Developing an efficient route to the synthesis of nucleoside 1-alkynylphosphonates

Article abstract of DOI:10.1016/j.tet.2009.05.064

A series of ribonucleoside 1-alkynylphosphonates have been synthesized using a palladium-catalyzed phosphonylation of terminal 1,1-dibromo-1-alkene nucleosidic derivatives and high selectivity for product distribution was observed during this step. Both n

Full text of DOI:10.1016/j.tet.2009.05.064

Tetrahedron 65 (2009) 6039–6046
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Developing an efficient route to the synthesis of nucleoside
1-alkynylphosphonates
*
´
Ma¨ıa Meurillon, Franck Gallier, Suzanne Peyrottes , Christian Perigaud
IBMM, UMR 5247 CNRS-UM1-UM2, Equipe Nucle´osides & Effecteurs Phosphoryle´s, Universite´ Montpellier 2, cc 1705, place E. Bataillon,
34095 Montpellier Cedex 05, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 April 2009
Received in revised form 19 May 2009
Accepted 26 May 2009
Available online 29 May 2009
A series of ribonucleoside 1-alkynylphosphonates have been synthesized using a palladium-catalyzed
phosphonylation of terminal 1,1-dibromo-1-alkene nucleosidic derivatives and high selectivity for
product distribution was observed during this step. Both nucleosidic and osidic pathways were explored
and the corresponding optimization study is reported herein.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Nucleotide analogue
1-Alkynylphosphonate
Sugar phosphonate
1. Introduction
(HO)2PO
HO
(R1O)2PO
R2O
B
B
HO
Alkynylphosphonate derivatives belong to an interesting family
as they permit among other transformations,1 the direct prepa-
ration of vinyl-phosphonate with Z-stereochemistry by a simple
reduction step.2 Besides classical methods,1 only a few pathways
have emerged for their efficient preparation.3–5 As example, syn-
thesis of such compounds may involve two key reactions: an al-
O
O
O
OR4
HO
OH
OH
OR3
Figure 1. Synthetic routes to nucleoside 1-alkynylphosphonates.
dehyde homologation leading to
a 1,1-dibromo-1-alkene as
2. Probing aldehyde’s homologation for osidic and
nucleosidic substrates
intermediate,6 followed by a Pd catalyzed phosphonylation origi-
nally reported by Hayes et al.4 The first step is comparable to
a Wittig reaction and leads to a 1,1-dibromo-1-alkene that also
allows the preparation of terminal alkynes following the well-
known Corey–Fuchs reaction.7 During the course of our ongoing
work studying 50-mononucleotide analogues bearing a stable P–C
bond,8,9 we were interested in the optimization of the overall
procedure for the synthesis of a variety of ribonucleoside 1-alky-
nylphosphonates. Basically, two synthetic routes may be envis-
aged to reach the targeted compounds: an osidic (involving the
synthesis of an alkynylphosphonate sugar derivative and further
condensation with various heterocycles) or a nucleosidic strategy
(Fig. 1). Both routes have been explored and results are reported
herein.
As the literature concerning experimental conditions for the
preparation of 1,1-dibromo-1-alkenes (one-carbon homologation
of an aldehyde) was abundant and somewhat puzzling,6,7,10 we
initially focused on the preparation of 1,1-dibromo-1-alkene de-
rivatives 3 and 4 (Scheme 1). Starting materials 1 and 2, corre-
sponding to the nucleosidic and osidic aldehydes, were obtained
using previously published procedures11–13,9 from commercially
available uridine and diacetone D-glucose.
Selected experimental conditions corresponding to the litera-
ture data were applied to aldehydes 1 and 2, and are presented in
Table 1. Briefly, we studied the effect of the purity of the starting
material, the sequential addition of the reagents, the order of ad-
dition and the additive effects on the yield of desired derivatives
obtained after column chromatography. In the case of the nucleo-
sidic starting material 1, the purity of the aldehyde appeared as
a key factor for the reaction to proceed and the use of crude ma-
terial from the oxidation step was detrimental. Furthermore, the
poor results obtained for the nucleosidic substrate were mainly due
* Corresponding author. Tel.: þ33 4 67 14 49 64; fax: þ33 4 67 54 96 10.
E-mail address: peyrottes@univ-montp2.fr (S. Peyrottes).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.05.064

6040
M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
Uridine
Diacetone D-glucose
derivative as sole nucleosidic substrate.4 Then, treatment of 5 with
HO
U
aqueous trifluoroacetic acid solution at room temperature removed
the 20,30-O-isopropylidene group and provided compound 6 in
modest yield.
O
O
O
HO
O
O
OH OH
O
O
O
O
O
(EtO)2
P
Br
U
U
U
Br
O
a
O
U
O
O
O
O
O
U
O
O
2
1
3
5
O
O
BzO
b
NaO
NaO
O
O
Br
P
(EtO)2
P
Br
U
Br
O
Br
O
c
O
O
O
BzO
O
3
4
O
O
OH OH
OH OH
7
6
R
R
Scheme 2. Reagents and conditions: (a) (EtO)2P(O)H, Pd(OAc)2, dppf, propylene oxide,
DMF, 90 ꢀC, overnight, 61%; (b) trifluoroacetic acid/H2O (7:3), rt, 24 h, 60%; (c) (i)
TMSBr, DMF, rt, 6 days (ii) TEAB, pH7, (iii) DOWEX Naþ, 96%.
R
PO(OEt)2
Scheme 1. Reactions studied for the optimization.
Finally, the ethyl phosphonate protecting groups were elimi-
nated by using bromotrimethylsilane (TMSBr) in DMF and after
purification by reverse-phase chromatography, and ionic exchange
the desired alkynylphosphonate analogue of uridine
7 was
Table 1
obtained as its sodium salt. As foreseen from the results of the
optimization study, derivative 7 was obtained in six steps from
uridine but in only 4% overall yield.
Optimization of the reaction conditions for the aldehyde homologation
Entry Substrate Addition order
Stoechiometry (equiv) Yielda (%)
1
2
3
4
5
6
7
8
1
2
1
2
1
Aldehyde
CBr4 then PPh3
Aldehyde
1
12
58
14
61
40
2 and 4
1
2 and 4ꢁ1
3.2. Osidic route
CBr4 then PPh3
Aldehyde (repurified) 1 equiv
CBr4 then PPh3
Aldehyde (repurified)
CBr4 then PPh3, MW
PPh3 then CBr4
Aldehyde
PPh3 then CBr4
Aldehyde (repurified)
PPh3, Zn, then CBr4
Aldehyde
We first envisaged to reach the key intermediate 9 (Scheme 3)
and then introduced variability through nucleobase condensations.
In this respect, the osidic alkynylphosphonate 8 was obtained in
44% yield from the osidic substrate 4 using the same conditions as
those used for the synthesis of 5 from 3. However, despite several
attempts (Ac2O/AcOH/H2SO4;17 TFA 80% then Ac2O, DMAP, pyri-
dine;18 and AcOH aq then Ac2O, DMAP, and pyridine19), we were
unable to isolate the per-acylated derivative 9 required for further
glycosylation. Back to the 1,1-dibromo-1-alkene 4, we decided to
perform per-acetylation and glycosylation steps prior to phospho-
nylation. Thus, key sugar intermediate 10 was isolated in 59% yield
using the classical procedure17 and glycosylation was performed in
standard Vorbru¨ggen conditions,20 leading to the corresponding
nucleoside analogues 11a–c in good yields (69–88%). Thus, the
following two steps, consisting of the removal of base-labile pro-
tecting groups and phosphonylation, may be performed in
interchangeable order and both routes were explored.
In the first pathway, protected nucleoside alkynylphosphonates
12a–c were obtained from corresponding 1,1-dibromo-1-alkenyl
nucleoside analogues using a slightly modified procedure com-
pared to substrate 3. Indeed, heating overnight at 90 ꢀC had a de-
teriorating effect on the reaction mixture corresponding to the
phosphonylation step, which led to the desired compounds in low
yields (<15%). Investigations towards optimum reaction conditions
were carried out. Based on the literature data,4,15 several parame-
ters were studied including different solvents, temperature, and the
nature of the scavenger. When DMF was replaced by toluene, a new
and unique product corresponding to the bromo-alkenylphospho-
nate 13 was isolated in good yield (52%). Formation of this de-
rivative may be due to an early coupling of the diethylphosphite
during the catalytic cycle (vide infra). Replacement of propylene
oxide (scavenger) by triethylamine was ineffective and the reaction
did not proceed at all. Finally, using DMF but decreasing the
2 and 4ꢁ1
1
2
1
2
1
1
39
41
24
61
29
2 and 4
5 and 2.5
1
5 and 2.5
1
1.97 and 2.05
1
1
2
1
2
4
48
6
Aldehyde
PPh3 supported then CBr4
1
4 and 2
42
a
Isolated after column chromatography.
to the difficulty in isolating pure batch of 1 (entries 2 and 3) and its
low stability.
Contrary to the data reported, the sequential addition of PPh3
(entries 1–2),14 the reagent addition order (entries 1 and 5), as well
as the presence of Zn powder7,15 (which allows the use of less
triphenylphosphine, entry 7) have minor effects on the yield.
As expected, the reaction time was shortened when using
microwave irradiations (MW, entries 1 and 4). Supported PPh3 was
used in order to easily isolate the reaction products (entry 8) but
did not lead to a real enhancement of the yield.16 Thus, the osidic
substrate 2 led to better results than the nucleosidic one 1.
3. Synthesis of ribonucleoside 1-alkynylphosphonates
3.1. Nucleosidic route
The transformation of intermediate 3 to alkynylphosphonate 5
was achieved using the Pd catalyzed phosphonylation procedure
(i.e., Pd(OAc)2, 1,10-bis(diphenylphosphinoferrocene) (dppf), diethyl
phosphite, propylene oxide in N,N-dimethylformamide (DMF)) in
61% yield (Scheme 2) previously reported for a 20-deoxythymidine

M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
6041
Br
O
(EtO)2
P
Br
a
O
O
O
BzO
O
4
O
BzO
O
8
b
Br
O
P
(EtO)2
Br
O
OAc
O
OAc
BzO
OAc
10
9
BzO
OAc
B
c
O
Br
Br
P(OEt)2
B
Br
Br
U
Br
O
O
f
O
d
15a, B=U
15b, B=C
15c, B=A
11a, B=U
11b, B=CBz
11c, B=ABz
BzO
OAc
HO
OH
13
BzO
OAc
a
a
O
O
O
P
(EtO)2
P
(EtO)2
P
(NaO)2
g
B
B
B
O
O
O
e
BzO
OAc
OH
OH
OH
OH
7, B=U
12a, B=U
6, B=U
16b, B=C
16c, B=A
12b, B=CBz
12c, B=ABz
14b, B=C
14c, B=A
Scheme 3. Osidic pathway to nucleoside alkynylphosphonates. (a) (EtO)2P(O)H, Pd(OAc)2, dppf, propylene oxide, DMF, 80 or 90 ꢀC, overnight, 44–76%; (b) AcOH, Ac2O, H2SO4cat
,
59%; (c) sylilated base, ACN, TMSOTf, 69–88%; (d) (EtO)2P(O)H, Pd(OAc)2, dppf, propylene oxide, toluene, 80 ꢀC, overnight, 52%; (e) NEt3, H2O, MeOH (1:1:5), rt, 3 h, 17–53%; (f)
NaOMe, MeOH, rt, 90–96%; (g) (i) TMSBr, DMF, rt, then TEAB (pH 7, 1 M), (ii) DOWEX Naþ
.
temperature from 90 to 80 ꢀC was conclusive and the isolated yield
of the desired compounds 12a–c was substantially increased (64–
76%) when the reaction mixture was first filtrated through a Celite
cake before removing the solvent in vacuum and performing the
silica gel chromatography of the resulting crude material.
We next turned our attention to the removal of the base-labile
protecting groups, thus treatment of derivatives 12a–c in standard
conditions (i.e., methanolic ammonia, sodium methanolate, etc.)
yielded complex mixtures. The expected compounds 6 and 14b,c
were only obtained in modest to low yields using aqueous tri-
ethylamine in methanol.
Thus, the second pathway that involved the removal of the
protecting groups before performing the phosphonylation was
tested. Derivatives 11a–c were treated in the presence of sodium
methoxide and afforded intermediates 15a–c in good yields
(w90%). These last products were then converted into the desired
alkynylphosphonates 6 and 14b,c using the previously reported
conditions.4
Scheme 4. Our hypothesis is based on the work of Shen et al.14 who
reported a ligand effect on the product distribution (i.e., alkyne
formation versus monocoupling) whereas we observed a solvent
effect. The nature of the solvent appeared as a key parameter of the
reaction course. Thus, formation of the alkynylphosphonate 12a
may result from two consecutive oxidative Pd(0) insertions. During
the first catalytic cycle, the formation of the alkynyl bromide de-
rivative 17 (path A) is due to a cis-b-hydrogen elimination from the
bromoalkene palladium complex 18. Then, a second Pd(0) insertion
lead to the alkynyl palladium complex 19 that undergoes coupling
with diethylphosphite to afford the desired alkynylphosphonate
derivative 12a. A working hypothesis is that in highly dipolar and
coordinating solvents such as DMF, the intermediate 17 is effi-
ciently formed (path A), or alternatively an elimination of HBr from
complex 18 is favoured and leads directly to the formation of
complex 19 (path B). When a non-polar and aprotic solvent such as
toluene was used path C was preponderant and gave rise to the
formation of the bromo-alkenylphosphonate 13. Additional ex-
periments carried out in toluene, with a postponed addition of the
diethylphosphite (47%) or increasing amount of the Pd catalyst
(48%), had no effect on the yield of the reaction and did not show
the formation of other derivatives than 13.
Starting from the 1,1-dibromo-1-alkenyl nucleoside analogues
11a–c, the second route appeared more attractive in term of yields
(45% compared to 30% over the two steps) and experimental
procedures.
Finally, the phosphonic acid protecting groups were eliminated
using TMSBr in DMF. The desired 1-alkynylphosphonate nucleoside
analogues 7 and 16b,c were obtained as their sodium salts after
purification by reverse-phase (RP-C18) chromatography and ionic
exchange on a DOWEX-resin.
4. Conclusion
The synthesis of novel 50-mononucleotide analogues bearing
a 50-alkynylphosphonate moiety (in the pyrimidine and purine
series) has been achieved. Nucleosidic and osidic synthetic strate-
gies have been explored. The latter appeared more convenient in
terms of overall yield and also allowed the coupling of various
nucleobases to an appropriate sugar derivative prior to phospho-
nylation. Interestingly, high selectivity for product distribution was
3.3. Mechanistic considerations
A possible mechanism, which accounts for the formation of both
alkynyl- and bromo-alkenylphosphonate derivatives, is proposed in

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M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
Pd(II)(OAc)2
de Vernaison (France). TLC was performed on precoated aluminium
sheets of silica gel 60 F254 (Merck, Art. 9385), visualization of
products being accomplished by UV absorbance followed by char-
ring with 5% ethanolic sulfuric acid with heating for carbohydrates
and nucleotides. Flash chromatography was carried out using
Br
Ligand (L=dppf)
U
Br
O
Br
Pd(0)L2
HO
O
63–100 mm silica gel (Merck Art. No. 115101) otherwise 40–63 mm
11a
BzO
OAc
silica gel (Merck Art. No. 109385) was used. Thin layer chroma-
tography was carried out using aluminium supported silica gel 60
plates (Merck Art. No. 105554). MW experiments were carried out
using a single mode cavity synthesizer to ensure reproducibility
and safety and were performed in a sealed Pyrex glass vessel
(2–5 mL content) under argon atmosphere, using a microwave
synthesizer Initiator 2.0 from Biotage (Biotage AB, Sweden) set at
300 W (frequency 2.45 GHz) with a 10 s premixing time. The
temperature was monitored with an internal infrared probe. Sol-
vents were reagent grade or purified by distillation prior to use, and
solids were dried over P2O5 under reduced pressure at rt. Moisture
sensitive reactions were performed under argon atmosphere using
oven-dried glassware. All aqueous (aq) solutions were saturated
with the specified salt unless otherwise indicated. Organic solu-
tions were dried over Na2SO4 after workup and solvents were re-
moved by evaporation at reduced pressure. Starting material such
BrL2Pd
Br
U
PdL2 HBr
O
18
BzO
O
OAc
Path C
O
P(OEt)2
Path A
HPO(OEt)2
U
Br
Br
O
13
U
BzO
Br
OAc
BzO
OAc
Pd(0)L2
17
HO
O
as diacetone-D-glucose was purchased from Acros Organics and
uridine was from Carbosynth.
5.2. Chemistry
5.2.1. 1-(20,30-O-Isopropylidene-50,60-dideoxy-60,60-dibromo-
b-D-
ribo-50-hexenofuranosyl)uracil, 3
PdL2Br
PdL2 HBr
O
Path B
Chromium(VI) oxide (17.0 g, 170 mmol) was suspended in an-
hydrous dichloromethane (170 mL) and DMF (40 mL). After 15 min
stirring, acetic anhydride (16 mL) and pyridine (28 mL) were added
U
O
19
(EtO)2
P
BzO
OAc
dropwise, at 0 ꢀC.
A
solution of 20,30-isopropylideneuridine11
(12.1 g, 43 mmol) in dichloromethane (170 mL) and DMF (40 mL)
was added at 0 ꢀC over 30 min. The reaction mixture was stirred for
1 h, the chromium salts were precipitated in cold ethyl acetate (2 L)
and the resulting suspension was filtered over silica gel. The crude
solution was concentrated under reduced pressure, co-evaporated
with toluene and dried over P2O5.
HPO(OEt)2
U
O
12a
BzO
OAc
Scheme 4. Proposed mechanism for the formation of alkynyl- and bromo-alkenyl-
phosphonate derivatives 12a and 13, respectively.
The crude aldehyde (6.1 g, 21.6 mmol) was dissolved in
dichloromethane (180 mL) and carbon tetrabromide (14.3 g,
43.2 mmol) and triphenylphosphine (22.6 g, 86.4 mmol) were
added. The mixture was stirred at room temperature for 22 h. The
mixture was diluted with dichloromethane and washed with water.
The organic layer was dried over Na2SO4, filtered and evaporated
under reduced pressure. Two column chromatography of the crude
materials on silica gel (toluene/EtOAc, 7:3, v/v) gave compound 3 as
a white solid (2.25 g, 12%).
observed during the palladium-catalyzed phosphonylation step.
Usefulness of this synthetic approach for the preparation of struc-
turally related nucleoside phosphonate analogues of biological
interest is currently being explored.
5. Experimental section
5.1. General
Rf (toluene/EtOAc, 1:1, v/v) 0.3. 1H NMR (300 MHz, DMSO-d6)
Unless otherwise stated, 1H NMR spectra were recorded at
300 MHz and 13C NMR spectra at 75 MHz with proton decoupling
at 25 ꢀC using a Bruker 300 Avance or DRX 400. Chemical shifts are
d
11.48 (br s, 1H exchangeable, NH), 7.75 (d, J¼8.0 Hz, 1H, H-6), 6.83
(d, J¼8.2 Hz, 1H, H-50), 5.77 (d, J¼1.1 Hz, 1H, H-10), 5.64 (dd, J¼2.1–
8.0 Hz, 1H, H-5), 5.14 (dd, J¼1.3–6.3 Hz, 1H, H-20), 4.87 (dd, J¼3.5–
6.3 Hz, 1H, H-30), 4.61 (dd, J¼3.5–8.1 Hz, 1H, H-40), 1.50, 1.29 (2s, 6H,
given in
d values referenced to the residual solvent peak (CDCl3 at
7.26 and 77 ppm or DMSO-d6 at 2.49 and 39.5 ppm) relative to TMS.
Deuterium exchange, decoupling and COSY experiments were
performed in order to confirm proton assignments. Coupling con-
stants, J, are reported in hertz. 2D 1H–13C heteronuclear COSY were
recorded for the attribution of 13C signals. Unless otherwise stated,
31P NMR spectra were recorded at ambient temperature at 121 MHz
with proton decoupling. Chemical shifts are reported relative to
external H3PO4. FAB mass spectra were recorded in the positive-ion
or negative-ion mode on a JEOL JMS-DX 300, using thioglycerol/
glycerol (1:1, v/v, GT) as matrix. Specific rotations were measured
with a Perkin–Elmer Model 341 spectropolarimeter (path length
1 cm) and are given in units of 10ꢂ1 deg cm2 gꢂ1. Elemental analyses
were carried out by the Service de Microanalyses du CNRS, Division
C(CH3)2). 13C NMR (75 MHz, DMSO-d6)
d 163.3 (C-4), 150.4 (C-2),
143.8 (C-6), 137.0 (C-50), 113.2 (C(CH3)2), 101.7 (C-5), 94.0 (C-10), 93.1
(C-60), 87.3 (C-40), 84.0, 83.9 (C-20,C-30), 26.8, 25.0 (C(CH3)2). SM
FAB>0 m/z 441, 439, 437 (MþH)þ. Relative intensity 1:2:1; FAB<0
m/z 439, 437, 435 (MꢂH)ꢂ. Relative intensity 1:2:1. UV
lmax¼255 nm (3max¼11,500), lmin¼230 nm (3min¼4200) (EtOH 95).
20
[a
]
þ76 (c 0.5, CH2Cl2). Anal. Calcd for C13H14Br2N2O5: C, 35.64; H,
D
3.22; N, 6.39. Found: C, 35.76; H, 3.34; N, 6.13.
5.2.2. 3-O-Benzoyl-6,6-dibromo-5,6-dideoxy-1,2-O-isopropylidene-
D-allofuranose, 4
The aldehyde 2 (0.144 g, 0.49 mmol) was dissolved in dry
dichloromethane (8 mL) and the solution was cooled to 0 ꢀC.

M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
6043
Carbon tetrabromide (0.328 g, 0.99 mmol) and triphenylphosphine
(0.518 g, 1.98 mmol, in four parts) were added. The mixture was
stirred at room temperature for 1 h and then diluted with
dichloromethane. The resulting organic layer was washed with
water, dried over MgSO4, filtered and evaporated under reduced
pressure. A column chromatography of the crude materials on silica
gel (CH2Cl2 to CH2Cl2/EtOAc 9:1, v/v) afforded compound 4 as
a white powder (0.134 g, 61%).
H-40), 4.20 (m, 2H, H-20, H-30), 4.10 (m, 4H, OCH2CH3), 1.29 (t,
J¼7.1 Hz, 6H, OCH2CH3). 13C NMR (75 MHz, DMSO-d6)
d 163.0 (C-4),
150.5 (C-2), 140.5 (C-6), 102.4 (C-5), 96.8 (C-50, d, J¼48.2 Hz), 89.8
(C-10), 77.2 (C-60, d, J¼286.8 Hz), 74.5, 72.6 (C-20, C-30), 72.4 (C-40, d,
J¼4.2 Hz), 63.2, 63.1 (OCH2CH3), 15.9, 15.8 (OCH2CH3). 31P NMR
(100 MHz, DMSO-d6)
d
ꢂ8.4. SM FAB>0 m/z 749 (2MþH)þ, 375
(MþH)þ, 263 (MꢂB)þ; FAB<0 m/z 747 (2MꢂH)ꢂ, 373 (MꢂH)ꢂ, 111
(B)ꢂ. UV lmax¼259 nm (3max¼9600), lmin¼228 nm (3min¼2300)
20
Rf (toluene/EtOAc, 9:1, v/v) 0.6. 1H NMR (400 MHz, DMSO-d6)
(EtOH 95).
[
a]
þ5.8 (c 0.86, MeOH). Anal. Calcd for
D
d
8.01 (m, 2H, H-Ar), 7.73 (m, 1H, H-Ar), 7.59 (m, 2H, H-Ar), 6.81 (d,
C14H19N2O8P$0.1H2O: C, 44.71; H, 5.15; N, 7.45; P, 8.24. Found: C,
J¼8.4 Hz, 1H, H-5), 5.94 (d, J¼3.6 Hz, 1H, H-1), 4.98 (m, 2H, H-2, H-
44.36; H, 5.34; N, 7.33; P, 8.29.
3), 4.84 (m,1H, H-4),1.49,1.30 (2s, 6H, C(CH3)2). 13C NMR (100 MHz,
b-D
5.2.5. 1-(50,60-Dideoxy-60-phosphono- -ribo-50-
DMSO-d6)
d 164.8 (C]O), 134.8 (C-5), 133.9, 129.3, 129.0, 128.6 (C-
Ar), 112.5 (C(CH3)2), 104.1 (C-1), 95.2 (C-6), 77.2 (C-4), 76.6, 75.6 (C-
2, C-3), 26.5, 26.4 (C(CH3)2). MS ESI>0 m/z 447, 449, 451 (MþH)þ.
Relative intensity 1:2:1. HRMS calcd for C16H17Br2O5: 446.9443;
hexynofuranosyl)uracil (disodium salt), 7
Derivative 6 (145 mg, 0.39 mmol) was dissolved in anhydrous
DMF (20 mL/mmol), and then TMSBr (10 equiv) was added at 0 ꢀC.
The mixture was stirred at room temperature until completion of
the reaction was indicated by TLC. The reaction mixture was neu-
tralized with 1 M aqueous TEAB and concentrated under high
vacuum. Column chromatography of the crude materials on reverse
phase (H2O) gave the corresponding phosphonic acid and the title
compound 7 was obtained as a white solid (135 mg, 96%) after ion
exchange on DOWEX Naþ and freeze-drying.
found: 446.9455. UV lmax¼272 nm (3max¼10,100), lmin¼249 nm
20
(
3min¼7000) (EtOH 95). [
a
]
D
þ97.6 (c 1.04, MeOH). Anal. Calcd for
C16H16Br2O5: C, 42.89; H, 3.60. Found: C, 43.28; H, 4.37.
5.2.3. 1-(20,30-O-Isopropylidene-50,60-dideoxy-60-diethyl
phosphono-b-D
-ribo-50-hexynofuranosyl)uracil, 5
Palladium(II) acetate (78 mg, 0.35 mmol) and dppf (383 mg,
0.7 mmol) were dissolved in DMF (9 mL). The mixture was stirred at
room temperature for 20 min. A solution of 1-(20,30-O-isopropylidene-
50,60-dideoxy-60,60-dibromo- -ribo-50-hexenofuranosyl)uracil (3)
b-D
Rf (iPrOH/NH4OH 30%/H2O, 7:1:2, v/v/v) 0.14. 1H NMR (300 MHz,
D2O)
d
7.65 (d, J¼8.1 Hz,1H, H-6), 5.81 (d, J¼6.1 Hz,1H, H-10), 5.79 (d,
J¼8.4 Hz,1H,H-5), 4.61(t, J¼3.1 Hz,H-40), 4.38(t, J¼5.0 Hz,H-20), 4.22
(t, J¼4.0 Hz, H-30). 13C NMR (75 MHz, D2O)
d 166.2 (C-4), 151.8 (C-2),
(760 mg, 1.7 mmol), diethylphosphite (0.45 mL, 3.5 mmol) and pro-
pylene oxide (0.22 mL, 5.2 mmol) in DMF (24 mL) was added dropwise
at room temperature. The solution was stirred for 16 h at 90 ꢀC. The
solution was evaporated under high reduce pressure and co-evapo-
rated with absolute ethanol. Column chromatography of crude mate-
rials on silica gel (EtOAc/cyclohexane, 3:1, v/v) gave the desired
compound as a yellow-orange foam (450 mg, 61%).
141.75 (C-6),103.0 (C-5), 89.3 (C-10), 88.5 (C60, d, J¼237.7 Hz), 87.0 (C-
50, d, J¼40.1 Hz), 74.9 (C-40), 74.1 (C-20, C-30). 31P NMR (100 MHz, D2O)
d
ꢂ10.8. SM FAB>0 m/z 363 (MþH)þ, 341 (Mþ2HꢂNa)þ; FAB<0 m/z
339 (MꢂNa)ꢂ, 317 (Mꢂ2NaþH)ꢂ. UV lmax¼260 nm (3max¼10,200),
20
lmin¼229 nm (3min¼2200) (H2O). [
a]
ꢂ6.6 (c 0.91, H2O). Anal. Calcd
D
for C10H9N2Na2O8P$2H2O: C, 30.16; H, 3.29; N, 7.04; P, 7.78. Found: C,
Rf (EtOAc) 0.2. 1H NMR (300 MHz, DMSO-d6)
d 11.48 (br s, 1H ex-
30.13; H, 3.40; N, 6.71; P, 8.10.
changeable, NH), 7.73 (d, J¼8.0 Hz,1H, H-6), 5.84 (s,1H, H-10), 5.62 (d,
J¼8.0 Hz,1H, H-5), 5.28 (d, J¼6.1 Hz,1H, H-20), 5.18 (dd, J¼2.9–6.0 Hz,
1H, H-30), 5.06 (t, J¼3.2 Hz, 1H, H-40), 4.1–4.0 (m, 4H, OCH2CH3), 1.48,
1.31 (2s, 6H, C(CH3)2), 1.26 (2t, J¼7.0 Hz, 6H, OCH2CH3). 13C NMR
5.2.6. 3-O-Benzoyl-5,6-dideoxy-6-diethylphosphono-1,2-O-
isopropylidene-b-D-allo-5-hexynofuranose, 8
Similar procedure as for derivative
5
was applied to 1,
(75 MHz, DMSO-d6)
d 163.3 (C-4), 150.2 (C-2), 143.6 (C-6), 113.19
1-dibromo-1-alkene 4 (90 mg, 0.20 mmol). The desired alkynyl-
phosphonate 8 (37 mg, 44%) was isolated as a yellow oil after pu-
rification by silica gel column chromatography using
dichloromethane/EtOAc (1:0 to 0:1, v/v) as eluent.
(C(CH3)2), 101.5 (C-5), 96.8 (C-50, d, J¼48.0 Hz), 93.9 (C-10), 84.3 (C-40,
d, J¼70.4 Hz), 76.5 (C-60, d, J¼286.3 Hz), 76.6 (C-20), 76.5 (C-30), 63.2–
63.1 (OCH2CH3), 26.4, 24.8 (C(CH3)2), 15.8, 15.7 (OCH2CH3). 31P NMR
(100 MHz, DMSO-d6)
d
ꢂ8.4. SM FAB>0 m/z 829 (2MþH)þ, 415
Rf (EtOAc) 0.49.1H NMR (300 MHz, DMSO-d6)
d 8.01 (m, 2H, H-Ar),
(MþH)þ; FAB<0 m/z 827 (2MꢂH)ꢂ, 413 (MꢂH)ꢂ, 111 (B)ꢂ. UV
7.76–7.54 (m, 3H, H-Ar), 5.97 (d, J¼3.6 Hz, 1H, H-1), 5.25 (dd, J¼4.6,
9.0 Hz, 1H, H-3), 5.08 (dd, J¼3.1, 9.0 Hz, 1H, H-4), 4.98 (dd, J¼4.1 Hz,
1H, H-2), 4.07 (m, 4H, OCH2CH3),1.49,1.28 (2s, 6H, C(CH3)2),1.25–1.20
lmax¼256 nm (3max¼9500), lmin¼225 nm (3min¼1500) (EtOH 95).
20
[a]
þ18.8 (c 0.85, MeOH). Anal. Calcd for C17H23N2O8P: C, 49.28; H,
D
5.59; N, 6.76; P, 7.48. Found: C, 49.38; H, 5.62; N, 6.61; P, 7.54.
(t, J¼7.0 Hz, 6H, OCH2CH3). 13C NMR (75 MHz, DMSO-d6)
d 164.6
(C]O), 134.1, 129.4, 129.2, 129.0, 128.7, 128.3 (C-Ar), 113.0 (C(CH3)2),
104.5 (C-1), 95.5 (d, J¼49.0 Hz, C-5), 79.0, 74.7 (d, J¼319.3 Hz, C-6),
76.7 (C-2), 75.9 (C-3), 66.9 (d, J¼4.5 Hz, C-4), 63.2 (OCH2CH3), 26.4
5.2.4. 1-(50,60-Dideoxy-60-diethylphosphono- -ribo-50-
b-D
hexynofuranosyl)uracil, 6
Compound 5 (430 mg, 1.04 mmol) was dissolved in an aqueous
solution of trifluoroacetic acid (70%, v/v, 8 mL/mmol) at room
temperature. After 4 h and additional trifluoroacetic acid (3 mL),
the reaction was still incomplete after 24 h. Thus, the solution was
evaporated under reduced pressure and co-evaporated with abso-
lute ethanol. Column chromatography of the crude materials on
reverse phase (H2O/CH3CN, 20–50%) gave the title compound as
a white solid (225 mg, 60%) after freeze-drying and the recovered
initial substrate (130 mg, 30%).
(C(CH3)2),15.7 (OCH2CH3). 31P NMR (121 MHz, DMSO-d6)
d
ꢂ8.90. MS
ESI >0 m/z 425 (MþH)þ. HRMS calcd for C20H26O8P: 425.1365; found:
425.1355.
UV
lmax¼271 nm
(
3max¼11,000),
lmin¼248 nm
20
(3min¼6800) (EtOH 95). [
a]
þ131.5 (c 1.0, MeOH). Anal. Calcd for
D
C20H25O8P: C, 56.60; H, 5.94; P, 7.30. Found: C, 56.80; H, 6.01; P, 6.80.
5.2.7. 1,2-Di-O-acetyl-3-O-benzoyl-6,6-dibromo-5,6-dideoxy-(
-ribo-50-hexenofuranose, 10
A solution of dibromoalkene 4 (5.16 g, 11.52 mmol) in glacial
a,b)-
D
Derivative 6 (24 mg, 42%) could also be prepared by treatment of
12a (80 mg, 0.15 mmol) with a mixture of MeOH/water/triethyl-
amine (5:1:1, v/v/v) for 3 h at room temperature.
acetic acid (43.8 mL), acetic anhydride (16.1 mL) and concentrated
sulfuric acid (1.7 mL) was stirred 1 h 30 min at room temperature.
The reaction mixture was diluted with dichloromethane. The
resulting organic layer was successively washed with aq saturated
NaHCO3 solution and water, dried over MgSO4, filtered and evap-
orated under reduced pressure. A column chromatography of the
Rf (CH2Cl2/MeOH, 9:1, v/v) 0.3. 1H NMR (300 MHz, DMSO-d6)
d
11.45 (br s, 1H exchangeable, NH), 7.54 (d, J¼8.1 Hz, 1H, H-6), 5.89
(sl, 1H exchangeable, OH), 5.78 (d, J¼2.4 Hz, 1H, H-10), 5.76 (br s, 1H
exchangeable, OH), 5.70 (d, J¼8.0 Hz, 1H, H-5), 4.68 (t, J¼3.9 Hz, 1H,

6044
M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
crude materials on silica gel (toluene to toluene/ethyl acetate 8:2,
v/v) gave a mixture of the two anomers (a/b in ratio 25:75) of
ESI>0 m/z 684, 686, 688 (MþK)þ. Relative intensity 1:2:1; ESI<0
m/z 645, 647, 649 (MꢂH)ꢂ. Relative intensity 1:2:1. HRMS calcd for
compound 10 as white foam (2.92 g, 59%).
C26H22Br2N3O7: 645.9824; found: 645.9830. UV lmax¼263 nm
20
Rf (toluene/EtOAc, 8:2, v/v) 0.5. 1H NMR (400 MHz, DMSO-d6)
(3max¼35,600), lmin¼243 nm (3min¼22,500) (EtOH 95). [
a]
þ29.3
D
d
8.00 (m, 2H, H-Ar), 7.73 (m, 1H, H-Ar), 7.59 (m, 2H, H-Ar), 7.00 (d,
(c 0.99, MeOH). Anal. Calcd for C26H21Br2N3O7: C, 48.25; N, 6.49.
J¼8.52 Hz,H-5
J¼4.24 Hz, H-1
6.87 Hz, H-3 -anomer), 5.50 (m, H-2
(d, J¼4.78 Hz, H-2 -anomer), 4.90 (m,1H, H-4), 2.16, 2.10 (2s, 6H, Ac).
13C NMR (100 MHz, DMSO-d6)
169.2,168.9,164.5 (CO),135.9 (C-5
anomer),134.5 (C-5 -anomer), 134.0,129.3,129.0,128.3 (C-Ar), 97.7
(C-1 -anomer), 95.4 (C-6 -anomer), 95.0 (C-6 -anomer), 93.0 (C-1
-anomer), 82.5(C-4 -anomer), 80.8 (C-4 -anomer), 73.6, 73.5(C-3,
C-2
a
a
-anomer), 6.92(d, J¼8.63 Hz, H-5
-anomer), 6.13 (s, H-1
-anomer), 5.58 (dd, J¼4.89,
-anomer, H-3 -anomer), 5.46
b
-anomer), 6.43(d,
Found: C, 47.94; N, 6.78.
b
b
a
a
5.3.3. N-6-Benzoyl-9-(20-O-acetyl-30-O-benzoyl-60,60-dibromo-
b-D
50,60-dideoxy- -ribo-50-hexenofuranosyl)adenine, 11c
b
d
b-
Column chromatography of the crude materials on silica gel
(CH2Cl2 to CH2Cl2/EtOAc 1:1, v/v) gave derivative 11c as white foam
(2.20 g, 81%).
a
b
b
a
a
a
b
Rf (CH2Cl2/EtOAc, 9:1, v/v) 0.4. 1H NMR (300 MHz, DMSO-d6)
b
-anomer), 72.0 (C-3, C-2
a-anomer), 20.8, 20.3 (Ac). MS ESI
d 11.32 (br s, 1H exchangeable, NH), 8.85, 8.78 (2s, 2H, H-2, H-8),
>0 m/z 491, 493, 495 (MþH)þ, 431, 433, 435 (MꢂOAcþH)þ. Relative
8.07 (m, 4H, H-Ar), 7.66 (m, 6H, H-Ar), 7.25 (d, J¼8.4 Hz, 1H, H-50),
6.54 (d, J¼5.1 Hz, 1H, H-10), 6.26 (t, J¼5.4 Hz, 1H, H-20), 5.99 (t,
J¼5.3 Hz, 1H, H-30), 5.00 (dd, J¼4.9, 8.4 Hz, 1H, H-40), 2.00 (s, 3H,
intensity 1:2:1. HRMS calcd for C15H13Br2O5: 430.9130; found:
430.9136. UV lmax¼271 nm
(
3max¼10,300), lmin¼249 nm
20
(
3min¼6900) (EtOH 95). [
a
]
þ28.1 (c 0.99, MeOH).
Ac). 13C NMR (75 MHz, DMSO-d6)
d 169.2, 165.6, 164.5 (C]O), 151.9,
D
151.7 (C-4, C-6), 151.9, 151.7 (2 Cq), 150.7, 143.6 (C-2, C-8), 134.7 (C-
50), 134.1, 133.2, 132.5, 129.5, 129.0, 128.5, 128.4, 125.9 (C-Ar), 95.3
(C-60), 85.9 (C-10), 81.4 (C-40), 73.1 (C-30), 72.3 (C-20), 59.7 (C-6), 20.7
(Ac). MS ESI>0 m/z 670, 672, 674 (MþK)þ. Relative intensity 1:2:1;
ESI<0 m/z 669, 671, 673 (MꢂH)ꢂ. Relative intensity 1:2:1. HRMS
calcd for C27H22Br2N5O6: 669.9937; found: 669.9943. UV
5.3. Standard procedure for glycosylation, 11a–c
The nucleobase (5 equiv) was dissolved in anhydrous acetoni-
trile (7 mL/mmol) and N,O-bis(trimethylsilyl) acetamide (10 equiv)
was added. The solution was refluxed for 2 h and the reaction
mixture was allowed to cool to room temperature, concentrated
under reduced pressure and the residue was dissolved in anhy-
drous acetonitrile. Then a solution of peracetylated sugar (1 equiv)
in anhydrous acetonitrile was added, followed by trimethylsilyl
trifluoromethane sulfonate (4 equiv) and the resulting solution was
stirred at 80 ꢀC overnight. The reaction mixture was allowed to cool
down to room temperature and diluted with dichloromethane. The
resulting organic layer was successively washed with aq saturated
NaHCO3 solution and water, dried over MgSO4, filtered and evap-
orated under reduced pressure.
lmax¼279 nm (3max¼26,500), lmin¼249 nm (3min¼16,700) (EtOH
20
95). [
a]
ꢂ17.6 (c 1.02, MeOH). Anal. Calcd for C27H21Br2N5O6: C,
D
48.31; N, 10.43. Found: C, 48.05; N, 10.03.
5.4. Standard procedure for phosphonylation, 12a–c and 14b,c
Palladium(II) acetate (0.2 equiv) and dppf (0.4 equiv) were dis-
solved in anhydrous DMF (25 mL/mmol of palladium complex). The
mixture was stirred at room temperature for 20 min. A solution of
nucleoside analogue (1 equiv), diethylphosphite (2 equiv) and
propylene oxide (3 equiv) in anhydrous DMF (15 mL/mmol of nu-
cleoside) was added dropwise at room temperature. The solution
was stirred overnight at 80 ꢀC. The solution was evaporated under
high reduced pressure and co-evaporated with absolute ethanol.
5.3.1. 1-(20-O-Acetyl-30-O-benzoyl-60,60-dibromo-50,60-dideoxy-
-ribo-50-hexenofuranosyl)uracil, 11a
Column chromatography of the crude materials on silica gel
b-
D
(CH2Cl2 to EtOAc) gave derivative 11a as white foam (980 mg, 88%).
Rf (toluene/EtOAc, 5:7, v/v) 0.4. 1H NMR (400 MHz, DMSO-d6)
5.4.1. 1-(20-O-Acetyl-30-O-benzoyl-50,60-dideoxy-60-
diethylphosphono-b-D
-ribo-50-hexynofuranosyl)uracil, 12a
d
11.50 (s, 1H exchangeable, NH), 8.01 (m, 2H, H-Ar), 7.82 (d,
J¼8.0 Hz, 1H, H-6), 7.70 (m, 1H, H-Ar), 7.57 (m, 2H, H-Ar), 7.04 (d,
J¼8.8 Hz, 1H, H-50), 5.98 (d, J¼4.4 Hz, 1H, H-10), 5.67 (m, 3H, H-5, H-
20, H-30), 4.81 (dd, J¼5.4, 8.4 Hz, 1H, H-40), 1.95 (s, 3H, Ac). 13C NMR
Column chromatography of crude materials on silica gel
(dichloromethane 100% to ethyl acetate 100%) gave the desired
compound 12a (328 mg, 73%) as a yellow foam.
(100 MHz, DMSO-d6)
d
169.3, 164.5 (C]O), 163.0 (C-4), 150.3 (C-2),
Rf (EtOAc) 0.5. 1H NMR (300 MHz, DMSO-d6)
d 11.62 (br s, 1H
142.3 (C-6), 137.3 (C-50), 134.0, 129.4, 129.0, 128.9, 128.4 (C-Ar),
102.4 (C-5), 95.2 (C-60), 88.9 (C-10), 80.9 (C-40), 72.7, 72.0 (C-20,C-30),
20.2 (Ac). MS ESI>0 m/z 543, 545, 547 (MþH)þ. Relative intensity
1:2:1; ESI<0 m/z 541, 543, 545 (MꢂH)ꢂ. Relative intensity 1:2:1.
HRMS calcd for C19H17Br2N2O7: 542.9402; found: 542.9393. UV
exchangeable, NH), 8.08 (m, 2H, H-Ar), 7.86 (d, J¼8.1 Hz, 1H, H-6),
7.70 (m, 3H, H-Ar), 6.06 (d, J¼4.6 Hz, 1H, H-10), 5.99 (dd, J¼5.9 Hz,
1H, H-30), 5.81 (m, 2H, H-20, H-5), 5.37 (dd, J¼3.4, 5.5 Hz, 1H, H-40),
4.21–4.11 (m, 4H, OCH2CH3), 2.06 (s, 3H, Ac), 1.35–1.30 (t, J¼7.1 Hz,
6H, OCH2CH3). 13C NMR (75 MHz, DMSO-d6)
d 169.2 (C]O), 164.3
lmax¼261 nm (3max¼23,900), lmin¼244 nm (3min¼18,600) (EtOH
(C-4), 163.0 (C-2), 150.2 (C-6), 142.4, 134.1, 129.4, 129.0, 128.2 (C-Ar),
102.4 (C-5), 94.9, 94.2 (C-50, d, J¼48.3 Hz), 89.8 (C-10), 79.4, 75.6 (C-
60, d, J¼284.9 Hz), 73.3 (C-30), 71.9 (C-20), 70.4 (C-40), 63.3, 63.2
(OCH2CH3), 20.2 (Ac), 15.8, 15.7 (OCH2CH3). 31P NMR (121 MHz,
20
95). [
a
]
þ20.2 (c 0.99, MeOH).
D
5.3.2. N-4-Benzoyl-1-(20-O-Acetyl-30-O-benzoyl-60,60-dibromo-
50,60-dideoxy- -ribo-50-hexenofuranosyl)cytidine, 11b
b
-D
DMSO-d6)
d
ꢂ8.84. MS ESI>0 m/z 521 (MþH)þ; ESI<0 m/z 519
Column chromatography of the crude materials on silica gel
(CH2Cl2 to CH2Cl2/EtOAc 1:1, v/v) gave derivative 11b as white foam
(183 mg, 69%).
(MꢂH)ꢂ. HRMS calcd for C23H24N2O10P: 519.1169; found: 519.1182.
UV lmax¼233 nm
(
3max¼18,000), lmin¼250 nm
(3min¼12,000)
20
(EtOH 95). [
a
]
þ1.6 (c 1.24, MeOH).
D
Rf (toluene/EtOAc, 5:7, v/v) 0.35. 1H NMR (300 MHz, DMSO-d6)
d
11.60 (s, 1H exchangeable, NH), 8.46 (d, J¼6.2 Hz, 1H, H-6), 8.21
5.4.2. N-4-Benzoyl-1-(20-O-acetyl-30-O-benzoyl-50,60-dideoxy-60-
diethylphosphono-
-ribo-50-hexyno furanosyl)cytosine, 12b
(m, 1H, H-Ar), 7.80 (m, 9H, H-Ar), 7.62 (d, J¼5.4 Hz, 1H, H-5), 7.30 (d,
b-D
J¼8.3 Hz, 1H, H-50), 6.23 (s, 1H, H-10), 5.95 (m, 2H, H-20, H-30), 5.10
Column chromatography of crude materials on silica gel
(dichloromethane 100% to ethyl acetate 100%) gave the desired
compound 12b (410 mg, 64%) as a yellow foam.
(m, 1H, H-40), 2.21 (s, 3H, Ac). 13C NMR (75 MHz, DMSO-d6)
d 171.6,
169.8, 168.0 (C]O), 165.0 (C-4), 154.8 (C-2), 148.1 (C-6), 135.4 (C-50),
134.6, 133.6, 133.4, 129.9, 129.6, 129.1, 129.0 (C-Ar), 97.4 (C-5), 96.0
(C-60), 92.3 (C-10), 81.8 (C-40), 73.5, 73.4 (C-20,C-30), 20.8 (Ac). MS
Rf (EtOAc) 0.5. 1H NMR (300 MHz, DMSO-d6)
d
11.51 (br s, 1H ex-
changeable, NH), 8.30–7.47 (m, 12H, H-Ar, H-6, H-5), 6.13–6.09 (m,

M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
6045
2H, H-10, H-30), 5.93 (dd, J¼3.6, 6.2 Hz, 1H, H-20), 5.43 (dd, J¼3.4,
6.2 Hz, 1H, H-40), 4.22–4.12 (m, 4H, OCH2CH3), 2.08 (s, 3H, Ac), 1.35–
Rf (EtOAc/MeOH, 3:1, v/v) 0.17. 1H NMR (300 MHz, DMSO-d6)
7.48 (d, J¼7.4 Hz, 1H, H-6), 7.32–7.24 (br s, 2H exchangeable, NH2),
d
1.30 (t, J¼7.0 Hz, 6H, OCH2CH3). 13C NMR (75 MHz, DMSO-d6)
d
169.2
5.85–5.73 (m, 4H, H-5, H-10, OH), 4.63 (dd, J¼3.4, 5.3 Hz, 1H, H-30),
(C]O),164.2 (C-4),164.0 (C]O),155.0 (C-2),147.6 (C-6),134.1,132.8,
129.4, 129.0, 128.5, 128.4, 128.3 (C-Ar), 96.9 (C-5), 95.1, 94.4 (C-50, d,
J¼48.2 Hz), 92.5 (C-10), 79.3, 75.6 (C-60, d, J¼285.2 Hz), 73.6 (C-30),
72.6 (C-20), 70.9 (C-40, d, J¼4.0 Hz), 63.3, 63.2 (OCH2CH3), 20.2 (Ac),
4.22 (m, 1H, H-20), 4.14–4.04 (m, 5H, H-40, OCH2CH3), 1.30–1.25 (t,
J¼7.1 Hz, 6H, OCH2CH3). 13C NMR (75 MHz, DMSO-d6)
d 165.6 (C-4),
155.0 (C-2), 141.0 (C-6), 97.8, 97.1 (C-50, d, J¼48.3 Hz), 94.2 (C-5),
91.0 (C-10), 78.6, 75.0 (C-60, d, J¼287.6 Hz), 74.6 (C-20), 73.2 (C-30),
72.0, 71.9 (C-40, d, J¼4.1 Hz), 63.2, 63.1 (OCH2CH3), 15.9, 15.8
15.8, 15.7 (OCH2CH3). 31P NMR (121 MHz, DMSO-d6)
d
ꢂ8.82. MS
ESI>0 m/z 624 (MþH)þ; ESI<0 m/z 622 (MꢂH)ꢂ. HRMS calcd for
(OCH2CH3). 31P NMR (100 MHz, DMSO-d6)
d
ꢂ8.36. MS ESI>0 m/z,
C30H31N3O10P: 624.1747; found: 624.1741. UV lmax¼263 nm
374 (MþH)þ, 396 (MþNa)þ; ESI<0 m/z 372 (MꢂH)ꢂ. HRMS calcd
20
(
3max¼30,900), lmin¼245 nm (3min¼20,800) (EtOH 95). [
a
]
þ10.0 (c
for C14H21N3O7P: 374.1117; found: 374.1118. UV lmax¼271 nm
D
20
1.00, MeOH). Anal. Calcd for C30H30N3O10P: C, 57.79; H, 4.85; N, 6.74.
Found: C, 57.29; H, 4.99; N, 6.14.
(
3max¼10,900), lmin¼232 nm (3min¼7900) (EtOH 95). [
a]
þ46.9 (c
D
0.97, MeOH). Anal. Calcd for C14H20N3O7P: C, 45.04. Found: C, 44.98.
5.4.3. N-6-Benzoyl-9-(20-O-acetyl-30-O-benzoyl-50,60-dideoxy-60-
5.4.6. 1-(50,60-Dideoxy-60-diethylphosphono- -ribo-50-
b-D
hexynofuranosyl)adenine, 14c
diethylphosphono-
b
-D
-ribo-50-hexyno furanosyl)adenine, 12c
Column chromatography of crude materials on silica gel
(dichloromethane 100% to ethyl acetate 100%) gave the desired
compound 12c (550 mg, 76%) as a yellow foam.
Column chromatography of the crude materials on reverse
phase (H2O/MeOH, 0–100%) gave the titled compound as a yellow
solid (194 mg, 59%) after freeze-drying.
Derivative 14c (36 mg, 17%) could also be prepared by treatment
of 12c (340 mg, 0.53 mmol) with a mixture of MeOH/water/tri-
ethylamine (5:1:1, v/v/v) for 2 h 30 min at room temperature.
Rf (EtOAc/MeOH, 7:3, v/v) 0.6. 1H NMR (300 MHz, DMSO-d6)
Rf (EtOAc) 0.2. 1H NMR (300 MHz, DMSO-d6)
d
11.35 (br s, 1H
exchangeable, NH), 8.88, 8.80 (2s, 2H, H-2, H-8), 8.15–7.60 (m, 10H,
H-Ar), 6.66–6.58 (m, 2H, H-10, H-20), 6.26 (dd, J¼4.7 Hz, 1H, H-30),
5.59 (dd, J¼3.7 Hz, 1H, H-40), 4.19–4.07 (m, 4H, OCH2CH3), 2.07 (s,
3H, Ac), 1.33–1.27 (t, J¼7.0 Hz, 6H, OCH2CH3). 13C NMR (75 MHz,
d
8.29, 8.16 (2s, 2H, H-2, H-8), 7.35 (br s, 2H exchangeable, NH2), 5.96
DMSO-d6)
d
169.2, 164.4 (Cq), 151.8, 144.0 (C-2, C-8), 150.8 (Cq),
(d, J¼5.1 Hz, 1H, H-10), 4.93 (dd, J¼4.9 Hz, 1H, H-20), 4.77 (dd,
J¼3.9 Hz, 1H, H-40), 4.58 (dd, J¼4.5 Hz, 1H, H-30), 4.13–4.02 (m, 4H,
OCH2CH3), 1.29–1.24 (m, 6H, OCH2CH3). 13C NMR (75 MHz, DMSO-
134.2, 133.2, 132.5, 129.5, 129.0, 128.5, 128.3, 126.0 (C-Ar), 94.7, 94.1
(C-50, d, J¼48.2 Hz), 86.3 (C-10), 79.7, 76.0 (C-60, d, J¼285.0 Hz), 74.1
(C-30), 71.8 (C-20), 71.0 (C-40), 63.3, 63.2 (OCH2CH3), 20.1 (Ac), 15.8,
d6) d 156.1,149.3 (Cq),152.7,139.7 (C-2, C-8),119.2 (C-4), 97.5, 96.9 (C-
15.7 (OCH2CH3). 31P NMR (121 MHz, DMSO-d6)
d
ꢂ8.82. MS ESI>0
50, d, J¼48.3 Hz), 88.0 (C-10), 78.7 (C-60), 74.9 (C-30), 72.7 (C-20), 72.6
m/z 648 (MþH)þ; ESI<0 m/z 646 (MꢂH)ꢂ. HRMS calcd for
(C-40, d, J¼4.5 Hz), 63.0 (OCH2CH3), 15.8 (OCH2CH3). 31P NMR
C31H29N5O9P: 646.1703; found: 646.1702. UV lmax¼279 nm
(100 MHz, DMSO-d6)
d
ꢂ8.27. MS ESI>0 m/z 398 (MþH)þ; ESI<0 m/z
20
(
3max¼21,900), lmin¼253 nm (3min¼13,300) (EtOH 95). [
a
]
ꢂ14.6
510 (MþTFA)ꢂ. HRMS calcd for C15H21N5O6P: 398.1229; found:
D
(c 1.03, MeOH).
398.1239. UV lmax¼259 nm
(
3max¼13,300), lmin¼228 nm
20
(
3min¼6200) (EtOH 95). [
a
]
þ27.4 (c 0.95, MeOH). Anal. Calcd for
D
5.4.4. 1-(20-O-Acetyl-30-O-benzoyl-50,60-dideoxy-60-
C15H20N5O6P$H2O: C, 43.38; H, 6.34; N, 16.86. Found: C, 43.86; H,
diethylphosphono-
b
-D
-ribo-50-hexynofuranosyl)uracil, 13
6.28; N, 16.58.
When phosphonylation reaction was performed in toluene in-
stead of DMF, compound 13 was observed as a unique product.
Column chromatography of crude materials on silica gel
(dichloromethane 100% to ethyl acetate 100%) gave the desired
compound as yellow foam (86 mg, 52%).
5.5. Standard procedure for removal of basolabile protecting
groups from 1,1-dibromo-1-alkene nucleosides, 15a–c
The per-acylated nucleoside (11a–c) was dissolved in anhydrous
methanol (25 mL/mmol), then sodium methanolate (4 equiv) was
added and the mixture was stirred at room temperature until
completion of the reaction was indicated by TLC. The reaction was
quenched by the addition of DOWEX 50WX2 under Hþ form, the
resin was filtered off and the filtrate was concentrated under reduce
pressure. Crude material was used with out further purification.
Rf (EtOAc) 0.29. 1H NMR (300 MHz, DMSO-d6)
d 11.60 (br s, 1H
exchangeable, NH), 8.08–7.57 (m, 5H, H-Ar), 7.95 (d, J¼8.1 Hz, 1H,
H-6), 7.40 (dd, J¼7.8, 14.4 Hz, 1H, H-50) 6.08 (d, J¼4.2 Hz, 1H, H-10),
5.87–5.76 (m, 3H, H-20, H-30, H-5), 5.14 (m, 1H, H-40), 4.11 (m, 4H,
OCH2CH3), 2.07 (s, 3H, Ac), 1.29 (m, 6H, OCH2CH3). 13C NMR
(75 MHz, DMSO-d6)
d 169.3, 164.4 (C]O), 163.0 (C-4), 150.3 (C-2),
144.3 (C-50, d, J¼14.9 Hz), 142.7 (C-6), 134.0, 129.3, 129.0, 128.8,
128.6, 128.3 (C-Ar), 117.9, 115.3 (C-60, d, J¼199.3 Hz), 102.3 (C-5),
89.9 (C-10), 79.7 (C-40, d, J¼16.1 Hz), 72.5, 72.3 (C-20, C-30), 63.0
(OCH2CH3), 20.2 (C(CH3)2), 15.8, 15.7 (OCH2CH3). 31P NMR
5.5.1. 1-(60,60-Dibromo-50,60-dideoxy- -ribo-50-
b-D
hexenofuranosyl)uracil, 15a
Derivative 15a was obtained as white foam (99 mg, 90%). Rf
(100 MHz, DMSO-d6)
d
ꢂ7 .9. MS ESI>0 m/z 601, 603 (MþH)þ.
(EtOAc) 0.3. 1H NMR (300 MHz, DMSO-d6)
d
11.44 (br s, 1H ex-
Relative intensity 1:1; ESI<0 m/z 599, 601 (MꢂH)ꢂ. Relative in-
changeable, NH), 7.77 (d, J¼8.1 Hz,1H, H-6), 7.06 (d, J¼8.8 Hz,1H, H-
50), 5.82 (d, J¼5.4 Hz, 1H, H-10), 5.71 (d, 1H, H-5), 5.59 (m, 2H, OH),
4.46 (dd, J¼4.2, 8.8 Hz, 1H, H-40), 4.24 (m, 1H, H-20), 4.02 (m, 1H, H-
tensity 1:1. HRMS calcd for C23H25BrN2O10P: 599.0430; found:
599.0436. UV lmax¼227 nm
(
3max¼21,900), lmin¼250 nm
(
3min¼12,200) (EtOH 95). [
a
]
þ0.9 (c 1.09, MeOH).
30). 13C NMR (75 MHz, DMSO-d6)
d 163.0 (C-4), 150.6 (C-2), 141.3 (C-
20
D
6), 136.7 (C-50), 102.0 (C-5), 93.5 (C-60), 88.7 (C-10), 83.3 (C-40), 73.1
(C-30), 72.4 (C-20). MS ESI<0 m/z 395, 397, 399 (MꢂH)ꢂ. Relative
intensity 1:2:1. HRMS calcd for C10H9Br2N2O5: 394.8878; found:
5.4.5. 1-(50,60-Dideoxy-60-diethylphosphono- -ribo-50-
b-D
hexynofuranosyl)cytosine, 14b
Column chromatography of the crude materials on reverse
phase (H2O/MeOH, 0–100%) gave the titled compound as a white
solid (163 mg, 45%) after freeze-drying.
Derivative 14b (32 mg, 53%) could also be prepared by
treatment of 12b (100 mg, 0.16 mmol) with a mixture of MeOH/
water/triethylamine (5:1:1, v/v/v) for 2 h 30 min, at room
temperature.
394.8875. UV lmax¼260 nm
(
3max¼10,300), lmin¼233 nm
20
(
3min¼3300) (EtOH 95). [
a]
D
þ30.6 (c 0.98, MeOH).
5.5.2. 1-(60,60-Dibromo-50,60-dideoxy- -ribo-50-
b-D
hexenofuranosyl)cytosine, 15b
Derivative 15b was obtained as light yellow foam (385 mg, 91%).
Rf (EtOAc) 0.1. 1H NMR (300 MHz, DMSO-d6)
d
7.67 (d, J¼7.5 Hz, 1H,

6046
M. Meurillon et al. / Tetrahedron 65 (2009) 6039–6046
H-6), 7.27 (br s, 1H exchangeable, NH2), 7.04 (d, J¼8.7 Hz, 1H, H-50),
5.81 (m, 2H, H-10, H-5), 5.50 (br s, 2H, OH), 4.45 (dd, J¼5.4, 8.7 Hz,
1H, H-40), 4.13 (dd, J¼4.6 Hz, 1H, H-20), 4.00 (dd, J¼5.2 Hz, 1H, H-30).
d
165.8 (C-4), 157.3 (C-2), 141.7 (C-6), 96.9 (C-5), 90.3 (C-10), 91.0–
88.0 (C60, d, J¼230.2 Hz), 86.7–86.2 (C-50, d, J¼39.5 Hz), 74.9 (C-20),
74.5 (C-30), 73.8 (C-40, d, J¼3.3 Hz). 31P NMR (121 MHz, D2O)
13C NMR (75 MHz, DMSO-d6)
d
165.6 (C-4), 155.1 (C-2), 142.0 (C-6),
d
ꢂ10.2. MS ESI<0 m/z 316 (MꢂH)ꢂ. HRMS calcd for C10H11N3O7P:
137.0 (C-50), 94.2 (C-60), 93.4, 90.5 (C-5, C-10), 82.6 (C-40), 73.3, 73.1
(C-30, C-20). MS ESI>0 m/z 396, 398, 400 (MþH)þ. Relative intensity
1:2:1. ESI<0 m/z 394, 396, 398 (MꢂH)ꢂ. Relative intensity 1:2:1.
HRMS calcd for C10H12Br2N3O4: 395.9195; found: 395.9203. UV
316.0335; found: 316.0327. UV lmax¼269 nm
(
3max¼10,700),
20
lmin¼226 nm (3min¼6500) (H2O). [
a
]
þ17.77 (c 1.01, H2O).
D
b-D
5.6.2. 1-(50,60-Dideoxy-60-phosphono- -ribo-50-
lmax¼271 nm (3max¼11,500), lmin¼235 nm (3min¼8600) (EtOH 95).
hexynofuranosyl)adenine (disodium salt), 16c
20
[
a]
þ55.3 (c 1.01, MeOH).
Column chromatography of the crude materials on reverse
phase (H2O) gave the corresponding phosphonic acid. The titled
compound was obtained after HPLC purification, ion exchange on
DOWEX Naþ and freeze-drying as a white solid (5 mg, 3.5%).
Rf (iPrOH/NH4OH 30%/H2O, 7:1:2, v/v/v) 0.13. 1H NMR (300 MHz,
D
5.5.3. 9-(60,60-Dibromo-50,60-dideoxy- -ribo-50-
b-D
hexenofuranosyl)adenine, 15c
Derivative 15c was obtained as light yellow foam (121 mg, 96%).
Rf (EtOAc/MeOH, 8:2, v/v) 0.4. 1H NMR (300 MHz, DMSO-d6)
d
8.39,
D2O)
d
8.47, 8.19 (2s, 2H, H-2, H-8) 6.10 (d, J¼6.02 Hz, 1H, H-10), 4.98
8.16 (2s, 2H, H-2, H-8), 7.34 (br s, 1H exchangeable, NH2), 7.16 (d,
J¼8.6 Hz,1H, H-50), 5.92 (d, J¼5.7 Hz,1H, H-10), 4.78 (t, J¼5.2 Hz,1H,
H-20), 4.52 (dd, J¼3.5, 8.6 Hz, 1H, H-40), 4.22 (t, J¼4.1 Hz, 1H, H-30).
(dd, J¼5.23 Hz, 1H, H-20), 4.84 (d, J¼2.71 Hz, 1H, H-40), 4.53 (d,
J¼3.59 Hz, 1H, H-30). 13C NMR (75 MHz, D2O)
d 152.9, 140.2 (C-2, C-
8), 86.9 (C-10), 74.9, 74.8 (C-20, C-30). 31P NMR (121 MHz, D2O)
13C NMR (75 MHz, DMSO-d6)
d
156.1 (C-4), 152.5, 140.1 (C-2, C-8),
d
ꢂ10.0. SM ESI<0 m/z 340 (MꢂH)ꢂ. HRMS calcd for C11H11N5O6P:
149.2 (C-6), 137.2 (C-50), 119.3 (C-60), 92.6 (C-5), 87.6 (C-10), 84.0 (C-
40), 73.7 (C-30), 72.8 (C-20). MS ESI>0 m/z 420, 422, 424 (MþH)þ.
Relative intensity 1:2:1. ESI<0 m/z 418, 420, 422 (MꢂH)ꢂ. Relative
intensity 1:2:1. HRMS calcd for C11H12Br2N5O3: 419.9307; found:
340.0447; found: 340.0473.
Acknowledgements
419.9308. UV lmax¼260 nm
(
3max¼15,400), lmin¼231 nm
This work was supported by Association pour la Recherche
contre le Cancer (ARC). M.M. and F.G. are grateful to the CNRS &
20
(
3min¼4300) (EtOH 95). [
a]
þ5.06 (c 0.99, MeOH).
D
´
Region Languedoc-Roussillon for their doctoral fellowships.
5.6. Standard procedure for removal of phosphonate
protecting groups, 16b,c
References and notes
The nucleoside diethylphosphonate derivative was dissolved in
anhydrous DMF (20 mL/mmol), then TMSBr (15 equiv) was added
at 0 ꢀC and the mixture was stirred at room temperature until
completion of the reaction was indicated by TLC. The reaction
mixture was neutralized with aqueous TEAB 1 M and concentrated
under high vacuum.
1. Iorga, B.; Eymery, F.; Carmichael, D.; Savignac, P. Eur. J. Org. Chem. 2000, 3103.
2. Lindlar, J.; Dubuis, R. Org. Synth. 1966, 46, 89.
3. Leclercle´, D.; Mothes, C.; Taran, F. Synth. Commun. 2007, 37, 1301.
4. Lera, M.; Hayes, C. J. Org. Lett. 2000, 2, 3873.
5. Chattha, M. S.; Aguiar, A. M. J. Org. Chem. 1971, 36, 2719.
6. Desai, N. B.; McKelvie, N.; Ramirez, F. J. Am. Chem. Soc. 1962, 84, 1745.
7. Corey, E.; Fusch, P. Tetrahedron Lett. 1972, 13, 3769.
8. Peyrottes, S.; Gallier, F.; Be´jaud, J.; Pe´rigaud, C. Tetrahedron Lett. 2006, 47, 7719.
5.6.1. 1-(50,60-Dideoxy-60-phosphono- -ribo-50-
b-D
´
9. Gallier, F.; Peyrottes, S.; Perigaud, C. Eur. J. Org. Chem. 2007, 925.
10. Sharma, R. A.; Bobek, M. J. Org. Chem. 1978, 43, 367.
11. Hampton, A. J. Am. Chem. Soc. 1961, 83, 3640.
12. More, J. D.; Finney, N. Org. Lett. 2002, 4, 3001.
13. Kralikova, S.; Budesinsky, M.; Tomeckova, I.; Rosenberg, I. Tetrahedron 2006, 62,
9742.
14. Shen, W.; Wang, L. J. Org. Chem. 1999, 64, 8873.
15. Thielges, S.; Meddah, E.; Bisseret, P.; Eustache, J. Tetrahedron Lett. 2004, 45, 907.
16. Hodge, P.; Khoshdel, E. React. Polym. 1985, 3, 143.
17. Rosowsky, A.; Lazarus, H.; Yamashita, A. J. Med. Chem. 1976, 19, 1265.
18. Lavaire, S.; Plantier-Royon, R.; Portella, C.; DeMonte, M.; Kirn, A.; Aubertin,
A. M. Nucleosides Nucleotides 1998, 17, 2267.
hexynofuranosyl)cytosine (disodium salt), 16b
Column chromatography of the crude materials on reverse
phase (H2O) gave the corresponding phosphonic acid and the titled
compound was obtained as a white solid (72 mg, 72%) after ion
exchange on DOWEX Naþ, dialysis with cellulose membrane and
freeze-drying.
Rf (iPrOH/NH4OH 30%/H2O, 7:1:2, v/v/v) 0.08. 1H NMR
(300 MHz, D2O)
d
7.79 (d, J¼7.15 Hz, 1H, H-6), 6.10 (d, J¼7.27 Hz, 1H,
H-5), 5.96 (d, J¼3.9 Hz, 1H, H-10), 4.74 (dd, J¼2.6 Hz, H-40), 4.44 (d,
19. Magnani, A.; Mikuriya, Y. Carbohydr. Res. 1973, 28, 158.
20. Vorbru¨ggen, H.; Krolokiewicz, K.; Bennua, B. Chem. Ber. 1981, 114, 1234.
J¼4.0 Hz, H-20), 4.35 (d, J¼3.8 Hz, H-30). 13C NMR (75 MHz, D2O)