Structure-Activity Relationships, Pharmacokinetics, and in Vivo Activity of CYP11B2 and CYP11B1 Inhibitors

Article abstract of DOI:10.1021/acs.jmedchem.5b00407

CYP11B2, the aldosterone synthase, and CYP11B1, the cortisol synthase, are two highly homologous enzymes implicated in a range of cardiovascular and metabolic diseases. We have previously reported the discovery of LCI699, a dual CYP11B2 and CYP11B1 inhibi

Full text of DOI:10.1021/acs.jmedchem.5b00407

Article
pubs.acs.org/jmc
Structure−Activity Relationships, Pharmacokinetics, and in Vivo
Activity of CYP11B2 and CYP11B1 Inhibitors
Julien P. N. Papillon,*,† Christopher M. Adams,† Qi-Ying Hu,† Changgang Lou,†,§ Alok K. Singh,†
Chun Zhang,† Jose Carvalho,† Srinivan Rajan,†,∞ Adam Amaral,† Michael E. Beil,‡ Fumin Fu,‡
Eric Gangl,†,∥ Chii-Whei Hu,‡ Arco Y. Jeng,‡,∞ Daniel LaSala,‡ Guiqing Liang,† Michael Logman,†,⊥
Wieslawa M. Maniara,†,∞ Dean F. Rigel,‡ Sherri A. Smith,†,# and Gary M. Ksander†,○
†Novartis Institutes for BioMedical Research, 250 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
‡Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, New Jersey 07936, United States
S
* Supporting Information
ABSTRACT: CYP11B2, the aldosterone synthase, and CYP11B1,
the cortisol synthase, are two highly homologous enzymes
implicated in a range of cardiovascular and metabolic diseases.
We have previously reported the discovery of LCI699, a dual
CYP11B2 and CYP11B1 inhibitor that has provided clinical
validation for the lowering of plasma aldosterone as a viable
approach to modulate blood pressure in humans, as well
normalization of urinary cortisol in Cushing’s disease patients. We
now report novel series of aldosterone synthase inhibitors with
single-digit nanomolar cellular potency and excellent physicochem-
ical properties. Structure−activity relationships and optimization of
their oral bioavailability are presented. An illustration of the impact
of the age of preclinical models on pharmacokinetic properties is
also highlighted. Similar biochemical potency was generally observed against CYP11B2 and CYP11B1, although emerging
structure−selectivity relationships were noted leading to more CYP11B1-selective analogs.
to contribute to resistant hypertension.7 The latter represents a
significant medical need; as much as 30% of the hypertensive
INTRODUCTION
■
Cytochrome P450s are a class of proteins that occupy a unique
place in the battles drug discovery scientists fight to bring safe
and effective small molecule therapeutics to patients. As greater
population may be resistant to treatment, with resulting higher
incidence of cardiovascular events.8 Elevated levels of plasma
aldosterone upon prolonged treatment with angiotensin-
than 75% of xenobiotics are metabolically cleared, with a major
proportion undergoing CYP450-mediated oxidation,1 designing
converting enzyme inhibitors or angiotensin-receptor blockers,
referred to as “aldosterone escape” or “aldosterone break-
compounds with low affinity and/or reactivity toward these
through”, have long been noted,9 and this may be a
heme-containing enzymes is of major concern to the medicinal
chemist.2 On the other hand, targeted inhibition of human
contributing factor to treatment resistance. Additionally,
extensive evidence exists that links aldosterone to proin-
cytochrome P450s for therapeutic purposes has historically
been the subject of less scrutiny.3 The efficacy of aromatase
flammatory states, cardiac and vascular fibrosis, and end-organ
failure, independent of blood pressure.10 Two decades ago, the
(CYP19) inhibitors such as letrozole and anastrozole as
poor prognosis for heart failure patients with elevated
adjuvant treatment of estrogen-receptor-positive breast cancers
aldosterone was recognized,11 and subsequently, blockade of
the mineralocorticoid receptor (MR) with spironolactone and
eplerenone was shown to have profound effects on mortality
and morbidity in patients with cardiac dysfunction.12 However,
those steroidal agents have limitations in terms of off-target
effects and on-target hyperkalemia, and their mechanism of
action does not lead to reduced aldosterone levels. This offers
one of several avenues for differentiation of aldosterone
synthase inhibitors (ASI) over MR antagonists, as many lines
is now well established.4 More recently, 17α-hydroxylase/
C17,20 lyase (CYP17A1) inhibitors have demonstrated their
utility, leading to the approval of abiraterone for the treatment
of castration-resistant prostate cancer.5 In this paper we
describe efforts targeting two other human steroidogenic
CYP450s CYP11B1 and CYP11B2. CYP11B1 converts
deoxycortisol to cortisol, while CYP11B2 transforms 11-
deoxycorticosterone to aldosterone. Chronic activation of the
renin−angiotensin−aldosterone system is central to the
pathophysiology of heart failure and hypertension. Elevated
serum aldosterone levels predispose subjects to the develop-
ment of hypertension,6 and high serum aldosterone is thought
Received: March 13, 2015
© XXXX American Chemical Society
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Table 1. Characteristics of Initial Racemic Lead Compounds 1−5
liver microsomes t1/2
IC50 (μM)
(min)
compd
A
B
H295-R aldosterone
CYP3A4
% inhibition (10 μM), CYP19
rat
human
1
2
3
4
5
S
CH2
CH2
O
0.007
0.007
0.073
0.079
0.055
0.17
0.11
81
59
30
77
3
<1.5
3
3
5
CH2
CH2
CH2
O
0.29
15
11
86
20
2
CH-(p-MeO-Ph)
<0.07
0.46
C(O)
315
of evidence suggest a pathological role of aldosterone via non-
MR mediated pathways.13 The study of the impact on the
aforementioned disease states of modulating aldosterone levels
(and those of its precursors) via CYP11B2 inhibition is
therefore of clear value. Although concomitant inhibition of
highly homologous CYP11B1 in the context of hypertensive
population is a potential safety concern, it is intriguing to note
that a recent analysis suggested that the predominant MR
agonist in the context of cardiomyocyte damage is cortisol.14
Our interest in this field was stimulated by the observation
that FAD286, the R-(+)-enantiomer of the racemic aromatase
inhibitor CGS016949A (fadrozole) was a potent inhibitor of
aldosterone synthase (CYP11B2).15 We subsequently showed
that chronic administration of FAD286 in rats led to a
reduction in cardiac inflammation and fibrosis and resulted in
slowing of the progression of heart failure following coronary
artery occlusion.16 Cardiac and renal protection, as well as a
reduction in several inflammatory markers, were demonstrated
with FAD286 in a study using a double-transgenic rat (dTG
rat) overexpressing human renin and angiotensinogen and
elevated angiotensin II and aldosterone levels.17 These and
subsequent studies18 suggested that pharmacological inhibition
of aldosterone synthase might be clinically useful, which led us,
and others,19−21 to engage in programs to discover novel
CYP11B2 inhibitors. Our initial forays led to the discovery of
LCI699, a potent dual inhibitor of CYP11B2 and CYP11B1.21
Studies with LCI699 confirmed and extended the findings that
ASI prevents development of cardiac and renal functional
abnormalities and prolonged survival of dTG rats, independent
of blood pressure.21b LCI699 has proven to be effective in
multiple cohorts of hypertensive patients.22 For instance, an 8-
week placebo-controlled dose−response study on patients with
essential hypertension reported a decrease in blood pressure
with a dose of 1 mg of LCI699 q.d., which had a
antihypertensive effect similar to that of 50 mg b.i.d.
eplerenone.22b This study also revealed that cortisol secretion
in response to adrenocorticotropic hormone (ACTH)
stimulation was blunted in 21% of patients. These findings
were confirmed in a separate ACTH stress test study,23
precluding exploration of high doses and determination of
optimal doses for blood pressure regulation with LCI699.
However, recognizing that options to normalize cortisol levels
in Cushing’s disease patients unwilling or unable to undergo
surgery are limited, we conducted a 10-week, 12 patients dose-
escalation study (4−100 mg/day), where LCI699 was shown to
normalize free urinary cortisol.24
The optimization efforts that led to the discovery of LCI699
were recently reported.21a As LCI699 illustrates, our initial
efforts toward bringing the first ASI to the clinic for human
proof-of-concept studies focused on imidazole series derived
from FAD286. Although the focus was primarily on
pharmacodynamics and selectivity over CYP19, it quickly
became apparent that achieving high oral bioavailability was a
significant challenge across all imidazole based series. The work
presented herein, which was conducted concurrently to the
progression of LCI699 to the clinic, describes our successful
attempts at identifying potent ASIs devoid of aromatase activity
and presents a general solution to the problem of achieving
high oral bioavailability. At the time this work was conducted,
the impact of modulating levels of mineralocorticoids, cortico-
steroids, and precursor steroids via inhibition of aldosterone
synthase in human was not known, and the relation between in
vitro selectivity and human pharmacology had not been
established. Moreover, data generated in our ACTH rat
model suggested that LCI699, despite low in vitro selectivity
for CYP11B2 over CYP11B1, may be selective in vivo, with
ED50 values 47-fold lower for aldosterone versus cortico-
sterone.21b Given this context, we did not set out to achieve
selectivity over CYP11B1 for the series described herein. We
did nonetheless test these compounds in a human recombinant
CYP11B1 assay and found some interesting trends toward
CYP11B1 selectivity, which we also report herein.
RESULTS AND DISCUSSION
■
Compounds 1−5 were identified from the Novartis compound
collection as potential starting points for lead optimization
because of their potent activity in our cellular aldosterone
secretion assay25 (Table 1). This class of racemic imidazole
carboxylates had previously been reported to be useful as
herbicides and antifungals by disrupting sterol biosynthesis
through inhibition of 14α-demethylase (P45014DM).26
As we embarked on this program, we focused on identifying
scaffolds devoid of aromatase activity, good selectivity over
CYP3A4 and with generally improved oral bioavailability. In
vitro−in vivo pharmacokinetic correlation analysis for 72
imidazole ASIs synthesized in-house prior to this work revealed
a clear relationship between rat liver microsome half-life and rat
oral bioavailability. Half-lives greater than 20 min were
necessary but not always sufficient to achieve oral bioavailability
greater than 30% (Figure 1). Hence, our initial investigations
focused on lactone 5, which was not the most potent ASI, but
had the best rat liver microsome half-life, and also displayed
greater selectivity against CYP19 (aromatase) and CYP3A4. It
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combination of both might explain the poor oral bioavailability
of ester 5E. With 12 in hand, we sought to better understand
how these lactones were metabolized.
Analysis of rat urine and plasma samples collected following
po dosing of 12 at 10 mg/kg in this model showed metabolites
resulting from transformation of the imidazole moiety only
(Figure 2). Consistent with this observation, we found that
better oral bioavailability was observed for compound 11, which
has no substitution on the imidazole ring, and also compound
14, where the difluoromethyl substitution would not be
expected to undergo rapid oxidative metabolism (Table 5).
Removing substitution on the imidazole ring to confer good
oral bioavailability proved to be a general solution to what had
been, in our experience, a vexing problem for ASIs up until then
(see Figure 1). Indeed compounds 27−29, where the lactone is
replaced by a different heterocycle, also showed excellent oral
bioavailability, in all cases superior to the corresponding analogs
with additional substitution on the imidazole ring (data not
shown). All the compounds described herein are weak bases
with high solubility and permeability (see Supporting
Information), and it is unlikely that these two parameters
significantly limit oral absorption. Metabolic clearance (first-
pass extraction) may then be the primary factor influencing oral
bioavailability, consistent with the observation that, for these
series of compounds, a microsomal half-life greater than 20 min
is largely predictive of good oral bioavailability.
As previously mentioned, the angiotensin II infusion
model18a using SD rats allowed us to establish PK−PD
relationships in the same experiment. The PD (plasma
aldosterone) data, expressed as time-weighted average
(TWA) for the 0−8 h period, are shown in Table 6. As
expected, given the good in vitro potency and favorable plasma
exposures, all compounds afforded robust lowering of
aldosterone secretion in vivo.
Despite the success with optimization of the lactones and
validation of our initial hypothesis, we did further evaluate lead
compounds 1−4,and in so doing came across an interesting
case of age-related metabolism. A curious in vitro−in vivo
metabolism correlation, distinct from the compounds described
so far, arose with compound 2E (eutomer of 2). Extremely low
in vivo clearance was measured for 2E (0.3 mL min−1 kg−1), in
sharp contrast with rapid clearance in rat liver microsomes (t1/2
= 2 min) and marginal oral bioavailability (0.2%). Again,
solubility (0.06 g/L, pH 6.8) and permeability (caco-2 A−B
33.10−6 cm/s) would not be expected to limit oral absorption.
Incubation of 2E with rat liver microsomes showed a major
metabolite M2 (34% surface area) after 5 min of incubation
(Figure 3), the mass of which was consistent with a single
hydroxylation.
Figure 1. Relationship between rat liver microsome half-life and rat
oral bioavailability for compounds prepared prior to selection of 5 as a
lead compound (bold lines indicates the 20 min and 30% mark for
half-life and bioavailability, respectively).
is intersting to note that for compounds 1−5, structure−
metabolic stability relationship followed a trend whereby
removing Csp3−H bonds in the bicyclic ring led to an increase
in stability in vitro. Resynthesis of 5 and chiral separation
revealed that only one of the two enantiomers, 5E, was a potent
CYP11B2 inhibitor, a finding that proved quite general across
the series. Exploration of the SAR for the imidazole side chain
is shown in Table 2.
A variety of functionalities at the 4-position of the imidazole
were tolerated and gave good on-target potency, with generally
only one of the two enantiomers displaying CYP11B2
inhibition.27 Substitution at C-2 or C-5 obliterated activity
(data not shown), consistent with putative binding of N-1 to
the heme iron. Excellent selectivity over CYP19 was observed
irrespective of the substitution, and good selectivity over
CYP3A4 was also generally observed. With the exception of
alkyl-substituted imidazole 12 and 13, all compounds appeared
to be more stable in human liver microsomes versus rat.
Replacement of the gem-dimethyl group with other alkyl
substituents (22−25) revealed a flat structure−activity relation-
ship, save for the tetrahydropyran (25), which afforded
improved metabolic stability, albeit at the expense of potency
(Table 3).
An angiotensin II infusion model18a using chronically
cannulated Sprague Dawley (SD) rats was used to establish
the PK−PD relationship for these compounds. Blood
samplings were conducted at 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8,
and 24 h time points following oral administration, and plasma
aldosterone and plasma compound concentrations were
measured. Pharmacokinetic parameters for various imidazole
substitution as in 5E (ester), 12 (ethyl), and 16 (alcohol) are
shown in Table 4. Consistent with our prior observations, the
low observed oral bioavailability of 12 was expected in view of
the poor microsomal stability. Breakdown of the correlation
between rat liver microsome clearance and oral bioavailability
was observed for ester 5E and alcohol 16. This is perhaps
expected in the case of 16, as hepatic microsomal clearance
grossly underpredict in vivo clearance, and liver microsomes
may not adequately model the metabolism that alcohols such as
16 undergo. However, the low bioavailability of 5E, which
exhibited low in vitro and in vivo clearance, was a bit more
surprising. Stability in the GI tract, intestinal clearance, or a
Ten micrograms of M2 could be isolated, an amount
1
sufficient to acquire a H NMR spectrum, which suggested
hydroxylation at the benzylic methylene. This metabolite was
synthesized, and the isomers were separated. Considering
hydroxylation occurs at the same position as the carbonyl in
compounds such as 5, we reasoned that M2 may be an active
metabolite. This proved to be the case; data for the most potent
isomer (30) are shown in Table 7 (the eutomer of the trans
analog was ∼4-fold less potent). With 30 in hand, which affords
a desirable in vivo PK profile with an oral bioavailability of 46%,
we did not seek to elucidate the sharp disconnect between the
extremely low in vivo clearance and low bioavailability of
compound 2E, reminiscent of that observed for structurally
related ester 5E. The good oral bioavailability of 30 was
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Table 2. Cellular Aldosterone Secretion, CYP3A4, Aromatase and Microsomal Stability Data of ASIs from a Lactone Series
a
b
Compounds are single enantiomers (>98% ee), unless otherwise stated. % inhibitory activity at 1 μM distomer is shown in parentheses.
c
d
e
Racemate. The eutomer from the other diastereomer (not shown) is 8-fold less potent in the cellular assay. Racemate data.
confirmed in a dose escalation study using water as vehicle,
albeit with AUC increasing in a less than dose-proportional
manner, i.e., AUClast(0−24 h) of 21, 56, and 90 μM·h at 3, 10,
and 30 mg/kg dose, respectively.
However, the disconnect between high predicted hepatic
clearance (RLM t1/2 = 4 min) and low in vivo clearance (7 mL
min−1 kg−1) as was observed with 2E remained, and we sought
to investigate this further. We considered the possibility of an
age specific metabolic event for 2E and 30, since the PK data
were generated from 10-months-old cannulated SD rats while
the rat liver microsomes were derived from the liver of 10-
weeks-old SD rats. Thus, we decided to run PK studies with 10-
weeks-old SD rats. What we found was a severe discrepancy
between the PK properties of compounds 2E and 30 in 10-
weeks-old versus 10-months-old SD rats (Table 8). Whereas
plasma clearance for 2E was determined to be 0.3 mL min−1
kg−1 in 10-months-old rats, the clearance in 10-weeks-old rats
was found to be 143 mL min−1 kg−1, which was indeed
consistent with clearance predicted from microsomal data but
obviously also indicative of extra-hepatic clearance. No
compound was detected in plasma after oral administration,
consistent with complete first-pass hepatic extraction. Com-
D
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Table 3. Modification of the gem-Dimethyl Group
a
b
Compounds are single enantiomers (>98% ee), unless otherwise stated. Racemate.
Table 4. Pharmacokinetic Data
in vivo rat PK dose (mg/kg): 1 (po), 0.3 (ia)
a
b
compd
H295-R aldosterone IC50 (μM)
rat liver microsomes t1/2 (min)
CL (mL min−1 kg−1
)
AUC(0−24 h) (nM·h) po
F (%)
5E
12
16
0.024
0.003
165
17
2
25
34
1024
257
3
8
0.004
163
342
19
a
b
All compounds are single enantiomers. Distomer data for 12 and 16 as shown in Table 2; the distomer of 5E shows 22% inhibition at 1 μM.
Figure 2. Mass chromatograms of rat urine, 30 min after a 10 mg/kg oral dose of 12.
pound 30, the hydroxylated analog of 2E that had been isolated
from liver microsomes incubates, showed much reduced
clearance compared to 2E (35 mL min−1 kg−1). Unfortunately
in the case of 10-weeks-old SD rats, 30 failed to offer significant
benefits over 2E in terms of oral bioavailability, with GI stability
or intestinal metabolism perhaps accounting for the very high
first-pass extraction.
As stated in the Introduction, achieving selectivity for
CYP11B2 over CYP11B1 was not a specific objective of this
program. However, these series of imidazole-containing
compounds were profiled in human recombinant CYP11B2
and CYP11B1 assays28 in order to determine their in vitro
selectivity and were found to have no meaningful selectivity for
CYP11B2 over CYP11B1. On the other hand, CYP11B1
selectivity was observed, and some SAR data suggest that
E
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Table 5. Pharmacokinetic Data
in vivo rat PK, dose (mg/kg): 1 (po), 0.3 (ia)
a
b
compd
H295-R aldosterone IC50 (μM)
rat liver microsomes t1/2 (min)
CL (mL min−1 kg−1
)
AUC(0−24 h) (nM·h) po
F (%)
14
11
26
27
28
29
0.001
0.027
0.010
0.010
0.005
>400
23
4
30
28
23
20
8
3446
1031
1479
2253
4040
5442
26
55
256
93
50
62
88
114
55
0.082
228
a
b
All compounds are single enantiomers. Distomer data for 14 and 11 as shown in Table 2; % inhibitory activity at 1 μM distomer of 26, 27, 28, and
29 are 0%, 23%, 42%, and 27%, respectively.
or the lactone for a methylene, as in 32, rebuilds some of the
potency against CYP11B2, with no effect on CYP11B1.
Potency on CYP11B2 can also be regained by adding
hydroxymethyl substitution to 31 to give 33. Interestingly, in
the case of analogs of 33, selectivity for CYP11B1 can be
increased with judicious choice of substitution on the indanone
ring (see 34 versus 35). Additional strategies for optimization
of CYP11B1 selectivity are suggested by compounds 37 and 36
(versus 38) and compound 39 (versus 11). Although the
selectivities observed here are fairly modest, they suggest that a
focused effort on optimization of CYP11B1 selectivity in these
series could lead to highly selective CYP11B1 inhibitors,29
which are expected to be useful for the treatment of Cushing’s
disease.24
Table 6. PK/PD Relationships
TWA0−8h
H295-R
rat
compd
concn
(nM)
TWA0−8h % reduction
of plasma aldosterone
concentration
aldosterone recCYP11B2
a
compd
IC50 (μM)
IC50 (μM)
b
5E
0.024
0.003
0.004
0.001
0.027
0.010
0.010
0.005
0.082
nd
110
28
76
87
84
75
45
64
68
77
75
c
12
nd
16
14
11
26
27
28
0.003
nd
22
255
129
149
281
429
540
nd
0.002
nd
0.001
nd
d
29
a
All compounds were dosed po at 1 mg/kg using 1.5 equiv of HCl/
water as a vehicle except for those compounds where the following
CHEMISTRY
■
b
c
vehicles were used. Vehicle: cornstarch. Vehicle: 1.5 equiv of HCl,
cornstarch. Vehicle: water.
The challenges in synthesizing these heterocycle-substituted
imidazoles revolved mainly around regisoselective alkylation of
the imidazole ring, and several strategies were employed to
achieve this, depending on imidazole substitution, as shown in
Schemes 1−6. (1H-Imidazol-5-yl)methanol 40 was used as
starting material for many C5-substituted imidazoles (Scheme
1). N-tritylation of 40 occurs at the least hindered nitrogen, and
subsequent TBS protection of the alcohol enables regioselective
d
further optimization of CYP11B1 selectivity is possible (Table
9). For instance, although the unfunctionalized lactone 11
shows no selectivity, ring contraction to either the ether 29 or
ketone 31 confers some selectivity for CYP11B1, via loss of
potency against CYP11B2. Substituting either the ether oxygen
Figure 3. Metabolite identification study for compound 2E in rat liver microsomes.
F
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Table 7. Profile of Compounds 2E and 30
in vivo rat PK dose (mg/kg): 1 (po), 0.3 (ia)
a
compd
aldosterone IC50 (μM)
rat liver microsomes t1/2 (min)
CL (mL min−1 kg−1
)
AUC(0−24 h) (nM·h)
F (%)
2E
30
0.006
0.014
2
4
0.3
7
467
0.2
46
3566
a
All compounds are single enantiomers.
Table 8. Comparison of in Vitro and in Vivo PK Parameters
in 10-Weeks-Old and 10-Months-Old SD Rats for 2E and 30
Finally, imidazole carboxylate-containing indanes and
tetrahydronaphthalene rings were most efficiently prepared
using Mitsunobu conditions (Scheme 6). The nitrogen distal to
the carboxylate is the most nucleophilic, and the use of strong
bases such as potassium hydroxide or sodium hydride yields the
undesired regiochemistry. On the other hand, Mitsunobu
conditions typically yield greater than 20:1 ratio for the desired
compound under mild conditions when an electron with-
drawing group resides at the 5 postion of the imidazole.
Compounds 65, 66, 67, and 73 were used as intermediates to
prepare 30, 33, 34, and 35, respectively, as described in Scheme
6.
2E
30
10-months 10-weeks 10-months 10-weeks
old
old
old
old
RLM t1/2 (min)
N/A
N/A
2
N/A
N/A
4
predicted CLh
53
50
(mL min−1 kg−1
)
CL (mL min−1 kg−1
)
0.3
0.3
21
143
1.9
7
35
4.4
3.4
11
11
VDss (L/kg)
3.8
T1/2 (h)
0.2
15
Cmax (nM), 1 mpk po
184
467
BQL
BQL
1268
3566
AUC(0−24 h) (nM·h),
CONCLUSION
1 mpk po
■
F (%)
0.2
NR
46
0.3
Novel series of soluble and permeable imidazole-based ASIs
with single-digit nanomolar cellular potency and high selectivity
over aromatase were optimized for oral exposure. A general
solution to the problem of low oral bioavailability was found by
removing substitution on the imidazole ring. Although these
compounds were not optimized for CYP11B2 versus CYP11B1
selectivity, some emerging structure−selectivity relationships
were observed leading to more CYP11B1-selective analogs. The
combination of highly favorable ADME properties and nascent
selectivity for CYP11B1 over CYP11B2 creates an opportunity
to further develop these series of imidazole toward the
treatment of cortisol-driven disorders.
benzylation at N1 to give 42. Quenching of the lithium anion
derived from 42 with acetone followed by acid-mediated ring
closure afforded alcohol 16, a common precursor to a number
of analogs. Alcohol 16 was used to access ethers 19 and 21, the
synthesis of which proved quite challenging, and was best
achieved via SN2 on the primary chloride derived from 16.
Alcohol 16 was also transformed directly to esters 5 and 6 using
a one-pot cyanide-mediated oxidation.30 A similar one-pot
methodology was employed to access nitrile 9,31 the precursor
to acid 7, amides 8 and 36−38, as well as oxadiazole 10.
Alcohol 16 was oxidized by MnO2 to give aldehyde 45, the
precursor to 14, 15, 17, 18, and 20.
Ethyl- and isopropyl-substituted imidazoles 12, 13, and 22−
25 were synthesized from the iodoimidazole precursor 48,
which was accessed by reacting N-Boc-4-iodoimidazole with the
triflate derived from alcohol 47, as depicted in Scheme 2.
Lactone-containing unsubstituted imidazole such as 11, 26,
and 39 were prepared by reacting the sodium anion of
imidazole with 2-cyanobenzyl bromide in DMF at room
temperature, followed by the same lithium anion-trapping/acid-
catalyzed ring closing sequence as previously described
(Scheme 3).
The synthesis of lactam 60 was accomplished via a
Beckmann rearrangement of indanone 31, which was prepared
by reacting imidazole with the triflate derived from alcohol 57,
as depicted in Scheme 4. Trapping of the sodium anion of 60
with methyl iodide yielded 27.
Another method we employed to alkylate imidazole with
sterically hindered heterocycles, which was used to prepare
reverse lactam 28, indane 32, and dihydrobenzofuran 29, was to
react carbonyl-1,1-diimidazole with the corresponding alcohol,
as depicted in Scheme 5.
EXPERIMENTAL SECTION
■
Pharmacology Studies. Measurement of cellular aldosterone
synthase inhibition,25 aromatase inhibition,21a recombinant human
CYP11B1, and human and rat CY11B2 inhibition28 were conducted as
previously described.
For in vitro measurement of cellular aldosterone activity, human
adrenocortical carcinoma NCI-H295R cells were seeded in NBS 96-
well plates at a density of 25 000 cells/well in 100 μL of a growth
medium containing DMEM/F12 supplemented with 10% FCS, 2.5%
Nu-serum, 1 μg ITS/mL, and 1× antibiotic/antimycotic. The medium
was changed after culturing for 3 days at 37 °C under an atmosphere
of 5% CO2/95% air. On the following day, cells were rinsed with 100
μL of DMEM/F12 and incubated with 100 μL of treatment medium
containing 1 μM Ang II and a compound at different concentrations in
quadruplicate wells at 37 °C for 24 h. At the end of incubation, 50 μL
of medium was withdrawn from each well for measurement of
aldosterone production by an RIA using mouse anti-aldosterone
monoclonal antibodies. Measurement of aldosterone activity could
also be performed using a 96-well plate format. Each test sample was
incubated with 0.02 μCi of D-[1,2,6,7-3H(N)]aldosterone and 0.3 μg
of anti-aldosterone antibody in phosphate buffered saline (PBS)
containing 0.1% Triton X-100, 0.1% bovine serum albumin, and 12%
glycerol in a total volume of 200 μL at room temperature for 1 h. Anti-
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Table 9. Emerging CYP11B1 Selectivity
a
b
Compounds are single enantiomers, except otherwise noted. Racemate.
mouse PVT SPA beads (50 μL) were then added to each well and
incubated overnight at room temperature prior to counting in a
Microbeta plate counter. The amount of aldosterone in each sample is
calculated by comparing with a standard curve generated using known
quantities of the hormone.
For measurement of recombinant CYP11B2 enzyme activity,
material from frozen CYP11B2 preparations was thawed on ice on
the day of experiment and then diluted in an ice-cold assay buffer
containing 8.5 mM MgCl2, 3.1 mM KCl, 7.6 mM NaCl, and 50 mM
Tris/HCl, pH 7.4, to a protein concentration of 1−3 mg/mL. The
CYP11B2 assays were performed in 96-well U-bottom non-tissue-
culture-treated plates. Depending on the experiment, 5−125 μg of
protein (62.5 μg for IC50 determinations) in 35 μL was incubated with
75 μL of assay buffer or a compound at the desired concentration and
20 μL of substrate mix (1.08× NADPH regeneration solution A, 6.5×
NADPH regeneration solution B, 810 μM NADPH, 6.5 μM 11-
deoxycorticosterone in assay buffer) for 2 h at 25 °C in a shaking
incubator. The reaction was stopped by adding 10 μL of 1.4% Triton
H
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a
Scheme 1
a
(a) TrCl (1.1 equiv), Et3N (2.3 equiv), DMF, rt, 16 h; (b) TBSCl (1.1 equiv), imidazole (3 equiv), DMAP (0.1 equiv), DMF, rt, 2 h; (c) 2-
cyanobenzyl bromide (1.05 equiv), acetonitrile, 60 °C, 16 h, then Et2NH, 30 min, then methanol, 30 min; (d) LHMDS, THF, −78 °C, 20 min, then
acetone, 40 min; (e) aq H2SO4, THF, reflux, 16 h; (f) NaCN (1.1 equiv), MnO2 (15 equiv), methanol, THF, reflux, 2 days; (g) NaCN (1.1 equiv),
MnO2 (15 equiv), ethanol, THF, reflux, 2 days; (h) thionyl chloride, 60 °C, 2 h; (i) anhydrous ethanol, DIPEA (1.5 equiv), reflux, 16 h; (j) glycol,
DIPEA (1.5 equiv), 80 °C, 16 h; (k) MnO2 (15 equiv), dioxane, 60 °C, 16 h; (l) DAST (5 equiv), DCE, reflux, 16 h; (m) EtNH2 (1.5 equiv),
Na(OAc)3BH (3 equiv), DCE, 50 °C, 5 h; (n) MeMgBr (1.3 equiv), THF/dibutyl ether, −78 °C to rt, 16 h; (o) methoxymethyltriphenyl-
phosphonium chloride (7 equiv), NaHMDS (8 equiv), THF, rt, 15 min, then 45, rt, 1 h; (p) H2 balloon, Pd/C, methanol, rt, 48 h; (q) MgSO4 (14
equiv), NH3 (2 M in iPrOH, 4.5 equiv), MnO2 (14 equiv), THF, rt, 48 h; (r) aq H2SO4, THF, reflux, 16 h; (s) DMF (0.7 equiv), oxalyl chloride (2.5
equiv), DCM, 0 °C to rt, 2 h, then dry in vacuo then amine (3 equiv), DCM, rt, 1 h; (t) oxalyl chloride (2.5 equiv), DCM, 0 °C to rt, 3 h, then dry in
vacuo then N-hydroxyacetamidine (1.3 equiv), chloroform, reflux, 72 h.
X-100 and briefly shaking the plates. Plates were then centrifuged at
2400 rpm for 6 min, and 80 μL of supernatant was removed for
measurement of aldosterone content by scintillation proximity assay
(SPA).
Measurement of recombinant CYP11B1 enzyme activity was carried
out in a manner similar to that of the CYP11B2 assay except that 50−
300 μg of protein from the CYP11B1 preparations and 500 nM 11-
deoxycortisol were used as enzyme source and substrate, respectively.
The reaction was stopped by adding 10 μL of 1.4% Triton X-100 and
briefly shaking the plates. Plates were then centrifuged at 2400 rpm for
6 min, and 50 μL of supernatant was removed for measurement of
cortisol content by SPA.
The study protocols for the rat model of Ang II-stimulated
aldosterone synthesis have been described.21b Briefly, an initial loading
dose of 300 ng/kg angiotensin II (Ang II) was followed by 100 ng/kg/
min intravenous (iv) infusion for 9 h. After 1 h of Ang II or ACTH
infusion, a blood sample was collected for determining the post-Ang II
“baseline” (i.e., secretagogue-elevated) plasma aldosterone concen-
trations. Infusion continued for a further 8 h after test article
administration. Blood samples were withdrawn in heparin (final
concentration of 15 U/mL) from the arterial cannula at 0.25, 0.5, 1, 2,
3, 4, 5, 6, 7, 8, and 24 h postdosing. Plasma aldosterone was
determined by radioimmunoassay and test article by liquid
chromatography separation coupled with tandem mass spectrometric
detection (LC−MS/MS).
Liver Microsomal Stability and Metabolite Identification.
The in vitro half-life (t1/2) and predicted metabolic clearance (CLh) in
rat or human liver microsomes (RLM or HLM) (BD Gentest,
Woburn, MA) was determined based on published method.32 In brief,
1 μM test compound was incubated at 37 °C in pooled RLM or HLM
(containing 0.5 mg of microsomal protein per mL) in the presence of
25 μg of alamethacin per mg protein, 1.0 mM NADPH, 1.0 mM
UDPGA, and 2 mM MgCl2. The half-life (t1/2) was derived by
monitoring the disappearance of test compound over a short period of
time (e.g., 30 min) by LC/MS/MS. The CLh was calculated using a
modified “well-stirred model” that accounted for portal blood flow
I
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a
Scheme 2
a
i
(a) AlCl3 (1.3 equiv), Et2NH (2.5 equiv), DCE, 45 min, rt; (b) Tf2O (1.1 equiv), PrEt2N (1.2 equiv), DCM, −78 °C, 30 min, then N-Boc-4-
iodoimidazole (0.7 equiv), −78 °C to rt, 18 h; (c) LDA (1 equiv), THF, −78 °C, 15−30 min, then ketone (5 equiv), 1−2 h; (d) KOH, H2O/
dioxane, 60 °C, 13−30 h, then add conc HCl until pH = 1, then 60 °C, 16−24 h; (e) tributylvinyltin (2 equiv), Pd2dba3·CHCl3 (0.02 equiv), PPh3
(0.08 equiv), DMF, 90 °C, 3−6 h; (f) tributylisopropenyltin (2 equiv), Pd2dba3·CHCl3 (0.1 equiv), trifuran-2-ylphosphane (0.15 equiv), NMP, 90
°C, 24 h; (g) 10% Pd/C (0.05 equiv), H2, methanol, 3−72 h.
a
Scheme 3
a
(a) NaH (1.5 equiv), DMF, rt, 30 min, then appropriate 2-cyanobenzyl bromide (1 equiv), 30 min; (b) LHMDS (1.5 equiv), THF, −78 °C, 30
min, then acetone (1.5 equiv), 30 min; (c) aq H2SO4, dioxane, reflux, 2−16 h; (d) LHMDS (3.5 equiv), THF, −78 °C, 10 min, then benzaldehyde
(4.5 equiv), 1 min.
a
Scheme 4
a
(a) 50% KF on Celite (∼5 equiv), MeI (3 equiv), acetonitrile, 70 °C, 14 h; (b) NaBH4 (0.3 equiv), ethanol, −30 °C, 1 h; (c) Tf2O (3 equiv),
DIPEA (4 equiv), DCM, −78 °C, 10 min, then −10 °C, 10 min, then imidazole (6 equiv), −78 °C to rt; (d) NH2OH. HCl (2.5 equiv), pyridine (12
equiv), methanol, 55 °C, 14 h; (e) p-TsCl (2 equiv), DMAP (0.03 equiv), pyridine, 50 °C, 14 h; (f) pyridine, 190 °C (microwave), 35 min; (g) NaH
(1.3 equiv), DMF, −10 °C, 10 min, then MeI (2 equiv), −10 °C to rt, 20 min.
J
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a
Scheme 5
a
(a) 1-Methoxy-1-(trimethylsiloxy)-2-methyl-1-propene (1.2 equiv), Sc(OTf)3 (0.03 equiv), DCM, −78 to 0 °C, 1 h, then 1 M HCl, 1 h; (b) 10%
Pd/C, H2 (balloon), methanol, 5 h; (c) carbonyl-1,1-di-imidazole (2.0 equiv), acetonitrile, reflux, 5 h.
a
Scheme 6
a
(a) PPh3 (1−2 equiv), DMAD or DIAD or DTBAD (1−2 equiv), THF, 0 °C to rt, 1−15 h; (b) NaBH4 (1.5 equiv), MeOH, 0 °C, 10 min; (c)
LiAlH4 (1.5 equiv), THF, 0 °C, 30 min; (d) imidazole (1.1 equiv), TBSCl (1 equiv), DMF, rt, 14 h; (e) MnO2 (20 equiv), 1,4-dioxane, 100 °C, 1−2
h; (f) 4 M HCl in 1,4-dioxane, rt, 2 h; (g) Ac2O (2 equiv), pyridine (10 equiv), DCM, rt, 1 h.; (h) NaBH4 (3 equiv), EtOH, rt, 2 h; (i) 4 M HCl in
1,4-dioxane, methanol, rt, 30 min.
(Qh) and considered no difference between plasma protein binding
and microsomal protein binding of the test compounds. In the
metabolite identification, 10 μM test compound was incubated at 37
°C in pooled RLM or HLM (containing 1 mg of microsomal protein
per mL) in the presence of 60 μg of alamethacin per mg protein, 2.0
mM NADPH, 4.0 mM UDPGA, and 5 mM MgCl2. Following in vitro
incubation and protein precipitation, samples were analyzed by LC/
MS/MS for detection and characterization of the metabolites formed.
Rat Pharmacokinetic Studies for 2E and 30. Male Sprague
Dawley rats (200−300 g) (Harlan Laboratories Inc., Indianapolis, IN,
USA) were used in the experiments. All animal experiments were
performed in accordance with IACUC protocol. Two rats received 0.3
mg/1 mL/kg (free base equivalents) by slow intravenous injection via
the jugular vein, and three rats received 1 mg/5 mL/kg in solution of
suspension via oral gavage. Approximately 0.2 mL of venous whole
blood was collected from the jugular vein catheter of each animal at 5
min (iv dose only) and 0.25, 0.5, 1, 2, 4, 6, and 8 h postdose and
transferred to a EDTA tube. The blood was centrifuged at 3000 rpm,
and the plasma was transferred to a polypropylene tube, capped, and
stored frozen (−20 °C) for parent compound analysis. Protein
precipitation was employed for sample preparation. A 25 μL aliquot of
sample was subjected to protein precipitation using 150 μL of
acetonitrile containing 100 ng/mL of internal standard (Glyburide).
After vortex and centrifugation for 5 min at 4000 rpm, the supernatant
(125 μL) was transferred to a 1 mL 96-well plate, followed by the
addition of 50 μL of water. The analysis was conducted by using
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HPLC separation coupled with mass spectrometric detection. All
pharmacokinetic (PK) parameters were derived from concentration−
time data by noncompartmental analyses. All pharmacokinetic
parameters were calculated with the computer program WinNonlin
(Enterprise, version 5.2) purchased from Pharsight Corporation (St.
Louis, MO).
(R)- or (S)-4-(5-Hydroxymethylimidazol-1-yl)-3,3-dimethyl-
isochroman-1-one (R- and S-16). Crude 43 (3 g) was dissolved
in THF (80 mL). Water (1.6 mL) and sulfuric acid (1.6 mL) were
added, and the mixture was stirred at reflux overnight. After cooling
down, the mixture was poured in water. The two phases were
separated, and the pH of the aqueous phase was adjusted to ∼9 with
aqueous sodium bicarbonate. Extraction with ethyl acetate, drying over
Na2SO4, and concentration in vacuo gave a solid which is recrystallized
from ethyl acetate. 4-(5-Hydroxymethylimidazol-1-yl)-3,3-dimethyl-
isochroman-1-one (1.7 g, 20%, 3 steps) was obtained as a white solid.
Resolution of the racemate achieved by chiral HPLC using the
ChiralPak IA column with a 7:2:1 heptane−dichloromethane−ethanol
mobile phase gave 16; tR = 8.3 min (distomer tR = 7.1 min); ESI-MS
m/z 272.9 (M + H)+; 1H NMR (400 MHz, CDCl3) δ ppm 1.29 (s, 3
H), 1.54 (s, 3 H), 4.71 (d, J = 13.6 Hz, 1 H), 4.82 (d, J = 13.9 Hz, 1
H), 5.51 (s, 1 H), 6.89 (s, 1 H), 7.29 (s, 1 H), 7.41 (d, J = 7.6 Hz, 1
H), 7.53−7.58 (m, 1 H), 7.59−7.65 (m, 1 H), 8.25 (dd, J = 7.6, 1.5
Hz, 1 H).
(R)- or (S)-3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imida-
zole-4-carboxylic Acid Ethyl Ester (6). To a solution of 16 (0.56 g,
2.0 mmol) in THF (10 mL) were added ethanol (0.6 mL), sodium
cyanide (0.111 g, 2.26 mmol), and manganese dioxide (2.69 g, 30.9
mmol). The mixture was stirred at reflux for 2 days, filtered, and
concentrated in vacuo. The residue was purified by silica gel
chromatography (heptane−ethyl acetate, 4:1 to 1:9) to give 3-(3,3-
dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-carboxylic acid ethyl
ester as oil (230 mg, 36%). Resolution of the racemate was achieved by
chiral HPLC using the ChiralPak AS-H column with a 4:1 hexanes−
isopropanol mobile phase to give 6; tR = 12.4 min (distomer tR = 10.5
min); ESI-MS m/z 315.1355 [(M + H)+, calcd for C17H18N2O4,
315.1345]; 1H NMR (400 MHz, CD3OD) of the HCl salt δ ppm 1.24
(s, 3 H), 1.43 (t, J = 7.1 Hz, 3 H), 1.55 (s, 3 H), 4.46 (q, J = 7.1 Hz, 2
H), 6.83 (s, 1 H), 7.53 (d, J = 7.6 Hz, 1 H), 7.66−7.71 (m, 2 H), 7.78
(td, 1 H), 7.91 (s, 1 H), 8.26 (dd, J = 7.8, 1.3 Hz, 1 H).
General Chemical Methods. Starting materials, reagents, and
solvents were obtained from commercial sources and used as received.
THF and diethyl ether were anhydrous grade. Progress of the
reactions was monitored by thin-layer chromatography (TLC) analysis
(Merck, 0.2 mm silica gel 60 F254 on glass plates) or by analytical
LC−MS using an Agilent 1100 series with UV detection at 214 and
254 nm and an electrospray mode (ESI) coupled with a Waters ZQ
single quad mass detector. Purification of intermediates and final
products was carried out on normal phase using an ISCO CombiFlash
system or an Analogix Intelliflash 280 or a Biotage SP1 system and
prepacked SiO2 cartridges eluted with optimized gradients of either
heptane−ethyl acetate mixture or dichloromethane−methanol as
described. Preparative high pressure liquid chromatography (HPLC)
was performed on Waters or Gilson instruments. Systems were run
with either a 5−95% or 10−90% acetonitrile/water gradient with
either a 0.1% TFA or 0.1% NH4OH modifier. All target compounds
had purity of >95% as established by analytical HPLC. Resolution of
the racemates was carried out by preparative HPLC using the
conditions described, and enantiomeric excesses were >98%. NMR
spectra were recorded on a Bruker AV400 (Avance 400 MHz)
instrument. Chemical shifts (δ) are reported in parts per million
(ppm) relative to deuterated solvent as the internal standard (CDCl3
7.26 ppm, DMSO-d6 2.50 ppm, CD3OD 3.31), and coupling constants
(J) are in hertz (Hz). Peak multiplicities are expressed as follows:
singlet (s), doublet (d), doublet of doublets (dd), triplet (t), quartet
(q), multiplet (m), and broad singlet (br s).
4-(tert-Butyldimethylsilanyloxymethyl)-1-trityl-1H-imida-
zole (41). Trityl chloride (45.57 g, 0.163 mol), (1H-imidazol-4-
yl)methanol (20.00 g, 0.148 mol), and triethylamine (37.46 g, 0.370
mol) in DMF (150 mL) were stirred at rt for 16 h, whereupon the
mixture was poured into ice-cold water. The precipitate was filtered off
and dried under high vacuum to give (1-trityl-1H-imidazol-4-
yl)methanol as a solid. Crude (1-trityl-1H-imidazol-4-yl)methanol
(26.4 g, 0.077 mol), imidazole (15.88 g, 0.233 mol), DMAP (0.950 g,
7.7 mmol), and TBSCl (12.89 g, 0.085 mol) in DMF (0.1 L) were
stirred at rt for 2 h, whereupon water was added. The mixture was
extracted three times with dichloromethane. The organic layer was
dried over Na2SO4 and concentrated in vacuo. The residue was
purified by silica gel flash chromatography (elution with hexanes−ethyl
acetate, 7:3) to yield 41 as a white solid; ESI-MS m/z 455 (M + H)+.
2-[5-(tert-Butyldimethylsilanyloxymethyl)imidazol-1-
ylmethyl]benzonitrile (42). 41 (12.9 g, 28.4 mmol) and 2-
cyanobenzyl bromide (6.12 g, 31.2 mmol) in acetonitrile (100 mL)
were heated to 60 °C overnight, whereupon diethylamine (30 mL)
was added. After 30 min, methanol (2 mL) was added. After 30 min
the volatiles were removed in vacuo. The residue was taken up in
dichloromethane and washed with water. The organic layer was dried
over Na2SO4 and concentrated in vacuo. The residue was purified by
silica gel flash chromatography (elution with dichloromethane−
methanol, 49:1) to yield partially purified 42 which was used in the
next step without further purification; ESI-MS m/z 328.2 (M + H)+.
2-{1-[5-(tert-Butyldimethylsilanyloxymethyl)imidazol-1-yl]-
2-hydroxy-2-methylpropyl}benzonitrile (43). Crude 42 (7.6 g)
was dried azeotropically with toluene and then dissolved in THF (100
mL) and cooled to −75 °C. LHMDS (1 M in THF, 35 mL, 35 mmol)
was added dropwise. Ten minutes after the end of addition, acetone
(2.0 g, 35 mmol) was added. Thirty minutes after the end of addition,
saturated aqueous sodium bicarbonate (2 mL) was added and the
mixture was allowed to warm to rt, then poured into water. After
extraction with ethyl acetate the organic phase was dried over Na2SO4
and concentrated in vacuo to give crude 43 (3 g), which was used in
the next step without further purification; ESI-MS m/z 386.1 (M +
H)+.
(R)- or (S)- 3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imi-
dazole-4-carboxylic Acid Methyl Ester (5). Compound 5 was
prepared following the same procedure as 6, using methanol instead of
ethanol. Resolution of the racemate was achieved by chiral HPLC
using the ChiralPak AS-H column with a 9:1 hexanes−isopropanol
mobile phase to give 5; tR1= 30.9 min (distomer tR = 22.0 min); ESI-
MS m/z 301.0 (M + H); H NMR (400 MHz, CD3OD) δ ppm 1.26
(s, 3 H), 1.58 (s, 3 H), 4.00 (s, 3 H), 6.81 (s, 1 H), 7.47 (s, 1 H), 7.54
(d, J = 7.6 Hz, 1 H), 7.71 (td, J = 7.8, 1.3 Hz, 1 H), 7.79 (dd, J = 7.6,
1.5 Hz, 1 H), 7.82 (d, J = 1.0 Hz, 1 H), 8.28 (dd, J = 7.7, 1.4 Hz, 1 H).
(R)- and (S)-4-(5-Ethoxymethylimidazol-1-yl)-3,3-dimethyl-
isochroman-1-one (19). A solution of 16 (1.0 g, 3.6 mmol) in
thionyl chloride (50 mL) was heated to 60 °C for 2 h. The volatiles
were removed in vacuo to give 4-(5-chloromethylimidazol-1-yl)-3,3-
dimethylisochroman-1-one. A portion (0.15 g, 0.52 mmol) was
redissolved in anhydrous ethanol (5 mL). Diisopropylethylamine
(0.100 g, 0.77 mmol) was added, and the mixture was stirred at reflux
overnight. The mixture was purified by semipreparative reverse phase
HPLC to give 4-(5-ethoxymethylimidazol-1-yl)-3,3-dimethyl-
isochroman-1-one (70 mg, 44%, 2 steps). Resolution of the racemate
was achieved by chiral HPLC using the ChiralPak IA column with a
7:2:1 heptane−dichloromethane−ethanol mobile phase to give 19; tR
= 8.9 min (distomer tR = 6.3 min); ESI-MS m/z 301.0 (M + H)+; 1H
NMR (400 MHz, CD3OD) δ ppm 1.26 (s, 3 H), 1.29 (t, J = 6.1 Hz, 3
H), 1.54 (s, 3 H), 3.62 (br s, 2 H), 4.70 (br s, 2 H), 5.59 (s, 1 H), 7.02
(s, 1 H), 7.29 (br s, 1 H), 7.52 (d, J = 7.8 Hz, 1 H), 7.63 (td, J = 7.8,
1.3 Hz, 1 H), 7.74 (td, J = 7.6, 1.3 Hz, 1 H), 8.21 (dd, J = 7.8, 1.3 Hz, 1
H).
4-[5-(2-Hydroxyethoxymethyl)imidazol-1-yl]-3,3-dimethyl-
isochroman-1-one (20). Compound 20 was prepared following the
same procedure as 19, using glycol instead of ethanol. ESI-MS m/z
1
317.0 (M + H)+; H NMR (400 MHz, CDCl3) δ ppm 1.31 (s, 3 H),
1.55 (s, 3 H), 1.76 (br s, 1 H), 3.55−3.69 (m, 2 H), 3.78−3.86 (m, 2
H), 4.65−4.75 (m, 2 H), 5.46 (s, 1 H), 7.06 (s, 1 H), 7.34 (d, J = 8.3
Hz, 2 H), 7.55 (td, J = 7.6, 1.3 Hz, 1 H), 7.62 (td, J = 7.6, 1.5 Hz, 1 H),
8.25 (dd, J = 7.8, 1.5 Hz, 1 H).
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3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
baldehyde (45). To a solution of racemic 16 (2.72 g, 10 mmol) in
dioxane (150 mL) was added manganese dioxide (13 g, 150 mmol),
and the reaction mixture was heated to 60 °C overnight. Filtration
through Celite and concentration in vacuo gave a residue which was
purified by silica gel chromatography (dichloromethane−methanol) to
afford 45 (2.5 g, 93%). Crude 45 was of sufficient purity before
chromatography and was typically used without purification; ESI-MS
m/z 271.1 (M + H)+.
4-[5-(1-Hydroxy-1-methylethyl)imidazol-1-yl]-3,3-dimethyl-
isochroman-1-one (18). To a solution of 17 and its three
stereoisomers (0.100 g, 0.35 mmol) in dioxane (2 mL) was added
manganese dioxide (0.46 g, 5.2 mmol), and the reaction mixture was
heated to 60 °C overnight. Filtration through Celite and concentration
in vacuo gave crude 4-(5-acetylimidazol-1-yl)-3,3-dimethylisochroman-
1-one. The crude ketone (0.150 g, 0.50 mmol) was dissolved in THF
(2 mL) at −78 °C, 1 M methylmagnesium bromide in dibutyl ether
(0.65 mL, 0.65 mmol) was added, and the mixture was allowed to
warm to rt overnight. This process was repeated twice before
quenching with acetone. The mixture was poured into water and
extracted with ethyl acetate. The combined organic phase was washed
with water, dried over Na2SO4, and concentrated in vacuo. The residue
(R)- or (S)-4-(5-Difluoromethylimidazol-1-yl)-3,3-dimethyl-
isochroman-1-one (14). To a solution of 45 (0.135 g, 0.50
mmol) in dichloroethane (5 mL) under nitrogen was added DAST
(0.403 g, 2.5 mmol), and the mixture was heated to reflux overnight.
After another 2 h, an additional portion of DAST (0.060 g, 0.372
mmol) was added. The organic phase was shaken with saturated
aqueous sodium bicarbonate and filtered through Celite. The organic
phase was dried over magnesium sulfate, filtered and the residue was
purified by reverse phase HPLC using C18 Xbridge and acetonitrile/
NH4OH gradient to give 4-(5-difluoromethylimidazol-1-yl)-3,3-
dimethylisochroman-1-one. Resolution of the racemate was achieved
by chiral HPLC using the ChiralPak IA column with a 3:1 heptane−
isopropanol mobile phase to give 14 (14 mg, 10%); tR = 13.3 min
1
was purified by reverse phase HPLC to give 18 (50 mg, 47%); H
NMR (400 MHz, CDCl3) δ ppm 8.30 (dd, J = 7.7, 1.4 Hz, 1H), 7.97−
7.90 (m, 1H), 7.75 (td, J = 7.6, 1.5 Hz, 1H), 7.68 (td, J = 7.6, 1.1 Hz,
1H), 7.58 (s, 1H), 7.04 (s, 1H), 6.59 (s, 1H), 3.04 (s, 1H), 1.90 (s,
3H), 1.78 (s, 3H), 1.59 (s, 3H), 1.33 (s, 3H).
(R)- or (S)-4-[5-(2-Methoxyethyl)imidazol-1-yl]-3,3-dimethyl-
isochroman-1-one (21). To a solution of methoxymethyltriphenyl-
phosphonium chloride (0.914 g, 2.67 mmol) in THF (10 mL) was
added lithium hexamethyldisilazide (1 M in THF, 2.9 mL, 2.9 mmol),
and the mixture was stirred for 15 min. 45 (0.60 g, 2.22 mmol) in
THF (0.2 mL) was then added, and the mixture was stirred for 1 h. It
was then quenched with methanol. The organic phase was
concentrated to dryness in vacuo. The residue was dissolved in
methanol, and 10% Pd/C was added. The reaction vessel was flushed
with hydrogen gas and stirred under balloon pressure for 48 h. The
mixture was filtered, and the filtrate was concentrated in vacuo to give
a residue which was purified by reverse phase HPLC using C18
Xbridge and acetonitrile/NH4OH gradient to give 4-[5-(2-
methoxyethyl)imidazol-1-yl]-3,3-dimethylisochroman-1-one. The race-
mate was resolved chiral HPLC using the ChiralPak IA column with a
65:35 hexanes−reagent alcohol mobile phase to give 21 (70 mg, 10%,
2 steps); tR = 11.8 min (distomer tR = 9.2 min); HR-ESI-MS m/z
1
(distomer tR = 21.4 min); ESI-MS m/z 293.0 (M + H)+; H NMR
(400 MHz, CDCl3) δ ppm 1.32 (s, 3 H), 1.57 (s, 3 H), 5.50 (s, 1 H),
6.86 (t, J = 52.7 Hz, 1 H), 7.32 (t, J = 2.6 Hz, 1 H), 7.43 (s, 1 H), 7.44
(m, 1 H), 7.54−7.63 (m, 1 H), 7.63−7.71 (m, 1 H), 8.27 (dd, J = 7.7,
1.3 Hz, 1 H).
4-(5-Ethylaminomethylimidazol-1-yl )-3,3-dimethyl-
isochroman-1-one (15). To a solution of 45 (0.133 g, 0.49
mmol) in dichloroethane (2 mL) were added ethylamine (0.37 mL,
0.738 mmol) and sodium triacetoxyborohydride (0.313 g, 1.477
mmol). The reaction mixture was stirred at 50 °C for 5 h. The mixture
was cooled to room temperature, washed with saturated aqueous
sodium bicarbonate, and extracted with ethyl acetate. The organic
phase was dried over Na2SO4 and concentrated in vacuo. The residue
was dissolved purified by reverse phase HPLC to give 15 (65 mg,
44%); HR-ESI-MS m/z 300.1705 [(M + H)+, calcd for C17H22N3O2,
300.1712]; 1H NMR (400 MHz, CD3OD) of the TFA salt δ ppm 1.27
(s, 3 H), 1.46 (t, J = 6.8 Hz, 3 H), 1.59 (s, 3 H), 3.35−3.40 (m, 2 H),
4.65 (br s, 2 H), 5.82 (s, 1 H), 7.51 (br s, 1 H), 7.64 (d, J = 7.3 Hz, 1
H), 7.75 (td, J = 7.8, 1.0 Hz, 1 H), 7.84 (td, J = 7.6, 1.3 Hz, 1 H), 7.92
(br s, 1 H), 8.30 (dd, J = 7.8, 1.3 Hz, 1 H).
1
301.1555 [(M + H)+, calcd for C17H20N2O3, 301.1552]; H NMR
(400 MHz, CD3OD) δ ppm 1.25 (s, 3 H), 1.56 (s, 3 H), 3.13 (br s, 2
H), 3.45 (br s, 3 H), 3.70−3.79 (m, 2 H), 5.71 (s, 1 H), 6.90 (s, 1 H),
7.15 (br s, 1 H), 7.52 (d, J = 7.6 Hz, 1 H), 7.60−7.72 (m, 1 H), 7.74−
7.86 (m, 1 H), 8.24 (dd, J = 7.8, 1.5 Hz, 1 H).
(R)- or (S)-3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imida-
zole-4-carbonitrile (9). To a solution of 16 (1.0 g, 3.76 mmol) in
THF (30 mL) were added magnesium sulfate (4.79 g, 0.055 mol) and
ammonia (2 M isopropanol, 9 mL, 0.018 mol). Manganese dioxide (9
mL, 0.055 mol) was then added, and the reaction mixture was stirred
at room temperature for 48 h. Filtration through Celite and
concentration in vacuo afford a residue, which was purified by
reverse-phase HPLC to give 3-(3,3-dimethyl-1-oxoisochroman-4-yl)-
3H-imidazole-4-carbonitrile (546 mg, 55%). Resolution of the
racemate was achieved by chiral HPLC using the ChiralPak IA
column with a 7:3 heptane−ethanol mobile phase to give 9; tR = 42.7
min (distomer tR = 13.5 min); ESI-MS m/z 268.0 (M + H)+; 1H NMR
(400 MHz, MeOD) δ ppm 1.33 (s, 3 H), 1.60 (s, 3 H), 5.87 (s, 1 H),
7.57 (d, J = 7.6 Hz, 1 H), 7.67−7.78 (m, 1 H), 7.78−7.98 (m, 3 H),
8.28 (dd, J = 7.7, 1.4 Hz, 1 H).
3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
boxylic Acid (7). 9 (0.100 g, 0.374 mmol) was dissolved in a mixture
of tetrahydrofuran (2 mL) and water (0.2 mL). Sulfuric acid (0.2 mL,
1.872 mmol) was added, and the mixture was stirred at reflux for 16 h.
Concentration in vacuo gave a residue which was purified by reverse
phase HPLC to give 7 (45 mg, 41%); ESI-MS m/z 287.0 (M + H)+.
3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
boxylic Acid Benzylamide (8). 7 (0.100 g, 0.349 mmol) was
dissolved in dichloromethane (2 mL). Catalytic amount of
dimethylformamide (0.002 mL,0.0262 mmol) was added to the
reaction mixture and cooled to 0 °C. Oxalyl chloride (0.076 mL, 0.874
mmol) was added, and the cooling bath was removed. The mixture
was stirred at room temperature for 2 h and then concentrated in
vacuo. The residue obtained was redissolved in dichloromethane, and
benzylamine (0.114 mL, 1.04 mmol) was added. Reaction mixture was
(R,R)-, (S,S)-, (R,S)-, (S,R)-4-[5-(1-Hydroxyethyl)imidazol-1-yl]-
3,3-dimethylisochroman-1-one (17 and Stereoisomers). To a
solution of 45 (0.500 g, 1.852 mmol) in THF (20 mL) at −78 °C was
added 1 M methyl magnesium bromide in dibutyl ether (2.41 mL, 2.41
mmol). The reaction mixture was stirred at −78 °C for 3 h,
whereupon acetone (2 mL) was added. The mixture was allowed to
warm to ambient temperature and then poured into water (50 mL).
The mixture was extracted with ethyl acetate. The combined organic
phase was washed with water, dried over Na2SO4, and concentrated in
vacuo. The residue was purified by silica gel chromatography (DCM−
methanol, 99:1 to 19:1) to give 4-[5-(1-hydroxyethyl)imidazol-1-yl]-
3,3-dimethylisochroman-1-one (400 mg, 75%). Resolution of all four
stereoisomers was achieved by chiral HPLC. Using a ChiralPak IA
column using an 85:15 heptane−isopropanol mobile phase afforded
17. The remaining three stereoisomers were resolved with a ChiralPak
AD using an 85:15 heptane−ethanol mobile phase to give stereo-
isomer B (tR = 61.4 min), stereoisomer C (tR = 76.7 min) and
stereoisomer D (tR = 94.9 min).
1
17 and stereoisomer D: ESI-MS m/z 287.0 (M + H)+; H NMR
(400 MHz, CDCl3) δ ppm 1.26 (s, 3 H), 1.54 (s, 3 H), 1.79 (d, J = 6.6
Hz, 3 H), 1.84 (d, J = 8.6 Hz, 1 H), 4.91−5.01 (m, 1 H), 5.67 (s, 1 H),
7.01 (s, 1 H), 7.24 (s, 1 H), 7.47 (d, J = 8.1 Hz, 1 H), 7.52−7.58 (m, 1
H), 7.59−7.64 (m, 1 H), 8.25 (dd, J = 7.7, 1.4 Hz, 1 H).
1
Stereoisomers B and C: ESI-MS m/z 287.1 (M + H)+; H NMR
(400 MHz, CDCl3) δ ppm 1.40 (s, 3 H), 1.56 (s, 3 H), 1.77 (d, J = 6.6
Hz, 3 H), 1.85 (br s, 1 H), 5.06−5.12 (m, 1 H), 5.60 (s, 1 H), 6.99 (s,
1 H), 7.23 (d, J = 7.6 Hz, 1 H), 7.40 (s, 1 H), 7.54 (td, J = 7.8, 1.3 Hz,
1 H), 7.61 (td, J = 7.6, 1.5 Hz, 1 H), 8.24 (dd, J = 7.7, 1.4 Hz, 1 H).
M
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Journal of Medicinal Chemistry
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stirred at room temperature for 1 h. The mixture was washed with
saturated aqueous sodium bicarbonate and extracted with dichloro-
methane. The combined organic phase was dried over Na2SO4 and
concentrated in vacuo. The residue was purified by silica gel
chromatography (dichlromethane−methanol, 19:1) to give 8 (38
mg, 29%); ESI-MS m/z 376.0 (M + H)+; 1H NMR (400 MHz,
CD3OD) δ ppm 1.24 (s, 3 H), 1.53 (s, 3 H), 4.62 (s, 2 H), 6.98 (s, 1
H), 7.26−7.35 (m, 1 H), 7.35−7.46 (m, 5 H), 7.57 (d, J = 7.6 Hz, 1
H), 7.64−7.73 (m, 2 H), 7.74−7.84 (m, 1 H), 8.26 (dd, J = 7.8, 1.5
Hz, 1 H).
Hz), 7.32 (1 H, td, J = 7.4, 1.5 Hz), 7.39 (1 H, td, J = 7.4, 1.5 Hz), 7.44
(1 H, td, J = 7.4, 1.5 Hz).
N,N-Diethyl-2-(5-iodoimidazol-1-ylmethyl)benzamide (48).
A flask was charged with dichloromethane (200 mL) and
trifluoromethanesulfonic anhydride (19.34 g, 67.20 mmol) and cooled
to −78 °C. A solution of diisopropylethylamine (9.57 g, 73.30 mmol)
and 47 (12.92 g, 61.09 mmol) in dichloromethane (40 mL) was added
over 10 min. After 30 min, a solution of 4-iodoimidazole-1-carboxylic
acid tert-butyl ester (12.83 g, 42.76 mmol) in dichloromethane (40
mL) was added. The mixture was allowed to gradually warm overnight,
and after 18 h, saturated aqueous sodium bicarbonate (100 mL) was
added and the mixture was stirred vigorously for 30 min. The aqueous
layer was extracted with dichloromethane. The combined organic
phase was dried over MgSO4, filtered through a cotton plug, and
concentrated in vacuo. The residue was purified by silica gel flash
chromatography (dichloromethane−methanol, 49:1) to afford 48
(5.32 g, 32%); ESI-MS m/z 384.1 (M + H)+.
N,N-Diethyl-2-[2-hydroxy-1-(5-iodoimidazol-1-yl)-2-
methylpropyl]benzamide (49). To a solution of diisopropylamine
(0.97 g, 6.39 mmol) in THF (50 mL) at −78 °C under nitrogen was
added n-BuLi (2.5 M in hexanes, 3.8 mL, 9.6 mmol), and the mixture
was warmed to 0 °C. After 15 min, the LDA solution was cooled to
−78 °C and a solution of 48 (2.45 g, 6.39 mmol) in THF (5 mL) was
added over 15 min. Thirty minutes after the end of addition, acetone
(1.86 g, 31.97 mmol) in THF (5 mL) was added to the brown solution
and the mixture was stirred for 1 h, whereupon 10% acetic acid in
water was added. The mixture was poured in ethyl acetate, and the two
phases were separated. The organic phase was washed with saturated
aqueous sodium bicarbonate. The combined aqueous phase was
extracted twice with ethyl acetate. The combined organic phase was
dried over MgSO4, filtered through a cotton plug, and concentrated in
vacuo. The residue was purified by silica gel flash chromatography
(elution with dichloromethane−methanol, 49:1 to 97:3 to 24:1) to
afford crude 49 as a yellow solid which was used in the next step with
no further purification; ESI-MS m/z 442.0 (M + H)+.
3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
boxylic Acid (2-Fluorobenzyl)methylamide (36). Compound 36
was prepared using the same procedure as 8, using N-methyl-2-
fluorobenzylamine instead of benzylamine. ESI-MS m/z 408.1 (M +
1
H)+; H NMR (400 MHz, CD3OD) δ ppm 1.25 (s, 3 H), 1.52 (s, 3
H), 3.24 (br s, 3 H), 4.93 (br s, 2 H), 6.26 (s, 1 H), 7.17−7.40 (m, 2
H), 7.37−7.53 (m, 4 H), 7.64−7.73 (m, 2 H), 7.80 (td, J = 7.3, 1.3 Hz,
1 H), 8.26 (d, J = 7.8 Hz, 1 H).
3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
boxylic Acid (4-Fluorobenzyl)methylamide (37). Compound 37
was prepared using the same procedure as 8, using N-methyl-4-
fluorobenzylamine instead of benzylamine. ESI-MS m/z 408.1 (M +
1
H)+; H NMR (400 MHz, CD3OD) δ ppm 1.24 (s, 3 H), 1.53 (s, 3
H), 3.23 (br s, 3 H), 4.82 (br s, 2 H), 6.30 (s, 1 H), 7.18 (t, J = 8.7 Hz,
2 H), 7.38−7.45 (m, 4 H), 7.66 (br d, J = 7.6 Hz, 1 H), 7.70 (td, J =
7.6, 1.3 Hz, 1 H), 7.81 (td, J = 7.6, 1.4 Hz, 1 H), 8.26 (dd, J = 7.6, 1.3
Hz, 1 H).
3-(3,3-Dimethyl-1-oxoisochroman-4-yl)-3H-imidazole-4-car-
boxylic Acid (4-Fluoro)benzylamide (38). Compound 38 was
prepared using the same procedure as 8, using 4-fluorobenzylamine
instead of benzylamine. ESI-MS m/z 394.3 (M + H)+; 1H NMR (400
MHz, CD3OD) δ ppm 1.23 (s, 3 H), 1.53 (s, 3 H), 4.59 (s, 2 H), 6.97
(s, 1 H), 7.07−7.19 (m, 2 H), 7.36 (s, 1 H), 7.40−7.48 (m, 2 H), 7.55
(d, J = 7.6 Hz, 1 H), 7.65−7.73 (m, 1 H), 7.75−7.82 (m, 2 H), 8.26
(d, J = 7.8 Hz, 1 H).
4-(5-Iodoimidazol-1-yl)-3,3-dimethylisochroman-1-one (50).
Dioxane (22 mL) and 1 M aqueous KOH (22 mL, 22 mmol) were
added to 49 (1.65 g), and the mixture was heated to 60 °C. After 13.5
h, the mixture was cooled to 0 °C and acidified to pH 1 with conc
HCl. The mixture was heated to 60 °C. After 24 h, the mixture was
diluted with ethyl acetate and washed with saturated aqueous sodium
bicarbonate, water, and brine, dried over magnesium sulfate, and
filtered through a cotton plug. Concentration in vacuo gave an orange
solid, which was purified by silica gel flash chromatography (methylene
chloride−methanol, 49:1) to give 50 (1.00 g, 42%, 2 steps) as a yellow
3,3-Dimethyl-4-[5-(3-methyl[1,2,4]oxadiazol-5-yl)imidazol-
1-yl]isochroman-1-one (10). 7 (0.538 g, 1.88 mmol) was dissolved
in dichloromethane (4 mL) and cooled to 0 °C. Oxalyl chloride (0.41
mL, 4.702 mmol) was added, and the cooling bath was removed. The
mixture was stirred at room temperature for 3 h. The reaction mixture
was concentrated in vacuo. The residue obtained was redissolved in
chloroform, and N-hydroxyacetamidine (0.181 g, 2.44 mmol) was
added. The reaction mixture was stirred at reflux for 72 h. The mixture
was cooled to room temperature, washed with saturated solution of
sodium bicarbonate, and extracted with dichloromethane. The organic
phase was dried over Na2SO4 and concentrated in vacuo. The residue
was purified by silica gel chromatography (hexane−ethyl acetate, 3:7)
to give 10 (100 mg, 16%) as a white solid; ESI-MS m/z 325.0 (M +
1
solid; ESI-MS m/z 369.0 (M + H)+; H NMR (400 MHz, CDCl3) δ
ppm 1.30 (s, 3 H), 1.57 (s, 3 H), 5.39 (s, 1 H), 7.19 (s, 1 H), 7.28 (br
d, J = 7.6 Hz, 1 H), 7.39 (s, 1 H), 7.59 (td, J = 7.6, 1.3 Hz, 1 H), 7.66
(td, J = 7.6, 1.3 Hz, 1 H), 8.27 (dd, J = 7.6, 1.4 Hz, 1 H).
1
H)+; H NMR (400 MHz, CD3OD) δ ppm 1.26 (s, 3 H), 1.61 (s, 3
4-(5-Vinylimidazol-1-yl)-3,3-dimethylisochroman-1-one
(51). DMF (30 mL) was added to 50 (1.62 g, 4.18 mmol),
tributylvinyltin (2.40 g, 8.36 mmol), Pd2dba3·CHCl3 (0.087 g, 0.084
mmol), and triphenylphosphine (0.089 g, 0.334 mmol) under
nitrogen. The mixture was heated to 90 °C to give a clear tan
solution. After 3 h, the mixture was cooled down, diluted with
isopropyl acetate, and washed twice with water and brine. The
combined organic phase was dried over magnesium sulfate and filtered
through a cotton plug. The residue was purified by silica gel flash
chromatography (10 wt % silica gel/KF, elution with dichloro-
methane−methanol, 49:1 to 24:1) to give 51 as a yellow solid; ESI-MS
m/z 269.2 (M + H)+; 1H NMR (400 MHz, CD3OD) δ ppm 1.20 (s, 3
H), 1.51 (s, 3 H), 5.42 (br s, 1 H), 5.69 (s, 1 H), 5.81 (br s, 1 H), 6.95
(br s, 1 H), 7.14 (br s, 1 H), 7.21 (s, 1 H), 7.42 (d, J = 7.6 Hz, 1 H),
7.58−7.69 (m, 1 H), 7.70−7.80 (m, 1 H), 8.21 (dd, J = 7.8, 1.3 Hz, 1
H).
H), 2.55 (s, 3 H), 6.94 (s, 1 H), 7.56 (d, J = 7.1 Hz, 1 H), 7.63 (s, 1
H), 7.72 (td, J = 7.6, 1.3 Hz, 1 H), 7.80 (td, J = 7.6, 1.3 Hz, 1 H), 8.01
(s, 1 H), 8.30 (dd, J = 7.8, 1.3 Hz, 1 H).
N,N-Diethyl-2-hydroxymethylbenzamide (47). To a suspen-
sion of aluminum trichloride (12.67 g, 94.98 mmol) in dichloroethane
(40 mL) was added diethylamine (13.5 g, 182.7 mmol) in
dichloroethane (20 mL) while the temperature was maintained
below 25 °C with an ice bath. After another 25 min at rt, phthalide
(10.00 g, 74.5 mmol) was added in three portions and formation of a
precipitate was observed. After 45 min, water and ice were added and
the mixture was stirred for 30 min and filtered through Celite. The
aqueous phase was extracted with dichloromethane. After drying the
combined organic phase over MgSO4 and filtering through a cotton
plug, the volatiles were removed in vacuo to give a residue, which was
purified by silica gel flash chromatography (dichloromethane−
methanol, 49:1 to 97:3 to 19:1) to give 47 as a crude orange oil
(12.92 g), which was used in the next step with no further purification;
1H NMR (400 MHz, CDCl3) δ 1.09 (3 H, t, J = 7.0 Hz), 1.28 (3 H, t, J
= 7.0 Hz), 3.24 (2 H, q, J = 7.0 Hz), 3.55 (1 H, t, J = 6.8 Hz), 3.58 (2
H, q, J = 7.0 Hz), 4.52 (2 H, d, J = 6.8 Hz), 7.24 (1 H, dd, J = 7.4, 1.5
(R)- or (S)- 4-(5-Ethylimidazol-1-yl)-3,3-dimethylisochroman-
1-one (12). To a solution of 51 (0.049 g, 0.173 mmol) in methanol (1
mL) was added Pd/C (10 wt %, 0.009 g, 0.009 mmol), and the flask
was flushed with hydrogen. The mixture was stirred under balloon
pressure. After 3 h, another portion of catalyst (0.009 g) was added.
N
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After 7 h, the mixture was filtered and concentrated in vacuo to give 4-
(5-ethylimidazol-1-yl)-3,3-dimethylisochroman-1-one as a white solid.
The racemate was resolved by chiral HPLC using the ChiralPak IA
column with a 9:1 hexanes−ethanol mobile phase to give 12 (60 mg,
44%) as a white solid; tR = 23.8 min (distomer tR = 34.3 min); ESI-MS
m/z 271.2 (M + H)+; 1H NMR (400 MHz, CD3OD) δ ppm 1.25 (s, 3
H), 1.43 (br s, 3 H), 1.56 (s, 3 H), 2.87 (br s, 2 H), 5.55 (br s, 1 H),
6.83 (s, 1 H), 7.17 (br s, 1 H), 7.45 (d, J = 7.6 Hz, 1 H), 7.67 (td, J =
7.6, 1.0 Hz, 1 H), 7.78 (td, J = 7.6, 1.3 Hz, 1 H), 8.24 (dd, J = 7.6, 1.0
Hz, 1 H).
acetone. Resolution of racemate was achieved by chiral HPLC using
the ChiralPak IA column with a 9:1 heptane−isopropanol mobile
phase to give 22 as a white solid; tR = 21.5 min (distomer tR = 14.8
1
min); ESI-MS m/z 299.1 (M + H)+; H NMR (400 MHz, CDCl3) δ
ppm 0.96 (t, J = 7.3 Hz, 3 H), 0.97 (t, J = 7.3 Hz, 3 H), 1.42 (t, J = 7.3
Hz, 3 H), 1.46 (masked, 1 H), 1.51 (dq, J = 14.6, 7.3 Hz, 1 H), 1.73
(dq, J = 14.6, 7.3 Hz, 1 H), 1.95 (dq, J = 14.8, 7.3 Hz, 1 H), 2.73 (q, J
= 7.3 Hz, 2 H), 5.16 (s, 1 H), 6.84 (s, 1 H), 7.18 (d, J = 7.3 Hz, 1 H),
7.24 (s, 1 H), 7.50−7.56 (m, 1 H), 7.61 (dt, J = 7.3, 1.3 Hz, 1 H), 8.23
(dd, J = 7.7, 1.4 Hz, 1 H).
N,N-Diethyl-2-[(1-hydroxycyclobutyl)-(5-iodoimidazol-1-yl)-
methyl]benzamide (75). To a solution of diisopropylamine (0.38 g,
3.76 mmol) in THF (25 mL) at −78 °C under nitrogen was added n-
BuLi (2.5 M in hexanes, 1.50 mL, 3.75 mmol), and the mixture was
warmed to 0 °C. After 15 min, the LDA solution was cooled to −78
°C and a solution of 48 (1.00 g, 2.51 mmol) in THF (5 mL) was
added over 10 min. Fifteen minutes after the end of addition,
cyclobutanone (0.90 g, 12.53 mmol) in THF (2 mL) was added to the
brown solution. After 1.5 h, 10% acetic acid in water was added. The
organic phase was washed with saturated aqueous sodium bicarbonate,
and the combined organic phase was dried over MgSO4, filtered
through a cotton plug, and concentrated in vacuo. The residue was
purified by silica gel flash chromatography (elution with dichloro-
methane−methanol, 49:1 to 97:3) to afford 75 as a crude product
which was used in the next step with no further purification; ESI-MS
m/z 454.2 (M + H).
[4-(5-Iodoimidazol-1-yl)isochroman-1-one]-3-spirocyclobu-
tane (76). Dioxane (12 mL) and aqueous KOH (9 mmol) were added
to crude 75 (0.61 g), and the mixture was heated to 60 °C. After 30 h,
the mixture was cooled to 0 °C and acidified to pH 1 with conc HCl,
and the mixture was heated to 65 °C. After 16 h, the mixture was
diluted with ethyl acetate and washed with saturated aqueous sodium
bicarbonate, water, and brine. The combined aqueous phase was back-
extracted twice with ethyl acetate, and the combined organic phase was
dried over magnesium sulfate and filtered through a cotton plug.
Concentration in vacuo gave a residue which was purified by silica gel
flash chromatography (methylene chloride−methanol, 49:1) to give,
after trituration with chloroform, 76 (0.31 g, 32%, 2 steps) as a pale
yellow foam; ESI-MS m/z 381.0 (M + H).
[4-(5-Vinylimidazol-1-yl)isochroman-1-one]-3-spirocyclobu-
tane (77). DMF (5 mL) was added to 76 (0.31 g, 0.77 mmol),
tributylvinyltin (0.46 g, 1.39 mmol), Pd2dba3.CHCl3 (0.016 g, 0.015
mmol), and triphenylphosphine (0.016 g, 0.062 mmol) under
nitrogen. The mixture was heated to 90 °C. After 6 h, the mixture
was cooled down, diluted with isopropyl acetate, and washed twice
with water and brine. The combined organic phase was dried over
magnesium sulfate and filtered through a cotton plug. The residue was
purified by silica gel flash chromatography (10 wt % KF in silica gel,
elution with dichloromethane−methanol, 49:1) to give 77 (0.195 g,
90%) as a pale yellow solid; ESI-MS m/z 281.2 (M + H).
(R)- or (S)-[4-(5-Ethylimidazol-1-yl)isochroman-1-one]-3-spi-
rocyclobutane (23). To a solution of 77 (0.193 g, 0.654 mmol) in
methanol (4 mL) was added Pd/C (10 wt %, 0.035 g, 0.033 mmol),
and the flask was flushed with hydrogen. The mixture was stirred
under balloon pressure. After 3.5 h, the mixture was filtered and
concentrated in vacuo. The residue was purified by silica gel flash
chromatography (elution with dichloromethane−methanol, 49:1) to
give [4-(5-ethylimidazol-1-yl)isochroman-1-one]-3-spirocyclobutane
(0.165 g, 89%). The racemate was resolved by chiral HPLC using
the ChiralPak IA column with a 4:1 heptane−isopropanol mobile
phase to give 23 as a faint yellow solid; tR = 36.0 min (distomer tR =
15.0 min); mp 178−179 °C; ESI-MS m/z 283.1 (M + H)+; 1H NMR
(400 MHz, CDCl3) δ ppm 1.43 (t, J = 7.5 Hz, 3 H), 1.68−1.80 (m, 1
H), 2.03−2.15 (m, 3 H), 2.36−2.47 (m, 2 H), 2.71−2.86 (m, 2 H),
5.29 (s, 1 H), 6.85 (d, J = 1.3 Hz, 1 H), 7.29−7.35 (m, 1 H), 7.31 (s, 1
H), 7.56 (td, J = 7.6, 1.3 Hz, 1 H), 7.64 (td, J = 7.6, 1.5 Hz, 1 H), 8.22
(dd, J = 7.7, 1.4 Hz, 1 H).
(R)- or (S)-[4-(5-Ethylimidazol-1-yl)isochroman-1-one]-3-spi-
rocyclopentane (24). Compound 24 was prepared from 48 using
the same sequence employed to prepare 12, using cyclopentanone
instead of acetone. Resolution of racemate was achieved by chiral
HPLC using the ChiralPak IA column with a 85:15 heptane−
isopropanol mobile phase to give 24 as a white solid; tR = 31.5 min
1
(distomer tR = 17.7 min); ESI-MS m/z 297.1 (M + H)+; H NMR
(400 MHz, CDCl3) δ ppm 1.39 (t, J = 7.5 Hz, 3 H), 1.61−2.05 (m, 8
H), 2.63−2.78 (m, 2 H), 5.12 (s, 1 H), 6.83 (d, J = 1.0 Hz, 1 H), 7.22
(d, J = 7.6 Hz, 1 H), 7.34 (s, 1 H), 7.54 (dt, J = 7.6, 1.3 Hz, 1 H), 7.61
(dt, J = 7.6, 1.3 Hz, 1 H), 8.22 (dd, J = 7.6, 1.3 Hz, 1 H).
[4-(5-Ethylimidazol-1-yl)isochroman-1-one]-3-spiro(4-tetra-
hydropyran) (25). Compound 25 was prepared from 48 using the
same sequence employed to prepare 12, using tetrahydropyran-4-one
1
instead of acetone. ESI-MS m/z 313.1 (M + H)+; H NMR (400
MHz, CDCl3) δ ppm 1.36−1.45 (m, 4 H), 1.64−1.72 (m, 1 H), 1.81−
1.89 (m, 2 H), 2.65−2.80 (m, 2 H), 3.79−3.95 (m, 4 H), 5.03 (s, 1 H),
6.86 (s, 1 H), 7.22 (br s, 1 H), 7.24 (d, J = 7.8 Hz, 1 H), 7.58 (dd, J =
7.6, 1.3 Hz, 1 H), 7.66 (dd, J = 7.3, 1.3 Hz, 1 H), 8.26 (dd, J = 7.7, 1.4
Hz, 1 H).
4-(5-Isopropenylimidazol-1-yl)-3,3-dimethylisochroman-1-
one (52). To a solution of 50 (0.700 g, 1.90 mmol) in NMP (5 mL)
was added tris(dibenzylideneacetone)dipalladium (0.196 g, 0.19
mmol) and trifuryl-2-ylphospane (0.066 g, 0.285 mmol). Tributyliso-
propenyltin (1.25g, 3.80 mmol) was added to the reaction mixture,
and it was heated to 90 °C for 24 h. The mixture was then allowed to
cool to room temperature, washed with water, and extracted with ethyl
acetate. The organic phase was dried over Na2SO4 and concentrated in
vacuo. The residue was purified by silica gel chromatography
(dichloromethane−methanol, 19:1) to give 52 (0.45 g, 84%) as a
white solid; ESI-MS m/z 283.0 (M + H)+; 1H NMR (400 MHz,
CD3OD) δ ppm 1.21 (s, 3 H), 1.50 (s, 3 H), 2.24 (br s, 3 H), 5.31 (br
s, 1 H), 5.56 (br s, 1 H), 5.73 (s, 1 H), 7.02 (br s, 1 H), 7.28 (br s, 1
H), 7.51 (d, J = 7.8 Hz, 1 H), 7.69 (td, J = 7.8, 1.0 Hz, 1 H), 7.81 (td, J
= 7.6, 1.3 Hz, 1 H), 8.25 (d, J = 7.8 Hz, 1 H).
(R)- or (S)-4-(5-Isopropylimidazol-1-yl)-3,3-dimethylisochro-
man-1-one (13). To a solution of 52 (0.225 g, 0.797 mmol) in
methanol (5 mL) was added 10% Pd/C (0.225 g). The reaction vessel
was flushed with hydrogen gas and stirred under balloon pressure for
72 h. The mixture was filtered and the filtrate concentrated in vacuo to
give a 4-(5-isopropylimidazol-1-yl)-3,3-dimethylisochroman-1-one
(0.210 g) as a yellow solid. Resolution of the racemate was achieved
by chiral HPLC using the ChiralPak IA column with a 9:1 heptane−
isopropanol mobile phase to give 13; tR = 13.7 min (distomer tR = 11.3
min); ESI-MS m/z 285.0 (M + H)+; 1H NMR (400 MHz, CD3OD) δ
ppm 1.24 (s, 3 H), 1.41 (d, J = 6.6 Hz, 3 H), 1.45 (d, J = 6.8 Hz, 3 H),
1.56 (s, 3 H), 3.23 (br s, 1 H), 5.60 (br s, 1 H), 6.88 (br s, 1 H), 7.15
(br s, 1 H), 7.44 (d, J = 7.3 Hz, 1 H), 7.68 (td, J = 7.6, 1.1 Hz, 1 H),
7.79 (td, J = 7.6, 1.3 Hz, 1 H), 8.25 (dd, J = 7.8, 1.3 Hz, 1 H).
2-Imidazol-1-ylmethylbenzonitrile (53a). To a solution of
imidazole (1.0 g, 14.6 mmol) in DMF (10 mL) was added sodium
hydride (60% wt in mineral oil, 0.887 g, 22.17 mmol) at room
temperature. The mixture was stirred for 30 min, whereupon 2-
cyanobenzyl bromide (2.87 g, 14.6 mmol) was added. After an
additional 30 min, water was added and the mixture was extracted with
ethyl acetate. The aqueous phase was poured into aqueous sodium
bicarbonate and extracted with dichloromethane. The combined
organic phase was dried over sodium sulfate, filtered, and concentrated
in vacuo to give a residue which was purified by silica gel
(R)- or (S)- 4-(5-Ethylimidazol-1-yl)-3,3-diethylisochroman-1-
one (22). Compound 22 was prepared from 48 following the same
sequence employed to prepare 12, using diethylketone instead of
O
DOI: 10.1021/acs.jmedchem.5b00407
J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
chromatography (dichloromethane−methanol, 19:1) to give 53a (1.1
g, 41%); ESI-MS m/z 184.3 (M + H).
2,2-Dimethylindan-1,3-dione (56). Potassium fluoride on Celite
(50% wt, 24 g, 210 mmol) was heated at 135 °C for 2 h under vacuum
(<20 Torr). The solid was then permitted to cool to room
temperature and placed under a nitrogen atmosphere at which time
a solution of indan-1,3-dione (6.11 g, 42 mmol) in acetonitrile (60
mL) was added followed by iodomethane (7.9 mL, 126 mmol). The
reaction was heated in a sealed vessel at 70 °C overnight. The reaction
mixture was cooled to room temperature and filtered through a pad of
Celite. The resulting residue was purified by silica gel flash
chromatography (ethyl acetate−heptane, 0:1 to 1:9) to give 56
2-(2-Hydroxy-1-imidazol-1-yl-2-methylpropyl)benzonitrile
(54a). 53a (1.0 g, 5.49 mmol) was dissolved in THF (10 mL) and
cooled to −75 °C. LHMDS (1 M in THF, 8.24 mL, 8.24 mmol) was
added dropwise. Ten minutes after the end of addition, acetone (0.48
g, 8.24 mmol) was added. Thirty minutes after the end of addition,
saturated aqueous sodium bicarbonate (10 mL) was added and the
mixture was allowed to warm to rt, then poured into water. After
extraction with ethyl acetate, the organic phase was dried over Na2SO4
and concentrated in vacuo to give 54a (1.75 g), which was used in the
next step without further purification; ESI-MS m/z 242.1 (M + H).
(R)- or (S)-4-(Imidazol-1-yl)-3,3-dimethylisochroman-1-one
(11). Crude 54a (1.75 g) was dissolved in dioxane (15 mL) and water
(15 mL). Sulfuric acid (1.5 mL, 29.0 mmol) was added, and the
mixture was stirred at reflux for 2 h. After cooling down, the pH was
adjusted with solid sodium bicarbonate. The mixture was extracted
with ethyl acetate, and the combined organic phase was washed with
water, dried over Na2SO4 and concentrated in vacuo. The residue was
purified by silica gel chromatography (dichloromethane−methanol,
19:1) to give 4-(imidazol-1-yl)-3,3-dimethylisochroman-1-one (780
mg, 58%, 2 steps). Resolution of the racemate was achieved by chiral
HPLC using the ChiralPak AS-H column with a 9:1 heptane−ethanol
mobile phase to give 11; tR = 10.1 min (distomer tR = 16.6 min); ESI-
MS m/z 242.9 (M + H)+; 1H NMR (400 MHz, CD3OD) δ ppm 1.30
(s, 3 H), 1.53 (s, 3 H), 5.76 (s, 1 H), 6.98 (s, 1 H), 7.09 (s, 1 H), 7.52
(d, J = 7.6 Hz, 1 H), 7.64−7.73 (m, 1 H), 7.76−7.85 (m, 1 H), 7.89 (s,
1 H), 8.25 (dd, J = 7.7, 1.4 Hz, 1 H).
1
(6.11 g, 94%); H NMR (400 MHz, CDCl3) δ ppm 1.30 (s, 6 H),
7.84−7.89 (m, 2 H), 7.96−8.02 (m, 2 H).
3-Hydroxy-2,2-dimethylindan-1-one (57). To a solution of 56
(430 mg, 2.47 mmol) in ethanol (80 mL) at −30 °C was added a
solution of NaBH4 (29 mg, 0.74 mmol) in ethanol (3 mL). After 1 h
the reaction was quenched with saturated aqueous NH4Cl and the
mixture was brought to room temperature. The reaction mixture was
concentrated to approximately half of its original volume and then
diluted with ethyl acetate and washed with water. The aqueous layer
was then back-extracted twice with ethyl acetate. The organic layers
were combined, dried with Na2SO4, filtered, and concentrated. The
resulting residue was purified by silica gel flash chromatography (ethyl
acetate−heptane, 0:1 to 1:6) to afford 57 (320 mg, 74%); ESI-MS m/z
177.0 (M + H)+.
(R)- or (S)-3-Imidazol-1-yl-2,2-dimethylindan-1-one (31). To
a solution of trifluoromethansulfonic anhydride (1.13 mL, 6.75 mmol)
in dichloromethane (10 mL) at −78 °C was added, via cannula, a
solution of diisopropylethylamine (1.8 mL, 10.1 mmol) and 57 (400
mg, 2.25 mmol) in dichloromethane (5 mL). The reaction was stirred
at −78 °C for 10 min and then was placed at −10 °C for 10 min. The
reaction was then recooled to −78 °C, and a solution of imidazole
(920 mg, 13.5 mmol) in dichloromethane (12 mL) was added via
cannula. The reaction was then placed at room temperature for 1 h, at
which time it was diluted with saturated aqueous NaHCO3 and ethyl
acetate. The layers were separated and the aqueous layer was extracted
twice with ethyl acetate. The combined organic layers were dried with
MgSO4, filtered, and concentrated. The resulting residue was purified
by silica gel flash chromatography (ethyl acetate−dichloromethane, 1:3
to 1:0) to afford 3-imidazol-1-yl-2,2-dimethylindan-1-one (318 mg,
62%). The resolution of the racemate was achieved by chiral HPLC
using a ChiralPak IA column with 4:1 heptane−ethanol to give 31; tR
= 5.8 min (other enantiomer tR = 7.7 min); ESI-MS m/z 227 (M +
H)+; 1H NMR (400 MHz, CDCl3) δ ppm 0.80 (s, 3 H), 1.41 (s, 3 H),
5.52 (s, 1 H), 6.73 (s, 1 H), 7.12 (s, 1 H), 7.51 (d, J = 7.6 Hz, 1 H),
7.56 (s, 1 H), 7.62 (t, J = 7.5 Hz, 1 H), 7.70−7.80 (m, 1 H), 7.91 (d, J
= 7.6 Hz, 1 H).
4-Imidazol-1-yl-3,3-dimethyl-3,4-dihydro-2H-isoquinolin-1-
one (60). To a solution of racemic 31 (350 mg, 1.55 mmol) in
methanol (19 mL) were added pyridine (1.6 mL, 19.6 mmol) and then
hydroxylamine hydrochloride (270 mg, 3.9 mmol). The reaction was
stirred at 55 °C for 14 h and then cooled to room temperature. The
reaction was concentrated in vacuo to approximately half of the
original volume. The mixture was then diluted with ethyl acetate and
50% saturated aqueous NaCl. The layers were separated, and the
aqueous layer was extracted two additional times with ethyl acetate.
The organic layers were combined, dried over Na2SO4, filtered, and
concentrated. The resulting residue was dissolved in pyridine (10 mL)
and placed at 0 °C. DMAP (6 mg, 0.05 mmol) and p-toluenesulfonyl
chloride (615 mg, 3.22 mmol) were added, and the mixture was stirred
at room temperature for 1 h. The reaction was then warmed to 50 °C
and stirred for 14 h. The reaction was then cooled to room
temperature, diluted with saturated aqueous NaHCO3 and ethyl
acetate. The layers were separated, and the organic layer was washed
with brine, dried over Na2SO4, filtered, and concentrated. From the
resulting residue 293 mg was dissolved in pyridine (11 mL) and
heated by microwave irradiation at 190 °C for 35 min in a sealed
vessel. The reaction was cooled to room temperature, quenched with
saturated aqueous NaHCO3, and diluted with ethyl acetate. The
mixture was then dried with Na2SO4, filtered, and concentrated. The
resulting residue was purified by silica gel flash chromatography
(R)- or (S)-7-Fluoro-4-imidazol-1-yl-3,3-dimethyl-
isochroman-1-one (26). Compound 26 was prepared following
the same procedure as 11, using 2-cyano-4-fluorobenzyl bromide
instead of 2-cyanobenzyl bromide. Resolution of the racemate was
achieved by chiral HPLC using the Chiralcel OD column with a 9:1
hexanes−ethanol mobile phase to give 26; tR = 13.6 min (distomer tR
1
= 17.4 min); ESI-MS m/z 261.3 (M + H)+; H NMR (400 MHz,
CD3OD) δ ppm 1.28 (s, 3 H), 1.53 (s, 3 H), 5.74 (s, 1 H), 6.91 (s, 1
H), 7.03 (s, 1 H), 7.43−7.61 (m, 2 H), 7.77 (s, 1 H), 7.93 (dd, J = 8.3,
2.3 Hz, 1 H).
(3R,4R)- or (3S,4S)-4-Imidazol-1-yl-3-phenylisochroman-1-
one (39) and (3R,4S) and (3S,4R) Isomers. 53 (0.84 g, 4.36
mmol) was dissolved in THF (40 mL) and cooled to −78 °C.
LHMDS (1.0 M in THF, 15.2 mL, 15.2 mmol) was added, followed
after 10 min with benzaldehyde (2.10 g, 19.60 mmol). After 1 min, the
reaction was quenched with 1 M aqueous sodium hydrogen sulfate.
The pH was adjusted to 12 with 4 M aqueous sodium hydroxide and
extracted with ethyl acetate. The organic phase was dried over MgSO4
and concentrated in vacuo to give a residue, which was purified by
silica gel flash chromatography (dichloromethane−methanol, 1:0 to
23:1 gradient) to give after concentration of the fractions a yellow
residue (1.40 g), which was redissolved in dioxane (40 mL). 10 M
aqueous H2SO4 (2.2 mL, 22 mmol) was added. The mixture was
heated to 90 °C. After overnight stirring, the mixture was diluted with
ethyl acetate and washed with saturated aqueous bicarbonate and
brine. The organic phase was dried over MgSO4 and concentrated in
vacuo to give a gum (1.12 g). Purification and resolution of the four
isomers of 4-imidazol-1-yl-3-phenylisochroman-1-one was achieved by
chiral HPLC using the ChiralPak OD-RH column with a 7:3 heptane−
ethanol mobile phase to give 39 (0.131 g, 10%); tR = 14.0 min
(distomer tR = 16.7 min); ESI-MS m/z 291.0 (M + H); 1H NMR (400
MHz, DMSO-d6) δ ppm 6.06 (d, J = 2.9 Hz, 1 H), 6.29 (d, J = 2.9 Hz,
1 H), 6.59 (s, 1 H), 6.72 (s, 1 H), 7.09 (s, 1 H), 7.16−7.22 (m, 2 H),
7.28−7.34 (m, 3 H), 7.60 (d, J = 7.1 Hz, 1 H), 7.71 (td, J = 7.7, 1.3 Hz,
1 H), 7.81 (td, J = 7.6, 1.5 Hz, 1 H), 8.19 (dd, J = 7.8, 1.3 Hz, 1 H).
The two enantiomers of the trans diastereomer eluted as third (tR =
23.2 min) and fourth peaks (tR = 43.2 min); ESI-MS m/z 291.0 (M +
1
H); H NMR (400 MHz, DMSO-d6) δ ppm 6.19 (d, J = 10.5 Hz, 1
H), 6.36 (d, J = 10.5 Hz, 1 H), 6.70 (d, J = 7.8 Hz, 1 H), 6.91 (s, 1 H),
7.19 (t, J = 1.3 Hz, 1 H), 7.30−7.36 (m, 3 H), 7.37−7.44 (m, 2 H),
7.56−7.64 (m, 2 H), 7.72 (td, J = 7.6, 1.4 Hz, 1 H), 8.10 (dd, J = 7.7,
1.1 Hz, 1 H).
P
DOI: 10.1021/acs.jmedchem.5b00407
J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
(methanol−dichloromethane, 0:1 to 1:10) to provide 60 (47 mg,
27%) (52% BORSM); HRESI-MS m/z 242.1293 [(M + H)+, calcd for
C14H16N3O, 242.1293]; H NMR (400 MHz, CDCl3) δ ppm 1.15 (s,
3 H), 1.40 (s, 3 H), 5.09 (s, 1 H), 5.73 (br s, 1 H), 6.82 (s, 1 H), 7.04
(s, 1 H), 7.21−7.26 (m, 1 H), 7.50−7.60 (m, 3 H), 8.17−8.26 (m, 1
H).
215.1187 [(M + H)+, calcd for C13H14N2O, 215.1184]. The HCl salt
of 29 was prepared by dissolution in diethyl ether, followed by
treatment with an excess of 1 N HCl in diethyl ether and removal of
the volatiles in vacuo; 1H NMR (400 MHz, CD3OD) δ ppm 1.17 (s, 3
H), 1.55 (s, 3 H), 5.90 (s, 1 H), 6.99 (d, J = 8.08 Hz, 1 H), 7.06 (t, J =
7.58 Hz, 1 H), 7.25 (s, 1 H), 7.40 (d, J = 7.58 Hz, 1 H), 7.42−7.49 (m,
1 H), 7.59 (s, 1 H), 8.81 (s, 1 H).
1
(R)- or (S)-4-Imidazol-1-yl-2,3,3-trimethyl-3,4-dihydro-2H-
isoquinolin-1-one (27). To a solution of 60 (140 mg, 0.58 mmol)
in DMF (8 mL) at −10 °C was added NaH (60% dispersion in oil, 30
mg, 0.75 mmol). After 10 min, the reaction was warmed to room
temperature for 5 min and then recooled to −10 °C. The reaction was
then charged with methyl iodide (0.075 mL, 1.2 mmol) and placed at
room temperature. After 20 min, the reaction was cooled to −10 °C,
quenched with saturated aqueous NH4Cl, and diluted with saturated
aqueous NaHCO3 and ethyl acetate. The layers were separated, and
the aqueous layer was extracted two times with ethyl acetate. The
combined organic layers were dried over Na2SO4, filtered, and
concentrated. The resulting residue was purified by silica gel flash
chromatography (methanol−dichloromethane, 0:1 to 1:12) to afford
4-imidazol-1-yl-2,3,3-trimethyl-3,4-dihydro-2H-isoquinolin-1-one (110
mg, 75%). The resolution of the racemate was achieved by chiral
HPLC using a ChiralPak AS-H column with 85:15 heptanes−reagent
alcohol to give 27; tR = 10.9 min (distomer tR = 22.9 min); HRESI-MS
m/z 256.1448 [(M + H)+, calcd for C15H18N3O, 256.1450]; 1H NMR
(400 MHz, CDCl3) δ ppm 1.22 (s, 3 H), 1.33 (s, 3 H), 3.09 (s, 3 H),
5.01 (s, 1 H), 6.78 (s, 1 H), 7.02 (s, 1 H), 7.20 (d, J = 3.8 Hz, 1 H),
7.47−7.57 (m, 3 H), 8.20−8.28 (m, 1 H).
(R)- or (S)-4-Imidazol-1-yl-3,3-dimethyl-3,4-dihydro-1H-qui-
nolin-2-one (28). 1-Methoxy-1-(trimethylsiloxy)-2-methyl-1-propene
(10.4 g, 60 mmol) was added to a suspension of 2-nitrobenzaldehyde
(6.0 g, 40 mmol), scandium(III) trifluoromethanesulfonate (1.0 g, 2.0
mmol) in DCM (150 mL) at −78 °C. The resulting mixture was
warmed to 0 °C over 3 h, quenched with 1 M aqueous HCl, and
stirred at room temperature for 1 h. The mixture was extracted with
ethyl acetate, and the combined organic fraction was washed with
brine, dried over Na2SO4. After filtration and evaporation, the residue
was purified by silica gel flash chromatography to give a yellow oil (7.0
g). A portion (6.55 g) was redissolved in methanol (100 mL).
Palladium on carbon (10%, 650 mg) was added, and the mixture was
stirred for 5 h under hydrogen at balloon pressure. The mixture was
then filtered through a pad of Celite, which was washed with
methanol. After concentration the residue was washed with ether to
give a solid (4.23 g). A portion (0.20 g, 1.06 mmol) and CDI (0.20 g,
1.27 mmol) were dissolved in acetonitrile (4 mL) and heated to reflux
for 3 h. Two additional portions of CDI (69 mg, 0.43 mmol) were
added. After another 2 h, the solvent was removed in vacuo. The
residue was taken up in dichloromethane and washed with water. The
organic phase was dried over Na2SO4. After filtration and evaporation,
the residue was purified by silica gel flash chromatography (dichloro-
methane−methanol, 1:0 to 97:3) to give a colorless solid (0.12 g,
46%). The resolution of the racemate was achieved by chiral HPLC
using a ChiralPak AS-H column with 9:1 heptane−ethanol to give 28;
tR = 18.4 min (distomer tR = 22.5 min); ESI-MS m/z 242.1288 [(M +
H)+, calcd for C14H15N3O, 242.1293]; 1H NMR (400 MHz, CD3OD)
δ ppm 7.70 (s, 1 H), 7.37 (t, J = 8.0 Hz, 1 H), 7.31 (d, J = 8.0 Hz, 1
H), 7.10−7.03 (m, 2H), 6.95 (s, 2 H), 5.30 (s, 1 H), 1.26 (s, 3 H),
1.02 (s, 3 H).
(R)- and (S)-1-(2,2-Dimethylindan-1-yl)-1H-imidazole (32).
Compound 32 was prepared using the same procedure as 29. Starting
from 63 (1.0 g, 6.16 mmol), 1-(2,2-dimethylindan-1-yl)-1H-imidazole
(0.82 g, 63%) was obtained. Resolution of the racemate was achieved
by chiral HPLC using a ChiralPak IA column with 1:4 isopropanol−
heptane to give 32; tR = 13.7 min (distomer tR = 15.9 min); ESI-MS
m/z 213.2 (M + H)+; 1H NMR (400 MHz, CDCl3) δ ppm 0.75 (s, 3
H), 1.28 (s, 3 H), 2.70−3.03 (m, 2 H), 5.19 (s, 1 H), 6.73 (s, 1 H),
7.07 (s, 1 H), 7.15−7.38 (m, 4 H), 7.46 (s, 1 H);
3-(2,2-Dimethyl-3-oxoindan-1-yl)-3H-imidazole-4-carboxylic
Acid Methyl Ester (66). To a solution of 57 (3.22 g, 18.3 mmol) in
THF (40 mL) were added methyl 4-imidazolecarboxylate (3.22 g, 21.9
mmol) and triphenylphosphine (3.56 g, 13.6 mmol) .The reaction was
cooled to 0 °C, and di-tert-butyl azodicarboxylate (5.74 g, 21.9 mmol)
was added. The reaction was placed at room temperature and
permitted to stir for 3 h. The reaction mixture was cooled to 0 °C and
quenched with 4 N HCl in dioxane and stirred for 30 min. The
reaction was concentrated to near dryness and diluted with ethyl
acetate. The organic layer was extracted three times with 1 N aqueous
HCl. The aqueous extracts were combined, neutralized with Na2CO3,
and extracted three times with ethyl acetate. The combined organic
layers were dried with Na2SO4, filtered, and concentrated. The
resulting residue was purified by silica gel flash chromatography (ethyl
acetate−dichloromethane, 0:1 to 3:7) to furnish 66 (4.02 g, 77%);
ESI-MS m/z 285.1246 [(M + H)+, calcd for C16H16N2O3, 285.1239];
1H NMR (400 MHz, CDCl3) δ ppm 0.82 (s, 3 H), 1.46 (s, 3 H), 4.02
(s, 3 H), 6.70 (s, 1 H), 7.39 (s, 1 H), 7.47−7.52 (m, 1 H), 7.72 (t, J =
7.45 Hz, 1 H), 7.79−7.86 (m, 1 H), 7.93−7.99 (m, 2 H).
cis- and trans-3-(5-Hydroxymethylimidazol-1-yl)-2,2-dime-
thylindan-1-ol (68). To a solution of 66 (4.02 g, 14.1 mmol) in THF
(200 mL) at 0 °C was added LiAlH4 (800 mg, 21.2 mmol). The
reaction was permitted to stir for 30 min, at which time it was
quenched at 0 °C by the consecutive addition of 9:1 THF−H2O (12
mL), 2 M aqueous NaOH (15 mL), and H2O (9 mL). The reaction
was warmed to room temperature and diluted with THF (100 mL).
After addition of MgSO4 (20 g), the heterogeneous mixture was stirred
for 15 min and then filtered through a pad of Celite. The pad of Celite
was washed with ethyl acetate and the combined filtrate was
concentrated to afford an approximately 5.5:1 diastereomeric mixture
of 68 (3.8 g) which was used with no further purification; ESI-MS m/z
1
259.0 (M + H)+; H NMR (400 MHz, CD3OD) major diastereomer,
δ ppm 0.77 (s, 3 H), 1.25 (s, 3 H), 4.69 (s, 1 H), 4.73 (s, 2 H), 5.43 (s,
1 H), 6.96 (br s, 1 H), 7.18 (d, J = 7.6 Hz, 1 H), 7.30−7.57 (m, 4 H);
minor diastereomer, δ ppm 0.82 (s, 3 H), 1.14 (s, 3 H), 4.73 (s, 2 H),
4.97 (s, 1 H), 5.59 (s, 1 H), 6.96 (br s, 1 H), 7.23 (d, J = 7.3 Hz, 1 H),
7.31−7.57 (m, 4 H).
3-[5-(tert-Butyldimethylsilanyloxymethyl)imidazol-1-yl]-2,2-
dimethylindan-1-one (70). To a solution of 68 (3.8 g, 14.1 mmol)
in DMF (150 mL) was added imidazole (1.05 g, 15.5 mmol), and the
reaction was cooled to −20 °C. Then a solution of tert-
butyldimethylsilyl chloride (2.12 g, 14.1 mmol) in DMF (10 mL)
was added. The reaction was allowed to warm to room temperature
overnight. The next morning the reaction was concentrated to near
dryness and diluted with water and ethyl acetate. The layers were
separated, and the aqueous layer was extracted with ethyl acetate. The
organic layers were combined, dried with Na2SO4, filtered, and
concentrated to give 3-[5-(tert-butyldimethylsilanyloxymethyl)-
imidazol-1-yl]-2,2-dimethylindan-1-ol (6.8 g), which was taken up in
1,4-dioxane (120 ml), and manganese(IV) oxide (24.5 g, 282 mmol)
was added. The reaction was then heated at 100 °C for 1 h, cooled to
room temperature, filtered, and concentrated. The residue was purified
by silica gel chromatography (ethyl acetate−dichloromethane, 0:1 to
1:0) to afford 70 (4.35 g, 83%); ESI-MS m/z 371.1 (M + H)+.
(R)- or (S)-1-(2,2-Dimethyl-2,3-dihydrobenzofuran-3-yl)-1H-
imidazole (29). To a solution of 64 (260 mg, 1.58 mmol) in
acetonitrile (5 mL) was added 1,1′-carbonyldiimidazole (310 mg, 1.90
mmol). The mixture was then heated at reflux overnight. The reaction
was cooled to room temperature and concentrated. The resulting
residue was dissolved in dichloromethane and washed with saturated
aqueous NaHCO3 and brine. The organic solution was dried with
Na2SO4, filtered, and concentrated. The resulting residue was purified
by silica gel flash chromatography (ethyl acetate−dichloromethane, 0:1
to 4:1) to furnish 1-(2,2-dimethyl-2,3-dihydrobenzofuran-3-yl)-1H-
imidazole (176 mg, 52%). Resolution of the racemate was achieved by
chiral HPLC using a ChiralPak IA column with 9:1 heptane−ethanol
to give 29; tR = 13.0 min (distomer tR = 15.0 min); HRESI-MS m/z
Q
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(R)- or (S)- 3-(5-Hydroxymethylimidazol-1-yl)-2,2-dimethyl-
indan-1-one (33). To 70 (370 mg, 1 mmol) was added 4 N HCl in
1,4-dioxane (20 mL). The reaction was permitted to stir for 2 h, at
which time it was quenched with saturated aqueous NaHCO3 and
diluted with ethyl acetate. The layers were separated, and the aqueous
layer was extracted twice with ethyl acetate. The combined organic
layers were dried with Na2SO4, filtered, and concentrated. The
resulting residue was purified by silica gel flash chromatography
(methanol−dichloromethane, 0:1 to 1:20) to furnish 3-(5-
hydroxymethylimidazol-1-yl)-2,2-dimethylindan-1-one (150 mg,
58%). The resolution of the racemate was achieved by chiral HPLC
using a ChiralPak IA column with 85:15 heptane−ethanol to give 33;
tR = 13.6 min (distomer tR = 15.7 min); ESI-MS m/z 257.1295 [(M +
organic extracts were washed successively with 4 N aqueous HCl and
saturated aqueous NaHCO3, dried over Na2SO4, filtered, and
concentrated. The resulting residue was then diluted with ethanol
(10.0 mL) and cooled to −10 °C. The solution was then charged with
a solution of NaBH4 (100 mg, 2.63 mmol) in ethanol (6 mL). The
reaction was permitted to warm to room temperature over 1 h, at
which time additional NaBH4 (50 mg, 1.31 mmol) was added. The
reaction was permitted to stir for another 1.5 h and then diluted with
saturated aqueous NH4Cl. The reaction mixture was concentrated to
remove the organic volatiles and then extracted three times with ethyl
acetate. The organic extracts were combined, dried over Na2SO4,
filtered, and concentrated. The resulting residue was purified by silica
gel flash chromatography (ethyl acetate−heptane, 0:1 to 1:2) to give
73 (235 mg, 70%); ESI-MS m/z 237.17 (M−OH)+
3-(3-Acetoxy-7-chloro-2,2-dimethylindan-1-yl)-3H-imida-
zole-4-carboxylic Acid Methyl Ester (74). To a solution of 73
(1.55 g, 6.1 mmol) in THF (30 mL) were added methyl 4-
imidazolecarboxylate (1.53 g, 12.2 mmol) and triphenylphosphine (3.2
g, 12.2 mmol). The reaction was cooled to 0 °C, and di-tert-butyl
azodicarboxylate (2.81 g, 12.2 mmol) was added. The reaction was
placed at room temperature and permitted to stir for 12 h and then
was heated to 40 °C for 1.5 h. The reaction mixture was cooled to 0
°C, quenched with 4 N HCl in dioxane (20 mL, 80 mmol), and stirred
for 30 min. The reaction was concentrated to near dryness and diluted
with ethyl acetate. The organic layer was extracted three times with 1
N aqueous HCl. The aqueous extracts were combined, neutralized
with Na2CO3, and extracted three times with ethyl acetate. The
combined organic layers were dried with Na2SO4, filtered, and
concentrated. The resulting residue was purified by silica gel flash
chromatography (ethyl acetate−dichloromethane, 0:1 to 1:3) to give
74 (1.4 g, 63%); ESI-MS m/z 332.04 (M + H)+.
(R)- or (S)- 4-Chloro-3-(5-hydroxymethylimidazol-1-yl)-2,2-
dimethylindan-1-one (35). To a solution of 74 (1.4 g, 3.86 mol) in
THF (30 mL) at 0 °C was added lithium aluminum hydride (290 mg,
7.71 mmol) in three portions. The reaction was permitted to stir for
30 min, at which time it was quenched at 0 °C by the consecutive
addition of 9:1 THF−H2O (4.0 mL), 2 M aqueous NaOH (4.5 mL),
and H2O (3.0 mL). The reaction was warmed to room temperature
and diluted with THF (30 mL). MgSO4 (4.5 g) was then added, and
the resulting heterogeneous mixture was stirred for 15 min and then
filtered through a pad of Celite. The pad of Celite was washed with
ethyl acetate, and the combined filtrate was concentrated. The
resulting residue was dissolved in DMF (30 mL) and cooled to 0 °C.
To the resulting solution was added imidazole (350 mg, 5.1 mmol)
followed by TBSCl (640 mg, 4.24 mmol). The reaction was placed at
room temperature and permitted to stir for ∼15 h. The reaction was
then quenched with ethanol, concentrated to near dryness, and diluted
with saturated aqueous NaHCO3 and ethyl acetate. The layers were
separated, and the aqueous layer was extracted with ethyl acetate. The
organic layers were combined, dried with Na2SO4, filtered, and
concentrated. The resulting residue was dissolved in 1,4-dioxane (30
mL), and manganese(IV) oxide (7.5 g, 75 mmol) was added. The
resulting heterogeneous solution was heated at 110 °C for 90 min,
cooled to room temperature, filtered, and concentrated. The resulting
residue was purified by silica gel flash chromatography (ethyl acetate−
heptane, 0:1 to 1:4) to afford 3-[5-(tert-butyldimethyl-
silanyloxymethyl)imidazol-1-yl]-4-chloro-2,2-dimethylindan-1-one;
ESI-MS m/z 405.11 (M + H)+. To a solution of 3-[5-(tert-
butyldimethylsilanyloxymethyl)imidazol-1-yl]-4-chloro-2,2-dimethyl-
indan-1-one (2.4 g, 5.9 mmol) in methanol (40 mL) was added a 4 N
solution of HCl in 1,4-dioxane (9 mL, 36 mmol). The reaction was
permitted to stir for 30 min, at which time the reaction was cooled to 0
°C and diluted with saturated aqueous NaHCO3. The reaction mixture
was then concentrated in vacuo to approximately one-fourth of the
original volume and diluted with ethyl acetate. The layers were
separated, and the aqueous layer was extracted two times with ethyl
acetate. The combined organic extracts were dried over Na2SO4,
filtered, and concentrated. The resulting residue was purified by silica
gel flash chromatography (methanol−dichloromethane, 0:1 to 1:19) to
give 4-chloro-3-(5-hydroxymethylimidazol-1-yl)-2,2-dimethylindan-1-
1
H)+, calcd for C15H17N2O2, 257.1290]; H NMR (400 MHz, CDCl3)
δ ppm 0.87 (s, 3 H), 1.46 (s, 3 H), 4.69−4.97 (m, 2 H), 5.93 (s, 1 H),
7.16 (s, 1 H), 7.19 (s, 1 H), 7.54 (d, J = 7.6 Hz, 1 H), 7.65 (t, J = 7.5
Hz, 1 H), 7.72−7.82 (m, 1 H), 7.93 (d, J = 7.6 Hz, 1 H).
(R)- or (S)- 6-Chloro-3-(5-hydroxymethylimidazol-1-yl)-2,2-
dimethylindan-1-one (34). To a solution of 67, which can be
prepared starting from 5-chloroindanone as described for 66 (740 mg,
2.3 mmol) in THF (25 mL) at 0 °C was added lithium aluminum
hydride (140 mg, 3.68 mmol) in three portions. The reaction was
permitted to stir for 30 min, at which time it was quenched at 0 °C by
the consecutive addition of 9:1 THF−H2O (2.0 mL), 2 M aqueous
NaOH (2.3 mL), and H2O (1.5 mL). The reaction was warmed to
room temperature and diluted with THF (15 mL). After addition of
MgSO4 (2.2 g), the heterogeneous mixture was stirred for 15 min and
then filtered through a pad of Celite. The pad of Celite was washed
with ethyl acetate, and the combined filtrate was concentrated. The
resulting residue was dissolved in DMF (25 mL) and cooled to 0 °C.
To the resulting solution was added imidazole (290 mg, 4.26 mmol)
followed by TBSCl (425 mg, 2.8 mmol). The reaction was placed at
room temperature and permitted to stir for 2.5 h. The reaction was
quenched with ethanol, concentrated to near dryness, and diluted with
saturated aqueous NaHCO3 and ethyl acetate. The layers were
separated, and the aqueous layer was extracted with ethyl acetate. The
organic layers were combined, dried with Na2SO4, filtered, and
concentrated. The resulting residue was purified by silica gel flash
chromatography (ethyl acetate−heptane, 1:4 to 1:0) to provide 3-[5-
(tert-butyldimethylsilanyloxymethyl)imidazol-1-yl]-6-chloro-2,2-
dimethylindan-1-ol as a diastereomeric mixture; ESI-MSm/z 407.2 (M
+ H)+. The alcohol (400 mg) was dissolved in 1,4-dioxane (15 mL),
and manganese(IV) oxide (2.0 g, 20 mmol) was added. The resulting
heterogeneous solution was heated at 80 °C for 60 min, cooled to
room temperature, filtered, and concentrated. The resulting residue
was then dissolved in methanol, cooled to 0 °C, and treated with 4 N
hydrochloric acid in 1,4-dioxane (1 mL, 4.0 mmol). The reaction was
placed at room temperature and permitted to stir for 3 h, at which
time the reaction was cooled to 0 °C and diluted with saturated
aqueous NaHCO3. The reaction mixture was then concentrated in
vacuo to approximately one-fourth of the original volume and diluted
with ethyl acetate. The layers were separated, and the aqueous layer
was extracted two times with ethyl acetate. The combined organic
extracts were dried over Na2SO4, filtered, and concentrated. The
resulting residue was purified by silica gel flash chromatography
(ethanol−ethyl acetate, 0:1 to 1:10) to furnish 6-chloro-3-(5-
hydroxymethylimidazol-1-yl)-2,2-dimethylindan-1-one (250 mg,
37%). Resolution of the racemate was achieved by chiral HPLC
using a ChiralPak IA column with 85:15 heptane−ethanol to give 34;
tR = 8.4 min (distomer tR = 13.0 min); ESI-MS m/z 291.0891 [(M +
H)+, calcd for C15H16N2O2Cl, 291.0900]; 1H NMR (400 MHz,
CDCl3) δ ppm 0.87 (s, 3 H), 1.44 (s, 3 H), 1.89 (br s, 1 H), 4.70−4.92
(m, 2 H), 5.75 (s, 1 H), 6.92 (s, 1 H), 7.07 (s, 1 H), 7.41 (d, J = 8.1
Hz, 1 H), 7.69 (dd, J = 8.3, 2.0 Hz, 1 H), 7.87 (d, J = 2.0 Hz, 1 H).
Acetic Acid 4-Chloro-3-hydroxy-2,2-dimethylindan-1-yl
Ester (73). To a solution of 7-chloro-3-hydroxy-2,2-dimethylindan-
1-one (287 mg, 1.36 mmol) in dichloromethane (15 mL) were added
pyridine (1.1 mL, 13.6 mmol) and acetic anhydride (0.26 mL, 2.72
mmol). The reaction was permitted to stir for 1 h and was then diluted
with water and extracted twice with dichloromethane. The combined
R
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Journal of Medicinal Chemistry
Article
one (1.34 g, 81%). Resolution of the racemate was achieved by chiral
HPLC using a ChiralPak IA column with 90:10 heptane−ethanol to
give 35; tR = 12.0 min (distomer tR = 18.2 min); HRESI-MS m/z
was removed. After 15 h, the mixture was concentrated and the
resulting residue was dissolved in ethyl acetate (250 mL) and was
extracted five times with 1 M aqueous HCl (40 mL portions). The
acidic aqueous phases were cooled to 0 °C, and the pH was adjusted to
∼12 with 4 M aqueous NaOH at 0 °C. The aqueous phase was then
extracted three times with dichloromethane. The combined organic
layers were dried over MgSO4 and filtered and concentrated. The
resulting residue was purified by silica gel flash chromatography
(dichloromethane−methanol, 49:1) to give 3-(2,2-dimethyl-4-oxo-
1,2,3,4-tetrahydronaphthalen-1-yl)-3H-imidazole-4-carboxylic acid
1
291.0909 [(M + H)+, calcd for C15H16N2O2Cl, 291.0909]; H NMR
(400 MHz, CD3OD) δ ppm 0.91 (s, 3 H), 1.40 (s, 3 H), 4.80 (d, J =
4.29 Hz, 2 H), 5.88 (s, 1 H), 6.89 (s, 1 H), 6.97 (s, 1 H), 7.69 (t, J =
7.71 Hz, 1 H), 7.79−7.87 (m, 2 H).
Acetic Acid 2,2-Dimethyl-1,2,3,4-tetrahydronaphthalen-1-yl
Ester (80). To a suspension of 60% NaH in an oil dispersion (20 g,
500 mmol) in THF (600 mL) at 0 °C was added a solution of α-
tetralone (24.8 g, 166.5 mmol) in THF (40 mL) via cannula, followed
by iodomethane (119 g, 833 mmol). The reaction was permitted to
warm to room temperature and after 1 h was quenched with 1 M
aqueous sodium bisulfate. The reaction mixture was partitioned
between water and ethyl acetate, and the organic layer was washed
with brine, dried over magnesium sulfate, filtered, and concentrated.
The resulting residue was then dissolved in methanol (600 mL) and
dichloromethane (100 mL). Sodium borohydride (37.8 g, 262 mmol)
was then added in five portions over 20 min. After 1 h the reaction was
diluted with water, and the organic solvents were then evaporated in
vacuo. The resulting mixture was extracted with ethyl acetate, and the
organic extract was dried with magnesium sulfate, filtered, and
concentrated. The resulting residue was then dissolved in dichloro-
methane (300 mL). To the resulting solution was added triethylamine
(50 g, 490 mmol) and 4-dimethylaminopyridine (4 g, 33 mmol). The
reaction was cooled to 0 °C and charged with acetic anhydride (42 g,
408 mmol). The reaction was permitted to stir for 10 min, then was
diluted with ethyl acetate and washed with 1 M aqueous NaHSO4,
followed by saturated aqueous NaHCO3. The organic phase was dried
with magnesium sulfate, filtered, and concentrated. The resulting oil
was then purified by distillation (110 °C at 0.2 Torr) to give 80 (34.6
g, 95%); 1H NMR (400 MHz, CDCl3) δ ppm 0.95 (s, 3 H), 1.01 (s, 3
H), 1.50−1.63 (m, 1 H), 1.84−1.99 (m, 1 H), 2.10 (s, 3 H), 2.76−2.94
(m, 2 H), 5.74 (s, 1 H), 7.08−7.31 (m, 4 H).
1
methyl ester; ESI-MS m/z 299.0 (M + H)+; H NMR (400 MHz,
CDCl3) δ ppm 0.97 (s, 3 H), 1.15 (s, 3 H), 2.63 (d, J = 16.8 Hz, 1 H),
2.74 (d, J = 16.8 Hz, 1 H), 3.93 (s, 3 H), 6.79 (s, 1 H), 7.02 (d, J = 7.6
Hz, 1 H), 7.35 (s, 1 H), 7.47 (t, J = 7.6 Hz, 1 H), 7.55 (td, J = 7.6, 1.5
Hz, 1 H), 7.86 (s, 1 H), 8.13 (dd, J = 7.6, 1.5 Hz, 1 H). Resolution of
racemic 65 was achieved by chiral HPLC using ChiralPak IA at 14
mL/min using heptane−reagent alcohol, 7:3, to give enantiomer A
(14.7 min) (0.53 g, 18%) and enantiomer B (21.1 min) (0.53 g, 18%)
as white crystalline powders.
(1R)- or (1S)-3-(trans-4-Hydroxy-2,2-dimethyl-1,2,3,4-
tetrahydronaphthalen-r-1-yl)-3H-imidazole-4-carboxylic Acid
Methyl Ester (30) and (1R)- or (1S)-3-(cis-4-Hydroxy-2,2-
dimethyl-1,2,3,4-tetrahydronaphthalen-r-1-yl)-3H-imidazole-
4-carboxylic Acid Methyl Ester (83). To a solution of 65
(enantiomer A, 0.130 g, 0.431 mmol) in methanol (4 mL) at 0 °C
was added NaBH4 (0.025 g, 0.647 mmol). After 10 min, aqueous
buffer, pH 7, was added and the mixture was extracted with
dichloromethane. The organic phase was dried over magnesium
sulfate and filtered through a cotton plug to give a residue, which was
purified by silica gel flash chromatography (dichloromethane−
methanol, 99:1 to 49:1) to give 30 (18 mg, 14%) as a white solid
and 83 (12 mg, 10%) as a white solid.
30: ESI-MS m/z 301.0 (M + H)+; 1H NMR (400 MHz, MeOD) δ
ppm 0.95 (s, 3 H), 1.09 (s, 3 H), 1.87 (dd, J = 13.5, 8.7 Hz, 1 H), 2.19
(dd, J = 13.5, 5.9 Hz, 1 H), 3.94 (s, 3 H), 5.01 (dd, J = 8.7, 5.9 Hz, 1
H), 6.63 (s, 1 H), 6.70 (d, J = 7.6 Hz, 1 H), 7.26 (t, J = 7.6 Hz, 1 H),
7.39 (t, J = 7.6 Hz, 1 H), 7.55 (s, 1 H), 7.69 (d, J = 7.6 Hz, 1 H), 7.83
(d, J = 1.0 Hz, 1 H).
Acetic Acid 2,2-Dimethyl-4-oxo-1,2,3,4-tetrahydronaphtha-
len-1-yl Ester (81). To a solution of 80 (380 mg, 1.71 mmol) in 1,2-
dichloroethane (7 mL) was added dirhodium(II) tetrakis-
(caprolactam) [Rh2(cap)4, CAS no. 138984-26-6] (15 mg, 0.017
mmol) followed by a 5.5 M decane solution of tert-butyl hydro-
peroxide [TBHP] (3.1 mL, 17.1 mmol). The reaction mixture was
placed at 40 °C. After 4 h the reaction was charged with additional
Rh2(cap)4 (7.5 mg, 0.008 mmol) and TBHP (1.55 mL, 8.53 mmol).
After stirring at 40 °C for an additional 20 h, the reaction mixture was
charged again with Rh2(cap)4 (7.5 mg, 0.008 mmol) and TBHP (1.55
mL, 8.53 mmol). After a total of 48 h the reaction was cooled to room
temperature, diluted with water, and extracted twice with dichloro-
methane. The organic extracts were then treated with 1.6 M aqueous
FeSO4, and the resulting biphasic solution was permitted to stir for 30
min, at which time the layers were separated and the organic layer was
dried with magnesium sulfate, filtered, and concentrated. The resulting
residue was purified by silica gel flash chromatography (ethyl acetate−
hexanes, 1:9 to 1:4) to provide 81 (0.32 g, 81%); 1H NMR (400 MHz,
CDCl3) δ ppm 1.04 (s, 3 H), 1.09 (s, 3 H), 2.14 (s, 3 H), 2.45−2.53
(m, 1 H), 2.85 (d, J = 17.2 Hz, 1 H), 5.94 (s, 1 H), 7.38−7.49 (m, 2
H), 7.54−7.64 (m, 1 H), 8.05 (dd, J = 7.7, 1.4 Hz, 1 H).
83: ESI-MS m/z 301.0 (M + H)+; 1H NMR (400 MHz, MeOD) δ
ppm 0.77 (s, 3 H), 1.18 (s, 3 H), 1.82 (dd, J = 13.9, 10.4 Hz, 1 H),
1.95 (dd, J = 13.9, 6.8 Hz, 1 H), 3.97 (s, 3 H), 6.32 (s, 1 H), 7.08 (d, J
= 7.6 Hz, 1 H), 7.30 (t, J = 7.6 Hz, 1 H), 7.44 (t, J = 7.6 Hz, 1 H), 7.49
(s, 1 H), 7.75 (s, 1 H), 7.78 (d, J = 7.6 Hz, 1 H).
(R)- and (S)-3-(2,2-Dimethyl-1,2,3,4-tetrahydronaphthalen-
1-yl)-3H-imidazole-4-carboxylic Acid Methyl Ester (2). Reso-
lution of racemic 2 (which was obtained from the Novartis compound
collection) was achieved by chiral HPLC using a ChiralPak IA column
with a 1:4 ethyl acetate−hexanes mobile phase to provide 2E; tR =12.7
1
min (distomer tR = 14.8 min); ESI-MS m/z 285.1; (M + H)+. H
NMR (400 MHz, CD3OD) of the HNO3 salt: δ ppm 0.87 (s, 3 H),
1.17 (s, 3 H), 1.67−1.74 (m, 1 H), 1.80−1.88 (m, 1 H), 2.97−3.15
(m, 2 H), 4.06 (s, 3 H), 6.57 (s, 1 H), 7.09 (d, J = 7.8 Hz, 1 H), 7.22−
7.26 (m, 1 H), 7.32−7.40 (m, 2 H), 8.32 (d, J = 1.3 Hz, 1 H), 8.61 (s,
1 H).
(R)- or (S)-3-(2,2-Dimethyl-4-oxo-1,2,3,4-tetrahydronaphtha-
len-1-yl)-3H-imidazole-4-carboxylic Acid Methyl Ester (65). To
a solution of 81 (4.03 g, 16.7 mmol) in methanol (50 mL) and
dichloromethane (10 mL) was added potassium carbonate (2.33 g,
16.66 mmol). The reaction was permitted to stir for 8 h at which time
it was diluted with ethyl acetate, and the resulting solution was washed
successively with water and brine. The aqueous phases were then back-
extracted with dichloromethane and the organic phases were then
combined, dried over magnesium sulfate, filtered, and concentrated to
furnish 4-hydroxy-3,3-dimethyl-3,4-dihydro-2H-naphthalen-1-one,
which was used in the next step with no further purification. To a
portion (2.87 g, 13.88 mmol) and methyl 4-imidazolecarboxylate (1.25
g, 9.72 mmol) in THF (80 mL) at 0 °C were added
triphenylphosphine (3.68 g, 13.88 mmol) and dimethyl azodicarbox-
ylate (40% in toluene, 5.14 mL, 13.88 mmol), and the cooling bath
ASSOCIATED CONTENT
■
S
* Supporting Information
Solubility and permeability data for compounds 2E, 5E, 11, 12,
16, 26, and 28−30; experimental procedures for the synthesis
of 63, 64, and 79. The Supporting Information is available free
of charge on the ACS Publications website at DOI: 10.1021/
acs.jmedchem.5b00407.
AUTHOR INFORMATION
■
Corresponding Author
*Phone: +1 617 871 7653. E-mail: julien.papillon@novartis.
com.
S
DOI: 10.1021/acs.jmedchem.5b00407
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Journal of Medicinal Chemistry
Article
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hypertension: Diagnosis, evaluation, and treatment. A scientific
statement from the American Heart Association Professional
Education Committee of the Council for High Blood Pressure
Research. Hypertension 2008, 51, 1403−1419.
Present Addresses
§C.L.: Honigman Miller Schwartz and Cohn LLP, Kalamazoo,
MI 49007.
∥E.G.: AstraZeneca R&D, Waltham, MA 02451.
⊥M.L: Thermo Fisher Scientific, Cambridge, MA 02139.
#S.A.S.: Epizyme, Cambridge, MA 02139.
Notes
The authors declare no competing financial interest.
∞S.R., A.Y.J., and W.M.M. retired.
○G.M.K.: Deceased.
(8) Daugherty, S. L.; Powers, J. D.; Magid, D. J.; Tavel, H. M.;
Masoudi, F. A.; Margolis, K. L.; O’Connor, P. J.; Selby, J. V.; Ho, P. M.
Incidence and prognosis of resistant hypertension in hypertensive
patients. Circulation 2012, 125, 1635−1642.
ACKNOWLEDGMENTS
■
We gratefully acknowledge the contribution of Dr. Trixie
Wagner, who determined the absolute configuration of 16 from
X-ray crystallography experiments.
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ABBREVIATIONS USED
■
Ac, acetyl; Tr, trityl; DMF, dimethylformamide; TBS, tert-
butyldimethylsilyl; DMAP, 4-dimethylaminopyridine; LHMDS,
lithium hexamethyldisilazide; THF, tetrahydrofuran; DIPEA,
N-diisopropyl-N-ethylamine; DAST, N,N-diethylaminosulfur
trifluoride; DCE, dichloroethane; DCM, dichloromethane;
LDA, lithium N,N-diisopropylamine; dba, dibenzylideneace-
tone; NMP, N-methylpyrrolidine; Tf, trifluoromethylsulfonyl;
DMAD, dimethyl azodicarboxylate; DIAD, diisopropyl azodi-
carboxylate; DTBAD, di-tert-butyl azodicarboxylate
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