σ-Complexes in the pyrimidine series. 14. Dihydropyrimidine analogs of acyclonucleosides. Synthesis of 2,3-dihydroxypropyl derivatives of 4-aryl-6-methyl-5-nitro- 1,4(3,4)-dihydropyrimidin-2-ones

Article abstract of DOI:10.1023/A:1023764207348

Methods have been developed for the synthesis of 5-nitro-1,4- and 5-nitro-3,4-dihydropyrimidin-2-one analogs of acyclonucleosides containing a 2,3-dihydroxypropyl fragment in positions 1 and 3 respectively of the dihydropyrimidine ring.

Full text of DOI:10.1023/A:1023764207348

Chemistry of Heterocyclic Compounds, Vol. 39, No. 2, 2003
σ-COMPLEXES IN THE PYRIMIDINE SERIES.
14*. DIHYDROPYRIMIDINE ANALOGS OF
ACYCLONUCLEOSIDES. SYNTHESIS OF
2,3-DIHYDROXYPROPYL DERIVATIVES
OF 4-ARYL-6-METHYL-5-NITRO-
1,4(3,4)-DIHYDROPYRIMIDIN-2-ONES
S. A. Kravchenko, V. V. Pirozhenko, S. I. Vdovenko, A. E. Sorochinsky,
and G. Ya. Remennikov
Methods have been developed for the synthesis of 5-nitro-1,4- and 5-nitro-3,4-dihydropyrimidin-2-one
analogs of acyclonucleosides containing a 2,3-dihydroxypropyl fragment in positions 1 and 3
respectively of the dihydropyrimidine ring.
Keywords: anionic σ-complexes, acyclonucleosides, nitrodihydropyrimidinones, allylation.
In recent years compounds possessing a wide spectrum of biological action have been found in the
hydrogenated pyrimidine series [2]. In particular derivatives of 3,4-dihydroquinazolin-2-one have been
described which are nonnucleoside inhibitors of reverse transcriptase [3-5]. From the anionic σ-complexes of
5-nitropyrimidine we have obtained [6] 5-nitro-2,5- and 5-nitro-1,6-dihydropyrimidine analogs of
acyclonucleosides, which at a lower cytotoxicity possess activity against HIV-1 comparable with the activity of
azidothymidine [6,7]. On the basis of these data it may be assumed that the hydrogenated pyrimidine fragment
participates in the antiviral action. In the present work, which continues investigation of dihydropyrimidine
analogs of acyclonucleosides, approaches have been developed for the synthesis of 2,3-dihydroxypropyl
derivatives of 4-aryl-6-methyl-5-nitro-1,4-dihydropyrimidin-2-ones. Choice of the latter as the heterocyclic
fragment is also due to the fact that these compounds display the properties of modulators of cellular calcium
[8,9] and are aza-analogs of 4-aryl-1,4-dihydropyrimidines, potentiators of antiviral and anticancer preparations
[10-13].
We showed previously that methylation of 4-aryl-2-methoxy-5-nitro-1,4-dihydropyrimidines is effected
at a nitrogen atom of the pyrimidine ring [14,15]. It is possible to consider this reaction as a model for the
synthesis of dihydropyrimidine analogs of nucleosides containing an acyclic substituent in positions 1 and 3 of
the heterocycle.
_______
* For Part 13 see [1].
__________________________________________________________________________________________
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of the Ukraine,
Kiev 02094; e-mail: okravchenko@mail.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2,
pp. 216-222, February, 2003. Original article submitted January 10, 2000; revision submitted February 16, 2001.
188
0009-3122/03/3902-0188$25.00©2003 Plenum Publishing Corporation

4-Aryl-2-methoxy-6-methyl-5-nitro-1,4-dihydropyrimidines 2a-c, synthesized from 1-arylidene-1-nitro-
2-propanones 1a-c, form stable anionic σ-complexes 3a-c in alkaline media. On interacting these complexes
with allyl bromide in benzene in the presence of benzyltriethylammonium chloride (BTEAC) N(3)-allyl-4-aryl-6-
methyl-5-nitro-3,4-dihydropyrimidines 4a-c were obtained, which are converted in acidic medium into
N(3)-allyl-3,4-dihydropyrimidin-2(1H)ones 5a-c (Table 1). The singlet form of the signal of the geminal proton
1
of the pyrimidine ring in the H NMR spectra of these compounds (Table 2) unequivocally proves the position
of the allyl substituent. Selective oxidation of the double bond of the allyl fragment in compounds 5a-c leads to
4-aryl-N(3)-(2,3-dihydroxypropyl)-6-methyl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones 6a-c.
R3
R2
R3
R2
R1
NO2
R1
NO2
NH
KOH
+
N
MeO
MeOH
NH2
MeO
N
H
2a–c
Me
COMe
R3
H
1a–c
R3
R2
R1
R2
Br
R1
HCl
EtOH
.
.
NO2
BTEAC, benzene
NO2
.
N
.
.
.
.
N
_
+
.
.
.
K
MeO
MeO
N
N
Me
R2
Me
R3
3a–c
4a–c
R3
R2
R1
R1
KMnO4
EtOH/H2O, –10 oC
NO2
NO2
HO
N
N
OH
O
N
H
N
H
Me
Me
O
5a–c
6a–c
1–6 a R1 = Cl, R2 = R3 = H; b R1 = H, R2 = R3 = OMe; c R1 = H, R2 + R3 = –OCH2O–
This is confirmed by the disappearance from the IR spectra of compounds 6a-c of absorption bands for
the stretching vibrations of the allyl group double bond (Table 1) and by the presence of absorption bands at
3600-3700 cm-1 corresponding to the stretching vibrations of hydroxyl groups. The presence of two singlet
1
signals at 5.66-6.52 ppm in the H NMR spectra of compounds 6a-c (Table 2), corresponding to the geminal
proton, indicates that the carbacyclonucleosides were isolated as a mixture of two diastereomers. However the
close values of the chemical shifts do not permit specific assignments to be made.
With the aim of obtaining N(1)-allyl derivatives of 4-aryl-5-nitro-1,4-dihydropyrimidin-2-one the
interaction has been studied of 6-methyl-5-nitro-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (7) with allyl
bromide in DMSO in the presence of sodium hydride. However nucleophilic attack occurred at the N(3) atom
189

TABLE 1. Characteristics of the Compounds Synthesized
Found, %
——————
IR spectrum* (KBr),
UV spectrum (CH3OH),
Com-
Empirical
formula
mp, °С
Yield, %
ν, cm-1
λmax, nm (log ε)
Calculated, %
pound
(ethanol)
С
Н
N
C14H14ClN3O3
C16H19N3O5
C15H15N3O5
C14H16ClN3O5
C16H21N3O7
C15H17N3O7
C17H19N3O3
C14H14ClN3O3
C16H19N3O5
C15H15N3O5
C14H16ClN3O5
C16H21N3O7
C15H17N3O7
55.12
54.64
4.82
4.59
13.70
13.65
147-149
167-169
160-162
Oil
1681, 1637, 3412
239 (3.78); 341 (3.76)
236 (3.94); 340 (3.8)
240 (4.1); 340 (4.0)
240 (3.8); 342 (3.79)
236 (3.9); 340 (3.87)
240 (4.05); 342 (3.98)
344 (4.05)
86
83
84
9
5а
5b
5c
57.98
5.84
12.84
1693, 1643, 3418
57.65
5.75
12.61
56.13
56.78
4.80
4.76
13.35
13.24
1681, 1643, 3412
49.94
5.04
12.36
1681, 3418, 3600, 3687
1681, 3412, 3600, 3675
1690, 3412, 3606, 3687
1681, 1631, 3412
6а
6b
6c
49.20
4.72
12.30
52.80
52.31
5.94
5.76
11.21
11.44
Oil
15
12
9
52.00
4.92
12.01
186-189
165-168
175-177
205-206
192-195
108-112
137-139
132-135
51.28
4.88
11.96
65.19
65.16
6.09
6.11
13.67
13.41
8
54.91
4.62
13.86
1681, 1631, 3431
230 (3.8); 344 (3.76)
230 (3.9); 342 (3.8)
239 (4.05); 346 (3.9)
345 (3.8)
42
34
40
12
9
9а
9b
9c
54.64
4.59
13.65
57.94
57.65
6.01
5.75
12.97
12.61
1689, 1637, 3418
57.59
4.74
13.31
1693, 1618, 3418
56.78
4.76
13.24
49.35
49.20
4.79
4.72
12.72
12.30
1675, 3431, 3606, 3681
1675, 3425, 3600, 3694
1672, 3425, 3600, 3686
10а
10b
10c
52.41
5.73
11.48
238 (3.96); 342 (3.9)
234 (3.95); 346 (3.89)
52.31
5.76
11.44
51.34
51.28
4.89
4.88
11.95
11.96
14
_______
* Bands at 1672-1693, 1618-1643, 3412-3431, and 3600-3687 cm-1 correspond to the absorption of C=O, CH=CH2, NH,
and OH groups respectively.

TABLE 2. 1H NMR Spectra of the Compounds Synthesized
Com-
Chemical shifts, δ, ppm (coupling constants, J, Hz)*
pound
N–H
H-4
CH3, s
N–CH2
Other signals
5.74, br. s*2
5.93 (d*2, J = 2.2)
2.58*2
—
—
3.95 s*2 (OCH3)
2a
2c
5.74, br. s*2; 6.25, s*3
5.78 (d*2, J = 2.4);
2.58*2, 2.51*3
3.97 s*2, 3.85 s*3 (OCH3); 5.90 s (CH2)
5.84, s*3
—
—
—
—
—
6.28, s
5.96, s
5.81, s
6.25, s
5.66, s
5.62, s
6.14, s
5.63, s
2.53
2.44
2.50
2.60
2.58
2.57
2.59
2.56
2.56
2.56
2.53
2.55
—
—
—
3.98 s (OCH3)
4.03 s (OCH3)
6.00 (CH2); 4.00 s (OCH3)
3а
3b
3c
4а
4b
4c
5a
5b
5c
5.19, m
5.66 s (CH); 3.98 s (OCH3); 4.08-3.57 m (=CH2)
5.26 m (CH+NCH2); 3.99 s, 3.86 s (OCH3); 4.25-3.47 m (=CH2)
5.94 s (CH2); 5.25 m (CH+NCH2); 3.98 s (OCH3); 4.25-3.51m (=CH2)
5.71 m (CH); 4.39-3.35 m (=CH2)
5.72 m (CH); 3.88 s (OCH3); 4.54-3.32 m (=CH2)
5.98 s (CH2); 5.73 m (CH); 4.54-3.29 m (=CH2)
4.23 m (CHOH); 4.50–3.38 m (CH2OH)
4.29 m (CHOH); 3.97 s (OCH3); 4.20-3.38 m (CH2OH)
5.98 s (CH2); 4.42 m (CHOH); 4.20-3.29 m (CH2OH)
5.73 s (CH); 5.30-5.00 m (CH+NCH2); 4.56-3.25 m (=CH2); 2.50 m (CH2)
5.85 m (CH); 4.46 m (=CH2)
5.87 m (CH); 4.63 m (=CH2); 3.84 s, 3.82 s (OCH3)
5.96 s (CH2); 5.93 m (CH); 4.47 m (=CH2)
4.24 m (CHOH); 4.50-3.37 m (CH2OH)
—
9.50, s
8.71, s
9.64, s
8.92, s
8.92, s
8.84, s
8.97, s
5.26, m
5.28, m
5.30, m
5.64, m
5.57, s
6.52, s; 5.96, s
5.98, s; 5.75, s
5.71, s; 5.66, s
5.63, s
6.14 (d, J = 3.3)
5.72 (d, J = 3.4)
5.68 (d, J = 3.0)
3.76, m
6а
6b
6c
5.58, d; 5.03, d
5.44, dd; 5.17, dd
—
8
6.08 (d; J = 3.3)
6.91 (d, J = 3.4)
6.05 (d, J = 3.0)
7.97, br. s; 7.74, br. s
7.34, br. s; 7.32, br. s
7.33, br. s; 7.20, br. s
2.76
2.61
2.63
1.65, 1.63
1.64, 1.63
1.63, 1.62
5.23, m
5.20, m
5.23, m
5.65, m
9а
9b
9c
10а
10b
10c
3.71, m
3.92, m
5.48, d, 5.03, d
5.42, dd, 5.07, dd
4.39 m (CHOH); 3.88 s, 3.87 s (OCH3); 4.20-3.34 m (CH2OH)
6.15 s, 6.14 s (CH2); 4.47 m (CHOH); 4.20-3.33 m (CH2OH)
_______
1
* The H NMR spectra of compounds 2a,c, 4a-c, and 8 were obtained in CDCl3, and of the remaining compounds in
DMSO-d6; the signals of the aromatic protons resonate at 6.92-7.54 ppm.
*2 Signals of the 3,4-dihydro tautomeric form.
*3 Signals of the 1,4-dihydro tautomeric form.

and the methyl group forming 3-allyl-6-(3-butenyl)-5-nitro-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (8), the
structure of which was demonstrated by spectral data (Tables 1 and 2).
Br
NO2
NO2
Me
N
HN
NaH/DMSO, 90 oC
O
N
H
8
O
N
H
7
For the purpose-directed introduction of an allyl fragment into position 1 of the dihydropyrimidin-2-one
ring a three-component cyclocondensation of the appropriate aromatic aldehyde, nitroacetone, and N-allylurea
in acid medium was used. This led to N(1)-allyl-4-aryl-6-methyl-5-nitro-1,4-dihydropyrimidin-2(3H)-one 9a-c.
The structures of these compounds were confirmed by their spectral characteristics.
R3
R2
R1
O
O
HCl
NO2
+
+
H2N
N
H
Me
R2
EtOH, ∆
CHO
R3
R3
R2
R1
NO2
R1
NO2
KMnO4
EtOH/H2O, –10 oC
HN
HN
O
N
Me
OH
O
N
Me
HO
9a–c
10a–c
9, 10 a R1 = Cl, R2 = R3 = H; b R1 = H, R2 = R3 = OMe; c R1 = H, R2 + R3 = –OCH2O–
1
In the H NMR spectra the signal of the geminal proton of the pyrimidine ring was displayed as a
doublet due to coupling with the proton on the nitrogen atom (Table 2). On interacting these compounds with
KMnO4 a selective oxidation occurs of the double bond of the allyl fragment with the formation of 4-aryl-N(1)-
(2,3-dihydroxypropyl)-6-methyl-5-nitro-1,4-dihydropyrimidin-2(3H)-ones 10a-c. The double set of signals in
the 1H NMR spectra of these compounds (Table 2) indicates that in this case also the carbacyclonucleosides are
isolated as a mixture of two diastereomers. It is interesting to note that the signals corresponding to the geminal
proton and the methyl group protons in compounds 10a-c were displaced significantly towards high field
compared with the signals of the initial compounds.
A new type of acyclonucleoside, containing a 5-nitrodihydropyrimidin-2-one fragment as the
heterocyclic base, has therefore been synthesized. The methods thereby developed enable selective introduction
of a dihydroxyalkyl substituent into positions 1 and 3 of the pyrimidine ring.
192

EXPERIMENTAL
1
The H NMR spectra were recorded on a VXR-300 (300 MHz) spectrometer, internal standard was
TMS. The IR spectra were obtained on a Specord M-80 instrument, and the UV spectra on a Specord M-40
instrument. A check on the course of reactions and the homogeneity of compounds was effected by TLC on
Silufol UV 254 plates in the solvent system chloroform–methanol, 50:1, visualization was in UV light.
Nitroacetone, 1-arylidene-1-nitro-2-propanones 1a-c, 5-nitro-1,4-dihydropyrimidine 2b (Found, %:
C 54.63; H 5.80; N 13.71. C14H17N3O5. Calculated, %: C 54.7; H 5.60; N 13.80), and 5-nitrodihydropyrimidin-2-
one 7 were obtained as described in [16,17,15,14] respectively.
2-Methoxy-6-methyl-5-nitro-4-(2-chlorophenyl)-1,4-dihydropyrimidine (2a).
A
mixture of
1-(2-chlorobenzylidene)-1-nitro-2-propanone (0.78 g, 3.46 mmol) and free O-methylisourea (0.30 g, 4.0 mmol)
was triturated without solvent for 2 h, then treated with chloroform (100 ml), the mixture dried over MgSO4,
evaporated to dryness, and product 2a was isolated from the residue by column chromatography on silica gel
(eluent chloroform). Yield 0.32 g (28%); mp 145-146°C (ethanol). Found, %: C 51.24; H 4.59; N 14.81.
C12H12ClN3O3. Calculated, %: C 51.16; H 4.29; N 14.92.
2-Methoxy-6-methyl-4-(3,4-methylenedioxyphenyl)-5-nitro-1,4-dihydropyrimidine
(2c)
was
obtained analogously from 3,4-methylenedioxybenzylidene-1-nitro-2-propanone. Yield 17%. Oil. Found, %:
C 52.73; H 4.42; N 14.10. C13H13N3O5. Calculated, %: C 53.61; H 4.50; N 14.43.
Potassium 4-(2-Chlorophenyl)-2-methoxy-6-methyl-5-nitro-4H-pyrimidinide (3a). Finely powdered
potassium hydroxide (0.04 g, 0.71 mmol) was added with stirring to a solution of dihydropyrimidine 2a (0.20 g,
0.71 mmol) in dry methanol (5 ml). After 1 h 30 min the reaction mixture was evaporated to 1/5 initial volume
and the anionic σ-complex 3a precipitated with ether (200 ml). Yield 0.19 g (83%).
Anionic σ-Complexes 3b (79% yield) and 3c (84% yield) were obtained analogously from compounds
2b and 2c. Complexes 3a-c did not have sharp melting points and melted above 300°C. Due to incomplete
combustion of these compounds it was not possible to determine data on their elemental composition.
3-Allyl-4-(2-chlorophenyl)-2-methoxy-6-methyl-5-nitro-3,4-dihydropyrimidine (4a). Allyl bromide
(0.28 ml, 3.3 mmol) was added with stirring to a suspension of σ-complex 3a (0.48 g, 1.50 mmol) and BTEAC
(0.36 g, 1.6 mmol) in dry benzene (10 ml). After 20 h the solid was filtered off, the solvent was evaporated in
vacuum, and product 4a was isolated from the residue by column chromatography on silica gel (eluent
chloroform).
3-Allyl-4-aryl-2-methoxy-6-methyl-5-nitro-3,4-dihydropyrimidines 4b,c were obtained analogously
from anionic σ-complexes 3b,c respectively.
3-Allyl-4-(2-chlorophenyl)-6-methyl-5-nitro-3,4-dihydropyrimidin-2(1H)-one (5a). Conc. HCl
(0.1 ml) was added to a solution of 3,4-dihydropyrimidine 4a (0.34 g, 1.10 mmol) in methanol (25 ml). After 4 h
the reaction mixture was evaporated to dryness, and the residue dissolved in chloroform (120 ml). The solution
was washed with water to neutral reaction, and dried over MgSO4. The solvent was evaporated in vacuum, and
the residue crystallized from ethanol.
3-Allyl-4-aryl-6-methyl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones 5b,c were obtained analogously
from 4b,c respectively.
3-Allyl-6-(3-butenyl)-5-nitro-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (8). An 80% suspension of
sodium hydride (0.37 g, 12.3 mmol) was added in portions in a stream of argon with stirring to a solution of
compound 7 (1.0 g, 4.2 mmol) in DMSO (20 ml). After 2h, after complete evolution of hydrogen, allyl bromide
(1.9 ml, 21.0 mmol) was added. The reaction mixture was stirred at 90°C for 2 h, diluted with water (200 ml),
and extracted with ethyl acetate (350 ml). The extract was dried over MgSO4, the solvent removed to dryness in
a waterpump vacuum, and product 8 was isolated from the residue by column chromatography on silica gel
(eluent chloroform).
193

1-Allyl-4-(2-chlorophenyl)-6-methyl-5-nitro-1,4-dihydropyrimidin-2(3H)-one (9a). Conc. HCl
(1.0 ml) was added with stirring to a mixture of 2-chlorobenzaldehyde (0.37 ml, 3.3 mmol), nitroacetone
(0.34 g, 3.3 mmol), and N-allylurea (0.66 g, 6.6 mmol) in absolute ethanol (75 ml). The reaction mixture was
boiled for 6 h, the precipitated solid product 9a was filtered off, and dried.
1-Allyl-4-aryl-6-methyl-5-nitro-1,4-dihydropyrimidin-2-ones (9b,c) were obtained analogously from
the corresponding substituted benzaldehydes.
General Procedure for Obtaining 2,3-Dihydroxypropyl Derivatives of Dihydropyrimidin-2-ones
6a-c and 10a-c. A mixture of KMnO4 (0.55 g, 3.5 mmol) and MgSO4·7H2O (0.86 g, 3.56 mmol) in water
(60 ml) was added with stirring during 30 min to a solution of the appropriate N-allyl derivative 5a-c (or 9a-c)
(3.5 mmol) in ethanol (50 ml) cooled to -10°C. After 4 h the solid was filtered off, the filtrate was evaporated to
dryness, and product 6 or 10 was isolated from the residue by column chromatography on silica gel (eluent
chloroform–methanol, 10:1).
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194