Synthesis and antiviral activities of fluorinated acyclic nucleoside phosphonates

Article abstract of DOI:10.1039/a805929b

Novel α-fluoro derivatives of PME and HPMP were synthesized by electrophilic fluorination of 1-tert-butyldimethylsiloxy-2-[(diethoxyphosphoryl)methoxy]ethane 15 and 3-O-benzyl-2-O-[(diethoxyphosphoryi)methyl]-1-O-(tert-butyldimethylsiloxy) glycerol 22, respectively. The first series of acyclic nucleoside phosphonates possessing the α-fluoro(phosphoryl)methoxy group were prepared by coupling of F-PME or F-HPMP derivatives 18, 26, or 27 with the corresponding purine or pyrimidine nucleic bases under either modified Mitsunobu conditions or base-catalyzed alkylation conditions. Treatment of the diesters of F-PMEA 25a-c, F-PMEG 25f and F-PMEC 25g with concentrated aqueous ammonia led to the formation of the corresponding monoammonium salts of monoethyl phosphonate 30a, 30d, 30f and 30g. The synthesized fluorinated acyclic nucleoside phosphonates were tested against herpes viruses, respiratory viruses, hepatitis B virus and HIV. The monoammonium salt of the monoethyl ester of F-PMEA 30a was found to be active against human cytomegalovirus (HCMV), Epstein-Barr virus and measles with EC₅₀ values of 5.6, 1.6 and 32 μg mL^-1, respectively.

Full text of DOI:10.1039/a805929b

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Synthesis and antiviral activities of fluorinated acyclic nucleoside
phosphonates
Wei Chen,*a Michael T. Flavin,a Robert Fillerb and Ze-Qi Xua
a MediChem Research, Inc., 12305 South New Avenue, Lemont, IL 60439, USA
b Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology,
Chicago, IL 60616, USA
Received (in Austin, TX, USA) 29th July 1998, Accepted 28th September 1998
Novel α-fluoro derivatives of PME and HPMP were synthesized by electrophilic fluorination of 1-tert-butyl-
dimethylsiloxy-2-[(diethoxyphosphoryl)methoxy]ethane 15 and 3-O-benzyl-2-O-[(diethoxyphosphoryl)methyl]-1-O-
(tert-butyldimethylsiloxy)glycerol 22, respectively. The first series of acyclic nucleoside phosphonates possessing the
α-fluoro(phosphoryl)methoxy group were prepared by coupling of F-PME or F-HPMP derivatives 18, 26, or 27
with the corresponding purine or pyrimidine nucleic bases under either modified Mitsunobu conditions or base-
catalyzed alkylation conditions. Treatment of the diesters of F-PMEA 25a–c, F-PMEG 25f and F-PMEC 25g with
concentrated aqueous ammonia led to the formation of the corresponding monoammonium salts of monoethyl
phosphonate 30a, 30d, 30f and 30g. The synthesized fluorinated acyclic nucleoside phosphonates were tested against
herpes viruses, respiratory viruses, hepatitis B virus and HIV. The monoammonium salt of the monoethyl ester of
F-PMEA 30a was found to be active against human cytomegalovirus (HCMV), Epstein–Barr virus and measles
with EC50 values of 5.6, 1.6 and 32 µg mLϪ1, respectively.
viruses.12a,b The fluoromethyl derivative FPMPA 11 was found
Introduction
to be active both in vitro and in vivo against retroviruses.6c
A
Analogues of acyclic nucleoside phosphonates, in which the
furanose ring of a nucleotide is replaced with an acyclic side
chain and the POCH2 unit of the monophosphate is replaced
with a bioisostere, PCH2O, have attracted considerable atten-
tion recently for their broad-spectrum antiviral activity against
several DNA and RNA viruses.1 For example, 9-[2-(phosphono-
methoxy)ethyl]adenine (PMEA 1) (Scheme 1) exhibits in vitro
series of analogues modified in the PME and HPMP skeleton
as well as in the heterocyclic portion has been synthesized and
studied for structure–activity relationships.1,13a,b
In our efforts to search for new antiviral agents with
improved activity and selectivity, we were interested in investi-
gating the α-fluoromethoxy analogues of acyclic nucleoside
phosphonates. Blackburn14 and Chambers15 and their co-
workers have demonstrated that α-fluoroalkylphosphonates are
more effective analogues of phosphates compared with the non-
fluorinated phosphonates because the CFH or CF2 group can
both sterically and electronically mimic an oxygen,16 enabling
the second dissociation constant, pKa2, to more closely mirror
those of the phosphates due to the electron-withdrawing effect
of fluorine. In addition, fluorine can act as a possible electron
pair donor and retain the capacity of being a hydrogen bond
acceptor, thus providing a possible additional binding site for
enzymes. It is anticipated that replacement of the α-CH2 group
by CHF or CF2 functionality in the PME- and HPMP-based
acyclic nucleoside phosphonates would lead to enhanced thera-
peutic efficacy and improved pharmacological properties.
During the course of our study, we have developed a
method for the preparation of the key intermediates diethyl
(2-hydroxyethoxy)fluoromethylphosphonate18and3-O-benzyl-
2-O-[(diethoxyphosphoryl)fluoromethyl]glycerol 24, and, for
the first time, successfully synthesized a series of novel fluorin-
ated analogues of the acyclic nucleoside phosphonates. These
synthesized compounds were screened for their antiviral activ-
ities. The preliminary results on the synthesis of 18 were
reported previously.17 Herein we report our results concerning
the synthesis and the in vitro biological activities of these
fluorine-containing acyclic nucleoside phosphonates.
Scheme 1
and in vivo activities against human immunodeficiency virus
(HIV),2 herpes simplex virus (HSV),3 murine cytomegalovirus
(MCMV),4 hepatitis B virus (HBV),5 as well as other DNA
viruses and retroviruses.6a,b PMEA is undergoing clinical trials
against HBV infection,7 and the bis(pivaloyloxymethyl) ester
prodrug of PMEA, bis(POM)-PMEA 4, is now in phase II/III
clinical trials for the treatment of HIV infection.8a,b PMEDAP 2
displays antiviral activities against HIV, CMV and Murine
Sarcoma Virus (MSV).9a,b PMEG 3 has remarkable activity
against papillomaviruses.10 (S)-HPMPA 5, (S)-HPMPDAP 6
and (S)-HPMPG 7 also show potent activities against
retroviruses.11a–c HPMPC 8 (Vistide) has been approved by the
FDA for the treatment of CMV retinitis in AIDS patients.8b
The R-enantiomers of the PMP derivatives (R)-PMPA and
(R)-PMPDAP possess potent antiviral effects against retro-
Results and discussion
Retrosynthetic analysis of the target compounds revealed that
the fluorine-containing PMEA, PMEC and HPMPC analogues
can be constructed by the coupling of fluorine-containing PME
and HPMP side chains with the corresponding purine and
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988
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Scheme 2
pyrimidine heterocyclic bases (Scheme 2). The α-fluoro-
phosphono ether functionality can be introduced by electro-
philic fluorination of the alkylphosphonate carbanion formed
by deprotonation of a phosphorylmethoxy ether using a base.
Thus, the PME side chain 12 was prepared according to a
literature procedure (Scheme 3).18,19 Electrophilic fluorination
Scheme 4 Reagents: i, Amberlyst (Hϩ) ion-exchange resin, MeOH; ii,
TBDMS-Cl, DMAP, CH2Cl2; iii, n-BuLi, (PhSO2)2NF; iv, Dowex (Hϩ)
resin, EtOH.
side chain intermediate 22 (Scheme 4). The HPMP intermediate
20 was prepared according to a literature procedure,21 and
initially attempted for electrophilic fluorination. However, only
starting compound 20 was recovered. The monomethoxytrityl
(MMTr) protecting group was then removed by treatment of 20
with Amberlyst-15 (Hϩ) ion-exchange resin in MeOH at room
temperature to provide the alcohol 21 in 60% yield. Treatment
of 21 with tert-butyldimethylsilyl chloride in the presence of
triethylamine and DMAP furnished the TBDMS-protected side
chain 22 in 93% yield.
Fluorination of compound 22 at Ϫ78 ЊC by using (PhSO2)2-
NF as the fluorinating agent and sec-BuLi as the base produced
the desired compound, 1-O-(tert-butyldimethylsiloxy)-3-O-
benzyl-2-O-[(diethoxyphosphoryl)fluoromethyl]glycerol 23 in
only 5% yield. The unfavorable steric interactions between the
OTBDMS-protected HPMP side chain and sec-BuLi may
account for the low yield. Thus, sec-BuLi was replaced by
n-BuLi and the fluorination was carried out under similar
conditions to afford compound 23 in 29% yield (Scheme 4).
Investigation of this reaction using other bases has also been
conducted. However, replacement of n-BuLi with NaH, KH,
LDA or KHMDS did not lead to the formation of the desired
product. Only starting compound 22 was recovered from the
reactions. Removal of the TBDMS group of 23 was accom-
plished by treatment with Dowex (Hϩ) ion exchange resin to
afford compound 24 in 76% yield after column chromato-
graphic purification.
In our previous work, we have identified the Mitsunobu reac-
tion to be an efficient method for direct coupling of adenine to
a variety of free alcohol side chains.19 Modified Mitsunobu
conditions were thus applied to coupling the fluorine-
containing free alcohol, diethyl (2-hydroxyethoxy)fluoro-
methylphosphonate 18, with purine bases (Scheme 5). It
appeared that the outcome of the Mitsunobu coupling reaction
depended strongly on the reaction temperature. While N9-
Scheme 3 Reagents: i, sec-BuLi, (PhSO2)2NF; ii, Dowex (Hϩ) resin;
iii, TBDMS-Cl, DMAP, Et3N.
of diethyl (2-acetoxyethoxy)methylphosphonate 12 was initially
attempted using N-fluoro-N-(phenylsulfonyl)benzenesulfon-
amide [(PhSO2)2NF]20 in the presence of NaH as a base. Instead
of the desired product, a hydrolyzed alcohol 13 and a dimeric
fluorine-substituted cyclic hemiketal 14 were obtained. A
mechanism for the formation of the hemiketal was proposed
previously,17 which involves migration of the acyl group from
O to C, followed by the electrophilic fluorination and dimeriz-
ation. Changing the base from NaH to LDA, LHMDS,
KHMDS or sec-BuLi did not affect the course of the reaction.
Compound 12 was then converted into tert-butyldimethyl-
silyl (TBDMS)-protected compound 15 in a two-step process
(Scheme 3). Fluorination of 15 was carried out at Ϫ78 to 0 ЊC
by using (PhSO2)2NF as the fluorinating agent and sec-BuLi as
the base.17 The key intermediate 1-(tert-butyldimethylsiloxy)-2-
[(diethoxyphosphoryl)fluoromethoxy]ethane 16 was formed in
moderate yield (27%), along with a small amount of dimer 17
(~5% yield). Treatment of 16 with Dowex (Hϩ) ion exchange
resin at ambient temperature yielded diethyl (2-hydroxyethoxy)-
fluoromethylphosphonate 18 in 57% yield after purification by
column chromatography on silica gel. Dimer 17 was also
desilylated under similar conditions to yield compound 19 in
53% yield.
The fluorine-containing HPMP side chain 24 was syn-
thesized by electrophilic fluorination of the protected HPMP
Scheme 5 Reagents: i, Nucleic base, DEAD, Ph3P, DMF; ii, H2, Pd/C,
EtOH.
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ethyladenine was isolated as the major product in 42% yield
when the reaction was run at 0 ЊC, the desired 9-{2-[(diethoxy-
phosphoryl)fluoromethoxy]ethyl}adenine 25a was obtained in
46% yield when 18 was coupled with adenine at Ϫ10 ЊC. The
same procedure was applied to the coupling of 6-chloropurine
with 18 to afford compound 25b in 32% isolated yield. The
corresponding 2-amino-6-chloropurine derivative 25c was also
prepared at Ϫ30 ЊC in 45% yield. However, under various reac-
tion conditions, 2,6-diaminopurine led to the formation of
N9-ethyl-2,6-diaminopurine as the sole product, without any
detection of the desired product 25d. It is noteworthy that no
other regioisomers have been detected from these Mitsunobu
reactions.
Attempted coupling of guanine with F-PME side chain 18
under Mitsunobu conditions failed to afford the expected
product. The extremely low solubility of guanine in the reaction
medium unfavorably influences the process of its alkylation. To
circumvent the problem of low solubility, 2-amino-6-benzyl-
oxypurine was then chosen as a precursor of guanine, which
was synthesized according to literature reports.22a,b Coupling of
2-amino-6-benzyloxypurine with 18 under Mitsunobu condi-
tions at Ϫ40 ЊC afforded the corresponding 2-amino-6-benzyl-
oxypurine derivative 25e in 24% yield (Scheme 5). Removal of
the benzyl protecting group was accomplished by hydrogen-
olysis using palladium on activated carbon as the catalyst23
to provide the diethyl ester of F-PMEG (25f) in 37% yield. It
should be noted that attempts to couple the fluorinated dimeric
side chain 19 (Scheme 3) with adenine under Mitsunobu condi-
tions failed to yield the corresponding dimeric alkylated
adenine-based product.
using Cs2CO3 as a base at elevated temperature to produce the
corresponding acyclic nucleoside phosphonates 28a and 28b.
Bromotrimethylsilane (TMSBr) has been frequently used as
an efficient reagent for dealkylation of phosphonate dialkyl
ester to generate the corresponding phosphonic acid.24a–c
Hydrolysis of the nonfluorinated PMEA diethyl ester using
TMSBr proceeded smoothly to afford PMEA in 49% yield.17,19
However, removal of the ethyl groups from 9-{2-[(diethoxy-
phosphoryl)fluoromethoxy]ethyl}adenine 25a using the typical
procedure (room temperature) did not afford the desired
product. Instead, cleavage at the ether bond was observed,
which led to the formation of the N9-(2-hydroxyethyl)adenine.
The decomposition was possibly caused by the hydrogen
bromide released during the reaction and the sensitivity of the
resulting α-fluoro phosphonomethoxy ether moiety. Never-
theless, direct attack of the ether oxygen by TMSBr could not
be ruled out. When the reaction was carried out at a lower
temperature (Ϫ10 ЊC), a mixture of 9-[2-(phosphonofluoro-
methoxy)ethyl]adenine 29 and 9-(2-hydroxyethyl)adenine was
obtained (Scheme 8). Compound 29 was stable upon storage,
Base-catalyzed alkylation conditions were used for coupling
cytosine with the mesylate of the F-PME side chain (26) since
the fluorinated side chain 18 did not couple with cytosine under
Mitsunobu conditions (Scheme 6). Thus, upon treatment with
Scheme 8 Reagents: i, TMSBr, CH2Cl2; ii, conc. aqueous NH3.
but it gradually degraded in a week to N9-hydroxyethyladenine
in aqueous solution when stored in a refrigerator below 0 ЊC.
Alternatively, the hydrolysis of the diesters of F-PME and
F-HPMP nucleoside phosphonates under mild alkaline
conditions was then investigated. Treatment of the diesters of
F-PMEA 25a, F-PMEG 25f and F-PMEC 25g with concen-
trated aqueous ammonia led to the formation of the corres-
ponding monoammonium salts of monoethyl phosphonate
30a, 30f and 30g, respectively (Scheme 8). The same treatment
of fluorine-containing 6-chloropurine and 2-amino-6-chloro-
purine derivatives 25b and 25c with concentrated aqueous
ammonia resulted in the corresponding monoesters 30a and
30d, with concomitant replacement of the chlorine by an amino
group. This replacement under such mild conditions was
surprising because the chlorine attached to the 6-position of
the purine ring is quite stable and its replacement by an amino
group usually has to be performed with methanolic NH3 at
elevated temperature in a sealed vessel.
Scheme 6 Reagents: i, MsCl, Et3N, CH2Cl2; ii, cytosine, CsCO3, DMF.
mesyl chloride in the presence of triethylamine, compound 18
was converted into the corresponding mesylate 26. Coupling of
13b
26 with cytosine in the presence of Cs2CO3
successfully
formed the desired N1-derivative, the diethyl ester of F-PMEC
25g, in 26% yield.
The fluorine-containing derivatives of HPMP nucleoside
phosphonates were also synthesized, including 1-{2-[(diethoxy-
phosphoryl)fluoromethoxy]-3-benzyloxypropyl}cytosine 28a
and 1-{2-[(diethoxyphosphoryl)fluoromethoxy]-3-benzyloxy-
propyl}adenine 28b (Scheme 7). The initial attempts to couple
The monoesters 30a and 30d were remarkably stable and
resistant to further hydrolysis under both basic and enzymatic
conditions. Attempts to remove the second ethyl group from
compound 30a were carried out according to a literature
procedure25 using phosphodiesterases (such as C. atrox phos-
phodiesterase and phosphodiesterase I from crotalus ademan-
tens veron) in 0.1 M triethylammonium bicarbonate buffer
(TEAB, pH 7.4–8.5). However, no reaction occurred over a two
day period. It should be noted that further treatment of the
monoester with TMSBr led to degradation, resulting in the
formation of N9-(2-hydroxyethyl)adenine.
For purposes of comparison, the non-fluorinated diesters of
31a–d were also prepared by coupling the non-fluorinated side
chain 13 with the corresponding purine nucleic bases under
Mitsunobu conditions (Scheme 9).19 The diesters 31a–d were
then treated with concentrated aqueous ammonia. The reac-
Scheme 7 Reagents: i, MsCl, Et3N, CH2Cl2; ii, nucleic base, CsCO3,
DMF.
the F-HPMP side chain 24 with cytosine or adenine under Mit-
sunobu conditions failed to afford the expected products. A
small amount of N9-ethyladenine (6% yield) was separated
from the adenine reaction. Fluorine-containing alcohol 24 was
then converted to mesylate 27 by treatment with mesyl chlor-
ide and triethylamine. The coupling of mesylate fluorine-
containing side chain 27 with cytosine or adenine was achieved
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988
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Table 1 19F NMR Spectra of diesters and monoesters of fluorine-containing PME and HPMP nucleoside phosphonate analogues
Compounds
δ1 (ppm)
2JP, F (Hz)
2JH,F (Hz)
δ2 (ppm)
2JP, F (Hz)
2JP, F (Hz)
diester
25a
25b
25c
25f
25g
28a
28b
Ϫ143.0
97.4
95.3
97.5
99.8
96.4
100.9
97.6
58.7
58.2
57.4
57.2
59.2
58.0
57.8
—
—
—
—
—
Ϫ137.4
Ϫ138.0
—
—
—
—
—
100.7
101.0
—
—
—
—
—
57.5
57.5
Ϫ143.5
Ϫ143.3
Ϫ142.8
Ϫ141.9
Ϫ139.9
Ϫ141.0
monoester
30a
30d
30f
30g
Ϫ140.7
Ϫ143.5
Ϫ143.6
Ϫ142.2
80.7
86.4
84.2
82.2
57.7
59.1
58.0
58.8
—
—
—
—
—
—
—
—
—
—
—
—
Table 2 13C NMR shifts for the heteroaromatic ring carbons of
diesters and monoesters of PME purine nucleotide phosphonate
analogues
Compound
δ2 (ppm) δ4 (ppm) δ5 (ppm) δ6 (ppm) δ8 (ppm)
diester
Scheme 9 Reagents: i, Purine base, DEAD, Ph3P, DMF; ii, conc.
25a
25b
25c
31a
31b
31c
31d
153.1
146.1
154.3
152.9
146.3
153.8
156.1
149.9
133.5
149.5
149.5
132.1
151.2
151.9
119.5
129.0
123.3
119.5
128.5
125.0
114.0
155.7
152.1
160.0
155.7
151.8
159.2
160.0
141.3
131.7
143.3
141.4
131.4
143.3
138.8
aqueous NH3.
tions of 31a and 31c appeared much slower than those of the
corresponding fluorinated analogues 25a and 25c. Approxi-
mately 50% of 31a was converted to 32a in 10 days. For 31b and
31c, the major products were 31a and 31d, with small amounts
of 32a and 32d being detected. It is not surprising that the rates
of hydrolysis of the non-fluorinated derivatives decrease in
comparison with the fluorinated analogues. The strong
electron-withdrawing effect of the fluorine atom enhances the
rate of removal of ethoxide ion. It has also been reported that
introduction of fluorine into the cyclic phosphates increased
the rate of their hydrolysis.26
monoester
30a
30d
152.0
154.5
149.3
152.5
118.5
113.0
155.7
160.0
141.5
137.0
(HBV), Herpes viruses (HSV-1, HSV-2, CMV, VZV and EBV)
and respiratory viruses (adenovirus type 1, measles, para-
influenza type 3, influenza A, influenza B and respiratory syn-
cytial virus). The results for compound 30a are summarized
in Table 3. Compound 30a was not active against HIV and
hepatitis B virus (HBV) in the in vitro assays, suggesting that
either the monoester of F-PMEA may not be phosphorylated
in these cells or its diphosphate, if formed, may have low
binding affinity to the reverse transcriptase of HIV and HBV.
However, despite poor activity against HSV-1 and HSV-2,
compound 30a exhibited potent activity against both human
cytomegalovirus (HCMV) and Epstein–Barr virus (EBV), but
somewhat less potent activity against measles.
The fact that the corresponding non-fluorinated monoethyl
ester has been reported to be antivirally inactive27 implies that
introduction of fluorine into the α-position of the phosphonate
plays a key role in maintaining the biological activity of 30a,
which may be due to the increased acidity of the phosphonic
acid or altered mechanism of action. These results appear to
suggest a significant level of phosphorylation of 30a, either
directly or via the hydrolyzed product of 30a by host enzymes;
however, its diphosphate may be a poor inhibitor of herpes
simplex virus (HSV-1 and HSV-2) DNA polymerase, but an
effective inhibitor of the HCMV DNA polymerase. Whether
30a acts as a prodrug of 29 or exerts an antiviral effect without
cleavage of the ester group will be a subject of future studies.
All the diesters and monoesters of the fluorine-containing
PME nucleotide analogues 25a,b,c,f,g and 30a,d,f,g exhibit
doublet of doublet peaks at about Ϫ140 ppm in their 19F NMR
2
spectra, with coupling constants being JP, F = 97–100 Hz and
2JH,F = 57–58 Hz (Table 1). For derivatives of F-HPMP nucleo-
side phosphonates 28a and 28b, two sets of doublet of doublets
are observed in their 19F NMR spectra, indicating different
chemical shifts for the diastereomers. The coupling constants
between fluorine and phosphorus in the monoesters 30a,d,f,g
are smaller (2JP, F = 80–86 Hz) than those of the diesters
(2JP, F = 95–100 Hz). The 13C NMR chemical shift of the hetero-
cyclic carbons of the synthesized fluorine-containing and the
nonfluorinated PME nucleoside phosphonate analogues are
summarized in Table 2.
Biological evaluation and discussion
9-[2-(Phosphonofluoromethoxy)ethyl]adenine 29 and its diester
25a were screened in the in vitro XTT assay for (XTT = 2,3-
bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carb-
oxanilide) for anti-HIV activity. It was found that these two
compounds were inactive against HIV-1. As a PMEA analogue,
the diester 25a must be hydrolyzed and phosphorylated into the
corresponding mono- and di-phosphonate in order to confer
anti-HIV activity. The fact that 25a is inactive implies that it
might not be hydrolyzed and phosphorylated in the course of
the assay. The inactivity of the acid 29 may be accounted for by
its instability in aqueous solution. The monoesters 30a, 30d, 30f
and 30g were evaluated for their antiviral activities against
HIV. It was observed that these monoammonium salts were
not active against HIV in the in vitro assay. Ethyl ammonium
[2-(adenin-9-yl)ethoxy]fluoromethylphosphonate 30a was also
evaluated for its antiviral activities against hepatitis B virus
Experimental
Melting points were obtained with a Laboratory Devices
Mel-Temp apparatus and were corrected. TLC analyses were
performed on analytical thin layer plates coated with silica gel
60 F254 (Merck) and components were visualized under UV
light and/or stained with iodine. Column chromatography was
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Table 3 Antiviral activity of ethyl ammonium [2-(adenin-9-yl)ethoxy]fluoromethylphosphonate 30aa
Compound 30a
Positive
Drug Control
Virus cell strain
EC50/µg mLϪ1
IC50/µg mLϪ1
SI (IC50/EC50)
EC50/µg mLϪ1
HIV-1/CEM-SS/RF
HBV/2.2.15 cells
inactiveb
inactiveb
non-toxicb
non-toxicb
HSV-1/HFF/E-377
HSV-2/HFF/MS
HCMV/HFF/AD-169
Adenovirus type 1/A549/adenoid
Epstein–Barr virus/DAUDI/P3HR-1
Measles/CV-1/CC
Parainfluenza type 3/MA-104/C243
Respiratory syncytial virus/MA-104/Utah 89
>100
>100
5.6
>100
1.6
32
>100
>100
>100
>100
94.8
>100
>50
>100
>100
>100
0.08 (Acyclovir)
0.5 (Acyclovir)
0.05 (Ganciclovir)
10 (HPMPA)
1.2 (Acyclovir)
1 (Ribavirin)
16.9
>31
>3
10 (Ribavirin)
8 (Ribavirin)
a EC50 value is the concentration required to inhibit viral cytopathogenicity by 50%; IC50 value is the concentration required to inhibit cell
proliferation by 50%. b The value was >100 µM.
performed using silica gel 60 (70–230 mesh from EM Science).
1H, 13C, 19F, and 31P NMR spectra were recorded on a Varian
VX-300 NMR spectrometer or a Varian Gemini 2300 NMR
spectrometer. Chemical shifts (δ) are expressed in ppm and
J values are given in Hz. Me4Si was used as an internal stand-
solution of the protected PME alcohol 15 (1.65 g, 5.06 mmol)
in anhydrous THF (6 mL) was added dropwise to the light
yellow solution. The reaction mixture was stirred at Ϫ78 ЊC
for 0.5 h, followed by dropwise addition of N-fluoro-N-(phenyl-
sulfonyl)benzenesulfonamide (3.0 g, 9.52 mmol) in anhydrous
THF (20 mL). The resulting mixture was stirred at Ϫ78 ЊC for 2
h, gradually warmed to 0 ЊC, and then diluted with Et2O (100
mL). Saturated aqueous NH4Cl (30 mL) was added and the
organic layer was separated, washed successively with H2O
(30 mL), brine (30 mL), and dried over anhydrous Na2SO4.
The crude product (3 g), obtained after concentration under
vacuum, was purified by column chromatography on silica gel
(EtOAc) to afford the desired product 16 (480 mg, 27% yield) as
a pale yellow oil (Found: C, 44.93; H, 8.54. Calc. for
C13H30FO5PSi: C, 45.33; H, 8.78%); νmax/cmϪ1 3430, 2934, 2859,
1651, 1474, 1393, 1254, 1163, 1026, 835, 777; δH(300 MHz;
1
ard for H NMR and 13C NMR, while trifluoroacetic acid
(TFA) and phosphoric acid (H3PO4) were used as external
standards for 19F NMR and 31P NMR, respectively. The infra-
red spectra were recorded on a Midac M series FT-IR. Mass
spectra were recorded on a Finnegan MAT 90 mass spec-
trometer or a Finnegan MAT LCQ-MS spectrometer. UV
spectra were measured in MeOH solution on a Hitachi U-2000
UV–VIS spectrophotometer. Elemental analyses were carried
out at Midwest Microlab, Indianapolis, Indiana. Chemical
reagents and anhydrous solvents were purchased from Aldrich
Chemical Co. unless otherwise stated.
1
2
CDCl3) 5.57 (1H, dd, JF, H 58.6, JP, H 14.0, CHFP), 4.26 (4H,
quintet, J 7.0, 2CH2O), 3.84 (4H, m, 2CH2O), 1.36 (6H, t, J 7.0,
2CH3), 0.89 [9H, s, (CH3)3CSi], 0.06 [6H, s, (CH3)2Si]; δC(75
MHz; CDCl3) 107.92 (dd, 1JC,P 230.8, 1JC,F 216.9, CHFP), 73.25
(d, 2JC,P 15.1, CH2OP), 63.77 (dd, 3JC,F 12.6 , 3JC,P 6.2, CH2O),
62.12 (CH2OSi), 25.78 (Me3CSi), 18.22 (SiCMe3), 16.40 (d, 3JC,P
5.5, CH3), Ϫ5.49 (Me2Si); δF(280 MHz; CDCl3; TFA) Ϫ141.76
(dd, 2JF, P 99.2, 2JF, H 58.6); m/z (CI) 345 (Mϩ ϩ 1).
1-(tert-Butyldimethylsiloxy)-2-[(diethoxyphosphoryl)methoxy]-
ethane 15
To a 100 mL single-necked round bottom flask equipped with a
magnetic stirrer were added 2-[(diethoxyphosphoryl)methoxy]-
ethanol 1321 (5.0 g, 23.6 mmol), anhydrous CH2Cl2 (40 mL),
tert-butyldimethylsilyl chloride (3.9 g, 25.9 mmol), triethyl-
amine (3.6 g, 35.4 mmol) and 4-dimethylaminopyridine (0.1 g,
0.8 mmol). The mixture was stirred under nitrogen at room
temperature for 16 h, after which time it was diluted with
CH2Cl2 (70 mL) and washed successively with 10% aqueous
K2CO3 (40 mL) and brine (40 mL). The organic layer was sep-
arated and dried over anhydrous Na2SO4. After concentration
under vacuum, 8 g of pale yellow oil was obtained. Purification
by column chromatography on silica gel (EtOAc) provided the
desired product 15 (6.4 g, 83% yield) as a colorless oil (Found:
C, 47.87; H, 9.29. Calc. for C13H31O5PSi: C, 47.83; H, 9.57%);
νmax/cmϪ1 3479, 2932, 2959, 1472, 1254, 1030, 963; δH(300 MHz;
CDCl3) 4.11 (4H, quintet, J 7.1, 2CH2OP), 3.81 (2H, d, J 8.2,
OCH2P), 3.72 (2H, t, J 4.8, CH2O), 3.59 (2H, t, J 5.0, CH2O),
1.28 (6H, t, J 7.1, 2CH3), 0.83 [9H, s, (CH3)3CSi], 0.00 [6H, s,
Compound 17 was separated and characterized as the
monofluoro dimer by-product. The yield of the dimer varied
from 5 to 30% depending on the reaction conditions. The dimer
17 was more polar than 16. Compound 17 was obtained as a
pale yellow oil (Found: C, 46.60; H, 8.90; F, 3.13. Calc. for
C24H55FO9P2Si2: C, 46.14; H, 8.87; F, 3.04%); νmax/cmϪ1 3499,
2932, 2859, 1640, 1474, 1258, 1101, 1026, 959, 835, 777; δH(300
MHz; CDCl3) 4.30–4.13 (10 H, m, CH2PO, 3CH2OP,
CH2OCF), 3.80 (6H, m, 3CH2O), 1.36 (9H, m, 3CH3), 0.88
(18H, 2s, 2Me3CSi), 0.05 (12 H, 2s, 2Me2Si); δC(75 MHz;
2
CDCl3) 115.85–97.66 (m, CFP), 75.11 (d, JC,P 7.6, CH2OP),
1
3
69.14 (m, CH2O), 66.44 (d, JC,P 110.8, CH2P), 64.92 (d, JC,P
2
2
6.7, CH2O), 64.30 (d, JC,P 7.1, CH2OP), 63.51 (d, JC,P 7.3,
CH2OP), 62.46 (CH2OSi), 61.96 (CH2OSi), 25.86 (Me3CSi),
25.76 (Me3CSi), 16.40 (d, 3JC,P 6.0, CH3), Ϫ5.37 (Me2Si), Ϫ5.45
2
(CH3)2Si]; δC(75 MHz; CDCl3) 74.68 (d, JC,P 11.3, CH2OP),
65.47 (d, 1JC,P 165.2, CH2P), 62.58 (CH2OSi), 62.30 (d, 3JC,P 6.6,
2
(Me2Si); δF(280 MHz; CDCl3; TFA) Ϫ135.59 (dd, JF, P 106.1,
3
2JF, P 85.3); δP(146 MHz; CDCl3; H3PO4) 34.21 (dd, JF, P 85.3, JP, P
61.2), 8.91 (dt, 2JP, F 99.9, 2JP, P 60.8); m/z (CI) 625(Mϩ ϩ 1).
CH2O), 25.80 [(CH3)3CSi], 18.30 [SiC(CH3)3], 16.40 (d, JC,P
5.7, CH3), Ϫ5.42 [(CH3)2Si]; m/z (EI) 311(Mϩ Ϫ CH3), 269
(Mϩ Ϫ C4H9).
Diethyl (2-hydroxyethoxy)fluoromethylphosphonate 18
1-(tert-Butyldimethylsiloxy)-2-[(diethoxyphosphoryl)fluoro-
methoxy]ethane 16
Into a 50 mL single-necked round bottom flask equipped with
a magnetic stirrer were placed the protected F-PME alcohol
16 (1.23 g, 3.58 mmol), ethanol (20 mL) and Dowex 50WX8
(Hϩ-form) ion exchange resin (3 g), which had been prewashed
thoroughly with ethanol. The mixture was stirred at room
temperature overnight and completion of the reaction was
determined by TLC analysis. The mixture was filtered, the resin
Anhydrous THF (20 mL) in a three-necked round bottom flask
equipped with a thermometer, a magnetic stirrer, and an addi-
tion funnel was cooled to Ϫ78 ЊC under nitrogen, to which a
solution of sec-BuLi (1.3 M in hexanes, 4.7 mL, 6.07 mmol)
was added. After the temperature had equilibrated to Ϫ78 ЊC, a
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988
3983

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washed with ethanol (3 × 30 mL), and the combined filtrates
were concentrated under vacuum. The residue was purified by
column chromatography on silica gel (CH2Cl2–MeOH, 9:1) to
afford the desired product 18 (0.35 g, 43% yield) as a colorless
oil (Found: C, 37.87; H, 7.42. Calc. for C7H16FO5P: C, 36.53; H,
7.01%); νmax/cmϪ1 3422, 2986, 2935, 1447, 1395, 1248, 1163,
solution was cooled to Ϫ78 ЊC and a solution of n-BuLi (5.6
mL, 2.5 M in hexane, 14.0 mmol) was then added. The reaction
mixture was stirred at Ϫ78 ЊC for 1.5 h and N-fluoro-N-(phenyl-
sulfonyl)benzenesulfonamide (4.7 g, 14.9 mmol) in anhydrous
THF (50 mL) was added dropwise. The resulting mixture was
stirred at Ϫ78 ЊC for 2.5 h and then gradually warmed to
Ϫ10 ЊC. The reaction mixture was then diluted with Et2O (100
mL). Saturated aqueous NH4Cl (2 × 80 mL) was added and the
organic layer was separated, washed with brine (80 mL), and
dried over anhydrous Na2SO4. The crude product (6 g),
obtained after concentration under vacuum, was purified by
column chromatography on silica gel (hexane–EtOAc, 7:3, 1 L;
hexane–EtOAc, 1:1, 1 L; EtOAc 500 mL) to afford the desired
product 23 (1.2 g, 29% yield) as a pale yellow oil (Found: C,
2
2
1024; δH(300 MHz; CDCl3) 5.59 (1H, dd, JF, H 57.0, JP, H 14.0,
CHF), 4.26 (4H, m, 2CH2OP), 3.89 (1H, s, OH), 3.83 (4H, m,
CH2OH and CH2O), 1.36 (6H, m, 2CH3); δC(75 MHz; CDCl3)
1
1
2
108.0 (dd JC,P 229.7, JC,F 213.4, CHF), 74.5 (d, JC,P 14.1,
CH2OP), 63.7 (dd, 3JC,F 37.3, 3JC,P 6.2, CH2O), 61.4 (CH2OH),
16.4 (d, 3JC,P 5.0, CH3); δF(280 MHz; CDCl3; TFA) Ϫ140.5 (dd,
2JF, P 99.8, 2JF, H 57.5); m/z (CI) 231 (Mϩ ϩ 1).
53.61; H, 8.22. Calc. for C21H38FO6PSi: 54.30; H, 8.24%); νmax
/
Diethyl á-[ethoxy(2-hydroxyethoxymethyl)phosphoryl]-á-
(2-hydroxyethoxy)fluoromethylphosphonate 19
cmϪ1 2955, 2932, 2859, 1472, 1391, 1258, 1165, 1100, 1026, 980,
837, 779; δH(300 MHz; CDCl3) 7.35–7.29 (5H, m, C6H5), 5.78
The dimer OH side chain 19 was prepared from the TBDMS
protected F-PME dimer 17 under conditions similar to those
used for the preparation of the fluorinated F-PME alcohol
18. After purification by column chromatography on silica gel
(CH2Cl2–MeOH, 9:1), compound 19 (53% yield) was obtained
as a colorless oil (Found: C, 36.74; H, 6.97; P, 14.46. Calc. for
C12H27FO9P2: C, 36.37; H, 6.87; P, 15.63%); νmax/cmϪ1 3414,
2986, 1651, 1445, 1370, 1252, 1163, 1024, 982; δH(300 MHz;
CDCl3) 4.32 (8H, m, 2CH2O, CH2OP, and CH2P), 3.76 (8H, 2t,
2CH2OP and 2CH2OH), 1.40 (9H, 2t, J 4.4, 3CH3); δC(75 MHz;
CDCl3) 111.79 (ddd, 1JC,P 251.5, 1JC,P 251.3, 1JC,F 112.7, CPFP),
2
2
(1H, dd, JF, H 58.5, JP, H 14.1, PCHF), 4.55 (2H, s, OCH2Ph),
4.20–4.26 (4H, m, POCH2), 4.03 (1H, m, 2-H), 3.82–3.62 (4H,
m, 1-H and 3-H), 1.30–1.37 (6H, m, CH3), 0.88 [9H, s,
(CH3)3Si], 0.06 (6H, s, 2CH3Si); δC(75 MHz; CDCl3) 138.10,
138.03, 128.46, 128.44, and 127.71 (aromatic), 109.04 (dd, 1JC,P
1
2
2
227.9, JC,F 217.0, CHFP), 106.0 (dd, JC,P 231.3, JC,F 219.0,
3
3
CHFP), 81.94 (d, JC,F 14.0, C-2), 81.73 (d, JC,F 14.0, C-2),
73.50 and 73.47 (2s, OCH2Ph), 69.51 (C-3), 63.75 (C-1), 63.18
(CH2OP), 62.76 (CH2OP), 25.68 [(CH3)3Si], 18.05 (CSi), 16.29
(d, J 5.1, CH3), Ϫ5.70 (CH3Si); δF(280 MHz; CDCl3; TFA)
Ϫ138.50 (dd, JF, P 100.7, JF, H 58.7), Ϫ138.86 (dd, JF, P 100.7,
2JF, H 58.7); m/z (ESI) 482.4 (Mϩ ϩ 1).
2
2
2
2
1
75.45 (d, JC,P 9.5, CH2OP), 69.65 (m, CH2OP), 66.10 (d, JC,P
3
3
113.4, CH2P), 65.20 (d, JC,P 6.6, CH2O), 64.58 (d, JC,P 6.8,
3
CH2O), 63.68 (d, JC,P 7.5, CH2O), 61.32 (CH2OH), 61.16
2-O-[(Diethoxyphosphoryl)fluoromethyl]-3-O-benzylglycerol 24
(CH2OH), 16.46 (CH3), 16.38 (CH3); δF(280 MHz; CDCl3;
2
2
To a 50 mL single-necked round bottom flask equipped with a
magnetic stirrer were added 1-O-(tert-butyldimethylsiloxy)-2-
O-[(diethoxyphosphoryl)fluoromethyl]-3-O-benzylglycerol 23
(1.1 g, 2.37 mmol), ethanol (20 mL), and Dowex 50WX8
(Hϩ-form) ion exchange resin (3 g). The mixture was stirred at
room temperature overnight and completion of the reaction
was determined by TLC analysis. The mixture was filtered, the
resin washed with ethanol (3 × 30 mL), and the combined fil-
trates were concentrated under vacuum. The residue was puri-
fied by column chromatography on silica gel (CH2Cl2–MeOH,
93:7) to provide the desired product 24 (0.6 g, 76% yield) as a
colorless oil (Found: C, 50.91; H, 7.12. Calc. for C15H24FO6P,
51.43; H, 6.91%); vmax/cmϪ1 3414, 2984, 2942, 1454, 1370,
1250, 1163, 1100, 1026, 982, 741, 700; δH (300 MHz; CDCl3)
TFA) Ϫ136.11 (dd, JF, P 100.8, JF, P 85.5; δP(146 MHz; CDCl3;
2
2
2
2
H3PO4) 34.0 (dd, JF, P 85.5, JP, P 62.3), 8.3 (dd, JF, P 100.0, JP, P
63.0); m/z (CI) 397 (Mϩ ϩ 1).
1-O-(tert-Butyldimethylsiloxy)-2-O-[(diethoxyphosphoryl)-
methyl]-3-O-benzylglycerol 22
To a 250 mL single-necked round bottom flask equipped with a
magnetic stirrer were added 2-O-[(diethoxyphosphoryl)methyl]-
3-O-benzylglycerol 2121 (4.0 g, 12.1 mmol), anhydrous CH2Cl2
(60 mL), tert-butyldimethylsilyl chloride (2.0 g, 12.3 mmol), tri-
ethylamine (1.8 g, 18.1 mmol) and 4-dimethylaminopyridine
(0.1 g, 0.8 mmol). The mixture was stirred under nitrogen at
room temperature for 16 h, after which it was diluted with
CH2Cl2 (100 mL) and washed successively with 10% aqueous
K2CO3 (80 mL) and brine (80 mL). The organic layer was dried
over anhydrous Na2SO4, filtered, and concentrated under
vacuum to yield 8 g of a pale yellow oil. Purification by column
chromatography on silica gel (EtOAc) provided the desired
product 22 (5.0 g, 93% yield) as a pale yellow oil (Found:
C, 56.33; H, 8.67. Calc. for C21H39O6PSi: 56.48; H, 8.80%);
νmax/cmϪ1 3474, 3032, 2955, 2930, 2859, 1497, 1472, 1391, 1254,
1100, 1028, 996, 837, 779, 738.8, 698; δH(300 MHz; CDCl3)
7.32–7.34 (5H, m, C6H5), 4.54 (2H, s, OCH2Ph), 4.15–4.18 (4H,
m, POCH2), 4.02 (2H, d, J 8.7, OCH2P), 3.56–3.71 (5H, m, 1-H,
2-H, and 3-H), 1.29–1.35 (6H, m, CH3), 0.88 [9H, s, (CH3)3Si],
0.05 (6H, s, 2CH3Si); δC(75 MHz; CDCl3) 138.27, 128.41, and
127.66 (aromatic C), 81.83 (d, 3JC,P 10.9, C-2), 73.37 (OCH2Ph),
70.09 (C-3), 64.56 (d, 1JC,P 166.0, OCH2P), 62.89 (C-1), 62.23(d,
2
2
7.31–7.33 (5H, m, C6H5), 5.75 (1/2H, dd, JF, H 57.9, JP, H 13.2,
PCHF), 5.72 (1/2H, dd, 2JF, H 55.4, 2JP, H 13.8, PCHF), 4.55 (2H,
s, OCH2Ph), 4.21–4.28 (4H, m, POCH2), 4.05 (1H, m, H-2),
3.74–3.66 (4H, m, 1-H and 3-H), 2.56 (2H, br s, OH), 1.30–1.39
(6H, m, 2CH3); δC(75 MHz; CDCl3) 137.84, 137.68, 128.53,
128.49, 127.92, 127.85, 127.73, and 127.70 (aromatic H), 107.66
1
1
3
(2dd, JC,P 254.5, JF, C 218.5, CHFP), 84.67 (d, JC,F13.1, C-2),
82.40 (d, 3JC,F 13.7, C-2), 73.60 and 73.51 (2s, OCH2Ph), 70.09
and 69.66 (C-3), 63.86 (C-1), 63.04 (CH2OP), 62.61 (CH2OP),
3
16.30 (d, JC,P 5.1, CH3); δF(280 MHz; CDCl3; TFA) Ϫ136.44
(dd, 2JF, P 103.9, 2JF, H 55.7), Ϫ137.86 (dd, 2JF, P 101.7, 2JF, H 59.4);
m/z (ESI) 351.3 (Mϩ ϩ 1).
1-O-(Methylsulfonyl)- 2-O-[(diethoxyphosphoryl)fluoromethyl]-
3-O-benzylglycerol 27
2JC,P 6.3, CH2OP), 25.71[(CH3)3Si], 18.07 (CSi), 16.32 (d, JC,P
3
5.1, CH3), Ϫ5.65 (CH3Si); m/z (ESI) 447.5 (Mϩ ϩ 1).
To a solution of 2-O-[(diethoxyphosphoryl)fluoromethyl]-3-O-
benzylglycerol 24 (130 mg, 0.37 mmol) and methanesulfonyl
chloride (50 mg, 0.43 mmol) in 5 mL of anhydrous CH2Cl2 was
added triethylamine (75 mg, 0.74 mmol) dropwise at 0 ЊC under
a nitrogen atmosphere. The resulting solution was stirred at
0 ЊC for 1 h, then gradually warmed to room temperature and
stirred overnight. Ice-water (10 mL) was added to the solution
and the aqueous layer was separated and extracted with CH2Cl2
(2 × 10 mL). The combined CH2Cl2 extracts were dried over
1-O-(tert-Butyldimethylsiloxy)-2-O-[(diethoxyphosphoryl)-
fluoromethyl]-3-O-benzylglycerol 23
To a 500 mL three-necked round bottom flask equipped with a
thermometer, a magnetic stirrer and an addition funnel were
added the TBDMS-protected glycerol derivative 22 (3.9 g, 8.74
mmol) and 250 mL of anhydrous THF under nitrogen. The
3984
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988

View Article Online
anhydrous sodium sulfate and filtered, and solvent was
removed under vacuum to afford 150 mg (94% yield) of desired
compound 27 as a pale yellow oil, which was used in the next
reaction without further purification; νmax/cmϪ1 2986, 2933,
2870, 1725, 1454, 1358, 1258, 1177, 1024, 974, 833, 745, 700;
δH(300 MHz; CDCl3) 7.30–7.35 (5H, m, C6H5), 5.68 and 5.61
(1H, 2dd, 2JF, H 57.8, 2JP, H 12.8, CHFP), 4.55 (2H, s, OCH2Ph),
4.32–4.50 (2H, m, 1-H), 4.16–4.28 (4H, m, CH2OP), 3.76–3.61
(3H, m, 2-H and 3-H), 3.06 (3H, s, OCH3), 1.39–1.31 (6H, m,
2CH3); m/z (ESI) 429.3 (Mϩ ϩ 1).
ether, mp 53–55 ЊC (Found: C, 39.01; H, 4.62; N, 14.90. Calc.
forC12H17ClFN4O4P:C,39.30;H,4.67;N,15.28%);λmax(MeOH)/
nm 264.5 (ε/dm3 molϪ1 cmϪ1 9,000); νmax(KBr)/cmϪ1 3451, 2986,
2932, 1595, 1501, 1404, 1335, 1254, 1148, 1024, 934; δH(300
MHz; CDCl3) 8.76 (1H, s, 2-H), 8.28 (1H, s, 8-H), 5.42 (1H, dd,
2JF, H 57.3, 2JP, H 12.9, CHFP), 4.60 (2H, m, CH2N), 4.19 (6H, m,
CH2O and 2CH2OP), 1.33 (6H, 2t, 2CH3); δC(75 MHz; CDCl3)
152.1 (C-6), 146.1 (C-2), 133.5 (C-4), 131.7 (C-8), 129 (C-5),
1
1
2
107.4 (dd, JC,P 234.9, JC,F 216.4, CHFP), 69.4 (d, JC,P 14.9,
3
3
CH2OP), 64.2 (d, JC,P 6.9, CH2O), 43.8 (CH2N), 16.3 (d, JC,P
2
5.7, CH3); δF(280 MHz; CDCl3; TFA) Ϫ143.5 (dd, JF, P 95.3,
Procedure A. General procedure for the coupling of fluorinated
alcohol side chains with purine bases under Mitsunobu
conditions—preparation of compounds 25a, 25b, 25c and 25e
2JF, H 58.2); m/z (CI) 367 (Mϩ ϩ 1), 347 (Mϩ Ϫ HF).
2-Amino-6-chloro-9-{2-[(diethoxyphosphoryl)fluoromethoxy]-
ethyl}purine 25c. The title compound was obtained from
2-amino-6-chloropurine and the alcohol 18 according to
procedure A (Ϫ30 ЊC) in 45% yield after purification by column
chromatography on silica gel (CH2Cl2–MeOH, 9:1). An
analytical sample was obtained by recrystallization from
CH2Cl2–hexane as a white solid, mp 103–105 ЊC (Found: C,
37.92; H, 4.80; N, 18.32. Calc. for C12H18ClFN5O4P: C, 37.76;
H, 4.75; N, 18.35%); λmax(MeOH)/nm 309.0 (ε/dm3 molϪ1 cmϪ1
8,250) and 246.5 (7,000); νmax(KBr)/cmϪ1 3399, 3341, 3225,
2996, 1651, 1615, 1566, 1532, 1474, 1418, 1354, 1242, 1157,
1051, 1015, 907; δH(300 MHz; DMSO-d6) 8.07 (1H, s, 8-H),
A mixture of a purine base (1 mol), diethyl (2-hydroxyethoxy)-
fluoromethylphosphonate 18 (1 mol) and triphenylphosphine
(1.5 mol) in anhydrous DMF was stirred at room temperature
for 30 min. The reaction mixture was then cooled to Ϫ5 to
Ϫ40 ЊC and a solution of diethyl azodicarboxylate (DEAD)
(2 mol) in anhydrous DMF was added dropwise at such a rate
as to maintain the reaction temperature at Ϫ5 to Ϫ40 ЊC. The
reaction mixture was stirred for 3 h and then allowed to warm
to room temperature and stirred overnight. Any unreacted pur-
ine base was removed by filtration and solvent was removed
under vacuum. The crude product was purified by column
chromatography on silica gel (CH2Cl2–MeOH) to afford the
desired products.
2
2
6.92 (2H, s, NH2), 5.81 (1H, dd, JF, H 57.1, JP, H 13.7, CHFP),
4.33 (2H, m, CH2N), 4.20 (2H, m, CH2O), 4.01 (4H, m,
1
CH2OP), 1.16 (6H, 2t, J 6.9, 2CH3); δC(75 MHz; DMSO-d6)
160 (C-6), 154.3 (C-2), 149.5 (C-4), 143.4 (C-8), 123.3 (C-5),
Procedure B. General procedure for the coupling of fluorinated
side chains with purine and pyrimidine bases under base-
catalyzed conditions—preparation of compounds 25g, 28a and
28b
1
1
3
107.3 (dd, JC,P 227.5, JC,F 211.7, CHFP), 69.1 (d, JC,P 5.4,
2
3
CH2O), 63.2 (d, JC,P 6.9, CH2OP), 42.6 (CH2N), 16.0 (d, JC,P
5.1, CH3); δF(280 MHz; DMSO-d6; TFA) Ϫ143.2 (dd, 2JF, P 97.5,
2JF, H 57.4); m/z (CI) 382 (Mϩ ϩ 1).
A mixture of 1-O-(methylsulfonyl)-2-[diethoxyphosphoryl)-
fluoromethoxy]ethane 26 or 1-O-(methylsulfonyl)-2-O-[(di-
ethoxyphosphoryl)fluoromethyl]-3-O-benzylglycerol 27 (1
mol), purine or pyrimidine base (1 mol), caesium carbonate (1.5
mol) and anhydrous DMF was stirred at 60–80 ЊC under a
nitrogen atmosphere for 5–7 h. The solvent was removed under
reduced pressure and the residue purified by column chrom-
atography on silica gel to afford the desired compounds.13b
2-Amino-6-benzyloxy-9-{2-[(diethoxyphosphoryl)fluoro-
methoxy]ethyl}purine 25e. The title compound was obtained
from 2-amino-6-benzyloxypurine22a,b and the alcohol 18
according to procedure A at Ϫ40 ЊC. The crude product was
purified by column chromatography on silica gel (CH2Cl2–
MeOH, 93:7) to afford the desired product 25e as a thick oil in
24% yield, which semi-solidified upon standing at room tem-
perature for a couple of days. An analytical sample was
obtained by triturating with hexane–EtOAc. λmax(MeOH)/nm
283.5 (ε/dm3 molϪ1 cmϪ1 11,370) and 247.0 (10,830); νmax(KBr)/
cmϪ1 3327, 3212, 2994, 1582, 1458, 1412, 1356, 1248, 1028, 982,
791, 700; δH(300 MHz; CDCl3) 7.70 (1H, s, 8-H), 7.49–7.33 (5H,
9-{2-[(Diethoxyphosphoryl)fluoromethoxy]ethyl}adenine 25a.
Compound 25a was prepared from adenine and the alcohol 18
according to procedure A (Ϫ5 ЊC) in 39% yield after purifi-
cation by column chromatography on silica gel (CH2Cl2–
MeOH, 9:1). An analytical sample was obtained by recrystal-
lizing twice from EtOAc to afford 25a as an off-white solid, mp
148–150 ЊC (Found: C, 41.88; H, 5.52; N, 19.75. Calc. for
C12H19FN5O4P: C, 41.51; H, 5.51; N, 20.14%); λmax(MeOH)/nm
260.0 (ε/dm3 molϪ1 cmϪ1 10,300); νmax(KBr)/cmϪ1 3356, 3283,
3129, 2978, 1715, 1678, 1605, 1422, 1366, 1256, 1024; δH(300
MHz; CDCl3 ) 8.35 (1H, s, 2-H), 7.94 (1H, s, 8-H), 5.80 (2H, s,
NH2), 5.41 (1H, dd, 2JF, H 58.2, 2JP, H 13.0, CHFP), 4.48 (2H, m,
CH2N), 4.15 (6H, m, CH2O and 2CH2OP), 1.30 (6H, 2t, 2CH3);
δC(75 MHz; CDCl3) 155.7 (C-6), 153.1 (C-2), 149.9 (C-4), 141.3
2
2
m, C6H5), 5.57 (1H, s, OCH2Ph), 5.41 (1H, dd, JF, H 57.8, JP, H
13.1, CHFP), 4.83 (2H, br s, NH2), 4.35–4.09 (8H, m, CH2N,
CH2O, and 2CH2OP), 1.33–1.29 (6H, m, 2CH3); δC(75 MHz;
CDCl3) 161.21, 159.31, 154.09, 140.50, 136.55, 129.01, 128.44,
1
1
128.33, 128.04, 128.02, 115.57, 107.58 (dd, JC,P 233.9, JC,F
2
216.1, CHF), 100.19, 97.42, 69.9 (d, JC,P 15.5, CH2OP), 64.0
(d, JC,P 6.9, CH2O), 43.26 (CH2N), 16.3 (d, JC,P 5.7, CH3);
m/z (ESI) 454.5 (Mϩ ϩ 1).
3
3
9-{2-[(Diethoxyphosphoryl)fluoromethoxy]ethyl}guanine 25f.
A suspension of 2-amino-6-benzyloxy-9-{2-[(diethoxyphos-
phoryl)fluoromethoxy]ethyl}purine 25e (200 mg, 0.442 mmol)
and palladium on activated carbon (10%, 20 mg) in 20 mL of
absolute ethanol was stirred overnight under a hydrogen
atmosphere at room temperature. The catalyst was removed by
filtration and the filtrate concentrated under vacuum to afford
120 mg of crude product as a sticky residue, which was purified
by column chromatography on silica gel (CH2Cl2–MeOH, 8:2)
to afford the desired compound 25f (50 mg, 37% yield) as a
white solid, mp 120 ЊC (decomp.); λmax(MeOH)/nm 270 (ε/dm3
molϪ1 cmϪ1 7,480) and 253.0 (10,880); νmax(KBr)/cmϪ1 3331,
3135, 2980, 2764, 1688, 1611, 1539, 1481, 1375, 1256, 1161,
1024, 980, 781, 693; δH(300 MHz; CD3OD) 7.74 (1H, s, 8-H),
1
1
(C-8), 119.5 (C-5), 107.5 (dd, JC,P 234.4, JC,F 216.2, CHFP),
2
3
70.0 (d, JC,P 15.5, POCH2), 64.0 (d, JC,P 6.3, CH2O), 43.3
3
(CH2N), 15.5 (d, JC,P 3.4, CH3); δF(280 MHz; CDCl3; TFA)
Ϫ143.0 (dd, JF, P 97.4, JF, H 58.7); m/z (CI) 348 (Mϩ ϩ 1), 328
2
2
(Mϩ Ϫ HF).
6-Chloro-9-{2-[(diethoxyphosphoryl)fluoromethoxy]ethyl}-
purine 25b. The title compound was synthesized from 6-
chloropurine and the alcohol 18 according to procedure A
(Ϫ10 ЊC) in 32% yield. The desired product 25b was obtained as
a thick oil after purification by column chromatography on
silica gel (CH2Cl2–MeOH, 95:5), which solidified upon stand-
ing at room temperature for a couple of days. An analytical
sample was obtained by triturating with hexane and diethyl
2
2
5.64 (1H, dd, JF, H 57.5, JP, H 13.7, CHFP), 4.36–4.25 (3H, m,
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988 3985

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1
1
CH2N and 1/2CH2O), 4.19–4.07 (5H, m, 1/2CH2O and
128.1, 128.1, 127.9, 107.21 (2dd, JC,P 251.4, JC,F 218.7,
2
3
2CH2OP), 1.30–1.23 (6H, m, 2CH3); δC(75 MHz; CD3OD)
CHFP), 80.4 (d, JC,P 14.9, POCH2), 78.8 (d, JC,P 14.3, C-2Ј),
73.8 (s, OCH2Ph), 69.7 (C-3Ј), 44.7 (C-1Ј), 16.3 (CH3); δF(280
1
164.69, 155.53, 154.09, 140.25, 140.09, 108.70 (dd, JC,P 231.6,
2
2
2
1JC,F 216.7, CHF), 70.98 (d, JC,P 16.1, CH2OP), 64.0 (d,
MHz; CDCl3; TFA) Ϫ138.04 (dd, JF, P 101.0, JF, H 57.5,
2 2
3
3JC,P 6.3, CH2O), 44.09 (CH2N), 16.62 (d, JC,P 5.7, CH3);
CHFP), Ϫ141.04 (dd, JF, P 97.6, JF, H 57.8, CHFP); m/z (ESI)
468.3 (Mϩ ϩ 1).
δF(280 MHz; CDCl3; TFA) Ϫ142.83 (dd, 2JF, P 99.8, 2JF, H 57.2);
m/z (ESI) 364.3 (Mϩ ϩ 1).
1-{3-Benzyloxy-2-[(diethoxyphosphoryl)fluoromethoxy]-
propyl}cytosine 28b. The title compound was prepared from
cytosine and 1-O-(methylsulfonyl)-2-O-[(diethoxyphosphoryl)-
fluoromethyl]-3-O-benzylglycerol 27 according to procedure B.
The reaction mixture was stirred at 70 ЊC under a nitrogen
atmosphere for 7 h. After purification by column chrom-
atography on silica gel (CH2Cl2–MeOH, 9:1), compound 28b
(41% yield) was obtained as an off-white solid, mp 50–55 ЊC
(soften), 130 ЊC (decomp.) (Found: C, 50.92; H, 6.34; N, 9.27.
1-{2-[(Diethoxyphosphoryl)fluoromethoxy]ethyl}cytosine 25g.
The title compound was obtained as an off-white solid from
cytosine and 1-O-(methylsulfonyl)-2-(diethoxyphosphoryl-
fluoromethoxy)ethane 26 according to procedure B in 26%
yield after purification by column chromatography on silica gel
(CH2Cl2–MeOH, 4:1). An analytical sample was obtained by
recrystallization from MeOH–CH2Cl2 (95:5), mp 164–166 ЊC
(decomp.) (Found: C, 40.55; H, 5.97; N, 12.87. Calc. for
C11H19FN3O5P: C, 40.87; H, 5.92; N, 13.00%); λmax(MeOH)/nm
272.5 (ε/dm3 molϪ1 cmϪ1 6,700) and 252.2 (4,800); νmax(KBr)/
cmϪ1 3343, 3153, 2990, 1659, 1618, 1510, 1487, 1391, 1250,
1163, 1028, 980, 791, 689; δH(300 MHz; CDCl3) 7.30 (1H, d,
Calc. for C19H27FN3O6P: 51.47; H, 6.14; N, 9.48%); λmax
-
(MeOH)/nm 272 (ε/dm3 molϪ1 cmϪ1 3,800) and 253.0 (2,800);
νmax(KBr)/cmϪ1 3349, 2920, 1653, 1491.1, 1389, 1248, 1157,
1024, 984, 789, 700; δH(300 MHz; CDCl3) 7.67 (1H, 2d, J 7.2,
6-H), 7.36–7.34 (5H, m, C6H5), 7.01 (2H, br s, NH2), 5.84 (1H,
2dd, 2JF, H 57.6, 2JP, H 13.2, PCHF), 5.64 (1H, 2d, J 7.2, 5-H), 4.52
(2H, s, OCH2Ph), 4.31 (1H, m, 2Ј-H), 4.14 (4H, m, POCH2),
3.76–3.51 (4H, m, 1Ј-H and 3Ј-H), 1.26–1.18 (6H, m, 2CH3);
δC(75 MHz; CDCl3) 166.1, 156.6, 156.4, 137.7, 137.6, 128.5,
2
J 7.2, 5-H), 5.62 (1H, d, J 7.2, 6-H), 5.34 (1H, dd, JF, H 58.1,
2JP, H 13.4, CHFP), 4.13 (4H, m, CH2O and CH2OP), 4.04 (2H,
m, CH2N), 1.27 (6H, 2t, 2CH3); δC(75 MHz; CDCl3) 166.14
1
1
(C-4), 156.44 (C-2), 147.01 (C-6), 107.73 (dd, JC,P 233.6, JC,F
2
217.0, CHFP), 93.86 (C-5), 70.32 (d, JC,P 15.5, CH2O), 64.02
(d, JC,P 6.3, CH2O), 49.84 (CH2N), 16.35 (d, JC,P 5.1, CH3);
δF(280 MHz; CDCl3; TFA) Ϫ141.9 (dd, JF, P 96.2, JH,F 59.2;
m/z (CI) 323 (Mϩ ϩ 1).
3
3
1
1
128.0, 127.9, 127.8, 105.4 (dd, JC,P 234.7, JC,F 219.9, CHFP),
1 1
2
2
105.4 (dd, JC,P 232.6, JC,F 219.2, CHFP), 93.6, 93.5, 80.5
2 2
(d, JC,P 14.9, CH2OP), 79.5 (d, JC,P 14.9, CH2OP), 73.6
(OCH2Ph), 70.3 (C-3), 63.6 (C-2), 51.5 and 51.0 (CH2N), 16.30
3
1-O-(Methylsulfonyl)-2-[(diethoxyphosphoryl)fluoromethoxy]-
ethanol 26. To a solution of the fluorinated alcohol 18 (550 mg,
2.18 mmol) and methanesulfonyl chloride (265 mg, 2.3 mmol)
in anhydrous CH2Cl2 (30 mL) was added dropwise triethyl-
amine (380 mg, 4.35 mmol) at 0 ЊC under a nitrogen
atmosphere. The resulting solution was stirred at 0 ЊC for 1 h,
then gradually warmed to room temperature and stirred for an
additional 3 h. Ice-water (30 mL) was added to the solution and
the aqueous layer was separated and extracted with CH2Cl2
(2 × 50 mL). The combined CH2Cl2 extracts were dried over
Na2SO4 and concentrated under vacuum. The residue was
purified by column chromatography on silica gel (CH2Cl2–
MeOH, 95:5) to provide the title compound 26 as a pale yellow
oil in quantitative yield (Found: C, 32.38; H, 6.12. Calc. for
C8H18FO7PS: C, 31.17; H, 5.89%); νmax/cmϪ1 2988, 2940, 1354,
1254, 1175, 1024, 976, 926, 797; δH(300 MHz; CDCl3) 5.49 (1H,
dd, 2JF, H 57.6, 2JP, H 12.9, CHFP), 4.45 (2H, t, J 5.1, CH2N), 4.25
(4H, m, CH2O and CH2OP), 3.09 (3H, s, CH3SO2), 1.37 (6H, t,
(d, JC,P 5.1, CH3); δF(280 MHz; CDCl3; TFA) Ϫ137.41 (dd,
2JF, P 100.7, 2JF, H 57.5, CHFP), Ϫ139.9 (dd, 2JF, P 100.9, 2JF, H 58.0,
CHFP); m/z (ESI) 444.3 (Mϩ ϩ 1).
9-[2-(Phosphonofluoromethoxy)ethyl]adenine 29
9-{2-[(Diethoxyphosphoryl)fluoromethoxy]ethyl}adenine 25a
(100 mg, 0.29 mmol) was dissolved in anhydrous CH2Cl2 (4 mL)
and cooled to Ϫ10 ЊC in an ice-water bath, to which was added
bromotrimethylsilane (0.4 mL, 2.9 mmol) dropwise while stir-
ring. The resulting mixture was stirred at Ϫ10 ЊC for 4.5 h and
then gradually warmed to ambient temperature and stirred
overnight. Solvent was removed under vacuum to afford a white
foam solid, which was dissolved in H2O (1 mL). Acetone (2 mL)
was added to the aqueous solution and the mixture was stirred
at ambient temperature for 15 min. A white precipitate formed
and was collected by filtration to afford 36 mg (43% yield) of
compound 1, mp 210 ЊC (decomp.); δH(300 MHz; DMSO-d6)
8.21 (1H, s, 2-H), 8.18 (1H, s, 8-H), 7.70 (2H, s, NH2), 5.51
(1H, dd, 2JF, H 57.6, 2JP, H 12.0, CHFP), 4.39 (2H, m, CH2N), 3.95
(2H, m, CH2O); δF(280 MHz; DMSO-d6; TFA) Ϫ143.75 (dd,
2JF, P 92.1, 2JF, H 58.2, CHFP).
1
1
J 6.6, CH3); δC(75 MHz; CDCl3) 107.6 (dd, JC,P 234.7, JC,F
216.4, CHFP), 69.5 (d, 2JC,P 16.1, CH2OP), 67.9 (s, CH2O), 64.2
3
3
(d, JC,P 6.9, CH2O), 37.7 (CH3SO2), 16.3 (d, JC,P 5.7, CH3);
2
2
δF(280 MHz; CDCl3; TFA) Ϫ143.03 (dd, JF, P 96.0, JF, C 57.7,
CHFP); m/z (CI) 309 (Mϩ ϩ 1), 289 (Mϩ Ϫ HF).
Procedure C. General procedure for the hydrolysis of diesters of
the fluorinated acyclic nucleoside phosphonates under basic
conditions—preparation of compounds 30a, 30d, 30f, 30g, 32a
and 32d
9-{3-Benzyloxy-2-[(diethoxyphosphoryl)fluoromethoxy]-
propyl}adenine 28a. The title compound was prepared from
adenine
and
2-(diethoxyphosphorylfluoromethoxy)-1-O-
(methylsulfonyl)ethanol 27 according to procedure B. The reac-
tion mixture was stirred at 70 ЊC under a nitrogen atmosphere
for 7 h. After purification by column chromatography on silica
gel (CH2Cl2–MeOH, 9:1), compound 28a (28% yield) was
obtained as a semi-solid; λmax(MeOH)/nm 259.5 (ε/dm3 molϪ1
cmϪ1 17,040); νmax(KBr)/cmϪ1 3331, 3198, 3003, 2868, 1651,
1599, 1478, 1418, 1300, 1250, 1154, 1024, 984, 799, 743, 700,
650; δH(300 MHz; CDCl3) 8.36 and 8.35 (1H, 2s, 2-H), 7.93 and
7.92 (1H, 2s, 8-H), 7.36–7.27 (5H, m, C6H5), 5.66 (1/2H, dd,
2JF, H 57.5, 2JP, H 13.1, PCHF), 5.62 (2H, br s, NH2), 5.39 (1/2H,
A suspension of a diester of fluorinated acyclic nucleoside
phosphonate in concentrated aqueous ammonia was stirred at
room temperature for 1–10 days. Solvent was removed under
vacuum at 30 ЊC to leave a crude product, which was further
purified to afford the desired product.
Ethyl ammonium [2-(adenin-9-yl)ethoxy]fluoromethylphos-
phonate 30a. Compound 30a was prepared from 9-{2-[(di-
ethoxyphosphoryl)fluoromethoxy]ethyl}adenine 25a according
to procedure C with a reaction time of 2 days. The crude prod-
uct was recrystallized from MeOH–CH2Cl2 to afford the
desired product 30a (55% yield) as a white solid, mp 180 ЊC
(decomp.) (Found: C, 35.15; H, 5.26; N, 23.43. Calc. for C10H18-
FN6O4P: C, 35.72; H, 5.40; N, 24.99%); λmax(MeOH)/nm 259.5
2
2
dd, JF, H 57.3, JP, H 12.8, PCHF), 4.52 (2H, s, OCH2Ph), 4.42
(2H, m, H-1Ј), 4.14 (4H, m, POCH2), 3.71–3.64 (2H, m, H-3Ј),
3.55–3.52 (1H, m, H-1Ј), 1.35–1.28 (6 H, m, 2CH3); δC(75 MHz;
CDCl3) 155.5, 153.2, 153.1, 142.0, 141.8, 137.5, 137.4, 128.6,
3986
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988

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3
(ε/dm3 molϪ1 cmϪ1 11,700); νmax(KBr)/cmϪ1 3351, 3187, 2988,
2890, 1669, 1615, 1499, 1419.7, 1333, 1202, 1146, 1050, 976,
790, 652; δH(300 MHz; DMSO-d6) 8.22 (1H, s, 2-H), 8.13 (1H,
(d, JC,P 5.7, CH3); δF(280 MHz; CD3OD; TFA) Ϫ142.2 (dd,
2JF, P 82.2, 2JH,F 58.8, CHFP); m/z (ϩve FAB) 294 (Mϩ Ϫ NH2);
ϩ
m/z (Ϫve FAB) 296 (MϪ Ϫ NH4 ).
2
2
s, 8-H), 7.27 (2H, s, NH2), 5.17 (1H, dd, JFH 57.9, JP, H
9.6, CHFP), 4.34 (2H, t, J 5.0, CH2N), 4.03 (2H, m, CH2O),
3.67 (2H, m, CH2OP), 1.00 (3H, t, J 7.1, CH3); δC(75 MHz;
DMSO-d6) 155.7(C-6), 152.0 (C-2), 149.3 (C-4), 141.5 (C-8),
Ethyl ammonium [2-(adenin-9-yl)ethoxy]methylphosphonate
32a. The title compound 32a was prepared from 9-[2-(di-
ethoxyphosphorylmethoxy)ethyl]adenine19 according to pro-
cedure C with a reaction time of 9 days. The crude product was
purified by trituration with CH2Cl2 to afford 32a (24% yield)
as a white solid, mp 220 ЊC (decomp.); λmax(MeOH)/nm 260.0
(ε/dm3 molϪ1 cmϪ1 13,980); νmax(KBr)/cmϪ1 3285, 3152, 2978,
2798, 2214, 1935, 1682, 1609, 1481, 1422, 1312, 1253, 1119,
1065, 935.5, 799, 714, 648; δH(300 MHz; DMSO-d6) 8.20 (1H, s,
2-H), 8.12 (1H, s, 8-H), 7.16 (2H, s, NH2), 4.29 (2H, t, J 5.0,
CH2N), 3.82 (2H, t, J 4.8, CH2O), 3.66 (2H, app. quintet, J 7.1,
CH2OP), 3.42 (2H, d, 2JP, H 8.1, CH2P), 1.02 (3H, t, J 7.2, CH3).
1
1
118.5 (C-5), 110.6 (dd, JC,P 228.6, JC,F 191.3, CHF), 68.2 (d,
2JC,P 12.6, CH2OP), 60.1 (d, 3JC,P 4.1, CH2O), 42.7 (CH2N), 16.9
2
(CH3); δF(280 MHz; DMSO-d6; TFA) Ϫ140.7 (dd, JF, P 80.7,
2JF, H 57.7; m/z (ϩve FAB) 320 (MϪ Ϫ NH2); m/z (Ϫve FAB) 318
ϩ
(M Ϫ NH4 ).
Ethyl ammonium [2-(2,6-diaminopurine-9-yl)ethoxy]fluoro-
methylphosphonate 30d. The title compound 30d was prepared
from
2-amino-6-chloro-9-{2-[(diethoxyphosphoryl)fluoro-
methoxy]ethyl}purine 25d according to procedure C with a
reaction time of 3 days. The crude product was triturated with
CH2Cl2 twice to afford compound 30d (87% yield) as an off-
white solid. An analytical sample was obtained by recrystalliz-
ation from MeOH, mp 230 ЊC (decomp.) (Found: C, 33.40; H,
4.96; N, 23.29. Calc. for C10H19FN7O4P: C, 34.19; H, 5.45; N,
27.92%); λmax(MeOH)/nm 280.5 (ε/dm3 molϪ1 cmϪ1 10,500) and
247.5 (9,600); νmax(KBr)/cmϪ1 3644, 3366, 3138, 1671, 1586,
1535, 1483, 1410, 1331, 1200, 1073, 965, 768; δH(300 MHz;
Ethyl ammonium [2-(2,6-diaminopurin-9-yl)ethoxy]methyl-
phosphonate 32d. The title compound 32d was prepared from
2-amino-6-chloro-9-[2-(diethoxyphosphorylmethoxy)ethyl]-
purine21 according to procedure C with a reaction time of 10
days. The crude product was triturated with CH2Cl2 twice to
afford 32d (25% yield) as an off-white solid, mp 190 ЊC
(decomp.); λmax(MeOH)/nm 281.0 (ε/dm3 molϪ1 cmϪ1 3,630)
and 254 (3,180); δH(300 MHz; DMSO-d6) 7.80 (1H, s, H-8),
7.01 (2H, br s, NH2), 6.14 (2H, br s, NH2), 4.14 (2H, t, J 4.8,
CH2N), 3.76 (4H, m, CH2P and CH2O), 1.08 (3H, t, J 6.9,
CH3).
2
2
acetic acid-d4) 8.11 (1H, s, 8-H), 5.72 (1H, dd, JF, H 59.1, JP, H
11.7, CHFP), 4.30 (4H, m, CH2N and CH2O), 4.13 (2H, app.
quartet, J 6.9, CH2OP), 1.27 (3H, t, J 6.9, CH3); δC(75 MHz;
acetic acid-d4) 160.0 (C-6), 154.5 (C-2), 152.5 (C-4), 137.0 (C-8),
1
1
116.0 (dd, JC,P 282.8, JC,F 188.6, CHFP), 113.0 (C-5), 69.9
(CH2OP), 63.6 (CH2O), 46.2 (CH2N), 16.9 (CH3); δF(280 MHz;
Acknowledgements
2
2
acetic acid-d4; TFA) Ϫ143.5 (dd, JF, P 86.4, JF, H 59.1, CHFP);
m/z (ϩve FAB) 335 (Mϩ Ϫ 18); m/z (Ϫve FAB) 333
(MϪ Ϫ NH2).
The authors wish to thank Dr Robert Buckheit of Southern
Research Institute for the in vitro XTT assay against HIV-1 and
acknowledge Dr Christopher K. H. Tseng of the National
Institute of Allergy and Infectious Diseases (NIAID) for
arranging the biological assays against other viruses, which
were performed by Dr Earl Kern of the University of Alabama
at Birmingham, Dr Robert Sidwell of Utah State University,
and Dr Brent Korba of Georgetown University. The work
described herein was supported in part by a Small Business
Innovation Research (SBIR) Grant (1 R43 AI 37349) from
NIAID/NIH, Bethesda, Maryland.
Ethyl ammonium [2-(guanin-9-yl)ethoxy]fluoromethylphos-
phonate 30f. The title compound 30f was prepared from
9-{2-[(diethoxyphosphoryl)fluoromethoxy]ethyl}guanine 25f
according to procedure C with a reaction time of 2 days. The
crude product was purified by recrystallization from CH2Cl2–
MeOH to afford compound 30f (52% yield) as a white solid, mp
190 ЊC (decomp.); λmax(MeOH)/nm 275 (ε/dm3 molϪ1 cmϪ1
4,990) and 253.5 (7,990); νmax(KBr)/cmϪ1 3381, 3138, 2998,
2360, 1684, 1586, 1476, 1366, 1220, 1046, 953; δH(300 MHz;
2
2
CD3OD) 7.85 (1H, s, 8-H), 5.33 (1H, dd, JF, H 58.4, JP, H 11.0,
CHFP), 4.33–4.30 (2H, m, CH2N), 4.08–4.03 (2H, m, CH2O),
3.93–3.86 (2H, m, CH2OP), 1.19–1.14 (3H, t, J 7.1, CH3); δC(75
MHz; CD3OD) 159.54, 155.46, 153.28, 140.67, 121.0, 115.18
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1
1
2
(dd, JC,P 231.3, JC,F 199.2, CHFP), 73.87 (d, JC,P 13.7,
3
CH2OP), 66.48 (d, JC,P 5.7, CH2O), 48.11 (CH2N), 20.75 (d,
3JC,P 5.7, CH3); δF(280 MHz; CD3OD; TFA) Ϫ143.62 (dd, 2JF, P
84.2, 2JF, H 58.0, CHFP).
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H. Dvorakova, Z. Hao, R. Snoeck, P. Herdedwijn, D. G. Johns and
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7 L. Naesens, J. Neyts, J. Balzarini, N. Bischofberger and E. De
Clercq, Nucleosides Nucleotides, 1995, 14, 767.
Ethyl ammonium [2-(cytosin-1-yl)ethoxy]fluoromethylphos-
phonate 30g. The title compound 30g was prepared from
1-{2-[(diethoxyphosphoryl)fluoromethoxy]ethyl}cytosine 25g
according to procedure C with a reaction time of 1 day. The
crude product was triturated with CH2Cl2 twice to afford com-
pound 30g (77% yield) as an off-white solid, mp 120 ЊC
(decomp.) (Found: C, 34.68; H, 5.81; N, 14.89. Calc. for
C9H18FN4O5P: C, 34.62; H, 5.81; N, 17.94%); λmax(MeOH)/nm
277.5 (ε/dm3 molϪ1 cmϪ1 10,700) and 249.5 (5,100); νmax(KBr)/
cmϪ1 3352, 3187, 3086, 2984, 1719, 1655, 1495, 1366, 1283,
1223, 1160, 1049, 955, 785; δH(300 MHz; CD3OD) 7.67 (1H, d,
2
J 7.2, 5-H), 5.79 (1H, d, J 7.2, 6-H), 5.25 (1H, dd, JF, H 58.4,
2JP, H 10.4, CHFP), 3.89 (4H, m, CH2O and CH2N), 3.80 (2H,
apparent quartet, J 7.2, CH2OP), 1.10 (3H, t, J 7.2, CH3); δC(75
MHz; CD3OD) 168.19 (C-4), 153.5 (C-2), 148.03 (C-6), 110.60
8 (a) K. C. Cundy, P. A. Barditch-Crovo, R. E. Walker, A. C. Collier,
D. Ebeling, J. Toole and H. S. Jaffe, Antimicrob. Agents Chemother.,
1995, 39, 2401; (b) S. E. G. Stein, M. J. M. Hitchock and J. F.
Milligan, International Antiviral News, 1996, 4, 171.
1
1
2
(dd, JC,P 229.6, JC,F 191.8, CHF), 92.96 (C-5), 67.91 (d, JC,P
12.5, CH2OP), 60.24 (d, 3JC,P 5.7, CH2O), 48.53 (CH2N), 16.86
J. Chem. Soc., Perkin Trans. 1, 1998, 3979–3988
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