Human β3-adrenergic receptor agonists containing 1,2,3-triazole-substituted benzenesulfonamides

Article abstract of DOI:10.1016/S0960-894X(00)00422-4

Compounds containing a 1,2,3-triazole-substituted benzenesulfonamide were prepared and found to be potent and selective human β₃-adrenergic receptor agonists. The most interesting compound, trifluoromethylbenzyl analogue 12e (β₃ EC

Full text of DOI:10.1016/S0960-894X(00)00422-4

Bioorganic & Medicinal Chemistry Letters 10 (2000) 2111±2114
Human ꢀ3-Adrenergic Receptor Agonists Containing
1,2,3-Triazole-Substituted Benzenesulfonamides
Linda L. Brockunier,* Emma R. Parmee, Hyun O. Ok, Mari R. Candelore,
Margaret A. Cascieri, Lawrence F. Colwell, Jr., Liping Deng, William P. Feeney,
Michael J. Forrest, Gary J. Hom, D. Euan MacIntyre, Laurie Tota,
Matthew J. Wyvratt, Michael H. Fisher and Ann E. Weber
Departments of Medicinal Chemistry, Biochemistry and Physiology, Pharmacology, and Comparative Medicine,
Merck Research Laboratories, Rahway, NJ 07065, USA
Received 17 May 2000; accepted 14 July 2000
AbstractÐCompounds containing a 1,2,3-triazole-substituted benzenesulfonamide were prepared and found to be potent and
selective human b3-adrenergic receptor agonists. The most interesting compound, tri¯uoromethylbenzyl analogue 12e (b3
EC50=3.1 nM with >1500-fold selectivity over binding to both b1- and b2 receptors), stimulates lipolysis in the rhesus monkey
(ED50=0.36 mg/kg) and is 25% orally bioavailable in the dog. # 2000 Elsevier Science Ltd. All rights reserved.
Activation of the b3-adrenergic receptor (b3-AR), a dis-
crete b-adrenoceptor subtype located on the plasma
membranes of adipocytes, leads to an increase in meta-
bolic rate. Consequently, selective b3-AR agonists may
prove to be practicable therapeutic agents for the treat-
ment of obesity.1 Work from these laboratories has
shown that while aryl sulfonamides such as urea 1a and
imidazolone 1b are potent and selective b3-AR agonists
(b3 EC50=6.3 and 14 nM, respectively), both compounds
su€er from poor oral bioavailability in the dog (%F=
<1 and 7, respectively).2 Recent publications from
Merck describe the successful substitution of oxazole3a
and oxadiazole3b,c functionalities for the urea moiety,
resulting in compounds of general structure 2a and 2b.
These series of compounds were found to be b3-AR
agonists with improved pharmacokinetic pro®les.
Wishing to identify other suitable heterocyclic replace-
ments for the urea functionality, we have targeted sev-
eral series of 1,2,3-triazoles. A number of di€erent
substitution patterns about the triazole ring were
explored as shown below. Analogues in which the ben-
zenesulfonamide was linked to the triazole moiety at the
4-position (3a and 3b) were moderately potent partial
agonists of the b3-AR (b3 EC50's of 15±80 nM). These
compounds, however, were nonselective for activation
of the b3 receptor over binding to the b1- and b2-ARs
(data not shown) and as such, did not warrant further
investigation. Signi®cantly improved in vitro results were
seen for analogues in which the point of attachment of
the benzenesulfonamide was at either the 1- or the 2-
position of the triazole functionality (3c and 3d, respec-
tively). Of these two series, it was found that, for max-
imal potency and selectivity, 2,4-disubstitution (3d) was
preferred. Herein we report the synthesis and biological
activity of analogues in this series. Recent work suggests
that comparable b3-AR agonist activity is observed when
¯uorinated aromatic rings are substituted for aliphatic
*Corresponding author. Tel.:+1-723-594-6160; fax: +1-732-594-7877;
e-mail: linda_brockunier@merck.com
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00422-4

2112
L. L. Brockunier et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2111±2114
side chains.3a,c As these functionalities are less prone to
oxidative metabolism than aliphatic groups, our e€orts
concentrated on the preparation of these derivatives.
acid 8a6 to the Weinreb amide followed by chloro-
sulfonylation provided sulfonyl chloride 9. Condensa-
tion with aniline 6a and removal of the BOC protecting
group was followed by treatment with a large excess of
an appropriately substituted Grignard reagent to give
ketones 10. Reduction of the ketone with sodium boro-
hydride provided the corresponding alcohols 11, which
were then treated with triethylsilane and TFA giving the
desired benzylic compounds 12. Reduction of aldehyde
8b6 followed by bromination of the resultant alcohol and
chlorosulfonylation provided the sulfonyl chloride 13.
As this compound contained a reactive benzylic bro-
mide, use of the less nucleophilic aniline 6b was necessary
to provide sulfonamides 14 in good yield. Displacement of
the bromide by appropriately substituted phenoxides,
followed by removal of the chlorine atom and the BOC
protecting group provided the desired phenoxymethyl
analogues 15.
Chemistry
Treatment of arenes 4a4 (Scheme 1) with chlorosulfonic
acid provided sulfonyl chlorides 5, which were then
coupled with aniline 6a.2a Removal of the BOC pro-
tecting group with tri¯uoroacetic acid (TFA) furnished
the desired diaryl-substituted products 7. In an alternate
route, aryl bromides 4b were lithiated and converted to
the corresponding sulfonyl chlorides via the sul®nic acid
salt.5
The remaining triazole analogues were synthesized by
the routes shown in Scheme 2. Conversion of carboxylic
Scheme 1. Reagents: (a) HOSO2Cl, NaCl, 50 ꢀC; (b) nBuLi, THF, 78 ꢀC, then SO2; (c) N-chlorosuccinimide, CH2Cl2, 25 ꢀC; (d) aniline 6a, pyri-
dine, CH2Cl2, 25 ꢀC; (e) TFA, CH2Cl2, 25 ꢀC.
Scheme 2. Reagents: (a) ClCOCOCl, CH2Cl2, cat. DMF, 25 ꢀC; (b) H3CONHCH3HCl, Et3N, CH2Cl2, 25 ꢀC; (c) HOSO2Cl, 50 ꢀC; (d) aniline 6a,
pyridine, CH2Cl2, 25 ꢀC; (e) TFA, CH2Cl2, 25 ꢀC; (f) 10±20 equiv R0PhMgX, THF, 50 ꢀC; (g) NaBH4, MeOH, 25 ꢀC; (h) Et3SiH, TFA, CH2Cl2,
25 ꢀC; (i) CBr4, PPh3, Et2O, 25 ꢀC; (j) aniline 6b, pyridine, CH2Cl2, 25 ꢀC; (k) R0PhO Na+, DMF, 25 ꢀC; (l) H2, Pd(OH)2, MeOH, 25 ꢀC.

L. L. Brockunier et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2111±2114
Table 1. Comparison of b3-AR agonist activity and b1- and b2-AR binding anities8
2113
b
b
Compound
R
b3 EC50 (nM)
b1 Binding IC50
(nM)
b2 Binding IC50
(nM)
(% act)a
7a
7b
7c
7d
7e
7f
3-F-Ph
4-F-Ph
3,4-Di¯uoro-Ph
3-F, 4-OCH3-Ph
4-CF3-Ph
52 (89)
24 (91)
14 (82)
22 (80)
14 (90)
18 (84)
8700
40,000
2600
5600
21,000
1300
8800
9300
1300
2500
21,000
1600
4-OCF3-Ph
12a
12b
12c
12d
12e
12f
12g
3-F-PhCH2±
4-F-PhCH2±
2,6-Di¯uoro-PhCH2±
3,4-Di¯uoro-PhCH2±
4-CF3-PhCH2±
6.4 (87)
14 (75)
24 (84)
7.2 (86)
3.1 (85)
4.1 (91)
48 (83)
3000
2500
28,000
2000
20,000
2600
10,000
380
780
5000
1000
4700
860
4-OCF3-PhCH2±
2,4,6-Tri¯uoro-PhCH2±
8800
15a
15b
15c
3,4-Di¯uoro-PhOCH2±
4-CF3-PhOCH2±
4-OCF3-PhOCH2±
10 (63)
11 (72)
14 (75)
930
920
6200
690
730
620
aAdenylyl cyclase activation given as % of the maximal stimulation with isoproterenol.
bReceptor binding assays were carried out with membranes prepared from CHO cells expressing the cloned human adrenoceptor in the presence of
125I-iodocyanopindolol.
Results and Discussion
However, preliminary pharmacokinetic studies in the
dog showed that not only was the ketone 10b metabo-
lized to the corresponding alcohol 11b, but also that the
alcohol itself had a low AUC after oral administration.
Thus, due to the metabolic lability and inadequate
pharmacokinetic properties of these compounds, further
investigation of these analogues was not pursued.
Compounds 7, 12, and 15 were tested in vitro for their
ability to stimulate increases in cAMP in CHO cells
expressing the cloned human b-ARs.7,8 The in vitro
results are presented in Table 1. In general, all of these
analogues activated the b3 receptor to a high degree
(63±91% activation) with no signi®cant ecacy at the
b1- and b2-ARs (<50% activation at 10 mM, data not
shown). As a rule, potencies were good to moderate
with b3 EC50's ranging from 3.1 to 52 nM. In both the
phenyl and benzyl series, the 4-tri¯uoromethyl analo-
gues 7e and 12e were the most potent analogues with b3
EC50's of 14 and 3.1 nM, respectively. These derivatives
were also signi®cantly more selective than all other
analogues, none of which showed such impressive
selectivity (>1500-fold) for activation of the b3-AR over
binding to both the b1- and the b2-ARs. Interestingly,
this trend did not translate to the phenoxymethyl series,
as in this case the 4-tri¯uoromethyl analogue showed
poor selectivity over binding at the b1- and b2-ARs (84-
and 66-fold, respectively). Within the benzyl series, bis
ortho-substitution appeared to be detrimental, as com-
pounds 12c and 12g were 2- to 8-fold less potent than
the other analogues shown.
The pharmacokinetic properties of select analogues
were studied in dogs (3 mg/kg iv, and 10 mg/kg po) and
found to be far superior to the oral bioavailabilities of
the acyclic and cyclic urea leads 1a and 1b. Compounds
12d and 12e were 38% and 25% orally bioavailable with
half-lives of 4 and 6 h, respectively. Analogue 7e had an
oral bioavailability of 18% with an excellent half-life of
15 h.
The ecacy of the most potent and selective derivative
(12e) was examined in a rising dose infusion study in
anesthetized rhesus monkeys.8b This compound elicited
hyperglycerolemia (ED50=0.36 mg/kg) and produced a
maximum response equivalent to 95% of that of the full
agonist isoproterenol. This compound displayed excel-
lent separation between lipolytic potency and tachy-
cardia, as heart rate e€ects were minimal (<5%) even
at the highest dose of 10 mg/kg.
The advanced intermediate ketones and alcohols (com-
pounds 10 and 11, respectively) were also submitted for
screening in the b3 assay (data not shown). Analogues
10b and 11b (R0=4-F) were the most potent derivatives
in these series with b3 EC50's of 6.4 nM and 3.3 nM,
respectively. These analogues also exhibited excellent
selectivities of >2500-fold for activation of the b3
receptor over binding to both the b1- and b2-ARs.
Conclusion
We have identi®ed a new series of human b3-adrenergic
receptor agonists containing 1,2,3-triazoles as hetero-
cyclic urea replacements which show markedly improved
oral bioavailabilities while maintaining potency, selec-

2114
L. L. Brockunier et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2111±2114
tivity, and in vivo ecacy. In particular, 4-tri¯uoro-
methylbenzyl analogue 12e is an exceptionally selective
human b3 agonist (b3 EC50=3.1 nM; with 6500- and
1500-fold selectivity over binding to b1- and b2 recep-
tors, respectively). When administered intravenously to
rhesus monkeys, 12e elicits a lipolytic response at low
dose with minimal e€ects on heart rate. The 25% oral
bioavailability of this compound in dogs is a marked
improvement over the low bioavailability of acyclic and
cyclic urea leads 1a and 1b.
lore, M. R.; Cascieri, M. A.; Colwell, L. F., Jr.; Forrest, M. J.;
Hom, G. J.; MacIntyre, D. E.; Stearns, R. A.; Strader, C. D.;
Wyvratt, M. J.; Fisher, M. H.; Weber, A. E. Bioorg. Med.
Chem. Lett. 2000, 10, 1431.
4. For the synthesis of 2,4-diaryl-1,2,3-triazoles (4a,b) from
substituted phenylglyoxals see El Khadem, H.; El-Sadik, M.
M.; Meshreki, M. H. J. Chem. Soc. 1968, 2097. The requisite
phenylglyoxals were prepared by selenium dioxide oxidation
of appropriately substituted acetophenones according to
Joshi, K. C.; Dubey, K.; Dandia, A. Heterocycles 1981, 16,
1545.
5. Graham, S. L.; Ho€man, J. M.; Gautheron, P.; Michelson,
S. R.; Scholz, T. H.; Schwam, H.; Shepard, K. L.; Smith, A.
M.; Smith, R. L.; Sondey, J. M.; Sugrue, M. F. J. Med. Chem.
1990, 33, 749.
Acknowledgements
6. For the synthesis of 2-phenyl-1,2,3-triazole-4-carboxylic
acid (8a) and the corresponding carboxaldehyde (8b) from
fructose see Riebsomer, J. L.; Sumrell, G. J. Org. Chem. 1948,
13, 807.
We thank Mr. Paul Cunningham and Mr. Donald
Hora, Jr. for assistance with the in vivo experiments,
Ms. Amy Bernick for mass spectral analyses, and Pro-
fessor James G. Grannemann (Wayne State University)
for supplying the cloned human b3-AR.
7. The human b3-AR was obtained from Professor J. Gran-
nemann (Wayne State University), Grannemann, J. G.; Lah-
ners, K. N.; Rao, D. D. Mol. Pharmacol. 1992, 42, 964. The
human b1- and b2-ARs were cloned as described in Frielle, T.;
Collins, S.; Daniel, K. W.; Caron, M. G.; Lefkowitz, R. J.;
Kobilka, B. K. Proc. Natl. Acad. Sci. U.S.A. 1987, 84, 7920
and Kobilka, B. K.; Dixon, R. A.; Frielle, T.; Dohlman, H.
G.; Bolanoski, M. A.; Sigal, I. S.; Yan-Feng, T. L.; Francke,
U.; Caron, M. G.; Lefkowitz, R. J. Proc. Natl. Acad. Sci.
U.S.A. 1987, 84, 46. The receptors were expressed in CHO
cells at receptor densities of 46±88 fmol/mg (b3 receptors) or
300±500 fmol/mg (b1- and b2-ARs).
References and Notes
1. For recent reviews see: (a) Weyer, C.; Gautier, J. F.; Dan-
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E. Bioorg. Med. Chem. Lett. 1998, 8, 3087. (b) Parmee, E. R.;
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8. (a) The activity of an agonist at the b3-AR is best described
by its ability to stimulate adenylyl cyclase in a functional assay
(EC50), since this method measures anity for the high-a-
nity, G-protein coupled state of the receptor. This assay accu-
rately predicts the lipolytic potential of compounds in native
adipocytes.8b The b3-AR IC50 values are a measure of the
compound's binding anity for both the high and low anity
states of the b3-AR, thus are lower than the respective EC50
values. The triazoles exhibited low ecacy at the b1- and b2-
ARs (<50% activation at 10 mM), hence the selectivity of the
compounds is most accurately represented by comparing the
b3 EC50 values with the b1- and b2 IC50 values. (b) For
experimental details see Fisher, M. H.; Amend, A. M.; Bach,
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Stearns, R. A.; Thompson, G. M.; Tota, L.; Vicario, P. P.;
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