Antiviral activity of adamantyl-containing β-aminoketones, enaminoketones, and related compounds

Full text of DOI:10.1023/A:1014086507352

Pharmaceutical Chemistry Journal
Vol. 35, No. 9, 2001
SEARCH FOR NEW DRUGS
ANTIVIRAL ACTIVITY OF ADAMANTYL-CONTAINING
b-AMINOKETONES, ENAMINOKETONES, AND RELATED COMPOUNDS
N. V. Makarova,1 E. I. Boreko,2 I. K. Moiseev,1 N. I. Pavlova,2 M. N. Zemtsova,1
S. N. Nikolaeva,1 and G. V. Vladyko2
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 9, pp. 17 – 20, September, 2001.
Original article submitted March 6, 2001.
Despite considerable achievements in the chemistry of
OH
enaminoketones, the compounds are still used predominantly
CHCH2CH2N(CH3)2
as initial materials in the synthesis of potentially biologically
active heterocycles. Data on the biological activity of enami-
noketones are also very restricted. In particular, it was repor-
ted that b-aminovinylketones represent a new class of effec-
tive antiinflammatory agents [1] and possess antimicrobial
properties as well [2]. Another class of potentially biologi-
cally active compounds is offered by derivatives of carbo-
nyl-containing compounds substituted at the keto group. For
example, antiviral activity was observed in oximes [3, 4].
In continuation of the previous investigation devoted to
the search for new biologically active compounds among
aminocarbonyl derivatives of adamantane [5], we have synt-
hesized and characterized with respect to antiviral properties
a series of adamantyl-containing b-aminoketones, including
N,N-dialkyl-3-(1-adamantyl)-1-aminopropan-3-one hydroc-
hlorides (Ia – Id) and 1-[N-(1-adamantyl)-N-methylami-
no]butan-3-one hydrochloride (II); b-aminovinylketones re-
presented by 1-(1-adamantylamino)-3-R-1-propen-3-ones
(IIIa, IIIb); and derivatives of compounds I – III including
3-(1-adamantyl)-1-morpholinopropan-3-one oxime (IV),
3-(1-adamantyl)-1-(dimethylamino)propan-3-ol (V), and
4-(1-adamantyl)-1-(phenylamino)butan-3-ol (VI).
V
NaBH4
O
CH2O, NHR2 · HCl
O
CCH3
2 · HCl
CCH2CH2NR
VII
Ia – Id
NH2OH
NOH
CCH CH
2N
O
2
IV
I: R = CH3 (a), CH2C6H5 (b), NR2 = piperidyl (c), NR2 = morpholyl (d).
Aminoketone II was synthesized by the Mannich reacti-
on from acetone, paraformaldehyde, and N-(1-adaman-
tyl)-N-methylamine hydrochloride:
O
O
CH2O, CH3CCH3
NHCH3
CH3
NCH2CH2CCH3
·
·
HCl
HCl
II
The initial reagent in the synthesis of compounds I, IV,
and V was (1-adamantyl)methyl ketone (VII). b-Aminoketo-
nes Ia – Id were obtained from ketone VII by Mannich reac-
tions with paraformaldehyde and amine hydrochlorides; the
subsequent oximation of compound Id yielded oxime IV,
while reduction of ketone Ia yielded alcohol V:
Reactions of arylmethyl ketones (acetophenone or 2-ace-
tylthiophen) with ethyl formate and sodium in benzene yielded
1-hydroxy-3-R-1-propen-3-one sodium salts (VIIIa, VIIIb). In-
teraction of these salts with 1-aminoadamantane hydrochlori-
de led to enaminoketones IIIa and IIIb. Similarly, (1-adaman-
tyl)acetone (IX) was used to obtain 4-(1-adamantyl)-1-hyd-
roxy-1-buten-3-one sodium salt (X). Reacted with aniline
hydrochloride, the latter salt yielded 4-(1-adamantyl)-1-(phe-
nylamino)-1-buten-3-one (XI). Finally, aminovinylketone XI
1
Research Institute of Epidemiology and Virology, Minsk, Belarus.
2
Samara State Technical University, Samara, Russia.
480
0091-150X/01/3509-00480$25.00 © 2001 Plenum Publishing Corporation

Antiviral Activity of Adamantyl-Containing b-Aminoketones
481
was reduced to aminoalcohol VI by reaction with sodium bo-
rohydride in methanol:
pitated product was separated by filtration and washed with
anhydrous diethyl ether.
1-(1-Adamantylamino)-3-R-1-propen-3-ones (IIIa, IIIb).
To a suspension of 0.66 g (28.5 mmole) of sodium in 5 ml of
benzene was added dropwise a solution of 2.63 g (31 mmole)
of ethyl formate and the mixture was kept with cooling for
40 min. To this mixture was added 12.9 mmole of the corres-
ponding arylmethylketone in 5 ml of benzene and the reacti-
on mass was allowed to stand for 12 h. The precipitated salt
VIII was separated by filtration, washed with acetone, and
dried. A mixture of 2.1 mmole of sodium salt VIII and
2.1 mmole of 1-aminoadamantane hydrochloride in 10 ml of
a 50% aqueous ethanol solution was boiled for 4 – 8 h. The
precipitated compound (IIIa, IIIb) was separated by filtration
and recrystallized from ethanol.
O
O
RCCH3
RCCH CHONa
VIIIa, VIIIb
HCOOC2H5 + Na
NH2
·
HCl
O
CH2CCH3
CHCR
NHCH
O
IX
IIIà, IIIb
CH2CCH CHONa
O
X
HCl
·
3-(1-Adamantyl)-1-morpholinopropan-3-one oxime
(IV). A solution of 0.5 g (1.8 mmole) aminoketone Id, 0.13 g
(1.8 mmole) hydroxylamine hydrochloride, and 0.2 g Na2CO3
in ethanol was boiled for 6 h. The precipitated compound IV
was separated by filtration.
NH2C6H5
O
CH2CCH CHNHC6H5
XI
3-(1-Adamantyl)-1-(dimethylamino)propan-3-ol (V).
Hydrochloride Ia (4.0 g, 14.7 mmole) was treated with a
10% aqueous NaOH solution. The product was extracted
with diethyl ether, the extract was dried, and the residual et-
her was distilled off. To a solution of the residue (aminoketo-
ne base) in 10 ml of methanol was added by small portions at
room temperature 0.28 g (7.4 mmole) of sodium borohydri-
de. The mixture was allowed to stand for 5 h at room tempe-
rature, neutralized with a 10% aqueous HCl solution to
pH 5 – 6, and diluted with water. The precipitate of compo-
NaBH4
CH2CHCH2CH2NHC6H5
OH
VI
III: R = C6H5 (a), 2-thienyl (b).
EXPERIMENTAL CHEMICAL PART
1
The H NMR spectra were recorded on a
Bruker AC-300 spectrometer (working frequen-
cy, 300.13 MHz) using DMSO as the solvent and
HMDS as the internal standard. The IR absorpti-
on spectra were measured with a Specord M-80
spectrophotometer using samples pelletized with
KBr. Purity of the synthesized compounds was
checked by TLC on Silufol UV-254 plates.
Yields and physicochemical characteristics of the
synthesized compounds are presented in Tables 1
and 2.
N,N-Dialkyl-3-(1-adamantyl)-1-aminopro-
pan-3-one hydrochlorides (Ia – Id). Compo-
unds Ia – Id were synthesized according to the
general method described elsewhere [6]. The
physicochemical properties were reported for
compound Ia in [7] and for the Mannich base Id
in [8].
TABLE 1. Yields and Physicochemical Characteristics of the Synthesized
Compounds
IR spectrum, n, cm – 1
Com- Yield,
M.p.,
°C
Empirical
formula
Rf
…
…
…
pound
%
CH2 (Ad) C(=O)
other
…
Ib
48 220 – 222
37 173 – 175
2900,
2850
1700
1680
1710
C27H33NO × HCl
C18H29NO × HCl
C15H25NO × HCl
Ic
2900,
2850
…
…
II
39
65
> 300
2900,
2850
IIIa
IIIb
IV
V
93 – 94
0.771) C19H23NO
2900,
2850
1640 3400 (NH)
1630 3400 (NH)
59 150 – 151 0.711) C17H21NOS
57 183 – 185 0.682) C17H28N2O2
2900,
2850
2900,
2850
…
…
–
3400 (NH),
1600 (C = N)
34
63 – 65
0.281) C15H27NO
2900,
2850
3400 (OH)
3420 (OH)
1-[N-(1-Adamantyl)-N-methylamino]bu-
tan-3-one hydrochloride (II). A mixture of 1.0 g
(5.2 mmole) 1-methylaminoadamantane hydroc-
hloride, 0.32 g paraformaldehyde, and 0.58 ml
(7.8 mmole) of acetone in 10 ml of isopropyl al-
cohol was boiled for 18 h and cooled. The preci-
VI
XI
75 131 – 132 0.762) C20H29NO
57 108 – 110 0.401) C20H25NO
2920,
2870
2900,
2850
1650 3450 (NH)
Notes. Eluent: 1) acetone – CCl4 (1 : 12); 2) acetone – CCl4 (1 : 4).

482
N. V. Makarova et al.
TABLE 2. 1H NMR Spectra of the Synthesized Compounds
Proton chemical shift d, ppm
Com-
pound
CH2 (Ad)
CH (Ad)
other protons
Ib
Ic
1.65 – 1.75 (d, 12H)
1.85 (s, 3H)
3.65 (t, 2H, C(=O)CH2), 2.56 (t, 2H, CH2N), 3.55 (s, 4H, 2CH2C6H5), 6.8 – 7.28 (m, 10H,
2CH2C6H5)
1.70 – 1.75 (d, 12H)
2.01 (s, 3H)
3.15 (m, 2H, C(=O)CH2), 2.75 (t, 2H, CH2N), 1.35 (m, 2H, CH2 p-piperidyl), 1.6 (m, 4H, 2CH2
m-piperidyl), 2.5 (m, 4H, 2CH2 o-piperidyl)
II
1.65 – 1.75 (d, 12H)
1.65 – 1.75 (d, 12H)
1.98 (s, 3H)
1.90 (s, 3H)
3.84 (t, 2H, C(=O)CH2), 2.67 (t, 2H, CH2N), 2.06 (s, 3H, CH3C(=O)), 2.12 (s, CH3, CH3N)
IIIa
5.65 (d, 1H, C(=O)CH=, J 8 Hz, cis-), 5.80 (d, 1H, C(=O)CH=, J 16 Hz, trans-), 7.25 (t, 1H,
=CHN, cis-), 7.55 (t, 1H, =CHN, trans-), 7.40 – 7.80 (m, 5H, C6H5), 10.65 (d, 1H, NH, J 16 Hz)
IIIb
1.65 – 1.70 (d, 12H)
1.85 (s, 3H)
5.55 (d, 1H, C(=O)CH=, J 7 Hz, cis-), 5.85 (d, 1H, C(=O)CH=, J 16 Hz, trans-), 7.05 (t, 1H,
=CHN, cis-), 7.70 (t, 1H, =CHN, trans-), 7.20 – 7.55 (m, 3H, thienyl), 10.25 (bs, 1H, NH,
J 18 Hz)
V
1.65 – 1.75 (d, 12H)
1.65 – 1.70 (d, 12H)
1.95 (s, 3H)
1.95 (s, 3H)
2.50 (q, 2H, CHCH2), 2.65 (m, 6H, N(CH3)2), 2.75 (d, CH2N), 3.85 (d, 1H, OH), 4.85 (q, 1H,
CH)
XI
2.50 (s, 2H), 5.20 (d, 1H, C(=O)CH=, J 7 Hz, cis-), 5.55 (d, 1H, C(=O)CH=, J 14 Hz, trans-),
6.90 (t, 1H, =CHN, cis-), 7.78 (t, 1H, =CHN, trans-), 7.05 – 7.78 (m, 5H, C6H5), 11.7 (d, 1H, NH,
J 14 Hz)
und V was separated by filtration and recrystallized from et-
hanol.
EXPERIMENTAL BIOLOGICAL PART
The antiviral properties of compounds Ib, Ic, IV, and V
were studied in experiments with cell cultures of herpes sim-
plex virus of type I (HSV-I, strain 1C), white pox vaccine
(Pox, strain B-52), influenza virus (INFL, strain A/Ros-
tock/34(H7N1)), respiratory syncytial virus (RSV, strain
Long), vesicular stomatitis (VST, strain Indiana), Venezuela
horse encephalomyelitis (VHE, strain VHE-230), rotavirus
(Rota, strain SA-11), and ECHO 6. Compounds IIIa and VI
were characterized only with respect to HSV-I and influenza,
and compound II – with respect to VHE and influenza. The
tests with RSV were performed with an inoculated culture of
rabbit lung cells (RL-33); the test with ECHO 6 was conduc-
ted in a passed culture of human embryo dermatomuscular
cells; the tests with other viruses were carried out with a pri-
mary culture of chicken embryo fibroblasts. The compounds
to be tested were initially dissolved in bidistilled water or
DMSO.
4-(1-Adamantyl)-1-(phenylamino)butan-3-ol (VI). To
a suspension of 0.26 g (11 mmole) sodium in 10 ml of an-
hydrous benzene was slowly added 1 ml (13 mmole) of ethyl
formate and the mixture was allowed to stand for 30 min. To
this mixture was carefully added a solution of 1 g (5.2 mmo-
le) of ketone IX in 10 ml of benzene and the reaction mixture
was allowed to stand for 6 h. The precipitate of sodium salt
X was filtered, washed with diethyl ether, and dried. A mix-
ture of 0.5 g (2.1 mmole) of salt X and 0.27 g (2.1 mmole) of
freshly prepared aniline hydrochloride in 10 ml of a 50%
aqueous ethanol solution was boiled for 18 h and cooled. The
precipitated enaminoketone XI was separated by filtration
(see Tables 1 and 2). To a solution of 0.2 g (0.68 mmole) of
enaminoketone XI in 10 ml of methanol was added by small
portions with stirring at room temperature 0.05 g (1.4 mmo-
le) of sodium borohydride and the mixture was allowed to
stand for 12 h. Then the reaction mass was acidified with a
10% aqueous HCl solution to pH 5 – 6 and diluted with wa-
ter. The precipitate of compound VI was separated by filtrati-
on and recrystallized from chloroform.
Primary assessment of the antiviral activity was perfor-
med by screening. Monolayer cell cultures grown in 10-mm
Petri dishes were washed from the growth medium and ino-
TABLE 3. Antiviral Activity Spectrum of the Tested Adamantyl-Containing Ketones
MTC,
mg/ml
Compound
HSV-I
–
Pox
–
INFL
RSV
+
VST
–
VHE
+++
ECHO 6
–
Rota
–
Ib
Ic
25
–
++
–
II
–
IIIa
IV
V
+++
+
200
50
++++
–
+
–
–
++
VI
+++

Antiviral Activity of Adamantyl-Containing b-Aminoketones
TABLE 4. Antiviral Properties of Adamantyl-Containing Ketones
483
Difference
from control,
log [pfu/ml]
Com-
pound
Test
virus
Concentration,*
Titer ± Sx,
log [pfu/ml]
IC50 (I95),
mg/ml
MTC/IC50
mg/ml
Ib
RSV
25
12
6
< 3.00
3.30 ± 0.30
3.74 ± 0.04
3.90 ± 0.30
4.32 ± 0.02
< 6.00
> 1.32
1.02
0.58
0.42
–
< 3.12
8
3
0
VHE
INFL
12
6
> 1.61
> 1.61
0.50
–
< 3.12
8
< 6.00
3
7.11 ± 0.03
7.61 ± 0.01
< 3.00
0
Ic
400
200
100
50
25
12
0
> 3.95
> 3.95
1.15
0.49
0.12
0.06
–
38.18 (42.82 – 34.04)
10.48
< 3.00
5.80 ± 0.03
6.46 ± 0.01
6.83 ± 0.01
6.89 ± 0.02
6.95 ± 0.05
7.39 ± 014
7.42 ± 0.02
7.88 ± 0.06
7.90 ± 0.08
4.30 ± 0.13
4.30 ± 0.13
6.18 ± 0.13
6.18 ± 0.13
6.30 ± 0.13
7.00 ± 0.26
6.30 ± 0.13
< 3.00
IIIa
INFL
25
12
6
0.51
0.48
0.02
–
13.26 (15.20 – 11.57)
60.42 (63.39 – 57.59)
1.88
3.31
0
HSV-I
200
100
50
25
12
6
2.00
2.00
0.12
0.12
0
–0.70
–
0
IV
VI
INFL
200
100
50
25
0
> 1.32
> 1.32
> 1.32
> 1.32
–
< 25
> 8
< 3.00
< 3.00
< 3.00
4.32 ± 0.02
5.3 ± 0.26
6.0 ± 0.53
6.3 ± 0.22
7.3 ± 0.22
7.3 ± 0.22
7.3 ± 0.22
HSV-I
400
200
100
50
25
0
2.0
81.72 (86.17 – 77.50)
4.89
1.3
1.0
0
0
–
* Maximum of the presented values corresponds to MTD for the given cell culture. Abbreviations: pfu, plaque-forming
units; Sx, arithmetic mean error; IC50, half-inhibiting concentration; I95, 95% confidence interval.
culated with viruses at 0.0001 – 0.00001 pfu/viral cell. After
a 1-h contact with the virus-containing solution, the mono-
layer cell culture was poured with melted nutrient medium
(concentrated medium 199 with 1% bactoagar and 0.005%
Neutral Red, all reagents from Sigma). Upon cooling, round
troughs were cut in the agar medium and glass tubes were in-
serted into these depressions. Each tube contained 0.05 ml of
a stock solution (5 mg/ml) of the substance tested. The re-
sults were estimated after the appearance of viral plaques
(36 – 48 h incubation in a thermostat). The results were eva-
luated by measuring the diameters of the concentric zones of
toxicity manifestation and the zone of plaque growth inhibi-

484
N. V. Makarova et al.
tion surrounding the tubes with substances, which formed as
a result of test solution diffusion in the agar medium. If the
diameter of the zone of plaque growth inhibition was below
10 mm, the substance was considered as not possessing anti-
viral properties. The other (qualified) substances were repea-
tedly tested using the method of serial dilutions in solutions
of preset concentrations.
The tests with preset concentrations were performed eit-
her using a method based on plaque number reduction under
agar coating or by determining the cytopathic viral effect (for
HSV-I with compounds IIIa and VI). According to the for-
mer procedure, monolayer cell cultures grown in flasks were
washed of the growth medium and inoculated with various
viruses in solutions diluted within 0.01 – 0.00001 pfu/viral
cell (1-h contact with 0.1 ml of a virus-containing suspension
at 37°C). Then the cells were poured with melts of the above
indicated nutrient medium containing various concentrations
of the compounds to be tested. After solidification of the coa-
ting, the flasks were incubated for 36 h in a thermostat. Upon
termination of the exposure, the numbers of plaques were co-
unted and the titers of viruses were determined. The maxi-
mum tolerated concentration (MTC) of each substance, not
toxic for the cell culture, was determined upon staining the
monolayer.
number of infection units, the Reed – Mench method, and
small-n statistics in a non-grouped data series [9 – 11]. The
drug concentrations inhibiting the viral growth by half (IC50)
values were determined using probit analysis and weighted
linear regression techniques [12]. The MTC/IC50 ratio was
calculated to characterize the breadth of therapeutic action
(nontoxic but active concentrations) of the compounds
tested.
RESULTS AND DISCUSSION
In the series of substances studied, antiviral properties
were found in compounds Ib, Ic, IIIa, IV, V, and VI (Tables 3
and 4). A moderate activity was observed for b-aminoketone
Ib with respect to respiratory syncytial virus and Venezuela
horse encephalomyelitis; aminoketone Ic, to influenza virus;
aminoalcohols V and VI, to HSV-I. Enaminoketone IIa was
also mostly active toward HSV-I, but in addition also weakly
affected the influenza virus; oxime IV showed a high activity
with respect to the latter viral species. Thus, most of the synt-
hesized compounds possess antiviral properties.
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