The enantiomers of the 1′,6′-isomer of neplanocin A: Synthesis and antiviral properties

Article abstract of DOI:10.1016/j.bmc.2014.07.051

Both enantiomers of 1′,6′-isoneplanocin have been prepared from a common substituted cyclopentane epoxide in 7 steps. Both compounds were subjected to DNA and RNA viral assessments with moderate to high activity found for both towards human cytomegaloviru

Full text of DOI:10.1016/j.bmc.2014.07.051

Bioorganic & Medicinal Chemistry 22 (2014) 5315–5319
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
0
0
The enantiomers of the 1 ,6 -isomer of neplanocin A: Synthesis
and antiviral properties
⇑
Wei Ye, Stewart W. Schneller
Molette Laboratory for Drug Discovery, Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, United States
a r t i c l e i n f o
a b s t r a c t
0
0
Article history:
Both enantiomers of 1 ,6 -isoneplanocin have been prepared from a common substituted cyclopentane
epoxide in 7 steps. Both compounds were subjected to DNA and RNA viral assessments with moderate
to high activity found for both towards human cytomegalovirus, measles, Ebola, norovirus, and dengue.
The D-like congener also showed vaccinia and HBV effectiveness. In many of the other antiviral assays
both compounds showed cytotoxicity making, in some cases, an EC50 determination not possible. The
S-adenosylhomocysteine hydrolase inhibitory effects showed the D-like target to be equal that of nepla-
nocin itself and better than 3-deazaneplanocin whereas the L-like analogue was 13 to 30 times less inhib-
itory than 3-deazaneplanocin and neplanocin, respectively.
Received 31 May 2014
Revised 21 July 2014
Accepted 30 July 2014
Available online 7 August 2014
Keywords:
Carbocyclic nucleosides
DNA and RNA viruses
S-Adenosylhomocysteine hydrolase
Common precursor to two
enantiomeric isoneplanocins
Ó 2014 Elsevier Ltd. All rights reserved.
1
. Introduction
The naturally occurring neplanocin series of carbocyclic nucleo-
1
sides (Fig. 1) offers a unique substitution pattern within the cyclo-
pentyl appendage not found elsewhere. This collection of
nucleosides is conformationally constrained by the alkene and
epoxide functionalities. Additionally, both of these structural cen-
ters provide for access to a variety of molecular modifications in
a laboratory analogue pursuit building upon the biological activity
NH2
N
NH2
N
N
N
N
N
OH
HOH2C
HOH2C
N
N
O
OH
HO
OH
2
of the neplanocins, particularly neplanocin A (1).
1
Neplanocin B
Several years ago we became interested in affecting change at
Neplanocin A
0
0
0
the C-1 of the neplanocins by generating the C-1 /C-6 isomer of
O
N
NH2
neplanocin A (that is 2, Fig. 2). That research produced a short syn-
N
N
N
3
NH
thetic communication. We now wish to report the details of that
N
O
effort with improved preparative procedures to 2 and its newly
described enantiomer 3 (Fig. 2) together with their antiviral data.
N
HOH2C
HOH2C
N
HO
OH
HO
OH
2
2
. Results and discussion
Neplanocin C
Neplanocin D
.1. Synthesis
NH2
N
N
In seeking a more adaptable procedure (for future development
OH
of various unique neplanocin analogues) the known substituted
cyclopentyl epoxide 4 (available from cyclopentadiene in 2 steps)
HOH2C
N
N
4
fulfilled this intention. Thus, the synthesis of 2 and 3 began with
OH
Neplanocin F
⇑
Corresponding author. Tel.: +1 334 844 6947; fax: +1 334 844 0239.
E-mail address: schnest@auburn.edu (S.W. Schneller).
Figure 1. Naturally occurring neplanocins.
http://dx.doi.org/10.1016/j.bmc.2014.07.051
968-0896/Ó 2014 Elsevier Ltd. All rights reserved.
0

5
316
W. Ye, S.W. Schneller / Bioorg. Med. Chem. 22 (2014) 5315–5319
NH2
N
NH2
N
2.2. Antiviral and enzyme assay results
N
N
N
N
Compounds 2 and 3 were evaluated against both DNA and RNA
viruses. Table 1 lists where activity was observed. Noteworthy is
the activity of both enantiomers towards human cytomegalovirus
(HCMV), measles, Ebola, norovirus, and dengue (albeit with some
accompanying toxicity). Compound 2 displayed activity towards
hepatitis B virus and vaccinia virus.
6
'
6'
N
1'
5,6
HOH2C
HO
N
CH OH
2
1
'
OH
HO
OH
L-like"
3
2
"
"
D-like"
As a consequence of 2 and 3 being isomers of neplanocin A,
Figure 2. Target neplanocin analogues.
whose potent inhibition of S-adenosylhomocysteine hydrolase
2
(
SAHase) is one agreed upon source of its antiviral activity, they
were screened against this enzyme (source: rabbit erythrocytes).
This assay produced the following results (IC50 in nm): neplanocin
A (structure in Fig. 1, 0.9); D-like isoneplanocin A (2, 0.9); L-like
isoneplanocin A (3, 27), and 3-deazaneplanocin (structure not
shown, 2). As can be seen, 2 possesses an effect on SAHase compa-
rable to neplanocin A but 2 orders of magnitude better than
protection of the secondary hydroxyl of 4 with a p-methoxybenzyl
PMB) group to 5 (Scheme 1). A regioselective ring opening of 5
with lithium bis(trimethylsilyl) amide (LiHMDS) provided the ver-
satile alkene 6. Subsequent oxidation of 6 with m-chloroperoxy-
(
benzoic acid (mCPBA) proceeded to the
a-epoxide 7, which
availed an entry point into the requisite carbocyclic nucleoside
3
-deazaneplanocin while enantiomer 3 is less effective.
scaffold. (Confirmation of the stereochemistry of 7 came with its
3
movement to the known 2 ).
3
. Conclusion
In the latter direction, reaction of 7 with adenine in the pres-
ence of 1,8-diazabicycloundec-7-ene (DBU) yielded a mixture of
0
0
The C-1 /C-6 isoneplanocin enantiomers have been prepared
8
and 9 (1.6:1). Acidic removal of the PMB group of 8 to 10 fol-
lowed by glycol protection gave 11. Mesylation of 11 resulted in
2, which underwent elimination in the presence of sodium meth-
from a common precursor (that is, 7) and were found to possess
antiviral activity against a variety of important viruses. In cases
where both were active 2 was slightly more effective than 3.
On the other hand, only 2 affected hepatitis B virus and vaccinia
virus, the former more strongly. These properties may be due to
their different effects on SAHase. However, the potent effect of 3
versus Ebola coupled with its weaker properties towards SAHase
suggests that SAHase inhibition is not the only site where 3 is act-
ing towards, at least, this virus. More work in this area is foreseen
1
oxide to provide 13. Debenzylation of 13 with subsequent deketal-
ization yielded target 2.
The final steps to 3 began with glycol protection of 9 to 15,
which, upon oxidative deprotection with 2,3-dichloro-5,6-dicy-
ano-1,4-benzoquinone (DDQ), was converted into 16. As with 11,
mesylation of 16 to 17 and subsequent sodium methoxide pro-
moted elimination produced 18, analogous to 13. Deprotection
7
since 3 opens-up the L-like carbocyclic nucleoside as a potential
scaffold for anti-Ebola drug discovery endeavors. To date very little
1
8, as with 13, to 19 and then 1 N hydrochloric acid, resulted in
target 3.
HO
HO
BnO
O
BnO
BnO
c
b
on 5
O
RO
PMBO
PMBO
4
5
4, R=H
, R=PMB
6
7
a
d
NH2
N
N
N
NH2
N
NH2
N
RO
O
BnO
N
N
N
N
N
N
HO
OPMB
OBn
BnO
f
N
O
on 10
RO
OH
HO
OH
9
1
1
1, R=H
8, R=PMB
10, R=H
g
e
2, R=Ms
f
h
NH2
NH2
N
NH2
N
N
N
N
N
N
N
OR
N
OBn
N
RO
OR
N
j
on 14
N
h
j
on 17
2
3
O
O
on 19
O
O
O
O
1
5, R=PMB
k
g
1
1
3, R=Bn
4, R=H
18, R=Bn
19, R=H
16, R=H
i
i
17, R=Ms
Scheme 1. Synthetic steps to targets 2 and 3. Reagents and conditions: (a) NaH, PMBBr, TBAI, THF, 95%; (b) LiHMDS, THF, 84%; (c) mCPBA, CH
DMF, 50% for 8, 31% for 9; (e) 1 N HCl/MeOH, 94%; (f) p-TsOHꢀH O, CH(OEt) , acetone, 77% for 11, 84% for 15; (g) MsCl, Et N, CH Cl , 93% for 12, 90% for 17; (h) NaOMe, THF/
MeOH, 89% for 13, 90% for 18; (i) Pd(OH) /C, cyclohexene, EtOH, 87% for 14, 87% for 19; (j) 2 N HCl/MeOH, 90% for 2, 92% for 3; (k) DDQ, CH Cl /H O, 93%.
2 2
Cl , 84%; (d) adenine, DBU,
2
3
3
2
2
2
2
2
2

W. Ye, S.W. Schneller / Bioorg. Med. Chem. 22 (2014) 5315–5319
5317
Table 1
30 min and 4-methoxylbenzyl bromide (0.72 mL, 5.59 mmol) and
tetrabutylammonium iodide (20 mg, 0.05 mmol) were added. After
Antiviral activity of 2 and 3 (in
l
M)
Compound 2
Virus
Compound 3
24 h, the reaction mixture was quenched with saturated NH
solution and extracted with EtOAc. The organic layer was dried
(Na SO ), filtered and the solvent was removed by rotary evapora-
4
Cl
(
host cell line)
HBV
EC50 7.2
EC90 35
CC50 >100
SI50 >14
SI90 >3
Inactive
2
4
(
2.2.15)
tion. The pure product (1.65 g, 95%) was isolated using column
chromatography (2:1, hexanes/EtOAc) as a clear liquid: 1H NMR
(
3
400 MHz, CDCl ) d ppm 7.30–7.24 (m, 5H), 7.20 (d, J = 8.8 Hz,
2
H), 6.81 (d, J = 8.8 Hz, 2H), 4.46 (s, 2H), 4.38 (d, J = 2.7 Hz, 2H),
Vaccinia
EC50 10.08
EC90 >300
CC50 >300
SI50 >30
Inactive
3.86 (d, J = 7.3 Hz, 1H), 3.75 (s, 3H), 3.50 (m, 1H), 3.43 (d,
(
HFF)
J = 2.6 Hz, 1H), 3.37 (m, 2H), 2.57 (t, J = 5.9 Hz, 1H), 2.13 (m, 1H),
13
2
1
5
3
.03 (m, 1H); C NMR (100 MHz, CDCl ) d ppm 159.0, 138.0,
30.4, 129.3, 128.4, 127.6, 113.8, 80.5, 73.1, 70.4, 69.2, 60.3, 59.6,
7.9, 55.2, 47.4, 37.8. HRMS calcd for C21H O Na [M+Na] :
24 4
SI90
1
+
HCMV
EC50 0.11
EC90 >12
CC50 49.33
SI50 448
SI90 <4
EC50 3.70
EC90 6.86
CC50 >300
SI50 >81
363.1572; found 363.1564.
(
HFF)
4
.3. (1R,4S,5S)-5-((Benzyloxy)methyl)-4-((4-methoxybenzyl)-
oxy)cyclopent-2-enol (6)
SI90 >44
NOV
EC50 0.784
EC90 8.884
CC50 >100
SI50 >128
SI90 >11
EC50 11
EC90 89
CC50 >300
SI50 >9
To a solution of 5 (450 mg, 1.32 mmol) in THF (40 mL), lithium
hexamethyldisilazide (7 mL, 1.0 M in THF, 7 mmol) was added
dropwise at room temperature. The reaction mixture was heated
at 60 °C for 3 h. The resulting solution was cooled to room
(
HG23)
SI90 >1
temperature, quenched with saturated NH
extracted with EtOAc. The organic phases were combined, washed
with brine, dried (Na SO ) and concentrated under reduced
4
Cl solution and
Dengue
EC50 1.1, 1.5
CC50 25.3, 23.8
SI50 17, 21
EC50 6.1, 5.7
CC50 87, 122
SI50 15, 21
(
Vero 76)
2
4
pressure. The crude residue was purified by column chromatogra-
Measles
EC50 <0.38
EC90 ND
CC50 >1.33
SI50 >3.5
EC50 0.72, 0.72
EC90 ND
CC50 12.2, 15.2
SI50 17, 21
phy (1:1, EtOAc/hexanes) to give 6 (380 mg, 84%) as a yellow
a
a
1
(
Vero 76)
liquid: H NMR (600 MHz, CDCl
3
) d ppm 7.33–7.29 (m, 5H), 7.22
(
(
d, J = 8.4 Hz, 2H), 6.83 (d, J = 8.4 Hz, 2H), 5.91 (s, 2H), 4.53–4.46
m, 4H), 4.42 (d, J = 4.3 Hz, 1H), 4.24 (d, J = 4.6 Hz, 1H), 3.76
13
Ebola (Zaire)
EC50 0.38
CC50 1.3
SI50 3.5
EC50 0.76
CC50 11.4
SI50 15
(s, 3H), 3.58 (m, 2H), 2.77 (br, 1H), 2.26 (m, 1H); C NMR
(150 MHz, CDCl ) d ppm 159.2, 138.3, 136.2, 133.2, 130.6, 129.4,
28.4, 127.70, 127.68, 113.8, 83.6, 77.8, 73.2, 70.1, 70.0, 55.8,
(Vero)
3
1
+
a
24 4
55.3. HRMS calcd for C21H O Na [M+Na] : 363.1572; found
ND, not determined.
3
63.1577.
effort has been devoted to the antiviral properties of L-like carbo-
cyclic nucleosides.
4
.4. (1S,2S,3S,4R,5R)-3-((Benzyloxy)methyl)-4-((4-methoxyben-
8
zyl)oxy)-6-oxabicyclo[3.1.0]hexan-2-ol (7)
4
4
. Experimental
To a solution of 6 (220 mg, 0.65 mmol) in CH Cl (20 mL) was
added mCPBA (335 mg, 77%, 1.5 mmol) at 0 °C. This mixture was
stirred overnight and quenched with sodium bisulfite. The reaction
2
2
.1. Materials and methods
mixture was diluted with CH
2 2 3
Cl and washed with NaHCO , brine,
Melting points were recorded on a Meltemp II melting point
apparatus and the values were uncorrected. H and C NMR spec-
tra were recorded on either a Bruker AC 600 spectrometer
600 MHz for proton and 150 MHz for carbon) or a Bruker AV
00 spectrometer (400 MHz for proton and 100 MHz for carbon),
dried (Na SO ) and concentrated under reduced pressure. The
2
4
1
13
crude residue was purified by column chromatography (1:1,
EtOAc/hexanes) to give 7 (380 mg, 84%) as a white solid, mp 72–
1
(
4
73 °C; H NMR (400 MHz, CDCl ) d ppm 7.32–7.24 (m, 7H), 6.85
3
(d, J = 8.3 Hz, 2H), 4.61 (d, J = 11.7 Hz, 1H), 4.48 (dd, J = 11.8,
15.6 Hz, 2H), 4.39 (d, J = 11.9 Hz, 1H), 4.03 (d, J = 7.9 Hz, 1H), 3.76
(s, 3H), 3.65 (dd, J = 2.7, 9.4 Hz, 1H), 3.50 (m, 3H), 2.69 (br, 1H),
referenced to internal tetramethylsilane (TMS) at 0.0 ppm. The
mass spectral data was determined using a Waters Micromass Q-
TOF Premier Mass Spectrometer. The reactions were monitored
by thin-layer chromatography (TLC) using 0.25 mm Whatman
Diamond silica gel 60-F254 precoated plates with visualization by
irradiation with a Mineralight UVGL-25 lamp. Column chromatog-
raphy was performed on Whatman silica, 230–400 mesh, and 60 Å
using elution with the indicated solvent system. Yields refer to
1
3
1.80 (m, 1H); C NMR (100 MHz, CDCl ) d ppm 159.3, 138.2,
3
130.2, 129.4, 128.3 (2C), 127.6, 113.8, 77.0, 73.1, 71.8, 71.1, 66.9,
56.7, 55.2, 54.5, 44.9. HRMS calcd for C21H24O Na [M+Na] :
379.1521; found 379.1511.
+
5
4.5. (1S,2R,3S,4S,5R)-2-(6-Amino-9H-purin-9-yl)-4-((benzyloxy)-
methyl)-5-((4-methoxybenzyl)oxy)cyclopentane-1,3-diol (8)
and (1S,2R,3R,4R,5S)-3-(6-Amino-9H-purin-9-yl)-5-((benzyloxy)-
methyl)-4-((4-methoxybenzyl)oxy)cyclopentane-1,2-diol (9)
1
13
chromatographically and spectroscopically ( H and
C NMR)
homogeneous materials.
4
.2. (1S,2R,3S,5R)-2-((Benzyloxy)methyl)-3-((4-methoxybenzyl)-
oxy)-6-oxabicyclo[3.1.0]-hexane (5)
Adenine (1.23 g, 9.1 mmol) and 7 (1.30 g, 3.65 mmol) were sus-
2
pended in DMF (20 mL) under N for 15 min at room temperature.
To a solution of 44 (1.12 g, 5.08 mmol) in THF (20 mL) was
treated with NaH (60%, 224 mg, 6.10 mmol) at 0 °C. The reaction
mixture was allowed to stir at room temperature for additional
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU, 1.64 mL, 10.9 mmol)
was added and the reaction mixture was heated at 90 °C for 8 h.
After the reaction was cooled to room temperature, the resulting

5
318
W. Ye, S.W. Schneller / Bioorg. Med. Chem. 22 (2014) 5315–5319
solid was removed by filtration over Celite and then rinsed with
CH Cl . The filtrate was evaporated under reduced pressure and
the residue purified by column chromatography to afford 8
reaction mixture was quenched with saturated NaHCO
and extracted with CH Cl . The organic phases were dried (Na2-
SO ). The residue, after filtration and evaporation, was loaded onto
silica gel. Column chromatography (30:1, EtOAc/MeOH) afforded
3
solution
2
2
2
2
4
(
(
900 mg, 50%) and 9 (550 mg, 31%) as white solid and white foam
20:1, CH Cl /MeOH and 10:1, CH Cl /MeOH, respectively):
Compound 8: mp 163–165 °C: H NMR (400 MHz, DMSO) d
ppm 8.13 (s, 1H), 8.10 (s, 1H), 7.36–7.27 (m, 7H), 7.16 (s, 2H),
1
2
2
2
2
3
12 (100 mg, 93%) as a white foam: H NMR (400 MHz, CDCl ) d
1
ppm 8.32 (s, 1H), 7.84 (s, 1H), 7.41–7.34 (m, 5H), 6.28 (s, 2H),
5.78 (t, J = 9.2 Hz, 1H), 5.15 (m, 1H), 4.82 (ddd, J = 9.3, 8.0, 5.6 Hz,
2H), 4.61 (s, 2H), 3.83 (dd, J = 9.7, 4.0 Hz, 1H), 3.76 (dd, J = 9.7,
6
.87 (d, J = 8.7 Hz, 2H), 5.83 (d, J = 5.4 Hz, 1H), 5.06 (d, J = 7.1 Hz,
1
(
(
H), 4.61–4.50 (m, 6H), 4.27 (m, 1H), 3.76–3.73 (m, 4H), 3.58
4.0 Hz, 1H), 2.63–2.55 (m, 1H), 2.53 (s, 3H), 1.59 (s, 3H), 1.30 (s,
3H); C NMR (100 MHz, CDCl ) d ppm 155.8, 152.3, 149.9, 140.5,
3
137.8, 128.5, 127.9, 127.8, 120.3, 113.5, 81.2, 79.2, 77.5, 73.5,
dd, J = 4.2, 9.4 Hz, 1H), 3.51 (m, 1H), 2.10 (m, 1H); 13C NMR
100 MHz, DMSO) d ppm 158.7, 156.1, 152.0, 149.9, 141.2, 138.6,
13
1
7
30.8, 129.3, 128.3, 127.5, 127.4, 119.6, 113.6, 77.8, 72.2, 71.1,
0.5, 70.3, 69.2, 67.6, 55.1, 50.7. HRMS calcd for C26
66.9, 66.7, 49.1, 37.5, 27.5, 25.1. HRMS calcd for C22
[M+H] : 490.1760; found 490.1782.
H
28
N
5
O
6
S
+
H
30
N
5
O
5
+
[
M+H] : 492.2247; found 492.2241.
Compound 9: 1H NMR (600 MHz, MeOD) d ppm 8.07 (s, 1H),
.96 (s, 1H), 7.42–7.30 (m, 5H), 6.69 (d, J = 8.2 Hz, 2H), 6.47 (d,
4
.9. 9-((3aS,6R,6aR)-6-((Benzyloxy)methyl)-2,2-dimethyl-6,6a-
dihydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)-9H-purin-6-amine
13)
7
J = 8.5 Hz, 2H), 4.72 (t, J = 9.0 Hz, 1H), 4.58 (m, 3H), 4.41 (t,
J = 7.1 Hz, 1H), 4.28 (d, J = 12.1 Hz, 1H), 4.18 (d, J = 12.1 Hz, 1H),
4
(
.04 (m, 1H), 3.63 (m, 5H), 2.31 (m, 1H); 13C NMR (150 MHz,
To a solution of 12 (70 mg, 0.14 mmol) in THF (5 mL) was
MeOD) d ppm 160.6, 157.1, 153.2, 150.9, 142.9, 139.9, 131.0,
added sodium methoxide (25 mg, 0.46 mmol) in MeOH (0.5 mL)
and the reaction mixture was refluxed for 4 h. The residue, after
evaporation under reduced pressure, was loaded onto silica gel,
which was then added to a column for chromatographic purifica-
1
7
4
30.5, 129.5, 129.1, 128.9, 120.9, 114.3, 78.6, 74.4, 73.4, 72.9,
+
2.6, 70.8, 68.7, 55.7, 52.7. HRMS calcd for C26
92.2247; found 492.2243.
30 5 5
H N O [M+H] :
tion (50:1, EtOAc/MeOH) to afford 13 (50 mg, 89%) as white solid,
1
4
.6. (1R,2S,3R,4S,5S)-3-(6-Amino-9H-purin-9-yl)-5-((benzyloxy)-
mp 187–188 °C: H NMR (400 MHz, CDCl
3
) d ppm 8.40 (s, 1H),
methyl)-cyclopentane-1,2,4-triol (10)
8.26 (s, 1H), 7.33–7.28 (m, 5H), 6.70 (d, J = 2.7 Hz, 1H), 6.16 (s,
H), 5.53 (dd, J = 5.8, 1.1 Hz, 1H), 4.73 (d, J = 5.8 Hz, 1H), 4.54
(s, 2H), 3.69 (dd, J = 9.4, 4.6 Hz, 1H), 3.48 (dd, J = 9.4, 6.1 Hz,
2
To a solution of 8 (100 mg, 0.20 mmol) in MeOH (2 mL) was
added 1 N HCl (2 mL) and the solution was stirred at 50 °C for
13
1H), 3.25 (m, 1H), 1.42 (s, 3H), 1.41 (s, 3H);
(100 MHz, CDCl ) d ppm 155.5, 153.4,150.1, 138.7, 138.6, 135.3,
128.4, 127.7, 127.6, 119.8, 119.2, 111.6, 82.9, 80.6, 73.2, 70.6,
C NMR
4
h. The solvent was removed under reduced pressure to give 10
3
(
70 mg, 94%) as white solid that was used directly in this form in
1
+
the next step. H NMR (600 MHz, MeOD) d ppm 8.59 (s, 1H), 8.44
s, 1H), 7.42–7.29 (m, 5H), 4.89 (m, 1H), 4.63 (m, 3H), 4.53 (m,
50.1, 27.4, 25.9. HRMS calcd for C21
24 5 3
H N O [M+H] : 394.1879;
(
found 394.1873.
1
C
H), 4.17 (m, 1H), 3.76 (m, 2H), 2.23 (m, 1H). HRMS calcd for
+
18
H
22
N
5
O
3
[M+H] : 372.1672; found 372.1666.
4
4
.10. ((3aR,4R,6aS)-6-(6-Amino-9H-purin-9-yl)-2,2-dimethyl-
,6a-dihydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)methanol (14)
4
.7. (3aS,4R,5S,6S,6aR)-4-(6-Amino-9H-purin-9-yl)-6-((benzylo-
xy)methyl)-2,2-dimethyltetrahydro-3aH-
cyclopenta[d][1,3]dioxol-5-ol (11)
2
A solution of 13 (300 mg, 0.76 mmol) and 20% Pd(OH) /C
(375 mg) in cyclohexene (5 mL) and EtOH (8 mL) was heated at
reflux for 12 h and then filtered through Celite. The filtrate was
evaporated to dryness under reduced pressure and purified by
column chromatography (9:1, EtOAc/MeOH) to give 14 (200 mg,
To a solution of 10 (70 mg, 0.19 mmol) in acetone (5 mL) was
added triethyl orthoformate (0.25 mL, 1.50 mmol) and p-TsOHꢀH
2
O
1
(
65 mg, 0.33 mmol). The reaction mixture was stirred at room tem-
87%) as a white solid. H NMR (400 MHz, MeOD) d ppm 8.34 (s,
perature for 4 h, quenched with saturated NaHCO
3
solution
1H), 8.26 (s, 1H), 6.60 (d, J = 2.7 Hz, 1H), 5.65 (dd, J = 1.2, 5.8 Hz,
1H), 4.75 (d, J = 5.6 Hz, 1H), 4.62 (br, 1H, OH), 3.77 (dd, J = 4.9,
11.1 Hz, 1H), 3.63 (dd, J = 5.8, 11.1 Hz, 1H), 3.09 (m, 1H), 1.42
(
10 mL) and extracted with EtOAc. The combined organic phases
were dried (Na SO ), filtered and evaporated under reduced pres-
2
4
1
3
sure. The residue was purified via column chromatography (20:1,
EtOAc/MeOH) to give 11 (60 mg, 77%) as a white foam: H NMR
(s, 3H), 1.38 (s, 3H); C NMR (100 MHz, MeOD) d ppm 157.6,
1
154.5, 151.0, 140.4, 137.1, 121.3, 120.5, 112.6, 84.1, 81.9, 64.0,
+
(
5
(
1
1
7
C
400 MHz, CDCl
H), 5.80 (s, 2H), 4.80 (t, J = 7.02 Hz, 1H), 4.70–4.63 (m, 2H), 4.60
s, 2H), 4.42 (dd, J = 6.8, 9.6 Hz, 1H), 3.78 (m, 2H), 2.50 (m, 1H),
3
) d ppm 8.26 (s, 1H), 8.00 (s, 1H), 7.36–7.24 (m,
53.8, 27.8, 26.0. HRMS calcd for C14
found 304.1411.
18
H N
5
O
3
[M+H] : 304.1410;
.61 (s, 3H), 1.38 (s, 3H); 13C NMR (100 MHz, CDCl
) d ppm
3
4
.11. (1R,2S,5R)-3-(6-Amino-9H-purin-9-yl)-5-(hydroxymethyl)
55.6, 152.0, 149.4, 140.6, 137.9, 128.3, 127.6, 119.3, 113.3, 79.6,
cyclopent-3-ene-1,2-diol (2)
7.9, 73.3, 73.2, 69.3, 67.9, 50.1, 27.1, 24.8. HRMS calcd for
+
21
H
26
N
5
O
4
[M+H] : 412.1985; found 412.1975.
To a solution of 14 (190 mg, 0.63 mmol) in MeOH (2 mL) was
added 2 N HCl (5 mL) and the reaction mixture was stirred at room
temperature for 4 h. The solution was then neutralized with IRA-67
4
.8. (3aS,4S,5S,6R,6aR)-4-(6-Amino-9H-purin-9-yl)-6-((benzylo-
xy)methyl)-2,2-dimethyltetrahydro-3aH-cyclopenta[d][1,3]dio-
xol-5-yl methanesulfonate (12)
resin and the filtrate was evaporated to give 2 (150 mg, 90%) as a
1
pale white solid, mp 195–196 °C: H NMR (600 MHz, D
2
O) d ppm
8
.00 (s, 1H), 7.83 (s, 1H), 6.17 (d, J = 2.1 Hz, 1H), 4.86 (dd, J = 1.3,
To a solution of 11 (90 mg, 0.22 mmol) in anhydrous CH
20 mL) were added, dropwise, triethylamine (0.06 mL,
.44 mmol), methanesulfonyl chloride (0.02 mL, 0.26 mmol) and
-dimethylaminopyridine (5 mg, 0.04 mmol) at 0 °C under N
The mixture was stirred at room temperature overnight. The
2 2
Cl
5.9 Hz, 1H), 4.09 (t, J = 5.8 Hz, 1H), 3.76 (dd, J = 4.6, 11.5 Hz, 1H),
1
3
(
0
4
3.63 (dd, J = 5.5, 11.5 Hz, 1H), 2.87 (m, 1H); C NMR (150 MHz,
O) d ppm 154.9, 152.3, 147.8, 139.5, 134.5, 123.6, 117.8, 73.0,
D
2
+
2
.
14 5 3
71.0, 61.0, 50.8. HRMS calcd for C11H N O [M+H] : 264.1097;
found 264.1093. [
2
2.9
a
]
D
2
38.5° (c 0.18, H O).

W. Ye, S.W. Schneller / Bioorg. Med. Chem. 22 (2014) 5315–5319
5319
4
.12. 9-((3aR,4S,5R,6R,6aS)-6-((Benzyloxy)methyl)-5-((4-metho-
4.17. (1S,2R,5S)-3-(6-Amino-9H-purin-9-yl)-5-(hydroxymethyl)-
xybenzyl)oxy)-2,2-dimethyltetrahydro-3aH-
cyclopent-3-ene-1,2-diol (3)
cyclopenta[d][1,3]dioxol-4-yl)-9H-purin-6-amine (15)
Following the procedure for the preparation of 2, compound 3
was obtained from 19 (70 mg, 0.23 mmol) as a white solid
(56 mg, 92%), mp 191–193 °C. The H and C NMR spectroscopic
To a solution of 9 (90 mg, 0.18 mmol) in acetone (5 mL) was
1
13
added triethyl orthoformate (0.18 mL, 1.08 mmol) and p-TsOHꢀH
2
O
(
41 mg, 0.21 mmol). The reaction mixture was stirred at room tem-
measurements were consistent with that reported above for 2.
+
perature for 4 h, quenched with saturated NaHCO
3
solution
HRMS calcd for C11
H
14
N
2
O).
5
O
3
[M+H] : 264.1097; found 264.1090.
2
3.0
(
10 mL) and extracted with EtOAc. The combined organic phases
[a
]
D
ꢁ32.8° (c 0.04, H
were dried (Na SO ), filtered and evaporated under reduced pres-
2
4
sure. The resulting residue was purified via column chromatogra-
4.18. Antiviral assays
phy (20:1, EtOAc/MeOH) to give 15 (80 mg, 84%) as a white
1
foam: H NMR (400 MHz, CDCl
3
) d ppm 8.26 (s, 1H), 7.71 (s, 1H),
See Ref. 5 for the necessary details.
4.19. S-Adenosylhomocysteine hydrolase (SAHase) assay
See Ref. 9 for the necessary details.
Acknowledgments
7
6
4
9
3
1
1
2
5
.40–7.31 (m, 5H), 6.71 (d, J = 8.7 Hz, 2H), 6.52 (d, J = 8.7 Hz, 2H),
.03 (s, 2H), 5.10 (m, 1H), 4.76–4.70 (m, 3H), 4.69–4.63 (m, 2H),
.15 (d, J = 11.6 Hz, 1H), 4.00 (d, J = 11.6 Hz, 1H), 3.76 (dd, J = 3.6,
.6 Hz, 1H), 3.70–3.64 (m, 4H), 2.37 (m, 1H), 1.54 (s, 3H), 1.28 (s,
H); 1 C NMR (100 MHz, CDCl
3
) d ppm 159.1, 155.5, 152.4, 149.6,
3
40.9, 138.1, 129.5, 129.1, 128.4, 127.72. 127.69, 120.5, 113.3,
12.9, 78.63, 78.60, 77.4, 73.2, 72.8, 68.5, 67.6, 55.1, 50.1, 27.5,
5.0. HRMS calcd for C29
32.2568.
+
H
34
N
5
O
5
[M+H] : 532.2560; found
This research has been partially supported by funds from the
Department of Health and Human Services (Al 56540), which is
appreciated. We are grateful to the Molette Fund and Auburn
University for support and to Gloria Kozamin of Microbiotix, Inc.
Worcester, MA for the SAHase assays. We are also indebted to
the following individuals for providing the antiviral data following
4
.13. (3aR,4S,5R,6R,6aS)-4-(6-Amino-9H-purin-9-yl)-6-((benzyl-
oxy)methyl)-2,2-dimethyltetrahydro-3aH-cyclopenta[d][1,3]di-
oxol-5-ol (16)
5
their standard protocols: Dr. Donald Smee, Utah State University;
To a solution of 15 (70 mg, 0.13 mmol) in CH
mL) was added 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
60 mg, 0.26 mmol) at 0 °C. After 5 h, the reaction mixture was
poured into saturated NaHCO , extracted with CH Cl and the
organic layers combined, dried (Na SO ), filtered and evaporated
2
Cl
2
/H
2
O (20:1,
Dr. Brent Korba, Georgetown University; Dr. Mark Prichard,
University of Alabama at Birmingham; and, other laboratories that
are part of the non-clinical evaluation program funded by the
National Institute of Allergy and Infectious Diseases.
5
(
3
2
2
2
4
under reduced pressure. The residue was purified via column chro-
References and notes
matography (20:1, EtOAc/MeOH) to give 16 (50 mg, 93%) as a
+
1. Kinoshita, K.; Yaginuma, S.; Hayashi, M.; Nakatsu, K. Nucleosides Nucleotides
white solid, mp 172–174 °C. HRMS calcd for C21
26
H N
5
O
4
[M+H] :
1985, 4, 661.
4
12.1985; found 412.1966.
2.
Tosh, D. K.; Kim, H. O.; Pal, S.; Lee, J. A.; Jeong, L. S. In Herdewijn, Ed.; Modified
Nucleosides; Wiley-VCH: Weinheim, 2008; pp 525–566.
3
4
.
.
Yin, X.-Q.; Schneller, S. W. Tetrahedron Lett. 2005, 46, 1927.
4
.14. (3aR,4R,5R,6S,6aS)-4-(6-Amino-9H-purin-9-yl)-6-((benzyl-
(a) Ludek, O. R.; Meier, C. Synthesis 2003, 13, 2101; (b) Biggadike, K.; Borthwick,
A. D.; Evans, D.; Exall, A. M.; Kirk, B. E.; Roberts, S. M.; Stephenson, L.; Youds, P. J.
Chem. Soc., Perkin Trans. 1 1988, 549.
oxy)methyl)-2,2-dimethyltetrahydro-3aH-cyclopenta[d][1,3]di-
oxol-5-yl methanesulfonate (17)
5
.
Details for the assay methods can be found in (a) Das, S. R.; Schneller, S. W.;
Balzarini, J.; De Clercq, E. Antiviral Chem. Chemother. 2001, 12, 119; (b) Siddiqi, S.
M.; Chen, X.; Schneller, S. W.; Ikeda, S.; Snoeck, R.; Andrei, G.; Balzarini, J.; De
Clercq, E. J. Med. Chem. 1994, 37, 551; (c) Yang, M.; Schneller, S. W.; Korba, B. J.
Med. Chem. 2005, 48, 5043; (d) Roy, A.; Schneller, S. W.; Keith, K. A.; Hartlikne, C.
B.; Kern, E. Bioorg. Med. Chem. 2005, 13, 4443; (e) Smee, D. F.; Morris, J. L.;
Barnard, D. L.; Van Aerschot, A. Antiviral Res. 1992, 18, 151; (f) Ojwang, J. O.; Ali,
S.; Smee, D. F.; Morrey, J. D.; Shimasaki, C. D.; Sidwell, R. W. Antiviral Res. 2005,
Following the procedure for the preparation of 12, compound
1
7 was obtained from 16 (220 mg, 0.54 mmol) as a white foam
1
13
(
240 mg, 90%). The H and C NMR spectroscopic measurements
were consistent with that reported above for 12. HRMS calcd for
C
+
22
H
28
N
5
O
6
S [M+H] : 490.1760; found 490.1782.
6
8, 49; (g) Julander, J. G.; Bowen, R. A.; Rao, J. R.; Day, C.; Shafer, K.; Smee, D. F.;
Morrey, J. D.; Chu, C. K. Antiviral Res. 2008, 80, 309; (h) Gowen, B. B.; Wong, M.
H.; Jung, K. H.; Smee, D. F.; Morrey, J. D.; Furuta, Y. Antiviral Res. 2010, 86, 121; (i)
Roy, A.; Serbessa, T.; Schneller, S. W. Bioorg. Med. Chem. 2006, 14, 4980; (j)
http://www.usu.edu/iar/htm/in-vitro-antiviral-testing (May 22, 2014).; (k)
http://www.southernresearch.org/life-sciences/infectious-diseases/virology
4
.15. 9-((3aR,6S,6aS)-6-((Benzyloxy)methyl)-2,2-dimethyl-6,6a-
dihydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)-9H-purin-6-amine
18)
(
(
May 22, 2014).
Following the procedure for the preparation of 13, compound
8 was obtained from 17 (210 mg, 0.42 mmol) as a white solid
6
.
There was no activity by either of the target compounds towards (host cell) Rift
Valley Fever (Vero 76), Tacaribe (Vero 76), yellow fever (Vero), Japanese equine
encephalitis (Vero 76), Pichinde (Vero), polio-3 (Vero 76), Punta Toro (Vero 76),
Venezuelan equine encephalitis (Vero 76), hepatitis C virus (Huh), rabies (BHK
1
(
1
13
150 mg, 90%). The H and C NMR spectroscopic measurements
were consistent with that reported above for 13. HRMS calcd for
2
1), Nipah (Vero). In these instances, 2 and 3 showed toxicity to the host cells.
+
C
21
H
24
N
5
O
3
[M+H] : 394.1879; found 394.1848.
7. For leading references on the synthesis of L-like carbocyclic nucleosides see (a)
Song, G. Y.; Paul, V.; Choo, H.; Morrey, J.; Sidwell, R. W.; Schinazi, R. F.; Chu, C. K.
J. Med Chem. 2001, 44, 3985; (b) Marce, P.; Diaz, Y.; Matheu, M. I.; Castillon, S.
Org. Lett. 2008, 10, 4735; (c) Mahler, M.; Reichardt, B.; Hartjen, P.; van Lunzen, J.;
Meier, C. Chem. Eur. J. 2012, 18, 11046.
4
4
.16. ((3aS,4S,6aR)-6-(6-Amino-9H-purin-9-yl)-2,2-dimethyl-
,6a-dihydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)methanol (19)
8.
(a) Schneller, S. W.; Seley, K. L.; Hegde, V. R.; Rajappan, K. In Recent Advances in
Nucleosides; Chu, C. K., Ed.; Elsevier: Amsterdam, 2002; p 291; (b) Wang, J.; Jin,
Y.; Rapp, K.; Bennett, M.; Schinazi, R.; Chu, C. K. J. Med. Chem. 2005, 48, 3736.
The method used for the SAHase assay (rabbit erythrocytes, Sigma) is available
from Microbiotix, Inc, One Innovation Drive, Worcester, MA 01605 (http://
www.microbiotix.com, July 17, 2014).
Following the procedure for the preparation of 14, compound
9 was obtained from 18 (120 mg, 0.30 mmol) as a white solid
1
(
9.
1
13
80 mg, 87%). The H and C NMR spectroscopic measurements
were consistent with that reported above for 14. HRMS calcd for
+
14 18 5 3
C H N O [M+H] : 304.1410; found 304.1401.