(19)
(11)EP 0 609 643 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
24.07.1996 Bulletin 1996/30

(21)Application number: 93830506.7

(22)Date of filing:  15.12.1993
(51)Int. Cl.6C07C 227/32, C07C 229/22

(54)

Process for manufacturing L-(-)-carnitine from a waste product having opposite configuration

Verfahren zur Herstellung einer L-(-)Carnitin aus einem Abfallprodukt mit der gegengesetzter Konfiguration

Procédé pour la fabrication de L-(-)carnitine à partir de déchets ayant la configuration apposée


(84)Designated Contracting States:
AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL PT SE

(30)Priority: 21.12.1992 IT RM920915

(43)Date of publication of application:
10.08.1994 Bulletin 1994/32

(73)Proprietor: Sigma-Tau Industrie Farmaceutiche Riunite S.p.A.
I-00144 Roma (IT)

(72)Inventors:
  • Giannessi, Fabio
    I-00189 Rome (IT)
  • Bolognesi, Maria Laura
    I-40133 Bologna (IT)
  • Tinti, Maria Ornella
    I-00182 Rome (IT)
  • De Angelis, Francesco
    I-00136 Rome (IT)

(74)Representative: Fassi, Aldo 
c/o Sigma-Tau Industrie Farmaceutiche Riunite S.p.A., Viale Shakespeare 47
I-00144 Rome
I-00144 Rome (IT)


(56)References cited: : 
US-A- 4 254 053
  
     
    Remarks:
    The file contains technical information submitted after the application was filed and not included in this specification
     
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND OF THE INVENTION


    Field of the Invention



    [0001] The present invention relates to a process for manufacturing L-(-)-carnitine from a starting compound containing an asymmetrical carbon atom having a configuration opposite to that of L-(-)-carnitine. The process of the present invention overcomes the drawbacks of conventional processes which first convert a starting compound into an achiral intermediate, generally crotonobetaine or gamma-butyrobetaine, and then convert the achiral intermediate to L-(-)-carnitine. The process of the present invention uses D-(+)-carnitine or a derivative thereof as a starting compound.

    Discussion of the Background



    [0002] Carnitine contains a single center of asymmetry and therefore exists as two enantiomers, designated D-(+)-carnitine and L-(-)-carnitine. Of these, only L-(-)-carnitine is found in living organisms, where it functions as a vehicle for transporting fatty acids across mitochondrial membranes. Whilst L-(-)-carnitine is the physiologically-active enantiomer, racemic D,L-carnitine has conventionally been used as a therapeutic agent. It is now recognized, however, that D-(+)-carnitine is a competitive inhibitor of carnitine acyltransferases, and that it diminishes the level of L-(-)-carnitine in myocardium and skeletal muscle.

    [0003] It is therefore essential that only L-(-)-carnitine be administered to patients undergoing haemodialysis treatment or treatment for cardiac or lipid metabolism disorders. The same requirement applies to the therapeutic utilization of acyl derivatives of carnitine for treating disorders of the cerebral metabolism, peripheral neuropathies, peripheral vascular diseases and the like. These disorders are typically treated with acetyl L-(-)-carnitine and propionyl L-(-)-carnitine, which are obtained by acylating L-(-)-carnitine.

    [0004] Various chemical procedures have been proposed for the industrial-scale production of carnitine. Unfortunately, these procedures are not stereospecific and produce racemic mixtures of D-(+)- and L-(-)-isomers. It is thus necessary to apply resolution methods in order to separate the enantiomeric constituents of the racemate.

    [0005] Typically, the D,L-racemic mixture is reacted with an optically active acid (e.g. D-(-)-tartaric acid, D-(+)-camphorsulfonic acid, (+)-dibenzoyl-D-(-)-tartaric acid, N-acetyl-L-(+)-glutamic acid and D-(+)-camphoric acid) to obtain two diastereoisomers which can be separated from each other. In the classic process disclosed in U.S. Patent 4,254,053, D-(+)-camphoric acid is used as the resolution agent of a racemic mixture of D,L-carnitinamide, obtaining D-(+)-carnitinamide as a by-product, and L-(-)-carnitinamide which, by hydrolysis, gives L-(-)-carnitine.

    [0006] However, these resolution procedures are complex and costly, and in all cases result in the production of equimolar quantities of L-(-)-carnitine and D-(+)-carnitine or a precursor thereof as by-product, having configuration opposite to that of L-(-)-carnitine. Several microbiological processes have recently been proposed for producing L-(-)-carnitine via stereospecific transformation of achiral derivatives obtained from the huge amounts of D-(+)-carnitine (or of a precursor thereof, such as D-(+)-carnitinamide) which are generated as by-products in the industrial production of L-(-)-carnitine.

    [0007] These processes are generally predicated upon the stereospecific hydration of crotonobetaine to L-(-)-carnitine, and differ principally by virtue of the particular microorganism employed to accomplish the biotransformation of interest. See, for example, the processes disclosed in: EP 0 12 1444 (HAMARI), EP 0 122 794 (AJINOMOTO), EP 0 148 132 (SIGMA-TAU), JP 62275689 (BIORU), JP 61067494 (SEITETSU), JP 61234794 (SEITETSU), JP 61234788 (SEITETSU), JP 61271996 (SEITETSU), JP 61271995 (SEITETSU), EP 0 410 430 (LONZA), EP 0 195 944 (LONZA), EP 0 158 194 (LONZA), and EP 0 457 735 (SIGMA-TAU).

    [0008] On the other hand, JP 62044189 (SEITETSU) discloses a process for stereoselectively producing L-(-)-carnitine starting from gamma-butyrobetaine, which is in turn obtained enzymically from crotonobetaine.

    [0009] All of these processes have several drawbacks. First, D-(+)-carnitine must first be converted to an achiral compound (crotonobetaine, gamma-butyrobetaine) before it can be used as the starting compound in all of the aforesaid microbiological processes.

    [0010] In addition, the microbiological procedures proposed to date have not proven practicable for manufacturing L-(-)-carnitine on an industrial scale for one or more of the following reasons:

    (i) the yield of L-(-)-carnitine is extremely low;

    (ii) the microorganisms must be cultivated in a costly nutritive medium;

    (iii) the microorganism can only tolerate low concentrations [up to 2-3% (w/v)] of crotonobetaine;

    (iv) side reactions occur, such as the reduction of crotonobetaine to gamma-butyrobetaine or the oxidation of L-(-)-carnitine to 3-dehydrocarnitine. These side reactions reduce the final yield of L-(-)-carnitine.


    SUMMARY OF THE INVENTION



    [0011] Accordingly, one object of the present invention is to provide an efficient method for producing L-(-)-carnitine from a derivative of D-(-)-carnitine.

    [0012] The process of the present invention overcomes all of the aforesaid drawbacks of the known processes, allowing high yields of L-(-)-carnitine to be obtained starting from a by-product having configuration opposite to that of L-(-)-carnitine with no need to first convert the starting by-product into an achiral intermediate.

    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS



    [0013] The process of the invention is illustrated in the following reaction scheme:



    [0014] With reference to the reaction scheme, the D-(+)-carnitinamide salt 1, wherein X is any suitable counterion is hydrolyzed to D-(+)-carnitine 2 via conventional procedures (see, for example JP 287065/1989).

    [0015] X is suitably a halogen, preferably chloride; phosphate; perchlorate; metaperiodate; tetraphenylborate; an alkylsulfonate having 1-12 carbon atoms, preferably dodecylsulphonate; trifluoroacetate; tetrahalogenborate; fumarate or an alkylsulphate having 10-14 carbon atoms.

    [0016] D-(+)-carnitine 2 is then converted to the ester 3 in order to protect the carboxyl group. Suitable esters 3 are those wherein R1 is (1) a straight or branched alkoxy group having 1-11 carbon atoms or (2) an arylalkoxy or diarylalkoxy group wherein the aryl is a monocyclic or bicyclic aryl and the alkyl has 1-4 carbon atoms. Suitable monocyclic or bicyclic aryl groups contain 5-12 carbon atoms and can be optionally substituted with a lower alkyl group having 1-4 carbon atoms; an alkoxy group having 1-4 carbon atoms; halogen, preferably fluorine or chlorine; a nitro group or an amino group. Suitable arylalkoxy or diarylalkoxy groups include p-methoxybenzyloxy, 1-naphthalenemethoxy, 2-naphthalenemethoxy, and diphenylmethoxy. A particularly preferred arylalkoxy group is benzyloxy.

    [0017] The esterification of 2 to 3 is carried out via conventional procedures. For instance, when R1 is benzyloxy, the preparation of D-(+)-carnitine benzyl ester is carried out as disclosed in Biochim. Biophys. Acta (1967) 137:98, incorporated herein by reference.

    [0018] The ester 3 is then converted to the acyl derivative 4. Y-, which can be the same as X-, is preferably a counterion imparting solubility to 4. OR is a leaving group wherein R is an alkylsulfonyl group having 1-12 carbon atoms, formyl, trifluoroacetyl p-toluenesulfonyl (tosyl), p-bromobenzenesulfonyl (brosyl) and p-nitrobenzenesulfonyl (nosyl). Preferably, the alkylsulfonyl group is selected from methanesulfonyl (mesyl), trifluoromethanesulfonyl (triflyl), nonafluorobutanesulfonyl (nonaflyl) and 2,2,2-trifluoroethanesulfonyl (tresyl). Mesyl is particularly preferred.

    [0019] The acylation of 3 to 4 is carried out by reacting the ester 3 with an acylating agent RY wherein Y is halogen, or RY itself is an anhydride and R is an acyl group as defined above. Preferably RY is the chloride of the selected acyl group.

    [0020] The acylation reaction is suitably carried out in pyridine, alkylpyridines, or other basic solvents such as triethylamine or in a mixture of an anhydrous, inert organic solvent such as acetonitrile or methylene chloride with a base such as pyridine, lutidine, picoline or polyvinylpyridine.

    [0021] The acylating agent is suitably added at ratios ranging from 1:1 to 1:10, preferably 1:3. The resulting reaction mixture is kept under stirring at temperatures comprised between 0°C and 50°C, for 1-24 hours. Compound 4 is isolated by precipitation with a suitable solvent such as ethyl ether or hexane and purified by dissolving it in water and extracting with an organic solvent.

    [0022] The carboxyl group is restored into compound 4 via known procedures, to yield acyl D-(+)-carnitine 5. In some instances, if needed, compound 4 is subjected to hydrogenation.

    [0023] Hydrogenation of 4 is suitably carried out in an aqueous solution, at pH 2-4, or in methanol at 0°C-25°C, for 1-8 hours, at 1-4 hydrogen atmospheres (1.013-4.053x105Pa), in the presence of a hydrogenation catalyst such as 5% or 10% Pd/C. Acyl D-(+)-carnitine 5 can be isolated by filtering off the catalyst and lyophilizing or concentrating the aqueous solution.

    [0024] Acyl D-(+)-carnitine 5 is then converted to the lactone 6 of L-(-)-carnitine. The lactonization is suitably carried out in an aqueous basic environment: either with NaHCO3 (ratio 1:1) or with an AMBERLITE IRA-402 (manufactured by Rohm & Haas Co., GERMANY) basic resin activated in HCO3- form or with an LA2 resin (Rohm & Haas). The lactone is isolated by evaporating the aqueous solution or precipitating it as a salt (for example, as tetraphenylborate or reineckate).

    [0025] Finally, lactone 6 is suitably converted to L-(-)-carnitine inner salt 7. The lactone is dissolved in water and the resulting solution treated with a base such as NaHCO3 (ratio 1:1), for 8-24 hours.

    [0026] L-(-)-carnitine can suitably be purified from the salts which are formed from the X- anion, from the excess, if any, of the acyl halogenide, from pyridine, and the like, by chromatographing the aqueous solution on a strongly acidic resin such as IR 120 (Rohm & Haas), eluting with water and then with NH4OH, or alternatively eluting first on a strongly basic resin such as AMBERLITE IRA 402 (Rohm & Haas) activated in OH form and thereafter on a weakly acid resin such as AMBERLITE IRC-50 (Rohm & Haas).

    [0027] It should be understood that, whereas the process disclosed above has been described, for the sake of clarity, as a sequence of six distinct operating steps, the corresponding industrial process consists of four steps only. When the process of the present invention is carried out as an industrial process, the acyl D-(+)-carnitine ester 4 can be directly converted to L-(-)-carnitine inner salt 7 without isolating either the acyl D-(+)-carnitine 5 or the lactone 6.

    [0028] In fact, the ester of acyl D-(+)-carnitine 4 is hydrogenated and the hydrogenation catalyst filtered off. The resulting aqueous solution is brought to pH 7-9, preferably 8-9 and kept at this pH value for 30-50 hours yielding L-(-)-carnitine. L-(-)-carnitine thus obtained is purified by removing the salts by treatment with acidic and basic resins.

    [0029] In the following example which describes one embodiment of the process of the invention, the intermediate compounds 4, 5 and 6 were isolated so as to exhaustively characterize them from a physico-chemical standpoint, insofar as these intermediates are novel compounds.

    [0030] It will be, however, apparent to any expert in organic synthesis that the industrial process comprises the following steps only:

    (a) hydrolysis of D-(+)-carnitinamide 1 to D-(+)-carnitine 2;

    (b) esterification of D-(+)-carnitine 2 to the ester 3 to protect the carboxyl group;

    (c) acylation of the hydroxyl group of ester 3 with an acylating agent RY wherein Y is a halogen or RY itself an anhydride, with the resulting formation of a leaving group OR wherein R has the previously defined meanings, thus obtaining the ester 4 of D-(+)-carnitine; and

    (d) conversion of 4 to L-(-)-carnitine inner salt 7.



    [0031] In the following example, the conversion of D-(+)-carnitinamide to D-(+)-carnitine and the conversion of the latter compound to ester 3 are not described for the sake of brevity and since those conversions can be carried out via procedures well-known to any expert in organic synthesis.

    [0032] Moreover, with reference to the numbering of the compound show in the reaction scheme, the lower-case letters "a", "b" and "c" are used in the example to indicate X- = perchlorate, chloride and methanesulfonate, respectively.

    EXAMPLE


    Preparation of methanesulfonyl D-(+)-carnitine benzyl ester perchlorate (4a).



    [0033] Methanesulfonyl chloride (25.77g; 225 mmoles) was added in the space of five minutes to a solution of D-(+)-carnitine benzylester perchlorate (24.4g; 75 mmoles) in anhydrous pyridine (100 mL) cooled in an ice bath. At the end of the addition, the solution was kept under stirring at room temperature for 1 hour and 45 minutes. The solution was then poured into an Erlenmeyer flask containing 500 mL Et2O under stirring.

    [0034] The oily precipitate obtained by decantation of Et2O was taken up with CH2Cl2 (300 mL), the solution was washed with 2N HCl (4x5 mL), saturated solution of NaCl (1x20 mL) and dried over anhydrous Na2SO4.

    [0035] Following evaporation of the organic phase, 22 g of an amorphous solid were obtained. Yield 70%. Differential thermal analysis: it decomposes at about 180°C. [α]

    = + 20.0° [c=1% MeOH)
    TLC = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 28 / 7 /10.5/10.5
    Rf = 0.5
    Elementary analysis for C15H24ClNO9S
     C%H%N%Cl%
    Calculated 41.91 5.63 3.25 8.25
    Found 41.81 4.72 3.28 8.10
    1H NMR ((CD3)2CO): δ7.45-7.30 (m, 5H, aromatics); 5.71-5.62 (m, 1H, -CHOMs); 5.20 (s, 2H, -CH2Ph); 4.24-4.02 (m, 2H, -CH2N+Me3); 3.47 (s, 9H, -N+Me3); 3.30 (s, 3H, CH3SO3-) 3.20 (2H, d, -CH2COO-)
    13C NMR ((CD3)2 CO): δ169.413; 136.685; 129.153; 71.902 67.496; 54.683; 39.387; 38.640
    IR (KBr) = ν(cm-1) 1735 (-C=O), 1341 and 1174 (CH3SO3-)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 9.35 min
    Detector
    = RI Waters 410

    Preparation of methanesulfonyl D-(+)-carnitine benzyl ester chloride (4b).



    [0036] 18.3 g (42.6 mmoles) of methanesulfonyl D-(+)-carnitine benzyl ester perchlorate were dissolved in 300 mL CH3OH and few mL CH3CN (till complete dissolution). The solution thus obtained was percolated through AMBERLYST A-21 resin (300 g) activated by percolating therethrough 1N HCl, then H2O till neutrality and finally CH3OH. Following methanol evaporation, 15.5 of a solid product were obtained.
    Yield: quantitative.
    Differential thermal analysis: it decomposes at about 150°C.
    [α]

    = + 22.6° [c=1% MeOH)
    TLC = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 28 / 7 /10.5/10.5
    Rf = 0.5
    Elementary analysis for C15H24ClNO5S
     C%H%N%Cl%
    Calculated (+3.3% di · H2O) 47.62 6.76 3.70 9.37
    Found 47.88 7.52 3.77 9.04
    1H NMR (D2O): δ7.50-7.45 (m, 5H, aromatics); 5.70-5.62 (m, 1H, -CHOMS); 5.40-5.30 (m, 2H, -CH2Ph); 4.03-3.72 (m, 2H, -CH2N+Me3); 3.25 (s, 3H, CH3SO3-) 3.22 (s, 9H -N+Me3); 3.15 (2H, d, -CH2COO-)
    13C NMR (D20): δ172.789; 137.950; 131.695; 73.929; 70,651; 56,831; 41.475; 40,920
    IR (pure) = ν(cm-1) 1734 (-C=O), 1340 and 1174 (CH3SO3-)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 9.41 min
    Detector
    = RI Waters 410

    Preparation of methanesulfonyl D-(+)-carnitine perchlorate (5a).



    [0037] 10% Pd/C (300 mg) was added to a solution of methanesulfonyl D-(+)-carnitine benzyl ester perchlorate (3.0 g; 7 mmoles) in CH3OH (50 mL).

    [0038] The resulting mixture was kept under stirring in a hydrogen atmosphere at 45 p.s.i. (219.7 kg/m2) in a Parr apparatus for 4 hours. After the catalyst was filtered off and the solvent evaporated, 2.3 g of a white solid product were obtained.
    Yield: quantitative.
    Differential thermal analysis: incipient decomposition at about 170°C.
    [α]

    = + 19.6° [c=1% MeOH)
    TLC = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 20 / 7 /10.5/10.5
    Rf = 0.15
    Elementary analysis for C8H18ClNO9S
     C%H%N%Cl%
    Calculated 28.28 5.34 4.12 10.43
    Found 28.78 5.34 4.15 10.23
    1H NMR (D2O): δ5.68-5.59 (m, 1H, -CHOMs,); 4.05-3.75 (m, 2H, -CH2N+Me3); 3.33 (s, 3H, CH3SO3-) 3.27 (s, 9H -N+Me3); 3.15-3.00 (m, 2H, -CH2COOH)
    13C NMR (D20): δ175.192; 74.423; 70.838; 56.971; 41.662; 40.774
    IR (KBr) = ν(cm-1) 1731 (C=O), 1340 and 1174 (CH3SO3-)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 11.33 min
    Detector
    = RI Waters 410

    Preparation of methanesulfonyl D-(+)-carnitine chloride (5b).



    [0039] 10% Pd/C (500 mg) was added to a solution of methanesulfonyl D-(+)-carnitine benzyl ester chloride (5.1 g; 13.9 mmoles) in H2O (60 mL) acidified to pH 4 with 1N HCl. The resulting mixture was kept under stirring in a hydrogen atmosphere, at 45 p.s.i. (219·7 kg/m2) in a Parr apparatus for 4 hours.

    [0040] The catalyst was filtered off and the aqueous solution lyophilized, giving 3.8 g of a white solid product.
    Yield: quantitative.
    Differential thermal analysis: it decomposes at about 150°C.
    [α]

    = + 29.5° [c=1% H2O)
    TCL = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 20 / 7 /10.5/10.5
    Rf = 0.15
    Elementary analysis for C8H18ClNO5S
     C%H%N%Cl%
    Calculated 34.84 6.58 5.10 12.86
    Found 35.37 6.82 5.24 12.45
    1H NMR (D2O): δ5.70-5.60 (m, 1H, -CHOMs,); 4.06-3.75 (m, 1H, -CH2N+Me3); 3.33 (s, 3H, CH3SO3-) 3.27 (s, 9H -N+Me3); 3.15-3.00 (m, 2H, -CH2COOH)
    13C NMR (D20): δ175.326; 74.530; 70.851; 56.964; 41.668; 40.914
    IR (KBr) = ν(cm-1) 1720 (C=O), 1335 and 1175 (CH3SO3-)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 11.38 min
    Detector
    = RI Waters 410

    Preparation of the lactone of L-(-)-carnitine chloride (6 b).



    [0041] NaHCO3 (0.46 g; 5.4 mmoles) was added to a solution of methanesulfonyl D-(+)-carnitine chloride (1.5 g; 5.4 mmoles) in H2O (25 mL) and the resulting solution was kept under stirring for 20 hours. The solution was then lyophilized, the residue taken up with CH3CN and the undissolved solid filtered off. Following solvent evaporation, 0.98 g, of the title compound were obtained.
    Yield: quantitative.
    TLC = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 28 / 7 /10.5/10.5
    Rf = 0.1
    1H NMR (D2O): δ5.33-5.24 (m, 1H, -CHOCO-); 3.96-3.88 (m, 3H, -CH2N+Me3, -CHHCOO-); 3.53-3.44 (m, 1H, -CHHCOO-); 3.24 (s, 9H, -N+Me3)
    13C NMR (D20): δ172.428; 70.671; 68.094; 56.991; 41.394
    IR (KBr) = ν(cm-1) 1850 (C=O)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 19.23 min
    Detector
    = RI Waters 410

    Preparation of the lactone of L-(-)-carnitine methanesulfonate (6c).



    [0042] An aqueous solution of methanesulfonyl D-(+)-carnitine chloride (1.5 g; 5.4 mmoles) was perchlorated through an IRA-402 resin (30 g) activated to HCO3- form and cooled to 5°C, eluting with water at 5°C till complete elution (controlled by TCL). The eluate was kept at room temperature for 4 hours. Following evaporation of the aqueous solution, 1.3 g of a raw product which was taken up with CH3CN, were obtained. Evaporation of the organic solvent yielded 1 g of a white solid.
    Yield: 80%
    Differential thermal analysis: incipient decomposition at 160°C.
    [α]

    = + 24.7° (c=1% MeOH)
    TCL = silica gel Eluant = CHCl3/MeOH/iPrOH/H2O/AcOH 42 / 28 / 7 /10.5/10.5
    Rf = 0.1
    Elementary analysis for C8H17NO5S
     C%H%N%
    Calculated 40.16 7.16 5.85
    Found 39.61 7.13 5.77
    1H NMR (D2O): δ5.35-5.25 (m, 1H, -CHOCO-); 3.98-3.89 (m, 3H, -CH2N+Me3, -CHHCOO-), 3.54-3.46 (m, 1H, -CHHCOO-); 3.26 (s, 9H, -N+Me3); 2.81 (s, 3H, CH3SO3-)
    13C NMR (D20): δ172.428; 70.671; 68.094; 56.991; 45.320; 41.394
    IR (KBr) = ν(cm-1) 1835 (C=O)
    HPLC
    Column
    = Nucleosil 5-SA; diameter = 4 mm; length = 200 mm
    Eluant
    = CH3CN/KH2PO4 50 mM (65/35) pH = 3.5 with H3PO4
    Flow rate
    = 0.75 ml/min
    Retention time
    = 19.48 min
    Detector
    = RI Waters 410

    Preparation of L-carnitine inner salt (7) from the lactone of L-(-)-carnitine methanesulfonate (6c).



    [0043] NaHCO3 (0.34 g; 4 mmoles) was added to a solution of the lactone of L-(-)-carnitine methanesulfonate (0.96 g; 4 mmoles) in H2O (20 mL) and the resulting solution was kept under stirring at room temperature for 20 hours. The solution was then percolated through AMBERLITE IR-120 resin (20 g) eluting first with water till neutrality to remove methanesulfonic acid and then with 2% NH3 aqueous solution collecting the eluate till complete elution of L-(-)-carnitine inner salt (controlled by TLC).

    [0044] Following evaporation of the aqueous solution, 0.64 g of L-(-)-carnitine inner salt were obtained.

    [0045] Alternatively, the reaction mixture was percolated through IRA-402 resin (20 g) activated to OH- form, eluting with H2O till neutrality. The eluate was then percolated through IRC-50 resin (20 g) till complete elution of L-carnitine inner salt (controlled by TLC). Following evaporation of the aqueous solution, 0.64 g of L-(-)-carnitine inner salt were obtained.
       Yield: quantitative
       The enantiomeric excess (e.e.) was assessed via the following HPLC method, after L-(-)-carnitine was derivatized with a chiral reagent. As chiral reagent, (+)-1-(9-fluorenyl) ethyl chloroformate (FLEC) was used.
    column: Nova-pak C18(4 µ) Cartridge
    length: 100 mm
    diameter: 5.0 mm

    Eluant:



    [0046] 
    Solution A:  5mM tetrabutylammonium hydroxide (TBA+ OH-),
    50 mM KH2PO4 75 mL
    Acetonitrile 25 mL
    brought to pH 7 with 1N KOH
    Solution B:  
    Acetonitrile 75 mL
    5 mM KH2PO4 25 mL


    [0047] 
    Elution schedule
    Time%A%B
    0 100 0
    15 100 0
    16 0 100
    22 0 100
    23 100 0
    30 stop  
    Detector = Perkin-Elmer Fluorimeter Excitation = 260 nm
    Slit = 10 nm
    Emission = 315 nm
    Slit = 5 nm


    [0048] L-(-)-carnitine had previously been derivatized with FLEC via the following method:

    [0049] 50 µL of L-(-)-carnitine solution (prepared by dissolving 10 mg carnitine in 50 mL of 50 mM TBA+OH- brought to pH 7 with concentrated H3PO4) and 200 µL of solution consisting of 1 mL FLEC in 3 mL acetone, were kept under stirring at 80°C for 20 minutes.

    [0050] The solution was cooled and 4 mL of solution A were added thereto, 5 µL of the resulting solution were injected
    L-(-)-carnitine K1 = 5.79
    D-(+)-carnitine K1 = 4.82, absent


    Preparation of L-carnitine inner salt (7) from methanesulfonyl-D-carnitine chloride (5b).



    [0051] NaHCO3 (0.46g; 5.4 mmoles) was added to a solution of methanesulfonyl-D-carnitine chloride (1.5 g; 5.4 mmoles) in H2O (25 mL) and the resulting solution was kept under stirring at room temperature for 20 hours. Further NaHCO3 (0.46; 5.4 mmoles) was then added and the solution was kept under stirring at room temperature for further 20 hours. The title compound was isolated as previously described for the isolation of 7 from 6 b.

    [0052] L-carnitine is obtained from methanesulfonyl-D-carnitine through the formation of the lactone 6, as evidenced by NMR, HPLC, IR and TLC analysis carried out on a sample obtained by lyophilizing a portion of the solution 20 hours following first NaHCO3 addition.


    Claims

    1. A process for producing L-(-)-carnitine from D-(+)-carnitinamide which comprises:

    (a) hydrolyzing a salt of D-(+)-carnitinamide 1 of the general formula

    wherein X- is any counterion to obtain D-(+)-carnitine 2

    (b) esterifying said D-(+)-carnitine 2 to an ester 3 of the general formula

    wherein R1 is (i) a straight or branched alkoxy group having 1-11 carbon atoms or (ii) an arylalkoxy or diarylalkoxy group wherein the aryl group is a monocyclic or bicyclic aryl group containing 5 to 12 carbon atoms and the alkyl group has 1-4 carbon atoms, and wherein said arylalkoxy or diarylalkoxy groups can be optionally substituted with a lower alkyl group having 1-4 carbon atoms, an alkoxy group having 1-4 carbon atoms, halogen, a nitro group or an amino group;

    (c) acylating said ester 3 to an acyl derivative 4 of the general formula

    wherein
    Y-, which is the same as or different than X-, is a counterion imparting solubility to 4 and OR is a leaving group wherein R is selected from an alkylsulfonyl having 1-12 carbon atoms, formyl, trifluoroacetyl, p-toluenesulfonyl (tosyl), p-bromobenzenesulfonyl (brosyl) and p-nitrobenzenesulfonyl (nosyl),
       by reacting 3 with an acylating agent of the formula RY wherein Y is a halogen or RY is an anhydride and R has the above defined meaning, with an organic base, in a basic solvent or in at least one inert organic solvent, at 0°C-50°C, for 1-24 hours;

    (d) converting the COR1 group of said acylderivative 4 to a carboxylic group, to obtain an acyl D-(+)-carnitine 5 of the formula

    (e) lactonizing said acyl D-(+)-carnitine 5 to a lactone 6 of L-(-)-carnitine of the formula

    by treating 5 in a basic environment, and

    (f) converting said lactone 6 to L-(-)-carnitine by treating 6 in a basic solution and isolating L-(-)-carnitine inner salt.


     
    2. The process of claim 1, wherein step (d) comprises hydrogenating said acylderivative 4 in an aqueous solution at pH 2-4, at 0°C-25°C, for 1-8 hours, at 1-4 hydrogen atmospheres (1.013-4.053x105Pa), in the presence of a hydrogenation catalyst.
     
    3. The process of claim 1, wherein said steps (d), (e) and (f) are carried out as a single step, without isolating said intermediate compounds 5 and 6.
     
    4. The process of claim 1, wherein:

    X   is a halogen, phosphate, perchlorate, metaperiodate, tetraphenylborate, or alkylsulfonate having 1-12 carbon atoms;

    R1   is benzyloxy; and

    R   is methanesulfonyl (mesyl), trifluoromethanesulfonyl (triflyl), nonafluorobutanesulfonyl (nonaflyl) or 2,2,2-trifluoroethansulfonyl (tresyl).


     
    5. An ester of acyl D-(+)-carnitine of the formula 4

    wherein
       Y is any counterion;
       R1 is (i) a straight or branched alkoxy group having 1-11 carbon atoms or (ii) an arylalkoxy or diarylalkoxy group wherein the aryl is a monocyclic or bicyclic aryl and the alkyl has 1-4 carbon atoms, optionally substituted with lower alkyl having 1-4 carbon atoms, alkoxy having 1-4 carbon atoms, halogen, nitro or amino; and
       R is an alkylsylfonyl having 1-12 carbon atoms, formyl, trifluoroacetyl, p-toluenesulfonyl (tosyl), p-bromobenzenefulfonyl (brosyl) or p-nitrobenzenesulfonyl (nosyl).
     
    6. The ester of claim 5, wherein
       R1 is benzyloxy, and
       R is methanelfonyl (mesyl),
    trifluoromethanesulfonyl (triflyl), nonafluorobutanesulfonyl (nonaflyl) or 2,2,2-trifluoroethanesulfonyl (tresyl).
     
    7. The ester of Claim 5, wherein
       Y- is perchlorate, chloride or methanesulfonate; and
       R is methanesulfonyl.
     
    8. An acyl D-(+)-carnitine of the formula 5

    wherein Y- is any counterion and
       R is an alkylsulfonyl having 1-12 carbon atoms, formyl, trifluoroacetyl, p-toluenesulfonyl (tosyl), p-bromobenzenefulfonyl (brosyl) or p-nitrobenzenzsulfonyl (nosyl).
     
    9. The acyl D-(+)-carnitine of claim 8, wherein
       R is methanesulfonyl (mesyl), trifluoromethanesulfonyl (triflyl), nonafluorobutanesulfonyl (nonaflyl) or 2,2,2-trifluoroethanesulfonyl (tresyl).
     
    10. A lactone of L-(-)-carnitine of the formula 6

    wherein Y- is any counterion.
     
    11. The lactone of claim 10, wherein
       Y- is a halogen, sulphate, phosphate, perchlorate, metaperiodate, tetraphenylborate or alkylsulphonate.
     


    Ansprüche

    1. Verfahren zu Erzeugung von L-(-)-Carnitin aus D-(+)-Carnitinamid, umfassend:

    (a) Hydrolysierung eines Salzes von D-(+)-Carnitinamid 1 der allgemeinen Formel

    worin X- irgendein Gegenion ist unter Erhalt von D-(+)-Carnitin 2

    (b) Veresterung des D-(+)-Carnitins 2 zu einem Ester 3 der allgemeinen Formel

    worin R1 (i) eine geradkettige oder verzweigte Alkoxy-Gruppe mit 1 bis 11 Kohlenstoffatomen oder (ii) eine Arylalkoxy- oder Diarylalkoxy-Gruppe ist, worin die Aryl-Gruppe eine monocyclische oder bicyclische Aryl-Gruppe ist, umfassend 5 bis 12 Kohlenstoffatome, und die Alkyl-Gruppe 1 bis 4 Kohlenstoffatome hat und worin die Arylalkoxy- oder Diarylalkoxy-Gruppe wahlweise mit einer Niedrigalkyl-Gruppe mit 1 bis 4 Kohlenstoffatomen, einer Alkoxy-Gruppe mit 1 bis 4 Kohlenstoffatomen, Halogen, einer Nitro-Gruppe oder einer Amino-Gruppe substituiert sein kann;

    (c) Acylierung des Esters 3 in ein Acyl-Derivat 4 der allgemeinen Formel

       worin
       Y-, das gleich ist wie X- oder davon verschieden ist, ein Gegenion ist, das 4 eine Löslichkeit verschafft, und worin OR eine Abspaltgruppe ist, worin R ausgewählt ist aus einem Alkylsulfonyl mit 1 bis 12 Kohlenstoffatomen, Formyl, Trifluoracetyl, p-Toluolsulfonyl (Tosyl), p-Brombenzolsulfonyl (Brosyl) und p-Nitrobenzolsulfonyl (Nosyl);
       durch Reaktion von 3 mit einem Acylierungsmittel der Formel RY, worin Y ein Halogen ist oder worin RY ein Anhydrid ist und R die oben angegebene Bedeutung hat, mit einer organischen Base in einem basischen Lösungsmittel oder in zumindest einem inerten, organischen Lösungsmittel bei 0 bis 50°C für 1 bis 24 h;

    (d) Umwandlung der COR1-Gruppe des Acyl-Derivates 4 in eine Carboxyl-Gruppe, unter Erhalt eines Acyl-D-(+)-carnitins 5 der Formel

    (e) Lactonisierung des Acyl-D-(+)-carnitins 5 in ein Lacton 6 von L-(-)-Carnitin der Formel

    durch Behandlung von 5 in einer basischen Umgebung, und

    (f) Umwandlung des Lactons 6 in L-(-)-Carnitin durch Behandlung von 6 in einer basischen Lösung und Isolierung des inneren Salzes von L-(-)-Carnitin.


     
    2. Verfahren nach Anspruch 1, worin der Schritt (d) die Hydrierung des Acyl-Derivates 4 in einer wäßrigen Lösung bei pH 2 - 4 bei 0 - 25°C für 1 - 8 h bei 1 - 4 Wasserstoffatmosphären (1,013 - 4,053 x 105 Pa) in der Gegenwart eines Hydrierungs-Katalysators umfaßt.
     
    3. Verfahren nach Anspruch 1, worin die Schritte (d), (e) und (f) als ein einzelner Schritt ohne Isolierung der Zwischenverbindungen 5 und 6 durchgeführt werden.
     
    4. Verfahren nach Anspruch 1, worin
    X- ein Halogen, Phosphat, Perchlorat, Metaperjodat, Tetraphenylborat oder Alkylsulfonat mit 1 bis 12 Kohlenstoffatomen ist;
    R1 Benzyloxy ist; und
    R Methansulfonyl (Mesyl),
    Trifluormethansulfonyl (Triflyl), Nonafluorbutansulfonyl (Nonaflyl) oder 2,2,2-Trifluorethansulfonyl (Tresyl) ist.
     
    5. Ester von Acyl D-(+)-Carnitin der Formel 4

    worin
    Y- irgend ein Gegenion ist;
    R1 (i) eine geradkettige oder verzweigte Alkoxy-Gruppe mit 1 bis 11 Kohlenstoffatomen oder (ii) eine Arylalkoxy- oder Diarylalkoxy-Gruppe ist, worin das Aryl ein monocyclisches oder bicyclisches Aryl ist und das Alkyl 1 bis 4 Kohlenstoffatome hat, wahlweise substituiert mit Niedrigalkyl mit 1 bis 4 Kohlenstoffatomen, Alkoxy mit 1 bis 4 Kohlenstoffatomen, Halogen, Nitro oder Amino; und
    R ein Alkylsulfonyl mit 1 bis 12 Kohlenstoffatomen, Formyl, Trifluoracetyl, p-Toluolsulfonyl (Tosyl), p-Brombenzolsulfonyl (Brosyl) oder p-Nitrobenzolsulfonyl (Nosyl) ist.
     
    6. Ester nach Anspruch 5, worin
    R1 Benzyloxy und
    R Methansulfonyl (Mesyl), Trifluormethansulfonyl (Triflyl), Nonafluorobutansulfonyl (Nonaflyl) oder 2,2,2-Trifluorethansulfonyl (Tresyl) sind.
     
    7. Ester nach Anspruch 5, worin
    Y- Perchlorat, Chlorid oder Methansulfonat und R Methansulfonyl sind.
     
    8. Acyl-D-(+)-Carnitin der Formel 5

    worin Y- irgendein Gegenion ist und
    R ein Alkylsulfonyl mit 1 bis 12 Kohlenstoffatomen, Formyl, Trifluoroacetyl, p-Toluolsulfonyl (Tosyl), p-Brombenzolsulfonyl (Brosyl) oder p-Nitrobenzolsulfonyl (Nosyl) ist.
     
    9. Acyl-D-(+)-carnitin nach Anspruch 8, worin R Methansulfonyl (Mesyl), Trifluoromethansulfonyl (Triflyl), Nonafluorobutansulfonyl (Nonaflyl) oder 2,2,2-Trifluorethansulfonyl (Tresyl) ist.
     
    10. Lacton von L-(-)carnitin der Formel 6

    worin Y- irgendein Gegenion ist.
     
    11. Lacton nach Anspruch 10, worin Y- ein Halogen, Sulfat, Phosphat, Perchlorat, Metaperjodat, Tetraphenylborat oder Alkylsulfonat ist.
     


    Revendications

    1. Procédé pour la production de L-(-)-carnitine à partir de D-(+)-carnitinamide qui comprend :

    (a) l'hydrolyse d'un sel de D-(+)-carnitinamide 1 de formule générale

    dans laquelle X- est un contre-ion quelconque, pour obtenir la D-(+)-carnitine 2

    (b) l'estérification de ladite D-(+)-carnitine 2 en un ester 3 de formule générale

    dans laquelle R1 est (i) un groupe alcoxy à chaîne droite ou ramifiée, ayant 1 à 11 atomes de carbone, ou (ii) un groupe arylalcoxy ou diarylalcoxy dont le groupe aryle est un groupe aryle monocyclique ou bicyclique contenant 5 à 12 atomes de carbone et le groupe alkyle comporte 1 à 4 atomes de carbone, et où lesdits groupes arylalcoxy ou diarylalcoxy peuvent facultativement être substitués avec un groupe alkyle inférieur ayant 1 à 4 atomes de carbone, un groupe alcoxy ayant 1 à 4 atomes de carbone, un atome d'halogène, un groupe nitro ou un groupe amino ;

    (c) l'acylation dudit ester 3 en un dérivé acylé 4 de formule générale

    dans laquelle Y-, qui est le même que X- ou qui est différent, est un contre-ion conférant de la solubilité à 4 et OR est un groupe partant dans lequel R est choisi parmi un groupe alkylsulfonyle ayant 1 à 12 atomes de carbone, un groupe formyle, un groupe trifluoroacétyle, un groupe p-toluènesulfonyle (tosyle), un groupe p-bromobenzènesulfonyle (brosyle) et un groupe p-nitrobenzènesulfonyle (nosyle),
       par réaction de 3 avec un agent d'acylation de formule RY, dans laquelle Y est un atome d'halogène, ou RY est un anhydride et R est tel que défini ci-dessus, avec une base organique, dans un solvant basique ou dans au moins un solvant organique inerte, entre 0°C et 50°C pendant 1 à 24 heures ;

    (d) la conversion du groupe COR1 dudit dérivé acylé 4 en un groupe carboxylique pour obtenir une acyl-D-(+)-carnitine 5 de formule

    (e) la lactonisation de ladite acyl-D-(+)-carnitine 5 en une lactone 6 de la L-(-)-carnitine de formule

       par traitement de 5 en milieu basique et

    (f) la conversion de ladite lactone 6 en L-(-)-carnitine par traitement de 6 dans une solution basique et l'isolement du sel interne de L-(-)-carnitine.


     
    2. Procédé selon la revendication 1, dans lequel l'étape (d) comprend l'hydrogénation dudit dérivé acylé 4, dans une solution aqueuse à un pH de 2 à 4 entre 0°C et 25°C pendant 1 à 8 heures, sous une pression d'hydrogène de 1 à 4 atmosphères (1,013 à 4,053 × 105 Pa), en présence d'un catalyseur d'hydrogénation.
     
    3. Procédé selon la revendication 1, dans lequel lesdites étapes (d), (e) et (f) sont effectuées en une étape unique, sans isolement desdits composés intermédiaires 5 et 6.
     
    4. Procédé selon la revendication 1, dans lequel :
       X- est un ion halogène, phosphate, perchlorate, métaperiodate, tétraphénylborate ou alkylsulfonate ayant 1 à 12 atomes de carbone ;
       R1 est un groupe benzyloxy ; et
       R est un groupe méthanesulfonyle (mésyle), un groupe trifluorométhanesulfonyle (triflyle), un groupe nonafluorobutanesulfonyle (nonaflyle) ou un groupe 2,2,2-trifluoroéthanesulfonyle (trésyle).
     
    5. Ester de l'acyl-D-(+)-carnitine de formule 4

    dans laquelle
       Y- est un contre-ion quelconque ;
       R1 est (i) un groupe alcoxy à chaîne droite ou ramifiée, ayant 1 à 11 atomes de carbone, ou (ii) un groupe arylalcoxy ou diarylalcoxy dont le groupe aryle est un groupe aryle monocyclique ou bicyclique et le groupe alkyle comporte 1 à 4 atomes de carbone, facultativement substitués avec un groupe alkyle inférieur ayant 1 à 4 atomes de carbone, un groupe alcoxy ayant 1 à 4 atomes de carbone, un atome d'halogène, un groupe nitro ou un groupe amino ; et
       R est un groupe alkylsulfonyle ayant 1 à 12 atomes de carbone, un groupe formyle, un groupe trifluoroacétyle, un groupe p-toluènesulfonyle (tosyle) un groupe p-bromobenzènesulfonyle (brosyle) ou un groupe p-nitrobenzènesulfonyle (nosyle).
     
    6. Ester selon la revendication 5, dans lequel
       R1 est un groupe benzyloxy et
       R est un groupe méthanesulfonyle (mésyle), un groupe trifluorométhanesulfonyle (triflyle), un groupe nonafluorobutanesulfonyle (nonaflyle) ou un groupe 2,2,2-trifluoroéthanesulfonyle (trésyle).
     
    7. Ester selon la revendication 5 dans lequel
       Y- est un ion perchlorate, chlorure ou méthanesulfonate ; et
       R est un groupe méthanesulfonyle.
     
    8. Acyl-D-(+)-carnitine de formule 5

    dans laquelle Y- est un contre-ion quelconque et
       R est un groupe alkylsulfonyle ayant 1 à 12 atomes de carbone, un groupe formyle, un groupe trifluoroacétyle, un groupe p-toluènesulfonyle (tosyle), un groupe p-bromobenzènesulfonyle (brosyle) ou un groupe p-nitrobenzènesulfonyle (nosyle).
     
    9. Acyl-D-(+)-carnitine selon la revendication 8, dans laquelle R est un groupe méthanesulfonyle (mésyle), un groupe trifluorométhanesulfonyle (triflyle), un groupe nonafluorobutanesulfonyle (nonaflyle) ou un groupe 2,2,2-trifluoroéthanesulfonyle (trésyle).
     
    10. Lactone de la L-(-)-carnitine de formule 6

    dans laquelle Y- est un contre-ion quelconque.
     
    11. Lactone selon la revendication 10, dans laquelle
       Y- est un ion halogène, sulfate, phosphate, perchlorate, métaperiodate, tétraphénylborate ou alkylsulfonate.