Keto-fluorothiopyranosyl nucleosides: A convenient synthesis of 2- and 4-keto-3-fluoro-5-thioxylopyranosyl thymine analogs

Article abstract of DOI:10.1016/j.carres.2011.05.013

A novel series of fluorinated keto-β-D-5-thioxylopyranonucleosides bearing thymine as the heterocyclic base have been designed and synthesized. Deprotection of 3-deoxy-3-fluoro-5-S-acetyl-5-thio-D-xylofuranose (1) and selective acetalation gave the desire

Full text of DOI:10.1016/j.carres.2011.05.013

Carbohydrate Research 346 (2011) 2011–2015
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Keto-fluorothiopyranosyl nucleosides: a convenient synthesis
of 2- and 4-keto-3-fluoro-5-thioxylopyranosyl thymine analogs
⇑
Evangelia Tsoukala, Stella Manta, Niki Tzioumaki, Christos Kiritsis, Dimitri Komiotis
Department of Biochemistry and Biotechnology, Laboratory of Organic Chemistry, University of Thessaly, 26 Ploutonos Str., 41221 Larissa, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of fluorinated keto-b-
base have been designed and synthesized. Deprotection of 3-deoxy-3-fluoro-5-S-acetyl-5-thio-
D
-5-thioxylopyranonucleosides bearing thymine as the heterocyclic
-xylof-
Received 21 January 2011
Received in revised form 9 May 2011
Accepted 12 May 2011
D
uranose (1) and selective acetalation gave the desired isopropylidene 5-thioxylopyranose precursor 3.
Acetylation and isopropylidene removal followed by benzoylation led to 3-deoxy-3-fluoro-1,2-di-J-ben-
Available online 19 May 2011
zoyl-4-O-acetyl-50-thio-
D-xylopyranose (6). This was condensed with silylated thymine and selectively
deacetylated to afford 1-(20-J-benzoyl-30-deoxy-30-fluoro-50-thio-b-
D-xylopyranosyl)thymine (8). Oxida-
Keywords:
tion of the free hydroxyl group in the 40-position of the sugar led to the formation of the target 40-keto
compound together with the concomitant displacement of the benzoyl group by an acetyl affording, 1-
Xylopyranonucleosides
Ketonucleosides
Fluoronucleosides
5-Thionucleosides
(20-O-acetyl-30-deoxy-30-fluoro-b- -xylopyranosyl-40-ulose)thymine (9). Benzoylation of 3 and removal
D
of the isopropylidene group followed by acetylation, furnished 3-deoxy-3-fluoro-1,2-di-J-acetyl-4-O-
benzoyl-50-thio-
-xylopyranose (12). Condensation of thiosugar 12 with silylated thymine followed by
selective deacetylation led to the 1-(40-J-benzoyl-30-fluoro-50-thio-b-
-xylopyranosyl)thymine (14). Oxi-
D
D
dation of the free hydroxyl group in the 20-position and concomitant displacement of the benzoyl group
by an acetyl gave target 1-(40-O-acetyl-30-deoxy-30-fluoro-b-
D
-xylopyranosyl-20-ulose)thymine (15).
Ó 2011 Elsevier Ltd. All rights reserved.
Nucleosides and their analogs have far been proven to take an
important place in medicinal chemistry as the structural basis for
the development of therapeutic agents.1–3 In spite of the initial suc-
cess obtained with modified nucleosides, both the undesirable side
effects of certain nucleosides and the demand for new antiviral and
antitumor agents have prompted the search for further novel
nucleosides with improved biological and chemical properties.4–6
In seeking to investigate new biologically active agents, we have
previously designed and synthesized fluorinated pyranonucleo-
sides, evaluated their potential antiviral, antitumor,7,8 and antioxi-
dant9 properties and their activity at molecular level.10,11 More
recently, in our attempts to arrive at new modified analogs, we have
demonstrated that insertion of a keto group and removal of the pri-
mary hydroxymethyl function in the sugar moiety led to various
uncommon nucleosides,7,8,12–15 which showed promising antitu-
mor and antiviral activities. It also appeared that these nucleosides
represent novel types of prodrugs,13 while they may act as acceptors
in a Michael-addition mechanism.12
while thionucleosides have been recognized as a novel and impor-
tant class of antiviral agents and promising antitumor candidates.21
It is noteworthy that the replacement of the oxygen atom by sulfur
in the sugar ring of the fluorinated analog of cytosine (FAC) led to an
increase of its activity against various human tumor cell lines, while
a new more biologically important compound was obtained.22,23
In view of the above observations and considering the utility of
derivatives containing sulfur in the ring, as biologically important
targets in medicinal chemistry, we found intriguing to further ex-
plore structure–activity relationships of fluorinated ketopyranonu-
cleosides, by replacing the ring oxygen atom by sulfur. We thus
present the synthesis of a novel class of xylopyranonucleosides of
thymine, possessing a ring sulfur atom and a keto group in the
20- or 40-position of the sugar portion.
Retrosynthetic analysis suggested that 20-keto- and 40-keto-
thionucleosides could be obtained by utilizing the available 5-thio-
xylopyranosyl nucleoside of thymine I and its corresponding fully
unprotected analog II, respectively (Scheme 1). However, neither
selective deacetylation24,25 of thio-analog I, nor specific benzoyla-
tion,26 pivaloylation,27 or silyl protection28 of 5-thioxylopyranonu-
cleoside II led to the desirable partially protected precursors, but
only to the corresponding deacetylated derivative II, along with
the fully protected analogs III, respectively.
In the field of modified nucleosides, considerable interest has
been drawn in the synthesis of thiosugars16 and thionucleoside
analogs17–19 in which the ring oxygen atom is replaced by sulfur.
The biological interest in thiosugars has expanded to studies on dia-
betes, enzyme inhibition, and antiviral and antitumor activities,20
Since all attempts to selectively deprotect or protect the 5-thio-
xylopyranosyl analogs of thymine were unsuccessful, we altered
the retrosynthetic routes for the synthesis of the desirable
⇑
Corresponding author. Tel.: +30 2410 565285; fax: +30 2410 565290.
E-mail address: dkom@bio.uth.gr (D. Komiotis).
0008-6215/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2011.05.013

2012
E. Tsoukala et al. / Carbohydrate Research 346 (2011) 2011–2015
O
O
N
O
N
NH
NH
NH
S
S
S
i
ii
HO
RO
AcO
N
O
O
O
F
F
F
OH
OR
OAc
II
III
I
R=Bz or Pv or TBDMSi
Scheme 1. Reagents: (i) (a) NaOH/EtOH/pyridine or (b) HONH2ꢁHCl/NaOAc/pyridine; (ii) (a) BzCl/pyridine or (b) PvCl/pyridine or (c) TBDMSCl/pyridine.
40-keto- and 20-keto-30-fluoro-5-thioxylopyranosyl nucleosides, 9
and 15, respectively. In both routes, the suitable key precursor is
the newly synthesized 1,2-O-isopropylidene analog of 5-thioxylo-
pyranose 3.
oriented thymine ring. When selective deprotection of the fully
protected thionucleoside 7 with NaOH–ethanol–pyridine24 was
employed, partially benzoyl analog of thymine 8 was formed. The
crucial step of this synthetic pathway proved to be the oxidation of
the suitably protected precursor 8. However, the target ketone 9
was obtained, only when the oxidation reaction was performed
by pyridinium dichromate (PDC)/Ac2O at 60 °C for 15 min, while
surprisingly, a simultaneous replacement of the benzoyl group by
an acetyl was observed. The IR spectrum measured immediately
after completion of the reaction workup revealed a characteristic
absorption of a carbonyl group at 1712 cmꢀ1, confirming the
presence of the desired ketonucleoside 9. It is of interest to men-
tion that when the duration of the aforementioned oxidation reac-
30-Deoxy-30-fluoro-40-keto-5-thio-b-
D
-xylopyranonucleoside
(9) was prepared according to the synthetic route outlined in
Scheme 2. Deprotection of 3-deoxy-3-fluoro-5-S-acetyl-5-thio-
D
-
xylofuranose (1) in methanolic ammonia29 gave the glycosyl do-
nor, 5-thioxylopyranose 2. Specific acetalation of the free hydroxyl
groups in the 1,2-position of the sugar moiety of 2 with 2,2-dime-
thoxypropane [(CH3)2C(OCH3)2], in the presence of p-toluenesul-
fonic acid (p-TsOH) in N,N-dimethylformamide (DMF),30 afforded
the desired isopropylidene 5-thioxylopyranose 3, in 70% yield.
Acetylation of the free hydroxyl group in the 4-position of the thio-
sugar 3 with Ac2O/pyridine furnished the acetylated derivative 4.
The isopropylidene group of compound 4 was removed under
acidic conditions and the resulting compound 5 was reacted with
benzoyl chloride (BzCl) and pyridine to give the 1,2-di-O-benzoyl
derivative 6. Compound 6 was readily converted into the 1-(20-J-
tion was extended,
a mixture of untreatable products was
obtained. Furthermore, when oxidation of 8 was performed by a
modified Albright–Goldman reaction, using the DMSO/EtOAc/
Ac2O system,32 Pfitzner–Moffatt,33 Garegg–Samuelsson,34 Swern,35
Dess–Martin,36 and pyridinium dichromate (PDC)/3E molecular
sieves37 methods, resulted in a mixture of intractable and unsepa-
rable materials. The IR spectra of the crude reaction mixtures
exhibited characteristic absorptions of S@O and O@S@O groups
at 1055 and 1140 cmꢀ1, respectively, convincing the instability of
sulfur versus oxidative step.
benzoyl-40-O-acetyl-30-deoxy-30-fluoro-50-thio-b-
D-xylopyrano-
syl)thymine (7), in 68% yield, upon reaction with silyl-protected
thymine in the presence of tin chloride (IV) as catalyst.31 The
participation of 20-benzoyloxy group led to the exclusive formation
of the b-anomer 7. As expected, the 1H NMR spectrum of 7 showed
a large coupling between protons H-10 and H-20 (J = 10.6 Hz),
indicating an axial orientation of both protons and an equatorially
For the synthesis of the 30-deoxy-30-fluoro-20-keto-5-thio-b-
D-
xylopyranonucleoside (15), a synthetic route starting from the
isopropylidene 5-thioxylopyranose 3 was devised (Scheme 2).
O
S
S
i
ii
AcS
F
OH
HO
RO
F
F
OH
OH
O
O
OH
2
1
3: R=H
4: R=Ac
10: R=Bz
iii
C
v
Me2
iv
O
NH
S
S
OBz
S
vi
AcO
v
RO
F
BzO
iii
N
O
F
F
OR
OR
OR
5: R=H
6: R=Bz
OR
11: R=H
7: R=Ac
8: R=H
vii
12: R=Ac
viii
vi
O
O
N
O
N
NH
NH
NH
O
S
S
viii
S
BzO
N
O
O
O
AcO
F
F
F
OR
O
OAc
13: R=Ac
14: R=H
15
9
vii
Scheme 2. Reagents: (i) Ammonia/MeOH; (ii) (CH3)2C(OCH3)2)/p-TsOH/DMF; (iii) Ac2O/pyridine; (iv) 90% TFA; (v) BzCl/pyridine; (vi) silylated thymine/SnCl4/CH3CN; (vii)
NaOH/EtOH/pyridine; (viii) PDC/Ac2O/60 °C/15 min.

E. Tsoukala et al. / Carbohydrate Research 346 (2011) 2011–2015
2013
The benzoyl derivative 10 was prepared by protection of the free
hydroxyl group in the 4-position of the key isopropylidene thio-
sugar 3, in the presence of BzCl in pyridine. The fully protected
thiosugar 12 was readily available from derivative 10 through
hydrolysis with 90% aqueous trifluoroacetic acid (TFA) at room
temperature followed by acetylation of the resulting compound
11. 5-Thioxylopyranose 12 was then coupled to silylated thy-
mine using tin chloride (IV) as activator31 to give the protected
b-nucleoside, 1-(40-J-benzoyl-20-O-acetyl-30-deoxy-30-fluoro-50-
1.2. Synthesis of 3-deoxy-3-fluoro-1,2-O-isopropylidene-5-thio-
-xylopyranose (3)
D
1.2.1. 3-Deoxy-3-fluoro-5-thioxylopyranose (2)
A mixture of methanolic ammonia (382 mL) and compound 117
(9.2 mmol, 1.95 g) was stirred for 2 h at room temperature. The
reaction mixture was evaporated to dryness to give 1.40 g (72%)
of compound 2 as a viscous oil, and it was used without further
purification (EtOAc, Rf 0.4).
thio-b-D
-xylopyranosyl)thymine (13), in 66% yield. The 1H NMR
spectrum of 13 showed large JH,H coupling value of J = 10.6 Hz,
indicative for the b-configuration of the sugar moiety. Selective
deacetylation of the protected thionucleoside 13 with NaOH–
ethanol–pyridine24 afforded the 40-J-benzoyl analog of thymine
14. In the final step, oxidation of the fluoro benzoyl thionucleo-
side precursor 14, performed by PDC/Ac2O at 60 °C for 15 min,
and concomitant displacement of the benzoyl group by an acetyl
1.2.2. 3-Deoxy-3-fluoro-1,2-O-isopropylidene-5-thio-a-D-
xylopyranose (3)
To a stirred suspension of 2 (7.79 mmol, 1.31 g) in anhydrous
DMF (98.5 mL) and 2,2-dimethoxypropane (31.15 mL) was added
p-toluenesulfonic acid monohydrate (1.56 mmol, 0.029 g). After
20 h the resulting solution was neutralized with Et3N so that pH
did not exceed 7. The solution was concentrated and the residue
was purified by flash chromatography (4:6 hexane–EtOAc, Rf
0.35) to give 1.13 g (70%) of 3 as a yellow syrup: Anal. Calcd for
C8H13FO3S: C, 46.14; H, 6.29. Found: C, 46.32; H, 6.37. ESIMS: m/
z 209.3 [M+H+].
gave the desired 1-(40-O-acetyl-30-deoxy-30-fluoro-b-
D-xylopyr-
anosyl-20-ulose)thymine (15), well characterized by NMR, mass
and IR spectroscopy.
It is noteworthy that, when oxidation is performed on fluoro-
thioxylopyranosyl nucleosides, simultaneous b-elimination reac-
tion does not occur, as it happens in the case of the corresponding
fluoro-pyranonucleosides. This may be due to the smaller dihedral
angle J4–C4–C3–H3 in thiopyranonucleosides 9 and 15, compared
to that in ketopyranosyl analogs (<35° vs >50°), as shown by
molecular modeling studies.
1.3. Synthesis of 1-(30-deoxy-30-fluoro-20-O-acetyl-b-
D-
xylopyranosyl-40-ulose)thymine (9)
In conclusion, we present herein a convenient synthesis of a
novel class of keto-fluoro-thioxylopyranosyl nucleosides, relied
on suitable and selective protection/deprotection sequences.
Our synthesis highlighted the efficient installation of keto group
in the sugar moiety and construction of keto-thiopyranose skel-
eton, by overcoming sulfur sensitivity during oxidation reaction.
The preparation of the new keto-thiopyranonucleosides is an
interesting and primary approach in the field of keto-thiosugar
analogues.
1.3.1. 3-Deoxy-3-fluoro-1,2-O-isopropylidene-4-O-acetyl-5-
thio- -xylopyranose (4)
a-D
Compound 3 (5.45 mmol, 1.13 g) was dissolved in a mixture of
pyridine (27 mL) and Ac2O (4.9 mmol, 0.46 mL). The reaction was
carried out at room temperature for 1 h, then was quenched with
MeOH at 0 °C and was concentrated in vacuum. The residue was
diluted with EtOAc, washed with saturated sodium bisulfate, so-
dium bicarbonate, and water. The organic extract was dried over
anhydrous sodium sulfate, filtered, and evaporated to dryness.
The residue was purified by flash chromatography (6:4 hexane–
EtOAc, Rf 0.30) to give 1.21 g (89%) of compound 4 as a yellow syr-
1. Experimental
up: ½a 2D2
ꢂ
+26 (c 0.1, CHCl3); 1H NMR (CDCl3, 400 MHz): d 5.24 (d,
1H, J = 5.0 Hz, H-1), 4.49 (dtr, 1H, J = 49.8 Hz, J = 9.0 Hz, H-3),
4.40–4.31 (m, 2H, H-2 and H-4), 2.91–2.85 (m, 1H, H-5b), 2.68–
2.64 (m, 1H, H-5a), 2.10 (s, 3H, OAc), 1.58 (s, 3H, CH3), 1.42 (s,
3H, CH3). Anal. Calcd for C10H15FO4S: C, 47.99; H, 6.04. Found: C,
48.07; H, 6.17. ESIMS: m/z 251.3 [M+H+].
1.1. General procedure
Melting points were recorded in a Mel-Temp apparatus and
are uncorrected. Thin layer chromatography (TLC) was per-
formed on Merck precoated 60F254 plates. Reactions were moni-
tored by TLC on silica gel, with detection by UV light (254 nm)
or by charring with sulfuric acid. Flash column chromatography
was performed using silica gel (240–400 mesh, Merck). 1H and
13C NMR spectra were obtained at room temperature with a
Brucker 400 spectrometer at 400 and 100 MHz, respectively,
using CDCl3 and MeOH-d4 (CD3OD) with internal tetramethylsil-
ane (TMS).
The chemical shifts are expressed in parts per million (d) and
the following abbreviations were used: s = singlet, d = doublet,
dd = doublet doublet, dtr = doublet triplet and m = multiplet.
UV–vis spectra were recorded on a PG T70 UV–VIS spectrometer
and mass spectra were obtained with a Micromass Platform LC
(ESI-MS). Optical rotations were measured using an Autopol I
1.3.2. 3-Deoxy-3-fluoro-4-O-acetyl-5-thio-D-xylopyranose (5)
A soln of thioxylopyranose 4 (4.85 mmol, 1.21 g) in 90% TFA
(24.2 mL) was stirred for 10 min at room temperature. The mixture
was concentrated under diminished pressure to leave a residue,
which was purified by flash chromatography (3:7 hexane–EtOAc,
Rf 0.20) to give 0.92 g (90%) of diol 5 as a colorless syrup: Anal.
Calcd for C7H11FO4S: C, 39.99; H, 5.27. Found: C, 40.08; H, 5.12.
ESIMS: m/z 211.2 [M+H+].
1.3.3. 3-Deoxy-3-fluoro-1,2-O-benzoyl-4-O-acetyl-5-thio-D-
xylopyranose (6)
Compound 5 (4.36 mmol, 0.92 g) was dissolved in a mixture of
pyridine (16 mL) and BzCl (10.9 mmol, 1.27 mL). The reaction was
carried out at room temperature for 1 h, and then was concen-
trated in vacuum. The residue was purified by flash chromatogra-
phy (6:4 hexane–EtOAc, Rf 0.36) to give 1.51 g (83%) of
polarimeter. Infrared spectra were obtained with
Scientific Nicolet IR100 FT-IR spectrometer.
a Thermo
All reactions were carried out in dry solvents. CH2Cl2 was
distilled from phosphorous pentoxide and stored over 4T molec-
ular sieves. Acetonitrile was distilled from calcium hydride and
stored over 3E molecular sieves. DMF was also stored over 3E
molecular sieves, and pyridine was stored over potassium
hydroxide pellets.
compound 6 as a yellow syrup: ½a D22
ꢂ
+21 (c 0.1, CHCl3); 1H NMR
(CDCl3, 400 MHz): d 8.20–7.96 and 7.72–7.34 (m, 5H, Yarom benzoyl
group), 5.93 (br s, 1H, H-1), 5.75–5.70 (m, 1H, H-2), 5.46–5.39 (m,
1H, H-4), 5.09 (dtr, 1H, J = 50.9 Hz, J = 9.4 Hz, H-3), 3.22–3.02 (m,

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E. Tsoukala et al. / Carbohydrate Research 346 (2011) 2011–2015
1H, H-5a), 2.95–2.84 (m, 1H, H-5b), 2.19 (s, 3H, OAc). Anal. Calcd
for C21H19FO6S: C, 60.28; H, 4.58. Found: C, 60.17; H, 4.37. ESIMS:
m/z 419.4 [M+H+].
1.4. Synthesis of 1-(30-deoxy-30-fluoro-40-O-acetyl-b-
D-
xylopyranosyl-20-ulose)thymine (15)
1.4.1. 3-Deoxy-3-fluoro-1,2-O-isopropylidene-4-O-benzoyl-5-
thio- -xylopyranose (10)
1.3.4. 1-(30-Deoxy-30-fluoro-20-O-benzoyl-40-O-acetyl-5-thio-b-
D-
xylopyranosyl)thymine (7)
A mixture of thymine (5.05 mmol, 0.63 g), hexamethyldisilaz-
ane (HMDS) (6.26 mmol, 1.3 mL), and saccharin (0.23 mmol,
40.1 mg) in dry CH3CN (18 mL) was refluxed for 30 min under
nitrogen. To this were added 3-deoxy-3-fluoro-1,2-O-benzoyl-4-
a-D
Compound 3 (6.24 mmol, 1.3 g) was dissolved in a mixture of
pyridine (30.8 mL) and BzCl (12.48 mmol, 1.46 mL). The reaction
was carried out at room temperature for 1 h and the mixture
was concentrated in vacuum. The residue was purified by flash
chromatography (6:4 hexane–EtOAc, Rf 0.32) to give 1.7 g (87%)
of compound 10 as a yellow syrup: ½a D22
ꢂ
+8 (c 0.1, CHCl3); kmax
O-acetyl-5-thio-D-xylopyranose (6) (3.61 mmol, 1.51 g) and SnCl4
(CHCl3) 242 nm (e
8757); 1H NMR (CDCl3, 400 MHz): d 8.07 (d,
(5.05 mmol, 0.59 mL). The reaction mixture was refluxed for 3 h,
neutralized with saturated sodium bicarbonate, and then ex-
tracted with TtOAc (2 ꢃ 250 mL). The organic extract was dried
over anhydrous sodium sulfate, filtered, and evaporated to dry-
ness. The residue was purified by flash chromatography (4:6
hexane–EtOAc, Rf 0.32) to give 1.04 g (68%) of compound 7 as
1H, Yarom benzoyl group), 7.58 and 7.45 (2 tr, 4H, Yarom benzoyl
group), 5.43–5.33 (m, 1H, H-4), 5.20 (d, 1H, J = 5.0 Hz, H-1), 4.68
(dtr, 1H, J = 49.8 Hz, J = 8.8 Hz, H-3), 4.47–4.40 (m, 1H, H-2),
3.02–2.97 (m, 1H, H-5a), 2.86–2.81 (m, 1H, H-5b), 1.63 (s, 3H,
CH3), 1.45 (s, 3H, CH3). Anal. Calcd for C15H17FO4S: C, 57.68; H,
5.49. Found: C, 57.47; H, 5.27. ESIMS: m/z 313.3 [M+H+].
a white foam: ½a 2D2
ꢂ
+38 (c 0.1, CHCl3); kmax (CHCl3) 260 nm (e
9700); 1H NMR (CDCl3, 400 MHz): d 8.05–7.15 (m, 6H, Ythymine
and benzoyl group), 5.92 (d, 1H, J = 10.6 Hz H-10), 5.73 (m, 1H,
H-20), 5.31–5.24 (m, 1H, H-40), 4.62 (dtr, 1H, J = 49.8 Hz,
J = 9.1 Hz, H-30), 3.11–3.02 (m, 1H, H-50b), 2.92–2.83 (m, 1H, H-
50a), 2.13 (s, 3H, OAc), 1.95 (s, 3H, 5-CH3). Anal. Calcd for
1.4.2. 3-Deoxy-3-fluoro-4-O-benzoyl-5-thio-D-xylopyranose
(11)
Thioxylopyranose 11 was synthesized from 10 by the similar
procedure as described for 5. It was purified by flash chromatogra-
phy (3:7 hexane–EtOAc, Rf 0.23) to give 1.32 g (89%) of diol 11 as a
colorless syrup: Anal. Calcd for C12H13FO4S: C, 52.93; H, 4.81.
Found: C, 52.82; H, 4.62. ESIMS: m/z 273.3 [M+H+].
C
19H19FN2O6S: C, 54.02; H, 4.53; N, 6.63. Found: C, 54.27; H,
4.73; N, 6.38. ESIMS: m/z 423.4 [M+H+].
1.3.5. 1-(30-Deoxy-30-fluoro-20-O-benzoyl-5-thio-b-
D-
1.4.3. 3-Deoxy-3-fluoro-1,2-O-acetyl-4-O-benzoyl-5-thio-D-
xylopyranosyl)thymine (8)
xylopyranose (12)
Compound 7 (2.46 mmol, 1.04 g) was dissolved in EtOH–pyr-
idine (25 + 7.4 mL), 2 M NaOH (4.9 mL) was added and the mix-
ture stirred at 0 °C for 30 min. Amberlite IR-120 (H+) was added
to neutralize the base. The suspension was filtered, the resin was
washed with EtOH and pyridine (50 + 50 mL), and the filtrate
was evaporated. The solid residue was purified by flash chroma-
tography (3:7 hexane–EtOAc, Rf 0.30) to give 0.54 g (58%) of
Compound 11 (4.77 mmol, 1.3 g) was dissolved in a mixture of
pyridine (23 mL) and Ac2O (4.3 mmol, 0.4 mL). The reaction was
carried out at room temperature for 1 h, and then was concen-
trated in vacuum. The residue was purified by flash chromatogra-
phy (6:4 hexane–EtOAc, Rf 0.35) to give 1.46 g (86%) of
compound 12 as a yellow syrup: ½a D22
ꢂ
+5 (c 0.1, CHCl3); kmax (CHCl3)
compound 8 as a white foam: ½a D22
ꢂ
+29 (c 0.1, CHCl3); kmax
244 nm (e
9147); 1H NMR (CDCl3, 400 MHz): d 8.20–7.96 and 7.72–
(CHCl3) 260 nm (
e
9137); 1H NMR (CDCl3, 400 MHz): d 8.13–
7.34 (m, 5H, benzoyl group), 6.14 (br s, 1H, H-1), 5.49–5.45 (m, 1H,
H-4), 5.41–5.37 (m, 1H, H-2), 4.90 (dtr, 1H, J = 51.1 Hz, J = 9.4 Hz,
H-3), 3.07–2.95 (m, 2H, H-50a and Y-50b), 2.19 (s, 3H, OAc), 2.09
(s, 3H, OAc). Anal. Calcd for C16H17FO6S: C, 53.93; H, 4.81. Found:
C, 53.87; H, 4.67. ESIMS: m/z 357.4 [M+H+].
7.21 (m, 5H, Yarom benzoyl group), 7.19 (s, 1H, H-6), 5.93 (d,
1H, J = 10.5 Hz, H-10), 5.74–5.65 (m, 1H, H-20), 4.45 (dtr, 1H,
J = 50.0 Hz, J = 8.9 Hz, H-30), 4.24–4.17 (m, 1H, H-40) 2.96–2.88
(m, 2H, H-50a and Y-50b), 1.92 (s, 3H, 5-CH3). Anal. Calcd for
C
17H17FN2O5S: C, 53.68; H, 4.50; N, 7.36. Found: C, 53.47; H,
4.33; N, 7.08. ESIMS: m/z 381.4 [M+H+].
1.4.4. 1-(30-Deoxy-30-fluoro-40-O-benzoyl-20-O-acetyl-5-thio-b-
D-
xylopyranosyl)thymine (13)
A mixture of thymine (5.72 mmol, 0.72 g), HMDS (6.26 mmol,
1.3 mL) and saccharin (0.26 mmol, 50 mg) in dry CH3CN (19 mL)
was refluxed for 30 min under nitrogen. To this were added 3-
1.3.6. 1-(30-Deoxy-30-fluoro-20-O-acetyl-b- -xylopyranosyl-40-
D
ulose)thymine (9)
deoxy-3-fluoro-1,2-O-acetyl-4-O-benzoyl-5-thio-D-xylopyranose
To a solution of 8 (1.42 mmol, 0.54 g) in dry CH2Cl2 (7.3 mL) was
added PDC (2.13 mmol, 0.8 g) and Ac2O (7.1 mmol, 0.67 mL). The
mixture was heated at 60 °C for 15 min, then cooled to room tem-
perature, EtOAc (1.6 mL) was added and the mixture was evapo-
rated to dryness. The residue was purified by flash
chromatography (4:6 hexane–EtOAc, Rf 0.4) to give 0.22 g (50%) of
(12) (4.09 mmol, 1.46 g) and SnCl4 (5.73 mmol, 1.02 mL). The reac-
tion mixture was refluxed for 3 h, neutralized with saturated so-
dium bicarbonate, and then extracted with TtOAc (2 ꢃ 250 mL).
The organic extract was dried over anhydrous sodium sulfate, fil-
tered, and evaporated to dryness. The residue was purified by flash
chromatography (4:6 hexane–EtOAc, Rf 0.34) to give 1.59 g (66%)
compound 9 as a foam: ½a D22
ꢂ
+20 (c 0.1, CHCl3); kmax (CHCl3)
of compound 13 as a white foam: ½a D22
ꢂ
+18 (c 0.1, CHCl3); kmax
260 nm (e
14548); IR (Neat); 1712 cmꢀ1 (keto group); 1H NMR
(CHCl3) 260 nm (e
10087); 1H NMR (CDCl3, 400 MHz): d 8.13–
(CDCl3, 400 MHz): d 7.26 (s, 1H, H-6), 6.37 (d, 1H, J = 10.7 Hz H-
10), 5.97 (m, 1H, J = 9.2 Hz, H-20), 5.03 (dtr, 1H, J = 48.1 Hz, H-30),
3.69–3.58 (m, 2H, H-50a and Y-50b), 2.18 (s, 3H, OAc), 1.97 (s, 3H,
5-CH3); 13C NMR (CDCl3, 100 MHz): d 193.4, 166.33, 163.01,
147.45, 139.17, 109.22, 95.32, 67.50, 62.55, 40.85, 20.66, 12.36;
19F NMR: d ꢀ65.0. Anal. Calcd for C12H13FN2O5S: C, 45.57; H, 4.14;
N, 8.86. Found: C, 45.74; H, 4.38; N, 8.78. ESIMS: m/z 317.4 [M+H+].
8.04 and 7.62–7.19 (m, 6H, Ythymine and benzoyl group), 5.82 (d,
1H, J = 10.6 Hz, H-10), 5.55 (m, 1H, H-20), 5.48–5.41 (m, 1H, H-40),
4.67 (dtr, 1H, J = 49.8 Hz, J = 9.1 Hz, H-30), 3.18–3.13 (m, 1H, H-
50b), 2.94–2.89 (m, 1H, H-50a), 2.06 (s, 3H, OAc), 1.96 (s, 3H, 5-
CH3). Anal. Calcd for C19H19FN2O6S: C, 54.02; H, 4.53; N, 6.63.
Found: C, 54.31; H, 4.27; N, 6.82. ESIMS: m/z 423.4 [M+H+].

E. Tsoukala et al. / Carbohydrate Research 346 (2011) 2011–2015
2015
1.4.5. 1-(30-Deoxy-30-fluoro-40-O-benzoyl-5-thio-b-
D-
xylopyranosyl)thymine (14)
2. Zhou, W.; Gumina, G.; Chong, Y.; Wang, J.; Schinazi, R. F.; Chu, C. K. J. Med.
Chem. 2004, 47, 3399–3408.
3. Komiotis, D.; Manta, S.; Tsoukala, E.; Tzioumaki, N. Curr. Med. Chem. Anti-Infect.
Agents 2008, 7, 219–244.
4. Van Rompay, A. R.; Johansson, M.; Karlsson, A. Pharmacol. Ther. 2003, 100,
119–139.
5. Brady, R. C.; Bernstein, D. I. Antiviral Res. 2004, 61, 73–81.
6. Zhou, X. X.; Littler, E. Curr. Top. Med. Chem. 2006, 6, 851–865.
Compound 13 (3.31 mmol, 1.4 g) was dissolved in EtOH–pyri-
dine (33 + 9.9 mL), 2 M NaOH (6.7 mL) was added and the mixture
stirred at 0 °C for 30 min. Amberlite IR-120 (H+) was added to neu-
tralize the base. The suspension was filtered, the resin was washed
with EtOH and pyridine (65 + 65 mL), and the filtrate was evapo-
rated. The solid residue was purified by flash chromatography
(3:7 hexane–EtOAc, Rf 0.32) to give 0.72 g (57%) of compound 14
´
ˇ
7. Manta, S.; Agelis, G.; Botic, T.; Cencic, A.; Komiotis, D. Bioorg. Med. Chem. 2007,
15, 980–987.
ˇ
8. Manta, S.; Agelis, G.; Botic´, T.; Cencic, A.; Komiotis, D. Eur. J. Med. Chem. 2008,
43, 420–428.
as a white foam: ½a D22
ꢂ
+11 (c 0.1, CHCl3); kmax (CHCl3) 260 nm (e
9. Spanou, C.; Manta, S.; Komiotis, D.; Dervishi, A.; Kouretas, D. Int. J. Mol. Sci.
2007, 8, 695–704.
10. Balatsos, N. A. A.; Vlachakis, D.; Maragozidis, P.; Manta, S.; Anastasakis, D.;
Kyritsis, A.; Vlassi, M.; Komiotis, D.; Stathopoulos, C. Biochemistry 2009, 48,
6044–6051.
11. Tsirkone, G. V.; Tsoukala, E.; Lamprakis, C.; Manta, S.; Hayes, M. J.; Skamnaki, T.
V.; Drakou, C.; Zographos, E. S.; Komiotis, D.; Leonidas, D. D. Bioorg. Med. Chem.
2010, 18, 3413–3425.
12. Tzioumaki, N.; Tsoukala, E.; Manta, S.; Agelis, G.; Balzarini, J.; Komiotis, D. Arch.
Pharm. 2009, 342, 353–360.
9960); 1H NMR (CDCl3, 400 MHz): d 8.13–7.21 (m, 6H, Ythymine
and benzoyl group), 5.93 (d, 1H, J = 10.5 Hz, H-10), 5.75–5.62 (m,
1H, H-40), 4.41 (dtr, 1H, J = 49.8 Hz, J = 9.0 Hz, H-30), 4.19–4.11
(m, 1H, H-20), 2.96–2.88 (m, 2H, H-50a and Y-50b), 1.97 (s, 3H, 5-
CH3). Anal. Calcd for C17H17FN2O5S: C, 53.68; H, 4.50; N, 7.36.
Found: C, 53.72; H, 4.64; N, 7.53. ESIMS: m/z 381.4 [M+H+].
13. Tzioumaki, N.; Manta, S.; Tsoukala, E.; Voorde, V. J.; Liekens, S.; Komiotis, D.;
Balzarini, J. Eur. J. Med. Chem. 2011, 46, 993–1005.
14. Manta, S.; Tzioumaki, N.; Tsoukala, E.; Panagiotopoulou, A.; Pelecanou, M.;
Balzarini, J.; Komiotis, D. Eur. J. Med. Chem. 2009, 44, 4764–4771.
15. Manta, S.; Tsoukala, E.; Tzioumaki, N.; Kiritsis, C.; Balzarini, J.; Komiotis, D.
Bioorg. Chem. 2010, 38, 48–55.
16. Robina, I.; Vogel, P.; Witczak, J. Z. Curr. Org. Chem. 2001, 5, 1177–1214 and
references cited therein.
17. Tsoukala, E.; Manta, S.; Tzioumaki, N.; Agelis, G.; Komiotis, D. Carbohydr. Res.
2008, 343, 1099–1103.
18. Yokoyama, M. Synthesis 2000, 1637–1655.
19. Zheng, F.; Zhang, X.-H.; Qiu, X.-L.; Zhang, X.; Qing, F.-L. Org. Lett. 2006, 8, 6083–
6086 and references cited therein.
20. Uenishi, J.; Ohmiya, H. Tetrahedron 2003, 59, 7011–7022 and references cited
therein.
21. Gunaga, P.; Moon, R. H.; Choi, J. W.; Shin, H. D.; Park, G. J.; Jeong, S. L. Curr. Med.
Chem. 2004, 11, 2585–2637.
1.4.6. 1-(30-Deoxy-30-fluoro-40-O-acetyl-b- -xylopyranosyl-20-
D
ulose)thymine (15)
To a solution of 14 (1.42 mmol, 0.54 g) in dry CH2Cl2 (7.3 mL)
was added PDC (2.13 mmol, 0.8 g) and Ac2O (7.1 mmol, 0.67 mL).
The mixture was heated at 60 °C for 30 min, then cooled to room
temperature, EtOAc (1.6 mL) was added and the mixture was evap-
orated to dryness. The residue was purified by flash chromatogra-
phy (4:6 hexane–EtOAc, Rf 0.38) to give 0.28 g (52%) of compound
15 as a foam: ½a 2D2
ꢂ
+17 (c 0.1, CHCl3); kmax (CHCl3) 260 nm (e
15609); IR (Neat); 1720 cmꢀ1 (keto group); 1H NMR (CDCl3,
400 MHz): d 7.21 (s, 1H, H-6), 6.07 (d, 1H, J = 10.6 Hz, H-10), 5.75
(m, 1H, J = 9.1 Hz, H-40), 4.83 (dtr, 1H, J = 48.0 Hz, H-30) 3.58–3.43
(m, 2H, H-50a and Y-50b), 2.17 (s, 3H, OAc), 1.96 (s, 3H, 5-CH3);
13C NMR (CDCl3, 100 MHz): d 195.05, 171.60, 163.00, 147.22,
137.54, 112.23, 98.57, 66.39, 64.61, 30.31, 20.84, 12.36; 19F NMR:
d ꢀ63.2. Anal. Calcd for C12H13FN2O5S: C, 45.57; H, 4.14; N, 8.86.
Found: C, 45.69; H, 4.08; N, 8.97. ESIMS: m/z 317.4 [M+H+].
22. Yoshimura, Y.; Kitano, K.; Yamada, K.; Satoh, H.; Watanabe, M.; Miura, S.;
Sakata, S.; Sasaki, T.; Matsuda, A. J. Org. Chem. 1997, 62, 3140–3152.
23. Miura, S.; Yoshimura, Y.; Endo, M.; Machida, H.; Matsuda, A.; Tanaka, M.;
Sasaki, T. Cancer Lett. 1998, 129, 103–110.
24. Milecki, J.; Foldesi, A.; Fischer, A.; Adamiak, R. W.; Chattopadhyaya, J. J. Labelled
Compd. Radiopharm. 2001, 44, 763–783.
25. Gosselin, G.; Bergogne, M. C.; Imbach, J. L. Nucleosides Nucleotides 1984, 3, 265–
275.
26. Kondo, Y. Carbohydr. Res. 1982, 107, 303–311.
Acknowledgments
27. Santoyo-González, F.; Uriel, C.; Calvo-Asín, J. A. Synthesis 1998, 1787–1792.
28. Viña, D.; Wu, T.; Renders, M.; Laflammeb, G.; Herdewijn, P. Tetrahedron 2007,
63, 2634–2646.
29. Vanheusden, V.; Busson, R.; Herdewijn, P.; Van Calenbergh, S. J. Org. Chem.
2004, 69, 4446–4453.
30. Leclercq, F.; Antonakis, K. Carbohydr. Res. 1989, 193, 307–313.
31. Vorbruggen, H.; Hofle, G. Chem. Ber. 1981, 114, 1256–1268.
32. Albright, J. D.; Goldman, L. J. Org. Chem. 1965, 30, 1107–1110.
33. Pfitzner, K. E.; Moffatt, J. G. J. Am. Chem. Soc. 1965, 87, 5661–5670.
34. Garegg, P. J.; Samuelsson, B. Carbohydr. Res. 1978, 67, 267–270.
35. Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651–1660.
36. Dess, D. B.; Martin, J. C. J. Org. Chem. 1983, 48, 4155–4156.
37. Serafinowski, P. J.; Barnes, C. L. Tetrahedron 1996, 52, 7929–7938.
This work was supported in part by the Postgraduate Pro-
grammes ‘Biotechnology-Quality assessment in Nutrition and the
Environment’, ‘Application of Molecular Biology-Molecular Genet-
ics-Molecular Markers’, Department of Biochemistry and Biotech-
nology, University of Thessaly.
References
1. Plunkett, W.; Gandhi, V. Purine and Pyrimidine Nucleoside Analogues; in: G.
Giaccone, R. Schilsky, P. Sondel (Eds.), Cancer Chemotherapy and Biological
Response Modifiers, Elsevier Science B. V., 2001. pp. 21–45.