Nucleosides and nucleotides. 185. Synthesis and biological activities of 4'α-C-branched-chain sugar pyrimidine nucleosides

Article abstract of DOI:10.1021/jm990050i

A series of 4'α-C-branched-chain pyrimidine nucleosides was synthesized from 2'-deoxycytidine or uridine. In the 2'-deoxycytidine series, the substituent at the 4'α-position affected cytotoxicity against L1210 mouse leukemic cells in vitro in the order Me (23) > CN (22)> C≡CH (21) > CH=CH₂ (19) > Et (24) > CH=CHCl (20). However, uridine and cytidine derivatives with ethynyl and cyano groups at the 4'α-position did not show any cytotoxicity. The antiviral activities of these nucleosides against HSV-1, HSV-2, and HIV- 1 in vitro were also examined. Compounds 22 and 23 showed antiviral activities against HSV-1 and HSV-2 without showing significant toxicity to the host cells (MRC-5 cells). Although almost all of the nucleosides showed anti-HIV-1 activities, they were also cytotoxic to the host cells (MT-4).

Full text of DOI:10.1021/jm990050i

J . Med. Chem. 1999, 42, 2901-2908
2901
Nu cleosid es a n d Nu cleotid es. 185. Syn th esis a n d Biologica l Activities of
4′r-C-Br a n ch ed -Ch a in Su ga r P yr im id in e Nu cleosid es
Makoto Nomura,†,‡ Satoshi Shuto,† Motohiro Tanaka,§ Takuma Sasaki,§ Shuichi Mori, Shiro Shigeta, and
Akira Matsuda*,†
Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, J apan,
Hanno Research Center, Taiho Pharmaceutical Company Ltd., 1-27 Misugidai, Hanno, Saitama 357-8527, J apan,
Cancer Research Institute, Kanazawa University, Takara-machi, Kanazawa 920-0934, J apan,
and Department of Bacteriology, Fukushima Medical College, Fukushima 960-1247, J apan
Received J anuary 28, 1999
A series of 4′R-C-branched-chain pyrimidine nucleosides was synthesized from 2′-deoxycytidine
or uridine. In the 2′-deoxycytidine series, the substituent at the 4′R-position affected cytotoxicity
against L1210 mouse leukemic cells in vitro in the order Me (23) > CN (22) > CtCH (21) >
CHdCH2 (19) > Et (24) > CHdCHCl (20). However, uridine and cytidine derivatives with
ethynyl and cyano groups at the 4′R-position did not show any cytotoxicity. The antiviral
activities of these nucleosides against HSV-1, HSV-2, and HIV-1 in vitro were also examined.
Compounds 22 and 23 showed antiviral activities against HSV-1 and HSV-2 without showing
significant toxicity to the host cells (MRC-5 cells). Although almost all of the nucleosides showed
anti-HIV-1 activities, they were also cytotoxic to the host cells (MT-4).
Nucleoside antimetabolites play an important role in
cancer and viral chemotherapy. Several branched-chain
sugar nucleosides have been synthesized and evaluated
as potential antitumor or antiviral agents. Some of
these nucleosides, such as 1-(2-deoxy-2-methylene-â-
D-erythro-pentofuranosyl)cytosine (DMDC),1-3 1-(2-
cyano-2-deoxy-â-D-a ra bino-pentofuranosyl)cytosine
(CNDAC),4-7 1-(2-deoxy-2-fluoromethylene-â-D-erythro-
pentofuranosyl)cytosine (FMDC),8 and 1-(3-C-ethynyl-
â-D-ribo-pentofuranosyl)cytosine (ECyd)9-11 and its uracil
congener (EUrd),9-11 have shown potent antitumor
activities both in vitro and in vivo. Recently, some 4′R-
C-branched 2′-deoxynucleosides, such as 4′R-C-methyl-
2′-deoxycytidine12,13 and 4′R-C-fluoromethyl-2′-deoxy-
cytidine,14 have also been reported to have potent
antileukemic activities. Moreover, we recently found
that 4′R-C-ethyl-, -ethenyl-, and -ethynylthymidines
showed antiviral activities against herpes simplex virus
type-1 (HSV-1) and human immunodeficiency virus
type-1 (HIV-1) in vitro.15 Although the activities of these
nucleosides are not superior to those of reference
nucleosides such as acyclovir (ACV) and zidovudine
(AZT), they are essentially not cytotoxic to host RPMI
18226 and MT-4 cells. On the basis of these findings,
we became interested in the biological activities of 4′R-
C-carbon-substituted pyrimidine nucleosides. Since there
are currently few examples of 4′R-C-branched nucleo-
sides, to clarify the structure-activity relationships, we
synthesized a series of 4′R-C-branched-chain sugar
nucleosides and evaluated their cytotoxicity against
L1210 mouse leukemic and KB human pharyngeal
carcinoma cells and their antiviral activity against HSV-
1, HSV-2, and HIV-1 in vitro.
Ch em istr y
In a 2′-deoxycytidine series, the biological activities
of 4′R-C-methyl (23),12,13 -fluoromethyl,14 and -cyano
(22)16 derivatives have been reported. The former two
nucleosides have been synthesized starting from D-
glucose. However, this method is rather lengthy, and
overall yields are quite low. On the other hand, Moffatt’s
group has introduced a hydroxymethyl group at the 4′R-
position of nucleosides using an appropriately protected
nucleoside 5′-aldehyde under Cannizzaro reaction
conditions.17-19 Since this method is much shorter and
effective, we adopted this method to synthesize our
target nucleosides: 4′R-C-ethenyl, -chloroethenyl, -ethy-
nyl, and -ethyl derivatives of 2′-deoxycytidine. We also
prepared the known 4′R-C-methyl and -cyano deriva-
tives using the same intermediate to evaluate their
biological activities. Ribonucleoside counterparts, such
as 4′R-C-ethynyl- and -cyanouridines and -cytidines,
were also prepared from uridine.
We used N4-benzoyl-3′-O-[tert-butyldimethylsilyl
(TBS)]-2′-deoxycytidine (3) as a starting material, which
was readily prepared from 2′-deoxycytidine in four steps
(Scheme 1). The 5′-OH of 3 was oxidized by a slightly
modified original method using 1-(3-dimethylaminopro-
pyl)-3-ethylcarbodiimide (EDC) hydrochloride instead of
1,3-dicyclohexylcarbodiimide (DCC).18 The desired al-
dehyde 4 was obtained in a good yield and subsequently
treated with aqueous HCHO and NaOH in dioxane for
14 h at room temperature. However, the desired 4′-C-
hydroxymethyl derivative 5 was not obtained, perhaps
due to deprotection of the benzoyl and TBS groups.
Therefore, the crude 4 was treated under the same
conditions for only 10 min; NaBH4 was then added to
reduce the resulting aldehyde at the 4′-position to give
5 in 44% yield. This aldol reaction followed by reduction
* To whom correspondence and reprint requests should be ad-
dressed. Phone: +81-11-706-3228. Fax: +81-11-706-4980. E-mail:
matuda@pharm.hokudai.ac.jp.
† Hokkaido University.
‡ Taiho Pharmaceutical Co. Ltd.
§ Kanazawa University.
Fukushima Medical College.
10.1021/jm990050i CCC: $18.00 © 1999 American Chemical Society
Published on Web 07/02/1999

2902 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15
Nomura et al.
Sch em e 1
Sch em e 2
is better than the original Cannizzaro conditions when
the starting materials have base-labile protecting groups.
After manipulation of the protecting groups, the result-
ing 7 was oxidized to the corresponding 4′R-C-aldehyde
under Swern conditions with a slight modification20 to
give 8 in 82% yield as crystals, which was used as a
common intermediate to prepare our target nucleosides.
confirmed the stereochemistry of the original formyl
group in 8 to be 4′R.
Both 4′R-C-substituted uridine and cytidine deriva-
tives were prepared from a common uracil intermediate,
1-(2,3,5-tri-O-TBS-4R-C-formyl-â-D-ribo-pentofurano-
syl)uracil (32), since the uracil moiety can be easily
converted into the corresponding cytosine moiety after
transformation of the sugar moiety. The 5′-O-TBS group
of 2′,3′,5′-tris-O-TBS-uridine 25 was selectively depro-
tected with TFA in aqueous THF to give 26 (Scheme
2). 4′-C-Hydroxymethyl-2′,3′-O-bis-TBS-uridine (28) was
obtained from 26 using the reactions previously de-
scribed with cytosine series. Oxidation of the hydroxyl
group in 26, followed by treatment of the resulting 27
under conditions similar to those described for the
synthesis of 5, gave the diol 28. The 4′R-C-hydroxy-
methyl group in 28 was selectively protected with a
DMTr group,21 and the resulting free 5′-hydroxyl group
was then protected with a TBS group, followed by
deprotection of the DMTr group with AcOH to give 31.
Modified Swern oxidation of 31 gave the desired alde-
hyde 32.
Wittig reactions of 8 with Ph3PdCH2 and Ph3PdCHCl
gave 4′R-C-ethenyl and -2-chloroethenyl derivatives 9
and 10 (Z:E ) 20:1), respectively, in yields of 92%.
Compound 10 was further treated with BuLi in THF
at -78 °C to give debenzoylated 4′-C-ethynyl derivative
11 in 72% yield. Compound 8 was also converted into
oxime 12, which was then dehydrated in NaOAc-Ac2O
and debenzoylated with 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU) in MeOH to give 4′R-C-cyano derivative 13.
4′R-C-Methyl derivative 15 was prepared from 7. Using
an iodine-imidazole-Ph3P system, 7 was converted into
the 4′-C-iodomethyl derivative 14, which was hydroge-
nated with Pd/C in the presence of Et3N to give 15 in
54% yield from 7. The protecting groups of 9-18 were
removed by usual methods to give the target compounds
19-23 in good yields. Hydrogenation with Pd/C of 19
gave ethyl derivative 24.
We were unable to unequivocally establish the ste-
reochemisty of the 4′-C-aldehyde group in 8 at this
stage. However, NOE (0.9%) between the 4′R-C-methyl
protons and H-1′ in the 4′-C-methyl derivative 23
The formyl group in 32 was transformed into a cyano
or ethynyl group by methods similar to those used for
2′-deoxycytidine derivatives. Compound 32 was con-
verted into 4′R-C-[2(Z)-chloroethenyl] derivative 33 via

4′R-C-Branched-Chain Sugar Pyrimidine Nucleosides
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15 2903
Ta ble 1. Biological Activities of 4′R-C-Substituted Pyrimidine Nucleosides
antiviral activity
HSV-2b
cytotoxicity
IC50 (µM)a
HSV-1b
EC50 (µM)
HIV-1b
EC50 (µM)
compd
L1210
KB
IC50 (µM)
EC50 (µM)
IC50 (µM)
IC50 (µM)
19
20
21
22
23
24
39
40
41
42
ACV
AZT
21
200
>350
>350
>350
>350
>350
>350
>350
>350
>350
>350
ND
>350
>350
200
3.6
3.1
>350
NDc
ND
ND
ND
>350
>350
>350
>350
260
>350
ND
ND
ND
>350
>350
>350
21
0.58
>350
ND
ND
ND
ND
1.1
>350
>350
>350
>350
260
>350
ND
ND
ND
0.0086
2.1
0.18
4.6
0.80
0.33
0.16
55
>350
>350
>350
>350
ND
0.0022
0.0012
0.062
0.013
ND
ND
ND
ND
ND
0.16
0.17
0.062
0.77
ND
ND
ND
ND
ND
ND
>350
ND
ND
>350
ND
0.36
ND
ND
ND
ND
0.0041
3.2
a
Tumor cells (2 × 103 cells/well) were incubated in the presence or absence of compounds for 72 h. MTT reagent was added to each
well, and the plate was incubated for an additional 4 h. The resulting MTT-formazan was dissolved in DMSO, and the OD (540 nm) was
measured. Percent inhibition was calculated as follows: % inhibition ) [1 - OD (540 nm) of sample well/OD (540 nm) of control well] ×
b
100. IC50 (µM) is the concentration that inhibits cell growth by 50%.22 To evaluate anti-HSV-1, anti-HSV-2, and anti-HIV-1 activities,
HSV-1 Kos strain vs MRC-5 cells, HSV-2 G strain vs MRC-5 cells, and HIV-1 IIIb strain vs MT-4 cells were used, respectively. Briefly,
cells were infected with viruses at a multiplicity of infection of 0.02. Immediately after the virus infection, a cell suspension (100 µL) was
placed into each well containing various concentrations of the compounds (100 µL). After 4 days of incubation at 36 °C, the number of
viable cells was determined by the MTT method. IC50 (µM) is the concentration that inhibits cell growth by 50%.23,24 c ND, not determined.
the Wittig reaction. Compound 33 was then dehydro-
halogenated with BuLi to give ethynyl derivative 34 and
deprotected with HCl/dioxane in MeOH to give 39.
Compound 32 was also converted into the corresponding
oxime 35, which was further transformed into 4′R-C-
cyano derivative 36. Compound 36 was deprotected as
described above to give 40. Cytidine derivatives 37 and
38 were prepared from uridine derivatives 34 and 36,
respectively, using a 2,4,6-triisopropylbenzenesulfonyl
chloride (TPSCl)-Et3N-DMAP system, followed by
NH4OH treatment. Compounds 37 and 38 were desily-
lated with HF-Et3N to give 41 and 42, respectively.
more strict than that of dCK at the 4′R-position.
However, none of the nucleosides described here were
cytotoxic to KB cells. This difference between L1210 and
KB cells might be related to the activity of certain
activation enzymes, although any definite conclusions
would require further studies.
The antiviral activities of the nucleosides against
HSV-1, HSV-2, and HIV-1 were also examined in vitro
(Table 1). Unlike the 4′R-C-substituted thymidines,15
only 4′R-C- cyano and -methyl derivatives 22 and 23
were active against HSV-1 and HSV-2 without showing
significant toxicity to the host cells (MRC-5 cells). On
the other hand, almost all of the nucleosides described
here showed significant anti-HIV-1 activities. However,
all of these nucleosides showed significant cytotoxicity
to the host cells (MT-4 cells). On the basis of these
results together with our previous data,15 the nucleobase
moiety affects not only the activity but also the selectiv-
ity.
Biologica l Activities
The cytotoxicities of a series of 4′R-C-branched nu-
cleosides 19-21, 24, and 39-42, including the known
22 and 23, were investigated in vitro using mouse L1210
leukemia and human KB pharyngeal carcinoma cells,
and the results are summarized in Table 1. As in
previous studies,12,13 2′-deoxycytidine derivative 23,
which has a methyl group at the 4′R-position, showed
significant antileukemic activities against L1210 cells,
with IC50 values of 0.16 µM. The corresponding 4′R-C-
cyano, -ethynyl, -ethenyl, and -ethyl derivatives 22, 21,
19, and 24 also had antileukemic activity, with IC50
values of 0.33, 0.80, 21, and 55 µM, respectively.
However, 4′R-C-[2(Z)-chloroethenyl] derivative 20 showed
only insignificant activity. Therefore, in the 2′-deoxy-
cytidine series, the substituents at the 4′R-position affect
cytotoxicity in the order Me (23) > CN (22) > CtCH
(21) > CHdCH2 (19) > Et (24) > CHdCHCl (20).
Therefore, the activity seems to be related to the
bulkiness of the 4′R-C-substituents. Since these 2′-
deoxycytidine analogues can be phosphorylated by
deoxycytidine kinase (dCK), the relative cytotoxicity
might be dependent on the susceptibility to dCK. On
the other hand, ribonucleoside derivatives 39-42 did
not show any cytotoxicity. These ribonucleosides were
thought to be phosphorylated by uridine/cytidine kinase,
and the substrate specificity of this kinase might be
Exp er im en ta l Section
Melting points were measured on a Yanagimoto MP-3
micromelting point apparatus (Yanagimoto, J apan) and are
uncorrected. The 1H NMR spectra were recorded on a J EOL
AL-400 (400-MHz) or J EOL J NM-EX 270 (270-MHz) spec-
trometer with tetramethylsilane as an internal standard.
Chemical shifts are reported in parts per million (δ), and
signals are expressed as s (singlet), d (doublet), t (triplet), q
(quartet), m (multiplet), or br (broad). All exchangeable protons
were detected by disappearance on the addition of D2O. 13C
NMR spectra were recorded on a J EOL AL-400 (400-MHz) or
J EOL J NM-EX 270 (270-MHz) spectrometer. Fast atom bom-
bardment mass spectrometry (FAB-MS) was done on a J EOL
J MS-HX110 instrument at an ionizing voltage of 70 eV. TLC
was done on Merck silica gel 60 F254 precoated plates. The silica
gel used for column chromatography was Merck silica gel 60
(70-230 mesh).
N4-Ben zoyl-3′-O-(ter t-bu tyld im eth ylsilyl)-2′-d eoxycyti-
d in e (3). A suspension of dimethoxytrityl chloride (35.5 g, 105
mmol) and N4-benzoyl-2′-deoxycytidine (22.7 g, 68.5 mmol) in
pyridine (140 mL) was stirred for 1 h at room temperature.
MeOH (2 mL) was added to the mixture, and the mixture was
concentrated in vacuo to give a residue which was partitioned

2904 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15
Nomura et al.
between EtOAc (400 mL) and H2O (400 mL). The separated
organic layer was dried (Na2SO4) and concentrated to give
crude 1. A mixture of the crude 1, imidazole (11.2 g, 164 mmol),
and TBSCl (12.4 g, 82.2 mmol) in DMF (140 mL) was stirred
for 15 h at room temperature, quenched with EtOH (15 mL),
and evaporated to dryness. EtOAc (500 mL) was added to the
mixture, which was washed with H2O (4 × 300 mL) and brine
(200 mL). The organic layer was dried (Na2SO4) and evapo-
rated. A mixture of the crude 2 in CH2Cl2 (500 mL) containing
TFA (15.8 mL) was stirred for 2 h at room temperature,
additional TFA (10.5 mL) was added, and the mixture was
stirred for a further 1 h. The mixture was cooled to 0 °C in an
ice bath and neutralized with 5 M NaOH. The separated
organic layer was washed with saturated NaHCO3 (2 × 200
mL), dried (Na2SO4), and concentrated. The residue was
purified on a silica gel column with 0-5% MeOH in CHCl3 to
give the crude product 3, which was crystallized from Et2O-
H2O to give 3 (16.1 g, 51% as a white powder): mp 93-95 °C;
FAB-MS m/z 446 (MH+). Anal. (C22H31N3O5Si‚H2O) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-2-d eoxy-
4r-h yd r oxym eth yl-â-D-r ibo-p en tofu r a n osyl]cytosin e (5).
A solution of 3 (13.9 g, 30.0 mmol) in EtOAc (100 mL) was
dried (Na2SO4) and concentrated to dryness. A mixture of the
above residue and EDC hydrochloride (17.3 g, 90.2 mmol) was
dissolved in a mixture of benzene (100 mL) and DMSO (15
mL), and the mixture was stirred for 30 min at room temper-
ature. The mixture was diluted with EtOAc (300 mL) and
washed with H2O (3 × 300 mL) and brine (300 mL). The
separated organic layer was dried (Na2SO4) and evaporated
to dryness. Hexane (300 mL) was added to a solution of the
residue in EtOAc (120 mL). The resulting precipitate was
collected by filtration and air-dried to give a crude 4, which
was dissolved in a mixture of aqueous 37% HCHO (5.5 mL)
and 1,4-dioxane (70 mL) containing 2 M NaOH solution (24
mL). The mixture was stirred for 10 min at room temperature
and neutralized with AcOH (4.8 mL). The mixture was
evaporated to dryness, and the residue was partitioned
between H2O and CHCl3. The organic layer was dried (Na2-
SO4) and evaporated to dryness. NaBH4 (604 mg, 16.0 mmol)
was added to a suspension of the residue in EtOH (240 mL)
at 0 °C. After being stirred for 20 min at the same temperature,
the mixture was quenched with AcOH (2.3 mL) and evaporated
to dryness. The residue was partitioned between H2O and
CHCl3. The organic layer was washed with saturated NaHCO3,
dried (Na2SO4), and evaporated to dryness. The residue was
purified on a silica gel column with 50-100% EtOAc in CHCl3
to give 5 (6.20 g, 44% as a white foam): FAB-MS m/z 476
(MH+). Anal. (C23H33N3O6Si) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
bu tyld ip h en ylsilyl)-2-d eoxy-4r-h yd r oxym eth yl-â-D-r ibo-
p en tofu r a n osyl]cytosin e (7). A mixture of 5 (2.59 g, 5.45
mmol) and dimethoxytrityl chloride (2.30 g, 6.81 mmol) in
pyridine (11 mL) was stirred for 50 min at room temperature
and quenched with H2O (80 mL). The mixture was diluted with
EtOAc (100 mL) and washed with H2O (100 mL) and brine
(100 mL). The organic layer was dried (Na2SO4) and evapo-
rated to dryness. The residue was purified on a silica gel
column with 33% EtOAc in CHCl3 to give crude 6 as a yellow
foam. A solution of the crude 6 (2.77 g), imidazole (945 mg,
13.9 mmol), and TBDPSCl (1.2 mL, 4.6 mmol) in DMF (7.5
mL) was stirred for 1.5 h at room temperature and quenched
with EtOH (0.4 mL). CHCl3 (140 mL) was added to the
mixture, which was washed with H2O (3 × 100 mL). The
organic layer was dried (Na2SO4) and evaporated to dryness.
The residue in a mixture of THF (6 mL) and aqueous 80%
AcOH (22 mL) was stirred for 12 h at room temperature. After
addition of 28% NH4OH (16 mL), the mixture was extracted
with CHCl3 (80 mL). The extract was washed with saturated
NaHCO3, dried (Na2SO4), and evaporated. The residue was
purified on a silica gel column with 33-67% EtOAc in CHCl3
to give a solid, which was crystallized from EtOAc-hexane to
give 7 (1.86 g, 48% as fine colorless needles): mp 157-157.5
°C; FAB-MS m/z 714 (MH+). Anal. (C39H51N3O6Si2) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
b u t yld ip h en ylsilyl)-2-d eoxy-4r-for m yl-â-D-r ibo-p en t o-
fu r a n osyl]cytosin e (8). Dimethyl sulfoxide (0.35 mL, 5.0
mmol) was added to a solution of trichloroacetic anhydride
(0.66 mL, 3.6 mmol) in CH2Cl2 (6 mL) at -78 °C under an Ar
atmosphere. The mixture was stirred for 20 min at the same
temperature, and a solution of 7 (1.79 g, 2.50 mmol) in CH2-
Cl2 (6 mL) was added to the mixture, which was stirred for a
further 30 min at the same temperature. After addition of Et3N
(1.67 mL, 12.0 mmol), the reaction mixture was allowed to
warm to room temperature and stirred for 1 h. Water (30 mL)
was added to the mixture, and the separated organic phase
was washed with H2O (30 mL), dried (Na2SO4), and evapo-
rated. The residue was purified on a silica gel column with
33% EtOAc in CHCl3 to give a solid, which was crystallized
from EtOAc-hexane to give 8 (1.45 g, 82% as fine colorless
needles): mp 174-174.5 °C; FAB-MS m/z 712 (MH+). Anal.
(C39H49N3O6Si2) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
b u t yld ip h en ylsilyl)-2-d eoxy-4r-et h en yl-â-D-r ibo-p en t o-
fu r a n osyl]cytosin e (9). A hexane solution of BuLi (1.66 M,
2.89 mL, 4.80 mmol) was added to a suspension of methylt-
riphenylphosphonium bromide (1.72 g, 4.80 mmol) in THF (12
mL) at -78 °C under an Ar atmosphere. The mixture was
stirred for 30 min at 0 °C, followed by addition of a solution of
8 (854 mg, 1.20 mmol) in THF (10 mL). The reaction mixture
was stirred for 1 h at room temperature. A saturated NH4Cl
(20 mL) was added to the mixture, which was extracted with
EtOAc (100 mL). The separated organic layer was washed with
brine (100 mL), dried (Na2SO4), and concentrated in vacuo.
EtOAc and hexane (each 20 mL) were added to the residue,
and the resulting precipitate was filtered. The crude product
was purified on a silica gel column with 6% MeOH in CHCl3
to give a solid, which was crystallized from EtOAc-hexane to
give 9 (782 mg, 92% as fine colorless needles): mp 181.5-182.5
°C; FAB-MS m/z 710 (MH+). Anal. (C40H51N3O5Si2) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
bu tyldiph en ylsilyl)-4r-(2-ch lor oeth en yl)-2-deoxy-â-D-r ibo-
p en tofu r a n osyl]cytosin e (10). A hexane solution of BuLi
(1.66 M, 1.21 mL, 2.0 mmol) was added to a suspension of
chloromethyltriphenylphosphonium chloride (694 mg, 2.0 mmol)
in THF (4 mL) at -78 °C under an Ar atmosphere. The
mixture was stirred for 50 min at -78 °C, and a solution of 8
(356 mg, 0.50 mmol) in THF (3 mL) was added to the mixture.
The mixture was warmed to 0 °C and stirred for 2.3 h.
Saturated aqueous NH4Cl (20 mL) was added to the mixture,
which was extracted with EtOAc (25 mL). The separated
organic layer was washed with brine (25 mL), dried (Na2SO4),
and concentrated in vacuo. The residue was purified on a silica
gel column with 50% EtOAc in hexane to give 10 (343 mg,
92% as a white foam): FAB-MS m/z 744 (MH+). Anal. (C40H50
-
ClN3O5Si2) C, H, N.
1-[3-O-(ter t-Bu t yld im et h ylsilyl)-5-O-(ter t-b u t yld ip h e-
n ylsilyl)-2-d eoxy-4r-eth yn yl-â-D-r ibo-p en tofu r a n osyl]cy-
tosin e (11). A hexane solution of BuLi (1.66 M, 2.89 mL, 4.8
mmol) was added to a solution of 10 (298 mg, 0.40 mmol) in
THF (11 mL) at -78 °C under an Ar atmosphere. The mixture
was stirred for 2 h at -78 °C, and a saturated aqueous NH4Cl
(20 mL) was added to the mixture, which was extracted with
EtOAc (20 mL). The extract was washed with brine (20 mL),
dried (Na2SO4), and concentrated in vacuo. The residue was
purified on a silica gel column with 7-10% MeOH in CHCl3
to give a crude product, which was purified on a silica gel
column with EtOAc and 10% MeOH in CHCl3 to give 11 (174
mg, 72% as a white foam): FAB-MS m/z 604 (MH+). Anal.
(C33H45N3O4Si2‚1/2H2O) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
bu tyld ip h en ylsilyl)-2-d eoxy-4r-h yd r oxyim in om eth yl-â-
D-r ibo-p en tofu r a n osyl]cytosin e (12). A mixture of 8 (534
mg, 0.750 mmol) and HONH2‚HCl (104 mg, 1.50 mmol) in
pyridine (6.0 mL) was stirred for 5 min at 50 °C and cooled to
room temperature. The mixture was diluted with EtOAc (100
mL) and washed with H2O (2 × 100 mL). The separated
organic layer was dried (Na2SO4) and concentrated in vacuo,

4′R-C-Branched-Chain Sugar Pyrimidine Nucleosides
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15 2905
and the crude product was crystallized from Et2O to give 12
(495 mg, 91%, as a white powder): mp 207-207.5 °C; FAB-
MS m/z 727 (MH+). Anal. (C39H50N4O6Si2) C, H, N.
in MeOH was heated under reflux. The reaction mixture was
cooled to room temperature, and silica gel was added to the
mixture, which was evaporated to dryness. The residue was
placed on top of a silica gel column, which was eluted with
MeOH in CHCl3.
1-(2-De oxy-4r-e t h e n yl-â-D -r ibo-p e n t ofu r a n osyl)cy-
tosin e (19). From 16 (394 mg, 0.64 mmol), 19 (150 mg, 91%)
was obtained as a white foam. An analytical sample was
obtained as an HCl salt: mp 184-186 °C dec; 1H NMR
(DMSO-d6) 7.82 (d, 1 H, H-6, J 6,5 ) 7.5 Hz), 7.11, 7.04 (each
br s, each 1 H, 4-NH2), 6.04 (dd, 1 H, H-1′, J 1′-2′a ) 6.8, J 1′-2′b
) 4.4 Hz), 5.90 (dd, 1 H, 4′-CHadCHbHc, J Ha,Hb ) 17.3, J Ha,Hc
) 10.8 Hz), 5.69 (d, 1 H, H-5, J 5,6 ) 7.5 Hz), 5.32 (dd, 1 H,
4′-CHadCHbHc, J Hb,Ha ) 17.3, J Hb,Hc )2.1 Hz), 5.16-5.20 (m,
3 H, 4′-CHadCHbHc, 3′, 5′-OH), 4.37 (td, 1 H, H-3′, J 3′,2′ ) 7.0,
1-[3-O-(ter t-Bu t yld im et h ylsilyl)-5-O-(ter t-b u t yld ip h e-
n ylsilyl)-4r-cya n o-2-d eoxy-â-D-r ibo-p en t ofu r a n osyl]cy-
tosin e (13). A suspension of 12 (451 mg, 0.62 mmol) and
NaOAc (305 mg, 3.72 mmol) in Ac2O (5.5 mL) was stirred for
2.5 h at 130 °C. The reaction mixture was cooled to room
temperature, and saturated aqueous NaHCO3 (100 mL) was
added to the mixture, which was stirred for 30 min at room
temperature. The mixture was extracted with EtOAc (100 mL),
which was washed with saturated NaHCO3 (2 × 100 mL). The
organic layer was dried (Na2SO4) and concentrated in vacuo.
A mixture of the above residue in MeOH (30 mL) containing
DBU (0.19 mL, 1.24 mmol) was stirred for 45 min at room
temperature, and silica gel was added to the mixture, which
was evaporated to dryness. The residue was placed on top of
a silica gel column, which was eluted with 7% MeOH in CHCl3
to give a solid, which was crystallized from EtOH to give 13
(263 mg, 70% as a white powder): mp 258.5-260 °C; FAB-
MS m/z 605 (MH+). Anal. (C32H44N4O4Si2) C, H, N.
J 3′,OH ) 5.3 Hz), 3.52 (dd, 1 H, H-5′a, J 5′a,5′b ) 11.7, J 5′a,OH
)
5.6 Hz), 3.36 (d, 1 H, H-5′b, J 5′b,5′a ) 11.7, J 5′b,OH ) 5.6 Hz),
2.07 (ddd, 1 H, H-2′a, J 2′a,1′ ) 6.8, J 2′a,2′b ) 12.9, J 2′a,3′ ) 7.0
Hz), 1.99 (ddd, 1 H, H-2′b, J 2′b,1′ ) 4.4, J 2′b,2′a ) 12.9, J 2′b,3′
)
7.0 Hz); 13C NMR (DMSO-d6) 165.43, 154.92, 141.08, 136.55,
114.70, 93.48, 89.01, 83.11, 69.15, 63.44, 39.63; FAB-MS m/z
254 (MH+). Anal. (C11H16ClN3O4) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
bu tyldiph en ylsilyl)-2-deoxy-4r-iodom eth yl-â-D-r ibo-pen to-
fu r a n osyl]cytosin e (14). A mixture of 7 (714 mg, 1 mmol),
Ph3P (1.05 g, 4 mmol), I2 (508 mg, 2 mmol), and imidazole (272
mg, 4 mmol) in benzene (10 mL) was stirred for 30 h at 80 °C
under an Ar atmosphere. The mixture was cooled to room
temperature and diluted with EtOAc (50 mL), which was
washed with saturated aqueous sodium thiosulfate (2 × 50
mL) and H2O (50 mL). The organic layer was dried (Na2SO4)
and concentrated in vacuo. The residue was purified on a silica
gel column with 50-60% EtOAc in hexane to give a crude
product, which was crystallized from EtOAc-hexane to give
14 (580 mg, 70% as fine colorless needles): mp 180-181.5 °C;
FAB-MS m/z 824 (MH+). Anal. (C39H50IN3O5Si2) C, H, N.
N4-Ben zoyl-1-[3-O-(ter t-b u t yld im et h ylsilyl)-5-O-(ter t-
b u t yld ip h en ylsilyl)-2-d eoxy-4r-m et h yl-â-D-r ibo-p en t o-
fu r a n osyl]cytosin e (15). A mixture of 14 (453 mg, 0.55
mmol), 10% Pd/C (150 mg), and Et3N (0.12 mL) in EtOH (9
mL) and EtOAc (9 mL) was stirred for 2 h at room temperature
under a hydrogen atmosphere. The reaction mixture was
filtered through a Celite pad, and the filtrate was evaporated.
Water and CHCl3 were added to the residue, and the separated
organic layer was dried (Na2SO4) and concentrated in vacuo.
The residue was purified on a silica gel column with 11-17%
EtOAc in CHCl3 to give a solid, which was crystallized from
EtOAc-hexane to give 15 (296 mg, 77% as colorless needles):
mp 160-160.5 °C; FAB-MS m/z 698 (MH+). Anal. (C39H51N3O5-
Si2) C, H, N.
Gen er a l Meth od for Dep r otection of th e N4-Ben zoyl
Gr ou p . A mixture of the N4-benzoyl derivative and DBU (1.5
equiv) in MeOH was stirred for 30 min at room temperature.
Silica gel was added to the mixture, which was evaporated to
dryness. The residue was placed on top of a silica gel column,
which was eluted with MeOH in CHCl3 to give the product.
1-[3-O-(ter t-Bu t yld im et h ylsilyl)-5-O-(ter t-b u t yld ip h e-
n ylsilyl)-2-d eoxy-4r-eth en yl-â-D-r ibo-p en tofu r a n osyl]cy-
tosin e (16). From 9 (639 mg, 0.90 mmol), 16 (486 mg, 89%)
was obtained as fine colorless needles: mp 108-109.5 °C
(CHCl3-hexane); FAB-MS m/z 606 (MH+). Anal. (C33H47N3O4-
Si2‚1/2H2O) C, H, N.
1-[4r-[2(Z)-Ch lor oeth en yl]-2-d eoxy-â-D-r ibo-p en tofu r a -
n osyl]cytosin e (20). From 17 (192 mg, 0.3 mmol), 20 (47 mg,
54%) was obtained as colorless needles: mp 205-206 °C
1
(EtOAc-hexane); H NMR (DMSO-d6) 7.93 (d, 1 H, H-6, J 6,5
) 7.4 Hz), 7.11, 7.05 (each br s, each 1 H, 4-NH2), 6.41 (d, 1H,
4′-CHadCHbCl, J Hb,Ha ) 8.0 Hz), 6.11 (t, 1 H, H-1′, J 1′-2′ ) 5.9
Hz), 5.96 (d, 1 H, 4′-CHadCHbCl, J Ha,Hb ) 8.0 Hz), 5.70 (d, 1
H, H-5 J 5,6 ) 7.4 Hz), 5.36 (d, 1 H, 3′-OH, J OH,3′ ) 4.7 Hz),
5.29 (d, 1 H, 5′-OH, J OH,5′ ) 5.6 Hz), 4.39 (td, 1 H, H-3′, J 3′,2′
)
6.2, J 3′,OH ) 4.7 Hz), 3.64 (dd, 1 H, H-5′a, J 5′a,5′b ) 12.0, J 5′a,OH
) 5.6 Hz), 3.58 (dd, 1 H, H-5′b, J 5′b,5′a ) 12.0, J 5′b,OH ) 5.6 Hz),
2.09 (ddd, 1 H, H-2′a, J 2′a,1′ ) 5.9, J 2′a,2′b ) 13.2, J 2′a,3′ ) 6.2
Hz), 2.05 (ddd, 1 H, H-2′b, J 2′b,1′ ) 5.9, J 2′b,2′a ) 13.2, J 2′b,3′
)
6.2 Hz); 13C NMR (DMSO-d6) 165.37, 154.89, 140.94, 129.08,
119.76, 93.63, 88.91, 83.64, 69.86, 62.15; FAB-MS m/z 288, 290
(MH+). Anal. (C11H14ClN3O4) C, H, N.
1-(2-De oxy-4r-e t h yn yl-â-D -r ibo-p e n t ofu r a n osyl)cy-
tosin e (21). From 11 (167 mg, 0.276 mmol), 21 (49 mg, 67%)
was obtained as a white powder: mp 219.5-221 °C (EtOH);
1H NMR (DMSO-d6) 7.76 (d, 1 H, H-6, J 6,5 ) 7.8 Hz), 7.17,
7.10 (each br s, each 1 H, 4-NH2), 6.12 (dd, 1 H, H-1′, J 1′-2′a
)
7.2, J 1′-2′b ) 4.7 Hz), 5.70 (d, 1 H, H-5, J 5,6 ) 7.8 Hz), 5.45 (d,
1 H, 3′-OH, J OH,3′ ) 5.4 Hz), 5.38 (t, 1 H, 5′-OH, J OH,5′ ) 5.9
Hz), 4.29 (td, 1 H, H-3′, J 3′,2′ ) 7.3, J 3′,OH ) 5.4 Hz), 3.63 (dd,
1 H, H-5′a, J 5′a,5′b ) 12.1, J 5′a,OH ) 5.9 Hz), 3.56 (dd, 1 H, H-5′b,
J 5′b,5′a ) 12.1, J 5′b,OH ) 5.9 Hz), 3.47 (s, 1 H, 4′-ethynyl), 2.24
(ddd, 1 H, H-2′a, J 2′a,1′ ) 7.2, J 2′a,2′b ) 13.2, J 2′a,3′ ) 7.3 Hz),
2.05 (ddd, 1 H, H-2′b, J 2′b,1′ ) 4.7, J 2′b,2′a ) 13.2, J 2′b,3′ ) 7.3
Hz); 13C NMR (DMSO-d6) 165.50, 154.90, 141.03, 93.98, 84.35,
83.27, 81.33, 78.58, 69.29, 63.72, 39.03; FAB-MS m/z 252
(MH+). Anal. (C11H13N3O4‚2/3H2O) C, H, N.
1-(4r-C y a n o -2-d e o x y -â-D -r i b o-p e n t o fu r a n o s y l)c y -
tosin e (22). From 13 (212 mg, 0.350 mmol), 22 (56.1 mg, 62%
as a white powder) was obtained: mp 230-231 °C (MeOH)
dec; 1H NMR (DMSO-d6) 7.60 (d, 1 H, H-6, J 6,5 ) 7.3 Hz), 7.25,
7.22 (each br s, each 1 H, 4-NH2), 6.32 (t, 1 H, H-1′, J 1′-2′
)
6.8 Hz), 6.19 (d, 1 H, 3′-OH, J OH,3′ ) 5.1 Hz), 5.74 (d, 1 H, 5′-
OH, J OH,5′ ) 6.1 Hz), 5.72 (d, 1 H, H-5, J 5,6 ) 7.3 Hz), 4.41
(ddd, 1 H, H-3′, J 3′,2′a ) 6.5, J 3′,2′b ) 5.4, J 3′,OH ) 5.1 Hz), 3.72
(dd, 1 H, H-5′a, J 5′a,5′b ) 11.6, J 5′a,OH ) 6.1 Hz), 3.66 (dd, 1 H,
H-5′b, J 5′b,5′a ) 11.6, J 5′b,OH ) 6.1 Hz), 2.25 (ddd, 1 H, H-2′a,
J 2′a,1′ ) 6.8, J 2′a,2′b ) 13.7, J 2′a,3′ ) 6.5 Hz), 2.05 (ddd, 1 H, H-2′b,
J 2′b,1′ ) 6.8, J 2′b,2′a ) 13.7, J 2′b,3′ ) 5.4 Hz); 13C NMR (DMSO-
d6) 165.58, 155.02, 141.53, 117.98, 95.00, 86.17, 85.56, 71.02,
63.34, 37.86; FAB-MS m/z 253 (MH+). Anal. (C10H12N4O4‚1/
4H2O) C, H, N.
1-[3-O-(ter t-Bu t yld im et h ylsilyl)-5-O-(ter t-b u t yld ip h e-
n ylsilyl)-4r-(2-ch lor oeth en yl)-2-deoxy-â-D-r ibo-pen tofu r a-
n osyl]cytosin e (17). From 10 (313 mg, 0.42 mmol), 17 (229
mg, 85%) was obtained as colorless needles: mp 173-174 °C
(EtOAc-hexane); FAB-MS m/z 640 (MH+). Anal. (C33H46
ClN3O4Si2) C, H, N.
-
1-[3-O-(ter t-Bu t yld im et h ylsilyl)-5-O-(ter t-b u t yld ip h e-
n ylsilyl)-2-d eoxy-4r-m eth yl-â-D-r ibo-p en tofu r a n osyl]cy-
tosin e (18). From 15 (244 mg, 0.350 mmol), 18 (203 mg, 98%)
was obtained as a white foam: FAB-MS m/z 594 (MH+). Anal.
(C32H47N3O4Si2‚1/3H2O) C, H, N.
1-(2-De oxy-4r-m e t h yl-â-D -r ibo-p e n t ofu r a n osyl)c y-
tosin e (23). From 18 (160 mg, 0.270 mmol), 23 (38 mg, 58%)
was obtained as a white powder: mp 200-201 °C (EtOH); 1H
NMR (DMSO-d6) 7.81 (d, 1 H, H-6, J 6,5 ) 7.4 Hz), 7.02, 6.95
(each br s, each 1 H, 4-NH2), 6.00 (t, 1 H, H-1′, J 1′-2′ ) 6.3
Hz), 5.62 (d, 1 H, H-5, J 5,6 ) 7.4 Hz), 5.02 (d, 1 H, 3′-OH, J OH,3′
Gen er a l Meth od for Dep r otection of th e Silyl Gr ou p s.
A mixture of the silyl-protected nucleoside and NH4F (20 equiv)

2906 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15
Nomura et al.
) 5.0 Hz), 4.97 (d, 1 H, 5′-OH, J OH,5′ ) 5.5 Hz), 4.10 (ddd, 1 H,
H-3′, J 3′,2′a ) 4.9, J 3′,2′b ) 6.3, J 3′,OH ) 5.0 Hz), 3.33 (dd, 1 H,
H-5′a, J 5′a,5′b ) 11.7, J 5′a,OH ) 5.5 Hz), 3.31 (dd, 1 H, H-5′b,
layer was dried (Na2SO4) and evaporated to give a crude
product, which was purified on a silica gel column with 33-
67% EtOAc in CHCl3 to give 28 (13.6 g, 39% as a white
powder): mp 188-189.5 °C; FAB-MS m/z 503 (MH+). Anal.
(C22H42N2O7Si2‚1/2H2O) C, H, N.
J 5′b,5′a ) 11.7, J 5′b,OH ) 5.5 Hz), 2.12 (ddd, 1 H, H-2′a, J 2′a,1′
6.3, J 2′a,2′b ) 13.2, J 2′a,3′ ) 4.9 Hz), 2.05 (ddd, 1 H, H-2′b, J 2′b,1′
) 6.3, J 2′b,2′a ) 13.2, J 2′b,3′ ) 6.3 Hz), 0.99 (s, 3 H, 4′-CH3); 13
)
C
1-[2,3-Bis-O-(tert-butyldimethylsilyl)-4r-[(4,4′-dimethoxy-
tr ityl)oxym eth yl]-â-D-r ibo-p en tofu r a n osyl]u r a cil (29). A
mixture of 28 (2.26 g, 4.50 mmol) and dimethoxytrityl chloride
(1.98 g, 5.85 mmol) in pyridine (10 mL) was stirred for 1.5 h
at room temperature. The mixture was diluted with EtOAc
(70 mL) and washed with H2O (4 × 100 mL). The organic layer
was dried (Na2SO4) and evaporated. The residue was purified
on a silica gel column with 40-60% EtOAc in CHCl3 to give a
crude product, which was crystallized from EtOAc-hexane to
give 29 (2.31 g, 64% as a white powder): mp 213-213.5 °C;
FAB-MS m/z 804 (M+). Anal. (C43H60N2O9Si2) C, H, N.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-h yd r oxym -
eth yl-â-D-r ibo-p en tofu r a n osyl]u r a cil (31). A mixture of 29
(2.00 g, 2.48 mmol), TBSCl (561 mg, 3.72 mmol), and imidazole
(760 mg, 11.2 mmol) in DMF (7 mL) was stirred for 13.5 h at
room temperature. The reaction was quenched with EtOH (1
mL), and the mixture was diluted with EtOAc and washed
with H2O (5 × 100 mL). The organic layer was dried (Na2SO4)
and evaporated to give 30. The crude 30 was dissolved in a
mixture of THF (10 mL) and aqueous 80% AcOH (35 mL). The
mixture was stirred for 5 h at room temperature and then
cooled to 0 °C. After addition of 28% NH4OH (25 mL) to the
mixture, the whole was extracted with EtOAc (80 mL), which
was successively washed with H2O (80 mL) and saturated
aqueous NaHCO3 (80 mL). The separated organic layer was
dried (Na2SO4) and evaporated. The residue was purified on
a silica gel column with 20% EtOAc in CHCl3 to give 31 (1.32
g, 86% as a white foam): FAB-MS m/z 617 (MH+). Anal.
(C28H56N2O7Si3) C, H, N.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-for m yl-â-D-
r ibo-p en tofu r a n osyl]u r a cil (32). Compound 31 (1.23 g, 2.00
mmol) was stirred for 30 min in a mixture of DMSO (0.28 mL,
4.0 mmol) and trichloroacetic anhydride (0.53 mL, 2.90 mmol)
in CH2Cl2 (5 mL) at -78 °C, followed by treatment with Et3N
(1.34 mL, 9.60 mmol). After workup as described for the
synthesis of 8, 32 (1.04 g, 85%) was obtained as a white foam:
FAB-MS m/z 615 (MH+). Anal. (C28H54N2O7Si3) C, H, N.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-[2(Z)-ch lo-
r oeth en yl]-â-D-r ibo-p en tofu r a n osyl]u r a cil (33). Compound
32 (71.4 mg, 0.116 mmol) was treated with Ph3PdCHCl
[prepared from BuLi (1.58 M, 0.294 mL, 0.464 mmol) and
chloromethyltriphenylphosphonium chloride (161 mg, 0.464
mmol) in THF (1 mL) at -78 °C] for 45 min at 0 °C. After
workup as described for the synthesis of 10, 33 (60.2 mg, 80%)
was obtained as a white foam: FAB-MS m/z 647 (MH+). Anal.
(C29H55ClN2O6Si3) C, H, N.
NMR (DMSO-d6) 165.34, 154.92, 141.08, 93.53, 87.24, 83.63,
70.41, 65.90, 40.51,17.79; FAB-MS m/z 242 (MH+). Anal.
(C10H15N3O4‚1/3H2O) C, H, N.
1-(2-D e o x y -4r-e t h y l-â-D -r i b o-p e n t o fu r a n o s y l)c y -
tosin e (24). A mixture of 19 (53 mg, 0.21 mmol) and 10% Pd/C
(30 mg) in MeOH (3 mL) was stirred for 30 min at room
temperature under a hydrogen atmosphere. The mixture was
filtered through a Celite pad, and the filtrate was evaporated.
The residue was purified on a silica gel column with 20-25%
MeOH in CHCl3 to give 24 (50 mg, 93% as a white foam). An
analytical sample was obtained as an HCl salt: mp 171-173
1
°C dec; H NMR (DMSO-d6) 7.84 (d, 1 H, H-6, J 6,5 ) 7.4 Hz),
7.10, 7.03 (each br s, each 1 H, 4-NH2), 6.07 (t, 1 H, H-1′, J 1′-2′
) 6.4 Hz), 5.68 (d, 1 H, H-5, J 5,6 ) 7.4 Hz), 5.04 (d, 1 H, 3′-
OH, J OH,3′ ) 4.9 Hz), 4.95 (d, 1 H, 5′-OH, J OH,5′ ) 5.0 Hz), 4.21
(ddd, 1 H, H-3′, J 3′,2′a ) 3.9, J 3′,2′b ) 6.4, J 3′,OH ) 4.9 Hz), 3.37-
3,45 (m, 2 H, H-5′), 2.14 (ddd, 1 H, H-2′a, J 2′a,1′ ) 6.4, J 2′a,2′b
)
13.8, J 2′a,3′ ) 3.9 Hz), 2.04 (ddd, 1 H, H-2′b, J 2′b,1′ ) 6.4, J 2′b,2′a
) 13.8, J 2′b,3′ ) 6.4 Hz), 1.59 (dq,1 H, CHaCH3, J 6′a,6′b ) 13.0,
J 6′a,7′ ) 7.5 Hz), 1.49 (dq,1 H, CHbCH3, J 6′b,6′a ) 13.0, J 6′b,7′
)
7.5 Hz), 0.84 (t, 3 H, CH2CH3, J 7′,6′ ) 7.5 Hz); 13C NMR (DMSO-
d6) 159.18, 146.98, 144.36, 93.32, 90.46, 84.96, 70.25, 62.73,
40.61, 23.61, 8.29; FAB-MS m/z 256 (MH+). Anal. (C11H18
-
ClN3O4) C, H, N.
2′,3′-Bis-O-(ter t-bu tyld im eth ylsilyl)u r id in e (26). A solu-
tion of uridine (48.8 g, 200 mmol), imidazole (136 g, 660 mmol),
and TBSCl (100 g, 660 mmol) in DMF (150 mL) was stirred
for 7 h at room temperature. The reaction was quenched with
EtOH (30 mL) and then diluted with EtOAc (1 L). The mixture
was washed with H2O (8 × 800 mL), dried (Na2SO4), and
concentrated in vacuo to give 25. The crude 25 was suspended
in a mixture of aqueous 80% AcOH (960 mL) and THF (80
mL). TFA (40 mL) was added to the mixture, and the whole
was stirred for 1 h at room temperature and for 1.5 h at 0 °C.
The resulting precipitate was collected by filtration and
washed with aqueous 80% AcOH. NH4OH (28%, 80 mL) was
added to the filtrate, and the resulting precipitate was collected
by filtration and washed with aqueous 80% AcOH. The
combined precipitates were dissolved in CHCl3 (1 L), which
was washed with saturated NaHCO3 (4 × 800 mL). The
organic layer was dried (Na2SO4) and evaporated to give a
crude product, which was crystallized from Et2O to give 26
(55.8 g, 59% as a white powder): mp 226-227 °C; FAB-MS
m/z 473 (MH+). Anal. (C21H40N2O6Si2) C, H, N.
1-[2,3-Bis-O-(ter t-bu tyldim eth ylsilyl)-4r-h ydr oxym eth yl-
â-D-r ibo-p en tofu r a n osyl]u r a cil (28). EDC hydrochloride
(40.3 g, 210 mmol) was added to a solution of 26 (33.1 g, 70
mmol) in a mixture of pyridine (7.4 mL, 91 mmol), TFA (3.5
mL, 45 mmol), DMSO (37 mL, 11 mmol), and benzene (250
mL). The mixture was stirred for 25 min at room temperature,
diluted with EtOAc (250 mL), and washed with brine (4 × 200
mL) and H2O (200 mL). The separated organic layer was dried
(Na2SO4) and evaporated. The residue was purified on a silica
gel column with 25-33% EtOAc in CHCl3 to give 27 (24.6 g
as a foam). An aqueous solution of HCHO (37%, 11 mL, 150
mmol) and 2 M NaOH (50 mL) was added to a solution of 27
in 1,4-dioxane (150 mL). The mixture was stirred for 50 min
at room temperature, AcOH (10 mL) was added to the mixture,
and the whole was evaporated to dryness. The residue was
suspended in H2O (500 mL), which was successively extracted
with CHCl3 (2 × 500 mL), and the combined organic layer was
dried (Na2SO4) and evaporated. The residue was dissolved in
EtOH (430 mL) and cooled to 0 °C. After addition of NaBH4
(81.6 g, 45.0 mmol), the reaction mixture was stirred for 30
min at the same temperature and quenched with AcOH (5.1
mL). The mixture was evaporated, and the residue was
suspended in CHCl3 (1 L), which was washed with H2O (800
mL) and saturated aqueous NaHCO3 (800 mL). The organic
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-eth yn yl-â-
D-r ibo-p en tofu r a n osyl]u r a cil (34). Compound 33 (477 mg,
0.737 mmol) in THF (20 mL) was treated with BuLi (1.58 M,
4.93 mL, 7.80 mmol) for 1 h at -78 °C. After workup as
described for 11, 34 (371 mg, 82%) was obtained as a white
foam: FAB-MS m/z 611 (MH+). Anal. (C29H54N2O6Si3) C, H,
N.
1-[2,3,5-Tr is-O-(ter t-b u t yld im et h ylsilyl)-4r-h yd r oxy-
im in om eth yl-â-D-r ibo-p en tofu r a n osyl]u r a cil (35). A mix-
ture of 32 (923 mg, 1.50 mmol) and HONH2‚HCl (208 mg, 3.00
mmol) in pyridine (12 mL) was stirred for 40 min at room
temperature. After workup as described for the synthesis of
12, 35 (938 mg, 99%) was obtained as a white foam: FAB-MS
m/z 630 (MH+). Anal. (C28H55N3O7Si3) C, H, N.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-cya n o-â-D-
r ibo-p en tofu r a n osyl]u r a cil (36). A mixture of 35 (882 mg,
1.40 mmol) and NaOAc (689 mg, 8.40 mmol) in Ac2O (12.5 mL)
was stirred for 2.5 h at 130 °C. After workup described for
the synthesis of 13, 36 (724 mg, 85%) was obtained as colorless
needles: mp 170.5-171 °C (EtOAc-hexane); FAB-MS m/z 612
(MH+). Anal. (C28H53N3O6Si3) C, H, N.
Gen er a l Meth od for Con ver sion of th e Ur a cil Moiety
to th e Cytosin e Moiety. TPSCl (2 equiv) was added to a

4′R-C-Branched-Chain Sugar Pyrimidine Nucleosides
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15 2907
mixture of 34 (0.58 mmol) or 36 (0.66 mmol), DMAP (2 equiv),
and Et3N (2 equiv) in CH3CN (4 mL). The mixture was stirred
for 1.5 h at room temperature, and a mixture of 28% NH4OH
(2 mL) and CH3CN (2 mL) was added to the mixture. After
being stirred for 30 min, the mixture was diluted with CHCl3
(100 mL) and washed with H2O (100 mL), 0.1 M HCl (100 mL),
and saturated aqueous NaHCO3 (100 mL). The organic layer
was dried (Na2SO4) and concentrated in vacuo. The residue
was purified on a silica gel column.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-eth yn yl-â-
D-r ibo-p en tofu r a n osyl]cytosin e (37). Compound 37 (140
mg, 69%) was obtained as a white foam: FAB-MS m/z 610
(MH+). Anal. (C29H55N3O5Si3‚1/4H2O) C, H, N.
1-[2,3,5-Tr is-O-(ter t-bu tyld im eth ylsilyl)-4r-cya n o-â-D-
r ibo-p en tofu r a n osyl]cytosin e (38). Compound 38 (282 mg,
80%) was obtained as a white foam: FAB-MS m/z 611 (MH+).
Anal. (C28H54N4O5Si3‚1/2H2O) C, H, N.
1-(4r-Eth yn yl-â-D-r ibo-p en tofu r a n osyl)u r a cil (39). A
solution of 34 (122 mg, 0.2 mmol) in a mixture of MeOH (10
mL) and concentrated HCl (1.5 mL) was stirred for 24 h at
room temperature. The mixture was evaporated, and the
residue was purified on a silica gel column with 17% MeOH
in CHCl3 to give 39 (34.9 mg, 65% as a white foam): 1H NMR
After workup, the resulting powder was dissolved in H2O and
purified on an ODS column (YMC-Pack R&D D-ODS-5-A 250-
mm i.d. S-5 µm, 120 Å) with 0-2% CH3CN in H2O to give a
solid, which was crystallized from H2O to give 42 (43.9 mg,
41% as colorless needles): mp 224-225 °C dec; 1H NMR
(DMSO-d6) 7.64 (d, 1 H, H-6, J 6,5 ) 7.3 Hz), 7.26, 7.24 (each
br s, each 1 H, 4-NH2), 5.98 (d, 1 H, 3′-OH, J OH-3′ ) 5.3 Hz),
5.91 (d, 1 H, H-1′, J 1′-2′ ) 4.0 Hz), 5.77 (t, 1 H, 5′-OH, J OH-5′
) 5.9 Hz), 5.72 (d, 1 H, H-5, J 5,6 ) 7.3 Hz), 5.54 (d, 1 H, 2′-
OH, J OH-2′ ) 5.3 Hz), 4.14-4.21 (m, 2 H, H-2′, H-3′), 3.73 (dd,
1 H, H-5′a, J 5′a,5′b ) 11.9, J 5′a,OH ) 5.9 Hz), 3.65 (d, 1 H, H-5′b,
J 5′b,5′a ) 11.9, J 5′b,OH ) 5.9 Hz); 13C NMR (DMSO-d6) 165.49,
154.97, 142.05, 117.90, 94.68, 90.53, 83.79, 71.76, 70.73, 63.70;
FAB-MS m/z 269 (MH+). Anal. (C10H12N4O5‚1/6H2O) C, H, N.
Ack n ow led gm en t . This investigation was sup-
ported in part by a Grant-in-Aid for Scientific Research
on Priority Areas from the Ministry of Education,
Science, Sports, and Culture of J apan and by the
Second-Term Comprehensive Ten-Year Strategy for
Cancer Control form the Ministry of Health and Welfare
of J apan.
Su p p or tin g In for m a tion Ava ila ble: 1H and 13C NMR
data for the nontarget compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
(DMSO-d6) 11.35 (br s, 1 H, 3-NH), 7.77 (d, 1 H, H-6, J 6,5
)
8.1 Hz), 5.88 (d, 1 H, H-1′, J 1′-2′ ) 6.4 Hz), 5.67 (d, 1 H, H-5,
J 5,6 ) 8.1 Hz), 5.53 (t, 1 H, 5′-OH, J OH,5′ ) 5.7 Hz), 5.37 (d, 1
H, 2′-OH, J OH,2′ ) 6.1 Hz), 5.29 (d, 1 H, 3′-OH, J OH,3′ ) 5.9
Hz), 4.12 (ddd, 1 H, H-2′, J 2′,1′ ) 6.4, J 2′,3′ ) 5.6, J 2′,OH ) 6.1
Hz), 4.04 (dd, 1 H, H-3′, J 3′,2′ ) 5.6, J 3′,OH ) 5.9 Hz), 3.56 (dd,
1 H, H-5′a, J 5′a,5′b ) 11.7, J 5′a,OH ) 5.7 Hz), 3.54 (dd, 1 H, H-5′b,
J 5′b,5′a ) 11.7, J 5′b,OH ) 5.7 Hz), 3.49 (s, 1 H, 4′-ethynyl); 13C
NMR (DMSO-d6) 162.93, 150.73, 140.74, 102.21, 87.26, 83.74,
81.13, 78.94, 72.56, 70.86, 65.47; FAB-MS m/z 269 (MH+);
FAB-HRMS calcd for C11H13N2O6 269.0774, found 269.0786.
Anal. (C11H12N2O6‚1/2H2O) C, H, N.
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nyl-â-D-ribo-pentofuranosyl)uracil, and their nucleobase ana-
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1-(4r-Cya n o-â-D-r ibo-p en tofu r a n osyl)u r a cil (40). Tri-
ethylamine (1.12 mL, 8.0 mmol) and 1,4-dioxane (4 mL) were
added to a solution of 36 (245 mg, 0.4 mmol) in CH3CN (10
mL) containing 48% HF (0.26 mL, 8.0 mmol). The mixture was
stirred for 22 h at 50 °C and evaporated. Water (20 mL) was
added to the residue, and the mixture was washed with CHCl3
(3 × 20 mL). The H2O layer was loaded on Diaion PK 212 (H+
form) column and eluted with H2O. The eluate was evaporated
to dryness, and the residue was purified on a silica gel column
with 20% MeOH in CHCl3 to give a foam, which was crystal-
lized from EtOH-CHCl3 to give 40 (32 mg, 36% as a white
1
powder): mp 146-147 °C; H NMR (DMSO-d6) 11.36 (br s, 1
H, 3-NH), 7.72 (d, 1 H, H-6, J 6,5 ) 7.9 Hz), 6.12 (d, 1 H, OH,
J OH, ) 5.3 Hz), 5.91 (d, 1 H, H-1′, J 1′-2′ ) 5.9 Hz), 5.84 (t, 1 H,
5′-OH, J OH,5′ ) 5.9 Hz), 5.67 (d, 1 H, H-5, J 5,6 ) 7.9 Hz), 5.66
(d, 1 H, OH, J OH ) 5.3 Hz), 4.16-4.27 (m, 2 H, H-2′, H-3′),
3.74 (dd, 1 H, H-5′a, J 5′a,5′b ) 11.9, J 5′a,OH ) 5.9 Hz), 3.67 (dd,
1 H, H-5′b, J 5′b,5′a ) 11.9, J 5′b,OH ) 5.9 Hz); 13C NMR (DMSO-
d6) 162.78, 150.51, 140.94, 117.59, 102.38, 88.68, 84.13, 71.28,
70.63, 63.52; FAB-MS m/z 270 (MH+). Anal. (C10H11N3O6‚1/
5H2O) C, H, N.
1-(4r-E t h yn yl-â-D-r ibo-p en t ofu r a n osyl)cyt osin e H y-
d r och lor id e (41). A solution of 37 (110 mg, 0.2 mmol) in a
mixture of MeOH (10 mL) and HCl in dioxane (4 M, 2 mL)
was stirred for 24 h at room temperature. The resulting
precipitates were collected by filtration and washed with a
small amount of EtOH to give 41 (55.5 mg, 77% as a white
1
powder, 1:1 mixture with dioxane): mp 201-203 °C dec; H
NMR (DMSO-d6) 9.81 (br s, 1 H, NH), 8.70 (br s, 1 H, NH),
8.19 (d, 1 H, H-6, J 6,5 ) 7.8 Hz), 6.17 (d, 1 H, H-5, J 5,6 ) 7.8
Hz), 5.84 (d, 1 H, H-1′, J 1′-2′ ) 5.1 Hz), 4.15 (dd, 1 H, H-2′,
J 2′,1′ ) 5.1, J 2′,3′ ) 5.4 Hz), 4.09 (d, 1 H, H-3′, J 3′,2′ ) 5.4 Hz),
3.61 (d, 1 H, H-5′a, J 5′a,5′b ) 12.2 Hz), 3.58 (d, 1 H, H-5′b, J 5′b,5′a
) 12.2 Hz), 3.55 (s, 8 H, dioxane), 3.54 (s, 1 H, 4′-ethynyl); 13
C
(11) Takatori, S.; Kanda, H.; Takenaka, K.; Wataya, Y.; Matsuda,
A.; Fukushima, M.; Shimamoto, Y.; Tanaka, M.; Sasaki, T.
Antitumor mechanisms and metabolism of novel antitumor
nucleoside analogues, 1-(3-C-ethynyl-â-D-ribo-pentofuranosyl)-
cytosine and 1-(3-C-ethynyl-â-D-ribo-pentofuranosyl)uracil. Can-
cer Chemother. Pharmacol., in press.
NMR (DMSO-d6) 159.10, 147.34, 144.50, 94.40, 88.76, 84.44,
80.94, 79.39, 73.56, 70.46, 66.41 (dioxane), 65.02. Anal. (C11H14
-
ClN3O5‚C4H8O2‚1/6H2O) C, H, N.
1-(4r-Cyan o-â-D-r ibo-pen tofu r an osyl)cytosin e (42). Com-
pound 38 (222 mg, 0.363 mmol) was deprotected as for 40.

2908 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 15
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