CN104447822A - For preparing 4-, (10B) Compound of dihydroxy boron group-L-phenylalanine - Google Patents

Abstract

The present invention relates to a compound for preparing 4-( ^10B ) dihydroxyboryl-L-phenylalanine. The compound has a structure as shown in formula (I), wherein R represents a protecting group, and the protecting group is selected from the group consisting of tert-butyloxycarbonyl, trityl, 3,5-dimethoxyphenylisopropyloxycarbonyl, 2-(4-biphenylyl)isopropyloxycarbonyl and 2-nitrophenylsulfinyl. The ^10B purity of the compound is greater than or equal to 98%, and the enantiomeric excess is greater than or equal to 99%.

Description

Compounds for the preparation of 4-(10B)dihydroxyboryl-L-phenylalanine

technical field

The present invention relates to a compound for preparing 4-( ¹⁰ B) dihydroxyboryl-L-phenylalanine (4-( ¹⁰ B) borono-L-phenylalanine, L- ¹⁰ BPA), in particular to a Compound for the preparation of L ^-10 BPA with high isotopic purity and high optical purity.

Background technique

4-Dihydroxyboryl-L-phenylalanine (4-borono-L-phenylalanine, L-BPA) is an important boron compound known to be able to treat cancer with boron neutron capture therapy (BNCT) ; and 4-( ¹⁰ B) dihydroxyboryl-L-phenylalanine (4-( ¹⁰ B) borono-L-phenylalanine, ^{L- 10} BPA) containing 10 boron is a key factor for accumulation in tumor cells , which can then use thermal neutron beams to irradiate boron accumulated in tumor cells to kill tumor cells by capturing high-energy particles generated by the reaction, thereby achieving the purpose of treating cancer. Therefore, ¹⁰ boron can promote L- ¹⁰ BPA as a method of treating cancer through boron neutron capture therapy.

However, the boron element present in nature contains about 19.9% of ¹⁰ boron and about 80.1% of ¹¹ boron. Therefore, many researchers are positively developing the synthetic method that can be applicable to the L-BPA that is rich in ¹⁰ boron; Prepare L- ¹⁰ BPA.

For example, U.S. Patent Publication No. 6,031,127 discloses a method and an intermediate for preparing 4-dihydroxyboryl-L-phenylalanine. The intermediate has a structure represented by the following formula (c):

According to the aforementioned patent literature, the boron source used to prepare the intermediate is bis(pinacolato)diboron and 4,4',6,6'-tetraphenyl-2,2'-bis (1,3,2-dioxaborinane) (4,4',6,6'-tetraphenyl-2,2'-bi(1,3,2,-dioxaborinane)). The above two compounds are not commercially available compounds, and the preparation of such compounds is difficult, and can only be obtained through the reaction of diboron and propane diols. Therefore, the method disclosed in this patent document has disadvantages such as difficult preparation and time-consuming.

In order to overcome the above disadvantages, the present invention provides a compound for preparing 4-( ¹⁰ B)dihydroxyboryl-L-phenylalanine, thereby alleviating or avoiding the above disadvantages.

Contents of the invention

In view of the difficulties faced in the preparation of 4-( ¹⁰ B) dihydroxyboryl-L-phenylalanine in the prior art and the shortcomings such as the need to obtain L- ¹⁰ BPA through a hydrogenation reaction, it cannot be applied to the preparation of rich in ¹⁰ boron Regarding the problem of L-BPA, one of the objects of the present invention is to provide a compound that can be used to prepare L- ¹⁰ BPA in a simple and easy way without hydrogenation. Accordingly, the compound of the present invention can be suitable for preparing L- ¹⁰ BPA, and the obtained L- ¹⁰ BPA can have the advantages of high isotopic purity and high optical purity.

In order to achieve the above object, the present invention provides a compound for preparing 4-( ^10B ) dihydroxyboryl-L-phenylalanine, which has the structure shown in the following formula (I):

Wherein R is selected from the group consisting of: tert-butoxycarbonyl group (tert-butoxycarbonyl group, t-Boc or Boc), trityl group (trityl group, Trt), 3,5-dimethoxyphenisopropyl Oxycarbonyl (3,5-dimethoxyphenyl isopropoxycarbonyl group, Ddz), 2-(4-biphenyl) isopropoxycarbonyl group (2-(4-Biphenyl)isopropoxycarbonyl group, Bpoc) and 2-nitrophenylsulfinyl (2-nitrophenylsulfenyl group, Nps), and the ¹⁰ boron purity ( ¹⁰ B purity) of the compound is greater than or equal to 98%.

The present invention provides a novel compound for the preparation of 4-( ¹⁰ B)dihydroxyboryl-L-phenylalanine, especially a compound that is easy to prepare from generally commercially available starting materials , and the compound has high isotopic purity and high optical purity. In addition, the compound provided by the present invention only needs to undergo a simple deprotection step (such as an acidification deprotection step) to prepare 4-( ¹⁰ B)dihydroxyboryl-L-benzene with high isotopic purity and high optical purity. Alanine, therefore, the compound provided by the invention can be applied to the preparation of 4-( ¹⁰ B) dihydroxyboryl-L-phenylalanine.

Preferably, the enantiomeric excess of the compounds provided by the invention is greater than or equal to 99%.

Preferably, R is tert-butoxycarbonyl.

Hereinafter, other objectives, advantages and innovative technical features of the present invention will be made clearer through the following detailed description.

Detailed ways

Below, take the compound prepared by (S)-N-tert-butoxycarbonyl-4-iodophenylalanine ((S)-N-Boc-4-iodophenylalanine) as one of the preferred examples, and use This (S)-N-tert-butoxycarbonyl-4-iodo-phenylalanine prepares 4-( ¹⁰ B) dihydroxyboryl-L-type phenylalanine, thereby illustrating that the present invention overcomes the technology of the prior art Implementation of the defect. Those skilled in the art can easily understand the advantages and effects that the present invention can achieve through the content of this specification, and make various modifications and changes without departing from the spirit of the present invention, so as to implement or apply the content of the present invention, and at the same time It is understood that the enumerated embodiments are not intended to limit the scope of rights claimed by the present invention.

Example 1

(1) Prepare (S)-N-tert-butoxycarbonyl- 4-( ¹⁰ B)dihydroxyborylphenylalanine

First, a 3-liter three-necked bottle equipped with a mechanical stirrer, a thermometer, and a nitrogen inlet joint sealed with a rubber gasket was prepared. Inject 750 milliliters of 2-methyltetrahydrofuran into the three-necked flask, then add 128 millimoles (50.0 grams, 100% purity) of (S)-N-tert-butoxycarbonyl-4-iodophenylalanine, The two were uniformly stirred to form a solution; then, 393 mmol (90.1 g, 106 ml) of ¹⁰ tributyl borate was added to the solution to form a mixed solution.

Next, the mixed solution was cooled to between -85°C and -76°C, and a 1.6M (600 mmol, 375 ml) hexane solution of n-butyllithium (n-butyllithium) was added dropwise to the mixture over 3 hours. Mix the solutions to obtain a reaction mixture.

Then, the reaction mixture was stirred at -80°C for 0.5 hours, and a small amount of the reaction mixture sample was quickly added to water for HPLC analysis to determine the starting material (S)-N-tert-butoxycarbonyl-4-iodobenzene The content of alanine has been reduced to less than 0.5%.

Afterwards, 900 ml of cold water was slowly added dropwise to the reaction mixture within 15 to 20 minutes, after that, the reaction mixture after adding water was returned to the temperature between 5°C and 10°C, and stirred uniformly for 10 to 20 minutes, and then filtered through The insoluble matter in the reaction mixture was removed by means, and washed with 100 ml of water, and then the filtrate and washings were combined into a separatory funnel for liquid phase extraction.

Next, separate the lower aqueous layer in the separatory funnel to obtain the first aqueous layer; then use isobutanol to extract the first aqueous layer in the separatory funnel, and separate the lower aqueous layer to obtain the second water layer.

Next, adjust the temperature of the second water layer to between 20°C and 25°C, and use 37% hydrochloric acid solution to adjust its pH value to between 3.0 and 4.0, thereby making (S)-N-tert Butoxycarbonyl-4-( ¹⁰ B)dihydroxyborylphenylalanine ((S)-N-Boc-4-( ¹⁰ B)boronophenylalanine) started to precipitate in the second aqueous layer. Continue to stir the second water layer for 30 minutes, and adjust its pH value to 3.0, and then continue to stir for 2 hours between 20°C and 25°C to facilitate the precipitation of more (S)-N-tert-butoxy Carbonyl-4-( ¹⁰ B)dihydroxyborylphenylalanine solid.

Finally, filter the solid product in the second water layer; wash the solid twice with water, and place it in a vacuum drying oven at 50° C. for at least 4 hours until its loss on drying is less than 0.5%, obtaining 25.8 grams of (S )-N-tert-butoxycarbonyl-4-( ¹⁰ B)dihydroxyborylphenylalanine as a white solid.

The chemical purity was 98.6% by HPLC analysis, and the yield was 65.1%.

The melting point of (S)-N-tert-butoxycarbonyl-4-( ¹⁰ B) dihydroxyboryl phenylalanine (instrument: Electrothermal9100), specific rotation, ^1H NMR spectrum ( ¹ H- NMR), ¹³ carbon nuclear magnetic resonance ( ¹³ C-NMR), infrared spectroscopy (infrared spectroscopy, IR) and high resolution mass spectrometry (high resolution mass spectrometry, HRMS) analysis results are as follows:

Melting point: 150°C (decomposition temperature);

: +14° (c=0.5, methanol);

¹ H-NMR (500MHz, DMSO-d ₆ ): δ8.0(s, 2H), 7.7(d, J=7.7Hz, 2H), 7.2(d, J=7.6Hz, 2H), 7.0(d, J=8.4Hz,2H), 4.1(m,1H), 3.0(dd,J=13.8,4.5Hz,1H), 2.8(dd,J=13.7,10.3Hz,1H), 1.3(s,9H);

¹³ C-NMR (125MHz, DMSO-d ₆ ): δ173.63, 155.48, 139.96, 134.06, 131.94, 128.18, 78.13, 55.06, 36.53, 28.19;

_and ^_

HRMS (ESI): Anal. Calcd. for C ₁₄ H ₂₀ ¹⁰ BNO ₆ 307.1420 ([MH] ⁻ ), found 307.1333.

In this specification, 25 in the specific rotation analysis result means that the temperature at the time of measurement is 25°C; D means D sodium light; c means the sample concentration, and the unit is g/ml. In this specification, s in the NMR spectrum analysis results stands for singlet; d stands for doublet; dd stands for doublet of doublets; m stands for multiplet; J stands for Coupling constants in Hertz (Hz); DMSO-d ₆ is dimethyl sulfoxide with protons replaced by deuterium. In this specification, ν in the result of infrared spectroscopic analysis represents a wave number, and the unit is 1/cm (cm ^-1 ). In this specification, the m/z of the mass spectrometry results represents the ratio of mass to charge; (MH) ^- represents the fragment ion after the sample lacks one hydrogen ion.

(2) Preparation of 4-( ¹⁰ B) dihydroxyboryl-L-type phenylalanine from (S)-N-tert-butoxycarbonyl-4-( ¹⁰ B) dihydroxyboryl phenylalanine

Add 66.2 mmol (20.5 g, purity 99.6%) of (S)-N-tert-butoxycarbonyl-4-( ¹⁰ B) dihydroxyboryl phenylalanine to a solution containing 122 ml of acetone and 14 ml of water In the mixture, and make it evenly stirred, then add 14 ml of 37% concentrated hydrochloric acid to form an acidic mixture. Stirring of the acidic mixture was continued at 55°C for 1.5 to 2 hours, and the reaction was confirmed to be complete by HPLC.

Afterwards, the fully reacted acidic mixture is cooled to room temperature, and its pH value is adjusted to 1.5 using aqueous sodium hydroxide solution, thereby making 4-( ¹⁰ B) dihydroxyboryl-L-type phenylalanine in the acidic mixture Started to precipitate out, and continued to stir for 50 minutes. After that, adjust the pH value of the acidic mixture to 6.2 using aqueous sodium hydroxide solution, and stir at room temperature for at least 25 minutes to ensure that more 4-( ^10B )dihydroxyboryl-L-type phenylalanine is precipitated acid solids.

Finally, filter the acidic mixture to obtain solid crystals; then wash the solid crystals with water and 50% acetone aqueous solution, and dry them in a vacuum oven at 80°C for at least 6 hours to constant weight to obtain 13.3 grams of 4- ( ¹⁰ B) Dihydroxyboryl-L-phenylalanine is a white solid.

Its chemical purity is 99.9% through HPLC analysis, and productive rate is 96.4%; And this white crystal is confirmed after chiral HPLC analysis, and the prepared 4-( ^10B ) dihydroxyboryl-L-type phenylalanine (L - ¹⁰ BPA) in a 100:0 ratio of the L-enantiomer to the D-enantiomer (ie, 100% enantiomeric excess).

The melting point, specific rotation, ¹ H-NMR, ¹³ C-NMR, IR, inductively coupled plasma mass spectrometry (ICP-MS) and HRMS of the prepared L- ¹⁰ BPA are as follows:

Melting point: 275°C to 280°C (decomposition temperature);

: -5.4° (c=0.5, 1M hydrochloric acid);

¹ H-NMR (500MHz, D ₂ O, CF ₃ COOD): δ7.2(d, J=8.0Hz, 2H), 6.8(d, J=8.0Hz, 2H), 3.9(dd, J=7.8, 5.7Hz, 1H), 2.8(dd, J=14.6, 5.6Hz, 1H), 2.7(dd, J=14.6, 7.9Hz, 1H);

¹³ C-NMR (125MHz, D ₂ O, CF ₃ COOD): δ171.80, 137.31, 135.16, 132.37, 129.65, 54.64, 36.32;

IR(KBr) _νmax : 3585, 3148, 3038, 2923, 1636, 1610, 1507, 1410, 1398, 1345, 1085, 716cm ^-1 ;

ICP-MS: The content of ¹⁰ B relative to ¹¹ B (the isotopic purity of ¹⁰ B) is 99.4% (w/w%); and

HRMS (ESI): Anal. Calcd. for C ₉ H ₁₃ ¹⁰ BNO ₄ 209.0974 ([M+H] ⁺ ), found 209.0970.

The above-mentioned embodiments are only examples for convenience of description, and the scope of rights claimed by the present invention should be determined by the claims, rather than limited to the above-mentioned embodiments.

Claims (3)

1. A compound for preparing 4-( ^10B ) dihydroxyboryl-L-phenylalanine, which has a structure shown in the following formula (I): Wherein R is selected from the group consisting of tert-butoxycarbonyl, trityl, 3,5-dimethoxyphenylisopropoxycarbonyl, 2-(4-biphenyl)isopropoxycarbonyl and 2-nitrophenylsulfinyl, the compound has ^{a 10-} boron purity greater than or equal to 98%. 2. The compound for preparing 4-( ^10B ) dihydroxyboryl-L-phenylalanine according to claim 1, the enantiomeric excess of the compound is greater than or equal to 99%. 3. The compound for preparing 4-( ¹⁰ B)dihydroxyboryl-L-phenylalanine according to claim 1 or 2, wherein R is tert-butoxycarbonyl.