Preparation and Antibacterial Activity of 3-Methyl-1-p-substituted Phenylpyrazole-5-thiol

Article abstract of DOI:10.1002/1521-4184(200203)335:2/3<99::AID-ARDP99>3.0.CO;2-2

3-Methyl-1-phenylpyrazole-5-thiol (3a) and its p-nitro- (5) and p-fluorophenyl (8) derivatives were prepared as potential antimicrobial agents in relatively good yields. Compounds 3a and 8 showed good antibacterial activities against MRSA, S. aureus, S. epidermidis, E. faecalis, E.faecium, and S. pyogenes. Moreover, compound 3a also showed a synergistic effect with some aminoglycosides.

Full text of DOI:10.1002/1521-4184(200203)335:2/3<99::AID-ARDP99>3.0.CO;2-2

Arch. Pharm. Pharm. Med. Chem. 2002, 2, 99–103
3-Methyl-1-p-substituted Phenylpyrazole-5-thiol 99
a
Yoshinobu Tagawa ,
Preparation and Antibacterial Activity of
3-Methyl-1-p-substituted Phenylpyrazole-5-thiol
a
Shin’ichi Minami ,
b
Toshio Yoshida ,
a
Keitaro Tanaka ,
b
3-Methyl-1-phenylpyrazole-5-thiol (3a) and its p-nitro- (5) and p-fluorophenyl (8) de-
rivatives were prepared as potential antimicrobial agents in relatively good yields.
Compounds 3a and 8 showed good antibacterial activities against MRSA, S.
aureus, S. epidermidis, E. faecalis, E. faecium, and S. pyogenes. Moreover, com-
pound 3a also showed a synergistic effect with some aminoglycosides.
Shuji Sato ,
Yoshinobu Goto ,
Kenji Yamagata
a
a
aFaculty of Pharmaceutical
Sciences, Fukuoka University,
8
-19-1 Nanakuma, Jonan-ku, Keywords: 3-Methyl-1-p-substituted phenylpyrazole-5-thiol; Antibacterial; Syner-
Fukuoka 814-0180, Japan
Hisamitsu Pharmaceutical
Co., Inc., 1-25-11 Kannondai,
Tsukuba, Ibaraki,
gistic effect; MRSA; Tautomerism
b
Received: September 25, 2001 [FP635]
3
05-0856, Japan
Introduction
Pyrazolone derivatives such as antipyrine, aminopyrine,
or sulpyrine have been used clinically for a long time as
antipyretic analgesics which affect the central nervous
system; however, some serious allergenic and carcino-
genic side effects have been found. Recently, through
computationally directed broad screening, a novel 1,5-
diphenylpyrazole class of HIV-1 non-nucleoside reverse
transcriptase inhibitors has been discovered [1]. Thus,
we were interested in developing new analogues of pyra-
zolone or pyrazole derivatives. Among them, 3-methyl-
1
-p-substituted phenylpyrazole-5-thiol was selected on
the basis of the random screening using high throughput
screening (HTS) techniques for new good antibacterial
agents.We now report the preparation of some 3-meth-
yl-1-p-substituted phenylpyrazole-5-thiols and the relat-
ed compounds, and the results of the minimal inhibitory
concentration (MIC) and synergy testing for gram-
positive bacteria.
Scheme 1
In this reaction, the existence of 3 kinds of tautomers
1
13
3
a–3c is possible, and the H- and C-NMR spectra in
various solvents (CDCl , C D , and DMSO-d ) indicate
3
6
6
6
very strongly that it exists predominantly as the SH form,
a [2]. Furthermore, D O exchange experiments show
3
2
that the hydrogen of 4-position has high acidity, in keep-
ing with the experimental finding that sulfonation, bromi-
nation, and chlorination of 1-phenylpyrazolin-5-ones all
involve 4-substitution before attack on the phenyl ring
Results and Discussion
Chemistry
The most basic structure of this series, 3-methyl-1-phe-
nylpyrazole-5-thiol (3a) was prepared in 80% yield by
the reaction of commercially available 3-methyl-1-phe-
nyl-5-pyrazolone (1) with Lawesson’s reagent (2), along
with (4-methoxyphenyl)-phosphonotrithioic acid bis-(5-
methyl-2-phenyl-2H-pyrazol-3-yl) ester (4) in 8% yield
as by-product (Scheme 1).
[
3]. The optimal reaction conditions for preparing 3a
were investigated by varying the solvent, reaction tem-
perature, and reaction time:3a was obtained in the high-
est yield (85%) when the reaction mixture was heated at
6
0°C for 1 h in benzene.
The nitration of the para-position of the phenyl ring at 3a
seems to be difficult because of the above-mentioned
highly acidic hydrogen at the 4-position of the pyrazole
ring;actually, nitration of 1-phenylpyrazolin-5-ones using
nitric acid alone only gives the 4-nitropyrazolinone prod-
ucts [3]. However, we selectively obtained 3-methyl-1-p-
Correspondence: Yoshinobu Tagawa, Faculty of Pharmaceu-
tical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-
ku, Fukuoka 814-0180, Japan. Phone: +92 871 6631, Fax:
+
92 863 0389, e-mail: tagawa@fukuoka-u.ac.jp.
©
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2002
0365-6233/02–03/0099 $ 17.50+.50/0

1
00 Tagawa et al.
Arch. Pharm. Pharm. Med. Chem. 2002, 335, 99–103
microdilution method and are shown in Table 1. Com-
pounds 3a and 8 showed an MIC range of 6.3–25 µg/mL
which is comparable with that of linezolid.We found that
3
a showed low cytotoxicity of HeLa and COS7 cells by
standard MTS assay [4] (IC50 > 240 µg/mL) [5]. On the
other hand, 3a, 5, and 8 showed hardly any antibacterial
activity against gram-negative bacteria such as E. coli
MC1061, Klebsiella pneumoniae, Proteus vulgaris, and
Serratia marcescens (all >100 µg/mL).
Table 1. Antibacterial activity (MIC, µg/mL) of 3a, 5, 8,
linezolid and vancomycin.
Com-
S.
S.
E.
E.
S. MRSA
pound aureus epider- faeca- faeci- pyo-
Scheme 2
midis
lis
um
genes
3
5
8
a
6.3
100
6.3
6.3
25.0
12.5
12.5
6.3
nitrophenylpyrazole-5-thiol (5) in 76% yield by using ni-
tric acid-sulfuric acid at 0°C (Method A) (Scheme 2).
>100 >100 >100 >100 >100
25.0
3.2
12.5
3.2
25.0
12.5
0.8
25.0 12.5
Linezo-
lid
Vanco-
mycin 1.6
Compound 5 was also obtained in 58% yield by the reac-
tion of Lawesson’s reagent with 3-methyl-1-p-nitrophen-
ylpyrazol-5-ol (6) (69%), which was prepared via ring
closure reaction of ethyl acetoacetate and p-nitrophenyl-
hydrazine (Method B) (Scheme 2).
a)
3.2
3.2
0.2
3.2
1.6
0.8
1.6
a
(
S)-N-[3-[3-fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-
We are also interested in the biological activity of the p-
fluorophenyl derivative of 3a, so we synthesized 3-meth-
yl-1-p-fluorophenylpyrazole-5-thiol (8) by the reaction of
Lawesson’s reagent with 3-methyl-1-p-fluorophenyl-5-
pyrazolone (7), which was obtained via ring closure re-
action of ethyl acetoacetate and p-fluorophenylhydra-
zine, along with (4-methoxyphenyl)-phosphonotrithioic
acid bis[2-(4-fluorophenyl)-5-methyl-2H-pyrazol-3-yl]-
ester (9) (Scheme 3).
oxazolidiniyl]methylacetamide (Pharmacia).
As 3a gave the best antibacterial activity result com-
pared to 5 and 8 (Table 1), taking the structural similarity
of these 3 compounds into consideration, only the syner-
gistic effect of 3a in combination with known drugs active
against a variety of bacteria was further investigated.
The effects of combinations of the known drugs with 3a
were evaluated by the checkerboard method [6]. As de-
fined by Elion et al. [7], the fractional inhibitory concen-
tration (FIC) is the ratio of the MIC of a drug in the combi-
nation to the MIC of the drug alone expressed as a deci-
mal fraction.The FIC index (FICI) is the sum of the FICs
for each of the drugs in a particular combination. Drug
interaction was classified as“synergism (FICI ≤ 0.5)”and
“
partial synergism (0.5 < FICI < 1)”.When the FICI is less
than unity, synergy is suggested [8].
The synergistic activity of 3a with the known drugs, such
as cephems, aminoglycosides, glycopeptide, tetracy-
cline, macrolides, quinolones, and so on against MRSA
was examined and 3a indicated the strong synergy ef-
fect with several aminoglycosides (Table 2).
Furthermore, we examined the effects of combination of
4 kinds of aminoglycosides and tetracycline with 3a
against gram-positive bacteria as shown in Table 3.
Compound 3a has a good synergistic effect against
gram-positive bacterial strains tested as shown in
Scheme 3
Pharmacology
The compounds 3a, 5, and 8 prepared above were test-
ed in vitro against several gram-positive bacterial strains
as compared with linezolid (Pharmacia) and vancomy-
cin. MIC values were determined using arranged broth

Arch. Pharm. Pharm. Med. Chem. 2002, 335, 99–103
3-Methyl-1-p-substituted Phenylpyrazole-5-thiol 101
JEOL A-500 (500 MHz); 13C-NMR spectra, JEOL GX-400
Table 2. FICIs for 3a and the known drugs in combina-
tion against MRSA.
(
100 MHz) and JEOL A-500 (125 MHz); MS spectra, JMS-
HX100 for FAB-MS. The H-COSY, DEPT, and HMQC experi-
ments were also used for the assignments of the structures.
The chemical shifts are given on the δ scale. Elemental analy-
ses were performed on a Yanaco CHN CORDER MT-6 instru-
ment. Medium pressure liquid chromatography (MPLC) was
carried out withYamazen 540 FMI-C pump and Wakogel FC-40
Drugs
FICI
Vancomycin
Streptomycin
Gentamycin
Dibekacin
Amikacin
Arbekacin
Isepamicin
Tetracycline
Levofloxacin
Rifampicin
0.66
0.69
0.50
0.50
0.44
0.39
0.31
0.88
0.75
0.63
(
20–40 µm, Wako). Column chromatography was carried out
with Kieselgel 60 (70–230 mesh, Merck). High-performance
thin layer chromatography (HPTLC) for the yields shown in
Table 1 was conducted on Shimadzu high speed thin layer
chromatoscanner (CS-9300PC) with the detector set at λ =
2
54 nm.
Reaction of 1 with 2
mixture of 3-methyl-1-phenyl-5-pyrazolone (0.5 g,
A
2
.87 mmol) and Lawesson’s reagent (0.68 g, 1.69 mmol) in dry
toluene (30 mL) was refluxed for 2 hours and the solvent was
evaporated. The resulting residue was chromatographed on
MPLC to give 3-methyl-1-phenylpyrazole-5-thiol (3a) (with the
mixed solvent of n-hexane:AcOEt = 50:1) and (4-methoxy-
phenyl)-phosphonotrithioic acid bis-(5-methyl-2-phenyl-2H-
pyrazol-3-yl) ester (4) (with the mixed solvent of n-hexane:
AcOEt = 1:1).Compound 3a was recrystallised from n-hexane-
Table 3. FICIs for the combination of 4 kinds of aminogly-
cosides and tetracycline with 3a against gram-positive
bacteria.
Et O to give colorless needles, mp 111–112°C. 0.44 g (80%).
2
Anal. Calcd. for C H N S: H, 5.30; C, 63.13; N, 14.72. Found:
1
0
10
2
–
1
H, 5.37;C, 63.03;N, 14.60.IR (KBr):ν (cm ) 3141, 2539, 1559,
1
Strain
A
B
C
D
E
1495, 1359, 692. H-NMR (CDCl ): δ 2.30 (3H, s, CH ), 3.36
3
3
(
1H, s, SH), 6.25 (1H, s, H-4), 7.36–7.39 (1H, m, Ar-H), 7.44–
7
.47 (2H, m, Ar-H), 7.48–7.52 (2H, m, Ar-H). (C D ): δ 2.21
6
6
S. aureus
S. epidermidis
E. faecalis
E. faecium
S. pyogenes
0.63 0.50 0.50 0.57 0.75
0.53 0.52 0.60 0.60 0.57
(3H, s, CH ), 2.87 (1H, s, SH), 6.01 (1H, s, H-4), 6.96–6.97
3
(
1H, m, Ar-H), 7.04–7.07 (2H, m, Ar-H), 7.48–7.50 (2H, m, Ar-
H).(DMSO-d ):δ 2.21 (3H, s, CH ), 3.35 (1H, s, SH), 6.41 (1H,
6
3
0.63
–
–
–
0.63
1.0
13
s, H-4), 7.21–7.51 (5H, m, Ar-H). C-NMR (CDCl ): δ 13.5 (q,
3
0.51 0.38 0.57 0.50
CH ), 111.7 (d, C-4), 125.4 (d, Ar), 127.2 (s, Ar), 127.9 (d, Ar),
3
0.60 0.42 0.29 0.57 0.63
128.9 (d, Ar), 139.3 (s, Ar), 149.6 (s, Ar).(C D ):δ 13.6 (q, CH ),
6
6
3
1
12.4 (d, C-4), 125.4 (d, Ar), 125.7 (s, Ar), 127.4 (d, Ar), 128.7
(
d, Ar), 128.8 (d, Ar), 140.2 (s, Ar), 149.6 (s, Ar). (DMSO-d ): δ
6
A = 3a + Gentamycin, B = 3a + Amikacin, C = 3a + Ar-
bekacin, D = 3a + Isepamicin, E = 3a + Tetracycline.
13.2 (q, CH ), 114.7 (d, C-4), 124.6 (d, Ar), 125.2 (d, Ar), 125.3
3
(
1
d, Ar), 127.8 (d, Ar), 128.6 (d, Ar), 128.9 (d, Ar), 138.5 (s, Ar),
48.7 (s, Ar). MS (FAB ); 191 (M + H). Compound 4 was re-
+
+
crystallised from n-hexane-AcOEt to give pale pink prisms, mp
1
4
72.5–173.5°C.0.06 g (8%).Anal.Calcd.for C H N OPS :H,
27 25 4 3
Table 3, but had low or no synergistic activity against
gram-negative bacterial strains.
.59; C, 59.10; N, 10.21. Found: H, 4.68; C, 59.09; N, 10.04. IR
–
1
(KBr): ν (cm ) 3071, 2918, 2360, 1589, 1518, 1496, 1261,
1
1
096. H-NMR (CDCl ): δ 2.30 (6H, s, CH × 2), 3.85 (3H, s,
3
3
OCH ), 6.30 (2H, s, H-4 × 2), 6.74–6.76 (2H, dd, J = 3.4 Hz,
3
Ar-H), 7.31–7.33 (10H, m, Ar-H), 7.48–7.53 (2H, dd, J =
Acknowledgement
13
9
.0 Hz, Ar-H). C-NMR (CDCl ): δ 13.7 (q, CH ), 55.5 (q,
3
3
OCH ), 113.9 (d, Ar), 114.0 (d, Ar), 116.2 (d, C-4), 116.3 (d, C'-
3
The authors are grateful to Ms. M. Nakashima, Mr. K.
Atarashi, and Dr.K.Ikesue (Fundamental Research Lab-
oratory of Hisamitsu Pharmaceutical Co., Inc.) for their
excellent technical assistances.
4
), 124.7 (d, Ar), 125.8 (d, Ar), 125.8 (d, Ar), 126.1 (d, Ar), 127.8
(d, Ar), 128.5 (d, Ar), 133.2 (d, Ar), 133.3 (d, Ar), 139.0 (s, Ar),
149.5 (s, Ar), 163.2 (s, Ar). MS (FAB ); 549 (M + H).
+
+
3-Methyl-1-(p-nitrophenyl)pyrazole-5-thiol (5) – method A
Compound 3a (0.5 g, 2.63 mmol) was dissolved in sulfuric acid
(
(
20 mL) and the solution was cooled to –10°C.Then nitric acid
0.24 g, 3.73 mmol) was added to the solution and the reaction
Experimental
Chemistry
mixture was stirred 12 hours at 0°C. After the reaction, the mix-
ture was added to ice to give the yellow precipitate which was
recrystallised from n-hexane-AcOEt to give yellow powder, mp
165°C, 0.47 g (76%). Anal. Calcd. for C H N O S: H, 3.86; C,
Melting points were measured on a Yanagimoto micro melting
point apparatus and are uncorrected. Spectral data were re-
corded on the following spectrometers: IR spectra, JASCO FT/
1
0
9
3
2
51.05; N,17.86. Found: H, 3.64; C, 51.14; N, 17.84. IR (KBr): ν
1
–1
1
IR-470 Plus; H-NMR spectra, JEOL GX-400 (400 MHz) and
(cm ) 3125, 2360, 1594, 1519, 1340, 854. H-NMR (CDCl ):
3

1
02 Tagawa et al.
Arch. Pharm. Pharm. Med. Chem. 2002, 335, 99–103
δ 1.55 (1H, s, SH), 2.28 (3H, s, CH ), 6.35 (1H, s, H-4), 7.67
from Et O to give colorless prisms, mp 121–122°C, 0.25 g
3
2
1
3
(
2H, d, J = 9.2 Hz, Ar-H), 8.26 (2H, d, J = 9.2 Hz, Ar-H). C-
(16%). Anal. Calcd. for C H F N OPS : H, 3.97; C, 55.47; N,
2
7
23
2
4
3
–
1
NMR (CDCl ): δ 13.5 (q, CH ), 117.5 (d, C-4), 124.3 (d, Ar),
9.58. Found: H, 4.09; C, 55.39; N, 9.40. IR (KBr): ν (cm ) 3122,
3
3
1
1
24.7 (d, Ar), 133.5 (s, Ar), 143.8 (s, Ar), 146.4 (s, Ar), 151.1 (s,
2928, 2361, 1592, 1509, 1229, 1101, 835. H-NMR (CDCl ): δ
3
+
+
Ar). MS (FAB ); 236 (M + H).
2.30 (6H, s, CH × 2), 3.86 (3H, s, OCH ), 6.31 (2H, s, H-
3
3
4
× 2), 6.78–6.80 (2H, dd, J = 3.7 Hz, Ar-H), 6.98–7.00 (4H,
m, Ar-H), 7.26–7.31 (4H, m, Ar-H), 7.50–7.55 (2H, dd, J =
.0 Hz, Ar-H). 13C-NMR (CDCl ): δ 13.7 (q, CH ), 55.5 (q,
Method B
9
3
3
A mixture of 3-methyl-1-( p-nitrophenyl)pyrazol-5-ol (6) (0.5 g,
OCH ), 114.0 (d, Ar), 115.3 (d, Ar), 115.4 (d, Ar), 116.4 (d, C-4),
3
2
.28 mmol) and Lawesson’s reagent (0.54 g, 1.35 mmol) in dry
1
16.4 (d, C'-4), 124.7 (s, Ar), 125.4 (s, Ar), 126.0 (s, Ar), 128.0
toluene (20 mL) was refluxed for 3.5 hours and the solvent was
evaporated. The residue was chromatographed on MPLC to
give 5 (with the mixed solvent of n-hexane :AcOEt = 10:1),
(
d, Ar), 133.2 (d, Ar), 135.0 (s, Ar), 149.6 (s, Ar), 161.0 (s, Ar),
+
+
1
62.9, (s, Ar), 163.4 (s, Ar). MS (FAB ): 585 (M + H).
0
.31 g (58%).
Pharmacology
3-Methyl-1-(p-nitrophenyl)pyrazol-5-ol (6)
Antibacterial Agents
A mixture of ethyl acetoacetate (2.55 g, 19.6 mmol), 4-nitrophe-
nylhydrazine (3.0 g, 19.6 mmol) and sodium acetate (1.0 g,
Streptomycin, Dibekacin, Amikacin, Tetracycline, Rifampicin
were purchased from Sigma-Aldrich, Inc. Vancomycin, Gen-
tamycin were purchased from Wako Pure Chemical Industries,
Ltd. Arbekacin (Meiji Seika), Isepamicin (Schering Plough),
Levofloxacin (Daiichi), were prepared from pharmaceutical so-
lutions. Linezolid (Pharmacia), (S)-N-[3-[3-fluoro-4-(4-mor-
pholinyl)phenyl]-2-oxo-5-oxazolidiniyl]methyl-acetamide was
synthesized.
1
2.1 mmol) in 50% ethanol (90 mL) was refluxed for 4 hours.Af-
ter the reaction, on cooling to room temperature a brown pre-
cipitate appeared.The precipitate was filtered off and recrystal-
lised from methanol to give 6, yellow prisms, mp 223–224°C,
2
1
3
.96 g (69%). Anal. Calcd. for C H N O : H, 4.14; C, 54.79; N,
10 9 3 3
–1
9.17. Found: H, 4.30; C, 54.61; N, 18.93. IR (KBr): ν (cm )
1
124, 2360, 1627, 1580, 1507, 1333, 786. H-NMR (DMSO-
Antibacterial Activity Assays
d ): δ 2.16 (3H, s, CH ), 5.43 (1H, s, H-4), 8.06 (2H, d, J =
6
3
9
.2 Hz, Ar-H), 8.30 (2H, d, J = 9.2 Hz, Ar-H), 10.5–12.0 (1H,
The synthesized pyrazole derivatives were screened for their in
vitro activities against MRSA (methicillin-resistant Staphylo-
coccus aureus) (Chiba University, Clinical isolate), Staphylo-
coccus aureus (IFO127232 (ATCC6538P)), Staphylococcus
epidermidis (JCM2414 (ATCC14990)), Enterococcus faecalis
13
OH). C-NMR (DMSO-d ):δ 13.9 (q, CH ), 89.1 (d, C-4), 117.2
6
3
(
d, Ar), 118.9 (d, Ar), 124.8 (d, Ar), 143.2 (s, Ar), 143.8 (s, Ar).
+ +
MS (FAB ); 220 (M + H).
3-Methyl-1-(p-fluorophenyl)-5-pyrazolone (7)
(
JCM7738 (ATCC29212)), Enterococcus faecium (JCM5804
A mixture of ethyl acetoacetate (4.0 g, 30.7 mmol), 4-fluoro-
phenylhydrazine hydrochloride (5.0 g, 30.7 mmol), and sodium
acetate (1.55 g, 18.9 mmol) in 50% ethanol (150 mL) was re-
fluxed for 3 hours. After the reaction, the solvent was evaporat-
(ATCC19434)), Streptococcus pyogenes (JCM5674
(ATCC12344)) and Escherichia coli (IFO3972 (ATCC8739)),
Klebsiella pneumoniae (JCM1662 (ATCC13883)), Proteus vul-
garis (JCM1668 (ATCC13315)), Serratia marcescens
ed and the residue was extracted with Et O. The residue from
(JCM1239
(ATTC13880)),
Pseudomonas
aeruginosa
2
the Et O extract was recrystallised from n-hexane-Et O to give
(IFO13275 (ATCC9027)). The MICs of the compounds were
determined by the Japanese Society of Chemotherapy Stand-
ards broth microdilution method [9].The compounds dissolved
in DMSO (final concentration;1%) were tested at different con-
centrations (from 100 to 0.05 µg/mL). The MICs were meas-
ured after 20 hours’ incubation at 35°C.
2
2
7
, pale brown powder, mp 151–152°C, 3.83 g (65%). Anal.
Calcd. for C H N OF: H, 4.72; C, 62.49; N, 14.58. Found: H,
1
0
9
2
–
1
4
1
3
.68; C, 62.47; N, 14.49. IR (KBr): ν (cm ) 1622, 1506, 1404,
1
333, 1224, 823, 781. H-NMR (CDCl ): δ 2.18 (3H, s, CH ),
3
3
.41 (2H, s, H-4), 7.05–7.08 (2H, m, Ar-H), 7.81–7.84 (2H, m,
1
3
Ar-H). C-NMR (CDCl ):δ 16.9 (q, CH ), 43.0 (t, C-4), 115.4 (d,
3
3
Checkerboard method
Ar), 115.5 (d, Ar), 120.6 (d, Ar), 120.6 (d, Ar), 134.3 (s, Ar),
34.3 (s, Ar), 156.3 (s, Ar), 158.9 (s, Ar), 160.9 (s, Ar), 170.3 (s,
1
Interactions between antibacterial agents can be studied in vit-
ro using checkerboard titrations with serial doubling dilutions.
Antibacterial agents and 3a dissolved in DMSO (final concen-
tration; 1%) were tested at different concentrations (antibacte-
rial agents: from 0.2 to 200 µg/mL; 3a: from 3.2 to 200 µg/mL).
Each was made to cross as 3a in a vertical direction and the an-
tibacterial agents in a horizontal direction.Then bacterial solu-
tion (ca. 107 cells/mL, 100 µL) was added. The FICIs were
measured after 20 hours’ incubation at 35°C.
+
+
Ar). MS (FAB ); 193 (M + H).
Reaction of 7 with Lawesson’s reagent
A mixture of 7 (0.62 g, 3.23 mmol) and Lawesson’s reagent
(
3
0.77 g, 1.91 mmol) in dry toluene (18 mL) was refluxed for
.5 hours and the solvent was evaporated. The residue was
chromatographed on MPLC to give 3-methyl-1-( p-fluorophen-
yl)pyrazole-5-thiol (8) (with the mixed solvent of n-hexane:
AcOEt = 20:1) and (4-methoxyphenyl)-phosphonotrithioic acid
bis[2-(4-fluorophenyl)-5-methyl-2H-pyrazol-3-yl] ester (9) (with
the mixed solvent of n-hexane:AcOEt = 1:1). Compound 8 was
distilled under reduced pressure to give dark yellow viscous oil,
0
1
2
.42 g (62%). Anal. Calcd. for C H N SF: H, 4.36; C, 57.68; N,
10 9 2
–1
3.45. Found: H, 4.15; C, 57.76; N, 13.43. IR (neat): ν (cm )
1
References
928, 1511, 1365, 1226, 839, 605. H-NMR (CDCl ): δ 2.28
3
(
(
1
3H, s, CH ), 3.34 (1H, s, SH), 6.25 (1H, s, H-4), 7.05–7.16
3
13
[
1] M. J. Genin, B. J. Keiser, S. M. Poppe, S. M. Swaney, W. G.
2H, m, Ar-H), 7.26–7.49 (2H, m, Ar-H). C-NMR (CDCl ): δ
3
Tarpley, Y. Yagi, D. L. Romero, J. Med. Chem. 2000, 43,
3.5 (q, CH ), 111.9 (d, C-4), 114.9 (d, Ar), 115.7 (d, Ar), 115.8
3
1
034–1040.
(
1
d, Ar), 127.2 (d, Ar), 127.3 (d, Ar), 133.7 (s, Ar), 135.1 (s, Ar),
35.3 (s, Ar), 135.4 (s, Ar), 149.5 (s, Ar), 161.0 (s, Ar), 162.9 (s,
[2] J.J.Bergman, B.M.Lynch, J.Heterocycl.Chem.1974, 11,
+
+
Ar). MS (FAB ); 209 (M + H). Compound 9 was recrystallised
135–137.

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3-Methyl-1-p-substituted Phenylpyrazole-5-thiol 103
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