RU2450011C1 - Method of producing n-pyrazinoyl-l-phenylalanyl-l-leucine boronic acid or anhydride thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves reaction of trifluoroacetate (1S,2S,3R,5S)-pinanediol-(R)-1-ammonium-3-methylbutane-1-boronate with N-pyrazinoyl-L-phenylalanyl with ultrasonic activation using a suitable condensing agent in the presence of a suitable base. The formed (1S,2S,3R,5S)-pinanediol N-pyrazinoyl-L-phenylalanyl-L-leucine-boronate undergoes an exchange reaction with isobutyl boronic acid in an acidic medium to form N-pyrazinoyl-L-phenylalanyl-L-leucine boronic acid or anhydride thereof.

EFFECT: method enables to obtain an end product of higher purity and high output, and a more efficient and safer technique.

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Description

The invention relates to the field of chemistry of biologically active substances, in particular to a method for producing N-pyrazinoyl-L-phenylalanyl-L-leucineboronic acid (1) or its anhydride, which can be used to treat certain types of cancer (NAPetasis. Aust. J. Chem., 2007, 60, 795-798).

International application WO 2005/097809 describes a convergent method for the synthesis of N-pyrazinoyl-L-phenylalanyl-L-leucineboronic acid (1) or its anhydride based on the stereoselective rearrangement of the "onium" salt obtained from dichloromethyl lithium and (1S, 2S, 3R, 5S) -Pinanediol ester of isobutylboronic acid, under the action of a Lewis acid such as ZnCl ₂ (Matteson rearrangement; DSMatteson, Chem. Rev., 1989, 89, 1535-1551; EJCorey, D.Barnes-Seeman, TWLee. Tetrahedron Asymm., 1997, 8 (22), 3711-3713), to obtain the corresponding chiral α-halogen-boron ether, while the reaction mixture contains e an aqueous solvent slightly miscible with water, or a mixture thereof with a coordinating co-solvent, treating the α-halogen-boron ester with an alkali metal disilamide to form a compound in which the amino group is protected by two silyl groups, removing the silyl groups using trifluoroacetic acid to obtain the corresponding amine salt ( 2) (FIG. 2), which was further reacted with N-pyrazinoyl-L-phenylalanine (3) and N, N'-dicyclohexylcarbodiimide to give (1S, 2S, 3R, 5S) -pinanediol-N-pyrazinoyl-L -phenylalanil-L-leucine boronate with yield 95.5% (containing an admixture of 2% N, N-dicyclohexylurea), which, by reaction with isobutylboronic acid in the presence of hydrochloric acid, was converted into N-pyrazinoyl-L-phenylalanyl-L-leucineboronic acid anhydride with a yield of 81.8% in crude or 57 , 2% after precipitation with methyl tert-butyl ether from ethyl acetate (the purity of the product thus obtained is not indicated), and the total yield in the last two stages, including purification, was 54.6% (see international application WO 2005/097809, paragraph 84 of the claims).

Further improvement of the convergent approach to the synthesis of compound (1) is based on the condensation of N-pyrazinoyl-L-phenylalanine (3) with the known amine trifluoroacetate under the action of (3-oxide-1H-1,2,3-benzotriazol-1-yl ) -N, N, N ', N'-tetramethylformamidinium tetrafluoroborate (TBTU), which provides a low degree of racemization, and diisopropylethylamine in methylene chloride, followed by removal of the (1S, 2S, 3R, 5S)-pinanediol inductor in an acidic medium (Tetrahedron, 2009 65, 7105-7108, see FIG. 2). As a result, the total yield in the last two stages of the synthesis after purification was 71%.

The disadvantages of the method described in international application WO 2005/097809 are that the target product is obtained with an admixture (2%) of N, N'-dicyclohexylurea. Contamination of peptide synthesis products with this impurity along with N-acyl-N, N'-dicyclohexylureas is inevitable when using N, N'-dicyclohexylcarbodiimide as a condensing agent. This often requires additional purification of the product (JSAlbert, ADHamilton, 1,3-dicyclohexylcarbodiimide, in "Encyclopedia of Reagents for Organic Synthesis", LAPaquette Ed. - in - Chief; John Wiley & Sons, Inc., Chichester, 2005 (electronic version)), which complicates the technology. Another significant drawback of the described approach is the crystallization of the above ammonium trifluoroacetate using a significant excess of trifluoroacetic acid. Trifluoroacetic acid is an extremely corrosive substance requiring special safety measures when working (S. Nova, Trifluoroacetic acid, in "Encyclopedia of Reagents for Organic Synthesis", LAPaquette Ed. - in - Chief; John Wiley & Sons, Inc., Chichester , 2005 (electronic version)).

The disadvantages of the improved convergent method for obtaining the target compound (Tetrahedron, 2009, 65, 7105-7108) include the fact that TBTU, used as a condensing agent in the combination of amine (2) and carboxylic acid (3), is insoluble in methylene chloride, in which the reaction is carried out, which leads to a slower course of the reaction, complicates its scaling in industrial use.

Thus, the objective of the invention is to develop a new method that allows to obtain the target product with higher purity, with greater yield and more efficient and safe technology.

The above problem is solved by the proposed method for producing N-pyrazinoyl-L-phenylalanyl-L-leucineboronic acid (1) or its anhydride using the reaction of trifluoroacetate (1S, 2S, 3R, 5S) -pinanediol- (R) -1-ammonium-3- methylbutane-1-boronate (2) with N-pyrazinoyl-L-phenylalanine (3) using ultrasonic activation under the action of a suitable condensing agent from the class of uronium compounds, for example (3-oxide-1H-1,2,3-benzotriazole-1 -yl) -N, N, N ', N'-tetramethylformamidinium tetrafluoroborate (TBTU), O- (benzotriazol-1-yl) -N, N, N', N'-tetramethyluronium hexafluorophosphate (HBTU ), phosphonic acid anhydrides, for example, cyclic 2-propanephosphonic acid anhydride (T3R), carbodiimides, phosphonium compounds, mixed anhydrides and other classes of condensing reagents used to create an amide bond, in the presence of a suitable base, preferably a tertiary amine, such as diisopropylethylamine, N -methylmorpholine or triethylamine, with the formation of (1S, 2S, 3R, 5S) -pinanediol-N-pyrazinoyl-L-phenylalanyl-L-leucine boronate (4), which is then subjected to acid hydrolysis according to the known method with the formation of N-pi rasinoyl-1-phenylalanyl-1-leucinboronic acid or its anhydride.

The synthesis of the target compound (1) was carried out in two stages from compounds (2) and (3) obtained by known methods. In the first stage, the amine salt (2) reacted with a carboxylic acid (3) upon exposure to ultrasound under the action of a condensing agent in the presence of diisopropylethylamine. In the second stage, the chiral inductor of pinanediol was removed by the exchange reaction of intermediate (4) with isobutylboronic acid (3) in an acidic medium according to the known method. The total yield in the last two stages of the synthesis (after purification) was 74-77%, which is higher than in the sources described in the prior art. In addition, the condensation reaction proceeded faster due to the use of ultrasonic activation.

The reaction is carried out according to the following scheme:

The invention is illustrated by the following examples, which do not limit its scope.

Example 1 (1S, 2S, 3R, 5S) -Pinanediol N-pyrazinoyl-L-phenylalanyl-L-leucine boronate (4) (comparisons)

A mixture of 7.1 g (0.0187 mol) of the amine salt (2), 5.08 g (0.019 mol) of N-pyrazinoyl-L-phenylalanine (3) and 6.62 g (0.021 mol) (3-oxide-1H -1,2,3-benzotriazol-1-yl) -N, N, N ′, N′-tetramethylformamidinium tetrafluoroborate (TBTU) was suspended in 75 ml of methylene chloride. Under vigorous stirring, 9.5 ml (6.80 g, 0.058 mol) of diisopropylethylamine in 35 ml of methylene chloride were added at a temperature of −5 ° C. over 2 hours. Stirring was continued at −5 ° C. for 1.5 hours, and then warmed to room temperature. The solvent was removed in vacuo and the residue was dissolved in 110 ml of ethyl acetate. The resulting solution was washed successively with 75 ml of water, 4 × 50 ml of a 3% aqueous solution of potash, 75 ml of water, 3 × 50 ml of a 3% aqueous solution of citric acid and 75 ml of water. It was dried over sodium sulfate, and then the solvent was removed in vacuo. The residue was dissolved in 50 ml of diethyl ether, chromatographed through a 2.5 × 1.5 cm silica gel layer (100 ml of diethyl ether was eluted). The solvent was removed in vacuo. Received 8.14 g of compound (4) (yield 84%). ESI-MS: m / z 519.8 [M + H] ⁺ , 1038.1 [2M + H] ⁺ . ¹ H NMR (acetone-d6): δ 3.05-0.7 (m, 25H, α CH -B, 5CH ₃ , 3CH2, 3CH); 3.2 (t, 2H, CH ₂ Ph); 4.30 (dd, 1H, J = 8.64, 1.8 Hz, CH _pinane-O ); 4.93 (m, 1H, αCH _Phe ); 7.10-7.33 (m, 5H, CH _Ph ); 7.61 (broad s, 1H, NH); 8.40 (broad d, 1H, NH); 8.63 (m, 1H, CH _pyrazine ); 8.82 (d, 1H, J = 2.16 Hz, CH _pyrazine ); 9.20 (d, 1H, J = 1.44 Hz, CH _pyrazine ).

Example 2 (1S, 2S, 3R, 5S) -Pinanediol N-pyrazinoyl-L-phenylalanyl-L-leucine boronate (4)

A mixture of 7.1 g (0.0187 mol) of the amine salt (2), 5.08 g (0.019 mol) of N-pyrazinoyl-L-phenylalanine (3) and 6.62 g (0.021 mol) (3-oxide-1H -1,2,3-benzotriazol-1-yl) -N, N, N ′, N′-tetramethylformamidinium tetrafluoroborate (TBTU) was suspended in 75 ml of methylene chloride. Under vigorous stirring and ultrasonic irradiation, 9.5 ml (6.80 g, 0.058 mol) of diisopropylethylamine in 35 ml of methylene chloride were added at a temperature of -5 ° C for 1 hour. Stirring and irradiation with ultrasound was continued at -5 ° C for 1 hour, after which the reaction mass was warmed to room temperature. The solvent was removed in vacuo and the residue was dissolved in 110 ml of ethyl acetate. The resulting solution was washed successively with 75 ml of water, 4 × 50 ml of a 3% aqueous solution of potash, 75 ml of water, 3 × 50 ml of a 3% aqueous solution of citric acid and 75 ml of water. It was dried over sodium sulfate, and then the solvent was removed in vacuo. The residue was dissolved in 50 ml of diethyl ether, chromatographed through a 2.5 × 1.5 cm silica gel layer (100 ml of diethyl ether was eluted). The solvent was removed in vacuo. Received 8.92 g of compound (4) (yield 92%).

Example 3 (1S, 2S, 3R, 5S) -Pinanediol N-pyrazinoyl-1-phenylalanyl-L-leucine boronate (4)

To 12 ml of methylene chloride were added 1.0 g (2.64 mmol) of the amine salt (2), 715 mg (2.64 mmol) of N-pyrazinoyl-L-phenylalanine (3) and 3.164 mmol of 2-propanephosphonic acid anhydride in the form of 50% solution in N, N-dimethylformamide. The reaction mass was cooled to 0 - -5 ° C and 1.02 g (7.91 mmol) of diisopropylethylamine in 6 ml of methylene chloride was added with vigorous stirring at a temperature of -5 ° C for 2 hours. Stirring was continued at -5 ° C for 30 minutes, then warmed to room temperature. The solvent was removed in vacuo and the residue was dissolved in 12 ml of ethyl acetate. The resulting solution was washed successively with 8 ml of water, 4 × 6 ml of a 3% aqueous solution of potash, 8 ml of water, 3 × 6 ml of a 3% aqueous solution of citric acid and 8 ml of water. It was dried over sodium sulfate, and then the solvent was removed in vacuo. The residue was dissolved in 10 ml of diethyl ether, chromatographed through a silica gel layer (eluent was diethyl ether). The solvent was removed in vacuo. Received 1.09 g of compound (4) (yield 79%).

Example 4 (1S, 2S, 3R, 5S) -Pinanediol N-pyrazinoyl-L-phenylalanyl-L-leucine boronate (4)

To 12 ml of methylene chloride were added 1.0 g (2.64 mmol) of the amine salt (2), 715 mg (2.64 mmol) of N-pyrazinoyl-L-phenylalanine (3) and 3.164 mmol of 2-propanephosphonic acid anhydride in the form of 50% solution in N, N-dimethylformamide. The reaction mass was cooled to 0 - -5 ° C and 1.02 g (7.91 mmol) of diisopropylethylamine in 6 ml of methylene chloride were added at -5 ° C for 45 minutes under ultrasound irradiation and vigorous stirring. Stirring and sonication of the reaction mixture was continued at -5 ° C for 30 minutes, after which it was warmed to room temperature. The solvent was removed in vacuo and the residue was dissolved in 12 ml of ethyl acetate. The resulting solution was washed successively with 8 ml of water, 4 × 6 ml of a 3% aqueous solution of potash, 8 ml of water, 3 × 6 ml of a 3% aqueous solution of citric acid and 8 ml of water. It was dried over sodium sulfate, and then the solvent was removed in vacuo. The residue was dissolved in 10 ml of diethyl ether, chromatographed through a silica gel layer (eluent was diethyl ether). The solvent was removed in vacuo. 1.22 g (2.43 mmol) of compound (4) were obtained (88% yield).

Example 5. N-pyrazinoyl-L-phenylalanyl-L-leucinboronic acid anhydride (1)

6.8 g (13.12 mmol) of ether (4) were dissolved in 50 ml of methanol and 50 ml of hexane, and 29 ml of 1N hydrochloric acid was added. The solution was cooled to 10 ° C., 2.4 g (23.54 mol) of isobutylboronic acid (3) was added with stirring, and stirring was continued for 17 hours at room temperature. The upper layer was separated, and the lower was washed with 3 × 10 ml of hexane. From the combined hexane fractions, the isobutylboronic acid pinanediol ester containing a valuable chiral inducer was regenerated. 3 g of sodium bicarbonate was added to the acidic methanol solution and stirred for 30 minutes. The resulting mixture was extracted with 850 ml of ethyl acetate, the organic phase was dried over sodium sulfate and chromatographed on a column containing 20 g of silica gel. After evaporation, 4.5 g (yield 94%) of the crude product (1) were obtained. Crystallization from ethyl acetate gave 4.0 g (84% yield) of a product with a purity of 98.8% according to HPLC. ¹ H NMR (CDCl ₃ ): 0.76 (d, 6H, J = 6.60, 2CH ₃ ); 1.30, 1.17 (2m, 2H, CH ₂ - ⁱ Pr); 1.52 (m, 1H, C H (CH ₃ ) ₂ ); 2.64 (br m, 1H, α CH -B); 3.15 (m, 2H, CH ₂ Ph): 4.86 (m, 1H, αCH _Phe ); 7.10-7.30 (m, 5H, CH _Ph ); 8.70 (m, 1H); 8.80 (s, 1H); 8.82 (d, 2H, J = 2.4); 9.08 (d, 1H, J = 1.2). ¹³ C NMR (CDCl ₃ ): δ 22.28, 22.77, 24.87, 37.18 (CH ₂ ), 39.80 (CH ₂ ), 42.70, 51.53, 126.23, 127.79, 127.86, 129.08, 136.64, 143.09, 143.17, 143.29, 143.89, 147.49 , 162.30, 172.49.

The proposed method allows to improve the technology, increase the yield and purity, the time of synthesis of N-pyrazinoyl-L-phenylalanyl-L-leucinboronic acid or its anhydride due to the use of ultrasonic activation at the stage of combination of N-pyrazinoyl-1-phenylalanine and trifluoroacetate , 3R, 5S) pinanediol-1-ammonium-3-methylbutane-1-boronate in the presence of a suitable base. The condensing agents presented in the examples provide easy isolation of the product in pure form by extraction, achieved due to the ionic nature of the by-products.

Claims (7)

1. The method of obtaining N-pyrazinoyl-L-phenylalanyl-L-leucineboronic acid or its anhydride, characterized in that the reaction of trifluoroacetate (1S, 2S, 3R, 5S) -pinanediol- (R) -1-ammonium-3-methylbutane- 1-boronate with N-pyrazinoyl-L-phenylalanine is carried out by ultrasound activation using a suitable condensing agent, in the presence of a suitable base, with the resulting (1S, 2S, 3R, 5S) -pinanediol N-pyrazinoyl-L-phenylalanyl-L- leucine boronate is subjected to an exchange reaction with isobutylboronic acid in an acidic medium to form N-pyrazinoyl-L-phenylalan -L-leytsinboronovoy acid or its anhydride. 2. The method according to claim 1, characterized in that the compounds of uronium type are used as the condensing agent. 3. The method according to claim 2, characterized in that TBTU or HBTU is used as the uronium type condensing agent. 4. The method according to claim 1, characterized in that phosphonic anhydrides are used as the condensing agent. 5. The method according to claim 4, characterized in that cyclic anhydride of 2-propanephosphonic acid is used as a condensing agent from the group of phosphonic acid anhydrides. 6. The method according to claim 1, characterized in that tertiary amines are used as the base. 7. The method according to claim 6, characterized in that diisopropylethylamine, triethylamine or N-methylmorpholine is used as a tertiary amine.