JPS635040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing highly pure 9-(β-D-arabinofuranosyl)adenine in high yield.

9-(β-D-arabinofuranosyl)adenine (hereinafter abbreviated as arabinofuranosyl adenine) is
Herpes simplex virus (Herpes)
It is a compound that has antiviral effects against Vaccinia Virus (Simplex Virus) and Vaccinia Virus, and is used as a treatment for herpetic keratitis and encephalitis.

Until now, the method for producing arabinofuranosyladenine has been to produce 2',3'-epoxyadenosine and subject it to a ring-opening reaction (J.Am.Chem.
Soc. Vol. 82, p. 2648), Direct condensation of substituted arabinose and adenine derivatives (J.
Org.Chem., Volume 28, Page 3004), a method of condensing arabinofuranothioxazolidine and nitropyrimidine, reducing and refluxing this to produce mercaptopurine nucleoside, and desulfurizing this (US Pat. No. 3,948,883). Specification), Method for cleaving 8,2'-type purine cyclonucleosides (Specification)
7271, Japanese Patent Application Laid-open No. 14694), 3′, 5′-
A method of oxidizing O-acyladenosine derivatives to convert them into keto derivatives, and then reducing them (Japanese Patent Application Laid-open No. 1986-
73795) have been proposed.

However, the method via 2′,3′-epoxyadenosine and the method of reacting substituted arabinose with an adenine derivative require many reaction steps;
Furthermore, since many by-products are produced during the condensation reaction, complicated purification treatments are required and the yield is inevitably low. Furthermore, the method starting from arabinofuranothioxazolidine and a nitropyrimidine derivative requires a long time for the reaction and the operation of the condensation cyclization reaction is also troublesome, and cannot be said to be suitable as an industrial production method. Furthermore, in the method involving 8,2'-type purine cyclonucleoside, the cleavage reaction must be carried out at high temperature and pressure for a long time, and the desulfurization reaction requires heating using a special catalyst such as Raney nickel. There are problems in terms of equipment and cost. Finally, the method starting from 3',5'-O-acyladenosine requires separation and purification of the acyl form, and in addition, an ion exchange resin column must be used to purify the oxidation product and reduction product. Since this is essential, there is a drawback that production efficiency inevitably decreases.

As described above, all of the methods for producing arabinofuranosyladenine known so far have some drawbacks as a method for industrial mass production, and cannot be said to be necessarily satisfactory.

The present inventors have overcome the drawbacks of such conventional methods and have developed an industrial method for producing highly purified arabinofuranosyl adenine from inexpensive raw materials with simple operations and in good yield. As a result of intensive research to develop a suitable method, 3',5'-O-
(Tetraisopropyldisiloxane-1,3-diyl)adenosine is used as a starting material, treated with dimethyl sulfoxide and acetic anhydride, and then the reaction product is reduced, which can easily convert it to arabinofuranosyladenine. 9—[3′,5′—
O-(tetraisopropyldisiloxane-1,3
-diyl)-β-D-arabinofuranosyl]adenine and the starting material 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine are produced; It has been found that since no other by-products are involved, there is no need for complicated purification using ion exchange resins or other special purification means, and based on this knowledge, the present invention has been accomplished.

That is, the present invention provides a method for treating (a) 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine with dimethyl sulfoxide and acetic anhydride.
(b) a step of reducing the 2'-keto form obtained in step (b); (c) converting the reaction mixture of step (b) into 9-[3',5' -O-
(Tetraisopropyldisiloxane-1,3-
A step of separating diyl)-β-D-arabinofuranosyl]adenine and 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine and recycling the latter to step (a). and (d) removing the protecting group from the 9-[3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)-β-D-arabinofuranosyl]adenine separated in step (c). By desorption, 9-(β-
The present invention provides a method for producing 9-(β-D-arabinofuranosyl)adenine, which comprises a step of obtaining D-arabinofuranosyl)adenine.

Used as a starting material in the method of the present invention
3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine is a readily available and inexpensive adenosine with 1,3-dichloro-
It is a compound obtained in quantitative yield by reacting 1,1,3,3-tetraisopropyldisiloxane, and this compound can be used in the subsequent process as it is without any purification treatment, so it is industrially suitable. It is suitable as a starting material for the method carried out.

Step (a) of the method of the present invention is the above-mentioned 3',5'-O-
(Tetraisopropyldisiloxane-1,3-diyl)adenosine was dissolved in 8 to 12 times the amount of dimethyl sulfoxide at room temperature, then 4 to 6 times the amount of acetic acid as the raw material was added thereto, and after stirring for a while. , by leaving it for 5 to 20 hours.

Next, this is hydrolyzed, extracted with a suitable solvent such as ethyl acetate, and after washing, the solvent is distilled off to obtain a highly pure corresponding keto compound.

In this way, step (a) proceeds according to the following reaction formula.

(R in the formula is an isopropyl group) Next, in step (b) of the method of the present invention, the 2′-
The reaction is carried out by dissolving the keto compound in a suitable solvent such as a benzene-ethanol mixture, adding a conventional reducing agent such as 2 to 3 times the mole of sodium borohydride, and reacting with cooling. Through this treatment, the keto group at the 2'-position is reduced to a hydroxyl group, but surprisingly, the arabinofuranosyl form in which the 2'-hydroxyl group takes a trans configuration with respect to the 3'-substituent is overwhelmingly produced. A large amount is produced in the cis-configuration, and a small amount is produced in the cis-configuration.

This step (b) proceeds according to the following reaction formula.

(R in the formula is the same as above) In step (c) of the method of the present invention, the trans type obtained as above, that is, 9-[3',
5′-O-(tetraisopropyldisiloxane-
1,3-diyl)-β-D-arabinofuranosyl]adenine and the cis form, i.e. 3′,5′-O
-(Tetraisopropyldisiloxane-1,3-
(diyl)adenosine and the latter is recycled to step (a) for reuse. This separation can be easily performed, for example, by chromatography using silica gel or alumina. 9-[3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)-β-D separated in this step
-arabinofuranosyl]adenine is a new compound that has not been described in the literature and is usually obtained in an amorphous form.

This product has the characteristics that it can be easily separated from other coexisting substances, and that it is easy to remove the protecting group and purify the product after the removal.

In step (2) of the method of the present invention, the 9-[3',5'-O-tetraisopropyldisiloxane-1,3-diyl)-β-D-arabinofuranosyl]adenine separated in the previous step is For example, the protecting group is removed by dissolving in a solvent such as tetrahydrofuran and adding tetrabutylammonium fluorite to the solution for reaction. The target arabinofuranosyladenine obtained in this way can be recovered almost quantitatively by simply adding water-containing methanol and crystallizing it, without using any special purification means such as ion exchange chromatography. Ru.

The infrared absorption spectrum and ultraviolet absorption spectrum of the arabinofuranosylalanine thus obtained completely matched those of the standard product.

This (d) step proceeds according to the following reaction formula.

The method of the present invention uses 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine, which is easily produced from readily available adenosine, as a starting material, and produces high yields in a small number of steps. In addition to being able to obtain the target arabinofuranosyladenine with high purity, the only by-product produced during the manufacturing process is 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl). ) Since adenosine can be recycled and reused as it is as a starting material, it is suitable as an industrial method.

Next, the present invention will be explained in more detail with reference to Examples.

Reference example 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine production 8.0g (30mmole) of adenosine was mixed with 150ml of pyridine.
A mixed solution of 10.4 g (33 mmole) of 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and 15 ml of pyridine was added dropwise over 10 minutes while stirring at room temperature. After stirring for 1 hour, 15 ml of dimethylformamide was added and the mixture was stirred for an additional hour until the reaction mixture became a solution.
Next, the reaction solution was distilled off under reduced pressure, and the resulting residue was dissolved in 300 ml of ethyl acetate, washed with an aqueous sodium bicarbonate solution and then with water, dehydrated with anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. 15.3 g of the amorphous title compound was obtained. Crude yield: 100.3% This product can be used in the next step without purification.

Example 1 5.1 g (10 mmole) of 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine obtained in Reference Example was mixed with 60 g of dimethyl sulfoxide.
ml, 30 ml of acetic anhydride was added thereto, and the mixture was stirred overnight to allow sufficient reaction. The resulting reaction mixture was added to 200 g of ice, stirred for 2 hours, extracted twice with 300 ml of ethyl acetate, the extracted organic layer was washed several times with an aqueous sodium bicarbonate solution and then with water, and anhydrous magnesium sulfate was added. It was dehydrated and dried. Next, the solvent was distilled off under reduced pressure, and the resulting syrup was mixed with a benzene-ethanol (1:1 v/v) mixture.
After dissolving in 150 ml and cooling to 0°C, 1 g (26 mmole) of sodium borohydride was added, and the mixture was kept at the same temperature for 2 hours with stirring. This and acetone 10
After stirring for an additional 30 minutes, the reaction solution was distilled off under reduced pressure, and the residue was dissolved in 100 ml of water. Next, 10% hydrochloric acid was added to adjust the pH to 2, followed by extraction twice with 200 ml of ethyl acetate, and the extracted organic layer was washed several times with brine and then with water, and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure, and the resulting syrup was developed with chloroform-methanol (95:5 v/v) 1.2 using a column filled with silica gel, and the first elution was carried out.
0.8 was taken as the first fraction, and the subsequent 0.4 was collected as the second fraction into separate receivers. From each fraction,
from the first fraction by distilling off the solvent, respectively.
1.2 g of 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine and amorphous 9-[3',5'-O-(tetraisopropyldisiloxane) from the second fraction. -1,3-diyl)-
β-O-arabinofuranosyl]adenine 2.9g
(yield 74.0%).

3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine was reused by mixing it with newly produced raw materials according to the reference example, but no problems were observed. Ta.

Next, the amorphous 9-
2.9 g of [3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)-β-D-arabinofuranosyl]adenine and 14.5 g of tetrahydrofuran
A solution of tetrabutylammonium fluoride in tetrahydrofuran (1M) is dissolved in this.
After adding 14.5 ml and stirring at room temperature for 10 minutes, 5 ml of water was added and the reaction solution was distilled off under reduced pressure. The syrup obtained here was dissolved in a mixed solution of 12 ml of water and 60 ml of methanol, seeded, and allowed to stand overnight at room temperature.

The precipitated crystals were collected by filtration, washed with a small amount of methanol, and then dried to obtain 1.45 g of crystals of 9-(β-D-arabinofuranosyl) adenine, yield 95.4.
%, melting point 255-257゜, λ _nax (EtOH) 258.5nm
(ε13800), and the infrared absorption spectrum and thin layer chromatography measurement results for this product completely matched those of the standard product.

Claims (1)

[Scope of Claims] 1 (a) 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine is converted to the corresponding 2′-keto form by treating with dimethyl sulfoxide and acetic anhydride. (b) A step of reducing the 2'-keto form obtained in step (a), (c) Reducing 9-[3',5'-O- from the reaction mixture of step (b)
(Tetraisopropyldisiloxane-1,3-
A step of separating diyl)-β-D-arabinofuranosyl]adenine and 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)adenosine and recycling the latter to step (a). and (d) removing the protecting group from the 9-[3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)-β-D-arabinofuranosyl]adenine separated in step (c). By desorption, 9-(β-
A method for producing 9-(β-D-arabinofuranosyl)adenine, which comprises a step of obtaining D-arabinofuranosyl)adenine.