Synthesis of a new family of acyclic nucleoside phosphonates, analogues of TPases transition states

Article abstract of DOI:10.1039/c2ob25131k

A 6-step procedure was developed for the synthesis of a new family of acyclic nucleoside phosphonates (ANPs), "PHEEPA" [(2-pyrimidinyl-2-(2- hydroxyethoxy)ethyl)phosphonic acids] in overall yields ranging from 4.5% to 32%. These compounds, which possess on one side a hydroxy function and on the other side a phosphonate group, can be considered either as potential antiviral agents or as transition state analogues of nucleoside phosphorylases such as thymidine phosphorylase.

Full text of DOI:10.1039/c2ob25131k

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PAPER
Synthesis of a new family of acyclic nucleoside phosphonates, analogues of
TPases transition states†
Bénédicte Dayde,a,b Samira Benzaria,b Claire Pierra,b Gilles Gosselin,b,c Dominique Surleraux,b
Jean-Noël Volle,a Jean-Luc Pirata and David Virieux*a
Received 17th January 2012, Accepted 29th February 2012
DOI: 10.1039/c2ob25131k
A 6-step procedure was developed for the synthesis of a new family of acyclic nucleoside phosphonates
(ANPs), “PHEEPA” [(2-pyrimidinyl-2-(2-hydroxyethoxy)ethyl)phosphonic acids] in overall yields
ranging from 4.5% to 32%. These compounds, which possess on one side a hydroxy function and on the
other side a phosphonate group, can be considered either as potential antiviral agents or as transition state
analogues of nucleoside phosphorylases such as thymidine phosphorylase.
of cytomegalovirus virus infections in immunosuppressed
patients (Fig. 1).
Introduction
For several decades, nucleoside and nucleotide analogues have
proved to be promising therapeutic agents, in particular as anti-
virals.1 Among them, the acyclic nucleoside phosphonate family
(ANPs) represents a prominent class of nucleotide analogues
with a broad-spectrum of antiviral activity (HIV, HBV, papil-
loma-, adeno-, herpes- and poxviruses).2 Some of them have
been approved worldwide by regulatory agencies for clinical
uses.3 Indeed, one of the first ANP derivatives, (S)-9-(3-
hydroxy-2-phosphonomethoxypropyl)adenine [(S)-HPMPA] 1,
was developed 30 years ago, and exhibited a notable activity
against virtually all DNA viruses. This structural motif is shared
by the group of acyclic nucleoside phosphonates for which Teno-
fovir 2, Adefovir 3 and Cidofovir 4 are the well-known block-
blusters. Adefovir 3 (9-(2-phosphonylmethoxyethyl)adenine,
PMEA, Adefovir dipivoxil: Hepsera®) is a large-spectrum
nucleotide analogue active against herpes-, hepadna- and retro-
viruses used in standard therapy of chronic HBV infection. Teno-
fovir 2 ((R)-9-(2-phosphonylmethoxypropyl)adenine), PMPA,
Tenofovir disoproxil fumarate: Viread®) is prescribed for the
treatment of both AIDS and HBV infections, whereas Cidofovir
Their modes of action are similar: in cell, the phosphonate
group is transformed into di- and/or triphosphate bioconjugates
which inhibit DNA polymerase and/or reverse transcriptase.
We present herein the synthesis of a new family of ANPs in
the pyrimidinyl series 5 (Fig. 2). The acyclic sugar chain of
these new compounds is terminated, on one side by a hydroxy
function and, on the other side, by a phosphonate group. The
latter is less polar than the phosphate part and should prevent
Fig. 1 Marketed acyclic nucleoside analogues.
4
(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine,
HPMPC, Vistide®) is a commonly prescribed drug for treatment
aAM2N, Institut Charles Gerhardt, UMR 5253, ENSCM, 8 rue de
l’Ecole Normale, F-34296 Montpellier, France. E-mail: david.virieux@
enscm.fr; Fax: +33 (0)467 14 43 19; Tel: +33 (0)467 14 43 14
bIdenix Pharmaceuticals, Medicinal Chemistry Laboratory, Cap
Gamma, 1682 rue de la Valsière, BP50001, 34189 Montpellier Cedex 4,
France
cUMR5247 CNRS-UM1-UM2 (IBMM), Université Montpellier 2, 34095
Montpellier Cedex 5, France
†Electronic supplementary information (ESI) available: Copies of the
relevant spectra or analyses (1H NMR, 13C NMR, 31P NMR, MS,
HRMS). See DOI: 10.1039/c2ob25131k
Fig. 2 Targeted acyclic nucleoside analogues and transition state
derivative of thymidine phosphorylase.
3448 | Org. Biomol. Chem., 2012, 10, 3448–3454
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Scheme 1 Synthesis of benzyloxyethyloxyethylenylphosphonate 6.
Scheme 2 Iodo-base introduction on 6.
enzymatic degradation and/or facilitate the nucleoside activation
step by avoiding problems during the intracellular first phos-
phorylation step. Moreover, the pseudo-anomeric carbon is pre-
served and the central oxygen of the aminal function could
behave as the classical ether function of ANPs. Indeed, it has
been suggested that the oxygen atom would contribute to the for-
mation of reactive species in the active site of the nucleic acid
polymerases by a metal ion binding.4 Another interest can be
found in the structural analogy with the transition state involved
in pyrimidine or purine nucleoside phosphorylase enzymes as
illustrated with TPase (Fig. 2).5
Scheme 3 Reduction and debenzylation steps.
Results and discussion
Using these conditions, the addition of pyrimidine nucleo-
bases was carried out using uracil, thymine and N-benzoyl-cyto-
sine. The reaction was fully stereo- and regioselective affording
only one regio- and diastereomer 9a–c. Formerly, the stereo-
chemical outcome of this addition led to a racemic mixture
where iodine and nucleobase were introduced relatively in the
trans position (Scheme 2).
Further, removal of the iodine was effective using the radical
deiodination mediated by tributyltin hydride (Scheme 3).13 The
expected products 10a–c (U, T and C-Bz) were obtained in
yields ranging from 66 to 85%. Benzoyl protection of the cyto-
sine base was removed using sodium methoxide to afford the
free cytosine derivative 10c in 79% yield.14 The following step
was the debenzylation of the terminal hydroxyl group which
occurred selectively and completely with uracil 11a and thymine
11b using a continuous flow reactor (H-Cube apparatus) and a
Pd/C 10% cartridge in full H2 mode with a flow of 1 mL min−1
in ethanol. Unfortunately the debenzylation failed under the
same conditions with the unprotected cytosine 10c. After opti-
mization, the best conditions for the debenzylation of cytosine
derivative 10c were found using boron tribromide in dichloro-
methane (1.0 M) at −30 °C.15 The expected product 11c was iso-
lated in 44% yield along with a partial P-ester cleavage.
The strategy to access these new compounds 5 was based on the
introduction of the nucleobase on a key intermediate, the diethyl
2-[2-(benzyloxyl)ethoxy]ethenylphosphonate 6 (Scheme 1). This
vinylphosphonate derivative 6 was synthesized from the (E)-
diethyl 2-ethoxyvinylphosphonate 8, accessible in two steps
starting from the reaction of triethyl phosphite with bromoacetal-
dehyde diethylacetal.6 The second step was scarcely described
and currently uses strong bases and/or high temperature.7 In this
work, the elimination reaction was performed under milder con-
ditions, with 0.1 equivalent of p-toluenesulfonic acid. Ethanol
was removed during the reaction by azeotropic distillation.
Under these new conditions, the expected vinylphosphonate 8
was obtained quantitatively after 6 h heating and isolated in large
scale in 80% yield after distillation. The ethenylphosphonate 6
was finally prepared by an addition–elimination step using ben-
zyloxyethanol. Despite a substoichiometric amount of this
reagent, 15–20% of the bis(benzyloxyethyl)acetal was observed
which was probably in equilibrium with the expected product 6
in the reaction mixture. Nevertheless, the key precursor 6 was
synthesized in 65% yield and with purity higher than 95% by
31P NMR after distillation.
The key step for the synthesis of targets 5 was the addition of
appropriate nucleobases to the unsaturated intermediate 6. The
reactivity of this unusual double bond was not described before.
Our first attempts at the addition of nucleobase used Michael-
type conditions. Unfortunately, no reaction was observed either
in basic8 or acidic conditions.9 In order to get a better knowledge
of the reactivity and the behavior of this alkene function, we
tried to perform dihydroxylation10 and epoxidation reactions.11
Whatever the reagent, no reaction was observed under the tested
conditions.
Finally, the phosphonate ester deprotection of this new series
was achieved using either LiBr16 for an access to the monophos-
phonate esters 12a–c, or TMSBr17 to get the free phosphonic
acids 13a–c (Scheme 4).
Conclusions
In summary, we successfully developed a methodology for the
access to a new family of ANPs in the pyrimidinyl series,
keeping the aminal function. It allowed the preparation of orig-
inal nucleotide analogues in only 6–7 steps and in overall yields
ranging from 4.5% and 32%. The activity evaluations of such
compounds will be presented in a dedicated paper.
The α,β-unsaturated phosphonate 6 was successfully reacted
in the presence of iodine and O-silyl uracil (Scheme 2).12 By
contrast, the addition of purines such as adenine appeared
inefficient.
This journal is © The Royal Society of Chemistry 2012
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After return to rt, the reaction mixture was concentrated under
vacuum and distilled (bp = 84–87 °C, P = 32 × 10−3 mbar) to
afford 8 as a colorless oil (13.72 g, 80%).§ 31P NMR (CDCl3,
161.97 MHz) δ = 22.6; 1H NMR (CDCl3, 400.13 MHz) δ =
3
3
7.14 (dd, JHH = 13.6 Hz, JPH = 11.5 Hz, 1H, OCH), 4.64 (dd,
3JHH = 13.6 Hz, 2JPH = −10.0 Hz, 1H, PCH), 4.05–3.93 (m, 4H,
2 CH2), 3.83 (q, 3JHH = 13.6 Hz, 2H, OCH2), 1.27 (t, 3JHH = 7.1
Hz, 3H, CH3), 1.12 (t, 3JHH = 7.1 Hz, 6H, 2 CH3).
Scheme 4 Synthesis of free phosphonic acid and mono-lithium salt
derivatives 5a–c and 12a–c.
(E)-Diethyl 2-[2-(benzyloxy)ethoxy]vinylphosphonate (6)
In a 100 mL two-necked flask under nitrogen equipped with a
Dean Stark apparatus were introduced (E)-diethyl (2-ethoxy)
vinylphosphonate 8 (8.00 g, 38 mmol) in toluene (360 mL), ben-
zyloxyethanol (5.67 g, 37 mmol) and p-toluenesulfonic acid
(0.32 g, 1.9 mmol). The reaction mixture was heated 6 h in order
to remove the toluene–ethanol azeotrope. After return to rt, the
reaction mixture was concentrated under vacuum. The impurities
were removed by distillation (b.p. = 150–170 °C, 60–70 × 10−3
mbar) affording a yellow oil as residue 6 (9.09 g, 79%). 31P
(CDCl3, 161.97 MHz) δ = 22.0; 1H NMR (CDCl3, 400.13 MHz)
δ = 7.45–7.23 (m, 6H, CH and OCH), 4.74 (dd, 3JHH = 13.6 Hz,
2JPH = −9.7 Hz, 1H, PCH), 4.56 (s, 2H, PhCH2), 4.10–3.97 (m,
Experimental section
General considerations: Before use, commercial reagents were
purified by distillation or sublimation. All manipulations were
carried out using standard Schlenck techniques. Solvents were
dried according to current methods, distilled and stored under
nitrogen atmosphere. All reactions involving air or moisture sen-
sitive reagents or intermediates were carried out under dry nitro-
gen in flame-dried glassware. Melting points were measured on
a Büchi B-540 apparatus and are uncorrected. All new com-
pounds were characterized by H NMR, 13C NMR, 31P NMR
1
using a Bruker DRX 400 MHz NMR spectrometer or a Bruker
Avance 250 MHz NMR spectrometer. All NMR experiments
performed on phosphorus were recorded with proton-decoupled.
All NMR recorded during reaction were done with a closed
capillary DMSO-d6 probe in the NMR tube. Low and high resol-
ution mass spectra were determined on an electrospray ionization
(RSI) WATERS Micromas Q-Tof spectrometer with as internal
reference H3PO4 (0.1% in water–acetonitrile, 1 : 1).
3
6H, 3 CH2), 3.72–3.69 (m, 2H, CH2), 1.30 (t, JHH = 6.9 Hz,
6H, 2 CH3); 13C NMR (CDCl3, 100.61 MHz) δ = 163.4 (d, 2JCP
= 21.5 Hz, OCH), 137.6 (s, C), 128.4 (s, CH), 127.8 (s, CH),
127.7 (s, CH), 88.5 (d, 1JCP = 200.5 Hz, PCH), 73.3 (s, PhCH2),
2
69.9 (s, OCH2), 67.8 (s, OCH2), 61.8 (d, JCP = 5.2 Hz, OCH2),
16.3 (d, 3JCP = 6.7 Hz, CH3); MS-ESI+ m/z = 315.1 (31%) [M +
H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for C15H23O5P:
315.1361; found 315.1359.
Diethyl (2,2-diethoxyethyl)phosphinate (7)
General procedure for the synthesis of 9a–9c
In a 100 mL two-necked flask under nitrogen equipped with a
Dean Stark apparatus were successively introduced 2-bromoace-
taldehyde diethyl acetal (20.00 g, 101 mmol) and triethyl phos-
phite (33.70 g, 202 mmol). The reaction mixture was heated at
165 °C for 4 h. The resulting bromoethane was distilled off in
the Dean Stark (∼6 mL). Then, the reaction mixture was cooled
to room temperature and distilled under vacuum (bp = 78–81 °C,
P = 93 × 10−3 mbar) affording 7 as a colorless oil (21.01 g,
81%).‡ 31P NMR (CDCl3, 161.97 MHz) δ = 26.4; 1H NMR
In a 100 mL two-necked flask under nitrogen were introduced
(E)-diethyl 2-[2-(benzyloxy)ethoxy]vinylphosphonate 6 (1 eq.)
and CH2Cl2 (1 volume, concentration 0.1 mol × L−1). The reac-
tion mixture was cooled at −30 °C. The appropriate trimethyl-
silyl nucleobase (3 eq.) and iodine (1.8 eq.) were added while
maintaining the temperature at −30 °C for 5 h. Then, the reaction
mixture was allowed to reach rt for the night. After addition of
CH2Cl2 (5 volumes), the organic layer was washed with a sol-
ution of 10% Na2S2O3 (2.5 volumes) until it became colorless
and then the organic layer was washed with water. The organic
layers were dried over MgSO4 and concentrated under vacuum
giving the crude material which was purified by column chrom-
atography on silica gel.
3
3
(CDCl3, 400.13 MHz) δ = 4.80 (dt, JPH = 5.5 Hz, JHH = 5.3
Hz, 1H, OCHO), 4.06–3.99 (m, 4H, 2 CH2), 3.61–3.54 (m, 1H,
CH2), 3.50–3.42 (m, 1H, CH2), 2.11 (dd, 2JPH = −18.7 Hz, 3JHH
3
= 5.7 Hz, 2H, PCH2), 1.26 (t, JHH = 7.1 Hz, 6H, CH3), 1.12 (t,
3JHH = 7.2 Hz, 6H, CH3).
( )-(1R,2R)-Diethyl 2-[2-(benzyloxy)ethoxy]-2-(2,4-dioxo-3,4-
dihydropyrimidin-1(2H)-yl)-1-iodoethylphosphonate (9a). Ester
6 (0.50 g, 1.60 mmol, 1 eq.) was reacted according to the
general procedure. The crude reaction mixture was purified by
chromatography on silica gel (25 g, gradient CH2Cl2–AcOEt
(E)-Diethyl (2-ethoxy)vinylphosphonate (8)
In a 100 mL two-necked flask under nitrogen equipped with a
Dean Stark apparatus were introduced diethyl 2,2-diethoxyethyl-
phosphonate 7 (20.97 g, 82 mmol) in toluene (100 mL) and p-
toluenesulfonic acid (1.37 g, 8 mmol). The reaction mixture was
heated 6 h in order to remove the toluene–ethanol azeotrope.
(80 : 20 to 20 : 80)) affording 9a as a clear oil (0.35 g, 40%). 31
P
NMR (CDCl3, 161.97 MHz) δ = 16.6; 1H NMR (CDCl3,
§The formation of 8 was already described in literature using basic con-
ditions (LDA): Kouno et al.7a
‡The phosphonate 7 was already described by Varlet et al.6
3450 | Org. Biomol. Chem., 2012, 10, 3448–3454
This journal is © The Royal Society of Chemistry 2012

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3
400.13 MHz) δ = 9.55 (s, 1H, NH), 7.55 (d, JHH = 8.1 Hz, 1H,
CH3); MS ESI+ m/z = 656 (100%) [M + H]+; HRMS-ESI+ (m/z):
3
4
NCH), 7.31–7.20 (m, 5H, CH), 5.57 (dd, JHH = 8.1 Hz, JHH
1.7 Hz, 1H, CH), 5.41 (t, JHH = JPH = 3.2 Hz, 1H, OCHN),
=
[M + H]+ calcd for C26H32N3O7IP: 656.1023; found 656.1017.
3
3
2
4.49 and 4.45 (2 d, 2H, JHH = −11.9 Hz, PhCH2), 4.35 (dd,
2JPH = 14.3 Hz, JHH = 3.2 Hz, 1H, PCH), 4.24–4.05 (m, 4H, 2
3
General procedure for the deiodination reaction – synthesis of
10a–c
OCH2), 3.92–3.50 (m, 4H, CH2CH2), 1.28 and 1.27 (2 t, 3JHH
=
4.1 Hz, 6H, 2 CH3); 13C NMR (CDCl3, 100.61 MHz) δ = 162.6
(s, CvO), 149.3 (s, CvO), 139.0 (s, NCH), 136.6 (s, C), 126.8
(s, CH), 126.6 (s, CH), 127.5 (s, CH), 100.2 (s, CH), 82.8 (s,
OCHN), 72.2 (s, PhCH2), 69.3 (s, OCH2), 67.4 (s, OCH2), 63.2,
Iodophosphonate 9a–c (1 eq, concentration 0.024 mol L−1 in
toluene – 1 volume) was dissolved in a two-necked round-
bottom flask with a condenser and under nitrogen. AIBN (0.8
eq) and nBu3SnH (1.8 eq) were added to the solution and the
mixture was heated for 5 h at 70 °C. After cooling at room temp-
erature, saturated NH4Cl solution was added (1 volume) and the
resulting phases separated. The aqueous layer was extracted 3
times by AcOEt (1 volume) and the organic layers were dried
over MgSO4, filtered and concentrated under vacuum. The crude
mixture was purified by chromatography on silica gel.
2
1
62.9 (2 d, JCP = 6.6 Hz, OCH2), 18.1 (d, JCP = 145.6 Hz,
PCH), 15.3 (d, JCP = 5.9 Hz, CH3); MS-ESI+ m/z = 553.0
3
(100%) [M + H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for
C19H27IN2O7P: 553.0601; found 553.0607.
( )-(1R,2R)-Diethyl 2-[2-(benzyloxy)ethoxy]-2-(5-methyl-2,4-
dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-1-iodoethylphosphonate
(9b). Ester 6 (1.02 g, 3.20 mmol, 1 eq.) was reacted according
to the general procedure. The crude reaction mixture was
purified by chromatography on silica gel (25 g, gradient 100%
CH2Cl2 to 100% AcOEt) affording 9b as a clear oil (0.81 g,
45%). 31P NMR (CDCl3, 161.97 MHz) δ = 16.6; 1H NMR
(CDCl3, 400.13 MHz) δ = 8.03 (s, 1H, NH), 7.36 (s, 1H,vCH–
( )-Diethyl 2-[2-(benzyloxy)ethoxy]-2-(2,4-dioxo-3,4-dihydro-
2H-pyrimidin-1-yl)ethylphosphonate (10a). Iodophosphonate 9a
(0.61 g, 1.10 mmol, 1 eq.) was reacted according to the general
procedure. The crude reaction mixture was purified by chromato-
graphy on silica gel (gradient 100% AcOEt–50%–50% AcOEt–
(AcOEt–EtOH 9 : 1)) affording 10a as a colorless oil (0.398 g,
85%). 31P NMR (CDCl3, 161.97 MHz) δ = 22.9; 1H NMR
(CDCl3, 400.13 MHz) δ = 8.78 (s, 1H, NH), 7.34 (d, 3JHH = 8.1
3
3
N), 7.30–7.20 (m, 5H, CH), 5.42 (t, JHH = JPH = 3.3 Hz, 1H,
2
OCHN), 4.48 and 4.46 (2 d, 2H, JHH = −11.8 Hz, PhCH2),
3
4.31 (dd, 2JPH = −14.1 Hz, 3JHH = 3.3 Hz, 1H, PCH), 4.18–4.09
(m, 4H, POCH2), 3.84–3.50 (m, 4H, 2 CH2), 1.28 and 1.27 (2 t,
3JHH = 7.3 Hz, 6H, CH3); 13C NMR (CDCl3, 100.61 MHz) δ =
163.7 (s, CvO), 150.2 (s, CvO), 139.0 (s, CHN), 137.7 (s,
PhC), 128.5 (s, CH), 127.9 (s, CH), 127.7 (s, CH), 109.8 (s,
CMe), 83.6 (s, OCHN), 73.3 (s, CH2Ph), 70.1 (s, OCH2), 68.5
Hz, 1H, NCH), 7.31–7.18 (m, 5H, CH), 5.95 (ddd, JPH = 7.80
3
3
3
Hz, JHH = 6.6 Hz, JHH = 6.1 Hz, 1H, OCHN), 5.64 (dd, JHH
4
= 8.1 Hz, JHH = 2.2 Hz, 1H, CHC(O)), 4.45 (s, 2H, PhCH2),
4.07–3.99 (m, 4H, 2 OCH2), 3.73–3.47 (m, 4H, CH2CH2), 2.30
3
2
3
(ddd, JPH = −18.3 Hz, JHH = −15.4 Hz, JHH = 6.1 Hz, 1H,
3
2
3
PCH2), 2.23 (ddd, JPH = −18.9 Hz, JHH = −15.4 Hz, JHH
=
3
2
2
6.6 Hz, 1H, PCH2), 1.22 and 1.23 (2 t, JHH = 7.0 Hz, 6H, 2
CH3), 13C NMR (CDCl3, 100.61 MHz) δ = 162.9 (s, CvO),
150.4 (s, CvO), 139.2 (s, NCH), 137.7 (s, C), 128.5 (s, CH),
127.8 (s, CH), 127.7 (s, CH), 102.9 (s, CH), 81.6 (s, OCHN),
73.3 (s, CH2), 68.9 (s, CH2), 68.6 (s, CH2), 62.4, 62.1 (2 d, 2JCP
(s, OCH2), 64.2 (d, JCP = 5.9 Hz, OCH2), 63.9 (d, JCP = 6.6
Hz, OCH2), 18.9 (d, 1JCP = 145.6 Hz, PCH), 16.4 (d, JCP = 5.9
3
Hz, CH3), 12.5 (s, CH3); MS-ESI+ m/z = 567.2 (100%) [M +
H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for C20H29N2O7IP:
567.0757; found 567.0757.
1
= 6.6 Hz, OCH2), 32.4 (d, JCP = 142.0 Hz, PCH2), 16.4 (d,
3JCP = 6.6 Hz, 2 CH3); MS ESI+ m/z = 427.2 (100%) [M + H]+,
m/z = 853.5 (92%) [2M + H]+; HRMS-ESI+ (m/z): [M + H]+
calcd for C19H28N2O7P: 427.1634; found 427.1633.
( )-(1R,2R)-Diethyl 2-[2-(benzyloxy)ethoxy]-2-[2-(4-benzoyl-
amino-2-oxo-2H-pyrimidin-1-yl)]-1-iodoethylphosphonate (9c).
Ester 6 (0.94 g, 3.00 mmol, 1 eq.) was reacted according to the
general procedure. The crude reaction mixture was purified by
chromatography on silica gel (40 g, gradient 100% CH2Cl2 to
100% AcOEt) affording 9c as a yellow solid (0.62 g, 32%). 31P
NMR (CDCl3, 161.97 MHz) δ = 17.1; 1H NMR (CDCl3,
( )-Diethyl 2-(2-(benzyloxy)ethoxy)-2-(5-methyl-2,4-dioxo-3,4-
dihydro-2H-pyrimidin-1-yl)ethylphosphonate (10b). Iodophos-
phonate 9b (0.64 g, 1.10 mmol, 1 eq.) was reacted according to
the general procedure. The crude reaction mixture was purified
by chromatography on silica gel (gradient 100% AcOEt–50%–
50% AcOEt–(AcOEt–EtOH 9 : 1)) affording 10b as a colorless
oil (0.416 g, 84%). 31P NMR (CDCl3, 161.97 MHz) δ = 23.2;
1H NMR (CDCl3, 400.13 MHz) δ = 8.92 (s, 1H, NH),
3
400.13 MHz) δ = 8.99 (s, 1H, NH), 8.03 (d, JHH = 7.5 Hz, 1H,
NCH), 7.87–7.83 (m, 2H, CH), 7.56–7.40 (m, 4H, CH and CH),
3
7.32–7.19 (m, 5H, CH), 5.45 (t, JHH
=
3JPH = 2.6 Hz, 1H,
2
3
OCHN), 4.62 (dd, JPH = −14.6 Hz, JHH = 2.6 Hz, 1H, PCH),
4.48 and 4.45 (2 d, JHH = −10.0 Hz, 2H, PhCH2), 4.20–4.08
2
3
7.30–7.14 (m, 6H, CH and PhCH), 5.96 (ddd, JPH = 7.6 Hz,
2
3
3
(m, 4H, 2 POCH2), 3.88 (ddd, JHH = −9.9 Hz, JHH = 4.3 Hz,
3JHH = 2.0 Hz, 1H, OCH2), 3.75–3.62 (m, 2H, OCH2), 3.54
(ddd, 3JHH = 6.7 Hz, 2JHH = 4.3 Hz, 3JHH = 2.0 Hz, 1H, OCH2),
3JHH = 6.7 Hz, JHH = 6.2 Hz, 1H, OCHN), 4.44 (s, 2H, CH2),
4.07–3.99 (m, 4H, OCH2), 3.70–3.47 (m, 4H, CH2CH2), 2.30
2
2
3
(ddd, JPH = −20.3 Hz, JHH = −16.8 Hz, JHH = 6.7 Hz, 1H,
1.26 (t, JHH = 7.0 Hz, 6H, 2 CH3); 13C NMR (CDCl3,
PCH2), 2.23 (ddd, JPH = −19.7 Hz, JHH = −16.8 Hz, JHH =
3
2
2
3
3
100.61 MHz) δ = 162.8 (s, CvO), 145.1 (s, CH), 137.7 (s, C),
133.1, 128.9, 128.5, 127.8, 127.6, 127.5 (6 s, CH), 95.8 (s, CH),
84.5 (s, OCHN), 73.2 (s, PhCH2), 70.5 (s, OCH2), 68.4 (s,
6.2 Hz, 1H, PCH2), 1.79 (s, 3H, CH3), 1.21 and 1.23 (2 t, JHH
= 7.2 Hz, 6H, 2 CH3); 13C NMR (CDCl3, 100.61 MHz) δ =
163.7 (s, CvO), 150.6 (s, CvO), 137.8 (s, C), 134.7 (s, CH),
128.4 (s, CH), 127.8 (s, CH), 127.6 (s, CH), 111.5 (s, C), 81.0
(s, OCHN), 73.3 (s, PhCH2), 68.7 (s, 2 CH2), 62.3 (d, 2JCP = 5.9
2
2
OCH2), 64.1 (d, JCP = 6.3 Hz, OCH2), 63.8 (d, JCP = 6.8 Hz,
OCH2), 19.8 (d, 1JCP = 145.6 Hz, PCH), 16.4 (d, 3JCP = 6.1 Hz,
This journal is © The Royal Society of Chemistry 2012
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2
1
Hz, OCH2), 62.0 (d, JCP = 6.6 Hz, OCH2), 32.4 (d, JCP
=
H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for C19H29N3O6P:
426.1794; found 426.1791.
3
142.0 Hz, PCH2), 16.4 (d, JCP = 5.9 Hz, CH3), 12. 5 (s, CH3);
MS ESI+ m/z = 441.2 (100%) [M + H]+, m/z = 881.5 (92%) [2M
+ H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for C20H30N2O7P:
441.1791; found 441.1790.
( )-Diethyl 2-(2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-2-(2-
hydroxyethoxy)ethylphosphonate (11a). O-Benzyl phosphonate
10a (52 mg, 0.12 mmol, 1 eq.) was dissolved in anhydrous
ethanol (6 mL) and the solution was reacted using a H-cube
(Pd/C 10%, 1 mL min−1, full H2 mode). The reaction mixture was
concentrated under vacuum giving 11a as a colorless oil (43 mg,
quantitative). 31P NMR (CDCl3, 161.97 MHz) δ = 24.6; 1H
NMR (CDCl3, 400.13 MHz) δ = 9.76 (s, 1H, NH), 7.40 (d, 3JHH
( )-Diethyl 2-[2-(benzyloxy)ethoxy]-2-[2-(4-benzoylamino-2-
oxo-2H-pyrimidin-1-yl)]ethylphosphonate (Bz-10c). Iodophos-
phonate 9c (0.33 g, 0.50 mmol, 1 eq.) was reacted according to
the general procedure. The crude reaction mixture was purified
by chromatography on silica gel (gradient 100% AcOEt–50%–
50% AcOEt–(AcOEt–EtOH 9 : 1)) affording a white solid
3
3
= 8.1 Hz, 1H, NCH), 6.03 (ddd, JHH = 10.2 Hz, JPH = 5.7 Hz,
3JHH = 3.3 Hz, 1H, OCHN), 5.75 (d, JHH = 8.1 Hz, 1H, CH),
3
(0.177 g, 66%). 31P NMR (CDCl3, 161.97 MHz) δ = 23.5; H
1
4.18–4.00 (m, 4H, OCH2), 3.80–3.40 (m, 4H, CH2CH2), 2.27
NMR (CDCl3, 400.13 MHz) δ = 9.05 (s, 1H, NH), 7.91 (d, 3JHH
= 7.5 Hz, 1H, NCH), 7.88–7.83 (m, 2H, CH), 7.55–7.50 (m, 2H,
CH), 7.47–7.39 (m, 3H, PhCH and CH), 7.30–7.17 (m, 5H, CH),
2
2
3
(ddd, JPH = −18.3 Hz, JHH = −15.3 Hz, JHH = 10.2 Hz, 1H,
PCH2), 2.25 (ddd, 2JPH = −18.8 Hz, 2JHH = 15.3 Hz, 3JHH = 3.3
3
Hz, 1H, PCH2), 1.28 and 1.29 (2 t, JHH = 7.1 Hz, 6H, 2 CH3);
3
3
3
13C NMR (CDCl3, 100.61 MHz) δ = 163.5 (s, CvO), 150.5 (s,
CvO), 138.5 (s, NCH), 103.4 (s, CH), 81.0 (s, OCHN), 71.5 (s,
6.03 (ddd, JPH = 9.8 Hz, JHH = 7.7 Hz, JHH = 4.3 Hz, 1H,
OCHN), 4.44 (s, 2H, PhCH2), 4.09–3.98 (m, 4H, OCH2),
3.78–3.69 (m, 1H, OCH2), 3.63–3.56 (m, 2H, OCH2), 3.55–3.48
2
2
OCH2), 62.7 (d, JCP = 6.6 Hz, OCH2), 62.5 (d, JCP = 6.6 Hz,
OCH2), 60.3 (s, CH2OH), 32.6 (d, 1JCP = 142.0 Hz, PCH2), 16.4
(d, 3JCP = 5.9 Hz, CH3), 16.3 (d, 3JCP = 7.0 Hz, CH3); MS ESI+
m/z = 337.2 (100%) [M + H]+, m/z = 673.4 (94%) [2M + H]+,
m/z = 359.5 (20%) [M + Na]+; HRMS-ESI+ (m/z): [M + H]+
calcd for C12H22N2O7P: 337.1165; found 337.1158.
2
2
(m, 1H, OCH2), 2.43 (ddd, JPH = −18.8 Hz, JHH = −15.3 Hz,
3JHH = 4.3 Hz, 1H, PCH2), 2.27 (ddd, JPH = −18.0 Hz, JHH
=
=
2
2
−15.3 Hz, 3JHH = 7.7 Hz, 1H, PCH2), 1.22 and 1.21 (2 t, 3JHH
7.1 Hz, 6H, 2 CH3); 13C NMR (CDCl3, 100.61 MHz) δ = 162.4
(s, CvO), 144.1 (s, NCH), 137. 8 (s, PhC), 133.1, 128.9, 128.4,
128.9, 127.8, 127.7, 127.6 (7 s, CH), 97.2 (s, CH), 83.5 (s,
OCHN), 73.2 (s, CH2), 69.9 (s, OCH2), 68.6 (s, OCH2), 62.0,
( )-Diethyl 2-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-
2
1
1-yl)-2-(2-hydroxyethoxy)ethylphosphonate
(11b). O-Benzyl
61.7 (2 d, JCP = 6.2 Hz, 2 OCH2), 32.5 (d, JCP = 140.9 Hz,
PCH2), 16.4 (d, JCP = 6.2 Hz, CH3); MS ESI+ m/z = 530.8
3
phosphonate 10b (50 mg, 0.11 mmol, 1 eq.) was dissolved in
anhydrous ethanol (5.5 mL) and the solution was reacted using a
H-cube (Pd/C 10%, 1 mL min−1, full H2 mode). The reaction
mixture was concentrated under vacuum giving 11b as colorless
oil (33 mg, 86%). 31P NMR (CDCl3, 161.97 MHz) δ = 24.8; 1H
NMR (CDCl3, 400.13 MHz) δ = 9.59 (s, 1H, NH), 7.19 (s, 1H,
(100%) [M + H]+; HRMS-ESI+ (m/z): [M + H]+ calcd for
C26H33N3O7P: 530.2056; found 530.2060.
( )-Diethyl 2-(4-amino-2-oxo-2H-pyrimidin-1-yl)-2-[2-(benzy-
loxy)ethoxy]ethylphosphonate (10c). To a solution of benzoyl
phosphonate Bz-10c (378 mg, 0.71 mmol, 1 eq.) in anhydrous
methanol (9 mL) was added a solution of sodium methoxide
(0.5 M, 9 mL, 4.5 mmol, 6.3 eq.). The reaction mixture was
stirred at rt for 3h 30 min. Then methanol (25 mL) was added
and the resulting solution was acidified to pH = 2 by a hydro-
chloric acid (1 N). Methanol was removed under vacuum and
the aqueous phase extracted by AcOEt (2 × 25 mL). The
aqueous phase was basified using NaOH (1 M) until pH > 12
and then extracted by AcOEt (4 × 25 mL). The organic phases
were dried over MgSO4, filtered and concentrated under vacuum
giving 10c as a colorless oil (240 mg, 79%). 31P NMR (CDCl3,
161.97 MHz) δ = 24.0; 1H NMR (CDCl3, 400.13 MHz) δ =
3
3
3
NCH), 6.04 (ddd, JHH = 9.9 Hz, JPH = 5.8 Hz, JHH = 3.4 Hz,
1H, OCHN), 4.40 (s, 1H, OH), 4.18–4.02 (m, 4H, OCH2),
2
2
3.80–3.40 (m, 4H, CH2CH2), 2.29 (ddd, JPH = −18.2 Hz, JHH
3
2
= −15.1 Hz, JHH = 9.8 Hz, 1H, PCH2), 2.21 (ddd, JPH = 18.9
Hz, JHH = 15.1 Hz, JHH = 3.4 Hz, 1H, PCH2), 1.88 (d, 4JHH
=
2
3
3
0.8 Hz, 3H, CH3), 1.28 and 1.29 (2 t, JHH = 6.9 Hz, 6H, CH3);
13C NMR (CDCl3, 100.61 MHz) δ = 164.0 (s, CvO), 150.6 (s,
CvO), 134.0 (s, NCH), 112.0 (s, C), 80.5 (s, OCHN), 71.3 (s,
2
2
OCH2), 62.6 (d, JCP = 6.4 Hz, OCH2), 62.4 (d, JCP = 6.6 Hz,
OCH2), 60.3 (s, CH2OH), 32.5 (d, 1JCP = 141.5 Hz, PCH2), 16.4
3
3
(d, JCP = 3.3 Hz, CH3), 16.3 (d, JCP = 3.3 Hz, CH3); 12. 7 (s,
CH3); MS ESI+ m/z = 351.2 (100%) [M + H]+, m/z = 701.4
(86%) [2M + H]+, m/z = 373.2 (28%) [M + Na]+; HRMS-ESI+
(m/z): [M + H]+ calcd for C13H23N2O7P: 351.1321; found
351.1317.
7.45 (d, JHH = 7.4 Hz, 1H, NCH), 7.32–7.14 (m, 5H, PhCH),
6.01 (ddd, JPH = 8.8 Hz, JHH = 7.8 Hz, JHH = 4.7 Hz, 1H,
3
3
3
3
3
OCHN), 5.76 (d, JHH = 7.5 Hz, 1H), 4.44 (s, 2H, PhCH2),
4.07–3.99 (m, 4H, 2 OCH2), 3.70–3.47 (m, 4H, CH2CH2), 2.27
( )-Diethyl 2-(4-amino-2-oxo-2H-pyrimidin-1-yl)-2-(2-hydro-
2
2
3
(ddd, JPH = −18.7 Hz, JHH = 15.5 Hz, JHH = 4.7 Hz, 1H,
xyethoxy)ethylphosphonate (11c). To
a two-necked round
PCH2), 2.23 (ddd, 2JPH = −18.1 Hz, 2JHH = 15.5 Hz, 3JHH = 7.8
bottom flask under nitrogen containing benzyl phosphonate 10c
(0.12 g, 0.28 mmol, 1 eq.) dissolved in anhydrous CH2Cl2
(3 mL) at −80 °C was added dropwise boron tribromide
(0.28 mL, 2.8 mmol, 10 eq.). The heterogeneous mixture was
kept for 2h 30 min between −50 °C and −30 °C. Then metha-
nol–CH2Cl2 (1 : 1, 6 mL) was added and the reaction mixture
was allowed to return to rt. The reaction was concentrated under
vacuum and purified by flash chromatography using C18 reverse
3
Hz, 1H, PCH2), 1.21 and 1.22 (2 t, JHH = 7.1 Hz, 6H, 2 CH3);
13C NMR (CDCl3, 100.61 MHz) δ = 165.5 (s, CvO), 155.9 (s,
CNH2), 140.3 (s, CHN), 138.0 (s, PhC), 128.4, 127.7, 127.6 (s,
PhCH), 95.3 (s, CH), 82.1 (s, OCHN), 73.1 (s, PhCH2), 68.8,
2
68.7 (2 s, CH2CH2), 62.2, 61.9 (d, JCP = 6.3 Hz, 2 CH2), 32. 6
1
3
(d, JCP = 140.7 Hz, PCH2), 16.4 (d, JCP = 6.2 Hz, CH3); MS
ESI+ m/z = 426.3 (100%) [M + H]+, m/z = 851.6 (42%) [2M +
3452 | Org. Biomol. Chem., 2012, 10, 3448–3454
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2
3
phase leading to 11c as a viscous oil (35 mg, 37%). 31P NMR
(CDCl3, 161.97 MHz) δ = 25.7; 1H NMR (CDCl3, 400.13 MHz)
2JPH = −17.3 Hz, JHH = −15.3 Hz, JHH = 6.2 Hz, 1H, PCH2),
1.79 (s, 3H, CH3), 1.07 (t, JHH = 7.1 Hz, 3H, CH3); 13C NMR
(D2O, 100.61 MHz) δ = 166.6 (s, CvO), 151.9 (s, CvO),
3
3
3
δ = 7.45 (d, JHH = 7.5 Hz, 1H, NCH), 6.07 (ddd, JHH = 9.6
Hz, 3JPH = 6.1 Hz, 3JHH = 3.3 Hz, 1H, 3CH), 5.99 (d, 3JHH = 7.5
137.4 (s, NCH), 111.7 (s, C), 82.5 (s, OCHN), 69.7 (s, OCH2),
2
Hz, 1H, CH), 4.21–3.96 (m, 4H, 2 OCH2), 3.71 (ddd, JHH
=
60.6 (d, 2JCP = 5.7 Hz, OCH2), 60.0 (s, CH2OH), 32.1 (d, 1JCP
=
−10.7 Hz, 3JHH = 6.5 Hz, 3JHH = 3.8 Hz, 1H, OCH2), 3.65–3.56
133.4 Hz, PCH2), 15.8 (d, JCP = 6.4 Hz, CH3), 11.5 (s, 3H,
CH3); MS ESI+ m/z = 323.2 (100%) [M + H]+, 329.2 (22%) [M
+ Li + H]+; HRMS-ESI+ (m/z): [M + Li + H]+ calcd for
C11H19N2O7PLi: 329.1090; found 329.1088.
3
(m, 2H, OCH2), 3.44 (ddd, 2JHH = 11.3 Hz, 3JHH = 6.3 Hz, 3JHH
2
2
= 3.0 Hz, 1H, OCH2), 2.29 (ddd, JPH = −17.6 Hz, JHH
=
3
2
−15.2 Hz, JHH = 9.6 Hz, 1H, PCH2), 2.18 (ddd, JPH = −18.5
Hz, 2JHH = −15.2 Hz, JHH = 3.3 Hz, 1H, PCH2), 1.27 and 1.26
3
( )-Lithium ethyl 2-(4-amino-2-oxo-2H-pyrimidin-1-yl)-2-(2-
hydroxyethoxy)ethylphosphonate (12c). Diethyl cytosine phos-
phonate 11c (25.0 mg, 0.07 mmol, 1 eq.) was reacted according
to the general procedure and afforded after concentration 12c as
a white solid 20.0 mg (85%, purity 80%). 31P NMR (D2O,
161.97 MHz) δ = 19.0; H NMR (D2O, 400.13 MHz) δ = 7.64
(d, JHH = 7.4 Hz, 1H, NCH), 6.01 (d, JHH = 7.4 Hz, 1H, CH),
5.87 (m, 1H, OCHN), 3.84–3.65 (m, 2H, OCH2), 3.60–3.44 (m,
(2 t, JHH = 7.1 Hz, 6H, 2 CH3), 13C NMR (CDCl3,
3
100.61 MHz) δ = 165.9 (s, C), 156.2 (s, CvO), 139.3 (s, NCH),
96.3 (s, C), 81.4 (s, OCHN), 71.2 (s, OCH2), 62.4 (d, 2JCP = 6.5
1
Hz, OCH2); 60.4 (s, CH2OH), 32.6 (d, JCP = 140.4 Hz, PCH2),
3
3
16.4 (d, JCP = 2.3 Hz, CH3), 16.3 (d, JCP = 2.4 Hz, CH3); MS
ESI+ m/z = 336.0 (100%) [M + H]+, m/z = 671.0 (12%) [2M +
H]+, m/z = 358.0 (15%) [M + Na]+; HRMS-ESI+ (m/z):
[M + H]+ calcd for C12H23N3O6P: 336.1324; found 336.1317.
1
3
3
4H, CH2CH2), 2.23–2.09 (m, 2H, PCH2), 1.79 (s, 3H, CH3),
3
1.12 (t, JHH
=
7.1 Hz, 3H, CH3); 13C NMR (D2O,
100.61 MHz) δ = 165.9 (s, CvO), 157.6 (s, C–N), 141.6 (s,
General procedure for the mono-deprotection of phosphonate
NCH), 96.6 (s, C), 83.4 (s, OCHN), 69.9 (s, OCH2), 60.7 (d,
ester – synthesis of compounds 12a–c
1
2JCP = 5.7 Hz, OCH2), 60.0 (s, CH2OH), 32.4 (d, JCP = 132.6
Hz, PCH2), 15.6 (d, 3JCP = 6.4 Hz, CH3).
The appropriate diethyl phosphonate 11a–c was dissolved in
acetonitrile (1 volume, 0.07 mol L-1). Then lithium bromide (2
eq.) was added and the reaction mixture was heated to 80 °C for
3.5 days. After cooling to rt, the suspension was filtered off and
the solid dissolved in water and extracted by CH2Cl2 in order to
remove apolar organic impurities. The aqueous phase was con-
centrated under vacuum affording the desired mono lithium salt.
General procedure for double deprotection of phosphonate
ester – synthesis of compounds 5a–c
The appropriate diethyl phosphonate 11a–c was dissolved in
CH2Cl2 (1 volume, 0.07 mol L-1). Then TMS-Br (10 eq.) was
added and the reaction mixture was stirred 16 h at rt. The reac-
tion mixture was concentrated under vacuum and methanol was
added. The reaction mixture was stirred for 30 min, then concen-
trated under vacuum and purified by chromatography on reverse
phase.
( )-Lithium ethyl 2-(2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-
yl)-2-(2-hydroxyethoxy)ethylphosphonate (12a). Diethyl uracyl
phosphonate 11a (21.0 mg, 0.06 mmol, 1 eq.) was reacted
according to the general procedure and afforded after concen-
tration 12a as a white solid 15.0 mg (76%). 31P NMR (D2O,
1
161.97 MHz) δ = 18.5; H NMR (D2O, 400.13 MHz) δ = 7.68
( )-2-(2,4-Dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-2-(2-hydro-
xyethoxy)ethylphosphonic acid triethylammonium salt (5a).
Diethyl uracil phosphonate 11a (162.0 mg, 0.48 mmol, 1 eq.)
was reacted according to the general procedure. 5a is obtained as
the triethylammonium salt by trituration in a mixture of triethyl-
amine–methanol and concentration under vacuum as a colorless
3
3
3
(d, JHH = 8.1 Hz, 1H, NCH), 5.84 (ddd, JHH = 7.1 Hz, JPH
=
3
6.8 Hz, JHH = 5.9 Hz, 1H, OCHN), 3.85–3.74 (m, 2H, OCH2),
2
2
3.72–3.48 (m, 4H, CH2CH2), 2.21 (ddd, JPH = −17.5 Hz, JHH
3
2
= −15.3 Hz, JHH = 7.1 Hz, 1H, PCH2), 2.12 (ddd, JPH
=
−17.4 Hz, 2JHH = −15.3 Hz, 3JHH = 5.9 Hz, 1H, PCH2), 1.13 (t,
3JHH = 7.1 Hz, 3H, CH3); 13C NMR (D2O, 100.61 MHz) δ =
166.4 (s, CvO), 151.8 (s, CO), 141.9 (s, NCH), 102.6 (s, C),
83.0 (s, OCHN), 70.1 (s, OCH2), 60.7 (d, 2JCP = 5.7 Hz, OCH2),
60.1 (s, CH2OH), 32.2 (d, 1JCP = 133.3 Hz, PCH2), 15.9 (d, 3JCP
= 6.4 Hz, CH3); MS ESI+ m/z = 315.2 (100%) [M + Li + H]+;
HRMS-ESI+ (m/z): [M + Li + H]+ calcd for C10H17N2O7PLi:
315.0933; found 315.0924.
1
oil (60.0 mg, 44%). 31P NMR (D2O, 161.97 MHz) δ = 20.5; H
3
NMR (D2O, 400.13 MHz) δ = 7.73 (d, JHH = 8.1 Hz, 1H,
3
3
3
NCH), 5.92 (ddd, JHH = 8.1 Hz, JPH = 5.9 Hz, JHH = 4.9 Hz,
3
1H, OCHN), 5.88 (d, JHH = 8.1 Hz, 1H, CH), 3.80–3.48 (m,
4H, CH2CH2), 3.16 (q, JHH = 7.3 Hz, 4H, CH2(NEt3)), 2.22
3
2
2
3
(ddd, JPH = −17.1 Hz, JHH = −15.1 Hz, JHH = 8.1 Hz, 1H,
2
2
3
PCH2), 2.06 (ddd, JPH = −17.6 Hz, JHH = −15.1 Hz, JHH
=
4.9 Hz, 1H, PCH2), 1.24 (t, JHH = 7.3 Hz, 6H, CH3(NEt3)); 13C
3
( )-Lithium ethyl 2-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyri-
midin-1-yl)-2-(2-hydroxyethoxy)ethyl
Diethyl thymine phosphonate 11b (25.0 mg, 0.07 mmol, 1 eq.)
was reacted according to the general procedure and afforded
after concentration 12b as a white solid 20.0 mg (85%). 31P
NMR (D2O, 161.97 MHz) δ = 18.7; 1H NMR (D2O,
NMR (D2O, 100.61 MHz) δ = 168.8 (s, CvO), 154.3 (s,
CvO), 144.3 (s, NCH), 105.0 (s, CH), 85.8 (s, OCHN), 72.6 (s,
phosphonate
(12b).
1
OCH2), 62.5 (s, CH2OH), 49.1 (s, CH2(NEt3)), 36.5 (d, JCP
=
130.3 Hz, PCH2), 10.7 (s, CH3(NEt3)); MS ESI+ m/z = 280.9
(100%) [M + H]+, 560.8 (5%) [2M + H]+, 382.0 (3%) [M +
NEt3
C8H14N2O7P: 281.0539; found 281.0547.
+ +
H]+; HRMS-ESI+ (m/z): [M H]+ calcd for
3
400.13 MHz) δ = 7.48 (s, 1H, NCH), 5.80 (ddd, JHH = 6.8 Hz,
3
3JPH = 6.5 Hz, JHH = 6.2 Hz, 1H, OCHN), 3.80–3.68 (m, 2H,
2
OCH2), 3.66–3.42 (m, 4H, CH2CH2), 2.16 (ddd, JPH = −17.6
( )-2-(5-Methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-2-
(2-hydroxyethoxy)ethylphosphonic acid (5b). Diethyl thymine
2
3
Hz, JHH = −15.3 Hz, JHH = 6.8 Hz, 1H, PCH2), 2.21 (ddd,
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 3448–3454 | 3453

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phosphonate 11b (187.0 mg, 0.53 mmol, 1 eq.) was reacted
according to the general procedure. 5b was isolated as a white
solid (116 mg, 74%). 31P NMR (D2O, 161.97 MHz) δ = 20.9;
1H NMR (D2O, 250.13 MHz) δ = 7.35 (s, 1H, NCH), 5.75 (ddd,
Technical Research (Association Nationale de la Recherche
Technique, ANRT) for a doctoral fellowship.
3
3
3JHH = 7.1 Hz, JPH = 6.5 Hz, JHH = 6.0 Hz, 1H, OCHN),
2
2
3.65–3.24 (m, 4H, CH2CH2), 2.26 (ddd, JPH = −18.7 Hz, JHH
Notes and references
3
2
= −15.7 Hz, JHH = 7.1 Hz, 1H, PCH2), 2.13 (ddd, JPH
=
−18.1 Hz, 2JHH = −15.7 Hz, 3JHH = 6.0 Hz, 1H, PCH2), 1.67 (d,
4JHH = 2.2 Hz, 3H, CH3); 13C NMR (D2O, 62.90 MHz) δ =
166.3 (s, CvO), 151.7 (s, CvO), 136.7 (s, NCH), 111.9 (s, C),
81.6 (s, OCHN), 69.9 (s, OCH2), 60.0 (s, CH2OH), 30.8 (d, 1JCP
= 133.8 Hz, PCH2), 11.4 (s, CH3); MS ESI+ m/z = 295.0 (100%)
[M + H]+, 589.1 (28%) [2M + H]+; HRMS-ESI+ (m/z):
[M + H]+ calcd for C9H16N2O7P: 295.0695; found 295.0685.
1 E. De Clercq, Future Virol., 2008, 3, 393.
2 (a) P. Doláková, M. Dracínský, J. Fanfrlík and A. Holý, Eur. J. Org.
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and A. Holý, Nat. Rev. Drug Discovery, 2005, 4, 928;
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( )-2-(4-Amino-2-oxo-2H-pyrimidin-1-yl)-2-(2-hydroxyethoxy)-
ethylphosphonic acid (5c). Diethyl cytosine phosphonate 11c
(100.0 mg, 0.53 mmol, 1 eq.) was reacted according to the
general procedure. 5c was isolated as a colorless oil (81 mg,
97%). The product was also isolated as the triethylamine salt.
31P NMR (D2O, 161.97 MHz) δ = 20.3 (acidic form) or 19.1
(mono triethylammonium salt); 1H NMR (D2O, 400.13 MHz,
3
triethylammonium salt) δ = 7.81 (d, JHH = 7.6 Hz, 1H, NCH),
3
3
6.14 (d, JHH = 7.6 Hz, 1H, CHOH), 5.98 (ddd, JHH = 8.2 Hz,
3JPH = 7.0 Hz, JHH = 4.6 Hz, 1H, OCHN), 3.84–3.51 (m, 4H,
3
3
CH2CH2), 3.20 (q, JHH = 7.3 Hz, 2H, CH2(NEt3)), 2.56 (ddd,
2JPH = −17.1 Hz, JHH = −15.1 Hz, JHH = 8.2 Hz, 1H, PCH2),
2
3
2
2
3
2.14 (ddd, JPH = −17.8 Hz, JHH = −15.1 Hz, JHH = 4.6 Hz,
1H, PCH2), 1.27 (t, JHH = 7.3 Hz, 3H, CH3(NEt3)); 13C NMR
3
(D2O, 100.61 MHz, acidic form) δ = 159.0 (s, CvO), 148.3 (s,
C), 144.0 (s, NCH), 95.7 (s, 7C), 83.5 (s, OCHN), 70.8 (s,
1
OCH2), 60.0 (s, CH2OH), 32.6 (d, JCP = 135.4 Hz, PCH2); MS
ESI+ m/z = 280.1 (70%) [M + H]+, 281.1 (100%) [M + D]+;
HRMS-ESI+ (m/z): [M + H]+ calcd for C8H15N3O6P: 280.0698;
found 280.0699.
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Acknowledgements
16 H. Krawczyk, Synth. Commun., 1997, 27, 3151.
17 P. Shahgaldian, A. W. Coleman and V. I. Kalchenko, Tetrahedron Lett.,
2001, 42, 577.
The first author (B. Dayde) is particularly grateful to Idenix
Pharmaceuticals and to the French National Association for
3454 | Org. Biomol. Chem., 2012, 10, 3448–3454
This journal is © The Royal Society of Chemistry 2012