Synthesis of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines as antiplatelet agents

Article abstract of DOI:10.1016/j.ejmech.2012.03.047

A series of novel N⁶-alkyl(aryl)-2-alkyl(aryl)thioadenosines were synthesized, and their human antiplatelet aggregation activities were evaluated by the stimulation of adenosine 5′-diphosphate (ADP). Some of these compounds showed strong activity, among which compound 5b₁₁ displayed the highest activity with an IC₅₀ value of 29 ± 3 μM. Furthermore, five compounds were tested against arachidonic acid (AA)-induced human platelet aggregation. The results showed that compound 5b₁₀ exhibited the highest activity with an IC₅₀ value of 3 ± 2 μM. The adenosine derivatives substituted with a phenethyl group at the N⁶ position and a methylthio or ethylthio group at the C-2 position displayed high antiplatelet aggregation activity.

Full text of DOI:10.1016/j.ejmech.2012.03.047

European Journal of Medicinal Chemistry 53 (2012) 114e123
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines as antiplatelet agents
,
Guocheng Liu a, Jiaxi Xu a, Ning Chen a, Si Zhang b, Zhongren Ding b, Hongguang Du a
*
a State Key Laboratory of Chemical Resource Engingeering, Department of Organic Chemistry, College of Science, Beijing University of Chemical Technology, Beijing 100029, China
b Key Laboratory of Molecular Medicine, Ministry of Education and Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College,
Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
A series of novel N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines were synthesized, and their human anti-
platelet aggregation activities were evaluated by the stimulation of adenosine 50-diphosphate (ADP).
Some of these compounds showed strong activity, among which compound 5b11 displayed the highest
Article history:
Received 9 February 2011
Received in revised form
14 March 2012
Accepted 23 March 2012
Available online 4 April 2012
activity with an IC50 value of 29 ꢀ 3
mM. Furthermore, five compounds were tested against arachidonic
acid (AA)-induced human platelet aggregation. The results showed that compound 5b10 exhibited the
highest activity with an IC50 value of 3 ꢀ 2
mM. The adenosine derivatives substituted with a phenethyl
group at the N6 position and a methylthio or ethylthio group at the C-2 position displayed high anti-
platelet aggregation activity.
Keywords:
N6-alkyl(aryl)-2-alkyl(aryl)thioadenosine
Antiplatelet activity
Synthesis
Ó 2012 Elsevier Masson SAS. All rights reserved.
1. Introduction
drawbacks, such as low activity and serious undesirable side effects
[19]. In 1999, the AR-C compounds have been reported as the P2Y12
Platelets play a pivotal role in atherothrombosis [1]; their acti-
vation, adhesion and aggregation are important processes in the
initiation of thrombus formation at sites showing high-grade
stenosis, ruptured atheromatous plaque and endothelial damage
within arteries [2,3]. Platelet-mediated thrombus formation in the
coronary artery is a primary factor in the development of throm-
botic disorders, such as acute coronary syndromes [4], including
unstable angina, myocardial infarction and symptomatic peripheral
artery disease [5e7]. Current antiplatelet agents include available
drugs, such as aspirin, ticlopidine, clopidogrel and glycoprotein IIb/
IIIa antagonists [8,9]. However, these current antiplatelet drugs are
still not satisfactory in terms of efficacy and safety [10e12].
Therefore, intensive efforts are urgently desirable to develop novel
antiplatelet agents.
Adenosine is a potent inhibitor of platelet aggregation [13], but
it has intense effects on the cardiovascular system and is readily
inactivated by contact with erythrocytes or platelets [14]. There-
fore, a lot of adenosine derivatives have been prepared and evalu-
ated for their ability to inhibit platelet aggregation, such as 2-
chloroadenonsine [15], 2-(substituted thio) adenosines [16,17], 2-
(substituted amino) adenosines [17] and N6-substituted adenosines
[18]. However, these adenosine derivatives still have various
receptor antagonists by Ingall and his co-workers [20]. The P2Y12
receptor is a G protein-coupled receptor, primarily a specific
platelet receptor, which is an attractive therapeutic target for
selective modulation of ADP-induced platelet activation [21]. The
AR-C compounds are also adenosine derivatives with the alkylthio
group at C-2 position, the alkyl substituent at N6 position and the
triphosphate side chain at the 50 position. Among these AR-C
compounds, cangrelor (Fig. 1) is one of the most potent inhibitors
of ADP-induced human platelet aggregation (IC50 ¼ 0.4 nM, 30
mM
ADP, human washed platelets) [20,22], which does not require
conversion to an active metabolite, and is immediately active after
intravenous infusion. However, the synthetic route of the AR-C
compounds consists of a long multistep process. What is more,
the unwieldy 50-triphosphate group is not necessary to be recog-
nized by the P2Y12 receptor [23,24]. Ticagrelor (Fig. 1) is one of the
examples with a high affinity for the P2Y12 receptor and is currently
under clinical trials [25]. Considering these findings, we modified
the C-2 and N6 substituents of the adenosine scaffold and obtained
a series of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines (Fig. 1). To
date, a few of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines have been
reported [26e29], but their biological evaluations as antiplatelet
agents have not been studied.
In our attempt to develop novel and potent antiplatelet agents,
a series of new N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines were
synthesized and evaluated as antiplatelet agents together with
their primary structureeactivity relationships.
* Corresponding author. College of Science, Beijing University of Chemical Tech-
nology, Beijing 100029, China. Tel./fax: þ86 10 64439218.
E-mail address: dhg@mail.buct.edu.cn (H. Du).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.03.047

G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
115
2. Results and discussion
groups at the N6 position decreases the activity. The results are
consistent with previous conclusions that a hydrogen binding
moiety and a lipophilic moiety are critical for P2Y12 receptor
antagonist activity [35]. Phenethyl substituent, a relatively larger
hydrophobic group, can increase the ligand and receptor binding.
Therefore, the N6-phenethyladenosine derivatives show better
activity than others. Furthermore, the N6-phenethyladenosine
derivatives showed a broad spectrum of antiplatelet action against
both ADP and AA-induced aggregations (Table 2, entries 18e21).
Additionally, the weak antiplatelet activity of compound 5a8
confirmed that dialkylation at N6 position of adenosine decreased
the activity [20], revealing that a hydrogen atom at N6 position is
important for the activity.
The results also indicated that a small thio-substituted group at C-
2 was optimal for the antiplatelet activity, methylthio and ethylthio
showing high antiplatelet activity (Table 2, entries 10, 18, 19, 25 and
29), while bulky phenylthio and benzylthio illustrating dramatically
low inhibitory activity (Table 2, entries 22 and 23). It was assumed
that there is a steric interference between the two substituents on N6
and C-2 due to the partial overlap between the N6 and C-2 aryl-
binding pockets. The distal aryl groups at N6 and C-2 would occupy
their respective pockets when present alone, but could not occupy
the overlapping portion of the two pockets whenpresent in the same
molecule[26]. Inthis case, one of the two aryl groupswould beforced
into an unfavorable position, resulting in the loss of activity.
2.1. Chemistry
The synthesis of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines is
outlined in Scheme 1.
2-Amino-6-chloro-9-(20,30,50-tri-O-acetyl-
b-D-ribofuranosyl)-9H-
purine (3) was synthesized from the starting material guanosine (1)
via acetylation and chlorination by a well-established procedure
[30,31]. Next, compound 3 was diazotized with isoamyl nitrite and
then reacted with dialkyl(aryl) disulfides to afford 2-alkyl(aryl)thio-
6-chloro-9-(20,30,50-tri-O-acetyl-
b-D-ribofuranosyl)-9H-purines (4).
However, in the previous procedure for synthesis of 4, abundant
dialkyl(aryl) disulfide (10 equiv of 3) was used in each of cases
[20,32,33], and the reaction was kept for a long time (16 h). To
improve the synthetic efficiency, we optimized the conditions of
diazotizationealkylthionation with dibutyl disulfide. The results are
summarized in Table 1. It can be found that the optimum molar ratio
is 1:5 (3:dibutyl disulfide) and the reaction time can be shortened to
6 h (Table 1, entries 3 and 8). A series of 2-alkyl(aryl)thio-6-chloro-9-
(20,30,50-tri-O-acetyl-
b-D-ribofuranosyl)-9H-purines (4aeg) were
obtained in moderate yields (43e66%) under the modified reaction
conditions.
Subsequently, thetarget compounds 5wereobtainedin goodyields
via the reaction of compounds 4 and various amines in ethanol using
triethylamine as an acid binding agent and sodium ethanoxide as
a deacetylating agent. Comparing with the previously reported
method [20], the current method shows advantages of short reaction
time and complete deacetylation due tothe better solubility in ethanol.
Thirty-twoN6-alkyl(aryl)-2-alkyl(aryl)thioadenosines(Table 2,5a1ea8
and 5b1eb24) were obtained under our modified conditions.
3. Conclusions
In summary, we have prepared a series of novel N6-alkyl(aryl)-2-
alkyl(aryl)thioadenosines and evaluated for their ability to inhibit
human platelet aggregation induced by ADP in vitro. The most
promisingcompoundsin thisseries are 5b10, 5b11, 5b12, 5b13 and 5b21.
Especially, compound 5b11 showed the highest activity with an IC50
2.2. Antiplatelet activity evaluation
value of 29 ꢀ 3
mM. Furthermore, the five compounds were tested for
their antiplatelet aggregation activities induced by AA. It was found
All the synthesized compounds were evaluated for the ability to
inhibit human platelet aggregation induced by ADP in vitro using
the Born’s method [34]. Furthermore, five promising compounds
5b10, 5b11, 5b12, 5b13 and 5b21 were tested against AA-induced
platelet aggregation (Table 2).
that compound 5b10 displayed the best activity with an IC50 value of
3 ꢀ 2
m
M. Interestingly, the presence of a phenethyl group at the N6
position and methylthio or ethylthio group at the C-2 position of
adenosine is optimal to the antiplatelet activity, while the electron-
donating groups substituted on the benzene ring at the N6 position
decrease the activity. Finally, the present study demonstrates that
some N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines exhibit broad spec-
trum antiplatelet activity against both ADP and AA induced aggre-
gations. The results might provide a basis for the development of new
candidates with potent antiplatelet aggregation activities.
As can be seen from Table 2, most of the synthesized compounds
5 exhibited high potencies in antiplatelet aggregation activities.
Among them, 2-ethylthio-N6-phenethyladenosine (5b11) displayed
the best activity against ADP-induced platelet aggregation with an
IC50 value of 29 ꢀ 3
(5b10) exhibited the highest potency against AA-induced platelet
M. However, the methoxy
m
M and 2-methylthio-N6-phenethyladenosine
aggregation with an IC50 value of 3 ꢀ 2
m
substituted N6-phenethyladenosine derivatives showed low inhi-
bition activity in comparison with N6-phenethyladenosine deriva-
tives (Table 2, entries 18, 19, 24, 25, 28 and 29), and a similar
tendency was also obtained by the further examination of the
activities of N6-benzyladenosine derivatives (Table 2, entries 9e12,
15e17). This reveals that the phenethyl group at the N6 position of
adenosine is crucial to the antiplatelet activity, while the electron-
donating groups on the benzene ring of the benzyl and phenethyl
4. Experimental section
4.1. General
All reagents were purchased and used without further purifi-
cation, and solvents used in reactions were dried prior to use by
standard procedures. Melting points were measured on a Yanaco
MP-500 melting point apparatus without correction. IR spectra
F
S
NHR1
N
HN
HN
N
F
N
N
N
N
N
N
N
N
Cl
Cl
HO
O
P
S
O
P
OH
N
O
P
OH
N
N
SR
S
O
CF3
HO
O
O
HO
O
O
OH
OH OH
OH OH
OH OH
Ticagrelor
Cangrelor
Fig. 1. Structures of cangrelor, ticagrelor and N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines.

116
G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
O
N
O
Cl
N
N
N
N
N
NH
NH2
N
N
NH
N
a
b
N
NH2
NH2
HO
AcO
AcO
O
O
O
OAc
OAc
2
OAc
OAc
OH OH
1
3
NR1R2
N
Cl
N
N
N
N
N
N
c
d
N
SR
SR
HO
AcO
O
O
OH OH
5
OAc OAc
4
R = alkyl, aryl; R1 = alkyl, aryl; R2 = H or R1.
Scheme 1. Synthesis of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines. Reagents and conditions: (a) Ac2O, DMAP, Et3N, CH3CN, r.t.; (b) POCl3, Et4NCl, N,N-dimethylaniline, CH3CN,
reflux; (c) isoamyl nitrite, MeCN, RSSR, 60 ꢂC; (d) 1) HNR1R2, Et3N, EtOH, reflux; 2) Na, reflux.
were recorded on PerkinElmer Spectrum 100 spectrophotometer
and values were represented in cmꢁ1. The NMR spectra were
recorded with Varian Mercury plus 200 (200 MHz), Varian Mercury
plus 300 (300 MHz), Bruker 400 AMX (400 MHz) or Bruker 600
AMX (600 MHz) spectrometer. Chemical shifts were expressed in
at room temperature for 30 min under N2 atmosphere. Then isoamyl
nitrite (4.25 g, 36.3 mmol) was added dropwise into the mixture.
After stirring for 10 min, the solution was heated at 60 ꢂC for 6 h. The
solvent was evaporated in vacuo, and the resulting residue was
purified by silica gel column chromatography (EtOAc/petroleum
ether, 2:3e1:1, v/v) to afford corresponding product 4 as yellow oil.
parts per million on
d
scale relative to the internal TMS (1H). High
resolution mass spectra (HRMS-ESI) were obtained on an Agilent
LC/TOF mass spectrometer. Cangrelor was obtained from AstraZe-
neca (Loughborough, UK). ADP was purchased from Chrono-Log
(Havertown, PA, USA); Arachidonic acid and sodium citrate were
purchased from Sigma (St Louis, MO).
4.2.1. 6-Chloro-2-methylthio-9-(20,30,50-tri-O-acetyl-
b-D-
ribofuranosyl)-9H-purine (4a) [33]
Compound 3 was allowed to react with dimethyl disulfide
according to the general procedure. The product was purified by
column chromatography to give 4a. Yield: 66%.
4.2. General procedure for the synthesis of 2-alkyl(aryl)thio-6-
chloro-9-(20,30,50-tri-O-acetyl-
b-D-ribofuranosyl)-9H-purines
4.2.2. 6-Chloro-2-ethylthio-9-(20,30,50-tri-O-acetyl-
b-D-
ribofuranosyl)-9H-purine (4b) [20]
(4aeg)
Compound 3 was allowed to react with diethyl disulfide
according to the general procedure. The product was purified by
column chromatography to give 4b. Yield: 62%.
A solution of compound 3 (2.5 g, 5.85 mmol) and a corresponding
dialkyl disulfide (29.25 mmol) in dry acetonitrile (35 mL) was stirred
Table 1
Optimizing reaction conditions of the diazotizationealkylthionation reaction.
Cl
Cl
N
N
N
N
N
S
N
N
N
NH2
AcO
AcO
i-AmONO
CH3CN, 60 oC
+
(n-BuS)2
O
O
OAc
3
OAc OAc
OAc
4e
Entry
(n-BuS)2 (equiv)
i-AmONO (equiv)
Time (h)
Product 4e (Yield, %)
1
2
3
4
5
6
7
8
9
10
7
5
4
2
1
0.5
5
5
5
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
16
16
16
16
16
16
16
6
54
53
53
46
43
39
23
52
45
30
4
2
10

G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
117
Table 2
The structures and antiplatelet activity evaluations of N6-alkyl(aryl)-2-alkyl(aryl)thioadenosines (5).
NR1R2
N
N
N
N
SR
HO
O
OH OH
5
Entry
Compound 5
R
R1
R2
IC50 (m
M)a
ADP
ncb
AA
1
2
3
4
5
6
7
8
5a1
5a2
5a3
5a4
5a5
5a6
5a7
5a8
5b1
5b2
5b3
5b4
5b5
5b6
5b7
5b8
Et
CH2(CH2)4CH3
H
H
H
H
H
H
H
n-Bu
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
n-Pr
n-Bu
Et
n-Pr
i-Pr
n-Bu
Et
Me
Et
n-Pr
n-Bu
Me
Et
Me
Et
n-Pr
Me
Et
n-Pr
n-Bu
Ph
CH2Ph
Me
Et
CH2(CH2)4CH3
CH2(CH2)4CH3
c-C6H11
c-C6H11
c-C6H11
c-C6H11
n-Bu
CH2Ph
CH2Ph
102 ꢀ 11
nc
104 ꢀ 7
151 ꢀ 9
187 ꢀ 15
83 ꢀ 4
nc
9
nc
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
176 ꢀ 16
216 ꢀ 12
202 ꢀ 20
nc
nc
nc
CH2Ph
CH2Ph
p-MePhCH2
p-MePhCH2
p-MeOPhCH2
p-MeOPhCH2
p-MeOPhCH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
nc
5b9
181 ꢀ 14
36 ꢀ 5
29 ꢀ 3
52 ꢀ 3
59 ꢀ 6
nc
5b10
5b11
5b12
5b13
5b14
5b15
5b16
5b17
5b18
5b19
5b20
5b21
5b22
5b23
5b24
3 ꢀ 2
30 ꢀ 9
44 ꢀ 7
>300
PhCH2CH2
nc
p-MeOPhCH2CH2
p-MeOPhCH2CH2
p-MeOPhCH2CH2
p-MeOPhCH2CH2
m-MeOPhCH2CH2
m-MeOPhCH2CH2
m-MeOPhCH2CH2
m-MeOPhCH2CH2
CH(CH3)Ph
153 ꢀ 13
89 ꢀ 10
267 ꢀ 18
93 ꢀ 7
nc
38 ꢀ 4
69 ꢀ 5
nc
n-Pr
n-Bu
Me
Et
n-Pr
n-Bu
Et
>300
197 ꢀ 12
a
IC50 values were expressed as mean ꢀ S.E.M. (n ¼ 3) and calculated when platelet aggregation was below 50% of control (10
m
M ADP or 0.5 mM AA was used as agonist).
mM (10 mM ADP as agonist).
b
nc ¼ not calculated, because maximal inhibition of aggregation was lower than 50% at final concentration of 300
4.2.3. 6-Chloro-2-propylthio-9-(20,30,50-tri-O-acetyl-
ribofuranosyl)-9H-purine (4c) [20]
Compound 3 was allowed to react with dipropyl disulfide
according to the general procedure. The product was purified by
column chromatography to give 4c. Yield: 57%.
b
-D
-
CDCl3):
d
8.11 (1H, s, H-8), 6.14 (1H, d, J ¼ 4.8 Hz, H-10), 5.89 (1H, dd,
J ¼ 5.2, 5.3 Hz, H-20), 5.58 (1H, dd, J ¼ 5.3, 5.4 Hz, H-30), 4.44 (1H,
ddd, J ¼ 3.1, 4.2, 5.4 Hz, H-40), 4.41 (1H, dd, J ¼ 3.1, 12.3 Hz, H-50a),
4.33 (1H, dd, J ¼ 4.2, 12.3 Hz, H-50b), 3.20 (2H, t, J ¼ 7.3 Hz, SCH2),
2.13 (3H, s, CH3CO), 2.10 (3H, s, CH3CO), 2.08 (3H, s, CH3CO), 1.74
(2H, quint, J ¼ 7.3 Hz, SCH2CH2), 1.48 (2H, sextet, J ¼ 7.3 Hz,
SCH2CH2CH2), 0.95 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz,
4.2.4. 6-Chloro-2-isopropylthio-9-(20,30,50-tri-O-acetyl-
b-D-
ribofuranosyl)-9H-purine (4d) [32]
CDCl3): d 170.0, 169.2, 169.0, 166.7, 151.7, 150.9, 142.0, 128.7, 86.5,
Compound 3 was allowed to react with diisopropyl disulfide
according to the general procedure. The product was purified by
column chromatography to give 4d. Yield: 43%.
79.7, 72.9, 69.8, 62.5, 31.04, 30.6, 21.7, 20.4, 20.2, 20.1, 13.4; HRMS
(ESI): m/z [M þ H]þ calcd for C20H26ClN4O7S: 501.1205; found:
501.1212.
4.2.5. 2-Butylthio-6-chloro-9-(20,30,50-tri-O-acetyl-
b
-D-
4.2.6. 6-Chloro-2-phenylthio-9-(20,30,50-tri-O-acetyl-
b-D-
ribofuranosyl)-9H-purine (4e)
ribofuranosyl)-9H-purine (4f) [27]
Compound 3 was allowed to react with dibutyl disulfide
according to the general procedure. The product was purified by
column chromatography to give 4e. Yield: 50%; IR (film): 3443,
Compound 3 was allowed to react with diphenyl disulfide
according to the general procedure. The product was purified by
column chromatography (petroleum ether to EtOAc/petroleum
ether, 2:3, v/v) to give 4f. Yield: 45%.
3110, 2962, 1748, 1546, 1360, 1224 cmꢁ1 1H NMR (600 MHz,
;

118
G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
4.2.7. 2-Benzylthio-chloro-9-(20,30,50-tri-O-acetyl-
ribofuranosyl)-9H-purine (4g)
Compound 3 was allowed to react with dibenzyl disulfide
according to the general procedure. The product was purified by
column chromatography (petroleum ether to EtOAc/petroleum
ether, 2:3, v/v) to give 4g. Yield: 50%; IR (film): 3445, 3025, 2927,
b
-D-
d 163.7, 153.9, 149.4, 138.5, 117.3, 87.5, 85.6, 73.4, 70.6, 61.6, 39.7,
32.4, 31.0, 29.0, 26.1, 22.9, 22.1, 13.9, 13.3; HRMS (ESI): m/z [M þ H]þ
calcd for C19H32N5O4S: 426.2170; found: 426.2178.
4.3.3. 2-Butylthio-N6-hexyladenosine (5a3)
Compound 4e was allowed to react with n-hexylamine for 9 h
according to the general procedure. The product was recrystallized
from MeOH to give 5a3. Yield: 81%, mp 186e188 ꢂC; IR (KBr): 3433,
1750, 1494, 1360, 1231, 822, 755, 700 cmꢁ1
acetone-d6):
;
1H NMR (300 MHz,
8.57 (1H, s, H-8), 7.53 (2H, d, J ¼ 7.2 Hz, ArH), 7.33
d
(2H, t, J ¼ 7.2 Hz, ArH), 7.26 (1H, t, J ¼ 7.2 Hz, ArH), 6.36 (1H, d,
J ¼ 4.6 Hz, H-10), 6.08 (1H, dd, J ¼ 4.6, 5.8 Hz, H-20), 5.71 (1H, dd,
J ¼ 5.8, 5.8 Hz, H-30), 4.55 (2H, s, SCH2), 4.48 (1H, ddd, J ¼ 3.5, 5.1,
5.8 Hz, H-40), 4.42 (1H, dd, J ¼ 3.5, 12.2 Hz, H-50a), 4.32 (1H, dd,
J ¼ 5.1, 12.2 Hz, H-50b), 2.10 (3H, s, CH3CO), 2.08 (3H, s, CH3CO), 2.06
3337, 3125, 1627, 1393, 1117 cmꢁ1 1H NMR (600 MHz, DMSO-d6):
;
d
8.19 (1H, s, H-8), 7.90 (1H, br s, NH), 5.80 (1H, d, J ¼ 5.8 Hz, H-10),
5.37 (1H, d, J ¼ 5.4 Hz, OH), 5.12 (1H, d, J ¼ 3.0 Hz, OH), 5.04 (1H, br
s, OH), 4.58 (1H, ddd, J ¼ 5.4, 5.7, 5.8 Hz, H-20), 4.12 (1H, ddd, J ¼ 3.0,
3.4, 5.7 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.4, 4.1, 5.6 Hz, H-40), 3.64 (1H,
ddd, J ¼ 4.1, 4.7, 11.9 Hz, H-50a), 3.53 (1H, ddd, J ¼ 4.7, 5.6, 11.9 Hz, H-
50b), 3.44 (2H, br s, NCH2), 3.09 (1H, dt, J ¼ 13.5, 7.3 Hz, SCHH), 3.08
(1H, dt, J ¼ 13.5, 7.3 Hz, SCHH), 1.66 (2H, quint, J ¼ 7.3 Hz, SCH2CH2),
1.58 (2H, quint, J ¼ 6.9 Hz, NCH2CH2), 1.42 (2H, sextet, J ¼ 7.3 Hz,
SCH2CH2CH2), 1.33e1.25 (6H, m, NCH2CH2CH2CH2CH2), 0.91 (3H, t,
J ¼ 7.3 Hz, CH3), 0.86 (3H, t, J ¼ 6.4 Hz, CH3); 13C NMR (50 MHz,
(3H, s, CH3CO); 13C NMR (75 MHz, CDCl3):
d 170.1, 169.3, 169.2,
166.0, 151.8, 150.9, 142.0, 136.6, 129.0, 128.9, 128.3, 127.2, 86.4, 79.9,
72.9, 70.0, 62.6, 35.9, 20.6, 20.4, 20.2; HRMS (ESI): m/z [M þ H]þ
calcd for C23H24ClN4O7S: 535.1049; found: 535.1048.
4.3. General procedure for the synthesis of N6-alkyl(aryl)-2-
alkyl(aryl)thioadenosines (5a1ea8 and 5b1eb24
)
DMSO-d6): d 163.7, 153.9, 149.4, 138.5, 117.3, 87.5, 85.6, 73.4, 70.6,
61.6, 39.8, 31.7, 31.0, 30.1, 29.1, 26.1, 22.1, 21.6,13.8,13.5; HRMS (ESI):
A solution of compound 4 (0.7 mmol), a corresponding amine
(3.5 mmol) and triethylamine (0.7 mmol) in ethanol (20 mL) was
refluxed for the time reported below. When the starting material
disappeared as monitored by TLC (MeOH/EtOAc, 1:15, v/v), sodium
(0.05 equiv) was added into the resulting mixture. After the
deacetylations were completed, the solvent was evaporated in
vacuo. The resulting residue was purified by flash column chro-
matography (Et3N-neutralized silica gel, gradient elution separa-
tion with MeOH/EtOAc, 1:30e1:15, v/v) and/or recrystallization,
affording the product 5 as white crystals.
m/z [M þ H]þ calcd for C20H34N5O4S: 440.2326; found: 440.2323.
4.3.4. N6-cyclohexyl-2-ethylthioadenosine (5a4)
Compound 4b was allowed to react with cyclohexylamine for
10 h according to the general procedure. The product was purified
by flash column chromatography, and followed by recrystallization
from EtOAc to give 5a4. Yield: 80%, mp 166e168 ꢂC; IR (KBr): 3423,
3128, 1612, 1337, 1088 cmꢁ1 1H NMR (400 MHz, DMSO-d6):
; d 8.21
(1H, s, H-8), 7.73 (1H, br s, NH), 5.81 (1H, d, J ¼ 5.8 Hz, H-10), 5.41
(1H, br s, OH), 5.18 (1H, br s, OH), 5.07 (1H, br s, OH), 4.58 (1H, dd,
J ¼ 5.4, 5.5 Hz, H-20), 4.13 (1H, dd, J ¼ 3.6, 3.6 Hz, H-30), 3.92 (1H,
ddd, J ¼ 3.4, 3.6, 5.6 Hz, H-40), 4.02 (1H, br s, NCH), 3.64 (1H, d,
J ¼ 11.8 Hz, H-50a), 3.53 (1H, d, J ¼ 11.8 Hz, H-50b), 3.07 (1H, dq,
J ¼ 13.6, 7.3 Hz, SCHH), 3.06 (1H, dq, J ¼ 13.6, 7.3 Hz, SCHH),
1.94e1.57 (6H, m, cyclohexyl), 1.33 (3H, t, J ¼ 7.3 Hz, CH3), 1.31e1.07
4.3.1. 2-Ethylthio-N6-hexyladenosine (5a1)
Compound 4b was allowed to react with n-hexylamine for 7 h
according to the general procedure. The product was recrystallized
from MeOH to give 5a1. Yield: 83%, mp 180e182 ꢂC; IR (KBr): 3446,
3343, 3151, 2927, 1622, 1396, 1120 cmꢁ1
;
1H NMR: (600 MHz,
(4H, m, cyclohexyl); 13C NMR (50 MHz, DMSO-d6):
d 163.6, 153.2,
DMSO-d6):
d
8.20 (1H, s, H-8), 7.92 (1H, br s, NH), 5.80 (1H, d,
149.6, 138.5, 117.1, 87.52, 85.6, 73.4, 70.6, 61.6, 49.1, 32.4, 32.2 (2C),
25.2, 25.0 (2C), 15.1; HRMS (ESI): m/z [M þ H]þ calcd for
C18H28N5O4S: 410.1857; found: 410.1864.
J ¼ 5.6 Hz, H-10), 5.38 (1H, d, J ¼ 6.0 Hz, OH), 5.14 (1H, d, J ¼ 4.8 Hz,
OH), 5.04 (1H, br s, OH), 4.56 (1H, ddd, J ¼ 4.4, 5.6, 6.0 Hz, H-20), 4.13
(1H, ddd, J ¼ 3.6, 4.4, 4.8 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.6, 4.7, 5.7 Hz,
H-40), 3.64 (1H, ddd, J ¼ 4.2, 4.7, 11.9 Hz, H-50a), 3.53 (1H, ddd,
J ¼ 4.4, 5.7, 11.9 Hz, H-50b), 3.43 (2H, br s, NCH2), 3.07 (2H, q,
J ¼ 7.3 Hz, SCH2), 1.58 (2H, quint, J ¼ 6.9 Hz, NCH2CH2), 1.33 (3H, t,
J ¼ 7.3 Hz, CH3), 1.30e1.24 (6H, m, NCH2CH2CH2CH2CH2), 0.86 (3H,
4.3.5. N6-cyclohexyl-2-propylthioadenosine (5a5)
Compound 4c was allowed to react with cyclohexylamine for
9 h according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5a5. Yield: 82%, mp 162e164 ꢂC; IR (KBr): 3423,
t, J ¼ 6.4 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.6, 154.0,
149.3, 138.5, 117.3, 87.5, 85.6, 73.4, 70.6, 61.6, 39.7, 31.0, 29.0, 26.1,
24.7, 22.1, 15.0, 13.9; HRMS (ESI): m/z [M þ H]þ calcd for
C18H30N5O4S: 412.2013; found: 412.2021.
3128, 1611, 1399, 1089 cmꢁ1 1H NMR (300 MHz, DMSO-d6):
; d 8.21
(1H, s, H-8), 7.72 (1H, br s, NH), 5.81 (1H, d, J ¼ 5.9 Hz, H-10), 5.42
(1H, d, J ¼ 6.1 Hz, OH), 5.18 (1H, d, J ¼ 4.8 Hz, OH), 5.10 (1H, dd,
J ¼ 4.2, 4.6 Hz, OH), 4.59 (1H, ddd, J ¼ 5.0, 5.9, 6.1 Hz, H-20), 4.14 (1H,
ddd, J ¼ 3.4, 4.8, 5.0 Hz, H-30), 4.05 (1H, br s, NCH), 3.94 (1H, ddd,
J ¼ 3.4, 4.6, 6.0 Hz, H-40), 3.65 (1H, ddd, J ¼ 4.6, 4.6, 11.9 Hz, H-50a),
3.54 (1H, ddd, J ¼ 4.2, 6.0, 11.9 Hz, H-50b), 3.04 (2H, t, J ¼ 7.3 Hz,
SCH2), 1.90e1.87 (2H, m, cyclohexyl), 1.73 (2H, sextet, J ¼ 7.3 Hz,
SCH2CH2), 1.69e1.10 (8H, m, cyclohexyl), 0.99 (3H, t, J ¼ 7.3 Hz,
4.3.2. N6-hexyl-2-propylthioadenosine (5a2)
Compound 4c was allowed to react with n-hexylamine for 8 h
according to the general procedure. The product was recrystallized
from MeOH to give 5a2. Yield: 84%, mp 186e188 ꢂC; IR (KBr): 3436,
3346, 3154, 2920,1617,1399,1120 cmꢁ1; 1H NMR (600 MHz, DMSO-
d6):
d
8.19 (1H, s, H-8), 7.92 (1H, br s, NH), 5.80 (1H, d, J ¼ 5.8 Hz, H-
CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.6, 153.1, 149.5, 138.4,
10), 5.37 (1H, d, J ¼ 6.0 Hz, OH), 5.13 (1H, d, J ¼ 4.8 Hz, OH), 5.06 (1H,
br s, OH), 4.58 (1H, ddd, J ¼ 5.6, 5.8, 6.0 Hz, H-20), 4.13 (1H, ddd,
J ¼ 3.8, 4.8, 5.6 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.8, 4.4, 5.4 Hz, H-40),
3.64 (1H, ddd, J ¼ 4.4, 4.6, 11.9 Hz, H-50a), 3.53 (1H, ddd, J ¼ 4.6, 5.4,
11.9 Hz, H-50b), 3.44 (2H, br s, NCH2), 3.07 (1H, dt, J ¼ 13.5, 7.3 Hz,
SCHH), 3.05 (1H, dt, J ¼ 13.5, 7.3 Hz, SCHH), 1.70 (2H, sextet,
J ¼ 7.3 Hz, SCH2CH2), 1.58 (2H, quint, J ¼ 6.9 Hz, NCH2CH2),
1.33e1.25 (6H, m, NCH2CH2CH2CH2CH2), 0.99 (3H, t, J ¼ 7.3 Hz,
CH3), 0.86 (3H, t, J ¼ 6.6 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
117.2, 87.52, 85.6, 73.3, 70.5, 61.6, 49.0, 32.4, 32.2 (2C), 25.2, 25.0
(2C), 23.0, 13.4; HRMS (ESI): m/z [M þ H]þ calcd for C19H30N5O4S:
424.2013; found: 424.2021.
4.3.6. N6-cyclohexyl-2-isopropylthioadenosine (5a6)
Compound 4d was allowed to react with cyclohexylamine for
9 h according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5a6. Yield: 77%, mp 136e138 ꢂC; IR (KBr): 3429,

G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
119
3127, 3125, 1604, 1399, 1088, 896, 784, 627 cmꢁ1
;
1H NMR
6.2 Hz, H-20), 4.14 (1H, ddd, J ¼ 3.3, 4.9, 5.2 Hz, H-30), 3.91 (1H, ddd,
J ¼ 3.3, 4.8, 5.3 Hz, H-40), 3.65 (1H, ddd, J ¼ 4.7, 5.3, 12.0 Hz, H-50a),
3.53 (1H, ddd, J ¼ 4.5, 4.8, 12.0 Hz, H-50b), 2.43 (3H, s, SCH3); 13C
(400 MHz, DMSO-d6): 8.20 (1H, s, H-8), 7.72 (1H, br s, NH), 5.80
d
(1H, d, J ¼ 5.8 Hz, H-10), 5.39 (1H, d, J ¼ 6.1 Hz, OH), 5.15 (1H, d,
J ¼ 4.7 Hz, OH), 5.07 (1H, dd, J ¼ 4.5, 4.5 Hz, OH), 4.57 (1H, ddd,
J ¼ 5.6, 5.8, 6.1 Hz, H-20), 4.00 (1H, ddd, J ¼ 3.7, 4.7, 5.6 Hz, H-30),
4.01 (1H, br s, NCH), 3.91 (1H, ddd, J ¼ 3.5, 4.7, 6.1 Hz, H-40), 3.84
(1H, heptet, J ¼ 6.1 Hz, SCH), 3.63 (1H, ddd, J ¼ 4.5, 4.7, 11.8 Hz, H-
50a), 3.52 (1H, J ¼ 4.5, 6.1, 11.8 Hz, H-50b), 1.88e1.60 (6H, m, cyclo-
hexyl), 1.37 (6H, d, J ¼ 6.1 Hz, SCH(CH3)2), 1.32e1.11 (4H, m, cyclo-
NMR (75 MHz, DMSO-d6):
d 164.2, 153.6, 149.6, 140.0, 138.9, 128.3,
127.3, 126.7, 117.2, 87.4, 85.6, 73.4, 70.6, 61.6, 43.1, 13.9.
4.3.10. N6-benzyl-2-ethylthioadenosine (5b2)
Compound 4b was allowed to react with benzylamine for 8 h
according to the general procedure. The product was purified by
flash column chromatography (gradient elution separation with
MeOH/EtOAc, 1:50e1:25, v/v), and followed by recrystallization
from EtOAc to give 5b2. Yield: 82%, mp 172e174 ꢂC; IR (KBr): 3414,
3132, 1614, 1396, 854, 784, 694 cmꢁ1, 1H NMR: (600 MHz, DMSO-
hexyl); 13C NMR (50 MHz, DMSO-d6):
d 163.8, 153.2, 149.6, 138.5,
117.2, 87.5, 85.6, 73.4, 70.6, 61.7, 49.1, 35.4, 32.3 (2C), 25.2, 25.0 (2C),
23.0 (2C); HRMS (ESI): m/z [M þ H]þ calcd for C19H30N5O4S:
424.2013; found: 424.2021.
d6):
d 8.51 (1H, br s, NH), 8.24 (1H, s, H-8), 7.33e7.28 (4H, m, ArH),
4.3.7. 2-Butylthio-N6-cyclohexyladenosine (5a7)
7.21 (1H, t, J ¼ 7.0 Hz, ArH), 5.82 (1H, d, J ¼ 5.9 Hz, H-10), 5.39 (1H, d,
J ¼ 6.1 Hz, OH), 5.15 (1H, d, J ¼ 4.7 Hz, OH), 5.04 (1H, dd, J ¼ 4.2,
4.5 Hz, OH), 4.66 (2H, br s, NCH2), 4.58 (1H, ddd, J ¼ 5.6, 5.9, 6.1 Hz,
H-20), 4.12 (1H, ddd, J ¼ 3.4, 4.7, 5.6 Hz, H-30), 3.91 (1H, ddd, J ¼ 3.4,
4.7, 5.7 Hz, H-40), 3.63 (1H, ddd, J ¼ 4.2, 4.7,12.0 Hz, H-50a), 3.53 (1H,
ddd, J ¼ 4.5, 5.7, 12.0 Hz, H-50b), 3.00 (2H, q, J ¼ 7.3 Hz, SCH2), 1.28
Compound 4e was allowed to react with cyclohexylamine for
9 h according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5a7. Yield: 88%, mp 138e140 ꢂC; IR (KBr): 3317,
3205, 1610, 1400, 1092 cmꢁ1; 1H NMR (400 MHz, DMSO-d6):
d 8.20
(1H, s, H-8), 7.72 (1H, br s, NH), 5.80 (1H, d, J ¼ 5.6 Hz, H-10), 5.40
(1H, d, J ¼ 5.8 Hz, OH), 5.15 (1H, d, J ¼ 4.5 Hz, OH), 5.08 (1H, dd,
J ¼ 4.1, 4.3 Hz, OH), 4.57 (1H, ddd, J ¼ 4.9, 5.6, 5.8 Hz, H-20), 4.12 (1H,
ddd, J ¼ 3.2, 4.5, 4.9 Hz, H-30), 4.03 (1H, br s, NCH), 3.91 (1H, ddd,
J ¼ 3.2, 4.6, 6.0 Hz, H-40), 3.64 (1H, J ¼ 4.3, 4.6, 11.9 Hz, H-50a), 3.53
(1H, J ¼ 4.1, 6.0, 11.9 Hz, H-50b), 3.06 (2H, t, J ¼ 7.3 Hz, SCH2),
1.89e1.74 (4H, m, cyclohexyl), 1.65 (2H, quint, J ¼ 7.3 Hz, SCH2CH2),
1.43 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2CH2), 1.38e1.11 (6H, m, cyclo-
hexyl), 0.92 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
(3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.7, 153.8,
149.7, 140.0, 138.8, 128.2, 127.1, 126.7, 117.3, 87.5, 85.6, 73.4, 70.6,
61.6, 43.1, 24.7, 15.0; HRMS (ESI): m/z [M þ H]þ calcd for
C19H24N5O4S: 418.1544; found: 418.1552.
4.3.11. N6-benzyl-2-propylthioadenosine (5b3)
Compound 4c was allowed to react with benzylamine for 8 h
according to the general procedure. The product was purified by
flash column chromatography (gradient elution separation with
MeOH/EtOAc, 1:50e1:25, v/v), and followed by recrystallization
from EtOAc to give 5b3. Yield: 79%, mp 168e170 ꢂC; IR (KBr): 3420,
d
163.7, 153.2, 149.5, 138.4, 117.2, 87.5, 85.6, 73.3, 70.5, 61.6, 49.0,
32.2, 31.9 (2C), 30.1, 25.2, 25.0 (2C), 21.7, 13.6; HRMS (ESI): m/z
[M þ H]þ calcd for C20H32N5O4S: 438.2170; found: 438.2177.
3196, 1613, 1396, 851, 781, 640 cmꢁ1
d6):
;
1H NMR (600 MHz, DMSO-
d
8.52 (1H, br s, NH), 8.24 (1H, s, H-8), 7.28e7.31 (4H, m, ArH),
4.3.8. N6,N6-dibutyl-2-ethylthioadenosine (5a8)
7.20e7.22 (1H, t, J ¼ 7.0 Hz, ArH), 5.81 (1H, d, J ¼ 5.7 Hz, H-10), 5.40
(1H, d, J ¼ 6.0 Hz, OH), 5.15 (1H, d, J ¼ 4.5 Hz, OH), 5.04 (1H, dd,
J ¼ 4.3, 4.5 Hz, OH), 4.67 (2H, br s, NCH2), 4.59 (1H, ddd, J ¼ 5.4, 5.7,
6.0 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.2, 4.5, 5.4 Hz, H-30), 3.92 (1H, ddd,
J ¼ 3.2, 4.3, 5.8 Hz, H-40), 3.64 (1H, ddd, J ¼ 4.3, 4.3, 11.7 Hz, H-50a),
3.53 (1H, ddd, J ¼ 4.5, 5.8, 11.7 Hz, H-50b), 2.98 (2H, t, J ¼ 7.3 Hz,
SCH2), 1.59 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2), 0.89 (3H, t, J ¼ 7.3 Hz,
Compound 4b was allowed to react with dibutylamine for 14 h
according to the general procedure. The product was purified by
flash column chromatography (gradient elution separation with
EtOAc/petroleum ether, 1:10e1:1, v/v), and followed by recrystal-
lization from hexane to give 5a8. Yield: 58%, mp 88e90 ꢂC; IR (KBr):
3414, 3138, 1575, 1396, 1229 cmꢁ1 1H NMR (400 MHz, DMSO-d6):
;
d
8.24 (1H, s, H-8), 5.82 (1H, d, J ¼ 6.0 Hz, H-10), 5.41 (1H, d,
CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.7, 153.7, 149.6, 139.9,
J ¼ 6.2 Hz, OH), 5.17 (1H, d, J ¼ 4.8 Hz, OH), 5.07 (1H, dd, J ¼ 4.0,
4.6 Hz, OH), 4.55 (1H, ddd, J ¼ 5.3, 6.0, 6.2 Hz, H-20), 4.13 (1H, ddd,
J ¼ 3.4, 4.9, 5.3 Hz, H-30), 4.11e4.01 (2H, m, 2NHH), 3.92 (1H, ddd,
J ¼ 3.4, 4.6, 6.2 Hz, H-40), 3.67 (1H, ddd, J ¼ 4.6, 4.6, 11.8 Hz, H-50a),
3.65e3.55 (2H, m, 2NHH), 3.54 (1H, ddd, J ¼ 4.0, 6.2, 11.8 Hz, H-50b),
3.10 (1H, dq, J ¼ 13.5, 7.3 Hz, SCHH), 3.06 (1H, dq, J ¼ 13.5, 7.3 Hz,
SCHH), 1.62 (4H, quint, J ¼ 7.4 Hz, 2NCH2CH2), 1.34 (4H, sextet,
J ¼ 7.4 Hz, 2NCH2CH2CH2), 1.33 (3H, t, J ¼ 7.3 Hz, SCH2CH3), 0.92
138.8, 128.2, 127.0, 126.6, 117.3, 87.5, 85.5, 73.3, 70.5, 61.6, 43.0, 32.3,
22.7, 13.2; HRMS (ESI): m/z [M þ H]þ calcd for C20H26N5O4S:
432.1700; found: 432.1708.
4.3.12. N6-benzyl-2-butylthioadenosine (5b4)
Compound 4e was allowed to react with benzylamine for 8 h
according to the general procedure. The product was purified by
flash column chromatography (gradient elution separation with
MeOH/EtOAc, 1:50e1:25, v/v), and followed by recrystallization
from EtOAc to give 5b4. Yield: 80%, mp 170e172 ꢂC; IR (KBr): 3372,
(6H, t, J ¼ 7.4 Hz, 2CH3); 13C NMR (50 MHz, CDCl3):
d 163.4, 153.2,
150.1, 137.8, 118.8, 90.5, 86.8, 72.6, 72.5, 63.3, 49.3, 48.4, 31.1, 29.6,
25.4, 20.0 (2C), 14.7, 13.9 (2C); HRMS (ESI): m/z [M þ H]þ calcd for
C20H34N5O5S:440.2326; found: 440.2334.
3308, 3141, 1752, 1614, 1396, 845, 748, 633 cmꢁ1
(600 MHz, DMSO-d6):
;
1H NMR
8.50 (1H, br s, NH), 8.24 (1H, s, H-8),
d
7.28e7.31 (4H, m, ArH), 7.21 (1H, t, J ¼ 7.0 Hz, ArH), 5.81 (1H, d,
J ¼ 5.9 Hz, H-10), 5.39 (1H, d, J ¼ 6.0 Hz, OH), 5.14 (1H, d, J ¼ 4.7 Hz,
OH), 5.04 (1H, dd, J ¼ 4.3, 4.5 Hz, OH), 4.67 (2H, br s, NCH2), 4.59
(1H, ddd, J ¼ 5.5, 5.9, 6.1 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.6, 4.7, 5.5 Hz,
H-30), 3.92 (1H, ddd, J ¼ 3.6, 4.6, 5.4 Hz, H-40), 3.64 (1H, ddd, J ¼ 4.3,
4.6, 11.8 Hz, H-50a), 3.53 (1H, ddd, J ¼ 4.5, 5.4, 11.8 Hz, H-50b), 3.00
(2H, t, J ¼ 7.3 Hz, SCH2), 1.56 (2H, quint, J ¼ 7.3 Hz, SCH2CH2), 1.32
4.3.9. N6-benzyl-2-methylthioadenosine (5b1) [28]
Compound 4a was allowed to react with benzylamine for 8 h
according to the general procedure. The product was purified by
flash column chromatography (gradient elution separation with
MeOH/EtOAc, 1:50e1:25, v/v), and followed by recrystallization
from EtOAc to give 5b1. Yield: 83%, mp 180e182 ꢂC; IR (KBr): 3442,
3138, 2986, 1653, 1140, 864, 787, 620 cmꢁ1
;
1H NMR: (300 MHz,
8.55 (1H, br s, NH), 8.25 (1H, s, H-8), 7.33e7.27 (4H, m,
(2H, sextet, J ¼ 7.3 Hz, SCH2CH2CH2), 0.89 (3H, t, J ¼ 7.3 Hz, CH3); 13
C
DMSO-d6):
d
NMR (75 MHz, DMSO-d6): d 163.8, 153.7, 149.6, 139.9, 138.8, 128.2,
ArH), 7.22 (1H, t, J ¼ 7.0 Hz, ArH), 5.83 (1H, d, J ¼ 6.0 Hz, H-10), 5.44
(1H, d, J ¼ 6.2 Hz, OH), 5.20 (1H, d, J ¼ 4.9 Hz, OH), 5.06 (1H, dd,
J ¼ 4.5, 4.7 Hz, OH), 4.67 (2H, br s, NCH2), 4.59 (1H, ddd, J ¼ 5.2, 6.0,
127.0, 126.6, 117.3, 87.5, 85.6, 73.3, 70.5, 61.6, 42.9, 31.5, 30.1, 21.5,
13.5; HRMS (ESI): m/z [M þ H]þ calcd for C21H28N5O4S: 446.1857;
found: 446.1865.

120
G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
4.3.13. N6-(4-methylbenzyl)-2-methylthioadenosine (5b5) [29]
Compound 4a was allowed to react with 4-methylbenzylamine
for 9 h according to the general procedure. The product was puri-
fied by flash column chromatography, and followed by recrystalli-
zation from EtOAc to give 5b5. Yield: 83%, mp 188e190 ꢂC; IR (KBr):
J ¼ 4.6, 5.4, 11.9 Hz, H-5b0), 3.04 (2H, q, J ¼ 7.3 Hz, SCH2), 1.26 (3H, t,
J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.7, 158.1, 153.8,
149.6,138.7,131.9,128.5,117.3,113.6, 87.5, 85.6, 73.4, 70.6, 61.6, 55.0,
42.5, 24.7, 15.0; HRMS (ESI): m/z [M þ H]þ calcd for C20H26N5O5S:
448.1649; found: 448.1648.
3445, 3333, 2986, 1616, 1392, 1126, 858, 787, 618 cmꢁ1
;
1H NMR
8.49 (1H, br s, NH), 8.24 (1H, s, H-8), 7.22
(300 MHz, DMSO-d6):
d
4.3.17. N6-(4-methoxybenzyl)-2-propylthioadenosine (5b9)
(2H, d, J ¼ 8.0 Hz, ArH), 7.10 (2H, d, J ¼ 8.0 Hz, ArH), 5.83 (1H, d,
J ¼ 5.9 Hz, H-10), 5.43 (1H, d, J ¼ 6.2 Hz, OH), 5.19 (1H, d, J ¼ 4.8 Hz,
OH), 5.05 (1H, dd, J ¼ 5.4, 6.0 Hz, OH), 4.61 (2H, br s, NCH2), 4.58
(1H, ddd, J ¼ 5.9, 6.1, 6.2 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.4, 4.8, 6.1 Hz,
H-30), 3.91 (1H, ddd, J ¼ 3.4, 4.4, 4.6 Hz, H-40), 3.66 (1H, ddd, J ¼ 4.6,
5.4, 11.9 Hz, H-5a0), 3.54 (1H, ddd, J ¼ 4.4, 6.0, 11.9 Hz, H-5b0), 2.44
(3H, s, CH3), 2.25 (3H, s, PhCH3); 13C NMR (75 MHz, DMSO-d6):
Compound
4c
was
allowed
to
react
with
4-
methoxybenzylamine for 11 h according to the general procedure.
The product was purified by flash column chromatography, and
followed by recrystallization from EtOAc to give 5b9. Yield: 81%, mp
152e154 ꢂC; IR (KBr): 3436, 3333, 3119, 1610, 1399, 810, 781,
672 cmꢁ1; 1H NMR (200 MHz, DMSO-d6):
d 8.46 (1H, br s, NH), 8.25
(1H, s, H-8), 7.26 (2H, d, J ¼ 8.6 Hz, ArH), 6.86 (2H, d, J ¼ 8.6 Hz,
ArH), 5.84 (1H, d, J ¼ 6.0 Hz, H-10), 5.47 (1H, d, J ¼ 6.1 Hz, OH), 5.22
(1H, d, J ¼ 4.8 Hz, OH), 5.14 (1H, dd, J ¼ 5.2, 5.7 Hz, OH), 4.61 (2H, br
s, NCH2), 4.58 (1H, ddd, J ¼ 5.8, 6.0, 6.1 Hz, H-20), 4.16 (1H, ddd,
J ¼ 3.4, 4.8, 5.8 Hz, H-30), 3.95 (1H, ddd, J ¼ 3.4, 3.9, 4.6 Hz, H-40),
3.70 (3H, s, OCH3), 3.65 (1H, ddd, J ¼ 4.6, 5.2, 11.9 Hz, H-5a0), 3.57
(1H, ddd, J ¼ 3.9, 5.7, 11.9 Hz, H-5b0), 3.02 (2H, t, J ¼ 7.3 Hz, SCH2),
1.63 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2), 0.92 (3H, t, J ¼ 7.3 Hz, CH3);
d
164.2, 153.7, 149.6, 138.8, 136.9, 135.7, 128.8, 127.3, 117.3, 87.4, 85.6,
73.4, 70.6, 61.6, 42.8, 20.7, 13.9.
4.3.14. 2-Ethylthio-N6-(4-Methylbenzyl)adenosine (5b6)
Compound 4b was allowed to react with 4-methylbenzylamine
for 9 h according to the general procedure. The product was puri-
fied by flash column chromatography, and followed by recrystalli-
zation from EtOAc to give 5b6. Yield: 79%, mp 184e186 ꢂC; IR (KBr):
3411, 3321, 3141, 1614, 1345, 854, 776, 627 cmꢁ1; 1H NMR (600 MHz,
13C NMR (50 MHz, DMSO-d6):
d 163.9, 158.2, 153.8, 149.7, 138.9,
131.9, 128.5, 117.4, 113.7, 87.6, 85.7, 73.4, 70.6, 61.7, 55.1, 42.5, 32.4,
22.8, 13.4; HRMS (ESI): m/z [M þ H]þ calcd for C21H28N5O5S:
462.1806; found: 462.1812.
DMSO-d6):
d 8.48 (1H, br s, NH), 8.23 (1H, s, H-8), 7.21 (2H, d,
J ¼ 7.9 Hz, ArH), 7.10 (2H, d, J ¼ 7.9 Hz, ArH), 5.81 (1H, d, J ¼ 5.9 Hz, H-
10), 5.43 (1H, d, J ¼ 6.1 Hz, OH), 5.18 (1H, d, J ¼ 4.8 Hz, OH), 5.07 (1H,
dd, J ¼ 4.9, 5.2 Hz, OH), 4.61 (2H, brs, NCH2), 4.58(1H, ddd, J ¼ 5.6, 5.9,
6.1 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.5, 4.8, 5.6 Hz, H-30), 3.91 (1H, ddd,
J ¼ 3.2, 3.9, 5.6 Hz, H-40), 3.63 (1H, ddd, J ¼ 3.9, 4.9, 11.8 Hz, H-5a0),
3.52(1H, ddd, J ¼ 5.2, 5.6,11.8 Hz, H-5b0), 3.01 (2H, q, J ¼ 7.3 Hz, SCH2),
2.25 (3H, s, PhCH3), 1.24 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz,
4.3.18. 2-Methylthio-N6-phenethyladenosine (5b10
)
Compound 4a was allowed to react with phenethylamine for 9 h
according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5b10. Yield: 85%, mp 156e158 ꢂC; IR (KBr): 3349,
DMSO-d6):
d
163.8, 153.8, 149.7, 138.9, 136.9, 135.7, 128.8, 127.2, 117.3,
3132, 2920, 1613, 1399, 858, 781, 634 cmꢁ1
;
1H NMR (300 MHz,
87.6, 85.6, 73.4, 70.6, 61.7, 42.9, 24.8, 20.7, 15.0; HRMS (ESI): m/z
DMSO-d6): d 8.22 (1H, s, H-8), 8.02 (1H, br s, NH), 7.30e7.25 (3H, m,
[M þ H]þ calcd for C20H26N5O4S: 432.1700; found: 432.1708.
ArH), 7.20e7.17 (2H, m, ArH), 5.83 (1H, d, J ¼ 5.6 Hz, H-10), 5.45 (1H,
d, J ¼ 5.5 Hz, OH), 5.20 (1H, d, J ¼ 4.2 Hz, OH), 5.08 (1H, dd, J ¼ 5.0,
5.4 Hz, OH), 4.60 (1H, ddd, J ¼ 5.4, 5.5, 5.6 Hz, H-20), 4.14 (1H, ddd,
J ¼ 3.4, 4.2, 4.6 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.4, 4.5, 4.9 Hz, H-40),
3.78e3.65 (2H, m, NCH2), 3.63 (1H, ddd, J ¼ 4.6, 5.0, 11.9 Hz, H-50a),
3.54 (1H, ddd, J ¼ 4.2, 5.4, 11.9 Hz, H-50b), 2.90 (2H, t, J ¼ 7.6 Hz,
4.3.15. N6-(4-methoxybenzyl)-2-methylthioadenosine (5b7) [29]
Compound
4a
was
allowed
to
react
with
4-
methoxybenzylamine for 11 h according to the general procedure.
The product was purified by flash column chromatography, and
followed by recrystallization from EtOAc to give 5b7. Yield: 80%, mp
200e202 ꢂC; IR (KBr): 3447, 3324, 2984, 1616, 1392, 1125, 859, 785,
NCH2CH2), 2.50 (3H, s, SCH3); 13C NMR (75 MHz, DMSO-d6):
d 164.2,
153.8, 149.5, 139.8, 138.6, 128.6, 128.3, 126.1, 117.2, 87.3, 85.5, 73.4,
70.5, 61.6, 41.4, 35.0, 13.9; HRMS (ESI): m/z [M þ H]þ calcd for
C19H24N5O4S: 418.1544; found: 418.1552.
618 cmꢁ1; 1H NMR (300 MHz, DMSO-d6):
d 8.48 (1H, br s, NH), 8.24
(1H, s, H-8), 7.27 (2H, d, J ¼ 8.6 Hz, ArH), 6.86 (2H, d, J ¼ 8.6 Hz,
ArH), 5.82 (1H, d, J ¼ 6.0 Hz, H-10), 5.43 (1H, d, J ¼ 6.0 Hz, OH), 5.19
(1H, d, J ¼ 5.5 Hz, OH), 5.05 (1H, dd, J ¼ 5.7, 5.8 Hz, OH), 4.60 (2H, br
s, NCH2), 4.58 (1H, ddd, J ¼ 5.9, 6.0, 6.0 Hz, H-20), 4.14 (1H, ddd,
J ¼ 4.0, 5.5, 5.9 Hz, H-30), 3.91 (1H, ddd, J ¼ 3.8, 4.0, 4.5 Hz, H-40),
3.70 (3H, s, OCH3), 3.60 (1H, ddd, J ¼ 4.5, 5.7, 11.8 Hz, H-5a0), 3.53
(1H, ddd, J ¼ 4.0, 5.8, 11.8 Hz, H-5b0), 2.46 (3H, s, SCH3); 13C NMR
4.3.19. 2-Ethylthio-N6-phenethyladenosine (5b11
)
Compound 4b was allowed to react with phenethylamine for 9 h
according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5b11. Yield: 84%, mp 130e132 ꢂC; IR (KBr): 3426,
(75 MHz, DMSO-d6):
d
164.2, 158.2, 153.6, 149.6, 138.8, 131.9, 128.7,
;
3330, 3119, 1612, 1399, 864, 778, 701 cmꢁ1 1H NMR (400 MHz,
117.3, 113.6, 87.4, 85.6, 73.4, 70.6, 61.6, 55.0, 42.5, 14.0.
DMSO-d6): d 8.22 (1H, s, H-8), 8.02 (1H, br s, NH), 7.32e7.18 (5H, m,
ArH), 5.81 (1H, d, J ¼ 5.7 Hz, H-10), 5.42 (1H, d, J ¼ 6.1 Hz, OH), 5.17
(1H, d, J ¼ 4.8 Hz, OH), 5.07 (1H, dd, J ¼ 5.0, 5.4 Hz, OH), 4.58 (1H,
ddd, J ¼ 5.6, 5.7, 6.1 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.5, 4.8, 5.6 Hz, H-
30), 3.92 (1H, ddd, J ¼ 3.5, 4.3, 4.8 Hz, H-40), 3.75e3.65 (2H, m,
NCH2), 3.63 (1H, ddd, J ¼ 4.8, 5.0, 11.9 Hz, H-50a), 3.53 (1H, ddd,
J ¼ 4.3, 5.4, 11.9 Hz, H-50b), 3.11 (2H, q, J ¼ 7.3 Hz, SCH2), 2.91 (2H, t,
J ¼ 7.0 Hz, NCH2CH2), 1.34 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz,
4.3.16. 2-Ethylthio-N6-(4-methoxybenzyl)adenosine (5b8)
Compound
4b
was
allowed
to
react
with
4-
methoxybenzylamine for 11 h according to the general procedure.
The product was purified by flash column chromatography, and
followed by recrystallization from EtOAc to give 5b8. Yield: 80%, mp
164e166 ꢂC; IR (KBr): 3433, 3324, 3135, 1617, 1402, 858, 778,
675 cmꢁ1; 1H NMR (300 MHz, DMSO-d6):
d
8.48 (1H, br s, NH), 8.23
DMSO-d6): d 163.7, 153.8, 149.6, 139.4, 138.6, 128.6, 128.3, 126.1,
(1H, s, H-8), 7.21 (2H, d, J ¼ 7.9 Hz, ArH), 7.09 (2H, d, J ¼ 7.9 Hz, ArH),
5.81 (1H, d, J ¼ 5.9 Hz, H-10), 5.40 (1H, d, J ¼ 6.0 Hz, OH), 5.21 (1H, d,
J ¼ 4.7 Hz, OH), 5.10 (1H, dd, J ¼ 5.3, 5.4 Hz, OH), 4.63 (2H, br s,
NCH2), 4.60 (1H, ddd, J ¼ 5.2, 5.9, 6.1 Hz, H-20), 4.16 (1H, ddd, J ¼ 3.4,
4.7, 5.2 Hz, H-30), 3.94 (1H, ddd, J ¼ 3.4, 4.4, 4.6 Hz, H-40), 3.70 (3H, s,
OCH3), 3.64 (1H, ddd, J ¼ 4.4, 5.3, 11.9 Hz, H-5a0), 3.55 (1H, ddd,
117.3, 87.4, 85.6, 73.4, 70.5, 61.6, 41.4, 35.1, 24.7, 15.1; HRMS (ESI): m/
z [M þ H]þ calcd for C20H26N5O4S: 432.1700; found: 432.1706.
4.3.20. N6-phenethyl-2-propylthioadenosine (5b12
)
Compound 4c was allowed to react with phenethylamine for 9 h
according to the general procedure. The product was purified by

G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
121
flash column chromatography, and followed by recrystallization
from EtOAc to give 5b12. Yield: 80%, mp 110e112 ꢂC; IR (KBr): 3430,
30), 3.93 (1H, ddd, J ¼ 3.5, 4.1, 4.7 Hz, H-40), 3.75e3.65 (2H, m,
NCH2), 3.63 (1H, ddd, J ¼ 4.9, 5.3, 11.8 Hz, H-50a), 3.54 (1H, ddd,
J ¼ 4.1, 5.8, 11.8 Hz, H-50b), 2.89 (2H, t, J ¼ 7.0 Hz, NCH2CH2); 13C
3330, 3129, 1612, 1391, 906, 738, 697 cmꢁ1 1H NMR (300 MHz,
;
DMSO-d6):
d
8.22 (1H, s, H-8), 8.03 (1H, br s, NH), 7.32e7.26 (3H, m,
NMR (50 MHz, DMSO-d6): d 163.3, 153.8, 149.4, 139.4, 138.6, 128.8,
ArH), 7.24e7.17 (2H, m, ArH), 5.82 (1H, d, J ¼ 5.9 Hz, H-10), 5.44 (1H,
d, J ¼ 6.2 Hz, OH), 5.18 (1H, d, J ¼ 4.8 Hz, OH), 5.10 (1H, dd, J ¼ 5.2,
5.5 Hz, OH), 4.59 (1H, ddd, J ¼ 5.4, 5.9, 6.2 Hz, H-20), 4.14 (1H, ddd,
J ¼ 3.5, 4.2, 4.8 Hz, H-30), 3.93 (1H, ddd, J ¼ 3.5, 4.6, 5.2 Hz, H-40),
3.76e3.65 (2H, m, NCH2), 3.63 (1H, ddd, J ¼ 4.6, 5.2, 11.9 Hz, H-50a),
3.54 (1H, ddd, J ¼ 4.2, 5.5, 11.9 Hz, H-50b), 3.09 (2H, t, J ¼ 7.3 Hz,
SCH2), 2.91 (2H, t, J ¼ 7.0 Hz, NCH2CH2), 1.70 (2H, sextet, J ¼ 7.3 Hz,
SCH2CH2), 0.97 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (75 MHz, DMSO-
128.6, 128.3, 126.8, 126.1, 117.4, 87.3, 85.5, 73.6, 70.5, 61.5, 41.5, 35.0,
34.5; HRMS (ESI): m/z [M þ H]þ calcd for C25H28N5O4S: 494.1857;
found: 494.1860.
4.3.24. N6-(4-methoxyphenethyl)-2-methylthioadenosine (5b16
Compound 4a was allowed to react with
)
4-
methoxyphenethylamine for 12 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b16. Yield:
82%, mp 152e154 ꢂC; IR (KBr): 3433, 3327, 3129, 1611, 1400, 858,
d6): d 163.8, 153.8, 149.5, 139.4, 138.6, 128.6, 128.3, 126.1, 117.3, 87.4,
85.5, 73.3, 70.5, 61.6, 41.4, 35.0, 32.4, 22.8, 13.3; HRMS (ESI): m/z
[M þ H]þ calcd for C21H28N5O4S: 446.1857; found: 446.1865.
784, 631 cmꢁ1 1H NMR (400 MHz, DMSO-d6):
; d 8.22 (1H, s, H-8),
7.98 (1H, br s, NH), 7.16 (2H, d, J ¼ 7.9 Hz, ArH), 6.85 (2H, d,
J ¼ 8.5 Hz, ArH), 5.83 (1H, d, J ¼ 5.8 Hz, H-10), 5.42 (1H, d, J ¼ 6.2 Hz,
OH), 5.18 (1H, d, J ¼ 4.8 Hz, OH), 5.05 (1H, dd, J ¼ 5.5, 6.0 Hz, OH),
4.60 (1H, ddd, J ¼ 5.4, 5.8, 6.2 Hz, H-20), 4.14 (1H, ddd, J ¼ 3.5, 4.8,
5.4 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.5, 4.3, 4.6 Hz, H-40), 3.71 (3H, s,
OCH3), 3.65 (1H, ddd, J ¼ 4.6, 5.5, 11.8 Hz, H-50a), 3.64e3.58 (2H, m,
NCH2), 3.54 (1H, ddd, J ¼ 4.3, 6.0, 11.8 Hz, H-50b), 2.85 (2H, t,
J ¼ 7.4 Hz, NCH2CH2), 2.51 (3H, s, SCH3); 13C NMR (50 MHz, DMSO-
4.3.21. 2-Butylthio-N6-phenethyladenosine (5b13
)
Compound 4e was allowed to react with phenethylamine for 9 h
according to the general procedure. The product was purified by
flash column chromatography, and followed by recrystallization
from EtOAc to give 5b13. Yield: 81%, mp 124e126 ꢂC; IR (KBr): 3340,
3112, 2927, 1613, 1348, 784, 711, 632 cmꢁ1
DMSO-d6):
;
1H NMR (400 MHz,
8.20 (1H, s, H-8), 8.01 (1H, br s, NH), 7.31e7.26 (3H, m,
d
ArH), 7.25e7.18 (2H, m, ArH), 5.80 (1H, d, J ¼ 5.6 Hz, H-10), 5.41 (1H,
d, J ¼ 6.1 Hz, OH), 5.16 (1H, d, J ¼ 4.7 Hz, OH), 5.07 (1H, dd, J ¼ 5.7,
5.8 Hz, OH), 4.57 (1H, ddd, J ¼ 5.6, 5.7, 6.1 Hz, H-20), 4.12 (1H, ddd,
J ¼ 3.7, 4.7, 5.7 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.7, 4.6, 5.8 Hz, H-40),
3.76e3.65 (2H, m, NCH2), 3.61 (1H, ddd, J ¼ 4.6, 5.7, 11.4 Hz, H-50a),
3.53 (1H, ddd, J ¼ 5.0, 5.8, 11.4 Hz, H-50b), 3.10 (2H, t, J ¼ 7.3 Hz,
SCH2), 2.91 (2H, t, J ¼ 7.5 Hz, NCH2CH2), 1.66 (2H, quint, J ¼ 7.3 Hz,
SCH2CH2), 1.41 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2CH2), 0.89 (3H, t,
d6): d 164.3, 157.7, 153.8, 149.5, 138.7, 131.4, 129.7, 117.3, 113.9, 87.5,
85.6, 73.5, 70.6, 61.7, 55.0, 41.8, 34.2, 14.0; HRMS (ESI): m/z [M þ H]þ
calcd for C20H26N5O5S: 448.1649; found: 448.1655.
4.3.25. 2-Ethylthio-N6-(4-methoxyphenethyl)adenosine (5b17
Compound 4b was allowed to react with
)
4-
methoxyphenethylamine for 12 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b17. Yield:
81%, mp 140e142 ꢂC; IR (KBr): 3340, 3119, 2920, 1614, 1399, 793,
J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.8, 153.8, 149.5,
139.4, 138.6, 128.6, 128.3, 126.1, 117.3, 87.5, 85.6, 73.4, 70.6, 61.6,
41.4, 35.1, 31.6, 30.2, 21.6, 13.6; HRMS (ESI): m/z [M þ H]þ calcd for
C22H30N5O4S: 460.2013; found: 460.2021.
787, 627 cmꢁ1 1H NMR (400 MHz, DMSO-d6):
; d 8.21 (1H, s, H-8),
7.99 (1H, br s, NH), 7.15 (2H, d, J ¼ 8.0 Hz, ArH), 6.86 (2H, d,
J ¼ 8.6 Hz, ArH), 5.81 (1H, d, J ¼ 5.9 Hz, H-10), 5.42 (1H, d, J ¼ 6.2 Hz,
OH), 5.22 (1H, d, J ¼ 4.8 Hz, OH), 5.18 (1H, dd, J ¼ 5.5, 6.2 Hz, OH),
4.58 (1H, ddd, J ¼ 5.4, 5.9, 6.2 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.4, 4.8,
5.4 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.4, 4.2, 4.6 Hz, H-40), 3.70 (3H, s,
OCH3), 3.65 (1H, ddd, J ¼ 4.6, 5.5, 11.9 Hz, H-50a), 3.63e3.57 (2H, m,
NHCH2), 3.54 (1H, ddd, J ¼ 4.2, 6.2, 11.9 Hz, H-50b), 3.11 (2H, q,
J ¼ 7.3 Hz, SCH2), 2.84 (2H, t, J ¼ 7.1 Hz, NCH2CH2), 1.34 (3H, t,
4.3.22. N6-phenethyl-2-phenylthioadenosine (5b14
)
Compound 4f was allowed to react with phenethylamine for 15 h
according tothegeneralprocedure. The product was purified by flash
column chromatography, and followed by recrystallization from
EtOAc to give 5b14. Yield: 75%, mp 134e136 ꢂC; IR (KBr): 3444, 3112,
2991,1635,1392,1137, 861, 790, 617 cmꢁ1; 1H NMR(600 MHz, DMSO-
d6):
d
8.22 (1H, s, H-8), 8.02 (1H, br s, NH), 7.63e7.62 (2H, m, ArH),
J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.7, 157.7, 153.9,
7.42e7.41 (3H, m, ArH), 7.26 (2H, t, J ¼ 7.3 Hz, ArH), 7.18 (1H, t,
J ¼ 7.2 Hz, ArH), 7.00 (2H, d, J ¼ 7.2 Hz, ArH), 5.76 (1H, d, J ¼ 5.8 Hz, H-
10), 5.39 (1H, d, J ¼ 6.0 Hz, OH), 5.11 (1H, d, J ¼ 4.3 Hz, OH), 5.01 (1H,
dd, J ¼ 4.9, 5.0 Hz, OH), 4.56 (1H, ddd, J ¼ 5.7, 5.8, 6.0 Hz, H-20), 4.03
(1H, br s, H-30), 3.89 (1H, br s, H-40), 3.55 (1H, ddd, J ¼ 4.3, 4.9,11.8 Hz,
H-50a), 3.45 (1H, ddd, J ¼ 5.0, 5.5, 11.8 Hz, H-50b), 3.42e3.37 (2H, m,
NCH2), 2.67 (2H, t, J ¼ 7.2 Hz, NCH2CH2); 13C NMR (75 MHz, DMSO-
149.5, 138.7, 131.3, 129.6, 117.4, 113.8, 87.6, 85.7, 73.5, 70.6, 61.7, 55.0,
41.8, 34.3, 24.8, 15.1; HRMS (ESI): m/z [M þ H]þ calcd for
C21H28N5O5S: 462.1806; found: 462.1810.
4.3.26. N6-(4-methoxyphenethyl)-2-propylthioadenosine (5b18
Compound 4c was allowed to react with
)
4-
methoxyphenethylamine for 12 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b18. Yield:
83%, mp 170e172 ꢂC; IR (KBr): 3430, 3344, 3133, 1617, 1400, 781,
d6): d 163.4, 153.9, 149.4, 139.3, 139.1, 135.0, 130.7, 128.9, 128.7, 128.2,
126.0, 117.8, 87.6, 85.7, 73.2, 70.5, 61.6, 41.1, 34.9; HRMS (ESI): m/z
[M þ H]þ calcd for C24H26N5O4S: 480.1700; found: 480.1715.
697, 633 cmꢁ1 1H NMR (300 MHz, DMSO-d6):
; d 8.21 (1H, s, H-8),
4.3.23. 2-Benzylthio-N6-phenethyladenosine (5b15
)
8.00 (1H, br s, NH), 7.15 (2H, d, J ¼ 8.0 Hz, ArH), 6.85 (2H, d,
J ¼ 8.0 Hz, ArH), 5.81 (1H, d, J ¼ 5.8 Hz, H-10), 5.42 (1H, d, J ¼ 5.8 Hz,
OH), 5.17 (1H, d, J ¼ 4.6 Hz, OH), 5.08 (1H, br s, OH), 4.59 (1H, ddd,
J ¼ 5.3, 5.8, 5.8 Hz, H-20), 4.13 (1H, br s, H-30), 3.92 (1H, ddd, J ¼ 3.5,
4.6, 5.6 Hz, H-40), 3.71 (3H, s, OCH3), 3.64e3.48 (4H, m, NCH2 þ H-
50a þ H-50b), 3.09 (2H, t, J ¼ 7.3 Hz, SCH2), 2.84 (2H, t, J ¼ 7.5 Hz,
NCH2CH2), 1.70 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2), 0.98 (3H, t,
Compound 4g was allowed to react with phenethylamine for
12 h according to the general procedure. The product was purified
by flash column chromatography, and followed by recrystallization
from EtOAc to give 5b15. Yield: 78%, mp 262e264 ꢂC; IR (KBr): 3436,
3112, 2991, 1635, 1397, 1139, 858, 778, 619 cmꢁ1
;
1H NMR
(300 MHz, DMSO-d6):
d 8.25 (1H, s, H-8), 8.10 (1H, br s, NH), 7.43
(2H, d, J ¼ 7.1 Hz, ArH), 7.32e7.18 (8H, m, ArH), 5.85 (1H, d,
J ¼ 5.8 Hz, H-10), 5.45 (1H, d, J ¼ 6.2 Hz, OH), 5.22 (1H, d, J ¼ 4.9 Hz,
OH), 5.10 (1H, dd, J ¼ 5.3, 5.8 Hz, OH), 4.55 (1H, ddd, J ¼ 5.3, 5.8,
6.2 Hz, H-20), 4.43 (2H, s, SCH2), 4.12 (1H, ddd, J ¼ 3.5, 4.1, 4.9 Hz, H-
J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.8, 157.7, 153.7,
149.4, 138.6, 131.3, 129.5, 117.2, 113.8, 87.4, 85.6, 73.3, 70.5, 61.6,
54.9, 41.6, 34.1, 32.4, 22.7, 13.3; HRMS (ESI): m/z [M þ H]þ calcd for
C22H30N5O5S: 476.1962; found: 476.1960.

122
G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
4.3.27. 2-Butylthio-N6-(4-methoxyphenethyl)adenosine (5b19
Compound 4e was allowed to react with
)
76%, mp 120e122 ꢂC; IR (KBr): 3459, 3132, 2920, 1614, 1578, 1399,
867, 781, 691 cmꢁ1; 1H NMR (300 MHz, DMSO-d6):
8.22 (1H, s, H-
4-
d
methoxyphenethylamine for 12 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b19. Yield:
80%, mp 122e124 ꢂC; IR (KBr): 3433, 3334, 3122, 1604, 1399, 822,
8), 8.01 (1H, br s, NH), 7.20 (1H, t, J ¼ 8.0 Hz, ArH), 6.82e6.75 (3H, m,
ArH), 5.81 (1H, d, J ¼ 5.9 Hz, H-10), 5.43 (1H, d, J ¼ 6.1 Hz, OH), 5.18
(1H, d, J ¼ 4.8 Hz, OH), 5.09 (1H, dd, J ¼ 4.8, 4.9 Hz, OH), 4.60 (1H,
ddd, J ¼ 5.7, 5.9, 6.1 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.4, 4.8, 5.7 Hz, H-
30), 3.92 (1H, ddd, J ¼ 3.3, 4.0, 4.5 Hz, H-40), 3.72 (3H, s, OCH3),
3.69e3.64 (2H, m, NCH2), 3.62 (1H, ddd, J ¼ 4.5, 4.8, 11.5 Hz, H-50a),
3.51 (1H, ddd, J ¼ 4.0, 4.9, 11.5 Hz, H-50b), 3.09 (2H, t, J ¼ 7.3 Hz,
SCH2), 2.89 (2H, t, J ¼ 7.0 Hz, NCH2CH2), 1.68 (2H, sextet, J ¼ 7.3 Hz,
SCH2CH2), 0.98 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-
781, 701 cmꢁ1 1H NMR (400 MHz, DMSO-d6):
; d 8.21 (1H, s, H-8),
7.98 (1H, br s, NH), 7.15 (2H, d, J ¼ 8.0 Hz, ArH), 6.85 (2H, d,
J ¼ 8.2 Hz, ArH), 5.80 (1H, d, J ¼ 5.8 Hz, H-10), 5.41 (1H, d, J ¼ 6.1 Hz,
OH), 5.16 (1H, d, J ¼ 4.8 Hz, OH), 5.07 (1H, dd, J ¼ 4.8, 5.2 Hz, OH),
4.58 (1H, ddd, J ¼ 5.2, 5.8, 6.1 Hz, H-20), 4.13 (1H, ddd, J ¼ 3.8, 4.8,
5.2 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.8, 4.3, 4.6 Hz, H-40), 3.71 (3H, s,
OCH3), 3.66 (1H, ddd, J ¼ 4.3, 4.8, 11.1 Hz, H-50a), 3.63e3.58 (2H, m,
NCH2), 3.53 (1H, ddd, J ¼ 4.6, 5.2, 11.1 Hz, H-50b), 3.10 (2H, t,
J ¼ 7.3 Hz, SCH2), 2.84 (2H, t, J ¼ 7.4 Hz, NCH2CH2), 1.67 (2H, quint,
J ¼ 7.3 Hz, SCH2CH2), 1.41 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2CH2), 0.89
d6): d 163.8, 159.3, 153.8, 149.5, 141.0, 138.6, 129.3, 120.9, 117.4, 114.3,
111.6, 87.5, 85.6, 73.4, 70.6, 61.6, 54.9, 41.3, 35.1, 32.4, 22.8, 13.3;
HRMS (ESI): m/z [M þ H]þ calcd for C22H30N5O5S: 476.1962; found:
476.1968.
(3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (75 MHz, DMSO-d6):
d
163.8, 157.7,
4.3.31. 2-Butylthio-N6-(3-methoxyphenethyl)adenosine (5b23
Compound 4e was allowed to react with
)
153.8, 149.5, 138.6, 131.3, 129.5, 117.2, 113.7, 87.4, 85.6, 73.3, 70.6,
61.6, 54.9, 41.6, 34.1, 31.5, 30.2, 21.5, 13.6; HRMS (ESI): m/z [M þ H]þ
calcd for C23H32N5O5S: 490.2119; found: 4890.2125.
3-
methoxyphenethylamine for 11 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b23. Yield:
81%, mp 124e126 ꢂC; IR (KBr): 3429, 3330, 3129, 1611, 1396, 1338,
4.3.28. N6-(3-methoxyphenethyl)-2-methylthioadenosine (5b20
Compound 4a was allowed to react with
)
3-
781, 700, 637 cmꢁ1; 1H NMR (400 MHz, DMSO-d6):
d 8.21 (1H, s, H-
methoxyphenethylamine for 11 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b20. Yield:
82%, mp 164e166 ꢂC; IR (KBr): 3425, 3336, 3124, 1619, 1400, 1253,
8), 8.00 (1H, br s, NH), 7.21 (1H, t, J ¼ 8.0 Hz, ArH), 6.80e6.75 (3H, m,
ArH), 5.81 (1H, d, J ¼ 5.7 Hz, H-10), 5.41 (1H, d, J ¼ 6.1 Hz, OH), 5.15
(1H, d, J ¼ 4.8 Hz, OH), 5.06 (1H, dd, J ¼ 4.6, 4.7 Hz, OH), 4.37 (1H,
ddd, J ¼ 5.6, 5.7, 6.1 Hz, H-20), 4.12 (1H, ddd, J ¼ 3.7, 4.8, 5.6 Hz, H-
30), 3.92 (1H, ddd, J ¼ 3.7, 4.2, 5.1 Hz, H-40), 3.72 (3H, s, OCH3),
3.71e3.64 (2H, m, NCH2), 3.63 (1H, ddd, J ¼ 4.2, 4.6, 11.2 Hz, H-50a),
3.53 (1H, ddd, J ¼ 4.7, 5.5, 11.2 Hz, H-50b), 3.11 (2H, t, J ¼ 7.3 Hz,
SCH2), 2.89 (2H, t, J ¼ 7.1 Hz, NCH2CH2), 1.66 (2H, quint, J ¼ 7.3 Hz,
SCH2CH2), 1.41 (2H, sextet, J ¼ 7.3 Hz, SCH2CH2CH2), 0.89 (3H, t,
783, 752, 675 cmꢁ1; 1H NMR (300 MHz, DMSO-d6):
d 8.22 (1H, s, H-
8), 8.02 (1H, br s, NH), 7.19 (1H, t, J ¼ 8.0 Hz, ArH), 6.82e6.74 (3H, m,
ArH), 5.82 (1H, d, J ¼ 5.8 Hz, H-10), 5.42 (1H, d, J ¼ 6.2 Hz, OH), 5.18
(1H, d, J ¼ 4.8 Hz, OH), 5.05 (1H, dd, J ¼ 5.0, 5.2 Hz, OH), 4.58 (1H,
ddd, J ¼ 5.5, 5.8, 6.2 Hz, H-20), 4.14 (1H, ddd, J ¼ 3.5, 4.8, 5.5 Hz, H-
30), 3.91 (1H, ddd, J ¼ 3.5, 4.2, 4.6 Hz, H-40), 3.71 (3H, s, OCH3),
3.68e3.64 (2H, m, NCH2), 3.62 (1H, ddd, J ¼ 4.2, 5.0, 11.6 Hz, H-50a),
3.53 (1H, ddd, J ¼ 4.6, 5.2, 11.6 Hz, H-50b), 2.88 (2H, t, J ¼ 7.2 Hz,
J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz, DMSO-d6):
d 163.8, 159.3, 153.8,
149.4, 141.0, 138.6, 129.3, 120.8, 117.3, 114.2, 111.5, 87.4, 85.5, 73.3,
70.5, 61.6, 54.8, 41.2, 35.0, 31.5, 30.1, 21.5, 13.6; HRMS (ESI): m/z
[M þ H]þ calcd for C23H32N5O5S: 490.2119; found: 490.2128.
NCH2CH2), 2.50 (3H, s, SCH3); 13C NMR (50 MHz, DMSO-d6):
d 164.2,
159.3, 153.7, 149.4, 141.0, 138.6, 129.3, 120.9, 117.2, 114.2, 111.6, 87.3,
85.6, 73.4, 70.5, 61.6, 54.8, 41.3, 35.0,13.9; HRMS (ESI): m/z [M þ H]þ
calcd for C20H26N5O5S: 448.1649; found: 448.1648.
4.3.32. 2-Ethylthio-N6-(1-phenylethyl)adenosine (5b24
)
Compound 4b was allowed to react with 1-phenylethylamine
for 8 h according to the general procedure. The product was puri-
fied by flash column chromatography, and followed by recrystalli-
zation from cyclohexane to give 5b24. Yield: 72%, mp 84e86 ꢂC; IR
4.3.29. 2-Ethylthio-N6-(3-methoxyphenethyl)adenosine (5b21
Compound 4b was allowed to react with
)
3-
methoxyphenethylamine for 11 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b21. Yield:
84%, mp 110e112 ꢂC; IR (KBr): 3318, 2915, 1617, 1577, 1397, 861, 785,
(KBr): 3423, 3324, 3125, 1604, 1393, 781, 710, 637 cmꢁ1
;
1H NMR
(600 MHz, DMSO-d6):
d 8.40 (1H, br s, NH), 8.24 (1H, s, 8-H), 7.40
(2H, d, J ¼ 7.1 Hz, ArH), 7.30 (2H, t, J ¼ 7.5 Hz, ArH), 7.18 (1H, t,
J ¼ 7.3 Hz, ArH), 5.80 (1H, d, J ¼ 5.9 Hz, H-10), 5.41 (1H, br s, NCH),
5.38 (1H, d, J ¼ 6.1 Hz, OH), 5.13 (1H, d, J ¼ 4.8 Hz, OH), 5.05 (1H, dd,
J ¼ 4.6, 4.9 Hz, OH), 4.58 (1H, ddd, J ¼ 5.7, 5.9, 6.1 Hz, H-20), 4.12 (1H,
ddd, J ¼ 3.7, 4.8, 5.7 Hz, H-30), 3.92 (1H, ddd, J ¼ 3.6, 4.2, 4.3 Hz, H-
40), 3.63 (1H, ddd, J ¼ 4.2, 4.6, 11.9 Hz, H-50a), 3.53 (1H, ddd, J ¼ 4.3,
4.9, 11.9 Hz, H-50b), 2.98 (2H, q, J ¼ 7.3 Hz, SCH2), 1.53 (3H, d,
J ¼ 6.8 Hz, CHCH3), 1.21 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR (50 MHz,
698 cmꢁ1 1H NMR (300 MHz, DMSO-d6):
; d 8.22 (1H, s, H-8), 8.01
(1H, br s, NH), 7.20 (1H, t, J ¼ 8.0 Hz, ArH), 6.81e6.75 (3H, m, ArH),
5.82 (1H, d, J ¼ 5.7 Hz, H-10), 5.43 (1H, d, J ¼ 6.1 Hz, OH), 5.18 (1H, d,
J ¼ 4.8 Hz, OH), 5.08 (1H, dd, J ¼ 5.0, 5.6 Hz, OH), 4.59 (1H, ddd,
J ¼ 5.4, 5.7, 6.1 Hz, H-20), 4.14 (1H, ddd, J ¼ 3.7, 4.8, 5.4 Hz, H-30), 3.93
(1H, ddd, J ¼ 3.7, 4.5, 4.6 Hz, H-40), 3.72 (3H, s, OCH3), 3.71e3.64
(2H, m, NCH2), 3.63 (1H, ddd, J ¼ 4.6, 5.0, 11.7 Hz, H-50a), 3.54 (1H,
ddd, J ¼ 4.5, 5.6, 11.7 Hz, H-50b), 3.11 (2H, q, J ¼ 7.3 Hz, SCH2), 2.89
(2H, t, J ¼ 6.9 Hz, NCH2CH2), 1.34 (3H, t, J ¼ 7.3 Hz, CH3); 13C NMR
DMSO-d6):
d 163.5, 153.1, 149.7, 145.3, 138.6, 128.1, 126.5, 126.0,
117.2, 87.4, 85.5, 73.4, 70.5, 61.5, 49.3, 24.6, 22.5, 15.0; HRMS (ESI):
m/z [M þ H]þ calcd for C20H26N5O4S: 432.1700; found: 432.1709.
(50 MHz, DMSO-d6):
d 163.7, 159.3, 153.9, 149.6, 141.0, 138.7, 129.4,
120.9, 117.3, 114.2, 111.6, 87.5, 85.6, 73.4, 70.6, 61.6, 54.9, 41.3, 35.1,
24.8, 15.1; HRMS (ESI): m/z [M þ H]þ calcd for C21H28N5O5S:
462.1806; found: 462.1813.
4.4. In vitro antiplatelet aggregation activity
All experiments using human subjects were performed in
accordance with the Declaration of Helsinki and approved by the
Institutional Review Board Fudan University. Blood was sampled
from the cubital vein of healthy volunteers without taking aspirin
or other nonsteroidal anti-inflammatory drugs for at least 14 days
and the informed consent was obtained before blood collection.
The blood sample was collected in 50 mL plastic tubes containing
4.3.30. N6-(3-methoxyphenethyl)-2-propylthioadenosine (5b22
Compound 4c was allowed to react with
)
3-
methoxyphenethylamine for 11 h according to the general proce-
dure. The product was purified by flash column chromatography,
and followed by recrystallization from EtOAc to give 5b22. Yield:

G. Liu et al. / European Journal of Medicinal Chemistry 53 (2012) 114e123
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1 min before platelet activation with agonists, the extent of
aggregation was quantified by determining the maximum height of
the aggregation tracing. Each sample was allowed to aggregate for
at least 3 min. The chart recorder (Model 707, Chrono-Log, Haver-
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the PPP as blank. The platelet aggregation inhibitory activity was
expressed as percent inhibition by comparison with that measured
in the presence of an equivalent amount of vehicle (DMSO) alone.
Data are presented as mean ꢀ S.E.M. from 3 separate experi-
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linear regression using GraphPad Prism 5.0 and the IC50 values
were derived from this analysis.
Acknowledgments
This work was supported by National Drug Innovative Program
from Ministry of Science and Technology of China (No:
2009ZX09301-011) and National Natural Science of Foundation of
China (No. 30973529).
Appendix A. Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.ejmech.2012.03.047. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
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