Synthesis and antiviral evaluation of 2′,3′-dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides

Article abstract of DOI:10.1515/hc-2015-0174

The synthesis of new 2,6-disubstituted purine 2′,3′-dideoxy-2′,3′-difluoro-D-arabino nucleosides is reported. Their ability to block HIV and HCV replication along with their cytotoxicity toward Huh-7 cells, human lymphocyte, CEM and Vero cells was also assessed. Among them, β-2,6-diaminopurine nucleoside 25 and guanosine derivative 27 demonstrate potent anti-HIV-1 activity (EC₅₀ = 0.56 and 0.65 μm; EC₉₀ = 4.2 and 3.1 μm) while displaying only moderate cytotoxicity in primary human lymphocytes.

Full text of DOI:10.1515/hc-2015-0174

Heterocycl. Commun. 2015; 21(5): 315–327
Raymond F. Schinazi*, Grigorii G. Sivets, Mervi A. Detorio, Tami R. McBrayer, Tony Whitaker,
Steven J. Coats and Franck Amblard
Synthesis and antiviral evaluation of 2′,3′-dideoxy-
2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted
purine nucleosides
DOI 10.1515/hc-2015-0174
Introduction of a fluorine atom into nucleoside analogs
can lead to a change in biological activity, lipophilicity, or
bioavailability. The small size and strong electronegativity
of the fluorine atom, which can mimic either a hydrogen or
a hydroxyl group, may critically influence the pharmacoki-
netic properties and/or toxicity of a drug [1]. It has been
established that fluorination of either the sugar moiety or
the heterocyclic base of a nucleoside may alter its affinity
with various metabolic enzymes and can radically affect
the conformation of the pentofuranose ring of the nucleo-
side in solution [6, 7]. Nucleosides containing fluorine at C2′
exhibit potent biological activities [8, 9]. Among them, C2′-
β-fluoro purine nucleosides are of special interest because
the location of the fluorine atom in the β-orientation can
affect their phoshorylation, the metabolic stability of the
glycosidic bond and potentially their antiviral and anti-
cancer activities. For instance, fluorinated nucleosides
such as sofosbuvir and gemcitabine (Figure 1) have been
approved for the treatment of hepatitis C virus (HCV) and
various cancers, respectively. On the other hand, lodeno-
sine (2′-β-fluoro-2′,3′-dideoxyadenosine, 1) displays in vitro
activity against HIV-1 and appears chemically and meta-
Received August 14, 2015; accepted September 11, 2015
Abstract: The synthesis of new 2,6-disubstituted purine
2′,3′-dideoxy-2′,3′-difluoro-D-arabino
nucleosides
is
reported. Their ability to block HIV and HCV replication
along with their cytotoxicity toward Huh-7 cells, human
lymphocyte, CEM and Vero cells was also assessed. Among
them, β-2,6-diaminopurine nucleoside 25 and guanosine
derivative 27 demonstrate potent anti-HIV-1 activity (EC50 ꢀ=ꢀ
0.56 and 0.65 μm; EC90 ꢀ=ꢀ 4.2 and 3.1 μm) while displaying
only moderate cytotoxicity in primary human lymphocytes.
Keywords: fluorine; HCV; HIV; nucleoside; purine.
Dedication: This work is dedicated to our friend and colleague
Dr. Kyoichi (Kyo) Watanabe who passed away on April 7, 2015.
We will miss his wisdom, encyclopedic memory on nucleosides,
and adorable smiling face.
Introduction
The chemical synthesis and biochemical properties of bolically stable (Figure 1) [10].
fluorine-containing nucleosides have been the focus of
A number of other purine nucleosides with the 2′-fluoro-
numerous studies over the years [1]. Recent advances in β-D-arabinofuranosyl moiety have been synthesized and
medicinal chemistry indicate conclusively that synthetic tested for their antitumor activity, including 9-(2′-deoxy-2′-
fluorinated nucleoside analogs represent
class of drugs for the treatment of various diseases [2–5]. activity against human leukemic T-cell lines [11, 12]. In addi-
tion, 3′-α-fluoro-2′,3′-dideoxyguanosine (4) was studied
a valuable fluoro-β-D-arabinofuranosyl)guanine (3), which displays
clinically for the treatment of HIV and HBV infected patients
*Corresponding author: Raymond F. Schinazi, Center for AIDS
Research, Laboratory of Biochemical Pharmacology, Department of
Pediatrics, Emory University School of Medicine, Atlanta, GA 30322,
(http://www.medivir.se/v5/en/uptodate/pressrelease.cfm).
USA; and Veterans Affairs Medical Center, Decatur, GA 30033, USA,
e-mail: rschina@emory.edu
Grigorii G. Sivets: Institute of Bioorganic Chemistry, National
Academy of Sciences, Acad. Kuprevicha 5, 220141 Minsk, Belarus
Mervi A. Detorio and Franck Amblard: Center for AIDS Research,
Laboratory of Biochemical Pharmacology, Department of Pediatrics,
Emory University School of Medicine, Atlanta, GA 30322, USA; and
Veterans Affairs Medical Center, Decatur, GA 30033, USA
Tami R. McBrayer, Tony Whitaker and Steven J. Coats: Cocrystal
Pharma, Inc., Tucker, GA 30084, USA
(Figure 1) [13, 14]. The HBV studies were subsequently aban-
doned due to a lack of advantage versus standard of care
In earlier investigations, we disclosed 9-(2′,3′-dideoxy-2′,3′-
difluoro-β-D-arabinofuranosyl)adenine (2), a unique difluor-
inated nucleoside that was more potent in vitro against HIV-1
than lodenosine 1 [15]. Based on this work, we have decided
to further evaluate this new class of compounds and wish to
describe herein the synthesis of new D-arabino-2′,3′-dideoxy-
2′,3′-difluoronucleosides along with their biological evalua-
tion for in vitro anti-HIV-1 and anti-HCV activities.
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316ꢀ
ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
NH2
O
[15], allowed for the formation of 1-O-acetyl derivative 6
in 87% yield (α/β ratio ca. 3:1) with no traces of acyclic
compound 7 formed. Treatment of 6 with TMSBr in anhy-
drous CH2Cl2 in the presence of the inexpensive and
easily available catalyst ZnBr2 lead to almost quantitative
formation of 1′-α-bromide 8. The α-anomeric configura-
tion of bromo sugar 8 was confirmed by the 3JH-1,F-2 and 3JH-
N
NH
O
N
O
N
O
HO
O
O
N
P
O
O
H
O
F
Me
O
F
HO
F
HO
Sofosbuvir
Gemcitabine
NH2
N
NH2
N
values (12.6 Hz and ꢀ<ꢀ 1.0 Hz, respectively) observed
1,H-2
N
N
N
1
by H NMR (Figure 2) and by comparison with known
HO
N
HO
N
1′-α-bromo anomer of 3,5-di-O-benzoyl-2-deoxy-2-fluoro-
D-arabinofuranose [16]. Next, reaction of 5-O-benzoyl-
2,3-dideoxy-2,3-difluoro-α-D-ara-binofuranosyl bromide
(8) with the sodium salt of 2,6-dichloropurine [17] gave
a 4:1 mixture of protected nucleosides 9 and 10, which
were separated by column chromatography on silica gel
(Scheme 1). In an effort to improve the β/α ratio during
the glycosylation reaction [18–20], the use of the potas-
sium salt of 2,6-dichloropurine was evaluated. Interest-
ingly using this salt in anhydrous acetonitrile led to the
formation of N9-β-D-nucleoside 9 and –α-D-protected
nucleoside 10 in 73% and 8% yield, respectively (9/1
ratio). An alternative linear approach to the key inter-
mediate 9 was also investigated from known fluoro-
deoxysugar 11 (Scheme 1) [21]. Thus, compound 11 was
N
O
F
O
F
1
F
2
O
O
N
N
N
NH
NH2
NH
NH2
HO
HO
N
O
N
N
O
F
F
HO
4
3
Figure 1ꢀFDA approved 2′-fluoro nucleosides and biologically active
fluorine containing purine nucleosides 1–4.
Results and discussion
In order to prepare our library of purine nucleosides, the first acetylated in 86% and then allowed to react in a
synthesis of key 2,6-dichloropurine nucleoside 9 was opti- mixture of Ac2O/AcOH/H2SO4 to give acetyl derivatives
mized (Scheme 1).
13 in 97% yield (α/β ratio ≈ 1:1). The glycosylation of 13
Thus, treatment of 5 in a mixture of acetic acid/acetic with a silylated 2,6-dichloropurine under Vorbrüggen
anhydride/H2SO4 at room temperature (instead of 4°C) conditions was investigated. Thus, the coupling reaction
Cl
BzO
N
N
N
O
OAc
F
BzO
BzO
BzO
Cl
BzO
N
O
O
O
O
a
c
b
F
F
F
6
F
F
Br
+
OMe
F
N
Cl
F
F
N
N
F
8
9
5
BzO
OAc
10
N
OAc
OMe
h
F
Cl
Cl
F
Cl
7
N
N
N
N
BzO
BzO
BzO
BzO
N
N
Cl
Cl
N
N
OMe
O
OAc
O
O
O
e
g
f
F
OAc
F
OH
F
OAc
F
OR
12
13
14
15
d
BzO
OMe
11
O
F
OH
Scheme 1ꢀReagents and conditions: (a) AcOH/Ac2O/cc H2SO4 0°C to 4°C (6, 77%; 7, 10–12%); or 0°C to rt, (6, 87%); (b) TMSBr/CH2Cl2/ZnBr2,
0°C to rt; 95%; (c) i) Na salt of 2,6-dichloropurine/CH3CN, rt (9, 55%, 10, 13%); ii) K salt of 2,6-dichloro purine/CH3CN, rt, (9, 73%, 10, 8%);
(d) Ac2O/Py, rt, 86%; (e) AcOH/Ac2O/conc. H2SO4, rt, 97%; (f) TMSOTf, silylated 2,6-dichloropurine/CH3CN/DCE, rt, 89%; (g) NaHCO3, MeOH,
rt, 63%; (h) DAST/CH2Cl2/Py, rt, 35%.
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R.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosidesꢂ
ꢂ317
C6H5C0
H-1
J=12.6 Hz
H-2
H-3
H-5
H-5′
H-4
8.0
7.0
6.0
5.0
ppm (t1)
H-5′
J=1.0 Hz
H-8
H-5′′
d, J=2.4 Hz
H-1′
ddd, J=2.4 Hz
H-3′
H-2′
H-4′
8.0
7.0
6.0
5.0
4.0
ppm (t1)
Figure 2ꢀ1H NMR spectra of 1-α-bromide 8 and β-2′,3′-difluoroarabinonucleoside of 2,6-diaminopurine 26.
in the presence of TMSOTf under reflux in acetonitrile saturated methanolic ammonia gave 2-chloro-6-ben-
gave a complicated mixture of products from which zylaminopurine analog 19 in 82% yield. Reaction of
β-2,6-dichloropurine nucleoside 14 (26%) was isolated. each β- and α-protected nucleosides of 2,6-dichloropu-
On the other hand, coupling of acetate derivative 13 with rine 9 and 10 with LiN3 in EtOH under reflux afforded
silylated 2,6-dichloropurine in a mixture of acetonitile- 2,6-diazido derivatives 20 and 21 in 97% yield. The
1,2-dichloroethane, and in the presence of TMSOTf gave reduction of both azido groups with SnCl2 in a mixture
desired 2,6-dichloropurine 14 in 89% yield. Selective of dichloromethane-methanol [23] resulted in the for-
deprotection of nucleoside 14 with NaHCO3 in metha- mation of 5′-O-benzoyl derivatives of N9-β- and N9-α-
nol produced 15 in 63% yield and final fluorination with arabinosides 23 (87%) and 24 (91%). It is noteworthy
diethylaminosulfur trifluoride (DAST) in the presence of that 2-azido-6-amino derivative 22 was also isolated in
pyridine in dichloromethane at room temperature gave 4% yield after reduction of β-protected nucleoside 20
β-2′,3′-difluoro arabinonucleoside 9 in 35% yield.
Treatment of protected nucleoside
with stannous chloride (Scheme 2). Subsequent deben-
with 1.1 zoylation of intermediates 23 and 24 with saturated
9
equivalents of sodium methoxide in methanol at room methanolic ammonia, gave pure 2′,3′-dideoxy-2′,3′-
temperature produced 2-chloro-6-methoxypurine ara- difluoronucleosides 2,6-diaminopurine 25 and 26 in
binoside 16, in 84% yield. 2,6-Dimethoxypurine ara- 72% and 79% yield, respectively. Guanine nucleoside
binoside 17 was prepared in 52% yield by reaction of 28 was prepared by enzymatic deamination of N9-β-
9 with 2.7 equivalents of sodium methoxide in metha- nucleoside 25 in water with calf intestine adenosine
nol (Scheme 2) [22]. The treatment of nucleoside 9 with deaminase in 85% yield (Scheme 2).
5.0 equivalents of benzylamine in methanol at 55°C
An alternative approach to prepare guanine analog
afforded 2-chloro-6-benzylaminopurine arabinoside 28 from bromide 8 was also investigated (Scheme 3).
18 in 78% yield. Removal of the acyl group in 18 with Treatment of 2-amino-6-chloropurine with potassium
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318ꢀ
ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
R1
R1
N
Cl
N
N
N
N
N
N
N
N
N
N
R2
NH2
R3O
HO
BzO
N
Cl
O
O
O
a, b, c, d
e
F
F
F
F
F
F
9
16: R1 = OMe; R2= Cl; R3= H
17: R1 = R2 = OMe; R3 = H
19: R1= NHBn
25: R1= NH2
27: R1= OH
g
18: R1= NHBn; R2 = Cl; R3 = Bz
20: R1 = R2 = N3; R3 = Bz
22: R1= NH2; R2 = N3; R3 = Bz
23: R1 = R2 = NH2; R3 = Bz
f
BzO
HO
BzO
O
F
O
O
d
e
F
F
F
N
R2
N
Cl
N
NH2
N
N
N
N
N
N
F
F
N
N
N
26
10
R1
Cl
NH2
21: R1 = R2 = N3
f
24: R1 = R2 = NH2
Scheme 2ꢀReagents and conditions: (a) MeONa/MeOH, rt, 16, 84%; (b) MeONa/MeOH, rt and then reflux, 17, 52%; (c) BnNH2/MeOH, 55°C,
18, 78%; (d) LiN3/EtOH, reflux, (20, 97%, 21, 97%); (e) saturated NH3/MeOH, rt, (19, 82%, 25, 72%, 26, 79%); (f) SnCl2/CH2Cl2/MeOH, rt, (22,
4%, 23, 87%; 24, 91%); (g) Adenosine deaminase/H2O, rt, 27, 85%.
t-butoxide in 1,2-dimethoxyethane followed by coupling
Structures of nucleosides 9, 10, 14, 16–30 were con-
of the resulting salt with bromo sugar 8 in acetonitrile firmed by 1H, 19F and 13C NMR, UV and mass spectroscopy.
at room temperature gave a mixture of N9-β- and N9-α- Assignment of the configurations of synthesized nucleo-
1
nucleosides 28 and 29 which were separated by column sides at the anomeric centers are based upon H NMR
chromatography in 50% and 4% yields, respectively. The analysis (long-range couplings between the H-8 proton of
benzoyl-protected 2-amino-6-chloropurine analog 28 the purine and the 2′-β fluorine atom for the β-anomers)
was converted to guanine derivative 27 (71%) by treat- and 13C NMR data (characteristic JC-1′,F-2′ coupling constants
ment with 2-mercaptoethanol and sodium methoxide in for β- and α-anomers of purine 2′,3′-difluoro-D-arab-
refluxing methanol. Finally, in order to extend our series inofuranosyl nucleosides) (Tables 1–4). The resonance
of novel purine nucleosides, debenzoylation of protected signal of the purine H-8 proton for 2,6-diaminopurine
1
β-nucleoside 28 with saturated methanolic ammonia at nucleoside 25 is displayed as a doublet in its H NMR
room temperature afforded 2-amino-6-chloropurine spectrum and the magnitude of the 5JH,F coupling is 2.4 Hz
analog 30 in 77% yield.
(Figure 2). It should be noted that two 4JH,F the long-range
Cl
N
R
N
N
N
N
N
BzO
HO
N
NH2
N
NH2
BzO
O
O
O
O
F
F
a
b or c
28
F
F
F
Br
F
27: R = OH
30: R = Cl
8
BzO
F
N
Cl
F
N
N
N
29
Cl
Scheme 3ꢀReagents and conditions: (a) K salt of 2-amino-6-chloropurine/CH3CN, rt, (28, 50%, 29, 4%); (b) saturated NH3/MeOH, rt, 77%;
(c) HSCH2CH2OH/MeONa/MeOH, reflux, 71%.
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ꢂ319
Table 1ꢀ1H NMR Chemical shifts of 2′,3′-dideoxy-2′,3′-difluoro nucleosides 9, 10, 16, 17, 25–27 with D-arabino-configurations.
Compoundꢁ H-1′ ꢁ H-2′ ꢁ H-3′ ꢁ H-4′ ꢁ H-5′
ꢁ
H-5″ ꢁ Others
9
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
6.60ꢃ 5.46 ꢃ 5.35 ꢃ 4.74ꢃ 4.65–4.71ꢃ
dt br.dd ddd dm
6.55ꢃ 5.84 ꢃ 5.47 ꢃ 5.09ꢃ 4.64
dd ddt ddt dd
6.55ꢃ 5.52 ꢃ 5.49 ꢃ 4.29ꢃ 3.87
dd dddd dddd dm dd
6.49ꢃ 5.51 ꢃ 5.45 ꢃ 4.26ꢃ 3.85
ddd dddd dddd dm dd
6.32ꢃ 5.44 ꢃ 5.40 ꢃ 4.22ꢃ 3.84
ddd dddd dddd dm ddd
6.22ꢃ 5.99 ꢃ 5.36 ꢃ 4.69ꢃ 3.75
dd ddt dddd ddt dd
6.15ꢃ 5.60 ꢃ 5.56 ꢃ 4.10ꢃ 3.65
dd dddd dddd dm br.m
ꢃ
8.32 (d, 1H, Jꢃ=ꢃ2.63, H-8), 7.46-8.07 (m, 5H, Bz)
m
10
16
17
25
26
27
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
4.57ꢃ 8.24 (s, 1H, H-8), 7.47–8.08 (m, 5H, Bz)
d
dd
3.84ꢃ 8.46 (d, 1H, Jꢃ=ꢃ2.10, H-8), 4.17 (s, 3H, OCH3)
dd
3.83ꢃ 8.24 (d, 1H, Jꢃ=ꢃ2.13, H-8), 4.13 and 4.02 (2s, 6H, 2ꢃ×ꢃOCH3)
dd
3.82ꢃ 7.91 (d, 1H, Jꢃ=ꢃ2.42, H-8)
dd
3.72ꢃ 7.84 (s, 1H, H-8)
dd
3.61ꢃ 10.66 (brs, 1H, NH), 7.74 (d, 1H, Jꢃ=ꢃ2.9, H-8), 6.51 (brs, 2H, NH2), 5.17 (t, 1H,
br.m J ꢃ=ꢃ 5.64, 5′-OH)
Spectra were obtained in CDCl3 for nucleosides 9, 10; in CD3OD for 16, 17, 25, 26, and DMSO-d6 for nucleoside 27. δ in ppm, J in Hz.
Table 2ꢀCoupling constants (in Hz) for 1H NMR data of 2′,3′-dideoxy-2′,3′-difluoro nucleosides 9, 10, 16, 17, 25–27 with D-arabino-
configurations.
3
3
ꢁ
ꢁ
J(H,H)ꢁ
J(H,F)ꢁ
Others
ꢁ
ꢁ
1′,2′ꢁ
2′,3′ꢁ
3′,4′ꢁ
4′,5′/4′,5″
H1′,F2ꢁ
H3′,F2ꢁ
H2′,F3ꢁ
H4′,F3
9
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
2.56ꢃ
ꢃ<ꢃ1.0ꢃ
2.38ꢃ
4.37/n.d.ꢃ
21.8ꢃ
9.2ꢃ
11.94ꢃ
n.dꢃ
5JF2′,H8 ꢃ=ꢃ 2.63
4J1′,F3′ ꢃ=ꢃ 2.56
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
gem
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
J
J
J
J
ꢃ=ꢃ 50.03
ꢃ=ꢃ 49.51
ꢃ=ꢃ 11.2
2′,F2′
3′,F3′
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
H5′,H5″
gem
gem
10ꢃ
ꢃ<ꢃ1.0ꢃ
1.8ꢃ
1.7ꢃ
5.48/5.5ꢃ
15.02ꢃ
12.6ꢃ
11.22ꢃ
23.34ꢃ
ꢃ=ꢃ 48.14
2′,F2′
3′,F3′
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ=ꢃ 50.12
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
JH5′, H5″ ꢃ=ꢃ12.14
5JF2′,H8 ꢃ=ꢃ 2.1
4J1′,F3′ ꢃ=ꢃ 1.64
16ꢃ
4.16ꢃ
2.28ꢃ
3.90ꢃ
3.31/2.53ꢃ
16.93ꢃ
15.45ꢃ
12.87ꢃ
24.10ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
J
ꢃ=ꢃ 50.65
ꢃ=ꢃ 51.29
ꢃ=ꢃ 12.1
2′,F2′
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
3′,F3′
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
H5′, H5″
17ꢃ
3.89ꢃ
2.19ꢃ
3.80ꢃ
3.85/5.12ꢃ
17.29ꢃ
15.70ꢃ
12.50ꢃ
24.36ꢃ
5J
ꢃ=ꢃ 2.13
F2′,H8
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
4J1′,F3′ ꢃ=ꢃ 1.8
J ꢃ=ꢃ 50.33
2′,F2′
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
ꢃ=ꢃ 49.51
ꢃ=ꢃ 11.2
3′,F3′
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
H5′, H5″
25ꢃ
3.87ꢃ
2.0ꢃ
3.85ꢃ
4.62/5.33ꢃ
18.37ꢃ
12.18ꢃ
14.69ꢃ
25.0ꢃ
5J
ꢃ=ꢃ 2.42
F2′,H8
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
4J1′,F3′ ꢃ=ꢃ 2.0
ꢃ=ꢃ 51.29
gem
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
2′,F2′
J
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ=ꢃ 50.65
3′,F3′
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
ꢃ=ꢃ 12.8
H5′, H5″
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
4J5′,F3′ ꢃ=ꢃ 1.0
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
4J5′,F3′ ꢃ=ꢃ ꢃ<ꢃ1.0
gem
gem
26ꢃ
2.56ꢃ
2.88ꢃ
4.17ꢃ
4.40/3.7ꢃ
15.37ꢃ
16.35ꢃ
14.42ꢃ
20.52ꢃ
J
ꢃ=ꢃ 11.5
H5′, H5″
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
ꢃ=ꢃ 52.25
ꢃ=ꢃ 50.33
3′,F3′
J
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
2′,F2′
27ꢃ
4.16ꢃ
3.2ꢃ
3.21ꢃ
5.48/5.42ꢃ
16.34ꢃ
16.03ꢃ
14.42ꢃ
22.91ꢃ
5JF2′,H8 ꢃ=ꢃ 2.9
gem
gem
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
J
J
ꢃ=ꢃ 50.64
2′,F2′
ꢃ=ꢃ 51.61
3′,F3′
J
gem
ꢃ=ꢃ 12.8
H5′, H5″
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320ꢀ ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
Table 3ꢀ13C NMR Data of 2′,3′-difluoro nucleosides 9, 10, 16, 17, 25–27, 30.
Compoundꢁ
ꢁ
Chemical shifts, δTMS, ppm [J(C,F) in Hz]
ꢁ
ꢁ
Others
C-1′
ꢁ
C-2′
ꢁ
C-3′
ꢁ
C-4′
ꢁ
C-5′
9
ꢃ
ꢃ
ꢃ
83.73 d
ꢃ
93.64 ddꢃ
96.09 ddꢃ
93.42 ddꢃ
91.57 ddꢃ
94.64 ddꢃ
92.69 ddꢃ
81.31 d
ꢃ
62.46 dꢃ
62.40 dꢃ
60.16 dꢃ
166.17 (s, Ph-Cꢃ=ꢃO),
128.81–133.85 (Ph-Cꢃ=ꢃO and C-5),
153.57, 152.56, 152.35 (C-6, 2, 4),
144.88 (d, 4JC8,F2′ ꢃ=ꢃ 5.6, C-8)
166.08 (s, Ph-Cꢃ=ꢃO),
10
16
88.92 d
ꢃ
84.23 d
ꢃ
128.13–133.78 (Ph-Cꢃ=ꢃO and C-5),
153.71, 152.58, 152.29 (C-6, 2, 4),
143.35 (d, 4J
161.35 (C-6)C8,F2′
153.34 (C-2)
152.63 (C-4)
ꢃ=ꢃ 3.8, C-8)
83.07 ddꢃ
82.79 ddꢃ
82.17 ddꢃ
81.96 ddꢃ
142.79 (d, 4JC8,F2′ ꢃ=ꢃ 4.23, C-8)
119.48 (C-5)
54.44 (OCH )
17
ꢃ
93.51 ddꢃ
92.76 ddꢃ
60.19 dꢃ
162.26 (C-63or C-2)
162.02 (C-2 or C-6)
153.07 (C-4)
140.73 (d, 4JC8,F2′ ꢃ=ꢃ 4.14, C-8)
115.98 (C-5)
54.50 and 53.69 (2ꢃ×ꢃOCH3)
25
26
27
30
ꢃ
ꢃ
ꢃ
ꢃ
82.63 ddꢃ
87.12 ddꢃ
81.40 ddꢃ
82.62 ddꢃ
93.65 ddꢃ
96.58 ddꢃ
94.10 ddꢃ
93.65 ddꢃ
92.60 ddꢃ
93.99 ddꢃ
92.62 ddꢃ
92.68 ddꢃ
81.82 ddꢃ
84.35 ddꢃ
81.16 ddꢃ
60.32 dꢃ
60.37 dꢃ
60.55 dꢃ
60.25 dꢃ
160.74 (C-6)
156.33 (C-4)
151.32 (C-2)
137.19 (d, 5JC8,F2′ ꢃ=ꢃ 4.38, C-8)
112.36 (C-5)
160.77 (C-6)
156.36 (C-4)
151.35 (C-2)
136.23 (d, 5JC8,F2′ ꢃ=ꢃ ꢃ<ꢃ2.0, C-8)
113.23 (C-5)
157.24 (C-6)
154.48 (C-4)
151.46 (C-2)
136.60 (d, 5JC8,F2′ ꢃ=ꢃ 4.36, C-8)
116.59 (C-5)
82.1 dd
ꢃ
160.51 (C-2)
153.46 (C-6)
150.52 (C-4)
141.79 (d, 5JC8,F2′ ꢃ=ꢃ 4.37, C-8)
123.16 (C-5)
Table 4ꢀThe 13C NMR Data of 2′,3′-difluoro nucleosides 9, 10, 16, 17, 25–27, 30 (Coupling constants given in Hz).
Compoundꢁ
F-2′ꢁ
F-3′
ꢁ
ꢁ
ꢁ
2
3
4
3
2
3
J(C,F)ꢁ
J(C,F)ꢁ
J(C,F)
J(C,F)ꢁ
J(C,F)ꢁ
J(C,F)
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
C1′,F2′ꢁ
C3′,F2′
C4′,F2′
C5′,F2′
C1′,F3′
C2′,F3′ꢁ
C4′,F3′
C5′,F3′
9
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
16.71ꢃ
36.25ꢃ
17.21ꢃ
17.88ꢃ
17.08ꢃ
35.54ꢃ
16.85ꢃ
16.90ꢃ
30.20ꢃ
29.92ꢃ
28.81ꢃ
28.15ꢃ
28.67ꢃ
28.12ꢃ
25.08ꢃ
28.80ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
3.08ꢃ
2.12ꢃ
1.48ꢃ
1.50ꢃ
3.99ꢃ
2.99ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
ꢃ<ꢃ1.0ꢃ
3.76ꢃ
3.35ꢃ
2.35ꢃ
4.99ꢃ
4.99ꢃ
2.90ꢃ
30.70ꢃ
30.92ꢃ
28.28ꢃ
28.65ꢃ
28.74ꢃ
28.16ꢃ
26.85ꢃ
28.90ꢃ
27.27ꢃ
26.00ꢃ
25.45ꢃ
25.43ꢃ
24.93ꢃ
24.92ꢃ
24.83ꢃ
24.93ꢃ
8.71
7.67
6.26
6.10
6.51
5.14
5.22
5.31
10
16
17
25
26
27
30
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R.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosidesꢂ
ꢂ321
Table 5ꢀIn vitro antiviral activity and cytotoxicity of compounds 9, 10, 16, 17, 19, 20, 22, 25–28 and 30.
Compoundꢁ
ꢁ
Anti-HIV-1 activity (μm)ꢁ
Anti-HCV activity (μm)ꢁ
Cytotoxicity, CC50 (μm)
ꢁ
ꢁ
EC50
ꢁ
EC90
EC50
ꢁ
EC90
PBMꢁ
CEMꢁ
Veroꢁ
Huh-7
9
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
18ꢃ
13ꢃ
17ꢃ
46ꢃ
27ꢃ
60ꢃ
ꢃ<ꢃ10aꢃ
ꢃ<ꢃ10aꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
2.9ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
4.7ꢃ
ꢃ<ꢃ10aꢃ
ꢃ<ꢃ10aꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
9.9ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ10ꢃ
10ꢃ
23ꢃ
54ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
53ꢃ
95ꢃ
40ꢃ
58ꢃ
17ꢃ
30ꢃ
7.6ꢃ
4.9ꢃ
11ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
14ꢃ
24ꢃ
52ꢃ
91ꢃ
4.9ꢃ
62ꢃ
NDꢃ
NDꢃ
33ꢃ
23ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
56ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
90ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
56ꢃ
ꢃ<ꢃ10a
ꢃ<ꢃ10a
ꢃ>ꢃ10
ꢃ>ꢃ10
26
ꢃ>ꢃ10
ꢃ>ꢃ10
ꢃ>ꢃ10
ꢃ>ꢃ10
ꢃ>ꢃ10
9.1
10
16
17
19
20
22
25
26
27
28
30
AZT
ꢃ>ꢃ100ꢃ
32ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
4.2ꢃ
14ꢃ
3.1ꢃ
18ꢃ
2.4ꢃ
0.047ꢃ
ꢃ>ꢃ100ꢃ
21ꢃ
41ꢃ
0.56ꢃ
2.4ꢃ
0.66ꢃ
2.4ꢃ
0.65ꢃ
0.0037ꢃ
48ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ 10ꢃ
1.8ꢃ
ꢃ>ꢃ10ꢃ
ꢃ>ꢃ 10ꢃ
5.8ꢃ
14ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ10
14ꢃ
ꢃ>ꢃ100ꢃ
NDa
2′ꢃ<ꢃ-C-MeCbꢃ
ꢃ>ꢃ100ꢃ
ꢃ>ꢃ10
aCytotoxicity in Huh-7 cells did not allow for anti-HCV activity determination.
bAZT and 2′-C-MeC (2′-C-methylcytidine) were used as positive controls for HIV and HCV assays, respectively.
coupling constants of 2.0 Hz and 1.0 Hz between sugar
Conclusions
H-1′ and H-5′ protons, and F-3′ substituent, respectively,
are exhibited also in the spectrum of difluoride 25 due to
A new and efficient procedure for the preparation of key
1′-α-bromosugar 8 by bromination of known acetate 6
under mild catalytic conditions was described. In addition,
new and selective synthetic approaches to the key inter-
mediates 9 and 28 were developed. With these compounds
in hand, twelve 2′,3′-difluoro-D-arabinofuranosyl 2,6-dis-
ubstituted purine nucleosides were prepared which were
evaluated as potential anti-HIV-1 and anti-HCV agents. The
SAR results indicate that modifications at 2 and 6-positions
have effects on antiviral activity and host cell toxicity. The
β-2,6-diaminopurine nucleoside 25 demonstrates selective
in vitro anti-HIV-1 activity (EC50 ꢀ=ꢀ 0.56 μm) while displaying
only moderate cytotoxicity in human lymphocytes. Based
on these encouraging results, further structural modifica-
tions of the base should allow us to improve the antiviral
potency and selectivity of these compounds.
the W-arrangements between these protons and fluorine
atom at C-3′.
To determine the spectrum of activity of the synthe-
sized purine nucleosides, anti-HIV-1 activity was evalu-
ated versus HIV-1LAI in primary human peripheral blood
mononuclear (PBM) cells and 3′-azido-3′-deoxythymidine
(AZT) was used as a positive control. Cytotoxicity was
determined in human PBM, human T-lymphoblastoid
(CEM), and African Green monkey (Vero) cells [24, 25]. All
of the modified purine nucleosides were also evaluated
for inhibition of HCV RNA replication at 10 μm in human
hepatoma cells (Huh-7) using a subgenomic HCV replicon
system and 2′-C-methyl-cytidine (2′-C-MeC) as a positive
control [26]. Cytotoxicity in Huh-7 cells was determined
simultaneously with anti-HCV activity by extraction
and amplification of both HCV RNA and ribosomal RNA
(rRNA) [27]. The antiviral and cytotoxicity results are sum-
marized in Table 5. In general, all of the fluoro-containing
nucleoside analogs inhibit HIV replication at micromolar
concentrations, but show cytotoxicity in the same range
in most of the cell systems tested. It is noteworthy though,
that 2,6-diaminopurine analog 25 displays submicromolar
activity against HIV (EC50 ꢀ=ꢀ 0.56 μm) while showing only
modest cytotoxicity in PBM and CEM (CC50 ꢀ=ꢀ 58 and 91 μm,
respectively) and no toxicity in Vero at concentration up
to 100 μm.
Experimental
Column chromatography was performed on silica gel 60 H (70–230
mesh; Merck, Darmstadt, Germany). All anhydrous solvents were
distilled over CaH2, P2O5 or magnesium prior to the use. The UV spec-
1
tra were recorded on Specord M-400 (Carl Zeiss, Germany). The H,
13C and 19F NMR spectra were recorded in CDCl3, CD3OD and DMSO-
d6 with Bruker Avance-500-DRX spectrometer at 500.13, 126.76 and
470.59 MHz, respectively. Chemical shifs δ are reported in ppm
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322ꢀ ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
downfield from internal SiMe4 (1H,13C) or external CFCl3 (19F). J values
are reported in Hz. NMR assignments were confirmed by 2D (1H,1H
and 1H,13C) correlation spectroscopy. Melting points were determined
on a Boetius apparatus and were uncorrected. High resolution mass
spectra were measured on a mass spectrometer Agilent Q-TOF 6550
(USA) using electrospray ionization.
12.8, H-5), 4.62 (dd, 1H, J5,4 ꢀ=ꢀ 4.4, H-5′); 13C NMR (CDCl3): δ 166.1 (s,
Cꢀ=ꢀO, Bz), 133.6, 129.93, 129.28, 128.65 (4s, C6H5CO-), 100.1 (dd, JC-2,F-2 ꢀ=ꢀ
190.5, JC-2,F-3 ꢀ=ꢀ 26.37, C-2), 93.89 (dd, JC-3,F-2 ꢀ=ꢀ 32.01, JC-3,F-3 ꢀ=ꢀ 188.6, C-3),
86.57 (dd, JC-1,F-3 ꢀ=ꢀ 14.8, JC-1,F-2 ꢀ=ꢀ 31.95, C-1), 83.65 (d, JC-4, F-3 ꢀ=ꢀ 28.8, C-4),
61.9 (d, JC-5,F-3 ꢀ=ꢀ 5.65, C-5); 19F NMR (CDCl3): δ -170.98 (dm, F-2, JF-2,F-3 ꢀ=ꢀ
8.5), -188.31 (dt, F-3).
2,6-Dichloro-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,
3′-difluoro-β-D-arabinofuranosyl)purine (9) and
2,6-dichloro-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,
3′-difluoro-α-D-arabinofuranosyl)purine (10)
1-O-Acetyl-5-O-benzoyl-2,3-dideoxy-2,3-difluoro-α/β-
D-arabinofuranoside (6)
Method AꢁAcetolysis of 5 (0.337 g, 1.24 mmol) for 18 h in a mixture
of acetic acid/acetic anhydride/H2SO4 was accomplished as described
earlier [9]. The product was chromatographed on silica gel, eluting
with EtOAc/hexane (ratio 1:5, 1:3 and 1:1) to give 6 (0.286 g, 77%) as a
Method AꢁA solution of 1-α-bromide 8 (0.073 g, 0.227 mmol) in
anhydrous MeCN (4 mL) was added to a suspension of the sodium
salt of 2,6-dichloropurine, prepared from 2,6-dichloropurine (0.045
g, 0.238 mmol) and NaH (7.7 mg of 80% in oil, 0.024 mmol) in anhy-
drous MeCN (4 mL) under argon. The reaction mixture was stirred at
room temperature overnight. Insoluble materials were removed by
filtration and washed with MeCN (5 mL). The combined filtrate and
washings were concentrated and the residue was chromatographed
on silica gel (140 mL), eluting with EtOAc/toluene (ratio 1:8 and 1:4)
to afford β- nucleoside 9 (0.054 g, 55%) as a colorless oil which crys-
tallized during storage and α-nucleoside 10 (0.013 g, 13%) as a syrup.
1
syrup and a diastereomeric mixture of 7 (0.046 g, 10%, oil). H NMR
(CDCl3): (ratio of diastereomers α and β ca. 1.0:0.43), δ 7.45–8.05 (m,
ArH), 6.06 (dd, 1H, H-1a, J1,F-2 ꢀ=ꢀ 5.2, J1,2 ꢀ=ꢀ 7.37), 5.99 (t, 0.43H, H-1b, J1,F-2 ꢀ=ꢀ
6.4, J1,2 ꢀ=ꢀ 6.4), 5.48 (m, H-4a and H-4b), 5.21 (dm, H-2b), 4.97 (ddd,
H-3a), 4.80–4.86 (m, H-5a and H-5b), 4.65 (dm, H-3b), 4.50 (ddd, H-2a),
4.44–4.48 (m, H-5′a and H-5′b), 3.58 (s, OCH3 b), 3.54 (s, OCH3 a), 2.17 (s,
OAc a), 2.15 (s, OAc b), 2.11 (s, OAc b), 2.10 (s, OAc a); 13C NMR (CDCl3): δ
170.7, 169.9, 169.4, 166.2 (4s, 2Cꢀ=ꢀO, Ac and 2Cꢀ=ꢀO, Bz), 133.4, 129.9, 129.8,
128.8, 129.7, 128.6 (s, 2C6H5CO-), 94.4 (dd, JC-1,F-2 ꢀ=ꢀ 30.1, JC-1,F-3 ꢀ=ꢀ 6.3, C-1b),
94.3 (dd, JC-1,F-2 ꢀ=ꢀ 29.2, JC-1,F-3 ꢀ=ꢀ 6.9, C-1a), 88.74 (dd, JC-2,F-2 ꢀ=ꢀ 185.5, JC-2,F-3 ꢀ=ꢀ
16.9, C-2b), 88.33 (dd, JC-2,F-2 ꢀ=ꢀ 183.5, JC-2,F-3 ꢀ=ꢀ 16.0, C-2a), 87.5 (dd, JC-3,F-3 ꢀ=ꢀ
181.5, JC-3,F-2 ꢀ=ꢀ 17.9, C-3a and C-3b), 68.1 (dd, C-4b), 67.9 (dd, C-4a), 62.0
(s, C-5a and C-5b), 58.63 (s, OCH3 b), 58.0 (s, OCH3 a), 21.06 (s, CH3CO),
21.02 (s, CH3CO), 20.9 (s, CH3CO); 19F NMR (CDCl3): δ -214.07 (F-2, dddd),
-214.4 (F-3, m, JF-2,F-3 ꢀ=ꢀ 9.3) (compound α), -212.74 (F-2, dddd), -213.29
(F-3, m, JF-2,F-3 ꢀ=ꢀ 6.4) (compound β). HRMS (EI). Calcd for C17H20O7F2Na
Nucleoside 9
Mp 143–144°C; UV (EtOH), λmax, nm, (ε): 274 (5660), 231 (7300); 19F NMR
(CDCl3): δ -188.77 (dm, F-2′or F-3′), -203.62 (m, F-3′ or F-2′). HRMS (EI).
+
Calcd for C17H13N4O3F2Cl2 [M+H] : m/z 429.0411. Found: m/z 429.0418.
Nucleoside 10
+
UV (EtOH), λmax, nm, (ε): 274 (5660), 231 (7300); 19F NMR (CDCl3): δ
-190.48 (m, F-3′), -191.43 (m, F-2′). HRMS (EI). Calcd for C17H13N4O3F2Cl2
[M+Na] : m/z 397.1100. Found: m/z 397.1106.
+
[M+H] : m/z 429.0411. Found: m/z 429.0416.
Method BꢁConcentrated H2SO4 (0.03 mL) was added to a solution of
α-methyl glycoside 1 (0.1 g, 0.37 mmol) in acetic acid (0.78 mL) and
acetic anhydride (0.19 mL) at 0°C. The reaction mixture was stirred at
this temperature for 20 min and then 2 h at room temperature. The
solution was poured into ice. Afer the ice melted, the aqueous phase
was extracted with CH2Cl2 (3 ꢀ×ꢀ 20 mL). The combined organic phases
were washed with aqueous NaHCO3, dried over anhydrous Na2SO4
and evaporated to dryness. The residue was chromatographed on a
silica gel to afford 6 (0.096 g, 87%) as a syrup.
Method BꢁTo a solution of 2,6-dichloropurine (0.14 g, 0.74 mmol)
in anhydrous 1,2-dimethoxyethane (11.5 mL) under argon at 0°C was
added potassium t-butoxide (0.085 g, 0.75 mmol) and then the result-
ing solution was stirred for 12 min at room temperature before con-
centration. A solution of bromide 8 (0.2 g, 0.62 mmol) in anhydrous
MeCN (17 mL) was added, under argon, to a suspension of the prepared
potassium salt of purine in anhydrous MeCN (20 mL). The mixture was
stirred under argon at room temperature for 18 h. Insoluble materials
were removed by filtration and the solids were washed with MeCN (20
mL). The combined filtrate and washings were concentrated. The resi-
due was dissolved in anhydrous CH2Cl2 (25 mL), and insoluble materi-
als were filtered off and washed with CH2Cl2. The solvent was removed
under reduced pressure and the residue was chromatographed on sil-
ica gel, eluting with EtOAc/toluene (ratio 1:8 and 1:4) to afford nucleo-
side 9 (0.195 g, 73%) and nucleoside 10 (0.02 g, 8%).
5-O-Benzoyl-2,3-dideoxy-2,3-difluoro-α-
D-arabinofuranosyl bromide (8)
To a suspension of 6 (0.36 g, 1.2 mmol) and anhydrous ZnBr2 (0.065 g,
0.29 mmol) in anhydrous CH2Cl2 (10 mL) TMSBr (0.38 mL, 2.9 mmol)
was added at 0°C. The resulting mixture was stirred at 0°C for 1 h,
then 18 h at room temperature. The reaction mixture was poured into
a cooled saturated solution of NaHCO3, extracted with CH2Cl2 (3 ꢀ×ꢀ
30 mL). The combined organic extracts were dried over anhydrous
Na2SO4, evaporated to dryness, and co-evaporated with anhydrous
toluene to give 8 (0.365 g, 95%) as a yellowish oil which was used in
Methyl 5-O-benzoyl-2-O-acetyl-3-deoxy-3-fluoro-β-
D-ribofuranoside (12)
1
the next step without purification. H NMR (CDCl3): δ 7.46–8.04 (m,
Acetic anhydride (0.24 mL) was added to a solution of β-methyl
riboside 11 (0.171 g, 0.63 mmol) in pyridine (3.5 mL) at room tem-
perature. The mixture was stirred at this temperature for 48 h and
then poured onto ice. Afer the ice melted, the aqueous phase was
5H, Bz), 6.55 (d, 1H, J1,2 ꢀ<ꢀ 1.0, J1,F-2 ꢀ=ꢀ 12.64, H-1), 5.57 (dd, 1H, J2,3 ꢀ<ꢀ 1.0,
J2,F-2 ꢀ=ꢀ 49.65, J2,F-3 ꢀ=ꢀ 10.68, H-2), 5.21 (ddd, 1H, J3,4 ꢀ=ꢀ 3.7, J3,F-2 ꢀ=ꢀ 19.1, J3,F ꢀ=ꢀ
51.4, H-3), 4.85 (ddt, 1H, J4,F ꢀ=ꢀ 20.2, H-4), 4.67 (dd, 1H, J5,4 ꢀ=ꢀ 3.8, J5,5′ ꢀ=ꢀ
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ꢁꢀꢀꢀ
R.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosidesꢂ
ꢂ323
extracted with CH2Cl2 (3 ꢀ×ꢀ 20 mL). The combined organic phases were 52.7, H-3′), 4.79–4.82 (m, 2H, H-4′ and H-5′), 4.61 (dm, 1H, H-5″), 2.19
washed with aqueous NaHCO3, dried over anhydrous Na2SO4 and con- (s, 3H, COCH3); 13C NMR (CDCl3): δ 169.7 (s, Cꢀ=ꢀO, Bz), 165.8 (s, Cꢀ=ꢀO,
centrated. The product was chromatographed on silica gel, eluting OAc), 153.4, 152.60, 152.40 (3s, C-2, C-4, C-6), 144.0 (s, C-8), 133.8, 131.4,
with EtOAc/hexane (ratio 1:6 and 1:4) to afford the acetate 12 (0.170 g, 129.67, 129.58, 128.8 (5s, C6H5CO-, C-5), 89.3 (d, JC-3′,F-3′ ꢀ=ꢀ 190.98, C-3′),
86%) as a syrup. 1H NMR (CDCl3): δ 7.26–8.08 (m, 5H, Ar-H), 5.31 (dt, 85.9 (s, C-1′), 81.8 (d, JC-2′,F-3′ ꢀ=ꢀ 24.5, C-2′), 73.45 (dd, JC-4′,F-3′ ꢀ=ꢀ 15.58, C-4′),
1H, J3,F ꢀ=ꢀ 52.6, H-3), 5.19 (m, 1H, H-2), 4.99 (t, 1H, J1,2 ꢀ=ꢀ J1,F-3 ꢀ=ꢀ1.6, H-1), 62.95 (d, JC-5,F-3 ꢀ=ꢀ 8.93, C-5′), 20.6 (s, COCH3); 19F NMR (CDCl3): δ -198.59
4.52–4.91 (dm, 2H, 2H-5), 4.42 (dm, 1H, H-4), 3.36 (s, 3H, OCH3), 2.16 (dt, F-3′); UV (EtOH), λmax, nm, (ε): 274 (6500), 230 (11300). HRMS (EI).
+
(s, 3H, COCH3); 13C NMR (CDCl3): δ 169.8 (s, Cꢀ=ꢀO, Bz), 166.1 (s, Cꢀ=ꢀO, Calcd for C14H14O5F [M-base] : m/z 281.0925. Found: m/z 281.0928.
OAc), 133.3, 129.75, 129.62, 129.40 (4s, C6H5CO-), 106.05 (s, C-1), 90.0
(d, JC-3,F-3 ꢀ=ꢀ 193.7, C-3), 79.25 (d, JC-2,F-2ꢀ=ꢀ 25.2, C-2), 75.0 (d, JC-4,F-3ꢀ=ꢀ13.97,
C-4), 63.92 (d, JC-5,F-3 ꢀ=ꢀ 4.68, C-5), 55.75 (s, OCH3), 20.61 (s, COCH3); 19F
2,6-Dichloro-9-(5′-O-benzoyl-3′-deoxy-3′-fluoro-β-
D-ribofuranosyl)purine (15)
NMR (CDCl3): δ -210.63 (ddd, F-3). HRMS (EI). Calcd for C15H17O6FNa
+
[M+Na] : m/z 335.0997. Found: m/z 335.1005.
A cooled solution of nucleoside 14 (0.175 g, 0.37 mmol) in anhydrous
MeOH (14.0 mL) was treated with solid anhydrous NaHCO3 (0.117 g,
1,2-Di-O-acetyl-5-O-benzoyl-3-deoxy-3-fluoro-α/β-
1.4 mmol). The reaction mixture was stirred at room temperature
D-ribofuranose (13)
for 1 h, then neutralized with glacial acetic acid, concentrated, and
co-evaporated with ethanol to dryness. The residue was chromato-
β-Methyl riboside 12 (0.17 g, 0.54 mmol) was dissolved in a mixture graphed on silica gel, eluting with EtOAc/hexane (ratio 1:2 and 1:1) to
1
of acetic acid (1.16 mL), acetic anhydride (0.28 mL) and concentrated afford nucleoside 15 (0.1 g, 63%) as an amorphous powder. H NMR
H2SO4 (0.05 mL) at 0–5°C. The mixture was stirred at this tempera- (CDCl3 +CD3OD): δ 8.35 (s, 1H, H-8), 7.43–8.01 (m, 5H, Bz), 6.11 (d, 1H,
ture for 5 min and then 150 min at room temperature. The solution J1′,2′ ꢀ=ꢀ 7.0, H-1′), 5.30 (ddd, 1H, J3′,2′ ꢀ=ꢀ 4.4, J3′,4′ ꢀ=ꢀ 1.85, J3′,F-3′ ꢀ=ꢀ 53.5, H-3′),
was poured onto ice. Afer the ice melted, the aqueous phase was 5.04 (ddd, 1H, J2′,F-3′ ꢀ=ꢀ 20.49, H-2′), 4.64–4.79 (m, 2H, H-4′ and H-5′),
extracted with CHCl3 (3 ꢀ×ꢀ 20 mL), and then afer adding cold aqueous 4.58 (dd, 1H, H-5″); 13C NMR (CDCl3): δ 166.1 (s, Cꢀ=ꢀO, Bz), 153.0, 152.6,
5% NaHCO3 to the aqueous phase, it was again extracted with CHCl3 151.8 (3s, C-2, C-4, C-6), 145.1 (s, C-8), 133.5, 131.1, 128.80, 128.50 (4s,
(2 ꢀ×ꢀ 20 mL). The combined organic phases were dried over anhydrous C6H5CO-), 129.4 (C-5), 91.1 (d, JC-3′,F-3′ ꢀ=ꢀ 190.98, C-3′), 88.0 (s, C-1′), 80.9
Na2SO4 and concentrated to dryness to afford 13 (0.179 g, 97%) as a (d, JC-4′,F-3′ ꢀ=ꢀ 24.5, C-4′), 72.8 (dd, JC-2′,F-3′ ꢀ=ꢀ 15.58, C-2′), 63.0 (d, JC-5′,F-3′ ꢀ=ꢀ
syrup. 1H NMR (CDCl3): (ratio of α and β anomers ca. 1.0:1.0), δ 8.09 (d, 8.93, C-5′); 19F NMR (CDCl3): -200.58 (dt, F-3′); UV (EtOH) λmax, nm, (ε):
+
2H, Bz), 8.04 (d, 2H, Bz), 7.60 (t, 2H, Bz), 7.49 (m, 4H, Bz), 6.53 (d,1H, 274 (5580), 231 (9500). HRMS (EI). Calcd for C17H14N4O4FCl2 [M+H] :
J1,2 ꢀ=ꢀ 4.6, H-1a), 6.26 (t, 1H, J1,2 ꢀ=ꢀ J1,F-3 ꢀ=ꢀ1.8, H-1b), 5.37 (dt, 1H, H-3a), m/z 427.0368. Found: m/z 427.0363.
5.26 (dm, 1H, H-3b), 4.81 (dm, 1H, H-4a), 4.63–4.71 (2m, 2H, 2H-5b),
4.55 (dd, 1H, H-5a), 4.49 (dd, 1H, H-5′a), 4.46 (dm, 1H, H-4b), 2.20,
2.19, 2.17 and 1.97 (4s, 12H, 4 COCH3); 13C NMR (CDCl3): δ 169.91, 169.78,
2,6-Dichloro-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,
169.59, 169.10, 165.89, 165.85 (6s, Cꢀ=ꢀO, 2Bz and 4Ac), 133.53, 133.45,
3′-difluoro-β-D-arabinofuranosyl)purine (9)
129.74, 129.45, 129.18, 128.65, 128.54 (8s, 2C6H5CO-), 98.2 and 93.7 (2s,
from nucleoside 15
C-1a, C-1b), 89.1 and 88.4 (2d, JC-3,F-3 ꢀ=ꢀ 194.4, JC-3,F-3 ꢀ=ꢀ 191.56, C-3a, C-3b),
82.25 and 80.7 (2d, JC-2,F-2ꢀ =ꢀ 25.2, JC-2,F-2 ꢀ=ꢀ 25.0, C-2a, C-2b), 74.7 and 71.2
To a suspension of nucleoside 15 (0.1 g, 0.23 mmol) in anhydrous
dichloromethane (4.5 mL) was added pyridine (0.058 mL, 0.72 mmol)
and diethylaminosulfur trifluoride (0.086 mL, 0.64 mmol) at 0°C. The
reaction mixture was stirred at room temperature (25°C) for 14 h, and
then poured onto cold aqueous 5% solution of NaHCO3. The aqueous
phase was extracted with CHCl3 (3 ꢀ×ꢀ 30 mL), the combined organic
phases were dried over anhydrous Na2SO4 and concentrated to dry-
ness. The residue was chromatographed on silica gel, using a linear
gradient AcOEt in hexane (0→33%) to afford nucleoside 9 (0.035 g,
35%) as a colorless oil.
(2d, JC-4,F-3ꢀ =ꢀ 14.4, JC-4,F-3 ꢀ=ꢀ 15.1, C-4a, C-4b), 63.36 and 63.14 (2d, JC-5a,F-3a ꢀ=ꢀ
9.16, JC-5b,F-3b ꢀ=ꢀ 5.21, C-5a, C-5b), 21.1, 20.1, 20.47, 20.37 (4s, COCH3); 19F
NMR (CDCl3): δ 197.91 (dd, F-3a), -184.78 (dt, F-3b). HRMS (EI). Calcd
+
for C16H17O7FNa [M+Na] : m/z 363.0947. Found: m/z 363.0952.
2,6-Dichloro-9-(5′-O-benzoyl-2′-O-acetyl-3′-deoxy-
3′-fluoro-β-D-ribofuranosyl)purine (14)
A mixture of 2,6-dichloropurine (0.148 g, 0.33 mmol) and a catalytic
amount of (NH4)2SO4, HMDS (3 mL) and anhydrous toluene (12 mL)
was heated under reflux for 2 h under argon. Afer cooling the clear
solution was concentrated under reduced pressure to give a residue.
To a solution of this trimethylsilyl derivative and the diacetate 13
(0.217 g, 0.64 mmol) in a mixture of anhydrous MeCN (10.8 mL) and
2-Chloro-6-methoxy-9-(2′,3′-dideoxy-2′,3′-difluoro-β-
D-arabinofuranosyl)purine (16)
1,2-dichloroethane (2.7 mL) was added TMSOTf (0.18 mL, 0.96 mmol) To a solution of nucleoside 9 (0.008 g, 0.019 mmol) in anhydrous
and the reaction mixture was stirred at room temperature for 90 min. MeOH (1.7 mL), 0.1 mL of a 0.22 N solution of sodium methoxide in
Afer the standard work-up, the residue was purified by chroma- methanol was added. The reaction mixture was stirred at room tem-
tography on silica gel, eluting with EtOAc/hexane (ratio 1:2 and 1:1) perature for 18 h, then neutralized with acetic acid, concentrated,
1
to yield nucleoside 14 (0.266 g, 89%) as a syrup. H NMR (CDCl3): δ and co-evaporated with a mixture of toluene/ethanol (1:1, 20 mL) to
8.21 (s, 1H, H-8), 7.44-8.03 (m, 5H, Bz), 6.31 (d, 1H, J1′,2′ ꢀ=ꢀ 7.1, H-1′), 5.92 dryness. The residue was chromatographed on silica gel, eluting with
(ddd, 1H, J2′,3′ ꢀ=ꢀ 4.7, J2′,F-3′ ꢀ=ꢀ 18.65, H-2′), 5.65 (ddd, 1H, J3′,4′ ꢀ=ꢀ 1.82, J3′,F-3′ ꢀ=ꢀ CHCl3/MeOH (ratio 20:1 and 10:1) to afford nucleoside 16 (0.005 g,
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ꢀꢀꢀꢁ
324ꢀ ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
84%); mp 174–176°C (EtOH); UV (EtOH) λmax, nm, (ε): 207 (14250), C-2′), 92.7 (dd, JC-3′,F-2′ ꢀ=ꢀ 28.6, JC-3′,F-3′ ꢀ=ꢀ 192.0, C-3′), 82.9 (d, JC-1′, F-2′ ꢀ=ꢀ 1 7.7,
258 (10100); 19F NMR (CD3OD): δ -196.61 (m, F-2′ or F-3′), -204.7 (m, C-1′), 82.0 (d, JC-4′,F-3′ ꢀ=ꢀ 26.0, C-4′), 60.2 (d, JC-5′,F-3′ ꢀ=ꢀ 4.6, C-5′), 43.9 (s,
+
F-3′ or F-2′). HRMS (EI). Calcd for C11H12N4O3F2Cl [M+H] : m/z 321.0566. C6H5CH2-); 19F NMR (CD3OD): δ -196.1 (m, F-2′ or F-3′), -204.58 (m, F-3′
Found: m/z 321.0562.
or F-2′); UV (MeOH) λmax, nm, (ε): 211 (12600), 271 (8900). HRMS (EI).
+
Calcd for C17H17N5O2F2Cl [M+H] : m/z 396.1039. Found: m/z 396.1034.
2,6-Dimethoxy-9-(2′,3′-dideoxy-2′,3′-difluoro-β-
D-arabinofuranosyl)purine (17)
2,6-Diazido-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,3′-difluoro-
β-D-arabinofuranosyl)purine (20)
To a solution of nucleoside 9 (0.031 g, 0.072 mmol) in anhydrous
MeOH (2.5 mL), 0.22 mL of a 1 N solution of sodium methoxide in Nucleoside 9 (0.075 g, 0.175 mmol) was treated with LiN3 (0.045 g, 0.92
methanol was added. The reaction mixture was stirred at room tem- mmol) in EtOH (10 mL) under reflux for 110 min. The reaction mix-
perature for 18 h, heated under reflux for 90 min, neutralized with ture was concentrated and the residue was dissolved in chloroform
acetic acid, and concentrated and co-evaporated with a mixture of (5 mL). Afer filtration, the filtrate was concentrated and the residue
toluene/ethanol (1:1, 50 mL) to dryness. The residue was chroma- was chromatographed on silica gel, eluting with EtOAc/petroleum
tographed on silica gel, eluting with CHCl3, CHCl3/hexane/MeOH ether (ratio 1:5, 1:4 and 1:2) to afford nucleoside 20 (0.075 g, 97%) as
1
(10:5:1) to afford nucleoside 17 (0.012 g, 52%) as a syrup. UV (EtOH) an amorphous powder. H NMR (CDCl3): δ 8.10 (d, 1H, JH-8, F-2′ ꢀ=ꢀ 1.93,
λmax, nm, (ε): 212 (6500), 240 (9500), 262 (10300); 19F NMR (CD3OD): H-8), 7.44–8.06 (3m, 5H, Bz), 6.53 (dt, 1H, J1′,2′ ꢀ=ꢀ 2.56, J1′,F-2′ ꢀ=ꢀ 22.1,
δ -196.28 (m, F-2′ or F-3′), -204.6 (m, F-3′ or F-2′). HRMS (EI). Calcd J1′,F-3′ ꢀ=ꢀ 2.56, H-1′), 5.44 (dd, 1H, J3′,4′ ꢀ<ꢀ 1.0, J3′,F-2′ ꢀ=ꢀ 12.42, J3′,F′ ꢀ=ꢀ 50.44,
+
for C12H15N4O4F2 [M+H] : m/z 317.1061. Found: m/z 317.1066. Calcd for H-3′), 5.31 (ddd, 1H, J2′,3′ ꢀ<ꢀ 1.0, J2′,F-2′ ꢀ=ꢀ 49.51, J2′,F-3′ ꢀ=ꢀ 9.46, H-2′), 4.62 (dm,
+
C12H14N4O4F2Na [M+Na] : m/z 339.0081. Found: m/z 339.0081.
1H, H-4′), 4.69 (dd, 1H, H-5′), 4.65 (dd, 1H, H-5″); 13C NMR (CDCl3): δ
166.1 (s, Cꢀ=ꢀO, Bz), 133.7, 129.85, 129.19, 128.8 (C6H5CO-), 156.6, 154.2,
153.5 (C-2, C-4, C-6), 142.5 (d, JC-8,F-2′ ꢀ=ꢀ 6.0, C-8), 121.0 (C-5), 93.04 (dd,
JC-2′,F-2′ ꢀ=ꢀ 184.7, JC-2′,F-3′ ꢀ=ꢀ 30.3, C-2′), 93.89 (dd, JC-3′,F-2′ ꢀ=ꢀ 30.0, JC-3′,F-3′ ꢀ=ꢀ 192.1,
C-3′), 83.4 (d, JC-1′, F-2′ ꢀ=ꢀ 16.8, C-1′), 80.8 (d, JC-4′,F-3′ ꢀ=ꢀ 27.1, C-1′), 62.55 (d,
JC-5′,F-3′ ꢀ=ꢀ 8.9, C-5′); 19F NMR (CDCl3): δ -188.9 (m, F-2′), -203.74 (m, F-3′);
UV (EtOH) λmax, nm, (ε): 232 (7300), 270 (2240), 297 (1120). HRMS (EI).
2-Chloro-6-benzylamino-9-(5′-O-benzoyl-2′,3′-dideoxy-
2′,3′-difluoro-β-D-arabinofuranosyl)purine (18)
+
To a solution of nucleoside 9 (0.011 g, 0.025 mmol) in anhydrous
MeOH (2.3 mL) was added benzylamine (0.014 mL, 0.128 mmol). The
reaction mixture was stirred at 55°C for 4 h, and then concentrated.
The residue was chromatographed on silica gel, eluting with EtOAc/
hexane (ratio 2:3 and 3:2) to afford nucleoside 18 (0.01 g, 78%); mp
164–166°C (MeOH); 1H NMR (CDCl3): δ 7.3–8.07 (5m, 10H, Bz and
C6H5CH2-), 7.92 (br.s, 1H, H-8), 6.53 (dt, 1H, J1′,F-2′ ꢀ=ꢀ 22.6, H-1′), 6.29 (br.s,
Calcd for C17H13N10O3F2 [M+H] : m/z 443.1140. Found: m/z 443.1140.
2,6-Diazido-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,3′-difluoro-
α-D-arabinofuranosyl)purine (21)
1H, NH), 5.25-5.48 (m, 2H, H-2′ and H-3′), 4.82 (br.s, 2H, -CH2C6H5), Starting from α-nucleoside 10 (0.014 g, 0.033 mmol) and using the
4.54-4.7 (m, 3H, H-5′, H-5″ and H-4′); 13C NMR (CDCl3): δ 166.2 (s, Cꢀ=ꢀO, procedure described above for the preparation of 20, nucleoside 21
Bz), 156.1, 149.8, 137.9 (C-6, C-2, C-4), 139.45 (d, JC-8,F-2′ ꢀ=ꢀ 4.6, C-8), 137.9, (0.014 g, 97%) was obtained as a syrup. 1H NMR (CDCl3): δ 8.02 (s, 1H,
133.7, 129.94, 129.86, 129.25, 128.93, 128.75, 128.19, 127.85 (C6H5CO- and H-8), 7.46–8.08 (m, 5H, Bz), 6.44 (dd, 1H, J1′,2′ ꢀ=ꢀ 1.0, J1′,F-2′ ꢀ=ꢀ 15.6, H-1′),
C6H5CH2-), 118.2 (C-5), 93.9 (dd, JC-2′,F-2′ ꢀ=ꢀ 183.5, JC-2′,F-3′ ꢀ=ꢀ 30.3, C-2′), 92.0 5.88 (ddt, 1H, J2′,F-2′ ꢀ=ꢀ 48.82, J2′,F-3′ ꢀ=ꢀ 12.3, H-2′), 5.44 (dddd, 1H, J3′,4′ ꢀ=ꢀ
(dd, JC-3′,F-3′ ꢀ=ꢀ 192.49, JC-3′,F-2′ ꢀ=ꢀ 30.1, C-3′), 83.2 (d, JC-1′, F-2′ ꢀ=ꢀ 16.8, C-1′), 80.6 2.5, J3′,F-2′ ꢀ=ꢀ 13.4, J3′,F-3′ ꢀ=ꢀ 50.0, H-3′), 5.05 (dm, 1H, H-4′), 4.62 (dd, 1H,
(d, JC-4′,F-3′ ꢀ=ꢀ 27.2, C-4′), 62.7 (d, JC-5′,F-3′ ꢀ=ꢀ 9.3, C-5′), 45.0 (s, C6H5CH2-); H-5′), 4.57 (dd, 1H, H-5″); 13C NMR (CDCl3): δ 166.0 (Cꢀ=ꢀO, Bz), 133.6,
19F NMR (CDCl3): δ -188.8 (m, F-2′ or F-3′), -203.78 (m, F-3′ or F-2); UV 129.83, 129.10, 128.6 (C6H5CO-), 156.6, 154.4, 153.1 (C-2, C-4, C-6), 141.2
(MeOH) λmax, nm, (ε): 216 (17300) 232 sh, 272 (12100). HRMS (EI). Calcd (d, JC-8,F-2′ ꢀ=ꢀ 3.6, C-8), 121.7 (C-5), 96.3 (dd, JC-2′,F-2′ ꢀ=ꢀ 188.0, JC-2′,F-3′ ꢀ=ꢀ 28.9,
+
for C24H20N5O3F2ClNa [M+Na] : m/z 522.1120. Found: m/z 522.1126.
C-2′), 94.2 (dd, JC-3′,F-2′ ꢀ=ꢀ 29.1, JC-3′,F-3′ ꢀ=ꢀ 184.87, C-3′), 88.5 (dd, JC-1′,F-2′ ꢀ=ꢀ 36.9,
JC-1′,F-3′ ꢀ=ꢀ 2.18, C-1′), 83.45 (d, JC-4′,F-3′ ꢀ=ꢀ 25.88, C-4′), 62.4 (d, JC-5′,F-3′ ꢀ=ꢀ 7.3,
C-5′); 19F NMR (CDCl3): δ -191.47 (dm, F-2′), -191.85 (m, F-3′); UV (EtOH)
λmax, nm (ε): 228 (7300), 271 (2240), 298 (1120). HRMS (EI). Calcd for
2-Chloro-6-benzylamino-9-(2′,3′-dideoxy-2′,3′-difluoro-
β-D-arabinofuranosyl)purine (19)
+
C17H13N10O3F2 [M+H] : m/z 443.1140. Found: m/z 443.1142.
A solution of nucleoside 18 (0.01 g, 0.02 mmol) in MeOH (6 mL) satu-
rated at 0°C with ammonia was kept for 24 h at room temperature and
then evaporated. The residue was chromatographed on silica gel,
2,6-Diamino-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,3′-difluoro-
β-D-arabinofuranosyl)purine (23)
eluting with CH2Cl2, then CH2Cl2/MeOH (ratio 30:1 and 6:1) to afford
1
nucleoside 19 (0.0065 g, 82%) as a syrup. H NMR (CD3OD): δ 8.19 Anhydrous SnCl2 (0.081 g, 0.427 mmol) was added at room tempera-
(br.s, 1H, H-8), 7.21–7.39 (d and 2t, 5H, C6H5CH2-), 6.53 (ddd, 1H, H-1′), ture, under argon, to a solution of nucleoside 20 (0.075 g, 0.169 mmol)
5.36–5.45 (m, 2H, H-2′ and H-3′), 4.74 (br.s, 2H, -CH2C6H5), 4.26 (ddt, in a mixture of anhydrous CH2Cl2 (10 mL) and MeOH (1.2 mL). The
1H, H-4′), 3.85 (dd, 1H, H-5′), 3.82 (dd, 1H, H-5″); 13C NMR (CD3OD): δ reaction mixture was stirred for 2 h, and then poured onto a cooled
154.6, 149.6, 131.6 (C-6, C-2, C-4), 140.0 (br.s, C-8), 129.4, 128.25, 127.5, saturated aqueous solution of NaHCO3. Afer stirring, the prepared
128.3, 127.0 (C6H5CH2-), 117.7 (C-5), 93.6 (dd, JC-2′,F-2′ ꢀ=ꢀ 182.1, JC-2′,F-3′ ꢀ=ꢀ 28.3, suspension was filtered and the precipitate was washed with CHCl3
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R.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosidesꢂ
ꢂ325
(30 mL). Afer separation of the organic phase, the aqueous layer afford nucleoside 25 (0.031 g, 72%); mp 236–238°C (EtOH); UV (EtOH)
was extracted again with CHCl3 (3 ꢀ×ꢀ 30 mL). The combined organic λmax, nm (ε): 215 (18450), 256 (7020), 277 (7280); 19F NMR (CD3OD): δ
layers were dried over anhydrous Na2SO4 and concentrated. The resi- -195.19 (m, F-2′ or F-3′), -204.95 (m, F-3′ or F-2′). HRMS (EI). Calcd for
+
due was chromatographed on silica gel, eluting with EtOAc/hexane C10H13N6O2F2 [M+H] : m/z 287.1100. Found: m/z 287.1103.
(2:1) and EtOAc/hexane/MeOH (ratio 20:10:2) to afford nucleoside 22
(0.003 g, 4%) as a syrup and nucleoside 23 (0.058 g, 87%).
2,6-Diamino-9-(2′,3′-dideoxy-2′,3′-difluoro-α-
Nucleoside 22ꢁ1H NMR (CDCl3): δ 7.92 (d, 1H, JH-8, F-2′ ꢀ=ꢀ 3.1, H-8), 7.46–
D-arabinofuranosyl)purine (26)
8.08 (m, 5H, Bz), 6.48 (dt, 1H, J1′,2′ ꢀ=ꢀ J1′,F-3′ ꢀ=ꢀ 2.56, J1′,F-2′ ꢀ=ꢀ 22.7, H-1′), 5.73
(br.s, 2H, NH2), 5.44 (dd, 1H, J3′,4′ ~ 1.6, J3′,F-2′ ꢀ=ꢀ 12.6, J3′,F′ ꢀ=ꢀ 49.7, H-3′), 5.26
Starting from α-nucleoside 24 (0.012 g, 91%) and using the proce-
(ddd, 1H, J2′,3′ ꢀ<ꢀ 1.0, J2′,F-2′ ꢀ=ꢀ 49.4, J2′,F-3′ ꢀ=ꢀ 9.3, H-2′), 4.69 (dd, 1H, H-5′),
dure described above for the preparation 23, nucleoside 26 (0.007 g,
79%) was prepared as an amorphous powder; UV (EtOH) λmax, nm
(ε): 215 (18400), 256 (7000), 277 (7240); 19F NMR (CDCl3): δ -196.56 (m,
F-2′ or F-3′), -197.764 (m, F-3′ or F-2′). HRMS (EI). Calcd for C10H13N6O2F2
4.56–4.66 (m, 2H, H-5″ and H-4′); 13C NMR (CDCl3): δ 166.15 (s, Cꢀ=ꢀO,
Bz), 157.2, 156.0, 151.2 (C-6, C-4, C-2), 139.4 (d, JC-8,F-2′ ꢀ=ꢀ 6.0, C-8), 133.7,
129.86, 129.28, 128.7 (C6H5CO-), 116.6 (C-5), 93.9 (dd, JC-2′,F-2′ ꢀ=ꢀ 184.4,
JC-2′,F-3′ ꢀ=ꢀ 30.16, C-2′), 91.7 (dd, JC-3′,F-2′ ꢀ=ꢀ 29.8, JC-3′,F-3′ ꢀ=ꢀ 191.29, C-3′), 83.2
(d, JC-1′,F-2′ ꢀ=ꢀ 16.9, C-1′), 80.5 (d, JC-4′,F-3′ ꢀ=ꢀ 27.9, C-4′), 62.7 (d, JC-5′,F-3′ ꢀ=ꢀ 8.9,
C-5′); 19F NMR (CDCl3): δ -188.88 (m, F-2′ or F-3′), -203.85 (m, F-3′ or
F-2′); IR (film): 2120 cm-1 (N3); UV (EtOH) λmax, nm, (ε): 232 (12400), 270
+
[M+H] : m/z 287.1100. Found: m/z 287.1104.
+
(8100). HRMS (EI). Calcd for C17H15N8O3F2 [M+H] : m/z 417.1235. Found:
9-(2′,3′-Dideoxy-2′,3′-difluoro-β-D-arabinofuranosyl)
guanine (27) from nucleoside 25
m/z 417.1239.
1
Nucleoside 23ꢁmp 90–92°C; H NMR (CDCl3): δ 7.73 (d, 1H, JH-8, F-2′ ꢀ=ꢀ
To a solution of nucleoside 25 (0.02 g, 0.07 mmol) in water (3 mL)
was added adenosine deaminase (15 μL). The resulting solution was
stirred at 23°C for 48 h, and concentrated afer addition of methanol.
The residue was chromatographed on silica gel, eluting with CHCl3,
CHCl3/MeOH (ratio 10:1 and 5:1) to afford nucleoside 25 (0.017 g, 85%);
3.2, H-8), 7.46–8.05 (3m, 5H, Bz), 6.37 (dt, 1H, J1′,2′ ꢀ=ꢀ J1′,F-3′ ꢀ=ꢀ 3.2, J1′,F-2′ ꢀ=ꢀ
23.02, H-1′), 5.67 (br.s, 2H, NH2), 5.41 (ddd, 1H, J3′,4′ ꢀ=ꢀ 1.3, J3′,F-2′ ꢀ=ꢀ 12.9,
J3′,F′ ꢀ=ꢀ 49.95, H-3′), 5.26 (ddd, 1H, J2′,3′ ꢀ<ꢀ 1.0, J2′,F-2′ ꢀ=ꢀ 49.46, J2′,F-3′ ꢀ=ꢀ 9.71,
H-2′), 4.85 (br.s, 2H, NH2), 4.66 (dd, 1H, H-5′), 4.62 (dd, 1H, H-5″), 4.56
(ddt, 1H, H-4′); 13C NMR (CDCl3): δ 166.2 (s, Cꢀ=ꢀO, Bz), 160.2, 156.1, 151.9
(C-6, C-4, C-2), 137.1 (d, JC-8,F-2′ ꢀ=ꢀ 6.4, C-8), 133.7, 129.88, 129.32, 128.73,
128.47 (C6H5CO-), 113.7 (C-5), 94.1 (dd, JC-2′,F-2′ ꢀ=ꢀ 183.7, JC-2′,F-3′ ꢀ=ꢀ 30.2, C-2′),
91.8 (dd, JC-3′,F-2′ ꢀ=ꢀ 29.8, JC-3′,F-3′ ꢀ=ꢀ 191.42, C-3′), 82.8 (d, JC-1′, F-2′ ꢀ=ꢀ 16.9, C-1′),
80.1 (d, JC-4′,F-3′ ꢀ=ꢀ 27.0, C-4′), 62.8 (d, JC-5′,F-3′ ꢀ=ꢀ 8.5,C-5′); 19F NMR (CDCl3): δ
-188.85 (m, F-2′ or F-3′), -203.75 (m, F-3′ or F-2′); UV (EtOH) λmax, nm, (ε):
235 (7350), 256 (6690), 277 (6180). HRMS (EI). Calcd for C17H17N6O3F2
mp ꢀ>ꢀ 260°C (MeOH); UV (H2O) λmax, nm (ε): 251 (14200), 270 (sh); 19
F
NMR (DMSO-d6): δ -191.72 (m, F-2′ or F-3′), -194.23 (m, F-3′ or F-2′).
+
HRMS (EI). Calcd for C10H12N5O3F2 [M+H] : m/z 288.0908. Found: m/z
+
288.0904. Calcd for C10H11N5O3F2Na [M+Na] : m/z 310.0728. Found:
m/z 310.0724.
+
[M+H] : m/z 391.1396. Found: m/z 391.1422.
2-Amino-6-chloro-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,
3′-difluoro-β-D-arabinofuranosyl)purine (28) and
2-amino-6-chloro-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,
3′-difluoro-α-D-arabinofuranosyl)purine (29)
2,6-Diamino-9-(5′-O-benzoyl-2′,3′-dideoxy-2′,3′-difluoro-
α-D-arabinofuranosyl)purine (24)
2-Amino-6-chloropurine potassium salt was prepared by adding
(0.024 g, 0.151 mmol) potassium t-butoxide to a solution of 2-amino-
6-chloropurine (0.036 g, 0.21 mmol) in anhydrous 1,2-dimethox-
yethane (11 mL) under argon at 0°C and the resulting solution was
stirred for 40 min at room temperature and then concentrated. To
a suspension of the prepared potassium salt of 2-amino-6-chloropu-
rine in anhydrous MeCN (9 mL) was added, under argon, a solution
of bromide 8 (0.060 g, 0.187 mmol) in anhydrous MeCN (5 mL). The
reaction mixture was stirred under argon at room temperature for
18 h. Insoluble materials were removed by filtration and the solids
were washed with MeCN (5 mL). The combined filtrate and washings
were concentrated. The residue was dissolved in anhydrous CH2Cl2
(5 mL), filtered off and insoluble materials were washed with CH2Cl2.
The solvent was removed under reduced pressure, and the residue
was chromatographed on silica gel, eluting with EtOAc/hexane (1:1)
to afford β-nucleoside 28 (0.038 g, 50%) as a white amorphous pow-
der and α-nucleoside 29 (0.003 g, 8%) as a syrup.
Starting from α-nucleoside 21 (0.015 g, 0.034 mmol) and using the
procedure described above for the preparation of 20, nucleoside 24
(0.012 g, 91%) was obtained as a syrup; 1H NMR (CDCl3): δ 7.63 (s, 1H,
H-8), 7.42–8.07 (m, 5H, Bz), 6.26 (dd, 1H, J1′,2′ꢀ<ꢀ1.0, J1′,F-2′ ꢀ=ꢀ 16.5, J1′,F-3′ ꢀ=ꢀ
1.56, H-1′), 6.01 (ddt, 1H, J2′,3′ ꢀ=ꢀ 1.9, J2′,F-2′ ꢀ=ꢀ 49.7, J2′,F-3′ ꢀ=ꢀ 13.1, H-2′), 5.44
(br.s, 2H, NH2), 5.38 (ddd, 1H, J3′,4′ ꢀ=ꢀ 1.3, J3′,F-2′ ꢀ=ꢀ 16.0, J3′,F′ n.d., H-3′), 5.01
(dq, 1H, H-4′), 4.77 (br.s, 2H, NH2), 4.60 (dd, 1H, H-5′), 4.57 (dd, 1H,
H-5″); 19F NMR (CDCl3): δ -191.72 (m, F-2′ or F-3′), -194.23 (m, F-3′ or F-2′);
UV (EtOH) λmax, nm, (ε): 235 (7350), 256 (6600), 277 (6150). HRMS (EI).
+
Calcd for C17H17N6O3F2 [M+H] : m/z 391.1396. Found: m/z 391.1420.
2,6-Diamino-9-(2′,3′-dideoxy-2′,3′-difluoro-β-
D-arabinofuranosyl)purine (25)
A solution of nucleoside 23 (0.058 g, 0.164 mmol) in MeOH (25 mL)
saturated at 0°C with ammonia was kept for 18 h at room tempera-
ture and then concentrated. The residue was chromatographed on β-Nucleoside 28ꢁ1H NMR (CDCl3): δ 7.97 (d, 1H, JH-8, F-2′ ꢀ=ꢀ 2.8, H-8),
silica gel, eluting with CHCl3, CHCl3/MeOH (ratio 15:1 and 5:1) to 7.45–8.05 (m, 5H, Bz), 6.41 (dt, 1H, J1′,2′ ꢀ=ꢀ 2.5, J1′,F-2′ ꢀ=ꢀ 19.8, H-1′), 5.46
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326ꢀ ꢀR.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosides
(dd, 1H, J2′,3′ ꢀ<ꢀ 1.0, J2′,F-2′ ꢀ=ꢀ 49.9, J2′,F-3′ ꢀ=ꢀ 12.78, H-2′), 5.29 (ddd, 1H, J3′,4′ ꢀ=ꢀ
2.46, J3′,F-2′ ꢀ=ꢀ 25.0, J3′,F′ ꢀ=ꢀ 49.95, H-3′), 5.29 (br.s, 2H, NH2), 4.67 (d, 2H,
H-5′ and H-5″), 4.58 (ddt, 1H, H-4″); 13C NMR (CDCl3): δ 166.2 (s, Cꢀ=ꢀO,
Bz), 133.7, 129.85, 129.19, 128.75 (C6H5CO-), 159.2, 153.4, 151.9 (C-2, C-6,
C-4), 141.1 (d, JC-8,F-2′ ꢀ=ꢀ 6.1, C-8), 125.0 (C-5), 94.1 (dd, JC-2′,F-2′ ꢀ=ꢀ 183.9,
JC-2′,F-3′ ꢀ=ꢀ 30.0, C-2′), 91.68 (dd, JC-3′,F-2′ ꢀ=ꢀ 30.0, JC-3′,F-3′ ꢀ=ꢀ 192.07, C-3′), 83.15
(d, JC-1′,F-2′ ꢀ=ꢀ 16.7, C-1′), 80.6 (d, JC-4′, F-3′ ꢀ=ꢀ 27.1, C-4′), 62.6 (d, JC-5′,F-3′ ꢀ=ꢀ 8.9,
C-5′); 19F NMR (CDCl3): δ -188.82 (m, F-2′ or F-3′), -203.76 (m, F-3′ or F-2′);
is the Chairman and a major shareholder of CoCrystal
Pharma, Inc. Emory University received no funding from
Cocrystal Pharma, Inc., to perform this work and vice
versa.
UV (MeOH) λmax, nm, (ε): 232 (16350), 308 (6600). HRMS (EI). Calcd References
+
for C17H15N5O3F2Cl [M+H] : m/z 410.0831. Found: m/z 410.0834.
[1] Meng, W. D.; Qing, F. L. Fluorinated nucleosides as antiviral and
α-Nucleoside 29ꢁ1H NMR (CDCl3): δ 7.88 (s, 1H, H-8), 7.46–8.08 (3m,
5H, Bz), 6.34 (d, 1H, J1′,F-2′ ꢀ=ꢀ 15.8, H-1′), 5.90 (dd, 1H, J2′,3′ ꢀ<ꢀ 1.0, J2′,F-2′ ꢀ=ꢀ
48.6, J2′,F-3′ ꢀ=ꢀ 12.49, H-2′), 5.42 (ddd, 1H, J3′,4′ ꢀ=ꢀ 2.46, J3′,F-2′ ꢀ=ꢀ 25.0, J3′,F′ ꢀ=ꢀ
49.95, H-3′), 5.16 (br.s, 2H, NH2), 5.02 (dm, 1H, H-4′). 4.61 (dd, 1-H,
H-5′), 4.58 (dd, 1H, H-5″); 13C NMR (CDCl3): δ 166.0 (Cꢀ=ꢀO, Bz), 133.6,
129.83, 129.17, 128.6 (C6H5CO-), 159.1, 153.0, 152.0 (C-2, C-6, C-4), 139.8
(d, JC-8,F-2′ ꢀ=ꢀ 3.2, C-8), 125.7 (C-5), 96.3 (dd, JC-2′,F-2′ ꢀ=ꢀ 187.8, JC-2′,F-3′ ꢀ=ꢀ 29.1,
C-2′), 94.3 (dd, JC-3′,F-2′ ꢀ=ꢀ 29.6, JC-3′,F-3′ ꢀ=ꢀ 185.7, C-3′), 88.2 (dd, JC-1′,F-2′ ꢀ=ꢀ 36.4,
JC-1′,F-3′ ꢀ=ꢀ 2.9, C-1′), 83.1 (d, JC-4′,F-3′ ꢀ=ꢀ 25.6, C-4′), 62.5 (d, JC-5′,F-3′ ꢀ=ꢀ 6.6, C-5′);
19F NMR (CDCl3): δ -191.63 (m, F-2′ or F-3′), -192.6 (m, F-3′ or F-2′); UV
(MeOH) λmax, nm, (ε): 232 (16450), 308 (6700). HRMS (EI). Calcd for
antitumor agents. Curr. Top Med. Chem. 2006, 6, 1499–1528.
[2] Ray, A. S.; Schinazi, R. F.; Murakami, E.; Basavapathruni, A.;
Shi, J.; Zorca, S. M.; Chu, C. K.; Anderson, K. S. Probing the
mechanistic consequences of 5-fluorine substitution on
cytidine nucleotide analogue incorporation by HIV-1 reverse
transcriptase. Antivir. Chem. Chemother. 2003, 14, 115–125.
[3] Coats, S. J.; Garnier-Amblard, E. C.; Amblard, F.; Etheshami, M.;
Amiralaei, S.; Zhang, H.; Zhou, L.; Boucle, S. R. L.; Lu, X.;
Bondada, L.; et al. Chutes and ladders in hepatitis C
nucleoside drug development. Antiv. Res. 2014, 102, 119.
[4] Clark, J. L.; Hollecker, L.; Mason, J. C.; Stuyver, L. J.;
Tharnish, P. M.; Lostia, S.; McBrayer, T. R.; Schinazi R. F.;
Watanabe, K. A.; Otto, M. J.; et al. Design, synthesis, and anti-
viral activity of 2′-deoxy-2′-fluoro-2′-C-methylcytidine, a potent
inhibitor of hepatitis C virus replication. J. Med. Chem. 2005,
48, 5504–5508.
+
C17H15N5O3F2Cl [M+H] : m/z 410.0831. Found: m/z 410.0833.
2-Amino-6-chloro-9-(2′,3′-dideoxy-2′,3′-difluoro-β-
D-arabinofuranosyl)purine (30)
[5] Jordheim, L. P.; Durantel, D.; Zoulim, F.; Dumontet, C. Advances
in the development of nucleoside and nucleotide analogues
for cancer and viral diseases. Nat. Rev. Drug Discov. 2013, 12,
447–464.
[6] Michailidis, E.; Marchand, B.; Kodama, E. N.; Singh, K.;
Matsuoka, M.; Kirby, K. A.; Ryan, E. M.; Sawani, A. M.; Nagy, E.;
Ashida, N.; et al. Mechanism of inhibition of HIV-1 reverse
transcriptase by 4′-Ethynyl-2-fluoro-2′-deoxyadenosine
triphosphate, a translocation-defective reverse transcriptase
inhibitor. J. Biol. Chem. 2009, 284, 35681–35691.
[7] Mikhailopulo, I. A.; Pricota, T. I.; Sivets, G. G.; Altona, C.
2′-chloro-2′,3′-dideoxy-3′-fluoro-d-ribonucleosides: synthesis,
stereospecificity, some chemical transformations, and
conformational analysis. J. Org. Chem. 2003, 68, 5897–5908.
[8] Shi, J.; Zhou, L.; Zhang, H.-W.; McBrayer, T. R.; Detorio, M. A.;
Johns, M.; Bassit, L.; Powdrill, M. H.; Whitaker, T.; Coats, S. J.;
et al. Synthesis and antiviral activity of 2′-deoxy-2′-fluoro-2′-
C-methyl-7-deazapurine nucleosides, their phosphoramidate
prodrugs and 5′-triphosphates. Bioorg. Med. Chem. Lett. 2011,
21, 7094–7098.
[9] Guo, X.; Li, Y.; Tao, L.; Wang, Q.; Wang, S.; Hu, W.; Pan, Z.;
Yang, Q.; Cui, Y.; Ge, Z.; et al. Synthesis and anti-HIV-1
activity of 4-substituted-7-(2′-deoxy-2′-fluoro-4′-azido-β-
D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine analogues. Bioorg.
Med. Chem. Lett. 2011, 21, 6770–6772.
A solution of nucleoside 28 (0.018 g, 0.043 mmol) in MeOH (5 mL)
saturated at 0°C with ammonia was kept for 18 h at room tempera-
ture and then concentrated. The residue was chromatographed on
silica gel, eluting with CHCl3, then CHCl3/MeOH (ratio 15:1 and 5:1) to
afford nucleoside 30 (0.01 g, 77%) as a syrup; UV (EtOH) λmax, nm, (ε):
1
220 (18900), 247 (9000), 309 (7600); H NMR (CD3OD): δ 8.21 (d, 1H,
JH-8, F-2′ ꢀ=ꢀ 2.4, H-8), 6.43 (ddd, 1H, J1′,2′ ꢀ=ꢀ 3.5, J1′,F-2′ ꢀ=ꢀ 17.3, J1′,F-3′ ꢀ=ꢀ 1.9, H-1′),
5.40–5.45 (dm, 2H, H-2′ and H-3′), 4.25 (dm, 1H, H-4′), 3.85 (dd, 1H,
H-5′), 3.83 (dd, 1H, H-5″); 19F NMR (CD3OD): δ -195.72 (m, F-2′ or F-3′),
+
-204.7 (m, F-3′ or F-2′). HRMS (EI). Calcd for C10H11N5O2F2Cl [M+H] : m/z
306.0569. Found: m/z 306.0573.
9-(2′,3′-Dideoxy-2′,3′-difluoro-β-D-arabinofuranosyl)
guanine (27) from nucleoside 28
To a solution of nucleoside 28 (0.02 g, 0.049 mmol) in MeOH (2 mL),
2-mercaptoethanol (0.14 mL, 0.2 mmol) and sodium methoxide
0.011 g (0.2 mmol) were added. The reaction mixture was heated
under reflux for 3 h. Afer cooling to room temperature, the resulting
solution was neutralized with acetic acid and solvents were removed
under reduced pressure. The residue was purified on silica gel, elut-
ing with CHCl3, then CHCl3/MeOH (ratio 10:1 and 5:1) to afford nucleo-
side 27 (0.01 g, 71%).
[10] Marquez, V. E.; Tseng, C. K.-H.; Kelly, J. A.; Mitsuya, H.;
Broder, S.; Roth, J. S.; Driscoll J. S. 2′,3′-Dideoxy-2′-fluoro-
ara-A. An acid-stable purine nucleoside active against human
immunodeficiency virus (HIV). Biochem. Pharmacol. 1987, 36,
2719–2722.
[11] Chu, C. K.; Matulic-Adamic, J.; Huang, J. T.; Chou, T. C.;
Burchenal, J. H.; Fox, J. J.; Watanabe K. A. Nucleosides.
CXXXV. Synthesis of some 9-(2-deoxy-2-fluoro-beta-D-
Acknowledgments: This work was supported in part by
NIH grant 5P30-AI-50409 (CFAR), by the Department of
Veterans Affairs and by the Belarus State Program of FOI
‘Chempharmsynthesis’(Grants 2.19 and 4.20). Dr. Schinazi
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ꢁꢀꢀꢀ
R.F. Schinazi et al.: 2′,3′-Dideoxy-2′,3′-difluoro-D-arabinofuranosyl 2,6-disubstituted purine nucleosidesꢂ
ꢂ327
arabinofuranosyl)-9H-purines and their biological activities.
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9-(2-Deoxy-2-fluoro-beta-D-arabinofuranosyl)guanine: a
metabolically stable cytotoxic analogue of 2′-deoxyguanosine.
J. Med. Chem. 1986, 29, 2389–2392.
synthesis of deoxy fluoro sugars and nucleosides. Chim. Acta
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[22] Zhang, H.-W.; Coats, S. J.; Bondada, L.; Amblard, F.;
Detorio, M.; Asif, G.; Fromentin, E.; Solomon, S.; Obikhod, A.;
Whitaker, T.; et al. Synthesis and evaluation of 3′-azido-2′,
3′-dideoxypurine nucleosides as inhibitors of human immuno-
deficiency virus. Bioorg. Med. Chem. Lett. 2010, 20, 60–64.
[23] Tennilä, T.; Azhayeva, E.; Vepsäläinen, J.; Laatikainen, R.;
Azhayev, A.; Mikhailopulo I. A. Oligonucleotides containing
9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-adenine and
-guanine: synthesis, hybridization and antisense properties.
Nucleosides, Nucleotides Nucleic Acids 2000, 19, 1861–1864.
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