Patent Description:
Prostaglandins (PGs) are a general term for a group of endogenous bioactive substances that are synthesized in vivo from arachidonic acid by cyclooxygenase metabolism. There are numerous types of prostaglandins and prostaglandin H<NUM>, prostaglandin D<NUM>, prostaglandin E<NUM>, prostaglandin E<NUM>, prostaglandin F<NUM>α, prostaglandin I<NUM>, and the like are known. Prostaglandins are involved in diverse physiological functions via the respective specific G-protein-coupled receptors thereof.

The chemical structure of prostaglandins is characterized by being provided with a cyclopentane ring with four chiral carbons and two aliphatic side chains. For this reason, prostaglandins have long attracted attention as the target of synthetic research or the seeds of drug discovery and various prostaglandin derivatives have been developed so far.

(3aS,4R,<NUM>,6aR)-(+)-hexahydro-<NUM>-hydroxy-<NUM>-(hydroxymethyl)-<NUM>-cycl openta[b]furan-<NUM>-one, used as a common intermediate for the above, is also called "Corey lactone". The chemical structures of Corey lactone and typical commercially available prostaglandin derivatives are shown below.

Prostaglandins have a functionalized cyclopentane ring in the center of the chemical structure thereof and long aliphatic side chains on two adjacent carbon atoms, one of which has a carboxy group or carboxylic acid ester. Prostaglandins are generally produced by the following methods, via a common synthetic intermediate, with the oxidation stage of the substituent adjusted in subsequent steps. Many prostaglandins have a cis-type double bond in the aliphatic side chains and the problem is how to remove the geometrical isomers thereof when carrying out the chemical synthesis. Compounds with a cis-type double bond are also called Z-isomers and compounds with a trans-type double bond are called E-isomers.

The present invention has an object of providing a method for separating compounds having a structure similar to prostaglandins from the geometrical isomers thereof.

The present invention provides the following [<NUM>] to [<NUM>].

According to the present invention, it is possible to provide a method for separating compounds having a structure similar to prostaglandins from geometrical isomers thereof.

A detailed description will be given below of the present invention.

One embodiment of the present invention is method for separating a compound represented by Formula (<NUM>) or (<NUM>) from a geometrical isomer thereof, in which the geometrical isomer is a geometrical isomer in a double bond included in A, the method including processing a mixture containing the compound and the geometrical isomer thereof by a chromatographic method using an acidic functional group-modified silica gel as a stationary phase. <CHM>
[in the formula, P<NUM> and P<NUM> are each independently a hydrogen atom or a protective group of a hydroxyl group, R<NUM> is a linear or branched C<NUM>-<NUM> alkyl group that may be substituted with a phenyl group, A is a C<NUM>-<NUM> alkenylene group, R<NUM> is a hydroxyl group, a C<NUM>-<NUM> alkoxy group, a mono(C<NUM>-<NUM> alkyl)amino group, or a di(C<NUM>-<NUM> alkyl)amino group, and
<CHM>
is a single bond or double bond.

The combination of two or more geometrical isomers as separation targets in the method according to the present embodiment is a compound represented by Formula (<NUM>) or (<NUM>), which is in a cis-isomer and trans-isomer relationship in the double bond included in A. In a case where the double bond is also present in the other side chain (the side chain having R<NUM>), it is possible for a total of four types of geometrical isomers to be present.

P<NUM> and P<NUM> are each independently a hydrogen atom or a protective group of a hydroxyl group. The protective group of the hydroxyl group is a substituent used for the purpose of protecting the hydroxyl group to prevent reaction with a reactant in an organic synthetic reaction. The protective group of the hydroxyl group is not particularly limited and examples thereof include acetal-based protective groups such as a methoxymethyl group, an ethoxyethyl group, a benzyloxymethyl group, or a tetrahydropyranyl group, ether-based protective groups such as a benzyl group, a p-methoxybenzyl group, or a p-nitrobenzyl group, acyl-based protective groups such as an acetyl group, a pivaloyl group, a benzoyl group, and a p-methoxybenzoyl group, and silyl-based protective groups such as a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethyl group, a triphenylsilyl group, and a phenyldimethylsilyl group.

R<NUM> is a linear or branched C<NUM>-<NUM> alkyl group that may be substituted with a phenyl group. A linear or branched C<NUM>-<NUM> alkyl group is an alkyl group having <NUM> to <NUM> carbon atoms and specific examples thereof include a methyl group, an ethyl group, a <NUM>-propyl group, a <NUM>-propyl group, a <NUM>-butyl group, a <NUM>-butyl group, a tert-butyl group, a <NUM>-pentyl group, a <NUM>-pentyl group, a <NUM>-pentyl group, a <NUM>,<NUM>-dimethyl propyl group, <NUM>-hexyl group, <NUM>-hexyl group, a <NUM>-hexyl group, and the like. R<NUM> may be the linear or branched C<NUM>-<NUM> alkyl group described above substituted with a phenyl group.

A is a C<NUM>-1O alkenylene group and specific examples thereof include a propenylene group, a butenylene group, a pentenylene group, a hexenylene group, a heptenylene group, an octenylene group, a nonylene group, or a decenylene group. The position of the double bond in A is not particularly limited. According to the separation method according to the present embodiment, it is possible to separate the geometrical isomers (cis-isomer and trans-isomer) in the double bond.

R<NUM> is a hydroxyl group, a C<NUM>-<NUM> alkoxy group, a mono(C<NUM>-<NUM> alkyl)amino group or a di(C<NUM>-<NUM> alkyl)amino group. A C<NUM>-<NUM> alkoxy group is a group in which an alkyl group having <NUM> to <NUM> carbon atoms is substituted for an oxygen atom and specific examples thereof include a methoxy group, an ethoxy group, a <NUM>-propoxy group, or a <NUM>-propoxy group. A mono(C<NUM>-<NUM> alkyl)amino group is a group in which one alkyl group having <NUM> to <NUM> carbon atoms is substituted for a nitrogen atom and specific examples thereof include a monomethylamino group, a monoethylamino group, a mono(<NUM>-propyl)amino group, a mono(<NUM>-propyl)amino group, and the like. A di(C<NUM>-<NUM> alkyl)amino group is a group in which two alkyl groups having <NUM> to <NUM> carbon atoms are substituted for a nitrogen atom and specific examples thereof include a dimethyl amino group, a diethyl amino group, a di(<NUM>-propyl)amino group, a di(<NUM>-propyl)amino group, an ethyl(methyl)amino group, and the like.

The separation method according to the present embodiment includes treating the mixture of geometrical isomers by a chromatographic method using an acidic functional group-modified silica gel as a filling material (stationary phase).

The acidic functional group-modified silica gel used as the stationary phase in the chromatographic method may be any silica gel modified with acidic functional groups. Examples of acidic functional group-modified silica gels include carboxy group-modified silica gels, sulfo group-modified silica gels, and the like. The chromatographic method described above is preferably normal-phase chromatography.

The shape of the acidic functional group-modified silica gel may be spherical or crushed, preferably spherical. Spherical silica gel has a constant surface area and is able to be packed uniformly in a column, thus, the degree of separation is further improved when carrying out separation by the chromatographic method.

The average particle size of the acidic functional group-modified silica gel may be <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

The length of the column may be <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. A column length of <NUM> or longer improves the degree of separation and widens the eluent selection range.

For the eluent (mobile phase), it is possible to use organic solvents well known to a person skilled in the art. Examples of organic solvents include aliphatic hydrocarbon-based solvents such as pentane, hexane, and heptane; aromatic hydrocarbon-based solvents such as toluene; halogenated hydrocarbon-based solvents such as dichloromethane and chloroform; ester-based solvents such as ethyl acetate and propyl acetate; alcohol-based solvents such as methanol, ethanol, and <NUM>-propanol, and the like. It is possible to select these solvents as appropriate in consideration of the solubility of the crude product for purification which is the separation target and also to mix and use these solvents in any ratio in consideration of mutual compatibility. Examples of mixed solvents include binary mixed solvents such as a combination of hexane and ethanol, hexane and isopropanol, or hexane and ethyl acetate, and ternary mixed solvents such as a combination of hexane, methanol, and isopropanol.

In the present specification, "separating a compound represented by Formula (<NUM>) or (<NUM>) from the geometrical isomer thereof" means that, in a case where the content of the desired compound is <NUM>, the content of the corresponding geometrical isomer is <NUM> or less, preferably <NUM> or less, and more preferably <NUM> or less. In addition, the purity of the compound represented by Formula (<NUM>) or (<NUM>) after separation may be <NUM>% or more, <NUM>% or more is preferable, and <NUM>% or more, <NUM>% or more, or <NUM>% or more is more preferable.

A more detailed description will be given below of the present invention using Examples and Comparative Examples.

Abbreviations used in the Examples and the like are to be understood with the meanings well-known to a person skilled in the art, unless otherwise noted. For example, the meanings of some abbreviations are given below.

A crude product for purification (EZ mixture of IFL-FA, <NUM>) was dissolved in dichloromethane and purified by a chromatographic method according to the following separation conditions and the fractions where the E-isomer was not detected under the following analysis conditions were collected to obtain the Z-isomer (yield amount: <NUM>, yield rate: <NUM>%).

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram obtained under the analysis conditions described above. (E)-IFL-FA is (E)-<NUM>-[(1R,2R,3R,<NUM>)-<NUM>,<NUM>-dihydroxy-<NUM>-[(3R)-<NUM>-hydroxy-<NUM>-phenylpentyl ]cyclopentyl]hepto-<NUM>-enoic acid.

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram obtained under the analysis conditions described above. The content ratio of the E-isomer was <NUM>% and the Z-isomer was obtained with high purity.

A crude product for purification (EZ mixture of IFL-PPF, <NUM>) was dissolved in a mixture of hexane and ethyl acetate and purified by a chromatographic method according to the following separation conditions and the fractions having <NUM>% or less of the E-isomer were collected under the following analysis conditions to obtain the Z-isomer (yield amount: <NUM>, yield rate: <NUM>%). Analysis was performed after concentrating approximately <NUM> of the fraction, dissolving the residue in <NUM> of <NUM>-propanol, adding a catalytic amount of paratoluenesulfonic acid monohydrate and carrying out a reaction at room temperature for approximately <NUM> hours to deprotect and derivatize to IFL-FA (refer to Example <NUM>).

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram. (E)-IFL-PPF is (E)-<NUM>-[(1R,2R,3R,<NUM>)-<NUM>-hydroxy-<NUM>-[(3R)-<NUM>-phenyl-<NUM>-[(tetrahydro-<NUM>-p yran-<NUM>-yl)oxy]pentyl]-<NUM>-[(tetrahydro-<NUM>-pyran-<NUM>-yl)oxy]cyclopentyl]he pto-<NUM>-enoic acid. The E-isomer included in the Z-isomer after separation was <NUM>% when measured under the above analysis conditions. In addition, it was also possible to separate triphenylphosphine, which was included to a large extent in the crude product for purification.

The crude product for purification (EZ mixture of latanoprost, <NUM>) was dissolved in a mixture of hexane and ethyl acetate and purified by the chromatographic method according to the following separation conditions and the fractions having <NUM>% or less of the E-isomer were collected under the following analysis conditions to obtain the Z-isomer (yield amount: <NUM>, yield rate: <NUM>%).

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram. (E)-Latanoprost is a propan-<NUM>-yl (E)-<NUM>-[(1R,2R,3R,<NUM>)-<NUM>,<NUM>-dihydroxy-<NUM>-[(3R)-<NUM>-hydroxy-<NUM>-phenylpentyl ]cyclopentyl]hepto-<NUM>-enoate. The content ratio of the E-isomer was <NUM>% under the above analysis conditions and it was possible to obtain the Z-isomer with high purity.

The crude product for purification (EZ mixture of IFL, <NUM>) was dissolved in a mixture of hexane and ethyl acetate and purified by the chromatographic method according to the following separation conditions and the fractions having <NUM>% or less of the E-isomer were collected under the following analysis conditions to obtain the Z-isomer (yield amount: <NUM>, yield rate: <NUM>%).

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram. The content ratio of the E-isomer was <NUM>% and it was possible to obtain the Z-isomer with high purity.

The crude product for purification (EZ mixture of IEL, <NUM>) was dissolved in dichloromethane and purified by the chromatographic method according to the following separation conditions and the fractions where the E-isomer was not detected under the following analysis conditions were collected to obtain the E-isomer (yield amount: <NUM>, yield rate: <NUM>%).

The content ratios of each isomer before and after separation are shown in Table <NUM>. The content ratio of each compound was calculated based on the area under the curve of the chromatogram. (Z)-IEL is (Z)-<NUM>-((1R,2R,3R)-<NUM>-hydroxy-<NUM>-((<NUM>,<NUM>,E)-<NUM>-hydroxy-<NUM>-methylnon-<NUM>-e n-<NUM>-yl)-<NUM>-oxocyclopentyl)hepto-<NUM>-enoic acid, and AT-IEL is (E)-<NUM>-((1R,<NUM>)-<NUM>-((<NUM>,<NUM>,E)-<NUM>-hydroxy-<NUM>-methylnon-<NUM>-en-<NUM>-yl)-<NUM>-oxoc yclopent-<NUM>-en-<NUM>-yl)hepto-<NUM>-enoic acid. The content ratio of the E-isomer included in the Z-isomer after separation was <NUM>% under the above analysis conditions. In addition, it was also possible to separate AT-IEL, which was included to a large extent in the crude product for purification.

The crude product for purification (EZ mixture, <NUM>) was dissolved in a mixed solvent of hexane and ethyl acetate and purified by the chromatographic method according to the following separation conditions to obtain the (Z) isomer (yield amount: <NUM>, yield rate: <NUM>%). In all recovered fractions, (E)-latanoprost was detected and was not able to be separated. Analysis was performed by concentrating approximately <NUM> of the fractions, dissolving the residue in <NUM> of <NUM>-propanol, adding a catalytic amount of paratoluenesulfonic acid monohydrate, and carrying out a reaction at room temperature for approximately <NUM> hours to deprotect and derivatize to IFL-FA (refer to Example <NUM>).

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram.

The crude product for purification (EZ mixture of latanoprost, <NUM>) was dissolved in a mixture of hexane and ethyl acetate and purified by the chromatographic method according to the following separation conditions to obtain (Z)-latanoprost (yield amount: <NUM>, yield rate: <NUM>%). In all fractions including (Z)-latanoprost, (E)-latanoprost was detected under the following analysis conditions and was not able to be separated.

The content ratio of each isomer before and after separation is shown in Table <NUM>. The content ratio of each isomer content was calculated based on the area under the curve of the chromatogram.

The crude product for purification (mixture of PGE<NUM> and PGA<NUM>, <NUM>) was dissolved in dichloromethane and purified by the chromatographic method according to the following separation conditions and the fractions not including PGA2 were collected under the following analysis conditions to obtain PGE2 (yield amount: <NUM>, yield rate: <NUM>%).

The content ratios of each isomer before separation and after separation are shown in Table <NUM>. The content ratio of each isomer was calculated based on the area under the curve of the chromatogram obtained under the following analysis conditions.

Claim 1:
A method for separating a compound represented by Formula (<NUM>) or (<NUM>) from a geometrical isomer thereof, wherein the geometrical isomer is a geometrical isomer in a double bond included in A, the method comprising:
processing a mixture containing the compound and the geometrical isomer thereof by a chromatographic method using an acidic functional group-modified silica gel as a stationary phase,
<CHM>
in the formulae, P<NUM> and P<NUM> are each independently a hydrogen atom or a protective group of a hydroxyl group, R<NUM> is a linear or branched C<NUM>-<NUM> alkyl group that may be substituted with a phenyl group, A is a C<NUM>-<NUM> alkenylene group, R<NUM> is a hydroxyl group, a C<NUM>-<NUM> alkoxy group, a mono(C<NUM>-<NUM> alkyl)amino group, or a di(C<NUM>-<NUM> alkyl)amino group, and
<CHM>
is a single bond or a double bond.