Biphenyl derivatives as novel dual NK(1)/NK(2)-receptor antagonists.

Article abstract of DOI:10.1016/S0960-894X(02)00382-7

In a continuation of our efforts to simplify the structure of our neurokinin antagonists, a series of substituted biphenyl derivatives has been prepared. Several compounds exhibit potent affinities for both the NK(1) receptor (<10nM) and for the NK(2) rec

Full text of DOI:10.1016/S0960-894X(02)00382-7

Bioorganic & MedicinalChemistry Letters 12 (2002) 2065–2068
Biphenyl Derivatives as Novel Dual
NK1/NK2-Receptor Antagonists
Robert Mah,a,b,* Marc Gerspacher,a Andreas von Sprecher,a Stefan Stutz,b
Vincenzo Tschinke,a,b Gary P. Anderson,c Claude Bertrand,d
Natarajan Subramaniana and Howard A. Balla
aPharma Research, Novartis Pharma AG, CH-4002 Basel, Switzerland
bSpeedel Experimenta AG, Gewerbestrasse 14, CH-4123 Allschwil, Switzerland
cDepartment of Pharmacology, University of Melbourne, Parkville, 3052 VIC, Australia
dInflammatory Disease Unit, Roche Biosciences, Palo Alto, CA, USA
Received 26 March 2002; accepted 23 May 2002
Abstract—In a continuation of our efforts to simplifly the structure of our neurokinin antagonists, a series of substituted biphenyl
derivatives has been prepared. Severalcompounds exhibit potent affinities for both the NK receptor (<10 nM) and for the NK2
1
receptor (<50 nM). Details on the design, synthesis, biological activities, SAR and conformational analysis of this new class of dual
NK1/NK2 receptor antagonists are presented. # 2002 Elsevier Science Ltd. All rights reserved.
Neurokinins (NKs), also referred to as tachykinins
(TKs), are a family of peptide neurotransmitters and
neuromodulators implicated in a variety of biological
disorders such as anxiety, arthritis, asthma and airway
diseases, cancer, depression, emesis, migraine and schizo-
phrenia.1 Within the lungs, the release of neuropeptides,
notably substance P (SP) and neurokinin A (NKA),
from sensory nerves as well as from inflammatory cells
results in an inflammatory response characterized by
bronchoconstriction, microvascular leakage and mucus
hypersecretion—typicalpathool gicalfeatures of asthma
and chronic bronchitis.2 The effects of SP (primarily
microvascular leakage and mucus hypersecretion) and
NKA (predominantly hyper-responsiveness) are medi-
ated through specific receptors—mainly NK1 for SP and
mainly NK2 for NKA—and thus the simultaneous
blockade of both receptors offers an attractive strategy
for the treatment of asthma and airway diseases.3
amides, A5), analysis with molecular models suggested
that a suitably substituted biphenyl derivative (B) would
place the two aromatic rings—comprising the postu-
lated pharmacophore elements (for the NK1 receptor)—
in the correct orientation as required for receptor bind-
ing6 (Fig. 1). In addition to eliminating an additional
stereocenter,7 molecules of this type were envisioned
to be amenable for rapid optimization of biological
activity as a result of the projected synthesis (aryl–aryl
coupling).
In a continuation of our efforts to simplify the struc-
tures of our NK-antagonists (e.g., the selective NK1
antagonist CGP498234 and the dualNK /NK2 antago-
nists such as 5-aryl-4-benzoylamino-pent-2-ene-carbox-
1
*Corresponding author. Tel.: +41-61-206-4074; fax: +41-61-206-
4001; e-mail: robert.mah@speedelgroup.com
Figure 1. Simplification of NK-antagonist structures leading to sub-
stituted biphenyls.
0960-894X/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(02)00382-7

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R. Mah et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2065–2068
The requisite 1,3-disubstituted biphenylderivatives ( 2)
were prepared using a Cu-catalyzed cross-coupling
reaction between bromide 1 and a suitably substituted
aryliodide, and subsequent Raney nickelreduction of
the nitro group. Sequential acylation and alkylation of
the free amine provided esters 3. The target compounds
(4–17) were obtained following saponification and
ensuing reaction of the acid intermediates with various
amines under standard peptide coupling conditions
(Scheme 1).
fected CHO-cells expressing human recombinant NK2
receptors was assessed.9 (Table 1). A number of com-
pounds (9, 13–14) demonstrated potent affinities for
both the NK1 and NK2 receptors—comparable to the
reference compound.5 It was found that a wide variety
of substituents are tolerated at various positions in the
molecule leading to compounds with high affinity to the
NK1 receptor, thus suggesting that the orientation of
the two pendant aromatic rings (vide infra) is solely
responsible for the binding activity to the NK1 receptor.
NK2 receptor affinity, however, is much more depen-
dent on the nature of the substitution pattern—the lar-
gest effects resulted from variations of the R4R5-
substituents (8, 14–17) and of the R1-substituent (4–5,
14). Moreover, in addition to the potent NK receptor
binding affinities, severalcompounds exhibited good
inhibition of either Sar9-SP-induced bronchoconstric-
tion10 (79 and 60% for 6 and 7 respectively, 1 mg kgÀ1
po) or b-Ala8-NKA-induced bronchoconstriction10
(72% for 8, 10 mg kgÀ1 po) when administered to gui-
nea pigs 2 h prior to agonist challenge.
Subsequent to the initiation of synthetic activities,
modelling studies11 with CGP49823, A (Ar=4-Cl-
Scheme 1. Preparation of compounds 4–17: (a) R2-aryl-I, Cu; (b) H2,
Ra(Ni); (c) R1-aryl-COCl, Et3N, DMAP; (d) R3-I, NaH; (e) LiOH,
H2O, THF, MeOH; (f) R4R5-NH, Et3N, EDC, DMAP.
phenyl, NR1R2=2-piperidin-1-yl-ethylamine) and
8
were undertaken to test the validity of the original
hypothesis and to aid in the identification of specific
structuralfeatures for enhancing the NK -antagonistic
activity. In confirmation of the originalsupposition,
analysis of the lowest energy conformations highlighted
The affinity of 4–17 for the NK1 receptor was deter-
3
mined by measuring the inhibition of binding of H-
Sar9-SP in bovine retina membranes.8 For the NK2
receptor, the inhibition of 125I-NKA binding to trans-
2
Table 1. In vitro binding affinities of compounds 4–17 to NK1- and NK2-receptors
Compd
R1
R2
R3
NR4R5
NK1
IC50 (nM)a
NK2
IC50 (nM)a
4
5
H
4-F
4-F
CH3
CH3
3.5
34
>1000
3,5-(CF3)2
168
6
3,5-(CF3)2
4-H
CH3
1.5
560
(d,l)
7
8
9
10
11
12
3,5-(CF3)2
3,5-(CF3)2
3,5-(CF3)2
3,5-(CF3)2
3,4,5-(OCH3)3
3,4,5-(OCH3)3
4-CH3
4-ClCH
4-F
3,4-(Cl)2
4-ClH
4-ClCH
CH3
d-a-Amino-e-caprolactam
d-a-Amino-e-caprolactam
d-a-Amino-e-caprolactam
d-a-Amino-e-caprolactam
d-a-Amino-e-caprolactam
d-a-Amino-e-caprolactam
6
2.7
1
0.8
0.7
13
181
70
28
43
3
CH3
CH3
>1000
162
3
13
14
3,4,5-(OCH3)3
3,5-(CF3)2
4-ClH
9
3
30
51
4-ClCH
3
15
16
17
3,5-(CF3)2
3,5-(CF3)2
3,5-(CF3)2
4-ClCH
4-ClCH
4-ClCH
N(CH2)3N(CH3)2
N(CH3)2
N(OH)CH3
1
4
0.6
108
500
>1000
3
3
3
aValues are means of three experiments.

R. Mah et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2065–2068
2067
spacher, M.; von Sprecher, A. Drugs Future 1999, 24, 883. (d)
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Bialecki, R.; Davenport, T.; Dedinas, R. F.; Dembofsky, B. T.;
Koether, G.; Kosmider, B. J.; Kirkland, K.; Ohnmacht, C. J.;
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Ofner, S.; Auberson, Y.; Betschart, C.; Schilling, W.; Ander-
son, G. P.; Ball, H.; Bertrand, C.; Subramanian, N.; Hauser,
K. 5-Aryl-4-benzoyl-amino-pent-2-ene-carboxamides: a new
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For example, the compound with Ar=4-Cl-phenyl and
NR1R2=2-piperidin-1-yl-ethylamine exhibited IC50 values of
10 nM (NK1) and 49 nM (NK2).
6. (a) Harrison, T.; Williams, B. J.; Swain, C. J.; Ball, R. G.
Bioorg. Med. Chem. Lett. 1994, 4, 2545. (b) Desai, M. C.;
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Figure 2. Overlap of CGP49823 (gray), A (light green) and 8 (dark
green).
the pair of closely spaced, staggered aromatic rings6 as
the most striking common feature. Furthermore, the
presence of a H-bond accepting group (e.g., a carbonyl)
at approximately 6 A from the centroid of the first of the
two staggered rings was identified as an important con-
tributor for NK2 binding activity (Fig. 2)
In conclusion, a novel class of dual NK1/NK2 receptor
antagonists has been discovered. Severalof the reported
compounds exhibit potent affinities for both the NK1
receptor (IC50 <10 nM) and for the NK2 receptor (IC50
<50 nM). Additionally, some of the compounds dis-
played potent in vivo po activities in guinea pigs against
either NK1 or NK2 agonist-induced bronchoconstric-
tion. In addition to eliminating a stereocenter, the rigid
nature of the target molecules allows for rapid con-
formational analysis using computer-assisted molecular
modeling which, in turn, may aid in the optimization of
binding activities.
7. See also: Gerspacher, M.; La Vecchia, L.; Mah, R.; von
Sprecher, A.; Anderson, G. P.; Subramanian, N.; Hauser, K.;
Bammerlin, H.; Kimmel, S.; Pawelzik, V.; Ryffel, K.; Ball, H.
Bioorg. Med. Chem. Lett. 2001, 11, 3081.
8. For experimentaldetaisl see: Bittiger, H; Heid, J. In Sub-
stance P; Skrabanek, P., Powell, D. Boole; Dublin, 1983; p. 198.
9. Inhibition of 125I-NKA binding to transfected chinese
hamster ovary cells (CHO cells) expressing recombinant
human neurokinin 2 receptors: The assay was performed in
96-well plates (Nunclon) containing 200 mL 20 mM HEPES
buffer, pH 7.4 containing 2 mM MnSO4 and 6 mM MgCl2, 3 Â
105 h NK2 CHO cells, 0.05 nM 125I-NKA (2200 Ci mmolÀ1
)
and various drug concentrations. Nonspecific binding was
estimated in the presence of 50 nM NKA. The mixture was
incubated for 20 min at room temperature after which the
unbound ligand was removed by rapid filtration and washed
four times with ice-cold Tricine buffer. Filter bound radio-
activity was counted in Microscint 20 in a scintillation coun-
ter. All samples were measured in triplicate. Culture
conditions and cell isolation for hr NK2 CHOcells: Sub-
ramanian, N.; Ruesch, C.; Bertrand, C. Biochem. Biophys.
Res. Comm. 1994, 200, 1512.
10. Dunkin-Hartley guinea-pigs (500–700 g) were anaes-
thetized with ip urethane (1.5 g kgÀ1), tracheotomized and
ventilated with a constant-volume ventilator (Model 683;
Harvard apparatus Co., S. Natick, MA, USA) at a frequency
of 60 breaths minÀ1. Pavulon (pancuronium bromide, Orga-
non, 1 mg kgÀ1) and atropine (Fluka, 1 mg kgÀ1) were admi-
nistered (iv) to prevent spontaneous breathing and cholinergic
reflexes, respectively. The tidal volume was adjusted to about
1 mL 100 gÀ1 body weight so as to maintain normalarterial
blood gases. Intratracheal pressure was measured with a dif-
ferentialpressure transducer (ModelDP 45–28, Vaidl yne
Engineering Corp., Northridge, CA, USA). Polyethylene
catheters (250 I.U. mLÀ1 heparin in 0.9% NaCl) were inserted
into the right jugular vein for drug injection and the left
carotid for blood pressure measurements (Statham transducer
P23XL). All signals were recorded using a computer data-
acquisition system (Mi2 Bio Report software, Modular
Instruments). The timing of anaesthesia and animalprepara-
tion were such that after a baseline period was obtained, Sar9-
SP (3 mg kgÀ1; ED80 dose for increase in intratrachealpres-
sure) or b-Ala8-NKA (0.8 mg kgÀ1 ED80 dose) was injected,
corresponding to a time of 2, 4 or 12 h since the oraldosing of
vehicle or drug. The antagonists were given in doses ranging
Acknowledgements
The authors wish to thank H. Bammerlin, E. Braun, A.
Cosenti, M. Erard, C. Ferraretto, S. Fuhrer, H. Het-
trich, S. Kimmel, M. Kuhn, Th. Kull, M. Modena, C.
Mouzo, T. Osman, V. Pawelzik, C. Ruesch, K. Ryffel,
N. Stuber, A. Widmer and D. Wyss for their excellent
technicalassistance.
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R. Mah et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2065–2068
from 0.01 to 1 mg kgÀ1 in a vehicle consisting of 0.0067–0.67%
DMSO in 0.5% methylcellulose, in a volume of 10 mL kgÀ1
logarithmically transformed dose data and the ED50 value
interpolated.
.
Five to six animals per dose were studied. The percent inhibi-
tion for each animal was calculated by dividing the elicited
change in intratrachealpressure for the antagonist-treated
animals by the mean value obtained for the vehicle-treated
group. A linear regression analysis was then performed of the
11. Conformation analysis simulations were carried out using
the Monte Carlo method as implemented in MacroModel 5.0,
including solvation effects in water. Visualization, clustering
and superposition of the molecular structures were performed
using Insight II.