JP6766432B2 - Method for producing polyamino acids - Google Patents

Description

The present invention relates to a method for producing a polyamino acid. More specifically, the present invention relates to a method for producing a polyamino acid having an N-substituted peptide chain, a synthetic intermediate thereof, and a method for producing the synthetic intermediate.

N-substituted peptides (peptoids) do not form hydrogen bonds between amides and can easily take higher-order structures such as helix structure and sheet structure than peptides. Therefore, peptide drugs, antifouling materials, cell culture substrates, etc. It is attracting attention as a new functional material in the field of drug transport carriers and the like, and it is desired to improve the efficiency of N-substituted peptide synthesis.

On the other hand, as a method for synthesizing a polyamino acid, a method of obtaining an N-carboxyanhydride of an amino acid and ring-opening polymerization thereof, a method of polycondensing the amino acid in the presence of a molten salt compound, and the like are known. However, all of them have problems that there are many reaction steps, toxic phosgen is required, heating at a high temperature is required and racemization is likely to occur, or it is not suitable for industrial production.

Japanese Unexamined Patent Publication No. 2004-307558 JP-A-2009-74035 Japanese Unexamined Patent Publication No. 2015-12878

Yamada, S.A. Koga, K.K. Sudo, A.I. Goto, M. et al. Endo, T.I. J. Polym. Sci. PART A: Polm. Chem. , 2013, 51, 3726-3731 Yamada, S.A. Sudo, A.I. Goto, M. et al. Endo, T.I. RSC Adv. , 2014, 4, 29890-29896

Therefore, in recent years, as a method for producing a polyamino acid without using phosgen, a method for polycondensing an amino acid carbamate compound synthesized from an amino acid and a phenol derivative has been proposed (Patent Documents 2 and 3, Non-Patent Document 1). 2, 2). Unlike the N-carboxyanhydride of amino acids, the carbamate compound used in this method has high stability in the atmosphere, and polyamino acids can be easily produced by this method. However, this method can be used to produce N-substituted peptides. The application has not yet been investigated.

Against the background as described above, it is an object of the present invention to provide a method capable of easily producing a polyamino acid having an N-substituted peptide chain in a high yield.

As a result of diligent studies, the present inventors have found that a polyamino acid having an N-substituted peptide chain can be easily produced in high yield by polycondensing an N-substituted amino acid carbamate compound, and completed the present invention.

That is, the present invention provides the following <1> to <7>.

<1> A method for producing a polyamino acid, which comprises a step of polycondensing an N-substituted amino acid carbamate compound (hereinafter, also referred to as a method for producing a polyamino acid of the present invention).
<2> The production method according to <1>, wherein the N-substituted amino acid carbamate compound is an N-[(aryloxy) carbonyl] -N-substituted amino acid.
<3> The production method according to <1> or <2>, wherein the N-substituted amino acid carbamate compound is a compound represented by the following formula (1).

[In equation (1),
R ¹ and R ² independently represent a hydrogen atom or an organic group, respectively.
Y indicates an electron-withdrawing group,
m represents an integer from 0 to 5. ]

<4> The production method according to <3>, wherein the polycondensation is carried out in the presence of a basic compound.
<5> The production method according to <4>, wherein the basic compound is a primary or secondary amine compound, and the polyamino acid is represented by the following formula (5-2).

[In equation (5-2),
R ³ represents a secondary or tertiary amino group,
n indicates an integer of 2 or more,
R ¹ and R ² are synonymous with the above. ]

<6> A compound represented by the following formula (1) (hereinafter, also referred to as compound (1)).

[In equation (1), R ¹ , R ² , Y and m have the same meanings as described above. ]

<7> A method for producing a compound (1), which comprises a step of opening a ring of a compound represented by the following formula (4).

[In equation (4), R ¹ , R ² , Y and m have the same meanings as described above. ]

According to the method for producing a polyamino acid of the present invention, a polyamino acid having an N-substituted peptide chain can be easily produced in a high yield.

It is a figure which shows the MALDI-TOF MS spectrum of poly (N-methylalanine). It is a figure which shows the CD spectrum of poly (N-methylalanine). It is a figure which shows the conversion rate of a monomer and NCA when polymerized at 60 degreeC. It is a figure which shows the conversion rate of a monomer and NCA when polymerized at 80 degreeC.

<Manufacturing method of polyamino acid>
The method for producing a polyamino acid of the present invention is characterized by including a step of polycondensing an N-substituted amino acid carbamate compound. In the present specification, "polyamino acid" is a concept including an N-substituted peptide, a copolymer of a peptide and an N-substituted peptide, and the like. According to the present invention, a polyamino acid having an N-substituted peptide chain can be produced.

As used herein, the term "N-substituted amino acid carbamate compound" means a compound having a substituent on the nitrogen atom in the urethane bond of the amino acid carbamate compound. If the N-substituted amino acid carbamate compound has an optical isomer, any optical isomer may be used, or even if one type of optical isomer is used alone, a plurality of optical isomers may be combined. May be used.
As the N-substituted amino acid carbamate compound, N-[(aryloxy) carbonyl] -N-substituted amino acid is preferable from the viewpoint of reaction efficiency. Further, in this compound, as the "aryloxy group" bonded to the carbonyl group, the group represented by the following formula (A) is preferable from the viewpoint of reaction efficiency.
Among the N-substituted amino acid carbamate compounds, the compound represented by the following formula (1) is particularly preferable from the viewpoint of reaction efficiency.

[In formula (A),
Y indicates an electron-withdrawing group,
m represents an integer from 0 to 5 and represents
* Indicates a bonder. ]

[In equation (1),
R ¹ and R ² independently represent a hydrogen atom or an organic group, respectively.
Y and m are synonymous with the above. ]

In the formula (A) and the formula (1), examples of the electron-withdrawing group represented by Y include a nitro group; a halogen atom such as a chlorine atom, a bromine atom and a fluorine atom; a perfluoroalkyl group and a perchloroalkyl group. (Here, examples of the alkyl group include linear, branched or cyclic saturated or unsaturated alkyl groups having 1 to 8 carbon atoms); acetyl group; cyano group; benzoyl group and the like. Can be mentioned. Of these, a nitro group is preferred. When m is an integer of 2 to 5, m Ys may be the same or different.
Further, in the formula (A) and the formula (1), m represents an integer of 0 to 5, but an integer of 0 to 2 is preferable, and 0 is more preferable.

In formula (1), R ¹ and R ² each independently represent a hydrogen atom or an organic group.
Examples of the organic group represented by R ¹ and R ² include a substituted or unsubstituted hydrocarbon group, a substituted or unsubstituted heterocyclic group and the like.

The hydrocarbon groups represented by R ¹ and R ² may be linear, branched or cyclic, and may be saturated hydrocarbon groups or unsaturated hydrocarbon groups. As the hydrocarbon group, an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group are preferable.
The alkyl groups represented by R ¹ and R ² may be linear or branched. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group and the like. Can be mentioned. The cycloalkyl group preferably has 3 to 12 carbon atoms, more preferably 3 to 6 carbon atoms. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and the like. The aryl group preferably has 6 to 10 carbon atoms. Examples of the aryl group include a phenyl group and a naphthyl group. As the aralkyl group, C _6-10 aryl-C _1-6 alkyl group and di C _6-10 aryl-C _1-6 alkyl group are preferable, and C _6-10 aryl-C _1-3 alkyl group and di C ₆ are preferable. _-10aryl- C _1-3 alkyl groups are more preferred. Examples of the aralkyl group include a benzyl group, a phenethyl group, a diphenylmethyl group and the like.

Examples of the group that can be substituted with the hydrocarbon group include a hydroxy group, a mercapto group, a carboxy group, a sulfinyl group, a sulfonyl group, a carbamoyl group, an amino group, and a group in which these substituents are protected. The protected groups include an alkoxy group, an aralkyloxy group, an alkylthio group, an aralkylthio group, an alkoxycarbonyl group, an aralkyloxycarbonyl group, an alkylsulfinyl group, an aralkylsulfinyl group, an alkylsulfonyl group, an aralkylsulfonyl group and a triarylalkyl group. Examples thereof include a carbamoyl group, an alkoxycarbonylamino group, an aralkyloxycarbonylamino group, an alkanoylamino group, and an arylcarboxyamino group.
Examples of the alkoxy group include C _1-6 alkoxy groups such as a methoxy group and an ethoxy group. Examples of the aralkyloxy group include a C _6-10 aryl-C _1-3 alkyloxy group such as a benzyloxy group. Examples of the alkylthio group include a C _1-6 alkylthio group such as a methylthio group. Examples of the aralkylthio group include a C _6-10 aryl-C _1-3 alkylthio group such as a benzylthio group. Examples of the alkoxycarbonyl group include C _1-6 alkoxycarbonyl groups such as a methoxycarbonyl group, an ethoxycarbonyl group, and a butoxycarbonyl group. Examples of the aralkyloxycarbonyl group include a C _6-10 aryl-C _1-3 alkyloxycarbonyl group such as a benzyloxycarbonyl group. Examples of the alkylsulfinyl group include C _1-6 alkylsulfinyl groups such as a methylsulfinyl group. Examples of the aralkylsulfinyl group include C _6-10 aryl-C _1-3 alkylsulfinyl groups such as a benzylsulfinyl group. Examples of the alkylsulfonyl group include a C _1-6 alkylsulfonyl group such as a methylsulfonyl group. Examples of the aralkylsulfonyl group include a C _6-10 aryl-C _1-3 alkylsulfonyl group such as a benzylsulfonyl group. The triaryl alkylcarbamoyl groups include tri C _6-10 aryl -C _1-6 alkylcarbamoyl group such as tri-Chi carbamoyl group. Examples of the alkoxycarbonylamino group include a C _1-6 alkoxycarbonylamino group such as a butoxycarbonylamino group. Examples of the aralkyloxycarbonylamino group include a C _6-10 aryl-C _1-3 alkyloxycarbonylamino group such as a benzyloxycarbonylamino group. Examples of the alkanoylamino group include a C _2-7 alkanoylamino group such as an acetylamino group. Examples of the arylcarboxyamino group include C _6-10 arylcarboxyamino groups such as a benzoylamino group.

Examples of the heterocyclic group represented by R ¹ and R ² include an indolyl group, a pyrrolidinyl group, an imidazolyl group, a pyrrolyl group, a piperidinyl group, a dihydroquinolinyl group and the like. Examples of the group that can be substituted with a heterocyclic group include an alkyl group in addition to the group that can be substituted with the above hydrocarbon group. As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferable.

The substitution positions and the number of substituents in R ¹ and R ² are arbitrary, but the number is preferably 1 or 2. Further, when R ¹ and R ² contain an amino group and a polyamino acid is produced without protecting the amino group, it is also possible to produce a polyamino acid having a dendron structure or a hyperbranched structure.

As R ¹ , a hydrogen atom, a substituted or unsubstituted hydrocarbon group is preferable, a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group is more preferable, and hydrogen. Atomic, substituted or unsubstituted alkyl groups, substituted or unsubstituted aralkyl groups are more preferred, hydrogen atoms, methyl groups, hydroxydiphenylmethyl groups (-C (OH) (C ₆ H ₅ ) ₂ ) are even more preferred, hydrogen. Atoms are particularly preferred.
As R ² , a hydrogen atom, a substituted or unsubstituted hydrocarbon group is preferable, and a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aralkyl group are more preferable. Examples of the group that can be substituted with the alkyl group represented by R ² include an alkoxy group, an aralkyloxy group, an alkylthio group, an aralkylthio group, an aralkyloxycarbonyl group, a triarylalkylcarbamoyl group, an alkylsulfinyl group, an aralkylsulfinyl group and an alkylsulfonyl group. A group, an aralkylsulfonyl group is preferable, and an aralkyloxy group is preferable as a group that can be substituted with the aralkyl group represented by R ² . Among such R ² , hydrogen atoms, groups represented by the following formulas (i) to (xviii) are more preferable, and hydrogen atoms, groups represented by the following formulas (i) to (xiv) are further preferable. A hydrogen atom and a group represented by the following formulas (i) to (ix) are more preferable, and a hydrogen atom and a group represented by the following formulas (i) to (v) are particularly preferable. In formulas (i) to (xviii), * indicates a bond.

From the viewpoint of reaction efficiency, the method for producing the polyamino acid of the present invention preferably includes the following steps 3, more preferably steps 2 and 3, and particularly preferably steps 1 to 3.

[In the formula, n represents an integer of 2 or more, and each of the other symbols has the same meaning as described above. ]

<Step 1>
Step 1 is a step of reacting the amino acid carbamate compound (2) with the aldehyde (3) to obtain an oxazolidinone derivative (4).

The amino acid carbamate compound (2) may be a carbamate compound of a natural amino acid, a carbamate compound of an unnatural amino acid, a carbamate compound of an active hydrogen-substituted amino acid, or the like. Examples of unnatural amino acids include D-isomers of natural amino acids.
Specific examples of the amino acid carbamate compound (2) include N- (phenoxycarbonyl) -alanine, N- (phenoxycarbonyl) -isoleucine, N- (phenoxycarbonyl) -glycine, and N- (phenoxycarbonyl) -valine. N- (Phenylalanine) -Phenylalanine, N- (Phenyloxycarbonyl) -O-benzyl-Tyrosine, N- (Phenoxycarbonyl) -γ-benzyl-Glutamate, N- (Phenyloxycarbonyl) -β-benzyl-aspartate, N -(Phenyloxycarbonyl) -methionine, N- (phenoxycarbonyl) -leucine, N- (4-nitrophenoxycarbonyl) -alanine, N- (4-nitrophenoxycarbonyl) -isoleucine, N- (4-nitrophenoxycarbonyl) -Glycin, N- (4-nitrophenoxycarbonyl) -valine, N- (4-nitrophenoxycarbonyl) -phenylalanine, N- (4-nitrophenoxycarbonyl) -O-benzyl-tyrosine, N- (4-nitrophenoxy) Carbonyl) -γ-benzyl-glutamate, N- (4-nitrophenoxycarbonyl) -β-benzyl-aspartate, N- (4-nitrophenoxycarbonyl) -methionine, N- (4-nitrophenoxycarbonyl) -leucine, etc. Can be mentioned. These may be used alone or in combination of two or more.
Amino acid carbamate compound (2) is described in J. Am. Polym. Sci. PART A: Polm. Chem. , 2013, 51, 3726-3731, RSC Adv. , 2014, 4, 29890-29896, International Publication No. 10/023892, Japanese Patent Application Laid-Open No. 2009-74035, Japanese Patent Application Laid-Open No. 2015-12878, and the like can be used for synthesis.

Examples of the aldehyde (3) include formaldehyde, a polymer thereof, acetaldehyde, benzyl aldehyde and the like. These may be used alone or in combination of two or more.
The amount of the aldehyde (3) used is usually about 1 to 5 mol, preferably 2 to 3 mol, based on 1 mol of the amino acid carbamate compound (2).

Further, the step 1 is preferably performed in the presence of an acid catalyst. The acid catalyst is preferably Bronsted acid, and specific examples thereof include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid; and organic acids such as p-toluenesulfonic acid and trifluoroacetic acid. These may be used alone or in combination of two or more.
The amount of the acid catalyst used is usually about 0.001 to 1 mol, preferably 0.01 to 0.1 mol, based on 1 mol of the amino acid carbamate compound (2).

In addition, step 1 is usually performed in the presence of a solvent. Examples of such a solvent include aromatic hydrocarbon solvents such as benzene, toluene and xylene; aliphatic alkane solvents such as pentane, hexane, heptane and octane; and cycloalkane solvents such as cyclohexane and cycloheptane. .. These may be used alone or in combination of two or more.
The amount of the solvent used is usually 100 to 10000 parts by mass, preferably 500 to 2000 parts by mass, based on 100 parts by mass of the total amount of the amino acid carbamate compound (2) and the aldehyde (3).

The reaction temperature in step 1 may be appropriately selected below the boiling point of the solvent, but is preferably 100 to 130 ° C. The reaction time is preferably 10 to 20 hours.

<Process 2>
Step 2 is a step of opening the ring of the oxazolidinone derivative (4) to obtain the compound (1).

Step 2 is preferably carried out in the presence of a reducing agent. Examples of the reducing agent include trialkylsilanes such as triethylsilane.
The amount of the reducing agent used is usually about 1 to 10 mol, preferably 1 to 3 mol, based on 1 mol of the oxazolidinone derivative (4).
Further, in step 2, it is preferable to use an acid catalyst together with the reducing agent. Examples of the acid catalyst include those similar to the acid catalyst used in the above step 1.
The amount of the acid catalyst used is usually about 1 to 50 mol, preferably 10 to 20 mol, based on 1 mol of the oxazolidinone derivative (4).

In addition, step 2 is usually performed in the presence of a solvent. Examples of such a solvent include haloalcan solvents such as chloroform and dichloromethane; amide solvents such as dimethylacetamide, dimethylformamide and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; and ketone solvents such as methyl ethyl ketone and acetone; Ester-based solvents such as ethyl acetate and butyl acetate; nitrile-based solvents such as acetonitrile; ether-based solvents such as tetrahydrofuran and cyclopentane monomethyl ether can be mentioned. These may be used alone or in combination of two or more.
The amount of the solvent used is usually 100 to 10000 parts by mass, preferably 500 to 1000 parts by mass with respect to 100 parts by mass of the oxazolidinone derivative (4).

The reaction temperature in step 2 may be appropriately selected below the boiling point of the solvent, but is preferably 20 to 30 ° C. The reaction time is preferably 10 to 20 hours.

Further, the compound (1) obtained in the step 2 is a novel compound. Such compound (1) is useful as a synthetic intermediate for polyamino acids having an N-substituted peptide chain. Further, according to the method for producing the compound (1) containing step 2 (preferably steps 1 and 2), a synthetic intermediate useful for producing a polyamino acid having an N-substituted peptide chain can be easily and obtained in good yield. Can be done.

<Step 3>
Step 3 is a step of polycondensing the compound (1) to obtain a polyamino acid (5). By heat-treating the compound (1) or the like, the phenols (6) and carbon dioxide are desorbed to form an amide bond, and a polyamino acid (5) is produced.

Here, in the formula (5), n represents an integer of 2 or more, but since the polymer usually has a molecular weight distribution, the polyamino acid (5) is a component having an integer of about n = 2 to 500,000. Is a collection of.
The number average molecular weight (M _n ) of the polyamino acid (5) is preferably 100 to 500,000, more preferably 300 to 50,000, further preferably 500 to 10000, and particularly preferably 800 to 5000. The molecular weight distribution (M _w / M _n ) of the polyamino acid (5) is preferably 1.0 to 5.0, more preferably 1.0 to 2.0.
The number average molecular weight (M _n ) and the molecular weight distribution (M _w / M _n ) can be measured by size exclusion chromatography (SEC) or the like.

Further, in step 3, a monomer other than the compound (1) may be copolymerized together with the compound (1). Examples of the monomer include the amino acid carbamate compound (2). As a result, a copolymer of the peptide and the N-substituted peptide can be obtained.

Further, the step 3 can be performed in the presence or absence of the solvent, but it is preferably performed in the presence of the solvent. As such a solvent, the same solvent as that used in Step 2 may be used, but an amide-based solvent and a sulfoxide-based solvent are preferable from the viewpoint of obtaining a high yield and giving a sufficient molecular weight, and an amide-based solvent is preferable. Is more preferable.
The amount of the solvent used is preferably such that the concentration of the compound (1) with respect to the solvent is 0.01 to 20 mol / L from the viewpoint of obtaining a high yield and giving a sufficient molecular weight, and is 0.1 to 10 mol / L. The amount of L is more preferable, the amount of 0.5 to 5 mol / L is more preferable, the amount of 1 to 5 mol / L is further preferable, and the amount of 1.5 to 5 mol / L is particularly preferable.

Further, the step 3 is preferably performed in the presence of a basic compound from the viewpoint of reaction efficiency.
Examples of the basic compound include zeolites such as molecular sieves; basic alkali metal salts such as sodium hydrogen carbonate; triethylamine, 1,8-diazabicyclo [5.4.0] undec-7-ene, 1,4. -Diazabicyclo [2.2.2] Tertiary amine compounds such as octane; Aromatic amine compounds such as pyridine; Pyrrolidone compounds such as methylpyrrolidone and polyvinylpyrrolidone; Primary or secondary amine compounds; Basic group-containing polymer compounds And so on.
Among these, a primary or secondary amine compound and a basic group-containing polymer compound are preferable, and a primary or secondary amine compound is particularly preferable. The primary or secondary amine compound or the basic group-containing polymer compound also acts as an initiator, and when the primary or secondary amine compound or the basic group-containing polymer compound is used as the basic compound, it is mild. The target compound can be obtained in good yield in a short time under various conditions.

(Primary or secondary amine compound)
Examples of the primary or secondary amine compound include primary or secondary amines having a linear or branched hydrocarbon group having 1 to 24 carbon atoms; cyclic amines; aromatic amines such as aniline, and the like. A primary or secondary amine having a linear or branched hydrocarbon group having 1 to 24 carbon atoms is preferable. The number of carbon atoms of such a hydrocarbon group is preferably 1 to 12, and more preferably 1 to 6. Preferable specific examples of the primary or secondary amine having a linear or branched hydrocarbon group having 1 to 24 carbon atoms include C _1-24 alkylamine and NH _2- (R ^a NH) _t-. amine represented by H and the like (R ^a represents a linear or branched alkanediyl group having 1 to 24 carbon atoms, t represents an integer of 1 to 10. Note that, t is 2 for integer of to 10, t pieces of R ^a may be the same or different.). As the C _1-24 alkylamine, C _1-12 alkylamine is preferable, and C _1-6 alkylamine is more preferable. Specific examples of the C _1-24 alkylamine include n-butylamine and isobutylamine. The carbon number of the alkanediyl group represented by ^Ra is preferably 1 to 12, more preferably 1 to 6, and particularly preferably 1 to 3. Specific examples of the amine represented by NH _2- (R ^a NH) _t −H include triethylenetetramine and the like.

Further, as the primary or secondary amine compound, a primary or secondary amine compound having a polymerizable unsaturated bond may be used. Examples of the polymerizable unsaturated bond include a vinyl group, an allyl group, a (meth) acryloyl group, and the like, and a vinyl group and an allyl group are preferable.
Examples of the primary or secondary amine compound having a polymerizable unsaturated bond include a polymerizable unsaturated bond such as N-vinylaniline, N-allylaniline, 4-aminostyrene, 4-vinylbenzylamine, and 2-isopropenylaniline. In addition to primary or secondary amine compounds having an aromatic ring, allylamine, allylcyclopentylamine, allylcyclohexylamine and the like can be mentioned. Among these, a primary or secondary amine compound having a polymerizable unsaturated bond and an aromatic ring is preferable, and a primary or secondary amine compound having a polymerizable unsaturated bond and a benzene ring is more preferable.

When a primary or secondary amine compound is used as the basic compound, a polyamino acid having a secondary or tertiary amino group derived from the primary or secondary amine compound at the end, as shown in the following formula. (5-2) is obtained. Such polyamino acids (5-2) have an amide bond at the C-terminus.

[In the formula, R ³ represents a secondary or tertiary amino group (when a primary or secondary amine compound having a polymerizable unsaturated bond is used as the primary or secondary amine compound, R ³ is , A secondary or tertiary amino group having a polymerizable unsaturated bond). Each other symbol has the same meaning as described above. ]

The polyamino acid obtained when a primary or secondary amine compound having a polymerizable unsaturated bond is used as the primary or secondary amine compound (hereinafter, also referred to as a polymerizable unsaturated bond-containing polyamino acid) is Since it has a polymerizable unsaturated bond, it can also be used as a macromonomer. The polymerization of the polyamino acid containing a polymerizable unsaturated bond may be carried out according to a conventional method using a polymerization initiator such as an azo-based initiator. Examples of the solvent used for the polymerization reaction of the polymerizable unsaturated bond-containing polyamino acid include those used in step 2, and the reaction time is usually about 1 to 96 hours, and the reaction temperature is usually 20. It is about ~ 100 ° C. By such a polymerization reaction, a polyamino acid-based graft copolymer can be obtained.

(Basic group-containing polymer compound)
Further, as the basic group-containing polymer compound, a polymer compound having a basic group at the terminal or a side chain is preferable. As such a basic group, an amino group is preferable, and a primary or secondary amino group is more preferable. Examples of the basic group-containing polymer compound include those represented by the following formula (7).

[In formula (7), R ⁴ represents the organic chain segment of the skeleton portion to which the amino group of the amine compound is bonded, and R ⁵ and R ⁶ are the hydrogen atoms bonded to the nitrogen atom of the amino group independently. Alternatively, it indicates an organic group, and p indicates the number of amino groups bonded to the organic chain segment. ]

Examples of the polymer compound having a basic group at the end include polymer compounds having an amino group at one end or both ends, such as terminal amino group-substituted polyethylene glycol, terminal amino group-substituted polypropylene glycol, and terminal amino group-substituted liquid rubbers. Is a suitable specific example.
Further, as the polymer compound having the basic group in the side chain, a polymer compound having an amino group such as chitosan in the side chain can be mentioned as a suitable specific example.

When a basic group-containing polymer compound is used as the basic compound, a polyamino acid-based copolymer can be obtained. In particular, when a polymer compound having a basic group at the end is used as the basic group-containing polymer compound, a polyamino acid-based block copolymer having an organic chain segment can be obtained, and the basic group content is high. When a polymer compound having a basic group in the side chain is used as the molecular compound, a polyamino acid-based graft copolymer having an organic chain segment can be obtained.

Further, the step 3 can also be performed in the presence of an organic acid compound instead of the basic compound. As exemplified by the following formula, the organic acid compound (for example, carboxylic acids) reacts with the compound (1), and after the decarboxylation reaction, a new amide bond, a carboxy group, and phenols are generated. The newly generated carboxy group attacks other carbamate compounds and continues the polymerization. The acid anhydride bond in the newly formed polymer is converted into an amide bond by a decarboxylation reaction.

[In the formula, R ⁷ indicates an organic group or an organic chain segment of the skeleton portion to which the carboxy group of the organic acid compound is bonded, and each other symbol has the same meaning as described above. ]

The organic acid compound may be any organic acid compound having a carboxy group, a phosphoric acid group, a sulfo group or the like in the molecule, but an aliphatic carboxylic acid or an aromatic carboxylic acid having at least one carboxy group; an acidic group. Examples include contained polymer compounds.

As the acidic group-containing polymer compound, a polymer compound having an acidic group at the terminal or side chain is preferable. As such an acidic group, a carboxy group, a phosphoric acid group and a sulfo group are preferable. Examples of the acidic group-containing polymer compound include those represented by the following formula (8).

[In formula (8), R ⁸ indicates the organic chain segment of the skeleton portion to which the carboxy group of the organic acid compound is bonded, and q indicates the number of carboxy groups bonded to the organic chain segment. ]

As the polymer compound having an acidic group at the end, a polycarboxylic acid having a carboxy group at one end or both ends such as polyethylene glycol having a terminal carboxy group and polyester having a terminal carboxy group can be mentioned as a preferable specific example.
Further, as the polymer compound having an acidic group in the side chain, a polycarboxylic acid having a carboxy group such as poly (meth) acrylic acid in the side chain can be mentioned as a preferable specific example.

When an acidic group-containing polymer compound is used as an organic acid compound, a polyamino acid-based copolymer can be obtained. In particular, when a polymer compound having an acidic group at the end is used as the acidic group-containing polymer compound, a polyamino acid-based block copolymer having an organic chain segment is obtained, and an acidic group is obtained as the acidic group-containing polymer compound. When a polymer compound having the above in the side chain is used, a polyamino acid-based graft copolymer having an organic chain segment can be obtained.

The amount of the basic compound or organic acid compound used is preferably 0.001 to 1 mol, more preferably 0.01 to 0.1 mol, based on 1 mol of the compound (1).
When a basic group-containing polymer compound or an acidic group-containing polymer compound is used, their number average molecular weight (M _n ) is preferably 1000 to 10000, and their molecular weight distribution (M _w / M _n ) is It is preferably 1.0 to 2.0.

The polymerization temperature in step 3 is preferably 10 ° C. or higher, more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, particularly preferably 55 ° C. or higher, and from the viewpoint of obtaining a high yield and sufficient molecular weight. The temperature is preferably 120 ° C. or lower, more preferably 90 ° C. or lower, still more preferably 80 ° C. or lower, still more preferably 75 ° C. or lower, and particularly preferably 65 ° C. or lower. According to the production method of the present invention, the target compound can be obtained in good yield under such mild conditions.
The reaction time of step 3 is preferably 1 hour or longer, more preferably 3 hours or longer, further preferably 12 hours or longer, particularly preferably 18 hours or longer, and from the viewpoint of obtaining a high yield and sufficient molecular weight. From the viewpoint of giving, it is preferably 200 hours or less, more preferably 100 hours or less, still more preferably 50 hours or less, still more preferably 40 hours or less, and particularly preferably 32 hours or less. According to the production method of the present invention, the target compound can be obtained in good yield in such a short time.

In each of the above steps, isolation of each reaction product is performed by filtration, washing, drying, recrystallization, reprecipitation, dialysis, centrifugation, extraction with various solvents, neutralization, chromatography, etc., as necessary. The usual means may be combined as appropriate.

The polyamino acid obtained by the production method of the present invention is easier to take a higher-order structure such as a helix structure or a sheet structure than a peptide, and has high water solubility. In addition, the polyamino acid is useful as a functional material in the fields of peptide medicines, antifouling materials, cell culture substrates, drug transport carriers and the like.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Synthesis Example 1 Synthesis of N- (phenoxycarbonyl) -L-alanine N- (phenoxycarbonyl) -L-alanine was synthesized according to the following synthetic route.

L-alanine (17.8 g) and tetrabutylammonium hydroxide (154.1 g) were dissolved in methanol (300 mL) and stirred at room temperature for 2 hours. The reaction solution was concentrated under reduced pressure, diphenyl carbonate (42.8 g) and ethyl acetate (250 mL) were added, and the mixture was stirred at room temperature for 3 hours. 1M Hydrochloric acid was added to the reaction solution to adjust the pH to 2-3, and the aqueous layer was extracted 3 times with ethyl acetate. The obtained organic layer was washed with saturated brine and dehydrated with anhydrous sodium sulfate. This solution is concentrated under reduced pressure, purified by silica column chromatography (ethyl acetate / hexane = 1/3 → 1/0), and then recrystallized from ethyl acetate and hexane to give the title compound (26.0 g). (Yield 62%). The melting point is 112-113 ° C.
For the obtained N- (phenoxycarbonyl) -L-alanine, ¹ H NMR, ¹³ C NMR (measuring device: ECS-400 manufactured by JEOL), and IR (measuring device: iS10 manufactured by Thermo Scientific Nicolet) were measured.
^{1 1} H NMR (400 MHz, CDCl ₃ , δ, ppm): 1.50-1.60 (m, 3H), 4.42-4.54 (m, 1H), 5.66 (d, 1H, J = 7.6 Hz), 7.08-7.15 (m) , 2H), 7.16-7.24 (m, 1H), 7.31-7.39 (m, 2H)
¹³ C NMR (100 MHz, CDCl ₃ , δ, ppm): 18.47, 49.76, 121.67, 125.71, 129.46, 150.78, 154.27, 177.73
IR (neat, cm ^-1 ): 3297,2995,1696,1524,1491,1240,1211,1175,1157,687

Synthesis Example 2 Synthesis of N-methyl-N- (phenoxycarbonyl) -alanine N-methyl-N- (phenoxycarbonyl) -alanine was synthesized according to the following synthetic route.

(1) N- (phenoxycarbonyl) -L-alanine (10 g), paraformaldehyde (3.2 g), p-toluenesulfonic acid monohydrate (91 mg) are suspended in toluene (100 mL) and azeotropically distilled. The mixture was refluxed for 12 hours while removing the water produced by. After completion of the reaction, the temperature was returned to room temperature, washed with saturated brine, and dehydrated with anhydrous sodium sulfate. The solution was filtered once, concentrated under reduced pressure, and then recrystallized using ethyl acetate and hexane. 8.7 g of the target compound was obtained as white crystals (yield 82%). The melting point is 76 ° C.
¹ H NMR, ¹³ C NMR (measuring device: ECS-400 manufactured by JEOL), and IR (measuring device: Nicolet iS10 manufactured by Thermo Scientific) were measured for the obtained compound.
¹ H NMR (400 MHz, CDCl ₃ , δ, ppm): 1.50-1.80 (s, 3H), 4.30-4.60 (m, 1H), 5.25-5.75 (m, 2H), 7.11-7.18 (m, 2H) , 7.22-7.30 (m, 1H), 7.35-7.44 (m, 2H)
¹³ C NMR (100 MHz, CDCl ₃ , δ, ppm): 16.30, 17.24, 51.05, 121.50, 126.28, 129.69, 150.31, 172.61
IR (neat, cm ^-1 ): 1801, 1722, 1386, 1372, 1241, 1196, 1172, 1030, 987, 777, 753, 731, 691
(2) The N- (phenoxycarbonyl) -4-methyloxazolidinone (2.0 g) and triethylsilane (1.44 mL) obtained above were dissolved in a mixed solution of trifluoroacetic acid (10 mL) and dichloromethane (10 mL). , Stirred at room temperature for 15 hours. The solution was concentrated under reduced pressure, purified by silica column chromatography (ethyl acetate / hexane = 1/1), and recrystallized from ethyl acetate and hexane to give the title compound (1.8 g) (yield 90%). .. The melting point is 108-112 ° C.
With respect to the obtained N-methyl-N- (phenoxycarbonyl) -alanine, ¹ H NMR, ¹³ C NMR (measuring device: ECS-400 manufactured by JEOL), and IR (measuring device: Nicolet iS10 manufactured by Thermo Scientific) were measured. ..
^{1 1} H NMR (400 MHz, CDCl ₃ , mixture of rotamers, δ, ppm): 1.52 / 1.57 (d, total 3H, J = 7.6 / 7.2 Hz, ratio 63:37), 3.00 / 3.08 (s, total 3H, ratio 37:63), 4.85-4.95 (m, 1H), 7.05-7.16 (m, 2H), 7.16-7.7.23 (m, 1H), 7.30-7.40 (m, 2H)
¹³ C NMR (100 MHz, CDCl ₃ , mixture of rotamers, δ, ppm), 14.69, 15.31, 31.22, 31.41, 54.63, 54.87, 121.82, 125.62, 129.41, 151.24, 151.36, 154.78, 155.54, 177.21, 177.25
IR (neat, cm ^-1 ): 3167, 1737, 1678, 1593, 1457, 1394, 1365, 1318, 1189, 1165, 1096, 824, 754, 693

Synthesis Example 3 Synthesis of poly (N-methylalanine) Poly (N-methylalanine) was synthesized according to the following synthetic route.

After dissolving N-methyl-N- (phenoxycarbonyl) -alanine (224 mg, monomer concentration 0.5 M) and n-butylamine (5 μL) in N, N-dimethylacetamide (2 mL), the system was replaced with argon. The mixture was stirred at 60 ° C. for 48 hours. After completion of the polymerization, the solution was washed with water using a regenerated cellulose membrane (MWCO: 500) and then freeze-dried to recover the title compound. Table 1 shows the conversion rate, yield, Mn, and Mw / Mn of the obtained polymer. The measurement conditions for the conversion rate, Mn, and Mw / Mn are as shown below.

<Conversion rate>
At the end of polymerization, the reaction solution was sampled and calculated by ^{1 1} H-NMR spectrum under the following conditions.
Measuring device: JEOL ECS-400
Internal standard: TMS
Solvent: CDCl ₃
¹ H NMR (400 MHz, CDCl ₃ , δ, ppm): 1.10-1.60 (br, 3H), 2.60-3.30 (br, 3H), 4.10-6.20 (br, 1H)

<Mn (number average molecular weight) and Mw / Mn (molecular weight distribution)>
The number average molecular weight (M _n ) and molecular weight distribution (M _w / M _n ) were measured using size exclusion chromatography (SEC).
Specifically, the polymer is dissolved in N, N-dimethylformamide containing 10 mM LiBr, filled in SEC at a flow rate of 0.5 mL / min and a temperature of 40 ° C., the elution time is measured, and then the polystyrene standard is calibrated. M _n and M _w / M _n were obtained based on the line. N, N-dimethylformamide containing 10 mM LiBr was used as the weaving solution.
Measuring device: HLC-8220 made by TOSOH
Columns: SuperAW4000 (φ = 6 μm), Super-AW3000 (φ = 4 μm), Super-AW2500 (φ = 4 μm)

In addition, the MALDI-TOF MS spectrum, CD spectrum, and IR spectrum of the obtained poly (N-methylalanine) were measured under the following conditions. The MALDI-TOF MS spectrum is shown in FIG. 1 and the CD spectrum is shown in FIG.

<MALDI-TOF MS spectrum>
It was measured under the following conditions.
Measuring device: AXIMA Confidence (manufactured by SHIMADZU)
Matrix reagent: CHCA
<CD spectrum>
The sample and water are mixed so that the concentration becomes 0.02 mg / mL, this solution is injected into a cell having an optical path length of 10 mm, and using J-1500 (manufactured by JASCO), the temperature is 20 ° C. and the resolution is 0.2 nm. , The scanning speed was 50 nm / min, and the number of integrations was one.
<IR spectrum>
Nicolet IS10 (Thermo Ltd. Scientific) was measured in the region of 4000 cm ^-1 from 600 cm ^-1 using.
IR (cm ^-1 ): 3477, 2981, 2936, 2427, 1625, 1575, 1480, 1398, 1271, 1074

Synthesis Example 4 to Synthesis Example 7 Synthesis of poly (N-methylalanine) Synthesis except that the amount of N-methyl-N- (phenoxycarbonyl) -alanine used, the polymerization temperature, and the polymerization time were changed to those shown in Table 1. Poly (N-methylalanine) was synthesized in the same manner as in Example 3.
In addition, the conversion rate, yield, and Mn and Mw / Mn of the obtained polymer were measured in the same manner as in Synthesis Example 3. The measurement results are shown in Table 1.

Test Example 1 Tracking conversion rate A polymerization reaction was carried out in the same manner as in Synthesis Example 3, and during this reaction, 0 minutes, 30 minutes, 1 hour, 2 hours, and 3 hours after the start of the reaction. The reaction solution was sampled after 4 hours, 5 hours, 6 hours, and 9 hours, and ^{1 1} H-NMR spectrum (measuring device: JEOL ECS-400, internal standard substance: TMS, solvent: CDCl). ₃₎ the N- methyl -N- (phenoxycarbonyl) - were followed conversion and NCA conversion of alanine. The results are shown in FIG. 3 (polymerization temperature: 60 ° C.).

Test Example 2 Tracking conversion rate A polymerization reaction was carried out in the same manner as in Synthesis Example 5, and during this reaction, 0 minutes, 30 minutes, 60 minutes, 90 minutes, and 2 hours after the start of the reaction. After 3, 3 hours, 4 hours, 5 hours, 6 hours, and 9 hours, the reaction solution was sampled and ^{1 1} H-NMR spectrum (measuring device: JEOL ECS-400, internal standard substance: The conversion rates of N-methyl-N- (phenoxycarbonyl) -alanine and NCA conversion rates were followed by TMS, solvent: CDCl ₃ ). The results are shown in FIG. 4 (polymerization temperature: 80 ° C.).

Test Example 3 Solubility test 1 mg of the poly (N-methylalanine) obtained in Synthesis Example 6 and 1 mL of various solvents were mixed, and the solubility was confirmed. It was completely dissolved in water and dimethyl sulfoxide. Methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide, acetonitrile, and tetrahydrofuran produced some undissolved residue, but were completely dissolved in a mixed solvent with 1 mL of water added. From this result, it was found that the poly (N-methylalanine) obtained in Synthesis Example 6 was highly water-soluble.

Synthesis Example 8 Synthesis of copolymer of L-alanine and N-methylalanine A copolymer of L-alanine and N-methylalanine was synthesized according to the following synthetic route.

After dissolving N- (phenoxycarbonyl) -L-alanine (209.2 mg) and N-methyl-N- (phenoxycarbonyl) -alanine (223.2 mg) in N, N-dimethylacetamide (4 mL), n- Butylamine (10 μL) was added, the inside of the system was replaced with argon, and the mixture was stirred at 60 ° C. for 48 hours. After completion of the polymerization, reprecipitation was carried out using diethyl ether, and the diethyl ether insoluble portion was recovered. The diethyl ether soluble part was recovered by separating phenol by silica column chromatography (ethyl acetate → methanol).
With respect to the obtained copolymer, ¹ H NMR (measuring device: ECS-400 manufactured by JEOL) and IR (measuring device: Nicolet iS10 manufactured by Thermo Scientific) were measured.
^{1 1} H NMR (400 MHz, CDCl ₃ , δ, ppm, composition ratio: 47/53, alanine / N-methylalanine): 1.20-1.80 (br, 13H), 2.80-3.60 (br, 7H), 4.10-5.50 (br, 4H)
IR (neat, cm ^-1 ): 3274, 2936, 1624, 1533, 1455, 1077

Claims (4)

A method for producing a compound represented by the following formula (1), which comprises a step of opening a ring of the compound represented by the following formula (4).

[In equation (4),
R ¹ and R ² independently represent a hydrogen atom or an organic group, respectively.
Y indicates an electron-withdrawing group,
m represents an integer from 0 to 5. ]

[In equation (1), R ¹ , R ² , Y and m have the same meanings as described above. ] A method for producing a polyamino acid, which comprises a step of obtaining a compound represented by the formula (1) by the method according to claim 1 and polycondensing the compound represented by the formula (1). The production method according to claim 2, wherein the polycondensation is carried out in the presence of a basic compound. The production method according to claim 3, wherein the basic compound is a primary or secondary amine compound, and the polyamino acid is represented by the following formula (5-2).

[In equation (5-2),
R ³ Indicates a secondary or tertiary amino group,
n indicates an integer of 2 or more,
R ¹ And R ² Is synonymous with the above. ]

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