JP2004107329A - Method for producing 4'-c-ethynyl-2'-deoxypurine nucleoside - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing 4'-C-ethynyl-2'-deoxypurine nucleoside by using 2'-deoxypurine nucleoside as a starting material. <P>SOLUTION: This method for producing 4'-C-ethynyl-2'-deoxypurine nucleoside is provided by oxidizing a hydroxymethyl group at the 4' position of a compound expressed by formula [VII] to an aldehyde group, then converting it to a bromovinyl group, converting again to an ethynyl group by treating with a strong base to obtain a compound expressed by formula [VIII], then removing blocking groups at 3' and 5' positions of the compound to obtain a compound of which R is H, further phosphorylating as desired to obtain a compound expressed by formula [I]. In each of the above formulae, B is a purine (including azapurine or deazapurine) base; R is H or phosphate residue; and R2 to R4 are each a protecting group. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method for producing 4'-C-ethynyl-2'-deoxypurine nucleoside using 2'-deoxypurine nucleoside as a starting material.

The general group synthesized 4′-C-ethynyl-2′-deoxypurine nucleosides represented by the following formula [I] and measured the anti-HIV activity of those compounds. As a result, (1) equivalent to AZT or AZT (2) It has been shown that it has superior anti-HIV activity, and (2) it is also effective against multidrug-resistant virus strains that are resistant to multiple anti-HIV agents such as AZT, ddI, ddC, d4T, and 3TC (J. Med. Chem., 43 (2000), 4516-4525).

　　　　　　　　　　［Ｉ］
（式中、Ｂはプリン塩基を示し、Ｒは水素原子またはリン酸残基を示す。）

[I]
(In the formula, B represents a purine base, and R represents a hydrogen atom or a phosphate residue.)

Regarding the synthesis of purine nucleoside derivatives having an ethynyl group at the 4′-position, a method of synthesizing a saccharide with an ethynyl group-introduced saccharide and a nucleobase using a saccharide as a starting material has been widely reported (J Med. Chem., 43 (2000), 4516-4525), which is not always the best method because of the long number of steps and low yield.

As for the synthesis of nucleosides having an ethynyl group at the 4'-position from nucleosides as starting materials, only the synthesis of pyrimidine nucleosides has been reported (Bioorganic and Medicinal Chemistry Letters, 9 (1999), 385-388, J. Med. Chem., (1999), 42, 2901-2908), and there has been no report on the synthesis of a purine nucleoside having an ethynyl group at the 4'-position from a nucleoside as a starting material.

J. Med.Chem., 43 (2000), 4516-4525 Bioorganic and Medicinal Chemistry Letters, 9 (1999), 385-388 J. Med.Chem., (1999), 42, 2901-2908

The present inventors have studied a method for synthesizing 4′-C-ethynyl-2′-deoxypurine nucleoside using a nucleoside as a starting material in order to solve the above-mentioned problems of the conventional method using a sugar as a starting material. It has been confirmed that the previously reported method for synthesizing 4'-C-ethynylpyrimidine nucleoside cannot be directly employed as a method for synthesizing purine nucleosides having an ethynyl group at the 4'-position. That is, in the previous report, for example, a compound having an aldehyde group at the 4'-position is synthesized from thymidine, the aldehyde group of the compound is converted to a chlorovinyl group by Wittig reaction, and further treated with butyllithium to obtain 4'-C -Ethynyl thymidine. When these conditions were applied to purine nucleosides, the conversion of the chlorovinyl group to the ethynyl group hardly proceeded, and the desired compound could be obtained only in low yield.

In addition, butyl lithium used for conversion of a chlorovinyl group to an ethynyl group must be reacted at a very low temperature of -78 ° C in a system in which moisture, oxygen, etc. are completely excluded, and a large-scale reaction is required. It is not considered appropriate.

The present inventors have conducted intensive studies to overcome the above problems, and as a result, by using a bromovinyl group instead of a chlorovinyl group, a strong base other than butyllithium can be used. The present inventors have found that the conversion reaction can be carried out easily and under mild conditions, and that an ethynyl compound can be synthesized with a good yield, thereby completing the present invention.

Accordingly, the present invention relates to a method for producing 4'-C-ethynyl-2'-deoxypurine nucleoside represented by the above formula [I], comprising the following first to fifth steps.

The first step;
A step of protecting the 3′-hydroxyl group of the compound represented by the formula [II] to obtain a compound represented by the formula [IV]

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[II] [III] [IV]

The second step;
Step of introducing a hydroxymethyl group at the 4′-position of the compound represented by the formula [IV] to obtain a compound represented by the formula [V]

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[IV] [V]

Third step;
A step of protecting the 5′-hydroxyl group of the compound represented by the formula [V] to obtain a compound represented by the formula [VII]

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[V] [VI] [VII]

Fourth step;
After oxidizing the 4'-hydroxymethyl group of the compound represented by the formula [VII] to an aldehyde group, this is converted to a bromovinyl group, and subsequently treated with a strong base to convert it to an ethynyl group. For obtaining a compound represented by the formula VIII]

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[VII] [VIII]

Fifth step;
Step of removing the protecting group at the 3 ′, 5′-position of the compound represented by the formula [VIII] to obtain a compound in which R is hydrogen, and further, if necessary, phosphorylating to obtain a compound represented by the formula [I]

　　　　［ＶＩＩＩ］　　　　　　　　　　　　　　　　　［Ｉ］
（上記各式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒは水素原子またはリン酸残基を示し、Ｒ２〜Ｒ４は保護基を示す。）

[VIII] [I]
(In each of the above formulas, B represents a purine (including azapurine or deazapurine) base, R represents a hydrogen atom or a phosphate residue, and R2 to R4 represent protecting groups.)

As described above, the present invention can efficiently synthesize a target 4′-C-ethynyl-2′-deoxypurine nucleoside using deoxynucleosides as a starting material, and is therefore suitable for mass production. Manufacturing method.

The compound obtained by the method of the present invention is represented by the above formula [I], and as the base represented by B in the formula, a purine (including azapurine and deazapurine) base can be exemplified. .

Such purine bases include halogen atoms, alkyl groups, haloalkyl groups, alkenyl groups, haloalkenyl groups, alkynyl groups, amino groups, alkylamino groups, hydroxyl groups, hydroxyamino groups, aminoxy groups, alkoxy groups, mercapto groups, alkylmercapto groups. It may have a substituent such as a group, an aryl group, an aryloxy group, and a cyano group, and the number and position of the substituent are not particularly limited.

ハ ロ ゲ ン Examples of the halogen atom as a substituent include chlorine, fluorine, iodine, and bromine. Examples of the alkyl group include lower alkyl groups having 1 to 7 carbon atoms such as methyl, ethyl and propyl. Examples of the haloalkyl group include haloalkyl groups having an alkyl having 1 to 7 carbon atoms, such as fluoromethyl, difluoromethyl, trifluoromethyl, bromomethyl, and bromoethyl. Examples of the alkenyl group include alkenyl groups having 2 to 7 carbon atoms such as vinyl and allyl. Examples of the haloalkenyl group include haloalkenyl groups having 2 to 7 carbon atoms, such as bromovinyl and chlorovinyl. Examples of the alkynyl group include alkynyl groups having 2 to 7 carbon atoms, such as ethynyl and propynyl. Examples of the alkylamino group include alkylamino groups having 1 to 7 carbon atoms such as methylamino and ethylamino.

Examples of the alkoxy group include C1-C7 alkoxy groups such as methoxy and ethoxy. Examples of the alkyl mercapto group include alkyl mercapto groups having alkyl having 1 to 7 carbon atoms, such as methyl mercapto and ethyl mercapto. Examples of the aryl group include a phenyl group; an alkylphenyl group having 1 to 5 carbon atoms such as methylphenyl and ethylphenyl; an alkoxyphenyl group having 1 to 5 carbon atoms such as methoxyphenyl and ethoxyphenyl; Examples thereof include an alkylaminophenyl group having an alkylamino having 1 to 5 carbon atoms such as phenyl and diethylaminophenyl; and a halogenophenyl group such as chlorophenyl and bromophenyl.

Specific examples of purine bases include purine, 6-aminopurine (adenine), 6-hydroxypurine, 6-fluoropurine, 6-chloropurine, 6-methylaminopurine, 6-dimethylaminopurine, 6 -Trifluoromethylaminopurine, 6-benzoylaminopurine, 6-acetylaminopurine, 6-hydroxyaminopurine, 6-aminooxypurine, 6-methoxypurine, 6-acetoxypurine, 6-benzoyloxypurine, 6-methyl Purine, 6-ethylpurine, 6-trifluoromethylpurine, 6-phenylpurine, 6-mercaptopurine, 6-methylmercaptopurine, 6-aminopurine-1-oxide, 6-hydroxypurine-1-oxide, 2- Amino-6-hydroxypurine (guanine), 2,6-diaminop 2-amino-6-chloropurine, 2-amino-6-iodopurine, 2-aminopurine, 2-amino-6-mercaptopurine, 2-amino-6-methylmercaptopurine, 2-amino-6- Hydroxyaminopurine, 2-amino-6-methoxypurine, 2-amino-6-benzoyloxypurine, 2-amino-6-acetoxypurine, 2-amino-6-methylpurine, 2-amino-6-cyclopropylamino Methyl purine, 2-amino-6-phenylpurine, 2-amino-8-bromopurine, 6-cyanopurine, 6-amino-2-chloropurine (2-chloroadenine), 6-amino-2-fluoropurine ( 2-fluoroadenine), 6-amino-3-deazapurine, 6-amino-8-azapurine, 2-amino-6-hydroxy-8-a Purine, 6-amino-7-deazapurine, 6-amino-1-deazapurine, such as 6-amino-2-azapurine the like.

Hereinafter, the method of the present invention will be described step by step.

The first step is a step of protecting the 3′-hydroxyl group of the compound represented by the formula [II] to obtain a compound represented by the formula [IV].

　　　［ＩＩ］　　　　　　　　　［ＩＩＩ］　　　　　　　　［ＩＶ］
（式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒ１、Ｒ２は保護基を示す。）

[II] [III] [IV]
(In the formula, B represents a purine (including azapurine or deazapurine) base, and R1 and R2 represent protecting groups.)

The compound represented by the formula [IV] is obtained by protecting the 5'-hydroxyl group of the compound represented by the formula [II], and then protecting the 3'-hydroxyl group with a protecting group different from the 5'-protecting group. Subsequently, the protective group at the 5′-position hydroxyl group can be selectively removed to obtain the compound.

The protecting group for the 5′-hydroxyl group represented by R1 may be any one that is commonly used as a protecting group for the 5′-hydroxyl group of a nucleoside, and specifically, dimethoxytrityl, methoxytrityl, trityl, t- Examples thereof include butyldimethylsilyl, t-butyldiphenylsilyl, and a benzoyl group. The protecting group for the hydroxyl group at the 3'-position represented by R2 may be any of those commonly used for a hydroxyl group, such as an ether-based protecting group, an acyl-based protecting group, a silyl-based protecting group, and an acetal-based protecting group. And the like.

More specifically, the ether-based protecting groups include methyl ether, tertiary butyl ether, benzyl ether, methoxybenzyl ether, and trityl ether; the acyl-based protecting groups include acetyl, benzoyl, and pivaloyl; As the group, t-butyldimethylsilyl, t-butyldiphenylsilyl, trimethylsilyl, triethylsilyl, and the like, and as the acetal-based protecting group, isopropylidene, ethylidene, methylidene, benzylidene, tetrahydropyranyl, methoxymethyl, and the like can be used. it can.

The subsequent removal of the 5'-protecting group may be appropriately selected from ordinary processing methods such as acidic hydrolysis, alkaline hydrolysis, tetrabutylammonium fluoride treatment, and catalytic reduction, depending on the protecting group used.

The second step is a step of introducing a hydroxymethyl group at the 4'-position of the compound represented by the formula [IV] to obtain a compound represented by the formula [V].

　　　　　［ＩＶ］　　　　　　　　　　　　　　　　　［Ｖ］
（式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒ２は保護基を示す。）

[IV] [V]
(In the formula, B represents a purine (including azapurine or deazapurine) base, and R2 represents a protecting group.)

The compound represented by the formula [V] is obtained by converting the 5'-position of the compound represented by the formula [IV] to an aldehyde group, introducing an hydroxymethyl group into the 4'-position by an aldol reaction with formaldehyde, and adding an aldehyde group. Can be synthesized through reduction.

Examples of the oxidizing agent for converting the 5′-hydroxymethyl group of the compound represented by the formula [IV] to an aldehyde include chromic anhydride, a complex reagent of pyridine and acetic anhydride, pyridine chlorochromate and pyridine dichromate. Chromium-based oxidizing agents; high-valent iodine oxidizing agents such as Dess-Martin reagent; dimethylsulfoxide-based oxidizing agents using dimethylsulfoxide in combination with acetic anhydride, oxalyl chloride or dicyclohexylcarbodiimide;

The reaction conditions vary depending on the oxidizing agent to be used. For example, when oxidizing using 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride and dimethyl sulfoxide, if necessary, a mixed solvent of an organic solvent such as toluene and dimethyl sulfoxide may be used. Under an atmosphere of an inert gas such as argon or nitrogen, 1 to 5 mol of 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride is used per 1 mol of the compound of the formula [IV] at a temperature of 10 to 50 ° C. and 1 to 2 mol. The reaction can be carried out by reacting for about an hour.

Next, introduction of a hydroxymethyl group at the 4'-position can be carried out by an aldol reaction between the obtained aldehyde compound and formaldehyde.

The aldolization is carried out in an organic solvent such as tetrahydrofuran or dioxane in the presence of 1 to 5 mol of a base such as sodium hydroxide, by reacting with 1 to 10 mol of formaldehyde with respect to 1 mol of the aldehyde compound. Can be.

Subsequent reduction of the aldehyde group is performed using a reducing agent such as sodium borohydride or lithium aluminum hydride in an organic solvent such as methanol, ethanol, diethyl ether or tetrahydrofuran in an amount of 1 to 5 moles per mole of the aldehyde compound. The reaction may be carried out at -78 ° C to room temperature for about 15 minutes to 1 hour.

The third step is a step of introducing a protecting group at the 5′-position of the compound represented by the formula [V].

　　　　　［Ｖ］　　　　　　　　　　　［ＶＩ］　　　　　　　　［ＶＩＩ］
（式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒ２とＲ４は保護基を示す。）　　　

[V] [VI] [VII]
(In the formula, B represents a purine (including azapurine or deazapurine) base, and R2 and R4 represent protecting groups.)

The compound represented by the formula [VII] is obtained by protecting the 4′-hydroxymethyl group of the compound represented by the formula [V] and then removing the 5′-hydroxyl group from the protecting group of the 4′-hydroxymethyl group. And the protective group at the 4′-position hydroxymethyl group is then selectively removed.

The protecting group for the 4'-hydroxymethyl group represented by R3 may be any one that is commonly used as a protecting group for the 5'-hydroxyl group of a nucleoside, and specifically, dimethoxytrityl, methoxytrityl, trityl, Examples thereof include t-butyldimethylsilyl, t-butyldiphenylsilyl, and a benzoyl group. The protecting group for the 5'-hydroxyl group represented by R4 may be any one which is usually used as a hydroxyl group, such as an ether-based protecting group, an acyl-based protecting group, a silyl-based protecting group, and an acetal-based protecting group. And the like.

More specifically, the ether-based protecting groups include methyl ether, tertiary butyl ether, benzyl ether, methoxybenzyl ether, and trityl ether; the acyl-based protecting groups include acetyl, benzoyl, and pivaloyl; As the group, t-butyldimethylsilyl, t-butyldiphenylsilyl, trimethylsilyl, triethylsilyl, and the like, and as the acetal-based protecting group, isopropylidene, ethylidene, methylidene, benzylidene, tetrahydropyranyl, methoxymethyl, and the like can be used. it can.

The removal of the protecting group at the 4′-hydroxymethyl group may be appropriately selected from ordinary processing methods such as acidic hydrolysis, alkaline hydrolysis, tetrabutylammonium fluoride treatment, and catalytic reduction depending on the protecting group used. Good.

The fourth step is a step of converting the 4′-hydroxymethyl group of the compound represented by the formula [VII] to an ethynyl group.

　　　　　　［ＶＩＩ］　　　　　　　　　　　　　　　　［ＶＩＩＩ］
（式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒ２とＲ４は保護基を示す。）

[VII] [VIII]
(In the formula, B represents a purine (including azapurine or deazapurine) base, and R2 and R4 represent protecting groups.)

The reaction against the ethynyl group is performed by oxidizing the 4'-hydroxymethyl group of the compound of the formula [VII] to an aldehyde group, converting it to a bromovinyl group, and then subjecting it to a dehydrobromination treatment by a strong base treatment. Can be implemented.

When converting the 4′-hydroxymethyl group of the compound represented by the formula [VII] to an aldehyde group, oxidizing agents used include chromic anhydride, a complex reagent of pyridine and acetic anhydride, pyridine chlorochromate, pyridine dichromate Oxidizing agents such as chromium-based oxidizing agents; high-valent iodine oxidizing agents such as Dess-Martin reagent; dimethylsulfoxide-based oxidizing agents using a combination of dimethylsulfoxide and acetic anhydride, oxalyl chloride or dicyclohexylcarbodiimide.

The reaction conditions vary depending on the oxidizing agent to be used. For example, when oxidizing using 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride and dimethyl sulfoxide, if necessary, a mixed solvent of an organic solvent such as toluene and dimethyl sulfoxide may be used. Under an atmosphere of an inert gas such as argon or nitrogen, 1 to 5 mol of 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride is used per 1 mol of the compound of the formula [IV] at a temperature of 10 to 50 ° C. and 1 to 2 mol. The reaction can be carried out by reacting for about an hour.

The conversion of the aldehyde group into a bromovinyl group is performed by using 1 to 5 mol of bromomethylene triphenylphosphorane or a combination of carbon tetrabromide and triphenylphosphine with respect to 1 mol of the aldehyde compound in an organic solvent such as tetrahydrofuran. The reaction can be carried out at -78 ° C to room temperature.

The strong base used for the dehydrobromination treatment of the bromovinyl compound can be carried out by using alkyllithium, an organic metal reagent such as a Grignard reagent, a metal amide such as diisopropylamine or hexamethyldisilazane, or potassium t-butoxide. Particularly, potassium t-butoxide is preferred.

Conditions for the dehydrobromination treatment differ depending on the reagent used. For example, when potassium t-butoxide is used, 1 to 5 mol of potassium t-butoxide is used per mol of a halovinyl compound in an organic solvent such as tetrahydrofuran at -40 ° C. The reaction can be carried out at room temperature for about 15 minutes to 2 hours.

The fifth step is a step of removing the protecting group of the compound [VIII] thus obtained to obtain a compound in which R is hydrogen, and phosphorylating as necessary to obtain a compound of the formula [I].

　　　　　　［ＶＩＩＩ］　　　　　　　　　　　　　　　　　［Ｉ］
（式中、Ｂはプリン（アザプリンまたはデアザプリンも含む）塩基を示し、Ｒは水素原子またはリン酸残基を示し、Ｒ２とＲ４は保護基を示す。）

[VIII] [I]
(Wherein, B represents a purine (including azapurine or deazapurine) base, R represents a hydrogen atom or a phosphate residue, and R2 and R4 represent protecting groups.)

The removal of the protecting group may be appropriately selected from ordinary processing methods such as acidic hydrolysis, alkaline hydrolysis, tetrabutylammonium fluoride treatment, and catalytic reduction, depending on the protecting group used.

Further, if it is desired to deaminate the amino group in the base, it is possible to deaminate by a conventional method using various deaminase such as adenosine deaminase and cytidine deaminase.

When a compound in which R is a phosphate residue such as a monophosphate residue or a diphosphate residue is obtained, a compound in which R is a hydrogen atom is substituted with 5 ′ of a nucleoside such as phosphorus oxychloride or tetrachloropyrophosphate. By reacting with a phosphorylating agent used for selective phosphorylation at the position, a free acid type or salt type target compound can be obtained.

The compound of formula [I] thus obtained and its intermediates can be obtained by a method used for isolating and purifying general nucleosides and nucleotides (eg, recrystallization, ion exchange column chromatography, adsorption column chromatography, etc.). ) Can be appropriately combined for separation and purification.

Hereinafter, the present invention will be described specifically with reference to Synthesis Examples, but the present invention is not limited thereto.
Synthesis Example 1: Synthesis of 4′-C-ethynyl-2′-deoxyadenosine (1) Synthesis of N ⁶ -benzoyl-3′-O-tert-butyldimethylsilyl-2′-deoxyadenosine (Compound 2)

N ⁶ -benzoyl-2′-deoxy-5′-O-dimethyloxytrityladenosine 1 (2.00 g, 3.04 mmol) was dissolved in dimethylformamide (6.00 ml), imidazole (0.83 g, 12.2 mmol), tert. -Butylchlorodimethylsilane (0.92 g, 6.10 mmol) was added, and the mixture was stirred at room temperature overnight.

After the reaction was stopped by adding methanol, the reaction solution was diluted with ethyl acetate, and the organic layer was washed with water and dried (over anhydrous magnesium sulfate). After the desiccant was removed by filtration, the filtrate was concentrated under reduced pressure. The obtained residue was dissolved in chloroform (70.0 ml), and a methanol solution (30.0 ml) of toluenesulfonic acid monohydrate (2.00 g) was added dropwise under ice-cooling, followed by stirring at the same temperature for 30 minutes. .

(5) A saturated aqueous sodium hydrogen carbonate solution was added to the reaction solution, and the mixture was stirred, and then the organic layer was dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (silica gel @ 100 cc, hexane: ethyl acetate = 1: 3) to give compound 2 as a white foam (1.20 g, 2.56 mmol, 84.2%). Got.

_{^{1 H-NMR (CDCl 3)}} δ 9.05 (1H, s, NH), 8.78 (1H, s, H-8), 8.10 (1H, s, H-2), 8.09- 7.52 (5H, m, aromatic), 6.37 (1H, dd, H-1 ', J = 5.36, 9.28), 5.78 (1H, dd, 5'-OH, J = 1.92, 11.2), 4.74 (1H, d, H-3 ', J = 4.88), 4.17 (1H, s, H-4'), 4.00-3.74. (2H, m, H-5 '), 3.07 (1H, m, H-2'a), 2.27 (1H, m, H-2'b), 0.94 (9H, s, t) -Bu), 0.13 (6H, s, Me).

(2) Synthesis of N ⁶ -benzoyl-3′-O-tert-butyldimethylsilyl-2′-deoxy-4′-C-hydroxymethyladenosine (Compound 3)

Compound # 2 (2.55 g, 5.43 mmol) was dissolved in toluene (10.0 ml) and dimethyl sulfoxide (15.0 ml), and 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride (3.12 g, 16 0.3 mmol), pyridine (0.41 ml) and trifluoroacetic acid (0.21 ml), and the mixture was stirred at room temperature for 2 hours. After diluting the reaction solution with ethyl acetate, the organic layer was washed with water and dried (over anhydrous magnesium sulfate). After removing the drying agent by filtration, the filtrate was concentrated under reduced pressure to obtain a crude aldehyde. The crude aldehyde was dissolved in dioxane (15.0 ml), a 37% aqueous formaldehyde solution (2.86 ml) and a 2N aqueous sodium hydroxide solution (2.86 ml) were added, and the mixture was stirred at room temperature for 1 hour.

(4) The reaction solution was neutralized with acetic acid, diluted with ethyl acetate, washed with water and dried. After removing the desiccant by filtration, the filtrate was concentrated under reduced pressure, and the obtained residue was dissolved in ethanol (25.0 ml). Under ice cooling, sodium borohydride (0.21 g, 5.55 mmol) was added. Stir for 30 minutes. The reaction solution was neutralized with acetic acid, diluted with ethyl acetate, washed with water and dried (over anhydrous magnesium sulfate). After removing the desiccant by filtration, the filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (silica gel @ 300 cc, hexane: ethyl acetate = 1: 3-1 to 1: 4-1: 5) to give a pale yellow foam. Compound # 3 (1.68 g, 3.36 mmol, 61.9%) was obtained.

_{^{1 H-NMR (CDCl 3)}} δ 9.05 (1H, s, NH), 8.79 (1H, s, H-8), 8.08 (1H, s, H-2), 8.04- 7.52 (5H, m, aromatic), 6.44 (1H, dd, H-1 '), 5.56 (1H, br.d, OH), 4.94 (1H, dd, H-3'). , J = 1.48, 5.88), 3.86-3.63 (4H, m, H-5 'and H-6'), 3.24 (1H, m, H-2'a), 2.67 (1H, br.s, OH), 2.38 (1H, m, H-2'b), 0.96 (9H, s, t-Bu), 0.19, 0.18 (each 3H, s, Me).

(3) Synthesis of N ⁶ -benzoyl-3′-O-tert-butyldimethylsilyl-4′-C-dimethyoxytrityloxymethyladenosine (Compound 4)

Compound # 3 (0.84 g, 1.68 mmol) was dissolved in dichloromethane (17.0 ml), and triethylamine (0.47 ml, 3.37 mmol) and dimethoxytrityl chloride (0.85 g, 2.51 mmol) were added under ice-cooling. The mixture was stirred for 30 minutes. After stopping the reaction by adding methanol, the organic layer was washed with a saturated aqueous solution of sodium hydrogen carbonate. The organic layer was dried over anhydrous magnesium sulfate, concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (silica gel @ 200 cc, hexane: ethyl acetate = 2: 1 to 1: 1) to give pale yellow foamy compound # 4 (0.91 g, 1.13 mmol, 67.3%).

_{^{1 H-NMR (CDCl 3)}} δ 9.30 (1H, bs, NH), 8.94 (1H, s, H-8), 8.24 (1H, s, H-2), 8.18- 6.94 (18H, m, aromatic), 6.41 (1H, dd, H-1 ', J = 5.84, 8.80), 5.36 (1H, br.s, OH); 85 (1H, d, H-3 ', J = 3.92), 4.42 (1H, br.d, H-5'a), 3.91 (6H, s, OMe), 3.78 ( 1H, br, t, H-5'b), 3.66 (1H, d, H-6'a, J = 10.76), 3.28 (1H, m, H-2'a), 3 .20 (1H, d, H-6'b, J = 10.76), 2.41 (1H, m, H-2'b), 0.89 (9H, s, t-Bu), 0. 13, 0.11 (each 3H, s, Me).

(4) Synthesis of N ⁶ -benzyl-3 ′, 5′-di-O-tert-butyldimethylsilyl-2′-deoxy-4′-C-hydroxymethyladenosine (Compound 5)

Compound # 4 (1.61 g, 2.01 mmol) was dissolved in dimethylformamide (8.00 ml), and imidazole (0.41 g, 6.02 mmol) and tert-butylchlorodimethylsilane (0.45 g, 2.99 mmol) were added. The mixture was stirred overnight at room temperature. After stopping the reaction by adding methanol, the reaction solution was diluted with ethyl acetate, and the organic layer was washed with water and dried (over anhydrous magnesium sulfate). The drying agent was removed by filtration, and the filtrate was concentrated under reduced pressure. The obtained residue was dissolved in chloroform (70.0 ml), and a methanol solution (30.0 ml) of toluenesulfonic acid monohydrate (1.00 g) was added dropwise under ice cooling, followed by stirring at the same temperature for 30 minutes. . After adding a saturated aqueous sodium hydrogen carbonate solution to the reaction solution and stirring, the organic layer was dried over anhydrous magnesium sulfate. The obtained solution was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (silica gel @ 200 cc, hexane: ethyl acetate = 3: 1) to give compound # 5 as a white foam (1.00 g, 1.63 mmol, 81.1). %).

_{^{1 H-NMR (CDCl 3)}} δ 9.09 (1H, bs, NH), 8.80 (1H, s, H-8), 8.28 (1H, s, H-2), 8.04- 7.51 (5H, m, aromatic), 6.52 (1H, t, H-1 ', J = 6.32), 4.87 (1H, dd, H-3', J = 4.40, 6.36), 3.90-3.72 (4H, m, H-5 'and H-6'), 3.03 (1H, m, H-2'a), 2.60 (1H, m , H-2'b), 2.53 (1H, br.s, OH), 0.95, 0.89 (each 9H, s, t-Bu), 0.16, 0.06 (each 6H, s, Me).

(5) Synthesis of N ⁶ -benzoyl-3 ′, 5′-di-O-tert-butyldimethylsilyl-4′-C-ethynyl-2′-deoxyadenosine (compound 6)

Compound # 5 (1.84 g, 3 mmol) was dissolved in dimethyl sulfoxide (9.6 ml) in toluene (4.8 ml), and 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (1.57 g, 8.19 mmol), pyridine (0.22 ml) and trifluoroacetic acid (0.11 ml) were added, and the mixture was stirred at room temperature for 30 minutes. After diluting the reaction solution with ethyl acetate, the organic layer was washed with water and dried (over anhydrous magnesium sulfate). After removing the drying agent by filtration, the filtrate was concentrated under reduced pressure to obtain a crude aldehyde.

Bromomethyltriphenylphosphonium bromide (2.64 g, 6.05 mmol) was suspended in tetrahydrofuran (34.8 ml), and potassium tert-butoxide (1.01 g, 9.00 mmol) was added at −40 ° C., and under an argon atmosphere. And stirred at the same temperature for 1 hour. To this suspension, a solution of the above crude aldehyde in tetrahydrofuran (5.8 ml) was added dropwise, and the mixture was stirred at the same temperature for 1 hour. After adding a saturated aqueous ammonium chloride solution (30 ml), the mixture was stirred at room temperature for 10 minutes, and the liquid was diluted with ethyl acetate. After liquid separation, the organic layer was washed with saturated saline and dried over anhydrous sodium sulfate. The residue was purified by silica gel column chromatography (silica gel @ 35 g, hexane: ethyl acetate = 4: 1 to 3: 1 to 2: 1) to obtain 1.84 g of a crude bromovinyl compound.

The crude bromovinyl compound was dissolved in tetrahydrofuran (61 ml), potassium tert-butoxide (0.897 g, 8.00 mmol) was added at -40 ° C, and the mixture was stirred at the same temperature for 30 minutes under an argon atmosphere. After adding a saturated ammonium chloride aqueous solution (30 ml), the mixture was stirred at room temperature for 10 minutes. After diluting the reaction solution with ethyl acetate, liquid separation was performed, and the organic layer was washed with brine and dried over anhydrous sodium sulfate. The residue was purified by silica gel column chromatography (silica gel @ 17 g, hexane: ethyl acetate = 4: 1 to 2: 1: 2: 3) to give a foamed compound # 6 (1.2 g, 1.97 mmol). , 66%).

¹ H-NMR (CDCl ₃ ) δ 8.99 (1 H, br.s, NH), 8.81 (1 H, s, H-8), 8.30 (1 H, s, H-2), 8. 04-7.51 (5H, m, aromatic), 6.54 (1H, dd, H-1 ', J = 7.3, 4.9), 4.83 (1H, t, H-3', J = 6.8), 3.97 (1H, d, H-5'a, J = 11.2), 3.81 (1H, d, H-5'b, J = 11.2), 2 .82-2.75 (1H, m, H-2 '), 2.72-2.64 (1H, m, H-2'), 2.57 (1H, s, ethynyl), 0.94, 0.89 (each 9H, s, t-Bu), 0.14, 0.13, 0.08, 0.04 (each 3H, s, Me).

(6) Synthesis of 4'-C-ethyl-2'-deoxyadenosine (compound 7)

{Compound} 6 (0.118 g, 0.235 mmol) was dissolved in tetrahydrofuran (3.2 ml), tetrabutylammonium fluoride (1 M tetrahydrofuran solution, 0.7 ml, 0.7 mmol) was added, and the mixture was stirred at room temperature for 30 minutes. After the reaction solution was concentrated under reduced pressure, the residue was roughly purified by silica gel column chromatography (silica gel @ 8 cc, chloroform: methanol = 20: 1) to obtain a desilylated product.

The desilylated compound was dissolved in methanol (2.1 ml), 28% aqueous ammonia (0.7 ml) was added, and the mixture was stirred at room temperature overnight. After the reaction solution was concentrated under reduced pressure, the residue was purified by silica gel column chromatography (silica gel @ 8 cc, chloroform: methanol = 20: 1 to 10: 1) to give compound 7 (0.057 g, 0.207 mmol, 88.2%). ) Got.

_{^{1 H-NMR (DMSO-d}} 6) δ 8.33 (1H, s, purine-H), 8.15 (1H, s, purine-H), 7.30 (2H, br s, NH 2), 6.36 (1H, t, J = 6.4 Hz, H-1 '), 5.54 (1H, d, J = 5.4 Hz, OH), 5.53 (1H, t, J = 5.4 Hz) , OH), 4.58 (1H, q, J = 5.9 Hz, H-3 '), 3.66 (1H, dd, J = 12.2, 5.4 Hz, H-5'); 56 (1H, dd, J = 11.7, 7.3 Hz, H-5 '), 3.50 (1H, s, ethylyl-H), 2.76 (1H, dt, J = 13.2, 6 .4 Hz, H-2 '), 2.41 (1H, dt, J = 13.2, 6.8 Hz, H-2').

Synthesis Example 2: Synthesis of 4'-C-ethynyl-2'-deoxyinosine (Compound 8)

Adenosine deaminase (0.044 ml, 20 units) was added to a solution of Compound 7 (22 mg, 0.08 mmol) in Tris-HCl buffer (6 ml, pH 7.5), and the mixture was stirred at 40 ° C. for 2.5 hours. After cooling to room temperature, the mixture was applied to a reverse-phase ODS silica gel column (50 g), desalted by flowing water (500 ml), and then a 2.5% aqueous ethanol solution was passed to elute Compound 8. Further powdering was carried out with isopropanol to obtain 16 mg (72%) of compound 8.

_{^{1 H-NMR (DMSO-d}} 6) δ 12.28 (1H, brs, NH), 8.29 (1H, s, purine-H), 8.06 (1H, s, purine-H), 6. 32 (1H, dd, J = 6.8, 4.9 Hz, H-1 ′), 5.57 (1H, d, J = 5.4 Hz, OH), 5.32 (1H, t, J = 5) 9.5 Hz, OH), 4.56 (1H, dt, J = 6.4, 5.4 Hz, H-3 ′), 3.65 (1H, dd, J = 12.2, 5.9 Hz, H−) 5 '), 3.57 (1H, dd, J = 11.7, 6.4 Hz, H-5'), 3.50 (1H, s, ethylyl-H), 2.66 (1H, dt, J = 12.2, 5.9 Hz, H-2 '), 2.46 (1H, dt, J = 13.2, 6.9 Hz, H-2').

Synthesis Example 3: Synthesis of 9- (2-deoxy-4-C-ethynyl-β-D-ribo-pentofuranosyl) -2,6-diaminopurine (1) 9- (2-deoxy-β-D- Synthesis of ribo-pentofuranosyl) -2,6-dibenzamidopurine (compound 10)

Compound 9 (26.2 g, 100 mmol) was azeotroped twice with pyridine, suspended in pyridine (400 ml), and chlorotrimethylsilane (88 ml, 700 mmol) was added dropwise at 0 ° C. over 10 minutes. After stirring at 0 ° C. for 30 minutes, benzoyl chloride (82 ml, 700 mmol) was added dropwise over 20 minutes, and the mixture was further stirred at room temperature for 2 hours. Ice water (200 ml) was slowly poured into the reaction solution at 0 ° C., and the mixture was stirred for 15 minutes, and then concentrated ammonia water (300 ml) was added dropwise at the same temperature, followed by stirring for 30 minutes. The solvent was distilled off under reduced pressure, and ethyl acetate (600 ml) and saturated aqueous sodium hydrogen carbonate (600 ml) were poured into the residue, followed by stirring at 0 ° C. for 1 hour. The precipitated crystals were collected by filtration, washed with water and ethyl acetate, and dried under vacuum to obtain colorless crystalline compound 10 (36.22 g, 76%).

¹ H-NMR (DMSO-d ₆ ) δ 11.19, 10.98 (each 1H, s, NH), 8.61 (1H, s, H-8), 8.07-7.50 (10H, s, aromatic, 6.42 (1H, t, H-1 ', J = 7.32), 5.33 (1H, d, 3'-OH, J = 3.88), 4.93 (1H) , T, 5'-OH, J = 5.36), 4.44 (1H, bm, H-3 '), 3.88 (1H, bm, H-4'), 3.62 (1H, m, H-5'a), 3.55 (1H, m, H-5'b), 2.79 (1H, m, H-2'a), 2.33 (1H, m, H-2'b).

(2) Synthesis of 9- (2-deoxy-3-O-tert-butyldimethylsilyl-β-D-ribo-pentofuranosyl) -2,6-dibenzamidopurine (Compound 11)

Compound 10 (36.22 g, 76.4 mmol) was azeotropically dehydrated twice with pyridine, then dissolved in pyridine (300 ml), dimethoxytrityl chloride (37.6 g, 111 mmol) was added at room temperature, and the mixture was stirred for 3 hours. Ethanol (10 ml) was added to the reaction solution, and the solvent was distilled off under reduced pressure. The residue was suspended in ethyl acetate (250 ml), water was added, and the mixture was filtered through celite to remove insolubles. The organic layer was collected, further washed twice with water and once with a saturated saline solution, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was purified by silica gel column chromatography (silica gel @ 300 g, chloroform-chloroform: methanol = 200: 1 to 100: 1 to 50: 1). The obtained residue (69.9 g) was azeotropically dehydrated twice with dimethylformamide, then dissolved in dimethylformamide (370 ml), and imidazole (8.8 g, 129 mmol) and tert-butylchlorodimethylsilane (16.5 g, 109 mmol) and stirred at room temperature overnight.

水 Water was poured into the reaction solution, and the solvent was distilled off under reduced pressure. The residue was dissolved in ethyl acetate (500 ml), washed with water (500 ml × 3) and brine, and dried over anhydrous sodium sulfate. The solvent was distilled off, the obtained residue was dissolved in chloroform (510 ml), and a solution of toluenesulfonic acid monohydrate-methanol (14.6 g, {76.8 mmol} in {220 ml} of MeOH) was slowly added dropwise at 0 ° C ( 5 minutes). After stirring at 0 ° C. for 15 minutes, saturated sodium bicarbonate solution (600 ml) was added for neutralization. The organic layer was collected, washed with saturated saline, and dried over anhydrous sodium sulfate. The solvent was distilled off and azeotroped with ethyl acetate (150 ml). Ethyl acetate (300 ml) was added to the residue, and the mixture was stirred at room temperature for 30 minutes, and the precipitated crystals were collected by filtration. The crystals were washed with ethyl acetate and then dried in vacuo to obtain colorless crystalline compound 11 (28.76 g, 64%).

_{^{1 H-NMR (CDCl 3)}} δ 9.33,9.17 (each 1H, s, NH), 8.07-7.45 (10H, m, aromatic), 6.29 (1H, dd, H- 1 ′, J = 6.36, 7.80), 4.95 (1H, bm, H-3 ′), 4.86 (1H, bt, 5′-OH), 4.04 ( 1H, bd, H-4 '), 3.95 (1H, m, H-5'a), 3.85 (1H, m, H-5'b), 1.42 (1H, m, H-2'a), 2.30 (1H, m, H-2'b).

(3) Synthesis of 9- (2-deoxy-3-O-tert-butyldimethylsilyl-4-C-hydroxymethyl-β-D-ribo-pentofuranosyl) -2,6-dibenzamidopurine (Compound 12)

Compound 11 (50.0 g, 85.0 mmol) was dissolved in dimethyl sulfoxide (290 ml) -toluene (190 ml), and 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride (24.6 g, {127. 5 mmol), pyridine (6.9 ml, 85.0 mmol) and trifluoroacetic acid (3.3 ml, 42.5 mmol) were added and stirred for 2 hours. Ethyl acetate (750 ml) and ice water (750 ml) were added to the reaction solution at 0 ° C., and the mixture was stirred for 1 hour. The precipitated crystals (part of the formyl compound) were collected by filtration, and the organic layer of the filtrate was recovered. The organic layer was washed twice with water and once with saturated saline, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue and the collected crystals were combined to obtain a crude aldehyde. The crude aldehyde was dissolved in dioxane (240 ml), a 37% aqueous formaldehyde solution (45 ml) and a 2N aqueous sodium hydroxide solution (45 ml) were added at room temperature, and the mixture was stirred at room temperature for 3 hours.

The reaction solution was neutralized with glacial acetic acid (8.6 ml) and extracted with ethyl acetate (700 ml). The organic layer was washed with water, saturated aqueous sodium hydrogen carbonate, and saturated saline, and then dried over anhydrous sodium sulfate. The solvent was distilled off, the obtained residue was dissolved in ethanol (360 ml), sodium borohydride (3.2 g, 85.0 mmol) was added at 0 ° C., and the mixture was stirred at the same temperature for 30 minutes. Glacial acetic acid (2.5 ml) was added to the reaction solution to stop the reaction, and the mixture was extracted with chloroform-methanol (10: 1) (1.1 L). The organic layer was washed with water and saturated saline, and then dried over anhydrous sodium sulfate. The solvent was distilled off, and azeotroped with ethyl acetate (200 ml). Ethyl acetate (500 ml) was added to the residue, and the mixture was stirred at room temperature for 5 minutes, and the precipitated crystals were collected by filtration. The crystals were washed with ethyl acetate and dried under vacuum to obtain 30.83 g (59%) of compound 12 as colorless crystals.

_{^{1 H-NMR (DMSO-d}} 6) δ 11.21,11.01 (each 1H, s, NH), 8.63-7.50 (12H, m, aromatic), 6.43 (1H, t, H-1 ', J = 6.32), 4.91 (1H, t, OH, J = 5.36), 4.78 (1H, t, H-3', J = 5.84), 4 .47 (1H, t, OH, J = 6.36), 3.65-3.52 (4H, m, H-5 'and H-6'), 2.96 (1H, m, H-2) 'a), 2.43 (1H, m, H-2'b), 0.89 (9H, s, t-Bu), 0.10 (6H, s, Me).

(4) Synthesis of 9- (2-deoxy-3-O-tert-butyldimethylsilyl-4-C-dimethyoxytriethyloxymethyl-β-D-ribo-pentofuranosyl) -2,6-dibenzamidopurine (Compound 13)

Compound 12 (24.8 g, 40.0 mmol) was azeotropically dehydrated once with dimethylformamide, then dissolved in dimethylformamide (200 ml), triethylamine (11.2 ml, 80.0 mmol), dimethoxytrityl chloride (20.3 g) , 60.0 mmol) and stirred at room temperature for 1 hour. The reaction solution was extracted with ethyl acetate (600 ml), washed with water (600 ml × 3) and brine, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was purified by silica gel column chromatography (silica gel @ 600 g, chloroform-chloroform-ethyl acetate 5: 1 to 2: 1 to 1: 2 to 1: 3 to ethyl acetate) to give compound 13 (22 .2 g, 60%).

_{^{1 H-NMR (CDCl 3)}} δ 9.33,9.24 (each 1H, s, NH), 8.13-6.89 (25H, m, aromatic), 6.27 (1H, t, H- 1 ′, J = 6.84), 5.14 (1H, dd, H-3 ′, J = 3.92, 6.36), 4.59 (1H, dd, 5′-OH, J = 5) .40, 8.32), 4.30 (1H, dd, H-5'a, J = 5.36, 12.72), 3.87 (6H, s, OMe), 3.82 (1H, dd, H-5'b, J = 8.80, 12.2), 3.59 (1H, d, H-6'a, J = 1.76), 3.27 (1H, m, H-) 2'a), 3.18 (1H, d, H-6'b, J = 10.72), 2.48 (1H, m, H-2'b), 0.84 (9H, s, t) -Bu), 0.09, 0.07 (each 3H Me).

(5) Synthesis of 9- (2-deoxy-3,5-di-O-tert-butyldimethylsilyl-4-C-hydroxymethyl-β-D-ribo-pentofuranosyl) -2,6-dibenzamidopurine (Compound 14)

Compound 13 (29.9 g, 32.5 mmol) was azeotropically dehydrated twice with dimethylformamide, then dissolved in dimethylformamide (100 ml), imidazole (3.3 g, 48.8 mmol), tert-butylchlorodimethylsilane ( 5.9 g, 39.0 mmol) and stirred at room temperature overnight. The reaction solution was extracted with ethyl acetate (300 ml), washed with water (300 ml × 3) and brine, and dried over anhydrous sodium sulfate. The solvent was distilled off, the obtained residue was dissolved in chloroform (620 ml), and a toluenesulfonic acid-methanol solution (6.2 g, 32.5 mmol in 190 ml of MeOH) was slowly added dropwise at −10 ° C. (5 minutes). . After stirring at the same temperature for 20 minutes, saturated aqueous sodium hydrogen carbonate (300 ml) was added to neutralize. The organic layer was recovered, washed with saturated saline, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was purified by silica gel column chromatography (silica gel @ 300 g, chloroform-chloroform-ethyl acetate 2: 1 to 1: 1 to 1: 2) to obtain colorless compound 14 (17.5 g, 74). %).

_{^{1 H-NMR (CDCl 3)}} δ 9.20,9.16 (each 1H, s, NH), 8.13 (1H, s, H-8), 8.03-7.48 (10H, m, aromatic), 6.45 (1H, t, H-1 ', J = 6.32), 4.99 (1H, t, H-3', J = 6.36), 3.91-3.73. (4H, m, H-5 'and H-6'), 3.12 (1H, m, H-2'a), 2.71 (1H, b.dd, OH), 2.54 (1H, m, H-2'b), 0.93, 0.86 (each 9H, s, t-Bu), 0.16, 0.15, 0.02, 0.007 (each 3H, s, Me) .

(6) Synthesis of 9- (2-deoxy-3,5-di-O-tert-butyldimethylsilyl-4-C-ethynyl-β-D-ribo-pentofuranosyl) -2,6-dibenzamidopurine (Compound 15)

Compound 14 (510 mg, 0.7 mmol) was dissolved in a mixed solvent of dimethyl sulfoxide (2.4 ml) and toluene (1.6 ml), and 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride was added at room temperature. (400 mg, 2.1 mmol), pyridine (57 ml, 0.7 mmol) and trifluoroacetic acid (27 ml, 0.35 mmol) were added and stirred for 5 hours. The reaction solution was extracted with ethyl acetate, washed with water and saturated saline, and dried over anhydrous sodium sulfate. The solvent was distilled off to obtain an unpurified aldehyde.

Bromotriphenylphosphonium bromide (611 mg, 1.4 mmol) was suspended in tetrahydrofuran (8 ml), potassium tert-butoxide (236 mg, 2.1 mmol) was added at −40 ° C., and the mixture was stirred at the same temperature for 2 hours, and phosphorane was added. Prepared. At −40 ° C., a tetrahydrofuran solution of the aldehyde compound (8 ml) was added dropwise, and the mixture was stirred for 1.5 hours. Saturated aqueous ammonium chloride was added, and the mixture was extracted with ethyl acetate. After washing with saturated saline, it was dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was roughly purified by silica gel column chromatography (silica gel @ 20 g, hexane: ethyl acetate 3: 1 to 2: 1 to 1: 1) to obtain 459 mg (81%) of a bromovinyl compound.

The bromovinyl compound (459 mg, 0.57 mmol) was dissolved in tetrahydrofuran (13 ml), potassium tert-butoxide (255 mg, 2.28 mmol) was added, and the mixture was stirred at room temperature for 30 minutes. A saturated aqueous ammonium chloride solution was added to the reaction solution, and the mixture was extracted with ethyl acetate. After washing with saturated saline, it was dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was roughly purified by silica gel column chromatography (silica gel @ 5 g, hexane: ethyl acetate 2: 1 to 1: 1) to obtain Compound 15 (325 mg, 78%).

_{^{1 H-NMR (CDCl 3)}} δ 9.25,9.17 (each 1H, s, NH), 8.19 (1H, s, H-8), 8.04-7.44 (10H, m, aromatic), 6.53 (1H, dd, H-1 ', J = 4.88, 6.84), 4.84 (1H, t, H-3', J = 6.84), 4.02. (1H, d, H-5'a, J = 10.76), 3.83 (1H, d, H-5'b, J = 11.24), 2.84 (1H, m, H-2) 'a), 2.67 (1H, m, H-2'), 2.55 (1H, s, ethylyl), 0.94 (9H, s, t-Bu), 0.90 (9H, s, t-Bu), 0.15 (3H, s, Me), 0.13 (3H, s, Me), 0.08 (3H, s, Me), 0.06 (3H, s, Me).

(7) Synthesis of 9- (2-deoxy-4-C-cyano-β-D-ribo-pentofuranosyl) -2,6-diaminopurine (Compound 16)

Compound 15 (212 mg, 0.29 mmol) was dissolved in tetrahydrofuran (4 ml), tetrabutylammonium fluoride (1 M tetrahydrofuran solution, 1.2 ml, 1.2 mmol) was added, and the mixture was stirred at room temperature for 30 minutes. Silica gel (1.5 g) was added to the reaction solution, and the solvent was distilled off. The residue was roughly purified by silica gel column chromatography (silica gel @ 10 g, chloroform: methanol = 100: 1 to 50: 1), and 94 mg of the desilyl compound (94 mg) 65%).

(4) The desilylated product (28 mg, 0.06 mmol) was dissolved in methanol (1 ml), a 40% aqueous solution of methylamine (2 ml) was added, and the mixture was stirred at room temperature overnight. The solvent was distilled off, and the residue was roughly purified by silica gel column chromatography (silica gel @ 3 g, chloroform: -methanol = 50: 1 to 20: 1 to 10: 1) to obtain 11 mg of compound 16 as colorless crystals (68%). )Obtained.

¹ H-NMR (DMSO-d ₆ ) δ 7.89 (1H, s, H-8), 6.71 (2H, brs, NH ₂ ), 6.20 (1H, t, J = 6.3 Hz) , H-1 ′), 5.74 (2H, brs, NH ₂ ), 5.59 (1H, t, J = 5.9 Hz, OH), 5.47 (1H, d, J = 4.9 Hz) , OH), 4.50 (1H, q, J = 5.9 Hz, H-3 '), 3.65 (1H, dd, J = 11.7, 5.4 Hz, H-5'); 56 (1H, dd, J = 11.7, 7.3 Hz, H-5 '), 3.46 (1H, s, ethylyl-H), 2.64 (1H, dt, J = 12.7, 6) .4 Hz, H-2 '), 2.32 (1H, dt, J = 13.2, 6.4 Hz, H-2').

Synthesis Example 4: Synthesis of 4′-C-ethynyl-2′-deoxyguanosine (Compound 17)

Adenosine deaminase (0.057 ml, 20 units) was added to a solution of compound 16 (30 mg, 0.103 mmol) in Tris-HCl buffer (7.8 ml, pH 7.5), and the mixture was stirred at 40 ° C for 2 hours. After cooling to room temperature, the reaction solution was applied to a reverse-phase ODS silica gel column (50 g), desalted by flowing water (500 ml), and then a 2.5% aqueous ethanol solution was passed to elute Compound 17. Further, recrystallization was performed from water to obtain 15 mg (50%) of compound 17.

_{^{1 H-NMR (DMSO-d}} 6) δ 10.61 (1H, br s, NH), 7.90 (1H, s, H-8), 6.48 (2H, br s, NH 2), 6 .13 (1H, dd, J = 7.3, 5.9 Hz, H-1 ′), 5.51 (1H, d, J = 4.9 Hz, OH), 5.30 (1H, t, J = 5.9 Hz, OH), 4.47 (1 H, dt, J = 6.4, 5.4 Hz, H-3 '), 3.62 (1 H, dd, J = 12.2, 6.4 Hz, H −5 ′), 3.54 (1H, dd, J = 12.2, 6.4 Hz, H−5 ′), 3.47 (1H, s, ethylyl-H), 2.56 (1H, dt, J = 12.2, 6.4 Hz, H-2 '), 2.36 (1H, dt, J = 12.7, 6.8 Hz, H-2').

Claims (1)

A method for producing 4′-C-ethynyl-2′-deoxypurine nucleoside represented by the following formula [I], comprising the following first to fifth steps:

[I]
(In the formula, B represents a purine base, and R represents a hydrogen atom or a phosphate residue.)
The first step;
A step of protecting the 3′-hydroxyl group of the compound represented by the formula [II] to obtain a compound represented by the formula [IV]

[II] [III] [IV]
The second step;
Step of introducing a hydroxymethyl group at the 4′-position of the compound represented by the formula [IV] to obtain a compound represented by the formula [V]

[IV] [V]
Third step;
A step of protecting the 5′-hydroxyl group of the compound represented by the formula [V] to obtain a compound represented by the formula [VII]

[V] [VI] [VII]
Fourth step;
After oxidizing the 4'-hydroxymethyl group of the compound represented by the formula [VII] to an aldehyde group, this is converted to a bromovinyl group, and subsequently treated with a strong base to convert it to an ethynyl group. For obtaining a compound represented by the formula VIII]

[VII] [VIII]
Fifth step;
Removing the protecting groups at the 3 ′ and 5′-positions of the compound represented by the formula [VIII] to obtain a compound in which R is hydrogen, and optionally phosphorylating to obtain a compound represented by the formula [I]

[VIII] [I]
(In each of the above formulas, B represents a purine (including azapurine or deazapurine) base, R represents a hydrogen atom or a phosphate residue, and R2 to R4 represent protecting groups.)