Novel substituted 4-aminomethylpiperidines as potent and selective human β3-agonists. Part 1: Aryloxypropanolaminomethylpiperidines

Article abstract of DOI:10.1016/S0960-894X(02)00607-8

The synthesis and SAR of a series of human β₃ adrenoreceptor agonists based on a template derived from a common pharmacophore coupled with 4-aminomethylpiperidine is described. Potent and selective agents were identified such as 26 that was in vitro active in CHO cells expressing human β₃-AR (EC₅₀=49 nM, IA=1.1), and in vivo active in a transgenic mouse model.

Full text of DOI:10.1016/S0960-894X(02)00607-8

Bioorganic & Medicinal Chemistry Letters 12 (2002) 2957–2961
Novel Substituted 4-Aminomethylpiperidines as Potent and
Selective Human ꢀ3-Agonists. Part 1:
Aryloxypropanolaminomethylpiperidines
Robert J. Steffan,a,* Mark A. Ashwell,a William R. Solvibile,a Edward Matelan,a
Elwood Largis,b Stella Han,b Jeffery Tilletb and Ruth Mulveyb
aChemical Sciences, Wyeth Research, 500 Arcola Rd, Collegeville, PA 19426, USA
bCardiovascular/Metabolic Diseases, Wyeth Research, 500 Arcola Rd, Collegeville, PA 19426, USA
Received 13 March 2002; accepted 1 July 2002
Abstract—The synthesis and SAR of a series of human b3 adrenoreceptor agonists based on a template derived from a common
pharmacophore coupled with 4-aminomethylpiperidine is described. Potent and selective agents were identified such as 26 that was
in vitro active in CHO cells expressing human b3-AR (EC50=49 nM, IA=1.1), and in vivo active in a transgenic mouse model.
# 2002 Elsevier Science Ltd. All rights reserved.
Stimulation of b3 adrenoreceptors (AR), expressed on
the cell surface of adipocytes in brown and white adi-
pose tissue, is viewed as a potential treatment for obe-
sity and non-insulin-dependent diabetes mellitus.
Agonists of the b3-AR activate an intracellular signaling
process to initiate the lipolysis of triglycerides.1 The
resulting free fatty acids are processed by uncoupling
protein (UCP) leading to thermogenesis.
mined in b3-AR knockout mice (KO) expressing no b3-
AR. Compounds showing thermogenesis only in the mice
with human b3-AR are selective human b3-AR agonists.
A program at Wyeth was established to develop a sec-
ond generation of agonists selective to the human b3-
AR but devoid of agonism or antagonism at b1-AR and
b2-AR. The template shown in Figure 1 was designed as
a hybrid of a common pharmacophore5 of b-AR bind-
ing ligands and 4-amino-methylpiperidine for the devel-
opment of human b3-AR agonists. The piperidinyl
nitrogen provided a synthetically easy scaffold upon
which to rapidly explore a variety of different substitu-
tions without the introduction of a second chiral center.
The first generation of potent rat b3-AR selective agonists
was reported to show antiobesity and antihyperglycemic
effects in animal models. One such clinical candidate2
CL-316,243 was found to be 100- to 1000-fold less
active at the human b3-AR. Thus the rat b3-AR did not
effectively predict activity at the human b3-AR.
Variations to the aryl moiety (Ar) and the R group were
planned to find the optimal substituents to meet the
program goals. Aryloxypropanolamines of Figure 1 are
prepared by regiospecific ring opening of a chiral epox-
ide with a substituted aminomethylpiperidine in metha-
nol at 60 ꢀC overnight as shown in Scheme 1.
An in vitro assay to more accurately predict activity at
the human receptor has been developed employing the
use of cloned chinese hamster ovary cells (CHO cells)
expressing human b-AR’s.3 An increase in cAMP levels
generated from stimulation of the human b3-AR by an
agonist is determined as a measure of lipolysis. Themo-
genesis is determined in an in vivo model using trans-
genic mice expressing the human b3-AR.4 An increase in
themogenesis in these mice is compared to values deter-
A variety of chiral epoxides were synthesized. The epoxide
1 of Scheme 2 was prepared by alkylation of (2S)-(+)-
oxiranylmethyl-3-nitrobenzenesulfonate with 4-hydroxy-
carbazole6 over potassium carbonate in 2-butanone.
A series of t-butyldiphenylsilyl (TBDPS) protected
epoxides 2b, 3b, and 4b was prepared by the reaction of
*Corresponding author. Fax: +1-484-865-9398; e-mail: steffar@
wyeth.com
0960-894X/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(02)00607-8

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R. J. Steffan et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2957–2961
Figure 1. Aminomethylpiperidine template for development of b3
aderenoreceptor agonism.
Scheme 1. (a) Methanol, 60 ꢀC, 18 h, (25–55%).
Scheme 5. (a) R-(+)-glycidol, Ph3P, DEAD, 30%; (b) RaNi, H;2 (c)
phosgene, DIEA, 69% for steps b and c.
The R substitutions of Figure 1 were obtained via
alkylation of one of three intermediates (amide, imide10
or Boc) outlined in Scheme 7 with RX (R=aryl, alkyl,
acyl, sulfonyl, X=halogen) in the presence diisopropy-
lethyl amine (DIEA). When R=carbamoyl, compounds
were prepared by reaction with an isocyanate.
Scheme 2. (a) H2O, PhNHNH2 91%;2 (b) trifluoroacetic acid (TFA),
reflux, 65%; (c) 10% Pd/C mesityline, reflux, 46%; (d) (2S)-(+)-oxi-
ranylmethyl-3-nitrobenzenesulfonate, K2CO3, 2-butanone, reflux,
A more specific series of analogues where R=4-ureido-
benzenesulfonyl was synthesized from two convergent
routes. Starting from either the Boc protected piperidine
8 or aniline 9 depending upon the availability of pre-
cursors the target molecules 15 were prepared as out-
lined in Scheme 8.
mono-protected bis-phenolic precursors 2a, 3a and 4a
with R-(+)-glycidol under Mitsunobu7 conditions as
shown in Scheme 3.
Specifically, sulfonylation of 8 gave the core inter-
mediate structure 10. The conversion of the anilino
function of 10 into a ureido group was conveniently
A similar approach was used in the preparation of 5b
from mono-benzyl protected 5a as shown in Scheme 4.
Mitsunobu conditions were also used to form the chiral
epoxides 6 and 7. As outlined in Scheme 5 the epoxide is
attached prior to the benzimidazole formation, a slight
variation of literature conditions.8 The 4-hydroxy-oxi-
ndole of Scheme 6 was prepared by literature conditions.9
Scheme 6. (a) NaCN, EtOH aq., 99%; (b) HCl, H2SO4, 97%; (c) H2,
10% Pd/C, 97%; (d) 48% HBr, 73%; (e) R-(+)-glycidol, Ph3P,
DEAD, 53%.
Scheme 3. (a) Ph3P, diethylazodicarboxylate (DEAD), R-(+)-glyci-
dol, (56–70%).
Scheme 4. (a) 40% HBr, 80%; (b) K2CO3, benzyl bromide, acetone,
27%; (c) (2S)-(+)-oxiranylmethyl-3-nitrobenzenesulfonate, K2CO3,
2-butanone, 82%.
Scheme 7. (a) RX, DIEA THF, (50–90%); (b) B2H6 or LAH,, THF,
30–75%; (c) PhCHO, Dean-Stark trap, toluene;10 (d) 2 N HCl, diox-
ane, 80–95%.

R. J. Steffan et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2957–2961
2959
A series of analogues was prepared to develop a SAR of
a variety of functional groups at the R position of Fig-
ure 1. The aryl group was held constant (Ar=4-carba-
zolyl a moiety that is present in the beta blocker
Carazolol, which also shows activity as an agonist at the
human b3-AR). The in vitro agonist activity at the
human b-AR’s, expressed as EC50’s and the intrinsic
activity versus isoproterenol, for the various R varia-
tions are shown in Table 1.
In general the compounds containing the carbazole
moiety showed good selectivity for b3-AR over the
other b-AR’s. The analogues 16–23 showed partial to
complete agonism for the b3-AR with EC50’s in the sub-
micromolar range. The most potent compound 21
(EC50=48 nM, IA=0.62) was found to be significantly
less active as an antagonist11 relative to the beta blocker
Carazolol: (1000-fold less at the b1-AR and 25-fold less at
b2-AR). However, no compound containing the carbazole
moiety showed any in vivo activity in the transgenic
mouse model described earlier. As a result, further SAR
development was focused on related analogues of 21.
Substitutions to 15 were approached in a stepwise fash-
ion with aryl functions other than the carbazole. The 4-
hyroxyphenyl group, known to be active in related ser-
ies, was chosen as a preferable aryl group from which to
optimize the ureido function. A variety of ureas were
prepared as outlined in Scheme 8. The results are tabu-
lated in Table 2.
Scheme 8. (a) 4-aminobenzenesulfonyl chloride, DIEA, THF, 82%;
(b) RNCO, dioxane (or triphosgene and RNH2); (c) HCl dioxane (d)
chiral epoxides 1–7, MeOH, (TBAF to remove TBDPS if necessary);
(e) RNCO, dioxane (or triphosgene and RNH2); (f) chlorosulfonic
acid, 70%; (g) 4-bocaminomethylpiperidine, DIEA, THF, 95%.
carried out either from reaction with triphosgene and a
second amine or by treatment with a substituted isocy-
anate to give 13. The same conditions were applied to
the preparation of 11 from 9. In the case of 11, the sul-
fonyl chloride was installed by treatment with chloro-
sulfonic acid in a regiospecific fashion to give 12. Thus
the piperidine 8 was sulfonylated with 12 to give the
common intermediate to both routes 13. Deprotection
of 13 to the free amine 14 followed by reaction with a
chiral epoxide provided the target molecules 15.
Compounds 25–32 were fully efficacious with a wide
selectivity over the other b-AR’s. Compound 26 was the
most in vivo active compound with an increase in ther-
mogenesis in the b3 transgenic mice of 30Æ14% at an ip
dose of 10 mg/kg. The two of the more active uredio
groups, octyl in 26 and 2,5-difluorobenzyl in 30, were
held constant and the variety of other aryl groups were
evaluated. These results are tabulated in Table 3.
Full experimental details for the compounds in the
schemes reported above and following tables are avail-
able in the published patent application.12
The most potent Ar replacement compound was 35
showing potent in vitro activity (EC50=1 nM, IA=1.0)
with greater than 300-fold selectivity over b1-AR and
Table 1. In vitro agonist activity at human b-AR’s for R variationsb
Compd
R
ꢀ3 EC50 nMa (IA)
ꢀ1 EC50 nMa (IA)
ꢀ2 EC50 nM
16
17
18
19
20
21
22
23
24
3,3,3-Trifluoropropyl
Propyl
Isopropyl
187 (0.99)
870 (0.56)
290 (1.06)
319 (0.43)
665 (0.79)
48 (0.62)
380 (0.49)
70 (0.29)
iac
417 (0.13)
>1000
ntd
ntd
ntd
ntd
Pentyl
Hexyl
ntd
ntd
>1000
>1000
ntd
>1000
ntd
>1000
>1000 (0.08)
ntd
>1000 (0.05)
ntd
4–Hexylureido–C6H4SO2–
2-Naphthyl–SO2–
3-(HOOC)–C6H4NHCO–
3-CF3-2-pyridyl
ab-AR agonist activities are expressed as EC50 values by a measurement of cAMP levels in CHO cells expressing human b-ARs.
bIntrinsic activity (IA) was determined as the maximal response of the compound divided by the maximal response of isoproterenol at 10 mM.
cia=inactive.
dnt=not tested.

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R. J. Steffan et al. / Bioorg. Med. Chem. Lett. 12 (2002) 2957–2961
Table 2. In vitro agonist activity at human b-AR’s for R variations of 15 when Ar=4-HO-phenyl
Compd
R
ꢀ3 EC50 nM (IA)
ꢀ1 EC50 nM (IA)
ꢀ2 (IA)
25
26
27
28
29
30
31
32
Hexyl
Octyl
Phenyl
Cyclohexyl
Isobutyl
58Æ10 (0.83)
49 (1.1)
135 (0.83)
60 (1.1)
126 (0.9)
29 (0.82)
20 (0.95)
26 (0.92)
10,900 (0.28)
887 (0.16)
489 (0.38)
1015 (0.29)
nt
1010 (0.24)
2050 (0.62)
(0.18)
0.2
0.02
0
0
nt
0
0
0.01
2,5-DiF-benzyl
3-(2-Thienyl)propyl–
2-Pyridyl–
See footnotes for Table 1.
Table 3. In vitro agonist activity at human b-AR’s for Ar and R variations of 15
Compd
Ar
R
ꢀ-3 EC50 nM (IA)
ꢀ-1 EC50 nM (IA)
bÀ2 EC50 nM (IA)
33
45 (0.83)
525 (0.19)
(0)
34
35
36
37
38
Octyl
306 (0.82)
1 (1.0)
nt
353 (049)
390 (0.63)
nt
nt
454 (0.7)
680 (0.26)
nt
Octyl
Octyl
Hexyl
5 (0.91)
55 (052)
10 (0.53)
nt
nt
See footnotes for Table 1.
over 400-fold selectivity over b2-AR. Compound 35 was
also in vivo active with an increase in thermogenesis of
18+2% at an ip dose of 10 mg/kg. Compound 35
however showed an increase in antagonistic activity at
b1-AR and b2-AR when compared to 26. (IC50=27 nM
versus 6156 nM at b1-AR and IC50=4 nM vs 268 nM at
b2-AR). The oxindole 37 and benzimidazole 38 analo-
gues had low EC50’s but the IA fell to around 50% of
isoproterenol. Compounds 37 and 38 also demonstrated
antagonism at b1-AR and b2-AR.
2. Bloom, J. D.; Dutia, M. D.; Johnson, B. D.; Wissner, A.;
Burns, M. G.; Largis, E. E.; Dolan, J. A.; Claus, T. H. J. Med.
Chem. 1992, 35, 3081.
3. Wilson, S.; Chambers, J. K.; Park, J. E.; Ladurner, A.;
Cronk, D. W.; Chapman, C. G.; Kallender, H.; Browne, M. J.;
Murphy, G. J.; Young, P. W. J. Pharm. Exp. Ther. 1996, 279, 214.
4. Susulic, V. S.; Frederich, R. C.; Lawitts, J.; Tozzo, E.;
Kahn, B. B.; Harper, M.-E.; Himms-Hagen, J.; Flier, J. S.;
Lowell, B. B. J. Biol. Chem. 1995, 270, 29483.
5. (a) b3-AR active compounds share a common pharmaco-
phore as reported by Mejean A.; Guillaume, J.-L.; Strosberg,
A. D. Eur. J. Pharm. 1995, 291, 359. (b) A subset of com-
pounds based on this template has been published by Bovy, P.
R.; Cecchi, R.; Venier, O. Int. Pat. Appl. WO 0144227, 2001.
Chem. Abstr. 2001, 135, 46110, Cecchi, R. Int. Pat. Appl.
WO0143744, 2001, Chem. Abstr. 2001, 135, 46105 and Cecchi,
R.; Croci, T.; Guzzi, U.; Marsault, E. Int. Pat. Appl. WO
9965895 1999, Chem Abstr. 1999, 132, 35618.
6. (a) Berridge, M. S.; Cassidy, E. H.; Terris, A. H.; Vesselle,
J. M. Nucl. Med. Biol. 1992, 19, 563. (b) Dubois, E. A.; van
den Bos, J. C.; Doornbos, T.; van Doremalen, P. A. P. M.;
Somsen, G. A.; Vekemans, J. A. J. M.; Janssen, A. G. M.;
Batink, H. D.; Boer, G. J.; Pfaffendorf, M.; van Royen, E. A.;
van Zwieten, P. A. J. Med. Chem. 1996, 39, 3260.
In conclusion, most analogues of the aryloxypropanol
aminomethylpiperidines of Figure 1 were identified as in
vitro potent and selective b3-AR agonists. Compounds
26 and 35 also induced thermogenesis in the in vivo
model and are potentially useful as antiobesity and
antihyperglycemic agents in humans.
References and Notes
1. (a) Dow, R. L. Exp. Opin. Invest. Drugs 1997, 6, 1811. (b)
Strosberg, A. D. Annu. Rev. Pharmacol. Toxic. 1997, 37, 421.
7. Mitsunobu, O.; Yamada, M. Bull. Soc. Chem. Jpn. 1967,
60, 2380.

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Heldoorn, M.; Vaalburg, W. J. Med. Chem. 1997, 40, 3829.
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binding assay using CHO cells transfected with human b1-AR
or b2-AR. IC50 values were determined by incubation of the
test compound, at various concentrations, and the radioligand
[
125I]iodocyanopindolol with these cells.
10. Prugh, J. D.; Birchenough, L. A.; Egbertson, M. S. Synth.
Comm. 1992, 22, 2357.
11. Selected compounds were evaluated as antagonists in a
12. For full experimental details see. Steffan R. J.; Ashwell M.
A.; Solvibile W. R.; Matelan, E. US21875300P, application
submitted July 17, 2000.