Strategic targeting of multiple water-mediated interactions: A concise and rational structure-based design approach to potent and selective MMP-13 inhibitors

Full text of DOI:10.1002/cmdc.201300278

CHEMMEDCHEM
COMMUNICATIONS
DOI: 10.1002/cmdc.201300278
Strategic Targeting of Multiple Water-Mediated
Interactions: A Concise and Rational Structure-Based
Design Approach to Potent and Selective MMP-13
Inhibitors
Thomas Fischer and Rainer Riedl*[a]
In memoriam Claudia Nothnagel
Water is an essential molecule in biological systems based on
its role as the solvent for life.[1] Understanding the dynamics of
the interaction between water and proteins represents
a highly active field of research in molecular recognition,
chemical biology, and drug discovery.[2,3] In chemical biology,
water-mediated interactions offer tremendous opportunities
for the development of novel chemical structures with biologi-
cal activity, but due to its small size on the one hand and to its
overwhelming abundance as a solvent on the other hand,
water is often neglected when it comes to the detailed study
of biological processes on a molecular or atomic level. Here,
we report the very efficient use of X-ray crystallographic data
containing structural water molecules for the design and syn-
thesis of potent and selective matrix metalloproteinase-13
(MMP-13) inhibitors by targeting multiple water-mediated
interactions between the protein target and the inhibitor.
MMP-13 is a highly relevant and validated target for a multi-
tude of severe diseases, such as cancer, osteoarthritis and rheu-
matoid arthritis.[4] MMP-13 is a member of the zinc-dependent
endopeptidase family. It is the dominant MMP involved in
type II collagen cleavage in the degradation process of extra-
cellular matrix during growth and tissue remodeling.[4b,5,6] Early
attempts at finding inhibitors against MMPs resulted in pepti-
domimetics derived from natural substrates with modified moi-
eties close to the scissile amide bond.[4g] The potency of these
inhibitors was further enhanced by introducing zinc-chelating
groups in order to bind to the zinc ion in the active site of the
enzyme. Hydroxamates turned out to be the most efficient
zinc binders.[7,8] Because of unsatisfying bioavailability and
severe side effects due to a lack of selectivity, all clinical candi-
dates containing strong zinc binding groups failed in clinical
trials.[9] While doxycycline, an antibiotic tetracycline that exhib-
its off-target MMP inhibition, has been the only inhibitor to
reach the market so far, this does indicate that the target pro-
tein family is indeed druggable.[4g] In order to overcome the
deleterious side effects of strong zinc binding inhibitors, a new
class of MMP inhibitors has been developed recently that does
not bind to the catalytic zinc but rather binds deep within the
S1’ pocket.[10] This finding leads to new opportunities for the
discovery of selective MMP-13 inhibitors based on the structur-
al differences in the S1’ binding site among different MMPs.
In chemical biology and medicinal chemistry, there is a con-
stant need for novel small molecules modulating biological ac-
tivity in order to achieve insights into the underlying biological
processes on a molecular level. In particular, pharmaceutical
companies spend a considerable amount of their budget in
the development of potent and selective scaffolds of biologi-
cally active molecules. Those small-molecule modulators can
either be discovered by extensive and resource-intensive
screening campaigns or by rational design approaches. Rather
than performing screening activities, we approached this prob-
lem by analyzing co-crystal structures of the target protein in-
cluding structural water molecules in order to define the phar-
macophore and substitution pattern for inhibitor scaffolds.
Here, our focus was on using structural water molecules as
binding partners for novel small-molecule modulators.
Analysis of the co-crystal structure PDB 2OW9[10h] (Figure 1)
allowed us to design a novel scaffold of MMP-13 inhibitors
[a] T. Fischer, Prof. Dr. R. Riedl
Institute for Chemistry and Biological Chemistry
Zurich University of Applied Sciences (ZHAW)
Einsiedlerstrasse 31, 8820 Wꢀdenswil (Switzerland)
E-mail: rainer.riedl@zhaw.ch
Homepage: www.icbc.zhaw.ch/organic-chemistry
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cmdc.201300278.
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial License, which permits use, distribution and
reproduction in any medium, provided the original work is properly
cited and is not used for commercial purposes.
Figure 1. Analyzing the pharmacophore of the co-crystallized inhibitor in
PDB 2OW9[10h] allowed for the generation of novel phthalimide scaffold 4.
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemMedChem 2013, 8, 1457 – 1461 1457

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
that was subsequently optimized with regard to its binding
affinity by targeting water-mediated interactions.
Conserving the hydrogen-bonding capabilities to the back-
bone NH of Thr224, Thr226 and Met232 as well as the p–p in-
teraction to His201 yielded phthalimide scaffold 4. Molecular
modeling of 4 in the S1’ binding site using force field
MMFF94x[11] supported the expected binding orientation of 4
(Figure 2).
Scheme 1. Synthesis of phthalimides 4–6. Reagents and conditions: a) BnBr
(2)/4-(bromomethyl)pyridine (3) (1.0 equiv), KOH (1.0 equiv), DMF, RT, 18 h,
59% (2); 77% (3); b) phenylacetyl chlorides (1.2 equiv), DIPEA (1.5 equiv),
THF, RT, 2 h, 81% (4); 86% (5); 50% (6).
Table 1. MMP inhibitory data for compounds 4–6.
Compd
MMP-13
MMP-2
MMP-12
MMP-14
4
5
6
9.80,[a] 25[b]
1.57[a]
0.49[a]
4[b]
>100[a]
>100[a]
11[b]
>100[a]
>100[a]
8[b]
>100[a]
>100[a]
[a] IC50 values [mm]; confidence intervals are given in the Supporting In-
formation. [b] % Inhibition at 6.5 mm; for further details, see the Support-
ing Information.
Figure 2. Rational design of phthalimide inhibitor 4 in the MMP-13 S1’ bind-
ing site: direct hydrogen bonding to the protein.
Furthermore, molecular modeling of 4 within the S1’ binding
sites of MMP-2 (PDB 3AYU),[12] MMP-12 (PDB 1Y93),[13] and
MMP-14 (PDB 3MA2)[14] indicated that 4 does not fit into the
MMP-2, MMP-12 and MMP-14 binding sites due to a clash in
the selectivity loop deep within the S1’ pocket. This finding
suggested good selectivity of phthalimide scaffold 4 for MMP-
13 over MMP-2, MMP-12 and MMP-14, which is in contrast to
classical zinc binding inhibitors.
Analyzing the close surroundings within 5 ꢁ of the terminal
phenyl groups of the designed phthalimide scaffold in the S1’
binding site of PDB 2OW9 with a resolution of 1.74 ꢁ revealed
several water molecules as attractive binding partners based
on their distance from the inhibitor scaffold: water molecules
HOH747, HOH813, HOH836, HOH915 on the right-hand side
and HOH794, HOH822, HOH890 on the left-hand side (number-
ing based on protein chain A of PDB 2OW9; Figure 3).
Based on our molecular modeling results and supported by
the positive evaluation in medicinal chemistry filtering process-
es such as the Lipinski concept,[15] the parent compound of
phthalimide scaffold 4 was synthesized in a two-step synthesis
starting from 4-aminophthalimide 1 via 2-substituted 5-amino-
isoindoline-1,3-diones 2[16] and 3 (Scheme 1). The ease of its
synthesis makes the phthalimide scaffold an ideal candidate
for subsequent library synthesis for the optimization of binding
properties.
In order to get a better understanding of the water mole-
cules that are in the proximity of phthalimide scaffold 4, over-
Compound 4 was tested for its biological activity against
MMP-2, MMP-12, MMP-13 and MMP-14 at an inhibitor concen-
tration of 6.5 mm in single-point determinations, which were
averaged over three measurements. Compound 4 showed in-
hibitory activity of 25% at 6.5 mm against MMP-13 and moder-
ate selectivity over the antitargets MMP-2, MMP-12 and MMP-
14, which supported our molecular modeling results (Table 1).
The promising potency and selectivity data of the designed
phthalimide scaffold allowed us to perform the second step of
our design concept, which was targeting water-mediated inter-
actions in order to improve the potency of the inhibitor struc-
ture.
Figure 3. Analysis of water molecules in proximity to phthalimide scaffold 4
within the S1’ binding site of PDB 2OW9.
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1457 – 1461 1458

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
lays of different MMP-13 co-crystal structures were analyzed.
The overlay of PDB 2OW9 and PDB 2OZR[10h] indicated that on
the right-hand side, HOH747, HOH813 and HOH836 can be
considered as structural water molecules that can be targeted
as valuable binding partners in order to improve the binding
affinity of phthalimide scaffold 4. Compared with their counter-
parts in PDB 2OZR, those water molecules are located at very
similar positions and share the same binding motifs to the
target protein: HOH747 binds to the backbone NH of Leu164,
HOH813 binds to the carboxylate side chain of Glu202, and
HOH836 binds to the catalytic zinc ion as well as to the back-
bone carbonyl of Pro221. HOH915 on the other hand, which is
also located in close proximity to the phthalimide scaffold,
binds differently compared with its closest counterpart in PDB
2OZR (Figure 4).
Figure 5. Detailed analysis of water molecules in proximity to the left-hand
side of phthalimide scaffold 4. Overlay of PDB 2OW9 (water molecules and
binding amino acid residues in green) and PDB 1XUD (water molecules and
binding amino acid residues in red).
Figure 4. Detailed analysis of water molecules in proximity to the right-hand
side of phthalimide scaffold 4. Overlay of PDB 2OW9 (water molecules and
binding amino acid residues in green) and PDB 2OZR (water molecules and
binding amino acid residues in red).
Figure 6. Targeting structural water molecules by introducing a para-
methoxy group to the phthalimide inhibitor scaffold; compound 5 shows
water-mediated binding to Glu202 by HOH813.
On the left-hand side, HOH794 and HOH822 in PDB 2OW9
bind in very similar positions compared with their counterparts
in PDB 1XUD.[10a] Again, those water molecules share the same
binding motifs: HOH794 binds to the side chain carboxamide
NH of Asn194, and HOH822 binds to the backbone NH of
Phe231 as well as to the side chain amino functionality of
Lys119. HOH890 and its counterpart from PDB 1XUD do not
show hydrogen bonding to the MMP-13 target protein
(Figure 5).
alytic zinc ion involving structural water molecules HOH813
and HOH836, as well as the carboxylate from the bridging
Glu202 (Figure 6). Therefore, phthalimide inhibitor compound
5 can be considered a supramolecular inhibitor, which is pre-
dicted to bind in the non-zinc-binding S1’ binding site while
interacting via structural water molecules with the catalytic
zinc ion.
First, the right-hand portion of inhibitor scaffold 4, the
phenylacetic acid fragment, was modified with a para-methoxy
substituent in order to introduce an interaction with the struc-
tural water molecule that is bound to Glu202. Energy-mini-
mized poses of the para-methoxy-substituted inhibitor struc-
ture in the S1’ binding site indeed predict hydrogen bonding
to the water molecule HOH813 interacting with Glu202
(Figure 6).
para-Methoxy-substituted compound
5 was synthesized
(Scheme 1) and evaluated in vitro. Compound 5 exhibited
a drastic improvement in potency against MMP-13 over parent
compound 4. Not only the potency but also the selectivity im-
proved over the antitargets MMP-2, MMP-12 and MMP-14
(Table 1). The sixfold increase in affinity for MMP-13 equals
a change in Gibbs free energy at 298 K of about À4.5 kJmolÀ1
.
Molecular modeling of para-methoxy-substituted phthali-
mide scaffold 5 into the S1’ binding site showed a hydrogen-
bonding network ranging from the methoxy group to the cat-
This value is within the estimated range from crystalline salt
hydrates for the maximal change in Gibbs free energy when
transferring a water molecule from bulk solvent and including
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1457 – 1461 1459

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
it in an interaction between a protein and an inhibitor mole-
cule (max. À7.0 kJmolÀ1).[3i,k]
Encouraged by the successful implementation of a water-
mediated interaction on the right-hand side of the inhibitor
structure and based on our analysis of the water molecules in
proximity to the left-hand side of phthalimide scaffold 4
(Figure 5), we identified structural water molecules HOH794
and HOH822 as possible binding partners to further optimize
our inhibitor scaffold.
Replacing the benzylic fragment by a 4-pyridylmethylene
fragment in order to form a hydrogen bond to water HOH822
yielded compound 6 (Figure 7). Compound 6 was subsequent-
Figure 8. Interaction map of inhibitor 6: hydrogen-bonding network to
structural water molecules in addition to direct hydrogen bonding to
Thr224, Thr226 and Met232.
design concept of targeting structural water molecules to
other target proteins to show the broad applicability of this
approach in the efficient design of novel molecules with tail-
ored biological activity.
Experimental Section
Details of the synthetic protocols and characterization data for
novel compounds can be found in the Supporting Information
along with details of the biological methods used to evaluate
these compounds.
Acknowledgements
Figure 7. Targeting structural water molecules by introducing a 4-pyridyl-
methylene fragment to the phthalimide inhibitor scaffold; compound 6
shows additional water-mediated binding to Lys119 by HOH822.
The authors are grateful to the Zurich University of Applied Scien-
ces (ZHAW) for financial support.
ly synthesized (Scheme 1), and the determination of its inhibi-
tory activity confirmed an additional improvement in potency
against MMP-13 while retaining the very attractive selectivity
profile with respect to the antitargets (Table 1).
Keywords: chemical biology
inhibitors · structure-based drug design · structure–activity
relationships · water-mediated interactions
·
matrix metalloproteinase
Compound 6 represents a novel chemical scaffold with
nanomolar inhibitory activity against MMP-13, which was de-
signed as a chemical scaffold that binds to the biological
target by direct hydrogen bonds, as well as through a network
of water-mediated interactions (Figure 8).
[1] a) P. Ball, Chem. Rev. 2008, 108, 74–108; b) D. Eisenberg, W. Kauzmann,
The Structure and Properties of Water, Clarendon Press, Oxford University
Press, 1969.
[2] a) N. V. Nucci, M. S. Pometun, A. J. Wand, Nat. Struct. Mol. Biol. 2011, 18,
245–249; b) M. Nakasako, Philos. Trans. R. Soc. London Ser. B 2004, 359,
1191–1206; c) S. K. Pal, A. H. Zewail, Chem. Rev. 2004, 104, 2099–2124;
d) G. Otting, E. Liepinsh, K. Wꢂthrich, Science 1991, 254, 974–980.
[3] a) N. Huang, B. K. Shoichet, J. Med. Chem. 2008, 51, 4862–4865; b) S.
Grzesiek, A. Bax, L. K. Nicholson, T. Yamazaki, P. Wingfield, S. J. Stahl, C. J.
Eyermann, D. A. Torchia, C. N. Hodge, P. Y. S. Lam, P. K. Jadhav, C.-H.
Chang, J. Am. Chem. Soc. 1994, 116, 1581–1582; c) S. E. Wong, F. C.
Lightstone, Expert Opin. Drug Discovery 2011, 6, 65–74; d) H. Gohlke, G.
Klebe, Angew. Chem. 2002, 114, 2764–2798; Angew. Chem. Int. Ed. 2002,
41, 2644–2676; e) A. Biela, N. N. Nasief, M. Betz, A. Heine, D. Hangauer,
G. Klebe, Angew. Chem. 2013, 125, 1868–1876; Angew. Chem. Int. Ed.
2013, 52, 1822–1828; f) O. Villacanas, S. Madurga, E. Giralt, I. Belda,
Curr. Comput.-Aided Drug Des. 2009, 5, 145–154; g) R. Paulini, K. Mꢂller,
F. Diederich, Angew. Chem. 2005, 117, 1820–1839; Angew. Chem. Int. Ed.
2005, 44, 1788–1805; h) S. B. A. de Beer, N. P. E. Vermeulen, C. Oosten-
brink, Curr. Top. Med. Chem. 2010, 10, 55–66; i) J. D. Dunitz, Science
1994, 264, 670; j) J. Michel, J. Tirado-Rives, W. L. Jorgensen, J. Am. Chem.
Soc. 2009, 131, 15403–15411; k) J. E. Ladbury, Chem. Biol. 1996, 3, 973–
980.
In conclusion, we have demonstrated how to use co-crystal
structures of therapeutically relevant proteins very efficiently
for the design of inhibitors by targeting multiple water-mediat-
ed interactions with the target protein. By following this ra-
tional design concept of targeting multiple structural water
molecules as binding partners for small organic molecules, we
could enhance the binding affinity of our rationally designed
phthalimide scaffold by a factor of 20. This led to a potent and
selective nanomolar MMP-13 inhibitor without any screening
activities by a highly decreased number of synthesized com-
pounds compared with classical medicinal chemistry or screen-
ing approaches and emphasizes the importance of structural
water molecules for the design and discovery of novel small-
molecule inhibitors. We are currently expanding this structural
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1457 – 1461 1460

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
[4] a) A. D. Rowan, D. J. Litherland, W. Hui, J. M. Milner, Expert Opin. Ther.
Targets 2008, 12, 1–18; b) T. E. Cawston, A. J. Wilson, Best Pract. Res.
Clin. Rheumatol. 2006, 20, 983–1002; c) N.-G. Li, Z.-H. Shi, Y.-P. Tang, Z.-J.
Wang, S.-L. Song, L.-H. Qian, D.-W. Qian, J.-A. Duan, Curr. Med. Chem.
2011, 18, 977–1001; d) C. R. Flannery, Curr. Drug Targets 2010, 11, 614–
619; e) P. S. Burrage, K. S. Mix, C. E. Brinckerhoff, Front. Biosci. 2006, 11,
529–543; f) S. Rakashanda, F. Rana, S. Rafiq, A. Masood, S. Amin, Bio-
technol. Mol. Biol. Rev. 2012, 7, 90–101; g) J. F. Fisher, S. Mobashery,
Cancer Metastasis Rev. 2006, 25, 115–136; h) L. G. Monovich, R. A. Tom-
masi, R. A. Fujimoto, V. Blancuzzi, K. Clark, W. D. Cornell, R. Doti, J.
Doughty, J. Fang, D. Farley, J. Fitt, V. Ganu, R. Goldberg, R. Goldstein, S.
Lavoie, R. Kulathila, W. Macchia, D. T. Parker, R. Melton, E. O’Byrne, G.
Pastor, T. Pellas, E. Quadros, N. Reel, D. M. Roland, Y. Sakane, H. Singh, J.
Skiles, J. Somers, K. Toscano, A. Wigg, S. Y. Zhou, L. J. Zhu, W.-C. Shieh,
S. Xue, L. W. McQuire, J. Med. Chem. 2009, 52, 3523–3538; i) V. La Pietra,
L. Marinelli, S. Cosconati, F. S. Di Leva, E. Nuti, S. Santamaria, I. Pugliesi,
M. Morelli, F. Casalini, A. Rosello, C. La Motta, S. Taliani, R. Visse, H.
Nagase, F. De Settimo, E. Novellino, Eur. J. Med. Chem. 2012, 47, 143–
152.
Chem. Lett. 2011, 21, 4215–4219; c) J. Roth, D. Minond, E. Darout, Q.
Liu, J. Lauer, P. Hodder, G. B. Fields, W. R. Roush, Bioorg. Med. Chem. Lett.
2011, 21, 7180–7184; d) A. M. Panico, P. Vicini, A. Geronikaki, M. Incerti,
V. Cardile, L. Crasci, R. Messina, S. Ronsisvalle, Bioorg. Chem. 2011, 39,
48–52; e) M. E. Schnute, P. M. O’Brien, J. Nahra, M. Morris, W. H. Roark,
C. E. Hanau, P. G. Ruminski, J. A. Scholten, T. R. Fletcher, B. C. Hamper,
J. N. Carroll, W. C. Patt, H. S. Shieh, B. Collins, A. G. Pavlovsky, K. E. Palm-
quist, K. W. Aston, J. Hitchcock, M. D. Rogers, J. McDonald, A. R. John-
son, G. E. Munie, A. J. Wittwer, C.-F. Man, S. L. Settle, O. Nemirovskiy, L. E.
Vickery, A. Agawal, R. D. Dyer, T. Sunyer, Bioorg. Med. Chem. Lett. 2010,
20, 576–580; f) C. Gege, B. Bao, H. Bluhm, J. Boer, B. M. Gallagher, B.
Korniski, S. Powers, C. Steeneck, A. G. Tavares, V. M. Baragi, J. Med.
Chem. 2012, 55, 709–716; g) S. J. Taylor, A. Abeywardane, S. Liang, I.
Muegge, A. K. Padyna, Z. Xiong, M. Hill-Drzewi, B. Farmer, X. Li, B. Col-
lins, J. X. Li, A. Heim-Reither, J. Proudfoot, Q. Zhang, D. Goldberg, L.
Zuvela-Jelaska, H. Zaher, J. Li, N. A. Farrow, J. Med. Chem. 2011, 54,
8174–8187; h) A. R. Johnson, A. G. Pavlovsky, D. F. Ortwine, F. Prior, C.-F.
Man, D. A. Bornemeier, C. A. Banotai, W. T. Mueller, P. McConnell, C. Yan,
V. Baragi, C. Lesch, W. H. Roark, M. Wilson, K. Datta, R. Guzman, H.-K.
Han, R. D. Dyer, J. Biol. Chem. 2007, 282, 27781–27791; i) L. Devel, B.
Czarny, F. Beau, D. Georgiadis, E. Stura, V. Dive, Biochimie 2010, 92,
1501–1508.
[5] H. Nagase, R. Visse in Drug Design of Zinc-Enzyme Inhibitors (Eds.: C. T.
Supuran, J.-Y. Winum), Wiley, Hoboken, 2009, pp. 489–517.
[6] a) H. Nagase, J. F. Woessner, Jr., J. Biol. Chem. 1999, 274, 21491–21494;
b) I. Bertini, V. Calderone, M. Fragai, C. Luchinat, M. Maletta, K. J. Yeo,
Angew. Chem. 2006, 118, 8120–8123; Angew. Chem. Int. Ed. 2006, 45,
7952–7955.
[11] T. A. Halgren, J. Comput. Chem. 1996, 17, 490–519.
[12] H. Hashimoto, T. Takeuchi, K. Komatsu, K. Miyazaki, M. Sato, S. Higashi,
J. Biol. Chem. 2011, 286, 33236–33243.
[7] R. E. Babine, S. L. Bender, Chem. Rev. 1997, 97, 1359–1472.
[8] M. Whittaker, C. D. Floyd, P. Brown, A. J. H. Gearing, Chem. Rev. 1999, 99,
2735–2776.
[13] I. Bertini, V. Calderone, M. Cosenza, M. Fragai, Y.-M. Lee, C. Luchinat, S.
Mangani, B. Terni, P. Turano, Proc. Natl. Acad. Sci. USA 2005, 102, 5334–
5339.
[9] a) R. A. Tommasi, S. Weiler, L. W. McQuire, O. Rogel, M. Chambers, K.
Clark, J. Doughty, J. Fang, V. Ganu, J. Grob, R. Goldberg, R. Goldstein, S.
LaVoie, R. Kulathila, W. Macchia, R. Melton, C. Springer, M. Walker, J.
Zhang, L. J. Zhu, M. Shultz, Bioorg. Med. Chem. Lett. 2011, 21, 6440–
6445; b) J. A. Sparano, P. Bernardo, P. Stephenson, W. J. Gradishar, J. N.
Ingle, S. Zucker, N. E. Davidson, J. Clin. Oncol. 2004, 22, 4683–4690.
[10] a) C. K. Engel, B. Pirard, S. Schimanski, R. Kirsch, J. Habermann, O. Klin-
gler, V. Schlotte, K. U. Weithmann, K. U. Wendt, Chem. Biol. 2005, 12,
181–189; b) C. De Savi, A. D. Morley, A. Ting, I. Nash, K. Karabelas, C. M.
Wood, M. James, S. J. Norris, G. Karoutchi, N. Rankine, G. Hamlin, P. A.
MacFaul, D. Ryan, S. V. Baker, D. Hargreaves, S. Gerhardt, Bioorg. Med.
[14] M. Grossman, D. Tworowski, O. Dym, M.-H. Lee, Y. Levy, G. Murphy, I.
Sagi, Biochemistry 2010, 49, 6184–6192.
[15] C. A. Lipinski, F. Lombardo, B. W. Dominy, P. J. Feeney, Adv. Drug Delivery
Rev. 1997, 23, 3–25.
[16] Z.-Q. Shi, Y.-Q. Feng, N. Song, H.-W. Wang, Synth. Commun. 2008, 38,
983–990.
Received: June 21, 2013
Published online on July 26, 2013
ꢀ 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1457 – 1461 1461