A fluorinated [5] rotaxane and its synthesis method and application

Abstract

The present invention provides a fluorinated [5] rotaxane and its synthesis method and application, the present invention uses fluorinated crown ether as "wheel-shaped molecule" and 19 The F NMR signal source is based on a TPE molecule with four secondary ammonium salt cationic side chains as the "axis molecule" and a fluorescent molecule to develop a pH-sensitive 19 F MRI-FLI dual-modality imaging contrast agent. This contrast agent significantly improves the imaging performance by utilizing 144 equivalent fluorine atoms in four "wheel-shaped molecules" as well as the hydrogen bonding and fluorine effect within the molecule. 19 The sensitivity of F MRI and FLI is improved, and the response of the secondary ammonium salt in the molecule to different pH values ​​is used to achieve the supermolecular motion state and 19 Modulation of contrast sensitivity in F MRI-FLI dual-modality imaging.

Description

Technical Field

[0001] The present invention belongs to the fields of magnetic resonance imaging technology and fluorescence imaging technology, and specifically relates to a synthesis method and application of a fluorinated [5] rotaxane. Background Art

[0002] Multimodal imaging agents that combine two or more imaging technologies can combine the advantages of different imaging technologies, overcome the limitations of a single imaging technology, and provide comprehensive information on the target with high temporal and spatial resolution, and have attracted much attention (Louie, A. Chem. Soc. Rev. 2010, 110, 3146-3195; Wang, M.; Wang, Y.; Fu, Q. Mater. Today Bio 2024, 26, 101027). Among them, fluorine-19 magnetic resonance-fluorescence ( 19 F MRI-FLI dual-modality imaging contrast agents, due to their complementary advantages, can provide a "hotspot imaging" method with multiple advantages such as high sensitivity and resolution and no background interference, and have extremely high biomedical research value (Li, Y.; Zhang, J.; Zhu, L. et al. Adv. Healthcare Mater. 2023, 12, 2300941.). However, how to overcome the millimolar (mmol) sensitivity problem in a single contrast agent? 19 The huge sensitivity difference between F MRI and FLI with micromolar (μmol) sensitivity has led to the following challenges in integrating the two: (1) the low solubility, high aggregation tendency, and aggregation fluorescence quenching (ACQ) of FL molecules limit the application of most FL molecules at mmol concentrations; (2) in order to improve the 19 F MRI sensitivity, a large number of fluorine-19 nuclear magnetic resonance spectroscopy ( 19 The equivalent fluorine atoms in the FNMR) signal peak bring great trouble in chemical synthesis (Wu, T.; Li, A.; Chen, K. et al. Chem. Commun. 2021, 57, 7743-7757).

[0003] To overcome the above challenges, the spin-lattice relaxation time (T1) is shortened by restricting the movement of fluorine atoms and enhancing 19 FMRI resonance signal intensity is to improve 19Effective strategies for increasing F MRI sensitivity (Mo, Y.; Huang, C.; Liu, C. et al. Macromol. Rapid Commun. 2023, 44(16), 2200744). Currently known strategies mainly include chelating paramagnetic metals, coupling with macromolecules, or self-assembly into nanoparticles. However, challenges in selective coupling, self-assembly operations, and scale-up preparation have hindered their application. In addition, the spin-spin relaxation process (T2) of fluorine-19 is more sensitive to the movement of fluorine atoms, and too short T2 will broaden the spectrum. 19 F NMR peak, decreased 19 Therefore, while limiting the movement of fluorine atoms, increasing the T2 / T1 ratio is the key to improving the sensitivity of F MRI. 19 Ideal strategy for F MRI sensitivity (Mo, Y.; Huang, C.; Liu, C. et al. Macromol. Rapid Commun. 2023, 44, 2200744.).

[0004] Previously, the fluorinated [2]rotaxanes we developed have been used to restrict the movement of fluorine atoms in order to shorten 19 F's T1, while maintaining high T2 / T1, improves 19 The sensitivity of F MRI was improved (Yang, L.; Li, Y.; Jiang, M. et al. Chin. Chem. Lett. 2024.10.1016 / j.cclet.2024.109512). On this basis, tetraphenylethylene (TPE) was introduced as a sensitive fluorophore, which can not only integrate 19 F MRI and FLI, achieving dual-modality imaging. The fluorinated [5] rotaxane structure with multiple side chains can further increase the fluorine content of the molecule and restrict the motion state of fluorine atoms and TPE, thereby coordinating and improving 19 F Sensitivity of MRI-FLI dual-modality imaging contrast agents. Summary of the Invention

[0005] Based on the above-mentioned prior art, the present invention provides a fluorinated [5] rotaxane and its synthesis method and application. The present invention uses fluorinated crown ether as "wheel-shaped molecule" and 19 The F NMR signal source is based on a TPE molecule with four secondary ammonium salt cationic side chains as the "axis molecule" and a fluorescent molecule to develop a pH-sensitive 19 F MRI-FLI dual-modality imaging contrast agent. This contrast agent significantly improves the imaging performance by utilizing 144 equivalent fluorine atoms in four "wheel-shaped molecules" as well as the hydrogen bonding and fluorine effect within the molecule. 19 The sensitivity of F MRI and FLI is improved, and the response of the secondary ammonium salt in the molecule to different pH values ​​is used to achieve the supermolecular motion state and19 Regulation of contrast sensitivity in F MRI-FLI dual-modality imaging.

[0006] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0007] A fluorinated [5] rotaxane, comprising a fluorinated [5] rotaxane containing a hydrogen bond having the following general structural formula:

[0008]

[0009] or a fluorinated [5] rotaxane having a dehydrogenated bond comprising the following general structure:

[0010]

[0011] Among them, R is tert-butyl, trifluoromethyl or benzyloxy, R f trifluoromethyl, perfluorotert-butoxy or (CH2) n OC(CF3)3, n is a natural number not greater than 20, and F is fluorine-19.

[0012] A method for synthesizing a fluorinated [5]rotaxane comprises the following steps:

[0013] S1. Under alkaline conditions, 4-hydroxybenzaldehyde and 3-bromopropyne undergo Williamson ether synthesis reaction to produce a compound of formula (I), and the reaction formula is as follows:

[0014]

[0015] S2. In the absence of water and oxygen and in the presence of a reducing agent, the compound of formula (I) undergoes reductive amination with 4-(aminomethyl)benzyl alcohol to produce a compound of formula (II), as shown in the following reaction formula:

[0016]

[0017] S3. Under alkaline conditions, the compound of formula (II) undergoes an esterification reaction with di-tert-butyl dicarbonate to generate a tert-butyloxycarbonyl-protected compound of formula (III), the reaction formula of which is as follows:

[0018]

[0019] S4. Under an inert gas atmosphere, the compound of formula (III) undergoes Appel reaction with carbon tetrabromide and triphenylphosphine to generate a compound of formula (IV), the reaction formula of which is as follows:

[0020]

[0021] S5. Under alkaline conditions, tetrakis-(4-hydroxyphenyl)ethylene and the compound of formula (IV) undergo Williamson ether synthesis reaction to generate a compound of formula (V), the reaction formula of which is as follows:

[0022]

[0023] S6. The compound of formula (V) is first subjected to removal of the tert-butyloxycarbonyl group under acidic conditions, and then undergoes an ion exchange reaction with ammonium hexafluorophosphate to generate a compound of formula (VI). The reaction formula is as follows:

[0024]

[0025] S7. Under the conditions of an inert gas atmosphere and the presence of a catalyst, the fluorinated crown ether compound, the compound of formula (6) and the azide compound undergo a click reaction to generate a fluorinated [5] rotaxane containing a hydrogen bond, the reaction formula of which is as follows:

[0026] The synthesis method of fluorinated crown ether compounds and azide compounds refers to the method disclosed in the Chinese patent application "A fluorinated rotaxane molecule and its preparation method and application" (202311432346.4).

[0027]

[0028] S8. Under alkaline conditions, the hydrogen-bonded fluorinated [5] rotaxane undergoes a dehydrogenation reaction to generate a dehydrogenated fluorinated [5] rotaxane. The reaction formula is as follows:

[0029]

[0030] Furthermore, in step S1, the base is potassium carbonate, acetone is used as the reaction solvent, the reaction temperature is 60-80° C., the reaction time is 2-8 hours, and the molar ratio of 4-hydroxybenzaldehyde, 3-bromopropyne and potassium carbonate is 1.0:2.0-4.0:2.0-4.0.

[0031] Furthermore, in step S2, in the first condensation reaction, the additive is magnesium sulfate, the reaction solvent is anhydrous ethanol, the reaction temperature is 70-100°C, the reaction time is 12-30 hours, and the molar ratio of the compound of formula (I), 4-(aminomethyl)benzyl alcohol, and magnesium sulfate is 1.0:1.0:1.0-2.0; in the second reduction reaction, the reducing agent is sodium cyanoborohydride and its derivatives, the reaction solvent is tetrahydrofuran and methanol, the reaction temperature is 20-40°C, the reaction time is 12-24 hours, and the molar ratio of the compound of formula (I) to the reducing agent is 1.0:2.0-6.0.

[0032] Furthermore, in step S3, the base is sodium bicarbonate, the reaction solvent is a mixed solution of tetrahydrofuran and water, the reaction temperature is 20-40° C., the reaction time is 2-12 hours, and the molar ratio of the compound of formula (II), di-tert-butyl dicarbonate and sodium bicarbonate is 1.0:1.0-2.0:2.0-3.0.

[0033] Furthermore, in step S4, the reaction solvent is dichloromethane, the reaction temperature is 20-40° C., the reaction time is 2-12 hours, and the molar ratio of the compound of formula (III), carbon tetrabromide and triphenylphosphine is 1.0:2.0-3.0:2.0-3.0.

[0034] Furthermore, in step S5, the base is sodium hydride, the reaction solvent is N,N-dimethylformamide, the reaction temperature is 20-40° C., the reaction time is 12-24 hours, and the molar ratio of tetrakis-(4-hydroxyphenyl)ethylene, sodium hydride and the compound of formula (IV) is 1.0:5.0-8.0:4.0-5.0.

[0035] Furthermore, in step S6, in the first step of the reaction of removing the tert-butyloxycarbonyl protecting group, the acid is trifluoroacetic acid, the cation capture agent is anisole, the reaction solvent is dichloromethane, the reaction temperature is 20-40° C., the reaction time is 4-12 hours, and the molar ratio of the compound of formula (V), trifluoroacetic acid and anisole is 1.0:20.0-30.0:10.0-20.0; in the second step of the ion exchange reaction, the reaction solvent is a mixed solvent of acetone and water, the reaction reagent is a saturated aqueous solution of ammonium hexafluorophosphate, the reaction temperature is 20-40° C., the reaction time is 3-8 hours, and the molar ratio of the compound of formula (V) to ammonium hexafluorophosphate is 1.0:20.0-50.0.

[0036] Furthermore, in step S7, the solvent used for pre-stirring the compound of formula (VI) and the fluorinated crown ether is dichloromethane, the pre-stirring temperature is 40-60°C, and the pre-stirring time is 4-6 hours. The catalyst used in the subsequent click reaction is tetraethylcyanocopper (I) hexafluorophosphate, the azide compound is 3,5-tert-butylazidomethylbenzene, the reaction temperature is 20-40°C, the reaction time is 24-72 hours, and the molar ratio of the compound of formula (VI), the fluorinated crown ether, the catalyst and the azide compound is 1.0:5.0-7.0:4.0-6.0:6.0-9.0.

[0037] Furthermore, in step S8, the reaction solvent is dichloromethane, the base is sodium hydroxide, and the reaction temperature is 20-40°C.

[0038] Application of a fluorinated [5]rotaxane in the preparation of a dual-modality imaging contrast agent.

[0039] Furthermore, the dual-modality imaging is fluorescence imaging and fluorine-19 magnetic resonance imaging.

[0040] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0041] 1. The fluorinated [5] rotaxane of the present invention consists of two parts: the first part is a TPE molecule with a side chain, and the second part is a fluorinated crown ether molecule as a fluorine signal source. On the one hand, the spatial effect of the fluorine-containing crown ether on the rotaxane and the fluorine effect significantly affect the movement and aggregation behavior of TPE, which helps to adjust the intensity of fluorescence imaging; on the other hand, the hydrogen bonding between the fluorine-containing crown ether and the TPE mother core and the fluorine effect also significantly limit the movement state of the fluorine atoms on the fluorine-containing crown ether molecule, which helps to adjust and improve the T1 and T2 values ​​of fluorine-19, thereby achieving high sensitivity. 19 F MRI.

[0042] 2. The fluorinated [5]rotaxane of the present invention contains 144 magnetically equivalent fluorine-19 atoms, which can produce a single, strong and stable fluorine signal, significantly improving the sensitivity of fluorine-19 magnetic resonance spectroscopy or imaging.

[0043] 3. The hydrogen bonding within the fluorinated [5] rotaxane molecule of the present invention provides the molecule with significant pH responsiveness, which is beneficial to the realization of acid-base response. 19 F MRI and FLI.

[0044] 4. The synthetic route design of the fluorinated [5]rotaxane molecule of the present invention is relatively reasonable, the synthetic conditions are relatively mild, and the operation is simple, so the synthetic cost is relatively low and it has good practical application prospects.

[0045] 5. Within the fluorine concentration range of 36 mM to 2.25 mM, the fluorine signal of the fluorinated [5]rotaxane molecule of the present invention shows a good linear relationship with its concentration. This linear relationship facilitates the quantitative monitoring of the molecule in imaging applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The fluorinated [5] rotaxane 1 prepared in Example 1 19 F NMR spectrum.

[0047] Figure 2 The fluorinated [5] rotaxane 2 prepared in Example 2 19 F NMR spectrum.

[0048] Figure 3 for fluorinated [5] rotaxane 1, fluorinated [5] rotaxane 2 and fluorinated crown ether 19 F MRI comparison images.

[0049] Figure 4 The acid-base response of fluorinated [5]rotaxane 119 Comparison of F MRI and FLI.

[0050] Figure 5 This is the linear fitting diagram of the longitudinal relaxation rate of fluorinated [5] rotaxane 1 and fluorinated [5] rotaxane 2 versus temperature.

[0051] Figure 6 This is the linear fitting diagram of the transverse relaxation rate of fluorinated [5] rotaxane 1 and fluorinated [5] rotaxane 2 versus temperature.

[0052] Figure 7 This is a standard curve diagram of the fluorine concentration and imaging intensity of fluorinated [5] rotaxane 1 and fluorinated [5] rotaxane 2. DETAILED DESCRIPTION

[0053] The present invention is described in detail below with reference to specific embodiments.

[0054] Example 1

[0055] 1. Synthesis of Compound I:

[0056] To a round-bottom flask equipped with a magnetic rod, an acetone (250 mL) solution of 4-hydroxybenzaldehyde (10.00 g, 82.00 mmol), 3-bromopropyne (21.2 mL, 246.0 mmol) and potassium carbonate (34.0 g, 246.0 mmol) was added, followed by reflux reaction. After reflux for 4 hours, the mixture was cooled to room temperature and then quenched by adding water. The resulting mixed product was extracted three times with dichloromethane, and the organic phases were combined and dried over anhydrous magnesium sulfate. After dichloromethane was distilled off under reduced pressure, the residue was purified by column chromatography (eluent: petroleum ether and ethyl acetate) to give a light yellow solid (Compound I, 13.1 g) with a yield of 99%.

[0057] 1 H NMR (500MHz, CDCl3) δ9.85 (s, 1H), 7.80 (d, J = 8.8Hz, 2H), 7.04 (d, J = 8.8Hz, 2H), 4.74 (d, J = 2.4Hz, 2H), 2.57 (s, 1H).

[0058] 2. Synthesis of Compound II:

[0059] Under a nitrogen atmosphere, 4-(aminomethyl)benzyl alcohol (4.12 g, 30.00 mmol) and anhydrous magnesium sulfate (7.22 g, 60.00 mmol) were added to a solution of compound I (4.81 g, 30.00 mmol) in anhydrous ethanol (120 mL). The mixture was refluxed for 24 hours. After the reaction was complete, the ethanol in the resulting mixture was removed by rotary evaporation. The residue was then dissolved in a mixture of tetrahydrofuran (60 mL) and methanol (60 mL), and the reducing agent, sodium cyanoborohydride (7.54 g, 120.00 mmol), was slowly added in portions. After the addition of the reducing agent was completed, the resulting mixed solution was placed at room temperature and continued to react overnight. The reaction was then quenched with a saturated aqueous ammonium chloride solution, followed by extraction three times with ethyl acetate. The organic phases were combined and dried over anhydrous magnesium sulfate. The ethyl acetate was distilled off under reduced pressure, and the residue was purified by column chromatography (eluent: dichloromethane: methanol = 10:1, volume ratio) to give a light yellow oily liquid (Compound II, 5.32 g) with a yield of 63%.

[0060] 1 H NMR (500MHz, CDCl3) δ7.29(s,4H),7.25(d,J=8.6Hz,2H),6.94(d,J=8.6Hz,2H),4.68(d,J =2.4Hz,2H),4.63(s,2H),3.76(s,2H),3.73(s,2H),2.60(br,2H),2.52(t,J=2.4Hz,1H).

[0061] 13 C NMR (126MHz, CDCl3) δ156.9,140.1,138.8,132.5,129.7,128.6,127.3,115.0,78.7,75.7,65.0,56.0,52.7,52.4.

[0062] HRMS(ESI + )m / z:[M+H] + calculated for C 18 H 20 NO2 + ,282.1489;found,282.1490.

[0063] 3. Synthesis of Compound III:

[0064] A solution of Compound II (2.93 g, 10.41 mmol) in tetrahydrofuran (10 mL) and a solution of sodium bicarbonate (1.75 g, 20.82 mmol) in water (10 mL) were added to a round-bottom flask equipped with a magnetic rod. The resulting mixed solution was pre-stirred at room temperature for 10 minutes, and then di-tert-butyl dicarbonate (3.27 g, 15.00 mmol) was added and stirred at room temperature for 4 hours. After the reaction was completed, the white solid in the resulting mixed product was filtered off, the filtrate was collected, and vacuum concentrated. The concentrate was purified by column chromatography (petroleum ether: ethyl acetate = 2:1) to obtain a colorless oily liquid (Compound III, 3.51 g) with a yield of 88%.

[0065] 1 H NMR(500MHz, CDCl3)δ7.32(d,J=7.8Hz,2H),7.20-7.13(m,4H),6.93(d,J=8.7Hz,2H), 4.69-4.67(m,4H),4.38-4.26(m,4H),2.53(t,J=2.4Hz,1H),1.96(s,1H),1.49(s,9H).

[0066] 13 C NMR (126MHz, CDCl3) δ156.8,156.0,140.0,137.4,131.0,129.4,128.8,12 8.2,127.6,127.2,115.0,80.1,78.6,75.6,65.1,55.9,48.6,48.5,28.5.

[0067] HRMS(ESI + )m / z:[M+Na] + calculated for C 23 H 27 NO4Na + ,404.1832;found,404.1832.

[0068] 4. Synthesis of Compound IV:

[0069] Under a nitrogen atmosphere, to a solution of compound III (3.51 g, 9.20 mmol) in dichloromethane (30 mL) were added a solution of carbon tetrabromide (6.10 g, 18.40 mmol) and triphenylphosphine (4.83 g, 18.40 mmol) in dichloromethane (10 mL). The mixture was stirred uniformly, and the resulting mixed solution was stirred at room temperature for 4 hours. After completion of the reaction, the solvent was removed by rotary evaporation, and the residue was purified by column chromatography (petroleum ether:ethyl acetate = 5:1) to give a colorless oily liquid (compound IV, 2.37 g) in a yield of 58%.

[0070] 1 H NMR (500MHz, CDCl3) δ7.35 (d, J = 7.9 Hz, 2H), 7.20-7.13 (m, 4H), 6.93 (d, J = 8.6 Hz, 2H), 4. 69(d,J=2.4Hz,2H),4.50(s,2H),4.38-4.28(m,4H),2.53(t,J=2.4Hz,1H),1.49(s,9H).

[0071] 13 C NMR (126MHz, CDCl3) δ156.9,155.9,136.8,130.9,129.3,128.8,128.4,127.8,115.0,80.2,78.6,75.6,55.9,48.9,48.6,33.4,28.5.

[0072] HRMS(ESI + )m / z:[M+Na] + calculated for C 23 H 26 BrNO3Na + ,466.0988;found,466.0992.

[0073] 5. Synthesis of Compound V:

[0074] To a solution of tetrakis-(4-hydroxyphenyl)ethylene (45.1 mg, 0.11 mmol) in N,N-dimethylformamide (5 mL) was added sodium hydride (36.5 mg, 0.91 mmol, 60% in mineral oil) at 0°C and pre-stirred for 30 minutes. To the resulting mixed solution was then slowly added a solution of compound IV (227.4 mg, 0.51 mmol) in N,N-dimethylformamide (5 mL). The resulting mixed solution was stirred at room temperature overnight. After completion of the reaction, the resulting mixed product was washed with water (50 mL) and then extracted with ethyl acetate (2 x 30 mL). The organic phase was collected and dried over anhydrous magnesium sulfate, concentrated by distillation under reduced pressure, and the concentrate was purified by column chromatography (eluent: petroleum ether: ethyl acetate = 1:1, volume ratio) to give a white waxy solid (compound V, 200 mg) with a yield of 95%.

[0075] 1 H NMR (500MHz, CDCl3) δ7.39(d,J=7.7Hz,8H),7.26-7.16(m,16H),6.98(d,J=8.2Hz,8H),6.95(d,J=8.3Hz,8H),6. 76(d,J=8.3Hz,8H),4.98(s,8H),4.69(d,J=2.4Hz,8H),4.42-4.29(m,16H),2.53(t,J=2.4Hz,4H),1.51(s,36H).

[0076] 13 C NMR (126MHz, CDCl3) δ157.2,157.0,156.0,138.6,137.2,136.1,132.7,131.1,129.5,128.9,1 28.3,128.0,127.7,115.1,114.0,80.2,78.7,75.7,69.8,56.0,49.0,48.8,48.6,48.5,28.6.

[0077] HRMS(ESI + )m / z:[M+Na] + calculated for C 118 H 120 N4O 16 Na + ,1871.8592; found,1871.8612.

[0078] 6. Synthesis of Compound VI:

[0079] To a solution of compound V (1.0 g, 0.54 mmol) in dichloromethane was added trifluoroacetic acid (803.3 μL, 10.8 mmol) and anisole (587.0 μL, 5.4 mmol) at room temperature and stirred for 4 hours. After completion of the reaction, the resulting mixture was concentrated by rotary evaporation and then extracted with water (150 mL) and ethyl acetate (3 × 100 mL). The organic phase was collected, dried over anhydrous magnesium sulfate, and concentrated by vacuum distillation to yield a pale yellow solid.

[0080] The obtained light yellow solid was dissolved in 10 mL of acetone, and saturated aqueous ammonium hexafluorophosphate solution (5 mL) was added. The resulting mixture was stirred at room temperature for 5 hours. After the reaction was completed, the mixed product was concentrated, the concentrate was washed with water, and then extracted with ether. The obtained organic phase was air-dried to obtain a light yellow solid (Compound VI, 920.0 mg) with a yield of 84%.

[0081] 1 H NMR(500MHz,DMSO-d6)δ7.50(s,16H),7.43(d,J=8.4Hz,8H),7.05(d,J=8.4Hz,8H),6.89(d,J=8.4Hz,8H), 6.80(d,J=8.4Hz,8H),5.02(s,8H),4.83(d,J=2.4Hz,8H),4.14(s,8H),4.09(s,8H),3.57(t,J=2.4Hz,4H).

[0082] 13 C NMR (126MHz, DMSO-d6) δ157.6,156.6,138.1,137.7,136.5,132.0,131.4,130.0,128.1,124.9,115.0,114.0,79.1,78.4,68.8,55.4,49.8,49.7.

[0083] HRMS(ESI + )m / z:[M-4PF6 - ] 4+ calculated for C 98 H 92 N4O8 4+ ,363.1723;found,363.1761.

[0084] 7. Synthesis of fluorinated [5] rotaxane 1:

[0085] Under a nitrogen atmosphere, a dichloromethane solution of compound VI (200 mg, 0.098 mmol) and a fluorinated crown ether (850.1 mg, 0.59 mmol) was pre-stirred at 45°C for 4 hours. 3,5-tert-Butylazidomethylbenzene (193 mg, 0.79 mmol) and [Cu(CH3CN)4]PF6 (160.7 mg, 0.43 mmol) were then added and the reaction continued at room temperature for two days. After the reaction was complete, the mixture was diluted with dichloromethane (100 mL) and washed with water (3 × 100 mL). The organic phase was collected and dried over anhydrous magnesium sulfate, concentrated by distillation under reduced pressure, and purified by column chromatography (eluent: dichloromethane:methanol = 50:1) to obtain a white waxy compound (fluorinated [5] rotaxane 1, 361 mg) with a yield of 42%.

[0086] 1 H NMR(500MHz,CD3CN)δ7.85(s,4H),7.45-7.42(m,12H),7.37(d,J=8.4Hz,8H),7.26(d,J=7.9Hz, 8H),7.22-7.21(m,8H),7.04(d,J=7.9Hz,8H),6.93(d,J=8.6Hz,8H),6.85(d,J=8.6Hz,8H),6.83 (s,16H),6.66(d,J=8.4Hz,8H),5.51(s,8H),5.10-5.05(m,32H),5.01(s,8H),4.76-4.69(m,16H ),4.64-4.62(m,8H),4.11-4.04(m,32H),3.84-3.75(m,32H),3.69-3.63(m,32H),1.28(s,72H).

[0087] 19 F NMR (471MHz, CD3CN) δ -71.33 (s, 144F), -73.28 (d, J = 706.7Hz, 24F).

[0088] 13C NMR (126MHz, CD3CN) δ159.9,158.1,152.6,148.9,144.3,139.7,138.9,138.3,136.1,133.3,132.5,132.0,130.4,127.9,127.4,125.4,124.7,1 23.6,123.5,121.4(q,J=292.7,292.0Hz),115.9,115.0,114.6,81.3-80 .1(m),71.8,71.0,70.0,69.7,69.2,62.3,55.1,53.0,52.9,35.6,31.6.

[0089] MALDI-TOF-MS m / z:[M-4PF6 - -3H] + calculated for C 334 H 325 F 144 N 16 O 56 + ,8191.078;found,8192.009.

[0090] The structural formula of fluorinated [5] rotaxane 1 is as follows:

[0091]

[0092] Example 2

[0093] Synthesis of fluorinated [5] rotaxane 2:

[0094] The fluorinated [5]rotaxane molecule 1 (30.0 mg, 0.0034 mmol) was dissolved in 10 mL of dichloromethane solution, and sodium hydroxide aqueous solution (20 mL x 3) was added for repeated washing and separation. The organic phase was collected, dried over anhydrous magnesium sulfate, and concentrated by distillation under reduced pressure to obtain a white waxy compound (fluorinated [5]rotaxane 2, 27.7 mg) with a yield of 99%.

[0095] 1H NMR(500MHz,CD3CN)δ7.40(t,J=1.8Hz,4H),7.29-7.25(m,8H),7.22(d,J=7.7Hz,8H),7.17-7.13(m,12H),7.06-7.01(m,8H),6.95(s,16H),6.91- 6.89(m,16H),6.83(d,J=8.2Hz,8H),5.38-5.33(m,16H),5.11-5.05(s,4 0H),4.04-4.02(m,32H),3.65-3.58(m,48H),3.13(s,32H),1.23(s,72H).

[0096] 19 F NMR (471 MHz, CD3CN) δ-71.30.

[0097] 13 C NMR (126MHz, CD3CN) δ158.7,158.3,152.6,152.4,150.0,146.0,144.8,141.6,136.2,136.1,132.8,129.8,129.0,128.4,127.0 ,123.7,123.4,121.4(q,J=293.3Hz),115.7,115.0,82.0-79.4(m),70.3,70.1,69.5,62.9,54.9,53.3,53.1,52.0,35.5,31.6.

[0098] MALDI-TOF-MS m / z:[M+H] + calculated for C 334 H 325 F 144 N 16 O 56 + ,8191.078;found,8191.861.

[0099] The structural formula of fluorinated [5] rotaxane 2 is as follows:

[0100]

[0101] Fluorinated [5] rotaxane 1 was subjected to 19 F NMR spectrum analysis (internal standard: perfluorobenzene, δ-164.9), the obtained 19 F NMR spectrum Figure 1 As shown, the 144 equivalents on the fluorinated crown ether in the fluorinated [5] rotaxane 1 molecule have a single and strong signal peak at -71.33.

[0102] Fluorinated [5] rotaxane 2 19 F NMR spectrum analysis (internal standard: perfluorobenzene, δ-164.9), the obtained 19 F NMR spectrum Figure 2 As shown, the 144 equivalents on the fluorinated crown ether in the fluorinated [5] rotaxane 2 molecule have a single and strong signal peak at -71.30.

[0103] Experiment 1: In vitro 19 F MRI experiments

[0104] Experimental methods:

[0105] 1. Dissolve fluorinated [5] rotaxane 1, fluorinated [5] rotaxane 2 and fluorinated crown ether in acetonitrile respectively to prepare fluorinated [5] rotaxane 1 solution, fluorinated [5] rotaxane 2 solution and fluorinated crown ether solution with a concentration of 25 μM (compound concentration) to obtain three sample solutions.

[0106] 2. Transfer 2.5 mL of each sample solution to a 10 mm NMR sample tube and perform tuning and field shimming in a 400M magnetic resonance imaging spectrometer. 19 In the F MRI imaging experiment, the RARE sequence was used for data acquisition, with 64 repeated sampling, a sampling matrix of 32 × 32, and a scan time of 409 s. The other sampling parameters were set as follows: acceleration factor RARE factor = 4, repetition time TR = 800.0 ms, and echo time TE = 3 ms.

[0107] Experimental results:

[0108] Fluorinated [5] rotaxane 1 solution, fluorinated [5] rotaxane 2 solution and fluorinated crown ether solution at 25 μM concentration 19 F MRI images Figure 3 As shown. Figure 3 It can be seen that at a concentration of 25 μM, the fluorinated crown ether, fluorinated [5] rotaxane 2 and fluorinated [5] rotaxane 1 19 The FMRI imaging signal intensity gradually increases. This shows that restricting the motion of fluorine atoms in molecules can significantly improve their 19 F MRI imaging sensitivity.

[0109] Experiment 2: Acid-base response of fluorinated [5] rotaxane 1 and fluorinated [5] rotaxane 2 19 F MRI and FLI experiments

[0110] Experimental methods:

[0111] 1. Dissolve fluorinated [5]rotaxane 1 in 20 mL of chloroform to prepare a 25 μM fluorinated [5]rotaxane 1 solution (compound concentration). Remove 2.5 mL of the solution as sample 1. The remaining fluorinated [5]rotaxane 1 solution is then washed with a 1.0 M NaOH solution, the organic phase is collected, and 2.5 mL of the solution is removed as sample 2. The remaining organic phase is washed with 1.0 M hydrochloric acid, the organic phase is collected, and 2.5 mL of the organic phase is removed as sample 3. Finally, the remaining organic phase is washed with a 1.0 M NaOH solution, the organic phase is collected, and 2.5 mL of the organic phase is removed as sample 4.

[0112] 2. Transfer samples 1-4 into 10mm NMR sample tubes respectively and perform tuning and field shimming in a 400M magnetic resonance imaging spectrometer. 19 In the F MRI imaging experiment, the RARE sequence was used for data acquisition, with 64 repeated sampling, a sampling matrix of 32 × 32, and a scan time of 409 s. The other sampling parameters were set as follows: acceleration factor RARE factor = 4, repetition time TR = 800.0 ms, and echo time TE = 3 ms.

[0113] 3. Transfer samples 1-4 into cuvettes respectively and take a set of fluorescence photos under 365nm ultraviolet light.

[0114] Experimental results:

[0115] The concentration of 25 μM fluorinated [5] rotaxane 1 solution under acid-base response 19 F MRI and FLI images are shown in Figure 4 As shown by Figure 4 It can be seen that at a concentration of 25 μM, changing the pH can easily regulate the mutual conversion of fluorinated [5] rotaxanes 1 and 2, and adjust 19 F MRI signal intensity and fluorescence intensity.

[0116] Experiment 3: Experimental Study on the Relationship between the Relaxation Rate and Temperature of the Fluorinated [5] Rotaxane of the Present Invention

[0117] Experimental methods:

[0118] 1. Dissolve fluorinated [5]rotaxane 1 and fluorinated [5]rotaxane 2 in acetonitrile to prepare fluorinated [5]rotaxane 1 solution and fluorinated [5]rotaxane 2 solution, respectively, with a concentration of 1.0 mM (compound concentration).

[0119] 2. Transfer 0.5 mL of the fluorinated [5]rotaxane 1 solution prepared in step 1 to a 5 mm NMR sample tube and perform tuning and field shimming in a 400 M magnetic resonance imaging spectrometer. Determine T1 using the inversion recovery method and T2 using the CPMG method.

[0120] 3. The fluorinated [5] rotaxane 2 prepared in step 1 is processed according to the method of step 2.

[0121] Experimental results:

[0122] The linear relationship between the longitudinal relaxation rate and temperature of 1.0 mM fluorinated [5] rotaxane 1 solution and 1.0 mM fluorinated [5] rotaxane 2 solution is shown in the figure. Figure 5 As shown in the figure, the linear relationship between the transverse relaxation rate and temperature of the 1.0 mM fluorinated [5] rotaxane 1 solution and the fluorinated [5] rotaxane 2 solution is shown in the figure. Figure 6 As shown by Figure 5 and Figure 6 It can be seen that the relaxation rates of fluorinated [5]rotaxanes 1 and 2 both decrease with increasing temperature, and the two are in a linear relationship.

[0123] Experiment 4: Concentration of the fluorinated [5] rotaxane of the present invention and 19 F MRI signal intensity relationship experiment

[0124] Experimental methods:

[0125] 1. Fluorinated [5]rotaxane 1 was dissolved in acetonitrile to prepare solutions of fluorinated [5]rotaxane 1 with concentrations of 36.0, 18.0, 9.0, 4.5, and 2.25 mM (concentration of the compound). Fluorinated [5]rotaxane 2 was dissolved in acetonitrile to prepare solutions of fluorinated [5]rotaxane 2 with concentrations of 36.0, 18.0, 9.0, 4.5, and 2.25 mM (concentration of the compound).

[0126] 2. Take 2.5 mL of each concentration of fluorinated [5] rotaxane 1 solution prepared in step 1 and transfer it to a 10 mm NMR sample tube, and tune and homogenize it in a 400M magnetic resonance imaging spectrometer. 19 In the F MRI imaging experiment, the RARE sequence was used for data acquisition, with 64 repeated sampling, a sampling matrix of 32 × 32, and a scan time of 307 s. The other sampling parameters were set as follows: acceleration factor RARE factor = 4, repetition time TR = 600.0 ms, and echo time TE = 17.5 ms.

[0127] 3. Take the concentration lg function of fluorinated [5] rotaxane 1 as the horizontal axis and the concentration of fluorinated [5] rotaxane 1 as the horizontal axis. 19 The lg function of the FMRI signal intensity is used as the vertical coordinate. A plot is drawn based on the test data, and a standard curve is obtained after fitting.

[0128] 4. Operate each concentration of fluorinated [5] rotaxane 2 prepared in step 1 according to the method of steps 2-3.

[0129] Experimental results:

[0130] The concentration of fluorinated [5] rotaxane 1 and fluorinated [5] rotaxane 2 is related to 19 The standard curve of F MRI signal intensity is as follows Figure 7 As shown by Figure 7 It can be seen that at a fluorine concentration as low as 2.25 mM, obvious fluorine signals can still be seen, and the fluorinated [5] rotaxane 1 19 The F MRI signal intensity is higher than that of fluorinated [5]rotaxane 1. As can be seen from the standard curve, there is a good linear relationship between the fluorine concentration of fluorinated [5]rotaxane 1 and the corresponding fluorine signal intensity of fluorinated [5]rotaxane 2.

Claims

1. A fluorinated [5] rotaxane, characterized in that: The invention includes hydrogen-bonded fluorinated [5] rotaxanes of the following general structure: or a fluorinated [5] rotaxane having a dehydrogenated bond of the following general structure Among them, R is tert-butyl, trifluoromethyl or benzyloxy, R f trifluoromethyl, perfluorotert-butoxy or (CH2) n OC(CF3)3, n is a natural number not greater than 20, and F is fluorine-19.

2. A method for synthesizing a fluorinated [5] rotaxane, characterized in that The steps include: S1. Under alkaline conditions, 4-hydroxybenzaldehyde and 3-bromopropyne undergo Williamson ether synthesis reaction to produce a compound of formula (I), and the reaction formula is as follows: S2. In an anhydrous and oxygen-free atmosphere and the presence of a reducing agent, the compound of formula (I) undergoes reductive amination with 4-(aminomethyl)benzyl alcohol to produce a compound of formula (II), as shown in the following reaction formula: S3. Under alkaline conditions, the compound of formula (II) undergoes an esterification reaction with di-tert-butyl dicarbonate to generate a tert-butyloxycarbonyl-protected compound of formula (III), the reaction formula of which is as follows: S4. Under an inert gas atmosphere, the compound of formula (III) undergoes Appel reaction with carbon tetrabromide and triphenylphosphine to generate a compound of formula (IV), the reaction formula of which is as follows: S5. Under alkaline conditions, tetrakis-(4-hydroxyphenyl)ethylene and the compound of formula (IV) undergo Williamson ether synthesis reaction to generate a compound of formula (V), the reaction formula of which is as follows: S6. The compound of formula (V) is first subjected to removal of the tert-butyloxycarbonyl group under acidic conditions, and then undergoes an ion exchange reaction with ammonium hexafluorophosphate to generate a compound of formula (VI). The reaction formula is as follows: S7. Under the conditions of an inert gas atmosphere and the presence of a catalyst, the fluorinated crown ether compound, the compound of formula (VI) and the azide compound undergo a click reaction to generate a fluorinated [5] rotaxane containing a hydrogen bond, the reaction formula of which is as follows: S8. Under alkaline conditions, the hydrogen-bonded fluorinated [5] rotaxane undergoes a dehydrogenation reaction to generate a dehydrogenated fluorinated [5] rotaxane. The reaction formula is as follows:

3. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S1, the base is potassium carbonate, acetone is used as the reaction solvent, the reaction temperature is 60-80° C., the reaction time is 2-8 hours, and the molar ratio of 4-hydroxybenzaldehyde, 3-bromopropyne and potassium carbonate is 1.0:2.0-4.0:2.0-4.

0.

4. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S2, in the first condensation reaction, the additive is magnesium sulfate, the reaction solvent is anhydrous ethanol, the reaction temperature is 70-100° C., the reaction time is 12-30 hours, and the molar ratio of the compound of formula (I), 4-(aminomethyl)benzyl alcohol, and magnesium sulfate is 1.0:1.0:1.0-2.0; in the second reduction reaction, the reducing agent is sodium cyanoborohydride and its derivatives, the reaction solvent is tetrahydrofuran and methanol, the reaction temperature is 20-40° C., the reaction time is 12-24 hours, and the molar ratio of the compound of formula (I) to the reducing agent is 1.0:2.0-6.

0.

5. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S3, the base is sodium bicarbonate, the reaction solvent is a mixed solution of tetrahydrofuran and water, the reaction temperature is 20-40° C., the reaction time is 2-12 hours, and the molar ratio of the compound of formula (II), di-tert-butyl dicarbonate, and sodium bicarbonate is 1.0:1.0-2.0:2.0-3.

0.

6. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S4, the reaction solvent is dichloromethane, the reaction temperature is 20-40° C., the reaction time is 2-12 hours, and the molar ratio of the compound of formula (III), carbon tetrabromide and triphenylphosphine is 1.0:2.0-3.0:2.0-3.

0.

7. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S5, the base is sodium hydride, the reaction solvent is N,N-dimethylformamide, the reaction temperature is 20-40° C., the reaction time is 12-24 hours, and the molar ratio of tetrakis-(4-hydroxyphenyl)ethylene, sodium hydride, and the compound of formula (IV) is 1.0:5.0-8.0:4.0-5.

0.

8. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S6, in the first step of the de-tert-butyloxycarbonylation reaction, the acid is trifluoroacetic acid, the cation capture agent is anisole, the reaction solvent is dichloromethane, the reaction temperature is 20-40° C., the reaction time is 4-12 hours, and the molar ratio of the compound of formula (V), trifluoroacetic acid, and anisole is 1.0:20.0-30.0:10.0-20.0; in the second step of the ion exchange reaction, the reaction solvent is a mixed solvent of acetone and water, the reaction temperature is 20-40° C., the reaction reagent is a saturated aqueous solution of ammonium hexafluorophosphate, the reaction time is 3-8 hours, and the molar ratio of the compound of formula (V) to ammonium hexafluorophosphate is 1.0:20.0-50.

0.

9. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S7, the solvent used for pre-stirring the compound of formula (VI) and the fluorinated crown ether is dichloromethane, the pre-stirring temperature is 40-60° C., and the pre-stirring time is 4-6 hours; in the subsequent click reaction, the catalyst used is copper (I) tetraacetonitrile hexafluorophosphate, the azide compound is 3,5-tert-butylazidomethylbenzene, the reaction temperature is 20-40° C., the reaction time is 24-72 hours, and the molar ratio of the compound of formula (VI), the fluorinated crown ether, the catalyst, and the azide compound is 1.0:5.0-7.0:4.0-6.0:6.0-9.

0.

10. The method for synthesizing a fluorinated [5] rotaxane according to claim 2, wherein: In step S8, the reaction solvent is dichloromethane, the base is sodium hydroxide, and the reaction temperature is 20-40°C.

11. Use of the fluorinated [5]rotaxane according to claim 1 in the preparation of a dual-modality imaging contrast agent.

12. The use of the fluorinated [5] rotaxane according to claim 11, characterized in that: The dual-modality imaging is fluorescence imaging and fluorine-19 magnetic resonance imaging.

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