Synthesis and biological activity of ethyl 2-(substituted benzylthio)-4-(3-(ethoxycarbonyl)biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine- 5-carboxylate derivatives

Article abstract of DOI:10.1002/ardp.201100133

In the present study, a new series of ethyl 2-(substituted benzylthio)-4-(3-(ethoxycarbonyl)-biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine- 5-carboxylate derivatives was synthesized. The newly synthesized compounds were characterized by ¹H-NMR,

Full text of DOI:10.1002/ardp.201100133

Arch. Pharm. Chem. Life Sci. 2012, 345, 163–168
163
Full Paper
Synthesis and Biological Activity of Ethyl 2-(substituted
benzylthio)-4-(30-(ethoxycarbonyl)biphenyl-4-yl)-6-methyl-1,4-
dihydropyrimidine-5-carboxylate Derivatives
Suresh Maddila and Sreekantha B. Jonnalagadda
School of Chemistry, University of Kwa-Zulu Natal, Durban, South Africa
In the present study, a new series of ethyl 2-(substituted benzylthio)-4-(30-(ethoxycarbonyl)-biphenyl-4-
yl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate derivatives was synthesized. The newly synthesized
compounds were characterized by 1H-NMR, mass and C, H, N analyses. All newly synthesized
compounds were screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas
aeruginosa, Streptococcus pyogenes and Klebsiella pneumoniae) and antifungal (Aspergillus flavus, Aspergillus
fumigatus, Candida albicans, Penicillium marneffei and Trichophyton mentagrophytes) activity. The results
revealed that all synthesized compounds have a significant biological activity against the tested
microorganisms. Compounds 8a, 8b, 8c, 8e, 8f, 8i, and 8j exhibited good antimicrobial activity.
Keywords: Antibacterial activities / Antifungal activities / Biphenyl pyrimidine
Received: April 8, 2011; Revised: June 27, 2011; Accepted: July 6, 2011
DOI 10.1002/ardp.201100133
Introduction
the existing oxygen atom bonded to C-2 in uridine base [9].
Due this reason, 2-TPs have attracted substantial interest of
synthetic-biochemists [10]. A European patent [11] revealed
the scope of 2-TP derivatives in preparation of cardiotonic
drugs. Pathak et al. have evaluated and reported the existence
of primary activity of 2-TP derivatives against Mycobacterium
tuberculosis (Mtb) [12].
Heterocycles are ubiquitous among pharmaceutical com-
pounds [1]. Pyrimidine moiety is an important class of N-
containing heterocyclics, which are widely used as key build-
ing blocks for pharmaceutical agents. Pyrimidine moiety
exhibits a wide spectrum of pharmacophores as it acts as
bactericidal, fungicidal [2], analgesic [3], antihypertensive [4]
and antitumor agent [5]. Among the pyrimidine containing
heterocyclics, thiouracils are used as for antiinflammatory
and virucidal agents [6]. Also, preclinical data from literature
survey indicate continuing research in poly substituted pyr-
imidines as potential antitumor agents [7]. The biological and
synthetic significance places this scaffold at a prestigious
position in medicinal chemistry research. The key role pyr-
imidines play in cellular processes has made them valuable
leads for drug discovery. Another important class of pyrimi-
dine is 2-thiopyrimidine (2-TP) and its derivatives, which are
also well known as 2-mercaptopyrimidine compounds [8]. In
2-TP ring sulfur atom serves as an interesting replacement for
Biginelli, in 1893, reported one-step synthesis of 3,4-dihy-
dropyrimidin-2(1H)-one by three-component condensation of
aldehydes, ethyl acetoacetate and urea in alcohol using
strong mineral acid [13]. These Biginelli compounds
possess several pharmaceutical properties like antibacterial,
antiviral, antiinflammatory, antihypertensive and antitumor
agents [14]. In continued quest of new antimicrobial agents,
we designed and synthesized novel biphenylpyrimidines
having substituted benzylthio groups. Structures of the prod-
ucts were characterized by 1H-NMR, LCMS mass spectrometry
and elemental analysis. Results of biological activities
indicate that some compounds possess potential antimicro-
bial activity.
Results and discussion
Correspondence: Prof. Sreekantha B. Jonnalagadda, School of
Chemistry, University of KwaZulu-Natal, Westville Campus, P Bag X
54001, Durban 4000, South Africa.
E-mail: jonnalagaddas@ukzn.ac.za
Fax: þ2731 260 3091
Chemistry
The synthesis of ethyl 2-(substituted benzylthio)-4-(30-(ethoxy-
carbonyl)biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine-5-
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

164
S. Maddila and S. B. Jonnalagadda
Arch. Pharm. Chem. Life Sci. 2012, 345, 163–168
carboxylate derivatives 8a–j was achieved through the versa-
tile and efficient synthetic route outlined in Scheme 1. The
desired compounds were synthesized as follows. Initially,
when 3-bromobenzoic acid (1) was treated with 4-formylphe-
nylboronic (2) acid in the presence of cesium carbonate and
bis(triphenylphosphine)palladium(II) chloride, it afforded
the corresponding 40-formyl-biphenyl-3-carboxylic acid (3).
Compound 3 reacted with ethyl acetoacetate (4), thiourea
(5) in ethanol and a few drops of HCl to obtain 4-(30-ethoxy-
carbonyl-biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic acid ethyl ester (6) [15]. Finally,
ethyl 2-(substituted benzylthio)-4-(30-(ethoxycarbonyl)biphenyl-
4-yl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate deriva-
tives (8a–j) were synthesized by the reaction of (6), substituted
benzyl halides (7) and potassium carbonate in DMF solution.
Its structural assignment was proved by spectroscopic
analyses. Its 1H-NMR spectrum revealed singlet signals at d
10.20 and 13.10 ppm due to CHO and COOH proton, respect-
ively, beside an aromatic multiplet in the region of d 7.48–
8.50 ppm. Moreover, the LCMS mass spectrum showed m/z at
227 (MþH). The structure of compound 4 was proven by its
analytical and spectral analyses. The LCMS mass spectrum
showed at m/z 425 (MþH). 1H-NMR (DMSO-d6) showed the
protons at d 8.95–9.15 ppm due to 2 NH protons and at d
5.20 ppm due to CH protons. The target molecules (8a–j) were
also proved by their analytical and spectral analyses. 1H-NMR
HO
OH
OH
B
O
Br
O
O
S
(i)
+
CHO
+
+
OEt
H2N
NH2
COOH
5
CHO
2
4
3
1
(ii)
OEt
OEt
R
S
S
O
O
H
N
N
(iii)
NH
NH
CH3
+
Br
R
O
CH3
O
OEt
8 a-j
OEt
7
6
Compound
8a
R
Compound
8f
R
N(CH3)2
Cl
8b
8c
8d
8e
8g
8h
8i
Br
C2H5
CH3
CH(CH3)2
C(CH3)3
NO2
8j
OMe
Reagents and conditions: (i) Pd(PPh3)2Cl2, Cs2CO3, dioxane, reflux, 10 h; (ii) HCl, reflux, 16 h; (iii) DMF, K2CO3,
1 h.
Scheme 1. Synthetic pathway for compounds 8 a–j.
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Arch. Pharm. Chem. Life Sci. 2012, 345, 163–168
Synthesis and Biological Activity of Ethyl
165
(DMSO-d6) showed proton regions at d 3.35 to 3.45, d 5.10 to
5.25 ppm due to NH, SCH2 protons and at d 4.10 to 4.21 ppm
due to CH2 protons.
tored visually and spectrophotometrically. The lowest con-
centration (highest dilution) required to arrest the growth of
bacteria was regarded as minimum inhibitory concen-
trations (MIC). Ciprofloxacin was used as a standard drug.
The diameter of the zone of inhibition and minimum inhibi-
tory concentration values are given in Table 1.
Compounds (8a–j) were screened for their antibacterial
activity against Staphylococcus aureus, Escherichia coli,
Pseudomonas aeruginosa, Klebsiella pneumoniae and Streptococcus
pyogenes by comparing them with standard ciprofloxacin, and
antifungal activity against Aspergillus fumigatus, Aspergillus fla-
vus, Trichophyton mentagrophytes, Penicillium marneffei and
Candida albicans was compared with the standard fungicide
amphotericin. It is interesting to observe that the maximum
compounds had very good antifungal and antibacterial
activity.
The newly synthesized compounds were screened for their
antibacterial activity against Escherichia coli, Staphylococcus aur-
eus, Pseudomonas aeruginosa, Streptococcus pyogenes and Klebsiella
pneumoniae (recultured) bacterial strains by disc diffusion
method [16, 17]. The investigation of antibacterial screening
data revealed that all the tested compounds showed moder-
ate to good bacterial inhibition. The compounds 8a, 8b, 8e,
8f, 8i and 8j showed very good activity against all the bac-
terial strains.
Pharmacological assay
Antibacterial assay
Antifungal assay
A standard inoculum (1–2 ꢀ 107 colony-forming unit (c.f.u)/
cm3 0.5 McFarland standards) was introduced onto the sur-
face of sterile agar plates, and a sterile glass spreader was
used for even distribution of the inoculum. The discs measur-
ing 6.25 mm in diameter were prepared from Whatmann
no.1 filter paper and sterilized by dry heat at 1408C for 1 h.
The sterile disc previously soaked in a known concentration
of the test compounds were placed in nutrient agar medium.
Solvent and growth controls were kept. The plates were
inverted and incubated for 24 h at 378C. The inhibition zones
were measured and compared with the controls. Minimum
inhibitory concentration (MIC) was determined by broth
dilution technique. The nutrient broth, which contained
logarithmic serially two-fold diluted amount of test com-
pound and controls was inoculated with approximately
5 ꢀ 105 c.f.u of actively dividing bacteria cells. The cultures
were incubated for 24 h at 378C and the growth was moni-
Sabourauds agar media was prepared by dissolving 1 g pep-
tone, 4 g D-glucose, and 2 g agar in 100 cm3 distilled water,
and adjusting pH to 5.7 using buffer. Normal saline was used
to make a suspension of spore of fungal strain for lawning. A
loop full of particular fungal strain was transferred to 3 cm3
saline to get a suspension of corresponding species. 20 cm3 of
agar media was poured into each Petri dish. Excess of sus-
pension was decanted and the plates were dried by placing in
a incubator at 378C for 1 h. Using an agar punch, wells
were made and each well was labeled. A control was also
prepared in triplicate and maintained at 378C for 3–4 d. The
inhibition zones in diameter were measured and compared
with the controls. The nutrient broth, which contained
logarithmic serially two-fold diluted amount of test com-
pound and controls was inoculated with approximately
1.6 ꢀ 104-6 ꢀ 104 c.f.u cmꢁ3. The cultures were incubated
for 48 h at 358C and the growth was monitored. The lowest
Table 1. Antibacterial activity of pyrimidine-5-carboxylate derivatives, 8a–j (zone of inhibition).
Compound
no.
Staphylococcus
aureus
Escherichia
coli
Pseudomonas
aeruginosa
Klebsiella
pneumoniae
Streptococcus
pyogenes
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
Standarda
20 (6.25)
23 (6.25)
10 (12.5)
8 (25)
22 (6.25)
21 (6.25)
10 (12.5)
12 (12.5)
21 (6.25)
21 (6.25)
24 (6.25)
25 (6.25)
28 (6.25)
–
23 (6.25)
27 (6.25)
29 (6.25)
15 (25)
–
29 (6.25)
30 (6.25)
–
18 (6.25)
18 (6.25)
17 (6.25)
–
20 (6.25)
20 (6.25)
–
23 (6.25)
21 (6.25)
11 (6.25)
8 (12.5)
24 (6.25)
23 (6.25)
17 (12.5)
8 (25)
9 (25)
32 (6.25)
32 (6.25)
–
21 (6.25)
29 (6.25)
32 (6.25)
33 (6.25)
–
24 (6.25)
26 (6.25)
30 (6.25)
19 (6.25)
21 (6.25)
23 (6.25)
23 (6.25)
24 (6.25)
25 (6.25)
aCiprofloxacin was used as standard. – Indicates bacteria are resistant to the compounds at >100 mg/mL, MIC values are given in
brackets. MIC (mg/mL) ¼ minimum inhibitory concentration, i.e. lowest concentration to completely inhibit bacterial growth. In
parenthesis - Zone of inhibition in mm.
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166
S. Maddila and S. B. Jonnalagadda
Arch. Pharm. Chem. Life Sci. 2012, 345, 163–168
Table 2. Antifungal activity of pyrimidine-5-carboxylate derivatives, 8a–j (zone of inhibition).
Compound
no
Aspergillus
fumigatus
Aspergillus
flavus
Trichophyton
mentagrophytes
Penicillium
marneffei
Candida
albicans
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
Standard
22 (6.25)
8 (25)
22 (6.25)
15 (6.25)
5 (25)
24 (6.25)
11 (12.5)
9 (25)
22 (6.25)
21 (6.25)
25 (6.25)
22 (6.25)
–
20 (6.25)
–
18 (6.25)
21 (6.25)
12 (25)
–
19 (6.25)
26 (6.25)
21 (6.25)
25 (6.25)
12 (12.5)
22 (6.25)
7 (25)
22 (6.25)
–
20 (6.25)
17 (6.25)
17 (6.25)
18 (6.25)
17 (6.25)
18 (6.25)
14 (12.5)
10 (12.5)
19 (6.25)
24 (6.25)
19 (6.25)
25 (6.25)
21 (6.25)
12 (12.5)
23 (6.25)
–
–
21 (6.25)
–
12 (12.5)
20 (6.25)
32 (6.25)
23 (6.25)
9 (25)
23 (6.25)
21 (6.25)
25 (6.25)
– Indicates fungus is resistant to the compounds at >100 mg/mL, MIC values are given in brackets. MIC (mg/mL) ¼ minimum
inhibitory concentration, ie. lowest concentration to completely inhibit fungal growth. Zone of inhibition in mm. Amphotericin
was used as standard.
concentration (highest dilution) required to arrest the
growth of fungus was regarded as minimum inhibitory con-
centrations (MIC). Amphotericin B was used as the standard
drug. The diameter of zone of inhibition and minimum
inhibitory concentration values are given in Table 2.
standard. LCMS mass spectra were recorded on a MASPEC low
resolution mass spectrometer operating at 70 eV.
General procedure for the preparationof 40-formyl-
biphenyl-3-carboxylic acid 3
To a stirred solution of 3-bromobenzoic acid (1 mmol) in diox-
ane/water (20 mL, 4:1) was added cesium carbonate (1.5 mmol)
followed by addition of 4-formylphenylboronic acid (1.1 mmol)
and the resulting solution was stirred and degassed under nitro-
gen for 30 min. Bis(triphenylphosphine) palladium(II) chloride
(1.5 mmol) was added and the reaction mixture was stirred at
reflux temperature for 8 h. After completion (monitored by TLC),
solvent was removed under reduced pressure and diluted with
water. The aqueous phase was acidified by dilute HCl and then
extracted with ethyl acetate (100 mL). The combined organic
layers were dried (Na2SO4) and concentrated under reduced
pressure. The crude compound was purified by column chroma-
tography to afford the 40-formyl-biphenyl-3-carboxylic acid (3) as
pale yellow solid, 65% yield. 1H-NMR (300 MHz, DMSO-d6) 7.48-
8.50 (m, 8H, Ar-H), 10.20 (s, 1H), 13.10 (s, 1H, COOH); LCMS (m/z):
227 (MþH, 100%).
Newly prepared compounds were screened for their anti-
fungal activity against Aspergillus flavus, Aspergillus fumigatus,
Candida albicans, Penicillium marneffei and Trichophyton menta-
grophytes (recultured) in DMSO by serial plate dilution
method [18, 19]. The antifungal screening data showed
moderate to good activity. Compounds 8a, 8c, 8f, 8i and 8j
emerged as very active against all the fungal strains.
Conclusion
In the present study, novel ethyl 2-(substituted benzylthio)-4-
(30-(ethoxycarbonyl)-biphenyl-4-yl)-6-methyl-1,4-dihydropyr-
imidine-5-carboxylate derivatives were synthesized and
evaluated for their antibacterial and antifungal activity.
The investigation of antibacterial screening data reveals
that among the 10 compounds screened, five compounds
showed good antibacterial activity and six compounds
showed fungal inhibition almost equivalent to that of
standard.
General procedure for the preparation of 4-(30-
ethoxycarbonyl-biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-
tetrahydro-pyrimidine-5-carboxylic acid ethyl ester 6
To a stirred solution of ethyl acetoacetate (4) (1 mmol), were
added biaryl aldehyde (1.1 mmol) and thiourea (2 mmol) in
ethanol. It was followed by addition of catalytic amount of
HCl. The resulting solution was stirred at reflux for 12 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 concentrated
under reduced pressure. The crude compound was purified by
column chromatography to afford the 4-(30-ethoxycarbonyl-
biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-pyrimidine-5-
carboxylic acid ethyl ester (6) as solid.
Experimental
Chemistry
All reagents and solvents were purchased and used without
further purification. Melting points were determined on a
Fisher–Johns melting point apparatus and were uncorrected.
Crude products were purified by column chromatography on
silica gel of 60–120 mesh. NMR spectra were recorded on a
Varian 300 MHz spectrometer for 1H-NMR. The chemical shifts
were reported as ppm down field using TMS as an internal
Yellow solid, 50% yield; m.p. 141–1428C; 1H-NMR (300 MHz,
DMSO-d6) d 1.15–1.35 (t, 6H), 2.35 (s, 3H), 4.10–4.40 (q, 4H), 5.20
(s, 1H), 7.10–8.60 (m, 8H, Ar-H), 8.95–9.15 (s, 2H); LCMS (m/z): 425
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Arch. Pharm. Chem. Life Sci. 2012, 345, 163–168
Synthesis and Biological Activity of Ethyl
167
(MþH, 100%); anal. calcd. for C23H24N2O4S: C, 65.07; H, 5.70; N,
(s, 1H), 4.15–4.40 (q, 4H), 5.20 (s, 2H), 6.60–8.75 (m, 12H). LCMS
(m/z): 545 (MþH, 100%); anal. calcd. for C31H32N2O5S: C, 68.36; H,
5.92; N, 5.14. Found: C, 68.17; H, 5.69; N, 5.02.
6.60. Found: C, 64.84; H, 5.67; N, 6.66.
General procedure for the preparation of ethyl 2-
(substituted benzylthio)-4-(30-(ethoxycarbonyl)biphenyl-
Ethyl 2-(4-(dimethylamino)benzylthio)-4-
(30-(ethoxycarbonyl)biphenyl-4-yl)-6-methyl-1,4-
4-yl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8a–j
An ice cold solution of the cyclic compound 4-(30-ethoxycarbonyl-
biphenyl-4-yl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-pyrimidine-5-
carboxylic acid ethyl ester (6) (1 mmol) in DMF (4 vol%), potas-
sium carbonate (1.5 mmol) and substituted benzyl halides
(1.3 mmol) was taken in a 1-L round bottomed flask equipped
with magnetic stirrer and stirred for 1 h. The residual portion
was poured on to crushed ice, neutralized with dilute acid
and the obtained product ethyl 2-(substituted benzylthio)-4-(30-
(ethoxycarbonyl)biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine-
5-carboxylate derivatives (8a–j) was collected by filtration.
dihydropyrimidine-5-carboxylate 8f
Pale yellow solid, 82% yield; m.p. 210–2128C; 1H-NMR (300 MHz,
DMSO-d6) d 1.10–1.35 (t, 6H), 2.15 (s, 1H), 2.30 (s, 3H), 2.50–2.85
(s, 6H), 3.45 (s, 1H), 4.10–4.45 (q, 4H), 5.25 (s, 2H), 6.65–8.65
(m, 12H). LCMS (m/z): 558 (MþH, 100%); anal. calcd. for
C32H35N3O4S: C, 68.92; H, 6.33; N, 7.53. Found: C, 68.23; H,
6.09; N, 7.65.
Ethyl 2-(chlorobenzylthio)-4-(30-(ethoxycarbonyl)biphenyl-
4-yl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8g
Yellow solid, 80% yield; m.p. 252–2548C; 1H-NMR (300 MHz,
DMSO-d6) d 1.15–1.35 (t, 6H), 2.10 (s, 1H), 2.35 (s, 3H), 3.45
(s, 1H), 4.15–4.45 (q, 4H), 5.22 (s, 2H), 7.10–8.60 (m, 12H). LCMS
(m/z): 549 (MþH, 100%); anal. calcd. for C30H29ClN2O4S: C, 65.62;
H, 5.32; N, 5.10. Found: C, 65.43; H, 5.14; N, 4.95.
Ethyl 2-(benzylthio)-4-(30-(ethoxycarbonyl)biphenyl-4-yl)-
6-methyl-1,4-dihydropyrimidine-5-carboxylate 8a
Pale yellow solid, 69% yield; m.p. 196–1978C; 1H-NMR (300 MHz,
DMSO-d6) d 1.19–1.35 (t, 6H), 2.10 (s, 1H), 2.35 (s, 3H), 3.45 (s, 1H),
4.05–4.33 (q, 4H), 5.10 (s, 2H), 7.20–8.55 (m, 13H). LCMS (m/z): 515
(MþH, 100%); anal. calcd. for C30H30N2O4S: C, 70.05; H, 5.90; N,
5.45. Found: C, 69.84; H, 5.95; N, 5.70.
Ethyl 4-(30-(ethoxycarbonyl)biphenyl-4-yl)-2-
(4-isopropylbenzylthio)-6-methyl-1,4-dihydropyrimidine-5-
carboxylate 8h
Ethyl 2-(4-bromobenzylthio)-4-(30-(ethoxycarbonyl)-
biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine-5-
Pale yellow solid, 78% yield; m.p. 185–1878C; 1H-NMR (300 MHz,
DMSO-d6) d 0.95–1.35 (m, 12H), 2.10 (s, 1H), 2.28 (s, 3H), 2.60 (m,
1H), 3.35 (s, 1H), 4.10–4.40 (q, 4H), 5.10 (s, 2H), 7.15–8.65 (m, 12H).
LCMS (m/z): 557 (MþH, 100%); anal. calcd. for C33H36N2O4S: C,
71.20; H, 6.52; N, 5.03. Found: C, 70.85; H, 6.27; N, 5.25.
carboxylate 8b
Yellow solid, 64% yield; m.p. 214–2168C; 1H-NMR (300 MHz,
DMSO-d6) d 1.20–1.40 (t, 6H), 2.15 (s, 1H), 2.32 (s, 3H), 3.45
(s, 1H), 4.10–4.35 (q, 4H), 5.25 (s, 2H), 7.10–8.60 (m, 12H). LCMS
(m/z): 595 (Mþ2H, 100%); anal. calcd. for C30H29BrN2O4S: C, 60.71;
H, 4.92; N, 4.72. Found: C, 60.52; H, 4.71; N, 4.90.
Ethyl 2-(4-tert-butylbenzylthio)-4-(30-(ethoxycarbonyl)-
biphenyl-4-yl)-6-methyl-1,4-dihydropyrimidine-5-
carboxylate 8i
Ethyl 4-(30-(ethoxycarbonyl)biphenyl-4-yl)-2-
(4-ethylbenzylthio)-6-methyl-1,4-dihydropyrimidine-5-
Pale yellow solid, 71% yield; m.p. 202–2048C; 1H-NMR (300 MHz,
DMSO-d6) d 1.10–1.48 (m, 15H), 2.10 (s, 1H), 2.30 (s, 3H), 3.40 (s,
1H), 4.10–4.35 (q, 4H), 5.10 (s, 2H), 7.10–8.55 (m,12H). LCMS (m/z):
571 (MþH, 100%); anal. calcd. for C34H38N2O4S: C, 71.55; H, 6.71;
N, 4.91. Found: C, 71.19; H, 6.54; N, 4.68.
carboxylate 8c
Yellow solid, 75% yield; m.p. 175–1778C; 1H-NMR (300 MHz,
DMSO-d6) d 1.15–1.30 (t, 9H), 2.10 (s, 1H), 2.30 (s, 3H), 2.40–
2.55 (q, 2H), 3.40 (s, 1H), 4.10–4.35 (q, 4H), 5.15 (s, 2H), 6.75–
8.55 (m, 12H). LCMS (m/z): 543 (MþH, 100%); anal. calcd.
for C32H34BrN2O4S: C, 70.82; H, 6.31; N, 5.16. Found: C, 70.91;
H, 6.18; N, 5.32.
Ethyl 4-(30-(ethoxycarbonyl)biphenyl-4-yl)-6-methyl-2-
(4-nitrobenzylthio)-1,4-dihydropyrimidine-5-carboxylate 8j
Yellow solid, 67% yield; m.p. 221–2238C; 1H-NMR (300 MHz,
DMSO-d6) d 1.18–1.40 (t, 6H), 2.15 (s, 1H), 2.30 (s, 3H), 3.45
(s, 1H), 4.10–4.35 (q, 4H), 5.25 (s, 2H), 7.10–8.65 (m, 12H). LCMS
(m/z): 560 (MþH, 100%); anal. calcd. for C30H29N3O6S: C, 64.39; H,
5.19; N, 7.53. Found: C, 64.13; H, 5.28; N, 7.82.
Ethyl 4-(30-(ethoxycarbonyl)biphenyl-4-yl)-2-
(4-methylbenzylthio)-6-methyl-1,4-dihydropyrimidine-5-
carboxylate 8d
Pale yellow solid, 65% yield; m.p. 224–2258C; 1H-NMR (300 MHz,
DMSO-d6) d 1.15–1.30 (t, 6H), 2.10 (s, 1H), 2.30–2.45 (s, 6H), 3.45 (s,
1H), 4.10–4.35 (q, 4H), 5.10 (s, 2H), 6.90–8.55 (m, 12H). LCMS (m/z):
529 (MþH, 100%); anal. calcd. for C31H32N2O4S: C, 70.43; H, 6.10;
N, 5.30. Found: C, 70.03; H, 5.90; N, 5.45.
The authors acknowledge the financial support received from the
University of KwaZulu-Natal, in the form of postdoctoral bursary to SM.
The authors have declared no conflict of interest.
Ethyl 4-(30-(ethoxycarbonyl)biphenyl-4-yl)-2-
(4-methoxybenzylthio)-6-methyl-1,4-dihydropyrimidine-5-
References
carboxylate 8e
Yellow solid, 76% yield; m.p. 171–1738C; 1H-NMR (300 MHz,
DMSO-d6) d 1.10–1.35 (t, 6H), 2.15 (s, 1H), 2.35 (s, 3H), 3.45
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