EP2074109A1

EP2074109A1 - Method of production of enantiomer-enriched alkylene carbonates

Info

Publication number: EP2074109A1
Application number: EP07802871A
Authority: EP
Inventors: Harald GRÖGER; Wolfgang Wienand; Claudia Rollmann; Helge Werner; Dietmar Reichert
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2006-09-21
Filing date: 2007-08-24
Publication date: 2009-07-01
Also published as: CN101516866A; DE102006044519A1; WO2008034685A1

Abstract

The invention relates to a method of production of enantiomer-enriched alkylene carbonates (I), in particular (R)-propylene carbonate (I), by enantioselective enzymatic reduction of an O- substituted hydroxyacetone of type (II) and subsequent cyclization of the alcohol formed of type (III) and compounds of formula (III) and their regioisomers (IV).

Description

Method of production of enantiomer-enriched alkylene carbonates

The present invention relates to a method of production of enantiomer-enriched alkylene carbonates of formula (I)

, in particular (R) -propylene carbonate (Ia; R¹ = methyl) , by enantioselective enzymatic reduction of an O-substituted hydroxyacetone of type (II)

and subsequent cyclization of the alcohol formed of type (III)

or of their regioisomers (IV)

, which are formed by rearrangement from compounds of formula (III) . Enantiomer-enriched alkylene carbonates, in particular

(R) -propylene carbonate, are of pharmaceutical interest. Thus, (R) -propylene carbonate is used as an intermediate in the production of pharmaceutical active substances, as described in, among others, EP1243590,

EP915894 and L. M. Schultze, H. H. Chapman, N. J. P.

Dubree, R. J. Jones, K. M. Kent, T. T. Lee, M. S.

Louie, M. J. Postich, E. J. Prisbe, J. C. Rohloff, R.

H. Yu, Tetrahedron Lett. 1998, 39, 1853-1856.

(R) -propylene carbonate is generally synthesized "indirectly" in a two-stage process, in which, starting from chiral, preferably enantiomerically-pure (R)- propanediol already synthesized, isolated and purified in a first step, cyclization to (R) -propylene carbonate is carried out in a second step. Cyclization is carried out for example by reaction with a dialkyl carbonate in the presence of a base as catalyst in an alcohol as solvent (EP1243590, EP915894 and L. M. Schultze, H. H. Chapman, N. J. P. Dubree, R. J. Jones, K. M. Kent, T. T. Lee, M. S. Louie, M. J. Postich, E. J. Prisbe, J. C. Rohloff, R. H. Yu, Tetrahedron Lett. 1998, 39, 1853- 1856) . Using dimethyl carbonate as the dialkyl carbonate component, (R) -propylene carbonate is obtained at 65% yield (EP943612) . A number of methods are known for the production and isolation of (R) -1,2- propanediol, for example the separation of racemic mixtures of rac-1, 2-propanediol via oxidation of the

(S) -enantiomer (T. Kometani, H. Yoshii, Y. Takeuchi, R.

Matsuno, J. Ferm. Bioeng. 1993, 76, 414-415, T. Kometani, Y. Morita, H. Yoshii, Y. Kiyama, R. Matsuno, J. Ferm. Bioeng. 1995, 80, 180-184, JP2004041076, US2006019359) , the separation of racemic mixtures of rac-propylene oxide via epoxide opening (Y. Song, X. Yao, H. Chen, C. Bai, X. Hu, Z. Zheng, Tetrahedron Lett. 2002, 43, 6625-6627, D. E. White, E. N. Jacobsen, Tetrahedron: Asymmetry 2003, 14, 3633-3638, S. S. Thakur, W. Li, S. -J. Kim, G. -J. Kim, Tetrahedron Lett. 2005, 46, 2263-2266) or the asymmetric reduction of hydroxyacetone (DE3830253, K. Yamada-Onodera, N. Kawahara, Y. Tani, H. Yamamoto, Eng. Life Sci. 2004, 4, 413-417, JP 7059592) . In addition, the production of (R) -1, 2-propanediol starting from the already chiral compound (R) -glycidol has been reported (EP1243590, EP915894 and L. M. Schultze, H. H. Chapman, N. J. P. Dubree, R. J. Jones, K. M. Kent, T. T. Lee, M. S. Louie, M. J. Postich, E. J. Prisbe, J. C. Rohloff, R. H. Yu, Tetrahedron Lett. 1998, 39, 1853-1856) . Disadvantages of this are generally the production of the chiral compound - as the most cost-intensive stage - in a first step that is separate from the subsequent cyclization, and the need to isolate (R) -1, 2-propanediol . This therefore leads to high overall costs, especially when the losses in yield in the two stages are taken into account.

An alternative method for the production of (R) - propylene carbonate is the separation of racemic mixtures of rac-propylene oxide with carbon dioxide in the presence of a chiral metallic catalyst (X. -B. Lu, B. Liang, Y. -J. Zhang, T. -Z. Tian, Y. -M. Wang, C-X. Bai, H. Wang, R. Zhang, J. Am. Chem. Soc. 2004, 126, 3732-3733.). Using a catalyst system comprising a chiral salen-cobalt (III) complex and a quaternary ammonium salt, preferably tetra- (n-butyl) ammonium chloride, the desired reaction takes place with formation of (R) -propylene carbonate with an enantioselectivity of up to 70% ee at a conversion of - A -

40%. A disadvantage of these methods, apart from the enantioselectivity of max. 70% ee, which is too low for industrial pharmaceutical applications, is the general limitation of separation of racemic mixtures, with a maximum achievable conversion of (R) -propylene carbonate of 50%.

Furthermore, (R) -propylene carbonate can be produced starting from its racemate via enzymatic racemate separation (JP3747640). In the aqueous reaction mixture, using a microorganism Cryptococcus laurentii, the remaining (R) -propylene carbonate is obtained with an enantioselectivity of 98% ee . A disadvantage with this procedure is once again the general limitation of racemate separations with a maximum achievable conversion of (R) -propylene carbonate of 50%.

With a view to an economically highly attractive process, ideally the - most cost-intensive - key step should always be combined with the cyclization without isolation and in particular purification of the respective enantiomerically-pure intermediate. Accordingly, in principle the most efficient synthetic route is undoubtedly the direct, asymmetric conversion of a corresponding inexpensive and readily available prochiral substrate to the enantiomerically-pure intermediate and subsequent cyclization of the nonisolated or purified intermediate to (R) -propylene carbonate. Moreover, the asymmetric conversion of a prochiral substrate to the desired product would offer the possibility of quantitative conversion (with theoretically 100% conversion), which is a clear advantage especially relative to the currently known methods of racemate separation with max. 50% conversion .

However, no methods are known for this proposed

"direct" synthesis of (R) -propylene carbonate starting from an inexpensive, prochiral compound - with the exception of the aforementioned production of (R) -1,2- propanediol from hydroxyacetone and subsequent cyclization in a second step to (R) -propylene carbonate. In view of the large number of methods that have been developed for the production of (R) -propylene carbonate, this is extremely surprising.

The problem of the present invention was therefore to provide a method of production of enantiomer-enriched alkylene carbonates, in particular (R) -propylene carbonate, by which this compound can be produced in a simple manner starting from inexpensive prochiral compounds at a high degree of conversion and with high enantiomeric excess. Another problem of the present invention is to provide novel, particularly suitable intermediates for the production of enantiomer-enriched alkylene carbonates, especially (R) -propylene carbonate. A particular problem of the present invention was to design the production of enantiomer- enriched alkylene carbonates, especially (R) -propylene carbonate, in such a way that from the technical standpoint, the synthesis is advantageous against a background of economic and ecological considerations and in these respects is superior to the syntheses of the state of the art.

These problems, and others that follow obviously from the state of the art and are not further specified, are solved by a method according to Claim 1. Preferred embodiments of the method according to the invention are presented in the subclaims . The problem of providing novel, particularly suitable intermediates for the production of enantiomer-enriched alkylene carbonates, in particular (R) -propylene carbonate, is solved with compounds according to Claim 12.

In a method of production of enantiomer-enriched alkylene carbonates of general formula (I),

in which

R¹ represents a linear or arbitrarily branched (Ci-Cs) - alkyl or a (C3-C8) -cycloalkyl residue, the problem was solved in a simple, but no less advantageous manner for that, in that a derivative of formula (II)

in which

R² represents (Ci-C₈) -alkyl, (C₂-C₈) -alkoxyalkyl, (C₆- Ci₈) -aryl, (C₇-Ci₉) -aralkyl, (C₃-Ci₈) -heteroaryl, (C₄-Ci₉)- heteroaralkyl, (Ci-C₈) -alkyl- (C₆-Ci₈) -aryl, (Ci-C₈) -alkyl- (C₃-Ci₈) -heteroaryl, (C₃-C₈) -cycloalkyl, (Ci-C₈) -alkyl- (C₃-C₈) -cycloalkyl, (C₃-C₈) -cycloalkyl- (Ci-C₈) -alkyl or in the case when R² only represents a negative charge, can also signify their salts, is first converted to an enantiomer-enriched alcohol of formula (III) and this compound of formula (III)

or the regioisomers of formula (IV) formed from the alcohols of formula (III) by rearrangement

is then cyclized to the enantiomer-enriched alkylene carbonate (I) . By means of this stated procedure, the cyclic carbonates can be obtained at yields greater than 90% and correspondingly good enantiomeric purities also greater than 90% ee . The drop in yield through formation of by-products as a result of cleavage of the unstable carbonates in the aqueous medium, which was certainly to be expected, is surprisingly only observed to a negligible extent or not at all.

In particular, the method is used for the production of (R) -propylene carbonate, starting from the corresponding derivative (R = methyl in formula II above) .

The present invention includes, as a central step, enantioselective reduction of the keto function present in molecule (II) . The reduction can in principle be carried out by the methods that would be considered for this by a person skilled in the art. Catalytic methods are advantageous in particular. In this respect, conversion of the derivative of formula (II) to the alcohol of formula (III) using a chemical catalyst and/or biocatalyst is especially advantageous. Use of a biocatalyst is quite particularly advantageous. All the enzymes that a person skilled in the art would consider for the present purpose may be considered as the biocatalyst. However, alcohol dehydrogenases or glycerol dehydrogenases have in particular proved advantageous for the reduction in question. Preferably a person skilled in the art selects alcohol dehydrogenases for the stated purpose. All enzymes of this type that are known to a person skilled in the art can in principle be used as alcohol dehydrogenases that can be used as suitable biocatalysts in the method according to the invention, provided they are able to catalyse the conversion/reaction employed in the method according to the invention. This can be established in routine experiments. These dehydrogenases preferably originate from bacterial microorganisms or yeasts. The use of at least one alcohol dehydrogenase from the organisms Lactobacillus kefir (LK-ADH) , Lactobacillus brevis (LB-ADH) or Thermoanaerobium brockii (TB-ADH)

(ADH from Lactobacillus kefir: a) EP 456107; b) C. W.

Bradshaw, W. Hummel, C-H. Wong, J. Org. Chem. 1992,

57, 1532-1536; c) PCT/EP2005/06215. ) (ADH from L. brevis: a) EP796914; b) K. Niefind, B. Riebel, J. Muller, W. Hummel, D. Schomburg, Acta Crystallogr . , Sect. D: Biol. Crystallogr. 2000, D56, 1696-1698; c) M. Wolberg, W. Hummel, C. Wandrey, M. Muller, Angew. Chem. Int. Ed. 2000, 39, 4306-4308) (ADH from T. brockii: a) E. Keinan, E. K. Hafeli, K. K. Seth, R. Lamed, J. Am. Chem. Soc. 1986, 108, 162-169; b) T. R. Rδthig, K. D. Kulbe, F. Buckmann, G. Carrea, Biotechnol. Lett. 1990, 12, 353-356; c) J. Peters, M. R. KuIa, Biotechnol. Appl. BioChem. 1991, 13, 363-370) is preferred.

The alcohol dehydrogenase (s) can in principle be used in the method according to the invention in the forms that are familiar to a person skilled in the art (see below) . However, as alcohol dehydrogenases are, as oxidoreductases, cofactor-dependent enzymes, for successful execution of the reduction, the cofactor required for the enzyme used must be present in sufficient quantity in the reaction mixture, in order to ensure complete conversion of the ketone. As these cofactors are relatively expensive molecules, on economic grounds the use of the minimum possible amounts of cofactor is a decisive advantage. One possible way of being able to use less cofactor than the stoichiometrically required amount is to regenerate it with a second biocatalyst that is present in the charge. In such a system, enzymatic conversion of a (e.g. organic) compound takes place with "consumption" of a cofactor, and this cofactor is regenerated in situ by a second enzymatic system. As a result this leads to a reduction of the amount of expensive cofactors required. Thus, reaction by means of a coupled enzymatic system represents an advantageous technique. Coupled systems of this kind are mentioned for example in DE-A 10233046 or DE-A 10233107. Thus, the variant in which the derivative of formula (II) is reduced with the aid of a coupled enzymatic system, with the coupled enzymatic system comprising an alcohol dehydrogenase and an enzyme that regenerates the cofactor of the alcohol dehydrogenase, is preferred. The enzyme that regenerates the cofactor that is used, depends on the one hand on the cofactor used, but on the other hand also on the cosubstrate that is to be oxidized or reduced. Some enzymes for the regeneration of NAD(P)H are mentioned in Enzyme Catalysis in Organic Synthesis, Ed. : K. Drauz, H. Waldmann, 1995, VoI I, VCH, p.721. The so-called formate dehydrogenase (FDH) (see also DE-A 10233046) and alternatively the so- called glucose dehydrogenase (a) M. Kataoka, K. Kita, M. Wada, Y. Yasohara, J. Hasegawa, S. Shimizu, Appl . Microbiol. Biotechnol. 2003, 62, 437-445; b) PCT Pat. Appl. WO2005121350, 2005) are of commercial interest and are obtainable on a large scale, and are used at present for the synthesis of amino acids and alcohols, and are accordingly advantageous . They can therefore also be used preferably in the method according to the invention for the regeneration of the cofactor. Quite especially preferably the FDH is derived from the organism Candida boidinii. Further-developed mutants thereof can also be used, e.g. such as are described in DE-A 19753350. Moreover, a glucose dehydrogenase from Bacillus subtilis (see inter alia: W. Hilt, G. Pfleiderer, P. Fortnagel, Biochim. Biophys. Acta 1991, 1076, 298-304) or Thermoplasma acidophilum (see inter alia: J. R. Bright, D. Byrom, M. J. Danson, D. W. Hough, P. Towner, Eur. J. BioChem. 1993, 211, 549-554) can preferably be used.

Regeneration can, however, also be substrate-coupled, for example using isopropanol (examples of the technique of cofactor regeneration with isopropanol: a) W. Stampfer, B. Kosjek, C. Moitzi, W. Kroutil, K. Faber, Angew. Chem. 2002, 114, 1056-1059; b) M. Wolberg W. Hummel, C. Wandrey, M. Muller, Angew. Chem. 2000, 112, 4476-4478) . According to the method of the invention, the stereospecific conversion/reaction can take place in any media that are suitable for this reaction. Catalysis can for example be carried out in purely aqueous solutions or in water-containing media enriched with organic solvents. They may be single-phase or multiphase systems. The reaction medium selected is not limiting for the method according to the invention, provided the enzyme chosen can catalyse the desired stereoselective reaction in it.

Advantageously, with a view to high volumetric productivity, the method is carried out with high initial concentrations of substrate. These are typically >50 g/L, preferably >100 g/L and quite preferably >150 g/L. Moreover, the substrate concentrations can optionally be maintained by continuous supply of fresh substrate solution during the catalytic conversion.

The method can in principle be carried out at any suitable temperature. A person skilled in the art will preferably aim to obtain a yield of the desired product that is as high as possible, at highest possible purity and in the shortest possible time. Moreover, the enzymes used should be sufficiently stable at the temperatures used, and the reaction should proceed with highest possible enantioselectivity . When using enzymes from thermophilic organisms, for example, even temperatures of 100⁰C may be reached. The temperature is based primarily on the catalytic optimum of the enzyme used. As the lower limit in aqueous systems,

-15°C is undoubtedly sensible. A temperature range between 10⁰C and 60⁰C, especially preferably between 20⁰C and 40⁰C, is preferred for the method according to the invention and is based primarily on the criteria given above .

The pH value during the reaction is also based primarily on the stabilities of the enzymes and cofactors used and can be found by determining the conversion rates and adjusted accordingly for the method according to the invention. In general a preferred range for enzymes will be from pH 5 to 11, but in exceptional cases it may be above or below this, if one of the enzymes used has its catalytic maximum at a lower or higher value. Preferably, in the method according to the invention, a pH range from 5.5 to 10.0, especially from 6.0 to 9.0, can be used for carrying out the reaction.

For application, the enzymes in question, especially dehydrogenases, of the method according to the invention can be used either in free form as homogeneously purified compounds or as enzyme produced by recombinant technology. Furthermore, these polypeptides can also be used as a constituent of an intact "host organism" (genetically modified microorganism) or in conjunction with a cellular mass of the host organism that has been purified as required and if necessary digested.

When using isolated, " (cell-) free" enzymes, it is also possible to use these enzymes in immobilized form

(Sharma B. P.; Bailey L. F. and Messing R. A. (1982),

Immobilized Biomaterials - Techniques and Applications, Angew. Chem. 94, 836-852). Immobilization is preferably effected by lyophilization (Paradkar, V. M.; Dordick,

J. S. (1994), Aqueous-Like Activity of α-Chymotrypsin Dissolved in Nearly Anhydrous Organic Solvents, J. Am. Chem. Soc. 116, 5009-5010; Mori, T.; Okahata, Y. (1997), A variety of lipid-coated glycoside hydrolases as effective glycosyl transfer catalysts in homogeneous organic solvents, Tetrahedron Lett. 38, 1971-1974; Otamiri, M.; Adlercreutz, P.; Matthiasson, B. (1992), Complex formation between chymotrypsin and ethyl cellulose as a means to solubilize the enzyme in active form in toluene, Biocatalysis 6, 291-305). Lyophilization in the presence of surface-active substances, e.g. Aerosol OT, polyvinylpyrrolidone, polyethylene glycol (PEG) or Brij 52 (diethylene glycol mono-cetyl ether) (Kamiya, N.; Okazaki, S. -Y.; Goto, M.

(1997), Surfactant-horseradish peroxidase complex catalytically active in anhydrous benzene, Biotechnol. Tech. 11, 375-378), is quite especially preferred, though without being limited to these. Immobilization on Eupergit^® in particular Eupergit C^® and Eupergit 250L^® (Rohm) is especially preferred (Eupergit .RTM. C, a carrier for immobilization of enzymes of industrial potential. Katchalski-Katzir, E.; Kraemer, D. M. Journal of Molecular Catalysis B: Enzymatic (2000), 10(1-3), 157-176).

Immobilization on Ni-NTA in combination with a polypeptide supplemented with a His-Tag (hexa- histidine) is also preferred (Purification of proteins using polyhistidine affinity tags. Bornhorst, Joshua A.; Falke, Joseph J. Methods in Enzymology (2000), 326, 245-254) .

Use as CLECs is also conceivable (St. Clair, N.; Wang, Y. -F.; Margolin, A. L. (2000), Cofactor-bound cross- linked enzyme crystals (CLEC) of alcohol dehydrogenase, Angew. Chem. Int. Ed. 39, 380-383) .

These measures are also suitable for generating, from polypeptides which, in isolated "free" form, are made unstable by organic solvents, polypeptides that display catalytic activity in mixtures of aqueous and organic solvents or in a completely organic medium.

The method described here can admittedly also be carried out with isolated enzymes (or immobilizates derived therefrom) in suitable reaction media, but in an especially preferred embodiment the method according to the invention is carried out using a whole-cell catalyst for the reaction, i.e. a system containing (at least one) whole cell (s) , with the cells preferably being capable of simultaneous expression of the desired alcohol dehydrogenase and of the enzyme that regenerates the cofactor. Recombinant whole-cell catalysts are especially suitable (for the concept of method of using recombinant whole-cell catalysts for enantioselective reduction, see for example, among others: PCT/EP2005/06215) . The cell (s) thus preferably express (es) at least one enzyme (polypeptide) with alcohol dehydrogenase activity and at least one with activity for regeneration of the cofactor used. These enzymes and/or the cells used are preferably derived from the organisms stated previously.

Alternatively - when using cofactor regeneration with isopropanol - it is also possible to use cells that preferably express at least one enzyme (polypeptide) with alcohol dehydrogenase activity and only optionally one with activity for regeneration of the cofactor used. Suitable microorganisms that can be used are in principle all organisms known by a person skilled in the art for this purpose, e.g. yeasts such as Hansenula polymorpha, Pichia sp . , Saccharomyces cerevisiae, prokaryotes, such as E. coli, Bacillus subtilis or eukaryotes, such as mammalian cells, insect cells etc. Preferably strains of E. coli can be used for this purpose, in particular E. coli XLl Blue, NM 522, JMlOl, JM109, JM105, RRl, DH50C, TOP 10^" or HBlOl. These strains are commonly known and are available for purchase. Quite preferably an organism is used as host organism as stated in DE-A 10155928.

The advantage of such an organism is simultaneous expression of the two polypeptide systems suitable for the method according to the invention, so that just one recombinant (genetically modified) organism has to be employed for the method according to the invention. In order to match the expression of the polypeptides (enzymes) with respect to the desired catalytic activity, the corresponding coding nucleic acid sequences can lie on different plasmids with different numbers of copies and/or promoters of varying strength can be used for variable strength of expression of the nucleic acid sequences. With enzyme systems matched in this way, advantageously no accumulation of an intermediate occurs and the reaction in question can take place at an optimum overall velocity. This is, however, sufficiently familiar to a person skilled in the art (Gellissen, G.; Piontek, M.; Dahlems, U.; Jenzelewski, V.; Gavagan, J. W.; DiCosimo, R.; Anton, D. L.; Janowicz, Z. A. (1996), Recombinant Hansenula polymorpha as a biocatalyst. Coexpression of the spinach glycolate oxidase (GO) and the S. cerevisiae catalase T (CTTl) gene, Appl . Microbiol. Biotechnol. 46, 46-54; Farwick, M.; London, M.; Dohmen, J.; Dahlems, U.; Gellissen, G.; Strasser, A. W.; DE-A 19920712). Optionally a catalytic amount of cofactor can also be added to the whole-cell biocatalyst.

Production of the microorganism used as "whole-cell catalyst", genetically modified if necessary, can in principle be carried out by methods that are known to a person skilled in the art (Sambrook, J.; Fritsch, E. F. and Maniatis, T. (1989), Molecular cloning: a laboratory manual, 2^nd ed., Cold Spring Harbor

Laboratory Press, New York; Balbas, P. and Bolivar, F.

(1990), Design and construction of expression plasmid vectors in E. coli, Methods Enzymol. 185, 14-37; Rodriguez, R. L. and Denhardt, D. T (eds) (1988), Vectors: a survey of molecular cloning vectors and their uses, 205-225, Butterworth, Stoneham) . Regarding the techniques used in the general procedure (PCR, cloning, expression etc.) reference should be made to the following literature and to references cited there: Universal GenomeWalker™ Kit User Manual, Clontech, 3/2000 and references cited there; Triglia T.; Peterson, M. G. and Kemp, D.J. (1988), A procedure for in vitro amplification of DNA segments that lie outside the boundaries of known sequences, Nucleic Acids Res.

16, 8186; Sambrook, J.; Fritsch, E. F. and Maniatis, T.

(1989), Molecular cloning: a laboratory manual, 2^nd ed.,

Cold Spring Harbor Laboratory Press, New York;

Rodriguez, R. L. and Denhardt, D. T. (eds) (1988), Vectors: a survey of molecular cloning vectors and their uses, Butterworth, Stoneham. Preferably the reaction system is used for example in a stirred reactor, a cascade of stirred reactors or in membrane reactors, which can be operated both batchwise and continuously. However, any type of system in which the method according to the invention can be carried out is suitable. Within the scope of the invention, "membrane reactor" means any reaction vessel in which the catalyst is enclosed in a reactor, whereas low- molecular materials are supplied to the reactor or can leave it. The membrane can then be incorporated directly in the reaction space or can be installed outside in a separate filtration module, with the reaction solution flowing continuously or intermittently through the filtration module and the retained material is returned to the reactor. Suitable embodiments are described inter alia in WO98/22415 and in Wandrey et al . in Jahrbuch 1998, Verfahrenstechnik und Chemieingenieurwesen, VDI p. 151ff.; Wandrey et al . in Applied Homogeneous Catalysis with Organometallic Compounds, Vol. 2, VCH 1996, p.832 ff.; Kragl et al . , Angew. Chem. 1996, 6, 684f.

The continuous operating mode that is possible in this apparatus in addition to the batch and semicontinuous operation can for example be carried out in the cross- flow filtration mode or as dead-end filtration. Both process variants are described in principle in the state of the art (Engineering Processes for Bioseparations, Ed.: L. R. Weatherley, Heinemann, 1994, 135-165; Wandrey et al . , Tetrahedron Asymmetry 1999, 10, 923-928) . In a quite especially preferred embodiment, the method according to the invention is carried out as a one-pot reaction .

Enantiomer-enriched alcohols of formula (III) and of formula (IV)

in which

R² represents (Ci-C₈) -alkyl, (C₂-C₈) -alkoxyalkyl, (C₂-C₈)- alkenyl, (C₂-C₈) -alkynyl, (Cβ-Cis) -aryl, (C7-C19) -aralkyl, (C₃-Ci₈) -heteroaryl, (C₄-Ci₉) -heteroaralkyl, (Ci-C₈)- alkyl- (C₆-Ci₈) -aryl, (Ci-C₈) -alkyl- (C₃-Ci₈) -heteroaryl, (C₃-C₈) -cycloalkyl, (Ci-C₈) -alkyl- (C₃-C₈) -cycloalkyl, (C₃- C₈) -cycloalkyl- (Ci-C₈) -alkyl, or in the case when R² only represents a negative charge it can also represent salts thereof. Enantiomer-enrichment is preferably >90% ee, >95% ee or >96% ee and especially >97% ee .

For production of the alkylene carbonate, and in particular of (R) -propylene carbonate (I) by the method according to the invention, preferably the corresponding derivative of type (II) is first dissolved in a preferably water-containing solvent. Optionally all additives that are necessary for the biocatalyst and for stabilizing it are added and the pH is adjusted if necessary, the biocatalyst is added to the solution and reduction of derivative (II) is thus carried out, with formation of the desired diol derivative of type (III) . On completion of biotransformation the latter (or the regioisomers of formula (IV) optionally partly resulting therefrom) is then cyclized to the desired carbonate (I) . The cyclization step, preferably in an acid environment, can take place directly in the reaction solution and/or during processing, in particular extraction and/or after completion of processing and isolation if necessary.

In an especially preferred embodiment, a derivative (II) is dissolved directly in a cell medium suitable for the biocatalyst (expressing the desired enzymes) , the biocatalyst and optionally cofactors required for the enzymes are added and catalytic conversion to the desired enantiomer is carried out at a temperature at which the biocatalyst is stable and the enzymes have a high activity for the particular reaction that they catalyse .

Alternatively, however, the sequence of addition of the respective components can be varied as desired. Thus, a further preferred embodiment comprises addition of the biocatalyst before adding the respective derivative of type (II) .

The following are to be regarded as (Ci-Cs) -alkyl residues: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl or octyl plus all of their bond isomers. The (Ci-Cs) -alkoxy residue corresponds to the (Ci-Cs) - alkyl residue with the proviso that it is bound to the molecule via an oxygen atom. (C2-C8) -alkoxyalkyl means residues in which the alkyl chain is interrupted by at least one oxygen function, and two oxygen atoms cannot be joined together. The number of carbon atoms shows the total number of carbon atoms contained in the residue.

(C3-C8) -cycloalkyl means cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl residues etc. These can be substituted with one or more halogens and/or residues containing N-, O-, P-, S-, Si-atoms and/or can have N-, O-, P-, S-atoms in the ring, e.g. 1-, 2-, 3-, 4-piperidyl, 1-, 2-, 3-pyrrolidinyl, 2-, 3- tetrahydrofuryl, 2-, 3-, 4-morpholinyl .

(C₃-C₈) -cycloalkyl- (Ci-Cs) -alkyl residue designates a cycloalkyl residue as presented above, which is bound to the molecule via an alkyl residue as stated above.

(Ci-Cs) -acyloxy means, within the scope of the invention, an alkyl residue as defined above with max. 8 carbon atoms, which is bound to the molecule via a COO function.

(Ci-Cs) -acyl means, within the scope of the invention, an alkyl residue as defined above with max. 8 carbon atoms, which is bound to the molecule via a CO function.

A (C6-Cis) -aryl residue means an aromatic residue with 6 to 18 carbon atoms. In particular this includes compounds such as phenyl, naphthyl, anthryl, phenanthryl, biphenyl residues or systems of the type described previously, fused to the molecule in question, for example indenyl systems, which can optionally be substituted with halogen, (Ci-Cs) -alkyl, (Ci-C₈) -alkoxy, NH₂, NH (Ci-C₈) -alkyl, N ( (Ci-C₈) -alkyl) ₂, OH, CF₃, NH(Ci-C₈) -acyl, N ( (Ci-C₈) -acyl) 2, (Ci-C₈) -acyl, (Ci-C₈) -acyloxy.

A (C7-C19) -aralkyl residue is a (Cβ-Cis) -aryl residue bound to the molecule via a (Ci-C₈) -alkyl residue. The halogens (Hal) comprise fluorine, chlorine, bromine and iodine.

The term enantiomer-enriched or enantiomeric excess means, within the scope of the invention, the proportion of an enantiomer in the mixture with its optical antipode in a range of >50% and <100%. The ee value is calculated as follows: ( [enantiomeri] - [enantiomer₂] ) / ( [enantiomeri] + [enantiomer₂] ) = ee value (R) -propylene carbonate is any form of propylene carbonate in which the (R) -enantiomer is present relative to its optical antipode in the mixture at >90%ee, preferably >95%ee, >96%ee and especially preferably >97%ee.

The term diastereomer-enriched denotes the proportion of a diastereomer in the mixture with the other possible diastereomers of the compound in question.

The structures of compounds stated here comprise and disclose all theoretically possible enantiomers that can arise through variation of the configurations on the corresponding carbon atoms.

Experimental examples:

Example 1 Biocatalytic reduction of 0- (methoxycarbonyl) -hydroxyacetone, 2a :

4a

In a Titrino reaction vessel, the whole-cell catalyst of type E. coli DSM14459, containing an (R) -alcohol dehydrogenase from L. kefir and a glucose dehydrogenase from T. acidophilum (for production of the biocatalyst, see WO2005121350) , at a cell concentration of 55 g moist biomass / L, D-glucose (1.5 equivalents relative to the molar amount of ketone used) and 25 mmol 0-

(methyloxycarbonyl) -hydroxyacetone, 2a, (corresponding to a substrate concentration of 0.5M) are added to 30 mL of an aqueous phosphate buffer (0.026 M; adjusted to pH 7.0) and the volume is topped up to 50 mL with water. The reaction mixture is stirred for a reaction time of 25.5 hours at room temperature, maintaining constant pH at -6.5 by adding sodium hydroxide solution (5M NaOH). After a reaction time of 25.5 hours, conversion of >95% is determined (according to the consumption of sodium hydroxide solution and GC chromatography) . Processing is carried out by lowering the pH value to <3 with concentrated hydrochloric acid and addition of 3.75 g of the filter aid Celite Hyflo Supercel to the reaction mixture, followed by filtration with application of vacuum. The filter cake is washed 4 times with 50 mL MTBE and the aqueous phase is extracted correspondingly with the three organic MTBE fractions obtained. The solvent is removed from the combined organic phases after drying over magnesium sulphate, yielding as raw product the optically active alcohol 3a at a yield of 50% (of which 12.7 mol.% is rearranged to give the regioisomeric alcohol 4a and 63.6 mol.% has already been cyclized to the desired (R) -propylene carbonate 1) . The enantioselectivity of the reaction is 99.67% ee .

Example 2_Biocatalytic reduction of 0- (ethoxycarbonyl) - hydroxyacetone, 2b:

4b

In a Titrino reaction vessel, the whole-cell catalyst of type E. coli DSM14459, containing an (R) -alcohol dehydrogenase from L. kefir and a glucose dehydrogenase from T. acidophilum (for production of the biocatalyst, see WO2005121350) , at a cell concentration of 51 g moist biomass / L, D-glucose (1.5 equivalents relative to the molar amount of ketone used) and 25 mmol 0- (ethyloxycarbonyl) -hydroxyacetone, 2b, (corresponding to a substrate concentration of 0.5M) are added to 30 mL of an aqueous phosphate buffer (0.026 M; adjusted to pH 7.0) and the volume is topped up to 50 mL with water. The reaction mixture is stirred for a reaction time of 25.5 hours at room temperature, maintaining constant pH at -6.5 by adding sodium hydroxide solution (5M NaOH) . After a reaction time of 25.5 hours, conversion of >95% is determined (according to the consumption of sodium hydroxide solution and GC chromatography) . Processing is carried out by lowering the pH value to <3 with concentrated hydrochloric acid and addition of 3.75 g of the filter aid Celite Hyflo Supercel to the reaction mixture, followed by filtration with application of vacuum. The filter cake is washed 4 times with 50 mL MTBE and the aqueous phase is extracted correspondingly with the three organic

MTBE fractions obtained. The solvent is removed from the combined organic phases after drying over magnesium sulphate, yielding as raw product the optically active alcohol 3b at a yield of 71% (of which 37.3 mol.% is rearranged to give the regioisomeric alcohol 4a and

18.6 mol.% has already been cyclized to the desired

(R) -propylene carbonate 1) . The enantioselectivity of the reaction is 99.34% ee .

Example 3_Biocatalytic reduction of 0- (n- propoxycarbonyl) -hydroxyacetone, 2c :

_^ n-Pr

4c

In a Titrino reaction vessel, the whole-cell catalyst of type E. coli DSM14459, containing an (R) -alcohol dehydrogenase from L. kefir and a glucose dehydrogenase from T. acidophilum (for production of the biocatalyst, see WO2005121350) , at a cell concentration of 49 g moist biomass / L, D-glucose (1.5 equivalents relative to the molar amount of ketone used) and 25 mmol 0- (n- propoxycarbonyl) -hydroxyacetone, 2c, (corresponding to a substrate concentration of 0.5M) are added to 30 mL of an aqueous phosphate buffer (0.026 M; adjusted to pH 7.0) and the volume is topped up to 50 mL with water. The reaction mixture is stirred for a reaction time of 26 hours at room temperature, maintaining constant pH at -6.5 by adding sodium hydroxide solution (5M NaOH) . After a reaction time of 26 hours, conversion of >95% is determined (according to the consumption of sodium hydroxide solution and GC chromatography) . Processing is carried out by lowering the pH value to <3 with concentrated hydrochloric acid and addition of 3.8 g of the filter aid Celite Hyflo Supercel to the reaction mixture, followed by filtration with application of vacuum. The filter cake is washed 4 times with 50 mL MTBE and the aqueous phase is extracted correspondingly with the three organic MTBE fractions obtained. The solvent is removed from the combined organic phases after drying over magnesium sulphate, yielding as raw product the optically active alcohol 3c at a yield of 72% (of which 37.3 mol.% is rearranged to give the regioisomeric alcohol 4c and 8.9 mol.% has already been cyclized to the desired (R) -propylene carbonate 1) . The enantioselectivity of the reaction is 98.85% ee .

Example 4_Synthesis of (R) -propylene carbonate 1 by cyclization of the raw product from Example 2:

HO.

XH-,

4b

0.525 g of the optically active alcohol 3b obtained as raw product according to example 2 (which has partially been rearranged to give the regioisomeric alcohol 4b or has already been cyclized to the desired (R) -propylene carbonate according to the proportions stated in mol.% in example 2) is absorbed in 10 mL ethyl acetate, and p-toluenesulphonic acid (96 mg) is added. The reaction mixture is heated for 6 hours at a reaction temperature of 60⁰C. The desired (R) -propylene carbonate 1 is obtained in a proportion of -80% (relative to the molar quantity of substrate used from example 2) and with an enantioselectivity of 99.18% ee .

Claims

Patent claims :

1. Method of production of enantiomer-enriched alkylene carbonates of general formula (I),

in which

R¹ represents a linear or arbitrarily branched (Ci-

Cs) -alkyl or a (C3-C8) -cycloalkyl residue, characterized in that a derivative of formula (II)

in which

R¹ has the meaning given above and R² represents (Ci-Cs) -alkyl, (C2-C₈) -alkoxyalkyl, (C₆- Cis)-aryl, (C7-C19) -aralkyl, (C3-C18) -heteroaryl, (C₄- Ci₉) -heteroaralkyl, (Ci-C₈) -alkyl- (C₆-Ci₈) -aryl, (Ci- C₈) -alkyl- (C₃-Ci₈) -heteroaryl, (C₃-C₈) -cycloalkyl, (Ci- C₈) -alkyl- (C₃-C₈) -cycloalkyl, (C₃-C₈) -cycloalkyl- (Ci- C₈) -alkyl or in the case when R² only represents a negative charge, can also signify their salts, is first converted to an enantiomer-enriched alcohol of formula (III) and this compound of formula (III)

is then cyclized to the enantiomer-enriched alkylene carbonate (I) .

2. Method according to Claim 1, characterized in that this method is used for the production of (R) - propylene carbonate.

3. Method according to Claim 1 and/or 2, characterized in that the conversion of the derivative of formula (II) to the alcohol of formula (III) is carried out catalytically using a chemical catalyst and/or a biocatalyst.

4. Method according to one of the preceding claims, characterized in that an alcohol dehydrogenase or a glycerol dehydrogenase is used as biocatalyst.

5. Method according to one of the preceding claims, characterized in that the alcohol dehydrogenase used in the method is derived from an organism selected from the group comprising Lactobacillus kefir, Lactobacillus brevis and Thermoanaerobium brockii.

6. Method according to one of the preceding claims, characterized in that the conversion of derivative

(II) is carried out using a coupled enzymatic system, with the coupled enzymatic system comprising an alcohol dehydrogenase and an enzyme that regenerates the cofactor of alcohol dehydrogenase.

7. Method according to one of the preceding claims, characterized in that the conversion of derivative (II) is carried out at initial substrate concentrations of >50 g/L, preferably >100 g/L and especially >150 g/L.

8. Method according to one of the preceding claims, characterized in that the conversion of derivative (II) is carried out in a temperature range from -15 to 100⁰C, preferably 10 to 60⁰C, especially preferably 20 to 40°C.

9. Method according to one of the preceding claims, characterized in that the conversion of derivative (II) is carried out at a pH value from 5 to 11, preferably 5.5 to 10, especially preferably 6 to 9.

10. Method according to one of the preceding claims, characterized in that at least one microorganism is used in the method, said microorganism being capable of simultaneous expression of the alcohol dehydrogenase and of an enzyme that regenerates a cofactor.

11. Method according to one or more of the preceding claims, characterized in that the synthesis is carried out as a one-pot reaction.

12. Enantiomer-enriched alcohols of formula (III) or (IV)

in which

R² represents H, (Ci-C₈) -alkyl, (C₂-C₈) -alkoxyalkyl,

(C₂-C₈) -alkenyl, (C₂-C₈) -alkynyl, (C₆-C₁₈) -aryl, (C₇- Ci₉) -aralkyl, (C₃-Ci₈) -heteroaryl, (C₄-Ci₉)- heteroaralkyl, (Ci-C₈) -alkyl- (C₆-Ci₈) -aryl, (Ci-C₈)- alkyl- (C₃-Ci₈) -heteroaryl, (C₃-C₈) -cycloalkyl, (Ci-C₈)- alkyl- (C₃-C₈) -cycloalkyl, (C₃-C₈) -cycloalkyl- (Ci-C₈) - alkyl or, in the case when R² only represents a negative charge, can also signify their salts.