Synthesis and antitumor activity of some disubstituted 5-(3-methyl-4-alkoxybenzyl)pyrimidines

Full text of DOI:10.1023/A:1010398911988

Pharmaceutical Chemistry Journal
Vol. 34, No. 10, 2000
SYNTHESIS AND ANTITUMOR ACTIVITY OF SOME DISUBSTITUTED
5-(3-METHYL-4-ALKOXYBENZYL)PYRIMIDINES
M. A. Kaldrikyan,1 L. A. Grigoryan,1 V. A. Geboyan,1 F. G. Arsenyan,1
G. M. Stepanyan,1 and B. T. Garibdzhanyan1
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 34, No. 10, pp. 9 – 11, October, 2000.
Original article submitted December 14, 1999.
In continuation of the search for new compounds pos-
sessing antitumor activity [1], we have synthesized a series
of pyrimidines II – VI by the following scheme:
3-methyl-4-alkoxybenzyl chlorides with malonic ester in the
presence of sodium ethylate; the procedure was analogous to
that described in [2]. Subsequent cyclization of the substi-
tuted malonic esters I with thiourea or guanidine hydrochlo-
ride in anhydrous ethanol in the presence of sodium ethylate
led to the formation of pyrimidines II or III. Here, an impor-
tant factor is the amount of sodium ethylate. It was estab-
lished that 2-mercapto- and 2-amino-4,6-dihydroxypyrimi-
dines II and III can be obtained with high yields only if two
or three equivalents of sodium ethylate, respectively, are em-
ployed.
H3C
COOC2H5
CH
CH2
RO
COOC2H5
Ià – Id
NH2C(=S)NH2
NH2C(=NH)NH2 · HCl
CH3
OR
CH3
Pyrimidines II were converted into methylthio deriva-
tives IV by reaction with methyl iodide in a methanol solu-
tion of potassium hydroxide. The purity and identity of com-
pounds II – IV were checked by TLC. The proposed struc-
OH
N
OH
CH2
OR
CH2
N
N
HS
OH
H2N
N
OH
1
tures were confirmed by data of the IR, H NMR, and mass
spectroscopy.
IIà – IId
IIIà – IIId
POCl3
KOH CH3I
Pyrimidines III and IV were chlorinated by reaction with
freshly distilled phosphorus chloroxide (for IV, in the pres-
ence of pyridine). The target 4,6-dichloropyrimidines V and
VI appear as crystalline substances which, in contrast to the
corresponding hydroxy derivatives, are well soluble in many
organic solvents.
CH3
CH3
Cl
OH
CH2
OR
OR
CH2
N
N
H2N
N
Cl
VIà – VId
H3CS
N
OH
IVà – IVd
POCl3
Finally, we have studied the nucleophilic substitution of
diethylaminoethanol for chlorine atoms in 4,6-dichloropyri-
midine Vb
CH3
Cl
OR
CH2
The reaction in toluene with a fivefold excess of
diethylaminoethanol leads to the formation of a disubstituted
product VIII, while the process involving two moles of
diethylaminoethanol per mole of Vb yields a monosubstitu-
ted pyrimidine VII.
N
H3CS
N
Cl
Và – Vd
CH3
R = Me (a), Et (b), n-Pr (c), and i–Pr (d).
Cl
CH2
Cl
OC2H5
The initial reagents were (3-methyl-4-alkoxybenzyl)ma-
lonates (I) obtained by reaction of the corresponding
N
H3CS
N
Vb
1
Mndzhoyan Institute of Fine Organic Chemistry, National Academy of
Sciences of the Republic of Armenia, Yerevan, Armenia.
521
0091-150X/00/3410-0521$25.00 © 2001 Plenum Publishing Corporation

522
M. A. Kaldrikyan et al.
CH3
drous ethanol was boiled with stirring for 6 – 8 h. Then
120 ml of water was added and the product was extracted
with diethyl ether. The aqueous layer was acidified with con-
centrated HCl until to acid reaction to Congo Red. Upon
cooling, the precipitated crystals were filtered, washed with
water, and recrystallized from ethanol (Table 2). The param-
eters of the IR spectra are listed in Table 3.
Cl
N
OC2H5
CH2
N
H3CS
OCH2CH2N(C2H5)2
VII
+
CH3
Compound IIc, 1H NMR spectrum (d, ppm): 1.05 (t, 3H,
OCH2CH2CH3), 1.75 (m, 2H, OCH2CH2CH3), 2.10 (s, 3H,
CH3), 3.45 (s, 2H, CH2), 3.92 (t, 2H, OCH2CH2CH3), 4.70
(1H, SH) 6.85 (m, 3H, H arom), 11.5 (2H, 2OH).
O
(C2H5)2NCH2CH2
CH2
OC2H5
N
H3CS
N
OCH2CH2N(C2H5)2
VIII
2-Amino-4,6-dihydroxy-5-(3-methyl-4-alkoxybenzyl)
pyrimidines (IIIa – IIId). A mixture of sodium ethylate pre-
pared from 3.45 g (0.15 g-atom) of metal sodium and 100 ml
of anhydrous ethanol, 0.05 mole (3-methyl-4-alkoxyben-
zyl)malonate (Ia – Id), and 4.78 g (0.05 mole) guanidine hy-
drochloride was boiled with stirring for 10 – 12 h. Then
150 ml of water was added and the mixture was acidified
with acetic acid to pH 5 and allowed to stand in a refrigerator
for 10 – 12 h. The precipitated crystals were filtered, washed
with water, and recrystallized from acetic acid (Table 4). The
parameters of the IR spectra are listed in Table 3.
EXPERIMENTAL CHEMICAL PART
The TLC analyses were conducted on Silufol UV-254
plates; the spots were visualized by UV irradiation. The IR
spectra were recorded on an UR-20 spectrophotometer (Ger-
1
many). The H NMR spectra were measured on a Mercury
300 spectrometer at a working frequency of 300 MHz, using
DMSO-d6 as the solvent and TMS as the internal standard.
The mass spectra were obtained with an MX-1320 spectrom-
eter. The samples were introduced directly into the ionization
chamber at a temperature 40 – 50°C below the melting tem-
perature of the corresponding substance and ionized at an
electron impact energy of 30 eV. The data of elemental anal-
yses agreed with the results of analytical calculations accord-
ing to the empirical formulas.
Compound IIIc, 1H NMR spectrum (d, ppm): 1.00 (t, 3H,
OCH2CH2CH3), 1.70 (q, 2H, OCH2CH2CH3), 2.05 (s, 3H,
CH3), 3.40 (s, 2H, CH2), 3.95 (t, 2H, OCH2CH2CH3), 6.80
(2H, NH2), 6.90 (m, 3H, H arom), 10.4 (2H, 2OH).
2-Methylthio-4,6-dihydroxy-5-(3-methyl-4-alkoxyben
zyl)pyrimidines (IVa – IVd). To 5.6 g (0.1 mole) of potas-
sium hydroxide dissolved on heating in 250 ml of methanol
was added 0.1 mole of 2-mercaptopyrimidine (IIa – IId). The
mixture was heated on a water bath with stirring for
5 – 10 min and cooled. Then 21.3 g (0.15 mole) of methyl
iodide were added and the mixture heated for 15 – 20 min
and cooled. Upon cooling, 100 – 150 ml of water were added
and the mixture was allowed to stand overnight. The precipi-
tated crystals were filtered, washed with water, and
recrystallized from acetic acid (Table 2).
(3-Methyl-4-alkoxybenzyl)malonic acid diethyl esters
(Ia – Id). To sodium ethylate prepared from 2.3 g (0.1 g-atom)
of metal sodium and 100 ml of anhydrous ethanol were se-
quentially added 32 g (0.2 mole) of malonic aldehyde and
0.1 mole of the corresponding 3-methyl-4-alkoxybenzyl
chloride [3] and the mixture was heated on a water bath with
stirring for 10 – 12 h. Then ethanol was distilled off, water
added, and the product was extracted with diethyl ether. The
ether extracts were dried over calcined sodium sulfate. Then
ether was removed and the residues were distilled in vacuum
(Table 1).
2-Methylthio-4,6-dichloro-5-(3-methyl-4-alkoxybenzy
l)pyrimidines (Va – Vd). A mixture of 15.3 g (0.1 mole) of
2-Mercapto-4,6-dihydroxy-5-(3-methyl-4-alkoxyben-
zyl)pyrimidines (IIa – IId). A mixture of 0.05 mole of
TABLE 2. Yields and Physicochemical Characteristics of Com-
pounds II and IV
(3-methyl-4-alkoxybenzyl)malonate
(Ia – Id),
6.08 g
(0.08 mole) thiourea, and sodium ethylate prepared from
2.99 g (0.13 g-atom) of metal sodium and 70 ml of anhy-
Com-
pound
Empirical
formula
Rf
Yield, %
M.p., °C
IIa
90.0
88.4
72.8
75.2
84.7
79.4
74.1
78.3
110 – 112
140 – 142
114 – 115
104 – 105
210 – 212
232 – 234
267 – 268
259 – 260
0.49*
0.51*
C13H14N2O3S
C14H16N2O3S
C15H18N2O3S
C15H18N2O3S
C14H16N2O3S
C15H18N2O3S
C16H20N2O3S
C16H20N2O3S
IIb
IIc
0.50*
TABLE 1. Yields and Physicochemical Characteristics of Com-
pounds Ia – Id
IId
0.52*
IVa
IVb
IVc
IVd
0.65**
0.78**
0.61**
0.59**
Com-
pound
Yield,
%
B.p.,
Empirical
formula
nD20
d420
R
°C/2 Torr
Ia
CH3
60 177 – 178 1.4800 1.0865 C16H22O5
70 180 – 182 1.4798 1.0884 C17H24O5
69 178 – 182 1.4787 1.0899 C18H26O5
68 178 – 180 1.4780 1.0867 C18H26O5
Ib
Ic
Id
C2H5
n-C3H7
i-C3H7
*
Petroleum ether – acetone (3 : 2).
Benzene.
**

Synthesis and Antitumor Activity
523
TABLE 3. The IR Spectra of Compounds II – V (nmax, cm – 1
)
Pyrimidine
ring
C=Carom
CH3
SCH3
NH2, OH
Compound
C=N
C–O–C
SH
C–Cl
IIa – IId
1600
1950
1655
1680
1186
1210
1420
1420
1520
1530
2620
–
–
–
3200, 3320, 3560
–
–
IIIa – IIId
3090, 3250, 3390,
3600
IVa – IVd
Va – Vc
1600
1580
1675
1700
1180
1180
1425
1440
1535
1540
–
–
1290
1280
3350 – 3500
Missing
–
1720 – 1760
freshly distilled phosphorus chloroxide, 1.6 g pyridine, and
0.01 mole of 2-methylthiopyrimidine (IVa – IVd) was boiled
for 8 – 10 h. Then the excess phosphorus chloroxide was dis-
tilled off, the residue poured into a glass with ice, and the
mixture was allowed to stand overnight. The precipitated
crystals were filtered, washed with water, dried, and
recrystallized from anhydrous ethanol (Table 5).
EXPERIMENTAL BIOLOGICAL PART
The acute toxicity and antitumor activity of substituted
5-(3-methyl-4-alkoxybenzyl)pyrimidines II, III, and IV were
studied by conventional methods [4]. The toxicity was deter-
mined by single intraperitoneal injections to white mongrel mice.
The antitumor activity of the synthesized compounds
was assessed on mice inoculated with sarcoma 37 by subcu-
taneous injections of 0.3 ml of a 20% tumor culture suspen-
sion in physiological solution. All the compounds tested
were injected as suspensions in an 0.5% carboxymethylcel-
lulose solution. The injections were made in a single daily
dose of 1/10 LD100 over a period of six days beginning with
the 4th day after tumor inoculation.
2-Amino-4,6-dichloro-5-(3-methyl-4-alkoxybenzyl)py
rimidines (VIa – VId).
A mixture of 0.02 mole of
2-amino-4,6-dihydpyrimidines (IIIa – IIId) and 18 ml
(0.2 mole) of freshly distilled phosphorus chloroxide was
boiled for 10 h. Then the excess phosphorus chloroxide was
distilled off, the residue poured into a glass with ice, and the
mixture was allowed to stand in a refrigerator for 4 – 5 h.
The precipitated crystals were filtered and heated in 25 ml of
a 40% aqueous ammonia solution. Upon cooling, the crystals
were filtered, washed with water, and recrystallized from
acetic acid (Table 5).
The therapeutic effect was assessed the next day after the
last drug injection and evaluated as percentage tumor growth
inhibition (TGI). The experimental data were statistically
processed by the Student – Fisher method. The differences
from untreated control were considered as reliable for
p < 0.05.
2-Methylthio-4-chloro-6-diethylaminoethoxy-5-(3-me
thyl-4-alkoxybenzyl)pyrimidine (VII). A mixture of 15.3 g
(0.05 mole) of 2-methylthio-4,6-dichloropyrimidines Vb and
23.4 g (0.1 mole) of diethylaminoethanol in 30 ml of toluene
was boiled for 3 – 4 h. Then 100 ml of water were added and
the toluene layer was separated and dried over sodium sul-
fide. Finally, toluene was removed and the residue was dis-
tilled in vacuum; yield of compound VII, 48%; b.p., 250 –
252°C/4 Torr; Rf, 0.65 (petroleum ether); C21H30ClN3O2S.
2-Methylthio-4,6-di(diethylaminoethoxy)-5-(3-methyl-
4-alkoxybenzyl)pyrimidine (VIII). A mixture of 15.3 g
(0.05 mole) of 2-methylthio-4,6-dichloropyrimidines Vb and
29.2 g (0.25 mole) of diethylaminoethanol in 30 ml of tolu-
ene was boiled for 7 – 8 h and then treated as described
above. Compound VIII, 75%; b.p., 265 – 268°C/4 Torr; Rf,
0.60 (petroleum ether – acetone, 3 : 1); C27H44N4O3S.
It was established that all the compounds tested possess a
low acute toxicity: the absolute lethal dose is 2200 –
2500 mg/kg for compounds III and 1500 – 2000 mg/kg for
compounds II and IV. For this reason, the drug doses in the
chemotherapy experiments were 150 – 250 mg/kg.
Data on the antitumor activity of 2-mercapto-4,6-dihyd-
roxypyrimidines II showed that the therapeutic doses pro-
duced a weak antitumor effect (TGI = 35 – 42%, p £ 0.05)
while not producing any general toxic effect on the test ani-
mals. Among the 2-methylthio-4,6-dihydroxypyrimidine de-
rivatives IV, a reliable protective effect was observed only
TABLE 5. Yields and Physicochemical Characteristics of Com-
pounds V and VI
Com-
pound
Empirical
formula
Rf*
Yield, %
M.p., °C
TABLE 4. Yields and Physicochemical Characteristics of Com-
pounds IIIa – IIId
Va
84.5
81.2
80.8
89.6
89.3
85.4
84 – 85
95 – 97
0.60
0.62
0.65
0.51
0.56
0.53
C14H14Cl2N2OS
C15H16Cl2N2OS
C16H18Cl2N2OS
C13H13Cl2N3O
C14H15Cl2N3O
C15H17Cl2N3O
Com-
pound
Yield,
%
M.p.,
°C
Empirical
formula
Vb
Rf (methanol)
Vc
87 – 88
IIIa
76.6
74.6
73.4
75.0
> 300
> 300
0.69
0.66
0.65
0.60
C13H15N3O3
C14H17N3O3
C15H19N3O3
C15H19N3O3
VIa
VIb
200 – 202
188 – 190
159 – 160
IIIb
IIIc
IIId
289 – 290
304 – 306
VIc
*
Diethyl ether – petroleum ether (1 : 4).

524
M. A. Kaldrikyan et al.
for compounds with ethoxy (IVb) and propoxy (IVc) radicals
(TGI = 40 – 43%, p < 0.05). In contrast to the mercapto and
methylthio derivatives, aminopyrimidines III possessed a
somewhat more pronounced antitumor properties. For exam-
ple, the ethoxy (IIb) and propoxy (IIIc) derivatives showed
TGI = 55 and 62%, respectively ( p < 0.05).
REFERENCES
1. M. A. Kaldrikyan, A. V. Khekoyan, B. T. Garibdzhanyan, and G.
M. Stepanyan, Arm. Khim. Zh., 34(4), 318 – 321 (1981).
2. A. L. Mndzhoyan and V. V. Dovlatyan, Izv. Akad. Nauk ArmSSR,
Ser. Fiz.-Math., Est., Tech. Nauk, 8(1), 37 – 40 (1955).
3. A. L. Mndzhoyan and A. A. Aroyan, Izv. Akad. Nauk ArmSSR,
Ser. Fiz.-Math., Est., Tech. Nauk, 8(6), 29 – 31 (1955).
Thus, some of the newly synthesized 5-substituted
5-(3-methyl-4-alkoxybenzyl)pyrimidines possess a signifi-
cant antitumor activity in combination with low toxicity.
4. V. A. Chernov, Methods of Experimental Chemotherapy [in Rus-
sian], Medgiz, Moscow (1981), pp. 357 – 381.