6′-Chloro-7- or 9-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-7H- or 9H-purines and their corresponding sulfones as a new family of cytotoxic drugs

Article abstract of DOI:10.1016/j.tet.2006.10.023

A series of 1-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)pyrimidine derivatives were synthesized and two of them (8 and 9) showed a modest antiproliferative activity against the MCF-7 breast cancer cell line. We then decided to change the pyrimidine base for

Full text of DOI:10.1016/j.tet.2006.10.023

Tetrahedron 63 (2007) 183–190
60-Chloro-7- or 9-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-
7H- or 9H-purines and their corresponding sulfones
as a new family of cytotoxic drugs
a
b
b
c
´
´
ꢀ˜
Marıa C. Nunez, Fernando Rodrıguez-Serrano, Juan A. Marchal, Octavio Caba,
c
Antonia Aranega, Miguel A. Gallo, Antonio Espinosa and Joaquın M. Campos
a
a
a,
*
´
ꢀ
a
´
Departamento de Quımica Farmaceutica y Organica, Facultad de Farmacia, Universidad de Granada,
´
ꢀ
c/ Campus de Cartuja s/n, 18071 Granada, Spain
bDepartamento de Ciencias de la Salud, Facultad de Ciencias Experimentales y de la Salud,
´
Paraje de las Lagunillas s/n, 23071 Jaen, Spain
c
´
Departamento de Anatomıa y Embriologıa Humana, Facultad de Medicina, Avenida de Madrid s/n, 18071 Granada, Spain
´
Received 11 August 2006; revised 28 September 2006; accepted 10 October 2006
Available online 27 October 2006
Abstract—A series of 1-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)pyrimidine derivatives were synthesized and two of them (8 and 9)
showed a modest antiproliferative activity against the MCF-7 breast cancer cell line. We then decided to change the pyrimidine base for
the more lipophilic 60-chloropurine, and the N-90 purine (15) and N-70 purine (17) were obtained. The sulfone N-70-alkylated-6-chloropurine
18 was the most active derivative. Compound 17 was found to be slightly more active than its regioisomer 15, with an activity similar to that of
5-fluorouracil as a reference drug. Encouraged by these values, we tested these compounds against both the HT-29 human colon cancer cell
line and the IEC-6 normal rat intestinal epithelial cell line, and 15 was found to be 12.7-fold more active against HT-29 than versus IEC-6.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
has guided the design of novel drugs is bioisosterism, which
we have carried out as suitable structural modifications of
the seven-membered building block, such as the modifica-
tion O-1/S (at different oxidation states). Moreover, the
unnatural 5-fluorouracil (5-FU) base was changed by natu-
rally occurring bases. In this way, we have recently reported
that compounds 3 and 4, with a thymine linked to a sulfur-
containing seven-membered ring (Fig. 1), exhibited in vitro
antiproliferative activities (IC50¼12.74ꢀ4.79 and 30.05ꢀ
0.71 mM, respectively) against the MCF-7 human breast
cancer cell line,3 which had been used as an excellent exper-
imental model to improve the efficacy of different therapies
before their use in patients.4,5 Although compounds 3 and 4
Despite major breakthroughs in many areas of modern
medicine over the past 100 years, the successful treatment
of cancer remains a significant challenge at the start of the
21st century. Therefore, the development of new drugs
against cancer remains among the priorities of the develop-
ment of science and fundamental research. Because it is
difficult to discover novel agents that selectively kill tumour
cells or inhibit their proliferation without general toxicity,
the use of traditional cancer chemotherapy is still very lim-
ited. We have reported the synthesis and anticancer activities
of compounds 1–3,1,2 (Fig. 1). A fundamental approach that
O
S
O
R9
O
O
N
O
N
O
N
S
O
NH
NH
NH
F
O
O
O
O
O
O
R7
Me
Me
trans-4
1 R7= R9= H
2 R7= OMe; R9= H
3 R7 = H; R9= OMe
3
Figure 1. Several benzo-fused seven-membered alkylated pyrimidines that show antiproliferative activities against the human breast cancer cell line MCF-7.
Keywords: Antitumour compounds; Benzoxathiepins; Purines; Pyrimidines.
* Corresponding author. Tel.: +34 958 243848; fax: +34 958 243845; e-mail: jmcampos@ugr.es
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.10.023

184
M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
showed modest antiproliferative activities, this fact was
worth highlighting due to the presence of the natural base
thymine in the O,N-acetal6 framework. Up to now we have
found no reports on hemiaminalic7 compounds with natural
bases endowed with antiproliferative activities. A nucleoside
containing a dihydrooxepin ring at the sugar moiety was the
only reported case with a seven-membered ring, although
devoid of any anticancer and anti-HIV activity.8 In this
paper, we describe details and discussions of structure–
activity relationships (SARs) and antitumour activities that
have been revealed during the study. Therefore, these com-
pounds may serve as prototypes for the development of
even more potent structures.
temperature, the reaction was selective towards the acyclic
alkylated uracil 11, which was obtained with a 50% yield
(Table 1, entry 2). In this case, the relatively low rate of
silylation with 1,1,1,3,3,3-hexamethyldisilazane (HMDS)
was accelerated by adding catalytic amounts of an acidic
catalyst such as (NH4)2SO4 (Table 1, entry 2)9 or trimethyl-
chlorosilane (TCS) (entries 1, 3–10). When the reaction time
was increased up to 72 h, but the other experimental con-
ditions of entry 1 kept the same, in addition to 7 (15%),
the acyclic derivative 11 was obtained (55%, Table 1, entry
3). When the reaction mixture was warmed at 45 ꢁC10 for
20 h, the only product formed was the cyclic compound 7
(96%, Table 1, entry 4). In this case, the hypothesis that
the cyclic structure could be formed from the corresponding
acyclic one is supported by the reactivity of 5-FU 1,4-
dioxepane hemiaminals.11,12 The use of a Lewis acid (e.g.,
TMSOTf), whose role is solely to generate an oxonium
ion13 from the acetalic OMe group, should favour the forma-
tion of the acyclic structure and should not result in any
formation of the corresponding cyclic one (Table 1, entry
2). When the Lewis acid was changed [SnCl4 by Sc(OTf)3]
approximately equal amounts of both the cyclic seven-mem-
bered alkylated uracil 7 and the acyclic alkylated uracil 11
were obtained (Table 1, entry 5, 35% and 42%, respectively).
Finally, the cyclic seven-membered alkylated-5-bromouracil
and 5-(trifluoromethyl)uracil derivatives (Table 1, entries 6
and 7, respectively) were obtained under the optimal condi-
tions carried out with uracil (Table 1, entry 4).
2. Results and discussion
During our ongoing research we have planned the synthesis
of pyrimidine and purine 4,1-benzoxathiepin derivatives,
and the corresponding acyclic ones to be tested subsequently
against the human breast cancer cell line MCF-7.
The synthesis of the targets is depicted in Scheme 1. The
preparation of the pyrimidine O,N-acetals was carried out
between the seven-membered acetal 53 and the unnatural
bases such as 5-FU, 5-bromouracil and 5-trifluorouracil,
and the natural one, uracil. We have used several Lewis
acids, such as Sc(OTf)3 and a 1.0 M solution of tin(IV)
chloride (SnCl4) in dichloromethane. The results are sum-
marized in Table 1.
Once the N-10-alkylated pyrimidine derivatives had been
studied, we decided to shift to the more lipophilic purine
ones (Scheme 2). The condensation reaction between the
seven-membered acetal 5 and 6-chloropurine was accom-
plished using TMSOTf, TCS and HMDS in dry acetonitrile
for 24 h (Table 2, entry 1). It produced the N-90-seven-
membered 60-chloropurine (15, 56%) and the N-70-acyclic
alkylated-60-chloropurine (19, 13%) regioisomers, which
were separated by flash chromatography. When tin(IV) chlo-
ride was employed, the seven-membered alkylated N-70
isomer 17 (8%) was produced, together with the acyclic
N-90-alkylated-60-chloropurine 19 (4%, Table 2, entry 2).
The N-70 purine nucleosides are produced, presumably due
to prior complexation between the tin and nitrogen atoms
(N-90).14,15 When the starting reactant was the sulfone 14
(obtained from 5, using OxoneÒ as oxidizing agent, under
previously reported conditions16), with SnCl4 as Lewis
acid, the major product was the acyclic N-70-alkylated-
60-chloropurine 22 (19%), together with equimolecular
amounts of both N-70-seven-membered alkylated-60-chloro-
purine 18 (12%) and N-70-acyclic alkylated-60-chloropurine
20 (Table 2, entry 3, 12%).
R
OMe
N
R
S
S
S
a)
O
N
O
O
+
OMe
NH
OH
NH
O
O
O
5
10 R = F
11 R = H
12 R = Br
13 R = CF3
6 R = F
7 R = H
8 R = Br
9 R = CF3
Scheme 1. Synthetic route for the preparation of the pyrimidine target
molecules. Reagents and conditions: (a) pyrimidine base, HMDS, TCS,
Lewis acid, anhydrous MeCN.
Treatment of 5 with 5-FU and tin(IV) chloride, 1.0 M solu-
tion in dichloromethane, at room temperature during 20 h in
acetonitrile produced the cyclic seven-membered alkylated
pyrimidine 6 with a 14% yield (Table 1, entry 1). When
the reaction was carried out with uracil in the presence of tri-
methylsilyl trifluoromethanesulfonate (TMSOTf) at room
Table 1. Conditions studied for the reaction between 5 and several pyrimi-
dine bases
Sulfoxide 23 (Scheme 3) was obtained by the procedure used
by Matteucci et al.17 who used catalytic scandium trifluoro-
methanesulfonate that greatly increases the efficiency of
hydrogen-peroxide-mediated monooxidation of alkyl-aryl
sulfides and methyl cysteine-containing peptides. When
applied to sulfide 15, the reaction proved to be stereospecific
and trans-23 (96%) was the only product obtained, accord-
ing to Nun˜ez et al.:3 the chemical shift differences (CSDs)
between both the H-5 protons were d 0.77 ppm for trans-
1-(1-oxo-2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)uracil and
d 0.16 ppm for its cis isomer,3 whilst the CSD was
Entry Base
Time Lewis
(h) acid
Temp Cyclic
(ꢁC) alkylated
Acyclic
alkylated
pyrimidine (%) pyrimidine (%)
1
2
3
4
5
6
7
5-FU
U
U
U
U
20
24
72
20
24
SnCl4
rt
6 (14)
7 (—)
7 (15)
7 (96)
7 (35)
8 (51)
9 (38)
10 (—)
11 (50)
11 (55)
11 (—)
11 (42)
12 (—)
13 (—)
TMSOTfa rt
SnCl4
SnCl4
Sc(OTf)3 45
rt
45
5-BrU 20
5-F3CU 20
SnCl4
SnCl4
45
45
a
(NH4)2SO4 was used instead of TCS, according to Ref. 8.

M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
185
Cl
N
X
X
N
N
N
N
+
N
O
O
N
N
Cl
X
17 X = S
18 X = SO2
15 X = S
16 X = SO2
b)
OMe
O
OMe
N
Cl
N
OMe
5 X = S
14 X = SO2
N
X
a)
X
N
N
+
N
OH
OH
N
N
Cl
19 X = S
20 X = SO2
21 X = S
22 X = SO2
Scheme 2. Synthetic route for the preparation of the alkylated 60-chloropurines. Reagents and conditions: (a) OxoneÒ, MeOH, H2O; (b) 6-chloropurine, HMDS,
TCS, Lewis acid, anhydrous MeCN, 45 ꢁC, reaction time: 20 h.
Table 2. Comparison of the products obtained in the condensation reaction of 5 (and 14) with 6-chloropurine
Entry
Starting
O,O-acetal
Lewis
acid
Cyclic
N-90-alkylated
purine (%)
Cyclic
N-70-alkylated
purine (%)
Acyclic
N-90-alkylated
purine (%)
Acyclic
N-70-alkylated
purine (%)
1
2
3
5
5
14
TMSOTf
SnCl4
SnCl4
15 (56)
15 (—)
16 (—)
17 (—)
17 (8)
18 (12)
19 (13)
19 (4)
20 (12)
21 (—)
21 (—)
22 (19)
d 0.46 ppm for trans-23. Moreover, H-3 was more de-
shielded in trans-1-(1-oxo-2,3-dihydro-5H-4,1-benzoxa-
thiepin-3-yl)uracil (d 6.65 ppm) than in its cis analogue (d
6.40 ppm), whilst trans-23 showed a chemical shift of
d 6.60 ppm for its hemiaminalic proton.
alkylated pyrimidine and purine in both 1H and 13C spectra
are consistent with those observed for related pyrimidine3,18
and purine derivatives.19
The discrimination between N-90- and N-70-alkylated
purines relies on the correlation between H-3 of the seven-
membered moiety and C-40 and C-50, respectively. Very
important is the correlation between H-3 (d 6.29 ppm,
dd, J¼3.3 and 8.1 Hz) and the quaternary carbon at d
151.42 ppm, which has the following two consequences:
(a) this signal can be assigned to C-40 and (b) this correlation
proves unequivocally that the linkage between the seven-
membered moiety and the purine base takes place through
N-90 in compound 15. Moreover, assignments of N-90 versus
N-70 isomers can be readily made from the 13C NMR signal
of the C-40 peaks; for the N-90 isomers: d 151.85 ppm (16),
d 150.19 ppm (20), d 149.51 ppm (trans-23) and d
150.70 ppm (24); for the N-70 isomers: d 162.11 ppm (17),
d 161.81 ppm (18) and d 162.24 ppm (22). These values
agree with previous findings on acyclic alkylated adenine
derivatives.18
O
S
N
N
N
O
N
Cl
N
trans-23 (96%)
S
N
O
b)
15
N
N
24 (88%)
16 (100%)
OMe
Scheme 3. Several modifications on 15. Reagents and conditions: (a) H2O2
50%, Sc(OTf)3; (b) NaH/MeOH; (c) OxoneÒ, MeOH, H2O.
The oxidation of sulfide 15 with OxoneÒ (Scheme 3)16 pro-
duced the sulfone derivative 16 (N-90 isomer) with 100%
yield to obtain the regioisomer of 18 (N-70) and later on to
assay its antiproliferative activity and compare their biolog-
ical properties as a function of their isomerism. Finally, the
substitution of the chlorine atom of 15 by the methoxy group
(24, Scheme 3) will give us information about the relation-
ship between the nature of the functional group at position
60 and the biological activity.
2.2. Antiproliferative activity of the target molecules
Table 3 shows the antiproliferative activities against the
MCF-7 human breast cancer cell line for the target com-
pounds, including 5-FU as reference drug. As a rule the fol-
lowing can be stated: (a) the most active compounds are the
Table 3. Antiproliferative activities against the MCF-7 cell line for 5-FU,
alkylated pyrimidine and purine compounds
2.1. Spectroscopic analysis of the N-90- and the
N-70-alkylated purines
Compound IC50 (mM) Compound IC50 (mM) Compound IC50 (mM)
5-FU
6
8
9
10
4.32ꢀ0.02 11
>100 15
27.5ꢀ0.18 19
5.46ꢀ0.02 20
16.5ꢀ1.59 22
3.55ꢀ1.10 trans-23
2.58ꢀ0.08 24
40.0ꢀ3.90
63.8ꢀ6.42
81.9ꢀ11.9
74.9ꢀ3.76
44.6ꢀ0.50
The structures of the final compounds have been determined
by 1H and 13C NMR, DEPT, HMBC (Heteronuclear Multi-
ple Quantum Connectivity) experiments, HR LSIMS and
elemental analyses. The chemical shift patterns of the
44.1ꢀ4.23 16
34.9ꢀ3.96 17
>100
18

186
M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
Table 4. Antiproliferative activities against several cancerous and normal cell lines for 5-FU, 15, 17 and 18
Compound
IC50 MCF-7
IC50 MCF-10A
In vitro TIa (breast)
IC50 HT-29
IC50 IEC-6
In vitro TIb (intestinal)
5-FU
15
17
4.32ꢀ0.02
5.46ꢀ0.02
3.55ꢀ1.10
2.58ꢀ0.08
0.73ꢀ0.12
1.85ꢀ0.10
1.68ꢀ0.12
5.84ꢀ2.48
0.17
0.34
0.47
2.26
1.08ꢀ0.15
0.92ꢀ0.04
2.85ꢀ0.26
10.48ꢀ4.03
0.66ꢀ0.10
11.7ꢀ2.40
5.46ꢀ0.34
10.36ꢀ0.01
0.61
12.7
1.90
0.99
18
a
In vitro TI¼IC50 MCF-10A/IC50 MCF-7.
b
In vitro TI¼IC50 IEC-6/IC50 HT-29.
4,1-benzoxathiepin (15, 17) and 1,1-dioxo-4,1-benzoxathie-
pin-60-chloropurine derivatives (16, 18); (b) the N-70 purine
derivatives present a better activity (17, 18) than their N-90
(15, 16) regioisomers; (c) the most active compound is the
N-70-60-chlorosubstituted purine (18), which is nearly
2-fold more potent than 5-FU.
the genes implicated in the anticarcinogenic activities of
the three most potent compounds (15, 17 and 18).
4. Experimental
4.1. Chemistry
Encouraged by these results, we decided to extend our stud-
ies to other cancerous cell lines, such as the colon human-
derived cell line HT-29. This cell line was established
from a colon adenocarcinoma, one of the most frequent solid
human cancers that is also mainly resistant to chemother-
apy,20 making these cells appropriate for the search for
new antitumour drugs. Moreover, we established a compari-
son of the three most active compounds (15, 17 and 18)
between the cancerous lines (MCF-7 and HT-29) and the
corresponding normal ones, such as MCF-10 (non-cancer-
ous human mammary epithelial cells) and IEC-6 (a rat intes-
tinal epithelial cell line), in an intent to define the in vitro
therapeutic index as a measure of the selectivity. The in vitro
therapeutic index (TI) of a drug is defined as the ratio of the
toxic dose to the therapeutic dose. Table 4 shows the antipro-
liferative activities for 5-FU, 15, 17 and 18, and the corre-
sponding in vitro TIs. Compound 18 is the most selective
compound against the cancerous breast cancer cell line
(TI¼2.26) in relation to the normal one, while 15 is against
the cancerous colon cell line in relation to normal intestinal
cells (TI¼12.7). It has to be pointed out that, although in
a different therapeutic area, the selective cyclooxygenase-2
(COX-2) inhibitors, celecoxib and rofecoxib, which are in
clinical use, are 7.3- and 8.4-fold more potent as in vitro
COX-2 than COX-1 inhibitors.21 The unnatural pyrimidine
base 5-FU is not selective at all, with TI<1 in both epithelial
non-cancerous cells [in vitro TI (breast)¼0.17 and in vitro TI
(intestinal)¼0.61].
The general methods were the same as those previously
described.1,3 The HMBC spectra23 were measured using a
pulse sequence optimized for 10 Hz (inter-pulse delay for
the evolution of long-range couplings: 50 ms) and a 5:3:4
gradient combination. In this way, direct responses (1J cou-
plings) were not completely removed.
4.2. Starting material
4.2.1. Synthesis of (RS)-1,1-dioxo-3-methoxy-2,3-di-
hydro-5H-4,1-benzoxathiepin (14). Potassium peroxy-
monosulfate (OxoneÒ, 941 mg, 1.53 mmol) in H2O (4 mL)
was added to a solution of 5 in MeOH (12 mL) and the
resulting suspension was left at room temperature for 2 h.
After filtration and washing (H2O and CH2Cl2) the residue
was purified by gradient flash chromatography (CH2Cl2/
MeOH, 9.8/0.2/9.5/0.5) to yield 14 (160 mg, 91%) as an
amorphous white solid; mp: 131–133 ꢁC. 1H NMR
(CDCl3, 300 MHz) d (ppm) 8.07 (dd, J¼1.5, 7.6 Hz, 1H,
CH-arom); 7.58 (dt, J¼1.5, 7.3 Hz, 1H, CH-arom); 7.51
(dt, J¼1.5, 7.6 Hz, 1H, CH-arom); 7.37 (dd, J¼1.5,
7.3 Hz, 1H, CH-arom); 5.11 (dd, J¼2.3, 8.3 Hz, 1H,
CH-3); 5.06 (d, J¼14.2 Hz, 1H, CH2-5); 4.97 (d, J¼
14.2 Hz, 1H, CH2-5); 3.59 (d, J¼2.3, 14.7 Hz, 1H,
CH2-2); 3.53 (s, 1H, OMe); 3.42 (d, J¼8.3, 14.7 Hz, 1H,
CH2-2). 13C NMR (CDCl3, 75 MHz) d (ppm) 139.88;
137.13; 133.78; 130.40; 128.84; 127.71; 101.62 (CH-3);
67.17 (CH2-5); 60.27 (CH2-2); 56.55 (OMe). Anal. for
C10H12O4S: calcd: C 52.62; H 5.30; N 14.05. Found: C
52.83; H 5.15; N 13.89.
3. Conclusion
In short, we have synthesized 14 N-alkylated pyrimidine and
purine derivatives and tested their preliminary in vitro anti-
cancer activities. These results provide promising informa-
tion for the further development of potent antiproliferative
agents. It has been observed that the antiproliferative activity
of 15 is drastically increased in the HT-29 human colon
tumour compared to the normal tissue. The subject of our
current research22 is to overcome the shortcomings of the
present cancer chemotherapy, i.e., the synthesis of antitu-
mour drugs with a new mechanism of action, capable of
discriminating tumour cells from normal proliferative cells
and which exhibit selective toxicity against cancer. After
having described both the chemistry and preliminary biolog-
ical activities of the alkylated pyrimidine and purine deriva-
tives, we plan to carry out microarray studies to recognize
4.3. Final compounds
4.3.1. General procedure for the reaction between (RS)-
3-methoxy-2,3-dihydro-5H-4,1-benzoxathiepin (5) [or
(RS)-1,1-dioxo-3-methoxy-2,3-dihydro-5H-4,1-benzoxa-
thiepin (15)] and pyrimidine bases or 6-chloropurine.
4.3.1.1. Method A. Synthesis of (RS)-1-(2,3-dihydro-
5H-4,1-benzoxathiepin-3-yl)-5-fluorouracil (6). A 1.0 M
solution of SnCl4/CH2Cl2 (1.53 mL, 1.53 mmol) was added
dropwise with stirring to a suspension of 53 (250 mg,
1.27 mmol), 5-fluorouracil
1,1,1,3,3,3-hexamethyldisilazane
1.27 mmol) and trimethylchlorosilane (TCS, 0.16 mL,
1.27 mmol) in dry acetonitrile (4 mL) at 0 ꢁC, under argon.
After 20 h of stirring at room temperature, the reaction was
(181 mg,
(HMDS,
1.39 mmol),
0.27 mL,

M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
187
quenched by the addition of a concentrated aqueous solution
of K2CO3, then concentrated under diminished pressure, the
resulting residue was suspended (H2O) and extracted with
CH2Cl2 (3ꢂ20 mL). The organic layers were pooled, dried
(Na2SO4), filtered and the solvent removed under vacuum.
The residue was purified by flash chromatography using
a mixture of CH2Cl2/MeOH (9.9/0.1), and 6 (53 mg, 14%)
was obtained as an amorphous white solid; mp 213–
dry acetonitrile (6 mL) was prepared under argon. After
15 min at room temperature, the reaction mixture was cooled
to ꢃ25 ꢁC, and a 1.0 M solution of SnCl4/CH2Cl2 (2.45 mL,
2.45 mmol) in anhydrous acetonitrile (5 mL) was added
dropwise with stirring. After 10 min at ꢃ20 ꢁC the reaction
mixture was left to reach room temperature and then warmed
at 45 ꢁC for 20 h. After the usual workup the crude was tri-
turated with CH2Cl2 (5 mL), filtered and 7 was obtained
(540 mg, 96%).
1
215 ꢁC. H NMR (acetone-d6, 300 MHz) d (ppm) 10.50 (s,
1H, NH); 7.81 (d, 1H, CH-arom); 7.62 (m, 1H, CH-arom);
7.48 (m, 1H, CH-arom); 7.36 (m, 2H, CH-arom); 6.01 (dt,
J¼5.8 Hz, 1H, CH-3); 5.06 (d, J¼13.5 Hz, 1H, CH2-5);
4.98 (d, J¼13.5 Hz, 1H, CH2-5); 3.14 (d, J¼5.8 Hz, 2H,
CH2-2). 13C NMR (acetone-d6, 100 MHz): d (ppm) 155.87
(C]O); 147.79 (C]O); 141.87; 139.95 (d, J¼230.8 Hz,
C-50); 135.57; 131.73; 129.51; 128.24; 127.80; 124.05 (d,
J¼34.5 Hz, CH-60); 86.90 (CH-3); 72.97 (CH2-5); 36.80
(CH2-2). HR LSIMS calcd for C13H12N2O3FS (M+H)+
295.0554, found 295.0553. Anal. for C13H11FN2O3S: calcd:
C 53.05; H 3.77; N 9.52. Found: C 52.89; H 4.05; N 9.81.
4.3.1.5. Method E. Syntheses of 7 and 11. Compound 53
(110 mg, 0.56 mmol) was dissolved in anhydrous acetonitrile
(4 mL) under argon. After cooling the solution at ꢃ20 ꢁC, ura-
cil (63 mg, 0.56 mmol), TCS (72 mL, 0.56 mmol), HMDS
(0.117 mL, 0.56 mmol) and Sc(OTf)3 (276 mg, 0.56 mmol)
were added. After 10 min at room temperature, the reaction
mixturewas warmed to 45 ꢁC for 24 h. After the usual workup
and flash chromatography (CH2Cl2/MeOH, 9.9/0.1), 7
(51 mg, 35%) and 11 (65 mg, 42%) were obtained.
4.3.1.6. Synthesis of (RS)-1-(2,3-dihydro-5H-4,1-benz-
oxathiepin-3-yl)-5-bromouracil (8). Following Method D,
but starting from 53 (200 mg, 1.02 mmol), 5-bromouracil
(213 mg, 1.12 mmol), HMDS (0.22 mL, 1.02 mmol) and
TCS (0.13 mL, 1.02 mmol), and a 1.0 M solution of
SnCl4/CH2Cl2 (1.22 mL, 1.22 mmol) in anhydrous aceto-
nitrile (6 mL), 8 was obtained as an amorphous white solid
4.3.1.2. Method B. Synthesis of (RS)-1-[2-(2-hydroxy-
methylphenylthio)-1-methoxyethyl]uracil (11). A suspen-
sion of uracil (72 mg, 0.64 mmol), HMDS (3 mL, 14 mmol)
and (NH4)2SO4 (6.4 mg, 0.048 mmol) in anhydrous aceto-
nitrile (4 mL) under argon was heated to 130 ꢁC for 2 h.
The resulting solution was cooled to room temperature, con-
centrated under diminished pressure and more anhydrous
acetonitrile (4 mL) was added. Trimethylsilyl trifluoro-
methanesulfonate (TMSOTf, 0.12 mL, 0.67 mmol) and
then 53 (250 mg, 1.27 mmol) dissolved in anhydrous aceto-
nitrile (3 mL) were added dropwise at ꢃ45 ꢁC and the reac-
tion mixture was left at room temperature for 24 h. After the
usual workup and flash chromatography (CH2Cl2/MeOH,
9.8/0.2), 11 (88 mg, 50%) was obtained as an amorphous
1
(132 mg, 51%); mp 239–240 ꢁC. H NMR (CDCl3+some
drops of DMSO-d6, 300 MHz) d (ppm) 11.78 (s, 1H, NH);
7.69 (m, 1H, CH-arom); 7.51 (m, 1H, CH-arom); 7.26 (m,
3H, CH-arom); 5.88 (t, J¼5.5 Hz, 1H, CH-3); 4.95 (d,
J¼13.3 Hz, 1H, CH2-5); 4.84 (d, J¼13.4 Hz, 1H, CH2-5);
2.93 (d, J¼5.6 Hz, 2H, CH2-2). 13C NMR (CDCl3+some
drops of DMSO-d6, 75 MHz) d (ppm) 158.20 (C]O);
148.19 (C]O); 140.68; 138.32; 134.77; 131.39; 128.86;
127.71; 127.23; 95.66 (C-50); 86.25 (CH-3); 72.67
(CH2-5); 36.88 (CH2-2). Anal. for C13H11BrN2O3S: calcd:
C 43.96; H 3.12; N 7.89. Found: C 43.86; H 3.43; N 7.60.
1
white solid; mp 130–131 ꢁC. H NMR (CDCl3, 300 MHz)
d (ppm) 8.75 (m, 1H, NH); 7.45 (m, 2H, CH-arom); 7.27
(m, 3H, CH-arom); 5.71 (dd, J¼8.1, 2.0 Hz, 1H, CH-50);
5.67 (t, J¼5.9 Hz, 1H, CH); 4.72 (s, 2H, CH2OH); 3.22 (d,
J¼14.5 Hz, 1H, CH2S); 3.15 (d, J¼14.5 Hz, 1H, CH2S);
2.68 (s, 1H, OH). 13C NMR (CDCl3+some drops of
CD3OD, 75 MHz) d (ppm) 163.30 (C]O); 151.41 (C]O);
142.20; 138.40; 132.36; 131.52; 128.95; 128.40; 127.90;
103.40 (CH-50); 85.92 (CH); 62.83 (CH2OH); 57.01
(OMe); 38.60 (CH2S). Anal. for C14H16N2O4S: calcd: C
54.53; H 5.23; N 9.08. Found: C 54.76; H 5.35; N 9.30.
4.3.1.7. Synthesis of (RS)-1-(2,3-dihydro-5H-4,1-benz-
oxathiepin-3-yl)-5-trifluoromethyluracil (9). Following
Method D, but starting from 53 (200 mg, 1.02 mmol), 5-tri-
fluoromethyluracil (201 mg, 1.12 mmol), HMDS (0.22 mL,
1.02 mmol) and TCS (0.13 mL, 1.02 mmol), and a 1.0 M so-
lution of SnCl4/CH2Cl2 (1.22 mL, 1.22 mmol) in anhydrous
acetonitrile (6 mL), 9 was obtained as an amorphous white
solid (133 mg, 52%). 1H NMR (CDCl3, 300 MHz) d (ppm)
8.91 (s, 1H, NH); 7.86 (m, 1H, CH-arom); 7.63 (m, 1H,
CH-arom); 7.35 (m, 3H, CH-arom); 6.02 (dd, J¼1.7,
9.5 Hz, 1H, CH-3); 5.10 (d, J¼13.4 Hz, 1H, CH2-5); 4.95
(d, J¼13.4 Hz, 1H, CH2-5); 3.09 (dd, J¼1.7, 14.1 Hz, 1H,
CH2-2); 2.79 (dd, J¼9.5, 14.1 Hz, 1H, CH2-2). 13C NMR
(CDCl3, 75 MHz) d (ppm) 157.96 (C]O); 148.61 (C]O);
141.40 (C-arom); 140.82; 135.78; 132.94; 130.12; 129.27;
128.73; 121.74 (d, J¼268.9 Hz); 105.64 (d, J¼33.4 Hz);
87.79 (CH-3); 74.29 (CH2-5); 38.72 (CH2-2). HR LSIMS
calcd for C14H11N2O3F3NaS (M+Na)+ 367.0344; found
367.03444. Anal. for C14H11F3N2O3S: calcd: C 48.84; H
3.22; N 8.14. Found: C 48.98; H 3.42; N 8.54.
4.3.1.3. Method C. Syntheses of 7 and 11. A suspension
of 53 (400 mg, 2.04 mmol), uracil (250 mg, 2.23 mmol),
HMDS (0.43 mL, 2.04 mmol) and TCS (0.26 mL,
2.04 mmol) in dry acetonitrile (6 mL) was prepared under
argon. After 15 min at room temperature it was cooled to
ꢃ30 ꢁC and a 1.0 M solution of SnCl4/CH2Cl2 (2.45 mL,
2.45 mmol) in anhydrous acetonitrile (5 mL) was added
dropwise while stirring the suspension, and after 10 min at
ꢃ30 ꢁC, the corresponding solution was left at room temper-
ature for 72 h. After the usual workup and flash chromato-
graphy (CH2Cl2/MeOH, 9.9/0.1), 7 (86 mg, 15%) and 11
(310 mg, 55%) were obtained.
4.3.1.4. Method D. Synthesis of 7. A suspension of 53
(400 mg, 2.04 mmol), uracil (250 mg, 2.23 mmol), HMDS
(0.43 mL, 2.04 mmol) and TCS (0.26 mL, 2.04 mmol) in
4.3.1.8. Syntheses of (RS)-60-chloro-9-(2,3-dihydro-
5H-4,1-benzoxathiepin-3-yl)-9H-purine (15) and (RS)-
60-chloro-9-[2-(2-hydroxymethylphenylthio)-1-methoxy-

188
M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
ethyl]-9H-purine (19). Starting from 53 (0.500 g,
2.55 mmol), 6-chloropurine (394 mg, 2.55 mmol), HMDS
(0.53 mL, 2.55 mmol), TCS (0.33 mL, 2.55 mmol),
Sc(OTf)3 (1.25 g, 2.55 mmol), anhydrous acetonitrile
(20 mL), and following Method D a residue was obtained
and purified by gradient flash chromatography (EtOAc/
hexane, 3/7/4/6). A first fraction identified as 15
(0.456 g, 56%) was obtained as an amorphous white solid;
mp 185–187 ꢁC. HMBC experiments were carried out on
15. 1H NMR (CDCl3, 300 MHz) d (ppm) 8.76 (s, 1H,
CH-20); 8.28 (s, 1H, CH-80); 7.65 (m, 1H, CH-arom); 7.36
(m, 3H, CH-arom); 6.29 (dd, J¼3.3, 8.1 Hz, 1H, CH-3);
5.18 (d, J¼13.3 Hz, 1H, CH2-5); 5.01 (d, J¼13.3 Hz, 1H,
CH2-5); 3.27 (m, J¼indet., 6.1 Hz, 2H, CH2-2); 13C NMR
(CDCl3, 75 MHz) d (ppm) 152.23 (CH-20); 151.42 (C-40);
150.60 (C-60); 142.79 (CH-80), 141.75 (C-5a); 135.82
(C-9a); 132.84; 131.77 (C-50); 130.18; 129.20; 128.75;
87.77 (CH-3); 73.93 (CH2-5); 39.19 (CH2-2). Anal. for
C14H11ClN4OS: calcd: C 52.75; H 3.48; N 17.58. Found:
C 52.65; H 3.63; N 17.12.
4.3.1.10. Syntheses of (RS)-60-chloro-7-(1,1-dioxo-
2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-7H-purine (18),
(RS)-60-chloro-9-[1,1-dioxo-2-(2-hydroxymethylphenyl-
thio)-1-methoxyethyl]-9H-purine (20) and (RS)-60-chloro-
7-[1,1-dioxo-2-(2-hydroxymethylphenylthio)-1-methoxy-
ethyl]-7H-purine (22). Starting from 53 (137 mg,
0.60 mmol), 6-chloropurine (101 mg, 0.65 mmol), HMDS
(0.12 mL, 0.60 mmol), TCS (0.08 mL, 0.60 mmol) and
a 1.0 M solution of SnCl4/CH2Cl2 (0.72 mL, 0.72 mmol)
in anhydrous acetonitrile (4 mL), and following Method D
a residue was obtained and purified by flash chromatography
(CH2Cl2/MeOH, 9.8/0.2). A first fraction identified as 18
(29 mg, 12%) was obtained as an amorphous white solid;
mp 205–206 ꢁC. 1H NMR (CDCl3, 400 MHz) d (ppm)
8.89 (s, 1H, CH-20); 8.41 (s, 1H, CH-80); 8.13 (d, J¼
7.7 Hz, 1H, CH-arom); 7.67 (t, J¼7.4 Hz, 1H, CH-arom);
7.61 (t, J¼7.7 Hz, 1H, CH-arom); 7.43 (d, J¼7.4 Hz, 1H,
CH-arom); 6.97 (t, J¼6.0 Hz, 1H, CH-3); 5.55 (d,
J¼14.0 Hz, 1H, CH2-5); 4.99 (d, J¼14.0 Hz, 1H, CH2-5);
3.98 (d, J¼6.0 Hz, 2H, CH2-2). 13C NMR (CDCl3,
100 MHz) d (ppm) 161.81 (CH-40); 153.16 (C-20); 145.89
(C-80); 143.36 (CH-60); 138.93 (C-9a); 135.53 (C-5a);
134.79; 131.28; 129.68; 128.46; 121.50 (C-50); 84.41
(CH-3); 71.81 (CH2-5); 60.60 (CH2-2). Anal. for
C14H11ClN4O3S: calcd: C 47.94; H 3.16; N 15.97. Found:
C 47.97; H 3.40; N 16.08.
The second fraction, as an amorphous white powder was
identified as 19 (117 mg, 13%) as a brown dense oil;
HMBC experiments were carried out on 19. 1H NMR
(CDCl3, 300 MHz) d (ppm) 8.69 (s, 1H, CH-20); 8.21 (s,
1H, CH-80); 7.34 (dd, J¼1.6, 7.6 Hz, 1H, CH-arom); 7.22
(dd, J¼1.4, 7.6 Hz, 1H, CH-arom); 7.15 (dt, J¼1.4,
7.6 Hz, 1H, CH-arom); 7.05 (dt, J¼1.6, 7.6 Hz, 1H,
CH-arom); 5.73 (dd, J¼5.0, 7.8 Hz, 1H, CH-3); 4.72 (dd,
J¼12.8 Hz, 2H, CH2OH); 3.69 (dd, J¼7.1, 14.5 Hz, 1H,
CH2S); 3.57 (dd, J¼5.0, 14.5 Hz, 1H, CH2S); 3.31 (s, 3H,
OMe). 13C NMR (CDCl3, 75 MHz) d (ppm) 152.19
(CH-20); 151.70 (C-60); 151.39 (C-40); 143.23 (CH-80);
142.13; 132.12; 131.99; 131.87 (C-50); 129.06; 128.37;
128.24; 87.10 (CH); 63.37 (CH2OH); 57.34 (OMe); 39.45
(CH2S). Anal. for C15H15ClN4O2S: calcd: C 51.35; H
4.31; N 15.97. Found: C 51.00; H 4.16; N 15.87.
The second fraction, as an amorphous white powder was
1
identified as 20 (28 mg, 12%); mp 113–114 ꢁC. H NMR
(CD3OD, 300 MHz) d (ppm) 8.67 (s, 1H, CH-20); 8.62 (s,
1H, CH-80); 7.67 (m, 2H, CH-arom); 7.59 (dt, J¼1.4,
7.6 Hz, 1H, CH-arom); 7.33 (dt, J¼1.2, 7.6 Hz, 1H,
CH-arom); 6.18 (t, J¼6.1 Hz, 1H, CH-3); 5.02 (d, J¼
5.7 Hz, 2H, CH2OH); 4.61 (dd, J¼6.5, 14.8 Hz, 1H,
CH2S); 4.56 (t, J¼5.7 Hz, 1H, OH); 4.46 (dd, J¼6.1,
14.8 Hz, 1H, CH2S); 3.23 (s, 3H, Me). 13C NMR (CD3OD,
75 MHz) d (ppm) 151.99 (C-60); 151.84 (CH-20); 150.19
(C-40); 145.02 (CH-80); 141.79 (C-arom); 136.59
(C-arom); 134.09 (CH-arom); 131.83 (C-50); 129.47
(CH-arom); 129.42 (CH-arom); 127.46 (CH-arom); 82.07
(CH); 60.91 (CH2OH); 58.34 (CH2S); 56.11 (OMe). Anal.
for C15H15ClN4O4S: calcd: C 47.06; H 3.95; N 14.64.
Found: C 46.96; H 3.71; N 14.92.
4.3.1.9. Syntheses of (RS)-60-chloro-7-(2,3-dihydro-
5H-4,1-benzoxathiepin-3-yl)-7H-purine (17) and 19.
Starting from 53 (0.252 g, 1.28 mmol), 6-chloropurine
(216 mg, 1.40 mmol), HMDS (0.27 mL, 1.28 mmol), TCS
(0.16 mL, 1.28 mmol) and a 1.0 M solution of SnCl4/
CH2Cl2 (1.53 mL, 1.28 mmol) in anhydrous acetonitrile
(7 mL), and following Method D a residue was obtained
and purified by flash chromatography (CH2Cl2/MeOH, 9.9/
0.1). A first fraction identified as 17 (33 mg, 8%) was ob-
tained as an amorphous white solid. HMBC experiments
were carried out on 17. 1H NMR (CDCl3, 300 MHz)
d (ppm) 8.89 (s, 1H, CH-20); 8.43 (s, 1H, CH-80); 7.66 (m,
1H, CH-arom); 7.35 (m, 3H, CH-arom); 6.55 (dd, J¼1.8,
9.4 Hz, 1H, CH-3); 5.18 (d, J¼13.4 Hz, 1H, CH2-5); 5.02
(d, J¼13.4 Hz, 1H, CH2-5); 3.33 (dd, J¼1.8, 14.0 Hz, 1H,
CH2-2); 3.18 (dd, J¼9.4, 14.0 Hz, 1H, CH2-2). 13C NMR
(CDCl3, 75 MHz) d (ppm) 162.11 (CH-40); 152.83 (C-20);
145.97 (C-80); 142.91 (CH-60); 141.71 (C-5a); 135.42
(C-9a); 133.01; 130.19; 129.25; 128.90; 121.50 (C-50);
89.36 (CH-3); 73.95 (CH2-5); 39.80 (CH2-2). Anal. for
C14H11ClN4OS: calcd: C 52.75; H 3.48; N 17.58. Found:
C 52.87; H 3.54; N 17.74.
The third fraction, as an amorphous white powder was iden-
tified as 22 (43 mg, 19%); mp 131–132 ꢁC. 1H NMR
(DMSO-d6, 300 MHz) d (ppm) 8.99 (s, 1H, CH-20); 8.82
(s, 1H, CH-80); 7.77 (m, 3H, CH-arom); 7.40 (dt, J¼1.5,
7.6 Hz, 1H, CH-arom); 6.38 (dd, J¼5.0, 7.1 Hz, 1H,
CH-3); 5.52 (t, J¼5.5 Hz, 1H, OH); 4.88 (d, J¼5.5 Hz,
2H, CH2OH); 4.50 (dd, J¼7.2, 14.8 Hz, 1H, CH2S); 4.40
(dd, J¼5.0, 14.8 Hz, 1H, CH2S); 3.16 (s, 3H, Me). 13C
NMR (DMSO-d6, 75 MHz) d (ppm) 162.24 (C-40); 152.37
(CH-20); 149.68 (CH-80); 142.55 (C-60); 136.40; 134.77;
129.81; 129.56; 127.94; 122.51 (C-50); 83.23 (CH); 60.18
(CH2OH); 59.87 (CH2S); 56.72 (OMe). Anal. for
C15H15ClN4O4S: calcd: C 47.06; H 3.95; N 14.64. Found:
C 47.12; H 3.62; N 14.50.
4.3.1.11. Synthesis of (RS)-60-chloro-9-(1,1-dioxo-2,3-
dihydro-5H-4,1-benzoxathiepin-3-yl)-9H-purine
Following the experimental procedure for the preparation
(16).
The second fraction, as an amorphous white powder was
identified as 19 (18 mg, 4%).
of 14 (Section 4.2.1) and using OxoneÒ (578 mg,

M. C. Nuꢀn~ez et al. / Tetrahedron 63 (2007) 183–190
189
1
0.94 mmol), H2O (3 mL), 5 (150 mg, 0.47 mmol) and
MeOH (7 mL), compound 16 (165 mg, 100%) was obtained
as an amorphous white solid; mp 230–231 ꢁC. HMBC exper-
iments were carried out on 16. 1H NMR (CDCl3, 400 MHz)
d (ppm) 8.77 (s, 1H, CH-20); 8.27 (s, 1H, CH-80); 8.18 (dd,
J¼1.0, 7.6 Hz, 1H, CH-arom); 7.56 (dt, J¼1.2, 7.6 Hz, 1H,
CH-arom); 7.64 (dt, J¼1.0, 7.6 Hz, 1H, CH-arom); 7.46 (d,
J¼7.6 Hz, 1H, CH-arom); 6.66 (dd, J¼1.5, 10.5 Hz, 1H,
CH-3); 5.58 (d, J¼14.0 Hz, 1H, CH2-5); 5.01 (d, J¼
14.0 Hz, 1H, CH2-5); 4.31 (dd, J¼10.5, 14.0 Hz, 1H,
CH2-2); 3.98 (dd, J¼1.5, 14.0 Hz, 1H, CH2-2). 13C NMR
(CDCl3, 100 MHz) d (ppm) 152.55 (CH-20); 151.85 (C-40);
150.76 (C-60); 143.01 (CH-80); 139.32 (C-9a); 135.58 (C-
5a); 134.63; 131.95 (C-50); 131.32; 129.65; 128.43; 83.69
(CH-3); 72.09 (CH2-5); 59.97 (CH2-2). Anal. for
C14H11ClN4O3S: calcd: C 47.94; H 3.16; N 15.97. Found:
C 48.30; H 3.34; N 16.14.
carried out on 24. H NMR (CDCl3, 300 MHz) d (ppm)
8.55 (s, 1H, CH-20); 8.06 (s, 1H, CH-80); 7.64 (m, 1H, CH-
arom); 7.34 (m, 3H, CH-arom); 6.26 (dd, J¼3.9, 7.5 Hz,
1H, CH-3); 5.16 (d, J¼13.3 Hz, 1H, CH2-5); 4.99 (d, J¼
13.3 Hz, 1H, CH2-5); 4.18 (s, 3H, OMe); 3.27 (m, 2H,
CH2-2). 13C NMR (CDCl3, 75 MHz) d (ppm) 161.27
(CH-60); 152.40 (C-20); 150.70 (CH-40); 141.98 (C-5a);
139.69 (C-80); 135.99 (C-9a); 132.77; 130.10; 129.01;
128.58; 121.53 (C-50); 87.47 (CH-3); 73.78 (CH2-5); 54.34
(OMe); 39.19 (CH2-2). Anal. for C15H14N4O3S: calcd: C
54.53; H 4.27; N 16.96. Found: C 54.59; H 4.51; N 16.79.
4.4. Biological activity
The biological methods were the same as those previously
described.11,24
4.4.1. Cell lines. The cell lines IEC-6 (reference ECACC
No. 88071401), HT-29 (reference ECACC No. 91072201),
MCF-7 (reference ATCC No. CRL 1592) y MCF-10A
(reference ATCC No. CRL 10317) were selected for the
development of the different assays. All were obtained
from the cell culture service of the Scientific Instrumentation
Centre of the University of Granada. MCF-7 and HT-29 cells
were grown at 37 ꢁC in an atmosphere containing 5% CO2,
with Dubelcco’s modified Eagle Medium (DMEM) (Gibco,
Grand Island, NY) supplemented with 10% heat-inactivated
foetal bovine serum (FBS) (Gibco), 2% L-glutamine, 2.7%
sodium bicarbonate, 1% Hepes buffer, 40 mg/L gentamicin
and 500 mg/L ampicillin. For the IEC-6 the previous
medium supplemented with 0.1 IU/mL of insulin of bovine
pancreas was used. For the MCF-10A, the DMEM-F12
was used, supplemented with decomplemented horse serum,
10 mg/mL of insulin of bovine pancreas, 100 ng/mL of
choleric toxin, 0.5 mg/mL of hydrocortisone, 20 ng/mL of
epidermis growth factor and 100 mg/mL of penicillin/strep-
tomycin.
4.3.1.12. Synthesis of (1R*,3S*)-60-chloro-9-(1-oxo-
2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-9H-purine (23,
trans-23). H2O2, 50 wt % solution in water (0.03 mL,
0.56 mmol) was added to a solution of Sc(OTf)3 (46 mg,
0.09 mmol) in a mixture of EtOH (0.5 mL) and CH2Cl2
(4.5 mL). Compound 15 was added after 5 min and the re-
sulting solution was left at room temperature for 3.5 h. After
this, more H2O2 was added (0.05 mL) and the reaction was
left for 20.5 h. The mixture was diluted with CH2Cl2
(15 mL) and washed with H2O (2ꢂ10 mL), the organic layer
was dried (Na2SO4), concentrated and purified by flash chro-
matography using a mixture of EtOAc/MeOH, 9.9/0.1 to
produce trans-23 (150 mg, 96%) as an amorphous white
solid; mp: 271–273 ꢁC. HMBC and NOEdiff experiments
were carried out on trans-23. 1H NMR (CD3OD,
300 MHz) d (ppm) 8.22 (s, 1H, CH-80); 8.11 (dd, J¼1.5,
7.5 Hz, 1H, CH-9); 8.07 (s, 1H, CH-20); 7.72 (dt, J¼1.5,
7.2 Hz, 1H, CH-7); 7.65 (dt, J¼1.5, 7.6 Hz, 1H, CH-8);
7.55 (dd, J¼1.5, 7.5 Hz, 1H, CH-6); 6.60 (dd, J¼1.6,
10.6 Hz, 1H, CH-3); 5.47 (d, J¼14.1 Hz, 1H, CH2-5b);
5.01 (d, J¼14.1 Hz, 1H, CH2-5a); 4.58 (dd, J¼10.6,
14.5 Hz, 1H, CH2-2a); 4.08 (dd, J¼1.6, 14.5 Hz, 1H, CH2-
Acknowledgements
13
2b). C NMR (CD3OD, 75 MHz) d (ppm) 158.8 (C-60);
This study was supported by the Instituto de Salud Carlos III
149.51 (C-40); 147.18 (CH-20); 141.20 (C-9a); 140.27
(CH-80); 137.79 (C-5a); 135.52 (CH-7); 132.35 (CH-6);
130.37 (CH-8); 128.69 (CH-9); 125.46 (C-50); 84.10
(CH-3); 72.43 (CH2-5); 60.40 (CH2-2). Anal. for
C14H11ClN4O2S: calcd: C 50.23; H 3.31; N 16.74. Found:
C 50.12; H 3.36; N 16.49.
ꢀ
(Fondo de Investigacion Sanitaria) through Projects No. 01/
1092 and 01/928, and by the Junta de Andalucıa through the
´
Excellence Research Project No. 00636.
References and notes
4.3.1.13. Synthesis of (RS)-60-methoxy-9-(2,3-dihydro-
5H-4,1-benzoxathiepin-3-yl)-9H-purine (24). Anhydrous
MeOH (2 mL) at 0 ꢁC and under argon was added to a sus-
pension of NaH in mineral oil (10 mg, 0.24 mmol), and the
resulting solution was left at room temperature for 30 min.
To this clear solution, 15 (75 mg, 0.24 mmol) was added
dropwise and the mixture boiled at 90 ꢁC for 5 h. After re-
moving the solvent, the residue was treated with water
(10 mL), then extracted with dichloromethane (3ꢂ15 mL).
The combined organic phases were then dried (Na2SO4),
filtered and evaporated under reduced pressure to yield a res-
idue, which after flash chromatography (CH2Cl2/MeOH,
9.8/0.2) gave pure 24 (65 mg, 88% yield) as an amorphous
white solid; mp 205–206 ꢁC. HMBC experiments were
1. Saniger, E.; Campos, J.; Entrena, A.; Marchal, J. A.; S
ꢀuarez, I.;
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