7th International Electronic
Conference on Synthetic Organic Chemistry (ECSOC-7),
http://www.mdpi.net/ecsoc-7, 1-30 November 2003
[A012]
SYNTHESIS OF SOME CONDENSED PYRIMIDO[4,5-d]
PYRIMIDINES AS POTENTIAL ANTINEOPLASTIC AGENTS
Pratibha Sharma*,
Ashok kumar, Vamsi Krishna and Nilesh Rane
E Mail: drpratibhasharma@yahoo.com
ABSTRACT
A series of 4-(2’-chloro-phenyl)-6-aryl-3-arylazo-7-thioxo-4,6,7,8-tetrahydro-1H,3H-pyrimido[4,5-d]pyrimidine-2,5-diones have been synthesized in excellent yields and their structures were corroborated by elemental analysis and IR, 1H and 13C NMR and Mass spectral data. The purity of synthesized compounds has been ascertained on the basis of TLC resolution studies by using ethyl acetate-xylene (3:7, v/v) as eluent.
KEYWORDS
Tetrahydropyrimidine-5-carboxylates, synthesis, pyrimido[4,5-d]pyrimidine, anticancer , spectral data
INTRODUCTION
In recent years much
interest has been focused on the chemistry of
tetrahydropyrimidine-5-carboxylates and their derivatives known as “Biginelli
compounds”1-2, which are presented as valuable substitutents3-6
for 1,4-dihydropyridine drugs7,8
,clinically used in the treatment of cardiovascular diseases.
Buoyed from this and in view of the
involvement of pyrimidine nucleus in various antineoplastic drugs, the purpose
of the present work is to explore the synthetic potential of these compounds in
order to construct some novel pyrimido [4,5-d] pyrimidines as potential
anticancer agents. Such ring system is found in pteroylglutamic acid (PGA) and
several PGA antagonists such as aminopterin and in marine derived natural
products such as crambescidin9 and batzelladine10-12
alkaloids.
Pyrimido
[4,5-d] pyrimidines have been the subject of
substantial attention by the synthetic and medicinal chemists because of the
role of this heteroaromatic ring system in various pharmacological activities
and hence are used as fungicides13, antioxidant14 (as an
inhibitor of lipid peroxidation), and antiplatelet agent. Moreover these agents have potential application in several therapeutic areas, including
oncology (as potentiators of anti-metabolite agents), cardiovascular disease
and pain management.
It has
been demonstrated that pyrimidopyrimidine derivatives of which dipyridamole
(DPM) is the prototype are potentiators of antimetabolite agents in cancer
chemotherapy15. They exert their action by potentially inhibiting
the nucleoside transport across the plasma membrane.
In view of variegated importance
associated with these compounds, it was thought worthwhile to synthesize a
series of 4-(2’-chloro-phenyl)-6-aryl-3-arylazo-7-thioxo-4,6,7,8-tetrahydro-1H,3H-pyrimido[4,5-d]pyrimidine-2,5-diones
to obtain more potent pharmacologically active compounds.
RESULTS
AND DISCUSSION
Ø Synthesis
of ethyl
4-(2-chlorophenyl)-6-ethoxy-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(3a-c)
Compound (1) on
treatment with different substituted aryl diazonium chloride (2a-c)
under diazotised conditions afforded the compound (3a-c) in an excellent
yield as indicated in fig1. The synthesis has been characterized by elemental
analysis, IR, 1H & 13C-NMR and Mass spectral data
(Table 1-3).
Ø Synthesis of
4-(2’-Chloro-phenyl)-2-oxo-3-arylazo-6-(N-phenyl-thioureido)-1,2,3,4-tetrahydro-5-ethyl
carboxylato pyrimidine(4a-f)
Compounds (4a-f) were prepared by condensation of corresponding
diazotized pyrimidine precursors (3a-c) with substituted phenylthiourea
in ethanol at reflux temperature in 40-50% chemical yield. The reaction takes
place via the attack of amino group of phenylthiourea to ethoxy group directly
attached to the tetrahydropyrimidine ring at C-6. The structures of the
compounds are supported by spectral data (Table 2).
Ø
Formation of
Bicyclic Compound 4-(2’-Chloro-phenyl)-6-aryl-3-arylazo-7-thioxo-4,6,7,8-tetrahydro-1H,3H-pyrimido[4,5-d]pyrimidine-2,5-dione5(a-f)
The desired heterocycles (5a-f)
have been obtained by the cyclization of (4a-f). However cyclization was
carried out employing two different cyclization conditions and the yields obtain
via both the methods were compared. On thermal cyclization at 190-200oC
with stirring the compound 5 was obtained in a good to excellent yield
while cyclization in refluxing pyridine provided the identical compound but in
a lower yield. The
structures of the compounds are corroborated by spectral data (Table 2).
EXPERIMENTAL
General
Melting points were determined on an
electrothermal apparatus in open capillary tubes and are uncorrected. The NMR
spectra were recorded on a Gemini 200 MHz (1H) and Brucker DRX 300
MHz (13C) spectrometers. Chemical shift (d) are reported in ppm relative to tetramethylsilane (TMS) and coupling
constants(J) in Hz. IR spectra were recorded on Shimadzu FT-IR spectrometer
in KBr pellet. Mass spectra were recorded on Jeol D-300 spectrometer. Purity of
all the synthesized compound was ascertained by TLC resolution on silca gel G (
Ø
Ethyl
4-(2-Chlorophenyl)-6-ethoxy-2-oxo-3-arylazo-1,2,3,4-tetrahydropyrimidine-5- carboxylate (3a-c)
General procedure
To the cold solution (0-50C) of ethyl 4-(2-chlorophenyl)-6-ethoxy-2-oxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylate 1 (6.5g, 0.02 mol) in concentrated hydrochloric
acid (12N, 5mL) was added drop wise a freshly prepared aryl diazonium chloride 2a-c
(0.02 mole) over a period of 10 min. with constant stirring. The reaction
mixture was further stirred for 4 hr at the same temperature and neutralized
with sodium bicarbonate solution (50% w/v ) to pH 8
under cooling to get the solid. The reaction mixture was then allowed to attain
the room temperature and stirred for further 30 min the solid obtained was
filtered, washed with water, dried and crystallized from ethanol. (Table 1-3)
Ø
4-(2’-Chloro-phenyl)-2-oxo-3-arylazo-6-(N-phenyl-thioureido)-1,2,3,4-tetrahydro-5-ethyl
carboxylato pyrimidine(4a-f)
General procedure
A mixture of 3a-c (0.02 mol) and substituted phenylthiourea (0.02 mol) was
refluxed in an ethanol for a period of 8 hr. The reaction mixture was allowed
to cool, poured on to the crushed ice (25g), and the solid separated was filtered,
washed with water, dried and crystallized from ethanol. (Table 1-3)
Ø
4-(2’-Chloro-phenyl)-6-aryl-3-arylazo-7-thioxo-4,6,7,8-tetrahydro-1H,3H-pyrimido[4,5-d]
pyrimidine-2,5-dione(5a-f)
General procedure
Method A
Compound
4a-c(3.0g),
were heated in an oil bath with constant stirring till the mobile phase was
obtained. The temperature was then allowed to increase slowly up to 190-2000C
with stirring until the solidification occurred. The content was then cooled,
treated with ice water (50mL) followed with aqueous Na2CO3
solution (10mL, 10%w/v), filtered, washed with water dried and crystallized
from DMF. (Table 1-3)
Method B
Compound
4a-c (1.0g) in pyridine (10mL) was heated under reflux for 24hr. The
reaction mixture was allowed to cool, added to the crushed ice (25g), filtered,
washed with water, dried and crystallized with DMF.
Table-1:
Physical Characteristic of Some Synthesized Compounds
|
Compound no. |
M.P.0C |
Yield (%) |
Mol.Formula
|
Analysis Calcd. / ( found)
% |
||
|
C |
H |
N |
||||
|
3-a |
95 |
82 |
C22H23ClN4O4 |
59.66 (59.50) |
5.23 (5.12) |
12.65 (12.50) |
|
3-b |
99 |
85 |
C22H23ClN4O5 |
57.58 (57.45) |
5.05 (5.00) |
12.21 (12.11) |
|
3-c |
94 |
88 |
C21H21ClN4O5 |
56.70 (56.60) |
4.76 (4.56) |
12.59 (12.38) |
|
4-a |
116 |
50 |
C27H24Cl2N6O3S |
55.58 (55.37) |
4.15 (4.05) |
14.40 (14.31) |
|
4-b |
120 |
44 |
C27H24Cl2N6O3S |
55.58 (55.37) |
4.15 (4.05) |
14.40 (14.31) |
|
4-c |
119 |
49 |
C27H24Cl2N6O4S |
54.09 (53..92) |
4.04 (3.00) |
14.02 (13.86) |
|
4-d |
127 |
40 |
C27H24Cl2N6O4S |
54.09 (53.92) |
4.04 (3.00) |
14.02 (13.86) |
|
4-e |
123 |
43 |
C26H22Cl2N6O4S |
53.34 (53.21) |
3.79 (3.62) |
14.35 (14.21) |
|
4-f |
126 |
41 |
C26H22Cl2N6O4S |
53.34 (53.21) |
3.79 (3.62) |
14.35 (14.21) |
|
5-a |
260 |
83 |
C25H18Cl2N6O2S |
55.87 (55.71) |
3.38 (3.24) |
15.64 (15.60) |
|
5-b |
256 |
79 |
C25H18Cl2N6O2S |
55.87 (55.71) |
3.38 (3.24) |
15.64 (15.60) |
|
5-c |
269 |
81 |
C25H18Cl2N6O3S |
54.26 (54.12) |
3.28 (3.19) |
15.19 (15.10) |
|
5-d |
243 |
80 |
C25H18Cl2N6O3S |
54.26 (54.12) |
3.28 (3.19) |
15.19 (15.10) |
|
5-e |
255 |
75 |
C24H16Cl2N6O3S |
53.44 (53.32) |
2.99 (2.89) |
15.58 (15.48) |
|
5-f |
267 |
82 |
C24H16Cl2N6O3S |
53.44 (53.32) |
2.99 (2.89) |
15.58 (15.48) |
The absorption band due to N-H stretching
vibration (3310-3450 cm-1) and C=O (1750 cm-1, ester and
1710 cm-1, ring) were observed in the IR spectrum of (3).
Characterization of N=N stretching vibration in aromatic azo compound is
difficult because of the interference of C=C ring vibrations. However, La Fewre
et al 16 have reported the consistent appearance of N=N
stretching vibrations in the region 1585-1569 cm-1 for azo
functionality in aromatic azo compound and in the case of (3) the
characteristic band was found at 1580 cm-1.
The
1H NMR (CDCl3) spectra of 3 showed a triplet at d 0.9-1.2 integrating for 6H (J=8.0-9.0 Hz) and the quartet
at d 4.35-4.38 integrating for 4H (J=8.0-9.0 Hz) indicating the
presence of each of two methyl and methylene protons, respectively. The NH
protons resonated as broad singlet appears at d 5.85. Moreover, aromatic protons emerge as a multiplet
pattern at d 6.9-7.8.
Likewise, compound 4 exhibit IR bands near 1540-1350
and 930 cm-1 for NH-C=S functionality which were found in agreement
with those reported earlier for the same17. In the 1H NMR (CDCl3) spectra of 4
presence of two broad singlets each integrating for 1H in the region of d11.60-12.55 were suggestive of two NH group protons in
downfield region .The triplet (3H) and quartet (2H) at d 1.0 –1.13 (J=8.0 Hz) and d 4.14-4.40 (J=8.0 Hz), respectively were assignable to ethyl
protons of carbethoxy group. The cyclization of 4 was confirmed by the
absence of triplet and quartet for the ethyl protons in 1H NMR (CDCl3) spectra of 5.
Table-2: IR, 1H NMR and
Mass Spectral Data of the Synthesized Compounds
|
Comp.no. |
IR (KBr,
ν, cm-1) |
1H NMR (d ppm) |
MS : m/z(% RA) |
|
3a |
3300(N-H),
3060(C-H.sp2) , 2980(C-H,sp3), 1750 (C=O,ester),
1705(C=O,ring), 1597,1500,1480 (skeletal ring str), 1575(N=N),
685(C-Cl), |
0.9(t,6H,2×CH3,
J=8Hz), 2.3(s,3H,CH3),4.35(q,4H, 2×CH2 ,J=8Hz), 5.85 (s, 7.1(t,
2H,Hf,Hg,J=3Hz), 7.2(t,2H,Hb,Hc,Jac=Jbd=2Hz) 7.6(d,Hh,J=10Hz), 7.8(d,Ha,Jab=6Hz) |
442(M+,15),
444(M++2,5), 330(55), 323(35),369(45), 324(52),119(100),
91(90), 77(75),65(55), 39(15) 29(18),15(20). |
|
3b |
3250(N-H), 3050(C-H.sp2),
2972(C-H, sp3) , 1745(C=O,ester),
1710(C=O,ring),
1600,1500,1475(skeletal ring str), 1585(N=N), 1050 (C-O),680(C-Cl) |
1.2(t,6H,2×CH3,J=9Hz)
3.85(s,3H,OCH3), 4.38(q,4H,2×CH2,J=9Hz) 5.90 (s, 7.1-7.8(m,8H,Ar-H) |
458(M+,18),460(M++2,6), 385(35), 340(55), 205(50), 135(100),91(85),77(65), 65(45),38(187), 29(15), 15(25) |
|
4a |
3240(N-H),
3024((C-H.sp2),1740 (C=O,ester) ,1685(C=O,ring),1603,1501470 (skeletal ring str)
, 1575(N=N),1512,1450(NHC=S), 1195(C=S), 670 (C-Cl), |
1.0(t,3H,CH3,J=8Hz),
2.4(s,3H,CH3), 4.14
(q,2H,CH2,J=8Hz), 5.15(bs,NH, pyrimidine ring),6.9(t,2H,Hf,HgJfg=9Hz) 7.0(t,2H,Hc,Hk,Jac & Jik=3Hz)7.1(d,He,Jef=9Hz), 7.2(d,2H,Hd,Hl,Jcd & Jkl=10Hz),7.6(t,2H,Hb,Hj,Jbc &Jjl=3Hz),7.7(d,Hh,J=10Hz), 7.9(d,2H,Ha,Hi,Jab &Jij=6Hz) 13.5-14.1(bs, |
583(M+,9),585(M++2,3) 510(45),472(40),432(25), 119
(100),92(85),77(80) ,65(55),51(35),38(18), 29(30),15(12) |
|
4c |
3310(N-H),
3040((C-H.sp2), 1738(C=O,ester), 1703(C=O,ring), 1605,1502(skeletal ring str),
1580(N=N),1520,1450(NHC=S), 1217(C=S),
1050(C-O), 672(C-Cl),
|
1.13(t,3H,CH3,J=8Hz),
3.80(s,3H,OCH3), 4.40
(q, 2H,CH2, J=8Hz), 5.85(s,NH, pyrimidine ring), 7.1-7.8(m.12H,
Ar-H), 10.3(bs,2H,2×NH) |
599(M+,15),601(M++2,5) 526(35),464(20),353(35),280 (40),135(100),151(38),92(95) 77(75),65(55),38(35),
29(30) 15(18). |
|
5a |
3329(N-H),
1695(C=O,ring), 1600,1502,1465(skeletal ring str), 1573(N=N), 1396(NHC=S), 1205(C=S),
669(C-Cl) |
2.42(s,3H,CH3), 7.1(t,2H,Hf,Hg,Jfh &Jeg=3Hz) 7.2(t,4H,Hb,Hc,Hj,Hk, Jab,Jbc,Jej,Jjk=10Hz & Jbd,Jac, Jik,Jjl=2Hz)7.3(d,He,Jef=6.8Hz) 7.4(d,2H,Hd,Hl,Jcd & Jkl=8.6Hz) 7.6(d,Hh,Jgh=6Hz)7.8(d,2H,Ha,Hi, Jab &
Jij=8Hz)11.1(s,NH-C=S), 12.5(s,NH-C=O) |
537(M+,18),539(M++2,6), 541(M++4,2),418(35),426(38), 307(55),230(40),119(100), 91(95),77(55),65(48),39(25). |
|
5c |
3390(N-H),
1648(C=O,ring), 1595,1490,1440(skeletal ring
str), 1574(N=N), 1400(NHC=S), 1208(C=S), 665(C-Cl) |
3.40(s,3H,OCH3), 7.0-7.8(m,12H,Ar-H, J=2-9.5Hz),9.8(bs,NH-C=S),11.5(bs,NH-C=O) |
533(M+,9),535(M++2,3),537 (M++4,1),422(42),287(35), 210(40),135(100),91(90),77 (68),65(45),39(18). |
|
5f |
3450(O-H),
3297(N-H), 1657(C=O,ring),1610, 1508(skeletal
ring str), 1579(N=N), 1400(NHC=S), 1219(C=S), 660(C-Cl) |
7.2-7.9(m,12H,Ar-H, J=2-10Hz),9.5(s,NH-C=S) 11.1(s,NH-C=O),
14.1(bs,OH) |
539(M+,21),541(M++2,7),543 (M++4,5),428(35),306(15), 122(95),112(20),77(100),65 (41),51(35),39(20). |
Table-3: 13C-NMR
(d ppm)Data of 5a(CDCl3+DMF d6)
|
C-2 |
181.2 |
|
C-4 |
125.6 |
|
C-4a |
131.1 |
|
C-5 |
162.2 |
|
C-7 |
168.5 |
|
C-8a |
151.2 |
|
C-1’ ,
C’-3 |
128.6 |
|
C-2’ |
133.6 |
|
C-5’ |
120.1 |
|
C-4’,C-6’ |
125.4 |
|
CH3 |
18.1 |
|
C-1’’ |
143.8 |
|
C-2’’,
C-6’’ |
117.7 |
|
C-3’’ |
121.5 |
|
C-4’’ |
115.3 |
|
C-5’’ |
129.2 |
To
investigate the potential ability of newly synthesized derivatives of
pyrimido[4,5-d]pyrimidine ring system as nucleoside transport inhibitor, we
utilized the structures optimized in vacuo by SCF calculation with the
semi-empirical AM1 method18, to calculate the value of some
molecular descriptors18[Ionization potential ,Connolly accessible
area(CAA), HOMO and LUMO orbital energies]. Table 4 reports our findings on
compound 5, together with those of Dipyridamol(DPM)
and Mopidamol(MPM), an active drugs with the same ring structure and chosen as
reference drugs.
Table 4: Molecular Descriptors for Synthesizesd Compounds
and Reference Drugs
|
Compounds. |
HOMOa |
LUMOa |
Ionization Potentiala |
CAA ( Å2 ) |
|
DPM |
-8.565 |
-0.911 |
8.565 |
762.88 |
|
MPM |
-8.875 |
-1.256 |
8.875 |
666.45 |
|
5 a |
-9.182 |
-0.984 |
9.182 |
738.71 |
|
5 c |
-9.170 |
-1.096 |
9.170 |
779.92 |
|
5 e |
-9.066 |
-1.164 |
9.066 |
742.71 |
aeV
All
the new derivatives have LUMO and HOMO energies in the range calculated for the
known nucleoside transport inhibitors, and also all the other parameters are of
the same order of magnitude as the active compounds. Therefore, it can be
assumed that the new synthesized compounds can constitute a probable
pharmcophore for potential nucleoside transport inhibitory action.
CONCLUSION
In conclusion, in this paper we report the
synthesis of some new derivative of pyrimido[4,5-d]pyrimidine
from tetrahydropyrimidine-5-carboxylates as starting material. The derivatives
have shown to be potent anticancer agents in preliminary molecular modeling
studies.
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