Synthesis of 3′-halo-5′-norcarbocyclic nucleoside phosphonates as potent anti-HIV agents

Article abstract of DOI:10.1016/j.ejmech.2018.03.038

The synthesis and the antiviral evaluation of 3’-halo (iodo and fluoro) 5’-norcarbocyclic nucleoside phosphonates is described. No antiviral activity was observed against Zika virus, Dengue virus 2, HSV-1, HSV-2 and Chikungunya virus. In contrast, some of the synthesized compounds are potent inhibitors of the replication of HIV-1, comparatively to (R)-PMPA, with no concomitant cytotoxicity.

Full text of DOI:10.1016/j.ejmech.2018.03.038

European Journal of Medicinal Chemistry 150 (2018) 642e654
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Research paper
Synthesis of 30-halo-50-norcarbocyclic nucleoside phosphonates as
potent anti-HIV agents
ꢀ
ꢁ
ꢁ*
Nadege Hamon, Malika Kaci, Jean-Pierre Uttaro, Christian Perigaud, Christophe Mathe
ꢁ
ꢁ
ꢀ
Institut des Biomolecules Max Mousseron (IBMM), UMR 5247, Universite de Montpellier, CNRS, ENSCM, cc 1705, Site Triolet, Place Eugene Bataillon, 34095,
Montpellier cedex 5, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and the antiviral evaluation of 3'-halo (iodo and fluoro) 5'-norcarbocyclic nucleoside
phosphonates is described. No antiviral activity was observed against Zika virus, Dengue virus 2, HSV-1,
HSV-2 and Chikungunya virus. In contrast, some of the synthesized compounds are potent inhibitors of
the replication of HIV-1, comparatively to (R)-PMPA, with no concomitant cytotoxicity.
© 2018 Elsevier Masson SAS. All rights reserved.
Received 19 February 2018
Received in revised form
9 March 2018
Accepted 13 March 2018
Available online 14 March 2018
Dedicated to Dr. Gilles Gosselin at the
occasion of his retirement and his
outstanding career in the field of nucleoside
analogues as antiviral agents
Keywords:
Antiviral
HIV
Nucleoside analogues
Carbocycle
Phosphonates
1. Introduction
phosphonylmethoxypropyl)adenine (R-PMPA, Tenofovir), an acy-
clonucleoside phosphonate (Fig. 1).
More than three decades after the discovery of the Human Im-
munodeficiency Virus (HIV) as the etiologic agent of AIDS, there is
no vaccine available for the prevention of AIDS and drugs are the
only arsenal to treat HIV infections [1,2]. However, current treat-
ments do not allow the eradication of the virus but contain its
replication at undetectable level with the obligation for the infected
individuals to stay on treatment for life. This is a crucial issue
because all existing anti-HIV drugs have long-term side effects and
may be associated with the rapid emergence of resistant viral
strains in case of faulty observance to treatment or suboptimal
treatment. These concerns still promote the research for novel
molecular-based anti-HIV drugs. Among these later, nucleoside and
nucleotide analogues are an important class of anti-HIV drugs [3] as
illustrated with the clinical use of Abacavir, a carbocyclic nucleoside
analogue, and Tenofovir disoproxil fumarate (TDF), the corre-
In the case of carbocyclic nucleosides, such as Abacavir, the
replacement of the endocyclic oxygen of the furanose ring by a
methylene group confers chemical and metabolic stabilities. In the
case of nucleoside phosphonates, such as Tenofovir, the presence of
P-C bond instead of the hydrolysable P-O brings about a metabolic
stability of the linkage with the phosphate moiety. As a part of our
research on 50-norcarbocyclic nucleoside phosphonates as poten-
tial anti-viral agents [4], we describe here the synthesis and the
antiviral evaluation of their 30-halo (iodo and fluoro) corresponding
counterparts bearing purine bases.
2. Results and discussion
2.1. Chemistry
sponding
carbonate
prodrug
of
(R)-9-(2-
The strategy for the synthesis of 30-halo-50-norcarbocyclic
nucleoside phosphonates was based upon the preparation of
compound ( ) 6 as a common precursor (Scheme 1). Furfuryl
alcohol was used as starting material and provided carbocycle ( ) 1
* Corresponding author.
E-mail address: christophe.mathe@umontpellier.fr (C. Mathe).
ꢁ
https://doi.org/10.1016/j.ejmech.2018.03.038
0223-5234/© 2018 Elsevier Masson SAS. All rights reserved.

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
643
bearing adenine, N-cyclopropyl-6-aminopurine, hypoxanthine and
guanine (respectively compounds ( ) 12, ( ) (15), ( ) 18 and ( )
(20) is described in Scheme 2.
Starting with a Mitsunobu coupling reaction between alcohol
( ) 6 and an appropriate heterocyclic base, the N9-carbocyclic
nucleosides were obtained without concomitant formation of the
N7 regioisomer [12]. Compound ( ) 7, a common intermediate for
the synthesis of the target compounds ( ) 12, ( ) (15) and ( ) 18,
was obtained using 6-chloropurine as heterocyclic base whereas 2-
amino-6-chloropurine was used to provide carbocyclic nucleoside
( ) 8, precursor of the target compound ( ) 20. The stereochemical
assignments of compound ( ) 7 were achieved through NMR ex-
periments (Fig. 2). A NOE correlation between protons H10 and H40
was observed and support the cis orientation of these protons.
These data were in agreement with our previous results on 30-
methyl-50-norcarbocyclic nucleoside phosphonates [4] and confirm
the stereochemistry obtained under Mitsunobu reaction.
Treatment of compound ( ) 7 in the presence of methanolic
ammonia gave the adenine derivative ( ) 9 in 81% yield. Protection
of the amino group as a N,N-dimethylformamidine [13] in order to
avoid competing N-alkylation led to compound ( ) 10 in 93% yield.
O-Alkylation of ( ) 10 in the presence of LiOtBu and diethyl p-
toluene sulfonyloxymethyl phosphonate [14], followed by an acidic
treatment, afforded carbocyclic nucleoside ( ) 11 in 73% yield.
Finally, the target nucleotide ( ) 11 was obtained in 73% yield by
deprotection of the phosphonate group in the presence of TMSBr in
DMF. Concomitantly, nucleophilic substitution of compound ( ) 7
with cyclopropylamine followed by removal of the benzoate group
under basic conditions led readily to nucleoside ( ) 13. Conden-
sation of the phosphonate group with carbocycle ( ) 13 followed by
the hydrolysis of the diethyl phosphonate esters was performed
using as previously for ( ) 12. The phosphonic acid was then sub-
ject to an ion exchange chromatography to yield the target 30-iodo-
50-norcarbocyclic nucleoside phosphonate ( ) 15 as sodium salt.
Then, we planned the synthesis of the derivative ( ) 18 bearing
hypoxanthine as nucleobase. In this respect, treatment of ( ) 7 with
potassium carbonate in methanol allowed the nucleophilic sub-
stitution of the chlorine atom and hydrolysis of the benzoate group
to afford carbocyclic nucleoside ( ) 16 in good yield. Condensation
of the phosphonate group led to compound ( ) 17 and removal of
the diethyl phospho esters accompanied by the concomitant hy-
drolysis of the methoxy group in position 6 [4] gave the target
Fig. 1. Examples of anti-HIV carbocyclic nucleosides and acyclonucleoside phospho-
nates. Structures and numbering of the target 50-norcarbonucleoside phosphonate
analogues.
according to the procedure described by Curran [5]. The iodination
reaction on compound ( ) 1 was attempted according to the pro-
cedure described by Johnson (2 eq. of iodine in pyridine/CCl4) [6,7].
Nevertheless, the moderate yield obtained (61%) prompted us to
achieve the iodination reaction in the presence of pyridinium di-
chromate as a catalyst [8] and afforded a-iodinated enone ( ) 2 in
86% yield. Reduction of the ketone under Luche conditions [9,10]
gave a mixture of diastereoisomers ( ) 3 and ( ) 4. These com-
pounds were easily separated by purification on silica gel column
chromatography and the diastereoisomers ( ) 3 and ( ) 4 (92/8
ratio) were isolated in 93% yield. From ( ) 3, a Mitsunobu reaction
[11] in the presence of benzoic acid, PPh3, and DIAD or a direct
benzoylation of ( ) 4 provided carbocyclic ( ) 5 in 98% and 75%
yield, respectively. Finally, the removal of the TBDMS protecting
group in the presence of TBAF afforded the desired common pre-
cursor ( ) 6 in 95% yield.
Synthesis of 30-iodo-50-norcarbocyclic nucleoside phosphonates
Scheme 1. Synthesis of carbocycle ( ) 6. Reagents and conditions: (a) I2, PDC, CH2Cl2, rt, 46 h, 86%; (b) CeCl3, NaBH4, CH3OH, ꢀ78 ꢁC, 2 h, 93%; (c) benzoic acid, PPh3, DIAD, THF, 0 ꢁC,
1 h, 98%; (d) BzCl, pyridine/CH2Cl2, CH2Cl2, rt, 12 h, 75%; (e) TBAF, THF, 0 ꢁC, 2 h, 95%.

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N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
Scheme 2. Synthesis of 30-iodo-50norcarbocyclic nucleoside phosphonates ( ) 12, ( ) 15, ( ) 18 and ( ) 20. Reagents and conditions: (a) 6-chloropurine, DIAD, PPh3, THF, rt, 2 h,
43%; (b) i) 2-amino-6-chloropurine, DIAD, PPh3, THF, rt, 12 h; ii) K2CO3, MeOH, rt, 12 h, 44% over two steps; (c) methanolic ammonia, 70 ꢁC, 20 h, 81%; (d) N,N-dimethylformamide
dimethyl acetal, DMF, 50 ꢁC, 4 h, 93%; (e) (EtO)2P(O)CH2OTs, LiOtBu, THF, for ( ) 11: 30 ꢁC, 2 days, 73%; for ( ) 14, rt, 4 days, 76%; for ( ) 17: rt, 8 days, 67%; for ( ) 19: rt, 2 days, 53%;
(f) TMSBr, DMF, rt; for ( ) 12, 12 h, 67%; for ( ) 15, 12 h, 69%; for ( ) 18, 30 h, 72%; for ( ) 20, 30 h, 58%; (g) i) cyclopropylamine, THF, 50 ꢁC, 4 h; ii) K2CO3, MeOH, rt, 2 h, 85% over two
steps; (h) K2CO3, MeOH, rt, 15 h, 75%.
compound ( ) 18 in 72% yield, after purification by reversed-phase
column chromatography and ion exchange on a dowex resin. The
target compound ( ) 20 was obtained from ( ) 8 using similar
procedure as described for compound ( ) 18 from ( ) 16. The
synthesis of the 30-fluoro-50-norcarbocyclic nucleoside phospho-
nates was first envisioned from a fluorination reaction on the 30-
iodo-50-norcarbocyclic nucleosides previously obtained. Owing to
the strongly basic conditions used in the fluorination step, this step
has to be performed before the introduction of the phosphonate
moiety. So, we first applied the strategy to the 30-iodo-50-norcar-
bocyclic nucleoside ( ) 16 (Scheme 3). Since the fluorination step is
carried out in the presence of n-BuLi, preliminary protection of the
allylic alcohol as a silyl ether was required. The resulting compound
Fig. 2. Selected NOE effects on carbocyclic nucleoside ( ) 7.
( ) 21 was then submitted to an electrophilic fluorination in the

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
645
The syntheses of 30-fluoro-50-norcarbocyclic nucleoside phos-
phonates bearing adenine and guanine are reported in Scheme 5.
Condensation of the fluorocarbocycle ( ) 29 with 6-chloropurine or
2-amino-6-chloropurine was performed according to a Mitsunobu
coupling reaction and led to the carbocyclic nucleoside derivatives
( ) 31 and ( ) 32 respectively, without concomitant formation of
the N7-regioisomers. From compound ( ) 31, the desired carbon-
ucleoside ( ) 33 was obtained using a two steps procedure: the
nucleophilic substitution of the chlorine atom in the presence of
methanolic ammonia at 70 ꢁC accompanied by a concomitant hy-
drolysis of the silyl ether, followed by the protection of the exocyclic
amino function as N,N-dimethylformamidine group. Then, the
inversion of the C40-configuration was achieved using standard
Mitsunobu protocol in the presence of benzoic acid, triphenyl-
phosphine and DIAD in anhydrous THF and followed by the
removal of the resulting benzoate group with K2CO3 in methanol to
afford the carbonucleoside ( ) 34. This intermediate was converted
into the corresponding phosphonate ( ) 35 using a similar pro-
cedure as described for ( ) 11. Finally, the desired 30-fluoro-50-
norcarbocyclic nucleoside phosphonate bearing adenine was ob-
tained, as sodium salt, after deprotection of the phosphonate group
with TMSBr in anhydrous DMF at room temperature and purifica-
tion by reverse phase column chromatography and ion exchange
chromatography. The target guanine derivative ( ) 39 was obtained
from compound ( ) 32 following a nucleophilic substitution of the
chlorine atom in the presence of potassium carbonate in refluxing
methanol with the concomitant hydrolysis of the silyl ether to give
compound ( ) 37 in 80% yield. Inversion of the C40-configuration on
compound ( ) 37 was achieved using similar protocol developed
for ( ) 34. Finally, intermediate ( ) 38 was successively converted
into the phosphonate ( ) 39 using a similar procedure as described
for compound ( ) 20.
Scheme 3. Synthesis of 30-fluoro-50-norcarbocyclic nucleoside phosphonate ( ) 25.
Reagents and conditions: (a) TBDMSCl, imidazole, DMF, rt, 12 h, 87%; (b) i) NFSI, n-BuLi,
THF, ꢀ78 ꢁC, 45 min; ii) TBAF, THF, 0 ꢁC, 1 h, 21% over two steps for ( ) 22, 33% over two
steps for ( ) 23; (c) (Et2O)P(O)CH2OTs, LiOtBu, THF, rt, 12 days, 88%; (d) TMSBr, DMF, rt,
36 h, 70%.
presence of n-BuLi and NFSI [15] and led to an inseparable mixture
of the desired 30-fluoro-carbocyclic nucleoside and its unsaturated
dehalogenated counterpart. Removal of the silyl ether was directly
performed on the mixture, providing after purification by chro-
matography on silica gel compounds ( ) 22 and ( ) 23 in 21% and
33% yield, respectively from derivative ( ) 21. Condensation of the
phosphonate group with the 30-fluoro-carbocyclic nucleoside ( )
22 led to compound ( ) 24. Simultaneous deprotection of the
phosphonate group and the base in the presence of TMSBr in DMF
provided the 30-fluoro-50-norcarbocyclic nucleoside phosphonate
( ) 25 in 70% yield.
The stereochemical assignments of compounds ( ) 36 and ( )
39 were achieved through NMR experiments (Fig. 3). In the case of
compound ( ) 36, a NOE correlation was observed between H50b
and H8. Simultaneously, H50a showed a correlation between pro-
tons H10 and H4’. All these NOE correlations support the cis
orientation of protons H50a, H10 and H4’. In the case of compound
( ) 39, a direct correlation between protons H10 and H40 was
observed and gave proof of the cis orientation of protons H10 and
H4’.
Due to low yields and side-products obtained during the prep-
aration of the fluoro derivative ( ) 25, we envisioned to carry out
the fluorination step before the introduction of the heterocyclic
base via the Mitsunobu reaction. In a first attempt, this approach
was envisaged from trans-alcohol ( ) 4 (Scheme 4, pathway 1).
Nevertheless, the Mitsunobu reaction applied to the trans com-
pound gave very poor yield (16%, data not shown), probably due to
steric hindrance, generated between silyl ether and heterocyclic
base as incoming nucleophile, during the SN2 step occurring under
Mitsunobu mechanism. Consequently, the cis-iodocarbocycle ( ) 3
was used as starting material as implemented in Scheme 4
(pathway 2). A preliminary protection of the allylic alcohol before
the fluorination step was accomplished to give the tert-butyldi-
phenylsilyl ether ( ) 26. Fluorination reaction was achieved in the
presence of n-BuLi and NFSI leading to a mixture of carbocycles ( )
27 and ( ) 28. Under these conditions, the fluoro derivative was
obtained as the major compound (ratio ( ) 27/( ) 28: 7/3) as
determined by 1H NMR. However these compounds were very
difficult to separate by chromatography on silica gel. Then, the se-
lective hydrolysis of the tert-butyldimethylsilyl ether was per-
formed under mild acidic conditions on the mixture to give the
fluorinated carbocycle ( ) 29 and its unsaturated counterpart ( )
30. At this stage of the synthesis, these two compounds can be
easily separated by chromatography on silica gel to obtain 57% of
compound ( ) 29 and only 22% of dehalogenated counterpart ( )
30. As expected, this approach greatly improved the yield of the
desired fluorinated product ( ) 29 which was engaged in the
Mitsunobu coupling reaction with different heterocyclic bases.
2.2. Anti-HIV evaluation
The synthesized compounds ( ) 12, ( ) (15), ( ) 18, ( ) 20, ( )
(36) and ( ) 39 were evaluated for their antiviral activity in human
peripheral blood mononuclear cells (PBMC) infected with HIV-1.
The results are summarized in Table 1. (R)-PMPA was used as pos-
itive control. Among the tested compounds, the 30-iodo-50-norca-
bonucleoside phosphonate ( ) 12, bearing adenine as nucleobase,
exhibited moderate antiviral activity (EC50 ¼ 5.9
mM). Modification
of the adenine moiety by the introduction of a cyclopropyl group in
position 6, as in compound ( ) (15), resulted in the loss of activity.
Replacement of the halogen atom in position 30, as for 30-fluoro-50-
norcabonucleoside phosphonate ( ) 36 derivative of adenine
afforded
(EC50 ¼ 0.88
a
m
compound with potent antiviral activity
M).
M) comparatively to (R)-PMPA (EC50 ¼ 1.1
m
The others 30-iodo or fluoro-50-norcabonucleoside phosphonate
bearing a purine base distinct of adenine did not display any anti-
viral activity against HIV-1. No concomitant cytotoxicity for all the
target compounds was observed in PBM cells. The synthesized
compounds ( ) 12, ( ) (15), ( ) 18, ( ) 20, ( ) (36) and ( ) 39 were
also evaluated for their antiviral activity against Zika virus, Dengue
virus 2, HSV-1, HSV-2 and Chikungunya virus but did not show any
antiviral activity (data not shown).

646
N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
Scheme 4. Synthesis of the fluoro-carbocycle ( ) 29. Reagents and conditions: (a) TBDPSCl, imidazole, DMF, rt, 2 days, 98%; (b) NFSI, n-BuLi, THF, ꢀ78 ꢁC, 2 h; (c) TsOH, MeOH, rt, 1 h,
57% over two steps for ( ) 29, 22% over two steps for ( ) 30.
3. Conclusion
200 spectrometers. Chemicals shifts (d) are reported in parts per
millions using residual non deuterated solvents as internal refer-
ences and signals are indicated as s (singlet), d (doublet), t (triplet),
q (quartet), m (multiplet) and br (broad). MS and HRMS were
recorded in the positive or negative mode on a Micromass Q-TOF
Waters. UV spectra were recorded with an Uvikon 931 (Kontron)
The racemic synthesis of 30-iodo and 30-fluoro-50-norcarbocyclic
nucleoside phosphonates bearing purine bases was undertaken
and compounds were evaluated for their antiviral activity. No
antiviral activity was observed against Zika virus, Dengue virus 2,
HSV-1, HSV-2 and Chikungunya virus. In contrast, the 30-iodo and
30-fluoro-50-norcarbocyclic nucleoside phosphonates bearing
adenine as nucleobase, compound ( ) 12 and ( ) (36), exhibited
anti HIV-1 with no concomitant cytotoxicity. Remarkably, The 30-
fluoro-50-norcabonucleoside phosphonate ( ) 36 exhibited signif-
icant antiviral activity, comparatively to (R)-PMPA. These inter-
esting results warranty further studies, such as the synthesis of the
suitable corresponding prodrugs, on 30-fluoro-50-norcarbocyclic
nucleoside phosphonates as potential anti-HIV agents [16].
spectrophotometer,
l .
are expressed in nm and ε in L.molꢀ1.cmꢀ1
4.1.1. ( )-4-Hydroxy-2-cyclopentenone
A solution of furfuryl alcohol (50.11 g, 0.51 mol) in H2O (1.5 L)
was treated with KH2PO4 (2.50 g, 18 mmol). The solution was
adjusted to pH ¼ 4.1 with H3PO4, then heated to 90 ꢁC for 36 h. The
cooled solution was extracted with AcOEt. The combined organic
layers were washed with H2O and the aqueous layers combined
and evaporated to give a red oil. The red oil was dissolved in AcOEt,
dried (MgSO4) filtered through a pad of Celite and the filtrate was
evaporated in vacuo to give ( )-4-Hydroxy-2-cyclopentenone as a
dark oil (25 g, 0,26 mol, 50%) which was used without further pu-
rification. The physicochemical properties were similar to those
previously reported [5].
4. Experimental part
4.1. Chemistry
All air and/or moisture sensitive reactions were carried out
under an argon atmosphere with dry or freshly distilled solvents
and using standard syringe-cannula/septa techniques. All corre-
sponding glassware was oven-dried (100 ꢁC) and/or carefully dried
in line with a flameless heat gun. All solvents were distilled under
4.1.2. ( )-4-tert-butyldimethylsilyloxy-2-cyclopentenone (1)
To
a solution of ( )-4-Hydroxy-2-cyclopentenone (45.11 g,
460 mmol) and Et3N (102 mL) in THF (230 mL) was added with
DMAP (1.12 g, 9.2 mmol). The solution was cooled to 0 ꢁC and
treated with portionwise addition of TBDMSCl (65.78 g, 437 mmol)
to keep the temperature of the reaction mixture below 10 ꢁC. The
resulting mixture was stirred at rt for three days, then poured into
aqueous 0.5 N HCl. The phases were separated, and the aqueous
layer was extracted with CH2Cl2. The organic phases were com-
bined, washed with aqueous 0.5 N HCl, saturated NaHCO3, brine,
dried (MgSO4), filtered, and the filtrate was evaporated to give an
oil. This last was purified by distillation (P ¼ 0,05 mbar,
T ¼ 73e74 ꢁC) to give ( ) 1 as a colorless oil (60.65 g, 286 mmol,
62%). The physicochemical properties were similar to those previ-
ously reported [5].
argon atmosphere: THF from
a blue solution of sodium-
benzophenone ketyl radical prior to use, CH2Cl2 and DMF from
CaH2, pyridine from KOH. Routine monitoring of reactions was
performed using Merck silica gel 60 F254 aluminium supported TLC
plates; spots were visualized using a UV light and ethanolic acidic
p-anisaldehyde solution or 5% ethanolic sulfuric acid solution, fol-
lowed by heating. Purification by column chromatography was
performed with silica gel 60 (230e400 mesh) or with reversed
phase silica gel (RP-18, 25e40 mm). Ion exchange chromatography
was performed on DOWEX 50WX8-200 resins (Naþ form). 1H, 13
C
NMR, 31P and 19F spectra were recorded in CDCl3, MeOD, D2O or
DMSO-d6 solutions on Brucker AM-600, DRX 400, AM-300, DPX

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
647
Scheme 5. Synthesis of the 30-fluoro-50-norcarbocyclic nucleoside phosphonate ( ) 36 and ( ) 39. Reagents and conditions: (a) 2-amino-6-chloropurine or 6-chloropurine, PPh3,
DIAD, THF, rt, 4 h, 54% for ( ) 31; 52% for ( ) 32; (b) i) NH3/MeOH, 70 ꢁC, 30 h; ii) DMF-dimethylacetal, DMF, 50 ꢁC, 15 h, 70% over two steps; (c) i) benzoic acid, PPh3, DIAD, THF, rt,
3 h; ii) K2CO3, MeOH, rt; 2 h, 85% over two steps for ( ) 34; 16 h, 93% over two steps ( ) 38; (d) (Et2O)POCH2OTs, LiOtBu, THF, 60 ꢁC, 3 days, 71%; (e) TMSBr, DMF, rt, 38 h, 42% overall
yield; (f) K2CO3, MeOH, reflux, 4 h, 80%; (g) i) (Et2O)POCH2OTs, LiOtBu, THF, 60 ꢁC, 3 days; ii) TMSBr, DMF, rt, 16 h, 23% over two steps.

648
N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
Fig. 3. Selected NOE effects on compounds ( ) 36 and ( ) 39.
Table 1
Anti HIV-1 LAI and cytotoxic properties of 30-halo-50-norcarbocyclic nucleoside phosphonates and reference compound (R)-PMPA in human peripheral blood mononuclear
cells (PBMC).
Compounds
EC50
(m
M)a
CC50 (m
M)b
(
(
(
(
) 12
) (15)
) 18
) 20
) (36)
) 39
5.9
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
ꢃ10
0.88
ꢃ10
1.1
(
(
(R)-PMPA
a
EC50 Effective concentration of drug required to reduce viral replication by 50%. Data are the mean from 3 blood donors.
CC50 Cytotoxic concentration of drug required to reduce cell growth by 50%. Data are the mean from 3 blood donors.
b
4.1.3. ( )-4-tert-butyldimethylsilyloxy-2-iodocyclopent-2-enone
(2)
(7.68 mL, 39.1 mmol) was added dropwise. The solution was stirred
for 1 h and concentrated under reduced pressure. Purification by
column chromatography with petroleum ether/AcOEt (98/2) gave
( ) 5 (14.29 g, 32.9 mmol, 98%) as a yellow oil. Rf ¼ 0.27 (2% AcOEt
in petroleum ether).
From compound ( ) 4: Compound ( ) 4 (1.75 g, 5.1 mmol) was
dissolved at 0 ꢁC in dry pyridine/CH2Cl2 (96/4, 30 mL) and BzCl
(0.89 mL, 7.7 mmol) was added under an argon atmosphere. The
reaction mixture was stirred at rt for 12 h then poured at 0 ꢁC into
saturated NaHCO3 and extracted with CH2Cl2. The combined
organic layers were washed with NaHCO3, water and brine then
dried, filtered, and concentrated in vacuo. Purification by column
chromatography with a stepwise gradient of diethyl ether (1e2%)
in petroleum ether gave ( ) 5 (1.72 g, 75%) as a yellow oil. 1H NMR
To a stirred solution of ( ) 1 (9.92 g, 46.7 mmol) in CH2Cl2
(390 mL) under an argon atmosphere were added sublimated I2
(17.78 g, 70.0 mmol) and pyridinium dichromate (5.27 g,
14.0 mmol). The reaction mixture was stirred at rt for two days.
Water was added to the reaction mixture and the emulsion was
filtrated through a pad of Celite. The phases were separated and the
aqueous layer was extracted with CH2Cl2. The combined organic
phases were washed with Na2S2O3, brine, dried (MgSO4), filtrated
and the filtrate was evaporated to give an oil which was purified by
column chromatography on silica gel (Petroleum Ether/Et2O 95/5)
to give ( ) 2 (13.59 g, 40.1 mmol, 86%) as a brown oil. The physi-
cochemical properties were similar to those previously reported
[7].
(CDCl3, 300 MHz):
d
8.06 (d, J ¼ 9.2 Hz, 2H, ArH), 7.60e7.55 (m, 1H,
ArH), 7.48e7.43 (m, 2H, ArH), 6.48 (d, J ¼ 1.3 Hz, 1H, H3), 6.02e5.98
(m, 1H, H1), 4.96e4.91 (m, 1H, H4), 2.23e2.29 (m, 2H, H5), 0.90 (s,
4.1.4. ( )-4-tert-butyldimethylsilyloxy-2-iodocyclopent-2-enol (3)
and (4)
9H, t-Bu), 0.09 (s, 6H, 2 ꢂ CH3). 13C NMR (CDCl3, 75 MHz):
d 166.2
(Cq), 148.9 (C3), 133.3 (CAr), 130.1 (Cq), 129.9 (2 ꢂ CAr), 128.5
(2 ꢂ CAr), 98.0 (C2), 83.8 (C1), 76.6 (C4), 41.7 (C5), 25.9 (3 ꢂ CH3),
18.2 (Cq), ꢀ4.62 (CH3), ꢀ4.66 (CH3). HRMS (ASAPþ): calcd. for
To a stirred solution of ( ) 2 (23.15 g, 68.4 mmol) in CH3OH
(360 mL) was added CeCl3$7H2O (25.50 g, 68.4 mmol). The reaction
mixture was stirred at rt for 1 h and then cooled to ꢀ78 ꢁC NaBH4
(3.11 g, 82.2 mmol) was added portionwise and the reaction
mixture was stirred for 2 h. The reaction mixture was diluted with
CH2Cl2 and saturated NH4Cl and water were added. The phases
were separated and the aqueous layer was extracted with CH2Cl2.
The combined organic phases were dried (MgSO4) and volatiles
were evaporated. Purification by column chromatography on silica
gel (CH2Cl2) gave ( ) 3 (19.75 g, 58.0 mmol, 85%), and its diaste-
reoisomer ( ) 4 (1.80 g, 5.3 mmol, 8%) as a white solid. The physi-
cochemical properties of ( ) 3 and ( ) 4 were similar to those
previously reported [10].
C
18H24IOSi [M ꢀ H]þ 443.0539; found 443.0541.
4.1.6. ( )-4-Hydroxy-2-iodo-2-cyclopenten-1-yl benzoate (6)
To a stirred solution of ( ) 5 (37.94 g, 85.4 mmol) in dry THF
(600 mL) at 0 ꢁC was added dropwise a 1 M solution of TBAF
(102 mL, 102.0 mmol). The reaction mixture was stirred at 0 ꢁC for
2 h and then concentrated in vacuo. The residual oil was purified by
column chromatography with
a stepwise gradient of AcOEt
(25e50%) in petroleum ether to afford ( ) 6 (26.98 g, 81.7 mmol,
4.1.5. ( )-4-{[tert-butyl(dimethyl)silyl]oxy}-2-iodo-cyclopent-2-
en-1-yl benzoate (5)
95%) as a white solid. Rf ¼ 0.27 (30% AcOEt in petroleum ether). 1H
NMR (CDCl3, 300 MHz): d 8.07e8.05 (m, 2H, ArH), 7.61e7.56 (m, 1H,
From compound ( ) 3: To a stirred solution of PPh3 (10.25 g,
39.1 mmol) and BzOH (4.77 g, 39.1 mmol) in dry THF (90 mL) at rt
was cannulated a solution of ( ) 3 (11.08 g, 32.5 mmol) in dry THF
(160 mL). The reaction mixture was cooled to 0 ꢁC and DIAD
ArH), 7.48e7.43 (m, 1H, ArH), 6.58 (m, 1H, H3), 6.09e6.04 (m, 1H,
H1), 4.98e4.93 (m, 1H, H4), 2.40e2.36 (m, 2H, CH2). 13C NMR
(CDCl3, 75 MHz):
d 166.2 (Cq), 147.8 (C3), 133.4 (CAr), 129.9
(2 ꢂ CAr), 128.5 (2 ꢂ CAr), 100.1 (C2), 83.3 (C1), 76.4 (C4), 41.4 (C5).

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
649
4.1.7. ( )-4-(6-Chloro-9H-purin-9-yl)-2-iodo-2-cyclopenten-1-yl
benzoate (7)
1 h at 0 ꢁC diethyl p-toluene sulfonyloxymethyl phosphonate
(3.08 g, 9.6 mmol) was added and the mixture was stirred for 2 days
at rt. Few drops of AcOH were added and the mixture was
concentrated in vacuo. The crude product was solubilized in an
AcOH/H2O/CH3OH (9/1/1) solution (9 mL) and stirred for two days
at rt before concentration in vacuo. Purification by silica gel chro-
matography with AcOEt/CH3OH (80/20) gave ( ) 11 (0.647 g, 73%)
as a white foam. Rf ¼ 0.25 (20% CH3OH in AcOEt. 1H NMR (400 MHz,
To a stirred solution of PPh3 (4.31 g, 16.4 mmol) and 6-
chloropurine (2.54 g, 16.4 mmol) in dry THF (120 mL) at 0 ꢁC un-
der an argon atmosphere, was added dropwise DIAD (3.23 mL,
16.4 mmol) over 15 min. After stirring for 1 h, a solution of ( ) 6
(2.50 g, 7.5 mmol) in dry THF (60 mL) was added. The reaction
mixture was stirred at rt for 2 h then concentrated in vacuo. The
resulting syrup was purified by silica gel chromatography with a
stepwise gradient of AcOEt (10e50%) in petroleum ether to give ( )
7 (3.05 g, 6.5 mmol, 43%) as a white foam. Rf ¼ 0.27 (40% AcOEt in
CDCl3):
d
8.32 (s, 1H), 7.93 (s, 1H), 6.44 (d, J ¼ 2.5 Hz, 1H, H30), 6.21
(br s, 2H, NH2), 5.54 (dt, J ¼ 8.3, 3.1 Hz, 1H, H40), 4.59 (dd, J ¼ 6.9,
3.0 Hz, 1H, H10), 4.03 and 3.93 (ABX, J ¼ 13.7, 8.9 Hz, 2H, CH2), 2.99
(ddd, J ¼ 15.0, 8.2, 7.3 Hz, 1H, H50a), 2.13 (dt, J ¼ 14.6, 3.3 H, 1H,
H50b), 1.34 (t, J ¼ 7.1 Hz, 3H, CH3), 1.32 (t, J ¼ 7.1 Hz, 3H, CH3). 13C
petroleum ether). 1H NMR (CDCl3, 300 MHz):
d 8.76 (s, 1H, H2), 8.25
(s, 1H, H8), 8.08e8.04 (m, 2H, ArH), 7.64e7.59 (m, 1H, ArH),
7.51e7.45 (m, 2H, ArH), 6.63 (d, J ¼ 2.4 Hz, 1H, H30), 6.02 (dd, J ¼ 7.5,
3.3 Hz, 1H, H10), 5.76 (dt, J ¼ 7.9, 3.0 Hz, 1H, H40), 3.37 (ddd, J ¼ 15.1,
8.3, 7.5 Hz, 1H, H50a), 2.20 (dt, J ¼ 15.1, 3.5 Hz, 1H, H50b). 13C NMR
NMR (100 MHz, CDCl3):
d 155.8 (Cq), 153.1 (C2), 149.5 (Cq), 141.2
(C30),138.9 (C8),119.5 (Cq),102.6 (C20), 89.3 (d, J ¼ 11.8, C10), 64.3 (d,
J ¼ 166.8 Hz, OCH2P), 62.8e62.7 (m, 2 ꢂ CH2), 57.4 (C40), 38.2 (C50),
(CDCl3, 75 MHz):
d
165.6 (Cq), 152.3 (C2), 151.3 (Cq), 143.1 (C8), 141.1
16.6 (d, J ¼ 6.0 Hz, 2 ꢂ CH3). 31P (D2O, 162 MHz):
d
20.1. MS (ESIþ):
(C30), 133.8 (2 ꢂ CAr), 131.7 (Cq), 129.9 (Cq), 129.2 (Cq), 128.8
(2 ꢂ CAr), 102.4 (C20), 81.6 (C10), 58.7 (C40), 39.4 (C50). MS (ESIþ): m/
z ¼ 467 (M þ H)þ. UV (EtOH 95) lmax ¼ 265 nm (εmax ¼ 11000).
HRMS (ESIþ): calcd. for C17H13ClIN4O2 [MþH]þ 466.9772; found
466.9769.
m/z ¼ 494 (M þ H)þ. UV (EtOH 95) lmax ¼ 261 nm (εmax ¼ 16400).
HRMS (ESIþ): calcd. for C15H22IN5O4P [MþH]þ 494.0454; found
494.0458.
4.1.11. ( )-{[-4-(6-Amino-9H-purin-9-yl)-2-iodo-2-cyclopenten-1-
yl]oxy}methylphosphonic acid (12)
4.1.8. ( )-4-(6-Amino-9H-purin-9-yl)-2-iodo-2-cyclopenten-1-ol
(9)
To a stirred solution of phosphonate ester ( ) 11 (247 mg,
1.0 mmol) in dry DMF (8 mL) at 0 ꢁC under argon atmosphere was
added dropwise TMSBr (1.97 mL, 15.1 mmol). The solution was
stirred at rt for 12 h then neutralized with an aqueous triethy-
lammonium hydrogen bicarbonate solution (1 M, pH 7) and
concentrated to dryness under reduce pressure. Reverse-phase
column chromatography of the residue with H2O/CH3OH (100/
0 to 87/13) gave ( ) 12 (147 mg, 67%) as a white solid. Rf ¼ 0.22
A solution of ( ) 7 (1.23 g, 2.6 mmol) in methanolic ammonia
(2 M, 100 mL) was heated at 70 ꢁC in a Parr high pressure reactor for
20 h. The mixture was filtered, the solid was washed with CH3OH
and the filtrate was concentrated in vacuo. The residue was purified
by silica gel chromatography with a stepwise gradient of CH3OH
(0e8%) in CH2Cl2 to give ( ) 9 (0.75 g, 81%) as a yellow solid.
Rf ¼ 0.11 (5% CH3OH in CH2Cl2). 1H NMR (DMSO-d6, 300 MHz):
(isopropanol/NH4OH/H2O: 7/2/1). 1H NMR (D2O, 400 MHz):
d 8.20
d
8.13 (s, 1H, H2), 8.09 (s, 1H, H8), 7.30 (s, 2H, NH2), 6.43 (dd, J ¼ 2.3,
(s, 1H, H2), 8.20 (s, 1H, H8), 6.60 (dd, J ¼ 2.3, 1.0 Hz, 1H, H30),
5.46e5.42 (m, 1H, H40), 4.76e4.73 (m, 1H, H10), 3.64 (d, J ¼ 9.1 Hz,
2H, P-CH2-O), 3.14 (ddd, J ¼ 14.3, 8.3, 7.5 Hz, 1H, H50a), 2.16 (dt,
0.8 Hz, 1H, H30), 6.09 (d, J ¼ 8.3 Hz, 1H, OH), 5.41e5.36 (m, 1H, H40),
4.57e4.51 (m, 1H, H10), 2.97 (ddd, J ¼ 13.8, 8.2, 7.6 Hz,1H, H50a),1.92
(dt, J ¼ 13.8, 4.5 Hz, 1H, H50b). 13C NMR (DMSO-d6, 75 MHz):
d
156.1
J ¼ 14.3, 4.7 Hz, 1H, H50b). 13C NMR (D2O, 100 MHz):
d 155.4 (Cq),
(Cq), 152.2 (C2), 148.7 (Cq), 139.2 (C30), 138.4 (C8), 119.0 (Cq), 109.9
(C20), 79.0 (C10), 58.2 (C40), 40.2 (C50). MS (ESIþ): m/z ¼ 344
(M þ H)þ. UV (EtOH 95) lmax ¼ 261 nm (εmax ¼ 20500). HRMS
(ESIþ): calcd. for C10H11IN5O [MþH]þ 344.0008; found 344.0003.
152.3 (C2), 148.4 (Cq), 140.6 (C8), 140.0 (C30), 118.5 (Cq), 104.0 (C20),
88.1 (d, J ¼ 11.4 Hz, C10), 67.5 (d, J ¼ 149.9 Hz, P-CH2-O), 58.3 (C40),
37.2 (C50). 31P NMR (D2O, 162 MHz):
d
12.9. MS (ESIþ): m/z ¼ 438
(M þ H)þ. UV (EtOH 95) lmax ¼ 261 nm (εmax ¼ 8100). HRMS (ESIþ):
calcd. for C11H14IN5O4P [MþH]þ 437.9828; found 437.9823.
4.1.9. ( )-N'-{9-[-4-Hydroxy-3-iodo-2-cyclopenten-1-yl]-9H-
purin-6-yl}-N,N-dimethylimidoformamide (10)
4.1.12. ( )-4-[6-(cyclopropylamino)-9H-purin-9-yl]-2-iodo-2-
cyclopenten-1-ol (13)
To a stirred solution of ( ) 9 (0.70 g, 4.1 mmol) in dry DMF
(10 mL) under argon atmosphere was added DMF-dimethylacetal
(0.82 mL, 6.1 mmol) at rt. The mixture was heated at 50 ꢁC for 4 h
then concentrated in vacuo. The residue was purified by silica gel
chromatography with CH2Cl2/CH3OH (95/5) to afford ( ) 10 (0.76 g,
93%) as a white foam. Rf ¼ 0.58 (10% CH3OH in CH2Cl2). 1H NMR
To a solution of ( ) 7 (786 mg, 1.7 mmol) in dry THF (20 mL)
under argon atmosphere was added at rt cyclopropylamine (3.5 mL,
50.5 mmol). The mixture was stirred at 50 ꢁC for 4 h and concen-
trated in vacuo. Purification by silica gel chromatography (AcOEt)
gave the benzoate derivative (773 mg, 1.6 mmol, 94%) as a white
foam. This intermediate (707 mg, 1.5 mmol) was dissolved in dry
CH3OH (21 mL) and anhydrous K2CO3 (501 mg, 3.6 mmol) was
added at rt. After stirring for 2 h, the mixture was filtered through a
sintered funnel covered with Celite and silica gel and concentrated
in vacuo. Purification by silica gel chromatography with a stepwise
gradient of CH3OH (1e6%) in CH2Cl2 gave ( ) 13 (474 mg, 1.2 mmol,
85%) as a white foam. Rf ¼ 0.23 (3% CH3OH in CH2Cl2). 1H NMR
(CDCl3, 300 MHz):
d 8.93 (s, 1H, H2), 8.44 (s, 1H, H8), 7.88 (s, 1H,
N¼CH-N), 7.10 (br s, 1H, OH), 6.15 (d, J ¼ 2.5 Hz, 1H, H20), 5.20 (ddd,
J ¼ 9.3, 2.6, 1.6 Hz, 1H, H10), 4.68 (d, J ¼ 6.8 Hz, 1H, H40), 3.24 (d,
J ¼ 0.8 Hz, 3H, CH3), 3.20 (d, J ¼ 0.8 Hz, 3H, CH3), 3.11e3.01 (m, 1H,
H50a), 2.41 (d, J ¼ 15.3 Hz, 1H, H50b). 13C NMR (CDCl3, 75 MHz):
d
160.0 (Cq),158.3 (N¼CH-N),151.6 (C2),150.1 (Cq),141.6 (C30),137.3
(C8), 127.4 (Cq), 110.1 (C20), 81.5 (C40), 60.7 (C10), 41.5 (CH3), 38.7
(C50), 35.3 (CH3). MS (ESIþ): m/z ¼ 399 (M þ H)þ. UV (EtOH 95)
lmax ¼ 312 nm (εmax ¼ 28000). HRMS (ESIþ): calcd. for C13H16IN6O
[MþH]þ 399.0430; found 399.0433.
(CDCl3, 400 MHz): d 8.38 (s,1H, H2), 7.75 (s,1H, H8), 6.17 (s,1H, NH),
6.14 (d, J ¼ 2.6 Hz, 1H, H30), 5.16 (ddd, J ¼ 9.3, 2.3, 1.4 Hz, 1H, H40),
4.68 (d, J ¼ 7.5 Hz, 1H, H10), 3.10e3.02 (m, 2H, CH þ H50a), 2.41 (d,
J ¼ 15.4 Hz, 1H, H50b), 0.95e0.90 (m, 2H, CH2), 0.66e0.62 (m, 2H,
4.1.10. ( )-diethyl {[-4-(6-amino-9H-purin-9-yl)-2-iodo-2-
cyclopenten-1-yl]oxy}methylphosphonate (11)
To a stirred solution of ( ) 10 (0.72 g, 1.8 mmol) in dry THF
(25 mL) at 0 ꢁC was added dropwise LiOtBu (2.2 M solution in THF,
3.27 mL, 7.2 mmol) under an argon atmosphere. After stirring for
CH2). 13C NMR (CDCl3, 100 MHz):
d 156.2 (Cq), 152.4 (C2), 139.8 (C8),
137.3 (C30), 121.3 (Cq), 110.3 (C20), 81.5 (C10), 60.8 (C40), 38.6 (C50),
23.8 (CH), 7.5 (2 ꢂ CH2). MS (ESIþ): m/z ¼ 484 (M þ H)þ. UV (EtOH
95) lmax ¼ 272 nm (εmax ¼ 19000). HRMS (ESIþ): calcd. for
C
13H15IN5O [MþH]þ 384.0321; found 384.0319.

650
N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
4.1.13. ( )-diethyl ({-4-[6-(cyclopropylamino)-9H-purin-9-yl]-2-
iodo-2-cyclopenten-1-yl}oxy)methylphosphonate (14)
4.1.16. ( )-diethyl {[-2-iodo-4-(6-methoxy-9H-purin-9-yl)-2-
cyclopenten-1-yl]oxy}methylphosphonate (17)
To a stirred solution of ( ) 13 (248 mg, 0.65 mmol) in dry THF
(10 mL) at 0 ꢁC under an argon atmosphere was added LiOtBu
(2.2 M solution in THF,1.18 mL, 2.59 mmol). The solution was stirred
at 0 ꢁC for 1 h until addition of diethyl p-toluene sulfonyloxymethyl
phosphonate (1.11 g, 3.45 mmol). The reaction mixture was stirred
at rt for 4 days, and then quenched by addition of AcOH (few drops).
Concentration to dryness followed by purification by silica gel
chromatography with a stepwise gradient of CH3OH (1e10%) in
CH2Cl2 gave compound ( ) 14 (yellow oil, 262 mg, 76%). Rf ¼ 0.20
Compound ( ) 17 (440 mg, 0.9 mmol, 67%) was synthesized
from ( ) 16 (463 mg, 1.3 mmol) using a similar procedure as
described for ( ) 14 with 3 eq. of LiOtBu, 4 eq. of diethyl p-toluene
sulfonyloxymethyl phosphonate and stirred for 8 days at rt.
Rf ¼ 0.22 (5% CH3OH in CH2Cl2). 1H NMR (CDCl3, 400 MHz):
d 8.45
(s, 1H, H2), 7.98 (s, 1H, H8), 6.41 (d, J ¼ 2.4 Hz, 1H, H30), 5.53 (dt,
J ¼ 8.2, 3.0 Hz, 1H, H40), 4.56 (dd, J ¼ 7.0, 3.1 Hz, 1H, H10), 4.18e4.06
(m, 4H, 2 ꢂ CH2), 4.12 (s, 3H, OCH3), 4.00 and 3.89 (ABX, J ¼ 13.8,
8.7 Hz, 2H, CH2), 2.98 (m, ddd, J ¼ 15.2, 8.2, 7.3 Hz, 1H, H50a), 2.11
(dt, J ¼ 14.6, 3.3 Hz, 1H, H50b), 1.31e1.24 (m, 6H, 2 ꢂ CH3). 13C NMR
(5% CH3OH in CH2Cl2). 1H NMR (CDCl3, 300 MHz):
d 8.38 (s, 1H, H2),
7.82 (s, 1H, H8), 6.41 (br s, 1H, NH), 6.39 (d, J ¼ 2.2 Hz, 1H, H30), 5.48
(dt, J ¼ 7.7, 2.8 Hz, 1H, H40), 4.54 (dd, J ¼ 6.9, 3.0 Hz, 1H, H10),
4.18e4.06 (m, 4H, 2 ꢂ CH2), 3.97 and 3.87 (ABX, J ¼ 13.8, 8.8 Hz, 2H,
CH2), 3.03e2.90 (m, 2H, CH þ H50a), 2.06 (dt, J ¼ 14.6, 3.4 Hz, 1H,
H50b), 1.27 (q, J ¼ 7.2 Hz, 6H, 2 ꢂ CH3), 0.88e0.81 (m, 2H, CH2),
(CDCl3, 100 MHz): d 161.0 (Cq), 152.0 (C2), 151.4 (Cq), 140.7 (C8),
140.5 (C30), 121.4 (Cq), 102.8 (C20), 89.2 (d, J ¼ 10.9 Hz, C40), 64.2 (d,
J ¼ 166.3 Hz, OCH2P), 62.8 (d, J ¼ 6.8 Hz, CH2), 62.7 (d, J ¼ 6.8 Hz,
CH2), 57.7 (C10), 54.2 (OCH3), 38.1 (C50), 16.5e16.4 (m, 2xCH3). 31P
NMR (D2O, 162 MHz):
d
19.9 ppm. MS (ESIþ): m/z ¼ 509 (M þ H)þ.
0.60e0.55 (m, 2H, CH2). 13C NMR (CDCl3, 75 MHz):
d
155.8 (Cq),
UV (EtOH 95) lmax ¼ 250 nm (εmax ¼ 12700). HRMS (ESIþ): calcd.
for C16H23IN4O5P [MþH]þ 509.0451; found 509.0445.
153.1 (C2), 148.5 (Cq), 141.0 (C30), 138.1 (C8), 119.6 (Cq), 102.5 (C20),
89.1 (d, J ¼ 11.2 Hz, C10), 64.1 (d, J ¼ 166.5 Hz, OCH2P), 62.6 (d,
J ¼ 6.5 Hz, 2 ꢂ CH2), 57.3 (C40), 38.1 (C50), 23.7 (CH), 16.5e16.4 (m,
2 ꢂ CH3), 7.3 (2 ꢂ CH2). 31P (CDCl3, 121 MHz): 20.08 ppm MS (ESIþ):
m/z ¼ 534 (M þ H)þ. UV (EtOH 95) lmax ¼ 271 nm (εmax ¼ 18700).
HRMS (ESIþ): calcd. for C18H26IN5O4P [MþH]þ 534.0767; found
534.0764.
4.1.17. ( )-disodium {[-2-iodo-4-(6-oxo-1,6-dihydro-9H-purin-9-
yl)-2-cyclopenten-1-yl]oxy}methylphosphonate (18)
Compound ( ) 18 (white solid, 107 mg, 0.2 mmol, 72%) was
synthesized from ( ) 17 (156 mg, 0.3 mmol) using the similar
procedure as described for ( ) 15. Rf ¼ 0.27 (isopropanol/NH4OH/
H2O: 5/1/1). 1H NMR (D2O, 400 MHz):
d 8.14e8.13 (m, 2H, H2, H8),
6.56 (s, 1H, H30), 5.42 (br s, 1H, H40), 4.70 (br s, 1H, H10), 3.78e3.68
(m, 2H, P-CH2-O), 3.13e3.06 (m, 1H, H50a), 2.15 (d, J ¼ 14.3 Hz, 1H,
4.1.14. ( )-disodium ({-4-[6-(cyclopropylamino)-9H-purin-9-yl]-2-
iodo-2-cyclopenten-1-yl}oxy)methyl phosphonate (15)
H50b). 13C NMR (D2O, 100 MHz):
d 158.4 (Cq), 148.2 (Cq), 145.7 (C2),
140.3 (C30), 140.1 (C8), 123.3 (Cq), 103.7 (C20), 88.4 (d, J ¼ 12.0 Hz,
Compound ( ) 15 (white solid, 115 mg, 0.2 mmol, 69%) was
synthesized from ( ) 14 (171 mg, 0.3 mmol) using the similar pro-
cedure as described for ( ) 12 followed by ion exchange on DOWEX
50WX2 (Naþ form) and freeze-drying. Rf ¼ 0.42 (isopropanol/
C10), 66.2 (d, J ¼ 154.3 Hz, P-CH2-O), 58.8 (C40), 37.1 (C50). 31P NMR
(D2O, 162 MHz):
d
14.5 ppm. MS (ESIþ): m/z ¼ 439 (M þ H)þ. UV
(EtOH 95) lmax ¼ 250 nm (εmax ¼ 8500). HRMS (ESIþ): calcd. for
C
11H13IN4O5P [MþH]þ 438.9668; found 438.9673.
NH4OH/H2O: 7/2/1). 1H NMR (D2O, 400 MHz):
d 8.17 (s, 1H, H2),
8.08 (s,1H, H8), 6.56 (br s,1H, H30), 5.37 (br s,1H, H40), 4.73 (br s,1H,
H10), 3.72 (d, J ¼ 9.1 Hz, P-CH2-O), 3.14e3.07 (m, 1H, H50a), 2.80 (br
s, 1H, CH), 2.10 (br d, J ¼ 14.3 Hz, 1H, H50b), 0.90 (d, J ¼ 6.4 Hz, 2H,
4.1.18. ( )-4-(2-Amino-6-methoxy-9H-purin-9-yl)-2-iodo-2-
cyclopenten-1-ol (8)
To a stirred solution of 2-amino-6-chloro-9H-purine (1.25 g,
7.4 mmol) and PPh3 (1.95 g, 7.4 mmol) in dry THF (240 mL), at 0 ꢁC
under an argon atmosphere was added dropwise DIAD (1.44 mL,
7.4 mmol) over 5 min. After stirring for 1 h a solution of ( ) 6 (1.01 g,
3.1 mmol) in dry THF (80 mL) was added, and stirred at rt overnight.
The solution was concentrated in vacuo and the resulting syrup was
filtered through a Celite pad. Partial purification by silica gel
chromatography with a stepwise gradient of AcOEt (25e50%) in
petroleum ether gave benzoate intermediate as a white solid. This
intermediate was dissolved in dry CH3OH (30 mL) and anhydrous
K2CO3 (4.10 g, 29.6 mmol) was added at rt. After stirring overnight,
the mixture was filtered through a sintered funnel covered with
Celite and silica gel and concentrated in vacuo. Purification by silica
gel chromatography (AcOEt) gave ( ) 8 (504 mg, 1.3 mmol, 44%) as
CH2), 0.65 (s, 2H, CH2). 13C NMR (D2O, 100 MHz):
d 155.5 (Cq), 152.3
(C2), 147.5 (Cq), 140.3 (C30), 140.0 (C8), 118.9 (Cq), 103.9 (C20), 88.6
(d, J ¼ 11.6 Hz, C10), 66.5 (d, J ¼ 153.9 Hz, O-CH2-P), 58.5 (C40), 37.4
(C50), 23.4 (CH), 6.7 (2 ꢂ CH2). 31P NMR (D2O, 162 MHz):
d 14.3 ppm.
MS (ESIþ): m/z ¼ 478 (M þ H)þ. UV (EtOH 95) lmax ¼ 271 nm
(εmax ¼ 17600). HRMS (ESIþ): calcd. for C14H18IN5O4P [MþH]þ
478.0141; found 478.0149.
4.1.15. ( )-2-iodo-4-(6-methoxy-9H-purin-9-yl)-2-cyclopenten-1-
ol (16)
To a stirred solution of ( ) 7 (182 mg, 0.4 mmol) in CH3OH
(5.6 mL) at rt under an argon atmosphere was added anhydrous
K2CO3 (135 mg, 1.0 mmol) by portionwise. After stirring overnight,
the mixture was filtered through a sintered funnel covered with
Celite and concentrated. Purification by silica gel chromatography
with a stepwise gradient of AcOEt (70e75%) in petroleum ether
gave ( ) 16 (107 mg, 0.3 mmol, 75%) as a white foam. Rf ¼ 0.30
a white foam. Rf ¼ 0.15 (AcOEt). 1H NMR (MeOD, 400 MHz):
d 7.83
(s, 1H, H8), 6.36 (d, J ¼ 2.2 Hz, 1H, H30), 5.35e5.31 (m, 1H, H40), 4.64
(dd, J ¼ 7.4, 3.5 Hz, 1H, H10), 4.04 (s, 3H, OCH3), 3.05 (dt, J ¼ 14.4,
8.1 Hz, 1H, H50a), 2.04 (dt, J ¼ 14.4, 3.9 Hz, 1H, H50b). 13C NMR
(MeOD, 100 MHz):
d
162.7 (Cq), 161.5 (Cq), 154.1 (Cq), 140.0 (C20),
(AcOEt). 1H NMR (CDCl3, 400 MHz):
d
8.47 (s, 1H, H2), 7.95 (s, H8),
139.7 (C8), 115.6 (Cq), 109.5 (Cq), 81.4 (C40), 59.9 (C10), 54.2 (OCH3),
40.9 (C50). MS (ESIþ): m/z ¼ 374 (M þ H)þ. UV (EtOH 95)
lmax ¼ 252 nm (εmax ¼ 8400), lmax ¼ 280 nm (εmax ¼ 10000). HRMS
(ESIþ): calcd. for C11H13IN5O2 [MþH]þ 374.0114; found 374.0117.
6.49 (d, J ¼ 10.7 Hz, 1H, OH), 6.17 (d, J ¼ 2.6 Hz, 1H, H30), 5.26 (dt,
J ¼ 9.3, 2.2 Hz, 1H, H40), 4.71e4.67 (m, 1H, H10), 4.16 (s, 3H, OCH3),
3.09 (ddd, J ¼ 15.5, 9.2, 7.9 Hz, 1H, H50a), 2.38 (d, J ¼ 15.3 Hz, 1H,
H50b). 13C NMR (CDCl3,100 MHz):
d 161.5 (Cq),151.5 (C2),150.5 (Cq),
142.0 (C8), 137.3 (C30), 123.0 (Cq), 110.2 (C20), 81.3 (C10), 60.7 (C40),
54.5 (OCH3), 38.8 (C50). MS (ESIþ): m/z ¼ 359 (M þ H)þ. UV (EtOH
95) lmax ¼ 249 nm (εmax ¼ 10600). HRMS (ESIþ): calcd. for
4.1.19. ( )-diethyl {[-4-(2-amino-6-methoxy-9H-purin-9-yl)-2-
iodo-2-cyclopenten-1-yl]oxy}methylphosphonate (19)
Compound ( ) 19 (yellow oil, 342 mg, 0.6 mmol, 53%) was
synthesized from ( ) 8 (460 mg, 1.2 mmol) using the similar
C
11H12IN4O2 [MþH]þ 359.0005; found 359.0002.

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
651
procedure as described for ( ) 14 with 3 eq. of LiOtBu, 4.5 eq. of
diethyl p-toluene sulfonyloxymethyl phosphonate and stirred for 2
days at rt. Purification was achieved with AcOEt/CH3OH (95/5).
compounds. This mixture was diluted in dry THF (61 mL) and a 1 M
solution of TBAF (4.4 mL, 4.4 mmol) was added dropwise at 0 ꢁC.
The reaction mixture was stirred at 0 ꢁC for 1 h and then concen-
trated in vacuo. The residual oil was chromatographed with a
stepwise gradient of CH3OH (0e10%) in AcOEt to afford ( ) 22
(311 mg, 1.2 mmol, 21%) as a white foam and ( ) 23 (450 mg,
1.9 mmol, 33%) as a white solid. Compound ( ) 22: Rf ¼ 0.31 (5%
Rf ¼ 0.47 (5% CH3OH in EtOAc).1H NMR (CDCl3, 400 MHz):
d 7.65 (s,
1H, H8), 6.39 (d, J ¼ 1.8 Hz, 1H, H30), 5.31e5.30 (m, 1H, H10), 5.01 (s,
2H, NH2), 4.65 (dd, J ¼ 7.1, 3.8 Hz, 1H, H40), 4.23 (dd, J ¼ 13.9, 9.6 Hz,
1H, OCH2P), 4.20e4.16 (m, 4H, 2 ꢂ CH2), 4.05 (s, 3H, OCH3), 3.96
(dd, J ¼ 14.0, 8.3 Hz, 1H, OCH2P), 2.95e2.90 (m, 1H, H50a), 2.28 (dt,
J ¼ 14.5, 4.1 Hz, 1H, H50b), 1.34 (t, J ¼ 7.0 Hz, 6H, 2 ꢂ CH3). 13C NMR
CH3OH in AcOEt). 1H NMR (CDCl3, 300 MHz):
d 8.47 (s, 1H, H2), 7.96
(s, 1H, H8), 5.35e5.29 (m, 1H, H40), 5.23 (d, J ¼ 2.5 Hz, 1H, H30), 4.64
(d, J ¼ 7.1 Hz, 1H, H10), 4.16 (s, 3H, OCH3), 3.17e3.06 (m, 1H, H50a),
2.29 (dd, 1H, J ¼ 15.6, 1.9 Hz, 1H, H50b). 13C NMR (CDCl3, 75 MHz):
(CDCl3, 100 MHz):
d
161.7 (Cq), 159.4 (Cq), 153.4 (Cq), 141.7 (C30),
137.8 (C8), 115.8 (Cq), 102.2 (Cq), 88.8 (d, J ¼ 11.2 Hz, C10), 62.9 (d,
J ¼ 166.0 Hz, OCH2P), 62.8 (d, J ¼ 8.6 Hz, CH2), 62.7 (d, J ¼ 8.8 Hz,
CH2), 57.9 (C40), 53.9 (OCH3), 36.8 (C50), 16.6e16.5 (m, 2 ꢂ CH3). 31P
d
167.4 (d, J ¼ 290.4 Hz, C20), 161.4 (Cq), 151.4 (C2), 150.6 (Cq), 142.1
(C8), 123.0 (Cq), 104.2 (d, J ¼ 12.5 Hz, C30), 70.2 (d, J ¼ 22.1 Hz, C10),
55.1 (d, J ¼ 11.6 Hz, C40), 54.4 (OCH3), 38.0 (d, J ¼ 5.7 Hz, C50). 19F
NMR (CDCl3, 162 MHz):
d
20.8. MS (ESIþ): m/z ¼ 524 (M þ H)þ. UV
(EtOH
95)
lmax ¼ 246 nm
(εmax ¼ 6700),
lmax ¼ 282 nm
NMR (282 MHz, CDCl3):
d
122.7 (m). MS (ESIþ): m/z ¼ 251 (M þ H)þ.
(εmax ¼ 6600). HRMS (ESIþ): calcd. for C16H24IN5O5P [MþH]þ
UV (EtOH 95) lmax ¼ 250 nm (εmax ¼ 10300). HRMS (ESIþ): calcd.
for C11H12FN4O2 [MþH]þ 251.0944; found 251.0952. Compound ( )
23: Rf ¼ 0.28 (5% CH3OH in AcOEt). 1H NMR (CDCl3, 400 MHz):
524.0560; found 524.0524.
4.1.20. ( )-{[-4-(2-Amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-2-
iodo-2-cyclopenten-1-yl]oxy}methylphosphonic acid (20)
d
8.44 (s, 1H, H2), 7.96 (s, 1H, H8), 6.34e6.31 (m, 1H, H30), 6.06 (br s,
1H, OH), 5.82 (dd, J ¼ 5.5, 2.5 Hz, 1H, H20), 5.37e5.33 (m, 1H, H40),
4.85 (br s, 1H, H10), 4.15 (s, 3H, OCH3), 2.98 (ddd, J ¼ 15.6, 9.1, 7.7 Hz,
Compound ( ) 20 (white solid, 66 mg, 0.15 mmol, 58%) was
synthesized from ( ) 19 (130 mg, 0.25 mmol) using the similar
procedure as described for ( ) 15. Rf ¼ 0.13 (iPrOH/NH4OH/H2O: 7/
1H, H50a), 2.19 (d, J ¼ 15.4, 1H, H50b). NMR (CDCl3, 100 MHz):
d 161.4
(Cq), 151.2 (C2), 150.7 (Cq), 142.3 (C8), 140.0 (C30), 129.8 (C20),þ122.9
(Cq), 75.2 (C10), 60.2 (C40), 54.3 (OCH3), 39.6 (C50). MS (ESI ): m/
z ¼ 233 (M þ H)þ. UV (EtOH 95) lmax ¼ 250 nm (εmax ¼ 10500).
HRMS (ESIþ): calcd. for C11H13N4O2 [MþH]þ 233.1039; found
233.1039.
2/1). 1H NMR (D2O, 400 MHz): 7.85 (s, 1H, H8), 6.56 (br. s, 1H, H30),
d
5.29e5.27 (m, 1H, H40), 4.75e4.72 (m, 1H, H10), 3.87e3.76 (m, 2H,
OCH2P), 3.07 (dt, J ¼ 14.5, 7.9 Hz, 1H, H50a), 2.15 (dt, J ¼ 14.3, 4.6 Hz,
1H, H50b). 13C NMR (D2O, 100 MHz):
d 159.0 (Cq), 153.8 (Cq), 151.2
(Cq), 140.9 (C30), 138.3 (C8), 116.2 (Cq), 103.0 (Cq), 88.6 (d,
J ¼ 11.8 Hz, C10), 65.5 (d, J ¼ 156.6 Hz, OCH2P), 58.4 (C40), 37.0 (C50).
4.1.23. ( )-diethyl {[-2-fluoro-4-(6-methoxy-9H-purin-9-yl)-2-
cyclopenten-1-yl]oxy}methylphosphonate (24)
31P NMR (D2O, 162 MHz):
d
15.3. MS (ESIþ): m/z ¼ 454 (M þ H)þ. UV
(EtOH 95) lmax ¼ 252 nm (εmax ¼ 15400). HRMS (ESIþ): calcd. for
Compound ( ) 24 (yellow oil, 422 mg, 88%) was synthesized
from ( ) 22 (300 mg, 1.2 mmol) using a similar procedure as
described for ( ) 14 but lasting for 12 days. Rf ¼ 0.21 (5% CH3OH in
C
11H14IN5O5P [MþH]þ 453.9777; found 453.9756.
4.1.21. ( )-4-{[tert-butyl(dimethyl)silyl]oxy}-3-iodo-2-
AcOEt). 1H NMR (CDCl3, 400 MHz):
d 8.49 (s, 1H, H2), 8.11 (s, 1H,
cyclopenten-1-yl)-6-methoxy-9H-purine (21)
H8), 5.64e5.59 (m, 1H, H40), 5.48 (d, J ¼ 2.7 Hz, 1H, H30), 4.57 (dd,
J ¼ 7.4, 1.8 Hz, 1H, H10), 4.19e4.09 (m, 4H, 2 ꢂ CH2), 4.15 (s, 3H,
OCH3), 4.00 and 3.88 (ABX, J ¼ 13.8, 8.9 Hz, 2H, CH2), 3.03 (dt,
J ¼ 15.3, 7.8 Hz, 1H, H50a), 2.05 (br dd, J ¼ 15.1, 2.3 Hz, 1H, H50b), 1.31
(t, J ¼ 7.1 Hz, 3H, CH3), 1.29 (t, J ¼ 7.1 Hz, 3H, CH3). 13C NMR (CDCl3,
To a stirred solution of ( ) 16 (2.51 g, 7.0 mmol) and imidazole
(1.43 g, 21.0 mmol) in DMF (10 mL) at 0 ꢁC under an argon atmo-
sphere was added portionwise TBDMSCl (4.22 g, 28.0 mmol). The
mixture was stirred at rt for 12 h before concentration in vacuo.
Purification by silica gel chromatography with petroleum ether/
AcOEt (7/3) gave ( ) 21 (2.99 g, 6.3 mmol, 87%) as a white foam.
Rf ¼ 0.20 (30% AcOEt in petroleum ether). 1H NMR (CDCl3,
100 MHz):
d
165.1 (d, J ¼ 289.9 Hz, C20), 161.1 (Cq), 152.1 (C2), 151.5
(Cq), 140.7 (C8), 121.6 (Cq), 107.3 (d, J ¼ 11.7 Hz, C30), 79.0 (dd, 1H,
J ¼ 20.5, 11.1 Hz, C10), 64.2 (d, J ¼ 167.3 Hz, OCH2P), 62.7 (d,
J ¼ 6.5 Hz, 2 ꢂ CH2), 54.2 (OCH3), 51.5 (d, J ¼ 10.8 Hz, C40), 37.3 (d,
J ¼ 4.9 Hz, CH2), 16.5 (d, J ¼ 5.4 Hz, 2 ꢂ CH3). 31P NMR (D2O,
400 MHz):
d
8.50 (s, 1H, H2), 8.10 (s, 1H, H8), 6.33 (d, J ¼ 2.4 Hz, 1H,
H20), 5.58e5.54 (m, 1H, H10), 4.73 (dd, J ¼ 6.8, 3.2 Hz, 1H, H40), 4.16
(s, 3H, OCH3), 2.99 (ddd, J ¼ 14.8, 8.1, 7.0 Hz, 1H, H50a), 1.91 (dt,
J ¼ 14.1, 3.5 Hz, 1H, H50b), 0.90 (s, 9H, t-Bu), 0.19 (s, 3H, CH3), 0.08 (s,
162 MHz):
d
19.8 ppm.19F NMR (CDCl3, 375.6 MHz):
d
ꢀ119.7 (t,
J ¼ 2.7 Hz). MS (ESIþ): m/z ¼ 401 (M þ H)þ. UV (EtOH 95)
lmax ¼ 250 nm (εmax ¼ 12000). HRMS (ESIþ): calcd. for C16H23FN4O5
P [MþH]þ 401.1390; found 401.1388.
3H, CH3). 13C NMR (CDCl3, 100 MHz):
d 161.1 (Cq), 152.1 (C2), 151.5
(Cq), 140.9 (C8), 138.5 (C20), 121.5 (Cq), 108.9 (C30), 80.7 (C40), 57.8
(C10), 54,3 (OCH3), 42.1 (C50), 25.8 (3 ꢂ CH3), 18.1 (Cq), ꢀ4.4
(CH3), ꢀ4.6 (CH3). MS (ESIþ): m/z ¼ 473 (M þ H)þ. UV (EtOH 95)
lmax ¼ 249 nm (εmax ¼ 14500). HRMS (ESIþ): calcd. for
4.1.24. ( )-disodium {[-2-fluoro-4-(6-oxo-1,6-dihydro-9H-purin-9-
yl)-2-cyclopenten-1-yl]oxy}methylphosphonic acid (25)
Compound ( ) 25 (white solid, 228 mg, 70%) was synthesized
from ( ) 24 (350 mg, 0.9 mmol) using the similar procedure as
described for ( ) 15 with TMSBr (20 eq.) and stirred for 36 h.
Rf ¼ 0.23 (isopropanol/NH4OH/H2O: 7/2/1). 1H NMR (D2O,
C
17H26IN4O2Si [MþH]þ 473.0870; found 473.0866.
4.1.22. ( )-2-fluoro-4-(6-methoxy-9H-purin-9-yl)-2-cyclopenten-
1-ol (22) and ( )-4-(6-methoxy-9H-purin-9-yl)-2-cyclopenten-1-ol
(23)
300 MHz):
d
8.20 (s, 1H, H2), 8.13 (s, 1H, H8), 5.65 (d, J ¼ 2.6 Hz, 1H,
To a stirred solution of ( ) 21 (2.81 g, 5.9 mmol) and NFSI (3.00 g,
9.5 mmol) in dry THF (60 mL) at ꢀ78 ꢁC under an argon atmo-
sphere, was added dropwise n-BuLi (2.5 M in hexane, 9.52 mL,
23.8 mmol). After stirring at ꢀ78 ꢁC for 45 min, saturated NH4Cl
was added and the mixture was warmed to rt. The aqueous layer
was extracted with CH2Cl2 and the combined organic phases were
dried (MgSO4), filtered, and concentrated. The residue was purified
by silica gel chromatography with petroleum ether/AcOEt (6/4) to
give an inseparable mixture of the fluorinated and dehalogenated
H30), 5.50e5.43 (m, 1H, H40), 4.70 (dd, J ¼ 7.6, 3.1 Hz, 1H, H10), 3.69
(d, J ¼ 9.4 Hz, 2H, OCH2P), 3.10 (dt, J ¼ 15.1, 7.9 Hz, 1H, H50a),
2.10e2.02 (m, 1H, H50b). 13C NMR (D2O, 75 MHz):
d 164.5 (d,
J ¼ 286.4 Hz, C20), 158.5 (Cq), 148.2 (Cq), 145.6 (C2), 140.5 (C8), 123.4
(Cq), 106.7 (d, J ¼ 13.0 Hz, C30), 78.4 (dd, J ¼ 20.5, 12.3 Hz, C10), 65.9
(d, J ¼ 155.2 Hz, 2H, OCH2P), 52.4 (d, J ¼ 11.5 Hz, C40), 36.0 (d,
J ¼ 5.4 Hz, C50). 31P NMR (121 MHz, D2O):
d
14.9.19F NMR (282 MHz,
D2O):
d
ꢀ121.8 (d, J ¼ 5.5 Hz). MS (ESIþ): m/z ¼ 331 (M þ H)þ. UV
(EtOH 95) lmax ¼ 250 nm (εmax ¼ 8500). HRMS (ESIþ): calcd. for

652
N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
C11H13FN4O5P [MþH]þ 331.0608; found 331.0617.
1.72e1.64 (m, 1H, H5b), 1.09 (s, 9H, t-Bu). 13C NMR (CDCl3, 75 MHz):
d
164.8 (d, J ¼ 288.7 Hz, C3), 136.0 (CAr), 135.9 (2 ꢂ CAr), 133.7 (Cq),
4.1.25. ( )-tert-butyl[(-4-{[tert-butyl(diphenyl)silyl]oxy}-3-iodo-2-
cyclopenten-1-yl)oxy]dimethylsilane (26)
133.2 (Cq), 130.0 (CAr), 129.9 (CAr), 127.8 (2 ꢂ CAr), 127.7 (2 ꢂ CAr),
109.0 (d, J ¼ 7.2 Hz, C2), 70.9 (d, 7H, J ¼ 20.8 Hz, C4), 69.1 (d,
To a stirred solution of ( ) 3 (4.01 g, 11.8 mmol) and imidazole
(2.41 g, 35.4 mmol) in dry DMF (40 mL) at 0 ꢁC under an argon at-
mosphere, was added portionwise TBDPSCl (4.52 mL, 17.7 mmol).
The reaction mixture was stirred at rt for 48 h and poured onto a
solution of saturated NH4Cl (50 mL) and CH2Cl2 (50 mL) at 0 ꢁC. The
aqueous layer was extracted with CH2Cl2 and the combined organic
layers were washed with NaHCO3, water and brine then dried,
filtered, and concentrated in vacuo. Purification by column chro-
matography with petroleum ether/AcOEt (99/1) gave ( ) 26 (6.74 g,
11.6 mmol, 98%) as a colorless oil. Rf ¼ 0.74 (20% AcOEt in petroleum
J ¼ 10.9 Hz, C1), 43.3 (d, J ¼ 5.0 Hz, C5), 26.9 (3 ꢂ CH3), 19.2 (Cq). 19
F
NMR (CDCl3, 282 MHz):
d
ꢀ124.8 (dt, J ¼ 6.6, 1.9 Hz). MS (ESIþ): m/
z ¼ 355 (M ꢀ H)-. HRMS (ESIþ): calcd. for C21H24FO2Si [M ꢀ H]-
355.1530; found: 355.1549. The physicochemical properties of
compound ( ) 30 were similar to those previously reported [17].
4.1.28. ( )-9-((1S,4S)-4-{[tert-butyl(diphenyl)silyl]oxy}-3-fluoro-
2-cyclopenten-1-yl)-6-chloro-9H-purine (31)
To a stirred solution of PPh3 (4.24 g, 16.2 mmol) and 6-
chloropurine (2.50 g, 16.2 mmol) in dry THF (110 mL) at 0 ꢁC was
added dropwise DIAD (3.2 mL, 16.2 mmol) under an argon atmo-
sphere. The mixture was stirred at rt for 1 h then a solution of ( ) 29
(1.80 g, 5.1 mmol) in dry THF (30 mL) was added and stirred at rt for
1 h. The precipitate was filtrated through a pad of Celite, the filter-
cake was washed with Et2O and the filtrate was concentrated in
vacuo. Purification by silica gel chromatography with CH2Cl2/AcOEt
(95/5) afforded ( ) 31 as a white foam (1.34 g, 54%). Rf ¼ 0.30 (5%
ether). 1H NMR (CDCl3, 300 MHz):
d 7.80e7.70 (m, 4H, ArH),
7.44e7.35 (m, 6H, ArH), 6.20 (t, J ¼ 1.7 Hz,1H, H2), 4.49 (t, J ¼ 6.6 Hz,
1H, H4), 4.40e4.36 (m, 1H, H1), 2.18 (dt, J ¼ 12.7, 7.0 Hz, 1H, H5a),
1.64 (dt, J ¼ 12.7, 6.1 Hz, 1H, H5b), 1.12 (s, 9H, t-Bu), 0.85 (s, 9H, t-
Bu), ꢀ0.01 (s, 3H, CH3), ꢀ0.02 (s, 3H, CH3). 13C NMR (CDCl3,
75 MHz):
d
144.3 (C3), 136.5 (2 ꢂ CAr), 136.2 (2 ꢂ CAr), 134.2 (Cq),
133.3 (Cq), 129.8 (CAr), 129.8 (CAr), 127.6 (4 ꢂ CAr), 105.8 (C2), 79.2
(C1), 75.5 (C4), 44.4 (C5), 27.2 (3 ꢂ CH3), 25.9 (3 ꢂ CH3), 19.5 (Cq),
18.2 (Cq), ꢀ4.6 (CH3), ꢀ4.6 (CH3). MS (ESI>0): m/z ¼ 579.2 [MþH]þ.
AcOEt in CH2Cl2). 1H NMR (CDCl3, 400 MHz):
d 8.67 (s, 1H, H2), 7.96
(s, 1H, H8), 7.70e7.65 (m, 4H, ArH), 7.48e7.35 (m, 6H, ArH),
5.81e5.76 (m, 1H, H10), 5.39 (d, 1H, J ¼ 2.3 Hz, H20), 5.11 (br d,
J ¼ 2.5 Hz, 1H, H40), 2.60 (ddd, 1H, J ¼ 14.4, 8.3, 3.8 Hz, H50a), 2.16
(ddd, 1H, J ¼ 14.4, 7.2, 2.6 Hz, H50b), 1.10 (s, 9H, t-Bu). 13C NMR
4.1.26. ( )-tert-butyl[(-4-{[tert-butyl(diphenyl)silyl]oxy}-3-fluoro-
2-cyclopenten-1-yl)oxy]dimethylsilane (27)
To a stirred solution of ( ) 26 (5.05 g, 8.7 mmol) and NFSI (4.40 g,
13.9 mmol) in dry THF (60 mL) at ꢀ78 ꢁC under an argon atmo-
sphere, was added dropwise n-BuLi (2.5 M in hexane, 14 mL,
35.0 mmol). After stirring at ꢀ78 ꢁC for 2 h, saturated NH4Cl was
added and the mixture was warmed to rt. The aqueous layer was
extracted with CH2Cl2 and the combined organic phases were dried
(MgSO4), filtered, and concentrated to give a mixture of compound
( ) 27 and its dehalogenated derivative ( ) 28. This mixture was
used in the next step without further purification. A part of the
residue was purified by silica gel chromatography with a stepwise
gradient of CH2Cl2 (10e15%) in petroleum ether to afford com-
pound ( ) 27. Rf ¼ 0.53 (30% CH2Cl2 in petroleum ether). 1H NMR
(CDCl3, 100 MHz):
d
167.3 (d, J ¼ 291.8, C30), 152.0 (C2), 151.4 (Cq),
151.3 (Cq), 143.1 (C8), 135.9 (CAr), 135.9 (CAr), 133.3 (Cq), 132.8 (Cq),
132.2 (Cq),130.2 (CAr),130.2 (CAr),128.0 (CAr),127.9 (CAr),104.1 (d,
J ¼ 13.3 Hz, C20), 72.0 (d, J ¼ 20.3 Hz, C40), 54.5 (d, J ¼ 12.1 Hz, C10),
40.7 (d, J ¼ 5.1 Hz, C50), 26.9 (3 ꢂ CH3), 19.3 (Cq). 19F NMR (CDCl3,
376.5 MHz):
d
ꢀ118.1. UV (EtOH 95) lmax ¼ 265 nm (εmax ¼ 8000).
MS (ESIþ): m/z ¼ 493 (M þ H)þ. HRMS (ESIþ): calculated for
C
26H27ClFN4OSi [MþH]þ 493.1627; found: 493,1618.
4.1.29. ( )-N'-{9-[(1S,4S)-3-fluoro-4-hydroxy-2-cyclopenten-1-yl]-
9H-purin-6-yl}-N,N-dimethylimidoformamide (33)
A solution of ( ) 31 (1.2 g, 2.6 mmol) in methanolic ammonia
(2 M, 100 mL) was heated at 70 ꢁC in a stainless-steel Parr high
pressure reactor for 30 h. The mixture was filtered, the solid was
washed with CH3OH and the filtrate was concentrated in vacuo. The
residue was partially purified by silica gel chromatography with a
stepwise gradient of CH3OH (5e10%) in CH2Cl2. This residue was
used in the next step without further purification. Rf ¼ 0.19 (10%
CH3OH in CH2Cl2). MS (ESI>0): m/z ¼ 236 [MþH]þ. This residue was
converted into compound ( ) 33 (colourless oil, 528 mg, 70%) using
the similar procedure as described for ( ) 10 with heating at 50 ꢁC
overnight and purified with a stepwise gradient of CH3OH (0e10%)
in CH2Cl2. Rf ¼ 0.26 (10% CH3OH in CH2Cl2). 1H NMR (CDCl3,
(CDCl3, 300 MHz): d 7.74e7.69 (m, 4H, ArH), 7.46e7.36 (m, 6H, ArH),
5.20 (d, J ¼ 1.4 Hz, 1H, H2), 4.52e4.42 (m, 2H, H1þH4), 2.50e2.41
(m, 1H, H5a), 1.79e1.71 (m, 1H, H5b), 1.09 (s, 9H, t-Bu), 0.90 (s, 9H,
3 ꢂ CH3), 0.07 (s, 3H, CH3), 0.06 (s, 3H, CH3). 13C NMR (CDCl3,
75 MHz):
d
163.5 (d, J ¼ 287.0 Hz, C2), 136.0 (CAr), 136.0 (CAr), 135.9
(CAr), 134.0 (Cq), 133.5 (Cq), 129.8 (3 ꢂ CAr), 127.7 (4 ꢂ CAr), 109.2
(d, J ¼ 6.8 Hz, H3), 70.6 (d, J ¼ 20.3 Hz, C1), 68.6 (d, J ¼ 11.9 Hz, C4),
43.8 (d, J ¼ 4.9 Hz, C5), 26.9 (s, 3 ꢂ CH3), 26.0 (s, 3 ꢂ CH3), 19.3 (Cq),
18.2 (Cq), ꢀ4.5 (2 ꢂ CH3). 19F NMR (CDCl3, 282 MHz):
d
ꢀ126.52 (d,
J ¼ 6.7 Hz). MS (ESIþ): m/z ¼ 471 (M þ H)þ. HRMS (ESIþ): calcd. for
C
27H40FO2Si2 [MþH]þ 471.2551; found: 471.2563.
400 MHz):
d
8.92 (s, 1H, H2), 8.51 (s, 1H, H8), 7.84 (s, 1H, NCH¼N),
4.1.27. ( )-4-{[tert-butyl(diphenyl)silyl]oxy}-3-fluoro-2-
cyclopenten-1-ol (29)
5.78e5.73 (m, 1H, H10), 5.41 (d, 1H, J ¼ 2.5 Hz, H20), 5.18 (br s, 1H,
H40), 4.08 (br s, 1H, OH), 3.24 (s, 3H, CH3), 3.19 (s, 3H, CH3), 2.61
(ddd, 1H, J ¼ 13.8, 8.1, 3.8 Hz, H50a), 2.45 (ddd, 1H, J ¼ 14.6, 7.5,
To a stirred solution of crude mixture ( ) 27 and ( ) 28 (4.56 g)
in CH3OH (80 mL) at 0 ꢁC was added p-TsOH, 231 mg,1.2 mmol). The
reaction mixture was stirred at rt for 1 h and volatiles were evap-
orated to dryness. The residue was poured onto a solution of CH2Cl2
and saturated NaHCO3 at 0 ꢁC and extracted with CH2Cl2. The
organic layers were combined, dried (MgSO4) and concentrated in
vacuo. Purification by column chromatography with a stepwise
gradient of AcOEt (10e20%) in petroleum ether gave ( ) 29 (1.8 g,
57% over two steps) as a colorless oil and ( ) 30 (650 mg, 22% over
two steps). Compound ( ) 29. Rf ¼ 0.29 (20% AcOEt in petroleum
2.9 Hz, H50b). 13C NMR (CDCl3, 100 MHz):
d
166.8 (d, J ¼ 289.2 Hz,
C30), 159.7 (Cq), 158.2 (C2), 152.6 (C8), 151.4 (Cq), 139.4 (CH¼N),
126.4 (Cq), 104.8 (d, J ¼ 12.1 Hz, C20), 70.3 (d, J ¼ 2.0 Hz, C40), 53.6 (d,
J ¼ 12.1 Hz, C10), 41.3 (CH3), 40.2, (d, J ¼ 5.2 Hz, C50), 35.2 (CH3). 19F
NMR (CDCl3, 376.5 MHz):
d
ꢀ122.0. UV (EtOH 95) lmax ¼ 310 nm
(εmax ¼ 15000). MS (ESIþ): m/z ¼ 291 (M þ H)þ. HRMS (ESIþ):
calculated for C13H16FN6O [MþH]þ 291.1370; found 291.1367.
4.1.30. ( )-N'-{9-[(1S,4R)-3-fluoro-4-hydroxy-2-cyclopenten-1-
yl]-9H-purin-6-yl}-N,N-dimethylimidoformamide (34)
ether). 1H NMR (CDCl3, 300 MHz):
d 7.72e7.67 (m, 4H, ArH),
7.47e7.36 (m, 6H, ArH), 5.31 (d, J ¼ 2.4 Hz, 1H, H2), 4.54e4.50 (m,
To a solution of PPh3 (2.49 g, 9.5 mmol) and BzOH (1.16 g,
9.5 mmol) in dry THF (10 mL) at rt was cannulated a solution of ( )
1H, H4), 4.46e4.40 (m, 1H, H1), 2.51 (dt, J ¼ 14.3, 7.3 Hz, 1H, H5a),

N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
653
33 (553 mg,1.9 mmol) in dry THF (10 mL). The reaction mixture was
cooled down to 0 ꢁC and DIAD (1.87 mL, 9.5 mmol) was added
dropwised. The reaction mixture was stirred at rt for 3 h and vol-
atiles were evaporated to dryness. The residue was dissolved in
CH3OH (38 mL) and anhydrous K2CO3, (524 mg, 3.8 mmol) was
added. The reaction mixture was stirred at rt for 2 h then concen-
trated to dryness. Purification by silica gel chromatography with a
stepwise gradient of CH3OH (0e10%) in CH2Cl2 afforded ( ) 34
(472 mg, 85%) as a colourless oil. Rf ¼ 0.45 (10% CH3OH in CH2Cl2).
(529 mg, 1.5 mmol) in dry THF (11 mL) was added, and stirred at rt
for 4 h. The solution was concentrated in vacuo and the resulting
syrup was filtered through a pad of Celite. Purification by silica gel
chromatography with a stepwise gradient of AcOEt (20e30%) in
petroleum ether gave ( ) 32 as a white foam (396 mg, 0.8 mmol,
52%). Rf ¼ 0.18 (30% AcOEt in petroleum ether). Rf ¼ 0.31 (30%
AcOEt in petroleum ether). 1H NMR (CDCl3, 400 MHz):
d 7.70e7.65
(m, 4H, ArH), 7.60 (s, 1H, H8), 7.48e7.36 (m, 6H, ArH), 5.55e5.51 (m,
1H, H10), 5.31 (d, 1H, J ¼ 2.3 Hz, H20), 5.11 (br s, 1H, H40), 4.96 (s, 2H,
NH2), 2.53 (ddd, 1H, J ¼ 14.3, 8.3, 3.9 Hz, H50a), 2.15 (ddd, 1H, J ¼
14.3, 7.2, 2.4 Hz, H50b), 1.10 (s, 9H, t-Bu). 13C NMR (CDCl3, 100 MHz):
1H NMR (CDCl3, 400 MHz):
d 8.94 (s,1H, H2), 8.47 (s,1H, H8), 7.88 (s,
1H, CH¼N), 7.33 (br s, 1H, OH), 5.27e5.23 (m, 1H, H10), 5.21 (d, 1H,
J ¼ 2.6 Hz, H20), 4.62 (d, J ¼ 7.4 Hz, 1H, H40), 3.26 (s, 3H, CH3), 3.21 (s,
3H, CH3), 3.13e3.05 (m, 1H, H50a), 2.35 (dd, J ¼ 15.6, 2.3 Hz, 1H,
d
166.8 (d, J ¼ 290.9 Hz, C30), 158.9 (Cq), 153.2 (Cq), 151.3 (Cq), 140.3
(C8), 135.9 (2 ꢂ CAr), 135.8 (2 ꢂ CAr), 133.3 (Cq), 132.8 (Cq), 130.1
(2 ꢂ CAr), 127.9 (2 ꢂ CAr), 127.8 (2 ꢂ CAr), 125.6 (Cq), 104.2 (d,
J ¼ 12.8 Hz, C20), 72.1 (d, J ¼ 20.3 Hz, C40), 53.7 (d, J ¼ 12.0 Hz, C10),
40.3 (d, J ¼ 4.9 Hz, C50), 26.8 (3 ꢂ CH3), 19.3 (Cq). 19F NMR (CDCl3,
H50b). 13C NMR (CDCl3,100 MHz):
d
167.6 (d, J ¼ 290.2 Hz, C30),160.2
(Cq), 158.4 (C2), 151.6 (C8), 150.3 (Cq), 141.7 (CH¼N), 127.7 (Cq),
104.2 (d, J ¼ 12.2 Hz, C20), 70.4 (d, J ¼ 22.2 Hz, C40), 55.3 (d, J ¼
11.5 Hz, C10), 41.5 (CH3), 37.9 (d, J ¼ 5.7 Hz, C50), 35.4 (CH3). 19F NMR
376.5 MHz):
d
ꢀ119.2. UV (EtOH 95) lmax ¼ 311 nm (εmax ¼ 6200).
(CDCl3, 376.5 MHz):
d
ꢀ123.2. UV (EtOH 95) lmax ¼ 312 nm
MS (ESIþ): m/z ¼ 508 (M þ H)þ. HRMS (ESIþ): calculated for
(εmax ¼ 23400). MS (ESIþ): m/z ¼ 291.1 (M þ H)þ. HRMS (ESIþ):
calculated for C13H16N6OF [MþH]þ 291.1370; found: 291.1369.
C
26H28ClFN5OSi [MþH]þ 508.1736; found 508.1731.
4.1.34. ( )-(1S,4S)-4-(2-Amino-6-methoxy-9H-purin-9-yl)-2-
fluoro-2-cyclopenten-1-ol (37)
4.1.31. ( )-diethyl {[(1R,4S)-4-(6-amino-9H-purin-9-yl)-2-fluoro-
2-cyclopenten-1-yl]oxy}methylphosphonate (35)
Compound ( ) 35 (yellow oil, 187 mg, 71%) was synthesized
from ( )-34 (198 mg, 0.7 mmol) using the similar procedure as
described for ( ) 11 with 3 eq. of LiOtBu, 4 eq. of diethyl p-toluene
sulfonyloxymethyl phosphonate and stirred for 3 days at rt.
To a stirred solution of ( ) 32 (96 mg, 0.2 mmol) in CH3OH
(1.9 mL) was added anhydrous K2CO3 (262 mg, 1.9 mmol). The re-
action mixture was heated at reflux for 4 h and was concentrated in
vacuo. Purification by silica gel chromatography with a stepwise
gradient of CH3OH (0e10%) in CH2Cl2 afforded ( ) 37 (40 mg, 80%)
as a white solid. Rf ¼ 0.22 (5% CH3OH in CH2Cl2). 1HNMR (DMSO-d6,
Rf ¼ 0.46 (10% CH3OH in CH2Cl2). 1H NMR (300 MHz, MeOD):
d 8.21
(s, 1H, H2), 8.16 (s, 1H, H8), 5.69 (d, J ¼ 2.5 Hz, 1H, H30), 5.57e5.53
(m, 1H, H40), 4.87 (s, 2H, NH2), 4.65 (dd, J ¼ 7.0, 1.8 Hz, 1H, H10),
4.21e4.01 (m, 6H, 2xCH2), 3.06 (dt, J ¼ 15.2, 7.7 Hz, 1H, H50a), 2.09
(dd, J ¼ 15.0, 2.2 Hz, 1H, H50b), 1.34e1.28 (m, 6H, 2xCH3). 13C NMR
400 MHz):
d
7.83 (s, 1H, H8), 6.41 (s, 1H, NH2), 5.59 (d, 1H, J ¼ 6.3 Hz,
OH), 5.49e5.47 (m, 2H, H30 and H40), 4.99 (m, 1H, H10), 3.95 (s, 3H,
OCH3), 2.37 (ddd, 1H, J ¼ 14.0, 7.6, 2.7, H50a), 2.31e2.24 (m, 1H,
H50b). 13C NMR (DMSO-d6, 100 MHz):
d
166.5 (d, J ¼ 286.4 Hz, C20),
(75 MHz, MeOD):
d
166.2 (d, J ¼ 287.2 Hz, C20),157.3 (Cq),153.8 (C2),
160.6 (Cq), 159.7 (Cq), 153.7 (Cq), 137.8 (C8), 114.1 (Cq), 105.1 (d,
J ¼ 12.1 Hz, C30), 69.1 (d, J ¼ 21.1 Hz, C10), 53.1 (OCH3), 52.4 (d,
J ¼ 12.8 Hz, C40), C50 signal in DMSO peak. 19F NMR (DMSO-d6,
150.2 (Cq),140.7 (C8), 120.2 (Cq),108.5 (d, J ¼ 12.5 Hz, C30), 80.7 (dd,
J ¼ 21.0, 13.7 Hz, C10), 64.3 (d, J ¼ 167.8 Hz, OCH2P), 64.2 (d,
J ¼ 6.6 Hz, 2xCH2CH3), 53.3 (d, J ¼ 11.2 Hz, C40), 37.8 (d, J ¼ 5.3 Hz,
C50), 16.74 (d, J ¼ 5.7 Hz, 2xCH3). 31P NMR (121 MHz, MeOD):
376.5 MHz):
d
ꢀ124.0. UV (EtOH 95) lmax ¼ 250 nm (εmax ¼ 11100),
lmax ¼ 282 nm (εmax ¼ 11900). MS (ESIþ): m/z ¼ 266.1 (M þ Hþ).
HRMS (ESIþ): calculatedd for C11H13N5O2F [MþH]þ 266.1053;
found: 266.1052.
d
21.4.19F NMR (282 MHz, MeOD):
d
ꢀ123.2 (d, J ¼ 2.5 Hz). UV (EtOH
95) lmax ¼ 262 nm (εmax ¼ 13520). MS (ESIþ): m/z ¼ 386 (M þ H)þ.
HRMS (ESIþ): calculated for C15H22FN5O4P [MþH]þ 386.1393;
found 386.1405.
4.1.35. ( )-(1R,4S)-4-(2-Amino-6-methoxy-9H-purin-9-yl)-2-
fluoro-2-cyclopenten-1-ol (38)
4.1.32. ( )-disodium-{[(1R,4S)-4-(6-amino-9H-purin-9-yl)-2-
fluoro-2-cyclopenten-1-yl]oxy}methylphosphonic acid (36)
Compound ( ) 36 (white solid, 32 mg, 42%) was synthesized
from ( ) 35 (79 mg, 0.2 mmol) using the similar procedure as
described for ( ) 15. Rf ¼ 0.19 (iPrOH/NH4OH/H2O: 7/2/1). 1H NMR
To a stirred suspension of PPh3 (1.28 g, 4.9 mmol) and BzOH
(598 mg, 4.9 mmol) in dry THF (6 mL) under an argon atmosphere
was added a solution of ( ) 37 (260 mg, 1.0 mmol) in dry THF (6 mL)
at rt. The mixture was cooled to 0 ꢁC and DIAD (965
mL, 4.9 mmol)
(400 MHz, D2O):
d
8.12 (s, 1H, H2), 8.02 (s, 1H, H8), 5.62 (d,
was added dropwise. The reaction mixture was stirred at rt for 2.5 h
and then concentrated to dryness. The residue was dissolved in
CH3OH (18 mL) and anhydrous K2CO3 (276 mg, 2.0 mmol) was
added. The solution was stirred at rt for 16 h and concentrated in
vacuo. Purification by flash chromatography on silica gel with a
stepwise gradient of CH3OH (0e6%) in CH2Cl2 afforded ( ) 38
J ¼ 2.5 Hz, 1H, H30), 5.34e5.32 (m, 1H, H40), 4.67 (dd, J ¼ 7.4, 2.7 Hz,
1H, H10), 3.74e3.65 (m, 2H, OCH2P), 3.05 (dt, J ¼ 15.5, 7.9 Hz, 1H,
H50a), 1.96 (br d, J ¼ 14.9 Hz, 1H, H50b). 13C NMR (100 MHz, D2O):
d
164.6 (d, J ¼ 286.2 Hz, C20), 155.1 (Cq), 152.1 (C2), 148.1 (Cq), 140.6
(C8), 118.4 (Cq), 106.8 (d, J ¼ 13.3 Hz, C30), 78.7 (dd, J ¼ 20.3, 12.7 Hz,
C10), 65.8 (d, J ¼ 156.2 Hz, OCH2P), 52.07 (d, J ¼ 11.4 Hz, C40), 36.1
(240 mg, 93%) as a white foam. Rf ¼ 0.38 (5% CH3OH in CH2Cl2) 1
H
(C50). 31P NMR (162 MHz, D2O):
d
15.0.19F NMR (D2O, 376.5 MHz):
NMR (CDCl3, 400 MHz): d 7.59 (s, 1H, H8), 7.28e7.26 (m, 1H, OH),
d
ꢀ121.6. UV (EtOH 95) lmax ¼ 250 nm (εmax ¼ 10300). MS (ESIþ):
5.19 (d, 1H, J ¼ 2.6 Hz, H30), 5.15e5.12 (m, 1H, H40), 4.97 (s, 2H, NH2),
4.57 (t, J ¼ 8.4 Hz, 1H, H10), 4.05 (s, 3H, OCH3), 3.07e2.99 (m, 1H,
H50a), 2.24 (dd, J ¼ 15.5, 2.2 Hz, 1H, H50b). 13C NMR (CDCl3,
m/z ¼ 330 (M þ H)þ. HRMS (ESIþ): calculatedd for C11H14FN5O4P
[MþH]þ 330.0767 found 330.0743.
100 MHz):
d
167.3 (d, J ¼ 289.8 Hz, C20), 162.1 (Cq), 158.6 (Cq), 152.2
4.1.33. ( )-9-((1S,4S)-4-{[tert-butyl(diphenyl)silyl]oxy}-3-fluoro-
2-cyclopenten-1-yl)-6-chloro-9H-purin-2-amine (32)
(Cq), 139.4 (C8), 117.2 (Cq), 104.3 (d, J ¼ 12.1 Hz, C30), 70.3 (d, J ¼
22.3 Hz, C10), 54.8 (d, J ¼ 11.6 Hz, C40), 54.1 (OCH3), 38.0 (d, J ¼
To a stirred solution of 2-amino-6-chloro-9H-purine (553 mg,
5.7 Hz, C50). 19F NMR (CDCl3, 376.5 MHz):
d
ꢀ123.6. UV (EtOH 95)
3.3 mmol) and PPh3 (856 mg, 3.3 mmol) in dry THF (240 mL), at 0 ꢁC
lmax ¼ 282 nm (εmax ¼ 6500). MS (ESIþ): m/z ¼ 266 (M þ H)þ. HRMS
(ESIþ): calculatedd for C11H13FN5O2 [MþH]þ 266.1053; found
308.1164.
under argon atmosphere, was added dropwise DIAD (640
3.3 mmol) over 5 min. After stirring for 1 h a solution of ( )-29
mL,

654
N. Hamon et al. / European Journal of Medicinal Chemistry 150 (2018) 642e654
4.1.36. ( )-disodium-{[(1R,4S)-4-(2-amino-6-oxo-1,6-dihydro-9H-
purin-9-yl)-2-fluoro-2-cyclopenten-1-yl]oxy}methylphosphonic
acid (39)
assay (Promega) on day 7. Experiments were performed in tripli-
cate and repeated with another blood donors. Data analyses were
performed using SoftMax® Pro 4.6 sofware (Molecular Devices).
Percent of inhibition of RT activity or cell viability were plotted
versus compound concentration and fitted with quadratic curves to
determine 50% effective concentration (EC50) and 50% cytotoxic
concentration (CC50).
To a stirred solution of alcohol ( ) 38 (99 mg, 0.4 mmol) in dry
THF (5 mL) at 0 ꢁC under an argon atmosphere was added LiOtBu
(2.2 M solution in THF, 0.545 mL, 1.2 mmol). The solution was stirred
at 0 ꢁC for 1 h until addition of diethyl p-toluene sulfonyloxymethyl
phosphonate (516 mg, 1.6 mmol). The reaction mixture was stirred
at rt for 3 days, and then quenched by addition of AcOH (few drops).
Concentration to dryness followed by purification by silica gel
chromatography with a stepwise gradient of CH3OH (2e10%) in
AcOEt gave an inseparable mixture of phosphonate derivative and
hydroxymethylphosphonic acid. This mixture was used in the next
step without further purification. Rf ¼ 0.23 (10% CH3OH in AcOEt).
MS (ESIþ): m/z ¼ 416.1 (M þ H)þ. To a stirred solution of contam-
inated phosphonate derivative (239 mg) in dry DMF (5 mL) at 0 ꢁC
was added dropwise TMSBr (1.2 mL, 9.3 mmol) under an argon
atmosphere. The reaction mixture was stirred at rt for 16 h then
neutralized with an aqueous triethylamonium hydrogen bicar-
bonate solution (1 M, pH 7) and concentrated to dryness under
reduce pressure. Purification by flash chromatography on silica gel
with a stepwise gradient of iPrOH/NH4OH/H2O (7/2/1 to 9/9/1)
followed by reverse-phase column chromatography with H2O/
CH3OH (100/0 to 80/20), ion exchange on Dowex 50WX2 (Naþ
form) and freeze-drying gave ( ) 39 (34 mg, 23% over 2 steps) as a
white solid. Rf ¼ 0.10 (iPrOH/NH4OH/H2O: 7/2/1). 1H NMR (D2O,
Acknowledgements
ꢁ
N. H. and M. K. are particularly grateful to the Universite de
Montpellier for doctoral fellowship. We gratefully acknowledge
SATT AxLR, Languedoc - Roussillon for financial support and Dr. P.
Clayette (Laboratory Oncodesign biotechnology) for the biological
results.
Appendix A. Supplementary data
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.ejmech.2018.03.038.
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d
7.76 (s, 1H, H8), 5.51 (d, 1H, J ¼ 2.5 Hz, H30), 5.18e5.14
(m, 1H, H40), 4.62 (dd, 1H, J ¼ 7.6, 3.3 Hz, H10), 3.53e3.43 (m, 2H,
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12.2 Hz, C30), 78.2 (dd, J ¼ 19.9, 12.1, C10), 67.1 (d, J ¼ 150.1, CH2P),
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13.1.19F NMR (D2O, 376.5 MHz):
d
ꢀ122.9. UV (EtOH 95)
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ꢁ
neomycin), 10% fetal calf serum (FCS, previously inactivated by
heat) and 10 UI/mL of rHuIL-2. The HIV-1 LAI strain was previously
described [18].
4.2.2. Anti-HIV assay
PHA-P activated PBMCs (1.5 ꢂ 105 cells) were pre-treated for
30 min by increasing concentrations of the various compounds to
be tested and then infected with 100% infectious tissue culture
doses 50% (TCID50) of the HIV-1-LAI. Supernatants were collected at
day 7 post infection and stored at ꢀ20 ꢁC. Viral replication was
measured by quantifying reverse transcriptase activity in cell cul-
ture supernatants by the use of Lenti kit RT (Cavidi). Cytotoxicity of
the compounds was evaluated in uninfected PHA-P PBMC by MTT
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