A Novel Synthesis of 2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose

Article abstract of DOI:10.1021/jo9700540

Novel 2′-deoxycytidine antimetabolites, specifically several 2′-modified 2′-deoxy-4′-thiocytidines, were synthesized as potential new antineoplastic agents. Methyl 3-O-benzylxylofuranoside was converted to a 1,4-anhydro-4-thioarabitol 24. Protection of the primary alcohol of 24 gave a common intermediate (15) which was useful for the synthesis of various 2′-modified 2′-deoxy-4′-thionucleosides. Oxidation of the secondary hydroxyi group of 15, followed by the Wittig reaction or treatment with (diethylamido)sulfur trifluoride (DAST) produced 2-deoxy-2-methylene (26) and 2-deoxy-2,2-difluoro (34) derivatives, respectively. Unique Pummerer-type glycosylation between the corresponding sulfoxides and trimethylsilylated N⁴-acetylcytosine produced 2′-deoxy-2′-methylene- (10) and 2′-deoxy-2′,2′-difluoro-4′-thiocytidines (11). On the other hand, treatment of 15 with DAST introduced a fluorine atom with retention of the 2′-stereochemistry, yielding 40. In contrast, the Mitsunobu reaction of 3-O-benzoyl derivative 53 which was obtained from 15 in five steps, using diphenylphosphoryl azide gave azide derivative 54 with inverted stereochemistry. These derivatives were converted to the corresponding 1-O-acetyl derivatives via the usual Pummerer rearrangement, which were in turn used to synthesize 4′-thiocytidines 12 and 58. Among the 2′-modified 4′-thiocytidines obtained, 2′-methylene (10) and 2′-fluoro (12) derivatives were found to have potent antineoplastic properties in vitro.

Full text of DOI:10.1021/jo9700540

3140
J . Org. Chem. 1997, 62, 3140-3152
A Novel Syn th esis of 2′-Mod ified 2′-Deoxy-4′-th iocytid in es fr om
D-Glu cose1
Yuichi Yoshimura,*,† Kenji Kitano,† Kohei Yamada,† Hiroshi Satoh,† Mikari Watanabe,†
Shinji Miura,† Shinji Sakata,† Takuma Sasaki,‡ and Akira Matsuda§
Research and Development Division, Yamasa Corporation, 2-10-1 Araoicho, Choshi, Chiba 288, J apan,
Cancer Research Institute, Kanazawa University, 13-1 Takara-machi, Kanazawa 920, J apan, and Faculty
of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060, J apan
Received J anuary 9, 1997X
Novel 2′-deoxycytidine antimetabolites, specifically several 2′-modified 2′-deoxy-4′-thiocytidines,
were synthesized as potential new antineoplastic agents. Methyl 3-O-benzylxylofuranoside was
converted to a 1,4-anhydro-4-thioarabitol 24. Protection of the primary alcohol of 24 gave a common
intermediate (15) which was useful for the synthesis of various 2′-modified 2′-deoxy-4′-thionucleo-
sides. Oxidation of the secondary hydroxyl group of 15, followed by the Wittig reaction or treatment
with (diethylamido)sulfur trifluoride (DAST) produced 2-deoxy-2-methylene (26) and 2-deoxy-2,2-
difluoro (34) derivatives, respectively. Unique Pummerer-type glycosylation between the corre-
sponding sulfoxides and trimethylsilylated N4-acetylcytosine produced 2′-deoxy-2′-methylene- (10)
and 2′-deoxy-2′,2′-difluoro-4′-thiocytidines (11). On the other hand, treatment of 15 with DAST
introduced a fluorine atom with retention of the 2′-stereochemistry, yielding 40. In contrast, the
Mitsunobu reaction of 3-O-benzoyl derivative 53 which was obtained from 15 in five steps, using
diphenylphosphoryl azide gave azide derivative 54 with inverted stereochemistry. These derivatives
were converted to the corresponding 1-O-acetyl derivatives via the usual Pummerer rearrangement,
which were in turn used to synthesize 4′-thiocytidines 12 and 58. Among the 2′-modified
4′-thiocytidines obtained, 2′-methylene (10) and 2′-fluoro (12) derivatives were found to have potent
antineoplastic properties in vitro.
Ch a r t 1
The design of new effective agents for cancer chemo-
therapy is an important goal of synthetic chemists
working in the field of medicinal chemistry. Nucleoside
antimetabolites are considered to be promising candi-
dates: 1-â-D-arabinosylcytosine (araC, 1, Chart 1) is
clinically used for the treatment of acute myeloblastic
leukemia,2 and a new 2′-deoxycytidine analogue, gem-
citabine (2′-deoxy-2′,2′-difluorocytidine, 2), has been in-
troduced as a chemotherapeutic agent for solid tumors.3
Some nucleoside analogues are also used to inhibit
reverse transcriptase coded by human immunodeficiency
virus (HIV),4,5 a causative agent of acquired immunode-
ficiency syndrome (AIDS). In particular, 3′-thiacytidine
(3TC, 7)5 has recently been approved as an anti-HIV
† Yamasa Corporation.
‡ Kanazawa University.
agent by the United States Food and Drug Administra-
tion. On the basis of these considerations, our search
for new antineoplastic and antiviral agents has focused
on the synthesis of new nucleoside derivatives. Among
the numerous nucleoside analogues which have been
synthesized, 2′-deoxycytidine mimics are considered to
be very promising. The success of araC has prompted
many chemists to synthesize various 2′-substituted 2′-
deoxycytidine derivatives. As a result, several effective
derivatives have been found: 2′-deoxy-2′,2′-difluorocyti-
dine (gemcitabine, 2),3 1-(2-deoxy-2-C-methyl-â-D-ara-
bino-pentopuranosyl)cytosine (SMDC, 3),6 1-(2-C-cyano-
2-deoxy-â-D-arabino-pentofuranosyl)cytosine (CNDAC,
4),7 1-(2-deoxy-2-C-methylene-â-D-erythro-pentofurano-
syl)cytosine (DMDC, 5),8 and 1-(2-azido-2-deoxy-â-D-
arabinofuranosyl)cytosine (cytarazid, 6).9 These com-
pounds have been shown to possess a broad spectrum of
§ Hokkaido University.
X Abstract published in Advance ACS Abstracts, May 1, 1997.
(1) A part of this work has appeared: Yoshimura, Y.; Kitano, K.;
Satoh, H.; Watanabe, M.; Miura, S.; Sakata, S.; Sasaki, T.; Matsuda,
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S0022-3263(97)00054-6 CCC: $14.00 © 1997 American Chemical Society

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3141
Sch em e 1
potent antitumor activities against various solid tumors,
as well as leukemias.3,6-9
Another novel class of nucleoside antimetabolites is 4′-
thionucleosides. The first example of 4′-thionucleosides
was reported in 1964 by Reist et al., who synthesized the
4′-thio counterpart of naturally occurring adenosine.10 In
1968, 9-(4-thio-D-xylofuranosyl)adenine and 9-(4-thio-D-
arabinofuranosyl)adenine were synthesized.11 Since then,
several examples of 4′-thionucleosides have been re-
ported,12 including 4′-thio-araC (8), which is as active as
araC itself.13 However, the difficulty of synthesizing 4′-
thionucleosides has impaired further production of these
analogues, and only a few examples are known.14 More-
over, biologically interesting 2′-deoxy-4′-thionucleosides
had not been synthesized before 1990, except for a report
of a 5-fluorouracil derivative.14 In 1991, Walker15 and
Secrist16 independently reported the synthesis of pyri-
midine 2′-deoxy-4′-thionucleosides. The method devel-
oped by Walker, which included a new and efficient
synthesis of 2-deoxy-4-thioribose,17 was particularly use-
ful. At the same time, Uenishi and his co-workers
achieved an elegant, alternative synthesis of 2′-deoxy-
4′-thionucleosides using the Sharpless asymmetric ep-
oxidation.18 On the basis of these investigations, 2′-
deoxy-4′-thionucleosides have been shown to have potent
anti-herpes virus activities, and some analogues, espe-
cially 4′-thiothymidine and 2′-deoxy-4′-thiocytidine (9),
have been shown to possess potent cytotoxicity.15,16,18
Notably, the 4′-thionucleosides are resistant to hydrolytic
cleavage of glycosyl linkage catalyzed by nucleoside
phosphorylase.19 This is a major advantage of 4′-thio-
nucleosides, since several “4′-oxy” antivirals have fatal
drawbacks with regard to their metabolic stability caused
by nucleoside phosphorylase.20 In addition, the potent
antiviral activity and cytotoxicity of 4′-thionucleosides
suggest that they are well-recognized as substrates by
both viral and host cells kinases. Thus, the 4′-thio-
nucleosides have received considerable attention as
potential antiviral agents.21
The potent cytotoxicity of 2′-substituted cytidine ana-
logues and the specific properties of 4′-thionucleosides
prompted us to design and synthesize 2′-modified 2′-
deoxy-4′-thiocytidines 10-13 as potential antineoplastic
agents (Chart 1). As mentioned above, although several
alternative synthetic methods regarding 4′-thionucleo-
sides have been reported, these methods are limited to
the 2′-deoxy derivatives. Imbach and his colleagues22
reported the synthesis of 4′-thioribonucleosides using
the intramolecular Mitsunobu reaction as reported by
Walker.15 However, the choice of a 4′-thioribonucleoside
as a starting material might circumscribe the diversity
of 2′-substituents on 4′-thionucleosides: it would not be
applicable to the synthesis of 4′-thiogemcitabine, consid-
ering the original synthesis of the parental gemcitabine.3a
Thus, the development of a new synthetic method would
be a key to increasing the success of our project.
Str ategy for th e Syn th esis of 2′-Modified 2′-Deoxy-
4′-th iocytid in es. To prepare various 2′-deoxy-2′-sub-
stituted 4′-thiocytidines, a sole intermediate to which
various substituents could be introduced at the 2′-position
would be advantageous. Thus, the intermediate 14
should be ideal, if a glycosidic bond could be formed at
the R-methylene of the sulfide in this molecule (Scheme
1). The Pummerer rearrangement could be suitable for
introducing a base moiety at the 1-position of 14.
Considering the synthesis of intermediate 14, a recent
work on the synthesis of 3TC conducted by Chu et al.
was suggestive.5d They used an anhydrothiosugar (18)
to construct the oxathiolane skeleton of 3TC5d (Scheme
(7) (a) Matsuda, A.; Nakajima, Y.; Azuma, A.; Tanaka, M.; Sasaki,
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795. (b) Van Draanen, N. A.; Freeman, G. A.; Short, S. A.; Harvey, R.;
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L. Nucleosides Nucleotides 1994, 13, 2035-2050.

3142 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
derivative developed by Matsuda et al.8 which has potent
antineoplastic activity both in vitro and in vivo. Thus,
4′-thioDMDC should also be a potential antineoplastic
agent. The secondary hydroxyl group of 15 was oxidized
with DMSO-Ac2O,24 to give 25, which, without purifica-
tion, was treated with methylenetriphenylphosphorane
to give 26 in 74% yield from 15 (Scheme 5). Compound
26 was oxidized with m-CPBA to the corresponding
sulfoxide, which was treated with Ac2O at 110 °C to give
exclusively one product (27), but not the desired 28
(Chart 2). This was confirmed by 1H and 13C NMR
Sch em e 2
1
spectra: in the H NMR spectrum, a new singlet signal,
with 2H integration, at 4.65 ppm was observed instead
of exo-methylene signals. In addition, 13C NMR of 27
showed three peaks which corresponded to methylene
carbons (C2, C5, and benzyl methylene) at 70.18, 64.84,
and 61.02 ppm (confirmed by the DEPT spectrum, data
not shown). This result showed that Pummerer rear-
rangement had occurred at the allylic position.25 We
concluded that 27 may be a substrate for the glycosyla-
tion reaction, since similar reactions have recently been
reported.26 Treatment of 27 with a trimethylsilylated N4-
acetylcytosine and trimethylsilyl trifluoromethanesulfonate
(TMSOTf) at 0 °C gave the 4′-thioDMDC analogue 29 in
25% yield (3.8:1 mixture of the anomers) along with 30
(26% yield) which was attacked at the allylic position.
The formation of 30 increased with a prolonged reaction
time and an increase in the reaction temperature (data
not shown). This tendency suggested the possibility that
30 may have an O-alkylated structure, which might arise
from an allylic rearrangement of 29. However, the UV
spectra of 30, which were consistent with those of 29 in
both neutral and acidic methanol, suggest an N-glyco-
sylated structure (see Experimental Section). In the
HMBC spectrum of 30, cross peaks corresponding to 2′-
CH2/C-2 and C-6 were observed (data not shown). Since
this ruled out the O-alkylated structure, the structure
of 30 was unambiguously determined, as depicted in
Scheme 5.
Although several attempts were made to deprotect the
benzyl group of 29, none of the reaction conditions gave
the debenzylated product, due to the instability of 29
under these conditions. Thus, it was necessary to remove
the benzyl group prior to glycosylation. The reaction of
26 with boron trichloride (BCl3)27 proceeded smoothly to
give the debenzylated product 31 at over 90% efficiency
(Scheme 6). Pioneering works of Kita et al. led to the
application of the Pummerer reaction to the synthesis of
a C-C bond at the R-position of sulfoxides.28 O’Neil and
Hamilton also reported the syntheses of a tetrahy-
drothienylthymine and other derivatives using TMSOTf
as a catalyst under similar reaction conditions.29 On the
basis of these reactions, we designed an alternative
synthesis of 4′-thioDMDC which used sulfoxide 32 ob-
tained from m-CPBA oxidation of 31. Compound 32 was
treated with silylated N4-acetylcytosine (3 equiv) and
2). Following Chu’s tactics, three sets of chiral centers
at the 2′-, 3′-, and 4′-positions of 4′-thionucleosides could
be transferred from the chiralities of the 4-, 3-, and
5-carbons of inexpensive D-glucose via anhydrothiosugar
16. This encouraged us to synthesize the title compounds
by using a readily available D-glucose as a starting
material.
Syn th esis of th e 4-Th iosu ga r P or tion . Diisopro-
pylideneglucose 17 was converted to 3-O-benzylxylose 21
using known chemistry. 3-O-Benzylxylose 21 was then
subjected to acidic methanolysis to produce an anomeric
mixture of methyl 3-O-benzylxyloside (22) in high yield
(Scheme 3). The anomers were easily separated by a
silica gel column. The separated R- and â-anomers of 22
were mesylated, which produced R- and â-23, and then
treated with sodium sulfide in DMF to yield bicyclic R-
and â-16 in yields of 78 and 73%, respectively. We found
that R-16 was less stable than â-16 and was converted
to â-16 if allowed to stand in CDCl3 overnight. This
means that the conversion of R- to â-16 occurred under
slightly acidic conditions. In addition, â-16 was detected
on TLC when R-23 was reacted with sodium sulfide in
DMF, but no R-16 was formed in the reaction of â-23
under the same conditions. These results suggest that
steric repulsion between 1-OMe and H-3 could make R-16
unstable and accelerate the conversion of the R- to the
â-anomer, as shown in Scheme 4.
During the course of our investigation, Yuasa et al.
independently reported the synthesis of â-16, in which
they synthesized â-16 in moderate yield by the intramo-
lecular cyclization of methyl 3,5-di-O-benzyl-5-(benzylthio)-
R(and â)-D-xylofuranoside with an iodine, triphenylphos-
phine, and imidazole system.23 They reported that â-16,
but no R-16, was formed in moderate yield from the
reaction. They reasoned that the transition state of the
R-isomer lacked an anomeric effect, which made the
formation of R-16 unfavored. However, our experimental
results show that R-16 is unstable and is easily converted
to â-16. Thus, even in Yuasa’s case, it is likely that R-16,
which would be formed by the cyclization reaction of
methyl 5-(benzylthio)-R-D-xylofuranoside, would readily
be anomerized and converted to its â-isomer. This might
result in the predominant formation of â-16, as described
above. Hydrolysis of R,â-16, followed by borohydride
reduction, gave 1,4-anhydro-4-thioarabitol 24 in 90%
yield. The primary alcohol of 24 was selectively protected
with a tert-butyldiphenylsilyl (TBDPS) group to give the
common intermediate 15 in 87% yield.
(24) Yuasa, H.; Tamura, J .; Hashimoto, H. J . Chem. Soc. Perkin
Trans. 1 1990, 2763-2769.
(25) A 1,4 Pummerer reaction has already been reported: Koppel,
G. A.; McShane, L. J . J . Am. Chem. Soc. 1978, 100, 288-289.
(26) Booma, C.; Balasubramanian J . Chem. Soc., Chem. Commun.
1993, 1394-1395.
(27) Kakefuda, A.; Shuto, S.; Nagahata, T.; Seki, J .; Sasaki, T.;
Matsuda, A. Tetrahedron 1994, 507 10167-10182.
(28) (a) Kita, Y.; Yasuda, H.;Tamura, O.; Itoh, F.; Tamura, Y.
Tetrahedron Lett. 1984, 25, 4681-4682. (b) Kita, Y.; Tamura, O.;
Yasuda, H.; Itoh, F.; Tamura, Y. Chem. Pharm. Bull. 1985, 33, 4235-
4241.
Syn th esis of 4′-Th ioDMDC. As a first target among
2′-modified 2′-deoxy-4′-thiocytidine analogues, we chose
a 4′-thio analogue of DMDC. DMDC is a 2′-deoxycytidine
(23) Yuasa, H.; Kajimoto, T.; Wong, C.-H. Tetrahedron Lett. 1994,
35, 8243-8246.
(29) O’Neil, I. A.; Hamilton, K. M. Synlett 1992, 791-792.

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3143
Sch em e 3a
a
(a) BnBr, NaH, DMF, THF; (b) 2 M HCl, THF; (c) NaIO4, H2O, MeOH; (d) NaBH4, MeOH, 84% from 17; (e) 5% HCl/MeOH, 91%; (f)
MsCl, pyridine; (g) Na2S, DMF, 100 °C, 78% (R-anomer) and 73% (â-anomer) from 22; (h) 4 M HCl, THF; (i) NaBH4, MeOH, 90% from 16;
(j) TBDPSCl, imidazole, DMF, 87%.
Sch em e 4
Sch em e 6a
Sch em e 5a
a
(a) BCl3, CH2Cl2, -78 °C, then MeOH, pyridine, 92%; (b)
m-CPBA, CH2Cl2, -78 °C; (c) silylated N4-acetylcytosine, TMSOTf,
ClCH2CH2Cl, 0 °C, 74% from 31; (d) TBAF, THF; (e) aqueous NH3,
MeOH, then HPLC separation, 34% (R-anomer) and 13% (â-
anomer) from 33.
a
(a) Ac2O, DMSO; (b) Ph3P+CH3Br-, NaH, tert-amyl alcohol,
the mixture by HPLC (R, 34%; â, 13%). R,â-Stereochem-
istry was assessed by NOE experiments of the separated
isomers.30 Comparison of the chemical shift of the H-4′
proton could be more convenient. In general, the reso-
nance of each H-4′ proton in R-10 was shifted downfield,
compared with that of â-10, due to the deshielding effect
of the C2-keto group of the pyrimidine ring.31 A similar
tendency was observed with the other 2′-modified deriva-
tives of 2′-deoxy-4′-thiocytidine described below.
THF, 74% from 15; (c) m-CPBA, CH2Cl2, -78 °C; (d) Ac2O, 110
°C, 68%; (e) silylated N4-acetylcytosine, TMSOTf, ClCH2CH2Cl,
29 (25%) and 30 (24%).
Ch a r t 2
Syn th esis of 4′-Th iogem cita bin e. To clarify the
scope and limitations of our new strategy, this method
was applied to the synthesis of other 2′-modified 4′-
thiocytidines. We aimed at the synthesis of 4′-thiogem-
citabine as a second example. Like DMDC, gemcitabine
has prominent antineoplastic activities against various
solid tumors, as well as leukemias,3b and has shown
promising antitumor activities in clinical trials.32 In fact,
gemcitabine has been approved for the treatment of non-
TMSOTf (2 equiv) to produce the 4′-thioDMDC derivative
R,â-33 in 74% yield (R:â ) 2.5:1).30 Formation of allylic-
substituted product was negligible. However, â-selective
formation of 33 remains a problem. Finally, the R,â-
mixture of 33 was deprotected by tetrabutylammonium
fluoride (TBAF) followed by aqueous ammonia in metha-
nol. Pure R- and â-anomers of 10 were obtained from
(30) The stereochemistry at the anomeric carbon was determined
by an NOE analysis of the free nucleoside 10 (minor isomer). It showed
7.1% NOE at the H-3′ proton when irradiated H-6.
(31) (a) Okabe, M.; Sun, R.-C.; Tam, S. Y.-K.; Todaro, L. J .; Coffen,
D. L. J . Org. Chem. 1988, 53, 4780-4786. (b) Brånalt, J .; Kvarnstro¨m,
I.; Classon, B.; Samuelsson, B. J . Org. Chem. 1996, 61, 3604-3610.

3144 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
antitumor activities.37 On the other hand, a series of 2′-
fluoroarabinonucleosides are well-known as potent an-
tiviral nucleosides, e.g., 1-(2-deoxy-2-fluoro-â-D-arabino-
furanosyl)-5-iodocytosine (FIAC) and 1-(2-deoxy-2-fluoro-
â-D-arabinofuranosyl)thymine (FMAU).38 The latter also
has antitumor activity against murine leukemia.39 There-
fore, 4′-thio analogues of this class of nucleosides are
promising as both antitumor and antiviral antimetabo-
lites. In addition, to study the structure-activity rela-
tionship of the 2′-substituents of 2′-deoxy-4′-thiocytidines,
a comparison of biological activities between di- and
monosubstituted derivatives would be important. Hence,
we sought to synthesize 4′-thioFAC as an antitumor
candidate.
Sch em e 7a
To prepare 4′-thioFAC, we envisaged the introduction
of a fluorine atom at the 2-position of 15 with a retention
of stereochemistry. Marquez and his co-workers reported
that treatment of 1-(5-O-trityl-3-deoxy-4-thio-threo-pento-
furanosyl)uracil with DAST gave the 2′-fluorinated 4′-
thionucleoside with “threo” stereochemistry.40 This result
showed that the reaction proceeded via an episulfonium
intermediate.40,41 The ring sulfur atom is known to play
a role in the case of a 4-thiosugar, which results in the
formation of ring-contracted products.24,41 Indeed, treat-
ment of 15 with DAST produced a 2-deoxy-2-fluoro deri-
vative 40 (69% yield) with an “arabino” configuration,
which was confirmed after conversion to a free nucleoside
(12) (vide infra). This result shows that the expected epi-
sulfonium intermediate 39 was generated in situ (Scheme
8). In the case of 4′-thioDMDC and 4′-thiogemcitabine,
we have successfully applied a Pummerer-type glycosy-
lation using the sulfoxides as glycosyl donors. However,
similar reaction of the sulfoxide 41, which was obtained
from m-CPBA oxidation of 40, resulted in the exclusive
formation of the R-isomer (data not shown). To improve
the â-selective formation of 43, we planned to use 1-O-
acetate 42 for the glycosylation reaction. The Pummerer
rearrangement of 40 gave 42 in a 54% yield as an
anomeric mixture. Compound 42 was treated with the
silylated N4-acetylcytosine in the presence of SnCl4 to
give an anomeric mixture of 2′-deoxy-2′-fluoro-4′-thiocy-
tidines 43 in 93% yield (R:â ) 2.9:1). Stepwise depro-
tection of 43 [1. BBr3, 2. NH4F in MeOH, 3. concentrated
NH4OH in MeOH], followed by reversed-phase column
chromatography, gave pure R- and â-12 (R, 43%; â, 17%).
As in the case described above, the structure of â-12 was
unambiguously confirmed by an NOE experiment (Figure
1). NOE between H-2′ and H-4′ clearly indicates the 2′-
“up” configuration of the molecule. This is also supported
by a potent enhancement of the H-2′ signal with irradia-
tion at the 1′ proton. Similarly, â-stereochemistry at the
anomeric carbon was confirmed by an NOE of 8.0% at
the H-3′ signal when H-6 was irradiated.
a
(a) DAST, benzene, 0 °C, then room temperature 48%; (b) BCl3,
CH2Cl2, -78 °C, then MeOH, pyridine; (c) Bz2O, Et3N, DMAP,
CH3CN, 79% from 34; (d) m-CPBA, CH2Cl2, -78 °C; (e) silylated
N4-acetylcytosine, TMSOTf, ClCH2CH2Cl, 0 °C, 57% from 36; (f)
TBAF, THF; (g) aqueous NH3, MeOH, then HPLC separation, 36%
(R-anomer) and 15% (â-anomer) from 38.
small cell lung carcinoma (NSCLC) and pancreatic cancer
in Europe.
DAST treatment33 of ketone 25 produced the 2-deoxy-
2,2-difluoro derivative 34 in 48% yield. To circumvent
the problem described above, 34 was simultaneously
deprotected and benzoylated to give 36 (Scheme 7), which
was oxidized to produce 37. Pummerer-type glycosyla-
tion of 37 was used as with 4′-thioDMDC, since the 1-O-
acetyl derivative of 36 resisted Lewis acid-mediated
glycosylation due to the difluoro substituent at the
2-position (data not shown).34 Reaction of 37 with
silylated N4-acetylcytosine in the presence of TMSOTf
resulted in a 57% yield of protected 4′-thiogemcitabine
38 as an anomeric mixture (R:â ) 2.6:1).35 Deprotection
of 38, followed by HPLC separation, gave the R- and
â-derivatives of 4′-thiogemcitabine 11.
Syn th esis of 2′-Deoxy-2′-flu or o-4′-th ioa r a bin osyl-
cytosin e (4′-Th ioF AC). Monofluorosubstituted nucleo-
sides, especially those with an “arabino” configuration,
are also quite attractive. In 1970, 2′-deoxy-2′-fluoroara-
binosylcytosine (FAC) was synthesized as an araC mimic36
and was shown to have anti-leukemic activity.36a Ad-
enine analogues of this class of nucleosides are also
interesting: 2-chloro-9-(2-deoxy-2-fluoroarabinofurano-
syl)adenine (Cl-F-araA) has been shown to have potent
(32) (a) Abbruzzese, J . L.; Grunewald, R.; Weeks, E. A.; Gravel, D.;
Adams, T.; Nowak, B.; Mineishi, S.; Tarassoff, P.; Satterlee, W.; Raber,
M. N.; Plunkett, W. J . Clin. Oncol. 1991, 9, 491-498. (b) Poplin, E.
A.; Corbett, T.; Flaherty, L.; Tarassoff, P.; Redman, B. G.; Valdivieso,
M.; Baker, L. Invest. New Drugs 1992, 10, 165-170. (c) Lund, B.;
Kristjansen, P. E. G.; Hansen, H. H. Cancer Treat. Rev. 1993, 19, 45-
55.
(33) An, S.-H.; Bobek, M. Tetrahedron Lett. 1986, 27, 3219-3222.
(34) Difluoro substituent at the 2′-position potentiates the stability
of the glycosidic bond, due to its potent -I effect with destabilizing
â-cation.
(35) The stereochemistry at the 1′-position was determined, after
deprotection, by comparison of coupling constants of H-1′ with that of
gemcitabine described in ref 3a.
(36) (a) Wright, J . A.; Wilson, D. P.; Fox, J . J . J . Med. Chem. 1970,
13, 269-272. (b) Reichman, U.; Watanabe, K. A.; Fox, J . J . Carbohydr.
Res. 1975, 42, 233-240.
(37) (a) Secrist, J . A.; Shortnacy, A. T.; Montgomery, J . A. J . Med.
Chem. 1988, 31, 405-410. (b) Montgomery, J . A.; Shortnacy-Fowler,
A. T.; Clayton, S. D.; Riordan, J . M.; Secrist, J . A. J . Med. Chem. 1992,
35, 397-401. (c) Carson, D. A.; Wasson, D. B.; Esparza, L. M.; Carrera,
C. J .; Kipps, T. J .; Cottam, H. B. Proc. Natl. Acad. Sci. U.S.A. 1992,
89, 2970-2974.
(38) (a) Watanabe, K. A.; Reichmen, U.; Hirota, K.; Lopez, C.; Fox,
J . J . J . Med. Chem. 1979, 22, 21-24. (b) Watanabe, K. A.; Su, T.-L.;
Klein, R. S.; Chu, C. K.; Matsuda, A.; Chun, M. W.; Lopez, C.; Fox, J .
J . J . Med. Chem. 1983, 26, 152-156.
(39) Burchenal, J . H.; Chou, T.-C.; Lokys, L.; Smith, R. S.; Watanabe,
K. A.; Su, T.-L.; Fox, J . J . Cancer Res. 1982, 42, 2598-2600.
(40) J eong, L. S.; Nicklaus, M. C.; George, C.; Marquez, V. E.
Tetrahedron Lett. 1994, 35, 7569-7572.
(41) Hughes, N. A.; Kuhajda, K.-M.; Miljkovic, D. A. Carbohydr. Res.
1994, 257, 299-304.

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3145
Sch em e 8a
a
(a) DAST, CH2Cl2, -78 °C, 77%; (b) m-CPBA, CH2Cl2, -78 °C; (c) Ac2O, 100 °C, 77% from 40; (d) silylated N4-acetylcytosine, SnCl4,
CH3CN, 93%; (e) BBr3, then MeOH, saturated NaHCO3; (f) NH4F, MeOH, 60 °C; (g) aqueous NH3, MeOH, then ODS column separation,
43% (R-anomer) and 17% (â-anomer) from 43.
Sch em e 9a
F igu r e 1. Summary of NOE experiment of â-12.
Syn th esis of 2′-Azid o-2′-d eoxy-4′-th iocytid in e. As
a final target of our project, we intended to synthesize
4′-thiocytarazid. Akin to the 2′-deoxycytidine analogues
described above, cytarazid, which has an azido group at
the 2′-position with an arabino configuration, possesses
potent antineoplastic activity.9 Successful introduction
of a fluorine substituent with a retention of stereochem-
istry encouraged us to apply the Mitsunobu reaction to
prepare 4′-thiocytarazid. The Mitsunobu reaction of
intermediate 15 using diphenylphosphoryl azide (DPPA)9b
efficiently achieved the introduction of an azido group
a
(a) DPPA, DEAD, Ph3P, THF, 80%; (b) m-CPBA, CH2Cl2, -78
°C; (c) silylated N4-acetylcytosine, TMSOTf, ClCH2CH2Cl, 0 °C,
20% from 45; (d) Ac2O, 100 °C; 67% from 45; (e) silylated
N4-acetylcytosine, TMSOTf, ClCH2CH2Cl, 0 °C, 59% from 48.
at the 2-position (80% yield, Scheme 9). The resulting
product 45 consisted of only a single stereoisomer.
However, we could not determine the stereochemistry at
C-2 because 45 was not suitable for an NOE experiment,
due to overlapping of the H-2 proton with H-4 and H-5
(see Experimental Section). The difficulty of assigning
the stereochemistry forced us to convert 45 to 4′-thio-
nucleoside 47, the stereochemistry of which we attempted
to determine. The Pummerer-type glycosylation of 45 via
sulfoxide 46 gave an unsatisfactory result, with a low
yield of 47. On the other hand, the usual glycosylation
reaction via 1-O-acetate 48, as in the case of 4′-thioFAC,
gave 47 in 59% yield. In contrast with the examples
described above, the R,â-ratio of 47 was almost 1:1 in the
glycosylation reaction and did not depend on the glycosyl
donors (1-O-acetate vs sulfoxide). However, deprotection
of the benzyl groups of 47 and 45 was not successful.
Furthermore, 47 was an inseparable mixture of R,â-
anomers, so that its 1H NMR spectrum was rather
complicated and not suitable for an NOE experiment.
Failing to obtain a free 4′-thionucleoside, we changed
the substrate of the Mitsunobu reaction, in that the
protecting group at the 3-position was changed from
benzyl to an appropriate group. As shown in Scheme 10,
3-benzoylated derivative 53 was prepared from 15 in five
steps. Bis-silyl-protected 49 was debenzylated and sub-
sequently benzoylated to give 51. The silyl protecting
group of 51 was removed with ammonium fluoride in
MeOH,42 and selective protection of the primary hydroxyl
group of 52 gave 53 (62% from 15). The Mitsunobu
reaction of 53 gave a single stereoisomer (54), as in the
case of 45, in 83% yield. Surprisingly, the results of an
NOE experiment of 54 revealed that the products had a
(42) Zhang, W.; Robins, M. J . Tetrahedron Lett. 1992, 33, 1177-
1180.

3146 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
Sch em e 10a
F igu r e 2. Summary of NOE experiment of â-58.
Ta ble 1. An tin eop la stic Activities of 2′-Mod ified
4′-Th ion u cleosid es
antineoplastic activities IC50
(µg/mL)
CCRF-HSB-2a
comp
(anomer)
2′-substituent
KB cellsb
10 (R)
10 (â)
11 (R)
11 (â)
12 (R)
12 (â)
58 (R)
58 (â)
araC
dCH2
dCH2
F2
F2
F (arabino)
F (arabino)
N3 (ribo)
N3 (ribo)
>10
NDc
0.12
ND
17
ND
0.015
ND
82
0.0091
>10
1.5
>10
0.051
>10
8.6
0.052
0.022
0.26
0.44
DMDC
a
b
MTT assay.44 Dye uptake method.44 c Not determined.
The 5′-O-silyl group of the resulting 4′-thionucleoside
56 was deprotected with ammonium hydrogen fluoride
in MeOH. The mixture of R- and â-isomers of 57 could
easily be separated by silica gel column chromatography
(R, 43%; â, 45%), and the separated anomers were
converted to their free nucleosides 58 with aqueous
ammonia (R, 87%; â, 97%; from R- and â-57, respectively).
The NOE experiment of â-53 supported its structure, e.g.,
â-stereochemistry at the 1′-position and a ribo configu-
ration (Figure 2).
a
(a) TBSOTf, pyridine, CH2Cl2, (b) BCl3, CH2Cl2, -78 °C, then
MeOH, pyridine; (c) Bz2O, Et3N, DMAP, CH3CN, 93% from 15;
(d) NH4F‚HF, MeOH, 89%; (e) TBSCl, imidazole, DMF, 80%; (f)
DPPA, DEAD, Ph3P, THF, 83%; (g) m-CPBA, CH2Cl2, -78 °C; (h)
Ac2O, 100 °C, 53%; (i) silylated N4-acetylcytosine, TMSOTf,
ClCH2CH2Cl, 0 °C, 47%; (j) NH4F‚HF, MeOH, then silica gel
column separation, 43% (R-anomer) and 45% (â-anomer); (k)
aqueous NH3, MeOH, 87% (R-anomer) and 97% (â-anomer).
Biologica l Asp ects of 2′-Mod ified 4′-Th ion u cleo-
sid es. Antineoplastic activities of 2′-modified 2′-deoxy-
4′-thiocytidines were evaluated44 and are summarized in
Table 1. All of the R-anomers of 2′-deoxy-4′-thiocytidine
derivatives were inactive against human T-cell leukemia
CCRF-HSB-2 cells. In contrast, the â-4′-thiocytidines
showed significant cytotoxicity against the same cell line.
â-4′-ThioDMDC (10) and â-4′-thioFAC (12) had especially
potent antileukemic activities. These results suggest
that the â-configuration of 4′-thiocytidines is essential
for their cytotoxicity. Both 4′-thioDMDC (10) and 4′-
thioFAC (12) were also effective against human solid
tumor KB cells. The cytotoxicity of 4′-thioFAC (12) is
particularly noteworthy, and even 4′-thioDMDC (10) has
a greater activity against the same cell line than does
the parental DMDC (5) (IC50 ) 0.44 µg/mL). In contrast,
â-4′-thiogemcitabine (11) and â-2′-azido-4′-thiocytidine
(58), the latter of which has an unexpected ribo config-
uration, were rather inactive. This result shows that the
arabino configuration is also important for cytotoxicity,
as in the usual 4′-oxy counterparts. It is interesting that
4′-thioDMDC (10) has potent antineoplastic activity,
while 4′-thiogemcitabine (11) does not, even though both
of the parent compounds DMDC (5) and gemcitabine (2)
are highly active.3,8 One plausible explanation for this
difference is that the efficacy of phosphorylation of these
analogues by deoxycytidine kinase, a key enzyme which
ribo, rather than an arabino, configuration.43 Compound
54 was further converted to 1-O-acetoxy derivative 55,
by Pummerer rearrangement, which was in turn sub-
jected to Lewis acid-mediated glycosylation to give 56
(efficiency: 47%) as a 1:1 mixture of R,â-anomers.
Comparison of the 1H NMR spectra of 3-benzoyl 54 and
3-benzyl 45 (see Experimental Section) confirms their
ribo configurations at the 2-position. This strongly
suggests that the Mitsunobu reaction occurred without
participation of an episulfonium ion in both cases. This
is also implied by the results of the R/â ratio of the
glycosylation reaction and the resistance to the depro-
tection of benzyl groups. It is noteworthy that the mode
of the Mitsunobu reaction is opposite that of a DAST
reaction: in the DAST reaction of 15, nucleophilic attack
of the fluorine atom to the 2-position is rate-limiting due
to its weak nucleophilicity. Thus, the contribution of the
neighboring sulfur atom, as reported in the literature,40
lowered the transition energy even though the intermedi-
ate episulfonium ion is highly strained. In sharp con-
trast, nucleophilic attack of the azide anion is faster than
that of the fluoride anion and is even faster than the
attack of the sulfur atom. Thus, the contribution by way
of the strained episulfonium ion is not significant in the
Mitsunobu reaction of 53. As a consequence, the reaction
proceeds with inversion.
(44) Yoshimura, Y.; Kano, F.; Miyazaki, S.; Ashida, N.; Sakata, S.;
Haraguchi, K.; Itoh, Y.; Tanaka, H.; Miyasaka, T. Nucleosides Nucle-
otides 1996, 15, 305-324.
(43) The stereochemistry of 54 was determined by an NOE analy-
sis: a 1.5% NOE at H-5a was observed when H-2 was irradiated.

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3147
converts 2′-deoxycytidine analogues such as araC,2 DM-
DC,8 CNDAC,7 and gemcitabine3 to their corresponding
monophosphates, is different in the 4′-thiocytidine de-
rivatives. The potent antitumor activities of 4′-thioD-
MDC (10) and 4′-thioFAC (12) were further confirmed
by in vivo assay.45,46
In conclusion, we have designed and synthesized a
novel class of 2′-modified 2′-deoxy-4′-thiocytidines which
have methylene, azido, and both di- and monofluoro
groups at the 2′-position. To prepare these derivatives,
we developed a new synthetic route involving 2′-modified
2′-deoxy-4′-thionucleosides, starting from D-glucose. This
should be a useful and general method for the synthesis
of 2′-modified 2′-deoxy-4′-thionucleosides. Among the 2′-
deoxy-4′-thiocytidines synthesized, 4′-thioDMDC and 4′-
thioFAC were shown to have potent antineoplastic
activities. Further evaluation of these compounds is
underway, and the results will be reported elsewhere.
MeOH (150 mL), and the mixture was stirred at room
temperature for 3 h. The reaction was quenched with NaH-
CO3, and precipitates were removed by filtration. The filtrate
was concentrated. The residue was purified by column chro-
matography over silica gel (8.3 × 12 cm; 0-1-2-4% MeOH
in CHCl3). The less polar fraction contained â-22 (8.04 g), and
the more polar fraction contained R-22 (6.49 g, total 91%).
Da ta for r-22: 1H NMR (CDCl3) δ 7.38-7.29 (5H, m), 4.80
(1H, d, J ) 2.4 Hz), 4.72 (1H, d, J ) 11.7 Hz), 4.59 (1H, d, J
) 11.7 Hz), 4.35 (1H, ddd, J ) 4.4, 4.9, 6.8 Hz), 4.31 (1H, ddd,
J ) 2.4, 3.9, 4.8 Hz), 4.10 (1H, dd, J ) 3.9, 6.8 Hz), 3.80 (1H,
ddd, J ) 4.9, 6.6, 11.7 Hz), 3.76 (1H, ddd, J ) 4.4, 6.6, 11.7
Hz), 3.43 (3H, s), 2.56 (1H, t, J ) 6.6 Hz, D2O exchangeable),
2.27 (1H, d, J ) 4.8 Hz, D2O exchangeable); EI-MS m/ z 254
(M+). Anal. Calcd for C13H18O5‚0.25H2O: C, 60.34; H, 7.21.
Found: C, 60.08; H, 7.49. Da t a for â-22: mp 103-104 °C
1
(crystallized from hexane-AcOEt); H NMR (CDCl3) δ 7.39-
7.29 (5H, m), 4.96 (1H, d, J ) 4.9 Hz), 4.85 (1H, d, J ) 12.0
Hz), 4.61 (1H, d, J ) 12.0 Hz), 4.29 (1H, dt, J ) 4.9, 8.8 Hz),
4.26-4.23 (1H, m), 4.14 (1H, dd, J ) 4.9, 6.8 Hz), 3.84 (1H,
ddd, J ) 3.9, 4.9, 12.7 Hz), 3.77 (1H, ddd, J ) 4.4, 8.3, 12.7
Hz), 3.47 (3H, s), 2.66 (d, 1H, J ) 8.8 Hz, D2O exchangeable),
2.41 (1H, dd, J ) 4.9, 8.3 Hz, D2O exchangeable); EI-MS m/ z
254 (M+). Anal. Calcd for C13H18O5: C, 61.41; H, 7.13.
Found: C, 61.57; H, 7.43.
Exp er im en ta l Section
Gen er a l. Melting points are uncorrected. 1H NMR spectra
were recorded at 400 MHz (1H) and at 100 MHz (13C) using
CDCl3 or DMSO-d6 with TMS as internal standard. Mass
spectra were obtained by fast atom bombardment (FAB) mode.
Silica gel for chromatography was Merck kieselgel 60.
Met h yl 2,5-An h yd r o-3-O-b en zyl-2,5-d id eoxy-2-t h io-r-
D-a r a bin o-p en tofu r a n osid e (r-16). A mixture of MsCl (5.60
mL, 72.4 mmol) and R-22 (6.13 g, 24.1 mmol) in pyridine (60
mL) was stirred at room temperature for 1 h. H2O was added
to the mixture, and the solvent was removed under reduced
pressure. The residue was partitioned between AcOEt and
H2O. The organic phase was washed with saturated NaHCO3
and brine and then dried (Na2SO4). After concentration, the
residue was dissolved in DMF (80 mL). To the mixture was
added sodium sulfide (8.68 g, 36.2 mmol), and the mixture was
kept at 100 °C for 1 h. After the solvent was removed under
reduced pressure, the residue was partitioned between AcOEt
and H2O. The organic phase was washed with H2O (×3) and
brine and then dried (Na2SO4). After the solvent was removed
under reduced pressure, the residue was purified by column
chromatography over silica gel (4.7 × 16 cm; 10-20% AcOEt
in hexane) to give R-16 (4.75 g, 78%) as an oil: 1H NMR
(CDCl3) δ 7.39-7.30 (5H, m), 5.13 (1H, d, J ) 2.4 Hz), 4.66
(1H, d, J ) 11.7 Hz), 4.53 (1H, d, J ) 11.7 Hz), 4.36-4.35
(1H, br m), 4.29 (1H, t, J ) 2.4 Hz), 3.51 (1H, t, J ) 2.4 Hz),
3.47 (3H, s), 3.04 (1H, dd, J ) 2.2, 10.5 Hz), 2.95 (1H, dd, J )
1.2, 10.5 Hz); EI-MS m/ z 252 (M+). Anal. Calcd for
C13H16O3S‚0.25H2O: C, 60.80; H, 6.48. Found: C, 60.68; H,
6.34.
Meth yl 2,5-An h yd r o-3-O-ben zyl-2,5-d id eoxy-2-th io-â-D-
a r a bin o-p en tofu r a n osid e (â-16). Compound â-16 was syn-
thesized as described for the preparation of R-16. After
purification by silica gel column chromatography, â-16 (73%)
was obtained as an oil: 1H NMR (CDCl3) δ 7.36-7.29 (5H,
m), 4.89 (1H, s), 4.62 (1H, d, J ) 11.7 Hz), 4.52-4.48 (2H, m),
4.37-4.36 (1H, m), 3.34 (4H, s), 3.04 (1H, dd, J ) 2.0, 10.3
Hz), 2.77 (1H, dd, J ) 1.5, 10.3 Hz); EI-MS m/ z 252 (M+).
Anal. Calcd for C13H16O3S‚0.2H2O: C, 61.01; H, 6.46.
Found: C, 61.05; H, 6.34.
1,4-An h yd r o-3-O-ben zyl-4-th io-D-a r a bitol (24). A solu-
tion of 16 (9.50 g, 1:1 mixture of R- and â-anomers, 37.7 mmol)
in THF (200 mL) and aqueous HCl (4 M, 100 mL) was stirred
at room temperature for 1 h. The reaction was quenched with
NaHCO3. Precipitates were removed by filtration, and THF
was removed under reduced pressure. The whole was ex-
tracted with CHCl3 (×2) and dried (Na2SO4). After concentra-
tion, the residue was dissolved in MeOH (150 mL), and NaBH4
(1.43 g, 37.7 mmol) was added at 0 °C. After being stirred at
0°C for 45 min, the reaction was quenched by AcOH. After
concentration, the residue was partitioned between CHCl3 and
H2O. The water phase was extracted with CHCl3 (×2), and
the combined organic phase was washed with brine and dried
(Na2SO4). After the solvent was removed under reduced
pressure, the residue was purified by column chromatography
over silica gel (6.3 × 13 cm; 20-33-50% AcOEt in hexane) to
give 24 (8.18 g, 90%) as a syrup: 1H NMR (CDCl3) δ 7.38-
3-O-Ben zyl-1,2-O-isop r op ylid en e-r-D-xylo-p en t ofu r a -
n ose (21). A mixture of 1,2:5,6-di-O-isopropylideneglucose
(17) (20.0 g, 76.9 mmol) and added 60% NaH (3.69 g, 92.2
mmol) in THF (150 mL) was stirred for 30 min. DMF (50 mL)
and benzyl bromide (13.7 mL, 115 mmol) were added to this
mixture, and the whole was stirred at room temperature for 2
h. The reaction was quenched by the addition of AcOH. The
solvent was evaporated under reduced pressure. After water
workup, the concentrated residue was purified by column
chromatography over silica gel (7.9 × 14 cm; 2-10% AcOEt
in hexane) to give 18 (26.1 g, 97%) as an oil. A mixture of
3-benzyl derivative 20 (26.1 g, 74.5 mmol) in THF (200 mL)
and aqueous HCl (2 M, 200 mL) was stirred at room temper-
ature overnight. After neutralization by NaHCO3, precipitates
were removed by filtration. The filtrate was concentrated
under reduced pressure. The residue was extracted with
CHCl3, dried (Na2SO4), and concentrated. The residue was
dissolved in MeOH (100 mL). An aqueous solution of NaIO4
(17.5 g) in H2O (100 mL) was added to this mixture. After
being stirred for 30 min at room temperature, the reaction was
quenched by glycerin (5 mL). Precipitates were removed by
filtration, and the filtrate was concentrated. The residue was
dissolved in MeOH (100 mL), and NaBH4 (2.82 g) was added
at 0 °C. The mixture was stirred at 0 °C for 30 min and
neutralized by AcOH. The solvent was removed under reduced
pressure. The residue was partitioned between AcOEt and
H2O. The organic phase was washed with brine and dried
(Na2SO4). After the filtrate was concentrated under reduced
pressure, the residue was purified by column chromatography
over silica gel (3.7 × 17 cm; 33-50% of AcOEt in hexane) to
give 21 (17.6 g, 84%): 1H NMR (CDCl3) δ 7.39-7.30 (5H, m),
5.99 (1H, d, J ) 3.9 Hz), 4.72 (1H, d, J ) 11.7 Hz), 4.64 (1H,
d, J ) 11.7 Hz), 4.28 (1H, dt, J ) 3.4, 4.9 Hz), 4.02 (1H, d, J
) 3.4 Hz), 3.94 (1H, ddd, J ) 3.9, 4.9, 12.2 Hz), 3.85 (1H, ddd,
J ) 4.9, 8.8, 12.2 Hz), 2.11 (1H, dd, J ) 3.9, 8.8 Hz), 1.49,
1.36 (each 3H, s). Anal. Calcd for C15H20O5‚0.5H2O: C, 62.27;
H, 7.32. Found: C, 62.02; H, 7.20.
Met h yl 3-O-Ben zyl-r,â-D-xylo-p en t ofu r a n osid e (22).
Compound 21 (17.6 g, 62.7 mmol) was dissolved in 5% HCl/
(45) The biological results of 4′-thioDMDC have been appeared:
Miura, S.; Tanaka, M.; Yoshimura, Y.; Satoh, H.; Sakata, S.; Machida,
H.; Matsuda, A.; Sasaki, T. Biol. Pharm. Bull. 1996, 19, 1311-1315.
(46) 4′-ThioFAC administered i.p. daily for
8 consecutive days
increased the life span of mice bearing P388 leukemia, showing T/C
values of 163% and 205% at doses of 3 and 10 mg/kg/day, respectively.
In the same assay, araC showed T/C values of 184% and 200% at doses
of 3 and 10 mg/kg/day, respectively.

3148 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
7.27 (5H, m), 4.64 (2H, s), 4.38 (1H, dt, J ) 2.9, 4.4 Hz), 3.96
(1H, t, J ) 2.9 Hz), 3.78 (1H, dd, J ) 2.9, 11.7 Hz), 3.66 (1H,
dd, J ) 3.9, 11.7 Hz), 3.65 (1H, br, D2O exchangeable), 3.60
(1H, dt, J ) 2.9, 3.9 Hz), 3.21 (1H, dd, J ) 4.4, 11.2 Hz), 2.90
(1H, dd, J ) 2.9, 11.2 Hz), 2.61 (1H, br, D2O exchangeable);
FAB-MS m/ z 241 (M+ + H). Anal. Calcd for C12H16O3S‚
0.2H2O: C, 59.09; H, 6.78. Found: C, 59.03; H, 6.88.
(2H, s), 4.48 (1H, d, J ) 11.7 Hz), 3.85 (1H, ddd, J ) 1.2, 6.1,
9.0 Hz), 3.76 (1H, dd, J ) 6.1, 10.3 Hz), 3.55 (1H, dd, J ) 9.0,
10.3 Hz), 1.97 (3H, s), 1.07 (9H, s); 13C NMR (100.4 MHz,
CDCl3) δ 170.62, 138.10, 135.55 (2C), 135.52 (2C), 133.03,
130.78, 129.84 (2C), 128.90, 128.43, 128.39, 128.34 (2C), 127.75
(4C), 127.69, 127.64, 85.97, 70.18, 64.84, 61.02, 54.63, 26.80
(3C), 20.83, 19.23; FAB-MS m/ z 471 (M+ - OAc - 2H). Anal.
Calcd for C31H36O4SSi: C, 69.89; H, 6.81. Found: C, 69.77;
H, 6.98.
1,4-An h yd r o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-
4-th io-D-a r a bitol (15). TBDPSCl (6.22 mL, 23.9 mmol) was
added to a mixture of 24 (5.47 g, 22.8 mmol) and imidazole
(1.63 g, 23.9 mmol) in DMF (90 mL) at 0 °C. The mixture
was stirred at room temperature overnight. H2O was added
to the mixture, and the whole was stirred for 10 min. The
solvent was removed under reduced pressure. The residue was
partitioned between AcOEt and H2O. The organic phase was
washed with H2O (×2) and brine and then dried (Na2SO4).
After the solvent was removed under reduced pressure, the
residue was purified by colum chromatography over silica gel
(6.3 × 11 cm). The eluate with 2-4-10% AcOEt in hexane
was collected, and the solvent was removed under reduced
pressure to leave crystalline 15 (9.55 g, 87%): mp 46-47 °C;
1H NMR (CDCl3) δ 7.72-7.64 (4H, m), 7.46-7.26 (11H, m),
4.59 (1H, d, J ) 12.0 Hz), 4.54 (1H, d, J ) 12.0 Hz), 4.40 (1H,
brt, J ) 2.4 Hz), 4.00 (1H, t, J ) 2.0 Hz), 3.74 (1H, dd, J )
4.4, 10.7 Hz), 3.69 (1H, dd, J ) 5.4, 10.7 Hz), 3.56 (1H, dt, J
) 2.0, 4.9 Hz), 3.24-3.20 (2H, m, 1H was D2O exchangeable),
2.90 (1H, dd, J ) 2.4, 11.2 Hz), 1.07 (9H, s); FAB-MS m/ z 479
(M+ + H). Anal. Calcd for C28H34O3SSi: C, 70.25; H, 7.16.
Found: C, 69.91; H, 7.34.
1,4-An h yd r o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-
2-d eoxy-2-C-m eth ylen e-4-th io-D-er yth r o-p en titol (26). A
mixture of 15 (21.4 g 44.9 mmol) and Ac2O (120 mL) in DMSO
(240 mL) was stirred at room temperature overnight. After
dilution with H2O, the whole was extracted by ether. The
organic phase was washed with H2O (×3), saturated NaHCO3
(×2), and brine and then dried (Na2SO4). The solvent was
removed under reduced pressure, and the residue was passed
through a short silica gel column (eluate: 17% AcOEt in
hexane), giving 25. A mixture of methyltriphenylphosphonium
bromide (49.6 g, 139 mmol), amyl alcohol (16.6 mL), and 60%
NaH (6.10 g, 153 mmol) in THF (300 mL) was stirred at room
temperature for 2 h. To this ylide solution was added a THF
solution (120 mL) of 25 (20 g, 42.0 mmol) slowly at 0 °C, and
then the solution was stirred at room temperature overnight.
The reaction was quenched with 1 M NH4Cl, and the whole
was extracted with AcOEt (×2). The organic phase was
washed with H2O and brine and then dried (Na2SO4). The
solvent was removed under reduced pressure, and the residue
was purified by column chromatography over silica gel (9%
AcOEt in hexane) to give 26 (14.7 g, 74%) as a syrup: 1H NMR
(CDCl3) δ 7.60-7.55 (4H, m), 7.43-7.27 (11H, m), 5.13, 4.94
(each 1H, s), 4.64 (1H, d, J ) 12.7 Hz), 4.44 (1H, d, J ) 12.7Hz),
4.35 (1H, s), 3.62-3.31 (4H, m), 3.21 (1H, d, J ) 12.7 Hz),
0.99 (9H, s); FAB-MS m/ z 475 (M+ + H). Anal. Calcd for
C29H34O2SSi: C, 73.37; H, 7.22. Found: C, 73.12; H, 7.32.
(2R,3S)-3-(Acet oxym et h yl)-4-(b en zyloxy)-5-(((ter t-b u -
tyld ip h en ylsilyl)oxy)m eth yl)-2,3-d ih yd r oth iop h en e (27).
To a solution of 26 (115 mg, 0.242 mmol) in CH2Cl2 (4 mL) at
-78 °C was dropwise added 80% m-CPBA (52 mg, 0.242 mmol)
in CH2Cl2 (3 mL). The mixture was stirred at the same
temperature for 20 min. The reaction was quenched with
saturated NaHCO3, and the whole was extracted with CHCl3
(×2). The organic phase was washed with a 10% sodium
thiosulfate solution, saturated NaHCO3 (×2), and brine and
then dried (Na2SO4). The solvent was removed under reduced
pressure, and the residue was dissolved in Ac2O (4 mL). The
mixture was kept at 110 °C for 1.5 h and concentrared. The
residual Ac2O was removed by codistillation with toluene (×3).
The residue was partitioned between AcOEt and H2O. The
organic phase was washed with saturated NaHCO3 (×2) and
brine and then dried (Na2SO4). After the solvent was removed
under reduced pressure, the residue was purified by column
chromatography over silica gel (1.7 × 11.5 cm; 2-4% AcOEt
in hexane) to give 27 (88 mg, 68%) as a syrup: 1H NMR
(CDCl3) δ 7.67-7.64 (4H, m), 7.46-7.25 (11H, m), 6.41 (1H,
s), 4.87 (1H, d, J ) 1.2 Hz), 4.66 (1H, d, J ) 11.7 Hz), 4.65
4-Acetyl-1-(3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-2-
d eoxy-2-C-m et h ylen e-4-t h io-r,â-D-er yth r o-p en t ofu r a n o-
syl)cytosin e (29) a n d (2R,3S)-3-((4-Acetylcytosin -1-yl)-
m e t h y l)-4-(b e n zy lo x y )-5-(((t er t -b u t y ld ip h e n y ls ily l)-
oxy)m eth yl)-2,3-d ih yd r oth iop h en e (30). Compound 26
(1.14 g, 2.40 mmol) was converted to 27 as described above.
The obtained 27 was subjected to the following glycosylation
reaction without purification: A mixture of 27, silylated N4-
acetylcytosine (4.80 mmol), and TMSOTf (0.464 mL, 2.40
mmol) in ClCH2CH2Cl (20 mL) was stirred at 0 °C for 30 min.
The reaction was quenched by the addition of saturated
NaHCO3. The precipitated material was removed by suction.
The filtrate was extracted with CHCl3 (×3), which was washed
with brine, then dried (Na2SO4), and concentrated. The
residue was purified by column chromatography over silica gel
(0-1% MeOH in CHCl3) to give less polar 29 (an amorphous
foam of exclusive R-isomer; 369 mg, 25% from 26) and more
polar 30 (an amorphous foam; 356 mg, 24% from 26). Da ta
for 29 (r-a n om er ): UV (MeOH) λmax 303, 249, 221 nm; UV
(MeOH, H+) λmax 315, 222 nm;1H NMR (CDCl3) δ 9.06 (1H,
br, D2O exchangeable), 8.50 (1H, d, J ) 7.8 Hz), 7.71-7.21
(16H, m), 6.74 (1H, s), 5.69 (1H, s), 5.19 (1H, s), 4.43 (1H, d,
J ) 11.7 Hz), 4.40 (1H, s), 4.29 (1H, d, J ) 11.7 Hz), 3.77-
3.71 (1H, m), 3.66 (1H, dd, J ) 5.1, 10.3 Hz), 3.40 (1H, t, J )
10.3 Hz), 2.22 (3H, s), 1.01 (9H, s); FAB-MS m/ z 626 (M+
H). Anal. Calcd for C35H39N3O4SSi: C, 67.17; H, 6.28; N, 6.71.
+
Found: C, 67.03; H, 6.57; N, 6.33. Da ta for 30: UV (MeOH)
1
λmax 302, 248, 221 nm; UV (MeOH, H+) λmax 317, 221 nm; H
NMR (CDCl3) δ 9.06 (1H, br, D2O exchangeable), 7.65-7.16
(17H, m), 6.44 (1H, s), 4.74 (1H, s), 4.61 (1H, d, J ) 11.7 Hz),
4.57 (1H, d, J ) 14.2 Hz), 4.45 (1H, d, J ) 14.2 Hz), 4.38 (1H,
d, J ) 11.7 Hz), 3.84-3.81 (1H, m), 3.73 (1H, dd, J ) 6.4, 10.3
Hz), 3.49 (1H, t, J ) 10.3 Hz), 2.20 (3H, s), 1.06 (9H, s); 13C
NMR (100.4 MHz, CDCl3) δ 170.88, 162.66, 155.60, 148.33,
137.72, 135.52 (3C), 135.49 (3C), 132.93, 132.86, 131.99,
131.93, 131.89, 129.94, 129.91, 128.48, 128.02, 127.83 (3C),
127.36, 96.63, 86.43, 70.25, 64.80, 54.62, 48.08, 26.83 (3C),
24.78, 19.21; FAB-MS m/ z 626 (M+ + H). Anal. Calcd for
C35H39N3O4SSi‚H2O: C, 66.22; H, 6.35; N, 6.62. Found: C,
66.42; H, 6.46; N, 6.67.
1,4-An h yd r o-5-O-(ter t-bu tyld ip h en ylsilyl)-2-d eoxy-2-C-
m eth ylen e-4-th io-D-er yth r o-p en titol (31). A solution of
BCl3 (7.76 mL of a 1 M CH2Cl2 solution, 7.76 mmol) was added
slowly to a solution of 26 (1.84 g, 3.88 mmol) in CH2Cl2 (30
mL) at -78 °C. After being stirred at the same temperature
for 1 h, pyridine (10 mL) and MeOH (20 mL) were added to
the mixture. The mixture was stirred at -78 °C for 1 h and
allowed to warm to room temperature. The solvent was
removed under reduced pressure. After the residue was
partitioned between CHCl3 and H2O, the organic phase was
washed with aqueous HCl (0.5 M, ×2), saturated NaHCO3,
and brine and then dried (Na2SO4). The solvent was removed
under reduced pressure. The residue was purified by column
chromatography over silica gel (3.7 × 11 cm; 5-10% AcOEt
in hexane) to give 31 (1.34 g, 92%): 1H NMR (CDCl3) δ 7.67-
7.64 (4H, m), 7.46-7.37 (6H, m), 5.19 (1H, d, J ) 1.0 Hz), 5.05
(1H, d, J ) 1.5 Hz), 4.57 (1H, br dd, J ) 4.9, 5.4 Hz), 3.79
(1H, dd, J ) 5.4, 10.3 Hz), 3.64 (1H, dd, J ) 9.3, 10.3 Hz),
3.52 (1H, dd, J ) 1.0, 13.7 Hz), 3.45 (1H, dd, J ) 1.5, 13.7
Hz), 3.31 (1H, dt, J ) 5.4, 9.3 Hz), 2.61 (1H, d, J ) 4.9 Hz,
D2O exchangeable), 1.07 (9H, s); FAB-MS m/ z 385 (M+ + H).
Anal. Calcd for C22H28O2SSi‚0.75H2O: C, 66.37; H, 7.47.
Found: C, 66.56; H, 7.24.
4-Acet yl-1-(5-O-(ter t-b u t yld ip h en ylsilyl)-2-d eoxy-2-C-
m eth ylen e-3-O-(tr im eth ylsilyl)-4-th io-r(a n d â)-D-er yth r o-
p en tofu r a n osyl)cytosin e (r,â-33). A solution of m-CPBA
(80%, 509 mg, 2.36 mmol) in CH2Cl2 (15 mL) was added

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3149
dropwise to a solution of 31 (906 mg, 2.36 mmol) in CH2Cl2
(30 mL) at -78 °C. The mixture was stirred at the same
temperature for 30 min. The reaction was quenched with
saturated NaHCO3, and the whole was extracted with CHCl3
(×2). The organic phase was washed with 10% sodium
thiosulfate solution, saturated NaHCO3 (×2), and brine and
then dried (Na2SO4). The filtrate was concentrated to leave
the crude sulfoxide 32, which was dissolved in ClCH2CH2Cl
(35 mL). A mixture of silylated N4-acetylcytosine (7.08 mmol)
and TMSOTf (0.925 mL, 4.48 mmol) in ClCH2CH2Cl (10 mL)
was added to the solution of 32 at 0 °C. The mixture was
stirred at the same temperature for 30 min. The reaction was
quenched by the addition of saturated NaHCO3. The precipi-
tated material was removed by suction. The filtrate was
extracted with CHCl3 (×3). The organic phase was washed
with brine, then dried (Na2SO4), and concentrated. The
residue was purified by column chromatography over silica gel
(0-1% MeOH in CHCl3) to give 33 (1.06 g, 74%) as an
amorphous foam: UV (MeOH) λmax 304, 249 nm; 1H NMR
(CDCl3) δ 8.72 (1H, br, D2O exchangeable), 8.37 (0.74H, d, J
) 7.3 Hz), 7.89 (0.26H, d, J ) 7.8 Hz), 7.68-7.63 (4H, m),
7.46-7.34 (7H, m), 6.90 (0.26H, s), 6.75 (0.74H, s), 5.29, 5.22
(each 0.74H, s), 5.15, 4.99 (each 0.26H, s), 4.71 (0.26H, d, J )
4.9 Hz), 4.65 (0.74H, d, J ) 3.4 Hz), 3.78 (0.26H, dd, J ) 4.9,
10.7 Hz), 3.68 (0.74H, dd, J ) 4.9, 9.8 Hz), 3.64 (0.26H, dd, J
) 6.8, 10.7 Hz), 3.55 (0.74H, dd, J ) 8.3, 9.8 Hz), 3.50 (0.74H,
ddd, J ) 3.4, 4.9, 8.3 Hz), 3.33 (0.26H, dt, J ) 4.9, 6.8 Hz),
2.24, 2.23 (total 3H, s), 1.10, 1.08 (total 9H, s), 0.12, 0.10 (total
9H, s); FAB-MS m/ z 608 (M+ + H). Anal. Calcd for
C31H41N3O4SSi2: C, 61.25; H, 6.80; N, 6.91. Found: C, 60.90;
H, 7.08; N, 6.60.
trated. The residue was purified by column chromatography
over silica gel (4 × 23 cm; 3-5% AcOEt in hexane) to give 34
(876 mg, 48%) as a syrup: 1H NMR (CDCl3) δ 7.66-7.60 (4H,
m), 7.47-7.27 (11H, m), 4.80 (1H, d, J ) 11.7 Hz), 4.62 (1H,
d, J ) 11.7 Hz), 4.12-4.04 (1H, m), 3.77 (1H, ddd, J ) 1.5,
6.8, 10.7 Hz) 3.66 (1H, ddd, J ) 1.0, 6.4, 10.7 Hz), 3.48-3.55
(1H, m), 3.27 (1H, dt, J ) 12.6 Hz, J H,F ) 12.6, 16.1 Hz), 3.11
(1H, dd, J ) 12.6 Hz, J H,F ) 25.0 Hz), 1.04 (9H, s); FAB-MS
m/ z 499 (M+ + H). Anal. Calcd for C28H32F2O2SSi: C, 67.44;
H, 6.47. Found: C, 67.24; H, 6.53.
1,4-An h yd r o-3-O-ben zoyl-5-O-(ter t-bu tyld ip h en ylsilyl)-
2-d eoxy-2,2-d iflu or o-4-th io-D-er yth r o-p en titol (36). Com-
pound 34 (1.31 g, 2.63 mmol) was debenzylated as described
in the synthesis of 31. A mixture of crude debenzylated
product (0.922 g), Et3N (0.54 mL, 3.84 mmol), Bz2O (0.762 g,
3.36 mmol), and DMAP (54 mg) in CH3CN (11 mL) was stirred
at room temperature for 3 h. After concentration of the
mixture to dryness, the residue was partitioned between ether
and H2O. The organic phase was washed with aqueous HCl
(0.5 M) and saturated NaHCO3 and then dried (MgSO4). After
the solvent was removed under reduced pressure, the residue
was purified by column chromatography over silica gel (100
g; 3.5% AcOEt in hexane) to give 36 (1.06 g, 79%) as a syrup:
1H NMR (CDCl3) δ 8.08-8.04 (2H, m), 7.68-7.58 (5H, m),
7.50-7.30 (8H, m), 5.79-5.72 (1H, m), 3.89 (1H, ddd, J ) 1.0,
6.5, 10.7 Hz), 3.75 (1H, ddd, J ) 1.5, 6.8, 10.7 Hz), 3.66-3.60
(1H, m), 3.38-3.20 (2H, m), 1.04 (9H, s); FAB-MS m/ z 513.
(M+ + H). Anal. Calcd for C28H30F2O3SSi: C, 65.50; H, 5.90.
Found: C, 65.77; H, 5.98.
4-Ac e t y l-1-(5-O -(t er t -b u t y ld ip h e n y ls ily l)-3-O -b e n -
zoyl-2-d eoxy-2,2-d iflu or o-4-th io-r(a n d â)-D-er yth r o-p en to-
fu r a n osyl)cytosin e (r,â-38). Compound 36 (1.05 g, 2.04
mmol) was subjected to the glycosylation reaction as described
for the preparation of 33. Purification by column chromatog-
raphy over silica gel (130 g; 3% MeOH in CHCl3) gave 38 (0.778
g, 57%) as an amorphous foam: 1H NMR (CDCl3) δ 8.86
(0.72H, br, D2O exchangeable), 8.73 (0.28H, br, D2O exchange-
able), 8.29-8.23 (1H, m), 8.09-8.05 (0.56H, m), 8.00-7.96
(1.44H, m), 7.70-7.59 (5H, m), 7.52-7.30 (9H, m), 6.91-6.81
(1H, m), 5.90-5.81 (1H, m), 4.00-3.78 (2.72H, m), 3.71-3.67
(0.28H, m), 2.26 (2.16H, s), 2.25 (0.84H, s), 1.11 (2.52H, s),
1.06 (6.48H, s); FAB-MS m/ z 664 (M+ + H). Anal. Calcd for
C34H35F2N3O5SSi‚0.25H2O: C, 61.10; H, 5.35; N, 6.29.
Found: C, 61.08; H, 5.35; N, 6.22.
1-(2-Deoxy-2-C-m et h ylen e-4-t h io-r(a n d â)-D-er yth r o-
p en tofu r a n osyl)cytosin e (4′-Th ioDMDC, r,â-10). A mix-
ture of 33 (238 mg, 0.391 mmol) and TBAF (0.78 mL of 1 M
THF solution, 0.78 mmol) was stirred at room temperature
for 15 min. After concentration, the residue was passed
through a silica gel column. The eluate with 9% MeOH in
CHCl3 was collected and concentrated. The residue was
dissolved in MeOH (5 mL) and aqueous ammonia (5 mL). The
mixture was stirred at room temperature overnight. After the
solvent was removed under reduced pressure, the residue was
purified by HPLC (Develosil ODS-5, 10 × 250 mm, Nomura
Chemical Co.; 1% CH3CN in H2O, flow rate 4 mL/min;
retention time R, 27 min, â, 29 min) to give R-10 (34 mg) and
â-10 (13 mg, total 47% yield). Da ta for r-10: mp 220-222
°C (dec, crystallized from H2O); UV (H2O) λmax 276 nm (8300);
UV (0.1 N HCl) λmax 283 nm (11900), 219 nm (7600); 1H NMR
(DMSO-d6) δ 7.61 (1H, d, J ) 7.2 Hz), 7.24 (2H, br, D2O
exchangeable), 6.64 (1H, s), 5.85 (1H, br), 5.79 (1H, d, J ) 5.9
Hz, D2O exchangeable), 5.32 (1H, s), 4.98 (1H, t, J ) 5.4 Hz,
D2O exchangeable), 4.80 (1H, s), 4.28 (1H, br t, J ) 7.8 Hz),
3.81 (1H, ddd, J ) 3.9, 5.4, 10.7 Hz), 3.45 (1H, ddd, J ) 5.4,
7.8, 10.7 Hz), 3.37 (1H, dt, J ) 3.9, 7.8 Hz); 13C NMR (100.4
MHz, DMSO-d6) δ 165.0, 155.4, 150.4, 143.1, 111.2, 95.3, 74.1,
62.9, 58.8, 54.1; FAB-MS m/ z 256 (M+ + H). Anal. Calcd for
C10H13N3O3S‚0.5H2O: C, 45.44; H, 5.34; N, 15.90. Found: C,
45.73; H, 5.36; N, 16.12. Da ta for â-10: mp 221-222 °C
(crystallized from H2O); UV (H2O) λmax 276 nm (8700); UV (0.1
N HCl) λmax 282 nm (11800), 219 nm (7600); 1H NMR (DMSO-
d6) δ 7.57 (1H, d, J ) 7.3 Hz), 7.24, 7.20 (total 2H, br s, D2O
exchangeable), 6.66 (1H, s), 5.79 (1H, br d, J ) 7.3 Hz), 5.62
(1H, d, J ) 4.9 Hz, D2O exchangeable), 5.32 (1H, s), 5.07 (1H,
t, J ) 5.4 Hz, D2O exchangeable), 4.92 (1H, s), 4.49 (1H, br t,
J ) 4.9 Hz), 3.60 (1H, ddd, J ) 5.4, 6.4, 11.2 Hz), 3.49 (1H,
ddd, J ) 5.4, 6.4, 11.2 Hz), 3.12 (1H, dt, J ) 4.9, 6.4 Hz); 13C
NMR (100.4 MHz, DMSO-d6) δ 165.3, 155.7, 149.7, 142.5,
1-(2-Deoxy-2,2-diflu or o-4-th io-r(an d â)-D-er yth r o-pen to-
fu r a n osyl)cytosin e (4′-Th iogem cita bin e, r,â-11). Com-
pound 38 (0.773 g, 1.17 mmol) was deprotected, as described
for the preparation of 10, to give R-11 (119 mg) and â-11 (48
mg, total 51%). Da ta for r-11: mp 200-203 °C (crystallized
from H2O); UV (H2O) λmax 273 nm (8000); UV (0.1 N HCl) λmax
1
280 nm (14 700), 217 nm (9100); H NMR (DMSO-d6) δ 7.85
(1H, dd, J ) 2.5, 8.0 Hz), 7.36 (2H, br d, D2O exchangeable),
6.58 (1H, dd, J ) 9.5, 13.5 Hz), 6.38 (1H, br, D2O exchange-
able), 5.83 (1H, d, J ) 8.0 Hz), 5.18 (1H, br, D2O exchangeable),
4.27-4.16 (1H, m), 3.84-3.76 (1H, m), 3.59-3.48 (2H, m);
FAB-MS m/ z 280 (M+ + H). Anal. Calcd for C9H11F2N3O3S:
C, 38.71; H, 3.97; N, 15.05. Found: C, 38.74; H, 4.04; N, 14.82.
Da ta for â-11: UV (H2O) λmax 273 nm (9900); UV (0.1 N HCl)
1
λmax 280 nm (11 000), 219 nm (5700); H NMR (DMSO-d6) δ
8.05 (1H, d, J ) 7.5 Hz), 7.35 (2H, br d, D2O exchangeable),
6.36 (1H, br, D2O exchangeable), 6.36 (1H, dd, J ) 3.5, 12.0
Hz), 5.82 (1H, d, J ) 7.5 Hz), 5.40 (1H, br, D2O exchangeable),
4.16-4.04 (1H, m), 3.83-3.65 (2H, m), 3.16 (1H, m); FAB-MS
m/ z 280 (M+ + H). Anal. Calcd for C9H11F2N3O3S‚0.5H2O:
C, 37.50; H, 4.20; N, 14.58. Found: C, 37.87; H, 4.34; N, 14.14.
1,4-An h yd r o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-
2-d eoxy-2-flu or o-4-th io-D-a r a bitol (40). To a solution of
DAST (9.9 mL, 74.6 mmol) in anhydrous CH2Cl2 (80 mL) was
gradually added 15 (23.8g, 49.7 mmol) in CH2Cl2 (80 mL) at
-78 °C over 30 min. After being stirred at -78 °C for 3 h,
saturated NaHCO3 (200 mL) was added to the mixture. The
whole was stirred at room temperature for 30 min. The
separated H2O phase was extracted with CHCl3 (×2). The
combined organic phase was washed with brine, then dried
(MgSO4), and concentrated. The residue was purified by
column chromatography over silica gel (7.9 × 14 cm; 5% AcOEt
112.7, 95.5, 74.9, 63.2, 60.4, 54.4; FAB-MS m/ z 256 (M+
H). Anal. Calcd for C10H13N3O3S: C, 47.05; H, 5.13; N, 16.46.
Found: C, 46.87; H, 5.06; N, 16.45.
+
1,4-An h yd r o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-
2-d eoxy-2,2-d iflu or o-4-th io-D-er yth r o-p en titol (34). A ben-
zene solution (11 mL) of 25 (1.75 g, 3.68 mmol) was added
gradually to a solution of DAST (2 mL, 14.7 mmol) in
anhydrous benzene (11 mL) at 0 °C. After being stirred at
room temperature for 5 h, the mixture was poured into ice-
water and extracted with ether (×2). The organic phase was
washed with H2O and brine, then dried (MgSO4), and concen-

3150 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
in hexane) to give 40 (18.35g, 77%) as a syrup: 1H NMR
(CDCl3) δ 7.71-7.63 (4H, m), 7.47-7.28 (11H, m), 5.18 (1H,
dq, J ) 3.5, 50.5 Hz), 4.64 (1H, d, J ) 12.0 Hz), 4.60 (1H, d, J
) 12.0 Hz), 4.35 (1H, dt, J ) 2.9, 11.2 Hz), 3.76 (1H, t, J ) 9.5
Hz), 3.66 (1H, ddd, J ) 2.0, 6.1, 10.5 Hz), 3.57-3.53 (1H, m),
3.19 (1H, ddd, J ) 4.4, 12.2, 30.3 Hz), 3.06 (1H, ddd, J ) 3.4,
12.2, 18.1 Hz), 1.05 (9H, s); FAB-MS m/ z 423 (M+ - t-Bu).
Anal. Calcd for C28H33FO2SSi: C, 69.96; H, 6.92. Found: C,
70.03; H, 6.98.
residue was purified by column chromatography over silica gel
(4.4 × 11 cm; 10-20-30% MeOH in CHCl3). Then, R and
â-isomers were separated by reverse-phased ODS column
chromatography (Wakosil 40C18, 6.4 × 25 cm; 0-2% CH3CN
in H2O). The unseparable fractions were collected, concen-
trated, and rechromatographed (Wakosil 40C18, 3.7 × 18.5
cm; H2O) to give R-12 (991 mg) and â-12 (386 mg, total 60%
yield). Da ta for r-12: mp 204-205 °C (crystallized from
EtOH); UV (H2O) λmax 274 nm (8600); UV (0.1 N HCl) λmax
1
282 nm (12 300), 219 nm (6700); H NMR (DMSO-d6) δ 7.97
1-O-Acetyl-3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-2-
(1H, d, J ) 7.3 Hz), 7.26, 7.24 (2H, br d, D2O exchangeable),
6.15 (1H, dd, J ) 5.9, 17.5 Hz), 5.91 (1H, d, J ) 5.4 Hz, D2O
exchangeable), 5.79 (1H, d, J ) 7.3 Hz), 5.06 (1H, dt, J ) 6.4,
52.3 Hz), 5.03 (1H, dd, J ) 4.9, 5.4 Hz, D2O exchangeable),
4.09 (1H, ddt, J ) 5.4, 6.8, 13.7 Hz), 3.77 (1H, dt, J ) 4.9,
10.7 Hz), 3.59 (1H, dt, J ) 4.9, 7.3 Hz), 3.41 (1H, ddd, J ) 6.3,
7.8, 10.7 Hz); FAB-MS m/ z 262 (M+ + H). Anal. Calcd for
C9H12FN3O3S: C, 41.37; H, 4.63; N, 16.08. Found: C, 41.53;
H, 4.76; N, 15.83. Da ta for â-12: mp > 220 °C (dec,
crystallized from H2O); UV (H2O) λmax 274 nm (9000); UV (0.1
N HCl) λmax 282 nm (15 600), 219 nm (9400);1H NMR (DMSO-
d6) δ 7.98 (1H, dd, J ) 1.0, 7.3 Hz), 7.26, 7.19 (2H, br d, D2O
exchangeable), 6.47 (1H, dd, J ) 5.4, 13.2 Hz), 5.85 (1H, d, J
) 4.9 Hz, D2O exchangeable), 5.77 (1H, d, J ) 7.3 Hz), 5.22
(1H, t, J ) 5.4 Hz, D2O exchangeable), 4.91 (1H, dt, J ) 5.4,
50.8 Hz), 4.25 (1H, ddt, J ) 4.9, 5.4, 11.2 Hz), 3.72 (1H, dt, J
) 5.4, 11.2 Hz), 3.60 (1H, dt, J ) 5.9, 11.2 Hz), 3.22 (1H, dt,
J ) 5.4, 5.9 Hz); FAB-MS m/ z 262 (M+ + H). Anal. Calcd
for C9H12FN3O3S‚0.2H2O: C, 40.84; H, 4.66; N, 15.88.
Found: C, 40.73; H, 4.62; N, 15.77.
1,4-An h yd r o-2-a zid o-3-O-ben zyl-5-O-(ter t-bu tyld ip h e-
n ylsilyl)-2-d eoxy-4-th io-D-r ibitol (45). A mixture of DEAD
(0.47 mL, 3.0 mmol) and DPPA (0.65 mL, 3.0 mmol) in THF
(3 mL) was added dropwise to a solution of 15 (480 mg, 1.0
mmol) and triphenylphosphine (786 mg, 3.0 mmol) in THF (14
mL) at 0 °C. After the solution was stirred at room temper-
ature for 2 h, EtOH was added. After 30 min of stirring, the
solvent was removed under reduced pressure. The residue was
purified by column chromatography over silica gel (3.4 × 15
cm; 3.5% AcOEt in hexane) to give 45 (402 mg, 80%) as a
colorless oil: 1H NMR (CDCl3) δ 7.65-7.62 (4H, m), 7.46-7.29
(11H, m), 4.66 (1H, d, J ) 12.2 Hz), 4.62 (1H, d, J ) 12.2 Hz),
4.14 (1H, t, J ) 3.4 Hz), 3.73-3.54 (4H, m), 3.05 (1H, dd, J )
8.3, 10.7 Hz), 2.93 (1H, dd, J ) 5.9, 10.7 Hz), 1.06 (9H, s);
FAB-MS m/ z 504 (M+ + H); IR (neat) 2104 cm-1 (N3). Anal.
Calcd for C28H33N3O2SSi: C, 66.76; H, 6.60; N, 8.34. Found:
C, 67.00; H, 6.57; N, 8.21.
4-Acetyl-1-(2-a zid o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en yl-
silyl)-2-d eoxy-4-th io-r(a n d â)-D-r ibo-p en tofu r a n osyl)cy-
tosin e (r,â-47). (a ) F r om Su lfoxid e. Sulfoxide 46 (768 mg,
1.50 mmol) was prepared from 45 as described in the synthesis
of 42 (m-CPBA treatment). The crude products were passed
through a silica gel column (2.8 × 18 cm; 1% MeOH in CHCl3)
to give 46 (773 mg, quant.). A mixture of 46 (104 mg, 0.2
mmol), silylated N4-acetylcytosine (0.60 mmol), and TMSOTf
(0.15 mL, 0.8 mmol) in ClCH2CH2Cl (4 mL) was stirred at 0
°C for 2 h and then at room temperature overnight. The
reaction was quenched by the addition of saturated NaHCO3.
The precipitated material was removed by suction. The filtrate
was extracted with CHCl3 (×3), and the organic phase was
washed with brine, then dried (Na2SO4), and concentrated. The
residue was purified by column chromatography over silica gel
(1.1 × 22 cm; 0-1% MeOH in CHCl3) to give R,â-47 (27 mg,
20%) as a foam.
(b) F r om 1-O-Aceta te. A mixture of 48 (120 mg, 0.21
mmol), silylated N4-acetylcytosine (0.63 mmol), and TMSOTf
(0.15 mL, 0.8 mmol) in ClCH2CH2Cl (4 mL) was stirred at 0
°C for 1 h and then at room temperature overnight. The
reaction was quenched by the addition of saturated NaHCO3.
The precipitated material was removed by suction. The filtrate
was extracted by CHCl3 (×3), and the organic phase was
washed with brine, then dried (Na2SO4), and concentrated. The
residue was purified by column chromatography over silica gel
(1.1 × 22 cm; 0-1% MeOH in CHCl3) to give R,â-47 (81 mg,
59%) as a foam: 1H NMR (CDCl3) δ 9.51 (0.48H, br s, D2O
exchangeable), 9.25 (0.52H, br s, D2O exchangeable), 8.45
d eoxy-2-flu or o-4-th io-D-a r a bin o-p en tofu r a n ose (42).
A
solution of m-CPBA (80%, 3.0 g, 13.9 mmol) in CH2Cl2 (170
mL) was added dropwise to a solution of 40 (6.66 g, 13.9 mmol)
in CH2Cl2 (110 mL) at -78 °C. The mixture was stirred at
the same temperature for 1 h. The reaction was quenched by
the addition of saturated NaHCO3. The whole was extracted
with CHCl3 (×2). The organic phase was washed with a 10%
sodium thiosulfate solution, saturated NaHCO3 (×2) and brine
and then dried (Na2SO4). After the filtrate was concentrated,
the residue was dissolved in Ac2O (140 mL). The mixture was
kept at 100 °C for 2 h. After concentration, the residue was
partitioned between AcOEt and H2O. The organic phase was
washed with saturated NaHCO3 and brine and then dried
(Na2SO4). After the solvent was removed under reduced
pressure, the residue was purified by column chromatography
over silica gel (4.8 × 26 cm; 3-5% AcOEt in hexane) to give
42 (5.79 g, 77%) as a syrup: 1H NMR (CDCl3) δ 7.68-7.62
(4H, m), 7.46-7.25 (11H, m), 6.06 (1H, d, J ) 4.4 Hz), 5.11
(1H, ddd, J ) 4.4, 8.3, 51.0 Hz), 4.78 (1H, d, J ) 11.7 Hz),
4.60 (1H, d, J ) 11.7 Hz), 4.38 (1H, ddd, J ) 7.3, 8.3, 11.7
Hz), 3.81 (1H, dd, J ) 4.4, 10.5 Hz), 3.74 (1H, dd, J ) 5.9,
10.5 Hz), 3.34 (1H, ddd, J ) 4.4, 5.9, 7.3 Hz), 2.05 (3H, s),
1.07 (9H, s); FAB-MS m/ z 479 (M+ - OAc). Anal. Calcd for
C30H35FO4SSi‚H2O: C, 64.72; H, 6.70. Found: C, 64.97; H,
6.35.
4-Acetyl-1-(3-O-ben zyl-5-O-(ter t-bu tyld ip h en ylsilyl)-2-
d eoxy-2-flu or o-4-th io-r(a n d â)-D-a r a bin o-p en tofu r a n o-
syl)cytosin e (r,â-43). A mixture of 42 (108 mg, 0.20 mmol),
silylated N4-acetylcytosine (0.60 mmol), and SnCl4 (0.40 mL
of 1 M CH2Cl2 solution, 0.40 mmol) in anhydrous CH3CN (5
mL) was stirred at room temperature for 1.5 h. The reaction
was quenched by the addition of saturated NaHCO3. The
precipitated material was removed by suction. The filtrate
was extracted with CHCl3 (×3). The organic phase was
washed with brine, then dried (Na2SO4), and concentrated. The
residue was purified by column chromatography over silica gel
(1.5 × 6.5 cm; 0-1% MeOH in CHCl3) to give R,â-43 (117 mg,
93%) as a foam: UV (MeOH) λmax 301, 250 nm; 1H NMR
(CDCl3) δ 9.49 (1H, br, D2O exchangeable), 8.31 (0.74H, d, J
) 7.3 Hz), 8.22 (0.26H, dd, J ) 1.7, 7.3 Hz), 7.67-7.61 (4H,
m), 7.49-7.11 (12H, m), 6.70 (0.26H, d, J ) 4.4, 19.0 Hz), 6.32
(0.74H, d, J ) 14.2 Hz), 5.16 (1H, d, J ) 46.9 Hz), 4.64 (0.26H,
d, J ) 11.7 Hz), 4.59 (0.26H, d, J ) 11.7 Hz), 4.52 (0.74H, d,
J ) 11.7 Hz), 4.44 (0.74H, d, J ) 11.7 Hz), 4.36 (1H, br d, J )
10.3Hz), 3.95-3.62 (3H, m), 2.27, 2.26 (total 3H, s), 1.08, 1.06
(total 9H, s); FAB-MS m/ z 632 (M+ + H). Anal. Calcd for
C34H38FN3O4SSi‚0.5H2O: C, 63.72; H, 6.13; N, 6.56. Found:
C, 63.75; H, 6.05; N, 6.77.
1-(2-Deoxy-2-flu or o-4-th io-r(a n d â)-D-a r a bin o-p en to-
fu r a n osyl)cytosin e (4′-Th ioF AC, r,â-12). BBr3 (2.48 mL,
26.2 mmol) was added slowly to a solution of 43 (5.52 g, 8.74
mmol) in CH2Cl2 (80 mL) at -78 °C. After being stirred for
1.5 h at -78 °C, the reaction was quenched by the addition of
MeOH (12 mL) and saturated NaHCO3 (50 mL) and allowed
to warm to room temperature. The whole was extracted with
CHCl3 (×3), and the organic phase was washed with saturated
NaHCO3 and brine, then dried (Na2SO4), and concentrated.
The residue was dissolved in MeOH (80 mL) containing
ammonium fluoride (3.24 g, 87.4 mmol). The mixture was kept
at 60 °C for 2 h. After the solvent was removed under reduced
pressure, the residual product was roughly purified by a silica
gel column (4.9 × 14 cm; 2-20-30% MeOH in CHCl3). The
obtained N4-acetyl derivative was suspended in MeOH (25 mL)
and concentrated NH4OH (25 mL). The mixture was stirred
at room temperature overnight. The solvent was removed and
coevaporated with EtOH (×3) under reduced pressure. The

2′-Modified 2′-Deoxy-4′-thiocytidines from D-Glucose
J . Org. Chem., Vol. 62, No. 10, 1997 3151
(0.48H, d, J ) 7.8 Hz), 8.41 (0.52H, d, J ) 7.3 Hz), 7.68-7.20
(16H, m), 6.44 (0.52H, d, J ) 5.4 Hz), 6.08 (0.48H, d, J ) 3.9
Hz), 4.61 (0.52H, d, J ) 11.7 Hz), 4.57 (0.48H, d, J ) 11.7
Hz), 4.52 (0.52H, d, J ) 11.7 Hz), 4.50 (0.48H, d, J ) 11.7
Hz), 4.40 (0.52H, dd, J ) 3.9, 5.4 Hz), 4.20 (0.52H, dd, J )
3.9, 6.8 Hz), 4.11 (0.52H, dt, J ) 3.4, 6.8 Hz), 4.03 (0.48H, t,
J ) 3.9 Hz), 3.96-3.88 (1.52H, m), 3.82-3.75 (0.96H, m), 3.70
(0.48H, dt, J ) 3.9, 7.8 Hz), 2.27 (1.44H, s), 2.26 (1.56H, s),
1.12 (4.32H, s), 1.07 (4.68H, s); FAB-MS m/ z 655 (M+ + H).
Anal. Calcd for C34H38N6O4SSi‚0.17AcOEt: C, 62.19; H, 5.92;
N, 12.55. Found: C, 62.49; H, 5.99; N, 12.36.
m/ z 255 (M+ + H). Anal. Calcd for C12H14O4S: C, 58.66; H,
7.66. Found: C, 58.67; H, 7.58.
1,4-An h yd r o-3-O-ben zoyl-5-O-(ter t-bu tyld im eth ylsilyl)-
4-th io-D-a r a bitol (53). A mixture of 52 (1.77 g, 7.0 mmol),
TBSCl (1.06 g, 7.0 mmol), and imidazole (524 mg, 7.7 mmol)
in DMF (50 mL) was stirred at room temperature overnight.
H2O was added to the mixture, and the whole was stirred for
an additional 10 min. The solvent was removed under reduced
pressure. The residue was partitioned between AcOEt and
H2O, and the organic phase was washed with H2O (×2) and
brine and then dried (Na2SO4). After the solvent was removed
under reduced pressure, the residue was purified by column
chromatography over silica gel (3.6 × 20 cm; 5-16% AcOEt
in hexane) to give 53 (2.1 g, 80%) as a colorless oil: 1H NMR
(CDCl3) δ 8.02-8.00 (2H, m), 7.60-7.57 (1H, m), 7.45 (2H, t,
J ) 7.8 Hz), 5.36 (1H, br s), 4.50-4.42 (2H, m, including D2O
exchangeable 1H), 4.12 (1H, dd, J ) 3.4, 10.7 Hz), 3.72 (1H,
dd, J ) 3.4, 10.7 Hz), 3.67-3.65 (1H, m), 3.32 (1H, dd, J )
3.9, 11.7 Hz), 3.04 (1H, dd, J ) 2.0, 11.7 Hz), 0.94 (9H, s),
0.15 (3H, s), 0.14 (3H, s); FAB-MS m/ z 369 (M+ + H). Anal.
Calcd for C18H28O4SSi: C, 58.66; H, 7.66. Found: C, 58.67;
H, 7.58.
1,4-An h yd r o-2-a zid o-3-O-ben zoyl-5-O-(ter t-bu tyld im e-
th ylsilyl)-2-d eoxy-4-th io-D-r ibitol (54). Compound 53 (680
mg, 1.85 mmol) was subjected to the Mitsunobu reaction as
described for the synthesis of 45. After silica gel column
chromatography (2.7 × 18 cm; 3.5% AcOEt in hexane), 2-azido
derivative 54 (605 mg, 83%) was obtained as a colorless oil:
1H NMR (CDCl3) δ 8.10-8.07 (2H, m), 7.62-7.58 (1H, m),
7.49-7.45 (2H, m), 5.56 (1H, t, J ) 3.9 Hz), 4.32-4.28 (1H,
m), 3.82 (1H, dd, J ) 5.4, 10.3 Hz), 3.73 (1H, dd, J ) 5.4, 10.3
Hz), 3.69-3.65 (1H, m), 3.17 (1H, dd, J ) 5.9, 10.7 Hz), 3.09
(1H, dd, J ) 7.3, 10.7 Hz), 0.89 (9H, s), 0.06 (6H, s); FAB-MS
m/ z 394 (M+ + H). IR (neat) 2108 cm-1 (N3). Anal. Calcd
for C18H27N3O3SSi: C, 54.93; H, 6.91; N, 10.68. Found: C,
55.15; H, 6.86; N, 10.58.
1-O-Acetyl-2-a zid o-3-O-ben zoyl-5-O-(ter t-bu tyld im eth -
ylsilyl)-2-d eoxy-4-th io-D-r ibo-p en tofu r a n ose (55). Com-
pound 54 (1.35 g, 3.44 mmol) was subjected to the Pummerer
rearrangement as described for the synthesis of 46 and 48.
After silica gel column chromatography (3.6 × 20 cm; 2-5%
AcOEt in hexane), 55 (816 mg, 53%) was obtained as a
colorless oil: 1H NMR (CDCl3) δ 8.15-8.07 (2H, m), 7.63-7.59
(1H, m), 7.50-7.45 (2H, m), 6.37 (0.55H, d, J ) 4.4 Hz), 5.92
(0.45H, d, J ) 2.9 Hz), 5.74 (0.55H, dd, J ) 1.5, 4.4 Hz), 5.70-
5.68 (0.45H, m), 4.54 (0.45H, dd, J ) 2.9, 3.9 Hz), 4.05 (0.55H,
t, J ) 4.4 Hz), 3.96 (0.55H, dd, J ) 4.4, 10.7 Hz), 3.85-3.74
(1.9H, m), 3.65 (0.55H, dd, J ) 4.4, 10.7 Hz), 2.24 (1.65H, s),
2.12 (1.35H, s), 0.91 (4.95H, s), 0.87 (4.05H, s), 0.09 (3.3H, s),
0.04 (2.7H, s); FAB-MS m/ z 492 (M+ - OAc). Anal. Calcd
for C20H29N3O5SSi: C, 53.19; H, 6.47; N, 9.30. Found: C,
53.43; H, 6.50; N, 9.32.
4-Acetyl-1-(2-a zid o-3-O-ben zoyl-5-O-(ter t-bu tyld im eth -
ylsilyl)-2-d eoxy-4-th io-r(a n d â)-D-r ibo-p en tofu r a n osyl)-
cytosin e (r,â-56). Compound 55 (596 mg, 1.32 mmol) was
subjected to the glycosylation reaction as described for the
synthesis of 47b). After silica gel column chromatography (2.2
× 24 cm; 2% MeOH in CHCl3), 56 (342 mg, 47%) was obtained
as a foam: 1H NMR (CDCl3) δ 9.18 (1H, br s, D2O exchange-
able), 8.73 (0.5H, d, J ) 7.8 Hz), 8.44 (0.5H, d, J ) 7.8 Hz),
8.07-8.01 (2H, m), 7.63-7.60 (1H, m), 7.50-7.43 (3H, m), 6.63
(0.5H, d, J ) 5.4 Hz), 6.35 (0.5H, d, J ) 3.9 Hz), 5.60 (0.5H,
dd, J ) 4.4, 6.8 Hz), 5.53 (0.5H, dd, J ) 3.9, 6.4 Hz), 4.81 (0.5H,
dd, J ) 4.4, 5.4 Hz), 4.42 (0.5H, t, J ) 3.9 Hz), 4.12-3.84 (3H,
m), 2.28 (3H, s), 0.94 (4.5H, s), 0.89 (4.5H, s), 0.13 (3H, s),
0.07 (3H, s); FAB-MS m/ z 544 (M+ + H). Anal. Calcd for
C24H32N6O5SSi‚0.2AcOEt: C, 52.97; H, 6.02; N, 14.94.
Found: C, 53.03; H, 6.00; N, 14.88.
1-O-Acetyl-2-a zid o-3-O-ben zyl-5-O-(ter t-bu tyld ip h en yl-
silyl)-2-d eoxy-4-th io-D-r ibo-p en tofu r a n ose (48). A solu-
tion of 46 (490 mg, 0.94 mmol) in Ac2O (10 mL) was kept at
100 °C for 1.5 h. After concentration, the residue was purified
by column chromatography over silica gel (2.2 × 23 cm; 2-5%
AcOEt in hexane) to give 48 (356 mg, 67%) as a colorless oil:
1H NMR (CDCl3) δ 7.67-7.29 (15H, m), 6.19 (0.67H, d, J )
4.9 Hz), 5.83 (0.33H, d, J ) 2.9 Hz), 4.71 (0.67H, d, J ) 12.2
Hz), 4.66-4.59 (1.33H, m), 4.36 (0.33H, q, J ) 3.9 Hz), 4.31
(0.67H, dd, J ) 2.0, 4.9 Hz), 4.08 (0.33H, dd, J ) 2.9, 3.9 Hz),
3.81 (0.67H, q, J ) 4.9 Hz), 3.78-3.74 (0.67H, m), 3.65-3.60
(1H, m), 3.53 (0.66H, t, J ) 4.9 Hz), 3.48 (0.67H, dd, J ) 7.3,
11.2 Hz), 2.15 (2.01H, s), 2.04 (0.99H, s), 1.06 (9H, s); FAB-
MS m/ z 504 (M+ - tBu). Anal. Calcd for C30H35N3O4SSi: C,
64.14; H, 6.28; N, 7.48. Found: C, 63.87; H, 6.17; N, 7.39.
1,4-An h yd r o-3-O-ben zoyl-2-O-(ter t-bu tyld im eth ylsilyl)-
5-O-(ter t-bu tyldiph en ylsilyl)-4-th io-D-ar abitol (51). A mix-
ture of 15 (3.4 g, 7.1 mmol), pyridine (1.72mL, 21.3 mmol),
and TBSOTf (2.5 mL, 10.7 mmol) in CH2Cl2 (70 mL) was
stirred at room temperature for 2 h. After the addition of
saturated NaHCO3, the whole was extracted with CHCl3. The
organic phase was washed with brine, then dried (Na2SO4),
and concentrated. The residual pyridine was removed by
codistillation with toluene (×3) to give crude 49, which was
dissolved in CH2Cl2 (70 mL). A solution of BCl3 (32 mL of 1.0
M CH2Cl2 solution, 32 mmol) was gradually added to the
mixture at -78 °C. After being stirred for 6.5 h at the same
temperature, the reaction was quenched by the addition of
MeOH-pyridine (48 mL, 2:1). The mixture was allowed to
warm to room temperature and was stirred for 1 h. After the
most of organic solvents were removed under reduced pressure,
the whole was extracted with AcOEt (×2). The organic phase
was washed with H2O and brine and then dried (Na2SO4). The
solvent was removed under reduced pressure to leave crude
50. A mixture of crude 50, Bz2O (2.40 g, 10.7 mmol), Et3N
(1.70 mL, 12.1 mmol), and DMAP (83 mg, 0.70 mmol) in CH3-
CN (70 mL) was stirred at room temperature for 5 h. After
the addition of saturated NaHCO3, the whole was extracted
with AcOEt (×2). The organic phase was washed with brine,
then dried (Na2SO4), and concentrated. The residue was
purified by column chromatography over silica gel (3.6 × 24
cm; 5% AcOEt in hexane) to give 51 (4.01 g, 93%) as a colorless
oil: 1H NMR (CDCl3) δ 8.04-8.01 (2H, m), 7.67-7.30 (13H,
m), 5.53 (1H, t, J ) 3.4 Hz), 4.54-4.50 (1H, m), 4.01 (1H, dd,
J ) 7.3, 9.8 Hz), 3.79 (1H, dd, J ) 7.3, 9.8 Hz), 3.52 (1H, dt,
J ) 3.4, 7.3 Hz), 3.10 (1H, dd, J ) 4.9, 11.2 Hz), 2.87 (1H, dd,
J ) 4.4, 11.2 Hz), 1.04 (9H, s), 0.82 (9H, s), 0.07 (3H, s), 0.05
(3H, s); FAB-MS m/ z 549 (M+
C34H46O4SSi2: C, 67.28; H, 7.64. Found: C, 67.38; H, 7.84.
-
tBu). Anal. Calcd for
1,4-An h yd r o-3-O-ben zoyl-4-th io-D-a r a bitol (52). A mix-
ture of 51 (4.78 g, 7.89 mmol) and NH4F‚HF (9.0 g, 158 mmol)
in MeOH (100 mL) was stirred at room temperature for 43 h.
After concentration, the residue was partitioned between
AcOEt and H2O. The organic phase was washed with H2O
and brine, then dried (Na2SO4), and concentrated. The residue
was purified by column chromatography over silica gel (3.4 ×
10 cm; 5-50% AcOEt in hexane) to give 52 (1.78 g, 89%) as a
crystal: mp 110-111 °C (crystallized from hexane-AcOEt);
1H NMR (DMSO-d6) δ 7.98-7.96 (2H, m), 7.70-7.66 (1H, m),
7.54 (2H, t, J ) 7.8 Hz), 5.56 (1H, d, J ) 4.4 Hz, D2O
exchangeable), 5.30 (1H, t, J ) 3.9 Hz), 5.00 (1H, t, J ) 5.4
Hz, D2O exchangeable), 4.41-4.36 (1H, m), 3.75-3.70 (1H, m),
3.52-3.46 (1H, m), 3.39 (1H, dt, J ) 3.9, 6.8 Hz), 3.07 (1H,
dd, J ) 5.4, 11.2 Hz), 2.80 (1H, dd, J ) 4.4, 11.2 Hz); FAB-MS
4-Acetyl-1-(2-azido-3-O-ben zoyl-2-deoxy-4-th io-r(an d â)-
D-r ibo-p en tofu r a n osyl)cytosin e (r,â-57). A mixture of 56
(319 mg, 0.59 mmol) and NH4F‚HF (336 mg, 5.90 mmol) in
MeOH (10 mL) was stirred at room temperature overnight.
After the solvent was removed under reduced pressure, the
residue was purified by column chromatography over silica gel
(1.6 × 27 cm; 2% MeOH in CHCl3) to give less polar â-57
(crystal; 115 mg, 45%) and more polar R-57 (crystal; 110 mg,

3152 J . Org. Chem., Vol. 62, No. 10, 1997
Yoshimura et al.
43%). Da ta for r-57: mp 208-210 °C (dec, crystallized from
MeOH); 1H NMR (DMSO-d6) δ 10.90 (1H, br s, D2O exchange-
able), 8.59 (1H, d, J ) 7.3 Hz), 7.93 (2H, d, J ) 7.3 Hz), 7.71-
7.67 (1H, m), 7.50 (2H, t, J ) 7.3 Hz), 7.27 (1H, d, J ) 7.3
Hz), 6.55 (1H, d, J ) 5.9 Hz), 6.70-6.68 (1H, m), 5.31 (1H, t,
J ) 5.4 Hz, D2O exchangeable), 5.00 (1H, dd, J ) 4.9, 5.9 Hz),
4.03-3.99 (1H, m), 3.73-3.69 (1H, m), 3.63-3.58 (1H, m), 2.12
(3H, s); FAB-MS m/ z 431 (M+ + H). Anal. Calcd for
C18H18N6O5S: C, 50.23; H, 4.21; N, 19.52. Found: C, 50.35;
H, 4.30; N, 19.29. Da ta for â-57: mp 204-206 °C (dec,
crystallized from CHCl3); 1H NMR (DMSO-d6) δ 11.03 (1H, br
s, D2O exchangeable), 8.60 (1H, d, J ) 7.8 Hz), 8.03-8.01 (2H,
m), 7.75-7.71 (1H, m), 7.62-7.58 (2H, m), 7.33 (1H, d, J )
7.8 Hz), 6.32 (1H, d, J ) 7.3 Hz), 5.73 (1H, t, J ) 3.9 Hz), 5.50
(1H, br s, D2O exchangeable), 4.85 (1H, dd, J ) 3.9, 7.3 Hz),
3.80-3.68 (3H, m), 2.12 (3H, s); FAB-MS m/ z 431 (M+ + H).
Anal. Calcd for C18H18N6O5S‚0.25H2O: C, 49.71; H, 4.29; N,
19.32. Found: C, 49.98; H, 4.19; N, 19.15.
4.4 Hz, D2O exchangeable), 4.31-4.26 (2H, m), 3.75-3.70
(1H, m), 3.60-3.55 (1H, m), 3.48-3.42 (1H, m); FAB-MS m/ z
285 (M+ + H). IR (KBr) 2120 cm-1 (N3). Anal. Calcd for
C9H12N6O3S‚1.3MeOH: C, 37.95; H, 5.32; N, 25.78. Found:
C, 37.90; H, 5.14; N, 25.54. Da ta for â-58: UV (H2O) λmax 275
nm (8400); UV (0.1 N HCl) λmax 282 nm (12 100), 219 nm
1
(6400); H NMR (DMSO-d6) δ 7.97 (1H, d, J ) 7.8 Hz), 7.28,
7.26 (total 2H, br d, D2O exchangeable), 6.25 (1H, d, J ) 8.3
Hz), 5.98 (1H, d, J ) 4.9 Hz, D2O exchangeable), 5.80 (1H, d,
J ) 7.8 Hz), 5.23 (1H, t, J ) 5.4 Hz, D2O exchangeable),
4.30 (1H, dd, J ) 3.4, 7.3 Hz), 3.98 (1H, dd, J ) 3.4, 8.3
Hz), 3.67-3.54 (2H, m), 3.28-3.24 (1H, m); FAB-MS m/ z 285
(M+ + H); IR (KBr) 2116 cm-1 (N3). Anal. Calcd for
C9H12N6O3S‚1.1MeOH: C, 37.96; H, 5.17; N, 26.30. Found:
C, 38.09; H, 4.87; N, 25.97.
In Vitr o Assa y for An titu m or Effects. Cytotoxicities
against CCRF-HSB-2 and KB cells were evaluated as reported
previously.44 Typically, cells (5000 cells/well) were exposed to
drugs in a 96-well plate for 72 h and the growth inhibition
rates were determined by MTT assay47 or the dye uptake
method.48
1-(2-Azid o-2-d eoxy-4-th io-r(a n d â)-D-r ibo-p en tofu r a n o-
syl)cytosin e (r,â-58). A suspension of â-57 (89 mg, 0.21
mmol) in MeOH (3 mL) and concentrated NH4OH (3 mL) was
stirred at room temperature for 2 h. After the solvent was
removed under reduced pressure, the remaining H2O was
removed by codistillation with EtOH (×3). The residue was
purified by column chromatography over silica gel (1.0×14 cm;
17% MeOH in CHCl3) to give â-58 (58 mg, 97%) as an
amorphous solid. In a similar way, R-57 (90 mg, 0.21 mmol)
was converted to R-58 (an amorphous foam, 52 mg, 87%).
Da ta for r-58: UV (H2O) λmax 275 nm (8700); UV (0.1 N HCl)
Ack n ow led gm en t. The authors are grateful to Dr.
K. Kodama, Yamasa Corporation, for his encouragement
throughout this work. The authors also acknowledge
Mr. M. Morozumi and Dr. H. Machida, Yamasa Corpo-
ration, for their helpful discussions.
J O9700540
1
λmax 282 nm (12 500), 219 nm (6300); H NMR (DMSO-d6) δ
8.02 (1H, d, J ) 7.8 Hz), 7.03 (2H, br s, D2O exchangeable),
6.35 (1H, d, J ) 5.4 Hz), 5.83 (1H, d, J ) 3.9 Hz, D2O
exchangeable), 5.76 (1H, d, J ) 7.8 Hz), 4.88 (1H, t, J )
(47) Mossman, T. J . Immunol. Methods 1983, 65, 55-63.
(48) Finter, N. B. J . Gen. Viol. 1969, 5, 419-427.