New aminoadamantane derivatives with antiproliferative activity

Article abstract of DOI:10.1007/s00044-013-0798-7

1-Benzyl-2-aminoadamantanes 2a-c, conformationally constrained aminoadamantanes 3a, b and 4 and diaminoadamantanes derivatives 5a-c, 6a-c were synthesized and tested as antiproliferative agents. The in vitro biological evaluation showed a significant difference in activity between 1-phenyl and 1-benzyl derivatives. Springer Science+Business Media 2013.

Full text of DOI:10.1007/s00044-013-0798-7

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2014) 23:1966–1975
DOI 10.1007/s00044-013-0798-7
ORIGINAL RESEARCH
New aminoadamantane derivatives with antiproliferative activity
•
Ioannis Papanastasiou Andrew Tsotinis
•
•
Nicolas Kolocouris Spyros P. Nikas
•
Alexandre Vamvakides
Received: 19 June 2013 / Accepted: 12 September 2013 / Published online: 27 September 2013
Ó Springer Science+Business Media New York 2013
Abstract 1-Benzyl-2-aminoadamantanes 2a–c, conform-
ationally constrained aminoadamantanes 3a, b and 4 and
diaminoadamantanes derivatives 5a–c, 6a–c were synthe-
sized and tested as antiproliferative agents. The in vitro
biological evaluation showed a significant difference in
activity between 1-phenyl and 1-benzyl derivatives.
anti-Parkinson (Chakrabarti et al., 1976) activity. More-
over, it is well documented that the incorporation of the
adamantyl moiety into the skeleton of various molecules
increases their antiproliferative potency, possibly due to the
lipophilic character of adamantane or its unique structure.
Such examples include aromatic carboxylic acids (Cinci-
nelli et al., 2003; Dawson et al., 2008), pyrimidines, pyr-
idines (Kazimierczuk et al., 2001) and cyclic imides
(Shibata et al., 1995; Tsuji et al., 2000; Wang et al., 1997,
1998, 2002) with anticancer activity. Recently, aminoaro-
matic adamantane (Wang et al., 2004) and bisubstituted
adamantane derivatives, with marked antiproliferative
activity on different human cell lines, were reported (Ze-
firova et al., 2002; Smith et al., 2006; Wang et al., 2003).
In our effort to develop new antiproliferative agents, we
have synthesized 1-benzyl-2-aminoadamantanes 2a–c and
the conformationally constrained fused three-membered
ring systems 3 and 4. We have also introduced into the
skeleton of derivatives 2 a second nitrogen atom, 2 or 3
carbon atoms away from the first nitrogen (diamines 5 and
6, respectively) to probe the influence on anticancer
potency of two nitrogens in these scaffolds (Fig. 1).
Keywords Aminoaromatic adamantanes Á Synthesis Á
Antiproliferative activity
Introduction
Adamantane derivatives have a broad pharmacological
profile, involving antibacterial (Aigami et al., 1975), anti-
fungal (Kadi et al., 2007), antiviral (Kolocouris et al.,
1994, 1996), trypanocidal (Papanastasiou et al., 2008) and
I. Papanastasiou (&) Á A. Tsotinis Á N. Kolocouris
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
University of Athens, Panepistimioupoli-Zografou,
157 71 Athens, Greece
e-mail: papanastasiou@pharm.uoa.gr
Materials and methods
S. P. Nikas
Center for Drug Discovery, Northeastern University, 116 Mugar
Life Sciences Building, 360 Huntington Avenue,
Boston, MA 02115, USA
Cell cultures and cell lines
All human cancer cell lines were obtained from the
National Cancer Institute, NIH (Bethesda, MD, USA). All
cell lines were adapted to propagate in RPMI 1640 medium
supplemented with 5 % heat-inactivated fetal calf serum,
2 mM L-glutamine and antibiotics. The cultures were
grown in a humidified 37 °C incubator in 5 % CO2
atmosphere.
S. P. Nikas
Institute of Organic and Pharmaceutical Chemistry, National
Hellenic Research Foundation, 48 Vass. Constantinou,
116 35 Athens, Greece
A. Vamvakides
Anavex Life Sciences, 27 Marathonos Avenue, 153 51 Pallini,
Athens, Greece
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Med Chem Res (2014) 23:1966–1975
1967
Fig. 1 New adamantane
derivatives with
antiproliferative activity
X
C
H
H
NH2
H
H
2
NH2
NH2
NH2
NH
H
1
:
:
:
=
3a
2a
2b
2c
X H
3b
4
=
X F
=
X
H
3O
C
H
C
2
R1
R2
H
C
R1
2
N
NH
H
(C
)
N
NH
H
(C )
2 2
2 3
R2
R1
R1
R2
H
C
H
H
C
3
3
=
=
=
=
=
N
N
N
N
N
N
N
N
N
N
:
:
6a
6b
6c
5a
5b
5c
R2
H
C
C
3
3
R1
R2
R1
R2
O
:
:
:
N
N
R1
R2
R1
R2
=
:
NH
N
1
In vitro cytotoxic activity
a Perkin-Elmer 833 spectrometer. H NMR spectra were
recorded on a Bruker MSL 400 and 13C NMR spectra were
taken on a Bruker AC 200 spectrometer using CDCl3 as
solvent and TMS as internal standard. Carbon multiplicities
were established by DEPT experiments. 2D NMR experi-
ments (HMQC, COSY and NOESY) were performed for
the elucidation of the structures of the new compounds.
Microanalyses were carried out by the Service Central de
Microanalyse (CNRS), France, and the results obtained had
a maximum deviation of 0.4 % from the theoretical
values.
Cell viability was assessed at the beginning of each experi-
ment by the trypan blue dye exclusion method and was
always greater than 95 %. Cells were seeded into 96-well
microtiter plates in 100 lL of medium at the corresponding
density (3,500–30,000 cells per well) and, subsequently, the
plates were incubated at standard conditions for 24 h to allow
the cells to resume exponential growth prior to addition of the
agents to be tested. Then to measure the cell population, cells
in one plate were fixed in situ with TCA followed by SRB
staining, as described elsewhere (Skehan et al., 1990;
Keepers et al., 1991). To determine the activity, each com-
pound was dissolved in DMSO and then added at tenfold
dilutions (from 100 to 0.01 lM) and incubation continued for
an additional period of 48 h. The assay was terminated by
addition of cold TCA followed by SRB staining and absor-
bance measurement at 540 nm, in a DAS plate reader, to
determine GI50, that is, the concentration required in the cell
culture to inhibit cell growth by 50 %, and TGI, the con-
centration that is required to completely inhibit cell growth
(Skehan et al., 1990; Keepers et al., 1991).
General procedure for the synthesis of 1-
benzyltricyclo[3.3.1.13,7]decan-2-ketoxime (8a), 1-(4-
fluorobenzyl)-tricyclo[3.3.1.13,7]decan-2-ketoxime (8b)
and 1-(4-methoxybenzyltricyclo[3.3.1.13,7]decan-2-
ketoxime (8c)
Hydroxylamine hydrochloride (1.4 g, 20.2 mmol) and
sodium acetate trihydrate (4.26 g, 31.3 mmol) were added
to a 90° ethanolic solution (50 mL) of ketones 7a (Papa-
nastasiou et al., 2008), 7b (Papanastasiou et al., 2009) and
7c (Papanastasiou et al., 2009) (10.1 mmol), respectively,
and the resulting mixture was refluxed for 5 h. Upon
completion of the reaction, ethanol was evaporated, chilled
water (20 mL) was added and the precipitate formed was
filtered off, washed with water and dried to give 8a, 8b and
Synthesis
Melting points were determined using a Bu¨chi capillary
apparatus and are uncorrected. IR spectra were recorded on
123

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Med Chem Res (2014) 23:1966–1975
8c, respectively, as solids in quantitative yield; 8a: mp
210 °C (ether), 8b: mp 216 °C (ether–pentane), 8c: mp
182 °C (ether–pentane).
the organic phase was washed with H2O (3 9 15 mL) and
dried over Na2SO4. The organic phase was partially evapo-
rated (40–50 mL) at 30 °C, acetone was added, followed by
evaporation;thisprocedure wasrepeatedtwice. Then, acetone
was added to give a volume of 150–200 mL, and the solution
was oxidized with Jones reagent (*33 mL, 1 M) at 15 °C.
The reaction mixture was stirred overnight at 20 °C, then
quenched by the addition of isopropyl alcohol (3 mL) and
filtered through cotton wool. H2O (20 mL) was added to the
filtrate and acetone was removed under reduced pressure. The
residue was extracted with ether and the organic extracts were
washed with an aqueous solution of NaOH (5 %). The com-
bined aqueous phases were washed with ether and acidified
with conc. HCl at 0 °C. The crystals formed were filtered off,
washed with H2O and dried to afford carboxylic acid 12
General procedure for the synthesis of 1-
benzyltricyclo[3.3.1.13,7]decan-2-amine (2a), 1-(4-fluoro-
benzyl)tricyclo[3.3.1.13,7]decan-2-amine (2b) and 1-(4-
methoxybenzyltricyclo[3.3.1.13,7]decan-2-amine (2c)
Oximes 8a, 8b and 8c (13.7 mmol) in absolute ethanol
(40 mL) were hydrogenated under pressure (55 psi) over
Raney-Ni (200 mg) for 5 h, at 70 °C. The catalyst was
filtered off through Celite and the solvent was evaporated
under vacuum to give the crude title compounds as viscous
oils; amines 2a and 2b were crystallized upon standing. 2a
1
1
mp 38 °C (Papanastasiou et al., 2008); 2b mp 40 °C. H
(4.73 g, 70 %); mp: 127 °C (ether); H NMR (CDCl3) d
NMR (CDCl3) d 1.26–1.97 (13H, m, H3–10), 1.98 (2H, brs,
NH2, D2O exchangeable), 2.36–2.49 (2H, AB, J = 13.2,
Dm = 0.05, CH2Ph), 2.61 (1H, s, H2), 6.84–7.03 (4H, m,
1.51–2.75 (13H, m, H3–10), 3.04 (1H, s, H2), 7.06–7.24 (5H,
m, H-arom.), 10.5 (1H, brs, COOH); 13C NMR (CDCl3) d
27.9(C5), 28.8(C7), 31.6(C6), 31.8(C3), 35.1(C4), 36.8(C10),
37.5 (C1), 38.0 (C9), 47.1 (C8), 53.8 (C2), 124.9 (C2,6-arom.),
125.8 (C4-arom.), 128.1 (C3,5-arom.), 148.5 (C1-arom.), 179.0
(CO); IR (Nujol): m = 1,689–1,634 cm-1(CO).
H
2,3,5,6-arom.); 13C NMR (CDCl3) d 28.0 (C5), 28.1 (C7),
30.4 (C6), 35.64 (C4), 35.8 (C3), 36.8 (C1), 37.0 (C10), 37.4
(C9), 40.9 (C8), 45.0 (CH2Ph), 57.8 (C2), 114.2–114.4
(C3,5-arom.), 131.8–133.9 (C2,6-arom.), 133.4 (C1-arom.),
162.6 (C4-arom.); 2c, 1H NMR (CDCl3): d 1.25–1.83 (13H,
m, H3–10), 1.85 (2H, brs, NH2, D2O exchangeable),
2.39–2.50 (2H, AB, J = 13.6, Dm = 0.04, CH2Ph), 2.66
Indeno[1,2-a]tricyclo[3.3.1.13,7]decan-5(5aH)-one (13)
Carboxylic acid 12 (3 g, 11.7 mmol) was treated with
freshly distilled thionyl chloride (8 mL), at 65 °C, during
15–20 min. After removal of residual thionyl chloride by
co-evaporation with benzene under reduced pressure, car-
bon disulfide (45 mL) and anhydrous aluminum chloride
(1.8 g, 13.4 mmol) were added to the reaction mixture,
which was stirred at RT for 30 min and then refluxed for
30 min. The reaction was cooled, quenched by the addition
of ice and extracted with diethyl ether (3 9 20 mL). The
combined organic phases were washed with H2O, dried
over Na2SO4 and evaporated to afford a residue, which
crystallized upon standing. Further purification by flash
column chromatography over silica gel at gradient eluent
(pentane to pentane:ether, 6:1) gave compound 13 (2.81 g,
almost quantitative) mp: 56 °C; 1H NMR (CDCl3) d
1.93–2.57 (13H, m, H6–13), 2.57 (1H, s, H5a), 7.19–7.66
(4H, m, H-arom.); 13C NMR (CDCl3) d 26.9 (C8), 27.9
(C10), 28.6 (C6), 32.10 (C9), 36.0 (C7), 38.2 (C13), 38.7
(C12), 41.5 (C11a), 46.9 (C11), 62.8 (C5a), 121.6 (C1), 124.0
(C3), 127.0 (C2), 133.3 (C4), 135.7 (C11b), 164.5 (C4a),
204.6 (CO); IR (Nujol): m = 1,724 cm-1(CO).
(1H, s, H3), 3.78 (3H, s, CH3O), 6.78–7.05 (4H, m, H2,3,5,6
-
arom.); 13C NMR (CDCl3) d 28.1 (C5), 28.2 (C7), 30.5
(C6), 35.7 (C4), 35.8 (C3), 37.1 (C10), 37.5 (C9), 42.6 (C1),
40.9 (C8), 44.9 (CH2Ph), 55.1 (CH3O) 55.7 (C2),
112.9–113.1 (C3,5-arom.), 129.8 (C1-arom.), 131.4 (C2,6
-
arom.), 157.7 ppm (C4-arom.). Elemental analyses mea-
surements were performed on the hydrochloride salts of
amines 2b and 2c. 2b (hydrochloride, mp [250 °C); Anal
calcd for C17H23ClFN: C 69.02, H 7.84, found C 68.86, H
7.86. 2c (hydrochloride, mp [250 °C); Anal calcd for
C18H26ClNO: C 70.22, H 8.51, found C 70.31, H 8.43.
1-Phenyltricyclo[3.3.1.13,7]decan-2-carboxylic acid (12)
Dry dimethylsulfoxide (105 mL) was added dropwise to a
mixture of trimethylsulfoxonium iodide (7.92 g, 36 mmol)
and sodium hydride 60 % (1.44 g, 36 mmol), under an argon
atmosphere, and stirred for 30 min before ketone 9 (Lenoir,
1973; Tseng et al., 1998) (6 g, 26.5 mmol) was added. The
resulting mixture was stirred at 20 °C for 30 min and then
heated at 55–58 °C for 2 h. The mixture was then poured into
chilled water and extracted with n-hexane 3 9 20 mL with-
out shaking the separatory funnel. The combined organic
layers were dried over Na2SO4 and evaporated at 40 °C to
afford 6.21 g of a liquid, which was diluted with dry benzene
(120 mL) and shaken well with BF3ÁEt2O complex (3.6 g,
recently distilled) in the separatory funnel. After 3 min at rest,
Indeno[1,2-a]tricyclo[3.3.1.13,7]decan-5-ketoxime (14)
A mixture of ketone 13 (0.31 g, 1.3 mmol), hydroxylamine
hydrochloride (0.27 g, 3.9 mmol) and sodium acetate tri-
hydrate (0.81 g, 6 mmol) in ethanol (90°) (15 mL) was
123

Med Chem Res (2014) 23:1966–1975
1969
refluxed for 7 h. The reaction mixture was then cooled to
room temperature, ethanol was evaporated and chilled
water was added. The precipitate formed was filtered off,
washed with water and dried to give ketoxime 14 as a solid
(0.32 g, yield quantitative) mp: 164 °C (ethanol–water,
then dried with hexane).
[255 °C. Anal. calcd for C17H22ClN: C 74.03, H 8.04, found
C 73.91, H 8.12. Hydrochloride (cis-amine) 3b; mp[255 °C.
Anal. calcd for C17H22ClN: C 74.03, H 8.04, found C 73.96, H
8.05.
5H,6H-tricyclodecan[1,2-a]isoquinoline (4)
5,5a-Dihydroindeno[1,2-a]tricyclo[3.3.1.13,7]decan-5-
A mixture of oxime 14 (0.9 g, 3.55 mmol) and phosphorus
pentachloride (1 g, 4.79 mmol) in benzene (20 mL) was
refluxed for 1 h. After cooling, ice was added and the mixture
extracted with benzene. The organic phase was washed
sequentially with a saturated aqueous solution of NaHCO3
and H2O, dried over Na2SO4 and evaporated to give a residue,
which was treated with a mixture of ether: n-pentane (1:1) and
chilled to give a precipitate, which was filtered off and washed
with n-pentane. Recrystallization from methanol gave 16
amines (3a) and (3b)
Acetic anhydride (4.32 g, 42.4 mmol) was added to a chilled
solution of oxime 14 (0.59 g, 2.34 mmol) in pyridine (10 mL).
The reaction mixture was stirred at 0 °C for 7 h and 18 h at
3 °C and then diluted with diethyl ether prior to addition of ice.
The aqueous phase was discarded and the organic layer
sequentially washed with H2O, saturated aqueous solution of
NaHCO3 and H2O. The organic phase was dried over Na2SO4
and concentrated in vacuo to give oxime-ester 15 (0.72 g,
yield almost quantitative); IR (net): m = 1,764 cm-1 (CO),
1,644 cm-1 (CN). To a stirred solution of oxime-ester 15
(0.7 g, 2.17 mmol) in anhydrous tetrahydrofuran (10 mL) was
added sodium borohydride (0.65 g, 17.4 mmol) and a solution
of iodine (1.67 g, 6.61 mmol) in dry tetrahydrofuran (10 mL)
at 0 °C. The reaction mixture was refluxed for 8 h and then
quenched at 0 °C by the addition of an aqueous solution of HCl
(3N). The mixture was then made alkaline with aqueous conc.
KOH, extracted with diethyl ether, washed with H2O and dried
over anhydrous Na2CO3. Theetherealphase was treated with a
saturated ethanolic solution of gaseous HCl under ice cooling
and the precipitate formed was filtered off, washed with cold
diethyl ether and dried to afford the respective hydrochloride
salts of the desired compounds, which were then converted to
the free bases by the addition of a solution of Na2CO3. These
were further purified by flash column chromatography, eluting
with a 1:1 MeOH–Et2O solution to give viscous oils, which
were then separated to the two diastereomers, respectively,
eluting with a 13:1 Et2O–MeOH mixture. The less polar
compounds correspond to the cis-diastereomers, which are
solids, while the more polar to the trans-diastereomers, which
are liquid (80 mg each diastereomer, total yield 31.5 %). 3a:
1H NMR (CDCl3) d 1.35–2.22 (16H, m, H5a–13, NH2), 4.12
(1H, d, J = 10.6, H5), 6.99–7.14 (4H, m, H-arom.); 13C NMR
(CDCl3) d 27.7 (C8), 28.1 (C10), 29.1 (C6), 31.10 (C9), 37.4
(C7), 39.1 (C13), 40.6 (C12), 40.8 (C11), 42.5 (C11a), 55.7 (C5a),
64.0 (C5), 120.6–123.7–126.4–126.9 (C1–4), 146.7–151.5
(260 mg,
29 %);
mp [250 °C;
IR
(Nujol):
m = 3,435–3,175 cm-1(NH), 1,667 cm-1(CO). Compound
16 (238 mg, 0.94 mmol) was then added dropwise into a
suspension of lithium aluminum hydride (400 mg,
10.5 mmol) in anhydrous tetrahydrofuran (30 mL) and the
reaction mixture was refluxed for 12 h. Quenching by the
sequential addition of H2O and an aqueous solution of NaOH
(5 %) gave a suspension, which was filtered off, the filtrate
dried over Na2CO3 and the solvent evaporated to give a res-
idue, which was transformed into the hydrochloride salt of 4.
The salt was recrystallized from ethanol–ether and then
converted to the free base 4 upon treatment with Na2CO3.
Base 4 was further purified by flash column chromatography
using a 1:9 MeOH–Et2O mixture as eluent to give 4 as a
viscous oil, which was crystallized on standing (0.13 g,
58 %); mp: 79 °C; 1H NMR (CDCl3) d 1.50–2.31 (13H, m,
H6a–14, NH), 2.83 (1H, s, H6a), 4.01–4.18 (2H, AB, J = 16,
H5), 6.91–7.22 (4H, m, H-arom.); 13 C NMR (CDCl3) d 28.4
(C9), 28.9 (C11), 30.68 (C10), 33.9 (C7), 35.5 (C12a), 37.2 (C8),
37.6 (C14), 40.6 (C13), 41.2 (C12), 49.4 (C5), 62.2 (C6a),
124.9–125.5–126.0–126.2 (C1–4), 134.6–144.5 (C4a–12b);
hydrochloride salt: mp[250 °C. Anal calcd for C17H22ClN:
C 74.03, H 8.04, found C 74.15, H 8.08.
General procedure ofsynthesisof1-benzyltricycle[3.3.1.13,7
]
decan-2-(2-dimethylaminoethyl)amine (5a), 1-benzyltricycle
[3.3.1.13,7]decan-2-(N-piperidinylethyl)amine (5b),
1-benzyltricyclo[3.3.1.13,7]decan-2-(N-piperazinylethyl)
amine (5c), 1-benzyltricyclo[3.3.1.13,7]decan-2-(3-dimethyl
aminopropyl)amine (6a), 1-benzyltricyclo[3.3.1.13,7]decan-2-
(N-morpholinopropyl)amine (6b) and 1-benzyltricyclo
[3.3.1.13,7]decan-2-(1-imidazolylpropyl)amine (6c)
(C4a–11b). 3b: 1H NMR (CDCl3) d 1.66–2.29 (16H, m, H5a–13
,
NH2), 4.25 (1H, d, J = 7.16, H5), 7.05–7.15 (4H, m, H-arom);
13C NMR (CDCl3) d 28.2 (C8), 29.7 (C10), 30.0 (C6), 33.0 (C9),
37.5 (C7), 39.1 (C11a), 40.9 (C13), 42.0 (C12), 44.3 (C11), 54.0
(C5a), 58.6 (C5), 121.6–125.3–126.7–127.5 (C1–4),
146.9–152.6 (C4a–11b). The precipitation of the hydrochloride
salts from the ethereal solution of the amine was effected by
the addition of n-pentane. Hydrochloride (trans-amine) 3a; mp
A mixture of ketone 7a (8.66 mmol) and the requisite diamine
(10 mmol) in anhydrous toluene (20 mL) was refluxed for 6 h,
while removing H2O azeotropically. The solvent was then
evaporated to give a viscous oil, which was reduced with
123

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Med Chem Res (2014) 23:1966–1975
lithium aluminum hydride (50 mmol) in anhydrous diethyl
ether (30 mL), upon refluxing for 10 h. The reaction was then
quenched by the sequential addition of H2O and an aqueous
solution of NaOH (5 %) and the solid filtered off. The filtrate
was dried over Na2CO3 and evaporated to give a residue, which
was further purified by flash column chromatography over
silica gel using a mixture of Et2O:MeOH as eluent to give the
desired amine, as an oil, which was transformed to the
respective fumarate salt. Compound 5a: purification by column
chromatography-eluent system Et2O:MeOH (2:1), yield 67 %;
1H NMR (CDCl3) d 1.32–1.90 (13H, m, H3–10), 2.18 (7H, s,
(CH3)2N, CHNH), 2.31–2.63 (2H, AB, J = 12.8, CH2Ph),
2.40–2.43 (3H, m, NHCHH ? CH2N(CH3)2), 2.74 (1H, m,
NHCHHCH2N(CH3)2), 7.07–7.17 (5H, m, H-arom.); 13C
NMR (CDCl3) d 28.1 (C5), 28.2 (C7), 30.3 (C3), 30.7 (C6), 37.2
(C4), 37.3 (C10), 37.4 (C9), 41.6 (C8), 45.0
(NHCH2CH2N(CH3)2), 45.5 ((CH3)2N), 45.8 (CH2Ph), 59.7
(NHCH2CH2N(CH3)2), 63.7 (C2), 71.8 (C1), 125.5 (C4-arom.),
127.4 (C2,6-arom), 130.8 (C3,5-arom.), 138.5 (C1-arom.);
fumarate, mp: 171 °C. Anal calcd for C25H36N2O4: C 70.06, H
8.47, found C 69.97, H 8.41. Compound 5b: purification by
column chromatography-eluent system Et2O:MeOH (1:1),
28.2 (C7), 28.9 (CH2CH2CH2), 30.1 (C3), 30.8 (C6), 37.16 (C4),
37.3 (C10), 37.4 (C9), 41.7 (C8), 45.6 ((CH3)2N), 45.8
(NHCH2CH2CH2N(CH3)2), 45.8 (CH2Ph), 58.3 (NHCH2CH2
CH2N(CH3)2), 63.7 (C2), 71.8 (C1), 125.5 (C4-arom.), 127.4
(C2,6-arom.), 130.7 (C3,5-arom.), 138.6 (C1-arom.); fumarate,
mp: 170 °C. Anal calcd for C26H38N2O4: C 70.56, H 8.65,
found C 70.45, H 8.71. Compound 6b:purification by column
chromatography-eluent system Et2O:MeOH (3:2), yield 52 %;
1H NMR (CDCl3) d 1.24–2.00 (15H, m, H3–10, CH2CH2CH2),
2.27 (1H, *s, CHNH), 2.37–2.70 (8H, m, AB, J = 14,
CHHPh, NHCHHCH2CH2N, H3,5-morph.), 2.73–2.85 (2H, m,
AB, J = 14, CHHPh, NHCHHCH2CH2N), 3.72–3.77 (4H, m,
H2,6-morph.), 7.13–7.26 (5H, m, H-arom.); 13C NMR (CDCl3)
d 27.5 (CH2CH2CH2), 28.2 (C5), 28.3 (C7), 30.1 (C3), 30.9
(C6), 37.2 (C4), 37.3 (C10), 37.6 (C9), 41.7 (C8), 45.9
(NHCH2CH2CH2N), 46.0 (CH2Ph), 53.9 (C3,5-morph.), 57.9
(NHCH2CH2CH2N), 63.6 (C2), 67.1 (C2,6-morph.), 71.8 (C1),
125.5 (C4-arom.), 127.4 (C2,6-arom), 130.7 (C3,5-arom.), 138.6
(C1-arom.); fumarate, mp: 178 °C. Anal calcd for
C28H40N2O5: C 69.39, H 8.32, found C 69.43, H 8.47. Com-
pound 6c: purification by column chromatography-eluent
1
system Et2O:MeOH (2:1), yield 60 %; H NMR (CDCl3) d
yield 92 %;1H NMR (CDCl3) d 1.13–1.78 (19H, m, H3–10
3,4,5-piper.), 2.20 (1H, *d, CHNH), 2.33–2.45 (8H, AB,
,
1.26–1.97 (15H, m, H3–10, CH2CH2CH2), 2.27 (1H, *s,
CHNH), 2.41 (1H, quint, NHCHHCH2CH2N), 2.58 (8H, AB,
J = 13.2, CHHPh), 2.72 (1H, quint, NHCHHCH2CH2N), 4.12
(2H, t, NHCH2CH2CH2N), 6.94–7.50 (8H, m, H-phen.?i-
mid.); 13C NMR (CDCl3) d 27.9 (C5), 28.1 (C7), 30.1 (C3), 30.7
(C6), 32.07 (NHCH2CH2CH2N) 36.9 (C4), 37.0 (C10), 37.3
(C9), 41.7 (C8), 43.6 (NHCH2CH2CH2N), 44.9
(NHCH2CH2CH2N), 46.0 (CH2Ph), 64.0 (C2), 118.8 (C-imid.),
125.6 (C4-phen.), 127.5 (C2,6-phen.), 129.3 (C-imid.),130.6
(C3,5-arom.), 137.2 (C-imid.), 138.3 (C1-phen.); fumarate, mp:
171 °C. Anal calcd for C27H35N3O4: C 69.65, H 7.58, found C
69.54, H 7.66.
H
J = 12.8, CHHPh, NHCHH ? CH2N, H2,6-piper.), 2.64 (1H,
AB, J = 12.8, CHHPh), 2.60–2.64 (1H, m, NHCHHCH2N),
7.08–7.18 (5H, m, H-arom.); 13C NMR (CDCl3) d 24.4 (C4-
pip), 26.0 (C3,5-piper.), 28.1 (C5), 28.2 (C7), 30.3 (C3), 30.7
(C6), 37.1–37.2–37.3 (C4,9,10), 41.5 (C8), 44.36
(NHCH2CH2N), 45.8 (CH2Ph), 54.7 (C1,6-piper.), 59.0
(NHCH2CH2N), 64.0 (C2), 71.8 (C1), 125.5(C4-arom.), 127.4
(C2,6-arom.), 130.7 (C3,5-arom.), 138.5 (C1-arom.); fumarate,
mp: 187 °C. Anal calcd for C28H40N2O4: C 71.76, H 8.60,
found C 71.82, H 8.63. Compound 5c: purification by column
chromatography-eluent system Et2O:MeOH (3:2), yield 40 %;
1H NMR (CDCl3) d 1.43–1.97 (13H, m, H3–10), 2.27 (1H, *s,
J = 0.2, CHNH), 2.40–2.53 (8H, AB, J = 12.8, CHHPh,
NHCHH ? CH2N, H3,5-piperaz.), 2.64 (1H, AB, J = 12.8,
CHHPh), 2.81 (1H, m, NHCHHCH2N), 2.90 (4H, m, H2,6-
piperaz.), 7.14–7.26 (5H, m, H-arom.); 13C NMR (CDCl3) d
28.2 (C5), 28.3 (C7), 30.4 (C3), 30.8 (C6), 37.2–37.3–37.4
(C4,9,10), 41.6 (C8), 44.1 (NHCH2CH2N), 45.9 (CH2Ph), 46.3
(C4-piperaz.), 54.7 (C2-piperaz.), 59.0 (NHCH2CH2N), 64.0
(C2), 125.5 (C4-arom.), 127.4 (C2,6-arom.), 130.7 (C3,5-arom.),
138.5 (C1-arom.); fumarate, mp: 168 °C. Anal calcd for
C27H39N3O4: C 69.05, H 8.37, N 8.95, found C 69.12, H 8.32.
Compound 6a: purification by column chromatography-eluent
Results and discussion
Chemical synthesis
For the preparation of 1-benzyl-2-aminoadamantanes 2a–c,
the previously reported ketones 7a–c (Papanastasiou et al.,
2009) were converted to their respective oximes 8a–c,
which were then catalytically reduced to the desired amines
2a–c (Scheme 1).
Amine 1 was prepared from 1-phenyl-2-adamantanone
(Lenoir, 1973; Tseng et al., 1998; Zoidis et al., 2010), in a
similar way to amines 2. For the preparation of the dia-
stereomeric amines 3a and 3b, phenylketone 9 (Lenoir,
1973; Tseng et al., 1998) was treated with the appropriate
sulfur ylide to give epoxide 10. This was treated with
BF3ÁEt2O complex to give aldehyde 11, which was
immediately oxidized, under Jones conditions, to the
1
system Et2O:MeOH (3:2), yield 61 %; H NMR (CDCl3) d
1.25–2.00 (15H, m, H3–10, CH2CH2CH2), 2.24 (6H, s,
(CH3)2N), 2.28 (1H, *s, CHNH), 2.36–2.43 (4H, m, AB,
J = 12.8, CHHPh, NHCHHCH2CH2N(CH3)2), 2.68–2.78
(2H, m, AB, J = 12.8, CHHPh, NHCHHCH2CH2N(CH3)2),
7.14–7.26 (5H, m, H-arom.); 13C NMR (CDCl3) d 28.1 (C5),
123

Med Chem Res (2014) 23:1966–1975
1971
X
X
X
O
N H
O
NH
NH
a
b
H
=
C
H
H
C
C
2
2
2
O
1
N H
O
NH2
8
7
14
16
4
2
3
a
b
9
1
0
Scheme 3 Reagents and conditions: a PCl5, anhydrous C6H6, reflux
for 1 h. b LiAlH4, anhydrous THF, reflux 12 h
6
5
4
:
:
:
7a
7b
7c
:
:
:
=
X H
:
:
:
=
8a
8b
8c
X H
2a
2b
2c
X H
=
=
X F
=
X F
X F
The elucidation of the structure of amine 4 was based on
the NMR spectra. Thus, the 5-CH2 peak appears as an AB
system with J = 16.1 Hz, which justifies its linkage to the
phenolic ring and not with the C2 carbon atom of the ad-
amantane skeleton.
=
=
X
H
3O
C
=
X
H
3O
C
X
H
3O
C
Scheme 1 Reagents and conditions:
a
NH2OH HCl, CH3CO-
ONaÁ3H2O, EtOH, reflux for 5 h, (quant.); b H2/Ni-Raney, EtOH,
55 psi, 70 °C for 5 h, (91–95 %)
The synthesis of the ethanodiamines 5 and propanodi-
amines 6 was effected by heating the appropriate diamines
with ketone 7a, followed by azeotropic removal of water.
The intermediate imines 18 were not isolated, but reduced
directly to the corresponding amines 5a, 5b, 5c and 6a, 6b,
6c (Scheme 4).
carboxylic acid 12 in good yield. This acid was then con-
verted to its chloride, which, in the presence of AlCl3, was
cyclized to ketone 13. Treatment of 13 with hydroxylamine
gave oxime 14, which was transformed to the oxime-ester
15. This was reduced by diborane, prepared in situ from
NaBH4 and iodine, to the diastereomeric amines 3a and 3b.
The two diastereomers were separated by flash column
chromatography and characterized by NMR spectral ana-
lysis. J6H–6aH & 7.16 Hz coupling is attributed to the cis-
3b amine and J6H–6aH & 10.6 Hz to the trans-3a amine
(Scheme 2).
Pharmacology
The results from the in vitro drug screening of the new
compounds on cancer cell lines (colon, prostate, breast,
ovarian, central nervous system, leukemia, pancreas, liver)
and on normal cell lines are shown in Table 1.
Beckmann rearrangement of oxime 14 on treatment with
PCl5 led to the formation of lactam 16, which was selec-
tively reduced by LiAlH4 to provide amine 4 (Scheme 3).
The selectivity of this reaction can be attributed to the
stability of the produced cation 16a, which leads to lactam
16. Conversely, cation 17a is less stable and thus the cor-
responding lactam 17 is not formed (Fig. 2).
Considering the antiproliferative activity of the active
analogs on various cancer cell lines, it appears that amino-
adamantanes 2a–c are the most potent compounds, derivative
2b being the most active across all examined cancer cell lines.
Moreover, the OMe-substituted analog 2c proved to be more
efficient than the parent compound 2a. The C2-diamino-
substituted adamantanes (compounds 5b and 6a) show a
Scheme 2 Reagents and
conditions:
a trimethylsulfoxonium iodide,
NaH, anhydrous DMSO, 20 °C
O
H
COO
O
for 30 min, 55–58 °C for 2 h.
b BF3ÁEt2O, anh. C6H6. c CrO3,
H2SO4 (8N), 15–20 °C.
d SOCl2, 65 °C for 15 min.
e AlCl3, CS2, rt for 30 min,
reflux for 30 min.
H
C O
O
b
a
f
e
c
d
,
11
13
12
9
10
f NH2OH.HCl,
CH3COONaÁ3H2O, EtOH,
reflux for 7 h, (quant.).
g (CH3CO)2O, Py, 0 °C for 7 h
and 3 °C for 18 h, (quant.).
h NaBH4/I2, anhydrous. THF,
reflux for 8 h
H
NH2
H
H
N H
O
N
H
3
OCOC
NH2
g
h
H
+
a
3
14
3b
15
123

1972
Med Chem Res (2014) 23:1966–1975
Fig. 2 Mechanism of formation
of lactam 16 versus 17
3
4
2
O
a
4
5
1
H
2O
N
6
a
12
13
NH
a
6
12
14
11
7 16
16a
9
10
8
NOH
N
NH
14
H
2O
O
17a
17
R1
R2
H
C
2
R1
R2
H
C
H
C
2
2
O
(CH2)n
N
N
NH
H
)
n
2
(C
N
a
b
: n=2
: n=3
5a b c
, ,
a
7
18
6a b c
, ,
Scheme 4 Reagents and conditions: a n = 2, i, 2-dimethylamino-
ethylamine, toluene, reflux for 6 h. ii, 2-(piperidin-1-yl)ethylamine,
toluene, reflux for 6 h. iii, 2-(piperazin-1-yl)ethylamine, reflux for
6 h; n = 3, i, 3-dimethylaminopropylamine, toluene, reflux for 6 h. ii,
3-morpholinopropylamine, toluene, reflux for 6 h. iii, 3-(1H-imida-
zol-1-yl)propylamine, toluene, reflux for 6 h. b LiAlH4, anhydrous
Et2O, reflux 10 h, (40–92 %)
Table 1 Results from the in vitro drug screening
Cancer cell lines
Colon
Renal
Caki
Prostate
DU145
Breast
Compound
Valuesa
Colo205
HCT-116
HCT-15
PC3
LNCap
MDA MB231
MCF7
1b
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
100
100
89.3
100
69.3
9.5
84.53
33.23
7.12
100
82.92
2ab
2bb
2cb
3ab
3bb
4
35.84
6.59
26.84
6.54
29.77
6.68
46.6
6.68
5.5
17.46
5.6
53.82
19.39
75.05
38.81
8.7
4.6
52.17
18.49
42.3
7.4
69.89
34.95
37.62
26.63
66.13
31.45
61.2
62.47
32.62
28.53
56.74
21.34
100.0
63.92
55.87
24.02
100.0
52.0
5ac
59.94
25.44
54.7
54.09
25.86
24.36
123

Med Chem Res (2014) 23:1966–1975
1973
Table 1 continued
Cancer cell lines
Colon
Renal
Caki
Prostate
DU145
Breast
Compound
Valuesa
Colo205
HCT-116
HCT-15
PC3
LNCap
MDA MB231
MCF7
5bc
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
51.69
9.94
33.2
6.75
5cc
50.0
52.72
21.1
7.02
6ac
34.8
42.85
9.11
6.76
6bc
100.0
43.98
64.7
58.54
28.94
56.15
26.96
[100
8.40
6cc
26.82
[100
9.51
5-FU
ETO
Cancer cell lines
Ovarian
CNS
Non small lung
Small lung Melanoma Normal cells
Compound Valuesa IGROV-1 OVCAR-5 ADR-res NCI SF268 U251 NCI-H460 EKVX A549 DMS 114 SK-MEL-28 hMSC NHDF
1b
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
TGI
GI50
100
100 100
100 100
100
2ab
2bb
2cb
3ab
3bb
4
36.5
7.6
37.8
8.35
30.00
6.7
56.82
20.98
29.25 43.7
6.94 8.67
45.56
9.55
24.4
7.4
37.44 50.87 51.95
7.83 21.81 13.72
50.7 57.98 62.38
21.17 31.23 31.18
56.23
50.39
9.38
44.98
13.24
60.71
31.79
52.8
17.9
55.3
29.3
73.94
40.05
56.05 58.8
24.83 27.7
31.15
56.56
33.05
100.0
100.0
57.05
29.34
45.85
13.09
53.61
22.19
40.93
9.09
100.0
100.0
5ac
5bc
5cc
6ac
6bc
6cc
58.07
26.48
32.18
6.32
46.78
7.49
25.83
5.78
100.0
56.39
62.77
28.78
100.0
50.73
67.52
31.48
123

1974
Med Chem Res (2014) 23:1966–1975
Table 1 continued
Cancer cell lines
Ovarian
CNS
Non small lung
Small lung Melanoma Normal cells
Compound Valuesa IGROV-1 OVCAR-5 ADR-res NCI SF268 U251 NCI-H460 EKVX A549 DMS 114 SK-MEL-28 hMSC NHDF
5-FU
TGI
GI50
TGI
GI50
[100
49.21
92.67
4.21
[100
5.95
ETO
5-FU 5-fluorouracil, ETO etoposide
a
TGI is the concentration (lM) resulting in total growth inhibition, GI50 is the concentration (lM) resulting in growth inhibition of 50 %
b
c
Hydrochloride
Monofumarate
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