Phenylcyclobutyl triazoles as selective inhibitors of 11β-hydroxysteroid dehydrogenase type I

Article abstract of DOI:10.1016/j.bmcl.2008.04.014

3-(Phenylcyclobutyl)-1,2,4-triazoles were identified as selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). These were active both in vitro and in an in vivo mouse pharmacodynamic (PD) model. Fluorine substitution of the cyclobutan

Full text of DOI:10.1016/j.bmcl.2008.04.014

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 3412–3416
Phenylcyclobutyl triazoles as selective inhibitors
of 11b-hydroxysteroid dehydrogenase type I
Yuping Zhu,a,* Steven H. Olson,a Donald Graham,a Gool Patel,a
Anne Hermanowski-Vosatka,b Steven Mundt,b Kashmira Shah,b Marty Springer,b
Rolf Thieringer,b Samuel Wright,b Jianying Xiao,b Hratch Zokian,b
Jasminka Dragovicc and James M. Balkoveca
aDepartment of Medicinal Chemistry, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA
bDepartment of Cardiovascular Disease, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA
cDepartment of Preclinical DMPK, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA
Received 30 January 2008; revised 28 March 2008; accepted 7 April 2008
Available online 10 April 2008
Abstract—3-(Phenylcyclobutyl)-1,2,4-triazoles were identified as selective inhibitors of 11b-hydroxysteroid dehydrogenase type 1
(11b-HSD1). These were active both in vitro and in an in vivo mouse pharmacodynamic (PD) model. Fluorine substitution of
the cyclobutane ring improved the pharmacokinetic profile significantly. The synthesis and structure–activity relationships are
presented.
Ó 2008 Elsevier Ltd. All rights reserved.
11b-Hydroxysteroid dehydrogenase enzymes (11b-
HSD) interconvert cortisol and cortisone in man, and
corticosterone and 11-dehydrocorticosterone in rodents.
The type I isoform (11b-HSD1), which is located in the
membranes of the endoplasmic reticulum, converts 11-
keto steroid into active glucocorticoids in the presence
of NADPH.1 The type II isoform (11b-HSD2) utilizes
NAD2 to convert glucocorticoids to 11-keto compounds
which have low affinity for glucocorticoid and mineral-
Scheme 1. Enzymatic interconversion of cortisone and cortisol.
ocorticoid receptors3 (Scheme 1).
in sodium retention, hypokalemia and hypertension.6,7
Glucocorticoids are important regulators of glucose and
lipid homeostasis, acting largely via intracellular gluco-
The discovery and development of selective 11b-HSD1
corticoid receptors in the liver, adipose tissue, and mus-
inhibitors is an important area of academic and pharma-
cle. Glucocorticoid excess, epitomized by Cushing’s
syndrome in humans, leads to insulin resistance/type 2
ceutical research.8
diabetes, dyslipidemia, and a redistribution of fat to vis-
ceral depots associated with increased cardiovascular
Previously, we identified adamantyl triazole 1a as a po-
tent and selective inhibitor of human and mouse 11b-
HSD1 by high-throughput screening. It was determined
to have an IC50 versus human 11b-HSD1 of 7.8 nM
(98 nM against the mouse enzyme) using a SPA-based
assay.9 In a human 11b-HSD2 counterscreen, the com-
pound had an IC50 of >3000 nM (>10,000 nM against
the mouse). A pharmacodynamic (PD) mouse model
of 11b-HSD1 inhibition was developed to measure the
in vivo activity of the inhibitors. In this model, a test
risk.4,5 Therefore, selective inhibition of the 11b-HSD1
enzyme may lead to an effective treatment for metabolic
syndrome. The selectivity over 11b-HSD2 is very impor-
tant since the inhibition of 11b-HSD2 is known to result
Keywords: 11b-HSD1; Phenylcyclobutyl triazole; Metabolic syndrome.
*
Corresponding author. Tel.: +1 732 594 0017; fax: +1 732 594
3007; e-mail: yuping_zhu@merck.com
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.04.014

Y. Zhu et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3412–3416
3413
compound or vehicle is administered orally (typically at
10 mg/kg) and after a predetermined time interval, [3H]-
cortisone is injected intravenously via the tail vein. After
2 min, blood is collected by cardiac puncture. Steroids
are then extracted from the serum and analyzed by
HPLC. The relative levels of [3H]-cortisone and [3H]-
cortisol are measured, and the percent inhibition of
conversion of 11-ketosteroid to 11-hydroxysteroid is
calculated.9 In the PD assay, 1a showed 59% inhibition
at 1 h and 17% inhibition at 4 h.
Scheme 2. Synthesis of phenylcyclobutyl triazoles.
has previously been described (Scheme 2).10 In the phen-
ylcyclohexyl series, substitution on phenyl did not im-
prove in vivo activity as desired. However, we found
that reducing the ring size resulted in the improvement
of both in vitro and in vivo activity (Table 1). Going
from cyclohexane to cyclopentane, the in vitro activity
improved about tenfold (2k vs 2d or 2g vs 2b in Table
1). From cyclopentane to cyclobutane, a further
improvement in in vitro and in vivo activity was
achieved (2l–2u). The four-membered ring size was opti-
mal for mouse since the cyclopropyl analogs 2v–2y re-
sulted in a loss of in vitro activity against the mouse
enzyme. A number of analogs with phenyl substituents
were prepared and evaluated. The para-chloro analog
in the cyclobutyl series (2p) possessed the best overall
activity as measured in the in vitro and pharmacody-
namic assays. This compound was further optimized
as described below.
We have also described the SAR on the right-hand side
of 1a and the superior 11b-HSD1 inhibitory activity of
the corresponding eight-membered ring analog 1b. The
adamantyl group was identified as a metabolic liability
and therefore, we sought to replace it with a more inert
left-hand fragment. Phenyl cyclohexane is a bulky
hydrophobic group similar to adamantane and not sur-
prisingly, compound 2a was a potent and selective inhib-
itor of 11b-HSD1 in our in vitro assays. A series of 1-
phenyl-1-triazolylcycloalkane analogs based on 2a were
prepared from the corresponding acylhydrazides and the
eight-membered imino ether in a one pot reaction that
Table 1. SAR of substituted phenylcycloalkyl triazoles
Compound
Ring size
R =
11b-HSD1 IC50 (nM)
11b-HSD2 IC50 (nM)
Mouse pharmacodynamic assaya
n =
Human
Mouse
Human
Mouse
1 h
4 h
2a
2b
2c
2d
6
6
6
6
H
13
27
32
15
100
494
454
374
1037
1174
613
>4000
>4000
>4000
>4000
25
—
—
—
0
—
—
—
b
p-F
p-Cl
p-Me
216
2e
2f
2g
2h
2i
5
5
5
5
5
5
5
H
o-F
2
1
12
27
18
41
61
57
25
1035
1270
>4000
NT
>4000
>4000
>4000
NT
73
57
58
—
3
37
18
30
—
21
22
3
p-F
8
p-Cl
m-OH
m-Me
p-Me
2
43
10
2
>4000
1961
503
>4000
>4000
>4000
2j
2k
20
35
2l
4
4
4
4
4
4
4
4
4
4
H
o-F
1
1
2
3
1
1
2
2
5
2
8
16
4000
<4000c
4000
>4000
>4000
>4000
>4000
>4000
>4000
>4000
>4000
>4000
>4000
88
90
87
68
91
23
17
48
—
—
72
53
68
55
77
21
22
28
—
—
2m
2n
2o
2p
2q
2r
2s
2t
m-F
p-F
19
37
>4000
>4000
3318
p-Cl
o-Me
m-Me
p-Me
o-CF3
p-CF3
14
78
52
19
>4000
2006
355
115
>4000
>4000
2u
2v
3
3
3
3
H
8
2
1
2
172
230
332
199
>4000
>4000
>4000
1964
>4000
>4000
>4000
>4000
63
—
45
—
2w
2x
2y
p-Cl
p-Me
o,p-di-
Cl
—
—
a % Inhibition of the conversion of [3H]-cortisone to [3H]-cortisol after a single oral dose of compound at 10 mg/kg.
b Not tested.
c 60% inhibition at 4 lM.

3414
Y. Zhu et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3412–3416
Table 2. SAR of small group substitutions of 3-phenylcyclobutyl-4,5-dicyclopropyl-1,2,4-triazoles
Compound
R3 =
11b-HSD1 IC50 (nM)a
Mouse pharmacodynamic assayb
Human
Mouse
1 h
4 h
5a
5b
5c
anti-F
syn-F
F,F
5
22
35
16
38
92
—
—
91
—
—
c
107
a The human and mouse 11b-HSD2 IC50s were >4000 nM for all the compounds.
b % Inhibition of the conversion of [3H]-cortisone to [3H]-cortisol after oral dosing with compound at 10 mg/kg.
c Not tested.
Previous SAR studies on the right-hand side of triazole
1a demonstrated that replacing the ring with acyclic
forms such as 4-methyl-5-phenyl- or 4,5-dicyclopropyl-
1,2,4-triazole improved in vivo activity significantly.10,11
In the mouse pharmacodynamic assay, compound 3
showed 74% inhibition 4 h after an oral dose of
10 mpk while 1b showed only 24% inhibition. Therefore,
a series of phenylcyclobutyl triazole analogs possessing
two cyclopropyl substituents were prepared. Improved
in vitro and in vivo activity was observed by replacing
the eight-membered ring with two cyclopropyl
substituents in the phenylcyclobutyl series (Table 2).
The synthesis of phenyl cyclobutyl–dicyclopropyl
triazoles was similar to the adamantyl triazoles
(Scheme 3).
Scheme 4. Briefly, the hydroxycyclobutane fragment was
prepared by reaction of the lithium anion of commer-
cially available (4-chlorophenyl)acetonitrile with epi-
chlorohydrin followed by the regeneration of the anion
with methyl magnesium iodide. The resultant syn- and
anti-hydroxy isomers (syn:anti ꢀ 1:3.3) were separated
through their benzoyl derivatives. DAST was used to
convert the hydroxyl-cyclobutane to the corresponding
fluoro-cyclobutane with an inversion of configuration.
The fluoro-cyclobutane nitrile was then reduced to the
aldehyde which was oxidized to carboxylic acid,12 which
was further converted to the corresponding methyl ester
and hydrazide. The hydrazide was reacted with the in
situ generated imino ether of cyclopropyl cyclopropa-
mide to give the desired triazoles as described previ-
ously.10 The di-fluoro analog 5c was prepared from
the ketone derivative of hydroxyl triazoles 5a or 5b using
DAST.
Despite the excellent in vitro and in vivo activity that
was observed in this series, pharmacokinetic measure-
ments in mice showed high plasma clearance rates. In li-
ver microsome studies, it was determined that the
hydroxylation of the cyclobutane was a significant pro-
cess. In order to improve the pharmacokinetic profile,
we sought to block this metabolic site. Fluoro-cyclobu-
tane derivatives of 4b, 4c, and 4d were prepared. The flu-
oro derivative of 4b, where the fluorine atom was anti-
to the triazole (5a), was superior to the other three ana-
logs (data not shown). The syn- and difluoro analogs 5b
and 5c were less potent inhibitors of 11b-HSD1 than 5a
(see Table 3). The preparation of the anti-fluoro-deriva-
tives of 4b, 4c and 4d is similar to that shown for 5a in
Regarding the pharmacokinetic properties of the fluoro-
versus non-fluoro-analogs, a comparison of compounds
4b and 5a shows comparable in vitro activity but better
PD activity for 5a. This compound had much higher
plasma concentrations than the non-fluoro analog when
dosed at 10 mg/kg (Fig. 1). More importantly, this com-
pound had an excellent pharmacokinetic profile includ-
ing low clearance with improved half life and oral
bioavailability. Compound 5a was selected for more
extensive biological evaluation and will be the subject
of a future communication (Table 4).
Scheme 3. Synthesis of phenylcyclobutyl-dicyclopropyl triazoles.

Y. Zhu et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3412–3416
3415
Table 3. SAR of substitutions on cyclobutane of 3-phenylcyclobutyl-4,5-dicyclopropyl-1,2,4-triazoles
Compound
R3 =
11b-HSD1 IC50 (nM)a
Mouse pharmacodynamic assayb
Human
Mouse
1 h
4 h
5a
5b
5c
anti-F
syn-F
F,F
5
22
35
16
38
92
—
91
—
—
c
107
—
a The human and mouse 11b-HSD2 IC50s were >4000 nM for all the compounds.
b % Inhibition of the conversion of [3H]-cortisone to [3H]-cortisol after oral dosing with compound at 10 mg/kg.
c Not tested.
Scheme 4. Stereoselective Synthesis of 5a.
Table 4. Pharmacokinetic parameters for 4b and 5a in C57B6 mice
Compound
IV nAUC0!24 h (lM h/mg/kg)
Clp (mL/min/kg)
t1/2 (h)
Oral nAUC0!24 h (lM h/mg/kg)
Foral (%)
4b
5a
0.70
4.68
81
10.7
0.3
1.5
0.19
5.44
27
ꢁ100
In conclusion, a novel class of potent and selective inhib-
itors of mouse and human 11b-HSD1 has been identi-
fied. These analogs showed potent in vivo 11b-HSD1
activity in a mouse pharmacodynamic model. It was
found that fluoro-substitution on the cyclobutyl group
improved the pharmacokinetic profile dramatically
while maintaining excellent in vitro activity. Compound
5a was selected for more extensive biological evaluation.

3416
Y. Zhu et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3412–3416
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0.1
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Time (hr)
Figure 1. Plasma exposure in mice of non-fluoro analog 4b and fluoro
analog 5a.
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