Biaryl amide glucagon receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2004.02.056

Biaryl amides derived from a reported series of ureas 1 were evaluated and found to be potent human glucagon receptor antagonists. The benzofuran analogue 6i was administered in Sprague-Dawley rats and blocked the effects of an exogenous glucagon challenge.

Full text of DOI:10.1016/j.bmcl.2004.02.056

Bioorganic & Medicinal Chemistry Letters 14 (2004) 2047–2050
Biaryl amide glucagon receptor antagonists
Ravi Kurukulasuriya,* Bryan K. Sorensen, James T. Link, Jyoti R. Patel, Hwan-Soo Jae,
Marty X. Winn, Jeffrey R. Rohde, Nelson D. Grihalde, Chun W. Lin,
Christopher A. Ogiela, Andrew L. Adler and Christine A. Collins
Metabolic Disease Research, Global Pharmaceutical Research and Development, Abbott Laboratories,
100 Abbott Park Road, Abbott Park, IL 60064-6098, USA
Received 8 January 2004; revised 11 February 2004; accepted 12 February 2004
Abstract—Biaryl amides derived from a reported series of ureas 1 were evaluated and found to be potent human glucagon receptor
antagonists. The benzofuran analogue 6i was administered in Sprague–Dawley rats and blocked the effects of an exogenous glu-
cagon challenge.
ꢀ 2004 Elsevier Ltd. All rights reserved.
As the incidence of type 2 diabetes reaches epidemic
proportions the search for new potential treatments has
intensified. The discovery of agents that moderate
hepatic glucose production (HGP) for the treatment of
the disease has developed into an active research area.1
Glucagon, a twenty-nine amino acid peptide, is the
primary counter regulatory hormone to insulin in glu-
cose homeostasis. Glucagon acts primarily in the liver
where it binds to the G-protein coupled glucagon
receptor (GlucR) to initiate gluconeogenesis and glyco-
genolysis via the adenylate cyclase mediated activation
of protein kinase A. Protein kinase A also suppresses
glycogen synthesis and glycolysis and promotes keto-
genesis. There is substantial evidence to suggest GlucR
antagonists will be useful in the treatment of diabetes. In
type 2 diabetics, glucagon mediated HGP is elevated and
does not decrease appropriately in the postprandial state
giving rise to hyperglycemia.2 The target has also been
the focus of validation studies in rodent models of dia-
betes. Immunoneutralization of endogenous glucagon
with a monoclonal antibody significantly lowered blood
glucose levels of STZ rats and ob/ob mice.3 Further-
more, in GlucR)/) knockout mice, glucose levels fall
within the normal range in both the fed and fasted
states.4 Therefore glucagon receptor antagonism has
been pursued as a promising approach to treat hyper-
glycemia.
Multiple classes of small molecule glucagon receptor
antagonists have been reported.5 Bayer has advanced
one of their biaryl antagonists into evaluation in healthy
human volunteers and has demonstrated its ability to
block the effect of a glucagon challenge.6 Recently Novo
Nordisk patented a novel series of urea based glucagon
receptor antagonists.7 One example is urea 1, with a
human glucagon receptor binding (h-GlucRbind) Ki of
63 nM and a moderate glucagon induced adenylate
cyclase inhibition (h-GlucRcyclase) Ki of 254 nM under
our assay conditions (Fig 1).8 Structure–activity stud-
ies indicated that all three groups attached to the urea
were critical to the binding and functional activity of the
molecule. The template was evaluated for further mod-
ification to increase binding and functional activity, and
potentially to improve the pharmacokinetic profile.
Initially we replaced the tertiary nitrogen of the urea
with a carbon and investigated the resulting amides.9
OCF3
O
N
N
H
1
H
HO
N
Keywords: Glucagon receptor antagonist; Hepatic glucose production
inhibitors.
O
O
* Corresponding author. Tel.: +1-847-935-5699; fax: +1-847-938-1674;
e-mail: ravi.kurukulasuriya@abbott.com
Figure 1. Urea glucagon receptor antagonist.
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.02.056

2048
R. Kurukulasuriya et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2047–2050
OH
O
O
H
a
O
+
EtO
N
OH
OBn
a-c
d, e
Br
Br
OBn
O
O
7
8
9
O
Cl
Cl
OMe
HO
3
2
O
b, c
d-f
O
O
OH
N
O
H
O
H
EtO
N
H
Br
10
11b
HO
N
O
O
O
O
O
O
f
OH
N
H
Scheme 2. Reagents and conditions: (a) BnBr, Cs2CO3, DMF, 87%;
(b) NaH, DMF; (c) H2, 10% Pd/C, MeOH, 53%; (d) 4-bromoaniline,
DCC, DMAP, Tol, 100 ꢁC; (e) 2,4-dichlorophenylboronic acid,
Pd(OAc)2, P(o-tolyl)3, K3PO4, THF, water, 70 ꢁC; (f) NaOH, MeOH,
water, 50%.
H
N
H
N
EtO
EtO
4
5
O
O
O
O
O
O
g
N
H
compounds (h-GlucRcyclase Ki > 150 nM). As illustrated
by 6a and 6b, not all amides were tolerated. In general
aromatic, nonpolar groups were superior to polar and/
or alkyl amides (data not shown). Secondary amines
generally performed poorly except for phenyl piper-
azines like 6c that showed modest binding activity.
However, amides derived from anilines, and particularly
biphenyl anilines, provided a series of potent antago-
nists. Substitution of the para position of an aniline
enhanced binding activity compared to the meta posi-
tion as in 6d and 6e, although both were inactive in the
functional assay. However p-trifluoromethoxy aniline 6f
showed a h-GlucRbind Ki of 51 nM and a h-GlucRcyclase
Ki of 110 nM, which was more potent in the functional
assay than the parent urea 1. Biphenyl amides derived
from nonpolar aromatic units on the 4-position of the
aniline were the most potent binders and dramatically
improved the functional activity as well. When the
4-position of the anilino-amide was substituted with a
phenyl group as in 6g, the h-GlucRcyclase Ki ¼ 300 nM. A
2,4-dichlorophenyl 6h, or a benzofuran substitution 6i
decreased the functional Ki substantially (h-GlucRcyclase
Ki ¼ 33 nM and 29 nM). However, heterocyclic substi-
tutions 6j, 6k, and 6l, or polar phenyl moieties 6m on the
4-position of the aniline remained potent binders but
significantly decreased functional potency. Binding and
functional potencies of the compounds did not change
when the carbon linker was altered to an ether as in 11a
compared to 12. A trend towards increasing functional
potency was observed when amides were derived from
changing the side chain from a tert-butylphenyl to a
n-hexyl as illustrated by potent h-GlucR antagonists
(11a, 11b, and 12).
H
6i
HO
N
O
O
Scheme 1. Reagents and conditions: (a) NaOH, MeOH, water; (b)
BnBr, Cs2CO3, DMF; (c) LiHMDS, THF, )78 ꢁC then p-Li(O)BnBr,
THF, )78 ꢁC fi 25 ꢁC, 80%; (d) H2N(CH2)2COOEt Æ HCl, TBTU,
i-Pr2NEt, DMF; (e) H2, Pd/C, MeOH, 95%; (f) p-bromoaniline, DCC,
DMAP, Tol, 100 ꢁC, 80%; (g) 2-benzofuranboronic acid,
Pd(PPh3)2Cl2, Na2CO3, DME, EtOH, water, microwave, 125 ꢁC then
NaOH, MeOH, water, 70%.
Antagonists were synthesized from ester 3, prepared by
hydrolysis and esterification of methyl tert-butylphenyl
acetate 2 followed by alkylation with the lithium salt of
a-bromo-p-toluic acid using LiHMDS at )78 ꢁC.10 The
b-alanine ethyl ester was then attached by a TBTU11
mediated coupling reaction. Subsequent deprotection of
the benzyl ester by hydrogenation afforded the acid 4,
for further derivatization to amides with a variety of
amines. For the preparation of biaryl amides, a DCC
coupling12 of p-bromoaniline with acid 4 that yielded
aryl bromide 5 was utilized. Suzuki reaction13 and ester
hydrolysis gave the final product biaryl amide 6i.
Related amides were synthesized by similar procedures
(Scheme 1).
The amide template was further modified by introduc-
tion of a heteroatom to replace the benzylic carbon
connecting the urea to the b-alanine substituted phenyl
ring. This was achieved by preparing the benzyl ester of
the a-bromo acid 7, followed by reaction with phenol 9.
Deprotection of the resultant ester gave the acid core 10
that was derivatized to amide analogues with different
amines. Biaryl amide was formed by DCC coupling12 of
p-bromoaniline followed by a Suzuki reaction13 and
ester hydrolysis to give the desired product 11b. Related
amides were prepared similarly (Scheme 2).
Changes to the b-alanine drastically altered the func-
tional activity profile of the compounds (Table 2).
Substitution by an amino tetrazole as in 14 decreased
binding and functional activity. Surprisingly, subtle
changes to the b-alanine moiety such as introduction of
a OH or F substitution in compounds 15 and 16
dramatically weakens the functional potency while pre-
serving most of the binding activity.
Table 1 summarizes the h-GlucR antagonist activity of
the amides in binding and cyclase assays.8 Although the
binding assay was consistent across a range of potencies,
the cyclase assay showed some variability for less potent
By altering the urea scaffold 1, we have discovered
potent glucagon receptor antagonists. However none of

R. Kurukulasuriya et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2047–2050
Table 1. Binding and functional activity Ki of amide h-GlucR antagonists
2049
O
R1
R2
X
H
N
HO
O
O
Compound
R1
R2
X
Binding Ki (nM)a
Cyclase Ki (nM)a
HN
6a
CH2
CH2
CH2
CH2
CH2
5000
>2000
>2000
>2000
>2000
>2000
OCF
3
6b
6c
6d
6e
N
N
>5000
400
80
N
N
HN
26
HN
HN
HN
OCF
6f
CH2
CH2
51
11
110
300
3
6g
Cl
6h
CH2
6
33
HN
Cl
6i
CH2
CH2
CH2
4
70
73
29
>2000
>2000
HN
HN
O
N
6j
N
6k
HN
HN
N
6l
CH2
11
610
N
HN
HN
6m
CH2
O
29
3
1000
17
OH
O
11a
n-Hexyl
n-Hexyl
n-Hexyl
Cl
11b
O
6
6
14
20
HN
HN
Cl
12
CH2
O
a Values are geometric means of two experiments.

2050
R. Kurukulasuriya et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2047–2050
Table 2. Binding and functional activity (Ki, nM) of selected h-GlucR
antagonists
Acknowledgements
We would like to thank Matt Perham and Tom Farb for
assistance with the rat glucagon challenge experiments
and Dave Beno for the rat pharmacokinetic studies.
O
N
H
O
References and notes
H
N
R
1. (a) Kurukulasuriya, R.; Link, J. T.; Madar, D. J.; Pei, Z.;
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O
Compound
R
Binding Ki
Cyclase Ki
(nM)a
(nM)a
13
14
–CH2CH2COOH
9
144
317
N
N
66
NH
N
15
16
–CH2CHFCOOH 26
–CH2CH(OH)COOH 112
>2000
>2000
a Values are geometric means of two experiments.
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the representative analogues that were selected for fur-
ther evaluation showed good pharmacokinetic profiles
in rat. Compounds were also affected by protein bind-
ing. Bovine serum albumin (BSA) was found to decrease
the in vitro functional activity of the compounds. For
example 6i had less than 5% oral bioavailability. Also its
h-GlucRcyclase Ki decreased from 29 to 140 nM in the
presence of 10% BSA. The functional activity of 6i was
similar for human, murine (mu-GlucRcyclase Ki ¼ 29 nM)
and monkey (m-GlucRcyclase Ki ¼ 15 nM) glucagon
receptors but showed a decrease for the rat receptor
(r-GlucRcyclase Ki ¼ 69 nM). To test the efficiency of
glucagon receptor blockade in vivo, 6i was examined in
Sprague–Dawley rats against a exogenous glucagon
challenge. A 50 mg/kg iv dose of 6i reduced the glucagon
(3 nmol/kg)) induced glucose excursion by 50% within
30 min of dosing when compared to vehicle.
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In summary a series of potent biaryl amide glucagon
receptor antagonists was discovered. One of these
antagonists was demonstrated to blunt the effects of a
glucagon challenge in vivo when dosed intravenously.
Of future interest is the discovery of antagonists for use
in oral dosing long-term studies.
13. Reviews: (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95,
2457; (b) Suzuki, A. In Metal Catalyzed Cross-Coupling
Reactions; Diedrich, F., Stang, P. J., Eds.; Wiley–VCH:
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263–303; (d) Suzuki, A. J. Organomet. Chem. 1999, 576, 147.