Substituted heterocyclic thiourea compounds as a new class of anti-allergic agents inhibiting IgE/FcεRI receptor mediated mast cell leukotriene release

Article abstract of DOI:10.1016/S0968-0896(02)00531-X

Mast cell derived leukotrienes (LT's) play a vital role in pathophysiology of allergy and asthma. We synthesized various analogues of indolyl, naphthyl and phenylethyl substituted halopyridyl, thiazolyl and benzothiazolyl thioureas and examined their in vitro effects on the high affinity IgE receptor/FcεRI-mediated mast cell leukotriene release. Of the 22 naphthylethyl thiourea compounds tested, there were 7 active compounds and N-[1-(1-naphthyl)ethyl]-N′-[2-(ethyl-4-acetylthiazolyl)]thiourea (17 and 16) (IC₅₀=0.002 μM) and N-[1-(1R)-naphthylethyl]-N′-[2-(5-methylpyridyl)]thiourea (compound 5) (IC₅₀=0.005 μM) were identified as the lead compounds. Among the 11 indolylethyl thiourea compounds tested, there were seven active compounds and the halopyridyl compounds N-[2-(3-indolylethyl)]-N′-[2-(5-chloropyridyl)]thiourea (24) and N-[2-(3-indolylethyl)]-N′-[2-(5-bromopyridyl)]thiourea (25) were the most active agents and inhibited the LTC₄ release with low micromolar IC₅₀ values of 4.9 and 6.1 μM, respectively. The hydroxylphenyl substituted compounds N-[2-(4-hydroxyphenyl)ethyl]-N′-[2-(5-chloropyridyl)]thiourea (37; IC₅₀=12.6 μM), N-[2-(4-hydroxyphenyl)ethyl]-N′-[2-(5-bromopyridyl)]thiourea (50; IC₅₀=16.8 μM) and N-[2-(4-hydroxyphenyl)ethyl]-N′-[2-(pyridyl)]thiourea (35; IC₅₀=8.5 μM) were the most active pyridyl thiourea agents. Notably, the introduction of electron withdrawing or donating groups had a marked impact on the biological activity of these thiourea derivatives and the Hammett sigma values of their substituents were identified as predictors of their potency. In contrast, experimentally determined partition coefficient values did not correlate with the biological activity of the thiourea compounds which demonstrates that their liphophilicity is not an important factor controlling their mast cell inhibitory effects. These results establish the substituted halopyridyl, indolyl and naphthyl thiourea compounds as a new chemical class of anti-allergic agents inhibiting IgE receptor/FcεRI-mediated mast cell LTC₄ release. Further lead optimization efforts may provide the basis for new and effective treatment as well as prevention programs for allergic asthma in clinical settings.

Full text of DOI:10.1016/S0968-0896(02)00531-X

Bioorganic & Medicinal Chemistry 11 (2003) 1095–1105
Substituted Heterocyclic Thiourea Compounds as a New Class of
Anti-allergic Agents Inhibiting IgE/Fc"RI Receptor Mediated
Mast Cell Leukotriene Release
T. K. Venkatachalam,a S. Qazi,b P. Samuelc and F. M. Uckund,e,f,
*
aDepartment of Chemistry, Parker Hughes Institute, 2699 Patton Road, Roseville, MN 55113, USA
bDepartment of Bioinformatics, Parker Hughes Institute, 2699 Patton Road, Roseville, MN 55113, USA
cDepartment of Pharamaceutical Sciences, Parker Hughes Institute, 2699 Patton Road, Roseville, MN 55113, USA
dDepartment of Immunology, Parker Hughes Institute, 2699 Patton Road, Roseville, MN 55113, USA
eDrug Discovery Program, Parker Hughes Center for Clinical Immunology, 2848 Patton Road, Roseville, MN 55113, USA
fDrug Discovery Program, Parker Hughes Cancer Center, 2848 Patton Road, Roseville, MN 55113, USA
Received 18 July 2002; accepted 4 September 2002
Abstract—Mast cell derived leukotrienes (LT’s) play a vital role in pathophysiology of allergy and asthma. We synthesized various
analogues of indolyl, naphthyl and phenylethyl substituted halopyridyl, thiazolyl and benzothiazolyl thioureas and examined their
in vitro effects on the high affinity IgE receptor/FceRI-mediated mast cell leukotriene release. Of the 22 naphthylethyl thiourea
compounds tested, there were 7 active compounds and N-[1-(1-naphthyl)ethyl]-N0-[2-(ethyl-4-acetylthiazolyl)]thiourea (17 and 16)
(IC50=0.002 mM) and N-[1-(1R)-naphthylethyl]-N0-[2-(5-methylpyridyl)]thiourea (compound 5) (IC50=0.005 mM) were identified as
the lead compounds. Among the 11 indolylethyl thiourea compounds tested, there were seven active compounds and the halopyr-
idyl compounds N-[2-(3-indolylethyl)]-N0-[2-(5-chloropyridyl)]thiourea (24) and N-[2-(3-indolylethyl)]-N0-[2-(5-bromopyr-
idyl)]thiourea (25) were the most active agents and inhibited the LTC4 release with low micromolar IC50 values of 4.9 and 6.1 mM,
respectively. The hydroxylphenyl substituted compounds N-[2-(4-hydroxyphenyl)ethyl]-N0-[2-(5-chloropyridyl)]thiourea (37;
IC50=12.6 mM), N-[2-(4-hydroxyphenyl)ethyl]-N0-[2-(5-bromopyridyl)]thiourea (50; IC50=16.8 mM) and N-[2-(4-hydro-
xyphenyl)ethyl]-N0-[2-(pyridyl)]thiourea (35; IC50=8.5 mM) were the most active pyridyl thiourea agents. Notably, the introduction
of electron withdrawing or donating groups had a marked impact on the biological activity of these thiourea derivatives and the
Hammett sigma values of their substituents were identified as predictors of their potency. In contrast, experimentally determined
partition coefficient values did not correlate with the biological activity of the thiourea compounds which demonstrates that their
liphophilicity is not an important factor controlling their mast cell inhibitory effects. These results establish the substituted halo-
pyridyl, indolyl and naphthyl thiourea compounds as a new chemical class of anti-allergic agents inhibiting IgE receptor/FceRI-
mediated mast cell LTC4 release. Further lead optimization efforts may provide the basis for new and effective treatment as well as
prevention programs for allergic asthma in clinical settings.
# 2003 Elsevier Science Ltd. All rights reserved.
Introduction
activity of 5-LO results in oxygenation of the 20-carbon
fatty acid arachidonic acid to form 5-hydro-
peroxyeicosatetraenoic acid (5-HPETE). Next, the
dehydrase activity of 5-LO catalyzes the conversion of
5-HPETE to an unstable epoxide intermediate (LTA4),
which is either converted by a zinc-dependent cytosolic
hydrolase to leukotriene B4 (LTB4) or conjugated by a
glutathione S transferase (viz., LTC4 synthase) to glu-
tathione to form the C6-peptide leukotriene C4 (LTC4).6
LTB4 as a potent chemotactic peptide can initiate a
local inflammatory response by recruiting neutrophils7,8
and eosinophils.7,9,10 LTC4 is converted to the other
C6-peptide leukotrienes LTD4 and LTE4).6 The
Mast cells participate in the pathophysiology of allergy
and asthma through the release of chemical mediators,
including the pro-inflammatory leukotrienes (LTs) after
crosslinking of their high affinity surface IgE receptors/
FceRI.1ꢀ4 LT synthesis in mast cells is triggered by
activation of the 5-lipoxygenase (5-LO) pathway.5 As a
first step in this multistep process, the monooxygenase
*Corresponding author. Tel.: +1-651-796-5450; fax: +1-651-796-
5493; e-mail: fatih_uckun@ih.org
0968-0896/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00531-X

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T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
C6-peptide leukotrienes LTC4, LTD4 and LTE4, as
potent smooth muscle contractiles and vasoactive fac-
tors comprising the slow-reacting substance of anaphy-
laxis, participate in the pathophysiology of reactive
airway disease and asthma by (i) inducing contractions
of the airway smooth muscles11ꢀ15 increasing micro-
vascular permeability and contributing to edema for-
mation in the bronchial wall16 both of which lead to
bronchoconstriction, and (ii) stimulating mucus secre-
tion in the airways9 which can aggravate the airway
obstruction. Furthermore, LTD4 is selectively chemo-
tactic for eosinophils17 and LTE4 may also promote
eosinophil chemotaxis.18 Repeated stimulation of mast
cells in patients with allergic asthma may cause sustained
synthesis and release of LTs contributing to the sig-
nificant and persistent bronchoconstriction and inflam-
matory airway response during episodes of exacerbation.
In recent years, several strategies aimed at inhibiting the
synthesis and release of leukotrienes (e.g., use of 5-LO
inhibitors) or blocking their action at the receptor level
(e.g., use of specific LTD4 antagonists) have been
explored as treatment modalities for asthma.15,19ꢀ21
Indolylethylamine dissolved in 10 mL of dimethylfor-
mamide was added to this solution, and the reaction
mixture was heated to 110 ꢁC over an oil bath for 15 h.
After this period, the reaction mixture was cooled to
room temperature and poured into crushed ice/water
mixture and the contents were stirred for an additional
h. The precipitate was filtered, washed with cold water
several times and dried under vacuum. The dried pre-
cipitate was then dissolved in chloroform and washed
with brine, water and finally the separated chloroform
layer was dried over anhydrous magnesium sulfate. Fil-
tration and evaporation of the solvent yielded the target
thiourea compounds. Compounds were further purified
using silica gel column chromatography and finally
recrystallized using ethanol as a solvent. A similar pro-
cedure was followed for other substituted compounds
using either thiazolyl or benzothiazolyl precursors. The
chiral thiourea derivatives were synthesized starting
from their respective chiral amines and their chirality
was confirmed using optical rotation values. The optical
purity of the compounds was >99% consistent with the
purity as measured by HPLC (see ref 30). The structures
of the compounds were altered by changing the sub-
stituents on the pyridyl ring. Halo and methyl substitu-
tions were chosen to determine the effects of electron
withdrawing and donating groups, respectively, on the
mast cell inhibitory activity. For the indolylethyl-sub-
stituted thioureas, we maintained the indolyl group in
the structure while we changed the pyridyl, thiazolyl
and benzothiazolyl groups. We substituted the pyridyl
moiety with various substituents and introduced thia-
zolyl and benzothiazolyl moiety into their structures. In
the case of phenylethyl pyridyl substituted thioureas,
the substituents were changed with H, Me, Br, Cl, OH,
OMe while keeping the pyridyl moiety constant with
halosubstituent at position 5.
The purpose of the present study was to examine mem-
bers of our thiourea compound library26ꢀ29 for mast cell
inhibitory activity in an attempt to identify thiourea
compounds capable of inhibiting FceRI-mediated LTC4
release from mast cells.
Results and Discussion
Indolyl-substituted halopyridyl thiourea compounds
were synthesized according to Scheme 1. Thiocarbonyl
imidazole and 2-amino-5-halo pyridine were added to
100 mL of dry acetonitrile under nitrogen atmosphere
and stirred at room temperature for 12–15 h. The pre-
cipitate was filtered, washed with cold acetonitrile, and
dried thoroughly under vacuum to yield the thiocarbonyl
intermediates. In the subsequent step, these inter-
mediates were taken up in a dry flask under nitrogen,
50 mL of anhydrous dimethylformamide was added, and
the contents were stirred for 30 min at room temperature.
Structure–activity relationship among thiourea compounds
Incubation of IgE-sensitized RBL-2H3 mast cells with
the specific antigen DNP-BSA for 30 min caused them
to release significant amounts of LTC4. A 1-h exposure
of IgE-sensitized mast cells to some of the chiral

T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
1097
naphthylethylthiourea compounds prior to the antigen
challenge reduced the released amounts of LTC4 after
antigen challenge in a concentration-dependent fashion
with nanomolar to micromolar IC50 values (Tables 1
and 2). Table 1 shows the biological activity observed
for chiral naphthyl thioureas. Chirality of these com-
pounds did not influence their biological activity.
benzothiazolyl-substituted compounds showed only
marginal activity. Introduction of methyl or methoxy
substituents on the benzothiazolyl moiety eliminated the
biological activity of the parent compound. Of the 22
naphthylethyl thiourea compounds tested, N-[1-(1-naph-
thylethyl]-N0-[2-(ethyl-4-acetylthiazolyl)]thiourea (16 and
17) (IC50=0.002 mM) and N-[1-(1R)-naphthylethyl]-N0-
[2-(5-methylpyridyl)]thiourea (5) (IC50=0.005 mM) were
identified as the lead compounds.
Except for the methyl substituted compound
5
(IC50=0.005 mM) and 7 (IC50=1.6 mM), none of these
compounds was active (IC50>100 mM). Compounds 5
and 7 were more potent than the mast cell inhibitory
control dimethoxyquinazoline compound WHI-P97.24
Active inhibitors of LTC4 release were also identified
among indolylethyl thiourea compounds. Table 3 shows
the biological activity observed for indolyl ethyl-sub-
stituted thioureas. In the pyridyl substituted com-
pounds, halo substitution produced active compounds.
The most active compound in the series was the chlor-
opyridyl substituted thiourea compound 24. Thiazolyl-
substituted compounds were also active albeit with less
potency. Interestingly, the ester analogue of thiazolyl
substituted compound 31 showed higher potency. Ben-
zothiazolyl compounds in this series were inactive.
Table 2 shows the biological activity of chiral naphthyl
thioureas when the pyridyl ring is replaced with a thia-
zolyl or benzothiazolyl moiety. The thiazolyl substituted
compounds with methyl groups inhibited LTC4 release
from IgE/antigen-stimulated mast cells at micromolar
concentrations. Notably, the ester analogues 16 and 17
exhibited potent activity with low nanomolar IC50
values in the nanomolar range (R) and (S) isomers of
these thiazolyl-substituted compounds were equally
potent implying that stereochemistry does not sig-
nificantly affect their biological activity. By comparison,
Table 4 shows the biological activity obtained for 29
differently substituted phenylethyl thioureas. Only the
hydroxy substituted compounds exhibited mast cell
inhibitory activity. Substituents such as methyl, fluoro,
bromo and chloro yielded inactive compounds, irre-
spective of the position of substituent in the phenyl ring.
We also examined the activity of thiazolyl and ben-
zothiazolyl substituted phenylethyl thiourea compounds
and found that none of the compounds in the series
showed potent biological activity. Substitutions in the
thiazolyl ring or the benzothiazolyl ring did not improve
their potency. Table 5 shows the biological activity
obtained for 33 symmetrical diphenylthiourea com-
pounds. None of the compounds in this series inhibited
mast cells, indicating that the presence of a heterocyclic
moiety in the structure is critical for the mast cell inhi-
bitory activity of thiourea compounds.
Table 1. Structure and activity of N-naphthyl-N0-pyridylthioureas
Compd
Isomer
X
Activity (mM)
1
2
3
4
5
6
7
8
R
S
S
R
R
S
S
S
R
S
R
—
5-Cl
5-Br
5-Br
5-Cl
5-Me
5-Me
6-Me
4,6-diMe
4,6-diMe
H
>100
>100
>100
>100
0.005
>100
1.6
>100
>100
>100
>100
6.8a
9
10
We next sought to determine if the lipophilicity of the
compounds could be an important factor for their bio-
logic activity since lipophilic compounds are likely to
enter mast cells more easily resulting in higher intracel-
lular concentrations of the compound. To this end, we
estimated their partition coefficients using the octanol /
water distribution ratio. An HPLC method was used to
estimate the amount of compound distribution among
these two phases. Table 6 shows the log P values
obtained for the selective compounds. No statistically
significant correlation between the Log P values and
IC50 values was observed by regression analysis
(slope=ꢀ28.0ꢂ16.2, t-ratio=ꢀ1.72, df=15, p=0.1)
demonstrating that liphophilicity does not significantly
influence the activity of these thiourea compounds. We
also investigated the role played by various electron
donating and electron withdrawing groups on leuko-
triene C4 release. A significant correlation was found
for the indolyl ethyl substituted compounds: Figure 1
shows the regression between Hammett s and the IC50
values observed for indolyl ethyl substituted thiourea
compounds. Introducing electron withdrawing groups
such as Br and Cl resulted in more potent compounds
11
WHI-P97
H
—
aRef 24.
Table 2. Structure and activity of N-naphthyl-N0-thiazolyl and ben-
zothiazolyl thioureas
Compd
Isomer
Y
Z
Activity (mM)
12
13
14
15
16
17
18
19
20
21
22
S
R
S
R
S
R
R
S
H
H
Me
Me
NA
NA
NA
NA
NA
NA
H
>100
>100
83.2
25.9
CH2COOEt
CH2COOEt
NA
0.002
0.002
18.9
NA
NA
NA
NA
H
>100
>100
>100
>100
S
R
R
4-Me
4-Me
6-OMe

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T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
Table 3. Structure and activity of indolylethyl-substituted thioureas
Compd
X
Y
Z
Activity (mM)
23
24
25
26
27
28
29
30
31
32
33
H
5Cl
5Br
5Me
6Me
4,6 diMe
NA
NA
NA
NA
NA
NA
NA
NA
NA
H
Me
NA
NA
NA
NA
NA
NA
NA
NA
10
5
6
>100
24
>100
36
23
17
100
>100
CH2COOEt
NA
NA
NA
6-OMe
4-Me
NA
NA
Table 4. Structure and activity of phenylethyl substituted heterocyclic thioureas
Compd
R
X
Y
Z
Activity (mM)
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
4-Br
4-OH
4-Me
4-OH
2,5-diOMe
2-OMe
4-OMe
3-OMe
2-F
3-F
4-F
4-Br
4-Me
2-Cl
3-Cl
4-Cl
4-OH
H
H
H
H
Cl
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
H
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
H
25.1
8.5
28.3
12.6
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
16.8
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
Br
H
H
CF3
CF3
CF3
CF3
Cl
NA
NA
NA
NA
NA
NA
2,5-diOMe
2-F
3-F
4-Me
OH
4-Me
4-Me
4-Me
4-Me
4-Me
CH2COOEt
Me
H
NA
NA
6-OMe
that showed a statistically significant relationship
between s and activity (p<0.001).
compounds does not play a vital role. In the case of
indolyl ethyl substituted thiourea series, the halopyridyl
moiety was found to be more beneficial than both
thiazolyl and benzothiazolyl units in the structure.
Halo substitutions on the pyridyl ring showed
improved potency. In the case of phenyl ethyl sub-
stituted thioureas, the hydroxy substituent on the
phenyl ring showed improved potency compared to
other substituents. In addition we found that pyridyl
ring in the structure was an essential feature of these
In summary, among the three classes of thiourea com-
pounds studied for mast cell inhibitory activity, naph-
thyl substituted thiazolyl thioureas exhibited the most
potent activity followed by indolylethyl and phenylethyl
thiourea compounds. The mast cell inhibitory activity
shown by both (R) and (S) isomers of naphthyl thiourea
compounds demonstrates that stereochemistry of these

T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
1099
Table 5. Structure activity of substituted symmetrical phenyl ethyl
thioureas
release. The lead compounds N-[1-(1-naphthylethyl]-N0-
[2-(ethyl-4-acetylthiazolyl)]thiourea and N-[1-(1R)-
naphthylethyl]-N0-[2-(5-methylpyridyl)]thiourea
are
nanomolar inhibitors of mast cell LTC4 release. Further
lead optimization efforts may provide the basis for new
and effective treatment as well as prevention programs
for allergic asthma in clinical settings.
Compd
X
Y
Activity (mM)
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
4-F
H
H
4-OMe
4-OMe
4-F
4-F
4-F
4-F
4F
4-F
4-F
4-F
4-F
4-F
4-F
4-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
4-F
4-F
4-Cl
4-Cl
4-Cl
4-OMe
4-Br
4-F
3-Cl
2-Cl
3-Cl
4-Cl
3-F
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
80.0
Materials and Methods
All chemicals were purchased from Aldrich (Milwaukee,
WI, USA) and were used without further purification.
The chiral naphthyl amines were obtained as pure indi-
vidual enantiomers and were used as such without pur-
ification. Unless otherwise noted, each reaction vessel
was secured with a rubber septa, and the reaction was
4-F
performed under nitrogen atmosphere. H, 13C NMR
1
2-OMe
3-OMe
3,4-diOMe
2,5-diOMe
2-F
were obtained on a Varian Mercury 300 instrument at
ambient temperature in DMSO-d6. Chemical shifts are
reported as d values in parts per million downfield from
tetramethylsilane (d=0.0 ppm) as an internal standard
or from the residual dimethylsufloxide signal
(d=2.49 ppm for 1H NMR or d=39.7 ppm for 13C
NMR). Splitting patterns are designated as follows: s,
singlet; d, doublet; t, triplet; m, multiplet; br, broad
peak. FT-IR spectra were recorded on a Nicolet Protege
460 spectrometer. Mass spectra were performed on a
Hewlett Packard MALDI-TOF spectrometer (Model
G2025A LD-TOF). UV spectra were recorded from a
Beckmann Model # DU 7400 UV/Vis spectrometer
using a cell path length of 1 cm. Melting points were
determined using a Melt John’s apparatus and are
uncorrected. HPLC’s were done using a Hewlett Pack-
ard 1100 series instrument consisting of an automatic
sampler, an electronic degasser, a thermostatic control
unit, a diode array detector in conjunction with a chem
station software assembly. The column used was an
analytical RP-18 Lichrospher column (4.6ꢃ150 mm)
and eluent was 35:65, H2O (0.1% ACOH): ACN. The
flow rate was maintained at 1.0 mL/min and the detec-
tion wavelength was set at 275 nm. The column was
maintained at room temperature throughout the analy-
sis. Column chromatography was performed using silica
gel obtained from the J. T. Baker Company. The sol-
vents used for elution varied depending on the com-
pound and included either one or a combination of the
following: ethylacetate, methanol, chloroform, hexane,
methylene chloride, THF and ether. Compounds were
made by condensing indolyl ethyl amine and thio-
carbonylimidazole derivatives of 5 and 60-substituted
amino pyridines in anhydrous dimethylformamide
(Scheme 1). Indolylethylamine was purchased from
Aldrich Chemical Company and was used without fur-
ther purification. Thiazolyl and benzothiazolyl sub-
stituted thioureas were prepared in a similar fashion
using thiocarbaimidazole derivatives of either sub-
stituted amino thiazoles or benzothiazoles respectively.
4-Br
4-OH
3-F
2-F
4-Br
4-OH
2-Cl
3-Cl
4-Cl
3-OMe
2-OMe
4,5-diOMe
2,5-diOMe
4-Me
4-Me
4,5-diOMe
4-Cl
>100
>100
>100
>100
80.0
>100
64.3
>100
>100
3-Cl
Table 6. Partition coefficient values for thiourea derivatives
Compd
LogP
7
5
6
4.1
4.2
4.2
4.1
3.2
3.9
3.7
3.7
3.9
4.0
3.8
4.2
3.9
3.9
3.6
4.0
3.7
4.1
3.2
3.3
10
14
15
16
17
18
23
24
27
29
30
31
34
35
36
37
50
phenyl ethyl thiourea compounds. Substituted halopyr-
idyl, indolyl and naphthyl thiourea compounds repre-
sent a new chemical class of anti-allergic agents
inhibiting IgE/FceRI receptor mediated mast cell LTC4
Partition coefficients
The octanol/water partition coefficients were deter-
mined by the shake flask method. A known amount of

1100
T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
Figure 1. Structure–activity relationship for indolyethyl-substituted thioureas. Hammett sigma values predicted Log 10 transformed IC50 values for
indolyethyl substituted thioureas (solid line, R-squared=67%, slope=ꢀ1.55ꢂ0.3, t-ratio=ꢀ5.24, df=13, p=0.0003). 95% confidence for the
regression is shown by the dotted line.
Mast cell cultures
the thiourea analogues was added to 3 mL of water and
3 mL of octanol in a glass vial. The mixture was shaken
for 4 h at room temperature. The two phases were care-
fully separated and filtered through a Millipore filter
and analyzed by HPLC. The wavelength of detection
was kept at 254 nm. Methanol was used as eluent with a
flow rate of 1 mL/min. The partition coefficient was
calculated using the ratio of the area under the curve for
octanol and water respectively.
Stimulation of mast cells. RBL-2H3 rat mast cells were
sensitized with monoclonal anti DNP IgE antibody
(0.24 mg/mL) for 1 h at 37 ꢁC in a 48-well tissue culture
plate. Unbound IgE was removed by washing the cells
with PIPES-buffered saline. After washing, PIPES-buf-
fered saline containing 1 mM calcium chloride was
added to the monolayers of the RBL-2H3 cells. The cells
were challenged with 20 ng/mL DNP-BSA for 30 min at
37 ꢁC. The plate was centrifuged at 200 g for 10 min at
4 ꢁC, Supernatants were removed and saved. To study
the effect of test drugs, RBL-2H3 rat mast cells were
incubated with the drugs at the indicated concentrations
or vehicle for 30 min prior to antigen challenge.
Determination of optical rotation
The optical rotation of the chiral naphthyl derivatives
was determined using a polarimeter (Digi Pol, Model
#781, Automatic Polarimeter, Rudolph Instruments,
Fairfield, NJ, USA). The active chiral thiourea deriva-
tives were weighed and transferred into a standard flask
of 10 mL capacity. Chloroform (5 mL) was used to dis-
solve the derivatives. The solution (1 mL) containing the
respective thioruea derivatives was taken and intro-
duced into the polarimeter tube. The optical rotation
was measured at room temperature, and the values with
their signs are shown in the physical constants section.
RBL-2H3 mast cell line and mast cell cultures.
RBL-2H3 cells were supplied by Dr. R. P. Siraganian
(Laboratory of Microbiology and immunology,
National Institute of Dental Research, National Insti-
tute of Health). This adherent mucosal mast cell line
expresses 105–106 high affinity IgE receptors/FceRI per
cell. RBL-2H3 cells serve as a convenient model to
study mast cell functions.22,23 RBL-2H3 cells were
maintained as monolayers in 175 cm2 culture flasks in
Eagle’s minimum essential medium with Earle’s salts
(without l-glutamine) supplemented with 20% fetal
bovine serum and 2 mM l-glutamine.23
Statistical analysis
IC50 values were reported for each compound. The IC50
values were correlated with Log P values and Hamett s
using a linear regression model (JMP software, SAS
institute Inc, Cary, NC, USA). Slope parameters were
estimated and the t-ratios compared to zero slope were
calculated to assess the statistical significance. p-Values
of less than 0.05 were deemed significant.
Stimulation of mast cells and mediator assays. RBL-2H3
cells were sensitized with a monoclonal anti-dini-
trophenyl (DNP) IgE antibody (0.24 mg/mL) for 1 h at
37 ꢁC in a 48-well tissue culture plate. Unbound IgE was

T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
1101
removed by washing the cells with phosphate buffered
saline, pH 7.4. After washing the BMMC were re-sus-
pended in RPMI-hepes buffer whereas PIPES-buffered
saline containing 1 mM calcium chloride was added to
the monolayers of the RBL-2H3 cells. In order to study
the biologic effects of the test compounds, sensitized
mast cells were further incubated with the test com-
pounds at the indicated concentrations (or vehicle
alone) for 1 h. The cells were then challenged with 20 ng/
mL DNP-BSA for 30 min at 37 ꢁC. The plates were
centrifuged at 200 g for 10 min at 4 ꢁC. Supernatants
were removed and saved. LTC4 levels were also deter-
mined in cell free supernatants.24,25
23. Wong, A.; Cook, M. N.; Hwang, S. M.; Sarau, H. M.;
Foley, J. J.; Crooke, S. T. Biochemistry 1992, 31, 4046.
24. Malaviya, R.; Chen, C. L.; Navara, C.; Malaviya, R.; Liu,
X. P.; Keenan, M.; Waurzyniak, B.; Uckun, F. J. Pharmacol.
Exp. Ther. 2000, 295, 912.
25. Tibbles, H. E.; Vassilev, A.; Wendorf, H.; Schonhoff, D.;
Zhu, D.; Lorenz, D.; Waurzyniak, B.; Liu, X. P.; Uckun, F. M.
J. Biol. Chem. 2001, 276, 17815.
26. Vig, R.; Mao, C.; Venkatachalam, T. K.; Tuel-Ahlgren,
L.; Sudbeck, E. A.; Uckun, F. M. Bioorg. Med. Chem. 1998, 6,
1789.
27. Mao, C.; Sudbeck, E. A.; Venkatachalam, T. K.; Uckun,
F. M. Bioorg. Med. Chem. Lett. 1999, 9, 1593.
28. Mao, C.; Sudbeck, E. A.; Venkatachalam, T. K.; Uckun,
F. M. Antiviral Chem. Chemother. 1999, 10, 233.
29. Venkatachalam, T. K.; Sudbeck, E. A.; Mao, C.; Uckun,
F. M. Bioorg. Med. Chem. Lett. 2000, 10, 2071.
30. Physicochemical properties of selected thiourea com-
pounds
N-[1-(1R)-(1-Naphthylethyl)]-N0-[2-(5-methylpyridyl)]thiourea
(5). Mp 186–187 ꢁC; 1H NMR (DMSO-d6) d 12.22 (d, 1H,
J=8.1 Hz), 10.59 (s, 1H), 8.19 (d, 1H, J=8.1 Hz), 7.92 (d, 2H,
J=8.4 Hz), 7.83 (d, 1H, J=7.8 Hz), 7.56–7.46 (m, 5H), 7.06
(d, 1H, J=8.4 Hz), 6.32 (t, 1H), 2.11 (s, 3H), 1.65 (d, 3H,
J=6.9 Hz); 13C NMR (DMSO-d6) d 178.5, 152.0, 144.9, 139.9,
139.1, 133.6, 130.6, 128.9, 127.9, 127.0, 126.6, 125.8*, 123.4,
122.9, 112.4, 50.5, 21.6, 17.4; IR n 3440, 3232, 3027, 2969,
1600, 1562, 1492, 1195, 798 cmꢀ1; UV (MeOH) l 203, 222,
Acknowledgements
The authors thank R. Malaviya for technical assistance
and performing the LTC4 release assays.
References and Notes
1. Galli, S. J. N. Engl. J. Med. 1993, 328, 257.
2. Ishizaka, T.; Ishizaka, K.; Orange, R. P.; Austen, K. F.
J. Immunol. 1971, 106, 1267.
3. Malaviya, R.; Malaviya, R.; Jakschik, B. A. J. Biol. Chem.
1993, 268, 4939.
4. Wasserman, S. I. J. Allergy Clin. Immunol. 1990, 86, 590.
5. Jakschik, B. A.; Lee, L. H. Nature 1980, 287, 51.
6. An, S.; Goetzl, E. J. In Allergy, Principles and Practice;
Middleton, C. E. R. E., Ellis, E. F., Adkinson, N. F., Yun-
ginger, J. W. Busse, W. W. Eds.; Mosby-Year Book: St. Louis,
MO, 1998; Vol. 1, Chapter 14.
250,
272,
294 nm;
MALDI-TOF
m/z
322.8
(C19H19N3S2+2H+). [a]: ꢀ31.0; 0.5HPLC Rt: 14.01 min%
purity 99.0, elemental analysis: calcd: C: 70.99, H: 5.96,
N:13.07; found: C: 71.04, H: 6.04, N: 13.17.
N-[1-(1S)-(1-Naphthylethyl)]-N0-[2-(5-methylpyridyl)]thiourea
(6). Mp 186–187 ꢁC; 1H NMR (DMSO-d6) d 12.23 (d, 1H,
J=7.8 Hz), 10.61 (s, 1H), 8.20 (d, 1H, J=8.7 Hz), 7.91 (d, 2H,
J=8.0 Hz), 7.83 (d, 1H, J=8.1 Hz), 7.59–7.46 (m, 5H), 7.06
(d, 1H, J=8.4 Hz), 6.33 (m, 1H), 2.10 (s, 3H), 1.66 (d, 3H,
J=6.6 Hz); 13C NMR (DMSO-d6) d 178.4, 152.0, 144.9, 139.9,
139.1, 133.6, 130.6, 128.9, 127.8, 127.0, 126.5, 125.8*, 123.4,
122.9, 112.4, 50.4, 21.6, 17.4; IR n 3232, 3027, 2969, 1600,
1527, 1195, 779 cmꢀ1; UV (MeOH) l 224, 249, 272, 294 nm;
MALDI-TOF m/z 322.8 (C19H19N3S2+2H+). [a]: +30.5;
HPLC Rt: 13.97 min% purity 100.0, elemental analysis: calcd:
C: 70.99, H: 5.96, N:13.07; found: C: 70.78, H: 6.00, N: 13.01.
N-[1-(1S)-(1-Naphthylethyl)]-N0-[2-(4-methylthiazolyl)]thiourea
7. Spada, C. S.; Krauss, A. H.; Nieves, A. L.; Woodward,
D. F. Adv. Exp. Med. Biol. 1997, 400B, 699.
8. Zhang, Y.; Ramos, R.; Jakschik, B. A. Science 1992, 258,
1957.
9. Henderson, W. R., Jr.; Lewis, D. B.; Albert, R. K.; Zhang,
Y.; Lamm, W. J.; Chiang, G. K.; Jones, F.; Eriksen, P.; Tien,
Y. T.; Jonas, M.; Chi, E. Y. J. Exp. Med. 1996, 184, 1483.
10. Takeda, K.; Hamelmann, E.; Joetham, A.; Shultz, L. D.;
Larsen, G. L.; Irvin, C. G.; Gelfand, E. W. J. Exp. Med. 1997,
86, 449.
11. Arm, J. P.; Lee, T. H. Adv. Immunol. 1992, 51, 323.
12. Dahlen, S. E.; Hansson, G.; Hedqvist, P.; Bjorck, T.; Gran-
strom, E.; Dahlen, B. Proc. Natl. Acad. Sci. U.S.A. 1983, 80, 1712.
13. Drazen, J. M.; Austen, K. F.; Lewis, R. A.; Clark, D. A.;
Goto, G.; Marfat, A.; Corey, E. J. Proc. Natl. Acad. Sci.
U.S.A. 1980, 77, 4354.
(14). Mp 186–187 ꢁC; H NMR (DMSO-d6) d: 11.50 (s, 1H),
1
10.17 (s, 1H), 8.15 (q, 1H), 7.95 (t, 1H), 7.86 (t, 1H), 7.55 (m,
4H), 6.61 (d, 1H, J=8.7 Hz), 6.20 (m, 1H), 2.16 (d, 3H,
J=4.8 Hz), 1.64 (t, 3H); 13C NMR (DMSO-d6) d: 177.2, 161.2,
138.7, 133.5, 130.4, 128.8, 127.8, 126.5, 125.8, 125.6, 123.2,
122.8, 106.2, 49.9, 21.2, 16.7; IR n 3448, 3170, 3020, 2969,
1581, 1531, 1502, 1207, 777 cmꢀ1; UV (MeOH) l 224, 266,
294 nm; MALDI-TOF MS m/z 329.0 (C17H17N3O2+2H+).
[a]: +21.5; HPLC Rt: 11.65 min.% purity 99.0, elemental
analysis: calcd: C: 62.35, H: 5.23, N:12.83; found: C: 62.46, H:.
5.30, N: 12.81.
14. Drazen, J. M.; Israel, E.; O’Byrne, P. M. N. Engl. J. Med.
1999, 340, 197.
15. Sorkness, C. A. Pharmacotherapy 1997, 17, 50S.
16. Ramos, B. F.; Zhang, Y.; Angkachatchai, V.; Jakschik,
B. A. J. Pharmacol. Exp. Ther. 1992, 262, 559.
17. Spada, C. S.; Nieves, A. L.; Krauss, A. H.; Woodward,
D. F. J. Leukocite Biol. 1994, 55, 183.
18. Laitinen, L. A.; Laitinen, A.; Haahtela, T.; Villka, V.;
Spur, B. W.; Lee, T. H. Lancet 1993, 341, 989.
19. Gorenne, I.; Labat, C.; Gascard, J. P.; Norel, X.; Muller-
Peddinghaus, R.; Mohrs, K. H.; Taylor, W. A.; Gardiner, P. J.;
Brink, C. J. Pharmacol. Exp. Ther. 1994, 268, 868.
20. Smith, L. J. Arch. Intern. Med. 1996, 156, 2181.
21. Tan, R. A. Curr. Opin. Pulm. Med. 1998, 4, 25.
22. Hamawy, M. M.; Siraganian, R. P. J. Immunol. Meth.
1997, 201, 11.
N - [1 - (1R) - (1 - Naphthylethyl)] - N0 - [2 - (4 - methylthiazo-
lyl)]thiourea (15). Mp 186–187 ꢁC; 1H NMR (DMSO-d6) d:
11.52 (s, 1H), 10.17 (s, 1H), 8.15 (d, 1H, J=8.4 Hz), 7.94 (d,
1H, J=8.1 Hz), 7.85 (d, 1H, J=7.5 Hz), 7.52 (m, 4H), 6.61 (s,
1H), 6.21 (m, 1H), 2.16 (s, 3H), 1.64 (d, 3H, J=6.6 Hz); 13C
NMR (DMSO-d6) d: 177.9, 162.0, 139.4, 134.1, 131.0, 129.4,
128.4, 127.1, 126.5, 126.2, 123.8, 123.4, 106.8, 50.6, 21.8, 17.3;
IR n 3423, 3170, 3018, 2968, 1581, 1531, 1502, 1205, 779 cmꢀ1
;
UV (MeOH) l 207, 224, 284, 293 nm; MALDI-TOF MS m/z
329.2 (C17H17N3O2+2H+). [a]: ꢀ21.2; HPLC Rt: 12.31 min%
purity 100.0.
N - [1 - (1S) - (1 - Naphthylethyl)] - N0 - [2 - (ethyl - 4 - acet-
ylthiazolyl)]thiourea (16) Mp 107–109 ꢁC; H NMR (DMSO-
1

1102
T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
d6) d 11.54 (s, 1H), 10.10 (s, 1H), 8.15 (t, 1H), 7.96 (t, 1H), 7.86
(t, 1H), 7.61–7.50 (m, 4H), 6.89 (s, 1H), 6.21 (s, 1H), 4.05–4.00
(m, 2H), 3.64 (s, 2H), 1.62 (d, 3H, J=3.9 Hz), 1.16–1.09 (m,
3H); 13C NMR (DMSO-d6) d 177.2, 170.3, 161.5, 143.9, 139.3,
134.1, 131.0, 129.4, 128.4, 127.2, 126.5, 126.2, 123.7, 123.3,
109.9, 61.1,. 50.5, 31.2, 21.9, 14.9; IR n 3444, 3185, 3047, 2927,
N-[2-(3-Indolylethyl)]-N0 -[2-(5bromopyridyl)]thiourea (25).
Mp: 211–212 ꢁC; H NMR (DMSO-d6) d 11.18 (t, 1H), 10.90
1
(s, 1H), 10.65 (s, 1H), 7.97 (s, 1H), 7.90 (m, 1H), 7.62 (d, 1H,
J=7.5 Hz), 7.35 (d, 1H, J=7.5 Hz), 7.27 (s, 1H), 7.08 (s, 1H),
7.05 (t, 1H), 6.95 (t, 1H), 3.86 (q, 2H), 3.03 (t, 2H); 13C NMR
(DMSO-d6) d 178.1, 152.3, 145.7, 141.3, 136.4, 127.1, 123.5,
121.1, 118.5, 118.4, 114.4, 111.8, 111.5, 111.3, 45.9, 24.2; IR n
3347, 3207, 3035, 2941, 1591, 1556, 1529, 1456, 1189,
1577, 1554, 1519, 1230 cmꢀ1
; MALDI-TOF m/z 401.0
(C20H21N3O2S2+2H+); [a]: +22.8; HPLC Rt: 6.91 min%
purity 100.0, elemental analysis: calcd: C: 60.13, H: 5.30,
N:10.52; found: C: 60.06, H: 5.30, N: 10.50.
;
736 cmꢀ1 MALDI-TOF m/z 376 (C16H15BrN4S+2H+);
HPLC Rt: 6.60 min.
N - [1 - (1R) - (1 - Naphthylethyl)] - N0 - [2 - (ethyl - 4 - acet-
N-[2-(Indolylethyl)]-N0-[2-(5-methylpyridyl)]thiourea (26). Mp:
209–210 ꢁC; 1H NMR (DMSO-d6) d 11.63 (t, 1H), 10.90 (s,
1H), 10.45 (s, 1H), 7.79 (s, 1H), 7.64 (d, 1H, J=7.5 Hz), 7.52
(d, 1H, J=7.0 Hz), 7.36 (m, 1H), 7.26 (s, 1H), 7.10–6.94 (m,
3H), 3.89 (q, 2H), 3.05 (t, 2H), 2.16 (s, 3H); 13C NMR
(DMSO-d6) d 179.0, 151.8, 144.6, 139.6, 136.4, 127.1, 126.5,
123.4, 121.1, 118.4 (d), 112.0, 111.5 (d), 45.7, 24.5, 17.5; IR n
3320, 3251, 3054, 2931, 1527, 1488, 1257, 748 cmꢀ1; UV
(MeOH) l 209, 211, 223, 269, 292 nm; MALDI-TOF m/z
312.1 (C17H18N4S+2H+).
ylthiazolyl)]thiourea (17). Mp 105–107 ꢁC; H NMR (DMSO-
1
d6) d 11.54 (s, 1H), 10.09 (s, 1H), 8.14 (d, 1H, J=7.8 Hz), 7.95
(d, 1H, J=7.8 Hz), 7.86 (t, 1H), 7.62–7.50 (m, 4H), 6.89 (s,
1H), 6.20 (t, 1H), 4.02 (q, 2H), 3.63 (s, 2H), 1.62 (d, 3H,
J=5.4 Hz), 1.12 (t, 3H); 13C NMR (DMSO-d6) d 176.5, 169.7,
160.8, 143.3, 138.7, 133.5, 130.4, 128.8, 127.8, 126.5, 125.9,
125.6, 123.1, 122.7, 109.4, 60.5, 49.9, 36.6, 21.3, 14.3; IR n
3463, 3166, 2981, 1743, 1573, 1535, 1508, 1380, 1211, 1164,
794 cmꢀ1; MALDI-TOF m/z 401.2 (C20H21N3O2S2+2H+);
[a]: ꢀ25.5; HPLC Rt: 9.89 min% purity 99.9, elemental analy-
sis: calcd: C: 60.13, H: 5.30, N:10.52; found: C: 60.40, H: 5.36,
N: 10.53.
N-[2-(3-Indolylethyl)]-N0 -[2-(6-methylpyridyl)]thiourea (27).
ꢁ
1
Mp: 188–189 C; H NMR (DMSO-d6) d 11.83 (t, 1H), 10.84
(s, 1H), 10.43 (s, 1H), 7.62–7.52 (m, 2H), 7.34 (d, 1H,
J=7.8 Hz), 7.20 (s, 1H), 7.05 (t, 1H), 6.96–6.88 (m, 2H), 6.76
N-[1-(1R)-(1-Naphthylethyl)]-N0-[2-(benzothiazolyl)]thiourea
(18). Mp 174–175 ꢁC; H NMR (DMSO-d6) d 11.86 (s, 1H),
(d, 1H, J=7.5 Hz), 3.97 (q, 2H), 3.04 (t, 2H), 2.05 (s, 3H); 13
C
1
10.30 (s, 1H), 8.17 (d, 1H, J=8.4 Hz), 7.95 (d, 1H, J=8.1 Hz),
7.87 (d, 2H, J=7.8 Hz), 7.62–7.51 (m, 5H), 7.38 (t, 1H), 7.25 (t,
1H), 6.24 (m, 1H), 1.69 (d, 3H, J=6.3 Hz); 13C NMR (DMSO-
d6) d 178.6, 161.6, 138.6, 133.5, 130.5, 128.8, 127.9, 126.5, 126.3,
125.9, 125.6, 123.6, 123.2, 121.8, 118.950.2, 50.1, 21.1; IR n
3563, 3182, 3039, 2973, 1565, 1523, 1199 cmꢀ1; MALDI-TOF
m/z 367.2 (C20H17N3S2+4H+); [a]: ꢀ39.5; HPLC Rt: 18.84
min% purity 99.7, elemental analysis: calcd: C: 66.09, H: 4.71,
N:11.56; found: C: 65.89, H: 4.75, N: 11.36.
NMR (DMSO-d6) d 179.4, 154.6, 153.3, 139.1, 136.5, 127.3,
123.0, 121.2, 118.5 (d), 116.9, 111.6 (d), 109.4, 45.3, 24.8, 23.5;
IR n 3417, 3224, 3047, 2985, 1612, 1542, 1450, 1226 cmꢀ1
;
MALDI-TOF m/z 311.6 (C17H18N4S+H+); HPLC Rt:
5.64 min.
N-[2-(3-Indolylethyl)]-N0 -[2-(4,6-dimethylpyridyl)]thiourea
(28). Mp: 195–196 ꢁC; H NMR (DMSO-d6) d 11.91 (t, 1H),
1
10.84 (s, 1H), 10.37 (s, 1H), 7.61 (d, 1H, J=8.1 Hz), 7.34 (d,
1H, J=7.8 Hz), 7.20 (d, 1H, J=1.5 Hz), 7.06 (t, 1H), 6.95 (t,
1H), 6.72 (s, 1H), 6.59 (s, 1H), 3.97 (q, 2H), 3.04 (t, 2H), 2.15
(s, 3H), 2.02 (s, 3H); 13C NMR (DMSO-d6) d 179.4, 154.0,
153.4, 149.7, 136.4, 127.2, 122.9, 121.1, 118.5, 118.3, 118.0,
111.5, 111.4, 109.3, 45.2, 24.7, 23.2, 20.9; IR n 3507, 3261,
N-[1-(1S)-(1-Naphthylethyl)]-N0-[2-(benzothiazolyl)]thiourea
(19). Mp 193–194 ꢁC; H NMR (DMSO-d6) d 11.88 (s, 1H),
1
10.31 (s, 1H), 8.18 (d, 1H, J=8.4 Hz), 7.94 (d, 1H, J=8.1 Hz),
7.87 (dd, 2H, J=3.9, 4.5, 7.5 Hz), 7.62–7.50 (m, 5H), 7.37 (t,
1H), 7.25 (t, 1H), 6.25 (m, 1H), 1.69 (d, 3H, J=6.3 Hz); 13C
NMR (DMSO-d6) d 178.3, 162.4, 139.2, 134.1, 131.1, 129.4,
128.5, 127.2, 126.9, 126.5, 126.3, 124.3, 123.8, 123.5, 122.4,
119.7, 50.8, 21.7; IR n 3452, 3166, 3031, 1573, 1523,
1203 cmꢀ1; MALDI-TOF m/z 364.8 (C20H17N3S2+2H+); [a]:
+38.9; HPLC Rt: 18.84 min% purity 99.9, elemental analysis:
calcd: C: 66.09, H: 4.71, N:11.56; found: C: 66.12, H: 4.67, N:
11.53.
3035, 2917, 1618, 1591, 1537, 1456, 1346, 1211, 833 cmꢀ1
;
MALDI-TOF m/z 326.5 (C18H20N4S+2H+); HPLC Rt:
10.13 min.
N-[2-(2-Indolylethyl)]-N0 -[2-(thiazolyl)]thiourea (29). Mp
212–213 ꢁC; 1H NMR (DMSO-d6) d 11.56 (s, 1H), 10.86 (s,
1H), 9.73 (s, 1H), 7.62 (d, 1H, J=7.5 Hz), 7.35 (s, 1H), 7.31 (t,
1H), 7.20 (s, 1H), 7.07 (d, 1H, J=6.9 Hz), 7.03 (s, 1H), 6.96 (t,
1H), 3.81 (q, 2H), 3.00 (t, 2H); 13C NMR (DMSO-d6) d 178.4,
162.3, 136.9, 127.7, 123.8, 121.7, 119.1, 118.9, 112.7, 112.1,
111.8, 102.8, 45.9, 24.9; IR n 3386, 3164, 3076, 3035, 1560,
1514, 1184, 750 cmꢀ1; UV (MeOH) l 204, 207, 221, 285 nm;
MALDI-TOF MS m/z 304.2 (C14H14N4S2+2H+).
N - [2 - (3 - Indolylethyl)] - N0 - [2 - (pyridyl)]thiourea (23). Mp
188.5 ꢁC; H NMR (DMSO-d6) d 11.67 (s, 1H), 10.88 (s, 1H),
1
10.51 (s, 1H), 7.96 (t, 1H), 7.74–7.64 (m, 2H), 7.35 (d, 1H,
J=8.1 Hz), 7.25 (s, 1H), 7.12–7.04 (m, 2H), 6.99–6.95 (m, 2H)
3.88 (q, 2H), 3.05 (t, 2H); 13C NMR (DMSO-d6) d 179.8,
154.3, 145.9, 139.4, 136.9, 127.7, 123.9, 121.7, 119.1, 118.9,
118.2, 113.0, 112.1, 112.0, 102.8, 46.4, 25.0; IR n 3326, 3236,
3056, 2912, 1604, 1564, 1537, 1481, 1317, 1238, 1176, 1149,
1091, 771, 754 cmꢀ1; UV (MeOH) l 223, 267, 285, 291 nm;
MALDI-TOF MS m/z 296.2 (C16H16N4S+).
N-[2-(Indolylethyl)]-N0 -[2-(4-methylthiazolyl)]thiourea (30).
Mp: 177–178 ꢁC; H NMR (DMSO-d6) d 11.53 (s, 1H), 10.89
1
(s, 1H), 9.94 (s, 1H), 7.62 (d, 1H, J=7.6 Hz), 7.34 (d, 1H,
J=7.0 Hz), 7.22 (s, 1H), 7.06 (t, 1H), 6.97 (t, 1H), 6.60 (s, 1H),
3.85 (q, 2H), 3.01 (t, 2H), 2.12 (s, 3H); 13C NMR (DMSO-d6)
d 178.3, 161.7, 137.0, 127.7, 123.8, 121.7, 119.1, 118.9, 112.1,
111.8, 106.6, 45.8, 25.0, 17.4; IR n 3407, 3174, 3025, 2917,
1560, 1508, 1213, 742 cmꢀ1; UV (MeOH) l 201, 208, 212, 223,
N-[2-(3-Indolylethyl)]-N0 -[2-(5-chloropyridyl)]thiourea (24).
Mp 168 ꢁC (dec.); H NMR (DMSO-d6) d 11.20 (t, 1H), 10.91
1
(s, 1H), 10.67 (s, 1H), 7.93 (d, 1H, J=2.7 Hz), 7.84–7.80 (d,
1H, J=9.0 Hz), 7.64–7.61 (d, 1H, J=7.5 Hz), 7.37–7.34 (d,
1H, J=7.8 Hz), 7.28 (d, 1H, J=1.5 Hz), 7.14–7.11 (d, 1H,
J=8.4 Hz), 7.09–7.04 (dd, 1H, J=6.7, 8.1 Hz), 6.99–6.93 (dd,
1H, J=8.1, 6.9 Hz), 3.87 (q, 2H), 3.04 (t, 2H); 13C NMR
(DMSO-d6) d 179.4, 152.6, 144.1, 139.3, 136.9, 127.7, 124.2,
124.1, 121.7, 119.1, 118.9, 114.6, 112.1, 111.9, 46.5, 24.8; IR n
3357, 3209, 3155, 3082, 3037, 2916, 2870, 1662, 1597, 1556,
1531, 1467, 1321, 1263, 1228, 1192, 1109, 737, 590 cmꢀ1; UV
(MeOH) l 203, 208, 210, 220, 264, 267, 274 nm; MALDI-TOF
MS m/z 332.0 (C16H15ClN4S+2H+).
289,
292 nm;
MALDI-TOF
MS
m/z
318.4
(C15H16N4S2+2H+).
N-[2-(Indolylethyl)]-N0 -[2-(ethyl-4-acetylthiazolyl)]thiourea
(31). Mp: 144–145 ꢁC; H NMR (DMSO-d6) d 11.61 (s, 1H),
1
10.87 (s, 1H), 9.45 (s, 1H), 7.61 (d, 1H, J=7.5 Hz), 7.35 (d,
1H, J=7.5 Hz), 7.20 (d, 1H, J=2.1 Hz), 7.07 (t, 1H), 6.97 (dd,
1H, J=8.0, 6.5 Hz), 6.84 (s, 1H), 4.07 (q, 2H), 3.82 (q, 2H),
3.60 (s, 2H), 3.00 (t, 2H), 1.17 (t, 3H); 13C NMR (DMSO-d6) d
177.6, 169.9, 160.9, 143.2, 136.3, 127.1, 123.1, 121.1, 118.4 (d),
111.5, 111.2, 109.1, 60.6, 45.1, 36.6, 24.4, 14.4; IR n 3371,
3170, 3018, 1727, 1569, 1203, 742 cmꢀ1; UV (MeOH) l 207,

T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
1103
223, 289, 291 nm; MALDI-TOF MS m/z 390.0
(C18H20N4O2S2+H+).
2H), 2.24 (s, 3H), 2.14 (d, 3H); 13C NMR (DMSO-d6) d 178.0,
161.2, 146.1, 135.9, 135.3, 129.1, 128.6, 106.1, 46.1, 33.8, 20.9,
N-[2-(4-Bromophenylethyl)]-N0-[2-(pyridyl)]thiourea (34). Mp:
16.8; IR n 3463, 3174, 3022, 2921, 1571, 1508, 1203, 715 cmꢀ1
;
146–148 ꢁC; H NMR (DMSO-d6) d: 11.65 (d, 1H), 10.57 (s,
UV (MeOH) l 207, 215, 259, 293 nm; MALDI-TOF MS m/z
1
1H), 8.05 (m, 1H), 7.71 (m, 1H), 7.48 (m, 2H), 7.25 (m, 2H )
7.11 (m, 1H), 6.98 (t, 1H), 3.82 (q, 2H), 2.90 (t, 2H); 13C NMR
(DMSO-d6) d: 179.5, 153.7, 145.3, 138.9, 138.6, 131.2 (d),
119.5, 117.8, 112.5, 46.1, 33.7; IR n 3237, 3104, 3018, 2931,
1602, 1537, 1479, 1319, 1010, 773 cmꢀ1; UV (MeOH) l 206,
213, 223, 247, 266, 293 nm; MALDI-TOF MS m/z 337.2
(C14H14BrN3S+H+).
292.8 (C14H17N3S2+H+).
N-[2-(4-Methylphenyl)ethyl)]-N0-[2-(thiazolyl)]thiourea (60).
Mp: 162–163 ꢁC; 1H NMR (DMSO-d6) d 11.59 (s, 1H), 9.66 (s,
1H), 7.33–7.32 (m, 1H), 7.15–7.08 (m, 5H), 3.73 (q, 2H), 2.83
(t, 2H), 2.24 (s, 3H); 13C NMR (DMSO-d6) d 178.0, 161.8,
136.7, 135.8, 135.3, 129.1, 128.7, 112.1, 46.1, 33.9, 20.9; IR n
3448, 3170, 3000, 2946, 1565, 1511, 1280, 1157, 702 cmꢀ1
;
N-[2-(4-Hydroxyphenylethyl)]-N0 -[2-(pyridyl)]thiourea (35).
MALDI-TOF m/z 279.1 (C13H15N3S2+2H+); HPLC Rt:
6.99 min.
Mp: 192.5 ꢁC; H NMR (DMSO-d6) d 11.64 (t, 1H), 10.51 (s,
1
1H), 9.22 (s, 1H), 8.05 (d, 1H, J=4.8 Hz), 7.74–7.68 (td, 1H),
7.08 (q, 2H), 7.00–7.96 (m, 1H), 6.69 (m, 2H), 3.74 (q, 2H),
2.79 (t, 2H); 13C NMR (DMSO-d6) d 179.9, 156.4, 154.3,
145.9, 139.5, 130.3, 118.3, 115.8, 113.1, 102.8, 47.4, 34.2; IR n
3245, 3008, 2935, 1606, 1511, 1211, 1149, 1108 769 cmꢀ1; UV
(MeOH) l 202, 248, 268, 291 nm; MALDI-TOF MS m/z 274.9
(C14H15N3OS+2H+).
N-[2-(4-Methylphenylethyl)]-N0 -[2-(benzothiazolyl)]thiourea
(61). Mp: 186–87 ꢁC; 1H NMR (DMSO-d6) d 11.89 (s, 1H),
10.09 (s, 1H), 7.86 (d, 1H, J=6.6 Hz), 7.53 (d, 1H, J=6.0 Hz),
7.38 (t, 1H), 7.26–7.09 (m, 5H), 3.81 (m, 2H), 2.88 (t, 2H), 2.24
(s, 3H); 13C NMR (DMSO-d6) d 178.3, 161.1, 148.9, 147.9,
135.8, 135.3, 129.1, 128.7, 126.3, 123.7, 121.8, 119.5, 46.2, 33.7,
20.9; IR n 3178, 3039, 2931, 1573, 1519, 1234, 748 cmꢀ1
MALDI-TOF m/z 329.3 (C17H17N3S2+2H+).
;
N-[2-(4-Methylphenylethyl)]-N0-[2-(pyridyl)]thiourea (36). Mp:
143–145 ꢁC; 1H NMR (DMSO-d6) d 11.67 (t, 1H), 10.54 (s,
1H), 8.05 (dd, 1H, J=5.1 Hz), 7.72 (dd, 1H, J=8.7, 6.9 Hz),
7.17 (d, 2H, J=8.1 Hz), 7.10 (d, 3H, J=8.1 Hz), 6.99 (dd, 1H,
J=6.9 Hz), 3.80 (m, 2H), 2.87 (t, 2H), 2.25 (s, 3H); 13C NMR
(DMSO-d6) d 179.4, 153.7, 145.3, 138.9, 136.0, 135.3, 129.0,
128.7, 117.7, 112.5, 46.6, 33.9, 20.9; IR n 3203, 3018, 2925,
1565, 1479, 1317, 1228, 1166, 1147, 772 cmꢀ1; UV (MeOH) l
205, 209, 266 nm; MALDI-TOF MS m/z 271.1 (C15H17N3S+).
N-[2-(4-Hydroxyphenylethyl)]-N0-[2-(5-chloropyridyl)]thiourea
N - [2 - (4 - Methylphenylethyl)] - N0 - [2 - (6 - methox-
ybenzothiazolyl)]thiourea (62). Mp: 202–203 ꢁC; 1H NMR
(DMSO-d6) d 11.73 (s, 1H), 10.15 (s, 1H), 7.49 (d, 1H,
J=2.4 Hz), 7.45 (d, 1H, J=8.7 Hz), 7.19 (d, 2H, J=8.1 Hz),
7.10 (d, 2 H, J=8.1 Hz), 7.00 (dd, 1H, J=2.4, 8.7 Hz), 3.80 (q,
2H), 3.77 (s, 3H), 2.89 (t, 2H), 2.25 (s, 3H); 13C NMR
(DMSO-d6) d 177.9, 158.1, 156.1, 142.9, 135.8, 135.3, 131.2,
129.1, 128.7, 120.2, 114.6, 105.3, 55.8, 46.2, 33.7, 20.9; IR n
3178, 3047, 2931, 1558, 1535, 1473, 1218 cmꢀ1; MALDI-TOF
m/z 358.8 (C18H19N3OS2+2H+).
(37). Mp: 192–193 ꢁC; H NMR (DMSO-d6) d 11.18 (s, 1H),
1
10.60 (s, 1H), 9.08 (s, 1H), 7.97 (t, 1H), 7.70–7.65 (m, 1H),
7.12 (dd, 1H, J=9, 6.0 Hz), 7.02 (m, 2H), 6.70–6.66 (m, 2H),
3.75 (q, 2H), 2.78 (t, 2H); 13C NMR (DMSO-d6) d 179.7,
156.4, 152.7, 143.8, 138.9, 130.1, 129.5, 124.3, 115.8, 114.6,
47.4, 34.2; IR n?3226, 3174, 3030, 2937, 1591, 1560, 1519,
1483, 1230 cmꢀ1; UV (MeOH) l 209, 215, 224, 273, 304 nm;
MALDI-TOF MS m/z 309.4 (C14H14ClN3OS2+2H+).
N-[2-(4-Chlorophenethyl)]-N0-[2-(4-fluorophenethyl)]-thiourea
(63). Yield: 84%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3266,
3210, 3050, 2931, 2860, 1556, 1510, 1349, 1218, 1095, 1014,
1
819, 694, 665, 594, 486 cmꢀ1; H NMR (CDCl3) d 7.17–6.84
(m, 8H), 5.91 (s, 2H), 3.49 (q, 4H), 2.74–2.69 (t, 4H); 13C
NMR (CDCl3) d 181.5, 130.1, 129.9, 128.7, 115.6, 115.3, 45.3,
45.2, 34.4, 34.2; 19F NMR (CDCl3) d ꢀ40.37; MALDI-TOF
found: 337.9 (M+1), calcd: 336.9.
N-[2-(4-hydroxyphenylethyl]-N0-[2-(5-bromopyridyl)]thiourea
(50). Mp: 159 ꢁC; 1H NMR (DMSO-d6) d 11.30 (bs, 1H), 10.17
(bs, 1H), 8.78 (bs, 1H), 8.03–8.02 (s, 1H), 7.67–7.65 (d, 1H,
J=6.0 Hz), 7.11–7.09 (d, 1H, J=6.0 Hz), 7.03–7.99 (d, 1H,
J=3.0 Hz), 6.82–6.80 (d, 2H, J=6.0 Hz), 3.96–3.90 (q, 2H),
2.92–2.83 (t, 2H), 13C NMR (CDCl3) d 178.9, 155.4, 151.9,
145.4, 140.3, 129.2, 128.9, 114.9, 113.9, 111.6, 46.7, 33.5, IR n
3224, 3159, 3089, 3041, 2933, 2870, 1595, 1558, 1533, 1514,
1332, 1306, 1265, 1227, 1186, 1136, 1094, 1007, 910, 862, 827,
708 cmꢀ1; UV (MeOH) l 205, 208, 274, 305 nm, MALDI-TOF
m/z 353.0 (C14H14N3OSBr+H+). Anal: C, H,N, Br, S.
N-[2-(4-Hydroxyphenylethyl)]-N0-[2-(thiazolyl)]thiourea (57).
Mp: 160–161 ꢁC; 1H NMR (DMSO-d6) d 11.57 (s, 1H), 9.66 (s,
1H), 9.22 (s, 1H), 7.33 (d, 1H, J=3.6 Hz), 7.06 (t, 3H), 6.68 (d,
2H, J=8.1 Hz), 3.68 (q, 2H), 2.76 (t, 2H); 13C NMR (DMSO-
d6) d 178.5, 162.3, 156.4, 137.3, 130.3, 129.5, 115.9, 112.7, 46.9,
34.1; IR n 3437, 3050, 1581, 1556, 1518 cmꢀ1; UV (MeOH) l
209, 219, 225, 260, 289 nm; MALDI-TOF MS m/z 280.6
(C12H13N3OS2+H+).
N-[2-(2-Chlorophenethyl)]-N0-[2-(4-fluorophenethyl)]-thiourea
(68). Yield: 60%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3353,
3264, 3062, 2933, 2865, 1710, 1550, 1510, 1442, 1355, 1222,
1157, 1053, 827, 754, 680, 530 cmꢀ1; 1H NMR (CDCl3) d 7.37–
7.96 (m, 8H), 5.90 (s, 1H), 5.80 (s, 1H), 3.64 (q, 4H), 3.02–2.98
(t, 2H), 2.88–2.83 (t, 2H); 13C NMR (CDCl3) d 181.7, 133.8,
131.0, 130.1, 130.0, 129.6, 128.3, 127.2, 115.7, 115.4, 45.5, 43.7,
34.3, 32.9; 19F NMR (CDCl3) d.48; MALDI-TOF found:
338.5 (M+2), calcd: 336.9.
N-[2-(3-Chlorophenethyl)]-N0-[2-(4-fluorophenethyl)]-thiourea
(69). Yield: 79%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3259,
3062, 2935, 2861, 1560, 1508, 1309, 1222, 1004, 829, 783, 684,
514 cmꢀ1; 1H NMR (CDCl3) d 7.26–6.96 (m, 8H), 5.86 (s, 1H),
5.85 (s, 1H), 3.63–3.61 (q, 4H), 2.87–2.81 (m, 4H); 13C NMR
(CDCl3) d 181.7, 163.2, 160.0, 140.3, 134.4, 133.8, 130.1,
130.02, 129.97, 128.7, 126.9, 115.7, 115.4, 45.3, 45.1, 34.7, 34.2;
19F NMR (CDCl3) d ꢀ40.37; MALDI-TOF found: 337.3
(M+1), calcd: 336.9.
N - [2 - (4 - Methylphenylethyl)] - N0ꢁ - [2 - (ethyl - 4 - acet-
N-[2-(3-Fluorophenethyl)]-N0-[2-(4-fluorophenethyl)]-thiourea
(71). Yield: 92%; UV (CHCl3) lmax: 255 nm; IR (KBr) n 3259,
3058, 2929, 2860, 1556, 1510, 1446, 1384, 1309, 1220, 1141,
1
ylthiazolyl)]thiourea (58). Mp: 132–133 C; H NMR (DMSO-
d6) d 11.60 (s, 1H), 9.47 (s, 1H), 7.13 (q, 4H), 6.85 (s, 1H), 4.08
(q, 2H), 3.72 (q, 2H), 3.60 (s, 2H), 2.82 (t, 2H), 2.25 (s, 3H),
1.14 (t, 3H); 13C NMR (DMSO-d6) d 177.6, 169.8, 160.8,
143.2, 135.8, 135.3, 129.1, 128.6, 109.1, 60.5, 45.9, 42.4, 36.5,
33.8, 20.9, 14.3; IR n 3448, 3170, 3006, 2937, 1731, 1573, 1508,
1220, 713 cmꢀ1; UV (MeOH) l 206, 208, 214, 260, 293 nm;
MALDI-TOF MS m/z 364.9 (C17H21N3O2S2+H+).
1
1118, 1002, 937, 831, 784, 690, 511 cmꢀ1; H NMR (CDCl3) d
7.30–6.87 (m, 8H), 5.95 (s, 2H), 3.62–3.61 (q, 4H), 2.88–2.80
(m, 4H); 13C NMR (CDCl3) d 181.6, 164.4, 163.2, 161.2,
160.0, 140.7, 133.8, 130.2, 130.1, 130.0, 124.3, 115.6, 115.3,
113.7, 113.4, 45.3, 45.1, 34.8, 34.2 ; 19F NMR (CDCl3) d
ꢀ40.44, ꢀ34.18; MALDI-TOF found: 322.8 (M+2), calcd:
320.4.
N-[2-(4-Fluorophenethyl)]-N0-[2-(4-fluorophenethyl)]-thiourea
(72). Yield: 93%; UV (CHCl3) lmax: 254 and 273 nm; IR
N-[2-(4-Methylphenylethyl)]-N0-[2-(4-methylthiazolyl]thiourea
(59). Mp: 161–162 ꢁC; H NMR (DMSO-d6) d 11.56 (s, 1H),
1
9.89 (s, 1H), 7.11 (q, 5H), 6.60 (s, 1H), 3.76 (m, 2H), 2.84 (t,

1104
T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
(KBr) n 3259, 3058, 2927, 2854, 1600, 1556, 1510, 1450, 1311,
1218, 1118, 1010, 823, 757, 680, 523, 499 cmꢀ1 1H NMR
(CDCl3) d 7.30–6.87 (m, 8H), 5.96 (s, 2H), 3.64–3.63 (q, 4H),
2.88–2.83 (t, 4H); 13C NMR (CDCl3) d 181.6, 164.4, 161.2,
140.7, 130.2, 130.1, 124.3, 115.6, 115.3, 113.7, 113.4, 45.1, 34.8;
19F NMR (CDCl3) d ꢀ37.17, ꢀ37.15; MALDI-TOF found:
321.4 (M+1), calcd: 320.4.
;
(CDCl3) d 7.27–6.96 (m, 8H), 5.84 (s, 2H), 3.61–3.59 (q, 4H),
2.85–2.81 (t, 4H); 13C NMR (CDCl3) d 181.6, 163.2, 160.0,
130.1, 130.0, 115.6, 115.4, 45.4, 34.2; 19F NMR (CDCl3) d
ꢀ40.38; MALDI-TOF found: 321.4 (M+1), calcd: 320.4.
N - [2 - (4 - Fluorophenethyl)] - N0 - [2 - (2 - methoxyphenethyl)] -
thiourea (73). Yield: 80%; UV (CHCl3) lmax: 255, 273, and
279 nm; IR (KBr) n 3303, 3232, 3068, 2935, 2867, 1600, 1564,
1510, 1315, 1245, 1220, 1155, 1118, 1031, 825, 763, 684,
499 cmꢀ1; 1H NMR (CDCl3) d 7.27–6.84 (m, 8H), 6.27 (s, 1H),
5.88 (s, 1H), 3.75 (s, 3H), 3.68 (s, 2H), 3.45 (s, 2H), 2.90–2.82
(m, 4H); 13C NMR (CDCl3) d 181.3, 163.2, 160.0, 157.1,
130.6, 130.2, 130.1, 128.3, 121.1, 115.6, 115.3, 110.5, 55.4, 45.9,
45.4, 34.4, 29.8; 19F NMR (CDCl3) d ꢀ40.61; MALDI-TOF
found: 333.5 (M+1), calcd: 332.4.
N - [2 - (4 - Fluorophenethyl)] - N0 - [2 - (3 - methoxyphenethyl)] -
thiourea (74). Yield: 84%; UV (CHCl3) lmax: 255, 274, and
283 nm; IR (KBr) n 3263, 3064, 2939, 2861, 1600, 1556, 1508,
1384, 1311, 1259, 1222, 1166, 1122, 1037, 1002, 833, 669, 576,
514 cmꢀ1; 1H NMR (CDCl3) d 7.27–6.73 (m, 8H), 5.71 (s, 2H),
3.79 (s, 3H) 3.62–3.60 (q, 4H), 2.86–2.80 (m, 4H); 13C NMR
(CDCl3) d 181.7, 163.3, 159.9, 139.8, 133.8, 130.1, 130.0, 129.8,
120.9, 115.7, 115.4, 114.5, 112.0, 55.2, 45.4, 45.2, 34.1, 34.3;
19F NMR (CDCl3) d ꢀ40.49; MALDI-TOF found: 334.6
(M+2), calcd: 332.4.
N-[2-(4-Fluorophenethyl)]-N0 -[2-(3,4-dimethoxyphenethyl)]-
thiourea (75). Yield: 73%; UV (CHCl3) lmax: 255 and 273 nm;
IR (KBr) n 3259, 3058, 2942, 2854, 1600, 1556, 1510, 1450,
1311, 1218, 1118, 1016, 823, 757, 682, 532, 499 cmꢀ1; 1H NMR
(CDCl3) d 7.13–6.68 (m, 7H), 6.04 (s, 2H), 3.79 (s, 3H), 3.78 (s,
3H), 3.64 (q, 4H), 2.83–2.78 (m, 4H); 13C NMR (CDCl3) d
181.6, 163.0, 159.8, 148.1, 147.4, 133.9, 130.7, 130.0, 129.9,
120.4, 115.4, 115.1, 111.6, 111.1, 55.7, 45.3, 34.5, 34.2; 19F
NMR (CDCl3) d ꢀ40.57; MALDI-TOF found: 364.8 (M+2),
calcd: 362.5.
N-[2-(2-Fluorophenethyl)]-N0-[2-(3-fluorophenethyl)]-thiourea
(77). Yield: 75%; UV (CHCl3) lmax: 255 nm; IR (KBr) n 3411,
3261, 3062, 2935, 2865, 1616, 1587, 1552, 1490, 1450, 1386,
1348, 1230, 1188, 1141, 1002, 937, 891, 757, 692, 520,
457 cmꢀ1; 1H NMR (CDCl3) d 7.30–6.89 (m, 8H), 5.92 (s, 1H),
5.84 (s, 1H), 3.66 (q, 4H), 2.93–2.86 (m, 4H); 13C NMR
(CDCl3) d 181.7, 164.5, 162.7, 161.2, 159.5, 140.8, 131.1, 131.0,
130.2, 130.1, 128.7, 128.6, 125.1, 124.4, 115.7, 115.5, 115.4,
115.2, 113.8, 113.5, 45.1, 44.2, 34.8, 28.7; 19F NMR (CDCl3) d
ꢀ42.88, ꢀ42.85, ꢀ42.81, ꢀ42.79, ꢀ37.25, ꢀ37.23; MALDI-
TOF found: 321.9 (M+1), calcd: 320.4.
N-[2-(2-Fluorophenethyl)]-N0-[2-(3-fluorophenethyl)]-thiourea
(81). Yield: 75%; UV (CHCl3) lmax: 255 nm; IR (KBr) n 3411,
3261, 3062, 2935, 2865, 1616, 1587, 1552, 1490, 1450, 1386,
1348, 1230, 1188, 1141, 1002, 937, 891, 757, 692, 520,
457 cmꢀ1; 1H NMR (CDCl3) d 7.30–6.89 (m, 8H), 5.92 (s, 1H),
5.84 (s, 1H), 3.66 (q, 4H), 2.93–2.86 (m, 4H); 13C NMR
(CDCl3) d 181.7, 164.5, 162.7, 161.2, 159.5, 140.8, 131.1, 131.0,
130.2, 130.1, 128.7, 128.6, 125.1, 124.4, 115.7, 115.5, 115.4,
115.2, 113.8, 113.5, 45.1, 44.2, 34.8, 28.7; 19F NMR (CDCl3) d
ꢀ42.88, ꢀ42.85, ꢀ42.81, ꢀ42.79, ꢀ37.25, ꢀ37.23; MALDI-
TOF found: 321.9 (M+1), calcd: 320.4.
N-[2-(3-Fluorophenethyl)]-N0-[2-(4-bromophenethyl)]-thiourea
(82). Yield: 91%; UV (CHCl3) lmax: 255 nm; IR (KBr) n 3405,
3259, 3060, 2931, 2863, 1616, 1589, 1552, 1488, 1448, 1346,
1
1251, 1141, 1072, 1010, 937, 891, 810, 784, 690, 520 cmꢀ1; H
NMR (CDCl3) d 7.43–6.87 (m, 8H), 5.86 (s, 2H), 3.61 (q, 4H),
2.88–2.79 (m, 4H); 13C NMR (CDCl3) d 181.7, 164.5, 140.7,
137.1, 131.7, 130.4, 130.3, 130.1, 124.3, 120.5, 115.6, 115.4,
113.7, 113.5, 45.1, 34.8, 34.5; 19F NMR (CDCl3) d ꢀ37.10;
MALDI-TOF found: 383.1 (M+2), calcd: 381.3.
N-[2-(3-Fluorophenethyl)]-N0-[2-(4-hydroxyphenethyl)]-thiourea
(83). Yield: 31%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3276,
3066, 2935, 2863, 1614, 1589, 1556, 1513, 1448, 1346, 1247,
1
1141, 1110, 1008, 908, 829, 784, 732, 692, 520 cmꢀ1; H NMR
(CDCl3) d 7.27–6.73 (m, 8H), 6.38 (s, 1H), 5.94 (s, 1H), 5.85 (s,
1H), 3.61 (m, 2H), 3.50 (m, 2H), 2.83–2.79 (t, 2H), 2.75–2.70
(t, 2H); 13C NMR (CDCl3) d 181.1, 154.6, 141.8, 130.2, 130.1,
129.7, 124.3, 115.7, 115.3, 113.7, 113.4, 45.4, 34.8, 34.0; 19F
NMR (CDCl3) d ꢀ37.20, ꢀ37.18; MALDI-TOF found: 319.6
(M+1), calcd: 318.4.
N-[2-(2-Chlorophenethyl)]-N0-[2-(3-fluorophenethyl)]-thiourea
(84). Yield: 90%; UV (CHCl3) lmax: 256 nm; IR (KBr) n 3405,
3261, 3064, 2935, 2863, 1616, 1589, 1552, 1488, 1446, 1384,
1346, 1299, 1251, 1195, 1141, 1053, 1002, 937, 908, 784, 754,
732, 692, 520, 455 cmꢀ1 1H NMR (CDCl3) d 7.36–6.88 (m,
;
8H), 6.05 (s, 1H), 5.93 (s, 1H), 3.66 (q, 4H), 3.01–2.97 (t, 2H),
2.90–2.85 (t, 2H); 13C NMR (CDCl3) d 181.6, 164.5, 161.2,
140.7, 135.7, 133.8, 131.0, 130.2, 130.1, 129.6, 128.3, 127.1,
124.3, 115.6, 115.4, 113.7, 113.4, 45.2, 43.7, 34.8, 32.9; 19F
NMR (CDCl3) d ꢀ37.19; MALDI-TOF found: 338.6 (M+2),
calcd: 336.9.
N-[2-(3-Chlorophenethyl)]-N0-[2-(3-fluorophenethyl)]-thiourea
(85). Yield: 96%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3409,
3257, 3060, 2933, 2863, 1616, 1589, 1552, 1488, 1448, 1346,
N-[2-(4-Fluorophenethyl)]-N0-[2-(4-bromophenethyl)]-thiourea
(78). Yield: 93%; UV (CHCl3) lmax: 256 nm; IR (KBr) n 3406,
3251, 3060, 2927, 2863, 1600, 1548, 1508, 1346, 1222, 1157,
1072, 1010, 823, 657, 497 cmꢀ1; 1H NMR (CDCl3) d 7.43–6.96
(m, 8H), 5.86 (s, 2H), 3.60 (q, 4H), 2.84–2.80 (m, 4H); 13C
NMR (CDCl3) d 181.6, 163.2, 160.0, 137.2, 133.7, 131.7,
130.4, 130.1, 130.0, 120.5, 115.6, 115.4, 45.4, 45.1, 34.5, 34.2;
19F NMR (CDCl3) d ꢀ40.37; MALDI-TOF found: 382.5
(M+1), calcd: 381.3.
1
1251, 1141, 1080, 1010, 937, 887, 783, 692, 520, 443 cmꢀ1; H
NMR (CDCl3) d 7.29–6.87 (m, 8H), 6.07 (s, 2H), 3.62 (q, 4H),
2.87–2.81 (m, 4H); 13C NMR (CDCl3) d 181.6, 164.4, 161.1,
140.8, 140.7, 140.3, 134.3, 130.2, 130.1, 129.9, 128.7, 126.83,
126.78, 124.3, 115.6, 115.3, 113.7, 113.4, 45.0, 34.7; 19F NMR
(CDCl3) d ꢀ37.10; MALDI-TOF found: 337.3 (M+1), calcd:
336.9.
N-[2-(4-Fluorophenethyl)]-N0-[2-(4-hydroxyphenethyl)]-thiourea
(79). Yield: 90%; UV (CHCl3) lmax: 256, 273, and 284 nm; IR
(KBr) n 3272, 3066, 2923, 2850, 1600, 1556, 1510, 1440, 1346,
N-[2-(4-Chlorophenethyl)]-N0-[2-(3-fluorophenethyl)]-thiourea
(86). Yield: 93%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3409,
3251, 3060, 2917, 2848, 1614, 1589, 1550, 1490, 1448, 1346,
1253, 1139, 1091, 1014, 937, 811, 783, 690, 520 cmꢀ1; 1H NMR
(CDCl3) d 7.30–6.87 (m, 8H), 5.91 (s, 2H), 3.62 (q, 4H), 2.88–
2.80 (m, 4H); 13C NMR (CDCl3) d 181.7, 164.4, 161.2, 140.7,
136.6, 132.5, 130.2, 130.1, 130.0, 128.8, 124.3, 115.6, 115.4,
113.7, 113.5, 45.1, 34.8, 34.4; 19F NMR (CDCl3) d ꢀ37.13;
MALDI-TOF found: 338.2 (M+1), calcd: 336.9.
1220, 1105, 1014, 825, 759, 505 cmꢀ1 1H NMR (CDCl3) d
;
7.27–6.76 (m, 8H), 5.74 (s, 2H), 5.61 (s, 1H), 3.59 (q, 4H),
2.84–2.75 (m, 4H); 13C NMR (CDCl3) d 181.4, 163.3, 160.0,
154.6, 133.8, 130.2, 130.1, 123.8, 115.1, 115.4, 45.4, 34.3, 34.1;
19F NMR (CDCl3) d ꢀ40.40; MALDI-TOF found: 319.8
(M+1), calcd: 318.4.
N-[2-(3-Fluorophenethyl)]-Nꢀ-[2-(3-fluorophenethyl)]-thiourea
(80). Yield: 83%; UV (CHCl3) lmax: 255 nm; IR (KBr) n 3415,
3257, 3062, 2933, 2863, 1616, 1589, 1552, 1488, 1450, 1348,
N - [2 - (3 - Fluorophenethyl)] - N0 - [2 - (3 - methoxyphenethyl)] -
thiourea (87). Yield: 95%; UV (CHCl3) lmax: 255 nm; IR
(KBr) n 3258, 3057, 2937, 2834, 1585, 1548, 1487, 1451, 1385,
1
1251, 1141, 1012, 937, 892, 783, 690, 520, 455 cmꢀ1; H NMR
1346, 1257, 1152, 1043, 910, 783, 731, 693, 571, 520, 456 cmꢀ1
;

T. K. Venkatachalam et al. / Bioorg. Med. Chem. 11 (2003) 1095–1105
1105
1H NMR (CDCl3) d 7.29–6.72 (m, 8H), 5.93 (s, 2H), 3.77 (s,
3H), 3.75–3.61 (q, 4H), 2.85–2.80 (t, 4H); 13C NMR (CDCl3) d
181.5, 164.4, 161.2, 159.7, 140.8, 139.8, 130.2, 130.0, 129.7,
124.3, 120.9, 115.6, 115.3, 114.4, 113.6, 113.4, 111.9, 55.1, 45.2,
35.0, 34.8; 19F NMR (CDCl3) d ꢀ37.23, ꢀ37.20; MALDI-
TOF found: 333.8 (M+1), calcd: 332.4.
(CDCl3) d 7.29–6.85 (m, 8H), 5.92 (s, 1H), 5.86 (s, 1H), 3.60
(q, 4H), 2.85–2.78 (m, 4H), 2.31 (s, 3H); 13C NMR (CDCl3) d
181.5, 164.4, 161.2, 140.7, 136.3, 134.9, 130.1, 130.0, 129.4,
128.5, 124.3, 115.6, 115.3, 113.6, 113.4, 45.3, 45.0, 34.8, 34.6,
21.0; 19F NMR (CDCl3) d ꢀ37.19; MALDI-TOF found: 317.5
(M+1), calcd: 316.4.
N - [2 - (3 - Fluorophenethyl)] - N0 - [2 - (2 - methoxyphenethyl)] -
thiourea (88). Yield: 94%; UV (CHCl3) lmax: 254 nm; IR
(KBr) n 3349, 3253, 3062, 2917, 2836, 1587, 1552, 1492, 1346,
N-[2-(4-Fluorophenethyl)]-N0-[2-(4-methylphenethyl)]-thiourea
(92). Yield: 72%; UV (CHCl3) lmax: 253 nm; IR (KBr) n 3423,
3264, 3156, 3049, 2928, 2862, 1600, 1543, 1510, 1383, 1343,
1
1
1290, 1243, 1029, 937, 892, 754, 690, 520, 457 cmꢀ1; H NMR
1224, 1158, 1097, 1022, 904, 826, 736, 650, 555, 500 cmꢀ1; H
(CDCl3) d 7.29–6.84 (m, 8H), 6.38 (s, 1H), 6.00 (s, 1H), 3.75 (s,
3H), 3.78–3.45 (q, 4H), 2.93–2.83 (m, 4H); 13C NMR (CDCl3)
d 181.2, 164.4, 161.2, 157.0, 141.0, 130.5, 130.1, 130.0, 128.2,
126.4, 124.4, 121.0, 115.7, 11534, 113.6, 113.3, 110.4, 55.3,
45.5, 34.9, 29.8; 19F NMR (CDCl3) d ꢀ37.36; MALDI-TOF
found: 332.9 (M+1), calcd: 332.4.
NMR (CDCl3) d 7.26–6.95 (m, 8H), 5.79 (s, 2H), 3.59 (q, 4H),
2.86–2.78 (m, 4H), 2.31 (s, 3H); 13C NMR (CDCl3) d 181.5,
163.2, 160.0, 136.3, 134.9, 133.8, 130.1, 130.0, 129.4, 128.5,
115.6, 115.3, 45.4, 34.6, 34.3, 21.0; 19F NMR (CDCl3) d
ꢀ40.47; MALDI-TOF found: 317.4 (M+1), calcd: 316.4.
N-[2-(4-Chlorophenethyl)]-N0-[2-(4-chlorophenethyl)]-thiourea
(94). Yield: 48%; UV (CHCl3) lmax: 253 nm; IR (KBr) n 3267,
3062, 2938, 2916, 2853, 1584, 1489, 1406, 1349, 1273, 1125,
N-[2-(3-Fluorophenethyl)]-N0 -[2-(2,5-dimethoxyphenethyl)]-
thiourea (90). Yield: 80%; UV (CHCl3) lmax: 252 and 293 nm;
IR (KBr) n 3345, 3253, 3060, 2996, 2935, 2833, 1614, 1589,
1552, 1500, 1448, 1346, 1282, 1224, 1139, 1045, 867, 784, 692,
520, 457 cmꢀ1; 1H NMR (CDCl3) d 7.29–6.70 (m, 7H), 6.45 (s,
1H), 6.01 (s, 1H), 3.74 (s, 3H), 3.70 (s, 3H), 3.50–3.46 (q, 4H),
2.93–2.80 (m, 4H); 13C NMR (CDCl3) d 181.2, 164.4, 161.2,
153.7, 151.2, 145.0, 130.1, 130.0, 124.4, 116.7, 115.6, 115.4,
1096, 1002, 907, 807, 729, 651, 514, 440 cmꢀ1 1H NMR
;
(CDCl3) d 7.29–7.09 (m, 8H), 5.77 (s, 2H), 3.62–3.60 (q, 4H),
2.85–2.80 (t, 4H); 13C NMR (CDCl3) d 181.8, 136.6, 132.5,
130.0, 128.8, 45.2, 34.4; MALDI-TOF found: 353.3, calcd:
353.3.
N-[2-(3-Chlorophenethyl)]-N0-[2-(4-chlorophenethyl)]-thiourea
(95). Yield: 77%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3409,
3253, 3062, 2931, 2865, 1663, 1597, 1550, 1491, 1431, 1346,
113.6, 113.3, 112.1, 111.4, 55.9, 55.6, 45.5, 34.9, 31.5, 29.3; 19
F
NMR (CDCl3) d ꢀ37.34; MALDI-TOF found: 363.6 (M+1),
1
calcd: 362.5.
1292, 1203, 1092, 1015, 908, 816, 783, 732, 684, 534 cmꢀ1; H
N-[2-(3-Fluorophenethyl)]-N0-[2-(4-methylphenethyl)]-thiourea
(91). Yield: 60%; UV (CHCl3) lmax: 254 nm; IR (KBr) n 3228,
3060, 2966, 2933, 2865, 1569, 1486, 1448, 1386, 1346, 1249,
NMR (CDCl3) d 7.28–7.05 (m, 8H), 5.96 (s, 2H), 3.62 (q, 4H),
2.86–2.80 (m, 4H); 13C NMR (CDCl3) d 181.7, 140.3, 136.6,
134.3, 132.4, 130.0, 128.7, 126.9, 45.1, 34.7, 34.4; MALDI-
TOF found: 354.7 (M+1), calcd: 353.3.
1
1141, 1008, 937, 871, 810, 788, 759, 692, 505 cmꢀ1; H NMR