WO2003014106A1

WO2003014106A1 - METHOD FOR PREPARING OPTICALLY ACTIVE α-SUBSTITUTED HETEROCYCLICCARBOXYLIC ACID ESTER

Info

Publication number: WO2003014106A1
Application number: PCT/KR2002/001488
Authority: WO
Inventors: Ki-Nam Uhm
Original assignee: Genofocus Co., Ltd.
Priority date: 2001-08-06
Filing date: 2002-08-06
Publication date: 2003-02-20
Also published as: KR20030012964A

Abstract

The present invetion relates to a method for preparing an optically active compound from a racemic α-substituted heterocycliccarboxylic acid ester, more particularly, relates to method for preparing an optically active α-substituted heterocycliccarboxylic acid ester of the formula II and/or an optically active α-substituted heterocycliccarboxylic acid amide of the formula III, which comprises the steps of: (a) dissolving in an organic solvent a racemic compound of α-substituted heterocycliccaboxylic acid ester represented by the formula I; (b) adding an enzyme selected from the group consisting of lipase, protease and esterase, and R-NH2 to a solution containing the racemic compound; and (c) isolating the optically active compounds of the formula II and the formula III from the reaction mixture.

Description

METHOD FOR PREPARING OPTICALLY ACTIVE α -SUBSTITUTED HETEROCYCLICCARBOXYLIC ACID ESTER

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates to a method for preparing an optically active compound, more particularly, relates to a method for preparing an optically active compound from an racemic α-substituted heterocycliccarboxylic acid ester.

DESCRIPTION OF THE RELATED ART

Optically active tetrahydro-2-furoic acid (THFA), a representative compound of optically active α-substituted heterocycliccarboxyic acids has a wide variety of uses as a chiral building block. For example, R- (+) -tetrahydro-2- furoic acid is useful as a side chain intermediate of penem antibiotics, and S- (-) -tetrahydro-2-furoic acid is useful as a chiral intermediate of organic synthesis. In order to prepare optically active THFA from racemic THFA, an optical resolution must be performed. The optical resolution of racemates has been performed first by Belanger in 1983 { Can . J. Chem. 61:1383(1983)). However, the method had economic demerits using expensive brucine and ephedrine as resolving agents. Also, JP Publication No. 1989-216983 discloses a method for optical resolution of R, S-tetrahydro-2-furoic acid conversed into a diastereomer salt using l-(4- phenylhalide) ethylamine as a resolving agent. However, the method also has problems such as high expense of optically active amines, very low concentration of R, S-tetrahydro-2- furoic acid and low purity and yield of products. In addition, for resolving racemates, (a) hydrolysis in aqueous solution using enzymes such as esterase, lipase and protease and (b) transesterification have been proposed. In recent years, studies of optical resolution by enzymatic non-aqueous aminolysis have been intensively made. For example, Gotor, V. et al . have succeeded in conversing racemic 2-chloropropionate ethyl ester into 40- 95%ee (S) -2-chloropropionate amide by optical resolution using Candida cylindracea lipase { Tetrahedron Lett . 29:6973-697491988)). Gotor, V. et al . also have reported that reacting racemic 2-methylbutylrate ethyl ester with Candida cylindracea lipase (CCL) and Pseudomonas cepacia lipase (PCL) could produce chiral amide ( Tetrahedron Lett . 47 :9207-9214 (1991) ) . In addition, Gotor, V. et al . have proposed that S-hydroxybutylate amide could be prepared in high purity by reacting racemic 3-hydroxybutylate ethyl ester with Candida antarctica lipase (CAL) { Tetrahedron : Asymmetry 3:1519-1522 (1992) ) .

Optical resolution process of racemic amino ester with enzymatic aminolysis has been known in the art. Sheldon, R. A. et al . have optically resolved D, L-phenylglycine methyl ester into .R-phenylglycine amide and S-phenylglycine ester with Candida antarctica lipase (CAL) in t-butanol {J. Molec . Catal . B:Enzym. 5:155-157(1998)).

Optical resolutions of racemic amine have been reported, for example, Reetz, M. T. et al . have resolved racemic 2- phenylethylamine using Candida antarctica lipase (CAL) in purity of 99%ee by acylation of .R-isomeric amine ( Chimia . 48:570(1994)). This method has been known to be applicable to optical resolutions of other amines .

Chiou, T. . et al . have reported an optical resolution method of amino alcohol such as propranol using Candida cylindracea lipase (CCL) through N-acylation (Bioorg-. Med. Chem. Lett . 7:433-436(1997)).

As described previously, the racemic compounds that may be optically resolved into chiral compounds by aminolysis using lipase include a wide variety of compounds.

Meanwhile, Wong, C. H. et al . have reported the results of optical resolution in which 1- (1-naphthyl) ethylamine and racemic alcohol as racemic amine are reacted with diallylyl carbonate and subtilisin, respectively { Tetrahedron Lett . 37:6287-6290(1996)), which represents one example of aminolysis by protease, a kind of hydrolytic enzyme.

However, although many researches as described previously have been made, no research for optical resolution of α-substituted heterocycliccarboxylic acid ester by enzymatic aminolysis has been reported yet, which may be ascribed to significantly slow reaction rates depending on ester types and frequent non-occurrence of enantioselectivity.

Throughout this application, various patents and publications are referenced and citations are provided in parentheses. The disclosure of these patents and publications in their entities are hereby incorporated by references into this application in order to more fully describe this invention and the state of the art to which this invention pertains.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a method for preparing an optically active α-substituted heterocycliccarboxylic acid ester and/or an optically active α-substituted heterocycliccarboxylic acid amide.

It is another object of this invention to provide a method for preparing an optically active α-substituted heterocycliccarboxylic acid. It is still another object of this invention to provide a method for preparing an optically active .R-tertrahydro-2- furoic acid and/or S-tetrahydro-2-furoic acid.

DETAILED DESCRIPTION OF THE INVENTION In one aspect of this invention, there is provided a method for preparing an optically active α-substituted heterocycliccarboxylic acid ester of the formula II and/or an optically active α-substituted heterocycliccarboxylic acid amide of the formula III, which comprises the steps of: (a) dissolving in an organic solvent a racemic compound of α-substituted heterocycliccarboxylic acid ester represented by the formula I; (b) adding an enzyme selected from the group consisting of lipase, protease and esterase, and R-NH₂ to a solution containing the racemic compound; and (c) isolating the optically active compounds of the formula II and the formula III from the reaction mixture;

(ID

CONHR

( I I I ) wherein R_x is non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl ; R is H or non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is 0, S or N; and n is an integer of 1-5.

The principle reaction mechanism of this invention is summarized by the Scheme I :

( I )

According the method of this invention, the compound with R or S configuration among racemic α-substituted heterocycliccarboxylic acid ester as starting material, is resolved through aminolysis by an enzyme that interacts only a specific enantiomer and R-NH₂ to form an amide compound, whereas non-reacted compound remains as ester compound. An enantiomer is resolved by the enantiomer- specific reaction. The reaction of this invention is defined as aminolysis used herein, including ammonolysis as well as usual meaning of aminolysis. As described hereinafter, although ammonolysis- occurs when ammonia is used as R-NH₂, it is also considered to occurrence of aminolysis herein.

In this invention, the racemic compound of α-substituted heterocycliccarboxylic acid ester by the formula I, an starting material, may be prepared from α-substituted heterocycliccarboxylic acid by the conventional methods known in the art, preferably by reacting with alcohols. The terms used herein "racemic compound" , "racemate" and "racemic mixture" have the same meaning, and each means a mixture of enantiomers deficient in optical activity in which each enantiomer is mixed substantially at a ratio of 50:50.

The racemic α-substituted heterocycliccarboxylic acid may be dissolved in a variety of organic solvents, which include but not limited to oxane, ester, ether, alcohol solvents and mixtures thereof, more preferably is oxane, alcohol organic solvents or combination thereof.

The preferred oxane organic solvent of this invention includes 1,4-dioxane or 1, 3 , 5-trioxane .

According to a preferred embodiment of this invention, the ester organic solvent includes ethylacetate, ethylpropionate, ethylbutyrate, butylbutyrate and butylacetate.

The preferred ether organic solvent includes diethylether, methylethylether, methyl tert-butylether, methylisobutylether and petroleum ether.

According to the most preferable embodiment of this invention, the organic solvent is alcohol. In addition, where an alcohol organic solvent is used, a different reaction from one represented by the Scheme I is produced. That is, transesterification as well as aminolysis occurs simultaneously. Therefore, in another aspect of this invention, there is provided a method for preparing an optically active α- substituted heterocycliccarboxylic acid ester of the formula II, an optically active α-substituted heterocycliccarboxylic acid ester of the formula IV and/or an optically active α-substituted heterocycliccarboxylic acid amide of the formula III, which comprises the steps of: (a) dissolving in an alcoholic organic solvent of R₂-0H a racemic compound of the α-substituted heterocycliccarboxylic acid ester of the formula I; (b) adding an enzyme selected from the group consisting of lipase, protease and esterase, and R-NH₂ to a solution containing the racemic compound; and (c) isolating the optically active compounds of the formula II and the formula IV from the reaction mixture;

(i)

(ID

CONHR

(HI)

(IV) wherein R_x and R₂ is independently non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; R is H or non-^' substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is O, S or N; and n is an integer of 1-5.

In case that alcohol organic solvent is used, one enantiomer is subject to aminolysis by enzymes and R-NH₂ and R₂-0^" acts on non-reacted another enantiomer to form a new ester compound (formula IV) .

Where racemic α-substituted heterocycliccarboxylic acid ester is optically resolve by aminolysis in an organic solvent, if the reaction time is too long, the yield of optically active α-substituted heterocycliccarboxylic acid ester may be reduced due to overreaction. In this case, if alcohol organic solvent is used to produce transesterification and aminolysis simultaneously, the optical purity and the yield of final products can be improved and reaction time can be reduced as well.

The final products include 2 types of optically active α-substituted heterocycliccarboxylic acid esters and a α- substituted heterocycliccarboxylic acid amide having an opposite optical activity.

Though many researches have reported that transesterification or aminolysis was attempted for optical resolution of a racemic compound (e.g., Enzyme . Microb . Technol . , 15:367-382(1993)), it has not been reported that the two reactions may be proceeded simultaneously in one reactor as the present invention.

According to a preferred embodiment of this invention, Ri and R₂ is independently non-substituted or substituted Cι-C₆ alkyl, Cι-C₆ alkenyl, Cι-C_e alkynyl, C₃-C₆ cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; R is H or non- substituted or substituted Cι-C₆ alkyl, Cι-C₆ alkenyl, Cι-C₆ alkynyl, C₃-C₆ cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is 0; and n is an integer of 1-3.

The alcohol organic solvent useful in this invention preferably includes but not limited to methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, tert- butanol, isoamylalcohol and benzylalcohol .

The enzyme used in this invention is hydrolytic enzyme such as lipase, protease and esterase. They have been used in optical resolution of certain compounds as described in Lana E. Janes, et al . , Chem. Eur. J. , 4:2324-2331(1998) and US 5,928,933. The selection of the enzymes is highly dependent on a structure of compounds. For example, in the Examples described below representing the most preferable embodiments of this invention, it is lipase that shows the most outstanding enantioselectivity and yield to tetra-2- furoic acid butylester among many α-substituted heterocycliccarboxylic acid esters.

As a result, the subject matter of this invention is that α-substituted heterocycliccarboxylic acid esters can be optically resolved by aminolysis with hydrolytic enzymes such as lipase, protease and esterase. Therefore, it would be appreciated that other lipase, protease or esterase in addition to one described in the following Examples can play a role in optical resolution of other α-substituted heterocycliccarboxylic acid esters in addition to tetrahydro-2-furoic acid.

According to a preferred embodiment of this invention, the enzyme used in optical resolution is lipase. The lipase used in optical resolution exhibits different patterns in a favorable type of enantiomer and compound to be reacted, and reactivity, which is depended largely on its source

(Lana E. Janes, et al . Chem. Eur. J. , 4:2324-2331(1998) and

US 5,928,933). Therefore, according to more preferable embodiment of this invention, the lipase is derived from

Candida cylindracea, Pseudomonas sp. Candida rugosa or Candida antarctica and the most preferable is derived from Candida Antarctica . The R-NH₂ useful in aminolysis of this invention includes ammonia., methylamine, ethylamine, prophylamine, isoprophylamine, n-butylamine, isobutylamine, tert- butylamine, diethylamine, dimethylamine, methylethylamine and benzylamine, more preferably n-butylamine, tert- butylamine or ammonia and the most preferably ammonia .

The aminolysis described above may be usually performed at 4-70^°C, more preferably at 10-40^°C.

If the aminolysis is completed at a time of achieving a desirable optical purity, there remain α-substituted heterocycliccarboxylic acid amide formed by enzyme reaction and its enantiomer, non-reacted α-substituted heterocycliccarboxylic acid ester. The isolation of optically active ester and amide may be carried out by various methods known in the art. For example, this step may be performed by adding an organic solvent to the reaction mixture and standing at a low temperature (-80°C to 4^°C) to deposit α-substituted heterocycliccarboxylic acid amide; in which the organic solvent (for example, ethers such as diethylether, methylethylether, methyl fcert- butylether, methylisobutylether and petroleum ether) is capable of dissolving α-substituted heterocycliccarboxylic acid ester and incapable of dissolving α-substituted heterocycliccarboxylic acid amide. The deposition enables an optically active amide to be crystallized and isolated, and an optically active ester to be remained in an organic solvent layer.

The optically active ester remained in the organic solvent layer is collected by removing the organic solvent with an evaporator and the like. The optical purity of optically active amide isolated by crystallization may be improved where redissolved in alcohol organic solvents or ether organic solvents and recrystallized. The alcohol organic solvent includes but not limited to ethanol, methanol and propanol , and the ether organic solvent includes but not limited to diethylether, methylethylether, methyl tert-butylether, methylisobutylether and petroleum ether.

The optically active ester and amide are further treated to convert into optically active carboxylic acid.

Therefore, in still another aspect of this invention, there is provided a method for preparing a J?-α-substituted heterocycliccarboxylic acid of the formula V and/or a S-α- substituted heterocycliccarboxylic acid of the formula VI through an acid or alkali hydrolysis of the α-substituted heterocycliccarboxylic acid ester and/or the α-substituted heterocycliccarboxylic acid amide prepared by the present method described above :

(v)

(VI) wherein X is 0, S or N; and n is an integer of 1-5.

The cleavage of ester bond may be carried out by any methods known in the art; for example, for acidic hydrolysis, inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like may be used, and for alkaline hydrolysis, inorganic alkali such as sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide and the like may be used.

According to the most preferable embodiment of the present invention, the α-substituted heterocycliccarboxylic acid ester is tetrahydro-2-furoic acid ester, the α- substituted heterocycliccarboxylic acid amide is tetrahydro-2-furoic acid amide and the α-substituted heterocycliccarboxylic acid is tetrahydro-2-furoic acid.

Therefore, in further aspect of this invention, there is provided a method for preparing an optically active R- tetrahydro-2-furoic acid and/or S-tetrahydro-2-furoic acid, which comprises the steps of: (a) dissolving a racemic compound of tetrahydro-2-furoic acid ester in an alcohol organic solvent; (b) adding lipase derived from Candida antarctica and ammonia to the solution containing the racemic compound; (c) isolating the optically active compounds of the formula II, the formula III and the formula IV from the reaction mixture; and (d) hydrolyzing the isolated optically active compound with acid or alkali.

It has been known that the conventional methods for optical resolution are uneconomic because of using chiral amines to form diastereomers and using a large amount of organic solvents. In this regard, it is surprising that the method of this invention can avoid the necessity for the expensive optical resolution agents, simplify the processes, obtain R- and S- enantiomers simultaneously and increase highly the optical purity and yield.

The present invention provides a method for preparing an optically active α-substituted heterocycliccarboxylic acid ester and/or an optically active α-substituted heterocycliccarboxylic acid amide. In addition, this invention provides a method for an optically active α- substituted heterocycliccarboxylic acid. Further to this, this invention provides an optically active .R-tetrahydro-2- furoic acid and/or S-tetrahydro-2-furoic acid. The methods of this invention can avoid the necessity for the expensive optical resolution agents, simplify the processes, obtain R- and S- enantiomers simultaneously and increase highly the optical purity and yield.

The following specific examples are intended to be illustrative of the invention and should not be construed as limiting the scope of the invention as defined by appended claims .

EXAMPLES

Example I: Screening of Enzymes Showing Specificity for Tetrahydro-2-Furoic Acid (THFA) Ester

2% (w/v) of racemic tetrahydro-2-furoic acid butyl ester (Aldrich, USA) and 0.1% (w/v) of each enzyme indicated in Table I (Sigma, USA; Roche, USA; and Amano Enzyme, USA) were added to 500 μl of reaction solvent (0.5 M ammonia in 1,4-dioxane) and reacted for 20 hr at 30^°C. 100 μl of the reacted solution was dissolved in 1 m# of ethanol and analyzed using gas chromatography and chiral gas chromatography (Table I) . Gas chromatography was performed with HP-5 column (Hewlett-Packard, USA) at initial temperature of 80 ^°C and final temperature of 200 ^°C. The chiral gas chromatography was performed with β -dextrin column (Chrompack, USA) at initial temperature of 110 ^°C and final temperature of 200°C. Table I

Strain Optical Enantiomer of purity (%ee) remained ester

Ester Amide

Protease Bacillus subtilis 2.0 0.0 Aspergillus oryzae 0.0 0.0 Aspergillus saitol 2.3 0.0 Rhizopus sp. 0.0 0.0 Bacillus 2.7 3.0 1 i cheni formi s Bacillus 0.0 0.0 amyloliguefaciens

Lipase Candida cylindracea 30.0 2.3 S Pseudomonas sp . 1.0 0.0 Porcine pancreatic Candida Antarctica 99.6 85 R Candida rugosa 20.1 0.0 R Rhizomucor miehei

Estease Porcine liver

As shown in Table I, the reaction employing lipase from Candida antarctica gave the highest optical purity (99.6%ee) and the highest yield of remained tetrahydro-2- furoic acid butyl ester. Therefore, the following experiments were performed with the lipase from Candida antarctica.

Example II: Specificity for Other Tetrahydro-2-Furoic

Acid (THFA) Ester

Reaction was performed in the same manner as Example I, except that 10% (w/v) of racemic tetra-2-furoic acid species and other forms of substrates such as tetrahydro-2-furoic acid benzyl ester, tetrahydro-2-furoic acid butyl ester and tetrahydro-2-furoic acid ethyl ester were employed. The resultants then were analyzed.

99.6%ee optical purity of tetrahydro-2-furoic acid ester was achieved in 26 hr for THFA benzyl ester, 21 hr for THFA butyl ester and 36 hr for THFA ethyl ester. These results indicate that THFA butyl ester is the most preferred substrate due to the fastest optical resolution; thus tetrahydro-2-furoic acid benzyl ester was used as a substrate in the following experiments.

Example III: Optical Resolution of Tetrahydro-2-Furoic

Acid (THFA) Ester

This example shows the method for optical resolution of racemic THFA ester in organic solvent into optically active THFA ester and THFA amide by reacting with the enzyme under the presence of amine compound.

2.5 g of THFA butyl ester and 0.4 g of lipase from Candida antarctica were added in 25 m£ of reaction solvent (0.5 M of ammonia in 1,4-dioxane) and the mixture was reacted at 20 ^°C with agitation. Small portions of reaction mixture were sampled at constant interval, analyzed by chiral chromatography in Example I, revealing that the optical purity of ester compound was 99%ee at 28 hr and that of amide compound was 88%ee.

After the reaction was completed, the enzyme was filtered through Whattman Filter No.5, 50 ml of ether was mixed into filtrate, allowed to stand overnight at -20 ^°C and crystals formed thus were collected by filtering on Whattman Filter No.5. Consecutively, 1.1 g of the crystal was dissolved in 10 ml of heated ethanol, THFA amide crystal after 1 day crystallization at -20 ^°C was gained and dried, 0.8 g of the final THFA amide was acquired and the optical purity of that was measured by the chiral chromatography in Example I. The result indicated 99.8%ee of optical purity. Furthermore, 72 ml of the filtrate after precipitation by ether described above was evaporated by rotary evaporator (Buehi, Germany) to dry organic solvent yielding 0.9 g of final THFA butyl ester (corresponding to 72% of theoretical yield) . Analysis using chiral chromatography in Example I showed 99.8%ee of optical purity.

Example IV: Optical Resolution Depending on Type of

Amines

10% (w/v) of racemic THFA butyl ester and 0.1% (w/v) of Candida antarctica lipase were added into 1 ml of 1,4- dioxane reaction solvent, amine compound (n-butyl amine, benzyl amine or tert-butyl amine) in an amount of 1.1 times

(w/v) of the THFA butyl ester was added and the mixture was reacted for 11 hr at 30^°C. Thereafter, 100 μi of the reacted mixture was dissolved in 1 ml of ethanol and optical purity was measured by the gas chromatography and . chiral chromatography employed in Example I (Table II)

Table II

Amine compound Optical Purity (%ee) Enantiomer of remained ester

Ester Amine n-butyl amine 23.1 1.3 R tert-butyl amine 2.8 1.0 R

Benzyl amine 39.2 7.4 R

As shown in Table II, the reactions occurred rapidly using benzyl amine and 23-butyl amine but the reaction hardly occurred employing tert-butyl amine. The optical purities of the remained ester and produced amine were inferior to those of Example I employing ammonia.

Example V: Optical Resolution Depending on Organic

Solvents

10% (w/v) racemic THFA butyl ester and 1% (w/v) Candida antarctica lipase was added into 1 ml of each reaction solvents indicated in Table III containing 0.5 M ammonia and the mixtures were allowed to react for 24 hr at 25°C. Thereafter, optical purity was measured by chiral chromatography used in Example I (Table III) . Table III

Organic Solvents Optical Purity Enantiomer of (%ee) remained ester

Ester Amide

1, 4-dioxane 59.5 22 .6 R

1, 4-dioxane : ethanol 100 83, .1 R

(50:50)

Ethanol 99.8 79, .5 R

As shown in Table III, the mixture of ethanol and 1,4- dioxane showed the highest optical purity and ethanol solvent showed higher optical purity than 1,4-dioxane.

Example VI: Simultaneous Occurrence of Transesterification and Aminolysis

In an effort to verify the effect of solvents of various compositions of 1,4-dioxane and ethanol on optical purity, experiment was done as follows:

10% (w/v) racemic THFA butyl ester and 1% (w/v) Candida antarctica lipase were added into 1 ml of the reaction solvents in Table IV containing 0.5 M ammonia, and the mixture was reacted for 19 hr at 25°C . Thereafter, optical purity was measured by chiral gas chromoatography used in Example I (Table IV) . Table IV

Organic Solvent Optical Purity Enantiomer of (%ee) remained ester

Ester Amide

1, 4-dioxane -.ethanol 81.5 100 R

(2.3:1) 1,4-dioxane: ethanol 85.1 90.2 R

(1.5:1) 1, 4-dioxane: ethanol 91.5 89.8 R

(0.6:1) 1, 4-dioxane .-ethanol 96.1 85.2 R

(0.3:1)

Ethanol 99.1 76.1 R

After reaction, there remained 3 compound species, i.e. THFA butyl ester, THFA ethyl ester and THFA amide. Among them, THFA ethyl ester was produced by transesterification in which the ester bond of the non-reactive isomer was attacked by CH₃CH₂0^" of ethanol and catalyzed by lipase; in which the non-reactive isomer among the substrate, racemic THFA butyl ester, is one not reacted with lipase in aminolysis. Consequently, the THFA ethyl ester was produced by simultaneous reactions of transesterification and aminolysis. It is impossible for such transesterification to occur in the absence of lipase.

In addition, ethanol alone showed higher optical purity and yield of produced THFA ethyl ester and remained THFA butyl ester than that of mixture with 1,4-dioxane.

Example VII: Optical Resolution by Simultaneous Reactions of Transesterification and Aminolysis This Example shows the method for optical resolution with high yield of optically active THFA ester and THFA amide by dissolving racemic THFA ester into ethanol and reacting with enzyme in the presence of amine compound, thereby permitting simultaneous reactions of transesterification and aminolysis.

21 g of THFA butyl ester and 0.9 g of Candida antarctica lipase were added into 30 ml of reaction solvent

(2 M ammonia in ethanol) , the mixture was reacted at 20^°C under stirring, and ammonia gas was injected into at regular time interval . The mixture was sampled at regular time interval to apply on the chiral gas chromatography employed in Example I, and the results showed 99.5%ee of optical purity of THFA butyl ester and THFA ethyl ester and 77.5%ee of optical purity of THFA amide at 11 hr. After reaction, the enzyme was discarded by Whattman Filter No.5 and ethanol was dried under vacuum by rotary evaporator resulting in 14 g of product. Thereinafter, 2 volumes of ether was added, precipitated for 6 hr at -20°C and crystal was gained on Whattman Filter No .5. 11 g of the crystal was dissolved in 50 ml of heated ethanol and allowed to stand overnight at -20°C to from recrystallized THFA amide. The recrystallized THFA amide was dried and its optical purity was measured using the chiral gas chromatography in Example I. The analysis showed 99.8%ee of optical purity. Furthermore, 42 ml of the filtrate after precipitation by ether described above was evaporated by rotary evaporator (Buehi, Germany) to dry organic solvent producing 9 g of optically active THFA butyl ester and THFA ethyl ester (90% of theoretical yield), and 99.8%ee of optical purity was analyzed by the chiral gas chromatography used in Example I . Table V shows the yield of THFA ester compared to that of Example III performing aminolysis with only 1,3-dioxane as organic solvent .

Table V

Yield of THFA Reaction time ester (%) (hr)

Example III 36% 28

Example VII 45% 11

As shown in Table V, although good yield (corresponding to 72% of theoretical yield) was acquired by sole aminolysis as Example III, the enhanced yield and shortened reaction time were gained by simultaneous reactions of transesterification and aminolysis employing different alcohols from that contained in the THFA ester solution as organic solvent (in this Example, substrate was THFA butyl ester and organic solvent was ethanol) .

Example VIII: Conversion of R-Tetrahydro-2-Furoic Acid Ester into R-Tetrahydro-2-Furoic Acid This Example shows the method for the production of optically active THFA by hydrolyzing the optically active THFA ester of Example VII with acid or alkali.

12.5 % (w/v) of R-THFA ester (98.7%ee) was added into 5 ml of I N HCl or 1 N NaOH and hydrolysis was performed for 3 hr at 60^°C . And then, non-reacted substrate was extracted by addition of 5 ml of ethyl acetate, aqueous layer was acidified to pH 2 with HCl solution, and 0.46 g of .R-THFA was extracted by addition of 10 ml of ethyl acetate. Furthermore, in an effort to measure the optical purity of the final .R-THFA, 5 mg of .R-THFA was converted into butyl ester species by adding 0.2 ml of butanol. Analysis using chiral gas chromatography in Example I indicated the optical purity was constantly maintained. The data are summarized in Table VI.

Table VI

Condition for Hydrolysis Optical Purity (%ee)

Used substrate 98.7 1 N NaOH 98.0 1 N HCl 98.0 Example IX: Conversion of S-Tetrahydro-2-Furoic Acid Amide into S-Tetrahydro-2-Furoic Acid

This Example shows the method for the production of optically active THFA by hydrolyzing the optically active THFA amide of Example VII with acid or alkali.

12.5 % (w/v) of S-THFA amide (99%ee) was added into 5 ml of 1 N HCl or 1 N NaOH and hydrolysis was performed for 3 hr at 60^°C. And then, non-reacted substrate was extracted by addition of 5 ml of ethyl acetate, aqueous layer was acidified to pH 2 with HCl solution, and 0.6 g of S-THFA was extracted by addition of 10 ml of ethyl acetate. Furthermore, in an effort to measure the optical purity of the final S-THFA, 5 mg of R-THFA was converted into butyl ester species by adding 0.2 ml of butanol. Anaylsis using the chiral gas chromatography in Example I indicated the optical purity was constantly maintained. The data are summarized in Table VII.

Table VII

Condition for Hydrolysis Optical Purity (lee)

Used Substrate 99.0

IN NaOH 98.4

IN HCl 98.2

Claims

What is claimed is:

1. A method for preparing an optically active α- substituted heterocycliccarboxylic acid ester of the formula II and/or an optically active α-substituted heterocycliccarboxylic acid amide of the formula III, which comprises the steps of:

(a) dissolving in an organic solvent a racemic compound of α-substituted heterocycliccarboxylic acid ester represented by the formula I ;

(b) adding an enzyme selected from the group consisting of lipase, protease and esterase, and R-NH₂ to a solution containing the racemic compound; and

(c) isolating the optically active compounds of the formula II and the formula III from the reaction mixture ;

(I)

(III) wherein Ri is non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; R is H or non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is 0, S or N; and n is an integer of 1-5.

2. A method for preparing an optically active α- substituted heterocycliccarboxylic acid ester of the formula II, an optically active α-substituted heterocycliccarboxylic acid ester of the formula IV and/or an optically active α-substituted heterocycliccarboxylic acid amide of the formula III, which comprises the steps of: (a) dissolving in an alcoholic organic solvent of R₂-0H a racemic compound of the α-substituted heterocycliccarboxylic acid ester of the formula I;

(c) isolating the optically active compounds of the formula II and the formula IV from the reaction mixture ,-

(ID

CONHR

(iv) wherein Ri and R₂ is independently non-substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; R is H or non- substituted or substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is O, S or N; and n is an integer of 1-5.

3. A method for preparing a R-α-substituted heterocycliccarboxylic acid of the formula V and/or a S-α- substituted heterocycliccarboxylic acid of the formula VI through an acid or alkali hydrolysis of the α-substituted heterocycliccarboxylic acid ester and/or the α-substituted heterocycliccarboxylic acid amide prepared by the method of claim 1 or 2;

(v)

(C

(VI) wherein X is O, S or N; and n is an integer of 1-5.

4. The method according to any one of claims 1 to 3, wherein Ri and R₂ is independently non-substituted or substituted Cι-C₆ alkyl, Cι-C₆ alkenyl, Cχ-Cβ alkynyl, C₃-C₆ cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; R is H or non-substituted or substituted Cι~C₆ alkyl, Cι-C₆ alkenyl, C_x-C₆ alkynyl, C₃-C₆ cycloalkyl, aryl, arylalkyl, heteroarylalkyl or alkaryl; X is 0; and n is an integer of 1-3.

5. The method according to any one of claims 1 to 3 , wherein the racemic compound of α-substituted heterocycliccarboxylic acid ester of the formula I is prepared by reacting a racemic α-substituted heterocycliccarboxylic acid with an alcohol.

6. The method according to any one of claims 1 to 3, wherein the organic solvent is selected from the group consisting of oxane, ester, ether, alcohol solvents and combinations thereof.

7. The method according to claim 6, wherein the oxane organic solvent is 1,4-dioxane or 1, 3 , 5-trioxane .

8. The method according to claim 6, wherein the ester organic solvent is selected from the group consisting of ethylacetate, ethylpropionate, ethylbutyrate, butylbutyrate and butylacetate.

9. The method according to claim 6, wherein the ether organic solvent is selected from the group consisting of diethylether, methylethylether, methyl tert-butylether, methylisobutylether and petroleum ether.

10. The method according to claim 6, wherein the alcohol organic solvent is selected from the group consisting of methanol, ethanol, isopropanol, π-propanol, π-butanol, isobutanol, tert-butanol, isoamylalcohol and benzylalcohol .

11. The method according to any one of claims 1 to 3 , wherein the enzyme is lipase.

12. The method according to claim 11, wherein the lipase is derived from Candida antarctica .

13. The method according to any one of claims 1 to 3 , wherein R-NH₂ is selected from the group consisting of ammonia, methylamine, ethylamine, prophylamine, isoprophylamine, n-butylamine, isobutylamine, tert- butylamine, diethylamine, dimethylamine, methylethylamine and benzylamine .

14. The method according to claim 3, wherein the acid used in hydrolysis is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

15. The method according to claim 3, wherein the alkali used in hydrolysis is selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide and calcium hydroxide.

16. The method according to any one of claims 1 to 3, wherein the α-substituted heterocycliccarboxylic acid ester is tetrahydro-2-furoic acid ester, the α-substituted heterocycliccarboxylic acid amide is tetrahydro-2-furoic acid amide and the α-substituted heterocycliccarboxylic acid is tetrahydro-2-furoic acid.

17. The method according to any one of claims 1 to 3 , wherein the step of isolating the optically active compound is performed by adding an organic solvent to the reaction mixture and standing at a low temperature to deposit α- substituted heterocycliccarboxylic acid amide; in which the organic solvent is capable of dissolving α-substituted heterocycliccarboxylic acid ester and incapable of dissolving α-substituted heterocycliccarboxylic acid amide.

18. The method according to claim 17, wherein the organic solvent used in the depositing step is ether organic solvent selected from the group consisting of diethylether, methylethylether, methyl tert-butylether, methylisobutylether and petroleum ether.

19. The method according to claim 17, which further comprises dissolving the deposited α-substituted heterocycliccarboxylic acid amide in an alcohol organic solvent or ether organic solvent and recrystallizing.

20. The method according to claim 19, wherein the alcohol organic solvent is selected from the group consisting of ethanol, methanol and propanol, and the ether organic solvent is selected from a group consisting of diethylether, methylethylether, methyl tert-butylether, methylisobutylether and petroleum ether.

21. A method for preparing an optically active R- tetrahydro-2-furoic acid and/or £-tetrahydro-2~furoic acid, which comprises the steps of:

(a) dissolving a racemic compound of tetrahydro-2- furoic acid ester in an alcohol organic solvent;

(b) adding lipase derived from Candida antarctica and ammonia to the solution containing the racemic compound;

(c) isolating the optically active compounds of the formula II, the formula III and the formula IV from the reaction mixture; and

(d) hydrolyzing the isolated optically active compound with acid or alkali.