New thymine-based derivative of nitrogen mustards

Article abstract of DOI:10.1080/15257770.2011.649330

This work deals with the synthesis of a new nitrogen mustard derivative based on thymine. To introduce the bis(2-chloroethyl)amine group to position 4 of the pyrimidine base, many strategies were explored and the desired compound was finally obtained, thanks to a synthetic pathway in five steps. Copyright Taylor and Francis Group, LLC.

Full text of DOI:10.1080/15257770.2011.649330

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New Thymine-Based Derivative of
Nitrogen Mustards
a
a
b
Benjamin Boëns , Karine Teste , Amel Hadj-Bouazza , Jihane
c
a
Ismaili & Rachida Zerrouki
a
Laboratoire de Chimie des Substances Naturelles EA1069, Faculté
des Sciences et Techniques, Limoges, France
b
Centre de Recherche sur les Matériaux Lignocellulosiques,
Université du Québec à Trois-Rivières, Trois-Rivières (QC), Canada
c
Laboratoire de Chimie Organique, Université du Québec à Trois-
Rivières, Trois-Rivières (QC), Canada
Version of record first published: 22 Feb 2012.
To cite this article: Benjamin Boëns , Karine Teste , Amel Hadj-Bouazza , Jihane Ismaili & Rachida
Zerrouki (2012): New Thymine-Based Derivative of Nitrogen Mustards, Nucleosides, Nucleotides and
Nucleic Acids, 31:3, 197-205
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Nucleosides, Nucleotides and Nucleic Acids, 31:197–205, 2012
Copyright ꢀC Taylor and Francis Group, LLC
ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770.2011.649330
NEW THYMINE-BASED DERIVATIVE OF NITROGEN MUSTARDS
1
1
2
3
Benjamin Bo e¨ ns, Karine Teste, Amel Hadj-Bouazza, Jihane Ismaili,
1
and Rachida Zerrouki
Laboratoire de Chimie des Substances Naturelles EA1069, Facult e´ des Sciences et
1
Techniques, Limoges, France
2
Centre de Recherche sur les Mat e´ riaux Lignocellulosiques, Universit e´ du Qu e´ bec a`
Trois-Rivi e` res, Trois-Rivi e` res (QC), Canada
3
Laboratoire de Chimie Organique, Universit e´ du Qu e´ bec a` Trois-Rivi `e res, Trois-Rivi e` res
QC), Canada
(
2
This work deals with the synthesis of a new nitrogen mustard derivative based on thymine. To
introduce the bis(2-chloroethyl)amine group to position 4 of the pyrimidine base, many strategies
were explored and the desired compound was finally obtained, thanks to a synthetic pathway in five
steps.
Keywords Base modification; nitrogen mustards; thymine
INTRODUCTION
Nitrogen mustards like chlorambucil, melphalan, cyclophosphamide,
and ifosfamide are a major class of anticancer drugs for the treatment of
various cancers.[ They are bifunctional alkylating molecules and can re-
act with the 7-N position of two different guanines in the major groove of
1]
[2,3]
DNA after the formation of aziridinium ions.
Assuming that these gua-
nines belong to different strands, these two reactions result in a cross-link,
which prevents uncoiling of the DNA double-helix. If the two guanines lie
in the same strand, the result is called “limpet attachment” and so prevents
vital DNA processing enzymes from accessing DNA. The outcomes of all
these alkylation reactions are an inhibition of cell division or a triggering
[
4]
of apoptosis. In connection with our research program on the synthesis
of new alkylating agents designed for cancer therapy, we were interested
in chlorambucil (4-[4-bis(2-chloroethyl)aminophenyl]butyric acid (CLB)),
Received 5 October 2011; accepted 7 December 2011.
Address correspondence to Rachida Zerrouki, Laboratoire de Chimie des Substances Naturelles
EA1069, Facult e´ des Sciences et Techniques, 123 Avenue Albert Thomas, F-87060 Limoges, France.
E-mail: rachida.zerrouki@unilim.fr
1
97

1
98
B. Bo ¨e ns et al.
which is an alkylating drug used in the chemotherapy of chronic lympho-
cytic leukemia,[ Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, ovarian
and breast cancer, some other tumors, and certain autoimmune diseases.
CLB is predominantly metabolized by β-oxidation of the butyric acid side
5]
[6]
chain, giving the major metabolite 4-bis(2-chloroethyl)aminophenylacetic
acid (phenylacetic acid mustard, PAM). This metabolite has a well-known
high antitumor activity and high toxicity toward normal tissues. In our previ-
[
4]
ous work, the introduction of pyrimidine moiety led to some encouraging
results in biological assays. In the line of this work, we decided to replace the
aromatic ring by a natural pyrimidine base to obtain a thymine derivative of
the CLB metabolite (Scheme 1).
SCHEME 1 CLB metabolite and thymine derivative.
RESULTS AND DISCUSSION
To obtain this analogue, we planned the 1-N regioselective alkylation of
thymine, then the introduction in position 4 of a leaving group followed by
a nucleophilic substitution by bis(2-chloroethyl)amine (Scheme 2).
SCHEME 2 First strategy of synthesis. Reagents and conditions: (i) (1) NaH (1.1 equiv), DMF, MW
◦
◦
(
100 C, 300 W, 3 min), (2) ethyl bromoacetate (1.1 equiv), MW (100 C, 300 W, 3 min); (ii) Compound
2
: Mesitylenesulfonyl chloride (1.5 equiv), DMAP (0.06 equiv), Et3N (5 equiv), C2H4Cl2, r.t. 4 days;
◦
Compound 3: Lawesson’s reagent (2 equiv), C2H4Cl2, MW (80 C, 350 W, 34 min); Compound 4: 1,2,4-
triazole (9.6 equiv), POCl3 (2 equiv), Et3N (9.2 equiv), CH3CN, 0 C, 3 h.
◦

New Thymine-Based Derivative of Nitrogen Mustards
199
As shown in Scheme 2, we first alkylated the thymine using the Hadj-
Bouazza method.[ The 1-N alkylated product was obtained in 74% yield.
Then, we proceeded to the introduction of different leaving groups in the
4]
4-C position of compound 1.
The introduction of a mesitylenesulfonyl group was realized accord-
ing to the Grunder-Koltz method.[ The 1-ethoxycarbonylmethylthymine
was reacted with mesitylenesulfonyl chloride, triethylamine, and 4-
dimethylaminopyridine (DMAP) in dichloroethane. The reaction led to
intermediate 2 in 56% yield after purification. This intermediate was re-
acted with bis(2-chloroethyl)amine hydrochloride and triethylamine. Thin
layer chromatography (TLC) monitoring did not show any evolution. We
then used Starrett’s method[ to synthesize thioketone intermediate 3.
Compound 1 was reacted with Lawesson’s reagent (1.5 equiv) in reflux-
ing dichloroethane. Intermediate 3 was obtained in a quantitative yield.
7]
8]
◦
In this case, the use of microwave irradiation (80 C, 350 W) has allowed
a considerably decrease of reaction time, from 8 h to 34 min. The nucle-
ophilic substitution by bis(2-chloroethyl)amine did not lead to the desired
[9]
compound. We then turned to Rahman’s method via triazolylation of
compound 1, and intermediate 4 was obtained in a quantitative yield. In this
case we also did not obtain the substitution product.
Faced with these failures in the direct introduction of this bis(2-
chloroethyl)amine group, we decided to try a two-step strategy starting from
compounds 2, 3, and 4. We first planned nucleophilic substitution by di-
ethanolamine and then the chlorination of hydroxyl groups. Unfortunately,
only in the case of using ethanol as a solvent, we noticed an evolution result-
ing from a direct nucleophilic attack on the carbonyl of ester function, as
observed in the previous work.[
4]
To avoid the reactivity of ester, we replaced the ethoxy group by the less
reactive tert-butoxy group. We chose to use triazole as a leaving group be-
cause a simple recrystallization is required to yield the triazolyl intermediate
in a quantitative manner.
Compound 6 was obtained in 75% overall yield in two steps: 1-N re-
gioselective alkylation to give compound 5, followed by its triazolylation.
Once again, the nucleophilic substitution of the triazolyl group by di-
ethanolamine showed no progress except in the case of using refluxing
ethanol. After 16 h of reaction, TLC showed the total disappearance of
1
-(tert-butoxycarbonylmethyl)-4-(1,2,4-triazolyl) thymine and the formation
of three products (Scheme 3).
The first compound 7 derives from direct amidation of the ester func-
tion. The replacement of the ethoxy group by the tert-butoxy group did
not prevent this substitution. The second compound 8 results in a double
reaction of diethanolamine in position 4 but also on the ester function. The
last isolated compound 9 is the expected one, obtained in 6% yield.

2
00
B. Bo ¨e ns et al.
SCHEME 3 Products obtained by reaction of diethanolamine with compound 6.
Unfortunately, because all the binding assays of diethanolamine or bis(2-
chloroethyl)amine did not give satisfying results, we then questioned the
nucleophilicity of those secondary amines based on their steric effect. We
decided to introduce an amino group on compound 6 followed by its alky-
lation (Scheme 4).
◦
SCHEME 4 Products of N-alkylation. Reagents and conditions: (i) NH3/MeOH (7 M), 45 C, 4 h; (ii)
K2CO3 (5 equiv), BrCH2CH2Cl (5 equiv), DMF, 80 C, 5 days.
◦
The substitution was realized in methanolic ammonia solution. After 4-h
reaction, compound 10 was obtained in 70% yield. We then realized the
alkylation of amine function in DMF in the presence of potassium carbon-
◦
ate and 1-bromo-2-chloroethane at 80 C. After five days, several products
appeared, including two major ones (Scheme 4).
NMR spectroscopy showed that one of the (12%) results of monoalky-
lation of amine function, and the other one corresponds to the expected
product in a modest but significant 23% yield. Mass spectrometry confirmed
those two structures.
We tried to increase the yield by using 1-chloro-2-iodoethane as alkylating
agent. Unfortunately, we did not observe significant amelioration. In this
case, compound 11 was obtained in 27% yield. Finally, compound 11 was
treated with trifluoroacetic acid (TFA), giving the desired thymine derivative
in a quantitative yield.
CONCLUSION
The transformation of carbonyl in position 4 of alkylated thymine proved
complex and required the use of several strategies. Introduction of a leaving

New Thymine-Based Derivative of Nitrogen Mustards
201
group, such as mesitylene, sulfur, and triazole, was undertaken. However,
these intermediates have not led to the expected nucleophilic substitution.
We also observed that the protective group of carboxylic acid might compete
in this nucleophilic substitution. Finally, the last strategy has enabled us to
obtain the expected compound in two steps via amino intermediate. The
following step to this work will be the biological evaluation of this thymine
derivative.
EXPERIMENTAL
General Methods
All the solvents and chemicals were commercially available and, unless
otherwise stated, were used as received. Reactions were monitored by TLC
on precoated 0.2-nm silica gel 60 F254 (Merck) plates and visualized with an
ultraviolet light source at 254 nm. Microwave irradiations were performed
by means of Ethos 1600 MicroSynth reactor from Milestone. Temperature
was measured with a fiber optic thermometer (ATC-FO)/Ethos. 1H NMR
spectra were recorded at 400.13 MHz with a Br u¨ ker DPX spectrometer.
Chemical shifts (δ) are expressed in ppm with Me Si as an internal standard
4
(
δ = 0). Data are reported as follows: chemical shift, multiplicity (s, singlet; d,
doublet; t, triplet; q, quartet; m, mutiplet, and br, broad), coupling constants
Hz), and assignment. Melting points (mp) were determined with a digital
(
melting point apparatus IA9000 series from Electrothermal.
Synthesis
1-Ethoxycarbonylmethylthymine (1)
To a solution of thymine (765 mg, 6 mmol) in 20 mL of dry DMF
was added 1.1 equiv of sodium hydride (264 mg, 6.6 mmol). The reaction
◦
mixture was activated by microwave irradiation for 3 min (100 C and 300 W).
1
.1 equiv of ethyl bromoacetate (750 µL, 6.6 mmol) is injected in the reaction
◦
mixture, then activated by microwave irradiation (2 × 3 min, 100 C, 300 W).
After removal of the solvent, the product was purified by silica gel column
chromatography using a gradient of petroleum ether/acetone as eluent.
This product 1 was obtained as a white solid (999 mg, 74% yield). mp =
◦
−1
1
1
66 C. IR (cm ): 3100 (N-H), 1720 (C = O, ester), 1700 (C = O, thym),
1
670 (C = C). H NMR (DMSO-d6, δ): 11.30 (s, 1H, N-H), 7.48 (br s, 1H,
H6), 1.76 (br s, 3H, CH -thym), 4.45 (s, 2H, CH ), 4.14 (q, 2H, J = 7.1
3
2
1
3
Hz, CH CH ), 1.21 (t, 3H, J = 7.1 Hz, CH CH ). C NMR (DMSO-d6, δ):
2
3
2
3
168.07 (COO), 164.15 (C4), 150.82 (C2), 141.43 (C6), 108.44 (C5), 60.98
(
(
OCH CH ), 48.30 (CH ), 13.89 (CH thymine), 11.71 (OCH CH ). MS
FAB) m/z 213 (M+H) .
2
3
2
3
2
3
+

2
02
B. Bo ¨e ns et al.
1
-(Ethoxycarbonylmethyl)-4-(O-mesitylenesulfonyl)thymine (2)
To a solution of compound 1 (200 mg, 0.943 mmol) in 20 mL of
dichloroethane was added 2 equiv of mesitylenesulfonyl chloride (412 mg,
.886 mmol) and 0.06 equiv of DMAP (7 mg, 0.057 mmol). To the stirred
1
solution, triethylamine (0.655 mL, 4.715 mmol) was added dropwise. The
reaction was stopped after four days, the mixture was concentrated in vac-
uum and purified by column chromatography over silica gel (CHCl ) to give
3
1
5
as a colorless oil (207 mg, 56% yield). H NMR (CDCL3, δ): 7.31 (q, 1H,
J = 0.8 Hz, H6), 2.04 (d, 3H, J = 0.8 Hz, CH -thym), 4.47 (s, 2H, CH ), 4.20
3
2
(
2
q, 2H, J = 7.1 Hz, CH CH ), 1.26 (t, 3H, J = 7.1 Hz, CH CH ), 6.95 (s,
2
3
2
3
13
H, CH-Ar), 2.73 (s, 6H, CH ortho), 2.29 (br s, 3H, CH para). C NMR
3
3
(
CDCl , δ): 167.22 (COO), 166.55 (C4), 154.19 (C2), 147.37 (C6), 131.92 (C-
3
Ar), 104.45 (C5), 62.22 (OCH CH ), 48.61 (CH ), 22.75 (CH para), 21.15
2
3
2
3
(
(
CH ortho), 14.05 (OCH CH ), 12.15 (CH thymine).MS (FAB) m/z 379
M+H) .
3 2 3 3
+
1-(Ethoxycarbonylmethyl)-4-thiothymine (3)
To a solution of 1 (700 mg, 3.3 mmol) in 50 ml of dichloroethane was
added 1.5 equiv Lawesson’s reagent (2.065 mg, 4.95 mmol). The reaction
◦
mixture was activated by microwave irradiation for 34 min (17 × 2 min, 80 C,
3
50 W). After removal of the solvent, the product was purified by silica gel
column chromatography using a gradient of CHCl /EtOH as eluent. This
3
◦
1
product 3 was obtained as a yellow solid (694 mg, 99% yield). mp = 144 C. H
NMR (CDCl , δ): 9.98 (s, 1H, N-H), 6.97 (q, 1H, J = 0.8 Hz, H6), 2.10 (d, 3H, J
3
=
0.8 Hz, CH thymine), 4.60 (s, 2H, CH ), 4.26 (q, 2H, J = 7.1 Hz, CH CH ),
3
2
2
3
13
1
1
4
.31 (t, 3H, J = 7.1 Hz, CH CH ). C NMR (CDCl , δ): 191.00 (C4),
2
3
3
66.94 (COO), 148.30 (C2), 136.63 (C6), 119.58 (C5), 62.44 (OCH CH ),
2
3
9.07 (CH ), 17.20 (CH thymine), 14.11 (OCH CH ). MS (FAB) m/z 229
2
3
2
3
+
(
M+H) .
1-(Ethoxycarbonylmethyl)-4-(1,2,4-triazolyl)thymine (4)
To a solution of 1,2,4-triazole (2.760 g, 0.04 mol, 9.6 equiv) in 50 mL of
acetonitrile was added 780 µL of phosphorous oxychloride (8.4 mmol, 9.2
◦
equiv). The mixture was cooled down to 0 C and 5.40 mL of triethylamine
(
0.04 mol, 9.2 equiv) was added dropwise. 1 g of Compound 1 was added to
the mixture at room temperature. After 3 h, the reaction was stopped with
the addition of 3.5 mL of triethylamine and 2 mL of water. After 10 min,
the solvent was evaporated in vacuo. The crude product is then dissolved
in 50 mL of chloroform and washed with 10 mL of concentrated solution
of sodium hydrogenocarbonate. The phases were separated. The aqueous
phase was extracted with chloroform (50 mL). The combined organic layers
were dried (MgSO ) and evaporated in vacuo. Compound 4 was obtained
4
1
as yellow oil in a quantitative yield (1.24 g). H NMR (DMSO-d6, δ): 9.32 (s,
H, H5 triazole), 8.37 (s, 1H, H3 triazole), 8.26 (q, 1H, J = 0.9 Hz, H6), 4.78
ꢁ
ꢁ
1

New Thymine-Based Derivative of Nitrogen Mustards
203
(
s, 2H, N-CH -CO), 4.18 (q, 2H, J = 7.1 Hz, CH CH ) 2.30 (d, 1H, J = 0.9
2
2
3
13
Hz, CH thymine), 1.23 (t, 3H, J = 7.1 Hz, CH CH ). C NMR (DMSO-d6,
3
2
3
ꢁ
δ): 166.43 (COO), 158.35 (C4), 153.73 (C3 triazole), 153.33 (C2), 146.78
ꢁ
(
1
C6), 145.25 (C5 triazole), 104.41 (C5), 61.27 (OCH CH ), 50.49 (CH ),
2
3
2
+
5.59 (CH thymine), 13.89 (OCH CH ). MS (FAB) m/z 263 (M+H) .
3
2
3
1
-tert-Butoxycarbonylmethylthymine (5)
Compound 5 was synthesized according to the synthesis of compound 1
using tert-butyl bromoacetate (1.07 mL, 6.6 mol). Compound 5 was obtained
◦
1
as a white solid (1.08 g, 75% yield). mp = 193 C. H NMR (DMSO-d6, δ):
1
1.34 (s, 1H, N-H), 7.48 (q, 1H, J = 1.0 Hz, H6), 4.34 (s, 2H, CH ), 1.75 (d,
2
13
3
H, J = 1.0 Hz CH thymine), 1.41 (s, 9H, C(CH ) ). C NMR (DMSO-d6,
3
3 3
δ): 167.27 (COO), 164.20 (C4), 150.91 (C2), 141.70 (C6), 108.34 (C5), 81.75
C(CH ) ), 48.98 (CH ), 27.65 (C(CH ) ), 11.85 (CH thymine). MS (FAB)
(
3
3
2
3 3
3
+
m/z 241 (M+H) .
1-(tert-Butoxycarbonylmethyl)-4-(1,2,4-triazolyl)thymine (6)
Compound 6 was synthesized according to the synthesis of compound 4
using compound 5 as starting material (1.0 g, 4.2 mmol). Compound 6 was
obtained by recrystallization from dichloromethane and diethyl ether as a
◦
1
white powder (1.21 g) in a quantitative yield. mp = 242 C. H NMR (DMSO-
ꢁ
ꢁ
d6, δ): 9.34 (s, 1H, H5 triazole), 8.38 (s, 1H, H3 triazole), 8.32 (q, 1H, J =
0
9
(
.9 Hz, H6), 4.66 (s, 2H, CH ), 2.34 (d, 3H, J = 0.9 Hz, CH thymine), 1.41 (s,
2
3
13
H, C(CH ) ). C NMR (DMSO-d6, δ): 167.76 (COO), 163.79 (C4), 153.73
3
3
ꢁ
ꢁ
C3 ), 150.98 (C2), 146.58 (C6), 145.25 (C5 ), 100.35 (C5), 81.75 (C(CH ) ),
3 3
4
8.48 (CH ), 27.65 (C(CH ) ), 15.59 (CH thymine). MS (FAB) m/z 291
2 3 3 3
+
(
M+H) .
Nucleophilic Substitution on Compound 6
A mixture of compound 6 (1 mmol, 291 mg) and diethanolamine (10
mmol, 995 µL) in ethanol (10 mL) was refluxed. After 16 h, the reaction
mixture was evaporated in vacuo and purified by flash chromatography
(
CHCl /EtOH). Three products were isolated (7, 8, and 9).
3
N,N-bis(2-Hydroxyethyl)-2-(thymin-1-yl)acetamide (7)
1
(
2
10%); H NMR (DMSO-d6, δ): 7.17 (q, 1H, J = 1.0 Hz, H6), 4.73 (s, 2H,
-
2
CH -COO), 3.79 (t, J = 5.2 Hz, 2H, CH hydroxyethyl), 3.74 (t, J = 5.5 Hz,
2
H, CH hydroxyethyl), 3.57 (t, J = 5.2 Hz, 2H, CH hydroxyethyl), 3.53 (t,
2
2
J = 5.5 Hz, 2H, CH hydroxyethyl), 1.91 (d, J = 1.0 Hz, 1H, CH 5-methyl),
2
3
+
1
.42 (s, 9H, -C(CH ) ). MS (FAB) m/z 272 (M+H) .
3
3

2
04
B. Bo ¨e ns et al.
(N4,N4-bis(2-Hydroxyethyl)-5-methylcytosin-1-yl)-N,N-bis(2-hydroxyethyl)
acetamide (8)
1
(
12%); H NMR (DMSO-d6, δ): 7.42 (br s, 1H, H6), 4.31 (s, 2H, -CH -
2
COO), 3.40–3.65 (m, 16H, CH hydroxyethyl), 2.12 (br s, CH 5-methyl).
2
3
+
MS (FAB) m/z 356 (M+H) .
1-(tert-Butoxycarbonylmethyl)-N4,N4-bis(2-hydroxyethyl)-5-methylcyto
sine (9)
1
(
6%); H NMR (DMSO-d6, δ): 7.56 (br s, 1H, H6), 4.41 (s, 2H, -CH -
2
COO), 3.93 (t, J = 6.8 Hz, 2H, CH ), 3.45 (t, J = 5.6 Hz, 2H, CH ), 2.75 (t,
2
2
J = 6.8 Hz, 2H, CH ), 2.66 (t, J = 5.6 Hz, 2H, CH ), 1.81 (br s, CH 5-methyl),
2
2
3
+
1
.42 (s, 9H, -C(CH ) ). MS (FAB) m/z 328 (M+H) .
3
3
1-(tert-Butoxycarbonylmethyl)-5-methylcytosine (10)
2
91 mg of compound 6 (1 mmol) was dissolved in 10 mL of solution of
◦
ammonia in methanol (7 M). The mixture was heated at 45 C for 4 h. After
evaporation to dryness, the crude is purified by column chromatography
(
(
CHCl /EtOH, 10:0 to 5:5). The pure product was obtained as white crystals
3
◦
1
168 mg) in 70% yield. mp = 216 C. H NMR (DMSO-d6, δ): 8.28 (s, 2H,
NH ), 7.38 (br s, 1H, H6), 4.29 (s, 2H, N-CH -COO), 1.81 (br s, 3H, 5-
methyl), 1.41 (s, 9H (CH ) ). C NMR (DMSO-d6, δ): 167.8 (N-CH -COO),
2
2
13
3
3
2
1
65.9 (C4), 155.7 (C2), 143.6 (C6), 100.3 (C5), 81.0 (C-(CH ) ), 50.1 (N-
3 3
+
CH -COO), 27.6 (C-(CH ) ), 12.8 (5-methyl). MS (FAB) m/z 240 (M+H) .
2
3 3
1
-(tert-Butoxycarbonylmethyl)-N4,N4-bis(2-chloroethyl)-5-methylcyto
sine (11)
6 mg of compound 10 (0.23 mmol) was dissolved in 5 mL of DMF in
5
presence of 160 mg of potassium carbonate (1.15 mmol) and 96 µL of 1-
◦
bromo-2-chloroethane (1.15 mmol). The mixture was heated at 80 C. After
five days of reaction, the mixture was filtered and concentrated in vacuo.
The crude product was purified by preparative TLC (eluent CHCl /EtOH,
3
5
0/50, v/v). The expected product is isolated as yellowish oil (20 mg, 23%
1
yield). H NMR (DMSO-d6, δ): 7.81 (q, 1H, J = 1.4 Hz, H6), 4.63 (s, 2H,
-
CH -COO), 4.42-4.12 (m, 8H, CH bis-2-chloroethyl), 1.81 (d, 3H, J = 1.4
2
2
Hz, CH 5-methyl), 1.43 (s, 9H, -C(CH ) ). MS (FAB) m/z 364, 366, 368
3
3 3
+
(
M+H) .
1
-(tert-Butoxycarbonylmethyl)-N4-(2-chloroethyl)-5-methylcytosine (12)
1
Yellowish oil (7 mg, 12% yield). H NMR (DMSO-d6, δ): 6.98 (q, 1H, J =
1
1
3
.0 Hz, H6), 4.24 (s, 2H, -CH -COO), 3.84–3.73 (m, 4H, CH chloroethyl),
2
2
.77 (d, 3H, J = 1.0 Hz, 5-methyl), 1.42 (s, 9H, -C(CH ) ). MS (FAB) m/z
3
3
+
02, 304 (M+H) .

New Thymine-Based Derivative of Nitrogen Mustards
REFERENCES
205
1
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