Potent cholesteryl ester transfer protein inhibitors of reduced lipophilicity: 1,1′-spiro-substituted hexahydrofuroquinoline derivatives

Article abstract of DOI:10.1021/jm500431d

A series of 1,1′-spiro-substituted hexahydrofuroquinoline derivatives exhibiting potent cholesteryl ester transfer protein (CETP) inhibition at reduced lipophilicity was identified. A focused structure-activity relationship (SAR) exploration led to the potent and comparatively polar CETP inhibitor 26 showing robust high density lipoprotein-cholesterol (HDL-C) elevation and low density lipoprotein-cholesterol (LDL-C) reduction in transgenic hCETP/hApoB-100 mice. Compound 26 was also shown to positively differentiate from highly lipophilic CETP inhibitors in its complete elimination from fat tissue in hCETP transgenic mice as evident within 21 days after cessation of treatment. In addition, compound 26 showed no significant effects on aldosterone secretion from H295R cells, as well as no significant effects on blood pressure and electrocardiogram parameters in telemetrized cynomolgus monkeys.

Full text of DOI:10.1021/jm500431d

Article
pubs.acs.org/jmc
Potent Cholesteryl Ester Transfer Protein Inhibitors of Reduced
Lipophilicity: 1,1′-Spiro-Substituted Hexahydrofuroquinoline
Derivatives
Thomas Trieselmann,*,† Holger Wagner,† Klaus Fuchs,† Dieter Hamprecht,‡ Daniela Berta,‡
Paolo Cremonesi,‡ Rudiger Streicher,§ Gerd Luippold,§ Astrid Volz,⊥ Michael Markert,⊥
̈
and Herbert Nar∥
§
⊥
∥
†Departments of Medicinal Chemistry, Cardiometabolic Diseases, Drug Discovery Support, and Lead Identification, Boehringer
Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, 88397 Biberach an der Riss, Germany
‡BI Research Italia S.a.s. di BI IT S.r.l., Via Lorenzini 8, 20139 Milan, Italy
S
* Supporting Information
ABSTRACT: A series of 1,1′-spiro-substituted hexahydrofuroquinoline derivatives exhibiting potent cholesteryl ester transfer
protein (CETP) inhibition at reduced lipophilicity was identified. A focused structure−activity relationship (SAR) exploration led
to the potent and comparatively polar CETP inhibitor 26 showing robust high density lipoprotein-cholesterol (HDL-C)
elevation and low density lipoprotein-cholesterol (LDL-C) reduction in transgenic hCETP/hApoB-100 mice. Compound 26 was
also shown to positively differentiate from highly lipophilic CETP inhibitors in its complete elimination from fat tissue in hCETP
transgenic mice as evident within 21 days after cessation of treatment. In addition, compound 26 showed no significant effects on
aldosterone secretion from H295R cells, as well as no significant effects on blood pressure and electrocardiogram parameters in
telemetrized cynomolgus monkeys.
levels. In a clinical phase III study (dal-OUTCOMES), the
covalent but weakly binding CETP inhibitor dalcetrapib
(Figure 1) showed only modest effects on lipoproteins
(negligible LDL-C reduction, HDL-C increase of 30%) and
failed to effect a clinically meaningful reduction in CV events.6
The competitive and more potent CETP inhibitors anacetrapib
and evacetrapib (Figure 1) however have been shown to reduce
LDL-C levels in humans by more than 30% and to increase
HDL-C levels by more than 120%.7 Consequently a strong
motivation to evaluate these agents and CETP inhibitors of
comparable efficacy in cardiovascular outcome trials remains.
Since the hydrophobic nature of the CETP binding pocket8
determines the physicochemical properties of potential
inhibitors, it is no surprise that all published CETP inhibitors
are highly lipophilic. This includes the structurally related
CETP inhibitors torcetrapib, anacetrapib, and evacetrapib
(Figure 1) that have reached clinical phase III trials.
INTRODUCTION
■
Cardiovascular disease is the leading cause of mortality and
morbidity in the developed world. Elevated levels of low
density lipoprotein-cholesterol (LDL-C) are considered to be a
major risk factor for cardiovascular events.1 The development
of the statins (3-hydroxy-3-methylglutaryl-coenzyme A (HMG-
CoA) reductase inhibitors) has helped to reduce LDL-C levels
in patients at risk for cardiovascular events by approximately
30%.2 However, a considerable risk remains.3 Epidemiological
studies have linked increased levels of high density lipoprotein-
cholesterol (HDL-C) with a decreased number of cardiovas-
cular events.4 Inhibition of cholesteryl ester transfer protein
(CETP) is considered to be one of the most powerful
mechanisms for raising HDL-C levels and could therefore
answer the key question whether raising HDL-C translates
directly and on top of statins into a reduced risk for
cardiovascular events.
High lipophilicity however represents a significant risk in
drug development due to its effects on solubility, drug
CETP is a glycoprotein that mediates the exchange of
cholesteryl ester from HDL with triglycerides from the
apolipoprotein B (apoB)-containing lipoproteins, primarily
very low density lipoprotein (VLDL).5 The net effects of this
exchange are increased LDL-C levels and decreased HDL-C
Received: March 19, 2014
© XXXX American Chemical Society
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Figure 1. CETP inhibitors that reached phase III clinical trials.
Figure 2. Design of hexahydrofuroquinoline CETP inhibitors.
a
Scheme 1. Synthetic Route
a
Reagents: (a) HC(CO2Et)3, reflux, 49%; (b) (i) POCl3, 80 °C, 62%, (ii) AcCl, NaI, MeCN, 94%; (c) (i) (1R,2S)-(+)-cis-1-amino-2-indanol,
borane−diethylaniline complex, THF, 0−25 °C, 78%, (ii) TBSOTf, 2,6-lutidine, THF, 0 °C, 99%; (d) iPrZnBr, Pd(dppf)Cl2, THF/PhMe, 85 °C,
31%; (e) (i) iBu2AlH, DCM, 0 °C, 81%, (ii) Dess−Martin periodinane, DCM, 0 °C, 60%; (f) 4-iodobenzotrifluoride, iPrMgCl, THF, −20 °C, 84%;
(g) 2-cyclopent-1-enyl-4,4,5,5-tetramethyl-[1,3,2]-dioxaborolane, CsF, Pd(dppf)Cl2, THF, 50 °C, 74%; (h) ICl, DCM, 25 °C, 50%; (i) (i) H2, 10
bar, Pd/C, MeOH, 65%, (ii) TBAF, THF, 25 °C, 58%.
B
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disposition, and promiscuity.9 Hence the pharmacokinetics of
the nonionizable and poorly water-soluble clinical compounds
torcetrapib and anacetrapib show significant food effects and
require special lipid formulations.10 In addition, long terminal
elimination half-lives of torcetrapib (221 h),11 anacetrapib (83
h),12 and evacetrapib (44 h)13 after single oral dosing in
humans have been reported and were associated with their high
lipophilicity.
group using tetrabutylammonium fluoride furnished CETP
inhibitor 2.
Using an identical synthetic sequence, we transformed
diastereomer 9a into the diastereomeric CETP inhibitor 2a,
which is over 20-fold less potent than 2 (Figure 3).
A phase III clinical trial with torcetrapib (ILLUMINATE)
was terminated prematurely since increased cardiovascular
events were observed in the torcetrapib-treated group versus
placebo. Patients in the torcetrapib-treated group showed
elevated mean systolic blood pressure, as well as an increase in
aldosterone levels. Studies in preclinical species have
recapitulated the effects of torcetrapib on aldosterone and
blood pressure and have shown that they occur independent of
CETP inhibition.14 Therefore, there is continued interest in the
development of potent small-molecule CETP inhibitors
without adverse effects on cardiovascular parameters.
Figure 3. Diastereomeric CETP inhibitors 2 and 2a.
Initial modifications focused on the 3′-4-trifluorophenyl
substituent and the 4′-isopropyl substituent of compound 2
(Table 1). While the high potency for lipophilic substituents in
the 3′-position is eminent (e.g., compounds 2, 16, and 18), we
were gratified to see that subtle introduction of polarity allowed
for reduction in lipophilicity without loss of potency (e.g.,
compounds 15, 19, and 20).
Results from the modification of the 4′-isopropyl substituent
showed that a branched substituent seems to be optimal for
potency (see reduced potency for compound 21). Again, it was
possible to increase polarity without loss of potency
(compound 23).
Modifications of the 1,1′-spiro-substituent (Table 2) were
limited by the requirements of the Suzuki−iodospirocycliza-
tion−hydrogenation sequence for its synthesis. However,
within these limitations, a more polar and potent tetrahy-
dropyranyl substituent was identified (compound 26).
The enantiomeric excess of compound 26 was determined to
be >95% using a chiral HPLC-method. In addition, the relative
and absolute stereochemistry of compound 26 was unambig-
uously proven by crystal structure analysis. For further
comparison, the enantiomer ent-26 was synthesized and
shown to be over 30-fold less potent than compound 26
(Figure 4). Compound 26 was also shown to be a potent
CETP inhibitor in the presence of 88% human plasma (FTIC50
(hplasma) = 151 nM).
Since the in vivo pharmacokinetic profile of compound 26 in
mice looked promising,21 it was advanced to evaluation in
pharmacodynamic models. Compound 26 dose-dependently
inhibited plasma CETP activity in male hCETP transgenic
mice.22 This resulted in a robust dose-dependent increase of
HDL-cholesterol after 5 days of treatment of up to +74% for
the 10 mg/kg dose (Figure 5). In this experimental setting, the
3 mg/kg dose of 26 showed similar efficacy to a 10 mg/kg dose
of anacetrapib.
RESULTS AND DISCUSSION
■
In an effort to reduce the development risk of potential CETP
inhibitors, we focused on starting points of reduced lip-
ophilicity. After a careful literature review, we got interested in
the published tetrahydroquinoline class of CETP inhibitors.
Compound 1, described in the patent literature,15 is
significantly more polar than anacetrapib. We hypothesized
that potency of 1 could be improved by conformational
restriction16 of the fluorobenzylic side chain. While several
cyclization efforts did not lead to compounds with improved
potency, the hexahydrofuroquinoline derivative 2 showed a
significant improvement in the hCETP fluorescence transfer17
IC50 (FTIC50). Gratifyingly, the increase in potency versus 1
was accompanied by a significant reduction in lipophilicity
(Figure 2).
Developing a robust synthetic route to access various
analogues of 2 presented a formidable challenge. However, a
sequence employing a Hantzsch-type tetrahydroquinoline
synthesis was identified and utilized for the exploration of
modifications in different positions (Scheme 1).
Dimedone enamine 3 was submitted to condensation with
triethylmethanetricarboxylate to give tetrahydroquinoline 4.
Compound 4 was dichlorinated with phosphorus oxychloride
and then transferred into the diiodide 5 using acetyl chloride/
sodium iodide. The 5-oxo substituent was reduced enantiose-
lectively18 using a modified CBS-reagent19 and then TBS-
protected to give 5-(S)-trimethylsilylether 6. The desired 2-
substituent was introduced by a regioselective Negishi-type
coupling with isopropyl zinc bromide to give 2-isopropyl-
tetrahydroquinoline 7. For elaboration of the substituent in the
3-position, the ester 7 was transferred into aldehyde 8 via
reduction with diisobutylaluminum hydride and oxidation using
the Dess−Martin periodinane. Addition of 4-(trifluoromethyl)-
phenyl magnesium bromide gave a 40:60 mixture20 of the
(3R,5S)-alcohol 9 and its (3S,5S)-diastereomer 9a, which could
be separated by flash chromatography. The substituent in the 4-
position was introduced via Suzuki coupling to give 4-
cyclopentenyl-tetrahydroquinoline 10. Spirocyclization of the
free hydroxyl onto the cyclopentenyl substituent was affected
with iodine chloride, yielding iodo-spiro-hexahydrofuroquino-
line 11 as a mixture of diastereomers. Finally, removal of the
iodine by hydrogenation and cleavage of the TBS-protecting
Compound 26 also dose-dependently elevated HDL-
cholesterol up to +37% and reduced LDL-cholesterol down
to −60% in hCETP/hApoB-100 transgenic mice23 at doses of
10 mg/kg (Figure 6).
In a recent analysis of a clinical trial with the clinical CETP
inhibitor anacetrapib (DEFINE), drug levels after cessation of
active treatment were shown to decrease only to approximately
40% of on-treatment trough levels at 12 weeks after dosing.24
Significant drug concentrations were still detectable in plasma
2−4 years after the last dosing. The extremely slow elimination
of anacetrapib was linked to a delayed clearance from adipose
tissue due to its high lipophilicity. To differentiate compound
C
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Table 1. Structure−Activity Relationship (SAR) of 3′- and 4′-Substituent
a
95% confidence limit.
26 from the extremely long terminal half-life characteristics of
the more lipophilic anacetrapib, the elimination of both
compounds was followed in the hCETP transgenic mouse
model described above. Drug exposure in different tissues was
measured at day 3 and day 21 after cessation of treatment for 5
days with doses of similar efficacy on HDL-C of 10 mg/kg for
D
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anacetrapib and 3 mg/kg for compound 26 (Figure 5). At day 3
after cessation of treatment, both compounds showed high
exposure in all tissues investigated (Figure 7). On day 21 after
cessation of treatment, high levels of anacetrapib were observed
in muscle, kidney, testes, and adipose tissue suggesting an
extremely slow elimination from these compartments. In
contrast to this, exposure of the less lipophilic CETP inhibitor
compound 26 on day 21 after cessation of treatment was below
the limit of quantification (LLQ = 30 nM) in all analyzed
tissues, suggesting a significantly faster elimination.
Table 2. SAR of the Spiro-Substituent
Unlike torcetrapib,14d compound 26 showed no effects up to
10 μM on aldosterone secretion from the H295R human
adrenal carcinoma cell line. To further differentiate from blood
pressure effects reported for torcetrapib,25 compound 26 was
evaluated in an acute telemetry study in conscious cynomolgus
monkeys. Compound 26 showed no significant effects on blood
pressure, left ventricular pressure, myocardial contractility, or
heart rate and had no significant effect on the electrocardiogram
(ECG) parameters (PR-interval, QRS-complex, QT-interval)
up to doses of 100 mg/kg with sustained high exposure (Cmax
10 μM, MRT > 20 h).
>
In summary, a hexahydrofuroquinoline scaffold was identified
from conformational restriction of a known literature series. A
synthesis was developed and utilized for the introduction of
structural modifications. Initial SAR revealed that polar
substituents were tolerated in a number of positions. Based
on its in vitro properties and its PK profile, compound 26 was
selected for in vivo evaluation. Compound 26 demonstrated
dose dependent CETP inhibition and HDL-cholesterol
elevation in hCETP transgenic mice. Compound 26 also
showed robust HDL-cholesterol elevation and LDL-cholesterol
reduction in hCETP/hApoB-100 mice. In contrast to the
clinical CETP inhibitor anacetrapib, compound 26 eliminated
completely from tissues of hCETP transgenic mice 21 days
after cessation of treatment for 5 days at a fully efficacious dose.
Compound 26 also showed no significant effects on
aldosterone secretion from H295R cells up to 10 μM, as well
as no significant effects on blood pressure and ECG parameters
in telemetrized cynomolgus monkeys. The studies described
herein led to the selection of the CETP inhibitor 26 as a
development candidate.
a
95% confidence limit.
Figure 4. Enantiomeric CETP inhibitors 26 and ent-26.
Figure 5. Effects on HDL-C and plasma exposure of anacetrapib and compound 26 in hCETP transgenic mice.
E
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Figure 6. Effects of 26 on HDL-C and LDL-C in hCETP/hApoB-100 transgenic mice.
Figure 7. Exposure of anacetrapib and compound 26 in different tissues of male hCETP transgenic mice at day 3 and day 21 after cessation of oral
treatment for 5 days with either 10 mg/kg of anacetrapib or 3 mg/kg of compound 26.
Plasma Lipoprotein Analysis. Plasma was assayed for the HDL and
EXPERIMENTAL SECTION
■
LDL cholesterol fraction, using the Cobas Integra 400 Plus system.26
Methods. CETP Activity Measurement. The determination of
Statistics. The data are presented as mean standard error of the
CETP activity (FTIC50) was based on the transfer of a neutral
fluorescence labeled lipid from donor vesicles to acceptor vesicles by
mean. Statistical comparisons were conducted by one-way ANOVA
followed by Bonferroni post-test (using GraphPad Prism 6 software).
CETP. The manufacturer’s protocol of the ROAR CETP RP activity
assay kit, 250 assays, was adapted to a 384-well format by reducing the
total assay volume to 100 μL. Test compound (2.5 μL) dissolved in
DMSO was incubated at 37 °C for 3 h with 97.5 μL of a master mix
(containing 2 μL of donor particles, 2 μL of acceptor particles, and 0.8
μL of human recombinant CETP in assay buffer). Typical hCETP
concentrations were 0.2−1 mg/mL. The change of fluorescence at
485/535 nm is an indicator of CE-transfer. The inhibition of transfer
was measured. IC50 values were calculated by nonlinear regression
analysis using a four-parameter logistic equation (sigmoidal dose−
response model, variable slope).
Animals. Hemizygous human CETP transgenic male mice (B6.SJL-
Tg(APOA-CETP)1Dsg N11), as well as hemizygous human CETP/
human apolipoprotein B100 (apoB100) transgenic male mice (B6.SJL-
Tg(APOA-CETP)1Dsg Tg(APOB)1102Sgy N10), were purchased
from Taconic (Laven, Denmark). Mice at an age of 26−30 weeks were
housed in a temperature- (22 2 °C) and humidity-controlled (55%
10%) environment and were fed ad libitum a standard chow diet
with free access to water. All animal studies were performed in
accordance with the German law on the protection of animals. Animal
experiments were approved by the local animal ethics committee.
Treatment and Blood Sampling for Lipoprotein Analysis. For the
treatment studies, anacetrapib and compound 26 were suspended in
the vehicle (0.5% aqueous hydroxyethylcellulose). Animals were
treated with indicated compound for 5 or 14 consecutive days via oral
gavage in the morning. Blood was collected into EDTA coated tubes
from animals 7 h post-dosing either in the fed state (5-day treatment)
or after a 4 h fast (14-day treatment) via bleeding of the vena facialis
under isoflurane anesthesia.
A p value <0.05 was considered to show a statistically significant
difference.
Tissue Drug Exposure Analysis Using LC/MS/MS Quantification.
Samples were prepared for LC/MS/MS measurement by protein
precipitation with acetonitrile/methanol (1:1, v:v) using a generic
internal standard. Tissue sample aliquots were first diluted with
phosphate buffered saline (6:1 PBS/(brain/liver/testis), 12:1 PBS/
muscle); fat sample aliquots were diluted with acetonitrile (6:1 ACN/
fat), homogenized, and then further processed as plasma samples. The
LC/MS/MS system consisted of Agilent 1100 series binary pumps
(flow rate 0.4 mL/min), a CTC Analytics HTC PAL autosampler, a
YMC ODS AQ C18 column (33 mm × 2.1 mm, 3 μm ID), and an AB
Sciex API 4000 triple quadrupole mass spectrometer. The mass
spectrometer was operated in a positive turbo ionspray and multiple
reaction monitoring mode with parent to product ion transitions of
467.2 to 448.2 for compound 26 and 638.2 to 283.0 for anacetrapib.
Calibration standards were freshly prepared, and the linear calibration
range for compound 26 and anacetrapib was from 5 to 2500 nM and
12.5 to 2500 nM, respectively. For each compound, quality controls
(QCs) at concentrations of 4.0, 50, and 1000 nM and additional QCs
in each matrix at concentrations of 10, 100, and 1000 nM were used.
Measurements of two sets of QC samples were within 30% of the
target concentrations. All samples were stored at −20 °C.
General Analytics. NMR spectra were recorded on a Bruker 400
MHz instrument. Chemical shifts are given in parts per million (ppm)
downfield from internal reference tetramethylsilane in δ units. Selected
data are reported in the following manner: chemical shift, multiplicity
(s = singlet, d = doublet, dd = double doublet, t = triplet, q = quartet,
m = multiplet), coupling constants (J), integration. Analytical thin-
layer chromatography (TLC) was carried out using Merck silica gel 60
F
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F254 plates. All compounds were visualized as single spots using short
wave UV light (254 nm). Low resolution mass spectra were obtained
using a liquid chromatography mass spectrometer (HPLC-MS) that
consisted of an Agilent 1100 series LC coupled to an Agilent 6130
quadrupole mass spectrometer (electrospray positive ionization) and
an Agilent G1315C DAD SL detector operating at 254−360 nm
(typically 254 nM was used for compound detection). Unless
otherwise specified, the purity of all intermediates and final
compounds was determined to be >95% by HPLC-MS using the
eluents water containing 0.1% formic acid (eluent A), acetonitrile
containing 0.1% formic acid (eluent B), water containing 0.1%
trifluoro actetic acid (eluent C), acetonitrile containing 0.1% trifluoro
actetic acid (eluent D), and methanol (eluent E) and the following
conditions: Agilent Zorbax Bonus RP, 50 mm × 2.1 mm, 3.5 μm, 1.2
mL/min, gradient 4.5 min 10% → 99% eluent B in eluent A (method
1); Agilent Zorbax Bonus RP, 50 mm × 2.1 mm, 3.5 μm, 1.2 mL/min,
gradient 1.0 min 10% → 75%, 0.3 min 75%, 1.0 min 75% → 99%
eluent B in eluent A (method 2); Varian Microsorb 100 C18, 30 mm
× 4.6 mm, 3.5 mL/min, gradient 2.0 min 5% → 98% eluent D in
eluent C (method 3); Merck Chromolith Flash RP18e, 25 mm × 4.6
mm, 1.6 mL/min, gradient 2.0 min 10% → 90%, 5.00 min 90% eluent
B in eluent A (method 4); BEH C18, 50 mm × 2.1 mm, 1.7 μm, 0.85
mL/min, gradient 1.2 min 50% → 90% eluent D in eluent C (method
5); Varian Microsorb 100 C18, 30 mm × 4.6 mm, 3.5 mL/min,
gradient 3.95 min 5% → 100% eluent E in eluent C (method 6);
Atlantis dC18, 50 mm × 4.6 mm, 5 μm, 1.3 mL/min, gradient 3.5 min
10% → 90% eluent D in eluent C/eluent D 9:1 (method 7);
Symmetry Shield RP8, 150 mm × 4.6 mm, 5 μm, 1.0 mL/min,
gradient 1.5 min 5%, 10 min 5% → 95% eluent A/eluent B 1:9 in
eluent A/eluent B 9:1 (method 8); Symmetry Shield RP8, 150 mm ×
4.6 mm, 5 μm, 0.85 mL/min, gradient 1.5 min 30% → 50%, 7.0 min
50% → 100% eluent A/eluent B 1:9 in eluent A/eluent B 9:1 (method
9); Daicel ODH, 250 mm × 4.6 mm, 4 mL/min, gradient 10 min
supercritical carbon dioxide containing 10% ispropanol and 2%
diethylamine (chiral HPLC).
Synthesis Procedures. Ethyl 2,4-Dihydroxy-7,7-dimethyl-5-oxo-
5,6,7,8-tetrahydroquinoline-3-carboxylate (4). 3-Amino-5,5-dimeth-
yl-2-cyclohexen-1-one [3 (10 g, 71.8 mmol)] and 2-ethoxycarbonyl-
malonic acid diethyl ester (25 g, 108 mmol) were combined and
heated for 10 min at 210 °C (bath temperature). Thereafter the
mixture was cooled to room temperature and triturated with diethyl
ether. The crystalline precipitate was collected by filtration and dried
in vacuo. Yield: 9.9 g (49% of theory). LCMS (ESI+) calculated for
C14H17NO5 [M + H]+ m/z 280.11, found 280.1. Rf-value: 0.45 (silica
gel, dichloromethane/methanol 9:1). 1H NMR (400 MHz,
(CD3)2SO) δ 12.88 (s, 1H), 12.35 (s, 1H), 4.18 (q, J = 7.1 Hz,
2H), 2.73 (s, 2H), 2.49 (s, 2H), 1.23 (t, J = 7.1, 3H), 1.04 (s, 6H).
Ethyl 2,4-Dichloro-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquino-
line-3-carboxylate. Compound 4 (9.9 g, 35.5 mmol) was suspended
in phosphoroxychloride (50 mL, 545 mmol). After addition of N,N-
dimethylformamide (0.5 mL), the mixture was heated to 80 °C for 12
h. Then the phosphoroxychloride was evaporated in vacuo, and the
residue was dissolved in dichloromethane. After washing with water,
saturated aqueous sodium bicarbonate solution, and brine, the solution
was dried with magnesium sulfate. The solvent was evaporated in
vacuo, and the residue was chromatographed on silica gel cyclo-
hexane/ethyl acetate (90:10 to 50:50). Yield: 6.95 g (62% of theory).
LCMS (ESI+) calculated for C14H15Cl2NO3 [M + H]+ m/z 316.14,
found 316.1 (100% intensity), 317.1 (15% intensity), 318.1 (65%
intensity), 319.1 (10% intensity), 320.1 (11% intensity), 320.1 (1.8%
intensity). Rf-value: 0.44 (silica gel, petroleum ether/ethyl acetate 4:1).
1H NMR (400 MHz, (CD3)2SO) δ 4.43 (q, J = 7.1 Hz, 2H), 3.06 (s,
mixture was diluted with diethyl ether (100 mL) and then washed with
saturated aqueous sodium bicarbonate solution (50 mL), saturated
aqueous sodium thiosulfate (50 mL), and brine (50 mL). After drying
with magnesium sulfate, the solvents were evaporated in vacuo. Yield:
10.3 g (94% of theory). LCMS (ESI+) calculated for C14H15I2NO3 [M
+ H]+ m/z 500.01, found 500.2. HPLC (method 1): retention time =
1
3.484 min. H NMR (400 MHz, (CD3)2SO) δ 4.39 (q, J = 7.0 Hz,
2H), 3.04 (s, 2H), 2.63 (s, 2H), 1.36, (t, J = 7.0 Hz, 3H), 1.00 (s, 6H).
(S)-Ethyl 5-Hydroxy-2,4-diiodo-7,7-dimethyl-5,6,7,8-tetrahydro-
quinoline-3-carboxylate. (1R,2S)-(+)-cis-1-Amino-2-indanol (500
mg, 3.35 mmol) was dissolved in tetrahydrofuran (100 mL), and to
this solution of a borane−diethylaniline complex (7.3 mL, 41.1 mmol)
was added dropwise. After completion of gas evolution, the solution
was cooled to 0 °C, and ethyl 2,4-diiodo-7,7-dimethyl-5-oxo-5,6,7,8-
tetrahydroquinoline-3-carboxylate (10.3 g, 20.6 mmol) in tetrahy-
drofuran (20 mL) was added cautiously over 5 min. The temperature
was raised during 28 h to room temperature, methanol (20 mL) was
added dropwise, and the mixture was stirred for additional 10 min.
The solution was diluted with diethyl ether (100 mL) and washed with
1 N hydrochloric acid (50 mL), saturated aqueous sodium bicarbonate
solution (50 mL), and brine (50 mL). After drying with magnesium
sulfate, the solvents were evaporated in vacuo, and the residue was
chromatographed on silica gel (cyclohexane/ethyl acetate 90:10 to
30:70). Yield: 8.1 g (78% of theory). LCMS (ESI+) calculated for
C14H17I2NO3 [M + H]+ m/z 502.03, found 502.2. HPLC (method 1):
retention time = 3.286 min. Rf-value: 0.21 (silica gel, petroleum ether/
ethyl acetate 4:1). 1H NMR (400 MHz, (CD3)2SO) δ 5.15 (d, J = 5.6
Hz, 1H), 4.68 (m, 1H), 4.37 (q, J = 7.1 Hz, 2H), 2.73 (d, J = 16.9 Hz,
1H), 2.56 (d, J = 16.9 Hz, 1H), 1.85 (dd, J = 14.0, 5.5, Hz, 1H,), 1.75
(dd, J = 14.0, 4.2 Hz, 1H), 1.35, (t, J = 7.1 Hz, 3H), 1.05 (s, 3H), 0.92
(m, 3H).
(S)-Ethyl 5-(tert-butyldimethylsilyloxy)-2,4-diiodo-7,7-dimethyl-
5,6,7,8-tetrahydro-quinoline-3-carboxylate (6). (S)-Ethyl 5-hy-
droxy-2,4-diiodo-7,7-dimethyl-5,6,7,8-tetrahydroquinoline-3-carboxy-
late (8.1 g, 16.2 mmol) was dissolved in tetrahydrofuran (70 mL) and
cooled to 0 °C, 2,6-lutidine (3.2 mL) and tert-butyldimethylsilyl
trifluoromethanesulfonate (5 mL, 21.8 mmol) were added dropwise,
and the mixture was stirred for further 12 h while warming to room
temperature. The solvents were evaporated in vacuo, and the residue
was chromatographed on silica gel (cyclohexane/ethyl acetate 90:10 to
30:70). Yield: 9.8 g (99% of theory). LCMS (ESI+) calculated for
C20H31I2NO3Si [M + H]+ m/z 616.03, found 616.1. HPLC (method
1): retention time = 4.916 min. Rf-value: 0.71 (silica gel, petroleum
ether/ethyl acetate 4:1). 1H NMR (400 MHz, (CD3)2SO) δ 5.02 (dd,
J = 3.5, 4.6 Hz, 1H), 4.37 (q, J = 7.2 Hz, 2H), 2.88 (d, J = 16.2 Hz,
1H), 2.55 (d, J = 16.2 Hz, 1H), 1.91 (dd, J = 14.5, 3.2, Hz, 1H,), 1.75
(dd, J = 14.5, 4.5 Hz, 1H), 1.35, (t, J = 7.2 Hz, 3H), 1.13 (s, 3H), 1.16
(d, J = 6.9 Hz, 3H), 0.89 (m, 3H), 0.89 (m, 9H), 0.20 (s, 3H).
(S)-Ethyl 5-(tert-butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-di-
methyl-5,6,7,8-tetrahydro-quinoline-3-carboxylate (7). Under
argon, 6 (9.8 g, 15.9 mmol) was dissolved in toluene (25 mL) and
tetrahydrofuran (25 mL). 1,1′-Bis(diphenylphosphino)-ferrocene-
dichloro-palladium(II) (800 mg, 1.09 mmol) was added, the mixture
was heated to 85 °C, and a 0.5 M solution of isopropyl-zinc-bromide
in tetrahydrofuran (50 mL, 25.0 mmol) was added dropwise. After
completion of the addition, the mixture was heated for 12 h at reflux.
The mixture was cooled to room temperature, diluted with diethyl
ether (50 mL), and washed with saturated ammonium chloride
solution (30 mL) and brine (30 mL). The solvents were evaporated
under reduced pressure, and the residue was chromatographed on
silica gel (cyclohexane/ethyl acetate 90:10 to 60:40). Yield: 2.63 g
(31% of theory). LCMS (ESI+) calculated for C23H38INO3Si [M +
H]+ m/z 532.17, found 532.1. Rf-value: 0.85 (silica gel, petroleum
ether/ethyl acetate 4:1). 1H NMR (300 MHz, (CD3)2SO) δ 5.03 (dd,
J = 3.5, 4.6 Hz, 1H), 4.37 (q, J = 7.1 Hz, 2H), 2.91 (d, J = 16.1 Hz,
1H), 2.91−2.80 (m, 1H), 2.55 (d, J = 16.1 Hz, 1H), 1.91 (dd, J = 3.3,
14.3 Hz, 1H), 1.74 (dd, J = 4.6, 14.4 Hz, 1H), 1.33 (t, J = 7.1 Hz, 3H),
1.19 (d, J = 1.7 Hz, 3H), 1.17 (d, J = 1.6 Hz, 3H), 1.15 (s, 3H), 0.87
(s, 3H), 0.85 (s, 9H), 0.20 (s, 3H), 0.18 (s, 3H). 13C NMR (101 MHz,
(CD3)2SO) δ 168.1, 160.4, 158.3, 134.1, 133.3, 110.9, 72.6, 61.7, 46.7,
2H), 2.62 (s, 2H), 1.33 (t, J = 7.1 Hz, 3H), 1.04 (s, 6H). 13C NMR
(101 MHz, (CD3)2SO) δ 194.6, 165.8, 162.6, 148.1, 141.3, 129.4,
123.2, 62.7, 52.4, 46.0, 31.7, 27.4 (2C), 13.7.
Ethyl 2,4-Diiodo-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquinoline-
3-carboxylate (5). Ethyl 2,4-dichloro-7,7-dimethyl-5-oxo-5,6,7,8-tetra-
hydroquinoline-3-carboxylate (6.95 g, 22.0 mmol) was dissolved in
acetonitrile (100 mL) and reacted with sodium iodide (10 g, 66.7
mmol) and acetyl chloride (1.6 mL, 22.5 mmol) for 3 h at 50 °C. The
G
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Journal of Medicinal Chemistry
Article
44.3, 33.5, 30.3, 30.0, 30.0, 26.1 (3C), 22.3, 22.0, 17.9, 13.8, −2.9,
−3.9.
HPLC (method 1): retention time = 5.256 min. Rf-value: 0.56 (silica
gel, petroleum ether/ethyl acetate 4:1). 1H NMR (400 MHz,
(CD3)2SO) δ 7.69 (d, J = 8.2 Hz, 2H), 7.40 (d, J = 8.2 Hz, 2H),
6.69−6.65 (m, 1H), 6.48 (br, 1H), 5.15−5.12 (m, 1H), 3.26−3.18 (m,
1H), 2.95 (d, J = 15.6 Hz, 1H), 2.53 (d, J = 15.6 Hz, 1H), 1.95 (dd, J =
14.3, 3.5, 1H), 1.74 (dd, J = 14.3, 4.7 Hz, 1H), 1.19 (s, 3H), 1.11 (d, J
= 6.6 Hz, 3H), 0.93 (s, 3H), 0.93 (s, 9H), 0.46 (d, J = 6.6 Hz, 3H),
0.22 (s, 3H), 0.18 (s, 3H).
(R)-((S)-5-(tert-Butyldimethylsilyloxy)-4-cyclopentenyl-2-isoprop-
yl-7,7-dimethyl-5,6,7,8-tetrahydroquinolin-3-yl)(4-(trifluoromethyl)-
phenyl)methanol (10). Under argon, 9 (490 mg, 0.773 mmol) and 2-
cyclopent-1-enyl-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane (900 mg,
2.782 mmol) were dissolved in tetrahydrofuran (20 mL). Cesium
fluoride (900 mg, 5.93 mmol) was added, and the mixture was purged
(S)-(5-(tert-Butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-dimeth-
yl-5,6,7,8-tetrahydro-quinolin-3-yl)methanol. Compound 7 (2.63 g,
4.95 mmol) was dissolved in dichloromethane (50 mL) and cooled to
0 °C. A 1 M solution of diisobutylaluminumhydride in dichloro-
methane (16.5 mL, 16.5 mmol) was added dropwise, and the solution
was stirred for another 2 h. Then the solution was diluted with
dichloromethane, and 1 N hydrochloric acid (1 mL) was added
dropwise under vigorous stirring. After 5 min magnesium sulfate was
added and stirring was continued for further 5 min. Filtration and
evaporation of the solvents in vacuo gives a crude product, which was
chromatographed on silica gel (cyclohexane/ethyl acetate 90:10 to
60:40). Yield: 1.96 g (81% of theory). LCMS (ESI+) calculated for
C21H36INO3Si [M + H]+ m/z 490.16, found 490.4. HPLC (method
1): retention time = 4.100 min. Rf-value: 0.55 (silica gel, petroleum
for
5 min with argon. After the addition of 1,1′-bis-
(diphenylphosphino)-ferrocene-dichloro-palladium-(II) (50 mg,
0.068 mmol), the mixture was heated to 50 °C for 36 h. Then the
mixture was diluted with diethyl ether (30 mL), washed with saturated
aqueous ammonium chloride (20 mL) and brine (20 mL), and dried
with magnesium sulfate. The solvents were evaporated in vacuo, and
the residue was chromatographed on silica gel (cyclohexane/ethyl
acetate 95:5 to 60:40). Yield: 330 mg (74% of theory). LCMS (ESI+)
calculated for C33H46F3NO2Si [M + H]+ m/z 574.33, found 574.4. Rf-
1
ether/ethyl acetate 4:1). H NMR (400 MHz, (CD3)2SO) δ 4.94−
4.90 (m, 1H), 4.89−4.85 (m, 1H), 4.59−4.54 (m, 2H), 3.35−3.26 (m,
1H), 2.73 (d, J = 15.6 Hz, 1H), 2.34 (d, J = 15.6 Hz, 1H), 1.74 (dd, J =
14.3, 3.3 Hz, 1H,), 1.50 (dd, J = 14.3, 4.6 Hz, 1H), 1.03 (s, 3H), 1.01
(s, 3H), 0.99 (s, 3H), 0.68 (s, 3H), 0.67 (s, 9H), 0.30 (s, 3H), 0.00 (s,
3H).
(S)-5-(tert-Butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-dimeth-
yl-5,6,7,8-tetrahydro-quinoline-3-carbaldehyde (8). (S)-(5-(tert-Bu-
tyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-dimethyl-5,6,7,8-tetrahy-
droquinolin-3-yl) methanol (1.96 g, 4.00 mmol) was dissolved in
dichloromethane (60 mL), cooled to 0 °C, and mixed with 1,1-
dihydro-1,1,1-triacetoxy-1,2-benziodoxol-3(1H)-one (Dess−Martin
periodinane, 15 g, 5.31 mmol). The mixture was stirred for 12 h
while warming to room temperature. Then the solvent was evaporated
in vacuo, and the residue was chromatographed on silica gel
(cyclohexane/ethyl acetate 95:5 to 80:20). Yield: 1.17 g (60% of
theory). LCMS (ESI+) calculated for C21H34INO3Si [M + H]+ m/z
488.15, found 488.1. HPLC (method 1): retention time = 5.106 min.
Rf-value: 0.45 (silica gel, petroleum ether/ethyl acetate 16:1). 1H
NMR (400 MHz, (CD3)2SO) δ 10.12 (s, 1H), 5.15 (dd, J = 3.6, 4.5
Hz, 1H), 3.48−3.40 (m, 1H), 2.95 (d, J = 16.3 Hz, 1H), 2.58 (d, J =
16.3 Hz, 1H), 1.95 (dd, J = 14.3, 3.3 Hz, 1H,), 1.77 (dd, J = 14.3, 5.0
Hz, 1H), 1.19 (d, J = 6.7 Hz, 3H), 1.17 (s, 3H), 1.16 (d, J = 6.9 Hz,
3H), 0.88 (s, 3H), 0.85 (s, 9H), 0.21 (s, 3H), 0.20 (s, 3H).
(R)-((S)-5-(tert-Butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-di-
methyl-5,6,7,8-tetrahydro-quinolin-3-yl)(4-(trifluoromethyl)phenyl)-
methanol (9) and (S)-((S)-5-(tert-Butyldimethylsilyloxy)-4-iodo-2-
isopropyl-7,7-dimethyl-5,6,7,8-tetrahydroquinolin-3-yl)(4-
(trifluoromethyl)phenyl)methanol (9a). 4-Iodobenzotrifluoride (1.1
mL, 7.34 mmol) was dissolved in tetrahydrofuran (60 mL) and cooled
to −20 °C. Isopropylmagnesium chloride (3.7 mL of a 2 M solution in
tetrahydrofuran, 7.40 mmol) was added dropwise, and the solution
was stirred for further 5 h. Then the solution was cooled to −40 °C,
and 8 (1.17 g, 2.40 mmol) in tetrahydrofuran (5 mL) was added
dropwise. The mixture was stirred for 12 h while warming to room
temperature. Then it was cooled to 0 °C, methanol (10 mL) was
added, and it was stirred for 30 min. The solvents were evaporated in
vacuo, and the residue was chromatographed on silica gel (cyclo-
hexane/ethyl acetate 95:5 to 80:20).
1
value: 0.37 (silica gel, petroleum ether/ethyl acetate 8:1). H NMR
(400 MHz, (CD3)2SO) δ 7.68 (d, J = 8.2 Hz, 2H), 7.40 (d, J = 8.2 Hz,
2H), 6.26−6.20 (m, 1H), 5.88−5.83 (m, 1H), 5.67 (br, 1H), 4.89 (br,
1H), 3.03 (d, J = 14.3 Hz, 1H), 2.65−2.60 (m, 1H), 2.55−2.43 (m,
2H), 2.01−1.91 (m, 2H), 1.54−1.42 (m, 1H), 1.25−1.22 (m, 2H),
1.12−1.07 (m, 2H), 1.23 (s, 3H), 1.10 (d, J = 6.0 Hz, 3H), 0.84 (s,
9H), 0.79 (s, 3H), 0.48 (d, J = 6.0 Hz, 3H), 0.13 (s, 3H), −0.02 (s,
3H).
(3′R,9′S)-9′-(tert-Butyldimethylsilyloxy)-2-iodo-4′-isopropyl-7′,7′-
dimethyl-3′-(4-(trifluoromethyl)phenyl)-6′,7′,8′,9′-tetrahydro-3′H-
spiro[cyclopentane-1,1′-furo[3,4-c]quinoline] (11). Compound 10
(105 mg, 0.183 mmol) was dissolved in dichloromethane (4 mL),
mixed with iodinechloride (500 μL of a 1 M solution in
dichloromethane, 0.500 mmol), and stirred for 24 h. Then the
solution was diluted with diethyl ether (30 mL) and washed with
saturated aqueous sodium bicarbonate solution (20 mL), saturated
aqueous sodium thiosulfate solution (20 mL), and brine (20 mL).
After drying with magnesium sulfate, the solvents were evaporated in
vacuo, and the residue was chromatographed on silica gel (cyclo-
hexane/ethyl acetate 98:2 to 80:20). Yield: 64 mg (50% of theory).
LCMS (ESI+) calculated for C33H45F3INO2Si [M + H]+ m/z 700.23,
found 700.2. Rf-value: 0.57 (silica gel, petroleum ether/ethyl acetate
8:1). 1H NMR (400 MHz, (CD3)2SO) δ 7.77 (d, J = 8.1 Hz, 2H), 7.60
(d, J = 8.1 Hz, 2H), 6.20 (s, 1H), 5.16−5.13 (m, 1H), 4.44−4.38 (m,
1H), 3.15 (d, J = 13.7 Hz, 1H), 2.56 (d, J = 13.7 Hz, 1H), 2.49−2.42
(m, 1H), 2.23−2.12 (m, 4H), 2.06−2.00 (m, 2H), 1.83−1.72 (m, 2H),
1.23 (s, 3H), 1.10 (d, J = 6.7 Hz, 3H), 0.82 (s, 9H), 0.73 (s, 3H), 0.64
(d, J = 6.0 Hz, 3H), 0.22 (s, 3H), 0.76 (s, 3H).
(3′R,9′S)-9′-(tert-Butyldimethylsilyloxy)-4′-isopropyl-7′,7′-di-
methyl-3′-(4-(trifluoromethyl)phenyl)-6′,7′,8′,9′-tetrahydro-3′H-
spiro[cyclopentane-1,1′-furo[3,4-c]quinoline]. To a solution of 11
(60 mg, 0.086 mmol) in methanol (5 mL) was added triethylamine
(25 μL, 0.179 mmol) and palladium (10% on charcoal, 90 mg, 0.085
mmol). The mixture was hydrogenated at 10 bar for 12 h. After
filtration, the solvent was evaporated in vacuo, and the residue was
chromatographed on silica gel (cyclohexane/ethyl acetate 98:2 to
80:20). Yield: 32 mg (65% of theory). LCMS (ESI+) calculated for
C33H46F3NO2Si [M + H]+ m/z 574.33, found 574.4. HPLC (method
2): retention time = 2.797 min. Rf-value: 0.52 (silica gel, petroleum
ether/ethyl acetate 8:1). 1H NMR (400 MHz, (CD3)2SO) δ 7.75 (d, J
= 8.2 Hz, 2H), 7.47 (d, J = 8.2 Hz, 2H), 6.23 (s, 1H), 5.19−5.16 (m,
1H), 3.12 (d, J = 13.7 Hz, 1H), 2.68−2.65 (m, 1H), 2.53 (d, J = 13.7
Hz, 1H), 2.48−2.42 (m, 1H), 2.33−2.31 (m, 1H), 2.05−1.95 (m, 3H),
1.87−1.76 (m, 4H), 1.64 (dd, J = 14.3, 4.8 Hz, 1H), 1.23 (s, 3H), 1.09
(d, J = 6.6 Hz, 3H), 0.86 (s, 9H), 0.69 (s, 3H), 0.56 (d, J = 6.6 Hz,
3H) 0.20 (s, 3H), 0.09 (s, 3H).
(R)-((S)-5-(tert-Butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-di-
methyl-5,6,7,8-tetrahydroquinolin-3-yl)(4-(trifluoromethyl)phenyl)-
methanol (9). Yield: 496 mg (33% of theory). LCMS (ESI+)
calculated for C28H39F3INO2Si [M + H]+ m/z 634.18, found 634.2.
HPLC (method 1): retention time = 5.195 min. Rf-value: 0.62 (silica
gel, petroleum ether/ethyl acetate 4:1). 1H NMR (400 MHz,
(CD3)2SO) δ 7.69 (d, J = 8.2 Hz, 2H), 7.40 (d, J = 8.2 Hz, 2H),
6.62 (d, J = 4.13, 1H), 6.51 (br, 1H), 5.24−5.20 (m, 1H), 3.30−3.20
(m, 1H), 2.84 (d, J = 16.3 Hz, 1H), 2.56 (d, J = 16.3 Hz, 1H), 1.96
(dd, J = 14.3, 2.6, 1H), 1.82 (dd, J = 14.2, 4.8 Hz, 1H), 1.16 (s, 3H),
1.09 (d, J = 6.6 Hz, 3H), 0.92 (s, 3H), 0.89 (s, 9H), 0.46 (d, J = 6.6
Hz, 3H), 0.28 (s, 3H), 0.25 (s, 3H).
(S)-((S)-5-(tert-Butyldimethylsilyloxy)-4-iodo-2-isopropyl-7,7-di-
methyl-5,6,7,8-tetrahydro-quinolin-3-yl)(4-(trifluoromethyl)phenyl)-
methanol (9a). Yield: 782 mg (51% of theory). LCMS (ESI+)
calculated for C28H39F3INO2Si [M + H]+ m/z 634.18, found 634.2.
H
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Journal of Medicinal Chemistry
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(3′R,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-
c]quinolin]-9′-ol (2). To a solution of (3′R,9′S)-9′-(tert-butyldime-
thylsilyloxy)-4′-isopropyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]-
quinoline] (30 mg, 0.051 mmol) in tetrahydrofuran (2 mL) was added
tetrabutylammonium fluoride (150 μL of a 1 M solution in
tetrahydrofuran, 0.150 mmol). The solution was stirred for 12 h at
room temperature, then the solvent was evaporated in vacuo, and the
residue was chromatographed on silica gel (cyclohexane/ethyl acetate
90:10 to 50:50). Yield: 14 mg (58% of theory). HRMS (ESI+)
calculated for C27H32F3NO2 [M + H]+ m/z 460.2463, found 460.2464.
HPLC (method 1): retention time = 2.800 min. Rf-value: 0.50 (silica
gel, petroleum ether/ethyl acetate 4:1). 1H NMR (400 MHz,
(CD3)2SO) δ 7.74 (d, J = 8.2 Hz, 2H), 7.48 (d, J = 8.2 Hz, 2H),
6.19 (s, 1H), 5.01 (d, J = 5.3 Hz, 1H), 4.93 (dd, J = 11.0, 5.5 Hz, 1H),
2.93−2.84 (m, 1H), 2.84 (d, J = 16.4 Hz, 1H), 2.59 (d, J = 16.4 Hz,
1H), 2.51−2.42 (m, 1H), 2.17−2.07 (m, 1H), 1.87−1.64 (m, 8H),
1.14 (s, 3H), 1.09 (d, J = 6.6 Hz, 3H), 0.88 (s, 3H), 0.61 (d, J = 6.6
Hz, 3H).
C30H38N2O2 [M + H]+ m/z 459.30, found 459.4. HPLC (method 1):
retention time = 2.440 min. Rf-value: 0.47 (silica gel, petroleum ether/
ethyl acetate 2:1). H NMR (400 MHz, (CD3)2SO) δ 7.50 (d, J = 82
1
Hz, 2H), 7.30 (d, J = 8.2 Hz, 2H), 6.08 (s, 1H), 4.98 (d, J = 5.1 Hz,
1H), 4.95−4.90 (m, 1H), 3.28−3.26 (m, 1H), 2.92−2.85 (m, 1H),
2.84 (d, J = 16.2 Hz, 1H), 2.50−2.45 (m, 1H), 2.58 (d, J = 16.2 Hz,
1H), 2.07 (m, 1H), 1.86−1.65 (m, 7H), 1.67 (s, 6H), 1.15 (s, 3H),
1.08 (d, J = 6.8 Hz, 3H), 0.87 (s, 3H), 0.60 (d, J = 6.8 Hz, 3H).
(3′R,9′S)-3′-(4-tert-Butylphenyl)-4′-isopropyl-7′,7′-dimethyl-
6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]-
quinolin]-9′-ol (16). HRMS (ESI+) calculated for C30H41NO2 [M +
H]+ m/z 448.3216, found 448.3220. HPLC (method 6): retention
1
time = 3.45 min. H NMR (400 MHz, (CD3)2SO) δ 7.40 (d, J = 8.1
Hz, 2H), 7.19 (d, J = 8.1 Hz, 2H), 6.20 (s, 1H), 5.00−4.95 (m, 1H),
2.99 (d, J = 16.7 Hz, 1H), 2.94−2.85 (m, 1H), 2.80 (d, J = 16.7 Hz,
1H), 2.73−2.63 (m, 1H), 2.21−2.11 (m, 1H), 1.94−1.66 (m, 8H),
1.27 (s, 9H), 1.18 (m, 6H), 0.93 (s, 3H), 0.70 (d, J = 7.0 Hz, 3H), OH
not visible.
(3′R,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(3-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-
c]quinolin]-9′-ol (17). HRMS (ESI+) calculated for C27H32F3NO2 [M
+ H]+ m/z 460.2463, found 460.2469. HPLC (method 1): retention
Synthesis of Compounds 2a and 12−26. By an analogous
synthetic sequence to that for the synthesis of compound 2, the
compounds 2a and 12−26 were obtained.
1
time = 2.800 min. HPLC (method 4): retention time = 2.46 min. H
NMR (400 MHz, (CD3)2SO) δ 7.72 (d, J = 7.6 Hz, 1H), 7.64 (d, J =
7.6 Hz, 1H), 7.62−7.57 (m, 2H), 6.29 (s, 1H), 4.95 (dd, J = 11.2, 5.6
Hz, 1H), 2.92−2.85 (m, 1H), 2.91 (d, J = 16.1 Hz, 1H), 2.72−2.63
(m, 1H), 2.58−2.51 (m, 1H), 2.20−2.10 (m, 1H), 1.90−1.66 (m, 8H),
1.16 (s, 3H), 1.14 (d, J = 6.9 Hz, 3H), 0.89 (s, 3H), 0.64 (d, J = 6.9
Hz, 3H), OH not visible.
(3′S,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-
c]quinolin]-9′-ol (2a). Obtained starting from diasteromer 9a. HRMS
(ESI+) calculated for C27H32F3NO2 [M + H]+ m/z 460.2463, found
460.2464. HPLC (method 1): retention time = 2.792 min. Rf-value:
1
0.29 (silica gel, petroleum ether/ethyl acetate 4:1). H NMR (400
MHz, (CD3)2SO) δ 7.72 (d, J = 8.0 Hz, 2H), 7.47 (d, J = 8.0 Hz, 2H),
6.16 (s, 1H), 5.04−4.95 (m, 1H), 4.96 (d, J = 6.0 Hz, 1H), 2.78 (d, J =
16.7 Hz, 1H), 2.65−2.38 (m, 3H), 2.56 (d, J = 16.7 Hz, 1H,) 1.93−
1.64 (m, 8H), 1.10 (s, 3H), 1.03 (d, J = 6.7 Hz, 3H), 0.91 (s, 3H), 0.50
(d, J = 6.7 Hz, 3H). 13C NMR (101 MHz, (CD3)2SO) δ 158.2, 155.9,
152.2, 146.9, 133.1, 129.1 (2C), 128.6 (d, J = 20 Hz), 125.2 (2C),
124.7, 124.1 (d, J = 185 Hz), 96.9, 79.6, 63.3, 46.9, 45.7, 39.0, 36.7,
30.2, 31.2, 29.8, 27.5, 25.0, 24.4, 21.7, 20.6.
(3′R,9′S)-7′,7′-Dimethyl-3′-phenyl-4′-(propan-2-yl)-6′,7′,8′,9′-tet-
rahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]quinoline]-9′-ol
(12). HRMS (ESI+) calculated for C26H33NO2 [M + H]+ m/z
392.2590, found 392.2592. HPLC (method 4): retention time = 2.52
min. 1H NMR (400 MHz, (CD3)2SO) δ 7.41−7.31 (m, 3H), 7.26 (dd,
J = 7.8, 1.6 Hz, 2H), 6.20 (s, 1H), 4.96 (dd, J = 6.4, 5.3 Hz, 1H), 2.95
(d, J = 17.0 Hz, 1H), 2.94−2.84 (m, 1H), 2.74 (d, J = 17.0 Hz, 1H),
2.68−2.59 (m, 1H), 2.20−2.09 (m, 1H), 1.92−1.65 (m, 8H), 1.17 (s,
3H), 1.16 (d, J = 6.7 Hz, 3H), 0.92 (s, 3H), 0.69 (d, J = 6.7 Hz, 3H);
OH not visible.
(3′R,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(4-(trifluoromethoxy)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-
c]quinolin]-9′-ol (18). LCMS (ESI+) calculated for C27H32F3NO3 [M
+ H]+ m/z 476.24, found 476.4. HPLC (method 6): retention time =
3.18 min. 1H NMR (400 MHz, (CD3)2SO) δ 7.39 (d, J = 8.7 Hz, 2H),
7.35 (d, J = 8.7 Hz, 2H), 6.14 (s, 1H), 4.99 (d, J = 5.1 Hz, 1H), 4.95−
4.90 (m, 1H), 2.95−2.87 (m, 1H), 2.84 (d, J = 16.4 Hz, 1H), 2.58 (d, J
= 16.4 Hz, 1H), 2.51−2.45 (m, 1H), 2.13−2.04 (m, 1H), 1.86−1.67
(m, 8H), 1.14 (s, 3H), 1.09 (d, J = 6.6 Hz, 3H), 0.87 (s, 3H), 0.59 (d, J
= 6.6 Hz, 3H).
(3′S,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(5-(trifluoromethyl)-
pyridin-2-yl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-
furo[3,4-c]quinolin]-9′-ol (19). HRMS (ESI+) calculated for
C26H31F3N2O3 [M + H]+ m/z 461.2416, found 461.2420. HPLC
(method 7): retention time = 3.46 min. 1H NMR (400 MHz,
(CD3)2SO) δ 8.93 (m, 1H), 8.24 (dd, J = 8.3, 2.4 Hz, 1H), 7.64 (d, J =
8.3 HZ, 1H), 6.25 (s, 1H), 5.01 (d, J = 5.6 Hz, 1H), 4.93 (m, 1H),
2.89−2.83 (m, 1H), 2.82 (d, J = 16.4 Hz, 1H), 2.63 (m, 1H), 2.61−
2.52 (m, 3 H), 2.36 (m, 1H), 2.21−2.15 (m, 2H), 1.89−1.65 (m, 4H),
1.13 (s, 3H), 1.11 (d, J = 6.8 Hz, 3H), 0.87 (s, 3H), 0.57 (d, J = 6.8
Hz, 3H).
(3′R,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(6-(trifluoromethyl)-
pyridin-3-yl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-
furo[3,4-c]quinolin]-9′-ol (20). HRMS (ESI+) calculated for
C26H31F3N2O3 [M + H]+ m/z 461.2418, found 461.2420. HPLC
(method 8): retention time = 5.83 min. 1H NMR (400 MHz, CDCl3)
δ 8.76 (s, 1H), 7.73 (d, J = 8,5 Hz, 1H), 7.64 (d, J = 8,5 Hz, 1H) 6.16
(s, 1H), 5.10 (m, 1H), 3.04 (d, J = 16.4 Hz, 1H), 2.83 (d, J = 16.4 Hz,
1H), 2.77 (m, 1H), 2.50 (m, 1H), 2.12 (m, 1H), 2.04−1.92 (m, 2H),
1.93−1.79 (m, 7H), 1.25 (s, 3H), 1.22 (d, J = 6,6 Hz, 3H), 1.01 (s,
3H), 0.85 (d, J = 6.6 Hz, 3H).
(3′R,9′S)-3′-(4-Fluorophenyl)-4′-isopropyl-7′,7′-dimethyl-
6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]-
quinolin]-9′-ol (13). HRMS (ESI+) calculated for C26H32FNO2 [M +
H]+ m/z 410.2495, found 410.2499. HPLC (method 3): retention
1
time = 1.41 min. H NMR (400 MHz, (CD3)2SO) δ 7.29 (d, J = 8.3
Hz, 2H), 0.7.18 (d, J = 8.3 Hz, 2H), 6.10 (s, 1H), 4.97 (d, J = 5.1, 1H),
4.95−4.87 (m, 1H), 3.28 (s, 1H), 2.93−2.83 (m, 1H), 2.84 (d, J = 16.3
Hz, 1H), 2.58 (d, J = 16.3 Hz, 1H), 2.53−2.45 (m, 1H), 2.12−2.02
(m, 1H), 1.87−1.66 (m, 7H), 1.15 (s, 3H), 1.09 (d, J = 6.7 Hz, 3H),
0.88 (s, 3H), 0.31 (d, J = 6.7 Hz, 3H). 13C NMR (101 MHz,
(CD3)2SO) δ 161.6 (d, J = 244 Hz), 158.3, 156.5, 152.1, 138.9, 132.5,
130.1 (2C), 124.9, 115.1 (d, J = 21 Hz, 2C), 96.5, 80.5, 63.1, 46.7,
45.4, 40.8, 38.9, 31.4, 30.6, 30.0, 28.8, 25.0 (2C), 21.5, 20.9.
(3′R,9′S)-4′-Ethyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)phenyl)-
6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]-
quinolin]-9′-ol (21). LCMS (ESI+) calculated for C26H30F3NO2 [M +
H]+ m/z 446.23, found 446.5. HPLC (method 3): retention time =
1.58 min. 1H NMR (400 MHz, (CD3)2SO) δ 7.74 (d, J = 8.0 Hz, 2H),
7.49 (d, J = 8.0 Hz, 2H), 6.16 (s, 1H), 5.02 (d, J = 5.1 Hz, 1H), 4.96−
4.90 (m, 1H), 2.94−2.84 (m, 1H), 2.83 (d, J = 16.2 Hz, 1H), 2.58 (d, J
= 16.2 Hz, 1H,) 2.32−2.21 (m, 1H), 2.21−2.04 (m, 2H), 1.88−1.66
(m, 8H), 1.14 (s, 3H), 0.87 (s, 3H), 0.79 (t, J = 7.5 Hz, 3H).
(3′R,9′S)-4′-Cyclopentyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-
4-((3′R,9′S)-9′-Hydroxy-4′-isopropyl-7′,7′-dimethyl-6′,7′,8′,9′-tet-
rahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]quinoline]-3′-yl)-
benzonitrile (14). HRMS (ESI+) calculated for C27H32N2O2 [M + H]+
m/z 417.2542, found 417.2544. HPLC (method 5): retention time =
1
1.09 min. H NMR (400 MHz, CDCl3) δ 7.64 (d, J = 8.1 Hz, 2H),
7.40 (d, J = 8.1 Hz, 2H), 6.06 (s, 1H), 5.09 (m, 1H), 2.98 (m, 1H),
2.82−2.66 (m, 2H), 2.46 (m, 1H), 2.15−1.72 (m, 10H), 1.25−1.23
(m, 3H), 1.00 (s, 3H), 0.91−0.84 (m, 6H).
2-(4-((3′R,9′S)-9′-Hydroxy-4′-isopropyl-7′,7′-dimethyl-6′,7′,8′,9′-
tetrahydro-3′H-spiro[cyclopentane-1,1′-furo[3,4-c]quinoline]-3′-yl)-
phenyl)-2-methylpropanenitrile (15). LCMS (ESI+) calculated for
I
dx.doi.org/10.1021/jm500431d | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
c]quinolin]-9′-ol (22). HRMS (ESI+) calculated for C29H34F3NO2 [M
Author Contributions
+ H]+ m/z 486.2620, found 486.2620. HPLC (method 5): retention
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript. All authors contributed equally.
1
time = 1.22 min. H NMR (400 MHz, CDCl3) δ 7.59 (d, J = 8.3 Hz,
2H), 7.40 (d, J = 8.3 Hz, 2H), 6.08 (s, 1H), 5.09 (m, 1H), 2.96 (d, J =
16.6 Hz, 1H), 2.77−2.65 (m, 2H), 2.57 (m, 1H), 2.16−1.61 (m, 12H),
1.57−1.41 (m, 1H), 1.39−1.26 (m, 2H), 1.24 (s, 3H), 1.05 (m, 1H),
0.95 (s, 3H), 0.94−0.76 (m, 2H).
Notes
The authors declare no competing financial interest.
(3′R,9′S)-7′,7′-Dimethyl-4′-(tetrahydro-2H-pyran-4-yl)-3′-(4-
(trifluoromethyl)phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro-
[cyclopentane-1,1′-furo[3,4-c]quinolin]-9′-ol (23). LCMS (ESI+)
calculated for C29H34F3NO2 [M + H]+ m/z 502.26, found 502.6.
HPLC (method 1): retention time = 2.891 min. Rf-value: 0,25 (silica
gel, petroleum ether/ethyl acetate 4:1). 1H NMR (400 MHz,
(CD3)2SO) δ 7.75 (d, J = 8.1 Hz, 2H), 7.54 (d, J = 8.1 Hz, 2H),
6.23 (s, 1H), 5.02 (d, J = 5.2 Hz, 1H), 4.93 (dd, J = 11.9, 5.4 Hz, 1H),
3.85 (dd, J = 11.5, 3.6 Hz, 1H), 3.57 (dd, J = 11.0, 3.6 Hz, 1H), 3.25−
3.16 (m, 1H), 2.97−2.88 (m, 1H), 2.85 (d, J = 16.7 Hz, 1H), 2.80−
2.71 (m, 1H), 2.45−2.34 (m, 1H), 2.58 (d, J = 16.7 Hz, 1H), 2.07 (m,
1H), 1.95−1.68 (m, 9H), 1.55−1.40 (m, 2H), 1.15 (s, 3H), 0.87 (s,
3H), 0.43−0.36 (m, 1H). 13C NMR (101 MHz, (CD3)2SO) δ 156.8,
156.0, 152.2, 147.2, 132.8, 129.0 (2C), 128.6, 125.3 (2C), 125.2, 124.1,
97.0, 80.5, 66.9, 66.5, 63.1, 46.6, 45.5, 40.7, 39.1, 38.9, 30.9, 30.6, 30.4,
30.0, 28.9, 24.9 (2C).
ACKNOWLEDGMENTS
■
We gratefully acknowledge the research facilities and materials
provided by the departments of Medicinal Chemistry,
Cardiometabolic Diseases, Drug Discovery Support, and Lead
Identification at Boehringer Ingelheim Pharma GmbH & Co.
KG and BI Research Italia S.a.s. di BI IT S.r.l.
ABBREVIATIONS
■
hApoB, human apolipoprotein B; CBS reduction, Corey−
Bakshi−Shibata reduction; CL, confidence limit; Cpd, com-
pound; hCETP, human cholesteryl ester transfer protein; LLQ,
lower limit of quantification; tg, transgenic
(3R,9S)-4-Isopropyl-1,1,7,7-tetramethyl-3-(4-(trifluoromethyl)-
phenyl)-1,3,6,7,8,9-hexahydrofuro[3,4-c]quinolin-9-ol (24). LCMS
(ESI+) calculated for C25H30F3NO2 [M + H]+ m/z 434.23, found
434.2. HPLC (method 1): retention time = 2.551 min. Rf-value: 0,46
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1
(silica gel, petroleum ether/ethyl acetate 4:1). H NMR (400 MHz,
(CD3)2SO) δ 7.75 (d, J = 8.0 Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H), 6.22
(s, 1H), 4.98 (dd, J = 11.7, 5.6 Hz, 1H), 3.17, (d, 5.2 Hz, 1H), 2.83 (d,
J = 16.2 Hz, 1H), 2.60 (d, J = 16.2 Hz, 1H), 2.50−2.42 (m, 1H), 1.83
(dd, J = 13.5, 5.4 Hz, 1H), 1.75 (dd, J = 13.5, 5.5 Hz, 1H), 1.67 (s,
3H), 1.54 (s, 3H), 1.14 (s, 3H), 1.09 (d, J = 6.7 Hz, 3H), 0.88 (s, 3H),
0.68 (d, J = 6.7 Hz, 3H).
(3′R,9′S)-4′-Isopropyl-7′,7′-dimethyl-3′-(4-(trifluoromethyl)-
phenyl)-6′,7′,8′,9′-tetrahydro-3′H-spiro[cyclohexane-1,1′-furo[3,4-
c]quinolin]-9′-ol (25). LCMS (ESI+) calculated for C28H34F3NO2 [M
+ H]+ m/z 474.26, found 474.3. HPLC (method 1): retention time =
3.040 min. Rf-value: 0,52 (silica gel, petrol ether/ethyl acetate 4:1). 1H
NMR (400 MHz, (CD3)2SO) δ 7.74 (d, J = 8.0 Hz, 2H), 7.53 (d, J =
8.0 Hz, 2H), 6.23 (s, 1H), 5.09−5.02 (m, 1H), 4.97(d, J = 5.0 Hz,
1H), 2.87 (d, J = 16.2 Hz, 1H), 2.58 (d, J = 16.2 Hz, 1H), 2.59−2.51
(m, 1H), 2.52−2.44 (m, 1H), 2.03−1.92 (m, 1H), 1.83−1.55 (m, 6H),
1.49−1.40 (m, 2H), 1.34−1.20 (m, 2H), 1.16 (s, 3H), 1.08 (d, J = 6.8
Hz, 3H), 0.86 (s, 3H), 0.63 (d, J = 6.8 Hz, 3H).
(3R,9S)-4-Isopropyl-7,7-dimethyl-3-(4-(trifluoromethyl)phenyl)-
2′,3′,5′,6,6′,7,8,9-octahydro-3H-spiro[furo[3,4-c]quinoline-1,4′-
pyran]-9-ol (26). HRMS (ESI+) calculated for C27H32F3NO2 [M +
H]+ m/z 476.2413, found 476. 2416. HPLC (method 9): retention
time = 4.96 min. Chiral HPLC: retention time = 2.45 min for 26 and
1
2.17 min for ent-26. H NMR (400 MHz, (CD3)2SO) δ 7.75 (d, J =
8.0 Hz, 2H), 7.54 (d, J = 8.0 Hz, 2H), 6.30 (s, 1H), 5.11 (d, J = 4.6 Hz,
1H), 5.04 (dd, J = 10.1, 5.2 Hz, 1H), 3.80 (dd, J = 10.8, 4.9 Hz, 1H),
3.76−3.70 (m, 1H), 3.68 (dd, J = 10.1, 4.9 Hz, 1H), 3.55−3.46 (m,
1H), 2.98 (dt, J = 13.4, 5.2 Hz, 1H), 2.86 (d, J = 16.4 Hz, 1H), 2.60 (d,
J = 16.4 Hz, 1H), 2.52−2.43 (m, 1H), 2.31 (dt, J = 12.8, 5.6 Hz, 1H),
1.86−1.76 (m, 2H), 1.60−1.46 (m, 2H), 1.16 (s, 3H), 1.09 (d, J = 6.8
Hz, 3H), 0.86 (s, 3H), 0.64 (d, J = 6.8 Hz, 3H).
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ASSOCIATED CONTENT
* Supporting Information
■
S
Determination of absolute stereochemisty and crystal data of
compound 26. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
■
*Phone: +49 7351 54 5465. E-mail: thomas.trieselmann@
boehringer-ingelheim.com.
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