Myelin-specific magnetic resonance contrast agent and preparation method and application thereof

Abstract

The present invention relates to a myelin-specific magnetic resonance contrast agent, a preparation method and an application thereof. The contrast agent has a structure shown in Formula I: #imgabs0# wherein X is a linking group selected from -CO(CH2) n NH-, #imgabs1#; the NH end in the linking group X is connected to R, n, n1, n2, n3, n4, n5 are each independently an integer selected from 0-6, R1 is selected from C1-C6 alkyl or halogen, and R1 is ortho-, meta- or para-substituted; R is a Gd chelating group selected from #imgabs2#

Description

Technical Field

[0001] The invention belongs to the field of medical technology, and in particular relates to a myelin sheath-specific magnetic resonance contrast agent and a preparation method and application thereof. Background Art

[0002] The axons of vertebrate neurons are surrounded by a cell membrane composed of fatty tissue, called the myelin sheath, which plays a role in protecting the axons and facilitating impulse transmission. The formation of myelin is one of the most fundamental physiological processes in the vertebrate nervous system. Myelin pathology is present in many neurological diseases, such as multiple sclerosis (MS), traumatic spinal cord injury (SCI), and various leukodystrophies. Myelin damage is considered a major contributing factor in autoimmune diseases such as multiple sclerosis (MS), a disease in which myelin function degenerates. Disease may lead to a slowing of the transmission of information to the muscles and ultimately a loss of muscle control.

[0003] Magnetic resonance imaging (MRI) has become the main tool for diagnosing and monitoring the progression of MS and related diseases; however, changes in conventional MRI signal intensity only reflect changes in tissue water content and cannot distinguish demyelinating lesions from other inflammatory lesions. It has no guiding role in the degree of myelination and the prognosis of myelin regeneration. It is only a non-specific measurement of overall changes in macroscopic tissue damage. Special MRI functional sequences have reasons such as long imaging time and poor microscopic resolution, and cannot intuitively and accurately reflect changes in myelin.

[0004] Therapeutic interventions for myelin damage focus on protecting myelin integrity and promoting myelin repair, which requires direct detection and quantification of myelin content in vivo. However, histological probes used for myelin visualization are antibodies or charged histochemical reagents that do not enter the brain. Studies of myelin-specific MR contrast agents are based solely on Luxol Fast Blue (LFB), a histological stain with paramagnetic copper nuclei. However, LFB has low relaxivity, low solubility, and limited tissue permeability. Therefore, there is a need for an effective imaging tool that correlates disease progression with the degree of myelination, can easily enter the brain and selectively bind to myelinated areas, and has high relaxivity.

[0005] In order to solve the above problems, the present invention selects diphenyl substituted ethylene derivatives as myelin-specific compounds, gadopentetate dimeglumine and gadoteric acid dimeglumine as magnetic resonance contrast agent groups, and develops myelin-specific magnetic resonance contrast agents by optimizing the intermediate connecting arms to achieve the purpose of optimizing pharmacokinetics. Summary of the invention

[0006] The present invention provides a myelin-specific magnetic resonance contrast agent, characterized in that the contrast agent has a structure shown in Formula I:

[0007]

[0008] Wherein, X is a linking group selected from -CO(CH 2 ) n NH-, ; The NH end of the linking group X is connected to R, n, n 1 、n 2 、n 3 、n 4 、n 5 Each independently selected from an integer of 0-6, preferably 1, 2, 3, 4, 5, R 1 is selected from C1-C6 alkyl or halogen, R 1 is substituted at the ortho, meta or para position;

[0009] R is a Gd chelating group selected from

[0010] Another embodiment of the present invention provides a myelin-specific magnetic resonance contrast agent of the above formula I, characterized in that it is selected from the following compounds 6a-d, 12, 18a-b, 24a-d:

[0011]

[0012] Another embodiment of the present invention provides an intermediate II for synthesizing a myelin-specific magnetic resonance contrast agent of formula I, characterized in that the structure of the intermediate II is as follows:

[0013]

[0014] Wherein, X is a linking group selected from -CO(CH 2 ) n NH-, ; The NH end of the connecting group X and R 2 Connect, n, n 1 、n 2 、n 3 、n 4 、n 5 Each independently selected from an integer of 0-6, preferably 1, 2, 3, 4, 5, R 1 is selected from C1-C6 alkyl or halogen, R 1 Ortho and meta

[0015] The intermediate of formula II is selected from the following compounds 5a-d, 11, 17a-b, 23a-d:

[0016]

[0017] Another embodiment of the present invention provides use of the compound of formula I in the preparation of a myelin-specific magnetic resonance contrast agent.

[0018] Another embodiment of the present invention provides the use of the compound of formula I in the detection of myelin sheath damage.

[0019] The "C1-C6 alkyl" mentioned in the present invention is preferably methyl, ethyl, propyl, isopropyl, cyclopropyl, etc.; the "halogen" is preferably fluorine, chlorine, bromine, iodine. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the excitation wavelength (Em 370 ± 10 nm) emission wavelength (Ex 460 ± 10 nm) of compounds and 6a-d, 18a-b, 24a-d, 12 and MeDAS;

[0021] Figure 2 are T1WI images of compounds 6a-d, 18a-b, 24a-d, 12, Gd-DOTA and Gd-DTPA as their concentrations change;

[0022] Figure 3 is the relaxivity of compounds 6a-d, 18a-b, 24a-d, 12, Gd-DOTA, and Gd-DTPA;

[0023] Figure 4 are the metal transfer properties of compounds 18a, 18b, Gd-DOTA, and Gd-DTPA;

[0024] Figure 5 are the staining images of compounds 6a-d, 18a-b, 24a-d, and 12 in the brain area;

[0025] Figure 6 are the staining images of compounds 6a-d, 18a-b, 24a-d, and 12 in the cerebellum;

[0026] Figure 7 are the staining images of compounds 6a-d, 18a-b, 24a-d, and 12 in the spinal cord;

[0027] Figure 8 It is the staining image of compound 6a on the ischemic ipsilateral and contralateral side of the brain in the MCAO model group, and compared with commercial LFB;

[0028] Fig. 9 are the T1WI images of compound 18a before and after immersion in the rat control group and MCAO group;

[0029] Fig.10: After compound 18a was administered into the lateral ventricle of the rat control group and MCAO group, T1WI and T1 mapping images were scanned;

[0030] Fig.11 AB: MRI scan T1WI and T1mapping images after tail vein administration of compound 6a in MCAO mice; CD: in vivo fluorescence images of small animals in the MCAO control group and the MCAO tail vein administration group (from left to right, from top to bottom: brain, heart, liver, spleen, lung, and kidney).

[0031] The present invention is described in detail below through specific preparation examples and embodiments, but the use and purpose of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, nor limit the protection scope of the present invention to this. DETAILED DESCRIPTION

[0032] Example 1 Preparation of myelin-specific magnetic resonance contrast agents 6a-6d

[0033]

[0034] The myelin-specific magnetic resonance contrast agents 6a to 6d of the present invention can be prepared by the following general formula:

[0035] In summary, the preparation of the myelin sheath-specific magnetic resonance contrast agent linked by simple amino acids of the present invention comprises the following steps:

[0036] Dmedas undergoes acylation reaction with Boc-protected amino acids of different carbon chain lengths under the catalysis of a condensing agent, and the obtained product is freed from the Boc protecting group under trifluoroacetic acid to obtain the modified Dmedas.

[0037] Dmedas modified with amino acids of different carbon chain lengths under the catalysis of a condensation agent underwent acylation reaction with DTPA with a single carboxyl group exposed, and then the tert-butyl protecting group was removed under trifluoroacetic acid to expose four carboxyl groups. Three of the four carboxyl groups chelated with trivalent gadolinium ions, and compounds 6a to 6d were obtained after separation and purification.

[0038] The specific synthesis method is as follows:

[0039] In a 100mL conical flask, Boc-glycine (1.1g, 6.3mmol), HBTU (3.2g, 8.4mmol), DIPEA (3.66ml, 21mmol) were added in sequence and dissolved in DMF, stirred at room temperature for 0.5h, 1 (1g, 4.2mmol) was added, and stirred at room temperature overnight. After the reaction was completed by TLC detection, water was added to the reaction solution to quench, ethyl acetate was extracted, saturated brine was washed, dried over anhydrous magnesium sulfate, and silica gel column chromatography (PE:EA=30:1-2:1) was performed to collect the product brown-red solid 678mg, with a yield of 46%. That is compound 2a. MS (ESI): m / z: 396.22 [M+H] +

[0040] 1 H NMR (400MHz, DMSO) δ9.94(s,1H),7.56(d,J=8.6Hz,2H),7.46(d,J=8.6Hz,2H),7.40(d,J=8.8Hz,2H),7.02(d,J=11 .9Hz,1H),6.91(d,J=16.4Hz,1H),6.71(d,J=8.8Hz,2H),3.72(d,J=6.1Hz,2H),2.92(s,6H),1.39(d,J=7.5Hz,9H).

[0041] 13 C NMR (101 MHz, DMSO-d 6 )δ168.54,156.42,150.29,138.07,133.34,129.93,129.24,127.77,126.70,125.63,123.69,119.63,112.75,112.19,78.52,44.23,28.68.

[0042] The synthesis method of 2b~2d is the same as 2a, except that the Boc-glycine in the raw material is replaced with 4-Boc-aminobutyric acid, 5-Boc-aminovaleric acid, and 6-Boc-aminocaproic acid in sequence.

[0043] 2b, brown-red solid, yield 49%, MS (ESI): m / z: 424.25 [M+H] + , 1H NMR(400MHz,)δ9.87(s,1H),7.53(d,J=8.6Hz,2H),7.41(d,J=8.7Hz,2H),7.36(d,J=8.7Hz,2H),6.92(d,J=32.3Hz,2H),6.82( t,J=6.3Hz,1H),6.67(d,J=8.7Hz,2H),2.96–2.91(m,3H),2.88(s,6H),2.25(d,J=7.5Hz,2H),1.68–1.62(m,2H),1.34(s,8H). 13 C NMR(101MHz,)δ171.27,156.14,150.32,138.51,133.19,127.80,127.76,126.67,125.71,123.81,119.65,112.81,77.99,34.37,28.80,26.09.

[0044] 2c, brown-red solid, yield 47%, MS (ESI): m / z: 437.26, [M+H] + , 1 H NMR (400 MHz, DMSO-d 6 )δ9.90(s,1H),7.58(d,J=8.7Hz,2H),7.45(d,J=8.5Hz,2H),7.39(d,J=8.8Hz,2H),7.04–6.88(m,2H),6.84–6.77(m,1H),6.70(d,J=8 .9Hz,2H),2.94(d,J=7.5Hz,2H),2.92(s,6H),2.30(q,J=3.8Hz,2H),1.58(dd,J=7.5,2.8Hz,2H),1.42(t,J=3.7Hz,2H),1.38(s,9H).

[0045] 13 C NMR (101 MHz, DMSO-d 6 )δ171.51,156.06,150.25,138.49,127.74,126.61,125.66,123.76,119.61,1 12.74,77.81,38.70,36.88,36.56,29.84,29.66,28.74,26.52,25.38,22.99.

[0046] 2d, brown-red solid, yield 51%, MS (ESI): m / z: 452.28, [M+H] + , 1H NMR (400 MHz, DMSO-d 6 )δ9.91(s,1H),7.58(d,J=8.4Hz,2H),7.44(d,J=8.4Hz,2H),7.40(d,J=8.4Hz,2H),6.96(d,J=31.7Hz,2H),6.79(s,1H),6.7 1(d,J=8.5Hz,2H),2.92(s,6H),2.90–2.88(m,2H),2.32–2.28(m,2H),1.60(d,J=7.4Hz,2H),1.51–1.43(m,2H),1.37(s,9H).

[0047] 2a (678 mg, 1.78 mmol) was added to a 50 mL conical flask and dissolved in DCM. TFA was added under ice bath and the reaction was allowed to proceed overnight at room temperature. After the reaction was completed by TLC, the reaction solution was evaporated to dryness, 20 ml of dichloromethane was added and evaporated to dryness again. This was repeated three times to obtain 506 mg of a brown solid product. Compound 3a was obtained with a yield of 98%. MS (ESI): m / z: 296.1688 [M+H] + .

[0048] The synthesis methods of 3b~3d are the same as 3a, except that 2a in the raw material is replaced by 2b, 2c, and 2d respectively.

[0049] 3b, brown solid, yield 98%, MS (ESI): m / z: 324.20 [M+H] + .

[0050] 3c, brown solid, yield 97%, MS (ESI): m / z: 338.21 [M+H] + .

[0051] 3d, brown solid, yield 98%, MS (ESI): m / z: 352.23 [M+H] + .

[0052] In a 50mL conical flask, DTPA-3tBu (1.59g, 2.57mmol), HATU (1.3g, 3.43mmol), DIPEA (1.5ml, 8.58mmol) were added in turn and dissolved in DMF. The mixture was stirred at room temperature for 0.5h, and 3a (506mg, 1.72mmol) was added. The mixture was reacted overnight at room temperature. After TLC detection, the reaction solution was quenched with water, extracted with EA, washed with saturated brine, dried with anhydrous magnesium sulfate, and chromatographed on a silica gel column (DCM-DCM:MeOH=20:1). After separation, 100mg of the product brown-red oily liquid was collected, with a yield of 6.7%. That is compound 4a. MS (ESI): m / z: 895.54 [M+H] +

[0053] 1 H NMR (400 MHz, DMSO-d 6 )δ9.97(s,1H),8.37(s,1H),7.54(d,J=8.6Hz,1H),7.48–7.44(m,2H),7.40(d,J=8.8Hz,1H),7.2 3–7.18(m,1H),7.10–7.06(m,1H),6.96(d,J=30.6Hz,1H),6.73–6.70(m,1H),6.60–6.55(m,1H), 6.42–6.30(m,1H),3.91(t,J=5.7Hz,2H),3.40(d,J=3.1Hz,8H),3.10(d,J=3.9Hz,2H),2.92(s,2 H),2.74(dt,J=6.7,3.7Hz,4H),2.59(t,J=5.9Hz,4H),2.51–2.50(m,4H),1.39(d,J=4.2Hz,36H).

[0054] The synthesis methods of 4b~4d are the same as 4a, except that 3a in the raw material is replaced by 3b, 3c, and 3d respectively.

[0055] 4b. Brown-red oily liquid, yield 7%, MS (ESI): m / z: 923.57 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6)δ9.94(s,1H),7.58(d,J=8.4Hz,2H),7.44(d,J=8.5Hz,2H),7.39(d,J=8 .6Hz,2H),6.96(d,J=31.2Hz,2H),6.71(d,J=8.6Hz,2H),5.76(s,1H),3. 38(s,8H),3.16(d,J=6.8Hz,2H),3.04(s,2H),2.92(s,6H),2.71(s,4H), 2.54(d,J=6.6Hz,4H),2.30(s,2H),1.75(d,J=7.2Hz,2H),1.40(s,36H). 13 C NMR (101 MHz, DMSO-d 6 )δ171.09,170.69,127.72,127.64,126.56,125.67,123.78,119.58,112.73,80.71,55.93,53.41,52.01,38.48,34.54,28.23,26.06.

[0056] 4c. Brown-red oily liquid, yield 9%, MS (ESI): m / z: 937.59 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.88(d,J=5.2Hz,1H),7.59–7.55(m,2H),7.44(d,J=8.3Hz,2H),7.39(d,J=8.6 Hz,2H),7.04–6.88(m,2H),6.71(d,J=8.8Hz,2H),5.76(s,1H),3.36(d,J=6.5Hz, 10H),3.10(t,J=6.5Hz,2H),3.00(d,J=5.6Hz,2H),2.92(s,6H),2.68(d,J=6.7Hz ,4H),2.52–2.49(m,4H),2.30(t,J=7.1Hz,2H),1.62–1.56(m,2H),1.40(s,36H). 13 C NMR (101 MHz, DMSO-d 6 )δ170.69,127.72,127.65,126.58,125.67,123.77,119.58,112.75,80.71,55.92,55.38,53.44,52.05,36.86,28.24,28.15,25.38.

[0057] 4d. Brown-red oily liquid, yield 7%, MS (ESI): m / z: 951.60 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.86(s,1H),8.18(s,1H),7.55(s,2H),7.43(s,2H),7.39(d,J=5.0Hz,2H),6.99(s,2H),6.70(s,2H),3.62(s,2H),3.41(s,2H),3.37(s ,8H),3.13(d,J=7.8Hz,2H),3.10–3.08(m,2H),2.92(s,6H),2.69(s,4H),2.29(s,2H),1.58(d,J=7.5Hz,4H),1.46(s,2H),1.40(s,36H). 13 C NMR (101 MHz, DMSO-d 6 )δ170.66,127.73,127.66,126.59,123.77,119.58,119.17,112.75,80.70,55.9 1,54.05,53.48,52.07,42.30,36.85,28.24,26.64,25.37,18.54,17.18,12.97.

[0058] 4a (100 mg, 0.114 mmol) was added to a 50 mL conical flask and dissolved in DCM. TFA was added and the mixture was reacted overnight at room temperature. After the reaction was completed by TLC, the reaction solution was evaporated to dryness and methanol was added twice to obtain 5a 73 mg as a colorless oily liquid with a yield of 98%. MS (ESI): m / z: 669.29 [MH] - , 1 H NMR (400 MHz, DMSO-d 6 )δ10.18(s,1H),8.90(t,J=5.8Hz,1H),7.57(d,J=8.4Hz,2H),7.48(d,J=8.7Hz,2H),7.43(d,J=8.4Hz,2H),7.00(d,J=27.2Hz,2H),6 .79(d,J=8.4Hz,2H),4.28(s,2H),4.02(d,J=5.6Hz,2H),3.55(s,8H),3.41(s,2H),3.17(s,4H),3.10(d,J=5.9Hz,4H),2.95(s,6H).

[0059] 13 C NMR (101 MHz, DMSO-d6 )δ173.25,167.15,165.75,158.89,137.89,127.81,126.81,124.11,119.78,113.37,54.74,54.12,52.51,49.14,49.06,43.20,40.85.

[0060] The synthesis methods of 5b~5d are the same as 5a, except that 4a in the raw material is replaced by 4b, 4c, and 4d respectively.

[0061] 5b, colorless oily liquid, yield 98%, MS (ESI): m / z: 697.32 [MH] - .

[0062] 5c, colorless oily liquid, yield 99%, MS (ESI): m / z: 711.34 [MH] - .

[0063] 5d, colorless oily liquid, yield 98%, MS (ESI): m / z: 725.35 [MH] - .

[0064] In a 50 mL conical flask, 5a (19 mg, 0.023 mmol) was dissolved in MeOH / H 2 O (4:1) mixed solution, the pH was adjusted to 5.5-6 by pH meter, GdCl 3 6H 2 O (8 mg, 0.022 mmol) was dissolved in water and added dropwise to the above solution in four equal portions. The reaction was stirred at room temperature for 5 h and at 60 °C for 12 h. The mass spectrometry was confirmed. After the reaction was completed by TLC detection, the reaction solution was evaporated to dryness. After separation and purification, 6a 13 mg was obtained as a white powdery solid with a yield of 50%. HRMS: m / z[M+H] + calcdfor C 32 H 39 G JZ 6 O 10 ,826.1969,found 826.1977

[0065] The synthesis methods of 6b~6d are the same as 6a, except that 5a in the raw material is replaced by 5b, 5c and 5d respectively.

[0066] 6b, white powdery solid, yield 50%. HRMS: m / z[M+H] + Calculate for C 34 H 43 G JZ 6 O 10,85.24282,found 854.2285.

[0067] 6c, white powdery solid, yield 52%. HRMS: m / z [M+H] + Calculate for C 35 H 45 G JZ 6 O 10 ,868.2438,found 868.2444.

[0068] 6d, white powdery solid, yield 50%. HRMS: m / z[M+H] + Calculate for C 36 H 47 G JZ 6 O 10 ,882.2595,found 882.2588

[0069] Example 2 Preparation of myelin-specific magnetic resonance contrast agent 12

[0070] In summary, the preparation of the myelin-specific magnetic resonance contrast agent linked by triazole of the present invention comprises the following steps:

[0071] Dmedas undergoes an acylation reaction with 4-azido-1-butyric acid under the catalysis of a condensation agent to obtain DMedas modified by butyric acid.

[0072] Propargylamine undergoes an acylation reaction with DTPA with a single carboxyl group exposed under the catalysis of a condensation agent to obtain DTPA modified with a propynyl group.

[0073] After a click reaction between DMedas modified with butyric acid and DTPA modified with propynyl under the catalysis of cuprous iodide, the tert-butyl protecting group was removed under trifluoroacetic acid to expose four carboxyl groups. Three of the four carboxyl groups chelated with trivalent gadolinium ions and 12 was obtained after separation and purification.

[0074] The specific synthesis method is as follows:

[0075]

[0076] 7 (2 g, 3.24 mmol), propargylamine (150 uL, 2.16 mmol), PyBOP (2.25 g, 4.32 mmol), DIPEA (1.88 ml, 10.8 mmol) and DMF were added to a 50 mL conical flask in sequence, and the reaction was stirred overnight at room temperature. After the reaction was completed by TLC detection, the reaction solution was quenched with water, extracted with EA, washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated to obtain 2.16 g of a yellow oily liquid with a yield of 87%. It was used directly in the next step without purification. That is compound 8. MS (ESI): m / z: 655.42 [M+H] + , 1 HNMR (400 MHz, DMSO-d 6 )δ8.45(t,J=5.8Hz,1H),3.85(dd,J=5.8,2.5Hz,2H),3.37(s,8H),3.33(s,2H),3. 06(s,2H),2.89(s,1H),2.68(d,J=6.5Hz,4H),2.54(d,J=6.5Hz,4H),1.41(s,36H). 13 C NMR (101 MHz, DMSO-d 6 )δ170.62,80.69,72.70,58.38,55.91,53.38,52.07,28.26.

[0077] In a 50mL conical flask, 1 (1g, 4.2mmol), 4-azidobutyric acid (815mg, 6.3mmol), PyBOP (4.37g, 8.4mmol), DIPEA (3.66ml, 21mmol) were added in sequence and dissolved in DMF, and the reaction was stirred overnight at room temperature. After the reaction was completed by TLC detection, the reaction solution was quenched with water, extracted with EA, washed with saturated brine, dried over anhydrous magnesium sulfate, and chromatographed on a silica gel column (PE:EA=30:1-2:1), and 700mg of the product was collected, with a yield of 50%. That is, compound 9 was a red powdery solid. MS (ESI): m / z: 350.19 [M+H] + , 1 H NMR (400 MHz, DMSO-d 6 )δ9.99(s,1H),7.58(d,J=8.4Hz,2H),7.45(d,J=8.4Hz,2H),7.39(d,J=8.5Hz,2H),7.04–6.88(m,2H), 6.70(d,J=8.5Hz,2H),3.40(t,J=6.8Hz,2H),2.92(s,6H),2.41(t,J=7.3Hz,2H),1.85(p,J=7.0Hz,2H). 13C NMR (101 MHz, DMSO-d 6 )δ170.63,150.26,138.37,133.23,127.76,126.63,125.64,123.73,119.66,112.74,50.78,33.72,24.76.

[0078] In a 50 mL conical flask, 8 (281 mg, 0.43 mmol), 9 (75 mg, 0.215 mmol), CuI (8 mg, 0.04 mmol), and DIPEA (174 ul, 1 mmol) were added in sequence and dissolved in DMF. 2 The reaction was stirred at room temperature overnight under protection. After the reaction was completed by TLC, the reaction solution was evaporated to dryness, and the plate was scraped to collect 90 mg of solid with a yield of 42%. That is, compound 10 was a red oily liquid. MS (ESI): m / z: 1004.61 [M+H] + , 1 H NMR (400 MHz, DMSO-d 6 )δ9.98(s,1H),7.90(s,1H),7.57(d,J=8.3Hz,2H),7.50(s,1H),7.45(d,J=8. 6Hz,2H),7.40(d,J=8.7Hz,2H),6.96(d,J=32.1Hz,2H),6.72(d,J=8.9Hz,2H) ,4.39(d,J=6.9Hz,2H),4.35(s,2H),3.36(s,10H),2.93(s,6H),2.88(s,2H), 2.70(s,4H),2.34(q,J=6.6,6.0Hz,4H),2.11(d,J=4.5Hz,2H),1.39(s,36H). 13 C NMR (101 MHz, DMSO-d 6 )δ170.65,150.27,145.77,133.21,129.15,127.74,126.60,125.64,123.73,122.90,119.62, 119.53,112.75,80.69,58.48,55.87,53.35,52.03,49.27,34.70,34.59,33.34,28.23,26.15.

[0079] In a 50 mL conical flask, 10 (40 mg, 0.0399 mmol) was added in turn and dissolved in 10 ml DCM, and 6 ml TFA was added, and the mixture was shaken at room temperature for 5 h. After the reaction was completed by TLC, the reaction solution was evaporated to dryness, washed twice with methanol, and directly used for the next step. Compound 11 was obtained with a yield of 98%, and was a red oily liquid. MS (ESI): m / z: 778.36 [MH]-.

[0080] In a 50 mL conical flask, 11 (35 mg, 0.045 mmol) was dissolved in MeOH / H 2 O (4:1) mixed solution, the pH was adjusted to 5.5-6 by pH meter, GdCl 3 6H 2 O (16 mg, 0.0426 mmol) was dissolved in water and added dropwise to the above solution in four equal portions. The reaction was stirred at room temperature for 5 h and at 80 °C for 12 h. The mass spectrometry was used for confirmation. Post-treatment: The reaction solution was concentrated, purified by dialysis, and freeze-dried. 12 24 mg was obtained with a yield of 50%, as a green powdery solid. HRMS: m / z[M+H] + Calculate for C 37 H 46 G JZ 9 O 10 ,935.2609,found 935.2619.

[0081] Example 3 Preparation of myelin-specific magnetic resonance contrast agents 18a, 18b

[0082] In summary, the preparation of the myelin-specific magnetic resonance contrast agent linked by a substituted sulfonyl amidine group of the present invention comprises the following steps:

[0083] Dmedas undergoes a substitution reaction with propargyl bromide under base catalysis to obtain alkynyl-modified Dmedas. Alkynyl-modified Dmedas undergoes a three-component coupling reaction with para-substituted benzenesulfonyl azide and mono-Boc-protected propylenediamine under the catalysis of cuprous iodide to generate an intermediate with a sulfonyl amidine group. The intermediate removes the Boc protecting group under trifluoroacetic acid conditions, undergoes an acylation reaction with DOTA with a single carboxyl group exposed, and removes the tert-butyl protecting group under trifluoroacetic acid conditions to expose four carboxyl groups. Three of the four carboxyl groups chelate with trivalent gadolinium ions, and 18a to 18b are obtained after separation and purification.

[0084]

[0085] The specific synthesis method is as follows:

[0086]

[0087] In a 50 mL conical flask, 1 (2 g, 8.4 mmol) was added and dissolved in DMF, followed by 3-bromopropyne (1.5 g, 12.6 mmol) and DIPEA (4.4 mL, 25 mmol), and the mixture was stirred at room temperature for 5 to 6 h. After the reaction was completed by TLC, the mixture was quenched with water, extracted with EA, washed with saturated brine, dried over anhydrous magnesium sulfate, and chromatographed on a silica gel column: PE:EA = 10:1 to 5:1 to obtain 377 mg of 13 as a pink solid, with a yield of 37%. MS (ESI): m / z: 277.1624 [M+H] +

[0088] 1 H NMR (400 MHz, DMSO-d 6 )δ7.36–7.32(m,2H),7.32–7.28(m,2H),6.83(s,2H),6.71–6.68(m,2H),6.64–6.6 1(m,2H),6.10(t,J=6.2Hz,1H),3.88(dd,J=6.2,2.4Hz,2H),3.08(t,J=2.4Hz,1H). 13 C NMR (101 MHz, DMSO-d 6 )δ149.86,147.38,127.25,127.05,126.40,124.77,124.46,113.38,112.88,82.69,73.49,32.56.

[0089] In a 50 mL conical flask, N-tert-butyloxycarbonyl-1,3-propanediamine (94 mg, 0.54 mmol) was added in sequence and dissolved in DCM. Triethylamine was added and stirred at room temperature under nitrogen protection for 10 min. 13 (150 mg, 0.54 mmol), 4-fluorobenzenesulfonyl azide (128 mg, 0.65 mmol), and CuI (10.2 mg, 0.054 mmol) were added and stirred overnight. After the reaction was completed by TLC detection, appropriate amount of water and DCM were added to the reaction to dilute, and the reaction was stirred for 30 min. DCM extraction was performed, washed with saturated brine, dried over anhydrous magnesium sulfate, concentrated, and silica gel column chromatography: PE:EA = 30:1 to 1:1, and 240 mg of solid was obtained, which was a green oily liquid with a yield of 46%, namely compound 14a. MS (ESI): m / z: 625.29 [M+H] +

[0090] 1 H NMR (400 MHz, DMSO-d 6)δ8.67(t,J=5.3Hz,1H),7.72(d,J=8.2Hz,2H),7.33(t,J=8.2Hz,4H),7.28(d,J=8.3Hz,2H),6.82(s,2H),6.69(d,J=8.4Hz,2H),6.61(d,J=8 .3Hz,2H),5.87(t,J=5.9Hz,1H),3.14(q,J=6.6Hz,2H),2.93(d,J=6.8Hz,4H),2.90(s,6H),2.35(s,3H),1.59(q,J=6.9Hz,2H),1.37(s,9H). 13 C NMR (101 MHz, DMSO-d 6 )δ166.75,156.08,142.02,141.96,129.71,127.39,127.20,126.16,112.89,112.70,78.03,41.84,37.97,28.71,21.39.

[0091] The synthesis method of 14b is the same as 14a, except that 4-fluorobenzenesulfonyl azide in the raw material is replaced with p-toluenesulfonyl azide. 14b is a green oily liquid with a yield of 49%. MS (ESI): m / z: 620.31 [M+H] +

[0092] In a 50 mL conical flask, 14a (240 mg, 0.39 mmol) was added in sequence and dissolved in 7 ml of DCM, then 3 mL of TFA was added and stirred at room temperature overnight. TLC (DCM: MeOH = 10: 1). After the reaction was completed by TLC detection, the reaction solution was evaporated to dryness, triethylamine was added to adjust the pH to alkaline, and the reaction solution was concentrated and evaporated to dryness to obtain a brown-red oily liquid, namely compound 15a, with a yield of 95%. MS (ESI): m / z: 524.24 [M+H] +

[0093] The synthesis method of 15b is the same as 15a, except that 14a in the raw material is replaced by 14b. 15b is a green oily liquid with a yield of 96%. MS (ESI): m / z: 520.26 [M+H] +

[0094] 15a (182 mg, 0.351 mmol), DOTA-3tBu (301 mg, 0.526 mmol), HATU (266 mg, 0.701 mmol), DIPEA (305 uL, 1.75 mmol) were added to a 50 mL conical flask in sequence and dissolved in 5 ml DMF, and stirred at room temperature overnight. After the reaction was completed by TLC, the mixture was quenched with water, extracted with DCM, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, concentrated and evaporated, and chromatographed on a silica gel column: DCM: MeOH = 10:1. The plate was scraped to collect 74.5 mg of the product as a light yellow oily liquid, namely compound 16a, with a yield of 20%. MS (ESI): m / z: 1078.60 [M+H] +

[0095] 1 H NMR (400 MHz, DMSO-d 6 )δ8.77(t,J=5.3Hz,1H),7.72(s,2H),7.35(d,J=2.9Hz,2H),7.33(d,J=2.5Hz,2H) ,7.28(s,2H),6.82(s,2H),6.69(d,J=8.7Hz,2H),6.60(d,J=8.3Hz,2H),3.14(d,J= 6.2Hz,2H),3.08(d,J=6.1Hz,2H),2.90(s,6H),2.69(s,8H),2.37(s,3H),2.35(s, 2H),2.04–1.95(m,4H),1.62(t,J=6.9Hz,2H),1.42(d,J=4.1Hz,27H),1.38(s,9H).

[0096] The synthesis method of 16b is the same as 16a, except that 15a in the raw material is replaced by 15b. 16b is a light yellow oily liquid with a yield of 23%. MS (ESI): m / z: 1074.62 [M+H] +

[0097] 16a (124 mg, 0.156 mmol) was added to a 50 mL conical flask and dissolved in 10 mL TFA, and the mixture was stirred at room temperature for 3 h. After the reaction was completed by TLC, the reaction solution was evaporated to dryness to obtain compound 17a, which was a green oily liquid with a yield of 95%. MS (ESI): m / z: 908.42 [MH] -1 H NMR (600 MHz, DMSO-d 6)δ8.81(s,1H),8.49(s,1H),7.66(s,2H),7.33(s,2H),7.29(s,2H),7.24(s,2H),6.83(d,J=16.5Hz,2H),6.76(s,2H),6.56(s,2H), 4.03(s,4H),3.86(s,4H),3.34(s,8H),3.28(s,4H),3.14(s,4H),3.07(s,8H),2.89(s,6H),2.86(s,4H),2.31(s,3H),1.60(s,2H).

[0098] The synthesis method of 17b is the same as 17a, except that 16a in the raw material is replaced by 16b. 17b is a light yellow oily liquid with a yield of 95%. MS (ESI): m / z: 904.44 [MH] - .

[0099] 17a (20 mg, 0.022 mmol) was added to a 50 mL conical flask, dissolved in deionized water, and adjusted to pH 5. GdCl 3 6H 2 O (25 mg, 0.066 mmol) was dissolved in deionized water and added to the above solution in 4 portions, keeping the pH of the solution at 5.5-6, stirring the reaction at room temperature for 5 h, and then transferring to 60 ° C and stirring the reaction for 12 h. The reaction solution was cooled and centrifuged, and the supernatant was separated and collected to obtain a total of 4 mg of the product. That is, 18a 14 mg was a green powdery solid with a yield of 50%. HRMS: m / z [M+H] + Calculate for C 44 H 57 FWf 9 O 9 S,1065.3225,found 1065.3228.

[0100] The synthesis method of 18b is the same as 18a, except that 17a in the raw material is replaced by 17b. 18b is a white powdery solid with a yield of 50%. HRMS: m / z [M+H] + Calculate for C 45 H 60 G JZ 9 O 9 S,1061.3476,found1061.3476.

[0101] Example 4 Preparation of Myelin Specific Magnetic Resonance Contrast Agents 24a-24d

[0102]

[0103] In summary, the preparation of the myelin-specific magnetic resonance contrast agent linked by a substituted sulfonyl amidine group of the present invention comprises the following steps:

[0104] Dmedas undergoes a condensation reaction with acetylic acids of different carbon chain lengths under base catalysis to obtain alkynyl-modified Dmedas. Alkynyl-modified Dmedas undergoes a three-component coupling reaction with para-substituted benzenesulfonyl azide and mono-Boc-protected propylenediamine under the catalysis of cuprous iodide to generate an intermediate with a substituted sulfonyl amidine group. The intermediate removes the Boc protecting group under trifluoroacetic acid conditions, undergoes an acylation reaction with DTPA with a single carboxyl group exposed, and removes the tert-butyl protecting group under trifluoroacetic acid conditions to expose four carboxyl groups. Three of the four carboxyl groups chelate with trivalent gadolinium ions, and are separated and purified to obtain 24a-24d.

[0105] The myelin sheath-specific magnetic resonance contrast agents 24a-24d of the present invention can be prepared by the following general formula:

[0106]

[0107] The specific synthesis method is as follows:

[0108] In a 10 mL conical flask, 5-hexynoic acid (706 mg, 6.3 mmol), PyBOP (4.4 g, 8.4 mmol), and DIPEA (3.66 ml, 21 mmol) were dissolved in DMF in sequence, stirred at room temperature for 0.5 h, and 1 (1 g, 4.2 mmol) was added, and stirred at room temperature overnight. After the reaction was completed by TLC detection, water was added to the reaction solution to quench, ethyl acetate was extracted, saturated brine was washed, dried over anhydrous magnesium sulfate, and silica gel column chromatography (PE: EA = 30: 1-2: 1) was performed to collect 641 mg of the product as a yellow powdery solid with a yield of 46%. That is compound 19a. MS (ESI): m / z: 332.1899 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.97(s,1H),7.58(d,J=8.3Hz,2H),7.45(d,J=8.4Hz,2H),7.40(d,J=8.4Hz,2H),6.97(d,J=32.6Hz,2H),6.72(d,J=8.3H z,2H),2.93(d,J=1.3Hz,6H),2.84(d,J=2.4Hz,1H),2.43(t,J=7.4Hz,2H),2.24(td,J=7.1,2.7Hz,2H),1.80–1.74(m,2H). 13 C NMR (101 MHz, DMSO-d 6)δ170.90,150.26,138.41,133.18,127.75,126.63,125.67,123.76,119.64,112.77,84.52,72.15,35.57,24.42,17.87.

[0109] The synthesis method of 19b is the same as that of 19a, except that 5-hexynoic acid in the raw material is replaced by 6-heptynoic acid. 19b is a yellow powdery solid with a yield of 48%. MS (ESI): m / z: 346.18 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.92(s,1H),7.58(d,J=8.4Hz,2H),7.45(d,J=8.5Hz,2H),7.40(d,J=8.7Hz,2H),6.97(d,J=32.1Hz,2H),6.72(d,J=8 .6Hz,2H),2.93(s,6H),2.79(s,1H),2.33(s,2H),2.22–2.19(m,2H),1.68(d,J=7.7Hz,2H),1.50(dd,J=8.9,6.2Hz,2H). 13 C NMR (101 MHz, DMSO-d 6 )δ150.25,133.16,127.75,127.71,126.63,123.77,119.62,112.77,84.80,71.82,36.29,28.04,24.76,17.98.

[0110] In a 50 mL conical flask, N-tert-butyloxycarbonyl-1,3-propanediamine (52 mg, 0.3 mmol) was added in turn and dissolved in DCM. Triethylamine was added and stirred at room temperature under nitrogen protection for 10 min. 19a (100 mg, 0.3 mmol), 4-fluorobenzenesulfonyl azide (73 mg, 0.36 mmol), and CuI (6 mg, 0.003 mmol) were added and stirred overnight. After the reaction was completed by TLC detection, appropriate amount of water and DCM were added to the reaction to dilute, and the reaction was stirred for 30 min. DCM extraction was performed, the mixture was washed with saturated brine, dried over anhydrous magnesium sulfate, concentrated, and chromatographed on a silica gel column: PE:EA=30:1~1:1 to obtain 130 mg of a red oily liquid with a yield of 61%. Compound 20a. MS (ESI): m / z: 680.32 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6)δ9.93(s,1H),8.70(d,J=5.3Hz,1H),7.86(d,J=3.3Hz,2H),7.58(d,J=8.5Hz,2H),7. 45(d,J=8.6Hz,2H),7.40(d,J=8.7Hz,2H),7.32(d,J=8.8Hz,2H),6.93(s,1H),6.80(s ,1H),6.77–6.69(m,3H),3.35(s,2H),3.13(d,J=6.3Hz,2H),2.92(s,6H),2.90(d,J=4 .7Hz,2H),2.65(s,2H),2.30(s,2H),1.61(d,J=3.6Hz,2H),1.56(s,2H),1.36(s,9H). 13 C NMR (101 MHz, DMSO-d 6 )δ171.21,169.03,156.05,150.27,138.46,133.16,129.00,128.90,127.74,127.71,126.62,12 3.76,119.63,116.39,116.16,112.75,78.00,38.04,36.49,33.61,28.75,28.70,27.81,25.43.

[0111] The synthesis methods of 20b, 20c and 20d are the same as that of 20a, except that 19a in the raw material is replaced by 19b, 19c, 19d, and 4-fluorobenzenesulfonyl azide is replaced by p-toluenesulfonyl azide, 4-fluorobenzenesulfonyl azide and p-toluenesulfonyl azide, respectively.

[0112] 20b, red oily liquid, yield 64%. MS (ESI): m / z: 676.34 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6)δ9.93 (singlet, 1H), 8.59 (triplet, J = 5.4 Hz, 1H), 7.69 (singlet, 2H), 7.58 (doublet, J = 7.7 Hz, 2H), 7.47 (singlet, 2H), 7.40 (doublet, J = 8.5 Hz, 2H), 7.30 (doublet, J = 8.0 Hz, 2H), 6.97 (doublet, J = 31.5 Hz, 2H), 6.81 (singlet, 1H), 6.73–6.71 (multiplet, 2H), 3.36 (singlet, 2H), 3.12 (singlet, 2H), 2.93 (singlet, 6H), 2.91 (singlet, 2H), 2.63 (singlet, 2H), 2.35 (singlet, 3H), 2.31–2.29 (multiplet, 2H), 1.60 (singlet, 2H), 1.58 (singlet, 2H), 1.37 (singlet, 9H). 13 C NMR (101 MHz, DMSO-d 6 )δ171.23, 150.27, 142.17, 141.83, 133.15, 129.65, 127.74, 127.71, 126.62, 126.12, 125.66, 123.76, 119.63, 119.54, 112.75, 78.00, 37.92, 36.50, 33.43, 28.70, 27.82, 25.44, 22.58, 21.37.

[0113] 20c, red oily liquid, yield 65%. MS (ESI): m / z: 694.33 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.90 (singlet, 1H), 8.57 (triplet, J = 5.3 Hz, 1H), 7.68 (singlet, 2H), 7.58 (doublet, J = 8.2 Hz, 2H), 7.46 (doublet, J = 8.5 Hz, 2H), 7.39 (singlet, 2H), 6.97 (doublet, J = 31.6 Hz, 2H), 6.82 (triplet, J = 5.7 Hz, 1H), 6.72 (doublet, J = 8.5 Hz, 2H), 3.12 (singlet, 2H), 2.93 (singlet, 6H), 2.91 (singlet, 2H), 2.60 (singlet, 2H), 2.36 (singlet, 3H), 2.29 (singlet, 2H), 1.56 (singlet, 6H), 1.37 (singlet, 9H), 1.30 (doublet, J = 6.4 Hz, 2H). 13 C NMR (101 MHz, DMSO-d 6)δ150.26,142.21,141.84,133.12,129.65,127.74,127.69,126.63,126.13,125.67,12 3.77,119.59,119.50,112.76,78.02,37.94,36.71,33.46,29.01,28.70,25.21,21.37.

[0114] 20d, red oily liquid, yield 64%. MS (ESI): m / z: 690.36 [M+H] + . 1 H NMR (400 MHz, DMSO-d 6 )δ9.89(s,1H),8.66(s,1H),7.86–7.84(m,2H),7.57(d,J=8.5Hz,2H),7.46(s ,2H),7.41(s,2H),7.34(s,2H),6.96(d,J=31.5Hz,2H),6.80(t,J=4.1Hz,1H), 6.71(d,J=8.9Hz,2H),3.12(d,J=6.3Hz,2H),2.92(s,6H),2.90(d,J=4.6Hz,2 H),2.62(s,2H),2.30(s,2H),1.57(d,J=7.3Hz,6H),1.36(s,9H),1.31(s,2H). 13 C NMR (101 MHz, DMSO-d 6 )δ171.45,169.24,156.06,150.27,138.49,133.12,129.00,128.90,127.74,126.63,125.67,123.7 7,119.59,116.39,116.16,112.76,78.01,38.05,36.72,33.65,28.98,28.74,28.70,27.91,25.20.

[0115] In a 50 mL conical flask, 20a (130 mg, 0.19 mmol) was added in sequence and dissolved in 7 ml of DCM, then 3 mL of TFA was added and stirred at room temperature overnight. TLC (DCM: MeOH = 10: 1). After the reaction was completed by TLC detection, the reaction solution was evaporated to dryness, triethylamine was added to adjust the pH to alkaline, and the reaction solution was concentrated and evaporated to dryness to obtain a brown-red oily liquid with a yield of 96%, namely compound 21a. MS (ESI): m / z: 580.26 [M+H] + .

[0116] The synthesis methods of 21b, 21c and 21d are the same as those of 21a, except that 20a in the raw material is replaced by 20b, 20c, and 20d, respectively.

[0117] 21b, brown-red oily liquid, yield 97%. MS (ESI): m / z: 576.29 [M+H] + .

[0118] 21c, brown-red oily liquid, yield 96%. MS (ESI): m / z: 594.28 [M+H] + .

[0119] 21d, brown-red oily liquid, yield 97%. MS (ESI): m / z: 590.30 [M+H] + .

[0120] In a 50mL conical flask, DTPA-3tBu (1.05g, 1.71mmol), PyBOP (1.19g, 2.28mmol), DIPEA (0.93ml, 5.7mmol) were added in turn and dissolved in DMF, stirred at room temperature for 0.5h, 21a (400mg, 1.14mmol) was added, and the reaction was allowed to react overnight at room temperature. After TLC detection, the reaction solution was quenched with water, extracted with EA, washed with saturated brine, dried with anhydrous magnesium sulfate, and chromatographed on a silica gel column (DCM-DCM:MeOH=20:1), and then separated to collect 496mg of the product as a reddish brown oily liquid, with a yield of 37%. That is compound 22a. MS (ESI): m / z: 1179.64 [M+H] +

[0121] The synthesis methods of 22b, 22c and 22d are the same as that of 22a, except that 21a in the raw material is replaced by 21b, 21c, 21d in sequence.

[0122] 22b, reddish brown oily liquid, yield 39%, MS (ESI): m / z: 1175.67 [M+H] +

[0123] 22c, reddish brown oily liquid, yield 45%, MS (ESI): m / z: 1193.66 [M+H] +

[0124] 22d, reddish brown oily liquid, yield 44%, MS (ESI): m / z: 1189.68 [M+H] +

[0125] 22a (100 mg, 0.08 mmol) was added to a 50 mL conical flask and dissolved in DCM. TFA was added and the mixture was reacted at room temperature overnight. After the reaction was completed by TLC, the reaction solution was evaporated to dryness and methanol was added twice to obtain 23a98 as a red-brown oily liquid with a yield of 98%. MS (ESI): m / z: 953.39 [MH] -

[0126] The synthesis methods of 23b, 23c and 23d are the same as those of 23a, except that 22a in the raw material is replaced with 22b, 22c and 22d in sequence.

[0127] 23b, reddish brown oily liquid, yield 97%, MS (ESI): m / z: 949.42 [MH] -

[0128] 23c, reddish brown oily liquid, yield 96%, MS (ESI): m / z: 967.41 [MH] -

[0129] 23d, reddish brown oily liquid, yield 97%, MS (ESI): m / z: 963.43 [MH] -

[0130] In a 50 mL conical flask, 23a (100 mg, 0.10 mmol) was dissolved in MeOH / H 2 O (4:1) mixed solution, the pH was adjusted to 5.5-6 by pH meter, GdCl 3 6H 2 O (117 mg, 0.3 mmol) was dissolved in water and added dropwise to the above solution in four equal portions. The reaction was stirred at room temperature for 5 h and at 60 °C for 12 h. The mass spectrometry was confirmed. After the reaction was completed by TLC detection, the reaction solution was evaporated to dryness and separated. 24a 68 mg was obtained as a pink powdery solid with a yield of 50%. HRMS: m / z[M+H] + calcdfor C 45 H 56 FWf 8 O 12 S,1110.2963,found 1110.2967.

[0131] The synthesis methods of 24b, 24c and 24d are the same as that of 24a, except that 23a in the raw material is replaced by 23b, 23c and 23d respectively.

[0132] 24b, pink powdery solid, yield 47%. HRMS: m / z [M+H] + Calculate for C 46 H59 G JZ 8 O 12 S,1106.3214,found 1106.3219.

[0133] 24c, pink powdery solid, yield 53%. HRMS: m / z [M+H] + Calculate for C 46 H 58 FWf 8 O 12 S,1124.3120,found 1124.3125.

[0134] 24d, pink powdery solid, yield 55%. HRMS: m / z[M+H] + Calculate for C 47 H 61 G JZ 8 O 12 S,1120.3371,found 1120.3376

[0135] Example 5

[0136] 1. Fluorescence properties

[0137] Compounds 6a-d, 18a-b, 24a-d, 12 and MeDAS were prepared into PBS solution (2 ml, 10 μM), and the peak and range of excitation wavelength and emission wavelength were determined using a fluorescence spectrophotometer ( Figure 1 ).

[0138] 2. Magnetic resonance relaxation rate

[0139] Compounds 6a-d, 18a-b, 24a-d, 12, Gd-DTPA and Gd-DOTA dispersions (in PBS, pH = 7.0) with different Gd concentrations (0-0.8 mM) were placed in 300 μL centrifuge tubes and detected using a 7.0T MR imaging scanner (Biospec 70 / 20, Bruker, Germany). Scanning T1 weighted imaging: parameters TR / TE = 693 / 6ms. T1 inversion recovery fast spin echo sequence (T1_map_RARE) was performed. T1_map_RARE parameters: TE = 8.5ms, TR = 60-5500ms. By using the ParaVision 6.0.1 tool provided by Bruker, the same horizontal region of interest was selected in each sample, and the T1 relaxivities (r1) of compounds 6a-d, 18a-b, 24a-d, 12, Gd-DTPA and Gd-DOTA were obtained by curve fitting of 1 / T1 relaxation time (s-1).

[0140] The longitudinal proton relaxation times (T1) of compounds 6a-d, 18a-b, 24a-d, 12, Gd-DTPA and Gd-DOTA were determined to be similar to those of Gd 3+ Function of concentration. Figure 2 It shows that the MRI signal increases with the Gd 3+ The signal intensity increases with the increase of concentration, and the signal intensity changes from weak to strong. In the 7.0T MRI system, the longitudinal relaxation (r1) of contrast agents 6a-d, 24a-d, 12, 18a, and 18b can meet the requirements of MRI angiography ( Figure 3 ). Therefore, the experimental results show that the compounds synthesized by us have the potential to be effective contrast agents for T1-weighted MRI.

[0141] 3. Magnetic resonance metal transfer

[0142] At t = 0 min, 1 ml of 2.5 mM Gd complex was added to phosphate buffer (pH = 7.0, 50 mM) and 10 μl of 250 mM ZnCl 2 The aqueous solution was mixed to prepare the gadolinium complex sample. A little turbidity appeared, and 0.3 ml was taken for measurement after stirring (homogenization). Note that some zinc phosphate precipitation may appear in the 0.3 ml sample. The scanning parameters were the same as above. The diamagnetic contribution of proton water relaxation was subtracted from the observed relaxation rate (1 / T1) to obtain the change in relaxation rate over time.

[0143] like Figure 4 As shown, compounds 18a, 18b and Gd-DOTA are macrocyclic contrast agents, so under the condition of zinc chloride, no precipitation will occur over time, and therefore, the relaxation rate will not decrease. However, the linear contrast agent compound Gd-DTPA will decrease its relaxation rate over time, but it can still be used for MNR imaging.

[0144] 4. Dyeing

[0145] The myelinated brain tissues (cerebrum, cerebellum, spinal cord) of mice were soaked in paraformaldehyde for 24 hours, and then sequentially immersed in 10%, 20%, and 30% sucrose gradient for dehydration, and then embedded in OCT to make frozen sections. Compounds 6a-d, 18a-b, 24a-d, and 12 were incubated with them for 30 minutes, washed with PBS for 10 minutes, and then placed under confocal imaging.

[0146] like Figure 5 As shown, the compounds showed clear fluorescence in the myelinated corpus callosum and striatum, and were clearly distinguished from the non-myelinated areas. This was not only applicable to the brain, but also to the cerebellum and spinal cord, indicating that our compounds have a good ability to target myelin.

[0147] 5. Myelin damage staining in MCAO model of ischemic stroke

[0148] On the same side of the ischemic stroke, the myelin sheath is severely damaged, and the fluorescence intensity of compound 6a is low. On the other side of the ischemic stroke, the myelin sheath is not damaged, the myelin sheath structure is clearly visible, and the fluorescence intensity is strong. When compared with commercial LFB staining, similar results were found, indicating that compound 6a can distinguish the site of myelin damage.

[0149] 6. In vitro MRI immersion experiment

[0150] The brain tissues of rats and mice in the control group and the MCAO group were cut into 2 mm thick slices, immersed in PBS solutions of compound 18a and compound 6a for 24 h (5 mM, 1 ml), and then washed with PBS solution for seven days, with the PBS solution replaced once a day. T1WI scans were performed before and after immersion.

[0151] The contrast of myelin sheath in the control group after immersion was clearer than that before immersion, and the distribution was symmetrical on the left and right. The signal intensity of the striatum in the MCAO group after immersion increased, indicating that the myelin sheath in this area was damaged. Compounds 18a and 6a can clearly identify the damaged myelin sheath under magnetic resonance conditions.

[0152] 7. In vivo MRI imaging

[0153] Intraventricular administration

[0154] The rat was fixed on a brain stereotaxic apparatus, a 3 cm longitudinal incision was made on the head skin, and then a circular incision was made at the bregma (AP = ±1.5 mm, ML = 0.5 mm, DV = 4.3 mm) using a dental drill, and 5 μl, 7 mM compound 18a was injected on both sides.

[0155] like Fig.10 As shown, compared with before administration, the whole brain T1WI image signal of the control group after administration decreased, the signal of the myelin sheath was even lower, and the T1 mapping image showed a clearer resolution of the myelin sheath. In the MCAO group, the T1WI signal on the injured side was slightly higher, and T1mapping showed that the relaxation time of the striatum on the injured side did not decrease. This shows that the compound of the present invention can bind to the myelin sheath in rats and be monitored by magnetic resonance.

[0156] 8. Tail vein administration

[0157] Compound 6a was prepared into a concentration of 40 mg / kg and injected into mice through the tail vein. After scanning the magnetic resonance T1WI and T1mapping sequences, the mice were killed for small animal in vivo fluorescence imaging (430 nm, 500 nm).

[0158] Compared with before administration, the TIWI signal of mice decreased after tail vein administration, and the signal on the side of cerebral infarction increased. T1mapping showed that the contrast of the uninjured side of the myelin sheath was more obvious. The fluorescence of small animal living fluorescence showed that there was fluorescence on the side of cerebral infarction, while no fluorescence was seen in other parts of the heart, liver, spleen, lung and kidney. This shows that our compound 6a can circulate through the tail vein and bind to the myelin sheath in the skull through the side of the blood-brain barrier damaged by cerebral infarction. It was also monitored by MRI and small animal living fluorescence.

Claims

1. A myelin-specific magnetic resonance contrast agent, characterized in that The contrast agent has a structure shown in Formula I: Wherein, X is a linking group selected from -CO(CH2) n NH-, ; The NH end of the linking group X is connected to R, n, n1, n2, n3, n4, n5 are each independently selected from integers of 0-6, R1 is selected from C1-C6 alkyl or halogen, and R1 is substituted at the ortho, meta or para position; R is a Gd chelating group selected from 2. The myelin-specific magnetic resonance contrast agent of claim 1, characterized in that n, n1, n2, n3, n4, n5 are each independently selected from 1, 2, 3, 4, 5, and R1 is selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, fluorine, chlorine, bromine, and iodine.

3. The myelin-specific magnetic resonance contrast agent according to any one of claims 1 to 2, characterized in that Selected from the following compounds 6a-d, 12, 18a-b:

4. A myelin-specific magnetic resonance contrast agent, characterized in that The contrast agent has the structure shown in compound 24a-d:

5. An intermediate II for synthesizing the myelin-specific magnetic resonance contrast agent according to any one of claims 1 to 3, characterized in that The structure of intermediate II is as follows: Wherein, X is a linking group selected from -CO(CH2) n NH-, The NH end of the linking group X is connected to R2, n, n1, n2, n3, n4, and n5 are each independently selected from integers of 0 to 6, R1 is selected from C1-C6 alkyl or halogen, and R1 is substituted at the ortho, meta, or para position; R2 is selected from 6. The intermediate II according to claim 5, characterized in that n, n1, n2, n3, n4, and n5 are each independently selected from 1, 2, 3, 4, and 5.

7. The intermediate II according to any one of claims 5 to 6, characterized in that Selected from the following compounds 5a-d, 11, 17a-b:

8. An intermediate for synthesizing the myelin-specific magnetic resonance contrast agent according to claim 4, characterized in that The intermediate has the structure shown in compound 23a-d:

9. Use of the myelin sheath-specific magnetic resonance contrast agent according to any one of claims 1 to 4 in the preparation of a myelin sheath-specific magnetic resonance contrast agent.

10. Use of the myelin-specific magnetic resonance contrast agent according to any one of claims 1 to 4 in the preparation of a drug for detecting myelin damage.

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