Methylene-2-ethynylcyclopropanes: synthesis and biological activity of (Z)- and (E)-9-{[2-ethynyl-2-(hydroxymethyl)cyclopropylidene]methyl}adenine and -guanine

Article abstract of DOI:10.1016/j.tet.2007.06.109

Synthesis of methylene-2-ethynylcyclopropane analogues of nucleosides 12a, 12b, 13a, and 13b is described. Ethyl methylenecyclopropane carboxylate 14 was hydroxymethylated to give alcohol 15, which was reduced to diol 16. Selective protection with tert-bu

Full text of DOI:10.1016/j.tet.2007.06.109

Tetrahedron 63 (2007) 9406–9412
Methylene-2-ethynylcyclopropanes: synthesis and
biological activity of (Z)- and (E)-9-{[2-ethynyl-2-
(hydroxymethyl)cyclopropylidene]methyl}adenine and -guanine
Shaoman Zhou,a Mark N. Prichardb and Jiri Zemlickaa,
*
aDevelopmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine,
Detroit, MI 48201-1379, USA
bDepartment of Pediatrics, The University of Alabama School of Medicine, Birmingham, AL 35233, USA
Received 27 April 2007; revised 5 June 2007; accepted 28 June 2007
Available online 10 July 2007
Abstract—Synthesis of methylene-2-ethynylcyclopropane analogues of nucleosides 12a, 12b, 13a, and 13b is described. Ethyl methylene-
cyclopropane carboxylate 14 was hydroxymethylated to give alcohol 15, which was reduced to diol 16. Selective protection with tert-butyl-
dimethylsilyl group gave derivative 17, which was oxidized to aldehyde 18. Wittig reaction with CBr4 gave dibromoalkene 19. Elimination of
both bromine atoms afforded methylene-2-ethynylcyclopropane 20. Bromoselenenylation using N-bromosuccinimide and diphenyldiselenide
gave intermediate 21. Alkylation of adenine and 2-amino-6-chloropurine with 21 provided the Z,E-isomeric mixtures 22a and 22c. Oxidation
afforded selenoxides 23a and 23c. Mild thermolysis furnished methylenecyclopropanes Z-24a, E-24a, and 24c. Deprotection and separation
of Z,E-isomers gave adenine analogues 12a and 13a, and 2-amino-6-chloropurine intermediates 12c and 13c. Hydrolytic dechlorination of
12c and 13c afforded guanine analogues 12b and 13b. Adenine Z-isomer 12a inhibits replication of Epstein-Barr virus through its cytotoxicity.
The E-isomer 13a is a substrate for adenosine deaminase.
Ó 2007 Published by Elsevier Ltd.
1. Introduction
isomers 7 are effective only exceptionally.12–14 Introduction
of substituents next to the hydroxymethyl group led to
several effective antivirals. For example, the guanine bis-
hydroxymethyl analogue cyclopropavir (8b) is a potent
anti-cytomegalovirus agent15,16 that is currently undergoing
preclinical studies. Again, the E-isomers 9 are inactive or
much less potent antivirals. By contrast, Z- and E-fluoro ana-
logues 10 and 11 yielded several agents effective against
HIV-1, human cytomegalovirus (HCMV), Epstein-Barr virus
(EBV) or varicella zoster virus (VZV).17 The position of the
ethynyl group in methylenecyclopropane analogues 12 and
13 approximates that of nucleosides 2 and 3. It was then of
interest to synthesize ethynyl methylenecyclopropanes 12a,
12b, 13a, and 13b and investigate their biological properties.
40-Substituted 20-deoxynucleosides have received much
attention as anti-HIVagents effective against various labora-
tory and clinical strains of the virus. Thus 40-azido analogues
1 derived from all DNA bases exhibited a submicromolar po-
tency against HIV-1 in vitro.1 More recently, the 40-ethynyl-
20-deoxynucleosides 2 were found to inhibit HIV-1 with
EC50s in a similar concentration range.2–4 It has been sug-
gested5 that the presence of the 30-OH group is indispensable
for a high anti-HIV potency of cytosine ethynyl analogue 2d
(Chart 1). Thus the 30-deoxy derivative of 2d was inactive but
its triphosphate was a potent inhibitor of HIV-1 reverse tran-
scriptase. However, a high potency6–9 of ethynyl analogues
of stavudine 3a and 3b lacking the 30-OH has indicated that
the presence of the latter function is not a prerequisite for
anti-HIV activity of 40-substituted nucleosides. By contrast,
30-fluoro-40-ethynyl unsaturated nucleosides 4a, 4d, and 5a
exhibited only borderline antiviral effects.10,11 The exact
role of the ethynyl group for a high anti-HIV potency of
analogues 2, 3a, and 3b has not been elucidated.
2. Results and discussion
The synthesis of analogues 12a, 12b, 13a, and 13b started
with hydroxymethylation of the methylenecyclopropane
carboxylate18 14 via the corresponding carbanion using
formaldehyde as recently described for diethyl ester of
Feist’s acid19 (Scheme 1). The hydroxymethyl derivative
15 was obtained in 66% yield. When gaseous formaldehyde
was replaced by paraformaldehyde the yield of 15 was
50–55%. Reduction with LiAlH4 in THF afforded
The Z-methylenecyclopropane analogues of purine nucleo-
sides 6 are established antiviral agents whereas the E-
* Corresponding author. E-mail: zemlicka@karmanos.org
0040–4020/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.tet.2007.06.109

S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
HO
B
9407
B
HO
Thy
B
OH
HO
R
O
X
O
O
F
F
1
4
3
5
OH
3a: X = O
3b: X = S
1: R = -N=N=N
CH
2: R = -C
HO
B
B
HO
F
HO
OH
B
B
B
9
OH
7
HO
HO
8
10
6
O
NH2
N
B
N
N
NH
N
HO
HO
N
F
N
NH2
O
N
11
HO
12a
12b
NH2
Cl
N
N
N
N
NH
N
N
N
HO
N
N
N
N
NH2
NH2
13b
13a
12c
HO
HO
Cl
N
N
In formulas 1, 2 and 4 through 11 series a: B = Ade,
N
series b: B = Gua, series c: B = 2-amino-6-chloropurine,
series d: B = Cyt
N
NH2
13c
HO
Chart 1.
methylenecyclopropane diol 16 (83%). It should be noted
that sequence methylenecyclopropane carboxylate 14/
alcohol 15/diol 16 is an alternate synthesis of the key
intermediate 16 in the synthesis of cyclopropavir15,20 (8b).
Selective protection of a single hydroxymethyl group was
achieved using 1 M equivalent of TBDMSCl in pyridine
and DMAP as a catalyst to give intermediate 17 in 84%
yield. Oxidation21 with pyridinium chlorochromate (PCC)
CO2Et
CO2Et
HO
TBDMSO
2
a
c
b
1
d
OH
OH
OH
14
15
16
3
17
TBDMSO
TBDMSO
TBDMSO
e
g
f
O
18
19
20
Br
Br
5'
TBDMSO
TBDMSO
TBDMSO
Br
SePh
B
B
h
j
2'
i
4'
3'
1'
SePh
SePh
O
22
21
23
22a, 23a: B = Ade
22c, 23c: B = ACP
TBDMSO
B
k
l
12c, 13c
12b, 13b
12a, 13a or 12c, 13c
24
Z-24a: B = Ade, Z-isomer
E-24a: B = Ade, E-isomer
24c: B = ACP, Z,E-isomers
ACP = 2-amino-6-chloropurine
g. NBS, Ph2Se2, CH2Cl2.
a. LiCl, LDA, CH2O (g), THF, -78 °C, Ar.
h. B-H, K2CO3, DMF.
b. LiAlH4, THF,
.
i. 30% H2O2, CH2Cl2.
j. Toluene, 80 °C.
c. TBDMS, DMAP, pyridine, CH2Cl2.
d. PCC, CH2Cl2.
e. CBr4, Ph3P, CH2Cl2.
f. BuLi, -78 °C, THF, Ar.
k. Bu4NF, THF.
l. 1. 80% HCO2H, Δ. 2. NH3, MeOH, 0 °C.
Scheme 1.

9408
S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
Table 2. The NOE enhancements of relevant 1H NMR signals of methylene-
2-ethynylcyclopropanes 12a and 13a
in CH2Cl2 gave aldehyde 18 (84%). The aldehyde/ethynyl
transformation followed the Corey protocol22 that was also
used for the synthesis of analogues3 2. Thus the reaction
of aldehyde 18 with CBr4–Ph3P reagent in CH2Cl2 afforded
dibromoethenyl derivative 19 in 95% yield. Conversion to
ethynyl derivative 20 was performed using BuLi in THF
at ꢀ78 ꢁC under argon (89%). To the best of our knowledge,
compound 20 is the first methylenecyclopropane substituted
with ethynyl in the cyclopropane portion. The simplest
member of this series, methylene-2-ethynylcyclopropane,
is an isomer of benzene and it was a subject of a theoretical
study.23 In addition, synthesis of methylenecyclopropane
derivatives is of much current interest.24,25
NH2
6
NH2
6
5
4
5
4
N
N
N
N
N
8
8
HO
2
3'
4'
5'
2
N
1'
4'
N
N
1'
2'
2'
3'
5'
12a
13a
OH
Compound Hiir
d
Hobs
d
NOE (%)
0
12a
H8
H5
H5
H8
8.62
3.83
3.32
8.62
H5
H8
H8
3.32
8.62
8.62
3.92
1.30
0.85
0.53
0.87
3.24
1.88
0
0
C^CH 3.04
C^CH 3.06
OH
H3
H1
H8
H8
8.62
8.62
7.48
The simultaneous presence of a double and triple bond in 20
might have complicated a selective synthesis of vicinal
dibromide for the alkylation–elimination procedure.12,13
Therefore, a method previously employed for the fluorome-
thylenecyclopropanes26 and methylenecyclopropane phos-
phonates27 was adapted as follows. Bromoselenenylation
of 20 using PhSeBr generated in situ from N-bromosuccin-
imide (NBS) and Ph2Se2 in CH2Cl2 gave intermediate 21 in
40% yield. Unlike the previous cases, where carbethoxy26
or phosphonate27 substituents were capable of directing the
addition of PhSeBr to a syn face of the double bond, the
reaction was not stereoselective giving cis–trans isomeric
mixture of 21. Alkylation of adenine with 21 gave compound
22a (83%). Oxidation with 30% H2O2 in CH2Cl2 provided
crude selenoxide 23a, which was subjected to thermolysis
in toluene at 80 ꢁC to afford the Z- and E-isomers of
compounds Z-24a and E-24a, which were separated by chro-
matography in 43% and 36% yields, respectively. Desilyla-
tion of the individual isomers with Bu4NF in THF gave the
target analogues 12a (87%) and 13a (90%). In a similar
fashion, alkylation of 2-amino-6-chloropurine with 21 gave
intermediate 22c in 79% yield. Oxidation led to crude selen-
oxide 23c whose thermolysis furnished the Z,E-isomeric
mixture of silylated methylene-2-ethynylcyclopropane 24c
(81%). Desilylation provided the Z- and E-isomers 12c and
13c, which were separated by chromatography in 41% and
45% yields, respectively. Hydrolytic dechlorination with
80% HCO2H gave the target guanine analogues 12b (86%)
and 13b (81%). Elemental analysis indicated the presence
of 0.7 mol of silica gel (H2SiO3), which must have been
already present in starting compounds 12c and 13c. Attempts
to remove this contaminant by crystallization or chromato-
graphy on Dowex 1 (OH(ꢀ)) column28 failed but a simple ab-
sorption on Dowex 50 (H(+)) and elution with water followed
by NH4OH provided pure analogues 12b and 13b.
5.46
0
0
0
1.85–1.81 H1
H3
0
7.47
1.85–1.81 2.20
0
0
13a
H8
H3
H3
8.48
2.00
2.00
H3
H8
H1
2.00
8.48
7.63
1.53
5.08
0.48
0
0
As in previous cases12–14 of methylenecyclopropane ana-
logues, the Z-isomers 12 are always less polar, moving faster
on silica gel, than E-isomers 13. Comparison of the 1H and
13C NMR chemical shifts of 12a, 12b, 13a, and 13b gave
patterns comparable with the reference compounds 8a, 8b,
0
9a, and 9b (Table 1). Thus, the H8, OH, and C4 signals of
the Z-isomers 8a, 8b, 12a, and 12b are located downfield
from those of the E-isomers 9a, 9b, 13a, and 13b. An oppo-
0
0
site trend was observed in the H1 and C3 chemical shifts.
These assignments were confirmed by NOE experiments
(Table 2). In the Z-isomer 12a, the NOE enhancements
were observed between the cis-orientated protons of H8
0
and H5 , C^CH, and OH whereas none were seen between
0
the H8 and trans-positioned H3 . By contrast, the NOE inter-
0
actions were noted between the H8 and H3 of the E-isomer
13a. As expected, the enhancements between the cis-config-
0
0
ured H1 and H3 were much stronger in the Z-isomer 12a
than in E-isomer 13a where this relationship is trans.
The antiviralactivityof analogues12a, 13a, 12b, and13bwas
tested against the following viruses: HIV-1, HBV, HSV-1,
HSV-2, HCMV, VZV, and EBV. The adenine Z-analogue
12a had EC50 >3.2 mM against EBV in Akata cell culture
but this effect was poorly separated from cytotoxicity (CC50
13.2 mM). The EC50 of acyclovir used as a control was
4.3 mM. No significant activity was found against other
tested viruses. The adenine E-isomer 13a was deaminated
from 70% after 24 h incubation with adenosine deaminase
(ADA) at room temperature whereas the Z-isomer 12a was
resistant. The reactivity toward ADA-catalyzed deamina-
tion (E-isomer>Z-isomer) is in accord with the previous
results.12,13
Table 1. Chemical shifts (d) of the relevant 1H NMR signals of 2,2-disubsti-
tuted methylenecyclopropanes 8a, 9a, 8b, 9b, 12a, 13a, 12b, and 13b
Compounda
OH
H1
H8
C3
0
0
0
C4
8a
9a
8b
9b
12a
13a
12b
13b
5.07
4.76
4.99
4.76
5.47
5.14
5.42
5.13
7.37
7.48
7.07
7.21
7.47
7.63
7.16
7.35
8.82
8.49
8.41
8.03
8.62
8.48
8.18
8.02
11.7
14.4
11.5
14.3
15.7
18.5
15.6
18.3
31.4
29.7
31.3
29.5
20.0
18.8
19.9
18.6
3. Conclusions
The synthesis of methylene-2-ethynylcyclopropane ana-
logues of purine nucleosides 12a, 12b, 13a, and 13b is
described. A new method of preparation of methylenecyclo-
propane diol 16, a key intermediate in the synthesis of anti-
cytomegalovirus agent cyclopropavir (8b) is also reported.
a
CD3SOCD3 as solvent. For numbering of signals, see Table 2. Values for
8a, 9a, 8b, and 9b were taken from Ref. 15.

S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
9409
The first synthesis of a methylene-2-ethynylcyclopropane
scaffold can be of interest in areas other than nucleoside an-
alogues. The adenine Z-isomer 12a inhibited the replication
of EBV but it was cytotoxic. The E-isomer 13a is a substrate
for adenosine deaminase.
8 mL) was added. The insoluble portion was filtered off and
the filter cake was washed with EtOAc (150 mL). Evapora-
tion of the solvent gave the crude product, which was
chromatographed on a silica gel column in hexanes–Et2O
(10:1–3:1) to give diol 16 (3.34 g, 83%) as a colorless oil,
which was identical (1H NMR) with an authentic sam-
ple.15,20 13C NMR (CDCl3) 13.6 (C3), 28.4 (C2), 67.2
(CH2OH), 104.5 (CH2]), 135.5 (C1).
4. Experimental
4.1. General methods
4.1.3. 2-tert-Butyldimethylsilyloxymethyl-2-hydroxy-
methyl-1-methylenecyclopropane (17). Diol 16 (3.2 g,
28.1 mmol) was dissolved in CH2Cl2 (20 mL). TBDMSCl
(4.2 g, 28 mmol), DMAP (0.5 g, 4.1 mmol), and pyridine
(6.4 mL, 82.7 mmol) were added and the mixture was stirred
for 24 h at room temperature. The volatile components were
evaporated and the residue was chromatographed on a silica
gel column in hexane–Et2O (10:1–6:1) to give product 17
(5.25 g, 82%) as a colorless oil. A sample for analysis was
The UV spectra were measured in ethanol and NMR spectra
were determined at 300 or 400 MHz (1H), 75 or 100 MHz
(13C) in CD3SOCD3 unless otherwise stated. Mass spectra
were determined in electrospray ionization mode (ESI-MS,
methanol–NaCl).
4.1.1. Ethyl 2-hydroxymethyl-1-methylenecyclopropane
2-carboxylate (15). Using gaseous formaldehyde. A stirred
mixture of ethyl methylenecyclopropane carboxylate18 (14,
2.78 g, 22.2 mmol) and LiCl (5.67 g, 0.13 mol, dried at
room temperature and 0.01–0.02 Torr for 48 h and 80–
90 ꢁC/0.2 Torr for 3 h) in THF (90 mL) was kept under Ar
at ꢀ78 ꢁC. After 10 min, LDA in THF (1.8 M, 14.83 mL,
26.7 mmol) was added dropwise during 15 min. The stirring
was continued for 45 min whereupon gaseous formaldehyde
generated from paraformaldehyde (1.32 g, 44 mmol, dried
for 2 days over P2O5 at room temperature and atmospheric
pressure) at 180–200 ꢁC was introduced into the reaction
mixture. The stirring was continued for another 30 min at
ꢀ78 ꢁC. The reaction was quenched with 5% HCl (5%,
50 mL), THF was evaporated in vacuo, and ether (200 mL)
was added. The organic phase was successively washed
with HCl (5%, 3ꢂ30 mL), water (3ꢂ30 mL), and aqueous
sodium hydrogen carbonate (3ꢂ30 mL), and it was dried
with sodium sulfate. Evaporation of the solvent gave the
crude product, which was chromatographed on a silica gel
column in hexanes–Et2O (10:1 to 5:1 to 3:1) to give 2.27 g
(66%) of compound 15 as a colorless oil. 1H NMR
(CDCl3) d 1.25 (t, 3H, J¼7.2 Hz, CH3), 1.57 (dt, 1H,
J¼9.2, 2.4 Hz), 2.05 (d, 1H, J¼8.8 Hz, H3), 2.42 (br s, 1H,
OH), 3.57, 3.85 (AB, 2H, JAB¼12.2 Hz, CH2OH), 4.15
(m, 2H, CH2 of Et), 5.48 (t, 1H, J¼1.6 Hz), 5.52 (t, 1H,
J¼5.6 Hz, CH2]). 13C NMR 14.3 (C3), 17.0 (CH3), 30.0
(C2), 61.3 (CH2 of Et), 65.1 (CH2OH), 104.4 (CH2]),
133.4 (C1), 173.1 (CO). ESI-MS 157.0 (M+H, 10.5), 179.0
(M+Na, 100.0).
1
distilled at 50–55 ꢁC (bath temperature) and 0.15 Torr. H
NMR (CDCl3) d 0.06 (s, 6H, Si(CH3)2), 0.90 (s, 9H, CH3
of t-Bu), 1.14, 1.25 (AB, 2H, JAB¼8.4 Hz, H3), 2.73 (br s,
1H, OH), 3.56 (d, 2H, J¼10.0 Hz), 3.75, 3.79 (2d, 2H,
J¼11.2, 10.8 Hz, CH2OH, CH2OTBDMS), 5.37 (s, 1H),
5.44 (t, 1H, J¼3.2 Hz, CH2]). 13C NMR ꢀ5.24, ꢀ5.21
(Si(CH3)2), 13.9 (C3), 18.4 (C of t-Bu), 26.1 (CH3 of
t-Bu), 28.1 (C2), 67.8, 68.6 (CH2OH, CH2OTBDMS),
104.2 (CH2]), 135.9 (C1). ESI-MS 229 (M+H, 7.4), 251
(M+Na, 100.0). Anal. Calcd for C12H24O2Si: C, 63.10; H,
10.59. Found: C, 62.82; H, 10.81.
4.1.4. 2-tert-Butyldimethylsilyloxymethyl-2-formyl-1-
methylenecyclopropane (18). Compound 17 (5.2 g,
22.8 mmol) was dissolved in CH2Cl2 (40 mL) and PCC
(10.29 g, 27.4 mmol) was added in portions at room tem-
perature with stirring, which was continued for 34 h. The
solids were filtered off, washed with ether (100 mL), and
the filtrate was concentrated. The crude product was chroma-
tographed on a silica gel column in hexanes–Et2O (30:1–
10:1) to give aldehyde 18 (4.31 g, 83.5%) as a colorless oil.
1H NMR (CDCl3) d 0.02 (s, 6H, Si(CH3)2, 0.84 (s, 9H, CH3
of t-Bu), 1.84 (m, 2H, H3), 3.75, 4.05 (AB, 2H, JAB¼13.6 Hz,
CH2O), 5.52 (t, 1H, J¼3.6 Hz), 5.58 (poorly resolved t, 1H,
CH2]), 8.78 (s, 1H, CH]O). 13C NMR ꢀ5.30, ꢀ5.26
(Si(CH3)2), 14.2 (C3), 18.5 (C of t-Bu), 26.0 (CH3 of t-Bu),
39.6 (C2), 60.6 (CH2O), 107.0 (CH2]), 131.7 (C1), 197.3
(CH]O). ESI-MS 227 (M+H, 100.0), 249 (M+Na, 80.1).
4.1.5. 2-tert-Butyldimethylsilyloxymethyl-2-(2,2-dibro-
moethenyl)-1-methylenecyclopropane (19). A mixture of al-
dehyde 18 (4.30 g, 19.0 mmol), CBr4 (12.62 g, 38.0 mmol),
and Ph3P (19.91 g, 76 mmol) in CH2Cl2 (100 mL) was stirred
for 1 h at 0 ꢁC and then 30 min at room temperature. Triethyl-
amine (16 mL, 0.115 mol) was added and the mixture was
poured into hexane (400 mL). The insoluble portion was
filtered off and the filtrate was concentrated. The crude
product was chromatographed on a silica gel column using
hexanes–Et2O (100:0–50:1) to give compound 19 as a color-
Using paraformaldehyde. A stirred mixture of compound 14
(250 mg, 2 mmol), LiCl (510 mg, 12 mmol), and LDA
(2.4 mmol) obtained as described in Method A was kept un-
der N2 at ꢀ78 ꢁC for 45 min. Paraformaldehyde (180 mg,
6 mmol) was added and the stirring was continued for
30 min. The work-up followed the procedure described in
Method A. Chromatography in hexanes–ether (5:1–3:1) af-
forded compound 15 (160 mg, 51%) identical with the product
obtained by Method A.
1
less oil (6.87 g, 94.6%). H NMR (CDCl3) d 0.04, 0.05 (2s,
4.1.2. 2,2-Bis(hydroxymethyl)-1-methylenecyclopropane
(16). LiAlH4 (1.62 g, 42.6 mmol) was added in portions to
a solution of compound 15 (5.5 g, 35.2 mmol) in THF
(55 mL) with stirring and external ice cooling. The mixture
was then refluxed for 4 h, cooled, and aqueous NaOH (10%,
6H, Si(CH3)2), 0.89 (s, 9H, CH3 of t-Bu), 1.41 (m, 2H, H3),
3.56, 3.75 (AB, 2H, JAB¼9.8 Hz, CH2O), 5.45 (s, 1H), 5.65
(t, 1H, J¼2.8 Hz, CH2]), 6.64 (s, 1H, CH]). 13C NMR
ꢀ5.1 (Si(CH3)2), 15.2 (C3), 18.6 (C of t-Bu), 26.1 (CH3 of
t-Bu), 29.5 (C2), 66.8 (CH2O), 93.3 (CBr2]), 105.5

9410
S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
(CH2]), 135.6 (C1), 137.5 (CH]). Compound 19 is not
stable under the conditions of MS.
2H, NH2), 7.20–7.28, 7.47–7.49, 7.67–7.69 (3m, 5H, Ph),
7.84, 8.25, 8.29, 8.33 (4s, 2H, H8, H2). ESI-MS (MeOH)
512, 514 (M+H, 51.8, 100.0).
4.1.6. 2-tert-Butyldimethylsilyloxymethyl-2-ethynyl-1-
methylenecyclopropane (20). BuLi (2.5 M in hexanes,
17.8 mL, 44.5 mmol) was added to a solution of compound
19 (6.8 g, 17.79 mmol) in THF (60 mL) at ꢀ78 ꢁC under Ar
and the mixture was stirred for 30 min at the same tempera-
ture. After addition of water (100 mL), the mixture was
warmed to room temperature whereupon it was extracted
with Et2O (4ꢂ50 mL). The organic phase was dried over
MgSO4 and the solvent was evaporated. The residue was
chromatographed on a silica gel column using pentane to
give compound 20 (3.52 g, 89%) as a colorless oil. 1H
NMR (CDCl3) d 0.06, 0.07 (2s, 6H, Si(CH3)2), 0.89 (s, 9H,
CH3 of t-Bu), 1.52 (dt, 1H, J¼8.8, 2.4 Hz), 1.59 (m, 1H, H3),
1.95 (s, 1H, C^CH), 3.59, 3.72 (AB, 2H, JAB¼10.6 Hz,
CH2O), 5.45 (t, 1H, J¼4.4 Hz), 5.59 (t, 1H, J¼5.6 Hz,
CH2]). 13C NMR ꢀ5.03, ꢀ5.00 (Si(CH3)2), 16.7 (C3), 18.1
(C2), 18.6 (C of t-Bu), 26.1 (CH3 of t-Bu), 66.0 (^CH), 66.8
(CH2O), 85.7 (C^), 104.5 (CH2]), 134.9 (C1). ESI-MS
(MeOH+NaCl+KOAc) 118 (100.0), 245 (M+Na, 48.8), 261
(M+K, 30.4). Anal. Calcd for C13H22OSi$0.15H2SiO3: C,
66.69; H, 9.60. Found: C, 66.80; H, 9.41. A sample of 20
was distilled at room temperature and 0.15 Torr (the receiver
was cooled in dry ice–acetone mixture). Anal. Calcd for
C13H22OSi$0.3H2O: C, 68.54; H, 10.00. Found: C, 68.18;
H, 9.56.
4.1.9. (Z)- and (E)-9-[2-(tert-Butyldimethylsilyloxy-
methyl-2-ethynylcyclopropylidene)methyl]adenine (Z-
24a) and (E-24a). Aqueous H2O2 (30%, 1.4 mL, 12.3 mmol)
was added dropwise to a solution of compound 22a (1.80 g,
3.51 mmol) in CH2Cl2 (35 mL) at room temperature with
stirring. The stirring was continued for 3.5 h and the solvent
was evaporated to give a crude selenoxide 23a (1.85 g,
100%). UV lmax 203 (3 24,400), 260 nm (3 10,900). ESI-
MS 528, 530 (M+H, 51.5, 100.0). A solution of this product
(1.85 g, 3.5 mmol) in toluene (40 mL) was stirred at 80 ꢁC
for 20 min. Solvent was evaporated and the residue was chro-
matographed on a silica gel column using EtOAc–hexanes
(2:1 to 100% EtOAc) to give the faster moving Z-isomer
Z-24a (540 mg, 42.8%) followed by E-isomer E-24a
(450 mg, 35.7%). In addition, phenylselenenyl derivative
22a (100 mg, 5.6%) was also obtained.
Z-isomer Z-24a: mp 185–187 ꢁC. UV lmax 229 (3 26,400),
279 nm (3 9700). H NMR (CDCl3) d 0.04, 0.06 (2s, 6H,
1
Si(CH3)2), 0.87 (s, 9H, CH3 of t-Bu), 1.76, 1.89 (dAB, 2H,
0
JAB¼9.0, 1.6 Hz, H3 ), 2.11 (s, 1H, C^CH), 3.49, 4.13
0
(2d, 2H, J¼9.6 Hz, H5 ), 5.95 (s, 2H, NH2), 7.53 (s, 1H,
H1 ), 8.38 (s, 1H, H2), 8.75 (s, 1H, H8). 13C NMR ꢀ5.24,
0
0
0
ꢀ5.18 (Si(CH3)2), 15.5 (C3 ), 18.7 (C of t-Bu), 19.8 (C4 ),
26.06, 26.08 (CH3 of t-Bu), 67.6 (^CH), 68.78, 68.85
0
0
0
4.1.7. (cis,trans)-1-Bromomethyl-2-ethynyl-2-tert-butyl-
dimethylsilyloxymethyl-1-phenylselenenylcyclopropane
(21). NBS (2.81 g, 15.8 mmol) and Ph2Se2 (2.46 g,
7.88 mmol) were added to a stirred solution of compound
20 (3.5 g, 15.8 mmol) in CH2Cl2 (45 mL) at ꢀ20 ꢁC. The
stirring was continued for 10 min at ꢀ20 ꢁC and 15 min at
ꢀ10 ꢁC. Solvent was evaporated and the residue was chro-
matographed on a silica gel column using hexanes–Et2O
(100:1–50:1) to give product 21 (2.93 g, 40.4%) as a color-
less oil (isomeric ratio 2:1). 1H NMR (CDCl3) d 0.08,
0.11, 0.12 (3s, 6H, Si(CH3)2), 0.89, 0.93 (2s, 9H, CH3 of
t-Bu), 1.22 (J¼6.4 Hz), 1.35 (J¼6.0 Hz), 1.52, 1.49 (AB,
(C5 ), 83.2 (^C), 111.4 (C1 ), 115.7 (C2 ), 119.5 (C5),
139.2 (C8), 149.0 (C4), 153.3 (C2), 155.6 (C6). ESI-MS
356 (M+H, 100.0), 378 (M+Na, 47.8).
E-isomer E-24a: mp 164–165 ꢁC. UV lmax 228 (3 28,800),
278 nm (3 9500). H NMR (CDCl3) d 0.062, 0.078 (2s,
6H, CH3 of Si(CH3)2), 0.87 (s, 9H, CH3 of t-Bu), 1.97 (m,
1
0
2H, H3 ), 2.04 (s, 1H, C^CH), 3.77, 3.82 (AB, 2H,
0
0
JAB¼10.4 Hz, H5 ), 6.03 (s, 2H, NH2), 7.71 (s, 1H, H1 ),
8.22, 8.39 (2s, 2H, H2, H8). 13C NMR ꢀ5.07, ꢀ5.04
0
(Si(CH3)2), 17.5 (C3 ), 18.4, 18.6 (C of t-Bu, C4 ), 26.03,
0
0
26.04 (CH3 of t-Bu), 66.0 (^CH), 67.50, 67.56 (C5 ), 83.9
0
0
0
2H, JAB¼5.6 Hz, H3 ), 2.12, 2.21 (2s, 1H, C^CH), 3.73,
(^C), 112.2 (C1 ), 116.4 (C2 ), 119.6 (C5), 137.3 (C8),
149.2 (C4), 153.6 (C2), 155.7 (C6). ESI-MS 356 (M+H,
100.0), 378 (M+Na, 14.7).
3.94, 4.05, 4.24 (m, 4H, CH2Br, CH2O), 7.25–7.30, 7.63–
7.65, 7.68–7.70 (3m, 5H, Ph). ESI-MS 479, 481, 483
(M+Na, 44.8, 100.0, 80.0).
4.1.10. (Z)-9-[(2-Hydroxymethyl-2-ethynylcyclopropyl-
idene)methyl]adenine (12a). A mixture of the Z-isomer
Z-24a (450 mg, 1.11 mmol) and tetrabutylammonium fluo-
ride (1.0 M in THF, 1.5 mL, 1.5 mmol) in THF (12.5 mL)
was stirred at room temperature for 2 h. The solvent was re-
moved and the residue was chromatographed on a silica
gel column using EtOAc–MeOH (30:0–20:1) to give the
Z-isomer 12a (263 mg, 87.2%), mp 197–199 ꢁC. UV lmax
4.1.8. (cis,trans)-9-[(2-tert-Butyldimethylsilyloxymethyl-
2-ethynyl-1-phenylselenenyl-1-cyclopropyl)methyl]ade-
nine (22a). A mixture of compound 21 (150 mg, 0.33 mmol),
adenine (50 mg, 0.37 mmol), and K2CO3 (140 mg,
1.01 mmol) in DMF (15 mL) was stirred for 16 h at room
temperature. The insoluble portion was filtered through a sil-
ica gel pad, which washed with DMF (45 mL). Solvent was
evaporated in vacuo and the residue was chromatographed on
a silica gel column using hexanes–EtOAc (2:1 to 100%
EtOAc) to give the product 22a (140 mg, 83%) as a white
solid, mp 154–155 ꢁC. UV lmax 203 (3 27,000), 263 nm (3
12,900). 1H NMR (CDCl3) d 0.13, 0.16, 0.18, 0.21 (4s, 6H,
Si(CH3)2), 0.967, 0.972 (2s, 9H, CH3 of t-Bu), 1.24, 1.87
(J¼5.6 Hz) 1.32, 1.68 (2AB, 4H, J¼6.4 Hz, H3), 2.16, 2.18
(2s, 1H, C^CH), 4.90, 4.13 (J¼14.4 Hz), 4.58, 4.44
(J¼14.4 Hz), 4.47, 3.92 (J¼11.6 Hz), 4.26, 3.91 (four partly
1
226 (3 30,600), 276 nm (3 10,900). H NMR d 1.85, 1.81
0
(AB, 2H, JAB¼9.0 Hz, H3 ), 3.06 (s, 1H, C^CH), 3.36,
0
3.39, 3.84, 3.87 (2AB, 1H, JAB¼5.6 Hz, H5 ), 5.47 (t, 1H,
13
0
J¼5.6 Hz, OH), 7.37 (s, 2H, NH2), 7.47 (s, 1H, H1 ), 8.18
0
(s, 1H, H2), 8.62 (s, 1H, H8). C NMR 15.7 (C3 ), 20.0
0
0
0
(C4 ), 65.9 (C5 ), 71.3 (^CH), 84.5 (^C), 111.2 (C1 ),
0
116.3 (C2 ), 118.9 (C5), 138.2 (C8), 148.7 (C4), 153.9 (C2),
156.8 (C6). ESI-MS 242 (M+H, 95.2), 264 (M+Na, 100.0).
Anal. Calcd for C12H11N5O$0.15H2O: C, 59.08; H, 4.67;
N, 28.70. Found: C, 59.24; H, 4.71; N, 28.43.
0
0
overlapped AB, 4H, J¼10.4 Hz, H1 , H5 ), 5.86, 5.97 (2br s,

S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
9411
4.1.11. (E)-9-[(2-Hydroxymethyl-2-ethynylcyclopropyl-
idene)methyl]adenine (13a). The protocol described for
the Z-isomer 12a was followed with the E-isomer E-24a
(400 mg, 0.99 mmol) to give compound 13a (240 mg,
89.6%), mp 217–219 ꢁC. UV lmax 226 (3 29,700), 276 nm
(3 10,100). 1H NMR d 2.01, 1.96 (dAB, 2H, JAB¼8.4,
2.31 mmol) in THF (15 mL). The stirring was continued
for 30 min, THF was evaporated, and the residue was chro-
matographed on a silica gel column using hexanes–EtOAc
(2:1–1:4) to give the Z-isomer 12c (262 mg, 41.2%) fol-
lowed by E-isomer 13c (285 mg, 44.8%).
0
1.6 Hz, H3 ), 2.91 (s, 1H, C^CH), 3.45–3.54 (two overlap-
Z-isomer 12c: mp 184–186 ꢁC. UV lmax 233 (3 30,900),
311 nm (3 8100). H NMR d 1.83 (two overlapped AB,
1
0
ped AB, 2H, H5 ), 5.14 (t, 1H, J¼6.2 Hz, OH), 7.36 (s, 2H,
13
0
NH2), 7.63 (s, 1H, H1 ), 8.18 (s, 1H, H2), 8.48 (s, 1H, H8).
0
2H, H3 ), 3.07 (s, 1H, C^CH), 3.31, 3.85, 3.87 (2AB, over-
0
C NMR 18.5 (C3 ), 18.8 (C4 ), 65.8 (C5 ), 70.1 (^CH),
0
0
lapped with H2O, J¼4.8–6.4 Hz), 5.47 (t, 1H, J¼5.8 Hz,
13
0
0
0
OH), 7.06 (s, 2H, NH2), 7.28 (s, 1H, H1 ), 8.59 (s, 1H, H8).
85.6 (^C), 112.1 (C2 ), 117.4 (C1 ), 119.1 (C5), 138.1
(C8), 149.1 (C4), 153.9 (C2), 156.8 (C6). ESI-MS 242
(M+H, 100.0), 264 (M+Na, 30.5). Anal. Calcd for
C12H11N5O$0.2H2O: C, 58.86; H, 4.69; N, 28.60. Found:
C, 59.01; H, 4.67; N, 28.35.
0
C NMR 15.8 (C3 ), 20.1 (C4 ), 65.9 (C5 ), 71.5 (^CH),
0
0
0
0
84.4 (C^), 110.8 (C1 ), 117.1 (C2 ), 123.6 (C5), 140.2
(C8), 150.5 (C4), 153.0 (C2), 160.9 (C6). ESI-MS 186
(100.0), 276, 278 (M+H, 40.7, 12.0), 298, 300 (M+Na,
21.9, 6.9).
4.1.12. (cis,trans)-2-Amino-6-chloro-9-[(2-tert-butyl-
dimethylsilyloxymethyl-2-ethynyl-1-phenylselenenyl-1-
cyclopropyl)methyl]purine (22c). A mixture of compound
21 (2.02 g, 4.41 mmol), 2-amino-6-chloropurine (785 mg,
4.64 mmol), and K2CO3 (183 mg, 13.26 mmol) in DMF
(25 mL) was stirred for 24 h at room temperature. The
work-up followed the protocol described for compound
22a. Chromatography in hexanes–EtOAc (5:1–2:1) gave
product 22c (1.91 g, 79.2%) as a white solid, mp 137–
139 ꢁC. UV lmax 222 (3 28,900), 243 (3 9100), 311 nm (3
E-isomer 13c: mp 190–191 ꢁC. UV lmax 232 (3 30,500), 311
1
(3 7900). H NMR 1.95, 2.02 (dAB, 2H, JAB¼9.8, 1.6 Hz,
0
H3 ), 2.92 (s, 1H, C^CH), 3.43, 3.53, 3.46, 3.51 (2AB,
0
2H, JAB¼6.4, 5.6 Hz, H5 ), 5.15 (t, 1H, J¼6.2 Hz, OH),
7.03 (s, 2H, NH2), 7.47 (s, 1H, H1 ), 8.43 (s, 1H, H8). 13C
0
0
0
NMR 18.7 (C3 ), 18.9 (C4 ), 65.8 (C5 ), 70.1 (^CH), 85.5
0
0
0
(C^), 111.8 (C1 ), 118.5 (C2 ), 123.8 (C5), 140.4 (C8),
150.4 (C4), 153.4 (C2), 160.8 (C6). ESI-MS (MeOH+KOAc)
123 (100.0), 314, 316 (M+K, 48, 20).
1
8200). H NMR (CDCl3) d 0.09, 0.13, 0.14, 0.18 (4s, 6H,
Si(CH3)2), 0.92, 0.93 (2s, 9H, CH3 of t-Bu), 1.26, 1.75,
4.1.15. (Z)-9-[(2-Hydroxymethyl-2-ethynylcyclopropyl-
idene)methyl]guanine (12b). A solution of compound 12c
(150 mg, 0.544 mmol) in formic acid (80%, 12 mL) was
heated at 80 ꢁC with stirring for 3 h. After cooling, the vol-
atile components were evaporated in vacuo and the residue
was stirred in 4% NH3 in methanol (50 mL) at 0 ꢁC for
1 h. NH3 and methanol were evaporated and the product
was recrystallized from methanol to give the Z-isomer 12b
(120 mg, 86%, mp >300 ꢁC. UV lmax 232 (3 25,000),
273 nm (3 10,600). 1H NMR d 1.77, 1.80 (AB, 2H,
0
1.29, 1.63 (2AB, 2H, J¼5.6–6.4 Hz, H3 ), 2.15, 2.18 (2s,
1H, C^CH), 3.82, 3.87, 4.04, 4.20, 4.32, 4.40, 4.41, 4.68
0
0
(four partly overlapped AB, J¼10.4–15.6 Hz, 4H, H1 , H5 ),
5.43 (br s, 2H, NH2), 7.17–7.28 (m, 3H), 7.43 (poorly re-
solved dd, 1H), 7.60 (poorly resolved dd, 1H, Ph), 7.75,
8.11 (2s, 1H, H8). ESI-MS (MeOH) 546, 548, 550 (M+H,
40.4, 81.1, 41.6), 88 (100.0).
4.1.13. (Z,E)-2-Amino-6-chloro-9-[(2-tert-butyldimethyl-
silyloxymethyl-2-ethynyl-cyclopropylidene)methyl]pur-
ine (24c). The procedure described for adenine derivatives
Z-24a and E-24a was followed using compound 22c (1.85 g,
3.38 mmol) and 30% H2O2 (30%, 1.15 mL, 10.1 mmol), re-
action time 1 h to give crude selenoxide 23c (1.90 g, 99.8%).
UV lmax 222 (3 27,000), 245 (3 9100), 310 nm (3 7300). ESI-
MS 562, 564, 566 (M+H, 49.7, 100.0, 50.6), 600, 602, 604
(M+Na, 13.2, 24.0, 11.4). Thermolysis of this product in tol-
uene (35 mL) at 80–85 ꢁC for 20 min gave, after chromato-
graphy in EtOAc–hexanes (4:1–1:1), the Z,E-isomeric
mixture 24c (948 mg, 81%), mp 162–164 ꢁC. UV lmax 234
0
JAB¼8.6 Hz, H3 ), 3.05 (s, 1H, C^CH), 2.76–3.84, 3.32–
3.38 (2AB partly overlapped with H2O), 5.42 (t, 1H,
0
13
J¼5.6 Hz, OH), 6.68 (s, 2H, NH2), 7.16 (s, 1H, H1 ), 8.18
0
(s, 1H, H8), 10.81 (s, 1H, NH). C NMR 15.6 (C3 ), 19.9
0
0
0
(C4 ), 65.7 (C5 ), 71.3 (^CH), 84.5 (C^), 111.1 (C1 ),
0
115.8 (C2 ), 116.8 (C5), 134.7 (C8), 150.4 (C4), 155.0 (C2),
157.3 (C6). ESI-MS 107 (100.0), 258 (M+H, 5.3), 280
(M+Na, 35.9), 537 (2M+Na, 12.2). Anal. Calcd for
C12H11N5O2$0.7H2SiO3: C, 46.21; H, 4.01; N, 22.45.
Found: C, 46.25; H, 4.04; N, 22.79. The silica gel was re-
moved from this product as follows. Compound 12b
1
(3 30,000), 311 nm (3 7900). H NMR (CDCl3) d 0.04,
0.05, 0.06, 0.08 (4s, 6H, Si(CH3)2), 0.86, 0.87 (2s, CH3 of
(67 mg, 0.22 mmol) was absorbed on Dowex 50 (H(+)
,
100–200 mesh, 3.5ꢂ1.8 cm) column as an aqueous suspen-
sion. The column was eluted with water (50 mL) and
NH4OH (28%, 100 mL). The latter eluate was concentrated
and the resultant solid was washed with CHCl3 (25 mL) and
water (25 mL). It was dried at 0.03–0.04 Torr and room tem-
perature for 24 h to give the Z-isomer 12b (57.4 mg, 97%).
t-Bu), 1.77, 1.88 (split AB, 1H, JAB¼8.8 Hz), 1.97 (poorly
0
resolved t, 1H, H3 ), 2.04, 2.10 (2s, 1H, C^CH), 3.51,
0
4.09 (AB, JAB¼10.6 Hz), 3.79 (s, 2H, H5 ), 5.18 (s, 2H,
0
NH2), 7.35, 7.54 (2s, 1H, H1 ), 8.66, 8.15 (2s, 1H, H8).
ESI-MS 88 (100.0), 390, 392 (M+H, 78.4, 29.0), 412, 414
(M+Na, 17.4, 6.0). In addition, phenylselenenyl derivative
22c (210 mg, 11.4%) was obtained.
1
UV lmax 232 (3 26,000), 271 nm (3 11,000). Mp and H
NMR were identical with that of the product containing
silica gel. Anal. Calcd for C12H11N5O2$0.65H2O: C,
53.59; H, 4.61; N, 26.04. Found: C, 53.59; H, 4.37; N, 25.71.
4.1.14. (Z)- and (E)-2-Amino-6-chloro-9-[(2-hydroxy-
methyl-2-ethynylcyclopropylidene)methyl]purine (12c)
and (13c). Tetrabutylammonium fluoride (1.0 M in THF,
2.5 mL, 2.5 mmol) was added dropwise with stirring at
room temperature into isomeric mixture 24c (0.9 g,
4.1.16. (E)-9-[(2-Hydroxymethyl-2-ethynylcyclopropyl-
idene)methyl]guanine (13b). The protocol for the Z-isomer
12b was followed using E-isomer 13c (190 mg, 0.69 mmol)

9412
S. Zhou et al. / Tetrahedron 63 (2007) 9406–9412
to give compound 13b (143 mg, 81%), mp >300 ꢁC. UV
lmax 232 (3 23,400), 273 nm (3 10,000). H NMR d 1.90,
5. Siddiqui, M. A.; Hughes, S. H.; Boyer, P. L.; Mitsuya, H.; Van,
Q. N.; George, C.; Sarafinanos, S. G.; Marquez, V. E. J. Med.
Chem. 2004, 47, 5041–5048.
6. Haraguchi, K.; Takeda, S.; Tanaka, H.; Nitanda, T.; Baba, M.;
Dutschman, G. E.; Cheng, Y.-C. Bioorg. Med. Chem. Lett.
2003, 13, 3775–3777.
1
0
1.96 (AB, 2H, JAB¼9.0 Hz, H3 ), 2.89 (s, 1H, C^CH),
0
3.40–3.51 (m, 2H, H5 ), 5.13 (poorly resolved t, 1H, OH),
0
6.61 (s, 2H, NH2), 7.35 (s, 1H, H1 ), 8.02 (s, 1H, H8),
13
0
10.78 (s, 1H, NH). C NMR 18.3 (C3 ), 18.6 (C4 ), 65.8
0
0
(C5 ), 69.9 (^CH), 85.7 (C^), 112.0 (C1 ), 117.0, 117.1
0
(C2 , C5), 134.5 (C8), 150.7 (C4), 154.9 (C2), 157.3 (C6).
0
7. Dutschman, G. E.; Grill, S. P.; Gullen, E. A.; Haraguchi, K.;
Takeda, S.; Tanaka, H.; Baba, M.; Cheng, Y.-C. Antimicrob.
Agents Chemother. 2004, 48, 1640–1646.
8. Tanaka, H.; Haraguchi, K.; Kumamoto, H.; Baba, M.; Cheng,
Y.-C. Antiviral Chem. Chemother. 2005, 16, 217–221.
9. Kumamoto, H.; Nakai, T.; Haraguchi, K.; Nakamura, K. T.;
Tanaka, H.; Baba, M.; Cheng, Y.-C. J. Med. Chem. 2006, 49,
7861–7867.
10. Chen, X.; Zhou, W.; Schinazi, R. F.; Chu, C. K. J. Org. Chem.
2004, 69, 6034–6041.
11. Chu, C. K.; Gadthula, S.; Chen, X.; Choo, H.; Olgen, S.;
Barnard, G. L.; Sidwell, R. W. Antiviral Chem. Chemother.
2006, 17, 285–289.
12. Zemlicka, J. Recent Advances in Nucleosides: Chemistry and
Chemotherapy; Chu, C. K., Ed.; Elsevier: Amsterdam, 2002;
pp 327–357.
13. Zemlicka, J.; Chen, X. Frontiers in Nucleosides and Nucleic
Acids; Schinazi, R. F., Liotta, D. C., Eds.; IHL: Tucker, GA,
2004; pp 267–307.
14. Zemlicka, J. Advances in Antiviral Drug Design; De Clercq, E.,
Ed.; Elsevier: Amsterdam, The Netherlands, Vol. 5, in press.
15. Zhou, S.; Breitenbach, J. M.; Borysko, K. Z.; Drach, J. C.;
Kern, E. R.; Gullen, E.; Cheng, Y.-C.; Zemlicka, J. J. Med.
Chem. 2004, 47, 566–575.
ESI-MS 258 (M+H, 32.8), 280 (M+Na, 100.0), 537
(2M+Na, 21.3). Anal. Calcd for C12H11N5O2$0.7H2SiO3:
C, 46.21; H, 4.01; N, 22.45. Found: C, 46.24; H, 4.17; N,
22.83. The silica gel was removed as described for the Z-iso-
mer 12b to give the E-isomer 13b. UV lmax 232 (3 27,500),
271 nm (3 11,500). Mp and 1H NMR were identical with that
of the product containing silica gel. Anal. Calcd for
C12H11N5O2$0.65H2O: C, 53.59; H, 4.61; N, 26.04. Found:
C, 53.54; H, 4.37; N, 25.71.
4.1.17. Adenosine deaminase (ADA) assay. Compounds
12a and 13a (2.2 mmol) were magnetically stirred with
ADA from calf intestine (Worthington Biochemical Corp.,
Lakewood, New Jersey, dry powder, 0.59 U) in 0.05 M
Na2HPO4 (pH 7.4, 0.4 mL) at room temperature. Aliquots
were periodically withdrawn and examined by TLC in
CH2Cl2–MeOH (10:1). The extent of deamination of 13a
was 70–75% after 24 h. Compound 12a was not deaminated.
Acknowledgements
16. Kern, E. R.; Bidanset, D. J.; Hartline, C. B.; Yan, Z.; Zemlicka,
J.; Quenelle, D. C. Antimicrob. Agents Chemother. 2004, 48,
4745–4753.
17. Zhou, S.; Kern, E. R.; Gullen, E.; Cheng, Y.-C.; Drach, J. C.;
Matsumi, S.; Mitsuya, H.; Zemlicka, J. J. Med. Chem. 2004,
47, 6964–6972.
18. Guan, H.-P.; Ksebati, M. B.; Cheng, Y.-C.; Drach, J. C.; Kern,
E. R.; Zemlicka, J. J. Org. Chem. 2000, 65, 1280–1290.
19. Zhou, S.; Zemlicka, J. Nucleosides Nucleotides Nucleic Acids
2007, 26, 391–402.
We thank L.M. Hrihorczuk from the Central Instrumentation
Facility of the Department of Chemistry, Wayne State
University for mass spectra. The work described herein
was supported by Grant RO1-CA32779 from the National
Cancer Institute and Contract NO1-AI-30049 from the Na-
tional Institute of Allergy and Infectious Diseases, National
Institutes of Health, Bethesda, Maryland, USA.
References and notes
20. Yan, Z.; Kern, E. R.; Gullen, E.; Cheng, Y.-C.; Drach, J. C.;
Zemlicka, J. J. Med. Chem. 2005, 48, 91–99.
21. Corey, E. J.; Suggs, J. W. Tetrahedron Lett. 1975, 16, 2647–
2650.
22. Corey, E. J.;Fuchs, P. L. TetrahedronLett. 1972, 13, 3769–3772.
23. Dinadayalane, T. C.; Priyakumar, U. D.; Sastry, G. N. J. Phys.
Chem. 2004, 108, 11433–11448.
24. Brandi, A.; Goti, A. Chem. Rev. 1998, 98, 589–635.
25. Brandi, A.; Cicchi, S.; Cordero, F. M.; Goti, A. Chem. Rev.
2003, 103, 1213–1270.
1. Prisbe, E. J.; Maag, H.; Verheyden, J. P. H.; Rydzewski, R. M.
Nucleosides and Nucleotides as Antitumor and Antiviral
Agents; Chu, C. K., Baker, D. C., Eds.; Plenum: New York,
NY, 1993; pp 101–113.
2. Hayakawa, H.; Kohgo, S.; Kitano, K.; Ashida, N.; Kodama, E.;
Mitsuya, H.; Ohrui, H. Antiviral Chem. Chemother. 2004, 15,
169–187.
3. Ohrui, H.; Kohgo, S.; Kitano, K.; Sakata, S.; Kodama, E.;
Yoshimura, K.; Matsuoka, M.; Shigeta, S.; Mitsuya, H.
J. Med. Chem. 2000, 43, 4516–4525.
4. Kodama, E.; Kohgo, S.; Kitano, K.; Machida, H.; Gatanaga, H.;
Shigeta, S.; Matsuoka, M.; Ohrui, H.; Mitsuya, H. Antimicrob.
Agents Chemother. 2001, 45, 1539–1546.
26. Zhou, S.; Zemlicka, J. Tetrahedron 2005, 61, 7112–7116.
27. Yan, Z.; Zhou, S.; Kern, E. R.; Zemlicka, J. Tetrahedron 2006,
62, 2608–2615.
28. Dekker, C. A. J. Am. Chem. Soc. 1965, 87, 4027–4029.