Communication
Organic & Biomolecular Chemistry
in vitro AChE inhibitory activity, highlighting compound 6b,
with an IC50 = 0.2 mM, as the most potent inhibitor of this
enzyme (Table 5).
Table 5 Criteria for the selection of the best conditions for the reaction of the
N-benzylmaleimides 4a with furfurylamine 5
Compound
IC50 a (mM)
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
7a
7b
7c
0.233 0.003
0.200 0.004
0.267 0.008
0.315 0.014
0.293 0.004
0.235 0.011
0.279 0.015
0.249 0.012
0.262 0.012
0.302 0.008
0.419 0.026
0.236 0.006
0.287 0.009
0.212 0.008
0.173 0.009b
Conclusions
In summary, the present work is the first example of an easy,
efficient and green protocol for the synthesis of both novel
7-oxa-2-azabicyclo[2.2.1]hept-5-enes and 4-aminomethyl-7-oxa-
bicyclo [2.2.1]hept-5-enes, further investigations of the scope
and the reaction mechanism of this synthetic method could
extend its application to the synthesis of some natural and bio-
logically active molecules.
Through zebrafish embryo in vivo screening it was discov-
ered that 6g is a novel inhibitor of early-stage zebrafish embryo
development and an extremely toxic agent.
Possessing several degrees of structural diversity, both types
of bicycloheptenes 6a–k and 7a–c are novel, interesting models
for zebrafish embryo in vivo screening that encourage our syn-
thetic and biological investigations on phenotypic characteriz-
ation of a whole vertebrate organism in order to exploit this
platform for medium to high throughput compound testing.
Physostigmine
a IC50 values are the mean SEM of at least three different experiments
in duplicate. b IC50 values are expressed in μM.
mechanism proposed in Scheme 3, the nucleophilicity of the
furfurylamine nitrogen plays a key role in the ring closure
during the formation of the bicyclic system, so the acetylation
of this nitrogen probably would avoid the ring closure and
allow the DAR between the reactants.
From this hypothesis we performed the reaction between
N-acetylfurfurylamine 5b and maleimides 4b, 4j and 4k under
the same conditions studied above. We were pleased that
N-substituted DNCs 7a–c were obtained in excellent yields
(Table 4).
Acknowledgements
We acknowledge the financial support given by Universidad
Industrial de Santander during the development of this study.
Finally and as part of our current chemical-biology
program, preliminary studies were carried out to establish the
possible biological activity of molecules 6a–k and 7a–c.
We addressed the zebrafish (Danio rerio, Cyprinidae) as a
system for biomedical research. Through zebrafish embryo
in vivo screening11 we discovered that compound 6g was a
novel inhibitor of early-stage zebrafish embryo development
and an extremely toxic agent at diverse concentrations. The
embryos treated with 100, 150 and 200 μM died after 72 hours
after chemical exposure. The head–trunk angle, used as a
measure of developmental rate (normal angle from the middle
of the ear and eye to the notochord: 148° at 96 hpf), indicates
that the embryos treated with 60 μM, and below, are slightly
delayed in development, head–trunk angle 134.4° (red dotted
line). The yellow dotted line indicates that the embryos,
treated with 60 μM and below, did not consume their yolk at
the same rate to the control fish, putting in evidence the diges-
tive damage (DD) (Fig. 1B).
Additionally, we followed the method described by
Ellman12 and adapted in our laboratory with some modifi-
cations.13 Compounds 6a–k and 7a–c were evaluated as inhibi-
tors of the enzyme acetylcholinesterase (AChE) from
Electrophorus electricus (type V-S). Comparing the AChE inhibi-
tory activity for the evaluated compounds with the obtained
inhibitory activity for the reference compound (physostig-
mine), we found that these compounds possess moderate
Notes and references
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Areniz and C. M. Meléndez Gómez, Synthesis, 2011, 4011;
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410 | Org. Biomol. Chem., 2013, 11, 407–411
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