KR20190030527A - Linker compound for imaging application - Google Patents

Abstract

The present invention relates to an imaging linker compound which can be applied to an imaging composition by being combined with a dye or the like. The imaging linker compound is represented by chemical formula 1a. In chemical formula 1a, R is succinimidyloxyl or ethenesulfonylC_(1-6)alkylaminyl, A is C_(1-3)alkyleneoxyC_(1-3)alkylene, and n is an integer of 1 to 100.

Description

Linker compound for imaging application

The present invention relates to a multipurpose linker compound, and more particularly, to a linker compound which can be used as a composition for imaging by bonding with a dye or the like.

It is well known that many low molecular weight compounds used in medicinal applications have significant toxicity, and for many years there have been various attempts to reduce the cytotoxicity of these low molecular weight compounds and to improve their medicinal efficacy.

One approach to reduce toxicity and improve efficacy of low molecular weight drugs is to induce a targeting agent-induced drug delivery system. In order to solve the above-mentioned problems, researches on the development of a linker including a targeting moiety and a biologically active moiety are carried out in various angles.

On the other hand, studies on the application of disease to diagnosis and treatment have been actively conducted through researches on protein interactions and gene information. One of the key points in such studies is a technique of immobilizing proteins at specific sites.

Korean Patent No. 10-0448880 discloses a method for immobilizing a protein by directly activating an activating group on a substrate using a plasma. Korean Patent No. 10-0577694 discloses a method for immobilizing a solid substrate surface A method of fixing a protein by physically adsorbing the porous thin film after forming a porous sol-gel thin film having a sufficiently increased specific surface area by a sol-gel method is disclosed in Korean Patent Laid-Open No. 10-2003 -034136 discloses a method for immobilizing a protein using an immobilized enzyme in which a cationic amino residue joins two or more enzymes that are continuously fused to two enzymes.

However, such a conventional method has a disadvantage in that the protein immobilization method which depends only on the denaturation and physical adsorption of the protein by the chemical process has a deterioration in the immobilization ability of the protein, the surface modification cost is high, the mass production is difficult, and the manufacturing process is difficult .

Therefore, it is urgently required to develop a new linker that can solve the above-described problems and be used for various purposes.

1. Korean Patent No. 10-0448880 2. Korean Patent No. 10-0577694 3. Korean Patent Publication No. 10-2003-034136

The first object of the present invention is to provide a linker compound which can be used for various purposes. A second problem to be solved by the present invention relates to the application of the linker compound.

The present invention provides a linker compound which can be used as a composition for imaging by bonding with a dye or the like. The inventors of the present invention have made efforts to develop a linker compound capable of stably immobilizing a target substance on a substrate surface while being able to control the surface characteristics of the substrate, Linker compound comprising a functional group capable of interacting with a substance has been developed. This linker structure is chemically bonded to various substrates and exhibits an excellent modifying effect on the surface of the substrate, and has excellent immobilization ability The present invention has been completed. In order to achieve the above object, the present invention provides a linker compound represented by the following general formula (1).

The present invention provides a novel linker that can be used versatile. The linker according to the present invention can bind to a substrate such as a low molecular weight polymer, a polymeric nanoparticle, a quantum dot or a magnetic nanoparticle to modify the surface or prevent oxidation of the magnetic nanoparticle and improve the reactivity with the target substance .

1 is a result of checking the reactivity of a linker compound with a substrate according to an embodiment of the present invention.
TLC conditions
The reaction solution (isobutanol: n-propanol: ethyl acetate: DW = 2: 4: 1: 3)
① lane: dye
② lane: dye + succinimidyloxyl linker (Examples 1, 3, 5, 7, 9, 11, 13)
Vinyl sulfonyl linkers (Examples 2, 4, 6, 8, 10, 12, 14)

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

One aspect of the present invention relates to a linker compound represented by the following formula (1a).

[Formula 1a]

Wherein R is succinimidyl-oxyl (succinimidyloxyl) or a sulfonyl tenseol C _{1 - 6} alkyl amino and carbonyl, and n is an integer from 1 to 100.

The linker according to the present invention comprises (i) a moiety chemically bonded to a substrate surface; (ii) a spacer portion that controls the surface properties of the substrate; And (iii) a portion that binds to biomolecules, and is largely composed of three parts.

In order to chemically bonded to the substrate surface, in order to bond the linker to the substrate surface and the chemical to an end in accordance with the present invention, succinimidyl tenseol dill oxyl sulfonyl or C _{1 - 6} alkyl groups include amino carbonyl. Spacers not only control the physico-chemical properties of the substrate surface but also increase the surface area of the substrate and improve the binding ability with the target material. In the spacer according to the present invention, n may be selected from an integer of 1 to 100. In order to bind with the target substance, the linker according to the present invention contains a carboxy group at the other end.

According to the present invention, the target substance may be a biomolecule such as a protein or a nucleic acid molecule. The protein may specifically be an antigen, an antibody, and an enzyme, but is not limited thereto.

In one embodiment, the linker compound has the structure of Formula 1b below.

[Chemical Formula 1b]

In another embodiment, the linker compound has the structure of the following formula (1) or (3).

In another embodiment, the linker compound has the structure of any one of the following formulas (4) to (21).

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. It is natural that it belongs to the claims.

In addition, the experimental results presented below only show representative experimental results of the embodiments and the comparative examples, and the respective effects of various embodiments of the present invention which are not explicitly described below will be specifically described in the corresponding part.

Example

Synthetic example  1: Preparation of compound 1

Diethylene glycol (0.28 mL, 3.00 mmol) was dissolved in pyridine (10 mL), succinic anhydride (721 mg, 7.20 mmol) was added, and the mixture was stirred at room temperature for 72 hours and then concentrated. The reaction was dissolved in brine (100 mL) and 2N aqueous sodium hydroxide solution was added. The reaction solution was extracted three times with ethyl acetate (EA), and the aqueous layer was acidified to pH 2 with a 6N hydrochloric acid solution. After the reaction solution was extracted three times with ethyl acetate, water remaining in the organic layer was removed with magnesium sulfate and concentrated to obtain Compound 1 (1450 mg, 80.2%) as a white solid.

¹ H NMR (400 MHz, DMSO):? 4.21-4.23 (m, 4H), 3.68-3.71 (m, 4H), 2.59-2.63

Synthetic example  2: Preparation of compound 2

A white compound 2 was prepared (1600 mg, 82.3%) in the same manner as in Synthesis Example 1, except that triethylene glycol was used in place of diethylene glycol.

^{1 H NMR (400 MHz, DMSO} ): δ 4.09-4.11 (m, 4H), 3.57-3.59 (m, 4H), 3.52 (s, 4H), 2.50-2.52 (m, 4H), 2.45-2.49 (m , 4H)

Synthetic example  3: Preparation of compound 3

The desired compound 3 (950 mg, 78%) was obtained in the same manner as in Synthesis Example 1, except that tetraethylene glycol was used in place of triethylene glycol.

^{1 H NMR (400 MHz, DMSO} ): δ 4.11-4.13 (m, 4H), 3.58-3.61 (m, 4H), 3.53 (s, 8H), 2.47-2.52 (m, 8H)

Synthetic example  4: Preparation of compound 4

(1000 mg, 77.6%) was obtained in the same manner as in Synthesis Example 1, except that pentaethylene glycol was used in place of tetraethylene glycol.

¹ H NMR (400 MHz, DMSO):? 4.21-4.23 (m, 4H), 3.68-3.70 (m, 4H), 3.64 (s, 12H), 2.58-2.62

Synthetic example  5: Preparation of compound 5

(800 mg, 79.7%) was obtained in the same manner as in Synthesis Example 1, except that hexaethylene glycol was used in place of pentaethylene glycol.

¹ H NMR (400 MHz, DMSO):? 4.21-4.23 (m, 4H), 3.68-3.70 (m, 4H), 3.64

Synthetic example  6: Preparation of Compound 6

(500 mg, 75%) was obtained in the same manner as in Synthesis Example 1, except that heptaethylene glycol was used in place of hexaethylene glycol.

^{1 H NMR (400 MHz, DMSO} ): δ 4.21-4.23 (m, 4H), 3.68-3.70 (m, 4H), 3.63 (s, 20H), 2.58-2.64 (m, 8H)

Synthetic example  7: Preparation of Compound 7

White Compound 3 (600 mg, 75.4%) was obtained in the same manner as in Synthesis Example 1, except that octaethylene glycol was used in place of heptaethylene glycol.

¹ H NMR (400 MHz, DMSO):? 4.21-4.23 (m, 4H), 3.68-3.70 (m, 4H)

Synthetic example  1-1: Preparation of Compound 1-1

Triethylamine (40.0 mL, 17.21 mmol) was added to 1,10-decanediol (10.0 g, 57.37 mmol, 1 eq) in an argon stream, . Methanesulfonylchloride (4.7 mL, 4.07 mmol) was slowly added to the reaction mixture, stirred at 0 ° C. for 1 hour, then heated to room temperature and further stirred for 18 hours. After completion of the reaction, the reaction mixture was washed with ice water, and purified water and dichloromethane were added. After stirring briefly, the organic layer and the water layer were separated and the organic layer was collected and washed with a 10% sodium chloride aqueous solution. The residue was purified by silica gel column chromatography (eluent: 80% EtOAc-Hexanes) to give Compound 1-1 as a yellow solid (g, 31.6%).

Synthetic example  1-2: Preparation of Compound 1-2

To a solution of Compound 1-1 (4.00 g, 12.10 mmol), benzyl-4-hydroxybenzoate (1.85 g, 8.06 mmol) and potassium carbonate in 60 mL of dimethylformamide (DMF) (1.35 g, 9.68 mmol) was dissolved, and the mixture was stirred at 50 占 폚 for 18 hours under an argon stream. After completion of the reaction, the reaction mixture was cooled to room temperature, and ethyl acetate and purified water were added thereto. After stirring briefly, the organic layer and the water layer were separated and the organic layer was washed with purified water. The residue was purified by silica gel column chromatography (eluent: 30% EtOAc-Hexane) to obtain Compound 1-2 as a white solid (2.3 g, 41%).

^{1 H NMR (400 MHz, CDCl3} ): δ 8.00 (d, J = 7.2Hz, 2H), 7.25-7.44 (m, 5H), 6.90 (d, J = 7.2Hz, 2H), 5.33 (s, 2H) , 4.20-4.22 (m, 2H), 3.98-3.01 (m, 2H), 3.12 (m, 3H), 1.71-1.81 (m, 4H), 1.31-1.46 (m, 12H).

Synthetic example  1-3: Preparation of Compound 1-3

Compound (1-2) (3.6 g, 7.78 mmol), methyl-4-hydroxybenzoate (1.80 g, 11.67 mmol) and potassium carbonate (1.60 g, 11.67 mmol) were dissolved in 72 mL of DMF Then, the mixture was stirred at 50 DEG C under an argon stream for 18 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, and ethyl acetate and purified water were added thereto, followed by stirring. The organic layer and the water layer were separated and the organic layer was washed with purified water. The residue was purified by silica gel column chromatography (eluent: 30% EtOAc-Hexane) to obtain Compound (1-3) (3.1 g, 77.6%) as a white solid after removing water remaining in the organic layer with magnesium sulfate.

^{1 H NMR (400 MHz, CDCl3} ): δ 7.96-8.02 (m, 4H), 7.32-7.44 (m, 5H), 6.87-6.90 (m, 4H), 5.33 (s, 2H), 3.97-4.00 (m , 4H), 3.87 (s, 3H), 1.75 - 1.81 (m, 4H), 1.31 - 1.46 (m, 12H).

Synthetic example  1-4: Preparation of compounds 1-4

Compound 2-3 and Pd / C (10 wt%, 75 mg) were added to 50 mL of THF and stirred for 4 hours in a hydrogen stream. After completion of the reaction, the filtrate was subjected to Celite filtration, and the collected filtrate was concentrated and purified by silica gel column chromatography (eluent: 5% MeOH-CH 2 Cl 2) to obtain Compound (1-4) as a white solid (278 mg, 67%).

^{1 H NMR (400 MHz, CDCl3} ): δ 8.03-8.06 (m, 2H), 7.96-7.98 (m, 2H), 6.89-6.93 (m, 4H), 3.99-4.03 (m, 4H), 3.99 (s , 3H), 1.78-1.82 (m, 4H), 1.25-1.34 (m, 12H).

Synthetic example  2-1: Preparation of Compound 2-1

The desired compound 2-1 was obtained as yellow oil (700 mg, 78%) in the same manner as in Synthesis Example 1-1, except that tetraethylene glycol was used instead of hexaethylene glycol.

¹ H NMR (400 MHz, CDCl 3):? 4.30-4.34 (m, 4H), 3.69-3.74 (m, 4H), 3.57-3.64 (m, 8H), 3.02 (s, 6H).

Synthetic example  2-2: Preparation of Compound 2-2

The desired compound 2-2 was obtained as a transparent oil (2.750 mg, 52%) in the same manner as in Synthesis Example 1-2, except that Compound 2-1 was used instead of Compound 1-1.

^{1 H NMR (400 MHz, CDCl3} ): δ 8.00 (d, J = 9.0Hz, 2H), 7.29-7.43 (m, 5H), 6.90 (d, J = 9.0Hz, 2H), 5.31 (s, 2H) , 4.32-4.35 (m, 2H), 4.15-4.17 (m, 2H), 3.83-3.85 (m, 2H), 3.63-3.74 (m, 10H), 3.03 (s, 6H).

Synthetic example  2-3: Preparation of Compound 2-3

The desired compound 2-3 was obtained as a transparent oil (2.620 mg, 83%) in the same manner as in Synthesis Example 1-3, except that Compound 2-2 was used instead of Compound 1-2.

^{1 H NMR (400 MHz, CDCl3} ): δ 7.93-8.00 (m, 2H), 7.29-7.43 (m, 5H), 6.88-6.90 (m, 4H), 5.31 (s, 2H), 4.12-4.15 (m , 4H), 3.82-3.84 (m, 3H), 3.85 (s, 4H), 3.65-3.70 (m, 8H).

Synthetic example  2-4: Preparation of compound 2-4

The desired compound 2-4 was obtained as a white solid (482 mg, 84%) in the same manner as in Synthesis Example 1-4, except that Compound 2-3 was used instead of Compound 1-3.

^{1 H NMR (400 MHz, CDCl3} ): δ 8.00 (d, J = 8.8Hz, 2H), 7.95 (d, J = 9.2Hz, 2H), 6.94-6.87 (m, 4H), 4.13-4.18 (m, 4H), 3.84-3.88 (m, 7H), 3.60-3.73 (m, 8H).

Synthetic example  3-1: Preparation of Compound 3-1

The desired compound 3-1 (2g) was obtained as a transparent oil in the same manner as in Synthesis Example 1-1, except that polyethylene glycol (average Mn 1,000) was used instead of hexaethylene glycol and the purification procedure was omitted.

Synthetic example  3-2: Preparation of Compound 3-2

Compound 3-1 (2 g, 2 mmol) was dissolved in 20 mL of DMF and then 334 μL (3 mmol) of 3-hydroxypropionic acid and potassium carbonate (691 mg, 5 mmol) 52%), and the mixture was stirred at 50 占 폚 under an argon stream for 18 hours (1.3 g).

Synthetic example  4-1: Preparation of compound 4-1

The desired compound 4-1 was obtained as a transparent oil (2.5 g) in the same manner as in Synthesis Example 3-1 except that polyethylene glycol (average Mn 4,000) was used instead of polyethylene glycol (average Mn 1,000).

Synthetic example  4-2: Preparation of compound 4-2

The desired compound 4-2 was obtained as a clear oil (2.2 g) in the same manner as in Synthesis Example 3-2, except that Compound 4-1 was used instead of Compound 3-1.

Example  1: Preparation of compound of formula (4)

[Chemical Formula 4]

Compound 1 prepared in Synthesis Example 1 was dissolved in 6.5 mL of dimethylformamide (DMF) and 6.5 mL of pyridine, and N, N, N ', N'-tetramethyl-O- (N-succinimidyl) N-succinimidyl) uronium tetrafluoroborate (TSTU) (1324 mg, 4.398 mmol) was dissolved in 1 mL of dimethylformamide and added to a solution of 3 Lt; / RTI > After completion of the reaction, the compound was lyophilized to remove pyridine and then purified by reverse phase column chromatography (eluent: 20% MeCN-H ₂ O) to obtain a pink oil (430 mg, 69.3%).

LC / MS, calculated C ₁₆ H ₂₁ NO ₁₁ 403.1, found 402.1

Example  2: Preparation of compound of formula (5)

[Chemical Formula 5]

To a solution of the compound of Example 1 (48 mg, 0.119 mmol) and 2- (2-chloroethylsulfonyl) ethanamine hydrochloride (74 mg, 0.357 mmol) in 5 mL of dimethylformamide, , N, N-diisopropylethylamine (DIPEA) (0.207 mL, 1.19 mmol) was added thereto, and the mixture was stirred at room temperature for 12 hours under a nitrogen stream. After completion of the reaction, the particles were precipitated with diethyl ether, separated by centrifugal separation, and then dried in a vacuum drier to obtain a compound of Formula 5 (11 mg, 22.1%).

LC / MS, calculated C ₁₆ H ₂₅ NO ₁₀ S 423.1, measured 422.1

Example  3: Preparation of compound of formula (6)

[Chemical Formula 6]

Compound (6) of the formula (6) was prepared (1226 mg, 64.8%) as a pink oil by the procedure of Example 1, except that the compound 2 prepared in Synthesis Example 2 was used instead of the compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₁₈ H ₂₅ NO ₁₂ 447.1, found 446.1

Example  4: Preparation of compound of formula (7)

(7)

Compound (7) (15.2 mg, 20.8%) was prepared by the method of Example 2, except that the compound of Formula 6 prepared in Example 3 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₁₈ H ₂₉ NO ₁₁ S 467.2, found 466.1

Example  5: Preparation of compound of formula 8

[Chemical Formula 8]

Compound (8) of yellow oil (535 mg, 49.1%) was prepared by the method of Example 1, except that Compound 3 prepared in Synthesis Example 3 was used instead of Compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₂₀ H ₂₉ NO ₁₃ 491.2, found 490.1

Example  6: Preparation of compound of formula 9

[Chemical Formula 9]

Compound (9) (10.8 mg, 20%) was prepared by the method of Example 2, except that the compound of Formula 8 prepared in Example 5 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₂₀ H ₃₃ NO ₁₂ S 511.2, measured 510.1

Example  7: Preparation of compound of formula 10

[Chemical formula 10]

The compound of Formula 10 of the pink oil was prepared (601 mg, 49.4%) by the method of Example 1, except that the compound 4 prepared in Synthesis Example 4 was used instead of the compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₂₂ H ₃₃ NO ₁₄ 535.2, found 534.1

Example  8: Preparation of the compound of formula (11)

(11)

Compound (11) (7.4 mg, 21.6%) was prepared by the method of Example 2 except that the compound of Formula 10 prepared in Example 7 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₂₂ H ₃₇ NO ₁₃ S 555.2, found 554.1

Example  9: Preparation of compound of formula (12)

[Chemical Formula 12]

Compound (12) of yellow oil (450 mg, 47.4%) was prepared by the method of Example 1, except that Compound 5 prepared in Synthesis Example 5 was used instead of Compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₂₄ H ₃₇ NO ₁₅ 579.22, found 578.6

Example  10: Preparation of the compound of formula (13)

[Chemical Formula 13]

Compound (13) (18.7 mg, 23%) was prepared by the method of Example 2, except that the compound of Formula 12 prepared in Example 9 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₂₄ H ₄₁ NO ₁₄ S 599.2, measured 598.2

Example  11: Preparation of compound of formula 14

[Chemical Formula 14]

A compound of formula 14 (140 mg, 24.9%) was prepared as a clear oil by the method of Example 1, except that the compound 6 prepared in Synthesis Example 6 was used instead of the compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₂₆ H ₄₁ NO ₁₆ 623.2, found 622.5

Example  12: Preparation of compound of formula (15)

[Chemical Formula 15]

The compound of Formula 15 was prepared (3.6 mg, 16%) by the method of Example 2 except that the compound of Formula 14 prepared in Example 11 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₂₆ H ₄₅ NO ₁₅ S 643.3, found 642.4

Example  13: Preparation of compound of formula (16)

[Chemical Formula 16]

A compound of formula 16 (250 mg, 36.8%) was prepared as a clear oil by the procedure of Example 1, except that the compound 7 prepared in Synthesis Example 7 was used instead of the compound 1 prepared in Synthesis Example 1.

LC / MS, calculated C ₂₈ H ₄₅ NO ₁₇ 667.3, found 666.4

Example  14: Preparation of compound of formula (17)

[Chemical Formula 17]

Compound (17) (16.7 mg, 19.8%) was prepared by the method of Example 2 except that the compound of Formula 16 prepared in Example 13 was used instead of the compound of Formula 4 prepared in Example 1.

LC / MS, calculated C ₂₈ H ₄₉ NO ₁₆ S 687.3, found 686.4

Example  15: Preparation of compound of formula 18

A compound of formula 18 (1.3 g, quantative) was prepared as a clear oil by the procedure of Example 1, except that the compound 3-2 prepared in Synthesis Example 3-2 was used instead of the compound 1 prepared in Synthesis Example 1.

Example  16: Preparation of compound of formula 19

The compound of Formula 19 was prepared (600 mg, quantative) by the method of Example 2 except that the compound of Formula 18 prepared in Example 15 was used instead of the compound of Formula 4 prepared in Example 1.

Example  17: Preparation of compound of formula 20

A compound of the formula (16) as a transparent oil was prepared by the method of Example 1 except that the compound 4-2 prepared in Synthesis Example 4-2 was used instead of the compound 1 prepared in Synthesis Example 1

Example  18: Preparation of compound of formula 21

Compound (21.7 mg, 19.8%) was prepared by the method of Example 2 except that the compound of Formula 20 prepared in Example 17 was used instead of the compound of Formula 4 prepared in Example 1.

Test Example  1: Reactivity test of compound

The reactivity of the compounds according to the invention was confirmed. The compounds of Examples 1 to 14 were each dissolved in DMF (100 mg / mL) and then 1 mg of Flamma 552 Amine dye (BioActs, inchon, KOREA) was added. To a solution containing a dye-containing compound with vinylsulfonyl and succinimidyloxyl, 1 mL of 0.1 M sodium carbonate-sodium bicarbonate buffer (pH 9.0, 37 ° C) was added for 1 hour at 37 ° C., After reacting for a period of time, the reactivity was confirmed by thin film chromatography. The results are shown in FIG. 1.

Referring to FIG. 1, it was confirmed that the compounds of Examples 1 to 14 having a vinylsulfonyl or succinimidyloxyl group in the linker compound according to the present invention bind to a target substance having an amine group.

Claims (4)

A linker compound represented by the following formula (1a):
[Formula 1a]

Wherein R is a succinimidyl tenseol dill oxyl sulfonyl or C _{1 - 6} alkyl, and amino carbonyl,
And A is C _{1 - 3} alkylene C _{1 - 3} alkylene,
And n is an integer of 1 to 100. The linker compound according to claim 1, wherein the linker compound has a structure represented by the following formula (1b):
[Chemical Formula 1b]

. The linker compound according to claim 1, wherein the linker compound has a structure represented by the following formula (2) or (3):
(2)

(3)

. The linker compound according to claim 1, wherein the linker compound has a structure of any one of the following formulas (4) to (21):
[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

[Chemical Formula 12]

[Chemical Formula 13]

[Chemical Formula 14]

[Chemical Formula 15]

[Chemical Formula 16]

[Chemical Formula 17]

[Chemical Formula 18]

[Chemical Formula 19]

[Chemical Formula 20]

[Chemical Formula 21]

.

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