DE10014961A1 - Enantiomer separation of 3,5-disubstituted 2-oxazolidinones, useful as drugs or intermediates, by chromatography using substituted polysaccharide sorbent and alcohol eluant - Google Patents

Abstract

Chromatographic enantiomer separation of 3,5-disubstituted 2-oxazolidinone compounds (I) is carried out using (a) a sorbent containing a substituted polysaccharide selected from aromatic ester- or carbamate-substituted amylose or microcrystalline cellulose and (b) an eluant containing 1-5C alcohols. Chromatographic enantiomer separation of oxazolidinone compounds of formula (I) is carried out using (a) a sorbent containing a substituted polysaccharide selected from aromatic ester- or carbamate-substituted amylose or microcrystalline cellulose and (b) an eluant containing 1-5C alcohols. [Image] R1, R21-6C alkyl, optionally having one or more CH2 groups replaced by O, S, SO, SO2, NH, CO or C(=NH) and/or having unsaturated C-C bonds; phenyl or biphenyl (both optionally substituted by 1-3 of halo, CN, OH, hydroxyalkyl, cyanoalkyl, alkoxy or alkyl, or by another optionally mono-, di- or tri-substituted aromatic, aliphatic or heterocyclic ring, where the ring systems may be condensed); or a saturated, partially unsaturated or completely unsaturated 5-10 membered mono- or bicyclic heterocyclic residue containing 1 or 2 of N, S, O, CO, SO and/or CO (optionally substituted by 1 or 2 of halo, CN, OH, hydroxyalkyl, cyanoalkyl, alkoxy, alkyl and/or aryl).

Description

The invention relates to the chromatographic separation of enantiomers, in particular by means of continuous processes, of compounds of the formula I,

wherein R ¹ and R ² each independently represent hydroxyalkyl, cyanoalkyl, alkyl or aryl radicals, aralkyl, heterocycles (het) or hetalkyl. In R ¹ and R ² of formula I are preferably each independently
Alkyl is a linear or branched alkyl group with up to 6 carbon atoms, in which one or more CH ₂ groups can also be replaced by -O-, -SO ₂ -, -SO-, -S-, -NH-, -CO -, -C (= NH) - and / or also unsaturated CC bonds,
Aryl is a phenyl or biphenyl ring which can be mono-, di- or trisubstituted by Hal, CN, OH, hydroxyalkyl, cyanoalkyl, Oalkyl or alkyl, a further unsubstituted or again mono-, di- or trisubstituted aromatic, aliphatic ring or heterocyclic in nature, the ring systems also being able to be present in condensed form,
Het is a saturated, partially or completely unsaturated mono- or bicyclic heterocyclic radical having 5 to 10 ring members, 1 or 2 N and / or S and / or O atoms and / or CO or SO or SO ₂ groups can be present and this radical can also be substituted once or twice by Hal, CN, OH, hydroxylalkyl, cyanoalkyl, Oalkyl, alkyl and / or aryl, and
Hal fluorine, chlorine, bromine or iodine.

R1 is preferably monosubstituted phenyl.

Different 3,5-disubstituted 2-oxazolidinones are - especially in enantiomerically pure state - potent drugs in several indication areas. A number of the derivatives of compound II are considered effective antibiotics (Drugs of the Future 1996, 21 (11); 1116-1123),

wherein R can assume the meanings given for R ¹ .

The compound III (formula in Fig. 1), a glycoprotein (GP IIb / IIIa) antagonist with antithrombotic activity is disclosed in DE 195 16 483. All of these compounds are synthesized using complex, multistage processes which involve reaction with enantiomerically pure glycidol derivatives. This is a major disadvantage because the synthetic effort to prepare these educts is very large (Sharpless synthesis) and only moderate ee values (approx. 90%) are achieved.

Important intermediates for the synthesis of III and similar compounds are compounds of the formulas IV and V which result from formula I when R ¹ = 4-cyanophenyl and R ² = hydroxymethyl (formula IV) or R ¹ = 4-cyanophenyl and R ² = methanesulfonyloxymethyl (formula V).

It was surprisingly found that the pure enantiomers of these Compounds (formulas IV and V) can be obtained by chromatography can. Thus, enantiomerically pure compounds of the formula I are in easily accessible.

Basically, enantiomers can be separated on chiral sorbents. A large number of chiral sorbents, for example, are known to the person skilled in the art those based on cellulose derivatives, cyclodextrins, or Poly (meth) acrylamide derivatives with an optically active side chain are known. Such chiral sorbents and their use are for example in EP-A-0 147 804, EP-A-0 155 637, DE 36 19 303, DE 40 05 868 or DE 40 06 923 discloses.  

In particular, chiral separation phases are the substituted polysaccharides included, common for many separation processes.

So far, the enantiomer separation of z. B. 3- (4-cyanophenyl) -5- (hydroxymethyl) -oxazolidin-2-one (compound of formula IV) in a row usual chiral sorbents not possible.

It has surprisingly been found, however, that a separation on amylose tris (3,5-dimethylphenyl carbamate) is possible [Chiralpak ^® AD, Daicel Fa.]: Separation of amylose-tris (3,5-dimethylphenylcarbamate) [Chiralpak ^® AD] was with good separation factors with ethanol as eluent possible both by means of column chromatography (batch method) and by means of continuous "simulated moving bed" chromatography (SMB chromatography). But showed up at comparable sorbents with cellulose-tris- (3,5-dimethylphenylcarbamate) [Chiralcel ^® OD, Fa. Daicel], or cellulose tris (phenylcarbamate) [Chiralcel ^® OC, Fa. Daicel] as the chiral selector no separation.

However, a separation of IV was also possible on microcrystalline Triacetyl cellulose (CTA) both in methanol as the mobile phase and in Ethanol. Similarly, separations on this sorbent are aqueous Eluent possible.

The invention therefore relates to processes for the enantiomer separation of 3,5-disubstituted 2-oxazolidinones of the formula I in which R ¹ and R ² each independently of one another denote hydroxyalkyl, cyanoalkyl, alkyl or aryl radicals, aralkyl, heterocycles (het) or hetalkyl, which thereby are characterized in that the separations are carried out on sorbents which contain substituted polysaccharides selected from the group consisting of amylose or microcrystalline triacetylcellulose substituted with aromatic esters or carbamates, and that eluents containing C ₁ to C ₅ alcohols are used.

The separation of compounds is particularly preferred Sub-formula IV, which acts as intermediate stages for the representation of the Compound of formula III are very important.

Compounds of the formula VI are preferably also separated. Formula VI is a sub-formula of Formula II, wherein R ^{2 represents} a hydroxymethyl group. Compounds according to formula VI are extremely important as intermediates for the compounds of formula II.

These compounds of formula II and their intermediates (formula VI) are described in detail in the literature "Drugs of the Future 1996, 21 (11); 1116-1123)". All the radicals mentioned for R in formula II are contained in R ^{1 of} the general formula I. Thus, all the compounds described there are included in this invention and their separation, or the separation of their precursors, are also the subject of this invention.

As a preferred separator material amylose tris (3,5-dimethylphenyl carbamate) [Chiralpak ^® AD, Fa. Daicel] or triacetyl cellulose is used.

Particularly suitable eluents are C ₁ to C ₅ alcohols, in particular methanol and ethanol, or mixtures thereof. In addition, mixtures of C ₁ to C ₅ alcohols and C ₅ to C ₁₀ hydrocarbons, in particular mixtures of hexane or heptane with 2-propanol, may also be suitable in some cases. Another suitable eluent is acetonitrile - and mixtures with it.

In addition to compound IV, it is also possible to separate the mesylate from compound IV (= compound of the formula V) on chiral stationary phases. However, while in the compound V, the separation was not optimal at substituted with aromatic esters or carbamates of amylose, so could an enantiomer of microcrystalline triacetylcellulose and in particular also on a chiral stationary phase with a poly- [N- acryloyl-phenylalanine] (Chiraspher ^®, Merck KGaA ) be performed. In addition to the alcohols already mentioned, in particular ethers such as dioxane, tetrahydrofuran or methyl tert-butyl ether or mixtures thereof, and also water, or aqueous / alcoholic mixtures, are suitable as eluents for the separation on triacetyl cellulose.

The separation of mesylates of the formula V on triacetyl cellulose or on Chiraspher® are also the subject of this invention. It is also possible to compound IV on poly- [N-acryloyl-phenylalanine ethyl ester] separate, however the separation is not optimal for a preparative purpose enough. One would normally do the separation on triacetyl cellulose or on amylose substituted with aromatic esters or carbamates prefer.

According to the invention, the C ₁ to C ₅ alcohols mentioned as eluents mean methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol; methanol or ethanol are preferred. Acetonitrile can also be used as the eluent. Mixtures of these alcohols, including with acetonitrile, can also be used according to the invention.

According to the invention, mixed eluents or solvents containing alcohols are mixtures of the C ₁ to C ₅ alcohols already mentioned and linear, branched or cyclic C ₅ to C ₁₀ hydrocarbons, the mixtures comprising more than one of the alcohols mentioned and more can exist as one of these hydrocarbons. Examples of the linear, branched or cyclic C ₅ -C ₁₀ -hydrocarbons may be mentioned: n-pentane, isopentane, n-hexane, isohexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane. Likewise, the mixtures can consist of one or more alcohols and acetonitrile or water, with between 1 and 99% alcohols being contained. Mixtures of hydrocarbons with ethers such as dioxane, tetrahydrofuran or methyl tert-butyl ether can also be used, with between 1 and 99% hydrocarbons being present.

Fig. 1 shows the structure of compounds of formula III.

Figures 2 and 3 show elution diagrams; the experimental details can be found in the description of Example 1 and Comparative Example A.

Fig. 4 shows an internal concentration profile of an SMB separation of compound IV on amylose-tris (3,5-dimethylphenylcarbamate) [Chiralpak ^® AD].

The separation according to the invention can be carried out in a conventional batch process be carried out. The separation by means of the continuous is preferred working SMB process. The experimental realization of the Separation was carried out on an SMB system, which after the four Zone model works. Explanations can be found in WO 97/47617. According to the invention, SMB systems can also be used, which according to other models, e.g. B. work the three-zone model. Suitable Process variants are known to the person skilled in the art from the literature.  

The prerequisite for enantiomer separation in preparative The yardstick is the best possible separation (baseline separation, higher Selectivity factor α). Since the usual batch-wise chroma tography at a given time of separation only the area of Separation column is used in which the material to be separated is just opening its way through the column, one needs very powerful Separation columns (high number of theoretical plates). Overall, the conventional column separation especially the time-volume performance not very high; Such processes are correspondingly cost-intensive. When using continuous processes, such as the SMB Chromatography will significantly improve time-volume performance reached. SMB chromatography is a continuous countercurrent process in which the mobile and the stationary phase in opposite directions (Chirality 5, 267 ff. (1993)). In contrast to the batch process, this means that the entire stationary phase is used at any point in time of a separation, which significantly increases the selectivity of the separation system. Compared to the Batch chromatography is therefore required considerably with SMB lower number of theoretical floors.

Due to the counterflow principle, the SMB is for the separation of two material mixtures (e.g. the two enantiomers of a racemate) in an ideal Way suitable.

Even without further explanations, it is assumed that a Expert can use the above description in the broadest scope. The preferred embodiments are therefore only as descriptive, in no way as limiting in any way To understand revelation.  

The complete disclosure of all those listed above and below Registrations and publications are by reference in this Registration introduced.

Examples

The following examples are intended to illustrate the invention; they do not mean a limitation of the inventive concept. Various variants of the enantiomer separation according to the invention using compounds IV and V are described by way of example. The chromatograms for Example 1 and Comparative Example A are shown in Figs. 2 and 3. The chromatograms of the other examples have a comparable appearance.

Insofar as mixtures are specified as the eluent, the Figures in volume ratios (v: v).

example 1 Enantiomer separation of compound IV: 3- (4-cyanophenyl) -5- (hydroxymethyl) - oxazolidin-2-one Experimental conditions

Column: amylose tris (3,5-dimethylphenyl carbamate)
Eluent: methanol
Column dimensions: 8. (93 mm. 50 mm ID)
Flow rate: 171 ml / min
Detection: UV at 215 nm
Temperature: 30 ° C

Result

The first enantiomer is eluted after 10.59 minutes, the second after 14.16 minutes (α = 1.77); see Fig. 2.

Example 2 Enantiomer separation of compound IV: 3- (4-cyanophenyl) -5- (hydroxymethyl) - oxazolidin-2-one Experimental conditions

Column: microcrystalline triacetyl cellulose
Eluent: methanol
Column dimensions: 300. 16 mm ID
Flow rate: 1.0 ml / min
Detection: UV at 240 nm
Temperature: 25 ° C

Result

The first enantiomer becomes after 26.39 minutes, the second eluted after 31.25 minutes (α = 1.25);

Example 3 Enantiomer separation of compound IV: 3- (4-cyanophenyl) -5- (hydroxymethyl) - oxazolidin-2-one Experimental conditions

Column: microcrystalline triacetyl cellulose
Eluent: ethanol
Column dim .: 250. 4 mm ID
Flow rate: 0.5 ml / min
Detection: UV at 254 nm
Temperature: 25 ° C

Result

The first enantiomer becomes after 15.27 minutes, the second eluted after 21.90 minutes (α = 1.58);

Comparative Example A Enantiomer separation of compound IV: 3- (4-cyanophenyl) -5- (hydroxymethyl) oxazolidin-2-one Experimental conditions

Column: cellulose tris (3,5-dimethylphenyl carbamate)
Eluent: ethanol
Column dim .: 250. 4 mm ID
Flow rate: 1.0 ml / min
Detection: UV at 254 nm
Temperature: 25 ° C

Result

Both enantiomers elute separately after 3.20 minutes (α = 1.00); see Fig. 3.

Comparative Example B Enantiomer separation of compound IV: 3- (4-cyanophenyl) -5- (hydroxymethyl) oxazolidin-2-one Experimental conditions

Column: cellulose tris (4-methylphenyl carbamate)
Eluent: ethanol
Column dim .: 250. 4 mm ID
Flow rate: 0.5 ml / min
Detection: UV at 254 nm
Temperature: 25 ° C

Result

Both enantiomers continue to elute separately 8.50 minutes (α = 1.00);

Example 4 Enantiomer separation of compound V: 3- (4-cyanophenyl) -5- (methanesulfonyloxymethyl) - oxazolidin-2-one Experimental conditions

Column: Poly- [N-acryloyl-phenylalanine ethyl ester]
Eluent: methyl tert-butyl ether / THF 70/30
Column dim .: 250. 4 mm ID
Flow rate: 1.0 ml / min
Detection: UV at 265 nm
Temperature: 25 ° C

Result

The first enantiomer becomes after 8.48 minutes, the second eluted after 10.23 minutes (α = 1.29);  

Example 5 Enantiomer separation of compound V 3- (4-cyanophenyl) -5- (methanesulfonyloxymethyl) - oxazolidin-2-one Experimental conditions

Column: microcrystalline triacetyl cellulose
Eluent: methanol
Column dim .: 250. 10 mm ID
Flow rate: 1.0 ml / min
Detection: UV at 265 nm
Temperature: 25 ° C

Result

The first enantiomer becomes after 76.80 minutes, the second eluted after 109.59 minutes (α = 1.51);

Comparative Example C Enantiomer separation of compound V: 3- (4-cyanophenyl) -5- methanesulfonyloxymethyl) oxazolidin-2-one Experimental conditions

Column: cellulose tris (4-methylphenyl carbamate)
Eluent: ethanol
Column dim .: 250. 4 mm ID
Flow rate: 0.5 ml / min
Detection: UV at 254 nm
Temperature: 25 ° C

Result

The first enantiomer becomes after 20.42 minutes, the second eluted after 22.60 minutes (α = 1.14); the selectivity is enough for one  preparative separation does not rule out;

Comparative Example D Enantiomer separation of compound V: 3- (4-cyanophenyl) -5- methanesulfonyloxymethyl) oxazolidin-2-one Experimental conditions

Column: cellulose tris (3,5-dimethylphenyl carbamate)
Eluent: ethanol
Column dim .: 250. 4 mm ID
Flow rate: 1.0 ml / min
Detection: UV at 254 nm
Temperature: 25 ° C

Result

Both enantiomers continue to elute separately 4.68 minutes (α = 1.00);

Example 6 Enantiomer separation using SMB chromatography of compound IV

SMB system: Licosep® 12. 50
Column dimension: 8. (50 mm ID. 100 mm length)
stationary phase: Chiralpak ^®

AD, 20 µm
mobile phase: methanol
Flow rates: Recycling: 248 ml / min
Feed: 17.0 ml / min
Raffinate: 28.0 ml / min
Eluent: 84.0 ml / min
Cycle time: 1.30 min
Feed conc .: 20 g racemate / l
Purity extract: 96.36%
Purity raffinate: 99.20%

Fig. 4 shows the internal concentration profile of the separation conditions described above. The concentrations in g / l are plotted on the ordinate. The numbers 1 to 8 above the curves indicate the numbers of the columns. The solid line of the graphic shows the extract, the broken line the raffinate. Z1, Z2, Z3 and Z4 on the abscissa denote zones 1, 2, 3 and 4. El, Ex, F and R stand for eluent, extract, feed and raffinate.

Summary of examples

Claims (7)

1. Process for the chromatographic separation of compounds of the formula I,
wherein R ¹ and R ² each independently of the other alkyl is a linear or branched alkyl group having up to 6C atoms, in which one or more CH ₂ groups can also be replaced by -O-, -SO ₂ -, -SO-, -S -, -NH-, -CO-, -C (= NH) - and / or also unsaturated CC bonds,
Aryl is a phenyl or biphenyl ring which can be mono-, di- or trisubstituted by Hal, CN, OH, hydroxyalkyl, cyanoalkyl, Oalkyl or alkyl, a further unsubstituted or again mono-, di- or trisubstituted aromatic, aliphatic ring or heterocyclic in nature, the ring systems also being able to be present in condensed form,
Het is a saturated, partially or completely unsaturated mono- or bicyclic heterocyclic radical having 5 to 10 ring members, 1 or 2 N and / or S and / or O atoms and / or CO or SO or SO ₂ groups can be present and this radical can also be substituted once or twice by Hal, CN, OH, hydroxylalkyl, cyanoalkyl, Oalkyl, alkyl and / or aryl, characterized in that the separation on a sorbent containing a substituted polysaccharide selected from the group the amyloses or microcrystalline triacetylcellulose substituted with aromatic esters or carbamates, and an eluent containing C ₁ -C ₅ -alcohols is used. 2. The method according to claim 1, characterized in that enantiomers of the formula IV
be separated. 3. The method according to any one of claims 1 to 2, characterized characterized in that amylose-tris (3,5- dimethylphenyl carbamate) is used. 4. The method according to any one of claims 1 to 2, characterized characterized that as a sorbent microcrystalline Triacetyl cellulose is used. 5. The method according to any one of claims 1 to 4, characterized in that C ₁ to C ₅ alcohols or mixtures thereof are used as eluents. 6. The method according to any one of claims 1-5, characterized characterized that the process in batch is performed. 7. The method according to any one of claims 1-5, characterized characterized that the process continuously after the SMB process is carried out.