Synthesis and biological evaluation of heterocycle containing adamantane 11β-HSD1 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2006.07.055

A series of metabolically stable adamantane amide 11β-HSD1 inhibitors have been synthesized and biologically evaluated. These compounds exhibit excellent HSD1 potency and HSD2 selectivity and good pharmacokinetic and pharmacodynamic profiles.

Full text of DOI:10.1016/j.bmcl.2006.07.055

Bioorganic & Medicinal Chemistry Letters 16 (2006) 5414–5419
Synthesis and biological evaluation of heterocycle containing
adamantane 11b-HSD1 inhibitors
Vince S. C. Yeh,* Jyoti R. Patel,* Hong Yong, Ravi Kurukulasuriya, Steven Fung,
Katina Monzon, William Chiou, Jiahong Wang, Deanne Stolarik, Hovis Imade,
David Beno, Michael Brune, Peer Jacobson, Hing Sham and J. T. Link
Metabolic Disease Research, Abbott Laboratories, 100 Abbott Park Road, AP-10,304B, Abbott Park, IL 60064, USA
Received 30 May 2006; revised 15 July 2006; accepted 17 July 2006
Available online 8 August 2006
Abstract—A series of metabolically stable adamantane amide 11b-HSD1 inhibitors have been synthesized and biologically evaluat-
ed. These compounds exhibit excellent HSD1 potency and HSD2 selectivity and good pharmacokinetic and pharmacodynamic
profiles.
Ó 2006 Elsevier Ltd. All rights reserved.
Cl
11b-Hydroxysteroid dehydrogenase type 1 (11b-HSD1)
has attracted significant attention from the pharmaceu-
tical research community as a target for the treatment of
metabolic syndrome.1 This endoplasmic reticulum-asso-
H
N
O
O
O
H N
2
1
ciated enzyme converts the glucocorticoid receptor (GR)
inactive cortisone (dehydrocorticosterone in rodents)
into the GR active hormone cortisol (corticosterone in
rodents). In the liver, cortisol stimulates gluconeogenesis
through upregulation of enzymes such as phosphoenol-
pyruvate carboxykinase and glucose 6-phosphatase, and
in adipose tissue, cortisol promotes adipogenesis and
lipolysis.2 A related enzyme, 11b-HSD2, catalyzes the
reverse reaction which in tissues like kidney protects
the mineralocorticoid receptor from activation by corti-
sol.3 The current hypothesis is that a small molecule
therapeutic that selectively targets 11b-HSD1 can be a
viable strategy for the treatment of metabolic syndrome.
mouse PK:
Clp: 4.2 L/h/Kg
F: 20%
in vitro profiles:
h-HSD1
h-HSD2
IC : 32 nM
50
IC : > 100 uM
50
m-HSD1 IC : 71 nM
50
m-HSD2 IC : 40 uM
50
HEK HSD1 IC : 22 nM
50
Figure 1. Adamantane amide 11b-HSD inhibitor.
as determined by in vitro mouse liver microsomal sta-
bility studies, and primary amide hydrolysis in mouse
serum. The primary carboxamide on the adamantane
contributes to its potent activity as well as the meta-
bolic stability of the adamantane head group. Easily
accessible secondary and tertiary adamantane carbox-
amide analogs were either not active or lacked accept-
able PK profiles. Moreover, analogs related to 1 that
contain non-polar aromatic phenoxy groups have lim-
ited metabolic stability.
We have identified adamantane amides exemplified by
14 from initial hit to lead work, which are potent
inhibitors of human and mouse 11b-HSD1 with selec-
tivity over 11b-HSD2 (Fig. 1). Although 1 has an
excellent in vitro activity against the targeted enzymes,
it has a poor pharmacokinetic (PK) profile in mice.
This is due to metabolism of the phenoxy side chain,
Our goal is to discover compounds that will provide
long enough coverage for BID dosing for in vivo efficacy
studies in rodents. Hence, desirable compounds should
have a PK profile with greater bioavailability and lower
clearance. We attempted to address these challenges via
Keywords: 11b-HSD1; Adamantane amide; Heterocycles; Metabolic
syndrome; Metabolic stability.
*
Corresponding authors. Fax: +1 847 938 1674; e-mail addresses:
vince.yeh@abbott.com; jyoti.patel@abbott.com
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.07.055

V. S. C. Yeh et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5414–5419
5415
two concerted approaches: (1) identify hydrolytically
stable carboxamide bioisosteres that maintain high
potency and selectivity; (2) prepare compounds contain-
ing more polar heteroaromatic side chains which exhibit
metabolic stability and improvements in PK profile. In
this paper, we report our initial results.
Cl
H
H
N
a
N
R'
O
O
O
O
O
MeO
HO
2
3
b
d
H
H
N
R'
N
R'
O
NC
O
O
H
4
5
Cl
c
R' =
O
H
N
R'
O
O
6
Scheme 1. Reagents and conditions: (a) KOTMS, THF, rt; (b) i—LiAlH4, THF, 0 °C; ii—Dess–Martin periodinane, CH2Cl2; (c) i—acetyleneMgBr,
THF, 0 °C; ii—Dess–Martin periodinane, CH2Cl2; (d) i—EDCI, HOBT, i-Pr2NEt, then NH3; ii—TFAA, Et3N, CH2Cl2, 0 °C.
H
N
H
R'
N
R'
HO
O
N
N
f
O
O
O
N
H2N
H
11
12
e
NC
H
N
R'
Cl
N
H
H2N
H2N
O
O
N
7
O
a, b, c, d
O
H
N
R
O
R'
N
N
N
8
N
H
3 = CO2H
4 = CHO
5 = CN
H
N
R'
O
O
O
N
H
9
6 =
H
N
R'
10
N
O
H
N
R'
g, h, or i for 13
j, k for 15
O
O
O
HO2C
N
13
H
N
R'
14
Cl
N
NH
N
H
N
R' =
R'
O
HO2C
15
Scheme 2. Reagents and conditions: (a) 3, 2-amino-malononitrile, EDCI, pyr, rt; (b) i—3, aminoguanidine, EDCI, Et3N, DMF, rt; ii—tol, 100 °C;
(c) 4, glyoxal, NH3, MeOH, rt; (d) 6, NH2OH, DBU, DMF, 80 °C; (e) 5, NH2OH, DBU, DMSO, 100 °C; (f) CDI, DBU, CH3CN, rt; (g) 4,
TOSMIC, KOtBu, DME, MeOH; (h) ZnBr2, NaN3, H2O, 150 °C; (i) 1 N HCl, reflux; (j) 4, Ph3P@CHCO2Me, CH2Cl2; (k) i—H2, Pd/C, MeOH;
ii—LiOH, MeOH/H2O.

5416
V. S. C. Yeh et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5414–5419
Ester 2 was converted into compounds 3–6 using stan-
dard functional group transformations (Scheme 1).
Compounds 3–6 served as starting materials for the syn-
theses of a number heterocycle bioisosteres of the pri-
mary amide.
27 (Table 2). The syntheses of these side chains are
depicted in Schemes 3 and 4.
The O-linked hetroaryl analogs were prepared by nucle-
ophilic aromatic substitution of a chloropyridine by hy-
droxy ester 16 followed by the attachment of
adamantane 214 and conversion to primary carboxam-
ide (Scheme 3). Pyridyl bromide 22 was further elaborat-
ed via copper (I) catalyzed C–N coupling6 to give 24–26.
Acid 3 was converted into amino oxazole 75 and amino
triazole 8 (see Scheme 2 and Table 1). Aldehyde 4 was
transformed into imidazole 9. Isoxazole 10 was derived
from alkynone 6. Addition of hydroxylamine to cyanide
5 gave hydroxyamidine 11, which was then converted
into 12. In addition, we also explored the possibility of
extending the polar group 1 or 2 carbons away from
the adamantane head group. The syntheses of homolo-
gated analogs utilized either TOSMIC or stabilized Wit-
tig reagents on aldehyde 4 (Scheme 2), followed by
tetrazole synthesis (14) or hydrolysis to give the corre-
sponding acids 13 and 15.
The C-linked analogs such as 28 were synthesized by a
palladium catalyzed coupling7 of silyl ketene acetal 19
with a pyridyl bromide such as 18 followed by acylation
with adamantane 21 and conversion to the correspond-
ing carboxamide by similar methods as those described
for 22 (Scheme 4). The amino substituents of 28 and
29 were attached by nucleophilic substitution reactions.
These compounds were tested against both human and
mouse 11b-HSD1 and 11b-HSD2 enzymes as well as a
cell based assay with 11b-HSD1 overexpressed in hu-
man embryonic kidney cells (HEK).8 In addition, meta-
bolic stability of these compounds was determined using
mouse liver microsomal incubation studies.
Modification of the side chain was achieved by replacing
the phenoxy group of 1 by a pyridyl group. The heteroa-
romatic group can either be linked through an oxygen
spacer, such as 22, or be directly attached to the quater-
nary carbon bearing the gem-dimethyl groups, such as
Table 1. In vitro inhibition and metabolic stability data for 6–14
Cl
H
N
O
R
O
a
IC50 (nM)
Compound
R
Microsomal stabilityb
(% remaining)
h-HSD1/h-HSD2
146/>100,000
m-HSD1/m-HSD2
h-HSD1 HEK
306
NC
N
7
205 / 50,000
25
H N
2
O
N N
8
9
35/55,000
10/11,000
105/15,000
39/100,000
53/>100,000
11/100,000
71/15,000
476
110
31
41
3
H2N
N
H
N
N
H
N O
10
11
30
64
HO
N
26/>100,000
124
H2N
O N
12
13
14
15
358/35,000
45/52,000
101/100,000
92/20,700
87/7,000
532
82
Not determined
O
N
H
HO C
94
79
78
2
N
N
N
41/>100,000
89/100,000
119
455
N
H
74/28,000
H2OC
a Values are means of two experiments.
b % remaining after a 30 min incubation with mouse liver microsome.

V. S. C. Yeh et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5414–5419
Table 2. In vitro inhibition and metabolic stability data for 22–29
5417
H
N
X
H2NOC
O
Microsomal stabilityb (% remaining)
a
IC50 (nM)
Compound
X
h-HSD1/h-HSD2
6/49,000
m-HSD1/m-HSD2
4/>100,000
h-HSD1 HEK*
18
O
N
22
23
87
90
Br
O
O
N
N
28/>100,000
36/>100,000
373
CN
N
24
25
26
27
28
29
44/>100,000
185/>100,000
5/>100,000
51/>100,000
519/>100,000
11/>100,000
65/15,000
444
>10,000
38
89
ND
83
O
O
O
N
N
N
NMe
N
N
N
14/>100,000
47/>100,000
29/>100,000
165
100
87
CN
N
N
N
59/>100,000
310/>100,000
169
O
246
83
N
H
ND, not determined as in Table 1.
a Values are means of two experiments.
b % remaining after a 30 min incubation with mouse liver microsomes.
O
O
a, b
OH
O
N
MeO
HO
TMSO
a
MeO
R
16
F
17
R = Br, CN
19
O
Br
N
HO
R
N
F
b
H
N
O
18
20
c, d
N
H NOC
2
O
22 R =Br ,
23 R = CN
H
N
c, d
N
H NOC
2
O
O
NR
2
F
H
N
e
O
N
H NOC
2
O
H
N
24-26
N
e
H NOC
2
NH
2
N
21 =
MeO C
O
2
28
Scheme 3. Reagents and conditions: (a) NaH, 5-bromo-2-fluoro-
pyridine, THF/DMPU rt; (b) KOTMS, THF, rt; (c) 17, 21, HATU,
i-Pr2NEt, CH2Cl2; (d) i—KOTMS, THF; ii—EDCI, HOBT, NH3,
CH2Cl2; (e) 22, morpholine, CuI, proline, K2CO3, DMSO, 120 °C.
Scheme 4. Reagents and conditions: (a) 19, ZnF2, Pd2(dba)3,
P(t-Bu)3HBF4, DMA, 120 °C; (b) KOTMS, THF, rt; (c) 20, 21,
HATU, i-Pr2NEt, CH2Cl2; (d) i—KOTMS, THF; ii—EDCI, HOBT,
NH3, CH2Cl2; (e) morpholine, i-Pr2NEt, i-PrOH 100 °C.

5418
V. S. C. Yeh et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5414–5419
Table 4. Mouse PK dataa
Data for compounds from the adamantane head group
modification are shown in Table 1. Polar heterocycles
such as 8 and 9 were found to be potent and selective
for the 11b-HSD1 enzymes. However, most of these
compounds generally showed a shift in potency in the
HEK assays. Currently, we do not fully understand
the cause for the differences in the magnitude of potency
shifts between compounds. Presumably, it is due to sub-
tle differences in ionization of these polar groups which
led to poorer cell penetration. The cellular assay was
used to give us rough estimates on the ability of these
compounds to inhibit 11b-HSD1 in vivo, therefore,
potency shifts up to 10-fold were considered acceptable
in this assay. A better predictor of in vivo performance
is the metabolic stability assay, unfortunately, heterocy-
cles 7–10 were rapidly metabolized in microsomal stabil-
ity screen. Hydroxyamidine 11 was a potent and
selective inhibitor which exhibited better metabolic sta-
bility than the above heterocyclic compounds. On the
other hand, the homologated analogs 13–15 performed
very well in all the in vitro assays, including remarkably
improved metabolic stability.
Compound nAUC (lg*h/mL) CLp (L/h/Kg) t1/2 (h) F (%)
11
13
14
15
1.35
46.7
3.4
4.6
0.2
1.2
0.8
0.4
2.0
2.3
2.6
61.6
96.1
39.7
86.3
11.4
a Calculated from 10 mg/kg iv and oral po dosing. Measured in
plasma.
(Table 4, entry 1). This observation might be attributed
to an active metabolite. The one carbon homologated
acid 13 displayed long-acting PD activity in fat tissue,
but shorter activity in the liver. The PK profile of 13 fea-
tures low clearance, long half-life, and excellent bio-
availability. Tetrazole 14 gives good inhibition of 11b-
HSD1 in both liver and fat tissues, and it is mostly
excluded from brain. The two carbon homologated acid
15 showed robust activity in fat, liver, and brain. Com-
pound 15 is also accompanied with excellent PK data.
Compound 22 showed moderate activity at 7 h (Table
3), but no activity in liver at 16 h. This might be due
to extensive primary amide hydrolysis to the corre-
sponding inactive acid at longer time points. In fat 22
shows higher activity than liver. All the compounds that
we have evaluated in PK studies showed significantly
improved bioavailability as compared to 1.
Table 2 shows the biological results of compounds with
polar heteroaromatic side chains. Several of these com-
pounds are potent with pyrazolyl analog 26 reaching
5 nM with excellent selectivity against HSD2. Many of
these compounds also possess good metabolic stability.
Similar to our earlier observation in Table 1, com-
pounds with fully basic groups at the side chain such
as 25 suffered poor cellular penetration as determined
by the HEK assay. In order to identify compounds suit-
able for in vivo efficacy studies in rodent models, select-
ed compounds from Tables 1 and 2 were further
examined in mouse ex vivo pharmacodynamic (PD)9
as well as PK studies and the results are summarized
in Tables 3 and 4. We were interested in compounds that
exhibit robust inhibition of 11b-HSD1 in liver and fat
tissues at extended time points (i.e., 7 and 16 h) post-
dose. We hypothesize that compounds with such charac-
teristics will allow sufficient coverage using a BID dosing
regiment. The inhibition of 11b-HSD1 in brain has been
implicated in enhancing memory and learning.10 There-
fore, inhibition of the target enzyme was also measured
in brain tissue to help us determine the ability of these
compounds to either enter or be excluded from the
brain.
In conclusion, we have identified a series of modifica-
tions to the 11b-HSD inhibitor 1 that resulted in im-
proved PD and PK profiles. Efforts are currently
underway to combine a favorable functional group at
the adamantane head group with a polar heterocycle
containing side chain that we have identified over the
course of this work into one molecule. We anticipate
that these hybrid molecules will have good combined
PK and PD profiles in addition to other desirable prop-
erties such as increased water solubility. The results
from this effort will be reported in due course.
References and notes
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Ren, N.; Robertson, N.; Schaeffer, J. M.; Shah, K.;
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Vosatka, A.; LeGrand, C. B.; Mundt, S. S.; Robbins, M.
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Thieringer, R.; Wright, S. D.; Balkovec, J. M. Bioorg.
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Koo, G. C.; Koprak, S. L.; LeGrand, C. B.; Mundt, S. S.;
Shah, K.; Springer, M. S.; Tan, E. Y.; Thieringer, R.;
Hermanowski-Vosatka, A.; Zokian, H. J.; Balkovec, J.
Hydroxyamidine 11 showed robust inhibition of
11b-HSD1 in liver, fat, and brain tissues through 16 h.
However, it showed rapid clearance and a short half-life
Table 3. Ex vivo pharmacodynamic dataa
Compound % inhibition in % inhibition in % inhibition in
liver 7 h/16 h
fat 7 h/16 h
brain 7 h/16 h
11
13
14
15
22
89/84
40/0
92/67
70/35
17/20
50/37
47/23
85/79
ND
62/37
99/93
57/0
11/9
67/18
ND
ND, not determined.
a See Ref. 9 for a description of the assay.

V. S. C. Yeh et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5414–5419
5419
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ed by adding the non-selective 11b-HSD-1 inhibitor 18b-
GA. The radioactive cortisol generated in the assay was
captured by a monoclonal anti-cortisol antibody and
SPA beads coated with anti-mouse antibodies. The plate
was read using a Microbeta Liquid Scintillation Counter
(Perkin-Elmer Life Sciences). The percent inhibition was
calculated relative to a non-inhibited control and plotted
against compound concentration to generate the IC50
results. HEK assays: cellular activity of the compounds
was evaluated in HEK293 cells which were stably
transfected with full-length human 11b- HSD-1 cDNA.
Cells were plated on poly-D lysine-coated plates (Becton–
Dickinson Biocoat 35-4461) in DMEM containing 10%
FBS, 300 lg/mL geneticin, 100 U/mL penicillin, 100 lg/
mL streptomycin, and 0.25 lg/mL Fungizone. The cells
were pretreated with compounds for 30 min, followed by
incubation with 1 lM of substrate (cortisone) in dPBS
buffer for 2 h at 37 °C in a 5% CO2 atmosphere. The cell
media were harvested and the cortisol concentration in
the media was determined by fluorescence polarization
immuno-assay (FPIA). A mixture of fluorescein-labeled
cortisol and monoclonal anti-cortisol antibody was added
to the well in the FPIA diluent buffer (Abbott Labora-
tories) to a final concentration 4 nM (cortisol) and 10 nM
(mAb). The resulting fluorescent signal was read using an
Analyst plate reader (LJL). The percent inhibition was
calculated relative to a non-inhibited control and plotted
against compound concentration to generate the IC50
results.
4. Patel, J. R.; Shuai, Q.; Link, J. T.; Rohde, J. J.; Dinges, J.;
Sorensen, B. K.; Winn, M.; Yong, H.; Yeh, V. S. World
Patent 074244, 2006, manuscript in preparation.
5. Freeman, F.; Chen, T.; van der Linden, J. B. Synthesis
1997, 861.
6. (a) Zhang, H.; Cai, Q.; Ma, D. J. Org. Chem. 2005, 70,
5164; (b) Yeh, V. S. C.; Wiedeman, P. E. Tetrahedron Lett.
2006, 47, 6011.
7. Liu, X.; Hartwig, J. F. J. Am. Chem. Soc. 2004, 126, 5182.
8. The in vitro 11b-HSD-1 enzymatic assays are similar to
the methods described in Ref.1a. Truncated human or
mouse 11b-HSD-1, lacking the first 24 amino acids, was
expressed in Escherichia coli using the pET28 expression
system and the crude lysates were used as the enzyme
9. Compounds were dissolved in 1% Tween 80 in 0.2%
hydroxypropyl methylcellulose and administered to DIO
mice as a single oral dose at 30 mpk. At 1, 7, and 16 h
post-dose, fresh tissues including liver, epididymal fat pad
(EFP), and brain were removed, immersed in PBS buffer,
and weighed (3 mice per data point were used). The total
volume of PBS buffer added was equivalent to approxi-
mately five times the mass of tissue. Tissues were minced
into 2–3 mm pieces and the substrate (cortisone) was
added to a final concentration of 10 lM. The tissues were
then incubated at 37 °C in a 5% CO2 atmosphere for
20 min for liver and three hours for brain and adipose
tissue. The cortisol concentration in the media was
determined by LC-MS detection. The percent inhibition
of 11b-HSD-1 activity was calculated relative to a vehicle
control treated group. Ex vivo 11b-HSD-1 assays in ob/ob
mice and other strains of rodents were conducted
similarly.
source. The reaction was carried out with
a total
substrate (cortisone) concentration of 175 nM which
contained 75 nM 3H-cortisone and 181 lM of the co-
factor NADPH in 50 mM Tris–HCl, at pH 7.2 with
1 mM EDTA. The final enzyme concentration was
0.015 mg/mL to keep the substrate consumption rate
below 25% at the end of the reaction. To ensure the
reaction proceeds in the reductase direction, a NADPH
regeneration system with 1 mM G-6-P and 1 U/mL G-6-
PDH was included in the reaction. After incubating at
room temperature for 30 min, the reaction was terminat-
10. Sandeep, T. C.; Yau, J. L.; MacLullich, A. M., et al. Proc.
Natl. Acad. Sci. U.S.A. 2004, 101, 6734.