Synthesis and biological activities of 4-phenyl-5-pyridyl-1,3-thiazole derivatives as selective adenosine A3 antagonists

Article abstract of DOI:10.1248/cpb.56.1126

To investigate the potency of an adenosine A₃ receptor (A ₃AR) antagonist as an anti-asthmatic drug, a novel series of 4-phenyl-5-pyridyl-1,3-thiazole derivatives was synthesized and evaluated in human adenosine A₁, A

Full text of DOI:10.1248/cpb.56.1126

1126
Chem. Pharm. Bull. 56(8) 1126—1137 (2008)
Vol. 56, No. 8
Synthesis and Biological Activities of 4-Phenyl-5-pyridyl-1,3-thiazole
Derivatives as Selective Adenosine A3 Antagonists
Seiji MIWATASHI,* Yasuyoshi ARIKAWA, Tatsumi MATSUMOTO, Keiko UGA, Naoyuki KANZAKI,
Yumi N. IMAI, and Shigenori OHKAWA
Pharmaceutical Research Division, Takeda Pharmaceutical Company, Ltd.; 2–17–85 Jusohonmachi, Yodogawa-ku, Osaka
532–8686, Japan. Received March 4, 2008; accepted May 20, 2008; published online May 22, 2008
To investigate the potency of an adenosine A3 receptor (A3AR) antagonist as an anti-asthmatic drug, a novel
series of 4-phenyl-5-pyridyl-1,3-thiazole derivatives was synthesized and evaluated in human adenosine A1, A2A
and A3 receptor and rat adenosine A3 receptor binding assays. From investigation of the SAR study, compound
7af was identified as a highly potent human and rat A3AR antagonist. This compound inhibited IB-MECA-in-
duced plasma protein extravasation in the skin of rats and showed good oral absorption. Also, compound 7af sig-
nificantly inhibited antigen-induced hyper-responsiveness to acetylcholine in actively sensitized Brown Norway
rats. These results show that 4-phenyl-5-pyridyl-1,3-thiazole derivatives are potential candidates to enable the
evaluation of A3AR antagonists. Further evaluation of this class of compounds may afford a novel anti-inflamma-
tory agent such as an anti-asthmatic drug.
Key words 5-pyridyl-1,3-thiazole; adenosine A3 receptor antagonist; antiphlogistic; rat antigen-induced asthma model; Brown
Norway rat
Adenosine, an endogenous purine nucleoside, modulates a
variety of physiological functions in various organs and tis-
sues, and interacts with four specific G-protein-coupled re-
ceptor subtypes (GPCRs), classified as A1, A2A, A2B, and
A3.1,2) All four receptors are coupled via G proteins to the
adenylate cyclase—cAMP signal transduction pathway. Acti-
vation of A1 and A3 receptors inhibits adenylate cyclase
Fig. 1. Chemical Structure and Biological Profiles of Lead Compound 7a
through Gi coupling, while activation of A2A and A2B recep-
tors stimulates adenylate cyclase through Gs coupling.3) In ed us to evaluate the potential of A3AR antagonist as a thera-
particular, the adenosine A3 receptor (A3AR) is distributed in peutic target. From high throughput screening, 4-phenyl-5-
different organs (lung, liver, kidney, heart and brain),4) and pyridyl-1,3-thiazole derivative 7a was identified as the
the potential therapeutic applications of antagonizing this re- preferable lead compound. We have already reported 1,3-thi-
ceptor are proposed to be useful for the treatment of inflam- azole derivatives as p38 MAP kinase inhibitors.30,31) These
mation,5) myocardial and brain ischemia,6—8) and cancer.9,10)
compounds were bound at the ATP binding site of the kinase,
As human adenosine A3 receptor (hA3AR) antagonists, and ATP is an adenosine-related compound. We therefore fo-
many potent and selective antagonists, such as xanthine cused our attention on compound 7a and investigated further.
derivatives,11) 1,4-dihydropyridines,12—15) triazoloquinazo- In the in vitro binding assay, compound 7a showed strong
lines,16,17) flavonoids,18) triazolonaphthyridines,19) thiazolopy- hA3AR antagonistic activity (Kiꢀ0.16 nM) and good hA3AR
rimidines,19,20) isoquinolines,21,22) quinazolines,21) pyrazolotri- selectivity, as shown in Fig. 1. Moreover, the rA3AR antago-
azolopyrimidines,23—25) thiazoles and thiadiazoles,26) and tri- nistic activity of this compound was moderate (Kiꢀ23 nM).
azolopurines27,28) have been reported as new hA3AR antago- To evaluate the efficacy of the rat asthma model, improve-
nists. Although these antagonists showed strong hA3AR an- ment of the rA3AR antagonistic activity of 7a was critical.
tagonistic activity and good selectivity against other adeno- In the present paper, we report the discovery of a series of
sine receptor subtypes, they were found to be weak or inef- 2-acylamino-4-phenyl-5-pyridyl-1,3-thiazole derivatives as
fective against rat A3AR (rA3AR),1,11,12,15,28,29) and could novel and potent antagonists against human and rat A3AR
therefore not be evaluated in rat in vivo models. The homol- through structural modification based on screening hit 7a.
ogy of A3AR among several species was reported and the
only 72% homology between human and rat A3AR was one Chemistry
reason for species differences.28) As selective hA3AR antago-
The general approach for the several 4,5-disubstituted 2-
nists that showed moderate affinity to rA3AR, only MRS acylamino-1,3-thiazoles 7 is outlined in Chart 1, according to
119114) and MRS 152315) (Kiꢀ1.42, 0.113 mM, respectively) the previous report.30)
have been reported, but these activities seemed to be insuffi-
The N-benzoyl-2-methylaziridines 2 were prepared from
cient for evaluation in rat models. Thus, A3AR antagonists the corresponding acid chlorides and commercially available
which show equipotent affinity and selectivity in different 2-methylaziridine, according to the Schotten–Baumann pro-
species have been desired for pharmacological probes on ani- cedure. The N-benzoyl-2-methylaziridines 2 were condensed
mal models, and the evaluation and selection of new drugs in with the lithium anion of methylpyridine 3 to afford the cor-
preclinical phase candidates is likely to be easier.
Our focus on an anti-asthmatic research program prompt- ation at methyl proton was occurred and no product from
responding ketones 4.30,32) In this reaction, the selective lithi-
∗ To whom correspondence should be addressed. e-mail: Miwatashi_Seiji@takeda.co.jp
© 2008 Pharmaceutical Society of Japan

August 2008
1127
Reagents: (a) 47% HBr (aq.), reflux; (b) MeCOCl (5 eq.), DMAP, DMA, 70 °C; (c)
K2CO3, rt.; (d) tBuOK, DMA, 0 °C, then alkyl iodide.
Reagents: (a) 2-methylaziridine, ether, 2 N NaOH, 0 °C; (b) LDA, hexane, THF,
ꢁ78 °C then ꢁ20 °C; (c) 2, ꢁ78 °C; (d) Br2, AcOH, 70 °C; (e) H2NC(S)NHR3, Et3N,
CH3CN, 80 °C; (f) R2COCl, DMAP, DMA, 70 °C.
Chart 3. Synthesis of 4-Alkoxyphenylthiazole Derivatives (11)
Chart 1. Synthesis of 2-Acylaminothiazole Derivatives (7)
Reagents: (a) 2 N-NaOH (aq.), rt.; (b) EtOH, reflux.
Chart 4. Synthesis of 2-Methylthiazole Derivative (12)
Hydrolysis of ethyl 2-thiazoleacetate 6aa and decarboxyla-
tion provided the desired 2-methyl compound 12, as shown
in Chart 4, according to the previous report.31) All of the syn-
thesized thiazole derivatives are listed in Table 1.
Reagents: (a) LDA, hexane, THF, ꢁ78 °C then ꢁ20 °C; (b) ethyl 4-(N,N-dimethyl-
amino)benzoate 8, ꢁ10 °C; (c) Br2, 30% HBr (aq.), AcOH, 70 °C; (d) H2NC(S)NH2,
Et3N, CH3CN, 80 °C; (h) CH3COCl, DMAP, DMA, 70 °C.
Chart 2. Synthesis of 4-[4-(N,N-Dimethylamino)phenyl]thiazole Deriva-
tive (7q)
Results and Discussion
All compounds were tested in radioligand binding assays
lithium anion of pyridine core was observed. Ketones 4 were to determine their affinities for adenosine A3, A1, and A2A re-
brominated to give a-bromoketones 5. Cyclization of ceptors. Ki values are summarized in Tables 2, 3, 4, and 5.
bromoketones 5 and thioureas provided 2-amino-1,3-thia-
Effects of Amide Group at C-2 Position and Pyridine
zoles 6. Acylation of 2-amino-1,3-thiazoles 6 was carried out Ring at C-5 Position First, the effect of the substituent on
using various acid chlorides with a catalytic amount of N,N- the 2-position (R2) of thiazole ring was evaluated with 6a, 12
dimethylaminopyridine (DMAP) in N,N-dimethylacetamide and 7a, as shown in Table 2. Although the acetamide 7a
(DMA) at 70 °C.
showed strong affinity to hA3AR, removal of the acetyl group
In order to obtain 4-[4-(N,N-dimethylamino)phenyl]thia- or replacement with a methyl group led to weak affinity (7a
zole derivative 7q, we tried to take a slightly different ap- vs. 6a and 12). Introduction of a methyl group into the 2-
proach as shown in Chart 2. 1-[4-(N,N-Dimethylamino)- acetamide 7a also reduced affinity (7a vs. 7e). These results
phenyl]-2-(4-pyridyl)ethanone 4q was obtained from ethyl 4- suggested that the carbonyl group and hydrogen atom of
(N,N-dimethylamino)benzoate 8 and 4-pyridylmethyllithium, amide at the C-2 position were important to interact with the
which was prepared from 4-methylpyridine 3a and lithium receptor. The structure–activity relationships (SAR) around
diisopropylamide (LDA), because of a failure to obtain 4- the pyridine ring at the C-5 position of the thiazole nucleus
(N,N-dimethylamino)benzoyl-2-methylaziridine. Although were evaluated with 7a—d. The 2-pyridyl derivative 7c and
direct bromination of ketone 4q was unsuccessful due to the 5-unsubstituted derivative 7d were less active than 4- or 3-
N,N-dimethylamino moiety, we achieved bromination using pyridyl derivatives 7a and 7b, indicating that nitrogen atoms
the hydrobromide salt of 4q, which was prepared with hydro- of 3- and 4-pyridyl groups are important for hA3AR affinity.
bromic acid in situ. Cyclization reaction of 5q and acylation The role of these substituents will be discussed in the Molec-
of 6q was carried out under the same condition.
ular Modeling Section.
The 4-methoxyphenyl derivative 6a was converted to 4-
The rA3AR affinity of the 3-pyridyl derivative 7b, 5-un-
alkoxyphenyl derivative 11, as shown in Chart 3. Acid hy- substituted compound 7d and N-methylacetamide compound
drolysis of the methoxy group of 6a yielded 4-hydroxy- 7e was examined; however, these compounds showed less
phenyl derivative 6z and acetylation of 6z was performed affinity than the lead compound 7a.
using acetyl chloride and DMAP in DMA to give diacetyl
SAR of the Substituent on Benzene Ring at C-4 Posi-
derivative 9. Saponification of compound 9 provided 4-hy- tion of 1,3-Thiazole Because of fairly good rA3AR affin-
droxyphenyl derivative 10 and the alkylation of intermediate ity, we selected the 4-pyridyl group at C-5 position of the thi-
10 using the corresponding alkyl iodide (RI) gave the alkoxy azole ring, and the influence of substituents on the phenyl
derivative 11.
ring at C-4 position of thiazole was investigated, as shown in

1128
Vol. 56, No. 8
Table 1. Physicochemical Properties of 5-Pyridyl-1,3-thiazole Derivatives
Compd.
Py
R1
R2
Formula
C15H13N3OS
C15H13N3OS
C15H13N3OS
C10H10N2OS
C16H15N3OS·0.5H2O
C15H13N3OS
C15H13N3OS·0.2H2O
C15H13N3S
C15H13N3S
C15H13N3S·0.2H2O
C14H10ClN3S
C14H10ClN3S
C14H10ClN3S
C16H15N3S
C17H17N3S
C18H19N3S·0.5H2O
C17H17N3S
C18H19N3S·0.5H2O
C16H16N4S
C16H15N3S
C16H15N3S
C16H15N3O2S
C15H11N3O2S
C18H19N3S
C16H15N3S
C16H15N3OS·3H2O
C19H18N2O3S
C17H15N3O2S
C17H15N3O2S
C17H15N3O2S
C12H12N2O2S
C18H17N3O2S
C17H15N3O2S·0.3H2O
C17H15N3O2S
C17H15N3OS
C17H15N3OS
C17H15N3OS
C16H12ClN3OS·0.2H2O
C16H12ClN3OS
C16H12ClN3OS
C18H17N3OS·0.1H2O
C19H19N3OS·0.2H2O
C20H21N3OS
C19H19N3OS
C20H21N3OS
C18H18N4OS·0.2H2O
C18H17N3OS
C18H17N3OS·0.1H2O
C18H17N3O3S
C17H13N3O3S
C21H23N3OS
C24H27N3OS
C25H23N3OS
C24H22N4OS
C24H22N4OS
C19H19N3OS
C22H23N3OS
C23H19N3OS
C22H18N4OS
C22H18N4OS·0.2H2O
C20H21N3OS·0.3H2O
C24H22N4OS
C18H17N3O2S
C22H18N4OS
C18H15N3O3S·0.2H2O
C16H13N3O2S·0.7H2O
C18H17N3O2S
mp (°C)
Anal.
6a
6b
6c
6d
6e
4-Py
3-Py
2-Py
H
4-MeO
4-MeO
4-MeO
4-MeO
4-MeO
3-MeO
2-MeO
4-Me
NH2
NH2
NH2
NH2
282—284
265—266
217—218
203—204
175—177
232—234
213—215
296—298
255—258
235—238
ꢂ300
256—258
232—235
285—288
240—242
204—206
267—269
254—257
309—311
248—250
242—244
218—219
273—275
239—241
237—240
323—326
Oil
282—284
119—120
230—232
192—193
180—181
234—236
259—261
308—309
287—289
272—274
317—320
290—293
292—293
294—295
256—258
259—261
295—297
280—281
289—291
248—250
284—286
265—267
295—296
295—297
309—311
292—294
326—328
326—329
291—293
275—278
285—286
267—270
302—304
228—230
251—253
288—289
277—278
254—257
285—287
206—209
201—203
132—133
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
NHMe
NH2
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
6q
6r
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
3-Me
2-Me
4-Cl
3-Cl
2-Cl
4-Et
4-nPr
4-nBu
4-iPr
4-tBu
6s
6t
4-Py
4-Py
4-Py
4-Py
4-Py
3-Py
3-Py
4-Py
4-Py
4-Py
3-Py
2-Py
H
4-Me2N
3,4-diMe
3,5-diMe
3,4-di(MeO)
3,4-(OCH2O)
4-tBu
6u
6v
6w
6x
6y
6z
6aa
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
7r
NH2
NH2
NH2
NH2
3,5-diMe
4-HO
4-MeO
4-MeO
4-MeO
4-MeO
4-MeO
4-MeO
3-MeO
2-MeO
4-Me
CH2CO2Et
NHAc
NHAc
NHAc
NHAc
NMeAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHAc
NHCOEt
NHCO(cPen)
NHCOPh
NHCO(3-Py)
NHCO(4-Py)
NHCOEt
NHCO(cPen)
NHCOPh
NHCO(3-Py)
NHCO(4-Py)
NHAc
NHCO(3-Py)
NHAc
NHCO(3-Py)
NHAc
NHAc
NHAc
NHAc
Me
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
3-Py
3-Py
3-Py
3-Py
4-Py
4-Py
4-Py
4-Py
4-Py
3-Me
2-Me
4-Cl
3-Cl
2-Cl
4-Et
4-nPr
4-nBu
4-iPr
4-tBu
7s
7t
4-Me2N
3,4-diMe
3,5-diMe
3,4-di(MeO)
3,4-(OCH2O)
4-tBu
7u
7v
7w
7x
7y
7z
7aa
7ab
7ac
7ad
7ae
7af
7ag
7ah
7ai
7aj
7ak
9
4-tBu
4-tBu
4-tBu
4-tBu
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
4-tBu
4-tBu
3,5-diMe
3,5-diMe
4-AcO
4-HO
10
11a
11b
12
4-EtO
4-nBuO
4-MeO
C20H21N3O2S
C16H14N2OS·0.1H2O

August 2008
1129
Table 2. Binding Affinity for Human A3, A1 and A2a, and Rat A3 Recep- Table 3. Effect of Substituent on 4-Phenyl Ring
tors
Ki (nM)
Ki (nM)
Compd.
Py
R2
Compd.
R
hA3
hA1
hA2A
rA3
23
69
1100
32
140
ꢂ1000
480
ꢂ1000
2100
81
hA3
hA1
hA2A
rA3
7a
7f
7g
7h
7i
7j
7k
7l
4-MeO
3-MeO
2-MeO
4-Me
3-Me
2-Me
4-Cl
0.16
0.12
1.1
0.08
0.15
1.8
0.10
0.15
0.73
0.20
0.28
0.26
0.40
0.21
22
ꢂ666
110
46
9.3
25
200
61
350
27
29
460
56
18
110
6a
12
7a
4-Py
4-Py
4-Py
3-Py
2-Py
(H)
NH2
Me
ꢂ285
ꢂ285
0.16
0.08
9.0
NTa)
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
NTa)
ꢂ826
200
145
160
NTa)
NTa)
23
NHAc
NHAc
NHAc
NHAc
NMeAc
7b
7c
160
NTa)
ꢂ980
360
7db)
7e
5.8
7.9
ꢂ826
ꢂ826
62
20
17
59
4-Py
3-Cl
a) NT indicates ‘not tested’. b) 7d is 5-unsubstituted derivative.
7m 2-Cl
7n
7o
7p
7q
7r
11a
11b
7s
4-Et
70
130
4-nPr
180
ꢂ666
ꢂ666
ꢂ666
170
ꢂ666
ꢂ666
34
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
49
64
56
Table 3.
4-nBu
4-iPr
180
45
ꢂ980
230
49
9.7
4.1
93
33
Introduction of methoxy (7a, f), methyl (7h, i) and chloro
(7k, l) substituents into 4- and 3-positions of the phenyl ring
showed potent activity for hA3AR, and substitution (7a, h, k)
at 4-position of the phenyl ring was more favored for rA3AR
than corresponding substitution (7f, i, l) at 3-position. The in-
troduction of substituents (7g, j, m) into the 2-position of the
phenyl ring led to significant reduction of hA3AR activity. As
for receptor sub-type selectivity, methyl (7h—j) and chloro
(7k—m) derivatives exhibited somewhat potent activity for
hA1AR and hA2AAR. In general, the 2- (7g, j, m) or 3-substi-
tuted (7f, i, l) compounds showed less hA3AR selectivity than
the corresponding 4-substituted compounds (7a, f, g).
4-tBu
4-EtO
4-nBuO
4-Me2N
3,4-diMe
3,5-diMe
3,4-di(MeO)
130
0.26
0.20
0.25
0.30
0.29
7t
7u
7v
ꢂ666
ꢂ666
19
ꢂ826
ꢂ826
25
7w 3,4-(OCH2O)
SAR of Acyl Group at 2-Position on 1,3-Thiazole The
influence of substituents at 2-position of thiazole was evalu-
Therefore, we focused the substituent at 4-position on the ated, as shown in Table 4. Among 4-tert-buthyl derivatives,
benzene ring, and examined further to identify the effect of it was observed that propionyl 7x and isonicotinoyl 7ab
activity and selectivity. Introduction of the bulky substituent retained activity, and cyclopentylcarbonyl 7y, benzoyl 7z
at 4-position slightly diminished hA3AR affinity but in- and nicotinoyl 7aa slightly reduced hA3AR affinity. 3,5-
creased hA3AR selectivity and rA3AR affinity. The 4-ethyl Dimethylphenyl derivatives 7ac—ag showed comparable
7n and 4-propyl 7o derivatives gave slightly less hA3AR and hA3AR activity to acetyl compound 7u. For rA3AR affinity,
rA3AR affinity than 4-methyl 7h, whereas the hA3AR selec- introduction of an aromatic acyl substituent such as benzoyl
tivity of these compounds increased. Although compounds 7z, 7ae, nicotinoyl 7aa, 7af, or isonicotinoyl 7ag led to a dra-
7p and 7q showed good hA3AR affinity and poor rA3AR matic increase in rA3AR affinity. Among these compounds,
affinity, the 4-tert-butyl derivative 7r showed potent rA3AR benzoyl derivative 7ae and nicotinoyl derivatives 7aa, 7af
affinity as 4-methyl derivative 7h. Although alkoxy deriva- showed the best results for receptor binding activity for both
tives 11a and 11b were synthesized and tested for their affin- hA3AR and rA3AR as well as selectivity over hA1AR and
ity, these compounds showed less affinity for hA3AR than hA2AAR.
methoxy derivative 7a. The 4-dimethylamino derivative 7s
Finally, we investigated the adenosine receptor affinity of
showed good hA3AR affinity and selectivity. These results compounds which have 3-pyridyl at 5-position on 1,3-thia-
suggested that the steric effect of the substituent would be a zole, as shown in Table 4, because 3-pyridyl derivative 7b
more important factor than the electronic effect for hA3AR (hA3; Kiꢀ0.08 nM) was stronger than the relative 4-pyridyl
selectivity and rA3AR affinity.
derivative 7a (hA3; Kiꢀ0.16 nM). Among 4-tert-butylphenyl
As for disubstitued derivatives, 3,4-dimethyl 7t and 3,4- derivatives, replacement of 4-pyridyl with 3-pyridyl led to
methylenedioxy derivatives 7w showed good hA3AR affinity, the reduction of both hA3AR and rA3AR affinity (7r vs. 7ah,
but the selectivity was insufficient. Dimethoxy 7v and 3,4- and 7u vs. 7aj). In 3,5-dimethylphenyl derivatives, 2-
methylenedioxy compounds 7w gave potent hA3AR affinity acetamide 7aj showed strong hA3AR activity; however, its
as well as good selectivity, but showed moderate rA3AR rA3AR activity was weak. Although 2-nicotinoyl derivative
affinity. Among these disubstituted derivatives, the 3,5-di- 7ak showed stronger rA3AR affinity than 7aj, its affinity for
methyl derivative 7u showed potent human and rat A3AR both A3AR was less than that of the corresponding 4-pyridyl
affinity as well as good selectivity.
derivative 7af.
On the basis of these results, we chose 4-tert-butyl and
Molecular Modeling Study To explain the above SAR,
3,5-dimethyl groups as representative substituents on the we tried to perform a docking study using a homology model
benzene ring for the next SAR study around 2-position of the of the hA3AR constructed from the crystal structure of
thiazole.
bovine rhodopsin (PDBID: 1F88) as a template, based on

1130
Vol. 56, No. 8
Table 4. Effect of Acyl Group at 2-Position on Thiazole
Ki (nM)
Compd.
Py
R1
R2
hA3
hA1
hA2A
rA3
7r
7x
7y
7z
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
3-Py
3-Py
4-Py
4-Py
4-Py
4-Py
4-Py
4-Py
3-Py
3-Py
4-tBu
NHCOMe
0.21
0.32
0.88
1.0
0.50
0.35
7.7
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ666
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
ꢂ826
76
45
30
11
2.5
4.3
4-tBu
NHCOEt
4-tBu
NHCO(cPen)
NHCOPh
4-tBu
7aa
7ab
7ah
7ai
7u
7ac
7ad
7ae
7af
7ag
7aj
7ak
4-tBu
NHCO(3-Py)
NHCO(4-Py)
NHCOMe
NHCO(3-Py)
NHCOMe
4-tBu
130
ꢂ1000
550
4.1
4-tBu
4-tBu
19
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
3,5-diMe
0.25
0.24
0.24
0.42
0.36
0.34
0.50
2.1
NHCOEt
7.0
3.5
1.2
1.6
NHCO(cPen)
NHCOPh
ꢂ826
ꢂ826
ꢂ826
63
NHCO(3-Py)
NHCO(4-Py)
NHCOMe
4.0
ꢂ1000
120
NHCO(3-Py)
ꢂ826
Fig. 2. Schematic Model for Binding hA3AR with Compound 7af
mutational studies, as previously reported.33,34) The homol- ity than 3-pyridyl compound 7b and 4-pyridyl compound 7a.
ogy model of hA3AR was constructed using the molecular Although this model can explain some SAR of these com-
operating environment (MOE 2005.06, Chemical Computing pounds for hA3AR, it was difficult to explain the SAR of the
Group: Montreal, Canada), and docking was performed man- substituent at 4-position on the phenyl ring from the results
ually using GOLD v3.0.35) Figure 2 shows the most reason- of our study. In this model, the substituent of the 4-position
able binding mode between A3AR and compound 7af.
of thiazole was directed toward the extracellular loop and
In this model, the amide moiety at 2-position of thiazole in subtype selectivity of the compound might be explained by
7af interacted with Asn250 (TM6) and His95 (TM3), sug- interaction with the loop. In general, extracellular loops are
gesting that the amine 6a and methyl derivative 12 without so flexible that modeling studies of these areas are very diffi-
an acyl group showed weak hA3AR binding activity. The cult. As a species difference, Leu264 (TM7) replaced Ser
pyridyl group at 2-position of 7af was placed in the hy- and Thr87 (TM3) replaced Met in rA3AR, with the model
drophobic pocket bordered by Phe208 (TM5) and Trp243 suggesting that the space for the ligand binding site in rA3AR
(TM6), and it was predicted that no residue of hA3AR would was wider than hA3AR. Better accommodation might be one
interact with the nitrogen atom of the pyridyl group. The re- reason that 3,5-dimethyl and 4-tert-butyl phenyl moieties
placement of Phe208 with Leu in rA3AR and p–p interac- showed good rA3AR affinity.
tion between Trp243 and the aryl substituent of 2 position of
In Vivo Efficacy of Selected A3AR Antagonists On the
thiazole could explain the increased affinity of rA3AR. The basis of the adenosine receptor binding assay, the six com-
third hydrogen bond between the nitrogen atom of the pyri- pounds listed were selected and evaluated for inhibition
dine ring and His272 (TM7) was predicted and the 4-position activity on IB-MECA (N6-(3-iodobenzyl)-9-[5-(methylcar-
of the phenyl ring of 7af was surrounded by Leu264 (TM7) bamoyl)-b-D-ribofuranosyl]adenine)-induced plasma protein
and Thr87 (TM3). This result also suggested that 2-pyridyl extravasation in the skin of rats, as shown in Table 5. Al-
compound 7c and hydrogen compound 7d showed less activ- though compounds 7z and ae showed no significant activity

August 2008
1131
in this model at a dose of 10 mg/kg, p.o., the other four com- (9.9%).
pounds 7u, 7aa, 7af and 7ag showed significant inhibitory
To determine the potency of A3AR antagonist as an anti-
activity in this model. Compounds 7u and 7af, in particular asthmatic drug, the selected compound 7af was evaluated in
completely inhibited dye leakage at 10 mg/kg, p.o. and PK an antigen-induced asthma model using Brown Norway (BN)
data of compounds 7u and 7af in rats is shown in Table 5. rats. Compound 7af dose-dependently inhibited antigen-in-
Compound 7af demonstrated a good oral absorption profile duced hyper-responsiveness to acetylcholine in actively sen-
and bioavailability (62.5ꢃ19.0%), whereas compound 7u sitized BN rats and this effect was statistically significant at
showed a poor oral absorption profile and low bioavailability oral administration of 10 mg/kg (Fig. 3). Compound 7af in-
creased the anti-asthmatic effect of dexamethasone by com-
bination therapy and these results suggested that the A3AR
antagonist could become a new type of anti-asthma drug as
an enhancer of steroids.
Conclusion
In this study, we found a novel series of 4-phenyl-5-
pyridyl-1,3-thiazole derivatives with human A3AR affinity,
which had received considerable attention for their structural
similarity to p38 MAPK inhibitors.30,31) The SAR of these
compounds was summarized as 1) pyridyl moiety at 5-posi-
tion of thiazole is important for affinity of hA3AR and
rA3AR; 2) the substituent on the phenyl ring at 4-position of
thiazole is related to adenosine receptor subtype selectivity;
3) the acyl moiety at 2-position of thiazole is important for
affinity of rA3AR, as shown in Fig. 4. As a result of the SAR
study, the highly potent hA3AR and rA3AR antagonist 7af
has been identified. This compound inhibited IB-MECA-in-
duced plasma protein extravasation in the skin of rats, and
showed good oral absorption in rats. Compound 7af signifi-
cantly inhibited antigen-induced hyper-responsiveness to
acetylcholine in actively sensitized BN rats. These results
show that 4-phenyl-5-pyridyl-1,3-thiazole derivatives are po-
Fig. 3. Effect of Combined Administration of 7af and Dexamethasone on
Antigen-Induced Airway Hyper-Responsiveness to Acetylcholine in Ac-
tively Sensitized BN Rats
BN rats were actively sensitized and 3 weeks later were challenged with saline or 1%
OVA. Airway responsiveness to acetylcholine was measured 23—30 h after antigen
challenge. Compound 7af (10 mg/kg) and dexamethasone (0.01 mg/kg) were orally ad-
ministered 1 h before and 7 h after antigen challenge. Data are the meanꢃS.E. of 8 rats.
##
pꢄ0.01, vs. saline-inhaled group, ∗∗ pꢄ0.01, vs. OVA-inhaled control group (two-
way ANOVA).
Table 5. Inhibition Activity on IB-MECA Induced Plasma Protein Extravasation in the Skin of Rats and Plasma Concentration after Oral Administration in
Rats
IB-NECA rat (%inh.)
rat PKa)
Ki (nM)
Dose (mg/kg, p.o.)
Dose (10 mg/kg, p.o.)
Compd.
R1
R2
hA3AR
rA3AR
Cmax
(mg/ml)
AUC0—24 h
(mg·h/ml)
BA
(%)
1
10
7u
7z
7aa
7ae
7af
7ag
3,5-Me2
4-tBu
NHCOMe
NHCOPh
NHCO(3-Py)
NHCOPh
NHCO(3-Py)
NHCO(4-Py)
0.25
1.0
0.50
0.42
0.36
0.34
4.1
2.5
4.3
1.2
1.6
4.0
73**
41
43**
48
83**
77**
107**
78
91**
77
102**
80**
0.035ꢃ0.011 0.263ꢃ0.053
9.9ꢃ2.0
NTb)
NTb)
NTb)
NTb)
NTb)
NTb)
NTb)
4-tBu
NTb)
3,5-Me2
3,5-Me2
3,5-Me2
NTb)
62.5ꢃ19.0
0.871ꢃ0.268 4.273ꢃ1.302
NTb) NTb)
∗∗ pꢄ0.01 vs. IB-MECA injection control (Dunnett’s test). nꢀ6. a) nꢀ3. b) NT indicates ‘not tested’.
Fig. 4. Structural Factors of Thiazole Compounds Affected the Binding Profile

1132
Vol. 56, No. 8
was cooled to ꢁ78 °C and a solution of 1.6 M n-butyllithium in hexane
(68.3 ml) was added dropwise to the solution. After addition, the solution
was stirred for 10 min and a solution of 4-methylpyridine (3a) (9.31 g) in
tetrahydrofuran (10 ml) was added dropwise to the LDA solution. The reac-
tion mixture was allowed to warm up to ꢁ10 °C and stirred for 20 min. The
resulting mixture was cooled to ꢁ78 °C and a solution of 2j (18.9 g) in
tetrahydrofuran (10 ml) was added dropwise to the mixture. After addition,
the mixture was stirred for 1 h at ꢁ78 °C and then the reaction mixture was
allowed to warm to room temperature. Water (300 ml) was added to the mix-
ture and the organic phase was separated. The aqueous phase was extracted
with ethyl acetate and the combined organic phases were dried and concen-
trated to give crude crystals, which were recrystallized from ethyl acetate–
isopropyl ether to afford 9.78 g (yield 43%) of 4l as a solid, mp 87—89 °C
(ethyl acetate–isopropyl ether), 1H-NMR (CDCl3) d: 1.26 (3H, t, Jꢀ7.5 Hz),
2.72 (2H, q, Jꢀ7.5 Hz), 4.27 (2H, s), 7.21 (2H, d, Jꢀ6.2 Hz), 7.31 (2H, d,
Jꢀ8.4 Hz), 7.93 (2H, d, Jꢀ8.4 Hz), 8.56 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for
C15H15NO: C, 79.97; H, 6.71; N, 6.22. Found: C, 79.83; H, 6.72; N, 6.20.
1-(4-Propylphenyl)-2-(4-pyridyl)ethanone (4m) This compound was
prepared from 2k as described in the synthesis of 4l as a solid, yield 32%,
mp 71—72 °C (ethyl acetate–hexane), 1H-NMR (CDCl3) d: 0.95 (3H, t,
Jꢀ7.3 Hz), 1.57—1.76 (2H, m), 2.66 (2H, t, Jꢀ7.7 Hz), 4.27 (2H, s), 7.21
(2H, d, Jꢀ6.2 Hz), 7.29 (2H, d, Jꢀ8.6 Hz), 7.92 (2H, d, Jꢀ8.6 Hz), 8.56
(2H, d, Jꢀ6.2 Hz). Anal. Calcd for C16H17NO: C, 80.30; H, 7.16; N, 5.85.
Found: C, 80.33; H, 7.16; N, 5.79.
1-(4-Butylphenyl)-2-(4-pyridyl)ethanone (4n) This compound was
prepared from 2l as described in the synthesis of 4l as a solid, yield 20%, mp
41—43 °C (isopropyl ether–hexane), 1H-NMR (CDCl3) d: 0.93 (3H, t,
Jꢀ7.1 Hz), 1.26—1.47 (2H, m), 1.54—1.72 (2H, m), 2.68 (2H, t,
Jꢀ7.7 Hz), 4.27 (2H, s), 7.21 (2H, d, Jꢀ6.0 Hz), 7.29 (2H, d, Jꢀ8.6 Hz),
7.92 (2H, d, Jꢀ8.6 Hz), 8.56 (2H, d, Jꢀ6.0 Hz). Anal. Calcd for C17H19NO:
C, 80.60; H, 7.56; N, 5.53. Found: C, 80.55; H, 7.31; N, 5.47.
1-[4-(1-Methylethyl)phenyl]-2-(4-pyridyl)ethanone (4o) This com-
pound was prepared from 2m as described in the synthesis of 4l as a solid,
yield 43%, mp 86—88 °C (isopropyl ether–hexane), 1H-NMR (CDCl3) d:
1.27 (6H, d, Jꢀ7.0 Hz), 2.87—3.06 (1H, m), 4.27 (2H, s), 7.21 (2H, d,
Jꢀ6.2 Hz), 7.34 (2H, d, Jꢀ8.4 Hz), 7.94 (2H, d, Jꢀ8.4 Hz), 8.56 (2H, d,
Jꢀ6.2 Hz). Anal. Calcd for C16H17NO: C, 80.30; H, 7.16; N, 5.85. Found: C,
80.29; H, 7.18; N, 5.84.
tential candidates to evaluate A3AR antagonists as new drugs
for the treatment of inflammatory diseases, such as asthma.
Experimental
General Melting points (mp) were determined on a Yanagimoto micro
melting point apparatus or Büche B-545 and are uncorrected. Proton nuclear
magnetic resonance (NMR) spectra were recorded on a Varian Gemini-200
(200 MHz) spectrometer, with tetramethylsilane as the internal standard.
TLC analyses were carried out on Merck Kieselgel 60 F254 plates. Elemental
analyses were carried out by Takeda Analytical Laboratories, Ltd., and are
within ꢃ0.4% of the theoretical values unless otherwise noted. THF was
distilled over calcium hydride prior to use and other solvents and reagents
were used without purification. Extracted solutions were dried over anhy-
drous Na2SO4 unless otherwise noted and the concentration of the organic
solution was carried out under reduced pressure. Chromatographic purifica-
tion was carried out on silica gel columns (Kieselgel 60, 0.063—0.22 mm,
Merck) unless otherwise noted. The yields reported are not optimized.
The 1-benzoyl-2-methylaziridines 2a—i, 1-phenyl-2-pyridylethanones
4a—k and 4p, 2-bromo-1-phenyl-2-pyridylethanones 5a—k and 5p, 4-
phenyl-5-pyridyl-1,3-thiazol-2-ylamines 6a—c, 6f—m, and 6r, and N-(4-
phenyl-5-pyridyl-1,3-thiazol-2-yl)acetamides 7a—c, 7f—m and 7r were
prepared according to a previous report.30)
The 1-benzoylaziridine derivatives 2 were unstable under silica gel col-
umn chromatography or distillation, so these compounds were used for next
reaction without purification as following typical condition.
1-(4-Ethylbenzoyl)-2-methylaziridine (2j) A solution of 2-methylaziri-
dine (14.3 ml, 0.183 mol) in diethyl ether (170 ml) was added to 2 N aqueous
sodium hydroxide solution (95 ml). This mixture was cooled to 0 °C and 4-
ethylbenzoyl chloride (28.0 g, 0.166 mol) was added dropwise to the mix-
ture. After the addition, the mixture was further stirred for 1 h at 0 °C. The
organic phase was separated and the aqueous phase was extracted with di-
ethyl ether. The combined organic phase was dried, and concentrated to af-
1
ford 36.4 g (yield quant.) of 2j as an oil, H-NMR (CDCl3) d: 1.27 (3H, t,
Jꢀ7.6 Hz), 1.39 (3H, d, Jꢀ5.5 Hz), 2.12 (1H, d, Jꢀ2.9 Hz), 2.50—2.61 (2H,
m), 2.71 (2H, q, Jꢀ7.6 Hz), 7.47 (2H, d, Jꢀ8.8 Hz), 7.96 (2H, d, Jꢀ8.8 Hz).
1-(4-Propylbenzoyl)-2-methylaziridine (2k) This compound was pre-
pared from 4-propylbenzoyl chloride as described in the synthesis of 2j, as
1
an oil, yield quant., H-NMR (CDCl3) d: 0.96 (3H, t, Jꢀ7.3 Hz), 1.39 (3H,
d, Jꢀ5.5 Hz), 1.57—1.75 (2H, m), 2.12 (1H, d, Jꢀ3.3 Hz), 2.50—2.59 (2H,
m), 2.65 (2H, t, Jꢀ7.7 Hz), 7.26 (2H, d, Jꢀ8.1 Hz), 7.94 (2H, d, Jꢀ8.1 Hz).
1-(4-Butylbenzoyl)-2-methylaziridine (2l) This compound was pre-
pared from 4-butylbenzoyl chloride as described in the synthesis of 2j, as an
oil, yield quant., 1H-NMR (CDCl3) d: 0.94 (3H, t, Jꢀ7.1 Hz), 1.26—1.47
(5H, m), 1.54—1.73 (2H, m), 2.12 (1H, d, Jꢀ2.9 Hz), 2.51—2.62 (2H, m),
2.67 (2H, t, Jꢀ7.7 Hz), 7.26 (2H, d, Jꢀ8.1 Hz), 7.94 (2H, d, Jꢀ8.1 Hz).
1-[4-(1-Methylethyl)benzoyl]-2-methylaziridine (2m) This compound
was prepared from 4-(1-methylethyl)benzoyl chloride as described in the
synthesis of 2j, as an oil, yield quant., 1H-NMR (CDCl3) d: 1.28 (6H, d,
Jꢀ7.0 Hz), 1.40 (3H, d, Jꢀ5.4 Hz), 2.12 (1H, d, Jꢀ3.2 Hz), 2.51—2.63 (2H,
m), 2.87—3.03 (1H, m), 7.31 (2H, d, Jꢀ8.4 Hz), 7.96 (2H, d, Jꢀ8.4 Hz).
1-(3,4-Dimethylbenzoyl)-2-methylaziridine (2o) This compound was
prepared from 3,4-dimethylbenzoyl chloride as described in the synthesis of
2j, as an oil, yield quant., 1H-NMR (CDCl3) d: 1.39 (3H, d, Jꢀ5.5 Hz), 2.12
(1H, d, Jꢀ3.3 Hz), 2.32 (6H, s), 2.49—2.61 (2H, m), 7.21 (1H, d, Jꢀ
7.7 Hz), 7.77 (1H, dd, Jꢀ7.7, 1.8 Hz), 7.80 (1H, d, Jꢀ1.8 Hz).
1-(3,5-Dimethylbenzoyl)-2-methylaziridine (2p) This compound was
prepared from 3,5-dimethylbenzoyl chloride as described in the synthesis of
2j, as an oil, yield quant., 1H-NMR (CDCl3) d: 1.39 (3H, d, Jꢀ5.5 Hz), 2.13
(1H, d, Jꢀ3.7 Hz), 2.37 (6H, s), 2.47—2.62 (2H, m), 7.19 (1H, s), 7.64 (2H,
s).
1-(3,4-Dimethoxybenzoyl)-2-methylaziridine (2q) This compound
was prepared from 3,4-dimethoxybenzoyl chloride as described in the syn-
thesis of 2j, as an oil, yield quant., 1H-NMR (CDCl3) d: 1.41 (3H, d,
Jꢀ5.5 Hz), 2.12 (1H, d, Jꢀ3.3 Hz), 2.51—2.63 (2H, m), 3.94 (3H, s), 3.95
(3H, s), 6.92 (1H, d, Jꢀ8.5 Hz), 7.56 (1H, d, Jꢀ2.2 Hz), 7.69 (1H, dd,
Jꢀ8.5, 2.2 Hz).
1-[4-(N,N-Dimethylamino)phenyl]-2-(4-pyridyl)ethanone (4q) Under
argon atmosphere, a solution of diisopropylamine (15.4 ml) in tetrahydrofu-
ran (100 ml) was cooled to ꢁ78 °C and a solution of 1.6 M n-butyllithium in
hexane (68.3 ml) was added dropwise to the solution. After addition, the so-
lution was stirred for 10 min and a solution of 4-methylpyridine (3a) (9.31 g)
in tetrahydrofuran (10 ml) was added dropwise to the LDA solution. The re-
action mixture was allowed to warm up to ꢁ10 °C and stirred for 1 h. A so-
lution of ethyl 4-(N,N-dimethylamino)benzoate (21.3 g) in tetrahydrofuran
(10 ml) was added dropwise to the mixture. After addition, the mixture was
stirred for 1 h at ꢁ10 °C and then the reaction mixture was allowed to warm
to room temperature. Water (100 ml) was added to the mixture and the or-
ganic phase was separated. The aqueous phase was extracted with ethyl ac-
etate and the combined organic phases were washed, dried and concentrated
to give crude crystals, which were recrystallized from ether to afford 7.19 g
(yield 30%) of 4q as a solid, mp 189—192 °C, 1H-NMR (CDCl3) d: 3.07
(6H, s), 4.19 (2H, s), 6.66 (2H, d, Jꢀ9.0 Hz), 7.22 (2H, d, Jꢀ5.9 Hz), 7.90
(2H, d, Jꢀ9.0 Hz), 8.53 (2H, d, Jꢀ5.9 Hz). Anal. Calcd for C15H16N2O: C,
74.97; H, 6.71; N, 11.66. Found: C, 74.98; H, 6.78; N, 11.65.
1-(3,4-Dimethylphenyl)-2-(4-pyridyl)ethanone (4r) This compound
was prepared from 2o as described in the synthesis of 4l as a solid, yield
40%, mp 81—83 °C (ethyl acetate–isopropyl ether), 1H-NMR (CDCl3) d:
2.33 (6H, s), 4.26 (2H, s), 7.21 (2H, d, Jꢀ5.9 Hz), 7.24 (1H, d, Jꢀ7.9 Hz),
7.73 (1H, dd, Jꢀ7.9, 1.8 Hz), 7.77 (1H, d, Jꢀ1.8 Hz), 8.56 (2H, d,
Jꢀ5.9 Hz). Anal. Calcd for C15H15NO: C, 79.97; H, 6.71; N, 6.22. Found: C,
79.89; H, 6.72; N, 6.15.
1-(3,5-Dimethylphenyl)-2-(4-pyridyl)ethanone (4s) This compound
was prepared from 2p as described in the synthesis of 4l as a solid, yield
1
58%, mp 90—91 °C (ethyl acetate–hexane), H-NMR (CDCl3) d: 2.38 (6H,
1-(1,3-Benzodioxol-5-ylcarbonyl)-2-methylaziridine (2r) This com-
pound was prepared from 1,3-benzodioxol-5-ylcarbonyl chloride as de-
scribed in the synthesis of 2j, as an oil, yield 92%, 1H-NMR (CDCl3) d: 1.38
(3H, d, Jꢀ4.9 Hz), 2.11 (1H, d, Jꢀ3.1 Hz), 2.48—2.64 (2H, m), 6.05 (2H,
s), 6.86 (1H, d, Jꢀ8.2 Hz), 7.48 (1H, d, Jꢀ1.7 Hz), 7.65 (1H, dd, Jꢀ8.2,
1.7 Hz).
s), 4.26 (2H, s), 7.20 (2H, d, Jꢀ5.9 Hz), 7.24 (1H, s), 7.60 (2H, s), 8.56 (2H,
d, Jꢀ5.9 Hz). Anal. Calcd for C15H15NO: C, 79.97; H, 6.71; N, 6.22. Found:
C, 79.83; H, 6.73; N, 6.18.
1-(3,4-Dimethoxyphenyl)-2-(4-pyridyl)ethanone (4t) This compound
was prepared from 2q as described in the synthesis of 4l as a solid, yield
29%, mp 110—111 °C (ethyl acetate–hexane), 1H-NMR (CDCl3) d: 3.94
(3H, s), 3.97 (3H, s), 4.26 (2H, s), 6.91 (1H, d, Jꢀ8.4 Hz), 7.22 (2H, d,
Jꢀ5.9 Hz), 7.55 (1H, d, Jꢀ2.0 Hz), 7.64 (1H, dd, Jꢀ8.4, 2.0 Hz), 8.56 (2H,
1-(4-Ethylphenyl)-2-(4-pyridyl)ethanone (4l) Under argon atmos-
phere, a solution of diisopropylamine (15.4 ml) in tetrahydrofuran (100 ml)

August 2008
1133
mide (5t) This compound was prepared from 4t as described in the syn-
thesis of 5l as a solid, yield 79%, 1H-NMR (DMSO-d6) d: 3.85 (3H, s), 3.89
(3H, s), 4.61 (1H, br s), 7.14 (1H, d, Jꢀ8.4 Hz), 7.28 (1H, s), 7.57 (1H, d,
Jꢀ1.8 Hz), 7.86 (1H, dd, Jꢀ8.4, 1.8 Hz), 8.01 (2H, d, Jꢀ6.2 Hz), 8.85 (2H,
d, Jꢀ6.2 Hz). Anal. Calcd for C15H14BrNO3·HBr·0.2H2O: C, 42.82; H,
3.69; N, 3.33. Found: C, 42.81; H, 3.81; N, 3.24.
d, Jꢀ5.9 Hz). Anal. Calcd for C15H15NO3: C, 70.02; H, 5.88; N, 5.44. Found:
C, 69.97; H, 5.81; N, 5.47.
1-(1,3-Benzodioxol-5-yl)-2-(4-pyridyl)ethanone (4u) This compound
was prepared from 2r as described in the synthesis of 4l as a solid, yield
36%, mp 126—127 °C (ethyl acetate–isopropyl ether), 1H-NMR (CDCl3) d:
4.21 (2H, s), 6.07 (2H, s), 6.87 (1H, d, Jꢀ8.2 Hz), 7.20 (2H, d, Jꢀ6.0 Hz),
7.46 (1H, d, Jꢀ1.7 Hz), 7.61 (1H, dd, Jꢀ8.2, 1.7 Hz), 8.56 (2H, d, Jꢀ
6.0 Hz). Anal. Calcd for C14H11NO3: C, 69.70; H, 4.60; N, 5.81. Found: C,
69.76; H, 4.53; N, 5.78.
1-(1,3-Benzodioxol-5-yl)-2-bromo-2-(4-pyridyl)ethanone Hydrobro-
mide (5u) This compound was prepared from 4u as described in the syn-
1
thesis of 5l as a solid, yield 91%, H-NMR (DMSO-d6) d: 5.02 (1H, br s),
6.19 (2H, s), 7.13 (1H, d, Jꢀ8.3 Hz), 7.24 (1H, s), 7.60 (1H, d, Jꢀ1.5 Hz),
7.82 (1H, dd, Jꢀ8.3, 1.5 Hz), 8.18 (2H, d, Jꢀ7.5 Hz), 8.92 (2H, d,
Jꢀ7.5 Hz). Anal. Calcd for C14H10BrNO3·HBr·0.2H2O: C, 41.55; H, 2.84;
N, 3.46. Found: C, 41.60; H, 2.92; N, 3.37.
1-[4-(1,1-Dimethylethyl)phenyl]-2-(3-pyridyl)ethanone (4v) This
compound was prepared from 2n and 3-methylpyridine as described in the
synthesis of 4l as an oil, yield 28%, 1H-NMR (CDCl3) d: 1.34 (9H, s), 4.28
(2H, s), 7.22—7.31 (1H, m), 7.50 (2H, d, Jꢀ8.4 Hz), 7.56—7.65 (1H, m),
7.94 (2H, d, Jꢀ8.4 Hz), 8.48—8.55 (2H, m). Anal. Calcd for C17H19NO: C,
80.60; H, 7.56; N, 5.53. Found: C, 80.56; H, 7.45; N, 5.41.
2-Bromo-[4-(1,1-dimethylethyl)phenyl]-2-(3-pyridyl)ethanone Hydro-
bromide (5v) This compound was prepared from 4v as described in the
1
synthesis of 5l as a solid, yield 66%, H-NMR (DMSO-d6) d: 1.36 (9H, s),
1-(3,5-Dimethylphenyl)-2-(3-pyridyl)ethanone (4w) This compound
was prepared from 2p and 3-methylpyridine as described in the synthesis of
4l as an oil, yield 11%, 1H-NMR (CDCl3) d: 2.38 (6H, s), 4.27 (2H, s),
7.24—7.30 (2H, m), 7.58—7.63 (3H, m), 8.50—8.52 (2H, m). Anal. Calcd
for C15H15NO: C, 79.97; H, 6.71; N, 6.22. Found: C, 79.89; H, 6.72; N, 6.13.
2-Bromo-1-(4-ethylphenyl)-2-(4-pyridyl)ethanone Hydrobromide (5l)
Bromine (1.1 ml, 22 mmol) was added dropwise to a solution of 4l (5.0 g,
22 mmol) in acetic acid (22 ml) and the mixture was stirred for 3 h at 80 °C.
The solvent was removed in vacuo and ethyl acetate was added to the
residue. The resulting crystals were collected by filtration and washed with
4.53 (1H, br s), 7.25 (1H, s), 7.63 (2H, d, Jꢀ8.5 Hz), 7.94—8.08 (1H, m),
8.09 (2H, d, Jꢀ8.5 Hz), 8.57—8.71 (1H, m), 8.84—8.93 (1H, m), 9.04—
9.13 (1H, m). Anal. Calcd for C16H16BrNO·HBr·H2O: C, 46.07; H, 4.59; N,
3.36. Found: C, 46.19; H, 4.22; N, 2.99.
2-Bromo-1-(3,5-dimethylphenyl)-2-(3-pyridyl)ethanone Hydrobro-
mide (5w) This compound was prepared from 4w as described in the syn-
thesis of 5l as a solid, yield 92%, 1H-NMR (DMSO-d6) d: 2.38 (6H, s), 6.45
(1H, br s), 7.28 (1H, s), 7.37 (1H, s), 7.78 (2H, s), 8.01—8.08 (1H, m),
8.65—8.69 (1H, m), 8.89—8.92 (1H, m), 9.10—9.11 (1H, m). Anal. Calcd
for C15H14BrNO·HBr·0.5H2O: C, 45.71; H, 4.09; N, 3.55. Found: C, 45.67;
H, 3.95; N, 3.49.
[4-(4-Methoxyphenyl)-1,3-thiazol-2-yl]amine (6d) Thiourea (3.3 g, 46
mmol) was added to a mixture of 4ꢅ-methoxyphenacyl bromide (10 g, 44
mmol) in acetonitrile (260 ml). The resulting solution was refluxed for 3 h.
The solvent was removed in vacuo and aqueous sodium hydrogen carbonate
was added to the residue. The precipitate was collected by filtration and the
resulting solid was washed with water and ether successively. The crude
crystals were recrystallized from ethanol to afford 6.5 g (yield 73%) of 6d as
a solid, mp 203—204 °C (ethanol), 1H-NMR (DMSO-d6) d: 3.77 (3H, s),
6.80 (1H, s), 6.91 (2H, d, Jꢀ8.8 Hz), 6.98 (2H, br s), 7.72 (2H, d, Jꢀ8.8 Hz).
Anal. Calcd for C10H10N2OS: C, 58.23; H, 4.89; N, 13.58. Found: C, 58.08;
H, 4.86; N, 13.91.
N-[4-(4-Methoxyphenyl)-1,3-thiazol-2-yl]methylamine (6e) N-
Methylthiourea (3.8 g, 43 mmol) was added to a mixture of 5a (15 g,
39 mmol) in acetonitrile (200 ml) and then triethylamine (5.7 ml, 41 mmol)
was added to the mixture. The resulting solution was refluxed for 3 h. The
solvent was removed in vacuo and aqueous sodium hydrogen carbonate was
added to the residue. The precipitate was collected by filtration and the re-
sulting solid was washed with water and ether successively. The crude crys-
tals were recrystallized from ethanol to afford 11 g (yield 88%) of 6e as a
solid, mp 175—177 °C (ethyl acetate), 1H-NMR (DMSO-d6) d: 2.88 (3H, d,
Jꢀ4.8 Hz), 3.78 (3H, s), 6.92 (2H, d, Jꢀ8.4 Hz), 7.08 (2H, d, Jꢀ6.0 Hz),
7.36 (2H, d, Jꢀ8.4 Hz), 7.91 (1H, q, Jꢀ4.8 Hz), 8.38 (2H, d, Jꢀ6.0 Hz).
Anal. Calcd for C16H15N3OS·0.5H2O: C, 62.72; H, 5.26; N, 13.71. Found:
C, 62.66; H, 5.05; N, 14.07.
1
ethyl acetate to afford 6.1 g (yield 71%) of 5l as a solid, H-NMR (DMSO-
d6) d: 1.22 (3H, t, Jꢀ7.6 Hz), 2.72 (2H, q, Jꢀ7.6 Hz), 6.38 (1H, br s), 7.29
(1H, s), 7.45 (2H, d, Jꢀ8.1 Hz), 8.07 (2H, d, Jꢀ8.1 Hz), 8.15 (2H, d,
Jꢀ6.2 Hz), 8.94 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for C15H14BrNO·
HBr·0.5H2O: C, 45.71; H, 4.09; N, 3.55. Found: C, 45.86; H, 3.99; N, 3.48.
2-Bromo-1-(4-propylphenyl)-2-(4-pyridyl)ethanone Hydrobromide
(5m) This compound was prepared from 4m as described in the synthesis
of 5l as a solid, yield 90%, 1H-NMR (DMSO-d6) d: 0.91 (3H, t, Jꢀ7.1 Hz),
1.53—1.74 (2H, m), 2.67 (2H, t, Jꢀ7.3 Hz), 5.14 (1H, br s), 7.25 (1H, s),
7.42 (2H, t, Jꢀ7.1 Hz), 8.06 (2H, d, Jꢀ7.1 Hz), 8.10 (2H, d, Jꢀ5.3 Hz), 8.91
(2H, d, Jꢀ5.3 Hz). Anal. Calcd for C16H16BrNO·HBr: C, 48.15; H, 4.29; N,
3.51. Found: C, 48.04; H, 4.19; N, 3.43.
2-Bromo-1-(4-butylphenyl)-2-(4-pyridyl)ethanone Hydrobromide (5n)
This compound was prepared from 4n as described in the synthesis of 5l as a
solid, yield 88%, 1H-NMR (DMSO-d6) d: 0.91 (3H, t, Jꢀ7.3 Hz), 1.22—
1.43 (2H, m), 1.51—1.69 (2H, m), 2.69 (2H, t, Jꢀ7.5 Hz), 6.12 (1H, br s),
7.29 (1H, s), 7.43 (2H, t, Jꢀ8.1 Hz), 8.07 (2H, d, Jꢀ8.1 Hz), 8.18 (2H, d,
Jꢀ5.9 Hz), 8.96 (2H, d, Jꢀ5.9 Hz). Anal. Calcd for C17H19BrNO·HBr·
1.5H2O: C, 46.39; H, 5.04; N, 3.18. Found: C, 46.61; H, 5.26; N, 3.05.
2-Bromo-1-[4-(1-methylethyl)phenyl]-2-(4-pyridyl)ethanone Hydro-
bromide (5o) This compound was prepared from 4o as described in the
1
synthesis of 5l as a solid, yield 93%, H-NMR (DMSO-d6) d: 1.24 (6H, d,
Jꢀ6.6 Hz), 2.92—3.09 (1H, m), 5.75 (1H, br s), 7.27 (1H, s), 7.48 (2H, d,
Jꢀ8.2 Hz), 8.08 (2H, d, Jꢀ8.2 Hz), 8.13 (2H, d, Jꢀ6.7 Hz), 8.93 (2H, d,
Jꢀ6.7 Hz). Anal. Calcd for C16H16BrNO·HBr: C, 48.15; H, 4.29; N, 3.51.
Found: C, 48.15; H, 4.23; N, 3.34.
[4-(4-Ethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6n) This
compound was prepared from 5l as described in the synthesis of 6e as a
solid, yield 71%, mp 285—288 °C (pyridine), H-NMR (DMSO-d6) d: 1.20
(3H, t, Jꢀ7.5 Hz), 2.62 (2H, q, Jꢀ7.5 Hz), 7.08 (2H, d, Jꢀ6.2 Hz), 7.17
(2H, d, Jꢀ8.1 Hz), 7.32 (2H, d, Jꢀ8.1 Hz), 7.40 (2H, br s), 8.37 (2H, d,
Jꢀ6.2 Hz). Anal. Calcd for C16H15N3S: C, 68.30; H, 5.37; N, 14.93. Found:
C, 68.14; H, 5.40; N, 15.09.
2-Bromo-1-[4-(N,N-dimethylamino)phenyl]-2-(4-pyridyl)ethanone Di-
hydrobromide (5q) Bromine (0.20 ml, 4.2 mmol) was added dropwise to a
solution of 4q (1.0 g, 4.2 mmol) in acetic acid (5 ml) and 30% hydrogen bro-
mide acetic acid solution (1.23 g, 4.6 mmol) and the mixture was stirred for
3 h at 80 °C. The precipitate was collected by filtration and washed with
ethyl acetate to afford 1.0 g (yield 50%) of 5q as a solid, 1H-NMR (DMSO-
d6) d: 3.07 (6H, s), 6.24 (2H, br s), 6.78 (2H, d, Jꢀ9.0 Hz), 7.20 (1H, s),
7.97 (2H, d, Jꢀ9.0 Hz), 8.22 (2H, d, Jꢀ6.6 Hz), 8.96 (2H, d, Jꢀ6.6 Hz).
Anal. Calcd for C15H15BrN2O·2HBr·1.5H2O: C, 35.46; H, 3.97; N, 5.51.
Found: C, 35.64; H, 4.03; N, 5.34.
1
[4-(4-Propylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6o) This
compound was prepared from 5m as described in the synthesis of 6e as a
1
solid, yield 94%, mp 240—242 °C (ethanol), H-NMR (DMSO-d6) d: 0.91
(3H, t, Jꢀ7.3 Hz), 1.50—1.72 (2H, m), 2.57 (2H, t, Jꢀ7.9 Hz), 7.08 (2H, d,
Jꢀ4.9 Hz), 7.16 (2H, d, Jꢀ7.9 Hz), 7.31 (2H, d, Jꢀ7.9 Hz), 7.42 (2H, br s),
8.38 (2H, d, Jꢀ4.9 Hz). Anal. Calcd for C17H17N3S: C, 69.12; H, 5.80; N,
14.22. Found: C, 68.86; H, 5.82; N, 14.25.
2-Bromo-1-(3,4-dimethylphenyl)-2-(4-pyridyl)ethanone Hydrobro-
mide (5r) This compound was prepared from 4r as described in the syn-
thesis of 5l as a solid, yield 94%, 1H-NMR (DMSO-d6) d: 2.33 (6H, s), 7.32
(1H, s), 7.37 (2H, d, Jꢀ7.7 Hz), 7.85—7.96 (2H, m), 8.20 (2H, d, Jꢀ
6.8 Hz), 8.97 (2H, d, Jꢀ6.8 Hz), 1H hidden. Anal. Calcd for C15H14BrNO·
Br: C, 46.78; H, 3.93; N, 3.64. Found: C, 46.51; H, 3.94; N, 3.43.
2-Bromo-1-(3,5-dimethylphenyl)-2-(4-pyridyl)ethanone Hydrobro-
mide (5s) This compound was prepared from 4s as described in the syn-
thesis of 5l as a solid, yield 81%, 1H-NMR (DMSO-d6) d: 2.38 (6H, s), 5.71
(1H, br s), 7.28 (1H, s), 7.38 (1H, s), 7.77 (2H, s), 8.16 (2H, d, Jꢀ5.5 Hz),
8.95 (2H, d, Jꢀ5.5 Hz). Anal. Calcd for C15H14BrNO·HBr: C, 46.78; H,
3.93; N, 3.64. Found: C, 46.68; H, 4.22; N, 3.40.
[4-(4-Butylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6p) This
compound was prepared from 5n as described in the synthesis of 6e as a
1
solid, yield 63%, mp 204—206 °C (ethanol), H-NMR (DMSO-d6) d: 0.91
(3H, t, Jꢀ7.1 Hz), 1.24—1.43 (2H, m), 1.49—1.66 (2H, m), 2.59 (2H, t,
Jꢀ7.7 Hz), 7.07 (2H, d, Jꢀ6.0 Hz), 7.15 (2H, d, Jꢀ7.9 Hz), 7.31 (2H, d,
Jꢀ7.9 Hz), 7.36 (2H, br s), 8.37 (2H, d, Jꢀ6.0 Hz). Anal. Calcd for
C18H19N3S·0.5H2O: C, 67.89; H, 6.33; N, 13.20. Found: C, 67.98; H, 6.13;
N, 13.23.
[4-[4-(1-Methylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6q)
2-Bromo-1-(3,4-dimethoxyphenyl)-2-(4-pyridyl)ethanone Hydrobro-

1134
Vol. 56, No. 8
This compound was prepared from 5o as described in the synthesis of 6e as
Calcd for C12H12N2O2S: C, 58.05; H, 4.87; N, 11.28. Found: C, 58.06; H,
a solid, yield 77%, mp 267—269 °C (pyridine), 1H-NMR (DMSO-d6) d: 4.69; N, 11.28.
1.22 (6H, d, Jꢀ6.9 Hz), 2.82—2.98 (1H, m), 7.10 (2H, d, Jꢀ6.1 Hz), 7.21
(2H, d, Jꢀ8.3 Hz), 7.34 (2H, d, Jꢀ8.3 Hz), 7.40 (2H, br s), 8.39 (2H, d,
N-[4-(4-Methoxyphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]-N-methylac-
etamide (7e) Acetyl chloride (3.8 g, 48 mmol) was added to a solution of
Jꢀ6.1 Hz). Anal. Calcd for C17H17N3S: C, 69.12; H, 5.80; N, 14.22. Found: 6e (10 g, 32 mmol) and 4-dimethylaminopyridine (1.2 g, 9.6 mmol) in N,N-
C, 69.08; H, 5.52; N, 14.25. dimethylacetamide (50 ml) and the resulting mixture was stirred at 80 °C for
[4-(N,N-Dimethylamino)phenyl-5-(4-pyridyl)-1,3-thiazol-2-yl]amine 14 h. Aqueous sodium hydrogen carbonate was added to the reaction mix-
(6s) This compound was prepared from 5q as described in the synthesis of ture and extracted with ethyl acetate. Extracts were washed with brine, dried
1
6e as a solid, yield 54%, mp 309—311 °C (pyridine), H-NMR (DMSO-d6) and concentrated to give a solid. The crude crystals were recrystallized from
d: 2.93 (6H, s), 6.65 (2H, d, Jꢀ9.0 Hz), 7.10 (2H, d, Jꢀ6.2 Hz), 7.25 (2H, d, ethanol to afford 7.0 g (yield 65%) of 7e as a solid, mp 180—181 °C
1
Jꢀ9.0 Hz), 7.32 (2H, br s), 8.36 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for (ethanol), H-NMR (DMSO-d6) d: 2.43 (3H, s), 3.71 (3H, s), 3.78 (3H, s),
C16H16N4S: C, 64.84; H, 5.44; N, 18.90. Found: C, 64.49; H, 5.40; N, 18.82.
6.94 (2H, d, Jꢀ8.4 Hz), 7.28 (2H, d, Jꢀ5.9Hz), 7.40 (2H, d, Jꢀ8.4 Hz), 8.52
[4-(3,4-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6t) (2H, d, Jꢀ5.9 Hz). Anal. Calcd for C18H17N3O2S: C, 63.70; H, 5.05; N,
This compound was prepared from 5r as described in the synthesis of 6e as 12.38. Found: C, 63.40; H, 5.01; N, 12.18.
a solid, yield 96%, mp 248—250 °C (pyridine), 1H-NMR (DMSO-d6) d:
N-[4-(4-Ethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide (7n)
2.19 (3H, s), 2.23 (3H, s), 7.05—7.11 (4H, m), 7.24 (1H, s), 7.37 (2H, br s), This compound was prepared from 6n as described in the synthesis of 7e as
8.36 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for C16H15N3S: C, 68.30; H, 5.37; N, a solid, yield 47%, mp 294—295 °C (ethanol), 1H-NMR (DMSO-d6) d: 1.20
14.93. Found: C, 68.62; H, 5.39; N, 15.13.
(3H, t, Jꢀ7.5 Hz), 2.19 (3H, s), 2.63 (2H, q, Jꢀ7.5 Hz), 7.21 (2H, d,
[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6u) Jꢀ8.1 Hz), 7.27 (2H, d, Jꢀ6.0 Hz), 7.36 (2H, d, Jꢀ8.1 Hz), 8.50 (2H, d,
This compound was prepared from 5s as described in the synthesis of 6e as a Jꢀ6.0 Hz), 12.45 (1H, br s). Anal. Calcd for C18H17N3OS·0.1H2O: C, 66.48;
1
solid, yield 55%, mp 242—244 °C (ethanol), H-NMR (DMSO-d6) d: 2.22 H, 5.33; N, 12.92. Found: C, 66.41; H, 5.03; N, 12.88.
(6H, s), 6.97 (1H, s), 7.01 (2H, s), 7.07 (2H, d, Jꢀ6.2 Hz), 7.39 (2H, br s),
N-[4-(4-Propylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide (7o)
8.37 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for C16H15N3S: C, 68.30; H, 5.37; N, This compound was prepared from 6o as described in the synthesis of 7e as
14.93. Found: C, 68.17; H, 5.34; N, 14.70.
[4-(3,4-Dimethoxyphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6v)
a solid, yield 57%, mp 256—258 °C (ethyl acetate), 1H-NMR (DMSO-d6) d:
0.91 (3H, t, Jꢀ7.3 Hz), 1.50—1.72 (2H, m), 2.19 (3H, s), 2.57 (2H, t,
This compound was prepared from 5t as described in the synthesis of 6e as a Jꢀ7.3 Hz), 7.18 (2H, d, Jꢀ8.1 Hz), 7.26 (2H, d, Jꢀ6.2 Hz), 7.35 (2H, d,
1
solid, yield 70%, mp 218—219 °C (pyridine), H-NMR (DMSO-d6) d: 3.68
Jꢀ8.1 Hz), 8.50 (2H, d, Jꢀ6.2 Hz), 12.42 (1H, br s). Anal. Calcd for
(3H, s), 3.81 (3H, s), 6.90—6.99 (2H, m), 7.02 (1H, s), 7.27 (2H, d, C19H19N3OS·0.2H2O: C, 66.91; H, 5.73; N, 12.32. Found: C, 66.82; H, 5.70;
Jꢀ6.8 Hz), 7.74 (2H, br s), 8.43 (2H, d, Jꢀ6.8 Hz). Anal. Calcd for N, 12.26.
C16H15N3O2S: C, 61.32; H, 4.82; N, 13.41. Found: C, 61.45; H, 4.40; N,
13.02.
N-[4-(4-Butylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide (7p)
This compound was prepared from 6p as described in the synthesis of 7e as
[4-(1,3-Benzodioxol-5-yl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6w) a solid, yield 57%, mp 259—261 °C (ethyl acetate), 1H-NMR (DMSO-d6) d:
This compound was prepared from 5u as described in the synthesis of 6e as 0.91 (3H, t, Jꢀ7.1 Hz), 1.25—1.43 (2H, m), 1.46—1.66 (2H, m), 2.19 (3H,
a solid, yield 79%, mp 273—275 °C (ethanol), 1H-NMR (DMSO-d6) d: 6.04 s), 2.59 (2H, t, Jꢀ7.5 Hz), 7.18 (2H, d, Jꢀ8.1 Hz), 7.25 (2H, d, Jꢀ6.2 Hz),
(2H, s), 6.83—6.92 (3H, m), 7.09 (2H, d, Jꢀ6.2 Hz), 7.37 (2H, br s), 8.39
7.35 (2H, d, Jꢀ8.1 Hz), 8.49 (2H, d, Jꢀ6.2 Hz), 12.42 (1H, br s). Anal.
(2H, d, Jꢀ6.2 Hz). Anal. Calcd for C15H11N3O2S: C, 60.59; H, 3.73; N, Calcd for C20H21N3OS: C, 68.35; H, 6.02; N, 11.96. Found: C, 68.10; H,
14.13. Found: C, 60.67; H, 3.81; N, 14.24.
5.81; N, 11.82.
[4-[4-(1,1-Dimethylethyl)phenyl]-5-(3-pyridyl)-1,3-thiazol-2-yl]amine
N-[4-[4-(1-Methylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]acet-
amide (7q) This compound was prepared from 6q as described in the syn-
(6x) This compound was prepared from 5v as described in the synthesis of
1
6e as a solid, yield 82%, mp 239—241 °C (ethanol–ethyl acetate), H-NMR thesis of 7e as a solid, yield 62%, mp 295—297 °C (ethanol), 1H-NMR
(DMSO-d6) d: 1.27 (9H, s), 7.21 (2H, br s), 7.30 (4H, s), 7.34 (1H, dd, (DMSO-d6) d: 1.22 (6H, d, Jꢀ7.0 Hz), 2.19 (3H, s), 2.82—2.99 (1H, m),
Jꢀ8.2, 4.9 Hz), 7.62 (1H, ddd, Jꢀ8.2, 2.2, 1.8 Hz), 8.38 (1H, d, Jꢀ2.2 Hz), 7.19—7.30 (4H, m), 7.37 (2H, d, Jꢀ8.1 Hz), 8.51 (2H, d, Jꢀ5.9 Hz), 12.42
8.41 (1H, dd, Jꢀ4.9, 1.8 Hz). Anal. Calcd for C18H19N3S: C, 69.87; H, 6.19; (1H, br s). Anal. Calcd for C19H19N3OS: C, 67.63; H, 5.68; N, 12.45. Found:
N, 13.58. Found: C, 69.75; H, 6.17; N, 13.43.
C, 67.66; H, 5.66; N, 12.55.
[4-(3,5-Dimethylphenyl)-5-(3-pyridyl)-1,3-thiazol-2-yl]amine (6y)
N-[4-[4-(N,N-Dimethylamino)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]-
This compound was prepared from 5w as described in the synthesis of 6e as acetamide (7s) A 4 N hydrogen chloride in ethyl acetate (0.37 ml) was
a solid, yield 52%, mp 237—240 °C (ethanol), 1H-NMR (DMSO-d6) d: 2.17 added to a solution of 6s (0.40 g, 1.4 mmol) in N,N-dimethylacetamide
(6H, s), 6.91 (1H, s), 6.97 (2H, s), 7.22 (2H, br s), 7.27—7.33 (1H, m),
7.55—7.59 (1H, m), 8.36—8.42 (2H, m). Anal. Calcd for C16H15N3OS: C,
68.30; H, 5.37; N, 14.93. Found: C, 68.03; H, 5.25; N, 14.87.
(4.0 ml) and acetyl chloride (0.16 g, 2.0 mmol) was added to the mixture.
The resulting mixture was stirred at 80 °C for 14 h. Aqueous sodium hydro-
gen carbonate was added to the reaction mixture and the precipitate was col-
[4-(4-Hydroxyphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]amine (6z) A so- lected by filtration. The precipitate was washed with water and dried. The
lution of 6a (7.3 g) in 47% hydrobromic acid (60 ml) was refluxed for 5 h. crude crystals were recrystallized from ethanol to afford 0.26 g (yield 56%)
The resulting mixture was cooled with an ice bath and neutralized with 8 N
aqueous sodium hydroxide. The precipitate was collected by filtration and (6H, s), 6.67 (2H, d, Jꢀ8.8 Hz), 7.24—7.32 (4H, m), 8.48 (2H, d,
washed with water. The crude crystals were washed with ethanol and dried Jꢀ6.3 Hz), 12.34 (1H, br s). Anal. Calcd for C18H18N4OS·0.2H2O: C, 63.21;
of 7s as a solid, mp 289—291 °C, 1H-NMR (DMSO-d6) d: 2.18 (3H, s), 2.93
to afford 7.09 g (28 mmol, yield quant.) of 6z as a solid, mp 323—326 °C
H, 5.42; N, 16.38. Found: C, 63.08; H, 5.40; N, 16.42.
N-[4-(3,4-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide
(ethanol), 1H-NMR (DMSO-d6) d: 6.76 (2H, d, Jꢀ8.8 Hz), 7.22 (2H, d,
Jꢀ6.6 Hz), 7.26 (2H, d, Jꢀ8.8 Hz), 7.69 (2H, br s), 8.41 (2H, d, Jꢀ6.6 Hz), (7t) This compound was prepared from 6t as described in the synthesis of
9.74 (1H, br s). Anal. Calcd for C14H11N3OS·3H2O: C, 52.00; H, 5.30; N, 7e as a solid, yield 29%, mp 248—250 °C (ethanol), H-NMR (DMSO-d6)
1
12.99. Found: C, 51.64; H, 4.99; N, 12.96.
d: 2.19 (6H, s), 2.24 (3H, s), 7.10 (2H, s), 7.22—7.30 (3H, m), 8.49 (2H, d,
Ethyl [4-(4-Methoxyphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetate Jꢀ5.9 Hz), 12.43 (1H, br s). Anal. Calcd for C18H17N3OS: C, 66.85; H, 5.30;
(6aa) This compound was prepared from ethyl thiocarbamoylacetate31) as N, 12.99. Found: C, 66.66; H, 5.28; N, 13.08.
1
described in the synthesis of 6a as an oil, yield 77%, H-NMR (DMSO-d6)
d: 1.33 (3H, t, Jꢀ7.0 Hz), 3.82 (3H, s), 4.12 (2H, s), 4.27 (2H, q, Jꢀ7.0 Hz),
6.86 (2H, d, Jꢀ9.0 Hz), 7.25 (2H, d, Jꢀ6.2 Hz), 7.41 (2H, d, Jꢀ9.0 Hz), 7e as a solid, yield 29%, mp 284—286 °C (ethanol), H-NMR (DMSO-d6)
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide
(7u) This compound was prepared from 6u as described in the synthesis of
1
8.54 (2H, d, Jꢀ6.2 Hz).
d: 2.19 (3H, s), 2.22 (6H, s), 7.00 (1H, s), 7.04 (2H, s), 7.26 (2H, d,
Jꢀ6.2 Hz), 8.50 (2H, d, Jꢀ6.2 Hz), 12.43 (1H, br s). Anal. Calcd for
C18H17N3OS·0.1H2O: C, 66.48; H, 5.33; N, 12.92. Found: C, 66.35; H, 5.21;
N, 13.07.
N-[4-(4-Methoxyphenyl)-1,3-thiazol-2-yl]acetamide (7d) A solution
of ethyl cyanoacetate (1.2 g, 10 mmol) and 6d (2.1 g, 10 mmol) in acetic acid
(10 ml) was refluxed for 38 h. The solvent was removed in vacuo and the re-
side was treated with aqueous sodium hydrogen carbonate. The crude crys-
N-[4-(3,4-Dimethoxyphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide
tals were collected by filtration and washed, and then recrystallized from (7v) This compound was prepared from 6v as described in the synthesis of
1
ethanol to afford 4.2 g (yield 47%) of 7d as a solid, mp 192—193 °C
7e as a solid, yield 62%, mp 265—267 °C (ethanol), H-NMR (DMSO-d6)
1
(ethanol), H-NMR (DMSO-d6) d: 2.16 (3H, s), 3.79 (3H, s), 6.98 (2H, d, d: 2.19 (3H, s), 3.62 (3H, s), 3.77 (3H, s), 6.94 (2H, s), 7.02 (1H, s), 7.29
Jꢀ8.8 Hz), 7.41 (1H, s), 7.82 (2H, d, Jꢀ8.8 Hz), 12.19 (1H, br s). Anal. (2H, d, Jꢀ5.7 Hz), 8.52 (2H, d, Jꢀ5.7 Hz), 12.45 (1H, br s). Anal. Calcd for

August 2008
1135
C18H17N3O3S: C, 60.83; H, 4.82; N, 11.82. Found: C, 60.70; H, 4.73; N,
11.83.
7.10 (2H, s), 7.32 (2H, d, Jꢀ6.0 Hz), 7.58—7.65 (1H, m), 8.45—8.56 (3H,
m), 8.81—8.84 (1H, m), 9.26—9.27 (1H, m), 13.21 (1H, br s). Anal. Calcd
for C22H18N4OS: C, 68.37; H, 4.69; N, 14.50. Found: C, 68.25; H, 4.57; N,
14.50.
N-[4-(1,3-Benzodioxol-5-yl)-5-(4-pyridyl)-1,3-thiazol-2-yl]acetamide
(7w) This compound was prepared from 6w as described in the synthesis
1
of 7e as a solid, yield 68%, mp 295—296 °C (ethanol), H-NMR (DMSO-
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]isonicotin-
amide (7ag) This compound was prepared from 6u and isonicotinoyl chlo-
ride hydrochloride as described in the synthesis of 7e as a solid, yield 32%,
d6) d: 2.19 (3H, s), 6.05 (2H, s), 6.86—6.96 (3H, m), 7.27 (2H, d,
Jꢀ6.0 Hz), 8.51 (2H, d, Jꢀ6.0 Hz), 12.40 (1H, br s). Anal. Calcd for
C17H13N3O3S: C, 60.17; H, 3.86; N, 12.38. Found: C, 60.04; H, 3.88; N,
12.44.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]pro-
pionamide (7x) This compound was prepared from 6r and propionyl chlo-
ride as described in the synthesis of 7a as a solid, yield 74%, mp 295—
297 °C (ethyl acetate–ethanol), 1H-NMR (DMSO-d6) d: 1.13 (3H, t,
Jꢀ7.5 Hz), 1.29 (9H, s), 2.49 (2H, q, Jꢀ7.5 Hz), 7.28 (2H, d, Jꢀ6.2 Hz),
7.38 (4H, s), 8.51 (2H, d, Jꢀ6.2 Hz), 12.41 (1H, br s). Anal. Calcd for
C21H23N3OS: C, 69.01; H, 6.34; N, 11.50. Found: C, 68.88; H, 6.36; N,
11.50.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]cy-
clopentanecarboxamide (7y) This compound was prepared from 6r and
cyclopentanecarbonyl chloride as described in the synthesis of 7e as a solid,
yield 74%, mp 309—311 °C (ethanol), 1H-NMR (DMSO-d6) d: 1.29 (9H, s),
1.53—2.01 (8H, m), 2.91—3.05 (1H, m), 7.27 (2H, d, Jꢀ6.2 Hz), 7.38 (4H,
s), 8.52 (2H, d, Jꢀ6.2 Hz), 12.40 (1H, br s). Anal. Calcd for C24H27N3OS: C,
71.08; H, 6.71; N, 10.36. Found: C, 71.00; H, 6.76; N, 10.26.
1
mp 302—304 °C (ethanol), H-NMR (DMSO-d6) d: 2.23 (6H, s), 7.02 (1H,
s), 7.09 (2H, s), 7.31 (2H, d, Jꢀ6.2 Hz), 8.03 (2H, d, Jꢀ6.2 Hz), 8.53 (2H, d,
Jꢀ5.9 Hz), 8.83 (2H, d, Jꢀ5.9 Hz), 13.29 (1H, br s). Anal. Calcd for
C22H18N4OS·0.2H2O: C, 67.74; H, 4.75; N, 14.36. Found: C, 67.81; H, 4.72;
N, 14.35.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(3-pyridyl)-1,3-thiazol-2-yl]ac-
etamide (7ah) This compound was prepared from 6x as described in
the synthesis of 7e as a solid, yield 67%, mp 228—230 °C (ethanol), 1H-
NMR (DMSO-d6) d: 1.28 (9H, s), 2.19 (3H, s), 7.35 (4H, s), 7.41 (1H,
dd, Jꢀ7.7, 4.8 Hz), 7.76 (1H, ddd, Jꢀ7.7, 2.2, 1.5 Hz), 8.48 (1H, d, Jꢀ
2.2 Hz), 8.52 (1H, dd, Jꢀ4.8, 1.5 Hz), 12.36 (1H, br s). Anal. Calcd for
C20H21N3OS·0.3H2O: C, 67.31; H, 6.10; N, 11.77. Found: C, 67.31; H, 6.11;
N, 11.53.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(3-pyridyl)-1,3-thiazol-2-yl]-
nicotinamide (7ai) This compound was prepared from 6x and nicotinoyl
chloride hydrochloride as described in the synthesis of 7e as a solid, yield
63%, mp 251—253 °C (ethanol), 1H-NMR (DMSO-d6) d: 1.29 (9H, s), 7.37
(2H, d, Jꢀ8.9 Hz), 7.42 (2H, d, Jꢀ8.9 Hz), 7.43 (1H, dd, Jꢀ7.7, 4.8 Hz),
7.60 (1H, dd, Jꢀ8.0, 4.8 Hz), 7.81 (1H, ddd, Jꢀ7.7, 2.2, 1.7 Hz), 8.48 (1H,
ddd, Jꢀ8.0, 2.1, 1.7 Hz), 8.54 (1H, d, Jꢀ2.2 Hz), 8.55 (1H, dd, Jꢀ4.8,
1.7 Hz), 8.82 (1H, dd, Jꢀ4.8, 1.7 Hz), 9.27 (1H, d, Jꢀ2.1 Hz), 12.37 (1H,
br s). Anal. Calcd for C24H22N4OS: C, 69.54; H, 5.35; N, 13.52. Found: C,
69.47; H, 5.39; N, 13.46.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]benz-
amide (7z) This compound was prepared from 6r and benzoyl chloride as
described in the synthesis of 7e as a solid, yield 74%, mp 292—294 °C
1
(ethyl acetate–ethanol), H-NMR (DMSO-d6) d: 1.31 (9H, s), 7.33 (2H, d,
Jꢀ6.1 Hz), 7.40 (2H, d, Jꢀ8.9 Hz), 7.48 (2H, d, Jꢀ8.9 Hz), 7.52—7.72 (3H,
m), 8.16 (2H, d, Jꢀ7.0 Hz), 8.55 (2H, d, Jꢀ6.1 Hz), 12.39 (1H, br s). Anal.
Calcd for C25H23N3OS: C, 72.61; H, 5.61; N, 10.16. Found: C, 72.53; H,
5.45; N, 10.28.
N-[4-(3,5-Dimethylphenyl)-5-(3-pyridyl)-1,3-thiazol-2-yl]acetamide
(7aj) This compound was prepared from 6y and acetyl chloride as de-
scribed in the synthesis of 7e as a solid, yield 71%, mp 288—289 °C
(ethanol–ethyl acetate), 1H-NMR (CDCl3) d: 1.88 (3H, s), 2.23 (6H, s), 6.95
(1H, s), 7.04 (2H, s), 7.20—7.26 (1H, m), 7.61—7.67 (1H, m), 8.51—8.55
(1H, m), 8.60—8.61 (1H, m), 10.47 (1H, br s). Anal. Calcd for C18H17N3OS:
C, 66.85; H, 5.30; N, 12.99. Found: C, 66.64; H, 5.29; N, 12.84.
N-[4-(3,5-Dimethylphenyl)-5-(3-pyridyl)-1,3-thiazol-2-yl]isonicotin-
amide (7ak) This compound was prepared from 6y and isonicotinoyl chlo-
ride hydrochloride as described in the synthesis of 7e as a solid, yield 64%,
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]-
nicotinamide (7aa) This compound was prepared from 6r and nicotinoyl
chloride hydrochloride as described in the synthesis of 7e as a solid, yield
73%, mp 326—328 °C (ethanol), 1H-NMR (DMSO-d6) d: 1.31 (9H, s), 7.32
(2H, d, Jꢀ5.9 Hz), 7.42 (4H, s), 7.59 (1H, dd, Jꢀ8.1, 4.8 Hz), 8.47 (1H, dd,
Jꢀ8.1, 2.2 Hz), 8.54 (2H, d, Jꢀ5.9 Hz), 8.81 (1H, d, Jꢀ4.8 Hz), 9.26 (1H, d,
Jꢀ2.2 Hz), 12.39 (1H, br s). Anal. Calcd for C24H22N4OS: C, 69.54; H, 5.35;
N, 13.52. Found: C, 69.51; H, 5.30; N, 13.82.
N-[4-[4-(1,1-Dimethylethyl)phenyl]-5-(4-pyridyl)-1,3-thiazol-2-yl]isoni-
cotinamide (7ab) This compound was prepared from 6r and isonicotinoyl
chloride hydrochloride as described in the synthesis of 7e as a solid, yield
74%, mp 326—329 °C (ethanol), 1H-NMR (DMSO-d6) d: 1.31 (9H, s), 7.32
(2H, d, Jꢀ6.2 Hz), 7.42 (4H, s), 8.03 (2H, d, Jꢀ6.2 Hz), 8.55 (2H, d,
Jꢀ6.2 Hz), 8.83 (2H, d, Jꢀ6.2 Hz), 12.40 (1H, br s). Anal. Calcd for
C24H22N4OS: C, 69.54; H, 5.35; N, 13.52. Found: C, 69.53; H, 5.32; N,
13.66.
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]propion-
amide (7ac) This compound was prepared from 6u and propionyl chloride
as described in the synthesis of 7e as a solid, yield 67%, mp 291—293 °C
(ethanol), 1H-NMR (CDCl3) d: 1.04 (3H, t, Jꢀ7.6 Hz), 2.01 (2H, q,
Jꢀ7.6 Hz), 2.27 (6H, s), 7.01 (1H, s), 7.08 (2H, s), 7.22—7.25 (2H, m),
8.50—8.53 (2H, m), 10.60 (1H, br s). Anal. Calcd for C19H19N3OS: C,
67.63; H, 5.68; N, 12.45. Found: C, 67.57; H, 5.52; N, 12.48.
1
mp 277—278 °C (ethanol), H-NMR (DMSO-d6) d: 2.20 (6H, s), 6.98 (1H,
s), 7.07 (2H, s), 7.40—7.46 (1H, m), 7.55—7.64 (1H, m), 7.76—7.80 (1H,
m), 8.45—8.53 (3H, m), 8.81 (1H, d, Jꢀ3.0 Hz), 9.26 (1H, s), 13.15 (1H,
br s). Anal. Calcd for C22H18N4OS: C, 68.37; H, 4.69; N, 14.50. Found: C,
68.14; H, 4.53; N, 14.51.
4-[2-(Acetylamino)-5-(4-pyridyl)-1,3-thiazol-4-yl]phenyl Acetate (9)
Acetyl chloride (10.0 g, 127 mmol) was added to a solution of 6z (6.5 g,
25 mmol) and 4-dimethylaminopyridine (0.93 g, 7.6 mmol) in N,N-dimethyl-
acetamide (50 ml), and the resulting mixture was stirred at 80 °C for 14 h.
Aqueous sodium hydrogen carbonate was added to the reaction mixture and
the precipitate was collected by filtration. The precipitate was washed with
water and dried. The crude crystals were recrystallized from ethanol to af-
ford 5.33 g (yield 59%) of 9 as a solid, mp 254—257 °C, 1H-NMR (DMSO-
d6) d: 2.20 (3H, s), 2.28 (3H, s), 7.14 (2H, d, Jꢀ8.8 Hz), 7.28 (2H, d,
Jꢀ6.0 Hz), 7.47 (2H, d, Jꢀ8.8 Hz), 8.52 (2H, d, Jꢀ6.0 Hz), 12.47 (1H, br s).
Anal. Calcd for C18H15N3O3S·0.2H2O: C, 60.56; H, 4.35; N, 11.77. Found:
C, 60.61; H, 4.23; N, 11.80.
N-[4-(4-Hydroxyphenyl)-5-(4-pyridinyl)-1,3-thiazol-2-yl]acetamide
(10) A mixture of 9 (5.0 g, 14 mmol) and potassium carbonate (2.2 g,
16 mmol) in methanol (500 ml) was stirred at room temperature for 1 h. The
solvent was removed in vacuo and the residue was treated with water. The
mixture was acidified with 3 N hydrochloric acid and extracted with tetrahy-
drofuran and ethyl acetate. Extracts were washed with brine, dried and con-
centrated in vacuo to give a solid. The crude crystals were recrystallized
from ethanol to afford 4.02 g (yield 91%) of 10 as a solid, mp 285—287 °C,
1H-NMR (DMSO-d6) d: 2.18 (3H, s), 6.74 (2H, d, Jꢀ8.8 Hz), 7.25 (2H, d,
Jꢀ8.8 Hz), 7.26 (2H, d, Jꢀ5.9 Hz), 8.49 (2H, d, Jꢀ5.9 Hz), 9.68 (1H, br s),
12.47 (1H, br s). Anal. Calcd for C16H13N3O2S·0.7H2O: C, 59.32; H, 4.48;
N, 12.97. Found: C, 59.34; H, 4.75; N, 13.12.
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]cyclopen-
tanecarboxamide (7ad) This compound was prepared from 6u and cy-
clopentanecarbonyl chloride as described in the synthesis of 7e as a solid,
1
yield 59%, mp 275—278 °C (ethanol), H-NMR (DMSO-d6) d: 1.52—1.98
(8H, m), 2.21 (6H, s), 2.92—3.00 (1H, m), 7.00 (1H, s), 7.05 (2H, s), 7.25—
7.28 (2H, m), 8.49—8.52 (2H, m), 12.43 (1H, br s). Anal. Calcd for
C22H23N3OS: C, 70.00; H, 6.14; N, 11.13. Found: C, 69.76; H, 6.05; N,
11.13.
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]benzamide
(7ae) This compound was prepared from 6u and benzoyl chloride as de-
scribed in the synthesis of 7e as a solid, yield 26%, mp 285—286 °C
(ethanol), 1H-NMR (CDCl3) d: 2.23 (6H, s), 6.93 (1H, s), 7.03 (2H, s),
7.26—7.29 (2H, m), 7.43—7.63 (3H, m), 7.87—7.91 (2H, m), 8.50—8.54
(2H, m), 10.37 (1H, br s). Anal. Calcd for C23H19N3OS: C, 71.66; H, 4.97;
N, 10.90. Found: C, 71.39; H, 4.91; N, 11.14.
N-[4-(4-Ethoxyphenyl)-5-(4-pyridinyl)-1,3-thiazol-2-yl]acetamide
(11a) A mixture of 10 (0.40 g, 1.3 mmol) and potassium butoxide (0.15 g,
1.4 mmol) in N,N-dimethylacetamide (4.0 ml) was stirred at 0 °C for 0.5 h.
Ethyl iodide (0.22 g, 1.4 mmol) was added to the mixture at 0 °C and allowed
to warm up to room temperature. The mixture was stirred at room tempera-
N-[4-(3,5-Dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]nicotinamide
(7af) This compound was prepared from 6u and nicotinoyl chloride hy-
drochloride as described in the synthesis of 7e as a solid, yield 61%, mp
1
267—270 °C (ethanol), H-NMR (DMSO-d6) d: 2.23 (6H, s), 7.03 (1H, s),

1136
Vol. 56, No. 8
ture for 16 h and 3 N hydrochloric acid was added to the mixture. Aqueous
MODEL683, Harvard Apparatus). Pancuronium bromide (1 mg/kg, Sigma
sodium hydrogen carbonate was added to the reaction mixture and the pre- Chemicals Co.) was then administered intravenously and 1 min later, propra-
cipitate was collected by filtration. The precipitate was washed with water nol (1 mg/kg) was given intravenously. One minute after propranol adminis-
and dried. The solid was chromatographed on silica gel eluting with
tration, the rat was given aerosolized saline for 15 s and baseline was de-
hexane–ethyl acetate (1 : 2) to give crude crystals, which were recrystallized cided. After 1.5 min, the rat was given aerosolized acetylcholine at an initial
from ethyl acetate to afford 0.08 g (yield 19%) of 11a as a solid, mp 206— dose of 3 mg/ml and then 10, 30, 100 and 300 mg/ml for 15 s at 2-min inter-
1
209 °C, H-NMR (DMSO-d6) d: 1.34 (3H, t, Jꢀ7.0 Hz), 2.45 (3H, s), 4.24 vals. The aerosol was generated with an ultrasonic nebulizer (Aerosonic
(2H, q, Jꢀ7.0 Hz), 6.75 (2H, d, Jꢀ6.2 Hz), 7.24—7.32 (4H, m), 8.50 (2H, d, MODEL5000D; Devilbiss). Intrapulmonary pressure was measured with a
Jꢀ6.2 Hz), 9.66 (1H, br s), 12.37 (1H, br s). Anal. Calcd for C18H17N3O2S:
transducer and the response was measured as the peak increase above the
C, 63.70; H, 5.05; N, 12.38. Found: C, 63.25; H, 4.99; N, 12.21.
baseline. Compound 7af (10 mg/kg) and dexamethasone (0.01 mg/kg) were
N-[4-(4-Butoxyphenyl)-5-(4-pyridinyl)-1,3-thiazol-2-yl]acetamide orally administered 1 h before and 7 h after antigen challenge.
(11b) This compound was prepared from butyl iodide as described in the
synthesis of 11a as a solid, yield 20%, mp 201—203 °C (ethyl acetate), H-
1
Acknowledgements We thank Dr. Yoshio Yamamoto for his contribu-
NMR (DMSO-d6) d: 0.96 (3H, t, Jꢀ7.1 Hz), 1.29—1.50 (2H, m), 1.66— tion to the modeling study calculation, Mr. Koji Ohnishi and Mr. Masashi
1.84 (2H, m), 2.45 (3H, s), 4.20 (2H, t, Jꢀ7.5 Hz), 6.75 (2H, d, Jꢀ8.8 Hz), Yamaguchi for pharmacokinetic studies, and Ms. Miho Fujisawa for techni-
7.27 (2H, d, Jꢀ5.9 Hz), 7.28 (2H, d, Jꢀ8.8 Hz), 8.51 (2H, d, Jꢀ5.9 Hz), cal assistance.
9.68 (1H, br s). Anal. Calcd for C20H21N3O2S: C, 65.37; H, 5.76; N, 11.44.
Found: C, 65.05; H, 5.81; N, 11.50.
References
4-(4-Methoxyphenyl)-2-methyl-5-(4-pyridyl)-1,3-thiazole (12) A 2 N
sodium hydroxide solution (8.5 ml, 17 mmol) was added to a solution of 6aa
(3.0 g, 8.5 mmol) in ethanol (8.5 ml) at room temperature and the resulting
mixture was stirred for 2 h. The solvent was removed in vacuo and the
residue was acidified with 3 N hydrochloric acid. The precipitate was col-
lected by filtration and dried. The crystal was added to ethanol (100 ml) and
the mixture was refluxed for 3 h. The solvent was removed in vacuo and the
crude crystals were recrystallized from ethanol to afford 1.5 g (yield 56%) of
11 as a solid, mp 132—133 °C, 1H-NMR (CDCl3) d: 2.76 (3H, s), 3.83 (3H,
s), 6.86 (2H, d, Jꢀ9.0 Hz), 7.21 (2H, d, Jꢀ6.2 Hz), 7.41 (2H, d, Jꢀ9.0 Hz),
8.52 (2H, d, Jꢀ6.2 Hz). Anal. Calcd for C16H14N2OS·0.1H2O: C, 67.63; H,
5.04; N, 9.86. Found: C, 67.60; H, 4.99; N, 9.75.
1) Fredholm B. B., Ijzerman A. P., Jacobson K. A., Klotz K. N., Linden
J., Pharmacol. Rev., 53, 527—552 (2001).
2) van Muijlwijk-Koezen J. E., Timmerman H., Ijzerman A. P., Prog.
Med. Chem., 38, 61—113 (2001).
3) Poulsen S.-A., Quinn R. J., Bioorg. Med. Chem., 6, 619—641 (1998).
4) Salvatore C. A., Jacobson M. A., Taylor H. E., Linden J., Johnson R.
G., Proc. Natl. Acad. Sci. U.S.A., 90, 10365—10369 (1993).
5) Ramkumar V., Stiles G. L., Beaven M. A., Ali H., J. Biol. Chem., 268,
16887—16890 (1993).
6) Mubagwa K., Flameng W., Cardiovasc. Res., 52, 25—39 (2001).
7) Liang B. T., Jacobson K. A., Proc. Natl. Acad. Sci. U.S.A., 95, 6995—
6999 (1998).
Human A1, A2A, and A3 Receptor and Rat A3 Binding Assay Binding
assay for A3AR was performed in 100 ml binding assay buffer (50 mM
Tris–HCl (pH 7.5), 1 mM EDTA, 10 mM MgCl2, 0.25 mM PMSF, 1 mg/ml
pepstatin, 20 mg/ml leupeptin) containing 10 mg of membrane protein and
20 nM [3H]-NECA (Amersham Life Sciences, Inc., Tokyo) in the presence of
8) von Lubitz D. K. J. E., Eur. J. Pharmacol., 371, 85—102 (1999).
9) Fishman P., Madi L., Bar-Yehuda S., Barer F., Del Valle L., Khalili K.,
Oncogene, 21, 4060—4064 (2002).
10) Merighi S., Prisco M., Varani K., Gessi S., Leung E., Baraldi P. G.,
Tabrizi M. A., Borea P. A., Pharmacol. Ther., 100, 31—48 (2003).
various concentrations of compounds. Following incubation at room temper- 11) Ji X.-D., von Lubitz D., Olah M. E., Stiles G. L., Jacobson K. A., Drug
ature for 1 h, the binding reaction was filtrated through the GF/C unifilter Dev. Res., 33, 51—59 (1994).
(Packard Instrument Company, Tokyo) and washed three times with ice-cold 12) van Rhee A. M., Jiang J.-L., Melman N., Olah M. E., Stiles G. L., Ja-
50 mM Tris–HCl (pH 7.5), using a Cell Harvester (Packard Instrument Com- cobson K. A., J. Med. Chem., 39, 2980—2989 (1996).
pany, Tokyo). The filter was dried and MicroScint-O was placed on the filter. 13) Jiang J.-L., van Rhee A. M., Melman N., Ji X.-D., Jacobson K. A., J.
Radioactivity retained on the filter was determined by Top-Count (Packard
Instrument Company, Tokyo).
IB-MECA Induced Plasma Protein Extravasation Assay Male
Sprague-Dawley rats (8 weeks old, CLEA Japan, Inc.) were used under light
Med. Chem., 39, 4667—4675 (1996).
14) Jiang J.-L., van Rhee A. M., Chang L., Patchornik A., Ji X.-D., Evans
P., Melman N., Jacobson K. A., J. Med. Chem., 40, 2596—2608
(1997).
ether anesthesia. The back of the animal was shaved and intravenously in- 15) Li A.-H., Moro S., Melman N., Ji X.-D., Jacobson K. A., J. Med.
jected with 1.0 ml of 0.5% Evans blue (Tokyo Chemical Industry Co., Ltd.) Chem., 41, 3186—3201 (1998).
in saline. Immediately, each animal was injected intradermally with 50 ml of 16) Kim Y. C., Ji X. D., Jacobson K. A., J. Med. Chem., 39, 4142—4148
IB-MECA (10 mM) and 50 ml of vehicle (PBS), respectively. Thirty minutes (1996).
after intradermal injections, rats were sacrificed and the dorsal skin was 17) Kim Y.-C., de Zwart M., Chang L., Moro S., von Frijtag Drabbe
carefully removed, and the injection sites were excised with a cork borer
(15 mm diameter). For dye recovery, the skin samples were placed in test
tubes containing 2 ml of a mixture of 0.3% Na2SO4 and acetone (3 : 7) at
room temperature overnight. Plasma protein extravasation was quantitated
Künzel J. K., Melman N., Ijzerman A. P., Jacobson K. A., J. Med.
Chem., 41, 2835—2845 (1998).
18) Karton Y., Jiang J.-L., Ji X.-D., Melman N., Olah M. E., Stiles G. L.,
Jacobson K. A., J. Med. Chem., 39, 2293—2301 (1996).
by measuring the absorbance of Evans blue at 610 nm with a spectropho- 19) Jacobson M. A., Chakravarty P. K., Johnson R. G., Norton R., Drug
tometer (TR-1000T, CORONA ELECTRIC). The compounds were orally
administered 1 h before IB-MECA intradermal injection.
Dev. Res., 37, 131 (1996).
20) Jacobson M. A., Norton R., PCT Int. Appl., WO 9921555 (1999).
Antigen-Induced Rat Asthma Model. Animals, Sensitization and 21) van Muijlwijk-Koezen J. E., Timmerman H., Link R., van der Goot H.,
Antigen Challenge Male Brown Norway rats (8 weeks old, Charles River Ijzerman A. P., J. Med. Chem., 41, 3987—3993 (1998).
Japan Inc., Yokohama, Japan) were sensitized by an intramuscular injection 22) van Muijlwijk-Koezen J. E., Timmerman H., Link R., van der Goot H.,
of 1 mg ovalbumin (OVA, Grade III, Sigma Chemical Co.) and 200 mg of Ijzerman A. P., J. Med. Chem., 41, 3994—4000 (1998).
aluminium hydroxide (Wako Pure Chemical Industries, Ltd.) in 1 ml of 23) Baraldi P. G., Cacciari B., Romagnoli R., Spalluto G., Klotz K.-N.,
saline. At the same time, 1 ml of Bordetella pertussis vaccine (Wako Pure
Leung E., Varani K., Gessi S., Merighi S., Borea P. A., J. Med. Chem.,
42, 4473—4478 (1999).
Chemical Industries, Ltd.) containing 1ꢆ1010 heat-killed bacilli in saline
was administered intraperitoneally as an adjuvant. Three weeks after sensiti- 24) Baraldi P. G., Cacciari B., Moro S., Spalluto G., Pastorin G., Da Ros
zation, animals were placed in a box (20ꢆ21ꢆ13 cm) and exposed to
aerosolized 1% OVA or saline for 5 min. The aerosol was generated with an
ultrasonic nebulizer (Atom Medical Systems).
Assessment of Airway Responsiveness Airway responsiveness to
acetylcholine was measured 23—30 h after antigen challenge. The rats were
T., Klotz K.-N., Varani K., Gessi S., Borea P. A., J. Med. Chem., 45,
770—780 (2002).
25) Maconi A., Pastorin G., Da Ros T., Spalluto G., Gao Z. G., Jacobson
K. A., Baraldi P. G., Cacciari B., Varani K., Moro S., Borea P. A., J.
Med. Chem., 45, 3579—3582 (2002).
anesthetized with an intraperitoneal injection of pentobarbital sodium 26) van Muijlwijk-Koezen J. E., Timmerman H., Vollinga R. C., Frijtag
(50 mg/kg, Abbott Laboratories). A tracheal cannula, through which the rat
was mechanically ventilated, was inserted via a tracheotomy. A cannula was
von Drabbe Künzel J., de Groote M., Visser S., Ijzerman A. P., J. Med.
Chem., 44, 749—762 (2001).
also inserted into the external jugular vein. The rat was mechanically venti- 27) Okamura T., Kurogi Y., Nishikawa H., Hashimoto K., Fujiwara H.,
lated (2—3 ml/breath, 90 breaths/min, 10 cm H2O) (rodent ventilator Nagao Y., J. Med. Chem., 45, 3703—3708 (2002).

August 2008
1137
28) Okamura T., Kurogi Y., Hashimoto K., Sato S., Nishikawa H., Kiryu
K., Nagao Y., Bioorg. Med. Chem. Lett., 14, 3775—3779 (2004).
29) Tchilibon S., Kim S. K., Gao Z. G., Harris B. A., Blaustein J., Gross
A. S., Melman N., Jacobson K. A., Bioorg. Med. Chem., 12, 2021—
2034 (2004).
H., Tanaka T., Asahi S., Ohkawa S., J. Med. Chem., 48, 5966—5979
(2005).
32) Wattanasin S., Kathawala F. G., Tetraheron Lett., 25, 811—814 (1984).
33) Jacobson K. A., Gao Z.-G., Chen A., Barak D., Kim S.-A., Lee K.,
Link A., van Rompaey P., van Calenbergh S., Liang B. T., J. Med.
Chem., 44, 4125—4136 (2001).
30) Miwatashi S., Arikawa Y., Naruo K., Igaki K., Watanabe Y., Kimura
H., Kawamoto T., Ohkawa S., Chem. Pharm. Bull., 53, 410—418 34) Gao Z.-G., Chen A., Barak D., Kim S.-K., Müller C. E., Jacobson K.
(2005). A., J. Biol. Chem., 277, 19056—19063 (2002).
31) Miwatashi S., Arikawa Y., Kotani E., Miyamoto M., Naruo K., Kimura 35) Jones G., Willett P., Glen R. C., J. Mol. Biol., 245, 43—53 (1995).