E. Maalej et al. / Bioorg. Med. Chem. Lett. 21 (2011) 2384–2388
2387
as compared to the initial structures (see Figs. S2 and S3, Supple-
mentary data) or in terms of residue fluctuations (see Figs. S4
and S5, Supplementary data). The MM-GBSA analysis showed the
same energetic behavior as the docking solutions: (R)-20 and (S)-
20 presented the same interactions energies (see Table S3, Supple-
mentary data). Besides, and as it was anticipated from the SAR
analysis, the same type of stabilizing interactions were also found
values’, not being smaller than ꢀ1.0, in particular compound 20
presents a log BB value of ꢀ0.53.
To sum up, in this manuscript we have reported the synthesis
and pharmacological analysis of 14-aryl-10,11,12,14-tetrahydro-
9H-benzo[5,6]chromeno[2,3-b]quinolin-13-amines, prepared by
Friedländer reaction of 3-amino-1-aryl-1H-benzo[f]chromene-2-
carbonitriles with suitable cycloalkanones. The biological evalua-
tion showed that these molecules are potent and selective inhibitors
of AChE, in the nanomolar range, the most potent inhibitor being
4-(13-amino-10,11,12,14-tetrahydro-9H-benzo[5,6]chromeno[2,3-
b]quinolin-14-yl)phenol (20) [IC50 (EeAChE) = 7 2 nM], a mixed-
type inhibitor for EeAChE with a Ki of 5.00 nM. From these results,
as well as the theoretical physicochemical properties, we conclude
that compound 20 can be considered as an attractive molecule on
a key pharmacological receptor playing a key role in the progress
of Alzheimer’s disease, that deserve further analyzes. In fact, and
according to the docking and molecular dynamics predictions
(Supplementary data), the resolution of the racemic compound
20, as well as their biological evaluation, are being investigated in
our laboratories, and the results reported in due course.
during the trajectories, namely the
p–p staking and hydrogen
bonding (see Figs. S6 and S7, Supplementary data). Therefore, these
results are in good agreement with the experimental observations
in the sense that both enantiomers interact in the same way
(equivalent pose), and with the same, moderate, energy, at the
PAS, giving rise to a common interaction pattern that could explain
the behavior of the racemic specie. To go a step further, and bear-
ing in mind that the MM-GBSA model does not take into account
an entropic term, we decided to perform this calculation for both
enantiomers. The results (see Table S3, Supplementary data)
showed a negative contribution to the total free energy in the case
of the (S)-20 enantiomer, whereas the opposite becomes true for
the (R)-20 enantiomer, with a difference around 8 kcal/mol favour-
ing the (S)-enantiomer. Looking at the average structures obtained
from the last, stable, part of the trajectory and comparing them
with the initial ones (see Fig. S8, Supplementary data), it can be
seen that this effect could be associated to a higher deformation
occurring at the binding site when trying to accommodate the
(R)-enantiomer, as compared to the spatial requirements of the
(S)-enantiomer. This would mean that the observed activity would
be due to just one of the enantiomers.
Acknowledgments
F.C. acknowledges the Ministry of Higher Education, Scientific
Research and Technology in Tunisia for financial support. A.S.
thanks CSIC for a I3P-post-doc contract. J.M.C. thanks MICINN
(SAF2006-08764-C02-01; SAF2009-07271), and Comunidad de
Madrid (S/SAL-0275-2006) for financial support. C.R.S. thanks
Fundación CIEN (ISCIII, MICINN) and Fundación Teófilo Hernando
for financial support. The authors thankfully acknowledge the com-
puter resources, technical expertise and assistance provided by the
Barcelona Supercomputing Center—Centro Nacional de Super-
computación. A.M. thanks Comunidad de Madrid for BIPPED project
financial support. J.M.C. thanks Dr. M. Villarroya, and Prof. L. Gandía
(Instituto Teófilo Hernando, Madrid, UAM, Madrid, Spain) for the
neuroprotective tests, and for the Ca+2 analyzes, respectively.
The neuroprotective profile of compounds 19–28 has also been
evaluated in the MTT reduction method in SH-SY5Y cells, showing
that these products were modest neuroprotective agents, with val-
ues lower than 17%.
In addition, and in order to explore the potential of the selected
compounds as putative voltage-dependent calcium channels
antagonist, changes in cytosolic Ca2+ signals ([Ca2+]c) elicited by
depolarizing solutions (70 mM K+) were evaluated in bovine chro-
maffin cell populations. In these experiments, the application of K+
(70 mM) elicited a sharp increase in [Ca2+]c that reached a plateau
and then tended to slowly decline along the 40 s recording. Incuba-
tion of the cells with compounds (at concentrations between 0.3
Supplementary data
M) did not promoted any significant change K+-induced
signal even at the highest concentration tested
Supplementary data (synthesis of compounds 17, 19–28, the
pharmacological, the molecular modeling methods and their theo-
retical physicochemical properties) associated with this article can
and 100
l
in [Ca2+
]
c
(100 lM). These results suggest that these compounds do not
behave as voltage-dependent calcium channel antagonists.
Finally, a series of theoretical calculations (see Supplementary
data) allowed us to describe the ADME (Absorption, Distribution,
Metabolism, and Excretion) properties of compounds 19–28 within
the organism. All these four criteria influence the drug levels, its
kinetics and exposure to the tissues, and hence the performance
and pharmacological activity of a drug. Lipinski’s rule of five37
(RO5) is a rule of thumb to evaluate the drug likeness of a molecule
based on some molecular descriptors representing ADME proper-
ties (see Table S1, Supplementary data). All the compounds fulfill
molecular weigh, and the number of hydrogen donors and accep-
tors, whereas a log Po/w <5 is met by only four of them (20, 24,
25 and 28). The solubility (log S) of organic molecules in water
has a significant impact on many ADME-related properties like up-
take, distribution, transport, and eventually bioavailability. Only
compounds 20 (log S = ꢀ6.3) and 24 (log S = ꢀ6.1) present solubil-
ity values within the limits (ꢀ6.5–0.5), while the rest of the com-
pounds show values between ꢀ6.5 and ꢀ7.3, being in the limits
of aqueous solubility. The most used parameter for Blood Brain
(BB) barrier penetration is log BB. The log BB of many prescribed
CNS drugs is >ꢀ0.5 and compounds with log BB <ꢀ1.0 penetrate
poorly into the brain, yet some commercial CNS drugs have
log BB <ꢀ1.0.38 Compounds 19–28 present acceptable log BB
References and notes
1. Goedert, M.; Spillantini, M. G. A. Science 2006, 314, 777.
2. Castro, A.; Martínez, A. Curr. Pharm. Des. 2006, 12, 4377.
3. Cummings, J. L. Rev. Neurol. Dis. 2004, 1, 60.
4. Scarpini, E.; Scheltens, P.; Feldman, H. Lancet Neurol. 2003, 2, 539.
5. Talesa, V. N. Mech. Ageing Dev. 2001, 122, 1961.
6. (a) Racchi, M.; Mazzucchelli, M.; Porrello, E.; Lanni, C.; Govoni, S. Pharmacol.
Res. 2004, 50, 441; (b) Darvesh, S.; Pottie, I. R.; Darvesh, K. V.; McDonald, R. S.;
Walsh, R.; Conrad, S.; Penwell, A.; Mataija, D.; Martin, E. Bioorg. Med. Chem.
2010, 18, 2232; (c) Katalinic, M.; Rusak, G.; Barovic, J. D.; Sinko, G.; Jelic, D.;
Antolovic, R.; Kovarik, Z. Eur. J. Med. Chem. 2010, 45, 186.
7. Inestrosa, N. C.; Álvarez, A.; Pérez, C. A.; Moreno, R. D.; Vicente, M.; Linker, C.;
Casanueva, O. I.; Soto, C.; Garrido, J. Neuron 1996, 16, 881.
8. Bartolini, M.; Bertucci, C.; Cavrini, V.; Andrisano, V. Biochem. Pharmacol. 2003,
65, 407.
9. Cavalli, A.; Bolognesi, M. L.; Capsoni, S.; Andrisano, V.; Bartolini, M.; Margotti,
E.; Cattaneo, A.; Recanatini, M.; Melchiorre, C. Angew. Chem. Int. Edit. 2007, 46,
3689.
10. Muñoz-Torrero, D.; Camps, P. Curr. Med. Chem. 2006, 13, 399.
11. Savini, L.; Gaeta, A.; Fattorusso, C.; Catalanotti, B.; Campiani, G.; Chiasserini, L.;
Pellerano, C.; Novellino, E.; McKissic, D.; Saxena, A. J. Med. Chem. 2003, 46, 1.
12. Decker, M. J. Med. Chem. 2006, 49, 5411.
13. Carlier, P. R.; Chow, E. S.; Han, Y.; Liu, J.; El Yazal, J.; Pang, Y. P. J. Med. Chem.
1999, 42, 4225.
14. Cavalli, A.; Bolognesi, M. L.; Minarini, A.; Rosini, M.; Tumiatti, V.; Recanatini,
M.; Melchiorre, C. J. Med. Chem. 2008, 51, 347.