Synthesis and antitubercular screening of novel imidazoline ...

Research article 

Int J Pharm Biomed Sci 2013, 4(1), 40-45 

ISSN No: 0976-5263 

Research Drops 

PharmaInterScience Publishers 

Synthesis and antitubercular screening of novel imidazoline 

derivatives 

T.Shalina Begum 1 , 

U.C.A.Jaleel 2 , P.M.Shafi 1 * 

1 Department of Chemistry, University of 

Calicut, Kerala-673 635, India 

2 Cheminformatics, Malabar Christian 

College, Kozhikode, Wayanad Road, 

Calicut, Kerala-673 001, India 

Correspondence: 

P.M.Shafi 

Tel: +91 9497450932 

E-mail: shafimuham@rediffmail.com 

4-Arylidene-2-aryl-2-imidazolin-5-ones were synthesised in good yield by 

three component condensations of aryl imidic acid ester, glycine ester and 

aromatic aldehydes in presence of a base. Aminoimidazolinone was also 

synthesised by tandem reaction between imidic acid ester and glycine ester in 

presence of a base. These molecules were screened for their tuberculosis activity 

and drug likeness computationally. All the twelve newly synthesised compounds 

revealed drug like properties and the aminopyrazinyl imidazolinone was found to 

be active against tuberculosis. 

Key words: Aminoimidazolinone, Antitubercular activity, 4-Arylidene-2-aryl-2- 

imidazolin-5-ones, Druggability, Tandem reaction 

Received: 22 Feb 2013 / Revised: 05 Mar 2013 / Accepted: 09 Mar 2013 / Online publication: 16 Mar 2013 

1. INTRODUCTION 

Imidazoles constitute a series of compounds which 

possess various biological properties such as antimicrobial 

[1], anticancer [2], immunomodulatory [3], L-DOPA 

prodrugs in the treatment of parkinson’s disease [4], 

leishmanicidal [5] and potential COX-2 inhibitors [6]. 

Several classes of drugs, notably metronidazole which is 

active against intestinal infections, the broad spectrum 

antifungal agent clotrimazole [7], antibacterial agent 

azomycine and anticancer drugs like misonidazole and 

metrozole [8] have imidazoline ring system in them. In view 

of these reports and as a continuation of our earlier studies, 

some new imidazoline derivatives were synthesised and their 

druggability and antitubercular screening carried out. 

2,4-Disubstituted-2- imidazolin-5-ones with an exocyclic 

double bond in the fourth position are called unsaturated 2,4- 

disubstituted-2-imidazolin-5-ones. These compounds can be 

synthesised from azlactone [9], amidine-glyoxal [10], imidic 

acid ester-glycine ester [11], and amidine–haloacetic ester 

[12] method. In the present work 4-arylidene-2-aryl-2- 

imidazolin-5-ones were synthesised from glycine ester and 

imidic acid ester, with hydroxyphenyl and pyrazinyl group at 

second position of the imidazolinone ring. 

Development and application of computational methods 

for drug discovery is of considerable interest. It permits the 

rapid and cost-effective elimination of poor candidates prior 

to synthesis. Various methods are available for effective 

screening of organic molecules to prioritize for their 

druglikeness and medicinal activity on a particular disease 

target. Protocols like structure based and ligand based drug 

discovery are commonly used. In the present study we used 

ligand based drug discovery approach for the development of 

models and subsequent screening of the molecules for their 

potential activity against selected Mycobacterium 

tuberculosis (Mtb) targets. Prediction of druggability of the 

newly synthesised molecules was done using Qikprop 

(Schrodinger). 

2. MATERIALS AND METHODS 

2.1. Apparatus 

Melting points of the synthesised compounds were 

determined on Toshniwal capillary melting point apparatus in 

open capillaries and are uncorrected. UV-Vis spectra were 

recorded in ethanol on a Shimadzu 1601 UV-Visible 

spectrometer. IR spectra were recorded as KBr pellets using 

Shimadzu 8101A FTIR equipment. The mass spectra were 

recorded on GC17AAFTW version 3 Shimadzu Japan 

spectrometer. The 1 H NMR spectra were recorded on a 

Brucker AM 360 spectrometer using TMS as internal 

standard, CHN analysis were carried out on a Vario-EI 

(Elementar) model. Purity of the compounds was checked by 

TLC on silica gel plates. 

©2013 PharmaInterScience Publishers. All rights reserved. www.pharmainterscience.com

T.Shalina Begum et al., Int J Pharm Biomed Sci 2013, 4(1), 40-45 

41 

O 

ClH . H 2 N OCH 3 

+ 

O 

N 

NH 

ClH . H 2 N 

OC 2 H 5 

NaHCO 3 

-C 2 H 5 OH 

OH 

OH 

C 6 H 5 CHO 

-H 2 O 

O 

C 6 H 5 

N 

NH 

OH 

Fig.1. Synthesis of 4-arylidene-2-p-hydroxyphenyl-2-imidazolin-5-ones 

O 

NH 

O 

O 

N 

N 

NH 2 

NH 2 

OC 2 H 5 

-C 2 H 5 OH 

N 

NH 

N 

N 

O 

O 

+ 

NH 

N 

base 

N 

NH 

N 

N 

N 

N 

N 

Fig.2. 4-(amino 2-pyrazinyl)methylene-2-(2-pyrazinyl)-2-imidazolin-5-one 

2.2. Synthesis of 4-arylidene-2-p-hydroxyphenyl-2- 

imidazolin-5-ones 

4-Arylidene-2-p-hydroxyphenyl-2-imidazolin-5-ones 

were synthesised from 4-hydroxybenzimidic acid methyl 

ester hydrochloride (0.03mol) obtained from p- 

hydroxybenzonitrile by Pinner method [13], refluxed with 

glycine ethyl ester hydrochloride (0.035 mol), 

sodiumbicarbonate and aromatic aldehyde (0.035mol) for an 

hour (Fig.1). The 4-arylidene-2-p-hydroxyphenyl-2- 

imidazolin-5-ones formed were filtered, washed with water, 

then with ethanol and dried. 

2.3. Synthesis of 4-arylidene-2-pyrazinyl-2-imidazolin-5- 

ones 

4-Arylidene-2-pyrazinyl-2-imidazolin-5-ones were 

synthesised by converting pyrazinecarbonitrile (0.02mol) into 

the corresponding imidic ester in presence of methanol and 

sodium methoxide [14]. The imidic ester formed was then 

refluxed with glycine ethyl ester hydrochloride, (0.025mol) 



42 

Fig.3. Virtual Screening for tuberculosis active molecules 

sodium bicarbonate and aromatic aldehyde (0.02mol) for half 

an hour. The product formed was filtered, washed with water 

and then with ethanol and dried. 

2.4. Synthesis of 4-(amino 2-pyrazinyl)methylene-2-(2- 

pyrazinyl)-2-imidazolin-5-one 

Imidic acid ester formed from pyrazinecarbonitrile 

(0.02mol) and glycine ethyl ester (0.01mol) were refluxed 

with sodiumbicarbonate in benzene for an hour and cooled. 

4-(amino 2-pyrazinyl)methylene-2-(2-pyrazinyl)-2- 

imidazolin-5-one formed (Fig.2) was filtered, washed with 

water and then with ethanol and dried. 

2.5. Druggability 

To develop orally available drugs, it is useful to optimise 

drug-like pharmacokinetic properties. It includes the study of 

the mechanism of absorption and distribution of an 

administered drug, the rate at which a drug action begins and 

the duration of the effect, the chemical changes of the 

substance in the body and the effects and routes of excretion 

of the metabolites of the drug [15] 

(http://www.credoreference.com/entry/6686418). Various 

media and high throughput insilico ADMET (absorption, 

distribution, metabolism, excretion and toxicity) screens are 

now in use. Qikprop (Schrodinger version 9.2) allows to 

predict pharmaceutically relevant properties for organic 

molecules, starting from their 3D structures and employing 

calculated physically significant descriptor like ADMET 

properties. 

2.6. Virtual Screening for tuberculosis active molecules 

Data mining tools with cost effective algorithm will 

provide effective platform to differentiate the tuberculosis 

active molecules from nontuberculosis active molecules. We 

applied Weka (version 3.6) classifier for the discovery of 

tuberculosis active molecules. The methodology is 

summarised in Fig.3. 

3. RESULTS AND DISCUSSION 

Imidic acid ester of p-hydroxybenzonitrile, glycine ester 

and aromatic aldehyde in equimolar ratio were refluxed in 

tolune in presence of sodiumbicarbonate as base, resulted in 

the formation of 4-arylidene-2-p-hydroxyphenyl-2- 

imidazolin-5-ones. Six aldehydes were thus condensed to get 

4-arylidene-2-p-hydroxyphenyl-2-imidazolin-5-ones in 41- 

76% yield. 

Imidic acid ester of pyrazine carbonitrile, glycine ester 

and aromatic aldehyde were refluxed in benzene in presence 

of sodium bicarbonate which resulted in the formation of 4- 

arylidene-2-pyrazinyl-2-imidazolin-5-ones. Five aldehydes 

were condensed to obtain 4-arylidene-2-pyrazinyl-2- 

imidazolin-5-ones in 20-59% yield. The synthesised 

compounds were purified by recrystallization from 

isopropanol. 



43 

Table 1 

Physical characteristics data of the new imidazolinone derivatives 

S. No. Name M.P. 

°C 

1 4-Benzylidene-2-p-hydroxyphenyl-2-Imidazolin-5-one 254 76 1687 391 10.50 10.61 

2 4-(4-Chlorobenzylidene)-2-p-hydroxyphenyl-2-imidazolin-5-one 288 72 1680 394 9.27 9.38 

3 4-(4-Methylbenzylidene)-2-p-hydroxyphenyl-2-imidazolin-5-one 258 54 1682 396 10.01 10.07 

4 4-(4-Methoxybenzylidene)-2-p-hydroxyphenyl-2-imidazolin-5-one 272 45 1676 401 9.40 9.52 

5 4-(2-Hydroxybezylidene)-2-p-hydroxyphenyl-2-imidazolin-5-one 262 60 1699 410 10.10 10.00 

6 4-(2-Chlorobenzylidene)-2-p-hydroxyphenyl-2-imidazolin-5-one 224 41 1710 393 9.26 9.38 

7 4-Benzylidene-2-pyrazinyl-2-imidazolin-5-one 248 30 1684 388 22.38 22.40 

8 4-(4-Chlorobenzylidene)-2-pyrazinyl-2-imidazolin-5-one 272 35 1677 308 19.55 19.68 

9 4-(4-Methylbenzyllidene)-2-pyrazinyl-2-imidazolin-5-one 273 40 1698 314 21.00 21.21 

10 4-(4-Methoxybenzylidene)-2-pyrazinyl-2-imidazolin-5-one 261 59 1697 314 19.90 20.00 

11 4-(2-Chlorobenzylidene)-2-pyrazinyl-2-imidazolin-5-one 215 20 1741 392 19.54 19.68 

12 4-(Amino2-pyrazinyl)methylene-2-(2-pyrazinyl)-2-imidazolin-5-one 192 37 1673 422 36.41 36.70 

Yeild 

(%) 

ʋ co 

(cm -1 ) 

λ max 

(nm) 

N% 

Found 

Calculated 

Table 2 

General druglike descriptors of imidazolinone derivatives 

S.No. 

Mol.weight 

(130/ 725) 

Dipole 

(1.0/ 12.5) 

Hydrophilic 

SASA(7.0/ 330) 

Hydrophobic 

SASA(0.0/ 750) 

Log p oct/water 

(-2.0/ 6.5) 

Log BB 

( -3.0 to1.2) 

Caco-2 ( 500 greater) 

Molecules similarity (>80%) 

1 264.283 5.053 148.982 12.387 2.177 -1.088 382 Valdecoxib, Sulfaphenazole, 

Oxazepam, 

Mebendazole, Phenytoin. 

2 298.728 5.481 153.573 12.436 2.637 -1.011 346 Flubendazole, Lorazepam, 

Valdecoxib, Sulfaphenazole, 

Mebendazole. 

3 278.310 4.162 144.009 100.627 2.477 -1.060 426 Afloqualone, Valdecoxib, 

Rosoxacin, Mebendazole, 

Sulfaphenazole. 

4 294.309 5.365 148.350 105.151 2.062 -1.175 388 Sulfaphenazole, Valdecoxib, 

Dantrolene, 

Oxyphenbutazone, Letrozole. 

5 280.282 5.341 193.426 9.512 1.508 -1.593 145 Sulfaphenazole, Dantrolene, 

Valdecoxib, Letrozole, 

Papaveroline. 

6 298.728 4.919 142.044 17.895 2.598 -0.886 445 Valdecoxib, Mebendazole, 

Sulfaphenazole, 

Flubendazole, Lorazepam. 

7 250.259 3.784 139.636 11.829 1.377 -0.917 469 Azathioprine, Valdecoxib, 

Piroxicam, Afloqualone, 

Tenoxicam. 

8 284.704 3.886 129.768 12.349 1.892 -0.638 582 Afloqualone, 

Valdecoxib, Nifenazone, 

piroxicam, Alosetron. 

9 264.286 4.003 134.917 100.517 1.681 -0.893 520 Valdecoxib, Afloqualone, 

Piroxicam, 

Rofecoxib, Metopon. 

10 280.285 5.027 129.797 105.066 1.529 -0.876 582 Piroxicam, Tenoxicam, 

Lornoxicam, Valdecoxib, 

Letrozole. 

11 284.704 3.643 132.763 17.832 1.731 -0.667 545 Valdecoxib, Afloqualone, 

Piroxicam, Nifenazone, 

Tenoxicam. 

12 267.249 2.307 222.592 0.000 -0.292 -1.766 76 Sulfacytine, 

Didanosine, Azathioprine, 

Isoxicam, Sulthiame. 

Imidic acid ester of pyrazine carbonitrile and glycine ester 

were taken in the molar ratio 2:1 and refluxed in benzene in 

presence of sodium bicarbonate base, resulted in the 

formation of 4-(amino 2-pyrazinyl)methylene-2-(2- 

pyrazinyl)-2-imidazolin-5-one by tandem reaction. The 

synthesised compound was recrystallized from ethanol. The 

elemental analysis and spectral data obtained supported the 

proposed structure. The physical characteristics of the new 

compounds were determined and are tabulated (Table 1). All 

the compounds given are reported for the first time. 

All the compounds synthesised gave satisfactory spectral 

data for their proposed structures. Some typical cases are as 

follows. 

i. 4-Benzylidene-2-p-hydroxyphenyl-2-imidazolin-5-one: 

IR:1684cm -1 (C=O), 3186cm -1 (b, N-H str), 3391cm -1 (O- 

H), 1637cm -1 (C=N). Mass spectrum m/z 265(M + +1) 



corresponds to its molecular mass 264. 1 H NMR: δ 6.89– 

8.29 (9H, aromatic protons and methyne proton), δ11.94 

(1H, NH of imidazolinone ring), δ10.94 (1H, O-H). 

ii. 4-Benzylidene-2-pyrazinyl-2-imidazolin-5-one: IR: 

1687cm -1 (C=O), 3181cm -1 (b, N-H str) and 1635cm -1 

(C=N). In mass spectrum m/z=250 corresponds to its 

molecular mass. 

1 H NMR: δ7.1–9.5 (8H, aromatic 

protons and methyne proton) and δ12.1 (1H, NH of 

imidazolinone ring). 

iii. 4-(Amino2-pyrazinyl)methylene-2-(2-pyrazinyl)-2- 

imidazolin-5-one: IR : 1673cm -1 (C=O), 3195 to 3290cm -1 

(3 medium intensity peaks, NH 2 and NH of imidazolinone 

ring ). Mass spectrum m/z 268 (M + +1) corresponds to its 

molecular mass 267. 1 H NMR: δ8.4–9.2 (6H, aromatic 

protons), δ10.2 and δ9.2 (2H of NH 2 chemically non 

equivalent) and δ12.12 (1H, NH of imidazolinone ring). 

3.1. Druggability 

The new imidazolinone molecules synthesised were 

modelled, energy minimised and uploaded for the descriptor 

and toxicity prediction using Qikprop (Schrodinger version 

9.2). All the imidazolinones analysed showed more drug like 

properties. The summarised results of each molecule are 

presented in Table 2 (molecules are numbered in the order of 

Table 1). The drug molecules similar to the imidazolinones 

were also tabulated. 

3.2. Anti Mtb activity 

The imidazolinones were screened for their antitubercular 

activity by using Weka classifier. It was found that 4-(amino 

2-pyrazinyl)methylene-2-(2-pyrazinyl)-2-imidazolin-5-one 

(Fig.4) is active towards tuberculosis. 

analysed for their antituberculosis activity by virtual 

screening. Thier analytical results are given below. 

Filename: J48.model 

Scheme: weka.classifiers.meta.CostSensitiveClassifier -costmatrix 

"[0.0 2.0; 1.0 0.0]" -S 1 -W weka.classifiers.trees.J48 - 

- -C 0.25 -M 2 

Relation: AID434987_train 

Attributes:132 

Predictions on test set 

Inst#Actual Predicted Error Probability Distribution 

1 1:Active 2:Inactive + 0 *1 

2 2:Inactive 2:Inactive 0 *1 


4 2:Inactive 1:Active + *0.857 0.143 

5 1:Active 2:Inactive 0 *1 













4. CONCLUSIONS 

Tuberculosis 

active 

The new imidazoline derivatives synthesised were 

obtained in good yield, their proposed structure were 

confirmed by spectral analysis. All the novel molecules 

synthesised showed drug-like properties. Most of the 

molecules are similar to non-steroidal antiinflammatory 

drugs, anticonvulsant and analgesic. Insilico screening of the 

synthesised compounds showed that, 4-(amino 2- 

pyrazinyl)methylene -2-(2-pyrazinyl)-2-imidazolin-5-one 

(Fig.4) possess antitubercular activity. Interestingly, the 

structure of 4-(amino 2-pyrazinyl)methylene -2-(2- 

pyrazinyl)-2-imidazolin-5-one closely resembles with 

didanosine, a well known anti-HIV drug. 

44 

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Fig.4.Structure of 4-(amino 2-pyrazinyl)methylene -2-(2-pyrazinyl)-2- 

imidazolin-5-one 

Virtual screening - Model information 

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