Design, Synthesis, and Structure-Activity Relationship Studies of (4-Alkoxyphenyl)glycinamides and Bioisosteric 1,3,4-Oxadiazoles as GPR88 Agonists

Article abstract of DOI:10.1021/acs.jmedchem.0c01581

Increasing evidence implicates the orphan G protein-coupled receptor 88 (GPR88) in a number of striatal-associated disorders. In this study, we report the design and synthesis of a series of novel (4-alkoxyphenyl)glycinamides (e.g., 31) and the corresponding 1,3,4-oxadiazole bioisosteres derived from the 2-AMPP scaffold (1) as GPR88 agonists. The 5-amino-1,3,4-oxadiazole derivatives (84, 88-90) had significantly improved potency and lower lipophilicity compared to 2-AMPP. Compound 84 had an EC50 of 59 nM in the GPR88 overexpressing cell-based cAMP assay. In addition, 84 had an EC50 of 942 nM in the [35S]GTPγS binding assay using mouse striatal membranes but was inactive in membranes from GPR88 knockout mice, even at a concentration of 100 μM. In vivo pharmacokinetic testing of 90 in rats revealed that the 5-amino-1,3,4-oxadiazole analogues may have limited brain permeability. Taken together, these results provide the basis for further optimization to develop a suitable agonist to probe GPR88 functions in the brain.

Full text of DOI:10.1021/acs.jmedchem.0c01581

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Article
Design, Synthesis, and Structure−Activity Relationship Studies of (4-
Alkoxyphenyl)glycinamides and Bioisosteric 1,3,4-Oxadiazoles as
GPR88 Agonists
Md Toufiqur Rahman, Ann M. Decker, Tiffany L. Langston, Kelly M. Mathews, Lucas Laudermilk,
Rangan Maitra, Weiya Ma, Emmanuel Darcq, Brigitte L. Kieffer, and Chunyang Jin*
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ABSTRACT: Increasing evidence implicates the orphan G protein-coupled receptor 88 (GPR88) in a number of striatal-associated
disorders. In this study, we report the design and synthesis of a series of novel (4-alkoxyphenyl)glycinamides (e.g., 31) and the
corresponding 1,3,4-oxadiazole bioisosteres derived from the 2-AMPP scaffold (1) as GPR88 agonists. The 5-amino-1,3,4-oxadiazole
derivatives (84, 88−90) had significantly improved potency and lower lipophilicity compared to 2-AMPP. Compound 84 had an
EC50 of 59 nM in the GPR88 overexpressing cell-based cAMP assay. In addition, 84 had an EC50 of 942 nM in the [35S]GTPγS
binding assay using mouse striatal membranes but was inactive in membranes from GPR88 knockout mice, even at a concentration
of 100 μM. In vivo pharmacokinetic testing of 90 in rats revealed that the 5-amino-1,3,4-oxadiazole analogues may have limited brain
permeability. Taken together, these results provide the basis for further optimization to develop a suitable agonist to probe GPR88
functions in the brain.
21% identity, respectively).1 Chemogenomic analysis, based on
the alignment of 30 critical residues predicted to line the
INTRODUCTION
■
The orphan G protein-coupled receptor 88 (GPR88) has
binding cavity of G protein-coupled receptors, clustered
recently attracted considerable interest in studying its bio-
GPR88 with metabotropic glutamate and GABAB receptors.23
logical functions, mainly through genetic interference. GPR88
In order to characterize GPR88 signaling mechanisms and
biological functions, our laboratory, as well as others, has
carried out a medicinal chemistry campaign to develop GPR88
synthetic agonist probes.24−32 We have previously reported
that a synthetic small-molecule, 2-PCCA [(1R,2R)-2-(pyridin-
2-yl)cyclopropane carboxylic acid ((2S,3S)-2-amino-3-methyl-
pentyl)-(4′-propylbiphenyl-4-yl)amide, Figure 1], was able to
activate GPR88 through a Gαi-coupled signaling pathway in
our time-resolved fluorescence energy transfer (TR-FRET)-
based Lance cAMP assay in GPR88 overexpressing CHO
cells.26 Recently, we have demonstrated that a potent, selective,
is highly expressed in the striatum of the brain and is involved
in both the striatonigral and striatopallidal pathways,
suggesting that the receptor may play a role in regulating
striatal functions.1−5 Genetic knockout6−15 and transcriptional
profiling studies3,16−20 in rodents have suggested that GPR88
plays an important role in regulating the dopaminergic system
and is implicated in a number of disorders such as Parkinson’s
disease, schizophrenia, anxiety, and drug addiction. Addition-
ally, human genetic studies have demonstrated positive
associations between the Gpr88 gene and schizophrenia21
and evidence that a Gpr88 variant was linked to childhood
speech delay, learning disabilities, and chorea, indicating the
relevance of GPR88 in the genetic risk for these diseases.22
Taken together, both animal and human data suggest that
GPR88 is a potential novel drug target.
Received: September 9, 2020
To date, the endogenous ligand for GPR88 has not been
discovered. GPR88 is most closely related to the biogenic
amine receptors and has the highest sequence homology with
the 5-HT1d receptor and the β3 adrenergic receptor (27 and
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the corresponding bioisosteric 1,3,4-oxadiazoles as GPR88
agonists.
RESULTS AND DISCUSSION
■
Chemistry. The overall synthetic approach followed the
methods detailed in our earlier publication.28 All the
synthesized target compounds were characterized by 1H
NMR, 13C NMR, and high-resolution mass spectra (HRMS)
and determined to be >95% pure by high-performance liquid
chromatography (HPLC) analyses. The characterization data
are in agreement with the assigned structures. The reaction
yield is presented in the Experimental Section. Compounds
12−28 were synthesized following procedures depicted in
Scheme 1. Boc-protection of the amino group in (R)-2-
phenylglycine methyl ester (5) afforded 6. O-Alkylation of 6
with an appropriate alcohol under Mitsunobu conditions or via
SN2 substitution with an alkyl p-toluenesulfonate gave ethers 7.
Reduction of the methyl ester with sodium borohydride in the
presence of lithium chloride, followed by the Boc group
deprotection with HCl led to amino alcohols 8. Boc-removal of
7, followed by 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethy-
luronium hexafluorophosphate (HBTU)-mediated coupling
with (S)-2-phenylpropionic acid provided amides 11. Alter-
natively, TIPS-protection of phenol 6 afforded 9, which was
subjected to Boc-deprotection, followed by HBTU-mediated
coupling with (S)-2-phenylpropionic acid and TIPS-depro-
tection to furnish phenol 10. Subsequent O-alkylation of the
phenol group also provided the common intermediate 11.
Finally, coupling of 8 with (S)-2-phenylpropionic acid using
HBTU or reduction of the ester function in 11 furnished the
target alcohols 12−28.
Figure 1. 2-PCCA scaffold-based GPR88 agonists.
and brain-penetrant GPR88 agonist RTI-13951-33 (Figure 1),
derived from the 2-PCCA scaffold, significantly reduced
alcohol self-administration and alcohol intake in a dose-
dependent manner in rats when administered intraperitoneally
and at doses that did not affect the locomotor activity and
sucrose self-administration.29 These findings support the
development and pharmacological validation of GPR88
agonists as a potential therapeutic to treat alcohol addiction.
2-AMPP [(2S)-N-((1R)-2-amino-1-(4-(2-methylpentyloxy)-
phenyl)ethyl)-2-phenylpropanamide (1, Figure 2)] is another
Figure 2. Structures of 2-AMPP (1) and 2−4 and preliminary SAR.
Synthesis of amides 30−69 is outlined in Scheme 2. Briefly,
acids 29, synthesized according to the procedure in our
previous publication,28 were coupled with an appropriate
amine using the standard amide coupling reagents, such as Boc
anhydride, EDC/HOBt, or by forming an acid chloride to give
the target amides 30−69.
promising GPR88 agonist scaffold for medicinal chemistry
optimization.14,28,31 Early structure−activity relationship
(SAR) studies of 1 have provided a preliminary understanding
of receptor tolerances at three distinct sites for agonist activity
(Figure 2).28,31,32 For example, the lipophilicity of the alkoxy
group on site A is favorable for potency. The amino group on
site B can be replaced by other functionalities (e.g., hydroxyl 2,
ester 3, and amide 4), all of which have comparable or slightly
improved EC50 values relative to 1. Site C, on the other hand,
has limited space for structural modifications, possibly
involving a sterically defined aromatic stacking interaction
with the GPR88 receptor.
2-AMPP was moderately potent with an EC50 of 414 nM in
our TR-FRET-based Lance cAMP assay28 and was reported to
have a poor brain penetration because of its high lipophilicity
(clog P = 4.53, calculated using Instant JChem 5.4.0,
ChemAxon Ltd.).31 Recently, 2-AMPP (referring to com-
pound 19 in the literature33) was shown to have an EC50 of
634 nM in the BRET-based cAMP assay in GPR88
overexpressing HEK293 cells, which is in line with our EC50
value of this compound. We faced two major challenges for the
development of 2-AMPP-based agonists as in vivo probes: (a)
potency and (b) brain bioavailability. To address these
questions, we planned to further explore the SAR on sites A
and B and reasoned that both potency and brain permeability
can be improved by fine-tuning the lipophilicity on site A and
modifying the functionality on site B. Herein, we report the
design, synthesis, and pharmacological evaluation of a series of
(4-alkoxyphenyl)glycinols, (4-alkoxyphenyl)glycinamides, and
Synthesis of 5-alkyl- and 5-amino-1,3,4-oxadiazoles is
outlined in Schemes 3 and 4. As depicted in Scheme 3, the
reaction of ester 3 or 11h,28 derived from 4-hydroxyphenyl-
acetic acid, with hydrazine hydrate in refluxing ethanol
afforded the corresponding hydrazides 70a,b. Coupling of
70a,b with trimethyl orthoformate or trimethyl orthoacetate in
the presence of catalytic acid provided target 1,3,4-oxadiazoles
71−74. On the other hand, oxadiazoles derived from 4-
hydroxyphenylpropanoic acid were synthesized according to
the procedure shown in Scheme 4. The reaction of acid 75
with acetyl chloride in methanol at 65 °C afforded the methyl
ester 76, which was protected with Boc anhydride to provide
the Boc-protected amine 77. The Mitsunobu reaction of 77
with the appropriate alcohol furnished the corresponding alkyl
ethers 78a−f. The removal of the Boc group from the amine
followed by HBTU-mediated coupling with (S)-2-phenyl-
propionic acid provided amides 80a−f. The ester function in
80 was converted to the corresponding hydrazide by heating
the ester with hydrazine hydrate in ethanol. Finally, hydrazides
81a−f were condensed with trimethyl orthoformate, trimethyl
orthoacetate, or cyanogen bromide to furnish the target 1,3,4-
oxadiazoles 82−91.
Pharmacological Evaluation and SAR Study. All
synthesized compounds in this study were evaluated for the
GPR88 agonist activity in our previously established in vitro
GPR88 Lance TR-FRET cAMP assay.26 The TR-FRET signal
B
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a
Scheme 1. Synthesis of Target Compounds 12−28
a
Reagents and conditions: (a) Boc2O, DIPEA, DCM, rt, overnight; (b) PPh3, DEAD, alcohol, THF, rt, overnight; (c) NaBH4, LiCl, THF-EtOH
(1:1), rt, 3 h; (d) 4 M HCl in dioxane, DCM, rt, 16 h; or TFA: DCM, rt, 6 h; (e) (S)-2-phenylpropionic acid, HBTU, TEA, MeCN, rt, 5 h; (f)
TIPSCl, imidazole, DCM, rt, overnight; (g) TBAF, THF, 0 °C, 3 h; (h) alkyl p-toluenesulfonate, K2CO3 MeCN, 65 °C, overnight.
a
(665 nm) was converted to fmol cAMP by interpolating from
the standard cAMP curve. fmol cAMP was plotted against the
log of compound concentration, and data were fit to a three-
parameter logistic curve to generate the maximum response
(Emax) and EC50 values. In our assay, 2-PCCA had an Emax of
100 2 (mean S.E.M.) and RTI-13951-33 had an Emax of
Scheme 2. Synthesis of Target Compounds 30−69
103
2 relative to 2-PCCA. Collectively, all of the active
compounds in this study had Emax values comparable to 2-
PCCA and RTI-13951-33, except for compounds 28 and 43,
which had Emax values of 84 and 83%, respectively. These
values might indicate that the compounds are partial agonists;
however, it is important to note that Emax was calculated
against synthetic agonists because the endogenous ligand for
GPR88 has not yet been discovered. Figure 3 displays the
concentration−response curves of representative compounds
a
Reagents and conditions: Method A (a) pyridine, dioxane,
NH4HCO3, Boc2O, rt, overnight; Method B (a) EDC hydrochloride,
HOBt, DIPEA, amine, DMF, rt, overnight; Method C (a) oxalyl
chloride, DMF (cat.), DCM, rt; then amine, Et3N, rt, overnight.
a
Scheme 3. Synthesis of Target Compounds 71−74
a
Reagents and conditions: (a) hydrazine monohydrate, EtOH, reflux, 3 h; (b) CH(OMe)3, PTSA, 85 °C, 2 h or CH3C(OMe)3, HOAc, m-xylene,
reflux, 6 h.
C
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a
Scheme 4. Synthesis of Target Compounds 82−91
a
Reagents and conditions: (a) acetyl chloride, MeOH, reflux, overnight; (b) Boc2O, DIPEA, DCM, rt, overnight; (c) PPh3, DEAD, alcohol, rt,
overnight; or alkyl p-toluenesulfonate, K2CO3, MeCN, 65 °C, overnight; (d) 4 M HCl in dioxane, DCM, rt, overnight; (e) (S)-2-phenylpropionic
acid, HBTU, TEA, MeCN, rt, 5 h; (f) hydrazine monohydrate, EtOH, reflux, 3 h; (g) CH(OMe)3, PTSA, 85 °C, 2 h; or CH3C(OMe)3, HOAc, m-
xylene, reflux, 6 h; or CNBr, MeOH, reflux, 3 h.
group was important as potency decreased from n-pentyl to n-
propyl (14, 18, and 20). Among the three cyclic alkyl
analogues (17, 19, and 21), only the cyclobutylmethyl 19 was
favored with an EC50 of 234 nM. Attempts to add an additional
oxygen atom into the side chain to reduce clog P resulted in a
10-fold loss of activity (22, 23). In general, the GPR88 agonist
activity was correlated with the lipophilicity of the compounds.
The potency decreased as the clog P of compounds 12−23
decreased. Compounds 16 and 19 with an (S)-2-methylbutyl
and a cyclobutylmethyl group, respectively, provided the best
balance between potency and lipophilicity. To further explore
SAR of the cyclobutylmethyl 19, we synthesized and tested a
Figure 3. Concentration−response curves of RTI-13951-33, 84, and
90 in the GPR88 Lance TR-FRET cAMP assay. The TR-FRET signal
(665 nm) was converted to fmol cAMP by interpolating from the
standard cAMP curve. Percent inhibition of forskolin-induced (300
nM) cAMP levels was plotted against the log of compound
concentration, and data were fit to a three-parameter logistic curve
to generate EC50 values. Each data point is the mean S.D. of at least
three independent experiments performed in duplicate.
series of substituted analogues 24−28. Unfortunately, all of
these compounds suffered from loss of potency; in particular,
24, 26, and 27 were completely inactive, suggesting that there
is a limited steric tolerance in this side-chain position.
We next investigated site B with a rationale that modification
of the amide functionality on this site would improve the
potency of 4 (EC50 = 616 nM, Figure 2). In addition, amide
formation with a variety of readily available amines can rapidly
expand the structural diversity for SAR. To this end, we
performed an in-depth examination of the substitution effects
on the amide nitrogen by varying the size, lipophilicity,
polarity, and electronic properties. The study began with the
aliphatic substitutions on the amide nitrogen, as shown in
Table 2. The primary amide 30 was equipotent to the tertiary
N-dimethyl 4, whereas a monomethyl group (31) improved
the potency by twofold. The agonist activity increased further
with an ethyl group (32), decreased with an n-propyl group
(33), and then maintained a moderate potency (EC50 = 200−
300 nM) with small-to-large-sized alkyl substitutions (34−42)
(RTI-13951-33, 84, and 90). Given the importance of an
alkoxy substitution on site A in the 2-AMPP scaffold for
GPR88 activity reported earlier, we first examined a series of
ether analogues 12−28 by varying the length, shape, and steric
and electronic properties, with the aim of identifying a side
chain that can lower the lipophilicity while maintaining the
potency of 2-{4-[(2-methylpentyl)oxy]phenyl}glycinol 2 (clog
P = 4.64, EC50 = 195 nM). As can be seen from Table 1, the
GPR88 agonist activity of this series was sensitive to the
branching and length of the alkoxy side chain. First, the
position of methyl branching was important for activity, as
both 1-methylpentyl 12 (EC50 = 380 nM) and 4-methylpentyl
13 (EC50 = 282 nM) were less potent than the 2-methylpentyl
analogue 2. Second, the branched alkyl was more potent than
the linear alkyl group, as exemplified by 16 (EC50 = 174 nM)
relative to 14 (EC50 = 295 nM). Third, the length of the alkyl
except for cyclohexyl (43). The N-ethyl analogue 32 (EC50
=
120 nM) emerged as the most potent compound in the amide
series. Further modifications by adding polar functionalities at
the terminal end of N-ethyl, such as ester (44), hydroxyl (45),
ether (46, 47), carbamate (48, 50), and amine (49), led to a
D
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Table 1. Biological Data of 4-Alkoxyphenylglycinols
a
b
clog P was calculated using Instant JChem 5.4.0 (ChemAxon Ltd.). pEC50 values are means standard error of at least three independent
c
d
experiments performed in duplicate. Emax value is % of 2-PCCA (mean standard error). Emax value is % of RTI-13951-33 (mean standard
error). N.D., not determined.
significant loss of potency. Interestingly, compounds (49, 51−
54) with a protonatable nitrogen had the least activity. This
SAR trend was also observed in the amide analogues with
aromatic substitutions (Table 3). Phenyl and benzyl groups
(55, 56) were favorable with an EC50 of 245 and 219 nM,
respectively, whereas pyridine rings (57−59), capable of
forming a salt to improve aqueous solubility, were less active.
Other polar five-membered heterocycles (60−69) were also
poorly tolerated. It appeared that the activity deteriorated with
heterocycles containing more heteroatoms. It should be noted
that although two different side chains (2-methylpentyl and
cyclobutylmethyl) on site B were used in Table 3, there was
little difference in potency contributions between the two
groups (60 vs 61). Overall, the SAR suggested that compounds
with a lipophilic alkyl substitution on the amide nitrogen tend
to have better potency.
Bioisosteric replacement is an essential tool in the SAR study
to improve potency, selectivity, and pharmacokinetics (PKs).34
The oxadiazole moiety is stable to chemical and enzymatic
degradation and capable of forming a hydrogen bond;
therefore, it has been broadly used as a nonclassical bioisostere
for ester and amide functionalities.35 Because the 1,3,4-
oxadiazoles have a lower lipophilicity (in general, an order of
magnitude of clog P) compared to its 1,2,4-isomers, we
selected 1,3,4-oxadiazole as our initial testing set. Replacement
of the amide group in 4 with a 1,3,4-oxadiazole or a 5-methyl-
1,3,4-oxadiazole moiety gave analogues 71 and 72, respectively,
which were equipotent to 4 with EC50 values in the 500−600
nM range (Table 4). There was no difference in potency
between the 2-methylpentyl and cyclobutylmethyl side chains
(73, 74 vs 71, 72). Interestingly, the addition of a methylene
linker between the oxadiazole moiety and the benzylic carbon
led to a 5-fold increase in potency (82, 83 vs 71, 72). Further
modification by attaching an amino group to the 5-position
gave the most potent compound 84 (EC50 = 59 nM) in the
series. Attempts to lower the lipophilicity by exchanging the 2-
methylpentyl side chain in 82−84 with the cyclobutylmethyl
group, unfortunately, resulted in less active compounds 85−
87. After identifying a favorable 1,3,4-oxadiazole pharmaco-
phore on site B, we turned our attention back to the side chain
on site A, in which we reasoned that the chiral center of the
methyl branching might have an impact on the potency. The
(S)-isomer 88 and the (R)-isomer 89 had equivalent GPR88
activity with EC50 values of 78 and 74 nM, respectively, in line
with the EC50 value of the racemic mixture 84. However, in the
case of the 2-methylbutyl side chain, (S)-90 was approximately
twofold more potent than (R)-91, which is consistent with the
observation in the corresponding hydroxyl (on site B)
E
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Table 2. Biological Data of 4-Alkoxyphenylglycinamides
a
b
pEC50 values are means standard error of at least three independent experiments performed in duplicate. Emax value is % of 2-PCCA (mean
c
standard error). Emax value is % of RTI-13951-33 (mean standard error). N.D., not determined.
analogues that (S)-2-methylbutyl 16 is slightly more potent
than racemic 15 (Table 1).
line, the rank order of the potency of compounds is consistent
between the two assay systems.
Solubility and Preliminary PK Studies. One of the
major challenges for the development of GPR88 probes is their
ability to cross the blood−brain barrier (BBB) and have
sufficient brain exposure to modulate receptor functions.
Calculated physicochemical properties, such as lipophilicity
(clog P) and topological polar surface area (TPSA), are useful
indicators of a successful CNS drug. In general, a balance
between clog P (2−4)36 and TPSA (<76 Å2)37 would lead to
good solubility and BBB permeability. Therefore, we tested the
kinetic aqueous solubility (at pH = 7.4) and PK properties of
select compounds to determine their drug-likeness. PK data for
the in vivo effective agonist RTI-13951-33 are also presented
for comparison.29 As shown in Table 5, both compounds 1 and
84 have a poor solubility of <1 μM, which is expected for
compounds with a high clog P (4.53 and 4.20, respectively).
Compound 90 (clog P = 3.76) has an increased solubility of
To further characterize the GPR88 agonist activity, we
tested our best compound in the [35S]GTPγS binding assay
using mouse striatal membrane preparations. RTI-13951-33
(cAMP: EC50 = 25 nM) increased [35S]GTPγS binding with
an EC50 = 535 nM (Emax = 200%).29 Emax is expressed as
percentage of activation above the basal binding, which is set as
100%, and the basal binding refers to binding in the absence of
the agonist. Compound 84 also exhibited strong enhancement
of the [35S]GTPγS binding activity (EC50 = 942 nM, Emax
=
229%) in mouse striatal membranes (Figure 4). Importantly,
the compound was inactive in membranes prepared from
GPR88 KO mice at concentrations tested up to 100 μM,
indicating that it had a GPR88-specific agonist signaling
activity in the striatum. It is worth noting that although the
GPR88 agonist activity in the [35S]GTPγS binding assay using
a native tissue system is approximately 10- to 20-fold less
potent than the cAMP assay in a GPR88 overexpressing cell
2.9
0.3 μM, which confirms that while solubility is a
challenge we still face, lowering lipophilicity does improve
F
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Table 3. Biological Data of 4-Alkoxyphenylglycinamides Containing Aromatics
a
b
pEC50 values are means standard error of at least three independent experiments performed in duplicate. Emax value is % of RTI-13951-33
(mean standard error).
solubility. Compound 90 was further evaluated in a
preliminary PK study to assess whether this compound has
sufficient brain exposure. Following an intraperitoneal (i.p.)
dose of 10 mg/kg in rats, 90 reached the peak plasma
concentration of 270 ng/mL at 30 min (the first time point
tested). The brain concentration also peaked at 30 min with a
group has carried out a medicinal chemistry campaign to
develop GPR88 small-molecule agonist probes based on the 2-
PCCA and 2-AMPP scaffolds.25−29 The present study
describes a series of novel (4-alkoxyphenyl)glycinols, (4-
alkoxyphenyl)glycinamides and the corresponding bioisosteric
1,3,4-oxadiazoles derived from 2-AMPP and explores their
SAR requirements for high potency at the GPR88 receptor.
Notably, 5-amino-1,3,4-oxadiazoles 84 (EC50 = 59 nM) and 90
(EC50 = 71 nM) emerged as the most potent compounds in
this study. Compound 84 exhibited a significant [35S]GTPγS
binding activity (EC50 = 942 nM) using the native tissue
sample from mouse striatum but was inactive in GPR88 KO
mouse striatal membranes, even at a concentration of 100 μM,
demonstrating that this type of compound has GPR88-specific
agonist activity in the striatum. However, a preliminary PK
study of 90 indicates limited brain permeability. Chemical
modifications of 2-AMPP on site B (Figure 2) with other five-
membered heterocycles, as well as on site C, to further
improve potency and ADME properties are currently under-
way. These studies will facilitate the identification of highly
Cmax of 39 ng/mL (92 nM), which is slightly above its EC50 of
71 nM in the cAMP functional assay. The overall brain to
plasma AUC ratio (B/P), as determined by AUC0−inf ratio, was
0.1, indicating that 90 has limited brain penetration. As a
comparison, RTI-13951-33 has a brain Cmax of 287 ng/mL
(539 nM) and a B/P ratio of 0.5 in rats (i.p., 10 mg/kg
dose).29 Compound 90 has a clog P of 3.76 but a high TPSA
of 103 Å2, which likely limits its brain permeability. Further
optimization of the 1,3,4-oxadiazole analogues is required to
improve brain permeability.
CONCLUSIONS
■
The orphan receptor GPR88 plays important roles in
mediation of dopaminergic activity and striatal functions. To
explore the therapeutic potential of this novel drug target, our
G
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Table 4. Biological Data of Bioisosteric 1,3,4-Oxadiazoles
a
b
clog P was calculated using Instant JChem 5.4.0 (ChemAxon Ltd.). pEC50 values are means standard error of at least three independent
c
d
experiments performed in duplicate. Emax value is % of RTI-13951-33 (mean standard error). Emax value is % of 2-PCCA (mean standard
error). Compounds were tested as the HCl salt.
e
by a combination of NMR, mass spectrometry, TLC, and HPLC
analyses. 1H and 13C NMR spectra were recorded on a Bruker Avance
DPX-300 (300 MHz) spectrometer and were determined in CDCl3,
DMSO-d6, or CD3OD with tetramethylsilane (TMS) (0.00 ppm) or
solvent peaks as the internal reference. Chemical shifts are reported in
ppm relative to the reference signal and coupling constant (J) values
are reported in hertz (Hz). Nominal mass spectra were obtained using
an Agilent InfinityLab MSD single quadrupole mass spectrometer
system (ESI). HRMS were obtained using Agilent 1290 Infinity
UHPLC-6230 TOF mass spectrometer (ESI). Thin-layer chromatog-
Figure 4. [35S]GTPγS binding of compound 84 in WT mouse striatal
raphy (TLC) was performed on EMD precoated silica gel 60 F254
membranes vs GPR88 KO mouse striatal membranes. The data are
the means of triplicate measurements with standard deviation shown
as error bars.
plates, and spots were visualized with UV light or iodine staining.
CMA80 for column chromatography is a mixture of 80:18:2
chloroform/MeOH/NH4OH. All final compounds were greater
than 95% pure as determined by HPLC on a Waters 2695 Separation
Module equipped with a Waters 2996 Photodiode Array Detector and
a Phenomenex Synergi 4 mm Hydro-RP 80A C18 250 × 4.6 mm
column using a flow rate of 1 mL/min starting with 1 min at 5%
solvent B, followed by a 15 min gradient of 5−95% solvent B,
followed by 9 min at 95% solvent B (solvent A, water with 0.1% TFA;
solvent B, acetonitrile with 0.1% TFA and 5% water; absorbance
monitored at 280 nm). All the synthesized target compounds were
characterized by 1H NMR, 13C NMR, and HRMS and determined to
be >95% pure by HPLC analyses.
potent and brain-penetrant agonists to probe GPR88 functions
in the brain.
EXPERIMENTAL SECTION
■
Chemistry. General Methods. All solvents and chemicals were of
reagent grade. Unless otherwise mentioned, all reagents and solvents
were purchased from commercial vendors and used as received. Flash
column chromatography was carried out on a Teledyne ISCO
CombiFlash Rf system using prepacked columns. Solvents used
include hexane, ethyl acetate (EtOAc), dichloromethane, and
methanol. Purity and characterization of compounds were established
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-(4-
hydroxyphenyl)acetate (6). To a solution of (R)-2-phenylglycine
methyl ester hydrochloride (5 g, 23 mmol) in DCM (175 mL) at 0
H
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Table 5. Physicochemical, Solubility, and PK Properties of Compounds 1, 84, and 90
rat PK (i.p., 10 mg/kg)
brain
plasma
cAMP EC50
(nM)
kinetic solubility at pH 7.4
Cmax
(ng/mL)
AUC0−inf
(ng/mL·h)
Cmax
(ng/mL)
AUC0−inf
(ng/mL·h)
a
b
b
compound
clog P TPSA
(μM)
B/P
1
84
90
414
59
71
4.53
4.20
3.76
3.34
64.3
103.3
103.3
<1
<1
2.9 0.3
270
874
1001
1510
39
287
95
825
0.1
0.5
c
RTI-13951-33
25
77.7
a
b
c
All compounds were tested as the HCl salt. clog P and TPSA were calculated using Instant JChem 5.4.0 (ChemAxon Ltd.). Data were obtained
from ref 29.
°C under nitrogen was added DIPEA (12 mL, 69 mmol), followed by
di-tert-butyldicarbonate (5.2 g, 23 mmol). The reaction mixture was
stirred at room temperature overnight and concentrated under
reduced pressure. The residue was dissolved in EtOAc (200 mL),
washed with 10% citric acid (3 × 50 mL) and brine (3 × 50 mL), and
dried (Na2SO4). Removal of the solvent under reduced pressure
afforded crude 6 (6.45 g, 100% yield) as a colorless oil. 1H NMR (300
MHz; CDCl3): δ 7.16 (d, J = 9.0 Hz, 2H), 7.13 (d, J = 9.0 Hz, 2H),
6.44 (s, 1H), 5.60 (br d, J = 6.0 Hz, 1H), 5.22 (d, J = 6.0 Hz, 1H),
3.71 (s, 3H), 1.44 (s, 9H); 13C NMR (75 MHz; CDCl3): δ 172.0,
156.3, 155.0, 128.5, 128.4, 115.8, 80.5, 57.1, 52.7, 28.3; MS (ESI) [M
+ H]+ m/z: 282.3.
d, J = 6.0 Hz, 1H), 5.25 (d, J = 9.0 Hz, 1H), 3.90 (d, J = 6.0 Hz, 2H),
3.70 (s, 3H), 2.84−1.68 (m, 1H), 2.19−2.06 (m, 2H), 2.01−1.80 (m,
4H), 1.43 (s, 9H); 13C NMR (75 MHz, CDCl3): δ 171.9, 159.4,
154.8, 128.8, 128.3, 114.9, 80.0, 72.1, 57.0, 52.6, 34.6, 28.3, 24.8, 18.6;
MS (ESI) m/z: 350.2 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-(4-
propoxyphenyl)acetate (7i). The procedure for the synthesis of 7b
was followed starting with 6 and n-propanol to give 7i (57% yield) as
1
a colorless oil. H NMR (300 MHz, CDCl3): δ 7.26 (d, J = 9.0 Hz,
2H), 6.86 (d, J = 9.0 Hz, 2H), 5.54 (br d, J = 9.0 Hz, 1H), 5.25 (d, J =
9.0 Hz, 1H), 3.89 (t, J = 7.5 Hz, 2H), 3.70 (s, 3H), 1.85−1.72 (m,
2H), 1.43 (s, 9H), 1.02 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 171.9, 159.3, 154.8, 128.7, 128.3, 114.8, 80.0, 69.5, 57.1,
52.5, 28.3, 22.5, 10.5; MS (ESI) m/z: 324.3 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-
(cyclopropylmethoxy)phenyl]acetate (7j). The procedure for the
synthesis of 7b was followed starting with 6 and cyclopropylmethanol
to give 7j (76% yield) as a colorless oil. 1H NMR (300 MHz, CDCl3):
δ 7.26 (d, J = 9.0 Hz, 2H), 6.87 (d, J = 9.0 Hz, 2H), 5.54 (br d, J = 9.0
Hz, 1H), 5.25 (d, J = 9.0 Hz, 1H), 3.78 (d, J = 9.0 Hz, 2H), 3.70 (s,
3H), 1.43 (s, 9H), 1.32−1.16 (m, 1H), 0.67−0.58 (m, 2H), 0.39−
0.28 (m, 2H); 13C NMR (75 MHz, CDCl3): δ 171.9, 159.1, 154.8,
128.9, 128.4, 114.9, 80.0, 72.8, 57.0, 52.5, 28.3, 10.2, 3.2; MS (ESI)
m/z: 336.3 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-(4-
methoxybutoxy)phenyl]acetate (7k). The procedure for the syn-
thesis of 7b was followed starting with 6 and 4-methoxybutan-1-ol to
give 7k (63% yield) as a colorless oil. 1H NMR (300 MHz, CDCl3): δ
7.26 (d, J = 9.0 Hz, 2H), 6.86 (d, J = 9.0 Hz, 2H), 5.56 (br d, J = 6.0
Hz, 1H), 5.25 (d, J = 9.0 Hz, 1H), 3.96 (t, J = 6.0 Hz, 2H), 3.70 (s,
3H), 3.43 (t, J = 6.0 Hz, 2H), 3.33 (s, 3H), 1.91−1.68 (m, 4H), 1.43
(s, 9H); 13C NMR (75 MHz, CDCl3): δ 171.9, 159.1, 154.8, 128.8,
128.3, 114.8, 80.0, 72.3, 67.7, 58.5, 57.0, 52.5, 28.3, 26.2, 26.0; MS
(ESI) m/z: 368.4 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-{4-[(4-
methylpentyl)oxy]phenyl}acetate (7b). To a solution of 6 (200
mg, 0.71 mmol), 4-methylpentanol (177 μL, 1.42 mmol), and PPh3
(316 mg, 1.21 mmol) in THF (10 mL) at room temperature under
nitrogen was slowly added DEAD (0.19 mL, 1.21 mmol) dropwise,
while keeping the reaction temperature below 35 °C. After addition,
the reaction mixture was stirred at room temperature overnight and
quenched with H2O (10 mL). The layers were separated, and the
aqueous layer was extracted with EtOAc (3 × 30 mL). The combined
organic layers were washed with brine (3 × 30 mL), dried (Na2SO4),
and concentrated under reduced pressure. The residue was subjected
to chromatography on silica gel using 0−20% EtOAc in hexanes to
afford 7b (130 mg, 50% yield) as a colorless oil. 1H NMR (300 MHz,
CDCl3): δ 7.26 (d, J = 9.0 Hz, 2H), 6.85 (d, J = 9.0 Hz, 2H), 5.50 (br
d, J = 6.0 Hz, 1H), 5.24 (d, J = 6.0 Hz, 1H), 3.92 (t, J = 6.0 Hz, 2H),
3.71 (s, 3H), 1.86−1.71 (m, 2H), 1.67−1.53 (m, 1H), 1.43 (s, 9H),
1.40−1.25 (m, 2H), 0.91 (d, J = 6.0 Hz, 6H); 13C NMR (75 MHz,
CDCl3): δ 171.9, 159.3, 154.8, 128.7, 128.3, 114.8, 80.0, 68.4, 57.1,
52.5, 35.1, 28.3, 27.8, 27.1, 22.5; MS (ESI) m/z: 366.6 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-(pentyloxy)-
phenyl]acetate (7c). The procedure for the synthesis of 7b was
followed starting with 6 and n-pentanol to give 7c (50% yield) as a
1
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-(4-
methoxypropoxy)phenyl]acetate (7l). The procedure for the
synthesis of 7b was followed starting with 6 and 3-methoxypropan-
colorless oil. H NMR (300 MHz, CDCl3): δ 7.26 (d, J = 9.0 Hz,
2H), 6.86 (d, J = 9.0 Hz, 2H), 5.50 (br d, J = 6.0 Hz, 1H), 5.25 (d, J =
9.0 Hz, 1H), 3.93 (t, J = 7.5 Hz, 2H), 3.71 (s, 3H), 1.82−1.71 (m,
2H), 1.43 (s, 9H), 1.42−1.25 (m, 4H), 0.92 (t, J = 7.5 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 171.9, 159.3, 154.8, 128.7, 128.3, 114.8,
80.0, 68.0, 57.1, 52.5, 28.9, 28.3, 28.2, 22.4, 14.0; MS (ESI) m/z:
352.3 [M + H]+.
1
1-ol to give 7l (68% yield) as a colorless oil. H NMR (300 MHz,
CDCl3): δ 7.26 (d, J = 9.0 Hz, 2H), 6.87 (d, J = 9.0 Hz, 2H), 5.55 (br
d, J = 6.0 Hz, 1H), 5.25 (d, J = 9.0 Hz, 1H), 4.03 (t, J = 6.0 Hz, 2H),
3.70 (s, 3H), 3.54 (t, J = 6.0 Hz, 2H), 3.34 (s, 3H), 2.08−1.97 (m,
2H), 1.43 (s, 9H); 13C NMR (75 MHz, CDCl3): δ 171.9, 159.1,
154.8, 128.9, 128.3, 114.8, 80.0, 69.1, 64.9, 58.6, 57.0, 52.5, 29.5, 28.3;
MS (ESI) m/z: 354.5 [M + H]+.
(2R)-2-Amino-2-{4-[(4-methylpentyl)oxy]phenyl}ethan-1-ol Hy-
drochloride (8b). To a suspension of NaBH4 (35 mg, 0.93 mmol)
in EtOH (1.5 mL) at 0 °C under nitrogen was added LiCl (39 mg,
0.93 mmol). After stirring at 0 °C for 10 min, a solution of 7b (130
mg, 0.36 mmol) in THF (1.5 mL) was added. The reaction mixture
was stirred at room temperature for 3 h and quenched with saturated
NH4Cl solution (5 mL), followed by addition of H2O (5 mL). The
mixture was extracted with EtOAc (3 × 20 mL). The combined
organic layers were washed with brine (20 mL), dried (Na2SO4), and
concentrated under reduced pressure to give 125 mg of the crude
intermediate alcohol. The Boc group was then deprotected with 4 M
HCl in dioxane (2 mL) and DCM (5 mL). The reaction mixture was
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-(butoxy)-
phenyl]acetate (7g). The procedure for the synthesis of 7b was
followed starting with 6 and n-butanol to give 7g (57% yield) as a
1
colorless oil. H NMR (300 MHz, CDCl3): δ 7.26 (d, J = 9.0 Hz,
2H), 6.86 (d, J = 9.0 Hz, 2H), 5.53 (br d, J = 9.0 Hz, 1H), 5.25 (d, J =
9.0 Hz, 1H), 3.94 (t, J = 7.5 Hz, 2H), 3.70 (s, 3H), 1.81−1.68 (m,
2H), 1.52−1.44 (m, 2H), 1.43 (s, 9H), 0.96 (t, J = 7.5 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 171.9, 159.3, 154.8, 128.7, 128.3, 114.8,
80.0, 67.7, 57.1, 52.5, 31.3, 28.3, 19.2, 13.8; MS (ESI) m/z: 338.6 [M
+ H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-[4-
(cyclobutylmethoxy)phenyl]acetate (7h). The procedure for the
synthesis of 7b was followed starting with 6 and cyclobutylmethanol
to give 7h (71% yield) as a colorless oil. 1H NMR (300 MHz,
CDCl3): δ 7.26 (d, J = 9.0 Hz, 2H), 6.87 (d, J = 9.0 Hz, 2H), 5.50 (br
I
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stirred at room temperature overnight and concentrated to give crude
8b (93 mg, 100% over two steps) as an off-white foamy solid. H
1.15−0.97 (m, 18H); 13C NMR (75 MHz, CDCl3): δ 174.4, 156.0,
132.2, 127.9, 120.1, 58.1, 52.3, 17.9, 12.6; MS (ESI) m/z: 322.0 [M +
H+ − NH3]+. To a solution of the amine intermediate (620 mg, 1.84
mmol) in MeCN (20 mL) at room temperature were added TEA
(0.77 mL, 5.52 mmol), (S)-2-phenylpropionic acid (0.36 g, 2.39
mmol), and HBTU (1.05 g, 2.76 mmol). After stirring for 5 h, the
reaction was quenched by H2O (10 mL), followed by addition of
EtOAc (50 mL). The layers were separated. The organic layer was
washed with saturated NaHCO3 (10 mL) and brine (2 × 20 mL),
dried (Na2SO4), and concentrated under reduced pressure. The
residue was subjected to chromatography on silica gel using 0−30%
EtOAc in hexanes to give the corresponding amide as a waxy solid. 1H
NMR (300 MHz, CDCl3): δ 7.37−7.16 (m, 5H), 7.02 (d, J = 8.6 Hz,
2H), 6.76 (d, J = 8.6 Hz, 2H), 6.32 (d, J = 7.0 Hz, 1H), 5.46 (d, J =
7.1 Hz, 1H), 3.73−3.52 (m, 4H), 1.49 (d, J = 7.1 Hz, 3H), 1.30−1.14
(m, 3H), 1.11−1.04 (m, 18H); 13C NMR (75 MHz, CDCl3): δ 173.3,
171.6, 156.2, 141.1, 128.8, 128.6, 128.2, 127.6, 127.2, 120.1, 55.9,
52.6, 46.7, 18.4, 17.9, 12.6; MS (ESI) m/z: 470.0 [M + H]+. To a
solution of the amide (864 mg, 1.84 mmol) in THF (20 mL) at 0 °C
was added TBAF (1.0 M in THF, 2.76 mL, 2.76 mmol) via a syringe.
After stirring at 0 °C for 4 h, the reaction was quenched by H2O (15
mL) and diluted with EtOAc (20 mL). The layers were separated, and
the aqueous layer was extracted with additional EtOAc (2 × 20 mL).
The combined organic layers were washed with brine (2 × 2 mL),
dried (Na2SO4), and concentrated under reduced pressure. The
residue was subjected to chromatography on silica gel using 0−100%
EtOAc in hexanes to furnish 10 (576 mg, 85% over two steps) as a
yellowish waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.48−7.16 (m,
5H), 6.96 (d, J = 8.5 Hz, 2H), 6.78 (br s, 1H), 6.60 (d, J = 8.6 Hz,
2H), 6.48 (d, J = 6.6 Hz, 1H), 5.40 (d, J = 6.7 Hz, 1H), 3.73−3.51
(m, 4H), 1.51 (d, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
171.4, 169.1, 153.9, 138.2, 126.4, 125.7, 125.1, 124.9, 113.3, 53.6,
50.3, 44.3, 15.7; MS (ESI) m/z: 314.0 [M + H]+.
1
NMR (300 MHz, CDCl3): δ 7.21 (d, J = 9.0 Hz, 2H), 6.87 (d, J = 9.0
Hz, 2H), 4.01−3.84 (m, 3H), 3.74−3.60 (m, 1H), 3.51 (t, J = 9.0 Hz,
1H), 1.84−1.70 (m, 2H), 1.66−1.51 (m, 1H), 1.38−1.21 (m, 3H),
0.92 (d, J = 9.0 Hz, 6H); MS (ESI) free base m/z: 238.3 [M + H]+.
(2R)-2-Amino-2-[4-(pentyloxy)phenyl]ethan-1-ol Hydrochloride
(8c). The procedure for the synthesis of 8b was followed starting
with 7c to give crude 8c (100% yield over two steps) as an off-white
foamy solid. 1H NMR (300 MHz, CDCl3): δ 7.22 (d, J = 9.0 Hz, 2H),
6.87 (d, J = 9.0 Hz, 2H), 4.05−3.84 (m, 3H), 3.75−3.61 (m, 1H),
3.51 (t, J = 9.0 Hz, 1H), 1.84−1.70 (m, 2H), 1.50−1.29 (m, 5H),
0.93 (t, J = 7.5 Hz, 3H); MS (ESI) free base m/z: 224.3 [M + H]+.
(2R)-2-Amino-2-(4-butoxyphenyl)ethan-1-ol Hydrochloride (8g).
The procedure for the synthesis of 8b was followed starting with 7g to
give crude 8g (100% yield over two steps) as an off-white foamy solid.
1H NMR (300 MHz, CD3OD): δ 7.35 (d, J = 9.0 Hz, 2H), 6.98 (d, J
= 9.0 Hz, 2H), 4.32−4.21 (m, 1H), 3.99 (t, J = 6.0 Hz, 2H), 3.87−
3.72 (m, 2H), 1.82−1.67 (m, 2H), 1.58−1.42 (m, 2H), 0.98 (t, J =
7.5 Hz, 3H); MS (ESI) free base m/z: 210.3 [M + H]+.
(2R)-2-Amino-2-(4-propoxyphenyl)ethan-1-ol Hydrochloride
(8i). The procedure for the synthesis of 8b was followed starting
with 7i to give crude 8i (100% yield over two steps) as an off-white
1
foamy solid. H NMR (300 MHz, CD3OD): δ 7.33 (d, J = 9.0 Hz,
2H), 6.95 (d, J = 9.0 Hz, 2H), 4.30−4.14 (m, 1H), 3.97−3.69 (m,
4H), 1.86−1.66 (m, 2H), 1.03 (t, J = 7.5 Hz, 3H); MS (ESI) free base
m/z: 196.2 [M + H]+.
(2R)-2-Amino-2-[4-(4-methoxybutoxy)phenyl]ethan-1-ol Hydro-
chloride (8k). The procedure for the synthesis of 8b was followed
starting with 7k to give crude 8k (100% yield over two steps) as an
off-white foamy solid. 1H NMR (300 MHz, CDCl3): δ 7.39 (d, J = 9.0
Hz, 2H), 6.83 (d, J = 9.0 Hz, 2H), 5.54−5.28 (m, 1H), 4.53−4.30 (m,
1H), 4.00−3.60 (m, 4H), 3.49−3.36 (m, 2H), 3.32 (s, 3H), 1.86−
1.57 (m, 4H); MS (ESI) free base m/z: 240.4 [M + H]+.
(2R)-2-Amino-2-[4-(3-methoxypropoxy)phenyl]ethan-1-ol Hy-
drochloride (8l). The procedure for the synthesis of 8b was followed
starting with 7l to give crude 8l (100% yield over two steps) as an off-
Methyl (2R)-2-[4-(Hexan-2-yloxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetate (11a). The procedure for the synthesis
of 7b was followed starting with 10 and 2-hexanol to give 11a (46%
1
yield) as a sticky solid. H NMR (300 MHz, CDCl3): δ 7.38−7.17
1
white foamy solid. H NMR (300 MHz, CDCl3): δ 7.39 (d, J = 9.0
(m, 5H), 7.11−7.00 (m, 2H), 6.83−6.68 (m, 2H), 6.33 (d, J = 6.9 Hz,
1H), 5.44 (d, J = 7.0 Hz, 1H), 4.39−4.23 (m, 1H), 3.67 (s, 3H),
3.66−3.55 (m, 1H), 1.80−1.63 (m, 1H), 1.63−1.52 (m, 1H), 1.50 (d,
J = 7.2 Hz, 3H), 1.43−1.28 (m, 4H), 1.25 (d, J = 6.1 Hz, 3H), 0.89
(m, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 171.6, 158.3, 141.1,
128.8, 128.2, 127.9, 127.6, 127.2, 115.9, 73.9, 56.0, 53.0, 46.8, 36.1,
27.7, 22.6, 19.7, 18.4, 14.0; MS (ESI) m/z: 398.0 [M + H]+.
Hz, 2H), 6.83 (d, J = 9.0 Hz, 2H), 5.47−5.36 (m, 1H), 4.47−4.33 (m,
1H), 3.98−3.84 (m, 3H), 3.80−3.68 (m, 1H), 3.49 (t, J = 6.0 Hz,
2H), 3.31 (s, 3H), 2.05−1.91 (m, 2H); MS (ESI) free base m/z:
226.2 [M + H]+.
Methyl (2R)-2-{[(tert-Butoxy)carbonyl]amino}-2-(4-{[tris(propan-
2-yl)silyl]oxy}phenyl)acetate (9). To a solution of 6 (1 g, 3.55 mmol)
in dry DCM (20 mL) were added imidazole (532 mg, 7.82 mmol)
and TIPS−Cl (837 mg, 3.91 mmol) at 0 °C. After stirring at room
temperature for 16 h, the reaction was quenched with H2O (2 mL),
and the layers were separated. The aqueous layer was extracted with
additional DCM (3 × 20 mL), and the combined organic layers were
washed with brine (3 × 30 mL) and dried (Na2SO4). The solvent was
removed under reduced pressure, and the residue was subjected to
chromatography on silica gel using 0−30% EtOAc in hexanes to
Methyl (2R)-2-[4-(2-Methylbutoxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetate (11d). The procedure for the synthesis
of 7b was followed starting with 10 and 2-methyl-1-butanol to give
1
11d (29% yield) as a waxy solid. H NMR (300 MHz, CDCl3): δ
7.40−7.20 (m, 5H), 7.19−7.01 (m, 2H), 6.86−6.75 (m, 2H), 6.31 (d,
J = 7.0 Hz, 1H), 5.44 (d, J = 6.9 Hz, 1H), 3.82−3.53 (m, 6H), 1.89−
1.75 (m, 1H), 1.63−1.42 (m, 4H), 1.37−1.10 (m, 1H), 0.99 (d, J =
6.7 Hz, 3H), 0.93 (t, J = 7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.3, 171.6, 159.4, 128.8, 128.2, 127.6, 127.2, 114.8, 72.9, 56.0, 52.6,
46.8, 34.7, 26.1, 18.4, 16.5, 11.2; MS (ESI) m/z: 384.0 [M + H]+.
Methyl (2R)-2-{4-[(2S)-2-Methylbutoxy]phenyl}-2-[(2S)-2-
phenylpropanamido]acetate (11e). The procedure for the synthesis
of 7b was followed with 10 and (S)-2-methyl-1-butanol to give 11e
1
furnish 9 (1.47 g, 95% yield) as a thick colorless oil. H NMR (300
MHz, CDCl3): δ 7.19 (d, J = 8.5 Hz, 2H), 6.84 (d, J = 8.6 Hz, 2H),
5.42 (d, J = 6.3 Hz, 1H), 5.23 (d, J = 7.3 Hz, 1H), 3.71 (s, 3H), 1.43
(s, 9H), 1.31−1.16 (m, 3H), 1.12−1.05 (m, 18H); 13C NMR (75
MHz, CDCl3): δ 172.0, 156.3, 155.0, 129.1, 128.3, 120.2, 80.1, 57.1,
52.5, 28.3, 17.9, 12.6; MS (ESI) m/z: 460.0 [M + Na]+.
1
(41% yield) as a waxy solid. H NMR (300 MHz, CDCl3): δ 7.38−
M e t h y l ( 2 R ) - 2 - ( 4 - H y d r o x y p h e n y l ) - 2 - [ ( 2 S ) - 2 -
phenylpropanamido]acetate (10). To a solution of 9 (968 mg,
2.25 mmol) in DCM (25 mL) was added TFA (2 mL) at 0 °C. After
stirring for 16 h, the reaction was quenched with saturated NaHCO3
(20 mL) and the layers were separated. The aqueous layer was
extracted with additional DCM (3 × 20 mL), and the combined
organic layers were washed with brine (3 × 20 mL), dried (Na2SO4),
and concentrated. The residue was subjected to chromatography on
silica gel using 0−30% EtOAc in hexanes (containing 1.5% Et3N) to
afford the free amine (650 mg, 85% yield) as a foamy solid. 1H NMR
(300 MHz, CDCl3): δ 7.22 (d, J = 8.6 Hz, 2H), 6.84 (d, J = 8.6 Hz,
2H), 4.58 (s, 1H), 3.69 (s, 3H), 2.33 (br s, 2H), 1.35−1.15 (m, 3H),
7.18 (m, 5H), 7.07 (t, J = 8.7 Hz, 2H), 6.78 (d, J = 8.7 Hz, 2H), 6.34
(d, J = 6.6 Hz, 1H), 5.44 (d, J = 6.9 Hz, 1H), 3.84−3.52 (m, 6H),
1.92−1.70 (m, 1H), 1.64−1.44 (m, 4H), 1.35−1.11 (m, 1H), 0.98 (d,
J = 6.7 Hz, 3H), 0.93 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 173.3, 171.6, 159.4, 141.1, 128.8, 128.2, 128.1, 127.6,
127.2, 114.8, 72.9, 56.0, 53.0, 46.8, 34.7, 26.1, 18.4, 16.5, 11.2; MS
(ESI) m/z: 384.0 [M + H]+.
Methyl (2R)-2-[4-(Cyclopentylmethoxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetate (11f). The procedure for the synthesis
of 7b was followed with 11 and (S)-2-methyl-1-butanol to furnish 9f
1
(27% yield) as a waxy solid. H NMR (300 MHz, CDCl3): δ 7.28
(ddd, J = 9.7, 7.3, 3.1 Hz, 5H), 7.08 (d, J = 8.7 Hz, 2H), 6.78 (d, J =
J
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8.7 Hz, 2H), 6.35 (d, J = 6.9 Hz, 1H), 5.44 (d, J = 6.9 Hz, 1H), 3.77
(d, J = 6.9 Hz, 1H), 3.72−3.52 (m, 4H), 2.41−2.22 (m, 1H), 1.91−
1.70 (m, 2H), 1.70−1.51 (m, 4H), 1.49 (d, J = 7.2 Hz, 3H), 1.43−
1.14 (m, 3H); 13C NMR (75 MHz, CDCl3): δ 173.3, 171.6, 159.4,
141.1, 128.8, 128.2, 127.6, 127.2, 114.8, 72.2, 56.0, 52.6, 46.8, 39.0,
29.4, 25.4, 18.4; MS (ESI) m/z: 396.0 [M + H]+.
114.8, 72.7, 72.2, 56.0, 52.6, 46.8, 31.2, 31.5, 30.6, 30.3, 27.0, 26.8,
22.3, 22.1, 18.4; MS (ESI) m/z: 396.0 [M + H]+.
Methyl (2R)-2-{4-[(3,3-Dimethylcyclobutyl)methoxy]phenyl}-2-
[(2S)-2-phenylpropanami do]acetate (11o). The procedure for the
synthesis of 11m was followed starting with 10 and (3,3-
dimethylcyclobutyl)methyl-4-methylbenzene-1-sulfonate to give 11o
1
(21% yield) as a waxy solid. H NMR (300 MHz, CDCl3): δ 7.40−
Methyl (2R)-2-[4-(Cyclobutylmethoxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetate (11h). To a solution of 7h (175 mg,
0.5 mmol) in DCM (5 mL) at room temperature was added 4 M HCl
in dioxane (3 mL). The reaction mixture was stirred at room
temperature overnight and concentrated to give crude amine
hydrochloride. The crude amine (90 mg, 0.35 mmol) was then
dissolved in MeCN (10 mL), followed by addition of TEA (0.16 mL,
1.1 mmol), (S)-2-phenylpropionic acid (56 mg, 0.37 mmol), and
HBTU (170 mg, 0.45 mmol). After stirring for 5 h, the reaction was
quenched by H2O (5 mL), followed by addition of EtOAc (50 mL).
The layers were separated. The organic layer was washed with
saturated NaHCO3 (10 mL) and brine (10 mL), dried (Na2SO4), and
concentrated under reduced pressure. The residue was subjected to
chromatography on silica gel using 0−30% EtOAc in hexanes to
7.23 (m, 5H), 7.16 (d, J = 8.7 Hz, 2H), 6.82 (d, J = 8.7 Hz, 2H), 6.34
(d, J = 6.8 Hz, 1H), 5.43 (d, J = 6.9 Hz, 1H), 3.86 (d, J = 6.6 Hz, 2H),
3.65 (s, 3H), 3.59 (q, J = 7.2 Hz, 1H), 2.75−2.50 (m, 1H), 1.96−1.81
(m, 2H), 1.68−1.54 (m, 2H), 1.50 (d, J = 7.2 Hz, 3H), 1.17 (s, 3H),
1.08 (s, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 171.4, 159.4,
140.9, 128.9, 128.3, 127.7, 127.3, 114.9, 73.0, 56.0, 52.6, 46.9, 37.7,
31.9, 30.9, 28.9, 27.2, 18.4; MS (ESI) m/z: 410.0 [M + H]+.
Methyl (2R)-2-[(2S)-2-Phenylpropanamido]-2-[4-({spiro[2.3]-
hexan-5-yl}methoxy)phenyl]acetate (11p). The procedure for the
synthesis of 11m (except, MeCN was used instead of DMF) was
followed starting with 10 and (3-methylidenecyclobutyl)methyl 4-
methylbenzene-1-sulfonate to give the corresponding olefin inter-
mediate methyl (2R)-2-{4-[(3-methylidenecyclobutyl)methoxy]-
phenyl}-2-[(2S)-2-phenylpropanamido] acetate (12% yield) as a
waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.43−7.21 (m, 5H), 7.16
(d, J = 8.6 Hz, 2H), 6.83 (d, J = 8.6 Hz, 2H), 6.39 (d, J = 6.7 Hz, 1H),
5.42 (d, J = 6.9 Hz, 1H), 4.88−4.68 (m, 2H), 3.93 (d, J = 6.7 Hz,
2H), 3.64 (s, 3H), 3.58 (q, J = 7.2 Hz, 1H), 2.92−2.78 (m, 2H),
2.78−2.62 (m, 1H), 2.56−2.44 (m, 2H), 1.49 (d, J = 7.2 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 173.4, 171.4, 159.2, 146.3, 140.9, 128.9,
128.6, 128.4, 127.7, 127.3, 114.9, 106.7, 71.6, 56.0, 52.6, 46.8, 34.6,
29.2, 18.5; MS (ESI) m/z: 394.0 [M + H]+. The olefin function of
this material was transformed into the corresponding cyclopropyl
function under Shi38 modified Simmons−Smith39 reaction. To a
solution of Et2Zn (171.5 μL, 0.17 mmol) in DCM (1 mL) at 0 °C was
added TFA (13.1 μL, 0.17 mmol). After stirring at 0 °C for 1 h,
diiodomethane (13.8 μL, 0.17 mmol) was added and stirred for
another 40 min at 0 °C. At that time, the olefin intermediate (27 mg,
0.07 mmol) was dissolved in DCM (1 mL) and added slowly to the
above reaction via a syringe at 0 °C. The reaction, which resulted, was
stirred under N2 at room temperature for 2 h. After that, the reaction
was quenched by cold saturated NH4Cl (2 mL) and diluted with
EtOAc (5 mL). The layers were separated, and the aqueous layer was
extracted with additional EtOAc (2 × 10 mL). The combined organic
layers were washed with saturated NaHCO3 (5 mL) and brine (3 ×
10 mL), dried (Na2SO4), and concentrated under reduced pressure.
The residue was subjected to column chromatography on silica gel
using 0−25% EtOAc in hexanes to furnish 11p (20 mg, 72% yield) as
1
furnish 11h (87 mg, 65% yield over two steps) as a colorless oil. H
NMR (300 MHz, CDCl3): δ 7.38−7.20 (m, 5H), 7.08 (d, J = 9.0 Hz,
2H), 6.79 (d, J = 9.0 Hz, 2H), 6.36 (d, J = 6.0 Hz, 1H), 5.44 (d, J =
6.0 Hz, 1H), 3.87 (d, J = 9.0 Hz, 2H), 3.67 (s, 3H), 3.66−3.56 (m,
1H), 2.81−2.65 (m, 1H), 2.18−2.05 (m, 2H), 2.02−1.72 (m, 4H),
1.49 (d, J = 6.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4,
171.6, 159.4, 141.1, 128.9, 128.2, 127.6, 127.3, 114.9, 101.6, 72.1,
55.1, 52.6, 46.8, 34.6, 24.8, 18.6, 18.5; MS (ESI) m/z: 382.5 [M +
H]+.
Methyl (2R)-2-[4-(Cyclopropylmethoxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetate (11j). The procedure for the synthesis
of 11h was followed starting with 7j to give 11j (63% yield over two
1
steps) as a colorless oil. H NMR (300 MHz, CDCl3): δ 7.33−7.20
(m, 5H), 7.08 (d, J = 9.0 Hz, 2H), 6.78 (d, J = 9.0 Hz, 2H), 6.43 (d, J
= 6.0 Hz, 1H), 5.44 (d, J = 6.0 Hz, 1H), 4.74 (d, J = 9.0 Hz, 2H), 3.66
(s, 3H), 3.65−3.56 (m, 1H), 1.49 (d, J = 9.0 Hz, 3H), 1.30−1.14 (m,
1H), 0.66−0.57 (m, 2H), 0.34−0.28 (m, 2H); 13C NMR (75 MHz,
CDCl3): δ 173.4, 171.6, 159.1, 141.1, 128.9, 128.3, 127.6, 127.3,
114.8, 72.7, 56.0, 52.7, 46.7, 18.5, 10.2, 3.2; MS (ESI) m/z: 368.5 [M
+ H]+.
Methyl (2R)-2-{4-[(1-Methylcyclobutyl)methoxy]phenyl}-2-[(2S)-
2-phenylpropanamido]acetate (11m). To a solution of 10 (200 mg,
0.64 mmol) in anhydrous DMF (15 mL) at room temperature were
added (1-methylcyclobutyl)methyl 4-methylbenzene-1-sulfonate (189
mg, 0.7 mmol) and K2CO3 (264 mg, 1.92 mmol). After stirring for 16
h at 60 °C, the reaction was quenched by H2O (10 mL), followed by
addition of EtOAc (15 mL). The layers were separated, and the
aqueous layer was extracted with additional EtOAc (2 × 10 mL). The
combined organic layers were washed with brine (4 × 15 mL), dried
(Na2SO4), and concentrated under reduced pressure. The residue was
subjected to column chromatography on silica gel using 0−50%
EtOAc in hexanes to furnish 11m (15 mg, 6% yield) as a waxy solid.
1H NMR (300 MHz, CDCl3): δ 7.41−7.23 (m, 5H), 7.17 (d, J = 8.7
1
a waxy solid. H NMR (300 MHz, CDCl3): δ 7.41−7.22 (m, 5H),
7.17 (d, J = 8.6 Hz, 2H), 6.85 (d, J = 8.7 Hz, 2H), 6.30 (d, J = 6.7 Hz,
1H), 5.43 (d, J = 6.9 Hz, 1H), 4.01 (d, J = 7.1 Hz, 2H), 3.66 (s, 3H),
3.59 (q, J = 7.2 Hz, 1H), 2.92−2.73 (m, 1H), 2.37−2.14 (m, 2H),
1.93 (dd, J = 12.3, 5.8 Hz, 2H), 1.51 (d, J = 7.2 Hz, 3H), 0.41 (s, 4H);
13C NMR (75 MHz, CDCl3): δ 173.4, 171.4, 159.4, 140.9, 128.9,
128.4, 128.3, 127.7, 127.3, 115.0, 72.5, 56.0, 52.6, 46.9, 33.4, 29.8,
18.4, 16.9, 12.1, 11.7; MS (ESI) m/z: 408.0 [M + H]+.
Hz, 2H), 6.86 (d, J = 8.7 Hz, 2H), 6.30 (d, J = 6.7 Hz, 1H), 5.43 (d, J
= 6.9 Hz, 1H), 3.73 (s, 2H), 3.66 (s, 3H), 3.59 (q, J = 7.2 Hz, 1H),
2.12−1.82 (m, 4H), 1.82−1.66 (m, 2H), 1.51 (d, J = 7.2 Hz, 3H),
1.21 (s, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 171.5, 159.8,
140.9, 128.9, 128.3, 127.7, 127.3, 114.9, 75.6, 56.0, 52.6, 46.9, 38.7,
30.1, 24.5, 18.4, 15.0; MS (ESI) m/z: 396.0 [M + H]+.
Methyl (2R)-2-{4-[(3-Methylcyclobutyl)methoxy]phenyl}-2-[(2S)-
2-phenylpropanamido]acetate (11n). The procedure for the
synthesis of 7b was followed starting with 10 and (3-
methylcyclobutyl)methanol to give 11n (27% yield) as a waxy solid.
1H NMR (300 MHz, CDCl3): δ 7.37−7.19 (m, 5H), 7.08 (dd, J = 8.7,
2.2 Hz, 2H), 6.85−6.70 (m, 2H), 6.32 (d, J = 6.6 Hz, 1H), 5.44 (d, J
= 6.9 Hz, 1H), 3.91 (d, J = 7.1 Hz, 1H), 3.80 (d, J = 6.3 Hz, 1H),
3.71−3.54 (m, 4H), 2.85−2.12 (m, 3H), 2.04−1.92 (m, 1H), 1.84−
1.67 (m, 1H), 1.49 (d, J = 7.2 Hz, 3H), 1.45−1.35 (m, 1H), 1.12 (d, J
= 6.9 Hz, 1.4 H), 1.04 (d, J = 6.1 Hz, 1.6 H); 13C NMR (75 MHz,
CDCl3): δ 173.3, 171.6, 159.3, 141.1, 128.8, 128.2, 127.6, 1272,
Methyl (2R)-2-{4-[(3,3-Difluorocyclobutyl)methoxy]phenyl}-2-
[(2S)-2-phenylpropanamido]acetate (11q). The procedure for the
synthesis of 11m was followed starting with 10 and (3,3-
difluorocyclobutyl)methyl 4-methylbenzene-1-sulfonate to give 11q
(8% yield) as a waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.38−7.21
(m, 5H), 7.09 (d, J = 8.6 Hz, 2H), 6.78 (d, J = 8.7 Hz, 2H), 6.34 (d, J
= 6.8 Hz, 1H), 5.45 (d, J = 6.9 Hz, 1H), 3.94 (d, J = 5.8 Hz, 2H),
3.72−3.54 (m, 4H), 2.84−2.34 (m, 5H), 1.49 (d, J = 7.1 Hz, 3H); MS
(ESI) m/z: 418.0 [M + H]+.
(2S)-N-[(1R)-1-[4-(Hexan-2-yloxy)phenyl]-2-hydroxyethyl]-2-phe-
nylpropanamide (12). To a suspension of NaBH4 (20.9 mg, 0.55
mmol) in EtOH (6 mL) at 0 °C under nitrogen was added LiCl (23.4
mg, 0.55 mmol). After stirring at 0 °C for 10 min, a solution of 11a
(88 mg, 0.22 mmol) in THF (6 mL) was added. The reaction mixture
was stirred at room temperature for 3 h and quenched with saturated
NH4Cl solution (5 mL), followed by the addition of H2O (10 mL).
The mixture was extracted with EtOAc (3 × 20 mL). The combined
K
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organic layers were washed with brine (20 mL), dried (Na2SO4), and
concentrated under reduced pressure. The residue was subjected to
column chromatography on silica gel using 0−30% EtOAc in hexanes
to furnish 12 (45 mg, 55% yield) as a white waxy solid. 1H NMR (300
MHz, CDCl3): δ 7.44−7.20 (m, 5H), 6.93 (d, J = 8.7 Hz, 2H), 6.74
(d, J = 8.7 Hz, 2H), 6.14 (d, J = 7.1 Hz, 1H), 4.94 (dd, J = 11.2, 6.0
Hz, 1H), 4.42−4.04 (m, 1H), 3.73 (d, J = 5.5 Hz, 2H), 3.62 (q, J =
7.1 Hz, 1H), 2.98 (br s, 1H), 1.79−1.61 (m, 1H), 1.61−1.46 (m, 4H),
1.46−1.28 (m, 4H), 1.25 (d, J = 6.1 Hz, 3H), 0.90 (t, J = 7.0 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 174.6, 157.7, 141.3, 130.6, 128.9,
solid. 1H NMR (300 MHz, CDCl3): δ 7.44−7.17 (m, 5H), 6.95 (d, J
= 8.7 Hz, 2H), 6.77 (d, J = 8.7 Hz, 2H), 6.01 (d, J = 6.9 Hz, 1H), 4.95
(dd, J = 11.9, 5.0 Hz, 1H), 3.76 (dd, J = 6.0, 3.2 Hz, 4H), 3.62 (q, J =
7.1 Hz, 1H), 2.67 (t, J = 6.0 Hz, 1H), 2.45−2.20 (m, 1H), 1.90−1.69
(m, 3H), 1.69−1.55 (m, 3H), 1.52 (t, J = 6.2 Hz, 3H), 1.34 (dt, J =
11.6, 7.2 Hz, 2H); 13C NMR (75 MHz, CDCl3): δ 174.6, 158.8,
141.2, 130.6, 128.9, 127.6, 127.5, 127.3, 114.8, 72.3, 66.7, 55.4, 47.1,
39.0, 29.4, 25.4, 18.4; HRMS (ESI) m/z: calcd for C23H29NO3 [M +
H]+, 368.2220; m/z: found, 368.2215.
(2S)-N-[(1R)-1-(4-Butoxyphenyl)-2-hydroxyethyl]-2-phenylpro-
panamide (18). The procedure for the synthesis of 13 was followed
127.6, 127.3, 116.0, 73.9, 66.5, 55.3, 47.0, 36.2, 27.7, 22.6, 19.7, 18.5,
14.0; HRMS (ESI) m/z: calcd for C23H31NO3 [M + H]+, 370.2377,
m/z: found, 370.2371.
1
starting with 8g to give 18 (33% yield) as a white solid. H NMR
(300 MHz, CDCl3): δ 7.36−7.23 (m, 5H), 6.96 (d, J = 9.0 Hz, 2H),
6.78 (d, J = 9.0 Hz, 2H), 5.99 (d, J = 6.0 Hz, 1H), 5.00−4.89 (m,
1H), 3.91 (t, J = 7.5 Hz, 2H), 3.76 (d, J = 3.0 Hz, 2H), 3.69−3.57 (m,
1H), 2.62 (br s, 1H), 1.82−1.66 (m, 2H), 1.52 (d, J = 6.0 Hz, 3H),
1.51−1.37 (m, 2H), 0.96 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 174.6, 158.7, 141.2, 130.6, 128.9, 127.6, 127.5, 127.3,
114.8, 67.7, 66.8, 55.4, 47.1, 31.3, 19.2, 18.4, 13.8; HRMS (ESI) m/z:
calcd for C21H27NO3 [M + H]+, 342.2064; m/z: found, 342.2071.
(2S)-N-{(1R)-1-[4-(Cyclobutylmethoxy)phenyl]-2-hydroxyethyl}-
2-phenylpropanamide (19). The procedure for the synthesis of 12
was followed starting with 11h to give 19 (83% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.37−7.22 (m, 5H), 6.95 (d, J = 9.0
Hz, 2H), 6.77 (d, J = 9.0 Hz, 2H), 6.09 (d, J = 6.0 Hz, 1H), 4.98−
4.88 (m, 1H), 3.86 (d, J = 6.0 Hz, 2H), 3.74 (br s, 2H), 3.68−3.56
(m, 1H), 2.86 (br t, J = 6.0 Hz, 1H), 2.81−2.65 (m, 2H), 2.20−2.04
(m, 2H), 2.20−1.75 (m, 4H), 1.51 (d, J = 9.0 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 174.6, 158.8, 141.2, 130.7, 128.9, 127.5, 127.3,
114.8, 72.1, 66.6, 55.3, 47.0, 34.6, 24.8, 18.5, 18.4; HRMS (ESI) m/z:
calcd for C22H27NO3 [M + H]+, 354.2064; m/z: found, 354.2064.
(2S)-N-[(1R)-2-Hydroxy-1-(4-propoxyphenyl)ethyl]-2-phenylpro-
panamide (20). The procedure for the synthesis of 13 was followed
starting with 8i to give 20 (32% yield) as a white solid. 1H NMR (300
MHz, CDCl3): δ 7.39−7.22 (m, 5H), 6.95 (d, J = 9.0 Hz, 2H), 6.77
(d, J = 9.0 Hz, 2H), 6.08 (d, J = 6.0 Hz, 1H), 4.99−4.90 (m, 1H),
3.96 (t, J = 7.5 Hz, 2H), 3.75 (br s, 2H), 3.67−3.56 (m, 1H), 2.83 (br
t, J = 4.5 Hz, 1H), 1.83−1.68 (m, 2H), 1.51 (d, J = 9.0 Hz, 3H), 1.01
(t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 174.6, 158.6,
141.2, 130.6, 128.9, 127.5, 127.3, 114.7, 69.5, 66.6, 55.3, 47.0, 22.5,
18.4, 10.4; HRMS (ESI) m/z: calcd for C20H25NO3 [M + H]+,
328.1907; m/z: found, 328.1911.
(2S)-N-[(1R)-2-Hydroxy-1-{4-[(4-methylpentyl)oxy]phenyl}ethyl]-
2-phenylpropanamide (13). To a solution of 8b (96 mg, 0.35 mmol)
in MeCN (10 mL) at room temperature were added TEA (0.16 mL,
1.1 mmol), (S)-2-phenylpropionic acid (56 mg, 0.37 mmol), and
HBTU (170 mg, 0.45 mmol). After stirring for 5 h, the reaction was
quenched by H2O (5 mL), followed by addition of EtOAc (50 mL).
The layers were separated. The organic layer was washed with
saturated NaHCO3 (10 mL) and brine (10 mL), dried (Na2SO4), and
concentrated under reduced pressure. The residue was subjected to
chromatography on silica gel using 0−30% EtOAc in hexanes to
provide 13 (55 mg, 43% yield) as a white solid. 1H NMR (300 MHz,
CDCl3): δ 7.38−7.20 (m, 5H), 6.95 (d, J = 9.0 Hz, 2H), 6.78 (d, J =
9.0 Hz, 2H), 6.08 (d, J = 9.0 Hz, 1H), 4.99−4.90 (m, 1H), 3.88 (t, J =
7.5 Hz, 2H), 3.75 (br s, 2H), 3.68−3.56 (m, 1H), 2.83 (br s, 1H),
1.81−1.69 (m, 2H), 1.64−1.54 (m, 1H), 1.51 (d, J = 9.0 Hz, 3H),
1.36−1.23 (m, 2H), 0.91 (d, J = 6.0 Hz, 6H); 13C NMR (75 MHz,
CDCl3): δ 174.6, 158.6, 141.2, 130.6, 128.9, 127.5, 127.3, 114.7, 68.3,
66.6, 55.3, 47.0, 35.1, 27.8, 27.1, 22.5, 18.4; HRMS (ESI) m/z: calcd
for C23H31NO3 [M + H]+, 370.2377; m/z: found, 370.2375.
(2S)-N-{(1R)-2-Hydroxy-1-[4-(pentyloxy)phenyl]ethyl}-2-phenyl-
propanamide (14). The procedure for the synthesis of 13 was
1
followed starting with 8c to give 14 (43% yield) as a white solid. H
NMR (300 MHz, CDCl3): δ 7.40−7.20 (m, 5H), 6.95 (d, J = 9.0 Hz,
2H), 6.77 (d, J = 9.0 Hz, 2H), 6.03 (d, J = 6.0 Hz, 1H), 5.00−4.89
(m, 1H), 3.89 (t, J = 6.0 Hz, 2H), 3.76 (d, J = 6.0 Hz, 2H), 3.68−3.55
(m, 1H), 2.73 (br s, 1H), 1.85−1.67 (m, 2H), 1.51 (d, J = 6.0 Hz,
3H), 1.46−1.25 (m, 4H), 0.92 (t, J = 7.5 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 174.6, 158.7, 141.2, 130.6, 128.9, 127.6, 127.5,
127.3, 114.7, 68.0, 66.7, 55.4, 47.1, 28.9, 28.2, 22.4, 18.4, 14.0; HRMS
(ESI) m/z: calcd for C22H29NO3 [M + H]+, 356.2220; m/z: found,
356.2219.
(2S)-N-[(1R)-2-Hydroxy-1-[4-(2-methylbutoxy)phenyl]ethyl]-2-
phenylpropanamide (15). The procedure for the synthesis of 12 was
followed starting with 11d to give 15 (67% yield) as a white waxy
solid. 1H NMR (300 MHz, CDCl3): δ 7.43−7.16 (m, 5H), 6.95 (d, J
= 8.6 Hz, 2H), 6.78 (d, J = 8.6 Hz, 2H), 5.98 (d, J = 6.9 Hz, 1H), 4.95
(dd, J = 11.8, 5.0 Hz, 1H), 3.81−3.72 (m, 3H), 3.71−3.57 (m, 2H),
2.61 (t, J = 5.7 Hz, 1H), 1.94−1.73 (m, 1H), 1.64−1.44 (m, 4H),
1.37−1.12 (m, 1H), 0.99 (d, J = 6.7 Hz, 3H), 0.93 (t, J = 7.4 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 174.6, 158.9, 141.2, 130.5, 128.9,
(2S)-N-{(1R)-1-[4-(Cyclopropylmethoxy)phenyl]-2-hydroxyethyl}-
2-phenylpropanamide (21). The procedure for the synthesis of 12
was followed starting with 11j to give 21 (82% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.38−7.19 (m, 5H), 6.94 (d, J = 9.0
Hz, 2H), 6.77 (d, J = 9.0 Hz, 2H), 6.11 (d, J = 6.0 Hz, 1H), 4.99−
4.88 (m, 1H), 3.73 (d, J = 6.0 Hz, 3H), 3.68−3.54 (m, 1H), 2.89 (br
t, J = 6.0 Hz, 1H), 1.50 (d, J = 6.0 Hz, 4H), 1.32−1.14 (m, 1H),
0.69−0.56 (m, 2H), 0.36−0.26 (m, 2H); 13C NMR (75 MHz,
CDCl3): δ 174.5, 158.5, 141.2, 130.8, 128.9, 127.5, 127.3, 114.8, 72.7,
66.5, 55.2, 47.0, 18.4, 10.2, 3.1; HRMS (ESI) m/z: calcd for
C21H25NO3 [M + H]+, 340.1907; m/z: found, 340.1910.
(2S)-N-[(1R)-2-Hydroxy-1-[4-(4-methoxybutoxy)phenyl]ethyl}-2-
127.6, 127.5, 127.3, 114.8, 72.9, 66.8, 55.4, 47.1, 34.7, 26.1, 18.4, 16.5,
11.2; HRMS (ESI) m/z: calcd for C22H29NO3 [M + H]+, 356.2220;
m/z: found, 356.2213.
phenylpropanamide (22). The procedure for the synthesis of 13 was
1
followed starting with 8k to give 22 (82% yield) as a white solid. H
NMR (300 MHz, CDCl3): δ 7.36−7.20 (m, 5H), 6.94 (d, J = 9.0 Hz,
2H), 6.74 (d, J = 9.0 Hz, 2H), 6.29 (d, J = 6.0 Hz, 1H), 4.97−4.86
(m, 1H), 3.90 (t, J = 6.0 Hz, 2H), 3.70 (br s, 2H), 3.66−3.55 (m,
1H), 3.41 (t, J = 6.0 Hz, 2H), 3.32 (s, 3H), 3.27 (br s, 1H), 1.86−1.63
(m, 4H), 1.48 (d, J = 9.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
174.5, 158.3, 141.2, 130.8, 128.8, 127.4, 127.1, 114.5, 72.2, 67.5, 66.2,
58.4, 55.1, 46.8, 26.1, 25.9, 18.4; HRMS (ESI) m/z: calcd for
C22H29NO4 [M + H]+, 372.2169; m/z: found, 372.2173.
(2S)-N-[(1R)-2-Hydroxy-1-[4-(3-methoxypropoxy)phenyl]ethyl}-
2-phenylpropanamide (23). The procedure for the synthesis of 13
was followed starting with 8l to give 23 (73% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.34−7.20 (m, 5H), 6.93 (d, J = 9.0
(2S)-N-[(1R)-2-Hydroxy-1-{4-[(2S)-2-methylbutoxy]phenyl}ethyl]-
2-phenylpropanamide (16). The procedure for the synthesis of 12
was followed starting with 11e to give 16 (69% yield) as a white waxy
solid. 1H NMR (300 MHz, CDCl3): δ 7.43−7.19 (m, 5H), 6.94 (d, J
= 8.6 Hz, 2H), 6.76 (d, J = 8.7 Hz, 2H), 6.11 (d, J = 7.1 Hz, 1H), 4.93
(dd, J = 11.9, 5.3 Hz, 1H), 3.82−3.51 (m, 5H), 2.90 (br s, 1H), 1.94−
1.72 (m, 1H), 1.61−1.43 (m, 4H), 1.33−1.14 (m, 1H), 0.99 (d, J =
6.7 Hz, 3H), 0.93 (t, J = 7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
174.6, 158.8, 141.3, 130.6, 128.9, 127.6, 127.5, 127.3, 114.7, 72.9,
66.6, 55.3, 47.0, 34.7, 26.1, 18.4, 16.5, 11.3; HRMS (ESI) m/z: calcd
for C22H29NO3 [M + H]+, 356.2220; m/z: found, 356.2214.
(2S)-N-[(1R)-1-[4-(Cyclopentylmethoxy)phenyl]-2-hydroxyethyl]-
2-phenylpropanamide (17). The procedure for the synthesis of 12
was followed starting with 11f to give 17 (58% yield) as a white waxy
Hz, 2H), 6.75 (d, J = 9.0 Hz, 2H), 6.36 (d, J = 6.0 Hz, 1H), 4.96−
4.87 (m, 1H), 3.97 (t, J = 6.0 Hz, 2H), 3.76−3.55 (m, 3H), 3.51 (t, J
L
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Journal of Medicinal Chemistry
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Article
= 6.0 Hz, 2H), 3.45 (br s, 1H), 3.32 (s, 3H), 2.05−1.93 (m, 2H), 1.47
(d, J = 6.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 174.5, 158.2,
141.2, 130.9, 128.7, 127.4, 127.1, 114.5, 69.1, 66.0, 64.7, 58.5, 55.0,
48.8, 29.4, 18.3; HRMS (ESI) m/z: calcd for C21H27NO4 [M + H]+,
358.2013; m/z: found, 358.2017.
(2S)-N-[(1R)-2-Hydroxy-1-{4-[(1-methylcyclobutyl)methoxy]-
phenyl}ethyl]-2-phenylpropanamide (24). The procedure for the
synthesis of 12 was followed starting with 11m to give 24 (83% yield)
as a white waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.46−7.21 (m,
5H), 7.08 (d, J = 8.6 Hz, 2H), 6.86 (d, J = 8.6 Hz, 2H), 5.91 (d, J =
6.5 Hz, 1H), 4.96 (dd, J = 11.1, 5.9 Hz, 1H), 3.86−3.67 (m, 4H), 3.60
(q, J = 7.2 Hz, 1H), 2.58 (t, J = 6.0 Hz, 1H), 2.09−1.81 (m, 4H),
1.81−1.68 (m, 2H), 1.54 (d, J = 7.2 Hz, 3H), 1.22 (s, 3H); 13C NMR
(75 MHz, CDCl3): δ 174.8, 159.4, 141.2, 130.6, 129.0, 127.6, 127.5,
127.4, 114.9, 75.7, 66.8, 55.7, 47.2, 38.7, 30.1, 24.5, 18.5, 15.0; HRMS
(ESI) m/z: calcd for C23H29NO3 [M + H]+, 368.2220; m/z: found,
368.2214.
(2S)-N-[(1R)-2-Hydroxy-1-{4-[(3-methylcyclobutyl)methoxy]-
phenyl}ethyl]-2-phenylpropanamide (25). The procedure for the
synthesis of 12 was followed starting with 11n to give 25 (65% yield)
as a white waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.39−7.09 (m,
5H), 6.94 (dd, J = 8.6, 2.0 Hz, 2H), 6.81−6.72 (m, 2H), 6.08 (d, J =
6.5 Hz, 1H), 4.94 (dd, J = 11.3, 5.5 Hz, 1H), 3.90 (d, J = 7.1 Hz, 1H),
3.80 (d, J = 6.4 Hz, 1H), 3.74 (br s, 2H), 3.61 (q, J = 7.1 Hz, 1H),
2.90−2.80 (m, 1H), 2.78−2.60 (m, 0.5 H), 2.60−2.35 (m, 1H),
2.35−2.14 (m, 1.5 H), 2.07−1.91 (m, 1H), 1.82−1.67 (m, 1H), 1.50
(d, J = 7.1 Hz, 3H), 1.46−1.31 (m, 1H), 1.12 (d, J = 6.8 Hz, 1.4H),
1.04 (d, J = 6.1 Hz, 1.6H); 13C NMR (75 MHz, CDCl3): δ 174.6,
158.8, 158.8, 141.3, 130.7, 130.7, 128.9, 127.6, 127.5, 127.3, 114.8,
72.8, 72.2, 66.6, 55.3, 47.1, 33.2, 31.5, 30.6, 30.3, 27.0, 26.8, 22.3,
22.1, 18.4; HRMS (ESI) m/z: calcd for C23H29NO3 [M + H]+,
368.2220; m/z: found, 368.2213.
(2S)-N-[(1R)-1-{4-[(3,3-Dimethylcyclobutyl)methoxy]phenyl}-2-
hydroxyethyl]-2-phenylpropanamide (26). The procedure for the
synthesis of 12 was followed starting with 11o to give 26 (75% yield)
as a white waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.44−7.20 (m,
5H), 7.06 (d, J = 8.6 Hz, 2H), 6.82 (d, J = 8.6 Hz, 2H), 5.95 (d, J =
6.7 Hz, 1H), 4.94 (dd, J = 11.4, 5.5 Hz, 1H), 3.86 (d, J = 6.6 Hz, 2H),
3.80−3.65 (m, 2H), 3.58 (q, J = 7.2 Hz, 1H), 2.75−2.44 (m, 2H),
1.98−1.76 (m, 2H), 1.67−1.57 (m, 2H), 1.52 (d, J = 7.2 Hz, 3H),
1.17 (s, 3H), 1.08 (s, 3H); 13C NMR (75 MHz, CDCl3): δ 174.8,
158.9, 141.2, 130.7, 129.0, 127.6, 127.5, 127.4, 114.9, 73.1, 66.7, 55.6,
47.2, 37.7, 31.9, 30.9, 28.9, 27.2, 18.5; HRMS (ESI) m/z: calcd for
C24H31NO3 [M + H]+, 382.2377; m/z: found, 382.2368.
(2R)-2-{4-[(2-Methylpentyl)oxy]phenyl}-2-[(2S)-2-
phenylpropanamido]acetic Acid (29a).28 To a solution of 3 (1.2 g,
3.02 mmol) in THF/H2O (10 mL, 1:1, v/v) was added 1 N NaOH
(6.04 mL, 6.04 mmol) at room temperature. After stirring for 1 h, the
reaction was cooled (ice bath) and acidified (pH = ∼4) with 1 N HCl
and extracted with EtOAc (3 × 20 mL). The combined EtOAc layers
were washed with brine (3 × 20 mL), dried (Na2SO4), and
concentrated under reduced pressure to furnish 29a (1.06 g, 92%) as
1
a white solid. H NMR (300 MHz, CDCl3): δ 7.40−7.17 (m, 5H),
7.11 (d, J = 8.1 Hz, 2H), 6.79 (d, J = 8.2 Hz, 2H), 6.21 (d, J = 6.1 Hz,
1H), 5.43 (d, J = 6.3 Hz, 1H), 3.82−3.72 (m, 1H), 3.71−3.57 (m,
2H), 2.01−1.78 (m, 1H), 1.49 (d, J = 7.1 Hz, 3H), 1.45−1.07 (m,
4H), 0.99 (d, J = 6.6 Hz, 3H), 0.91 (t, J = 6.7 Hz, 3H); MS (ESI) m/
z: 384.4 [M + H]+.
(2R)-2-[4-(Cyclobutylmethoxy)phenyl]-2-[(2S)-2-
phenylpropanamido]acetic Acid (29b). The procedure for the
synthesis of 29a was followed starting with 11h to give 29b (100%
yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ 7.32−7.20 (m,
6H), 7.10 (d, J = 8.7 Hz, 2H), 6.79 (d, J = 8.7 Hz, 2H), 6.25 (d, J =
6.6 Hz, 1H), 5.43 (d, J = 6.7 Hz, 1H), 3.87 (d, J = 6.7 Hz, 2H), 3.63
(q, J = 7.1 Hz, 1H), 2.82−2.62 (m, 1H), 2.22−2.03 (m, 2H), 2.03−
1.73 (m, 4H), 1.49 (d, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 174.3, 174.1, 159.5, 140.7, 128.9, 128.3, 127.6, 127.4, 127.4, 114.9,
72.1, 56.1, 46.7, 34.5, 24.8, 18.5, 18.2; MS (ESI) m/z: 368.0 [M +
H]+.
(2S)-N-[(R)-Carbamoyl({4-[(2-methylpentyl)oxy]phenyl})methyl]-
2-phenylpropanamide (30). To a solution of 29a (230 mg, 0.6
mmol) in dioxane (10 mL) at room temperature were added pyridine
(0.1 mL, 1.2 mmol), NH4HCO3 (95 mg, 1.2 mmol), and Boc
anhydride (262 mg, 1.2 mmol). The reaction mixture was stirred for 4
h. Another portion of NH4HCO3 (95 mg, 1.2 mmol) and Boc
anhydride (262 mg, 1.2 mmol) was added, and the mixture was stirred
overnight. The reaction was quenched by 10% citric acid (10 mL) and
extracted with EtOAc (3 × 30 mL). The combined extracts were
washed with 10% citric acid (10 mL), NaHCO3 (2 × 10 mL), and
brine (10 mL), dried (NaSO4), and concentrated under reduced
pressure. The residue was subjected to column chromatography on
silica gel using 0−3% MeOH in DCM to provide 30 (100 mg, 44%
yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ 7.37−7.15 (m,
5H), 7.09 (d, J = 9.0 Hz, 2H), 6.96 (d, J = 9.0 Hz, 1H), 6.72 (d, J =
9.0 Hz, 2H), 6.61 (s, 1H), 5.85 (s, 1H), 5.54 (d, J = 6.0 Hz, 1H),
3.84−3.54 (m, 3H), 1.98−1.81 (m, 1H), 1.44 (d, J = 9.0 Hz, 3H),
1.41−1.08 (m, 4H), 0.98 (d, J = 9.0 Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 173.7, 172.8, 159.2, 141.1, 129.4,
(2S)-N-[(1R)-2-Hydroxy-1-[4-({spiro[2.3]hexan-5-yl}methoxy)-
phenyl]ethyl]-2-phenylpropanamide (27). The procedure for the
synthesis of 12 was followed starting with 11p to give 27 (80% yield)
as a white waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.44−7.22 (m,
5H), 7.08 (d, J = 8.6 Hz, 2H), 6.86 (d, J = 8.6 Hz, 2H), 5.93 (d, J =
6.7 Hz, 1H), 4.96 (dd, J = 11.4, 5.5 Hz, 1H), 4.01 (d, J = 7.1 Hz, 2H),
3.86−3.67 (m, 2H), 3.60 (q, J = 7.1 Hz, 1H), 2.93−2.71 (m, 1H),
2.56 (t, J = 6.0 Hz, 1H), 2.32−2.11 (m, 2H), 2.04−1.81 (m, 2H),
1.54 (d, J = 7.2 Hz, 3H), 0.58−0.30 (m, 4H); 13C NMR (75 MHz,
CDCl3): δ 174.8, 159.0, 141.2, 130.7, 129.0, 127.7, 127.5, 127.4,
115.0, 72.6, 66.7, 55.7, 47.2, 33.4, 29.8, 18.5, 16.9, 12.1, 11.7; HRMS
(ESI) m/z: calcd for C24H29NO3 [M + H]+, 380.2220; m/z: found,
380.2214.
(2S)-N-[(1R)-1-{4-[(3,3-Difluorocyclobutyl)methoxy]phenyl}-2-
hydroxyethyl]-2-phenylpropanamide (28). The procedure for the
synthesis of 12 was followed starting with 11q to give 28 (50% yield)
as a white solid. 1H NMR (300 MHz, CDCl3): δ 7.41−7.22 (m, 5H),
6.97 (d, J = 8.6 Hz, 2H), 6.78 (d, J = 8.7 Hz, 2H), 6.00 (d, J = 7.0 Hz,
1H), 4.96 (dd, J = 11.8, 4.9 Hz, 1H), 3.94 (d, J = 5.9 Hz, 2H), 3.77
(d, J = 5.1 Hz, 2H), 3.63 (q, J = 7.1 Hz, 1H), 2.82−2.61 (m, 2H),
2.61−2.33 (m, 4H), 1.52 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 174.5, 158.2, 141.2, 131.4, 128.9, 127.6, 127.6, 127.3,
114.8, 70.1 (m), 55.2, 47.1, 37.7 (t, J = 23.0 Hz), 22.5 (dd, J = 12.0,
7.4 Hz), 18.4; 19F NMR (282 MHz, CDCl3): δ −83.8 (d, J = 193
Hz), −93.2 (d, J = 196 Hz); HRMS (ESI) m/z: calcd for
C22H25F2NO3 [M + H]+, 390.1875; m/z: found, 390.1867.
128.7, 128.1, 127.5, 127.1, 114.7, 73.2, 56.0, 46.6, 35.7, 32.8, 20.0,
18.3, 16.9, 14.3; HRMS (ESI) m/z: calcd for C23H30N2O3 [M + H]+,
383.2329; m/z: found, 383.2332.
(2S)-N-[(R)-(Methylcarbamoyl)({4-[(2-methylpentyl)oxy]phenyl})-
methyl]-2-phenylpropanamide (31). To a solution of 29a (115 mg,
0.3 mmol) in DMF (5 mL) under nitrogen were added EDC
hydrochloride (63 mg, 0.33 mmol), HOBt (45 mg, 0.33 mmol), and
DIPEA (0.16 mL, 0.9 mmol). After cooling to 0 °C, methylamine
hydrochloride (22 mg, 0.33 mmol) was added and the reaction
mixture was stirred at room temperature overnight. The reaction was
quenched with 10% citric acid solution (5 mL) and extracted with
EtOAc (3 × 20 mL). The combined organic layers were washed with
saturated NaHCO3 (10 mL) and brine (10 mL), dried (Na2SO4), and
concentrated under reduced pressure. The residue was subjected to
column chromatography on silica gel using 0−100% EtOAc in
1
hexanes to furnish 31 (56 mg, 47% yield) as a white solid. H NMR
(300 MHz, CDCl3): δ 7.38−7.18 (m, 5H), 7.17−6.96 (m, 4H), 6.68
(d, J = 9.0 Hz, 2H), 5.62 (d, J = 9.0 Hz, 1H), 3.79−3.54 (m, 3H),
2.70 (d, J = 6.0 Hz, 2H), 1.99−1.81 (m, 1H), 1.55−1.12 (m, 5H),
1.48 (d, J = 9.0 Hz, 3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.6, 171.0, 159.0, 141.2,
129.9, 128.7, 128.0, 127.5, 127.1, 114.6, 73.1, 56.2, 46.6, 35.7, 32.8,
26.3, 20.0, 18.4, 16.9, 14.2; HRMS (ESI) m/z: calcd for C24H32N2O3
[M + H]+, 397.2486; m/z: found, 397.2482.
(2S)-N-((1R)-2-(Ethylamino)-1-(4-((2-methylpentyl)oxy)phenyl)-
2-oxoethyl)-2-phenylpropanamide (32). The procedure for the
M
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Article
synthesis of 31 was followed starting with 29a and ethylamine to give
32 (53% yield) as a white solid. H NMR (300 MHz, CDCl3): δ
(2S)-N-((1R)-2-((3-Methylbutan-2-yl)amino)-1-(4-((2-
methylpentyl)oxy)phenyl)-2-oxoethyl)-2-phenylpropanamide (37).
The procedure for the synthesis of 31 was followed starting with 29a
and 1,2-dimethylpropylamine to give 37 (44% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.37−7.16 (m, 5H), 7.08 (d, J = 8.6
Hz, 2H), 6.82 (d, J = 6.5 Hz, 1H), 6.76 (d, J = 8.7 Hz, 2H), 5.53 (d, J
= 9.0 Hz, 1H), 5.30 (d, J = 6.5 Hz, 1H), 3.87−3.69 (m, 2H), 3.69−
3.41 (m, 2H), 2.04−1.75 (m, 1H), 1.73−1.10 (m, 8H), 1.01 (dd, J =
13.6, 6.7 Hz, 6H), 0.91 (t, J = 7.0 Hz, 3H), 0.69−0.58 (m, 6H); 13C
NMR (75 MHz, CDCl3): δ 173.3, 169.4, 159.1, 141.2, 130.3, 128.8,
128.1, 127.5, 127.1, 114.8, 73.3, 56.8, 50.4, 46.9, 35.7, 32.9, 32.9, 20.0,
18.4, 18.3, 18.0, 17.6, 16.9, 14.3; HRMS (ESI) m/z: calcd for
C28H40N2O3 [M + H]+, 453.3112; m/z: found, 453.3110.
(2S)-N-[(R)-(Cyclopropylcarbamoyl)({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (38). The procedure for the
synthesis of 31 was followed starting with 29a and cyclopropylamine
to give 38 (35% yield) as a white solid. 1H NMR (300 MHz, CDCl3):
δ 7.36−7.16 (m, 5H), 7.06−6.93 (m, 3H), 6.86 (d, J = 6.0 Hz, 1H),
6.88 (d, J = 9.0 Hz, 2H), 5.49 (d, J = 6.0 Hz, 1H), 3.79−3.56 (m,
3H), 2.68−2.57 (m, 1H), 1.98−1.85 (m, 1H), 1.51−1.10 (m, 4H),
1.48 (d, J = 6.0 Hz, 3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz,
3H), 0.76−0.57 (m, 2H), 0.52−0.29 (m, 2H); 13C NMR (75 MHz,
CDCl3): δ 173.5, 171.7, 159.0, 141.1, 129.7, 128.8, 128.0, 127.5,
127.1, 114.6, 73.2, 56.1, 46.7, 35.7, 32.9, 22.7, 20.0, 18.4, 17.0, 14.2,
6.4, 6.2; HRMS (ESI) m/z: calcd for C26H34N2O3 [M + H]+,
423.2642; m/z: found, 423.2647.
1
7.36−7.17 (m, 5H), 7.08 (d, J = 8.7 Hz, 2H), 6.77 (d, J = 8.7 Hz,
2H), 6.73 (d, J = 6.5 Hz, 1H), 5.64 (br s, 1H), 5.28 (d, J = 6.6 Hz,
1H), 3.76 (dd, J = 8.8, 5.8 Hz, 1H), 3.70−3.54 (m, 2H), 3.35−3.08
(m, 2H), 2.03−1.77 (m, 1H), 1.53−1.11 (m, 7H), 1.05 (t, J = 7.3 Hz,
3H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.5, 170.2, 159.0, 141.2, 130.0, 128.8, 128.1,
127.5, 127.1, 114.7, 73.2, 56.4, 46.7, 35.7, 34.6, 32.9, 20.0, 18.4, 17.0,
14.5, 14.3; HRMS (ESI) m/z: calcd for C25H34N2O3 [M + H]+,
411.2642; m/z: found, 411.2639.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}(propylcarbamoyl)-
methyl]-2-phenylpropanamide (33). The procedure for the syn-
thesis of 31 was followed starting with 29a and propylamine
hydrochloride to give 33 (39% yield) as a white solid. 1H NMR
(300 MHz, CDCl3): δ 7.39−7.17 (m, 5H), 7.06 (d, J = 9.0 Hz, 2H),
6.98 (d, J = 6.0 Hz, 1H), 6.70 (d, J = 9.0 Hz, 2H), 6.68−6.55 (m,
1H), 5.63 (d, J = 9.0 Hz, 1H), 3.78−3.55 (m, 3H), 3.23−3.03 (m,
2H), 1.98−1.81 (m, 1H), 1.55−1.10 (m, 6H), 1.48 (d, J = 9.0 Hz,
3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H), 0.79 (t, J = 7.5
Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 170.3, 159.0, 141.2,
130.0, 128.7, 128.0, 127.5, 127.1, 114.6, 73.2, 56.4, 46.7, 41.4, 35.7,
32.8, 22.6, 20.0, 18.4, 16.9, 14.2, 11.2; HRMS (ESI) m/z: calcd for
C26H36N2O3 [M + H]+, 425.2799; m/z: found, 425.2798.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}[(propan-2-yl)-
carbamoyl]methyl]-2-phenylpropanamide (34). The procedure for
the synthesis of 31 was followed starting with 29a and isopropylamine
to give 34 (41% yield) as a white solid. 1H NMR (300 MHz, CDCl3):
δ 7.38−7.16 (m, 5H), 7.03 (d, J = 9.0 Hz, 2H), 6.94 (d, J = 9.0 Hz,
1H), 6.68 (d, J = 9.0 Hz, 2H), 6.39 (d, J = 9.0 Hz, 1H), 5.49 (d, J =
6.0 Hz, 1H), 4.07−3.90 (m, 1H), 3.80−3.57 (m, 3H), 1.98−1.81 (m,
1H), 1.52−1.14 (m, 4H), 1.48 (d, J = 9.0 Hz, 3H), 1.12 (d, J = 6.0
Hz, 3H), 1.00 (d, J = 6.0 Hz, 3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J
= 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 169.4, 158.9,
141.2, 130.0, 128.7, 128.0, 127.5, 127.1, 114.6, 73.2, 56.3, 46.7, 41.7,
35.7, 32.9, 22.5, 22.3, 20.0, 18.5, 16.9, 14.2; HRMS (ESI) m/z: calcd
for C26H36N2O3 [M + H]+, 425.2799; m/z: found, 425.2804.
(2S)-N-((1R)-2-(tert-Butylamino)-1-(4-((2-methylpentyl)oxy)-
phenyl)-2-oxoethyl)-2-phenylpropanamide (35). To a solution of
29a (50 mg, 0.13 mmol) in THF (2 mL) were added 2-chloro-4,6-
dimethoxy-1,3,5-triazine (22.9 mg, 0.13 mmol) and N-methylmor-
pholine (15 μL, 13.5 mmol). The reaction that resulted was stirred at
room temperature. After 1 h, tert-butylamine (21 μL, 0.2 mmol) was
added to the above cloudy solution, and the reaction that resulted was
stirred overnight at room temperature. The solvent was evaporated,
and the residue was subjected to column chromatography on silica gel
using 0−50% EtOAc in hexanes to furnish 35 (28 mg, 49% yield) as a
white solid. 1H NMR (300 MHz, CDCl3): δ 7.35−7.13 (m, 5H), 7.08
(d, J = 8.7 Hz, 2H), 6.77 (d, J = 8.7 Hz, 2H), 6.70 (d, J = 6.6 Hz, 1H),
5.30 (br s, 1H), 5.19 (d, J = 6.7 Hz, 1H), 3.82−3.71 (m, 1H), 3.71−
3.50 (m, 2H), 2.05−1.72 (m, 1H), 1.46 (d, J = 7.1 Hz, 3H), 1.44−
1.13 (m, 13H), 1.00 (d, J = 6.7 Hz, 3H), 0.92 (t, J = 7.1 Hz, 3H). 13C
NMR (75 MHz, CDCl3): δ 173.2, 169.2, 159.1, 141.4, 130.3, 128.7,
128.2, 127.5, 127.0, 114.8, 73.2, 56.9, 51.7, 46.8, 35.8, 32.9, 28.6, 20.0,
18.5, 17.0, 14.3; HRMS (ESI) m/z: calcd for C27H38N2O3 [M + H]+,
439.2955; m/z: found, 439.2957.
(2S)-N-[(R)-[(Butan-2-yl)carbamoyl]({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (36). The procedure for the
synthesis of 31 was followed starting with 29a and butan-2-amine to
give 36 (42% yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ
7.36−7.16 (m, 5H), 7.07 (d, J = 9.0 Hz, 2H), 6.86 (d, J = 9.0 Hz,
1H), 6.72 (d, J = 9.0 Hz, 2H), 5.94−5.83 (m, 1H), 5.40 (d, J = 6.0
Hz, 1H), 3.90−3.55 (m, 4H), 1.99−1.83 (m, 1H), 1.53−1.12 (m,
6H), 1.48 (d, J = 6.0 Hz, 3H), 1.09 (d, J = 6.0 Hz, 3H), 0.99 (d, J =
6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H), 0.84 (t, J = 7.5 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 173.3, 169.6, 159.0, 141.2, 130.2, 128.8,
128.1, 127.5, 127.1, 114.7, 73.2, 56.6, 47.0, 46.8, 35.7, 32.9, 29.4, 20.4,
20.0, 18.5, 17.0, 14.3, 10.0; HRMS (ESI) m/z: calcd for C27H38N2O3
[M + H]+, 439.2955; m/z: found, 439.2952.
(2S)-N-((1R)-2-((Cyclopropylmethyl)amino)-1-(4-((2-
methylpentyl)oxy)phenyl)-2-oxoethyl)-2-phenylpropanamide (39).
The procedure for the synthesis of 31 was followed starting with 29a
and cyclopropylmethylamine hydrochloride to give 39 (49% yield) as
1
a white solid. H NMR (300 MHz, CDCl3): δ 7.35−7.18 (m, 5H),
7.07 (d, J = 8.7 Hz, 2H), 6.93 (d, J = 7.2 Hz, 1H), 6.70 (d, J = 8.7 Hz,
2H), 6.57 (t, J = 5.4 Hz, 1H), 5.53 (d, J = 7.2 Hz, 1H), 3.82−3.52 (m,
3H), 3.15−2.92 (m, 2H), 2.04−1.78 (m, 1H), 1.48 (d, J = 7.1 Hz,
3H), 1.45−1.11 (m, 4H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz,
3H), 0.88−0.77 (m, 1H), 0.47−0.35 (m, 2H), 0.15−0.05 (m, 2H);
13C NMR (75 MHz, CDCl3): δ 173.4, 170.3, 159.1, 141.3, 130.0,
128.8, 128.1, 127.5, 127.1, 114.7, 73.2, 56.4, 46.8, 44.3, 35.7, 32.9,
20.0, 18.5, 17.0, 14.3, 10.5, 3.3, 3.2; HRMS (ESI) m/z: calcd for
C27H36N2O3 [M + H]+, 437.2799; m/z: found, 437.2793.
(2S)-N-[(R)-(Cyclobutylcarbamoyl)({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (40). The procedure for the
synthesis of 31 was followed starting with 29a and cyclobutylamine to
give 40 (35% yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ
7.36−7.17 (m, 5H), 7.04 (d, J = 9.0 Hz, 2H), 6.86 (d, J = 6.0 Hz,
1H), 6.70 (d, J = 9.0 Hz, 2H), 6.59 (d, J = 9.0 Hz, 1H), 5.45 (d, J =
6.0 Hz, 1H), 4.36−4.20 (m, 1H), 3.80−3.56 (m, 3H), 2.35−2.13 (m,
2H), 1.97−1.57 (m, 5H), 1.54−1.10 (m, 4H), 1.49 (d, J = 6.0 Hz,
3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.4, 169.3, 159.0, 141.2, 129.9, 128.8, 128.1,
127.5, 127.1, 114.7, 73.2, 58.3, 46.8, 45.0, 35.7, 32.9, 30.8, 30.7, 20.0,
18.4, 17.0, 15.0, 14.3; HRMS (ESI) m/z: calcd for C27H36N2O3 [M +
H]+, 437.2799; m/z: found, 437.2806.
(2S)-N-((1R)-2-((1-Methylcyclobutyl)amino)-1-(4-((2-
methylpentyl)oxy)phenyl)-2-oxoethyl)-2-phenylpropanamide (41).
The procedure for the synthesis of 31 was followed starting with 29a
and 1-methylcyclobutylamine to give 41 (48% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.35−7.13 (m, 5H), 7.07 (d, J = 8.7
Hz, 2H), 6.75 (d, J = 8.7 Hz, 2H), 5.89 (s, 1H), 5.29 (d, J = 6.8 Hz,
1H), 3.76 (dd, J = 8.9, 5.8 Hz, 1H), 3.71−3.54 (m, 2H), 2.26−2.03
(m, 2H), 2.03−1.85 (m, 3H), 1.83−1.67 (m, 2H), 1.54−1.10 (m,
10H), 1.00 (d, J = 6.7 Hz, 3H), 0.92 (t, J = 7.0 Hz, 3H); 13C NMR
(75 MHz, CDCl3): δ 173.2, 168.9, 159.1, 141.3, 130.2, 128.8, 128.2,
127.5, 127.1, 114.8, 73.2, 56.6, 54.5, 46.8, 35.7, 34.4, 34.3, 32.9, 25.0,
20.0, 18.5, 17.0, 14.5, 14.3; HRMS (ESI) m/z: calcd for C28H38N2O3
[M + H]+, 451.2955; m/z: found, 451.2950.
(2S)-N-[(R)-(Cyclopentylcarbamoyl)({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (42). The procedure for the
synthesis of 31 was followed starting with 29a and cyclopentylamine
to give 42 (33% yield) as a white solid. 1H NMR (300 MHz, CDCl3):
N
https://dx.doi.org/10.1021/acs.jmedchem.0c01581
J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
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Article
δ 7.38−7.15 (m, 5H), 7.06 (d, J = 8.6 Hz, 2H), 6.87−6.64 (m, 3H),
5.90 (d, J = 7.3 Hz, 1H), 5.35 (d, J = 6.9 Hz, 1H), 4.28−4.02 (m,
1H), 3.75 (dd, J = 8.9, 5.8 Hz, 1H), 3.70−3.55 (m, 2H), 2.04−1.76
(m, 3H), 1.66−1.28 (m, 11H), 1.27−1.10 (m, 2H), 0.99 (d, J = 6.7
Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.3, 169.7, 159.1, 141.2, 130.0, 128.8, 128.1, 127.5, 127.1, 114.8,
73.2, 56.5, 51.5, 46.8, 35.7, 32.9, 32.8, 32.8, 23.7, 23.6, 20.0, 18.4,
17.0, 14.3; HRMS (ESI) m/z: calcd for C28H38N2O3 [M + H]+,
451.2955; m/z: found, 451.2952.
(2S)-N-[(R)-(Cyclohexylcarbamoyl)({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (43). The procedure for the
synthesis of 31 was followed starting with 29a and cyclohexylamine to
give 43 (54% yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ
7.39−7.15 (m, 5H), 7.06 (d, J = 8.7 Hz, 2H), 6.85−6.64 (m, 3H),
5.75 (d, J = 7.6 Hz, 1H), 5.33 (d, J = 6.9 Hz, 1H), 3.83−3.53 (m,
4H), 2.01−1.77 (m, 2H), 1.76−1.51 (m, 5H), 1.48 (d, J = 7.1 Hz,
3H), 1.46−1.03 (m, 8H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.3, 169.2, 159.1, 141.2,
130.1, 128.8, 128.2, 127.5, 127.1, 114.8, 73.2, 56.6, 48.6, 46.9, 35.7,
32.9, 32.8, 32.6, 25.4, 24.7, 24.6, 20.0, 18.4, 17.0, 14.3; HRMS (ESI)
m/z: calcd for C29H40N2O3 [M + H]+, 465.3122; m/z: found,
465.3111.
Methyl 2-[(2R)-2-{4-[(2-Methylpentyl)oxy]phenyl}-2-[(2S)-2-
phenylpropanamido]acetamido]acetate (44). The procedure for
the synthesis of 31 was followed starting with 29a and methyl 2-
aminoacetate hydrochloride to give 44 (46% yield) as a white solid.
1H NMR (300 MHz, CDCl3): δ 7.35−7.16 (m, 5H), 7.10 (d, J = 9.0
Hz, 2H), 6.88 (t, J = 4.5 Hz, 1H), 6.82−6.67 (m, 3H), 5.54 (d, J = 6.0
Hz, 1H), 3.93 (t, J = 6.0 Hz, 2H), 3.79−3.58 (m, 6H), 1.97−1.85 (m,
1H), 1.54−1.13 (m, 4H), 1.47 (d, J = 9.0 Hz, 3H), 0.99 (d, J = 6.0
Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.5, 170.6, 169.8, 159.2, 141.1, 129.3, 128.8, 128.2, 127.5, 127.1,
114.7, 73.2, 56.4, 52.3, 46.7, 41.3, 35.7, 32.8, 20.0, 18.4, 16.9, 14.3;
HRMS (ESI) m/z: calcd for C26H34N2O5 [M + H]+, 455.2540; m/z:
found, 455.2541.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}({[(oxolan-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (47). The pro-
cedure for the synthesis of 31 was followed starting with 29a and
1
tetrahydrofurfurylamine to give 47 (88% yield) as a waxy solid. H
NMR (300 MHz, CDCl3): δ 7.35−7.18 (m, 5H), 7.08 (d, J = 8.6 Hz,
2H), 6.82−6.66 (m, 3H), 6.19−6.03 (m, 1H), 5.35 (t, J = 7.2 Hz,
1H), 3.95−3.49 (m, 6H), 3.50−3.32 (m, 1H), 3.32−3.06 (m, 1H),
2.01−1.64 (m, 3H), 1.64−1.08 (m, 8H), 0.99 (d, J = 6.7 Hz, 3H),
0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.3, 173.2,
170.4, 170.3, 159.2, 159.2, 141.3, 141.2, 130.2, 129.8, 128.8, 128.2,
128.1, 127.6, 127.1, 114.8, 77.3, 73.3, 73.2, 68.1, 68.1, 56.8, 56.7, 46.8,
43.2, 42.9, 35.7, 32.9, 28.5, 28.2, 25.8, 20.0, 18.4, 17.0, 14.3; HRMS
(ESI) m/z: calcd for C28H38N2O4 [M + H]+, 467.2904; m/z: found,
467.2905.
tert-Butyl N-{2-[(2R)-2-{4-[(2-Methylpentyl)oxy]phenyl}-2-[(2S)-2-
phenylpropanamido]acetamido]ethyl}carbamate (48). The proce-
dure for the synthesis of 31 was followed starting with 29a and N-
Boc-ethylenediamine hydrochloride to give 48 (55% yield) as a
1
colorless oil. H NMR (300 MHz, CDCl3): δ 7.36−7.17 (m, 5H),
7.06 (d, J = 8.7 Hz, 2H), 6.84−6.65 (m, 4H), 5.35 (d, J = 6.7 Hz,
1H), 4.92 (d, J = 5.5 Hz, 1H), 3.74 (dd, J = 8.9, 5.8 Hz, 1H), 3.69−
3.55 (m, 2H), 3.40−3.04 (m, 4H), 2.05−1.73 (m, 1H), 1.47 (d, J =
7.1 Hz, 3H), 1.45−1.11 (m, 13H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J
= 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.5, 170.8, 159.2,
141.2, 129.6, 128.8, 128.1, 127.5, 127.2, 114.8, 79.7, 73.2, 56.8, 46.8,
40.8, 40.0, 35.7, 32.9, 28.3, 20.0, 18.4, 17.0, 14.3; HRMS (ESI) m/z:
calcd for C30H43N3O5 [M + H]+, 526.3275; m/z: found, 526.3267.
(2S)-N-[(R)-[(2-Aminoethyl)carbamoyl]({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide Hydrochloride (49). To a
solution of 48 (14.1 mg, 0.03 mmol) in DCM, HCl (4 M in dioxane,
67 μL, 0.27 mmol) was added at 0 °C. The reaction that resulted was
warmed to room temperature and stirred until completion. After the
completion of the reaction, the solvent was evaporated, and the
residue was redissolved in DCM and evaporated under reduced
pressure (three times). The residue was dried in vacuo to furnish 49 as
1
(2S)-N-[(R)-[(2-Hydroxyethyl)carbamoyl]({4-[(2-methylpentyl)-
oxy]phenyl})methyl]-2-phenylpropanamide (45). To a suspension
of NaBH4 (11 mg, 0.29 mmol) in EtOH (2 mL) at 0 °C under
nitrogen was added LiCl (12 mg, 0.29 mmol). After stirring at 0 °C
for 10 min, a solution of 44 (50 mg, 0.11 mmol) in THF (2 mL) was
added. The reaction mixture was stirred at room temperature for 3 h
and quenched with saturated NH4Cl solution (5 mL), followed by
addition of H2O (10 mL). The mixture was extracted with EtOAc (3
× 20 mL). The combined organic layers were washed with brine (20
mL), dried (Na2SO4), and concentrated under reduced pressure. The
residue was subjected to column chromatography on silica gel using
20−70% EtOAc in hexanes to afford 45 (38 mg, 81% yield) as a white
solid. 1H NMR (300 MHz, CDCl3): δ 7.28−7.08 (m, 5H), 7.07−6.88
(m, 3H), 6.76 (d, J = 6.0 Hz, 1H), 6.65 (d, J = 9.0 Hz, 2H), 5.39 (d, J
= 6.0 Hz, 1H), 3.71−3.44 (m, 4H), 3.44−3.26 (m, 1H), 3.20−3.04
(m, 1H), 1.92−1.74 (m, 1H), 1.46−1.01 (m, 6H), 1.40 (d, J = 9.0 Hz,
3H), 0.92 (d, J = 9.0 Hz, 3H), 0.84 (t, J = 7.5 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 174.1, 171.2, 159.2, 141.0, 129.2, 128.8, 128.1,
127.5, 127.2, 114.8, 73.2, 61.6, 56.7, 46.7, 42.5, 35.7, 32.9, 20.0, 18.4,
17.0, 14.3; HRMS (ESI) m/z: calcd for C25H34N2O4 [M + H]+,
427.2591; m/z: found, 427.2589.
hydrochloride salt (9.7 mg, 78%) as a thick colorless oil. H NMR
(300 MHz, CD3OD): δ 7.36−7.15 (m, 7H), 6.86 (d, J = 8.7 Hz, 2H),
5.11 (s, 1H), 3.84−3.53 (m, 4H), 3.37−3.22 (m, 1H), 3.19−2.94 (m,
2H), 2.00−1.76 (m, 1H), 1.57−1.14 (m, 7H), 1.00 (d, J = 6.7 Hz,
3H), 0.92 (t, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CD3OD): δ 177.3,
174.4, 161.0, 142.8, 130.2, 129.5, 129.1, 128.5, 128.0, 115.8, 74.3,
59.4, 48.4, 41.0, 38.3, 36.9, 34.1, 21.1, 18.9, 17.3, 14.6; HRMS (ESI)
free base m/z: calcd for C25H35N3O3 [M + H]+, 426.2751; m/z:
found, 426.2750.
tert-Butyl N-Methyl-N-{2-[(2R)-2-{4-[(2-methylpentyl)oxy]-
phenyl}-2-[(2S)-2-phenylpropanamido]acetamido]ethyl}-
carbamate (50). The procedure for the synthesis of 31 was followed
starting with 29a and N-Boc-N-methylethylenediamine to give 50
(32% yield) as a colorless oil. 1H NMR (300 MHz, CDCl3): δ 7.39−
7.15 (m, 5H), 7.06 (d, J = 8.6 Hz, 2H), 6.97 (br s, 1H), 6.84 (d, J =
6.7 Hz, 1H), 6.72 (d, J = 8.6 Hz, 2H), 5.62−4.88 (m, 1H), 3.80−3.57
(m, 3H), 3.27 (br s, 4H), 2.74 (br s, 3H), 2.01−1.78 (m, 1H), 1.46
(d, J = 7.2 Hz, 3H), 1.44−1.10 (m, 13H), 0.99 (d, J = 6.7 Hz, 3H),
0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.2, 170.6,
159.1, 156.8, 141.3, 129.9, 128.8, 128.1, 127.5, 127.1, 114.7, 79.9,
73.2, 56.6, 47.6, 46.7, 39.1, 35.7, 35.0, 32.9, 28.4, 20.0, 18.4, 17.0,
14.3; HRMS (ESI) m/z: calcd for C31H45N3O5 [M + H]+, 540.3432;
m/z: found, 540.3424.
(2S)-N-[(R)-[(2-Methoxyethyl)carbamoyl]({4-[(2-methylpentyl)-
oxy]phenyl})methyl]-2-phenylpropanamide (46). The procedure for
the synthesis of 31 was followed starting with 29a and 2-
(2S)-N-[(R)-{[2-(Methylamino)ethyl]carbamoyl}({4-[(2-
methylpentyl)oxy]phenyl})methyl]-2-phenylpropanamide Hydro-
chloride (51). The procedure for the synthesis of 49 was followed
starting with 50 to give 51 as hydrochloride salt (94%) as a thick
1
methoxyethan-1-amine to give 46 (42% yield) as a white solid. H
NMR (300 MHz, CDCl3): δ 7.29−7.09 (m, 5H), 7.00 (d, J = 9.0 Hz,
2H), 6.74 (d, J = 6.0 Hz, 1H), 6.66 (d, J = 9.0 Hz, 2H), 6.37 (br s,
1H), 5.35 (d, J = 6.0 Hz, 1H), 3.73−3.62 (m, 1H), 3.61−3.50 (m,
2H), 3.42−3.18 (m, 4H), 3.17 (s, 3H), 1.91−1.74 (m, 1H), 1.49−
1.05 (m, 4H), 1.40 (d, J = 6.0 Hz, 3H), 0.91 (d, J = 6.0 Hz, 3H), 0.84
(t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.3, 170.3,
159.1, 141.2, 129.8, 128.7, 128.1, 127.5, 127.1, 114.7, 73.2, 70.8, 58.7,
56.5, 46.7, 39.4, 35.7, 32.8, 20.0, 18.4, 16.9, 14.2; HRMS (ESI) m/z:
calcd for C26H36N2O4 [M + H]+, 441.2748; m/z: found, 441.2743.
1
colorless oil. H NMR (300 MHz, CD3OD): δ 8.62−8.38 (m, 1H),
7.37−7.12 (m, 7H), 6.85 (d, J = 8.7 Hz, 2H), 5.17−5.06 (m, 1H),
3.89−3.61 (m, 4H), 3.40−3.32 (m, 1H), 3.26−3.03 (m, 2H), 2.73 (s,
3H), 2.05−1.75 (m, 1H), 1.57−1.13 (m, 7H), 0.99 (d, J = 6.7 Hz,
3H), 0.92 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CD3OD): δ 179.9,
176.9, 163.6, 145.3, 132.7, 132.1, 131.6, 131.0, 130.5, 118.3, 76.9,
62.0, 53.0, 49.3, 39.6, 39.4, 36.6, 36.4, 23.6, 21.4, 19.8, 17.2; HRMS
O
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J. Med. Chem. XXXX, XXX, XXX−XXX

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Article
(ESI) free base m/z: calcd for C26H37N3O3 [M + H]+, 440.2908; m/z:
found, 440.2923.
(ESI) m/z: calcd for C27H37N3O3 [M + H]+, 452.2908; m/z: found,
452.2908.
(2S)-N-[(R)-{[2-(Dimethylamino)ethyl]carbamoyl}({4-[(2-
methylpentyl)oxy]phenyl})methyl]-2-phenylpropanamide (52). A
solution of 29a (77 mg, 0.20 mmol) in DCM (5 mL) was cooled
to 0 °C. To that above solution oxalyl chloride (0.4 mmol, 34 μL) and
DMF (catalytic) were added sequentially. The reaction that resulted
was stirred at room temperature for 2 h. At that time, the solvent was
removed, and the residue was dried in vacuo for 1 h. The yellow color
residue was redissolved in DCM (5 mL) and DIPEA (350 μL, 2.0
mmol), and N,N-dimethylethylenediamine (88.5 mg, 1.0 mmol) was
added. The reaction that resulted was stirred at room temperature for
14 h. The solvent was evaporated under reduced pressure. The
residue was subjected to column chromatography on silica gel using
0−50% CMA80 in DCM to furnish the amide 52 (37 mg, 41%) as a
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}(phenylcarbamoyl)-
methyl]-2-phenylpropanamide (55). The procedure for the syn-
thesis of 35 was followed starting with 29a and aniline to give 55
(65% yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ 8.22 (br
s, 1H), 7.41 (d, J = 7.9 Hz, 2H), 7.37−7.19 (m, 7H), 7.15 (d, J = 8.7
Hz, 2H), 7.06 (t, J = 7.4 Hz, 1H), 6.81 (d, J = 7.2 Hz, 1H), 6.75 (d, J
= 8.7 Hz, 2H), 5.67 (d, J = 7.0 Hz, 1H), 3.83−3.52 (m, 3H), 2.01−
1.78 (m, 1H), 1.51 (d, J = 7.1 Hz, 3H), 1.47−1.07 (m, 4H), 0.99 (d, J
= 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 173.9, 168.5, 159.4, 141.0, 137.4, 129.0, 128.9, 128.3, 127.6, 127.3,
124.5, 120.0, 115.0, 73.3, 57.3, 46.9, 35.7, 32.8, 20.0, 18.4, 17.0, 14.3;
HRMS (ESI) m/z: calcd for C29H34N2O3 [M + H]+, 459.2642; m/z:
found, 459.2642.
1
colorless oil. H NMR (300 MHz, CDCl3): δ 7.40−7.08 (m, 6H),
(2S)-N-[(R)-(Benzylcarbamoyl)({4-[(2-methylpentyl)oxy]phenyl})-
methyl]-2-phenylpropanamide (56). The procedure for the syn-
thesis of 31 was followed starting with 29a and benzylamine to give
6.95 (d, J = 6.7 Hz, 1H), 6.79 (dd, J = 18.1, 8.7 Hz, 2H), 6.69 (s, 1H),
5.33 (d, J = 6.7 Hz, 1H), 3.82−3.52 (m, 3H), 3.47−3.28 (m, 1H),
3.28−2.97 (m, 1H), 2.56−2.32 (m, 2H), 2.32−2.16 (m, 6H), 2.03−
1.78 (m, 1H), 1.62−1.09 (m, 8H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J
= 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.1, 170.0, 158.8,
140.7, 129.5, 128.3, 128.0, 127.3, 126.7, 114.4, 72.8, 57.0, 56.4, 46.5,
44.2, 36.0, 35.3, 32.4, 19.6, 18.1, 16.5, 13.8; HRMS (ESI) m/z: calcd
for C27H39N3O3 [M + H]+, 454.3064; m/z: found, 454.3059.
1
56 (45% yield) as a white solid. H NMR (300 MHz, CDCl3): δ
7.37−7.15 (m, 8H), 7.09 (d, J = 8.8 Hz, 4H), 6.80−6.68 (m, 3H),
6.12 (t, J = 5.6 Hz, 1H), 5.39 (d, J = 6.7 Hz, 1H), 4.51−4.13 (m, 2H),
3.88−3.44 (m, 3H), 2.06−1.63 (m, 1H), 1.60−1.08 (m, 7H), 0.99 (d,
J = 6.7 Hz, 3H), 0.92 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 173.4, 170.2, 159.3, 141.2, 137.6, 129.7, 128.8, 128.6,
128.3, 127.5, 127.4, 127.1, 114.9, 73.3, 56.8, 46.8, 43.7, 35.7, 32.9,
20.0, 18.4, 17.0, 14.3; HRMS (ESI) m/z: calcd for C30H36N2O3 [M +
H]+, 473.2799; m/z: found, 473.2797.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}({[(pyrrolidin-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (53). The pro-
cedure for the synthesis of 31 was followed starting with 29a and 1-
Boc-2-(aminomethyl)pyrrolidine to give N-Boc-53 (68% yield). The
N-Boc compound (100.0 mg, 0.18 mmol) was dissolved in DCM (2
mL) and cooled to 0 °C. To that above solution, HCl (4 M in
dioxane, 440 μL, 1.77 mmol) was added, and the reaction that
resulted was stirred at room temperature until complete conversion.
After that, the reaction was diluted with DCM (10 mL) and basified
with saturated NaHCO3 (10 mL). The organic layer was separated,
and the aqueous layer was extracted with additional DCM (2 × 10
mL). The combined organic layers were washed with brine, dried
(K2CO3), and evaporated to furnish the free base 53 (72 mg, 87%) as
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}({[(pyridin-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (57). The pro-
cedure for the synthesis of 31 was followed starting with 29a and 2-
1
picolylamine to give 57 (75% yield) as a white solid. H NMR (300
MHz, CDCl3): δ 8.47 (d, J = 4.3 Hz, 1H), 7.61 (td, J = 7.7, 1.8 Hz,
1H), 7.36−7.19 (m, 5H), 7.19−7.06 (m, 4H), 6.93 (d, J = 4.4 Hz,
1H), 6.78 (d, J = 8.7 Hz, 2H), 6.71 (d, J = 6.6 Hz, 1H), 5.43 (d, J =
6.6 Hz, 1H), 4.63−4.36 (m, 2H), 3.79−3.71 (m, 1H), 3.70−3.48 (m,
2H), 1.94−1.82 (m, 1H), 1.47 (d, J = 7.1 Hz, 3H), 1.45−1.09 (m,
4H), 0.99 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.3, 170.2, 159.2, 155.7, 149.0, 141.2, 136.7,
129.8, 128.8, 128.2, 127.6, 127.1, 122.4, 121.7, 114.9, 73.2, 56.8, 46.9,
44.5, 35.7, 32.9, 20.0, 18.4, 17.0, 14.3; HRMS (ESI) m/z: calcd for
C29H35N3O3 [M + H]+, 474.2751; m/z: found, 474.2749.
1
a colorless oil. H NMR (300 MHz, CDCl3): δ 7.35−7.18 (m, 5H),
7.08 (d, J = 8.6 Hz, 2H), 6.96 (dd, J = 6.8, 2.3 Hz, 1H), 6.90−6.81
(m, 1H), 6.72 (d, J = 8.6 Hz, 2H), 5.42 (dd, J = 6.9, 2.0 Hz, 1H),
3.82−3.53 (m, 3H), 3.37−2.90 (m, 3H), 2.90−2.57 (m, 2H), 2.32 (br
s, 1H), 2.07−1.82 (m, 1H), 1.79−1.06 (m, 11H), 0.99 (d, J = 6.7 Hz,
3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4,
173.4, 170.5, 170.4, 159.1, 141.3, 130.1, 130.1, 128.7, 128.1, 127.5,
127.1, 114.7, 73.2, 57.4, 57.4, 56.6, 46.7, 46.4, 46.3, 44.0, 43.8, 35.7,
32.9, 29.0, 28.8, 25.6, 25.6, 20.0, 18.4, 17.0, 14.3; HRMS (ESI) m/z:
calcd for C28H39N3O3 [M + H]+, 466.3064; m/z: found, 464.3077.
(2S)-N-[(R)-{[(Azetidin-3-yl)methyl]carbamoyl}({4-[(2-
methylpentyl)oxy]phenyl})methyl]-2-phenylpropanamide (54).
The procedure for the synthesis of 53 was followed starting with
29a and 1-Boc-3-(aminomethyl)azetidine to furnish N-Boc-54 (88%
yield) as a colorless oil. The amide, N-Boc-54 (75 mg, 0.13 mmol)
was dissolved in DCM (6 mL) and cooled to 0 °C. To that above
solution, TFA (0.4 mL) was added dropwise with a syringe, and the
reaction, which resulted, was stirred at 0 °C for 30 min. At that time,
the reaction was diluted with DCM (10 mL) and basified with
saturated aqueous NaHCO3 (15 mL). The organic layer was
separated, and the aqueous layer was extracted with additional
DCM (2 × 5 mL). The combined organic layers were dried with
K2CO3, and the residue was subjected to column chromatography on
silica gel using 0−40% CMA80/DCM to furnish 54 (38 mg, 62%) as
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}({[(pyridin-3-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (58). The pro-
cedure for the synthesis of 31 was followed starting with 29a and 3-
1
picolylamine to give 58 (71% yield) as a white solid. H NMR (300
MHz, CDCl3): δ 8.46 (dd, J = 4.8, 1.5 Hz, 1H), 8.39 (d, J = 1.8 Hz,
1H), 7.45−7.38 (m, 1H), 7.34−7.22 (m, 3H), 7.22−7.10 (m, 3H),
7.05 (d, J = 8.7 Hz, 2H), 7.02−6.94 (m, 1H), 6.79−6.68 (m, 3H),
5.54 (d, J = 7.0 Hz, 1H), 4.48−4.19 (m, 2H), 3.74 (dd, J = 8.9, 5.8
Hz, 1H), 3.69−3.53 (m, 2H), 1.98−1.84 (m, 1H), 1.58−1.07 (m,
7H), 0.99 (d, J = 6.7 Hz, 3H), 0.92 (t, J = 7.0 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.6, 170.6, 159.3, 148.9, 148.8, 141.0, 135.1,
133.5, 129.3, 128.8, 128.1, 127.5, 127.2, 123.4, 114.8, 73.3, 56.6, 46.8,
41.1, 35.7, 32.9, 20.0, 18.3, 17.0, 14.3; HRMS (ESI) m/z: calcd for
C29H35N3O3 [M + H]+, 474.2751; m/z: found, 474.2744.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}({[(pyridin-4-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (59). The pro-
cedure for the synthesis of 31 was followed starting with 29a and 4-
1
picolylamine to give 59 (74% yield) as a white solid. H NMR (300
MHz, CDCl3): δ 8.43 (d, J = 5.8 Hz, 2H), 7.39−7.20 (m, 4H), 7.19−
7.13 (m, 2H), 7.08 (d, J = 8.6 Hz, 2H), 6.95 (d, J = 5.7 Hz, 2H), 6.85
(d, J = 7.1 Hz, 1H), 6.73 (d, J = 8.5 Hz, 2H), 5.66 (d, J = 7.2 Hz, 1H),
4.33 (ddd, J = 48.7, 16.1, 6.0 Hz, 2H), 3.81−3.70 (m, 1H), 3.70−3.50
(m, 2H), 2.09−1.72 (m, 1H), 1.57−1.08 (m, 7H), 1.00 (d, J = 6.7 Hz,
3H), 0.90 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.8,
170.8, 159.4, 149.9, 147.0, 140.9, 129.3, 128.9, 128.1, 127.5, 127.3,
121.9, 114.8, 73.3, 56.5, 46.7, 42.3, 35.7, 32.9, 20.0, 18.3, 17.0, 14.3;
HRMS (ESI) m/z: calcd for C29H35N3O3 [M + H]+, 474.2751; m/z:
found, 474.2750.
1
a free base. H NMR (300 MHz, CDCl3): δ 9.68−8.74 (br s, 2H),
8.53 (s, 1H), 7.40−7.08 (m, 6H), 6.95 (d, J = 6.6 Hz, 1H), 6.76 (dd, J
= 26.9, 8.7 Hz, 2H), 5.59 (d, J = 6.6 Hz, 1H), 4.22−3.82 (m, 3H),
3.77−3.47 (m, 4H), 3.27−3.04 (m, 1H), 3.03−2.84 (m, 1H), 2.72−
2.24 (m, 1H), 1.96−1.78 (m, 1H), 1.59−1.05 (m, 7H), 0.96 (d, J =
6.7 Hz, 3H), 0.90 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
174.6, 171.8, 159.3, 140.9, 128.8, 128.1, 127.5, 127.3, 114.8, 73.2,
57.0, 48.7, 46.5, 40.1, 35.7, 32.8, 32.0, 20.0, 18.2, 16.9, 14.3; HRMS
P
https://dx.doi.org/10.1021/acs.jmedchem.0c01581
J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
pubs.acs.org/jmc
Article
(2S)-N-[(R)-{[(Furan-2-yl)methyl]carbamoyl}({4-[(2-
methylpentyl)oxy]phenyl})methyl]-2-phenylpropanamide (60).
The procedure for the synthesis of 31 was followed starting with
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(1,2-oxazol-3-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (65). The pro-
cedure for the synthesis of 31 was followed starting with 29b and
isoxazol-3-ylmethanamine hydrochloride to give 65 (60% yield) as a
white solid. 1H NMR (300 MHz, CDCl3): δ 8.25 (d, J = 1.6 Hz, 1H),
7.50−7.36 (m, 1H), 7.35−7.12 (m, 5H), 7.04 (d, J = 8.7 Hz, 2H),
6.84 (d, J = 7.2 Hz, 1H), 6.69 (d, J = 8.7 Hz, 2H), 6.13 (d, J = 1.6 Hz,
1H), 5.60 (d, J = 7.2 Hz, 1H), 4.51−4.31 (m, 2H), 3.84 (d, J = 6.7
Hz, 2H), 3.64 (q, J = 7.1 Hz, 1H), 2.84−2.60 (m, 1H), 2.23−2.02 (m,
2H), 2.02−1.69 (m, 4H), 1.43 (d, J = 7.1 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.8, 170.8, 160.0, 159.2, 158.7, 141.0, 129.3,
128.8, 128.1, 127.5, 127.2, 114.8, 103.6, 72.1, 56.4, 46.7, 35.2, 34.6,
24.8, 18.5, 18.3; HRMS (ESI) m/z: calcd for C26H29N3O4 [M + H]+,
448.2231; m/z: found, 448.2229.
1
29a and furfurylamine to give 60 (75% yield) as a white solid. H
NMR (300 MHz, CDCl3): δ 7.41−7.12 (m, 6H), 7.06 (d, J = 8.6 Hz,
2H), 6.74 (d, J = 8.6 Hz, 3H), 6.46−6.15 (m, 2H), 6.09 (d, J = 3.1
Hz, 1H), 5.43 (d, J = 6.9 Hz, 1H), 4.56−4.20 (m, 2H), 3.86−3.49 (m,
3H), 1.99−1.81 (m, 1H), 1.54−1.09 (m, 7H), 0.99 (d, J = 6.7 Hz,
3H), 0.90 (t, J = 7.0, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4,
170.1, 159.2, 150.7, 142.2, 141.1, 129.5, 128.8, 128.3, 127.5, 127.2,
114.8, 110.4, 107.4, 73.2, 56.6, 46.8, 36.8, 35.7, 32.9, 20.0, 18.4, 17.0,
14.3; HRMS (ESI) m/z: calcd for C28H34N2O4 [M + H]+, 463.2591;
m/z: found, 463.2585.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(furan-2-yl)methyl]-
carbamoyl})methyl]-2-phenylpropanamide (61). The procedure for
the synthesis of 31 was followed starting with 29b and furfurylamine
to give 61 (73% yield) as a waxy solid. 1H NMR (300 MHz, CDCl3):
δ 7.44−7.12 (m, 6H), 7.04 (d, J = 8.7 Hz, 2H), 6.82 (d, J = 7.1 Hz,
1H), 6.76 (t, J = 5.6 Hz, 1H), 6.70 (d, J = 8.7 Hz, 2H), 6.25 (dd, J =
3.1, 1.9 Hz, 1H), 6.08 (d, J = 2.7 Hz, 1H), 5.54 (d, J = 7.1 Hz, 1H),
4.35 (qd, J = 15.6, 5.6 Hz, 2H), 3.85 (d, J = 6.7 Hz, 2H), 3.61 (q, J =
7.1 Hz, 1H), 2.82−2.64 (m, 1H), 2.20−2.04 (m, 2H), 2.02−1.66 (m,
4H), 1.43 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.5,
170.2, 159.1, 150.8, 142.1, 141.1, 129.7, 128.8, 128.2, 127.5, 127.2,
114.8, 110.4, 107.3, 72.1, 56.4, 46.8, 36.7, 34.6, 24.8, 18.5, 18.3;
HRMS (ESI) m/z: calcd for C27H30N2O4 [M + H]+, 447.2278; m/z:
found, 447.2277.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(1,3-thiazol-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (66). The pro-
cedure for the synthesis of 31 was followed starting with 29b and 1,3-
thiazol-2-ylmethylamine hydrochloride to give 66 (65% yield) as a
waxy solid. 1H NMR (300 MHz, CDCl3): δ 7.63 (d, J = 3.3 Hz, 1H),
7.49−7.14 (m, 6H), 7.07 (d, J = 8.7 Hz, 2H), 6.81 (d, J = 7.1 Hz,
1H), 6.72 (d, J = 8.7 Hz, 2H), 5.58 (d, J = 7.1 Hz, 1H), 4.66 (d, J =
5.9 Hz, 2H), 3.85 (d, J = 6.7 Hz, 2H), 3.62 (q, J = 7.1 Hz, 1H), 2.95−
2.50 (m, 1H), 2.23−2.03 (m, 2H), 2.03−1.64 (m, 4H), 1.43 (d, J =
7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 170.5, 167.0, 159.2,
142.4, 141.1, 129.3, 128.8, 128.3, 127.5, 127.2, 126.2, 119.5, 114.9,
72.1, 56.5, 46.7, 41.2, 34.6, 24.8, 18.5, 18.4; HRMS (ESI) m/z: calcd
for C26H29N3O3S [M + H]+, 464.2002; m/z: found, 448.2000.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(1H-imidazol-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (67). The pro-
cedure for the synthesis of 31 was followed starting with 29b and
(1H-imidazol-2-yl)methanamine hydrochloride to give 67 (53%
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(thiophen-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (62). The pro-
cedure for the synthesis of 31 was followed starting with 29b and 2-
thiophenemethylamine to give 62 (80% yield) as a white waxy solid.
1H NMR (300 MHz, CDCl3): δ 7.35−7.23 (m, 3H), 7.23−7.14 (m,
1
yield) as a waxy solid. H NMR (300 MHz, CDCl3): δ 8.35 (t, J =
5.7 Hz, 1H), 7.38−7.15 (m, 6H), 7.02 (d, J = 8.7 Hz, 2H), 6.89−6.82
(m, 3H), 6.70 (d, J = 8.7 Hz, 2H), 5.41 (d, J = 6.8 Hz, 1H), 4.42 (dd,
J = 15.3, 6.3 Hz, 1H), 4.22 (dd, J = 15.3, 5.5 Hz, 1H), 3.83 (d, J = 6.7
Hz, 2H), 3.66 (q, J = 7.1 Hz, 1H), 2.81−2.52 (m, 1H), 2.18−1.66 (m,
6H), 1.46 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 229.0,
174.1, 171.9, 159.3, 145.2, 141.1, 128.8, 128.2, 127.5, 127.2, 122.0,
114.9, 72.1, 57.0, 46.6, 37.4, 34.6, 24.8, 18.5, 18.4; HRMS (ESI) m/z:
calcd for C26H30N4O3 [M + H]+, 447.2391; m/z: found, 447.2387.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(5-methyl-1,3,4-ox-
adiazol-2-yl)methyl]carbamoyl})methyl]-2-phenylpropanamide
(68). The procedure for the synthesis of 31 was followed starting with
29b and (5-methyl-1,3,4-oxadiazol-2-yl)methanamine oxalate to give
3H), 7.07 (d, J = 8.7 Hz, 2H), 6.89 (dd, J = 5.1, 3.5 Hz, 1H), 6.86−
6.80 (m, 1H), 6.76 (d, J = 8.7 Hz, 2H), 6.70 (d, J = 6.8 Hz, 1H),
6.26−6.17 (m, 1H), 5.38 (d, J = 6.7 Hz, 1H), 4.67−4.36 (m, 2H),
3.87 (d, J = 6.7 Hz, 2H), 3.61 (q, J = 7.1 Hz, 1H), 2.88−2.52 (m,
1H), 2.20−2.04 (m, 2H), 2.03−1.73 (m, 4H), 1.45 (d, J = 7.2 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 169.9, 159.2, 141.1,
140.2, 129.5, 128.8, 128.3, 127.5, 127.2, 126.8, 125.9, 125.2, 114.9,
72.1, 56.7, 46.8, 38.6, 34.6, 24.8, 18.5, 18.4; HRMS (ESI) m/z: calcd
for C27H30N2O3S [M + H]+, 463.2050; m/z: found, 463.2046.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(1H-pyrrol-2-yl)-
methyl]carbamoyl})methyl]-2-phenylpropanamide (63). The pro-
cedure for the synthesis of 31 was followed starting with 29b and
(1H-pyrrol-2-yl)methanamine to give 63 (58% yield) as a waxy solid.
1H NMR (300 MHz, CDCl3): δ 8.87 (br s, 1H), 7.45−7.15 (m, 5H),
7.11 (t, J = 5.7 Hz, 1H), 7.01 (d, J = 8.7 Hz, 2H), 6.79−6.55 (m, 4H),
6.04 (dd, J = 5.8, 2.8 Hz, 1H), 5.97−5.92 (m, 1H), 5.45 (d, J = 7.1
Hz, 1H), 4.33 (dd, J = 15.1, 6.0 Hz, 1H), 4.21−4.08 (m, 1H), 3.84 (d,
J = 6.7 Hz, 2H), 3.60 (q, J = 7.1 Hz, 1H), 2.81−2.61 (m, 1H), 2.20−
2.04 (m, 2H), 2.00−1.73 (m, 4H), 1.44 (d, J = 7.1 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 173.8, 171.3, 159.2, 141.0, 129.3, 128.9,
128.5, 128.1, 127.5, 127.3, 118.2, 114.9, 107.7, 106.8, 72.1, 56.6, 46.7,
37.1, 34.6, 24.8, 18.5, 18.4, HRMS (ESI) m/z: calcd for C27H31N3O3
[M + H]+, 446.2438; m/z: found, 446.2437.
1
68 (55% yield) as a white solid. H NMR (300 MHz, CDCl3): δ
7.39−7.16 (m, 5H), 7.10 (d, J = 8.7 Hz, 2H), 6.78 (d, J = 8.7 Hz,
2H), 6.59 (d, J = 6.4 Hz, 2H), 5.44 (d, J = 6.7 Hz, 1H), 4.57 (ddd, J =
38.1, 16.6, 5.8 Hz, 2H), 3.87 (d, J = 6.6 Hz, 2H), 3.63 (q, J = 7.1 Hz,
1H), 2.81−2.65 (m, 1H), 2.48 (s, 3H), 2.21−2.02 (m, 2H), 2.02−
1.73 (m, 4H), 1.47 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 229.0, 173.6, 170.6, 164.4, 163.0, 159.4, 141.0, 128.9, 128.4, 127.5,
127.2, 115.0, 77.2, 72.1, 56.7, 46.8, 34.6, 34.5, 24.8, 18.5, 18.4, 10.9;
HRMS (ESI) m/z: calcd for C26H30N4O4 [M + H]+, 463.2340; m/z:
found, 463.2337.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(1H-1,2,4-triazol-3-
yl)methyl]carbamoyl})methyl]-2-phenylpropanamide (69). The
procedure for the synthesis of 31 was followed starting with 29b
and (4H-1,2,4-triazol-3-yl)methanamine hydrochloride to give 69
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl]({[(5-methyl-1,3-oxa-
zol-2-yl)methyl]carbamoyl})methyl]-2-phenylpropanamide (64).
The procedure for the synthesis of 31 was followed starting with
29b and (5-methyloxazol-2-yl)methanamine to give 64 (46% yield) as
1
(47% yield) as a white solid. H NMR (300 MHz, CD3OD): δ 8.20
(s, 1H), 7.39−7.06 (m, 7H), 6.80 (d, J = 8.7 Hz, 2H), 5.37 (s, 1H),
4.52 (dd, J = 52.1, 15.8 Hz, 2H), 3.89 (d, J = 6.6 Hz, 2H), 3.80 (q, J =
7.0 Hz, 1H), 2.85−2.58 (m, 1H), 2.19−2.03 (m, 2H), 2.03−1.75 (m,
4H), 1.46 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CD3OD): δ
176.6, 173.1, 160.7, 158.4, 148.1, 142.9, 130.3, 129.9, 129.6, 128.5,
128.0, 115.7, 73.2, 58.4, 47.0, 37.2, 36.1, 25.7, 19.4, 18.8; HRMS
(ESI) m/z: calcd for C25H29N5O3 [M + H]+, 448.2343; m/z: found,
448.2342.
1
a waxy solid. H NMR (300 MHz, CDCl3): δ 7.36−7.15 (m, 5H),
7.09 (d, J = 8.7 Hz, 2H), 6.87 (t, J = 5.4 Hz, 1H), 6.81−6.67 (m, 3H),
6.59 (d, J = 1.2 Hz, 1H), 5.50 (d, J = 7.0 Hz, 1H), 4.51 (dd, J = 16.4,
5.8 Hz, 1H), 4.32 (dd, J = 16.4, 5.1 Hz, 1H), 3.86 (d, J = 6.7 Hz, 2H),
3.62 (q, J = 7.1 Hz, 1H), 2.84−2.52 (m, 1H), 2.24 (d, J = 1.1 Hz,
3H), 2.19−2.03 (m, 2H), 2.03−1.70 (m, 4H), 1.45 (d, J = 7.1 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 170.4, 159.2, 158.8,
149.4, 141.2, 129.5, 128.8, 128.3, 127.6, 127.2, 122.7, 114.8, 72.1,
56.5, 46.8, 37.0, 34.6, 24.8, 18.5, 18.4, 10.7; HRMS (ESI) m/z: calcd
for C27H31N3O4 [M + H]+, 462.2387; m/z: found, 462.2385.
(2S)-N-[(R)-(Hydrazinecarbonyl)({4-[(2-methylpentyl)oxy]-
phenyl})methyl]-2-phenylpropanamide (70a). A mixture of 3 (596
mg, 1.5 mmol) and hydrazine hydrate (2 mL) in EtOH (10 mL) was
Q
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refluxed for 3 h. After cooling to room temperature, the mixture was
concentrated under reduced pressure. The residue was crystallized
from MeOH/hexanes to give 70a (572 mg, 96% yield) as a white
MHz, CDCl3): δ 7.43−7.18 (m, 5H), 7.06 (d, J = 8.7 Hz, 2H), 6.78
(d, J = 8.7 Hz, 2H), 6.55 (d, J = 7.7 Hz, 1H), 6.24 (d, J = 7.7 Hz, 1H),
3.87 (d, J = 6.6 Hz, 2H), 3.66 (q, J = 7.1 Hz, 1H), 2.86−2.61 (m,
1H), 2.45 (s, 3H), 2.20−2.04 (m, 2H), 2.04−1.68 (m, 4H), 1.50 (d, J
= 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.3, 165.8, 164.3,
159.5, 140.9, 128.9, 128.3, 128.2, 127.6, 127.3, 115.0, 72.1, 49.5, 46.8,
34.5, 24.8, 18.5, 18.5, 10.9; HRMS (ESI) m/z: calcd for C24H27N3O3
[M + H]+, 406.2125; m/z: found, 406.2123.
Methyl (3S)-3-Amino-3-(4-hydroxyphenyl)propanoate (76). (S)-
3-Amino-3-(4-hydroxyphenyl)propanoic acid (75) (6.0 g, 33.15
mmol) was dissolved in dry MeOH (60 mL). Acetyl chloride (5
mL) was added to that above solution slowly via a syringe. The
reaction that resulted was stirred at 65 °C for 12 h. After that, the
solvent was evaporated under reduced pressure, and the residue was
dried in vacuo to furnish the methyl ester 76 as hydrochloride salt
(8.63 g, 115% crude yield) as a foamy solid which was used for the
next transformation without purification. 1H NMR (300 MHz,
CD3OD): δ 7.35−7.24 (m, 2H), 6.84 (d, J = 8.6 Hz, 2H), 4.63 (t, J =
7.2 Hz, 1H), 3.68 (s, 3H), 3.12 (ddd, J = 16.8, 7.9, 1.6 Hz, 1H), 2.98
(dd, J = 16.8, 6.6 Hz, 1H); 13C NMR (75 MHz, CD3OD): δ 171.8,
159.8, 129.8, 127.8, 117.0, 52.8, 52.7, 39.2; MS (ESI) m/z: 196.0 [M
+ H]+.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-(4-
hydroxyphenyl)propanoate (77). To a solution of 76 (8.6 g, 37.1
mmol) in DCM (200 mL), DIPEA (38.8 mL, 0.22 mol) was added
slowly via a syringe at 0 °C. To that above solution, Boc2O (8.09 g,
37.1 mmol) was added, and the reaction which resulted was stirred at
room temperature under nitrogen for 12 h. At that time, water (100
mL) was added to the reaction and the organic layer was separated.
The aqueous layer was extracted with additional DCM (2 × 50 mL)
and the combined organic layers were washed with brine and dried
(Na2SO4). The solvent was evaporated under reduced pressure, and
the residue was crystallized with DCM/hexanes to furnish 77 (11.5 g,
78%) as an off-white solid. 1H NMR (300 MHz, CDCl3): δ 7.04 (t, J
= 9.2 Hz, 3H), 6.67 (d, J = 8.1 Hz, 2H), 5.54 (br s, 1H), 5.00 (br s,
1H), 3.61 (s, 3H), 2.96−2.60 (m, 2H), 1.43 (s, 9H); 13C NMR (75
MHz, CDCl3): δ 171.7, 155.7, 155.4, 132.4, 127.3, 115.6, 80.0, 51.8,
50.9, 40.9, 28.3; MS (ESI) m/z: 318.0 [M + Na]+.
1
solid. H NMR (300 MHz, CDCl3): δ 7.55 (s, 1H), 7.42−7.16 (m,
5H), 7.07 (d, J = 9.0 Hz, 2H), 6.76 (d, J = 9.0 Hz, 2H), 6.61 (d, J =
6.0 Hz, 1H), 5.43 (d, J = 6.0 Hz, 1H), 3.81 (s, 2H), 3.80−3.69 (m,
1H), 3.69−3.55 (m, 2H), 2.01−1.81 (m, 1H), 1.56−1.12 (m, 4H),
1.50 (d, J = 9.0 Hz, 3H), 0.99 (d, J = 6.0 Hz, 3H), 0.91 (t, J = 7.5 Hz,
3H); MS (ESI) m/z: 398.4 [M + H]+.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl](hydrazinecarbonyl)-
methyl]-2-phenylpropanamide (70b). The procedure for the
synthesis of 70a was followed starting with 11h to give 70b (90%
1
yield) as a white solid. H NMR (300 MHz, CD3OD): δ 7.33−7.19
(m, 5H), 7.16 (d, J = 8.6 Hz, 2H), 6.79 (d, J = 8.7 Hz, 2H), 5.28 (s,
1H), 3.87 (d, J = 6.6 Hz, 2H), 3.78 (q, J = 7.1 Hz, 1H), 2.85−2.63
(m, 1H), 2.19−2.02 (m, 2H), 2.02−1.77 (m, 4H), 1.44 (d, J = 7.1 Hz,
1
3H); H NMR (300 MHz, CD3OD): δ 176.5, 172.2, 160.7, 142.9,
130.4, 129.6, 129.6, 128.5, 128.0, 115.7, 73.2, 56.8, 47.0, 36.1, 25.7,
19.3, 18.8; MS (ESI) m/z: 382.0 [M + H]+.
(2S)-N-[(R)-{4-[(2-Methylpentyl)oxy]phenyl}(1,3,4-oxadiazol-2-
yl)methyl]-2-phenylpropanamide (71). A mixture of 70a (70 mg,
0.18 mmol), trimethyl orthoformate (5 mL), and PTSA (45 mg, 0.23
mmol) was heated at 80 °C for 2 h. After cooling to room
temperature, the mixture was diluted with EtOAc (50 mL), washed
with NaHCO3 (3 × 10 mL) and brine (10 mL), dried (Na2SO4), and
concentrated under reduced pressure. The residue was subjected to
column chromatography on silica gel using 0−20% CMA80 in DCM
to furnish 71 (40 mg, 56% yield) as an off-white solid. 1H NMR (300
MHz; CDCl3): δ 8.31 (s, 1H), 7.43−7.19 (m, 5H), 7.05 (d, J = 9.0
Hz, 2H), 6.79 (d, J = 9.0 Hz, 2H), 6.54 (d, J = 9.0 Hz, 1H), 6.33 (d, J
= 6.0 Hz, 1H), 3.80−3.60 (m, 3H), 1.98−1.81 (m, 1H), 1.56−1.09
(m, 4H), 1.51 (d, J = 6.0 Hz, 3H), 0.98 (d, J = 6.0 Hz, 3H), 0.91 (t, J
= 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 165.9, 159.9,
163.2, 140.8, 128.9, 128.2, 127.7, 127.6, 127.4, 115.0, 73.3, 49.5, 46.7,
35.7, 32.8, 20.0, 18.4, 16.9, 14.2; HRMS (ESI) m/z: calcd for
C24H29N3O3 [M + H]+, 408.2282; m/z: found, 408.2278.
(2S)-N-[(R)-(5-Methyl-1,3,4-oxadiazol-2-yl)({4-[(2-methylpentyl)-
oxy]phenyl})-2-phenylpropanamide (72). A mixture of 70a (100 mg,
0.25 mmol), trimethyl orthoacetate (0.065 mL, 0.5 mmol), and acetic
acid (0.1 mL) in m-xylene (5 mL) was refluxed for 6 h. After cooling
to room temperature, the mixture was diluted with EtOAc (50 mL),
washed with NaHCO3 (3 × 10 mL) and brine (10 mL), dried
(NaSO4), and concentrated under reduced pressure. The residue was
subjected to column chromatography on silica gel using 0−20%
CMA80 in DCM to provide 72 (60 mg, 57% yield) as an off-white
solid. 1H NMR (300 MHz, CDCl3): δ 7.38−7.21 (m, 5H), 7.06 (d, J
= 9.0 Hz, 2H), 6.78 (d, J = 9.0 Hz, 2H), 6.60 (d, J = 9.0 Hz, 1H), 6.25
(d, J = 6.0 Hz, 1H), 3.79−3.60 (m, 3H), 2.44 (s, 3H), 1.95−1.83 (m,
1H), 1.53−1.12 (m, 4H), 1.50 (d, J = 6.0 Hz, 3H), 0.98 (d, J = 9.0
Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.2, 165.8, 164.2, 159.5, 140.8, 128.8, 128.2, 127.5, 127.2, 114.8,
73.1, 49.4, 46.8, 35.6, 32.7, 20.0, 18.4, 16.8, 14.2, 10.8; HRMS (ESI)
m/z: calcd for C25H31N3O3 [M + H]+, 422.2438; m/z: found,
422.2440.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-{4-[(2-
methylpentyl)oxy]phenyl}propanoate (78a). The procedure for
the synthesis of 7b was followed starting with 77 and 2-
1
methylpentanol to give 78a (87% yield) as a colorless oil. H NMR
(300 MHz, CDCl3): δ 7.19 (d, J = 8.6 Hz, 2H), 6.84 (d, J = 8.7 Hz,
2H), 5.32 (br s, 1H), 5.04 (br s, 1H), 3.79 (dd, J = 9.0, 5.8 Hz, 1H),
3.69 (dd, J = 8.9, 6.7 Hz, 1H), 3.61 (s, 3H), 2.82 (qd, J = 15.3, 6.2 Hz,
2H), 2.07−1.78 (m, 1H), 1.55−1.11 (m, 13H), 1.00 (d, J = 6.7 Hz,
3H), 0.91 (t, J = 7.1 Hz, 3H); MS (ESI) m/z: 402.0 [M + Na]+.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-[4-
(cyclobutylmethoxy)phenyl]propanoate (78b). The procedure for
the synthesis of 7b was followed starting with 77 and cyclo-
1
butylmethanol to give 78b (87% yield) as a colorless oil. H NMR
(300 MHz, CDCl3): δ 7.19 (d, J = 8.6 Hz, 2H), 6.90−6.77 (m, 2H),
5.36 (s, 1H), 5.04 (d, J = 5.0 Hz, 1H), 3.90 (d, J = 6.7 Hz, 2H), 3.61
(s, 3H), 2.94−2.59 (m, 3H), 2.23−2.04 (m, 2H), 2.01−1.78 (m, 4H),
1.42 (s, 9H); 13C NMR (75 MHz, CDCl3): δ 171.4, 158.7, 155.0,
133.1, 127.2, 114.7, 79.6, 72.1, 51.7, 50.9, 40.9, 34.6, 28.3, 24.8, 18.5;
MS (ESI) m/z: 386.0 [M + Na]+.
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl](1,3,4-oxadiazol-2-yl)-
methyl]-2-phenylpropanamide (73). The procedure for the syn-
thesis of 71 was followed starting with 70b and trimethyl
orthoformate to give 73 (65% yield) as a white solid. 1H NMR
(300 MHz, CDCl3): δ 8.31 (s, 1H), 7.43−7.18 (m, 5H), 7.05 (d, J =
8.7 Hz, 2H), 6.79 (d, J = 8.7 Hz, 2H), 6.52 (d, J = 7.6 Hz, 1H), 6.33
(d, J = 7.7 Hz, 1H), 3.86 (d, J = 6.6 Hz, 2H), 3.67 (q, J = 7.1 Hz, 1H),
2.90−2.53 (m, 1H), 2.22−2.02 (m, 2H), 2.02−1.66 (m, 4H), 1.51 (d,
J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.4, 165.9, 159.7,
153.2, 140.8, 128.9, 128.2, 127.8, 127.6, 127.4, 115.1, 72.1, 49.5, 46.8,
34.5, 24.8, 18.5, 18.4; HRMS (ESI) m/z: calcd for C23H25N3O3 [M +
H]+, 392.1969; m/z: found, 392.1967.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-(4-{[(2S)-2-
methylpentyl]oxy}phenyl)propanoate (78c). The procedure for the
synthesis of 7b was followed starting with 77 and (S)-2-
1
methylpentanol to give 78c (30% yield) as a colorless oil. H NMR
(300 MHz, CDCl3): δ 7.19 (d, J = 8.6 Hz, 2H), 6.84 (d, J = 8.7 Hz,
2H), 5.35 (br s, 1H), 5.04 (br s, 1H), 3.79 (dd, J = 9.0, 5.8 Hz, 1H),
3.69 (dd, J = 8.9, 6.7 Hz, 1H), 3.61 (s, 3H), 2.82 (qd, J = 15.3, 6.2 Hz,
2H), 2.01−1.77 (m, 1H), 1.55−1.09 (m, 13H), 1.00 (d, J = 6.7 Hz,
3H), 0.91 (t, J = 7.1 Hz, 3H); MS (ESI) m/z: 402.0 [M + Na]+.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-(4-{[(2R)-2-
methylpentyl]oxy}phenyl)propanoate (78d). The procedure for
the synthesis of 11m was followed starting with 77 and (2R)-2-
methylpentyl 4-methylbenzene-1-sulfonate to give 78d (35% yield) as
(2S)-N-[(R)-[4-(Cyclobutylmethoxy)phenyl](5-methyl-1,3,4-oxa-
diazol-2-yl)methyl]-2-phenylpropanamide (74). The procedure for
the synthesis of 72 was followed starting with 70b and trimethyl
1
orthoacetate to give 74 (72% yield) as a white solid. H NMR (300
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a colorless oil. H NMR (300 MHz, CDCl3): δ 7.19 (d, J = 8.6 Hz,
mmol), Et3N (1.80 mL, 12.82 mmol), and (S)-(+)-2-phenylpropionic
acid (642 mg, 4.27 mmol) were added, and the reaction that resulted
was stirred at room temperature 5 h. After the completion of the
reaction, EtOAC (20 mL) and saturated NaHCO3 (20 mL) were
added, and the organic layer was separated. The aqueous layer was
extracted with additional EtOAc, and the combined organic layers
were washed with brine and dried (Na2SO4). The solvent was
evaporated under reduced pressure. The residue was subjected to
column chromatography on silica gel using 0−50% EtOAc in hexanes
2H), 6.84 (d, J = 8.7 Hz, 2H), 5.38 (br s, 1H), 5.03 (br s, J = 5.4 Hz,
1H), 3.78 (dd, J = 9.0, 5.8 Hz, 1H), 3.68 (dd, J = 9.0, 6.7 Hz, 1H),
3.61 (s, 3H), 2.82 (qd, J = 15.3, 6.3 Hz, 2H), 2.00−1.76 (m, 1H),
1.56−1.11 (m, 13H), 1.00 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.1 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 171.4, 158.7, 155.0, 133.1,
127.2, 114.6, 79.6, 73.2, 51.6, 50.9, 40.9, 35.7, 32.9, 28.3, 20.0, 17.0,
14.3; MS (ESI) m/z: 402.0 [M + Na]+.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-{4-[(2S)-2-
methylbutoxy]phenyl}propanoate (78e). The procedure for the
synthesis of 7b was followed starting with 77 and (S)-2-
1
to furnish 80a (1.60 g, 91%) as a colorless oil. H NMR (300 MHz,
CDCl3): δ 7.39−7.19 (m, 5H), 6.95 (d, J = 8.7 Hz, 2H), 6.74 (d, J =
8.7 Hz, 2H), 6.38 (d, J = 8.4 Hz, 1H), 5.31 (dt, J = 8.3, 5.9 Hz, 1H),
3.75 (dd, J = 8.9, 5.8 Hz, 1H), 3.69−3.57 (m, 2H), 3.55 (s, 3H), 2.77
(qd, J = 15.5, 5.9 Hz, 2H), 2.00−1.77 (m, 1H), 1.51 (d, J = 57.2 Hz,
3H), 1.48−1.09 (m, 4H), 0.98 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.2, 171.5, 158.6, 141.3,
132.3, 128.9, 127.6, 127.2, 127.0, 114.5, 73.2, 51.7, 49.0, 47.1, 40.0,
35.7, 32.9, 20.0, 18.3, 17.0, 14.3; MS (ESI) m/z: 412.0 [M + H]+.
Methyl (3S)-3-[4-(Cyclobutylmethoxy)phenyl]-3-[(2S)-2-
phenylpropanamido]propanoate (80b). The procedure for the
synthesis of 80a was followed starting with 79b to give 80b (65%
1
methylbutanol to give 78e (95% yield) as a colorless oil. H NMR
(300 MHz, CDCl3): δ 7.20 (d, J = 8.7 Hz, 2H), 6.84 (d, J = 8.7 Hz,
2H), 5.42 (br s, 1H), 5.03 (br s, 1H), 3.79 (dd, J = 9.0, 6.0 Hz, 1H),
3.70 (dd, J = 9.0, 6.6 Hz, 1H), 3.61 (s, 3H), 2.82 (qd, J = 15.3, 6.3 Hz,
2H), 1.90−1.75 (m, 1H), 1.564−1.48 (m, 1H), 1.42 (s, 9H), 1.33−
1.15 (m, 4H), 1.00 (d, J = 6.7 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 171.3, 158.7, 155.0, 133.1, 127.2, 114.6, 79.5, 72.8, 51.6, 50.9, 40.9,
34.7, 28.3, 26.1, 16.5, 11.2; MS (ESI) m/z: 388 [M + Na]+.
Methyl (3S)-3-{[(tert-Butoxy)carbonyl]amino}-3-{4-[(2R)-2-
methylbutoxy]phenyl}propanoate (78f). The procedure for the
synthesis of 11m was followed starting with 77 and (2R)-2-
methylbutyl 4-methylbenzene-1-sulfonate to give 78f as a colorless
oil. 1H NMR (300 MHz, CDCl3): δ 7.19 (d, J = 8.7 Hz, 2H), 6.85 (d,
J = 8.7 Hz, 2H), 5.34 (br s, 1H), 5.04 (br s, 1H), 3.83−3.66 (m, 2H),
3.61 (s, 3H), 2.82 (qd, J = 15.3, 6.2 Hz, 2H), 1.96−1.71 (m, 1H),
1.65−1.48 (m, 1H), 1.42 (br s, 9H), 1.33−1.16 (m, 1H), 1.00 (d, J =
6.7 Hz, 3H), 0.94 (t, J = 7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
171.4, 158.7, 155.0, 133.0, 127.3, 114.6, 79.6, 72.9, 51.7, 50.9, 40.9,
34.7, 28.3, 26.1, 16.5, 11.3; MS (ESI) m/z: 388 [M + Na]+.
Methyl (3S)-3-Amino-3-{4-[(2-methylpentyl)oxy]phenyl}-
propanoate Hydrochloride (79a). A solution of 78a (1.63 g, 4.29
mmol) in DCM (20 mL) was cooled to 0 °C. To that above solution,
HCl (4 M in dioxane, 10.74 mL, 42.95 mmol) was added via a
syringe. The reaction which resulted was stirred at room temperature
for overnight. At that time, the solvent was removed under reduced
pressure, and the residue was redissolved in DCM and evaporated
(repeated three times). The residue was dried in vacuo to furnish 79a
(1.35 g, 99%) as a foamy solid. 1H NMR (300 MHz, CDCl3): δ 8.72
(br s, 3H), 7.42 (d, J = 8.3 Hz, 2H), 6.86 (d, J = 8.1 Hz, 2H), 4.64 (br
s, 1H), 3.87−3.64 (m, 2H), 3.60 (s, 3H), 3.35−3.15 (m, 1H), 3.00
(dd, J = 16.4, 6.5 Hz, 1H), 2.00−1.82 (m, 1H), 1.55−1.09 (m, 4H),
1.00 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); MS (ESI) free base
m/z: 263.0 [M + H+ − NH3]+.
Methyl (3S)-3-Amino-3-[4-(cyclobutylmethoxy)phenyl]-
propanoate Hydrochloride (79b). The procedure for the synthesis
of 79a was followed starting with 78b to give 79b as a waxy solid. MS
(ESI) free base m/z: 247.0 [M + H+ − NH3]+. This material was used
for the next transformation without further characterization.
Methyl (3S)-3-Amino-3-(4-{[(2S)-2-methylpentyl]oxy}phenyl)-
propanoate Hydrochloride (79c). The procedure for the synthesis
of 79a was followed starting with 78c to give 79c as a waxy solid. MS
(ESI) free base m/z: 263.0 [M + H+ − NH3]+. This material was used
for the next transformation without further characterization.
Methyl (3S)-3-Amino-3-(4-{[(2R)-2-methylpentyl]oxy}phenyl)-
propanoate Hydrochloride (79d). The procedure for the synthesis
of 79a was followed starting with 78d to give 79d as a waxy solid. MS
(ESI) free base m/z: 263.0 [M + H+ − NH3]+. This material was used
for the next transformation without further characterization.
Methyl (3S)-3-Amino-3-{4-[(2S)-2-methylbutoxy]phenyl}-
propanoate Hydrochloride (79e). The procedure for the synthesis
of 79a was followed starting with 78e to give 79e as a waxy solid. MS
(ESI) free base m/z: 249.0 [M + H+ − NH3]+. This material was used
for the next transformation without further characterization.
1
yield over 2 steps) as a white solid. H NMR (300 MHz, CDCl3): δ
7.29 (dd, J = 13.5, 6.6 Hz, 5H), 6.95 (d, J = 8.7 Hz, 2H), 6.74 (d, J =
8.7 Hz, 2H), 6.50 (d, J = 8.4 Hz, 1H), 5.31 (dt, J = 8.3, 6.0 Hz, 1H),
3.85 (d, J = 6.7 Hz, 2H), 3.59 (q, J = 7.1 Hz, 1H), 3.54 (s, 3H), 2.91−
2.64 (m, 3H), 2.18−2.00 (m, 2H), 1.96−1.63 (m, 4H), 1.50 (d, J =
7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 13.2, 171.5, 158.5,
141.3, 132.4, 128.9, 127.6, 127.2, 127.0, 114.6, 72.1, 51.7, 49.0, 47.1,
40.0, 34.6, 24.8, 18.5, 18.3; MS (ESI) m/z: 396.0 [M + H]+.
Methyl (3S)-3-(4-{[(2S)-2-Methylpentyl]oxy}phenyl)-3-[(2S)-2-
phenylpropanamido]propanoate (80c). The procedure for the
synthesis of 80a was followed starting with 79c to give 80c (61%
1
yield) as a sticky solid. H NMR (300 MHz, CDCl3): δ 7.38−7.21
(m, 5H), 6.95 (d, J = 8.7 Hz, 2H), 6.73 (d, J = 8.7 Hz, 2H), 6.46 (d, J
= 8.4 Hz, 1H), 5.32 (dt, J = 8.2, 5.9 Hz, 1H), 3.74 (dd, J = 8.9, 5.8 Hz,
1H), 3.69−3.58 (m 2H), 3.55 (s, 3H), 2.78 (qd, J = 15.5, 5.9 Hz,
2H), 2.01−1.80 (m, 1H), 1.52 (d, J = 7.2 Hz, 3H), 1.49−1.02 (m,
4H), 0.98 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.1 Hz, 3H); MS (ESI) m/
z: 412.0 [M + H]+.
Methyl (3S)-3-(4-{[(2R)-2-Methylpentyl]oxy}phenyl)-3-[(2S)-2-
phenylpropanamido]propanoate (80d). The procedure for the
synthesis of 80a was followed starting with 79d to give 80d (63%
yield over two steps) as a sticky solid. 1H NMR (300 MHz, CDCl3): δ
7.40−7.15 (m, 5H), 6.95 (d, J = 8.6 Hz, 2H), 6.74 (d, J = 8.7 Hz,
2H), 6.43 (d, J = 8.4 Hz, 1H), 5.36−5.25 (m, 1H), 3.79−3.70 (m,
1H), 3.69−3.56 (m, 2H), 3.54 (s, 3H), 2.77 (qd, J = 15.5, 5.9 Hz,
2H), 1.98−1.81 (m, 1H), 1.51 (d, J = 7.2 Hz, 3H), 1.49−1.11 (m,
4H), 0.98 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.3, 171.5, 158.6, 141.3, 132.3, 128.9, 127.6,
127.2, 127.0, 114.5, 73.2, 51.7, 49.0, 47.1, 40.0, 35.7, 32.9, 20.0, 18.3,
17.0, 14.3; MS (ESI) m/z: 412.0 [M + H]+.
Methyl (3S)-3-{4-[(2S)-2-Methylbutoxy]phenyl}-3-[(2S)-2-
phenylpropanamido]propanoate (80e). The procedure for the
synthesis of 80a was followed starting with 79e to give 80e (64%
yield over two steps) as a white solid. 1H NMR (300 MHz, CDCl3): δ
7.48−7.03 (m, 5H), 6.95 (d, J = 8.7 Hz, 2H), 6.74 (d, J = 8.7 Hz,
2H), 6.43 (d, J = 8.4 Hz, 1H), 5.30 (dd, J = 14.2, 6.0 Hz, 1H), 3.79−
3.66 (m, 3H), 3.54 (s, 3H), 2.77 (qd, J = 15.5, 6.0 Hz, 2H), 1.90−
1.75 (m, 1H), 1.64−1.37 (m, 4H), 1.36−1.08 (m, 1H), 0.98 (d, J =
6.7 Hz, 3H), 0.92 (t, J = 7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.2, 171.5, 158.6, 141.3, 132.3, 128.8, 127.6, 127.2, 127.1, 114.5,
72.8, 51.7, 49.0, 47.1, 40.0, 34.7, 26.1, 18.3, 16.5, 11.3; MS (ESI) m/z:
398.0 [M + H]+.
Methyl (3S)-3-{4-[(2R)-2-Methylbutoxy]phenyl}-3-[(2S)-2-
phenylpropanamido]propanoate (80f). The procedure for the
synthesis of 80a was followed starting with 79f to give 80f (54%
yield over two steps) as a white solid. 1H NMR (300 MHz, CDCl3): δ
7.40−7.20 (m, 5H), 6.99−6.88 (m, 2H), 6.80−6.69 (m, 2H), 6.38 (d,
J = 8.4 Hz, 1H), 5.35−5.25 (m, 1H), 3.79−3.71 (m, 1H), 3.70−3.56
(m, 2H), 3.55 (s, 6H), 2.77 (qd, J = 15.5, 5.9 Hz, 2H), 1.89−1.72 (m,
Methyl (3S)-3-Amino-3-{4-[(2R)-2-methylbutoxy]phenyl}-
propanoate Hydrochloride (79f). The procedure for the synthesis
of 79a was followed starting with 78f to give 79f as a waxy solid. MS
(ESI) free base m/z: 249.0 [M + H+ − NH3]+.
Methyl (3S)-3-{4-[(2-Methylpentyl)oxy]phenyl}-3-[(2S)-2-
phenylpropanamido]propanoate (80a). To a solution of 79a
(1.35 g, 4.27 mmol) in MeCN (50 mL), HBTU (2.43 g, 6.41
S
https://dx.doi.org/10.1021/acs.jmedchem.0c01581
J. Med. Chem. XXXX, XXX, XXX−XXX

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Article
1H), 1.62−1.45 (m, 4H), 1.32−1.13 (m, 1H), 0.98 (d, J = 6.7 Hz,
3H), 0.93 (t, J = 7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.2,
171.5, 158.6, 141.3, 132.3, 128.9, 127.6, 127.2, 127.0, 114.5, 72.9,
51.7, 49.0, 47.1, 40.0, 34.7, 26.1, 18.3, 16.5, 11.3; MS (ESI) m/z:
398.0 [M + H]+.
HRMS (ESI) m/z: calcd for C26H33N3O3 [M + H]+, 436.2595; m/z:
found, 436.2609.
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-{4-[(2-
methylpentyl)oxy]phenyl}ethyl]-2-phenylpropanamide Hydro-
chloride (84). To a solution of 81a (28 mg, 0.07 mmol) in dry
MeOH (2.5 mL), cyanogen bromide (8 mg, 0.075 mmol) was added,
and the reaction that resulted was heated to reflux under nitrogen for
4 h. The reaction was cooled to room temperature and quenched with
saturated NaHCO3 (5 mL) and extracted with EtOAc (3 × 10 mL).
The combined organic layers were washed with brine (2 × 10 mL)
and dried (Na2SO4). The solvent was evaporated, and the residue was
subjected to column chromatography on silica gel using 0−50%
CMA80 in DCM to furnish 84 (free base, 22 mg, 75% yield) as a
white solid. 1H NMR (300 MHz, CDCl3): δ 7.34−7.17 (m, 5H), 6.99
(d, J = 8.6 Hz, 2H), 6.74 (d, J = 8.7 Hz, 2H), 6.51 (d, J = 8.5 Hz, 1H),
5.45 (br s, 2H), 5.37 (dd, J = 14.4, 7.6 Hz, 1H), 3.73 (dd, J = 8.9, 5.8
Hz, 1H), 3.68−3.48 (m, 2H), 3.26−3.01 (m, 2H), 1.96−1.80 (m,
1H), 1.52−1.05 (m, 7H), 0.98 (d, J = 6.7 Hz, 3H), 0.90 (t, J = 7.0 Hz,
3H). The above solid was suspended in DCM (2 mL) and cooled to 0
°C. To that above suspension, HCl (126 μL, 2.0 M in diethyl ether)
was added dropwise. The solution that resulted was stirred for 30 min
at 0 °C. The solvent was evaporated, and the solid was triturated with
MeOH and hexanes to furnish the hydrochloride salt 84 as a white
(2S)-N-[(1S)-2-(Hydrazinecarbonyl)-1-{4-[(2-methylpentyl)oxy]-
phenyl}ethyl]-2-phenylpropanamide (81a). The procedure for the
synthesis of 70a was followed starting with 80a to give 81a (92%
yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ 7.39−7.21 (m,
5H), 6.93 (d, J = 8.7 Hz, 2H), 6.73 (d, J = 8.7 Hz, 2H), 6.68 (br s,
1H), 5.27−5.14 (m, 1H), 3.79−3.57 (m, 3H), 2.59 (qd, J = 14.6, 5.5
Hz, 2H), 1.99−1.82 (m, 1H), 1.65−1.09 (m, 9H), 0.99 (d, J = 6.7 Hz,
3H), 0.91 (t, J = 7.0 Hz, 3H); MS (ESI) m/z: 412.0 [M + H]+.
(2S)-N-[(1S)-1-[4-(Cyclobutylmethoxy)phenyl]-2-
(hydrazinecarbonyl)ethyl]-2-phenylpropanamide (81b). The pro-
cedure for the synthesis of 70a was followed starting with 80b to give
81b (90% yield) as a white solid. MS (ESI) m/z: 396.0 [M + H]+.
This material was used for the next transformation without further
characterization.
(2S)-N-[(1S)-2-(Hydrazinecarbonyl)-1-(4-{[(2S)-2-methylpentyl]-
oxy}phenyl)ethyl]-2-phenylpropanamide (81c). The procedure for
the synthesis of 70a was followed starting with 80c to give 81c (67%
1
yield) as a white solid. H NMR (300 MHz, CD3OD): δ 7.30−7.06
(m, 5H), 6.94 (d, J = 8.6 Hz, 2H), 6.63 (d, J = 8.7 Hz, 2H), 5.15 (t, J
= 7.1 Hz, 1H), 3.72−3.49 (m, 3H), 2.58−2.39 (m, 2H), 1.87−1.62
(m, 1H), 1.44−0.93 (m, 7H), 0.88 (d, J = 6.7 Hz, 3H), 0.82 (t, J = 7.1
Hz, 3H); MS (ESI) m/z: 412.0 [M + H]+.
1
solid. H NMR (300 MHz, CD3OD): δ 8.52 (d, J = 8.3 Hz, 1H),
7.34−7.19 (m, 5H), 7.16 (d, J = 8.6 Hz, 2H), 6.83 (d, J = 8.7 Hz,
2H), 5.37−5.18 (m, 1H), 3.86−3.59 (m, 3H), 3.24 (d, J = 7.3 Hz,
2H), 2.05−1.78 (m, 1H), 1.61−1.30 (m, 6H), 1.30−1.11 (m, 1H),
1.01 (d, J = 6.7 Hz, 3H), 0.97−0.87 (m, 3H); 13C NMR (75 MHz,
CD3OD): δ 176.5, 163.3, 160.4, 159.4, 142.7, 133.0, 129.5, 128.7,
128.4, 127.9, 115.7, 74.3, 51.4, 47.3, 36.9, 34.1, 32.8, 21.1, 18.8, 17.3,
14.6; HRMS (ESI) free base m/z: calcd for C25H32N4O3 [M + H]+,
437.2547; m/z: found, 437.2546.
(2S)-N-[((1S)-2-Hydrazinecarbonyl)-1-(4-{[(2R)-2-methylpentyl]-
oxy}phenyl)ethyl]-2-phenylpropanamide (81d). The procedure for
the synthesis of 70a was followed starting with 80d to give 81d (75%
yield) as a white solid. MS (ESI) m/z: 412.0 [M + H]+. This material
was used for the next transformation without further characterization.
(2S)-N-[(1S)-2-(Hydrazinecarbonyl)-1-{4-[(2S)-2-methylbutoxy]-
phenyl}ethyl]-2-phenylpropanamide (81e). The procedure for the
synthesis of 70a was followed starting with 80e to give 81e (97%
yield) as a white solid. 1H NMR (300 MHz, CDCl3): δ 7.43−7.17 (m,
5H), 6.95 (m, 4H), 6.73 (d, J = 8.7 Hz, 2H), 5.26−5.15 (m, 1H),
3.80−3.45 (m, 4H), 2.58 (qd, J = 14.6, 5.6 Hz, 2H), 1.91−1.41 (m,
6H), 1.34−1.12 (m, 1H), 0.98 (d, J = 6.7 Hz, 3H), 0.93 (t, J = 7.4 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.5, 171.2, 158.6, 141.3,
132.3, 128.8, 127.6, 127.2, 126.9, 114.6, 72.9, 49.9, 47.2, 40.1, 34.7,
26.1, 18.2, 16.5, 11.3; (ESI) m/z: 398.0 [M + H]+.
(2S)-N-[(1S)-2-(Hydrazinecarbonyl)-1-{4-[(2R)-2-methylbutoxy]-
phenyl}ethyl]-2-phenylpropanamide (81f). The procedure for the
synthesis of 70a was followed starting with 80f to give 81f (90%
yield) as a white solid. MS (ESI) m/z: 398.0 [M + H]+. This material
was used for the next transformation without further characterization.
(2S)-N-[(1S)-1-{4-[(2-Methylpentyl)oxy]phenyl}-2-(1,3,4-oxadia-
zol-2-yl)ethyl]-2-phenylpropanamide (82). The procedure for the
synthesis of 71 was followed starting with 81a and trimethyl
orthoformate to give 82 (35% yield) as a white solid. 1H NMR
(300 MHz, CDCl3): δ 8.27 (s, 1H), 7.28 (m, 5H), 6.96 (d, J = 8.6 Hz,
2H), 6.74 (d, J = 8.6 Hz, 2H), 6.29 (d, J = 8.3 Hz, 1H), 5.42 (dd, J =
14.1, 7.3 Hz, 1H), 3.78−3.69 (m, 1H), 3.68−3.51 (m, 2H), 3.43−
3.15 (m, 2H), 1.99−1.80 (m, 1H), 1.46 (d, J = 7.2 Hz, 3H), 1.43−
1.07 (m, 4H), 0.98 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C
NMR (75 MHz, CDCl3): δ 173.5, 164.0, 158.9, 153.0, 141.0, 131.2,
128.9, 127.6, 127.2, 127.1, 114.7, 73.2, 50.0, 47.0, 35.7, 32.8, 31.7,
20.0, 18.3, 17.0, 14.3; HRMS (ESI) m/z: calcd for C25H31N3O3 [M +
H]+, 422.2438; m/z: found, 422.2432.
(2S)-N-[(1S)-1-[4-(Cyclobutylmethoxy)phenyl]-2-(1,3,4-oxadia-
zol-2-yl)ethyl]-2-phenylpropanamide (85). The procedure for the
synthesis of 71 was followed starting with 81b and trimethyl
1
orthoformate to give 85 (57% yield) as a white solid. H NMR (300
MHz, CDCl3): δ 8.27 (s, 1H), 7.39−7.17 (m, 5H), 6.96 (d, J = 8.7
Hz, 2H), 6.75 (d, J = 8.7 Hz, 2H), 6.17 (d, J = 8.3 Hz, 1H), 5.42 (dd,
J = 14.0, 7.3 Hz, 1H), 3.85 (d, J = 6.6 Hz, 2H), 3.56 (q, J = 7.1 Hz,
1H), 3.45−3.22 (m, 2H), 2.79−2.63 (m, 1H), 2.24−1.98 (m, 2H),
1.97−1.70 (m, 4H), 1.47 (d, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 173.6, 164.0, 158.9, 153.0, 141.0, 131.3, 128.9, 127.6,
127.3, 127.1, 114.8, 72.1, 50.0, 47.0, 34.6, 31.7, 24.8, 24.5, 18.6, 18.3;
HRMS (ESI) m/z: calcd for C24H27N3O3 [M + H]+, 406.2125; m/z:
found, 406.2122.
(2S)-N-[(1S)-1-[4-(Cyclobutylmethoxy)phenyl]-2-(5-methyl-1,3,4-
oxadiazol-2-yl)ethyl]-2-phenylpropanamide (86). The procedure
for the synthesis of 72 was followed starting with 81b and trimethyl
1
orthoacetate to give 86 (88% yield) as a white solid. H NMR (300
MHz, CDCl3): δ 7.39−7.17 (m, 5H), 6.96 (d, J = 8.6 Hz, 2H), 6.83−
6.65 (m, 2H), 6.25 (d, J = 8.3 Hz, 1H), 5.39 (dd, J = 14.7, 6.6 Hz,
1H), 3.85 (d, J = 6.6 Hz, 2H), 3.57 (q, J = 7.1 Hz, 1H), 3.39−3.09
(m, 2H), 2.80−2.63 (m, 1H), 2.44 (s, 3H), 2.20−2.02 (m, 2H),
2.02−1.65 (m, 4H), 1.47 (d, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 173.5, 163.9, 158.8, 141.1, 131.6, 128.9, 127.6, 127.2,
127.1, 114.7, 72.1, 49.9, 47.0, 34.6, 31.9, 24.8, 18.5, 18.3, 10.8; HRMS
(ESI) m/z: calcd for C25H29N3O3 [M + H]+, 420.2282; m/z: found,
420.2281.
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-[4-
(cyclobutylmethoxy)phenyl]ethyl]-2-phenylpropanamide Hydro-
chloride (87). The procedure for the synthesis of 84 was followed
starting with 81b and cyanogen bromide to give 87 (80% yield) as a
(2S)-N-[(1S)-2-(5-Methyl-1,3,4-oxadiazol-2-yl)-1-{4-[(2-
methylpentyl)oxy]phenyl}ethyl]-2-phenylpropanamide (83). The
procedure for the synthesis of 72 was followed starting with 81a
and trimethyl orthoacetate to give 83 (93% yield) as a white solid. 1H
NMR (300 MHz, CDCl3): δ 7.38−7.16 (m, 5H), 6.97 (d, J = 8.6 Hz,
2H), 6.73 (d, J = 8.7 Hz, 2H), 6.41 (d, J = 8.4 Hz, 1H), 5.46−5.29
(m, 1H), 3.78−3.69 (m, 1H), 3.68−3.48 (m, 2H), 3.35−3.07 (m,
2H), 2.42 (s, 3H), 1.98−1.79 (m, 1H), 1.52−1.10 (m, 7H), 0.98 (d, J
= 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 173.5, 164.0, 163.9, 158.8, 141.1, 131.6, 128.8, 127.6, 127.2, 127.2,
114.7, 73.2, 49.9, 47.0, 35.7, 32.8, 31.8, 20.0, 18.3, 17.0, 14.3, 10.8;
1
white solid. H NMR [free base] (300 MHz, CD3OD): δ 7.36−7.14
(m, 5H), 7.10 (d, J = 8.7 Hz, 2H), 6.78 (d, J = 8.7 Hz, 2H), 5.28 (t, J
= 7.6 Hz, 1H), 3.87 (d, J = 6.6 Hz, 2H), 3.65 (q, J = 7.0 Hz, 1H), 3.16
(d, J = 7.6 Hz, 2H), 2.84−2.46 (m, 1H), 2.19−2.03 (m, 2H), 2.03−
1.64 (m, 4H), 1.39 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz,
CD3OD): δ 176.3, 165.8, 160.2, 159.3, 142.8, 133.6, 129.5, 128.6,
128.4, 127.9, 115.6, 73.2, 51.6, 47.4, 36.1, 32.9, 25.7, 19.3, 18.9;
T
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HRMS (ESI) free base m/z: calcd for C24H28N4O3 [M + H]+,
421.2234; m/z: found, 421.2231.
After incubating for 30 min at room temperature, Eu-cAMP tracer
and uLIGHT-anti-cAMP working solutions were added per the
manufacturer’s instructions. After incubation at room temperature for
1 h, the TR-FRET signal (ex 337 nm) was read on a CLARIOstar
multimode plate reader (BMG Biotech, Cary, NC).
Data Analysis. The TR-FRET signal (665 nm) was converted to
fmol cAMP by interpolating from the standard cAMP curve. fmol
cAMP was plotted against the log of compound concentration, and
data were fit to a three-parameter logistic curve to generate EC50
values (Prism, version 6.0, GraphPad Software, Inc., San Diego, CA).
The Emax value for each test compound relative to the control
compounds RTI-13951-33 or 2-PCCA was calculated using the
equation % control Emax = (maximal test compound signal/maximal
control signal) × 100.
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-(4-{[(2S)-2-
methylpentyl]oxy}phenyl)ethyl]-2-phenylpropanamide Hydro-
chloride (88). The procedure for the synthesis of 84 was followed
starting with 81c and cyanogen bromide to give 88 (60% yield) as a
white solid. 1H NMR (300 MHz, CDCl3): δ 7.40−7.16 (m, 5H), 6.98
(d, J = 8.7 Hz, 2H), 6.75 (d, J = 8.6 Hz, 2H), 6.30 (d, J = 8.4 Hz, 1H),
5.35 (dd, J = 14.8, 6.8 Hz, 1H), 5.06 (br s, 2H), 3.81−3.45 (m, 3H),
3.13 (d, J = 6.7 Hz, 2H), 1.95−1.76 (m, 1H), 1.46 (d, J = 7.2 Hz,
3H), 1.43−1.10 (m, 4H), 0.98 (d, J = 6.7 Hz, 3H), 0.91 (t, J = 7.0 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 173.6, 162.8, 158.8, 158.2,
141.1, 131.7, 128.8, 127.6, 127.2, 127.1, 114.7, 73.2, 49.9, 47.0, 35.7,
32.8, 32.0, 20.0, 18.3, 17.0, 14.3; HRMS (ESI) free base m/z: calcd
for C25H32N4O3 [M + H]+, 437.2547; m/z: found, 437.2537.
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-(4-{[(2R)-2-
methylpentyl]oxy}phenyl)ethyl]-2-phenylpropanamide Hydro-
chloride (89). The procedure for the synthesis of 84 was followed
starting with 81d and cyanogen bromide to give 89 (75% yield) as a
[35S]GTPγS Binding Assay. [35S]GTPγS binding assays were
performed on membrane preparations from wild-type (WT) mice
or GPR88 KO mice, following our previously published methods.14,15
To assess [35S]GTPγS binding in the whole striatal region, brains
were quickly removed after cervical dislocation and the whole striatal
region was dissected out, frozen, and stored at −80 °C until use.
Membranes were prepared by homogenizing brain samples in ice-cold
0.25 M sucrose solution 10 vol (mL/g wet weight of tissue). The
obtained suspensions were then centrifuged at 2500g for 10 min.
Supernatants were collected and diluted 10 times in buffer containing
50 mM Tris HCl (pH 7.4), 3 mM MgCl2, 100 mM NaCl, and 0.2
mM EGTA and then centrifuged at 23,000g for 30 min. The pellets
were homogenized in 800 μL ice-cold sucrose solution (0.32 M),
aliquoted, and kept at −80 °C. For [35S]GTPγS binding assays, 2 μg
of protein was used per well. Samples were incubated with and
without the test compound for 1 h at 25 °C in an assay buffer
containing 30 mM GDP and 0.1 nM [35S]GTPγS. Bound radioactivity
was quantified using a liquid scintillation counter. Nonspecific binding
was defined as binding in the presence of 10 μM GTPγS; basal
binding refers to binding in the absence of the agonist. Data were
expressed as a mean percentage of activation above the basal binding.
GTPγS binding by the agonist was plotted with X-axis representing
concentration and Y-axis representing the percentage of activation
against background. EC50 values were calculated using GraphPad
Prism software.
1
white solid. H NMR (300 MHz, CD3OD): δ 7.33−7.16 (m, 5H),
7.12 (d, J = 8.7 Hz, 2H), 6.80 (d, J = 8.6 Hz, 2H), 5.30 (t, J = 7.6 Hz,
1H), 3.84−3.60 (m, 3H), 3.18 (d, J = 7.5 Hz, 2H), 1.97−1.88 (m,
1H), 1.57−1.12 (m, 7H), 1.01 (d, J = 6.7 Hz, 3H), 0.94 (t, J = 7.0 Hz,
3H); 13C NMR (75 MHz, CD3OD): δ 176.3, 165.8, 160.2, 159.3,
142.8, 133.5, 129.5, 128.6, 128.4, 127.9, 115.6, 74.3, 51.6, 47.0, 36.9,
34.1, 32.9, 21.1, 18.9, 17.3, 14.6; HRMS (ESI) free base m/z: calcd
for C25H32N4O3 [M + H]+, 437.2547; m/z: found, 437.2539.
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-{4-[(2S)-2-
methylbutoxy]phenyl}ethyl]-2-phenylpropanamide Hydrochloride
(90). The procedure for the synthesis of 84 was followed starting with
81e and cyanogen bromide to give 90 (94% yield) as a white solid. 1H
NMR [free base] (300 MHz, CDCl3): δ 7.36−7.11 (m, 5H), 7.10−
6.97 (m, 3H), 6.71 (d, J = 8.6 Hz, 2H), 6.20 (br s, 2H), 5.41 (dt, J =
14.2, 7.2 Hz, 1H), 3.71 (dd, J = 9.0, 6.0 Hz, 1H), 3.58 (ddd, J = 21.3,
11.5, 6.8 Hz, 2H), 3.16 (qd, J = 15.2, 7.2 Hz, 2H), 1.89−1.71 (m,
1H), 1.63−1.44 (m, 1H), 1.39 (d, J = 7.1 Hz, 3H), 1.30−1.11 (m,
1H), 0.97 (d, J = 6.7 Hz, 3H), 0.92 (t, J = 7.4 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 173.9, 163.7, 158.8, 157.9, 141.2, 132.0, 128.7,
127.6, 127.2, 127.0, 114.7, 72.9, 49.9, 46.8, 34.7, 32.1, 26.1, 18.4, 16.5,
11.3; HRMS (ESI) free base m/z: calcd for C24H30N4O3 [M + H]+,
423.2391; m/z: found, 423.2388.
Solubility Determination. For kinetic solubility experiments, 10
mM DMSO stocks of compounds were directly diluted into 10 mM
phosphate buffer at pH 7.4 and shaken for 90 min at room
temperature. The final concentration of DMSO was 1%. After the
incubation, samples were filtered through a 0.4 μm filter plate
(Millipore). Filtrates were carefully collected. On each experimental
occasion, tamoxifen and caffeine were assessed as reference
compounds for low and high solubilities, respectively. All samples
were assessed in triplicate and analyzed by LC−MS/MS using
electrospray ionization against standards prepared in the same matrix.
PK Analysis. PK study of 90 was performed using male Long-
Evans rats (Paraza Pharma Inc., Montreal, Canada). Doses were
formulated in 5% dimethylacetamide in sesame oil. On the morning of
the PK study, animals were weighed, and dosing formulation volumes
were calculated accordingly. The compound was injected intra-
peritoneally to all animals. At selected time points (0.5, 1, 2, 4, and 8 h
postdose), animals were anesthetized to perform a cardiac puncture to
collect blood for pooled plasma analysis, followed by whole-body
perfusion with phosphate saline buffer (pH 7.4) to wash out any
remaining blood from the organs. Brains were harvested and
homogenized by polytron 1:4 (w/v) in 25% isopropanol in water.
Brain homogenates were further pooled per corresponding time point
and extracted for drug quantification of LC−MS/MS. Samples were
prepared and analyzed as follows: Plasma (10 μL) was mixed with 10
μL of 0.5% formic acid in water and 100 μL of internal standard
working solution (0.1 μM Glyburide/Labetalol in 0.5% ammonium
formate in methanol/acetonitrile), vortexed, and centrifuged at
10,000g for 10 min at 4 °C. The supernatant (100 μL) was
transferred to a 2 mL deepwell plate and diluted with 200 μL of 30%
acetonitrile/water. Brain homogenate (25 μL) was mixed with 25 μL
of 0.5% formic acid in water and 150 μL of internal standard working
(2S)-N-[(1S)-2-(5-Amino-1,3,4-oxadiazol-2-yl)-1-{4-[(2R)-2-
methylbutoxy]phenyl}ethyl]-2-phenylpropanamide Hydrochloride
(91). The procedure for the synthesis of 84 was followed starting with
81f and cyanogen bromide to give 91 (59% yield) as a white solid. 1H
NMR (300 MHz, CD3OD): δ 7.32−7.02 (m, 5H), 6.93 (d, J = 8.6
Hz, 2H), 6.63 (d, J = 8.7 Hz, 2H), 5.14 (t, J = 7.1 Hz, 1H), 3.77−3.48
(m, 3H), 2.50 (d, J = 7.1 Hz, 2H), 1.76−1.60 (m, 1H), 1.53−1.37 (m,
1H), 1.32 (d, J = 7.1 Hz, 3H), 1.23−1.06 (m, 1H), 0.88 (d, J = 6.7
Hz, 3H), 0.83 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CD3OD): δ
175.9, 172.0, 160.0, 142.9, 134.4, 129.5, 128.5, 128.5, 127.9, 115.4,
73.9, 51.4, 47.5, 41.3, 36.0, 27.2, 18.8, 16.8, 11.6; HRMS (ESI) free
base m/z: calcd for C24H30N4O3 [M + H]+, 423.2391; m/z: found,
423.2383.
Pharmacology. Materials. Cell culture materials were purchased
from Fisher SSI. Forskolin was purchased from Sigma-Aldrich. The
Lance Ultra kit (TRF0262) was purchased from PerkinElmer.
Lance Ultra cAMP Assay Using Stable PPLS-HA-GPR88 CHO
Cells. All cAMP assays were performed using our previously published
methods.26 Stimulation buffer containing 1× Hank’s balanced salt
solution, 5 mM HEPES, 0.1% BSA stabilizer, and 0.5 mM final IBMX
was prepared and titrated to pH 7.4 at room temperature. Serial
dilutions of the test compounds (5 μL) and 300 nM forskolin (5 μL),
both prepared at 4× the desired final concentration in 2% DMSO/
stimulation buffer, were added to a 96-well white 1/2 area microplate
(PerkinElmer). A cAMP standard curve was prepared at 4× the
desired final concentration in stimulation buffer and 5 μL was added
to the assay plate. Stable PPLS-HA-GPR88 CHO cells were lifted
with versene and spun at 270g for 10 min. The cell pellet was
resuspended in stimulation buffer and 4000 cells (10 μL) were added
to each well except for wells containing the cAMP standard curve.
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Article
solution (0.1 μM Glyburide/Labetalol in methanol/acetonitrile),
vortexed, and centrifuged at 10,000g for 10 min at 4 °C. The
supernatant (100 μL) was transferred to a 2 mL deepwell plate and
diluted with 100 μL of water. LC−MS/MS was conducted using an
Applied Biosystems API 4000 HPLC system. Chromatography was
performed with an Xbridge BEH C18 (2.1 × 30 mm, 2.5 μm) column.
Mobile phases were 0.1% formic acid in water (A), and 0.1% formic
acid in 25% isopropanol/acetonitrile (B). Initial conditions were 5% B
and held for 0.5 min, followed by a linear gradient to 95% B over 1.8
min. 95% B was held for 2.6 min before returning to initial conditions.
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Funding
This work was supported by the National Institute of Mental
Health (NIMH, grant MH103708 to C.J.) and the National
Institute on Alcohol Abuse and Alcoholism (NIAAA, grant
AA026820 to C.J. and B.K.), National Institutes of Health, US.
Notes
ASSOCIATED CONTENT
The authors declare no competing financial interest.
■
sı
* Supporting Information
ABBREVIATIONS
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.jmedchem.0c01581.
■
ADME, absorption, distribution, metabolism, and excretion; 2-
AMPP, (2S)-N-((1R)-2-amino-1-(4-(2-methyl-pentyloxy)-
phenyl)ethyl)-2-phenylpropanamide; cAMP, cyclic adenosine
monophosphate; BBB, blood−brain barrier; BRET, bio-
luminescence resonance energy transfer; CHO cells, Chinese
hamster ovary cells; DCM, dichloromethane; DEAD, diethyl
azodicarboxylate; DIPEA, N,N-diisopropylethylamine; DMF,
N , N- dime th ylfo r ma mid e; E D C, 1- e thyl -3-(3-
dimethylaminopropyl)carbodiimide; GPCR, G protein-
coupled receptor; HA, human influenza hemagglutinin;
HBTU, 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium
hexafluorophosphate; HEK293 cells, human embryonic kidney
cells; HOBt, hydroxybenzotriazole; KO, knockout; MS, mass
spectroscopy; 2-PCCA, (1R,2R)-2-(pyridin-2-yl)cyclopropane
carboxylic acid((2S,3S)-2-amino-3-methylpentyl)-(4′-propylbi-
phenyl-4-yl)amide; Pgp, P-glycoprotein; PPLS, pre-prolactin
leader sequence; PTSA, p-toluenesulfonic acid; TBAF,
tetrabutylammonium fluoride; TEA, triethylamine; TFA,
trifluoroacetic acid; THF, tetrahydrofuran; TIPS, triisopropyl-
silyl; TIPSCl, triisopropylsilyl chloride; TLC, thin-layer
chromatography; TPSA, topological polar surface area; SAR,
structure−activity relationship
1H NMR, 13C NMR, and HPLC analysis results of target
compounds (PDF)
Molecular formula strings with biological data (CSV)
AUTHOR INFORMATION
■
Corresponding Author
Chunyang Jin − Center for Drug Discovery, Research Triangle
Institute, Research Triangle Park, North Carolina 27709,
United States; orcid.org/0000-0001-6733-3094;
Phone: 919 541-6328; Email: cjin@rti.org; Fax: 919 541-
8868
Authors
Md Toufiqur Rahman − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States
Ann M. Decker − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States
Tiffany L. Langston − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States
Kelly M. Mathews − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States
Lucas Laudermilk − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States
Rangan Maitra − Center for Drug Discovery, Research
Triangle Institute, Research Triangle Park, North Carolina
27709, United States; orcid.org/0000-0001-6663-6800
Weiya Ma − Douglas Research Center, Department of
Psychiatry, McGill University, Montréal, Quebec H4H 1R3,
Canada
Emmanuel Darcq − Douglas Research Center, Department of
Psychiatry, McGill University, Montréal, Quebec H4H 1R3,
Canada; INSERM U1114, University of Strasbourg,
Strasbourg 67085, France; orcid.org/0000-0002-8377-
8015
Brigitte L. Kieffer − Douglas Research Center, Department of
Psychiatry, McGill University, Montréal, Quebec H4H 1R3,
Canada; INSERM U1114, University of Strasbourg,
Strasbourg 67085, France
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