclic aryl lower alkyl group, a lower alkoxy-substituted monocyclic aryl lower alkyl group or a lower cycloalkyl lower alkyl group. R ₂ represents a monocyclic aryl group having a lower alkoxy or a monocyclic aryl lower alkoxy as a substituent. X ₁ and X ₂ each represent a hydrogen atom or a halogen atom, or together represent a group —CH ₂ —CH═CH—CH ₂ —] and a complex of a Schiff base and copper (II). The present invention provides a separating agent for liquid chromatography, which is formed by coating a reverse phase carrier.

The above complex (hereinafter referred to as asymmetric copper complex) has the formula
(Ia)

[Chemical 3] It may be represented by [Tetrahedron Letters
(Tetrahedron Letters) 1975 (No. 21) No. 17
07-1710, and JP-B-57-14661
No.], formula (Ib)

[Chemical 4] It is thought that it should be shown in [[Organic synthetic chemistry]
Vol. 43, No. 12, p. 32 and "Catalyst" Vol. 19, No. 3
27-p., Especially p. 329].

The terms used in the above general formula (I) are explained below. "Lower alkyl" means alkyl having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, such as methyl,
It includes ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, hexyl and the like. "Lower alkoxy" represents a group represented by the formula (lower alkyl) -O-. "Monocyclic aryl" includes phenyl unsubstituted or substituted with lower alkyl. “Aryl” includes bicyclic aryl such as naphthyl and biphenylyl in addition to the above monocyclic aryl. The "lower cycloalkyl" includes cycloalkyl having 3 to 6 carbon atoms, for example, cyclopentyl, cyclohexyl and the like. "Halogen" includes fluorine, chlorine, bromine and iodine. When X ₁ and X ₂ together represent the group —CH ₂ —CH═CH—CH ₂ —,
This group, together with the benzene ring to which X ₁ and X ₂ are attached, forms a naphthalene nucleus.

The above-mentioned asymmetric copper complex can be produced by a three-way combination of a corresponding asymmetric amino alcohol, a salicylaldehyde derivative and a suitable cupric salt (for example, Japanese Patent Publication No. 53-43955). The asymmetric primary amine used in the production of the asymmetric copper complex is represented by the following general formula (II).

[Chemical 5] (In the formula, *, R ₁ and R ₂ have the same meanings as described above.)
As R ₂ of the asymmetric primary amine represented by the general formula (II), a phenyl group having a substituent at the 2-position is suitable. Examples of such R ₂ include 2-methoxyphenyl,
2-isopropoxyphenyl, 2-benzyloxyphenyl, 2-methoxy-5-methylphenyl, 2-isopropoxy-5-methylphenyl, 2-benzyloxy-5-methylphenyl and the like can be mentioned. General formula (I
Specific examples of the asymmetric primary amine represented by I) include the following compounds. Ie 2
-Amino-1,1-di (2-methoxyphenyl) -3-phenylpropanol-1,2-amino-1,1-di (2-
Methoxy-5-methylphenyl) -3-phenylpropanol-1,2-amino-1,1-di (2-ethoxyphenyl) -3-phenylpropanol-1,2-amino-
1,1-di (2-isopropoxyphenyl) -3-phenylpropanol-1,2-amino-1,1-di (2-butoxyphenyl) -3-phenylpropanol-1,2-
Amino-1,1-di (2-benzyloxyphenyl) -3
-Phenylpropanol-1,2-amino-1,1-di
(2-butoxy-5-t-butylphenyl) -3-phenylpropanol-1 and the like. These asymmetric primary amines represented by the general formula (II) can be produced by reacting an optically active α-amic acid ester with a Grignard reagent (for example, JP-B-51-13133).

The salicylaldehyde derivative used for the production of the Schiff base represented by the general formula (I) has the following general formula (I
It is represented by II).

[Chemical 6] (In the formula, X ₁ and X ₂ have the same meanings as described above.) Examples of the salicylaldehyde derivative represented by the general formula (III) include the following compounds.
That is, salicylaldehyde, 3,5-dibromosalicylaldehyde, 5-chlorosalicylaldehyde, 2-
Hydroxy-1-naphthaldehyde and the like.

The Schiff base (I) obtained by a conventional method from the compounds (II) and (III) is reacted with a copper (II) salt (eg, acetate) and treated with an alkali to obtain an asymmetric copper complex. The asymmetric copper complex is to be used in the form of a pure optical isomer or an isomer mixture in which one optical isomer is dominant.

[0012]

[Application] When a compound represented by the formula (I) is brought into contact with a compound having chirality such as β-aminoalcohol, physicochemically different qualitatively or qualitatively with respect to two optical isomers. Since they interact with each other, they can be used in liquid chromatography as a chirality discrimination agent. The simplest application in this application is the separation of two optical isomers or the removal of one optical isomer using a separating agent in which an asymmetric copper complex is bound to a solid.

As the separating agent, a solid support whose surface is coated with an asymmetric copper complex is convenient. As the solid carrier, reverse phase carrier granules are used. As such a carrier, an inorganic type or an organic type can be used as long as it has a hydrophobic surface. Preferred are silica gel surface-treated with an alkylsilane having 3 to 18 carbon atoms, porous glass surface-treated with an alkylsilane having an alkyl group having 3 to 18 carbon atoms, and styrene-based, acrylic Examples include hydrophobic polymer gels such as system. The shape of the carrier may be crushed or spherical, and may be porous or non-porous, but 1 to 50 μm
It is preferably a spherical porous carrier having a particle diameter of m. In this case, by using a porous carrier having a large surface area, the coating amount of the asymmetric copper complex can be increased, and the coating amount can be adjusted by controlling the surface area of the carrier. The pore diameter of the porous carrier is 10 to
It is preferable that the surface area is 1000 Å and the surface area is in the range of 1 to 1000 m ² . As a method for coating a solid support with an asymmetric copper complex, there is a method described in the literature [Chromography (Chrom
atographia) Vol. 13, p. 667 (1980)], and a hydrophilic solvent aqueous solution such as alcohol or tetrahydrofuran in which an asymmetric copper complex is dissolved is directly introduced into a column for liquid chromatography packed with a reverse phase carrier.
A coating method is convenient, and a method of mixing a reverse phase carrier and a solution of an asymmetric copper complex and distilling off the solvent under reduced pressure can also be used.

The carrier coated with the asymmetric copper complex is subjected to optical resolution of a racemate by a liquid chromatography method. This can be done, for example, as follows. A column made of glass, stainless steel, titanium or the like having an appropriate length, for example, 1 to 100 cm, is tightly packed with a separating agent, and a liquid feed pump and a sample injector are provided at the inlet side of the column, and On the outlet side, connect a detector such as an ultraviolet detector or an optical rotation detector and, if necessary, a fraction collector. Separation can be performed by a usual method. That is, after injecting the racemate, the eluent is sent by the liquid feed pump to develop the injected racemate in the column and divide it. Suitable eluents include aqueous solutions of copper salts, such as 0.1-10 mM copper sulfate or copper acetate. In this case, water-miscible organic solvent such as methanol or acetonitrile 0-30% by volume
When it is added to the eluent, favorable results are easily obtained. Generally, the retention time of the racemate tends to decrease as the amount of organic solvent added increases. Further, it is extremely preferable to keep the pH of the eluent constant in order to obtain a chromatogram with good reproducibility. The eluate eluted from the column is introduced into a detector such as an ultraviolet detector, each divided enantiomer is detected by the absorbance at 254 nm, and the chromatogram is recorded by a recorder.

[0015]

The separating agent of the present invention can separate various optical isomer mixtures, particularly optical isomers of aromatic amino alcohols, by a chromatographic method. Regarding aromatic amino alcohols, it is difficult to separate norepinephrine, norephedrine, etc., which have been conventionally separable, but it has been difficult to do so. The optical resolution of various racemates such as .beta.-aminocarboxylic acid and 1,2-diamine that coordinate with the above metal ions is possible. Moreover, the separating agent of the present invention has the advantages that it is easy to manufacture and has excellent durability.

[0016]

EXAMPLES The present invention will be described below with reference to examples.
The examples do not limit the invention. Example 1 (+) (R) -N-salicylidene-2-amino-1,1-di
Copper complex of (2-butoxy-5-t-butylphenyl) -3-phenylpropanol-1 (in the general formula (I), R ₁ =
Benzyl, R ₂ = 2-butoxy-5-t-butylphenyl, X ₁ = X ₂ = Schiff base complex corresponding to hydrogen) 0.
The reverse phase carrier was coated with 30 g by the following method. Average particle size 5μm surface-treated with octadecylsilane
First, a mixed liquid of 50% by volume of tetrahydrofuran and 50% by volume of water was flowed through a stainless steel column (inner diameter 4.6, length 150 mm) packed with 1.5 g of porous silica gel having the above. Then, 0.06% of the copper complex of (+) (R) -N-salicylidene-2-amino-1,1-di (2-butoxy-5-t-butylphenyl) -3-phenylpropanol-1 Tetrahydrofuran 50% by volume and water 50
0.5 liter of the volume% mixed solution was passed through the column at a rate of 0.6 ml / min, and then 60 ml of a 1 mmol / l copper sulfate aqueous solution was passed at a rate of 1.0 ml / min.

The column coated as described above was charged with 0.
Inject 1 to 5 μl of each racemic aqueous solution of amino alcohol and amino acid of 01 to 0.05% by weight to give 0.1 to 5
A millimolar / l copper sulfate aqueous solution was sent at a flow rate of 0.2 to 1.0 ml / min to develop a racemate. Tables 1 and 2 show examples of the results obtained by the resolution of racemates of various amino alcohols and amino acids in this manner. The measurement conditions were as follows. Temperature: Room temperature Eluent flow rate: 0.2-1.0 ml / min Detector: Ultraviolet absorption meter (wavelength: 254 nm) In this table, retention time is the racemate after injection into the column and each enantiomer. It means the time from the separation to the elution from the column, that is, the time that each enantiomer holds the column. The separation coefficient α, which represents the optical resolution of the separating agent, is calculated by the following equation. α = (t ₂ −t ₀ ) / (t ₁ −t ₀ ) t ₁ : Retention time of weaker adsorbed enantiomer t ₂ : Retention time of stronger adsorbed enantiomer t ₀ : Dead volume of column The retention time separation coefficient corresponding to .alpha. = 1 indicates that there is no optical resolution at all when .alpha. = 1, and the optical resolution increases as the difference from 1 increases.

[0018]

[Table 1]

[0019]

[Table 2]

The separating agent for (±) -phenylalaninol is shown in FIG. In Fig. 1, the peak number (1) is (-)-
Phenylalaninol, peak number (2) is (+)-
It is phenylalaninol. Further, an example of separating DL-tyrosine is shown in FIG. In Figure 2, peak number
(3) is D-tyrosine, and peak number (4) is L-tyrosine. As described above, it is understood that the column filled with the separating agent of the present invention can completely and efficiently separate the aromatic amino alcohol and the aromatic amino acid.

[Brief description of drawings]

FIG. 1 is a graph showing an elution curve when (±) -phenylalaninol was separated using the separating agent of the present invention.

FIG. 2 is a graph showing an elution curve when DL-tyrosine was resolved using the separating agent of the present invention.

[Explanation of symbols]

 1 (-)-phenylalaninol 2 (+)-phenylalaninol 3 D-tyrosine 4 L-tyrosine

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G01N 30/48 W 8105-2J (72) Inventor Reiko Nakamura 3-1, Niita-cho, Niihama-shi, Ehime 43 Incorporation company Sumika Chemical Analysis Center Niihama Sales Office (72) Inventor Fumiko Ao, 3-135 Kasugadaka, Konohana-ku, Osaka City, Osaka Prefecture Sumika Chemical Analysis Service Co., Ltd.

Claims (1)

[Claims] 1. A compound represented by the general formula (I): [In the formula, * represents an asymmetric carbon. R ₁ represents a lower alkyl group, a monocyclic aryl lower alkyl group, a lower alkoxy-substituted monocyclic aryl lower alkyl group or a lower cycloalkyl lower alkyl group. R ₂ represents a monocyclic aryl group having a lower alkoxy or a monocyclic aryl lower alkoxy as a substituent. X ₁ and X ₂ each represent a hydrogen atom or a halogen atom, or together represent a group —CH ₂ —CH═CH—CH ₂ —] and a complex of a Schiff base and copper (II). A separating agent for liquid chromatography, which is formed by coating a reverse phase carrier.