Preparation of C5-substituted O6,5′-cyclouridine

Article abstract of DOI:10.1016/j.tet.2009.02.077

The synthesis of hitherto unknown C5-substituted O⁶,5′-cyclouridines is described. The 2′,3′-isopropylidene-uridine was treated with N-halogenosuccinimides forming appropriate bridged 5-halogeno derivatives. Using lithiation method, bromine sub

Full text of DOI:10.1016/j.tet.2009.02.077

Tetrahedron 65 (2009) 4053–4059
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Preparation of C5-substituted O6,50-cyclouridine
,
Adam Mieczkowski a, Pauline Peltier a, Thomas Zevaco b, Luigi A. Agrofoglio a
*
a Institut de Chimie Organique et Analytique, UMR CNRS 6005, Universite´ d’Orle´ans, BP 6759, 45067 Orle´ans Cedex 2, France
b Forschungszentrum Karlsruhe (FZK), Postfach 3640, Karlsruhe D-76021, Germany
a r t i c l e i n f o
a b s t r a c t
The synthesis of hitherto unknown C5-substituted O6,50-cyclouridines is described. The 20,30-iso-
propylidene-uridine was treated with N-halogenosuccinimides forming appropriate bridged 5-halogeno
derivatives. Using lithiation method, bromine substituent at C5 position was exchanged into various alkyl
and alkenyl derivatives.
Article history:
Received 26 January 2009
Received in revised form 19 February 2009
Accepted 19 February 2009
Available online 5 March 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
the halogenation of nucleosides with N-halogenosuccinimides,14
after treatment of 5-iodonucleosides with alkoxides,15 or during
Modified nucleosides and nucleotides exhibit broad spectrum of
biological activities.1–5 Cyclonucleosides, compounds with great
structural similarity to classical nucleosides, but bearing additional
linkage between the heterocyclic ring and the sugar moiety, are
known from early fifties. The first cyclic purine nucleoside was
synthesized by Todd et al.6 in 1951 meanwhile the first pyrimidine
cyclonucleoside possessing a O6,50-anhydro linkage, the 5,5-diiodo-
5,6-dihydro-20-deoxy-O6,50-cyclouridine (1), was obtained by
Chang et al.7 in 1963 as a minor product during the investigation of
20-deoxycytidine iodination. The bridged structure was correctly
assigned two years later and further transformations of novel
compound leading to new bridged derivatives 2a,b were de-
scribed.8 Since then, the synthesis and properties of compounds
with O6,50-cyclopyrimidines have been reported.9 Those com-
pounds are mainly use as intermediates for the synthesis of various
nucleosides such as the anti-HIV stavudine.10 More recently, Schi-
nazi et al. reported11 a novel nucleoside-based N-cyclic compound,
which exhibited a potent in vitro anti-HCV activity, meanwhile Len
et al. reviewed the synthesis of C–C bridge cyclonucleosides.12
Additionally, multibridged nucleosides, e.g., 3, possessing O6,20- or
O6,30-bridge together with O6,50-bridge were also synthesized.13
Thus, based on our on-going research program, we decided to
report herein the synthesis of hitherto unknown cyclonucleoside
derivatives type 4, bearing a O6,50-anhydro bridge for potential
antiviral activities (Fig. 1).
treatment of protected pyrimidine nucleosides with lead tetraace-
tate.16 Sekine et al.17 observed the formation of O6,50-bridge during
the deoxygenation of thymidine derivatives, while Hirota et al.18
obtained the O6,50-cyclourididine derivatives during the oxidative
coupling of 20,30-isopropylideneuridine with methyl acrylate.
Thus, starting from halogenation of the 20,30-isopropylide-
neuridine (5), with excess of N-halogenosuccinimide,19 the 5,5-
dihalogeno nucleosides 6–8 were obtained in moderate yields,
respectively (Scheme 1). Compounds 7 and 8 were directly treated
with 1 M NaOH to the corresponding 5-halogeno derivatives 10
and 11, respectively.
In contrast, the dichloro intermediate 6 turns out to be stable in
basic conditions, at rt, and cannot be directly transformed into its
50-monochloroderivative 9. Dichlorinated analogue 6 has been
O
N
O
N
I
R
NH
NH
I
O
O
O
O
O
O
R=I, H
HO
X
HO
1
2a-b
O
O
R
O
NH
O
NH
X
O
2. Results and discussion
N
O
N
O
O
O
Early investigations10 showed that the O6,50-bridge is reversibly
formed in basic solutions of 20,30-O-isopopylideneuridine, during
HO
X=F, Br
3a-b
HO
OH
R=halogen, alkyl
4
* Corresponding author. Tel.: þ33 (0)2 3849 4582.
Figure 1.
E-mail address: luigi.agrofoglio@univ-orleans.fr (L.A. Agrofoglio).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.02.077

4054
A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
O
N
O
O
N
O
O
X
X
6
2’
3’
4’ 5’a
5’b
NH
NH
NH
X
O
O
O
O
N
O
O
a
O
b
O
O
HO
O
O
O
5
6 X=Cl
7 X=Br
8 X=I
9 X=Cl (not obtained)
10 X=Br (52%)
11 X=I (59%)
6
5’b
5’a
3’
Scheme 1. Reagents and conditions: (a) 3 equiv of NXS, DMF, rt, overnight; (b) 1 M
NaOH, 30 min, then 1 M HCl to pH¼7.
1’
4’
2’
O
N
O
O
N
O
Cl
Cl
Cl
Cl
NH
NH
H
O
O
O
O
H
O
O
O
O
6b, minor
6a, major
Figure 2.
isolated as a mixture of two diastereoisomers, a major one 6a and
a minor isomer 6b in a ratio 84:16 (Fig. 2).
Figure 4. 2D-NOESY of 6a with 3D view of the molecule.
These compounds were separated by column chromatography
with a total yield of 51%. Interestingly the two compounds crys-
tallized differently out of a CDCl3 solution: compound 6a yields fine
agglomerated needles whereas compound 6b afforded thin paral-
lelograms. A detailed NMR analysis allowed us to determine the
stereochemistry of 6a and 6b, respectively. 2D-NOESY spectra (re-
laxation delay 1 s, mixing time 800 ms) allowed the unequivocally
characterization 6a and 6b.
In the NOESY spectrum of 6b (Fig. 3) NOE interactions can be
clearly seen involving H6 proton (s at 4.44 ppm partly overlapping
the signal of H40) and both H20 (d at 4.80, 5.6 Hz) and H30 protons (d
at 4.68, 5.6 Hz) as it might be expected if one considers the con-
strained seven-membered ring involving cyclouridine and nucleo-
side. Protons H20 and H30 also display some weak interactions with
one of the methyl groups of the protecting ketal group. In addition,
weakercorrelations can be also seen between the H40 proton and the
protons of the bridging methylene group (H50a at 3.86 ppm, d,
12.7 Hz and H50b at 4.11 ppm, dd, 12.4 and 6 Hz) and between H30
and H50a. The latter weak cross peak allows quite precisely to dis-
tinguish between H20 and H30 and also to individually attribute the
signals of protons H50a and H50b of the methylene bridge.
3’ 2’ 4’ 5’b
6
5’a
The assignment of 1H and 13C NMR signals was confirmed based
on 1H, 13C, 1H–1H COSY, 1H, 13C COSY (gHMQC) and 1H, 13C-long
range correlation spectra (gHMBC).
In the NOESY spectrum of 6a (Fig. 4) the NOE contacts involving
H6 and H20 and H30 found in the spectrum of 6b are clearly missing.
Proton H6 strongly interacts with one proton (H50b) of the bridging
methylene group at 3.83 ppm (dd, 12.8 and 1.9 Hz) and, at a lesser
extend, with protons H40 (d, 1.8 Hz) and H10 (s, 6.33 ppm, not dis-
played on the figure). To supplement this, protons H20 and H30
clearly show correlation peaks with proton H50a and one of the
methyl group of the ketal protecting group.
5’b
6
5’a
1’
To obtain the desired 5-chloro-20,30-isopropylidene-O6,50-cyclo-
uridine (9), we have firstly hydrogenated the bromoderivative 10 to
the 20,30-isopropylidene-O6,50-cyclouridine(12),8 whichby treatment
with sulfuryl chloride20 (or NCS)13c gave 9 in 60% yield (Scheme 2).
4’
2’
3’
O
O
N
O
O
Br
Cl
O
NH
NH
NH
O
O
N
O
O
a
76%
b
60%
O
N
O
O
O
O
O
O
O
O
10
12
9
Scheme 2. Reagents and conditions: (a) H2/Pd/C, THF, pyridine; (b) SO2Cl2, CH2Cl2, rt,
Figure 3. 2D-NOESY of 6b with 3D view of the molecule.
overnight.

A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
4055
R2
O
N
O
R2
O
O
O
N
O
X
X
NH
R3
NH
NH
NH
R3
NH
R1
O
b
a
R1
O
O
O
O
a
N
O
O
O
N
O
O
O
N
O
O
O
O
O
(for 14)
O
O
O
HO
OH
HO
OH
O
16 (85%)
21 R1=R2=R3=H
9 X=Cl
10 X=Br
11 X=I
13 X=Cl (52%)
14 X=Br (40%)
15 X=I (49%)
25 R1=R2=R3=H
95%
93%
92%
22 R1=R2=H, R3=Me
23 R1=Me, R2=R3=H
26 R1=R2=H, R3=Me
27 R1=Me, R2=R3=H
Scheme 3. Reagents and conditions: (a) TFA/H2O 1:1; (b) H2/Pd/C, TEA, MeOH.
Scheme 5. Reagents and conditions: (a) Pd/C/H2, THF.
The obtained halogenated 20,30-isopropylidene-O6,50-cyclo-
uridine derivatives 6, 9–11 were then deprotected with 50% TFA
(Scheme 3) to 13–16, respectively, in yields ranging from 40% to
52%. The O6,50-cyclouridine (16) cannot be obtained from 12 as,
under acidic conditions, it is converted to the barbituric nucleosi-
de.15a,b Thus, to obtain the O6,50-cyclouridine (16), the bromoder-
ivative 14 was hydrogenated.8
O
O
R
R
O
NH
NH
a
O
N
O
O
O
N
O
O
O
Having halogenated O6,50-cyclouridine derivatives, we decided
to synthesize some 5-alkyl- and 5-alkenyl-derivatives of
O6,50-cyclouridine through a lithiation/alkylation step.21 For this
purpose, the 50-bromoderivative 10 was treated with 1 equiv NaH
and 2 equiv of BuLi followed by addition of 5 equiv of appropriate
nucleophile (Scheme 4). 5-Substitued derivatives 18–23 were
obtained with moderate yields together with various amount of
dehalogenated nucleoside 12. When using propyl iodide, no re-
action was observed except the dehalogenation of 10 to 12. When
4-chlorobenzyl bromide was applied, only the N-alkylated product
24 was isolated.
HO
OH
28 R=Me (76%)
29 R=Et (37%)
30 R=Bn (47%)
31 R=All (45%)
32 R=Crot (55%)
33 R=nPr (77%)
34 R=nBu (51%)
35 R=iBu (65%)
18 R=Me
19 R=Et
20 R=Bn
21 R=All
22 R=Crot
25 R=nPr
26 R=nBu
27 R=iBu
Scheme 6. Reagents and conditions: (a) 10% TFA in H2O, 1 h, 70 ꢀC.
For all cyclonucleosides, characteristic AB systems were ob-
served by 1H NMR data. For protected compounds, two AB systems
appeared, e.g., for C50 protons and for C20/C30 protons. For depro-
tected compounds, only AB system for C50 protons still existed,
while C20/C30 protons usually had identical shifts giving one
multiplet.
The introduction of alkenyl substituent at C5 position is of in-
terest as it can make possible further transformations of the
bridged molecule such as addition to the double bound. Because
the lithiation method allowed only the synthesis of methyl, ethyl,
and benzyl but not the propyl derivative, other 5-alkyl homologues
were obtained through the hydrogenation of alkenyl derivatives
such as 21–23. Compounds 25–27 were then obtained (Scheme 5).
All obtained alkyl and allyl derivatives 18–22 and 25–27 were
successfully deprotected with 10% TFA solution to final products
28–35 with moderate to high yield (Scheme 6).
3. Conclusion and perspectives
Finally, some O6,50-cyclouridine derivatives bearing halogeno-,
alkyl- and allyl-substituents at C5 position were synthesized. Ap-
plied method allowed synthesizing compounds with moderate
yield. No activity against HCV was found. Future modifications of 5-
halo-O6,50-cyclouridines under Pd(0) conditions will be reported
elsewhere.
O
N
O
O
N
Br
O
Li
O
NH
NNa
O
O
a
b
O
O
4. Experimental
4.1. General
Cl
O
O
O
O
O
10
17
O
Commercially available chemicals were used as received.
Reactions were monitored by thin-layer chromatography (TLC)
analysis using silica gel plates (Kieselgel 60 F254). Compounds were
visualized by UV irradiation and/or spraying with ethanol solution
(2.5%) in phosphomolybdic acid, followed by charring at 150 ꢀC.
Column chromatography was performed on silica gel 60 M (0.040–
0.063 mm).
O
N
O
R
O
N
NH
O
NH
O
O
O
N
O
N
O
O
+
O
O
O
O
O
The 1H and 13C NMR spectra were recorded on a Bruker
AVANCE DPX 250 (1H: 249.88 MHz, 13C: 62.84 MHz) and Varian
Inova Unity 400 spectrometer (1H 399.91 MHz, 13C: 100.54 MHz)
in DMSO-d6 or mixture of CDCl3/DMSO-d6. The NMR spectra
were recorded at rt. The chemical shifts are given in parts per
million relative to the residual signal of the solvent, TMS being
used as calibration standard with different deuterated solvents.
12
24
18 R=Me (54%)
19 R=Et (33%)
20 R=Bn (51%)
21 R=All (34%)
22 R= Crot (34%)
23 R=Methall (39%)
Scheme 4. Reagentsandconditions:(a)1 equiv NaH,10 min, rt, THFthen2 equiv BuLi, ꢁ78 ꢀC;
(b) 5 equiv nucleophile RI.

4056
A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
Signals are reported as s (singlet), d (doublet), dd (doublet of
doublet), t (triplet), q (quartet), qi (quintuplet), and m (multiplet)
with the relevant coupling constants J in hertz. For protected
compounds to differentiate signals from aliphatic chain and
isopropylidene group: i signals derived from isopropylidene
group, c signals from aliphatic chain in C5 position. Polarity index
was measured on Perkin–Elmer Model 341 polarimeter. Evidence
of purity has been done from a proton-decoupled 13C NMR
spectrum with a signal-to-noise ratio sufficient to permit seeing
peak with 5% of the intensity of the strongest peak.
(C2), 157.9 (C6), 159.5 (C4); HRMS (ESI): m/z calcd for
C
12H13BrN2O6Na (MþþNa): 384.1382, found: 384.1379.
4.3.2. 5-Iodo-20,30-isopropylidene-O6,50-cyclouridine (11)
[
a
]
þ72 (c 1.0, CH2Cl2). 1H NMR (250 MHz, DMSO-d6): 1.29
D
(s, 3H, CH3i),1.42 (s, 3H, CH3i), 4.02 (d,1H, J¼12.2 Hz, H50), 4.51–4.53
(m, 2H, H40, H50), 4.91 (d, 1H, J¼5.3 Hz, H30), 5.00 (d, 1H, J¼5.3 Hz,
H20), 6.25 (1H, s, H10), 11.71 (s, 1H, NH); 13C NMR (62 MHz, DMSO-
d6): 24.6 (CH3i), 25.9 (CH3i), 60.9 (C5), 76.8 (C50), 81.7 (C20), 83.4
(C40), 84.3 (C30), 89.4 (C10), 111.5 (CIVi), 149.4 (C2), 160.0 (C6), 161.1
(C4); HRMS (ESI): m/z calcd for C12H13IN2O6Na (MþþNa): 431.1387,
found: 431.1384.
4.2. Procedure for synthesis of dichloroderivative (6a, 6b)
4.3.3. 5-Chloro-20,30-isopropylidene-O6,50-cyclouridine (9)
3 g of 5-bromo-O6,50-cyclo-20,30-O-isopropylidene uridine (10)
(8.32 mmol, 1 equiv) was dissolved in 50 ml of THF, then 3.47 ml
(24.96 mmol, 3 equiv) of TEA was added followed by 100 mg of of
Pd/C. Hydrogen was connected and reaction mixture was stirred
overnight at rt. Solvent were evaporated and the residue purified by
liquid chromatography on silica gel (petroleum ether/EtOAc, 4:6) to
give 1.78 g of 12 as a white solid.
5 g of 20,30-isopropylideneuridine was dissolved in 150 ml of dry
DMF, then 3 equiv of NCS was added. Reaction mixture was stirred
overnight at rt then the solvent was evaporated and the residue
purified by liquid column chromatography on silica gel yielding
2.70 g of 6a and 0.53 g of 6b, respectively.
4.2.1. 5,5-Dichloro-5,6-dihydro-20,30-isopropylidene-O6,50-
cyclouridine (6a, major)
Physico-chemical data of 12: [
a]
þ77 (c 1.0, CH2Cl2). 1H NMR
D
[
a
]
ꢁ61 (c 1.0, CH2Cl2). 1H NMR (400 MHz, DMSO-d6): 1.27 (s,
D
(400 MHz, DMSO-d6): 1.28 (s, 3H, CH3i), 1.42 (s, 3H, CH3i), 3.98 (dd,
1H, J1¼0.9 Hz, J2¼12.8 Hz, H50), 4.56–4.63 (m, 2H, H40, H50), 4.89 (d,
H, J¼5.6 Hz, H30), 4.95 (d, H, J¼5.6 Hz, H20), 5.27 (1H, s, H5), 6.25
(1H, s, H10), 11.39 (s, 1H, NH); 13C NMR (100 MHz, DMSO-d6): 24.3
(CH3i), 25.9 (CH3i), 77.2 (C50), 81.6 (C20), 83.3 (C40), 84.4 (C30), 88.8
(C10), 89.7 (C5), 111.5 (CIVi), 149.9 (C2), 161.0 (C6), 163.1 (C4); HRMS
(ESI): m/z calcd for C12H14N2O6Na (MþþNa): 305.2421, found:
305.2418.
3H, CH3i), 1.42 (s, 3H, CH3i), 3.79 (dd, 1H, J1¼1.6, 12.6 Hz, H50), 4.40
(d, 1H, J¼12.6 Hz, H50), 4.54 (s, 1H, H40), 4.68 (d, 1H, J¼5.8 Hz, H30),
4.89 (d, 1H, J¼5.8 Hz, H20), 5.62 (s, 1H, H6), 6.11 (1H, s, H10), 11.53
(s, 1H, NH); 13C NMR (100 MHz, DMSO-d6): 24.4 (CH3i), 26.2 (CH3i),
76.1 (C50), 81.2 (C5), 82.1 (C20), 84.6 (C40), 86.0 (C30), 89.3 (C6), 90.5
(C10), 111.5 (CIVi), 148.8 (C2), 160.8 (C4); HRMS (ESI): m/z calcd for
C12H14Cl2N2O6Na (MþþNa): 376.1475, found: 376.1472.
1.7 g (6.0 mmol,1 equiv) of 12 was dissolved in CH2Cl2, then 0.54
(6.6 mmol, 1.1 equiv) of sulfuryl chloride was added. The reaction
mixture was stirred overnight in rt. Next day solvent was evapo-
rated and product was purified by chromatography using 1% MeOH
in CH2Cl2 to yield 1.13 g of 9 (60%).
4.2.2. 5,5-Dichloro-5,6-dihydro-20,30-isopropylidene-O6,50-
cyclouridine (6b, minor)
[
a
]
D þ29 (c 1.0, DMF). 1H NMR (400 MHz, DMSO-d6): 1.20 (s, 3H,
CH3i), 1.42 (s, 3H, CH3i), 3.94 (d, 1H, J2¼12.4 Hz, H50), 4.06 (dd, 1H,
J1¼6.2, 12.4 Hz, H50), 4.47 (d, 1H, H40), 4.83 (d, 1H, J¼5.7 Hz, H20),
5.20 (d, 1H, J¼5.7 Hz, H30), 5.22 (s, 1H, H6), 5.96 (1H, s, H10), 11.81
(s, 1H, NH); 13C NMR (100 MHz, DMSO-d6): 24.1 (CH3i), 25.6 (CH3i),
70.0 (C50), 77.7 (C5), 82.4 (C20), 84.0 (C40), 85.7, 89.9 (C30, C6), 89.2
(C10), 111.3 (CIVi), 151.0 (C2), 160.9 (C4); HRMS (ESI): m/z calcd for
C12H14Cl2N2O6Na (MþþNa): 376.1475, found: 376.1474.
Physico-chemical data of 9: [
a
]
þ80 (c 1.0, CH2Cl2). 1H NMR
D
(250 MHz, DMSO-d6): 1.29 (s, 3H, CH3i),1.42 (s, 3H, CH3i), 4.16 (d,1H,
J¼12.3 Hz, H50), 4.64 (s,1H, H40), 4.73 (d,1H, J¼12.3 Hz, H50), 4.94 (d,
1H, J¼5.6 Hz, H30), 5.00 (d, 1H, J¼5.6 Hz, H20), 6.25 (1H, s, H10), 11.88
(s, 1H, NH); 13C NMR (62 MHz, DMSO-d6): 24.3 (CH3i), 25.9 (CH3i),
77.6 (C50), 81.6 (C20), 83.5 (C40), 84.3 (C30), 89.7 (C10), 96.2 (C5), 111.5
(CIVi), 148.3 (C2), 156.9 (C6), 159.3 (C4); HRMS (ESI): m/z calcd for
C12H13ClN2O6Na (MþþNa): 339.6869, found: 339.6867.
4.3. General procedure for bromination or iodination
of uridine
4.4. General procedure for deprotection of halogenated
derivatives (6, 9–11)
1 equiv of 20,30-isopropylideneuridine (5) was dissolved in DMF
(50 mL), then 3 equiv of appropriate N-halogenosuccinimide
(either NBS or NIS) was added. The reaction mixture was stirred
overnight at rt, then the solvents were co-evaporated with toluene
(3ꢂ20 mL). The 5,5-dihaloderivatives (7 or 8) were purified by
precipitation with water. NMR showed that further purification is
not required. The 5,5-dibromoderivative 7 and the 5,5-diiododer-
ivative 8 were not isolated, but directly treated with large excess
of 1 M NaOH. The solution was neutralized with 1 M HCl and the
5-bromo derivative 10 and 5-iododerivative 11 precipitated, re-
spectively. After filtration, compounds were dried under reduced
pressure and used in the next steps without any further
purification.
Isopropylidene derivatives were, respectively, treated with 1 M
HCl (for 6) or with 50% TFA in H2O (for 9–11). The reaction mixture
was stirred at rt, then solvent was evaporated. Because of poor
solubility of final products, the residues were washed several times
with methanol, dried under the vacuum pump. Products 13–16
were obtained in a pure form, respectively.
4.4.1. 5-Chloro-O6,50-cyclouridine (13)
[
a
]
þ101 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 4.08 (d,
D
1H, J¼12.4 Hz, H50), 4.28–4.38 (m, 2H, H20, H30), 4.41 (s, 1H, H40),
4.69 (d, 1H, J¼12.4 Hz, H50), 4.93 (br s, 20OH, 30OH), 6.18 (s, 1H, H10),
13
11.84 (s, 1H, NH); C NMR (62 MHz, DMSO-d6): 71.9 (C30), 76.4
4.3.1. 5-Bromo-20,30-isopropylidene-O6,50-cyclouridine (10)
(C20), 77.7 (C50), 86.5 (C40), 92.3 (C10), 96.3 (C5), 148.2 (C2), 157.3
(C6),159.3 (C4); HRMS (ESI): m/z calcd for C9H9ClN2O6Na (MþþNa):
299.6223, found: 299.6219.
[
a
]
þ80 (c 1.0, CH2Cl2). 1H NMR (250 MHz, DMSO-d6): 1.28
D
(s, 3H, CH3i), 1.42 (s, 3H, CH3i), 4.12 (d, 1H, J¼12.3 Hz, H50), 4.64
(s, 1H, H40), 4.71 (d, 1H, J¼12.3 Hz, H50), 4.94 (d, 1H, J¼5.6 Hz, H30),
5.00 (d, 1H, J¼5.6 Hz, H20), 6.26 (1H, s, H10), 11.85 (s, 1H, NH); 13C
NMR (62 MHz, DMSO-d6): 24.3 (CH3i), 25.9 (CH3i), 77.3 (C50), 81.6
(C20), 83.5 (C40), 84.3 (C30), 85.6 (C5), 89.7 (C10), 111.5 (CIVi), 148.7
4.4.2. 5-Bromo-O6,50-cyclouridine (14)
[
a
]
þ93 (c 1.0, DMF). 1H NMR (400 MHz, DMSO-d6): 4.05 (dd,
D
1H, J1¼0.8, 12.4 Hz, H50), 4.24–4.38 (m, 2H, H20, H30), 4.41 (s, 1H,

A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
4057
H40), 4.67 (dd,1H, J1¼0.9,12.4 Hz, H50), 5.24 (d, 1H, J1¼4.1 Hz, 30OH),
5.44 (d, 1H, J1¼6.8 Hz, 20OH), 6.19 (s, 1H, H10), 11.80 (s, 1H, NH); 13C
NMR (100 MHz, DMSO-d6): 71.9 (C30), 76.4 (C20), 77.7 (C50), 86.5
(C40), 85.7 (C5), 92.3 (C10), 148.8 (C2), 158.3 (C6), 159.5 (C4); HRMS
(ESI): m/z calcd for C9H9BrN2O6Na (MþþNa): 344.0736, found:
344.0735.
24.6 (CH3i), 26.2 (CH3i), 77.1 (C50), 82.4 (C20), 84.0 (C40), 85.6 (C30),
89.9 (C10), 104.9 (C5), 113.0 (CIVi), 149.0 (C2), 157.0 (C6), 163.6 (C4);
HRMS (ESI): m/z calcd for C14H18N2O6Na (MþþNa): 333.2957,
found: 333.2956.
4.6.3. 5-Benzyl-20,30-isopropylidene-O6,50-cyclouridine (20)
[a
]
D þ115 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.32 (s, 3H,
4.4.3. 5-Iodo-O6,50-cyclouridine (15)
CH3i), 1.50 (s, 3H, CH3i), 3.48–3.52 (m, 2H, CH2c), 3.93 (d,
1H, J¼14.5 Hz, H50), 4.27 (dd, 1H, J1¼1.1 Hz, J2¼12.5 Hz, H50), 4.60
(s, 1H, H40), 4.90 (d, 1H, J¼5.6 Hz, H30), 4.91 (d, 1H, J¼5.6 Hz, H20),
6.58 (1H, s, H10), 7.13–7.31 (m, 5H, 5CHAr), 8.96 (s, 1H, NH); 13C NMR
(62 MHz, CDCl3): 24.7 (CH3i), 26.2 (CH3i), 28.6 (CH2c), 76.9 (C50),
82.4 (C20), 84.0 (C40), 85.6 (C30), 89.9 (C10), 103.3 (C5), 113.1 (CIVi),
126.3 (CHAr), 128.3 (CHAr), 128.5 (CHAr), 140.0 (CIVAr), 148.8 (C2),
157.9 (C6), 163.4 (C4); HRMS (ESI): m/z calcd for C19H20N2O6Na
(MþþNa): 395.3665, found: 395.3662.
[
a
]
D þ53 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 3.94 (d, H,
J¼12.3 Hz, H50), 4.32 (s, 2H, H20, H30), 4.62 (d, H, J¼12.3 Hz, H50),
4.41 (s, 1H, H40), 6.18 (s, 1H, H10), 11.68 (s, 1H, NH); 13C NMR
(62 MHz, DMSO-d6): 61.9 (C5), 73.0 (C30), 77.4 (C20), 77.9 (C50), 87.4
(C40), 93.0 (C10), 150.4 (C2), 161.4, 161.9 (C6, C4); HRMS (ESI): m/z
calcd for C9H9IN2O6Na (MþþNa): 391.0741, found: 391.0738.
4.5. Synthesis of O6,50-cyclouridine (16)
2 g of 5-bromo-O6,50-cyclouridine (14) was dispersed in 40 ml
mixture of MeOH/TEA 1:1, then Pd/C was added and hydrogen was
connected through septum. Reaction mixture was stirred overnight
at rt. After filtration, solvents were removed, and the residue was
washed again on funnel with DMF. Solution after washing with
DMF was collected, evaporated, and co-evaporated with toluene.
Obtained O6,50-cyclouridine (16) did not require further purifica-
4.6.4. 5-Allyl-20,30-isopropylidene-O6,50-cyclouridine (21)
[a
]
D þ96 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.36 (s, 3H,
CH3i), 1.54 (s, 3H, CH3i), 2.97–3.21 (m, 2H, CH2c), 3.93 (dd, 1H,
J1¼0.7 Hz, J2¼12.4 Hz, H50), 4.47 (dd, 1H, J1¼1.2 Hz, J2¼12.5 Hz, H50),
4.59 (s, 1H, H40), 4.84 (d, 1H, J¼5.6 Hz, H20), 4.94 (d, 1H, J¼5.6 Hz,
H20), 4.96–5.11 (2H, m, CH2]), 5.72–9.94 (1H, m, CH]), 6.60 (1H, s,
H10), 9.44 (s, 1H, NH); 13C NMR (62 MHz, CDCl3): 24.6 (CH3i), 26.2
(CH3i), 28.6 (CH2c), 77.1 (C50), 82.4 (C20), 84.0 (C40), 85.5 (C30), 89.9
(C10), 101.3 (C5), 113.0 (CIVi), 115.3 (CH2]), 135.3 (CH]), 149.0 (C2),
157.8 (C6), 163.4 (C4); HRMS (ESI): m/z calcd for C15H18N2O6Na
(MþþNa): 345.3067, found: 345.3065.
tion. Yield: 1.28 g (85%). [
a]
þ84 (c 1.0, DMF). 1H NMR (400 MHz,
D
DMSO-d6): 3.93 (dd, 1H, J1¼0.8, 12.6 Hz, H50), 4.23–4.34 (m, 2H, H20,
H30), 4.40 (s, 1H, H40), 4.54 (dd, 1H, J1¼1.2 Hz, J2¼12.6 Hz, H50), 5.19
(br s, 30OH), 5.26 (s, 1H, H5), 5.45 (d, 1H, J¼6.1 Hz, 20OH), 6.17 (s, 1H,
13
H10), 11.34 (s, 1H, NH); C NMR (100 MHz, DMSO-d6): 72.0 (C30),
76.6 (C20), 77.5 (C50), 86.3 (C40), 89.8 (C5), 91.3 (C10), 150.0 (C2),
161.5 (C6), 163.1 (C4); HRMS (ESI): m/z calcd for C9H10N2O6Na
(MþþNa): 265.1775, found: 265.1773.
4.6.5. 5-Crotyl-20,30-isopropylidene-O6,50-cyclouridine (22)
(as a E/Z mixture)
1H NMR (400 MHz, CDCl3): 1.36 (s, 3H, CH3i), 1.54 (s, 3H, CH3i),
1.63 (d, J¼5.3 Hz, CH3c), 1.71 (d, J¼6.8 Hz, CH3c), 2.93–3.16 (m, 2H,
CH2c), 3.88–3.97 (m, 1H, H50), 4.47 (dd, 1H, J1¼0.5 Hz, J2¼12.4 Hz,
H50), 4.58 (s, 1H, H40), 4.84 (d, H, J¼5.6 Hz, H30), 4.94 (d, H, J¼5.6 Hz,
H20), 5.28–5.53 (m, 2H, CH]), 6.59 (1H, s, H10), 9.30, 9.35 (2ꢂs, 1H,
NH); 13C NMR (100 MHz, CDCl3): 12.7, 17.7 (CH3c), 20.3, 25.5 (CH2c),
24.6, 26.2 (CH3i), 77.0, 77.1 (C50), 82.4 (C20), 84.0 (C40), 85.5 (C30),
89.9 (C10), 102.3, 102.7 (C5), 113.1 (CIVi), 124.9, 126.1, 127.0, 127.6
(CIII]), 149.0 (C2), 157.4 (C6), 163.4, 163.5 (C4); HRMS (ESI): m/z
calcd for C16H20N2O6Na (MþþNa): 359.3335, found: 359.3330.
4.6. General procedure of nucleophilic addition of alkyl
and allyl halides
1 equiv of 5-bromo-20,30-isopropylidene-O6,50-cyclouridine (10)
was dissolved in dry THF and 1 equiv of sodium hydride was added
followed by 3 equiv of HMPA (in case of alkenyl derivatives). The
reaction mixture was cooled down under nitrogen to ꢁ78 ꢀC, then
2 equiv of n-BuLi was added. After stirring for a 30 min, 5 equiv of
appropriate nucleophile was added. The reaction mixture was
stirred at ꢁ78 ꢀC overnight, then warmed up to rt. Satd NH4Cl
was added, organic phase was separated, and aqueous phase was
extracted three times with CH2Cl2. Organic phases were evaporated
and the residue was purified by liquid chromatography on silica gel
(petroleum ether/EtOAc, 7:3 then 6:4).
4.6.6. 5-Methallyl-20,30-isopropylidene-O6,50-cyclouridine (23)
[a
]
þ85 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.35 (s, 3H
D
CH3i), 1.54 (s, 3H CH3i), 1.75 (s, 3H, CH3i), 2.88–3.14 (m, 2H, CH2c),
3.92 (d,1H, J¼12.5 Hz, H50), 4.47 (dd,1H, J1¼0.8 Hz, J2¼12.4 Hz, H50),
4.60 (d, 2H, J¼11.6 Hz, CH2]), 4.74 (s, 1H, H40), 4.83 (d,1H, J¼5.6 Hz,
H30), 4.94 (d, 1H, J¼5.6 Hz, H20), 6.60 (1H, s, H10), 9.61 (s, 1H, NH);
13C NMR (62 MHz, CDCl3): 22.5 (CH3c), 24.6 (CH3i), 26.1 (CH3i), 30.2
(CH2c), 77.0 (C50), 82.3 (C20), 84.0 (C40), 85.5 (C30), 89.8 (C10), 101.3
(C5), 110.4 (CH2]), 113.0 (CIVi), 143.4 (CIVc), 149.0 (C2), 157.9 (C6),
163.7 (C4); HRMS (ESI): m/z calcd for C16H20N2O6Na (MþþNa):
359.3335, found: 359.3332.
4.6.1. 5-Methyl-20,30-isopropylidene-O6,50-cyclouridine (18)
[
a]
þ74 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.36 (s, 3H,
D
CH3i), 1.54 (s, 3H, CH3i), 1.85 (s, 3H, CH3c), 3.94 (dd, 1H, J1¼0.9 Hz,
J2¼12.4 Hz, H50), 4.51 (dd, 1H, J1¼1.3 Hz, J2¼12.4 Hz, H50), 4.60 (s,
1H, H40), 4.84 (d, 1H, J¼5.6 Hz, H30), 4.94 (d, 1H, J¼5.6 Hz, H20), 6.59
(1H, s, H10), 9.24 (s, 1H, NH); 13C NMR (62 MHz, CDCl3): 7.6 (CH3c),
24.6 (CH3i), 26.2 (CH3i), 76.7 (C50), 82.4 (C20), 84.0 (C40), 85.6 (C30),
89.9 (C10), 98.9 (C5), 113.0 (CIVi), 148.9 (C2), 156.9 (C6), 164.1 (C4);
HRMS (ESI): m/z calcd for C12H16N2O6Na (MþþNa): 307.2579,
found: 307.2577.
4.6.7. N3-(4-Chlorobenzyl)-20,30-isopropylidene-O6,50-
cyclouridine (24)
[
a
]
þ71 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.33 (s, 3H,
D
CH3i), 1.52 (s, 3H, CH3i), 3.98 (dd, 1H, J¼0.8, 12.5 Hz, H50), 4.45 (dd,
1H, J1¼1.3, 12.5 Hz, H50), 4.79 (d, 1H, J¼5.6 Hz, H30), 4.89 (d, 1H,
J¼5.6 Hz, H20), 5.03 (d, 1H, J¼2.4 Hz, CH2c), 5.45 (1H, s, H5), 6.61
(1H, s, H10), 7.26 (d, 2H, J¼8.5 Hz, CHAr), 7.43 (d, 2H, J¼8.5 Hz, CHAr);
13C NMR (62 MHz, CDCl3): 24.7 (CH3i), 26.2 (CH3i), 44.1 (CH2c), 77.4
(C50), 82.2 (C20), 83.9 (C40), 85.6 (C30), 90.5, 90.8 (C10, C5),113.1 (CIVi),
128.4 (CHAr), 130.8 (CHAr), 133.7 (CIVAr), 134.9 (CIVAr), 150.2 (C2),
159.8 (C6), 162.6 (C4); HRMS (ESI): m/z calcd for C19H19ClN2O6Na
(MþþNa): 429.8113, found: 429.8110.
4.6.2. 5-Ethyl-20,30-isopropylidene-O6,50-cyclouridine (19)
[
a
]
þ71 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 1.04 (t, 3H,
D
J¼7.4 Hz, CH3c), 1.37 (s, 3H, CH3i), 1.54 (s, 3H, CH3i), 2.35 (dq, 2H,
J1¼2.8 Hz, J2¼7.5 Hz, CH2c), 3.93 (dd,1H, J1¼0.7 Hz, J2¼12.4 Hz, H50),
4.53 (dd, 1H, J1¼1.2 Hz, J2¼12.4 Hz, H50), 4.60 (s, 1H, H40), 4.84
(d, 1H, J¼5.6 Hz, H30), 4.95 (d, 1H, J¼5.6 Hz, H20), 6.60 (1H, s, H10),
9.24 (s, 1H, NH); 13C NMR (62 MHz, CDCl3): 13.9 (CH3c), 16.1 (CH2c),

4058
A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
4.7. Hydrogenation of alkenyl derivatives 21–23
(d, 1H, J¼12.4 Hz, H50), 5.17 (br s, 1H, 30OH), 5.44 (d, 1H, J¼5.2 Hz,
20OH), 6.19 (s, 1H, H10), 11.34 (s, 1H, NH); 13C NMR (62 MHz,
DMSO-d6): 13.8 (CH3), 15.6 (CH2), 72.2 (C30), 76.5 (C20), 77.2 (C50),
86.4 (C40), 91.3 (C10), 103.1 (C5), 149.2 (C2), 157.0 (C6), 163.5 (C4);
HRMS (ESI): m/z calcd for C11H14N2O6Na (MþþNa): 293.2311,
found: 293.2307.
Alkenyl derivatives dissolved in THF (30 ml), palladium on
carbon, and hydrogen were stirred overnight at rt, respectively.
Catalyst was filtrated on Celite then solvent were evaporated
and the residue was chromatographed using petroleum ether/
EtOAc, 7:3.
4.8.3. 5-Benzyl-O6,50-cyclouridine (30)
4.7.1. 5-Propyl-20,30-isopropylidene-O6,50-cyclouridine (25)
[
a
]
D þ98 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 3.43–3.72
[a
]
þ61 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 0.91 (t, 3H,
(m, 3H, CH2, H50), 4.23–4.40 (m, 2H, H30, H40), 4.34 (s, 1H, H40), 4.52
D
J¼7.4 Hz, CH3c), 1.36 (s, 3H, CH3i), 1.54 (s, 3H, CH3i), 1.45 (q, J¼7.4 Hz,
2H, CH2), 2.20–2.40 (m, 2H, CH2c), 3.93 (d, 1H, J¼12.3 Hz, H50), 4.53
(dd, 1H, J1¼1.0, 12.4 Hz, H50), 4.60 (s, 1H, H40), 4.83 (d, 1H, J¼5.6 Hz,
H30), 4.95 (d, 1H, J¼5.6 Hz, H20), 6.60 (1H, s, H10), 9.49 (s, 1H, NH);
13C NMR (62 MHz, CDCl3): 13.84 (CH3c), 22.1 (CH2c), 24.5 (CH2c),
24.6 (CH3i), 26.2 (CH3i), 77.0 (C50), 82.4 (C20), 83.9 (C40), 85.5 (C30),
89.8 (C10), 103.3 (C5), 113.0 (CIVi), 149.1 (C2), 157.1 (C6), 163.9 (C4);
HRMS (ESI): m/z calcd for C15H20N2O6Na (MþþNa): 347.3225,
found: 347.3223.
(d, 1H, J¼12.6 Hz, H50), 5.18 (br s, 1H, 30OH), 5.44 (d, 1H, J1¼6.6 Hz,
20OH), 6.20 (s, 1H, H10), 7.10–7.33 (m, 5H, HAr), 11.45 (s, 1H, NH); 13
C
NMR (62 MHz, DMSO-d6): 27.7 (CH2), 72.1 (C30), 76.6 (C20), 77.0
(C50), 86.3 (C40), 91.4 (C10), 100.9 (C5), 125.8 (CHAr), 127.9 (CHAr),
128.2 (CHAr), 140.2 (CIVAr), 149.2 (C2), 157.9 (C6), 163.5 (C4); HRMS
(ESI): m/z calcd for C16H16N2O6Na (MþþNa): 355.3019, found:
355.3016.
4.8.4. 5-Allyl-O6,50-cyclouridine (31)
[
a
]
D þ92 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 2.93 (d, 2H,
4.7.2. 5-n-Butyl-20,30-isopropylidene-O6,50-cyclouridine (26)
J¼5.9 Hz, CH2), 3.82 (d, 1H, J¼12.6 Hz, H50), 4.23–4.33 (m, 2H, H30,
H40), 4.36 (s, 1H, H40), 4.57 (d, 1H, J¼12.6 Hz, H50), 4.87–5.05 (m, 2H,
CH2]), 5.18 (d, 1H, J1¼3.9 Hz, 30OH), 5.44 (d, 1H, J1¼6.4 Hz, 20OH),
5.66–5.87 (m, H, CH]), 6.19 (s, 1H, H10), 11.39 (s, 1H, NH); 13C NMR
(62 MHz, DMSO-d6): 26.2 (CH2), 72.2 (C30), 76.6 (C20), 77.2 (C50),
86.4 (C40), 91.4 (C10), 99.4 (C5),114 (CH2]), 135.9 (CH]), 149.3 (C2),
157.8 (C6), 163.3 (C4); HRMS (ESI): m/z calcd for C12H14N2O6Na
(MþþNa): 305.2421, found: 305.2417.
[a
]
D þ66 (c 1.0, CH2Cl2). 1H NMR (250 MHz, CDCl3): 0.91 (t, 3H,
J¼7.4 Hz, CH3c), 1.21–1.48 (m, 7H, CH3i, 2CH2c), 1.54 (s, 3H, CH3i),
2.15–2.43 (m, 2H, CH2c), 3.93 (d, 1H, J2¼12.3 Hz, H50), 4.51 (dd, 1H,
J1¼1.1 Hz, J2¼12.4 Hz, H50), 4.59 (s, 1H, H40), 4.83 (d, 1H, J¼5.6 Hz,
H30), 4.94 (d, 1H, J¼5.6 Hz, H20), 6.60 (1H, s, H10), 8.97 (s, 1H, NH);
13C NMR (62 MHz, CDCl3): 13.9 (CH3c), 22.4 (CH2c), 22.5 (CH2c), 24.7
(CH3i), 26.2 (CH3i), 31.2 (CH2c), 77.1 (C50), 82.4 (C20), 84.0 (C40), 85.6
(C30), 89.9 (C10), 103.6 (C5), 113.1 (CIVi), 148.9 (C2), 157.1 (C6), 163.6
(C4); HRMS (ESI): m/z calcd for C16H22N2O6Na (MþþNa): 361.3493,
found: 361.3488.
4.8.5. 5-Crotyl-O6,50-cyclouridine (32) (as a Z/E mixture)
1H NMR (400 MHz, DMSO-d6): 1.53–1.68 (m, 3H, CH3), 2.79–
3.03 (m, 2H, CH2), 3.81 (m, 1H, H50), 4.24–4.34 (m, 2H, H30, H40),
4.36 (s, 1H, H40), 4.57 (dd, 1H, J1¼4.2 Hz, J2¼12.4 Hz, H50), 5.17 (d,
1H, J¼3.2 Hz, 30OH), 5.23–4.43 (m, 2H, 2CH]), 5.45 (d, 1H,
J1¼6.1 Hz, 20OH), 6.18 (s, 1H, H10), 11.38 (s, 1H, NH); 13C NMR
(100 MHz, DMSO-d6): 12.6, 17.5 (CH3), 20.0, 25.0 (CH2), 72.2 (C30),
76.6 (C20), 77.1 (C50), 86.5 (C40), 91.3 (C10), 100.4, 100.9 (C5), 123.9,
124.9, 127.9, 128.6 (CH]), 149.2, 149.3 (C2), 157.5 (C6), 163.4, 163.5
(C4); HRMS (ESI): m/z calcd for C13H16N2O6Na (MþþNa): 319.2689,
found: 319.2687.
4.7.3. 5-iso-Butyl-20,30-isopropylidene-O6,50-cyclouridine (27)
1H NMR (250 MHz, CDCl3): 0.87 (d, 3H, J¼2.8 Hz, CH3c), 0.90 (d,
3H, J¼2.8 Hz, CH3c), 1.36 (s, 3H, CH3i), 1.54 (s, 3H, CH3i), 1.72–1.88
(m, 1H, CHc), 2.15–2.26 (m, 2H, CH2c), 3.93 (d, 1H, J¼12.4 Hz, H50),
4.49 (dd, 1H, J1¼1.1, 12.4 Hz, H50), 4.59 (s, 1H, H40), 4.81 (d, 1H,
J¼5.6 Hz, H30), 4.94 (d, 1H, J¼5.6 Hz, H20), 6.60 (1H, s, H10), 9.31 (s,
1H, NH); 13C NMR (62 MHz, CDCl3): 22.2 (CH3c), 22.6 (CH3c), 24.7
(CH3i), 26.2 (CH3i), 27.5 (CHc), 31.5 (CH2c), 77.0 (C50), 82.3 (C20), 83.9
(C40), 85.6 (C30), 89.8 (C10), 102.4 (C5), 113.0 (CIVi), 149.1 (C2), 157.3
(C6), 163.9 (C4); HRMS (ESI): m/z calcd for C16H22N2O6Na (MþþNa):
361.3493, found: 361.3489.
4.8.6. 5-n-Propyl-O6,50-cyclouridine (33)
[
a
]
D
þ66 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 0.83 (t,
3H, J¼7.3 Hz, CH3), 1.34 (q, J¼7.4 Hz, 2H, CH2), 2.16 (t, 2H, J¼7.4 Hz,
CH2), 3.84 (d, 1H, J¼12.3 Hz, H50), 4.30 (s, 2H, H20, H30), 4.36 (s, 1H,
H40), 4.59 (d, 1H, J¼12.3 Hz, H50), 5.4 (br s, 2H, 30OH, 20OH), 6.19 (s,
1H, H10), 11.4 (br s, 1H, NH); 13C NMR (62 MHz, DMSO-d6): 13.7
(CH3), 21.7 (CH2), 24.2 (CH2), 72.2 (C30), 76.6 (C20), 77.2 (C50), 86.4
(C40), 91.3 (C10), 101.3 (C5), 149.3 (C2), 157.3 (C6), 163.7 (C4); HRMS
(ESI): m/z calcd for C12H16N2O6Na (MþþNa): 307.2579, found:
307.2576.
4.8. General deprotection of 5-alkyl and allyl derivatives
Isopropylidene derivatives were treated with 10% TFA in H2O
for 1 h in 70 ꢀC. Solvent was evaporated and co-evaporated
with toluene. The residue was dissolved was purified by liquid
chromatography on silica gel (petroleum/EtOAc, from 5:5 to
7:3).
4.8.1. 5-Methyl-O6,50-cyclouridine (28)
4.8.7. 5-n-Butyl-O6,50-cyclouridine (34)
[a
]
D þ70 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 1.69 (s, 3H,
[
a
]
D þ67 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 0.86 (t, 3H,
CH3), 3.88 (d, 1H, J¼12.4 Hz, H50), 4.25–4.34 (m, 2H, H30, H40), 4.37
(s, 1H, H40), 4.57 (d, 1H, J¼12.4 Hz, H50), 5.19 (d, 1H, J¼3.7 Hz, 30OH),
5.45 (d, 1H, J1¼6.3 Hz, 20OH), 6.18 (s, 1H, H10), 11.34 (s, 1H, NH); 13C
NMR (62 MHz, DMSO-d6): 7.5 (CH3), 72.2 (C30), 76.5 (C20), 76.7 (C50),
86.5 (C40), 91.3 (C10), 97.0 (C5), 149.2 (C2), 156.9 (C6), 164.0 (C4);
HRMS (ESI): m/z calcd for C10H12N2O6Na (MþþNa): 279.2043,
found: 279.2039.
J¼6.9 Hz, CH3), 1.15–1.41 (m, 4H, 2ꢂCH2), 2.19 (t, 2H, J¼6.4 Hz, CH2),
3.84 (d, 1H, J¼12.3 Hz, H50), 4.25–4.33 (m, 2H, H20, H30), 4.36 (s, 1H,
H40), 4.59 (d, 1H, J¼12.3 Hz, H50), 5.17 (d, 1H, J¼3.2 Hz, 30OH), 5.44
(d, 1H, J1¼6.3 Hz, 20OH), 6.19 (s, 1H, H10), 11.33 (s, 1H, NH); 13C NMR
(62 MHz, DMSO-d6): 13.4 (CH3), 21.5 (CH2), 30.4 (CH2) (n-butyl),
71.8 (C30), 76.2 (C20), 76.8 (C50), 86.0 (C40), 90.9 (C10), 101.2 (C5),
148.9 (C2), 156.8 (C6), 163.3 (C4); HRMS (ESI): m/z calcd for
C13H18N2O6Na (MþþNa): 321.2847, found: 321.2845.
4.8.2. 5-Ethyl-O6,50-cyclouridine (29)
[
a
]
þ76 (c 1.0, DMF). 1H NMR (250 MHz, DMSO-d6): 0.94 (t,
4.8.8. 5-iso-Butyl-O6,50-cyclouridine (35)
D
3H, J¼7.3 Hz, CH3), 2.20 (q, 2H, J¼7.3 Hz, CH2), 3.86 (d, 1H,
[
a
]
þ79 (c 1.0, DMF). 1H NMR (250 MHz, CD3OD): 0.90 (t, 6H,
D
J¼12.4 Hz, H50), 4.25–4.42 (m, 2H, H30, H40), 4.36 (s, 1H, H40), 4.61
J¼6.3 Hz, 2CH3), 1.82 (m, J¼6.3 Hz, 1H, CH), 2.10–2.33 (m, 2H, CH2),

A. Mieczkowski et al. / Tetrahedron 65 (2009) 4053–4059
4059
3.96 (dd, 1H, J¼1.1, 12.5 Hz, H50), 4.45 (br s, 2H, H20, H30), 4.47 (s, 1H,
H40), 4.60 (dd, 1H, J1¼1.3 Hz, J2¼12.5 Hz, H50), 6.41 (s, 1H, H10), 8.00
(s, 1H, NH); 13C NMR (62 MHz, CD3OD): 22.6 (CH3), 23.0 (CH3), 29.0
(CH), 32.5 (CH2), 74.2 (C30), 78.4 (C20), 78.6 (C50), 88.3 (C40), 93.4
(C10), 103.0 (C5), 151.2 (C2), 159.8 (C6), 166.6 (C4); HRMS (ESI): m/z
calcd for C13H18N2O6Na (MþþNa): 321.2847, found: 321.2844.
11. (a) Chun, B.-K.; Wang, P.; Hassan, A.; Du, J.; Tharnish, P. M.; Stuyver, L. J.; Otto,
M. J.; Schinazi, R. F.; Watanabe, K. A. Tetrahedron Lett. 2005, 46, 2825–2827; (b)
Chun, B.-K.; Wang, P.; Hassan, A.; Du, J.; Tharnish, P. M.; Murakami, E.; Stuyver,
L. J.; Otto, M. J.; Schinazi, R. F.; Watanabe, K. A. Nucleosides Nucleotides 2007, 26,
83–97; (c) Hassan, A.; Wang, P.; McBrayer, T. R.; Tharnish, P.; Stuyver, P. M.;
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19. When our manuscript was in preparation, Qu et al. reported on the haloge-
nation–cyclization reactions of pyrimidine nucleosides: Qu, G.-R.; Ren, B.; Niu,
H.-Y.; Mao, Z.-J.; Guo, H.-M. J. Org. Chem. 2008, 73, 2450–2453. Compared to our
method, this procedure is only working with iodine, as with chlorine or bro-
mine no cyclization was observed.
Acknowledgements
This work was supported in part by Idenix Pharmaceuticals.
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ˇ
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ˇ
´
´
´
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