Synthesis and anti-HIV-1 evaluation of phosphonates which mimic the 5′-monophosphate of 4′-branched 2′,3′-didehydro- 2′,3′-dideoxy nucleosides

Article abstract of DOI:10.1016/j.bmc.2010.08.037

Synthesis of the 4′-ethynyl and 4′-cyano phosphonates 8-11, which mimic the 5′-monophosphate of 4′-branched 2′,3′- didehydro-2′,3′-dideoxy nucleosides, was investigated by employing the 3′,4′-unsaturated nucleosides (13 and 28) as the starting material. T

Full text of DOI:10.1016/j.bmc.2010.08.037

Bioorganic & Medicinal Chemistry 18 (2010) 7186–7192
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Bioorganic & Medicinal Chemistry
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Synthesis and anti-HIV-1 evaluation of phosphonates which mimic
the 50-monophosphate of 40-branched 20,30-didehydro-20,30-dideoxy nucleosides
Yutaka Kubota a, , Nobuhide Ishizaki a, Kazuhiro Haraguchi a, Takayuki Hamasaki b, Masanori Baba b,
⇑
Hiromichi Tanaka a
a School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
b Division of Antiviral Chemotherapy, Center for Chronic Viral Diseases, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
a r t i c l e i n f o
a b s t r a c t
Synthesis of the 40-ethynyl and 40-cyano phosphonates 8–11, which mimic the 50-monophosphate of
40-branched 20,30-didehydro-20,30-dideoxy nucleosides, was investigated by employing the 30,40-unsatu-
rated nucleosides (13 and 28) as the starting material. The synthesis was initiated by the electrophilic
addition of NIS/(EtO)2P(O)CH2OH to these unsaturated nucleosides. After introduction of the 20,30-double
bond, the 40-hydroxylmethyl group of the resulting adducts was transformed into the ethynyl or cyano
group. While the 40-cyano phosphonates 9 and 11 were not sufficiently stable to be isolated, the 40-ethy-
nyl counterparts (8 and 10) were obtained as their mono-ammonium salts. The adenine derivative 8
showed almost comparable anti-HIV-1 activity to that of d4T.
Article history:
Received 26 July 2010
Revised 16 August 2010
Accepted 16 August 2010
Available online 21 August 2010
Keywords:
Nucleoside
Phosphonate
Anti-HIV activity
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
O
Me
1 R = H (d4T)
20,30-Didehydro-30-deoxythymidine (1: d4T) is a well known
anti-HIV drug (Fig. 1).1 Synthesis of d4T analogues2 has provided
a various types of compounds, including branched-sugar deriva-
tives.3–5 In the course of our studies on the reaction of epoxy-sugar
nucleosides with organoaluminum and organo-silicon reagents,6
the 40-branched d4T analogues were synthesized.7 Although the
40-methyl (2) and 40-vinyl (3) analogues were not inhibitory to pro-
liferation of HIV, the 40-ethynyl derivative (4, Ed4T) was found to
be more potent than d4T and much less toxic to various cells as
well as to mitochondrial DNA synthesis.8 Furthermore, its activity
improves in the presence of a major mutation, K103N, a clinically
significant mutation with decreased sensitivity to non-nucleoside
reverse transcriptase inhibitor resistant HIV.8 The 40-cyano ana-
logue (5) synthesized later by a different method9 was almost as
active as d4T.
NH
O
2 R = Me
N
HO
3 R = CH=CH2
O
(Ed4T)
4 R = C CH
5 R = C N
R
Figure 1. Structure of d4T (1) and its 40-carbon-substituted derivatives (2–5).
O
Base
HO
HO
P
O
O
6 Base = adenin-9-yl
7 Base = thymin-1-yl
On the other hand, synthesis and anti-HIV activity of the
phosphonates 6 and 7 have been reported (Fig. 2).10,11 These com-
pounds were designed as an isosteric and isoelectronic analogue of
the 50-monophosphate derived from the 20,30-didehydro-20,30-dide-
oxy nucleoside. The adenine derivative 6 was reported to show
anti-HIV-1 activity comparable to that of d4T (1).
Figure 2. Structure of the phosphonates 6 and 7.
8 Base = adenin-9-yl,
9 Base = adenin-9-yl,
R = C CH
R = C N
O
P
This situation motivated us to carry out synthesis of the phos-
phonates 8–11 (Fig. 3) having an ethynyl or cyano group at the
Base
HO
HO
O
O
10 Base = thymin-1-yl, R = C CH
11 Base = thymin-1-yl, R = C N
R
⇑
Corresponding author. Tel.: +81 3 3784 8187; fax: +81 3 3784 8252.
E-mail address: y-kubota@pharm.showa-u.ac.jp (Y. Kubota).
Figure 3. Structure of the 40-carbon-substituted phosphonates 6 and 7.
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.08.037

Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
7187
O
O
P
O
Base
Base
Base
EtO
P
CH2O
HO
CH2O
R2
TBSO
NIS and EtO
P
CH2OH
O
O
O
OEt
TBSO
OH
OEt
R1
R1
I
A R1 = OTBS or H
8-11 R2 = ethynyl or cyano
B
Scheme 1. Synthetic strategy for the 40-carbon-substituted phosphonates 8–11.
40-position, which is the subject of this paper. The anti-HIV-1 activ-
ity of these compounds is also described.12
Attempted oxidation of the 40-CH2OH of 22 with Dess–Martin
periodinane resulted in recovery of the starting material. When
22 was oxidized with IBX (2-iodoxybenzoic acid)15 in refluxing
CH3CN for 1.5 h, silica gel column chromatography of the reaction
mixture gave the desired aldehyde 23 containing the hemiacetal
24 (Scheme 5). This mixture was converted to the 40-ethynyl deriv-
ative 25 (57% yield from 22) by reaction with CH3C(O)(N2)-
2. Results and discussion
Our synthetic strategy for the phosphonates 8–11 is shown in
Scheme 1. The 30,40-unsaturated nucleoside A is expected to under-
go electrophilic addition upon reaction with N-iodosuccinimide
(NIS)/(EtO)2P(O)CH2OH to give the anti-adduct B. The 40-CH2OTBS
in B serves as a building block to construct the 40-substituent R2
(ethynyl or cyano group). Introduction of the 20,30-double bond
could be achieved by simple elimination of HI in the case of
R1 = H; in the case of R1 = OTBS several steps are envisioned includ-
ing deiodination at the 30-position, removal of the TBS group, sulf-
onylation of the 20-hydroxyl group, and finally elimination of a
sulfonyloxy group.
Synthesis of the adenine derivatives was first examined. It has al-
ready been reported from our laboratory that the 30,40-unsaturated
adenosine 12 undergoes electrophilic addition by reacting with
NIS/MeOH to give 14 in quantitative yield (Scheme 2).13 Just by
replacing the MeOH with (EtO)2P(O)CH2OH, the adduct 15 was
formed, but it was difficult to separate 15 from (EtO)2P(O)CH2OH
by chromatography. Therefore, the N6-pivaloyl derivative 1314 was
used for the above electrophilic addition to give the anti-adduct 16
in 82% yield as a single isomer. The depicted stereochemistry of 16
was confirmed by NOE experiment: H-8/PCH2O (1.3%). The stereo-
chemical outcome observed here is consistent with that reported
for electrophilic addition to the furanoid glycal of adenine.10
Radical reduction of 16 with Bu3SnH/AIBN in refluxing benzene
gave the 30-deoxy derivative 17 in 99% yield (Scheme 3). When 17
was subjected to desilylation with Bu4NF in THF, the spiro deriva-
tive 19 was obtained as the major product (33%) along with the de-
sired diol 18 (18%). The presence of AcOH in the above reaction
medium avoided the intramolecular nucleophilic attack of the
50-alkoxide to the phosphorus center, and led to the sole formation
of 18 (87%).
16
PO(OEt)2 in EtOH in the presence of K2CO3 at rt for 1 week. For
the preparation of the 40-cyano derivative 27, the mixture of 23
and 24 was first converted to the oxime 26 (53% from 22). When
26 was treated with CH3SO2Cl in pyridine, spontaneous elimina-
tion occurred to give 27 in 74% yield.
Synthesis of the thymine derivatives was next examined. When
the 30,40-unsaturated thymine nucleoside 2817 was reacted with
NIS/MeOH as a model experiment, the two anti-adducts 29 and
30 were formed in 91% and 5% yields, respectively (Scheme 6).
However, quite unexpectedly, reaction of 28 with NIS/(EtO)2P(O)-
CH2OH under the same conditions gave a complex mixture of prod-
ucts as evidenced by TLC. HPLC purification (CHCl3/MeOH = 50:1)
of the mixture enabled us to isolate the desired anti-adduct 31,
but the yield was only 21%. At the present time, structures of other
products are not known. The stereochemistry of 31 was confirmed
on the basis of NOE experiments: H-10/H-50 (1.2%) and H-6/PCH2O
(1.9%).
The aldehyde 34 (Fig. 4), a common precursor of the target com-
pounds 10 and 11, was prepared by the following series of reac-
tions: (1) DBN-treatment of 31 to give 32 (90%), (2) desilylation
of 32 to form 33 (91%), and (3) oxidation of the 40-CH2OH of 33
with IBX, the product of which was obtained as a mixture of 34
and the hemiacetal 35 as was seen in the case of 23 in Scheme 5.
Preparation of the 40-ethynyl derivative 36 (41% yield from 33)
was carried out using the same procedure as that for 25. The 40-cy-
ano derivative 38 was prepared in 95% yield by way of the oxime
37 (obtained in 74% yield from 33).
Finally, reaction of the 40-carbon-substituted phosphonates (25,
27, 36, and 38) prepared above with Me3SiBr was examined. The
adenine derivative of 40-ethynyl phosphonate (25) was reacted
with Me3SiBr in DMF at rt for 9.5 h. The reaction mixture was evap-
orated to dryness, treated with ammonium hydroxide, and then
washed with CH2Cl2, After reverse-phase column chromatography,
the desire 40-ethynyl phosphonate 8 was obtained as mono-ammo-
nium salt in 70% yield. Likewise, from the thymine derivative 36,
the 40-ethynyl phosphonate 10 was isolated as mono-ammonium
Regioselective O-silylation of 18 was carried out by reaction
with TBDPSCl in pyridine to give 20 in 65% yield (Scheme 4). To
introduce the 20,30-double bond, 20 was first reacted with triflic
anhydride (Tf2O) in pyridine (0 °C to rt, for 3 h). Subsequent addi-
tion of DBN to the reaction mixture (rt, for 22 h) gave 21 in 81%
yield. Desilylation of 21 with Bu4NF was carried out again in the
presence of AcOH to give 22 in 92% yield.
NHR1
N
NHR1
N
N
NIS
N
MeOH or
(EtO)2P(O)CH2OH
R2O
TBSO
TBSO
N
N
N
N
O
O
14 R1 = H, R2 = Me
15 R1 = H, R2 = CH2P(O)(OEt)2
16 R1 = C(O)CMe3, R2 = CH2P(O)(OEt)2
CH2Cl2
OTBS
I
OTBS
12 R1 = H
13 R1 = C(O)CMe3
Scheme 2. Electrophilic addition to 12 and 13 by using NIS and ROH.

7188
Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
NHPiv
NHPiv
N
N
N
N
N
O
O
P
Bu4NF
(AcOH)
EtO
EtO
TBSO
P
EtO
EtO
HO
N
O
O
N
N
Bu3SnH/AIBN
benzene
O
O
16
THF
18
OTBS
OH
17
Piv = pivaloyl
NHPiv
N
N
N
O
P
O
N
EtO
O
O
19
OH
Scheme 3. Preparation of the phosphonate 18 from 16.
NHPiv
NHPiv
N
N
N
N
N
O
O
EtO
EtO
TBDPSO
P
EtO
EtO
PgO
P
N
O
O
N
N
TBDPSCl
pyridine
O
O
1) Tf2O/pyridine
2) DBN
18
OH
21 Pg = TBDPS
22 Pg = H
20
Piv = pivaloyl
Scheme 4. Preparation of compound 22.
NHPiv
N
N
O
EtO
EtO
P
N
O
N
O
1) IBX/CH3CN
22
23 R = CHO
24 R = CH(OH)OMe
2) Column chromatography
(CH2Cl2/MeOH = 10/1)
R
O
P
O
OMe
OMe
H2NOH.HCl
pyridine
N2
K2CO3/EtOH
NH2
N
NH2
NH2
N
N
N
N
N
N
O
P
O
P
O
P
EtO
EtO
EtO
EtO
EtO
EtO
N
N
N
O
O
N
O
N
O
O
O
MsCl
pyridine
NC
HON
26
27
25
Scheme 5. Preparation of compounds 25 and 27.
salt in 75% yield. In contrast to these, the 40-cyano derivatives 27
and 38 were found to decompose during purification by column
chromatography eluted with H2O as well as during evaporation
of the solvent, liberating the respective nucleobase. Therefore, we
were unable to isolate 9 and 11.
6, 7, and 1 (d4T) taken from Ref. 10 are also included in this Table.
A similar trend was seen to the reported data, in that the adenine
derivative (8 or 6) is more potent than the thymine derivative
(10 or 7). It was rather discouraging that the potency of 8 was
not improved compared with that of 6, which lacks the 40-ethynyl
group. Also seen here is that the thymine derivative 10 synthesized
in this study is devoid of activity, whereas the reported phospho-
nate 7 shows some activity against HIV-1.
The anti-HIV-1 activity of the 40-ethynyl phosphonates of ade-
nine (8) and thymine (10) was evaluated by the published proce-
dures18 and the results are summarized in Table 1. The data for

Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
7189
O
O
O
Me
Me
O
Me
O
NIS
MeOH or
(EtO)2P(O)CH2OH
NH
O
NH
O
NH
O
N
N
N
RO
I
TBSO
MeO
TBSO
O
I
CH2Cl2
TBSO
28
30
29 R = Me
31 R = CH2P(O)(OEt)2
Scheme 6. Electrophilic addition to 28 by using NIS and ROH.
O
N
O
Me
O
34 R = CHO
Me
NH
NH
O
O
P
35 R= CH(OH)OMe
36 R = C CH
O
P
EtO
EtO
O
EtO
EtO
N
O
O
O
32 Pg = TBS
33 Pg = H
37 R= CH=NOH
38 R = C N
PgO
R
Figure 4. Structure of compounds 32–38.
Table 1
Anti-HIV-1 activity of compounds 1, 6, 7, 8, and 10 in MT-4 cells
Industries, Ltd). Thin later chromatography (TLC) was performed on
silica gel (pre-coated silica gel plate F254, Merck) or ODS (pre-coated
TLC plate RP-8 F254, Merck). High performance liquid chromatogra-
phy (HPLC) was carried out on a Shimadzu LC-6AD with a Shim-Pack
PREP-SIL (H) KIT column (2 ꢀ 25 cm).
a
b
Compd
IC50
(lM)
CC50 (lM)
8
1.69
>100
1.5
12.0
1.2
>100
>100
>600
>600
>600
10
6c
7c
4.2. Chemical synthesis
1 (d4T)c
a
4.2.1. 9-[2,5-Bis-O-tert-butyldimethylsilyl-3-deoxy-4-(diethoxy-
phosphinyl)methoxy-3-iodo-
nine (16)
To a CH2Cl2 (5.0 mL) solution containing 13 (100 mg, 0.267
mmol) and NIS (120 mg, 0.535 mmol) was added diethyl hydrox-
ymethylphosphonate (0.131 mL, 0.891 mmol) at rt. The reaction
mixture was stirred for 5 h, evaporated, and partitioned between
saturated aqueous Na2S2O3 and AcOEt. Column chromatography
(CH2Cl2/MeOH = 70:1) of the organic layer gave 16 (121 mg, 79%)
Inhibitory concentration required to achieve 50% protection
a-L
-lyxofuranosyl]-N6-pivaloylade-
of MT-4cells against the cytopathic effect of HIV-1.
b
Cytotoxic concentration required to reduce the viability of
mock-infected MT-4 cells by 50%.
c
Data were taken from Ref. 10.
3. Conclusion
We planned to synthesize the adenine and thymine phospho-
nates (8–11) bearing an ethynyl or cyano group at the 40-position.
The synthetic sequence employed involves the following three
characteristics. The first is face-selective electrophilic addition to
the 30,40-unsaturated nucleosides (13 and 28) by reaction with
NIS/(EtO)2P(O)CH2OH. The second is utilization of the 40-hydroxy-
methyl group of the resulting adduct to construct the ethynyl or
cyano group. The third is the fact that the starting material (13
and 28) can be prepared from naturally occurring nucleosides.
Due to the instability of the 40-cyano phosphonates (9 and 11),
only the 40-ethynyl phosphonates 8 and 10 were obtained in pure
form. Anti-HIV-1 evaluation of these compounds revealed that the
adenine derivative 8 has almost comparable anti-HIV-1 activity to
that of d4T (1).
as a pale yellow foam. UV (MeOH) kmax 272 nm (e 18 500), kmin
232 nm (
e
3 400); 1H NMR (CDCl3) d ꢁ0.31, ꢁ0.01, 0.12 and 0.17
(12H, each as s), 0.77 and 0.94 (18H, each as s), 1.38 and 1.41
(6H, each as t, J = 7.1 Hz), 1.41 (9H, s), 3.85 (1H, t, J = 12.1 Hz),
3.94 (1H, t, J = 12.1 Hz), 4.02 (1H, d, J = 11.8 Hz), 4.16–4.32 (4H,
m), 4.19 (1H, d, J = 11.8 Hz), 4.53 (1H, dd, J = 5.3 and 6.5 Hz), 4.63
(1H, d, J = 5.3 Hz), 6.34 (1H, d, J = 6.5 Hz), 8.63 (1H, br), 8.80 (1H,
s), 8.82 (1H, s); 13C NMR (CDCl3) d ꢁ5.51, ꢁ5.24, ꢁ5.15, ꢁ4.99,
16.42, 16.44, 16.46, 16.50, 17.82, 18.10, 25.43, 25.73, 27.33,
37.87, 40.60, 56.62, 58.34, 62.50, 62.56, 62.96, 63.02, 64.21,
75.21, 87.39, 109.74, 109.88, 122.12, 141.77, 149.65, 152.02,
153.14, 175.72; FAB-MS (m/z) 856 (M++H). Anal. Calcd for C32H59I-
N5O8PSi2: C, 44.91; H, 6.95; N, 8.18. Found: C, 44.61; H, 6.81; N,
7.99.
4. Experimental section
4.1. General methods
4.2.2. 9-[2,5-Bis-O-tert-butyldimethylsilyl-3-deoxy-4-
(diethoxyphosphinyl)methoxy-
pivaloyladenine (17)
a-L
-lyxofuranosyl]-N6-
To
a benzene (5.0 mL) solution containing 16 (100 mg,
NMR spectra were recorded eitherat 400 MHz (JNM-GX400) or at
500 MHz (JNM-LA500). Chemical shifts are reported relative to
Me4Si. Mass spectra (MS) were taken in FAB mode with m-nitroben-
zyl alcohol as a matrix on a JNS-SX 102A. UV spectra were measured
on a JASCO Ubest-55 spectrophotometer. Column chromatography
was carried out on silica gel (Micro Bead Silica Gel PSQ 100B, Fuji
Silysia Chemical Ltd) or ODS (WakosilÒ 40C 18, Wako Pure Chemical
0.13 mmol) and AIBN (31.8 mg, 0.19 mmol) was added Bu3SnH
(0.10 mL, 0.39 mmol). The mixture was stirred under reflux for
1.5 h. Column chromatography (CH2Cl2/MeOH = 80:1) of the reac-
tion mixture gave 17 (90 mg, 99%) as a pale yellow foam. UV
(MeOH) kmax 272 nm (
(CDCl3) d ꢁ0.11, 0.03, 0.09 and 0.10 (12H, each as s), 0.81 and
e 16,800), kmin 232 nm (e
3200); 1H NMR

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Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
0.92 (18H, each as s), 1.34 and 1.36 (6H, each as t, J = 7.1 Hz), 1.39
(9H, s), 2.36 (1H, dd, J = 3.9 and 13.9 Hz), 2.40 (1H, dd, J = 5.9 and
13.9 Hz), 3.75 (1H, d, J = 11.1 Hz), 3.83 (1H, d, J = 11.1 Hz), 3.96
(1H, dd, J = 11.8 Hz), 4.12–4.24 (4H, m), 4.88 (1H, dt, J = 3.9 and
5.9 Hz), 6.10 (1H, d, J = 3.9 Hz), 8.50 (1H, s), 8.62 (1H, br s), 8.74
(1H, s); 13C NMR (CDCl3) d ꢁ5.12, ꢁ5.06, ꢁ4.78, ꢁ4.74, 16.73,
16.79, 18.12, 18.46, 25.89, 26.06, 27.71, 40.90, 41.05, 56.22,
57.93, 62.77, 63.02, 63.09, 64.15, 75.96, 91.51, 111.16, 111.30,
123.09, 142.32, 149.84, 151.64, 153.08, 175.98; FAB-MS (m/z)
730 (M++H). Anal. Calcd for C32H60N5O8PSi2: C, 52.65; H, 8.28; N,
9.59. Found: C, 52.46; H, 8.37; N, 9.62.
7.1 and 7.5 Hz), 6.09 (1H, d, J = 4.6 Hz), 7.39–7.47 (6H, m), 7.48–
7.71 (4H, m), 8.41 (1H, s), 8.64 (1H, s); 13C NMR (CDCl3) d 16.31,
16.37, 16.43, 19.23, 26.79, 27.32, 40.29, 40.57, 55.78, 57.49,
62.35, 62.41, 62.78, 62.85, 64.26, 74.77, 77.32, 91.10, 110.42,
110.56, 121.88, 127.89, 127.91, 130.06, 132.39, 132.49, 135.56,
135.59, 141.65, 148.93, 150.96, 152.48, 175.78; FAB-MS (m/z)
740 (M++H). Anal. Calcd for C36H50N5O8PSi: C, 58.44; H, 6.81; N,
9.46. Found: C, 58.17; H, 6.81; N, 9.41.
4.2.6. (2S,5R)-9-[2-tert-Butyldiphenylsilyl-2-(diethoxyphosphi-
nyl)methoxy-2,5-(dihydro)furan-5-yl]-N6-pivaloyladenine (21)
To a pyridine (15 mL) solution of 20 (300 mg, 0.405 mmol) was
added trifluoromethanesulfonic anhydride (0.08 mL, 0.486 mmol)
at 0 °C under Ar atmosphere. After stirring this mixture at rt for
3 h, DBN (0.1 mL, 0.810 mmol) was added. The resulting reaction
mixture was stirred at rt for 22 h and partitioned between
AcOEt/saturated aqueous NaHCO3. Column chromatography
(CH2Cl2/MeOH = 60:1) of the organic layer gave 21 (237 mg, 81%)
4.2.3. 9-[3-Deoxy-4-(diethoxyphosphinyl)methoxy-a-L-lyxofura-
nosyl]-N6-pivaloyladenine (18)
To a mixture of 17 (459 mg, 0.629 mmol) and AcOH (0.08 mL,
1.57 mmol) in THF (8.0 mL) was added Bu4NF (1 M THF solution,
1.57 mL, 1.57 mmol). The reaction mixture was stirred at rt for
24 h, evaporated to dryness, and subjected to silica gel column chro-
matography (CH2Cl2/MeOH = 20:1). This gave 18 (305 mg, 97%) as a
as colorless foam. UV (MeOH) kmax 272 nm (
e 19,400), kmin
colorless foam. UV (MeOH) kmax 272 nm (
e
16,500), kmin 232 nm (
e
235 nm (
e
7000); 1H NMR (CDCl3) d 1.08 (9H, s), 1.24 and 1.27
3100); 1H NMR (CDCl3) d 1.32 and 1.33 (6H, each as t, J = 7.1 Hz),
1.41 (9H, s), 2.47 (1H, dd, J = 7.7 and 13.7 Hz), 2.72 (1H, dd, J = 7.1
and 13.7 Hz), 3.54 (1H, dd, J = 8.3 and 14.4 Hz), 3.67 (1H, d,
J = 12.9 Hz), 3.94 (1H, dd, J = 8.9 and 14.4 Hz), 3.96 (1H, d,
J = 12.9 Hz), 4.09–4.21 (4H, m), 5.05 (1H, ddd, J = 4.4, 7.1 and
7.7 Hz), 6.09 (1H, d, J = 4.4 Hz), 8.24 (1H, s), 8.47 (1H, br s), 8.67
(1H, s); 13C NMR (CDCl3) d 16.32, 16.35, 16.37, 16.41, 27.27, 40.49,
41.19, 55.93, 57.64, 62.77, 62.84, 63.25, 63.32, 74.79, 91.64,
111.68, 111.77, 122.44, 141.24, 149.23, 151.17, 152.40, 175.97;
FAB-MS (m/z) 502 (M++H). Anal. Calcd for C20H32N5O8Pꢂ1/2H2O: C,
47.08; H, 6.52; N, 13.73. Found: C, 46.90; H, 6.42; N, 13.51.
(6H, each as t, J = 7.1 Hz), 1.41 (9H, s), 3.67 (1H, dd, J = 10.1 and
13.2 Hz), 3.77 (1H, dd, J = 11.3 and 13.2 Hz), 3.86 (1H, d,
J = 10.9 Hz), 3.93 (1H, d, J = 10.9 Hz), 4.00–4.13 (4H, m), 6.34 (1H,
dd, J = 1.8 and 5.9 Hz), 6.49 (1H, dd, J = 1.3 and 5.9 Hz), 6.97 (1H,
dd, J = 1.3 and 1.8 Hz), 7.38–7.48 (6H, m), 7.65–7.70 (4H, m), 8.13
(1H, s), 8.52 (1H, br s), 8.78 (1H, s); 13C NMR (CDCl3) d 16.33,
16.39, 19.21, 26.80, 27.39, 40.50, 56.51, 58.21, 62.35, 62.41,
62.65, 65.71, 65.75, 86.50, 115.20, 115.33, 122.78, 127.83, 129.94,
130.00, 130.31, 132.69, 132.74, 134.09, 135.55, 135.60, 141.08,
149.62, 151.52, 153.03, 175.66; FAB-MS (m/z) 722 (M++H). Anal.
Calcd for C36H48N5O7PSiꢂ1/5H2O: C, 59.60; H, 6.72; N, 9.65. Found:
C, 59.48; H, 6.67; N, 9.65.
4.2.4. Desilylation of 17 with Bu4NF in the absence of AcOH:
formation of the spiro derivative (19)
4.2.7. (2S,5R)-9-[2-(Diethoxyphosphinyl)methoxy-2,5-dihydro-
2-(hydroxymethyl)furan-5-yl]-N6-pivaloyladenine (22)
A mixture of 17 (100 mg, 0.137 mmol) and Bu4NF (1 M THF
solution, 0.343 mL, 0.343 mmol) in THF (5.0 mL) was stirred at rt
for 5 h. The reaction mixture was evaporated to dryness and the
residue was partially purified by silica gel column chromatography
(CH2Cl2/MeOH = 20:1). HPLC separation (CHCl3/MeOH = 10:1) of
the resulting crude products gave analytically pure 19 (21 mg,
33%, tR = 8.3 min, foam) and 18 (12 mg, 18%, tR = 9.8 min, foam).
Physical data for 19: 1H NMR (CDCl3) d 1.40 (6H, t, J = 8.4 Hz),
1.41 (9H, s), 2.18 (1H, dd, J = 7.1 and 13.4 Hz), 2.57 (1H, dd,
J = 6.8 and 13.4 Hz), 3.88 (1H, dd, J = 12.0 and 14.6 Hz), 4.13 (1H,
dd, J = 1.0 and 14.9 Hz), 4.20 and 4.24 (4H, each as dq, J = 7.1 and
8.4 Hz), 4.38 (1H, dd, J = 12.0 and 16.5 Hz), 5.00 (1H, dd, J = 2.9
and 14.9 Hz), 5.13 (1H, ddd, J = 4.4, 6.8 and 7.1 Hz), 5.54 (1H, s),
6.21 (1H, d, J = 4.4 Hz), 8.12 (1H, s), 8.51 (1H, s); 13C NMR (CDCl3)
d 16.37, 16.42, 27.30, 40.18, 40.50, 56.69, 58.12, 62.47, 62.54,
73.71, 73.79, 74.09, 91.61, 104.37, 104.41, 122.38, 140.79, 149.13,
151.02, 152.44, 175.97; FAB-HRMS (m/z) Calcd for C18H27N5O7P:
456.1648, found: 456.1637 (M++H).
To a THF (15 mL) solution containing 21 (1.26 g, 1.75 mmol)
and acetic acid (0.112 mL, 2.09 mmol) was added Bu4NF (1 M
THF solution, 2.09 mL, 2.09 mmol). The mixture was stirred at rt
for 10 h and evaporated to dryness. Silica gel column chromatogra-
phy (CH2Cl2/MeOH = 20:1) of the residue gave 22 (785 mg, 93%) as
a colorless foam. UV (MeOH) kmax 272 nm (
e 17,900), kmin 236 nm
(e
5600); 1H NMR (CDCl3) d 1.28 and1.34 (6H, each as t, J = 7.1 Hz),
1.41 (9H, s), 3.60 (1H, dd, J = 8.8 and 12.6 Hz), 3.66 (1H, dd, J = 8.5
and 14.3 Hz), 3.84 (1H, dd, J = 8.8 and 14.3 Hz), 4.01 (1H, dd, J = 5.7
and 12.6 Hz), 4.06–4.22 (4H, m), 4.54 (1H, dd, J = 5.7 and 8.8 Hz),
6.40 (1H, dd, J = 1.5 and 5.9 Hz), 6.56 (1H, dd, J = 1.7 and 5.9 Hz),
7.06 (1H, dd, J = 1.5 and 1.7 Hz), 8.16 (1H, s), 8.54 (1H, br), 8.76
(1H, s); 13C NMR (CDCl3) d 16.28, 16.33, 16.39, 27.32, 40.39,
56.44, 58.14, 62.68, 62.75, 63.10, 63.16, 86.11, 114.71, 114.79,
122.81, 128.64, 134.96, 140.98, 149.57, 151.62, 152.91, 175.73;
FAB-MS (m/z) 484 (M++H). Anal. Calcd for C20H30N5O7Pꢂ1/2H2O:
C, 48.77; H, 6.34; N, 14.22. Found: C, 48.64; H, 6.24; N, 14.06.
4.2.5. 9-[5-O-tert-Butyldiphenylsilyl-3-deoxy-4-(diethoxyphos-
4.2.8. Oxidation of 22: formation of 23 and its hemiacetal 24
A CH3CN (5.0 mL) solution containing 22 (100 mg, 0.206 mmol)
and 2-iodoxybenzoic acid (70 mg, 1.20 mmol) was stirred at
refluxing temperature for 1.5 h. The reaction mixture was filtered
through a Celite pad and the filtrate was evaporated to dryness. Sil-
ica gel column chromatography (CH2Cl2/MeOH = 10:1) of the resi-
due gave a mixture (84 mg) of 23 and the hemiacetal 24 as a pale
yellow foam.
phinyl)methoxy-a-L
-lyxofuranosyl]-N6-pivaloyladenine (20)
To a solution of 18 (298 mg, 0.595 mmol) in pyridine (8.0 mL)
was added tert-butyldiphenylsilyl chloride (0.61 mL, 2.38 mmol).
The mixture was stirred at rt for 4 days, and partitioned between
AcOEt/saturated aqueous NaHCO3. Silica gel column chromatogra-
phy (CH2Cl2/MeOH = 40:1) of the organic layer gave 20 (288 mg,
65%) as a foam. UV (MeOH) kmax 272 nm (
e 18,700), kmin 236 nm
(e
6100); 1H NMR (CDCl3) d 1.11 (9H, s), 1.24 and 1.26 (6H, each
as t, J = 7.1 Hz), 1.41 (9H, s), 2.58 (1H, dd, J = 7.5 and 13.8 Hz),
2.69 (1H, dd, J = 7.1 and 13.8 Hz), 3.67 (1H, dd, J = 10.3 and
12.7 Hz), 3.78 (1H, dd, J = 12.6 and 12.7 Hz), 3.80 and 3.83 (2H,
each as d, J = 11.1 Hz), 4.00–4.13 (4H, m), 4.95 (1H, ddd, J = 4.6,
4.2.9. (2S,5R)-9-[2-(Diethoxyphosphinyl)methoxy-2-ethynyl-
2,5-(dihydro)furan-5-yl]adenine (25)
To an EtOH (10 mL) solution containing a mixture of 23 and 24,
prepared from IBX-oxidation of 22 (100 mg, 0.206 mmol), were

Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
7191
added dimethyl 1-diazo(2-oxopropyl)phosphonate (100 mg,
0.521 mmol) and K2CO3 (84 mg, 0.609 mmol). The reaction mix-
ture was stirred at rt for 1 week and partitioned between CH2Cl2
and saturated aqueous NaHCO3. Silica gel column chromatography
(CH2Cl2/MeOH = 20:1) of the organic layer gave 25 (45 mg, 57%) as
265 nm (
e
10,300), kmin 233 nm (
e
2400); 1H NMR (CDCl3) d 0.02
and 0.14 (6H, each as s), 0.92 (9H, s), 1.33 and 1.35 (6H, each as
t, J = 6.9 Hz), 2.05 (3H, s), 2.60 (1H, dd, J = 5.7 and 14.5 Hz), 3.02
(1H, ddd, J = 5.9, 8.9 and 14.5 Hz), 3.77 (1H, t, J = 12.0 Hz), 3.89
(1H, t, J = 12.0 Hz), 4.06 (2H, s), 4.16 and 4.18 (4H, each as dq,
J = 6.9 and 14.6 Hz), 4.53 (1H, d, J = 5.9 Hz), 6.79 (1H, dd, J = 5.7
and 8.9 Hz), 7.64 (1H, s), 8.88 (1H, br); 13C NMR (CDCl3) d ꢁ5.56,
ꢁ5.32, 11.79, 16.43, 16.49, 18.05, 24.86, 25.71, 41.15, 56.39,
58.11, 62.35, 62.40, 62.96, 63.02, 63.79, 85.42, 109.88, 110.03,
113.06, 135.82, 150.72, 163.54; FAB-MS (m/z) 633 (M++H). Anal.
Calcd for C21H38IN2O8PSi: C, 39.88; H, 4.43; N, 6.06. Found: C,
39.93; H, 4.58; N, 6.04.
a pale yellow foam. UV (MeOH) kmax 260 nm (
e 14,700), kmin
226 nm (
e
2000); 1H NMR (CDCl3) d 1.30 and 1.34 (6H, each as t,
J = 7.1 Hz), 2.86 (1H, s), 3.92 (1H, dd, J = 10.8 and 13.1 Hz), 4.08–
4.20 (5H, m), 6.07 (2H, br), 6.32 (1H, dd, J = 1.5 and 5.6 Hz), 6.42
(1H, dd, J = 1.6 and 5.6 Hz), 7.16 (1H, dd, J = 1.5 and 1.6 Hz), 8.00
(1H, s), 8.37 (1H, s); 13C NMR (CDCl3) d 16.33, 16.39, 57.56,
59.28, 62.56, 62.62, 62.69, 62.75, 76.29, 76.69, 86.31, 105.43,
105.59, 119.19, 129.81, 133.72, 138.75, 149.41, 153.49, 155.86;
FAB-MS (m/z) 394 (M++H). Anal. Calcd for C16H20N5O5Pꢂ1/2H2O:
C, 47.77; H, 5.26; N, 17.40. Found: C, 48.02; H, 5.15; N, 17.07.
4.2.13. (2S,5R)-1-[2-(tert-Butyldimethylsiloxy)methyl-2-
(diethoxyphosphinyl)methoxy-2,5-(dihydro)furan-5-
yl]thymine (32)
4.2.10. (2R,5R)-9-[2-(Diethoxyphosphinyl)methoxy-2,5-
An CH3CN (10 mL) solution containing 31 (250 mg, 0.40 mmol)
and DBN (0.24 mL, 1.98 mmol) was stirred for 1.5 h at refluxing
temperature. The reaction mixture was partitioned between AcOEt
and saturated aqueous NH4Cl. Silica gel column chromatography
(CH2Cl2/MeOH = 50:1) of the organic layer gave 32 (182 mg, 90%)
dihydro-2-(hydroxyiminomethyl)furan-5-yl]adenine (26)
To a pyridine (5.0 mL) solution containing a mixture of 23 and
24, prepared from IBX-oxidation of 22 (100 mg, 0.206 mmol),
was added hydroxylamine hydrochloride (104 mg, 1.65 mmol).
The reaction mixture was stirred at 60 °C for 4 h and partitioned
between CH2Cl2 and saturated aqueous NaHCO3. Silica gel column
chromatography (CH2Cl2/MeOH = 10:1) of the organic layer gave
as a pale yellow foam. UV (MeOH) kmax 264 nm (
e 9300), kmin
234 nm (
e
2300); 1H NMR (CDCl3) d 0.02 and 0.03 (6H, each as s),
0.84 (9H, s), 1.28 and 1.29 (6H, each as t, J = 6.9 Hz), 1.89 (3H, d,
J = 1.2 Hz), 3.62 (1H, d, J = 11.0 Hz), 3.75–3.85 (2H, m), 3.87 (1H,
d, J = 11.0 Hz), 4.09 and 4.11 (4H, each as q, J = 6.9 Hz), 6.07 (1H,
dd, J = 1.5 and 5.8 Hz), 6.25 (1H, dd, J = 1.9 and 5.8 Hz), 6.83 (1H,
dd, J = 1.5 and 1.9 Hz), 7.16 (1H, d, J = 1.2 Hz), 9.67 (1H, br); 13C
NMR (CDCl3) d ꢁ5.65, ꢁ5.63, 12.26, 16.28, 16.34, 16.39, 18.05,
25.62, 56.29, 58.00, 62.34, 62.40, 62.64, 62.70, 64.18, 87.88,
111.73, 113.65, 113.78, 130.05, 134.10, 135.50, 150.73, 163.94;
FAB-MS (m/z) 505 (M++H). Anal. Calcd for C21H37N2O8PSi: C,
49.99; H, 5.55; N, 7.39. Found: C, 49.75; H, 5.69; N, 7.39.
26 (45 mg, 53%) as colorless foam. UV (MeOH) kmax 260 nm (
e
14,800), kmin 228 nm (
e
3200); 1H NMR (CD3OD) d 1.23 and 1.24
(6H, each as t, J = 7.1 Hz), 3.82 (1H, dd, J = 10.7 and 13.4 Hz), 3.89
(1H, dd, J = 10.5 and 13.4 Hz), 3.99–4.09 (4H, m), 6.53 (1H, dd,
J = 1.8 and 5.9 Hz), 6.63 (1H, dd, J = 1.5 and 5.9 Hz), 6.96 (1H, dd,
J = 1.5 and 1.8 Hz), 7.53 (1H, s), 8.20 (1H, s), 8.22 (1H, s); 13C
NMR (CD3OD) d 16.61, 16.63, 16.67, 16.69, 57.18, 58.87, 64.18,
64.25, 64.27, 64.34, 87.97, 112.97, 113.12, 120.21, 131.36, 134.39,
140.94, 147.92, 150.60, 154.26, 157.48; FAB-MS (m/z) 413
(M++H). Anal. Calcd for C15H21N6O6Pꢂ1/5H2O: C, 43.31; H, 5.14; N,
20.20. Found: C, 43.25; H, 5.14; N, 19.92.
4.2.14. (2S,5R)-1-[2-(Diethoxyphosphinylmethoxy)-2,5-dihydro-
2-(hydroxymethyl)furan-5-yl]thymine (33)
4.2.11. (2S,5R)-9-[2-Cyano-2-(diethoxyphosphinyl)methoxy-2,5-
(dihydro)furan-5-yl]adenine (27)
To a THF (8.0 mL) solution containing 32 (181 mg, 0.396 mmol)
and AcOH (0.025 mL, 0.479 mmol) was added Bu4NF (1 M solution
in THF, 0.48 mL, 0.48 mmol) at rt. The reaction mixture was stirred
for 41 h and evaporated to dryness. Silica gel column chromatogra-
phy (CH2Cl2/MeOH = 20:1) of the residue gave 33 (131 mg, 91%) as
To a pyridine (10 mL) solution of 26 (255 mg, 0.618 mmol) was
added CH3SO2Cl (0.14 mL, 1.9 mmol) at rt. The mixture was stirred
for 12 h and partitioned between CH2Cl2 and saturated aqueous
NaHCO3. Silica gel column chromatography (CH2Cl2/MeOH = 10:1)
of the organic layer gave 27 (180 mg, 74%) as a colorless foam. UV
a colorless foam. UV (MeOH) kmax 264 nm (e 8900), kmin 235 nm (e
2300); 1H NMR (CDCl3) d 1.34 and 1.37 (6H, each as t, J = 7.1 Hz),
1.92 (3H, d, J = 1.1 Hz), 3.50 (1H, dd, J = 8.5 and 12.9 Hz), 3.71
(1H, dd, J = 8.2 and 14.4 Hz), 3.98–4.03 (2H, m), 4.13–4.27 (4H,
m), 4.48 (1H, dd, J = 8.2 and 8.5 Hz), 6.07 (1H, dd, J = 1.5 and
5.9 Hz), 6.52 (1H, dd, J = 1.7 and 5.9 Hz), 6.98 (1H, dd, J = 1.5 and
1.7 Hz), 7.15 (1H, d, J = 1.1 Hz), 9.57 (1H, br); 13C NMR (CDCl3) d
12.38, 16.31, 16.34, 16.36, 16.40, 56.36, 58.06, 62.67, 62.73,
62.80, 63.14, 63.20, 77.32, 87.99, 111.79, 113.78, 113.87, 128.95,
134.78, 135.27, 150.90, 163.83; FAB-MS (m/z) 391 (M++H). Anal.
Calcd for C15H23N2O8Pꢂ1/4H2O: C, 45.63; H, 6.00; N, 7.09. Found:
C, 45.36; H, 6.15; N, 7.02.
(MeOH) kmax 259 nm (e 16,200), kmin 228 nm (e
5800); 1H NMR
(CDCl3) d 1.32 and 1.33 (6H, each as t, J = 7.1 Hz), 3.98–4.08 (2H,
m), 4.01–4.20 (4H, m), 6.10 (2H, br), 6.50 (1H, dd, J = 1.8 and
5.7 Hz), 6.56 (1H, dd, J = 1.5 and 5.7 Hz), 7.26 (1H, dd, J = 1.5 and
1.8 Hz), 7.89 (1H, s), 8.38 (1H, s); 13C NMR (CDCl3) d 16.32, 16.34,
16.37, 16.40, 59.02, 60.73, 62.86, 62.93, 63.05, 63.11, 87.07,
103.58, 103.74, 112.91, 119.16, 130.59, 132.78, 138.07, 149.41,
153.77, 155.89; FAB-MS (m/z) 391 (M++H). Anal. Calcd for
C
15H19N6O5Pꢂ3/4H2O: C, 44.18; H, 5.07; N, 20.61. Found: C, 44.35;
H, 4.91; N, 20.23.
4.2.12. 1-[5-O-tert-Butyldimethylsilyl-2,3-dideoxy-4-(diethoxy-
4.2.15. Oxidation of 33: formation of 34
phosphinyl)methoxy-3-iodo-
mine (31)
a
-
L
-threo-pentofuranosyl]thy-
To an CH3CN (10 mL) solution of 33 (226 mg, 0.579 mmol) was
added IBX (178 mg, 0.637 mmol). The resulting suspension was
stirred at refluxing temperature for 2 h and then filtered through
A
CH2Cl2 (10 mL) solution containing of 28 (100 mg,
0.295 mmol), NIS (199 mg, 0.885 mmol) and diethyl hydrox-
ymethylphosphonate (0.217 mL, 1.48 mmol) was stirred at rt for
5 h. After evaporation of the solvent, the residue was dissolved in
AcOEt and washed with saturated aqueous Na2S2O3 and then with
saturated aqueous NaHCO3. Silica gel column chromatography
(CH2Cl2/MeOH = 70:1) of the organic layer gave the crude product,
which was purified by HPLC (CHCl3/MeOH = 50:1) to give 31
(40 mg, 21%, tR = 6.2 min) as a pale yellow foam. UV (MeOH) kmax
a Celite pad. Silica gel column chromatography (CH2Cl2/
MeOH = 10:1) of the filtrate gave a mixture (210 mg) of 34 and
its hemiacetal 35 as a pale yellow foam.
4.2.16. (2S,5R)-1-[2-(Diethoxyphosphinyl)methoxy-2-ethynyl-
2,5-(dihydro)furan-5-yl]thymine (36)
To an ethanol(5.0 mL)solution containinga mixture of 34 and 35,
prepared from IBX-oxidation of 33 (80 mg, 0.205 mmol), were

7192
Y. Kubota et al. / Bioorg. Med. Chem. 18 (2010) 7186–7192
added dimethyl 1-diazo(2-oxopropyl)phosphonate (81 mg, 0.420
mmol) and K2CO3 (48 mg, 0.61 mmol). The reaction mixture was
stirred at rt for 29 h and then partitioned between CH2Cl2 and satu-
rated aqueous NaHCO3. Silica gel column chromatography (CH2Cl2/
MeOH = 50:1) of the organic layer gave 36 (32 mg, 41%) as a colorless
s); 13C NMR (D2O) d 60.99, 62.26, 78.39, 78.45, 85.91, 105.47,
105.59, 118.27, 130.11, 133.65, 139.20, 148.83, 152.90, 155.99;
FAB-MS (m/z) 338 (M++H). Anal. Calcd for C12H15N6O5Pꢂ9/5H2O: C,
37.27; H, 4.45; N, 21.73. Found: C, 37.57; H, 4.45; N, 21.48.
foam. UV (MeOH) kmax 264 nm (
e
9200), kmin 235 nm (
e
2800); 1H
4.2.20. (2S,5R)-1-[2-Ethynyl-2,5-dihydro-2-(phosphonometh-
oxy)furan-5-yl]-thymine mono-ammonium salt (10)
NMR (CDCl3) d 1.34 and 1.35 (6H, each as t, J = 7.1 Hz), 1.75 (1H, s),
1.95 (3H, s), 3.98 (1H, dd, J = 10.5 and 13.2 Hz), 4.12–4.25 (5H, m),
6.12 (1H, dd, J = 1.5 and 5.6 Hz), 6.32 (1H, dd, J = 1.7 and 5.6 Hz),
7.16 (1H, dd, J = 1.5 and 1.7 Hz), 7.16 (1H, s), 8.84 (1H, br); 13C
NMR (CDCl3) d 12.23, 16.27, 16.31, 16.36, 57.64, 59.35, 62.38,
62.44, 62.55, 62.61, 76.21, 77.32, 88.18, 105.13, 105.30, 112.10,
129.81, 133.76, 135.07, 150.63, 163.85; FAB-MS (m/z) 385 (M++H).
Anal. Calcd for C16H21N2O7Pꢂ1/2H2O: C, 48.86; H, 5.64; N, 7.12.
Found: C, 49.09; H, 5.66; N, 7.14.
To a DMF (5.0 mL) solution of 36 (50 mg, 0.130 mmol) was
added Me3SiBr (0.252 mL, 1.95 mmol) at 0 °C. The reaction mixture
was stirred for 9.5 h at rt, concentrated in vacuo, and neutralized
with NH4OH (2.0 mL). The resulting solution was washed with
CH2Cl2. Reverse phase column chromatography (H2O) of the aque-
ous layer gave 10 (34 mg, 75%) as a colorless foam. UV (H2O) kmax
267 nm (e 9700), kmin 235 nm (e
3000); 1H NMR (D2O) d 1.71 (3H,
d, J = 1.1 Hz), 3.19 (1H, s), 3.53 (1H, dd, J = 10.2 and 12.3 Hz), 3.81
(1H, dd, J = 11.0 and 12.3 Hz), 6.13 (1H, dd, J = 1.6 and 5.7 Hz),
6.34 (1H, dd, J = 1.7 and 5.7 Hz), 6.87 (1H, dd, J = 1.6 and 1.7 Hz),
7.10 (1H, d, J = 1.1 Hz); 13C NMR (DMSO-d6) d 11.97, 61.29, 62.53,
78.16, 78.50, 87.74, 105.09, 105.21, 110.82, 129.85, 133.91,
135.55, 150.42, 163.90; FAB-MS (m/z) 346 (M++H). Anal. Calcd for
4.2.17. (2S,5R)-1-[2-(Diethoxyphosphinyl)methoxy-2,5-dihydro-
2-(hydroxyiminomethyl)furan-5-yl]thymine (37)
To a pyridine (10 mL) solution containing a mixture of 34 and
35, prepared from IBX-oxidation of 33 (226 mg, 0.579 mmol),
was added hydroxylamine hydrochloride (188 mg, 2.70 mmol).
The reaction mixture was stirred at rt for 20 h and partitioned be-
tween CH2Cl2 and saturated aqueous NaHCO3. Silica gel column
chromatography (CH2Cl2/MeOH = 20:1) of the organic layer gave
C
12H16N3O7PꢂH2O: C, 39.68; H, 4.99; N, 11.57. Found: C, 39.91; H,
4.84; N, 11.71.
Acknowledgments
37 (172 mg, 74%) as a colorless foam. UV (MeOH) kmax 264 nm (
e
9 600), kmin 237 nm (
e
4700); 1H NMR (CDCl3) d 1.34 (6H, t,
Financial supports from Japan Society for the Promotion of Sci-
ence (KAKENHI No. 21590123 to K.H.) are gratefully acknowledged.
The authors are grateful to Y. Odanaka and T. Matsubayashi (Center
for Instrumental Analysis, Showa University) for technical assis-
tance with NMR, MS, and elemental analyses.
J = 7.1 Hz), 1.94 (3H, s), 3.90 (2H, d, J = 10.7 Hz), 4.12–4.21 (4H,
m), 6.15 (1H, dd, J = 1.2 and 5.9 Hz), 6.47 (1H, dd, J = 1.5 and
5.9 Hz), 7.07 (1H, dd, J = 1.2 and 1.5 Hz), 7.23 (1H, s), 7.56 (1H, s),
9.58 (1H, br), 10.3 (1H, br); 13C NMR (CDCl3) d 12.32, 16.39,
16.41, 16.44, 16.46, 56.94, 58.64, 62.78, 62.85, 62.94, 63.00,
88.47, 110.48, 110.62, 112.01, 130.00, 133.42, 135.73, 146.34,
150.67, 164.13; FAB-MS (m/z) 404 (M++H). Anal. Calcd for
References and notes
C
15H22N3O8Pꢂ1/2H2O: C, 43.69; H, 5.62; N, 10.19. Found: C, 44.01;
1. De Clerq, E. J. Clin. Virol. 2004, 30, 115.
H, 5.47; N, 9.96.
2. Huryn, D. M.; Okabe, M. Chem. Rev. 1992, 92, 1745.
3. For the 10-branched derivative: Faivre-Buet, V.; Grouiller, A.; Descotes, G.
Nucleosides Nucleotides 1992, 11, 1411.
4.2.18. (2S,5R)-1-[2-Cyano-2-(diethoxyphosphinyl)methoxy-2,5-
(dihydro)furan-5-yl]thymine (38)
4. For the 20- and 30-branched derivatives: (a) Kumamoto, H.; Tanaka, H. J. Synth.
Org. Chem., Jpn. 2002, 60, 145; (b) Onuma, S.; Kumamoto, H.; Tanaka, H.
Tetrahedron 2002, 58, 2497; (c) Haraguchi, K.; Itoh, Y.; Tanaka, H. J. Synth. Org.
Chem., Jpn. 2003, 61, 974.
To a pyridine (3.0 mL) solution of 37 (59 mg, 0.146 mmol) was
added CH3SO2Cl (0.068 mL, 0.876 mmol) at rt. The reaction mix-
ture was stirred for 20 h and partitioned between CH2Cl2/saturated
aqueous NaHCO3. Silica gel column chromatography (CH2Cl2/
MeOH = 40:1) of the organic layer gave 38 (54 mg, 95%) as a color-
5. For the 40-branched derivatives: Waga, T.; Ohrui, H.; Meguro, H. Nucleosides
Nucleotides 1996, 15, 287.
6. Tanaka, H.; Kubota, Y.; Takeda, S.; Haraguchi, K. Nucleosides, Nucleotides Nucleic
Acids 2007, 26, 547.
7. Haraguchi, K.; Takeda, S.; Tanaka, H.; Nitanda, T.; Baba, M.; Dutschman, G. E.;
Cheng, Y.-C. Bioorg. Med. Chem. Lett. 2003, 13, 3775.
less foam. UV (MeOH) kmax 262 nm (e 8700), kmin 234 nm (e 2900);
1H NMR (CDCl3) d 1.35 and 1.36 (6H, each as t, J = 7.1 Hz), 1.95 (3H,
d, J = 1.3 Hz), 4.05–4.14 (2H, m), 4.15–4.24 (4H, m), 6.35 (1H, dd,
J = 1.3 and 5.9 Hz), 6.40 (1H, dd, J = 1.8 and 5.9 Hz), 6.47 (1H, d,
J = 1.3 Hz), 7.27 (1H, dd, J = 1.3 and 1.8 Hz), 9.14 (1H, br); 13C
NMR (CDCl3) d 12.35, 16.39, 16.44, 16.49, 59.40, 61.12, 62.83,
62.90, 63.05, 63.12, 89.08, 103.39, 103.55, 112.87, 113.10, 130.87,
133.02, 134.14, 150.23, 163.22; FAB-MS (m/z) 386 (M++H). Anal.
Calcd for C15H20N3O7P: C, 46.76; H, 5.23; N, 10.42. Found: C,
46.88; H, 5.26; N, 10.75.
8. (a) Dutcshman, G. E.; Grill, S. P.; Gullen, E. A.; Haraguchi, K.; Takeda, S.; Tanaka,
H.; Baba, M.; Cheng, Y.-C. Antimicrob. Agents Chemother. 2004, 48, 1640; (b)
Nitanda, T.; Wang, X.; Kumamoto, H.; Haraguchi, K.; Tanaka, H.; Cheng, Y.-C.;
Baba, M. Antimicrob. Agents Chemother. 2005, 48, 3355.
9. Haraguchi, K.; Itoh, Y.; Takeda, S.; Honma, Y.; Tanaka, H.; Nitanda, T.; Baba, M.;
Dutschman, G. E.; Cheng, Y.-C. Nucleosides Nucleotides Nucleic Acids 2004, 23,
647.
10. Kim, C. U.; Luh, B. Y.; Martin, J. C. J. Org. Chem. 1991, 56, 2642.
11. Phosphonate analogues of carbocyclic nucleoside have also been reported:
Dyatkina, N.; Semizarov, D.; Victorova, L.; Krayevsky, A.; Theil, F.; von Janta-
Lipinski, M. Nucleosides Nucleotides 1995, 14, 723.
12. Synthesis of the phosphonate analogues of 40-carbon-substituted carbocyclic
nucleoside have recently been published: Boojamra, C. B.; Parrish, J. P.;
Sperandio, D.; Gao, Y.; Petrakovsky, O. V.; Lee, S. K.; Markevitch, D. Y.; Vela, J.
E.; Laflamme, G.; Chen, J. M.; Ray, A. S.; Barron, A. C.; Sparacino, M. L.; Desai, M.
C.; Kim, C. U.; Cihlar, T.; Mackman, R. L. Bioorg. Med. Chem. 2009, 17,
1739.
13. Kubota, Y.; Kunikata, M.; Ohsawa, R.; Odajima, Y.; Haraguchi, K.; Tanaka, H.
Nucleic Acids Symposium Series 2005, 49, 111.
14. Kubota, Y.; Haraguchi, K.; Kunikata, M.; Hayashi, M.; Ohkawa, M.; Tanaka, H. J.
Org. Chem. 2006, 71, 1099.
15. Frigerio, M.; Santagostino, M. Tetrahedron Lett. 1994, 35, 8019.
16. (a) Ohira, S. Synth. Commun. 1989, 19, 561; (b) Roth, G. J.; Liepold, B.; Muller, S.
G.; Bestmann, H. J. Synthesis 2004, 59.
17. Kubota, Y.; Nakamura, K.; Haraguchi, K.; Tanaka, H. Synth. Commun. 2010, 40,
1758.
4.2.19. (2S,5R)-9-[2-Ethynyl-2,5-dihydro-2-(phosphonomethoxy)-
furan-5-yl]-adenine mono-ammonium salt (8)
To a DMF (5.0 mL) solution of 25 (100 mg, 0.254 mmol) was
added Me3SiBr (0.329 mL, 2.54 mmol) at 0 °C. The reaction mixture
was stirred for 9.5 h at rt, concentrated in vacuo, and neutralized
with NH4OH (1.0 mL). The resulting solution was washed with
CH2Cl2. Reverse phase column chromatography (H2O) of the aque-
ous layer gave 8 (63 mg, 70%) as a pale yellow foam. UV (H2O) kmax
260 nm (e 15,700), kmin 226 nm (e
2500); 1H NMR (D2O) d 3.18
(1H, s), 3.37 (1H, dd, J = 10.2 and 12.4 Hz), 3.65 (1H, dd, J = 11.0
and 12.4 Hz), 6.38 (1H, dd, J = 1.2 and 5.9 Hz), 6.42 (1H, dd, J = 1.5
and 5.9 Hz), 6.81 (1H, dd, J = 1.2 and 1.5 Hz), 7.97 (1H, s), 7.98 (1H,
18. Pauwels, R.; De Clercq, E.; Desmyter, J.; Balzarini, J.; Goubau, P.; Herdewijn, P.;
Vanderhaeghe, H.; Vandeputte, M. J. Virol. Methods 1987, 16, 171.