Synthesis of Novel Environmentally Friendly

Dehydronor-Cantharidin Insecticides

Jianxin Sun

, Mengjing Feng

and Liangzhong Xu

1,2 c

College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042,

China

State Key Laboratory Base of Eco-chemcal Engineering, Qingdao 266042, China

Keywords:

Dehydronorcantharidin, Synhtesis, Biological Activity.

Abstract:

In order to find new environmentally friendly compounds with insecticidal activity, a series of

nornorcantharidin dihydrazide derivatives were synthesized by active substructure splicing method based on

the structure of norcantharidin and dihydrazide. the synthesized compounds were characterized by

H NMR,

C NMR and HRMS. The results of biological activity test showed that compound I

had the highest activity

(52% at the concentration of 1 mg/L against plutella xylostella and 70% at the concentration of 10 mg/L

against Tetranychus cinnabarinus).

1 INTRODUCTION

Insecticides from natural products are

environmentally compatible, so they are ideal sources

for developing environmentally friendly insecticides.

Cantharides (Zhang 2018) is a traditional Chinese

medicine, which comes from the dried bodies of

meloidae insects. It is mainly used in the treatment of

malignant tumors and tinea (Song 2020). It is difficult

to synthesize cantharidin artificially (Wang 2014), so

the main source of cantharidin is dry Mylabris

phalerata Pallas, so the main way to obtain

cantharidin is still natural extraction.

Cantharides

These factors seriously affect the development

and application of cantharidin. Norcantharidin (Zhou

https://orcid.org/0000-0002-2070-2443

https://orcid.org/0000-0002-6785-9245

https://orcid.org/0000-0002-8391-2739

2020) is one of the important derivatives of

cantharidin. It can be obtained from maleic anhydride

and furan by two steps of Diels-alder reaction and

catalytic hydrogenation reaction (Chi 2019, Ogura

2021). The synthesis route is simple, the atom

economy is good and the synthesis cost is low. It can

be used in large-scale industrial production. In

addition, there are some similarities in biological

activities between the two compounds (Yang 2016).

This paper refers to dihydrazide pesticides as the

main reference structure, through the use of

dehydronorcantharidin (Jin 2015, Li 2014) part and

dihydrazide key active intermediate tert butyl

hydrazine condensation, dehydronorcantharidin (He

2020) derivatives were obtained, and then applied the

active substructure splicing theory to synthesize a

series of compounds.

Norcantharidin

Sun, J., Feng, M. and Xu, L.

Synthesis of Novel Environmentally Friendly Dehydronor-cantharidin Insecticides.

DOI: 10.5220/0011297200003443

In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 833-837

ISBN: 978-989-758-595-1

833

2 SYNTHESIS OF THE TARGET

COMPOUNDS

2.1 Synthesis of the Target Compounds

Figure 1: Synthetic route of target compounds I

-I

2.1.1 General Information for Synthesis

All reagents and solvents were used as received from

commercial sources. All reactions were carried out

under air atmosphere and monitored by thin-layer

chromatography (TLC) performed on 0.25 mm silica

gel plates (GF254) purchased from Haiyang

Chemical Industry Co., Ltd (Qingdao, China). The

TLC plates were visualized with a X-4 ultraviolet

analyser. Column chromatographic purifications

were carried out on silica gel (200-300 mesh) using

petroleum ether (PE) and ethyl acetate (EA) as

eluents. All

H NMR and

C NMR spectra were

recorded using a Bruker AV-500 instrument.

Chemical shifts (δ) were expressed in parts per

million (ppm) with TMS used as an internal standard.

High resolution electro-spray ionization mass spectra

(HRMS-ESI) were obtained using a Waters G2-XS

instrument.

2.1.2 Synthesis of Nornorcantharidin (1)

A 250 mL three-necked round bottom flask equipped

with mechanical stirrer, addition funnel and

thermometer, then added 9.8 g (0.1 mol) maleic

anhydride and 80 mL ethyl acetate respectively, keep

the room temperature, then 34.3 g (0.5 mol) furan was

added, while slowly rise to 40℃, continue stirring for

8 hours, during which A lot of white solid appeared.

The reaction mixture was filtered and dried to obtain

15.3 g (compound 1). as a white solid.

2.1.3 Synthesis of Compound 2

To a solution of 18.7 g tert butylhydrazine

hydrochloride in 80 mL ethanol, 15.2 g of

trimethylamine was added dropwise. while keeping

internal temperature between 35℃-40℃), 16.6 g

compound 1 was added in portions, continue stirring

for 4h, 80 mL of water was added in one portion, then

a lot of white solid appeared. The reaction mixture

was filtered and dried to obtain 21.3 g (compound

2).as a white solid.

2.1.4 Synthesis of Compound I

To a solution of 2.36 g compound 2 and 1.32 g

Potassium pyrophosphate in 40 mL acetonitrile added

1.5 g benzoyl chloride dropwise, then maintaining

gentle reflux, after compound 2 disappears, 40 g

water was added. The reaction mixture was filtered

and the filter cake was dried to give a crude product.

After purified by the flash chromatography, 2.8 g I

was obtained as a white solid. (compound I

-I

were

obtain by the same method).

2.2 Data of Compounds

Data for the I

:white solid, yield 88%, m.p.169-

170℃.

H NMR (500 MHz, DMSO-d

), δ(ppm),

7.85-7.89, (m, 2H, Ar-H), 7.48-7.51(m, 3H, Ar-H),

6.15(s, 2H, CH), 4.76(s, 2H, CH), 2.97(s, 2H, CH),

1.40(s, 9H, CH3).

C NMR (125 MHz, DMSO-d

δ(ppm), 177.28, 177.28, 168.82, 139.46, 139.46,

139.44, 130.81, 128.12, 128.12, 128.00, 128.00,

80.21, 80.21, 58.14, 43.73, 43.73, 26.84, 26.84,

ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics

834

26.84. HRMS: Calcd for C

[M+H]

341.1511; Found: 340.1420.

Data for the I

: white solid, yield 67%, m.p.155-

157℃.

H NMR (500 MHz, DMSO-d

), δ(ppm),

7 .65-7.99(m, 4H, Ar-H), 6.15 (s, 2H, CH), 4.76 (s,

2H, CH), 2.97 (s, 2H, CH), 1.41 (s, 9H, CH3).

NMR (125 MHz, DMSO-d

), δ(ppm), 176.50,

176.50, 171.10, 139.46, 139.46, 134.50, 132.06,

129.46, 129.00, 128.18, 127.08, 126.15, 80.21, 80.21,

59.65, 43.73, 43.73, 26.28, 26.28, 26.28. HRMS

Calcd for C

[M+H]

: 409.1375; Found:

409.1382.

Data for the I

: white solid, yield 89%, m.p.166-

168℃.

H NMR (500 MHz, DMSO-d

)δ (ppm) 8.27-

7.76 (m, 4H, Ar-H), 6.15(s, 2H, CH), 4.76 (s, 2H,

CH), 2.97 (s, 2H, CH), 1.40 (s, 9H, CH3).

C NMR

(125 MHz, DMSO-d

)δ 177.28, 177.28, 167.11,

142.85, 139.46, 139.46, 132.91, 130.83, 125.88,

125.88, 124.90, 80.20, 80.20, 58.14, 43.73, 43.73,

26.84, 26.84, 26.84. HRMS: Calcd for

[M+H]

: 409.1375; Found: 408.1370.

Data for the I

: white solid, yield 70%, m.p.138-

139℃.

H NMR (500 MHz, DMSO-d

), δ(ppm),

7.63-7.05(m, 3H, Ar-H), 6.15(s, 2H, CH), 4.76(s, 2H,

CH), 2.97(s, 2H, CH), 1.42(s, 9H, CH3).

C NMR

(125 MHz, DMSO-d

), δ(ppm), 176.86, 176.86,

163.94, 159.76, 159.76, 139.46, 139.46, 132.31,

114.90, 111.44, 111.44, 80.21, 80.21, 58.22, 43.73,

43.73, 26.48, 26.48, 26.48. HRMS Calcd for

[M+H]

: 371.1313; Found: 376.1307.

Data for the I

:white solid, yield 85% m.p.140-

142℃. 1H NMR (500 MHz, DMSO-d

), δ(ppm),

7.91-7.52 (m, 3H, Ar-H), 6.15(s, 2H, CH), 4.76(s, 2H,

CH), 2.97(s, 2H, CH), 1.46(s, 9H, CH3). 13C NMR

(125 MHz, DMSO-d

), δ(ppm), 176.62, 176.62,

166.00, 139.46, 139.46, 137.61, 133.57, 133.57,

131.75, 127.57, 127.57, 80.21, 80.21, 57.34, 43.73,

43.73, 26.80, 26.80, 26.80. HRMS Calcd for

[M+H]

: 409.0722; Found:

408.0727.

3 INSECTICIDAL ACTIVITY

According to the methods from literatures, tested the

insecticidal activities against plutella xylostella and

Tetranychus cinnabarinus. The main contents of the

method were as follows: a certain concentration of

compound mother liquor was prepared with DMF,

and then diluted with 0.1% Tween-80 solution

according to different concentration gradients, so as

to prepare different concentrations of drug solutions.

Take out the fresh and clean cabbage leaves with a

punch with a diameter of 5 cm and uniform size and

shape. Place the cabbage leaves in different

concentrations of liquid medicine and soak them for

10-20 s. after that, put the dry cabbage leaves into a

Petri dish padded with two layers of filter paper. The

filter paper was wetted with clean water to ensure the

humidity in the Petri dish. 30 diamondback moth

larvae in the same growth state were cultured in a

Petri dish for 48 hours (temperature controlled at

25℃, photoperiod: L: D = 16:8, relative humidity

maintained at 60%). Checked and recorded the death

number of Plutella xylostella larvae and calculate the

mortality. During the experiment, clear water was set

as the blank control group, and each group was set

with three groups of repeated tests. The final

experimental results were the average of the three

groups of parallel tests.

Using spray method as test method, taking

Tetranychus cinnabarinus as test object. At first,

DMF was used to dilute the target compound into

different concentrations of liquid medicine, then

spray the leaves of the broad bean leaves with the

same number and growth form. Then the leaves were

placed in the observation room, and the condition of

Tetranychus cinnabaris was recorded after 48 h. The

death judgment method is to touch the mite body with

a brush, and if there is no response, it is regarded as

dead. Three groups of controls are set for each

concentration, and the average mortality of each three

parallel groups was taken as the mortality of this

concentration.

4 RESULTS AND DISCUSSION

The data in Table 1 showed that all compounds had

certain insecticidal activities. When the concentration

of compound was 10 mg/L, the insecticidal activities

of compound I

, I

and I

were higher than 90%.

When the concentration was reduced to 1 mg/L, the

insecticidal activities against plutella xylostella of

compound I

were higher than 52%.

The data in Table 2 showed that at the

concentration of 100 mg / L, the acaricidal activities

of compounds I

, I

, I4 and I

reached 100%, and the

acaricidal activities of I

and I

were more than 80%.

When the concentration of compound continued to

decrease to 50 mg / L, the acaricidal activities of

compounds I

and I

were 87% and 81% respectively.

According to the relationship between structure and

activity, the activity of o-trifluoromethylphenyl

compound is higher than that of other compounds.

Therefore, it shows that fluorine-containing groups

can significantly improve the activity of compounds,

and the position of fluorine-containing group

Synthesis of Novel Environmentally Friendly Dehydronor-cantharidin Insecticides

835

substituents is very important for insecticidal and

acaricidal activity. When the concentration was

reduced to 10 mg / L, the activity of I

was 70%, and

it still had high activity.

Table 1: Insecticidal activities against plutella xylostella of target compounds.

No. compound

lethality rate against plutella xylostella(%)

50 mg/L 20 mg/L 10 mg/L 5 mg/L 1 mg/L

1 I

100 100 95 72 33

2 I

100 100 96 83 52

3 I

100 100 93 43 9

4 I

100 100 86 76 33

5 I

82 56 37 0 0

Table 2: The insecticidal activity against Tetranychus cinnabarinus results of target compounds.

No. Compound

lethality rate against Tetranychus cinnabarinus (%)

100 mg/L 50 mg/L 10 mg/L

1 I

100 78 33

2 I

100 87 70

3 I

79 56 37

4 I

100 76 55

5 I

100 81 65

5 CONCLUSIONS

In summary, 5 novel types of norcantharidin

derivatives were designed and synthesized, the

preliminary insecticidal activity against plutella

xylostella and Tetranychus cinnabarinus test showed

that all 5 target compounds had certain insecticidal

activities. Among them, the compound containing o-

trifluoromethylphenyl (I

) had the highest insecticidal

activity against plutella xylostella, and the

insecticidal activity was 52% at the concentration of

1 mg/L and the acaricidal activity against

Tetranychus cinnabarinus was 70%, at the

concentration was reduced to 10 mg / L. The

synthesis of these compounds had high atom

utilization rate, less waste and high insecticidal

activity. Besides, norcantharidin had good

biocompatibility and degraded easily in nature, so

norcantharidin derivatives were ideal environmental

protection insecticides. This work also revealed that

compound I

could be used as novel lead structures

for further research.

REFERENCES

Chi J et al. (2019) Synthesis and anti-metastasis activities

of norcantharidin-conjugated carboxymethyl chitosan

as a novel drug delivery system. Carbohyd Polym;

214:80-89.

He H et al. (2020). Equilibrium solubility of exo-5,6-

dehydronorcantharidin in thirteen pure solvents:

Determination, correlation, Hansen solubility

parameter and thermodynamic properties. J Mol Liq;

312: 113384.

Jin X, Tan X, Zhang X, Han M, Zhao Y. (2015) In vitro and

in vivo anticancer effects of singly protonated

dehydronorcantharidin silver coordination polymer in

CT-26 murine colon carcinoma model. Bioorg Med

Chem Lett; 25: 4477-4480.

Li S et al. (2014). Singly protonated dehydronorcantharidin

silver coordination polymer induces apoptosis of lung

cancer cells via reactive oxygen species-mediated

mitochondrial pathway. Eur J Med Chem; 86:1-11.

Ogura A, Ito T, Moriya K, Horigome H, Takao K. (2021)

Asymmetric Diels–Alder reaction between furans and

propiolates. Tetrahedron Lett:153075.

Song M et al. (2020) Cantharidin suppresses gastric cancer

cell migration/invasion by inhibiting the PI3K/Akt

signaling pathway via CCAT1. Chem-Biol Interact;3

17: 108939.

ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics

836

Wang M et al. (2014) Design, synthesis and bioactivity

evaluation of novel acylthiourea derivatives of

cantharidin. Ind Crop Prod;5 5: 11-18.

Yang P et al. (2016) Norcantharidin induces apoptosis in

human prostate cancer cells through both intrinsic and

extrinsic pathways. Pharmacol Rep; 68: 874-880.

Zhang Y, Zhou X, Zhang J, Guan C, Liu L. (2018)

Cantharides poisoning: A retrospective analysis from

1996 to 2016 in China. Regul Toxicol Pharm; 96:142-

145.

Zhou J et al. (2020) Norcantharidin: research advances in

pharmaceutical activities and derivatives in recent

years. Biomed Pharmacother; 131:110755.

Synthesis of Novel Environmentally Friendly Dehydronor-cantharidin Insecticides

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