Microwave-assisted synthesis, in silico ADME prediction and antibacterial study of 2-(substituted acetamido)-5-nitrobenzophenone derivatives

Article abstract of DOI:10.14233/ajchem.2015.17914

A series of novel 2-amino-5-nitrobenzophenone derivatives (3-10) were synthesized and characterized by IR, ¹H NMR and CHN elemental studies. All the synthesized compounds were subjected to in silico ADME predictions for determination for drug like properties. The values of physico-chemical parameters like molecular weight, nON value, nOHNH value, n-violations and the number of rotatable bonds of all the synthesized compounds also lies between the ranges that are required for good bioavailability. The synthesized compounds were tested for their in vitro antibacterial activity against the Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Among all the compounds synthesized compounds 4, 9, 10 have shown the maximum antibacterial activity in their group whereas compounds 3, 6, 8 have shown the minimum antibacterial activity.

Full text of DOI:10.14233/ajchem.2015.17914

Asian Journal of Chemistry; Vol. 27, No. 7 (2015), 2452-2456
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2015.17914
Microwave-Assisted Synthesis, in silico ADME Prediction and Antibacterial
Study of 2-(Substituted acetamido)-5-Nitrobenzophenone Derivatives
1
2
1
2,*
TIANGANG LI , SANDEEP SINGH , XING ZHAI , XIANGQI MENG3,* and RAJESH K. SINGH
1Beijing University of Chinese Medicine, 11 Bei San Huan Dong Lu, ChaoYang District, Beijing 100029, P.R. China
2Department of Pharmaceutical Chemistry, Shivalik College of Pharmacy, Rupnagar-140126, India
3Beijing University of Chinese Medicine, Dongzhimen Hospital, Dongcheng District, Beijing 100700, P.R. China
*Corresponding authors: E-mail: rksingh244@gmail.com, xiangqimengbucm@126.com
Received: 29 April 2014;
Accepted: 23 June 2014;
Published online: 30 March 2015;
AJC-17054
A series of novel 2-amino-5-nitrobenzophenone derivatives (3-10) were synthesized and characterized by IR, 1H NMR and CHN elemental
studies. All the synthesized compounds were subjected to in silico ADME predictions for determination for drug like properties. The
values of physico-chemical parameters like molecular weight, nON value, nOHNH value, n-violations and the number of rotatable bonds
of all the synthesized compounds also lies between the ranges that are required for good bioavailability. The synthesized compounds were
tested for their in vitro antibacterial activity against the Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli)
bacteria. Among all the compounds synthesized compounds 4, 9, 10 have shown the maximum antibacterial activity in their group
whereas compounds 3, 6, 8 have shown the minimum antibacterial activity.
Keywords: 2-Aminobenzophenone, Physicochemical parameters, ADME, Lipinski's rule of five, Anti-bacterial activity.
INTRODUCTION
EXPERIMENTAL
2-Aminobenzophenone derivatives are important com-
pounds in organic chemistry because of their application in
heterocyclic synthesis and medicines1. 2-Aminobenzophenone
has been used as starting material for the synthesis of 1,4-
benzodiazepines2. Some heterocyclic compounds containing
aminobenzophenone moiety possess anti-inflammatory3-5, anti-
tumor6, antimitotic7 and skeletal muscle relaxant8 activities.
More recently, their use has been extended to various diseases
such as CNS cancer9, viral infections (non-nucleoside inhibitors
The melting points were determined onVeego-programm-
able melting point apparatus (microprocessor based) and are
uncorrected. H NMR spectra were obtained using Brucker
1
AC-400 F, 400 MHz spectrometer and are reported in parts
per million (ppm), downfield from tetramethylsilane (TMS)
as internal standard. Infrared (IR) spectra were obtained with
Perkin Elmer 882 spectrum and RXI, FT-IR model. Elemental
analysis was performed on Elementar Vario EL III. Synthesis
related to microwave irradiation are carried out in domestic
LG little chef microwave oven. Reactions were monitored and
the homogeneity of the products was checked by TLC which
were prepared with silica gel G and activated at 110 °C for
0.5 h. All the solvents were dried and freshly distilled prior to
use according to standard procedure. The starting compound
2-(chloroacetamido)-5-nitrobenzophenone was earlier synthe-
sized in our lab by microwave irradiation technique8.
of HIV-1 reverse transcriptase)10 and antivascular effects11,12
.
To the date, much research has been directed towards the
synthesis and the novel uses of aminobenzophenones deriva-
tives (Fig. 1).
Recent studies have revealed that aminobenzophenone and
its derivatives exhibit potent antimicrobial activities13,14 and
lots of works have been going on synthesis of substituted amino-
benzophenone as antibacterial chemotherapeutic regimen (Fig. 2).
The objective of present work was to synthesize 2-aminobenzo-
phenone derivatives by conventional and microwave tech-
niques and to evaluate them for their in vitro antibacterial activity
against different bacterial strains and to evaluate in silico
ADME (Absorption, Distribution, Metabolism and Excretion)
physico-chemical parameters using online software program15.
General method for the synthesis of 2-amino-5-nitrobenzo-
phenone derivatives
Conventional method: A mixture of 2-(chloroaceta-
mido)-5-nitrobenzophenone (2) (1.60 g, 5 mmol), various
amino substituents (5 mmol), anhydrous potassium carbonate
(1.38 g, 10 mmol), sodium iodide (0.75 g, 5 mmol) and DMF

Vol. 27, No. 7 (2015)
Study of 2-(Substituted acetamido)-5-Nitrobenzophenone Derivatives 2453
recrystallized from ethyl acetate to get pure compounds (3-
10).
O
R1
H3CO
H3CO
R2
R3
R5
Microwave irradiation method:A solution of equimolar
of 2-(chloroacetamido)-5-nitrobenzophenone and different
aniline derivatives in the presence of double mole of potassium
carbonate in a minimum quantity of DMF was irradiated for 3-
5 min in microwave oven (360 W) with 30 seconds intermittent
time interval. After that reaction mixture was poured into ice
cold water and the solid product thus separated was collected
through filtration. The crude solid products was recrystallized
from alcohol. The comparison of % yield and time taken for the
synthesis by conventional and microwave method is givenTable-1
and the comparison of % yield and time taken for synthesis by
conventional and microwave method is given in Table-2.
2-(2′-Methylanilino)acetamido-5-nitrobenzophenone
OCH3
R4
CH2COOH
NH2
O
HN
S
O
O
HO
Ph
OH
O
AMINOBENZOPHENONE
C
L
N
A
S
M
A
CT
I
O
S
S
E
D
O
N
A
V
P
N
A
T
I
V
E
P
Y
E
R
,
T
H
I
T
Y
N
A
N
O
O2N
N
T
I
C
NH
Ph
O
O
O
N
NH
2
H
N
N
N+
Cl
(3): m.p. 160-163 °C; Rf 0.71 (chloroform); IR (KBr, νmax
,
O-
cm-1): 3230 (sec N-H), 3117 (aromatic C-H), 1717 (ketonic
C=O), 1640 (amide C=O), 1579 bend (sec N-H), 1348 and
1614 str (N=O), 1442 and 1596 (aromatic C=C) and 1286
(C-N). 1H NMR (CDCl3) δ (ppm): 2.4 (s, 3H, CH3), 4.8 (s, 2H,
-COCH2N), 7.5-8.9 (m, 12H, ArH), 10.5 (brs, 1H, -NHCH2-)
and 11.8 (brs, 1H, -NHCOCH2-). Anal. Calcd (%) for
C22H19N3O4: C 67.86, H 4.92, N 10.79; Found (%): C 68.08,
H 4.159, N 10.13.
Fig. 1. Pharmacological activities exhibited by aminobenzophenone deriva-
tives
Potential antibacterial moiety
Potential antibacterial activity
O2N
and optimize ADME property
O2N
NH
LINKER
O
O
2-(4′-Nitroanilino)acetamido-5-nitrobenzophenone
(4): m.p. 157-158 °C; Rf 0.73 (chloroform:methanol (9:1); IR
(KBr, νmax, cm-1): 3344 (sec N-H), 3063 (aliphatic C-H), 1664
(amide C=O), 1610 (ArC=O), 1492 (aromatic C=C) and 1279
(C-N). 1H NMR (CDCl3) δ (ppm): 4.2 (s, 2H, -COCH2N), 7.3-
8.6 (m, 12H, ArH), 10.3 (brs, 1H, -NHCH2-) and 11.5 (brs, 1H
NHCOCH2-).Anal. Calcd (%) for C21H16N4O6: C 60.00, H 3.84,
N 13.33; Found: C 63.99, H 4.010, N 12.96.
O
X
NH
X
Various e– donating &
e– withdrawing aromatic
substituents
Aminobenzophenone
nucleus
Various substituted aminobenzophenone
derivatives
Fig. 2. Design of substituted 2-aminobenzophenone derivatives as potential
antibacterial agents
(10 mL) as solvent were stirred for 3 days. The reaction mixture
was poured into excess of water and the precipitated material
was filtered, washed with water and dried. The product was
2-(4′-Aminobenzoyloxy)acetamido-5-nitrobenzo-
phenone (5): m.p. 134-136 °C; Rf 0.71 (ethyl acetate); IR (KBr,
TABLE-1
COMPARISON OF % YIELD AND TIME TAKEN BY COMPOUNDS FROM BOTH METHODS
Conventional
Microwave
S.No.
Compounds
Yield (%)
Time (h)
20
Yield (%)
Time (min)
3.0
1.
2.
3.
4.
5.
6.
7.
8.
58
27
62
51
35
33
28
41
75
58
55
65
80
83
56
62
3
4
5
6
7
8
9
10
24
28
24
26
28
24
24
3.5
4.0
3.0
4.5
4.0
5.0
3.5
TABLE-2
ADME PHYSICO-CHEMICAL PARAMETERS VALUES OF
2-AMINOBENZOPHENONE DERIVATIVES WITH THEIR OPTIMUM RANGES
Parameters
miLOGP (< 5)
TPSA (< 160)
nAtoms
MWt. (< 500)
nON (≤ 10 )
(3)
4.709
104.02
29.0
389.41
7
2
0
7
(4)
4.267
149.84
31.0
420.38
10
2
0
8
(5)
3.33
144.32
31.0
419.39
9
3
0
8
(6)
4.757
104.02
29.0
389.41
7
2
0
7
(7)
4.219
149.84
31.0
420.38
10
2
0
8
(8)
4.308
104.02
28.0
375.38
7
2
0
7
(9)
2.595
164.18
32.0
454.46
10
4
0
8
(10)
4.986
104.02
29.0
409.82
7
2
0
nOHNH (≤ 5)
nViolations (1 or < 0)
nRotb (<10)
7
Volume < 400
346.32
353.10
356.62
346.32
353.10
329.76
372.48
343.30

2454 Li et al.
Asian J. Chem.
ν
max, cm-1): 3346 (sec N-H), 3062 (aromatic C-H), 2923
Calcd (%) for C21H17N3O4: C 67.19, H 4.56, N 11.19; Found:
C 68.81, H 4.04, N 11.26.
(aliphatic C-H), 1719 (ester C=O), 1644 (amide C=O), 1611
(ArC=O), 1493 (aromatic C=C), 1095 (C-N) and 1157 (C-O),
1529, 1279 str (N=O), 1746 str ester (C=O). 1H NMR (DMSO-
d6) δ (ppm): 4.6 (s, 2H, -COCH2-), 5.9 (s, 2H,ArNH2), 7.4-8.0
(m, 12H, ArH) and 10.6 (brs, 1H, -NHCOCH2-). Anal. Calcd
(%) for C22H17N3O6: C 63.01, H 4.09, N 10.02; Found: C 64.41,
H 4.130, N 10.85.
2-Sulphanilamidoacetamido-5-nitrobenzophenone (9):
m.p. 232-235 °C; Rf 0.75 (chloroform:methanol (9.5:0.5); IR
(KBr, νmax, cm-1): 3134 (sec N-H), 3046 (aromatic C-H), 2998
(aliphatic C-H), 1667 (amide C=O), 1667 (ArC=O), 1508
(aromatic C=C), 1226 (C-N) and 1620 and 1340 str (N=O),
1
910 str. (S-N). H NMR (DMSO-d6) δ (ppm): 4.2 (s, 2H,
2-(4′-Methylanilino)acetamido-5-nitrobenzophenone
(6): m.p. 120-124 °C; Rf 0.81 (chloroform); IR (KBr, νmax, cm-
1): 3320 (sec N-H), 3086 (aliphatic C-H), 1652 (amide C=O),
-COCH2NH-), 7.2-8.6 (m, 12H, ArH), 9.2 (s, 2H, Ar-NH2),
10.5 (brs, 1H, -NHCH2-) and 10.9 (brs, 1H, -NHCOCH2-).
Anal. Calcd (%) for C21H18N4O6S: C 55.80, H 3.99, N 12.33;
Found: C 56.04, H 3.678, N 12.95.
1
1620 (ArC=O), 1494 (aromatic C=C) and 1242 (C-N). H
NMR (DMSO-d6) δ (ppm): 2.4 (s, 3H, Ar-CH3), 4.5 (s, 2H,
-COCH2N), 7.5-8.9 (m, 12H, ArH), 10.5 (brs, 1H, -NHCH2-)
and 11.8 (brs, 1H, -NHCOCH2-).Anal. Calcd (%) for C22H19N3O4:
C 67.86, H 4.92, N 10.79; Found: C 68.10, H 4.378, N 11.13.
2-(2′-Nitroanilino)acetamido-5-nitrobenzophenone
(7): m.p. 137-139 °C; Rf 0.68 (chloroform:methanol (9:1); IR
(KBr, νmax, cm-1): 3332 (sec N-H), 3061 (aromatic C-H), 1677
(amide C=O), 1640 (ArC=O), 1505 (aromatic C=C), 1212 (C-N),
701 bend (C-H), 1577 and 1253 str (N=O). 1H NMR (DMSO-d6)
δ (ppm): 4.2 (s, 2H, -COCH2N), 7.2-8.1 (m, 12H, ArH), 9.8
(brs, 1H, -NHCH2-) and 12.6 (brs, 1H, -NHCOCH2-). Anal.
Calcd (%) for C21H16N4O6: C 60.00, H 3.84, N 13.33; Found:
C 61.49, H 3.669, N 13.96.
2-(4′-Chloroanilino)acetamido-5-nitrobenzophenone
(10): m.p. 112-114 °C; Rf 0.80 (chloroform:methanol (9:1);
IR (KBr, νmax, cm-1): 3239 (sec N-H), 1641 (amide C=O),
1618 (ArC=O), 1513 (aromatic C=C), 1090 (C-N), 1547 and
1328 str (N=O), 697 str (C-Cl). 1H NMR (DMSO-d6) δ (ppm):
4.2 (s, 2H, -COCH2NH-), 6.9-8.2 (m, 12H, ArH), 9.9 (brs,
1H, -NHCH2-) and 11.9 (brs, 1H, -NHCOCH2-). Anal. Calcd
(%) for C21H16N3O4Cl: C 61.54, H 3.94, N 10.25; Found: C
63.10, H 3.69, N 10.50.
RESULTS AND DISCUSSION
For the synthesis of target compounds, first, the 2-(chloro-
acetamido)-5-nitrobenzophenone (2) was prepared by treating
2-amino-5-nitrobenzophenone (1) with chloroacetylchloride
in the presence of toluene.After that the derivatives (3-10) were
prepared by the reaction of 2-(chloroacetamido)-5-nitrobenzo-
phenone (2) and different aniline derivatives in the presence
of potassium carbonate in a minimum quantity of DMF by
conventional and microwave method (Scheme-I). Microwave
irradiation method was found to give the better yield (Table-1).
2-Anilinoacetamido-5-nitrobenzophenone (8): m.p.
116-118 °C; Rf 0.70 (ethyl acetate); IR (KBr, νmax, cm-1): 3346
(sec N-H), 3062 (aromatic C-H), 2923 (aliphatic C-H), 1644
(amide C=O), 1611 (ArC=O), 1493 (aromatic C=C), 1279
1
(C-N), 1529 and 1337 str (N=O). H NMR (DMSO-d6) δ
(ppm): 4.5 (s, 2H, -COCH2N), 7.5-8.8 (m, 13H, ArH), 10.3
(brs, 1H, -NHCH2-) and 11.9 (brs, 1H, -NHCOCH2-). Anal.
O N
O N
2
2
C lCH C OCl
NHCOCH Cl
2
2
Coventional/
Microwave
N H
2
O
O
(2)
(1)
Covention al/
Microwave
R1
K CO /NaI, DMF
2
3
O
H3C
H
H
N
NO2
O
C
NH2
N
O N
2
4
5
3
O2N
NH
R1
H
N
H
H
N
CH3
N
O
O
6
8
7
O
H
H
N
S
NH2
Cl
N
O
(3-10)
10
9
Scheme-I: Synthesis of 2-amino-5-nitro-benzophenone derivatives (3-10)

Vol. 27, No. 7 (2015)
Study of 2-(Substituted acetamido)-5-Nitrobenzophenone Derivatives 2455
TABLE-3
ZONE OF INHIBITION (IN mm) OF Staphylococcus aureus AND Escherichia coli OF TEST
COMPOUNDS AT A CONCENTRATION OF 50, 100, 150 and 200 µg/mL
Zone of inhibition (mm)
Staphylococcus aureus
Escherichia coli
100 (µg/mL) 150 (µg/mL) 200 (µg/mL)
Compounds
50 (µg/mL)
100 (µg/mL) 150 (µg/mL) 200 (µg/mL)
50 (µg/mL)
Amoxycillin
Comp-3
Comp-4
Comp-5
Comp-6
Comp-7
Comp-8
Comp-9
Comp-10
12
2
3
2
2
2
2
3
13
4
5
3
4
3
3
3
16
5
6
6
5
5
4
5
17
6
8
7
6
7
6
8
10
2
3
2
2
2
2
2
12
2
4
2
3
3
4
4
15
5
6
4
4
5
6
5
18
6
8
6
5
7
7
8
3
4
5
8
2
3
5
8
The structures of the synthesized compounds were determined
by IR, NMR and CHN elemental studies.
18
16
14
12
10
8
Staphylococcus aureus
Molinspiration, web based software was used to obtain
parameter such as MiLogP, TPSA, drug likeness. MiLog P
parameter is used to check good permeability across the cell
membrane. TPSA is related to hydrogen bonding potential of
compound. Calculation of volume developed at molinspiration
is based on group contributors. Number of rotatable bonds
measures molecular flexibility. It is a very good description
of absorption and bioavailbility of drugs. Through drug like-
ness data of molecule, it can be checked molecular properties
and structure feature irrespect to known drugs.
50 µg/mL 100 µg/mL
150 µg/mL 200 µg/mL
6
4
2
0
According to the rule of five, compounds with number of
violations not more than 1 shows good bioavailability and all
the test compounds have zero number of violations of rule's
of five. Compounds with nOHNH value (H-bond donors) less
than 5 shows increase solubility in cellular membranes and all
the test compounds have nOHNH value in the range of 2 to 4
which is less than 5. All values of other physicochemical
parameters of all the synthesized compounds lie between the
ranges that are required for good oral absorption16 (Table-2).
Antibacterial activity of synthesized compounds was
tested by Agar plate diffusion method17 against two bacterial
strains: Staphylococcus aureus (gram+ve) (ATCC-29737) and
Escherichia coli (gram-ve) (ATCC-8739) procured from
IMTECH, Chandigarh. After the setting of media, 2 mL of
bacterial culture was poured in Petri dishes and sprayed over
agar media. Different concentrations of test compound (50,
100, 150 and 200 µg/mL) were placed in each hole of the
Petri dish. The plates were incubated at 37 °C for 24 h for
bacteria strains. The diameter of zones of inhibition formed
around the disc was measured after 24 h for the bacteria plates
(Table-3).Amoxycillin was used as standard or positive control
while DMSO was used as a solvent and as negative controls.
Although none of the synthesized compounds have shown to
have good antibacterial activity. However (compounds 4, 9,
10) have shown the maximum antibacterial activity in their
group whereas (compounds 3, 6, 8) have shown the minimum
antibacterial activity (Figs. 3 and 4).
Fig. 3. Graphical representation of zone of inhibition at 50, 100, 150 and
200 µg/mL of test compounds against Staphylococcus aureus
20
Escherichia coli
18
16
14
12
10
8
50 µg/mL 100 µg/mL
150 µg/mL 200 µg/mL
6
4
2
0
Fig. 4. Graphical representation of zone of inhibition at 50, 100, 150 and
200 µg/mL of test compounds against Escherichia coli
was found to give the better yield. All the synthesized com-
pounds were subjected to in silico ADME prediction for drug
like properties through experimental and online software.
The antibacterial activity of the synthesized compound was
evaluate. None of the compounds have exhibited significant
antibacterial activity. The study revealed that 2-aminobenzo-
phenone is a rich source of exploitation. Hence further modi-
fication of 2-aminobenzo-phenone moiety by substitution of
different groups at different positions may provide more potent
antibacterial agents in future.
Conclusion
In conclusion, a series of novel 2-amino-5-nitrobenzo-
phenone derivatives were prepared by both conventional and
microwave irradiation method. Microwave irradiation method

2456 Li et al.
Asian J. Chem.
7. J.P. Liou, C.W. Chang, J.S. Song, Y.N. Yang, C.F. Yeh, H.Y. Tseng,
Y.K. Lo, Y.L. Chang, C.M. Chang and H.P. Hsieh, J. Med. Chem., 45,
2556 (2002).
8. R.K. Singh, S. Devi and D.N. Prasad, Arab. J. Chem.; doi:10.1016/j.arabjc.
2011.11.013.
ACKNOWLEDGEMENTS
The authors are thankful Principal Dr. D.N. Prasad, Shivalik
College of Pharmacy, Nangal for providing the necessary
facilities to carry out the research work. The authors are also
thankful to Panjab University, Chandigarh, India and IIIM,
Jammu for cooperation in getting the spectral data and CHN
elemental studies respectively. This research was supported
by project YETP0821.
9. R.K. Singh, D.N. Prasad and T.R. Bhardwaj, Med. Chem. Res., 22,
5901 (2013).
10. P. Cheng, Q. Zhang, Y.-B. Ma, Z-Y. Jiang, X.M. Zhang, F.X. Zhang
and J.J. Chen, Bioorg. Med. Chem. Lett., 18, 3787 (2008).
11. J.-P. Liou, J.-Y. Chang, C.-W. Chang, C.-Y. Chang, N. Mahindroo, F.-M.
Kuo and H.-P. Hsieh, J. Med. Chem., 47, 2897 (2004).
12. J.P. Liou, Y.L. Chang, F.M. Kuo, C.W. Chang, H.Y. Tseng, C.C. Wang,
Y.N. Yang, J.Y. Chang, S.-J. Lee and H.-P. Hsieh, J. Med. Chem., 47, 4247
(2004).
REFERENCES
1. D.A. Walsh, Synthesis, 677 (1980).
2. L.H. Sternbach, R.I. Fryer, W. Metlesics, E. Reeder, G. Sach, G. Saucy
and A. Stempel. J. Org. Chem., 27, 3788 (1962).
13. L. Sun, J. Wu, M. Luo, X. Wang, M. Pan, Z. Gou and D. Sun, Molecules,
16, 9739 (2011).
14. A. Sakunpak and P. Panichayupakaranant, Food Chem., 130, 826 (2012).
15. Molinspiration Cheminformatics, Bratislava, Slovak Republic, Available
from: http://www.molinspiration.com/cgi-bin/properties.
16. C.A. Lipinski, F. Lombardo, B.W. Dominy and P.J. Feeney, Adv. Drug
Deliv. Rev., 23, 3 (1997).
17. Indian Pharmacopoeia. Government of India, Ministry of Health and
Welfare, Published by Controller of Publication, New Delhi, vol. II,
A105 (1996).
3. R.V. Coombs, R.P. Danna, M. Denzer, G.E. Hardtmann, B. Huegi, G. Koletar,
J. Koletar, H. Ott and E. Jukniewicz, J. Med. Chem., 16, 1237 (1973).
4. W.J. Welstead Jr., J.H.W. Moran, H.F. Stauffer, L.B. Turnbull and L.F.
Sancilio, J. Am. Chem. Soc., 22, 1074 (1979).
5. E.R. Ottosen, M.D. Sørensen, F. Björkling, T. Skak-Nielsen, M.S. Fjording,
H. Aaes and L. Binderup, J. Med. Chem., 46, 5651 (2003).
6. S. Cortez-Maya, E. Cortes, S. Hernández-Ortega, T.R. Apan and M.
Martínez-García, Synth. Commun., 42, 46 (2012).