Synthesis and anti-bacterial activity of new series of 4-(substituted biphenyl-4-yl)-6-methyl-2-oxo/thioxo-1,2,3, 4-tetrahydro-pyrimidine-5-carboxylic acid ethyl ester

Article abstract of DOI:10.1002/jhet.221

(Chemical Equation Presented) New series of 4-(substituted biphenyl-4-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl ester and 4-(substituted biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4- tetrahydro-pyrimidine-5-carboxylic acid ethyl ester has been synthesized and the structures of the new compounds were established on the basis of ¹H NMR, Mass (ES/MS), elemental analysis, and melting point. In-vitro antibacterial activity (MIC activity) was evaluated and compared with standard drugs ciprofloxacin, sparfloxacin, and trovafloxacin. Most of the compounds in this new series have shown moderate antibacterial activity against both Gram-positive and Gram-negative organisms.

Full text of DOI:10.1002/jhet.221

January 2010
Synthesis and Anti-bacterial Activity of New Series of 4-
(Substituted biphenyl-4-yl)-6-methyl-2-oxo/thioxo-1,2,3,
4-tetrahydro-pyrimidine-5-carboxylic Acid Ethyl Ester
33
Rahul R. Nagawade and Devanand B. Shinde*
Department of Chemical Technology, Dr. Babasaheb Ambedkar Marathwada University,
Aurangabad 431004, Maharashtra, India
*E-mail: devanandshinde@yahoo.com
Received October 5, 2008
DOI 10.1002/jhet.221
Published online 21 December 2009 in Wiley InterScience (www.interscience.wiley.com).
New series of 4-(substituted biphenyl-4-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic
acid ethyl ester and 4-(substituted biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-pyrimidine-5-car-
boxylic acid ethyl ester has been synthesized and the structures of the new compounds were established
1
on the basis of H NMR, Mass (ES/MS), elemental analysis, and melting point. In-vitro antibacterial ac-
tivity (MIC activity) was evaluated and compared with standard drugs ciprofloxacin, sparfloxacin, and
trovafloxacin. Most of the compounds in this new series have shown moderate antibacterial activity
against both Gram-positive and Gram-negative organisms.
J. Heterocyclic Chem., 47, 33 (2010).
INTRODUCTION
terial agents with activity against Gram-positive bacte-
ria. Linezolid [7] is well known as first promising candi-
date of oxazolidinone and works effectively against
numerous serious Gram-positive human pathogens
caused by MRSA and VRE. Quinolines and naphthyri-
dines are also emerging as a new class of synthetic anti-
bacterial agents.
Numerous antibiotics have been prescribed and found
to be effective on various infectious disorders. However,
the appearance of multidrug-resistant Gram-positive bac-
teria, in particular, methicillin-resistant Staphylococcus
aureus (MRSA) and vancomycin-resistant Enterococci
(VRE) is causing a serious menace. Moreover, the emer-
gence of vancomycin-resistant MRSA can be anticipated
in foreseeable future. For the treatment of these intracta-
ble infections, a new anti-infectious agent is needed.
The synthetic antibiotics include the sulphonamide
drugs, nitrofuran derivative, pyridine- carboxylic acid
analogues, fluoroquinolones, and oxazolidinones. The
semi-synthetic antibiotics include the penicillins, cepha-
losporins, tetracyclines, and macrolides. Among them,
the sulphonamide drugs, nitrofuran derivatives, penicil-
lins, and tetracyclines are scarcely used in clinical ther-
apy. Quinolone antibiotics are widely prescribed drugs
because of their safety, good tolerance, broad antibacte-
rial spectrum, and less resistance [1–4]. Macrolide anti-
biotics, including Erythromycin and related compounds,
continue to be an important therapeutic class against
Gram-positive organisms, with second generation
macrolides such as Clarithromycin and Azithromycin
being widely prescribed due to their efficacy, safety,
and lack of serious side effects [5]. Oxazolidinone anti-
bacterial agents [6] are newer class of synthetic antibac-
•
Dihydropyrimidones and their thione analogues
have been reported to exhibit wide range of biolog-
ical activities such as antiviral, antitumor agents,
anti-carcinogenic, anti-inflammatory, analgesic, and
most important anti-hypertensive activity. Dihydro-
pyrimidinones (DHPMS) have now been recog-
nized as vital drugs in the antihypertensive
treatment as well as calcium channel blockers, a-
1a-antagonists, and neuropeptide Y (NPY) antago-
nists [8]. Some of them are batzeladine alkaloids,
which have been found to be potent HIV gp 120-
CD4 inhibitors [9]. DHPMS and their sulfur ana-
logues are pharmacologically important because of
their antibacterial, antitumor, and anti-inflammatory
properties [10]. The biological activity of some
recently isolated alkaloids has also been attributed
to the presence of dihydropyrimidinone moiety in
the corresponding molecule [11]. Since dihydropyr-
imidones and thiones have been reported to exhibit
wide range of biological activity and so far none of
C
V
2009 HeteroCorporation

34
R. R. Nagawade and D. B. Shinde
Vol 47
Scheme 1
•
them have been evaluated for anti-bacterial activity,
we decided to synthesise new series of dihydropyri-
midones and thiones and evaluate them for anti-
bacterial activity.
Oxazolidinones,
a
new class of antibacterial
agent has many promising candidates with biaryl
moiety [15]. The excellent in vitro antibacterial
activity (MIC activity) has been attributed because
of biaryl part and accordingly new series of biaryl
dihydropyrimidones and thiones has been
synthesized.
•
In 1893, Biginelli [12] reported the first synthesis
of DHPMS by a simple one-pot condensation reac-
tion of ethyl acetoacetate, benzaldehyde, and urea.
In the following decades, the original cycloconden-
sation reaction had been extended widely to include
variation in all three components, allowing access
to a large number of multifunctionalized DHPMS
derivatives. However, it suffers from low yields of
the product particularly in the case of substituted
aromatic and aliphatic aldehydes. Recently, several
methods have been reported for preparing dihydro-
pyrimidines using different lewis acid such as
BF3.OEt2, LaCl3, La(OTf)3, Yb(OTf)3 ZnCl2,
ZnBr2, ZrCl4, BiCl3, Bi(OTf)3, LiBr, LiClO4,
Mn(OAc)3, CAN, FeCl3.6H2O, NiCl2.6H2O,
etc.[13] as well as protic acids such as H2SO4,
HOAc, conc. HCl [14] as promoters.
Herein, we describe the synthesis, characterization,
and biological evaluation of new series of 4-(substituted
biphenyl-4-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimi-
dine-5-carboxylic acid ethyl ester and 4-(substituted
biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-py-
rimidine-5-carboxylic acid ethyl ester as potential anti-
bacterials along with their in vitro biological activity
(MIC activity). The synthesis of [4-(substituted
biphenyl-4-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimi-
dine-5-carboxylic acid ethyl ester and 4-(substituted
biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-py-
rimidine-5-carboxylic acid ethyl ester is outlined in
Scheme 1.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

January 2010 Synthesis and Anti-Bacterial Activity of New Series of 4-(Substituted biphenyl-4-yl)-
6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic Acid Ethyl Ester
35
Scheme 2
Scheme 4
compounds are isolated as respective ethyl esters (4a–
4h, Scheme 1). The benzenesulphonamido side chain
was incorporated in biaryl aldehyde since sulphonamides
have been reported to exhibit good antibacterial activity.
However, during the reaction, the benzenesulphonamido
portion of biaryl aldehyde was hydrolysed to acid and
finally isolated as ethyl ester (4g, 4h, Scheme 1). The
Biginelli condensation of biaryl aldehyde, ethylacetoace-
tate, and urea is clean and high yielding (60–70% yield)
when compared with thiourea, where the yields are
between 45 and 60%.
The synthesis is achieved in two parts: first part
involves the synthesis of differentially substituted biaryl
aldehydes and the second part involves Biginelli con-
densation of these biaryl aldehydes with ethylacetoace-
tate and urea or thiourea to afford the desired com-
pounds. The biaryl aldehydes 1a (40-formyl-biphenyl-3-
carboxylic acid), 1b (40-formyl-biphenyl-2-yl-acetic
acid), and 1c (40-formyl-biphenyl-4-yl-acetic acid) have
been synthesized by Suzuki coupling of 4-formylphenyl-
boronic acid with respective aryl bromide using bis(tri-
phenylphosphine) palladium(II) chloride as a catalyst
and cesium carbonate as a base in dioxane: water as sol-
vent at reflux temperature (Schemes 2–4).
The new 4-(substituted-biphenyl-4-yl)-6-methyl-2-oxo/
thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic
acid
ethyl esters prepared above were tested in vitro versus a
panel of Gram-positive and Gram-negative clinical iso-
lates. Minimum inhibitory concentration (MIC) was
determined by standard agar dilution method as per
NCCLS guidelines and the values are shown in Table 1.
The data of ciprofloxacin, sparfloxacin, and trovafloxacin
were used as reference standards.
N-[2-(40-Formyl-biphenyl-2-yloxy)-acetyl]-benzene-
sulfonamide (1d). The synthesis starts with alkylation
of 3-bromo phenol (i) with chloroacetic acid in water
using sodium hydroxide as base to afford (2-bromo-phe-
noxy)-acetic acid (ii, CAS#1798-99-8). Second step
involves reaction of compound ii (acid chloride) with
benzene sulphonamide in DCM using triethylamine as a
base to afford N-[2-(2-bromo-phenoxy)-acetyl]-benzene-
sulfonamide (iii). Third step involves Suzuki coupling
of compound iii with 4-formylphenylboronic acid using
bis(triphenyl-phosphine)palladium(II) chloride as a cata-
lyst and cesium carbonate as a base in dioxane: water at
reflux temperature to afford the desired biaryl aldehyde
1d (Scheme 5).
Second part of synthesis involves Biginelli condensa-
tion of these biaryl aldehydes (1a, 1b, 1c, and 1d) with
ethylacetoacetate (2) and urea/thiourea (3) in ethanol
using catalytic HCl to afford the desired dihydropyrimi-
dones and thiones (4a–4h, Scheme 1). Since the reaction
is carried out with catalytic HCl in ethanol, all the final
Results of biological evaluation. Most of the com-
pounds in the series have shown moderate antibacterial
activity against both Gram-positive and Gram-negative
strains, except for Pseudomonas aeruginosa and E. fae-
cium, where all the tested compounds were inactive
(MIC > 32 lg/ml) in comparison with ciprofloxacin,
sparfloxacin, and trovafloxacin as reference standards. In
all the cases, the thioxo analogues have shown one-fold
better activity with respect to their oxo counterparts.
In summary, the synthesis of new 4-(substituted-
biphenyl-4-yl)-6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic acid ethyl esters has been
described. Most of the compounds in the series have
shown moderate antibacterial activity against S. aureus,
S. epidermis, E. coli, and Klebsiella species as compared
to ciprofloxacin, sparfloxacin, and trovafloxacin. Since
the preliminary series of novel dihydropyrimidones and
thiones have shown moderate antibacterial activity, the
possibility remains that more structural variation might
change/ improve the activity profile. In connection with
this notion, we point out for the first time dihydropyri-
midones and their thione analogues as potential antibac-
terial agents and suggest that the further study is
warranted.
Scheme 3
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

36
R. R. Nagawade and D. B. Shinde
Vol 47
Scheme 5
40-Formyl-biphenyl-3-carboxylic acid (1a). To a stirred so-
lution of 3-bromobenzoic acid (1 g, 4.98 mmol) in dioxane:
water (20 mL, 4:1) was added cesium carbonate (4.85 g, 14.92
mmol) followed by addition of 4-formylphenylboronic acid
(0.90 g, 5.96 mmol) and the resulting solution was stirred and
degassed under nitrogen for 15 min. Bis(triphenylphosphine)
palladium(II) chloride (0.17 g, 0.24 mmol) was added and the
reaction mixture was stirred at reflux temperature for 10 h. Af-
ter completion (monitored by TLC, 1:9 MeOH: CHCl3 as
EXPERIMENTAL
Melting points were determined on Quality Precise apparatus
1
and are uncorrected. H NMR spectra were recorded on Bruker
400-MHz spectrometer. Chemical shifts are reported in d units
(ppm) relative to TMS as internal standard. Electron spray ioni-
zation mass spectra (ES-MS) were recorded on Water-Micro-
mass Quattro-II spectrometer. All the solvents and reagents used
were of AR grade and were used without further purification.
Table 1
Minimum inhibitory concentration (lg/mL) of 4-(substituted-biphenyl-4-yl)-6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid
ethyl ester.
P. aeruginosa (n ¼ 26)
S. aureus (n ¼ 80)
E. coli (n ¼ 54)
S. epidermidis (n ¼ 33)
Comp.
MIC 50
MIC 90
Range
MIC
MIC
Range
MIC 50
MIC 90
Range
MIC50
MIC 90
Range
4a
4b
4c
4d
4e
4f
4g
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
1
16
8
>32
>16
>32
>16
>32
>16
>32
>16
4
8–32
4–>32
8–32
8
8
>16
>16
>16
>16
>16
>16
>16
>16
4–>32
2–>32
4–>32
2–>32
4–>32
2–>32
4–>32
2–>32
16
8
>32
>16
>32
>16
>32
>16
>32
>16
4
8–32
4–>32
8–32
16
8
16
8
16
8
1
8
16
8
16
8
16
8
1
4–>32
8–32
8
8
4–>32
8–32
4–>32
8–32
4–>32
0.5–8
0.5–4
0.25–4
8
8
4–>32
8–32
4h
8
4–>32
0.5–8
0.5–4
0.25–4
Cipro.
Spar.
Trova.
0.25
1.0
0.12–4
0.25–4
0.06–4
0.007
0.007
0.002
0.015
0.03
0.015
0.003–0.03
0.003–0.03
0.003–0.03
2
1
0.5
2
1
0.5
2
0.25
1
1
1
Klebsiella sp. (n ¼ 24)
E. faecium (n ¼ 16)
E. faecalis (n ¼ 24)
MIC 50
MIC 90
Range
MIC 50
MIC 90
Range
MIC 50
MIC 90
Range
4a
4b
4c
4d
4e
4f
4g
8
>32
>16
>32
>16
>32
>16
>32
>16
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
Inactive (>32)
>16
8
8
8
8
8
8
8
8
2
1
1
>32
>16
>32
>16
>32
>16
>32
>16
8
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
2–>32
0.5–16
0.5–8
8
8
8
8
8
8
8
4h
Cipro
Spar.
Trova.
0.01
0.01
0.025
0.02
0.02
0.1
0.01–0.5
0.01–0.25
0.06–0.4
>16
>16
16
NA
NA
NA
>16
16
4
2
0.5–4
n ¼ number of strains tested.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

January 2010 Synthesis and Anti-Bacterial Activity of New Series of 4-(Substituted biphenyl-4-yl)-
6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic Acid Ethyl Ester
37
mobile phase), solvent was removed under reduced pressure
and diluted with water. The aqueous phase was acidified upto
pH 4 by dilute HCl and then extracted with ethyl acetate (3 ꢀ
25 mL). The combined organic layers were dried (Na2SO4)
and concentrated under reduced pressure. The crude compound
was purified by column chromatography (60–120 mesh silica
gel) eluting with methanol: chloroform (2:98) to afford the
title compound 1a as light yellow solid (0.70 g, 65% yield).
1H NMR (400 MHz, DMSO-d6) d 7.65 (t, 1H), 7.95–7.97 (d, J
¼ 8.08 Hz, 2H), 8.00–8.03 (m, 4H), 8.26 (s, 1H), 10.07 (s,
1H), 13.20 (s, 1H, COOH); Mass (m/z): 228 (M þ H, 100%).
(40-Formyl-biphenyl-2-yl)-acetic acid (1b). To a stirred so-
lution of 2-bromophenylacetic acid (1 g, 4.65 mmol) in diox-
ane: water (20 mL, 4:1) was added cesium carbonate (4.53 g,
13.95 mmol) followed by addition of 4-formylphenylboronic
acid (0.84 g, 5.58 mmol) and the resulting solution was stirred
and degassed under nitrogen for 15 min. Bis(triphenyl-phos-
phine)palladium(II) chloride (0.16 g, 0.23 mmol) was added
and the reaction mixture was stirred at reflux temperature for 8
h. After completion (monitored by TLC, 1:9 MeOH: CHCl3 as
mobile phase), solvent was removed under reduced pressure
and diluted with water. The aqueous phase was acidified upto
pH 4 by dilute HCl and then extracted with ethyl acetate (3 ꢀ
25 mL). The combined organic layers were dried (Na2SO4)
and concentrated under reduced pressure. The crude compound
was purified by column chromatography (60–120 mesh silica
gel) eluting with methanol: chloroform (2:98) to afford the
title compound 1b as yellow solid (0.49 g, 45% yield). M.p.
171–173ꢁC; 1H NMR (400 MHz, DMSO-d6) d 3.54 (s, 2H),
7.35–7.40 (m, 2H), 7.53 (d, J ¼ 8.16 Hz, 2H), 7.89–7.92 (m,
2H), 7.96–8.02 (m, 2H), 10.07 (s, 1H), 12.31 (bs, 1H, COOH);
Mass (m/z): 241 (M þ H, 100%).
organic layers were dried (Na2SO4) and concentrated under
reduced pressure to afford the title compound ii as yellow
solid (4.67 g, 70% yield). 1H NMR (400 MHz, DMSO-d6) d
4.72 (s, 2H), 6.92–6.95 (m, 1H), 7.12–7.15 (m, 2H), 7.24 (t, J
¼ 7.84, 1.96 Hz, 1H), 13.09 (s, 1H, COOH); Mass (m/z): 232
(M þ H, 100%).
N-[2-(3-Bromo-phenoxy)-acetyl]-benzenesulfonamide (iii). A
stirred solution of compound ii (2.5 g, 10.82 mmol) in SOCl2
(15 mL) was refluxed under nitrogen atmosphere for 3 h. After
completion, solvent was removed completely under reduced
pressure to afford the acid chloride. To this acid chloride solu-
tion dissolved in DCM (25 mL) was added triethylamine (3
mL, 21.64 mmol) followed by addition of benzenesulphona-
mide (2.03 g, 12.98 mmol) under cooling. After addition, the
reaction mixture was stirred at room temperature for additional
2 h. After completion, the reaction mixture was quenched with
water (25 mL) and the organic phase was separated, dried
(Na2SO4), and concentrated under reduced pressure. The crude
compound was purified by column chromatography (60–120
mesh silica gel) eluting with 1:1 ethyl acetate: hexane to
afford the title compound iii (1.80 g, 45% yield). M.p. 207–
1
210ꢁC; H NMR (400 MHz, DMSO-d6) d 4.70 (s, 2H), 6.81–
6.84 (dd, J ¼ 2.32, 1.84 Hz, 1H), 7.02 (t, J ¼ 2.2, 1.96 Hz,
1H), 7.12 (d, J ¼ 8.08 Hz, 1H), 7.19 (m, 1H), 7.63 (m, 2H),
7.72 (m, 1H), 7.92 (m, 2H), 12.49 (bs, 1H, COOH); Mass (m/
z): 371 (M þ H, 100%).
N-[2-(40-Formyl-biphenyl-3-yloxy)-acetyl]-benzenesulfona-
mide (1d). To a stirred solution of N-[2-(3-bromo-phenoxy)-
acetyl]-benzenesulfonamide (iii) (1 g, 2.70 mmol) in dioxane:
water (20 mL, 4:1) was added cesium carbonate (2.63 g, 8.10
mmol) followed by addition of 4-formylphenylboronic acid
(0.49 g, 3.24 mmol) and the resulting solution was stirred and
degassed under nitrogen for 15 min. Bis(triphenylphosphine)pal-
ladium(II) chloride (0.094 g, 0.13 mmol) was added and the
reaction mixture was stirred at reflux temperature for 10 h. Af-
ter completion (monitored by TLC, 1:9 MeOH: CHCl3 as mo-
bile phase), solvent was removed under reduced pressure and
diluted with water. The aqueous phase was acidified upto pH 4
by dilute HCl and then extracted with ethyl acetate (3 ꢀ 25
mL). The combined organic layers were dried (Na2SO4) and
concentrated under reduced pressure. The crude compound was
purified by column chromatography (60–120 mesh silica gel)
eluting with methanol: chloroform (1:99) to afford the title com-
pound 1d as yellow solid (0.53 g, 50% yield). M.p. 143–145ꢁC;
1H NMR (400 MHz, DMSO-d6) d 4.77 (s, 2H), 6.88 (d, J ¼
7.84 Hz, 1H), 7.13 (s, 1H), 7.32–7.39 (m, 2H), 7.55–7.59 (m,
2H), 7.61–7.65 (m, 1H), 7.81 (d, J ¼ 8.08 Hz, 2H), 7.92 (d, J
¼ 7.80 Hz, 2H), 7.99 (d, J ¼ 8.12 Hz, 1H), 10.06 (s, 1H),
12.52 (bs, 1H, COOH); Mass (m/z): 396 (M þ H, 100%).
General procedure for synthesis of compounds 4a to
4h. To a stirred solution of ethyl acetoacetate (2) (2 mmol) in
ethanol was added biaryl aldehyde (1a-1d) (2 mmol), urea/thi-
ourea (3) (3 mmol) followed by addition of 0.5 mL of 6N
HCl. The resulting solution was stirred at reflux for 16 h. After
completion, solvent was removed under reduced pressure and
the residue obtained was extracted with ethyl acetate. The
combined organic layers were dried (Na2SO4) and concen-
trated under reduced pressure. The crude compound was puri-
fied by column chromatography (60–120 mesh silica gel) elut-
ing with ethyl acetate: hexane (1:1) to afford the title com-
pounds 4a–4h as solid.
(40-Formyl-biphenyl-4-yl)-acetic acid (1c). To a stirred so-
lution of 4-bromophenylacetic acid (1 g, 4.65 mmol) in diox-
ane: water (20 mL, 4:1) was added cesium carbonate (4.53 g,
13.95 mmol) followed by addition of 4-formylphenylboronic
acid (0.84 g, 5.58 mmol) and the resulting solution was stirred
and degassed under nitrogen for 15 min. Bis(triphenyl-phos-
phine)palladium(II) chloride (0.16 g, 0.23 mmol) was added
and the reaction mixture was stirred at reflux temperature for
12 h. After completion (monitored by TLC, 1:9 MeOH:
CHCl3 as mobile phase), solvent was removed under reduced
pressure and diluted with water. The aqueous phase was acidi-
fied upto pH 4 by dilute HCl and then extracted with ethyl ac-
etate (3 ꢀ 25 mL). The combined organic layers were dried
(Na2SO4) and concentrated under reduced pressure. The crude
compound was purified by column chromatography (60–120
mesh silica gel) eluting with methanol: chloroform (2:98) to
afford the title compound 1c as yellow solid (0.65 g, 60%
1
yield). H NMR (400 MHz, DMSO-d6) d 3.64 (s, 2H), 7.40 (d,
J ¼ 8 Hz, 2H), 7.72 (d, J ¼ 7.96 Hz, 2H), 7.91 (d, J ¼ 8.08
Hz, 2H), 7.99 (d, J ¼ 7.96 Hz, 2H), 10.05 (s, 1H), 12.41 (s,
1H, COOH); Mass (m/z): 241 (M þ H, 100%).
(3-Bromo-phenoxy)-acetic acid (ii). To a stirred solution of
3-bromo phenol (i) (5 g, 28 mmol) in water (50 mL) was
added NaOH (1.34 g, 33.6 mmol) followed by addition of
chloroacetic acid (2.89 g, 30.8 mmol) and the resulting solu-
tion was refluxed for 2 h. After completion, the reaction mix-
ture was acidified upto pH 4 by 6N HCl and the resulting mix-
ture was extracted ethyl acetate (3 ꢀ 50 mL). The combined
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

38
R. R. Nagawade and D. B. Shinde
Vol 47
4-(30-Ethoxycarbonyl-biphenyl-4-yl)-6-methyl-2-oxo-1,2,3,4-
4-(30-Ethoxycarbonylmethoxy-biphenyl-4-yl)-6-methyl-2-
oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl
ester (4g). Yellow solid; 50% yield; M.p. 151–152ꢁC, 1H NMR
(400 MHz, DMSO-d6) d 1.12 (t, J ¼ 7.12, 7.04 Hz, 3H), 1.20 (t,
J ¼ 7.20, 7.12 Hz, 3H), 2.26 (s, 3H), 3.97–4.03 (q, J ¼ 6.96,
7.08 Hz, 2H), 4.14–4.20 (q, J ¼ 7.12, 7.12 Hz, 2H), 4.85 (s, 2H),
5.17 (d, J ¼ 2.96 Hz, 1H), 6.89–6.92 (dd, J ¼ 1.96, 1.92 Hz
1H), 7.16 (bs, 1H), 7.23 (d, J ¼ 7.92 Hz, 1H), 7.30 (d, J ¼ 8.20
Hz, 2H), 7.36 (t, J ¼ 7.88, 8.00 Hz, 1H), 7.62 (d, J ¼ 8.24 Hz,
2H), 7.79 (s, 1H, NH), 9.25 (s, 1H, NH); Mass (m/z): 439 (M þ
H, 100%); Anal. Calcd. for C24H26N2O6: C, 65.74; H, 5.98; N,
6.39. Found: C, 66.02; H, 5.93; N, 6.43.
tetrahydro-pyrimidine-5-carboxylic acid ethyl ester (4a). Light
yellow solid; 65% yield; M.p. 128–130ꢁC; 1H NMR (400
MHz, DMSO-d6) d 1.12 (t, J ¼ 7.08, 7.08 Hz, 3H), 1.33 (t, J
¼ 7.12, 7.08 Hz, 3H), 2.26 (s, 3H), 3.98–4.03 (q, J ¼ 7.08,
7.16 Hz, 2H), 4.31–4.37 (q, J ¼ 7.04, 7.16 Hz, 2H), 5.20 (d, J
¼ 2.96 Hz, 1H), 7.35 (d, J ¼ 8.24 Hz, 2H), 7.59–7.63 (m,
2H), 7.66 (d, J ¼ 8.28 Hz, 2H), 7.91–7.95 (m, 2H), 8.15 (bs,
1H, NH), 9.25 (s, 1H, NH); Mass (m/z): 409 (M þ H, 100%);
Anal. Calcd. for C23H24N2O5: C, 67.63; H, 5.92; N, 6.86.
Found: C, 67.88; H, 5.97; N, 6.92.
4-(30-Ethoxycarbonyl-biphenyl-4-yl)-6-methyl-2-thioxo-
1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl
ester (4b). Yellow solid, 50% yield; M.p. 141–142ꢁC; 1H
NMR (400 MHz, DMSO-d6) d 1.15 (t, J ¼ 7.12, 7.08 Hz,
3H), 1.33 (t, J ¼ 7.12, 7.04 Hz, 3H), 2.40 (s, 3H), 4.02–4.06
(q, J ¼ 7.12, 7.12 Hz, 2H), 4.31–4.36 (q, J ¼ 7.08, 7.08 Hz,
2H), 5.36 (s, 1H), 7.27 (d, J ¼ 8.16 Hz, 2H), 7.55–7.64 (m,
5H), 7.90–7.94 (m, 2H), 8.14 (s, 1H); Mass (m/z): 425 (M þ
H, 100%); Anal. Calcd. for C23H24N2O4S: C, 65.07; H, 5.70;
N, 6.60. Found: C, 64.84; H, 5.67; N, 6.66.
4-(20-Ethoxycarbonylmethyl-biphenyl-4-yl)-6-methyl-2-
oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl
ester (4c). Off-white solid; 60% yield; M.P. 94–96ꢁC; 1H
NMR (400 MHz, DMSO-d6) d 1.05 (t, J ¼ 6.76, 6.68 Hz,
3H), 1.15 (t, J ¼ 6.48, 5.72 Hz, 3H), 2.26 (s, 3H), 3.58 (s,
2H), 3.90–3.94 (q, J ¼ 6.78, 6.92 Hz, 2H), 3.99–4.03 (q, J ¼
7.02, 7.02 Hz, 2H), 5.19 (s, 1H), 7.21–7.33 (m, 7H), 7.62 (m,
1H), 7.79 (s, 1H), 9.23 (s, 1H); Mass (m/z): 423 (M þ H,
100%); Anal. Calcd. for C24H26N2O5: C, 68.23; H, 6.20; N,
6.63. Found: C, 68.57; H, 6.25; N, 6.68.
4-(30-Ethoxycarbonylmethoxy-biphenyl-4-yl)-6-methyl-2-
thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic
acid
ethyl ester (4h). Yellow solid; 40% yield; M.p. 163–165ꢁC,
1H NMR (400 MHz, CDCl3) d 1.19 (t, J ¼ 7.12, 7.12 Hz,
3H), 1.29 (t, J ¼ 7.12, 7.12 Hz, 3H), 2.37 (s, 3H), 4.10–4.12
(q, J ¼ 7.08, 7.12 Hz, 2H), 4.25–4.30 (q, J ¼ 7.12, 7.16 Hz,
2H), 4.66 (s, 2H), 5.44 (d, J ¼ 2.40 Hz, 1H), 6.87 (d, J ¼
8.12 Hz, 1H), 6.99 (d, J ¼ 7.36 Hz, 1H), 7.10 (s, 1H), 7.17 (d,
J ¼ 7.92 Hz, 1H), 7.32–7.35 (m, 4H); Mass (m/z): 455 (M þ
H, 100%); Anal. Calcd. for C24H26N2O5S: C, 63.42; H, 5.77;
N, 6.16. Found: C, 63.11; H, 5.83; N, 6.23.
MIC determination. Bacterial isolates. The strains were
collected from major hospitals of India during the period
2003–2006 and were identified by standard laboratory
procedures.
MIC was determined by standard agar dilution method as
per CLSI (formerly, NCCLS) guidelines (Approved Standard
M7-A6, vol. 23, 2003) on Mueller-Hinton agar containing se-
rial two-fold dilutions of the compounds. Strains were grown
in Tryptic Soya Broth (TSB, HiMedia, India) for 18–24 h. The
overnight grown cultures were diluted appropriately so that the
final density is approximately 107 CFU/mL. A portion of this
diluted broth was transferred to seed block of a multipoint
inoculator (Applied Quality Services, United Kingdom). The
inoculating pins were standardized to inoculate 1–2 lL of this
broth, so that the final CFU was 1 ꢀ 104–5 ꢀ 104 CFU/ spot.
The inoculated plates were allowed to stand until the moisture
in the inoculum spot has been absorbed in the media.
The inoculated plates were inverted and incubated for 18–24 h
at 35ꢁC in an ambient air incubator (Newtronic, India). After the
completion of incubation period, the plates were read visually.
MIC was defined as the lowest concentration that inhibited
the growth of strain completely. Drug free plates were used to
ensure the growth of strains. Staphylococcus aureus ATCC
25923, Escherichia coli ATCC 25922 and Pseudomonas aeru-
ginosa ATCC 27853 were used as quality control strains for
each run of MIC determination.
4-(20-Ethoxycarbonylmethyl-biphenyl-4-yl)-6-methyl-2-thi-
oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl
1
ester (4d). Light yellow solid; 50% yield; M.p. 99–101ꢁC, H
NMR (400 MHz, DMSO-d6) d 1.04 (t, J ¼ 7.16, 7.08 Hz, 3H),
1.12 (t, J ¼ 7.08, 7.04 Hz, 3H), 2.30 (s, 3H), 3.58 (s, 2H), 3.89–
3.95 (q, J ¼ J ¼ 7.00, 7.04 Hz, 2H), 4.02-4.05 (q, J ¼ 7.08, 7.12
Hz, 2H), 5.21 (d, J ¼ 3.60 Hz, 1H), 7.20–7.26 (m, 5H), 7.31–
7.34 (m, 3H), 9.71 (s, 1H, NH), 10.39 (s, 1H, NH); Mass (m/z):
439 (M þ H, 100%); Anal. Calcd. for C24H26N2O4S: C, 65.73;
H, 5.98; N, 6.39. Found: C, 65.41; H, 5.93; N, 6.35.
4-(40-Ethoxycarbonylmethyl-biphenyl-4-yl)-6-methyl-2-oxo-
1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid ethyl ester
(4e). Yellow solid; 65% yield; M.p. 146–148ꢁC, 1H NMR
(400 MHz, DMSO-d6) d 1.12 (t, J ¼ 7.08, 7.08 Hz, 3H), 1.19
(t, J ¼ 7.08, 7.08 Hz, 3H), 2.26 (s, 3H), 3.69 (s, 2H), 3.97–
4.03 (q, J ¼ 7.08, 7.04 Hz, 2H), 4.06–4.11 (q, J ¼ 7.16, 7.08
Hz, 2H), 5.17 (d, J ¼ 3.08 Hz, 1H), 7.30–7.34 (m, 4H), 7.60
(m, 4H), 7.78 (s, 1H, NH), 9.24 (s, 1H, NH); Mass (m/z): 423
(M þ H, 100%); Anal. Calcd. for C24H26N2O5: C, 68.23; H,
6.20; N, 6.63. Found: C, 67.95; H, 6.16; N, 6.59.
REFERENCES AND NOTES
4-(40-Ethoxycarbonylmethyl-biphenyl-4-yl)-6-methyl-2-
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thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic
acid
ethyl ester (4f). Yellow solid; 55% yield; M.p. 134–136ꢁC,
1H NMR (400 MHz, DMSO-d6) d 1.06-1.20 (m, 6H), 2.28 (s,
3H), 3.67 (s, 2H), 3.99–4.07 (m, 4H), 5.18 (s, 1H), 7.25–7.32
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January 2010 Synthesis and Anti-Bacterial Activity of New Series of 4-(Substituted biphenyl-4-yl)-
6-methyl-2-oxo/thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic Acid Ethyl Ester
39
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