Ocean cyclopeptide as well as synthesis method and application thereof

Abstract

The invention belongs to the technical field of medicine research, and particularly relates to a marine cyclopeptide as well as a synthesis method and application thereof. The structural formula of the marine cyclopeptide is shown as a formula I in the specification. Compared with natural Galaxamide, the D-leucine-containing Galaxamide analogue provided by the invention has a greater inhibition effect on human cancer cells, and the more the number of introduced D-leucine is, the stronger the anticancer activity is. Meanwhile, other amino acids are used for replacing one L-leucine in the Galaxamide, and the synthesized Galaxamide derivative is more effective than natural Galaxamide and has the potential of inhibiting proliferation of human cancer cell lines HepG2, U87 and MCF-7; and # imgabs0 #.

Description

Technical Field

[0001] The invention belongs to the technical field of drug research, and specifically relates to a marine cyclic peptide and a synthesis method and use thereof. Background Art

[0002] Chemotherapy is one of the important methods for treating cancer, but most anti-tumor drugs have drug resistance. During the anti-tumor treatment process, the phenomenon that tumor cells are insensitive to anti-tumor drugs is called drug resistance. The emergence of anti-tumor drug resistance is one of the main reasons for the failure of cancer chemotherapy and one of the key issues facing cancer treatment. From the perspective of tumor cells, the mechanism of drug resistance may be the heterogeneity of tumor cells, changes in drug transport and metabolism, changes in the expression level of drug targets, activation of alternative pathways, epigenetic changes, epithelial-mesenchymal transition, etc. From the perspective of the tumor microenvironment, the occurrence of drug resistance is also closely related to other cells and components such as infiltrating immune and inflammatory cells, cancer-associated fibroblasts, and vascular endothelial cells in the tumor microenvironment.

[0003] Tumor resistance is common in small molecule targeted anticancer drugs, and it is challenging to design new small molecule drugs targeting their resistance mechanisms. Among the many strategies to deal with antitumor drug resistance, one of the most valuable strategies is to continuously screen and discover new drugs, interfere with specific signaling pathways of tumor growth, inhibit tumor cell proliferation, and improve treatment effects. After the tumor becomes resistant, there are new drugs that can be replaced, new drugs that can be used for combined or alternating treatments, and even new drugs that can reverse resistance, which is an important way to fight tumors and antitumor resistance. Therefore, new antitumor drugs are urgently needed to be discovered.

[0004] Galaxamide is a new marine cyclic peptide with anti-tumor activity and has the potential to become a new anti-cancer drug. Its unique chemical structure and pharmacological properties provide new research ideas and potential drug options for cancer treatment. However, Galaxamide still has the disadvantages of low anti-tumor activity and lack of broad-spectrum anti-tumor activity. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a marine cyclic peptide The specific technical solutions provided by the present invention are as follows: The present invention provides a marine cyclic peptide, the structural formula of which is shown in Formula 1: ; Among them, R is selected from D-leucine, D-proline, D-phenylalanine, L-valine, glycine, D-alanine, O-methyl-D-serine, O-methyl-D-tyrosine, methyl ester-D-aspartic acid, 3-fluoro-D-phenylalanine, 2-methyl-D-phenylalanine, 4-chloro-D-phenylalanine, 4-bromo-D-phenylalanine, D-cyclohexyl-glycine, D-phenyl-glycine, D-valine, D-methionine, 3-methyl-D-phenylalanine, and 4-methyl-D-phenylalanine; R2 to R5 are each independently selected from D-leucine or L-leucine.

[0006] As a preferred embodiment of the present invention, the structural formula of the marine cyclic peptide is shown as any of the following:

[0007]

[0008]

[0009]

[0010] 。

[0011] The present invention also provides a method for synthesizing the marine cyclic peptide, comprising the following steps: Performing a nitrogen methylation reaction with N-(tert-butoxycarbonyl)-L-leucine as a raw material to obtain Boc-N-methyl-L-leucine, or performing a nitrogen methylation reaction with N-(tert-butoxycarbonyl)-D-leucine as a raw material to obtain Boc-N-methyl-D-leucine; Performing a condensation reaction with the Boc-N-methyl-L-leucine and L-leucine benzyl ester p-toluenesulfonate as raw materials to obtain a dipeptide; or performing a condensation reaction with Boc-N-methyl-D-leucine and D-leucine benzyl ester p-toluenesulfonate as raw materials to obtain a dipeptide; Performing hydrogenation reduction on the dipeptide to remove its C-terminal benzyl group to obtain product D; Performing acid hydrolysis on the dipeptide to remove its N-terminal tert-butoxycarbonyl group to obtain product E; Mixing the product E with an amino acid to perform a condensation reaction to obtain a tripeptide, and removing the N-terminal Boc group to obtain product G; Mixing the product D and the product G to perform a condensation reaction to obtain a linear pentapeptide; sequentially removing the C-terminal benzyl group and the N-terminal Boc group of the linear pentapeptide to obtain product J; Performing a macrolactamization reaction on the product J to obtain the marine cyclic peptide.

[0012] As a preferred embodiment of the present invention, the molar ratio of Boc-N-methyl-L-leucine to L-leucine benzyl ester p-toluenesulfonate, or the molar ratio of Boc-N-methyl-D-leucine to D-leucine benzyl ester p-toluenesulfonate is 1:1 to 2; the mixed molar ratio of product E to amino acid is 1:1 to 2; the molar ratio of product D to product G is 1:1 to 2.

[0013] As a preferred embodiment of the present invention, the N-methylation reaction is stirred at -20 to -10 °C for 30 min to 60 min, and then stirred at room temperature for another 12 h to 18 h; the condensation reaction of Boc-N-methyl-L-leucine and L-leucine benzyl ester p-toluenesulfonate, or the condensation reaction of Boc-N-methyl-D-leucine and D-leucine benzyl ester p-toluenesulfonate is carried out at 0 °C to 10 °C for 6 h to 12 h; the hydrogenation reduction reaction at the C-terminus of the dipeptide is carried out at 10 °C to 20 °C for 6 h to 12 h under the action of catalyst palladium; the acid hydrolysis reaction at the N-terminus of the dipeptide is carried out at -20 °C to -10 °C for 6 h to 12 h; the condensation reaction of product E and amino acid is carried out at 0 °C to 10 °C for 6 h to 12 h; the condensation reaction of product D and product G is carried out at 0 °C to 10 °C for 6 h to 12 h; the macrocyclic lactamization reaction is carried out at 0 °C to 10 °C for 12 h to 24 h under the action of a coupling agent.

[0014] As a preferred embodiment of the present invention, the coupling agent is selected from 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate, propanephosphonic anhydride, diphenylphosphoryl azide, pentafluorophenyl diphenylphosphinate or (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate.

[0015] More preferably, the coupling agent is selected from (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate.

[0016] The present invention also provides the use of the marine cyclic peptide in the preparation of anti-cancer drugs.

[0017] As a preferred embodiment of the present invention, the anti-cancer effect is the inhibitory effect on non-small cell lung cancer, chronic myeloid leukemia, breast cancer, liver cancer, glioma, and immortalized embryonic kidney cells.

[0018] The present invention also provides an anti-cancer drug, which uses the marine cyclic peptide as the sole active ingredient.

[0019] As a preferred embodiment of the present invention, the drug is composed of the marine cyclic peptide and pharmaceutically acceptable excipients.

[0020] As a preferred embodiment of the present invention, the drug is an oral preparation or an injection preparation.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention designs and synthesizes two series of Galaxamide derivatives. The first series mainly involves changing L-leucine to D-leucine and varying the position and number of D-leucine. The second series includes replacing one L-leucine in Galaxamide with other amino acids, such as D-proline, D-phenylalanine, L-valine, glycine, D-alanine, O-methyl-D-serine, O-methyl-D-tyrosine, methyl ester-D-aspartic acid, 3-fluoro-D-phenylalanine, 2-methyl-D-phenylalanine, 4-chloro-D-phenylalanine, 4-bromo-D-phenylalanine, D-cyclohexyl-glycine, D-phenyl-glycine, D-valine, D-methionine, 3-methyl-D-phenylalanine, and 4-methyl-D-phenylalanine. On the one hand, compared with natural Galaxamide, Galaxamide analogs containing D-leucine exhibit greater inhibitory effects on human cancer cells. The more D-leucine introduced into Galaxamide, the stronger the anti-cancer activity. The analog containing four D-leucines shows the strongest apoptosis-inducing effect on various human cancer cell lines such as HepG2, MCF-7, SW480, and U87. On the other hand, by replacing one L-leucine in Galaxamide with other amino acids, the synthesized Galaxamide derivatives are more effective than natural Galaxamide and have the potential to inhibit the proliferation of human cancer cell lines HepG2, U87, and MCF-7.

[0022] The key step in preparing Galaxamide derivatives in the present invention is macrocyclic lactamization. The present invention conducts a preliminary analysis on the peptide coupling agents for the macrocyclic lactamization of intermediate J to produce Galaxamide derivatives: The reaction conversion rate of 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate and propanephosphonic anhydride is poor, while using diphenylphosphoryl azide and pentafluorophenyl diphenylphosphinate produces medium yields of macro-lactamization reactants, and (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate mainly produces the expected product, the marine cyclic peptide. When using a lower concentration of acetonitrile as the solvent and adding (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate and 4-dimethylaminopyridine, the dilution of the reaction solution reduces the formation of dimer products, and the yield reaches 50%. In addition, by slowly adding intermediate J within 4 h to simulate a highly diluted environment, this can prevent the generation of dimers and make the solvent concentration closer to the real reaction concentration. Detailed implementation manners

[0023] The raw materials involved in the embodiments of the present invention are abbreviated as follows: HATU: 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate; T3P: propanephosphonic anhydride; DPPA: diphenylphosphoryl azide; FDPP: pentafluorophenyl diphenylphosphinate; PyBOP: (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate; DMAP: 4-dimethylaminopyridine; CH3CN: acetonitrile; EtOAc: ethyl acetate; n-Hexane: n-hexane; Hexane: cyclohexane. The CAS number of 10% Pd / C is 7440-05-3.

[0024] Example 1 Cyclo(Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu) (1)N-Boc-Me-L-Leu-OH Take 9.0 g, 38.9 mmol of L-leucine, 25 g, 177.3 mmol of CH3I, and 5.5 g, 137.5 mmol of NaH dispersed in mineral oil. After mixing, stir at -10 °C for 30 min, and then stir at room temperature for another 18 h. Quench with 50 ml of aqueous solution, and wash the mixture with ethyl acetate. Thereafter, acidify the aqueous solution to pH = 2 with 1N HCl solution and extract with ethyl acetate. The obtained ethyl acetate extract is dried over Na2SO4, filtered and evaporated to obtain 9.0 g, 36.7 mol of colorless oily B2, namely N-Boc-Me-L-Leu-OH, with a yield of 94%, and the structural formula is as follows: 。

[0025] (2)N-Boc-Me-L-Leu-L-Leu-OBn. React 10.0 g, 40.8 mmol of B2 with 17.6 g, 44.9 mmol of L-leucine benzyl ester p-toluenesulfonate, 6.0 g, 44.9 mmol of HOBt, and 8.5 g, 44.9 mmol of EDCI at 0 °C for 12 h to synthesize C2. Use a mixture of n-hexane and ethyl acetate in a volume ratio of 90:10 as the elution solvent, and purify the crude product by silica gel chromatography to obtain 15.0 g, 33.4 mol of white solid C2, namely N-Boc-Me-L-Leu-L-Leu-OBn, with a yield of 82%, and the structural formula is as follows: 。

[0026] (3)N-Me-L-Leu-L-Leu-OBn. E2 was synthesized by reacting 15.0 g (33.4 mmol) of C2, 10 ml of TFA, and 40 ml of DCM at -20 °C for 12 h. Subsequently, the excess TFA and DCM were removed under vacuum to yield E2 as a colorless oil, namely N-Me-L-Leu-L-Leu-OBn, with a yield of 10.0 g (28.7 mmol) and a yield rate of 86%. Its structural formula is as follows: 。

[0027] (4)N-Boc-Me-L-Leu-L-Leu-OH. D2 was synthesized by reacting 15.0 g (33.4 mmol) of C2, 5 g (4.7 mmol) of 10% Pd / C, and 1 atm of H2 at 10 °C for 12 h. The mixture was filtered and concentrated under vacuum to obtain D2, namely N-Boc-Me-L-Leu-L-Leu-OH, with a yield of 10.0 g (27.9 mmol) and a yield rate of 84%. Its structural formula is as follows: 。

[0028] (5)N-Boc-D-Leu-Me-L-Leu-L-Leu-OBn F2 was synthesized by reacting 10.0 g (28.7 mmol) of E2, 7.2 g (31.5 mmol) of N-Boc-D-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI at 0 °C for 12 h. A mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F2 as a white solid, namely N-Boc-D-Leu-Me-L-Leu-L-Leu-OBn, with a yield of 14.0 g (24.9 mmol) and a yield rate of 86%. Its structural formula is as follows: 。

[0029] (6)N-D-Leu-Me-L-Leu-L-Leu-OBn G2 was synthesized by reacting 15.0 g (33.4 mmol) of F2, 10 ml of TFA, and 40 ml of DCM at -20 °C for 12 h. Subsequently, the excess TFA and DCM were removed under vacuum to yield G2 as a colorless oil, namely N-D-Leu-Me-L-Leu-L-Leu-OBn, with a yield of 13.2 g (28.7 mmol) and a yield rate of 86%. Its structural formula is as follows: 。

[0030] (7)N-Boc-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OBn. H2 was synthesized by reacting 10.0 g, 27.9 mmol of D2, 14.1 g, 30.7 mmol of G2, 4.1 g, 30.7 mmol of HOBT, and 5.9 g, 30.7 mmol of EDCI at 10 °C for 6 h. A mixture of n-hexane and ethyl acetate in a volume ratio of 70:30 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain H2 as a white solid, namely N-Boc-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OBn, with a yield of 20.0 g, 25.0 mmol and a yield of 89%, and the structural formula is as follows: 。

[0031] (8)N-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OBn I2 was synthesized by reacting 26.7 g, 33.4 mmol of H2, 10 ml of TFA, and 40 ml of DCM at -10 °C for 6 h. Thereafter, the excess TFA and DCM were removed under vacuum to obtain I2 as a colorless oil, namely N-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OBn, with a yield of 20.1 g, 28.7 mmol and a yield of 86%, and the structural formula is as follows: 。

[0032] (9)N-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OH J2 was synthesized by reacting 23.4 g, 33.4 mmol of I2, 5 g, 4.7 mmol of 10% Pd / C, and 1 atm of H2 at 20 °C for 6 h. The mixture was filtered and concentrated under vacuum to obtain J2, namely N-Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu-OH, with a yield of 17.0 g, 27.9 mmol and a yield of 84%, and the structural formula is as follows: 。

[0033] (10)Cyclo(Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu) 134 mg (0.22 mmol) of J2 was dissolved in 4.3 mM MeCN and added dropwise to a solution of 229 mg (0.44 mmol) of PyBOP and 80 mg (0.66 mmol) of DMAP in 1.0 mM MeCN at 0 °C over 10 h. The mixture was stirred for an additional 3 h. The solvent was removed under reduced pressure and the residue was suspended in H2O and purified by column chromatography using a 60:40 mixture by volume of cyclohexane and ethyl acetate as the eluent to afford the compound K2, Cyclo(Me-L-Leu-L-Leu-D-Leu-Me-L-Leu-L-Leu), as a white solid in 66 mg (0.11 mmol), 50% yield. The structural formula is as follows: 。

[0034] 1 H NMR (600 MHz, DMSO- d 6) δ 7.63 (d, J J = 8.1 Hz, 1H), 7.39 (d, J J = 8.2 Hz,1H), 7.20 (d, J J = 8.8 Hz, 1H), 5.11 (dd, J J = 9.5, 6.2 Hz, 1H), 4.77 (td, J J = 8.3,5.6 Hz, 1H), 4.71 (q, J J = 7.6 Hz, 1H), 4.49 (dd, J J = 10.4, 5.2 Hz, 1H), 4.15(ddd, J J = 10.4, 8.1, 5.2 Hz, 1H), 2.98 (s, 3H), 2.73 (s, 3H), 1.75 – 1.32 (m,15H), 1.02 – 0.61 (m, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 174.51, 172.25, 171.36, 170.83, 170.56, 57.93, 53.65, 51.38, 48.34, 47.70, 41.40, 41.09, 38.70, 37.23, 35.17, 31.34, 29.88, 25.26, 24.93, 24.87, 24.81, 24.78, 23.50, 23.40, 23.15, 23.03, 22.98, 22.07, 21.98, 21.92, 21.70. HRMS (ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4392. Example 2 Cyclo(Me-L-Leu-L-Leu-D-Pro-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced by N-Boc-D-Pro-OH, and the compound K3, namely Cyclo(Me-L-Leu-L-Leu-D-Pro-Me-L-Leu-L-Leu), in the form of a white solid is prepared, with a yield of 66 mg, 0.112 mmol, and a 51% yield. Its structural formula is as follows: .

[0035] 1 H NMR (600 MHz, DMSO- d 6) δ 7.37 (d, J = 7.3 Hz, 1H), 6.89 (d, J = 7.5 Hz, 1H), 4.91 (t, J = 7.8 Hz, 1H), 4.75 (td, J = 8.5, 8.1, 5.3 Hz, 2H), 4.60 (dd, J = 10.5, 5.8 Hz, 1H), 4.33 (ddd, J = 11.6, 7.5, 4.2 Hz, 1H), 3.51 (t, J = 8.5 Hz, 1H), 3.45 (q, J = 5.3, 3.8 Hz, 1H), 3.02 (d,J = 11.7 Hz, 6H), 2.17 (q, J = 6.4 Hz,1H), 2.04 – 1.91 (m, 1H), 1.88 (dd, J = 12.5, 6.6 Hz, 1H), 1.81 – 1.74 (m, 1H),1.74 – 1.66 (m, 1H), 1.65 – 1.29 (m, 11H), 0.99 – 0.69 (m, 24H). 13 C NMR (151MHz, DMSO- d 6) δ 173.85, 172.95, 171.28, 170.24, 169.51, 57.55, 56.01, 53.83,50.16, 47.93, 46.42, 42.25, 36.75, 36.33, 31.00, 30.79, 28.46, 25.41, 25.21,25.08, 24.87, 24.69, 23.69, 23.43, 23.25, 23.20, 22.73, 22.37, 21.95, 21.81.HRMS (ESI + ) calcd. for C 31 H 55 N5O5[M+Na] + : 600.4101; found: 600.4223. Example 3 Cyclo(Me-L-Leu-L-Leu-D-Phe-Me-L-Leu-L-Leu) differs from Galaxamide only in that N-Boc-D-Leu-OH is replaced by N-Boc-D-Phe-OH to give compound K4 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-D-Phe-Me-L-Leu-L-Leu), with a yield of 70 mg, 0.110 mmol, 51% yield, and its structural formula is as follows: .

[0036] 1 H NMR (600 MHz, DMSO- d 6) δ 7.60 (d, J = 7.8 Hz, 1H), 7.57 (d, J = 8.8 Hz,1H), 7.46 (d,J = 8.1 Hz, 1H), 7.35 – 7.04 (m, 5H), 5.06 (dd, J = 9.8, 6.0 Hz,1H), 4.87 (q, J = 7.9 Hz, 1H), 4.76 (q, J = 7.5 Hz, 1H), 4.58 (dd, J = 10.1, 5.6Hz, 1H), 4.12 (td, J = 8.8, 5.7 Hz, 1H), 3.05 (dd, J = 13.1, 8.4 Hz, 1H), 2.97(s, 3H), 2.76 (dd, J = 13.2, 6.2 Hz, 1H), 2.63 (s, 3H), 1.86 – 1.45 (m, 7H),1.40 (q, J = 8.2, 7.3 Hz, 4H), 1.24 – 1.07 (m, 1H), 0.97 – 0.59 (m, 24H). 13 C NMR(151 MHz, DMSO- d 6) δ 174.22, 171.82, 171.28, 170.86, 170.38, 138.17, 129.65,128.43, 126.63, 57.70, 53.65, 51.56, 51.17, 48.23, 41.40, 38.72, 37.83,37.20, 35.23, 31.20, 29.84, 25.24, 24.84, 24.75, 24.65, 23.47, 23.38, 23.18,22.16, 22.00, 21.88. HRMS (ESI + ) calcd. for C 35 H 57 N5O5[M+Na] + : 650.4257; found:650.4556. Example 4 Cyclo(Me-L-Leu-L-Leu-L-Val-Me-L-Leu-L-Leu) It is only different from Example 1 in that N-Boc-D-Leu-OH is replaced by N-Boc-L-Val-OH, and Compound K5 in the form of a white solid is prepared, namely Cyclo(Me-L-Leu-L-Leu-L-Val-Me-L-Leu-L-Leu), with a yield of 67 mg, 0.110 mmol, and a 51% yield. Its structural formula is as follows: .

[0037] 1 H NMR (600 MHz, DMSO- d 6) δ 8.39 – 7.83 (m, 1H), 7.83 – 7.61 (m, 1H),7.53 – 6.64 (m, 1H), 5.31 – 4.84 (m, 1H), 4.81 – 4.62 (m, 1H), 4.60 – 4.40(m, 1H), 4.20 – 3.93 (m, 1H), 3.93 – 3.52 (m, 1H), 3.36 (s, 1H), 3.17 (s,1H), 2.90 (s, 1H), 2.78 (s, 1H), 2.58 (d, J = 16.2 Hz, 1H), 2.42 (s, 1H), 1.73– 1.24 (m, 12H), 0.87 (dtdd, J = 37.4, 24.0, 13.2, 6.4 Hz, 30H). 13 C NMR (151MHz, DMSO- d 6) δ 174.07, 171.13, 170.83, 169.38, 167.86, 60.20, 57.76, 55.22,53.52, 50.98, 47.69, 42.98, 41.48, 38.17, 37.00, 29.07, 28.95, 25.29, 25.13,24.88, 24.75, 24.60, 24.55, 24.41, 23.25, 23.22, 23.18, 23.13, 23.08, 23.00,22.97, 22.81, 22.37, 22.35, 22.16. HRMS (ESI + ) calcd. for C 31 H 57 N5O5[M+H] + :602.4257; found: 602.4375. Example 5 Cyclo(Me-L-Leu-L-Leu-Gly-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-Gly-OH, and the compound K6 in the form of a white solid, namely Cyclo(Me-L-Leu-L-Leu-Gly-Me-L-Leu-L-Leu), is prepared. The yield is 62 mg, 0.112 mmol, and the yield rate is 52%. Its structural formula is as follows: 。

[0038] 1 H NMR (600 MHz, DMSO- d 6) δ 7.92 (dd, J = 65.6, 8.3 Hz, 1H), 7.76 – 7.38(m, 1H), 7.22 (d, J = 4.3 Hz, 1H), 5.04 (t, J = 7.7 Hz, 1H), 4.83 (td, J = 9.0, 4.6Hz, 1H), 4.60 (dd, J = 13.8, 9.1 Hz, 1H), 4.45 (dd, J = 9.7, 5.3 Hz, 1H), 4.09(ddd, J = 10.8, 8.1, 4.8 Hz, 1H), 3.25 (d, J = 13.7 Hz, 1H), 3.01 (s, 3H), 2.64(s, 3H), 1.78 – 1.30 (m, 12H), 1.03 – 0.62 (m, 24H). 13 C NMR (151 MHz, DMSO- d 6)δ 174.67, 171.72, 171.31, 170.27, 170.18, 58.09, 53.80, 51.83, 48.33, 43.17,41.45, 38.29, 37.36, 35.06, 31.62, 31.45, 30.35, 25.28, 24.84, 24.81, 24.75,23.62, 23.49, 23.35, 23.05, 22.26, 22.13, 22.00, 21.38. HRMS (ESI+ ) calculated for C 28 H 51 N5O5[M+Na] + : 560.3788; found: 560.3422. Example 6 Cyclo(Me-L-Leu-L-Leu-D-Ala-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced by N-Boc-D-Ala-OH, and compound K7, namely Cyclo(Me-L-Leu-L-Leu-D-Ala-Me-L-Leu-L-Leu), is obtained as a white solid, with a yield of 59 mg, 0.110 mmol, and a 49% yield. Its structural formula is as follows: .

[0039] 1 H NMR (600 MHz, DMSO- d 6) δ 7.78 (d, J = 8.3 Hz, 1H), 7.21 (d, J = 8.4 Hz,1H), 7.10 (d, J = 8.8 Hz, 1H), 5.13 (t, J = 7.6 Hz, 1H), 4.83 (td, J = 8.7, 5.0 Hz,1H), 4.74 (dd, J = 8.7, 6.1 Hz, 1H), 4.40 (dd, J = 10.1, 5.1 Hz, 1H), 4.12 (ddd, J = 12.1, 8.2, 4.3 Hz, 1H), 3.01 (s, 3H), 2.63 (s, 3H), 1.80 – 1.65 (m, 2H),1.65 – 1.29 (m, 10H), 1.12 (d, J = 6.3 Hz, 3H), 1.04 – 0.60 (m, 24H). 13 C NMR(151 MHz, DMSO- d6) δ 174.88, 172.24, 171.62, 170.87, 170.38, 58.31, 53.56, 51.46, 48.43, 45.25, 41.50, 38.45, 37.38, 35.00, 31.48, 29.57, 25.30, 24.84, 24.81, 23.68, 23.55, 23.31, 23.06, 22.28, 22.07, 21.92, 21.31, 17.85. HRMS(ESI + ) calcd. for C 29 H 53 N5O5[M+Na] + : 574.3944; found: 574.3212. Example 7 Cyclo(Me-L-Leu-L-Leu-O-Me-D-Ser-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced by N-Boc-O-methyl-D-serine, and the compound K8 in the form of a white solid, namely Cyclo(Me-L-Leu-L-Leu-O-Me-D-Ser-Me-L-Leu-L-Leu), is prepared with a yield of 67 mg, 0.112 mmol, and a 52% yield. Its structural formula is as follows: .

[0040] 1 H NMR (600 MHz, DMSO- d 6) δ 7.80 (d, J = 8.2 Hz, 1H), 7.31 (d, J = 8.4 Hz,1H), 7.09 (d, J = 9.0 Hz, 1H), 5.10 (t, J = 7.7 Hz, 1H), 4.82 (td, J = 8.2, 4.1 Hz,2H), 4.45 (dd, J = 10.1, 4.9 Hz, 1H), 4.13 (ddd, J = 10.8, 8.2, 4.6 Hz, 1H), 3.63(t, J = 8.6 Hz, 1H), 3.28 (dd, J= 9.4, 5.7 Hz, 1H), 3.23 (s, 3H), 2.99 (s, 3H), 2.67 (s, 3H), 1.78 – 1.65 (m, 2H), 1.64 – 1.31 (m, 10H), 1.05 – 0.57 (m, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ 174.72, 171.52, 171.25, 170.71, 170.27, 71.70, 58.77, 58.04, 53.60, 51.35, 48.59, 48.36, 41.40, 38.44, 37.26, 35.05, 31.39, 29.72, 25.27, 24.95, 24.80, 23.63, 23.51, 23.27, 23.12, 22.21, 22.01, 21.98, 21.48. HRMS (ESI + ) calcd. for C 30 H 55 N5O6[M+Na] + : 604.4050; found: 604.4212. Example 8 Cyclo(Me-L-Leu-L-Leu-O-Tyr-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-D-Leu-OH was replaced with N-Boc-O-methyl-D-tyrosine to obtain compound K9 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-O-Tyr-Me-L-Leu-L-Leu), with a yield of 77 mg, 0.112 mmol, 53% yield, and its structural formula is as follows: .

[0041] 1 H NMR (600 MHz, DMSO- d 6) δ 7.57 (t, J = 7.9 Hz, 2H), 7.45 (d, J = 8.2 Hz, 1H), 7.25 – 6.99 (m, 2H), 6.91 – 6.66 (m, 2H), 5.04 (dd, J = 9.9, 6.0 Hz, 1H), 4.78 (dtd, J= 39.0, 8.5, 6.1 Hz, 2H), 4.57 (dd, J = 10.2, 5.6 Hz, 1H), 4.11(ddd, J = 9.6, 7.9, 5.6 Hz, 1H), 3.70 (s, 3H), 2.96 (s, 3H), 2.94 (s, 1H), 2.69(dd, J = 13.1, 6.4 Hz, 1H), 2.62 (s, 3H), 1.78 – 1.44 (m, 7H), 1.39 (qd, J =13.1, 10.8, 5.0 Hz, 5H), 0.96 – 0.69 (m, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ174.14, 171.96, 171.27, 170.89, 170.38, 158.26, 130.68, 129.96, 113.89,57.69, 55.39, 53.61, 51.53, 51.33, 48.19, 41.37, 38.77, 37.15, 36.93, 35.26,31.18, 29.87, 25.23, 24.85, 24.75, 24.63, 23.47, 23.41, 23.38, 23.19, 22.19,22.01, 21.92. HRMS (ESI + ) calcd. for C 36 H 59 N5O6[M+Na] + : 680.4363; found:680.4532. Example 9 Cyclo(Me-L-Leu-L-Leu-Methylester-D-Asp-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-methyl ester-D-aspartic acid to obtain the compound K10 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-Methylester-D-Asp-Me-L-Leu-L-Leu), with a yield of 71 mg, 0.110 mmol, 52% yield, and its structural formula is as follows: .

[0042] 1 1H NMR (600 MHz, DMSO- d 6) δ 7.88 (d, J J = 8.0 Hz, 1H), 7.28 (dd, J J = 8.7, 6.4 Hz, 2H), 5.09 (dd, J J = 9.6, 6.0 Hz, 1H), 4.99 (td, J J = 9.6, 4.3 Hz, 1H), 4.80(td, J J = 8.9, 4.8 Hz, 1H), 4.47 (dd, J J = 9.9, 5.0 Hz, 1H), 4.05 (ddd, J J = 11.4, 8.0, 4.4 Hz, 1H), 3.55 (s, 3H), 3.00 (s, 3H), 2.78 (dd, J J = 16.1, 10.1 Hz, 1H), 2.67 (s, 3H), 2.47 (dd, J J = 16.1, 4.3 Hz, 1H), 1.78 – 1.28 (m, 13H), 0.88(dddd, J J = 47.8, 27.7, 10.8, 6.1 Hz, 24H). 13 13C NMR (151 MHz, DMSO- d 6) δ 174.66, 171.57, 171.15, 171.05, 170.84, 170.33, 57.80, 53.77, 51.81, 51.64, 48.37, 46.57, 41.30, 38.24, 37.35, 36.25, 34.91, 31.40, 29.62, 25.25, 24.80, 24.78, 23.64, 23.49, 23.43, 23.11, 22.07, 22.01, 21.94, 21.45. HRMS (ESI + ) calcd.for C 31 H 55 N5O7[M+Na] + : 632.3999; found: 632.3621. Example 10 Cyclo(Me-L-Leu-L-Leu-3-Flu-D-Phe-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-3-fluoro-D-phenylalanine to obtain Compound K11 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-3-Flu-D-Phe-Me-L-Leu-L-Leu), with a yield of 75 mg, 0.120 mmol, and a 53% yield. Its structural formula is as follows: 。

[0043] 1 H NMR (600 MHz, DMSO- d 6) δ 7.59 (t, J J = 9.1 Hz, 2H), 7.45 (d, J J = 8.1 Hz,1H), 7.27 (q, J J = 7.4 Hz, 1H), 7.10 – 6.83 (m, 3H), 5.07 (dd, J J = 10.0, 5.9 Hz,1H), 4.89 (q, J J = 7.8 Hz, 1H), 4.75 (q, J J = 7.8 Hz, 1H), 4.58 (dd, J J = 10.1, 5.6Hz, 1H), 4.09 (td, J J = 8.7, 5.6 Hz, 1H), 3.05 (dd, J J = 13.2, 7.8 Hz, 1H), 2.97(s, 3H), 2.79 (dd, J J = 13.2, 6.8 Hz, 1H), 2.66 (s, 3H), 1.71 – 1.15 (m, 13H),1.00 – 0.58 (m, 24H). 13 C NMR (151 MHz, DMSO- d6) δ 174.24, 171.70, 171.31, 170.84, 170.42, 163.27, 141.20, 141.15, 130.25, 130.20, 125.85, 116.49, 116.35, 60.18, 57.71, 53.72, 51.57, 50.91, 48.26, 41.32, 38.68, 37.41, 37.20, 35.25, 31.21, 29.88, 25.23, 24.85, 24.76, 24.69, 23.46, 23.40, 23.31, 23.17, 22.16, 22.00, 21.88, 21.80. HRMS (ESI + ) calcd. for C 35 H 56 FN5O5[M+Na] + : 668.4163; found: 668.4134. Example 11 Cyclo(Me-L-Leu-L-Leu-2-Me-D-Phe-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-2-methyl-D-phenylalanine to obtain compound K12 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-2-Me-D-Phe-Me-L-Leu-L-Leu), with a yield of 76 mg, 0.120 mmol, and a 53% yield. Its structural formula is as follows: .

[0044] 1 H NMR (600 MHz, DMSO- d 6) δ 7.66 (d, J = 8.0 Hz, 1H), 7.50 (d, J = 8.6 Hz, 1H), 7.45 (d, J = 8.3 Hz, 1H), 7.18 – 6.85 (m, 4H), 5.04 (dd, J = 9.9, 6.1 Hz, 1H), 4.90 (td, J = 8.8, 5.6 Hz, 1H), 4.76 (q, J = 7.6 Hz, 1H), 4.57 (dd, J= 10.3, 5.4 Hz, 1H), 4.12 (td, J = 8.8, 5.3 Hz, 1H), 3.08 (dd, J = 13.5, 9.0 Hz, 1H), 2.96 (s, 3H), 2.75 (dd, J = 13.5, 5.6 Hz, 1H), 2.59 (s, 3H), 2.32 (s, 3H), 1.77–1.29 (m, 11H), 1.18–1.04 (m, 1H), 1.00–0.53 (m, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ 174.18, 171.72, 171.26, 171.04, 170.25, 136.70, 136.12, 130.35, 130.08, 126.74, 125.88, 57.71, 53.61, 51.44, 49.88, 48.21, 41.43, 38.65, 37.15, 35.14, 34.92, 31.18, 29.80, 25.24, 24.81, 24.75, 24.61, 23.48, 23.39, 23.19, 22.14, 22.00, 21.88, 21.80, 19.54. HRMS (ESI + ) calcd. for C 36 H 59 N5O5[M + H] + : 664.4414; found: 664.4438. Example 12 Cyclo(Me-L-Leu-L-Leu-4-Chl-D-Phe-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-4-chloro-D-phenylalanine to give compound K13 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-4-Chl-D-Phe-Me-L-Leu-L-Leu), with a yield of 80 mg, 0.120 mmol, 55% yield, and its structural formula is as follows: .

[0045] 1 H NMR (600 MHz, DMSO- d6) δ 7.58 (dd, J J = 27.1, 8.2 Hz, 2H), 7.42 (dd, J J = 20.0, 8.1 Hz, 1H), 7.30 – 7.16 (m, 4H), 5.04 (dt, J J = 10.5, 5.2 Hz, 1H), 4.95 – 4.80 (m, 1H), 4.80 – 4.68 (m, 1H), 4.57 (dt, J J = 11.6, 5.8 Hz, 1H), 4.18 – 3.81 (m, 1H), 3.03 (ddd, J J = 20.0, 12.9, 8.0 Hz, 1H), 2.97 (s, 3H), 2.76 (dd, J J = 13.3, 6.4 Hz, 1H), 2.64 (d, J J = 12.2 Hz, 3H), 1.76 – 1.20 (m, 12H), 1.03 – 0.53 (m, 24H). 13 C NMR (151 MHz, DMSO- d d6) δ 174.22, 171.83, 171.30, 170.87, 170.40, 138.18, 131.65, 129.66, 128.45, 128.35, 57.75, 57.71, 53.66, 51.53, 51.15, 48.23, 41.36, 38.72, 37.18, 35.22, 31.21, 29.86, 25.23, 24.84, 24.76, 24.66, 23.47, 23.39, 23.35, 23.18, 22.17, 22.01, 21.90, 21.87. HRMS (ESI + ) calcd. for C 35 H 56 ClN5O5 [M+H] + : 684.3868; found: 684.3854. Example 13 Cyclo(Me-L-Leu-L-Leu-4-Bro-D-Phe-Me-L-Leu-L-Leu) It is only different from Example 1 in that N-Boc-D-Leu-OH is replaced by N-Boc-4-bromo-D-phenylalanine to obtain Compound K14 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-4-Bro-D-Phe-Me-L-Leu-L-Leu), with a yield of 87 mg, 0.122 mmol, and a 56% yield. Its structural formula is as follows: 。

[0046] 1 H NMR (600 MHz, DMSO- d 6) δ 7.58 (dd, J = 17.6, 8.3 Hz, 2H), 7.45 (d, J =8.1 Hz, 1H), 7.20 (ddt, J = 22.1, 14.2, 7.5 Hz, 5H), 5.05 (t, J = 7.9 Hz, 1H),4.87 (q, J = 8.0 Hz, 1H), 4.75 (q, J = 7.6 Hz, 1H), 4.57 (dd, J = 10.3, 5.6 Hz,1H), 4.11 (q, J = 7.8 Hz, 1H), 3.04 (dd, J = 13.1, 8.5 Hz, 1H), 2.97 (s, 3H),2.76 (dd, J = 13.3, 6.2 Hz, 1H), 2.63 (s, 3H), 1.92 – 1.08 (m, 13H), 1.04 –0.53 (m, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ 174.22, 171.83, 171.30, 170.87,170.40, 138.17, 129.66, 128.45, 126.66, 57.71, 53.66, 51.15, 48.23, 41.37,38.73, 37.81, 37.19, 35.23, 31.21, 29.86, 25.23, 24.84, 24.76, 24.66, 23.47,23.38, 23.19, 22.18, 22.00, 21.90, 21.87. HRMS (ESI+ ) calcd. for C 35 H 56 BrN5O5[M+H] + : 728.3363; found: 728.2113. Example 14 Cyclo(Me-L-Leu-L-Leu-D-cyclohexyl-Gly-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced by N-Boc-D-cyclohexyl-glycine, to obtain compound K15 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-D-cyclohexyl-Gly-Me-L-Leu-L-Leu), with a yield of 70 mg, 0.110 mmol, and a 51% yield. Its structural formula is as follows: .

[0047] 1 H NMR (600 MHz, DMSO- d 6) δ 7.63 (d, J = 7.8 Hz, 1H), 7.45 (d, J = 9.1 Hz,1H), 7.39 (d, J = 7.8 Hz, 1H), 5.10 (dd, J = 10.2, 6.0 Hz, 1H), 4.71 (t, J = 7.4Hz, 1H), 4.69 – 4.54 (m, 1H), 4.43 (t, J = 9.5 Hz, 1H), 4.24 (q, J = 7.6 Hz, 1H),2.95 (s, 3H), 2.81 (s, 3H), 1.77 (d, J = 11.1 Hz, 1H), 1.73 – 1.56 (m, 8H),1.57 – 1.22 (m, 10H), 1.13 (p, J = 12.9, 12.4 Hz, 3H), 0.97 – 0.73 (m, 26H). 13 CNMR (151 MHz, DMSO- d6) δ 173.99, 172.50, 171.08, 171.02, 170.70, 57.54, 54.13, 53.69, 51.32, 48.22, 41.24, 37.04, 35.61, 31.12, 30.27, 29.82, 28.58, 26.45, 25.91, 25.20, 24.96, 24.72, 23.46, 23.24, 22.24, 22.14, 21.90, 21.74. HRMS (ESI + ) calcd. for C 34 H 61 N5O5[M+Na] + : 642.4570; found: 642.5435. Example 15 Cyclo(Me-L-Leu-L-Leu-D-phenyl-Gly-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-D-phenyl-glycine to obtain compound K16 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-D-phenyl-Gly-Me-L-Leu-L-Leu), with a yield of 72 mg, 0.112 mmol, 52% yield. Its structural formula is as follows: .

[0048] 1 H NMR (600 MHz, DMSO- d 6) δ 7.89 (d, J = 8.2 Hz, 1H), 7.77 (d, J = 8.8 Hz, 1H), 7.31 (dt, J = 29.4, 7.8 Hz, 5H), 5.88 (d, J = 8.8 Hz, 1H), 5.08 (t, J = 7.8 Hz, 1H), 4.86 (td, J = 9.4, 4.0 Hz, 1H), 4.47 (dd, J = 9.9, 5.4 Hz, 1H), 4.20 (td, J= 9.4, 8.8, 4.7 Hz, 1H), 3.03 (s, 3H), 2.80 (s, 3H), 1.84 – 1.13 (m,13H), 0.89 (tdd, J = 59.3, 14.5, 6.6 Hz, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ174.79, 171.80, 171.29, 170.19, 138.81, 128.25, 128.09, 127.63, 58.46, 53.86,53.44, 51.38, 48.46, 41.42, 38.36, 37.45, 35.01, 31.47, 30.12, 25.29, 24.85,24.81, 24.78, 24.57, 23.64, 23.56, 23.31, 23.04, 22.25, 22.18, 21.90, 21.29.HRMS (ESI + ) calcd. for C 34 H 55 N5O5[M+Na] + : 636.4101; found: 636.4421. Example 16 Cyclo(Me-L-Leu-L-Leu-D-Val-Me-L-Leu-L-Leu) It is different from Example 1 only in that N-Boc-D-Leu-OH is replaced with N-Boc-D-Val-OH to obtain the compound K17 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-D-Val-Me-L-Leu-L-Leu), with a yield of 66 mg, 0.110 mmol, and a 51% yield. Its structural formula is as follows: .

[0049] 1 H NMR (600 MHz, DMSO- d 6) δ 7.62 (d, J = 7.8 Hz, 1H), 7.57 (d, J = 9.1 Hz,1H), 7.37 (d, J = 7.7 Hz, 1H), 5.12 (dd, J = 10.3, 5.7 Hz, 1H), 4.70 (d,J = 7.4 Hz, 1H), 4.63 (dd, J = 10.4, 5.7 Hz, 1H), 4.38 (t, J = 9.4 Hz, 1H), 4.24 (d, J = 7.4 Hz, 1H), 2.95 (s, 3H), 2.83 (s, 3H), 2.04 (dt, J = 9.7, 6.7 Hz, 1H), 1.76 – 1.18 (m, 12H), 0.94 – 0.77 (m, 26H). 13 C NMR (151 MHz, DMSO - d 6) δ 173.92, 172.68, 171.07, 170.99, 170.71, 57.49, 55.29, 53.65, 51.45, 48.19, 41.21, 39.12, 37.01, 35.66, 31.08, 30.30, 29.94, 25.20, 24.99, 24.95, 24.71, 23.49, 23.46, 23.25, 23.14, 22.27, 22.24, 21.89, 21.69, 19.62, 18.86. HRMS (ESI + ) calcd. for C 31 H 57 N5O5[M + H] + : 602.4257; found: 602.4375. Example 17 Cyclo(Me - L - Leu - L - Leu - D - Met - Me - L - Leu - L - Leu) Differs from Example 1 only in that N - Boc - D - Leu - OH is replaced with N - Boc - D - Met - OH, to give the compound K18 as a white solid, namely Cyclo(Me - L - Leu - L - Leu - D - Met - Me - L - Leu - L - Leu), with a yield of 70 mg, 0.110 mmol, 52% yield, and its structural formula is as follows: .

[0050] 1 H NMR (600 MHz, DMSO - d 6) δ 7.71 (d, J= 8.1 Hz, 1H), 7.33 (d, J = 8.2 Hz,1H), 7.26 (d, J = 8.9 Hz, 1H), 5.12 (dd, J = 9.5, 6.3 Hz, 1H), 4.81 (dq, J = 22.6,7.3 Hz, 2H), 4.47 (dd, J = 10.1, 5.0 Hz, 1H), 4.16 (ddd, J = 10.7, 8.0, 5.0 Hz,1H), 2.99 (s, 3H), 2.70 (s, 3H), 2.44 – 2.18 (m, 2H), 2.03 (s, 4H), 1.70(dtd, J = 19.1, 9.6, 9.1, 5.4 Hz, 3H), 1.66 – 1.44 (m, 7H), 1.39 (dt, J = 29.3,7.0 Hz, 3H), 0.88 (dddd, J = 48.4, 35.5, 14.9, 6.5 Hz, 24H). 13 C NMR (151 MHz, DMSO- d 6) δ 174.59, 171.62, 171.47, 171.11, 170.42, 58.02, 53.59, 51.41, 48.49, 48.36, 41.37, 38.55, 37.27, 35.06, 31.48, 31.37, 29.96, 29.78, 25.26, 24.86, 24.83, 24.78, 23.56, 23.52, 23.41, 23.12, 22.03, 22.00, 21.57, 14.91. HRMS (ESI + ) calcd. for C 31 H 57 N5O5S [M+Na] + : 634.3978; found: 634.3990. Example 18 Cyclo(Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu) (1)N-Boc-Me-D-Leu-OH Take 9.0 g, 38.9 mmol of N-Boc-D-leucine, 25 g, 177.3 mmol of CH3I, and 5.5 g, 137.5 mmol of NaH dispersed in mineral oil. After mixing, stir at -20 °C for 60 min, then stir at room temperature for another 12 h. Quench with 100 ml of aqueous solution, and wash the mixture with ethyl acetate. Thereafter, acidify the aqueous solution to pH = 5 with 1N HCl solution and extract with ethyl acetate. The obtained ethyl acetate extract is dried over Na2SO4, filtered, and evaporated to obtain B3 as a colorless oil, namely N-Boc-Me-D-Leu-OH, with a yield of 8.8 g, 35.8 mmol, and a 92% yield.

[0051] (2)N-Boc-Me-D-Leu-L-Leu-OBn Synthesize C3 by reacting 10.0 g, 40.8 mmol of B3 with 31.5 g, 44.9 mmol of L-leucine benzyl ester p-toluenesulfonate, 6.0 g, 44.9 mmol of HOBt, and 8.5 g, 44.9 mmol of EDCI at 10 °C for 6 h. Use a mixture of n-hexane and ethyl acetate in a volume ratio of 90:10 as the elution solvent, and purify the crude product by silica gel chromatography to obtain C3 as a white solid, namely N-Boc-Me-D-Leu-L-Leu-OBn, with a yield of 14.6 g, 32.6 mmol, and an 80% yield.

[0052] (2)N-Me-D-Leu-L-Leu-OBn Synthesize E3 by mixing 15.0 g, 33.4 mmol of C3, 10 ml of TFA, and 40 ml of DCM and reacting at -10 °C for 6 h. Thereafter, remove the excess TFA and DCM under vacuum to produce E3 as a colorless oil, namely N-Me-D-Leu-L-Leu-OBn, with a yield of 9.9 g, 28.4 mmol, and an 85% yield.

[0053] (4)N-Boc-Me-D-Leu-L-Leu-OH Synthesize D3 by reacting 15.0 g, 33.4 mmol of C3, 5 g, 4.7 mmol of 10% Pd / C, and 1 atm of H2 at 20 °C for 6 h. Filter the mixture and concentrate it under vacuum to obtain D3, namely N-Boc-Me-D-Leu-L-Leu-OH, with a yield of 9.6 g, 26.7 mmol, and an 80% yield.

[0054] (5)N-Boc-L-Leu-Me-D-Leu-L-Leu-OBn F3, namely N-Boc-L-Leu-Me-D-Leu-L-Leu-OBn, was synthesized by reacting 10.0 g (28.7 mmol) of E3 with 13.3 g (57.5 mmol) of N-Boc-L-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI at 10 °C for 6 h. The crude product was purified by silica gel chromatography using a mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 as the elution solvent, yielding 13.2 g (23.5 mmol) of F3 as a white solid with an 82% yield.

[0055] (6)N-L-Leu-Me-D-Leu-L-Leu-OBn G3, namely N-L-Leu-Me-D-Leu-L-Leu-OBn, was synthesized by reacting 15.0 g (33.4 mmol) of F3 with 10 ml of TFA and 40 ml of DCM at -10 °C for 6 h. Subsequently, the excess TFA and DCM were removed under vacuum to give G3 as a colorless oil, with a yield of 13.0 g (28.1 mmol) and an 84% yield.

[0056] (7)N-Boc-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OBn H3, namely N-Boc-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OBn, was synthesized by reacting 10.0 g (27.9 mmol) of D3 with 25.7 g (55.8 mmol) of G3, 4.1 g (30.7 mmol) of HOBT, and 5.9 g (30.7 mmol) of EDCI at 0 °C for 12 h. The crude product was purified by silica gel chromatography using a mixture of n-hexane and ethyl acetate in a volume ratio of 70:30 as the elution solvent, yielding 20.0 g (25.0 mmol) of H3 as a white solid with an 88% yield.

[0057] (8)N-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OBn I3, namely N-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OBn, was synthesized by reacting 26.7 g (33.4 mmol) of H3 with 10 ml of TFA and 40 ml of DCM at -20 °C for 12 h. Thereafter, the excess TFA and DCM were removed under vacuum to give I3 as a colorless oil, with a yield of 20.1 g (28.7 mmol) and an 85% yield.

[0058] (9)N-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OH J3 was synthesized by reacting 23.4 g, 33.4 mmol of I3, 5 g, 4.7 mmol of 10% Pd / C, and 1 atm of H2 at 10 °C for 12 h. The mixture was filtered and concentrated in vacuo to give J3, namely N-Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu-OH, with a yield of 17.0 g, 27.9 mmol, and 85% yield.

[0059] 134 mg, 0.22 mmol of J3 was dissolved in 4.3 mM MeCN and added dropwise to a solution of 229 mg, 0.44 mmol of PyBOP and 80 mg, 0.66 mmol of DMAP in 1.0 mM MeCN at 10 °C over 10 h. The crude residue was purified by column chromatography using a mixture of cyclohexane and ethyl acetate in a volume ratio of 60:40 as the eluent to give the compound K03, namely Cyclo(Me-D-Leu-L-Leu-L-Leu-Me-D-Leu-L-Leu), as a white solid, with a yield of 67 mg, 0.113 mmol, and 51% yield. Its structural formula is as follows: 。

[0060] 1 H NMR (600 MHz, DMSO- d 6) δ 8.29 (d, J J = 8.7 Hz, 1H), 7.45 (d, J J = 8.9 Hz,1H), 7.01 (d, J J = 9.4 Hz, 1H), 5.06 (t, J J = 7.8 Hz, 1H), 4.80 (td, J J = 9.1, 5.5 Hz,1H), 4.73 – 4.50 (m, 2H), 4.16 (td, J J = 9.5, 5.1 Hz, 1H), 2.95 (s, 3H), 2.54(s, 3H), 1.75 – 1.31 (m, 15H), 1.09 – 0.55 (m, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 173.74, 171.69, 171.50, 171.16, 169.72, 55.88, 53.48, 52.31, 47.62, 47.52, 41.65, 41.26, 40.92, 37.10, 34.91, 30.89, 29.31, 24.99, 24.88, 24.83, 24.76, 24.67, 23.43, 23.34, 23.22, 23.01, 22.88, 22.74, 22.27, 22.13, 21.37. HRMS(ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 19 Cyclo(Me-D-Leu-L-Leu-D-Leu-Me-D-Leu-L-Leu) It is different from Example 18 only in steps (2) and (5), specifically as follows: (2)N-Boc-Me-D-Leu-L-Leu-OBn C1 was synthesized by reacting 10.0 g, 40.8 mmol of N-Boc-Me-D-Leu-OH, 17.6 g, 44.9 mmol of D-leucine benzyl ester p-toluenesulfonate, 6.0 g, 44.9 mmol of HOBt, and 8.5 g, 44.9 mmol of EDCI at 5 °C for 8 h. A mixture of n-hexane and ethyl acetate in a volume ratio of 90:10 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain C1 as a white solid, namely N-Boc-Me-D-Leu-L-Leu-OBn, with a yield of 14.6 g, 32.6 mol, and an 80% yield.

[0061] (5)N-Boc-D-Leu-Me-D-Leu-L-Leu-OBn 10.0 g, 28.7 mmol of N-Me-D-Leu-L-Leu-OBn, 7.2 g, 31.5 mmol of N-Boc-D-Leu-OH, 4.2 g, 31.5 mmol of HOBT, and 6.0 g, 31.5 mmol of EDCI prepared according to the foregoing steps were reacted at 5 °C for 8 h to synthesize F1. A mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F1 in the form of a white solid, namely N-Boc-D-Leu-Me-D-Leu-L-Leu-OBn, with a yield of 13.7 g, 24.4 mmol, and a yield of 85%.

[0062] Compound K01 in the form of a white solid, namely Cyclo(Me-D-Leu-L-Leu-D-Leu-Me-D-Leu-L-Leu), was prepared using F1 according to the same procedure as in Example 18, with a yield of 71 mg, 0.120 mmol, and a yield of 55%. Its structural formula is as follows: 。

[0063] 1 H NMR (600 MHz, DMSO- d 6) δ 8.29 (d, J = 8.7 Hz, 1H), 7.45 (d, J = 8.9 Hz,1H), 7.01 (d, J = 9.4 Hz, 1H), 5.06 (t, J = 7.8 Hz, 1H), 4.80 (q, J = 3.6 Hz, 1H),4.69 – 4.52 (m, 2H), 4.16 (q, J = 4.3 Hz, 1H), 2.95 (s, 3H), 2.54 (s, 3H), 1.82– 1.29 (m, 15H), 1.06 – 0.61 (m, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 173.74,171.69, 171.50, 171.16, 169.72, 55.88, 53.48, 52.31, 47.62, 47.52, 41.65,41.26, 40.92, 37.10, 34.91, 30.89, 29.31, 24.99, 24.88, 24.83, 24.76, 24.67,23.43, 23.34, 23.22, 23.01, 22.88, 22.74, 22.27, 22.13, 21.37. HRMS (ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 20 Cyclo(Me-L-Leu-D-Leu-L-Leu-Me-L-Leu-D-Leu) It is different from Example 18 only in steps (1) and (5); specifically: (1)N-Boc-Me-L-Leu-OH. Take 9.0 g, 38.9 mmol L-leucine, 25 g, 177.3 mmol CH3I, 5.5 g, 137.5 mmol NaH dispersed in mineral oil. After mixing, stir at -20 °C for 60 min, then stir at room temperature for another 12 h. Quench with 100 ml aqueous solution, and wash the mixture with ethyl acetate. Thereafter, acidify the aqueous solution to pH = 5 with 1N HCl solution and extract with ethyl acetate. The obtained ethyl acetate extract is dried over Na2SO4, filtered and evaporated to obtain B21 as a colorless oil, namely N-Boc-Me-L-Leu-OH, with a yield of 9.0 g, 36.7 mol, 94% yield.

[0064] (5)N-Boc-L-Leu-Me-L-Leu-D-Leu-OBn 10.0 g (28.7 mmol) of N-Me-L-Leu-D-Leu-OBn, 7.2 g (31.5 mmol) of N-Boc-L-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI prepared by the foregoing steps were reacted at 10 °C for 6 h to synthesize F21. A mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F21 in the form of a white solid, namely N-Boc-L-Leu-Me-L-Leu-D-Leu-OBn, with a yield of 13.7 g (24.4 mmol) and a yield of 85%.

[0065] Using F21, the compound K21 in the form of a white solid, namely Cyclo(Me-L-Leu-D-Leu-L-Leu-Me-L-Leu-D-Leu), was finally obtained according to the method in Example 18, with a yield of 68 mg (0.115 mmol) and a yield of 52%, and its structural formula is as follows: 。

[0066] 1 H NMR (600 MHz, DMSO- d 6) δ 8.30 (d, J J = 8.7 Hz, 1H), 7.46 (d, J J = 8.8 Hz,1H), 7.01 (d, J J = 9.4 Hz, 1H), 5.06 (t, J J = 7.7 Hz, 1H), 4.79 (dd, J J = 9.2, 5.8 Hz,1H), 4.64 (t, J J = 8.4 Hz, 2H), 4.15 (dt, J J = 9.5, 4.7 Hz, 1H), 2.95 (s, 3H), 2.54(s, 3H), 1.88 – 1.15 (m, 15H), 1.15 – 0.41 (m, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 173.73, 171.69, 171.50, 171.15, 169.72, 55.87, 53.46, 52.30, 47.61, 47.51, 41.65, 41.24, 40.92, 37.09, 34.90, 30.89, 29.30, 24.98, 24.87, 24.82, 24.75, 24.66, 23.43, 23.35, 23.22, 23.02, 22.88, 22.74, 22.26, 22.12, 21.36. HRMS(ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 21 Cyclo(Me-L-Leu-D-Leu-D-Leu-Me-L-Leu-D-Leu) It is different from Example 18 only in steps (1) and (5), specifically: (1)N-Boc-Me-L-Leu-OH 9.0 g, 38.9 mmol of L-leucine, 25 g, 177.3 mmol of CH3I, and 5.5 g, 137.5 mmol of NaH dispersed in mineral oil were mixed and stirred at -20 °C for 60 min, and then stirred at room temperature for another 12 h. It was quenched with 100 ml of aqueous solution, and the mixture was washed with ethyl acetate. Thereafter, the aqueous solution was acidified to pH = 5 with 1N HCl solution and extracted with ethyl acetate. The obtained ethyl acetate extract was dried over Na2SO4, filtered and evaporated to obtain B22 as a colorless oil, namely N-Boc-Me-L-Leu-OH, with a yield of 9.0 g, 36.7 mol, and a 94% yield.

[0067] (5)N-Boc-D-Leu-Me-L-Leu-D-Leu-OBn 10.0 g (28.7 mmol) of N-Me-L-Leu-D-Leu-OBn prepared as described above, 7.2 g (31.5 mmol) of N-Boc-D-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI were reacted at 10 °C for 6 h to synthesize F22. A mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F22 as a white solid, namely N-Boc-D-Leu-Me-L-Leu-D-Leu-OBn, with a yield of 13.2 g (23.5 mmol), 82%.

[0068] Using F22, compound K22 as a white solid, namely Cyclo(Me-L-Leu-D-Leu-D-Leu-Me-L-Leu-D-Leu), was finally obtained according to the method in Example 18, with a yield of 67 mg (0.113 mmol), 51%, and its structural formula is as follows: 。

[0069] 1 H NMR (600 MHz, DMSO- d 6) δ 8.30 (d, J = 8.7 Hz, 1H), 7.46 (d, J = 8.8 Hz,1H), 7.01 (d, J = 9.4 Hz, 1H), 5.06 (t, J = 7.7 Hz, 1H), 4.79 (dd, J = 9.2, 5.8 Hz,1H), 4.64 (t, J = 8.4 Hz, 2H), 4.15 (dt, J = 9.5, 4.7 Hz, 1H), 2.95 (s, 3H), 2.54(s, 3H), 1.88 – 1.15 (m, 15H), 1.15 – 0.41 (m, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 173.73, 171.69, 171.50, 171.15, 169.72, 55.87, 53.46, 52.30, 47.61, 47.51, 41.65, 41.24, 40.92, 37.09, 34.90, 30.89, 29.30, 24.98, 24.87, 24.82, 24.75, 24.66, 23.43, 23.35, 23.22, 23.02, 22.88, 22.74, 22.26, 22.12, 21.36. HRMS(ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 22 Cyclo(Me-D-Leu-D-Leu-L-Leu-Me-D-Leu-D-Leu) It is different from Example 18 only in that steps (2) and (5) are different, specifically as follows: (2)N-Boc-Me-D-Leu-D-Leu-OBn C23 was synthesized by reacting 10.0 g, 40.8 mmol of N-Boc-Me-D-Leu-OH, 17.6 g, 44.9 mmol of D-leucine benzyl ester p-toluenesulfonate, 6.0 g, 44.9 mmol of HOBt, and 8.5 g, 44.9 mmol of EDCI at 10 °C for 6 h. A mixture of n-hexane and ethyl acetate in a volume ratio of 90:10 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain C23 as a white solid, namely N-Boc-Me-D-Leu-D-Leu-OBn, with a yield of 15.0 g, 33.4 mol, and an 81% yield.

[0070] (5)N-Boc-L-Leu-Me-D-Leu-D-Leu-OBn 10.0 g (28.7 mmol) of N-Me-D-Leu-D-Leu-OBn, 7.2 g (31.5 mmol) of N-Boc-D-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI prepared in the foregoing steps were reacted at 10 °C for 6 h to synthesize F23. n-Hexane and ethyl acetate were mixed in a volume ratio of 80:20 as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F23 in the form of a white solid, i.e., N-Boc-L-Leu-Me-D-Leu-D-Leu-OBn, with a yield of 13.7 g (24.4 mmol) and a yield of 85%.

[0071] Using F23, compound K23 in the form of a white solid, i.e., Cyclo(Me-D-Leu-D-Leu-L-Leu-Me-D-Leu-D-Leu), was finally obtained according to the method in Example 18, with a yield of 72 mg (0.122 mmol) and a yield of 56%. The structural formula thereof is as follows: .

[0072] 1 H NMR (600 MHz, DMSO- d 6) δ 7.63 (d, J J = 8.0 Hz, 1H), 7.39 (d, J J = 8.2 Hz,1H), 7.19 (d, J J = 8.8 Hz, 1H), 5.11 (t, J J = 7.6 Hz, 1H), 4.77 (d, J J = 7.4 Hz, 1H),4.71 (d, J J = 7.8 Hz, 1H), 4.49 (dd, J J = 10.1, 5.2 Hz, 1H), 4.27 – 3.96 (m, 1H),2.99 (s, 3H), 2.73 (s, 3H), 1.73 – 1.26 (m, 15H), 0.87 (tdd, J J = 33.3, 12.5,6.6 Hz, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 174.53, 172.27, 171.37, 170.84, 170.57, 57.94, 53.64, 51.37, 48.34, 47.69, 41.40, 41.09, 38.70, 37.23, 35.17, 31.34, 29.88, 25.26, 24.92, 24.87, 24.81, 24.77, 23.50, 23.40, 23.15, 23.02, 22.98, 22.06, 21.97, 21.91, 21.70. HRMS (ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 23 Cyclo(Me-D-Leu-D-Leu-D-Leu-Me-D-Leu-D-Leu) Differs from Example 18 only in steps (2) and (5), specifically: (2)N-Boc-Me-D-Leu-D-Leu-OBn C24 was synthesized by reacting 10.0 g, 40.8 mmol B3 with 17.6 g, 44.9 mmol D-leucine benzyl ester p-toluenesulfonate, 6.0 g, 44.9 mmol HOBt, and 8.5 g, 44.9 mmol EDCI at 10 °C for 6 h. The crude product was purified by silica gel chromatography using a mixture of n-hexane and ethyl acetate in a volume ratio of 90:10 as the elution solvent to obtain C24 as a white solid, namely N-Boc-Me-D-Leu-D-Leu-OBn, with a yield of 15.0 g, 33.4 mol, and an 81% yield.

[0073] (5)N-Boc-D-Leu-Me-D-Leu-D-Leu-OBn 10.0 g (28.7 mmol) of N-Me-D-Leu-D-Leu-OBn prepared as described above, 7.2 g (31.5 mmol) of N-Boc-D-Leu-OH, 4.2 g (31.5 mmol) of HOBT, and 6.0 g (31.5 mmol) of EDCI were reacted at 10 °C for 6 h to synthesize F24. A mixture of n-hexane and ethyl acetate in a volume ratio of 80:20 was used as the elution solvent, and the crude product was purified by silica gel chromatography to obtain F24 as a white solid, i.e., N-Boc-D-Leu-Me-D-Leu-D-Leu-OBn, with a yield of 13.7 g (24.4 mmol) and a yield of 85%.

[0074] Using F24, compound K24 as a white solid, i.e., Cyclo(Me-D-Leu-D-Leu-D-Leu-Me-D-Leu-D-Leu), was finally obtained according to the method in Example 18, with a yield of 71 mg (0.120 mmol) and a yield of 55%, and its structural formula is as follows: 。

[0075] 1 H NMR (600 MHz, DMSO- d 6) δ 7.63 (d, J J = 8.0 Hz, 1H), 7.39 (d, J J = 8.2 Hz,1H), 7.19 (d, J J = 8.8 Hz, 1H), 5.11 (t, J J = 7.6 Hz, 1H), 4.77 (d, J J = 7.4 Hz, 1H),4.71 (d, J J = 7.8 Hz, 1H), 4.49 (dd, J J = 10.1, 5.2 Hz, 1H), 4.27 – 3.96 (m, 1H),2.99 (s, 3H), 2.73 (s, 3H), 1.73 – 1.26 (m, 15H), 0.87 (tdd, J J = 33.3, 12.5,6.6 Hz, 30H). 13 C NMR (151 MHz, DMSO- d6) δ 174.53, 172.27, 171.37, 170.84, 170.57, 57.94, 53.64, 51.37, 48.34, 47.69, 41.40, 41.09, 38.70, 37.23, 35.17, 31.34, 29.88, 25.26, 24.92, 24.87, 24.81, 24.77, 23.50, 23.40, 23.15, 23.02, 22.98, 22.06, 21.97, 21.91, 21.70. HRMS (ESI + ) calcd. for C 32 H 59 N5O5[M+Na] + : 616.4414; found: 616.4393. Example 24 Cyclo(Me-L-Leu-L-Leu-3-Me-D-Phe-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-L-leucine is replaced with N-Boc-3-methyl-D-phenylalanine to obtain compound K19 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-3-Me-D-Phe-Me-L-Leu-L-Leu), with a yield of 75 mg, 0.12 mmol, and a 53% yield. Its structural formula is as follows: .

[0076] 1 H NMR (600 MHz, DMSO- d 6) δ 7.62 (d, J = 7.9 Hz, 1H), 7.55 (d, J = 8.8 Hz, 1H), 7.45 (d, J = 8.1 Hz, 1H), 7.11 (t, J = 7.5 Hz, 1H), 7.05 – 6.87 (m, 3H), 5.06 (dd, J = 9.8, 6.1 Hz, 1H), 4.84 (d, J = 7.7 Hz, 1H), 4.76 (t, J = 7.5 Hz, 1H), 4.57 (dd, J = 10.4, 5.5 Hz, 1H), 4.13 (d,J = 7.6 Hz, 1H), 3.01 (dd, J = 13.1, 8.5Hz, 1H), 2.97 (s, 3H), 2.71 (dd, J = 13.3, 6.2 Hz, 1H), 2.62 (s, 3H), 2.25 (s,3H), 1.64 – 1.31 (m, 10H), 1.31 – 1.10 (m, 2H), 1.00 – 0.50 (m, 24H). 13 C NMR(151 MHz, DMSO- d 6) δ 174.22, 171.85, 171.30, 170.85, 170.37, 138.09, 137.42,130.23, 128.36, 127.29, 126.69, 57.73, 53.64, 51.51, 51.12, 48.23, 41.40,38.69, 37.75, 37.19, 35.22, 31.21, 29.84, 26.82, 25.24, 24.84, 24.75, 24.67,23.48, 23.41, 23.19, 22.16, 21.98, 21.85, 21.38. HRMS (ESI + ) calcd. forC 36 H 59 N5O5[M+Na] + : 664.4414; found: 664.4423. Example 25 Cyclo(Me-L-Leu-L-Leu-3-Me-D-Phe-Me-L-Leu-L-Leu) Differs from Example 1 only in that N-Boc-L-leucine was replaced with N-Boc-4-methyl-D-phenylalanine to give compound K20 as a white solid, namely Cyclo(Me-L-Leu-L-Leu-3-Me-D-Phe-Me-L-Leu-L-Leu), with a yield of 77 mg, 0.122 mmol, 54% yield, and its structural formula is as follows: .

[0077] 1 H NMR (600 MHz, DMSO- d 6) δ 7.58 (t, J= 9.2 Hz, 2H), 7.45 (d, J = 8.1 Hz,1H), 7.31 – 6.75 (m, 4H), 5.03 (dd, J = 9.8, 5.9 Hz, 1H), 4.83 (q, J = 7.9 Hz,1H), 4.74 (q, J = 7.6 Hz, 1H), 4.57 (dd, J = 10.3, 5.6 Hz, 1H), 4.11 (q, J = 7.6Hz, 1H), 3.02 – 2.97 (m, 1H), 2.96 (s, 3H), 2.71 (dd, J = 13.2, 6.2 Hz, 1H),2.62 (s, 3H), 2.24 (s, 3H), 1.70 – 1.12 (m, 12H), 1.00 – 0.53 (m, 24H). 13 C NMR(151 MHz, DMSO- d 6) δ 174.13, 171.88, 171.27, 170.92, 170.36, 135.57, 135.01,129.52, 129.06, 57.67, 53.62, 51.55, 51.18, 48.19, 41.37, 38.78, 37.39,37.15, 35.26, 31.17, 29.87, 25.23, 24.85, 24.75, 24.63, 23.47, 23.41, 23.39,23.20, 22.19, 22.01, 21.91, 21.09. HRMS (ESI + ) calcd. for C 36 H 59 N5O5[M+Na] + :664.4414; found: 664.4423. Experimental Example 1 Use of Marine Cyclopeptides in Anticancer 1. Cell Culture A549, K562, MDA-MB-231, HepG2, U251, U87 MG and 293T cells were all purchased from the Cell Resource Center of the Institute of Basic Medicine, Chinese Academy of Medical Sciences. A549 cells and K562 cells were cultured in RPMI 1640 medium and 1% p / s. MDA-MB-231, HepG2, U251, U87MG and 293T cells were cultured in DMEM medium. These cells were all cultured in an incubator at 37 °C with 5% CO2. The DMEM medium contained 10% FBS and 1% p / s. The full name of p / s: penicillin-streptomycin.

[0078] 2. CCK-8 assay Multiple types of cells were respectively seeded into 96-well plates. After they recovered to the normal state, different concentrations of K01-K25 and Galaxamide were added and incubated for 48 h. Then, the relative viability of the cells was detected according to the CCK-8 kit instructions, and the analysis and calculation of the cell relative viability were performed using GraphPad Prism software. The catalog number of the CCK-8 kit: MA0218, Meilunbio, China.

[0079] 3. Results The IC 50 values of Galaxamide and its analogs against seven cell lines are shown in Table 1.

[0080] Table 1 The cytotoxicity of Galaxamide and its analogs against different human cancer cell lines

[0081] As can be seen from Table 1, multiple human tumor cell lines were cytotoxic to Galaxamide and K01-K25. All the evaluated compounds showed significant cytotoxic activity against HepG2 cells. Comparing Galaxamide and its 25 analogs, K09 showed the greatest cytotoxicity against the MDA-MB231 cell line. In addition, the anti-cancer efficacy of Galaxiamide analogs against tumor cell lines was significantly affected by the number of D-leucine. The IC 50The values are 14.36, 2.775, 1.446, and 0.075 µM, showing significant broad-spectrum anti-cancer activity. These activities are >5.57, 4.26, 55.32, and 11.47 times higher than Galaxamide, respectively. In addition, for HepG2 cells, each Galaxiamide analogue showed effective anti-cancer activity, indicating that Galaxiamide and its analogues may act more effectively on HepG2 than other tumor cell lines. K20 has five D-amino acids at positions 1-5. In contrast, K19 has two D-amino acids at positions 3 and 5, and K22 has three D-amino acids at positions 1, 2, and 4. Compared with other analogues, K20 is more effective, indicating that compounds containing five D-amino acids have more excellent activity than analogues with fewer D-amino acids such as K19-K24.

[0082] In addition, the change in the position of D-leucine significantly affected the anti-cancer efficacy of the analogues. The best analogue for preventing the proliferation of all cancer cells is K01, which has D-leucine at positions 1, 3, and 5. Its IC 50 value is half of that of Galaxamide, 24.24 for K562, 0.1230 for MDA-MB-231, 1.705 for HepG2, and 14.14 for 293T. In addition to K01, K02 has a D-amino acid at position 1 and shows strong inhibitory effects on K562, MDA-MB-231, HepG2, and U87MG, with IC 50 values of 8.6, 0.3979, 5.0, and 0.6945, respectively. The reason behind this may be that when D-amino acids are at positions 1, 3, and 5 in K02 and K01, Galaxamide obtains a more stable and restricted cyclic structure. K01 shows the most stable cyclic configuration, with the lowest energy and the most active amino acid residues against cancer cells. The anti-tumor activity of the Galaxamide analogue K21 is lower than that of analogues K01 and K02, which have D-amino acids at positions 2 and 4. Specifically, the anti-cancer potential of K01 is twice that of K21, with IC 50 values of 6.368 and 75.24 for the HepG2 and K562 cell lines, respectively. Compared with Galaxamide, the anti-tumor efficacy of K22 against A549, K562, and U87MG is slightly changed, with IC 50 values of >22, >80, and 0.5878, respectively. Since K22 and K21 showed less anti-cancer effects on the examined cancer cells, it is possible that when D-amino acids are at positions 2 and 4, the restricted structure of the Galaxamide analogue may be disrupted.

Claims

1. A marine cyclic peptide, characterized in that, Its structural formula is shown in Formula Ι: ； Among them, R is selected from D-leucine, D-proline, D-phenylalanine, L-valine, glycine, D-alanine, O-methyl-D-serine, O-methyl-D-tyrosine, methyl ester-D-aspartic acid, 3-fluoro-D-phenylalanine, 2-methyl-D-phenylalanine, 4-chloro-D-phenylalanine, 4-bromo-D-phenylalanine, D-cyclohexyl-glycine, D-phenyl-glycine, D-valine, D-methionine, 3-methyl-D-phenylalanine, and 4-methyl-D-phenylalanine; R2 to R5 are each independently selected from D-leucine or L-leucine.

2. The marine cyclic peptide according to claim 1, wherein The structural formula of the marine cyclic peptide is shown as any of the following: ； ； ； ； 。 3. The synthesis method of the marine cyclic peptide according to claim 1, characterized in that, It includes the following steps: Using N-(tert-butoxycarbonyl)-L-leucine as a raw material for N-methylation reaction to obtain Boc-N-methyl-L-leucine, or using N-(tert-butoxycarbonyl)-D-leucine as a raw material for N-methylation reaction to obtain Boc-N-methyl-D-leucine; Using the Boc-N-methyl-L-leucine and L-leucine benzyl ester tosylate as raw materials for condensation reaction to obtain a dipeptide; or using the Boc-N-methyl-D-leucine and D-leucine benzyl ester tosylate as raw materials for condensation reaction to obtain a dipeptide; Performing hydrogenation reduction on the dipeptide to remove its C-terminal benzyl group to obtain product D; Performing acid hydrolysis on the dipeptide to remove its N-terminal tert-butoxycarbonyl group to obtain product E; Mixing the product E with an amino acid for condensation reaction to obtain a tripeptide, and removing the N-terminal Boc group to obtain product G; Mixing the product D and the product G for condensation reaction to obtain a linear pentapeptide; sequentially removing the C-terminal benzyl group and the N-terminal Boc group of the linear pentapeptide to obtain product J; Performing macrocyclic lactamization reaction on the product J to obtain the marine cyclic peptide.

4. The synthesis method according to claim 3, wherein The molar ratio of the Boc-N-methyl-L-leucine to L-leucine benzyl ester tosylate, or the Boc-N-methyl-D-leucine to D-leucine benzyl ester tosylate is both 1:1 to 2; The mixed molar ratio of the product E and the amino acid is 1:1 to 2; The molar ratio of the product D to the product G is 1:1 to 2.

5. The synthesis method according to claim 4, wherein The N-methylation reaction is carried out with stirring at -20 to -10 °C for 30 min to 60 min, and then stirred at room temperature for 12 h to 18 h; The condensation reaction of the Boc-N-methyl-L-leucine and L-leucine benzyl ester tosylate, or the condensation reaction of the Boc-N-methyl-D-leucine and D-leucine benzyl ester tosylate are both carried out at 0 °C to 10 °C for 6 h to 12 h; The hydrogenation reduction reaction of the C-terminal of the dipeptide is carried out at 10 °C to 20 °C for 6 h to 12 h under the action of a palladium catalyst; The acid hydrolysis reaction of the N-terminal of the dipeptide is carried out at -20 °C to -10 °C for 6 h to 12 h; The condensation reaction of the product E and the amino acid is carried out at 0 °C to 10 °C for 6 h to 12 h; The condensation reaction of the product D and the product G is carried out at 0 °C to 10 °C for 6 h to 12 h; The macrocyclic lactamization reaction is carried out at 0 °C to 10 °C for 12 h to 24 h under the action of a coupling agent.

6. The synthesis method according to claim 5, characterized in that The coupling agent is selected from 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate, propanephosphonic anhydride, diphenylphosphoryl azide, pentafluorophenyl diphenylphosphinate or (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate.

7. Use of the marine cyclic peptide according to claim 1 in the preparation of an anticancer drug.

8. The use according to claim 7, characterized in that, The anticancer effect is the inhibitory effect on non-small cell lung cancer, chronic myeloid leukemia, breast cancer, liver cancer, glioma, and immortalized embryonic kidney cells.

9. An anticancer drug, characterized in that, It uses the marine cyclic peptide according to claim 1 as the sole active ingredient.

10. The anti-cancer drug according to claim 9, characterized in that, The drug is compounded by the marine cyclic peptide and a pharmaceutically acceptable excipient.

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