Design, synthesis and bioevalucation of novel 2,3-dihydro-1H-inden-1-amine derivatives as potent and selective human monoamine oxidase B inhibitors based on rasagiline

Article abstract of DOI:10.1016/j.ejmech.2018.01.029

Parkinson's disease (PD) is associated with elevated levels of hMAO-B in the brain, and MAO-B has been recognized a successful target for developing anti-PD drugs. Herein we report rasagiline derivatives as novel potent and selective hMAO-B inhibitors. Th

Full text of DOI:10.1016/j.ejmech.2018.01.029

Accepted Manuscript
Design, synthesis and bioevalucation of novel 2,3-dihydro-1H-inden-1-amine
derivatives as potent and selective human monoamine oxidase B inhibitors based on
rasagiline
Xuan Xiao, Xing-Xing Zhang, Mei-Miao Zhan, Kai Cheng, Shiyu Li, Zhouling Xie,
Chenzhong Liao
PII:
S0223-5234(18)30029-1
10.1016/j.ejmech.2018.01.029
EJMECH 10106
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 7 July 2017
Revised Date: 8 January 2018
Accepted Date: 9 January 2018
Please cite this article as: X. Xiao, X.-X. Zhang, M.-M. Zhan, K. Cheng, S. Li, Z. Xie, C. Liao, Design,
synthesis and bioevalucation of novel 2,3-dihydro-1H-inden-1-amine derivatives as potent and selective
human monoamine oxidase B inhibitors based on rasagiline, European Journal of Medicinal Chemistry
(2018), doi: 10.1016/j.ejmech.2018.01.029.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical abstract

ACCEPTED MANUSCRIPT
Design, Synthesis and Bioevalucation of Novel 2,3-Dihydro-1H-inden-1-amine
Derivatives as Potent and Selective Human Monoamine Oxidase B Inhibitors
Based on Rasagiline
1
1
Xuan Xiao , Xing-Xing Zhang , Mei-Miao Zhan, Kai Cheng, Shiyu Li, Zhouling Xie*,
Chenzhong Liao*
School of Biological and Medical Engineering, Hefei University of Technology,
Hefei, Anhui 230009, P. R. China
1
These authors contributed to this work equally.
*
Corresponding authors.
E-mail addresses: czliao@hfut.edu.cn, chenzhongliao@gmail.com (Chenzhong Liao),
zhoulingxie@hfut.edu.cn (Zhouling Xie)
-1-

ACCEPTED MANUSCRIPT
Abstract
Parkinson’s disease (PD) is associated with elevated levels of hMAO-B in the brain,
and MAO-B has been recognized a successful target for developing anti-PD drugs.
Herein we report rasagiline derivatives as novel potent and selective hMAO-B
inhibitors. They were designed by employing fragment-based drug design strategy to
link rasagiline and hydrophobic fragments, which may target a hydrophobic pocket in
the entrance cavity of hMAO-B. Different linkers such as -OCH -, -SCH -,
2
2
-
OCH CH -, -OCH CH O-, -OCH CH CH O- were tried. A promising selective
2 2 2 2 2 2 2
hMAO-B inhibitor D14 with similar inhibitory activity as rasagiline and improved
isoform selectivity was yielded. The selectivity profile of compounds reported herein
suggests that we can further develop more potent hMAO-B inhibitors with high
isoform selectivity through this strategy.
Keywords: hMAO-B, isoform selectivity, fragment-based drug design, structure
activity relationship
-2-

ACCEPTED MANUSCRIPT
1
. Introduction
Monoamine oxidase (MAO, EC 1.4.3.4), an enzyme of the protein family of flavin-
containing amine oxidoreductases, catalyzes the oxidative deamination of
monoamines and then influences their levels in brain by virtue of their roles in
neurotransmitter breakdown [1]. In humans there are two types of MAO, hMAO-A
and hMAO-B which share ~70% sequence identities. Both of them can be found in
the central nervous system, such as neurons and astroglia [2, 3]. hMAO-A catalyzes
the oxidative deamination of serotonin, adrenaline, and noradrenaline; whereas,
hMAO-B deaminates preferentially β-phenethylamine and benzylamine [4].
hMAO-A and hMAO-B have appealed lots of interests for developing drugs in the
fields of neurodegenerative conditions, including depression, Parkinson’s disease
(PD), Alzheimer’s disease (AD), etc. [5-8]. hMAO-A inhibitors, for example,
clorgiline (1 in Fig. 1) are used for depression; while hMAO-B inhibitors display a
critical role in the treatment of PD which are associated with elevated levels of
hMAO-B in the brain. Therefore, developing novel, potent, selective hMAO-B
inhibitors has gained extensive attentions in the treatment of these two diseases
[
9-18].
<Fig. 1>
Currently, several selective hMAO-B inhibitors had been approved including
selegiline (2), rasagiline (3) and safinamide (4) [19, 20]. Among them, selegiline and
rasagiline are irreversible inhibitors, utilizing the propargyl group to covalently bind
to the flavin ring of the cofactor, flavin adenine dinucleotide (FAD). In this way, the
-3-

ACCEPTED MANUSCRIPT
bound enzymes fail to work until the cell makes new enzymes. In contrast to
selegiline and rasagiline, safinamide is reversible inhibitor [21, 22].
Fragment based drug discovery (FBDD) is a rational design method by growing or
combining small chemical fragments having weak affinities to produce a lead with a
higher affinity [23, 24]. It has emerged as one of the most promising alternatives to
the traditional methods of drug development. In our lab, we employed a FBDD
strategy to link two biomedical interesting fragments, resveratrol and coumarin, and
got a series of novel hMAO-A and hMAO-B selective inhibitors with a scaffold of
3
-((E)-3-(2-((E)-styryl)phenyl)acryloyl)-2H-chromen-2-one [25].
A crystal structure of hMAO-B-rasagiline complex was reported, in which, a
fragment is in the entrance cavity [26]. We believed that linking fragments binding in
the entrance cavity to rasagiline could increase the potency and/or selectivity against
hMAO-B. In this work, we report our first endeavor to link chemical fragments into
rasagiline, which yielded a potent and selective hMAO-B inhibitor, D14, with an IC50
value of 20 nM against hMAO-B and a selectivity index (SI) of 466.5 of hMAO-B
over hMAO-A. The enzyme inhibitory activity of D14 is comparable with approved
drug rasagiline, and its selectivity is significantly increased. All result indicated that
D14 could be a candidate for further study.
2
. Results
The crystal structure of rasagiline binding to hMAO-B has been deposited in the
Protein Database Bank (PDB ID: 2FXQ) [26]. In this complex, a fragment of
-4-

ACCEPTED MANUSCRIPT
2
-(2-benzofuranyl)-2-imidazoline (2-BFI) is located in the entrance cavity that is
distinct from the substrate-binding cavity (Fig. 2A). 2-BFI inhibits recombinant
hMAO-B with a K of 8.3 µM, and increases binding energy of -3.9 kcal/mol to
i
tranylcypromine against hMAO-B. The benzofuran moiety of 2-BFI is in a
hydrophobic pocket composed of residues of Phe103, Trp119, Leu164, Leu167,
Phe168, Leu171, Ile199, Ile316, and Tyr326 and the imidazoline moiety forms two
hydrogen bonds with Tyr326 and Pro102, in addition, weak hydrophobic interactions
with Leu88 by the edge of imidazoline could be observed.
It is intuitive that linking 2-BFI or similar fragments to rasagiline at appropriate
positions may enhance potency and/or selectivity. When aligning the structures of
hMAO-A (PDB ID: 2Z5X [27]) and hMAO-B (PDB ID: 2FXQ), it was found that
there are two different residues in that hydrophobic pocket: Leu164 and Ile199 of
hMAO-B against Phe173, Phe208 of hMAO-A, respectively (Fig. 2B), leading to a
bulker hydrophobic pocket in hMAO-B than in hMAO-A. Therefore, compounds
targeting this pocket of hMAO-B may not only have strong enzyme inhibitory activity,
but have excellent isoform selectivity between hMAO-A and hMAO-B [28].
Meanwhile, selectivity of hMAO-A and hMAO-B inhibitors could be caused by the
structural differences arising from Ile-335 in hMAO-A versus Tyr326 in MAO-B [27,
2
9].
<
Fig. 2>
Based on these observation, we designed novel hMAO-B inhibitors by introducing
various benzene ring and its analogs to occupy the hydrophobic pocket with different
-5-

ACCEPTED MANUSCRIPT
carbon linkers such as -OCH2-, -SCH2-, -OCH CH -, -OCH CH O-,
2
2
2
2
-
OCH CH CH O- according to the strategy as shown in Fig. 3. We hope that a
2 2 2
candidate could be found as follow as the summary of SAR. From the crystal
structure of 2FXQ, it can be clearly seen that the best place in the
2
,3-dihydro-1H-indene moiety of rasagiline to extend a hydrophobic fragment is the 4
position.
<Fig. 3>
The designed hMAO-B inhibitors D1-D25 were then synthesized according to the
reactions shown in Scheme 1 and Scheme 2 (the groups represented by R and R are
1
2
presented in Table 1). The intermediates b1-b10, b16 and b18-b25 were synthesized
by introducing benzyl bromide or several substituted benzyl bromide to the hydroxyl
of a1 with potassium carbonate. While, b11-b14 and b17 were synthesized by
Mitsunobu reaction with substituted phenethyl alcohol. Additionally, b15’ was reacted
with benzyl mercaptane, affording intermediate b15 by Buchwald-Hartwig reaction.
Then, final compounds D1-D25 were obtained from b1-b25 by reacting with
propargylamine according to Borch Reduction (specific experimental procedures are
supplied in Supporting Information). All these target compounds (D1-D25) are
racemic.
<
Scheme 1>
Scheme 2>
<
Compounds D1-D25 were evaluated for their inhibitory activities against hMAO-A
and hMAO-B. The results are summarized in Table 1, in which IC s of hMAO-A
5
0
-6-

ACCEPTED MANUSCRIPT
and hMAO-B and the SIs to hMAO-B ([IC (hMAO-A)]/[IC (hMAO-B)]) of
5
0
50
D1-D25 and the positive control compounds clorgyline (1) [30], and rasagiline (3) are
listed.
<Table 1>
In our assay, compound D1, which introduces -OCH Ph to the 4-position of
2
rasagiline (racemic mixture) showed IC50 values of 15.44 and 1.97 µM against
hMAO-A and hMAO-B respectively with a SI of 7.84. Substitution at the
meta-position on the benzene ring of D1 by halogens or methyl group (D2-D5) led to
significantly improved inhibitory activities against hMAO-B and selectivity against
hMAO-A. Among them, D2 had an IC value of 0.28 µM against hMAO-B (~55 fold
5
0
increment) and a SI of 18.57 (~2 fold increment). Substitution at the para-position on
the benzene ring (D6-D9) also resulted in activity improvement but not so
significantly as D2-D5. D8 displayed a SI of > 43.17. Replacement of the benzene
ring of D1 by a naphthalene moiety (D10) decreased inhibitory activities against both
hMAO-A and hMAO-B. D15 is a compound using a sulfur atom to replace the
oxygen atom in the linker of D1. This replacement led to ~2.5 fold increment of
potency against hMAO-B.
When the linker was -OCH CH - (D11-D13), the potency against hMAO-B did not
2
2
changed considerably with D1. Surprisingly, the activity of compound D14 was
enhanced remarkably with an IC value of 0.02 µM against hMAO-B and a SI of
5
0
4
66.5. In our assay, rasagiline, the positive drug, exhibited an IC value of 0.01 µM
50
against hMAO-B and a SI of 101. Considering the compounds reported here are
-7-

ACCEPTED MANUSCRIPT
racemic, whereas rasagiline is a (R)-enantiomer, D14 played comparable inhibitory
activity with rasagiline, meanwhile, the SI was enhanced ~4.6-fold. Modeling study
indicated that the phenyl group of D11 could insert into the hydrophobic pocket in the
entrance cavity, but only partly occupying the area around the furan moiety of 2-BFI,
while the rasagiline part of D14 keeps the interactions rasagiline has in the crystal
complex (see more information in the docking study section). When attaching
4
-chloro-benzamide into the meta-position of the phenyl ring (D14), the amide group
could form a hydrogen bond with Pro102, mimicking the imidazoline of 2-BFI. At the
same time, the oxygen atom of the amide group in D14 is close to the hydroxyl group
of Tyr326, implying a possible hydrogen bond between them. It was reported that
selectivity of hMAO-A and hMAO-B inhibitors could be caused by the structural
differences arising from Ile-335 in hMAO-A versus Tyr326 in MAO-B [27, 29],
which is consistent with our finding reported herein. The 4-chloro-phenyl moiety on
the one hand forms hydrophobic interactions with Leu88 and Pro102, and on the other
hand, has NH-π interaction [31] with Thr201 (Fig. 4). These extra interactions of D14
compensate for the entropic lose induced by not totally fitting the hydrophobic pocket
that 2-BFI occupies. Compared with D11, the inhibitory activity against hMAO-B of
D14 was enhanced around 200-fold, and the SI was improved about 200-fold,
indicating D14 is a more potent and highly selective hMAO-B inhibitor.
<Fig. 4>
Prolonging the linker to four atoms (-OCH CH O-), the gotten compounds
2
2
D16-D19 did not demonstrate improved activity against hMAO-B. Though D18 also
-8-

ACCEPTED MANUSCRIPT
has an amide group at the meta-position of the phenyl ring, it did not show as potent
as D14. Additionally, when the linker was five atoms (-OCH CH CH O-), compounds
2
2
2
D20-D25 showed reduced inhibitory activities and SIs.
In the crystal structure of 2XFQ, rasagiline covalently binds to the cofactor FAD,
which challenged our docking study. To facilitate docking our compounds into the
active site of hMAO-B, structures of both of receptor and ligands were adjusted
according to Fig. 5 so that the ligands could be dockable. In this way, modified
rasagiline can interact with FAD by a hydrogen bond but not a covalent bond. A
hydrogen bond with Gln206 of hMAO-B observed in the crystal structure also could
be kept. Glide 6.7 SP of the Schrödinger suite was used for docking. When docking
compounds into the active site, constraints that docked compounds had to form two
hydrogen bonds with adjusted FAD and Gln206 were defined. Through this strategy,
modified rasagiline was docked into the active site of hMAO-B successfully and the
conformation of rasagiline in the crystal structure was reproduced with an RMSD
value of 0.1597, which guaranteed our modeling work.
<Fig. 5>
3
. Conclusion
hMAO-B has been recognized a successful target for developing anti-PD drugs.
Indeed, two irreversible and one reversible hMAO-B inhibitors are in the market for
the treatment of PD. However, these approved drugs could relief but not cure the PD
patients, and they have side effects. For example, rasagiline may cause severe
-9-

ACCEPTED MANUSCRIPT
hypertension, make people sleepy and motor control worse in some people. Therefore,
developing more potent and selective hMAO-B inhibitors has great significances for
therapeutic purposes.
In this article, we report novel potent and selective hMAO-B inhibitors, which are
rasagiline derivatives and were designed by employing a FBDD strategy to link
rasagiline and simple hydrophobic moieties, which may target a hydrophobic pocket
in the entrance cavity of hMAO-B. In a crystal structure of hMAO-B-rasagiline
complex, a fragment of 2-BFI is located in this pocket and inhibits recombinant
hMAO-B with a K of 8.3 µM. Linkers having different lengths such as -OCH -,
i
2
-
SCH -, -OCH CH -, -OCH CH O-, -OCH CH CH O- were tried. This strategy led to
2 2 2 2 2 2 2 2
the identification of a promising selective hMAO-B inhibitor D14. This racemic
compound showed comparable inhibitory activity with (R)-rasagiline. At the same
time, D14 demonstrated improved isoform selectivity over rasagiline.
This is our first endeavor to link fragments into rasagiline to get more potent and/or
selective hMAO-B inhibitors. The simplest fragment, benzene ring and its analogs
were employed. Actually, we screened a fragment library to try to get simpler
fragments than 2-BFI which can interact with hMAO-B as 2-BFI. We hope we can
link these simpler fragments into rasagiline to get more novel selective hMAO-B
inhibitors by employing the strategy reported herein, which can also be called a
diversity evolution strategy [32].
-10-

ACCEPTED MANUSCRIPT
Acknowledgments
This work was supported by the National Natural Science Foundation of China
21672050 and 21572003).
(
Appendix A. Supplementary data
Supplementary data related to this article can be found at
References
[
1] D.E. Edmondson, A. Mattevi, C. Binda, M. Li, F. Hubalek, Structure and
mechanism of monoamine oxidase, Curr Med Chem, 11 (2004) 1983-1993.
2] J.C. Shih, K. Chen, M.J. Ridd, Monoamine oxidase: from genes to behavior, Annu
Rev Neurosci, 22 (1999) 197-217.
3] J.C. Shih, K. Chen, Regulation of MAO-A and MAO-B gene expression, Curr
Med Chem, 11 (2004) 1995-2005.
4] D.E. Edmondson, C. Binda, A. Mattevi, Structural insights into the mechanism of
amine oxidation by monoamine oxidases A and B, Arch Biochem Biophys, 464
[
[
[
(2007) 269-276.
[
5] S. Chajkowski-Scarry, J.M. Rimoldi, Monoamine oxidase A and B substrates:
probing the pathway for drug development, Future Med Chem, 6 (2014) 697-717.
6] P. Riederer, T. Muller, Use of monoamine oxidase inhibitors in chronic
neurodegeneration, Expert Opin Drug Met, 13 (2017) 233-240.
7] Z. Cai, Monoamine oxidase inhibitors: promising therapeutic agents for
Alzheimer's disease (Review), Mol Med Rep, 9 (2014) 1533-1541.
8] C. De Monte, D.A. M, P. Guglielmi, V. Mancini, S. Carradori, Opening New
Scenarios for Human MAO Inhibitors, Cent Nerv Syst Agents Med Chem, 16 (2016)
8-104.
[
[
[
9
-11-

ACCEPTED MANUSCRIPT
[
9] E. Maccioni, S. Alcaro, R. Cirilli, S. Vigo, M.C. Cardia, M.L. Sanna, R. Meleddu,
M.
-Acetyl-2,5-diaryl-2,3-dihydro-1,3,4-oxadiazoles: a new scaffold for the selective
inhibition of monoamine oxidase B, J Med Chem, 54 (2011) 6394-6398.
10] A.H. Schapira, Monoamine oxidase B inhibitors for the treatment of Parkinson's
Yanez,
G.
Costa,
L.
Casu,
P.
Matyus,
S.
Distinto,
3
[
disease: a review of symptomatic and potential disease-modifying effects, CNS
Drugs, 25 (2011) 1061-1071.
[
11] Z.X. Pan, X. He, Y.Y. Chen, W.J. Tang, J.B. Shi, Y.L. Tang, B.A. Song, J. Li,
X.H. Liu, New 2H-chromene-3-carboxamide derivatives: design, synthesis and use as
inhibitors of hMAO, Eur J Med Chem, 80 (2014) 278-284.
[
12] S. Carradori, R. Silvestri, New Frontiers in Selective Human MAO-B Inhibitors,
J Med Chem, 58 (2015) 6717-6732.
13] R. Chen, J. Xiao, Y. Ni, H.F. Xu, M. Zheng, X. Tong, T.T. Zhang, C. Liao, W.J.
[
Tang, Novel tricyclic pyrazolo[1,5-d][1,4]benzoxazepin-5(6H)-one: Design,
synthesis, model and use as hMAO-B inhibitors, Bioorg Med Chem, 24 (2016)
1
741-1748.
[
14] M.H. Nam, M. Park, H. Park, Y. Kim, S. Yoon, V.S. Sawant, J.W. Choi, J.H.
Park, K.D. Park, S.J. Min, C.J. Lee, H. Choo, Indole-Substituted Benzothiazoles and
Benzoxazoles as Selective and Reversible MAO-B Inhibitors for Treatment of
Parkinson's Disease, ACS Chem Neurosci, (2017).
[
15] J. Reis, F. Cagide, D. Chavarria, T. Silva, C. Fernandes, A. Gaspar, E. Uriarte, F.
Remiao, S. Alcaro, F. Ortuso, F. Borges, Discovery of New Chemical Entities for Old
Targets: Insights on the Lead Optimization of Chromone-Based Monoamine Oxidase
B (MAO-B) Inhibitors, J Med Chem, 59 (2016) 5879-5893.
[
16] L. Pisani, R. Farina, O. Nicolotti, D. Gadaleta, R. Soto-Otero, M. Catto, M. Di
Braccio, E. Mendez-Alvarez, A. Carotti, In silico design of novel 2H-chromen-2-one
derivatives as potent and selective MAO-B inhibitors, Eur J Med Chem, 89 (2015)
9
8-105.
-12-

ACCEPTED MANUSCRIPT
[
17] M.C. Costas-Lago, P. Besada, F. Rodriguez-Enriquez, D. Vina, S. Vilar, E.
Uriarte, F. Borges, C. Teran, Synthesis and structure-activity relationship study of
novel 3-heteroarylcoumarins based on pyridazine scaffold as selective MAO-B
inhibitors, European Journal of Medicinal Chemistry, 139 (2017) 1-11.
[
18] N.T. Tzvetkov, H.G. Stammler, B. Neumann, S. Hristova, L. Antonov, M.
Gastreich, Crystal structures, binding interactions, and ADME evaluation of brain
penetrant N-substituted indazole-5-carboxamides as subnanomolar, selective
monoamine oxidase B and dual MAO-A/B inhibitors, European Journal of Medicinal
Chemistry, 127 (2017) 470-492.
[
19] S. Marconi, T. Zwingers, Comparative efficacy of selegiline versus rasagiline in
the treatment of early Parkinson's disease, Eur Rev Med Pharmacol Sci, 18 (2014)
879-1882.
20] D. Robakis, S. Fahn, Defining the Role of the Monoamine Oxidase-B Inhibitors
for Parkinson's Disease, CNS Drugs, 29 (2015) 433-441.
1
[
[
[
21] E.D. Deeks, Safinamide: first global approval, Drugs, 75 (2015) 705-711.
22] S. Perez-Lloret, O. Rascol, The safety and efficacy of safinamide mesylate for
the treatment of Parkinson's disease, Expert Rev Neurother, 16 (2016) 245-258.
23] D.E. Scott, A.G. Coyne, S.A. Hudson, C. Abell, Fragment-based approaches in
drug discovery and chemical biology, Biochemistry, 51 (2012) 4990-5003.
24] M. Congreve, G. Chessari, D. Tisi, A.J. Woodhead, Recent developments in
fragment-based drug discovery, J Med Chem, 51 (2008) 3661-3680.
25] B.F. Ruan, H.J. Cheng, J. Ren, H.L. Li, L.L. Guo, X.X. Zhang, C. Liao, Novel
H-chromen-2-one derivatives of resveratrol: Design, synthesis, modeling and use as
human monoamine oxidase inhibitors, Eur J Med Chem, 103 (2015) 185-190.
26] D. Bonivento, E.M. Milczek, G.R. McDonald, C. Binda, A. Holt, D.E.
[
[
[
2
[
Edmondson, A. Mattevi, Potentiation of Ligand Binding through Cooperative Effects
in Monoamine Oxidase B, J Biol Chem, 285 (2010) 36849-36856.
-13-

ACCEPTED MANUSCRIPT
[
27] S.Y. Son, J. Ma, Y. Kondou, M. Yoshimura, E. Yamashita, T. Tsukihara,
Structure of human monoamine oxidase A at 2.2-A resolution: the control of opening
the entry for substrates/inhibitors, Proc Natl Acad Sci U S A, 105 (2008) 5739-5744.
[
28] Y. Tsugeno, A. Ito, A key amino acid responsible for substrate selectivity of
monoamine oxidase A and B, J Biol Chem, 272 (1997) 14033-14036.
29] R.M. Geha, I. Rebrin, K. Chen, J.C. Shih, Substrate and inhibitor specificities for
[
human monoamine oxidase A and B are influenced by a single amino acid, J Biol
Chem, 276 (2001) 9877-9882.
[
30] D.L. Murphy, F. Karoum, D. Pickar, R.M. Cohen, S. Lipper, A.M. Mellow, P.N.
Tariot, T. Sunderland, Differential trace amine alterations in individuals receiving
acetylenic inhibitors of MAO-A (clorgyline) or MAO-B (selegiline and pargyline), J
Neural Transm Suppl, 52 (1998) 39-48.
[
31] C. Bissantz, B. Kuhn, M. Stahl, A Medicinal Chemist's Guide to Molecular
Interactions, Journal of Medicinal Chemistry, 53 (2010) 5061-5084.
32] C.Z. Liao, R.S. Yao, Diversity evolution and jump of Polo-like kinase 1
inhibitors, Sci China Chem, 56 (2013) 1392-1401.
[
-14-

ACCEPTED MANUSCRIPT
Table 1. Inhibitory activities of rasagiline derivatives D1-D25 against hMAO-A and
a
hMAO-B and selectivity of these compounds to hMAO-B.
IC (µM,
IC (µM,
Selectivity to
5
0
50
Compd
X
R
hMAO-A)
15.44
hMAO-B) hMAO-B (A/B)
D1
D2
O
O
O
O
O
O
O
O
O
O
O
O
O
1.97
0.28
0.33
0.65
0.55
1.87
1.09
1.39
1.41
6.21
3.87
2.51
5.87
7.84
18.57
21.21
14.69
20.36
4.17
5.20
7.00
9.55
11.20
7.80
4.33
D3
D4
D5
D6
D7
3.97
b
D8
NA
>43.17
5.12
D9
7.22
NA
D10
D11
D12
D13
>9.66
2.35
9.10
10.21
NA
4.07
>10.22
-1-

ACCEPTED MANUSCRIPT
D14
D15
O
S
9.33
NA
0.02
466.5
>9.62
3.08
6.24
4.57
3.39
5.52
6.91
10.22
18.01
10.49
5.38
NA
D16
O
O
O
O
O
O
O
O
O
O
-
14.09
NA
D17
>17.70
1.5
D18
8.30
NA
D19
>8.68
>5.87
>3.33
2.99
D20
NA
D21
NA
D22
31.40
42.67
NA
O
D23
7.93
D24
-
D25
NA
6.91
NA
>8.68
<0.0031
101
Clorgyline (1)
-
0.189
1.01
Rasagiline (3)
-
-
0.010
a
Each IC is the mean ± SEM from three experiments. Standard error of the IC
50
5
0
b
was generally less than 10%. IC is more than 60 µM.
5
0
-2-

ACCEPTED MANUSCRIPT
Fig. 1. Selected hMAO inhibitors in clinical use. Clorgiline (1) is a selective
hMAO-A inhibitor, and selegiline (2), rasagiline (3) and safinamide (4) are selective
hMAO-B inhibitors.
Fig. 2. (A) Crystal structure of rasagiline (yellow) binding to hMAO-B, in which, a
fragment of 2-BFI (purple) is located in the entrance cavity. (B) Structural differences
in the entrance cavity between hMAO-A and hMAO-B. Residues of Phe173 and
Phe208 of hMAO-A are colored in yellow, while, their corresponding residues
Leu164 and Ile199 in hMAO-B are colored in purple.
-1-

ACCEPTED MANUSCRIPT
HN
linkers
fragments
hMAO-B inhibitors
+
+
Fig. 3. Design of novel hMAO-B inhibitors by employing a fragment-based drug
design strategy and rasagiline as the lead compound.
Fig. 4. Putative binding mode of D14 shown as purple ball and stick mode. 2-BFI is
presented as green line and stick mode.
Fig. 5. For the docking purpose, covalently bound rasagiline and the cofactor FAD
were adjusted.
-2-

ACCEPTED MANUSCRIPT
Scheme 1. Regents and conditions: (i) R Br, potassium carbonate, acetonitrile, 85
,
1
3
h; (ii) R OH, Ph P, DBAD, THF, 30
, 12 h; (iii) mono-propargylamine, acetic
2 3
acid, STAB, CH Cl , 12 h.
2
2
Scheme 2. Regents and conditions: (i) benzyl mercaptane, Pd (dba) , xantphos,
2
3
cesium carbonate, 1,4-dioxane, 100
, 13 h; (ii) mono-propargylamine, acetic acid,
STAB, CH Cl ,12 h.
2
2
-3-

ACCEPTED MANUSCRIPT
Highlights:
ó
ó
ó
ó
FBDD strategy was employed to design novel selective hMAO-B inhibitors.
Selective hMAO-B inhibitors were gotten by linking rasagiline and fragments.
A hMAO-B inhibitor with greatly improved isoform selectivity was yielded.
More hMAO-B inhibitors with high selectivity can be developed by this strategy.