Synthesis and Biological Evaluation of Some 5-Nitro- and 5-Amino Derivatives of 2′-Deoxycytidine, 2′,3′-Dideoxyuridine, and 2′,3′-Dideoxycytidine

Article abstract of DOI:10.1081/NCN-120026403

In this article, we describe the synthesis of 5-nitro-1-(2-deoxy-α -D-erythro-pentofuranosyl)cytosine (4α), 5-nitro-1-(2-deoxy-β -D-erythro-pentofurano syl)cytosine (4β), 5-amino-1-(2-deoxy-α -D-erythro-pentofuranosyl)cytosine (5α), 5-nitro-1-(2-deoxy-β -D-erythro-pentofuranosyl)cytosine (5β), 5-nitro-1-(2,3-dideoxy-β -D-ribofuranosyl)uracil (6β), 5-amino-1-(2,3-dideoxy-α, β-D-ribofuranosyl)uracil (7), 5-nitro-1-(2,3-dideoxy-α,β -D-ribofuranosyl)cytosine (8) and 5-amino-1-(2,3-dideoxy-β -D-ribofuranosyl)cytosine (9β). The prepared compounds were tested for their activity against HIV and HBV viruses, but they did not show significant activity.

Full text of DOI:10.1081/NCN-120026403

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Synthesis and Biological Evaluation of Some 5-Nitro-
and 5-Amino Derivatives of 2′-Deoxycytidine, 2′,3′-
Dideoxyuridine, and 2′,3′-Dideoxycytidine
a
c
a b
a d
Evelina Colacino , Giovanni Sindona , Gilles Gosselin
& Christophe Mathé
a
Laboratoire de Chimie Organique Biomoléculaire de Synthèse, UMR 5625 CNRS Université
Montpellier II, Montpellier, France
b
Laboratoire Coopératif Idenix, UMR 5625 CNRS, Université Montpellier II, Montpellier,
France
c
Dipartimento di Chimica, Università della Calabria, Arcavacata di Rende, Cosenza, Italy
d
Laboratoire de Chimie Organique Biomoléculaire de Synthèse, UMR 5625 CNRS, Université
Montpellier II, case courrier 008, Place Eugène Bataillon, 34095, Montpellier Cedex 5,
France
Version of record first published: 31 Aug 2006.
To cite this article: Evelina Colacino , Giovanni Sindona , Gilles Gosselin & Christophe Mathé (2003): Synthesis and Biological
Evaluation of Some 5-Nitro- and 5-Amino Derivatives of 2′-Deoxycytidine, 2′,3′-Dideoxyuridine, and 2′,3′-Dideoxycytidine,
Nucleosides, Nucleotides and Nucleic Acids, 22:11, 2013-2026
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS
Vol. 22, No. 11, pp. 2013–2026, 2003
Synthesis and Biological Evaluation of Some 5-Nitro- and
0 0 0
5
-Amino Derivatives of 2 -Deoxycytidine, 2 ,3 -
0
0
Dideoxyuridine, and 2 ,3 -Dideoxycytidine
1
3
Evelina Colacino, Giovanni Sindona, Gilles Gosselin,
1,2
1
,
and Christophe Mathe´
*
1
Laboratoire de Chimie Organique Biomol e´ culaire de Synth e` se and
2
Laboratoire Coop e´ ratif Idenix, UMR 5625 CNRS, Universit e´ Montpellier II,
Montpellier, France
3
Dipartimento di Chimica, Universit a` della Calabria,
Arcavacata di Rende, Cosenza, Italy
ABSTRACT
In this article, we describe the synthesis of 5-nitro-1-(2-deoxy-a-D-erythro-pento-
furanosyl)cytosine (4a), 5-nitro-1-(2-deoxy-b-D-erythro-pentofuranosyl)cytosine
(
(
4b), 5-amino-1-(2-deoxy-a-D-erythro-pentofuranosyl)cytosine (5a), 5-nitro-1-
2-deoxy-b-D-erythro-pentofuranosyl)cytosine (5b), 5-nitro-1-(2,3-dideoxy-b-
D-ribofuranosyl)uracil (6b), 5-amino-1-(2,3-dideoxy-a,b-D-ribofuranosyl)uracil
7), 5-nitro-1-(2,3-dideoxy-a,b-D-ribofuranosyl)cytosine (8) and 5-amino-1-(2,3-
(
dideoxy-b-D-ribofuranosyl)cytosine (9b). The prepared compounds were tested
for their activity against HIV and HBV viruses, but they did not show significant
activity.
Key Words: 5-Substituted pyrimidine nucleoside analogues; HIV; HBV.
*
Correspondence: Christophe Math e´ , Laboratoire de Chimie Organique Biomol e´ culaire de
Synth e` se, UMR 5625 CNRS, Universit e´ Montpellier II, case courrier 008, Place Eug e` ne
Bataillon, 34095 Montpellier Cedex 5, France; Fax: 33-4-67-04-20-29; E-mail: Cmathe@
univ-montp2.fr.
2
013
DOI: 10.1081/NCN-120026403
Copyright # 2003 by Marcel Dekker, Inc.
1525-7770 (Print); 1532-2335 (Online)
www.dekker.com

2014
Colacino et al.
INTRODUCTION
Nucleoside analogues represent one of the main classes of therapeutic agents in
antiviral chemotherapy, and to date, near of twenty nucleoside analogues have been
approved for the treatment of various viral diseases including Herpes viruses,
[
1]
Human Immunodeficiency Virus (HIV) and Hepatitis B virus (HBV) infections.
In order to discover new nucleoside derivatives endowed with potent antiviral activ-
ity, modifications of the base and=or the sugar moiety of natural nucleosides can be
attempted. As a part of our ongoing research program on this topic we have synthe-
sized pyrimidine nucleosides bearing a nitro or amino group at C-5.
Several pyrimidine nucleoside analogues, variously modified at C-5 of the base
[
moiety, have been shown to present biological activity. De Clercq et al. have
2]
reported the anti HSV-1 and HSV-2 activities of 5-nitro-1-(2-deoxy-b-D-erythro-
pentofuranosyl)cytosine (5-NO dC) (4b) (Fig. 1) as well as its inhibitory effect on
2
[
3]
mouse leukaemia L1210 cell growth. Therefore we found it of interest to develop
a new chemical synthesis for compound (4b) and its 5-amino counterpart (5b) (Fig. 1),
all the more no biological data are available for the latter. Moreover, the synthesis
0
0
of other hitherto unknown compounds such as 5-nitro and 5-amino-2 ,3 -dide-
oxyuridine and cytidine derivatives (Fig. 1) as well as the biological evaluation
concerning their potential antiviral activity against HIV and HBV are reported.
RESULTS AND DISCUSSION
[
The first synthesis of 5-NO dC (4b) was reported by Huang et al. The nitro
4]
2
0
group on the pyrimidine ring of 2 -deoxycytidine was introduced by reaction of
0
the corresponding 5 -monophosphate with NO BF =sulfolane. A dephosphorylation
2
4
step to the free nucleoside (4b) was achieved by the action of alkaline phosphatase
with a 1.5% overall yield.
In our first approach, we tried without any success to perform from a suitably
0
[5]
protected 2 -deoxycytidine an Olah’s nitration reaction, already applied in the
0
[6]
synthesis of 5-nitrouridine and 5-nitro-2 -deoxyuridine. At this point a chemical
conversion of the 5-nitrouracil moiety of the nucleoside to the corresponding nucleo-
side bearing 5-nitrocytosine seemed to be appropriate. Indeed, according to conven-
tional routes, the C-4 position of the pyrimidine ring can be transformed in a two
step reaction following three different methodologies. Thus, in a first step the C-4
Figure 1.

5
-Substituted Pyrimidine Nucleosides
2015
[
7,8]
position of the uracil ring can be derivatized with a triazoyl-group,
[10]
an O-aryl
[9]
group or via a direct thionation reaction to a C-4-thiocarbonyl. In a second step,
ammonolysis should provided the cytosine nucleoside derivative. However, when
0
these methodologies were applied to protected 5-nitro-2 -deoxyuridine, none of them
0
provided the target 5-nitro-2 -deoxycytidine (4b). Thus, we chose another approach
involving the coupling of a suitable protected carbohydrate moiety with 5-nitrocyto-
[11]
sine (10) through a glycosylation reaction.
Thus, glycosylation of silylated 5-nitrocytosine with 1-chloro-2-deoxy-3,5-di-O-
[
12]
(
p-toluoyl)-a-D-erythro-pentofuranose
(11) in anhydrous CHCl , without any
3
catalyst at room temperature, gave an anomeric mixture (a=b, ratio 1:1) of the
protected nucleoside (12) which was isolated in a nearly quantitative yield (97%)
(
Sch. 1).
The anomeric ratio (a=b, ratio 1:1) of 12 was inferred from H NMR spectro-
scopy studies using the chemical shift of H-6 protons of 5-nitrocytosine moiety
1
0
because the H-1 protons were overlapping. Our efforts to resolve the 12a and 12b
anomers at their blocked stage were not successful. Thus, the protecting groups were
removed by treatment with NaOMe=MeOH to give a mixture of anomers (4a=4b,
ꢁ
ratio 1:1) in 72% yield. Fractional crystallization in MeOH at ꢀ18 C gave 5-nitro-
1-(2-deoxy-a-D-ribofuranosyl)cytosine (4a) (40% yield) and 5-nitro-1-(2-deoxy-
Scheme 1.

2016
Colacino et al.
b-D-ribofuranosyl)cytosine (4b) (22% yield) separately (Sch. 1). The anomeric
configuration of (4a) and (4b) was assigned through the comparison of their H
1
[13]
NMR spectra. Indeed, protons that are syn to the nucleobase are more deshielded
0
than those which are anti. Thus, the H-4 proton of the a-anomer (4.38 ppm)
0
appeared at a lower field than H-4 proton of the b-anomer (3.90 ppm). Moreover,
0
the H-5 protons of the a-anomer (3.44 ppm) appeared at a higher field than those
of the b-anomer (3.69 and 3.59 ppm). The structures of both compounds have been
since a NOE effect
1
also verified by means of H-NOE difference spectroscopy
[14]
0
(12%) was observed between protons H-6 and H-4 for the a-anomer (4a).
Then, we focused our attention on the synthesis of the hitherto unknown
-nitro-1-(2,3-dideoxy-b-D-ribofuranosyl)uracil (6b) and 5-nitro-1-(2,3-dideoxy-a,
5
b-D-ribofuranosyl)cytosine (8) (Sch. 2). For our purpose, we chose to synthesize a
suitably protected 2,3-D-dideoxyribofuranose as key intermediate which can be
further condensed with the appropriate heterocyclic moiety. 1-O-Acetyl-5-(tert-
[
13]
butyldimethylsilyl)-2,3-D-dideoxy-ribofuranose
(13) was obtained in three steps
starting from commercially available (S)-g-(hydroxymethyl)-g-butyrolactone.
Sugar 13 was condensed with silylated 5-nitrouracil (Sch. 2) using TMSOTf
ꢁ
as a catalyst in CH CN at ꢀ15 C to give 5-nitro-1-(5-O-tert-butyldimethylsilyl-
3
2
,3-dideoxy-D-ribofuranosyl)uracil (14) in 81% yield as a mixture of anomers
(a=b, ratio 1:1). The reaction was instantaneous and prolonged reaction times pro-
voked nucleoside decomposition. Treatment with p-toluenesulfonic acid monohy-
drate afforded an anomeric mixture of 5-nitro-1-(2,3-dideoxy-a,b-D-ribofuranosyl)
uracil (6) in 81% yield. The ratio of the two anomers (6) was determined by
Scheme 2.

5
-Substituted Pyrimidine Nucleosides
2017
1
H-NMR by measuring the integral associated to the H-6 protons of both anomers.
The b-anomer (6b) could be isolated with 13% yield after crystallization in aceto-
ꢁ
nitrile at ꢀ18 C (Sch. 2). Correct assignment was made by comparing chemical shifts
[6]
0
0
of H-6 proton in 5-nitro-2 ,3 -dideoxyuridine (6) with those of 5-nitrouridine
0
(
analysis of H NMR spectrum of (6) displayed the presence of two singlets at
9.74 ppm) and 5-nitro-2 -deoxyuridine (9.71 ppm) previously described. The
1
9
.64 ppm and 8.81 ppm respectively. They were assigned to H-6 protons of the two
0
anomers. Superposition of signals of H-1 protons for both anomers prevented the
exact attribution of stereochemistry.
1
Nevertheless, our attribution was confirmed by H-NOE difference spectroscopy
0
on the crystallized (6b) compound (Fig. 2), showing that H-1 (5.85 ppm) proton is
00
0
0
correlated to H-4 proton (4.11 ppm) and that H-5 =H-5 (3.78 ppm and 3.53 ppm)
protons are correlated with H-6 proton (9.64 ppm).
On the other hand, 5-nitro-1-(5-[(tert-butyldimethylsilyl)-2,3-dideoxy-D-ribofur-
anosyl]cytosine (15) was obtained as a mixture of anomers (a=b, ratio 1:1) by con-
densing silylated 5-nitrocytosine with 13 in 83% yield (Sch. 2). Crystallization in
ꢁ
acetonitrile at ꢀ10 C afforded pure a-anomer (15a) in 29% yield. The resulting fil-
trate provided an enriched b-anomeric mixture (a=b, ratio 0.2:1), which was directly
[
15]
deprotected by triethylamine tris(hydrogen fluoride) complex
(Et N, 3HF) at
3
0
0
room temperature. An inseparable mixture of a- and b-anomer of 5-nitro-2 ,3 -
dideoxycytidine (8) was obtained in 90% yield (a=b, ratio 0.2:1) (Sch. 2).
Hydrogenation of 5-nitro-1-(2-deoxy-a-D-ribofuranosyl)cytosine (4a), 5-nitro-
1-(2-deoxy-b-D-ribofuranosyl)cytosine (4b), 5-nitro-1-(2,3-dideoxy-a,b-D-ribofura-
nosyl)uracil (6) and 5-nitro-1-(2,3-dideoxy-a,b-D-ribofuranosyl)cytosine (8) afforded
the corresponding 5-amino-1-(2-deoxy-a-D-ribofuranosyl)cytosine (5a), 5-amino-1-
(
2-deoxy-b-D-ribofuranosyl)cytosine (5b), 5-amino-1-(2,3-dideoxy-a,b-D-ribofura-
nosyl)uracil (7), 5-amino-1-(2,3-dideoxy-b-D-ribofuranosyl)cytosine (9b) (Sch. 3).
From the 5-amino nucleosides 5a, 5b, 7 and 9b, only 5-amino-1-(2-deoxy-b-D-
[16,17]
ribofuranosyl)cytosine
(5b) was previously reported, by treating 5-bromo-1-
ꢁ
(
2-deoxy-b-D-ribofuranosyl)cytosine with ammonia solution at 55 C for 4 days,
giving (5b) with a low yield. In our approach, (5b) was obtained by simple reduction
of (4b) with palladium on charcoal (5%) in methanolic acetic acid, at room tempera-
ture with a nearly quantitative yield (95%).
Figure 2.

2018
Colacino et al.
Scheme 3.
BIOLOGICAL EVALUATION
All the unprotected nucleosides (4b), (4a), (5a), (5b), (6b), (7), (8) and (9b) were
tested for their in vitro inhibitory effects on the replication of HIV-1 in MT-4 cells.
However, none of these compounds showed marked antiviral effects or detectable
alteration of host-cell morphology at the highest concentration tested (generally
1
00 mM), with the exception of 5-nitro-1-(2-deoxy-b-D-ribofuranosyl)cytosine (4b)
[
MT-4 cells (CC ¼ 38 mM)] and 5-amino-1-(2,3-dideoxy-b-D-ribofuranosyl)cyto-
5
0
sine (9b) [MT-4 cells (CC ¼ 13 mM)]. When evaluated in anti-HBV assays in HepG2
5
0
cells, none of the tested compounds showed antiviral effect (up to a concentration of
1
0 mM) nor cytotoxicity (up to the same concentration of 10 mM).
CONCLUSION
In this work, the syntheses of some nucleoside analogues bearing 5-nitro- or
-amino-groups at C-5 position on uracil and cytosine were carried out. Glycosy-
5
lation reactions of 5-nitro-uracil or –cytosine with a suitable 2-deoxy or 2,3-
dideoxy sugar precursor followed by appropriate chemical modifications led to
5
-nitro-1-(2-deoxy-a-D-erythro-pentofuranosyl)cytosine (4a), 5-nitro-1-(2-deoxy-b-
D-erythro-pentofuranosyl)cytosine (4b), 5-amino-1-(2-deoxy-a-D-erythro-pentofur-
anosyl)cytosine (5a), 5-nitro-1-(2-deoxy-b-D-erythro-pentofuranosyl)cytosine (5b),
5
-nitro-1-(2,3-dideoxy-b-D-ribofuranosyl)uracil (6b), 5-amino-1-(2,3-dideoxy-a,b-
D-ribofuranosyl)uracil (7), 5-nitro-1-(2,3-dideoxy-a,b-D-ribofuranosyl)cytosine (8)

5
-Substituted Pyrimidine Nucleosides
2019
and 5-amino-1-(2,3-dideoxy-b-D-ribofuranosyl)cytosine (9b). All these compounds
were tested against the replication of HIV and HBV but they did not show sig-
nificant antiviral activities.
EXPERIMENTAL
1
13
H-NMR and C-NMR spectra were recorded at room temperature with a Bru-
1
ker DPX 200, AC 250 or DRX 400, in decoupled mode for C-NMR. The chemical
3
1
shifts for H-NMR and C-NMR are expressed in ppm with respect to the signal of
13
residual DMSO-d fixed at 2.49 ppm and 39.5 ppm. Deuterium exchange, COSY and
5
DEPT experiments were performed in order to confirm proton assignments. Cou-
1
pling constants J are expressed in Hertz (Hz). 2D H- C heteronuclear COSY were
13
1
3
recorded for the attribution of C signals. Diastereoisomeric ratios (a and b) were
determined by H-NMR of anomeric mixture and the correct attribution of struc-
1
tures was made by NOE experiments. FAB mass spectra were recorded with JEOL
JMS DX 300, by positive and negative FAB ionisation. The matrix was a mixture
(
cific rotations were measured on a Perkin-Elmer Model 241 spectropolarimeter (path
50:50, v=v) of glycerol and thioglycerol (G-T) or 3-nitrobenzylic alcool (NBA). Spe-
ꢀ1
2
ꢀ1
length 1 cm), and are given in units of 10 deg cm g . Elemental analyses were
carried out by the Service de Microanalyses du C.N.R.S. Division of Vernaison
(
France). Melting points are uncorrected and were measured by mean of a capillary
with a B u¨ chi melting point B-545. Ultra-Violet (U.V.) spectra were recorded with a
spectrophotometre Uvikon-xs (BIO-TEK instruments). Thin layer chromatography
(
TLC) was performed on Silica Gel Merck 60 F254 (art. 5554), visualization of pro-
ducts being accomplished by UV absorbency followed by charring with 5% ethanolic
sulfuric acid or by ninhydrine (200 mg) in abs. ethanol and heating. Column chroma-
tography was carried out on Silica Gel 60 (Merck, art. 9385). After elution or extrac-
tion, compounds were filtered through Millex HV-4 (0.45 mm, Millipore) units.
Reverse phase (C ) purification was performed by Silica Merck LiChroprep RP-
1
8
18 (25–40 mm). All moisture-sensitive reactions were carried out under rigorous
anhydrous conditions under an argon atmosphere using oven-dried glassware.
Solvents were dried and distilled prior to use and solids were dried over P O under
reduced pressure.
2
5
General Procedure for the Hydrogenation of Compounds 4b, 4a, 6, and 8. A solu-
tion of the nucleoside in MeOH (26 mL=mmol) and glacial acetic acid (44 ml=mmol,
except for compound 6 and 8) was hydrogenated in the presence of Pd=C 5%
(
100 mg=100 mg of nucleoside). After 20 min of stirring at room temperature, the
suspension was filtered through a sintered funnel covered with Celite and the filtrate
was evaporated to dryness and co-evaporated several times with toluene. The residue
was subjected to a RP 18 column chromatography with water as eluent.
5
-Nitro-1-(2-deoxy-3,5-di-O-p-toluoyl-a,b-D-erythro-pentofuranosyl)cytosine
[
11]
(
12). A mixture of 5-nitrocytosine
(10) (3.5 g, 22.4 mmol), hexamethyl-
disilazane (160 mL) and a catalytic amount of ammonium sulfate was refluxed
overnight. After distillation under vacuum, the crude was diluted with dry

2020
Colacino et al.
chloroform (40 mL) and a solution of 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-a-D-
[12]
erythro-pentofuranose
(6.09 g, 15.70 mmol) in dry chloroform (70 mL) was
added. The mixture was stirred for 4h30 at room temperature, neutralised with
a saturated solution of NaHCO3 (100 mL), washed with water (2 ꢂ 100 mL),
dried (sodium sulfate), and evaporated. Chromatography of the residue on a silica
gel column using petroleum ether=ethyl acetate (75:25) as eluent gave a white
ꢁ
foam which upon crystallization in MeOH at ꢀ18 C provided white crystals of
1
2 (7.74 g, 97% yield) as a mixture of anomers (a=b, ratio 1:1). R (system:
f
CHCl =Methanol 98:2 v=v) 0.33 (a), 0.38 (b); d [(CD ) SO] 8.89 (s, 1H,
3
H
3 2
6
4
2
4
3
2
2
-H ), 8.85 (s, 1H, 6-H ), 8.43 (s, 1H, 4-NH
and 4-NH2[b]), 7.94 (s, 1H,
-NH ), 7.89 (s, 1H, 4-NH ), 7.1–7.8 (m, 16H, ArH and ArH ), 6.03 (m,
[
b]
[a]
2[a]
2
0
[b]
2[a]
[a]
[b]
0
0
0
0
H, 1 -H[ and 1 -H ), 5.46 (m, 2H, 3 -H and 3 -H ), 5.04 (m, 1H, 4 -H ),
[a]
a]
[b]
[a]
[b]
0
0
.59 (m, 1H, 4 -H ), 5.53 (dd, 1H, J
0
0
0
¼ 3.6, J
0
00 ¼ 12.1, 5 -H ), 4.39 (m,
[
b]
5 -4
5 -5
[b]
0
0
00
0
0
H, 5 -H , 5 -H and 5 -H ), 2.86 (m, 1H, 2 -H ), 2.66 (m, 1H, 2 -H ),
[a]
[b]
[a]
[a]
[b]
00
0
.53 (m, 2H, 2 -H and 2 -H ), 2.27 (s, 3H, ArCH ), 2.24 (s, 6H, ArCH ),
[b]
[
a]
3
3
.22 (s, 3H, ArCH ); d [(CD ) SO] 166.34 (C ¼ O), 166.29 (C ¼ O), 166.1 (6-
3
C
3 2
C ), 165.5 (6-C ), 158.1 (4-C and 4-C ), 147.2 (2-C ), 146.8 (2-C ), 119.8
[b]
[
b]
[a]
[a]
0
[b]
[a]
0
0
0
(
7
5-C ), 119.7 (5-C ), 89.8 (1 -C ), 89.4 (1 -C ), 85.6 (4 -C ), 83.9 (4 -C ),
[a]
[b]
[a]
[b]
[a]
[b]
0 0 0 0 0
5.8 (3 -C ), 75.5 (3 -C ), 64.8 (5 -C ), 65.1 (5 -C ), 39.1 (2 -C ), 38.8
[b] [a] [a] [b] [a]
0
þ
þ
(
2 -C ), 22.1 (CH ); m=z (FAB > 0, G-T) 1017 [2M þ H] , 509 [M þ H] , 353
þ þ þ ꢀ
2 3
[b]
3
[
S] , 157 [BH ] , 119 [CH PhCO] ; m=z (FAB < 0, G-T) 1015 [2M-H] , 507
ꢀ
ꢀ
ꢀ
[M-H] , 389 [M- CH PhCO] , 155 [B] . Anal. Calcd. for C H N O ꢃ 0.3
MeOH: C, 58.65; H, 4.90; N, 10.81. Found: C, 58.58; H, 4.84; N, 10.93.
3
25 24
4
8
5-Nitro-1-(2-deoxy-a-D-erythro-pentofuranosyl)cytosine (4a) and 5-Nitro-1-(2-
Deoxy-b-D-erythro-pentofuranosyl)cytosine (4b). 5-nitro-1-(2-Deoxy-3,5-di-O-p-
toluoyl-a,b-D-erythro-pentofuranosyl)cytosine (12) (5.2 g, 10.2 mmol) in NaOMe=
MeOH (102 mL, 0.2 N) was stirred at room temperature for 1h30 then MeOH
(
70 mL) was added. The resulting solution was neutralised with DOWEX (50 ꢂ 2,
þ
H -form), and the resin was filtered and washed several times with hot MeOH.
The crude material was evaporated and the residue was diluted with water, washed
with dichloromethane (3 ꢂ 100 mL) and evaporated to dryness. The residue was sub-
jected to a RP 18 column chromatography and eluted with a stepwise gradient of
acetonitrile (0-1%) in methanol to afford 1.99 g (72% yield) of 5-nitro-1-(2-deoxy-
a,b-D-erythro-pentofuranosyl)cytosine as a mixture of its anomers (a=b, ratio 1:1).
ꢁ
Crystallization with MeOH and a minimum amount of water at ꢀ10 C gave 4a
(
1.1 g, 40% yield)) as white needles and 4b (600 mg, 22% yield) as white flakes. Rf
(
system: Et O=MeOH 90:10 v=v) 0.13 (a), 0.18 (b); R (system: CH CN=MeOH
2
f
3
9
9:1 v=v) 0.16 (a), 0.24 (b).
ꢁ
20
(
H, 6-H), 8.55 (s, 1H, 4-NH ), 8.08 (s, 1H, 4-NH ), 6.05 (dd, 1H, J
4a): m.p. 255 C (darkening); [a]D þ57.3 (c 1.1, Me SO); d [(CD ) SO] 9.11 (s,
2
H
3 2
1
0 0
¼ 6.9,
2
2
1 -2
0
0
0
1
-H), 5.31 (d, 1H, J3
0
0
0
0
¼ 2.5, 3 -OH), 4.97 (t, 1H, J
0
0
¼ 5.7, 5 -OH), 4.38
-3 OH
5 -5 OH
0
0
0
(
5
dd, 1H, J
0
00 ¼ 6.58, J
0
0
¼ 11.5, 4 -H), 4.26 (m, 1H, 3 -H), 3.44 (m, 2H, 5 -H et
4
-5=5
4 -3
00
00
-H), 2.59 (m, 1H, 2 -H), 2.54 (m, 1H, 2 -H); d [(CD ) SO] 158.7 (4-C), 152.7
C
3 2
0
0
0
0
(
2-C), 147.9 (6-C), 119.3 (5-C), 91.9 (4 -C), 89.7 (1 -C), 73.1 (3 -C), 62.5 (5 -C),
0
4
Found: C, 39.14; H, 5.07; N, 18.14.
1.1 (2 -C). Anal. Calcd. for C H N O ꢃ CH OH: C, 39.48; H, 5.30; N, 18.41:
9
12
4
6
3

5
-Substituted Pyrimidine Nucleosides
2021
ꢁ
ꢁ
[4]
20
(
4b): m.p. 188 C (literature: 190 C); [a]D ꢀ60 (c 1.0, Me SO); l (H O)=
2
max
2
þ
nm 322 (e 9500); l
278 (e 3200); m=z (FAB > 0, G-T) 273 [M þ H] , 157
min
þ
þ
ꢀ
[
BH ] , 117 [S] ; m=z (FAB < 0, G-T) 271 [M-H] ; d [(CD ) SO] 9.49 (s, 1H, 6-
2
H
3 2
0
H), 8.49 (s, 1H, 4-NH ), 8.03 (s, 1H, 4-NH ), 6.01 (t, 1H, J
0
0
0
0
¼ 5.8, 1 -H), 5.31
2
2
1 -2 =2
0
0
(
1
5
6
d, 1H, J ¼ 4.4, 3 -OH), 5.22 (t, 1H, J ¼ 4.5, 5 -OH), 4.23 (m, 1H, 3 -H), 3.90 (m,
0
0
00
0
H, 4 -H), 3.69 (m, 1H, 5 -H), 3.59 (m, 1H, 5 -H), 2.34 (m, 1H, 2 -H); d [(CD ) SO]
C
3 2
0
0
0
8.2 (4-C), 152.6 (2-C), 147.8 (6-C), 119.9 (5-C), 88.9 (4 -C), 88.0 (1 -C), 70.1 (3 -C),
0 0
1.1 (5 -C), 42.1 (2 -C). Anal. Calcd. for C H N O : C, 39.71; H, 4.44; N, 20.58.
9 12 4 6
Found: C, 39.45; H, 4.38; N, 20.45.
5
-Nitro-1-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-D-ribofuranosyl]uracil
14). A mixture of 5-nitrouracil (3.0 g, 19.1 mmol), hexamethyldisilazane (134 mL)
(
and a catalytic amount of ammonium sulfate was refluxed under argon overnight.
ꢁ
The solution was distilled under vacuum. The resultant oil was cooled at ꢀ15 C
[13]
and a solution of 13
(3.49 g, 12.7 mmol) in dry CH CN (130 mL) and trimethy-
3
silyltrifluromethane sulfonate (2.7 mL, 13.97 mmol) were added successively. The
reaction mixture was immediately diluted with CH Cl (130 mL) and neutralized
with cooled 5% NaHCO . The organic layers were separated, washed with water
2
2
3
(
200 mL ꢂ 2), dried (Na SO ) and evaporated in vacuo to dryness. The residue
2
4
was purified on silica gel using a stepwise gradient of ethyl acetate (0-10%) in diethyl
ether to afford a mixture of 5-nitro-1-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-
D-ribofuranosyl]uracil (14) (5.32 g; 81% yield). A crystallization in diethylether with
ꢁ
a minimum amount of MeOH at ꢀ18 C afforded 14 (a=b, ratio 1:1) as white crystals:
R (system: Et O=AcOEt 90:10 v=v) 0.65 (a); 0.52 (b); d [(CD ) SO] (a-anomer):
f
2
H
3 2
0
1
4
4
1
1.96 (s, 1H, 3-NH), 8.68 (s, 1H, 6-H), 5.84 (dd, 1H, J
0
0
0
¼ 6.3, J
0
00 ¼ 3.2, 1 -H),
1
-2
0
1 -2
.46 (m, 1H, 4 -H), 3.62 (dd, 1H, J
0
0
0
¼ 3.8, J
0
00 ¼ 11.1, 5 -H), 3.54 (dd, 1H, J
0
0
¼
5
-4
5 -5
5 -4
00
0
00
0
.6, J5
.72 (m, 1H, 2 -H), 0.81 (s, 3H, (CH ) C), 0.80 (s, 3H, (CH ) C), 0.79 (s, 3H,
00 ¼ 11.2, 5 -H), 2.34 (m, 1H, 3 -H), 2.08 (m, 1H, 3 -H), 1.94 (m, 1H, 2 -H),
-5
00
3
3
3 3
(
H), 5.85 (dd, 1H, J1
CH ) C), 0.00 (s, 6H, (CH )Si); (b-anomer): 11.97 (s, 1H, 3-NH), 8.96 (s, 1H, 6-
3
3
3
0
0
0
0
¼ 2.8, J
0
00 ¼ 6.0, 1 -H), 4.14 (m, 1H, 4 -H), 3.91 (dd, 1H,
-2
1 -2
0
00
J5
0
0
¼ 3.9, J
0
00 ¼ 11.2, 5 -H), 3.69 (dd, 1H, J
0
0
¼ 3.8, J
0
5 -5
00 ¼ 11.1, 5 -H), 2.32
-4
5 -5
5 -4
0
00
0
00
(
m, 1H, 2 -H), 2.12 (m, 1H, 2 -H), 1.82 (m, 1H, 3 -H), 1.72 (m, 1H, 3 -H), 0.82
(
s, 3H, (CH ) C), 0.81 (s, 3H, (CH ) C), 0.80 (s, 3H, (CH ) C), ꢀ0.02 (s, 6H,
3
3
3 3
3 3
(
CH ) Si); d [(CD ) SO] (a-anomer): 156.1 (4-C), 149.8 (2-C), 145.8 (6-C), 126.3
3
C
3 2
0
0
0
0
0
(
5-C), 90.5 (1 -C), 83.4 (4 -C), 66.1 (5 -C), 33.1 (2 -C), 27.02 ((CH ) C), 26.0 (3 -C),
3
3
1
1
9.2 ((CH ) C), ꢀ4.14 (CH Si); (b-anomer): 155.7 (4-C), 149.5 (2-C), 145.5 (6-C),
3
3
3
0
0
0
0
25.7 (5-C), 88.9 (1 -C), 83.0 (4 -C), 64.7 (5 -C), 33.2 (2 -C), 26.68 ((CH ) C), 24.8
3
3
0
(
3 -C), 19.1 ((CH ) C), ꢀ4.5 (CH Si), ꢀ4.64 (CH Si); m=z (FAB > 0, G-T) 743
3
3
3
þ
3
þ
þ
ꢀ
þ
2
[
2M þ H] ; 372 [M þ H] ; 216 [S] ; 158 [BH ] ; m=z (FAB < 0, G-T) 741 [2M-
ꢀ
ꢀ
H] ; 370 [M-H] ; 156 [B] . Anal. Calcd. for C H N O Si ꢃ 1=2 MeOH: C, 48.05;
1
5
25
3
6
H, 7.02; N, 10.84. Found: C, 47.75 ; H, 6.77; N, 11.12.
5-Nitro-1-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-D-ribofuranosyl]cytosine
15). A mixture of 5-nitrocytosine (10) (2.6 g, 16.4 mmol), hexamethyldisilazane
(
(
147 mL) and a catalytic amount of ammonium sulfate was refluxed overnight. After
ꢁ
distillation under vacuum, the resultant oil was cooled at ꢀ15 C and a solution of 13

2022
Colacino et al.
(3.0 g, 10.9 mmol) in dry CH CN (110 mL) and trimethylsilyltrifluoromethane sulfo-
3
nate (2.3 mL, 12.0 mmol) were successively added. The reaction mixture was imme-
diately diluted with dichloromethane (100 mL) and neutralised with a cooled
solution of 5% NaHCO . The organic layers were separated, washed with water
3
(
200 mL ꢂ 2), dried (Na SO ) and evaporated under reduced pressure. The crude
2
4
was purified on silica gel using a stepwise gradient of isopropanol (0-10%) in Et O
2
to afford 5-nitro-1-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-D-ribofuranosyl]-
cytosine (15) (3.47 g, 86% yield) (a=b, ratio 1:1). R (system: Et O=isopropanol
f
2
ꢁ
9
anomer (1.16 g, 29% yield). The resulting filtrate (2.2 g) provided a mixture enriched
0:10 v=v) 0.64 (a); 0.54 (b). Crystallization in CH CN at ꢀ10 C gave pure a-
3
with b-anomer (a=b, ratio 0.2:1); lmax (95% EtOH)=nm 319 (e 8800), lmin 277
(
e 1700); d [(CD ) SO] (a-anomer): 8.71 (s, 1H, 6-H), 8.42 (sl, 1H, 4-NH ), 7.95
H
3 2
2
0
0
(
3
sl, 1H, 4-NH ), 5.81 (dd, 1H, J
0
0
0
¼ 2.66, J
0
00 ¼ 6.1, 1 -H), 4.46 (m, 1H, 4 -H),
2
1 -2
1 -2
0
00
.63 (dd, 1H, J
0
0
0
¼ 3.9, J
00 ¼ 11.1, 5 -H), 3.55 (dd, 1H, J
0 0
5 -4
¼ 4.6, 5 -H), 2.36
5
-4
5 -5
0
00
00
(m, 1H, 3 -H), 1.98–1.88 (m, 2H, 2 -H and 3 -H), 1.71 (m, 1H, 2 -H), 0.82 (s, 9H,
(CH ) C), 0.00 (s, 6H, (CH ) Si); (b-anomer): 8.96 (s, 1H, 6-H), 8.42 (sl, 1H, 4-
3
3
3
0
0
NH ), 7.95 (sl, 1H, 4-NH ), 5.75 (t, 1H, J
2
3
H), 1.83 (m, 1H, 2 -H), 1.67 (m, 2H, 3 -H and 3 -H), 0.83 (s, 9H, (CH ) C), 0.00
0
0
00 ¼ 3.8, 1 -H), 4.17 (m, 1H, 4 -H),
2
1 -2 =2
0
0
00
0
.89 (dd, 1H, J5
0
0
¼ 2.6, J
0
00 ¼ 11.7, 5 -H), 3.68 (dd, 1H, 5 -H), 2.38 (m, 1H, 2 -
3 3
-4
5 -5
00
00
(
1
s, 6H, (CH ) Si); d [(CD ) SO] (a-anomer): 158.3 (4-C), 152.5 (2-C), 146.7 (6-C),
3
C
0
3 2
0
0
0
19.6 (5-C), 90.3 (1 -C), 82.9 (4 -C), 65.8 (5 -C), 33.1 (3 -C), 26.6 ((CH ) C), 25.6
0
3
3
(
(
2 -C), 18.8 ((CH ) C), ꢀ4.5 (CH Si); (b-anomer): 158.2 (4-C), 152.6 (2-C), 146.9
3
3
3
0 0 0 0
6-C), 119.4 (5-C), 89.3 (1 -C), 83.7 (4 -C), 64.9 (5 -C), 33.6 (3 -C), 26.7 ((CH ) C),
3 3
0
2
4.9 (2 -C), 19.0 ((CH ) C), ꢀ4.6 (CH Si), ꢀ4.7 (CH Si); m=z (FAB > 0, NBA)
3
þ
3
3
3
þ
þ
ꢀ
ꢀ
3
Anal. Calcd. for C H N O Si: C, 48.63; H, 7.07; N, 15.12. Found: C, 48.50; H,
71 [M þ H] , 215 [S] , 157 [BH ] ; m=z (FAB < 0, G-T) 369 [M-H] , 155 [B] .
2
1
5
26
4
5
6
.93; N, 14.74.
5-Nitro-1-(2,3-dideoxy-b-D-ribofuranosyl) Uracil (6b). To a solution of 5-nitro-
1
-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-D-ribofuranosyl]uracil (16) (931 mg,
2
monohydrate (506 mg, 2.66 mmol). After stirring at room temperature for 20 min,
.51 mmol) in MeOH (15 mL) and H O (2.3 mL) was added p-toluenesulfonic acid
2
MeOH (15 mL) was added and the solution was neutralised with DOWEX (1 ꢂ 2,
ꢀ
OH form). The resin was filtered off and washed several times with hot methanol.
The filtrate was concentrated and purified on a silica gel column using a stepwise
gradient of MeOH (0–6%) in CH Cl to afford of 5-nitro-1-(2,3-dideoxy-a,b-D-ribo-
2
2
furanosyl) uracil (6) (522 mg, 81%) as a mixture of anomers (a=b, ratio 1:1). Crystal-
ꢁ
lization in CH CN at ꢀ18 C afforded b-anomer (6b) (85 mg, 13.2% yield) as white
3
ꢁ
20
needles. M.p. 230 C; R (system: Et O=AcOEt 90:10 v=v) 0.41 (a); 0.35 (b); [a]
f
2
D
ꢀ
71.3 (c 1.01 in Me SO); l
(95% EtOH)=nm lmax 302 (e 10900), lmin 258 (e
2
max
2
1
1
500); d [(CD ) SO] 11.94 (s, 1H, 3-NH), 9.64 (s, 1H, 6-H), 5.85 (dd, 1H, J
0 0
¼
H
3 2
1 -2
0
0
0
.2, J
H, 5 -H), 3.53 (m, 1H, 5 -H), 2.32 (m, 1H, 2 -H), 2.12 (m, 1H, 2 -H), 1.75–1.84
0
00 ¼ 6.3, 1 -H), 5.26 (t, 1H, J ¼ 4.6, 5 -OH), 4.11 (m, 1H, 4 -H), 3.78 (m,
1
0
-2
00
0
00
0 00
(
(
m, 2H, 3 -H and 3 -H); d [(CD ) SO] 155.8 (4-C), 149.7 (2-C), 146.5 (6-C), 125.8
5-C), 88.4 (1 -C), 84.3 (4 -C), 61.4 (5 -C), 33.7 (2 -C), 24.0 (3 -C); m=z (FAB > 0,
þ
C
3 2
0
0
0
0
0
þ
þ
þ
G-T) 515 [2M þ H] , 258 [M þ H] , 158 [BH ] , 101 [S] ; m=z (FAB < 0, G-T)
2

5
-Substituted Pyrimidine Nucleosides
2023
ꢀ
ꢀ
ꢀ
513 [2M-H] ; 256 [M-H] ; 156 [B] . Anal. Calcd. for C H N O : C, 42.03; H, 4.31;
N, 16.34. Found: C, 42.07; H, 4.41; N, 16.22.
9
11
3
6
5-Nitro-1-(2,3-dideoxy-a,b-D-ribofuranosyl)cytosine (8). To a solution of 5-
nitro-1-[5-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a,b-D-ribofuranosyl] cytosine (15)
(
1.2 g, 3.24 mmol) (a=b 0.2:1) in dry THF (32 mL) was added triethylamine tris-
(
hydrogen fluoride) (3.2 mL, 19.44 mmol). The solution was stirred at room tempera-
ture for 6 h. Solvent was removed and the residue was purified on a silica gel column
using a stepwise gradient of MeOH (0-8%) in CH Cl to afford 5-nitro-1-(2,3-
2
2
dideoxy-a,b-D-ribofuranosyl)cytosine (8) (747 mg, 90% yield) as a mixture of ano-
mers (a=b, ratio 0.2:1). R (system: Et O=Isopropanol 80:20 v=v) 0.21 (a); 0.33 (b);
f
2
lmax (95% EtOH)=nm 322 (e 7400), lmin 280 (e 2100); d [(CD ) SO] (a-anomer):
H
3 2
0
.81 (s, 1H, 6-H), 8.38 (sl, 1H, 4-NH ), 7.94 (sl, 1H, 4-NH ), 5.82 (m, 1H, 1 -H),
2 2
8
4
5
0
0
0
.91 (t, 1H, J ¼ 5.8, 5 -OH), 4.12 (m, 1H, 4 -H), 3.61 (m, 1H, 5 -H), 3.42 (m, 1H,
00
0
0
00
00
-H), 2.33 (m, 1H, 3 -H), 1.98–1.88 (m, 2H, 2 -H et 3 -H), 1.70 (m, 1H, 2 -H);
(
b-anomer): 9.63 (s, 1H, 6-H), 8.38 (sl, 1H, 4-NH ), 7.94 (sl, 1H, 4-NH ), 5.80 (m,
2
2
0
0
0
0
1
3
3
H, 1 -H), 5.02 (t, 1H, J ¼ 4.5, 5 -OH), 3.89 (m, 1H, 4 -H), 3.76 (m, 1H, 5 -H),
0
0
0
00
0
.52 (m, 1H, 5 -H), 2.82 (m, 2H, 2 -H and 2 -H), 2.02 (m, 1H, 3 -H), 1.74 (m. 1H,
-H); d [(CD ) SO] (a-anomer): 158.3 (4-C), 152.7 (2-C), 147.9 (6-C), 119.6 (5-
00
C
3 2
0
0
0
0
0
C), 88.2 (1 -C), 82.9 (4 -C), 61.6 (5 -C), 33.9 (3 -C), 24.4 (2 -C); (b-anomer): 158.3
0 0 0
(
4-C), 152.7 (2-C), 146.9 (6-C), 119.6 (5-C), 88.7 (1 -C), 84.2 (4 -C), 61.6 (5 -C),
0
0
þ
þ
3
4.9 (3 -C), 23.9 (C-2 ); m=z (FAB > 0, NBA) 513 [2M þ H] , 257 [M þ H] , 201
þ þ ꢀ ꢀ ꢀ
2
[S] , 157 [BH ] ; m=z (FAB < 0, G-T) 511 [2M-H] , 255 [M-H] , 155 [B] .
5-Amino-1-(2-deoxy-b-D-erythro-pentofuranosyl)cytosine
(5b). 5-nitro-1-(2-
Deoxy-b-D-erythro-pentofuranosyl)cytosine (4b) (300 mg, 1.10 mmol) was hydroge-
nated following the general procedure to afford of 5-amino-1-(2-deoxy-b-D-erythro-
pentofuranosyl)cytosine (5b) (247 mg, 95% yield) as a yellow powder. m.p. 165 C
ꢁ
ꢁ
20
(
darkening), 175 C (melting); [a]D ꢀ21.9 (c 1.05, Me SO). R (system: CH CN=
2
f
3
H O 90:10 v=v) 0.10; l
(95% EtOH)=nm l
303 (e 8400), l
260 (e 4100);
2
max
max
min
d [(CD ) SO] 7.19 (sl, 1H, 4-NH ), 7.13 (s, 1H, 6-H), 6.53 (sl, 1H, 4-NH ), 6.10 (dd,
H
3 2
2
2
0
0
1
H, J1
0
0
¼ 6.0, J
0
00 ¼ 7.8, 1 -H), 5.08 (d, 1H, J ¼ 4.1, 3 -OH), 4.80 (t, 1H,
-2
1 -2
0
0
0
J ¼ 5.3, 5 -OH), 4.07 (m, 1H, 3 -H), 3.80 (sl, 2H, 5-NH ), 3.62 (m, 1H, 4 -H),
2
0
00
0
0
3
6
6
1
.42 (m, 2H, 5 -H and 5 -H), 1.92 (m, 1H, 2 -H), 1.78 (m, 1H, 2 -H); d [(CD ) SO]
C
3 2
0
0
0
1.6 (4-C), 154.7 (2-C), 122.7 (6-C), 116.9 (5-C), 87.7 (4 -C), 85.2 (1 -C), 71.6 (3 -C),
þ
0
0
þ
2.7 (5 -C), 40.5 (2 -C); m=z (FAB > 0, NBA) 485 [2M þ H] , 243 [M þ H] ,
þ
ꢀ
27 [BH ] ; m=z (FAB < 0, NBA) 241 [M-H] . Anal. Calcd. for C H N O ꢃ 1=2
2
9
14
4
4
H O: C, 43.03; H, 6.02; N, 22.30. Found: C, 43.37; H, 5.85; N, 21.95.
2
5-Amino-1-(2-deoxy-a-D-erythro-pentofuranosyl)cytosine
(5a). 5-nitro-1-(2-
Deoxy-a-D-erythro-pentofuranosyl)cytosine (4a) (500 mg, 1.84 mmol) was hydroge-
nated following the general procedure to afford 5-amino-1-(2-deoxy-a-D-erythro-
ꢁ
pentofuranosyl)cytosine (5a) (434 mg, 97% yield) as a white powder. m.p. 132 C;
2
0
[
a]D þ 16.2 (c 1.05, Me SO). R (system: CH CN=H O 90:10 v=v) 0.10; l
(95%
max
2
f
3
2
EtOH)=nm 303 (e 8400), l
260 (e 4100); d [(CD ) SO] 7.24 (s, 1H, 6-H), 7.09
min
H
3 2
0
(
sl, 1H, 4-NH ),6.03 (sl, 1H, 4-NH ), 6.07 (dd, 1H, J
0
0
¼ 4.0, J
0
00 ¼ 7.3, 1 -H),
2
2
1 -2
1 -2

2024
Colacino et al.
0
0
0
0
5
3
2
8
[
[
.27 (sl, 1H, 3 -OH), 4.84 (sl, 1H, 5 -OH), 4.18 (m, 1H, 3 -H), 4.05 (m, 1H, 4 -H),
0
0
00
.93 (sl, 2H, 5-NH ), 3.43 (m, 2H, 5 -H et 5 -H), 2.50 (m, 1H, 2 -H), 1.76 (m, 1H,
2
0
0
0
-H); d [(CD ) SO] 161.6 (4-C), 154.7 (2-C), 123.8 (6-C), 116.4 (5-C), 89.0 (4 -C),
C
3 2
0
0
0
0
6.5 (1 -C), 71.3 (3 -C), 62.6 (5 -C), 41.4 (2 -C); m=z (FAB > 0, NBA) 485
þ
þ
þ
ꢀ
2M þ H] , 243 [M þ H] , 127 [BH ] ; m=z (FAB < 0, G-T) 483 [2M-H] , 241
ꢀ ꢀ
2
M-H] , 125 [B] . Anal. Calcd. for C H N O 6.7 H O: C, 44.63; H, 5.83; N,
9 14 4 4 2
2
3.13. Found: C, 44.03; H, 5.88; N, 25.49.
5-Amino-1-(2,3-dideoxy-a,b-D-ribofuranosyl)uracil (7). 5-nitro-1-(2,3-dideoxy-
a,b-D-ribofuranosyl)uracil (6) (a=b 1.5:1) (430 mg, 1.67 mmol) was hydrogenated
following the general procedure. The residue was purified on a silica gel column
using a stepwise gradient of MeOH (0-6%) in CH Cl to afford of 5-amino-1-(2,3-
2
2
dideoxy-a,b-D-ribofuranosyl) uridine (7) (322 mg, 85% yield) (a=b, ratio 1.5:1) as
a yellow powder. R (system: CH Cl =MeOH 80:20 v=v) 0.49 (a); 0.34 (b);
f
2
2
lmax (H O)=nm 298 (e 7300), l
261 (e 2500); d [(CD ) SO] 11.21 (sl, 2H, 3-
2
min
H
3 2
NH[a] and 3-NH ), 6.96 (s, 1H, 6-H ), 6.83 (s, 1H, 6-H ), 6.06 (dd, 1H, J
0
0
0
¼
[b]
[b]
[a]
1 -2
0
4
.7, J1
0
00 ¼ 6.5, 1 -H ), 6.02 (dd, 1H, J
0
0
¼ 4.3, J
0
00 ¼ 6.9, 1 -H ), 4.82 (t, 1H,
-2
[a]
1 -2
1 -2
[b]
0
0
0
J ¼ 5.6, 5 -OH ), 4.74 (t, 1H, J ¼ 5.6, 5 -OH ), 4.30 (m, 1H, 4 -H ), 4.08
[
b]
[a]
[a]
0 0 00
and 5-NH ), 3.97 (m, 1H, 4 - H ), 3.56 (m, 2H, 5 -H and 5 -
[a] 2[b] [b] [b]
(
sl, 2H, 5-NH
2
0
00
0
00
H ), 3.40 (m, 2H, 5 -H and 5 -H ), 2.50 (m, 2H, 2 -H and 2 -H ), 2.23 (m,
0 00 0 00 0
H, 2 -H and 2 -H ), 1.88 (m, 2H, 3 -H and 3 -H ), 1.80 (m, 2H, 3 -H and
[b] [b] [a] [a] [b]
[
b]
[a]
[a]
[a]
[a]
2
3
0
0
-H ); d [(CD ) SO] 161.4 (4-C and 4-C ), 149.6 (2-C and 2-C ), 123.8 (6-
[
b]
C
3 2
[a]
[b]
[a]
[b]
0
0
0
C[a] and 6-C ), 115.7 (5-C and 5-C ), 86.1 (1 -C ), 85.1 (1 -C ), 82.1 (4 -C ),
[b]
[a]
[b]
[a]
[b]
[a]
0 0 0 0 0 0
1.5 (4 -C ), 64.4 (5 -C ), 63.9 (5 -C ), 31.8 (2 -C ), 31.5 (2 -C ), 26.9 (3 -C
[b] [a] [b] [a] [b] [a]
8
0
þ
þ
þ
and 3 -C ); m=z (FAB > 0, G-T) 455 [2M þ H] , 228 [M þ H] , 128 [BH ] , 101
[
b]
2
þ
ꢀ
ꢀ
[S] ; m=z (FAB < 0, G-T) 453 [2M-H] , 226 [M-H] . HRMS calcd. for
C H N O 228.0984, found 228.1008.
9
13
3
4
5
-Amino-1-(2,3-dideoxy-b-D-ribofuranosyl)cytosine (9b). 5-nitro-1-(2,3-Dideoxy-
a,b-D-ribofuranosyl)cytosine (8) (a=b, ratio 0.2:1) (300 mg, 1.17 mmol) in MeOH
30 mL) was hydrogenated following the general procedure to afford 5-amino-
-(2,3-dideoxy-b-D-ribofuranosyl)cytosine (9b) (125 mg, 58% yield) as a yellow
powder. R (system: CH Cl =MeOH 80:20 v=v) 0.12 (b). l (95% EtOH)=nm
(
1
f
2
2
max
3
05 (e 6500); lmin 267 (e 3400); d [(CD ) SO] 7.21 (s, 1H, 6-H), 6.02 (dd, 1H, J
0
H
3 2
1 -
0
0
0
0
¼ 3.8, J
0
00 ¼ 6.9, 1 -H), 4.95 (t, 1H, J ¼ 5.4, 5 -OH), 4.05–4.00 (m, 3H, 4 -H and
2
1 -2
0 00 0 00
-NH ), 3.65 (m, 2H, 5 -H and 5 -H), 2.41-2.23 (m, 2H, 2 -H and 2 -H), 1.98 (m,
2
5
1
1
(
(
0
00
H, 3 -H), 1.82 (m, 1H, 3 -H); d [(CD ) SO] 161.5 (4-C), 154.7 (2-C), 122.9 (6-C),
16.6 (5-C), 86.1 (1 -C), 81.6 (4 -C), 63.9 (5 -C), 32.4 (2 -C), 26.8 (3 -C); m=z
C
3 2
0
0
0
0
0
þ
þ
þ
þ
FAB > 0, G-T) 453 [2M þ H] , 227 [M þ H] , 127 [BH ] , 101 [S] ; m=z
ꢀ ꢀ
9 14 4 3
2
FAB < 0, G-T) 225 [M-H] , 125 [B] . HRMS calcd. for C H N O 226.2326,
found 226.2330.
BIOLOGICAL METHODS
The anti-HIV and anti-HBV assays on cell culture were performed by following
[
18]
previously established procedures.

5
-Substituted Pyrimidine Nucleosides
ACKNOWLEDGMENTS
We gratefully acknowledge Prof. P. La Colla (Universit a` di Cagliari, Cagliari,
2025
Italy) for the biological results. One of us (E.C.) thanks the Italian Ministry for
Scientific and Technology Research (MURST) for a doctoral fellowship.
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Received May 9, 2003
Accepted July 22, 2003