Radioisotope carbon-14 labeled methoprene and preparation method thereof

Abstract

The invention provides radioisotope carbon-14 labeled methoprene and a preparation method thereof, and the preparation method comprises the following steps: S1, preparing [cyano-14C] (R)-7-methoxy-3, 7-dimethyl octanenitrile; s2, preparing [aldehyde-14C] citronellal; and S3, preparing the carbon-14 labeled methoprene. The related field blank of radioisotope carbon-14 labeled methoprene is filled, accurate and reliable tracing information can be provided when behaviors of methoprene in organisms and environments are researched, a powerful tool is provided for deeply exploring the metabolic process, environmental behaviors, pharmacokinetics and the like of methoprene, and the method has the advantages of being high in practicability and wide in application prospect. And the development of research in related fields is promoted, such as optimization of the use strategy of methoprene in agricultural pest control.

Description

Technical Field

[0001] The invention relates to the field of radiochemical synthesis, and in particular to radioisotope carbon-14 labeled methoprene (E, E)-(RS)-11-methoxy-3,7,11-trimethyl dodeca-2,4-enoic acid isopropyl ester and a preparation method thereof. Background Art

[0002] Methoprene (English name: Methoprene; Chinese name: (E, E)-(RS)-11-methoxy-3,7,11-trimethyldodec-2,4-enoic acid isopropyl ester) is a biochemical insecticide. Due to its high activity, relative specificity to target organisms and good environmental safety, a large number of products have been developed, evaluated and promoted for the control of various pests. As an external insecticide, methoprene has target organism specificity and extremely high juvenile hormone activity. By destroying or interfering with the hormone balance in insects, larvae cannot complete growth metamorphosis and sexual maturity and die, and can also cause adult infertility, thereby reducing the pest population.

[0003] At present, the studies on the absorption, distribution, transfer, residues of methoprene in plants and its environmental behavior in water and soil rarely involve the metabolism / degradation products of methoprene. In other words, the studies on the metabolic process and environmental behavior of methoprene are still not in-depth enough. The radioactive isotope carbon-14 labeled methoprene [(E,E)-(RS)-11-methoxy-3,7,11-trimethyldodec-2,4-enoic acid isopropyl ester] is a radioactive tracer necessary for studying its safety and effectiveness in plant tests and pharmacokinetics (tissue distribution, metabolite structure identification, mass balance, etc.). Summary of the invention

[0004] The purpose of the present invention is to provide a radioactive isotope carbon-14 labeled methoprene and a preparation method thereof, so as to solve the problems of lack of effective radioactive tracers and insufficient research on metabolic processes and environmental behaviors in existing methoprene research.

[0005] In a first aspect, the present technical solution provides a method for preparing radioisotope carbon-14 labeled methoprene, comprising the following steps: S1: Preparation of [Cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile: Under the protection of inert gas at 0-60℃, dissolve 4-methylbenzenesulfonic acid-(2R)-6-methoxy-2,6-dimethylheptyl ester in a polar aprotic solvent, add an inorganic base and stir, then add [carbon- 14 C] Sodium cyanide was stirred to react until the reaction was complete, and a fat-soluble solvent was added to separate the liquids. The organic solution layer was dried and concentrated, and [cyano-14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile; S2: Preparation of [aldehyde- 14 C] Citronellal: At a reaction temperature of 0-50°C, [cyano- 14 C] (R) -7-methoxy-3,7-dimethyloctanonitrile and RaneyNi were reacted in an acid-base buffer solution until the reaction was complete, a fat-soluble solvent was added to separate the liquids, the organic solution layer was dried and concentrated, and [aldehyde- 14 C] citronellal; S3: Preparation of carbon-14 labeled methoprene: At 0 - 50 ° C, in an inert gas atmosphere and away from light, [aldehyde- 14 C] Citronellal, phosphorus ylide reagent and 18-crown ether-6 are reacted in an aprotic solvent until the reaction is completed, a fat-soluble solvent is added for separation, the organic solution layer is dried and concentrated, and carbon-14 labeled methoprene is obtained by rapid column chromatography.

[0006] The radioisotope carbon-14 labeled methoprene prepared in this scheme is labeled on the 7-carbon atom of the fatty chain in the methoprene molecule. The structural formula of the prepared radioisotope carbon-14 labeled methoprene is: [(E, E)-(RS)-11-methoxy-3,7,11-trimethyldodec-2,4-enoic acid isopropyl ester]. The chemical formula of the radioisotope carbon-14 labeled methoprene is shown in the following formula (I), wherein the asterisk indicates the labeling position of the isotope carbon-14: .

[0007] The radioactive isotope carbon-14 labeled methoprene synthesized in this scheme has a determined labeling site of the isotope carbon-14, and has the advantages of high radiochemical purity and chemical purity, short synthesis steps, and the nuclide carbon-14 is firmly labeled in the methoprene molecule and is not easy to fall off, which can meet the requirements of tracer experiments in organisms and the environment.

[0008] In step S1, the sulfonate group in (2R)-6-methoxy-2,6-dimethylheptyl 4-methylbenzenesulfonate has good leaving property. Under alkaline conditions, the inorganic base captures the cyanide anion in the carbon-14 labeled sodium cyanide, making it a nucleophilic reagent. The cyanide anion attacks the carbon atom of the sulfonate group, and a nucleophilic substitution reaction occurs to generate [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile. During the entire reaction process, polar aprotic solvents are beneficial to the nucleophilic substitution reaction. They can better dissolve and disperse the reactants and stabilize the reaction transition state.

[0009] Specifically, in some embodiments, the polar aprotic solvent in step S1 is selected from one or a combination of two or more of DMSO, DMF, and THF, preferably DMSO.

[0010] The inorganic base in step S1 is selected from one or a combination of two or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium bicarbonate, and potassium bicarbonate, preferably sodium hydroxide.

[0011] [Carbon- 14 C] cyanide includes a compound selected from [carbon- 14 C] sodium cyanide, [carbon- 14 C] potassium cyanide, [carbon- 14 C] copper cyanide, [carbon- 14 C] one or a combination of two or more zinc cyanides.

[0012] The fat-soluble solvent in step S1 is selected from one or a combination of two or more selected from ethyl acetate, isopropyl acetate, dichloromethane, chloroform, petroleum ether, ether, and benzene, preferably ethyl acetate.

[0013] [Cyano- 14 The chemical structure of (R)-7-methoxy-3,7-dimethyloctanonitrile is shown in the following formula (II), where the asterisk indicates the position of the isotope carbon-14: .

[0014] In some embodiments, in step S1, sodium cyanide labeled with carbon-14 is added and stirred for 1 to 24 hours, and pure water is added to terminate the reaction after monitoring the reaction solution with a cyanide detection reagent to see if there is no free cyanide ion. The advantage of doing so is that it can ensure that the reaction has been fully carried out. If there are still free cyanide ions in the reaction solution, it means that the reaction has not yet ended and there is still some sodium cyanide labeled with carbon-14 left, and the reaction needs to be continued to increase the target product [cyanide- 14 C] (R) -7-methoxy-3,7-dimethyloctanonitrile yield; at the same time, it can also avoid the occurrence of side reactions. After the target reaction is basically completed, the excess cyanide ion may cause unnecessary side reactions with other substances.

[0015] In step S2 of this protocol, [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile undergoes hydrogenation reduction reaction of cyano group under the catalysis of RaneyNi. RaneyNi provides active hydrogen atoms. The cyano group is first reduced to an imine intermediate, and then the imine intermediate is further reduced to an aldehyde group to obtain [aldehyde- 14C] Citronellal. The pyridine-acetic acid-water mixed solvent acts as an acid-base buffer solvent to adjust the pH value of the reaction system, allowing the reaction to proceed in a suitable acid-base environment, and at the same time helps to stabilize the activity of the reaction intermediates and catalysts.

[0016] In some embodiments, the acid-base buffer solvent includes, but is not limited to, a pyridine-acetic acid-water solution of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphite, and sodium hypophosphite. Specifically, in some embodiments, [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile and sodium hydrogen hypophosphite monohydrate are stirred in a mixed solvent, wherein the mixed solvent is a reagent formed by mixing pyridine, acetic acid and water.

[0017] In some embodiments, the reaction temperature of step S2 is 0-25°C.

[0018] In some embodiments, the fat-soluble solvent in step S2 is selected from one or a combination of two or more selected from ethyl acetate, isopropyl acetate, dichloromethane, chloroform, petroleum ether, ether, and benzene, preferably ethyl acetate.

[0019] In some embodiments, RaneyNi is added and reacted for 1 to 24 hours before pure water is added to terminate the reaction.

[0020] [aldehyde- 14 The structural formula of citronellal is shown in the following formula (III), wherein the asterisk indicates the position of the isotope carbon-14: .

[0021] In step S3 of this scheme, the phosphorus ylide reagent generates a carbon anion under alkaline conditions, and the carbon anion has a strong nucleophilicity. 14 The aldehyde group of C] citronellal acts as an electrophilic center and undergoes a Wittig reaction (coupling reaction) with the carbon anion generated by the phosphorus ylide reagent. The addition of 18-crown ether-6 can complex the cations in the reaction system, enhance the alkalinity of the inorganic base, and promote the generation of the phosphorus ylide reagent and the reaction. The reaction generates carbon-14 labeled methoprene. Aprotic solvents are beneficial to the reaction, can dissolve reactants and intermediates, and promote the smooth progress of the reaction.

[0022] In some embodiments, the phosphorus ylide reagent is dissolved in a non-polar solvent, and then an inorganic base and 18-crown ether-6 are added and stirred to obtain a reaction solution, and the [aldehyde- 14 C] Citronellal is dissolved in an aprotic solvent and added to the reaction solution to carry out the reaction.

[0023] In some embodiments, the aprotic solvent is selected from one of benzene and toluene.

[0024] In some embodiments, the non-polar solvent in step S3 is selected from one or a combination of two or more of benzene, toluene, chloroform, ethylene dichloride, and carbon tetrahalide, preferably benzene.

[0025] In some embodiments, the inorganic base in step S3 is selected from one or a combination of two or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium bicarbonate, and potassium bicarbonate, preferably sodium hydroxide.

[0026] In some embodiments, the reaction solution is added under light-proof conditions and stirred for 3 to 24 hours until the reaction is complete, and then water is added to terminate the reaction.

[0027] In some embodiments, the fat-soluble solvent in step S3 is selected from one or a combination of two or more selected from ethyl acetate, isopropyl acetate, dichloromethane, chloroform, petroleum ether, ether, and benzene, preferably ethyl acetate.

[0028] In a second aspect, the present invention provides a radioisotope carbon-14 labeled methoprene prepared according to the above-mentioned method for preparing radioisotope carbon-14 labeled methoprene, the structural formula of which is shown in the following formula (I): .

[0029] The radioisotope carbon-14 labeling site of the radioisotope carbon-14 labeled methoprene in this scheme is on the fatty chain of methoprene.

[0030] Compared with the prior art, this technical solution has the following characteristics and beneficial effects: This scheme innovatively provides a preparation method of radioisotope carbon-14 labeled methoprene, filling the gap in the relevant field. The various steps in its preparation process are closely linked, and high reaction efficiency and product purity are ensured by carefully selecting solvents, reagents and reaction conditions. At the level of reaction principle, the chemical properties of various substances are cleverly utilized, such as the leaving property of sulfonate groups, the catalytic hydrogenation of RaneyNi, and the nucleophilicity of phosphorus ylide reagents, to achieve precise labeling. In terms of practical application, the prepared labeled methoprene has a clear labeling site, high radiochemical purity and chemical purity, simple synthesis steps, and a firm nuclide labeling that is not easy to fall off. This enables it to provide accurate and reliable tracing information when studying the behavior of methoprene in organisms and the environment, providing a powerful tool for in-depth exploration of the metabolic process, environmental behavior and pharmacokinetics of methoprene, and helping to promote the development of research in related fields, such as optimizing the use strategy of methoprene in agricultural pest control. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 [Cyano- 14C] NMR spectrum of (R)-7-methoxy-3,7-dimethyloctanonitrile.

[0032] Figure 2 [aldehyde- 14 C] NMR spectrum of citronellal.

[0033] Figure 3 It is the nuclear magnetic spectrum of the radioisotope carbon-14 labeled methoprene synthesized in this example. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0035] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] Example 1 Synthesis of Radioisotope Carbon-14 Labeled Methoprene The reaction equation of this embodiment 1 is as follows: .

[0037] S1: Synthesis of [Cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile; Under nitrogen protection, sodium hydroxide (40 mg, 1.0 mmol) and [carbon- 14C] Sodium cyanide (102 mg, 2.0 mmol) was added to DMSO (5 mL), and 4-methylbenzenesulfonic acid (2R)-6-methoxy-2,6-dimethylheptyl ester (662.9 mg, 2.02 mmol) was dissolved in DMSO (1 mL) and added to the reaction solution. The mixture was stirred at 25 °C for 18 h. After the reaction solution was tested for free cyanide ions by a cyanide detection reagent, water (18 mL) was added. The mixture was extracted four times with ethyl acetate (20 mL). The organic phases were combined and dried, concentrated to dryness, and purified on a 5 cm diameter, 20 g (300-400 mesh) silica gel column. The eluents were PE (150 mL), PE:EA=20:1 (250 mL), and PE:EA=10:1 (100 mL). The flow rate was 1 mL / s. The effluent from PE:EA=20:1 was collected and concentrated to dryness to obtain [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile (325.4 mg, 1.77 mmol, 88.42% yield), [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile NMR spectrum is as follows Figure 1 shown.

[0038] Step S2: Synthesis of [aldehyde- 14 C] Citronellal: At 25°C, [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile (104.5 mg, 0.568 mmol) and sodium hypophosphite monohydrate (362.0 mg, 3.408 mmol) were dissolved in 3 mL of a mixed solvent of pyridine-acetic acid-water (4:2:1) and stirred rapidly. RaneyNi (0.42 mL) stored in water was quickly added. After stirring for 30 minutes, a second batch of RaneyNi (0.2 mL) stored in water was added. After reacting for 3 hours, pure water was added to terminate the reaction. The reaction was stopped, and the mixture was extracted with ethyl acetate (10 mL) for six times. The organic phases were combined, dried, concentrated to dryness, and purified on a 5 cm diameter, 20 g (300-400 mesh) silica gel column. The eluents were PE (100 mL), PE:EA=20:1 (200 mL), and PE:EA=10:1 (150 mL). The flow rate was 1 mL / s. The effluents of PE:EA=20:1 (200 mL) and PE:EA=10:1 (150 mL) were collected and concentrated to dryness to obtain [aldehyde- 14 C] citronellal (74.6 mg, 0.397 mmol, 69.86% yield), [aldehyde- 14 C]Citronellal NMR spectrum is as follows Figure 2 shown.

[0039] Step S3: Synthesis of carbon-14 labeled methoprene: Under nitrogen protection, phosphorus ylide reagent (435.9 mg, 1.425 mmol) was dissolved in benzene (2 mL), potassium hydroxide (122.9 mg, 2.192 mmol) and 18-crown-6 (57.6 mg, 0.218 mmol) were added, and the mixture was stirred rapidly at 25 °C for 5 minutes to obtain [aldehyde- 14 C] Citronellal (206.0 mg, 1.096 mmol) was dissolved in benzene (1 mL) and slowly added dropwise into the reaction solution in the dark. The reaction was terminated after 18 h of reaction at 25 °C in the dark. The mixture was extracted with ethyl acetate (5 mL) ten times. The organic phases were combined and dried. The mixture was concentrated to dryness and purified on a 5 cm diameter, 20 g (300-400 mesh) silica gel column. The eluent was PE (200 mL) and PE:EA=10:1 (200 mL). The flow rate was 1 mL / s. The effluent from PE:EA=10:1 (150 mL) was collected and concentrated to dryness to obtain carbon-14 labeled methoprene (264.0 mg, 0.846 mmol, 77.20% yield). Among them, (Z)-carbon-14 labeled methoprene was 14%, and (E)-carbon-14 labeled methoprene was 86%. The NMR spectrum of carbon-14 labeled methoprene synthesized in this example is shown in FIG. Figure 3 shown.

[0040] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0041] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A method for preparing radioisotope carbon-14 labeled methoprene, characterized in that: The following steps are involved: S1: Preparation of [Cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile: Under the protection of inert gas at 0-60℃, dissolve 4-methylbenzenesulfonic acid-(2R)-6-methoxy-2,6-dimethylheptyl ester in a polar aprotic solvent, add an inorganic base and stir, then add [carbon- 14 C] Sodium cyanide was stirred to react until the reaction was complete, and a fat-soluble solvent was added to separate the liquids. The organic solution layer was dried and concentrated, and [cyano- 14 C] (R)-7-methoxy-3,7-dimethyloctanonitrile; S2: Preparation of [aldehyde- 14 C] Citronellal: At a reaction temperature of 0-50°C, [cyano- 14 C] (R) -7-methoxy-3,7-dimethyloctanonitrile and RaneyNi were reacted in an acid-base buffer solution until the reaction was completed, a fat-soluble solvent was added to separate the liquids, the organic solution layer was dried and concentrated, and [aldehyde- 14 C] citronellal; S3: Preparation of carbon-14 labeled methoprene: At 0 - 50 ° C, inert gas protection and light-proof conditions, [aldehyde- 14 C] Citronellal, phosphorus ylide reagent and 18-crown ether-6 are reacted in an aprotic solvent until the reaction is completed, a fat-soluble solvent is added for separation, the organic solution layer is dried and concentrated, and carbon-14 labeled methoprene is obtained by rapid column chromatography.

2. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: Radioisotope carbon-14 labeled methoprene The radioisotope carbon-14 of methoprene is labeled on the 7-carbon atom of the fatty chain in the methoprene molecule, and the structural formula is shown in the following formula (I): 。 3. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: The polar aprotic solvent in step S1 is selected from one or more combinations of DMSO, DMF, and THF; the inorganic base is selected from one or more combinations of potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium bicarbonate, and potassium bicarbonate.

4. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: [carbon- 14 C] cyanide is selected from [carbon- 14 C] sodium cyanide, [carbon- 14 C] potassium cyanide, [carbon- 14 C] copper cyanide, [carbon- 14 C] zinc cyanide, one or a combination of two or more.

5. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: [Cyano- 14 The chemical structure of (R)-7-methoxy-3,7-dimethyloctanonitrile is shown in the following formula (II): 。 6. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: The acid-base buffer solvent includes, but is not limited to, a pyridine-acetic acid-water solution of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphite, and sodium hypophosphite.

7. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: [aldehyde- 14 C] The structural formula of citronellal is shown in the following formula (III): 。 8. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: The phosphorus ylide reagent is dissolved in a non-polar solvent, and then an inorganic base and 18-crown ether-6 are added and stirred to obtain a reaction solution. 14 C] Citronellal is dissolved in an aprotic solvent and added to the reaction solution to carry out the reaction.

9. The method for preparing radioisotope carbon-14 labeled methoprene according to claim 1, characterized in that: The aprotic solvent in step S3 is selected from benzene and toluene.

10. A radioactive isotope carbon-14 labeled methoprene, characterized in that: The method for preparing radioisotope carbon-14 labeled methoprene according to any one of claims 1 to 9 has a structural formula as shown in the following formula (I): 。

Images