Discovery of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides as selective antagonists of the kappa opioid receptor. Part 1

Article abstract of DOI:10.1016/j.bmcl.2010.07.113

Initial high throughput screening efforts identified highly potent and selective kappa opioid receptor antagonist 3 (κ IC₅₀ = 77 nM; μ:κ and δ:κ IC₅₀ ratios >400) which lacked CNS exposure in vivo. Modification of this scaffold resulted in development of a series of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides showing potent and selectivity κ antagonism as well as good brain exposure. Analog 6c (κ IC₅₀ = 20 nM; μ:κ = 36, δ:κ = 415) was also shown to reverse κ-agonist induced rat diuresis in vivo.

Full text of DOI:10.1016/j.bmcl.2010.07.113

Bioorganic & Medicinal Chemistry Letters 20 (2010) 5847–5852
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides as selective
antagonists of the kappa opioid receptor. Part 1
*
Todd A. Brugel , Reed W. Smith, Michael Balestra, Christopher Becker, Thalia Daniels, Tiffany N. Hoerter,
Gerard M. Koether, Scott R. Throner, Laura M. Panko, James J. Folmer, Joseph Cacciola, Angela M. Hunter,
Ruifeng Liu, Philip D. Edwards, Dean G. Brown, John Gordon, Norman C. Ledonne, Mark Pietras,
Patricia Schroeder, Linda A. Sygowski, Lee T. Hirata, Anna Zacco, Matthew F. Peters
CNS Discovery Research, AstraZeneca Pharmaceuticals, 1800 Concord Pike, Wilmington, DE 19850, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Initial high throughput screening efforts identified highly potent and selective kappa opioid receptor
Received 18 June 2010
Revised 21 July 2010
Accepted 26 July 2010
Available online 30 July 2010
antagonist 3 (
tion of this scaffold resulted in development of a series of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides
showing potent and selectivity antagonism as well as good brain exposure. Analog 6c ( IC50 = 20 nM;
= 36, d: = 415) was also shown to reverse -agonist induced rat diuresis in vivo.
Ó 2010 Published by Elsevier Ltd.
j IC50 = 77 nM; l:j and d:j IC50 ratios >400) which lacked CNS exposure in vivo. Modifica-
j
j
l:j
j
j
Keywords:
Opioid receptor
Kappa
Antagonist
Depression
Major depressive disorder (MDD), or depression, is a debilitat-
ing disease which effects anywhere from 8% to 10% of the global
population.1 The first line of treatment for those diagnosed with
depression is often selective serotonin reuptake inhibitors (SSRIs)
such as fluoxetine and escitalopram; however, 60% of patients trea-
ted with these medications fail to achieve remission.2 Therefore,
new methods of treatment that work through alternative mecha-
nisms are of great interest to the medical and pharmaceutical
community.
j preferring antagonists that interacted in either an orthosteric or
allosteric manner. Initially, we identified a series of potent and
highly selective bis-amide alkoxypiperidines represented by com-
pound 3 (Fig. 2). Unfortunately, these compounds showed poor
in vitro permeability (MDCK-MDR1 PappA > B = <10 nm/s) resulting
in minimal brain exposure (data not shown).
Realizing that the high MW of these compounds (>500 Da) could
limit permeability, we investigated the effects of truncating this
scaffold in an attempt to identify the most critical pharmacophore
Kappa (j) opioid receptors belong to a family of G-protein cou-
pled receptors (GPCRs) which include mu (
l
), delta (d) and the opi-
oid-like receptor (ORL-1). Historically, interest in the opioids has
focused on agonists for analgesia. Recent and accumulating evi-
dence indicates that two
(Fig. 1), have anxiolytic and anti-depressant-like activity in ro-
dents.5 This role for
in modulating mood appears to be conserved
since
agonists have profound depressant activity in humans.6
j
antagonists: nor-BNI 13 and JDTic 24
j
j
As part of our strategy to develop new small molecule treatments
for depression, we initiated a program to identify selective and brain
penetrant
j antagonists. We initiated a multifaceted campaign to
screen our corporate compound collection using both novel virtual
screening methods as well as an array of biological assays to identify
* Corresponding author. Tel.: +1 302 885 5759; fax: +1 302 885 1806.
E-mail addresses: brugel.ta@gmail.com, todd.brugel@astrazeneca.com (T.A.
Brugel).
Figure 1. Selective kappa opioid antagonists nor-BNI 1 and JDTic 2 (in-house data).
0960-894X/$ - see front matter Ó 2010 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2010.07.113

5848
T. A. Brugel et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5847–5852
Scheme 1. Reagents and conditions: (a) NaH, 3-fluorobenzonitrile, THF, 0–50 °C,
73%; (b) (i) ACE-Cl, DCM, reflux; (ii) MeOH, reflux; (iii) Boc2O, THF/H2O (1:1),
NaHCO3 (s), rt, 74%; (c) satd HCl/dioxane, dioxane, rt, 93%; (d) RCHO, DCM,
NaBH(OAc)3, rt; (e) KOH, t-BuOH, 80 °C.
features. When the meta-piperidin-4-yloxybenzamide sub-unit 4
was tested, we observed near complete loss of
sured using a [35S]GTP
S binding assay. Upon replacing the N-cyclo-
propylmethyl substituent with a benzyl (5, Fig. 2), we regained a
significant amount of potency ( IC50 = 923 nM) while still main-
taining excellent selectivity versus and d ( and d IC50 >30 M).
Additional modification to include an 8-azabicyclo[3.2.1]octane
jantagonism as mea-
c
j
j
l
l
l
Figure 2. 4-Alkoxypiperidine derived kappa opioid antagonists.
core (6) provided further enhancement of
j
antagonism and selec-
Table 1
N-substitution opioid antagonist SAR for 3-oxo-meta-benzamide-8-azabicyclo-[3.2.1]-octanes 6a–6i
35S]GTP
c
S IC50 (nM)
hERG IC50
(l
M)
d
Compd
R
[
ja
lb
dc
6a
6b
286 20
10,681 1413
9359 2275
27,442 250
0.61
0.43
S
S
215
20
5
3
>30,000
6c
722 47
8306 1635
0.26
2.8
O
6d
386 22
10,854 2630
22,049 150
6e
6f
754 292
342 11
424 23
659 74
2145 195
4000 900
0.38
0.25
6g
6h
49
2
3
482 112
2648 40
10,914 2660
11,076 300
0.14
0.52
148
6i
620 356
17,554
>30,000
0.62
a
Kappa (
j
) antagonism was determined in a human [35S]GTP
c
S assay using Dynorphin A(1–13) as the agonist stimulus. IC50’s are reported as the mean SEM (n P 2) and
S assay using DAMGO as the agonist stimulus. IC50’s are reported as the mean SEM (n P 2) and without SEM
cS assay using SNC-80 as the agonist stimulus. IC50’s are reported as the mean SEM (n P 2) and without SEM
without SEM where n = 1.
b
Mu (
where n = 1.
l c
) antagonism was determined in a human [35S]GTP
c
Delta (d) antagonism was determined in a human [35S]GTP
where n = 1.
d
Inhibition of the human ether-a-go-go (hERG) voltage-gated ion-channel was determined using an IonWorks™ electrophysiology assay.9 IC50’s are reported as the mean
of n P 2 experiments.

T. A. Brugel et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5847–5852
5849
Table 2
N-substitution opioid antagonist SAR for 3-oxo-meta-benzamide-8-azabicyclo-[3.2.1]-octanes 6j–6t
Compd
R
[
35S]GTP
c
S IC50 (nM)
hERG IC50 (lM)
j
l
d
N
N
6j
241 103
7854 135
>24,727
1.5
3.5
6k
431 133
2894 1325
>21,889
>30,000
6l
3159 1735
19,001 900
1.9
N
CH3
6m
6n
12,589
NDa
NDa
>33
7.3
6691 255
>30,000
>30,000
6o
6p
204 70
1826 875
307 17
>30,000
4842
2.0
O
O
11
39
1
5
0.62
CH3SO2
6q
576 39
5389 590
6.6
N
N
6r
6s
524 54
3411 540
345 36
9432 3900
21,090 1950
253 21
>27,287
>33
>33
0.72
O
O
>30,000
N
6t
2668 275
N
H
a
ND = not determined.
tivity. In the discussion that follows, we describe the synthesis and
emerging SAR of analogs of 6, as well as highlight additional
in vitro and in vivo properties.
(d:j ratio = 415) opioid selectivity. A similar trend was seen with
5-methyl-2-furanyl derivative 6d. When attempting to extend
the aromatic component further from the basic nitrogen with
phenethyl analog 6e and phenylpropyl analog 6f, we saw moderate
Synthesis of 3-oxo-meta-benzamide-8-azabicyclo-[3.2.1]-oc-
tanes 6 commenced with SNAr addition of tropine 7 to 3-fluoroben-
zonitrile (Scheme 1). This was followed by demethylation using 1-
chloroethyl chloroformate (ACE-Cl) to give crude NH tropane 8
after methanol mediated deprotection of the intermediate carba-
mate. To facilitate separation of the demethylated product from
unreacted starting material, the crude material was treated with
Boc2O and the respective t-butyl carbamate was isolated via
column chromatography. Deprotection with HCl/dioxane fur-
nished pure 8. Reductive amination of 8 with various aldehydes,
followed by hydration of the nitrile to the primary benzamide pro-
vided N-substituted-azabicyclooctanes 6a–6r.7
j
antagonism, but significant reduction in l and d selectivity ra-
tios. The effect of different substitution patterns on the benzyl ring
system was investigated with tolylmethyl analogs 6g–6i.
Analog 6g containing a para-tolylmethyl N-substitution showed
the greatest
analog 6i was weakest. Conversely, the
the opposite trend with 6i showing greater selectivity (
tio = 28) compared to 6g ( ratio = 10).
Although good levels of antagonism and opioid selectivity
j
antagonist potency, while the ortho-tolylmethyl
selectivity followed
ra-
l/j
l:j
l:j
j
were achieved with this early set of analogs, we were aware of
the potent hERG inhibition observed with many of these deriva-
Final compounds were tested for their ability to inhibit agonist-
stimulated activation of G-proteins using a [35S]GTP
cS binding as-
say in HEK membranes containing each of the cloned human opi-
oid receptor subtypes.8 Table 1 displays the results for a set of
azabicyclooctanes containing various lipophilic aromatic N-substi-
tutions. In addition to benzyl analog 6a, unsubstituted 2-thiophene
6b showed nearly identical potency and opioid selectivity. When
the thiophene group was substituted with a methyl group at the
5-position (6c) we observed a 10-fold improvement in
j antago-
Scheme 2. Reagents and conditions: (a) (i) Ti(O-i-Pr)4, acetophenone, 75 °C, 6 h; (ii)
NaBH4, EtOH; (b) KOH, t-BuOH, 80 °C.
nism (IC50 = 20 nM) without any loss in ratio = 36) or d
l (l:j

5850
T. A. Brugel et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5847–5852
tives. Sub-micromolar hERG potencies were found for all but one of
these initial analogs (Table 1). In order to address this issue, we
synthesized additional analogs which contained less lipophilic aro-
matic and non-aromatic N-substitutions. A subset of these com-
pounds is highlighted in Table 2.
therefore, we became focused on identifying ways by which to re-
duce hERG inhibition without negatively effecting potential brain
exposure.
During one phase of our SAR exploration of the azabicyclooc-
tane nitrogen substitution, we looked at effects of branching at
Incorporation of a 4- or 3-pyridylmethyl group (6j and 6k,
respectively) was well tolerated and showed a modest improve-
ment in hERG selectivity. Conversely, the 2-pyridylmethyl deriva-
the a-position of the N-substituent. The synthesis of these deriva-
tives required reductive amination between intermediate 8 and a
ketone. This was done through initial formation of the iminium
ion using titanium isopropoxide, followed by in situ reduction with
sodium borohydride.10 Subsequent hydration of the nitrile using
tive 6l showed a 10-fold decrease in
j activity versus the parent
benzyl derivative 6a. While smaller alkyl substituents like methyl
(6m) and cyclopropylmethyl (6n) were weakly potent, the more
standard conditions furnished
a-methyl-branched analogs such
hydrophobic cyclohexylmethyl derivative 6o showed good
j
as 9a (Scheme 2).
antagonism with a slight reduction in hERG inhibition relative to
its aromatic counterparts. Analogs 6p and 6q represent attempts
to incorporate more hydrophilic substituents onto the benzyl ring.
Table 3 displays the in vitro results for a set of a-branched ana-
logs 9a–9g. Compared to their des-methyl counterparts 6a, 6c, and
6i, branched derivatives 9a–9c showed a 3.5, 18 and 1.3-fold loss
We found that benzodioxole 6p provided one of our more potent
antagonists. Selectivity versus and d was also high, but hERG
inhibition remained sub-micromolar. The selectivity between
and hERG was still higher (hERG: ratio = 56) than many of the
more hydrophobic aromatic examples like 6c (hERG: ratio = 13).
Even better results were seen with benzylmethylsulfone 6q which
showed potent antagonism (IC50 = 39 nM) as well as elevated
hERG selectivity (hERG: ratio = 169). Pyrazolomethyl derivative
6r lacked any significant hERG inhibition, although antagonism
j
in j potency, respectively; however, this was in concurrence with
l
a 9.8, 6.1 and 7.9-fold reduction in hERG inhibition, respectively.
This was accomplished while maintaining the P-gp efflux ratio be-
low 2 for these branched analogs. Tetralone derived compound 9d
which fused the branched substituent to the benzyl ring showed
j
j
j
even further degradation of
sub-micromolar hERG activity. Cyclohexyl derivative 9e showed
similar potency to 9a and showed a reduced hERG IC50 of 15 M.
j antagonism while maintaining
j
j
l
j
Unfortunately, we noticed an increase in the P-gp efflux ratio of
became more moderate. Finally, several acetyl amide analogs were
this compound to 9.5, which lessened further interest in this mod-
synthesized and tested. Tertiary amides such as 6s lacked hERG
ification. Finally, quaternary substitution at the a-position was ex-
activity, but also suffered from poor
j
antagonism. Potency at
plored with gem-dimethyl analog 9f and spirocyclopropane 9g
which were synthesized in part through a modified Robinson
tropanone synthesis.11 This change to an achiral substitution pat-
the receptor was recovered through incorporation of more
j
hydrophobic amide substitutions as in 6t. Unfortunately, this also
resulted in similar enhancement of the hERG potency.
tern resulted in near total loss of
We proceeded to study the profile of individual enantiomers of
various -methyl-branched analogs. Racemic -methyl-4-pyridyl-
methyl analog 9h showed only modest antagonism and hERG inhi-
j antagonism.
With our success in finding several N-substitutions that could
alleviate some of the safety concerns involving high hERG activity
arose another potential issue regarding CNS penetration. For in-
a
a
j
stance, pyrazole 6r which showed one of the better
proved to be a P-gp efflux substrate (Papp B > A/Papp A > B ratio = 15)
when tested in our in vitro MDCK-MDR1 permeability assay;
j
:hERG ratios,
bition (Table 4). Upon separation of 9h into its individual (R)-9i and
(S)-9j enantiomers by chiral supercritical fluid chromatography
(SFC), a trend appeared.12 The more potent enantiomer 9i also
Table 3
SAR for racemic and achiral
a-branched 3-oxo-meta-benzamide-8-azabicyclo-[3.2.1]-octanes analogs 9a–9g
Compd
R
[
35S]GTP
c
S IC50 (nM)
hERG IC50
(
lM)
Efflux ratioa
j
l
9a
9b
1003 46
355 65
19,837 3200
6.0
1.6
1.4
1.9
S
8504 1120
16,785 200
9c
846 13
4.9
1.1
9d
2193 195
1126 188
22,696 700
9410 3695
0.95
15
1.7
9.5
9e
9f
13,266 400
NDa
4.7
4.8
1.6
1.9
9g
24,234 2900
>30,000
a
Efflux is measured as a ratio of transport from apical to basolateral (A > B) versus basolateral to apical (B > A) directions using stably expressed human multidrug-resistant
(MDR1) P-glycoprotein (P-gp) expressed MDCK cells.

T. A. Brugel et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5847–5852
5851
Table 4
SAR for racemic and chiral
a
-branched 3-oxo-meta-benzamide-8-azabicyclo-[3.2.1]-octanes analogs 9h–9o
Compd
R
[
35S]GTP
c
S IC50 (nM)
hERG IC50
(lM)
Efflux ratio
j
l
9h
9i
1410 300
683 18
>30,000
3.7
13
1.4
1.9
1.1
N
N
N
>24,383
9j
20,502 3350
111 16
>30,000
1.8
S
9k
9l
2698 125
2.8
4.6
1.7
9.5
O
46
5
2
1046 125
1896 205
9m
9n
9o
130
3.0
13
1.6
1.9
3.3
N
Cl
307 82
90 11
22,931 4200
1944 105
N
Cl
3.3
N
showed a greater decrease in hERG inhibition relative to the race-
mate 9h. Based on this result, several additional enantiomer pairs
were separated. Data for the most potent enantiomers 9k–9o are
We followed up our in vitro evaluation of select compounds in
this series with in vivo pharmacokinetic and/or CNS exposure stud-
ies in the rat. As summarized in Table 6, when dosed intravenously,
analogs 6c and 6o showed high plasma clearance and moderate
volumes of distribution (VDss) resulting in the observed short
half-lives. CNS exposure was observed to be high for both analogs,
with measured brain/plasma concentration ratios ([Br]/[Pl]) near
two-fold. The poor bioavailability (% F) seen for these compounds
was consistent with the observed high in vitro first pass clearance,
as evidenced by the high Clint observed in rat liver microsomes.
presented in Table 4.13 In all cases, the selectivity between
j
and
hERG was greatly improved relative to that which was observed
with the racemates or with the various non- -branched analogs de-
scribed in Tables 1 and 2. Particularly noteworthy was meta-meth-
oxy- -methylbenzyl derivative 9l which showed potent
antagonism (IC50 = 46 nM) and a large hERG: ratio of 100. Addi-
tionally, selectivity versus was 23-fold and the P-gp efflux ratio <2.
A pharmacophore model for was developed in-house using
several known potent and selective
antagonists.14 N-5-Methyl-
a
a
j
j
l
j
j
thiophene analog 6c was aligned to this model in order to generate
a plausible binding orientation. Figure 3 represents the results of
an overlay of low energy conformations of 6c and nor-BNI 1 in
the pharmacophore model. The Asp138 and His293 residues com-
prise the conserved region of opioid receptors referred to as the
‘message’. The Glu297 residue has been termed part of the ‘address’
region of
subtypes.15 Analog 6c and 1 are proposed to make salt-bridge
interactions with the Asp138 and Glu297 residues of . nor-BNI
j, conveying selectivity for kappa over the other opioid
j
makes additional interactions with the receptor including the
His293 residue in this model, which may explain, in part, its greater
potency.
Table 5 summarizes the in vitro ADME profile for a set of diverse
j
antagonists. Overall, most analogs in this series proved to be
metabolically stable in human liver microsomes. Analogs 6c and
6o showed higher rat microsomal instability, while the pyridine
analog 9m proved to be more stable. Permeability (MDCK-MDR1
PappA > B) and P-gp efflux ratios were seen as very good for 6c
and 6o, while the -branched analog 9m showed moderate perme-
a
ability but with an increased P-gp efflux ratio compared to the
other two analogs. All three representatives showed high unbound
levels of compound as measures in rat plasma protein binding
(PPB).
Figure 3. Overlay of nor-BNI
pharmacophore model of the kappa opioid receptor binding site.
1 (green carbons) and 6c (black carbons) in

5852
T. A. Brugel et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5847–5852
Table 5
In vitro DMPK properties for azabicyclo[3.2.1]octane derivatives 6c, 6o and 9m
a
a
Compd
j
IC50 (nM)
hCLint
rCLint
Papp A > Bb
Efflux ratioc
Rat PPB (% free)d
6c
6o
9m
20
204
130
31
<4
<4
379
196
14
130
83
91
1.4
2.6
4.0
50
46
81
a
Human and rat liver microsomal intrinsic clearance (hCLint) was measured as
Papp A > B is the rate (nm/s) of transport in the apical to basolateral (A > B) direction as measured across the MDR1-MDCK cell monolayer stably expressing the human
l
l/min/mg protein according to the standard liver microsomal stability assay protocol.
b
multidrug-resistant (MDR1) protein, P-glycoprotein.
c
See footnote a from Table 3 for efflux assay description.
Rat plasma protein binding (PPB) was determined as percent free (% free) compound available after incubation in male Sprague-Dawley rat plasma.
d
Table 6
Supplementary data
In vivo rat pharmacokinetic profile for azabicyclo[3.2.1]octane derivatives 6c and 6o
CLa (ml/min/kg)
t
(h)
VDss (L/kg)
[Br]/[Pl]a
% Fb
a
a
An experimental procedure detailing the preparation of 6c via
Compd
½
the route outlined in Scheme 1, as well as details pertaining to
6c
6o
113
184
1.0
1.0
5.1
9.5
1.7
1.8
4
5
the opioid [35S]GTP
cS assay, VDC studies, pharmacophore model-
ing and the rat diuresis in vivo model. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.bmcl.2010.07.113.
a
Plasma clearances (CL), half-lives (t ), volume of distributions (VDss
)
and
½
brain:plasma concentration ratios ([Br]/[Pl]) were measured after
a 2 lmol/kg
intravenous (iv) infusion dose in Sprague-Dawley rats.
b
Percent bioavailability (% F) was measured using the above iv data along with
mol/kg (6c) or 6 mol/kg (6o) oral (PO) dose in Sprague-Dawley rats.
data from a 2
l
l
References and notes
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Finally, the
possess moderate brain exposure (total brain/plasma ratio = 0.36
measured 2 h after a 5 mol/kg iv infusion dose). This result was
in agreement with the borderline permeability and P-gp efflux val-
ues observed in vitro.
a-branched methylpyridine analog 9m was found to
l
For
hibitive side effects is diuresis. Endogenous
to tonically regulate urine output since resting urine flow is not sig-
nificantly altered by antagonists (unpublished in-house results).
j
agonists that cross the blood–brain barrier, one of the pro-
j
agonists do not appear
j
Antagonists do, however, reverse agonist-induced diuresis in ro-
dents and this paradigm serves as a useful pharmacodynamic model
for evaluating in vivo effects that are CNS-mediated.16 Specifically,
6. Carlezon, W. A., Jr.; Beguin, C.; DiNieri, J. A.; Baumann, M. H.; Richards, M. R.;
Todtenkopf, M. S.; Rothman, R. B.; Ma, Z.; Lee, D. Y.; Cohen, B. M. J. Pharmacol.
Exp. Ther. 2006, 316, 440.
7. All new analogs were synthesized in >95% purity as determined by 1H NMR and
LCMS analysis.
j-selective agonist U50488 (2.5 mg/kg SC dose) induced diuresis
was dose dependently reversed with
j antagonist 6c (ID50 = 6 l-
8. Measured
[
35S]GTP
c
S
EC50’s for
j
and
M.
l functional agonism for select
mol/kg, p <0.01) as compared to administration of U50488 alone.17
compounds in this report were all >30
l
In summary, our lead generation efforts have identified a new
9. Schroeder, K.; Neagle, B.; Trezise, D. J.; Worley, J. J. Biomol. Screening 2003, 8, 50.
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class of low molecular weight (<400 Da)
an 8-azabicyclo[3.2.1]octan-3-yloxy-benzamide structure which
show excellent in vitro potency and selectivity versus and d opi-
j antagonists based on
l
12. Absolute configurations of 9i, 9j and 9l were determined using vibrational
circular dichroism (VCD). For a review of VCD see: Nodie, L. A.; Dukor, R. K. In
Applications of Vibrational Spectroscopy in Pharmaceutical Research and
Development; Pivonka, D. E., Chalmers, J. M., Griffiths, P. R., Eds.; John Wiley:
Chichester, 2007; pp 129–154.
oid receptors. Initial concerns with significant hERG inhibition and
high in vitro P-gp efflux were mitigated through modification of
the pendant N-substitution. Several analogs, including 6c and 6o,
showed good overall pharmacokinetic profiles. Methylthiophene
13. Absolute configuration assignments based on GTPcS data in conjunction with
analog 6c also displayed in vivo activity in reversing
j agonist
VCD results for 9i, 9j and 9l.
stimulated diuresis in rats.
14. See the Supplementary data section for
pharmacophore model.
a method description for the j
15. Metzger, T. G.; Paterlini, M. G.; Portoghese, P. S.; Ferguson, D. M. Neurochem.
Res. 1996, 21, 1287.
Acknowledgements
16. Gottlieb, H. B.; Varner, K. J.; Kenigs, V. A.; Cabral, A. M.; Kapusta, D. R. J.
Pharmacol. Exp. Ther. 2005, 312, 678.
17. See the Supplementary data section for a detailed description of the diuresis
results for 6c. A companion manuscript describing efficacy in an anxiety/
depression-like animal model for 6c (termed MTAB) is in preparation (Peters,
M.F. et al.).
We thank Jennifer Van Anda, David Coomber, Frances McLaren
and Xiaomei Ye for purification support; James Hall for NMR sup-
port; Timothy Blake for assistance with LCMS analysis; and Don
Pivonka for VCD studies.