Identification of novel NK1/NK3 dual antagonists for the potential treatment of schizophrenia

Article abstract of DOI:10.1016/j.bmcl.2011.07.116

During the lead optimization of NK₁/NK₃ receptor antagonists program, a focused exploration of molecules bearing a lactam moiety was performed. The aim of the investigation was to identify the optimal position of the carbonyl and hyd

Full text of DOI:10.1016/j.bmcl.2011.07.116

Bioorganic & Medicinal Chemistry Letters 21 (2011) 6899–6904
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Identification of novel NK1/NK3 dual antagonists for the potential treatment
of schizophrenia
⇑
,
Maria Pia Catalani a, , Giuseppe Alvaro a, Giovanni Bernasconi a, Ezio Bettini a, Steven M. Bromidge b,
Jag Heer b, Giovanna Tedesco a, Simona Tommasi a
a GlaxoSmithKline Medicines Research Centre, Neurosciences Centre of Excellence for Drug Discovery, Via Fleming 4, 37135 Verona, Italy
b GlaxoSmithKline Medicines Research Centre, New Frontiers Park, Third Avenue, Harlow, Essex CM19 5 AW, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
During the lead optimization of NK1/NK3 receptor antagonists program, a focused exploration of mole-
cules bearing a lactam moiety was performed. The aim of the investigation was to identify the optimal
position of the carbonyl and hydroxy methyl group in the lactam moiety, in order to maximize the
in vitro affinity and the level of insurmountable antagonism at both NK1 and NK3 receptors. The synthesis
and biological evaluation of these novel lactam derivatives, with potent and balanced NK1/NK3 activity,
were reported in this paper.
Received 4 July 2011
Revised 28 July 2011
Accepted 29 July 2011
Available online 6 August 2011
Keywords:
Neurokinin receptors
Schizophrenia
Ó 2011 Elsevier Ltd. All rights reserved.
Antipsychotic
NK1/NK3 receptor antagonist
O
HO
Neurokinin-1 (NK1), neurokinin-2 (NK2) and neurokinin-3 (NK3)
receptors are rhodopsin-like seven transmembrane Gq-protein
coupled receptors, which can be activated with different potencies
by peptides of the neurokinin/tachykinin family.1,2 The neurokinin/
tachykinin neurotransmitter family comprises three main neuro-
peptides: substance P (SP), neurokinin A (NKA) and neurokinin B
(NKB) which have highest affinity for NK1, NK2, and NK3, respec-
tively.1,2 Several lines of evidence suggest that NK1 and NK3 recep-
tors play a role in affective and psychiatric disorders.3,4 In the last
few years a large body of pre-clinical and clinical evidence has
been generated to support the effects of selective NK1 receptor
antagonists in the treatment of certain forms of anxiety and
depressive disorders5,6 while other clinical studies with selective
NK3 receptor antagonists proved efficacy, compared to placebo,
for the treatment of schizophrenia.7,8 Therefore, a potent, dual
antagonist of both human NK1 and NK3 receptors might be benefi-
cial not only to the positive and cognitive symptom domains of
schizophrenia, but also to the associated co-morbid depression
and sleep disturbances associated with the disease. Furthermore,
since both NK1 and NK3 receptor antagonists are well tolerated
in man a mixed profile antagonist is expected to be free of liabili-
ties, such as weight gain, sexual dysfunction and other side effects
associated with current antipsychotic medications.
S
N
CF3
CF3
N
F
N
N
F
O
O
CF 3
N
CF3
N
A
B
Figure 1. Compounds A and B from the literature.9,10 The lowest energy confor-
mation of A (grey) is shown superimposed to the lowest energy conformation of the
two isomers of B (green).13
⇑
Corresponding author.
E-mail address: mariapia.catalani@inwind.it (M.P. Catalani).
Present address: Aptuit (Verona) srl, Via Fleming 4, 37135 Verona, Italy.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.07.116

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M. P. Catalani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6899–6904
"arm"
-CH OH
antipsychotic for the treatment of multiple symptom domains of
schizophrenia and also allows the exploration of other therapy
areas such as bipolar disorder, psychosis in Alzheimer’s disease
and psychotic depression.
2
polar ''hat''
O
N
OH
N
CF3
R
To date there is limited literature precedent for combining both
NK1 and NK3 activity within a single molecule. However, a number
of pyridine derivatives (Fig. 1) were recently disclosed which, in
addition to potent NK1 activity, were claimed to be endowed with
NK3 activity.9–12 Interrogation of the reported SAR suggested that
to achieve NK3 activity in a known NK1 pyridine scaffold, either a
CH2OH ‘arm’ (such as in A) or a polar ‘hat’ (such as the carbonyl
group on the left hand side of B) were required, possibly suggesting
that these two moieties may make a H-bond within the antagonist
binding site of the NK3 receptor. This led us to speculate that the
combination of these two features in an appropriate three dimen-
sional arrangement might lead to compounds endowed with even
higher NK3 activity while maintaining high NK1 potency.
O
monomer
CF3
N
F
Figure 2. General structure of lactam derivatives 8a–22b.
Therefore, a dual activity NK1/NK3 receptor antagonist could
represent a potentially first in class, well tolerated and efficacious
CF3
CF3
O
CF3
Cl
N
F
N
F
N
F
O
O
H
O
a
b
CF3
N
CF3
N
CF3
N
2
1
3
Scheme 1. Reagents and conditions: (a) 2-ethenyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, Pd(PPh3)4, Na2CO3, 1,4-dioxane/water, 8 h, reflux, y = 84%; (b) 4% solution of
OsO4 in water, NaIO4, THF/water, 4 h, rt, y = 85%.
O
CF3
O
O
CF3
N
F
N
F
O
O
O
O
a
b
2
N
CF3
CF3
N
4
5
c
O
O
CF3
O
CF3
O
O
O
N
N
N
O
O
O
d
H
O
CF3
CF3
N
N
F
F
7
6
e
HO
HO
CF3
CF3
O
O
N
N
N
O
N
O
CF3
N
CF3
N
F
F
syn
8(8a;8b)
anti
9(9a;9b)
Scheme 2. Reagents and conditions: (a) (1) 4% solution of OsO4 in water, NaIO4, THF/water, rt, overnight, y = 39%; (a) (2) 1.25 M solution of HCl in MeOH, reflux, overnight,
y = 90%; (b) KOtBu, EtOAc, À75 °C, 4 h, y = 34%; (c) K2CO3, NaI, ethyl chloroacetate, acetone/DME, reflux, overnight, y = 50%; (d) ammonium acetate, NaBH3CN, MeOH, rt, 6 h,
y = 51%; (e) 2 M solution of LiBH4 in THF, THF, rt, overnight, y = 49%.

M. P. Catalani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6899–6904
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O
CF3
O
CF3
O
N
F
N
F
O2N
O
O
O
a
b
CF3
N
CF3
N
3
10
11
c
O
N
O
O
CF3
CF3
N
F
HN
N
F
O
O
O
d
N
CF3
N
CF3
13
12
e
O
O
O
OH
N
O
CF3
O
CF3
HN
N
N
O
O
O
CF3
N
f,g
CF3
N
F
F
15
i
14
O
*
OH
N
CF3
h
N
*
O
16a; 16b
CF3
N
F
17
l
17a
Scheme 3. Reagents and conditions: (a) ethyl (triphenyl-k5-phosphanylidene)acetate, toluene, 2 h, reflux, y = 92%; (b) nitromethane, DBU, rt, overnight; (c) H2 1 atm, Ni-
Raney, 4 h, rt, y = 81%; (d) Boc2O, DMAP, TEA, DCM, rt, overnight, y = 85%; (e) LiHMDS, methyl chloroformate, THF, À78 °C, 15 min, y = 79%; (f) TFA, DCM, 3 h, rt, y = 86%; (g)
CaCl2, NaBH4, MeOH, 2 h, rt, y = 80%; (h) HCl 1 M in Et2O, Et2O, 10 min; (i) NaH, MeI, DMF, 4 h, rt, y = 40%; (l) HCl 1 M in Et2O, Et2O, 10 min.
However, as the absolute stereochemistry of B is not known, at
least two different topological alignments are possible for these
two molecules as shown above (Fig. 1), which in turn correspond
to different three dimensional arrangements of the pharmaco-
phoric groups of interest.
To explore this hypothesis, a number of compounds were de-
signed and prepared carrying both a carbonyl and a CH2OH group
in different spatial orientations (Fig. 2).14 The preparation and the
biological evaluation of novel five member ring lactam derivatives
possessing potent and selective dual NK1/3 receptor antagonist
activities are reported in this Letter.
The nitrogen of the lactam on the ring could be in the 2 or 3 po-
sition and the –CH2OH arm in the 2 or 5 position with respect to
the pyridine ring.
The lactam series was constructed starting from intermediate 2
for the lactam with the nitrogen in the 2 position on the pyrrolid-
inone ring with respect to the pyridine ring and starting from inter-
mediate 3 for the lactam with the nitrogen in the 3 position.
Intermediate 2 was obtained from a Suzuki coupling of known
intermediate 1,10 and the aldehyde
was generated after
treatment of 2 with a 4% solution of OsO4 in water and NaIO4
(Scheme 1).
3
Preparation of the two diastereoisomers 8 and 9 is shown in
Scheme 2. Intermediate 2 was converted into methyl ester 4 by
treatment with OsO4 (4% solution in water) and NaIO4,15 and suc-
cessive esterification by methanolic HCl. Then, the reaction of ester
4 with KOtBu, in EtOAc at À78 °C,16 generated intermediate 5 that
was successively treated with ethylchloroacetate in the presence of
K2CO3 and NaI17 to afford the intermediate 6. Cyclization in the
presence of ammonium acetate and NaBH3CN gave lactam 7 as a
mixture of diastereoisomers (syn; anti).18 Finally, reduction with
LiBH4 gave the two diastereoisomeric alcohols 8 and 9, which were
subsequently separated by chiral HPLC19 affording the single enan-
tiomers 8a, 8b, 9a, and 9b.
Compound 15 was prepared as shown in Scheme 3. Wittig reac-
tion of the aldehyde 3 with ethyl (triphenyl-k5-phosphanylid-

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M. P. Catalani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6899–6904
O
O
CF3
CF3
HN
HN
R
N
F
N
F
O
O
a
b
HO
10
R
CF3
N
N
CF3
HO
18
19(19a;19b)
c
O
CF3
HN
N
F
O
R
N
CF3
20
d
O
CF3
*
HN
N
F
O
*
HO
N
CF3
21(21a;21b)
22(22a;22b)
R: -COOCH2CH3
Scheme 4. Reagents and conditions: (a) diethyl(acetylamino)propanedioate, C2H5OÀNa+, EtOH, DMSO, 110 °C, 18 h, y = 43%; (b) CaCl2, NaBH4, EtOH, water, rt, 18 h, y = 98%;
(c) NaOH, MeOH/water, 18 h, aq HCl 2 N, toluene/DMSO, 100 °C, 3 h, y = 71% (d) CaCl2, NaBH4, EtOH, water, rt, 18 h, y = 90%.
ene)acetate in toluene gave the intermediate 10 as a mixture of E/Z
isomers, which was treated with nitromethane in the presence of
DBU to afford the intermediate 11. The ensuing hydrogenation
gave directly the lactam 12 which was first N-BOC protected to
give 13 and then transformed into the anti-intermediate 14
through a diastereoselective reaction20 with LiHMDS and methyl
chloroformate. Subsequent removal of the N-BOC protecting group
and final reduction gave the desired product 15 as a racemate, that
was chirally resolved21 in order to afford enantiomerically pure
compounds 15a and 15b, that were tested as their HCl salts 16a
and 16b.
Emax,1 and Emax,3 values reported in Table 2 indicate the test
compounds inhibitory effect at 1 nM and 3 nM, respectively, on
the maximal response elicited by SP in the NK1 FLIPR assay.
All compounds tested showed an insurmountable profile, indic-
ative of a slow receptor dissociation kinetic,27 which is slowest for
compound 17a in the NK1 assay.
Similarly, Emax,30 and Emax,100 values reported in Table 3 indi-
cate the test compounds inhibitory effect at 30 and 100 nM,
respectively, inducing a dose dependent decrease in the maximal
response elicited by NKB in NK3 FLIPR assay. Compound 17a was
also found to show the most pronounced insurmountable effect
in the NK3 assay.
In summary, a number of novel potent dual NK1/3 receptor
antagonists have been discovered by judicious positioning of key
pharmacophoric features onto a pyrrolidine ring. These com-
pounds could represent a potentially first in class, well tolerated
and efficacious antipsychotic for the treatment of multiple symp-
tom domains of schizophrenia and also allow the exploration of
other therapy areas such as bipolar disorder, psychosis in Alzhei-
mer’s disease and psychotic depression. The detailed in vivo char-
acterization and further progression of selected compounds will be
reported in due course.
Compound 15b was methylated with MeI to give compound 17,
then successively treated with HCl to give 17a.
As shown in Scheme 4, diethyl(acetylamino)propanedioate was
added to intermediate 10, thus generating intermediate 18 that,
after reduction of the ester groups, gave compound 19 as a race-
mate that was separated by chiral preparative HPLC22 to give 19a
and 19b. Alternatively, after base-promoted decarboxylation 18
generated intermediate 20 as mixture of diasteroisomers.
Reduction of monoester 2023 afforded diastereoisomers 21 and
22, that were separated by chiral HPLC24 into the single enantio-
mers 21a, 21b, 22a, and 22b.
Table 1 shows monomers containing lactam and –CH2OH, and
their potency (fpKi) at NK1 and NK3 receptors, as measured in a func-
tional cell-based assay.25 Since it has been shown that insurmount-
able26 NK1 receptor antagonists have higher efficacy in vivo,27 the
surmountable/insurmountable28 profile of the selected antagonists
has been also assessed at NK1 (Table 2) and NK3 receptors (Table 3).
Acknowledgements
The authors thank Dr. Carla Marchioro’s group for structural
and analytical support, Agostino Marasco and Emiliano Castiglioni
for scientific discussions.

M. P. Catalani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6899–6904
6903
Table 1
Table 1 (continued)
Inhibitory effect (fpKi) on human recombinant NK1 or NK3 receptor for selected
compounds
Compds
Monomer
NK1 (fpKi)
NK3 (fpKi)
O
Compds
Monomer
NK1 (fpKi)
NK3 (fpKi)
O
N
*
*
22b
9.6
7.7
8.3
8.2
OH
*
N
HO
*
8a
10.1
7.4
anti enantiomer 2
O
anti enantiomer 2
*
N
OH
HO
HO
O
19
10.0
>9.8
*
N
8b
9a
9.3
9.6
6.3
8.3
racemate
syn enantiomer 2
O
*
OH
O
N
*
*
HO
N
19a
HO
enantiomer 1
anti enantiomer 1
O
*
OH
O
*
N
*
N
HO
9b
12
15
9.5
7.5
7.5
8.1
19b
>9.8
6.2
HO
anti enantiomer 2
O
enantiomer 2
⁄Indicates a stereo centre of fixed but unknown relative and absolute stereo-
chemistry, that is, either R or S stereochemistry; enantioner 1 or 2 means a com-
pound as a single enantiomer whose absolute configuration was not determinate
either R or S stereochemistry.14
N
O
>9.8
9.6
OH
N
Table 2
SP maximal stimulation (Emax) on human recombinant NK1 receptors: effect of
antagonists
anti racemate
O
*
Compds
NK1 (SP Emax,1
)
NK1 (SP Emax,3)
OH
N
*
8a
9a
9b
12
64
98
79
64
109
103
101
66
103
89
25
60
30
20
63
19
37
5
16a
16b
17a
10.3
9.8
7.1
8.8
9
anti enantiomer 1
O
15
*
16a
16b
17a
22a
19
OH
N
*
39
28
anti enantiomer 2
O
Emax,1 and Emax,3 values are SP Emax values in the presence of 1 and 3 nM of test
compound, respectively (n = 1).
*
OH
N
*
10.2
anti enantiomer 2
Table 3
NKB maximal stimulation (Emax) on human recombinant NK3 receptor: effect of
O
antagonists
N
*
Compds
NK3 (NKB Emax,30
)
NK3 (NKB Emax,100)
21a
21b
22a
>9.8
>9.8
9.6
7.6
6.1
8.7
*
HO
HO
HO
9a
17a
22a
83
67
101
74
56
76
syn enantiomer 1
O
Emax,30 and Emax,100 values are NKB Emax values in the presence of 30 and 100 nM of
test compound, respectively (n = 1).
N
*
*
References and notes
syn enantiomer 2
O
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Pharmacol. Rev. 2002, 54, 285.
2. Pennefather, J. N.; Lecci, A.; Candenas, M. L.; Patak, E.; Pinto, F. M.; Maggi, C. A.
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N
*
*
anti enantiomer 1

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M. P. Catalani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6899–6904
6. Herpfer, I.; Lieb, K. CNS Drugs 2005, 19, 275.
min. DAD:210-340 nM to give according to the order of elution 15a (anti
enantiomer 1) and 15b (anti enantiomer 2).
22. Compound 19 was separated using the following chiral HPLC preparative
7. Meltzer, H. Y.; Arvanitis, L.; Bauer, D.; Rein, W. Am. J. Psychiatry 2004, 161, 975.
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conditions: Column: Chiralpak IC (20 mm  250mm,
70:30 v/v pump-mixed; Flow rate = 17.0 ml/min; UV absorbance 215 nM;
Autosampler injection (500 l of 140.0 mg/ml sample in DCM/MeOH 8:2 on
5 lm); Heptane: IPA
l
column); isocratic run time = 50.0 min.
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24. Compounds 21a and 22b were isolated (in order of elution) from the mixture of
four diasteroisomers using the following preparative chiral HPLC conditions:
12. (a) Peters, J. U.; Hoffmann, T.; Schnider, P.; Stadler, H.; Koblet, A.; Alker, A.; Poli,
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Jablonski, P.; Knoflach, F.; Knust, H.; Malherbe, P.; Nettekoven, M.; Patiny-
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13. Structures were modeled within the Maestro [A] modeling environment.
Conformational analyses were carried out with BatchMin [B] using the
following parameters: 1000 steps/rotatable bond, OPLS_2005 FF, implicit
water model of solvation, 10000 minimisation steps with PRCG, relative energy
window for the minimized conformers within 3 kcal/mol. On the left hand side
of the compounds, H-bond acceptor (A2, A3) and donor (D4) pharmacophore
features were mapped using the Phase [C] module within Maestro.
[A] Maestro V8.5.111 (Schrodinger LLC).
Column: Chiralpak IA (20 mm  250mm, 5
90:10 v/v pump-mixed; Flow rate = 17.0 ml/min; UV Absorbance 215 nM;
Autosampler injection (900 l of 95.0 mg/ml sample in DCM:MeOH 8:2 on
column); isocratic run time = 50.0 min. The mixture of 21b and 22a was
subsequently separated (in order of elution) according the following chiral
lm); Heptane: Absolute Ethanol
l
HPLC condition: Column: Chiralpak IC (20 mm  250mm, 5
70:30 v/v pump-mixed; Flow rate = 17.0 ml/min; UV Absorbance 215 nM;
Autosampler injection (900 l of 95.0 mg/ml sample in DCM/MeOH 8:2 on
lm); Heptane: IPA
l
column); isocratic run time = 60.0 min.
25. The functional activity of compounds was tested on recombinant human NK1
or NK3 receptors, transiently expressed in U2-OS cells using the BacMam
methodology (see: Condreay, P.J.; Witherspoon, S.M.; Clay, W.C.; Kost, T.A.
Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 127). Compound modulation of
intracellular calcium levels induced by an EC80 concentration of Substance P,
or Neurokinin B, for NK1 or NK3 receptors, respectively, was assessed using
FLIPR/Ca2+ methodology (see: Sullivan, E.; Tucker, E.M.; Dale, I.L. In Calcium
Signaling Protocols: Lambert D.G., Ed.: Humana, Totowa, 1999; pp 125–133).
The Cheng–Prusoff equation was used to calculate functional pKi (fpKi) values
from the pIC50 values.
26. Different categories of receptor antagonists have been described. Some
antagonists produce parallel rightward shifts of the agonist concentration-
response curve, without affecting the maximal response. These are classified as
surmountable antagonists (Gaddum, J.H.; Hameed, K.A.; Hathway, D.E.;
Stephens, F.F. Q. J. Exp. Physiol. 1955, 40, 49). Insurmountable antagonists
are able to depress the maximal response.
[B] BatchMinV9.6 (Schrodinger LLC).
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19. The four stereoisomers obtained by reduction of 7 were separated by chiral
SFC. Preparative chromatography conditions: [Column: ChiralPak AD-H
(25 Â 2.1 cm); Modifier: 12% (EtOH + 0.1% isopropylamine) 12%, 15% after
27. Lindström, E.; Von Mentzer, B.; Påhlman, I.; Ahlstedt, I.; Uvebrant, A.;
Kristensson, E.; Martinsson, R.; Novén, A.; De Verdier, J.; Vauquelin, G. J.
Pharmacol. Exp. Ther. 2007, 322, 1286.
third peak; Flow rate 50.0 ml/min; UV detection 220 nM; Loop 500 ll].
Injection of 10 mg in the modifier to give in order to elution: 8a, 9a, 8b, and 9b.
20. Yan, L.; Budhu, R.; Huo, P.; Lynch, C. L.; Hale, J. J.; Mills, S. G.; Hajdu, R.;
Keohane, C. A.; Rosenbach, M. J.; Milligan, J. M.; Shei, G.-J.; Chrebet, G.;
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28. Four selected compound concentrations (0.3–1–3–10 nM and 3–10–30–
100 nM in the NK1 and NK3 assays, respectively) were tested in the
presence of 15 different agonist concentrations (Substance P, or Neurokinin
B, for NK1 or NK3 receptors, respectively), to assess
a compounds
21. Preparative
chromatographic
conditions:
Column:
ChiralPak
AD-H
surmountable/insurmountable profile. Agonist Emax in the presence of two
(25 Â 0.46 cm); Mobile phase: n-hexane/EtOH 65/35% v/v; Flow rate: 0.8 ml/
selected test compound concentrations is shown in Tables 2 and 3.