MOLPRINT 2D-based identification and synthesis of novel chromene based small molecules that target PLA2: Validation through chemo- and bioinformatics approaches

Article abstract of DOI:10.1039/c5ra13085a

Phospholipase A2 (PLA2) is known to regulate inflammation and hence it is considered as a validated drug-target by medicinal chemists. In this report, we have identified and considered a highly ranked ligand from the ZINC-drug-like compounds database that

Full text of DOI:10.1039/c5ra13085a

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VIVEK, S. Rangappa, J. Fuchs, B. Kumar, B. C. Krishna, L. M. Mervin, P. BABU SHUBHA, S. Basappa, S.
NanjundaSwamy, A. Bender and K. S. Rangappa, RSC Adv., 2015, DOI: 10.1039/C5RA13085A.
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MOLPRINT 2Dꢀbased identification and synthesis of novel chromene based small
molecules that target PLA2: Validation through chemo ꢀ and bioinformatics approach
Hosadurga K Keerthy ,1 Hamse K Vivek,2 Shobith Rangappa,3 Julian E. Fuchs,4
Hanumantharayappa Bharathkumar1, Krishna C. Bulusu,4 Lewis H. Mervin,4 Babu S Priya,5
Basappa,1,* Nanjuda Swamy S,2,* Andreas Bender,4,* Kanchugarakoppal S. Rangappa5,*
1Laboratory of Chemical Biology, Department of Chemistry, Bangalore University, Palace Road,
2
Bangaloreꢀ560001, India; Department of Biotechnology, Sri Jayachamarajendra College of
3
Engineering, JSS Technical Institutions Campus, Mysore, 570 006, Karnataka, India; Frontier
4
Research Centre for Postꢀgenome Science and Technology Hokkaido University, Japan; Centre
for Molecular Informatics, Department of Chemistry, University of Cambridge, Lensfield Road,
5
Cambridge CB2 1EW, United Kingdom; Department of Studies in Chemistry, University of
Mysore, Manasagangotri, Mysoreꢀ570 006, India;
*Corresponding Authors
Dr. Basappa
Department of Chemistry
Central College
Palace Road
Bangalore University
Bangaluruꢀ560001
Karnataka, INDIA
Phone: +91ꢀ80ꢀ22961346
Email: salundibasappa@gmail.com

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ABSTRACT:
Phospholipase A2 (PLA2) was known to regulate inflammation and hence it was considered as a
validated drugꢀtarget by medicinal chemists. In this report, we have identified and considered
highly ranked ligand of ZINCꢀdrugꢀlike compounds database, which targets PLA2 via
MOLPRINTꢀ2D based chemoinformatic drugꢀdesign approach. The computationally predicted
lead molecule was found to contain the core moiety of chromene ring, which was well known for
its varied biological properties. Here, a novel and efficient retroꢀsynthetic protocol for the
synthesis of highly substituted chromene libraries was made. Oneꢀpot synthesis of chromene was
carried out by using different aromatic primary alcohols, malanonitrile and 4ꢀhydroxy coumarin
in the presence of mild oxidant mixture called T3P®ꢀDMSO, followed by Suzuki coupling
reaction to obtain the lead molecules. All the tested compounds of chromene series displayed the
inhibition of the venom PLA2 with a range from 12 to 68 µM. Among the tested compounds, 2ꢀ
aminoꢀ4ꢀ(2'ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile (7b) showed maximum inhibitory efficacy against venom PLA2 with an IC50 value
of 12.5 µM. Furthermore, the designed PLA2 ligands bound to the active site of venom PLA2,
whose binding affinity was comparable to nimesulide, indicate the chromene moiety containing
ligands could be novel leadꢀstructure that serves as antiꢀinflammatory agents.
Keywords: Retroꢀsynthesis, 2ꢀamino chromeneꢀ3ꢀcarbonitrile, MOLPRINT 2D, Snake venom
PLA2.

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INTRODUCTION
Phospholipase A2 (PLA2) was the mostꢀstudied membraneꢀbound enzyme with a
molecular weight of 14 kDa[1ꢀ3]. It was a Ca2+ꢀdependent and disulphideꢀrich enzyme, and
mostly present in mammalian tissues and in the venoms of insects and snakes[4]. It hydrolyzes the
phospholipids from cellular membranes and lipoproteins at the snꢀ2 position releasing
lysophospholipids and free fatty acids[5]. PLA2s are known to aid the production of eicosanoids,
prostaglandins, leukotrienes and plateletꢀactivating factors (PAF), which exert hormoneꢀlike
function orchestrating various physiological events at lower concentrations [2]. However, higher
levels may induce serious pathological conditions such as inflammation, arthritis, atherosclerosis
and sepsis. Hence, PLA2 along with cyclooxygenases and lipoxygenases regulate inflammation
and associated inflammatory diseases. Among the secretary PLA2s, group IIA was known to
play a key role in both acute and chronic inflammation, which was regulated by multiple
intracellular signalling cascades[6]. Besides regulation of human diseases, snake venom
pathology was largely attributed to the presence of PLA2. Snake venoms have been
demonstrated to be a complex mixture of PLA2, matrix metalloproteinase, hyaluronidases and
other toxic nonꢀenzymatic peptides[7]. The combined action of these enzymatic and nonꢀ
enzymatic venom components are known to induce proteolysis, haemorrhage, necrosis, altered
haemostasis, shock and several other neurological dysfunctions [8]. Among them, venomꢀinduced
necrosis, edema and anticoagulation are directly accredited to the myotoxic PLA2 and other
myotoxins present in the venom.
In view of this, inhibition of PLA2 has been considered as a prime target in the
management of inflammatory diseases and snakebites. Thus, the aim of research in this
field was to identify safe and effective PLA2 inhibitors. The higher structural similarity

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between the snake venom sPLA2 and of humans suggests using snake venom PLA2
inhibitors to design novel drugs aiming human inflammatory diseases and vice versa [9, 10]
.
Also, the active site of sPLA2 was composed of substrate binding hydrophobic region and
substrate cleaving hydrophilic region, hence it was further requirement that a PLA2
inhibitor must bear hydrophobic and hydrophilic moieties in it[11]. To date, several
synthetic[12] and natural[13] inhibitors have been reported as PLA2 inhibitors. However this
search had limited success in finding novel class molecules which bear both hydrophobic
and hydrophilic moieties.
In continuation of our ongoing report on synthetic inhibitors that targets PLA2[14ꢀ15], and
other drugꢀtargets[16ꢀ22], presently, we herein, report the design of novel drugꢀlike small
molecules via chemꢀinformatics approaches followed by synthesis of lead structure, via a retroꢀ
synthetic approach as the starting point. Furthermore, we validate the efficacy of these inhibitors
against snake venom VRVꢀPLꢀVIIIaPLA2 isolated from vipera russelli venom and driven by the
in silico molecular interaction studies, this enabled us to discover novel inhibitors that target
PLA2.
RESULTS AND DISCUSSION
MOLPRINT 2Dꢀbased identification of drugꢀlike compounds targeting PLA2:
A MOLPRINTꢀ2D PLA2 model was queried with the drugꢀlike molecules of ZINC database [23]
.
The top ranked compounds are summarized in Table 1 & Figure 1. Among the ranked
compounds, ZINC00625534 (DCMB) was ranked 4th. This DCMB was considered as lead
molecule as other top ranked compounds failed to contain both hydrophobic and hydrophilic
moiety. Since DCMB contain ester linkage, we designed and prepared DCMB analogues.

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Synthesis of DCMB analogues:
The lead PLA2 inhibitor ZINC00625534 (DCMB) contains hydrophilic amino, lactone, nitrile,
methoxy and ester groups also hydrophobic aromatic rings. To achieve an effectual interaction
between sPLA2 active site and an inhibitor, we have replaced the ester group of DCMB by CꢀC
bond which enhances hydrophobicity of the inhibitor. To start with synthesis of DCMB
analogues (2ꢀamino chromeneꢀ3ꢀcarbonitriles), we have employed retroꢀsynthetic approach
(Supplementary Figure S1) where primary alcohol (1) and malanonitrile (2) reacts in presence of
T3P®ꢀDMSO and ethyl acetate as solvent to give swern oxidized product which further on
Knoevenagel condenzation gives product (3)[24]. The intermediate 3 undergoes Michael
cyclization with 4ꢀhydroxy coumarin (4) to form compound 5. Further, Suzuki coupling reaction
of 5 with aromatic and pyridine boronic acids (6) where we have used [1,10ꢀ
bis(diphenylphosphino)ferrocene]dichloro palladium catalyst (Pd(dppf)Cl2) and SCSꢀBi2O3base
in tetrahydrofuran solvent given DCMB analogue 7[25]. The detailed chemical synthesis and
characterization of DCMB analogs was presented (Figure 2).
Neutralization of snake venom PLA2 by the lead molecule libraries:
In order to test the efficacy of the synthesized inhibitors, they were tested against snake
venom PLA2 called VRVꢀPLꢀVIIIa isolated from vipera russelli venom. Inhibitory
effects of the series of lead molecules against PLA2 were tabulated (Table 2). All the
tested compounds displayed the inhibition of the venom PLA2 with a range from 12 to 68
µ
M. Among the tested compounds, 7b showed maximum inhibitory efficacy against
PLA2 with an IC50 value of 12.5 M (Table 3). Till date, several inhibitors from
synthesis, and also from various organisms including marine sponges, snakes, bees, plants
µ

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and mammals have been reported. However, this happens to be the first report that the
novel chromene molecule, which displayed a potent inhibition of snake venom PLA2.
In silico interaction studies of novel ligands that targets PLA2:
In order to understand structureꢀbased correlation with compound affinity, we conducted
molecular docking studies using crystal structure of PLA2 from Russel's viper that bound to
nimesulide (PDB: 1ZWP)[26]. The chromene ligands were docked into the PLA2 structure using
MOE[27]. We found the cyano functionality of our ligand series consistently replacing the nitro
group of nimesulide and forming hydrogen bonds to the backbone nitrogen of Glyꢀ32. The
exposed binding site of PLA2 allows for two binding modes of our compounds including these
interactions (see Figure 3). Both of them form πꢀπ interactions with the readily accessible indole
moiety of Trpꢀ31. Different orientation of the core ring system either allows the amine function
of the ligands to form hydrogen bonds to the carboxylate of Aspꢀ49 or to the backbone carbonyl
of Glyꢀ30. Both predicted binding modes are shown in Figure 3 for the two compounds 7a and
7b with highest PLA2 inhibition in vitro. Structureꢀactivity relationships within the ligand series
are not straightforward to interpret as groupꢀwise contributions since binding modes of the
ligands might change and thus give rise to different molecular interactions between PLA2 and
the respective compounds.
MATERIALS AND METHODS
In silico design of novel small molecule that target PLA2.
The ligand similarity searching protocol, as implemented in MOLPRINTꢀ2D, was trained using
bioactivity data from the ChEMBL database for the target PLA2. Bioactivity training data was
extracted from the ChEMBL16 database where activity values (IC50 / EC50 / Ki / Kd) less than

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or equal to 10ꢁM, and a ChEMBL confidence score of 8 or greater for ‘binding’ or ‘functional’
assays, giving 2,499 active compounds. 1,426 compounds exceeded the 10ꢁM threshold, which
were considered to be inactive and used as negative bioactivity training data. MOLPRINT 2D
descriptors were generated for the complete data set of active and inactive compounds [28, 29]. The
Naïve Bayes learner was subsequently trained on the training compounds and queried with the
MOLPRINT 2D fingerprints of 7,228 drugꢀlike compounds of ZINC database. The ZINC
molecules were ranked in terms of ‘probability of activity’ scores generated by models. A 10ꢀ
fold cross validation with a 50/50 random split of both active and inactive structures was
performed, confirming the predictive power of the models.
Chemical Synthesis:
All reagents were commercially available reagent grade were used without further purification.
Thin layer chromatography (TLC) was conducted on 0.25 mm silica gel plates (60F254, Merck).
Column chromatography separations were obtained on silica gel (200ꢀ400 mesh). IR spectra
1
were recorded on Bruker FTIR spectrophotometer. H NMR spectra were recorded on
BrukerAvanceꢀ300 instrument in CDCl3 solvent. 13C NMR spectra were obtained on
BrukerAvanceꢀ300 instrument at 75 MHz in DMSOꢀd6 solvent (few on Agilent NMR instrument
in CDCl3 solvent). Chemical shifts are expressed in ppm downfield relative to TMS. Mass
spectra were recorded on Agilent LCꢀMS and the elemental analyses were carried out using an
Elemental Vario Cube CHNS rapid Analyzer.
General procedure for synthesis of DCMB analogues: To the solvent mixture of ethyl acetate
and DMSO (1.5 ml: 0.75ml = 2: 1 ratio) 4ꢀbromo/3ꢀbromoꢀ4ꢀmethoxy benzyl alcohol 1 (1.0
mmol) and malanonitrile 2 (1.2 mmol) are added in presence of T3P® (2.5 mmol, 50% solution in

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ethyl acetate) at room temperature, which undergo inꢀsitu Swern oxidation followed by
Knoevenagel condensation to yield corresponding alkene 3 within 10 minutes. Complete
formation of alkene 3 was confirmed by TLC using hexane:EtOAc (7:3) system and has been
observed at Rf 0.78 under ultraviolet (UV) light. Without isolating the alkene 3, to this reaction
mixture 4ꢀhydroxy coumarin 4 (1.0 mmol) was added and stirred for 2ꢀ3 hours at room
temperature to form compound 5[30]. Reaction was monitored by TLC (Hexane: EtOAc 7:3) and
the compound 5 has been observed at Rf 0.42 under UV light. After completion of the reaction,
the mixture was diluted with about 5 ml of distilled water. The product was extracted with 10 ml
of ethyl acetate and the combined organic layers were washed with 10 ml of distilled water,
followed by 5 ml of brine solution. The organic phase was dried over anhydrous Na2SO4. The
solvent was removed under reduced pressure to afford a pure product. Compound 5 was obtained
with 98% yield.
Further the compound 5 (1 mmol) heated to 70 oC with variety of aryl/hetero boronic acids 6 (1.2
mmol) in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml
water and 4 ml of tetrahydrofuran solvent for 8ꢀ10 hours to obtain crude DCMB analogues (7 aꢀ
n) (Table 2). The formation of final products 7(aꢀn) was monitored by TLC (Hexane: EtOAc
8:2). This was further purified by column chromatography using hexane: ethyl acetate as eluent.
The final product 7(aꢀn) was eluted with 15% hexane:ethyl acetate system (85ml hexane: 15ml
ethyl acetate). Thus obtained DCMB analogues were enantiomers and are isolated as recemic
mixtures. These DCMB analogues are confirmed by spectral analysis without separation of the
recemic mixtures.. Spectral properties were consistent with their assigned structures.
7a
4ꢀ([1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ2ꢀaminoꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀbromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀ

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dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound 5) and phenyl boronic acid
6(1.2 mmol) at 70 oC in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol)
base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8 hours. 7a has been observed on TLC
at Rf 0.58 under UV light and was isolated as white solid by column chromatography with 15%
hexane:ethyl acetate system (85ml hexane: 15ml ethyl acetate).
1
IR νmax: 3323cmꢀ1 ν(NH2), 2194cmꢀ1 ν(CN), 1673cmꢀ1ν(cꢀo),1049cmꢀ1 ν(C=O); H NMR (CDCl3, 300
13
MHz):ꢀ δ 7.912ꢀ7.206 (m, 13H, ArꢀH), 4.856 (s, 1H, methine); C NMR (CDCl3, 75MHz) δ
161.13, 160.57, 158.53, 156.08, 148.44, 145.95, 134.46, 130.35, 129.75, 128.17, 126.57, 125.46,
124.53, 123.48, 117.66, 112.60, 103.83, 60.20, 35.13; LCMS (MM:ES+APCI) (M+H)+ 393;
Anal.Calcd for C25H16N2O3 : C 76.62, H 4.11, N 7.14; Found: C 76.14, H 4.19, N 7.42.
7b 2ꢀaminoꢀ4ꢀ(2'ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀbromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound 5) and oꢀtolylboronic acid
6(1.2 mmol) at 70 oC in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol)
base in 1 ml water and 4 ml of tetrahydrofuran solvent for 7 hours. 7b has been observed on TLC
at Rf 0.59 under UV light and was isolated as yellow solid by column chromatography with 15%
hexane:ethyl acetate system (85ml hexane: 15ml ethyl acetate).
IR νmax: 3256cmꢀ1 ν(NH2), 2196cmꢀ1 ν(CN), 1680cmꢀ1ν(cꢀo),1047cmꢀ1 ν(C=O);1H NMR (CDCl3, 300
MHz):ꢀ δ 7.831ꢀ7.295 (m, 12H, ArꢀH), 4.161 (s, 1H, Methine), 3.295 (s, 2H, ꢀNH2), 2.254 (s,
3H, ꢀCH3); LCMS (MM:ES+APCI) (M+H)+407; Anal.Calcd for C26H18N2O3: C 76.83, H 4.46,
N 6.89; Found: C 76.91, H 4.53, N 6.81.

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7c 2ꢀaminoꢀ4ꢀ(3'ꢀmethoxyꢀ[1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀbromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1
mmol)
(compound
5)
and
(3ꢀ
o
methoxyphenyl)boronic acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2 catalyst (0.001
mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8
hours. 7c has been observed on TLC at Rf 0.52 under UV light and was isolated as white solid by
column chromatography with 16% hexane:ethyl acetate system (84ml hexane: 16ml ethyl
acetate).
1
IR νmax: 3293cmꢀ1 ν(NH2), 2193cmꢀ1 ν(CN), 1673cmꢀ1 ν(cꢀo),1048cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 8.000ꢀ7.978 (m, 3H, ArꢀH), 7.792ꢀ7.746 (m, 2H, ArꢀH), 7.552ꢀ7.521 (m, 2H, ArꢀH),
7.434ꢀ7.394 (m, 4H, ArꢀH), 7.257 (s, 1H, ArꢀH), 3.884 (s, 1H, Methine), 3.846 (s, 3H, ꢀOCH3);
13C NMR (DMSOꢀD6, 75MHz) δ 162.52, 160.19, 143.72, 134.25, 131.56, 126.11, 125.87,
125.09, 124.35, 123.46, 122.92, 121.62, 120.95, 120.12, 117.57, 114.29, 112.52, 99.35, 57.28,
52.25, 35.28; LCMS (MM:ES+APCI) (M+H)+ 423; Anal.Calcd for C26H18N2O4 : C 73.92, H
4.29, N 6.63; Found: C 73.88, H 4.32, N 6.59.
7d
2ꢀaminoꢀ5ꢀoxoꢀ4ꢀ(2'ꢀ(trifluoromethyl)ꢀ[1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ4,5ꢀdihydropyrano[3,2ꢀ
c]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀ
bromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound 5)
o
and (2ꢀ(trifluoromethyl)phenyl)boronic acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2
catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran
solvent for 9 hours. 7d has been observed on TLC at Rf 0.50 under UV light and was isolated as
grey solid by column chromatography with 16% hexane:ethyl acetate system (84ml hexane:
16ml ethyl acetate).

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1
IR νmax: 3292cmꢀ1 ν(NH2), 2199cmꢀ1 ν(CN), 1669cmꢀ1 ν(cꢀo),1033cmꢀ1 ν(C=O); H NMR (CDCl3, 300
13
MHz):ꢀ δ 7.831ꢀ7.260 (m, 12H, ArꢀH), 4.714 (s, 1H, Methine); C NMR (CDCl3, 75MHz) δ
162.57, 161.43, 159.27, 158.12, 143.29, 141.25, 135.04, 132.81, 128.77, 126.92, 126.03, 125.12,
124.69, 123.14, 121.20, 120.07, 118.77, 116.83, 110.32, 100.05, 58.23, 38.48; LCMS
(MM:ES+APCI) (M+H)+ 461; Anal.Calcd for C26H15F3N2O3 : C 67.83, H 3.28, N 12.38; Found:
C 67.90, H 3.31, N 12.41.
7e
2ꢀaminoꢀ4ꢀ(4'ꢀchloroꢀ3'ꢀ(trifluoromethyl)ꢀ[1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀ
aminoꢀ4ꢀ(4ꢀbromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1
mmol)
o
(compound 5) and (4ꢀchloroꢀ3ꢀ(trifluoromethyl)phenyl)boronic acid 6(1.2 mmol) at 70 C in
presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and
4 ml of tetrahydrofuran solvent for 8.5 hours. 7e has been observed on TLC at Rf 0.50 under UV
light and was isolated as white solid by column chromatography with 16% hexane:ethyl acetate
system (84ml hexane: 16ml ethyl acetate).
1
IR νmax: 3293cmꢀ1 ν(NH2), 2200cmꢀ1 ν(CN), 1667cmꢀ1 ν(cꢀo),1050cmꢀ1 ν(C=O); H NMR (CDCl3, 300
13
MHz):ꢀ δ 7.842ꢀ7.260 (m, 11H, ArꢀH), 4.851 (s, 1H, Methine); C NMR (CDCl3, 75MHz) δ
161.08, 160.50, 158.19, 141.89, 135.08, 132.50, 130.19, 128.11, 127.47, 126.09, 124.05, 123.74,
122.29, 121.08, 119.85, 117.64, 115.24, 111.48, 101.56, 60.15, 36.22; LCMS (MM:ES+APCI)
(MꢀH)ꢀ 493; Anal.Calcd for C26H14ClF3N2O3 : C 63.11, H 2.85, N 5.66; Found: C 63.15, H 2.89,
N 5.70.
7f
2ꢀaminoꢀ5ꢀoxoꢀ4ꢀ(4ꢀ(pyridinꢀ3ꢀyl)phenyl)ꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀbromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀ

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dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound 5) and pyridinꢀ3ꢀylboronic
o
acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5
mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8.5 hours. 7f has been observed
on TLC at Rf 0.55 under UV light and was isolated as white solid by column chromatography
with 15% hexane:ethyl acetate system (85ml hexane: 15ml ethyl acetate).
IR νmax: 3323cmꢀ1 ν(NH2), 2195cmꢀ1 ν(CN), 1668cmꢀ1ν(cꢀo),1042cmꢀ1 ν(C=O);1H NMR (CDCl3, 300
MHz):ꢀ δ 8.922ꢀ8.918 (s, 1H, ArꢀNꢀCH), 8.688ꢀ8.673 (d, 1H, ArꢀH), 8.568ꢀ8.548 (d, 1H, ArꢀH),
7.996ꢀ7.961 (m, 2H, ArꢀH), 7.869ꢀ7.846 (m, 1H, ArꢀH), 7.586ꢀ7.589 (m, 3H, ArꢀH), 7.428ꢀ7.370
(m, 3H, ArꢀH), 4.747 (s, 1H, Methine), 1.566 (s, 2H, ꢀNH2); LCMS (MM:ES+APCI)
(M+H)+394; Anal.Calcd for C24H15N3O3 : C 73.27, H 3.84, N 10.68; Found: C 73.31; H, 3.88;
N, 10.73.
7g
2ꢀaminoꢀ4ꢀ(4ꢀ(5,6ꢀdichloropyridinꢀ3ꢀyl)phenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀ
This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(4ꢀ
c]chromeneꢀ3ꢀcarbonitrile:
bromophenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound 5)
o
and (4,6ꢀdichloropyridinꢀ3ꢀyl)boronic acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2
catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran
solvent for 9.5 hours. 7g has been observed on TLC at Rf 0.51 under UV light and was isolated
as white solid by column chromatography with 16% hexane:ethyl acetate system (84ml hexane:
16ml ethyl acetate).
1
IR νmax: 3320cmꢀ1 ν(NH2), 2192cmꢀ1 ν(CN), 1665cmꢀ1ν(cꢀo),1046cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 8.625 (s, 1H, ArꢀNꢀH), 8.462 (s, 1H, ArꢀH), 7.772 (m, 1H, ArꢀH), 7.595ꢀ7.501 (m, 1H,
ArꢀH), 7.386ꢀ7.324 (m, 2H, ArꢀH), 7.003ꢀ6.896 (m, 3H, ArꢀH), 3.725 (s, 1H, Methine); LCMS

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(MM:ES+APCI) (M+H)+ 463; Anal.Calcd for C24H13Cl2N3O3 : C 62.35, H 2.83, N 9.09; Found:
C 62.31, H 2.79, N 9.12.
7h 2ꢀaminoꢀ4ꢀ(6ꢀmethoxyꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀ
carbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀmethoxyphenyl)ꢀ
5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile (1 mmol) (compound 5) and phenyl
o
boronic acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—
Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8 hours. 7h has been
observed on TLC at Rf 0.56 under UV light and was isolated as yellow solid by column
chromatography with 15% hexane:ethyl acetate system (85ml hexane: 15ml ethyl acetate).
1
IR νmax:3286cmꢀ1 ν(NH2), 2197cmꢀ1 ν(CN), 1667cmꢀ1ν(cꢀo),1052cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 7.797ꢀ7.776 (s, 1H, ArꢀH), 7.772ꢀ7.7.52 (m, 1H, ArꢀH), 7.491ꢀ7.467 (m, 2H, ArꢀH),
7.374ꢀ7.336 (m, 6H, ArꢀH), 7.192ꢀ7.186 (m, 1H, ArꢀH), 6.939ꢀ.917 (m, 1H, ArꢀH), 3.867 (s,
1H, Methine), 3.750ꢀ3.715 (s, 3H, ꢀOCH3); LCMS (MM:ES+APCI) (MꢀH)ꢀ 421; Anal.Calcd for
C26H18N2O4 : C 73.92, H 4.29, N 6.63; Found: C 73.88, H4.26, N 6.67.
7i
2ꢀaminoꢀ4ꢀ(6ꢀmethoxyꢀ2'ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀ
c]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀ
methoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile (1 mmol) (compound
o
5) and oꢀtolylboronic acid 6(1.2 mmol) at 70 C in presence of Pd(dppf)2Cl2 catalyst (0.001
mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8.5
hours. 7i has been observed on TLC at Rf 0.57 under UV light and was isolated as white solid by
column chromatography with 15% hexane:ethyl acetate system (85ml hexane: 15ml ethyl
acetate).

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1
IR νmax: 3288cmꢀ1 ν(NH2), 2196cmꢀ1 ν(CN), 1668cmꢀ1ν(cꢀo),1057cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 7.775ꢀ7.758 (m, 1H, ArꢀH), 7.356ꢀ7.348 (m, 3H, ArꢀH), 7.260 (m, 3H, ArꢀH), 7.030ꢀ
6.902 (m, 4H, ArꢀH), 4.629 (1H, Methine, s), 3.734 (3H, ꢀOCH3, s), 2.069 (3H, ꢀCH3, s); LCMS
(MM:ES+APCI) (MꢀH)ꢀ 435; Anal.Calcd for C27H20N2O4 : C 74.30, H 4.62, N 6.42; Found:
C74.28, H 4.65, N 6.46.
7j
2ꢀaminoꢀ4ꢀ(3',6ꢀdimethoxyꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀ
c]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀ
methoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound
5) and (3ꢀmethoxyphenyl)boronic acid 6(1.2 mmol) at 70 oC in presence of Pd(dppf)2Cl2 catalyst
(0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent
for 9.5 hours. 7j has been observed on TLC at Rf 0.50 under UV light and was isolated as brown
solid by column chromatography with 16% hexane:ethyl acetate system (84ml hexane: 16ml
ethyl acetate).
1
IR νmax: 3287cmꢀ1 ν(NH2), 2197cmꢀ1 ν(CN), 1669cmꢀ1 ν(cꢀo),1053cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 7.791ꢀ7.773 (s, 1H, ArꢀH), 7.613ꢀ7.574 (m, 2H, ArꢀH), 7.354ꢀ7.335 (m, 3H, ArꢀH),
7.260 (m, 1H, ArꢀH), 7.065ꢀ7.037 (m, 2H, ArꢀH), 6.936ꢀ6.847 (m, 2H, ArꢀH), 6.847 (m, 11H,
13
ArꢀH), 3.811 (s, 1H, Methine), 3.779 (s, 6H ꢀOCH3); C NMR (DMSOꢀD6, 75MHz) δ 161.52,
160.25, 154.12, 152.74, 132.13, 126.98, 126.17, 125.01, 124.45, 123.85, 123.11, 122.92, 121.51,
119.25, 116.52, 113.32, 110.59, 100.50, 60.15, 56.72, 55.91, 36.71; LCMS (MM:ES+APCI) (Mꢀ
H)ꢀ 451; Anal.Calcd for C27H20N2O5 : C 71.67, H 4.46, N 6.19; Found: C 71.71, H 4.41, N 6.21.
7k
2ꢀaminoꢀ4ꢀ(6ꢀmethoxyꢀ2'ꢀ(trifluoromethyl)ꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀ

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aminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀmethoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile
o
(1 mmol) (compound 5) and (2ꢀ(trifluoromethyl)phenyl)boronic acid 6(1.2 mmol) at 70 C in
presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and
4 ml of tetrahydrofuran solvent for 8.2 hours. 7k has been observed on TLC at Rf 0.48 under UV
light and was isolated as brown solid by column chromatography with 17% hexane:ethyl acetate
system (83ml hexane: 17ml ethyl acetate).
IR νmax: 3301cmꢀ1 ν(NH2), 2198cmꢀ1 ν(CN), 1671cmꢀ1 ν(cꢀo),1053cmꢀ1 ν(C=O);1H NMR (CDCl3, 300
MHz):ꢀ δ 7.925ꢀ7.885 (m, 2H, ArꢀH), 7.815 (s, 1H, ArꢀH), 7.651ꢀ7.552 (m, 2H, ArꢀH), 7.450ꢀ
7.321 (m, 3H, ArꢀH), 7.250 (m, 2H, ArꢀH), 6.982 (s, 1H, ArꢀH), 4.297 (s, 1H, Methine), 3.306
13
(s, 3H, ꢀOCH3); C NMR (CDCl3, 75MHz) δ 162.19, 161.28, 159.14, 158.34, 133.65, 131.28,
129.52, 125.87, 125.19, 124.57, 124.01, 123.85, 123.08, 122.12, 117.12, 115.28, 103.52, 59.28,
55.71, 36.17;LCMS (MM:ES+APCI) (M+H)+ 491; Anal.Calcd for C27H17F3N2O4 : C 66.12, H
3.49, N 5.71; Found: C 66.13, H 3.52, N 5.73.
7l
2ꢀaminoꢀ4ꢀ(4'ꢀchloroꢀ6ꢀmethoxyꢀ3'ꢀ(trifluoromethyl)ꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀ
aminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀmethoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile
(1 mmol) (compound 5) and (4ꢀchloroꢀ3ꢀ(trifluoromethyl)phenyl)boronic acid 6(1.2 mmol) at 70
oC in presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml
water and 4 ml of tetrahydrofuran solvent for 9 hours. 7l has been observed on TLC at Rf 0.47
under UV light and was isolated as white solid by column chromatography with 17%
hexane:ethyl acetate system (83ml hexane: 17ml ethyl acetate).

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1
IR νmax: 3288cmꢀ1 ν(NH2), 2198cmꢀ1 ν(CN), 1671cmꢀ1 ν(cꢀo),1055cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 7.819ꢀ7.799 (d, 1H, ArꢀH), 7.638ꢀ7.616 (m, 2H, ArꢀH), 7.599ꢀ7.571 (m, 2H, ArꢀH),
7.504 (m, 2H, ArꢀH), 7.392ꢀ7.510 (m, 2H, ArꢀH), 6.869ꢀ6.848 (s, 1H, ArꢀH), δ 3.870 (s, 1H,
13
Methine), δ 3.787 (s, 3H ꢀOCH3); C NMR (DMSOꢀD6, 75MHz) δ 161.57, 160.16, 158.91,
144.15, 135.46, 133.48, 132.19, 125.45, 124.89, 124.25, 123.10, 122.59, 121.85, 121.41, 119.32,
116.28, 114.11, 113.42, 101.41, 59.12, 55.72, 36.29; LCMS (MM:ES+APCI) (MꢀH)ꢀ 523;
Anal.Calcd for C27H16ClF3N2O4 : C 61.78, H 3.07, N 5.34; Found: C 61.74, H 3.05, N 5.30.
7m
2ꢀaminoꢀ4ꢀ(4ꢀmethoxyꢀ3ꢀ(pyridinꢀ3ꢀyl)phenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀ
c]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀaminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀ
methoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile(1 mmol) (compound
5) and pyridinꢀ3ꢀylboronic acid 6(1.2 mmol) at 70 oC in presence of Pd(dppf)2Cl2 catalyst (0.001
mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and 4 ml of tetrahydrofuran solvent for 8
hours. 7m has been observed on TLC at Rf 0.51 under UV light and was isolated as white solid
by column chromatography with 16% hexane:ethyl acetate system (84ml hexane: 16ml ethyl
acetate).
1
IR νmax: 3292cmꢀ1 ν(NH2), 2199cmꢀ1 ν(CN), 1674cmꢀ1 1 ν(cꢀo),1066cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 8.718ꢀ8.672 (s, 1H, ArꢀH), 8.608ꢀ8.511 (s, 1H, ArꢀH), 8.112ꢀ7.941 (m, 2H, ArꢀH),
7.819ꢀ7.766 (m, 1H, ArꢀH), 7.606ꢀ7.588 (m, 2H, ArꢀH), 7.518ꢀ7.310 (m, 4H, ArꢀH), 4.627 (s,
1H, Methine), 3.656 (s, 3H ꢀOCH3) LCMS (MM:ES+APCI) (MꢀH)ꢀ 422; Anal.Calcd for
C25H17N3O4 : C 70.91, H 4.05, N 9.92; Found: C 70.89, H 4.09, N 9.90.
7n
2ꢀaminoꢀ4ꢀ(3ꢀ(4,6ꢀdichloropyridinꢀ3ꢀyl)ꢀ4ꢀmethoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀ
dihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile: This compound was obtained by heating 2ꢀ

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aminoꢀ4ꢀ(3ꢀbromoꢀ4ꢀmethoxyphenyl)ꢀ5ꢀoxoꢀ4,5ꢀdihydropyrano[3,2ꢀc]chromeneꢀ3ꢀcarbonitrile
o
(1 mmol) (compound 5) and (4,6ꢀdichloropyridinꢀ3ꢀyl)boronic acid 6(1.2 mmol) at 70 C in
presence of Pd(dppf)2Cl2 catalyst (0.001 mmol), SCS—Bi2O3 (0.5 mmol) base in 1 ml water and
4 ml of tetrahydrofuran solvent for 8.5 hours. 7n has been observed on TLC at Rf 0.48 under UV
light and was isolated as brown solid by column chromatography with 16% hexane:ethyl acetate
system (84ml hexane: 16ml ethyl acetate).
1
IR νmax: 3228cmꢀ1 ν(NH2), 2193 cmꢀ1 ν(CN), 1671cmꢀ1ν(cꢀo),1051cmꢀ1 ν(C=O); H NMR (CDCl3, 300
MHz):ꢀ δ 8.601 (s, 1H, ArꢀNꢀCH), 7.716ꢀ7.182 (m, 8H, ArꢀH), 4.112 (s, 1H, Methine), 3.603 (s,
3H, ꢀOCH3); LCMS (MM:ES+APCI) (M+H)+ 493; Anal.Calcd for C25H15Cl2N3O4 : C 60.99, H
3.07, N 8.54; Found: C 60.96, H 3.05, N 8.59.
Substrate preparation: Briefly, a working solution of 1mM DMPC (Substrate) was prepared in
methanol containing 2mM Triton Xꢀ100 in MilliꢀQ water. The resulting substrate solution was
spun at 1,500xg for 5min to form uniform mixed micelles.
LPC standardcurve: LPC (1ꢀmyristoylꢀ2ꢀhydroxyꢀSnꢀglycerolꢀ3ꢀphosphocholine) standard
curve was constructed using different LPC concentrations ranging from 0 to 100µM as reported
earlier[31]. Briefly, total reaction mixture of 100µL containing activity buffer (50mM Tris, pH
7.5, 10mM CaCl2) and 2mM LPC containing 4mM Triton Xꢀ100 (1:2 ratio) and incubated for 5
min at 37ºC. Quenching solution was added and vortexed for 30 Sec and incubated for 5 min at
RT. 2µL of reaction mixture was pipetted to measure RFU as described earlier.
Neutralization of VRVꢀPLꢀVIIIa (sPLA2) by the title compounds: sPLA2 activity was
assayed according to the method[32]. Briefly, a 50µl activity buffer containing 50mM TrisꢀHCl
buffer pH 7.5, 10mM CaCl2 and 10µl substrate stock were added and incubated for 5 min at
37ºC. Activity was initiated by adding 10ng of sPLA2 alone or pre incubated with different

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concentration of DCMB analogues ranging from 0ꢀ120µM for 5min at 37°C. Reaction mixture
was incubated for 45 min at 37ºC. 50µl of quenching solution was added at final concentration of
2mM NaN3, 50µM ANS and 50mM EGTA, vortexed for 30 sec and incubated for 5 min at RT.
2µl of this solution was pipetted to measure Relative fluorescence unit (RFU) in a Nano drop
ND3300 Ver 2.8 using excitation with UVꢀLED (370 ±10nm) and emission was recorded at
480nm in dark condition. Enzyme activity was calculated by Eq (1), where ꢂRFU is the change
in RFU of test (with sPLA2) with respect to control (without sPLA2) in presence of inhibitor.
The resultant RFU is compared with standard curve of LPC to determine the sPLA2 activity in
presence of inhibitor. 4th parameter logical (4PL) fit module of Graphpad Prism 6.05 was used to
compute IC50 values.
Equation 1
∆RFULPC = RFUc – RFUt
Molecular Docking Studies: We docked the series of fourteen synthesized compounds to the
crystal structure of PLA2 from Russel's viper in complex with nimesulide (PDB: 1ZWP). We
used identical settings as in an earlier study on imidazopyridineꢀbased PLA2inhibitors docking in
MOE. The protocol included a pharmacophore filter during docking to enforce a hydrogen bond
acceptor feature in the position of the nitro group of nimesulide. Predicted binding modes were
visualized in Pymol[33ꢀ35]
.
CONCLUSION
In conclusion, we herein report a simple, efficient, catalyst free and one potsynthetic route
to prepare triꢀsubstitutedꢀcondensedꢀimidazopyridines and ourin silico target prediction
presented PLA2 as a likely target for the newly synthesized compounds. The prediction
was experimentally validated using indirect haemolytic assay. Of the new compounds

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synthesized, 1ꢀ(2ꢀMethylꢀ8ꢀnaphthalenꢀ1ꢀylꢀimidazo [1,2ꢀα]pyridineꢀ3ꢀyl)ꢀethanone was
identified as the lead compound with an IC50 value of 14.3 ꢁM. Molecular docking
analysis displayed that the imidazopyridine compounds could make a favourable πꢀπ
stacking interactions with Trpꢀ31. Exploration of PLA2 inhibitory activity of
imidazopyridine derivatives contributes to the development of the title compounds as
therapeutic agents to block the PLA2 associated inflammatory diseases. Thus, synthesis
of more imidazopyridine derivatives and optimization of their biological activity
according to the identified structureꢀactivity relationship is envisaged.
Acknowledgements
This research was supported by University Grants Commission (41ꢀ257ꢀ2012ꢀSR), Vision Group
Science and Technology, Department of Science and Technology (NO. SR/FT/LSꢀ142/2012).
Keerthy HK, Bharathkumar H thanks to University Grants Commission for Basic Science
Research Fellowship. Andreas Bender thanks Unilever and the European Research Commission
(ERC Starting Grant 2013) for funding. Lewis Mervin thanks the BBSRC and AstraZeneca for
funding.

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Figure 1: Structural representation of in silico ranked structure ZINC0062553 (DCMB) and its
analogues.
Figure 2: Synthesis scheme for DCMB analogues 7(aꢀn).
Figure 3: Molecular interaction studies of novel ligands that targets PLA2. Predicted molecular
interactions between PLA2 and DCMB analogues: PLA2 is shown as grey cartoon with semiꢀ
transparent surface representation. Main interaction centres Aspꢀ49, Glyꢀ32, Trpꢀ31, and Glyꢀ30
(from left to right) are highlighted as lines in atomic colouring. A) Binding mode of nimesulide
within the coꢀcrystal structure used for docking (PDB: 1ZWP, [4]). a and 7b are predicted to bind
in two different modes to PLA2. Both of them replace the nitro group of nimesulide by a cyano
group and show πꢀπ interactions with Trpꢀ31 but form different molecular interactions via the
amine group (7a: Aspꢀ49, 7b: Glyꢀ30).

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Figure 1

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Figure 2

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Figure 3

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Table 1: List of ranked compounds targeting PLA2 based on the designing of MOLPRINT
2D.
Rank Zinc Accession
Compound name
Structure
Probability of
Activity
2ꢀ
1
ZINC00299345 (phenoxycarbonyl)p
henyl 2ꢀfuroate
2531.0
(5R,5'R)ꢀ5,5'ꢀ
oxybis(3,4ꢀ
ZINC08427108
2
2295.8
dibromofuranꢀ
2(5H)ꢀone)
(5S,5'S)ꢀ5,5'ꢀ
oxybis(3,4ꢀ
3
ZINC08427105
2295.8
dibromofuranꢀ
2(5H)ꢀone)

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4ꢀ(2ꢀaminoꢀ3ꢀcyanoꢀ
5ꢀoxoꢀ4H,5Hꢀ
pyrano[3,2ꢀ
4
ZINC00625534
1819.7
c]chromenꢀ4ꢀyl)ꢀ2ꢀ
methoxyphenyl
benzoate

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Table2: Newly synthesized DCMB analogues
Entry
1
6
7(aꢀn)
aYield%
NH2
OH
HO
OH
1
92
N
B
O
O
O
Br
7a
NH2
OH
OH
OH
HO
OH
2
3
4
90
89
84
N
B
O
O
O
Br
7b
NH2
HO
OH
N
B
O
O
O
O
O
Br
7c
NH2
HO
OH
N
B
O
CF3
CF3
O
O
Br
7d