Anti-Helicobacter pylori agents. 4. 2-(Substituted guanidino)-4-phenylthiazoles and some structurally rigid derivatives

Article abstract of DOI:10.1021/jm000169n

In order to find a new class of anti-Helicobacter pylori (H. pylori) agents, a series of 4-[(3-acetamido)phenyl]-2-(substituted guanidino)thiazoles and some structurally rigid analoges were synthesized and evaluated for antimicrobial activity against H. pylori. Among the compounds obtained, high anti-H. pyrori activities were observed in benzyl derivative 34 (MIC = 0.025 μg/mL) and phenethyl derivatives 35 and 36 (MIC = 0.037 μg/mL and 0.017 μg/mL). Though alkyl derivatives generally showed lower activity, the 2-methoxyethyl derivative 28 preserved significant activity (MIC = 0.32 μg/mL) and also exhibited more potent gastric antisecretory activity than ranitidine. Structural restriction by bridging between the thiazole and the phenyl rings with an alkyl chain did not improve the activity in this series.

Full text of DOI:10.1021/jm000169n

J . Med. Chem. 2000, 43, 3315-3321
3315
An ti-Helicoba cter pylor i Agen ts. 4. 2-(Su bstitu ted gu a n id in o)-4-p h en ylth ia zoles
a n d Som e Str u ctu r a lly Rigid Der iva tives
Yousuke Katsura,*,‡ Tetsuo Tomishi,‡ Yoshikazu Inoue,‡ Kazuo Sakane,‡ Yoshimi Matsumoto,† Chizu Morinaga,†
Hirohumi Ishikawa,† and Hisashi Takasugi‡
Medicinal Chemistry Research Laboratories and Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Company
Ltd., 2-1-6, Kashima, Yodogawa-ku, Osaka 532-8514, J apan
Received April 17, 2000
In order to find a new class of anti-Helicobacter pylori (H. pylori) agents, a series of 4-[(3-
acetamido)phenyl]-2-(substituted guanidino)thiazoles and some structurally rigid analoges were
synthesized and evaluated for antimicrobial activity against H. pylori. Among the compounds
obtained, high anti-H. pyrori activities were observed in benzyl derivative 34 (MIC ) 0.025
µg/mL) and phenethyl derivatives 35 and 36 (MIC ) 0.037 µg/mL and 0.017 µg/mL). Though
alkyl derivatives generally showed lower activity, the 2-methoxyethyl derivative 28 preserved
significant activity (MIC ) 0.32 µg/mL) and also exhibited more potent gastric antisecretory
activity than ranitidine. Structural restriction by bridging between the thiazole and the phenyl
rings with an alkyl chain did not improve the activity in this series.
In tr od u ction
from (acetamidomethyl)acetophenones (3 or 7) by bro-
mination followed by cyclization with amidinothiourea.
The tricyclic derivatives 45-52 in Table 2 were
prepared by the routes shown in Scheme 2. Alkylation
of acetamido- (8) or (acetamidomethyl)phenols (10a and
10b) with ethyl 4-bromobutylate followed by hydrolysis
with sodium hydroxide gave the phenoxybutylic acid
derivatives 12a -c, which were cyclized with polyphos-
phoric acid (PPA) to afford the benzoxepinones (14a -
c). Hydrogenation of 3-(4-cyanophenoxy)propionic acid
(13)23 with palladium on carbon followed by treatment
with acetic anhydride and then cyclization with PPA
afforded the benzopyranone derivative 14d . Bromina-
tion of the cyclic ketones (14a -d ) and subsequent
cyclization with the appropriate amidinothioureas3 af-
forded the desired compounds with the oxomethylene
bridge (45-49 and 52).
In our previous papers,1-3 we reported the structure-
activity relationships (SARs) of a series of furylthiazoles
as a novel class of bactericidal agents for Helicobacter
pylori (H. pylori) which has been widely accepted as a
major causative factor in peptic ulcer diseases.4-22 To
investigate further the SAR in this class of compounds,
we next tried to replace the furan ring with a phenyl
ring in expectation of a successful bioisosteric conver-
sion. In this publication, we describe the synthesis and
the pharmacological evaluation of a series of 4-[3-
(acetamidomethyl)phenyl]-2-(substituted guanidino)-
thiazoles and some structurally rigid derivatives.
Ch em istr y
The target compounds listed in Table 1 were synthe-
sized by the routes outlined in Scheme 1. 3-Cyanoac-
etophenone (1) was treated with boron trifluoride ether-
ate in the presence of ethylene glycol to generate 3-(2-
methyl-1,3-dioxolan-2-yl)benzonitrile (2). Reduction of
the nitrile group with lithium alminium hydride fol-
lowed by cleavage of the ketal with 1 N hydrochloric
acid and then treatment with acetyl chloride afforded
3-(acetamidomethyl)acetophenone (3). Bromination of 3
and subsequent cyclization with thiourea provided the
2-aminothiazole derivative 4. Treatment of 4 with
benzoyl isothiocyanate gave the benzoylthiourea deriva-
tive 5, which was hydrolyzed with sodium hydroxide to
yield the thiourea derivative 6. After methylation of 6
with methyl iodide, reaction with appropriate amines
afforded the desired 4-[3-(acetamidomethyl)phenyl]-2-
(substituted guanidino)thiazoles (24-44). Unsubsti-
tuted guanidino derivatives 22 and 23 were prepared
4-Nitrobenzylbromide (15) was converted to 4-(aceta-
midomethyl)nitrobenzene (17) via Gabriel amine syn-
thesis followed by treatment with acetic anhydride.
Reduction of the nitro group on 17 gave the aniline
derivative 18, which was successively treated with
sodium nitrite and thioglycolic acid to afford 3-[4-
(acetmidomethyl)phenylthio]propionic acid (20b). 3-[4-
(Acetamido)phenylthio]propionic acid (20a ) was ob-
tained by the reaction of 4-(acetamido)thiophenol (19)
with â-propiolactone. The carboxylic acids (20a and 20b)
were converted to acid chlorides by treatment with
thionyl chloride and then were cyclized in the presence
of aluminum chloride to provide the benzothiopyranone
derivatives 21a and 21b. The synthesis of the target
compounds with thiomethylene bridge (50 and 51) was
carried out in a manner similar to those of the oxo-
methylene bridged derivatives.
Resu lts a n d Discu ssion
* Address for correspondence: Research Planning, Research Divi-
sion, Fujisawa Pharmaceutical Co., Ltd., 2-1-6, Kashima, Yodogawa-
ku, Osaka 532-8514, J apan. Phone: +81-6-6390-1335. Fax: +81-6-
6304-5385. E-mail: yousuke_katsura@po.fujisawa.co.jp.
‡ Medicinal Chemistry Research Laboratories.
The compounds obtained were evaluated for antimi-
crobial activity against H. pylori. Several derivatives
with minimum inhibitory concentration (MIC) less than
1 µg/mL were also tested for H2 antagonist and gastric
† Medicinal Biology Research Laboratories.
10.1021/jm000169n CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/02/2000

3316 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Katsura et al.
Ta ble 1. Physical Properties for 2-(Substituted guanidino)-4-phenylthiazoles
mp
(°C)
recryst
yield
(%)
compd
R
position
solventa
formula
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
H
H
Me
Et
n-C4H9
HO(CH2)2
MeO(CH2)2
MeO(CH2)3
NC(CH2)2
Me2N(CH2)2
EtO
Ph
PhCH2
Ph(CH2)2
2-MeOPh(CH2)2
4-MeOPh(CH2)2
Ph(CH2)3
Ph2CH(CH2)2
PhO(CH2)2
PhCH2O(CH2)2
PhCONH(CH2)2
2-pyridyl-(CH2)2
4-imidazolyl-(CH2)2
p
248-249
240-241
162-163
167-169
154-155
148-150
123-124
154-155
150-151
138-140
115-117
185-186
124-125
118-119
155-156
110-111
135-136
162-163
164-165
143-144
126-127
139-140
163-164
EA/M
I/M/T
EA/T
A/E
EA
A
EA
EA
A/W
EA
76
44
89
50
69
61
42
48
15
40
36
34
57
56
33
20
17
26
17
17
13
51
50
C
C
C
C
13H15N5OS‚2HCl
13H15N5OS
14H17N5OS
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
15H19N5OS
C17H23N5OS
C15H19N5O2S
C16H21N5O2S
C17H23N5O2S
C16H18N6OS
C17H24N6OS‚1/2H2O
C
C
A/I
15H19N5O2S‚HCl‚H2O
19H19N5OS
A/W
A/W
A/I
A/I
EA
M/W
A
EA/M
A/I
A/W
EA
A/EA
C20H21N5OS‚1/2H2O
C21H23N5OS
C22H25N5O2S
C22H25N5O2S
C22H25N5OS
C28H29N5OS‚H2O
C21H23N5O2S
C22H25N5O2S
C22H24N6O2S‚H2O
C20H22N6OS
C18H21N7OS
a
b
A ) EtOH, E ) Et2O, EA ) ethyl acetate, I ) diisopropyl ether, M ) MeOH, T ) toluene, W ) H2O. Analyses for C, H, and N are
within (0.4% of the theoretical values.
Sch em e 1a
a
Reagents: (a) HO(CH2)2OH/BF3‚Et2O; (b) LiAlH4; (c) 1 N HCl/MeOH; (d) AcCl/Et3N; (e) (1) Br2, (2) H2NCSNH2; (f) (1) Br2, (2)
(H2N)2CdNCSNH2; (g) PhCONCS; (h) NaOH/aq MeOH; (i) (1) MeI, (2) RNH2.
antisecretory activities since the prototype compound
in this series was obtained from a study of H2 antago-
nists.24 The results are summarized in Tables 3 and 4.
Regarding the position of the acetamidomethyl group
on the phenyl ring, the meta substituted derivative 23
showed anti-H. pylori activity, whereas the para posi-
tional isomer 22 did not show any activity. Therefore,
for the substituted guanidino derivatives, we have
prepared only the meta positional isomer.
Introduction of alkyl substituents (24-26) enhanced
the anti-H. pylori activity. Replacement of one methyl-
ene on 26 with an oxygen (28) did not produce a marked
change in the activity. However, elongation of the alkyl
chain (29) resulted in a decrease in activity. In the
phenyl alkyl series, benzyl (34) and phenethyl (35) were
preferable to phenyl (33) and phenylpropyl (38). Simi-
larly to the alkyl series, replacement of the methylene
in 38 with an oxygen (40) showed little effect on activity,
and extension of the alkyl spacer (41) reduced the
activity. Incorporation of an additional phenyl (39) onto
the phenylpropyl on 38 displayed a considerable de-
crease in activity. Remarkable reduction in the activities
was caused by introduction of an ionizable hydrogen (27,
42, and 44). Introduction of nitrile (30) or amine (31)
also resulted in a great loss of activity. A similar
reduction in potency was observed when an ethoxy was

2-(Substituted guanidino)-4-phenylthiazoles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3317
Ta ble 2. Physical Properties for Tricyclic Derivatives
mp
(°C)
recryst
yield
(%)
compd
R
m
n
X
position
solventa
formulab
45
46
47
48
49
50
51
52
H
H
H
0
1
1
1
1
0
1
1
2
1
2
2
2
1
1
2
O
O
O
O
O
S
A
A
A
A
A
A
A
B
262-263
238-239
>250
110-112
202-204
255-256
218-220
>250
D/W
D/I/M
D/W
I/M
I/M/T
I/M
17
19
42
46
31
58
30
23
C14H15N5O2S‚1/2H2O
C
C
14H15N5O2S
15H17N5O2S
n-C4H9
2-MeOPh(CH2)2
H
n-C4H9
H
C19H25N5O2S
C24H27N5O3S
C13H13N5OS2‚1/2H2O
S
O
E/EA/M
I/T/M
C18H23N5OS2‚HCl
C15H17N5O2S
a
b
E ) Et2O, EA ) ethyl acetate, D ) N,N-dimethylformamide, I ) diisopropyl ether, M ) MeOH, T ) toluene, W ) H2O. Analyses
for C, H, and N are within (0.4% of the theoretical values.
Sch em e 2a
a
Reagents: (a) (1) LiAlH4, (2) Ac2O; (b) EtOOC(CH2)3Br/K2CO3; (c) 1 N NaOH/MeOH; (d) â-propiolactone; (e) (1) H2/Pd-C, (2) Ac2O; (f)
(1) PPA; (g) (1) Br2, (2) RHNC(dNH2)NCSNH2; (h) potassium phthalimide; (i) (1) H2NNH2‚H2O, (2) Ac2O; (j) Fe/NH4Cl; (k) (1) NaNO2, (2)
HOOC(CH2)2SH; (1) HOOC(CH2)2Br; (m) (1) SOCl2, (2) AlCl3.
directly introduced onto the guanidine (32). These
results indicate that the potency is regulated by both
the steric bulk and the lipophilic nature in this area of
the molecule, and benzyl and phenethyl are the optimal
substituents.
The unique feature of this class of compounds is the
replacement of the flexible alkyl chain in conventional
H2 antagonists with an aromatic moiety. Though we
observed the lack of anti-H. pylori activity in the
marketed H2 antagonist,24,25 we also examined the
compounds consisting of a guanidinothiazole ring and
acetamidoalkyl function as the next referenced com-
pounds for this series (Chart 1). The compounds 53 and
54, which replace the phenyl ring of 23 with a flexible
alkyl chain, did not show any activity (MIC > 200 µg/
mL). This result, indicating the importance of structural
rigidity in the spacer group between the thiazole and
acetamidomethyl moieties, prompted us to further
investigate a series of compounds with a more confor-
mationally restrained structure (45-52). The results are
summarized in Table 4. The activity of 47 was only
3-fold less potent than that of the appropriate rotatable
analogue 23. However, contrary to our expectation, the
introduction of substitution onto the guanidino moiety
did not contribute to improvement of the activity, and
the activities of 48 and 49 were 35-fold and 1100-fold
weaker than those of the corresponding rotatable ana-
logues 26 and 36, respectively.
Concerning the H2 antagonist and antisecretory
activities, alkyl derivatives are generally more potent

3318 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Katsura et al.
Ta ble 3. Pharmacological Activities of 2-(Substituted guanidino)-4-phenylthiazoles
inhibition, %
MIC (mg/µL)a
gastric secretionb
(rat, 1 mg/kg iv)
H2 antagonismc
compd
R
position
mean
range
(1 × 10-6 g/mL)
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
H
H
Me
Et
n-C4H9
HO(CH2)2
MeO(CH2)2
MeO(CH2)3
NC(CH2)2
Me2N(CH2)2
EtO
Ph
PhCH2
Ph(CH2)2
2-MeOPh(CH2)2
4-MeOPh(CH2)2
Ph(CH2)3
Ph2CH(CH2)2
PhO(CH2)2
PhCH2O(CH2)2
PhCONH(CH2)2
2-pyridyl-(CH2)2
4-imidazolyl-(CH2)2
p
>100
16.5
14.4
3.6
0.22
20
0.32
0.96
19.3
57
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
3.13-50
3.13-25
1.56-6.25
0.1-0.39
6.25-50
0.2-0.39
0.39-1.56
6.25-25
12.5-100
12.5-50
74
84
87
87
83
54
29
0.52
0.025
0.037
0.017
0.32
0.39
2.5
0.49
2.5
23
0.49
27
0.057
0.021
5.4
18
1130
>1600
0.2-0.78
0.00625-0.05
0.0125-0.1
0.0030-0.05
0.2-0.78
0.2-0.78
1.56-3.13
0.39-0.78
0.78-6.25
3.13-50
24
50
59
58
10
57
23
77
65
72
34
35
18
14
52
39
0.39-0.78
6.25-50
clarithromycin
amoxicillin
metronidazole
bismuth subcitrate
cimetidine
0.025-0.1
0.00625-0.1
1.56-25
12.5-25
800-1600
53
72
43
44
ranitidine
a
Minimum inhibitory concentration (MIC) was determined as the lowest drug concentration that inhibited macroscopic colonial growth.
b
Mean MIC and range of MICs were obtained from the results of 10 different strains. Inhibition of histamine-stimulated gastric acid
secretion in lumen-perfused stomach of anesthetized rats (n ) 2). c Inhibition of histamine-stimulated chronotropic response in isolated
guinea pig right atrium.
Ta ble 4. Antimicrobial Activity of Tricyclic Derivatives against
Helicobacter pylori
Ch a r t 1
MIC (µg/mL)a
compd
R
m
n
X
position mean
range
45
46
47
48
49
50
51
52
H
H
H
0
1
1
1
1
0
1
1
2
1
2
2
2
1
1
2
O
O
O
O
O
S
A
A
A
A
A
A
A
B
>100
62
50
25-100
12.5-100
3.13-12.5
6.25-50
n-C4H9
2-MeOPh(CH2)2
H
n-C4H9
H
7.7
18.9
>100
22
showed susceptibility for a variety of organisms. On the
other hand, the antimicrobial activities of 28 and 36
were specific for H. pylori.
S
O
6.25-50
>100
a
See Table 3.
In conclusion, we have described our experimental
results in a novel phenylthiazole series as anti-H. pylori
agents. Among the compounds obtained, 2-(2-methoxy-
phenyl)ethyl derivative 36 exhibited the highest anti-
H. pylori activity in this series, and the potency was
superior to that of amoxicillin. On the other hand,
though methoxyethyl derivative 28 showed less potent
anti-H. pylori activity than 36, this compound had more
potent antisecretory activity than ranitidine. Regarding
than arylalkyl derivatives. Among them, both activities
of methoxyethyl (28) and methoxypropyl (29) derivatives
are superior to those of ranitidine.
Finally, we have assessed the specificity of antimi-
crobial activity for H. pylori of two representative
compounds (28 and 36) (Table 5). The clinically avail-
able drugs for the treatment of H. pylori eradication,
bismuth salicylate, metronidazole, and amixicillin,

2-(Substituted guanidino)-4-phenylthiazoles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3319
Ta ble 5. Antimicrobial Activity of 28, 36, and the Reference Compounds against Various Organisms
MIC (µg/mL) (range)
organisms (n)
H. pylori (10)
28
36
bismuth salicylate
8.7
metronidazole
amoxicillin
0.32
(0.2-0.39)
>100
0.017
(0.0030-0.05)
20.5
(12.5-50)
>100
5.4
(1.56-25)
30
0.021
(0.0063-0.1)
2.2
C. jejuni (8)
7.4
(6.25-12.5)
50
(0.78-100)
(0.39-6.25)
C. difficile (4)
>100
>100
>100
>100
>100
0.2
0.28
(0.1-0.39)
1.75
(0.1-0.78)
0.027
C. perfrigens (6)
B. fragilis (10)
N. gonorrheas (10)
N. meningitidis (10)
>100
>100
>100
>100
>100
(0.78-3.13)
(0.025-0.05)
50
0.59
2.1
(0.39-0.78)
>100
(0.2-12.5)
7.7
4.7
(3.13-6.25)
(0.39-100)
12.5
>100
0.056
(3.13-100)
(0.05-0.1)
Acetyl chloride (32 g, 0.17 mol) was added dropwise to a
suspension of 3-(aminomethyl)acetophenone hydrochloride (31
g, 0.17 mol) and Et3N (37 g, 0.34 mol) in CH2Cl2 (300 mL) at
5-10 °C, and the mixture was stirred for 1 h at room
temperature. After removal of the solvent, the residue was
dissolved in water (600 mL). The solution was made basic to
pH 10 with 20% aqueous K2CO3 and extracted with AcOEt.
The extract was dried and concentrated to afford 3 (20 g, 31%)
the mode of anti-H. pylori action, both compounds (28
and 36) showed bactericidal effect (data to be published
elsewhere). We selected 28 and 36 as candidates for
further pharmacological evaluation, and the results on
one of them, 28 (FR145175), have been reported in a
journal of pharmacology.26
1
as an oil. IR (film): 3250, 1680, 1640 cm-1. H NMR: δ 1.88
Exp er im en ta l Section
(3H, s), 2.57 (3H, s), 4.31 (2H, d, J ) 6 Hz), 7.43-7.54 (2H,
m), 7.82-7.87 (2H, m), 8.43 (1H, t, J ) 6 Hz). MS: m/z 192
(M+ + 1).
Melting points were determined on a Thomas-Hoover capil-
lary melting point apparatus and are uncorrected. Infrared
(IR) spectra were taken using a Hitachi 260-10 spectrometer.
Proton nuclear magnetic resonance (1H NMR) spectra were
recorded in dimethyl sulfoxide-d6 (DMSO) with tetramethyl-
silane as an internal standard on a Bruker AC-200P spec-
trometer. Mass spectral measurements (MS) were made on a
J EOL J MS D-300 mass spectrometer. Analytical results are
within (0.4% of the theoretical values unless otherwise
indicated. All extracted solutions were dried over Mg2SO4 and
concentrated to dryness on a rotary evaporator under reduced
pressure.
4-[3-(Acet a m id om et h yl)p h en yl]-2-a m in ot h ia zole (4).
Bromine (7.9 g, 50 mmol) was added dropwise to a solution of
3 (9.0 g, 50 mmol) in dioxane (100 mL) at room temperature
with stirring. After being stirred for 2 h, the solution was
concentrated to dryness. A solution of the residue and thiourea
(3.8 g, 50 mmol) in EtOH (100 mL) was refluxed for 2 h with
stirring. After removal of the solvent, the residue was dissolved
in water (100 mL). The solution was made basic to pH 10 with
20% aqueous K2CO3 and extracted with AcOEt. The extract
was dried and concentrated to give a residue, which was
recrystallized from MeOH/diisopropyl ether (IPE) to afford 4
(8.0 g, 69%): mp 172-173 °C. IR (Nujol): 3300, 3120, 1640,
3-(2-Meth yl-1,3-d ioxola n -2-yl)ben zon itr ile (2). A mix-
ture of 3-acetylbenzonitrile (1) (50 g, 0.34 mol), boron tri-
fluoride etherate (1 mL, 8 mmol), and ethylene glycol (30 mL,
0.55 mol) in benzene (200 mL) was refluxed for 5 h under water
removing with a Dean-Stark apparatus. The resulting solu-
tion was washed with saturated aqueous NaHCO3 (200 mL),
dried, and concentrated to afford 2 (65 g, 99%) as an oil. IR
1610 cm-1 1H NMR: δ 1.87 (3H, s), 4.26 (2H, d, J ) 6 Hz),
.
6.97 (1H, s), 7.06 (2H, s), 7.13 (1H, d, J ) 7.5 Hz), 7.30 (1H, t,
J ) 7.5 Hz), 7.64-7.68 (2H, m), 8.35 (1H, t, J ) 6 Hz). Anal.
(C12H13N3OS) C, H, N.
4-[3-(Acet a m id om et h yl)p h en yl]-2-(3-b en zoylt h iou r e-
id o)th ia zole (5). A suspension of 4 (2.0 g, 8.0 mmol) and
benzoyl isothiocyanate (1.3 g, 8.0 mmol) in Me2CO (40 mL)
was refluxed for 5 h. The resulting precipitate was collected
by filtration to afford 5 (2.9 g, 89%): mp 225-226 °C. IR
(film): 2230 cm-1 1H NMR: δ 1.64 (3H, s), 3.73-3.79 (2H,
.
m), 4.04-4.11 (2H, m), 7.46 (1H, t, J ) 7.5 Hz), 7.59 (1H, dt,
J ) 7.5 and 1.5 Hz), 7.73 (1H, dt, J ) 7.5 and 1.5 Hz), 7.80
(1H, t, J ) 1.5 Hz). MS: m/z 190 (M+ + 1).
1
(Nujol): 3260, 1680, 1640 cm-1. H NMR: δ 1.89 (3H, s), 4.31
3-(Aceta m id om eth yl)a cetop h en on e (3). A solution of 2
(65 g, 0.34 mol) in tetrahydrofuran (THF) (400 mL) was added
dropwise to a suspension of LiAlH4 (26.3 g, 0.69 mol) in THF
(400 mL) at 5-10 °C with stirring under a N2 atmosphere.
The mixture was stirred for 2 h at room temperature. AcOEt
(200 mL) was added dropwise to the reaction mixture under
cooling in an ice bath, and then ice-water (200 mL) was
carefully added. After the resulting precipitate was removed
by filtration, the filtered solution was concentrated and the
residue was dissolved in CHCl3. The solution was washed with
water, dried, and concentrated to give 2-[3-(aminomethyl)-
phenyl]-2-methyl-1,3-dioxolan (57.2 g) as an oil. IR (film):
(2H, d, J ) 6 Hz), 7.24 (1H, d, J ) 7.5 Hz), 7.40 (1H, t, J ) 7.5
Hz), 7.57 (2H, t, J ) 7.5 Hz), 7.67-7.84 (4H, m), 8.03 (2H, dd,
J ) 1.5 and 7 Hz), 8.41 (1H, t, J ) 6 Hz), 12.21 (1H, s), 14.27
(1H, s). Anal. (C20H18N4O2S2) C, H, N.
4-[3-(Ace t a m id om e t h yl)p h e n yl]-2-(t h iou r e id o)t h ia -
zole (6). A solution of NaOH (5 g, 125 mmol) in water (40
mL) was added to a suspension of 5 (20 g, 50 mmol) in MeOH
(400 mL), and the mixture was stirred at 60 °C for 2 h. After
removal of the solvent, the residue was added to water-AcOEt.
The resulting precipitate was collected by filtration to afford
6 (13.5 g, 90%): mp 230-231 °C. IR (Nujol): 3400, 3300, 1620
1
3300, 3250 cm-1. H NMR: δ 1.66 (3H, s), 3.72-3.82 (2H, s),
cm-1 1H NMR: δ 1.89 (3H, s), 4.29 (2H, d, J ) 6 Hz), 7.20
.
4.01-4.08 (2H, m), 7.23-7.42 (4H, m).
(1H, d, J ) 7.5 Hz), 7.37 (1H, t, J ) 7.5 Hz), 7.50 (1H, s), 7.73
(1H, d, J ) 7.5 Hz), 7.74 (1H, s), 8.37 (1H, t, J ) 6 Hz), 8.78
(1H, br s), 11.73 (1H, s). Anal. (C13H14N4OS2) C, H, N.
A solution of 2-[3-(aminomethyl)phenyl]-2-methyl-1,3-di-
oxolan (57 g) in 1 N HCl (500 mL)-MeOH (500 mL) was
stirred at room temperature for 2 h. After removal of the
solvent, the residue was washed with MeOH (50 mL) to give
3-(aminomethyl)acetophenone hydrochloride (31.2 g): mp
4-[5-(Acetam idom eth yl)ph en yl]-2-[2-(2-m eth oxyph en yl)-
eth yl]gu a n id in o]th ia zole (36). Gen er a l P r oced u r e. A
suspension of 6 (5.8 g, 12 mmol) and MeI (2.0 g, 14 mmol) in
MeOH (40 mL) was refluxed for 3 h with stirring. After
removal of the solvent, 2-(2-methoxyphenyl)ethylamine (7.2
g, 48 mmol) and EtOH (100 mL) were added to the residue,
145-146 °C. IR (Nujol): 3180, 1680 cm-1 1H NMR: δ 2.61
.
(3H, s), 4.11 (2H, s), 7.58 (1H, t, J ) 7.5 Hz), 7.76 (1H, d, J )
7.5 Hz), 7.97 (1H, d, J ) 7.5 Hz), 8.15 (1H, s), 8.50 (3H, br s).

3320 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Katsura et al.
and the resulting mixture was refluxed for 40 h. The solution
was concentrated to dryness, and the residue was dissolved
in water. The solution was made basic to pH 10 with 20%
aqueous K2CO3 and extracted with AcOEt. The extract was
dried and concentrated to give a residue, which was recrystal-
lized from EtOH/IPE to afford 36 (1.6 g, 33%). IR (Nujol):
solution of 20b (3.4 g, 13 mmol) in THF (30 mL) at room
temperature, and the mixture was stirred for 3 h. After
removal of the solvent, the residue was dissolved in CH2Cl2
(30 mL), and AlCl3 (3.6 g, 26 mmol) was added portionwise to
the solution. After being stirred for 2 h at room temperature,
the mixture was added to cold water. The organic layer was
separated, dried, and concentrated to give a residue, which
was chromatographed on silica gel eluting with CHCl3/MeOH
(50/1) to afford 21b (1.2 g, 39%): mp 109-111 °C. IR (Nujol):
3310, 3280, 1620 cm-1 1H NMR: δ 1.88 (3H, s), 2.77-2.85
.
(2H, t, J ) 7 Hz), 3.37-3.43 (2H, m), 3.80 (3H, s), 4.28 (2H, d,
J ) 6 Hz), 6.84-6.99 (2H, m), 7.14-7.24 (4H, m), 7.32 (1H, t,
J ) 7.5 Hz), 7.44 (2H, br s), 7.63-7.68 (2H, m), 8.36 (1H, t, J
) 6 Hz).
3280, 1660, 1645 cm-1 1H NMR: δ 1.86 (3H, s), 2.86-2.92
.
(2H, m), 3.27-3.35 (2H, m), 4.21 (2H, d, J ) 6 Hz), 7.31 (1H,
d, J ) 8 Hz), 7.37 (1H, dd, J ) 8 and 1 Hz), 7.86 (1H, d, J )
1 Hz), 8.39 (1H, t, J ) 6 Hz). MS: m/z 236 (M+ + 1).
Eth yl 4-[4-(Acetam idom eth yl)ph en yloxy]bu tylate (11b).
A mixture of 4-(acetamidomethyl)phenol (8.6 g, 52 mmol), ethyl
4-bromobutylate (10.2 g, 52 mmol), and fine granule K2CO3
(7.2 g, 52 mmol) in N,N-dimethylformamide (80 mL) was
stirred at 70 °C for 10 h. After removal of the solvent, the
residue was added to water-AcOEt, and the organic layer was
separated. The solution was washed with water, dried, and
concentrated to give a residue, which was chromatographed
on silica gel eluting with CHCl3/MeOH (50/1) to afford 11b
(10.5 g, 71%). An analytical sample was obtained by recrys-
tallization from AcOEt-hexane: mp 67-68 °C. IR (Nujol):
9-(Acet a m id om et h yl)-2-[2-(2-m et h oxyp h em yl)et h yl]-
gu a n id in o-4,5-d ih yd r ot h ia zolo-[5,4-d ]b en zoxep in (49).
Gen er a l P r oced u r e. A solution of bromine (550 mg, 3.4
mmol) in CH2Cl2 (2 mL) was added dropwise to a solution of
14b (800 mg, 3.4 mmol) in CH2Cl2 (8 mL) at room temperature
with stirring. After being stirred for 5 h, the solution was
concentrated to dryness. A solution of the residue, [2-(2-
methoxyphenyl)ethylamidino]thiourea3 (860 mg, 3.4 mmol),
and NaHCO3 (580 mg, 6.8 mmol) in EtOH (10 mL) was
refluxed for 4 h with stirring. After removal of the solvent,
the residue was added to water-AcOEt. The resulting pre-
cipitate was collected by filtration and recrystallized from
MeOH/IPE to afford 49 (550 mg, 35%): mp 202-204 °C. IR:
3440, 3300, 1650 cm-1. 1H NMR: δ 1.86 (3H, s), 2.81 (2H, t, J
) 7.5 Hz), 3.11 (2H, t, J ) 5 Hz), 3.33-3.43 (2H, m), 3.80 (3H,
s), 4.21 (4H, d, J ) 5 Hz), 6.84-6.99 (3H, m), 7.03 (1H, dd, J
) 2 and 8 Hz), 7.17-7.24 (2H, m), 7.37 (2H br s), 7.95 (1H, d,
J ) 2 Hz), 8.32 (1H, t, J ) 6 Hz).
An tim icr obia l Activity. In vitro antimicrobial activity
against H. pylori was determined by the agar dilution method.
Test strain was precultured in Brucella agar containing 3%
horse serum and 2% starch at 37 °C for 3 days and then
suspended in buffered saline to give the turbidity equivalent
to McFarland No. 1. Next, 102-fold dilutions of the bacterial
suspensions were inoculated with a multipoint replicator onto
a Brucella agar plus 7% lysed horse blood plate containing
serial 2-fold dilutions of each drug at 37 °C for 3 days.
Incubation was carried out in an atmosphere of 10% CO2. MIC
was read after incubation as the lowest drug concentration
that inhibited macroscopic colonial growth. Mean MIC was
determined from the MICs in 10 strains: H. pylori 8001, 8003,
8004, 8007, 8008, 8009, 8011, 9005, FP1530, and FP1532.
The MICs for C. jejuni, C. difficile, C. perfrigens, B. fragilis,
N. gonorrheas, and N. meningitidis were determined according
to the J apan Society of Chemotherapy Guidelines.27
Hista m in e H2-Recep tor An ta gon ist Activity. The atrial
strip isolated from guinea pig was suspended under an initial
tension of 0.3-0.6 g in an organ bath containing Thyrode
solution at 30 °C and aerated by 95% O2-5% CO2 gas. The
beating rate and amplitude of contraction of the atrium were
recorded by means of a transducer and a polygraph. Histamine
hydrochloride (1 × 10-6 g/mL) was added to the beating fluid,
and the increase in beating rate after dosing was measured.
Addition of test compounds (1 × 10-6 g/mL) was done 30 min
after washing out the histamine hydrochloride. The percent
inhibitory effect of the test compound was calculated by
comparing histamine-induced increases in beating rate before
and 30 min after dosing with the test compounds.
Ga st r ic An t isecr et or y Act ivit y in Lu m en -P er fu sed
Ra ts. Male Sprague-Dawley rats weighing about 250 g were
used. Rats were deprived of food for 24 h. The animals were
anesthetized with 1.25 g/kg urethane intraperitoneally. The
abdomen was opened, and the gastric lumen was perfused with
saline throughout the experiment. The perfusate was titrated
by an autotitrator with 25 mM NaOH as a titrant. Gastric
secretion was stimulated by intravenous infusion with hista-
mine (3 mg/kg/h). After reaching a plateau, the test compound
(1 mg/kg) was given intravenously. The effect of the drug was
expressed as maximal inhibition by acid output.
3275, 1715, 1630 cm-1 1H NMR: δ 1.07 (3H, t, J ) 7 Hz),
.
1.85 (3H, s), 1.95 (2H, quint, J ) 7 Hz), 2.44 (2H, t, J ) 7 Hz),
3.96 (2H, t, J ) 7 Hz), 4.13 (2H, q, J ) 7 Hz), 4.24 (2H, d, J )
7 Hz), 6.86 (2H, d, J ) 7.5 Hz), 7.16 (2H, d, J ) 7.5 Hz), 8.26
(1H, t, J ) 7 Hz). MS: m/z 280 (M+ + 1).
4-[4-(Aceta m id om eth yl)p h en yloxy]bu tyr ic Acid (12b).
A mixture of 11b (9.6 g, 35 mmol) and 1 N NaOH (35 mL) in
MeOH (100 mL) was stirred at room temperature for 7 h. After
removal of the solvent, the residue was added to water-CH2-
Cl2. The aqueous layer was separated, made acidic with 1N
HCl, and extracted with AcOEt. The extract was washed with
water, dried, and concentrated to afford 12b (6.3 g, 73%). An
analytical sample was obtained by recrystallization from
MeOH/IPE: mp 135-136 °C. IR (Nujol): 3320, 1690, 1610
cm-1 1H NMR: δ 1.84 (3H, s), 1.90 (2H, quint, J ) 7 Hz),
.
2.37 (2H, t, J ) 7 Hz), 3.94 (2H, t, J ) 7 Hz), 4.16 (2H, d, J )
6 Hz), 6.86 (2H, d, J ) 8 Hz), 7.15 (2H, d, J ) 8 Hz), 8.26 (1H,
t, J ) 6 Hz), 12.14 (1H, br s). MS: m/z 252 (M+ + 1).
7-(Aceta m id om eth yl)-2,3,4,5-tetr a h yd r o-1-ben zoxep in -
5-on e (14b). Compound 12b (4.5 g, 18 mmol) was added
portionwise to polyphospholic acid (PPA), fleshly prepared from
H3PO4 (10.5 g, 108 mmol) and P2O5 (17.8 g, 126 mmol), and
the mixture was stirred at 80 °C for 4 h. The reaction mixture
was carefully added to cold water under cooling in an ice bath
and extracted with CH2Cl2. The extract was washed with
saturated aqueous NaHCO3, dried, and concentrated to afford
14b (0.9 g, 22%) as an oil. IR (Film): 1760, 1655 cm-1 1H
.
NMR: δ 1.85 (3H, s), 2.10 (2H, quint, J ) 6.5 Hz), 2.77 (2H,
t, J ) 6.5 Hz), 4.18 (2H, t, J ) 6.5 Hz), 4.21 (2H, d, J ) 6 Hz),
7.06 (1H, d, J ) 8 Hz), 7.38 (1H, dd, J ) 8 and 2 Hz), 7.51
(1H, d, J ) 2 Hz), 8.35 (1H, t, J ) 6 Hz). MS: m/z 244 (M+
1).
+
4-[4-(Acet a m id om et h yl)p h en ylt h io]p r op ion ic
Acid
(20b). A solution of NaNO2 (3.2 g, 46 mmol) in water (10 mL)
was added dropwise to a solution of 4-(acetamidomethyl)-
aniline (18) (6.3 g, 38 mmol) and concentrated HCl (10 mL,
114 mmol) in water (60 mL) at 0-5 °C, and the mixture was
stirred for 3 h. A solution of 2-mercaptopropionic acid (4.1 g,
38 mmol) and NaOH (7.7 g, 190 mmol) in water (60 mL) was
added dropwise to the mixture at 0-5 °C. The resulting
mixture was stirred at room temperature for 30 min and then
at 70 °C for 4 h. The reaction mixture was washed with AcOEt,
made acidic with 6 N HCl, and extracted with AcOEt. The
extract was dried and concentrated to give a residue, which
was chromatographed on silica gel eluting with CHCl3/MeOH
(9/1) to afford 20b (3.6 g, 38%): mp 119-120 °C. IR (Nujol):
3260, 1690, 1655 cm-1. 1H NMR: δ 1.86 (3H, s), 2.50 (2H, t, J
) 7 Hz), 3.10 (2H, t, J ) 7 Hz), 4.21 (2H, d, J ) 6 Hz), 7.20
(2H, d, J ) 8 Hz), 7.30 (2H, d, J ) 8 Hz), 8.33 (1H, t, J ) 6
Hz), 12.38 (1H, br s). MS: m/z 253 (M+ + 1).
Ack n ow led gm en t. We are grateful to Dr. Hirokazu
6-(Aceta m id om eth yl)ben zoth iopyr a n -4-on e (21b). Thio-
nyl chloride (4.9 mL, 65 mmol) was added dropwise to a
Tanaka and Dr. Glen W. Spears for their valuable

2-(Substituted guanidino)-4-phenylthiazoles
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17 3321
(13) Partipilio, M. L.; Woster, P. S. The role of Helicobacter pylori in
peptic ulcer disease. Pharmacotherapy 1993, 13, 330-339.
(14) Marshall, B. J . Helicobacter pylori. Am. J . Gastroenterol. 1994,
89, s116-s128.
(15) Larry, K. L.; Tanaka, K. Therapy of Helicobacter pylori infec-
tions: Current status and future directions. Annu. Rep. Med.
Chem. 1995, 151-158.
(16) Axon, A. T. R. Eradication of Helicobacter Pylori. Scand. J .
Gastroenterol. 1996, 31 (Suppl. 214), 47-53.
(17) Blum, A. L. Helicobacter Pylori and peptic ulcer disease. Scand.
J . Gastroenterol. 1996, 31 (Suppl. 214), 24-27.
suggestions. Thanks are also due to the staff members
of our analytical division for elemental analyses and
measurement of spectral data.
Su p p or tin g In for m a tion Ava ila ble: Elemental analyses.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Refer en ces
(18) van der Hulst, R. W.; Keller, J . J .; Rauws, E. A.; Tytgat, G. N.
Treatment of Helicobacter pylori infection: a review of the world
literature. Helicobacter 1996, 1, 6-19.
(1) Katsura, Y.; Tomishi, T.; Inoue, Y.; Sakane, K.; Matsumoto, Y.;
Ishikawa, H.; Takasugi, H. Anti-Helicobacter pylori Agents. 1.
2-Alkylguanidino-4-furylthiazoles and Related Compounds. J .
Med. Chem. 1997, 40, 2462-2465.
(2) Katsura, Y.; Nishino, S.; Tomishi, T.; Sakane, K.; Matsumoto,
Y.; Ishikawa, H.; Takasugi, H. Anti-Helicobacter pylori agents.
2. Structure activity relationships in a new series of 2-alky-
lguanidino-4-furylthiazoles. Bioorg. Med. Chem. Lett. 1998, 8,
1307-1312.
(3) Katsura, Y.; Nishino, S.; Ohno, M.; Sakane, K.; Matsumoto, Y.;
Morinaga, C.; Ishikawa, H.; Takasugi, H. Anti-Helicobacter
pylori Agents. 3. 2-[(Arylalkyl)-guanidino]-4-furylthiazoles. J .
Med. Chem. 1999, 42, 2920-2926.
(4) Warren, J . R.; Marshall, B. J . Unidentified curved bacilli in the
stomach of patients with gastritis and peptic ulceration. Lancet
1984, 1311-1315.
(5) Glupczynski, Y.; Buret, A. Drug therapy for Helicobacter pylori
infection: Problems and pitfalls. Am. J . Gastroenterol. 1990, 85,
1545-1551.
(19) Dunn, B. E.; Cohen, H.; Blaser, M. J . Helicobacter pylori. Clin.
Microbiol. Rev. 1997, 10, 720-741.
(20) Current European concepts in the management of Helicobacter
pylori infection. The Maastricht consensus report. Gut 1997, 41,
8-13.
(21) Pattison, C. P.; Combs, M. J .; Marshall, B. J . Helicobacter pylori
and peptic ulcer disease: evolution to revolution to resolution.
Am. J . Roengenol. 1997, 168, 1415-1420.
(22) Olafesson, S.; Berstad, A. Therapy and diagnostic tests used for
Helicobacter pylori infection in the Scandinavian Countries in
1998. Scand. J . Gastroenterol. 1999, 34, 849-855.
(23) Buckle, D. R., Eggleston, D. S., Houge-Frydrych, C. S. V., Pinto,
I. L., Readshaw, S. A., Smith, D. G., Webster, R. A. B. Confor-
mational and Steric Modifications of the Pyran Ring of the
Pottasium-Channel Activator Cromakalim. J . Chem. Soc., Perkin
Trans. 1 1991, 2763-2771.
(24) Katsura, Y.; Inoue, Y.; Tomishi, T.; Itoh, H.; Ishikawa, H.;
Takasugi, H. Studies on Antiulcer Drugs. VI. 4-Furyl-2-guani-
dinothiazoles and Related Compounds as Potent Histamine H2-
Receptor Antagonists. Chem. Pharm. Bull. 1992, 40, 2432-2441.
(25) In the clinical development H2 antagonists, Ebrotidine was
reported to have the susceptibility to H. pylori (MIC)75µg/
mL): Palacin, C.; Tarrago, C., Sacristan, A., Qrtz, J . A. In vitro
anti-Helicobacter pylori activity of ebrotidine. Arzneim.-Forsch./
Drug Res. 1997, 47 (I), 471-474.
(26) Ishikawa, H.; Ito, H.; Higaki, M.; Higaki, M.; Matsumoto, Y.;
Kamimura, T.; Katsura, Y.; Tomishi, T.; Inoue, Y.; Takasugi,
H.; Tomoi, M.; Krakowka, S.; Yoshida, K. FR145715, a novel
hisatamine H2 receptor antagonist, with specific anti-Helico-
bacter pylori activities. Eur. J . Pharmacol. 1999, 378, 299-310.
(27) The J apan Society of Chemotherapy Guidelines for MIC Deter-
mination. Chemotherapy 1981, 29, 76-79.
(6) Dooley, C. P. Helicobacter pylori: review of search findings.
Aliment. Pharmacol. Ther. 1991, 5 (Suppl. 1), 129-143.
(7) Heatley, R. V. The treatment of Helicobacter pylori infection.
Aliment. Pharmacol. Ther. 1992, 6, 291-303.
(8) Chiba, N.; Rao, B. V.; Rademaker, J . W.; Hunt, R. H. Meta-
analysis of the efficacy of antibiotic therapy in eradicating
Helicobacter pylori. Am. J . Gastroenterol. 1992, 87, 1716-1727.
(9) Alper, J . Ulcers as an infectious disease. Science 1993, 260, 159-
160.
(10) Tytgat, G. N. J .; Lee, A.; Graham, D. Y.; Dixon, M. F.; Rokkas,
T. The role of infectious agents in peptic ulcer disease. Gastro-
enterol. Int. 1993, 6, 76-89.
(11) Ateshkadi, A.; Lam, N. P.; J ohnson, C. A. Helicobacter pylori
and peptic ulcer disease. Clin. Pharmacol. 1993, 12, 34-38.
(12) Fletcher, P. J .; Craig, Q. M. The role and treatment of Helico-
bacter pylori infection in peptic ulcer disease: a review of the
relationship between Helicobacter pylori infection and peptic
ulcer disease. J . Clin. Pharmacol. Ther. 1993, 18, 311-316.
J M000169N