Design, Synthesis, and Antimicrobial Activity of Amide Derivatives Containing Cyclopropane

As an important small organic molecule, cyclopropane is widely used in drug design. In this paper, fifty-three amide derivatives containing cyclopropane were designed and synthesized by introducing amide groups and aryl groups into cyclopropane through the active splicing method, and their antibacterial and antifungal activities were evaluated in vitro. Among them, thirty-five compounds were new compounds, and eighteen compounds were known compounds (F14, F15, F18, F20–F26, F36, and F38–F44). Bioassay results disclosed that four, three, and nine of the compounds showed moderate activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, respectively. Three compounds were sensitive to Candida albicans, with excellent antifungal activity (MIC80 = 16 μg/mL). The molecular docking results show that compounds F8, F24, and F42 have good affinity with the potential antifungal drug target CYP51 protein.


Introduction
Infectious diseases caused by bacterial pathogens seriously affect human health and have been a main public health problem in recent years [1].The use of antibiotics has significantly improved the ability of humans to fight bacterial infections, which prolongs human life and improves the quality of human life [2].However, the continuous use of antibiotics leads to the emergence of bacterial resistance.At present, one of the major challenges of healthcare worldwide is bacterial resistance to antibiotics [3].Therefore, it is urgent to develop new, effective, and safe bactericides.
As an important small organic molecule, cyclopropane is widely found in natural products and drugs [4][5][6].Cyclopropane is a structurally stable bioisostere, which can be used to replace carbon-carbon double bonds.It has the effects of improving the efficacy of drugs, enhancing metabolic stability, reducing the off-target effect of drugs, improving the dissociation degree of drugs, and enhancing the affinity to receptors [7][8][9][10].Therefore, it is widely used in drug design.Compounds containing cyclopropane have certain drug properties and biological activities, including antibacterial [11,12], antifungal [13][14][15], antiviral [16,17], antitumor [18], antioxidant [19], and antidepressant activities [20][21][22].Therefore, compounds with cyclopropane structures have attracted extensive research due to their biological activity and low toxicity.
At present, drugs containing cyclopropane structure have been applied to treat respiratory diseases, infectious diseases, mental disorders, endocrine and metabolic diseases, nervous system diseases, and cardiovascular and cerebrovascular diseases [23].These include tranylcypromine, levomilnacipran, arotinib hydrochloride, cypermethrin, and fenpropathrin (Figure 1).Phenyl, as a scaffold that could be substituted with various groups, can enh stability and biological activity of drugs [24].The amide structure, as an importa ponent of proteins, is widely present in antibacterial and antioxidant agents, and important functional group in drug synthesis [25].Therefore, we speculate that th duction of substituted phenyl and cyclopropane with amide structure is likely to new lead compounds with excellent biological activity.
In this study, amide groups and aryl groups of benodanil [26] and cinnam derivatives [27] with excellent antibacterial activity were introduced into the C positions of cyclopropane by the active splicing method, and fifty-three amide der containing cyclopropane were synthesized (Figure 2).The antibacterial and antifu tivity of the target compounds in vitro was tested.Then, the mode of action and affinity of the ideal compounds with the highest antifungal activity and CYP51 were analyzed by molecular docking to preliminarily explore their antifungal mec

Synthesis
In order to explore the effect of different substituent groups on the activity a more potent compounds, based on the consideration of molecular diversity, 2-ph clopropane-1-carboxamide was used as a template to introduce different substitue the benzene ring and the amide part, respectively.
The synthetic rout is outlined in Scheme 1. Intermediate B was obta Knoevenagel condensation of substituted benzaldehyde A and malonic acid.Inter B was amidated with N,O-dimethylhydroxylamine hydrochloride to form inter C. Intermediate D was obtained from intermediate C and trimethylsulfonyl iodid rey-Chaykovsky cyclopropanation.Intermediate D was hydrolyzed to obtain int ate E. A series of amide compounds containing cyclopropane F1-F53 were obta amide reaction of intermediate E with aliphatic amine, methylaniline, ethyl N zinecarboxylate, and 2-aminothiazole, respectively.
Among the fifty-three cyclopropane amide derivatives synthesized in thi Phenyl, as a scaffold that could be substituted with various groups, can enhance the stability and biological activity of drugs [24].The amide structure, as an important component of proteins, is widely present in antibacterial and antioxidant agents, and it is an important functional group in drug synthesis [25].Therefore, we speculate that the introduction of substituted phenyl and cyclopropane with amide structure is likely to lead to new lead compounds with excellent biological activity.
In this study, amide groups and aryl groups of benodanil [26] and cinnamate ester derivatives [27] with excellent antibacterial activity were introduced into the C 1 and C 2 positions of cyclopropane by the active splicing method, and fifty-three amide derivatives containing cyclopropane were synthesized (Figure 2).The antibacterial and antifungal activity of the target compounds in vitro was tested.Then, the mode of action and binding affinity of the ideal compounds with the highest antifungal activity and CYP51 protein were analyzed by molecular docking to preliminarily explore their antifungal mechanism.Phenyl, as a scaffold that could be substituted with various groups, can enh stability and biological activity of drugs [24].The amide structure, as an importa ponent of proteins, is widely present in antibacterial and antioxidant agents, and important functional group in drug synthesis [25].Therefore, we speculate that th duction of substituted phenyl and cyclopropane with amide structure is likely to new lead compounds with excellent biological activity.
In this study, amide groups and aryl groups of benodanil [26] and cinnam derivatives [27] with excellent antibacterial activity were introduced into the C positions of cyclopropane by the active splicing method, and fifty-three amide der containing cyclopropane were synthesized (Figure 2).The antibacterial and antifu tivity of the target compounds in vitro was tested.Then, the mode of action and affinity of the ideal compounds with the highest antifungal activity and CYP51 were analyzed by molecular docking to preliminarily explore their antifungal mec

Synthesis
In order to explore the effect of different substituent groups on the activity a more potent compounds, based on the consideration of molecular diversity, 2-ph clopropane-1-carboxamide was used as a template to introduce different substitue the benzene ring and the amide part, respectively.
The synthetic rout is outlined in Scheme 1. Intermediate B was obta Knoevenagel condensation of substituted benzaldehyde A and malonic acid.Inter B was amidated with N,O-dimethylhydroxylamine hydrochloride to form inter C. Intermediate D was obtained from intermediate C and trimethylsulfonyl iodid rey-Chaykovsky cyclopropanation.Intermediate D was hydrolyzed to obtain int ate E. A series of amide compounds containing cyclopropane F1-F53 were obta amide reaction of intermediate E with aliphatic amine, methylaniline, ethyl N zinecarboxylate, and 2-aminothiazole, respectively.

Synthesis
In order to explore the effect of different substituent groups on the activity and find more potent compounds, based on the consideration of molecular diversity, 2-phenylcyclopropane-1-carboxamide was used as a template to introduce different substituents into the benzene ring and the amide part, respectively.
Among the fifty-three cyclopropane amide derivatives synthesized in this study, thirty-five compounds were new compounds, and eighteen compounds were known compounds (F14, F15, F18, F20-F26, F36, F38-F44).All of the synthesized compounds were characterized by 1 H NMR, 13 C NMR, and HRMS.The 1 H and 13 C NMR spectra and HRMS of the compounds above are shown in Supplementary Materials.

Antimicrobial Activity In Vitro
Three strains of bacteria, including Gram-positive bacteria (Staphylococcus aureus (S. aureus) and Escherichia coli (E.coli)) and Gram-negative bacteria (Pseudomonas aeruginosa (P.aeruginosa)), and one strain of fungu (Candida albicans (C.albicans)), which causes great harm to human health, were selected to test the biological activity of the compounds in vitro.The antibacterial activity and antifungal activity against all synthesized amide derivatives containing cyclopropane (F1-F53) were evaluated in vitro.The in vitro antibacterial and antifungal activities of the prepared compounds were determined by the MIC 80 value (minimum 80% inhibition concentration) using microdilution method with ciprofloxacin or fluconazole as positive controls, respectively.The results are listed in Table 1.Five compounds (F7, F30, F36, F49, and F51) showed some antibacterial activity against Staphylococcus aureus with the MIC 80 of 128 µg/mL, and four compounds (F5, F9, F29, and F53) showed moderate inhibitory activity against Staphylococcus aureus with the MIC 80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC 80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC 80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC 80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC 80 values (>128 µg/mL).F33 >128 >128 >128 128 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

F1
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

F2
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

F3
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos

F6
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

F7
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos Table 1.The results of antimicrobial and a

Fungus Comp
No. R

F8
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

F9
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.(F1-F9) Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Molecules 2024, 29, x FOR PEER REVIEW 4 of 17 MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
fluconazole, this class of compounds structure, easy synthesis, and low cos fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
fluconazole, this class of compounds structure, easy synthesis, and low cos

F15
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos

F16
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
activity with the MIC80 of 16 µg/mL.Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos

F18
MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sensitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.MIC80 of 32 and 64 µg/mL.Two compounds (F5 and F53) show antibacterial activity against Escherichia coli with the MIC80 of 128 µg/mL.Escherichia coli were relatively sen-sitive to three compounds (F9, F31, and F45) with the MIC80 of 32 and 64 µg/mL, respectively, but far lower than the antibacterial activ-ity of the positive control ciprofloxacin (MIC80 = 2 µg/mL).Pseudomonas aeruginosa was not sensitive to all compounds with high MIC80 values (>128 µg/mL).
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.
Although the activity of the synt fluconazole, this class of compounds structure, easy synthesis, and low cos
Although the activity of the synthesized compounds is inferior to ciprofloxacin and fluconazole, this class of compounds showed some attractive advantages, such as simple structure, easy synthesis, and low cost.

Molecular Docking Studies
Sterol 14-α demethylase (CYP51), as a key enzyme in the synthesis of biosterols, is a potential target for antifungal drugs.It has the functions of regulating and distributing proteins and changing the fluidity and permeability of membranes, and it is an enzyme necessary for the growth and development of various eukaryotes [29,30].In order to further explore the antifungal activity mechanism of the target compounds, molecular docking was used to predict the mode of action and binding affinity of excellent antifungal compounds (F8, F24, and F42) with CYP51 protein.The molecular docking results are shown in Figure 3. Compound F8 is able to bind with CYP51 by interaction with two amino residues of SER378 and HIE377.The binding modes involved one halogen bond and one π. ..π interaction.Compared with F8, F42 is mainly bound with CYP51 by interaction with TYR118 and HEM601 involved two π. ..π interaction.Compared with F42, F24 also forms two additional interactions with CYP51 including two hydrogen bond ((CO)N. ..TYR132, (CH 3 )O. ..HEM601).The compounds F8, F24, and F42 have good binding affinity with CYP51 and gave −6.087, −6.526, and −6.874 kcal/mol of docking scores, respectively.Compared with the reported compounds with excellent antifungal activity, the binding energies were slightly lower [13].This may be the reason why the antibacterial activity of the above compounds was lower than that of fluconazole.The results further verified the potential bacteriostatic effect of derivatives F8, F24 and F42.

General Synthesis Procedure for Intermediate D
To a solution of NaH (174 mmol) in anhydrous tetrahydrofuran (THF) (350 mL) was added intermediate C (60 mmol) dropwise under argon at 0 • C. The reaction mixture was allowed to be stirred at 0 • C for 0.5 h.Then trimethylsulfonyl iodide (79.8 mmol) was added.The reaction mixture was stirred at room temperature for 18 h, quenched with water, and extracted with ethyl acetate (50 mL × 3).The combined organic phase was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated to give the intermediate D in 76-82% yield [33].

General Synthesis Procedure for Intermediate E
The intermediate D (50 mmol) and sodium hydroxide (NaOH, 100 mmol) were dissolved in a mixed solution of methanol (75 mL) and water (10 mL) and stirred overnight at 25 • C. To the mixture was added diluted hydrochloric acid HCl to Ph = 3-4.The mixture was extracted with dichloromethane (DCM, 50 mL × 3).The combined organic phase was washed with brine, dried over anhydrous Na 2 SO 4 , and concentrated to give the intermediate E in 76-82% yield [34].

The Antimicrobial Activity In Vitro
Three strains of bacteria (S. aureus, E. coli, and P. aeruginosa) and one strain of fungal (C.albicans) were selected to determine the antimicrobial activity in vitro by the broth microdilution method.The fungal and bacterial strains were obtained from China General Microbiological Culture Collection Center.The bacteria and fungi were cultured to 1-5 × 10 3 CFU/mL in Mueller Hinton Broth medium and RPMI1640 medium, respectively, before use.The commercial ciprofloxacin or fluconazole was selected as the positive control.All compounds were dissolved in DMSO and serially diluted, and the concentrations of all tested compounds were 1, 2, 4, 8, 16, 32, 64, and 128 µg/mL.Then, the plates were continuously incubated at 37 • C for 24 h.The OD values were read on a Microplate reader at a wavelength of 600 nm.The plates without drugs acted as the growth control, while the plates without cells and drugs acted as blank control.The MIC 80 value was the lowest concentration; the inhibition rate was ≥80%.The test was performed in triplicates.

Molecular Docking Analysis
The 3D crystal structure of CYP51 (PDB code: 6AY6) was acquired from the RCSB Protein Date Bank (https://www.rcsb.org/structure/6AY6(accessed on 7 September 2017)).The molecular docking process was conducted for the investigation of the binding mode of compounds F8, F24, and F42 with CYP51 using Discovery Studio 2016 software (Accelrys, San Diego, CA, USA) [32].ChemBio 3D Ultra 14.0 software was used to generate the 3D structure of the above compounds and treated with energy minimization [36].Water molecules and the co-crystallized ligand of the 3D crystal structure of CYP51 were removed, and the crystal structure was hydrotreated before molecular docking.The parameters of docking were in accordance with the previously reported method [13].

Conclusions
In summary, a series of amide derivatives containing cyclopropane were designed and synthesized, and their antimicrobial activity in vitro was evaluated.The results showed that the four and three of the compounds exhibited moderate activity against Staphylococcus aureus and Escherichia coli, respectively.Three compounds were sensitive to Candida albicans and exhibited excellent antifungal activity, with great potential for further development.SAR analysis showed that introducing halogens into the benzene ring was beneficial for improving antibacterial and antifungal activity.The presence of thiazolamide contributed to the improvement of antibacterial activity, while benzamides were beneficial to the improvement of antifungal activity.Compounds F8, F24, and F42 showed the highest activity against C. albicans (MIC 80 = 16 µg/mL).The molecular docking results showed that the above compounds had a good binding affinity with the CYP51 protein.Thus, amide compounds containing cyclopropane can be considered promising antimicrobial lead compounds.It is necessary to further study the in vivo activity and mechanism of action of these compounds.

Figure 1 .
Figure 1.Structure of commercial drugs of cyclopropane.

Figure 2 .
Figure 2. Design strategy of title compounds.

Figure 1 .
Figure 1.Structure of commercial drugs of cyclopropane.

Figure 2 .
Figure 2. Design strategy of title compounds.

Figure 2 .
Figure 2. Design strategy of title compounds.
Intermediate B was amidated with N,O-dimethylhydroxylamine hydrochloride to form intermediate C. Intermediate D was obtained from intermediate C and trimethylsulfonyl iodide by Corey-Chaykovsky cyclopropanation.Intermediate D was hydrolyzed to obtain intermediate E. A series of amide compounds containing cyclopropane F1-F53 were obtained by amide reaction of intermediate E with aliphatic amine, methylaniline, ethyl N-piperazinecarboxylate, and 2-aminothiazole, respectively.

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and a fluconazole, this class of compounds structure, easy synthesis, and low cos

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and antifungal activity of tested compounds (MIC80, µg/mL).

Table 1 .
The results of antimicrobial and a

Table 1 .
The results of antimicrobial and a