Synthesis of novel [3,1]-benzothiazepine and [3,1]-benzoxazepine derivatives with antitumoral activity

Article abstract of DOI:10.1039/c3ra44937h

A new method for the synthesis of [3,1]-benzothiazepines and [3,1]-benzoxazepines from the reaction of C-allylanilines and isothiocyanates or isocyanates without the need for the isolation of any intermediate is described. The compounds were obtained in good to moderate yields and some exhibited cytotoxic activity against tumor cell lines. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c3ra44937h

RSC Advances
View Article Online
View Journal | View Issue
COMMUNICATION
Synthesis of novel [3,1]-benzothiazepine and [3,1]-
benzoxazepine derivatives with antitumoral
activity†
Cite this: RSC Adv., 2014, 4, 14715
Walter R. Martınez,a Gardenia C. G. Militao,b Teresinha G. da Silva,c Ricardo O. Silvaa
Received 6th September 2013
Accepted 12th March 2014
´
˜
a
*
and Paulo H. Menezes
DOI: 10.1039/c3ra44937h
www.rsc.org/advances
A new method for the synthesis of [3,1]-benzothiazepines and [3,1]- few reports in the literature describing the synthesis of this
benzoxazepines from the reaction of C-allylanilines and iso- class of compounds.7
thiocyanates or isocyanates without the need for the isolation of any
We initially focused on experiments to nd a route which
intermediate is described. The compounds were obtained in good to gave the required starting materials. Thus, allylation of
moderate yields and some exhibited cytotoxic activity against tumor commercially available anilines 1a–d was performed following a
cell lines.
literature procedure8 to yield the corresponding N-allylanilines
2a–d in good yields (Scheme 1).
Subsequent aza-Claisen rearrangement9 at 114–140 ꢀC
without the use of any solvent gave the corresponding C-ally-
lanilines 3a–d in good yields (Scheme 2).
C-Allylanilines, 3 were then reacted with commercially
available isothiocyanates, in dichloromethane to give in situ the
corresponding thioureas. Subsequent addition of iodine10 to the
reaction mixture gave the corresponding [3,1]-benzothiazepines
Benzothiazepines and benzoxazepines constitute important
building blocks in pharmaceutical research while they can be
found in many drugs and preclinical leads.1
The synthesis of different isomeric forms of these
compounds by varying the position of the heteroatoms in their
structures together with their unique pharmacological proper-
ties make the development of new methods for the synthesis of
medium-sized heterocycles containing N, S and O atoms a
subject of great interest. Thus, several isomers of benzothiaze-
pine2 and benzoxazepine3 rings were already described and
some of them exhibited a wide variety of pharmacological
effects.4
Herein, we wish to describe a new method for the synthesis
of [3,1]-benzothiazepines and [3,1]-benzoxazepines for further
evaluation of their antitumoral activities. The general method
for the synthesis of [3,1]-benzoxazepines is based on the
photochemical isomerization of quinoline N-oxides.5 However,
it requires a signicant number of steps for preparation of the
starting materials used in the cyclization event, and sometimes
proceed with a lack of regioselectivity.6 In the case of [3,1]-
benzothiazepines derivatives, to our knowledge there are even
Scheme 1 Synthesis of N-allylanilines 2a–d.
a
´
Universidade Federal de Pernambuco – Depto. Quımica Fundamental, Av. Jornalista
Anibal Fernandes s/n, 50670-901, Recife, PE, Brazil. E-mail: paulo.menezes@pq.
cnpq.br; Fax: +55-81-2126-8442
bUniversidade Federal de Pernambuco – Departamento de Fisiologia e Farmacologia,
´
CCB, Cidade Universitaria, Recife, PE, Brazil
c
´
Universidade Federal de Pernambuco – Departamento de Antibioticos, CCB, Cidade
´
Universitaria, Recife, PE, Brazil
† Electronic supplementary information (ESI) available: Experimental procedures,
Scheme 2 Synthesis of C-allylanilines 3a–d.
spectra and spectroscopic data for all compounds. See DOI: 10.1039/c3ra44937h
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 14715–14718 | 14715

View Article Online
RSC Advances
Communication
4 through a 7-exo-trig mode cyclization in good yields and with the reaction conditions. The only exception occurred when
without the isolation of any intermediate compound (Table 1). 3a was used as precursor, where a complex mixture of products
The reaction yield does not seem to be strongly inuenced by was observed. Further attempts to purify 4a from this mixture
the electronic effects on the groups attached to the aromatic were unsuccessful (Table 1, entry 1).
ring of both C-allylanilines 3 or isothiocyanates since the [3,1]-
Next, we extended the method for the synthesis of the [3,1]-
benzothiazepines bearing neutral, electron-withdrawing and benzoxazepines derivatives, 5a–c. In this case, the reaction
electron-donating groups in the aromatic rings were compatible solvent was replaced by tetrahydrofuran due to the low solu-
bility of intermediates N,N0-diarylureas in dichloromethane.
Thus, reaction of C-allylanilines, 3a–b with phenylisocyanate
Table 1 Synthesis of [3,1]-benzothiazepines 4 through iodocyclization
led to the formation in situ of the corresponding N,N0-diarylureas
aer one hour. Subsequent cyclisation using iodine gave the
corresponding [3,1]-benzoxazepines 5a–c in moderate yields
(Table 2). The reaction using isocyanates gave lower yields (38–
56%) when compared to the reaction using thiocyanates. This
result could be explained by the lower nucleophilic character of
the oxygen atom from the carbonyl group of the synthesized ureas
Entry 3 Ar
Time (h) [3,1]-Benzothiazepine
72
Yielda (%)
when compared to the sulfur atom present in the thioureas.
The cyclisation of ureas or thioureas could lead to two
isomers being the C]N bond endo or exo (Fig. 1). For example,
for compound 5a, if the signal attributed to the proton bonded
to nitrogen – Hb – presents an HMBC correlation with the
carbon nuclei Cb from ring B, the obtained compound should
have an endo C]N bond (Fig. 1, structure 5a). However, if the
hydrogen atom bonded to nitrogen –Ha – presents an HMBC
correlation with the carbon nuclei Ca from ring A, the obtained
compound should have an exo C]N bond (Fig. 1, structure 5a0).
From the spectrum obtained for 5a, ring A shows four
different signals in the 1H NMR spectrum at dH 7.74 (d, 8.1 Hz,
1H), 7.23 (d, 7.2 Hz, 1H), 7.14 (t, 8.1 Hz, 1H) and 6.93 (td, 7.5, 1.0
Hz, 1H). Conversely, ring B shows only three signals at dH 7.52
(dd, 8.7, 0.9 Hz, 2H), 7.34–7.26 (m, 2H) and 7.07–7.00 (m, 1H).
HMBC spectrum shown a correlation between the signal at dH
8.85, corresponding to N–H and the signals at dC 152.0 and
120.6. The signal at dC 152.0 was attributed to C]N. In addi-
tion, the signal at dC 120.6 showed an HMQC correlation with
the signal at dH 7.52, attributed to the proton at the ortho
b
1
2
3a C6H5
4a
—
3b 4-Cl-C6H4
99
4b 74
4c 37
3
4
5
6
3b 3,4-Me2-C6H3 72
3b C10H7
120
72
4d 63
4e 69
4f 76
3c 4-Cl-C6H4
3c C10H7
96
Table 2 Synthesis of [3,1]-benzoxazepines 5 through iodocyclization
7
8
3d C6H5
72
120
48
4g 52
4h 77
3d 4-Cl-C6H4
3d 4-F-C6H4
Entry
1
3
[3,1]-Benzoxazepine, 5
Yield (%)
47
9
4i 70
4j 64
3a
5a
5b
10
3d 4-MeO-C6H4 120
3d 3,4-Me2-C6H3 120
2
3
3b
3c
56
38
11
4k 74
5c
a
Isolated yield. b A complex mixture of products was obtained.
14716 | RSC Adv., 2014, 4, 14715–14718
This journal is © The Royal Society of Chemistry 2014

View Article Online
Communication
RSC Advances
an array of more potent target structures while the iodine atom
can be used as an additional point of diversity.
Acknowledgements
The authors gratefully acknowledge CNPq (484778/2011-0),
FACEPE (PRONEX APQ-0859-1.06/08), CAPES and INCT-INAMI
for nancial support. The authors are also thankful to Central
Fig. 1 HMBC correlation between the endo and exo compounds.
´
Analıtica (IQ-UNICAMP) for HRMS. P.H.M is thankful to CNPq
for his fellowship.
Table 3 IC50 and standard error values (mg mLꢁ1) of two different
experiments for compounds 4h and 4i
Notes and references
Compound
HL-60
NCI-H292
HT-29
1 (a) J. B. Bariwal, K. D. Upadhyay, A. V. Manvar, J. C. Trivedi,
J. S. Singh, K. S. Jain and A. K. Shah, Eur. J. Med. Chem., 2008,
43, 2279; (b) X. Wu, F. Liu and Y. Zhou, J. Heterocycl. Chem.,
2011, 48, 368; (c) R. Budriesi, B. Cosimelli, P. Ioan,
M. P. Ugenti, E. Carosati, M. Frosini, F. Fusi, R. Spisani,
S. Saponara, G. Cruciani, E. Novellino, D. Spinelli and
A. Chiarini, J. Med. Chem., 2009, 52, 2352; (d)
C. W. Lindsley, ACS Chem. Neurosci., 2010, 1, 343; (e)
C. W. Yin, S. K. Wo and Z. Zuo, J. Pharm. Biomed. Anal.,
2012, 58, 83; (f) S. Fukamachi, H. Konishi and
K. Kobayashi, Heterocycles, 2011, 83, 883.
2 Benzothiazepines synthesis: [1,5](a) Z. Q. Dong, F. M. Liu
and Z. L. Yuan, Mol. Diversity, 2011, 15, 963; (b)
D. B. Yadav, B. Dharmendra, G. L. Morgans,
B. A. Aderibigbe, L. G. Madeley, M. A. Fernandes,
J. P. Michael, C. B. de Koning and W. A. L. van Otterlo,
Tetrahedron, 2011, 67, 2991; (c) C. B. W. Phippen and
C. S. P. McErlean, Tetrahedron Lett., 2011, 52, 1490; (d)
E. Ayral, P. Gloanec, G. Berge, G. de Nanteuil,
P. Mennecier, A. Rupin, T. J. Verbeuren, P. Fulcrand,
J. Martinez and J. F. Hernandez, Bioorg. Med. Chem. Lett.,
2009, 19, 1386; [1,4]; (e) C. Spitz, V. Reboul and P. Metzner,
4h
8.2 ꢂ 0.2
2.1 ꢂ 0.9*
0.02 ꢂ 0.005
15.1 ꢂ 1.6
12.4 ꢂ 3.1
0.1 ꢂ 0.05
14.8 ꢂ 1.1
7.7 ꢂ 0.8*
0.4 ꢂ 0.05
4i
DOXa
a
Doxorubicin (DOX) was the positive control. *p < 0.05 compared
compound 4i to 4h by t test.
position in ring B. In this way, the signal at dC 120.6 was
attributed to the carbon at the ortho position in the ring B,
conrming the structure of the obtained compound as 5a.
The in vitro anticancer activity of benzoxathiepin,11 benzo-
dioxepin12 and benzoxazepines13 on MCF-7 cells has been
previously described. Further studies of 4,1-benzoxazepines by
microarray technology showed that the main molecular targets
of some of these compounds are pro-apoptotic genes with
protein kinase activity such as GP132, ERN1 or RAC1, which
prevent the metastatic progression. These facts prompt us to
submit the synthesized compounds to the MTT assay14 for the
evaluation of their cytotoxic effects on tumor cells.
The synthesized compounds were then screened at 25 mg mLꢁ1
against HL-60 (human pro-myelocytic leukemia), NCI-H292
(human lung carcinoma) and HT-29 (human colon carcinoma)
tumor cells lineages. The samples with growth inhibition over
90% were used to determine the IC50 values (concentration that
causes 50% growth inhibition). Analogues 4h and 4i exhibited
good cytotoxicities and their IC50 values (mg mLꢁ1) were deter-
mined. The results are described in Table 3.
From Table 3 it can be seen that compound 4h displayed
moderate cytotoxic activity against all tested cancer cell lines,
being more active for HL-60 cells. Compound 4i exhibited better
antiproliferative activity against HL-60 and HT-29 cell lines,15
being also more active for HL-60 with an IC50 ¼ 2.1 mg mLꢁ1
demonstrating the potential of the newly synthesized
compounds as antitumoral agents.
´
Tetrahedron Lett., 2011, 52, 6321; (f) L. Fodor, P. Csomos,
A. Csampai and P. Sohar, Synthesis, 2010, 2943; (g)
M. Incerti, D. Acquotti, P. Sandor and P. Vicini,
Tetrahedron, 2009, 65, 7487; [1,3]; (h) G. Campiani,
S. Butini, C. Fattorusso, B. Catalanotti, S. Gemma,
V. Nacci, E. Morelli, A. Cagnotto, I. Mereghetti, T. Mennini,
M. Carli, P. Minetti, M. A. Di Cesare, D. Mastroianni,
N. Scafetta, B. Galletti, M. A. Stasi, M. Castorina, L. Pacici,
M. Vertechy, S. di Serio, O. Ghirardi, O. Tinti and
P. Carminati, J. Med. Chem., 2004, 47, 143; (i) G. Campiani,
V. Nacci, S. Bechelli, S. M. Ciani, A. Garofalo, I. Fiorini,
H. Wikstrom, P. de Boer, Y. Liao, P. G. Tepper, A. Cagnotto
and T. Mennini, J. Med. Chem., 1998, 41, 3763; [1,2]; (j)
R. A. Abramovitch, R. A. Mavukel, B. Mavukel and
J. R. Stowers, J. Chem. Soc., Chem. Commun., 1983, 520; (k)
Y. Tamura, S. M. Bayomi, C. Mukai, M. Ikeda and
M. Murase, Tetrahedron Lett., 1980, 21, 533.
Conclusions
In conclusion, the method demonstrates to be useful for the
synthesis of [3,1]-benzothiazepines and [3,1]-benzoxazepines
derivatives without the need of the isolation of any intermediate.
Compounds 4h and 4i exhibit good antitumoral activity for
HL-60 cells and are promising intermediates for the synthesis of
3 Benzoxapines synthesis: [1,5]: (a) J. F. Liegeois, M. Deville,
S. Dilly, C. Lamy, F. Mangin, M. Resimont and F. I. Tarazi,
J. Med. Chem., 2012, 55, 1572; (b) Y. Uto, Y. Ueno,
Y. Kiyotsuka, Y. Miyazawa, H. Kurata, T. Ogata, T. Takagi,
S. Wakimoto and J. Ohsumi, Eur. J. Med. Chem., 2011, 46,
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 14715–14718 | 14717

View Article Online
RSC Advances
Communication
1892; (c) A. Levai, Heterocycles, 2008, 75, 2155; [1,4]; (d)
M. Ghandi, T. Momeni, M. T. Nazeri, N. Zarezadeh and
M. Kubicki, Tetrahedron Lett., 2013, 54, 2983; (e)
H. Kwiecien, M. Smist and A. Wrzesniewska, Curr. Org.
Synth., 2012, 9, 828; [1,3]; (f) N. Kakusawa, K. Sakamoto,
J. Kurita and T. Tsuchiya, Heterocycles, 1996, 43, 2091; (g)
A. R. Katrizky, O. Rubio, R. Awartani, N. Latif, N. Mishriky
and F. M. Assad, Heterocycles, 1984, 22, 1155; (h) A. Albini,
G. F. Bettinetti and G. Minoli, Tetrahedron Lett., 1979, 20,
3761; [1,2]; (i) T. Kametani and H. Nemoto, Chem. Pharm.
Bull., 1971, 19, 1325.
4 (a) K. Lombardo, M. A. Stasi and F. Borsini, Eur.
J. Pharmacol., 2009, 621, 53; (b) K. Lombardo, M. A. Stasi
and F. Borsini, Eur. J. Pharmacol., 2009, 621, 53; (c)
R. Coccurello, A. Caprioli, R. Conti, O. Ghirardi, F. Borsini,
P. Carminati and A. Moles, J. Med. Chem., 2004, 47, 143; (d)
R. Coccurello, A. Caprioli, R. Conti, O. Ghirardi, F. Borsini,
P. Carminati and A. Moles, J. Pharmacol. Exp. Ther., 2008,
326, 905; (e) G. Campiani, S. Butini, S. Gemma, V. Nacci,
6 (a) W. Y. Yang, S. A. Marrone, N. Minors, D. A. R. Zorio and
I. V. Alabugin, Beilstein J. Org. Chem., 2011, 7, 813; (b)
T. Besson, G. Guillaumet, C. Lamazzi and C. W. Rees,
Synlett, 1997, 704; (c) P. Dalidowicz and J. S. Swenton,
J. Org. Chem., 1993, 58, 4802; (d) G. Capozzi, R. Ottana and
G. Romeo, Heterocycles, 1987, 26, 39; (e) J. P. Le Roux,
P. L. Desbene and J. C. Cherton, J. Heterocycl. Chem., 1981,
18, 847; (f) Y. Ito, K. Kobayashi and T. Saegusa, Tetrahedron
Lett., 1978, 19, 2087; (g) C. Kaneko, H. Fujii, S. Kawai and
M. Somei, Chem. Lett., 1978, 1277; (h) C. Kaneko, S. Kawai
and M. Somei, Chem. Lett., 1978, 1281; (i) Y. Kobayashi,
I. Kumadaki, Y. Hirose and Y. Hanzawa, J. Org. Chem.,
1974, 39, 1836.
7 W. Fathalla, J. Marek and P. Pazdera, Heterocycl. Commun.,
2002, 8, 79.
´
8 I. Gonzalez, I. Bellas, A. Souto, R. Rodrıguez and J. Cruces,
Tetrahedron Lett., 2008, 49, 2002.
9 L. M. Acosta, A. Palma and A. Bahsas, Tetrahedron, 2010, 66,
8392.
C. Fattorusso, B. Catalanotti, G. Giorgi, A. Cagnotto, 10 (a) M. Jereb, D. Vrazic and M. Zupan, Tetrahedron, 2011, 67,
M. Goegan, T. Mennini, P. Minetti, M. A. Di Cesare,
D. Mastroianni, N. Scafetta, B. Galletti, M. A. Stasi,
M. Castorina, L. Pacici, O. Ghirardi, O. Tinti and
P. Carminati, J. Med. Chem., 2002, 45, 344.
5 (a) A. Albini, G. F. Bettinetti and G. Minoli, Org. Synth., 1990,
7, 23; (b) C. Kaneko, H. Fujii, K. Hashiba, Y. Karasawa,
1355; (b) K. Gilmore and I. V. Alabugin, Chem. Rev., 2011,
111, 6513; (c) B. Godoi, R. F. Schumacher and G. Zeni,
Chem. Rev., 2011, 111, 2937.
11 M. C. Nunez, F. Rodriguez-Serrano, J. A. Marchal, O. Caba,
A. Aranega, M. A. Gallo, A. Espinosa and J. M. Campos,
Tetrahedron, 2007, 63, 183.
M. Wakai, R. Hayashi and M. Somei, Chem. Pharm. Bull., 12 A. Conejo-Garcia, M. C. Nunez, J. A. Marchal, F. Rodriguez-
1982, 30, 74; (c) A. Albini, G. F. Bettinetti and G. Minoli,
Tetrahedron Lett., 1979, 20, 98; (d) C. Kaneko, A. Yamamoto
Serrano, A. Aranega, M. A. Gallo, A. Espinosa and
J. M. Campos, Eur. J. Med. Chem., 2008, 43, 1742.
and M. Hashiba, Chem. Pharm. Bull., 1979, 27, 946; (e) 13 (a) K. Samanta, B. Chakravarti, J. K. Mishra,
N. Hata, Chem. Lett., 1978, 7, 1359; (f) C. Kaneko and
R. Kitamura, Heterocycles, 1977, 6, 111; (g) R. Kitamura,
H. Fujii, K. Hashiba, M. Somei and C. Kaneko, Tetrahedron
Lett., 1977, 18, 2911; (h) S. Yamada, M. Ishikawa and
C. Kaneko, Chem. Pharm. Bull., 1975, 23, 2818; (i)
C. Kaneko, S. Hayashi and Y. Kobayashi, Chem. Pharm.
S. K. D. Dwivedi, L. V. Nayak, P. Choudhry, H. K. Bid,
R. Konwar, N. Chattopadhyay and G. Panda, Bioorg. Med.
Chem. Lett., 2010, 20, 283; (b) M. Diaz-Gavilan,
F. Rodriguez-Serrano, J. A. Gomez-Vidal, J. A. Marchal,
A. Aranega, M. A. Gallo, A. Espinosa and J. M. Campos,
Tetrahedron, 2004, 60, 11547.
Bull., 1974, 22, 2147; (j) A. Kubo, S.-I. Sakai, S. Yamada, 14 J. M. Edmondson, L. S. Armstrong and A. O. Martinez,
I. Yokoe and C. Kaneko, Chem. Pharm. Bull., 1968, 16, J. Tissue Cult. Methods, 1988, 11, 15.
1533; (k) C. Kaneko, I. Yokoe and M. Ishikawa, Tetrahedron 15 In order to understand if the IC50 values are statistically
Lett., 1967, 8, 5237; (l) C. Kaneko and I. Yokoe, Tetrahedron
Lett., 1967, 8, 5355; (m) O. Buchardt, Tetrahedron Lett.,
1966, 7, 6221.
signicant, the t test, comparing 4i to 4h was performed.
The results showed that the IC50 values for 4i and 4h are
different only for HL-60 and HT-29.
14718 | RSC Adv., 2014, 4, 14715–14718
This journal is © The Royal Society of Chemistry 2014