Enantiomeric synthesis of D- and L-cyclopentenyl nucleosides and their antiviral activity against HIV and West Nile virus

Article abstract of DOI:10.1021/jm010256v

Enantiomeric synthesis of D- and L-cyclopentenyl nucleosides and their antiviral activity against HIV and West Nile virus are described. The key intermediate (-)- and (+)-cyclopentenyl alcohols (7 and 15) were prepared from D-γ-ribonolactone and D-ribose,

Full text of DOI:10.1021/jm010256v

J . Med. Chem. 2001, 44, 3985-3993
3985
En a n tiom er ic Syn th esis of D- a n d L-Cyclop en ten yl Nu cleosid es a n d Th eir
An tivir a l Activity Aga in st HIV a n d West Nile Vir u s
Gyu Y. Song,† Vincent Paul,† Hyunah Choo,† J ohn Morrey,‡ Robert W. Sidwell,‡ Raymond F. Schinazi,§ and
Chung K. Chu*,†
College of Pharmacy, The University of Georgia, Athens, Georgia 30602, Institute for Antiviral Research,
Utah State University, Logan, Utah 84322, and Emory University School of Medicine, and Veterans Affairs Medical Center,
Decatur, Georgia 30033
Received J une 7, 2001
Enantiomeric synthesis of D- and L-cyclopentenyl nucleosides and their antiviral activity against
HIV and West Nile virus are described. The key intermediate (-)- and (+)-cyclopentenyl alcohols
(7 and 15) were prepared from D-γ-ribonolactone and D-ribose, respectively. Coupling of 7 with
appropriately blocked purine and pyrimidine bases via the Mitsunobu reaction followed by
deprotection afforded the target L-(+)-cyclopentenyl nucleosides (24-28, 31, 33, and 36). D-(-)-
Cyclopentenyl nucleosides (1, 40, 43, and 52-56) were also prepared by a similar procedure
for L-isomers from 15. The synthesized compounds were evaluated for their antiviral activity
against two RNA viruses: HIV and West Nile virus. Among the synthesized D-(-)-nucleosides,
adenine (1, neplanocin A), cytosine (55, CPE-C), and 5-fluorocytosine (56) analogues exhibited
moderate to potent anti-HIV activity (EC50 0.1, 0.06, and 5.34 µM, respectively) with significant
cytotoxicity in PBM, Vero, and CEM cells. Also, cytosine (55) and 5-fluorocytosine (56) analogues
exhibited the most potent anti-West Nile virus activity (EC50 0.2-3.0 and 15-20 µM,
respectively). Among L-(+)-nucleosides, only the cytosine (27) analogue exhibited weak anti-
HIV activity (EC50 58.9 µM).
In tr od u ction
(-)-Neplanocin A1 (NPA, 1, Figure 1), an olefinic
analogue of aristeromycin 2, is a naturally occurring
carbocyclic nucleoside in which a methylene group
replaces the oxygen atom in the furanose ring. The
unusual presence of the double bond in NPA attracted
a great deal of interest from synthetic organic chemists,
and consequently, several enantiomeric syntheses have
F igu r e 1. Structures of neplanocin A and aristeromycin.
been reported.2,3 NPA is a cyclopentenyl analogue of
been limited because of its significant cytotoxicity. The
cytotoxic effect could be attributed mainly to phospho-
rylation of the primary hydroxyl group at the 6′-position
(5′-position of the natural nucleosides) by adenosine
kinase, and subsequent phosphorylation to the triphos-
phate, which may inhibit cellular polymerases and/or
be incorporated into the host cells.11 NPA is also known
to be rapidly deaminated by adenosine deaminase to the
therapeutically inactive inosine congener,14 which may
reduce the therapeutic potency of the NPA. As indicated,
although NPA itself is not useful as an antiviral agent
because of its cytotoxicity, it may be a good lead for the
development of structurally related therapeutic agents.15
Therefore, a number of neplanocin analogues have been
synthesized and evaluated for their antiviral and anti-
cancer activities.16 Among them, cyclopentenylcytosine
(CPE-C) exhibited significant antiviral activity against
both DNA and RNA viruses in vitro as well as antitumor
activity.17 Recently, it was reported that neplanocin A
analogues inhibited the Tat-dependent and Tat-inde-
pendent transactivation of HIV-1.18,19
adenosine, which has been shown to possess both
antitumor and antiviral activity.4,5 Because of the
absence of a true glycosidic bond, carbocyclic nucleosides
are chemically more stable and, therefore, are not
substrates for the enzymes that cleave the glycosidic
linkage in conventional nucleosides.6 Several carbocyclic
nucleosides have been reported as potential anti-HIV7,8
and anti-HBV9 agents. Among them, carbovir8 and
abacavir10 are the most interesting compounds because
of their potent and selective anti-HIV activity. The FDA
recently approved abacavir for the treatment of HIV
infection.
The mechanism of the antiviral effect of NPA would
be in part due to the inhibition of S-adenosylhomocys-
teine (AdoHcy) hydrolase.11 Thus, AdoHcy has become
an attractive target for the design of antiviral agents.12
NPA is of interest as an antiviral agent because of its
broad spectrum of antiviral effects.13 However, the
therapeutic utility of NPA as an antiviral agent has
* To whom correspondence should be addressed. Tel: (706) 542-
5379. Fax: (706) 542- 5381. E-mail: dchu@rx.uga.edu.
† The University of Georgia.
West Nile virus (WNV) belongs to the family of
Flaviviridae, genus Flavivirus, which includes hepatitis
C, yellow fever, dengue, and J apanese encephalitis
viruses.20 The virus has been found in Africa, Western
‡ Utah State University.
§ Emory University School of Medicine, and Veterans Affairs Medical
Center.
10.1021/jm010256v CCC: $20.00 © 2001 American Chemical Society
Published on Web 10/03/2001

3986 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23
Song et al.
Sch em e 1a
a
Reagents: (a) (CH3)3COCH3, t-BuOK, sec-BuLi, THF, -78 °C, 3 h; (b) Ac2O, Et3N, DMAP, CH2Cl2, rt, 24 h; (c) PdCl2(CH3CN)2,
p-benzoquinone, THF, reflux, 24 h; (d) K2CO3, MeOH, rt, 1 h; (e) (t-BuOCH2)2CuLi, t-BuOMe, THF, -30 °C, 30 min; (f) PhSeBr, LDA,
THF, 0 °C, 2 h; (g) H2O2/H2O, CH2Cl2, rt, 30 min; (h) CeCl3; NaBH4, CH3OH, 0 °C, 30 min.
Europe, the Middle East, and the Mediterranean region
of Europe.21 WNV was recognized for the first time in
the Americas in August 1999 when an outbreak in New
York City resulted in 62 cases of acute encephalitis.
Seven patients died, and mortality among horses and
birds was substantial. Birds are the natural hosts for
this virus, which can be transmitted from infected birds
to humans and other animals through the bite of an
infected mosquito.22 Most human infections are mild,
and symptoms include fever, headache, and body aches,
often with skin rash and swollen lymph glands. More
severe infection may be marked by headache, high fever,
neck stiffness, coma, tremors, convulsions, muscle weak-
ness, paralysis, and death.23 There is no specific treat-
ment for WNV nor available vaccine against the virus.
Recently, it was reported that ribavirin inhibited WNV
replication.24 As part of our ongoing antiviral drug
discovery program, we synthesized the enantiomeric D-
and L-cyclopentenyl nucleosides as potential antiviral
agents for HIV and WNV.
pyrimidine and purine nucleosides for structure-activ-
ity relationship studies. For the synthesis of target
compounds, L-(+)-cyclopentenyl nucleosides (24-28, 31,
33, and 36), we utilized the intermediate, (-)-cyclopen-
tenone 3,27 previously prepared in four steps from
D-ribonolactone (Scheme 1). Addition of a carbanion of
(CH3)3COCH3, prepared from (CH3)3COCH3, (CH3)3-
COK, and sec-BuLi, to compound 3 in THF at -78 °C,
proceeded from the least hindered â-face to stereose-
lectively give the R-tertiary cyclopentenyl alcohol 4 in
78% yield. 4 was acetylated by Ac2O and Et3N in the
presence of DMAP in CH2Cl2 to give the cyclopentenyl
acetate 5 in 94% yield. The rearrangement of 5 was
accomplished by treatment with PdCl2(MeCN)2 and
p-benzoquinone in THF at reflux28 to give 6 in 91% yield,
which was then hydrolyzed with K2CO3 in MeOH to give
the key intermediate, (-)-cyclopentenyl alcohol 7, for
L-nucleosides. In addition, an alternative synthesis of
7 was developed (Scheme 1). We utilized an enantiomer,
(+)-cyclopentenone 8,29 which was previously prepared
in three steps from D-ribose. Treatment of 8 with a
solution of lithium bis(tert-butoxymethyl)cuprate at -30
°C gave optically pure cyclopentanone 9 as a single
isomer in 87% yield. Compound 9 was converted to
phenylselenyl ketone 10 as a mixture of two isomers
by LDA and phenylselenyl bromide. The selenides 10
Ch em istr y
Although D- and L-neplanocin A have been synthe-
sized by different synthetic methodologies,25,26 we de-
veloped an efficient synthetic procedure, as shown in
Scheme 1, which was used for the synthesis of various

Antiviral Activity of D- and L-Cyclopentenyl Nucleosides
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23 3987
Sch em e 2a
a
Reagents: (a) PPh3, DEAD, N3-benzoyluracil (for 16), N3-benzoylthymine (for 17), N3-benzoyl-5-fluorouracil (for 18), 6-chloropurine
(for 29), N2-acetylamino-6-chloropurine (for 34), rt, 17 h; (b) sat. NH3 in MeOH, 0 °C, 4 h; (c) 2,4,6-triisopropylbenzenesulfonyl chloride,
DMAP, Et3N, MeCN, 0 °C - rt, 24 h then 30% NH4OH, rt, 5 h; (d) CF3CO2H/H2O (2:1), 50 °C, 3 h; (e) sat. NH3 in MeOH, steel bomb, 80
°C, 15 h; (f) HSCH2CH2OH, NaOCH3, reflux, MeOH, 24 h.
was then oxidized by using a bi-phase method (dichlo-
romethane-hydrogen peroxide) buffered with pyridine
to give the cyclopentenone intermediate 11 in 35% yield.
Selective reduction of the carbonyl group of 11 by
sodium borohydride in the presence of cerium(III)
chloride exclusively gave the (-)-cyclopentenyl alcohol
7 in 93% yield. The stereoselectivity of the reaction from
11 to 7 is probably due to the electronic effect as well
as the steric hindrance of the oxygens of the isopropy-
lidene group, which prevents a nucleophile attack
(hydrogen) from the same side of the isopropylidene
group.
Coupling of 7 with appropriately blocked purine and
pyrimidine bases to L-nucleoside analogues 16-18, 29,
and 34 was carried out with the standard Mitsunobu
reaction30,31 to obtain the desired nucleosides (Scheme
2). Yields varied widely depending on the blocked
heterocycles used. To synthesize the pyrimidine ana-
logues, the (-)-cyclopentenyl alcohol 7 was treated with
N3-benzoyluracil,32,33 N3-benzoylthymine,32,33 and N3-
benzoyl-5-fluorouracil,34 in the presence of diethylazodi-
carboxylate (DEAD) and Ph3P in THF at room temper-
ature to give 16-18 in 64, 72, and 61% yield, respectively
(Scheme 2). Debenzoylation of 16-18 with saturated
ammonia in MeOH gave 19-21, followed by deprotec-
tion of the tert-butyl and isopropylidene groups with
CF3COOH/H2O (2:1, v/v) solution at 50 °C to give the
L-(+)-uracil nucleoside 24, L-(+)-thymine nucleoside 25,
and L-(+)-5-fluorouracil nucleoside 26, respectively. The
uracil 19 and 5-fluorouracil 21 analogues were con-
verted to the corresponding cytosine 22 and 5-fluorocy-
tosine 23 analogues by the reported method,35 followed
by deprotection to obtain the L-(+)-cytosine nucleoside
27 and L-(+)-5-fluorocytosine nucleoside 28, respectively
(Scheme 2). The purine analogues were also prepared
using a similar procedure. Treatment of 7 with 6-chlo-
ropurine and N2-acetylamino-6-chloropurine, as de-
scribed above, gave 29 and 34 in 70 and 75% yield,
respectively (Scheme 2).
Treatment of 29 with saturated ammonia in MeOH
in a steel bomb at 80 °C gave the adenine analogue 30
in 76% yield, followed by deprotection of tert-butyl and
isopropylidene groups to obtain the L-(+)-neplanocin A
(31) in 50% yield, which was further purified by recrys-
tallization from boiling 10% aqueous MeOH. Treatment
of 29 with mercaptoethanol and sodium methoxide in
refluxing methanol followed by deprotection of tert-butyl
and isopropylidene groups afforded the L-(+)-hypoxan-

3988 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23
Song et al.
Sch em e 3
The synthesized nucleosides were also evaluated
against West Nile virus in vitro (Table 1). D-Cytosine
(55) and D-5-fluorocytosine (56) analogues exhibited the
most potent antiviral activity (EC50 0.2-3.0 and 15-
20 µM, respectively). However, L-(+)-cyclopentenyl nu-
cleosides did not show any significant antiviral activity.
In summary, we have developed an efficient synthetic
methodology for a series of D- and L-cyclopentenyl
nucleosides and evaluated their anti-HIV and anti-West
Nile virus activities.
Ta ble 1. Anti-HIV and Anti-West Nile Virus Activities of D-
and L-Cyclopentenyl Nucleosides
Exp er im en ta l Section
Ch em istr y. Melting points were determined on a Mel-temp
II laboratory device and are uncorrected. NMR spectra were
recorded on a Brucker 400 AMX spectrometer at 400 (1H) and
100 MHz (13C) in the indicated solvents. UV spectra were
obtained on a Beckman DU-650 spectrophotometer. Optical
rotations were measured on a J ASCO DIP-370 digital pola-
rimeter. TLC was performed on Uniplates (silica gel) pur-
chased from Analtech Co. Mass spectra were recorded on a
Micromass Autospec high-resolution mass spectrometer in
FAB mode. Elemental analyses were performed by Atlantic
Microlab, Inc. Dry THF was obtained by distillation from Na
and benzophenone when the solution became purple.
EC50, µM
West Nile
cytotoxicity (IC50, µM)
PBM
cells
Vero
cells
CEM
cells
compd
HIV-1
virus
24
25
26
27
28
31
33
36
1
40
43
52
53
54
55
56
>100
>100
>100
58.9
>100
>100
>100
>100
0.1
>200
>200
>200
>200
>200
>200
>200
>200
>51
>100
>100
>100
>100
>100
>100
>100
>100
44.6
>100
>100
>100
>100
>100
>100
>100
>100
3.5
>100
>100
>100
>100
>100
>100
>100
>100
1.2
(1S,2R,3R)-1-(ter t-Bu toxym eth yl)-2,3-(isop r op ylid en e-
d ioxy)-4-cyclop en ten -1-ol (4). sec-Butyllithium solution (1.4
M in hexane, 34.7 mL, 48.6 mmol) was added dropwise to a
suspension of potassium tert-butoxide (5.94 g, 48.6 mmol) in
anhydrous tert-butylmethyl ether cooled to -70 °C over 5 min
at -70 °C under nitrogen atmosphere. After stirring 3.5 h at
this temperature, a solution of 3 (5 g, 32.4 mmol) in THF (100
mL) was added dropwise to the above solution, and the
resulting solution was stirred for 3 h at -70 °C. The cooling
bath was removed, and the reaction mixture was quenched
by addition of saturated aqueous NH4Cl solution (50 mL) then
extracted with CHCl3 (300 mL). The organic layer was washed
with brine, dried over anhydrous Na2SO4, and filtered; and
the filtrate was concentrated under vacuum. The residue was
purified by silica gel column chromatography (5% EtOAc in
>100
>100
>100
>100
93.1
>200
>200
>200
>200
>200
0.2 (3)a
15 (20)
ND
>100
>100
>100
>100
>100
6.5
>100
>100
>100
>100
>100
1.95
>100
>100
>100
>100
>100
0.08
0.06
5.34
73.7
27.4
51.8
AZTb
0.004
ND
>100
ND
29.0
>100
14.3
ND
6-azauridineb
1.2
a
b
Confirmation result. Positive control; ND, not determined.
thine nucleoside 33, which was further purified by
recrystallization from boiling MeOH. The L-(+)-guanine
nucleoside 36 was also prepared using the same proce-
dure for 33 from 34. For the synthesis of D-(-)-cyclo-
pentenyl nucleosides (1, 40, 43, and 52-56), we utilized
the intermediate (+)-cyclopentenone (8),29 the enanti-
omer of 3 (Scheme 1). The key intermediate (+)-
cyclopentenyl alcohol 15, the enantiomer of 7, was
prepared in four steps from 8 using the same procedure
for 7. After coupling of 15 with appropriately blocked
purine and pyrimidine bases, the final D-(-)-cyclo-
penetenyl nucleosides (1, 40, 43, and 52-56) were
prepared using the same procedure for L-(-)-cyclopen-
tenyl nucleosides (Scheme 3).
An tivir a l Activity. The synthesized nucleosides
were tested for their antiviral activities against HIV and
West Nile virus, as well as for their cytotoxicity. Anti-
HIV-1 activity of the synthesized nucleosides was evalu-
ated in human peripheral blood mononuclear (PBM)
cells infected with HIV-1.36 The results are summarized
in Table 1. It was found that among the synthesized
D-(-)-nucleosides, adenine (1, neplanocin A)4,5 and cy-
tosine (55, CPE-C)17 analogues exhibited potent anti-
viral activity (EC50 0.1 and 0.06 µM, respectively) with
significant cytotoxicity in PBM, CEM, and Vero cells.
5-Fluorocytosine (56) analogue exhibited moderately
potent antiviral activity (EC50 5.34 µM) with significant
cytotoxicity in PBM, CEM, and Vero cells, and 5-fluo-
rouracil (54) analogue exhibited weak antiviral activity
(EC50 93.1 µM). In the L-(+)-nucleoside series, only the
cytosine (27) analogue exhibited weak antiviral activity
(EC50 58.9 µM).
hexane) to give 4 (6.11 g, 78%) as a syrup. [R]24 -95.51° (c
D
1.1, CHCl3). 1H NMR (400 MHz, CDCl3) δ 1.15 (s, 9H, tert-
butyl), 1.39 (s, 3H, CH3), 1.44 (s, 3H, CH3), 3.17 (s, 1H, OH),
3.33 (d, J ) 8.75 Hz, 1H, 6a-H), 3.45 (d, J ) 8.75 Hz, 1H, 6b-
H), 4.47 (d, J ) 5.32 Hz, 1H, 2-H), 5.00 (d, J ) 5.32 Hz, 1H,
3-H), 5.70 (d, J ) 5.75 Hz, 1H, 5-H), 5.89 (dd, J ) 5.74, 1.59
Hz, 1H, 4-H). 13C NMR (CDCl3) δ 26.77, 27.37, 27.85, 65.83,
73.05, 80.86, 81.70, 83.99, 112.26, 132.83, 137.02. HR-FAB
MS Obsd, m/z 243.1579; calcd for C13H23O4, m/z 243.1596
(M + H)+. Anal. (C13H22O4) C, H.
(1S,2R,3R)-1-Acetoxy-2,3-(isopr op yliden edioxy)-1-(ter t-
bu toxym eth yl)-4-cyclop en ten (5). A mixture of 4 (4.8 g, 19.8
mmol), acetic anhydride (4.04 g, 39.6 mmol), DMAP (2.41 g,
19.8 mmol), and triethylamine (4.00 g, 39.6 mmol) in CH2Cl2
(200 mL) was stirred for 24 h at room temperature. The solvent
was evaporated, and the residue was partitioned between CH2-
Cl2 (300 mL) and water (200 mL). The organic layer was
washed with brine, dried over anhydrous Na2SO4, and filtered;
and the filtrate was concentrated under vacuum. The residue
was purified by silica gel column chromatography (5% EtOAc
in hexane) to give 5 (5.28 g, 94%) as a syrup. [R]24 -110.62°
D
(c 1.65, CHCl3). 1H NMR (400 MHz, CDCl3) δ 1.12 (s, 9H, tert-
butyl), 1.37 (s, 6H, CH3 × 2), 2.07 (s, 3H, acetyl), 3.67 (d, J )
8.81 Hz, 1H, 6a-H), 3.72 (d, J ) 8.78 Hz, 1H, 6b-H), 4.79 (d,
J ) 5.16 Hz, 1H, 2-H), 5.00 (d, J ) 4.90 Hz, 1H, 3-H), 5.95 (d,
J ) 5.85 Hz, 1H, 5-H), 5.89 (dd, J ) 5.83, 1.29 Hz, 1H, 4-H).
13C NMR (CDCl3) δ 22.06, 27.51, 27.75, 28.12, 63.55, 73.66,
81.30, 84.36, 89.51, 112.18, 133.96, 134.56, 170.51. HR-FAB
MS Obsd, m/z 285.1683; calcd for C15H25O5, m/z 285.1701
(M + H)+. Anal. (C15H24O5) C, H.
(1R,2S,3S)-1-Acetoxy-2,3-(isop r op ylid en ed ioxy)-4-(ter t-
bu toxym eth yl)-4-cyclop en ten (6). A mixture of 5 (2.68 g,
9.42 mmol), PdCl2(MeCN)2 (122 mg, 0.47 mmol), and p-

Antiviral Activity of D- and L-Cyclopentenyl Nucleosides
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23 3989
benzoquinone (407 mg, 3.76 mmol) in dry THF (200 mL) was
heated under reflux for 24 h. The reaction mixture was cooled
to room temperature, and the solvent was evaporated under
vacuum. The residue was purified by silica gel column chro-
matography (10% EtOAc in hexane) to give 6 (2.44 g, 91%) as
tion of LDA (1.5 M in cyclohexane, 1.64 mL, 2.47 mmol) in
dry THF (8.0 mL) was stirred under nitrogen at -78 °C and
9 (0.50 g, 2.06 mmol) in dry THF (10 mL) was added dropwise.
The solution was stirred for 2 h at 0 °C and benzeneselenyl
bromide (0.58 g, 2.47 mmol) in THF (2.5 mL) was added
rapidly. The reaction mixture was stirred for 2 h at 0 °C and
then warmed to room temperature while monitoring by TLC.
After completion of the reaction, the reaction mixture was
cooled to 0 °C with an ice bath, then H2O (1 mL) was slowly
added and the reaction mixture was neutralized with HOAc.
The solvent was evaporated under vacuum and the resulting
yellow oil was dissolved in ether. The organic phase was
washed with brine, dried over anhydrous sodium sulfate, and
filtered; and the filtrate was evaporated to dryness. The
resulting residue was purified by silica gel chromatography
(5-10% EtOAc in hexane) to give 10 (0.50 g, 61%) as an orange
oil mixture of two anomers. This anomeric mixture was used
a syrup. [R]24 +56.97° (c 1.28, CHCl3). 1H NMR (400 MHz,
D
CDCl3) δ 1.16 (s, 9H, tert-butyl), 1.30 (s, 3H, CH3), 1.32 (s, 3H,
CH3), 2.04 (s, 3H, acetyl), 3.96 (d, J ) 13.71 Hz, 1H, 6a-H),
3.72 (d, J ) 13.68 Hz, 1H, 6b-H), 4.86 (d, J ) 5.56 Hz, 1H,
2-H), 4.89 (d, J ) 5.56 Hz, 1H, 3-H), 5.29 (m, 1H, 1-H), 5.69
(br s, 1H, 5-H). 13C NMR (CDCl3) δ 19.85, 25.72, 26.27, 57.51,
72.53, 74.35, 81.85, 111.74, 124.48, 146.11, 169.62. HR-FAB
MS Obsd, m/z 285.1705; calcd for C15H25O5, m/z 285.1701
(M + H)+. Anal. (C15H24O5) C, H.
(1R,2R,3S)-2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u t oxy-
m eth yl)-4-cyclop en ten -1-ol (7). Meth od 1. A mixture of 6
(2.10 g, 7.39 mmol) and K2CO3 (2.04 g, 14.7 mmol) in CH3OH
(100 mL) was stirred for 1 h at room temperature. The solvent
was evaporated and the residue was partitioned between CH2-
Cl2 (300 mL) and water (200 mL). The organic layer was
washed with brine, dried over anhydrous Na2SO4, and filtered;
and the filtrate was concentrated under vacuum. The residue
was purified by silica gel column chromatography (30% EtOAc
in hexane) to give 7 (1.55 g, 87%) as a white solid. Meth od 2.
NaBH4 (0.37 g, 9.9 mmol) was added to a solution of 11 (1.6 g,
6.6 mmol) and CeCl3‚7H2O (2.48 g, 6.6 mmol) in MeOH (50
mL) at 0 °C. After 1 h, cold water was added and the mixture
was extracted with ether (300 mL). The organic layer was
washed with brine, dried over anhydrous Na2SO4, and filtered;
and the filtrate was concentrated under vacuum. The residue
was purified by silica gel column chromatography (30% EtOAc
in the next step without further purification. [R]25 +137.95°
D
(c 1.21, acetone). Anal. (C19H26O4Se‚0.7CH3COCH3) C, H.
(2S,3S)-2,3-(Isopr opyliden edioxy)-4-(ter t-bu toxym eth yl)-
4-cyclop en ten -1-on e (11). H2O2 (24 mL, dissolved in 200 mL
of H2O) was added dropwise to a solution of 10 (11.94 g, 30.04
mmol) in CH2Cl2 (600 mL) and pyridine (20 mL), while keeping
the temperature at 20-25 °C. The reaction mixture was stirred
at room temperature for 30 min and then washed with water
(50 mL). The organic phase was washed with 50 mL of
saturated sodium chloride, dried over anhydrous sodium
sulfate, and filtered; and the filtrate was concentrated under
vacuum. The resulting residue was purified by flash chroma-
tography (5% EtOAc in hexane) to give 11 (2.1 g, 30%) as a
yellow semisolid. [R]25D +7.48° (c 0.40, acetone). 1H NMR (400
MHz, CDCl3) δ 1.19 (s, 9H, tert-butyl), 1.39 (s, 3H, CH3), 1.41
(s, 3H, CH3), 4.23 (d, J ) 17.8 Hz, 1H, 6a-H), 4.42 (d, J ) 17.8
Hz, 1H, 6b-H), 4.50 (d, J ) 5.5 Hz, 1H, 3-H), 5.11 (d, J ) 5.5
Hz, 1H, 2-H), 6.15 (s, 1H, 5-H). Anal. (C13H20O4‚0.2H2O) C, H.
in hexane) to give 7 (1.5 g, 93%) as a white solid. mp 41-42
1
°C. [R]25 -37.60° (c 1.14, CHCl3. H NMR (400 MHz, CDCl3)
D
δ 1.23 (s, 9H, tert-butyl), 1.40 (s, 3H, CH3), 1.42 (s, 3H, CH3),
2.61 (br s, 1H, OH), 3.99 (d, J ) 13.18 Hz, 1H, 6a-H), 4.08 (d,
J ) 13.18 Hz, 1H, 6b-H), 4.54 (m, 1H, 1-H), 4.75 (t, J ) 5.5
Hz, 1H, 2-H), 4.95 (d, J ) 5.5 Hz, 1H, 3-H), 5.76 (br s, 1H,
5-H). 13C NMR (CDCl3) δ 26.67, 27.43, 27.64, 58.18, 73.32,
82.98, 112.40, 130.51, 144.01. HR-FAB MS Obsd, m/z 243.1603;
calcd for C13H23O4, m/z 243.1596 (M + H)+. Anal. (C13H22O4)
C, H.
(1R,2S,3S)-1-(ter t-Bu toxym eth yl)-2,3-(isop r op ylid en e-
d ioxy)-4-cyclop en ten -1-ol (12). Compound 12 was prepared
from 8 using the same procedure that was used for 4. 1H NMR
and 13C NMR data were identical to that of 4. [R]24D +96.40°(c
1.01, CHCl3). HR-FAB MS Obsd, m/z 243.1598; calcd for
C
13H23O4, m/z 243.1596 (M + H)+. Anal. (C13H22O4) C, H.
(1R,2S,3S)-1-Acetoxy-2,3-(isop r op ylid en ed ioxy)-1-(ter t-
(2S,3S,4S)-2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u t oxy-
m eth yl)-cyclop en ta n -1-on e (9). sec-Butyllithium (74.6 mL,
1.3 M in cyclohexane, 0.097 mol) was added dropwise to a
suspension of 95% potassium tert-butoxide (10.9 g, 0.097 mol)
in anhydrous tert-butylmethyl ether (400 mL) cooled to -70
°C over 10 min at -70 °C under nitrogen atmosphere. The
color became orange. After stirring 3.5 h at -70 °C. a solution
of LiBr (16.82 g, 0.19 mol) in dry THF (100 mL) was added
dropwise over 10 min at -70 °C then allowed to warm to -15
°C and stirred for 30 min. Upon recooling to -70 °C, a solution
of CuBr‚SMe2 (9.98 g, 0.048 mol) in diisopropyl sulfide (70 mL)
was added dropwise over 10 min. The solution of 8 (5 g, 0.032
mol) in dry THF (50 mL) was added dropwise over 5 min. The
reaction mixture was allowed to cool to -30 °C over 15 min,
stirred at this temperature for an additional 30 min, then
quenched with 50 mL of CH3OH/CH3COOH (1:1, v/v) and
poured into NH4Cl/NH4OH solution. After removal of the
aqueous layer, the organic layer was washed with a 1:1
mixture of saturated NH4Cl and 3% NH4OH solution, and then
with brine. The organic layer was dried over Na2SO4 and
filtered; and the filtrate was concentrated under vacuum. The
residue was purified by silica gel chromatography (15% EtOAc
bu toxym eth yl)-4-cyclop en ten (13). Compound 13 was pre-
pared from 12 using the same procedure that was used for 5.
1H NMR and 13C NMR data were identical to that of 5. [R]24
D
+109.52° (c 1.02, CHCl3). HR-FAB MS Obsd, m/z 285.1703;
calcd for C15H25O5, m/z 285.1701 (M + H)+. Anal. (C15H24O5)
C, H.
(1S,2R,3R)-1-Acetoxy-2,3-(isopr op yliden edioxy)-4-(ter t-
bu toxym eth yl)-4-cyclop en ten (14). Compound 14 was pre-
1
pared from 13 using the same procedure used for 6. H NMR
and 13C NMR data were identical to that of 6. [R]24 -56.29°
D
(c 1.41, CHCl3). HR-FAB MS Obsd, m/z 285.1711; calcd for
C
15H25O5, m/z 285.1701 (M + H)+. Anal. (C15H24O5) C, H.
(1S,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u t oxy-
m eth yl)-4-cyclop en ten -1-ol (15). Compound 15 was pre-
1
pared from 14 using the described procedure for 7. H NMR
and 13C NMR data were identical to that of 7. [R]24 +36.81°
D
(c 1.14, CHCl3). HR-FAB MS Obsd, m/z 243.1598; calcd for
C
13H23O4, m/z 243.1596 (M + H)+. Anal. (C13H22O4) C, H.
Gen er a l P r oced u r e for th e Mitsu n obu Con d en sa tion .
(1′S,2′R,3′S)-N3-Ben zoyl-1-[2,3-(isopr opylen edioxy)-4-(ter t-
bu toxym eth yl)-4-cyclop en ten -1-yl]u r a cil (16). A solution
of diethylazodicarboxylate (DEAD, 1.04 g, 5.98 mmol) in dry
THF was added dropwise to a solution of 7 (580 mg, 2.39
mmol), triphenylphosphine (1.57 g, 5.98 mmol), and N3-
benzoyluracil (1.03 g, 4.78 mmol) in dry THF at 0 °C under
nitrogen atmosphere. The mixture was stirred at room tem-
perature for 16 h, and then the solvent was removed under
vacuum. The residue was purified by silica gel column chro-
matography (50% EtOAc in n-hexane) to give 16 (670 mg, 64%)
as a white solid. mp 147-149 °C. [R]25D +17.97°(c 0.74, CHCl3).
UV(MeOH) λmax 253 nm. 1H NMR (400 MHz, CDCl3) δ 1.24
(s, 9H, tert-butyl), 1.34 (s, 3H, CH3), 1.41(s, 3H, CH3), 4.08 (d,
in hexane) to give 9 (6.90 g, 87%) as a white solid. mp 64-66
1
°C; [R]25 +178.3° (c 0.59 CHCl3). H NMR (400 MHz, CDCl3)
D
δ 1.11 (s, 9H, tert-butyl), 1.35 (s, 3H, CH3), 1.43 (s, 3H, CH3),
1.96 (d, J ) 17.8 Hz, 1H, 5a-H), 2.54 (d, J ) 8.9 Hz, 1H, 4-H),
2.72 (dd, J ) 17.9, 8.9 Hz, 1H, 5b-H), 3.35 (m, 1H, 6a-H), 3.54
(m, 1H, 6b-H), 4.23 (d, J ) 5.3 Hz, 1H, 3-H), 4.63 (d, J ) 5.4
Hz, 1H, 2-H). HR-FAB MS Obsd, m/z 241.1434; calcd for
C13H21O4, m/z 241.1440 (M + H)+. Anal. (C13H20O4‚0.2H2O)
C, H.
(2S,3S,4S)-2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u t oxy-
m eth yl)-5-selen o-ph en yl-4-cyclopen tan -1-on e (10). A solu-

3990 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23
Song et al.
J ) 15.13 Hz, 1H, 6′a-H), 4.15 (d, J ) 15.07 Hz, 1H, 6′b-H),
4.63 (d, J ) 5.71 Hz, 1H, 2′-H), 5.19 (d, J ) 5.66 Hz, 1H, 3′-
H), 5.38 (s, 1H, 1′-H), 5.63 (s, 1H, 5′-H), 5.80 (d, J ) 8.1 Hz,
1H, 5-H), 7.15 (d, J ) 8.1 Hz, 1H, 6-H), 7.48-7.95 (m, 5H,
phenyl). HR-FAB MS Obsd, m/z 441.2026; calcd for C24H29N2O6,
m/z 441.2025 (M + H)+. Anal. (C24H28N2O6) C, H, N.
concentrated to dryness under reduced pressure. The residue
was purified by silica gel column chromatography (5% MeOH
in CHCl3) to give 22 (409 mg, 84%) as a white solid. mp 228-
230 °C. [R]26D +34.38°(c 0.30, MeOH). UV(MeOH) λmax 275 nm.
1H NMR (400 MHz, CDCl3) δ 1.24 (s, 9H, tert-butyl), 1.33 (s,
3H, CH3), 1.43 (s, 3H, CH3), 4.08 (d, J ) 14.76 Hz, 1H, 6′a-H),
4.15 (d, J ) 15.07 Hz, 1H, 6′b-H), 4.55 (d, J ) 5.72 Hz, 1H,
2′-H), 5.16 (d, J ) 5.64 Hz, 1H, 3′-H), 5.44 (s, 1H, 1′-H), 5.58
(s, 1H, 5′-H), 5.80 (d, J ) 7.36 Hz, 1H, 5-H), 7.16 (d, J ) 7.36
Hz, 1H, 6-H). HR-FAB MS Obsd, m/z 336.1918; calcd for
(1′S,2′R,3′S)-N3-Ben zoyl-1-[2,3-(isop r op ylen ed ioxy)-4-
(ter t-bu toxym eth yl)-4-cyclopen ten -1-yl]th ym in e (17). Yield
72%. mp 70-72 °C. [R]24D +43.68° (c 0.53, CHCl3). UV(MeOH)
1
λmax 251.5 nm. H NMR (400 MHz, CDCl3) δ 1.25 (s, 9H, tert-
C
17H26N3O4, m/z 336.1923 (M + H)+. Anal. (C17H25N3O4‚
butyl), 1.34 (s, 3H, CH3), 1.41(s, 3H, CH3), 1.94 (s, 3H, COCH3),
4.10 (d, J ) 15.13 Hz, 1H, 6′a-H), 4.16 (d, J ) 15.07 Hz, 1H,
6′b-H), 4.64 (d, J ) 5.71 Hz, 1H, 2′-H), 5.20 (d, J ) 5.66 Hz,
1H, 3′-H), 5.38 (s, 1H, 1′-H), 5.62 (s, 1H, 5′-H), 6.93 (s, 1H,
6-H), 7.47-7.93 (m, 5H, phenyl). HR-FAB MS Obsd, m/z
455.2132. Calcd for C25H31N2O6, m/z 455.2182 (M + H)+.
0.1H2O) C, H, N.
(1′S,2′R,3′S)-1-[2,3-(Isop r op ylen ed ioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclop en ten -1-yl]-5-flu or ocytosin e (23). Com-
pound 23 was prepared from 21 using the same procedure as
for 22. Yield 76%. mp 194-196 °C. [R]26 +24.63° (c 1.30,
D
MeOH). UV (MeOH) λmax 285.5 nm.1H NMR (400 MHz, CDCl3)
δ 1.25 (s, 9H, tert-butyl), 1.33 (s, 3H, CH3), 1.49 (s, 3H, CH3),
4.09 (d, J ) 14.34 Hz, 1H, 6′a-H), 4.16 (d, J ) 15.01 Hz, 1H,
6′b-H), 4.55 (d, J ) 5.67 Hz, 1H, 2′-H), 5.15 (d, J ) 5.11 Hz,
1H, 3′-H), 5.44 (s, 1H, 1′-H), 5.59 (s, 1H, 5′-H), 7.16 (d, J )
5.98 Hz, 1H, 6-H). HR-FAB MS Obsd, m/z 354.1810; calcd
for C17H25FN3O4, m/z 354.1829 (M + H)+. Anal. (C17H24FN3O4‚
0.21CHCl3) C, H, N.
(1′S,2′R,3′S)-N3-Ben zoyl-1-[2,3-(isop r op ylen ed ioxy)-4-
(ter t-b u t oxym et h yl)-4-cyclop en t en -1-yl]-5-flu or ou r a cil
(18). Yield 61%. mp 72-73 °C. [R]24 +13.81°(c 0.70, CHCl3).
D
UV(MeOH) λmax 250 nm. 1H NMR (400 MHz, CDCl3) δ 1.25
(s, 9H, tert-butyl), 1.34 (s, 3H, CH3), 1.41 (s, 3H, CH3), 4.11 (d,
J ) 14.94 Hz, 1H, 6′a-H), 4.16 (d, J ) 15.17 Hz, 1H, 6′b-H),
4.61 (d, J ) 4.79 Hz, 1H, 2′-H), 5.20 (d, J ) 5.24 Hz, 1H, 3′-
H), 5.41 (s, 1H, 1′-H), 5.63 (s, 1H, 5′-H), 7.24 (d, J ) 6.03 Hz,
1H, 6-H), 7.50-7.94 (m, 5H, phenyl). HR-FAB MS Obsd, m/z
459.1935; calcd for C24H28FN2O6, m/z 459.1944 (M + H)+.
Gen er a l P r oced u r e for Dep r otection of ter t-Bu tyl a n d
Isop r op ylid en e Gr ou p s. (1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-
h yd r oxym eth yl-4-cyclop en ten -1-yl]u r a cil (24). Compound
19 (200 mg, 0.59 mmol) was dissolved in 50 mL of CF3COOH/
H2O (2:1, v/v) and heated to 50 °C for 3 h. The solvent was
removed under vacuum, and the residue was coevaporated
with ethanol (3 × 10 mL) under vacuum. The residue obtained
was purified by silica gel column chromatography (20% MeOH
Gen er a l P r oced u r e for Deben zoyla tion . (1′S,2′R,3′S)-
1-[2,3-(Isop r op ylen e- d ioxy)-4-(ter t-bu toxym eth yl)-4-cy-
clop en ten -1-yl]u r a cil (19). Compound 16 (380 mg, 0.85
mmol) was dissolved in saturated MeOH (30 mL) with NH3
and stirred for 4 h at room temperature. The solvent was
evaporated under vacuum, and the residue was purified by
silica gel column chromatography (5% MeOH in CHCl3) to give
in CHCl3) to give 24 (87 mg, 61%) as a white foam. [R]25
D
+79.87° (c 0.20, MeOH) [lit16a for D-isomer, [R]20D -84° (c 1.19,
MeOH)]. UV (H2O) λmax 268.0 (ꢀ 9 866) (pH 2), 268.0 (ꢀ 8 526)
(pH 7), 267.0 nm (ꢀ 6 640) (pH 11). 1H NMR (400 MHz, DMSO-
d6 + D2O) δ 3.84 (t, J ) 5.27 Hz, 1H, 2′-H), 4.04 (br s, 2H,
6′a,b-H), 4.29 (d, J ) 5.29 Hz, 1H), 5.31 (br s, 1H, 1′-H), 5.48
(s, 1H, 5′-H), 5.58 (d, J ) 7.74 Hz, 1H, 5-H), 7.31 (d, J ) 7.74
Hz, 1H, 6-H). HR-FAB MS Obsd, m/z 241.0826; calcd for
19 (267 mg, 93%) as a white solid. mp 147-149 °C. [R]25
D
+39.28°(c 0.70, MeOH). UV(MeOH) λmax 266 nm. 1H NMR (400
MHz, CDCl3) δ 1.24 (s, 9H, tert-butyl), 1.35 (s, 3H, CH3), 1.44
(s, 3H, CH3), 4.08 (d, J ) 14.94 Hz, 1H, 6′a-H), 4.15 (d, J )
15.07 Hz, 1H, 6′b-H), 4.55 (d, J ) 5.81 Hz, 1H, 2′-H), 5.17 (d,
J ) 5.66 Hz, 1H, 3′-H), 5.41 (s, 1H, 1′-H), 5.59 (s, 1H, 5′-H),
5.68 (d, J ) 8.0 Hz, 1H, 5-H), 7.04 (d, J ) 8.0 Hz, 1H, 6-H).
HR-FAB MS Obsd, m/z 337.1762; calcd for C17H25N2O5, m/z
337.1763 (M + H)+.
C
10H13N2O5, m/z 241.0824 (M + H)+. Anal. (C10H12N2O5‚
0.36CHCl3) C, H, N.
(1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]th ym in e (25). Yield 59% (recrystallized from
EtOH). mp 211 °C (dec) [lit16a for D-isomer, 210-211.5 °C
(1′S,2′R,3′S)-1-[2,3-(Isop r op ylen ed ioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclop en ten -1-yl]th ym in e (20). Yield 87%. mp
173-174 °C. [R]25D +111.15°(c 0.5, CHCl3). UV(MeOH) λmax 266
nm. 1H NMR (400 MHz, CDCl3) δ 1.25 (s, 9H, tert-butyl), 1.35
(s, 3H, CH3), 1.44 (s, 3H, CH3), 1.99 (s, 3H, COCH3), 4.10 (d,
J ) 15.13 Hz, 1H, 6′a-H), 4.16 (d, J ) 15.07 Hz, 1H, 6′b-H),
4.55 (d, J ) 5.71 Hz, 1H, 2′-H), 5.20 (d, J ) 5.66 Hz, 1H, 3′-
H), 5.41 (s, 1H, 1′-H), 5.59 (s, 1H, 5′-H), 6.82 (s, 1H, 6-H). HR-
FAB MS Obsd, m/z 351.1913; calcd for C18H27N2O5, m/z
351.1919 (M + H)+. Anal. (C18H26N2O5‚0.2H2O) C, H, N.
(dec)]. [R]27D +94.53° (c 0.70, MeOH) [lit16a for D-isomer, [R]24
D
-108° (c 0.65, MeOH)]. UV (H2O) λmax 273.0 (ꢀ 8 906) (pH 2),
272.0 (ꢀ 7 449) (pH 7), 273.5 nm (ꢀ 8 169) (pH 11). 1H NMR
(400 MHz, DMSO-d6 + D2O) δ 1.75 (s, 3H, CH3), 3.87 (t, J )
5.68 Hz, 1H, 2′-H), 4.05 (br s, 2H, 6′a,b-H), 4.29 (d, J ) 5.72
Hz, 1H, 3′-H), 5.34 (br s, 1H, 1′-H), 5.47 (s, 1H, 5′-H), 7.17 (s,
1H, 6-H). HR-FAB MS Obsd, m/z 255.0984; calcd for
C
11H15N2O5, m/z 255.0980 (M + H)+. Anal. (C11H14N2O5‚
(1′S,2′R,3′S)-1-[2,3-(Isop r op ylen ed ioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclopen ten -1-yl]-5-flu or ou r acil (21). Yield 83%.
0.9EtOH) C, H, N.
mp 198-200 °C. [R]24 +17.85° (c 0.50, CHCl3). UV(MeOH)
(1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clopen ten -1-yl]-5-flu or ou r acil (26). Yield 64%. [R]27D +76.82°
(c 0.34, MeOH). UV (H2O) λmax 274.5 (ꢀ 5 955) (pH 2), 275.5 (ꢀ
5 434) (pH 7), 273.5 nm (ꢀ 5 362) (pH 11). 1H NMR (400 MHz,
DMSO-d6 + D2O) δ 3.87 (t, J ) 5.39 Hz, 1H, 2′-H), 4.04 (br s,
2H, 6′a,b-H), 4.29 (d, J ) 5.57 Hz, 1H, 3′-H), 5.29 (br s, 1H,
1′-H), 5.48 (s, 1H, 5′-H), 7.64 (d, J ) 6.95 Hz, 1H, 6-H). HR-
FAB MS m/z 259.0743; calcd for C10H12FN2O5, m/z 259.0730
(M + H)+. Anal. (C10H11FN2O5‚0.5CH2Cl2) C, H, N.
D
1
λmax 273.5 nm. H NMR (400 MHz, CDCl3) δ 1.25 (s, 9H, tert-
butyl), 1.35 (s, 3H, CH3), 1.44 (s, 3H, CH3), 4.09 (d, J ) 14.93
Hz, 1H, 6′a-H), 4.16 (d, J ) 15.07 Hz, 1H, 6′b-H), 4.55 (d, J )
5.79 Hz, 1H, 2′-H), 5.18 (d, J ) 5.66 Hz, 1H, 3′-H), 5.43 (s,
1H, 1′-H), 5.59 (s, 1H, 5′-H), 7 (d, J ) 5.90 Hz, 1H, 6-H). HR-
FAB MS Obsd, m/z 355.1650; calcd for C17H24FN2O5, m/z
355.1669 (M + H)+. Anal. (C17H23FN2O5‚0.3H2O) C, H, N.
(1′S,2′R,3′S)-1-[2,3-(Isop r op ylen ed ioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclop en ten -1-yl]cytosin e (22). A mixture of 19
(500 mg, 1.47 mmol), 4-dimethylamino pyridine (359 mg, 2.94
mmol), triethylamine (297 mg, 2.94 mmol), and 2,4,6-triiso-
propylbenzene sulfonyl chloride (890 mg, 2.94 mmol) in dry
acetonitrile (50 mL) was stirred at room temperature for 24
h. After addition of 30% NH4OH (10 mL), the mixture was
further stirred for 5 h, then CHCl3 (200 mL) and water (100
mL) were added, and the resulting mixture was partitioned.
The organic phase was washed with saturated aqueous NH4-
Cl solution, dried over anhydrous Na2SO4, filtered, and then
(1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]cytosin e (26). Yield 62% (recrystallized from
MeOH). mp 138-140 °C [lit17a for D-form, 138-141 °C]. [R]26
D
103.42° (c 0.44, H2O) [lit16a for D-isomer, [R]20 -67.5° (c 1.84,
D
MeOH), lit17a for D-isomer, [R]23 -104.5° (c 0.13, H2O)]. UV
D
(H2O) λmax 284.5 (ꢀ 14 353) (pH 2), 275.0 (ꢀ 9 724) (pH 7), 275.5
1
nm (ꢀ 9 525) (pH 11). H NMR (400 MHz, DMSO-d6 + D2O) δ
3.81 (t, J ) 5.20 Hz, 1H, 2′-H), 4.04 (br s, 2H, 6′a,b-H), 4.31
(d, J ) 5.64 Hz, 1H, 3′-H), 5.33 (br s, 1H, 1′-H), 5.46 (s, 1H,
5′-H), 5.71 (d, J ) 7.32 Hz, 1H, 5-H), 7.29 (d, J ) 7.32 Hz, 1H,

Antiviral Activity of D- and L-Cyclopentenyl Nucleosides
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23 3991
65% (recrystallized from MeOH). mp 230-232 °C (dec) [lit16c
6-H)- HR-FAB MS Obsd, m/z 240.0990; calcd for C10H14N3-
O4, m/z 240.0984 (M + H)+. Anal. (C10H13N3O4‚0.2MeOH) C,
H, N.
for D-isomer, 229-231 °C (dec)]. [R]26 +141.24° (c 0.55, H2O)
D
[lit16c for D-isomer, [R]23 -143° (c 0.57, H2O)]. UV (H2O) λmax
D
249.5 (ꢀ 12 546) (pH 2), 249.5 (ꢀ 11 475) (pH 7), 254.5 nm (ꢀ 12
(1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
1
clop en ten -1-yl]-5-flu or ocytosin e (28). Yield 65%. [R]25
834) (pH 11). H NMR (400 MHz, DMSO-d6 + D2O) δ 4.09 (br
D
s, 2H, 6′a,b-H), 4.21 (t, J ) 5.22 Hz, 1H, 2′-H), 4.39 (d, J )
5.31 Hz, 1H, 3′-H), 5.33 (br s, 1H, 1′-H), 5.67 (s, 1H, 5′-H),
8.00 (s, 1H, 8-H), 8.01 (s, 1H, 2-H). HR-FAB MS Obsd, m/z
265.0972; calcd for C11H13N4O4, m/z 265.0936 (M + H)+. Anal.
(C11H12N4O4‚0.3H2O) C, H, N.
+63.8° (c 0.48, MeOH). UV (H2O) λmax 293.5 (ꢀ 6 906) (pH 2),
285.0 (ꢀ 4 798) (pH 7), 285.0 nm (ꢀ 6 851) (pH 11). 1H NMR
(400 MHz, DMSO-d6 + D2O) δ 3.81 (t, J ) 5.20 Hz, 1H, 2′-H),
4.04 (br s, 2H, 6′a,b-H), 4.31 (d, J ) 5.64 Hz, 1H, 3′-H), 5.33
(br s, 1H, 1′-H), 5.46 (s, 1H, 5′-H), 5.71 (d, J ) 7.32 Hz, 1H,
5-H), 7.29 (d, J ) 7.32 Hz, 1H, 6-H). HR-FAB MS Obsd,; m/z
258.0898; calcd for C10H13FN3O4, m/z 258.0890 (M + H)+. Anal.
(C10H12FN3O4‚0.85CH2Cl2) C, H, N.
(1′S,2′R,3′S)-N2-Acet yla m in o-9-[2,3-(isop r op ylid en e-
d ioxy)-4-(ter t-bu toxym eth yl)-4-cyclop en ten -1-yl]-6-ch lo-
r op u r in e (34). Compound 34 was prepared from 7 using the
same procedure used for 16. Yield 75%. mp 182-184 °C. [R]24
(1′S,2′R,3′S)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclopen ten -1-yl]-6-ch lor opu r in e (29). Com-
pound 29 was prepared from 7 using the same procedure as
D
+7.46° (c 0.18, MeOH). UV(MeOH) λmax 249.5 nm. 1H NMR
(400 MHz, CDCl3) δ 1.24 (s, 9H, tert-butyl), 1.36 (s, 3H, CH3),
1.48 (s, 3H, CH3), 2.55 (s, 3H, acetyl), 4.23 (d, J ) 6.8 Hz, 1H,
6′a-H), 4.26 (d, J ) 6.8 Hz, 1H, 6′b-H), 4.74 (d, J ) 5.74 Hz,
1H, 2′-H), 5.41 (d, J ) 5.44 Hz, 1H, 3′-H), 5.42 (br s, 1H, 1′-
H), 5.77 (s, 1H, 5′-H), 6.44 (br s, 1H, NH), 7.90 (s, 1H, 8-H).
HR-FAB MS Obsd, m/z 436.1737; calcd for C20H27ClN5O4, m/z
436.1751 (M + H)+. Anal. (C20H26ClN5O4) C, H, N.
for 16. Yield 70%. mp 134 °C. [R]25 +49.53° (c 0.39, CHCl3).
D
1H NMR (400 MHz, CDCl3) δ 1.19 (s, 9H, tert-butyl), 1.36 (s,
3H, CH3), 1.49 (s, 3H, CH3), 4.21 (d, J ) 15.4 Hz, 1H, 6′a-H),
4.29 (d, J ) 15.4 Hz, 1H, 6′b-H), 4.72 (d, J ) 5.61 Hz, 1H,
2′-H), 5.37 (d, J ) 6.00 Hz, 1H, 3′-H), 5.66 (br s, 1H, 1′-H),
5.82 (s, 1H, 5′-H), 8.04 (s, 1H, 8-H), 8.79 (s, 1H, 2-H). HR-
FAB MS Obsd, m/z 379.1526; calcd for C18H24ClN4O3, m/z
379.1536 (M + H)+. Anal. (C18H23ClN4O3‚0.4CH3COCH3) C,
H, N.
(1′S,2′R,3′S)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclop en ten -1-yl]gu a n in e (35). Compound
35 was prepared from 34 using the same procedure used for
(1′S,2′R,3′S)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclop en ten -1-yl]a d en in e (30). A solution
of 29 (900 mg, 2.4 mmol) in saturated methanol (100 mL) with
NH3 was heated at 80 °C in a steel bomb for 10 h. After the
solution was cooled, the solvent was removed under vacuum
and the residue was purified by silica gel column chromatog-
raphy (0-1% MeOH in CHCl3) to give 30 (660 mg, 76%) as a
white solid. mp 74 °C. [R]25D +46.71° (c 0.34, CHCl3). 1H NMR
(400 MHz, CDCl3) δ 1.26 (s, 9H, tert-butyl), 1.36 (s, 3H, CH3),
1.48 (s, 3H, CH3), 4.14 (d, J ) 13.96 Hz, 1H, 6′a-H), 4.21 (d,
J ) 14.43 Hz, 1H, 6′b-H), 4.69 (d, J ) 5.13 Hz, 2H, 2′-H), 5.32
(d, J ) 5.52 Hz, 1H, 3′-H), 5.58 (s, 1H, 1′-H), 5.81 (s, 1H, 5′-
H), 7.69 (s, 1H, 8-H), 8.40 (s, 1H, 2-H). HR-FAB MS Obsd,
m/z 360.2032; calcd for C18H26N5O3, m/z 360.2035 (M + H)+.
Anal. (C18H26N5O3‚0.3MeOH) C, H, N.
32. Yield 63%. mp > 300 °C (dec). [R]24 +33.88° (c 0.30,
D
MeOH). UV(MeOH) λmax 254 nm. 1H NMR (400 MHz, DMSO-
d6) δ 1.17 (s, 9H, tert-butyl), 1.27 (s, 3H, CH3), 1.34 (s, 3H,
CH3), 4.03 (d, J ) 15.08 Hz, 1H, 6′a-H), 4.26 (d, J ) 15.33 Hz,
1H, 6′b-H), 4.59 (d, J ) 5.5 Hz, 1H, 1′-H), 5.24 (s, 1H, 2′-H),
5.36 (d, J ) 5.60 Hz, 1H, 3′-H), 5.62 (s, 1H, 5′-H), 6.49 (br s,
1H, NH), 7.42 (s, 1H, 8-H). HR-FAB MS Obsd, m/z 376.1974;
calcd for C18H26N5O4, m/z 376.1984 (M + H)+. Anal. (C18H25N5O4)
C, H, N.
(1′S,2′R,3′S)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]gu a n in e (36). Compound 36 was prepared
from 35 using the same procedure as for 16. Yield 63%
[recrystallized from MeOH/H2O (2:1)]. mp > 220 °C (dec) [lit16a
for D-isomer, > 220 °C (dec)]. [R]27D +54.51° (c 0.15, H2O) [lit16a
for D-isomer, [R]20D -87° (c 0.15, N,N-dimethylformamide)]. UV
(H2O) λmax 254.5 (ꢀ 8 641) (pH 2), 252.5 (ꢀ 11 324) (pH 7), 256.5
(1′S,2′R,3′S)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]a d en in e [L-(+)-Nep la n ocin A, 31]. Com-
pound 31 was prepared from 30 using the same procedure that
was used for 24. Yield 50% [(recrystallized from MeOH-H2O
1
nm (ꢀ 8 317) (pH 11). H NMR (400 MHz, DMSO-d6 + D2O) δ
4.08 (br s, 2H, 6′a,b-H), 4.16 (t, J ) 5.11 Hz, 1H, 2′-H), 4.41
(d, J ) 5.5 Hz, 1H, 3′-H), 5.15 (s, 1H, 1′-H), 5.62 (s, 1H, 5′-H),
7.59 (s, 1H, 8-H). HR-FAB MS Obsd, m/z 280.1039; calcd for
(9:1)]. mp 220 °C [lit1 for D-isomer, 220 °C]. [R]25 +155° (c
D
0.3, H2O) [lit1 for D-isomer, [R]23D -157° (c 0.5, H2O)]. UV (H2O)
λmax 259.0 (ꢀ 17 456) (pH 2), 260.5 (ꢀ 17 170) (pH 7), 261.0 nm
(ꢀ 16 821) (pH 11). 1H NMR (400 MHz, Me2SO-d6+D2O) δ 4.10
(br s, 2H, 6′a,b-H), 4.27 (t, J ) 5.61 Hz, 1H, 2′-H), 4.40 (d, J )
5.56 Hz, 1H, 3′-H), 5.33 (br s, 1H, 1′-H), 5.69 (br s, 1H, 5′-H),
8.07 (s, 1H, 2-H), 8.11 (s, 1 H, 8-H). HR-FAB MS Obsd, m/z
264.1070; calcd for C11H14N5O3, m/z 264.1096 (M + H)+. Anal.
(C11H13N5O3‚0.1H2O) C, H, N.
C
11H14N5O4, m/z 280.1045 (M + H)+. Anal. (C11H13N5O4‚
1.2H2O) C, H, N.
Gen er a l P r oced u r e for th e D-Cyclop en ten yl Nu cleo-
sid es. The final D-cyclopentenyl nucleosides were prepared
from 15 using same procedure that was used for the L-
cyclopentenyl nucleosides. 1H NMR data were identical to that
of the L-isomer.
(1′R,2′S,3′R)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
(1′S,2′R,3′S)-9-[2,3-(Isop r op ylen ed ioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclop en ten -1-yl]h yp oxa n th in e (32). A mixture
of 29 (240 mg, 0.63 mmol), 2-mercaptoethanol (197 mg, 2.53
mmol), and sodium methoxide (136 mg, 2.53 mmol) was
refluxed for 24 h. After the mixture cooled, it was neutralized
with acetic acid, and the solvent was concentrated under
vacuum. The residue was purified by silica gel column chro-
matography (3% MeOH in CHCl3) to give 32 (190 mg, 88%)
toxym eth yl)-4-cyclopen ten -1-yl]-6-ch lor opu r in e (37). [R]24
D
-48.99° (c 0.35, CHCl3). HR-FAB MS Obsd, m/z 379.1516;
calcd for C18H24ClN4O3, m/z 379.1536 (M + H)+. Anal.(C18H23
ClN4O3‚0.22MeOH) C, H, N.
-
(1′R,2′S,3′R)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclopen ten -1-yl]aden in e (38). [R]24D -45.08°
(c 0.48, CHCl3). HR-FAB MS Obsd, m/z 360.2032; calcd for
C
N.
18H26N5O3, m/z 360.2035 (M + H)+. Anal. (C18H26N5O3) C, H,
as a white solid. mp 238-240 °C. [R]27 +50.32° (c 0.50,
D
MeOH). UV(MeOH) λmax 249.5 nm. 1H NMR (400 MHz, CDCl3)
δ 1.25 (s, 9H, tert-butyl), 1.37 (s, 3H, CH3), 1.49 (s, 3H, CH3),
4.13 (d, J ) 15.4 Hz, 1H, 6′a-H), 4.20 (d, J ) 15.4 Hz, 1H,
6′b-H), 4.68 (d, J ) 5.61 Hz, 1H, 2′-H), 5.31 (d, J ) 5.51 Hz,
1H, 3′-H), 5.59 (br s, 1H, 1′-H), 5.75 (s, 1H, 5′-H), 7.71 (s, 1H,
8-H), 8.10 (s, 1H, 2-H). HR-FAB MS Obsd, m/z 361.1878; calcd
for C18H25N4O4, m/z 361.1875 (M + H)+. Anal. (C18H24N4O4‚
0.15 MeOH) C, H, N.
(1′R,2′S,3′R)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]a d en in e [D-(-)-Nep la n ocin A, 1]. [R]24
D
-155° (c 0.3, H2O) [lit.1 [R]23D ) -157° (c 0.5, H2O)]. HR-FAB
MS Obsd, m/z 264.1092; calcd for C11H14N5O3, m/z 264.1096
(M + H)+. Anal. (C11H13N5O3‚0.2H2O) C, H, N.
(1′R,2′S,3′R)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclop en ten -1-yl]h yp oxa n th in e (39). [R]27
D
-52.48° (c 0.39, MeOH). HR-FAB MS Obsd, m/z 361.1897;
calcd for C18H25N4O4, m/z 361.1875 (M + H)+. Anal. (C18H24N4O4)
C, H, N.
(1′S,2′R,3′S)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl] h yp oxa n th in e (33). Compound 33 was
prepared from 32 using the same procedure as for 24. Yield

3992 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23
(1′R,2′S,3′R)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
Song et al.
An tivir a l Assa ys for West Nile Vir u s. A New York isolate
of West Nile virus from homogenized crow brain dated 8/20/
00 (Robert Lacniotti, Division of Vector-Borne Infectious
Diseases, Centers for Disease Control and Prevention, Ft.
Collins, CO) was used. African green monkey kidney (Vero 76,
ATCC CCL1587) were maintained during the antiviral experi-
ments in MEM with 1% FBS, 0.1% NaHCO3, and 50 µg/mL
gentamycin (Sigma, St. Louis, MO). The cytopathic effect
(CPE) inhibitory assay was described elsewhere37 with the
following modifications. Serial dilutions of test compounds
were added to lightly confluent Vero cells in 96-well micro-
clop en ten -1-yl] h yp oxa n th in e (40). [R]24 -143.8° (c 0.59,
D
H2O). HR-FAB MS Obsd, m/z 265.0972; calcd for C11H13N4O4,
m/z 265.0936 (M + H)+. Anal. (C11H12N4O4‚0.54H2O) C, H, N.
(1′R,2′S,3′R)-N2-Acet yla m in o-9-[2,3-(isop r op ylid en e-
d ioxy)-4-(ter t-bu toxym eth yl)-4-cyclop en ten -1-yl]-6-ch lo-
r op u r in e (41). [R]24 -8.02° (c 0.23, MeOH). HR-FAB MS
D
Obsd, m/z 436.1737; calcd for C20H27ClN5O4, m/z 436.1751
(M + H)+.
(1′R,2′S,3′R)-9-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclopen ten -1-yl]gu an in e (42). [R]24D -33.15°
(c 0.35, MeOH). HR-FAB MS Obsd, m/z 376.1974; calcd for
plates, after which 5 cell culture 50% infectious doses (CCID50
)
18H26N5O4, m/z 376.1984 (M + H)+.
of WNV New York isolate were added to the cells. Uninfected
cells, infected cells with no drug, and uninfected drug-treated
cells were used as controls. Duplicates of toxicity controls at
each drug concentration and triplicates of test samples were
performed. After 6 days post-virus exposure, cells were visually
scored for CPE. The 50% effective concentration (EC50) and
the 50% inhibitory cytotoxic concentration (IC50) were calcu-
lated by regression analysis using the means of the CPE
ratings at each concentration of the compound. Neutral red
vital stain was used to verify the visual CPE assay and to
provide a more quantitative result.38 After visually reading
the CPE, cells were incubated with neutral red for 2-3 h at
37 °C. Free dye was washed from the wells, and the uptake
dye was quantified using a microplate reader (Bio-Tek EL
1309, BioTek, Burlington, VT) at absorbance 540 and 405 nm.
Absorbance values were expressed as percentages of controls,
and EC50 and IC50 values were calculated by regression
analysis.
C
(1′R,2′S,3′R)-9-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]gu a n in e (43). [R]27 -53.96° (c 0.15, H2O).
D
HR-FAB MS Obsd, m/z 280.1039; calcd for C11H14N5O4, m/z
280.1045 (M + H)+. Anal. (C11H13N5O4‚1.2H2O) C, H, N.
(1′R,2′S,3′R)-N3-Ben zoyl-1-[2,3-(isop r op ylid en ed ioxy)-
4-(ter t-bu toxym eth yl)-4-cyclopen ten -1-yl]u r acil (44). [R]25
D
-16.74° (c 0.31, CHCl3). HR-FAB MS Obsd, m/z 441.2025;
calcd for C24H29N2O6, m/z 441.2025 (M + H)+.
(1′R,2′S,3′R)-N3-Ben zoyl-1-[2,3-(isop r op ylid en ed ioxy)-
4-(ter t-bu t oxym et h yl)-4-cyclop en t en -1-yl]t h ym in e (45).
[R]24 -42.83° (c 0.59, CHCl3). HR-FAB MS Obsd, m/z
D
455.2132; calcd for C25H31N2O6, m/z 455.2182 (M + H)+.
(1′R,2′S,3′R)-N3-Ben zoyl-1-[2,3-(isop r op ylid en ed ioxy)-
4-(ter t-b u t oxym et h yl)-4-cyclop en t en -1-yl]-5-flu or ou r a -
cil (46). [R]24 -12.89° (c 0.40, CHCl3). HR-FAB MS Obsd,
D
m/z 459.2035; calcd for C24H28FN2O6, m/z 459.1944 (M + H)+.
Anal. (C24H27FN2O6‚0.4H2O) C, H, N.
Ack n ow led gm en t. This research was supported in
part by U.S. Public Health Service Research Grants (AI
32351, UO1 AI 48495, Veterans Affairs) from the
National Institutes of Health and Korea Science and
Engineering Foundation (KOSEF). We thank Dr. Chris-
topher Tseng of the National Institute of Allergy and
Infectious Diseases, NIH, for encouraging us to evaluate
the synthesized nucleosides against West Nile virus.
(1′R,2′S,3′R)-1-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclop en ten -1-yl]u r a cil (47). [R]25D -41.15°
(c 0.75, MeOH). HR-FAB MS Obsd, m/z 337.1762; calcd for
C
17H25N2O5, m/z 337.1763 (M + H)+. Anal. (C17H24N2O5) C,
H, N.
(1′R,2′S,3′R)-1-[2,3-(Isopr opyliden edioxy)-4-(ter t-bu toxy-
m eth yl)-4-cyclop en ten -1-yl]th ym in e (48). [R]25 -110.16°
D
(c 0.54, CHCl3). HR-FAB MS Obsd, m/z 351.1913; calcd for
C
18H27N2O5, m/z 351.1919 (M + H)+.
(1′R,2′S,3′R)-1-[2,3-(isop r op ylen ed ioxy)-4-(ter t-bu toxy-
Refer en ces
m et h yl)-4′-cyclop en t en -1-yl]-5-flu or ou r a cil (49). [R]24
D
(1) Yaginuma, A.; Muto, N.; Tsujino, M.; Sudate, Y.; Hayashi, M.;
Otani, M. Studies on neplanocin A, New antitumor antibiotic.
I. Producing organism, isolation and characterization. J . Anti-
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-19.88° (c 0.42, CHCl3). HR-FAB MS Obsd, m/z 355.1650;
calcd for C17H24FN2O5, m/z 355.1669 (M + H)+.
(1′R,2′S,3′R)-1-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
toxym eth yl)-4-cyclopen ten -1-yl]cytosin e (50). [R]26D -34.46°
(c 0.35, MeOH). HR-FAB MS Obsd, m/z 336.1920; calcd for
(2) Arita, M.; Adachi, K.; Ito, Y.; Sawai, H.; Ohno, M. Enantio-
selective synthesis of the carbocyclic nucleoside, (-)-aristero-
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Am. Chem. Soc. 1983, 105, 4049-4055.
C
17H26N3O4, m/z 336.1923 (M + H)+.
(1′R,2′S,3′R)-1-[2,3-(Isop r op ylid en ed ioxy)-4-(ter t-b u -
(3) Lim, M. I.; Marquez, V. E. Total synthesis of (-)-neplanocin A1.
Tetrahedron Lett. 1983, 24, 5559-5562.
t oxym et h yl)-4-cyclop en t en -1-yl]-5-flu or ocyt osin e (51).
[R]26 -23.70° (c 1.30, MeOH). HR-FAB MS Obsd, m/z
(4) Marquez, V. E.; Lim, M. I. Carbocyclic nucleosides. Med. Res.
Rev. 1986, 6, 1-40.
D
354.1810; calcd for C17H25FN3O4, m/z 354.1815 (M + H)+.
(1′S,2′R,3′S)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
(5) Agrofoglio, L.; Suhas, E.; Farese, A.; Condom, R.; Challand, S.
R.; Earl, R. A.; Guedj, R. Synthesis of carbocyclic nucleosides.
Tetrahedron 1994, 50, 10611-10670.
clop en ten -1-yl]u r a cil (52). [R]25 -80.53° (c 0.25, MeOH).
D
HR-FAB MS Obsd, m/z 241.0826; calcd for C10H13N2O5, m/z
(6) Montgomery, J . A. Studies on the biologic activity of purine and
pyrimidine analogs. Med. Res. Rev. 1982, 2, 271-308.
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inhibit the replication of human immunodeficiency virus in T
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241.0824 (M + H)+. Anal. (C10H12N2O5) C, H, N.
(1′R,2′S,3′R)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]th ym in e (53). [R]27D -98.98° (c 0.75, MeOH).
HR-FAB MS Obsd, m/z 255.0984; calcd for C11H15N2O5, m/z
255.0980 (M + H)+. Anal. (C11H14N2O5) C, H, N.
(1′R,2′S,3′R)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
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Biochem. Biophys. Res. Commun. 1985, 129, 306-311.
clop en ten -1-yl]-5-flu or ou r a cil (54). [R]27 -78.21° (c 0.39,
D
MeOH); HR-FAB MS Obsd, m/z 259.0743; Calcd for C10H12
-
FN2O5, m/z 259.0730 (M + H)+. Anal. (C10H11FN2O5‚0.3H2O)
C, H, N.
(1′R,2′S,3′R)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]cytosin e (55). [R]23 -105.10° (c 0.34, H2O).
D
HR-FAB MS Obsd, m/z 240.0990; calcd for C10H14N3O4, m/z
240.0984 (M + H)+. Anal. (C10H13N3O4‚0.12MeOH) C, H, N.
(1′R,2′S,3′R)-1-[2,3-Dih yd r oxy-4-h yd r oxym et h yl-4-cy-
clop en ten -1-yl]-5-flu or ocytosin e (56). [R]25D -60.93° (c 0.50,
MeOH). HR-FAB MS Obsd, m/z 258.0898; calcd for C10H13
-
FN3O4, m/z 258.0890 (M + H)+. Anal. (C10H12FN3O4‚0.2MeOH)
C, H, N.

Antiviral Activity of D- and L-Cyclopentenyl Nucleosides
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 23 3993
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