Antiviral activity of compounds based on (1-adamantyl)bromomethyl ketone

Full text of DOI:10.1023/A:1012389520183

Pharmaceutical Chemistry Journal
Vol. 35, No. 6, 2001
ANTIVIRAL ACTIVITY OF COMPOUNDS BASED
ON (1-ADAMANTYL)BROMOMETHYL KETONE
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. 6, pp. 18 – 20, June, 2001.
Original article submitted March 13, 2001.
Aminoketones are known to possess a broad spectrum of
pharmacological activity [1], but their antiviral properties are
still insufficiently studied. There was a search for antiviral
agents among a-aminoketones of saturated lactone derivati-
ves [2]. Some data on the antiviral activity of thiosemicarba-
zones of ketones and aldehydes were reported in [3, 4].
In continuation of the investigation of aminocarbonyl de-
rivatives of adamantane [5], we have studied the antiviral
properties of a series of adamantyl-containing a-aminoke-
tones,
including
2-(1-adamantyl)aminoethan-2-ones
(Ia – If ), N,N-di(1-adamantanoylmethyl)aniline (diaminoke-
tone II), thiosemicarbazones of a-aminoketones (IIIa, IIIb),
O
O
1-(1-adamantyl)-2-toluidinoethylidenetolylamine
(Schiff
base IV), and 2-(1-adamantyl)-1-furanoyloxyethan-2-one
(ester V).
CCH2OC
V
O
COOH
NHRR'
The nitial reagent in the synthesis of all compounds was
(1-adamantyl)bromomethyl ketone (VI). Interacting with
amines in a 1 : 1 ratio (in ethanol in the presence of Na2CO3),
bromoketone VI yields monoaminoketones Ia – If; the same
process with reagents taken in a 2 : 1 ratio also yielded dia-
minoketone II. The reactions of aminoketones Id and If with
thiosemicarbazide in methanol yielded thiosemicarbazones
IIIa and IIIb, respectively. The reaction of Id with p-toluidine
led to the Schiff base IV. Ester V was obtained via interaction
of bromoketone VI with pyromucic acid in acetone in the
presence of triethylamine.
O
Et3N
O
CCH2 NC6H5
O
2
CCH2Br
VI
II
O
CCH2NRR'
Ia – If
NH2
CH3
ZnCl2
NH2NHCNH2
S
EXPERIMENTAL CHEMICAL PART
CCH2NH
N
CH3
The 1H NMR spectra were recorded on a Bruker AC-300
spectrometer (working frequency, 300.13 MHz) using
DMSO as the solvent and HMDS as the internal standard.
The IR absorption spectra were measured with a Specord
M-80 sectrophotometer in KBr disks. Purity of the synthesi-
zed compounds was checked by TLC on Silufol UV-254 pla-
tes. Yields and physicochemical characteristics of the synthe-
sized compounds are presented in Tables 1 and 2. The data of
elemental analyses (for C, H, N) agree with the results of
analytical calculations using empirical formulas.
CH3
CCH2NRR'
IV
NHCNH
N
2
S
IIIa, IIIb
I: R = H (a – d), R¢ = CH2CH2OH (a), 3-COOH-1-adamantyl (b), C6H5 (c),
4-CH3C6H4 (d), NRR¢ = piperidyl (e); NRR¢ = morpholyl (f);
III: R = H (a), R¢ = CH3C6H4 (a), NRR¢ = morpholyl (b).
2-(1-Adamantyl)aminoethan-2-ones (I) were synthesi-
zed as described previously [6].
1
Belarus Research Institute of Epidemiology and Microbiology, Minsk,
N,N-Di(1-adamantanoylmethyl)aniline (II). A mixture
of 3 g (11 mmole) bromoketone VI, 0.5 ml (5.5)mmole) ani-
Belarus.
2
Samara State Technical University, Samara, Russia.
308
0091-150X/01/3506-0308$25.00 © 2001 Plenum Publishing Corporation

Antiviral Activity of Compounds Based on (1-Adamantyl)Bromomethyl Ketone
309
line, 1.5 g Na2CO3, and 10 ml ethyl alcohol was boiled for
3 h and poured into water. The precipitated product was filte-
red and recrystallized from ethanol.
Thiosemicarbazones of a-aminoketones (IIIa, IIIb). A
solution of 4.8 mmole of aminoketone Id or If and 0.53 g
(5.7 mmole) of thiosemicarbazide in 15 ml of methanol was
boiled until precipitation ceased. The precipitated product
was filtered.
1-(1-Adamantyl)-2-toluidinoethylidenetolylamine (IV).
To a solution of 1.0 g (3.5 mmole) of aminoketone Id and
0.68 g (6.4 mmole) of p-toluidine in 10 ml toluene were ad-
ded by portions 0.079 g (0.58 mmole) ZnCl2. The reaction
mixture was heated for 6 h and poured into water. The pro-
duct was extracted with ether and dried. Finally, the solvent
was distilled off and the residue recrystallized from ethanol.
2-(1-Adamantyl)-1-furanoyloxyethan-2-one (V). A so-
lution of 0.5 g (1.9 mmole) bromoketone VI, 0.64 g
(5.7 mmole) pyromucic acid, and 0.82 ml (11 mmole) of
freshly distilled triethylamine in 15 ml acetone was boiled
until precipitation ceased. Then the reaction mass was dilu-
ted with a saturated Na2CO3 solution and the precipitate was
filtered and recrystallized from hexane.
EXPERIMENTAL BIOLOGICAL PART
The antiviral properties of the synthesized compounds
were studied in experiments with cell cultures containing
herpes simplex virus of type I (HSV-I, strain 1C), white pox
vaccine (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. The tests with RSV were
performed with an inoculated culture of rabbit lung cells
(RL-33); the test with ECHO 6 was conducted in a passed
culture of human embryo dermatomuscular cells; the tests
with other viruses were carried out with a primary culture of
chicken embryo fibroblasts.
The compounds to be tested were initially dissolved in
bidistilled water of DMSO, in accordance with the solubility
data (aqueous stock solution, 5 mg/ml; for substances inso-
luble in pure water, 10% DMSO was added).
Primary assessment of the antiviral activity was perfor-
med by screening. Monolayer cell cultures in 100-mm Petri
TABLE 1. Yields and Physicochemical Characteristics of the Synthesized Compounds
IR spectrum: n, cm – 1
Rf (eluent)
Compound Empirical formula
M.p., °C
Yield, %
CH2 Ad
C=O
NH
other
Ia
C16H27NO3
C23H33NO3
C18H23NO
C19H25NO
C17H27NO
C16H25NO2
C30H39NO2
C20H28N4S
C17H28N4OS
C26H32N2
97 – 99
154 – 155
205 – 206
117 – 118
55 – 57
2910, 2860
2900, 2850
2900, 2850
2910, 2860
2900, 2850
2900, 2850
2900, 2850
2900, 2850
2900, 2850
2900, 2850
2900, 2850
1710
1720
1690
1710
1710
1700
1680
–
–
3340 (OH)
0.161)
0.922)
0.302)
0.711)
0.461)
0.642)
0.821)
0.633)
0.733)
0.321)
0.581)
78
95
59
80
93
95
82
90
77
51
63
Ib
Ic
3290
3380
3390
–
–
–
Id
Ie
–
–
If
53 – 55
–
–
II
232 – 235
179 – 181
181 – 183
149 – 150
112 – 113
–
–
IIIa
IIIb
IV
V
3400
3400
3400
–
1600 (C=N)
1600 (C=N)
1590 (C=N)
–
–
–
C17H20O4
1730
Notes. 1) acetone – CCl4 (1 : 6); 2) hexane – chloroform (1 : 4); 3) ethanol.
TABLE 2. 1H NMR Spectra of the Synthesized Compounds
Proton chemical shift d, ppm
Compound
CH2 Ad
CH Ad
C(=O)CH2
NH
other
Ia
Ic
Id
Ie
1.60 – 1.75 (d, 12H)
1.60 – 1.75 (d, 12H)
1.65 – 1.70 (d, 12H)
1.70 – 1.80 (d, 12H)
2.00 (s, 3H)
2.00 (s, 3H)
1.90 (s, 3H)
2.00 (s, 3H)
2.90 (s, 2H)
3.82 (d, 2H)
4.05 (d, 2H)
3.35 (s, 2H)
–
3.10 (m, 2H, 2OH), 3.65 (m, 8H, 2CH2CH2OH)
7.20 – 7.39 (m, 5H, C6H5)
11.1 (bs, 1H)
4.9 (t, 1H)
–
2.15 (s, 3H, CH3), 6.55 – 6.95 (m, 4H, C6H4)
1.40 (m, 2H, CH2 p-piperidyl), 1.41 (m, 4H, 2CH2
m-piperidyl), 2.45 (m, 4H, 2CH2 o-piperidyl)
If
II
1.60 – 1.75 (d, 12H)
1.65 – 1.75 (d, 24 H)
1.65 – 1.75 (d, 12H)
1.70 – 1.72 (d, 12H)
1.97 (s, 3H)
2.02 (s, 6H)
2.00 (s, 3H)
1.90 (s, 3H)
3.56 (s, 2H)
4.46 (s, 4H)
3.12 (d, 2H)
5.10 (s, 2H)
–
2.6 (t, 4H, CH2NCH2), 3.66 (t, 4H, CH2OCH2)
6.30 – 7.33 (m, 5H, C6H5)
–
IV
V
4.72 (bs, 1H)
–
2.30 (s, 6H, 2CH3), 6.82 – 7.95 (m, 8H, 2C6H4)
6.55 (s, 1H), 7.25 (d, 1H), 7.85 (s, 1H)

310
N. V. Makarova et al.
TABLE 3. Results of the Antiviral Testing of Adamantyl-Con-
TABLE 4. Antiviral Activity of Adamantyl Derivatives
taining Compounds
Compound
Test virus
IC50, mg/ml
PTC/IC-50
Com- MTC,
pound mg/ml
Ortho- Para- Rha-
mixo mixo bdo
Picor-
na
Ia
Ic
INFL
HSV-I
RSV
< 6.0
19.72
14.23
10.33
46.57
19.61
64.04
18.14
354.76
> 8
2.5
Herpes Pox
Toga
Rota
Ia
Ib
50
+++
–
+
–
–
+
–
–
–
3.5
–
+
–
–
–
–
–
+
–
–
–
–
–
–
–
+++
–
Rota
4.8
Ic
50
50
–
–
Ie
VST
1.1
Ie
–
–
++
–
VHE
2.5
II
200
50
++
+
–
–
II
V
HSV-I
INFL
HSV-I
3.1
IIIa
IIIb
IV
V
–
–
22.05
2.25
–
–
–
–
–
and Mench infection units [7 – 9]. The IC50 vales were deter-
mined using probit analysis and weighted linear regression
techniques [10]. The MTC/IC50 ratio was calculated to cha-
racterize the breadth of nontoxic but active concentrations of
the compounds tested.
dishes were washed from the growth medium and inoculated
with viruses at 0.0001 – 0.00001 o.u./viral cell. After 1-h
contact with the virus-containing solution, the monolayer
cell culture was poured with melted nutrient medium (con-
centrated medium 199 with 1% bactoagar and 0.005% Neut-
ral Red, all from Sigma). Upon cooling, round troughs were
cut in the agar medium and glass tubes were inserted into
these holes. Each tube contained 0.05 ml of a stock solution
(5 mg/ml) of the substance tested. The results were estima-
ted after the appearance of viral plaques (36 – 48 h incubati-
on in a thermostat) visualized by the vital dye preset in the
nutrient medium. The results were evaluated by measuring
the diameters of the concentric zone of toxicity manifestation
and the zone of plaque growth inhibition around the sources
of the substances, which formed as a result of diffusion of the
test solution 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 antiviral properties. The ot-
her (qualified) substances were repeatedly tested using the met-
hod of serial dilutions in solutions of preset concentrations.
The test with preset concentrations was performed using
a method based on plaque number reduction under agar coa-
ting. According to this, monolayer cell cultures grown in
flasks were washed from the growth medium and inoculated
with various viruses in solutions diluted within
0.01 – 0.00001 o.u./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 the compounds to be tested. After solidification of
the coating, the flasks were incubated for 36 h in a thermos-
tat. Upon termination of the exposure, the numbers of plaqu-
es were counted and the titers of the viruses were determi-
ned. The maximum tolerated concentration (MTC) of each
substance, not toxic for the cell culture, was determined upon
staining the monolayer.
RESULTS AND DISCUSSION
In the series of substances studied, antiviral properties
were found in compounds Ia, Ic, Ie, II, and V (Tables 3 and
4). Compound Ia exhibited especially high activity with res-
pect to influenza virus, while compound Ic showed a broad
spectrum of antiviral action and was effective against herpes,
respiratory syncytial virus, and rotavirus. Compound Ie was
active with respect to vesicular stomatitis and Venezuela hor-
se encephalomyelitis and compound II inhibited herpes, but
these effects were observed only at the maximum concentra-
tions tolerated by cell cultures. Compound V inhibited the
growth of influenza and herpes viruses, the antiinfluenza ef-
fect being more pronounced (observed in a rather broad con-
centration range).
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