Design and synthesis of bioactive adamantanaminoalcohols and adamantanamines

Article abstract of DOI:10.1016/j.ejmech.2010.08.009

Adamantanamines 16, 18, 21, 24, 27, 28, 30, 32, 35, 36, 37, 40, 46 and 48 were synthesized and tested for anti-influenza A virus and trypanocidal activity. The stereoelectronic requirements for optimal antiviral and trypanocidal potency were investigated.

Full text of DOI:10.1016/j.ejmech.2010.08.009

European Journal of Medicinal Chemistry 45 (2010) 5022e5030
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design and synthesis of bioactive adamantanaminoalcohols
and adamantanamines
,
b
b
c
Grigoris Zoidis a, Nicolas Kolocouris a , John M. Kelly , S. Radhika Prathalingam , Lieve Naesens ,
*
Erik De Clercq c
a Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, GR-15771 Athens, Greece
b London School of Hygiene and Tropical Medicine, Department of Infectious and Tropical Diseases, Keppel Street, London WC1E 7HT, UK
c Rega Institute, Department of Microbiology and Immunology, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
a r t i c l e i n f o
a b s t r a c t
Article history:
Adamantanamines 16, 18, 21, 24, 27, 28, 30, 32, 35, 36, 37, 40, 46 and 48 were synthesized and tested for
anti-influenza A virus and trypanocidal activity. The stereoelectronic requirements for optimal antiviral
and trypanocidal potency were investigated. The effect of introducing a hydroxyl group close to the
amino group on this class of compounds was examined for the first time. Aminoalcohol 24 proved to be
the most active of the compounds tested against influenza A virus, being 6-fold more active than
amantadine, equipotent to rimantadine and 26-fold more potent than ribavirin. Aminoalcohols 36 and 37
were found to have considerable activity against bloodstream forms of the African trypanosome,
Trypanosoma brucei, being almost 10 times more potent than rimantadine.
Received 16 April 2010
Received in revised form
4 August 2010
Accepted 6 August 2010
Available online 12 August 2010
Keywords:
Adamantane aminoalcohols and diamines
Anti-influenza A virus agents
H3N2
Ó 2010 Elsevier Masson SAS. All rights reserved.
Rimantadine
Trypanocidal activity
NMR
1. Introduction
caused some 89 mild infections in the Netherlands and the death of
a veterinarian, while in the same year H9N2 viruses were isolated
Influenza is a highly contagious infectious disease that affects
millions of people every year. In the twentieth century, influenza
caused more fatalities in Europe than any other infectious disease
[1]. Current vaccines against influenza virus have limited effec-
tiveness due to the rapid emergence of strains with mutated viral
antigens. Thus, anti-influenza drugs are vital as a first line of
defense. At present, two classes of antivirals are available: the
neuraminidase inhibitors oseltamivir and zanamivir, and the M2
proton channel blockers amantadine and rimantadine [5].
The cumulative impact of recurrent annual epidemics is gener-
ally higher than that of the infrequent pandemics, although the
extreme mortality of the H5N1 avian influenza virus is a serious
reason for concern. This H5N1 virus originated in 1997 in Hong
Kong and has since spread (through birds) to Southeast Asia and
other countries, with occasional transmission to humans (almost
500 human cases, more than half of which were fatal). In 2003,
another highly pathogenic avian influenza virus (H7N7 subtype)
from individuals with mild influenza [2]. The “swine flu” pandemic
of 2009 was caused by a new H1N1 reassortant virus containing
genome segments from human, avian and swine influenza viruses.
Although the source of the outbreak in humans is still unknown,
cases were first discovered in Mexico and the U.S.A. [3]. This new
influenza pandemic prompted an unprecedented worldwide
response consisting of containment measures, antiviral therapy and
the development of a vaccine. The disease spectrum of this swine
flu H1N1 virus is comparable to that of other human influenza
viruses, although it remains unclear how the virus will evolve
during the forthcoming months [4].
Amantadine (1; Fig. 1) was the first anti-influenza drug to be
developed. At micromolar concentrations, amantadine inhibits the
function of the M2 proton channel of influenza A virus that is
involved in virus uncoating [6,7]. After endocytosis of the virions,
the M2 proton channel mediates acidification of the viral interior,
resulting in a conformational change of the viral hemagglutinin
(to its fusogenic form) and dissociation of viral ribonucleoprotein
from the matrix protein. In addition, the M2 protein has a role in
virus maturation, since it regulates the pH in the trans-Golgi
network to prevent premature conformational rearrangement of
* Corresponding author. Tel.: þ30 210 7274809; fax: þ30 210 7274747.
E-mail address: zoidis@pharm.uoa.gr (N. Kolocouris).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.08.009

G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
5023
H3C
NH2
NH2
CH3
R
R1
R2
N
OH
R3
Amantadine
Rimantadine
1 R1, R2, R3=H
5 R=CH3
2 R1, R3=H, R2=CH3
3 R1, R2=CH3, R3=H
4 R1, R2=H, R3=CH3
6 R=C2H5
7 R=n-C3H7
O
O
R
CH3
F
N
NH2
NH
11
8 R=CH3
12
13
9 R=C2H5
10 R=n-C3H7
Fig. 1.
the hemagglutinin [6b]. During the past fourteen years, we have
synthesized many potent aminoadamantane derivatives (Fig. 1)
[8,9]. The protonated forms of these compounds are considered to
block the tetrameric M2 ion channel pore [10], formed by its
transmembrane domain M2TM [11], and hence, its proton trans-
port function [12,13].
The desired property of new synthetic aminoadamantane
derivatives is of course the effective inhibition of virus replication.
The amantadinedM2 complex is probably stabilized through
formation of hydrogen bonding between the drug’s ammonium
group and specific residues, probably His-37 or Ser-31, within the
M2 acceptor site [10,12]. Here, we have examined the M2 binding
properties of aminoadamantane derivatives that have a hydroxyl
group at positions close to the amino group; the hydroxyl group
could possibly participate as donor or acceptor in hydrogen
bonding interaction with the receptor.
Among the many diseases that afflict humankind, those caused
by protozoan parasites occupy an important place because of the
large number of victims, the lack of efficient therapy, and their
continuing spread. Tsetse fly-transmitted parasites of the Trypa-
nosoma brucei species complex are the causative agents of Human
African Trypanosomiasis (HAT), one of the world’s great neglected
diseases. The World Health Organization reported 55,000 deaths in
2002 out of 500,000 cases of sleeping sickness in sub-Saharan
Africa [14]. Recently, the annual incidence has varied between
50,000 and 300,000 cases, with about 60 million people at risk [15],
and in some areas death rates exceed those of HIV/AIDS and
malaria. Trypanosomiasis also has a significant affect on human
nutrition through its impact on domesticated animals, for example,
killing 3 million cattle per year. In humans, the disease is caused by
infection with the sub-species Trypanosoma brucei gambiense
(western and central Africa) and Trypanosoma brucei rhodesiense
(eastern and southern Africa) and is invariably fatal unless treated.
In the past 25 years, only one drug, eflornithine [(R,S)-2-difluor-
omethylornithine (DFMO, initially developed as an anticancer
drug)], has been approved for HAT therapy [16]. Moreover, all four
front-line drugs (suramin, pentamidine, melarsoprol and eflorni-
thine) require hospitalization for administration, are expensive and
are associated with severe side effects. In addition, drug resistance
is commonly observed, and suramin and pentamidine are not
effective against the later stages of the disease, which occur when
parasites gain access to the central nervous system [17,18]. Treat-
ment of late stage East African trypanosomiasis is a particular
problem, since T. b. rhodesiense is refractory to eflornithine.
Melarsoprol, which is the only available drug, can cause arsenic
encephalopathy with 5e10% patient mortality [19]. Although there
is an urgent need for new anti-trypanosome drugs, the pharma-
ceutical industry has paid little attention to this relatively unprof-
itable area. The development of broad-spectrum, inexpensive,
highly efficient, and nontoxic drugs therefore remains a priority.
Recently, there have been reports that bloodstream forms of the
African trypanosome, T. brucei, are sensitive to the anti-influenza
virus drug rimantadine (IC50 ¼ 7
mM) and to a lesser extent aman-
tadine. The trypanocidal activity is pH-dependent and is enhanced
with increasing alkalinity. Rimantadine is also toxic to the trypa-
nosomatid parasites Trypanosoma cruzi and Leishmania major [20].
More recently, a number of other aminoadamantane derivatives
have been evaluated for their trypanocidal properties. These
studies revealed a correlation between increased lipophilicity and
potency against T. brucei (Fig. 1) [9e,f,21]. Here, by investigating the
trypanocidal properties of newly synthesized aminoadamantane
derivatives, our aim has been to provide greater insight into the
chemical features that may enhance this activity.
We now describe the synthesis and biological evaluation of
adamantanoaminoalcohols 16, 18, 21, 24, 27, 28, 30, 36 and 37,
adamantanodiamines 32, 35 and 40 and adamantanamines 46 and
48 (Fig. 2), and show that they contain structural features necessary
for antiviral activity.
2. Results and discussion
2.1. Chemistry
2-Aminomethyl-2-hydroxyadamantane 16 (Scheme 1) was pre-
pared by known methods from adamantanone in good yields [22].
In order to synthesize the 2-(2-aminoethyl)-2-hydroxy-
adamantane 18 we follow a concise and efficient synthesis. In this
approach, we have employed n-butyl lithium and acetonitrile in dry
THF for the preparation of 2-(2-hydroxy-2-adamantyl)acetonitrile
19 from adamantanone 14. In comparison with the other bases
reported in the literature [23], the use of n-butyl lithium allows the
synthesis of the hydroxyl nitrile 19 quantitatively (97%) without
side products and laborious purifications. Nitrile 19 was reduced
with LiAlH4 in tetrahydrofuran. As a result, 2-(2-aminoethyl)-2-
hydroxyadamantane was obtained in great yield, which was iso-
lated as hydrochloride.
The synthesis of the aminoalcohol 21 is illustrated in Scheme 1.
Hydroxymethylation of the 2-nitroadamantane 19 afforded the

5024
G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
Fig. 2.
2-nitro-2-adamantanemethanol 20. Catalytic reduction of the nitro
alcohol 20 resulted in the 2-amino-2-adamantanemethanol 21.
In order to synthesize the aminoalcohol 24 (Scheme 1), 2-ada-
mantanecarbonitrile 22 was used as a starting material [9c]. Thus,
lithiation at C-2 using LDA and reaction of the resulting carbanion
with methyl chloroformate gave cyanoester 23 in good yield [9e].
Reduction of the latter with LiAlH4 under mild heating afforded the
desired aminoalcohol 24, in excellent yield (93%).
afforded the desired hydroxyl nitrile 26 in a 95% yield. Reduction
of the latter with LiAlH4 gave aminoalcohol 27. Heating amino-
alcohol 27 in dioxane with H2SO4 (15%) afforded the target
compound 28 in an excellent yield (95%).
Tertiary alcohol 30 was synthesized from the reaction of ada-
mantanone 14 and 2-pyridinyl lithium. Catalytic hydrogenation of
the hydrochloride form of 29 over PtO2 catalyst led to the amino-
alcohol 30 [25].
The synthetic route to the aminoalcohol 28 is shown in
Scheme 1 and involved protoadamantanone 25 [24a], prepared
by a modification of the literature method from the reaction of
1-adamantanol with iodine and lead tetraacetate [24a,b], which
on treatment with n-butyl lithium and acetonitrile in dry THF
Diamine 32 was prepared starting from adamantanone 14 which
was successively transformed to 2-(N-methylimino)adamantane 31
(Scheme 2), in 98% yield, upon treatment with methylamine in dry
THF with 3 A molecular sieves at room temperature under nitrogen
overnight [26]. Imine 31 reacted with 2-bromopyridine, n-BuLi, in
ꢀ
O
OH
CN
OH
a
b
CH2NH2
14
15
16
CH2CN
OH
1
CH2CH2NH2
OH
8
7
b
2
3
9
10
6
5
4
17
18
NO2
CN
CH2OH
NO2
CH2OH
NH2
d
e
20
19
21
COOCH3
CH2OH
f
b
CN
CH2NH2
23
24
22
O
CH2CH2NH2
OH
CH2CN
OH
CH2CH2NH2
OH
4
3
5
2
c
b
g
6
1
8
7
9
10
26
25
28
27
Scheme 1. a: HCN, Pyridine, r.t., 24 h (82%); b: LiAlH4, THF, 20 ꢀC, 20 h (95%); c: n-BuLi, CH3CN, THF, ꢁ80 ꢀC, (97%); d: CH2O, NaOH, dioxane, reflux (60%); e: H2/Raney Ni, EtOH,
55 p.s.i., 50 ꢀC (99%); f: LDA, ꢁ70 ꢀC, THF, ClCOOCH3, 24 h, 20 ꢀC, (87%); g: dioxane, H2SO4 15%, 80 ꢀC, 2 h (96%).

G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
5025
the present of 1-(2-methoxyphenoxy)-N,N-dimethyl-3-phenyl-
propan-2-amine to give the target diamine 32.
converted to formate 42 via a C2eC3 to C4 metathesis. Saponifi-
cation of the in situ formed ester 42 gave the respective secondary
alcohol 43 in 96% yield, and that was then oxidized under Jones
reaction conditions to the corresponding 1-phenyl-2-one 44 [9d].
Treatment of ketone 44 with hydroxylamine hydrochloride in the
presence of sodium acetate led to the formation of the respective
oxime 45 quantitatively, which on hydrogenation over Raney Ni
catalyst was converted to amine 46, the yield of the latter was
found to increase upon heating and prolonged hydrogenation.
Finally, treatment of ketone 25 with hydroxylamine hydro-
chloride in the presence of sodium acetate led to the formation of
the respective oxime 47, which on hydrogenation over Raney Ni
catalyst was converted to protoadamantanamine 48.
The Strecker reaction [27] has been employed for the prepara-
tion of diamine 35 (Scheme 2). The conditions for preparing the
latter are consistent with mixing the bulky 1-adamantanecarbox-
aldehyde 33 with NaCN and CH3NH2, in a mixture of DMSO/water,
and leaving the mixture to react at ambient temperature. Catalytic
hydrogenation of the
a-aminonitrile 34 over PtO2 provided the
desired -aminomethyl adamantanemethanamine 35 [28].
a
The key intermediate 36 for the synthesis of compounds 37 and
40 was prepared from protoadamantanone 25, which was first
converted to the aminoalcohol 36 via a Grignard reaction between
ketone 25 and the magnesium derivative of 3-chloro-N,N-dime-
thylpropan-1-amine hydrochloride (Scheme 2). Heating amino-
alcohol 36 in dioxane with H2SO4 (15%) afforded compound 37
quantitatively via a C2eC3 to C4 metathesis [24b]. Oxidation of the
latter under Jones reaction conditions led to the aminoketone 38,
which was in turn converted to the respective oxime 39. Catalytic
hydrogenation of 39 over Raney Nickel afforded diamine 40 in
a 91% yield.
3. Biological activity
The antiviral efficacy of the new aminoadamantane derivatives
16,18, 21, 24, 27, 28, 30, 32, 35, 36, 37, 40, 46 and 48 was determined
in vitro against influenza A (H3N2 subtype; strain A/HK/7/87, which
carries a serine at position 31 of the M2 protein) and was compared
to the activity of amantadine, rimantadine and ribavirin (Table 1).
The antiviral assay used was identical to that previously reported
[29], and isbased on inhibitionof thevirus-induced cytopathic effect
(CPE) after multiple replication cycles at 72 h post infection, as
The synthesis of analogue 46 is shown in Scheme 3. Proto-
adamantanone 25, was treated with phenyl lithium to give the
corresponding tertiary alcohol 41 as an endo/exo (1:1) isomeric
mixture in 96% yield, which on treatment with formic acid was
O
N
N
H
a
b
OH
OH
14
29
30
c
N
CH3
N
d
N
H
CH3
31
32
e
f
H2C NH2
C
N
HC
CH=O
HC
N
H
CH3
35
N
CH3
33
34
H
CH3
O
CH3
CH3
HO
CH2CH2CH2N
CH2CH2CH2N
OH
CH3
h
3
4
5
g
2
6
1
i
8
7
9
10
25
36
37
CH3
CH3
CH3
CH2CH2CH2N
O
CH3
CH3
CH2CH2CH2N
CH2CH2CH2N
NH2
CH3
k
NOH
j
38
39
40
Scheme 2. a: 2-pyridinyl lithium, Et2O/THF, ꢁ60 ꢀC (82%); b: (1) gas HCl, EtOH; (2) H2/PtO2, EtOH and then Na2CO3 10% (97%); c: CH3NH2, THF, molecular sieves (3 A), 24 h (82%); d:
2-bromopyridine, n-BuLi, dry ether, 1-(2-methoxyphenoxy)-N,N-dimethyl-3-phenylpropan-2-amine, dry toluene, 3 h (53%); e: NaCN, CH3NHþ3 Clꢁ, DMSO/H2O 29:1, rt, 48 h, and
then HCl(g)/Et2O (66%); f: H2, PtO2, HCl(g)/MeOH, 45 lb/in2, rt, 6 h, and then NaOH 20% (85% for 8, 90% for 11); g: (CH3)2NCH2CH2CH2MgCl, THF, C6H6, reflux, 4 h (97%); h: dioxane,
H2SO4 15%, 80 ꢀC, 2 h (93%); i: CrO3, aq. H2SO4 (1 N), acetone, 15 ꢀC, then r.t., 24 h (87%); j: NH2OHeHCl, CH3COONa.3H2O, abs. EtOH, H2O (14:1), 3 h, reflux (quantitative); k: EtOH,
Ni-Raney, 55 p.s.i., 65 ꢀC, 5 h (95%).
ꢀ

5026
G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
O
HO
O CH
O
OH
a
O
b
c
d
25
41
42
44
43
e
e
NOH
NH2
NOH
NH2
f
f
45
47
48
46
Scheme 3. a: PhLi, THF; b: HCOOH, reflux, 30 min; c: NaOH/EtOH, D
; d: CrO3, aqueous H2SO4 (8 N), acetone, 15 ꢀC; e: NH2OHeHCl, CH3COONa.3H2O, abs. EtOH, H2O (10:1) (70%),
3 h, reflux (quantitative); f: EtOH, Ni-Raney, 55 p.s.i., 90 ꢀC, 8 h (70e81%).
assessed by microscopical scoring of the CPE and a formazan-based
cell viability assay. There was a good correlation between the anti-
viral EC50 values obtainedbythe CPEreduction and MTS cellviability
assay, and, hence, only the latter values are shown in Table 1.
The data presented in Table 1 indicate that compounds 21 and
24 elicit potent anti-influenza A virus activity, with a selectivity
index (SI) of at least 314 and 256, respectively. Aminoalcohol 24
was endowed with the most potent anti-influenza A virus activity;
it proved to be at least 6-fold more potent than amantadine,
equipotent to rimantadine and 26-fold more active than ribavirin.
Protoadamantanamine 48 was less active than rimantadine, while
this compound was comparable to amantadine in both antiviral
activity and cytotoxicity. Aminoalcohol 18, 27, and its metathesis
product 28, had intermediate activity (EC50 ranging from 6 to 9 M),
with 27 and 28 having promising selectivity (SI above 60).
Compounds 16, 30, 32, 35, 36, 37, 40 and 46 were devoid of anti-
influenza virus activity.
All compounds were inactive against influenza B virus, which is
in accordance with their putative mode of action, namely interac-
tion with the influenza A virus M2 protein, which is different in
influenza B virus. This is further supported by our observation that
none of the new derivatives displayed activity against the influenza
virus strain X-31, which carries the V27T and S31N substitutions in
M2, associated with amantadine resistance.
m
The numbered compounds in Table 2 were first tested at
5 m
g mlꢁ1 against bloodstream form T. brucei (strain 427) cultured
at pH 7.4. Compounds displaying significant inhibitory activity
(>50%) at this concentration were assessed further and their IC50
and IC90 values determined (Experimental section). The values
shown are the mean ꢂ standard deviation from three experiments,
with the values for rimantadine shown for comparison. N/A:
Table 1
Anti-influenza
A virus (H3N2) activity and cytotoxicity of aminoadamantane
derivativesa in MDCK cells.b
MCCd
(
mM)
SI (ratio MCC/EC50)
c,e
Compound
EC50
(m
M)
16
18
21
24
27
28
30
N/A
e
17
>459
87
512
512
e
3
>314
256
67
60
e
compounds with marginal activity at 5
examined further.
m
g mlꢁ1 which were not
6.24 ꢂ 7.80 (4)
1.46 ꢂ 0.27 (3)
0.34 ꢂ 0.12 (4)
7.68 ꢂ 1.68 (3)
8.60 ꢂ 1.99 (3)
N/A
In the preliminary screen, bloodstream form T. brucei, were
cultured for 2 days in the presence of aminoadamantane deriva-
tives at 5 m mM, depending on the compound). At this
g mlꢁ1 (20e30
208
32
N/A
264
e
35
N/A
404
e
36
37
40
46
N/A
N/A
N/A
N/A
>250
>250
>200
218
e
Table 2
e
Susceptibility of cultured bloodstream form T. brucei to aminoadamantane
derivatives.
e
e
48
1.5 ꢂ 0.3 (4)
107
69
>51
>276
2
Compound
IC50
(m
M)
IC90 (mM)
Amantadine
Rimantadine
Ribavirin
2.0
>100
>100
20
16
18
N/A
N/A
e
e
ꢃ0.362
8.7
21
24
27
28
30
32
35
36
37
40
46
48
9.4 ꢂ 1.1
18.2 ꢂ 1.1
N/A: not active at subtoxic concentrations or the highest concentration tested
(w500
M).
N/A
e
m
N/A
N/A
N/A
24.6 ꢂ 0.7
5.2 ꢂ 0.4
0.84 ꢂ 0.04
0.84 ꢂ 0.08
N/A
e
a
All compounds were tested as hydrochlorides. Aminoalcohols 27 and 36 were
e
tested as free bases.
e
b
MDCK, Madin-Darby canine kidney cells; virus strain: influenza A/Hong Kong/7/
>25
87 (H3N2).
7.8 ꢂ 0.4
1.7 ꢂ 0.1
1.8 ꢂ 0.1
e
c
Concentration producing 50% inhibition of virus-induced cytopathic effect, as
determined by measuring the cell viability with the colorimetric formazan-based
MTS assay.
d
Minimal cytotoxic concentration, or concentration that causes microscopically
11.1 ꢂ 5.7
>20
e
detectable changes in cell morphology.
N/A
e
Data are shown as mean ꢂ SD (in brackets: number of independent
Rimantadine
7.0 ꢂ 0.1
14.0 ꢂ 1.7
determinations).

G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
5027
concentration, compounds 16, 18, 24, 27, 28, 30, 40 and 48 showed
only slight inhibition (up to 30%) of parasite growth, while dian-
amine 32 was marginally more active (Table 2). In contrast, amine
46, aminoalcohol 21 and diamine 35 each exhibited trypanocidal
activity in a concentration range similar to that of rimantadine,
8), 1.83 (br d, 4H, H-5, 7, 10), 1.91 (br s, 2H, H-1, 3), 2.18 (br d, 3H, H-
4a, 9a, OH), 2.77 (s, 2H, CH2-CN); 13C NMR (100 MHz, CDCl3): 26.6
(C-5), 26.8 (C-7), 28.9 (CH2-CN), 32.4 (C-4, 9), 34.4 (C-8, 10), 36.7 (C-
1, 3), 37.7 (C-6), 73.9 (C-2), 117.7 (CN). Anal. Calcd. for C12H17NO.
Calcd, %: C 75.35; H 8.96. Found, %: C 75.33; H 8.90.
with lysis of all trypanosomes in the culture at 5 m
g mlꢁ1. Amino-
alcohols 36 and 37 were the most active of the compounds tested.
They displayed significant trypanocidal activity at sub-micromolar
levels and were found to be approximately 10-fold more potent
than rimantadine (Table 2).
5.2. 2-(2-Aminoethyl)tricyclo[3.3.1.1]decan-2-ol (18) [3,7]
To a stirred suspension of LiAlH4 (1.50 g, 31 mmol), in dry THF
(20 mL) was added dropwise a solution of hydroxy nitrile 2 (1.13 g,
5.9 mmol) in dry THF (10 ml). The reaction mixture was stirred for
20 h at 20 ꢀC and then hydrolyzed with water and NaOH (10%),
under ice cooling, and dried (Na2CO3). The inorganic precipitate
was filtered off and washed with THF; the filtrate was concentrated
in vacuo (T < 40 ꢀC) to give 1.13 g of the solid aminoalcohol 4
(quantitative yield), mp 131 ꢀC (ether). I.R. (Nujol): v: 3349, 3269,
3171 cmꢁ1. 1H NMR (400 MHz, CDCl3): 1.47 (br d, 2H, H-4e, 9e), 1.67
(br d, 4H, H-6, 8), 1.77 (br t, 8H, H-1, 3, 5, 7, 10, CH2CH2NH2), 2.27 (br
d, 2H, H-4a, 9a), 2.98 (t, 2H, J ¼ 11.6 Hz, CH2CH2NH2); 13C NMR
(100 MHz, CDCl3): 27.4 (C-5), 27.6 (C-7), 32.7 (C-4, 9), 34.6 (C-8, 10),
37.0 (CH2CH2NH2), 37.3 (CH2CH2NH2), 37.5 (C-1, 3), 38.5 (C-6), 75.5
(C-2). Anal. Calcd. for C12H22NOCl. Calcd, %: C 62.19; H 9.57. Found,
%: C 62.42; H 9.63.
The targets of adamantane derivatives in trypanosomes are
unknown. Likewise, the mechanisms of action of other trypanoci-
dal drugs, including pentamidine, suramin and melarsoprol have
yet to been identified [30]. However, the mode of action of the
nitroheterocycle nifurtimox has been resolved [31]. This drug, in
combination with eflornithine, is now recommended as the treat-
ment of choice for late stage West African sleeping sickness [32].
Nifurtimox-resistance is due to down-regulation of the type I
nitroreductase which activates the drug in vivo. There is no cross-
resistance with rimantadine [31].
4. Conclusion
The major conclusions from this study can be summarized as
follows: (a) Introduction of the hydroxyl group adjacent to the
amine resulted in good antiviral activity, comparable to that of
rimantadine. (b) It is apparent that for a series of aminoadamantane
compounds, the relative antiviral activity is not directly comparable
to the relative trypanocidal potencies in cell culture. (c) The two
most active adamantane analogues identified in this report, 36 and
37, illustrate the synergistic effect on anti-trypanosome activity of
the lipophilic character of the side chain and the hydroxyl group.
Finally, the simultaneous anti-influenza virus A and trypanocidal
activity of aminoalcohol 21, along with its very low cytotoxicity, are
of particular interest and merit further investigation.
5.3. 2-Cyano- tricyclo[3.3.1.1]decane-2-carboxylic acid methyl ester
(23) [3,7]
A solution of nitrile 22 (14.20 g, 88.0 mmol) in dry THF (60 ml)
was added dropwise to a solution of LDA, prepared by adding a dry
THF solution of freshly distilled diisopropylamine (17.20 g,
170.5 mmol) to a solution of n-BuLi (54.52 ml, 2.5 M or 60 mmol) in
hexane and stirring the resulting solution for 30 min at ꢁ70 ꢀC
under an argon atmosphere. After stirring the mixture for 2 h,
a solution of freshly distilled methyl chloroformate (48.28 g,
510 mmol) in dry THF (50 ml) was added and the mixture was
stirred overnight to slowly reach room temperature. The solution
was then poured into crashed ice, extracted with ether; the organic
phase was washed with water and brine, dried (Na2SO4) and
evaporated under reduced pressure. The crude oil was purified by
vacuum distillation (bp0.01 ¼120 ꢀC) to afford 16.85 g (88%) of ester
23 as a low melting point solid. mp 45 ꢀC (Et2O-n-pentane);
5. Experimental
Melting points were determined using a Büchi capillary appa-
ratus and are uncorrected. IR spectra were recorded on a Per-
kineElmer 833 spectrometer. 1H and 13C NMR spectra were
recorded on a Bruker MSL 400 spectrometer, respectively, using
CDCl3 as solvent and TMS as internal standard. Carbon multiplici-
ties were established by DEPT experiments. The 2D NMR experi-
ments (HMQC, COSY and NOESY) were performed for the
elucidation of the structures of the new compounds.
I.R.(Nujol): v (CN) 2238, (C]O) 1741 cmꢁ1
CDCl3), (ppm) 1.65e2.15 (m, 12H, H-4, 5, 6, 7, 8, 9, 10), 2.44 (br s,
2H, H-1, 3), 3.74 (s, 3H, CH3).
;
1H NMR (400 MHz,
d
5.4. 2-(2-Aminoethyl)tricyclo[3.3.1.1]decan-2-ol (24) [3,7]
Microanalyses were carried out by the Service Central de
Microanalyse (CNRS) France, and the results obtained had
a maximum deviation of ꢂ0.4% from the theoretical value.
To a stirred suspension of LiAlH4 (10.6 g, 279 mmol) in dry THF
(150 ml) was added dropwise a solution of the cyanoester 23
(14.8 g, 67.5 mmol) in dry THF (150 ml). The reaction mixture was
refluxed for 30 h and then hydrolyzed with water and NaOH (10%)
under ice cooling and dried (Na2CO3). The inorganic precipitate was
filtered off, washed with THF, and the filtrate was concentrated in
vacuo. The liquid residue dissolved in ether (150 ml) and extracted
with HCl 5% (100 ml) (the aqueous layer must be kept acid). The
aqueous layer extracted with ether and alkalized with KOH 30%
under ice cooling. The solution was cooled and the precipitated
aminoalcohol 24 was filtered, washed with cool water and dried:
yield 12.3 g (93%); mp 133 ꢀC (THF-n-pentane); IR (Nujol) v
5.1. 2-Hydroxy-tricyclo[3.3.1.1]decane-2-acetonitrile (17) [3,7]
To a stirred solution of n-butyl lithium 2.5 M in hexanes (22 ml,
50 mmol), in dry THF (22 ml) was added, over a period of 7 min,
a solution of acetonitrile (2.05 g, 50 mmol) in dry THF (50 ml) at
ꢁ80 ꢀC under an argon atmosphere. After stirring the mixture for
1 h at ꢁ80 ꢀC, a solution of adamantanone 1 (7.50 g, 50 mmol), in
dry THF (50 ml) was added over a period of 5 min. The cold bath
was removed and the resulting suspension was stirred for 10 min.
The mixture was treated with ice-water (50 ml) and concd HCl
(5 ml), extracted with Et2O (3 ꢄ 50 ml) and the organic phase was
washed with water (40 ml), dried (Na2SO4) and concentrated in
vacuo to afford 9.26 g of the solid hydroxy nitrile 2 (97%), mp 140 ꢀC
(THF e petr. ether). I.R. (Nujol): v: (OH) 3437, (CN) 2259 cmꢁ1. 1H
NMR (400 MHz, CDCl3): 1.62 (br d, 2H, H-4e, 9e), 1.71 (br d, 4H, H-6,
3378 cmꢁ1, 3175 cmꢁ1 (OH); 1H NMR (400 MHz, CDCl3),
d: 1.51 (br t,
4H, H-4e, 8, 9e), 1.64 (br d, 4H, H-1, 3, 6), 1.81 (br s, 2H, H-5, 7), 1.89
(br d, 1H, H-10), 2.00 (br d, 2H, H-4a, 9a), 2.59 (br s, 2H, NH2), 3.04
(s, 2H, CH2NH2), 3.83 (br s, 2H, CH2OH) (ppm); 13C NMR (CDCl3,
100 MHz),
d: 28.0 (C-5), 28.2 (C-7), 29.8 (C-1, 3), 32.7 (C-4, 9), 32.9
(C-8,10), 39.4 (C-6), 40.9 (C-2), 48.8 (CH2NH2), 70.8 (CH2OH) (ppm).

5028
G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
Anal. Calcd. for C12H22NOCl Calcd. (%): C: 62.19, H: 9.57, N: 6.04.
Found (%): C: 62.48, H: 6.50, N: 5.87.
Anal. Calcd. for C12H21NO Calcd. (%): C: 73.80, H: 10.84, N: 7.17.
Found (%): C: 73.71, H: 10.81, N: 7.31.
5.8. N-methyl-2-(2-pyridinyl)-tricyclo[3.3.1.1]decan-2-amine
(32) [3,7]
5.5. 4-Hydroxy-tricyclo[4.3.1.0]decan-4-acetonitrile (26) [3,8]
To a stirred solution of n-butyl lithium 2.5 M in hexanes
(10.6 ml, 26.6 mmol), in dry THF (10 ml) was added, over a period of
4 min, a solution of acetonitrile (1.09 g, 26.6 mmol) in dry THF
(20 ml) at ꢁ80 ꢀC under an argon atmosphere. After stirring the
mixture for 1 h at ꢁ80 ꢀC, a solution of protoadamantanone 25
(2.0 g, 13.3 mmol), in dry THF (20 ml) was added over a period of
10 min. The cold bath was removed and the resulting suspension
was stirred for 10 min. The mixture was treated with ice-water
(50 ml), extracted with Et2O (3 ꢄ 30 ml) and the organic phase was
washed with water (3 ꢄ 10 ml), dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
using as eluents Et2O-n-hexane 2/1 to afford 2.83 g of the solid
hydroxy nitrile 26 (95%), mp 61 ꢀC (Et2O-n-pentane). I.R. (Nujol): v
3464 cmꢁ1 (OH), 2253 cmꢁ1 (CN); 1H NMR (400 MHz, CDCl3)
To a stirred solution of 2.5 M n-BuLi in hexanes (12.2 ml,
30.5 mmol), a solution of 2-bromopyridine (4.81 g, 30.5 mol) in dry
ether (30 ml) was added dropwise at ꢁ85 ꢀC under argon atmo-
sphere. The mixture was then warmed to ꢁ42 ꢀC and a solution of
imine 31 (2.0 g, 12.2 mmol) and 1-(2-methoxyphenoxy)-N,N-
dimethyl-3-phenylpropan-2-amine (2.0 g, 13.3 mmol) in dry
toluene (25 ml) was added dropwise over 30 min. The reaction
mixture was stirred at ꢁ42 ꢀC for 3 h and allowed to reach slowly
room temperature and poured into water under ice cooling. The
organic layer was separated and the aqueous layer was extracted
with ether and the combined organic extracts were washed several
times with water, dried (Na2SO4), and evaporated in vacuo to give
a viscuous oil. After purification with flash column chromatography
through silica gel using ether as eluent the solid base 32 was
obtained (1.55 g, 53%); mp 71 ꢀC (n-hexane); 1H NMR (400 MHz,
endoeexo,
OH), 2.30e2.36 (q, 2H, H-3, 8), 2.52e2.72 (m, 3H, H-9a, CH2CN); 13
NMR (CDCl3, 100 MHz), (ppm) 28.2/29.2 (C-6), 32.0 (CH2CN), 33.0
d (ppm) 1.22e2.16 (complex m,12H, H-1, 2, 5, 6, 7, 9e,10,
C
CDCl3), d (ppm): 1.25 (bs, 1H, NH), 1.56e1.76 (m, 9H, H-4e, 6, 7, 8, 9e,
d
10), 1.82 (s, 1H, H-5), 1.84 (s, 3H, CH3), 2.32 (d, 2H, J ¼ 11.6 Hz, H-4a,
9a), 2.52 (s, 2H, H-1, 3), 7.02 (t, J ¼ 7.2 Hz, 5.2 Hz, 5-Hpyr), 7.25 (d,
J ¼ 8.0 Hz, 3-Hpyr), 7.58 (t, J ¼ 15.6 Hz, 8.0 Hz, 4-Hpyr), 8.54 (d,
(C-8), 33.6/34.3 (C-9), 35.3/35.6 (C-1), 35.8 (C-2), 39.5/39.6 (C-10),
41.6/41.8 (C-7), 42.2/42.6 (C-5), 44.7/45.5 (C-3), 72.2/73.6 (C-4),
118.0/118.2 (CN). Anal. Calcd. for C12H17NO Calcd. (%): C: 75.35, H:
8.96, N: 7.32. Found (%): C: 75.12, H: 8.89, N: 7.67.
J ¼ 4.8 Hz, 6-Hpyr); 13C NMR (100 MHz, CDCl3),
d (ppm): 27.1 (C-5),
27.5 (CH3), 27.9 (C-7), 32.0 (C-1, 3), 32.4 (C-4, 9), 34.1 (C-8, 10), 38.1
(C-6), 63.1 (C-2),120.8 (C-5pyr),121.2 (C-3pyr),135.2 (C-4pyr),149.1
(C-6pyr), 163.9 (C-2pyr). Anal. Calcd. for C16H22N2 Calcd. (%): C:
79.29, H: 9.15. Found (%): C: 79.61, H: 9.49.
5.6. 4-(2-Aminoethyl)tricyclo[4.3.1.0]decan-4-ol (27) [3,8]
To a stirred suspension of LiAlH4 (2.00 g, 52.0 mmol), in dry
ether (30 ml) was added dropwise a solution of hydroxy nitrile 26
(2.21 g, 11.5 mmol) in dry ether (20 ml). The reaction mixture was
stirred for 20 h at 20 ꢀC and then hydrolyzed with water and NaOH
(10%), under ice cooling, and dried (Na2CO3). The inorganic
precipitate was filtered off and washed with ether; the filtrate was
concentrated in vacuo (T < 40 ꢀC) to give 2.15 g of the solid ami-
noalcohol 27 (yield 95%), mp 100 ꢀC (Et2O-n-pentane), I.R.(Nujol) v
3364 cmꢁ1 (OH), 3290 cmꢁ1 (NH2); 1H NMR (400 MHz, CDCl3)
5.9. 4-[3-(Dimethylamino)propylo]-4-tricyclo[4.3.1.0]decanol
(36) [3,8]
A
solution of (3-chloropropyl)dimethylamine (8.09 g,
66.6 mmol) in dry benzene (50 ml) was added dropwise to
magnesium turnings (1.7 g, 0.071 g-at)] and the mixture was stirred
and heated until complete dissolution. Then a solution of proto-
adamantanone 25 (2.00 g, 13.3 mmol) in dry benzene (25 ml) was
added and the mixture was refluxed for 4 h and then was hydro-
lyzed under ice cooling by the addition of saturated NH4Cl solution.
The aqueous phase was extracted with Et2O (3 ꢄ 20 ml) and the
combined organic extracts were washed with water (3 ꢄ 20 ml)
and dried (Na2SO4). The solvent was evaporated in vacuo and the
residue formed was crystallized upon treatment with n-pentane.
The solid was filtered off and washed with a cold n-pentane to give
aminoalcohol 36 (3.06 g, 97%) as a white solid; mp 67 ꢀC (n-hexane)
endoeexo,
d (ppm) 1.25e2.00 (complex m, 14H, H-2, 5, 6, 7, 9, 10,
CH2CH2NH2, OH), 2.07e2.11 (t, 1H, H-1), 2.22e2.30 (m, 2H, H-3, 8),
2.74 (br s, 2H, NH2), 3.00e3.04 (m, 2H, CH2NH2); 13C NMR (CDCl3,
100 MHz), d (ppm) 28.7/29.7 (C-6), 32.6 (C-9), 33.3/33.6 (C-8), 33.9/
35.3 (C-2), 35.4/35.8 (C-1), 37.8/38.3 (CH2NH2), 40.0/40.1 (C-10),
42.3/42.6 (C-7), 42.6/42.8 (C-5), 42.9/43.1 (CH2CH2NH2), 45.3/45.5
(C-3), 74.4/75.5 (C-4). Anal. Calcd. for C12H21NO Calcd. (%): C: 73.80,
H: 10.84, N: 7.17. Found (%): C: 73.71, H: 10.81, N: 7.27.
I.R. (Nujol) v (OH) 3288 cmꢁ1. 1H NMR (400 MHz, CDCl3),
d (ppm):
5.7. 1-(2-Aminoethyl)tricyclo[3.3.1.1]decan-2-ol (28) [3,7]
1.26 (d, J ¼ 12.8 Hz, 1H, H-9e), 1.39 (dd, J ¼ 13.4 Hz, 1.6 Hz, 1H, H-
10e), 1.45 (dd, J ¼ 11.2 Hz, 2.8 Hz, 1H, H-5e), 1.52e1.83 (complex m,
9H, H-4e, 5a, 7e, 9a, 10a, CH2CH2CH2N, CH2CH2CH2N), 1.89e1.92 (m,
2H, H-6, 7a), 1.97 (dd, J ¼ 13.6 Hz, 2.8 Hz, 1H, H-2a), 2.06e2.12 (m,
3H, H-1, 3, 8), 2.19 (s, 6H, 2xCH3), 2.28 (t, J ¼ 11.6 Hz, 5.6 Hz, 2H,
CH2CH2CH2N), 6.30 (bs, 1H, OH); 13C NMR (100 MHz, CDCl3),
A solution of aminoalcohol 27 (1.10 g, 5.64 mmol), dioxane
(13 ml) and H2SO4 10% (4 ml) was heated for 2 h in a steam bath.
After evaporation of the dioxani in vacuo, water was added and the
mixture was alkalized with a solution of NaOH 20%. The aqueous
solution was extracted with ether (3 ꢄ 25 ml), dried (Na2CO3) and
concentrated in vacuo to give aminoalcohol 28 as a white solid
d
(ppm): 22.2 (CH2CH2CH2N), 29.9 (C-6), 32.6 (C-9), 33.5 (C-1), 34.2
(C-2), 35.5 (C-8), 40.2 (C-10), 41.4 (CH2CH2CH2N), 42.6 (C-7), 43.0
(C-5), 45.0 (2xCH3), 46.3 (C-3), 60.1 (CH2CH2CH2N), 71.5 (C-4). Anal.
Calcd. for C15H27NO Calcd. (%): C: 75.90, H: 11.46, N: 5.90. Found (%):
C: 76.11, H: 11.19, N: 6.27.
(1.05 g, 96%). Mp 87 ꢀC (Et2O-n-hexane), I.R.(Nujol): v 3358 cmꢁ1
3282 cmꢁ1 (NH); 1H NMR (400 MHz, CDCl3),
(ppm) 0.98e1.00 (d,
,
d
1H, H-9e), 1.12e1.15 (m, 1H, CHACH2NH2), 1.29e1.46 (complex m,
4H, 4e, 6, CHB-H), 1.53e1.66 (complex m, 3H, H-8, 10a), 1.72e1.83
(complex m, 3H, H-5, 7, 10e), 1.91 (d, 1H, H-3), 2.00e2.05 (m, 2H, 4a,
H-9a), 2.66e2.80 (m, 2H, CH2CH2NH2), 3.17 (br s, 3H, NH2, OH),
5.10. 1-[3-(dimethylamino)propyl]-tricyclo[3.3.1.1]decan-2-ol
(37) [3,7]
3.45e3.46 (d, 1H, H-2); 13C NMR (CDCl3, 100 MHz),
d (ppm) 28.1 (C-
5, 7), 30.8 (C-4), 34.5 (C-3), 35.3 (CH2NH2), 35.6 (C-9), 36.6 (C-10),
37.0 (C-1), 37.4 (C-8), 44.0 (C-6), 44.8 (CH2CH2NH2), 75.6 (C-2).
A solution of aminoalcohol 36 (2.30 g, 9.7 mmol) and H2SO4 15%
(10 ml) in dioxane (25 ml) was heated in a boiling steam bath for

G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
5029
2 h. After removal in vacuo of diaxane, the residue was alkalized
with an aq solution of NaOH 10%, extracted with Et2O and the
combined organic extracts were dried (Na2CO3). The solvent was
evaporated in vacuo to give 37 as a viscous oil (2.15 g, 93%), which
was converted to its hydrochloride salt. MpHCl 206 ꢀC (EtOH-Et2O).
(CH2CH2CH2N). Anal. Calcd. for C15H29ClN2: C: 66.03, H: 10.71.
Found: C: 66.39, H: 11.09.
5.14. (2E)-1-phenyl tricyclo[3.3.1.1]decan-2-one oxime (45) [3,7]
I.R.(Nujol) v (OH) 3190 cmꢁ1. 1H NMR (400 MHz, CDCl3),
d
(ppm):
A mixture of the ketone 44 [9d] (900 mg, 3.9 mmol), hydrox-
ylamine hydrochloride (490 mg, 7.0 mmol), and sodium acetate
trihydrate (1.90 g, 14.0 mmol) in EtOH (25 ml) and H2O (2.5 ml) was
refluxed for 3 h. After evaporation under reduced pressure of 1/3 of
the volume of the solvents, H2O was added to the residue and the
solid material formed was filtered, washed with H2O and dried to
give after recrystallization (EtOH/H2O) the desired oxime 45 as
a white crystalline solid (923 mg, 98%); mp 250 ꢀC (dec.). IR.
(Nujol): v 1662 cmꢁ1 (C]N).
1.03 (t, J ¼ 13.2 Hz, 4.6 Hz, 2H, CH2CH2CH2N),1.11 (bs,1H, H-9e), 1.14
(bs, 1H, H-10e), 1.28e1.94 (complex m, 13H, H-3, 4, 5, 6, 7, 8 9a, 10a,
CH2CH2CH2N), 2.16 (s, 6H, 2xCH3), 2.27 (t, J ¼ 11.6 Hz, 5.6 Hz, 2H,
CH2CH2CH2N), 3.51 (s, 1H, H-2), 3.82 (bs, 1H, OH); 13C NMR
(100 MHz, CDCl3), d (ppm): 19.7 (CH2CH2CH2N), 28.1 (C-5), 28.2 (C-
7), 30.9 (C-4), 34.7 (C-3), 36.5 (C-10), 36.9 (C-1), 37.0
(CH2CH2CH2N), 37.4 (C-6), 37.9 (C-9), 40.4 (C-8), 45.3 (2xCH3), 60.6
(CH2CH2CH2N), 75.2 (C-2). Anal. Calcd. for C15H27NO Calcd. (%): C:
75.90, H: 11.46, N: 5.90. Found (%): C: 76.25, H: 11.30, N: 6.07.
5.15. 1-Phenyl-tricyclo[3.3.1.1]decan-2-amine (46) [3,7]
5.11. 1-[3-(dimethylamino)propyl]-tricyclo[3.3.1.1]decan-2-one
(38) [3,7]
1-Phenyladamantan-2-one oxime (819 mg 3.4 mmol) in abso-
lute EtOH (25 ml) under H2 (55 psi) in the presence of Raney Ni was
heated at 90 ꢀC for 8 h. The resulting suspension was filtered
through Celite, and the filtrate was concentrated in vacuo to give
0.63 g of a viscous liquid product, which was treated with an HCl
saturated ethanolic solution. The solvent was evaporated, and
water was added to the resulting residue, which was chilled to 0 ꢀC.
The precipitate formed was filtered, washed with water, and dried
to give the hydrochloride salt of the title amine 46. Yield 81%.
Mp > 255 ꢀC (hydrochloride salt, EtOH/Et2O). 1H NMR (400 MHz,
To a solution of aminoalcoholol 37 (1.34 g, 5.6 mmol) in acetone
(25 ml) was added, during a 0.5 h period, Jones reagent (20.0 ml,
1 mM) at 15 ꢀC. After stirring for 24 h at ambient temperature,
isopropanol (3 ml) was added and stirring was continued for an
additional 1 h. The reaction mixture was filtered off and the filtrate
was evaporated in vacuo. The residue was alkalified with Na2CO3
and then was extracted with Et2O (3 ꢄ 20 ml). The combined
organic extracts were washed with water (2 ꢄ 10 ml), dried
(Na2CO3), concentrated in vacuo to afford aminoketone 38 (1.14 g,
CDCl3):
4, 5, 6, 7, 8, 9a, 10, NH2), 2.61 (s, 1H, H-2), 7.00e7.27 (m, 5H, H-
aromatic); 13C NMR (100 MHz, CDCl3),
(ppm) 28.3 (C-5, 7), 30.5
d
¼ 1.19 (d, 1H, J ¼ 12.0 Hz, H-9e), 1.31e2.03 (m, 14H, H-3, 3,
87%) as a viscous oil; I.R. (Nujol): v (C]O) 1710]cmꢁ1
.
1H NMR
d
(400 MHz, CDCl3), (ppm) 1.30e1.35 (m, 2H, CH2CH2CH2N),
d
(C-9), 35.9 (C-4), 36.1 (C-3), 37.2 (C-6), 37.6 (C-1, 8), 41.1 (C-10), 59.4
(C-2), 126.1 (Carom-4), 128.6 (Carom-2, 6), 131.6 (Carom-3, 5), 148.4
(Carom-1). Anal. Calcd. for C16H22ClN: C: 72.85, H: 8.41. Found: C:
72.52, H: 8.09.
1.37e1.46 (m, 2H, CH2CH2CH2N), 1.56e2.08 (complex m, 12H, H-4,
5, 6, 7, 8, 9, 10), 2.19 (s, 6H, 2xCH3), 2.23 (t, J ¼ 14.4 Hz, 6.8 Hz, 2H,
CH2CH2CH2N), 2.51 (bs,1H, H-3); 13C NMR (50 MHz, CDCl3),
d (ppm)
21.5 (eCH2CH2N), 28.1 (C-5, 7), 30.7 (eCH2CH2CH2N), 39.3 (C-4, 9),
44.1 (C-8, 10), 45.5 (2xCH3), 47.1 (C-3), 49.2 (C-1), 60.5
(CH2CH2CH2N), 218.2 (C]O). Anal. Calcd. for C15H25NO: C: 76.55, H:
10.71. Found: C: 76.86, H: 10.95.
5.16. Tricyclo[4.3.1.0]decan-4-one oxime (47) [3,8]
A
mixture of protoadamantanone 25 (700 mg, 4.7 mmol),
hydroxylamine hydrochloride (590 mg, 8.4 mmol), and sodium
acetate trihydrate (2.28 g, 16.8 mmol) in EtOH (25 ml) and H2O
(5 ml) was refluxed for 3 h. After evaporation under reduced
pressure of 1/3 of the volume of the solvents, H2O was added to the
residue and the solid material formed was filtered, washed with
H2O and dried to give after recrystallization (Et2O/PE) the desired
oxime 47 as a white crystalline solid (543 mg, 70%); mp 128 ꢀC
(dec.). IR. (Nujol): v 3209 cmꢁ1 (OH), 1666 cmꢁ1 (C]N).
5.12. 1-[3-(dimethylamino)propyl]-tricyclo[3.3.1.1]decan-2-one
oxime (39) [3,7]
A mixture of ketone 38 (0.70 g, 2.9 mmol), NH2OH$HCl (0.41 g,
6.0 mmol) and CH3COONa.3H2O (1.36 g, 10.0 mmol) and ethanol
90% (10 ml) was refluxed for 3 h. The ethanol was removed in vacuo
and the residue was alkalized with Na2CO3, extracted with ether,
dried (Na2CO3) and concentrated under reduced pressure to give 39
as a white low melting solid (0.77 g, quantitative yield); mp 64 ꢀC
(n-hexane). IR. (Nujol): v 1648 cmꢁ1 (C]N).
5.17. 4-Tricyclo[4.3.1.0]decanamime (48) [3,8]
Oxime 47 (330 mg 2.0 mmol) in absolute EtOH (15 ml) under H2
(55 psi) in the presence of Raney Ni was heated at 90 ꢀC for 8 h. The
resulting suspension was filtered through Celite, and the filtrate
was concentrated in vacuo to give 0.63 g of a viscous liquid product,
which was treated with an HCl saturated ethanolic solution. The
solvent was evaporated, and water was added to the resulting
residue, which was chilled to 0 ꢀC. The precipitate formed was
filtered, washed with water, and dried to give the hydrochloride
salt of the title amine 48. Yield 70%. Mp > 250 ꢀC (hydrochloride
salt, EtOH/Et2O). I.R.(Nujol) v 3280 cmꢁ1 (NH2); 1H NMR (400 MHz,
5.13. 2-Amino-N,N-dimethyl-tricyclo[3.3.1.1]decane-1-
propanamine (40) [3,7]
A solution of oxime 39 (550 mg, 2.2 mmol) in dry EtOH was
hydrogenated over Raney-Ni catalyst for 5 h, at 65 ꢀC, and under
pressure (55 psi). The catalyst was filtered off and the solvent was
evaporated under vacuum to afford a viscous oil (amine 40)
(570 mg, 95% yield), which was converted to its hydrochloride salt;
MpHCl > 250 ꢀC (EtOH); 1H NMR (400 MHz, CDCl3),
d (ppm) 0.93
(bd, 1H, 9e), 1.16e1.85 (complex m, 18H, H-3, 4a, 5, 6, 7, 8, 9, 10,
CH2CH2CH2N, CH2CH2CH2N, NH2), 2.18 (s, 6H, 2xCH3), 2.19 (t,
J ¼ 14.2 Hz, 6.5 Hz, 2H, CH2CH2CH2N), 2.67 (bs, 1H, H-2); 13C NMR
CDCl3) endo/exo, 1/1,,
6, 7, 8, 9, 10-H, NH2), 2.34 (t, 1H, 4-H); 13C NMR (CDCl3, 100 MHz),
(ppm) 28.8/28.9 (6-C), 31.1 (7-C), 31.8/31.9 (2-C), 34.6/34.7 (8-C),
35.1/35.2 (1-C), 39.7/39.9 (5-C), 41.3/41.6 (10-C), 42.6 (9-C), 43.3/
43.5 (3-C), 49.5/49.9 (4-C). Anal. Calcd. for C10H18ClN: C: 63.99, H:
9.67. Found: C: 63.75, H: 9.35.
d (ppm) 0.98e2.20 (complex m, 14H, 1, 2, 3, 5,
d
(50 MHz, CDCl3),
d
(ppm) 20.2 (eCH2CH2N), 28.2 (C-5), 28.4 (C-7),
30.6 (eCH2CH2CH2N), 35.6 (C-3), 35.7 (C-1), 36.8 (C-4), 37.2 (C-10),
37.4 (C-6), 37.5 (C-9), 41.1 (C-8), 45.5 (2xCH3), 57.3 (C-2), 60.6

5030
G. Zoidis et al. / European Journal of Medicinal Chemistry 45 (2010) 5022e5030
1534e1541;
5.18. T. brucei culturing and drug test
(h) G. Zoidis, D. Benaki, V. Myrianthopoulos, L. Naesens, E. De Clercq, E. Mikros,
N. Kolocouris, Tetrahedron Lett. 50 (2009) 2671e2675;
(i) E. De Clercq, Nat. Rev. Drug Disc. 5 (2006) 1015e1025;
Bloodstream form T. brucei (strain 427) were cultured at 37 ꢀC in
modified Iscove’s medium [33]. Trypanocidal activity was assessed
by growing parasites in 4 ml cultures for 48 h in the presence of
(j) A. Kolocouris, P. Spearpoint, S.R. Martin, A.J. Hay, M. López-Querol, F.X. Sureda,
E. Padalko, J. Neyts, E. De Clercq, Bioorg. Med. Chem. Lett. 18 (2008) 6156e6160.
[10] Recently an X-ray structure of M2TM and M2TMeamantadine complex was
published from the DeGrado’s group: (a) A.L. Stouffer, R. Acharya, D. Salom,
A.S. Levine, L. Di Costanzo, C.S. Soto, V. Tereshko, V. Nanda, S. Stayrook,
W. DeGrado, Nature 451 (2008) 596e599 The first work on the amantadine
location inside the M2 protein pore was a neutron diffraction study:;
(b) K.C. Duff, P.J. Gilchrist, A.M. Saxena, J.P. Bradshaw, Virology 202 (1994)
287e293 Elegant solid-state NMR studies on this system have been carried
out by N. Cross lab:;
a range of drug concentrations, from 0.1 to 25 mM, and determining
the levels which inhibited growth by 50% (IC50) and 90% (IC90). In
the case of untreated cultures, cell densities increased from
0.25 ꢄ105 to 1 ꢄ106 over this period. Cell densities at each drug
concentration were determined using a hemocytometer and drug
sensitivity was expressed as a percentage of growth of control cells.
(c) J. Hu, T. Asbury, S. Achuthan, C. Li, R. Bertram, J.R. Quine, R. Fu, T.A. Cross,
Biophys. J. 92 (2007) 4335e4343 For molecular dynamics studies of the
M2TMeamantadine or rimantadine complex see:;
Acknowledgments
(d) M.S.P. Sansom, I.D. Kerr, Protein Eng. 6 (1993) 65e74;
(e) M. Yi, T.A. Cross, H.-X. Zhou, J. Phys. Chem. B 112 (2008) 7977e7979;
(f) P. Intharathep, C. Laohpongspaisan, T. Rungrotmongkol, A. Loisruangsin,
M. Malaisree, P. Decha, O. Aruksakunwong, K. Chuenpennit, N. Kaiyawet,
P. Sompornpisut, S. Pianwanit, S. Hannongbua, J. Mol. Graph. Model. 27 (2009)
921e929.
Dr. Zoidis would like to thank the State Scholarship Foundation
of Greece and the University of Athens (ELKE Account) for financial
support. L. Naesens acknowledges the financial support from the
International Consortium for Anti-Virals (ICAV); the Flemish Fonds
voor Wetenschappelijk Onderzoek (FWO No. 9.0188.07) and the
Geconcerteerde Onderzoeksacties (GOA/10/014); and the technical
assistance from Leentje Persoons and Frieda De Meyer. J. Kelly
acknowledges support from the Wellcome Trust (Ref. 5632).
[11] (a) C. Wang, K. Takeuchi, L.W. Pinto, R.A. Lamb, J. Virol. 67 (1993) 5585e5594;
(b) I.V. Chizhmakov, F.M. Geraghty, D.C. Ogden, A. Hayhurst, M. Antoniou,
A.J. Hay, J. Physiol. 494 (1996) 329e336.
[12] (a) L. Pinto, R.A. Lamb, J. Biol. Chem. 281 (2006) 8997e9000;
(b) L. Pinto, R.A. Lamb, FEBS Lett. 560 (2004) 1e2;
(c) W.B. Fischer, M.S.P. Sansom, Biochim. Biophys. Acta 1561 (2002) 27e45;
(d) See the articles in, FEBS Lett. 552 (2003) 1.
[13] S. Grambas, A.J. Hay, Virology 190 (1992) 11e18.
References
[14] World Health Report, 2004, Statistical Annex Table 2.
[15] P.G.E. Kennedy, J. Clin. Invest. 113 (2004) 496e504.
[16] S.L. Croft, M.P. Barrett, J.A. Urbina, Trends Parasitol. 21 (2005) 508e512.
[17] W.E. Gutteridge, Brit. Med. Bull. 41 (1985) 162e168.
[18] F. Doua, F.B. Yapo, Acta Trop. 54 (1993) 163e168.
[19] P.G.E. Kennedy, Int. J. Parasitol. 36 (2006) 505e512.
[20] J.M. Kelly, M.A. Miles, A.C. Skinner, Antimicrob. Agents Chemother. 43 (1999)
985e987.
[1] (a) J.K. Taubenberger, A.H. Reid, R.M. Lourens, R. Wang, G. Jin, T.G. Fanning,
Nature 437 (2005) 889e893;
(b) R.J. Webby, R.G. Webster, Science 302 (2003) 1519e1522.
[2] (a) C.J. Russell, R.G. Webster, Cell 123 (2005) 368e371;
(b) R.G. Webster, R.J. Webby, E. Hoffmann, J. Rodenberg, M. Kumar, H.-J. Chu,
P. Seiler, S. Krauss, T. Songserm, Virology 351 (2006) 303e311;
(c) A.N. Abdel-Ghafar, T. Chotpitayasunondh, Z. Gao, F.G. Hayden,
D.H. Nguyen, M.D. de Jong, A. Naghdaliyev, J.S. Peiris, N. Shindo, S. Soeroso,
T.M. Uyeki, N. Eng. J. Med. 358 (2008) 261e273.
[21] J.M. Kelly, G. Quack, M.A. Miles, Antimicrob. Agents Chemother. 45 (2001)
1360e1366.
[22] J.L.M.A. Schlatmann, J.G. Korsloot, J. Schut, Tetrahedron 26 (1970) 949e954.
[23] M.Yu. Skomorokhov, M.V. Leonova, A.K. Shiryaev, Yu. N. Klimochkin, Russ. J.
Org. Chem. 39 (2003) 1360e1361.
[24] (a) Z. Majersky, Z. Hamesrak, Org. Synth. 50 (1988) 958e962;
(b) N. Kolocouris, G. Zoidis, C. Fytas, Synlett 7 (2007) 1063e1066.
[25] D. Setaki, D. Tataridis, G. Stamatiou, A. Kolocouris, G.B. Foscolos, G. Fytas,
N. Kolocouris, E. Padalko, J. Neyts, E. De Clercq, Bioorg. Chem. 34 (2006) 248e273.
[26] C.D. Jones, M. Kaselj, R.N. Salvatore, W.J. le Noble, J. Org. Chem. 63 (1998)
2758e2760.
[3] World Health Organization (WHO) (2009).
[4] (a) R.B. Belshe, N. Engl. J. Med. 353 (2005) 2209e2211;
(b) E. De Clercq, J. Neyts, Trends Pharmacol. Sci. 28 (2007) 280e285.
[5] (a) T.M. Tumpey, A. Garcva-Sastre, A. Mikulasova, J.K. Taubenberger, D.E. Swayne,
P. Palese, C.F. Basler, Proc. Natl. Acad. Sci. U.S.A. 99 (2002) 13849e13854;
(b) N.A. Ilyushina, N.V. Bovin, R.G. Webster, E.A. Govorkova, Antiviral Res. 70
(2006) 121e131.
[6] (a) A.J. Hay, A.J. Wolstenholme, J.J. Skehel, M.H. Smith, EMBO J. 4 (1985)
3021e3024;
[27] (a) Y.M. Shafran, V.A. Bakulev, V.S. Mokrushin, Russ. Chem. Rev. 58 (1989)
148e162;
(b) A.J. Hay, Semin. Virol. 3 (1992) 21e30.
[7] L.H. Pinto, L.J. Holsinger, R.A. Lamb, Cell 69 (1992) 517e528.
[8] In Burger’s Medicinal Chemistry, fifth ed.; Wolff, M.E., John Wiley & Sons: New
York; vol. 4, pp 590e591.
(b) N.A. Hassan, E. Bayer, J.C. Jochims, J. Chem. Soc., Perkin Trans. 1 (1998)
3747e3757.
[28] D. Tataridis, G. Fytas, A. Kolocouris, C. Fytas, N. Kolocouris, G.B. Foscolos,
E. Padalko, J. Neyts, E. De Clercq, Bioorg. Med. Chem. Lett. 17 (2007) 692e696.
[29] (a) E. Vanderlinden, F. Goktas, Z. Cesur, M. Froeyen, M.L. Reed, C.J. Russell,
N. Cesur, L. Naesens, J. Virol. (2010 Feb 24) (Epub ahead of print);
(b) L. Naesens, E. Vanderlinden, E. Roth, J. Jeko, G. Andrei, R. Snoeck,
C. Pannecouque, E. Illyés, G. Batta, P. Herczegh, F. Sztaricskai, Antiviral Res. 82
(2009) 89e94.
[30] S.R. Wilkinson, J.M. Kelly, Expert Rev. Mol. Med. 11 (2009) e31.
[31] S.R. Wilkinson, M.C. Taylor, D. Horn, J.M. Kelly, I. Cheeseman, Proc. Natl. Acad.
Sci. USA 105 (2008) 5022e5027.
[9] (a) N. Kolocouris, G.B. Foscolos, A. Kolocouris, P. Marakos, N. Pouli, G. Fytas,
S. Ikeda, E. De Clercq, J. Med. Chem. 37 (1994) 2896e2902;
(b) N. Kolocouris, A. Kolocouris, G.B. Foscolos, G. Fytas, J. Neyts, E. Padalko,
J. Balzarini, R. Snoeck, A. Graciela, E. De Clercq, J. Med. Chem. 39 (1996)
3307e3318;
(c) G. Zoidis, N. Kolocouris, G.B. Foscolos, A. Kolocouris, G. Fytas, P. Karayannis,
E. Padalko, J. Neyts, E. De Clercq, Antiviral Chem. Chemother. 14 (2003) 153e164;
(d) I. Papanastasiou, A. Tsotinis, N. Kolocouris, S.R. Prathalingam, J.M. Kelly, J. Med.
Chem. 51 (2008) 1496e1500;
(e) N. Kolocouris, G. Zoidis, G.B. Foscolos, G. Fytas, R.S. Prathalingham, J.M. Kelly,
L. Naesens, E. De Clercq, Bioorg. Med. Chem. Lett. 17 (2007) 4358e4362;
(f) G. Zoidis, A. Tsotinis, N. Kolocouris, J.M. Kelly, R.S. Prathalingham, L. Naesens,
E. De Clercq, Org. Biomol. Chem. 6 (2008) 3177e3185;
[32] O. Yun, G. Priotto, J. Tong, L. Flevaud, F. Chappuis, PLoS Negl. Trop. Dis. 4
(2010) e720.
[33] S.R. Wilkinson, R. Prathalingam, M.C. Taylor, A. Ahmed, D. Horn, J.M. Kelly,
Free Radic. Biol. Med. 40 (2006) 198e209.
(g) G. Zoidis, N. Kolocouris, L. Naesens, E. De Clercq, Bioorg. Med. Chem. 17 (2009)