JP2011148738A - Method for producing ribonucleoside derivative or salt thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively and easily producing a ribonucleoside from a 2, 2'-anhydro-1-arabinofuranosyl nucleoside derivative in a high yield. <P>SOLUTION: The ribonucleoside is produced by treating a 2, 2'-anhydro-1-arabinofuranosyl nucleoside derivative represented by formula (1) (wherein R<SB>1</SB>and R<SB>2</SB>are the same or different and each hydrogen or a protective group for the hydroxy group; X and Y are the same or different, and each hydrogen, a halogen, a 1-10C alkyl group which may be substituted, a 1-7C acyl group, a nitro group or an amino group which may be protected and an L-isomer, a D-isomer or a racemic mixture) with a carbonate or hydrogencarbonate of a metal selected from potassium, rubidium, and cesium. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a ribonucleoside derivative or a salt thereof, a uridine cesium salt, and a 5-methyluridine cesium salt.

  In general, ribonucleosides can be produced by coupling ribose and nucleobases. However, L-ribose, which is a non-natural sugar, is expensive and rare, and it has been difficult to produce a large amount of L-ribonucleoside using this. L-arabinose is the cheapest and most easily available L-sugar. It is known to produce L-ribose using this L-arabinose as a raw material (Non-patent Document 1). However, in this method, in order to invert the hydroxyl group at the 2-position, not only protection and deprotection of the other hydroxyl group but also a multi-step reaction of oxidation and reduction of the hydroxyl group at the 2-position is necessary. Moreover, in order to make it into L-ribonucleoside, coupling with a nucleobase must be further performed.

  On the other hand, 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil (Non-patent Document 2) or 2,2′-anhydro-1-β- (L-arabin) using L-arabinose as a raw material. Nofuranosyl) thymine (Patent Document 1) is known. These compounds are attractive raw materials for L-ribonucleoside synthesis because they can be synthesized in two or three steps and are already compounds in which sugar and nucleobase are coupled. However, it has been reported that these D-type compounds are hydrolyzed with acids and alkalis to quantitatively give D-arabinonucleosides (Non-patent Document 3).

  In recent years, a method for producing D-uridine by allowing potassium benzoate to act on 2,2′-anhydro-1-β- (D-arabinofuranosyl) uracil has been reported (Non-patent Document 4). However, the reaction time was 4 days and the temperature was high, so it was not a practical method. Further, it is reported that even when a base such as sodium hydrogencarbonate is allowed to act on the compound, it remains as it is without being converted to D-uridine (Non-patent Document 5). Thus, an efficient method for converting a 2,2'-anhydro-1-arabinofuranosyl nucleoside derivative into a ribonucleoside has not been known.

WO02 / 44194 pamphlet

Nucleosides & Nucleotides, 1999, 18, 187-195 Nucleic Acid Chemistry Part 1: Townsend, L. B. and Tipson, R. S. Eds., John Wiley & Sons, New York, pp 347-353 Synthetic Procedures in Nucleic Acid Chemistry Volume 1: Zorbach, W. W. and Tipson, R. S. Eds., John Wiley & Sons, New York, pp 369-374 J. Org. Chem. 2008, 73, 309-311 Nucleosides, Nucleotides & Nucleic Acids 2006, 25, 719-734

  The present invention is to provide a method for producing a ribonucleoside from a 2,2'-anhydro-1-arabinofuranosyl nucleoside derivative inexpensively, easily and in high yield.

As a result of intensive studies, the present inventors have found that the above problem can be achieved by treating with a specific metal salt.
That is, the present invention includes the following aspects.
[1] General formula (1):

(Wherein R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a hydroxyl-protecting group; X and Y are the same or different and each represents a hydrogen atom, a halogen atom or an optionally substituted C _{1; -10 represents} an alkyl group, a C _1-7 acyl group, a nitro group or an amino group which may be protected, and represents an L-form, a D-form or a racemate.)
The 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative represented by the formula (1) is treated with a carbonate or bicarbonate of a metal selected from potassium, rubidium and cesium: 2):

(Each symbol in the formula is as defined above.)
A method for producing a ribonucleoside derivative or a salt thereof, wherein
[2] The method according to [1], wherein the treatment is performed with a metal carbonate.
[3] The method according to [1] or [2], wherein the metal is cesium.
[4] The process according to any one of [1] to [3], wherein the treatment with a metal carbonate or bicarbonate is performed in a solvent containing an aprotic polar organic solvent. .
[5] The production method according to [4], wherein the aprotic polar organic solvent is selected from dimethyl sulfoxide and N, N-dimethylformamide.
[6] The solvent further contains water, and the addition amount is 0.001 to 5 mol with respect to 1 mol of the 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative. [4] The manufacturing method of description.
[7] The production method of [1], wherein X is a hydrogen atom or methyl, and Y is a hydrogen atom.
[8] The production method according to [1], wherein the 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative and the ribonucleoside derivative are both L-forms.
[9] Uridine cesium salt.
[10] Have intrinsic X-ray diffraction peaks at 7.0 °, 20.9 °, 26.1 °, 26.4 °, and 27.0 ° as diffraction angles (2θ ± 0.2 °, CuKα). A uridine cesium salt crystal characterized by
[11] 5-methyluridine cesium salt.
[12] The diffraction angle (2θ ± 0.2 °, CuKα) has intrinsic X-ray diffraction peaks at 6.4 °, 23.6 °, 26.5 °, 27.1 °, and 29.6 °. 5-methyluridine cesium salt crystals characterized by

  By treating with a specific metal salt, it has become possible to provide a method for producing a ribonucleoside from a 2,2'-anhydro-1-arabinofuranosyl nucleoside derivative inexpensively, easily and in high yield.

The powder X-ray diffraction chart of uridine cesium salt is shown. The powder X-ray-diffraction chart of 5-methyluridine cesium salt is shown.

  The present invention relates to a general formula (1):

(Wherein R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a hydroxyl-protecting group; X and Y are the same or different and each represents a hydrogen atom, a halogen atom or an optionally substituted C _{1; -10 represents} an alkyl group, a C _1-7 acyl group, a nitro group or an amino group which may be protected, and represents an L-form, a D-form or a racemate.)
2,2′-anhydro-1-arabinofuranosyl nucleoside derivative (hereinafter also referred to as compound (1)) is treated with a carbonate or bicarbonate of a metal selected from potassium, rubidium and cesium General formula (2):

(Each symbol in the formula is as defined above.)
A method for producing a ribonucleoside derivative represented by the following (hereinafter also referred to as compound (2)) or a salt thereof. Hereinafter, the production method of the present invention will be described in detail. First, the definition of each symbol in the general formulas (1) and (2) will be described in detail.

  The “halogen atom” in the present specification is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. Preferably, they are a fluorine atom, a chlorine atom or a bromine atom.

The “C _1-10 alkyl group” in the present specification is a linear or branched alkyl group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Examples thereof include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and the like.

As the substituent of the “optionally substituted C _1-10 alkyl group” in the present specification, a halogen atom, a C _1-6 alkoxy group, a hydroxy group, a nitro group, a cyano group, and optionally protected. An amino group etc. are mentioned. The number of substituents and the substitution position are not particularly limited.

The “C _1-6 alkoxy group” in the present specification is a linear or branched alkoxy group having 1 to 6 carbon atoms. Specific examples thereof include methoxy, ethoxy, propoxy, isopropoxy. , Butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy and the like.

Examples of the amino protecting group in the “optionally protected amino group” in the present specification include groups described in Protecting Groups in Organic Chemistry 2nd edition (John Wiley & Sons, Inc. 1991). Specifically, a formyl group, a C _1-6 alkyl-carbonyl group (for example, acetyl (Ac)), a C _1-6 alkoxy-carbonyl group (for example, tert-butoxycarbonyl (Boc), methoxycarbonyl (Moc)) , C _6-10 aryl-carbonyl group (eg, benzoyl (Bz)), C _7-11 aralkyl group (eg, benzyl, trityl), C _7-11 aralkyl-carbonyl (eg, phenylacetyl), C _7-11 Aralkyloxy-carbonyl (for example, benzyloxycarbonyl (Cbz)), 9-fluorenylmethoxycarbonyl (Fmoc), 2,2,2-trichloroethoxycarbonyl and the like can be mentioned.

Specific examples of the “ _optionally substituted C _1-10 alkyl group” include fluoromethyl, trifluoromethyl, chloromethyl, methoxymethyl, hydroxymethyl, nitromethyl, cyanomethyl, —CH ₂ —NH—Boc. , —CH ₂ —NH—Cbz, —CH ₂ —NH—Bz, —CH ₂ —NH—Ac and the like.

A preferable “optionally substituted C _1-10 alkyl group” is a C _1-10 alkyl group, more preferably a C _1-6 alkyl group, and particularly preferably methyl.

In the present specification, the “C _1-7 acyl group” includes an acyl group derived from an organic carboxylic acid having 1 to 7 carbon atoms. Specific examples include C _1-7 alkanoyl groups (eg, C _1-6 alkyl-carbonyl groups such as formyl, acetyl, propionyl, butyryl, isobutyryl, pentanoyl, hexanoyl, heptanoyl), benzoyl, C _1-6 alkoxy- Examples include carbonyl groups (eg, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, tert-butoxycarbonyl, etc.), phenoxycarbonyl, and the like.

In the present specification, the “hydroxyl-protecting group” is an aralkyl ether-type protecting group which may have a substituent such as benzyl, 1-phenylethyl, diphenylmethyl, 1,1-diphenylethyl, naphthylmethyl and the like ( Examples of the substituent include a C _1-6 alkyl group, a C _1-6 alkoxy group, a nitro group, a halogen atom, etc.); methyl, tert-butyl, 3,4,5,6-tetrahydro-2H— An alkyl ether-type protecting group which may have a substituent such as pyran-2-yl, methoxymethyl (the substituent includes a C _1-6 alkoxy group, a nitro group, a halogen atom, etc.); Silyl-type protecting groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl; acetyl, pivaloyl, benzoyl, 4-nitrobenzoy Ester-type protective groups such like. Preferred is benzyl, trimethylsilyl, tert-butyldimethylsilyl or benzoyl.

R ₁ and R ₂ are the same or different and each is preferably a hydrogen atom, benzyl, trimethylsilyl, tert-butyldimethylsilyl, or benzoyl, and particularly preferably a hydrogen atom.
X and Y are the same or different and each is preferably a hydrogen atom, a halogen atom or a C _1-6 alkyl group, more preferably a hydrogen atom, a methyl atom, a fluorine atom, a chlorine atom or a bromine atom, Methyl is particularly preferred. X is particularly preferably a hydrogen atom or methyl, and Y is particularly preferably a hydrogen atom.
M is preferably cesium.
Compound (1) may be L-form, D-form, or racemate, and L-form is preferred from the viewpoint that L-arabinose as a raw material is easily available.

  Examples of the salt of the compound (2) include alkali metal salts (for example, sodium salt, potassium salt, rubidium salt, cesium salt), alkaline earth metal salts (for example, calcium salt, magnesium salt), organic salts (for example, triethylamine salt) , Dicyclohexylamine salt) and the like. Among these, potassium salts, rubidium salts, and cesium salts are preferable, potassium salts and cesium salts are more preferable, and cesium salts are particularly preferable.

  Examples of the metal carbonate or hydrogen carbonate metal used in the present invention include alkali metals such as potassium, rubidium, and cesium. From the viewpoint of high solubility in aprotic polar organic solvents and high yield, metal carbonates are preferred, potassium carbonate, rubidium carbonate, cesium carbonate are more preferred, potassium carbonate, cesium carbonate are more preferred, and cesium carbonate is preferred. Particularly preferred.

  The amount of metal carbonate or bicarbonate used in the present invention is not particularly limited as long as the reaction proceeds, but the lower limit of the amount of carbonate or bicarbonate used is the compound (1). On the other hand, 0.3 equivalents are preferred, 0.4 equivalents are more preferred, 0.5 equivalents are more preferred, 0.6 equivalents are even more preferred, 0.7 equivalents are even more preferred, and 0.8 equivalents are particularly preferred. . On the other hand, the upper limit of the amount of carbonate or bicarbonate used is preferably 5 equivalents, more preferably 4 equivalents, still more preferably 3 equivalents, even more preferably 2 equivalents, relative to compound (1). The equivalent is particularly preferred, and 1.2 equivalent is particularly preferred.

  The solvent used in the present invention is not particularly limited as long as the reaction proceeds, but an aprotic polar organic solvent is preferable. Examples of the aprotic polar organic solvent include dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran, acetonitrile and the like. From the viewpoint that the compound (1), metal carbonate or hydrogen carbonate is dissolved and the product is obtained in high yield, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl -2-pyrrolidone is preferred, dimethyl sulfoxide, N, N-dimethylformamide is more preferred, and dimethyl sulfoxide is particularly preferred. The amount of the solvent used is not particularly limited as long as the reaction proceeds. However, 1 to 100 L is preferable and 2 to 10 L is more preferable with respect to 1 mol of compound (1).

  In addition, it is preferable to add water to the solvent from the viewpoint that the reaction can be promoted by dissolving the compound (1) and the metal carbonate or bicarbonate. The amount of water added is not particularly limited as long as the target reaction proceeds. However, the lower limit of the amount of water added is preferably 0.001 mol and 0.01 mol relative to 1 mol of compound (1). More preferably, 0.1 mol is still more preferable, 0.2 mol is still more preferable, 0.3 mol is still more preferable, and 0.4 mol is especially preferable. On the other hand, the upper limit of the amount of water added is preferably 5 mol, more preferably 3 mol, still more preferably 2 mol, still more preferably 1 mol, and even more preferably 0.9 mol with respect to 1 mol of compound (1). 0.8 mol is particularly preferable.

  The reaction temperature of the present invention is not particularly limited as long as the reaction proceeds, but is appropriately selected depending on the type of the compound (1), metal carbonate or hydrogen carbonate and solvent used, and preferably 50 to 180 ° C. 80 to 120 ° C. is more preferable. The reaction time of the present invention is not particularly limited as long as the reaction proceeds, but is preferably 1 to 100 hours, more preferably 5 to 90 hours, and still more preferably 10 to 80 hours.

  After completion of the reaction, the reaction solution is filtered to obtain the compound (2) in the form of a salt. This salt is the potassium, rubidium or cesium salt derived from the carbonate or bicarbonate used. By treating this salt with an acid such as hydrochloric acid or sulfuric acid in a solvent, compound (2) can be obtained in a free form. If necessary, it may be purified by a conventional method such as column chromatography. In addition, when compound (2) is other than potassium salt, rubidium salt and cesium salt, it can be obtained by treating free compound (2) with the corresponding base.

  In the above reaction, the 2-position hydroxyl group of arabinose is inverted and converted to the ribose type when the compound (1) is opened. Since the reaction system becomes almost neutral by the use of metal carbonate or hydrogen carbonate, the arabino nucleoside represented by the general formula (3), which is by-produced under alkaline conditions or acid conditions as in the prior art. The compound (2) or a salt thereof can be obtained in a high yield.

(Each symbol in the formula is as defined above.)

When R ₁ and R ₂ in the compound (2) are protecting groups for a hydroxyl group, the protecting group is removed by a conventional method such as catalytic reduction or hydrolysis of the compound (2) or a salt thereof, whereby R ₁ and R A compound (2) in which both ₂ are hydrogen atoms or a salt thereof is obtained.

  Moreover, the compound (1) which is a raw material can be easily synthesized from arabinose according to the method described in Non-Patent Document 2 or Patent Document 1. For example, Tetrahedron, 1975, 31, 1873-1877 can be referred to for a method for introducing a substituent other than methyl into X. Moreover, Tetrahedron Lett., 1973, 14, 1147-1150 can be referred for the method of introducing a substituent into Y. Moreover, the target compound is an important intermediate of the antiviral agents terbivudine and clevudine, and is used as a monomer unit of the oligo RNA aptamer drug Spiegelmer, which is a very useful L-form compound (2), that is, compound (2- L):

(Each symbol in the formula is as defined above.)
Alternatively, when it is a salt thereof, the L-form compound (1) as a raw material, that is, the compound (1-L):

(Each symbol in the formula is as defined above.)
Can be synthesized using L-arabinose, which is readily available from nature, as a starting material. Therefore, the compound (2-L) or a salt thereof can be produced at a low cost.

  In addition, potassium salt, rubidium salt or cesium salt of compound (2), that is, compound (2A):

(Wherein R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a hydroxyl-protecting group; X and Y are the same or different and each represents a hydrogen atom, a halogen atom or an optionally substituted C _{1; -10 represents} an alkyl group, a C _1-7 acyl group, a nitro group or an amino group which may be protected, M represents potassium, rubidium or cesium, and represents L, D or racemic.)
Is a novel compound. In particular, a cesium salt is insoluble in an organic solvent containing alcohol and N, N-dimethylformamide, and is a very useful compound because it can be easily isolated.
In general, the ribose body and the arabinose body have a difference in crystallinity. Therefore, if the reaction to the ribose body (compound (2)) proceeds as little as possible, the ribose body salt with high yield and high purity can be obtained. (Compound (2A)) can be isolated, and finally a high yield and high purity ribose (compound (2)) can be obtained.

  Compound (2) or a salt thereof (particularly compound (2A)) may be purified by recrystallization, column chromatography or the like. Since compound (2A) is a crystal, purification by recrystallization is preferred. The recrystallization solvent for the compound (2) is appropriately selected depending on the type of the compound and is not particularly limited, and examples thereof include dimethylformamide and dimethyl sulfoxide. The recrystallization solvent for the compound (2A) is appropriately selected depending on the type of the compound and is not particularly limited, and examples thereof include dimethylformamide and dimethyl sulfoxide.

  Further, among the compounds (2A), the compound (2A-L) which is L-form:

(Each symbol in the formula is as defined above.)
Is particularly useful when M is cesium.
L-uridine cesium salt has a diffraction angle (2θ ± 0.2 °, CuKα) of 7.0, 16.5, 18.2, 19.6, 20.9, 21.6, 22.1, 23.5, 25.2, 25.4, 26.1, 26.4, 27.0, 27.4, 29.5, 29.9 , Shows a new crystal with a diffraction peak at 27.4 °. Among these, 7.0, 20.9, 25.4, 26.1, 26.4, 27.0, 27.4, 29.5 ° are major, 7.0, 20.9, 26.1, 26.4, 27.0, 27.4, 29.5 ° are more major, 7.0, 20.9, 26.1 , 26.4, 27.0, 27.4 ° are more main, and 7.0, 20.9, 26.1, 26.4, 27.0 ° are particularly main (see FIG. 1).
The L-5-methyluridine cesium salt has diffraction angles (2θ ± 0.2 °, CuKα) diffracted to 6.4, 20.3, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6, 31.3, 37.5, 38.0, 39.3 °. A new crystal having a peak is shown. Among these, 6.4, 20.3, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6 ° are main, 6.4, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6 ° are more main, 6.4, 23.6, 25.5 , 26.5, 27.1, and 29.6 ° are more main, and 6.4, 23.6, 26.5, 27.1, and 29.6 ° are particularly main (see FIG. 2).

  Examples of the present invention are shown below, but the present invention is not limited by these examples. The powder X-ray diffraction peak was measured by a powder X-ray diffraction apparatus X′Pert PRO (manufactured by PANalytical) equipped with an array type semiconductor detector X′Celerator.

Reference Example 1 Synthesis of 2-amino-β-L-arabinofurano [1 ′, 2 ′: 4,5] -2-oxazoline L-arabinose (1.30 g, 8.66 mmol) of N, N-dimethylformamide (8 0.7 mL) solution was added with potassium carbonate (59.9 mg, 0.433 mmol) and cyanamide (437 mg, 10.4 mmol), and then stirred at 50 ° C. for 5 hours. After the solution was cooled to room temperature, ethyl acetate (8.7 mL) was added and stirred in a slurry state for 14 hours. The slurry was filtered and the crystals were washed with 1: 1 ethyl acetate / N, N-dimethylformamide (4.4 mL) and ethyl acetate (4.4 mL). The obtained crystals were dried under reduced pressure to obtain the desired product (1.46 g, yield 98%) as colorless crystals.
¹ H-NMR (D ₂ O) δ 3.51 (1H, dd, J = 12.2, 6.9 Hz), 3.58 (1H, dd, J = 12.2, 5.4 Hz), 3.97-4.02 (1H, m), 4.29-4.32 (1H, m), 4.91 (1H, dd, J = 5.6, 1.2 Hz), 5.89 (1H, d, J = 5.6 Hz).

Reference Example 2 Synthesis of 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil 2-amino-β-L-arabinofurano [1 ′, 2 ′: 4,5] -2-oxazoline ( To a mixed solution of 87.08 g (500.0 mmol) in water (500 mL) and ethanol (500 mL) was added methyl propiolate (73.58 g, 750 mmol), and the mixture was heated to reflux for 5 hours. After cooling the reaction solution to 20 ° C., the solvent was distilled off under reduced pressure as much as possible (920 mL). The concentrated residue (199.5 g) was placed in a constant temperature bath at 25 ° C., and acetone (500 mL) was added dropwise thereto over 30 minutes, cooled to 25 to 5 ° C., aged at this temperature for 2 hours and then filtered. The obtained crystals were washed with acetone (250 mL) and dried under reduced pressure to obtain the desired product (67.6 g, yield 60.0%) as colorless crystals.
¹ H-NMR (D ₂ O) δ3.52-3.62 (2H, m), 4.38-4.41 (1H, m), 4.66-4.67 (1H, m), 5.47 (1H, d, J = 5.9 Hz), 6.19 (1H, d, J = 7.4 Hz), 6.54 (1H, d, J = 5.9 Hz), 7.92 (1H, d, J = 7.4 Hz).

Example 1 Synthesis of L-uridine cesium salt Under a stream of argon, 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil (1.14 g, 5.04 mmol) and cesium carbonate (1.30 g) , 3.99 mmol) in N, N-dimethylformamide (11.4 mL) was heated and stirred at 100 ° C. for 14 hours. The HPLC quantitative yield at this point was 79.3%. The obtained suspension was filtered, washed with acetone (5.0 mL), and dried under reduced pressure to obtain L-uridine cesium salt as crystals.
¹ H-NMR (D ₂ O) δ 3.70 (1H, dd, J = 12.8, 4.6 Hz), 3.80 (1H, dd, J = 12.8, 3.0 Hz), 4.00-4.05 (1H, m), 4.10-4.14 (1H, m), 4.22-4.25 (1H, m), 5.73 (1H, d, J = 7.7 Hz), 5.83 (1H, d, J = 4.6 Hz), 7.62 (1H, d, J = 7.7 Hz) .
mp 201 ° C (dec.)
Diffraction angle (2θ ± 0.2 °, CuKα): 7.0, 16.5, 18.2, 19.6, 20.9, 21.6, 22.1, 23.5, 25.2, 25.4, 26.1, 26.4, 27.0, 27.4, 29.5, 29.9, 27.4 ° . Among them, 7.0, 20.9, 25.4, 26.1, 26.4, 27.0, 27.4, 29.5 ° are the main, 7.0, 20.9, 26.1, 26.4, 27.0, 27.4, 29.5 ° are the main, 7.0, 20.9, 26.1, 26.4 , 27.0 and 27.4 ° are more main, and 7.0, 20.9, 26.1, 26.4 and 27.0 ° are particularly main (see FIG. 1).

Example 2 Synthesis of L-uridine L-uridine cesium salt crystals obtained in Example 1 were dissolved in water (5.0 mL), and a 2 mol / L hydrochloric acid aqueous solution (2.7 mL) was added to adjust the pH to 7 And the solvent was distilled off under reduced pressure. Purification by chromatography (silica gel 80 g, eluent 10: 1 → 4: 1 dichloromethane-methanol) gave the desired product (0.83 g, yield 67.4%) as colorless crystals.
¹ H-NMR (D ₂ O) δ 3.70 (1H, dd, J = 12.8, 4.4 Hz), 3.80 (1H, dd, J = 12.8, 3.0 Hz), 4.01-4.05 (1H, m), 4.10-4.14 (1H, m), 4.23-4.27 (1H, m), 5.79 (1H, d, J = 8.1 Hz), 5.81 (1H, d, J = 5.1 Hz), 7.77 (1H, d, J = 8.1 Hz) .
ESI-MASS 243 (MH).

Example 3 Synthesis of L-5-methyluridine cesium salt Under a stream of argon, 2,2′-anhydro-1-β- (L-arabinofuranosyl) thymine (1.21 g, 5.04 mmol) and cesium carbonate ( A solution of 1.30 g, 3.99 mmol) in N, N-dimethylformamide (12.1 mL) was stirred with heating at 120 ° C. for 24 hours. The HPLC quantitative yield at this point was 84.2%. The obtained suspension was filtered, washed with acetone (5.0 mL), and dried under reduced pressure to obtain L-5-methyluridine cesium salt as crystals.
¹ H-NMR (D ₂ O) δ 1.77 (3H, d, J = 1.2 Hz), 3.70 (1H, dd, J = 12.7, 4.4 Hz), 3.80 (1H, dd, J = 12.7, 3.1 Hz), 3.97-4.02 (1H, m), 4.12-4.15 (1H, m), 4.22-4.25 (1H, m), 5.84 (1H, d, J = 4.9 Hz), 7.45 (1H, d, J = 1.2 Hz) .
mp 208 ° C (dec.)
Diffraction angles (2θ ± 0.2 °, CuKα): Diffraction peaks are shown at 6.4, 20.3, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6, 31.3, 37.5, 38.0, 39.3 °. Among them, 6.4, 20.3, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6 ° are main, 6.4, 21.0, 23.6, 25.5, 26.5, 27.1, 29.6 ° are more main, 6.4, 23.6, 25.5, 26.5 , 27.1 and 29.6 ° are more main, and 6.4, 23.6, 26.5, 27.1 and 29.6 ° are particularly main (see FIG. 2).

Example 4 Synthesis of L-5-methyluridine L-5-methyluridine cesium salt crystals obtained in Example 3 were dissolved in water (5.0 mL), and 2 mol / L hydrochloric acid aqueous solution (2.6 mL) was dissolved. Was added to adjust the pH to 7.5, and the solvent was distilled off under reduced pressure. Purification by chromatography (silica gel 80 g, eluent 10: 1 → 4: 1 dichloromethane-methanol) gave the desired product (0.94 g, yield 72.3%) as colorless crystals.
¹ H-NMR (D ₂ O) δ 1.79 (3H, d, J = 1.2 Hz), 3.70 (1H, dd, J = 12.8, 4.3 Hz), 3.81 (1H, dd, J = 12.8, 3.0 Hz), 3.99-4.03 (1H, m), 4.12-4.15 (1H, m), 4.23-4.26 (1H, m), 5.82 (1H, d, J = 4.8 Hz), 7.59 (1H, d, J = 1.2 Hz) .
ESI-MASS 257 (MH).

Example 5 Examination of base In an N, N-dimethylformamide (4.07 mL) solvent to which water (18 μL, 1 mmol) was added under an argon stream, the substrate 2,2′-anhydro-1-β- (L-arabi). Nofuranosyl) uracil (463.0 mg, 2.05 mmol), and 0. 0 for each base (2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil shown in Table 1. (Equivalent amount equivalent to 8 equivalents) was used, and the reaction was carried out with stirring at 100 ° C. The results of HPLC quantification at 9 hours are shown in Table 1.

  When potassium benzoate or sodium hydrogen carbonate is used as a base, the reaction hardly proceeds and the formation of arabino is dominant (Comparative Examples 1 and 2), but potassium carbonate, rubidium carbonate, cesium carbonate. Moreover, the production | generation of uridine was able to be confirmed with the favorable yield with potassium hydrogen carbonate (Examples 5-1 to 5-4).

Example 6 Examination of Added Water Substrate 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil (4.52 g) in N, N-dimethylformamide (40.71 mL) solvent under an argon stream , 20.00 mmol) using cesium carbonate (5.21 g, 16.0 mmol, 0.8 equivalent), the amount of water shown in Table 2 (2,2′-anhydro-1-β- (L- Arabinofuranosyl) (mole relative to uracil) was added, and the mixture was heated and stirred at 100 ° C. The results obtained by HPLC quantification are shown in Table 2.

  As compared with the case where the amount of added water is not added, the reaction is promoted as the amount is added (Examples 6-1 to 4). However, when the amount is too much, the production of arabino is increased (Example 6). 5-6-7).

Example 7 Preparation of L-uridine cesium salt 2,2′-Anhydro-1-β- (L-arabinofuranosyl) uracil (4.64 g, 20.0 mmol) of N, N-dimethylformamide (40.71 mL) ) After adding cesium carbonate (5.21 g, 16.0 mmol) and water (0.18 g, 20.0 mmol) to the solution, the mixture was heated and stirred at 100 ° C. for 24 hours. The obtained slurry was filtered and washed with N, N-dimethylformamide (2.0 mL), and then the crystals were dried at 50 ° C. under reduced pressure to obtain the desired product (8.38 g, 63.9 wt% as L-uridine). Yield 71%) as colorless crystals.

Example 8 Preparation of L -uridine A solution of L-uridine cesium salt (16.1 g, L-uridine content 54.2 wt%, 35.8 mmol) in water (36 mL) was placed in an ice bath, 6 mol / L aqueous hydrochloric acid was added, The pH was adjusted to 2.0. After returning to room temperature and stirring for 1 hour, the solvent was distilled off under reduced pressure. Methanol (160 mL) was added to the concentrated residue, heated and stirred at 50 ° C. for 30 minutes, then returned to room temperature, and the resulting slurry was filtered to remove insoluble crystals. The mother liquor was concentrated under reduced pressure, and the concentrated residue (19.99 g) was purified by chromatography (silica gel 200 g, eluent 4: 1 ethyl acetate / methanol) to obtain the desired product (8.57 g, 35.1 mmol, yield 98%). ) Was obtained as colorless crystals.

Comparative Example 1 Study of synthesis of L-uridine using potassium benzoate as a base 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil (226.2 mg, 1.0 mmol) under an argon stream And a solution of potassium benzoate (128.2 mg, 0.8 mmol) in N, N-dimethylformamide (2.0 mL) was heated and stirred at 100 ° C. for 17 hours. When HPLC quantification was performed at this time, 205.6 mg (90.9%) of 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil as a raw material remained, and L-uridine Was only 16.8 mg (6.9%).

Comparative Example 2 Study of synthesis of L-uridine using sodium bicarbonate as a base 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil (226.2 mg, 1.0 mmol) under an argon stream And a solution of sodium hydrogen carbonate (67.2 mg, 0.8 mmol) in N, N-dimethylformamide (2.0 mL) was heated and stirred at 100 ° C. for 14 hours. When HPLC quantification was performed at this time, 208.5 mg (92.2%) of 2,2′-anhydro-1-β- (L-arabinofuranosyl) uracil as a raw material remained, and L-uridine Was only 11.9 mg (4.9%).

  According to the present invention, ribonucleosides can be obtained inexpensively, easily and in high yield. Therefore, the present invention is a particularly useful production method for the production of L-ribonucleoside, which is an important intermediate of the antiviral agents terbivudine and clevudine and used as a monomer unit of the oligo RNA aptamer drug Spiegelmer.

Claims (12)

General formula (1):

(Wherein R ₁ and R ₂ are the same or different and each represents a hydrogen atom or a hydroxyl-protecting group; X and Y are the same or different and each represents a hydrogen atom, a halogen atom or an optionally substituted C _{1; -10 represents} an alkyl group, a C _1-7 acyl group, a nitro group or an amino group which may be protected, and represents an L-form, a D-form or a racemate.)
The 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative represented by the formula (1) is treated with a carbonate or bicarbonate of a metal selected from potassium, rubidium and cesium: 2):

(Each symbol in the formula is as defined above.)
A method for producing a ribonucleoside derivative or a salt thereof, wherein   The method according to claim 1, wherein the treatment is performed with a metal carbonate.   The method according to claim 1 or 2, wherein the metal is cesium.   The process according to any one of claims 1 to 3, wherein the treatment with a metal carbonate or bicarbonate is performed in a solvent containing an aprotic polar organic solvent.   The process according to claim 4, wherein the aprotic polar organic solvent is selected from dimethyl sulfoxide and N, N-dimethylformamide.   The solvent further contains water, and the addition amount thereof is 0.001 to 5 mol with respect to 1 mol of 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative. 4. The production method according to 4.   The production method according to claim 1, wherein X is a hydrogen atom or methyl, and Y is a hydrogen atom.   The production method according to claim 1, wherein the 2,2′-anhydro-1-arabinofuranosyl nucleoside derivative and the ribonucleoside derivative are both L-form.   Uridine cesium salt.   It has characteristic X-ray diffraction peaks at 7.0 °, 20.9 °, 26.1 °, 26.4 °, and 27.0 ° as diffraction angles (2θ ± 0.2 °, CuKα). Uridine cesium salt crystals.   5-methyluridine cesium salt.   It has characteristic X-ray diffraction peaks at 6.4 °, 23.6 °, 26.5 °, 27.1 °, and 29.6 ° as diffraction angles (2θ ± 0.2 °, CuKα). 5-methyluridine cesium salt crystals.

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