Synthesis, characterization, solvatochromic properties, and antimicrobial evaluation of 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-dione-based chalcones

Article abstract of DOI:10.1007/s00044-012-0395-1

A new series of chalcone analogs namely 5-(3-phenyl-acryloyl)-2-thioxo- dihydro-pyrimidine-4,6-dione have been synthesized from the key intermediate 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-dione 4′ with different aldehyde derivatives were performed to get the target compounds as thiobarbituric acid-based chalcones 5(a′-k′) and they were obtained in excellent yields. The newly synthesized compounds were characterized by spectral analysis (FT-IR, ¹H NMR, ¹³C NMR, and UV spectroscopy) and elemental analysis. The synthesized compounds were evaluated for their antimicrobial activity against five bacterial strains (S. aureus, S. pyogenes, E. coli, K. pneumoniae, and P. aeruginosa) and four fungal strains (C. albicans, A. clavatus, T. rubrum, and Penicillium wild strain). Among the screened compounds, 5e′ and f′ showed comparable activity (minimum inhibitory concentration = 500 μg/mL) nearly to that of standard antibiotics griseofulvin.

Full text of DOI:10.1007/s00044-012-0395-1

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:4075–4086
DOI 10.1007/s00044-012-0395-1
ORIGINAL RESEARCH
Synthesis, characterization, solvatochromic properties,
and antimicrobial evaluation of 5-acetyl-2-thioxo-dihydro-
pyrimidine-4,6-dione-based chalcones
•
Bhaveshkumar D. Dhorajiya Bhimji S. Bhakhar
•
Bharatkumar Z. Dholakiya
Received: 12 September 2012 / Accepted: 4 December 2012 / Published online: 20 December 2012
Ó Springer Science+Business Media New York 2012
Abstract A new series of chalcone analogs namely
5-(3-phenyl-acryloyl)-2-thioxo-dihydro-pyrimidine-4,6-dione
have been synthesized from the key intermediate 5-acetyl-
2-thioxo-dihydro-pyrimidine-4,6-dione 40 with different
aldehyde derivatives were performed to get the target
compounds as thiobarbituric acid-based chalcones 5(a0–k0)
and they were obtained in excellent yields. The newly
synthesized compounds were characterized by spectral
Introduction
The medicinal importance of pyrimidine derivatives such as
barbituric acid and thiobarbituric acid play vital role among
various heterocyclic compounds due to their anti-neoplastic
(Basavaraja et al., 2010; Holy et al., 2002), antiviral (Andres
and Marhold, 1996), antibiotic (Reddick et al., 2001), and
anti-inflammatory (Basavaraja et al., 2010) activity. The
pyrimidine ring system is present in various natural com-
pounds such as nucleic acids, vitamins, coenzymes, uric
acid, purines, and some marine microorganisms (e.g.,
sponge) (Kashman et al., 1989). Many synthetic drugs (e.g.,
barbituric and thiobarbituric acid) derivatives and chemo-
therapeutic agents (e.g., sulfadiazine) (Fattah et al., 2010).
The diverse biologic activity and coverage of a broad
chemical space make barbituric and thiobarbituric acid
derivatives excellent target compounds for organic and
medicinal chemists. Owing to their ready availability and
various functionalization possibilities, the parent barbituric
and thiobarbituric acid are convenient starting materials for
the preparation of different fused heterocycles and literature
survey also ascribes that 5-substituted derivatives are phar-
macologically active compounds (Nace and Danijel, 2011).
Chalcones and their derivatives are attractive molecular
scaffolds for the search of new biologically active molecules
(Nowakowska, 2007). Chalcones or 1,3-diaryl-2-propen-1-
ones are natural or synthetic compounds belonging to the
flavonoids family (Lee et al., 2006). Chalcone analogs are
very versatile as physiologically active compounds and
substrates for the evaluation of various organic syntheses.
Chalcones have been reported to possess many useful
properties, including anti-inflammatory (Tomar et al.,
2007), antimicrobial (Lopez et al., 2001), antifungal (Anto
et al., 1995), antioxidant (Lui et al., 2003), antimalarial (Yi
et al., 2000), antitumor (Hsu et al., 2006), and anticancer
1
analysis (FT-IR, H NMR, 13C NMR, and UV spectros-
copy) and elemental analysis. The synthesized compounds
were evaluated for their antimicrobial activity against
five bacterial strains (S. aureus, S. pyogenes, E. coli,
K. pneumoniae, and P. aeruginosa) and four fungal strains
(C. albicans, A. clavatus, T. rubrum, and Penicillium wild
strain). Among the screened compounds, 5e0 and f0 showed
comparable activity (minimum inhibitory concentra-
tion = 500 lg/mL) nearly to that of standard antibiotics
griseofulvin.
Keywords Chalcones ꢀ Antibacterial activity ꢀ
Antifungal activity
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-012-0395-1) contains supplementary
material, which is available to authorized users.
B. D. Dhorajiya ꢀ B. S. Bhakhar ꢀ B. Z. Dholakiya (&)
Department of Applied Chemistry, S.V. National Institute
of Technology, Ichchhanath, Surat 395007, Gujarat, India
e-mail: bharat281173@gmail.com
B. D. Dhorajiya
e-mail: bhavesh.orgchem@gmail.com
123

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(Siddiqui et al., 2011) activities. So, in light of the above
facts of pyrimidine, barbituric acid, thiobarbituric acid, and
chalcones, we have reported the synthesis and reaction
of 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-dione 40 with
different aldehydes to form chalcones 5(a0–k0). All the novel
derivatives were screened for their antimicrobial activity and
their results are discussed.
C-6, 166.23, C-2, 175.34); IR (KBr, cm-1): 1252 (C=S),
1698 (C=O), 3339 (N–H); Anal. Calcd. for C4H4N2O2S: C,
33.33; H, 2.80; N, 19.43 %. Found: C, 33.27; H, 2.89; N,
19.48 %.
Synthesis of 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-
dione (40)
To a solution of 2-mercapto-pyrimidine-4,6-dione 30
(6.4 g, 44.39 mmol) in acetic anhydride (150 mL), few
drops of H2SO4 was added and refluxed for 1 h. The
reaction in the beginning was a suspension; but, after about
10 min of reflux, it changes to brown color clear solution.
The reaction mixture was concentrated into 1/2 of its ori-
ginal volume and cooled at about 10 °C. The solid product
was formed, filtered, washed with hot water then acetone,
dried, and recrystallized from acetone to give compound 40
(7.4 g) yield, as a brown powder (Branko and Donna,
2001). Yield: 90 %, MW 174.19, mp 242–245 °C; 1H
NMR (DMSO-d6): d 2.60 (3H, s, –CH3), 2.62 (1H, s, CH of
pyrimidine ring), 11.01 (1H, s, NH of pyrimidine ring),
11.73 (1H, s, NH of pyrimidine ring); 13C NMR (DMSO-
d6): d (C-8, 27.52, C-5, 69.12, C-4, C-6, 168.12, C-2,
172.35, C-7, 178.69); IR (KBr, cm-1): 1250.52 (C=S),
1700.34 (C=O), 3034.69 (C–CH3), 3210.46 (CH of
pyrimidine ring), 3285.78 (NH of pyrimidine ring); Anal.
Calcd. for C6H6N2O3S: C, 38.70; H, 3.25; N, 15.05 %.
Found: C, 38.77; H, 3.21; N, 15.11 %.
Experimental
Chemicals and solvents were obtained from commercial
sources and used as received throughout the investigation.
Melting points were determined in open capillaries on a
Veego electronic apparatus VMP-D (Veego Instrument
Corporation, Mumbai, India) and are uncorrected. IR spectra
(4,000–400 cm-1) of the synthesized compounds were
recorded on a Perkin Elmer—Spectrum RX-IFTIR spectro-
photometer using KBr pellets. Thin layer chromatography
was performed on object glass slides (2 9 7.5 cm) coated
with silica gel-G and spots were visualized under UV irra-
1
diation. H- and 13C NMR spectra were recorded on an
Advance-II (Bruker) model using dimethyl sulfoxide
(DMSO) as a solvent and TMS as internal standard with 1H
resonant frequency of 400 MHz and 13C resonant frequency
of 100 MHz. The H- and 13C NMR chemical shifts were
1
reported as parts per million (ppm) downfield from TMS
(Me4Si). The splitting patterns are designated as follows; s,
singlet; br s, broad singlet; d, doublet; t, triplet; q, quartet; m,
multiplet. UV spectra were recorded on Maya pro 2000
(Ocean Optics, USA). All standard strains for screening of
antibacterial and antifungal activities were procured from
the Institute of Microbial Technology, Chandigarh. DMSO
was used as diluents/vehicle to get desired concentration of
drugs to test upon standard bacterial strains.
General method for the preparation of chalcones
5(a0–k0)
To
a
well-stirred solution of compound (0.2 g,
1.148 mmol) 40 in 40 % aqueous sodium hydroxide solu-
tion, equimolecular amount of the appropriate aldehydes
(for e.g., benzaldehyde 0.121 g, 1.148 mmol) was added.
The reaction mixture was stirred at room temperature for
about 12 h. The confirmation of the reaction was carried
out by TLC using chloroform–methanol and hexane–ethyl
acetate (4:1 v/v) mixture. After the completion of the
reaction, final compound was isolated from water at 6–7
pH. Further purification of isolated compound was done by
recrystallization in methanol. Similarly, other compounds
5(b0–k0) were synthesized (Dhorajiya et al., 2012).
Synthesis of 2-thioxo-dihydro-pyrimidine-4,6-dione
(30)
To a solution of diethylmalonate 10 (20 g, 118.9 mmol) and
20 thiourea (7.5 g, 98.5 mmol) in methanol, anhydrous
sodium methoxide was added and refluxed at 65 °C for 8 h.
A white solid separates. Then, in the above reaction mix-
ture, 125 mL of hot (50 °C) water was added and hydro-
chloric acid was used to make the solution acidic. After the
completion of the reaction, the resulting clear solution was
filtered and cooled in an ice bath overnight. The white
product formed was filtered, washed with 50 mL of cold
water, dried, and recrystallized from acetone to afford
compound 30 (10.2 g) as a white powder (Jacobson, 1937).
Yield: 72 %, MW 144.15, mp 252–255 °C; 1H NMR
(DMSO-d6): d 2.98 (2H, s, –CH2), 11.72 (1H, s, NH), 11.96
(1H, s, NH); 13C NMR (DMSO-d6): d (C-2, 44.12, C-4,
Characterization data of synthesized compounds
5(a0–k0)
5-(3-Phenyl-acryloyl)-2-thioxo-dihydro-pyrimidine-4,
6-dione (5a0)
Pale yellow powder, MW 274.30, Yield 77 %; mp
1
[250 °C; H NMR (DMSO-d6): d 2.53 (2H, s, J = 16.2,
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4077
trans-CH=CH), 3.82 (1H, s, –CH of pyrimidine ring at
C-5), 6.49–7.39 (5H, m, Ar–H), 7.91 (1H, s, barbituric acid
NH), 8.14 (1H, s, barbituric acid NH); 13C NMR (DMSO-
d6): d 77 (C-5), 114.32 (C-9), 114.67 (C-8), 122.95 (C-13),
127.12 (C-12, C-14), 129.27 (C-11, C-15), 132 (C-10), 155
(C-7), 163.15 (C-4, C-6), 168.05 (C-2); IR (KBr, cm-1):
1251.15 (C-SH), 1612.12 (C=C aromatic), 1696.23 (C=O),
3335.52 (N–H); kmax: 237.84, 274. 59, 308.37; €: 4.93,
5.00, 5.05; Anal. Calcd. for C13H10N2O3S: C 56.92, H
3.67, N 10.21 (%). Found: C 56.89, H 3.71, N 10.19 (%).
NMR (DMSO-d6): d 58.08 (C-18), 78.85 (C-5), 113.30
(C-9), 113.47 (C-8), 122.95 (C-11, C-15), 129.27 (C-12,
C-14), 131.17 (C-10, C-13), 157 (C-7), 162.66(C-4, C-6),
167.05 (C-2); IR (KBr, cm-1): 1260.73 (C–SH), 1603.57
(C=C aromatic), 1687.97 (C=O), 3343.39 (N–H); kmax
:
237.84, 272.24, 308.84; €: 4.89, 4.95, 5.00; Anal. Calcd.
for C14H12N2O4S: C 55.25, H 3.97, N 9.21 (%). Found: C
55.28, H 3.93, N 9.23 (%).
5-[3-(3,4-Dimethoxy-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5e0)
5-[3-(2-Hydroxy-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5b0)
1
Dark yellow, MW 334.35, Yield 74 %; mp [250 °C; H
NMR (DMSO-d6): d 2.53 (2H, s, J = 16.3, trans-CH=CH),
3.78 (1H, s, –CH of pyrimidine ring at C-5), 3.85 (3H, s,
m-OCH3), 4.09 (3H, s, p-OCH3), 6.75–7.18 (2H, dd,
Ar–H), 7.76 (1H, s, barbituric acid NH), 7.95 (1H, s, bar-
bituric acid NH); 13C NMR (DMSO-d6): d 58.08 (C-18,
C-17) 75.35 (C-5), 114.56 (C-9), 114.87 (C-8), 122.95
(C-11, C-15), 129.27 (C-12, C-14), 131.17 (C-10, C-13),
158 (C-7), 162.66 (C-4, C-5), 167.05 (C-2); IR (KBr,
cm-1): 1261.69 (C–SH), 1607.12 (C=C aromatic), 1685.43
(C=O), 3337.64 (N–H); kmax: 237.84, 275.06, 308.84; €:
4.85, 4.91, 4.96; Anal. Calcd. for C15H14N2O5S: C 53.88,
H 4.22, N 8.38 (%). Found: C 53.85, H 4.26, N 8.36 (%).
1
Light brown, MW 290.29, Yield 58 %; mp [250 °C; H
NMR (DMSO-d6): d 2.51 (2H, s, J = 16.1, trans-CH=CH),
3.72 (1H, s, –CH of pyrimidine ring at C-5), 6.59–7.49
(4H, m, Ar–H), 7.89 (1H, s, barbituric acid NH), 8.19 (1H,
s, barbituric acid NH), 9.29 (1H, s, o- Ar–OH); 13C NMR
(DMSO-d6): d 76 (C-5), 115.10 (C-9), 115.40 (C-8),
122.82 (C-13, C-14), 126.72 (C-12, C-15), 129.67 (C-11),
131.89 (C-10), 155.15 (C-7), 165.15 (C-4, C-6), 168.25
(C-2); IR (KBr, cm-1): 1253.21 (C–SH), 1608.14 (C=C
aromatic), 1693.36 (C=O), 3339.27 (N–H); kmax: 237.84,
283.99, 308.37; €: 4.91, 4.99, 5.05; Anal. Calcd. for
C13H10N2O4S: C 53.79, H 3.47, N 9.65 (%). Found (%): C
53.76, H 3.51, N 9.62 (%).
5-[3-(2-Chloro-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5f0)
5-[3-(4-Hydroxy-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5c0)
Brown powder, MW 308.74, Yield 84 %; mp [250 °C; 1H
NMR (DMSO-d6): d 2.51 (2H, s, J = 16.2, trans-CH=CH),
3.80 (1H, s, –CH of pyrimidine ring at C-5), 6.68–7.58
(2H, m, Ar–H), 7.74 (1H, s, barbituric acid NH), 7.97 (1H,
s, barbituric acid NH); 13C NMR (DMSO-d6): d 74.53
(C-5), 113.26 (C-9), 113.59 (C-8), 122.92 (C-13, C-14),
126.51 (C-12, C-15), 129.39 (C-11), 131.78 (C-10) 157.23
(C-7), 162.66 (C-4, C-6), 168.62 (C-2); IR (KBr, cm-1):
1254.71 (C–SH), 1615.42 (C=C aromatic), 1690.56 (C=O),
3334.28 (N–H); kmax: 237.84, 276, 309.78; €: 4.88, 4.95,
5.00; Anal. Calcd. for C13H9ClN2O3S: C 50.57, H 2.94, N
9.07 (%). Found: C 50.54, H 2.97, N 9.02 (%).
1
Dark brown, MW 290.29, Yield 82 %; mp [250 °C; H
NMR (DMSO-d6): d 2.54 (2H, s, J = 16.4, trans-CH=CH),
3.74 (1H, s, –CH of pyrimidine ring at C-5), 6.49–7.67
(2H, dd, Ar–H), 7.88 (1H, s, barbituric acid NH), 8.15 (1H,
s, barbituric acid NH) 9.37 (1H, s, p- Ar–OH); 13C NMR
(DMSO-d6): d 78 (C-5), 113.10 (C-9), 113.38 (C-8),
121.39 (C-13), 126.56 (C-12, C-14), 129.60 (C-11, C-15),
133.29 (C-10), 157.55 (C-7), 163.15 (C-4, C-6), 168.05
(C-2); IR (KBr, cm-1): 1257.33 (C–SH), 1614.17 (C=C
aromatic), 1689.15 (C=O), 3328.54 (N–H); kmax: 237.84,
277.41, 311.65; €: 4.91, 4.98, 5.03; Anal. Calcd. for
C13H10N2O4S: C 53.79, H 3.47, N 9.65 (%). Found: C
53.74, H 3.50, N 9.61 (%).
5-[3-(4-Chloro-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5g0)
5-[3-(3-Methoxy-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5d0)
Dark brown powder, MW 308.74, Yield 86 %; mp [250 °C;
1H NMR (DMSO-d6): d 2.53 (2H, s, J = 16.4, trans-
CH=CH), 3.90 (1H, s, –CH of pyrimidine ring at C-5),
6.57–7.48 (2H, dd, Ar–H), 7.83 (1H, s, barbituric acid NH),
7.97 (1H, s, barbituric acid NH); 13C NMR (DMSO-d6): d
76.37 (C-5), 113.67 (C-9), 113.87 (C-8), 122.92 (C-13),
126.43 (C-14, C-15), 129.63 (C-11, C-12), 131.45
(C-10) 157.12 (C-7), 162.27 (C-4, C-6), 168.67 (C-2);
Yellow powder, MW 304.32, Yield 62 %; mp [250 °C;
1H NMR (DMSO-d6): d 2.55 (2H, s, J = 16.6, trans-
CH=CH), 3.69 (1H, s, –CH of pyrimidine ring at C-5), 3.76
(3H, s, m-OCH3), 6.78–7.08 (2H, dd, Ar–H), 7.90 (1H, s,
barbituric acid NH), 7.93 (1H, s, barbituric acid NH); 13C
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Med Chem Res (2013) 22:4075–4086
IR (KBr, cm-1): 1604 (C=C aromatic), 1684 (C=O), 2527
(C=S), 3331 (N–H); kmax: 238.31, 281.64, 308.37; €: 4.88,
4.96, 4.99; Anal. Calcd. for C13H9ClN2O3S: C 50.57, H 2.94,
N 9.07 (%). Found: C 50.51, H 2.99, N 9.04 (%).
5-(3-Naphthalen-2-yl-acryloyl)-2-thioxo-dihydro-
pyrimidine-4,6-dione (5k0)
Dark brown powder, MW 324.35, Yield 65 %;
mp [250 °C; 1H NMR (DMSO-d6): d 2.56 (2H, s,
J = 16.3, trans-CH=CH), 3.83 (1H, s, –CH of pyrimidine
ring at C-5), 6.75–7.14 (7H, m, Ar–H), 7.89 (1H, s, bar-
bituric acid NH), 8.03 (1H, s, barbituric acid NH); 13C
NMR (DMSO-d6): d 76 (C-5), 114.52 (C-9), 114.77 (C-8),
122.95–132.67 (C-of naphthalene ring), 156.13 (C-7),
164.73 (C-4, C-6), 169.54 (C-2); IR (KBr, cm-1): 1610
(C=C aromatic), 1697 (C=O), 2527 (C=S), 3338 (N–H);
5-[3-(3-Nitro-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5h0)
Brown powder, MW 319.29, Yield 88 %; mp [250 °C; 1H
NMR (DMSO-d6): d 2.52 (2H, s, J = 16.7, trans-CH=CH),
3.65 (1H, s, –CH of pyrimidine ring at C-5), 6.78–7.08
(4H, m, Ar–H), 7.86 (1H, s, barbituric acid NH), 7.97 (1H,
s, barbituric acid NH); 13C NMR (DMSO-d6): d 78.53
(C-7), 113.26 (C-9), 113.68 (C-8), 121.29 (C-13), 126.43
(C-12, C-14), 129.58 (C-11, C-15), 133.18 (C-10), 157.53
(C-7), 161.35 (C-4, C-6), 169.34 (C-2); IR (KBr, cm-1):
1348 (C–NO2), 1609 (C=C aromatic), 1693 (C=O), 2536
(C=S), 3329 (N–H); kmax: 238.31, 275.06, 308. 37; €: 4.87,
4.93, 4.98; Anal. Calcd. for C13H9N3O5S: C 48.90, H 2.84,
N 13.16 (%). Found: C 48.87, H 2.91, N 13.14 (%).
k
max: 239.26, 279.76, 311.06; €: 4.86, 4.93, 4.98; Anal.
Calcd. for C17H12N2O3S: C 62.95, H 3.73, N 8.64 (%).
Found: C 62.92, H 3.69, N 8.67 (%).
Antimicrobial assay
The synthesized compounds 5(a0–k0) were examined for
antimicrobial activity against several bacterial strains
(S. aureus MTCC 96, S. pyogenes MTCC 442, E. coli
MTCC 443, K. pneumoniae MTCC 109, and P. aeruginosa
MTCC 1688) and four fungal strains (C. albicans MTCC
227, A. clavatus MTCC 1323, T. rubrum MTCC 296, and
Penicillium wild strain) species by agar cup diffusion
technique. Ciprofloxacin and griseofulvin were used as
control drugs for antibacterial and antifungal activity,
respectively. The lowest concentration (highest dilution)
required to arrest the growth of bacteria and fungi was
regarded as minimum inhibitory concentration (MIC),
whereas minimum bactericidal concentration (MBC) was
defined as the lowest drug concentration at which 99.9 %
of the inoculums were killed. The susceptibility was
assessed on the basis of diameter of zone of inhibition
against bacterial and fungal strains. Inhibition zones were
measured and compared with the controls.
5-[3-(4-Nitro-phenyl)-acryloyl]-2-thioxo-dihydro-
pyrimidine-4,6-dione (5i0)
Dark brown powder, MW 319.29, Yield 82 %;
mp [250 °C; 1H NMR (DMSO-d6): d 2.57 (2H, s,
J = 16.7, trans-CH=CH), 3.70 (1H, s, –CH of pyrimidine
ring at C-5), 6.68–7.28 (2H, dd, Ar–H), 7.79 (1H, s, bar-
bituric acid NH), 8.03 (1H, s, barbituric acid NH); 13C
NMR (DMSO-d6): d 78.53 (C-7), 113.26 (C-9), 113.68 (C-
8), 121.29 (C-13), 126.43 (C-12, C-14), 129.58 (C-11,
C-15), 133.18 (C-10), 157.53 (C-7), 161.35 (C-4, C-6),
169.34 (C-2); IR (KBr, cm-1): 1353 (C–NO2), 1613 (C=C
aromatic), 1687 (C=O), 2535 (C=S), 3327 (N–H); kmax
:
238.26, 276, 306.5; €: 4.87, 4.93, 4.98; Anal. Calcd. for
C13H9N3O5S: C 48.90, H 2.84, N 13.16 (%). Found: C
48.92, H 2.81, N 13.17 (%).
Determination of zone of inhibition method
Thioxo-5-(3-p-tolyl-acryloyl)-dihydro-pyrimidine-4,6-
dione (5j0)
In vitro, antibacterial and antifungal activities were
examined for all synthesized chalcone molecules. Anti-
bacterial and antifungal activities of synthesized com-
pounds against five pathogenic bacteria (two gram positive
and three gram negative) and four pathogenic fungi were
investigated by the agar disk diffusion method (Alzoreky
and Nakahara, 2003; Bauer et al., 1966; Rios et al., 1988).
Antimicrobial activity testing was carried out by agar cup
method. Each synthesized compounds were dissolved in
DMSO, sterilized by filtration using sintered glass filter,
and stored at 4 °C. For the determination of zone of inhi-
bition, pure gram-positive, gram-negative bacteria, and
fungal strains were taken as a standard antibiotic for
comparison of the results. All the newly synthesized
Brown powder, MW 288.32, Yield 75 %; mp [250 °C; 1H
NMR (DMSO-d6): d 2.54 (2H, s, J = 16.3, trans-CH=CH),
3.69 (1H, s, –CH of pyrimidine ring at C-5), 6.48–7.38
(2H, dd, Ar–H), 7.81 (1H, s, barbituric acid NH), 7.08 (1H,
s, barbituric acid NH); 13C NMR (DMSO-d6): d 77 (C-5),
113.45 (C-9), 113.76 (C-8), 121.78 (C-13), 126.34 (C-12,
C-14), 129.87 (C-11, C-15), 132.22 (C-10), 158.25 (C-7),
166.15 (C-4, C-6), 169.26 (C-2); IR (KBr, cm-1): 1607
(C=C aromatic), 1682 (C=O), 2544 (C=S), 3345 (N–H);
k
max: 238.31, 277.88, 306.5; €: 4.91, 4.98, 5.04; Anal.
Calcd. for C14H12N2O3S: C 58.32, H 4.20, N 9.72 (%).
Found: C 58.29, H 4.24, N 9.76 (%).
123

Med Chem Res (2013) 22:4075–4086
4079
molecules were screened for their antibacterial activities
against the (S. aureus MTCC 96, S. pyogenes MTCC 442,
E. coli MTCC 443, K. pneumoniae MTCC 109, and
P. aeruginosa MTCC 1688) and four fungal strains
(C. albicans MTCC 227, A. clavatus MTCC 1323, T. rubrum
MTCC 296, and Penicillium wild strain). The Sets of four
dilutions (25, 50, 100, and 250 lg/mL) and standard drugs
(25, 50, 100, and 250 lg/mL) were prepared in double
distilled water using nutrient agar tubes. Muller Hinton
sterile agar plates were seeded with indicator bacterial
strains (108 cfu) and allowed to stay at 37 °C for 3 h.
Control experiments were carried out under similar condi-
tion using ciprofloxacin for antibacterial activity and gris-
eofulvin for antifungal activity as standard drugs. All the
plates were incubated at 37 °C for 18–24 h for bacteria and
at 28 °C for 48–96 h for fungi. The zones of growth inhi-
bition around the disks were measured after 18–24 h of in
incubation at 37 °C for bacteria and 48–96 h for fungi at
28 °C. The sensitivity of the microorganism species to the
synthesized compounds were determined by measuring the
sizes of inhibitory zones (including the diameter of disk) on
the agar surface around the disks, and values \10 mm were
considered as not active against microorganisms. The
growth inhibition zone measured ranged from 10 to 23 mm
for all the sensitive bacteria, and ranged from 16 to 25 mm
for fungal strains.
that when chalcones forms –NH protons of thee pyrimidine
ring shifts toward the up field.
Tautomeric study is important for other areas of chemis-
try. 1H NMR signal at 12.34 d ppm indicates the presence of
–OH group proton which confirms the formation of tauto-
meric mixture but it is in the minor amount. Tautomers not
only have different colors but also have different tinctorial
strengths and different properties. Chalcones 5(a0–k0) can
exist in different ten possible tautomeric forms, namely the
T1, T2, T3, T4, T5, and T6 as shown in Fig. 1.
13C NMR spectra of compound 5d0 showed characteristic
peak at 58.08, 78.85, 113.30, 113.47, 122.95, 129.27, 131.17,
157, 162.66, and 167.05 d ppm. The FT-IR spectra of com-
pounds 5(a0–k0) revealed a characteristic bands between
3,010 and 3,085 cm-1 confirming the presence of (C=C)
groups. Furthermore, in the IR spectra, the bands between
1,682 and 1,697 cm-1 confirm the presence of C=O group.
Moreover, a characteristic band appeared at 2,526–
2,544 cm-1 corresponding to the presence of C=S groups.
The presence of –NO2 group at aryl ring for compound 5h0
and i0 was confirmed by IR spectrum which showed a char-
acteristic band at 1,348 and 1,353 cm-1, respectively.
Effects on UV spectra
The UV absorption spectra of chalcones 5(a0–k0) were
recorded over the range of between 230 and 350 nm using
DMSO as a solvent in concentrations (10-5). The first
absorption peak (kmax) in UV spectra of compounds
showed signals between 237.84 and 239.26 confirming
the presence of olefinic HC=CH double bond with conju-
gated C=O group. The second and third absorption peak
Chemistry
The synthetic strategy adopted to obtain the target com-
pounds is depicted in Scheme 1. Diethylmalonate 10 on
reaction with thiourea 20 at 65 °C yielded 2-thioxo-dihydro-
pyrimidine-4,6-dione 30. The key intermediate 5-acetyl-2-
thioxo-dihydro-pyrimidine-4,6-dione 40 was prepared in an
excellent yield by refluxing compound 40 in acetic anhy-
dride in the presence of H2SO4. Compound 40 when treated
with aromatic aldehydes (a0–k0) gave the corresponding
chalcone analogs 5(a0–k0).
(kmax
) revealed signals between 274.59–283.99 and
306.5–317.37, respectively, confirming the presence of
aromatic ring with different substitution group at different
position (Silverstein and Webster, 1997). Also, it has been
confirmed that in these types of chalcone molecules, p–p*
occurs due to the presence of unsaturated bonds and this
p–p* is responsible for biologic activities.
Results and discussion
Structure–activity relationship for microbial study
Spectral characteristics and tautomerism
The antimicrobial activity of the synthesized compounds
with their MIC, MBC, minimum fungal concentration
(MFC), and zone of inhibition values are summarized in
Tables 1, 2, 3, and 4, respectively.
The structures of the synthesized compounds were con-
firmed by spectral data and elemental analysis and they
were in full agreement with the proposed structures. The
1H NMR data of the compounds revealed signals between
6.48 and 7.58 d ppm for aromatic protons of substituted
Antibacterial studies
1
phenyl ring. The H NMR data of compounds revealed
A close investigation of the MIC values indicates that all
signals between 7.74 and 8.19 d ppm and –NH of pyrim-
the compounds exhibited a varied range of MIC
1
idine ring. The H NMR of compounds 40 and 5d0 proves
(62.5–500 lg/mL) of antibacterial activity against all the
123

4080
Med Chem Res (2013) 22:4075–4086
O
NH2
NH2
O
O
HN
a
+
S
C
EtO
OEt
C
H2
S
N
H
O
1'
2'
3'
b
R1
R2
O
O
OHC
R3
R3
R2
H
N
S
O
O
R1
HN
CH3
HN
c
S
N
O
H
O
5 (a'-k')
4'
Scheme 1
Reagents and Conditions: a-NaOMe/ Methanol-Refluxed, b-AC2O, H2SO4-Heat, c-Aqueous NaOH Solution, Room Temperature
Compounds R1, R2, R3 Groups
R1 R2
5a' -H -H
5b' -OH -H
R3
-H
-H
-OH
-OCH3
5c' -H
5d' -H
5e' -H
5f' -Cl
5g' -H
5h' -H
5i' -H
5j' -H
-H
-H
-OCH3 -OCH3
-H
-H
-NO2 -H
-H
-H
-H
-Cl
-NO2
-CH3
5k' -Naphthyl Ring
Scheme 1 Synthesis of compounds 5(a0–k0)
tested bacterial strains. The MIC, MBC, and zone of
inhibition in mm are given in Tables 1 and 2, respectively.
The compounds 5a0 without any substituent at ortho, meta,
and para position of the aryl ring attached as HC=CH of
chalcone moiety showed MIC = 250 lg/mL against both
gram-positive and gram-negative bacteria, except against
K. pneumoniae where the MIC = 200 lg/mL. In the case
of compound 5b0, which was having hydroxyl substituent
at ortho position of aryl ring at chalcone moiety, it
exhibited significant activity in terms of MIC = 125 lg/mL
against S. pyogenes at chalcone and E. coli same compound
showed similar MIC = 250 lg/mL against P. aeruginosa
and K. pneumoniae. Compound 5c0 having hydroxyl group
at para position of the phenyl ring showed better MIC
values against S. pyogenes, S. aureus, and K. pneumoniae
compared to compound 5b0. Chalcone 5d0 having electron
donating methoxy group on para position of aryl ring
showed good ability to inhibit all bacterial strain in terms
of MIC in the range of 100–200 lg/mL. Compound
5d0 was also found to exhibit best MIC = 100 lg/mL
and MBC = 125 lg/mL against P. aeruginosa along
with compound 5k0 among all the synthesized derivatives.
123

Med Chem Res (2013) 22:4075–4086
4081
OH
O
O
O
HN
HN
S
N
H
O
O
S
N
H
OH
O
R
R
T3
T2
O
OH
HN
N
S
N
H
O
O
HS
N
OH
R
T1
R
T6
OH
O
OH
N
HN
HS
N
O
S
N
OH
H
R
R
T4
T5
Fig. 1 Possible tautomers of compounds 5(a0–k0)
Table 1 MIC (lg/mL) and MBC (lg/mL) results of the compounds 5(a0–k0)
Compounds
Gram positive bacteria
Gram negative bacteria
S. pyogenes MTCC 442 S. aureus MTCC 96 E. coli MTCC 443 P. aeruginosa MTCC 1688 K. pneumoniae MTCC 109
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
5a0
5b0
5c0
5d0
5e0
5f0
5g0
5h0
5i0
250
125
100
200
62.5
250
100
200
100
250
250
500
200
250
250
100
250
125
250
100
200
250
250
500
250
200
500
250
100
200
125
125
200
100
250
500
500
250
500
500
100
250
200
125
250
250
125
250
200
500
250
125
100
250
100
250
25
500
200
250
250
500
500
125
100
500
200
500
250
250
250
100
200
250
200
125
250
250
100
25
250
250
500
125
200
500
250
200
250
500
125
200
200
125
200
250
200
100
62.5
200
100
125
25
250
250
200
250
500
250
125
100
200
100
200
5j0
5k0
Ciprofloxacin 50
MIC (lg/mL) minimum inhibitory concentration, that is, the lowest concentration of the compound to inhibit the growth of bacteria completely,
MBC (lg/mL) minimum bactericidal concentration, that is, the lowest concentration of the compound for killing the bacteria completely
123

4082
Med Chem Res (2013) 22:4075–4086
Table 2 Zone of inhibition (mm) of the compounds 5(a0–k0)
Compounds
Diameter of zone of inhibition (mm)
Gram positive bacteria
Gram negative bacteria
S. pyogenes MTCC 442
S. aureus MTCC 96
E. coli MTCC 443
25
50
100
250
25
50
100
250
25
50
5a0
5b0
5c0
5d0
5e0
5f0
12
15
15
17
10
13
15
17
12
15
(0.1)
13
(0.2)
15
(0.2)
16
(0.1)
17
(0.3)
11
(0.2)
13
(0.2)
17
(0.2)
19
(0.3)
13
(0.1)
15
(0.2)
15
(0.1)
17
(0.1)
16
(0.3)
17
(0.1)
10
(0.1)
14
(0.3)
16
(0.2)
18
(0.2)
15
(0.1)
17
(0.1)
15
(0.2)
18
(0.1)
20
(0.2)
21
(0.3)
13
(0.2)
17
(0.2)
18
(0.2)
21
(0.2)
15
(0.1)
18
(0.1)
12
(0.1)
16
(0.2)
18
(0.3)
21
(0.3)
11
(0.1)
15
(0.1)
18
(0.2)
20
(0.3)
12
(0.2)
16
(0.1)
13
(0.2)
14
(0.1)
15
(0.3)
16
(0.4)
10
(0.2)
14
(0.1)
17
(0.1)
18
(0.4)
13
(0.2)
14
(0.2)
11
(0.1)
14
(0.1)
17
(0.1)
19
(0.3)
11
(0.2)
12
(0.1)
13
(0.1)
15
(0.1)
11
(0.1)
14
5g0
5h0
5i0
(0.3)
15
(0.1)
17
(0.1)
18
(0.2)
18
(0.1)
14
(0.1)
16
(0.1)
17
(0.3)
19
(0.3)
15
(0.1)
17
(0.1)
12
(0.3)
15
(0.2)
19
(0.2)
23
(0.2)
11
(0.1)
13
(0.1)
18
(0.4)
20
(0.2)
12
(0.2)
15
(0.1)
15
(0.2)
15
(0.3)
18
(0.2)
19
(0.1)
10
(0.1)
12
(0.4)
16
(0.2)
17
(0.3)
15
(0.3)
15
5j0
(0.1)
14
(0.1)
16
(0.2)
18
(0.2)
21
(0.1)
10
(0.1)
12
(0.3)
15
(0.2)
19
(0.1)
14
(0.1)
16
5k0
(0.2)
(0.2)
(0.2)
(0.2)
(0.1)
(0.1)
(0.2)
(0.3)
(0.1)
(0.2)
Compounds
Diameter of zone of inhibition (mm)
Gram negative bacteria
E. coli MTCC 443
P. aeruginosa MTCC 1688
K. pneumoniae MTCC 109
100
250
25
50
100
250
17
25
50
100
250
5a0
5b0
5c0
5d0
5e0
5f0
15
17
10
13
15
10
12
14
17
(0.1)
16
(0.2)
17
(0.4)
11
(0.2)
13
(0.1)
17
(0.3)
19
(0.1)
12
(0.2)
13
(0.2)
15
(0.3)
17
(0.1)
16
(0.1)
17
(0.1)
10
(0.2)
14
(0.4)
16
(0.2)
18
(0.1)
10
(0.1)
11
(0.2)
16
(0.2)
18
(0.2)
20
(0.1)
21
(0.1)
13
(0.2)
17
(0.2)
18
(0.2)
21
(0.1)
11
(0.1)
13
(0.3)
14
(0.2)
17
(0.1)
18
(0.1)
21
(0.4)
11
(0.2)
15
(0.1)
18
(0.3)
20
(0.1)
14
(0.2)
15
(0.1)
18
(0.2)
19
(0.2)
15
(0.1)
16
(0.1)
10
(0.4)
14
(0.3)
17
(0.2)
18
(0.1)
12
(0.1)
13
(0.3)
15
(0.1)
18
(0.1)
17
(0.1)
19
(0.2)
11
(0.3)
12
(0.2)
13
(0.1)
15
(0.1)
13
(0.1)
15
(0.2)
17
(0.4)
20
5g0
5h0
(0.2)
18
(0.2)
18
(0.1)
14
(0.1)
16
(0.1)
17
(0.2)
19
(0.1)
10
(0.2)
14
(0.2)
17
(0.1)
18
(0.1)
(0.1)
(0.2)
(0.1)
(0.1)
(0.2)
(0.3)
(0.1)
(0.2)
(0.1)
123

Med Chem Res (2013) 22:4075–4086
4083
Table 2 continued
Compounds
Diameter of zone of inhibition (mm)
Gram negative bacteria
E. coli MTCC 443
P. aeruginosa MTCC 1688
K. pneumoniae MTCC 109
100
250
25
50
100
250
25
50
100
250
5i0
19
23
11
13
18
20
11
13
15
16
(0.4)
18
(0.3)
19
(0.1)
10
(0.3)
12
(0.2)
16
(0.1)
17
(0.1)
12
(0.2)
14
(0.2)
15
(0.1)
17
5j0
5k0
(0.3)
18
(0.2)
21
(0.2)
10
(0.1)
12
(0.3)
15
(0.1)
19
(0.1)
14
(0.2)
15
(0.1)
18
(0.2)
20
(0.2)
(0.3)
(0.1)
(0.1)
(0.3)
(0.4)
(0.1)
(0.1)
(0.3)
(0.2)
Table 3 MIC (lg/mL) and MFC (lg/mL) results of compounds 5(a0–k0)
Compounds
Fungal strains
C. albicans MTCC 227
A. clavatus MTCC 1323
MIC MFC
1000 1000
T. rubrum MTCC 296
MIC MFC
1000 1000
Penicillium wild strain
MIC
MFC
MIC
MFC
5a0
5b0
5c0
5d0
5e0
5f0
5g0
5h0
500
500
1000
[1000
[1000
[1000
500
1000
[1000
[1000
500
[1000
[1000
[1000
500
[1000
500
[1000
500
[1000
[1000
[1000
500
[1000
[1000
[1000
500
[1000
[1000
500
500
1000
1000
[1000
500
1000
1000
1000
250
1000
[1000
500
500
500
[1000
[1000
1000
[1000
[1000
1000
500
500
[1000
1000
[1000
1000
1000
1000
1000
[1000
100
1000
1000
1000
[1000
[1000
100
1000
5i0
5j0
5k0
1000
1000
1000
1000
500
500
1000
[1000
[1000
[1000
1000
[1000
1000
[1000
1000
[1000
1000
[1000
Griseofulvin
500
100
MIC (lg/mL) minimum inhibitory concentration, that is, the lowest concentration of the compound to inhibit the growth of fungus completely,
MFC (lg/mL) minimum fungicidal concentration, that is, the lowest concentration of the compound for killing the fungus completely
On the other hand, 5e0 which was having two methoxy
group one at meta and another at para position of phenyl
ring showed strong inhibition in terms of MIC = 62.5
lg/mL against S. pyogenes and compound was found to
be most potent against same bacteria among all the
chalcone analogs. A very interesting observation made for
compound 5d0 and e0 was that except activity against
S. pyogenes, 5d0 showed very good MIC and MBC values
compare to compound 5d0 against S. aureus, E. coli,
P. aeruginosa, and K. pneumoniae. In the case of com-
pound 5f0 and g0, which were having electron-withdrawing
chloro substituent respectively at the and position of
phenyl ring attached at chalcone shows effective inhibi-
tory effect with MIC range 100–250 lg/mL against all
bacterial strains. Compound 5g0 exhibited the greatest
activity against S. aureus in terms of MIC and
MBC = 100 lg/mL among all the compounds. Same
compound also showed similar MIC = 100 lg/mL and
MBC = 125 lg/mL against S. pyogenes and K. pneumo-
niae. In comparison of compounds 5f0 and g0 by means of
activity data compound 5g was found superior than
compound 5f0. Chalcones 5h0 and i0 with –NO2 group
substituted at phenyl ring on meta and para position,
respectively, exhibit MIC in the range of 62.5–250 lg/mL.
Compound 5h0 was found to exhibit strong inhibition
against gram-negative bacteria E. coli and K. pneumoniae
in terms of MIC = 100 lg/mL and 62.5 lg/mL, respec-
tively, with similar MBC = 100 lg/mL among all synthe-
sized derivatives. –NO2 group at para position containing
compound 5i0 showed MBC = 100 lg/mL against
S. pyogenes similar to most potent compound 5e0, but 5e0
showed better MIC = 62.5 lg/mL than 5i0 having
MIC = 100 lg/mL against S. pyogenes against all the
gram positive bacterial strains. Compound 5i0 was found
123

4084
Med Chem Res (2013) 22:4075–4086
to exhibit better activity (MIC and MBC) compare to 5h0
having superior activity than 5i0 against all gram-negative
bacterial strains. Antibacterial activity of electron donating
–CH3 substituent on phenyl ring containing compound 5j0
showed very good MIC = 100 lg/mL against E. coli along
with compound 5h0, but compared to 5h0 showed better
MBC = 100 lg/mL compared to MBC = 200 lg/mL of
compound 5j0. Compound 5j0 also showed similar MBC =
100 lg/mL along with the most active compound 5h0 against
K. pneumoniae. Compound 5k0 containing naphthalene ring
was found to be equipotent in terms of MIC = 100 lg/mL
and MBC = 125 lg/mL along with compound 5d0.
K. pneumoniae was effectively inhibited with good
MIC = 125 lg/mL by compound 5k0. In most of the cases,
the MBC of compounds were found to be one to two folds
than that of the corresponding MIC results.
Table 4 Zone of inhibition (mm) of the compounds 5(a0–k0)
Compounds Diameter of zone of inhibition (mm)
C. albicans MTCC 227
A. clavatus MTCC 1323
25
50
100
250
22
25
50
100
250
24
5a0
5b0
5c0
5d0
5e0
5f0
16
18
22
18
19
21
(0.2) (0.2) (0.3) (0.1) (0.1) (0.1) (0.2) (0.2)
17 19 22 24 18 19 20 22
(0.2) (0.1) (0.3) (0.2) (0.1) (0.1) (0.2) (0.1)
16 20 23 23 21 21 22 24
(0.3) (0.1) (0.2) (0.2) (0.1) (0.1) (0.2) (0.1)
18 21 24 24 20 21 23 24
(0.1) (0.3) (0.1) (0.1) (0.1) (0.1) (0.2) (0.1)
20 24 25 25 18 20 21 23
(0.3) (0.1) (0.1) (0.1) (0.2) (0.2) (0.1) (0.2)
21 22 22 23 18 19 21 22
(0.1) (0.2) (0.2) (0.1) (0.1) (0.2) (0.1) (0.1)
20 21 22 23 18 20 22 22
(0.1) (0.1) (0.1) (0.1) (0.2) (0.3) (0.1) (0.1)
21 22 23 24 20 22 22 24
(0.2) (0.1) (0.1) (0.2) (0.2) (0.1) (0.1) (0.2)
20 21 25 25 20 21 22 24
(0.1) (0.4) (0.2) (0.2) (0.1) (0.1) (0.2) (0.1)
19 20 21 24 21 22 22 25
(0.1) (0.1) (0.1) (0.3) (0.2) (0.1) (0.1) (0.3)
22 22 24 25 18 20 25 25
(0.1) (0.1) (0.2) (0.1) (0.2) (0.4) (0.1) (0.1)
5g0
5h0
5i0
Antifungal studies
Antifungal activity was also done by Kirby–Bauer disk
diffusion method. For assaying antifungal activity
C. albicans MTCC 227, A. clavatus MTCC 1323, T. rubrum
MTCC 296, and Penicillium wild strain were recultured in
DMSO by agar diffusion method. The MIC, MFC, and
zone of inhibition in mm are given in Tables 3 and 4,
respectively. A close investigation of the MIC values
indicates that all the compounds exhibited a varied range of
MIC (250–[1,000 lg/mL) of antifungal activity against all
the tested fungal strains. The antifungal screening data of
the compounds 5(a0–k0) showed good to moderate activity.
Compound 5a0 and k0 without any substituent at any
position of the aryl ring attached as CH=CH of chalcone
moiety showed MIC and MFC (1,000–[1,000 lg/mL)
against all the strains; but, in the case of 5a0, the presence
of small phenyl ring compared to naphthyl ring of 5k0
showed good MIC and MFC = 500 lg/mL in the case of
C. albicans as the fungal strain. In compound 5b0, the
presence of electron-releasing hydroxyl substituent at ortho
position showed moderate activity against all the strains.
While in the case of chalcone 5c0 containing same group,
but at para position, showed good MIC and MFC values
500 lg/mL for A. clavatus as a fungal strain. Chalcone
molecule 5d0 containing electron-releasing methoxy group
at para position showed good MIC 500 = lg/mL for
A. clavatus and MIC and MFC = 500 lg/mL for Penicil-
lium wild strains as fungal strains. Compound 5e0 possesses
same methoxy substituent at meta and para position showed
good and comparable MIC and MFC = 500 lg/mL for
C. albicans and T. rubrum as the fungal strains, respec-
tively. Chalcone derivatives 5f0 having electron-
releasing chlorine substituent at ortho position showed
5j0
5k0
Compounds Diameter of zone of inhibition (mm)
T. rubrum MTCC 296 Penicillium wild strain
25
50
100
250
25
50
100
250
5a0
5b0
5c0
5d0
5e0
5f0
20
24
24
25
19
21
22
24
(0.3) (0.1) (0.1) (0.2) (0.2)
18 21 21 22 18
(0.2) (0.1) (0.1) (0.2) (0.1)
22 22 24 24 18
(0.1) (0.1) (0.2) (0.2) (0.1)
19 20 21 22 21
(0.2) (0.1) (0.1) (0.2) (0.1)
21 22 23 24 19
(0.1) (0.1) (0.2) (0.1) (0.1)
19 20 19 21 18
(0.1) (0.2) (0.1) (0.3) (0.1)
18 20 21 22 19
(0.2) (0.1) (0.1) (0.2) (0.1)
18 21 22 27 18
(0.3) (0.1) (0.1) (0.4) (0.1)
20 22 23 25 21
(0.2) (0.1) (0.1) (0.2) (0.1)
19 20 22 25 18
(0.1) (0.2) (0.1) (0.3) (0.1)
18 20 22 23 18
(0.2) (0.1) (0.2) (0.1) (0.1)
(0.1)
19
(0.1)
22
(0.2)
23
(0.1)
19
(0.3)
22
(0.1)
24
(0.3)
21
(0.2)
23
(0.1)
25
(0.1)
20
(0.2)
22
(0.3)
24
(0.2)
18
(0.3)
21
(0.4)
22
(0.1)
22
(0.3)
23
(0.2)
25
5g0
5h0
5i0
(0.2)
20
(0.1)
21
(0.4)
22
(0.2)
21
(0.1)
23
(0.1)
25
(0.1)
18
(0.2)
19
(0.2)
22
5j0
(0.1)
18
(0.1)
21
(0.3)
23
5k0
(0.1)
(0.4)
(0.2)
123

Med Chem Res (2013) 22:4075–4086
4085
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Organic Pvt, Ltd, Baroda, Dr. K. Suresh Kumar and his team from
SVNIT, Surat, Gujarat, and Avtarsingh and Manishkumar from SAIF,
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