Synthesis and in vitro biological evaluation of novel pyrazole derivatives as potential antitumor agents

Article abstract of DOI:10.2174/157340612802084252

The synthesis of twenty seven novel pyrazole derivatives bearing aryl substituted groups at positions 1 and 3 of the pyrazole structural motif and various functional groups at position 4 is presented. The critical step for their synthesis is the TCT/DMF p

Full text of DOI:10.2174/157340612802084252

Medicinal Chemistry, 2012, 8, 779-788
779
Synthesis and In Vitro Biological Evaluation of Novel Pyrazole Derivatives
as Potential Antitumor Agents
Michael S. Christodoulou,a,b Nikolas Fokialakis,c Sangkil Nam,d Richard Jove,d Alexios-Leandros
Skaltsounisc and Serkos A. Haroutouniana,*
b
aChemistry Laboratory, Agricultural University of Athens; Iera odos 75, Athens 11855, Greece; Dipartimento di
c
Chimica Organica e Industriale, Università degli Studi di Milano, Via Venezian 21, 20133 Milano – Italy; Division of
Pharmacognosy and Chemistry of Natural Products, Faculty of Pharmacy, University of Athens; Panepistimiopolis,
Zografou 15771, Athens, Greece; and dDepartment of Molecular Medicine, Beckman Research Institute of City of Hope;
1500 East Duarte Road, Duarte, CA 91010, USA
Abstract: The synthesis of twenty seven novel pyrazole derivatives bearing aryl substituted groups at positions 1 and 3 of
the pyrazole structural motif and various functional groups at position 4 is presented. The critical step for their synthesis is
the TCT/DMF promoted cyclization of the corresponding hydrazine precursors, which provided the desired pyrazole
skeleton. The anticancer properties of the novel pyrazole derivatives were evaluated in vitro against human prostate
(DU145), melanoma (A2058) and breast cancer (MCF-7) cell lines. Among the compounds tested, pyrazole 5a and its
methoxy derivatives 3d,e were assayed as the most potent, displaying selective activity against the MCF-7 cell line with
IC50 values of 14, 10 and 12 μꢀ respectively. Results herein indicate that the reported backbone represents a promising
structural lead for further development as antitumor agents.
Keywords: Pyrazole, Antitumor activity, Breast cancer, Melanoma, Prostate cancer.
1. INTRODUCTION
which has recently been shown to display antitumor activity
against human breast [19], lung [20] and prostate cancer
[21].
Cancer constitutes one of the most formidable afflictions
of the world. Despite significant advances, which have re-
sulted in notable cure rates for various malignancies, cancer
is one of the leading causes of death worldwide [1,2]. Since
the inhibition of proliferative pathways is considered as an
effective strategy to fight cancer, much attention has recently
been devoted to the discovery and development of new,
more selective anticancer agents [3,4]. In this respect, the
incorporation of heterocyclic residues into perspective phar-
maceutical lead candidates constitutes an important strategy
which provides activity and safety features. Thus, a broad
variety of azaheterocycles compounds have been considered
as potent antitumor agents, while pyrazoles belong among
the most representative five-membered heterocyclic systems
[5,6]. Particularly, over the past two decades, pyrazole-
containing compounds have received considerable attention,
owing to their diverse chemotherapeutic potentials, including
versatile antineoplastic activities. Literature survey revealed
that various pyrazoles have been identified as potent antimi-
crobial [7,8], antiviral [9,10] and anticancer agents [11-13],
in addition to their capability to exert remarkable anticancer
effects through the inhibition of different types of enzymes
that play important roles in cell division [14-16]. Extensive
studies have been devoted to arylpyrazole derivatives such as
Celecoxib, a well-know cyclooxygenase-2 inhibitor [17,18],
Intrigued by our interest to contribute to these studies we
envisioned the synthesis of novel pyrazole derivatives bear-
ing substituted aryl groups at the positions 1 and 3 of the
pyrazole ring and a variety of functional groups on C-4. The
critical step for their synthesis is the 2,4,6-trichloro[1,3,5]
triazine (TCT)/DMF [22] promoted cyclization of the hydra-
zine substrates which provided the desired pyrazole deriva-
tives backbone. The in vitro anticancer activities of these
compounds were evaluated against three characteristic hu-
man cancer cell lines, namely DU145 prostate cancer, A2058
melanoma cancer and MCF-7 breast cancer cell lines.
2. EXPERIMENTAL
2.1. General Methods
All reactions were carried out in oven-dried glassware
under argon atmosphere. All starting materials were pur-
chased from Aldrich, while the solvents used were purified
by distillation prior to use. Solvent mixtures employed in
chromatography have been reported as volume to volume
ratios. Thin layer chromatography (TLC) was performed on
Merck pre-coated aluminium sheets of silica gel 60 F254
,
while the products visualization was accomplished by UV
absorbance at 254 nm and/or spraying an alcoholic solution
of anisaldehyde and heating. Flash column chromatography
was performed on silica gel (35-70 μm) purchased from
*Address correspondence to this author at the Department of Sciences,
Chemistry Laboratory, Agricultural University of Athens, Iera odos 75,
Athens 11855, Greece; Tel: +30 2105294247; Fax: +30 2105294265;
E-mail: sehar@aua.gr
1875-6638/12 $58.00+.00
© 2012 Bentham Science Publishers

780 Medicinal Chemistry, 2012, Vol. 8, No. 5
Christodoulou et al.
2.4. Synthesis of Esters 3f-h
SDS. Melting points were determined on a Stuart apparatus
(SMP3) and are uncorrected. IR spectra were recorded on a
Thermo electron corporation Nicolet 6700 FT-IR spectrome-
2.4.1. (E)-ethyl 3-(1’,3’-diphenyl)-1’H-pyrazol-4’-yl) Acry-
late (3f)
1
ter in dichloromethane in ZnSe round windows. H NMR
and 13C NMR spectra were recorded in the indicated solvents
on Bruker DRX-400 and DRX-200 spectrometers at 400 and
50 MHz respectively. Chemical shifts (ꢀ) for proton and car-
bon resonances are quoted in parts per million (ppm) relative
to tetramethylsilane (TMS), which was used as an internal
standard. MS spectra were recorded using the electrospray
ionisation (ESI) technique on a Thermo Accela LC TSQ
Quantum Access MS-MS spectrometer. The syntheses of
compounds 1a-e, 2a-e, 3a-e, 4b-e, 5a-e were performed in
accordance with previously reported procedures [23].
To a stirred solution of pyrazolocarboxaldehyde 2f (1.07
g, 4.3 mmol) in 14 mL of acetonitrile, Ph3PCHCO2CH2CH3
(1.6 g, 4.7 mmol) was added and the mixture was refluxed
overnight. The reaction mixture was quenched with 60 mL
ethyl acetate, washed with H2O, brine, dried over anhydrous
Na2SO4 and evaporated to dryness under reduced pressure.
The crude product was purified by flash column chromatog-
raphy (hexane/EtOAc, 8:2) to afford the ester 3f as a white
solid (80% yield). mp 133-134 °C; IR (film) ꢀ: 1696 cm-1;
1H NMR (CDCl3): ꢀ = 8.26 (1ꢁ, s, H-5’), 7.79 (2H, d, J 7.2
Hz, H-2’’’ and H-6’’’), 7.76 (1H, d, J 16 Hz, H-3), 7.70 (2H,
d, J 7.2 Hz, H-2’’), 7.53-7.44 (5H, m, H-3’’, H-4’’, H-3’’’
and H-5’’’), 7.36 (1H, t, J 6.8 Hz, H-4’’’), 6.30 (1H, d, J 16
Hz, H-2), 4.26 (2H, q, J 6.8 Hz, OCH2CH3), 1.34 (3H, t, J
6.8 Hz, OCH2CH3); 13C NMR (CDCl3): 167.0 (C-1), 153.3
(C-3’), 139.5 (C-1’’), 135.1 (C-3), 132.6 (C-4’), 129.5 (C-3’’
and C-1’’’), 128.8 (C-3’’’ and C-5’’’), 128.7 (C-2’’’ and C-
6’’’), 128.6 (C-4’’’), 127.2 (C-4’’), 126.4 (C-5’), 119.3 (C-
2’’), 117.6 (C-2), 60.38 (OCH2CH3), 14.36 (OCH2CH3); MS:
319.33 (M+H+). Anal. Calcd for C20H18N2O2: C, 75.45; H,
5.70; N, 8.80; Found: C, 75.63; H, 5.59; N 8.97.
2.2. Synthesis of 1-phenyl-2-(1’’-phenylethylidene) Hy-
drazine (1f)
To a stirred solution of acetophenone (2.4 mL, 20 mmol)
in 35 mL of ethanol and acetic acid (1.5 mL), was added a
solution of phenylhydrazine hydrochloride (3.5 g, 24 mmol)
and trimethylamine (4.2 mL, 30 mmol) in 40 mL of ethanol
and stirred overnight at room temperature. The resulting pre-
cipitate was filtered and washed with ethanol and dieth-
ylether to provide the hydrazine product 1f as a white solid
2.4.2. (E)-methyl 3-(1’-(4’’-methoxyphenyl)-3’-phenyl-1’H-
pyrazol-4’-yl) Acrylate (3g)
1
(95% yield). IR (film) ꢀ: 3349 cm-1; H NMR (DMSO): ꢀ =
9.30 (1H, s, NH), 7.81 (2H, d, J 5.6 Hz, H-2’’’ and H-6’’’),
7.40-4.26 (7H, m, H-2’, H-3’, H-3’’’, H-4’’’ and H-5’’’),
6.78 (1H, m, H-4’), 2.28 (3H, s, H-2’’); 13C NMR (DMSO):
ꢀ = 146.5 (C-1’’), 141.0 (C-1’), 139.9 (C-1’’’), 129.3 (C-3’’’
and C-5’’’), 128.7 (C-3’), 127.9 (C-4’’’), 125.6 (C-2’’’ and
C-6’’’), 119.3 (C-4’), 113.3 (C-2’), 13.26 (C-2’’); MS:
211.20 (M+H+). Anal. Calcd for C14H14N2: C, 79.97; H,
6.71; N, 13.32; Found: C, 79.84; H, 6.57; N 13.47.
To a stirred solution of pyrazolocarboxaldehyde 2a (0.42
g, 1.5 mmol) in 5.0 mL of acetonitrile, Ph3PCHCO2CH3
(0.60 g, 1.8 mmol) was added and the mixture was refluxed
overnight. The reaction mixture was quenched with 40 mL
of ethyl acetate, washed with H2O, brine, dried over anhy-
drous Na2SO4 and evaporated under reduced pressure. Puri-
fication by flash column chromatography (hexane/EtOAc,
8:2) provided compound 3g as a white solid (80% yield). mp
1
149-150 °C; IR (film)ꢀ: 1703 cm-1; H NMR (CDCl3): ꢀ =
2.3. Synthesis of 1,3-diphenyl-1H-pyrazole-4-carbalde-
hyde (2f)
8.16 (1ꢁ, s, H-5’), 7.75 (1H, d, J 16 Hz, H-3), 7.68 (4H, d, J
8.8 Hz, H-2’’, H-2’’’ and H-6’’’), 7.51 (2H, t, J 7.2 Hz, H-
3’’’ and H-5’’’), 7.45 (1H, t, J 7.2 Hz, H-4’’’), 7.01 (2H, d, J
8.8 Hz, H-3’’), 6.28 (1H, d, J 16 Hz, H-2), 3.88 (3H, s, C4’’-
OCH3), 3.80 (3H, s, OCH3); 13C NMR (CDCl3): 167.5 (C-1),
158.8 (C-4’’), 153.0 (C-3’), 135.5 (C-3), 133.2 (C-1’’),
132.3 (C-4’), 128.8 (C-3’’’ and C-5’’’), 128.7 (C-2’’’ and C-
6’’’), 128.5 (C-1’’’), 126.4 (C-4’’’), 121.0 (C-2’’), 117.2 (C-
5’), 116.8 (C-2), 114.6 (C-3’’), 55.61 (C4’’-OCH3), 51.57
(OCH3); MS: 335.33 (M+H+). Anal. Calcd for C20H18N2O3:
C, 71.84; H, 5.43; N, 8.38; Found: C, 71.63; H, 5.61; N 8.52.
2,4,6-Trichloro-[1,3,5]-triazine, TCT (11.2 g, 60 mmol)
was added to dimethylformamide (8.30 mL) and stirred at
room temperature to produce a white solid. After the con-
sumption of TCT (20 min, revealed by TLC), 2.63 g of hy-
drazine 1f (12.5 mmol) in DMF (32 mL) were added and the
stirring was continued for 2h. The reaction mixture was
cooled to 0 °C and quenched with water. The organic phase
was extracted twice with EtOAc and the combined organic
extracts were washed with saturated Na2CO3, brine, dried
over anhydrous Na2SO4 and evaporated under reduced pres-
sure. Purification by flash column chromatography (hex-
ane/EtOAc, 7:3) yielded compound 2f as a white solid (85%
2.4.3. (E)-methyl 3-(1’,3’-diphenyl-1’H-pyrazol-4’-yl) Acr-
ylate (3h)
1
yield). mp 146-147 °C; IR (film) ꢀ: 1672 cm-1; H NMR
(CDCl3): ꢀ = 10.1 (1H, s, CHO), 8.57 (1H, s, H-5), 7.85 (2H,
d, J 8.0 Hz, H-2’), 7.82 (2H, d, J 10.4 Hz, H-2’’ and H-6’’),
7.56-7.52 (5H, m, H-3’, H-4’, H-3’’, and H-5’’), 7.42 (1H, t,
J 7.2 Hz, H-4’’); 13C NMR (CDCl3): ꢀ = 185.2 (CHO), 154.8
(C-3), 139.0 (C-1’), 131.3 (C-1’’), 131.0 (C-5), 129.7 (C-3’),
129.3 (C-4’’), 129.0 (C-3’’ and C-5’’), 128.8 (C-2’’ and C-
6’’), 128.0 (C-4’), 122.5 (C-4), 120.0 (C-2’); MS: 249.18
(M+H+). Anal. Calcd for C16H12N2O: C, 77.40; H, 4.87; N,
11.28; Found: C, 77.29; H, 4.68; N 11.42.
The ester 3h was prepared from pyrazolocarboxaldehyde
2f according to the previously described procedure. Purifica-
tion by flash column chromatography (hexane/EtOAc, 8:2)
furnished 3h as a white solid (80% yield). mp 109-110 °C;
IR (film) ꢀ: 1712 cm-1; 1H NMR (CDCl3): ꢀ = 8.26 (1ꢁ, s, H-
5’), 7.79 (2H, d, J 7.6 Hz, H-2’’’ and H-6’’’), 7.76 (1H, d, J
16 Hz, H-3), 7.70 (2H, d, J 7.2 Hz, H-2’’), 7.53-7.44 (5H, m,
H-3’’, H-4’’, H-3’’’, and H-5’’’), 7.36 (1H, t, J 7.2 Hz, H-
4’’’), 6.30 (1H, d, J 16 Hz, H-2), 3.80 (3H, s, OCH3); 13C

Synthesis and In Vitro Biological Evaluation of Novel Pyrazole Derivatives
Medicinal Chemistry, 2012, Vol. 8, No. 5 781
(1H, d, J 16 Hz, H-2), 4.18 (3H, s, OCH3), 3.88 (3H, s, C4’’-
OCH3); 13C NMR (CDCl3): 203.2 (C-1), 158.8 (C-4’’), 153.6
(C-3’), 133.1 (C-1’’), 132.4 (C-4’), 131.3 (C-3), 128.8 (C-
1’’’, C-2’’’, C-3’’’, C-5’’’ and C-6’’’), 128.6 (C-4’’’), 128.0
(C-5’), 126.2 (C-2), 121.0 (C-2’’), 114.6 (C-3’’), 58.50 (O-
CH3), 55.62 (C4’’-OCH3); MS: 351.28 (M+H+). Anal. Calcd
for C20H18N2O2S: C, 68.55; H, 5.18; N, 7.99; Found: C,
68.69; H, 5.31; N 7.76.
NMR (CDCl3): 167.5 (C-1), 153.3 (C-3’), 139.5 (C-1’’),
135.4 (C-3), 132.2 (C-4’), 129.6 (C-3’’), 128.8 (C-3’’’ and
C-5’’’), 128.7 (C-2’’’ and C-6’’’), 128.6 (C-1’’’), 127.2 (C-
4’’’), 126.4 (C-5’), 119.3 (C-2’’), 117.6 (C-4’’), 117.1 (C-2),
51.61 (OCH3); MS: 305.29 (M+H+). Anal. Calcd for
C19H16N2O2: C, 74.98; H, 5.30; N, 9.20; Found: C, 74.73; H,
5.51; N 9.38.
2.5. Synthesis of Thioesters 4a, f-h
2.5.4. (E)-O-Methyl 3-(1’,3’-diphenyl-1’H-pyrazol-4’-
yl)prop-2-enethioate (4h)
2.5.1. (E)-O-Ethyl 3-(1’-(4’’-methoxyphenyl)-3’-phenyl-
1’H-pyrazol-4’-yl)prop-2-enethioate (4a)
Thioester 4h was obtained from compound 3h according
to the previously described procedure. Purification by flash
column chromatography (hexane/EtOAc, 8:2) produced 4h
as a yellow oil (80% yield). IR (film) ꢀ: 1247 cm-1; 1H NMR
(CDCl3): ꢀ = 8.29 (1ꢁ, s, H-5’), 7.80 (2H, d, J 7.2 Hz, H-2’’’
and H-6’’’), 7.77 (1H, d, J 16 Hz, H-3), 7.72 (2H, d, J 8.8
Hz, H-2’’), 7.55-7.46 (5H, m, H-3’’, H-4’’, H-3’’’, and H-
5’’’), 7.37 (1H, t, J 7.2 Hz, H-4’’’), 6.95 (1H, d, J 16 Hz, H-
2), 4.18 (3H, s, OCH3); 13C NMR (CDCl3): 203.1 (C-1),
153.9 (C-3’), 139.4 (C-1’’), 132.3 (C-4’), 131.1 (C-3), 129.6
(C-3’’), 128.8 (C-3’’’ and C-5’’’), 128.7 (C-2’’’ and C-6’’’),
128.6 (C-1’’’), 128.3 (C-4’’’), 127.3 (C-5’), 126.2 (C-2),
119.3 (C-2’’), 117.9 (C-4’’), 58.53 (OCH3); MS: 321.30
(M+H+). Anal. Calcd for C19H16N2OS: C, 71.22; H, 5.03; N,
8.74; Found: C, 71.37; H, 5.17; N 8.86.
To a stirred solution of ester 3a (80 mg, 0.23 mmol) in
3.0 mL of toluene, Lawesson’s reagent (0.74 g, 1.8 mmol)
was added and the mixture was refluxed overnight. The sol-
vent was removed under vacuum and the remaining residue
was purified by flash column chromatography (hex-
ane/EtOAc, 8:2) to provide the thioester 4a as yellow oil
1
(70% yield). IR (film) ꢀ: 1251 cm-1; H NMR (CDCl3): ꢀ =
8.19 (1ꢁ, s, H-5’), 7.78 (1H, d, J 16 Hz, H-3), 7.72-7.68
(4H, m, H-2’’, H-2’’’ and H-6’’’), 7.52 (2H, t, J 7.2 Hz, H-
3’’’ and H-5’’’), 7.46 (1H, t, J 7.2 Hz, H-4’’’), 7.02 (2H, d, J
8.4 Hz, H-3’’), 6.91 (1H, d, J 16 Hz, H-2), 4.63 (2H, q, J 7.2
Hz, OCH2CH3), 3.88 (3H, s, OCH3), 1.46 (3H, t, J 7.2 Hz,
OCH2CH3); 13C NMR (CDCl3): 203.5 (C-1), 158.8 (C-4’’),
153.5 (C-3’), 133.1 (C-1’’), 132.4 (C-4’), 131.3 (C-3), 128.7
(C-2’’’, C-3’’’ and C-5’’’), 128.5 (C-1’’’), 128.4 (C-4’’’),
126.2 (C-5’), 121.0 (C-2’’), 117.6 (C-2), 114.6 (C-3’’),
67.66 (OCH2CH3), 55.61 (OCH3), 13.82 (OCH2CH3); MS:
365.34 (M+H+). Anal. Calcd for C21H20N2O2S: C, 69.20; H,
5.53; N, 7.69; Found: C, 69.32; H, 5.61; N 7.76.
2.6. Demethylation of Ester 3g
2.6.1. (E)-Methyl 3-(1’-(4’’-hydroxyphenyl)-3’-phenyl-1’H-
pyrazol-4’-yl) Acrylate (5g)
To a stirred solution of ester 3g (0.19 g, 0.57 mmol) in
CH2Cl2 (18 mL) at -78°C, BBr3 (2.8 mmol, 1.0 M in CH2Cl2,
2.8 mL) was added drop wise and stirring was continued at -
78°C for 1 h. The reaction was allowed to reach the room
temperature and stirred for additional 16 h. at room tempera-
ture. Then, the reaction mixture was cooled to 0°C and
quenched with MeOH and HCl 1N. The organic phase was
extracted twice with ethyl acetate and the combined organic
extracts were washed with water and brine, dried over anhy-
drous Na2SO4 and evaporated to dryness under vacuum.
Purification by flash column chromatography (hex-
ane/EtOAc, 7:3) provided 5g as a white solid (85% yield).
2.5.2.
(E)-O-Ethyl
3-(1’,3’-diphenyl-1’H-pyrazol-4’-
yl)prop-2-enethioate (4f)
Thioester 4f was obtained from 3f according to the previ-
ously described procedure. Purification by flash column
chromatography (hexane/EtOAc, 8:2) furnished 4f as a yel-
low oil (75% yield). IR (film) ꢀ: 1265 cm-1; 1H NMR
(CDCl3): ꢀ = 8.29 (1ꢁ, s, H-5’), 7.80 (2H, d, J 8.0 Hz, H-2’’’
and H-6’’’), 7.79 (1H, d, J 16 Hz, H-3), 7.78 (2H, d, J 8.0
Hz, H-2’’), 7.53-7.48 (5H, m, H-3’’, H-4’’, H-3’’’ and H-
5’’’), 7.37 (1H, t, J 7.2 Hz, H-4’’’), 6.92 (1H, d, J 16 Hz, H-
2), 4.64 (2H, q, J 7.2 Hz, OCH2CH3), 1.46 (3H, t, J 7.2 Hz,
OCH2CH3); 13C NMR (CDCl3): 203.4 (C-1), 153.8 (C-3’),
139.4 (C-1’’), 132.3 (C-4’), 131.1 (C-3), 129.6 (C-3’’),
129.0 (C-1’’’), 128.8 (C-3’’’ and C-5’’’), 128.7 (C-2’’’ and
C-6’’’), 128.6 (C-4’’’), 128.5 (C-4’’), 127.2 (C-5’), 126.1
(C-2), 119.3 (C-2’’), 67.72 (OCH2CH3), 13.84 (OCH2CH3);
MS: 335.27 (M+H+). Anal. Calcd for C20H18N2OS: C, 71.83;
H, 5.42; N, 8.38; Found: C, 71.97; H, 5.31; N 8.16.
1
mp 209-210 °C; IR (film) ꢀ: 1670 cm-1; H NMR (acetone-
d6): ꢀ = 8.85 (1ꢁ, s, H-5’), 7.79 (2H, d, J 8.8 Hz, H-2’’),
7.71 (1H, d, J 16 Hz, H-3), 7.70 (2H, d, J 7.6 Hz, H-2’’’ and
H-6’’’), 7.56 (2H, t, J 7.6 Hz, H-3’’’ and H-5’’’), 7.50 (1H, t,
J 7.6 Hz, H-4’’’), 7.01 (2H, d, J 8.8 Hz, H-3’’), 6.44 (1H, d,
J 16 Hz, H-2), 3.73 (3H, s, OCH3); 13C NMR (acetone-d6):
166.8 (C-1), 156.6 (C-3’ and C-4’’), 135.0 (C-3), 132.8 (C-
4’), 132.4 (C-1’’), 128.6 (C-3’’’ and C-5’’’), 128.5 (C-2’’’
and C-6’’’), 128.4 (C-4’’’), 128.0 (C-1’’’), 127.3 (C-5’),
120.6 (C-2’’), 116.6 (C-2), 115.8 (C-3’’), 50.69 (OCH3);
MS: 321.28 (M+H+). Anal. Calcd for C19H16N2O3: C, 71.24;
H, 5.03; N, 8.74; Found: C, 71.41; H, 5.18; N 8.97.
2.5.3. (E)-O-Methyl 3-(1’-(4’’-methoxyphenyl)-3’-phenyl-
1’H-pyrazol-4’-yl)prop-2-enethioate (4g)
Compound 4g was obtained from ester 3g according to
the previously described procedure. Purification by flash
column chromatography (hexane/EtOAc, 8:2) gave 4g as a
2.7. General Procedure for the Synthesis of Amides 8a-e
yellow oil (80% yield). IR (film) ꢀ: 1251 cm-1; H NMR
1
2.7.1. (E)-N,N-diethyl-3-(1’-(4’’-methoxyphenyl)-3’-
phenyl-1’H-pyrazol-4’-yl) Acrylamide (8a)
(CDCl3): ꢀ = 8.19 (1ꢁ, s, H-5’), 7.78 (1H, d, J 16 Hz, H-3),
7.70 (2H, d, J 7.2 Hz, H-2’’’ and H-6’’’), 7.69 (2H, d, J 8.8
Hz, H-2’’), 7.53 (2H, t, J 7.2 Hz, H-3’’’ and H-5’’’), 7.47
(1H, t, J 7.2 Hz, H-4’’’), 7.02 (2H, d, J 8.8 Hz, H-3’’), 6.93
Diethylamine (0.4 mL, 3.8 mmol), was added drop wise
into a solution of carboxylic acid 6a (0.35 g, 1.1 mmol) in

782 Medicinal Chemistry, 2012, Vol. 8, No. 5
Christodoulou et al.
acetonitrile (12 mL) and stirred at room temperature for 30
min. Then, 0.53 g of TBTU (1.6 mmol) were added and the
stirring was continued until all starting material was con-
sumed. The reaction mixture was quenched with brine and
extracted twice with ethyl acetate. The combined organic
extracts were washed successively with HCl (1N), water, 5%
aqueous NaHCO3 and brine, dried over anhydrous Na2SO4
and evaporated under vacuum to a solid residue. The latter
was washed with DEE and dried over P2O5 to provide amide
8a as a white solid (80% yield). mp 159-160 °C; IR (film) ꢀ:
1654 cm-1 1H NMR (CDCl3): ꢀ = 8.12 (1ꢁ, s, H-5’), 7.77
(1H, d, J 16 Hz, H-3), 7.70 (2H, d, J 7.2 Hz, H-2’’’ and H-
6’’’), 7.69 (2H, d, J 8.8 Hz, H-2’’), 7.47 (2H, t, J 7.2 Hz, H-
3’’’ and H-5’’’), 7.41 (1H, t, J 7.2 Hz, H-4’’’), 7.00 (2H, d, J
8.8 Hz, H-3’’), 6.59 (1H, d, J 16 Hz, H-2), 3.87 (3H, s,
OCH3), 3.47 (2H, q, J 7.2 Hz, NCH2CH3), 3.35 (2H, q, J 7.2
Hz, NCH2CH3), 1.17 (6H, t, J 7.2 Hz, NCH2CH3); 13C NMR
(CDCl3): 165.8 (C-1), 158.6 (C-4’’), 152.5 (C-3’), 133.3 (C-
4’), 132.9 (C-1’’), 132.7 (C-3), 128.8 (C-2’’’ and C-6’’’),
128.6 (C-3’’’ and C-5’’’), 128.3 (C-1’’’), 126.6 (C-4’’’),
120.9 (C-2’’), 118.1 (C-5’), 117.1 (C-2), 114.6 (C-3’’),
55.60 (OCH3), 42.75 (NCH2CH3), 40.23 (NCH2CH3), 13.85
(NCH2CH3); MS: 376.36 (M+H+). Anal. Calcd for
C23H25N3O2: C, 73.57; H, 6.71; N, 11.19; Found: C, 73.78;
H, 6.93; N 11.34.
55.61 (C4’’-OCH3), 55.38 (C4’’’-OCH3), 42.15 (NCH2CH3),
41.02 (NCH2CH3), 15.06 (NCH2CH3) 13.29 (NCH2CH3);
MS: 406.13 (M+H+). Anal. Calcd for C24H27N3O3: C, 71.09;
H, 6.71; N, 10.36; Found: C, 71.24; H, 6.95; N 10.49.
2.7.4. (E)-N,N-diethyl-3-(1’-(4’’-methoxyphenyl)-3’-
(3’’’,4’’’-dimethoxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide
(8d)
According to the general procedure, amide 8d was obtai-
ned from acid 6d and purified by flash column chromatogra-
phy using EtOAc as eluent (white solid, 80% yield). mp 137-
1
138 °C; IR (film) ꢀ: 1650 cm-1; H NMR (CDCl3): ꢀ = 8.09
(1ꢁ, s, H-5’), 7.78 (1H, d, J 16 Hz, H-3), 7.68 (2H, d, J 8.8
Hz, H-2’’), 7.26 (1H, d, J 1.6 Hz, H-2’’’), 7.22 (1H, dd, J 8.4
Hz J 1.6 Hz, H-6’’’), 7.00 (2H, d, J 8.8 Hz, H-3’’), 6.96 (1H,
d, J 8.4 Hz, H-5’’’), 6.60 (1H, d, J 16 Hz, H-2), 3.96 (3H, s,
C3’’’-OCH3), 3.94 (3H, s, C4’’’-OCH3), 3.86 (3H, s, C4’’-
OCH3), 3.47 (2H, q, J 7.2 Hz, NCH2CH3), 3.36 (2H, q, J 7.2
Hz, NCH2CH3), 1.18 (6H, t, J 7.2 Hz, NCH2CH3); 13C NMR
(CDCl3): 165.8 (C-1), 158.6 (C-4’’), 152.4 (C-3’), 149.3 (C-
3’’’), 149.1 (C-4’’’), 133.3 (C-4’), 132.8 (C-1’’), 126.5 (C-
1’’’), 125.6 (C-3), 121.6 (C-5’), 120.9 (C-2’’), 118.0 (C-
6’’’), 117.0 (C-5’’’), 114.6 (C-3’’), 111.7 (C-2’’’), 111.3 (C-
2), 56.01 (C4’’-OCH3), 55.98 (C3’’’-OCH3), 55.58 (C4’’’-
OCH3), 42.20 (NCH2CH3), 41.00 (NCH2CH3), 15.00 (N-
CH2CH3) 13.26 (NCH2CH3); MS: 436.43 (M+H+). Anal.
Calcd for C25H29N3O4: C, 68.95; H, 6.71; N, 9.65; Found: C,
69.11; H, 6.92; N 9.79.
2.7.2. (E)-N,N-diethyl-3-(1’-(4’’-methoxyphenyl)-3’-(3’’’-
methoxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide (8b)
Acid 6b was converted to amide 8b as described previ-
ouly (white solid, 85% yield). mp 111-112 °C; IR (film) ꢀ:
2.7.5. (E)-N,N-diethyl-3-(1’-(4’’-methoxyphenyl)-3’-
(2’’’,5’’’-dimethoxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide
(8e)
1
1645 cm-1; H NMR (CDCl3): ꢀ = 8.09 (1ꢁ, s, H-5’), 7.76
(1H, d, J 16 Hz, H-3), 7.68 (2H, d, J 8.8 Hz, H-2’’), 7.36
(1H, t, J 8.0 Hz, H-5’’’), 7.28-7.24 (2H, m, H-2’’’ and H-
6’’’), 6.98 (2H, d, J 8.8 Hz, H-3’’), 6.96 (1H, d, J 8.0 Hz, H-
4’’’), 6.59 (1H, d, J 16 Hz, H-2), 3.86 (3H, s, C3’’’-OCH3),
3.85 (3H, s, C4’’-OCH3), 3.46 (2H, q, J 7.2 Hz, NCH2CH3),
3.33 (2H, q, J 7.2 Hz, NCH2CH3), 1.16 (6H, t, J 7.2 Hz,
NCH2CH3); 13C NMR (CDCl3): 165.8 (C-1), 159.8 (C-3’’’),
158.6 (C-4’’), 152.4 (C-3’), 134.2 (C-4’), 133.2 (C-1’’),
132.5 (C-3), 129.7 (C-1’’’), 126.6 (C-5’’’), 121.3 (C-5’),
120.9 (C-2’’), 118.1 (C-6’’’), 117.2 (C-4’’’), 114.5 (C-3’’),
114.4 (C-2’’’), 113.8 (C-2), 55.56 (C4’’-OCH3), 55.32
(C3’’’-OCH3), 42.15 (NCH2CH3), 40.98 (NCH2CH3), 13.36
(NCH2CH3) 13.24 (NCH2CH3); MS: 406.13 (M+H+). Anal.
Calcd for C24H27N3O3: C, 71.09; H, 6.71; N, 10.36; Found:
C, 71.22; H, 6.94; N 10.48.
Amide 8e was obtained as a white solid (80% yield) from
acid 6e according to the general procedure and flash column
chromatography purification (hexane/EtOAc, 3:7). mp 138-
1
139 °C; IR (film) ꢀ: 1651 cm-1; H NMR (CDCl3): ꢀ = 8.08
(1ꢁ, s, H-5’), 7.68 (2H, d, J 9.2 Hz, H-2’’), 7.58 (1H, d, J 16
Hz, H-3), 7.02 (1H, d, J 2.4 Hz, H-6’’’), 6.99 (2H, d, J 9.2
Hz, H-3’’), 6.97 (1H, d, J 8.8 Hz, H-3’’’), 6.96 (1H, dd, J 8.8
Hz J 2.4 Hz, H-4’’’), 6.37 (1H, d, J 16 Hz, H-2), 3.87 (3H, s,
C5’’’-OCH3), 3.81 (3H, s, C2’’’-OCH3), 3.79 (3H, s, C4’’-
OCH3), 3.43 (2H, q, J 6.8 Hz, NCH2CH3), 3.24 (2H, q, J 6.8
Hz, NCH2CH3), 1.11 (6H, t, J 6.8 Hz, NCH2CH3); 13C NMR
(CDCl3): 166.0 (C-1), 158.5 (C-4’’), 153.7 (C-3’), 151.7 (C-
5’’’), 149.8 (C-2’’’), 133.4 (C-4’), 132.8 (C-1’’), 128.6 (C-
3), 126.6 (C-5’), 120.8 (C-2’’), 119.4 (C-1’’’), 116.7 (C-
4’’’), 116.0 (C-3’’’), 115.6 (C-6’’’), 114.5 (C-3’’), 112.6 (C-
2), 56.36 (C4’’-OCH3), 55.86 (C5’’’-OCH3), 55.57 (C2’’’-
OCH3), 42.12 (NCH2CH3), 40.89 (NCH2CH3), 14.87 (N-
CH2CH3) 13.24 (NCH2CH3); MS: 436.27 (M+H+). Anal.
Calcd for C25H29N3O4: C, 68.95; H, 6.71; N, 9.65; Found: C,
69.13; H, 6.93; N 9.81.
2.7.3. (E)-N,N-diethyl-3-(1’-(4’’-methoxyphenyl)-3’-(4’’’-
methoxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide (8c)
According to the general procedure, amide 8c was obtai-
ned from acid 6c as white solid (85% yield). mp 141-142 °C;
1
IR (film) ꢀ: 1645 cm-1; H NMR (CDCl3): ꢀ = 8.09 (1ꢁ, s,
H-5’), 7.76 (1H, d, J 16 Hz, H-3), 7.68 (2H, d, J 8.8 Hz, H-
2’’’ and H-6’’’), 7.64 (2H, d, J 8.0 Hz, H-2’’), 7.01 (2H, d, J
8.0 Hz, H-3’’), 7.00 (2H, d, J 8.8 Hz, H-3’’’ and H-5’’’),
6.60 (1H, d, J 16 Hz, H-2), 3.87 (6H, s, C4’’-OCH3 and
C4’’’-OCH3), 3.48 (2H, q, J 6.8 Hz, NCH2CH3), 3.37 (2H, q,
J 6.8 Hz, NCH2CH3), 1.19 (6H, t, J 7.2 Hz, NCH2CH3); 13C
NMR (CDCl3): 165.8 (C-1), 159.8 (C-4’’’), 158.5 (C-4’’),
152.4 (C-3’), 133.3 (C-4’), 132.9 (C-1’’), 130.0 (C-2’’’ and
C-6’’’), 126.4 (C-3), 125.3 (C-1’’’), 120.9 (C-2’’), 117.9 (C-
5’), 116.8 (C-2), 114.5 (C-3’’’ and C-5’’’), 114.1 (C-3’’),
2.8. General Procedure for the Demethylation of Amides
8a, b, d, e
2.8.1. (E)-N,N-diethyl-3-(1’-(4’’-hydroxyphenyl)-3’-phenyl-
1’H-pyrazol-4’-yl) acrylamide (9a)
To a stirred solution of amide 8a (0.20 g, 0.53 mmol) in
CH2Cl2 (16 mL) at -78°C, BBr3 (2.7 mmol, 1.0 M in CH2Cl2,
5 equiv per protective group) was added drop wise and
stirred at -78°C for 1 h. The reaction was allowed to reach

Synthesis and In Vitro Biological Evaluation of Novel Pyrazole Derivatives
Medicinal Chemistry, 2012, Vol. 8, No. 5 783
the room temperature and stirred for additional 16 h. The
reaction mixture was cooled to 0°C and quenched with the
addition of MeOH and HCl 1N. Then, the organic phase was
extracted twice with EtOAc and the combined organic layers
were washed with water and brine, dried over anhydrous
Na2SO4 and evaporated under reduced pressure. The result-
ing residue was purified by flash column chromatography
(hexane/EtOAc, 3:7) to provide 9a as a white solid (85%
3’’), 115.7 (C-2’’’), 114.6 (C-2), 41.78 (NCH2CH3), 15.12
(NCH2CH3) 13.68 (NCH2CH3); MS: 394.35 (M+H+). Anal.
Calcd for C22H23N3O4: C, 67.16; H, 5.89; N, 10.68; Found:
C, 67.31; H, 5.74; N 10.83.
2.8.4. (E)-N,N-diethyl-3-(1’-(4’’-hydroxyphenyl)-3’-
(2’’’,5’’’-hydroxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide
(9e)
1
yield). mp 246-247 °C; IR (film) ꢀ: 1642 cm-1; H NMR
According to the general procedure, deprotected amide
9e was obtained from amide 8e after purification by flash
column chromatography (hexane/EtOAc, 4:6) and solvent
evaporation as a white solid (85% yield). mp 263-264 °C; IR
(DMSO): ꢀ = 9.02 (1ꢁ, s, H-5’), 7.72 (2H, d, J 8.4 Hz, H-
2’’), 7.61 (2H, d, J 6.8 Hz, H-2’’’ and H-6’’’), 7.53 (2H, t, J
6.8 Hz, H-3’’ and H-5’’’), 7.49 (1H, d, J 16 Hz, H-3), 7.48
(1H, t, J 6.8 Hz, H-4’’’), 6.96 (1H, d, J 16 Hz, H-2), 6.93
(2H, d, J 8.4 Hz, H-3’’), 3.42 (4H, q, J 7.2 Hz, NCH2CH3),
1.15 (3H, t, J 7.2 Hz, NCH2CH3), 1.06 (3H, t, J 7.2 Hz,
NCH2CH3); 13C NMR (DMSO): 165.2 (C-1), 156.9 (C-4’’),
151.7 (C-3’), 133.0 (C-4’), 132.0 (C-1’’), 131.8 (C-3), 129.2
(C-2’’’ and C-6’’’), 128.8 (C-3’’’, C-4’’’ and C-5’’’), 128.1
(C-1’’’), 120.9 (C-2’’), 117.9 (C-5’), 117.8 (C-2), 116.3 (C-
3’’), 41.84 (NCH2CH3), 15.68 (NCH2CH3), 13.68
(NCH2CH3); MS: 362.30 (M+H+). Anal. Calcd for
C22H23N3O2: C, 73.11; H, 6.41; N, 11.63; Found: C, 73.33;
H, 6.24; N 11.81.
1
(film) ꢀ: 1650 cm-1; H NMR (DMSO): ꢀ = 8.90 (1ꢁ, s, H-
5’), 7.66 (2H, d, J 8.8 Hz, H-2’’), 7.35 (1H, d, J 16 Hz, H-3),
6.91 (2H, d, J 8.8 Hz, H-3’’), 6.79 (1H, d, J 7.6 Hz, H-3’’’),
6.76 (1H, d, J 16 Hz, H-2), 6.71 (1H, d, J 2.4 Hz, H-6’’’),
6.70 (1H, dd, J 7.6 Hz J 2.4 Hz, H-4’’’), 3.36 (4H, q, J 6.8
Hz, NCH2CH3), 1.10 (3H, t, J 6.8 Hz, NCH2CH3), 1.10 (3H,
t, J 6.8 Hz, NCH2CH3); 13C NMR (DMSO): 165.3 (C-1),
156.7 (C-4’’), 150.3 (C-3’), 150.2 (C-5’’’), 148.1 (C-2’’’),
133.0 (C-4’), 132.0 (C-1’’), 127.5 (C-3), 120.6 (C-2’’),
120.3 (C-1’’’), 119.1 (C-5’), 117.3 (C-4’’’), 117.0 (C-3’’’),
116.9 (C-6’’’), 116.6 (C-2), 116.3 (C-3’’), 41.84 (NCH2CH3)
15.65 (NCH2CH3) 13.71 (NCH2CH3); MS: 394.36 (M+H+).
Anal. Calcd for C22H23N3O4: C, 67.16; H, 5.89; N, 10.68;
Found: C, 67.32; H, 5.72; N 10.85.
2.8.2. (E)-N,N-diethyl-3-(1’-(4’’-hydroxyphenyl)-3’-(3’’’-
hydroxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide (9b)
Amide 8b was demethylated according to the previously
described procedure to provide after purification by flash
column chromatography (Hexane/EtOAc, 4:6) the deprotec-
ted amide 9b as a white solid (85% yield). mp 233-234 °C;
2.9. Antitumor Activity Assays
The human cancer cell lines for A2058 melanoma, MCF-
7 breast cancer and DU145 prostate cancer were obtained
from ATCC. They were cultured in RPMI-1640 medium
containing 10% fatal bovine serum (FBS), 100 units/ml of
penicillin, and 100 ꢂg/ml streptomycin. All cells were main-
tained in a 5% CO2 atmosphere at 37 °C. To determine the
viability of the cells, MTS assays were performed as de-
scribed by the supplier (Promega; Madison, WI). Briefly,
cells (5,000/well) were seeded in 96-well plates and incu-
bated overnight at 37 °C in 5% CO2. Cells were treated for
48 h with 10 or 20 μM of each compound. Dimethyl sulfox-
ide (DMSO) was used as the vehicle control. Cell viability
was determined by tetrazolium conversion to its formazan
dye and absorbance of formazan was measured at 490 nm
using an automated ELISA plate reader. The production of
formazan dye was directly proportional to the number of
living cells. Each experiment was done in quadruplicate.
1
IR (film) ꢀ: 1650 cm-1; H NMR (CD3OD): ꢀ = 8.58 (1ꢁ, s,
H-5’), 7.64 (1H, d, J 16 Hz, H-3), 7.62 (2H, d, J 8.8 Hz, H-
2’’), 7.31 (1H, t, J 8.0 Hz, H-5’’’), 7.01 (1H, s, H-2’’’), 7.07
(1H, d, J 8.0 Hz, H-6’’’), 6.93-6.87 (3H, m, H-3’’ and H-
4’’’), 6.83 (1H, d, J 16 Hz, H-2), 3.47 (4H, q, J 7.2 Hz, N-
CH2CH3), 1.18 (6H, t, J 7.2 Hz, NCH2CH3); 13C NMR
(CD3OD): 166.9 (C-1), 157.5 (C-3’’’), 156.8 (C-4’’), 152.4
(C-3’), 133.8 (C-4’), 132.8 (C-3), 132.0 (C-1’’), 129.5 (C-
1’’’), 127.9 (C-5’’’), 121.0 (C-5’ and C-2’’), 119.7 (C-6’’’),
116.3 (C-4’’’), 115.5 (C-2’’’), 115.3 (C-3’’), 115.2 (C-2),
42.16 (NCH2CH3), 40.98 (NCH2CH3), 13.81 (NCH2CH3)
12.04 (NCH2CH3); MS: 378.15 (M+H+). Anal. Calcd for
C22H23N3O3: C, 70.01; H, 6.14; N, 11.13; Found: C, 70.29;
H, 6.01; N 11.28.
2.8.3. (E)-N,N-diethyl-3-(1’-(4’’-hydroxyphenyl)-3’-
(3’’’,4’’’-hydroxyphenyl)-1’H-pyrazol-4’-yl) Acrylamide
(9d)
3. RESULTS AND DISCUSSION
3.1. Chemical Synthesis
According to the general procedure, deprotected amide
9d was obtained from amide 8d after purification by flash
column chromatography (EtOAc) and solvent evaporation as
a white solid (85% yield). mp 257-258 °C; IR (film) ꢀ: 1643
The synthesis of pyrazolocarbaldehydes 2 was accom-
plished as outlined in Scheme 1. More specifically, the ace-
tophenone substrates were condensed with p-methoxy-
phenylhydrazine(or phenylhydrazine) hydrochlorides to pro-
vide efficiently the hydrazines 1a-f. The latterupon treatment
with an iminium salt {prepared by reacting the 2,4,6-
trichloro[1,3,5]triazine (TCT, cyanuric chloride) with DMF}
produced the corresponding pyrazolocarbaldehydes 2 in
good overall yields (48-80%). The Wittig olefination of car-
baldehydes 2 with the stabilized phosphoranes gave in excel-
lent yields (80-90%) the ꢁ,ꢂ unsaturated esters 3, which by
Lawesson’s reagent were transformed to the corresponding
1
cm-1; H NMR (CD3OD): ꢀ = 8.71 (1ꢁ, s, H-5’), 7.74 (1H,
d, J 16 Hz, H-3), 7.71 (2H, d, J 9.2 Hz, H-2’’), 7.24 (1H, d, J
2.0 Hz, H-2’’’), 7.08 (1H, dd, J 8.0 Hz J 2.0 Hz, H-6’’’),
6.99 (1H, d, J 16 Hz, H-2), 6.98 (2H, d, J 9.2 Hz, H-3’’),
6.96 (1H, d, J 8.0 Hz, H-5’’’), 3.47 (4H, q, J 7.2 Hz, N-
CH2CH3), 1.21 (3H, t, J 7.2 Hz, NCH2CH3), 1.14 (3H, t, J
7.2 Hz, NCH2CH3); 13C NMR (CD3OD): 165.1 (C-1), 156.8
(C-4’’), 149.2 (C-3’), 147.8 (C-3’’’), 147.6 (C-4’’’), 132.9
(C-4’), 132.0 (C-1’’), 125.4 (C-1’’’), 124.2 (C-3), 120.7 (C-
2’’), 118.8 (C-5’), 118.3 (C-6’’’), 117.9 (C-5’’’), 116.4 (C-

784 Medicinal Chemistry, 2012, Vol. 8, No. 5
Christodoulou et al.
R3
4'''
R3
R2
3''
R2
R1
R
4
5'''
4''
H2N
3'''
2
5''
.
HCl
NH
R4
R3
6'''
R1
2
2'''
2''
R2
R1
R4
1'''
6''
1''
1''
b
a
3
+
O
N
N
4
2''
NH
1
1' N
1'
2'
H
1
R5
5
O
2'
4'
R5 4'
R5
3'
3'
1
2
1a, 2a R1= H, R2= H, R3= H, R4= H, R5 = OCH3
1b, 2b R1= H, R2= OCH3, R3= H, R4= H, R5 = OCH3
1c, 2c R1= H, R2= H, R3= OCH3 , R4= H, R5 = OCH3
1d, 2d R1= H, R2= OCH3, R3= OCH3, R4= H, R5 = OCH3
1e, 2e R1= OCH3, R2= H, R3= H, R4= OCH3, R5 = OCH3
1f, 2f R1= H, R2= H, R3= H, R4= H, R5 = H
Scheme 1. Reagents and Conditions: (a) Acetic acid, Et3N, Ethanol; (b) TCT, Dichloromethane.
R3
R2
R4
R1
b
S
N
R3
R3
R2
R2
3'''
N
4'''
R6
5'''
R4
R4
R1
R1
2'
R5
2'''
6'''
4
1'''
3'
O
a
O
N
N
3
4'
1'
N
N
1
H
R6
2
1''
5'
2''
R5
R5
4''
R3
R2
3''
2
3
R4
R1
3a, 4a R1= H, R2= H, R3= H, R4= H, R5 = OCH3, R6 = OCH2CH3
3b, R1= H, R2= OCH3, R3= H, R4= H, R5 = OCH3, R6 = OCH2CH3
3c, R1= H, R2= H, R3= OCH3, R4= H, R5 = OCH3, R6 = OCH2CH3
3d, R1= H, R2= OCH3, R3= OCH3, R4= H, R5 = OCH3, R6 = OCH2CH3
3e, R1= OCH3, R2= H, R3= H, R4= OCH3, R5 = OCH3, R6 = OCH2CH3
3f, 4f R1= H, R2= H, R3= H, R4= H, R5 = H, R6 = OCH2CH3
3g, 4g R1= H, R2= H, R3= H, R4= H, R5 = OCH3, R6 = OCH3
3h, 4h R1= H, R2= H, R3= H, R4= H, R5 = H, R6 = OCH3
c
O
N
N
R6
HO
5
5a R1= H, R2= H, R3= H, R4= H, R6 = OCH2CH3
5b R1= H, R2= OH, R3= H, R4= H, R6 = OCH2CH3
5c R1= H, R2= H, R3= OH, R4= H, R6 = OCH2CH3
5d R1= H, R2= OH, R3= OH, R4= H, R6 = OCH2CH3
5e R1= OH, R2= H, R3= H, R4= OH, R6 = OCH2CH3
5g R1= H, R2= H, R3= H, R4= H, R6 = OCH3
Scheme 2. Reagents and conditions: (a) Wittig reagents, Acetonitrile, reflux; (b) Lawesson’s reagent, Toluene, Reflux; (c) BBr3, Dichloro-
methane, -78 °C.
ꢀ,ꢁ unsaturated thioesters 4 (70-80%). Finally, demethyla-
tion of the latter in the presence of BBr3 afforded the corre-
sponding phenol derivatives 5 (Scheme 2).
presence of BBr3 (compounds 7a-e, Scheme 3). On the other
hand, acids 6 were converted in very good yields (80-85%)
to amides 8 by reaction with diethylamine in the presence of
the uronium coupling reagent TBTU. Finally, their BBr3
promoted demethylation provided efficiently the correspond-
ing deprotected amides 9 (Scheme 4).
Esters 3 were hydrolyzed almost quantitavely furnishing
the acids 6, which were subsequently demethylated in the

Synthesis and In Vitro Biological Evaluation of Novel Pyrazole Derivatives
Medicinal Chemistry, 2012, Vol. 8, No. 5 785
R3
R3
R2
R3
R2
R2
R4
R4
R4
R1
R1
R1
b
a
O
O
O
N
N
N
N
N
N
OH
OH
R6
H3CO
HO
R5
6
7
3
7a R1= H, R2= H, R3= H, R4= H
7b R1= H, R2= OH, R3= H, R4= H
7c R1= H, R2= H, R3= OH, R4= H
7d R1= H, R2= OH, R3= OH, R4= H
7e R1= OH, R2= H, R3= H, R4= OH
6a R1= H, R2= H, R3= H, R4= H
6b R1= H, R2= OCH3, R3= H, R4= H
6c R1= H, R2= H, R3= OCH3, R4= H
6d R1= H, R2= OCH3, R3= OCH3, R4= H
6e R1= OCH3, R2= H, R3= H, R4= OCH3
Scheme 3. Reagents and Conditions: (a) Ethanol, DMSO, NaOH; (b) BBr3, Dichloromethane, -78 °C.
R3
R3
R3
R2
R2
R2
R4
R4
R4
R1
R1
R1
b
O
O
O
a
N
N
N
N
N
N
OH
N(CH2CH3)2
N(CH2CH3)2
H3CO
H3CO
HO
6
8
9
8a R1= H, R2= H, R3= H, R4= H
9a R1= H, R2= H, R3= H, R4= H
8b R1= H, R2= OCH3, R3= H, R4= H
8c R1= H, R2= H, R3= OCH3, R4= H
8d R1= H, R2= OCH3, R3= OCH3, R4= H
8e R1= OCH3, R2= H, R3= H, R4= OCH3
9b R1= H, R2= OH, R3= H, R4= H
9d R1= H, R2= OH, R3= OH, R4= H
9e R1= OH, R2= H, R3= H, R4= OH
Scheme 4. Reagents and Conditions: (a) Diethylamine, TBTU, Acetonitrile; (b) BBr3, dichloromethane, -78 °C.
3.2. Antitumor Activity
most active -among all tested esters- was compound 5a,
which bears only hydrogens in the B-phenyl moiety. This
compound displayed the highest reduction of cell viability in
the MCF-7 cancer cell line (79%), while further studies re-
vealed that ester 5a exhibits an IC50 value of 14μꢀ against
MCF-7 breast cancer cell line (Fig. 1).
In order to investigate the antitumor properties of the
novel synthetic pyrazole derivatives against human cancer
cells, we have determined the activities of the hydroxy com-
pounds 5a-e, 7a-e and 9a,b,d,e against human A2058 mela-
noma, MCF-7 breast and DU145 prostate cancer cells at 20
μM concentration for 48 h. The respective results are pre-
sented in Table 1 indicating that the acid derivatives 7 are
inactive against all cancer cell lines except compounds 7c
and 7e which reduced cell viability by 47% and 61% respec-
tively in DU145 prostate cancer cell lines. Similarly, amides
9 displayed very low reduction in the viability of all cancer
cell lines except compound 9b, which reduced cell viability
by 50% at the MCF-7 breast cancer cell line. On the con-
trary, esters 5 showed good efficiency for the reduction of
cell viability against all tested cancer cell lines (Table 1). In
respect to their substitution pattern, it is evident that the in-
troduction of a hydroxy group at R2 or R3 positions of their
B-phenyl moieties (esters 5b and 5c respectively) results in
the decrease of their activity without differentiating their cell
viabilities. On the other hand, the introduction of two hy-
droxy groups at both R2 and R3 made ester 5d totally inactive
against all cancer cell lines. As is depicted in Table 1, the
Based on the aforementioned results, we exploited the
modification of ester 5a scaffold and synthesized the com-
pounds 3f-h, 4a,f-h and 5g. The biological evaluation results
for these molecules and their precursors 3a-e against human
A2058 melanoma, MCF-7 breast and DU145 prostate cancer
cells at 10 μM concentrations for 48 h are presented in Table
2. It is noticeable that the transformation of ethylester to the
corresponding methylester 5g resulted in the complete loss
of activity. Similar findings were obtained for the methoxy
precursor of ester 5a which was also totally inactive. In addi-
tion, the displacement of the oxygen with a sulphur atom
(thioesters 4a,f-h) did not increase the activity, while esters
3f,h which bear a hydrogen atom in the place of the hydroxy
group of ester 5a on their A-phenyl moiety exhibited only
moderate activity, which was lower when compared to the
activity of ester 5a. The introduction of a methoxy group in
the positions R1, R2, R3 and R4 of B-phenyl ring derived the

786 Medicinal Chemistry, 2012, Vol. 8, No. 5
Christodoulou et al.
Table 1. Cell Viability Upon Treatmenta for 48h at 37 °C for Compounds 5a-e, 7a-e and 9a,b-d,e
R3
R2
R4
R1
O
N
N
R
HO
Compound
R
R1
R2
R3
R4
Cell Viability (% Control)
A2058
38±3*
60±4*
61±4*
>100
DU145
32±2*
38±3*
39±3*
85±5*
50±4*
72±5*
>100
MCF-7
21±2*
50±4*
54±3*
ꢀ100
5a
5b
5c
5d
5e
7a
7b
7c
7d
7e
9a
9b
9d
9e
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OH
H
H
H
OH
H
H
H
H
H
H
OH
OH
H
H
H
OH
H
H
OH
H
OH
H
52±4*
95±5*
ꢀ100
88±5*
>100
H
H
OH
H
OH
H
H
H
>100
OH
H
OH
OH
H
H
>100
53±3*
94±5*
39±3*
67±4*
79±4*
91±5*
62±4*
>100
OH
H
OH
H
H
>100
>100
OH
OH
H
OH
H
88±5*
76±5*
68±3*
>100
77±5*
72±5*
50±2*
92±5*
ꢀ100*
N(CH2CH3)2
N(CH2CH3)2
N(CH2CH3)2
N(CH2CH3)2
H
H
H
OH
OH
H
H
H
H
OH
H
H
OH
OH
75±4*
aCells (5,000 cells/each well) were treated with 20 μM of 5a-e, 7a-e and 9a,b-d,e for 48h at 37 °C. Cell viability was determined as described in the Experimental Methods.
*P< 0.05, compared with control.
150
100
50
0
DMSO
0.1
1
5
10
20
Concentration ( M)

Fig. (1). Viability of MCF-7 Cancer cell line treated with ester 5a at Concentrations 0.1, 1, 5, 10, 20 μM. The IC50 of ester 5a was 14 μꢁ.

Synthesis and In Vitro Biological Evaluation of Novel Pyrazole Derivatives
Medicinal Chemistry, 2012, Vol. 8, No. 5 787
Table 2. Cell Viability Upon Treatmenta for 48h at 37 °C for Compounds 3a-h, 4a,f-h, 5g and 8a-e
R3
R2
R4
R1
R7
N
N
R6
R5
Compound
R1
R2
R3
R4
R5
R6
R7
Cell Viability (% Control)
A2058 MCF-7
DU145
82±5*
64±4*
81±5*
62±4*
77±4*
80±5*
75±5*
78±5*
94±5*
88±5*
83±5*
87±5*
62±4*
3a
3b
3c
3d
3e
3f
H
H
H
OCH3
H
H
H
H
H
OCH3
OCH3
OCH3
OCH3
OCH3
H
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH3
O
O
O
O
O
O
O
O
S
95±5*
85±5*
76±5*
69±4*
90±5*
91±5*
81±5*
88±5*
99±5*
>100
> 100
81±5*
93±5*
50±3*
59±3*
79±5*
83±5*
68±4*
>100
H
OCH3
OCH3
H
H
H
OCH3
H
H
OCH3
H
OCH3
H
H
H
3g
3h
4a
4f
H
H
H
H
OCH3
H
H
H
H
H
OCH3
H
H
H
H
OCH3
H
OCH2CH3
OCH2CH3
OCH3
H
H
H
H
S
93±5*
>100
4g
4h
5g
H
H
H
H
OCH3
H
S
88±5*
98±5*
74±5*
H
H
H
H
OCH3
S
92±5*
ꢀ100
H
H
H
H
OH
OCH3
O
a Cells (5,000 cells/each well) were treated with 10 μM of -h, 4a,f-h, 5g and 8a-e for 48h at 37 °C. Cell viability was determined as described in the Experimental Methods.
*P< 0.05, compared with control.
CONFLICT OF INTEREST
compounds 3b and 3c, which displayed very low inhibition
capacity, while the introduction of a second methoxy group
(compounds 3d and 3e) increased considerably their activity.
It must be pointed out that compounds 3d and 3e were de-
termined as the most potent which are acting selectively
against the MCF-7 breast cancer cells (Table 2), exhibiting
IC50 values of 10 and 12 μꢁ respectively.
The author(s) confirm that this article content has no con-
flicts of interest.
ACKNOWLEDGEMENT
Declared none.
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Received: March 08, 2011
Revised: November 11, 2011
Accepted: November 22, 2011