Adamantane derivatives of thiazolyl-N-substituted amide, as possible non-steroidal anti-inflammatory agents

Article abstract of DOI:10.1016/j.ejmech.2008.05.029

A series of adamantane derivatives of thiazolyl-N-substituted amides were synthesized in a three-step reaction and tested for anti-inflammatory activity as well as lipoxygenase and cycloxygenase inhibitory actions. Theoretical calculation of their lipophilicity, as C log P was performed. The effect of the synthesized compounds on inflammation, using the carrageenin-induced mouse paw oedema model was studied and compared to indomethacin. In general, the studied compounds were found to be potent anti-inflammatory agents (29.6-81.5%). Anti-inflammatory activity was influenced by some structural characteristics of the synthesized compounds. The lipoxygenase inhibitory activity was tested by the conversion of sodium linoleate to 13-hydroperoxylinoleic acid. Low inhibitory activity was observed. Evaluation of COX-1 and COX-2 inhibitory activities of the compounds revealed a COX-1 inhibitory potential, comparable to that of naproxen for some of the compounds and a low to moderate COX-2 inhibitory potential. Comparison of the in vivo and in vitro results leads to the conclusion that most compounds of this series may be involved in other mechanisms of inflammation, too.

Full text of DOI:10.1016/j.ejmech.2008.05.029

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 44 (2009) 1198e1204
http://www.elsevier.com/locate/ejmech
Original article
Adamantane derivatives of thiazolyl-N-substituted amide,
as possible non-steroidal anti-inflammatory agents
b
Omar Kouatly a, Athina Geronikaki a, , Charalambos Kamoutsis ,
*
Dimitra Hadjipavlou-Litina a, Phaedra Eleftheriou a
a Department of Pharmaceutical Chemistry, School of Pharmacy, Aristotle University of Thessaloniki, Thessalonik 54124, Greece
b School of Health Sciences, Department of Pharmacy, Laboratory of Pharmaceutical Chemistry, University of Patras, Patras, Greece
Received 11 March 2008; received in revised form 23 May 2008; accepted 23 May 2008
Available online 7 July 2008
Abstract
A series of adamantane derivatives of thiazolyl-N-substituted amides were synthesized in a three-step reaction and tested for anti-inflamma-
tory activity as well as lipoxygenase and cycloxygenase inhibitory actions. Theoretical calculation of their lipophilicity, as C log P was per-
formed. The effect of the synthesized compounds on inflammation, using the carrageenin-induced mouse paw oedema model was studied
and compared to indomethacin. In general, the studied compounds were found to be potent anti-inflammatory agents (29.6e81.5%). Anti-in-
flammatory activity was influenced by some structural characteristics of the synthesized compounds. The lipoxygenase inhibitory activity
was tested by the conversion of sodium linoleate to 13-hydroperoxylinoleic acid. Low inhibitory activity was observed. Evaluation of COX-
1 and COX-2 inhibitory activities of the compounds revealed a COX-1 inhibitory potential, comparable to that of naproxen for some of the
compounds and a low to moderate COX-2 inhibitory potential. Comparison of the in vivo and in vitro results leads to the conclusion that
most compounds of this series may be involved in other mechanisms of inflammation, too.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Adamantane; COX; LOX; Anti-inflammatory; C log P; Thiazole derivatives
1. Introduction
A2, arachidonic acid may become substrate for various meta-
bolic pathways that produce biological mediators [1]. The
most important of these are the cycloxygenase and lipoxyge-
nase pathways.
Inflammation is one of the most important natural defence
mechanisms against internal and external threats. However,
the inflammatory elements produced can also be deadly to
the body when ‘‘switched on’’ for too long, a condition known
as chronic inflammation. Research has indicated that chronic
inflammation is common in the nerve cells of patients with
neurodegenerative diseases.
Eicosanoids are a family of lipid mediators derived from the
metabolism of arachidonic acid. Eicosanoids such as prosta-
noids and leucotrienes have a wide range of biological action,
including potent effects on inflammation and immunity. Once
liberated from cell membranes by the action of phospholipase
Non-steroidal anti-inflammatory drugs (NSAIDs), alleviate
inflammation by counteracting the cycloxygenase isoforms
(COX-1, COX-2) [2] preventing the synthesis of prostaglandins
and eliminating inflammation and pain. Although COX-2
is concerned to be the main isoenzyme related to inflammation,
most NSAIDs in the market today block both forms of COX
isoenzymes. Side effects such as gastrointestinal pain have
been associated with NSAID use due to the inhibition of
COX-1. Beside, COX-2 specific inhibition was associated
with cardiovascular problems. Balanced inhibition of COX-1/
2 isoenzymes combined to LOX inhibition seems to be the
choice of preference for some scientists in an effort to achieve
the goal of effective anti-inflammatory agents with low
side effects.
* Corresponding author.
E-mail address: geronik@pharm.auth.gr (A. Geronikaki).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.05.029

O. Kouatly et al. / European Journal of Medicinal Chemistry 44 (2009) 1198e1204
1199
Thiazole and benzothiazole derivatives have been found to
O
C
possess analgesic and anti-inflammatory actions also exhibit-
ing lipoxygenase inhibitory activity [3e11]. Adamantane
derivatives have been found to interfere with various enzymes
and possess a variety of therapeutic activities, such as anti-
inflammatory [12], anti-viral [13], anti-Parkinson [14] and
antimicrobialeanticancer activities as well as dihydrofolate
reductase (DHFR) inhibitory activity [15e17].
S
N
b
NH2
CH2Br
NH2
C
II
NH2
I
S
ClCO(CH2)nCl
N
III
NHCO(CH2)nCl
S
Moreover, adamantane has also been used as a brain-directed
drug carrier for poorly absorbed drugs. Tsuzuki et al. proved in
1994, that the introduction of the 1-adamantane moiety to
azidothymidine (AZT) resulted in the enhancement of the
BBB penetration [18].
c
N
NHCO(CH2)nNR2
S
IV
Several 2-[3-(1-adamantyl)-4-substituted-5-thioxo-1,2,4-
triazolin-1-yl]acetic acids, 2-[3-(1-adamantyl)-4-substituted-
5-thioxo-1,2,4-triazolin-1-yl] propionic acids and related
derivatives, 2-(1-adamantyl)-5-substituted-1,3,4-oxadiazoles
and 2-(1-adamantylamino)-5-substituted-1,3,4-thiadiazoles,
produced good in vivo dose-dependent anti-inflammatory ac-
tivities using the carrageenin-induced paw oedema method
in rats [19,20]. Since the combination of two pharmacophores
on the same scaffold is a well established approach to the syn-
thesis of more potent drugs [21,22] we decided to incorporate
an adamantane moiety to the thiazolyl ring in an effort to syn-
thesize new compounds with anti-inflammatory activity.
The synthesized compounds contain a thiazolyl ring linked
to different amino amides and to the highly lipophilic adaman-
tane group. These structural characteristics of the compounds
account for a high possibility to be potential inhibitors of the
enzymes involved in inflammation [23].
IV1: N(R)2 = N(CH3)2, n=1
IV2: N(R)2=pirrolidine, n=1
IV3: N(R)2=piperidine, n=1
IV4: N(R)2= morpholine, n=1
IV5: N(R)2 = Ph-piperazine, n=1
IV6: N(R)2 = Me-piperazine, n=1
IV7: N(R)2=N(CH3)2, n=2
IV8: N(R)2=pirrolidine, n=2
IV9: N(R)2= morpholine, n=2
IV10: N(R)2 = Ph-piperazine, n=2
Scheme 1. Synthetic procedure for the preparation of title compounds. Re-
agents and conditions. (a) Isopropanol, 0.5 h, r.t, yield 94%; (b) C6H6, reflux,
yield 99% (n ¼ 1) and 74% (n ¼ 2); (c) RNH2, EtOH, reflux, yield 43e87%.
derivatives are given in Section 4. IR (KBr) spectrum of this
compound showed bands at n ¼ 3030 cmꢀ1 (NeH) and
1652 cmꢀ1 (C]O). In the 1H NMR spectrum, the two singlets
observed at 3.32 ppm (methylen protons, COCH2) and
6.74 ppm (thiazolyl proton) are in agreement with the values
expected for these protons and with findings from studies of
similar compounds [11]. The protons of pyrrolidine and ada-
mantane revealed multiple signals at 2.48e2.53 ppm and
1.69e2.00 ppm. The results are consistent with the proposed
structures.
In the EI-mass spectra, the existence of daughter ions was
assigned from the suggested fragmentation pattern, which is
in agreement with the findings from pertinent studies of sim-
pler compounds [24,25]. Almost all substances gave stable
molecular ions. Initial loss of pyrrolidine (m/z 71) led to ion
with m/z 276 which in turn gave ion with m/z 261 by loosing
methyl. The latter ions with m/z 234, m/z 134 and m/z 85 and
m/z 84, which are the base peaks (thiazole) exhibit the ex-
pected fragmentation pattern of this kind of structure [24,25].
The anti-inflammatory properties of the adamantane deriv-
atives were evaluated by their ability to inhibit carrageenin-
induced mouse paw oedema. Moreover, lipoxygenase and
cycloxygenase, COX-1 and COXe2, inhibitory action of the
compounds were tested in an attempt to elucidate the mecha-
nism of anti-inflammatory action.
2. Results and discussion
2.1. Chemistry
The general method employed to prepare the final com-
pounds is shown in Scheme 1.
2.2. Physicochemical studies
The compounds of the title were prepared in two steps. Initial
4-(1-adamantanyl)-2-aminothiazole (II) was treated with chlor-
acetyl/propionyl chloride in benzene to give the corresponding
chloroacetamides/propionamides (III) which in the second step
undergo condensation with a series of secondary amines in
ethanol to give the title compounds (IV 1e10). Overall the
reactions proceeded smoothly in good yields. Yields, physical
properties and molecular formulae are given in Section 4.
Structures of all synthesized compounds were established on
the basis of elemental and spectral analyses (IR, 1H NMR, MS).
The IR spectra were in agreement with the proposed struc-
tures. IR spectra showed a sharp band in the region 1680e
1700 cmꢀ1 (NHC]O) [24]. As an example, spectral data of
compound 2 are presented here while spectral features of other
Since lipophilicity is a significant physicochemical prop-
erty that determines distribution, bioavailability, metabolic ac-
tivity and elimination we tried to theoretically calculate the
corresponding C log P values in n-octanol buffer [26].
2.3. Biological evaluation
2.3.1. In vivo inhibition of the carrageenin-induced oedema
Compounds IV1e10 were examined in vivo for their anti-
inflammatory activity using the carrageenin mouse paw oedema
as a model of inflammation and they are given in Table 1, as
percentage inhibition of weight increase at the right hind paw
in comparison to the uninjected left hind paw. Carrageenin-induced

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O. Kouatly et al. / European Journal of Medicinal Chemistry 44 (2009) 1198e1204
Table 1
Inhibition % of induced carrageenin rat paw oedema (CPE %); in vitro % inhibition of soybean lipoxygenase (LOX); in vitro % inhibition of cycloxygenase-1
(COX-1); C log P values
N
NHCO(CH2)nX
S
Compound
X
n
CPE %a (0.2 mmol/kg bw)
% LOXb inhibition
% COX-1b inhibition
% COX-2b inhibition
C log P
IV1
IV2
IV3
IV4
IV5
IV6
IV7
IV8
IV9
IV10
N(CH3)2
Pyrrolidinyl
Piperidinyl
1
1
1
1
1
1
2
2
2
2
48*
26.4%
5%
0%
25%
33.6%
nt
3.6%
12.2%
nt
3.562
4.360
4.995
3.726
6.264
4.350
3.790
4.633
3.923
6.461
69.7**
26.6*
57.8*
47.6*
30*
Morpholinyl
Ph-piperazinyl
Me-piperazinyl
N(CH3)2
0%
27.9%
43.6%
nt
35.3%
15.8%
nt
33%
nt
81.5**
36.8**
49.2**
55.9**
1%
nt
25.0%
nt
8.6%
nt
Pyrrolidinyl
Morpholinyl
Ph-piperazinyl
8.4%
39%
nt
28.6%
nt
17.3%
nt: Not tested.
a
Each value represents the mean of two independent experiments with six animals in each group, statistical studies were done with student’s T-test, **p < 0.01,
*p < 0.05.
b
Values are means of tree determinations and deviation from the mean is <10% of the mean value. Compound concentration for LOX-inhibition assay was
100 mM. Compound concentration in COX-1 and COX-2 inhibition assays was 200 mM with the exception of compound 10 which was tested at a concentration
of 20 mM because of solubility problems.
oedema is a non-specific inflammation resulting from a complex
of diverse mediators. Since oedema of this type is highly sensi-
tive to NSAIDs, carrageenin has been accepted as a useful agent
for studying new anti-inflammatory drugs. As shown in Table 1,
all the investigated compounds provided protection against car-
rageenin-induced paw oedema. Compound IV7 is the most po-
tent followed by compounds IV2, IV4 and IV10. Compound
IV3 is the less active. All compounds contain the adamantane
substituent. The structural modifications involve the nature of
the substituent X (alicyclic ring or chain) and the length of
the intermediate aliphatic chain (n ¼ 1 or 2). It was observed
that among the compounds with one-carbon bridge the most ac-
tive compound is the pyrrolidinyl derivative, IV2, (69.7%) fol-
lowed by morpholinyl, IV4, (57.8%) and dimethylamino, IV1,
(48%) derivatives. The less active in this series is piperidinyl
derivative, IV3, (26.6%). On the contrary, among compounds
with two-carbon atom bridge the dimethylamino derivative,
IV7, had the best anti-inflammatory action (81.5%), followed
by phenyl-piperazinyl, IV10, (55.9%) and morpholinyl deriva-
tives, IV9, (49.2%). The less active compound was pyrrolidinyl
derivative, IV8, (36.8%). As gathered by the comparison be-
tween the one-carbon and the two-carbon atom series, the
effect of the length of intermediate chain is ambiguous. Com-
pound IV1, with one-carbon intermediate chain has about
half of the activity (48%) of the two-carbon chain analogue,
compound IV7 (81.5%). A decrease in activity due to dimin-
ished length of the intermediate chain is also observed in the
phenyl-piperazinyl derivatives (compounds IV10 and IV5).
However, the opposite is observed when the activities of the
pyrrolidinyl- (IV8 and IV2) and morpholinyl- (IV9 and IV4)
derivatives are taken into account. It is of interest to note that
in the one-carbon chain series the five-atom heterocyclic sub-
stituent in the pyrrolidilyl derivative, IV2, (69.7%), strongly
favours anti-inflammatory activity compared to the six-atom
piperidinyl substituent in compound IV3 (26.6%). In the
series of piperazinyl derivatives (n ¼ 1), the presence of
a C6H5 group seems to be related with more active compounds
(compounds IV5, IV6). Besides, as lipophilicity increases, the
anti-inflammatory action increases too, but not continuously.
Comparison of the anti-inflammatory activity of the ada-
mantane derivatives with the activity of relevant compounds
lacking the adamantane group [11] may lead to interesting
conclusions (Table 2).
(a) For the dimethylamino amides, having one-carbon inter-
mediate chain (n ¼ 1), the presence of the adamantane
group, IV1, led to an increase of the activity
(1 > 1c >1b > 1d > 1a). The anti-inflammatory activity
of compound IV1 is similar to the phenyl-substituted de-
rivative 1c. A positive effect of adamantane is also ob-
served in case of dimethylamino amides IV7 and 7a,
having two-carbon intermediate chain (n ¼ 2). Compound
IV7, having the adamantane group, in the position 4 of thi-
azole ring exhibited much higher activity (81.5%) than de-
rivative, 7a, (53.4%), with p-OCH3-phenyl group in the
same position of the ring.
(b) The pyrrolidinyl derivatives with R ¼ adamantane and
n ¼ 1, are also more potent anti-inflammatory agents
(IV2 > 2b > 2a) whereas the presence of adamantane in
the piperidinyl- and piperazinyl-analogues is not corre-
lated with higher biological response.
2.3.2. In vitro soybean lipoxygenase inhibition
The synthesized compounds were further evaluated for inhi-
bition of soybean lipoxygenase LOX by the UV absorbance
based enzyme assay (Table 1). The conversion of sodium lino-
late to 13-hydroxy-peroxylinoleic acid measured at 234 nm was

O. Kouatly et al. / European Journal of Medicinal Chemistry 44 (2009) 1198e1204
1201
Table 2
Comparison of the in vivo data (new and previous reported results) [11]
correlation with lipophilicity theoretically calculated C log P
values. The higher activity corresponds to higher C log P
value.
R
N
In case of COX-2 inhibition, the most active compound was
morpholinyl derivative IV4 (35.3%), followed by phenylpiper-
azine derivatives IV10 and IV5 (17.3% and 15.8%, respec-
tively) while the less active compounds of both series were
dimethylamino derivatives IV1 and IV7 (3.6% and 8.6%,
respectively). These are in accordance to the COX-1 inhibitory
results. No correlation with C log P values was observed for
derivatives with n ¼ 1.
NHCO(CH2)nX
S
Compound
R
X
n
CPE %a
(0.2 mmol/kg bw)
IV1
1aa
1ba
1ca
1da
IV2
2aa
2ba
IV3
3aa
IV5
5aa
IV7
7aa
IV8
8aa
8ba
8ca
IV9
9aa
a
Adamantanyl
H
CH3
N(CH3)2
N(CH3)2
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
48
28.4
37.6
52
N(CH3)2
N(CH3)2
N(CH3)2
C6H5
p-OCH3eC6H4
Adamantanyl
C6H5
35
Pyrrolidinyl
Pyrrolidinyl
Pyrrolidinyl
Piperidinyl
Piperidinyl
Ph-piperazinyl
Ph-piperazinyl
N(CH3)2
69.7
49.2
55
3. Conclusions
p-OCH3-C6H4
Adamantanyl
p-OCH3-C6H4
Adamantanyl
H
The results prove that the presence of adamantane moiety
generally leads to thiazolyl-N-substituted amides with improved
anti-inflammatory properties compared to the thiazolyl-
N-substituted amides previously studied by our team [11].
Some of the compounds may act as COX/LOX inhibitors.
Ph-piperazinyl derivatives IV10 and IV5 exhibited the best
LOX and COX-1/2 inhibitory actions. Interestingly, derivative
IV10 exhibited considerable inhibitory action although added
in the reaction mixture at a much lower concentration (20 mM
instead of 200 mM) compared to other compounds and
naproxen, due to solubility problems. These compounds may
represent a good starting point for discovery of new COX/
LOX inhibitors of the N-[4-(1-adamantyl)-thiazol-2-yl]-2/3-
substituted aminoacetamide/propionamide series.
26.6
53.3
47.6
72.1
81.5
53.4
36.8
64.1
68.4
56.2
49.2
55.4
Adamantanyl
p-OCH3eC6H4
Adamantanyl
H
N(CH3)2
Pyrrolidinyl
Pyrrolidinyl
Pyrrolidinyl
Pyrrolidinyl
Morpholinyl
Morpholinyl
C6H5
p-OCH3eC6H4
Adamantanyl
p-OCH3eC6H4
As reported in reference [11].
recorded and compared with appropriate standard (NDGA).
The studied compounds were added in the reaction mixture at
a final concentration of 0.1 mM. While one may not extrapolate
the quantitative results of this assay to the inhibition of mamma-
lian 5-LOX, it has been shown that inhibition of plant LOX
activity by NSAIDs is qualitatively similar to their inhibition
of the rat mast cell LOX and may be used as a simple qualitative
screen for such activity. Phenyl-piperazinyl derivatives, IV10
(n ¼ 2) and IV5 (n ¼ 1), exhibited the best inhibitory action
(39% and 33% respectively). The dimethylamino derivative
with one-carbon intermediate chain, IV1, also showed consid-
erable inhibitory effect (26.4%). On the contrary, the two-
carbon intermediate chain dimethylamino derivative, IV7,
had no inhibitory activity (1%). All other compounds were
practically inactive.
However, Ph-piperazinyl derivative (n ¼ 2), IV10, exhibited
moderate anti-inflammatory action in the in vivo experiment.
On the contrary, the dimethylamino derivative (n ¼ 1), IV7,
with the best anti-inflammatory action had very low LOX and
COX-1/2 inhibitory activities. Since, other mechanisms are in-
volved at the first step of oedema formation a straight correla-
tion between in vitro results and LOX and COX inhibitory
activities cannot be obtained. As a matter of fact this contradic-
tion is commonly observed at the results of many researchers
[27] and further investigation is needed for the elucidation of
the mechanism of action of many potent anti-inflammatory
agents. In a future study, further investigation on the mechanism
of action of some of our compounds may reveal new series of
non-COX/LOX inhibitors with potent anti-inflammatory action.
4. Experimental
2.3.3. In vitro cycloxygenase inhibition
Cycloxygenase inhibitory action was measured using hu-
man recombinant COX-1 and ovine COX-2 isoenzymes in-
cluded in ‘‘COX inhibitor screening assay’’ kit purchased
by Cayman. It was found that Ph-piperazinyl derivatives of
both series IV5 (n ¼ 1) and IV10 (n ¼ 2) showed the highest
COX-1 inhibitory activity (43.6% and 28.6% respectively)
while the dimethylamino derivatives IV1 and IV7 exhibited
the lowest activity (25%). It should be mentioned that the
activity of compound IV5 was better than that of naproxen
under the same conditions (40%). Although the results are
preliminary, it was observed that the COX-1 inhibitory activ-
ity of compounds from the same series (n ¼ 1 or n ¼ 2) is in
4.1. Materials
All the chemicals used were of analytical grade and
commercially available by Merck, nordihydroguaretic acid
(NDGA) is purchased from the Aldrich Chemical Co. (Milwau-
kee, WI, USA). Soybean lipoxygenase, linoleic acid sodium salt
Arachidonic Acid (AA), and indomethacin were obtained from
Sigma Chemical, Co. (St. Louis, MO, USA) and carrageenin,
type K, was commercially available. COX Inhibitor Screening
Assay kit was provided by Cayman (Cayman Chemical Co.,
Ann Arbor, MI, USA, Catalog No. 560131). For the in vivo
experiments, male and female AKR mice were used.

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O. Kouatly et al. / European Journal of Medicinal Chemistry 44 (2009) 1198e1204
1H NMR spectra were recorded with a Mercury 200
2.25 (s, 6H, N(CH3)2), 3.18 (s, 2H, COCH2), 6.67 (s, 1H,
thiazole). MS for C17H25N3OS, m/z: Mþ 319.
(Varian) spectrometer using CDCl3 as solvent and hexame-
thyldisiloxane (HMDSO) as internal standard (for unsilylated
compounds). Melting points were determined on a Boetius
table and were uncorrected. The results of elemental analysis
for C, H, N, S were in agreement with the calculated.
4.2.5. N-[4-(1-adamantyl)-thiazol-2-yl]-2-pyrrolidino
acetamide (IV2)
Yield: 74%; mp 190e191 ꢁC (ethanol). TLC:
eluent ¼ benzeneeethanol
(8:2),
Rf ¼ 0.83.
IR(KBr):
4.2. Chemistry
n ¼ 3030 cmꢀ1 (NeH), 1652 cmꢀ1 (C]O). 1H NMR
(DMSO-d6): d ¼ 1.69e2.00 (m, 15H, adamantane and 4H
pyrrolidine), 2.48e2.53 (m, 4H, pyrrolidine), 3.32 (s, 2H,
COCH2), 6.74 (s, 1H, thiazolyl). MS for C19H27N3OS, m/z:
Mþ 345.
4.2.1. Synthesis N-[4-(1-adamantyl)]-2-aminothiazole (II)
To a solution of 1-adamantyl bromomethyl ketone, I,
(257 mg, 1 mmole) in 5 ml of isopropanol, a suspension of
thiourea (152 mg, 2 mmole) in 10 ml of isopropanol was
added. The mixture was stirred for half an hour. After this
time the resulting solution was poured into a solution of
sodium carbonate, and the precipitate formed was filtered
and dried to give, after recrystallization from ethyl acetate,
220 mg (94%) of pure product, II. M.p. 215e215.5 ꢁC.
IR(KBr): n ¼ 3050 cmꢀ1 (NeH), 1650 cmꢀ1 (C]O). 1H
NMR (DMSO-d6): d ¼ 1.65e2.00 (m, 15H adamantane),
6.00 (s, 1H, thiaz.), 6.75 (s, 2H, NH2).
4.2.6. N-[4-(1-adamantyl)-thiazol-2-yl]-2-piperidino
acetamide (IV3)
Yield: 78%; mp 144e145 ꢁC (ethanol). TLC: eluent ¼
benzeneeethanol (8:2), Rf ¼ 0.78. IR(KBr): n ¼ 3055 cmꢀ1
(NeH), 1680 cmꢀ1 (C]O). 1H NMR (DMSO-d6):
d ¼ 1.42e1.56 (m, 6H, piperidine), 1.75e1.91 (m, 15H, ada-
mantane), 2.06 (m, 4H piperidine), 3.24 (s, 2H, COCH2),
6.71 (s, 1H, thiazole). MS for C20H29N3OS, m/z: Mþ 359.
4.2.2. Synthesis of N-[(4-(1-adamantyl)-thiazol-2-yl)] 2/3-
chloroacetamide/propionamide (III)
4.2.7. N-[4-(1-adamantyl)-thiazol-2-yl]-2-morpholino
acetamide (IV4)
The synthesis was performed according to the procedure
described in our previous paper [24,28]. To a solution of 4-
adamantyl-2-aminothiazole (0.02 mol) in dry benzene a cooled
solution of chloroacetyl or 3-chloropropionyl chloride
(0.033 mol) in dry benzene (7.5 ml) was added drop wise.
The reaction mixture was refluxed in a water bath at 80 ꢁC
for 3 h. Benzene and excess 2-chloracetyl/3-chloropropionyl
chlorides were removed by distillation. The residue was
washed with aqueous sodium bicarbonate (5% w/v) followed
by cold water. The crude product was dried and crystallized
from ethanol.
Yield: 81%; mp 125e126 ꢁC (ethanol). TLC:
eluent ¼ benzeneeethanol
(8:2),
Rf ¼ 0.81.
IR(KBr):
n ¼ 3050 cmꢀ1 (NeH), 1680 cmꢀ1 (C]O). 1H NMR
(DMSO-d6): d ¼ 1.82e2.14 (m, 15H, adamantane), 2.63e
2.73 (m, 4H, morpholine CH2NCH2), 3.51 (br s, 2H,
COCH2), 3.67 (t, 4H, morpholine), 6.74 (s, 1H, thiazole).
MS for C19H27N3O2S, m/z: Mþ 361.
4.2.8. N-[4-(1-adamantyl)-thiazol-2-yl]-2-(40-
phenylpiperazino) acetamide (IV5)
Yield: 95%; mp 134e135 ꢁC (ethanol). TLC:
Yield: 99% and 74% for 2- and 3-chloroacetamides respec-
tively. M.p.185e187 ꢁC and 190e192 ꢁC, respectively.
eluent ¼ benzeneeethanol
(8:2),
Rf ¼ 0.80.
IR(KBr):
n ¼ 3120 cmꢀ1 (N-H), 1685 cmꢀ1 (C]O). 1H NMR
(DMSO-d6): d ¼ 1.70e2.01 (m, 15H adamantane), 2.64e
2.66 (m, 4H piperazine), 3.14 (m, 4H, piperazine), 3.30 (s,
2H, COCH2), 6.66 (s, 1H, thiazole), 6.73e6.78 (q, 1H,
ArH), 6.90e6.93 (d, 2H ArH, J ¼ 8.13 Hz), 7.17e7.22 (q,
2H, ArH). MS for C25H32N4OS, m/z: Mþ 436.
4.2.3. Synthesis of N-[(4-(1-adamantyl) thiazol-2-yl)] 2/3-
substituted acetamides/propionamides (IV 1e10)
The synthesis was performed according to the procedure
described in our previous paper [24,28]. A mixture of 2-chlor-
oacetamido or 3-chloropropionamido thiazole (0.006 mol),
amines (0.7 mol), absolute ethanol (15 ml) and anhydrous
sodium carbonate (1.48 g) was heated under reflux in a water
bath for 12 h. The excess of amine and ethanol was removed
by distillation and the residue was treated with 5% sodium
bicarbonate solution to remove acid impurities, filtered,
washed with water and dried. It was crystallized from ethanol
(95%) to give white crystals.
4.2.9. N-[4-(1-adamantyl)-thiazol-2-yl]-2-methylpiperazino
acetamide (IV6)
Yield: 87%; mp 184e186 ꢁC (ethanol). TLC: eluent ¼
benzeneeethanol (8:2), Rf ¼ 0.62.
IR(KBr): n ¼ 3150 cmꢀ1 (NeH), 1680 cmꢀ1 (C]O). H
1
NMR (DMSO-d6): d ¼ 1.69e2.01 (m, 15H, adamantane),
2.80 (s, 3H, NCH3), 3.48e3.68 (m, 8H, piperazine), 4.21 (s,
2H, COCH2), 6.78 (s, 1H, thiazole). MS for C20H30N4OS,
m/z: Mþ 374.
4.2.4. N-[4-(1-adamantyl)-thiazol-2-yl]-2 dimethylamino
acetamide (IV1)
Yield: 85%; mp 139e139.5 ꢁC (ethanol). TLC: eluent ¼
4.2.10. N-[4-(1-adamantyl)-thiazol-2-yl]-3-
dimethylaminopropionamide (IV7)
Yield: 77%; mp 133e135 ꢁC (ethanol). TLC:
eluent ¼ benzeneeethanol (8:2), Rf ¼ 0.71.
benzeneeethanol (8:2), Rf ¼ 0.74.
IR(KBr): n ¼ 3050 cmꢀ1 (NeH), 1680 nm (C]O). 1H
NMR (DMSO-d6): d ¼ 1.69e2.01 (m, 15H, adamantane),

O. Kouatly et al. / European Journal of Medicinal Chemistry 44 (2009) 1198e1204
1203
1
IR(KBr): n ¼ 3080 cmꢀ1 (NeH), 1685 cmꢀ1 (C]O). H
NMR (DMSO-d6): d ¼ 1.75e2.04 (m, 15H, adamantane),
2.39 (s, 6H, N(CH3)2), 2.64e2.67 (m, 4H, COCH2CH2N)
3.2 (s, 2H, COCH2), 6.4 (s, 1H, thiazole), 7.27 (s, 1H, NH),
MS for C18H27N3OS, m/z: Mþ 333.
compound (two groups of six animals). The difference be-
tween the weight of the injected and uninjected paws was cal-
culated for each animal. The change in paw weight was
compared with that in control animals (injected with water)
and expressed as a percent inhibition of the oedema (CPE
% values Table 1).
4.2.11. N-[4-(1-adamantyl)-thiazol-2-yl]-3-pyrrolidino
propionamide (IV8)
Indomethacin in 0.2 mmol/kg (44%) was administered as
a standard comparative drug.
Yield: 43%; mp 149e150 ꢁC (ethanol). TLC:
eluent ¼ benzeneeethanol (8:2), Rf ¼ 0.60.
4.4.2. In vitro soybean lipoxygenase inhibition
IR(KBr): n ¼ 3120 cmꢀ1 (NeH), 1680 cmꢀ1(C]O). 1H
NMR (DMSO-d6): d ¼ 1.68e1.97 (m, 15H, adamantane; 4H,
pyrrolidine), 2.42e2.68 (m, 8H pyrrolidine, COCH2CH2),
6.76 (s, 1H, thiazole), MS for C20H29N3OS, m/z: Mþ 359.
The tested compounds dissolved in DMSO were incubated
in different concentrations at room temperature with sodium
linoleate (0.1 mM) and 0.2 ml of enzyme solution (1/3 ꢂ 104
w/v in saline) added in a reaction mixture of 3 ml [7]. The con-
version of sodium linoleate to 13-hydroperoxylinoleic acid at
234 nm was recorded and compared with nordihydroguairetic
acid ((NDGA) ¼ 94.4% at 0.1 mM), an appropriate standard
inhibitor. The results are summarized in Table 1.
4.2.12. N-[4-(1-adamantyl)-thiazol-2-yl]-3-morpholino
propionamide (IV9)
Yield: 77%; mp 185e187 ꢁC (ethanol). TLC:
eluent ¼ benzeneeethanol (8:2), Rf ¼ 0.69.
1
IR(KBr): n ¼ 3100 cmꢀ1 (NeH), 1680 cmꢀ1 (C]O). H
4.4.3. In vitro cycloxygenase inhibition
NMR (DMSO-d6): d ¼ 1.67e1.95 (m, 15H, adamantane),
2.45e2.82 (m, 4H, morpholine and 4H, COCH2CH2), 3.75e
3.92 (m, 4H, morpholine), 6.78 (s, 1H, thiazole). MS for
C20H29N3O2S, m/z: Mþ 375.
The COX-1 and COX-2 activities of the compounds were
measured using ovine COX-1 and human recombinant COX-
2 enzymes included in the ‘‘COX Inhibitor Screening Assay’’
kit provided by Cayman (Cayman Chemical Co., Ann Arbor,
MI, USA) [29]. The assay directly measures PGF2a produced
by SnCl2 reduction of COX-derived PGH2. The prostanoids
production was quantified via enzyme immunoassay using
a broadly specific antibody that binds to all the major prosta-
glandin compounds.
Estimation of % inhibition (Table 1) was performed at a sub-
strate concentration of 0.1 mM. The compounds were added at
the reaction mixture at a final concentration of 200 mM with the
exception of compound IV10 which was tested at a concentra-
tion of 20 mM because of solubility problems. Naproxen, used
as positive control, was added to the reaction mixture at the
same concentration, 200 mM, as the tested compounds (COX-
1 inhibition: 40%, COX-2 inhibition 51%).
4.2.13. N-[4-(1-adamantyl)-thiazol-2-yl]-
3-(40-phenylpiperazine)-propionamide (IV10)
Yield: 75%; mp 230e232 ꢁC (ethanol). TLC:
eluent ¼ benzoleethanol (8:2), Rf ¼ 0.64.
1
IR(KBr): n ¼ 3080 cmꢀ1 (NeH), 1680 cmꢀ1 (C]O). H
NMR (DMSO-d6): d ¼ 1.65e2.00 (m, 15H, adamantane),
2.65 (br s, 4H, piperazine), 3.13 (br s, 4H, piperazine),
3.25e3.44 (m, 4H, COCH2CH2), 6.67 (9s, 1H, thiazole),
6.73e6.78 (t, 1H, ArH), 6.90e6.93 (d, 2H, ArH.
J ¼ 8.43 Hz), 7.17e7.22 (t, 2H ArH). MS for C26H34N4OS,
m/z: Mþ 450.
4.3. Physicochemical studies
Acknowledgements
4.3.1. Determination of lipophilicity as C log P
Lipophilicity was theoretically calculated as C log P values
in octanolewater-buffer by ClogP program of Biobyte. [26].
We would like to thank Dr. C. Hansch and Biobyte Corp.
201, West 4th Street, Suite 204, Claremont, CA 91711, USA
for free access to the C-QSAR program.
4.4. Biological evaluation
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4.4.1. In vivo inhibition of the carrageenin-induced oedema
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of Tween 80 and ground in a mortar before use and were
given intraperitoneally (i.p) at the same time as the carra-
geenin. The animals were euthanized 3.5 h after carrageenin
injection. The experiment was repeated twice for each
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