A carborane amino acid derivative, and a preparation method and application thereof

Abstract

This invention relates to the field of synthetic chemistry, and discloses a carborane amino acid derivative, its preparation method, and its applications. The structural formula of the carborane amino acid derivative is shown below: ; where is C, is BH; o, m, and p are each independently selected from C, R, and C, respectively. 3 Or BH; and when o is selected from CR 3 When m and p are selected from BH; when m is selected from CR 3 When o and p are selected from BH; when p is selected from CR 3 At that time, o and m were selected from BH; R 1 R 2 and R 3 Each of the following groups is independently derived from one or more of H, OH, SH, NH2, halogen, trimethylsilyl, substituted or unsubstituted alkyl groups of 1-15 carbon atoms, substituted or unsubstituted benzyl, substituted or unsubstituted aryl groups of 6-20 carbon atoms, boric acid, and borate ester groups. This invention provides an efficient and practical synthetic route to overcome the bottleneck in the preparation of carborane amino acid compounds, yielding novel boron carrier candidates with significantly superior performance compared to existing clinical drugs.

Description

Technical Field

[0001] This invention relates to the field of synthetic chemistry, and in particular to a carborane amino acid derivative, its preparation method, and its application. Background Technology

[0002] Boron neutron capture therapy (BNCT) is a type of radiotherapy based on binary targeting. Its principle is the selective delivery of non-radioactive isotopes to tumor cells. 10 B, subsequently irradiated with thermal neutrons, triggered 10 B(n,α) 7 Li nuclear reactions produce alpha particles with high linear energy transfer (LET) and recoil. 7 Li nuclei. These particles have an effective range of only about the diameter of a cell (5-9 μm), thus enabling them to precisely kill cells containing Li nuclei at the cellular scale. 10 B-cell tumor cells are targeted, while causing minimal damage to surrounding normal tissues. BNCT is characterized by a short treatment cycle and relatively low side effects, and is considered a cutting-edge precision oncology strategy (see...). Figure 1 However, the successful implementation of BNCT relies heavily on two core conditions: the formation of a sufficiently high flux of thermal neutron field at the tumor site, and the enrichment of a sufficient concentration of neutrons within the tumor cells. 10 B atoms (typically required to reach approximately 10) 9 (Atom / cell or 20 μg / g tissue). Among these, the development of safe, efficient, and highly selective boron carriers is a long-term key bottleneck restricting the clinical translation and efficacy improvement of BNCT.

[0003] The development of boron carriers has undergone several generations of evolution. Early first-generation carriers included sodium pentoborate and borax (see...). Figure 2 Due to its lack of tumor targeting, it causes toxicity to normal tissues (such as radiation dermatitis and cerebral edema) and fails to significantly prolong patient survival. Subsequent development of second-generation carriers, represented by 4-boronic acid-L-phenylalanine (BPA, often administered as a fructose complex) and sodium undecylmercaptododecoboride (BSH), has shown some potential in clinical practice. BSH can accumulate in brain tumors by crossing the damaged blood-brain barrier, but its tumor / blood concentration ratio is not ideal. BPA, on the other hand, leverages the metabolic demand for tyrosine by tumor cells (such as melanoma) through amino acid transport proteins (such as LAT1, see...). Figure 3 BPA is absorbed. However, BPA has significant inherent drawbacks: its boron content is low (approximately 5.2%), requiring high doses to reach the therapeutic threshold, which increases the metabolic burden; its boric acid groups are easily metabolized in the body, resulting in a short retention time in tumors and a limited therapeutic window; and its poor water solubility necessitates formulation modifications.

[0004] To overcome the shortcomings of boron-binding amino acids (BPA), research has focused on developing third-generation boron carriers based on their structural optimization. In recent years, a series of amino acid analogs targeting the LAT1 transporter have been designed, such as fluoroborate tyrosine (FBY), fluoroborate borophenylalanine (BBPA), and 3-boronic acid-L-tyrosine (BTS). These compounds have shown superior tumor uptake, retention, or tumor / blood ratios compared to BPA in preclinical studies (e.g., BTS has a T / B ratio of up to 28), and some have even integrated positron emission tomography (PET) imaging capabilities (e.g., FBY), achieving "therapeutic integration." Nevertheless, the core structure of these improved amino acid derivatives remains a monoboronic acid group, and their theoretical upper limit for boron atom loading is relatively low, limiting further enhancement.

[0005] Meanwhile, carboranes (especially closed-dicarbododecorane, C2B) 10 H 12 As a class of three-dimensional aromatic boron cluster compounds, carboranes are considered ideal modules for constructing high-performance boron carriers due to their extremely high boron atomic density (high boron content), excellent chemical and metabolic stability, and good biocompatibility, potentially overcoming the bottleneck of low boron loading in traditional single-boron compounds. However, the precise and efficient introduction of carborane structural units into biologically targeted molecules such as amino acids faces severe synthetic chemical challenges. Complex synthetic routes, low yields, and purification difficulties severely limit the construction and biological evaluation of carborane-based amino acid derivative libraries. Therefore, despite the significant theoretical advantages of carboranes, in the past decades of BNCT studies, no carborane-based amino acid derivative boron carrier has been successfully developed that surpasses the clinical gold standard BPA in overall efficacy.

[0006] In summary, the current BNCT field urgently needs to develop a new generation of boron carriers, which should possess the following characteristics: (1) high boron atom loading to improve the delivery of each molecule to the tumor. 10 (1) Number of boron atoms; (2) Highly efficient tumor targeting and excellent internalization ability, ensuring selective enrichment in cancer cells; (3) Good intratumoral retention to match the neutron irradiation time window; (4) Ideal plasma clearance characteristics and biosafety; (5) Feasible synthetic pathway to facilitate clinical translation. Existing technologies, including BPA / BSH and its optimized derivatives, are insufficient in terms of boron loading, stability, or overall efficacy; while the highly promising carborane system is limited by synthetic difficulties and has failed to translate its theoretical advantages into clinical efficacy. Therefore, developing a novel boron carrier that is synthetically feasible and has high boron loading, high targeting, and long retention time is of great significance for promoting the development of BNCT technology. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a carborane amino acid derivative, its preparation method and application, and to provide a method for preparing carborane amino acid derivatives.

[0008] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a carborane amino acid derivative, the structural formula of which is shown in Formula 1: ; in, C, For BH; o, m, and p are each independently selected from CR 3 Or BH; and when o is selected from CR 3 When m and p are selected from BH; when m is selected from CR 3 When o and p are selected from BH; when p is selected from CR 3 At that time, o and m were selected from BH; R 1 R 2 and R 3 Each of the following groups is independently derived from one or more of H, OH, SH, NH2, halogen, trimethylsilyl, alkyl with 1-15 carbon atoms (substituted or unsubstituted), benzyl with substituted or unsubstituted, aryl with 6-20 carbon atoms (substituted or unsubstituted), boric acid, or borate ester group.

[0009] Optionally, the carborane amino acid derivative is any one of the following compounds 1 to 56:

[0010]

[0011]

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned carborane amino acid derivative, the method comprising the following steps: The compound shown in Formula 2, the compound shown in Formula 3, and the additives are dissolved in a solvent and stirred under light irradiation at a preset temperature to obtain the compound of Formula 1, which is the carborane amino acid derivative. The synthetic route for the above reaction is as follows: .

[0013] Optionally, the additive is pyridine or potassium carbonate, etc., and the solvent is dichloromethane or acetonitrile, etc.

[0014] Optionally, the wavelength range of the light source is 365~450 nm; the preset temperature is room temperature; and the stirring time is 12-36 hours.

[0015] Optionally, the molar ratio of the compound shown in Formula 2, the compound shown in Formula 3, and the additive is (1~1.1):(1.5~2.0):(1.1~2.0).

[0016] In a third aspect, the present invention provides the use of the above-described carborane amino acid derivatives in the preparation of boron neutron capture therapeutic drugs.

[0017] Optionally, the boron neutron capture therapy includes tumor therapy drugs.

[0018] Optionally, the tumor includes at least one of malignant melanoma, head and neck squamous cell carcinoma, glioma, nasopharyngeal carcinoma, and breast cancer.

[0019] Optionally, the tumor includes malignant tumors or metastatic tumors that are not surgically resectable.

[0020] Beneficial effects: The photochemical preparation method and the resulting carborane amino acid derivatives provided by this invention have achieved the following significant advantages compared to existing technologies: 1. A revolutionary breakthrough in synthesis methods, solving long-standing synthetic problems: This invention, for the first time, utilizes a photochemical strategy to generate highly active carborane cage carbon free radicals in situ under mild conditions, and achieves one-step construction of carborane-amino acid bonds through their efficient free radical coupling reaction with tyrosine and its derivatives. This method is simple to operate, operates under mild conditions (such as room temperature reaction), and has good functional group tolerance, completely overcoming the challenges of cumbersome steps, harsh conditions, and low yields in the synthesis of carborane amino acid derivatives by traditional methods, providing an efficient and universal synthetic platform for the large-scale preparation of high-performance boron carriers with diverse structures. 2. The obtained products have excellent comprehensive performance as boron carriers: The carborane-tyrosine derivatives obtained by this invention have both high boron content (thanks to the high density of boron atoms in the carborane cluster) and excellent biocompatibility. Key in vitro cell experiments showed that the boron enrichment capacity of this series of derivatives in tumor cells was significantly increased by 5-10 times compared to the clinical gold standard drug BPA (4-boronic acid-L-phenylalanine). This significant improvement means that a lower dosage is required to achieve the same intratumoral boron concentration, or a stronger tumor-killing effect can be induced at the same dosage, greatly enhancing its therapeutic potential and application prospects as a boron carrier in BNCT. 3. Flexible space is reserved for subsequent product development and functionalization: The invention is ingeniously designed, retaining the phenolic hydroxyl group on the tyrosine structural unit in the product molecule. This group serves as an easily modified active reaction center, allowing the core structure provided by this invention to be easily further modified and functionalized (e.g., by connecting targeting groups, hydrophilic fragments, or imaging probes), thus laying a solid chemical foundation for the development of next-generation BNCT drugs with "therapeutic integration" or superior pharmacokinetic properties.

[0021] In summary, this invention not only provides an efficient and practical synthetic route to overcome the bottleneck in the preparation of carborane amino acid compounds, but also yields novel boron carrier candidates with significantly superior performance compared to existing clinical drugs, which has outstanding industrial application value for promoting the clinical advancement of boron neutron capture therapy (BNCT). Attached Figure Description

[0022] Figure 1 This is the basic principle of boron neutron capture therapy (BNCT) mentioned in the background of this invention.

[0023] Figure 2 These are the first and second generation BNCT boron drugs mentioned in the background section of this invention.

[0024] Figure 3 This is the novel amino acid-based BNCT boron carrier mentioned in the background section of this invention.

[0025] Figure 4 These are the enrichment results of carborane amino acid derivatives provided by this invention in cancer cells. Detailed Implementation

[0026] This invention provides a carborane amino acid derivative, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Traditional boron carriers for BNCTs, such as clinically used BPA, have borate groups directly attached to the benzene ring of phenylalanine. While structurally simple and exhibiting good affinity for the LAT1 transporter, they suffer from low boron loading and metabolic instability. Carborane clusters, with their high boron content, have previously been difficult to directly and efficiently bind to the active sites (especially aromatic rings) of amino acids. Most reported carborane-amino acid derivatives utilize lengthy alkyl or ether groups as linkers (structural diagram: carborane-linker-amino acid). This non-natural linking method can alter the physicochemical properties and spatial conformation of the parent amino acid, affecting its recognition and uptake by specific transporters (such as LAT1), and the complex synthetic steps also hinder further development. Our previous research also confirmed that carborane-phenylalanine or carborane-lysine derivatives synthesized via linkers did not achieve cellular uptake efficiency exceeding that of BPA.

[0028] Therefore, this invention aims to solve the key problem in the prior art of directly and efficiently introducing carboranes onto the naturally targeted amino acid backbone. The core concept of this invention lies in: abandoning the traditional linker strategy and creatively developing a novel synthetic method that can directly bond carborane clusters to the benzene ring of phenylalanine-like amino acids, thereby maximizing the preservation of the structural characteristics and biorecognition properties of the natural amino acid while significantly increasing the boron atom loading of the molecule.

[0029] Based on this, embodiments of the present invention provide a carborane amino acid derivative, the structural formula of which is shown in Formula 1: ; in, C, For BH; o, m, and p are each independently selected from CR 3 Or BH; and when o is selected from CR 3 When m and p are selected from BH; when m is selected from CR 3 When o and p are selected from BH; when p is selected from CR3 At that time, o and m were selected from BH; R 1 R 2 and R 3 Each of the following groups is independently derived from one or more of H, OH, SH, NH2, halogen, trimethylsilyl, alkyl with 1-15 carbon atoms (substituted or unsubstituted), benzyl with substituted or unsubstituted, aryl with 6-20 carbon atoms (substituted or unsubstituted), boric acid, or borate ester group.

[0030] In this embodiment, "substituted or unsubstituted alkyl group of 1-15 carbon atoms" includes straight-chain alkyl and branched-chain alkyl. The alkyl group can be a substituted alkyl group of 1-15 carbon atoms or an unsubstituted alkyl group of 1-15 carbon atoms. When the alkyl group is selected from substituted alkyl groups of 1-15 carbon atoms, the alkyl group can be substituted by one or more alkyl groups selected from deuterium, halogens, unsubstituted alkyl groups of 1-15 carbon atoms, or unsubstituted aryl groups of 6-20 carbon atoms; preferably, it is "substituted or unsubstituted alkyl group of 1-10 carbon atoms", more preferably, it is "substituted or unsubstituted alkyl group of 1-5 carbon atoms". "Substituted or unsubstituted benzyl group" can be a substituted benzyl group or an unsubstituted benzyl group. When a substituted benzyl group is selected, the benzyl group can be substituted by one or more alkyl groups selected from deuterium, halogens, unsubstituted alkyl groups of 1-15 carbon atoms, or unsubstituted aryl groups of 6-20 carbon atoms. "Substituted or unsubstituted aryl group with 6-20 carbon atoms" can be a substituted aryl group with 6-20 carbon atoms or an unsubstituted aryl group with 6-20 carbon atoms. When a substituted aryl group with 6-20 carbon atoms is selected, the aryl group can be substituted by one or more alkyl groups selected from deuterium, halogens, unsubstituted alkyl groups with 1-15 carbon atoms, or unsubstituted aryl groups with 6-20 carbon atoms; preferably, it is a "substituted or unsubstituted aryl group with 6-12 carbon atoms", more preferably a benzene ring. Furthermore, when the same description appears again below, it will not be explained further as described in this embodiment.

[0031] The carborane-amino acid derivative provided in this invention is characterized by the direct connection of the caged carbon atom of the carborane to the carbon atom of the benzene ring in the phenylalanine backbone (forming a C(cage carbon)-C(aromatic ring) bond). This design mimics the structural essence of successful drugs such as BPA and BTS (where the borate group is directly connected to the aromatic ring). This structure can: 1. Maintain the original spatial conformation and electron distribution of the parent amino acid to the greatest extent, which is beneficial for its effective recognition and active transport by amino acid transport proteins such as LAT1 overexpressed on the surface of tumor cells. 2. Achieve extremely high boron atom density. A carborane cluster (C2B) 10 H 12 It can provide 10 boron atoms, directly replacing monoboronic acid groups, which theoretically can achieve an order-of-magnitude increase in boron loading.

[0032] In some embodiments, the carborane amino acid derivative is any one of the following compounds 1 to 56:

[0033]

[0034]

[0035] In the field of boron neutron capture therapy (BNCT), developing boron carriers with high boron loading and high tumor targeting is a core challenge. Clinically successful boron carriers, such as 4-boronic acid-L-phenylalanine (BPA), are characterized by a boron functional group (-B(OH)2) directly linked to the aromatic ring of phenylalanine. This structure is considered crucial for its efficient uptake by tumor cells via L-amino acid transporter 1 (LAT1). However, the low boron content of BPA limits its efficacy.

[0036] Theoretically, carborane clusters (C2B) 10 H 12 Due to its extremely high boron atom density, carborane is an ideal boron source substitute. Those skilled in the art have attempted to introduce carborane into the amino acid backbone to construct high-performance boron carriers. However, due to the lack of an effective direct linking method, existing technologies almost entirely employ a "linker" strategy, i.e., linking carborane to the side chain or main chain of an amino acid via spacers such as alkyl chains or ether chains (forming, for example, a carborane-linker-phenylalanine structure). Previous research by the inventors has also shown that carborane-phenylalanine or carborane-lysine derivatives synthesized in this manner do not exhibit significantly better cellular uptake efficiency than BPA. This is likely because the lengthy linker disrupts the precise spatial and electronic requirements for the interaction between the phenylalanine core and the LAT1 transporter protein.

[0037] Achieving direct coupling (arylation) between carboranes and aromatic rings is a challenge in synthetic chemistry. Reported arylation reactions of carboranes via BH or CH bonds typically rely on transition metal catalysis (such as palladium or nickel) and often require strongly basic conditions, high temperatures, or the assistance of directing groups (see Acc. Chem. Res. 2021, 54, 4065-4079). These stringent reaction conditions are severely incompatible with the sensitive amino, carboxyl, and hydroxyl functional groups in amino acid molecules, easily leading to racemization, decomposition, or side reactions of the amino acids, making them unsuitable for direct synthesis of carborane amino acid derivatives.

[0038] Based on this, this invention abandons the traditional metal catalysis route and innovatively utilizes a photochemically promoted free radical reaction strategy. The core of this strategy lies in the in-situ generation of highly reactive, electron-deficient carborane cage carbon radicals through homolytic cleavage of the BI bond in the precursor compound under mild light irradiation. These radicals can directly attack electron-rich aromatic rings, achieving one-step coupling.

[0039] This invention provides a method for preparing the above-mentioned carborane amino acid derivative, the method comprising the following steps: The compound shown in Formula 2, the compound shown in Formula 3, and the additives are dissolved in a solvent and stirred under light irradiation at a preset temperature to obtain the compound of Formula 1, which is the carborane amino acid derivative. The synthetic route for the above reaction is as follows: .

[0040] In the preparation method of this invention, tyrosine (corresponding to compound 3) is preferred as the amino acid substrate. The design considerations are as follows: 1. Reactivity: The phenolic hydroxyl group on the benzene ring of tyrosine is a strong electron-donating group, which can significantly increase the electron density of the benzene ring, giving it a higher thermodynamic driving force and a faster reaction rate in its reaction with the electron-deficient carborane cage carbon radical. 2. Reaction selectivity: Compared with phenylalanine, the phenolic hydroxyl group of tyrosine can provide better regioselectivity in radical reactions, which is beneficial for obtaining a single target product and simplifying the purification process. 3. Potential for subsequent functionalization: The phenolic hydroxyl group retained in the product is a highly active and easily modified functional group, providing an excellent "handle" for derivatization, facilitating the subsequent connection of target groups, imaging probes, or adjustment of molecular physicochemical properties to achieve "therapeutic integration".

[0041] The preparation method provided in this embodiment has the following advantages: 1. Mild conditions: The entire reaction is carried out near room temperature, at normal pressure, and under visible light irradiation, without the need for strong bases, high temperatures, or sensitive metal catalysts, thus perfectly compatible with all sensitive functional groups in the amino acid substrate and avoiding side reactions such as racemization. 2. Simple steps: This method is a one-step coupling method, which does not require pre-protection and deprotection of the amino or carboxyl groups of amino acids. The synthetic route is short, the atom economy is high, and the operation is extremely simple. 3. Good functional group tolerance: The photochemical free radical mechanism described above shows good compatibility with various functional groups on the reactant molecules (such as -OH, -SH, -NH2, halogens, alkyl, aryl, borate esters, etc. as defined in Formulas 1 and 3), which facilitates the synthesis of a diverse library of derivatives.

[0042] By implementing the above preparation method, this invention has achieved the following significant effects: 1. Methodological breakthrough: A general method for the direct coupling of carborane radicals with aromatic rings to synthesize carborane-amino acid derivatives has been successfully developed, solving a long-standing synthetic bottleneck in this field and providing a powerful and practical chemical tool for the rapid construction of such high-performance boron carriers. 2. Excellent product performance: The carborane-tyrosine derivatives efficiently prepared using this method possess both a natural-like targeting structure and ultra-high boron content. In vitro biological evaluation confirmed that the boron enrichment capacity of this type of compound in tumor cells is 5-10 times higher than that of the clinical drug BPA, achieving the initial design intent and demonstrating great potential as a next-generation boron carrier for BNCT. 3. Strong platform scalability: This method is not only applicable to tyrosine, but its principle can be extended to other electron-rich aryl amino acid derivatives. Furthermore, the inherent phenolic hydroxyl groups in the product lay a solid foundation for subsequent precise modification and functional optimization, offering great development flexibility.

[0043] In summary, the preparation method provided by the embodiments of the present invention is not only highly innovative, with mild conditions and simple operation, but also directly leads to a series of high-performance candidate drug molecules, which has important practical application value for promoting the development of BNCT technology.

[0044] In some embodiments, the additive is pyridine or potassium carbonate, and the solvent is dichloromethane or acetonitrile.

[0045] In some embodiments, the wavelength range of the light source is 365~450 nm; the preset temperature is room temperature; and the stirring time is 12-36 hours.

[0046] In some embodiments, the molar ratio of the compound represented by Formula 2, the compound represented by Formula 3, and the additive is (1~1.1):(1.5~2.0):(1.1~2.0).

[0047] In the photochemical radical coupling reaction described in this invention embodiment, the molar ratio of each reaction component is one of the key parameters affecting reaction efficiency, selectivity, and final yield. Through extensive experimental optimization, we determined the optimal molar ratio range of the compound of formula 2 (iodocarborane precursor), compound 3 (tyrosine or its derivative), and additive to be (1~1.1):(1.5~2.0):(1.1~2.0). This ratio range was set based on the following comprehensive considerations: 1. Ensuring efficient conversion of the carborane radical precursor and driving reaction equilibrium: Setting the amount of compound 2 as a baseline (1 equivalent) and allowing a slight excess (1~1.1 equivalents) is primarily to ensure that compound 3 (amino acid) is fully consumed and the reaction is as complete as possible. In radical reactions, ensuring that the concentration of the radical precursor (formula 2) is sufficient to maintain the reaction chain is crucial. A slight excess of Formula 2 compound helps compensate for minor losses that may be caused by solvent effects, side reactions, or fluctuations in light efficiency, thereby improving the conversion rate of Formula 3 compound and the final yield of the target product (Formula 1). 2. Using an excess of amino acid substrate to suppress side reactions and improve reaction selectivity: Maintaining an excess of Formula 3 compound (tyrosine derivative) at 1.5 to 2.0 equivalents has multiple benefits: ① Improved reaction kinetics: Higher amino acid concentrations can accelerate the capture and coupling steps between the amino acid and the short-lived carborane cage carbon radical, which is beneficial for the competitive advantage of the main reaction pathway. ② Suppression of polyarylation side reactions: An excess of Formula 3 compound can minimize the possibility of the same carborane radical intermediate reacting with multiple amino acid molecules in successive reactions (e.g., generating diarylation byproducts), thereby improving the monosubstituted selectivity of the reaction and simplifying the product separation and purification process. ③ As a mild proton acceptor: Amino acid molecules themselves have a certain degree of basicity, and their excess can neutralize hydrogen iodide (HI) that may be generated in the reaction to a certain extent, which is beneficial for maintaining the stability of the reaction system. 3. Optimize the dosage of additives to ensure efficient free radical generation and a suitable reaction environment: The dosage of additives (the specific composition of which may vary depending on the example, such as organic bases, Lewis bases, or electron transfer agents) is controlled between 1.1 and 2.0 equivalents. This ratio range aims to: ① efficiently promote homolytic cleavage of the BI bond: sufficient additives can effectively assist in the photoinduced homolytic cleavage of the BI bond in the compound of formula 2, ensuring the continuous and stable generation of carborane cage carbon free radicals, which is the basis for the initiation and maintenance of the entire coupling reaction. ② quench byproducts and stabilize the system: additives can timely capture or neutralize reaction byproducts (such as HI), preventing their accumulation from leading to amino acid substrate ponification, reduced solubility, or other degradation side reactions, thereby maintaining the homogeneity and stability of the reaction system and ensuring the smooth progress of the reaction. ③ provide the optimal reaction medium environment: the dosage of additives is optimized to form the most suitable free radical reaction microenvironment in the reaction solvent, balancing the reactivity and the stability of the substrate / intermediate.

[0048] In summary, the precisely controlled molar ratios described above, combined with mild illumination conditions, achieved the following objectives: (a) maximizing the utilization efficiency of the carborane radical precursor; (b) ensuring the efficient and selective conversion of the amino acid substrate into the target product; and (c) effectively suppressing potential side reaction pathways and simplifying the post-processing. This optimized reactant ratio is a crucial guarantee for the method of this invention to obtain high-purity, high-yield carborane-tyrosine derivatives in a one-step, simple operation, and is also one of the key operating parameters for its good functional group tolerance and reproducibility.

[0049] This invention provides the application of the above-mentioned carborane amino acid derivatives in the preparation of boron neutron capture therapeutic drugs.

[0050] In some embodiments, the boron neutron capture therapy includes tumor therapy drugs.

[0051] In some embodiments, the tumor includes at least one of malignant melanoma, head and neck squamous cell carcinoma, glioma, nasopharyngeal carcinoma, and breast cancer.

[0052] In some embodiments, the tumor includes a malignant tumor or a metastatic, inoperable tumor.

[0053] The present invention will be further described below through specific embodiments.

[0054] In the following embodiments of the present invention, the photoreactor for obtaining the compound of formula 1 from the compound shown in formula 2 and the compound shown in formula 3 is from Beijing Nuozhi Technology, model PCL-08.

[0055] Preparation of the compound shown in Formula 2 in Example 1 Compound 2 is derived from existing technical literature (e.g., J. Org. Chem. 2015, 80, 4573–4580; Inorg. Chem. 2023, 62, 885). 892; J. Am. Chem. Soc. 2023, 145, 7331 It was prepared by the method described in J.Am. Chem. Soc. 2016, 138, 9081–9084; Eur. J. Inorg. Chem. 2013, 2488–2491; Angew. Chem. Int. Ed. 2017, 56, 712–716).

[0056] Example 2: Preparation of compounds 1 to 56 The structural formulas of compounds 1-56 are as follows:

[0057]

[0058] .

[0059] The general reaction formula is:

[0060] The specific preparation method is as follows: The compound shown in Formula 2 (0.1 mmol) and the compound shown in Formula 3 (0.2 mmol) prepared in Example 1 were placed in a flame-dried 10 mL Schlenk flask containing a small magnetic stir bar. Dry dichloromethane (2.0 mL) was added, the flask was sealed, and the mixture was stirred for 12-36 hours under a 15W 365 nm LED lamp to obtain the reaction mixture. After the reaction was complete, 1 mL of saturated sodium thiosulfate solution was added to the reaction system, and the mixture was stirred to quench the iodine generated during the reaction. The mixture was then extracted three times with ethyl acetate (3 mL × 3), the organic phases were combined, and dried with anhydrous sodium sulfate. After filtering to remove the desiccant, the organic phase was collected, and an appropriate amount of silica gel was added. The solvent was removed by rotary evaporation to obtain the crude product adsorbed on the silica gel. Finally, purification was performed by column chromatography using dichloromethane / ethyl acetate (40:1, v / v) as the eluent to obtain the target product.

[0061] Compound 1, prepared by the above method, was a white solid (yield 89%). NMR characterization of compound 1: 1 HNMR (500 MHz, CDCl3): δ [ppm] = 8.33 (s, 1H, -OH), 7.24 (s, 1H), 6.90 (d, J =8 Hz, 0.77 H), 6.81 (d, J = 8 Hz, 0.30 H), 6.57 (d, J = 8 Hz, 0.78 H), 6.40(d, J = 8 Hz, 0.22 H), 5.60 (s, Cage-H), 5.22 (d, J = 8Hz, 0.80 H), 4.97 (d,J = 8Hz, 0.20 H), 4.49 (m, 1 H), 3.76(s, 3 H), 2.99 (m, 2 H), 1.44(s, 9 H). 13C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 172.24, 155.64, 152.25, 133.06,130.97, 127.76, 119.38, 117.32, 81.16, 75.09, 59.78, 54.60, 52.78, 37.51,31.59, 28.28, 22.66, 14.14. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.47, -10.21. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.84, -9.30. Compound 2 is a white solid (yield 68%). NMR characterization of compound 2: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.33 (s, 1 H), 7.09 (d, J = 8 Hz, 1 H), 6.82 (d, J = 12 Hz,1 H), 5.32 (s, Cage CH), 5.02 (d, J = 8 Hz, 1 H), 4.58 (d, J = 12, 4 Hz, 1H), 3.82 (s, 3 H), 3.75 (s, 3 H), 3.06 (m, 2 H), 1.44 (s, 9 H). 13 C{1H} NMR(101 MHz, CDCl3, 298 K): δ [ppm] = 171.86, 154.96, 133.58, 131.53, 128.87,121.14, 112.39, 80.18, 74.82, 59.78, 55.91, 54.20, 52.49, 37.13, 28.29. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.14, -4.30, -8.56, -9.76, -12.71, -14.13. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.62, -9.09, -9.09, -11.23, -13.39. Compound 5 is a white solid (50% yield). NMR characterization of compound 5: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.17 (s, 1 H), 6.88 (d, J = 8 Hz, 1 H), 6.60 (d, J = 8 Hz, 1 H), 5.05 (d, J = 8 Hz, 1 H), 4.55 (d, J = 8 Hz, 1 H), 3.74 (s, 3 H), 3.00 (s, Cage CH), 2.96 (m, 2 H), 1.44 (s, 9 H). 13 C{1H} NMR (101 MHz, CDCl3, 298K): δ [ppm] = 172.25, 155.23, 152.87, 132.85, 130.81, 127.42, 119.90, 117.72,80.46, 75.32, 55.00, 54.34, 52.52, 37.35, 28.29. 11 B NMR (128 MHz, CDCl3, 298K): δ [ppm] = -2.82, -4.06, -10.38, -11.45, -12.98, -14.23, -15.32. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.51, -7.50, -10.04, -10.87, -13.63, -14.64, -14.65. Compound 8 is a white solid (yield 84%). NMR characterization of compound 8: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.20 (s, 1H), 6.92 (d, J = 8 Hz, 1 H), 6.63 (d, J = 8 Hz, 1H), 5.27 (s, Cage CH), 4.99 (d, J = 8 Hz, 1 H), 4.55(dd, J = 12, 8 Hz, 1 H), 3.87 (s, 2H), 3.74 (s, 3H), 3.01 (m, 2 H), 1.43 (s, 9H). 13C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 172.01, 154.94, 142.18, 131.84, 131.26, 128.38,121.54, 118.85, 80.15, 76.27, 59.35, 54.14, 52.45, 37.22, 28.31. 11 B NMR (128MHz, CDCl3, 298 K): δ [ppm] = -2.32, -3.49, -8.26, -9.46, -10.67, -12.42, -13.84. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.01, -8.89, -10.50, -13.21. Compound 13 was a white solid (yield 48%). NMR characterization of compound 13: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.85 (s, 1 H), 7.43 (d, J = 8 Hz, 1 H), 7.20 (s, 1 H), 6.79 (d, J = 8 Hz, 2 H), 6.67 (d, J = 8 Hz, 2 H), 6.61 (d, J = 8 Hz, 2 H), 4.84 (dD, J = 36, 8 Hz, 2 H), 4.95 (m, 1 H), 4.48 (d, J = 8 Hz, 1 H), 3.71 (s, 3H), 3.65 (s, 3 H), 2.95 (m, 2 H), 1.51 (s, 9 H). 13 C{1H} NMR (101 MHz, CDCl3,298 K): δ [ppm] = 171.66, 160.93, 155.04, 135.22, 132.58, 132.00, 127.59,125.32, 123.43, 118.09, 113.50, 109.75, 87.99, 84.07, 80.72, 56.40, 55.28,54.22, 52.39, 37.11, 28.39. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -1.24, -3.27, -9.88. 11B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -2.81, -10.19. Compound 14 was a white solid (yield 44%). NMR characterization of compound 14: 1 H NMR (400 MHz, Acetone, 298 K): δ [ppm] = 9.35 (s, 1 H), 7.85 (d, J = 8 Hz, 2 H), 7.64 (d, J= 8 Hz, 2 H), 7.52 (s, 1 H), 7.04 (d, J = 8 Hz, 2 H), 6.75 (d, J = 8 Hz, 2H), 6.08 (d, J = 8 Hz, 1 H), 4.28 (m, 2 H), 3.63 (m, 1 H), 2.90 (m, 2 H), 1.41 (s, 9 H). 13 C{1H} NMR (101 MHz, Acetone, 298 K): δ [ppm] = 172.90, 156.81,156.15, 136.31, 136.08, 134.09, 132.32, 129.44, 126.30, 126.26, 123.36,118.38, 115.77, 86.06, 79.68, 55.83, 52.36, 52.32, 36.87, 28.58. 11 B NMR (128MHz, Acetone, 298 K): δ [ppm] = -3.17, -10.42. 11 B{1H} NMR (128 MHz, Acetone, 298 K): δ [ppm] = -2.62, -3.69, -9.86, -10.99. Compound 27 was a white solid (55% yield). NMR characterization of compound 27: 1H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.55 (s, 1 H), 7.41 (d, J = 8 Hz, 1 H), 7.12 (d, J = 8 Hz,1 H), 5.19 (s, Cage CH), 4.96 (d, J = 8 Hz, 1 H), 4.61 (d, J = 8 Hz, 1 H), 3.74 (s, 3 H), 3.13 (m, 2 H), 1.44 (s, 9 H), 1.39 (s, 12 H). 13 C{1H} NMR (101MHz, CDCl3, 298 K): δ [ppm] = 170.61, 153.86, 137.24, 136.07, 134.37, 130.21,128.67, 84.04, 79.17, 60.37, 52.93, 51.49, 36.71, 28.68, 27.28, 23.77. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = 31.72, -2.21, -3.41, -8.52, -9.69, -12.15. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = 30.89, -2.90, -4.18, -9.22, -10.68, -13.05. Compound 40 is a white solid (yield 88%). NMR characterization of compound 40: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.95 (s, 1H, -OH), 7.24 (s, 1H), 6.92 (d, J = 8 Hz, 0.77H), 6.79 (d, J = 8 Hz, 0.21 H), 6.52 (d, J = 8 Hz, 0.75 H), 6.32 (d, J = 8Hz, 0.24 H), 5.60 (s, Cage-H), 5.21 (d, J = 8Hz, 0.71 H), 4.92 (d, J = 8Hz, 0.20 H), 4.53 (m, 1 H), 3.80 (s, 3 H), 3.07 (m, 2 H), 1.49(s, 9 H). 13C{1H} NMR(101 MHz, CDCl3, 298 K): δ [ppm] = 172.28, 155.51, 152.00, 133.16, 130.91,128.04, 119.39, 117.29, 81.10, 74.98, 59.76, 54.66, 52.81, 37.76, 31.61,28.29, 22.68, 14.15. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.61, -9.04, -13.67. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.47, -9.55. Compound 41 is a white solid (yield 81%). NMR characterization of compound 41: 1 H NMR (400 MHz, CD3OD, 298 K): δ [ppm] = 10.03 (s, 1 H, -OH), 7.39 (s, 1 H), 7.12 (d, J = 8 Hz, 1H), 6.88 (d, J = 8 Hz, 1 H), 6.43 (d, J = 8Hz, 1 H), 5.98 (s, Cage-H), 4.13 (m, 1 H), 3.65 (s, 3 H), 2.70 (m, 2 H), 2.05 (m, 2 H), 1.41 (s, 9 H). 13 C{1H} NMR(101 MHz, Acetone, 298 K): δ [ppm] = 173.82, 156.58, 153.06, 133.68, 132.34,131.64, 119.48, 118.08, 79.39, 76.93, 61.28, 53.92, 52.18, 34.29, 31.49,28.53. 11 B NMR (128 MHz, CD3OD, 298 K): δ [ppm] = -3.62, -4.77, -8.82, -10.02. 11 B{1H} NMR (128 MHz, CD3OD, 298 K): δ [ppm] = -3.62, -4.77, -8.82, -10.02. Compound 42 is a white solid (79% yield). NMR characterization of compound 42:1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 8.03 (s, 1 H, -OH), 7.46 (s, 1 H), 6.95 (d, J = 8 Hz, 1 H), 6.29 (d, J = 8 Hz, 1 H), 5.81 (m, 1 H), 5.53 (s, Cage-H), 5.16 (m, 1 H), 3.76(s, 3 H), 1.46(s, 9 H). 13 C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 171.02,155.34, 153.05, 129.81, 129.13, 128.53, 119.96, 117.32, 81.47, 74.72, 59.68,56.66, 53.21, 28.32. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.48, -8.90, -11.13. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.94, -9.62, -12.77. Compound 45 is a white solid (79% yield). NMR characterization of compound 45: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 8.52 (s, 1 H, -OH), 7.29 (s, 1 H), 6.88 (d, J = 8 Hz, 1 H), 6.54 (d, J = 8 Hz, 1 H), 5.64 (s, Cage-H), 5.03 (d, J = 8 Hz, 1 H), 3.75 (m, 2 H), 3.23 (s, 1 H, -OH) 2.74 (m, 2 H), 1.42 (s, 9 H). 13 C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 156.91, 152.07, 132.92, 131.03, 129.54, 119.46,117.43, 81.05, 75.38, 64.25, 59.90, 54.09, 36.67, 28.45. 11B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -4.09, -9.62. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ[ppm] = -4.07, -9.58. Compound 46 is a white solid (79% yield). NMR characterization of compound 46: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.35 (s, 1 H), 6.74 (m, 1 H), 6.14 (d, J = 8 Hz, 1 H), 5.58(s, Cage-H), 4.89 (d, J = 8 Hz, 1 H), 3.68 (s, 3 H), 2.81 (m, 2 H), 1.46 (s,9 H). 13 C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 171.71, 155.76, 152.52,136.10, 132.43, 128.51, 119.32, 117.22, 81.09, 75.05, 59.75, 52.27, 50.40,40.13, 28.37. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -3.95, -9.42, -13.11. 11 B{1H} NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -4.04, -9.75. Compound 53 was a white solid (79% yield). NMR characterization of compound 53: 1 H NMR (400 MHz, Acetone, 298 K): δ [ppm] = 9.35 (s, 1 H, -OH), 7.63 (s, 1 H), 7.25 (d, J = 8Hz, 1 H), 6.97 (d, J = 8 Hz, 1 H), 6.21 (d, J = 8 Hz, 1 H), 4.41 (m, 1 H), 3.13 (m, 2 H), 1.80 (s, 3 H), 1.35 (s, 9 H). 13C{1H} NMR (101 MHz, Acetone, 298K): δ [ppm] = 172.12, 155.96, 155.20, 135.22, 133.14, 128.85, 118.01, 115.03,80.91, 79.63, 78.55, 55.01, 51.50, 36.25, 27.64, 22.85. 11 B NMR (128 MHz, Acetone, 298 K): δ [ppm] = -2.26, -3.43, -5.34, -6.49, -9.72, -11.07. 11 B{1H}NMR (128 MHz, Acetone, 298 K): δ [ppm] = -2.94, -5.97, -9.17, -10.46. Compound 55 is a white solid (79% yield). NMR characterization of compound 55: 1 H NMR (400 MHz, CDCl3,298 K): δ [ppm] = 7.51 (d, J = 8 Hz, 2 H), 7.24 (d, J = 8 Hz, 1 H), 7.17 (m,2 H), 6.78 (d, J = 8 Hz, 2 H), 6.58 (s, 1 H), 6.49 (d, J = 8 Hz, 2 H), 4.84 (d, J =8 Hz, 1 H), 4.47 (m, 1 H), 3.66 (s, 3 H), 2.91 (m, 2 H), 1.50 (s, 9H). 13 C{1H} NMR (101 MHz, CDCl3, 298 K): δ [ppm] = 171.89, 155.18, 155.10,135.29, 132.65, 131.23, 130.60, 130.32, 128.52, 128.35, 127.71, 118.18,115.70, 87.34, 83.80, 80.83, 54.30, 52.59, 37.15, 28.50. 11 B NMR (128 MHz, CDCl3, 298 K): δ [ppm] = -1.36, -3.01, -9.96. 11B{1H} NMR (128 MHz, CDCl3, 298K): δ [ppm] = -2.58, -10.31. Performance testing of in vitro boron uptake experiments of carborane amino acid derivatives U251 (human glioma cancer cells), B16F10 (mouse melanoma cancer cells), FaDu (human pharyngeal squamous cell carcinoma cells), and HeLa (human cervical cancer cells) cell lines were purchased from the Cell Bank of the Chinese Academy of Sciences (Shanghai, China). All cells were cultured in Dulbecco modified Eagle Medium (DMEM, Gibco, USA) containing 10% fetal bovine serum (FBS, Gibco) and 1% penicillin-streptomycin (Gibco). All cells were cultured at 37°C in a humidified environment containing 5% CO2.

[0062] In 6 cm culture dishes, U251, B16F10, FaDu (human pharyngeal squamous cell carcinoma), HeLa, A375, and U87MG cells in logarithmic growth phase were digested with trypsin and then resuspended to 2 × 10⁻⁶ cells. 6 At a concentration of 1 cell / mL, 3 mL of cell suspension was inoculated and incubated at 37°C and 5% CO2 for 24 hours until the cells were fully adhered. The culture medium was then discarded, and the cells were gently washed once with pre-warmed PBS. Fresh culture medium containing 0.1 mM of the test compound (with 1.0 mM BPA as a positive control) was added, and the cells were incubated for another 3 hours. The culture medium was then discarded, and the cells were washed once with PBS. The cells were collected, counted, and centrifuged to obtain the cell pellet. The pellet was placed in a mixture of 1 mL concentrated nitric acid and 0.5 mL 30% hydrogen peroxide and heated at 80°C until completely dissolved. Finally, the boron content in the dissolved sample was determined using an inductively coupled plasma mass spectrometer (ICP-MS7900, Agilent Technologies).

[0063] The results are as follows Figure 4 As shown. Using 1.0 mM BPA as a positive control, compounds 1, 2, 40, 42, and 53 provided by this invention showed significantly higher boron enrichment in the U251, B16F10, FaDu, and HeLa cell lines than BPA, especially compounds 1 and 2, which showed 5-10 times enrichment. Compound 53 was at a similar level to BPA. Compound 41 showed lower boron enrichment in cells than BPA.

[0064] In summary, the carborane amino acid derivatives provided by this invention possess high boron content and excellent biocompatibility, making them ideal boron carriers and building blocks for boron drug synthesis in BNCT drugs. Furthermore, these carborane amino acid derivatives retain modifiable sites, facilitating the flexible introduction of various functionalized targeting groups, thus providing innovative synthetic building blocks for the precise design of BNCT drugs. In addition, the preparation method provided by this invention offers significant advantages such as simple operation, mild conditions, and good functional group tolerance. Cell experiments demonstrate that the compounds provided by this invention have great application potential in BNCT. In particular, compounds 1 and 2 exhibit five to ten times greater boron absorption than the marketed drug BPA in in vitro cell experiments.

[0065] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A carborane amino acid derivative, characterized in that, The structural formula of the carborane amino acid derivative is shown in Formula 1: ； in, C, For BH; o, m, and p are each independently selected from CR 3 Or BH; and when o is selected from CR 3 When m and p are selected from BH; when m is selected from CR 3 When o and p are selected from BH; when p is selected from CR 3 At that time, o and m were selected from BH; R 1 R 2 and R 3 Each of the following groups is independently derived from one or more of H, OH, SH, NH2, halogen, trimethylsilyl, alkyl with 1-15 carbon atoms (substituted or unsubstituted), benzyl with substituted or unsubstituted, aryl with 6-20 carbon atoms (substituted or unsubstituted), boric acid, or borate ester group.

2. The carborane amino acid derivative according to claim 1, characterized in that, The carborane amino acid derivative is any one of the following compounds 1 to 56: 。 3. A method for preparing the carborane amino acid derivative according to claim 1, characterized in that, The preparation method includes the following steps: The compound shown in Formula 2, the compound shown in Formula 3, and the additives are dissolved in a solvent and stirred under light irradiation at a preset temperature to obtain the compound of Formula 1, which is the carborane amino acid derivative. The synthetic route for the above reaction is as follows: 。 4. The method for preparing carborane amino acid derivatives according to claim 3, characterized in that, The additive is pyridine or potassium carbonate, and the solvent is dichloromethane or acetonitrile.

5. The method for preparing carborane amino acid derivatives according to claim 3, characterized in that, The wavelength range of the light source is 365~450 nm; the preset temperature is room temperature; and the stirring time is 12 to 36 hours.

6. The method for preparing carborane amino acid derivatives according to claim 3, characterized in that, The molar ratio of the compound shown in Formula 2, the compound shown in Formula 3, and the additive is (1~1.1):(1.5~2.0):(1.1~2.0).

7. The use of the carborane amino acid derivative of claim 1 in the preparation of boron neutron capture therapeutic drugs.

8. The application according to claim 7, characterized in that, The boron neutron capture therapy drugs include tumor therapy drugs.

9. The application according to claim 8, characterized in that, The tumor includes at least one of malignant melanoma, squamous cell carcinoma of the head and neck, glioma, nasopharyngeal carcinoma, and breast cancer.

10. The application according to claim 8, characterized in that, The tumors include malignant tumors or metastatic tumors that are not surgically resectable.

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