Production of cyclopentenones by enzyme resolution

A process for preparing an optically active cyclopentenone of the formula: ##STR1## wherein R is a hydrogen atom or a lower alkyl group and n is an integer of 4 to 8, which comprises contacting a dl-cyclopentenone ester of the formula: ##STR2## wherein R and n are each as defined above and R' is a lower alkyl group optionally substituted with halogen on an enzyme having a capability of hydrolyzing selectively either one of the d- or l-form isomer in the dl-cyclopentenone ester (II) in an aqueous medium for asymmetric hydrolysis.

This invention relates to production of cyclopentenones. More particularly, 
it relates to a novel process for production of optically active 
cyclopentenones of the formula: 
##STR3## 
wherein R is a hydrogen atom or a lower alkyl group and n is an integer of 
4 to 8. 
Said optically active cyclopentenones (I) are useful as intermediates in 
the synthesis of agricultural chemicals, pharmaceuticals (e.g. 
prostaglandins), perfumes, etc. 
For production of the cyclopentenones (I), there are known various 
processes, among which typical ones are set forth below. 
(1) Tetrahedron Letters, 49, 4959 (1973) 
##STR4## 
(2) J. Am. Chem. Soc., 97, 865 (1975) 
##STR5## 
(3) Acta Chimica Academiae Scientiarum Hungariae, Tomus 102(1), pp. 91-100 
(1979) 
##STR6## 
These conventional processes are, however, disadvantageous from the 
practical viewpoint. For instance, the objective compound in process (1) 
is not satisfactory with regard to its yield and optical purity. In 
addition, said process inevitably produces several kinds of by-products. 
Process (2) requires the use of a triketone, which is not readily 
available, as the starting material and many steps for its conversion into 
the objective compound. In Process (3), the starting 
(-)-cis-2-oxobicyclo[3.3.0]-oct-6-en-3-ol is required to be in an 
optically active form and the conversion into the objective compound is 
accomplished only through a number of troublesome steps. 
As the result of an extensive study for realization of an industrially 
advantageous process for production of the cyclopentenone (I) in a good 
yield, with a high purity and at a low production cost, it has now been 
found that the cyclopentenone (I) is obtainable from the corresponding 
dl-cyclopentenone ester of the formula: 
##STR7## 
wherein R and n are each as defined above and R' is a lower alkyl group 
optionally substituted with halogen in a single step, i.e. by subjecting 
the dl-cyclopentenone ester (II) to asymmetric hydrolysis with an enzyme 
capable of hydrolyzing selectively either one of the d- or l-form isomer 
in the dl-cyclopentenone ester (II). 
The asymmetric hydrolysis is accomplished by treating the starting 
dl-cyclopentenone ester (II) with an enzyme so as to hydrolyze either one 
of the optically active isomers, i.e. the d- or 1-form in the 
dl-cyclopentenone ester (II). As the enzyme, there may be used any 
esterase which can hydrolyze selectively either one of the optically 
active isomers (i.e. the d- or 1-form) in the dl-cyclopentenone ester 
(II). Such esterase is usually produced by microorganisms or obtainable 
from animals and plants. Yet, the term "esterase" used in this 
specification is to be construed broadly so as to cover "lipase" as well. 
The microorganism which can produce the esterase may be chosen from 
Enterobacter, Arthrobacter, Brevibacterium, Pseudomonas, Alcaligenes, 
Micrococcus, Chromobacterium, Microbacterium, Corynebacterium, Bacillus, 
Lactobacillus, Trichoderma, Candida, Saccharomyces, Rhodotorula, 
Cryptococcus, Tcrulopsis, Pychia, Penicillium, Aspergillus, Rhizopus, 
Mucor, Aureovacidium, Actynomucor, Nocardia, Streptomyces, Hansenula, 
Achromobacter, etc. Production of the esterase may be effected by 
cultivating said microorganism in a culture medium by a per se 
conventional procedure. For instance, the microorganism is inoculated in a 
sterilized liquid medium, which is then subjected to reciprocal shaking at 
a temperature of 20.degree. to 40.degree. C. for a period of 1 to 3 days. 
In case of the microorganism being chosen from fungi or yeasts, the 
culture medium may comprise, for instance, peptone (5 g), glucose (10 g), 
malt extract (3 g) and yeast extract (3 g) per 1,000 ml of water (pH 6.5) 
(maltose extract-yeast extract medium). In case of the microorganism being 
chosen from bacteria, the culture medium may comprise, for instance, 
glucose (10 g), peptone (5 g), meat extract (5 g) and NaCl (3 g) per 1,000 
ml of water (pH 7.2) (saccharide-added bouillon medium). 
Some microorganism-originated esterases are available on the market. 
Examples of such commercially available esterases as usable in this 
invention are lipase produced by Pseudomonas ("Lipase P"; Amano 
Pharmaceutical Co., Ltd.), lipase produced by Aspergillus ("Lipase AP"; 
Amano Pharmaceutical Co., Ltd.), lipase produced by Mucor ("Lipase M-AP"; 
Amano Pharmaceutical Co., Ltd.), lipase produced by Candida cylindracea 
("Lipase MY"; Meito Sangyo Co., Ltd.), lipase produced by Alcaligenes 
("Lipase PL"; Meito Sangyo Co., Ltd.), lipase produced by Achromobacter 
("Lipase AL"; Meito Sangyo Co., Ltd.), lipase produced Arthrobacter 
(Shin-Nippon Chemical Co., Ltd.), lipase produced by Chromobacterium 
(Toyojozo Co., Ltd.), lipase produced by Rhizopus delemar ("Talipase"; 
Tanabe Seiyaku Co., Ltd.), lipase produced by Rhizopus ("Lipase Saiken"; 
Osaka Saikin Kenkyuso), etc. 
Examples of the esterase obtainable from animals or plants and usable in 
this invention are steapsin, pancreatin, pig liver esterase, wheat germ 
esterase, etc. 
In the process of the invention, the esterase may be employed in any 
conventional form such as a purified form, a crude form, a mixture with 
other enzymes, a fermentation broth, a microbial body, a fermentation 
broth filtrate, etc. Further, the esterase as separated and the 
microorganism capable of producing the esterase may be used alone or in 
combination. Furthermore, the esterase or the microorganism having a 
capability of producing the esterase may be used in any immobilized form, 
e.g. in a form fixed on resinous particles. 
The asymmetric hydrolysis is normally performed by contacting the dl 
-cyclopentenone ester (II) with the esterase itself or the microorganism 
capable of producing the same in a buffer under vigorous agitation. As the 
buffer, there may be used the one comprising an inorganic salt(s) such as 
sodium phosphate or potassium phosphate and/or an organic salt(s) such as 
sodium acetate or sodium citrate. When an alkali-philic microorganism or 
an alkaline esterase is used, the buffer is preferred to be kept at a pH 
of 8 to 11. When the microorganism is not alkali-philic or the esterase is 
not resistant to alkali, the pH of the buffer is favored to be from about 
5 to 8. The concentration of the buffer may be usually from about 0.05 to 
2M, preferably from about 0.05 to 0.5M. The reaction temperature is 
normally from about 10.degree. to 60.degree. C., and the reaction time is 
generally from about 4 to 70 hours. 
As the result of the asymmetric hydrolysis, either one of the d- or l-form 
isomer in the dl-cyclopentenone ester (II) is selectively hydrolyzed to 
give the optically active cyclopentenone (I) while leaving the other 
isomer in the starting dl-cyclopentenone ester (II). Thus, the reaction 
mixture comprises &:he optically active cyclopentenone (I) as the 
hydrolyzed product and the optically active cyclopentenone ester as the 
non-hydrolyzed product. 
For recovery of those optically active compounds from the reaction mixture, 
the reaction mixture may be, for instance, extracted with an appropriate 
solvent (e.g. methylisobutylketone, ethyl acetate, diethyl ether). After 
removal of the solvent from the extract, the residue is subjected to 
further separation or purification such as distillation, column 
chromatography or recrystallization to collect the optically active 
cyclopentenone (I) and the ester of the optically active cyclopentenone 
(I) as an enantiomer of the former separately. When desired, the optically 
active cyclopentenone ester may be then converted into the corresponding 
optically active cyclopentenone by hydrolysis. 
Still, it may be noted that the asymmetric hydrolysis with a lipase 
produced by a microorganism belonging to Pseudomonas or Arthrobacter can 
generally afford the optically active cyclopentenone (I) with a fairly 
high purity. Further, the use of any organic solvent (e.g. toluene, 
chloroform, methylisobutylketone, dichloromethane) inert to the hydrolytic 
reaction in addition to the buffer is frequently advantageous, because the 
asymmetric hydrolysis is accomplished efficiently. 
The dl-cyclopentenone ester (II) as the starting material in the process of 
this invention is obtainable by reacting a hydroxycyclopentenone of the 
formula: 
##STR8## 
wherein R and n are each as defined above with an acylating agent to 
accomplish acylation and rearrangement simultaneously. 
The acylating agent usable in this invention comprises three kinds of 
compounds, i.e. (a) a lower fatty acid such as a lower alkanoic acid (e.g. 
acetic acid, propionic acid, butyric acid, valeric acid) or a 
halo(lower)alkanoic acid (e.g. chloroacetic acid, dichloroacetic acid), 
(b) a lower fatty acid anhydride such as a lower alkanoic acid anhydride 
(e.g. acetic anhydride, propionic anhydride, butyric anhydride, valeric 
anhydride) and (c) a lower fatty acid metal salt such as a lower alkanoic 
acid metal salt (e.g. lithium acetate, sodium acetate, sodium propionate, 
sodium butyrate, potassium acetate, potassium propionate, calcium acetate, 
calcium propionate, copper acetate, zinc acetate, palladium acetate, lead 
acetate, tin acetate, manganese acetate, cobalt acetate), etc. The lower 
fatty acid or its anhydride may be used in an amount of about one 
equivalent or more to the starting hydroxycyclopentenone (III). The lower 
fatty acid metal salt may be employed in an amount of about 0.01 to 5 
equivalent, preferably of about 0.01 to 0.5 equivalent to the 
hydroxycyclopentenone (III). The presence of the above three components as 
the acylating agent in the reaction system is quite important, because 
otherwise the cyclopentenone ester (II) will not be obtainable in an 
efficient yield. 
The reaction is usually carried out in an inert solvent such as a 
hydrocarbon, a halogenated hydrocarbon, an ether, a ketone, an amide or a 
sulfoxide. Specific examples of the solvent are hexane, benzene, toluene, 
chloroform, carbon tetrachloride, dichloromethane, dichloroethane, 
chlorobenzene, tetrahydrofuran, ethyl ether, acetone, methylethylketone, 
dimethylformamide, dimethylsulfoxide, etc. These may be employed solely or 
in combination. No particular limitation is present on the amount of the 
solvent. The lower fatty acid may be used as such as a reaction medium 
when it is in a liquid state. The reaction is normally effected at a 
temperature of about 0.degree. to 150.degree. C., preferably of about 
30.degree. to 140.degree. C. The reaction time is not limitative, but an 
unnecessarily long time is not favorable, because the once produced 
dl-cyclopentenone ester (II) may be partly decomposed. In general, it is 
between about 0.5 and 10 hours. 
For carrying out the reaction, all of the reactants, i.e. the 
hydroxycyclopentenone (III) as well as the lower fatty acid, the lower 
fatty acid anhydride and the lower fatty acid metal salt, may be charged 
into a reactor, followed by proceeding of the reaction. Alternatively, the 
hydroxycyclopentenone (III) as well as the lower fatty acid and the lower 
fatty acid anhydride may be charged in a reactor, followed by proceeding 
of the reaction for a certain period of time (e.g. about 0.1 to 5 hours); 
then, the lower fatty acid metal salt is added thereto, followed by 
further proceeding of the reaction. 
The hydroxycyclopentenone (III) as the starting compound in the above 
process can be prepared by rearrangement of a furan-carbinol of the 
formula: 
##STR9## 
wherein R and n are each as defined above in an aqueous medium in the 
presence or absence of a catalyst at a pH of about 3.5 to 6. 
The reaction medium may comprise water or its mixture with any inert 
organic solvent in a small amount. In other words, the reaction medium 
comprises always water as the major component. The organic solvent which 
may be optionally contained in a small proportion in the reaction medium 
is chosen usually from hydrocarbons, alcohols, fatty acids, ethers, 
esters, etc. Specific examples are ethylene glycol, 1,3-propanediol, 
methanol, ethanol, dioxane, tetrahydrofuran, dimethylformamide, 
dimelthylsulfoxide, ethyl acetate, acetic acid, dichlcromethane, toluene, 
dimethyl ether, etc. Usually, however, the sole use of water is 
sufficient. 
In the reaction, the catalyst is not necessarily required to use, but its 
use is usually preferred for acceleration of the reaction. The catalyst 
may be chosen from metal salts, organic quarternary ammonium salts, 
surfactants, alcohols, etc. Examples of the metal salts are phosphates, 
sulfates, chlorides, bromides, oxygenated salts, fatty acid salts, 
sulfonic acid salts, etc. of sodium, potassium, magnesium, zinc, iron, 
calcium, manganese, cobalt, aluminum, etc. Examples of the organic 
quarternary ammonium salts are tetrabutylammonium bromide, benzyl 
trimethylammonium chloride, tricapryl methylammonium chloride, dodecyl 
trimethylamonium chloride, capryl benzyl dimethylammonium chloride, etc. 
Examples of the surfactants are higher fatty acid salts, polyoxyethylene 
alkylphenol ether, higher fatty acid alcohols, etc. Examples of the 
alcohols are methanol, ethanol, ethylene glycol, etc. These may be used 
solely or in combination. The amount of the catalyst is normally within a 
range of about 1/200-5 parts by weight to one part by weight of the 
starting furan-carbinol, but this is not critical. The catalyst once used 
in the reaction may be recovered from the reaction mixture and subjected 
to re-use. 
The reaction medium is favorable to have a pH within a range of about 3.5 
to 6, especially of about 3.5 to 5.5. In order to keep this pH value, any 
suitable acidic or basic substance may be added to the reaction mixture. 
Examples of the acidic substance are inorganic or organic acids such as 
hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, acetic 
acid, propionic acid, toluene-sulfonic acid and methanesulfonic acid. 
Examples of the basic substance are inorganic or organic bases such as 
sodium hydroxide, potassium carbonate, sodium hydrogen carbonate, 
potassium hydrogen phosphate, organic amines, etc. Alternatively, a buffer 
comprising an acidic substance and a basic substance in combination may be 
used for adjustment of the pH value. Examples of such buffer are potassium 
hydrogen phosphate-phosphoric acid, sodium acetate-acetic acid, sodium 
acetate-phosphoric acid, phthalic acid- potassium carbonate, potassium 
hydrogen phosphate-hydrochloric acid, potassium dihydrogen phosphate 
potassium hydrogen carbonate, succinic acid-sodium hydrogen carbonate, 
etc. Usually, the use of a strong acid or base (e.g. hydrochloric acid, 
hydrobromic acid, sodium hydroxide, potassium hydroxide) is to be avoided 
for adjustment of the pH value. 
The reaction temperature may be within a range of about 0.degree. to 
200.degree. C., preferably of about 20.degree. to 160.degree. C. 
As the result of the above rearrangement, there is produced the 
hydroxycyclopentenone (III), usually together with a cyclopentenone 
compound of the formula: 
##STR10## 
wherein R and n are each as defined above. 
The thus produced hydroxycyclopentenone (III) may be used as the starting 
compound for production of the dl-cyclopentenone ester (II) with or 
without its previous separation from its mixture with the cyclopentenone 
compound (IV). From the industrial viewpoint, the use of a mixture of the 
hydroxycyclopentenone (III) and the cyclopentenone compound (IV) without 
their separation is favorable, because only acylation proceeds on the 
cyclopentenone compound (IV) to give the dl-cyclopentenone ester (II) when 
reacted with the acylating agent as above. 
In the procedure as stated above, acylation and isomerization proceeds 
simultaneously on the hydroxycyclopentenone (III) to give the 
dl-cyclopentenone ester (II). In place of said procedure, the 
hydroxycyclopentenone (III) may be first isomerized to the cyclopentenone 
compound (IV), which is then acylated to the dl-cyclopentenone ester (II), 
although said procedure comprising simultaneous proceeding of acylation 
and isomerization is more favorable from the viewpoints of the simplicity 
of the reaction operation, the yield of the product and so on. 
In the isomerization, the hydroxycyclopentenone (III) may be used in the 
form of a mixture with the cyclopentenone compound (IV) or in a pure form 
after separation from such mixture. From the industrial viewpoint, the use 
of the hydroxycyclopentenone (III) in the mixture form is advantageous, 
because the cyclopentenone compound (IV) is inert to the reaction in the 
isomerization while it is the objective compound in the isomerization. The 
isomerization may be carried out by treatment of the hydroxycyclopentenone 
(III) in an inert solvent in the presence or absence of a catalyst at a pH 
of 6 to 9. As the inert solvent, there may be exemplified water or its 
mixture with an organic solvent in a small amount. Examples of the organic 
solvent are alcohols (e.g. ethylene glycol, 1,3-propanediol, methanol, 
ethanol), ethers (e.g. dimethyl ether, dioxane, tetrahydrofuran), amides 
(e.g. dimethylformamide), sulfoxides (e.g. dimethylsulfoxide), esters 
(e.g. ethyl acetate), acids (e.g. acetic acid), hydrocarbons (e.g. 
benzene, toluene), halogenated hydrocarbons (e.g. dichloromethane, 
chloroform), etc. However, any advantage is usually not seen in 
incorporating such organic solvent into water. The catalyst is not 
necessarily required to use, but its use is usually favorable for 
promotion of the reaction rate. The catalyst may be chosen from metal 
salts, organic quarternary ammonium salts, surfactants, alcohols, etc. 
Examples of the metal salts are phosphates, sulfates, chlorides, bromides, 
oxygenated salts, fatty acid salts, sulfonic acid salts, etc. of sodium, 
potassium, magnesium, zinc, iron, calcium, manganese, cobalt, aluminum, 
etc. Examples of the organic quarternary ammonium salts are 
tetrabutylammonium bromide, benzyl trimethylammonium chloride, tricapryl 
methylammonium chloride, dodecyl trimethylammonium chloride, capryl benzyl 
dimethylammonium chloride, etc. Examples of the surfactants are higher 
fatty acid salts, polyoxyethylene alkylphenol ether, higher fatty acid 
alcohols, etc. Examples of the alcohols are methanol, ethanol, ethylene 
glycol, etc. These may be used solely or in combination. The amount of the 
catalyst is normally within a range of about 1/200-5 parts by weight to 
one part by weight of the starting hydroxycyclopentenone, but this is not 
critical. 
The reaction medium is favorable to have a pH within a range of about 6 to 
9, especially of about 7 to 9. In order to keep this pH value, any 
suitable acidic or basic substance may be added to the reaction mixture. 
Examples of the acidic substance are inorganic or organic acids such as 
hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, acetic 
acid, propionic acid, toluenesulfonic acid and methanesulfonic acid. 
Examples of the basic substance are inorganic or organic bases such as 
sodium hydroxide, potassium carbonate, sodium hydrogen carbonate, 
potassium hydrogen phosphate, organic amines, etc. Alternatively, a buffer 
comprising an acidic substance and a basic substance in combination may be 
used for adjustment of the pH value. Examples of such buffer are potassium 
hydrogen phosphate-phosphoric acid, sodium acetate-acetic acid, sodium 
acetate-phosphoric acid, phthalic acid-potassium carbonate, potassium 
hydrogen phosphate-hydrochloric acid, potassium dihydrogen 
phosphate-potassium hydrogen carbonate, succinic acid-sodium hydrogen 
carbonate, etc. It is usually preferred to avoid the use cf a strong acid 
or base (e.g. hydrochloric acid, hydrobromic acid, sodium hydroxide, 
potassium hydroxide) for adjustment of the pH value. 
The reaction temperature may be within a range of about 0.degree. to 
200.degree. C., preferably of about 20.degree. to 160.degree. C. 
After completion of the reaction, the reaction mixture may be subjected to 
per se conventional separation or purification treatment such as 
extraction, concentration, distillation, chromatography or 
recrystallization to obtain the cyclopentenone compound (IV). 
The isomerization may be also carried out by treating the 
hydroxycyclopentenone (III) in the presence of chloral and an organic 
amine in an inert solvent. In this treatment, chloral is normally used in 
an amount of about 0.005 to 1 mol, preferably of about 0.01 to 0.3 mol, to 
one mole of the hydroxycyclopentenone (III). The use of an organic amine 
is industrially advantageous, because it can reduce the amount of chloral. 
As the organic amine, the use of a tertiary amine (e.g. triethylamine, 
N-methylmorpholine, N-methylpiperazine, N,N'-dimethylpiperazine, pyridine, 
lutidine) is favored. Usually, the organic amine is employed in an amount 
of about 0.005 to 0.4 mol to one mol of the hydroxycyclopentenone (III). 
Examples of the inert solvent are ethers (e.g. tetrahydrofuran, dioxane), 
ketones (e.g. acetone), hydrocarbons (e.g. heptane, cyclohexane, benzene, 
toluene), halogenated hydrocarbons (e.g. chlorobenzene, dichloromethane, 
dichloroethane), esters (e.g. ethyl acetate), etc. The reaction 
temperature may be within a range of about -10.degree. to 100.degree. C., 
preferably of about 0.degree. to 90.degree. C. 
After completion of the reaction, the reaction mixture may be subjected to 
per se conventional separation or purification treatment such as 
extraction, concentration, distillation, chromatography or 
recrystallization to obtain the cyclopentenone compound (IV). 
The acylation of the cyclopentenone compound (IV) to the dl-cyclopentenone 
ester (II) may be performed by a per se conventional acylation procedure. 
For instance, the cyclopentenone compound (IV) is reacted with a lower 
fatty acid in a reactive form, if necessary, in the presence of any 
reaction aid in an inert solvent to give the dl-cyclopentenone ester (II). 
As the reactive form of the lower fatty acid, there are exemplified a 
lower fatty acid halide such as a lower alkanoyl halide (e.g. acetyl 
chloride, acetyl bromide, propionyl chloride, propionyl bromide, butyryl 
chloride, butyryl bromide) or a halogenated lower alkanoic acid talide 
(e.g. chloroacetyl chloride, chloroacetyl bromide, dichloroacetyl 
chloride, dichloroacetyl bromide), a lower fatty acid anhydride such as a 
lower alkanoic anhydride (e.g. acetic anhydride, propionic anhydride), 
etc. Usually, the lower fatty acid in a reactive form may be used in an 
amount of about one equivalent or more, particularly of about 1 to 4 
equivalents, to the cyclopentenone compound (IV). When an inert solvent is 
used in the reaction, such inert solvent may be chosen from ethers (e.g. 
tetrahydrofuran, diethyl ether), ketones (e.g. acetone, 
methylethylketone), hydrocarbons (e.g. hexane, toluene, benzene), 
halogenated hydrocarbons (e.g. chlorobenzene, dichloromethane, 
dichloroethane, chloroform, carbon tetrachloride), amides (e.g. 
dimethylformamide), etc. As the reaction aid, there is advantageously used 
an organic or inorganic basic substance (e.g. triethylamine, 
tri-n-butylamine, pyridine, picoline, sodium carbonate, sodium methoxide, 
potassium hydrogen carbonate) in an amount of about 1 to 5 equivalents to 
the cyclopentenone compound (IV) in order to effect the reaction smoothly 
and promptly. When an organic amine is used as a reaction medium, it may 
simultaneously serve as the reaction aid. An acidic substance such as 
toluenesulfonic acid, methanesulfonic acid or sulfuric acid is also usable 
as the reaction aid. 
The reaction temperature is usually within a range of about -20.degree. to 
150.degree. C., preferably of about -10.degree. to 120.degree. C. Any 
particular limitation is not present on the reaction time. 
After completion of the reaction, the reaction mixture may be post-treated 
according to a per se conventional separation or purification procedure 
such as extraction, separation, concentration or distillation to give the 
dl-cyclopentenone ester (II).

Practical and presently preferred embodiments of the invention are 
illustratively shown in the following Examples. 
EXAMPLE 1 
(1) Into a four necked-flask equipped with a stirrer and a thermometer, 
2-(1-hydroxy-7-methoxycarbonylheptyl)-furan 114 g), water (4560 g) and 
potassium monohydrogen phosphate-phosphoric acid buffer (3.8 g) were 
charged, and the resulting mixture (pH 4.2) was stirred at 100.degree. C. 
under nitrogen stream until the starting compound was consumed perfectly. 
The reaction mixture was cooled and extracted with methylisobutylketone 
(600 ml) two times. The extracts were combined together and concentrated 
under reduced pressure to give a mixture (92 g) of 
3-hydroxy-2-(6-methoxycarbonylhexyl)-4-cyclopentenone and 
4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone. Yield, 80.7%. 
(2) The above obtained mixture (12.0 g) was combined with acetic acid (17.0 
g), acetic anhydride (5.1 g) and anhydrous sodium acetate (0.29 g), and 
the resultant mixture was heated at 120.degree. C. for 4 hours. After 
termination of the reaction was confirmed by gas chromatography, the 
reaction mixture was concentrated under reduced pressure. To the 
concentrated residue, toluene (200 ml) and water (100 ml) were added 
thereto, followed by shaking. The organic layer was separated, washed with 
3% sodium bicarbonate solution and water in order, dried over anhydrous 
magnesium sulfate and concentrated to give 
4-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (13.1 g). Yield, 
93%. b.p., 180.degree.-185.degree. C./0.6 mmHg. 
(3) 4-Acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (4 g), 
dichloromethane (2 ml) and a lipase (400 mg) produced by a microorganism 
belonging to Pseudomonas ("Amano Lipase P" manufactured by Amano 
Pharmaceutical Co., Ltd.) were charged into a flask, and the resulting 
mixture was stirred vigorously at 25.degree. to 30.degree. C. for 13 
hours. After completion of the reaction, the reaction mixture was 
extracted with toluene (40 ml ) two times. The extracts were combined 
together and concentrated under reduced pressure to give a residue (3.98 
g), which was subjected to column chromatography using a mixture of 
toluene and ethyl acetate (5:3) as an eluting solvent to give 
4R(+)-hydroxy-2-(6-methoxycarbonylhexyl)- 2-cyclo-pentenone (1.01 g) 
([.alpha.].sub.D.sup.20 +15.1.degree. (c=1, methanol) (88% ee); m.p., 
58.degree. C.) and 
4S(-)-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (2.60 g) 
([.alpha.].sub.D.sup.20 -43.1.degree. (c=1, methanol); m.p., 41.degree. 
C.). 
(4) 4-Acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (4 g) and a 
lipase (400 mg) produced by a microorganism belonging to Pseudomonas 
("Amano Lipase P" manufactured by Amano Pharmaceutical Co., Ltd.) were 
charged into a flask, and the resulting mixture was stirred vigorously at 
40.degree. C. for 5 hours. After completion of the reaction, the reaction 
mixture was treated in the same manner as in Example 1 (3) to give 
4R(+)-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (0.98 g) 
([.alpha.].sub.D.sup.20 14.9.degree. (c=1, methanol) (86.7% ee)) and 
4S(-)-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (2.66 g) 
([.alpha.].sub.D.sup.20 43.5.degree. (c=1, methanol)). 
EXAMPLE 2 
(1) Into the same flask as in Example 1, a mixture of 
3-hydroxy-2-(6-methoxycarbonylhexyl)-4-cyclopentenone and 
4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (weight proportion, 
3:1) (72.0 g; 0.3 mol), water (2200 g) and acetic acid-1N sodium hydroxide 
buffer (2.4 g) were charged, and the resulting mixture (pH 8) was stirred 
at 100.degree. C. under nitrogen stream until the starting compound was 
consumed perfectly. After completion of the reaction, the reaction mixture 
was cooled and extracted with methylisobutylketone (600 g) two times. The 
extracts were combined together and concentrated under reduced pressure to 
give 4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (60 g). Yield, 
83.2%. n.sub.D.sup.25 =1.4875. 
(2) A mixture of 3-hydroxy-2-(6-methoxycarbonylhexyl)-4-cyclopentenone and 
4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (weight proportion, 
3:1) (5 g), chloral (0.46 g), pyridine (0.29 g) and toluene (20 ml) were 
charged in a reactor and stirred at 30.degree. to 40 .degree. C. for 6 
hours. After completion of the reaction, the reaction mixture was washed 
with water, 1% hydrochloric acid, 1% sodium bicarbonate solution and water 
in order. The organic layer was concentrated to give 
4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (4.9 g). Yield, 98%. 
(3) 4-Hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (24 g) was 
dissolved in chloroform (200 ml), followed by addition of acetyl chloride 
(7.9 g) thereto. Triethylamine [10.1 g) was dropwise added thereto while 
stirring at 0.degree. to 10.degree. C. After completion of the addition, 
stirring was continued at 25.degree. C. for 8 hours. The reaction mixture 
was washed with water, dried over anhydrous magnesium sulfate and 
concentrated under reduced pressure to give 
4-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (27.6 g). Yield, 
98%. 
(4) 4-Acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (4 g), 
dichloromethane (2 ml) and a lipase (300 mg) produced by a microorganism 
belonging to Arthrobacter (manufactured by Sin-Nippon Chemical Co., Ltd.) 
were charged into a reactor. Asymmetric hydrolysis was carried out in the 
same manner as in Example 1 (3), followed by post-treatment to give 
4R(+)-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (1.21 g) 
([.alpha.].sub.D.sup.20 +16.1.degree. (c=1, methanol) (94.8% ee)) and 
4S(-)-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (2.54 g) 
([.alpha.].sub.D.sup.20 -40.4.degree. (c=1, methanol)). 
(5) 4-Acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone (4 g) and a 
lipase (300 mg) produced by a microorganism belonging to Arthrobacter 
(manufactured by Sin-Nippon Chemical Co., Ltd.) were charged into a 
reactor, and the resulting mixture was treated in the same manner as in 
Example 1 (4) for asymmetric hydrolysis, followed by post-treatment to 
give 4R(+)-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone 
([.alpha.].sub.D.sup.20 +15.8.degree. (c=1, methanol) (92.3% ee)) and 
4S(-)-acetoxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone 
([.alpha.].sub.D.sup.20 -42.degree. (c=1, methanol)). 
EXAMPLE 3 
In the same manner as in Example 2 (1) but using a mixture of 
3-hydroxy-2-(4-methoxycarbonylbutyl)-4-cyclopentenone and 
4-hydroxy-2-(4-methoxycarbonylbutyl)-2-cyclopentenone (weight proportion, 
3:1) (0.25 mol; 52.5 g), there was produced 
4-hydroxy-2-(4-methoxycarbonylbutyl)-2-cyclopentenone (42.1 g). Yield, 
80.2%. 
The thus obtained 4-hydroxy-2-(4-methoxycarbonylbutyl)-2-cyclopetenone was 
subjected to asymmetric hydrolysis in the same manner as in Example 2 (3) 
or 2 (4) to give 
4R(+)-hydroxy-2-(4-methoxycarbonylbutyl)-2-cyclopentenone. 
EXAMPLE 4 
Into the same flask as in Example 1, 2-(1-hydroxy- 
7-ethoxycarbonylheptyl)-furan (18 g) and water (720 g) were charged, and 
the resultant mixture (pH, 4.2-4.5) was stirred at 100.degree. C. until 
the starting compound was consumed completely. After completion of the 
reaction, the reaction mixture was post-treated in the same manner as in 
Example 1 (1) to give a mixture of 
3-hydroxy-2-(6-ethoxycarbonylhexyl)-4-cyclopentenone and 
4-hydroxy-2-(6-ethoxycarbonylhexyl)-2-cyclopentenone (14.4 g). Yield, 
79.8%. 
To the mixture (12.7 g) as above obtained, sodium acetate (2.1 g), acetic 
anhydride (5.1 g) and acetic acid (40 g), and the resultant mixture was 
heated at 110.degree. C. for 4 hours. After completion of the reaction, 
the reaction mixture was treated in the same manner as in Example 1 (2) to 
give 4-acetoxy-2-(6-ethoxycarbonylhexyl)-2-cyclopentenone (14.9 g). Yield, 
95.1%. b.p., 189.degree.-193.degree. C./0.5 mmHg. 
The thus obtained 4-acetoxy-2-(6-ethoxycarbonylhexyl)-2-cyclopetenone was 
subjected to asymmetric hydrolysis in the same manner as in Example 1 (3) 
to give 4R(+)-hydroxy-2-(6-ethoxycarbonylhexyl)-2-cyclopentenone.