Efficient synthesis and characterization of novel indolizines: Exploration of: In vitro COX-2 inhibitory activity and molecular modelling studies

Article abstract of DOI:10.1039/c7nj05010k

A series of novel indolizine scaffolds incorporating a cyano group at position 7 as potential cyclooxygenase (COX)-2 inhibitors has been synthesized and characterized by FT-IR, NMR, LC-MS, and elemental analysis. A molecular modelling study was carried out to explore the COX-2 binding properties of the synthesized compounds, in an endeavour to provide additional insights into the inhibitory potential to treat and/or manage inflammation and pain. All compounds demonstrated comparable docking scores with that of indomethacin, a potent nonsteroidal anti-inflammatory drug. Additional empirical scoring functions were also investigated to estimate the best ligand orientation into the binding site. Halogen atoms at the para position of the benzoyl ring at the third position of the indolizine nucleus showed promising COX-2 inhibitory activity. The observed promising activity was favoured by the ethyl moiety at the second position of the indolizine nucleus. These findings will provide insights into structural requirements for designing novel indolizine scaffolds as potent COX-2 inhibitors.

Full text of DOI:10.1039/c7nj05010k

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S.
Chandrashekharappa, K. N. Venugopala, C. Tratrat, F. Mahomoodally, B. E. Al-Dhubiab, M. Haroun, R.
Venugopala, M. K. Mohan, R. S. Kulkarni, M. V. Attimarad, S. Harsha and B. Odhav, New J. Chem., 2018,
DOI: 10.1039/C7NJ05010K.
This is an Accepted Manuscript, which has been through the
Volume 40 Number
1 January 2016 Pages 1–846
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
Accepted Manuscripts are published online shortly after
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Page 1 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
Efficient synthesis and characterization of novel indolizines: exploration of
in vitro COX-2 inhibitory activity and molecular modelling studies
Sandeep Chandrashekharappa,a Katharigatta N. Venugopala,*bc Christophe Tratrat,c Fawzi M.
Mahomoodally,d Bandar E Aldhubiab,c Michelyne Haroun,c Rashmi Venugopala,e Mahendra
K. Mohan,a Rashmi S. Kulkarni,f Mahesh V. Attimarad,c Sree Harsha,c Bharti Odhav,b
a Institute for Stem Cell Biology and Regenerative Medicine, NCBS, TIFR, GKVK, Bellary
Road, Bangalore 560 065, India
b Department of Biotechnology and Food Technology, Faculty of Applied Science, Durban
University of Technology, Durban 4001, South Africa
c Department of Pharmaceutical Sciences, College of Clinical Pharmacy, King Faisal
University, AlꢀAhsa 31982, Kingdom of Saudi Arabia
d Department of Health Sciences, Faculty of Science, University of Mauritius, Réduit,
Mauritius
e Department of Public Health Medicine, University of KwaZuluꢀNatal, Howard College
Campus, Durban 4001, South Africa
f Department of Chemistry, Jain University, Bangalore 560 019, India
_____________________
Correspondence:
Katharigatta N. Venugopala (katharigattav@dut.ac.za), Department of Biotechnology and Food
Technology, Faculty of Applied Science, Durban University of Technology, Durban 4001, South
Africa. Eꢀmail: katharigattav@dut.ac.za; Tel No: +27 31 373 4887; Fax No: +27 86 2423534.
Keywords
Characterization
COXꢀ2 inhibition
Indolizine analogues
Molecular docking
Synthesis
1

New Journal of Chemistry
Page 2 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
Abstract
A series of novel indolizine scaffold incorporating cyano group at 7 position as potential
cyclooxygenase (COX)ꢀ2 inhibitors has been synthesized and characterized by FTꢀIR, NMR,
LCꢀMS, and elemental analysis. Molecular modelling study was carried out to explore the
COXꢀ2 binding properties of the synthesized compounds, in an endeavour to provide
additional insights on inhibitory potential to treat and/or manage inflammation and pain. All
compounds demonstrated comparable docking scores with that of Indomethacin, a potent
nonsteroidal antiꢀinflammatory drug. Additional empirical scoring functions were also
investigated to estimate the best ligand orientation into the binding site. Halogen atoms at
para position of the benzoyl ring at third position of indolizine nucleus showed promising
COXꢀ2 inhibitory activity. The observed promising activity was favoured by ethyl moiety at
second position of the indolizine nucleus. These findings will provide insights into structural
requirement for designing novel indolizine scaffolds as potent COXꢀ2 inhibitors.
Introduction
Nonsteroidal antiꢀinflammatory drugs (NSAIDs) are widely used therapeutic agents for the
management and treatment of chronic musculoskeletal pathologies namely rheumatoid
arthritis and osteoarthritis 1. They are known to act by inhibiting the biosynthesis of pain and
inflammation mediating prostaglandins. Opioid receptors are known for controlling severe to
2ꢀ7
8
chronic pain and various agonists
and antagonists have been reported. NSAIDs exert
their molecular mechanism of action as cyclooxygenase inhibitors (COX), which converts
arachidonic acid into prostanoids which appear as physiopathological effectors. COXꢀ1 and 2
are the two isoforms of COX enzyme. NSAIDs are classified into several chemical classes,
generally selective and nonꢀselective for COXꢀ2 enzyme inhibition. Some of the nonselective
and selective COXꢀ2 enzyme inhibitors are shown in Fig. 1. Inhibition of COXꢀ2 activity for
the production of prostaglandins produces good antiꢀinflammatory and antiꢀnociceptive
activities. Coincidently COXꢀ1 enzyme is also inhibited in this process, resulting in unwanted
side effects such as gastrointestinal tract disturbances and adverse cardiovascular effects. This
non selective nature of NSAIDs towards COX inhibition led to the development of selective
COXꢀ2 enzyme inhibitors. Indolizine represents an important class of nitrogenꢀfused
heterocycles that are ubiquitous in many natural products and biologically active compounds
9ꢀ11
.
2

Page 3 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
Fig. 1 Selective COXꢀ2 enzyme inhibitors (Ibuprofen, Indomethacin, Celecoxib, Rofecoxib,
and Etoricoxib).
Many synthetic indolizine derivatives have found wide applications in the pharmaceutical
15, 16
field as analgesic 12, antiꢀinflammatory inhibitors 13, anticancer 14, antidiabetic
,
antihistaminic 17, COXꢀ2 inhibition 18, 19, antileishmanic 20, antimicrobial 21, antimutagenic 22,
29
antioxidant 23, antitubercular 24, 25, antiviral 26, larvicidal 27, 28, and herbicidal activities
.
They are also useful in material science due to their distinctive photophysical properties 30, 31
.
Although several methods are reported for the construction of indolizines 32ꢀ39, the
development of general and efficient synthesis of functionalized indolizines is still highly
attractive 7, 40. Furthermore substituted indolizines and their derivatives have also been
extensively used as versatile building blocks for the synthesis of dyes 41, biological markers
42, 43, and electroluminescent materials with enhanced electronic and photonic properties 44, 45
.
Computational methods have been successfully applied for the development of novel
chemical entities with bioactivity expectations. It facilitates the prediction of the mechanism
of action of molecule through the investigation of the binding property within the cavity site
of the enzyme receptor 46, 47. Preliminary molecular modelling analysis of the indolizine
scaffold reveals the potential of incorporating the cyano group at 7 position of indolizine ring
intending to interact with the lipophilic cavity site of COXꢀ2 receptor, normally referred as
selective COXꢀ2 inhibitors. In continuation of our efforts in search of novel heterocyclic
scaffolds for promising pharmacological properties 48, 49 and polymorphism behavior 50, 51, we
wish to report our preliminary structure activity relationships of the new design incorporated
in the cyano group into the indolizine scaffold against COXꢀ2 inhibitory activity (Fig. 2).
3

New Journal of Chemistry
Page 4 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
Fig. 2 Design of novel indolizine scaffold incorporating cyano group at 7 position as
potential COXꢀ2 inhibitors.
Indomethacin and indolizine compounds were overlaid in the active site, demonstrating the
similarities of structures (Fig. 3). The requirement of this scaffold has been evaluated for the
inhibition of COXꢀ2 activity.
Fig. 3 3D overlay of Indomethacin (bleu) with Indolizine (salmon) in the active site of
COXꢀ2 receptor shown as grey (PDB code: 4COX).
The synthetic scheme for the construction of novel indolizine scaffold incorporating cyano
group at seventh position is described in Scheme 1.
4

Page 5 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
Scheme 1
Synthetic scheme for the construction of novel indolizine scaffolds (2a-k): (a)
acetone, r.t., 5h; (b) DMF, K2CO3, 30 min.
Table 1 Physicochemical constants of 1,2,3 trisubstituted 7ꢀcyano indolizine scaffolds 2a-k
Comp Mol formulae (Mol weight) R1
R2
Yielda,b (%)
ClogPc
4.9790
5.6990
m.p (°C)
133ꢀ134
168ꢀ169
2a
2b
C21H17FN2O3 (364)
C21H17BrN2O3 (424)
F
Br
C2H5
C2H5
87
91
2c
2d
2e
2f
C22H17ClN2O5 (424)
C21H15N3O3 (357)
C19H13BrN2O3 (396)
C21H18N2O4 (362)
C20H15BrN2O3 (410)
C22H20N2O4 (376)
C21H17ClN2O3 (380)
C23H17N3O5 (415)
C20H13N3O3 (343)
Cl
COOC2H5
89
88
92
86
89
87
85
91
90
179ꢀ180
182ꢀ183
174ꢀ175
136ꢀ137
123ꢀ124
110ꢀ111
128ꢀ129
184ꢀ185
189ꢀ190
4.0037
3.7863
4.6710
4.4701
5.1700
4.9991
5.5490
2.7645
3.2873
CN
Br
CH3
H
OCH3 CH3
Br CH3
OCH3 C2H5
2g
2h
2i
Cl
C2H5
2j
CN
CN
COOC2H5
H
2k
a All of the products were characterized by spectral and physical data.
b Yields after purification by column chromatography method.
c cLogP was calculated using ChemDraw Professional 16.
5

New Journal of Chemistry
Page 6 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
Experimental
Chemistry
All the commercially available chemicals were procured from SigmaꢀAldrich, India. All the
chemical reactions of Schemeꢀ1 were carried out under nitrogen atmosphere using dry
solvents. Progress of the chemical reactions was monitored on thin layer chromatography
(TLC). TLC was performed on SigmaꢀAldrich Silica gel on TLC aluminium foils with nꢀ
hexane and ethyl acetate (4:6) as solvent system and visualization in iodine chamber. Melting
points were determined on a Büchi melting point Bꢀ545 apparatus. The FTꢀIR spectra were
recorded on a Shimadzu FTꢀIR spectrometry. NMR (400 MHz) spectra were recorded at
ambient temperature using CDCl3 as a solvent using Brukerꢀ400 spectrometer. Chemical shift
values are measured in δ ppm and were referenced with TMS. The peak multiplicities were
given as follows; s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet. LCꢀMS analysis
was performed on Agilent LCꢀ1200 series coupled with 6140 single quad mass spectrometer
with ESI +ve mode, MS range 100ꢀ800. Elemental analysis was performed on Thermo
Finnigan FLASH EA 1112 CHN analyzer.
General procedure for the preparation of 4-cyano-1-(2-(4-fluorophenyl)-2-
oxoethyl)pyridin-1-ium bromide (1a-e)
To a stirred solution of isonicotinonitrile (1g, 9.60 mmol) in dry acetone (10 mL), 4ꢀfluoro
phenacylbromide (2.97g, 9.6 mmol) was added and stirred at room temperature for 5h.
Progress of the chemical reaction was monitored on TLC. The solid formed was separated by
filtration and dried under vacuum to afford 99% yield of 4ꢀcyanoꢀ1ꢀ(2ꢀ(4ꢀfluorophenyl)ꢀ2ꢀ
oxoethyl)pyridinꢀ1ꢀium bromide. Remaining compounds 1b-e were prepared by following
similar protocol.
General procedure for the synthesis of ethyl 7-cyano-2-ethyl-3-(4-
fluorobenzoyl)indolizine-1-carboxylate (2a)
To a stirred solution of 4ꢀcyanoꢀ1ꢀ(2ꢀ(4ꢀfluorophenyl)ꢀ2ꢀoxoethyl)pyridinꢀ1ꢀium bromide
(0.5g 1.5 mmol) in DMF, ethylpentynoate (0.197g 1.5 mmol), and K2CO3 (0.431g 3.1 mmol)
were added and stirred at room temperature for 30 min. Progress of the chemical reaction
was monitored by TLC. The reaction medium was evaporated under reduced pressure, diluted
with brine solution and the aqueous layer was extracted two times with ethyl acetate. The
6

Page 7 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
organic layer was collected and evaporated to obtain crude product and purified by column
chromatography using 60ꢀ120 mesh silica gel with hexane ethylacetate solvent mixture to
afford 0.48g (87% ) of ethyl 7ꢀcyanoꢀ2ꢀethylꢀ3ꢀ(4ꢀfluorobenzoyl)indolizineꢀ1ꢀcarboxylate
(2a) Remaining compounds from the series 2b-k were prepared by following the similar
procedure and physicochemical constants of 1,2,3 trisubstituted 7ꢀcyano indolizine scaffolds
2a-k are tabulated in Table 1.
Ethyl 7-cyano-2-ethyl-3-(4-fluorobenzoyl)indolizine-1-carboxylate (2a)
1
Yellow crystalline compound; IR (neat cmꢀ1): 2974, 2227, 1689, 1608, 1379, 1224; Hꢀ
NMR (400 MHz, CDCl3) δ = 9.29ꢀ9.27 (m, 1H), 9.10 (s, 1H), 7.81ꢀ7.74 (m, 2H), 7.24ꢀ7.16
(m, 2H), 6.98ꢀ6.96 (m, 1H), 4.49ꢀ4.44 (q, J = 7.2Hz, 2H), 2.83ꢀ2.77 (q, J = 7.2Hz, 2H), 1.49ꢀ
1.43 (t, J = 7.2Hz, 3H), 1.05ꢀ1.01 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 186.90,
166.94, 164.40, 163.73, 143.50, 136.48, 135.87, 135.84, 131.66, 131.56, 127.68, 125.90,
123.72, 117.63, 116.12, 115.90, 113.58, 108.43, 107.32, 60.51, 19.90, 15.85, 14.43. LCꢀMS
(ESI, Positive): m/z (M + H)+ 365.2; Anal calculated for: C21H17FN2O3: C, 69.22, H, 4.70, N,
7.69: Found: C, 69.20, H, 4.72, N, 7.72.
Ethyl 3-(4-bromobenzoyl)-7-cyano-2-ethylindolizine-1-carboxylate (2b)
Brown crystalline compound; IR (neat cmꢀ1): 2981, 2227, 1697, 1627, 1585, 1571, 1423,
1
1217; H NMR (400 MHz, CDCl3) δ 9.15ꢀ9.13 (m, 1H), 8.75 (s, 1H), 7.67ꢀ7.60 (m, 4H),
6.99ꢀ6.98 (m, 1H), 4.48ꢀ4.42 (q, J = 7.2Hz, 2H), 2.80ꢀ2.75 (q, J = 7.2Hz, 2H), 1.47ꢀ1.43 (t, J
= 7.2Hz, 3H), 1.05ꢀ1.01 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 186.86, 163.95,
138.60, 137.72, 136.49, 132.14, 130.61, 127.92, 127.87, 125.52, 124.12, 117.54, 113.90,
108.95, 108.40, 60.54, 14.92, 14.50. LCꢀMS (ESI, Positive): m/z (M + H)+ 425.1; Anal
calculated for: C21H17BrN2O3: C, 59.31, H, 4.03, N, 6.59: Found: C, 59.36, H, 3.59, N, 7.02.
Diethyl 3-(4-chlorobenzoyl)-7-cyanoindolizine-1,2-dicarboxylate (2c)
Brown crystalline compound; IR (neat cmꢀ1): 2948, 2231, 1739, 1706, 1629, 1583, 1517,
1
1446, 1228; H NMR (400 MHz, CDCl3) δ 9.53ꢀ9.51 (m, 1H), 8.77 (s, 1H), 7.84ꢀ7.81 (m,
2H), 7.68ꢀ7.65 (m, 2H), 7.18ꢀ7.16 (m, 1H), 4.48ꢀ4.42 (q, J = 7.2Hz, 2H), 2.80ꢀ2.75 (q, J =
7.2Hz, 2H), 1.47ꢀ1.43 (t, J = 7.2Hz, 3H), 1.05ꢀ1.01 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ 185.53, 164.14, 162.37, 139.23, 136.91, 135.42, 131.69, 130.18, 128.98, 128.71,
126.30, 122.31, 116.85, 110.40, 52.63, 52.25, 24.99, 22.46. LCꢀMS (ESI, Positive): m/z (M +
7

New Journal of Chemistry
Page 8 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
H)+ 425; Anal calculated for: C22H17ClN2O5: C, 62.20, H, 4.03, N, 6.59: Found: C, 62.16, H,
3.58, N, 6.49.
Ethyl 7-cyano-3-(4-cyanobenzoyl)-2-methylindolizine-1-carboxylate (2d)
Yellow crystalline compound; IR (neat cmꢀ1): 2977, 2227, 1697, 1618, 1593, 1515, 1217,
1
1112; H NMR (400 MHz, CDCl3) δ 9.34ꢀ9.32 (m, 1H), 8.73 (s, 1H), 7.69ꢀ7.66 (m, 2H),
7.51ꢀ7.48 (m, 2H), 7.03ꢀ7.01 (m, 1H), 4.47ꢀ4.41 (q, J = 7.2Hz, 2H), 2.29 (s 3H), 1.47ꢀ1.43 (t,
J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 186.73, 163.96, 139.36, 138.15, 137.67,
136.47, 130.52, 129.16, 127.86, 125.53, 124.16, 117.55, 113.87, 108.91, 108.38, 60.54,
14.90, 14.50. LCꢀMS (ESI, Positive): m/z (M)+ 357.2; Anal calculated for: C21H15N3O3: C,
70.58, H, 4.23, N, 11.76: Found: C, 70.54, H, 4.19, N, 11.72.
Ethyl 3-(4-bromobenzoyl)-7-cyanoindolizine-1-carboxylate (2e)
Brown crystalline compound; IR (neat cmꢀ1): 2989, 2231, 1703, 1622, 1583, 1525, 1465,
1
1346, 1222; H NMR (400 MHz, CDCl3) δ 9.94ꢀ9.92 (m, 1H), 8.79 (s, 1H), 7.87 (s, 1H),
7.70ꢀ7.69 (m, 4H), 7.19ꢀ7.17 (m, 1H), 4.45ꢀ4.40 (q, J = 7.2Hz, 2H), 1.45ꢀ1.40 (t, J = 7.2Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 184.78, 163.03, 137.63, 137.03, 131.97, 131.69, 130.58,
129.29, 128.73, 127.27, 125.64, 123.77, 117.18, 114.99, 109.99, 109.57, 60.89, 14.50. LCꢀ
MS (ESI, Positive): m/z (M + H)+ 397.1; Anal calculated for: C19H13BrN2O3: C, 57.45, H,
3.30, N, 7.05: Found: C, 57.39, H, 3.26, N, 7.12.
Ethyl 7-cyano-3-(4-methoxybenzoyl)-2-methylindolizine-1-carboxylate (2f)
Yellow crystalline compound; IR (neat cmꢀ1): 2979, 2223, 1691, 1627, 1600, 1514, 1257,
1
1224; H NMR (400 MHz, CDCl3) δ 9.14ꢀ9.12 (m, 1H), 8.71 (s, 1H), 7.76ꢀ7.73 (m, 2H),
7.00ꢀ6.93 (m, 3H), 4.47ꢀ4.41 (q, J = 7.2Hz, 2H), 3.91 (s, 3H), 2.34 (s 3H), 1.47ꢀ1.44 (t, J =
7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 186.78, 164.17, 163.81, 139.2, 136.45, 135.90,
132.07, 131.80, 127.56, 125.60, 124.78, 117.78, 114.07, 113.29, 107.99, 107.09, 60.39,
55.58, 14.69. LCꢀMS (ESI, Positive): m/z (M + H)+ 363.1; Anal calculated for: C21H18N2O4:
C, 69.60, H, 5.01, N, 7.73: Found: C, 69.58, H, 4.99, N, 7.72.
Ethyl 3-(4-bromobenzoyl)-7-cyano-2-methylindolizine-1-carboxylate (2g)
Yellow crystalline compound; IR (neat cmꢀ1): 2989, 2225, 1687, 1618, 1581, 1512, 1440,
1
1288, 1213; H NMR (400 MHz, CDCl3) δ 9.35ꢀ9.33 (m, 1H), 8.74 (s, 1H), 7.68ꢀ7.65 (m,
2H), 7.61ꢀ6.58 (m, 2H), 7.04ꢀ7.01 (m, 1H), 4.47ꢀ4.41 (q, J = 7.2Hz, 2H), 2.29 (s 3H), 1.47ꢀ
1.43 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 187.18, 163.68, 143.87, 138.47,
8

Page 9 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
136.65, 132.07, 130.44, 127.93, 127.80, 125.85, 123.57, 117.58, 113.72, 108.67, 107.43,
60.53, 19.93, 15.93, 14.92. LCꢀMS (ESI, Positive): m/z (M + H)+ 411.2; Anal calculated for:
C20H15BrN2O3: C, 58.41, H, 3.68, N, 6.81: Found: C, 58.42, H, 3.69, N, 6.82.
Ethyl 7-cyano-2-ethyl-3-(4-methoxybenzoyl)indolizine-1-carboxylate (2h)
Yellow crystalline compound; IR (neat cmꢀ1): 2979, 2225, 1687, 1614, 1595, 1515, 1438,
1
1377, 1271; H NMR (400 MHz, CDCl3) δ 8.88ꢀ8.86 (m, 1H), 8.72 (s, 1H), 7.78ꢀ7.74 (m,
2H), 7.01ꢀ6.98 (m, 2H), 6.92ꢀ6.90 (m, 1H), 4.48ꢀ4.42 (q, J = 7.2Hz, 2H), 3.91 (s, 3H), 2.88ꢀ
2.82 (q, J = 7.2Hz, 2H), 1.47ꢀ1.44 (t, J = 7.2Hz, 3H), 1.08ꢀ1.04 (t, J = 7.2Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ 187.06, 163.89, 142.38, 135.93, 131.80, 131.72, 127.36, 125.97, 124.30,
117.83, 114.07, 113.10, 107.59, 106.99, 60.39, 55.59, 19.89, 15.84, 14.45. LCꢀMS (ESI,
Positive): m/z (M + H)+ 377.1; Anal calculated for: C22H20N2O4: C, 70.20, H, 5.36, N, 7.44:
Found: C, 70.16, H, 5.38, N, 7.42.
Ethyl 3-(4-chlorobenzoyl)-7-cyano-2-ethylindolizine-1-carboxylate (2i)
Yellow crystalline compound; IR (neat cmꢀ1): 2968, 2229, 1685, 1602, 1585, 1521, 1379,
1
1215; H NMR (400 MHz, CDCl3) δ 9.30ꢀ9.28 (m, 1H), 8.64 (s, 1H), 7.77ꢀ7.74 (m, 2H),
7.53ꢀ7.50 (m, 2H), 7.16ꢀ7.13 (m, 1H), 4.46ꢀ4.41 (q, J = 7.2Hz, 2H), 2.76ꢀ2.72 (q, J = 7.2Hz,
2H), 1.47ꢀ1.44 (t, J = 7.2Hz, 3H), 1.06ꢀ1.02 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 186.76, 166.39, 164.66, 164.54, 163.87, 162.09, 144.21, 140.61, 140.53, 139.91, 137.93,
137.91, 137.07, 137.04, 131.26, 131.17, 130.72, 130.64, 128.08, 122.54, 122.51, 121.91,
116.72, 115.81, 115.61, 115.59, 115.41, 113.92, 113.70, 104.95, 59.93, 20.04, 16.01, 14.46.
LCꢀMS (ESI, Positive): m/z (M )+ 381.1; Anal calculated for: C21H17ClN2O3: C, 66.23, H,
4.50, N, 7.36: Found: C, 66.26, H, 4.49, N, 7.32.
Diethyl 7-cyano-3-(4-cyanobenzoyl)indolizine-1,2-dicarboxylate (2j)
Brown crystalline compound; IR (neat cmꢀ1): 2983, 2229, 1733, 1697, 1627, 1512, 1436,
1
1380, 1224; H NMR (400 MHz, CDCl3) δ 9.67ꢀ9.65 (m, 1H), 8.82 (s, 1H), 7.81ꢀ7.75 (m,
4H), 7.23ꢀ7.22 (m, 1H), 4.43ꢀ4.39 (q, J = 7.2Hz, 2H), 3.74ꢀ3.71 (q, J = 7.2Hz, 2H), 1.39ꢀ1.35
(t, J = 7.2Hz, 3H), 1.13ꢀ1.09 (t, J = 7.2Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 185.01,
164.70, 163.67, 161.78, 143.37, 142.24, 138.86, 135.97, 132.52, 132.17, 132.01, 131.81,
129.51, 129.24, 129.17, 128.89, 128.81, 126.22, 121.34, 120.14, 117.74, 116.61, 115.59,
114.96, 110.96, 107.81, 62.27, 61.37, 14.24, 13.59. LCꢀMS (ESI, Positive): m/z (M + H)+
416.1; Anal calculated for: C23H17N3O5: C, 66.50, H, 4.13, N, 10.12: Found: C, 66.49, H,
4.18, N, 10.13.
9

New Journal of Chemistry
Page 10 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
Ethyl 7-cyano-3-(4-cyanobenzoyl)indolizine-1-carboxylate (2k)
Yellow crystalline compound; IR (neat cmꢀ1): 2979, 2231, 1703, 1625, 1529, 1469, 1346,
1
1224; H NMR (400 MHz, CDCl3) δ 9.99ꢀ9.97 (m, 1H), 8.82 (s, 1H), 7.93ꢀ7.83 (m, 5H),
7.24ꢀ7.22 (m, 1H), 4.46ꢀ4.41 (q, J = 7.2Hz, 2H), 1.45ꢀ1.41 (t, J = 7.2Hz, 3H); 13C NMR (100
MHz, CDCl3) δ 183.98, 162.83, 142.53, 137.41, 132.50, 132.30, 129.42, 129.39, 129.31,
128.51, 125.65, 123.37, 119.70, 117.87, 117.70, 115.90, 115.67, 110.58, 109.97, 61.09,
14.48. LCꢀMS (ESI, Positive): m/z (M)+ 343.1; Anal calculated for: C20H13N3O3: C, 69.97, H,
3.82, N, 12.24: Found: C, 69.99, H, 3.86, N, 12.22.
In vitro cyclooxygenase (COX-2) inhibition study
The designed test compounds 2a-k were screened for in vitro human recombinant COXꢀ2
enzyme inhibitory activity as described previously 52.
Statistical analysis
The oneꢀway investigation of variance (ANOVA) was used to compare the in vitro COX 2
inhibitory activity of ethyl 7ꢀcyanoꢀ2ꢀsubsitutedꢀ3ꢀ(4ꢀsubstituedbenzoyl)indolizineꢀ1ꢀ
carboxylates 2a-k with nonselective (Indomethacin) and selective (Celecoxib) standard
compounds. Bonferroni test was used for post hoc analysis to account for the increased
possibility of type I error 53. Before ANOVA testing, data were transformed to ranks 54 to fit
better the assumptions of the test. In all cases, a value of p < 0.05 was considered statistically
significant.
Molecular docking
Docking studies of the studied compounds were carried out using Accelry’s Discovery Studio
4.0 software employing CHARMm force fields algorithm. The Xꢀray coꢀcrystal structure of
Indomathecin and COXꢀ2 enzyme was retrieved from the protein databank (PDB code:
4COX). All ligands and water molecules were extracted from the protein. The latter was
subjected to cleaning and protein preparation protocol for repairing protein by adding missing
amino acids and for removing any internal unfavorable interactions. The ligand structure of
indomethacin was then inserted into the prepared protein for defining the receptor’s binding
10

Page 11 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
site. Molecular Docking was performed by using CDocker protocol, where the flexible ligand
was docked into the rigid receptor. Docking scores of the ten best conformations were
reported as CDocker energy and CDocker interaction energy and were ranked according to
CDocker energy. The stronger negative CDocker scores indicate a more favorable binding
interaction. To ensure the optimal ligand orientation into the active binding site of the
receptor, the following scoring functions PLP1, PLP2, Jain, and PMF were further examined
to each ten binding complexes. The highest negative scores of PLP1, PLP2, Jain, and PMF,
indicating the strongest receptorꢀligand binding affinities, were considered.
Results and discussion
Synthesis of designed compounds
The novel indolizine scaffolds 2a-k incorporating cyano group at 7 position were obtained
according to the synthetic strategy described in Scheme 1. Substituted pyridinꢀ1ꢀium
bromides 1a-e as intermediates were prepared by reacting 4ꢀcyanopyridine with substituted
phenacylbromides at room temperature in acetone medium as shown in step one of Scheme 1.
The substituted indolizine derivatives 2a-k were prepared by stirring a solution of 4ꢀcyanoꢀ1ꢀ
(2ꢀ(4ꢀfluorophenyl)ꢀ2ꢀoxoethyl)pyridinꢀ1ꢀium
bromides
in
dimethyl
formamide,
ethylpentynoate, and K2CO3 room temperature for 30 min and the yield obtained were in the
range of 85ꢀ92%. All the synthesized compounds were characterized by spectroscopic
techniques. FTꢀIR spectra of indolizine scaffolds 2a-k revealed nitrile stretching in the range
of 2223ꢀ2231 cmꢀ1. In 13CꢀNMR carbonyl carbon of benzoyl and ester group is observed in
the range of 183.98ꢀ187.18 and 162.83ꢀ166.94, respectively. In LCꢀMS, molecular ion peak
of the title compounds was in compliance with molecular weight of the compounds.
ChemDraw Professional 16 was used to calculate cLogP of the title compounds and the
values were in the range of 2.7645ꢀ5.6990 (Table 1).
In vitro COX-2 inhibitory activity
The designed test compounds (2a-k) were screened for human recombinant COXꢀ2
inhibitory activity using an enzyme immune assay kit and the IC50 of the test and standard
compounds were evaluated and tabulated in Table 2. Compound 2a with fluorine atom at
para positon of benzoyl group appeared as the most promising candidate, whereas
compounds 2b and 2i with bromine and chlorine at para position of benzoyl group exhibited
11

New Journal of Chemistry
Page 12 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
IC50 values at 7.24 and 8.38 µM, respectively. In all the three promising compounds, 2a, 2b
and 2i, the ideal substituent at second position of indolizine nucleus was ethyl group.
Table 2 In vitro COXꢀ2 inhibitory activity of ethyl 7ꢀcyanoꢀ2ꢀsubsitutedꢀ3ꢀ(4ꢀ
substituedbenzoyl) indolizineꢀ1ꢀcarboxylate scaffolds 2a-k.
Substituents
Compound
IC50 (µM)a
R1
R2
2a
F
C2H5
6.63+0.03c
7.24+0.03a
11.81+0.03bd
8.36+0.03cd
14.21+0.03b
36.07+0.03c
10.33+0.03cd
39.24+0.03ab
8.38+0.03c
21.02+0.03e
9.51+0.03d
0.05+0.03bd
6.84+0.03a
2b
2c
2d
2e
2f
Br
Cl
C2H5
COOC2H5
CN
Br
CH3
H
OCH3
Br
CH3
2g
2h
2i
CH3
OCH3
Cl
C2H5
C2H5
2j
CN
CN
ꢀ
COOC2H5
2k
H
ꢀ
Celecoxib
Indomethacin
ꢀ
ꢀ
a
IC50 value is the concentration of test and standard compounds required to produce 50%
inhibition of human recombinant COXꢀ2 by means of three determinations using the enzyme
linked immuno sorbent assay kit. IC50 value not sharing the same superscript letter differ
significantly (p<0.05).
Molecular docking
Molecular modelling is an important tool at early stage of drug discovery process. It has been
accelerated by the increasing availability of Xꢀray structures of inhibitors complexes. The
12

Page 13 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
bioactivity of the molecule can be accurately predicted by analyzing the nature of ligandꢀ
receptor interactions through docking studies. To gain insights into the potency of the newly
synthesized compounds, the binding modes between the ligand and COXꢀ2 receptor were
examined to identify the interactions with key amino acid residues. Docking studies were
conducted through CDocker and scoring function modules in Accelry’s Discovery Studio 4.0
software. For structural similarities of the studied compounds with Indomethacin, the Xꢀray
structure of COXꢀ2 crystallized with the Indomethacin inhibitor (PDB: 4COX) was chosen.
Docking scores were reported as CDocker energy and CDocker interaction energy. CDocker
Energy represents the ligandꢀreceptor interaction energy and the internal ligand strain energy.
The strongest negative CDocker Energy and CDocker interaction Energy scores indicate the
most favorable binding. To predict the most plausible ligand orientation within the binding
57
active site, the scoring functions as Piecewise Linear Potential 1 (PLP1) 55, PLP2 56, Jain
and Potential of Mean Force (PMF) 58 for each pose were taken into account. Higher negative
scores of PLP1, PLP2, Jain, and PMF indicate stronger receptorꢀligand binding affinities. The
docking results showed that all studied compounds have favorable binding interaction with
the receptor similar with that observed for Indomethacin (Table 3). Two distinct binding
modes were observed among the docking conformation pose, resulting from the projection of
the cyano group of the indolizine ring towards HIS 90 participating in hydrogen bonding
interaction or towards ARG 120 exhibiting πꢀcation interaction with indolizine ring and
hydrogen bonding interaction with TYR355 from the oxygen of carbonyl ester. In addition,
the insertion of benzoyl ring occurred in the same region as pꢀchloro benzoyl moiety of
Indomethacin, interacting mainly with the amino acid residues TRP 387, TYR 385, PHE 381,
LEU 384, and MET 522 through hydrophobic interactions and van der Waals interactions
(Scheme 2). Most of compounds exhibited hydrogen bonding with one of the following
amino acid residues HIS 90, TYR 355 or ARG 120. With the exception of compound 2d, the
cyano group on benzoyl ring participates in hydrogen bonding with NH of TRP 387 showing
its good inhibitory activity. Preliminary structure activity relationships demonstrates that the
presence of the electron withdrawing group at para position of the benzoyl ring i.e. –F (2a), ꢀ
Br (2b) and –Cl (2i) is more favorable to the bioactivity compared to the electron donating
group i.e. –OCH3 (2h). For instance, compounds 2h and 2f, having ꢀOCH3 group, exhibited
weak activity and lack of critical hydrophobic interactions with the residues TRP 387, TYR
385, PHE 381, LEU 384, and MET 522. Another interesting binding feature is the
hydrophobic interaction of alkyl group at 2ꢀposition of indolizine ring with the residues LEU
531, VAL 349, and ALA 527 in comparison with compound 2b (ethyl group), 2g (methyl
13

New Journal of Chemistry
Page 14 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
group), and 2e (hydrogen group). The latter did not exhibit any interactions explaining the
diminishment of inhibitory activity. The replacement of alkyl group by ester at 2 position led
to compounds 2c and 2j. Interestingly, both showed positive CDocker scores and negative
CDocker interaction energy scores comparable to Indomethacin. Considering their high
internal ligand strain energies, they exerted significant activities. Compound 2c displayed
four hydrogen bonding interactions with the residues ARG120 and HIS90 conferring greater
activity over compound 2j, showing only one hydrogen bonding interaction with the amino
acid ARG120. Moving to compound 2g, the docking study revealed that the hydrophobic
interactions were the main interactions contributing to its good inhibitory activity (Fig. 4). To
ensure that, the predicted binding mode of the indolizine analogues is accurate, the docking
of Celecoxib, into the COXꢀ2 crystal structure’s active site containing Indomethacin, was
performed. Celecoxib was found to adopt identical orientation into the binding site as
reported in protein databank (PDB code: 3LN1), involving strong hydrogen bonding
interactions with the residues HIS90, PHE518, SER353, LEU 352 and GLN192. From the
molecular study, the nature of substituent on the position of indolizine ring and substituent at
para position of the benzoyl ring play a critical role in binding interaction with COXꢀ2
receptor. The introduction of cyano group at 7 position of indolizine ring, have a positive
impact on the bioactivity of compounds by generating molecular interaction within the
binding site. Some of the designed indolizines may possess some selectivity towards COXꢀ2
over COXꢀ1 inhibition. COXꢀ2 selectivity of inhibitors is attributed by the absence of ionꢀ
pair and/or hydrogen bonding interaction with the residue ARG 120 59ꢀ61. For instance,
compounds 2b and 2d do not involve such interaction and therefore they can be regarded as
potential selective inhibitors.
14

Page 15 of 21
New Journal of Chemistry
Table 3 COXꢀ2 inhibitory activity, docking scores of the best pose of the ligand complex into the active binding site of COXꢀ2 receptor (PDB code: 4COX).
The most favorable binding indicated by the strongest negative CDocker Energy and CDocker interaction Energy. Higher negative scores of PLP1, PLP2,
Jain and PMF indicate stronger receptorꢀligand binding affinities.
Comp code
COX-2
Inhibitory
(µM)
CDocker
Energy
(kcal/mol)
CDocker
Interaction
Energy
(kcal/mol)
ꢀ41
-PLP1
-PLP2
Jain
-PMF
Nb of H-
Bonding
Residues (interacting
ligand atom, H-bond
length A0)
6.6
7.2
39
8
ꢀ16
ꢀ17
ꢀ8
112
118
130
112
121
118
112
112
118
120
103
115
126
111
110
112
104
108
109
119
5.8
5.7
6.6
6.0
5.8
6.1
5.1
5.2
5.0
7.9
98
95
1
1
1
1
1
1
0
1
1
4
TYR355 (C=O ester, 2.34)
HIS90 (CN, 3.09)
2a
2b
2h
2i
2d
2f
2g
2e
2k
2c
ꢀ40
ꢀ43
ꢀ45
ꢀ45
ꢀ49
ꢀ46
ꢀ48
ꢀ44
ꢀ40
106
94
HIS90 (CN, 2.46)
ꢀ17
ꢀ22
ꢀ27
ꢀ25
ꢀ28
ꢀ23
5
TYR355 (C=O ester, 2.36)
TRP387 (CN benzoyl, 3.03)
TYR355 (C=O ester, 2.30)
8
90
36
10
14
9
107
91
89
ARG120 (O ester, 2.57)
ARG120 (O ester, 2.73)
89
12
87
ARG120 (C=O ester, 2.09,
3.01;
C=O ester, 2.99)
HIS90 (CN, 2.49)
ARG120 (C=O ester, 2.75)
21
6.8
6
ꢀ43
ꢀ49
ꢀ44
131
110
111
128
106
99
7.0
5.0
5.5
85
94
85
1
1
6
2j
ꢀ13
ꢀ9
ARG120 (C=O ester, 2.27)
Indomethacin
Celecoxib
0.02
HIS90 (SO2, 2.74)
PHE518 (SO2, 2.86)
SER353 (NH2, 2.17)
LEU352 (NH2, 1.91)
GLN192 (NH2, 2.75)
15

New Journal of Chemistry
Page 16 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
Fig. 4 Predicted binding modes of selected compounds (salmonꢀfilled spheres) with COXꢀ2
receptor (PDB code: 4COX), Dotted green line represents Hꢀbonding interaction, violet
dotted line represents hydrophobic interaction and amino acid residues are represented in
grey.
16

Page 17 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
Conclusion
In the present study, we have described the chemistry and the in vitro COXꢀ2 enzyme
inhibitory activity of 1,2,3 trisubstituted 7ꢀcyano indolizine scaffolds 2a-k. The reactions
performed to obtain indolizine derivatives 2a-k were ecoꢀfriendly and carried out at room
temperature with good yield. The test compounds 2a, 2b, and 2d exhibited promising COX 2
inhibition activity from the series when compared to standard Indomethacin and Celecoxib.
Halogen atoms at para position of the benzoyl ring at third position of indolizine nucleus
possess promising COXꢀ2 enzyme inhibitory activity. This promising activity was favoured
by ethyl moiety at second position of the indolizine nucleus. However, lowest homologous of
ester functional group at second position of indolizine nucleus didn’t favour the good activity.
Further biological evaluation must be conducted to confirm our molecular studies. Data
amassed in the present study could be taken into account to develop novel indolizine
scaffolds for improving the potency of this class of compound as potential selective COXꢀ2
inhibitors.
Acknowledgements
The authors are thankful to Durban University of Technology, South Africa, National
Research Foundation (96807 and 98884), South Africa and King Faisal University, Kingdom
of Saudi Arabia for support and encouragement.
Supplementary data
Electronic supplementary information (ESI) available: FTꢀIR, 1H & 13C NMR spectra.
Competing interests
The authors declare that they have no competing interests.
Notes and references
1.
2.
L. J. Crofford, Arthritis Research & Therapy, 2013, 15, S2ꢀS2.
A. Mollica, S. Pelliccia, V. Famiglini, A. Stefanucci, G. Macedonio, A. Chiavaroli, G.
Orlando, L. Brunetti, C. Ferrante, S. Pieretti, E. Novellino, S. Benyhe, F. Zador, A.
Erdei, E. Szucs, R. Samavati, S. Dvrorasko, C. Tomboly, R. Ragno, A. Patsilinakos
and R. Silvestri, Journal of enzyme inhibition and medicinal chemistry, 2017, 32, 444ꢀ
451.
17

New Journal of Chemistry
Page 18 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
3.
A. Stefanucci, E. Novellino, S. Mirzaie, G. Macedonio, S. Pieretti, P. Minosi, E.
Szucs, A. I. Erdei, F. Zador, S. Benyhe and A. Mollica, ACS Medicinal Chemistry
Letters, 2017, 8, 449ꢀ454.
4.
5.
6.
T. Guo, Z. Gan, J. Chen, D. Wang, L. He, Q. Song and Y. Xu, Bioorganic &
medicinal chemistry, 2016, 24, 2964ꢀ2970.
S. Suzuki, Y. Sugawara, R. Tsuji, R. Tanimura, C. Kaneko, N. Yuzawa, M. Yagi and
K. Kawai, Bioorganic & Medicinal Chemistry Letters, 2017, 27, 3920ꢀ3924.
A. M. Sherwood, R. S. Crowley, K. F. Paton, A. Biggerstaff, B. Neuenswander, V.
W. Day, B. M. Kivell and T. E. Prisinzano, Journal of Medicinal Chemistry, 2017, 60,
3866ꢀ3878.
7.
C. R. Smith, E. M. Bunnelle, A. J. Rhodes and R. Sarpong, Organic Letters, 2007, 9,
1169ꢀ1171.
8.
9.
10.
11.
12.
F. I. Carroll and R. E. Dolle, ChemMedChem, 2014, 9, 1638ꢀ1654.
J. P. Michael, The Alkaloids. Chemistry and biology, 2001, 55, 91ꢀ258.
J. P. Michael, Natural Product Reports, 2008, 25, 139ꢀ165.
J. P. Michael, Natural Product Reports, 2007, 24, 191ꢀ222.
J. L. Vaught, J. R. Carson, R. J. Carmosin, P. S. Blum, F. J. Persico, W. E. Hageman,
R. P. Shank and R. B. Raffa, Journal of Pharmacology and Experimental
Therapeutics, 1990, 255, 1ꢀ10.
13.
S. K. Shrivastava, P. Srivastava, R. Bandresh, P. N. Tripathi and A. Tripathi,
Bioorganic & medicinal chemistry, 2017, 25, 4424ꢀ4432.
14.
15.
M. S. Butler, Natural Product Reports, 2008, 25, 475ꢀ516.
W. Mederski, N. Beier, L. T. Burgdorf, R. Gericke, M. Klein and C. Tsaklakidis, US
Patent, 2012, Jan 31, 8.
16.
C. Sandeep, B. Padmashali, K. N. Venugopala, R. S. Kulkarni, R. Venugopala and B.
Odhav, Asian J. Chem., 2016, 28, 1043ꢀ1048.
17.
18.
G. M. Cingolani, F. Claudi, M. Massi and F. Venturi, Cingolani, 1990, 25, 709ꢀ712.
S. Hagishita, M. Yamada, K. Shirahase, T. Okada, Y. Murakami, Y. Ito, T. Matsuura,
M. Wada, T. Kato, M. Ueno, Y. Chikazawa, K. Yamada, T. Ono, I. Teshirogi and M.
Ohtani, J Med Chem, 1996, 39, 3636ꢀ3658.
19.
C. Sandeep, K. Venugopala, M. Khedr, Basavaraj, P, S. R. Kulkarni, R. V and B.
Odhav, Indian Journal of Pharmaceutical Education and Research, 2017, 51, 452ꢀ
460.
20.
21.
P. Jaisankar, B. Pal, K. N. Manna, P. K. Pradhan, S. Medda, M. K. Basu and V. S.
Giri, ARKIVOC, 2003, 150ꢀ157.
A. Hazra, S. Mondal, A. Maity, S. Naskar, P. Saha, R. Paira, K. B. Sahu, P. Paira, S.
Ghosh, C. Sinha, A. Samanta, S. Banerjee and N. B. Mondal, European Journal of
Medicinal Chemistry, 2011, 46, 2132ꢀ2140.
22.
23.
P. Olejnikova, L. Birosova and L. Svorc, Sci Pharm, 2009, 77, 216.
A. I. Nasir, L. L. Gundersen, F. Rise, O. Antonsen, T. Kristensen, B. Langhelle, A.
Bast, I. Custers, G. R. Haenen and H. Wikstrom, Bioorganic & Medicinal Chemistry
Letters, 1998, 8, 1829ꢀ1832.
24.
25.
G. Dannhardt, W. Meindl, S. Gussmann, S. Ajili and T. Kappe, European Journal of
Medicinal Chemistry, 1987, 22, 505ꢀ510.
M. A. Khedr, M. Pillay, C. Sandeep, D. Chopra, B. E. Aldhubiab, M. Attimarad, O. I.
Alwassil, K. Mlisana, B. Odhav and K. N. Venugopala, Journal of Biomolecular
Structure and Dynamics, 2017, DOI: 10.1080/07391102.2017.1345325, 1ꢀ16.
B. B. Mishra and V. K. Tiwari, Opportunity, Challenge and Scope of Natural
Products in Medicinal Chemistry, 2011, 1ꢀ61.
26.
18

Page 19 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
27.
28.
C. Sandeep, K. N. Venugopala, S. K. Nayak, R. M. Gleiser, D. A. García, H. M.
Kumalo, R. S. Kulkarni, F. M. Mahomoodally, R. Venugopala, M. K. Mohan and B.
Odhav, Journal of Molecular Structure, 2018, 1156, 377ꢀ384.
C. Sandeep, K. N. Venugopala, R. M. Gleiser, A. Chetram, B. Padmashali, R. S.
Kulkarni, R. Venugopala and B. Odhav, Chemical Biology & Drug Design, 2016, 88,
899ꢀ904.
29.
30.
S. C. Smith, E. D. Clarke, S. M. Ridley, D. Bartlett, D. T. Greenhow, H. Glithro, A.
Y. Klong, G. Mitchell and G. W. Mullier, Pest Manag Sci, 2005, 61, 16ꢀ24.
B. Yan, Y. Zhou, H. Zhang, J. Chen and Y. Liu, Journal of Organic Chemistry, 2007,
72, 7783ꢀ7786.
31.
32.
T. Taguchi, Journal, 2003.
I. V. Seregin, V. Ryabova and V. Gevorgyan, Journal of the American Chemical
Society, 2007, 129, 7742ꢀ7743.
33.
34.
V. Boekelheide and R. J. Windgassen, Journal of the American Chemical Society,
1959, 81, 1456ꢀ1459.
J. Hurst, T. Melton and D. G. Wibberley, Journal of the Chemical Society (Resumed),
1965, DOI: 10.1039/jr9650002948, 2948ꢀ2955.
35.
36.
U. Bora, A. Saikia and R. C. Boruah, Org Lett, 2003, 5, 435ꢀ438.
G. Poissonnet, M.ꢀH. ThéretꢀBettiol and R. H. Dodd, The Journal of Organic
Chemistry, 1996, 61, 2273ꢀ2282.
37.
A. R. Katritzky, G. Qiu, B. Yang and H.ꢀY. He, The Journal of Organic Chemistry,
1999, 64, 7618ꢀ7621.
38.
39.
X. Fang, Y.ꢀM. Wu, J. Deng and S.ꢀW. Wang, Tetrahedron, 2004, 60, 5487ꢀ5493.
C. Sandeep, B. Padmashali and R. S. Kulkarni, Tetrahedron Letters, 2013, 54, 6411ꢀ
6414.
40.
41.
Y. Abe, A. Ohsawa and H. Igeta, CHEMICAL & PHARMACEUTICAL BULLETIN,
1982, 30, 881ꢀ886.
A. J. Huckaba, A. Yella, L. E. McNamara, A. E. Steen, J. S. Murphy, C. A. Carpenter,
G. D. Puneky, N. I. Hammer, M. K. Nazeeruddin, M. Grätzel and J. H. Delcamp,
Chemistry – A European Journal, 2016, 22, 15536ꢀ15542.
G. G. Surpateanu, M. Becuwe, N. C. Lungu, P. I. Dron, S. Fourmentin, D. Landy and
G. Surpateanu, Journal of Photochemistry and Photobiology A: Chemistry, 2007, 185,
312ꢀ320.
42.
43.
44.
45.
46.
H. Sonnenschein, G. Hennrich, U. ReschꢀGenger and B. Schulz, Dyes and Pigments,
2000, 46, 23ꢀ27.
J. Wan, C.ꢀJ. Zheng, M.ꢀK. Fung, X.ꢀK. Liu, C.ꢀS. Lee and X.ꢀH. Zhang, Journal of
Materials Chemistry, 2012, 22, 4502ꢀ4510.
M. Becuwe, D. Landy, F. Delattre, F. Cazier and S. Fourmentin, Sensors, 2008, 8,
3689.
M. C. N. Picot, G. Zengin, A. Mollica, A. Stefanucci, S. Carradori and M. F.
Mahomoodally, Medicinal chemistry (Shariqah (United Arab Emirates)), 2017, 13,
633ꢀ640.
47.
48.
S. Uysal, A. Aktumsek, C. M. N. Picot, A. Sahan, A. Mollica, G. Zengin and M.
Fawzi Mahomoodally, New Journal of Chemistry, 2017, 41, 13952ꢀ13960.
K. N. Venugopala, G. B. Dharma Rao, S. Bhandary, M. Pillay, D. Chopra, B. E.
Aldhubiab, M. Attimarad, O. I. Alwassil, S. Harsha and K. Mlisana, Drug Design,
Development and Therapy, 2016, 10, 2681ꢀ2690.
49.
K. N. Venugopala, S. K. Nayak, M. Pillay, R. Prasanna, Y. M. Coovadia and B.
Odhav, Chemical Biology & Drug Design, 2013, 81, 219ꢀ227.
19

New Journal of Chemistry
Page 20 of 21
View Article Online
DOI: 10.1039/C7NJ05010K
50.
51.
52.
53.
P. Panini, K. N. Venugopala, B. Odhav and D. Chopra, Acta Crystallographica Sect
B, 2014, 70, 681ꢀ696.
M. Parthapratim, K. N. Venugopala, B. S. Jayashree and T. N. G. Row, Cryst Growth
Des, 2004, 4, 1105ꢀ1107.
B. Hinz, O. Cheremina and K. Brune, FASEB journal : official publication of the
Federation of American Societies for Experimental Biology, 2008, 22, 383ꢀ390.
J. A. Di Rienzo, F. Casanoves, M. G. Balzarini, L. Gonzalez, M. Tablada and C. W.
Robledo, Available online at http://www.infostat.com.ar (visited August 12, 2017),
2014.
54.
55.
E. A. C. Shirley, J. R. Stat. Soc. Series C (Applied Statistics), 1987, 36, 205ꢀ213.
D. K. Gehlhaar, G. M. Verkhivker, P. A. Rejto, C. J. Sherman, D. B. Fogel, L. J.
Fogel and S. T. Freer, Chemistry & biology, 1995, 2, 317ꢀ324.
56.
D. K. Gehlhaar, D. Bouzida and P. A. Rejto, Rational Drug Design: Novel
Methodology and Practical Applications, 1999, ACS Symposium Series Vol. 719,
American Chemical Society, Washington DC, USA, 292ꢀ311.
57.
58.
59.
A. N. Jain, Journal of computerꢀaided molecular design, 1996, 10, 427ꢀ440.
I. Muegge and Y. C. Martin, Journal of Medicinal Chemistry, 1999, 42, 791ꢀ804.
A. S. Kalgutkar, B. C. Crews, S. W. Rowlinson, A. B. Marnett, K. R. Kozak, R. P.
Remmel and L. J. Marnett, Proceedings of the National Academy of Sciences of the
United States of America, 2000, 97, 925ꢀ930.
60.
61.
D. K. Bhattacharyya, M. Lecomte, C. J. Rieke, M. Garavito and W. L. Smith, Journal
of Biological Chemistry, 1996, 271, 2179ꢀ2184.
G. M. Greig, D. A. Francis, J. P. Falgueyret, M. Ouellet, M. D. Percival, P. Roy, C.
Bayly, J. A. Mancini and G. P. O'Neill, Molecular pharmacology, 1997, 52, 829ꢀ838.
20

Page 21 of 21
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ05010K
Table ofcontents
Efficient synthesis and characterization of novel indolizine scaffolds as COX-2
inhibiting agents including molecular modelling studies