Quinazolinone derivatives as orally available ghrelin receptor antagonists for the treatment of diabetes and obesity

Article abstract of DOI:10.1021/jm070071+

The peptide hormone ghrelin is the endogenous ligand for the type 1a growth hormone secretagogue receptor (GHS-R1a) and the only currently known circulating appetite stimulant. GHS-R1a antagonism has therefore been proposed as a potential approach for obe

Full text of DOI:10.1021/jm070071+

5202
J. Med. Chem. 2007, 50, 5202-5216
Quinazolinone Derivatives as Orally Available Ghrelin Receptor Antagonists for the Treatment
of Diabetes and Obesity
Joachim Rudolph,*,† William P. Esler,*,‡ Stephen O’Connor,† Philip D. G. Coish,† Philip L. Wickens,† Michael Brands,†
Donald E. Bierer,† Brian T. Bloomquist,‡ Georgiy Bondar,† Libing Chen,† Chih-Yuan Chuang,† Thomas H. Claus,‡ Zahra Fathi,‡
Wenlang Fu,† Uday R. Khire,† James A. Kristie,§ Xiao-Gao Liu,† Derek B. Lowe,† Andrea C. McClure,† Martin Michels,†
Astrid A. Ortiz,‡ Philip D. Ramsden,† Robert W. Schoenleber,† Tatiana E. Shelekhin,† Alexandros Vakalopoulos,†
Weifeng Tang,§ Lei Wang,† Lin Yi,† Stephen J. Gardell,‡ James N. Livingston,‡ Laurel J. Sweet,‡ and William H. Bullock†
Departments of Chemistry Research, Metabolic Disorders Research, and Research Technologies, Bayer Pharmaceuticals Corporation,
400 Morgan Lane, West HaVen, Connecticut 06516
ReceiVed January 18, 2007
The peptide hormone ghrelin is the endogenous ligand for the type 1a growth hormone secretagogue receptor
(GHS-R1a) and the only currently known circulating appetite stimulant. GHS-R1a antagonism has therefore
been proposed as a potential approach for obesity treatment. More recently, ghrelin has been recognized to
also play a role in controlling glucose-induced insulin secretion, which suggests another possible benefit for
a GHS-R1a antagonist, namely, the role as an insulin secretagogue with potential value for diabetes treatment.
In our laboratories, piperidine-substituted quinazolinone derivatives were identified as a new class of small-
molecule GHS-R1a antagonists. Starting from an agonist with poor oral bioavailability, optimization led to
potent, selective, and orally bioavailable antagonists. In vivo efficacy evaluation of selected compounds
revealed suppression of food intake and body weight reduction as well as glucose-lowering effects mediated
by glucose-dependent insulin secretion.
Introduction
and animals, its main function is regarded to be acute meal
initiation as well as long-term energy-balance and body-weight
regulation. Consequently, ghrelin blockade by GHS-R1a an-
tagonists has been put forth as a new concept for treating obesity,
and several pharmaceutical companies have recently revealed
activity in this area.6
It is estimated that currently some 194 million people
worldwide, or 5.1% in the adult population, have diabetes and
that this will increase to 333 million, or 6.3%, by 2025. It is
the fourth or fifth leading cause of death in most developed
countries, and there is substantial evidence that it is an epidemic
in many developing and newly industrialized nations.1
Obesity is the principal risk factor for type 2 diabetes. In
western countries, around 90% of type 2 diabetes cases are
attributable to weight gain, and childhood overweight issues
and obesity are now leading to an emergence of premature type
2 diabetes, which is particularly difficult to manage once
established.1 While even modest reductions in body weight and/
or adiposity have been shown to result in marked improvements
in insulin sensitivity or even elimination of diabetic symptoms,
weight loss is more difficult to achieve in diabetic individuals.1
To further complicate matters, many anti-diabetic therapies are
prone to increase body weight.2 New treatments that act directly
to improve glucose tolerance while simultaneously promoting
clinically meaningful weight loss could have tremendous value
for therapeutic intervention in type 2 diabetes.
While much of the literature on ghrelin has focused on its
effect on food intake, a growing body of data suggests that
ghrelin and its receptor play a direct role on the regulation of
glucose homeostasis. Ghrelin as well as its receptor GHS-R1a
are detectable in islet cells,7-13 and ghrelin has been found to
suppress insulin secretion in multiple islet model systems.11,12,14,15
The physiological relevance of this effect to glucose homeostasis
in animals and humans has been demonstrated by numerous
studies that show a clear negative correlation between ghrelin
levels and insulin secretion.12,16-25 Furthermore, peptide GHS-
R1a antagonists were found to block the effects of endogenous
ghrelin, to promote insulin secretion from isolated rat islets,
and to increase insulin secretion and improve glucose tolerance
in mice,12 but this effect has so far not been reported with
selective small molecule GHS-R1a antagonists.
A GHS-R1a receptor high-throughput screen conducted in
our laboratories identified the quinazolinone derivative 1 as hit
with high GHS-R1a affinity (Ki ) 36 nM). Functional activity
testing of this compound in a guanosine 5-O-(3-thiotriphosphate)
(GTPγS) binding assay revealed agonistic instead of the desired
antagonistic functional activity. As part of our initial structure-
activity relationship (SAR) studies, we investigated the influence
of N-alkylation on the piperidine nitrogen atom on functional
activity. We synthesized the N-ethyl piperidine derivative of 1,
compound 2,26 and found this compound to have a dramatically
different functional activity profile, namely, full antagonistic
activity with high GHS-R1a affinity (Ki ) 20 nM). Structurally
related tertiary amine analogues were tested, which likewise
exerted antagonistic GHS-R1a activity. The identified piperi-
dine-substituted quinazolinone series constitutes a new class of
Ghrelin, an acylated peptide hormone predominantly produced
in the stomach, is the natural ligand of the growth hormone
secretagogue receptor type 1a (GHS-R1a).a Because of its
recently recognized role as a powerful orexigenic (appetite
stimulant), ghrelin has attracted high interest over the past few
years.3-5 On the basis of numerous studies on ghrelin in humans
* To whom correspondence should be addressed. (J.R.) Tel: + 1 650
467 8867. Fax: + 1 650 467 8922. E-mail: rudolph.joachim@gene.com.
(W.E.)Tel: +18606861256.Fax: +1860-441-0548.E-mail: william.esler@pfizer.com.
† Department of Chemistry Research.
‡ Department of Metabolic Disorders Research.
§ Department of Research Technologies.
a Abbreviations: GHS-R1a, type 1a growth hormone secretagogue
receptor; GTPγS, guanosine 5-O-(3-thiotriphosphate); SPA, scintillation
proximity assay; DIO, diet-induced obese; IPGTT, intraperitoneal glucose
tolerance test.
10.1021/jm070071+ CCC: $37.00 © 2007 American Chemical Society
Published on Web 09/21/2007

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5203
Scheme 1a
a Reagents and conditions: (a) NEt3, CH2Cl2, 14 h; then Ac2O, 50 °C, 2 h, 62%. (b) 4-Chlorophenylboronic acid, K2CO3, PdCl2(dppf), 50 °C, 73%. (c)
Toluene, reflux; then ethylene glycol, LiOH, 135 °C, 63%. (d) TFA, CH2Cl2, 82%. (e) CH3CHO, CH3COOH, NaB(OAc)3H, 0 °C, 69%. (f) R1′′X, K2CO3,
CH3CN, 70 °C.
Scheme 2a
a Reagents and conditions: (a) C2H5I, acetone, 50 °C, 68%. (b) NaBH4, MeOH, CH2Cl2, 0 °C, 17%.
GHS-R1a antagonists, unprecedented and structurally distinct
from previously described GHS-R1a antagonists.6
Chart 1
nilic acid was reacted with 2-methylbenzoylchloride to form
benzoxazinone 3.27 Suzuki coupling and subsequent insertion28
of BOC-protected aminomethylpiperidine 5 led to intermediate
6, which was deprotected and subsequently alkylated using either
reductive amination or nucleophilic substitution conditions to
furnish compounds 8-14.
We also prepared the ethylpiperidine homologue 15, an
analogue with an extended alkyl chain, using the sequence
described in Scheme 1 and appropriate starting materials
(Chart 1).
The dehydropiperidine analogue of compound 8 was syn-
thesized as described in Scheme 2. Pyridine intermediate 16,
prepared according to the sequence described in Scheme 1, was
alkylated to form pyridinium salt 17, which was then regiose-
lectively reduced29 to give the dehydropiperidine derivative 18.
Morpholine derivative 23 was prepared from intermediate 3
and insertion of morpholine building block 19, followed by
Suzuki coupling, deprotection, and alkylation.
Poor oral bioavailability is a common deficiency of most
small-molecule GHS-R1a antagonists described in the literature.6
To get a preliminary read of the pharmacokinetic behavior of
our lead series, compound 2 (as its HCl salt) was orally
administered to rats at a dose of 10 mg/kg. We observed low
plasma exposure (Cmax < 20 nM), which was at least partly
due to high clearance. Metabolite identification studies revealed
the N-methyl-N-butyl moiety as a site of significant metabolism.
We therefore placed a particular focus on identifying replace-
ments for this group.
This account will describe systematic SAR studies on the
periphery of the quinazolinone core leading to the discovery of
potent GHS-R1a antagonists with favorable DMPK properties.
The optimized analogues 26 and 43 are active in food intake
and weight-loss models as well as in glucose tolerance animal
models and represent, together with other class members, the
first examples of orally available GHS-R1a antagonists with in
vivo efficacy in these models.
Compounds 6-13 in Scheme 1 contain a chiral center at the
heterocycle linkage position and were prepared as racemates.
Using the sequence described in Scheme 1 and substituting the
racemic piperidine building block 5 by its commercially
available (R)- and (S)-enantiomers, we synthesized both enan-
Chemistry
The majority of the quinazolinone analogues described in this
report was synthesized according to Scheme 1. 5-Bromoanthra-

5204 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Rudolph et al.
Chart 2
Scheme 3a
compound 28 (Scheme 4). This was accomplished using
2-amino-4-bromobenzoic acid instead of 2-amino-5-bromoben-
zoic acid as the starting material and applying otherwise
analogous procedures as described in Scheme 1.
Further modification at the eastern part of the quinazolinone
core included the synthesis of derivatives with truncated side
chains. These compounds were synthesized from the corre-
sponding anthranilic acids using the same sequence as described
in Scheme 1 and omitting the Suzuki coupling step (Scheme
5).
While alkoxy derivatives 30 and 31 were derived from
available anthranilic acid starting materials, phenoxy analogues
34 and 35 were formed using the Ullmann coupling reaction
(Scheme 6).30 The (S)-phenoxy analogues 36 and 37 were
synthesized in an analogous manner (Scheme 6).
a Reagents and conditions: (a) Toluene, 100 °C; ethylene glycol, LiOH,
135 °C, 67%. (b) 4-Chlorophenylboronic acid, K2CO3, PdCl2(dppf), 90 °C,
76%. (c) 1-Chloromethyl chloroformate, CH2ClCH2Cl, reflux, 91%. (d)
2-Bromopropane, K2CO3, CH3CN, 70 °C, 55%.
Scheme 4
As described in Scheme 7, a more concise method was used
to build the quinazolinone ring carrying small substituents (H,
CH3) at the 2-position (R2).31,32 Coupling of a phenyl or phenoxy
group at the 6-position of the quinazolinone ring was performed
as outlined in Schemes 1 and 6.
Results and Discussion
Scheme 5
In Vitro SAR Studies. Affinity for GHS-R1a was determined
using a [125I]ghrelin displacement assay [scintillation proximity
assay (SPA) format] employing membranes prepared from a
human embryonic kidney cell line (HEK293F) overexpressing
recombinant GHS-R1a. The functional activity of test com-
pounds was assessed by measuring GTPγS binding to mem-
branes likewise prepared from HEK293F cells overexpressing
recombinant GHS-R1a.
As we sought to replace the N-methyl-N-butyl moiety of lead
compound 2 due to its metabolic lability, we started our SAR
investigations at the 6- and 7-positions of the quinazolinone
ring (R3 and R4). Initial SAR studies had suggested as preferred
R1 (3-position of quinazolinone ring) an N-ethyl- or N-isopropyl-
substituted methylpiperidine moiety and as preferred R2 (2-
position of quinazolinone ring) an ortho-substituted phenyl
group. As can be seen from Table 1, a bulky group at the
tiomers of 8, compound 24 (S), and compound 25 (R).
Compounds 26 and 27 were prepared in the same fashion (Chart
2).
As part of our SAR investigation of the eastern part of the
molecule, we transposed the 4-chlorophenyl side chain from
the 6- to the 7-position of the quinazolinone scaffold to furnish
Scheme 6a,b
a Reagents and conditions: (a) Toluene, reflux; ethylene glycol, LiOH, 135 °C, 48%. (b) 4-Fluorophenol, CuCl, TMHD, Cs2CO3, NMP; 46%. (c) TFA,
CH2Cl2, 78%. (d) 2-Iodopropane, K2CO3, CH3CN, 70 °C, 86%. bCompounds 37 and 38 were synthesized in an analogous fashion using homochiral piperidine
building block 5a.

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5205
Scheme 7a
a Reagents and conditions: (a) K2CO3, THF, 70 °C, 86%. (b) 140 °C. (c) TFA, CH2Cl2. (d) 2-Iodopropane, K2CO3, CH3CN, 70 °C, 80% (three steps).
(e) 4-Chlorophenylboronic acid, Cs2CO3, PdCl2(dppf), DME, H2O, 60 °C. (f) 4-Fluorophenol, Cs2CO3, CuCl, TMHD, NMP, microwave, 205 °C.
Table 1. SAR Investigation at the 6- and 7-Positions of the Quinazolinone Corea
a Reported in vitro values are an average of at least two replicates. b Pharmacokinetic screening study in Wistar rat; compounds were orally administered
at 3 mg/kg in PEG400/methanesulfonic acid (80:20) vehicle. c GHS-R agonism EC50 ) 6.5 nM.
6-position (R3) is essential for activity. While phenoxy substit-
uents confer slightly higher binding affinities, the more rigid
phenyl analogues bear less potential for undesired partial
agonism. Interestingly, even the unsubstituted piperidine ana-
logue in the phenyl series (7) is an antagonist, which is opposite
from the corresponding phenoxy analogue 34 as well as the
amino-substituted screening hit 1. Following this observation,
we concentrated further SAR efforts on compounds carrying
phenyl groups at the 6-position.
< 20 nM at 10 mg/kg p.o., rat), indicating that the metabolic
instability of the N-methyl-N-butyl moiety of 2 had in fact
contributed to its weak exposure. We also determined the oral
bioavailability of the HCl salt of compound 8 in rat and found
it to be moderate (29%) (p.o. study conducted at 3 mg/kg, i.v.
study conducted at 1 mg/kg).
Among the two enantiomers of compound 8, the (S)-
stereoisomer 24 was found to be significantly more potent than
the (R)-isomer 25 (Table 2). This enantiospecific activity
appeared to be general for this class, also with substantially
modified analogues (see the Supporting Information). Extension
Plasma exposure (3 mg/kg p.o., rat) of compounds shown in
Table 1 was improved over the initial lead compound 2 (Cmax

5206 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Table 2. SAR Investigations at the Piperidine Ringa
Rudolph et al.
a Reported in vitro values are an average of at least two replicates. b Calculated using ACD software.34 c Pharmacokinetic screening study in rat; compounds
were orally administered at 3 mg/kg in PEG400/methanesulfonic acid (80:20) vehicle. d Not determined.
of the piperidine linker by one CH2 unit (15) resulted in loss of
activity. Particular attention was laid on studying the dependence
between activity and pKa, since the pKa of alkyl-substituted
piperidine analogues was very high (∼10), potentially compro-
mising pharmacokinetic properties.33 Modulation of the pKa was
achieved by introducing electronegative atoms at the ring itself
as well as at its periphery, and selected compounds derived from
these efforts are shown in Table 2. While pKa values down to
at least 8 were tolerated without substantial loss of GHS-R1a
affinity, none of these changes had any apparent effect on
plasma exposure in rats.
As a potential measure for improving DMPK properties, we
took an active effort to reduce lipophilicity.35 This pursuit led
us to the 2-position of the quinazolinone ring. As shown in Table
3, decreasing the size of the R2 substituent gradually weakened
activity, but the effect was relatively small, particularly for the
series with R3 ) phenoxy where even the unsubstituted analogue
45 (R2 ) H) still possesses ghrelin binding affinity of <50 nM.
Although activity losses arose from decreasing the size of the
R2 group, clear benefits resulted for other drug property features,
such as solubility and selectivity. For example, 2-phenyl
analogue 24 (R3 ) phenyl) displayed high binding affinity to
the 5-HT2c receptor and phenyl analogue 36 (R3 ) phenoxy)
was a potent CYP2D6 inhibitor, while analogues with
smaller groups were devoid of such selectivity issues and
furthermore showed superior aqueous solubility. Interestingly,
compounds with alkyl groups larger than ethyl on the piperidine
nitrogen in the R1 position (compounds 9-12) showed a trend
toward inverse agonism. A similar trend toward inverse agonsim
was also seen in the alkylated dehydropiperidine-derived
compound 18.36
In Vivo Studies. Further investigations were carried out on
the 2-isopropyl-6-phenyl derivative 26 and the 2-methyl-6-
phenoxy derivative 43. Both compounds are potent and selec-
tive38 GHS-R1a antagonists with Kb values of 14 and 11 nM,
respectively. Key pharmacokinetic data of 26 and 43 in rat are
shown in Table 4. Both compounds display high bioavailability,
moderate clearance, and very high volumes of distribution.
While a high volume of distribution was a general feature of
this compound class, clearance and bioavailability of 26 and
43 were significantly improved over first generation analogues.
There is compelling evidence that ghrelin plays a critical role
in modulating body weight through the control of food intake

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5207
Table 3. SAR Investigations at the 2-Position of the Quinazolinone Corea
a See the corresponding footnote in Table 1. b Calculated using Daylight software.37 c Kinetic solubility determined by HPLC; buffered aqueous test
solution contained 1% DMSO. d Assay information given in the Experimental Section. e Determined using CYPD26 supersomes and the fluorescent substrate
3-[2-(N,N-diethyl-N-methylamino)ethyl]-7-methoxy-4-methylcoumarin (AMMC). f Pharmacokinetic screening study in Wistar rat; compounds were orally
administered at 3 mg/kg in PEG400/methanesulfonic acid (80:20) vehicle. g Compound was found to be a 5-HT2c antagonist.
and/or regulation of fuel substrate efficiency. We therefore tested
the effects of the GHS-R1a antagonists 26 and 43 on food intake
in the mouse fasted-refed model. As shown in Figure 1, upon
oral administration at a dose of 30 mg/kg, both compounds
caused significant suppression of food intake throughout the
period from 1 to 24 h, with 26 being the more efficacious
compound.
Following the food intake studies, we examined the effects
of 26 and 43 on body weight in diet-induced obese (DIO) mice.
Over a period of 9 days, compounds were orally administered
once daily at doses of 3, 10, and 30 mg/kg (Figure 2). While
compound 26 lowered body weight at the 10 mg/kg dose,
compound 43, consistent with a weaker effect in the food intake
study, was efficacious only at the highest dose of 30 mg/kg,

5208 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Rudolph et al.
Table 4. Pharmacokinetic Profile of Compounds 26 and 43 in Rata
rently under evaluation by the FDA.39 This, to the best of our
knowledge, constitutes the first reported case of an orally
administered GHS-R1a antagonist that promotes chronic body
weight loss in animals. One of the concerns that has been raised
about the utility of GHS-R1a antagonists for treatment of obesity
is that in obese patients ghrelin levels are significantly reduced,40
with parallel observations made for obese rodents.41 Our data
show that, despite the decreased ghrelin levels in DIO mice,
the ghrelin tone is still sufficient to allow antagonists to be
effective.
compound
26
43
route
dose (mg/kg)
i.v.
0.7
p.o.
3
i.v.
1
p.o.
3
AUC0-t (mg h/L)
0.58
0.10
16
1.2
18.8
1.7
0.07
0.50
0.11
19
1.9
19.2
1.3
0.08
C
max (mg/L)
1/2 (h)
CL (L/kg h)
ss (L/kg)
F (%)
T
V
69
85
A possible explanation for the difference in efficacy between
compounds 26 and 43 despite comparable in vitro activity and
plasma exposure was a difference in brain exposure. Pharma-
cokinetic studies on both compounds and other quinazolinone
derivatives in fact revealed that the effect on food intake in mice
is dependent on the drug levels detected in the brain (Table 5).
Thus, compound 26, a highly brain-exposed compound, ef-
fectively lowered food intake in a mouse fasted-refed model,
while the lesser brain-exposed compound 43 was weaker in this
regard. Consistent with these findings, compound 46,42 a potent
ghrelin antagonist with high plasma exposure in mice, but
nondetectable brain levels, was entirely inactive in the food
intake model. These results are in agreement with data by others
showing that ghrelin antagonists with an effect on food intake
are exposed in the brain.43 Thus, given that the effects of 26
and 43 on body weight are driven by suppression of food intake,
the difference in brain exposure could contribute to the
difference in efficacy in the DIO mouse model. Further support
for this hypothesis would require detailed measurements of free
brain concentrations at various time points throughout the
chronic study and examination of compounds with greater
differences in brain exposure.
a The pharmacokinetic parameter estimates of compound 26 and 43 were
evaluated in male Wistar rats following single-dose i.v. administration at
∼1 mg/kg and oral administration at 3 mg/kg. Test compounds were freshly
prepared before dosing in rat plasma (2% DMSO) as a solution for i.v.
administration and in PEG400/methanesulfonic acid 10 mM (80:20, v/v)
as a solution for oral administration.
Figure 1. Acute effects of compounds 26 and 43 on food intake in
the mouse fasted-refed model (lean C57 black mice). Both compounds
were orally administered at a dose of 30 mg/kg (vehicle, PEG400/
water 50:50).
The different degree of brain exposure of the compounds
shown in Table 4 can partly be rationalized by differences in
their polar surface area and number of rotational bonds, two
important physicochemical determinants for blood-brain barrier
permeability (Table 5).44
Recent studies conducted by us and others have demonstrated
that ghrelin suppresses insulin secretion and that this effect is
mediated through GHS-R1a.12,14,46 Consequently, GHS-R1a
antagonism has been put forth as a potential approach for
improving glucose homeostasis and treatment of type 2 diabetes.
The quinazolinone derivatives 26 and 43 are potent and selective
GHS-R1a antagonists with favorable pharmacokinetic properties
and, hence, were well-suited small-molecule proof-of-concept
tools for this hypothesis.
As first indication of the validity of the hypothesis, we
demonstrated that GHS-R1a antagonists from the quinazolinone
class block the inhibitory effect of ghrelin on insulin secretion
in vitro.47 This finding is in agreement with data obtained with
peptidic GHS-R1a antagonists.12 Encouraged by these results,
we investigated the effects of our compounds on glucose
homeostasis in vivo, using an IP glucose tolerance test (IPGTT)
in rats (Figure 3). Upon glucose administration, 10 mg/kg oral
doses of compound 26 produced a 20% and compound 43 a
23% decrease in the glucose excursion relative to the vehicle-
treated animals. This effect was similar in magnitude to the
effect of parenterally administered ANC7-PEG, a peptide dual-
acting GLP-1 agonist and glucagon antagonist with a strong
glucose-lowering effect in glucose tolerance models.48 In another
study, we could demonstrate that the underlying mechanism of
promoting a decrease in glucose excursion is in fact increased
insulin secretion.47 To evaluate if GHS-R1a antagonists are
prone to causing hypoglycemia, the effect of superefficacious
Figure 2. Effect of compounds 26 and 43 on body weight in DIO
mice. The CB1 antagonist rimonabant was used as a positive control.
Compounds were administered by oral gavage once daily for 9 days
(vehicle, PEG400/water 50:50).
producing a 5% decrease in body weight. The effect of
compound 26 at the 30 mg/kg dose, on the other hand, was
very strong, and progression of body weight loss was compa-
rable to the effect achieved with the CB1 antagonist rimonabant,
5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-(piperi-
din-1-yl)-1H-pyrazole-3-carboxamide, an anti-obesity drug cur-

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5209
Table 5. Effect of GHS-R1a Antagonists with Differing CNS Exposures on Food Intake in the Fasted-Refed Model
a Plasma and brain exposure were tested 5 h after compound administration; studies were conducted in C57 lean black mice. b Twenty-four hours of
cumulative food intake at compound doses of 30 mg/kg in a mouse fasted-refed model; studies were conducted in C57 lean black mice. c Compound 46
was a racemate. d Topological PSA (TPSA) calculated according to Ertl et al.45
Table 6. Effect of GHS-R1a Antagonists with Differing CNS
Exposures on Glucose Excursion (AUC) in the Rat IPGTT Model
mouse PK, 3 mg/kg p.o.
brain level
(% of plasma
concn)
change in
blood glucose
at 10 mg/kga
Cmax
(µM)
no.
26
24
43
36
46b
0.8
2.2
3.4
3.1
5.7
76
22
19
-20%
-13%
-23%
-19%
n.d.
1
<0.001
a Decrease in blood glucose AUC relative to vehicle-treated group in
the rat IPGTT model. b Compound 46 was a racemate; this compound was
not tested in the IPGTT model because of insufficient plasma exposure in
rat.
compound doses on blood glucose levels in fasted animals was
examined, and no physiologically relevant changes in blood
glucose were observed.47 These data represent the first reported
case of an orally administered selective ghrelin antagonist with
a beneficial effect on glucose homeostasis.
Interestingly, compound 36 (Table 5), which displayed poor
(1%) mouse brain exposure and had a modest effect on feeding,
was found to be fully active in the rat IPGTT model. This
observation is consistent with the hypothesis that the effects of
ghrelin and GHS-R1a antagonists on glucose homeostasis are
peripherally driven through a direct effect on pancreatic islets.47
One caveat with this interpretation is that brain exposure was
measured in mice and that the IPGTT was conducted in rats.
Figure 3. Effect of compounds 26 and 43 in a rat IPGTT at 10 mg/kg
p.o. (vehicle, PEG400/10 mM methanesulfonic acid 80:20). Five hours
after compound p.o. administration, a 2 g/kg glucose challenge was
administered by intraperitoneal injection. A group treated with the
peptide ANC7-PEG48 was used as a positive control (i.p. administra-
tion). Relative to vehicle, compound 26 produced a 20% and
compound 43 a 23% decrease in glucose AUC over the course of the
experiment.
Summary
6-position of the quinazolinone core. At the slight sacrifice of
potency, but beneficial for selectivity and DMPK properties,
phenyl groups at the 2-position were then replaced by small
alkyl substituents. Two compounds emerging from this effort,
26 and 43, were found to show high bioavailability in pharma-
cokinetic studies in rats and were selected for in vivo efficacy
evaluation.
Piperidine-substituted quinazolinone derivatives were identi-
fied as a new class of small-molecule GHS-R1a modulators.
Starting from a GHS-R1a agonist with poor oral bioavailability,
structural optimization led to potent, selective, and orally
bioavailable antagonists. A key SAR finding was the identifica-
tion of phenyl or phenoxy groups as optimal substituents at the

5210 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Rudolph et al.
was defined using 10 µM 5-HT. Following a 1 h incubation at room
temperature, the amount of [125I]DIO bound to the membranes was
measured.
Ghrelin is known to play a critical role in modulating body
weight mainly through control of food intake. In a fasted-refed
model in mice, both 26 and 43 caused a significant suppression
of food intake. An independent in vivo study in DIO mice
showed that both compounds promoted weight loss; in fact, 26
demonstrated at the highest dose comparable efficacy to the
anti-obesity drug rimonabant, a CB1 antagonist.
In Vivo Assays. Glucose Tolerance Tests in Rats. Male Wistar
rats were fasted overnight (16-18 h) and then given ghrelin
antagonist or vehicle (PEG400/10 mM MSA 80:20) by oral gavage.
Five hours after dosing, the fasting blood glucose level was
measured from tail-tip blood using a Glucometer (Bayer Corp.,
Mishawaka, IN), and the animals were given 2 g/kg of glucose by
either intraperitoneal injection (IPGTT) or by oral gavage (OGTT).
Blood glucose was measured again after 15, 30, and 60 min for
the IPGTT. Additional blood glucose measurements were made after
90 and 120 min for the OGTT or after 90 min when an IPGTT
was performed with DIO rats. The area under the glucose curve
(AUC) from 0 to 60, 0 to 90, or 0 to 120 min was calculated using
the trapezoidal method, and the effect of the compound on the AUC
was expressed as a percentage of the AUC for the vehicle-treated
group. When insulin levels were measured, 0.05 mL of blood was
collected in a capillary tube at the same time periods as described.
Insulin was determined using an enzyme-linked immunosorbent
assay (Alpco Diagnostics, Windham, NH).
DIO Mouse Model. Male C57BL/6 mice were fed a high-fat
diet (containing 45% calories from fat) for 16 weeks before the
start of the studies. The animals included in the studies had an
average body weight greater than 4 standard deviations of the
mean body weight of mice that were fed a standard low-fat
diet (5% calories from fat). GHS-R1a antagonists, rimonabant, or
vehicle was administered orally approximately 0.5-1.0 h before
the feeding phase (dark cycle). Daily body weight and food
intake were recorded during treatment. Fat and lean mass were
measured in each animal at the start and end of the studies using
NMR imaging. Pair feeding was performed by measuring the
24 h food intake of compound-treated mice each day and
limiting food consumption to that amount in a group of vehicle-
treated mice.
Mouse Fasted Refed Model. Male C57BL/6 mice were fasted
overnight and dosed the following day, 1 h before refeeding. The
cumulative food intake was recorded for a period of 24 h after
food return.
General Chemistry. Purchased reagents and anhydrous solvents
were used as received. Air and moisture sensitive liquids and
solutions were transferred via syringe or cannula and introduced
into reaction vessels through rubber septa. Column chromatography
was performed on a Biotage system using 32-63 µm, 60 Å, silica
gel prepacked cartridges.
Purification using preparative reversed-phase HPLC chromatog-
raphy was accomplished using a Gilson 215 system, using a YMC
Pro-C18 AS-342 (150 mm × 20 mm i.d.) column and 1 mL/min
flow rate. Typically, the mobile phase used was a mixture of H2O
(A) and MeCN (B). The water could be mixed or not with 0.1%
TFA. A typical gradient was as follows: 0.5 min, 90% A and 10%
B; 11.0 min, 0% A and 100% B.
Chiral analytical HPLC experiments were performed using one
of the two following methods using a Varian Pro Star 1200. Method
A: Chiracel AD column, 4.6 mm (i.d.) × 250 mm; mobile phase:
A, 0.1% TFA in hexanes; B, 0.1% TFA in i-PrOH; isocratic: 95%
A (5% B), 20 min; flow rate, 1.5 mL/min; and UV detection, 284
nm. Method B: Chiracel AD column, 4.6 mm (i.d.) × 250 mm;
mobile phase: A, 0.1% TFA in hexanes; B, 0.1% TFA in i-PrOH;
isocratic: 95% A (5% B), 25 min; flow rate, 1.0 mL/min; and UV
detection, 284 nm.
On the basis of numerous literature reports, GHS-R1a
antagonism has been proposed as a concept for stimulating
insulin secretion with potential use in the treatment of type 2
diabetes. Therefore, compounds 26 and 43 were tested in a
glucose tolerance test in rats and, as well as other structural
analogues in this class, produced a decrease in glucose excursion
to a similar degree as a highly efficacious benchmark insulin
secretagogue. In vitro and in vivo studies demonstrated that the
underlying effect was compound-mediated glucose-dependent
stimulation of insulin secretion through action on GHS-R1a.
The compounds presented in this account, piperidine-
substituted quinazolinone derivatives, represent the first reported
examples of orally available GHS-R1a antagonists that promote
chronic body weight loss and improve glucose homeostasis in
animal models. These results suggest GHS-R1a antagonism as
an attractive approach for treating metabolic disorders through
improving the diabetic phenotype while targeting obesity as the
root cause of the disease.47
Experimental Section
In Vitro Assays. GHS-R1a Pharmacology. The affinity for
GHS-R1a was determined using a radioligand binding assay. Test
compound and 50 pM [125I]ghrelin were mixed in buffer (25 mM
HEPES, pH 7.4, 5 mM magnesium chloride, 1 mM calcium
chloride, 1 mM EDTA, and 0.1% BSA). A suspension of membrane
from HEK293S cells overexpressing ovine GHS-R1a was prein-
cubated for 30 min with 5 mg/mL wheatgerm agglutinin SPA beads
and then added to the wells containing test compound and [125I]-
ghrelin. Nonspecific binding is defined using 1 µM ghrelin peptide.
Following a 2 h incubation at room temperature, the amount of
[
125I]ghrelin bound to the membranes was measured.
The functional activity of the program compounds was measured
using GTPγS binding to membranes prepared from HEK293F cells
overexpressing recombinant GHS-R1a. GHS-R1a agonism was
deduced from stimulation of GTPγS binding above basal levels
by compound. In this assay, partial agonists were defined as
compounds that stimulated GTPγS binding 20-85% relative to
ghrelin (defined as 100%), while full agonists were defined as
compounds that stimulated GTPγS binding >85% relative to
ghrelin. Compounds that failed to show agonist or partial agonist
activities were evaluated for their ability to serve as antagonists.
Ghrelin dose-response curves were performed in the absence and
presence of a fixed concentration of the putative antagonist. The
membrane from HEK293S cells overexpressing GHS-R1 was mixed
with test compound and/or ghrelin in buffer (25 mM HEPES, 50
mM sodium chloride, 10 mM magnesium chloride, 1 µM GDP,
and 0.1% BSA, pH 7.4) and 200 pM [35S]GTPγS. After a 60 min
room temperature incubation, bound and free [35S]GTPγSs were
separated by filtering through GF/B membranes. After multiple
washes, the amount of [35S]GTPγS on the filtered membranes was
determined. Nonspecific binding was defined in the presence of
10 µM GTPγS.
5-HT2c Radioligand Binding Assay. The affinity for the 5-HT2c
receptor was determined using a radioligand binding assay. Test
compound and 250 pM (()-1-(2,5-dimethoxy-4-[125I]iodophenyl)-
2-aminopropane ([125I]DIO) were mixed in buffer (50 mM Tris,
pH 7.4, 10 mM magnesium chloride, 10 µM paragyline, 0.1%
sodium ascorbate, 0.5 mM EDTA, and 0.1% BSA). A suspension
of membrane from cells stably overexpressing the 5-HT2c receptor
and wheatgerm agglutinin SPA beads (200 µg) was added to the
wells containing test compound and [125I]DIO. Nonspecific binding
Electron impact mass spectra (EI-MS or GC-MS) were obtained
with a Hewlett-Packard 5989A mass spectrometer equipped with
a Hewlett-Packard 5890 Gas Chromatograph with a J & W DB-5
column (0.25 µM coating; 30 m × 0.25 mm). The ion source was
maintained at 250 °C, and spectra were scanned from 50 to 800
amu at 2 s per scan.
Two different methods were used to obtain HPLC-electrospray
mass spectra (HPLC-ES MS). HPLC-MS method 1: An Agilent
1100 HPLC system was equipped with an Agilent 1100 autosam-
pler, quaternary pump, and a diode array. The HPLC column used

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5211
was a Waters Sunfire C-18 column (2.1 mm × 30 mm, 3.5 µM).
The HPLC eluent was directly coupled with a 1:4 split to a Finnigan
LTQ ion trap mass spectrometer with electrospray ionization.
Spectra were scanned from 50 to 800 amu using a variable ion
time according to the number of ions in the source using positive
ion mode. The eluents were A, water with 0.1% formic acid, and
B, acetonitrile with 0.1% formic acid. Gradient elution from 10 to
90% B over 3.0 min at a flow rate of 1.0 mL/min was used with
an initial hold of 2.0 min and a final hold at 95% B of 1.0 min.
The total run time was 8.0 min.
The above intermediate (746 mg, 1.33 mmol) was added to a
dry round-bottom flask followed by ethylene glycol (10 mL) and
LiOH (112 m g, 2.65 mmol). The resulting mixture was stirred at
135 °C for 16 h. The reaction mixture was diluted with CH2Cl2
and water. The aqueous mixture was extracted with CH2Cl2 (20
mL × 2), and the organic solvent was removed under reduced
pressure. The crude product was then purified by silica gel flash
chromatography with 10-50% ethyl acetate in hexanes to give the
product (803 mg, 63%). LC-MS method 2: m/z 544.6 (MH+); RT
(min) 4.38.
HPLC-MS method 2: An Agilent 1100 HPLC system was
equipped with an Agilent 1100 autosampler, quaternary pump, and
a variable wavelength detector set at 254 nm. The HPLC column
used was a Waters Sunfire C-18 column (2.1 mm × 30 mm, 3.5
µM). The HPLC eluent was directly coupled without splitting to a
Finnigan LCQ DECA ion trap mass spectrometer with electrospray
ionization. Spectra were scanned from 140 to 1200 amu using a
variable ion time according to the number of ions in the source
using positive ion mode. The eluents were A, 2% acetonitrile in
water with 0.02% TFA, and B, 2% water in acetonitrile with 0.02%
TFA. Gradient elution from 10 to 90% B over 3.0 min at a flow
rate of 1.0 mL/min was used with an initial hold of 1.0 min and a
final hold at 95% B of 1.0 min. The total run time was 7.0 min.
For consistency in characterization data, the retention time (RT) is
reported in min at the apex of the peak as detected by the UV-vis
detector set at 254 nm.
6-(4-Chlorophenyl)-2-(2-methylphenyl)-3-(piperidin-3-ylmethyl)-
quinazolin-4(3H)-one (7). To a solution of tert-butyl 3-{[6-(4-
chlorophenyl)-2-(2-methylphenyl)-4-oxoquinazolin-3(4H)-yl]methyl}-
piperidine-1-carboxylate (450 mg, 0.83 mmol) in CH2Cl2 (8 mL)
was added TFA (4 mL), and the reaction mixture was stirred at rt
for 3 h. The solvents were removed, and the crude product was
redissolved in ethyl acetate. The organic layer was washed with
saturated aqueous NaHCO3 and brine and dried over Na2SO4.
Filtration and removal of the solvent under reduced pressure gave
the product (302 mg, 82%). 1H NMR (400 MHz, methanol-d4): δ
ppm 8.47 (d, J ) 2.14 Hz, 1 H), 8.12 (dd, J ) 8.48, 1.66 Hz, 1 H),
7.71-7.76 (m, 3 H), 7.50 (t, J ) 7.99 Hz, 4 H), 7.39-7.41 (m, 2
H), 4.08-4.23 (dd, J ) 13.74, 7.89 Hz, 1 H), 3.46-3.66 (dd, J )
13.64, 7.99 Hz, 1 H), 2.94 (s, 1 H), 2.90 (d, J ) 7.21 Hz, 1 H),
2.44-2.55 (m, 1 H), 2.17-2.28 (m, 3 H), 1.88 (s, 1 H), 1.85 (d, J
) 3.51 Hz, 1 H), 1.56-1.67 (m, 2 H), 1.33-1.43 (m, 2 H), 1.00-
1.11 (m, J ) 11.50, 11.50, 11.21, 8.48 Hz, 1 H). LC-MS method
1: m/z 444.3 (MH+); RT (min) 4.25. LC-MS method 2: m/z 444.2
(MH+); RT (min) 2.84.
6-(4-Chlorophenyl)-3-[(-1-ethylpiperidin-3-yl)methyl]-2-(2-
methylphenyl)quinazolin-4(3H)-one (8). To a solution of 7 (416
mg, 0.94 mmol) in THF (20 mL) was added acetaldehyde (0.06
mL, 1.03 mmol) at 0 °C, followed by rapid addition of AcOH (0.06
mL, 1.12 mmol) and sodium triacetoxyborohydride (278 mg, 1.31
mmol). The reaction mixture was stirred under nitrogen atmosphere
at rt for 4 h. Saturated aqueous NaHCO3 solution was added, and
the mixture was stirred at rt for 15 min. The mixture was diluted
with CH2Cl2 (50 mL), and the organic layer was separated, washed
with brine, dried over Na2SO4, filtered, and concentrated under
reduced pressure. The crude product was purified by HPLC with
10-80% CH3CN in water (0.1% TFA) to give the product (306
mg, 69%) as a light yellow oil. 1H NMR (400 MHz, methanol-d4):
δ ppm 8.49 (d, J ) 1.57 Hz, 1 H), 8.13 (dd, J ) 8.41, 2.15 Hz, 1
H), 7.75 (dd, J ) 8.31, 2.05 Hz, 3 H), 7.47-7.53 (m, 4 H), 7.38-
7.44 (m, 2 H), 4.15-4.21 (m, 1 H), 3.52-3.62 (m, 1 H), 2.84 (t,
J ) 9.49 Hz, 1 H), 2.76 (d, J ) 10.96 Hz, 1 H), 2.32-2.41 (m, 2
H), 2.28 (d, J ) 4.89 Hz, 3 H), 1.89-1.99 (m, 1 H), 1.80-1.89
(m, 1 H), 1.53-1.64 (m, 2 H), 1.41-1.47 (m, 1 H), 1.32-1.39
(m, 1 H), 1.02 (dt, J ) 9.78, 7.24 Hz, 3 H), 0.89-0.96 (m, 1 H).
LC-MS method 1: m/z 472.5 (MH+); RT (min) 4.24. LC-MS
method 2: m/z 472.3 (MH+); RT (min) 2.85.
1H NMR spectroscopy was performed on 300 or 400 MHz Varian
Mercury-plus as well as Bruker DRX500 spectrometers. The
samples were dissolved in deuterated solvents and transferred to 5
mm i.d. Wilmad NMR tubes. The spectra were acquired at 293 K.
The chemical shifts were recorded on the ppm scale and were
referenced to the appropriate residual solvent signals, such as 2.49
ppm for DMSO-d6, 1.93 ppm for CD3CN, 3.30 ppm for CD3OD,
5.32 ppm for CD2Cl2, and 7.26 ppm for CDCl3.
Synthetic Procedures and Compound Characterization. 6-Bro-
mo-2-(2-methylphenyl)-4H-3,1-benzoxazin-4-one (3). o-Toluoyl
chloride (10.0 g, 64.7 mmol) was added slowly into a mixture of
2-amino-5-bromobenzoic acid (12.7 g, 58.8 mmol) and triethy-
lamine (24.6 mL, 176.4 mmol) in CH2Cl2 (120 mL) at 0 °C. The
reaction mixture was stirred at rt for 14 h. Half of the CH2Cl2 was
removed under reduced pressure, acetic anhydride (50 mL)
was added, and the mixture was heated at 50 °C for 2 h. The
reaction mixture was cooled to rt, quenched by slow addition of
ice water, and diluted with CH2Cl2. The layers were separated, and
the organic layer was washed with NaHCO3 and brine and dried
over Na2SO4. After it was concentrated under reduced pressure,
the crude product was treated with ethanol and stirred for 10 min.
The solid was filtered and washed with additional ethanol. It was
then dried in a vacuum oven at 50 °C for 3 h to give 11.5 g (62%)
of the product. LC-MS method 2: m/z 316.3 (MH+); RT (min)
3.71.
6-(4-Chloro-phenyl)-2-methylphenyl-4H-3,1-benzoxazin-4-
one (4). Under an argon atmosphere, 6-bromo-2-(2-methylphenyl)-
4H-3,1-benzoxazin-4-one (3) (7.4 g, 23.4 mmol), 4-chlorophenyl-
boronic acid (5.5 g, 35.1 mmol), K2CO3 (19.4 g, 140.4 mmol), and
PdCl2(dppf) were combined in a mixture of toluene (40 mL), 1,4-
dioxane (10 mL), and water (8 mL). The reaction mixture was
stirred for 30 min at 50 °C and then cooled to rt, filtered, and
concentrated under reduced pressure. Silica gel flash chromatog-
raphy using a gradient of hexane f EtOAc/hexane 1:7 yielded the
product as a light yellow solid (5.9 g, 73%).
tert-Butyl 3-{[6-(4-Chlorophenyl)-2-(2-methylphenyl)-4-oxo-
quinazolin-3(4H)-yl]methyl}piperidine-1-carboxylate (6). tert-
Butyl 3-(aminomethyl)piperidine-1-carboxylate (600 mg, 2.80
mmol) in toluene (10 mL) was added to 6-(4-chlorophenyl)-2-(2-
methylphenyl)-4H-3,1-benzoxazin-4-one (811 mg, 2.33 mmol), and
the solution was stirred at reflux for 16 h under a nitrogen
atmosphere. The mixture was concentrated under reduced pressure
and passed through a silica gel plug (100% EtOAc). This gave the
intermediate product as a yellow oil, which was used for next step
without further purification.
6-(4-Chlorophenyl)-3-[(1-isopropylpiperidin-3-yl)methyl]-2-
(2-methylphenyl)quinazolin-4(3H)-one (9). To a mixture of 7
(200.0 mg, 0.45 mmol) and K2CO3 (249 mg, 1.80 mmol) in CH3-
CN (20 mL) was added 2-iodopropane (0.05 mL, 0.54 mmol), and
the reaction mixture was stirred at 70 °C for 14 h. The mixture
was cooled to rt and concentrated under reduced pressure. The crude
product was diluted with water (20 mL) and extracted with EtOAc
(2 × 20 mL). The solvent was removed under reduced pressure,
and the crude product was purified by HPLC using a gradient of
10-80% CH3CN in water (0.1% TFA) to give the product (77 mg,
1
35%) as a light yellow oil. H NMR (400 MHz, methanol-d4): δ
ppm 8.49 (t, J ) 1.85 Hz, 1 H), 8.12 (dd, J ) 8.58, 2.14 Hz, 1 H),
7.75 (dd, J ) 8.38, 2.53 Hz, 3 H), 7.47-7.53 (m, 4 H), 7.42 (d, J
) 7.80 Hz, 2 H), 7.39 (s, 1 H), 4.17 (dd, J ) 13.74, 5.55 Hz, 1 H),
3.55 (dd, J ) 13.54, 6.72 Hz, 1 H), 2.70-2.80 (m, 1 H), 2.63-
2.70 (m, 1 H), 2.55 (d, J ) 9.55 Hz, 1 H), 2.27 (d, J ) 2.34 Hz,
3 H), 1.99-2.09 (m, 1 H), 1.87-1.98 (m, 1 H), 1.55-1.66 (m, 1
H), 1.39-1.46 (m, 1 H), 1.31-1.37 (m, 1 H), 0.94-1.04 (m, 6 H),
0.90 (dd, J ) 12.38, 4.00 Hz, 1 H), 0.85 (dd, J ) 8.19, 3.70 Hz,

5212 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Rudolph et al.
1 H). LC-MS method 1: m/z 486.6 (MH+); RT (min) 4.26. LC-
MS method 2: m/z 486.3 (MH+); RT (min) 2.91.
LC-MS method 1: m/z 502.4 (MH+); RT (min) 4.27. LC-MS
method 2: m/z 502.3 (MH+); RT (min) 2.88.
6-(4-Chlorophenyl)-3-[(1-cyclobutylpiperidin-3-yl)methyl]-2-
(2-methylphenyl)quinazolin-4(3H)-one (10). 1H NMR (400 MHz,
methanol-d4): δ ppm 8.42 (d, J ) 1.17 Hz, 1 H), 8.05 (dd, J )
8.48, 2.05 Hz, 1 H), 7.64-7.70 (m, 3 H), 7.40-7.47 (m, 4 H),
7.32-7.37 (m, 2 H), 5.43 (s, 1 H), 4.05-4.16 (m, 1 H), 3.44-
3.56 (m, 1 H), 2.64-2.75 (m, 1 H), 2.18-2.23 (m, 4 H), 2.13-
2.16 (m, 1 H), 2.10 (dd, J ) 10.43, 6.92 Hz, 1 H), 1.80-1.91 (m,
2 H), 1.49-1.60 (m, 3 H), 1.40 (ddd, J ) 12.18, 8.38, 3.80 Hz, 1
H), 1.34 (s, 1 H), 0.82-0.87 (m, 1 H), 0.76-0.81 (m, 1 H), 0.34-
0.45 (m, 1 H), 0.01 (t, J ) 4.09 Hz, 1 H). LC-MS method 1: m/z
498.5 (MH+); RT (min) 4.32. LC-MS method 2: m/z 498.3 (MH+);
RT (min) 2.96.
6-(4-Chlorophenyl)-3-{[1-(2-methoxyethyl)piperidin-3-yl]-
methyl}-2-(2-methylphenyl)quinazolin-4(3H)-one (11). 1H NMR
(400 MHz, methanol-d4): δ ppm 8.48 (s, 1 H), 8.11 (dd, J ) 8.48,
2.24 Hz, 1 H), 7.71-7.76 (m, 3 H), 7.47-7.53 (m, 4 H), 7.37-
7.43 (m, 2 H), 4.11-4.20 (m, 1 H), 3.55 (td, J ) 13.20, 7.11 Hz,
1 H), 3.38-3.45 (m, 2 H), 3.29-3.35 (m, 3 H), 2.72-2.84 (m, 2
H), 2.42-2.51 (m, 2 H), 2.27 (d, J ) 2.53 Hz, 3 H), 1.88-1.99
(m, 2 H), 1.51-1.63 (m, 2 H), 1.43-1.49 (m, 1 H), 1.38-1.43
(m, 1 H), 0.87 (td, J ) 12.03, 3.80 Hz, 1 H). LC-MS method 1:
m/z 502.5 (MH+); RT (min) 4.28. LC-MS method 2: m/z 502.3
(MH+); RT (min) 2.87.
6-(4-Chlorophenyl)-3-{[1-(2-fluoroethyl)piperidin-3-yl]methyl}-
2-(2-methylphenyl)quinazolin-4(3H)-one (12). 1H NMR (400
MHz, methanol-d4): δ ppm 8.52 (d, J ) 1.56 Hz, 1 H), 8.17 (d, J
) 8.57 Hz, 1 H), 7.76 (m, 3 H), 7.52 (m, 4 H), 7.40-7.48 (m, 2
H), 4.80-4.88 (m, 1 H), 4.72 (d, J ) 3.90 Hz, 1 H), 4.34 (dd, J )
13.84, 7.60 Hz, 1 H), 4.20 (dd, J ) 14.03, 5.46 Hz, 1 H), 3.73 (dd,
J ) 13.74, 7.50 Hz, 1 H), 3.47-3.59 (m, 3 H), 3.39-3.47 (m, 2
H), 2.90 (d, J ) 12.28 Hz, 1 H), 2.65-2.75 (m, 1 H), 2.22-2.32
(m, 3 H), 1.89-1.99 (m, 1 H), 1.62-1.73 (m, 1 H), 1.13-1.24
(m, 1 H). LC-MS method 1: m/z 490.4 (MH+); RT (min) 4.28.
LC-MS method 2: m/z 490.2 (MH+); RT (min) 2.89.
6-(4-Chlorophenyl)-2-(2-methylphenyl)-3-{[1-(2,2,2-trifluoro-
ethyl)piperidin-3-yl]methyl}quinazolin-4(3H)-one (13). 1H NMR
(400 MHz, methanol-d4): δ ppm 8.51 (d, J ) 1.96 Hz, 1 H), 8.15
(dd, J ) 8.51, 1.27 Hz, 1 H), 7.72-7.79 (m, 3 H), 7.52 (d, J )
8.41 Hz, 3 H), 7.49 (d, J ) 2.74 Hz, 1 H), 7.39-7.49 (m, 2 H),
4.20 (dd, J ) 13.79, 6.94 Hz, 1 H), 4.12 (d, J ) 6.26 Hz, 1 H),
3.81-3.83 (m, 1 H), 3.75-3.79 (m, 1 H), 3.64-3.73 (m, 2 H),
3.18-3.22 (m, 1 H), 3.12 (q, J ) 9.72 Hz, 1 H), 3.00 (s, 1 H),
2.87-2.96 (m, 1 H), 2.35-2.47 (m, 1 H), 2.26-2.32 (m, 3 H),
2.10-2.14 (m, 1 H), 1.98-2.09 (m, 1 H), 1.95 (s, 1 H), 1.58-
1.68 (m, 1 H), 1.43-1.54 (m, 1 H), 1.36 (d, J ) 12.72 Hz, 1 H),
0.91-1.01 (m, 1 H). LC-MS method 1: m/z 526.3 (MH+);
RT (min) 5.70. LC-MS method 2: m/z 526.2 (MH+); RT (min)
3.93.
3-{[6-(4-Chlorophenyl)-2-(2-methylphenyl)-4-oxoquinazolin-
3(4H)-yl]methyl}-1-ethylpyridinium iodide (17). To a solution
of 6-bromo-2-(2-methylphenyl)-3-(pyridin-3-ylmethyl)quinazolin-
4(3H)-one (16) (400 mg, 0.91 mmol) in acetone (20 mL) was added
iodoethane (3.66 mL, 45.67 mmol), and the solution was stirred
under nitrogen for 36 h at 50 °C in a sealed reaction tube. The
mixture was cooled to rt and concentrated under reduced pressure,
and the solid was washed with ether and dried in a high vacuum
oven for 12 h. The obtained product (370 mg, 68%) was used in
the next step without further purification. LC-MS method 2: m/z
438.3 (MH+); RT (min) 3.15.
6-(4-Chlorophenyl)-3-[(1-ethyl-1,2,5,6-tetrahydropyridin-3-yl)-
methyl]-2-(2-methylphenyl)quinazolin-4(3H)-one (18). Com-
pound 17 (370 mg, 0.62 mmol) was dissolved in a mixture of
MeOH/CH2Cl2 (1:1). The solution was cooled to 0 °C, and NaBH4
(189 mg, 4.98 mmol) was added. The reaction mixture was
stirred at 0-5 °C for 3 h. Ice water was added, and the crude
mixture was extracted with CH2Cl2 (2 × 50 mL). The combined
organic layers were washed with brine, dried over Na2SO4,
and filtered. The solvent was removed under reduced pressure
and purified by HPLC with 10-80% CH3CN in water (0.1% TFA)
1
to give the product (56 mg, 17%) as a yellow oil. H NMR (400
MHz, methanol-d4): δ ppm 8.47-8.55 (m, 1 H), 8.13 (dd, J )
8.51, 2.25 Hz, 1 H), 7.73-7.80 (m, 3 H), 7.45-7.52 (m, 3 H),
7.39 (m, 3 H), 5.04 (s, 1 H), 4.73 (d, J ) 15.65 Hz, 1 H), 4.26 (d,
J ) 15.65 Hz, 1 H), 2.71-2.80 (m, 1 H), 2.59-2.68 (m, 1 H),
2.40-2.51 (m, 4 H), 2.24-2.31 (m, 3 H), 2.09 (d, J ) 1.37 Hz, 2
H), 1.06 (t, J ) 7.14 Hz, 3 H). LC-MS method 1: m/z 470.3 (MH+);
RT (min) 4.25. LC-MS method 2: m/z 470.2 (MH+); RT (min)
2.85.
3-[(4-Benzylmorpholin-2-yl)methyl]-6-bromo-2-(2-methylphe-
nyl)quinazolin-4(3H)-one (20). 1-(4-Benzylmorpholin-2-yl)metha-
namine (2.00 g, 9.70 mmol) in toluene (15 mL) was added to
compound 3 (2.55 g, 8.08 mmol), and the solution was stirred at
reflux for 16 h under a nitrogen atmosphere. The mixture was
concentrated under reduced pressure and passed through a silica
gel plug (100% EtOAc). The resulting intermediate (yellow oil)
(2.50 g, 4.79 mmol) was added to a dry round-bottom flask followed
by ethylene glycol (20 mL) and LiOH (0.40 g, 9.57 mmol). The
resulting mixture was stirred at 135 °C for 16 h. This mixture was
cooled to rt, diluted with CH2Cl2 and water, and extracted with
CH2Cl2 (2 × 50 mL). The combined organic fractions were
concentrated under reduced pressure. The residue was purified by
silica gel flash chromatography using a gradient of 10-50% ethyl
acetate in hexanes to afford 1.62 g (67%) of the product. 1H NMR
(400 MHz, methanol-d4): δ ppm 8.49 (d, J ) 1.56 Hz, 1 H), 8.10-
8.15 (m, 1 H), 7.71-7.77 (m, 3 H), 7.44-7.52 (m, 4 H), 7.33-
7.41 (m, 2 H), 4.26 (dd, J ) 13.45, 3.51 Hz, 1 H), 3.99-4.11 (m,
1 H), 3.81-3.88 (m, 1 H), 3.70-3.79 (m, 2 H), 3.42 (tt, J ) 11.42,
2.41 Hz, 1 H), 2.71-2.80 (m, 1 H), 2.57 (dt, J ) 13.11, 6.60 Hz,
1 H), 2.30-2.37 (m, 1 H), 2.12-2.23 (m, 3 H), 1.76-1.83 (m, 1
H), 1.03 (dd, J ) 6.43, 1.95 Hz, 6 H). LC-MS method 2: m/z
504.3 (MH+); RT (min) 2.83.
6-(4-Chlorophenyl)-2-(2-methylphenyl)-3-{[1-(3,3,3-trifluoro-
propyl)piperidin-3-yl]methyl}quinazolin-4(3H)-one (14). 1H NMR
(400 MHz, methanol-d4): δ ppm 8.53 (t, J ) 2.25 Hz, 1 H), 8.14-
8.21 (m, 1 H), 7.76 (d, J ) 8.41 Hz, 3 H), 7.50-7.54 (m, 4 H),
7.40-7.47 (m, 2 H), 4.29-4.39 (m, 1 H), 4.16 (s, 1 H), 3.78 (s, 1
H), 3.58-3.65 (m, 2 H), 3.55 (d, J ) 4.11 Hz, 1 H), 3.49 (dd, J )
3.42, 1.66 Hz, 1 H), 2.82-2.90 (m, 1 H), 2.75 (m, 2 H), 2.19-
2.28 (m, 3 H), 1.90-2.00 (m, 1 H), 1.58-1.69 (m, 1 H), 1.36-
1.46 (m, 1 H), 1.29-1.32 (m, 1 H), 1.12-1.23 (m, 1 H). LC-MS
method 1: m/z (MH+) 540.5; RT (min) 4.39. LC-MS method 2:
m/z 540.3 (MH+); RT (min) 3.04.
3-[(4-Benzylmorpholin-2-yl)methyl]-6-(4-chlorophenyl)-2-(2-
methylphenyl)quinazolin-4(3H)-one (21). To a dry 100 mL round-
bottom flask was 20 (2.44 g, 4.84 mmol) followed by anhydrous
toluene (20.0 mL), dioxane (5.00 mL), and water (2.5 mL). The
mixture was stirred under a nitrogen atmosphere, and 4-chlorophe-
nyl boronic acid (756 mg, 4.84 mmol), K2CO3 (4.01 g, 29.0 mmol),
and PdCl2(dppf) (395 mg, 0.48 mmol) were added. The reaction
mixture was heated to 90 °C for 12 h and then filtered through a
silica gel plug with EtOAc as the eluent (60 mL). Removal of the
solvent under reduced pressure and purification of the residue by
silica gel flash chromatography (80% hexanes:20% EtOAc) gave
6-(4-Chlorophenyl)-3-[2-(1-ethylpiperidin-3-yl)ethyl]-2-(2-
1
methoxyphenyl)quinazolin-4(3H)-one trifluoroacetate (15). H
NMR (300 MHz, methanol-d4): δ ppm 8.50 (d, J ) 1.47 Hz, 1
H), 8.14 (dd, J ) 8.59, 2.28 Hz, 1 H), 7.72-7.79 (m, 3 H), 7.60-
7.66 (m, 1 H), 7.49-7.55 (m, 3 H), 7.26 (d, J ) 8.37 Hz, 1 H),
7.20 (td, J ) 7.49, 0.88 Hz, 1 H), 4.20-4.35 (m, 1 H), 3.89 (s, 3
H), 3.80 (s, 1 H), 3.76 (ddd, J ) 13.62, 3.08, 2.97 Hz, 1 H), 3.35-
3.50 (m, 2 H), 3.05-3.14 (m, 2 H), 2.69-2.81 (m, 1 H), 2.45 (d,
J ) 11.45 Hz, 1 H), 1.89 (d, J ) 14.53 Hz, 1 H), 1.71 (s, 1 H),
1.63 (d, J ) 14.68 Hz, 4 H), 1.30 (td, J ) 7.34, 0.88 Hz, 3 H).
1
the product as a light yellow solid (1.99 g, 76%). H NMR (400
MHz, methanol-d4): δ 8.46-8.48 (m, 1 H), 8.10-8.12 (dd, 1 H),
7.72-7.75 (m, 3 H), 7.49-7.51 (d, 3 H), 7.35-7.36 (m, 3 H),
7.25-7.28 (m, 5 H), 4.18-4.22 (m, 1 H), 3.65-4.08 (m, 3 H),
3.30-3.48 (m, 3 H), 2.55-2.71 (m, 2 H), 2.20-2.31 (d, 3 H),

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5213
2.00-2.08 (m, 1 H), 1.63-1.69 (m, 1 H). LC-MS method 2: m/z
536.2 (MH+); RT (min) 2.89.
NMR (300 MHz, methanol-d4): δ ppm 8.31-8.39 (m, 1 H), 7.82-
7.91 (m, 2 H), 7.74 (d, J ) 8.51 Hz, 2 H), 7.63 (td, J ) 6.46, 1.76
Hz, 1 H), 7.48-7.60 (m, 3 H), 7.16-7.28 (m, 2 H), 4.20-4.40
(m, 1 H), 3.90 (s, 3 H), 3.00-3.80 (m, 5 H), 2.40-2.80 (m, 3 H),
1.00-2.00 (m, 7 H). LC-MS method 1: m/z 488.4 (MH+); RT
(min) 4.24. LC-MS method 2: m/z 488.3 (MH+); RT (min) 2.88.
3-[(1-Isopropylpiperidin-3-yl)methyl]-2-(2-methylphenyl)-
quinazolin-4(3H)-one (29). 1H NMR (400 MHz, methanol-d4): δ
ppm 8.28 (d, J ) 7.99 Hz, 1 H), 7.82-7.87 (m, 1 H), 7.67 (d, J )
8.19 Hz, 1 H), 7.59 (t, J ) 7.50 Hz, 1 H), 7.46-7.52 (m, 2 H),
7.37-7.43 (m, 2 H), 4.16 (dd, J ) 7.70, 5.94 Hz, 1 H), 4.13 (d, J
) 1.75 Hz, 1 H), 3.52 (dd, J ) 13.54, 6.92 Hz, 1 H), 2.75 (t, J )
10.33 Hz, 1 H), 2.60-2.69 (m, 2 H), 2.26 (d, J ) 1.95 Hz, 3 H),
2.02 (t, J ) 11.50 Hz, 1 H), 1.87-1.92 (ddd, J ) 10.52, 7.21, 3.70
Hz, 1 H), 1.62 (tt, J ) 10.52, 3.80 Hz, 1 H), 1.38-1.46 (m, 1 H),
1.31-1.36 (m, 1 H), 0.95-1.02 (m, 6 H), 0.82-0.90 (m, J ) 12.11,
12.11, 4.04, 3.90 Hz, 1 H). LC-MS method 1: m/z 376.4 (MH+);
RT (min) 3.81. LC-MS method 2: m/z 376.3 (MH+); RT (min)
2.22.
3-[(1-Ethylpiperidin-3-yl)methyl]-6-methoxy-2-(2-methoxy-
phenyl)quinazolin-4(3H)-one trifluoroacetate (30). 1H NMR (300
MHz, methanol-d4): δ ppm 7.59-7.72 (m, 3 H), 7.46-7.56 (m, 2
H), 7.21-7.28 (m, 1 H), 7.15-7.21 (m, 1 H), 4.20-4.50 (m, 1 H),
3.95 (s, 3 H), 3.90 (s, 3 H), 3.40-3.89 (m, 3 H), 3.10 (m, 2 H),
2.40-2.80 (m, 2 H), 2.00-2.25 (brs, 1 H), 1.00-2.00 (m, 7 H).
LC-MS method 1: m/z 408.3 (MH+); RT (min) 3.82. LC-MS
method 2: m/z 408.3 (MH+); RT (min) 2.23.
6-(4-Chlorophenyl)-2-(2-methylphenyl)-3-(morpholin-2-yl-
methyl)quinazolin-4(3H)-one (22). A solution of 21 (2.59 g, 4.84
mmol) in 1,2-dichloroethane (25 mL) was treated with 1-chlorom-
ethyl chloroformate (1.32 mL, 12.1 mmol) at rt for 30 min. The
reaction mixture was then heated under reflux for 2 h. The solvent
was evaporated under reduced pressure, and the residue was heated
in MeOH (20 mL) under reflux for another 2 h. The solvent was
removed under reduced pressure, and the residue was triturated with
hexane. The residue was washed with diethylether to provide the
product (1.96 g, 91%) as a white solid. LC-MS method 2: m/z
446.1 (MH+); RT (min) 2.63.
6-(4-Chlorophenyl)-3-[(4-isopropylmorpholin-2-yl)methyl]-2-
(2-methylphenyl)quinazolin-4(3H)-one (23). Starting from com-
pound 21, the title compound was prepared using the same
1
procedure as used for the preparation of compound 9. H NMR
(400 MHz, methanol-d4): δ ppm 8.49 (d, J ) 1.56 Hz, 1 H), 8.10-
8.15 (m, 1 H), 7.71-7.77 (m, 3 H), 7.44-7.52 (m, 4 H), 7.33-
7.41 (m, 2 H), 4.26 (dd, J ) 13.45, 3.51 Hz, 1 H), 3.99-4.11 (m,
1 H), 3.81-3.88 (m, 1 H), 3.70-3.79 (m, 2 H), 3.42 (tt, J ) 11.42,
2.41 Hz, 1 H), 2.71-2.80 (m, 1 H), 2.57 (dt, J ) 13.11, 6.60 Hz,
1 H), 2.30-2.37 (m, 1 H), 2.12-2.23 (m, 3 H), 1.76-1.83 (m, 1
H), 1.03 (dd, J ) 6.43, 1.95 Hz, 6 H). LC-MS method 1: m/z
488.5 (MH+); RT (min) 4.26. LC-MS method 2: m/z 488.3 (MH+);
RT (min) 2.85.
6-(4-Chlorophenyl)-3-{[(3S)-1-ethylpiperidin-3-yl]methyl}-2-
(2-methylphenyl)quinazolin-4(3H)-one (24). 1H NMR (400 MHz,
methanol-d4): δ ppm 8.49 (d, J ) 1.57 Hz, 1 H), 8.13 (dd, J )
8.41, 2.15 Hz, 1 H), 7.75 (dd, J ) 8.31, 2.05 Hz, 3 H), 7.47-7.53
(m, 4 H), 7.38-7.44 (m, 2 H), 4.15-4.21 (m, 1 H), 3.52-3.62
(m, 1 H), 2.84 (t, J ) 9.49 Hz, 1 H), 2.76 (d, J ) 10.96 Hz, 1 H),
2.32-2.41 (m, 2 H), 2.28 (d, J ) 4.89 Hz, 3 H), 1.89-1.99 (m, 1
H), 1.80-1.89 (m, 1 H), 1.53-1.64 (m, 2 H), 1.41-1.47 (m, 1 H),
1.32-1.39 (m, 1 H), 1.02 (dt, J ) 9.78, 7.24 Hz, 3 H), 0.89-0.96
(m, 1 H). LC-MS method 1: m/z 472.5 (MH+); RT (min) 4.24.
LC-MS method 2: m/z 472.3 (MH+); RT (min) 2.86.
6-(4-Chlorophenyl)-3-{[(3R)-1-ethylpiperidin-3-yl]methyl}-2-
(2-methylphenyl)quinazolin-4(3H)-one (25). 1H NMR (400 MHz,
methanol-d4): δ ppm 8.50 (d, J ) 1.56 Hz, 1 H), 8.13 (dd, J )
8.61, 2.15 Hz, 1 H), 7.75 (dd, J ) 8.51, 2.45 Hz, 3 H), 7.51 (ddd,
J ) 11.30, 4.65, 2.25 Hz, 4 H), 7.38-7.44 (m, 2 H), 4.13-4.23
(m, 1 H), 3.52-3.62 (m, 1 H), 2.84-2.91 (m, 2 H), 2.41 (dq, J )
13.60, 6.81 Hz, 2 H), 2.28 (d, J ) 5.48 Hz, 3 H), 1.90-2.00 (m,
J ) 10.83, 7.15, 7.15, 3.42 Hz, 2 H), 1.57-1.68 (m, 2 H), 1.40-
1.48 (m, 1 H), 1.33-1.38 (m, 1 H), 1.04 (dt, J ) 11.35, 7.24 Hz,
3 H), 0.88-0.97 (m, 1 H). LC-MS method 1: m/z 472.5 (MH+);
RT (min) 4.26. LC-MS method 2: m/z 472.3 (MH+); RT (min)
2.86.
3-[(1-Ethylpiperidin-3-yl)methyl]-2-(2-methylphenyl)-6-(tri-
1
fluoromethoxy)quinazolin-4(3H)-one (31). H NMR (400 MHz,
methanol-d4): δ ppm 8.11 (s, 1 H), 7.74-7.79 (m, 2 H), 7.49 (t, J
) 7.21 Hz, 2 H), 7.37-7.43 (m, 2 H), 4.14 (dd, J ) 13.64, 6.82
Hz, 1 H), 3.52-3.61 (m, 1 H), 2.79-2.87 (m, 1 H), 2.58 (m, 1 H),
2.32-2.41 (m, 2 H), 2.26 (d, J ) 4.48 Hz, 3 H), 1.85-1.96 (m, J
) 18.22, 11.01, 3.90, 3.70 Hz, 1 H), 1.84 (s, 1 H), 1.51-1.60 (m,
1 H), 1.31-1.38 (m, 1 H), 1.02 (dt, J ) 10.13, 7.21 Hz, 3 H), 0.89
(ddd, J ) 18.32, 12.08, 4.09 Hz, 1 H). LC-MS method 1: m/z
446.5 (MH+); RT (min) 4.05. LC-MS method 2: m/z 446.3 (MH+);
RT (min) 2.57.
tert-Butyl 3-{[6-bromo-2-(2-methylphenyl)-4-oxoquinazolin-
3(4H)-yl]methyl}piperidine-1-carboxylate (32). tert-Butyl 3-(ami-
nomethyl)piperidine-1-carboxylate (3.00 g, 14.0 mmol) in toluene
(20 mL) was added to 6-bromo-2-(2-methylphenyl)-4H-3,1-ben-
zoxazin-4-one (3.69 g, 11.7 mmol) (3), and the solution was stirred
at reflux for 16 h under a nitrogen atmosphere. The mixture was
concentrated under reduced pressure and passed through a silica
gel plug using EtOAc as the eluent. Removal of the solvent under
reduced pressure gave the intermediate as a yellow oil, which was
used in the next step without further purification.
The intermediate described above (3.00 g, 5.66 mmol) was added
to a dry round-bottom flask followed by ethylene glycol (20 mL)
and LiOH (0.48 g, 11.3 mmol). The resulting mixture was stirred
at 135 °C for 16 h, cooled to rt, and diluted with CH2Cl2 and water.
The mixture was extracted with CH2Cl2 (50 mL × 2), and the
combined organic layers were concentrated under reduced pressure.
Purification via silica gel column chromatography using a gradient
elution from 10 to 50% ethyl acetate in hexanes yielded the product
(1.4 g, 48%). LC-MS method 2: m/z 512.5 (MH+); RT (min) 4.01
tert-Butyl 3-{[6-(4-fluorophenoxy)-2-(2-methylphenyl)-4-oxo-
quinazolin-3(4H)-yl]methyl}piperidine-1-carboxylate (33). Under
a nitrogen atmosphere, 4-fluorophenol (210 mg, 1.87 mmol), 32
(800 mg, 1.56 mmol), copper(I) chloride (77.3 mg, 0.78 mmol),
2,2,6,6-tetramethylheptane-3,5-dione (TMHD) (116 mg, 0.39 mmol),
and Cs2CO3 (1.02 g, 3.12 mmol) were combined in a flask, and
1-methyl-2-pyrrolidone (2 mL) was added. The reaction mixture
was stirred for 12 h at 120 °C, cooled, and concentrated under
reduced pressure. The crude product was purified by HPLC to give
the product (392 mg, 46%).
6-(4-Fluorophenyl)-2-isopropyl-3-[(1-isopropylpiperidin-3-yl)-
1
methyl]quinazolin-4(3H)-one (26). H NMR (400 MHz, dichlo-
romethane-d2): δ ppm 8.40 (d, J ) 2.15 Hz, 1 H), 7.93 (dd, J )
8.51, 2.25 Hz, 1 H), 7.65-7.72 (m, 3 H), 7.15-7.22 (m, 2 H),
4.07-4.18 (m, 2 H), 3.31 (dt, J ) 13.06, 6.48 Hz, 1 H), 2.72 (m,
3 H), 2.29 (m, 1 H), 2.18 (m, 1 H), 2.03 (m, 1 H), 1.66-1.77 (m,
2 H), 1.49-1.61 (m, 1 H), 1.39 (t, J ) 6.46 Hz, 6 H), 1.21-1.32
(m, 1 H), 0.97-1.07 (m, 6 H). LC-MS method 1: m/z 422.4 (MH+);
RT (min) 4.20. LC-MS method 2: m/z 422.3 (MH+); RT (min)
2.57.
6-(4-Chlorophenyl)-2-isopropyl-3-{[(3S)-1-isopropylpiperidin-
3-yl]methyl}quinazolin-4(3H)-one (27). 1H NMR (400 MHz,
dichloromethane-d2): δ ppm 8.42 (d, J ) 2.14 Hz, 1 H), 7.94 (dd,
J ) 8.48, 2.24 Hz, 1 H), 7.65-7.73 (m, 3 H), 7.46 (ddd, J ) 8.92,
2.63, 2.29 Hz, 2 H), 4.12 (m, 2 H), 3.43 (d, J ) 4.09 Hz, 1 H),
2.68 (m, 2 H), 2.32 (m, 1 H), 2.20-2.30 (m, 1 H), 2.13 (m, 1 H),
1.90-1.98 (m, 1 H), 1.70 (m, 2 H), 1.39 (t, J ) 6.43 Hz, 6 H),
1.24-1.32 (m, 1 H), 1.22 (dd, J ) 8.96, 4.48 Hz, 1 H), 1.00 (m,
6 H). LC-MS method 1: m/z 438.5 (MH+); RT (min) 4.27. LC-
MS method 2: m/z 438.3 (MH+); RT (min) 2.90.
6-(4-Fluorophenoxy)-2-(2-methylphenyl)-3-(piperidin-3-yl-
methyl)quinazolin-4(3H)-one (34). Compound 33 (573.6 mg, 1.06
mmol) was dissolved in CH2Cl2 (5 mL), and TFA (5 mL) was
added. After it was stirred for 3 h at rt, the solvent was removed.
7-(4-Chlorophenyl)-3-[(1-ethylpiperidin-3-yl)methyl]-2-(2-
1
methoxyphenyl)quinazolin-4(3H)-one trifluoroacetate (28). H

5214 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
Rudolph et al.
Saturated aqueous NaHCO3 solution was added, and the product
was extracted with EtOAc (2×). The combined organic layers were
dried with Na2SO4 and filtered, and the solvent was removed under
was then removed under reduced pressure to give the product, which
was used in the next step without further purification. LC-MS
method 2: m/z 338.4 ([MH2 - BOC]+); RT (min) 3.47.
6-Bromo-2-methyl-3-[(3S)-piperidin-3-ylmethyl]quinazolin-
4(3H)-one (40). Compound 39 was treated with 20% TFA in CH2-
Cl2 (30 mL) at rt for 15 h. The solvent and excess TFA were
removed under reduced pressure.
1
reduced pressure to give the product as an oil (371 mg, 79%). H
NMR (400 MHz, methanol-d4): δ ppm 7.68 (d, J ) 9.00 Hz, 1
H), 7.60 (d, J ) 2.74 Hz, 1 H), 7.53 (dd, J ) 8.80, 2.74 Hz, 1 H),
7.45-7.50 (m, 2 H), 7.35-7.43 (m, 2 H), 7.11-7.20 (m, 4 H),
4.02-4.15 (dd, J ) 13.60, 7.73 Hz, 1 H), 3.42-3.60 (dd, J ) 13.50,
8.02 Hz, 1 H), 2.85 (d, J ) 12.32 Hz, 1 H), 2.79 (dd, J ) 12.32,
2.74 Hz, 1 H), 2.42 (qd, J ) 11.80, 2.74 Hz, 1 H), 2.20-2.26 (m,
3 H), 2.11 (dd, J ) 12.03, 10.66 Hz, 1 H), 1.78 (ddd, J ) 10.32,
6.80, 3.23 Hz, 1 H), 1.51-1.61 (m, 2 H), 1.28-1.39 (m, 2 H),
0.93-1.04 (m, 1 H). LC-MS method 1: m/z 444.4 (MH+); RT
(min) 4.16. LC-MS method 2: m/z 444.2 (MH+); RT (min) 2.74.
6-(4-Fluorophenoxy)-3-[(1-isopropylpiperidin-3-yl)methyl]-2-
(2-methylphenyl)quinazolin-4(3H)-one (35). Compound 34 (200
mg, 0.45 mmol), 2-iodopropane (91.9 mg, 0.54 mmol), and K2-
CO3 (249 mg, 1.8 mmol) were combined in acetonitrile and heated
to 70 °C for 16 h. The solid was filtered off, and the filtrate was
concentrated under reduced pressure. Saturated aqueous NaHCO3
solution was added, and the product was extracted with EtOAc
(2×). The combined organic layers were dried with Na2SO4 and
filtered, and the solvent was removed under reduced pressure to
6-Bromo-3-{[(3S)-1-isopropylpiperidin-3-yl]methyl}-2-methyl-
quinazolin-4(3H)-one (41). Intermediate 40 was treated with K2-
CO3 (16.8 g, 121 mmol) and 2-iodopropane (6.2 g, 36 mmol) in
acetonitrile (50 mL) at 70 °C for 15 h. The mixture was then cooled
to room temperature and diluted with water (200 mL) and EtOAc
(400 mL) to give a clear biphasic solution. The organic layer was
separated and washed with water and brine, dried over magnesium
sulfate, filtered, and evaporated to give 7.36 g of product (80%
from three steps). LC-MS method 2: m/z 378.3 (MH+); RT (min)
1.95.
6-(4-Chlorophenyl)-3-{[(3S)-1-isopropylpiperidin-3-yl]methyl}-
2-methylquinazolin-4(3H)-one (42). A mixture of compound 41
(6.2 mmol, 2.34 g), 4-chlorophenyl boronic acid (9.3 mmol, 1.45
g), cesium carbonate (12.4 mmol, 4.03 g), and 1,1′-bis(diphe-
nylphosphino)ferrocenepalladium(II) chloride dichloromethane ad-
duct (0.37 mmol, 0.3 g) in 1,2-dimethoxyethane (15 mL) and water
(5 mL) was degassed, flashed with nitrogen, and heated to 60 °C
for 12 h. The mixture was filtered, and the filtrate was separated
by preparative HPLC using 0.1% NH3 in water and 0.1% NH3 in
acetonitrile as the eluent (gradient from 25 to 80%) to afford pure
product (1.6 g, 63%). 1H NMR (400 MHz, chloroform-d): δ ppm
8.41 (d, J ) 1.96 Hz, 1 H), 7.92 (dd, J ) 8.51, 2.25 Hz, 1 H), 7.67
(d, J ) 8.41 Hz, 1 H), 7.61 (ddd, J ) 8.90, 2.54, 2.25 Hz, 2 H),
7.43 (ddd, J ) 8.85, 2.45, 2.20 Hz, 2 H), 4.03-4.14 (m, 2 H),
2.86 (d, J ) 8.41 Hz, 1 H), 2.67-2.79 (m, 5 H), 2.23 (d, J ) 4.89
Hz, 1 H), 2.17 (m, 1 H), 1.75 (m, 2 H), 1.54 (d, J ) 6.46 Hz, 1 H),
1.21-1.32 (m, 1 H), 1.15 (d, J ) 6.85 Hz, 1 H), 1.05 (s, 6 H).
LC-MS method 1: m/z 410.3 (MH+); RT (min) 4.10. LC-MS
method 2: m/z 410.2 (MH+); RT (min) 2.60.
1
give the product (188 mg, 86%). H NMR (400 MHz, methanol-
d4): δ ppm 7.68 (d, J ) 8.80 Hz, 1 H), 7.60 (d, J ) 2.74 Hz, 1 H),
7.45-7.54 (m, 3 H), 7.36-7.41 (m, 2 H), 7.10-7.19 (m, 4 H),
4.06-4.15 (m, 1 H), 3.45-3.55 (m, 1 H), 2.72 (t, J ) 9.68 Hz, 1
H), 2.59-2.67 (m, 2 H), 2.19-2.29 (m, 3 H), 1.96-2.03 (m, 1 H),
1.82-1.93 (m, 2 H), 1.58-1.63 (m, 1 H), 1.55 (dd, J ) 7.04, 4.11
Hz, 1 H), 1.27-1.34 (m, 1 H), 0.92-1.02 (m, 6 H), 0.78-0.84
(m, 1 H). LC-MS method 1: m/z 486.4 (MH+); RT (min) 4.28.
LC-MS method 2: m/z 486.4 (MH+); RT (min) 2.92.
6-(4-Fluorophenoxy)-3-{[(3S)-1-isopropylpiperidin-3-yl]methyl}-
2-(2-methylphenyl)quinazolin-4(3H)-one (36). 1H NMR (400
MHz, methanol-d4): δ ppm 7.69 (d, J ) 8.77 Hz, 1 H), 7.62 (d, J
) 2.73 Hz, 1 H), 7.53-7.57 (m, 1 H), 7.45-7.50 (m, 2 H), 7.37-
7.42 (m, 2 H), 7.13-7.22 (m, 4 H), 4.12 (dt, J ) 13.30, 5.63 Hz,
1 H), 3.50 (dd, J ) 13.54, 7.11 Hz, 1 H), 2.75 (t, J ) 10.62 Hz, 1
H), 2.65 (td, J ) 12.28, 6.63 Hz, 2 H), 2.24 (d, J ) 1.75 Hz, 3 H),
1.99-2.06 (m, 1 H), 1.83-1.94 (m, 2 H), 1.57-1.65 (m, 1 H),
1.36-1.45 (m, J ) 16.83, 8.40, 4.04, 4.04 Hz, 1 H), 1.34-1.36
(m, 1 H), 0.95-1.02 (m, 6 H), 0.80-0.91 (m, 1 H). LC-MS method
1: m/z 486.6 (MH+); RT (min) 4.2. LC-MS method 2: m/z 486.3
(MH+); RT 2.78 (min).
6-(4-Fluorophenoxy)-2-isopropyl-3-[(1-isopropylpiperidin-3-
yl)methyl]quinazolin-4(3H)-one (37). 1H NMR (400 MHz, dichlo-
romethane-d2): δ ppm 7.76-7.85 (m, 1 H), 7.57-7.65 (m, 1 H),
7.48-7.56 (m, J ) 5.87, 2.98, 2.98, 2.98, 2.98 Hz, 1 H), 7.04-
7.16 (m, 4 H), 4.26 (d, J ) 7.63 Hz, 1 H), 4.10 (dd, J ) 14.28,
5.87 Hz, 1 H), 3.41-3.51 (m, 3 H), 3.17-3.27 (m, J ) 6.75, 6.75,
6.75, 6.75, 6.75, 6.75 Hz, 1 H), 2.69-2.80 (m, 2 H), 2.50-2.61
(m, 1 H), 1.97-2.07 (m, 2 H), 1.87-1.95 (m, 1 H), 1.44-1.50
(m, 5 H), 1.38-1.42 (m, 1 H), 1.33 (dd, J ) 12.23, 6.75 Hz, 5 H).
LC-MS method 1: m/z 438.6 (MH+); RT (min) 4.18. LC-MS
method 2: m/z 438.3 (MH+); RT (min) 2.76.
tert-Butyl (3R)-3-{[(2-amino-5-bromobenzoyl)amino]methyl}-
piperidine-1-carboxylate (38). A mixture of 5-bromoisatoic
anhydride (20.3 g, 84 mmol), tert-butyl (3R)-3-(aminomethyl)-
piperidine-1-carboxylate 5a (15.0 g, 70.0 mmol), potassium carbon-
ate (19.3 g, 140 mmol), and THF (100 mL) was heated to 70 °C
for 20 h, followed by cooling to room temperature and the addition
of water to give a clear biphasic solution. Stirring was continued
for 4 h, and most of the organic solvent was removed under reduced
pressure. The solid was collected by filtration, washed with a
copious amount of water, and air-dried to give 24.9 g (86%) of
product. LC-MS method 2: m/z 312.3 ([MH2- BOC]+); RT (min)
3.26.
6-(4-Fluorophenoxy)-3-{[(3S)-1-isopropylpiperidin-3-yl]methyl}-
2-methylquinazolin-4(3H)-one (43). To a microwave reactor tube
was added compound 41 (620 mg, 1.64 mmol), 4-fluorophenol (220
mg, 1.97 mmol), cesium carbonate (1.6 g, 4.92 mmol), copper(I)
chloride (64.9 mg, 0.66 mmol), TMHD (97.7 mg, 0.33 mmol), and
NMP (8 mL). The tube was then sealed, degassed, flashed with
nitrogen, and heated to 205 °C in a microwave reactor [“Emrys
Optimizer” from Personal Chemistry (now Biotage)] for 20 min.
The reaction mixture was filtered, and the filtrate was purified using
a Gilson reversed-phase HPLC system with a gradient elution from
5 to 60% acetonitrile in water containing 1% TFA. The product
fractions were combined, treated with 10% Na2CO3, and extracted
with EtOAc (3×). The extract was then washed with water and
brine, dried over MgSO4, and evaporated to afford 255 mg (38%)
1
of the title product. H NMR (400 MHz, CD2Cl2): δ ppm 7.55-
7.60 (m, 2H), 7.39 (dd, 1 H), 7.15-7.00 (m, 4H), 3.96 (d, 2H),
2.75-2.61 (m, 3H), 2.60 (s, 3H), 2.22 (t, 1 H), 2.11-2.02 (m, 2
H), 1.78-1.54 (m, 2H), 1.49-1.40 (m, 1H), 1.21-1.09 (m, 1H),
0.95 (d, 6H). LC-MS method 1: m/z 410.5 (MH+); RT (min) 3.99.
LC-MS method 2: m/z 410.2 (MH+); RT (min) 2.44.
6-(4-Chlorophenyl)-3-[(1-isopropylpiperidin-3-yl)methyl]-
quinazolin-4(3H)-one (44). 1H NMR (400 MHz, methanol-d4): δ
ppm 8.47 (d, J ) 2.14 Hz, 1 H), 8.33 (s, 1 H), 8.13 (dd, J ) 8.57,
2.14 Hz, 1 H), 7.80 (d, J ) 8.38 Hz, 1 H), 7.69-7.75 (m, 2 H),
7.50 (d, J ) 8.38 Hz, 2 H), 4.11-4.18 (m, 1 H), 3.98-4.05 (m, 1
H), 3.49-3.58 (m, 1 H), 3.44 (d, J ) 11.89 Hz, 2 H), 2.93-3.01
(m, 2 H), 2.47 (m, 1 H), 2.08 (d, J ) 14.42 Hz, 1 H), 1.95 (m, 1
H), 1.79 (d, J ) 14.23 Hz, 1 H), 1.35-1.45 (m, 7 H). LC-MS
method 1: m/z 396.4 (MH+); RT (min) 4.07. LC-MS method 2:
m/z 396.3 (MH+); RT (min) 2.56.
6-(4-Fluorophenoxy)-3-{[(3S)-1-isopropylpiperidin-3-yl]-
methyl}quinazolin-4(3H)-one (45). 1H NMR (400 MHz, methanol-
d4): δ ppm 8.19-8.23 (m, 1 H), 7.70 (d, J ) 8.77 Hz, 1 H), 7.49-
7.57 (m, 2 H), 7.09-7.19 (m, 4 H), 3.88-3.99 (m, 2 H), 2.75-
2.84 (m, 2 H), 2.70-2.73 (m, 1 H), 2.20 (td, J ) 11.55, 2.44 Hz,
tert-Butyl (3R)-3-[(6-bromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)methyl]piperidine-1-carboxylate (39). A mixture of compound
38 (10 g, 24.3 mmol) and triethyl orthoacetate (30 mL) was heated
to 140 °C for 10 h while stirring. The excess triethyl orthoacetate

Quinazolinone DeriVatiVes as Ghrelin Receptor Antagonists
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21 5215
(16) Broglio, F.; Gottero, C.; Benso, A.; Prodam, F.; Destefanis, S.; et al.
Effects of ghrelin on the insulin and glycemic responses to glucose,
arginine, or free fatty acids load in humans. J. Clin. Endocrinol.
Metab. 2003, 88, 4268-4272.
1 H), 2.13 (td, J ) 6.97, 3.41 Hz, 1 H), 2.06 (d, J ) 10.52 Hz, 1
H), 1.68-1.79 (m, 2 H), 1.49-1.60 (m, 1 H), 1.11 (dd, J ) 11.60,
3.02 Hz, 1 H), 1.05 (dd, J ) 6.43, 5.07 Hz, 6 H). LC-MS method
1: m/z 396.5 (MH+); RT (min) 3.96. LC-MS method 2: m/z 396.2
(MH+); RT (min) 2.43.
2-[2-Fluoro-4-(2-hydroxyethoxy)phenyl]-6-(4-fluorophenoxy)-
3-[(1-isopropylpiperidin-3-yl)methyl]quinazolin-4(3H)-one (46).
The synthesis is described in the Supporting Information. 1H NMR
(300 MHz, methanol-d4): δ ppm 7.69 (t, J ) 8.07 Hz, 1 H), 7.49-
7.61 (m, 3 H), 7.10-7.22 (m, 4 H), 6.90-7.04 (m, 2 H), 4.07-
4.21 (m, 3 H), 3.86-3.97 (m, 2 H), 3.73 (m, 1 H), 2.64 (m, 3 H),
1.96-2.10 (m, 1 H), 1.91 (m, 2 H), 1.57 (m, 2 H), 1.39 (m, 2 H),
0.96 (m, 6 H). LC-MS method 1: m/z 550.3 (MH+); RT (min)
4.16. LC-MS method 2: m/z 550.3 (MH+); RT (min) 2.71.
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Acknowledgment. We thank Nicole Barucci, Yaxin Li, Su-
Ellen Brown, Michelle Daly, Lynn DeCarr, Lucinda Milardo,
David Molstad, Jian Zhu, Jefferson Chin, Anthony Paiva, Laszlo
Musza, and Katherine Backus for their contributions to this
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pressed in mammalian cells displays a high level of constitutive
activity, the physiological relevance of which has not yet been fully
understood. However, our observation that neutral antagonists
promote weight loss and improve glucose homeostasis in rodents
(vida infra) indicates that inverse agonism is not a prerequisite for
efficacy in these models. Comparison of the effects of a strong inverse
agonist with a neutral antagonist could provide further insight into
the physiologic relevance of GHS-R1a constitutive activity. Holst,
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Supporting Information Available: Synthetic procedures for
the preparation of compounds 1, 2, and 46. Comparison of the
ghrelin binding affinities of multiple enantiomeric pair members.
Analytical data and purity assessment of key compounds. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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5216 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 21
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JM070071+