Thio analogs of pyrimidine bases: Syntheses and EIMS study of new ortho-(meta- and para-)bromobenzyl S-mono and S-N-1-disubstituted 5-morpholinomethyl(5-piperidinomethyl)-2-thiouracils

Article abstract of DOI:10.1002/jhet.5570440109

(Chemical Equation Presented) Eleven new ortho-(meta- and para-)bromobenzyl S-mono and S-N-1-disubstituted derivatives of 5-morpholinomethyl-2-thiouracil (MMTU) and 5-piperidinomethyl-2-thiouracil (PMTU) have been prepared and their EI induced mass spectr

Full text of DOI:10.1002/jhet.5570440109

Jan-Feb 2007
55
Thio Analogs of Pyrimidine Bases: Syntheses and EIMS Study of
New ortho-(meta- and para-)Bromobenzyl S-Mono and S-N-1-
Disubstituted 5-Morpholinomethyl(5-piperidinomethyl)-2-thiouracils.
Elꢀbieta Wyrzykiewicz *, Tomasz Pospieszny
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznaꢀ, Poland
Received February 13, 2006
O
N
N
X
S
N
H
Br
O
CH2Br
Br
H
S
DMF K2CO3
room temp
O
N
N
+
X
N
N
N
H
X
S
N
Br
Br
Eleven new ortho-(meta- and para-)bromobenzyl S-mono and S-N-1-disubstituted derivatives of 5-
morpholinomethyl-2-thiouracil (MMTU) and 5-piperidinomethyl-2-thiouracil (PMTU) have been prepared
and their EI induced mass spectral fragmentation has been investigated. It has been shown that the data
derived from EIMS spectra can be used to differentiate the isomers.
J. Heterocyclic Chem., 44, 55 (2007).
p-)bromobenzyl-5-morpholino- methyluracils IXa-IXc and
2-o-(m- and p-)bromobenzylthio-1-o-(m- and p-)bromo-
benzyl-5-piperidinomethyluracils Xa-Xc. The structures of
all compounds obtained were determined by examining
their UV/VIS, IR, 1H NMR and 13C NMR spectra as well as
on the basis of elemental analyses (Tables 1-3). The
INTRODUCTION.
Thio derivatives of pyrimidine bases have remarkably
contributed to biological and medicinal chemistry.
Chemical modifications of these compounds have led to a
large number of mono- and di-S and N substituted analogs
showing therapeutic properties, especially antiviral,
antithyroid and antitumor activities [1-7].
1
UV/VIS, IR, H NMR, 13C NMR and EIMS spectra of 5-
piperidinomethyl-2-thiouracil IIIb have also been investi-
gated because this compound is unknown in literature. The
EIMS spectra of VIa-VIc, VIIa-VIIc, IXa-IXc and Xa-Xc
have been analysed to check the possibility of differentiation
of o-(m- and p-)bromo substituted in benzyl group isomers
on the basis of differences in the values of μ1, μ2 and μ3 i.e.
the ratio of the intensity of selected fragmentation peaks to
that of the parent ion peak, and to compare the data with
those obtained previously in our laboratory [9-11].
A new antimetabolite of thymine, 5-morpholinomethyl-
2-thiouracil (MMTU) has been synthesized via the
Mannich reaction of 2-thiouracil, formaldehyde and
morpholine by Kamalakannan et al [8]. However, to the
best of our knowledge, no work has been published on the
chemoselective and regioselective synthesis as well as on
physicochemical properties of the mono- and dibenzyl
substituted derivatives of MMTU. This fact has stimulated
us to investigate the chemoselectivity and regioselectivity of
the reaction of benzylation of MMTU, as well as unknown
in literature 5-piperidinomethyl-2-thouracils (PMTU).
PMTU has been synthesized by us via the Mannich reaction
of 2-thiouracil, formaldehyde and piperidine.
This paper deals with the synthesis and physico-
chemical properties of new, unknown in literature,
dihydrobromides of 2-o-(m- and p-)bromobenzylthio-5-
morpholinomethyl- uracils Va-Vc, 2-o-(m- and p-)bromo-
benzyl-5-morpholinomethyluracils VIa-VIc, 2-o-(m- and
p-)bromobenzylthio-5-piperidinomethyluracils VIIa-VIIc,
dihydrobromides of 2-o-(m- and p-)bromobenzylthio-1-
o-(m- and p-)bromobenzyl-5-morpholinomethyluracils
VIIIa-VIIIc, 2-o-(m- and p-)bromobenzylthio-1-o-(m- and
RESULTS AND DISCUSSION.
New 5-piperidinomethyl-2-thiouracil IIIb was
synthesized via the Mannich reaction of 2-thiouracil,
formaldehyde and piperidine (Scheme 1). The
structure of IIIb was determined by examining its
1
UV/VIS, IR, H NMR, 13C NMR and EIMS spectra as
well as on the basis of elemental analysis (Tables 1, 2,
3, 4). A series of new S-mono-o-(m- and p-)
bromobenzyl substituted derivatives of IIIa and IIIb,
as well as S-N-1-di-o-(m- and p-) bromobenzyl
substituted derivatives of IIIa and IIIb was
synthesized in the reactions of these compounds with

56
E. Wyrzykiewicz, T. Pospieszny
Vol 44
Scheme 1
O
N
O
s2
7
t1
8
4
H
S
C2H5OH
H
S
O
H
H
k3
9
5
6
N
N
N
+
H N
X
+
12
t1
2
H
H
X10
11
k3
N
H
s1
H
H
III
I
II
a X = O
a X = O
k4
CH
b X =
CH2
b X =
2
CH2Br
Br
III a,b
+
O
N
0,84 mmol
DMF
room temp
K2CO3
N
N
IV
O
a o-Br
b m-Br
S
III a,b : IV a-c
1.33 : 3.33
H
x 2 HBr
c
p-Br
Br
VIII
O
a o-Br
b m-Br
s2
t1
8
Br
4
7
k3
9
c
p-Br
0,14 mmol K2CO3
DMF
room temp
5
N
N
12
t1
s3
s1
6
26
2
13
10
k4
25
21
S
11
k3
N
H
K CO
10 %
CHCl
III a,b : IV a-c
1.32 : 1.46
1.
2
3
24
22
s4 14
16
2.
3
23
15
20
17
Br
X
O
18
O
t1
8
s2
7
19
a o-Br
b m-Br
p-Br
Br
4
t2
9
5
6
N
N
N
N
c
s3
12
t1
26
2
13
21
O
O
11
t2
25
24
10
S
N
S
N
H
H
H
s1
14
22
16
x 2 HBr
s4
23
15
20
17
Br
Br
O
IX
V
18
s2
t1
19
a o-Br
b m-Br
Br
8
7
a o-Br
b m-Br
k3
k4
4
5
N
9
N
K CO
1. 10 %
2
3
s3
c
p-Br
c
p-Br
CHCl
2.
26
12
2
6
10
3
13
t1
25
21
11
k3
S
N
H
H
s1
24
22
O
23
s2
7
t1
8
Br
VII
t2
4
9
5
N
N
s3
a o-Br
b m-Br
p-Br
12
t1
2
26
6
13
O10
25
24
21
22
11
t2
S
N
H
H
c
s1
23
Br
VI
a o-Br
b m-Br
c
p-Br
the corresponding o-(m- and p-)bromobenzyl bromides
IVa-IVc. Treatment of 1.32 mmole of IIIa with 1.46
mmole of the corresponding IVa-IVc at room
temperature in the solution of DMF in the presence of
0.83 mmole of K2CO3 afforded chemoselectively new
dihydrobromides of 2-o-(m- and p-)bromobenzylthio-
5-morpholinomethyluracils Va-Vc (Scheme 1, Table
1). Treatment of 1.32 mmole of IIIb with 1.46 mmole
of the corresponding IVa-IVc at room temperature in
the solution of DMF in the presence of 0.83 mmole of
K2CO3 afforded chemoselectively 2-o-(m- and p-)-
bromobenzylthio-5-piperidino- methyluracils VIIa-
VIIc (Scheme 1, Table 1).
A series of 1,2-di-o-(m- and p-)bromobenzyl substituted
dihydrobromides of 5-morpholinomethyl-2-thouracils
(VIIIa-VIIIc) was synthesized regioselectively in the
reaction of 1.33 mmole wth 3.33 mmoles of the
corresponding IVa-IVc in DMF solution in the presence
of 1.33 mmole of K2CO3 at room temperature. Va-Vc and
VIIIa-VIIIc dissolved 10 % K2CO3 water solution were
extracted with CHCl3 to give VIa-VIc and IXa-IXc
respectively (Scheme 1, Table 1).

Jan-Feb 2007
Thio Analogs of Pyrimidine Bases
57
Table 1
Chemical and Physical Data of Compounds III b, V a-c, VI a-c, VII a-c,VIII a-c, IX a-c, X a-c.
Comp.
Formula
(mol. weight)
M.p.
[oC]
Yield
[%]
Elemental analysis
calculated (found)
C
H
N
S
III b
V a
C10H15N3OS
225.31
C16H18N3O2SBr x 2 HBr
558.14
200
91
59
53.33
(53.42)
34.40
(34.16)
(34.75)
(34.36)
47.40
(47.29)
(47.30)
(47.03)
51.77
(51.42)
(51.81)
(51.65)
37.96
(37.90)
(37.65)
(37.63)
45.92
(45.82)
(45.62)
(45.67)
51.15
6.66
(6.72)
3.58
(3.54)
(3.56)
(3.60)
4.44
(4.48)
(4.40)
(4.18)
5.07
(5.15)
(5.06)
(5.10)
3.16
(3.21)
(3.18)
(3.12)
3.82
(3.51)
(3.78)
(3.87)
4.44
18.66
(18.71)
7.52
14.22
(14.32)
5.73
(5.72)
(5.59)
(5.73)
7.90
(7.60)
(7.82)
(6.89)
8.12
(8.05)
(7.85)
(7.97)
4.40
(4.60)
(4.20)
(4.30)
5.32
(5.52)
(5.29)
(5.04)
5.68
70-2
(7.50)
(7.55)
(7.50)
10.37
(10.32)
(10.30)
(10.28)
10.65
(10.63)
(10.39)
(10.46)
5.77
(5.93)
(5.62)
(5.99)
6.98
(6.62)
(6.69)
(6.68)
7.46
V b
V c
VI a
C16H18N3O2SBr x 2 HBr 558.14
C16H18N3O2SBr x 2 HBr 558.14
C16H18N3O2SBr x ꢀ H2O
405.31
C16H18N3O2SBr x ꢀ H2O 405.31
C16H18N3O2SBr x ꢀ H2O 405.31
C17H20N3OSBr
67-9
70-3
55-7
58
60
71
VI b
VI c
VII a
57-9
65-7
169-170
72
69
73
394.33
VII b
VII c
VIII a
C17H20N3OSBr 394.33
C17H20N3OSBr 394.33
C23H23N3O2SBr2 x 2 HBr
727.17
173-5
185
139-141
76
78
57
VIII b
VIII c
IX a
C23H23N3O2SBr2 x 2 HBr 727.17
C23H23N3O2SBr2 x 2 HBr 727.17
C23H23N3O2SBr2 x 2 H2O
601.36
C23H23N3O2SBr2 x 2 H2O 601.36
C23H23N3O2SBr2 x 2 H2O 601.36
C24H25N3OSBr2
55-7
85-7
85-7
55
59
68
IX b
IX c
X a
30-2
65-7
130
64
67
75
563.35
C24H25N3OSBr2 563.35
C24H25N3OSBr2 563.35
(51.18)
(51.30)
(51.30)
(4.49)
(4.50)
(4.39)
(7.38)
(7.58)
(7.42)
(5.60)
(5.70)
(5.78)
X b
X c
90-2
160
82
83
Table 2
UV/VIS, IR and 1H NMR Data of Compounds III b, VI a-c, VII a-c, IX a-c, X a-c.
1H NMR
s4
Comp.
UV/VIS
IR
ꢀC4=O
ꢀ max (lg ꢁ)
s1
s2
s3
t1
k3
k4
1.47
1.37
-
-
-
-
-
Ph-H
M
-
t2
2.50
-
ꢀC5=C6
1640
1569
1673
1534
1652
1558
1662
1528
1675
1473
III b
VI a
VI b
VI c
213.0 (4.08)
273.0 (4.14)
210.0 (4.29)
285.0 (3.86)
211.0 (4.30)
287.5 (3.90)
209.5 (4.21)
287.0 (3.94)
220.5 (4.34) 248.5
(4.01) 286.0
(4.01)
7.24
7.60
7.63
7.61
7.78
3.12
3.22
3.20
3.14
3.54
-
-
-
-
-
-
4.46
4.24
4.24
4.41
2.37
3.59
2.35
3.56
2.33
3.54
2.50
-
7.20-7.95
7.25-7.80
7.36-7.48
7.18 - 7.64
-
VII a
1.58
1.44
VII b
VII c
220.5 (4.33)
248.5 (3.98)
285.5 (3.99)
223.5 (4.36)
249.0 (4.03)
286.0 (4.00)
218.0 (4.37)
282.0 (4.05)
215.0 (4.43)
282.0 (4.10)
218.0 (4.43)
282.5 (4.05)
215.0 (4.31)
281.0 (3.94)
216.5 (4.34)
279.5 (3.87)
226.5 (5.37)
282.5 (4.89)
1675
1473
7.72
7.76
3.34
3.50
4.27
4.30
-
-
2.50
-
1.53
1.40
7.22–7.62
7.18-7.37
1675
1484
2.50
-
1.58
1.41
IX a
IX b
IX c
X a
1644
1568
1646
1569
1642
1486
1670
1589
1669
1582
1669
1583
8.32
8.32
8.35
8.58
8.51
8.50
3.34
3.31
3.30
3.35
3.35
3.39
4.43
4.33
4.35
4.53
4.53
4.50
5.15
5.20
5.10
5.54
5.42
5.43
2.37
3.55
2.36
3.57
2.33
3.55
2.50
-
2.50
-
2.50
-
-
-
-
-
-
7.19 –7.81
7.15 –7.95
7.35-7.48
7.21 –7.72
7.24 –7.81
7.36-7.48
-
1.62
1.41
1.60
1.41
1.62
1.44
X b
X c

58
E. Wyrzykiewicz, T. Pospieszny
Vol 44
A series of new 1,2-di-o-(m- and p-)bromobenzyl
were obtained. So, it is clear that these reactions are
largely governed by the structure of MMTU (or PMTU)
and by the nature of the benzylation agent.
substituted derivatives of 5-piperidinomethyl-2-thouracils
(Xa-Xc) was synthesized regioselectively in the reaction
of 1.33 mmole of PMTU (IIIb) with 3.33 mmoles of
corresponding IVa-IVc in DMF solution in the presence
of 1.33 mmole of K2CO3 at room temperature (Scheme 1,
Table 1). Noteworthy is the fact that the presence of the
piperidinomethyl substituent at the C-5 atom of the uracil
1
Assignments of the H NMR and 13C NMR resonances
of IIIb, VIa-VIc, VIIa-VIIc, IXa-IXc and Xa-Xc were
deduced on the bases of signal multiplicities, and by the
concerted application of two-dimensional NMR technique
HETCOR.
Table 3
13C NMR Shifts of III b, VI a-c, VII a-c, IX a-c and X a-c ꢀ (ppm).
Comp.
Carbon
2
4
5
6
7
13
14
8, 12
9, 11
10
IIIb
VIa
VIb
VIc
VIIa
VIIb
VIIc
IXa
IXb
IXc
Xa
174.92
163.11
163.00
163.18
163.20
163.10
163.68
169.39
166.35
166.30
166.42
166.82
166.78
161.39
160.08
160.02
160.00
160.00
160.04
160.12
160.49
161.22
161.20
161.19
162.63
162.70
113.84
117.60
117.60
117.61
117.60
117.66
117.60
117.26
117.13
117.77
117.90
117.80
117.84
139.31
161.75
151.70
151.87
153.03
154.43
152.95
151.96
151.83
151.80
153.20
151.58
154.70
53.04
52.96
52.95
52.95
52.60
53.92
52.66
55.98
55.97
55.53
56.20
56.00
55.56
-
-
-
-
-
-
-
-
53.57
53.50
53.52
53.54
54.46
55.05
53.47
53.17
53.15
53.07
52.66
53.46
52.11
25.50
66.05
66.03
66.04
24.10
24.74
24.18
61.45
61.45
61.40
22.63
22.60
22.61
23.76
-
-
-
22.73
23.44
22.79
-
-
-
30.30
31.00
32.60
34.29
32.76
32.77
34.16
33.90
33.90
35.13
33.92
33.64
66.10
66.10
66.16
68.19
68.07
67.99
20.90
19.36
20.96
Xb
Xc
Comp.
Carbon
21 (15)
22 (16)
23 (17)
24 (18)
25 (19)
26 (20)
VIa
VIb
VIc
VIIa
VIIb
VIIc
IXa
135.80
140.80
139.45
137.01
142.20
137.87
135.22
(135.11)
140.80
(139.59)
139.40
(138.96)
136.14
(135.52)
140.66
(138.12)
137.45
(137.26)
123.80
131.60
138.82
124.04
131.43
131.13
128.25
(127.96)
131.60
(131.40)
138.80
(138.78)
123.81
(122.60)
131.51
(131.09)
135.62
(135.26)
132.70
121.30
130.82
132.60
121.37
131.22
132.57
(132.34)
121.36
(121.27)
130.80
(130.52)
132.64
(132.55)
122.10
(121.97)
131.48
(131.36)
127.97
129.74
120.29
127.86
129.54
120.06
127.75
(127.65)
127.88
(127.79)
119.20
(119.11)
127.88
(127.80)
129.59
(128.31)
120.85
(120.31)
129.57
130.37
130.82
129.33
130.43
131.22
129.69
(129.27)
129.76
(129.69)
130.86
(130.52)
130.35
(129.41)
130.73
(130.19)
131.48
(131.36)
131.55
127.88
138.82
132.41
127.93
131.13
131.56
(131.25)
131.25
(131.40)
138.80
(138.78)
131.00
(130.41)
127.92
(127.32)
135.62
(135.26)
IXb
IXc
Xa
Xb
Xc
ring of the IIIb molecule changes the reactivity of this
compound in the reaction of bromobenzylation relative to
that of IIIa. In particular, the reactions of S-bromobenzyl-
ation and S-N-1-dibromobenzylation of IIIa afforded
dihydrobromides of mono bromobenzyl substituted deriv-
atives of MMTU (Va-Vc), and dihydrobromides of
dibromobenzyl substituted derivatives of MMTU (VIIIa-
VIIIc). In the reactions of benzylation of IIIb in the same
conditions only S-bromobenzylated and S-N-1-dibromo-
benzylated derivatives of PMTU (VIIa-VIIc, Xa-Xc)
On the basis of the low- and high-resolution electron
impact as well as B/E linked scan mass spectra (Table 4)
the principal mass spectral fragmentation routes of
compound IIIb are proposed. The characteristic features
of the mass spectral fragmentation of the molecular ion
IIIb are the cleavages of the three bonds of the piperidine
.
ring. By these cleavages the fragment ions [M-CH3 ] f,
[M-.CH2CH3] g, [M-.C3H7] h, [M-C4H8] j are derived. The
cleavages of the two Csp3-Csp3 bonds of this ring lead to
the ejection of C4H8 neutral molecules to give odd-

Jan-Feb 2007
Thio Analogs of Pyrimidine Bases
59
electron fragment ions j. By the simple inductive cleavage
of Csp3-N bond in the piperidinomethyl substituent the
complementary even-electron fragment ions [M-.C5H10N]+
l and [M-.C5H5N2SO]+ h (100 % rel. int.) are derived. The
cleavage of the Csp3-N bonds of the piperidinomethyl
substituent also involves H rearrangement and yields odd-
electron fragment ion k. Simple inductive cleavage of
Csp2-Csp3 bond between the uracil ring and the piperi-
dinomethyl substituent i.e. the cleavage of the ꢀ bond to
annular nitrogen atom of the piperidine ring has also been
observed (ion m). The common features of the mass
spectral fragmentations of the molecular ions of VIa-VIc
and VIIa-VIIc (Table 4) are the cleavages of Csp3-S
bonds in the bromobenzylthio substituent (ions i) and of
Csp3-N bond in the 5-piperidinomethyl (or 5-morpho-
linomethyl) substituent (ions e). In the fragmentation of
the molecular ions of VIa-VIc and VIIa-VIIc, simple
radical-site initiated ꢁ-cleavages of the Csp3-Csp2 bonds
of the 5-piperidinomethyl (or 5-morpholinomethyl) substi-
tuents have also been observed (ion m). The inductive
Table 4
Elemental composition and Relative Intensities of the Ion Peaks in the Spectra of IIIb,VIa - VIc and VIIa - VIIc according to high resolution Data.
Ion
m/z
Elemental
% Relative Intensity
composition
IIIb
VIa
VIb
VIc
VIIa
VIIb
VIIc
M+.a
225
395/397
393/395
337/339
308/310
229
226
224
210
196
C10H15N3OS
C16H18N3O2SBr
C17H20N3OSBr
C13H12N3OSBr
C12H9N2OSBr
C12H9N2OS
C9H12N3O2S
C10H14N3OS
C9H12N3OS
C8H10N3OS
C7H8N3OS
C7H6Br
C6H7N3OS
C6H6N2OS
C5H5N2OS
C5H10NO
C6H12N
C4H8NO
17
-
-
-
-
-
-
-
1
3
14
-
5
5
6
-
3
-
-
-
7/6
-
4/3
17/16
4
28
-
-
-
-
100/99
-
-
19
82
-
90
-
-
-
95
-
-
3/2
-
3/2
10/9
2
13
-
-
-
-
26/25
-
-
8
100
-
49
-
-
-
39
-
-
-
7/6
-
9/8
27
-
11
-
-
-
27/26
-
-
8
-
10
-
100
-
-
-
13
-
-
9/8
-
-
12/11
-
8/9
19/20
34
39
-
-
-
-
100/99
-
-
21
38
-
67
-
-
-
50
-
12/11
-
21/20
5
-
13
-
-
-
49/48
-
-
7
-
17
-
100
-
-
-
12
b
c
d
e
-
12/11
3
-
7
-
-
-
16/15
-
-
6
-
12
-
100
-
-
-
13
f
g
h
l
j
k
l
182
169/171
169
142
141
100
98
86
84
82
m
n
C5H10N
C4H4NO
C4H8N
C3H5O
100
22
5
-
19
o
p
r
70
57
55
C3H5N
Table 5
Elemental composition and Relative Intensities of the Ion Peaks in the Spectra of IXa - IXc and Xa - Xc according to high resolution Data.
Ion
m/z
Elemental compositon
% Relative intensity
IXa
IXb
IXc
Xa
Xb
Xc
M+. a
b
565
563
C23H23N3O2SBr
C24H25N3OSBr
C16H17N3O2SBr
C17H19N3OSBr
C12H10N2OSBr
C11H6N2OSBr
C11H9NOBr
C12H9N2OS
C9H12N3O2S
C10H14N3OS
C7H6Br
15
-
18/17
25
-
33/32
7
-
-
6
-
3
-
5/4
3/2
2/1
25/24
2
-
4
-
2
394/396
392/394
309/311
293/295
250/252
229
226
224
169/271
100
98
15/14
-
15/14
30/29
5/4
4
10
-
100/99
19
-
-
5/4
6/5
2/1
13/12
14
-
-
2/1
2/1
2/1
14/13
1
-
-
c
d
e
f
17/16
15/14
13/12
22
14
-
100/99
39
-
29
-
23
-
24/23
22/21
11/10
4
14
g
-
2
-
6
h
i
100/99
56
-
88
-
35
-
100/99
-
52
-
60
-
22
100/99
48/47
-
43
-
100
-
10
C5H10NO
C6H12N
C4H8NO
C5H10N
C3H5O
C3H5N
-
64
-
94
-
j
86
84
57
55
45
-
6
k
-
16

60
E. Wyrzykiewicz, T. Pospieszny
Vol 44
cleavages of Csp3-N bonds of 5-piperidinomethyl and
5-morpholinomethyl substituents of VIa-VIc and VIIa-
VIIb give the even-electron fragment ions n. The cleavage
of the same bonds with a simultaneous transfer of ꢀ-
hydrogen to the nitrogen atom of the piperidine (or
morpholine) ring leads to the odd-electron fragment ions c.
As shown in Table 5, the principal fragmentation
pathways of the molecular ions of IXa-IXc and Xa-Xc
are similar to those of VIa-VIc as well as VIIa-VIIc.
Inductive cleavages of the Csp3-S bonds of the bromo-
benzylthio substituent proceed with the retention of
charge, or the migration of charge and elimination of
bromobenzyl (or thiouracils radicals) to form the
complementary even-electron fragment ions b and h,
respectively.
VIc; VIIa-VIIc; IXa-IXc and Xa-Xc are expressed
quantitatively by comparing the calculated values of the
coefficients μ, i.e. the abundances of selected even-
electron fragment ions relative to the abundances of the
corresponding molecular ions. Table 6 presents the values
of μ1, μ2 and μ3. As shown in this table, the differences in
the values of μ1, μ2 and μ3 are sufficient to differentiate
among the isomeric sets VIa-VIc, VIIa-VIIc, IXa-IXc
and Xa-Xc.
Conclusions.
The Mannich reaction of 2-thiouracil, formaldehyde
and piperidine leads to 5-piperidinomethyl-2-tiouracil.
The reaction of 1.32 mmole of PMTU with 1.46 (or 3.33)
mmole of IVa-IVc in DMF in the presence of 0.83 (or
Table 6
The values of μ1-μ3 calculated from the EI mass spectra of metameric VIa-VIc; VIIa-VIIc; IXa-IXc; Xa-Xc
Comp
μ1
μ2
μ3
VIa
VIb
VIc
VIIa
VIIb
VIIc
IXa
IXb
IXc
Xa
3.25
4.50
4.33
0.63
0.77
1.08
6.66
4.00
14.28
16.60
33.33
24.00
2.91
11.71
33.33
0.31
1.22
4.08
2.60
2.24
2.71
8.66
5.58
12.85
13.00
14.28
11.11
8.33
1.93
3.52
6.42
10.00
31.33
50.00
Xb
Xc
21.33
21.50
% rel. abund. i ꢀ +
μ1 = ---------------------------
% rel. abund. a ꢀ +.
VIa-VIc
VIIa-VIIc
% rel. abund. h ꢀ +
μ1 = ------------------------
% rel. abund. a ꢀ +
IXa-IXc
Xa-Xc
% rel. abund. m ꢀ +
μ2 = ---------------------------
% rel. abund. a ꢀ +.
VIa-VIc
VIIa-VIIc
% rel. abund .i ꢀ +
μ2 = ----------------------
% rel. abund. a ꢀ +
IXa-IXc
Xa-Xc
% rel. abund. nꢀ +
μ3 = -------------------------
% rel. abund. a ꢀ +.
VIa-VIc
VIIa-VIIc
% rel. abund. j ꢀ +
μ3 = ----------------------
% rel. abund. a ꢀ +
IXa-IXc
Xa-Xc
The simultaneous cleavages of Csp3-S bonds in bromo-
benzylthio substituents as well as Csp3-N bonds in
morpholinomethyl (piperidinomethyl) substituent lead to
the even-electron fragment ions c. The inductive cleavage
of Csp3-N bonds of morpholinomethyl (piperidinomethyl)
substituent proceeds also with the retention of charge to
form even-electron fragment ions j. The inductive
cleavage of Csp3Csp2 bonds of these substituents leads to
even-electron fragment ions i.
1.33) mmole of K2CO3 at room temperature leads
chemoselectively to VIIa-VIIc or regioselectively to Xa-
Xc. The reaction of 1.32 mmole of MMTU with 1.46 (or
3.33) mmole of IVa-IVc in DMF in the presence of 0.83
(or 1.33) mmole of K2CO3 at room temperature leads
chemoselectively to Va-Vc or regioselectively to VIIIa-
VIIIc. Treatment of Va-Vc and VIIIa-VIIIc with 10 %
K2CO3 water solution affords the corresponding free bases
VIa-VIc and IXa-IXc.
The differences in the fragmentations within each of the
four sets of isomeric compounds within the series of VIa-
The differences in the values of the coefficients μ1, μ2
and μ3 calculated from the EIMS spectra of VIa-VIc;

Jan-Feb 2007
Thio Analogs of Pyrimidine Bases
61
General Procedure for the Preparation of VIa-VIc and
IXa-IXc. Compounds Va-Vc (or VIIIa-VIIIc) were dissolved in
10 % K2CO3 water solution and stirred for 10 minutes. Then the
reaction mixture was extracted with CHCl3. Half of the volume of
the solvent was evaporized, and the obtained VIa-VIc were
collected by filtration, washed with diethyl ether and dry air direct.
IXa-IXc were separated by silica gel column chromatography
(Merck 203-400 mesh) using the following solvent mixtures CH2Cl2
– CH3OH 80:1 (100 ml), CH2Cl2 – CH3OH 60:1 (100 ml), CH2Cl2 –
CH3OH 40:1 (100 ml). The fractions of 20 ml were collected. IXa-
IXc were present in fractions 5-8. On the basis of analytical TLC,
large fractions of products desired were obtained by combining 20
ml fractions. They were concentrated on a rotatory evaporator.
Compounds IXa-IXc were shown to be analytically pure.
General Procedure for the Preparation of VIIa-VIIc and
Xa-Xc. A mixture of 0.83 (or 1.32) mmole of K2CO3 and 1.33
mmole of PMTU in 10 ml of dry DMF was stirred at room
temperature for 2 hours. Next 1.45 (or 3.33) mmoles of the
corresponding IVa-IVc were added. After stirring at room
temperature for 24 hours, 10 ml of distilled water was added. The
reaction mixture was kept at room temperature for 24 hours. The oily
organic layer was separated, triturated with dry diethyl ether and left
for 24 hours in refrigerator. The obtained solid of VIIa-VIIc was
collected by filtration and crystallized from methanol. The crude solids
of Xa-Xc were separated by silica gel column chromatography
(Merck 203-400 mesh) using the following solvent mixtures CH2Cl2 –
CH3OH 80:1 (100 ml), CH2Cl2 – CH3OH 60:1 (100 ml), CH2Cl2 –
CH3OH 40:1 (100 ml). The fractions of 20 ml were collected. Xa-Xc
were present in fractions 6-9. On the basis of analytical TLC large
fractions of products desired were obtained by combining 20 ml
VIIa-VIIc; IXa-IXc and Xa-Xc (Table 6) allow a
differentiation of the isomers.
EXPERIMENTAL
The purity of all compounds described was checked by
m.p.’s, TLC and elemental analysis. Melting points
(uncorrected) were determined on a Böetius microscope stage
UV/VIS spectra were recorded with a Specord UV/VIS spectro-
photometer in methanol. IR spectra were recorded with a FT-IR
Bruker IFS–113 v spectrophotometer in KBr pellets. The 1H
NMR and 13C NMR spectra were determined with a Varian
Mercury Spectrometer operating at 300.07 MHz (proton) or
75.40 MHz (carbon). The data were obtained from DMSO-d6
solution at a concentration between 0.25 and 0.40 M at ambient
temperature. The chemical shifts were referred to tetramethyl-
1
silane. The heteronuclear 2D 13C NMR and H NMR chemical
shift correlation experiments were carried out using HETCOR
spectra. Elemental analyses were performed with a Vector Euro
EA 3000 analyzer. Low- and high-resolution mass spectra were
recorded on an AMD - Intectra GmbH-Harpstedt D-27243
Model 402 two - sector mass spectrometer (ionizing voltage 70
eV, accelerating voltage 8 kV, resolution 10 000). Samples were
introduced by a direct insertion probe at the source temperature
of ~150°C. The elemental compositions of the ions were
determined by
a
peak matching method relative to
perfluorokerosene and on the same instrument. All masses
measured were in agreement with the composition given in
column 3 of Tables 4 and 5 to within ± 2 ppm. The B/E linked
scan spectra in the first field - free region were measured on the
same spectrometer. The values of μ1, μ2 and μ3 were calculated as
averages of three measurements. 2-thiouracil and o-(m- and
p-)bromobenzyl bromides were available from Merck Company,
paraformaldehyde and piperidine from Fluka, morpholine from
Aldrich. MMTU was obtained according to the literature [8].
The synthesis of 5-piperidinomethyl-2-thiouracil (PMTU)
(IIIb). An equimolar mixture of 2-thiouracil (12.8 g), paraform-
aldehyde (3 g) and piperidine (9.87 ml) was suspended in 400
ml of ethanol and refluxed for 48 hours. The homogeneous
solution obtained was filtered and concentrated on a rotatory
evaporator to 200 ml. The reaction mixture was kept at room
temperature for 24 hours. The precipitated solid was isolated by
filtration, dried at room temperature, and recrystallized from
methanol.
fractions. They were concentrated on a rotatory evaporator.
Compounds Xa-Xc were shown to be analytically pure.
REFERENCES AND NOTES
[1] E. De Clercq, J. Balzarini, Il Farmaco, 50, 735-747 (1995).
[2] H. Tanaka, H. Takashima, M. Ubasawa, K. Sekiya, N.
Inouye, M. Baba, S. Shigeta, R. T. Walker, E. De Clercq, J. Med. Chem.,
38, 2860-2865 (1995).
[3] J. Crooks, in "Side Effects of Drugs." Expertia Medica, Eds.
L. Meyler, A. Herzheimer, Elsevier, Amsterdam 1972 p. 573-576.
[4] R. F. Berth, A. H. Soloway, R. G. Fairchild, Cancer Res., 50,
1061– 070 (1990).
[5] M. F. Hawthorne, Angew. Chem., 105, 997-1033 (1993).
[6] W. Tjarks, D. Gabel, J. Med. Chem., 34, 315-319 (1991).
[7] R. A. Nugent, S. T. Schlachter, M. J. Murphy, G. J. Cleek, T.
J. Poel, D. G. Wishka, D. R. Graber, Y. Yagi, B. J. Kaiser, R. A.
Olmsted, L. A. Kopta, S. M. Swaney, S. M. Poppe, J. Morris, W. G.
Tarpley, R. C. Thomas, J. Med. Chem., 41, 3793-3803 (1998).
[8] P. Kamalakannan, D. Venkappayya, T. Balasubramanian, J.
Chem. Soc. Dalton Trans., 3381-3391 (2002).
General Procedure for the Preparation of Va-Vc and
VIIIa-VIIIc. A mixture of 0.83 (or 1.32) mmole of K2CO3 and
1.32 mmole of MMTU in 10 ml of dry DMF was stirred at room
temperature for 2 hours. Next 1.46 (or 3.33) mmoles of
corresponding IVa-IVc were added. After stirring at room
temperature for 24 hours, 10 ml of distilled water was added.
The reaction mixture was kept at room temperature for 24 hours.
The oily organic layer was separated, triturated with dry diethyl
ether and left for 24 hours in a refrigerator. The product formed
was collected by filtration and crystallized from methanol.
[9] E. Wyrzykiewicz, T. Pospieszny, A. Barꢀóg, Rapid Commun.
Mass Spectrom., 19, 580-584 (2005).
[10] E. Wyrzykiewicz, A. Szponar - Krajewicz, Rapid Commun.
Mass Spectrom., 17, 1919-1923 (2003).
[11] E. Wyrzykiewicz, T. Pospieszny, S. Mielcarek, Phosphorus ,
Sulfur and Silicon and the Related Elements, 180, 2051-2070 (2005).