Synthesis, crystal structures, computational studies and α-amylase inhibition of three novel 1,3,4-oxadiazole derivatives

Journal Pre-proof Synthesis, crystal structures, computational studies and α-amylase inhibition of three novel 1,3,4-oxadiazole derivatives Syeda Shamila Hamdani, Bilal Ahmad Khan, Muhammad Naeem Ahmed, Shahid Hameed, Kulsoom Akhter, Khurshid Ayub, Tariq Mahmood PII:

S0022-2860(19)31185-8

DOI:

https://doi.org/10.1016/j.molstruc.2019.127085

Reference:

MOLSTR 127085

To appear in:

Journal of Molecular Structure

Received Date: 16 July 2019 Revised Date:

15 September 2019

Accepted Date: 15 September 2019

Please cite this article as: S.S. Hamdani, B.A. Khan, M.N. Ahmed, S. Hameed, K. Akhter, K. Ayub, T. Mahmood, Synthesis, crystal structures, computational studies and α-amylase inhibition of three novel 1,3,4-oxadiazole derivatives, Journal of Molecular Structure (2019), doi: https://doi.org/10.1016/ j.molstruc.2019.127085. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

Graphical Abstract

N

N O

S

R

(1-3)

R'

Synthesis, crystal structures, computational studies and α-amylase inhibition of three novel 1,3,4-oxadiazole derivatives

Syeda Shamila Hamdania,b, Bilal Ahmad Khana*, Muhammad Naeem Ahmeda, Shahid Hameedb, Kulsoom Akhtera, Khurshid Ayubc, Tariq Mahmood*c

a

Department of Chemistry, The University of Azad Jammu and Kashmir Muzaffarabad, 13100 Pakistan b

Department of Chemistry, Quaid-i- Azam University, Islamabad, 5320, Islamabad, Pakistan

c

Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, University Road, Tobe Camp, Abbottabad-22060, Pakistan

*To whom correspondence should be addressed: E-mail: [email protected] (T. M) and [email protected] (B. K).

1

Abstract Oxadiazoles have broad range of biological applications and have been investigated widely by the people. In this study we are reporting the synthesis, X-ray diffraction, density functional theory (DFT) and α-amylase inhibition of three 1,3,4-oxadiazole derivatives (1-3). The compounds are synthesized in good yields (70-83%) and final structures are analyzed completely with the help of different spectro-analytical techniques including single crystal X-ray diffraction as well. Density functional theory (DFT) calculations are performed to validate not only X-ray results, but also to investigate their reactivity and dispersion of charges through frontier molecular orbitals and molecular electrostatic potential (MEP) analyses. α-Amylase inhibition assay is performed in order to find out the enzyme inhibitory potential of synthesized compounds (1-3). The low IC50 value (86.83 ±0.23 µg/mL) of compound 2 reflects the potential α-amylase inhibitory activity of compound as compared to others.

Keywords: Oxadiazole; X-ray; DFT; α-Amylase inhibition

2

1 Introduction With the passage of time heterocycles specially oxadiazoles have become part and parcel of daily life, due their medicinal as well as agricultural use. Among oxadiazoles family, 1,3,4oxadiazoles have very important place in medicinal chemistry due to their versatile use in designing many biologically active compounds. Compounds comprising 1,3,4-oxadiazole motif have a widespread biological activities including analgesic [1], anticonvulsant [2], antibacterial [3,4], antifungal [5], insecticidal [6], antiviral [7], anti-tubercular [8], hypoglycemic [9], antiinflammatory [10], and anticancer potential [11]. Commercially marketed drugs containing 1,3,4-oxadiazole moiety include, Zibotentan an important anticancer agent [12,13], and Nesapidil as a antihypertensive agent [14] (Fig. 1). N N N O

HN O S OO

N N

N O

O

HO

O

CH3

N N

N Nesapidil

Zibotentan

Fig. 1: Structures of Zibotentan and Nesapidil Apart from medicinal importance, 1,3,4-oxadiazoles also have wide range of applications in pigment industry, either their use as dyes a or as fluorescent whiteners. In organic light emitting diodes these are also used as a fluorescent materials [15]. 1,3,4-Oxadiazole nucleus has also got attention in electro optical devices [16,17], and being used as a staple nucleus in liquid crystalline molecules. In polymers industry 1,3,4-oxadiazole containing compounds are considered as a high performance materials [18].

3

In continuation of our ongoing research regarding the synthesis of substituted hetrocycles and their bioactivities [19–21], herein we are reporting the synthesis, structural investigations and αamylase activity of three new 1,3,4-oxadiazole derivatives. All three compounds are synthesized in very good yields, characterized by spectroscopic analyses and finally, the structures are confirmed unambiguously by X-ray diffraction studies. The DFT simulations are performed not only to validate the X-ray data, along with other structural properties like frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) analyses.

2 Material and methods

2.1 Experimental All chemicals and reagents are used as obtained directly from Merk and Sigma-Aldrich. Melting points are recorded in open capillaries using a Gallenkamp melting point apparatus (MP-D) and are uncorrected. The reactions are monitored using thin layer chromatography, which is accomplished on Merck pre-coated plates (silica gel 60 F254, 0.25 mm) and visualized using fluorescence quenching under UV light (254 nm). 1H-NMR and

13

C-NMR spectra are recorded

on a Bruker AV-300 spectrometer (300 MHz and 75 MHz). FT-IR spectra are recorded on Shimadzu Fourier Transform Infra-Red spectrophotometer model using ATR mode (Attenuated Total Reflectance).

2.2 Synthesis

4

2.2.1 General Procedure for the synthesis of Compounds (1-3) The corresponding carboxylic acid (0.02 mol) as a starting material is dissolved in methanol (30 mL) and concentrated sulfuric acid (0.5 mL) is added followed by reflux for 8-10 hours. To monitor the progress of reaction TLC is employed at regular intervals. Then the mixture is concentrated on rotary evaporator upon completion. The reaction mixture is washed with saturated aqueous sodium bicarbonate solution (150 mL) and extracted with ethyl acetate (3×50 mL), organic layer is dried over anhydrous sodium sulfate and concentrated under vacuum to obtain pure product. Carboxylic acid hydrazides are synthesized following a modified procedure already reported in the literature [22].

Hydrazine hydrate (80%, 0.06 mol) is added slowly to a solution of

carboxylate esters (0.02 mol) in methanol (30 mL). The reaction mixture is subjected to reflux for 6- 8 hours. Upon completion of reaction, the mixture is cooled down to the room temperature and ice water is added. The precipitated solid product obtained was filtered, dried and recrystallized from methanol. The corresponding hydrazide is dissolved in methanol and a methanolic solution of potassium hydroxide (0.03 mol) is added. After ten minutes, CS2 (0.06, mol) is added drop wise into the stirring mixture. The color of mixture turned yellow and subjected to further reflux for 12-14 hours until the completion of reaction. The mixture is cooled to room temperature and concentrated then poured into ice cold water. Crude solid product precipitated out on treatment with dilute HCl up to pH 2. The precipitates are filtered, washed with warm water and recrystallized from methanol to afford target oxadiazole derivatives (1-3).

5

Scheme 1; Synthetic route for the synthesis of 1,3,4-oxadiazoles (1-3) 2.2.1.1 2-(3-(Trifluoromethyl)benzylthio)-5-(4-methoxyphenyl)-1,3,4-oxadiazole (1) N N O

S

CF3

O

Colorless solid; yield: 83%, Rf = 0.76 (Chloroform:Acetone, 9:1); M.P = 95-97 °C; 1H-NMR (300MHz, CDCl3): δ (ppm); 7.92(m, 2H), 7.73(d, J = 6 Hz, 1H), 7.69(s, 1H), 7.57(d, 6 Hz, 1H), 7.47(t, J = 15 Hz, 1H), 6.99(m, 2H), 4.55(s, 2H), 3.88(s, 3H),;

13

C-NMR (75 MHz, CDCl3;

166.0, 162.4, 162.3, 137.0, 132.6, 131.3, 130.9, 129.2, 128.4, 125.8, 125.8, 125.6, 124.94, 124.8, 122.0, 115.9, 114.4, 55.4, 36.1,;

IR (cm-1): 3023(C-H, aromatic), 2935(C-H, aliphatic),

1610(C=N), 1330(C-S), CHNS calculated for C17H13F3N2O2S (366.065): C, 55.73; H, 3.58; N, 7.65; S, 8.75. Observed: C, 55.70; H, 3.55; N, 7.60; S, 8.60.

6

2.2.1.2 2-(2-(trifluoromethyl)benzylthio)-5-(4-methoxyphenyl)-1,3,4-oxadiazole (2) N N S

O

F3C

O

Colorless solid; yield: 80 %, Rf = 0.70 (Chloroform:Acetone, 9:1); M.P = 64-68 °C; 1H-NMR (300MHz, CDCl3): δ (ppm); 7.94(m, 2H), 7.81(d, J = 9 Hz, 1H), 7.69(d, J = 9 Hz, 1H), 7.54(t, J = 15 Hz, 1H), 7.43(t, J = 15 Hz, 1H), 6.99(m, 2H), 4.72(s, 2H), 3.88(s, 3H),; 13C NMR (75 MHz, CDCl3; 166.0, 163.0, 162.3, 134.6, 132.4, 132.0, 128.8, 128.4, 128.3, 126.4, 126.3, 126.27, 126.0, 122.4, 116.0, 114.5, 55.4, 33.2 , IR (cm-1): 3020(C-H, aromatic), 2968(C-H, aliphatic), 1613(C=N), 1300(C-S), CHNS calculated for C17H13F3N2O2S (366.065): C, 55.73; H, 3.58; N, 7.65; S, 8.75. Observed: C, 55.75; H, 3.52; N, 7.56; S, 8.60.

2.2.1.3 2-(2-(Trifluoromethyl)benzylthio)-5-(4-fluorophenyl)-1,3,4-oxadiazole (3) F

N N O

CF3 S

White solid; yield: 70 %, Rf = 0.85 (Chloroform:Acetone, 9:1); M. P = 100-102 °C; 1H-NMR (300MHz, CDCl3): δ (ppm); 8.00(m, 2H), 7.82(d, J = 6 Hz, 1H), 7.70(d, J = 6 Hz, 1H), 7.54(t, J = 15 Hz, 1H), 7.44(t, J = 15 Hz, 1H), 7.21(m, 2H), 4.73(s, 2H),;

13

C NMR (75 MHz, CDCl3;

166.4, 165.2, 163.9, 163.0, 134.4, 132.4, 129.0, 128.9, 128.4, 128.3, 126.5, 126.4, 126.3, 126.3, 126.0, 122.4, 119.8, 119.8, 116.6, 116.3, 33.2,; IR (cm-1): 3060(C-H, aromatic), 2974(C-H, aliphatic), 1608(C=N), 1329(C-S), CHNS calculated for C16H10F4N2OS (354.045): C, 54.24; H, 2.84; N, 7.79; S, 9.05. Observed: C, 54.15; H, 2.80; N, 7.65; S, 9.00.

7

2.3 Crystal structure determination

The X-RAY diffraction data is collected on a SuperNova, Single source at offset, Atlas diffractometer with a 4 K CCD detector set 60.0 mm from the crystal. The crystals are cooled to100 ± 1 K temperature and intensity measurements is performed using graphite monochromatic Cu Kα radiation from a sealed ceramic diffraction tube (SIEMENS). Generator settings are 50 KV/40 mA. The structures is solved by Patterson method and an extension of model is accomplished by the direct method using the program DIRDIF or SIR2004. Final refinement on F2 is conducted by full matrix least squares techniques using SHELXL-2014/7 [23], a modified version of the program PLUTON (preparation of illustration) and PLATO package [24]. CIF files of 1-3 have been assigned CCDC numbers 1895555, 1895556 and 1895557 respectively, and can be obtained free of charge on demand to CCDC 12 Union Road, Cambridge CB21 EZ, UK. (Fax: (+44) 1223 336-033: [email protected]).

2.3 Computational methods All calculations are performed by using Gaussian 09 software [25], and results are visualized with the GaussView 5.0 [26]. Geometries of all three (1-3) compounds are optimized at B3LYP/6-31G(d,p) level of theory. B3LYP is hybrid functional, which is very famous for estimation of structural properties of organic compounds [27–29]. Vibrational analysis is performed for confirmation of true optimization. Rest of the properties like frontier molecular orbitals and molecular electrostatic potential (MEP) are also calculated at the same level of theory.

8

2.4 Enzyme inhibition activity

A slightly modified procedure is used to determine α-amylase inhibitory activity [30]. In 1.5 ml centrifuge tube a mixture containing legume extract (40µL), respective oxadiazole, distilled water (150µL) and 0.5% starch solution (40µL) is prepared. After that enzymatic solution is added and the mixture was incubated at 25 °C for 3 minutes. The 200µL of mixture is added to a separate tube containing 100µL DNS color reagent (96 mM 3,5-dinitrosalicylic acid, 5.31 M sodium potassium tartrate in 2 M NaOH). The enzyme is activated by placing into a thermos mixer at 95–177 °C for 10 minutes. Distilled water 900µL is added into the tube and mixed well. Then 200µL of mixture is taken and added into a 96-well plate and absorbance of reaction mixture is measured at 540 nm. To remove the background absorbance produced by legume extracts, an appropriate extract without enzyme is included. Type-1-amylase inhibitor from Triticum aestivum is also examined as a positive control. α-Amylase inhibitory potential is determined at 5 different concentrations, and IC50 values (mg/ml) were calculated by establishing a logarithmic regression curve.

α-amylase inhibition (%)=

[1-(A sample-A blank)] A Test - A control

X 100

where A sample is the absorbance of the mixture of extract, starch, enzyme and DNS colour reagent solution; A blank is the absorbance of the mixture of starch solution, extract and DNS colour reagent; A test is the absorbance of the mixture of starch, enzyme and DNS colour reagent; A control is the absorbance of the mixture of starch solution and DNS color reagent without enzyme.

3 Results and discussion 9

3.1 Molecular structures

In 2-(4-methoxyphenyl)-5-(sulfanyl)-1,3,4-oxadiazole (1), the benzene rings A (C1-C6) and B (C11-C16) are oriented at a dihedral angle of 80.92(11)°. The oxadizole ring C (C9/C10/N1/N2/O1) makes dihedral angle of 81.12(11)° and 2.14(11)° with benzene rings A and B, respectively. The torsion angle C1-C8-S1-C9 is 70.36 (19)°. The molecules are mainly stabilized by van der Waals forces [31,32]. ORTEP plot and packing is shown in Figs 2 and 3 and X-ray parameters are given in the Table 1. In 2-(4-methoxyphenyl)-5-({[2-(trifluoromethyl)phenyl]methyl}sulfanyl)-1,3,4-oxadiazole (2), the benzene rings A (C1-C6) and B (C11-C16) are oriented at a dihedral angle of 73.01(9)°. The oxadizole ring C (C9/C10/N1/N2/O1) makes dihedral angle of 75.87(9)° and 3.42(9)° with benzene rings A and B, respectively. The torsion angle C1-C8-S1-C9 is 80.80 (13)°. Similarly, in 2-(4-Fluorophenyl)-5-({[2-(trifluoromethyl)phenyl]methyl}sulfanyl)-1,3,4-oxadiazole (3), the benzene rings A (C1-C6) and B (C11-C16) are oriented at a dihedral angle of 50.53 (7)°. The oxadizole ring C (C9/C10/N1/N2/O1) makes dihedral angle of 53.15 (8)° and 7.08 (8)° with benzene rings A and B, respectively. The torsion angle C1-C8-S1-C9 is 97.24 (12)°.

10

1

2

3 Fig. 2 ORTEP plots of compounds 1-3

1

2

3

Fig. 3; Packing diagrams of compounds 1-3, showing the van der Waals forces. 3.2 Optimized geometries

The energy minima geometries of all three oxadiazoles 1, 2 and 3 are optimized (Fig. 4) at DFT method and geometric parameters (bond lengths and bond angles) obtained from X-ray analysis are compared with theoretical results. The important X-ray and theoretical bond lengths are narrated in Tables 2, whereas bond angles are narrated in Table 3.

11

The important X-ray values of bond lengths such as S1—C9, O1—C10, O2—C14, O2—C17, N1—N2, N1—C9, N2—C10, F1—C7, F2—C7, F3—C7 and S1—C8 (atomic labelling is in accordance with Fig. 2) in oxadiazole 1 are 1.73, 1.36, 1.37, 1.36, 1.42, 1.41, 1.29, 1.34, 1.33, 1.33, and 1.82Å, respectively. The computed values for the same bonds are 1.74, 1.35, 1.37, 1.35, 1.42, 1.39, 1.29, 1.29, 1.35, 1.34, 1.34 and 1.85Å, respectively. In 2, the experimental values of important bond lengths such as S1—C9, S1—C8, O1—C9, O1—C10, O2—C14, O2— C17, N1—C9, N1—N2, N2—C10, F1—C7, F2—C7 and F3—C7 are 1.73, 1.83, 1.36, 1.37, 1.35, 1.42, 1.28, 1.41, 1.28, 1.34, 1.33 and 1.33Å, respectively. The simulated values of same bonds are 1.74, 1.85, 1.35, 1.37, 1.35, 1.42, 1.29, 1.39, 1.29, 1.35, 1.34 and 1.34Å, respectively. Similarly, in 3 the X-ray and computed values corroborated to each other nicely. The X-ray values of important bonds such as S1—C9, S1—C8, O1—C9, O1—C10, N1—C9, N1—N2, N2—C10, F1—C7, F2—C7, F3—C7 and F4—C14 are 1.73, 1.83, 1.36, 1.37, 1.29, 1.41, 1.28, 1.34, 1.33, 1.34 and 1.35Å, respectively. Their theoretical values are 1.74, 1.86, 1.35, 1.37, 1.29, 1.39, 1.29, 1.35, 1.34, 1.35 and 1.34Å, respectively. The experimental and computed values of bond angles of all compounds (1, 2 and 3) are given in the Table 3. Excellent correlation is observed among the experimental and theoretical values of bond angles of all three compounds. In 1, the X-ray values of important bond angles such as C9—S1—C8, C9—O1—C10, C14—O2—C17, C9—N1—N2, C10—N2—N1, C1—C8—S1, N1—C9—O1, N1—C9—S1, O1—C9—S1, N2—C10—O1, N2—C10—C11 and O1—C10— C11 are 99.4, 102.2, 117.8, 105.8, 106.3, 114.0, 113.2, 131.0, 115.6, 112.3, 129.0 and 118.7o, respectively. The theoretical values of same bond angles are 99.0, 102.3, 118.7, 106.0, 106.9, 114.4, 112.9, 130.3, 116.6, 111.6, 129.0 and 119.2o, respectively. Similarly, the experimental and

12

theoretical bonds angles of compounds 2 and 3 corroborated nicely (for detailed values see Table 3).

1

2

3 Fig. 4 Optimized geometries of compounds 1-3

3.3 Frontier molecular orbitals (FMOs) analysis

Frontier molecular orbital (FMOs) analysis is performed for explaining the reactivities of all three compounds [33,34]. In compound 1, the EHOMO and ELUMO are -6.06 eV and -1.36 eV, respectively and the corresponding H-Lg is 4.7 eV. In compound 2 the EHOMO and ELUMO are 6.05 eV and -1.37 eV, respectively along with the H-Lg of 4.68 eV. Similarly, in 3 the corresponding EHOMO and ELUMO are -6.44 eV and -1. 69 eV, respectively, along with H-Lg of 4.75 eV. The H-Lg of all three compounds reflects the moderate reactivity of the corresponding compounds, and the results are in accordance with the literature [34]. The dispersion of 13

isodensity shows the similar trend in HOMOs and LUMOs of all three compounds. The isodensity is concentrated mainly on the benzene and oxadiazole moieties in both frontier molecular orbitals (HOMO/LUMO), and this is because both moieties are lying in the same plane and taking part in the electronic transitions. As a model only the HOMO/LUMO surfaces of 1 are given in the Fig. 5, for the others two compounds the surfaces are provided in the supplementary information (Fig. S4).

HOMO (1)

LUMO (1)

Fig. 5 HOMO and LUMO surfaces of compound (1)

3.4 Molecular electrostatic potential (MEP) analysis

MEP analysis is global reactivity descriptor and overall is used to locate the reactive sited inside the compounds [35]. The MEP surfaces of all three compounds are shown in the Fig. 6. The appearance of deep red color on the oxadiazole ring reflects that the corresponding portion is highly nucleophilic in nature (most suitable site for the positively charged species), while the other part of the compounds are almost neutral or having very low electronic density [36]. The dispersion of charges in 1 is in the range of -0.052 au to 0.052 au, in 2 is -0.049 au to 0.049 au and in 3 is from -0.043 au to 0.043 au, respectively.

14

1

2

3 Fig. 6 ESP surfaces of compounds 1-3

3.5 α-Amylase inhibition activity Amylase is an enzyme that catalyzes the breakdown of starch into sugars. In human body, the pancreas secretes amylase to hydrolyze dietary starch into disaccharides which is converted to glucose. Unceased reaction of amylase lead to accumulation of glucose and as a result hyperglycemia which can be controlled by decreasing the activity of amylase by using inhibitors [37]. Based on the results provided in Table 4, the all three compounds are found to be potential amylase inhibitors at concentration level of 250 µg/ml where compounds 1, 2 and 3 provided 100%, 83.51% and 84.83% inhibition of the enzyme respectively. A logarithmic regression curve was established using percent inhibition potential (%I) at four different concentrations of each compound to calculate the concentration of compound used to inhibit 50% of the enzyme activity (IC50 µg/ml). Acarbose, a commercially known α-amylase inhibitor showed strong inhibitory 15

activity with 93.61% inhibition at 250 µg/ml concentration and IC50 value of 8.80±0.21 µg/mL. Among three compounds, Compound 2 has low IC50 value (86.83 ±0.23 µg/ml) while compound 1 and 3 have almost similar IC50 values of 104.93 ±0.19 µg/ml and 104.95 ±0.21 µg/ml, respectively. These results indicate that the compound 2 has potential amylase inhibitory activity (graphical comparison is shown in the Fig. 7).

Fig. 7 Graphical representation of α-amylase inhibition of all three compounds at different concentrations There are many reports in literature that confirms that one of the effective method to control diabetes is to inhibit the activity of α- amylase enzyme which is responsible for the breakdown of starch to more simple sugars. This is attributed by the α-amylase inhibitors, which delays the glucose absorption rate therapy maintaining the cerum blood glucose in hyperglycemic individuals [38]. The role of these synthesized compounds in disease prevention is attributed to its antioxidant properties due to presence of certain reactive centers. Recently there is a great expedition for the discovery of dipeptidyl peptidase (DPP-IV) inhibitors as anti-diabetics, because of their glucose dependent effects and lesser hypoglycemia. The introduction of

16

oxadiazole moiety has brought a great improvement in the pharmacokinetics profiles of existing DPP-IV inhibitors [39]. The

molecule

2-(1-methoxy-2-methylpropan-2-ylamino)-1-(2-(2-phenyl-1,3,4-oxadiazole-5-

carbonyl)pyrrolidin-1-yl)ethenone (LC-150444) (Fig. 8) which acts as DPP-IV inhibitor. The presence of oxadiazole ring increased the biological activity of compound tremendously, and now is under clinical phase 1[40]. The synthesized compound may act as good drug candidates in comparison to the LC-150444 which is under clinical phase 1.

N N O

N O

O

NH O

Fig 8 Structure of 2-(1-methoxy-2-methylpropan-2-ylamino)-1-(2-(2-phenyl-1,3,4-oxadiazole-5carbonyl)pyrrolidin-1-yl)ethenone (LC-150444)

4 Conclusions In conclusion, there oxadiazole derivatives have been synthesized in good yields (70-83%) via substitution reaction between 1,3,4-oxadiazoles and substituted benzyl bromide. The final structures of all three compounds (1-3) are analyzed through different spectroscopic techniques and are confirmed by X-ray diffraction studies. DFT calculations showed that excellent correlation exists between X-ray and theoretical data. FMOs analysis revealed that all three compounds have H-Lg 4.68-4.75 eV, which reflects the moderate reactivity of these compounds. The ESP mapping showed that negative potential is concentrated on oxadiazole ring in all three

17

compounds. Enzyme inhibition potential of showed that all compounds have inhibitory activity against the α-amylase and among all, 2 has lowest IC50 value of 86.83 ±0.23 µg/mL.

Acknowledgements

The authors highly acknowledge Higher Education Commission of Pakistan (NRPU grant # 5309), COMSATS University Islamabad, Abbottabad Campus and University of Azad Jammu and Kashmir for financial support Supplementary material

cif files of all three compounds are provided in supporting information. Experimental 1H-NMRs and IRs are pasted in supporting information as Figs. S1-S3. HOMO and LUMO surfaces of compounds 2 and 3 are pasted and Fig. S4. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/

References [1]

M. Akhter, A. Husain, B. Azad, M. Ajmal, Aroylpropionic acid based 2,5-disubstituted1,3,4-oxadiazoles: Synthesis and their anti-inflammatory and analgesic activities, Eur. J. Med. Chem. 44 (2009) 2372–2378.

[2]

G. Chawla, 1,2,4-Oxadiazole as a Privileged Scaffold for Anti-inflammatory and Analgesic Activities: A Review, Mini-Reviews Med. Chem. 18 (2018) 1536–1547.

[3]

K. Manjunatha, B. Poojary, P.L. Lobo, J. Fernandes, N.S. Kumari, Synthesis and biological evaluation of some 1,3,4-oxadiazole derivatives, Eur. J. Med. Chem. 45 (2010)

18

5225–5233. [4]

Y. Li, H.-Q. Zhang, J. Liu, X.-P. Yang, Z.-J. Liu, Stereoselective Synthesis and Antifungal Activities of ( E )-α-(Methoxyimino)benzeneacetate Derivatives Containing 1,3,5-Substituted Pyrazole Ring, J. Agric. Food Chem. 54 (2006) 3636–3640.

[5]

S. Cao, X. Qian, G. Song, Q. Huang, Syntheses and insecticidal activity of new 2-(5(trifluoromethyl)pyridyloxymethyl)-1,3,4-oxadiazoles, J. Fluor. Chem. 117 (2002) 63–66.

[6]

S.N. Rampersad, J.D. Ovens, E. Huston, M.B. Umana, L.S. Wilson, S.J. Netherton, M.J. Lynch, G.S. Baillie, M.D. Houslay, D.H. Maurice, Cyclic AMP Phosphodiesterase 4D (PDE4D) Tethers EPAC1 in a Vascular Endothelial Cadherin (VE-Cad)-based Signaling Complex and Controls cAMP-mediated Vascular Permeability, J. Biol. Chem. 285 (2010) 33614–33622.

[7]

B.P. Mallikarjuna, B.S. Sastry, G.V. Suresh Kumar, Y. Rajendraprasad, S.M. Chandrashekar, K. Sathisha, Synthesis of new 4-isopropylthiazole hydrazide analogs and some derived clubbed triazole, oxadiazole ring systems – A novel class of potential antibacterial, antifungal and antitubercular agents, Eur. J. Med. Chem. 44 (2009) 4739– 4746.

[8]

B. Chandrakantha, P. Shetty, V. Nambiyar, N. Isloor, A.M. Isloor, Synthesis, characterization and biological activity of some new 1,3,4-oxadiazole bearing 2-flouro-4methoxy phenyl moiety, Eur. J. Med. Chem. 45 (2010) 1206–1210.

[9]

K.C. Ravindra, H.M. Vagdevi, V.P. Vaidya, B. Padmashali, Synthesis, Antimicrobial and Antiinflammatory Activities of 1,3,4-Oxadiazoles Linked to Naphtho[2,1-b]furan., ChemInform. 38 (2007).

[10]

D. Kumar, S. Sundaree, E.O. Johnson, K. Shah, An efficient synthesis and biological

19

study of novel indolyl-1,3,4-oxadiazoles as potent anticancer agents, Bioorg. Med. Chem. Lett. 19 (2009) 4492–4494. [11]

Y. Qian, Z. Lu, C. Lu, Z. Chen, Y. Cui, Synthesis and two-photon absorption properties of 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles, Dye. Pigment. 75 (2007) 641–646.

[12]

B. Grinsztejn, B.-Y. Nguyen, C. Katlama, J.M. Gatell, A. Lazzarin, D. Vittecoq, C.J. Gonzalez, J. Chen, C.M. Harvey, R.D. Isaacs, Safety and efficacy of the HIV-1 integrase inhibitor raltegravir (MK-0518) in treatment-experienced patients with multidrug-resistant virus: a phase II randomised controlled trial, Lancet. 369 (2007) 1261–1269.

[13]

B. Ahmad Khan, S. Zafar, E.U. Mughal, M. Naeem Ahmed, S. Shamila Hamdani, T. Akhter, I.- Haq, A. Sadiq, K. Mohammed Khan, Design and Synthesis of Novel 1,3,4Oxadiazole Derivatives Bearing Azo Moiety as Biologically Significant Scaffolds, Lett. Drug Des. Discov. 15 (2018).

[14]

M.N. Ahmed, B. Sadiq, N.A. Al-Masoudi, K.A. Yasin, S. Hameed, T. Mahmood, K. Ayub, M.N. Tahir, Synthesis, crystal structures, computational studies and antimicrobial activity of new designed bis((5-aryl-1,3,4-oxadiazol-2-yl)thio)alkanes, J. Mol. Struct. 1155 (2018) 403–413.

[15]

P. Mormile, L. Petti, M. Gillo, P. Laurienzo, M. Malinconico, A. Roviello, S. Lipson, W.. Blau, Optical properties of a novel alkoxy-substituted poly (p-phenylene 1,3,4oxadiazoles) for electro-optical devices, Mater. Chem. Phys. 77 (2003) 945–951.

[16]

M.B. Casu, P. Imperia, B. Schulz, S. Schrader, Electronic structure at the interface between metals and new materials for organic light emitting diodes, Surf. Sci. 507–510 (2002) 666–671.

[17]

C.K. Lai, Y.-C. Ke, J.-C.S. Chien-Shen, W.-R. Li, Heterocyclic 1,3,4-oxadiazole as

20

columnar core, Liq. Cryst. 29 (2002) 915–920. [18]

K.D. Patel, S.M. Prajapati, S.N. Panchal, H.D. Patel, Review of Synthesis of 1,3,4Oxadiazole Derivatives, Synth. Commun. 44 (2014) 1859–1875.

[19]

M.N. Ahmed, K.A. Yasin, S. Hameed, K. Ayub, I. Haq, M.N. Tahir, T. Mahmood, Synthesis, structural studies and biological activities of three new 2-(pentadecylthio)-5aryl-1,3,4-oxadiazoles, J. Mol. Struct. 1129 (2017) 50–59.

[20]

M. Arshad, M. Jadoon, Z. Iqbal, M. Fatima, M. Ali, K. Ayub, A.M. Qureshi, M. Ashraf, M.N. Arshad, A.M. Asiri, A. Waseem, T. Mahmood, Synthesis, molecular structure, quantum mechanical studies and urease inhibition assay of two new isatin derived sulfonylhydrazides, J. Mol. Struct. 1133 (2017) 80–89.

[21]

S. Abbas, H.H. Nasir, S. Zaib, S. Ali, T. Mahmood, K. Ayub, M.N. Tahir, J. Iqbal, Carbonic anhydrase inhibition of Schiff base derivative of imino-methyl-naphthalen-2-ol: Synthesis, structure elucidation, molecular docking, dynamic simulation and density functional theory calculations, J. Mol. Struct. 1156 (2018) 193–200.

[22]

M.N. Ahmed, I. Ashraf, K.A. Yasin. "Synthesis, characterization, anti-leishmanial activity and in silico studies of 5-(4-Methoxyphenyl)-2-(undecylthio)-1, 3, 4-oxadiazole. J. Chem. Soc. Pak. 40(2018) 773-781.

[23]

G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3–8.

[24]

L.J. Farrugia, WinGX and ORTEP for Windows : an update, J. Appl. Crystallogr. 45 (2012) 849–854.

[25]

J.L. W.C. Frisch, M.J.; Trucks, G.W.; Schlegel, H.B.; Scuseria, G.E.; Robb, M.A.; Cheeseman, J.R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G.A.; Nakatsuji, H.;

21

Caricato, M.; Li, X.; Hratchian, H.P.; Izmaylov, A.F.; Bloino, J.; Zheng, G.; Sonnenberg, Gaussian 09, Rev. C.01, Gaussian, Inc., Wallingford CT, 2010. [26]

R. Dennington, T. Keith, J. Millam, GaussView 5.0, Semichem Inc., 2009.

[27]

N. Kosar, M. Asgar, K. Ayub, T. Mahmood, Halides encapsulation in aluminum/boron phosphide nanoclusters: An effective strategy for high cell voltage in Na-ion battery, Mater. Sci. Semicond. Process. 97 (2019) 71–79.

[28]

F. Ullah, N. Kosar, K. Ayub, M.A. Gilani, T. Mahmood, Theoretical study on a boron phosphide nanocage doped with superalkalis: novel electrides having significant nonlinear optical response, New J. Chem. 43 (2019) 5727–5736.

[29]

T. Mahmood, N. Kosar, K. Ayub, DFT study of acceleration of electrocyclization in photochromes under radical cationic conditions: Comparison with recent experimental data, Tetrahedron. 73 (2017) 3521–3528.

[30]

B. Nickavar, N. Yousefian, Evaluation of α-amylase inhibitory activities of selected antidiabetic medicinal plants, J. Für Verbraucherschutz Und Leb. 6 (2011) 191–195.

[31]

N.S.M.

Mokhtaruddin,

E.N.M.

Yusof,

T.B.S.A.

Ravoof,

E.R.T.

Tiekink,

A.

Veerakumarasivam, M.I.M. Tahir, Unusual saccharin-N,O (carbonyl) coordination in mixed-ligand copper(II) complexes: Synthesis, X-ray crystallography and biological activity, J. Mol. Struct. 1139 (2017) 1–9. [32]

M.N. Ahmed, K.A. Yasin, R.A-H. Khan, T. Mahmood, K. Ayub, D. Malik, M. Hafeez, A. M. Khan, M. N. Tahir, Synthesis, Crystal Structure, Spectral Analysis, DFT Studies and Antimicrobial Activity of Ethyl 6-(4-(ethoxycarbonyl)-1H-1,2,3-triazol-1-yl)pyridine-3carboxylate, J.Chem.Soc.Pak., 39 (2017), 640-649.

[33]

M. Arshad, A. Bibi, T. Mahmood, A. Asiri, K. Ayub, Synthesis, Crystal Structures and

22

Spectroscopic Properties of Triazine-Based Hydrazone Derivatives; A Comparative Experimental-Theoretical Study, Molecules. 20 (2015) 5851–5874. [34]

N. Rasool, A. Kanwal, T. Rasheed, Q. Ain, T. Mahmood, K. Ayub, M. Zubair, K. Khan, M. Arshad, A. M. Asiri, M. Zia-Ul-Haq, H. Jaafar, One Pot Selective Arylation of 2Bromo-5-Chloro Thiophene; Molecular Structure Investigation via Density Functional Theory (DFT), X-ray Analysis, and Their Biological Activities, Int. J. Mol. Sci. 17 (2016) 912.

[35]

M.N. Arshad, A.M. Asiri, K.A. Alamry, T. Mahmood, M.A. Gilani, K. Ayub, A.S. Birinji, Synthesis, crystal structure, spectroscopic and density functional theory (DFT) study of N[3-anthracen-9-yl-1-(4-bromo-phenyl)-allylidene]-N-benzenesulfonohydrazine, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 142 (2015) 364–374.

[36]

S.M. Soliman, J. Albering, M.A.M. Abu-Youssef, On the isomers of pyridine-4carboxaldoxime and its nitrate salt, X-ray crystal structure and quantum chemical calculations, J. Mol. Struct. 1139 (2017) 17–30.

[37]

O.L. Franco, D.J. Rigden, F.R. Melo, M.F. Grossi-de-Sá, Plant α-amylase inhibitors and their interaction with insect α-amylases, Eur. J. Biochem. 269 (2002) 397–412.

[38]

A. Mitra, M. Manjunatha, B. Dineshkumar, A comparative study of alpha amylase inhibitory activities of common anti-diabetic plants at Kharagpur 1 block, Int. J. Green Pharm. 4 (2010) 115.

23

[39]

S. Rikta, T. Omprakash, M. Akranth, M. Alam, M. Akhter, Mymoona, Recent Updates on Biological Activities of Oxadiazoles, Mini Rev. Med. Chem. 13 (2013),

10271046. [40]

K.S. Lim, J.-Y. Cho, B.-H. Kim, J.-R. Kim, H.-S. Kim, D.-K. Kim, S.-H. Kim, H.J. Yim, S.-H. Lee, S.-G. Shin, I.-J. Jang, K.-S. Yu, Pharmacokinetics and pharmacodynamics of LC15-0444, a novel dipeptidyl peptidase IV inhibitor, after multiple dosing in healthy volunteers, Br. J. Clin. Pharmacol. 68 (2009) 883–890.

24

Table 1: Single crystal X-ray parameters of compounds (1-3) Crystal Parameters CCDC Reference

Compound 1 1895555

Compound 2 1895556

Compound 3 1895557

Chemical formula

C17H13F3N2O2S

C17H13F3N2O2S

C16H10F4N2OS

Mr

366.35

366.35

354.32

Crystal group

system,

space

Orthorhombic, Pna21

Monoclinic, P21/c

Temperature (K) a, b, c (Å)

150 12.7417 (3), 4.86105 (10), 26.3041 (5)

Monoclinic, P21/c

150

150

14.0517 (3), 4.45925 (9), 25.3792 (5), 90.9927 (18)

5.42566 (11), 38.5416 (7), 7.09709 (14), 100.724 (2)

1590.03 (5)

1458.18 (5)

V (Å3)

1629.22 (6)

Z

4

4

4

Radiation type

Cu Kα

Cu Kα

Cu Kα

µ (mm )

2.20

2.25

2.48

-1

Crystal size (mm) Data collection Diffractometer

0.36 × 0.14 × 0.09

0.47 × 0.19 × 0.13

0.30 × 0.16 × 0.07

SuperNova, Single source at offset, Atlas

SuperNova, Single source at offset, Atlas

SuperNova, Single source at offset, Atlas

Absorption correction

Multi-scan CrysAlis PRO 1.171.38.46 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Multi-scan CrysAlis PRO 1.171.38.46 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Multi-scan CrysAlis PRO 1.171.38.46 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Tmin, Tmax

0.506, 0.822

No. of measured, independent and observed [I> 2σ(I)] reflections Rint

5246, 2454, 2334

0.017

(sin θ/λ)max (Å ) -1

R[F2> 2σ(F2)], wR(F2), S

0.417, 0.754

0.519, 0.838

5448, 2862, 2601

5862, 2866, 2682

0.016

0.015

0.599

0.599 Refinement 0.028, 0.075, 1.06 0.035, 0.094, 1.04

0.622 0.032, 0.078, 1.08

No. of reflections

2454

2862

2866

No. of parameters

227

227

217

No. of restraints

1

1

1

H-atom treatment ∆〉 max, ∆〉 min (e Å-3)

H-atom parameters constrained 0.14, -0.21

H-atom parameters constrained 0.25, -0.30

H-atom parameters constrained 0.23, -0.26

Table 2: Important X-ray bond lengths (Å) of compounds 1-3, respectively (Atomic labels are with reference ORTEP plots Fig. 2).

1 S1—C9 O1—C9 O1—C10 O2—C14 O2—C17 N1—N2 N1—C9 N2—C10 F1—C7 F2—C7 F3—C7 S1—C8

Exp. 1.73 (2) 1.36 (3) 1.37 (3) 1.36 (3) 1.42 (3) 1.41 (3) 1.29 (3) 1.29 (3) 1.34 (3) 1.33 (3) 1.33 (3) 1.82 (2)

Theo. 1.74 1.35 1.37 1.35 1.42 1.39 1.29 1.29 1.35 1.34 1.34 1.85

2 S1—C9 S1—C8 O1—C9 O1—C10 O2—C14 O2—C17 N1—C9 N1—N2 N2—C10 F1—C7 F2—C7 F3—C7

Exp. 1.73 (17) 1.83 (17) 1.36 (2) 1.37 (19) 1.35 (2) 1.42 (2) 1.28 (2) 1.41 (2) 1.28 (2) 1.34 (2) 1.33 (2) 1.33 (2)

Theo. 1.74 1.85 1.35 1.37 1.35 1.42 1.29 1.39 1.29 1.35 1.34 1.34

3 S1—C9 S1—C8 O1—C9 O1—C10 N1—C9 N1—N2 N2—C10 F1—C7 F2—C7 F3—C7 F4—C14

Exp. 1.73 (15) 1.83 (15) 1.36 (17) 1.37 (17) 1.29 (2) 1.41 (18) 1.28 (19) 1.34 (2) 1.33(19) 1.34 (2) 1.35 (17)

Theo. 1.74 1.86 1.35 1.37 1.29 1.39 1.29 1.35 1.34 1.35 1.34

Table 3: Important X-ray bond angles (o) of compounds 1-3, respectively (Atomic labels are with reference ORTEP plots Fig. 2).

1 C9—S1— C8 C9— O1—C10 C14— O2—C17 C9— N1—N2 C10— N2—N1 C1—C8— S1 N1— C9—O1 N1— C9—S1

Exp. 99.4 (12) 102.2 (16) 117.8 (19) 105.8 (19) 106.3 (17) 114.0 (16) 113.2 (18) 131.0 (18)

Theo. 99.0 102.3 118.7 106.0 106.9 114.4 112.9 130.3

2 C9—S1— C8 C9— O1—C10 C14— O2—C17 C9— N1—N2 C10— N2—N1 C1—C8— S1 N1— C9—O1 N1— C9—S1

Exp. 99.9 (8) 101.8 (12) 117.6 (13) 105.5 (14) 106.7 (13) 114.4 (12) 113.5 (15) 130.3 (14)

Theo. 99.1 102.4 118.7 106.0 106.9 113.9 112.8 130.8

3 C9— S1—C8 C9— O1—C10 C9— N1—N2 C10— N2—N1 C1— C8—S1 N1— C9—O1 N1— C9—S1 O1— C9—S1

Exp. 99.3 (7) 101.8 (11) 105.4 (12) 106.5 (12) 113.1 (10) 113.4 (13) 130.0 (12) 116.4 (10)

Theo. 99.1 102.4 106.0 106.9 113.9 112.7 130.8 116.3

O1— C9—S1 N2— C10—O1 N2— C10—C11 O1— C10—C11

115.6 (15) 112.3 (19) 129.0 (19) 118.7 (19)

116.6 111.6 129.0 119.2

O1— 116.0 C9—S1 (11) N2— 112.2 C10—O1 (15) N2— 128.5 C10—C11 (15) O1— 119.2 C10—C11 (14)

116.3 111.7 129.0

N2— C10—O1 N2— C10—C11 O1— C10—C11

112.5 (13) 128.3 (13) 119.1 (12)

111.8 128.9 119.2

119.2

Table 4: α-Amylase inhibition effect of compounds (1-3) in comparison with reference drug acarbose Compound 1

2

3

Acarbose

Concentration (µg/ml) 10 100 200 250 10 100 200 250

% Inhibition

IC50 value (µg/ml)

15.12 43.03 90.08 100.00 35.16 52.21 72.37 83.51

104.93 ±0.19

10 100 200 250

27.13 48.19 75.11 84.83

104.95 ±0.21

10 100 200 250

55.21 73.83 82.55 93.61

8.80±0.21

86.83 ±0.23

Highlights (i)

Synthesis and structural properties of 1,3,4-oxadiazole derivatives have been investigated.

(ii)

X-ray geometric parameters are in strong agreement with the theoretical data.

(iii)

The low IC50 value value reflects the potential α-amylase inhibitory potential of all compounds.