Aromatic butadiynyl palmitic acid as well as preparation method and application thereof

Abstract

The invention discloses aromatic butadiyne palmitic acid as well as a preparation method and application thereof. The aromatic dialkynyl palmitic acid is efficiently synthesized by taking cyclopentadecanolide as a raw material, the cost is low, the synthesis process is simple, and the total yield is high; moreover, the limitation that a conjugated diyne structure cannot be constructed in the prior art is broken through, and the Raman signal intensity of the palmitic acid probe in a characteristic interval of 1600-2300cm <-1 > is improved by at least one order of magnitude through accurate introduction of an aromatic butadiyne group, so that the sensitivity requirement of ultra-multipath metabolic imaging is met; # imgabs0 #

Description

Technical Field

[0001] The invention relates to an aromatic diacetylene palmitic acid, a method for preparing the aromatic diacetylene palmitic acid by using cyclopentadecalactone as a raw material, and an application of the aromatic diacetylene palmitic acid as a Raman probe in cell imaging. Background Art

[0002] Aromatic diacetyl palmitic acid is a new generation of Raman probe. The conjugated aromatic diacetylene structure in its molecule can produce characteristic Raman scattering (half-peak width <5 cm) through the electron vibration coupling effect. -1 ), the signal intensity is increased by 2 to 3 orders of magnitude compared to traditional monoalkyne probes (Hu et al., Nat Methods 2018). However, existing synthesis technology has severely restricted the development and application of this type of probe. The current mainstream Thiele route (ACS Chem Biol 2012) requires ω-hydroxy fatty acids as raw materials and synthesizes monoalkyne palmitic acid through 7 steps of reaction, with a total yield of less than 15%, and it is impossible to construct a conjugated diyne structure. More importantly, the commercial price of ω-hydroxy fatty acids is as high as $850 / g (Sigma 2024), resulting in high probe synthesis costs.

[0003] The present invention innovatively uses the commodity chemical cyclopentadecalactone (<$5 / g) as the starting material, and the total yield is increased to more than 30%, successfully constructing a conjugated diacetylene structure with a strong Raman response. Compatibility tests with the polyacetylene probe system reported by Hu's team show that this product has a strong Raman response at 1600-2300 cm -1 The signal-to-noise ratio of the characteristic window is improved by 41 times, providing a key molecular tool for the development of ultra-multiplexed metabolic imaging technology with more than 16 channels. Summary of the Invention

[0004] The present invention provides an aromatic diacetylene palmitic acid and a preparation method and application thereof.

[0005] The present invention uses cheap cyclopentadecalactone (less than $5 / g) as a raw material to efficiently synthesize aromatic diacetylenic palmitic acid, overcoming the problems of the Thiele route, such as expensive ω-hydroxy fatty acid raw materials (>$800 / g), a cumbersome 7-step synthesis process, and a total yield of less than 15%.

[0006] Furthermore, the present invention breaks through the limitation of the existing technology that cannot construct a conjugated diyne structure. By precisely introducing the aromatic diacetylene group, the palmitic acid probe can be used in the range of 1600-2300 cm -1 The Raman signal intensity in the characteristic interval is increased by at least one order of magnitude, meeting the sensitivity requirements of ultra-multi-channel metabolic imaging.

[0007] The technical solutions of the present invention are as follows:

[0008] An aromatic diacetyl palmitic acid (18-phenyloctadecane-15,17-diynoic acid) having the structural formula shown in Formula I:

[0009]

[0010] The synthesis method of the aromatic diacetylene palmitic acid of the present invention is:

[0011] (1) reacting 15-olactone represented by formula VI with sodium methoxide to obtain 15-hydroxypentadecanoic acid methyl ester represented by formula V;

[0012] (2) reacting 15-hydroxypentadecanoic acid methyl ester represented by formula V with an oxidant to obtain 15-oxopentadecanoic acid methyl ester represented by formula IV;

[0013] (3) 15-oxopentadecanoic acid methyl ester represented by formula IV is reacted with dimethyl (1-diazo-2-oxopropyl)phosphonate and potassium carbonate to obtain hexadecyl-15-ynoic acid methyl ester represented by formula III;

[0014] (4) reacting hexadecyl-15-ynoic acid methyl ester represented by formula III with phenylacetylene to obtain 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II;

[0015] (5) 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II is reacted with sodium hydroxide to obtain aromatic diacetyl palmitate represented by formula I, i.e., 18-phenyloctadecane-15,17-diynoic acid;

[0016] The synthetic route is as follows:

[0017]

[0018] Specifically, step (1) is performed as follows:

[0019] Sodium is added to methanol. After the sodium is completely dissolved, 15-acid lactone represented by formula VI is added, and the mixture is reacted at 20-50° C. for 1-6 hours. The reaction solution is post-treated to obtain 15-hydroxypentadecanoic acid methyl ester represented by formula V;

[0020] The molar ratio of sodium to the 15-acid lactone represented by formula VI is 1:1 to 3, preferably 1:1;

[0021] The volume molar ratio of methanol to the 15-acid lactone represented by formula VI is 1 to 5:1, mL / mmol; preferably 2:1, mL / mmol;

[0022] Preferably, the reaction is carried out at 25°C for 3 hours;

[0023] The post-treatment method is as follows: adjusting the pH of the reaction solution to 3-5 (preferably pH = 3) with hydrochloric acid, filtering, collecting the white solid product and drying; extracting the filtrate with ethyl acetate, combining the organic layers, drying over anhydrous sodium sulfate, and evaporating the solvent. The residue is combined with the dried white solid product to obtain 15-hydroxypentadecanoic acid methyl ester represented by formula V.

[0024] Specifically, step (2) is performed as follows:

[0025] Dissolve 15-hydroxypentadecanoic acid methyl ester represented by formula V in dichloromethane, add an oxidant, react at 0-25° C. for 1-5 hours, and post-treat the reaction solution to obtain 15-oxopentadecanoic acid methyl ester represented by formula IV;

[0026] The oxidizing agent is selected from one or more of pyridinium chlorochromate, chromium trioxide, Dess-Martin periodinane, and activated manganese dioxide, preferably pyridinium chlorochromate;

[0027] The molar ratio of 15-hydroxypentadecanoic acid methyl ester represented by formula V to the oxidant is 1:1 to 2.5, preferably 1:1.5;

[0028] The volume molar ratio of dichloromethane to 15-hydroxypentadecanoic acid methyl ester represented by formula V is 0.5 to 2:1, mL / mmol; preferably 1:1, mL / mmol;

[0029] Preferably, the reaction is carried out at 8°C for 4 hours;

[0030] The post-treatment method is as follows: the reaction solution is mixed with silica gel, concentrated, and separated by column chromatography using a petroleum ether / ethyl acetate mixture with a volume ratio of 20:1 as an eluent, the eluate containing the target compound is collected, and the solvent is evaporated to obtain 15-oxopentadecanoic acid methyl ester represented by formula IV.

[0031] Specifically, step (3) is performed as follows:

[0032] 15-Oxopentadecanoic acid methyl ester represented by formula IV, (1-diazo-2-oxopropyl) phosphonic acid dimethyl ester, and potassium carbonate are added to methanol, and the mixture is reacted at 15-35° C. for 10-30 hours. The reaction solution is post-treated to obtain hexadecyl-15-ynoic acid methyl ester represented by formula III;

[0033] The molar ratio of 15-oxopentadecanoic acid methyl ester, (1-diazo-2-oxopropyl)phosphonic acid dimethyl ester and potassium carbonate represented by formula IV is 1:1-3:1-5, preferably 1:1:3;

[0034] The volume molar ratio of methanol to 15-oxopentadecanoic acid methyl ester represented by formula IV is 1 to 3:1, mL / mmol; preferably 1.5:1, mL / mmol;

[0035] Preferably, the reaction is carried out at 25°C for 16 hours;

[0036] The post-treatment method is as follows: the reaction solution is mixed with silica gel, and column chromatography is performed using a petroleum ether / ethyl acetate mixture with a volume ratio of 20:1 as an eluent, the eluate containing the target compound is collected, and the solvent is evaporated to obtain hexadecyl-15-ynoic acid methyl ester represented by formula III.

[0037] Specifically, step (4) is performed as follows:

[0038] Hexadecyl-15-ynoic acid methyl ester represented by formula III is added to a mixed solution of dichloromethane and acetone, and then phenylacetylene, tetramethylethylenediamine, and cuprous chloride are added, and the mixture is reacted at 15-45° C. for 3-24 hours. The reaction solution is post-treated to obtain 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II;

[0039] The molar ratio of hexadecyl-15-ynoic acid methyl ester represented by formula III, phenylacetylene, tetramethylethylenediamine, and cuprous chloride is 1:1-3:0.5-2:0.1-0.5, preferably 1:1.2:0.8:0.3;

[0040] The volume molar ratio of the mixed solution of dichloromethane and acetone to the methyl hexadecyl-15-ynoate represented by formula III is 0.5 to 2:1, mL / mmol; preferably 1:1, mL / mmol;

[0041] Preferably, the reaction is carried out at 25°C for 10 hours;

[0042] The post-treatment method is as follows: the reaction solution is mixed with silica gel, and column chromatography is performed using a petroleum ether / ethyl acetate mixture with a volume ratio of 20:1 as an eluent, the eluate containing the target compound is collected, and the solvent is evaporated to obtain 18-phenyloctadecane-15,17-diynoic acid methyl ester shown in formula II.

[0043] Specifically, step (5) is performed as follows:

[0044] Dissolve 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II in a mixed solution of tetrahydrofuran, methanol and water, add NaOH, react at 20-60° C. for 3-24 hours, and post-treat the reaction solution to obtain aromatic diacetylene palmitic acid represented by formula I;

[0045] The molar ratio of 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II to NaOH is 1:1 to 7, preferably 1:6;

[0046] The volume molar ratio of the mixed solution of tetrahydrofuran, methanol and water to 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II is 1 to 3:1, mL / mmol; preferably 1:1, mL / mmol;

[0047] Preferably, the reaction is carried out at 25°C for 10 hours;

[0048] The post-treatment method is: adjusting the pH of the reaction solution to 1-3 (preferably pH 1) with hydrochloric acid, then extracting with ethyl acetate, combining the organic phases, and drying the solvent to obtain the aromatic diacetylene palmitic acid shown in formula I.

[0049] The aromatic diacetyl palmitic acid of the present invention can be used as a Raman probe for cell imaging.

[0050] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0051] The invention develops an 18-phenyloctadecane-15,17-diynoic acid compound, and the preparation process has mild reaction conditions, readily available raw materials, convenient operation, and is conducive to industrial production.

[0052] The compound of the present invention shows a high Raman signal intensity, lays a foundation for the study of the metabolic mechanism of palmitic acid, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 : Microscopic imaging of HeLa cells incubated with aromatic diacetyl palmitate. Cells at 100 μM were imaged using a 55 mW Raman microscope. A, intracellular 2245 cm -1 (Aromatic diacetylenic palmitic acid) alkynyl Raman imaging and single-point Raman spectroscopy; B, extracellular 2245 cm -1 (Aromatic diacetylenic palmitic acid) alkynyl Raman imaging and single-point Raman spectrum; C, bright field image of HeLa cells under microscope; D, 2245cm -1 Alkynyl Raman imaging (2245 cm -1 The absorption peak of aromatic diacetyl palmitate alkynyl) E, 2950cm -1 CH Raman imaging (2950 cm -1 The absorption peak of the low-frequency CH bond is located at (1 / 4), indicating the distribution of lipids in cells).

[0054] Figure 2 :Raman characterization and intensity comparison of two labeled palmitic acids; A and B are the structural formulas of alkynyl palmitic acid and aromatic diacetyl palmitic acid, respectively; C is the Raman spectrum of the two labeled palmitic acids at 20 mM in DMSO (solvent); D is the Raman spectrum of 2000-2500 cm in C -1 Zoomed in image. DETAILED DESCRIPTION

[0055] The present invention is further described below by means of specific examples, but the protection scope of the present invention is not limited thereto.

[0056] Example 1

[0057] (1) Sodium (0.1 g, 4.35 mmol) was added to methanol (10 ml). After the sodium was completely dissolved, compound (VI) (2.0 g, 8.33 mmol) was added and the mixture was reacted at room temperature for 2 h. After the reaction, hydrochloric acid (1 mol / L, 13 mL, 13 mmol) was added. The precipitated white solid product was filtered and dried in an oven at 50°C for 3 h. The filtrate was extracted with ethyl acetate (4 × 30 ml). The organic layers were combined, dried over anhydrous sodium sulfate, evaporated to dryness under reduced pressure, and combined with the dried white solid product to obtain compound (V) (2.10 g, yield 92.6%).

[0058] 1 HNMR (400MHz, CDCL3) δ3.70(s,3H),3.66(t,J=6.8,Hz,1H),2.33(t,J=7.6Hz,2H),1.69–1.57(m,4H),1.38–1.22(m,22H).

[0059] (2) The above compound (V) (2.05 g, 7.53 mmol) was added to dichloromethane (7 ml), and pyridinium chlorochromate (2.10 g, 9.79 mmol) was added under ice-water bath. After 5 minutes, the mixture was transferred to room temperature and reacted for 3 hours. After the reaction, 2.5 g of silica gel was added to the sample, and the mixture was concentrated and separated by column chromatography (eluent: petroleum ether: ethyl acetate = 20:1, volume ratio). The eluate containing the target compound was collected and concentrated to dryness to obtain compound (IV) (1.80 g, yield 88.5%).

[0060] 1 HNMR (400MHz, CDCL3) δ9.75 (s, 1H), 3.65 (s, 3H), 2.41 (td, J = 7.2, 2.0Hz, 2H), 2.29 (t, J = 7.6Hz, 2H), 1.61 (m, 4H), 1.26 (m, 18H).

[0061] (3) The above compound (IV) (1.7 g, 6.30 mmol) was added to methanol (12 ml), and potassium carbonate (1.70 g, 12.4 mmol) and dimethyl (1-diazo-2-oxopropyl)phosphonate (1.56 g, 8.2 mmol) were added. The mixture was reacted at room temperature for 24 h. After the reaction was completed, the mixture was separated by column chromatography (eluent: petroleum ether: ethyl acetate = 20:1, volume ratio). The eluate containing the target compound was collected and concentrated to dryness to obtain compound (III) (1.3 g, yield 77.6%).

[0062] 1HNMR(400MHz,CDCL3)δ3.66(s,3H),2.30(t,J=7.6Hz,2H),2.18(td,J=7.2,2.4Hz,2H),1.93 (t,J=2.4Hz,1H),1.61(t,J=7.6Hz,2H),1.56-1.47(m,2H),1.42-1.35(m,2H),1.27(m,16H).

[0063] (4) The above compound (III) (1.25 g, 4.70 mmol) was added to dichloromethane (4 ml) and acetone (4 ml), and then phenylacetylene (0.53 g, 5.20 mmol), tetramethylethylenediamine (0.34 g, 3.00 mmol) and cuprous chloride (0.089 g, 0.90 mmol) were added. The mixture was reacted at room temperature in an oxygen-filled environment for 10 h. After the reaction, the reaction solution was concentrated and separated by column chromatography (eluent: petroleum ether: ethyl acetate = 20:1, volume ratio). The eluate containing the target compound was collected and concentrated, and then passed through a 20 cm × 20 cm silica gel preparation plate (developing solvent: petroleum ether: acetone = 40:1). The target product was collected and dissolved in methanol (10 ml) and dichloromethane (10 ml). The resulting solution containing the product was concentrated and dried to obtain the 18-phenyloctadecane-15,17-diynoic acid methyl ester compound represented by formula (II) (0.90 g, yield 52.3%).

[0064] 1 HNMR (400MHz, CDCL3) δ7.51-7.44(m,2H),7.36-7.25(m,3H),3.66(s,3H),2.35(t,J=6.8Hz,2H),2.30(t,J=7.6Hz,1H),1.44-1.05(m,22H).

[0065] (5) The above compound (II) (0.90 g, 2.46 mmol) was added to tetrahydrofuran (4 ml), methanol (4 ml) and water (1 ml), and sodium hydroxide (0.22 g, 5.00 mmol) was added to react at room temperature for 6 h. After the reaction was completed, the reaction solution was concentrated to remove tetrahydrofuran, hydrochloric acid (1 mol / L, 7 ml, 7.0 mmol) was added, and ethyl acetate (4×20 ml) was added for extraction. The organic layers were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated and distilled under reduced pressure to obtain the target compound 18-phenyloctadecane-15,17-diynoic acid (0.85 g, yield 98.2%) as shown in formula (I).

[0066] 1HNMR(400MHz,DMSO-d6)δ11.99(s,1H),7.55-7.50(m,2H),7.45-7.37(m,3H ),2.41(d,J=7.2Hz,2H),2.20-2.14(m,2H),1.55-1.41(m,4H),1.25(s,18H).

[0067] Example 2

[0068] The operation was the same as that in Example 1, except that the amount of sodium (0.10 g, 4.35 mmol) in step (1) was changed to (0.05 g, 2.17 mmol), to obtain compound (I) (0.60 g, total yield 20.5%).

[0069] Example 3

[0070] The operation was the same as that in Example 1, except that the amount of sodium (0.10 g, 4.35 mmol) in step (1) was changed to (0.13 g, 5.65 mmol), to obtain compound (I) (0.75 g, total yield 25.6%).

[0071] Example 4

[0072] The operation was the same as that in Example 1, except that the reaction temperature after adding compound VI in step (1) was changed from room temperature to 50°C, to obtain compound (I) (0.88 g, total yield 30%).

[0073] Example 5

[0074] The operation was the same as in Example 1, except that the reaction temperature after adding compound VI in step (1) was changed from room temperature to 35°C, to obtain compound (I) (0.73 g, total yield 24.9%).

[0075] Example 6

[0076] The operation was the same as that in Example 1, except that chromium trioxide (0.60 g, 6.00 mmol) was used instead of pyridinium chlorochromate in step (2) to obtain compound (I) (0.60 g, total yield 20.5%).

[0077] Example 7

[0078] The operation was the same as that in Example 1, except that active manganese dioxide (0.77 g, 8.90 mmol) was used instead of pyridinium chlorochromate in step (2) to obtain compound (I) (0.22 g, total yield 8%).

[0079] Example 8

[0080] The operation was the same as that in Example 1, except that in step (3), after adding dimethyl (1-diazo-2-oxopropyl)phosphonate, the reaction time was changed from 24 h to 10 h, to obtain compound (I) (0.80 g, total yield 27.3%).

[0081] Example 9

[0082] The operation was the same as that in Example 1, except that in step (3), after adding dimethyl (1-diazo-2-oxopropyl)phosphonate, the reaction time was changed from 24 h to 16 h, to obtain compound (I) (0.56 g, total yield 20%).

[0083] Example 10

[0084] The operation was the same as that in Example 1, except that the amount of potassium carbonate added in step (3) (1.70 g, 12.4 mmol) was changed to (2.40 g, 17.51 mmol), to obtain compound (I) (0.88 g, total yield 30%).

[0085] Example 11

[0086] The operation was the same as that in Example 1, except that the amount of dimethyl (1-diazo-2-oxopropyl)phosphonate added in step (3) (1.56 g, 8.2 mmol) was changed to (2.37 g, 12.3 mmol), to obtain compound (I) (0.75 g, total yield 25.5%).

[0087] Example 12

[0088] The operation was the same as that in Example 1, except that the amount of cuprous chloride (0.089 g, 0.90 mmol) in step (4) was changed to (0.133 g, 1.34 mmol), to obtain compound (I) (0.77 g, total yield 26.2%).

[0089] Example 13

[0090] The operation was the same as that in Example 1, except that the amount of cuprous chloride (0.089 g, 0.90 mmol) in step (4) was changed to (0.069 g, 0.70 mmol), to obtain compound (I) (0.69 g, total yield 23.5%).

[0091] Example 14

[0092] The operation was the same as that in Example 1, except that the amount of phenylacetylene (0.53 g, 5.20 mmol) in step (4) was changed to (0.90 g, 8.82 mmol), to obtain compound (I) (0.5 g, total yield 17%).

[0093] Example 15

[0094] The operation was the same as that of Example 1, except that the amount of tetramethylethylenediamine (0.34 g, 3.00 mmol) in step (4) was changed to (0.40 g, 3.44 mmol), to obtain compound (I) (0.85 g, total yield 29.0%).

[0095] Example 16: Raman signal detection of aromatic diacetyl palmitic acid and 15-alkynyl palmitic acid

[0096] Experimental steps:

[0097] 1) Sample preparation: For the soluble samples aromatic butadiynyl palmitic acid and 15-alkynyl palmitic acid, 3.5 mg of aromatic butadiynyl palmitic acid was weighed and dissolved in 500 μL DMSO, and 2.52 mg of 15-alkynyl palmitic acid was weighed and dissolved in 500 μL DMSO to prepare a sample solution with a concentration of 20 mM.

[0098] 2) Raman detection

[0099] Raman microscope parameters were set, including an excitation wavelength of 532 nm, a 60× objective magnification, a detection power of 30 mW, an integration time of 2.5 s, and three accumulations. Ten Raman spectra were measured at a 20 mM concentration for each sample. The experiment was repeated three times to obtain a total of 30 spectra. The average of these 30 spectra for each sample was used as the representative Raman intensity for aromatic diacetylenic palmitic acid and 15-acetylenic palmitic acid at that concentration.

[0100] It can be clearly observed from the spectral data that the characteristic vibration region of aromatic diacetylene (2245 cm -1 ) showed significant Raman scattering signals, which preliminarily indicated that aromatic diacetylene palmitic acid could effectively cross the cell membrane barrier, indicating that the molecule had obvious molecular-level interaction with the cell, which provided important clues for subsequent in-depth research on the function and mechanism of action of the compound in cells.

[0101] 3) Cell imaging

[0102] Cell plating: First, immerse the glass slide in anhydrous ethanol for 10 minutes, transfer to sterile PBS and soak for 5 minutes. Use sterile tweezers to place the slide into a 96-well plate, one slide per well. After trypsinization, the cells are neutralized with serum-containing medium, centrifuged, resuspended, and counted. Adjust the cell density to 4×10 4 / mL, add 100uL of suspension to each well (i.e. 4000 cells / well), shake the culture plate gently to evenly distribute the cells, let it stand for 10 minutes and then put it into the incubator.

[0103] Treatment with aromatic diacid palmitic acid: 100 μL of aromatic diacid palmitic acid diluted in culture medium was added to each well of HeLa cells (4000 cells / well) seeded 24 hours after incubation, resulting in a final concentration of 100 μM. After 24 hours of incubation, the medium was removed, the cells were washed twice with PBS, and the cells were fixed with 4% paraformaldehyde for 10 minutes. The 4% paraformaldehyde was then aspirated, the cells were rinsed twice with PBS, and sterile water was added to each well before storage at 4°C for Raman analysis.

Claims

1. An aromatic diacetylene palmitic acid, having the structural formula shown in Formula I:

2. A method for synthesizing aromatic diacetylene palmitic acid as shown in formula I, characterized in that: The synthesis method comprises: (1) reacting 15-olactone represented by formula VI with sodium methoxide to obtain 15-hydroxypentadecanoic acid methyl ester represented by formula V; (2) reacting 15-hydroxypentadecanoic acid methyl ester represented by formula V with an oxidant to obtain 15-oxopentadecanoic acid methyl ester represented by formula IV; (3) 15-oxopentadecanoic acid methyl ester represented by formula IV is reacted with dimethyl (1-diazo-2-oxopropyl)phosphonate and potassium carbonate to obtain hexadecyl-15-ynoic acid methyl ester represented by formula III; (4) reacting hexadecyl-15-ynoic acid methyl ester represented by formula III with phenylacetylene to obtain 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II; (5) 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II is reacted with sodium hydroxide to obtain aromatic diacetylene palmitic acid represented by formula I; The synthetic route is as follows:

3. The synthesis method according to claim 2, wherein Step (1) is as follows: Sodium is added to methanol. After the sodium is completely dissolved, 15-acid lactone represented by formula VI is added, and the mixture is reacted at 20-50° C. for 1-6 hours. The reaction solution is post-treated to obtain 15-hydroxypentadecanoic acid methyl ester represented by formula V; The molar ratio of sodium to the 15-acid lactone represented by formula VI is 1:1-3.

4. The synthesis method according to claim 2, wherein Step (2) is as follows: Dissolve 15-hydroxypentadecanoic acid methyl ester represented by formula V in dichloromethane, add an oxidant, react at 0-25° C. for 1-5 hours, and post-treat the reaction solution to obtain 15-oxopentadecanoic acid methyl ester represented by formula IV; The oxidizing agent is selected from one or more of pyridinium chlorochromate, chromium trioxide, Dess-Martin periodinane, and activated manganese dioxide; The molar ratio of 15-hydroxypentadecanoic acid methyl ester represented by formula V to the oxidant is 1:1 to 2.

5.

5. The synthesis method according to claim 2, wherein Step (3) is as follows: 15-Oxopentadecanoic acid methyl ester represented by formula IV, (1-diazo-2-oxopropyl) phosphonic acid dimethyl ester, and potassium carbonate are added to methanol, and the mixture is reacted at 15-35° C. for 10-30 hours. The reaction solution is post-treated to obtain hexadecyl-15-ynoic acid methyl ester represented by formula III; The molar ratio of 15-oxopentadecanoic acid methyl ester, (1-diazo-2-oxopropyl)phosphonic acid dimethyl ester and potassium carbonate shown in formula IV is 1:1-3:1-5.

6. The synthesis method according to claim 2, wherein Step (4) is as follows: Hexadecyl-15-ynoic acid methyl ester represented by formula III is added to a mixed solution of dichloromethane and acetone, and then phenylacetylene, tetramethylethylenediamine, and cuprous chloride are added, and the mixture is reacted at 15-45° C. for 3-24 hours. The reaction solution is post-treated to obtain 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II; The molar ratio of hexadecyl-15-ynoic acid methyl ester represented by formula III, phenylacetylene, tetramethylethylenediamine and cuprous chloride is 1:1-3:0.5-2:0.1-0.

5.

7. The synthesis method according to claim 2, wherein Step (5) is as follows: Dissolve 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II in a mixed solution of tetrahydrofuran, methanol and water, add NaOH, react at 20-60° C. for 3-24 hours, and post-treat the reaction solution to obtain aromatic diacetylene palmitic acid represented by formula I; The molar ratio of 18-phenyloctadecane-15,17-diynoic acid methyl ester represented by formula II to NaOH is 1:1-7.

8. Application of the aromatic diacetylene palmitic acid represented by Formula I as a Raman probe in cell imaging.

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