New neplanocin analogues. 6. Synthesis and potent antiviral activity of 6'-homoneplanocin A

Article abstract of DOI:10.1021/jm950853f

The design, synthesis, and antiviral activities of 6'-homoneplanocin A (HNPA, 3) and its congeners having nucleobases other than adenine, such as 3- deazaadenine (4), guanine (5), thymine (6), and cytosine (7), were described. Starting from the known cyclopentenone derivative 8, the optically active (mesyloxy)cyclopentene derivative 15 was prepared, which was condensed with nucleobases then deprotected to give target compounds 3-7. Of these compounds, HNPA showed an antiviral activity spectrum that was comparable to, and an antiviral specificity that was higher than, that of neplanocin A. HNPA proved particularly active against human cytomegalovirus, vaccinia virus, parainfluenza virus, vesicular stomatitis virus, and arenaviruses, which is compatible with an antiviral action targeted at S-adenosylhomocysteine hydrolase. HNPA appears to be a promising candidate drug for the treatment of these viruses.

Full text of DOI:10.1021/jm950853f

2392
J . Med. Chem. 1996, 39, 2392-2399
New Nep la n ocin An a logu es. 6. Syn th esis a n d P oten t An tivir a l Activity of
6′-Hom on ep la n ocin A1
Satoshi Shuto,† Takumi Obara,‡ Yasuyoshi Saito,‡ Graciela Andrei,§ Robert Snoeck,§ Erik De Clercq,§ and
Akira Matsuda*,†
Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060, J apan, Institute for Life
Science Research, Asahi Chemical Industry Co., Ltd., Mifuku, Ohito-cho, Shizuoka 410-23, J apan, and Rega Institute for
Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
Received November 20, 1995X
The design, synthesis, and antiviral activities of 6′-homoneplanocin A (HNPA, 3) and its
congeners having nucleobases other than adenine, such as 3-deazaadenine (4), guanine (5),
thymine (6), and cytosine (7), were described. Starting from the known cyclopentenone
derivative 8, the optically active (mesyloxy)cyclopentene derivative 15 was prepared, which
was condensed with nucleobases then deprotected to give target compounds 3-7. Of these
compounds, HNPA showed an antiviral activity spectrum that was comparable to, and an
antiviral specificity that was higher than, that of neplanocin A. HNPA proved particularly
active against human cytomegalovirus, vaccinia virus, parainfluenza virus, vesicular stomatitis
virus, and arenaviruses, which is compatible with an antiviral action targeted at S-
adenosylhomocysteine hydrolase. HNPA appears to be a promising candidate drug for the
treatment of these viruses.
In tr od u ction
6′-hydroxymethyl moiety of NPA to develop NPA de-
rivatives that are neither phosphorylated by Ado kinase
nor deaminated by Ado deaminase but inhibit AdoHcy
hydrolase significantly.9 Throughout the study we
found that (6′R)-6′-C-methylneplanocin A (RMNPA, 2a )
has excellent antiviral activity against various DNA and
RNA viruses, while its cytotoxicity was reduced signifi-
cantly compared with that of NPA.9a,c In fact, RMNPA
is assumed not to be phosphorylated by Ado kinase11
and not to be deaminated by Ado deaminase, although
it inhibits AdoHcy hydrolase significantly.9a Although
RMNPA has a potent antiviral effect, the corresponding
6′-diastereomer 2b (SMNPA) is almost completely bio-
logically inactive.9a,c This suggests that the conforma-
tion as well as the bulkiness around the 6′-hydroxyl
group of NPA would be important for being recognized
as the substrate by these three enzymes. It may also
be that the distance between the adenine base and the
primary 5′-hydroxyl of Ado (the 6′-hydroxyl of NPA) is
an essential factor for being recognized as the substrate
by the three enzymes. Accordingly, other modifications
of the 6′-position of NPA that change the three-
dimensional location of the 6′-hydroxyl group may be
of interest. Therefore, we planned to synthesize the 6′-
homologue of NPA (HNPA, 3), a regioisomer of RMNPA,
as another type of 6′-modified NPA derivative. The
location of the 6′-hydroxymethyl group of NPA in space
would be restricted, compared with the corresponding
5′-hydroxymethyl group of Ado, because the 6′-hy-
droxymethyl group of NPA is attached to a conforma-
tionally rigid 4′-sp2 carbon in the cyclopentene ring. The
6′-homologue of NPA would have increased conforma-
tional flexibility around the hydroxymethyl group, and
the distance between the adenine and the primary
hydroxyl in HNPA would be different from that in NPA.
S-Adenosylhomocysteine hydrolase (AdoHcy hydro-
lase), which is responsible for the hydrolysis of S-
adenosyl-L-homocysteine to adenosine (Ado) and L-ho-
mocysteine (Hcy),2,3 has been recognized as a good target
for broad-spectrum antiviral agents.2-4 AdoHcy hydro-
lase is a key enzyme in the transmethylation reaction
using S-adenosyl-L-methionine (AdoMet) as the methyl
donor. Such transmethylation reactions are involved
in the maturation of viral mRNAs and are critical in
the virus replicative cycle. Several Ado analogues are
assumed to achieve their broad-spectrum antiviral
activity through an inhibition of AdoHcy hydrolase. In
fact, a close correlation has been found between the
antiviral activity of a series of Ado analogues and their
inhibitory effects on AdoHcy hydrolase.5
Neplanocin A (NPA, 1, Chart 1),6 one of the most
potent AdoHcy hydrolase inhibitors, has broad-spectrum
antiviral activity.7 However, NPA itself is apparently
cytotoxic to host cells.8 It has been recognized that the
detrimental toxicity of NPA could be derived, for the
most part, from phosphorylation of the primary hydroxyl
group at its 6′-position (the 6′-position of NPA corre-
sponds to the 5′-position of Ado) by Ado kinase and
subsequent metabolism by cellular enzymes.8 NPA is
also rapidly deaminated by Ado deaminase to a chemo-
therapeutically inactive inosine congener,9a which may
account for the reduced therapeutic potency of NPA,
especially in vivo. On the basis of these observations,
chemical modifications of NPA have been extensively
studied to develop efficient antiviral agents.9,10
Because the 5′-hydroxymethyl moiety of Ado has an
essential role in recognition as a substrate by all of these
enzymes that interact with NPA, we have modified the
NPA congeners having nucleobases other than ad-
enine have been synthesized, and some of them have
excellent biological effects.10b,12 Especially, the cytosine
and 3-deazaadenine congeners of NPA have been known
to have significant antiviral10b,12c and antitumor ef-
* Author to whom correspondence should be addressed.
† Hokkaido University.
‡ Asahi Chemical Industry Co., Ltd.
§ Katholieke Universiteit Leuven.
X Abstract published in Advance ACS Abstracts, May 15, 1996.
S0022-2623(95)00853-3 CCC: $12.00 © 1996 American Chemical Society

New Neplanocin Analogues
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12 2393
Ch a r t 1
Sch em e 1a
a
Reagents: (a) (TMS)2NH, BuLi, EtOAc, THF; (b) LiBH4, THF; (c) TBSCl, imidazole, THF; (d) Ac2O, DMAP, Et3N, THF; (e)
PdCl2(MeCN)2, p-benzoquinone, THF; (f) K2CO3, MeOH; (g) MsCl, DMAP, CH2Cl2.
fects.12a,b Consequently, the biological activity of ana-
logues of HNPA having nucleobases other than adenine
would also be interesting. In this paper, we describe
the synthesis of HNPA (3) and its analogues, 4-7, and
the evaluation of their antiviral activity.
nucleophile by heating it at 80 °C in DMF in the
presence of 15-crown-5 to give the corresponding car-
bocyclic nucleoside derivative 17 in 30% yield (Scheme
2). Similarly, the 3-deazaadenine derivative 18 was
prepared. The guanine derivative 5 was synthesized
via the 2-amino-6-chloropurine derivative 19. Reaction
of 15 and 2-amino-6-chloropurine in DMF in the pres-
ence of K2CO3 and 18-crown-6 gave the desired 9-sub-
stituted derivative 19 and the corresponding 7-substi-
tuted derivative 20 in 54% and 12% yield, respectively.
The pyrimidine analogues, 6 and 7, were also synthe-
sized from 15. Reactions of 15 and thymine or uracil
were done under similar conditions for preparing
2-amino-6-chloropurine derivative 19 as described above
to give 22 and 23, respectively. The uracil derivative
22 was converted to the corresponding cytosine deriva-
tive 25 by the usual procedure.
Resu lts a n d Discu ssion
Ch em istr y. The target compounds 3-7 were syn-
thesized from optically active cyclopentene derivative
15 and nucleobases. We selected a cyclopentenone
derivative 8, which was readily prepared from D-
ribose,13 as a synthon to prepare 15. J ohnson and co-
workers showed that cyclopentenone 8 was an efficient
synthon for constructing the backbone structure of
NPA.14 Recently, we also synthesized 6′-modified NPA
derivatives starting from 8.9c
An addition reaction of a carbanion of EtOAc, which
was prepared by treating EtOAc with LiN(TMS)2,15 to
8 in THF at -82 °C proceeded from the least hindered
â-face highly stereoselectively to give 9 in 86% yield
(Scheme 1). Reduction of the ester group of 9 with
LiBH4 in THF afforded diol 10 in 74% yield, which was
then treated with TBSCl/imidazole in THF to give 11.
The tertiary hydroxyl of 11 was acetylated by treating
it with a large excess of Ac2O and Et3N in the presence
of DMAP to give acetate 12 in high yield. Allylic
rearrangement of the acetoxy group of 12 with Pd2+
catalyst16 was next investigated. When 12 was heated
with PdCl2(MeCN)2 and benzoquinone in THF,14 the
desired rearrangement proceeded effectively to give 13
in 88% yield. The acetyl group of 13 was removed by
treating it with K2CO3/MeOH to give 14, which was
then converted to the corresponding mesylate 15 by the
usual method. The mesylate 15 was used immediately
for the next reaction because of its instability. Al-
though, using TsCl instead of MsCl, formation of the
corresponding tosylate 16 from 14 was also detected on
TLC, it was too unstable to be isolated.
The protecting groups of 17 were removed simulta-
neously by treating with HCl in aqueous MeOH to give
HNPA (3) in high yield. On the other hand, treatment
of 18, 19, 23, and 25 with TBAF in THF, followed by
acidic hydrolysis of the isopropylidene group, gave the
desired carbocyclic nucleosides 4-7, respectively.
Biologica l Activity. First, the compounds newly
synthesized were preliminary evaluated for antiviral
activity against vesicular stomatitis virus (VSV) and
parainfluenza virus (PV-3), together with NPA as a
positive control. The results are summarized in Table
1. It was noteworthy that HNPA (3) had significant
antiviral effects with IC50 values of 1.0 µg/mL (VSV) and
0.35 µg/mL (PV-3), respectively, which are comparable
to those of NPA [IC50 ) 1.0 µg/mL (VSV); IC50 ) 0.74
µg/mL (PV-3)]. Yet, NPA was rather cytotoxic (CC50
)
152 µg/mL, Vero cells); HNPA did not show any cyto-
toxic effect on host cells at concentrations up to 500 µg/
mL. The 3-deazaadenine derivative 4 also showed
antiviral activity against VSV (IC50 ) 3.9 µg/mL);
however, it was inactive against PV-3. Although sig-
nificant antiviral activity of a cytosine congener of NPA,
27 (Chart 2), has been known,12b its 6′-homologue 7 was
An SN2 substitution reaction of 15 at the allylic
position was done with a sodium salt of adenine as a

2394 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12
Shuto et al.
Sch em e 2a
a
Reagents: (a) adenine or 3-deazaadenine, NaH, 15-crown-5, DMF; (b) HCl, aqueous MeOH; (c) TBAF, THF; (d) 2-NH2-6-Cl-purine,
thymine, or uracil, K2CO3, 18-crown-6, DMF; (e) 2 N HCl; (f) 70% HCOOH; (g) 2,4,6-triisopropylbenzenesulfonyl chloride, DMAP, MeCN,
then 28% NH4OH.
Ta ble 1. Antiviral Activity against VSV and PV-3 and
Cytotoxicity of Compounds 3-7 and NPA in Vero Cells
Ch a r t 2
antiviral activity
cytotoxicity
(IC50, µg/mL)a
(CC50, µg/mL)b
compd
VSV
PV-3
0.35
>25
>25
>25
>25
Vero cells
3
4
5
6
1.0
3.9
>500
>500
>500
>500
>500
>500
>500
>500
152
7
NPA
1.0
0.74
a
50% inhibitory concentration required to reduce virus-induced
rocytes. HNPA apparently inhibited the enzyme (IC50
) 0.87 µg/mL), while NPA did so at an IC50 of 0.004
µg/mL.
b
cytopathogenicity (VSV) or virus plaque formation (PV-3). 50%
cytotoxic concentration required to reduce the number of viable
cells by 50%.
The susceptibility of HNPA to Ado deaminase from
calf intestine was also investigated (Figure 1). HNPA
was completely resistant to the deamination by the
enzyme in spite of having a primary hydroxyl, which is
an essential functional group for Ado to be recognized
as a substrate by Ado deaminase.17 In contrast, NPA
was rapidly deaminated to the inactive inosine congener
under the same reaction conditions.
inactive. The derivatives having other nucleobases such
as guanine analogue 5 and thymine analogue 6 were
also inactive in this preliminary evaluation system.
Therefore, we decided to investigate in more detail the
biological activity of HNPA (3).
Because a close correlation between inhibitory effects
of adenosine analogues on AdoHcy hydrolase and their
antiviral potency has been demonstrated,5 the inhibitory
effect of HNPA on AdoHcy hydrolase was evaluated in
a cell-free system with the enzyme from rabbit eryth-
Next, the antiviral activity of HNPA (3), in direct
comparison with NPA, was examined in detail in human
embryonic skin muscle (E6SM) fibroblasts, human

New Neplanocin Analogues
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12 2395
which did show toxicity to the host cells at concentra-
tions of 10 µg/mL and higher (Table 2).
Based on the CC50/IC50 ratios, HNPA may be consid-
ered to be more selective in its antiviral action than
NPA; for example, for vaccinia virus, this ratio (selectiv-
ity index) could be estimated at >4000 for HNPA, as
compared to 100 for NPA. The antiviral activity spec-
trum displayed by HNPA encompasses, in particular,
human cytomegalovirus (HCMV), vaccinia virus, and
(-)-RNA viruses [i.e. vesicular stomatitis virus, parain-
fluenza virus and arenaviruses (J unin, Tacaribe)]. This
is compatible with an antiviral action targeted at
AdoHcy hydrolase, as has been previously documented
for neplanocin A itself7 and several other carbocyclic
adenosine analogues.4a,9a While the inhibitory effect of
HNPA of rabbit erythrocyte AdoHcy hydrolase was
weaker than that of NPA as described above, its
antiviral activity was almost equal to that of NPA.
Similarly, RMNPA and 2-fluoroneplanocin A also had
equal or more significant antiviral potency compared
with that of NPA, in spite of their rather weaker
inhibitory effects on AdoHcy hydrolase than NPA. Since
the three NPA derivatives are completely resistant to
Ado deaminase, concentrations of these derivatives in
vitro assay systems may be kept at relatively higher
levels compared with that of NPA. Accordingly, these
Ado deaminase resistant analogues of NPA would have
an excellent antiviral activity.
F igu r e 1. Effects of calf intestinal Ado deaminase on NPA
(b) and HNPA (O).
Ta ble 2. Antiviral Activity of HNPA (3) and NPA in Different
Assay Systems
IC50 or CC50 (µg/mL)a
compd 3
virus
cell
(HNPA)
NPA
HSV-1 (KOS)
HSV-2 (G)
E6SM
E6SM
E6SM
E6SM
E6SM
E6SM
>400
>400
>400
0.1
g70
g70
40
0.7
7
70
TK- HSV-1 (B2006)
vaccinia virus
VSV
1
The 6′-homologue of carbocyclic adenosine, 28, which
corresponds to the saturated analogue of HNPA, has
been synthesized.18 However, 28 has been known to be
biologically inactive, in contrast to the potent antiviral
effects of HNPA.18b This may suggest that the cyclo-
pentenyl structure of NPA as well as its derivatives
would be important for their biological activities.
The potency and selectivity of HNPA is such that it
should be further pursued for its therapeutic potential
as an antiviral drug.
cell morphology
>400
VZV (OKA)
VZV (YS)
HEL
HEL
HEL
HEL
HEL
HEL
HEL
>50
>50
>50
>50
0.15
0.5
15
9
10
TK- VZV (07/1)
TK- VZV (YS/R)
HCMV (AD-169)
HCMV (Davis)
cell growth
7
0.3
0.4
g20
>50
VSV
HeLa
HeLa
HeLa
HeLa
0.7
>200
>200
>400
2
g40
g40
g40
Coxsackie B4 virus
Polio-1 virus
cell morphology
Exp er im en ta l Section
PV-3
Reo-1 virus
Vero
Vero
Vero
Vero
Vero
Vero
Vero
2
70
>400
>400
5
20
>400
2
4
Melting points were determined on a Yanagimoto MP-3
micro-melting point apparatus and are uncorrected. The NMR
spectra were recorded with a J EOL EX-270 or -400 spectrom-
eter with tetramethylsilane as an internal standard. Chemical
shifts were reported in parts per million (δ), and signals are
expressed as s (singlet), d (doublet), t (triplet), q (quartet), m
(multiplet), or br (broad). All exchangeable protons were
detected by the addition of D2O. Mass spectra were measured
on a J EOL J MS-D300 spectrometer. Thin-layer chromatog-
Sindbis virus
Semliki forest virus
J unin virus
Tacaribe virus
cell morphology
>10
>10
0.5
2
g10
a
50% inhibitory concentration, required to reduce virus-induced
cytopathogenicity by 50%, or 50% cytotoxic concentration, required
to reduce cell growth by 50% or to cause microscopic alteration of
normal cell morphology by approximately 50%.
raphy was done on Merck coated plate 60F254
. Silica gel
chromatography and flash silica gel chromatography were
done with Merck silica gel 5715 and 9385, respectively.
(1R,2S,3S)-1-[(Eth oxyca r bon yl)m eth yl]-2,3-(isop r op y-
lid en ed ioxy)-4-cyclop en ten -1-ol (9). To a solution of HN-
(TMS)2 (3.42 mL, 16.2 mmol) in hexane (20 mL) was added
dropwise a BuLi solution (1.62 M in hexane, 10 mL, 16.2 mmol)
at -10 °C under an argon atmosphere. After 15 min, THF
(100 mL) was added to the solution and the mixture was cooled
to -82 °C. EtOAc (1.59 mL, 16.2 mmol) was added dropwise
to the solution at -82 °C, and the solution was stirred for 25
min at the same temperature. A solution of (2S,3S)-2,3-
(sopropylidenedioxy)-4-cyclopenten-1-one (8, 2.0 g, 13.0 mmol)
in THF (20 mL) was added dropwise to the above solution,
and the resulting solution was stirred at the same temperature
for 1.5 h. The cooling bath was removed, and the reaction
mixture was quenched by an addition of saturated NH4Cl (10
mL). To the mixture were added CHCl3 (400 mL) and water
(100 mL), and the mixture was partitioned. The organic layer
was dried over MgSO4 and evaporated. The residue was
embryonic lung (HEL) fibroblasts, as well as HeLa and
Vero cell cultures (Table 2). HNPA was found active
against vaccinia virus, vesicular stomatitis virus (VSV),
human cytomegalovirus (HCMV), parainfluenza virus,
and arenaviruses (J unin, Tacaribe) at concentrations
that were lower than (VSV, vaccinia virus), comparable
to (HCMV, PV-3), or higher than (reo- and arenaviruses)
the concentrations at which NPA inhibited these vi-
ruses. HNPA did not show activity against herpes
simplex virus (HSV), varicella-zoster virus (VZV) [in-
cluding TK- (thymidine kinase deficient) strains of HSV
and VZV], picornaviruses (Coxsackie, polio), and togavi-
ruses (Sindbis, Semliki forest virus). Under the condi-
tions used for the antiviral activity assays, HNPA did
not prove toxic to the host cells at concentrations up to
400 µg/mL. This contrasts with the behavior of NPA,

2396 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12
Shuto et al.
purified by flash chromatography (silica gel, hexane/EtOAc,
5:1) to give 9 as a syrup (2.7 g, 86%): 1H NMR (270 MHz,
CDCl3) 5.86 (d, 1 H, H-4 or -5, J ) 5.9 Hz), 5.83 (d, 1 H, H-4
or -5, J ) 5.9 Hz), 5.11 (d, 1 H, H-3, J ) 5.3 Hz), 4.72 (d, 1 H,
H-2, J ) 5.3 Hz), 4.13 (q, 2 H, CH2, J ) 6.9 Hz), 3.44 (s, 1 H,
OH), 2.73 (d, 1 H, H-6a, J ) 14.9 Hz), 2.62 (d, 1 H, H-6b, J )
14.9 Hz), 1.45 and 1.41 (each s, each 3 H, isopropyl-CH3), 1.26
(t, 3 H, CH3, J ) 6.9 Hz); MS (FAB) m/ z 243 (MH+).
(1R,2S,3S)-1-(2-H yd r oxyet h yl)-2,3-(isop r op ylid en ed i-
oxy)-4-cyclop en ten -1-ol (10). A solution of LiBH4 (292 mg,
13.4 mmol) and 9 (2.7 g, 11.2 mmol) in THF (30 mL) was
stirred for 2 days at room temperature and then heated under
reflux overnight. The mixture was cooled to room tempera-
ture, EtOAc (150 mL) was added, and the resulting mixture
was washed with brine (30 mL). The organic layer was filtered
through Whatman 1PS filter paper, and the filtrate was
evaporated. The residue was purified by flash chromatography
(silica gel, hexane/acetone, 5:1) to give 10 as a syrup (1.66 g,
74%): 1H NMR (270 MHz, CDCl3) 5.85 (d, 1 H, H-4 or -5, J )
5.9 Hz), 5.82 (d, 1 H, H-4 or -5, J ) 5.9 Hz), 5.05 (d, 1 H, H-3,
J ) 5.3 Hz), 4.46 (d, 1 H, H-2, J ) 5.3 Hz), 3.85 (dd, 2 H, H-7,
J ) 5.6, 5.6 Hz), 3.40 (s, 1 H, 4-OH), 2.92 (br s, 1 H, 7-OH),
1.88 (dt, 1 H, H-6a, J ) 5.6, 14.5 Hz), 1.77 (dt, 1 H, H-6b, J )
5.6, 14.5 Hz), 1.45 and 1.37 (each s, each 3 H, isopropyl-CH3);
MS (FAB) m/ z 201 (MH+).
(1R,2S,3S)-1-[2-[(ter t-Bu t yld im et h ylsilyl)oxy]et h yl]-
2,3-(isop r op ylid en ed ioxy)-4-cyclop en ten -1-ol (11). A mix-
ture of 10 (1.48 g, 7.4 mmol), imidazole (1.26 g, 18.5 mmol),
and TBSCl (2.23 g, 14.8 mmol) in THF (30 mL) was stirred at
room temperature overnight. The solvent was evaporated, and
the residue was partitioned between CHCl3 (150 mL) and
water (30 mL). The organic layer was filtered through
Whatman 1PS filter paper, and the filtrate was evaporated.
The residue was purified by flash chromatography (silica gel,
hexane/acetone, 25:1) to give 11 as a syrup (2.35 g, 100%): 1H
NMR (270 MHz, CDCl3) 5.81 (dd, 1 H, H-4, J ) 1.7, 5.6 Hz),
5.76 (d, 1 H, H-5, J ) 5.6 Hz), 5.04 (dd, 1 H, H-3, J ) 1.7, 5.3
Hz), 4.60 (d, 1 H, H-2, J ) 5.3 Hz), 3.83 (dt, 1 H, H-7a, J )
10.6, 5.9 Hz), 3.71 (dt, 1 H, H-7b, J ) 10.6, 6.9 Hz), 3.34 (s, 1
H, OH), 1.83 (m, 2 H, H-6), 1.44 and 1.38 (each s, each 3 H,
isopropyl-CH3), 0.89 (s, 9 H, t-Bu), 0.06 and 0.05 (each s, each
3 H, SiCH3); MS (FAB) m/ z 315 (MH+).
ture of 13 (616 mg, 1.73 mmol) and K2CO3 (478 mg, 3.46 mmol)
in MeOH (10 mL) was stirred at room temperature for 1.5 h.
The solvent was removed, the residue was dissolved in CHCl3
(50 mL), and the solution was washed with water (10 mL ×
2). The organic layer was filtered through Whatman 1PS filter
paper, and the filtrate was evaporated. The residue was
purified by flash chromatography (silica gel, hexane/acetone,
15:1) to give 14 as a syrup (510 mg, 94%): 1H NMR (270 MHz,
CDCl3) 5.54 (br s, 1 H, H-5), 4.86 (d, 1 H, H-3, J ) 5.6 Hz),
4.67 (dd, 1 H, H-2, J ) 5.6, 5.6 Hz), 4.48 (m, 1 H, H-1), 3.78
(m, 2 H, H-7), 2.67 (d, 1 H, OH, J ) 9.9 Hz), 2.39 (m, 2 H,
H-6), 1.41 and 1.40 (each s, each 3 H, isopropyl-CH3), 0.88 (s,
9 H, t-Bu), 0.05 (s, 6 H, SiCH3); MS (FAB) m/ z 315 (MH+).
(1S,2R,3R)-1-[(Meth ylsu lfon yl)oxy]-2,3-(isopr opyliden e-
d ioxy)-4-[2-[(ter t-bu tyld im eth ylsilyl)oxy]eth yl]-4-cyclo-
p en ten e (15). A mixture of 14 (98 mg, 0.31 mmol), DMAP
(114 mg, 0.94 mmol), and MsCl (48 µL, 0.62 mmol) in CH2Cl2
(3 mL) was stirred at room temperature for 3.5 h. Then CHCl3
(30 mL) and water (6 mL) were added, and the resulting
mixture was partitioned. The organic layer was washed with
water (6 mL) and filtered through Whatman 1PS filter paper.
The solvent was evaporated, and the residue was purified by
flash chromatography (silica gel, hexane/acetone, 10:1) to give
15 (90 mg , 74%) as a syrup: 1H NMR (270 MHz, CDCl3) 5.58
(d, 1 H, H-5, J ) 1.7 Hz), 5.39 (m, 1 H, H-1), 4.88 (m, 2 H, H-2
and 3), 3.76 (m, 2 H, H-7), 3.12 (s, 3 H, CH3SO2), 2.45 (m, 2 H,
H-6), 1.40 (s, 6 H, isopropyl-CH3), 0.88 (s, 9 H, t-Bu), 0.05 (s,
6 H, SiCH3); MS (FAB) m/ z 393 (MH+).
9-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu -
tyld im eth ylsilyl)oxy]eth yl]-4-cyclop en ten -1-yl]a d en in e
(17). A suspension of adenine (84 mg, 0.62 mmol) and NaH
(50% in oil, 30 mg, 0.62 mmol) in DMF (1 mL) was stirred at
room temperature for 1 h. To the resulting solution were
added 15-crown-5 (62 µL, 0.31 mmol) and a solution of 15 (90
mg, 0.23 mmol) in DMF (1 mL), and the mixture was stirred
at room temperature for 15 h, followed by heating at 80 °C for
2 h. The resulting mixture was cooled to room temperature
and evaporated. EtOAc (50 mL) was added to the residue,
and the resulting insoluble material was filtered off. The
filtrate was washed with water (10 mL) and filtered through
Whatman 1PS filter paper, and the filtrate was evaporated.
The residue was purified by flash chromatography (silica gel,
(1R,2S,3S)-1-Acet oxy-2,3-(isop r op ylid en ed ioxy)-1-[2-
[(ter t-bu tyld im eth ylsilyl)oxy]eth yl]-4-cyclop en ten e (12).
A mixture of 11 (2.35 g, 7.3 mmol), acetic anhydride (7.06 mL,
75 mmol), Et3N (20.9 mL, 150 mmol), and DMAP (914 mg,
7.5 mmol) in THF (100 mL) was stirred at room temperature
overnight. To the mixture were further added acetic anhydride
(3.53 mL, 37.4 mmol), and Et3N (10.4 mL, 75 mmol), and the
resulting mixture was stirred at room temperature overnight.
The solvent was evaporated, the residue was dissolved in
CHCl3 (150 mL), and the resulting solution was washed with
water (30 mL). The organic layer was filtered through
Whatman 1PS filter paper, and the filtrate was evaporated.
The residue was purified by flash chromatography (silica gel,
hexane/acetone, 20:1) to give 12 as a syrup (2.46 g, 92%): 1H
NMR (270 MHz, CDCl3) 6.00 (d, 1 H, H-5, J ) 5.9 Hz), 5.90
(dd, 1 H, H-4, J ) 5.9, 1.7 Hz), 5.05 (dd, 1 H, H-3, J ) 1.7, 5.3
Hz), 4.48 (d, 1 H, H-2, J ) 5.3 Hz), 3.64 (m, 2 H, H-7), 2.35
(dt, 1 H, H-6a, J ) 5.3, 14.2 Hz), 2.06 (m, 4 H, H-6b, Ac), 1.37
and 1.36 (each s, each 3 H, isopropyl-CH3), 0.89 (s, 9 H, t-Bu),
0.04 (s, 6 H, SiCH3); MS (FAB) m/ z 357 (MH+).
(1S,2R,3R)-1-Acet oxy-2,3-(isop r op ylid en ed ioxy)-4-[2-
[(ter t-bu tyld im eth ylsilyl)oxy]eth yl]-4-cyclop en ten e (13).
A mixture of 12 (1.0 g, 2.8 mmol), PdCl2(CH3CN)2 (37 mg, 0.14
mmol), and p-benzoquinone (122 mg, 1.12 mmol) in THF (30
mL) was heated under reflux overnight. The mixture was
cooled to room temperature and evaporated. The residue was
purified by flash chromatography (silica gel, hexane/acetone,
15:1) to give 13 as a syrup (878 mg, 88%): 1H NMR (270MHz,
CDCl3) 5.53 (br s, 1 H, H-5), 5.33 (m, 1 H, H-1), 4.87 (m, 2 H,
H-2, -3), 3.80 (m, 2 H, H-7), 2.44 (m, 2 H, H-6), 2.11 (s, 3 H,
Ac), 1.38 (s, 6 H, isopropyl-CH3), 0.88 (s, 9 H, t-Bu), 0.05 (s, 6
H, SiCH3); MS (FAB) m/ z 357 (MH+).
CHCl3
/CH OH, 15:1) to give 17 as a crystalline solid (30 mg,
3
1
30%): mp 133-134 °C; H NMR (270 MHz, CDCl3) 8.41 and
7.63 (each s, each 1 H, H-8 and -2), 6.00 (br s, 2 H, NH2), 5.65
(br s, 1 H, H-5′), 5.60 (br s, 1 H, H-1′), 5.28 (d, 1 H, H-3′, J )
5.6 Hz), 4.61 (d, 1 H, H-2′, J ) 5.6 Hz), 3.90 (m, 2 H, H-7′),
2.46 (m, 2 H, H-6′), 1.47, 1.36 (each s, each 3 H, isopropyl-
CH3), 0.90 (s, 9 H, t-Bu), 0.09 (s, 6 H, SiCH3); MS (FAB) m/ z
432 (MH+). Anal. (C21H33N5O3Si) C, H, N.
9-[(1R,2S,3R)-2,3-Dih yd r oxy-4-(2-h yd r oxyet h yl)-4-cy-
clop en ten -1-yl]a d en in e (3, HNP A). A solution of 17 (920
mg, 2.13 mmol) in a mixture of MeOH (20 mL) and 2 N HCl
(20 mL) was stirred at room temperature for 2 h. The solvent
was evaporated, the residue was dissolved in MeOH (5 mL)
and Et3N (3 mL), and then the solvent was evaporated. To
the residue was added CHCl3, and the resulting insoluble solid
was collected by filtration to give 3 as a crystalline solid (530
mg, 90%). An analytical sample was obtained by recrystalli-
zation from MeOH: mp 202-203 °C; [R]25 -144.1 (c ) 0.10,
D
1
MeOH); H NMR (270 MHz, CD3OD) 8.19 and 8.11 (each s,
each 1 H, H-8 and -2), 5.81 (d, 1 H, H-5′, J ) 1.7 Hz), 5.50 (m,
1 H, H-1′), 4.61 (d, 1 H, H-3′, J ) 5.3 Hz), 4.34 (dd, 1 H, H-2′,
J ) 5.3, 5.3 Hz), 3.82 (m, 2 H, H-7′), 2.54 (br t, 2 H, H-6′, J )
6.3 Hz); MS (FAB) m/ z 277 (MH+); UV λmax 260 (H2O), 258
(0.1 N HCl), 262 nm (0.1 N NaOH). Anal. (C12H15N5O3‚1/2H2O)
C, H, N.
9-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu -
t yld im et h ylsilyl)oxy]et h yl]-4-cyclop en t en -1-yl]-3-d ea -
za a d en in e (18). A suspension of 3-deazaadenine (214 mg,
1.59 mmol) and NaH (50% in oil, 77 mg, 0.62 mmol) in DMF
(5 mL) was stirred at room temperature for 2 h. A solution of
15 (285 mg, 0.73 mmol) in DMF (3 mL) and 15-crown-5 (158
µL, 0.80 mmol) was added, and the resulting mixture was
stirred at room temperature overnight, followed by heating
at 55 °C for 2.5 h. After cooling to room temperature, the
(1S,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu tyl-
d im eth ysilyl)oxy]eth yl]-4-cyclop en ten -1-ol (14). A mix-

New Neplanocin Analogues
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12 2397
mixture was evaporated. To the residue was added EtOAc
(50 mL), and the resulting insoluble material was filtered off.
The filtrate was washed with water (10 mL) and filtered
through Whatman 1PS filter paper, and the filtrate was
evaporated. The residue was purified by flash chromatography
(silica gel, CHCl3/CH3OH, 20:1) to give 18 as a crystalline solid
(85 mg, 25%). An analytical sample was obtained by recrys-
tallization from hexane: mp 148-149 °C; 1H NMR (270 MHz,
CDCl3) 7.85 (d, 1 H, H-2, J ) 5.9 Hz), 7.68 (s, 1 H, H-8), 6.82
(d, 1 H, H-3, J ) 5.9 Hz), 5.71 (br s, 1 H, H-5′), 5.31 (br s, 1 H,
H-1′), 5.28 (br s, 2 H, NH2), 5.23 (d, 1 H, H-3, J ) 5.9 Hz),
4.50 (d, 1 H, H-2′, J ) 5.9 Hz), 3.91 (m, 2 H, H-7′), 2.54 (m, 2
H, H-6′), 1.47, 1.35 (each s, each 3 H, isopropyl-CH3), 0.90 (s,
9 H, t-Bu), 0.09 (s, 6 H, SiCH3); MS (FAB) m/ z 431 (MH+).
Anal. (C22H34N4O3Si) C, H, N.
1PS filter paper, and the filtrate was concentrated to give 21
as a solid (145 mg, 64%): 1H NMR (270 MHz, CDCl3) 7.77 (s,
1 H, H-8), 5.71 (br s, 1 H, H-5′), 5.42 (br s, 2 H, NH2), 5.36 (d,
1 H, H-3′, J ) 5.6 Hz), 5.36 (s, 1 H, H-1′), 4.59 (d, 1 H, H-2′,
J ) 5.6 Hz), 3.91 (m, 2 H, H-7′), 3.58 (dd, 1 H, OH, J ) 8.3,
3.3 Hz), 2.61 (m, 2 H, H-6′), 1.49, 1.37 (each s, each 3 H,
isopropyl-CH3); MS (FAB) m/ z 352 (MH+).
9-[(1R,2S,3R)-2,3-Dih yd r oxy-4-(2-h yd r oxyet h yl)-4-cy-
clop en ten -1-yl]gu a n in e (5). A mixture of 21 (45 mg, 0.13
mmol) in 2 N HCl (6 mL) was stirred at room temperature for
2 h, and then the mixture was heated under reflux for 2 h.
The solvent was evaporated, and a small amount of water was
added to the residue, and the solvent was evaporated again.
After addition of water (5 mL) to the residue, the mixture was
neutralized with Et3N and then evaporated. To the residue
was added CHCl3, and the resulting insoluble solid was
collected by filtratation to give 5 (37 mg, 99%). An analytical
9-[(1R,2S,3R)-2,3-Dih yd r oxy-4-(2-h yd r oxyet h yl)-4-cy-
clop en ten -1-yl]-3-d ea za a d en in e (4). A solution of 18 (50
mg, 0.12 mmol) and TBAF (1 M in THF, 140 µL, 0.14 mmol)
in THF (2 mL) was stirred at room temperature for 1 h. The
resulting mixture was evaporated, and the residue was
partitioned between CHCl3 (100 mL) and water (10 mL). The
organic layer was washed with saturated NaHCO3 (20 mL)
and water (20 mL) and filtered through Whatman 1PS filter
paper, and the filtrate was evaporated. The residue was
purified by flash chromatography (silica gel, CHCl3/MeOH, 15:
1) to give a crystalline solid which was dissolved in HCl/CH3-
OH (8.9 M, 2 mL), and the mixture was stirred at room
temperature for 1 h. The solvent was evaporated, the residue
was dissolved in water (2 mL), and the solution was purified
by Dowex-1 column (OH-, 1 × 1 cm, eluted with 20% MeOH)
to give 4 as a crystalline solid (21 mg, 66%): mp 214-216 °C;
sample was obtained by recrystallizing from water: mp 203-
1
205 °C; [R]22 ) +7.99 (c ) 0.05, H2O); H NMR (270 MHz,
D
CD3OD) 8.93 (br s, 1 H, H-8), 5.77 (br s, 1 H, H-5′), 5.45 (m, 1
H, H-1′), 4.62 (d, 1 H, H-3′, J ) 5.6 Hz), 4.34 (dd, 1 H, H-2′, J
) 5.6, 4.6 Hz), 3.82 (t, 2 H, H-7′, J ) 6.3 Hz), 2.54 (br t, 2 H,
H-6′, J ) 6.3 Hz); MS (FAB) m/ z 294 (MH+); UV λmax 253
(H2O), 256 (0.1 N HCl), 268, 256 nm (0.1 N NaOH). Anal.
(C12H15N5O4‚H2O) C, H, N.
1-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu -
tyldim eth ylsilyl)oxy]eth yl]-4-cyclopen ten -1-yl]u r acil (22).
Compound 22 was prepared as described above for 19, with
uracil instead of 2-amino-6-chloropurine. After purification
by flash chromatography (silica gel, hexane/acetone, 4:1), 22
was obtained as a crystalline solid (201 mg, 35%): mp 166-
167 °C; 1H NMR (270 MHz, CDCl3) 8.54 (br s, 1 H, NH), 7.08
(d, 1 H, H-6, J ) 7.9 Hz), 5.63 (dd, 1 H, H-5, J ) 2.3, 7.9 Hz),
5.45 (br s, 1 H, H-5′), 5.42 (br s, 1 H, H-1′), 5.14 (br d, 1 H,
H-3′, J ) 5.6 Hz), 4.47 (d, 1 H, H-2′, J ) 5.6 Hz), 3.87 (m, 2 H,
H-7′), 2.49 (m, 2 H, H-6′), 1.34, 1.35 (each s, each 3 H,
isopropyl-CH3), 0.89 (s, 9 H, t-Bu), 0.07 (s, 6 H, SiCH3); MS
(FAB) m/ z 409 (MH+). Anal. (C20H32N2O5Si) C, H, N.
1-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu -
t y ld im e t h y ls ily l)o x y ]e t h y l]-4-c y c lo p e n t e n -1-y l]t h y -
m in e (23). Compound 23 was prepared as described above
for 19, with thymine instead of 2-amino-6-chloropurine. After
purification by flash chromatography (silica gel, CHCl3/
acetone, 5:1), 23 was obtained as a crystalline solid (192 mg,
31%): mp 43-45 °C; 1H NMR (270 MHz, CDCl3) 8.95 (br s, 1
H, NH), 6.82 (d, 1 H, H-6, J ) 1.3 Hz), 5.44 (br s, 1 H, H-5′),
5.41 (br s, 1 H, H-1′), 5.17 (br d, 1 H, H-3′, J ) 5.9 Hz), 4.49
(d, 1 H, H-2′, J ) 5.9 Hz), 3.88 (m, 2 H, H-7′), 2.49 (m, 2 H,
H-6′), 1.88 (d, 3 H, CH3, J ) 1.3 Hz), 1.43, 1.35 (each s, each
3 H, isopropyl-CH3), 0.90 (s, 9 H, t-Bu), 0.08 (s, 6 H, SiCH3);
MS (FAB) m/ z 423 (MH+). Anal. (C21H34N2O5Si‚1/2H2O) C,
H, N.
1-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-(2-h yd r oxy-
eth yl)-4-cyclop en ten -1-yl]th ym in e (24). A mixture of 23
(50 mg, 0.12 mmol) and TBAF (1 M in THF, 142 µL, 0.14
mmol) in THF (2 mL) was stirred for 4 h and then evaporated.
The residue was dissolved in water (30 mL) and washed with
CHCl3 (5 mL × 3). Activated charcoal (1 g) was added to the
aqueous layer, and then the charcoal was packed in a column
which was washed with water and eluted with 50% MeOH
followed by MeOH. The fractions containing 24 were evapo-
rated, a small amount of hot MeOH was added to the residue,
and the resulting insoluble material was filtered off. The
filtrate was evaporated, and the residue was purified by flash
chromatography (silica gel, CHCl3/MeOH, 10:1) to give 24 as
a crystalline solid (29 mg, 79%): mp 62-63 °C; 1H NMR (270
MHz, CDCl3) 9.47 (br s, 1 H, NH), 6.91 (d, 1 H, H-6, J ) 1.3
Hz), 5.46 (br s, 1 H, H-5′), 5.25 (d, 1 H, H-3′, J ) 5.6 Hz), 5.19
(br s, 1 H, H-1′), 4.64 (d, 1 H, H-2′, J ) 5.6 Hz), 3.85 (br s, 2
H, H-7′), 2.74 (br s, 1 H, OH), 2.55 (m, 2 H, H-6′), 1.88 (s, 3 H,
CH3), 1.46, 1.34 (each s, each 3 H, isopropyl-CH3); MS (FAB)
m/ z 309 (MH+). Anal. (C15H20N2O5‚H2O) C, H, N.
[R]28 -123.5 (c ) 0.10, H2O); 1H NMR (270 MHz, CD3OD)
D
8.07 (s, 1 H, H-8), 7.67 (d, 1 H, H-2, J ) 5.9 Hz), 6.93 (d, 1 H,
H-3, J ) 5.9 Hz), 5.84 (br s, 1 H, H-5′), 5.34 (m, 1 H, H-1′),
4.54 (br d, 1 H, H-3′, J ) 5.6 Hz), 4.19 (dd, 1 H, H-2′, J ) 5.6,
5.6 Hz), 3.84 (br t, 2 H, H-7′, J ) 6.3 Hz), 2.54 (br t, 2 H, H-6′,
J ) 6.3 Hz); MS (FAB) m/ z 277 (MH+); HR-MS (FAB) calcd
for C13H17N4O3 277.130, found 277.128. UV λmax 262 (H2O),
262 (0.1 N HCl), 267 nm (0.1 N NaOH). Anal. (C13H16N4O3‚1/
4H2O) C, H, N.
2-Am in o-6-ch lor o-9-[(1R,2S,3R)-2,3-(isop r op ylid en e-
d ioxy)-4-[2-[(ter t-bu tyl-d im eth ylsilyl)oxy]eth yl]-4-cyclo-
p en ten -1-yl]p u r in e (19) a n d 2-Am in o-6-ch lor o-7-[(1R,2S,-
3R)-2,3-(isop r op ylid en ed ioxy)-4-[2-[(ter t-b u t yld im et h -
ylsilyl)oxy]eth yl]-4-cyclop en ten -1-yl]p u r in e (20). A mix-
ture of 15 (874 mg, 2.23 mmol), 2-amino-6-chloropurine (1.54
g, 9.09 mmol), K2CO3 (1.26 g, 9.12 mmol), and 18-crown-6 (600
mg, 2.23 mmol) in DMF (35 mL) was stirred at room temper-
ature for 9 days. The solvent was evaporated, EtOAc (100 mL)
was added to the residue, and the resulting insoluble material
was filtered off. The filtrate was washed with water (20 mL)
and filtered through Whatman 1PS filter paper, and the
filtrate was evaporated. The residue was purified by flash
chromatography (silica gel, CHCl3/acetone, 10:1) to give 19
(crystalline solid, 567 mg, 55%) and 20 (crystalline solid, 122
mg, 12%), respectively. 19: mp 228-229 °C; 1H NMR (270
MHz, CDCl3) 7.63 (s, 1 H, H-8), 5.60 (br s, 1 H, H-5′), 5.44 (br
s, 1 H, H-1′), 5.26 (m, 3 H, H-3′ and NH2), 4.56 (d, 1 H, H-2′,
J ) 5.3 Hz), 3.89 (m, 2 H, H-7′), 2.53 (m, 2 H, H-6′), 1.46, 1.37
(each s, each 3 H, isopropyl-CH3), 0.89 (s, 9 H, t-Bu), 0.08 (s,
6 H, SiCH3); MS (FAB) m/ z 466 (MH+); UV λmax 310, 248, 223
nm (MeOH). Anal. (C21H32ClN5O3Si) C, H, N. 20: mp 145-
146 °C; 1H NMR (270 MHz, CDCl3) 7.86 (s, 1 H, H-8), 5.76 (br
s, 1 H, H-5′), 5.63 (br s, 1 H, H-1′), 5.09 (d, 1 H, H-3′, J ) 5.3
Hz), 5.03 (br s, 2 H and NH2), 4.45 (d, 1 H, H-2′, J ) 5.3 Hz),
3.84 (m, 2 H, H-7′), 2.48 (m, 2 H, H-6′), 1.37, 1.28 (each s, each
3 H, isopropyl-CH3), 0.84 (s, 9 H, t-Bu), 0.03 (s, 6 H, SiCH3);
MS (FAB) m/ z 466 (MH+); UV λmax 325, 225 nm (MeOH). Anal.
(C21H32ClN5O3Si‚H2O) C, H, N.
2-Am in o-6-ch lor o-9-[(1R,2S,3R)-2,3-(isop r op ylid en e-
dioxy)-4-(2-h ydr oxyeth yl)-4-cyclopen ten -1-yl]pu r in e (21).
A solution of 19 (300 mg, 0.65 mmol) and TBAF (1 M in THF,
780 µL, 0.78 mmol) in THF (15 mL) was stirred at room
temperature for 2.5 h. The solvent was evaporated, and the
residue was partitioned between CHCl3 (50 mL) and water (10
mL × 3). The organic layer was filtered through Whatman
1-[(1R,2S,3R)-2,3-Dih yd r oxy-4-(2-h yd r oxyet h yl)-4-cy-
clop en ten -1-yl]th ym in e (6). A solution of 24 (73 mg, 0.24
mmol) in 70% HCOOH (3 mL) was stirred at 70 °C for 40 h,
and then the solvent was removed. To the residue was added

2398 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12
Shuto et al.
8% NH4OH (3 mL), and the mixture was stirred for 1.5 h at
room temperature. The solvent was evaporated, and the
residue was purified by flash chromatography (silica gel,
CHCl3/CH3OH/H2O, 65:25:3) to give 6 as a crystalline solid
Refer en ces
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(42 mg, 66%): mp 166-167 °C; [R]24 -82.12 (c ) 0.21, H2O);
D
1H NMR (270 MHz, CD3OD) 7.26 (s, 1 H, H-6), 5.54 (s, 1 H,
H-5′), 5.45 (br s, 1 H, H-1′), 4.46 (br d, 1 H, H-3′, J ) 5.6 Hz),
4.01 (m, 1 H, H-2′), 3.79 (br t, 2 H, H-7′, J ) 6.3 Hz), 2.47 (br
t, 2 H, H-6′, J ) 6.3 Hz), 1.85 (s, 3 H, CH3); MS (FAB) m/ z
269 (MH+); HR-MS (FAB) calcd for C12H17N2O5 269.114; found
269.111; UV λmax 274 (H2O), 273 (0.1 N HCl), 271 nm (0.1 N
NaOH). Anal. (C12H16N2O5‚1/5H2O) C, H, N.
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1-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-[2-[(ter t-bu -
t yld im e t h ylsilyl)oxy]e t h yl]-4-cyclop e n t e n -1-yl]cyt o-
sin e (25). A mixture of 22 (155 mg, 0.78 mmol), DMAP (460
mg, 3.77 mmol), and 2,4,6-triisopropylbenzenesulfonyl chloride
(460 mg, 1.52 mmol) in CH3CN (5 mL) was stirred at room
temperature overnight. After addition of 25% NH4OH (5 mL),
the mixture was further stirred for 5 h, CHCl3 (50 mL) and
water (10 mL) were added, and the resulting mixture was
partitioned. The organic layer was washed with saturated
NH4Cl (10 mL) and filtered through Whatman 1PS filter
paper, and the filtrate was evaporated. The residue was
purified by flash chromatography (silica gel, CHCl3/MeOH, 10:
1) to give 25 as a crystalline solid (131 mg, 85%): mp 133-
135 °C; 1H NMR (270 MHz, CDCl3) 7.11 (d, 1 H, H-6, J ) 7.3
Hz), 5.85 (d, 1 H, H-5, J ) 7.3 Hz), 5.50 (br s, 1 H, H-5′), 5.40
(br s, 1 H, H-1′), 5.10 (br d, 1 H, H-3′, J ) 5.6 Hz), 4.55 (d, 1
H, H-2′, J ) 5.6 Hz), 3.85 (m, 2 H, H-7′), 2.47 (m, 2 H, H-6′),
1.41, 1.33 (each s, each 3 H, isopropyl-CH3), 0.89 (s, 9 H, t-Bu),
0.07 (s, 6 H, SiCH3); MS (FAB) m/ z 408 (MH+). Anal.
(C20H33N3O4Si) C, H, N.
1-[(1R,2S,3R)-2,3-(Isop r op ylid en ed ioxy)-4-(2-h yd r oxy-
eth yl)-4-cyclop en ten -1-yl]cytosin e (26). Compound 26 was
prepared as described above for 24. After purification by flash
chromatography (silica gel, CHCl3/CH3OH, 5:1), 26 was ob-
tained as a solid (37 mg, 86%): 1H NMR (270 MHz, CD3OD)
7.36 (d, 1 H, H-6, J ) 7.6 Hz), 5.85 (d, 1 H, H-5, J ) 7.6 Hz),
5.47 (br s, 1 H, H-5′), 5.40 (br s, 1 H, H-1′), 5.19 (br d, 1 H,
H-3′, J ) 5.9 Hz), 4.50 (d, 1 H, H-2′, J ) 5.9 Hz), 3.81 (m, 2 H,
H-7′), 2.50 (m, 2 H, H-6′), 1.40, 1.33 (each s, each 3 H,
isopropyl-CH3); MS (FAB) m/ z 294 (MH+).
1-[(1R,2S,3R)-2,3-Dih yd r oxy-4-(2-h yd r oxyet h yl)-4-cy-
clop en ten -1-yl]cytosin e (7). A mixture of 26 (37 mg, 0.13
mmol) in HCl/MeOH (8.9 M, 3 mL) was stirred at room
temperature for 1.5 h. The solvent was evaporated, the
residue was dissolved in water (1 mL), and the solution was
purified by a Dowex-1 column (OH-, 1 × 2 cm, eluted with
water) to give 7 as a crystalline solid (20 mg, 57%): mp >196
1
°C dec; [R]26 -35.13 (c ) 0.074, MeOH); H NMR (270 MHz,
EICAR, and (6′R)-6′-C-methylneplanocin
A against several
D
ortho- and paramyxoviruses. Antimicrob. Agents Chemother.
1992, 36, 435-439. (c) Shuto, S.; Obara, T.; Kosugi, Y.; Toriya,
M.; Yaginuma, S.; Shigeta, S.; Matsuda, A. New neplanocin
analogues. III. 6′R-Configuration is essential for the antiviral
activity of 6′-C-methyl-3-deazaneplanocin A′s. BioMed. Chem.
Lett. 1993, 4, 605-608. (d) Shuto, S.; Obara, T.; Itoh, H.; Kosugi,
Y.; Saito, Y.; Toriya, M.; Yaginuma, S.; Shigeta, S.; Matsuda, A.
New neplanocin analogues. IV. An adenosine deaminase-
resistant equivalent of neplanocin A. Chem. Pharm. Bull. 1994,
42, 1688-1690. (e) Obara, T.; Shuto, S.; Saito, Y.; Toriya, M.;
Ogawa, K.; Yaginuma, S.; Shigeta, S.; Matsuda, A. New nepl-
anocin analogues. V. A potent adenosylhomocysteine hydrolase
inhibitor lacking antiviral activity. Synthesis and antiviral
activity of 6′-carboxylic acid derivatives of neplanocin A. Nucleo-
sides Nucleotides, in press.
CD3OD) 7.46 (d, 1 H, H-6, J ) 7.3 Hz), 5.86 (d, 1 H, H-5, J )
7.3 Hz), 5.55 (d, 1 H, H-5′, J ) 1.6 Hz), 5.45 (m, 1 H, H-1′),
4.48 (br d, 1 H, H-3′, J ) 5.6 Hz), 3.99 (dd, 1 H, H-2′, J ) 4.0,
5.6 Hz), 3.78 (br t, 2 H, H-7′, J ) 6.6 Hz), 2.48 (br t, 2 H, H-6′,
J ) 6.6 Hz); MS (FAB) m/ z 254 (MH+); UV λmax 273 (H2O),
283 (0.1 N HCl), 273 nm (0.1 N NaOH). Anal. (C11H15N3O4‚2/
5H2O) C, H, N.
An tivir a l Assa ys. Antiviral assays were carried out ac-
cording to previously reported methods.7,9a,b,19
In h ibitor y Effect on Ra bbit Er yth r ocyte Ad oHcy Hy-
d r ola se a n d Effect of Ad en osin e Dea m in a se fr om Ca lf
In testin e. Assays were carried out according to previously
reported methods.9a
(10) For examples: (a) Borcherding, D. R.; Narayanan, S.; Hasobe,
M.; McKee, J . G.; Keller, B. T.; Borchadt, R. T. Potential
inhibitors of S-adenosylmethionine-dependent methyltransferas-
es. 11. Molecular dissections of neplanocin A as potential
inhibitors of S-adenosylhomocysteine hydrolase. J . Med. Chem.
1988, 31, 1729-1738. (b) Tsend, C. K. H.; Marquez, V. E.; Fuller,
R. W.; Goldstein, B. M.; Arnett, G.; Hollingshead, M.; Driscoll,
J . S. Synthesis of 3-deazaneplanocin A, a powerful inhibitor of
S-adenosylhomocysteine hydrolase with potent and selective in
vitro and in vivo antiviral activities. J . Med. Chem. 1989, 32,
1442-1446. (c) Hasobe, M.; McKee, J . G.; Borcherding, D. R.;
Borchardt, R. T. 9-(trans-2′,trans-3′-Dihydroxycyclopent-4′-enyl)-
adenine and 3-deazaadenine: analogs of neplanocin A which
retain potent antiviral activity but exhibit reduced cytotoxicity.
Antimicrob. Agents Chemother. 1987, 31, 1849-1851.
Ack n ow led gm en t. We thank Prof. Shiro Shigeta
and Drs. Satoshi Yaginuma and Minoru Toriya for
helpful discussion and encouragement throughout the
study. We also thank Anita Camps, Frieda De Meyer,
and Anita Van Lierde for excellent technical assistance
and Christiane Callebaut for dedicated editorial help.
This work was supported in part by grants from the
Belgian Fonds voor Geneeskundig Wetenschappelijk
Onderzoek (FGWO) and Belgian Geconcerteerde Onder-
zoeksacties (GOA).

New Neplanocin Analogues
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 12 2399
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