Discovery of adamantane ethers as inhibitors of 11β-HSD-1: Synthesis and biological evaluation

Article abstract of DOI:10.1016/j.bmcl.2006.10.074

A novel class of adamantane ethers 11β-hydroxysteroid hydrogenase type I inhibitors has been discovered. These compounds have excellent HSD-1 potency and selectivity against HSD-2. The structure-activity relationships, selectivity, metabolism, PK, ex vivo

Full text of DOI:10.1016/j.bmcl.2006.10.074

Bioorganic & Medicinal Chemistry Letters 17 (2007) 750–755
Discovery of adamantane ethers as inhibitors of 11b-HSD-1:
Synthesis and biological evaluation
*
Jyoti R. Patel, Qi Shuai, Jurgen Dinges, Marty Winn, Marina Pliushchev,
Steven Fung, Katina Monzon, William Chiou, Jiahong Wang, Liping Pan,
Seble Wagaw, Kenneth Engstrom, Francis A. Kerdesky, Kenton Longenecker,
Russell Judge, Wenying Qin, Hovis M. Imade, DeAnne Stolarik, David W. A. Beno,
Michael Brune, Linda E. Chovan, Hing L. Sham, Peer Jacobson and J. T. Link
Global Pharmaceutical Research & Development, Abbott Laboratories, R43G, AP52, 200 Abbott Park Road,
Abbott Park, IL-60064-6217, USA
Received 7 September 2006; revised 24 October 2006; accepted 25 October 2006
Available online 28 October 2006
Abstract—A novel class of adamantane ethers 11b-hydroxysteroid hydrogenase type I inhibitors has been discovered. These com-
pounds have excellent HSD-1 potency and selectivity against HSD-2. The structure–activity relationships, selectivity, metabolism,
PK, ex vivo pharmacodynamic data, and an X-ray crystal structure of one of these inhibitors bound to h-HSD-1 are discussed.
Ó 2006 Elsevier Ltd. All rights reserved.
5
,6
The combination of risk factors for cardiovascular dis-
ease such as insulin resistance, dyslipidemia, obesity,
and hypertension is referred to as metabolic syndrome.
ments. Improved hepatic insulin sensitivity and lipid
profiles were observed in 11b-HSD-1 knockout mice.
It is expected that the inhibition of 11b-HSD-1 in the liv-
er and fat will improve glucose and lipid metabolism
disorders.
1
Glucocorticoids (GCs) are important regulators of glu-
cose and lipid homeostasis. At the cellular level, GCs
bind to the glucocorticoid receptor and activate, or re-
press, downstream target genes leading to increased
hepatic glucose production and lipolysis in adipose tis-
sue. GCs circulate in an active (cortisol in humans, cor-
ticosterone in rodents) and an inactive form (cortisone
in humans, dehydrocortisone in rodents). Conversion
between two forms is catalyzed by the enzymes 11b-hy-
droxysteroid dehydrogenase type-1 (11b-HSD-1) and
type-2 (11b-HSD-2). While 11b-HSD-1 reduces corti-
sone to cortisol and is highly expressed in liver and adi-
pose tissue, 11b-HSD-2 oxidizes cortisol to cortisone
Multiple classes of 11b-HSD-1 inhibitors have been
reported.
7
–12
Potent and selective inhibitors of human
1
3
11b-HSD-1 have been discovered recently. These com-
pounds have excellent potency against human 11b-
HSD-1 and selectivity over 11b-HSD-2, but frequently
lack the desired rodent potency against m-11b-HSD-1
and selectivity over m-11b-HSD-2, for preclinical
evaluation.
We sought to discover compounds with improved
potency (<30 nM) and selectivity (>100-fold) in
rodents. We have identified adamantane aryl ethers
as potent and selective inhibitors of human and mouse
11b-HSD-1, and report their optimization in this
paper.
2
–4
and is primarily expressed in the kidney.
The hypothesis that the inhibition of 11b-HSD-1, med-
iated GC amplification may be therapeutically relevant
for metabolic syndrome is supported by rodent experi-
Reductive amination of adamantane ketone 1 gave an
amine intermediate, which was acylated to give amide 2
as a mixture of trans- and cis- isomers (4:1, Scheme 1).
The trans-isomer was isolated by chromatography and
was treated with oleum and formic acid, followed by
Keywords: Metabolic syndrome; 11b-HSD-1; 11b-HSD-2; Inhibitor;
Adamantane ethers; X-ray crystal structure.
*
Corresponding author. Tel.: +1 847 937 4381; e-mail:
jyoti.patel@abbott.com
0
960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.10.074

J. R. Patel et al. / Bioorg. Med. Chem. Lett. 17 (2007) 750–755
751
Scheme 1. Reagents and conditions: (a) i—NH
NaBH , rt, 98%; (b) 2-bromo-2-methylpropanoyl bromide, TEA,
DCM, rt, 48%; (c) oleum, formic acid, 60 °C, 71%; (d) SOCl , CH OH,
°C, 83%; (e) phenol, NaH, toluene, 100 °C, 29%; (f) NaOH, THF,
EtOH, H O, rt, 97%; (g) 30% NH OH, EDAC, HOBT, DCM, rt, 57%.
4 3
OH, CH OH, rt; ii—
3
2
3
0
2
4
Scheme 2. Reagents and conditions: (a) 1,1,1-trichloro-2-methylpro-
pan-2-ol, NaOH, acetone, rt, 65%; (b) 13, TBTU, DIEA, DMF, rt,
thionyl chloride and methanol, to yield the bromide 3.
Phenol was pretreated with sodium hydride then bro-
mide 3 was added and reaction mixture was heated to
provide ether 4. The ester in 4 was hydrolyzed to provide
acid 5, which was then converted into amide 6. Com-
pounds with substituted aryl ether (7–10, Table 1) were
synthesized using these procedures as exemplified by 5
and 6.
2 4
87%; (c) NaOH, THF, EtOH, H O, rt, 90%; (d) 30% NH OH, EDAC,
HOBT, DCM, rt, 85%.
coupled using TBTU and DIEA, and the resulting ester
was hydrolyzed to furnish acid 16. Further condensation
with methyl sulfonamide yielded acylsulfonamide 17.
Similarly, acid 9 and 4-(aminomethyl)benzonitrile were
coupled to yield an intermediate nitrile, which was fur-
ther reacted with sodium azide and triethylamine hydro-
chloride to provide tetrazole 18. Compounds 19–22 were
synthesized by similar procedures.
In some cases, the O-alkylation (using bromide 3) as de-
scribed above gave poor yields. In these cases, the acids
1
4
like 12 were prepared (Scheme 2). Amine 13 was syn-
thesized by reductive amination of 4-oxo-adamantane-
1
-carboxylic acid followed by esterification. Coupling
of 12 and 13 provided ester 14, which was then hydro-
lyzed and the resulting acid was converted into the
amide 15.
Synthesis of compounds prepared in an effort to replace
primary amide at C-5 of the adamantane is shown in
Scheme 4. Acid 9 was converted to amide 23 and was
also reduced to alcohol 24, which was alkylated to afford
acid 25. The amide 10 was dehydrated and the interme-
diate nitrile was converted to tetrazole 26 using sodium
Secondary amides were synthesized as shown in Scheme
3
. Acid 9 and methyl 4-(aminomethyl)benzoate were
Table 1. In vitro inhibition and metabolic stability data for 5–10 and 15
1
R
2
R
a
Compound
h-HSD-1 IC50
nM)
h-HSD-2
a
IC50 (nM)
m-HSD-1
a
IC50 (nM)
m-HSD-2
a
IC50 (nM)
h-HSD-1 HEK
a
IC50 (nM)
Microsomal
b
stability
(
5
6
7
8
9
OH
NH
OH
OH
OH
NH
NH
H
39
5
17,000
23,000
1800
119
4
1500
40,000
140
840
24
98
78
2
H
2-Cl
3-Cl
4-Cl
4-Cl
4-OCH
8
8
59
94
15
22
6
3500
51
70
3
540
1700
190
220
22
100
89
30,000
12,000
18,000
1
1
0
5
2
2
40,000
55,000
43
57
3
6
4
21
a
Values are means of at least two experiments.
%
b
remaining by HPLC analysis after a 30 min incubation with mouse liver microsomes.

752
J. R. Patel et al. / Bioorg. Med. Chem. Lett. 17 (2007) 750–755
Scheme 4. Reagents and conditions: (a) CH
DMF, rt, 55%; (b) BH
ÆTHF, THF, 65 °C, 20%; (c) ethyl 2-
iodoacetate, KOH, DMSO, 70 °C, 16%; (d) (CF CO) O, pyridine,
3 2
NH , TBTU, DIEA,
3
Scheme 3. Reagents and conditions: (a) methyl 4-(aminomethyl)ben-
zoate, TBTU, DIEA, DMF, rt, 84%; (b) NaOH, THF, EtOH, H O, rt,
0%; (c) methyl sulfonamide, DMAP, EDAC, DMF, rt, 53%; (d) 4-
aminomethyl)benzonitrile, TBTU, DIEA, DMF, rt, 80%; (e) NaN
NMP, Et
NÆHCl, 150 °C to rt, 52%.
3
2
2
dioxane, rt, 58%; (e) NaN , Me SnCl, toluene, 120 °C, 59%.
3
3
8
(
3
,
3
The central amide of 15 interacts with the active site res-
˚
˚
idues, where the carbonyl is within 2.8 A and 2.9 A from
the hydroxyl groups of Ser170 and Tyr183, respectively.
The gem-dimethyl and ether-linked phenyl groups ex-
tend into the hydrophobic cavity of the steroid-binding
site, where Tyr177 forms the base of the pocket. The
close packing around the phenyl moiety of the inhibitor
suggests the protein may adopt different conformations
to accommodate compounds with substituents at differ-
ent positions of the aromatic ring (Fig. 1).
azide. Compounds 27 and 28 were synthesized by proce-
dures similar to acylsulfonamide 17.
Inhibition of human and mouse 11b-HSD-1 and 11b-
HSD-2 enzymatic activity was determined by scintilla-
1
5
tion proximity assay (SPA). Cellular activity of the
compounds was evaluated in a HEK293 HSD-1 FPIA
assay and metabolic stability was determined using
1
5
mouse liver microsomes.
Table 1 shows the biological activity of the aryl ether
adamantanes. In general, aliphatic or alicyclic ethers
had comparable potency to aryl ethers but their meta-
bolic stability was poor (data not shown). Aryl ethers
with an acidic adamantane group (5 and 7–9) were gen-
erally less potent in the cellular assay and less selective
over m-HSD-2. They did show excellent metabolic sta-
bility. Primary amide adamantanes (6, 10, and 15) had
excellent potency and selectivity compared to the parent
acids. However, they had lower metabolic stability.
Compound 7, with ortho substitution on the phenyl ring
was more potent than the meta and para analogs but
showed loss of selectivity over mouse HSD-2.
An X-ray crystal structure of human 11b-HSD1 with 15
1
6
was obtained (PDB code 2IRW). Comparison with
previously determined structures of h-11b-HSD-1
reveals that the inhibitor 15 is bound in the steroid-bind-
Figure 1. Crystal structure of h-11b-HSD-1 with compound 15. Atoms
are colored according to atom type and the components differ by
carbon atom colors: the protein is gray, the NADP+ cofactor is cyan,
and compound 15 is green. The protein surface is also colored
according to atom color.
+
17
ing site neighboring the bound cofactor NADP . The
adamantyl moiety of 15 is located near the nicotinamide
portion of the cofactor and the primary amide is posi-
+
tioned close to the pyrophosphates of the NADP .

J. R. Patel et al. / Bioorg. Med. Chem. Lett. 17 (2007) 750–755
753
Plasma hydrolysis of the primary amide group at C-5
of the adamantane has been observed in the com-
pounds similar to 15 (data not shown). We designed
secondary amides (Table 2) to slow or halt the plasma
hydrolysis. The crystal structure of 15 with the
enzyme also suggests that extending off of the primary
amide with aryl or heterocyclic groups could be
accommodated.
most promising. Acid 16 showed an excellent in vitro
profile and microsomal stability, but is subject to
phase II metabolism of the free carboxyl group.
Therefore, compounds 17–19 with acid mimetic
groups were prepared. However, they showed a
decline in microsomal stability and cellular activity.
Metabolic stability was significantly reduced in
heterocycles such as 20 and 21. Amide 22 showed
excellent in vitro potency with a moderate decline
in metabolic stability, while N-methylamide (23)
showed decreased cellular activity.
Typically, secondary amides with a 1-carbon spacer
between the terminal group and the amide were
Table 2. Secondary amides: in vitro inhibition and metabolic stability data for 16–23
Compound
R
h-HSD-1
a
IC50 (nM)
h-HSD-2
a
IC50 (nM)
m-HSD-1
a
IC50 (nM)
m-HSD-2
a
IC50 (nM)
h-HSD-1 HEK
a
IC50 (nM)
Microsomal
b
stability
16
15
20,000
12
5800
59
94
HOOC
1
1
1
7
8
9
25
16
51
50,000
26,000
25
18
24
10,000
310
690
300
51
51
35
HN
S O
O
O
6200
HN
N
N
N
>30,000
16,000
S O
O
H N
2
2
2
0
1
S
27
25
13,000
5300
11
14
21,000
19,000
92
91
5
N
16
N
2
2
2
3
12
13
20,000
12,000
4
8
90,000
16,000
120
210
78
H N
2
O
CH NHCO
3
NT
a
Values are means of at least two experiments.
%
b
remaining by HPLC analysis after a 30 min incubation with mouse liver microsomes (NT, not tested).

754
J. R. Patel et al. / Bioorg. Med. Chem. Lett. 17 (2007) 750–755
Table 3. Primary amide replacement: in vitro inhibition and metabolic stability data for 24–28
1
R
2
R
Compound
h-HSD-1
a
IC50 (nM)
h-HSD-2
a
IC50 (nM)
m-HSD-1
a
IC50 (nM)
m-HSD-2
a
IC50 (nM)
h-HSD-1 HEK
a
IC50 (nM)
Microsomal
b
stability
2
4
5
CH
CH
2
OH
OCH
4-Cl
4-Cl
9
110
25,000
>100,000
6
210
>100,000
45,000
53
670
19
100
2
2
2
2
CO H
H
N
26
N
2-Cl-4-F
11
550
10
1200
54
87
N
N
2
7
8
CH
3
SO
2
NHCO
NHCO
2-Cl
2-Cl
96
500
580
NT
28
1000
1200
NT
744
NT
94
NT
2
PhSO
2
a
Values are means of at least two experiments, (NT, not tested).
%
b
remaining after a 30 min incubation with mouse liver microsomes (NT, not tested).
Table 4. Ex vivo pharmacodynamic data for selected compounds
Compound
% inhibition in
liver 1 h/7 h/16 h
% inhibition in
fat 1 h/7 h/16 h
% inhibition in
brain 1 h/7 h/16 h
Dose (mg/kg)
7
81/76/35
99/93/77
45/55/58
67/47/6
37/38/36
15/18/5
ND
ND
30
30
30
1
1
6
9
0/0/18
ND, not determined.
In an effort to improve overall profile of our com-
pounds, we replaced the primary amide group on C-5
of the adamantane with extended acid, acid mimetics,
and electron donating groups (Table 3). Compound 24
with the hydrogen donating hydroxymethyl group had
comparable potency to the primary amide, but lacked
metabolic stability. Compound 25 with a free carboxylic
acid group was potent but had poor cellular activity.
Acid mimetic groups like tetrazole and methylacylsulf-
onamide led to potent and metabolically stable com-
pounds (26 and 27, respectively) with the loss of the
selectivity over human HSD-2, while the phenylacylsulf-
onamide 28 showed a significant loss of HSD-1 activity.
These data indicate that compounds like 10 with a pri-
mary amide group have the best overall profile.
post-dose. Acids 7 and 16 exhibited moderate inhibition
in liver and fat after 7 h. Sulfonamide 19, with an acid
mimetic group, had an interesting profile. It showed
moderate inhibition in the liver but did not show signif-
icant inhibition in the fat or brain.
Compound 7 showed an excellent PK profile, which cor-
related its activity in ex vivo assay. Primary amide 10
had high clearance, short half-life, and low bioavailabil-
ity. When the primary amide group in 10 was replaced
with a secondary amide containing an acid mimetic
group (19), bioavailability increased leading to an im-
proved PK profile (Table 5, entry 3).
We have discovered adamantane ethers as potent and
selective inhibitors of human and mouse 11b-HSD-1.
Our SAR indicates that the primary amide group at
the C-5 of adamantane is optimal. We have introduced
secondary amides with large groups at C-5 of the ada-
mantane to provide potent and selective inhibitors of
human and mouse 11b-HSD-1. However, the resulting
compounds have lower metabolic stability or cellular
potency than the primary amides. We have been success-
ful in aquiring the crystal structure of amide 15 bound to
the active site of h-11b-HSD-1 enzyme, which will be
helpful in the design of future analogs with the improved
PK and PD profiles.
In order to identify compounds for efficacy studies,
selected compounds were advanced to ex vivo pharma-
codynamic and PK studies (Tables 4 and 5). In the ex vi-
vo pharmacodynamic assay, the compounds were
1
5,18
administered as a single oral dose to ob/ob mice.
Inhibition of 11b-HSD-1 in liver, fat, and brain tissues
was measured. We were looking for compounds with
strong inhibition in the liver and fat at 7 and 16 h
a
Table 5. Mouse PK data for selected compounds
Compound nAUC (lg h/mL) CLp (L/h/kg)
t1/2 (h) F (%)
7
1
1
5.8
1.2
5.7
0.9
4.2
0.9
3.9
0.3
3.8
100
20
Acknowledgments
0
9
44
We thank Dr. Larry Solomon, Dr. Karl Walter, and
Diane Bartley for cloning and expression of h-HSD-1
a
Calculated from 5 mg/kg IV and 10 mg/kg oral dosing.

J. R. Patel et al. / Bioorg. Med. Chem. Lett. 17 (2007) 750–755
755
constructs used in the crystallography experiments. We
thank Dr. Lan Gao and Mr. Steve Cepa for the LC/
MS measurement of cortisol in ex vivo activity assay.
Robin Shapiro, Brian Droz, Tom Fey, Victoria Kno-
urek-Segal, and Kelly Larson are thanked for their assis-
tance with the ex vivo experiments. Dr. Dan Plata is
acknowledged for process chemistry support.
11. (a) Olson, S.; Aster, S. D.; Brown, K.; Carbin, L.;
Graham, D. W.; Hermanowski-Vosatka, A.; LeGrand,
C. B.; Mundt, S. S.; Robbins, M. A.; Schaeffer, J. M.;
Slossberg, L. H. Bioorg. Med. Chem. Lett. 2005, 15, 4359;
(
b) Gu, X.; Dragovic, J.; Koo, G. C.; Koprac, S. L.;
LeGrand, C.; Mundt, S. S.; Shah, K.; Springer, M. S.;
Tan, E. Y.; Thieringer, R.; Hermanowski-Vosatka, A.
Bioorg. Med. Chem. Lett. 2005, 15, 5266.
1
1
2. Jaroskova, L.; Linders, J. T. M.; Van Der Veken, L. J. E.;
Willemsens, G. H. M.; Bischoff, F. P. PCT Int. Appl. WO
2006/024627, 2006.
3. Link, J. T.; Chen, Y.; Jae, H.; Patel, J. R.; Pliushchev, M.
A.; Rohde, J. J.; Shuai, Q.; Sorenson, B. K.; Winn, M.;
Wodka, D.; Yong, H.; Madar, D. J. US 2005/0277647.
References and notes
1
. (a) Wang, M. Curr. Opin. Invest. Drugs 2006, 7, 319; (b)
Stears, A. J.; Byrne, C. D. Diabetes Obes. Metab. 2001, 3,
1
29; (c) Grundy, S. M.; Brewer, H. B.; Cleeman, J. I.;
14. Deffieux, D.; Fabre, I.; Courseille, C.; Quideau, S. J. Org.
Chem. 2002, 67, 4458.
Smith, S. C., Jr.; Lenfant, C. Circulation 2004, 109, 433.
. Seckl, J. R.; Walker, B. R. Endocrinology 2001, 142, 1371.
. Tomlinson, J. W.; Stewart, P. M. Best Pract. Res. Clin.
Endocrinol. Metab. 2001, 15, 61.
. Holmes, M. C.; Kotelevtsev, Y.; Mullins, J. J.; Seckl, J. R.
Mol. Cell. Endocrinol. 2001, 171, 15.
2
3
15. (a) Patel, J. R.; Shuai, Q.; Link, J. T.; Rohde, J. R.;
Dinges, J.; Sorenson, B. K.; Winn, M.; Yong, H.; Yeh, V.
S. PCT Int. Appl. WO 2006/074244, 2006; (b) Rohde, J. J.;
Pliushchev, M. A.; Sorenson, B. K.; Wodka, D.; Shuai, Q.;
Wang, J.; Fung, S.; Monzon, K. M.; Chiou, W. J.; Pan, L.;
Deng, X.; Chovan, L. E.; Ramaiya, A.; Mullally, M.;
Henry, R. F.; Stolarik, D. F.; Imade, H. M.; Marsh, K. C.;
Beno, D. W. A.; Fey, T. A.; Droz, B. A.; McDowell, C.;
Brune, M. E.; Camp, H. S.; Sham, H. L.; Frevert, E. U.;
Jacobson, P. B.; Link, J. T. J. Med. Chem., accepted for
publication.
4
5
6
. Masuzaki, H.; Paterson, J.; Kenyon, C. J.; Mullins, J. J.;
Seckl, J. R.; Flier, J. S. Science 2001, 294, 2166.
. (a) Kotelevtsev, Y.; Holmes, M. C.; Burchell, A.; Houston,
P. M.; Schmoll, D.; Jamieson, P.; Best, R.; Brown, R.;
Edwards, C. R.; Seckl, J. R.; Mullins, J. J. Proc. Natl. Acad.
Sci. U.S.A. 1997, 94, 14924; (b) Yau, J. L.; Noble, J.;
Kenyon, C. J.; Hibberd, C.; Kotelevtsev, Y.; Mullins, J. J.;
Seckl, J. R. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 4716.
. Barf, T.; Vallgarda, J.; Emond, R.; Haggstrom, C.; Kurz,
Z.; Nygren, A.; Larwood, V.; Mosialou, E.; Axelsson, K.;
Olsson, R.; Engblom, L. J. Med. Chem. 2002, 45, 3813.
. Su, X.; VIcker, N.; Ganeshapillai, D.; Smith, A.; Purohit,
A.; Reed, M. J.; Potter, B. V. Mol. Cell. Endocrinol. 2005,
16. Recombinant protein was expressed as described in Ref.
17 and the protein was purified in the presence of
inhibitor 15. The protein-inhibitor complex was crystal-
lized by the vapor diffusion method using 2.0 M
ammonium sulfate, 0.1 M sodium citrate (pH 5.6), and
7
8
9
˚
0.2 M K/Na tartrate. X-ray data were collected to 3.1 A
resolution, and molecular replacement with refinement
revealed electron density for the cofactor NADP+ and
compound.
2
48, 214.
. Coppola, G. M.; Kukkola, P. J.; Stanton, J. L.; Neubert,
A. D.; Marcopulos, N.; Bilci, N. A.; Wang, H.; Tomaselli,
H. C.; Tan, J.; Aicher, T. D.; Knorr, D. C. J. Med. Chem.
17. Hosfield, D. J.; Wu, Yiqin; Skene, R. J.; Hilgers, M.;
Jennings, A.; Snell, G. P.; Aertgeerts, K. J. Biol. Chem.
2005, 280, 4639.
2
005, 48, 6696.
1
0. Xiang, J.; Ipek, M.; Suri, V.; Massefski, W.; Pan, N.; Ge,
Y.; Tam, M.; Xing, Y.; Tobin, J. F.; Xu, X.; Tam, S.
Bioorg. Med. Chem. Lett. 2005, 15, 2865.
18. Gao, L.; Chiou, W.; Cheng, X.; Camp, H.; Burns, D.;
Proceedings of the 54th ASMS Conference on Mass
Spectometry, Seattle, WA; May, 2006; Abstract MP072.