5,6,7,8-Tetrahydro-1,6-naphthyridine Derivatives as Potent HIV-1-Integrase-Allosteric-Site Inhibitors

Article abstract of DOI:10.1021/acs.jmedchem.8b01473

A series of 5,6,7,8-tetrahydro-1,6-naphthyridine derivatives targeting the allosteric lens-epithelium-derived-growth-factor-p75 (LEDGF/p75)-binding site on HIV-1 integrase, an attractive target for antiviral chemotherapy, was prepared and screened for activity against HIV-1 infection in cell culture. Small molecules that bind within the LEDGF/p75-binding site promote aberrant multimerization of the integrase enzyme and are of significant interest as HIV-1-replication inhibitors. Structure-activity-relationship studies and rat pharmacokinetic studies of lead compounds are presented.

Full text of DOI:10.1021/acs.jmedchem.8b01473

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Article
5,6,7,8-Tetrahydro-1,6-naphthyridine Derivatives
as Potent Allosteric Site HIV-1 Integrase Inhibitors
Kevin Peese, Christopher Allard, Timothy Connolly, Barry Johnson, Chen Li, Manoj Patel,
Margaret Sorensen, Michael Walker, Nicholas A. Meanwell, Brian McAuliffe, Beatrice
Minassian, Mark Krystal, Dawn Parker, Hal A. Lewis, Kevin Kish, Ping Zhang, Robert T
Nolte, Jean Simmermacher, Susan Jenkins, Christopher Cianci, and B Narasimhulu Naidu
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.8b01473 • Publication Date (Web): 04 Jan 2019
Downloaded from http://pubs.acs.org on January 6, 2019
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Journal of Medicinal Chemistry
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5,6,7,8-Tetrahydro-1,6-naphthyridine Derivatives as Potent
Allosteric Site HIV-1 Integrase Inhibitors
Kevin M. Peese,*,†,§ Christopher W. Allard,‡ Timothy Connolly,† Barry L. Johnson,† Chen Li,† Manoj
Patel,†,§ Margaret E. Sorensen,† Michael A. Walker,† Nicholas A. Meanwell,† Brian McAuliffe,†,§
Beatrice Minassian,‡ Mark Krystal,†,§ Dawn D. Parker,†,§ Hal A. Lewis,† Kevin Kish,† Ping Zhang,†
Robert T. Nolte,◊ Jean Simmermacher,†,§ Susan Jenkins,†,§ Christopher Cianci,‡ and B. Narasimhulu
Naidu†,§
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† Bristol-Myers Squibb Research & Development, Department of Discovery Chemistry, 5 Research Parkway, Wallingford,
Connecticut 06492
‡ Bristol-Myers Squibb Research & Development, Department of Virology Discovery Biology, 5 Research Parkway,
Wallingford, Connecticut 06492
◊ GlaxoSmithKline, Protein Cellular and Structural Sciences, 1250 South Collegeville Rd., Collegeville, PA 19426
§ Current address: ViiV Healthcare, 36 East Industrial Road, Branford, Connecticut, 06405
KEYWORDS: ALLINI, LEDGIN, NCINI, HIV integrase inhibitor, HIV integrase, LEDGF, allosteric inhibitor.
ABSTRACT: A series of 5,6,7,8-tetrahydro-1,6-naphthyridine derivatives targeting the allosteric lens epithelium-derived growth
factor p75 (LEDGF/p75) binding site on HIV-1 integrase, an attractive target for antiviral chemotherapy, was prepared and screened
for activity against HIV-1 infection in cell culture. Small molecules that bind within the LEDGF/p75 binding site promote aberrant
multimerization of the integrase enzyme and are of significant interest as HIV-1 replication inhibitors. SAR studies and rat
pharmacokinetic studies of lead compounds are presented.
and therefore offer the promise to provide an important clinical
INTRODUCTION
complement to INSTIs in drug combinations for the treatment
of HIV-1 infection.13,14,17 In the time since the initial disclosure
of this class, ALLINIs have become a focus of active research,
delivering the clinical candidate BI-224436 (1) while multiple
preclinical candidates have been described (Figure 1).15-17
Infection with HIV-1 represents a substantial global health
challenge. By the end of 2016, the World Health Organization
(WHO) estimated that there were approximately 36.7 million
people living with HIV-1 infection, including 1.8 million
newly-infected people in 2016.1 In recent years, significant
advances have been made in the treatment of HIV-1 infection;
however, due to the emergence of resistance and issues
associated with drug tolerability there remains a need for new
antiviral agents.2,3 HIV-1 integrase, one of three essential
enzymes encoded in the HIV-1 genome, is an attractive target
for chemotherapeutic intervention.4-7 Currently, four HIV-1
integrase inhibitors are approved for clinical use in combination
with other antiviral agents, including raltegravir, elvitegravir,
dolutegravir, and, most recently, bictegravir.8-12 All of the
clinically-approved inhibitors bind to the active site of
integrase, blocking the strand transfer step in which viral DNA
is integrated into the host genome, and are designated integrase
as strand transfer inhibitors (INSTIs). Recently, allosteric
inhibition of HIV-1 integrase has emerged as a promising,
complementary approach to active site-based inhibitors of
strand transfer.13-16 Allosteric integrase inhibitors (ALLINIs),
alternatively known as lens epithelium-derived growth factor
(LEDGF) inhibitors (LEDGINs), non-catalytic site integrase
inhibitors (NCINIs), and IN-LEDGF/p75 allosteric inhibitors
(INLAIs), are mechanistically differentiated, presenting a
biochemical profile that is distinct from active site inhibitors
LEDGF is a ubiquitous host transcriptional co-activator
nuclear protein that is a cellular co-factor taken advantage of by
HIV-1 virus to direct the activity of integrase.13,14 LEDGF
exists as two distinct isoforms, p75 and p52, of which only p75
has been shown to bind to HIV-1 integrase.21,22 Binding of
LEDGF/p75 to integrase promotes organization of the enzyme
as a tetramer and tethers the integration complex to chromatin,
thereby facilitating viral integration into host cell DNA.23
Disruption of the integrase-LEDGF/p75 protein-protein
interaction inhibiting integration is a conceptually attractive
approach to inhibit integration and block viral replication.13,14,18-
20
Studies of early disclosed allosteric integrase inhibitors
demonstrated, however, that while these agents do indeed bind
to the LEDGF/p75 interface on integrase in vitro, the primary
antiviral effect is to block viral particle maturation, i.e. a late
mechanism of action.18,24-26
Further elucidation of the
mechanism revealed that ALLINIs induce aberrant
multimerization of integrase during viral particle assembly,
ultimately leading to the production of structurally defective,
non-infectious virions.
Through a program of structure-based drug design employing
known inhibitors, including 1 and 2, we identified 5,6,7,8-
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tetrahydro-1,6-naphthyridine 3 as an inhibitor of HIV-1
Page 2 of 17
RESULTS AND DISCUSSION
1
integrase that binds to the LEDGF/p75 binding pocket.
Encouragingly, 3 exhibited modest antiviral activity in cell
culture against NL4-3 virus, establishing it as a useful lead
molecule. Consideration of a computational model of 3 bound
to integrase within the LEDGF/p75 binding site suggested that
the N-phenyl ring of 3 lies in a relatively open hydrophobic
pocket of the integrase protein bounded on the front and bottom
by threonine 124/threonine 125 (T124/T125), on the back by
tryptophan 131 (W131), and underneath by alanine 128 (A128)
(Figure 2). The projection of the phenyl ring in compound 3
differs considerably from contemporary reports of inhibitors
represented by 4 and 5 where substitution was directed in a
complementary vector away from this pocket.20 Analysis of the
model inspired a strategy designed to further explore this region
of the LEDGF/p75 binding pocket. The goal of this exercise
was to improve the antiviral potency of this series based upon
the hypothesis that projection of the N-phenyl ring further away
from the core heterocycle would more completely fill the
binding pocket and result in a concomitant increase in binding
efficiency. Consequently, we set out to explore approaches to
introduce linker elements between the phenyl ring and the
5,6,7,8-tetrahydro-1,6-naphthyridine core designed to project
the N-aryl group of 3 deeper into the hydrophobic pocket of
HIV-1 integrase.
Efforts to project the N-aryl ring of 3 further into the
hydrophobic LEDGF/p75 binding pocket began with a study of
the homologous series of linker elements between the phenyl
ring and the piperidine N atom (Table 1). These compounds
were evaluated in both a biochemical binding assay and in a cell
culture antiviral activity assay. The binding assay evaluated
compounds for their ability to displace a tritiated version of
compound 2 from the LEDGF/p75 binding site on integrase.
The cell culture antiviral activity assay evaluated the ability of
compounds to inhibit viral outgrowth of the NL4-3HIV-1 strain
replication in MT-2 cells. As antiviral activity is the ultimate
driver of efficacy for antiretroviral agents, the cell culture
antiviral assay was used as the primary means of evaluating new
compounds. Both the one and two carbon-linked compounds 6
and 7, respectively, demonstrated similar antiviral activity to
the prototype 3. However, the three carbon homolog 8
delivered an almost 50-fold increase in antiviral activity, with
an EC50 value of 0.010 μM. The next series of analogs explored
variation of the three atom spacer motif in 8. Replacement of
the benzylic carbon with an oxygen atom to afford the ether 9
resulted in reduced antiviral activity, as did the introduction of
an unsaturation into the spacer, alkene 10. In both cases, the
conformational preferences associated with these molecular
edits, which are similar in effect, presumably compromises the
optimal presentation of the phenyl ring to the hydrophobic
pocket of the enzyme.28-30 Conformational constraints proximal
to the heterocyclic core, examined in the context of amide 11,
carbamate 12, and urea 13, resulted in lower potency compared
to 8, with the EC50 values recorded for these compounds
comparable to the prototype 3. The incorporation of a phenyl
ring in the tether was also evaluated in an effort to further
illuminate the preferred binding conformation. Both the para-
biphenyl 14 and meta-biphenyl 15 exhibited antiviral activity
comparable to 3 while the ortho-biphenyl isomer 16, in which
the proximal phenyl ring is attached to the
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
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O
N
O
O
O
CO2H
CO2H
N
CO2H
N
N
N
1
2
(BI-224436)
Cl
O
tetrahydronaphthyridine ring via
a
methylene spacer,
O
O
demonstrated potent antiviral activity, EC50 = 0.070 μM,
although still attenuated relative to the activity of the
phenylpropyl-based 8. Finally, a series of analogs in which the
terminal phenyl ring was either replaced with alkyl substituents
or excised completely were probed in order to assess the
importance of an aromatic element at this site. Replacement of
the aryl ring of 8 with a cyclopentyl ring (17) was tolerated,
although this compound was 4-fold less active than the
prototype 8, while the simple n-pentyl analog 18 was 20-fold
less potent than 8. Finally, the N-methylamine 19, the
acetamide 20, the methyl carbamate 21, and the sulfonamide 22
all displayed reduced antiviral potency with EC50 values above
1 μM, consistent with the hypothesized advantage of occupying
the hydrophobic pocket. The results from the binding assay
generally tracked within 3-fold of the cell culture antiviral
assay, the primary exceptions being compounds lacking a
terminal aryl ring. However, SAR trends were generally more
consistent and interpretable in the cell culture assay, supporting
the decision to rely primarily on the cell culture assay.
CO2H
CO2H
N
N
N
4
5
O
Figure 1. Compounds 1–5.
In an effort to further optimize the potency of the chemotype,
attention focused on evaluating the effect of substitution on the
aryl ring of 8 (Table 2). This phase of the survey was performed
in the context of the 8-fluoro-5-methylchromane group at C-4
of the core heterocycle rather than the simpler tolyl substituent.
Adoption of the 8-fluoro-5-methylchromane group was based
on the description of this motif as a highly optimized substituent
Figure 2. Overlay of compounds 3 and 8 docked in the
LEDGF/p75 binding pocket of HIV-1 integrase.
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Journal of Medicinal Chemistry
antiviral activity.32 Replacement of the tolyl ring of 8 by the
identified in the course of the discovery of 2 that conferred a
significant increase in antiviral potency.19,31 As has been
observed by others, the atropisomeric stereogenic axis is stable
and must be in the R-configuration in order to obtain potent
chromane group gave 23 as the prototype of this series, a
1
2
3
4
5
6
7
8
O
R
N
CO2H
9
N
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
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43
44
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Compound
R
IC50 (μM)a,b
0.071
-
EC50 (μM)c
0.052
0.15
0.47
0.30
0.24
0.010
0.20
0.12
0.34
0.23
0.50
0.32
0.28
0.070
0.039
0.21
2.1
EC50 SD (μM)d
CC50 (μM)e
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
>40
1
NA
0.021
0.053
0.17
0.15
-
2
NA
3
Ph
0.23
0.83
0.85
0.070
0.17
0.16
0.76
0.14
0.31
0.22
0.43
0.08
0.24
1.1
6
PhCH2
7
PhCH2CH2
PhCH2CH2CH2
PhOCH2CH2
PhCH=CHCH2
PhCH2CH2CO.
PhCH2OCO.
PhCH2NHCO.
4-Ph-C6H4
3-Ph-C6H4
2-Ph-C6H4CH2
c-C5H9CH2CH2CH2
CH3CH2CH2CH2CH2
CH3
8
0.0037
0.084
0.044
0.071
0.055
-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
-
0.049
0.017
0.002
0.053
-
5.8
CH3CO.
17
1.9
-
CH3OCO.
CH3SO2
4.2
1.6
-
2.2
2.6
-
Table 1. Antiviral activity of 3 and 6-22 in a biochemical binding assay measuring the capacity of test compounds to displace tritiated
2 from integrase and activity in a cell culture antiviral HIV-1 infectivity assay.
a Binding assay which evaluated compounds for the ability to displace a tritiated version of compound 2 from the LEDGF binding site on
integrase. b Binding assay values based on single replicant. c Cell culture antiviral activity assay which evaluated the ability of compounds
d
to inhibit viral outgrowth of the NL4-3 HIV-1 strain in MT-2 cells.
Cell culture activity values based on multiple replicants- see
supplemental data for details. e Measured in MT-2 cells up to a maximal concentration of 40 μM of test substrate.
structural edit associated with potent antiviral potency, with
an EC50 value of 0.004 μM. An effort to constrain the pendent
phenyl ring in the hypothesized active conformation through
introduction of a syn cyclopropyl group in the tether provided
24, prepared as a 1:1 mixture of diastereomers. While the
strategic deployment of cyclopropyl rings for conformational
restriction has been reported in numerous medicinal chemistry
settings, in our context minimal or no enhancement of antiviral
activity compared to prototype 23 was observed.33 However,
24 experienced no loss in activity, an observation consistent
with the importance of the correct presentation of the phenyl
ring that further supports the conformational rationale presented
regarding the diminished antiviral activity of the ether (9) and
olefin (10) linkers in the tolyl series. Substitution of the phenyl
ring of 23 at the 2-, 3-, or 4-positions with fluoro or methyl,
explored with compounds 25-31, provided only modest or no
improvement compared to the parent 23. Interestingly, the
disubstituted 4-methyl, 3-fluorophenyl analog 27 was an
exception, with an EC50 of 0.001 μM in the cell culture assay.
In contrast to the effects of substitution at the 4- or 3-positions,
substitution at the 2-position was a more productive approach
to improving antiviral activity. The 2-fluorophenyl analogue 29
demonstrated an EC50 of 0.001 μM while the 2-methylphenyl
derivative 30 demonstrated an EC50 value of 0.002 μM in the
antiviral assay. In addition, replacement of the phenyl ring with
a pyridine heterocycle resulted in compound 32 with reduced
antiviral potency, a result consistent with the importance of
complementing the hydrophobic pocket of the LEDGF/p75
binding site with a lipophilic moiety.
HIV-1 integrase is highly polymorphic at threonine 124
(T124) and threonine 125 (T125) (NL4-3 sequence) which are
located in the LEDGF/p75 binding pocket of the catalytic core
domain (CCD) of HIV-1 integrase. Evaluation of 8 and 23
against the five most common polymorphic substitutions
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Page 4 of 17
observed
clinically
demonstrated
that this representing a 3-fold loss of antiviral activity compared to wild-
1
2
3
4
tetrahydronaphthyridine-based series is relatively insensitive to
these mutations (Table 3). The most challenging integrase
polymorph for the tolyl-substituted prototype 8 was the
T124A/T125A variant for which the EC50 value was 0.034 μM,
type virus. Similarly, the chromane derivative 23 exhibited an
EC50 of 0.004 μM for wild type T124/T125 integrase and an
EC50
of
0.007
μM
for
the
5
O
6
F
7
8
O
9
Ar
N
CO2H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
N
Compound
23
Ar
Ph
Ph
IC50 (μM)a,b
EC50 (μM)c
EC50 SD (μM)d
CC50 (μM)e
0.016
0.004
0.0015
>40
Ph
24
0.024
0.005
0.0010
>40
1:1
25
26
27
28
29
30
31
32f
4-F-Ph
0.015
0.012
0.044
0.029
0.008
0.019
0.011
0.040
0.004
0.002
0.004
0.002
0.001
0.002
0.001
0.058
-
>40
>40
>40
>40
>40
>40
>40
>40
4-Me-Ph
3-F-Ph
0.0007
-
3-Me-Ph
2-F-Ph
0.0001
-
2-Me-Ph
3-F,4-Me-Ph
4-C5H4N
0.0004
0.0001
0.028
Table 2. Activity of 23-32 in a biochemical binding assay measuring the capacity of test compounds to displace tritiated 2 from
integrase and activity in a cell culture antiviral HIV-1 infectivity assay.
a Binding assay which evaluated compounds for the ability to displace a tritiated version of compound 2 from the LEDGF binding site on
integrase. b Binding assay values based on single replicant. c Cell culture antiviral activity assay which evaluated the ability of compounds
d
to inhibit viral outgrowth of the NL4-3 HIV-1 strain in MT-2 cells. Cell culture activity values and standard deviations (SD) based on
multiple replicants- see supplemental data for details. e Measured in MT-2 cells up to a maximal concentration of 40 μM of test substrate.
f
1:1 mixture of atropisomers.
T125A polymorph. Polymorph potency shifts of 3-fold or
less are considered to be modest in nature, demonstrating that
the tetrahydronaphthyridine series is associated with broad
polymorph coverage. This polymorph antiviral activity profile
differs markedly from published series where the aryl
substituent projects in the southwest direction, as the molecules
are drawn. Compound 5 is a representative example,
experiencing a 12-fold loss in antiviral activity for the T124N
polymorph, a difference that further highlights a potential
advantage of the tetrahydronaphthyridine series.26
series, adopting a conformation very similar to that predicted
for the phenylpropyl analog 8 bound to integrase (Figure 3).28
The terminal aryl ring of 24 projects towards tryptophan 131 in
an edge to π face conformation and establishes close van der
Waals contacts with threonine 124, threonine 125, and alanine
128. The crystal structure of 24 bound to integrase provided
validation of the hypothesis that projecting a lipophilic aryl ring
deeper into the hydrophobic pocket of LEDGF/p75 would result
in increased binding efficiency, confirmed by the measured
antiviral activity.
To gain insight into the antiviral activity of the
tetrahydronaphthyridine series, a cocrystal structure of 24
bound to HIV-1 integrase was obtained (Figure 3). The X-ray
crystal structure was solved at 2.0 Å resolution by soaking
crystals of a construct of the CCD of HIV-1 integrase with the
diastereomeric mixture of 24, selectively binding a single
diastereomer of 24. The crystal structure of 24 confirmed that
the tetrahydronaphthyridine series binds to the LEDGF/p75
recognition pocket in a fashion comparable to previously
disclosed reports of structurally similar inhibitors.18
Importantly, the crystal structure of 24 bound to integrase
demonstrated projection of the terminal aryl ring into the
hydrophobic pocket adjacent to the LEDGF/p75 binding site in
support of the binding mode hypothesis developed for this
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Journal of Medicinal Chemistry
Figure 3. X-ray cocrystal structure of a single diastereomer of
1
compound 24 bound to the HIV-1 integrase CCD.
2
3
4
5
6
7
8
Several compounds were profiled in rat pharmacokinetic
studies designed to further assess the potential of this
tetrahydronaphthyridine chemotype (Table 4). Both the phenyl
derivative 23 and the 4-fluorophenyl homologue 25 exhibited
high clearance (CL) of 82 and 92 mL/min/kg and moderate to
high volumes of distribution (Vss) of 6 and 1 L/kg, respectively,
following IV ad-ministration. This high CL was unexpected as
9
10
11
12
13
14
15
16
17
18
19
20
Wild
Compound type EC50
(μM)
T124A
T125A
T124A/T125A
EC50 (μM)
T124N
EC50 (μM) EC50 (μM)
T124A/T125N
EC50 (μM)
EC50 (μM)
8
0.010
0.004
0.017
0.004
0.021
0.007
0.034
0.006
0.020
0.006
0.031
0.004
23
Table 3. Cell culture antiviral activity of 8 and 23 toward NL4-3 viruses incorporating mutations in HIV-1 integrase within the pol
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
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60
gene.
both 23 and 25 displayed good metabolic stability in an in
vitro rat liver microsome assay with 78% of each remaining
after a 10 minute incubation period at a concentration of 0.5
μM. Togain insight into the observed rat pharmacokinetic SAR,
further compounds with a range of structural features were also
profiled in rat in vivo studies. Analogs 3, 6, and 16, which place
the pendent aryl ring in close proximity to the core
tetrahydronaphthyridine, exhibited moderate CL values of 24,
21, and 24 mL/min/kg, respectively. In contrast, analogs 8, 11,
and 12 in which the aryl ring is spaced three atoms from the
tetrahydronaphthyridine ring demonstrated high CL values.
The hybrid biphenyl analog 16, which possesses an aryl
proximal to the tetrahydronaphthyridine in addition to a more
distant terminal aryl ring, delivered an improvement in the IV
pharmacokinetic profile with a moderate CL value of 24
mL/min/kg. Finally, replacement of the aryl ring with a
cyclopentyl ring, exemplified by 17, did not improve the
pharmacokinetic profile since this compound is also subject to
rapid clearance. The key finding of these pharmacokinetic
studies was that placement of an aryl ring close to the
tetrahydronaphthyridine was central to obtaining a good
pharmacokinetic profile. Most importantly, the hybrid biphenyl
16 recovered a positive pharmacokinetic profile, with low CL
that provides insight into a potential path forward for future
studies. As observed with 23 and 25, the in vitro rat liver
microsome stability profiles of 3, 6, 8, 11, 12, 16, and 17 were
not predictive of in vivo pharmacokinetic profiles. The lack of
correlation between the in vitro-derived microsomal stability
data and the high in vivo clearance values suggests that the
clearance is likely not driven by CYP-mediated oxidative
processes. This result is consistent with published data for 2
and related compounds for which enterohepatic recirculation
and biliary excretion of the unmodified parent and the
corresponding acyl glucuronide were found to be the primary
drivers of in vivo clearance.34 While we have no direct evidence
for glucuronidation or enterohepatic recirculation, biliary
clearance might be considered to be the likely primary mode of
in vivo clearance for this series considering the generally high
in vitro metabolic stability of representative compounds.
Table 4. Rat pharmacokinetic profiles of test compounds dosed
at 1 mg/kg IV and 5 mg/kg PO.a
CL
Vss
Compound
%Fd
(mL/min/kg)b
(L/kg)c
3
24
3
NAe
35%
NAe
NAe
71%
25%
32%
10%
10%
6
21
7
8
171
163
118
24
16
2
11
12
16
17
23
25
19
9
152
82
66
6
92
1
a
b
All compounds evaluated in vivo are included in Table 4.
Clearance (CL). c Steady state volume of distribution (Vss). d Oral
bioavailability. e PO arm was not evaluated.
Tetrahydronaphthyridines 3 and 6-32 were readily prepared
following the synthetic procedures outlined in Scheme 1.
Piperidine-catalyzed Knoevenagel condensation of tolyl
aldehyde 33 or chromane aldehyde 34 with ketoester 35
provided the respective enoate products. The lithium enolate of
ketone 36, generated by deprotonation with LiHMDS, was
added to the enoate. Treatment of the addition products with
NH4OAc/AcOH produced the dihydropyridines which were
readily oxidized with ceric ammonium nitrate (CAN) to deliver
the pyridine products 37. Following saponification of the alkyl
ester, Bode homologation of the carboxylate provided the keto
esters 39.35 Asymmetric reduction of the ketone utilizing the
Corey–Bakshi–Shibata (CBS) (R)-borane reagent gave the
chiral alcohol which was alkylated with t-butyl
acetate/perchloric acid to produce the t-butyl ethers 40.
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Deprotection of the benzyl carbamate (Cbz) under standard internal CHCl3 (δ = 7.26) and CDCl3 (δ = 77.0). LCMS
1
2
3
4
5
6
7
8
hydrogenation conditions provided the highly versatile amines
41. Using either reductive amination or acylation chemistry
followed by saponification of the ester led to target compounds
3 and 6-32.
obtained on Shimadzu LCMS 2020 system run with 2%-98%
MeCN/water gradient [0.05% TFA]. Purity of final compounds
was ≥95% based on analytical HPLC and NMR analysis.
(S)-2-(tert-Butoxy)-2-(2-methyl-6-phenyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (3). A
solution of methyl 2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt
(41a) (0.040 g, 0.095 mmol, 1 equiv), Et3N (0.013 mL, 0.095
mmol, 1 equiv) and bromobenzene (0.020 mL, 0.191 mmol, 2
equiv) was added to a mixture of trisdibenzylideneacetone-
dipalladium chloroform complex (5 mg, 4.77 µmol, 0.05
Scheme 1. Preparation of 3, 6-32.
O
Ar
N
O
O
F
Cbz
a, b, c, d
N
OR
OR
or
+
9
O
Cbz
N
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
O
37
O
35
33
34
CN
Br
equiv),
2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-
36
R = Me, tBu
e or f, g, h
biphenyl (S-Phos) (4 mg, 9.55 µmol, 0.10 equiv) and sodium t-
butoxide (0.018 g, 0.191 mmol, 2 equiv) in toluene (2 mL). The
resulting mixture was stirred at 110 °C for 4 h then cooled to
room temperature, diluted with EtOAc, and washed with water.
The organic phase was dried (Na2SO4) and concentrated in
vacuo to provide the product (0.051 g) as a yellow oil. LCMS
(ESI, M+1): 459.1. The crude coupling product was taken up
in dioxane (2 mL) and 1 N NaOH (1.1 mL, 1.11 mmol) was
added. The reaction was heated at 75 oC for 4 h. Upon cooling
to ambient temperature, the crude mixture was purified via
S
38
Ar
O
Ar
N
O
i, j
Cbz
OMe
O
Cbz
OMe
N
N
O
N
39
40
k
1
preparative HPLC to provide the product (17 mg, 41%). H
NMR (500 MHz, DMSO-d6) δ 7.38 (dd, J = 7.6, 15.0 Hz, 2H),
7.29 (d, J = 7.6 Hz, 1H), 7.24 (d, J=7.63 Hz, 1H), 7.17 (t, J=7.93
Hz, 2H), 6.66-6.82 (m, 3H), 4.80 (s, 1H), 4.07 (d, J=16.17 Hz,
1H), 3.63-3.73 (m, 2H), 3.55 (td, J=6.33, 12.97 Hz, 1H), 2.96
(br. s., 2H), 2.50 (s, 3H), 2.43 (s, 3H), 0.89 (s, 9H). LCMS (ESI,
M+1): 445.2.
Ar
O
l, m
3, 6 32
OMe
O
-
HN
N
41
(S)-2-(6-Benzyl-2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-
1,6-naphthyridin-3-yl)-2-(tert-butoxy)acetic acid (6). To a
solution of methyl 2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt
(41a) (0.042 g, 0.100 mmol, 1 equiv) in acetonitrile (2.5 mL)
were added BnBr (0.014 mL, 0.120 mmol, 1.2 equiv) followed
by DIPEA (0.052 mL, 0.300 mmol, 3 equiv). After 1.5 h, the
reaction was diluted with EtOAc and washed with water. The
organic phase was dried (Na2SO4) and concentrated in vacuo to
Reagents. a) piperidine, DCM; b) 36, LiHMDS, THF, -78 °C;
NH4OAc, AcOH, 60 °C; d) CAN, MeCN; e) LiCl, lutadine,
DMSO, 130 °C; f) TFA; g) (COCl)2, DMF (cat.), DCM; 38,
DIPEA, DCM; h) Oxone, MeOH, water; i) (R)-CBS borane,
catechol borane, toluene, -20 °C; j) 70% HClO4, t-BuOAc; k) 10%
Pd/C, H2, MeOH; l) reductive amination or acylation; m) 10 N
NaOH, MeOH, 60 °C.
CONCLUSION
give
methyl
2-(6-benzyl-2-methyl-4-(p-tolyl)-5,6,7,8-
In conclusion, we have identified a new series of tetra-
hydronaphthyridine inhibitors of the interaction of HIV-1
integrase with LEDGF/p75 that exhibit potent antiviral activity
in cell culture and display activity to-ward clinically-relevant
integrase polymorphic viruses. The discovery of this series was
based upon the rational structure-based hypothesis of exploring
extension of 3 toward occupation of a hydrophobic portion of
the LEDGF/p75 binding pocket on integrase, a strategy that
differs from previous optimization campaigns which explored
an alternative direction for structural optimization. Lead
compounds from this series were profiled in rat
pharmacokinetic studies but, as with other representatives of
this inhibitor class, balancing potent antiviral activity with an
acceptable pharmacokinetic profile remains a key challenge in
moving the series forward.
tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-butoxy)acetate
(0.048 g) as a colorless oil. 1H NMR (400 MHz, CDCl3) δ 7.39-
7.45 (m, 1H), 7.25-7.32 (m, 5H), 7.23 (d, J = 7.6 Hz, 1H), 7.14-
7.21 (m, 1H), 7.05 (dd, J = 1.7, 7.8 Hz, 1H), 4.96 (s, 1H), 3.70
(s, 3H), 3.44-3.66 (m, 2H), 3.12-3.41 (m, 2H), 2.96-3.08 (m,
2H), 2.63-2.85 (m, 2H), 2.62 (s, 3H), 2.44 (s, 3H), 0.98 (s, 9H).
LCMS (ESI, M+1): 473.4. To a solution of the crude
benzylation product in dioxane (3 mL) was added 1 N NaOH
(1.0 mL, 1.00 mmol, 10 equiv). The mixture was heated at 70
°C for 1 h. Upon cooling ambient temperature, the mixture was
quenched with 1 mL 1 N HCl and purified via preparative
1
HPLC to provide the product (30 mg, 65%). H NMR (500
MHz, DMSO-d6) δ 7.20-7.35 (m, 7H), 7.17 (d, J = 7.6 Hz, 1H),
7.09 (dd, J = 1.5, 7.6 Hz, 1H), 4.77 (s, 1H), 3.44-3.58 (m, 2H),
3.30 (br. s., 1H), 2.99 (d, J = 15.6 Hz, 1H), 2.81-2.89 (m, 2H),
2.75 (td, J = 5.5, 11.0 Hz, 1H), 2.56-2.65 (m, 1H), 2.48 (s, 3H),
2.37 (s, 3H), 0.87 (s, 9H). LCMS (ESI, M+1): 459.3.
EXPERIMENTAL SECTION
General Information. All materials were obtained from
commercial suppliers and used without purification. Dry
organic solvents were purchased from Sigma-Aldrich packaged
under nitrogen in Sure Seal bottles. NMR spectra were obtained
on Bruker 400 MHz or 500 MHz NMR spectrometers. The
chemical shifts of 1H and 13C NMR signals are cited relative to
(S)-2-(tert-Butoxy)-2-(2-methyl-6-phenethyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (7). To
a solution of methyl 2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt
(41a) (0.030 g, 0.072 mmol, 1 equiv) in THF (0.7 mL) was
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Journal of Medicinal Chemistry
added 2-phenylethanal (0.014 mL, 0.107 mmol, 1.5 equiv), To a suspension of methyl (S)-2-(tert-butoxy)-2-(2-methyl-4-
1
2
3
4
5
6
7
8
acetic acid (0.239 mL) and sodium triacetaoxyborohydride
(0.024 g, 0.107 mmol, 1.5 equiv). The resulting mixture was
stirred at room temperature for 2 h. The mixture was
concentrated and purified by preparative HPLC to provide the
tertiary amine. The amine was taken up in dioxane (1 mL) and
1 N NaOH (0.700 mL, 0.700 mmol, 10 equiv) was added. The
reaction was heated at 75 °C for 1 h. Upon cooling to ambient
temperature, the reaction was neutralized with 1 M HCl (0.7
mL) and then purified by preparative HPLC to provide the
(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl
salt (41a) (0.125 g, 0.298 mmol, 1 equiv) in acetonitrile (9 mL)
was added DIPEA (0.156 mL, 0.895 mmol, 3 equiv) followed
by (E)-(3-chloroprop-1-en-1-yl)benzene (0.055 g, 0.358 mmol,
1.2 equiv). After stirring 6 h, the solution was diluted with
EtOAc and washed with water (x2), brine, dried (Na2SO4), and
concentrated in vacuo. The crude product was purified by silica
gel flash chromatography (0-100% EtOAc/hexane) to provide
the product (72 mg, 48%) as a colorless oil. 1H NMR (400
MHz, CDCl3) 7.29-7.41 (m, 4H), 7.26 (s, 2H), 7.14-7.23
(m, 2H), 7.06 (dd, J = 1.7, 7.82 Hz, 1H), 6.49 (d, J = 15.9 Hz,
1H), 6.23 (td, J = 6.7, 15.9 Hz, 1H), 4.96 (s, 1H), 3.69 (s, 3H),
3.36 (d, J = 15.4 Hz, 1H), 3.02-3.29 (m, 5H), 2.92 (td, J = 5.5,
11.31 Hz, 1H), 2.78 (td, J = 5.7, 11.3 Hz, 1H), 2.62 (s, 3H), 2.42
(s, 3H), 0.98 (s, 9H). LCMS (ESI, M+1): 499.7. A mixture of
9
1
product (16 mg, 47%). H NMR (500 MHz, DMSO-d6) δ 7.29-
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7.38 (m, 2H), 7.21-7.26 (m, 2H), 7.09-7.21 (m, 5H), 4.77 (s,
1H), 3.26 (s, 1H), 2.95 (d, J = 15.0 Hz, 1H), 2.88 (br. s., 3H),
2.62-2.76 (m, 3H), 2.58 (d, J = 7.0 Hz, 2H), 2.48 (s, 3H), 2.40
(s, 3H), 0.87 (s, 9H). LCMS (ESI, M+1): 473.1.
(S)-2-(tert-Butoxy)-2-(2-methyl-6-(3-phenylpropyl)-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid
(8). To a solution of methyl (S)-2-(tert-butoxy)-2-(2-methyl-4-
(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl
salt (41a) (0.030 g, 0.072 mmol, 1 equiv) in acetonitrile (2 mL)
was added K2CO3 (0.022 g, 0.158 mmol, 2.2 equiv) followed
by (3-chloropropyl)benzene (0.010 ml, 0.072 mmol, 1 equiv).
The resulting mixture was stirred at 75 °C for 48 h. The reaction
mixture was concentrated and the residue was partitioned
between EtOAc and water. The organic fraction was dried
(Na2SO4) and concentrated in vacuo to give methyl (S)-2-(tert-
butoxy)-2-(2-methyl-6-(3-phenylpropyl)-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetate as a colorless oil
which was carried on without purification. LCMS (ESI, M+1):
501.4. A solution of the crude tertiary amine and 1 N NaOH
(0.720 mL, 0.720 mmol, 10 equiv) in dioxane (2 mL) was
heated at 75 °C for 1 h. Upon cooling to ambient temperature,
the reaction was neutralized with 1 N HCl (0.75 mL) and
concentrated and in vacuo. The crude product was purified by
preparative HPLC to provide the product (16 mg, 46%). 1H
NMR (500 MHz, DMSO-d6) δ 7.35 (d, J = 7.93 Hz, 1H), 7.30
(d, J = 7.6 Hz, 1H), 7.19-7.28 (m, 3H), 7.09-7.18 (m, 4H), 4.76
(s, 1H), 3.20 (d, J = 15.6 Hz, 1H), 2.83-2.94 (m, 3H), 2.79 (td,
J = 5.15, 10.8 Hz, 1H), 2.56-2.64 (m, 1H), 2.54 (br. s., 2H), 2.48
(s, 3H), 2.39 (s, 3H), 2.32 (t, J = 6.7 Hz, 2H), 1.63 (quin, J =
7.3 Hz, 2H), 0.87 (s, 9H). LCMS (ESI, M+1): 487.1.
methyl
(S,E)-2-(tert-butoxy)-2-(6-cinnamyl-2-methyl-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate (60 mg,
0.120 mmol, 1 equiv) and 1 N NaOH (1.20 mL, 1.20 mmol, 10
equiv) in MeOH was heated at 65 oC for 1.5 h. Upon cooling
to ambient temperature, the reaction was neutralized with 1 N
HCl and concentrated in vacuo. The crude product was purified
by preparative HPLC to provide the product (25 mg, 41%). 1H
NMR (400 MHz, CDCl3)  7.95 (br. s., 1H), 7.23-7.41 (m, 6H),
7.04-7.22 (m, 3H), 6.48 (d, J = 15.9 Hz, 1H), 6.09-6.33 (m, 1H),
4.84 (br. s., 1H), 2.99-3.52 (m, 7H), 2.82 (br. s., 1H), 2.65 (s,
3H), 2.37 (s, 3H), 0.98 (s, 9H). LCMS (ESI, M+1): 485.7.
(S)-2-(tert-Butoxy)-2-(2-methyl-6-(3-phenylpropanoyl)-
4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic
acid (11). To a solution of methyl (S)-2-(tert-butoxy)-2-(2-
methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-
yl)acetate, HCl salt (41a) (0.030 g, 0.072 mmol, 1 equiv) and
DIPEA (0.038 mL, 0.215 mmol, 3 equiv) in DCM (2 mL) was
added 3-phenylpropanoyl chloride (0.013 g, 0.079 mmol, 1.1
equiv). After stirring 4 h, the reaction was diluted with DCM,
washed with saturated aqueous sodium bicarbonate, dried
(Na2SO4), and concentrated in vacuo to give the crude product
which was carried on without purification. LCMS (ESI, M+1):
515.4. A solution of the crude amide and 1 N NaOH (0.720
mL, 0.720 mmol, 10 equiv) in dioxane (2 mL) was heated at 75
°C for 1 h. Upon cooling to ambient temperature, the reaction
was neutralized with 1 N HCl (0.72 mL) and concentrated in
vacuo. The crude product was purified by preparative HPLC to
provide the product (19 mg, 52%). 1H NMR (500 MHz,
DMSO-d6) δ 7.11-7.42 (m, 8H), 7.04 (d, J = 7.3 Hz, 1H), 4.71-
4.83 (m, 1H), 3.87-4.38 (m, 2H), 3.74-3.84 (m, 1H), 3.59-3.73
(m, 1H), 2.59-2.97 (m, 6H), 2.49 (s, 3H), 2.39-2.43 (m, 3H),
0.87 (s, 9H). LCMS (ESI, M+1): 501.3.
(S)-2-(tert-Butoxy)-2-(2-methyl-6-(2-phenoxyethyl)-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid
(9). To a suspension of methyl (S)-2-(tert-butoxy)-2-(2-methyl-
4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl salt (41a) (0.050 g, 0.119 mmol, 1 equiv) in acetonitrile (1
mL) was added DIPEA (0.104 mL, 0.597 mmol, 5 equiv)
followed by (2-iodoethoxy)benzene (0.089 g, 0.358 mmol, 3
equiv). After stirring the solution for 21 h, MeOH (1 mL), water
(0.1 mL), and LiOH monohydrate (0.050 g, 1.19 mmol, 10
equiv) were added. After stirring at ambient temperature for 4
d, the reaction was neutralized with 1 N HCl (1.2 mL) and
concentrated and in vacuo. The crude product was purified by
preparative HPLC to provide the product (55 mg, 91%). 1H
NMR (500 MHz, DMSO-d6) δ 7.34 (d, J = 7.6 Hz, 1H), 7.30 (d,
J = 7.9 Hz, 1H), 7.25 (dd, J = 8.5, 7.3 Hz, 2H), 7.19 (d, J = 7.6
Hz, 1H), 7.13 (d, J = 7.6 Hz, 1H), 6.91 (t, J = 7.3 Hz, 1H), 6.76
(d, J = 7.6 Hz, 2H), 4.78 (s, 1H), 4.08 - 3.96 (m, 2H), 3.39 - 3.37
(m, 2H), 2.96 - 2.86 (m, 3H), 2.76 (t, J = 5.6 Hz, 3H), 2.48 (s,
3H), 2.41 (s, 3H), 0.87 (s, 9H); LCMS (ESI, M+1): 489.6.
(S)-2-(6-((Benzyloxy)carbonyl)-2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-
butoxy)acetic acid (12). A solution of benzyl (S)-3-(1-(tert-
butoxy)-2-methoxy-2-oxoethyl)-2-methyl-4-(p-tolyl)-7,8-
dihydro-1,6-naphthyridine-6(5H)-carboxylate (41a) (25 mg,
0.048 mmol) and 1 N NaOH (0.48 mL, 0.480 mmol, 10 equiv)
in MeOH (1.5 mL) was stirred at 65 °C for 1 h. Upon cooling
to ambient temperature, the mixture was stirred a further 18 h.
The mixture was diluted with water and EtOAc and neutralized
with 1 N HCl (0.48 mL). The organic phase was washed with
brine, dried (Na2SO4), and concentrated in vacuo to provide the
crude product. The crude product was purified by preparative
HPLC to provide the product (21 mg, 81%) as a white solid. 1H
NMR (400 MHz, CDCl3) δ 7.29-7.59 (m, 8H), 7.05 (br. s., 1H),
5.13 (br. s., 2H), 5.03 (s, 1H), 4.44 (d, J = 18.1 Hz, 1H), 4.13
(S)-2-(tert-Butoxy)-2-(6-cinnamyl-2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (10).
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Journal of Medicinal Chemistry
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(d, J = 18.1 Hz, 1H), 3.22-3.47 (m, 2H), 2.85 (s, 3H), 2.48 (s, 1 equiv), TEA (0.013 mL, 0.095 mmol, 1 equiv) and 3-bromo-
1
2
3
4
5
6
7
8
3H), 1.01 (s, 9H). LCMS (ESI, M+1): 503.1.
1,1'-biphenyl (0.032 mL, 0.191 mmol, 2 equiv) in toluene (2
mL) was added to a mixture of trisdibenzylideneacetone
dipalladium chloroform complex (4 mg, 0.048 mmol, 0.05
(S)-2-(6-(Benzylcarbamoyl)-2-methyl-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-butoxy)acetic
acid (13). To a solution of methyl (S)-2-(tert-butoxy)-2-(2-
methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-
yl)acetate, HCl salt (41a) (0.030 g, 0.072 mmol, 1 equiv) and
TEA (0.040 mL, 0.286 mmol, 4 equiv) in DCM (2 mL) was
added (isocyanatomethyl)benzene (0.010 mL, 0.079 mmol, 1.1
equiv). After stirring 4 h, the reaction was diluted with DCM,
washed with saturated aqueous sodium bicarbonate, dried
(Na2SO4), and concentrated in vacuo to give the crude product
which was carried on without purification. A solution of the
crude urea and 1 N NaOH (0.720 mL, 0.720 mmol, 10 equiv)
in dioxane (2 mL) was heated at 75 °C for 1 h. Upon cooling
to ambient temperature, the reaction was neutralized with 1 N
HCl (0.72 mL) and concentrated in vacuo. The crude product
was purified by preparative HPLC to provide the product (28
mg, 77%). LCMS (ESI, M+1): 516.3. 1H NMR (500 MHz,
DMSO-d6) δ 7.11-7.41 (m, 10H), 4.78 (s, 1H), 4.11-4.24 (m,
3H), 3.98 (d, J = 17.1 Hz, 1H), 3.71-3.81 (m, 1H), 3.50-3.63
(m, 1H), 2.80-2.96 (m, 2H), 2.49 (s, 3H), 2.40 (s, 3H), 0.87 (s,
9H). LCMS (ESI, M+1): 502.3.
equiv),
2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-
biphenyl (S-Phos) (3.92 mg, 0.096 mmol, 0.10 equiv) and
sodium t-butoxide (0.018 g, 0.191 mmol, 2 equiv). The reaction
o
was heated to 110 C for 21 h. Upon cooling to ambient
temperature, the reaction was diluted with EtOAc and washed
with water. The organic phase was dried (Na2SO4) and
concentrated in vacuo to provide the crude product as a brown
oil. LCMS (ESI, M+1): 535.8. The amine was taken up in
dioxane (2 mL) and MeOH (2 mL). 1 N NaOH (0.95 mL, 0.950
mmol, 10 equiv) was added. The reaction was heated at 75 °C
for 4.5 h. Upon cooling to ambient temperature, the reaction
was neutralized with 1 M HCl and then purified by preparative
HPLC to provide the product (21 mg, 41%). 1H NMR (500
MHz, DMSO-d6) δ 7.52 (d, J = 7.0 Hz, 2H), 7.45 (t, J = 7.6 Hz,
2H), 7.42 - 7.32 (m, 3H), 7.31 - 7.18 (m, 3H), 7.00 (d, J = 7.9
Hz, 1H), 6.90 (s, 1H), 6.76 (dd, J = 8.1, 2.0 Hz, 1H), 4.84 (s,
1H), 4.14 (d, J = 16.2 Hz, 1H), 3.83 - 3.77 (m, 1H), 3.74 (d, J =
16.2 Hz, 1H), 3.68 - 3.62 (m, 1H), 2.97 (br. s., 2H), 2.49 (s, 3H),
2.42 (s, 3H), 0.89 (s, 9H). LCMS (ESI, M+1): 521.5.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(S)-2-(6-([1,1'-Biphenyl]-2-ylmethyl)-2-methyl-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-
butoxy)acetic acid (16). A solution of methyl (S)-2-(tert-
butoxy)-2-(2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-
(S)-2-(6-([1,1'-Biphenyl]-4-yl)-2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-
butoxy)acetic acid (14). A solution of methyl (S)-2-(tert-
butoxy)-2-(2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate, HCl salt (41a) (0.040 g, 0.095 mmol,
1 equiv), TEA (0.013 mL, 0.095 mmol, 1 equiv) and 4-bromo-
1,1'-biphenyl (0.032 mL, 0.191 mmol, 2 equiv) in toluene (2
mL) was added to a mixture of trisdibenzylideneacetone
dipalladium chloroform complex (4.94 mg, 0.048 mmol, 0.05
naphthyridin-3-yl)acetate, HCl salt (41a) (0.030 g, 0.078 mmol,
1 equiv), 2-phenylbenzaldehyde (0.029 g, 0.157 mmol, 2
equiv), and DIPEA (0.014 mL, 0.078 mmol, 1 equiv) in DCE
(0.5 mL) was added a solution of sodium triacetoxyborohyride
(62 mg, 0.235 mmol, 3 equiv) in DCE (0.5 mL). After stirring
24 h, the reaction was concentrated. The residue was dissolved
in MeOH (0.75 mL) and 1 N NaOH (0.75 mL) was added. The
reaction was heated to 65 oC for 1 h. Upon cooling to ambient
temperature, the reaction was neutralized with AcOH (0.1 mL)
and then purified by preparative HPLC to provide the product
(23 mg, 55%). 1H NMR (500 MHz, DMSO-d6)  7.49 - 7.42
(m, 1H), 7.40 - 7.21 (m, 9H), 7.19 - 7.16 (m, 1H), 7.14 (d, J =
7.6 Hz, 1H), 7.03 (dd, J = 7.6, 1.5 Hz, 1H), 4.76 (s, 1H), 3.43 -
3.38 (m, 1H), 3.21 - 3.10 (m, 2H), 2.88 - 2.79 (m, 3H), 2.72 -
2.64 (m, 1H), 2.56 - 2.53 (m, 1H), 2.47 (s, 3H), 2.40 (s, 3H),
0.87 (s, 9H); LCMS (ESI,M+1): 535.4.
equiv),
2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-
biphenyl (S-Phos) (3.92 mg, 0.096 mmol, 0.10 equiv) and
sodium t-butoxide (0.018 g, 0.191 mmol, 2 equiv). The reaction
o
was heated to 110 C for 21 h. Upon cooling to ambient
temperature, the reaction was diluted with EtOAc and washed
with water. The organic phase was dried (Na2SO4) and
concentrated in vacuo to provide the product (0.035 g) as a
1
yellow oil. H NMR (400 MHz, CDCl3) δ 7.50-7.60 (m, 2H),
7.44 (t, J = 7.5 Hz, 2H), 7.21-7.40 (m, 5H), 7.14 (dd, J = 1.7,
7.8 Hz, 1H), 6.98-7.08 (m, 2H), 6.79 (dd, J = 2.0, 8.3 Hz, 1H),
5.01 (s, 1H), 4.11 (d, J = 16.4 Hz, 1H), 3.86 (d, J=16.4 Hz, 1H),
3.58-3.82 (m, 5H), 3.19 (q, J = 5.8 Hz, 2H), 2.65 (s, 3H), 2.48
(s, 3H), 1.01 (s, 9H). LCMS (ESI, M+1): 535.1. The amine
was taken up in dioxane (2 mL) and 1 N NaOH (0.65 mL, 0.650
mmol, 6.8 equiv) was added. The reaction was heated at 75 °C
for 1 h. Upon cooling to ambient temperature, the reaction was
neutralized with 1 M HCl (0.75 mL) and then purified by
preparative HPLC to provide the product (16 mg, 33%). 1H
NMR (500 MHz, DMSO-d6) δ .53 (d, J = 7.6 Hz, 2H), 7.46 (t,
J = 7.6 Hz, 2H), 7.33-7.43 (m, 3H), 7.22-7.33 (m, 3H), 7.01 (d,
J = 7.6 Hz, 1H), 6.92 (s, 1H), 6.77 (dd, J = 2.1, 8.2 Hz, 1H),
4.85 (s, 1H), 4.15 (d, J = 16.2 Hz, 1H), 3.78-3.86 (m, 1H), 3.75
(d, J = 16.5 Hz, 1H), 3.66 (td, J = 6.5, 13.3 Hz, 1H), 2.93-3.03
(m, 2H), 2.47-2.50 (m, 3H), 2.43 (s, 3H), 0.90 (s, 9H). LCMS
(ESI, M+1): 521.1.
(S)-2-(tert-Butoxy)-2-(6-(3-cyclopentylpropyl)-2-methyl-
4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic
acid (17). To a solution of (S)-2-(tert-butoxy)-2-(2-methyl-4-
(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid
(S3) (20 mg, 0.54 mmol, 1 equiv), 3-cyclopentylpropanal (12
mg, 0.95 mmol, 1.75 mmol), and AcOH (0.016 mL, 0.271
mmol, 5 equiv) in MeOH (1 mL) was added sodium
cyanoborohydride (17 mg, 0.271 mmol, 5 equiv). After stirring
18 h, the mixture was purified by preparative HPLC to provide
the product (13 mg, 50%) as an off white solid. 1H NMR (500
MHz, CD3OD) δ 7.41 (dd, J = 7.7, 1.7 Hz, 1H), 7.35 (d, J = 7.9
Hz, 1H), 7.25 (d, J = 7.7 Hz, 1H), 7.14 (d, J = 7.3 Hz, 1H), 4.80
(s, 1H), 3.92 (d, J = 15.3 Hz, 1H), 3.51-3.61 (m, 2H), 3.26-3.31
(m, 2H), 3.11-3.17 (m, 1H), 2.88-3.05 (m, 2H), 2.64 (s, 3H),
2.45 (s, 3H), 1.69-1.80 (m, 3H), 1.49-1.67 (m, 7H), 1.31 (m,
2H), 1.00-1.10 (m, 2H), 0.92 (s, 9H); LCMS (ESI, M+1): 479.5.
(S)-2-(6-([1,1'-Biphenyl]-3-yl)-2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-
butoxy)acetic acid (15). A solution of methyl (S)-2-(tert-
butoxy)-2-(2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate, HCl salt (41a) (0.040 g, 0.095 mmol,
(S)-2-(tert-Butoxy)-2-(2-methyl-6-pentyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (18). A
solution of methyl (S)-2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
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Journal of Medicinal Chemistry
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-
1
2
3
4
5
6
7
8
(41a) (0.030 g, 0.078 mmol, 1 equiv), pentanal (0.014 g, 0.157
mmol, 2 equiv), and DIPEA (0.014 mL, 0.078 mmol, 1 equiv)
yl)acetate, HCl (41a) (0.040 g, 0.095 mmol, 1 equiv.) in THF
(2 mL) was added TEA (0.032 mL, 0.229 mmol, 2.2 equiv) and
methyl chloroformate (11 mg, 0.115 mmol, 1.2 equiv). The
reaction was stirred at room temperature for 1 h and then diluted
with EtOAc. The mixture was washed with water and the
organic phase was dried (Na2SO4 and concentrated in vacuo.
LCMS (ESI, M+1): 441.1. The crude carbamate was taken up
in dioxane (2 mL) and 1 N NaOH (0.95 mL, 0.95 mmol, 10
in DCE (0.5 mL) was added
a solution of sodium
triacetoxyborohyride (62 mg, 0.235 mmol, 3 equiv) in DCE (0.5
mL). After stirring 24 h, the reaction was concentrated. The
residue was dissolved in MeOH (0.75 mL) and 1 N NaOH (0.75
mL) was added. The reaction was heated to 65 oC for 1 h. Upon
cooling to ambient temperature, the reaction was neutralized
with AcOH (0.1 mL) and then purified by preparative HPLC to
provide the product (28 mg, 81%). 1H NMR (500 MHz,
DMSO-d6)  7.33 (dd, J = 17.4, 7.9 Hz, 2H), 7.19 (d, J = 7.6
Hz, 1H), 7.13 (dd, J = 7.9, 1.5 Hz, 1H), 4.77 (s, 1H), 3.23 - 3.16
(m, 1H), 2.93 - 2.84 (m, 3H), 2.81 - 2.74 (m, 1H), 2.62 - 2.55
(m, 1H), 2.48 (s, 3H), 2.40 (s, 3H), 2.29 (t, J = 7.2 Hz, 2H), 1.33
(quin, J = 7.2 Hz, 2H), 1.27 - 1.15 (m, 4H), 0.88 (s, 9H), 0.82
(t, J = 6.9 Hz, 3H); LCMS (ESI, M+1): 439.4.
o
equiv) was added. The reaction was heated to 75 C for 1 h.
9
Upon cooling to ambient temperature, the mixture was
neutralized with 1 N HCl (1.9 mL) and then purified by
preparative HPLC to give the product (23 mg, 56%). 1H NMR
(500 MHz, DMSO-d6) δ 7.21-7.43 (m, 3H), 7.15 (d, J = 7.9 Hz,
1H), 4.73 (br. s., 1H), 4.14-4.34 (m, 1H), 3.87-3.99 (m, 1H),
3.67-3.82 (m, 1H), 3.56 (br. s., 4H), 2.87 (t, J = 5.8 Hz, 2H),
2.49 (s, 3H), 2.41 (s, 3H), 0.86 (s, 9H); LCMS (ESI, M+1):
427.3.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(S)-2-(tert-Butoxy)-2-(2,6-dimethyl-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetic acid (19). To a
solution of methyl 2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt
(41a) (0.042 g, 0.10 mmol, 1 equiv) in THF (1 mL) and acetic
acid (0.33 mL) was added 37% formaldehyde (0.011 mL, 0.150
mmol, 1.5 equiv) and NaBH(OAc)3 (0.033 g, 0.150 mmol, 1.5
equiv). The resulting mixture was stirred at room temperature
for 2 h. The mixture was then purified by preparative HPLC to
provide the product (0.040 g) as a white paste. The tertiary
amine was then taken up in dioxane (3 mL) and 1 N NaOH (0.10
mL, 0.100 mmol, 1 equiv) was added. The reaction was heated
(S)-2-(tert-Butoxy)-2-(2-methyl-6-(methylsulfonyl)-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid
(22). To a solution of methyl 2-(tert-butoxy)-2-(2-methyl-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl
salt (41a) (0.042 g, 0.100 mol, 1 equiv) in DCM (2 mL) was
added TEA (0.049 mL, 0.350 mmol). The solution cooled to 0
°C (ice/water) and MsCl (8 µl, 0.100 mmol, 1 equiv) was added.
After 1.5 h, the reaction was quenched with saturated aqueous
NaHCO3. The reaction was partitioned between EtOAc and
water. The organic phase was dried (Na2SO4) and concentrated
in vacuo to provide the product (0.052 g) as a colorless oil that
crystallized upon standing. 1H NMR (400 MHz, CDCl3) δ 7.22-
7.35 (m, 2H), 7.16 (dd, J = 1.8, 7.7 Hz, 1H), 7.04 (dd, J = 1.71,
7.6 Hz, 1H), 4.93 (s, 1H), 4.11 (d, J = 16.1 Hz, 1H), 3.84 (d,
J=16.1 Hz, 1H), 3.70 (s, 3H), 3.51-3.69 (m, 2H), 3.15 (t, J = 6.0
Hz, 2H), 2.76 (s, 3H), 2.62 (s, 3H), 2.44 (s, 3H), 0.98 (s, 9H).
LCMS (ESI, M+1): 461.3. The sulfonamide was taken up in
dioxane (3 mL) and 1 N NaOH (1.0 mL, 1.00 mmol, 10 equiv)
o
to 70 C for 1 h. Upon cooling to ambient temperature, the
mixture was neutralized with 1 N HCl and then purified by
1
preparative HPLC to give the product (14 mg, 39%). H NMR
(500 MHz, DMSO-d6)  7.32 (dd, J = 7.9, 15.6 Hz, 2H), 7.24
(d, J = 7.3 Hz, 1H), 7.12 (dd, J=1.5, 7.63 Hz, 1H), 4.73 (s, 1H),
3.16 (s, 1H), 2.77-2.95 (m, 2H), 2.68-2.77 (m, 1H), 2.54-2.60
(m, 1H), 2.48 (s, 3H), 2.39 (s, 3H), 2.21 (s, 3H), 0.86 (s, 9H).
LCMS (ESI, M+1): 383.3.
o
was added. The reaction was heated to 70 C for 1 h. Upon
cooling to ambient temperature, the mixture was neutralized
with 1 N HCl and then purified by preparative HPLC to give
the product (39 mg, 88%). 1H NMR (500 MHz, DMSO-d6) δ
7.36 (dd, J = 7.9, 15.6 Hz, 2H), 7.27 (d, J = 7.6 Hz, 1H), 7.17
(dd, J = 1.7, 7.8 Hz, 1H), 4.75 (s, 1H), 4.11 (d, J = 15.6 Hz, 1H),
3.69 (d, J = 15.6 Hz, 1H), 3.56 (td, J = 5.7, 11.9 Hz, 1H), 3.40-
3.47 (m, 1H), 3.00 (t, J = 6.0 Hz, 2H), 2.86 (s, 3H), 2.52 (d, J =
1.8 Hz, 3H), 2.41 (s, 3H), 0.87 (s, 9H). LCMS (ESI, M+1):
447.3.
(S)-2-(6-Acetyl-2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-
1,6-naphthyridin-3-yl)-2-(tert-butoxy)acetic acid (20). To a
solution of methyl (S)-2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl (41a)
(0.040 g, 0.095 mmol, 1 equiv) in DCM (2 mL) was added
DIPEA (0.050 mL, 0.286 mmol, 3 equiv) followed by acetyl
chloride (0.007 mL, 0.105 mmol, 1.1 equiv). The reaction was
stirred for 18 h. Additional acetyl chloride (0.007 mL, 0.105
mmol, 1.1 equiv) and DIPEA (0.050 mL, 0.286 mmol, 3 equiv)
was added. The reaction was stirred an additional 6 h. The
mixture was dilted with EtOAc and washed with water. The
organic phase was dried (Na2SO4) and concentrated in vacuo to
give crude amide. The amide was taken up in dioxane (2 mL)
and 1 N NaOH (0.95 mL, 0.95 mmol, 10 equiv) was added. The
reaction was heated to 70 oC for 1 h. Upon cooling to ambient
temperature, the mixture was neutralized with 1 N HCl (0.95
mL) and then purified by preparative HPLC to give the product
(7 mg, 18%). 1H NMR (500 MHz, DMSO-d6) δ 7.36 (dd, J =
7.5, 16.0 Hz, 2H), 7.10-7.29 (m, 2H), 4.74-4.85 (m, 1H), 3.57-
3.84 (m, 2H), 2.79-3.02 (m, 2H), 2.54-2.68 (m, 2H), 2.50 (br.
s., 3H), 2.42 (s, 3H), 1.81-2.08 (m, 3H), 0.82-0.93 (m, 9H);
LCMS (ESI, M+1): 411.1.
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-2-methyl-6-(3-phenylpropyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetic acid (23). To a solution of methyl
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl salt (41b) (30 mg, 0.066 mmol,
1 equiv), 3-
phenylpropionaldehyde (0.026 mL, 0.197 mmol, 3 equiv), and
DIPEA (0.034 mL, 0.197 mmol, 3 equiv) in MeOH (0.5 mL)
was added sodium cyanoborohydride (21 mg, 0.329 mmol, 5
equiv). After 2 h, the reaction was diluted with ether and
washed with saturated aqueous sodium bicarbonate and brine.
The ether layer was dried (MgSO4) and concentrated in vacuo.
The crude amine was taken up in MeOH (0.5 mL) and water
(0.1 mL). Lithium hydroxide monohydrate (28 mg, 0.661
mmol, 10 equiv) was added and the reaction was heated at 80
oC for 2 h. Upon cooling to ambient temperature, the mixture
was purified by preparative HPLC to give the product (25 mg,
(S)-2-(tert-Butoxy)-2-(6-(methoxycarbonyl)-2-methyl-4-
(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic
acid (21). To a solution of methyl (S)-2-(tert-butoxy)-2-(2-
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Journal of Medicinal Chemistry
Page 10 of 17
54%). 1H NMR (500 MHz, DMSO-d6) δ 7.28 - 7.24 (m, J =
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
1
2
3
4
5
6
7
8
7.6 Hz, 2H), 7.19 - 7.13 (m, J = 8.2 Hz, 3H), 6.71 (d, J = 11.0
Hz, 1H), 4.20 (t, J = 5.2 Hz, 2H), 2.93 - 2.86 (m, J = 5.5 Hz,
3H), 2.73 - 2.64 (m, J = 3.7, 1.6, 1.6 Hz, 4H), 2.58 - 2.53 (m,
2H), 2.43 - 2.40 (m, 2H), 2.39 - 2.32 (m, 4H), 2.02 (dd, J = 6.7,
4.6 Hz, 2H), 1.79 (s, 3H), 1.70 - 1.63 (m, J = 6.4 Hz, 2H); LCMS
(ESI, M+1): 561.5.
6-yl)-2-methyl-6-(3-(p-tolyl)propyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetic acid (26). To a of solution of methyl
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl salt (41b) (20 mg, 0.041 mmol, 1 equiv), 3-(p-
tolyl)propanal (18 mg, 0.122 mmol, 3 equiv), and DIPEA
(0.021 mL, 0.122 mmol, 3 equiv) in MeOH (0.5 mL) was added
sodium cyanoborohydride (13 mg, 0.203 mmol, 5 equiv). After
18 h, the reaction was diluted with ether and washed with
saturated aqueous sodium bicarbonate and brine. The ether
layer was dried (MgSO4) and concentrated in vacuo. The crude
amine was taken up in MeOH (0.4 mL) and water (0.04 mL).
Lithium hydroxide (10 mg, 0.391 mmol, 10 equiv) was added
and the reaction was heated at 80 oC for 2 h. Upon cooling to
ambient temperature, the mixture was purified by preparative
HPLC to give the product (18 mg, 76%). 1H NMR (500 MHz,
DMSO-d6) δ 7.96 (s, 1H), 7.06 - 7.02 (m, 2H), 7.02 - 6.98 (m,
2H), 6.66 (d, J = 11.3 Hz, 1H), 4.69 (s, 1H), 4.20 (t, J = 5.0 Hz,
2H), 2.96 (d, J = 15.3 Hz, 1H), 2.89 - 2.79 (m, 3H), 2.70 - 2.61
(m, 4H), 2.54 (s, 3H), 2.49 - 2.45 (m, 2H), 2.29 (t, J = 6.7 Hz,
2H), 2.25 (s, 3H), 2.02 (q, J = 5.5 Hz, 2H), 1.75 (s, 3H), 1.61
(quin, J = 7.1 Hz, 2H), 1.01 (s, 9H); LCMS (ESI, M+1): 575.6.
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-2-methyl-6-(((1S,2R)-2-phenylcyclopropyl)methyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid and
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-6-
yl)-2-methyl-6-(((1R,2S)-2-phenylcyclopropyl)methyl)-
5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (24,
1:1 mixture). A solution of methyl (S)-2-(tert-butoxy)-2-((R)-
4-(8-fluoro-5-methylchroman-6-yl)-2-methyl-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt (41b) (20
mg, 0.041 mmol, 1 equiv), 2-phenylcyclopropanecarbaldehyde
(S9) (9 mg, 0.061 mmol, 1.5 equiv), sodium cyanoborohydride
(13 mg, 0.203, 5 equiv), and DIPEA (0.021 mL, 0.122 mmol, 3
equiv) in MeOH (1 mL) was stirred for 2 h. More 2-
phenylcyclopropanecarbaldehyde (S9) (9 mg, 0.061 mmol, 1.5
equiv) and sodium cyanoborohydride (13 mg, 0.203, 5 equiv)
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
were
added.
After
1
h,
more
2-
phenylcyclopropanecarbaldehyde (S9) (9 mg, 0.061 mmol, 1.5
equiv) and sodium cyanoborohydride (13 mg, 0.203, 5 equiv)
were added. After 1 h, the reaction was added to saturated
sodium bicarbonate and extracted with DCM (x3). The
combined DCM extracts were dired (Na2SO4) and concentrated
in vacuo. The crude amine was taken up in MeOH (1 mL) and
water (0.1 mL). Lithium hydroxide monohydrate (17 mg, 0.406
mmol, 10 equiv) was added and the reaction was heated at 60
oC for 40 min. Upon cooling to ambient temperature, the
mixture was purified by preparative HPLC to give the product
(12 mg, 52%) as a diastereomeric mixture. 1H NMR (500
MHz, DMSO-d6) δ 7.21 - 7.05 (m, 4H), 6.92 - 6.91 (m, 1H),
6.63 - 6.57 (m, 1H), 4.67 (d, J = 4 Hz, 1H), 4.20 (d, J = 4 Hz,
2H), 2.89 – 1.69 (m, 18H), 1.15 (m, 1H), 0.99 (s, 9H), 0.93 –
0.89 (m, 1H), 0.71 – 0.67 (m, 1H); LCMS (ESI, M+1): 573.6.
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-6-(3-(3-fluorophenyl)propyl)-2-methyl-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetic acid (27). To a of
solution of methyl (S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate, HCl salt (41b) (20 mg, 0.041 mmol,
1 equiv), 3-(3-fluorophenyl)propanal (19 mg, 0.122 mmol, 3
equiv), and DIPEA (0.021 mL, 0.122 mmol, 3 equiv) in MeOH
(0.5 mL) was added sodium cyanoborohydride (13 mg, 0.203
mmol, 5 equiv). After 18 h, the reaction was diluted with ether
and washed with saturated aqueous sodium bicarbonate and
brine. The ether layer was dried (MgSO4) and concentrated in
vacuo. The crude amine was taken up in MeOH (0.4 mL) and
water (0.04 mL). Lithium hydroxide (10 mg, 0.391 mmol, 10
equiv) was added and the reaction was heated at 80 oC for 1 h.
Upon cooling to ambient temperature, the mixture was purified
by preparative HPLC to give the product (30 mg, 100%). 1H
NMR (500 MHz, DMSO-d6) δ 7.28 (dd, J = 7.9, 7.0 Hz, 1H),
6.97 (d, J = 11.0 Hz, 3H), 6.66 (d, J = 11.9 Hz, 1H), 4.69 (s,
1H), 4.19 (t, J = 4.9 Hz, 3H), 2.96 (d, J = 15.9 Hz, 2H), 2.89 -
2.80 (m, 4H), 2.65 (dd, J = 18.9, 11.3 Hz, 3H), 2.58 - 2.53 (m,
6H), 2.30 (t, J = 6.7 Hz, 2H), 2.01 (d, J = 5.5 Hz, 2H), 1.74 (s,
3H), 1.69 - 1.60 (m, 2H), 1.00 (s, 9H); LCMS (ESI, M+1):
579.6.
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-6-(3-(4-fluorophenyl)propyl)-2-methyl-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetic acid (25). To a
solution of methyl (S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate, HCl salt (41b) (30 mg, 0.066 mmol,
1 equiv), 1-fluoro-4-(3-iodopropyl)benzene (52 mg, 0.197
mmol, 3 equiv), and DIPEA (0.034 mL, 0.197 mmol, 3 equiv)
in MeCN (0.5 mL) was added sodium cyanoborohydride (19
mg, 0.330 mmol, 5 equiv). THe reaction was stirred for 6 d.
Upon completion, the reaction was concentrated in vacuo. The
crude amine was taken up in MeOH (0.5 mL) and water (0.1
mL). Lithium hydroxide monohydrate (28 mg, 0.661 mmol, 10
equiv) was added and the reaction was heated at 80 oC for 2 h.
Upon cooling to ambient temperature, the mixture was purified
by preparative HPLC to give the product (30 mg, 68%). 1H
NMR (500 MHz, DMSO-d6) δ 7.20 - 7.15 (m, J = 8.5, 5.8 Hz,
2H), 7.09 - 7.04 (m, 2H), 6.69 (d, J = 11.3 Hz, 1H), 4.72 (s, 1H),
4.21 (t, J = 5.2 Hz, 2H), 2.98 (d, J = 15.0 Hz, 1H), 2.90 - 2.85
(m, 2H), 2.82 (d, J = 15.3 Hz, 1H), 2.72 - 2.63 (m, 4H), 2.56 -
2.53 (m, 4H), 2.31 (t, J = 7.0 Hz, 2H), 2.06 - 1.99 (m, J = 5.2
Hz, 2H), 1.75 (s, 3H), 1.64 (quin, J = 7.4 Hz, 2H), 1.02 (s, 9H);
LCMS (ESI, M+1): 579.4.
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-2-methyl-6-(3-(m-tolyl)propyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetic acid (28). To a of solution of methyl
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl salt (41b) (20 mg, 0.041 mmol, 1 equiv), 3-(m-
tolyl)propanal (18 mg, 0.122 mmol, 3 equiv), and DIPEA
(0.021 mL, 0.122 mmol, 3 equiv) in MeOH (0.5 mL) was added
sodium cyanoborohydride (13 mg, 0.203 mmol, 5 equiv). After
18 h, the reaction was diluted with ether and washed with
saturated aqueous sodium bicarbonate and brine. The ether
layer was dried (MgSO4) and concentrated in vacuo. The crude
amine was taken up in MeOH (0.4 mL) and water (0.04 mL).
Lithium hydroxide (9 mg, 0.391 mmol, 10 equiv) was added
and the reaction was heated at 80 oC for 1 h. Upon cooling to
ambient temperature, the mixture was purified by preparative
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Page 11 of 17
Journal of Medicinal Chemistry
HPLC to give the product (20 mg, 85%). 1H NMR (500 MHz,
methylphenyl)propanal (20 mg, 0.122 mmol, 3 equiv), and
1
2
3
4
5
6
7
8
DMSO-d6) δ 6.86 (t, J = 7.5 Hz, 1H), 6.73 - 6.66 (m, 2H), 6.63
(d, J = 7.3 Hz, 1H), 6.39 (d, J = 11.3 Hz, 1H), 4.43 (s, 1H), 3.92
(br. s., 2H), 2.72 (d, J = 15.0 Hz, 1H), 2.64 - 2.54 (m, 3H), 2.42
(br. s., 2H), 2.37 (br. s., 2H), 2.30 - 2.27 (m, 3H), 2.25 (br. s.,
3H), 2.24 - 2.20 (m, 2H), 2.04 (t, J = 6.7 Hz, 2H), 1.98 (s, 3H),
1.74 (d, J = 5.2 Hz, 2H), 1.48 (s, 3H), 1.39 - 1.32 (m, J = 6.9,
6.9 Hz, 2H), 0.74 (s, 9H); LCMS (ESI, M+1): 575.6.
DIPEA (0.021 mL, 0.122 mmol, 3 equiv) in MeOH (0.5 mL)
was added sodium cyanoborohydride (13 mg, 0.203 mmol, 5
equiv). After 18 h, the reaction was diluted with ether and
washed with saturated aqueous sodium bicarbonate and brine.
The ether layer was dried (MgSO4) and concentrated in vacuo.
The crude amine was taken up in MeOH (0.4 mL) and water
(0.04 mL). Lithium hydroxide (9 mg, 0.391 mmol, 10 equiv)
was added and the reaction was heated at 80 oC for 1 h. Upon
cooling to ambient temperature, the mixture was purified by
S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-6-(3-(2-fluorophenyl)propyl)-2-methyl-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetic acid (29). To a of
solution of methyl (S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-
9
1
preparative HPLC to give the product (19 mg, 66%). H NMR
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(500 MHz, DMSO-d6) δ 7.96 (s, 1H), 7.03 (d, J = 7.6 Hz, 1H),
6.97 (d, J = 9.2 Hz, 2H), 6.66 (d, J = 11.3 Hz, 1H), 4.68 (s, 1H),
4.20 (t, J = 4.9 Hz, 2H), 2.98 (d, J = 15.3 Hz, 1H), 2.89 - 2.79
(m, 3H), 2.72 - 2.60 (m, 4H), 2.54 (s, 3H), 2.30 (t, J = 6.7 Hz,
2H), 2.18 (s, 3H), 2.06 - 1.97 (m, J = 5.2 Hz, 2H), 1.75 (s, 3H),
1.62 (quin, J = 7.1 Hz, 2H), 1.01 (s, 9H); LCMS (ESI, M+1):
593.6.
naphthyridin-3-yl)acetate, HCl salt (41b) (20 mg, 0.041 mmol,
1 equiv), 3-(2-fluorophenyl)propanal (19 mg, 0.122 mmol, 3
equiv), and DIPEA (0.021 mL, 0.122 mmol, 3 equiv) in MeOH
(0.5 mL) was added sodium cyanoborohydride (13 mg, 0.203
mmol, 5 equiv). After 18 h, the reaction was diluted with ether
and washed with saturated aqueous sodium bicarbonate and
brine. The ether layer was dried (MgSO4) and concentrated in
vacuo. The crude amine was taken up in MeOH (0.4 mL) and
water (0.04 mL). Lithium hydroxide (9 mg, 0.391 mmol, 10
equiv) was added and the reaction was heated at 80 oC for 2 h.
Upon cooling to ambient temperature, the mixture was purified
by preparative HPLC to give the product (15 mg, 63%). 1H
NMR (500 MHz, DMSO-d6) δ 7.96 (s, 1H), 7.28 (dd, J = 9.2,
7.3 Hz, 1H), 7.01 - 6.93 (m, 3H), 6.66 (d, J = 11.3 Hz, 1H), 4.69
(s, 1H), 4.19 (t, J = 4.9 Hz, 2H), 2.97 (d, J = 15.3 Hz, 1H), 2.88
- 2.79 (m, 3H), 2.68 (t, J = 5.6 Hz, 2H), 2.66 - 2.61 (m, 2H),
2.59 - 2.53 (m, 5H), 2.30 (t, J = 6.6 Hz, 2H), 2.01 (d, J = 4.9
Hz, 2H), 1.75 (s, 3H), 1.65 (quin, J = 7.2 Hz, 2H), 1.01 (s, 9H);
LCMS (ESI, M+1): 579.6.
(2S)-2-(tert-butoxy)-2-(4-(8-fluoro-5-methylchroman-6-
yl)-2-methyl-6-(3-(pyridin-4-yl)propyl)-5,6,7,8-tetrahydro-
1,6-naphthyridin-3-yl)acetic acid, 1:1 mixture of
atropisomers (32). To a of solution of 1 mixture of
atropisomers of methyl (S)-2-(tert-butoxy)-2-(4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate, HCl salt (41b) (26 mg, 0.049 mmol,
1 equiv), 3-(pyridin-4-yl)propanal (20 mg, 0.1472 mmol, 3
equiv), and TEA (0.246 mL, 0.122 mmol, 5 equiv) in MeOH (1
mL) was added sodium cyanoborohydride (15 mg, 0.246 mmol,
5 equiv). After 2 h, the reaction was diluted with ethyl acetate
and washed with saturated aqueous sodium bicarbonate and
brine. The ethyl acetate layer was dried (Na2SO4) and
concentrated in vacuo. The crude amine was taken up in MeOH
(1 mL) and water (0.1 mL). Lithium hydroxide (21 mg, 0.491
mmol, 10 equiv) was added and the reaction was stirred for 18
h. The mixture was purified by preparative HPLC to give the
product (7 mg, 25%) as a mixture of atropisomers. 1H NMR
(500 MHz, DMSO-d6) δ 8.49 – 8.47 (m, 2H), 7.10 – 7.08 (m,
2H), 6.99 - 6.91 (m, 1H, atropisomer 1), 6.59 - 6.57 (m, 1H,
atropisomer 2), 4.67 (bs, 1H), 4.30 – 4.26 (m, 2H), 3.20 – 1.72
(m, 19H), 1.12 (s, 9H, atropisomer 1), 1.01 (s, 9H, atropisomer
2); LCMS (ESI, M+1): 562.2.
(S)-2-(tert-Butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-
6-yl)-2-methyl-6-(3-(o-tolyl)propyl)-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetic acid (30). To a of solution of methyl
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetate,
HCl salt (41b) (20 mg, 0.041 mmol, 1 equiv), 3-(o-
tolyl)propanal (18 mg, 0.122 mmol, 3 equiv), and DIPEA
(0.021 mL, 0.122 mmol, 3 equiv) in MeOH (0.5 mL) was added
sodium cyanoborohydride (13 mg, 0.203 mmol, 5 equiv). After
18 h, the reaction was diluted with ether and washed with
saturated aqueous sodium bicarbonate and brine. The ether
layer was dried (MgSO4) and concentrated in vacuo. The crude
amine was taken up in MeOH (0.4 mL) and water (0.04 mL).
Lithium hydroxide (9 mg, 0.391 mmol, 10 equiv) was added
and the reaction was heated at 80 oC for 1 h. Upon cooling to
ambient temperature, the mixture was purified by preparative
HPLC to give the product (19 mg, 81%). 1H NMR (500 MHz,
DMSO-d6) δ 6.87 - 6.76 (m, 4H), 6.40 (d, J = 11.3 Hz, 1H), 4.42
(s, 1H), 3.94 (br. s., 2H), 2.74 (d, J = 15.6 Hz, 1H), 2.64 (s, 1H),
2.63 - 2.54 (m, 3H), 2.48 (s, 1H), 2.46 - 2.33 (m, 3H), 2.10 (t, J
= 6.6 Hz, 2H), 1.94 (s, 3H), 1.76 (d, J = 4.6 Hz, 2H), 1.50 (s,
3H), 1.36 - 1.28 (m, J = 6.7 Hz, 2H), 0.75 (s, 9H); LCMS (ESI,
M+1): 575.6.
8-fluoro-5-methylchromane-6-carbaldehyde (34). To a
solution of 6-bromo-8-fluoro-5-methylchroman (10 g, 36.7
mmol, 1 equiv) (prepared following the procedure in
WO2010130842) in THF (200 mL) at -78 °C IPA/dry ice) was
added n-BuLi (22 mL of a 2.5 M solution in hexane, 55.1 mmol,
1.5 equiv) dropwise. After stirring for 30 min, DMF (5.69 mL,
73.4 mmol, 2 equiv) was added dropwise. Upon complete
addition, the reaction was warmed to 0°C (ice bath). After 30
min, the reaction was quenched with saturated aqueous NH4Cl.
The mixture was diluted with ether, washed with water, dried
(Na2SO4), and concentrated in vacuo to provide the crude
product as a reddish brown crystalline solid. The crude product
was triturated in a small amount of ether and hexane to deliver
the product (6.7 g, 94%) as creamy tan crystalline solid. 1H
NMR (400 MHz, CDCl3) δ 10.18 (d, J = 2.0 Hz, 1H), 7.43 (d, J
= 11.3 Hz, 1H), 4.33 - 4.26 (m, 2H), 2.74 (t, J = 6.7 Hz, 2H),
2.51 (s, 3H), 2.15 - 2.08 (m, 2H).
(S)-2-(tert-Butoxy)-2-((R)-6-(3-(3-fluoro-4-
methylphenyl)propyl)-4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic
acid (31). To a of solution of methyl (S)-2-(tert-butoxy)-2-((R)-
4-(8-fluoro-5-methylchroman-6-yl)-2-methyl-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetate, HCl salt (41b) (20
6-Benzyl 3-methyl 2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-
naphthyridine-3,6(5H)-dicarboxylate (37a). A solution of
LiHMDS (4.72 mL of a 1 N solution in THF, 4.72 mmol, 1.1
equiv) in THF (3 mL) was cooled to -78 °C. A solution of
mg,
0.041
mmol,
1
equiv),
3-(3-fluoro-4-
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Journal of Medicinal Chemistry
Page 12 of 17
benzyl 4-oxopiperidine-1-carboxylate (1.0 g, 4.29 mmol, 1 5.17 - 5.09 (m, 2H), 4.30 - 4.23 (m, 2H), 4.22 - 4.15 (m, 2H),
1
2
3
4
5
6
7
8
equiv) in THF (3.00 mL) was added dropwise over several
minutes. After stirring for 10 min at -78 °C, the solution was
allowed to warm to -20 °C and stirred for 15 min before cooling
to -78 °C again. A cold (-78 °C) solution of methyl 2-(4-
methylbenzylidene)-3-oxobutanoate (0.936 g, 4.29 mmol, 1
equiv) in THF (1.5 mL) was added via cannula and the resulting
yellow solution was stirred at -40 °C for 3 h. The reaction was
quenched with AcOH (1.23 mL, 21.44 mmol, 5 equiv) and
allowed to warm to ambient temperature. Water was added and
the aqueous phase was extracted with EtOAc (x3). The
combined organic phases were washed with brine, dried
(Na2SO4), and concentrated in vacuo to give the Michael
addition product as a brown oil (LCMS [M+1] = 452.4). The
oil was taken up in EtOH (12 mL) and stirred with NH4OAc
(2.64 g, 34.3 mmol, 8 equiv) and p-toluenesulfonic acid
monohydrate (0.041 g, 0.214 mmol, 0.05 equiv) at 80 °C. After
70 h, the mixture was allowed to cool to ambient temperature
and concentrated in vacuo to provide the dihydropyridine
intermediate as a thick amber oil. To the residue dissolved in
DCM (20 mL) was added cerium(IV) diammonium nitrate
(4.70 g, 8.57 mmol, 2 equiv) and TFA (0.330 mL, 4.29 mmol,
1 equiv). The resulting mixture stirred for 1.5 h. The reaction
mixture was then washed with water and the aqueous phase was
extracted with DCM (x2). The combined organic extracts were
dried (Na2SO4) and concentrated in vacuo. The crude product
was purified by silica gel flash column chromatography (0-
100% EtOAc/hexane) to give 6-benzyl 3-methyl 2-methyl-4-(p-
tolyl)-7,8-dihydro-1,6-naphthyridine-3,6(5H)-dicarboxylate
3.97 - 3.84 (m, 1H), 3.79 - 3.63 (m, 1H), 3.13 - 2.98 (m, 2H),
2.76 - 2.60 (m, 1H), 2.57 (s, 3H), 2.16 - 2.08 (m, 2H), 1.90 -
1.71 (m, 4H), 1.22 (s, 9H); LCMS (ESI, M+1): 547.35.
Benzyl 3-(2-methoxy-2-oxoacetyl)-2-methyl-4-(p-tolyl)-
7,8-dihydro-1,6-naphthyridine-6(5H)-carboxylate (39a). To
a suspension of 6-((benzyloxy)carbonyl)-2-methyl-4-(p-tolyl)-
5,6,7,8-tetrahydro-1,6-naphthyridine-3-carboxylic acid (S1)
(1.88 g, 4.51 mmol, 1 equiv) and DMF (cat.) in DCM (30 mL)
was added oxalyl chloride (11.3 mL of a 2 M solution in DCM,
22.55 mmol, 5 equiv). After 1 h, the mixture was concentrated
in vacuo and azeotroped with toluene (x2) to remove unreacted
oxalyl chloride. The residue was taken up in DCM (30 mL).
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
DIPEA (4.7 mL, 0.893 mmol,
6
equiv) and 1-
(cyanomethyl)tetrahydro-1H-thiophen-1-ium, bromide salt
(38) (1.74 g, 13.53 mmol, 3 equiv) were added. The reaction
was stirred for 20 h. The reaction was diluted with DCM,
washed with water, dried (Na2SO4), and concentrated in vacuo
to give an amber oil. The oil was dissolved in MeOH (60 mL).
A solution of Oxone (5.55 g, 9.02 mmol, 2 equiv) in water (30
mL) was added. The resulting suspension was stirred for 2 h.
The methanol was removed in vacuo and the remaining solution
extracted with EtOAc (x3). The combined organic extracts
were washed with brine, dried (Na2SO4), and concentrated in
vacuo. The crude product was purified by silica gel flash
chromatography (0-100% EtOAc/hexane) to the product (1.82
1
g, 88%) as a colorless oil. H NMR (400 MHz, CDCl3) δ 7.14-
7.51 (m, 7H), 6.92-7.11 (m, 2H), 5.13 (br. s., 2H), 4.28-4.52 (m,
2H), 3.44 (s, 3H), 3.25-3.38 (m, 2H), 3.11 (br. s., 2H), 2.50-2.63
(m, 3H), 2.41 (s, 3H); LCMS (ESI, M+1): 459.3.
1
(1.25 g, 67%) as an amber oil. H NMR (400 MHz, CDCl3) δ
7.34 (d, J = 4.4 Hz, 5H), 7.22 (d, J = 7.8 Hz, 2H), 7.07 (d, J =
7.8 Hz, 2H), 5.13 (s, 2H), 4.36 (s, 2H), 3.82 (t, J = 6.0 Hz, 2H),
3.54 (s, 3H), 3.07 (br. s., 2H), 2.57 (s, 3H), 2.41 (s, 3H). LCMS
(ESI, M+1): 431.4.
Benzyl 4-(8-fluoro-5-methylchroman-6-yl)-3-(2-methoxy-
2-oxoacetyl)-2-methyl-7,8-dihydro-1,6-naphthyridine-
6(5H)-carboxylate (39b).
To
a
solution of 6-
((benzyloxy)carbonyl)-4-(8-fluoro-5-methylchroman-6-yl)-2-
methyl-5,6,7,8-tetrahydro-1,6-naphthyridine-3-carboxylic acid
(S5) (2.42 g, 4.00 mmol, 1 equiv) from previous step and DMF
(0.046 mL, 0.60 mmol, 0.15 equiv) in DCM (40 mL) was added
oxalyl chloride (1.40 mL, 16.0 mmol, 4 equiv). Gas evolution!
After 1 h, the solution was concentrated in vacuo. The crude
acid chloride was taken up in DCM (40 mL) and DIPEA (4.19
mL, 24.0 mmol, 6 equiv) and 1-(cyanomethyl)tetrahydro-1H-
thiophen-1-ium, bromide salt (38) (2.50 g, 12.0 mmol, 3 equiv).
The mixture was stirred for 1 h, and then washed with saturated
aqueous sodium bicarbonate. The organic layer was dried
(Na2SO4) and concentrated in vacuo. The crude product was
purified by silica gel flash column chromatography (acetone) to
provide the sulfur ylide (1.11 g) as a tan solid. LCMS (ESI,
M+1): 600.35. The sulfur ylide was taken up in MeOH (19 mL)
and water (1 mL). Oxone (2.28 g, 3.70 mmol, 2 equiv) added.
Reaction is an orange slurry. After 18 h, the mixure was
cautiously added to saturated aqueous sodium bicarbonate and
extracted with ether (x3). The combined ether extracts were
dried (MgSO4) and concentrated in vacuo to provide the product
(1.07 g, 50% over 2 steps) as a tan foam. 1H NMR (400 MHz,
CDCl3) δ 7.43 - 7.29 (m, 5H), 6.58 (d, J = 10.8 Hz, 1H), 5.13
(br. s., 2H), 4.25 (t, J = 5.1 Hz, 4H), 3.91 (d, J = 3.5 Hz, 1H),
3.72 (s, 1H), 3.55 (s, 3H), 3.11 (br. s., 2H), 3.07 - 3.01 (m, 1H),
2.64 (s, 3H), 2.56 (s, 3H), 2.27 - 2.21 (m, 1H), 2.13 - 2.07 (m,
2H); LCMS (ESI, M+1): 533.35.
6-Benzyl 3-tert-butyl 4-(8-fluoro-5-methylchroman-6-yl)-
2-methyl-7,8-dihydro-1,6-naphthyridine-3,6(5H)-
dicarboxylate (37b). To a solution of LHMDS (9.9 mL of a 1
M solution in THF, 9.87 mmol, 1.1 equiv) in THF (15 mL) at -
78 oC (IPA/dry ice) was added dropwise a solution of benzyl 4-
oxopiperidine-1-carboxylate (2.09 g, 8.97 mmol, 1 equiv) in
THF (15 mL). After stirring 10 min, the temperature was raised
to -20 oC (IPA/dry ice) for 15 min and then recooled to -78 oC.
A solution of tert-butyl 2-((8-fluoro-5-methylchroman-6-
yl)methylene)-3-oxobutanoate (S4) (3.0 g, 8.97 mmol, 1 equiv)
in THF (15 mL) was added dropwise. After stirring 10 min, the
temperature was raised to -40 oC (MeCN/dry ice) and stirred for
3 h. The reaction was then quenched with AcOH and added to
water. The aqueous mixture was extracted with ether (x2). The
combined ether extracts were dried (MgSO4) and concentrated
in vacuo. The residue was taken up in EtOH (30 mL) and
ammonium acetate (6.9 g, 90 mmol, 10 equiv) was added. The
reaction was heated at reflux for 16 h. Upon cooling to ambient
temperature, the solution was concentrated in vacuo. The
residue was triturated with DCM and filtered. The filtrate was
then concentrated in vacuo. The crude dihydropyridine was
then taken up in MeOH (30 mL) and CAN (9.8 g, 17.9 mmol, 2
equiv) was added. After stirring 1 h, the mixture was added to
saturated aqueous sodium bicarbonate and extracted with ether
(x3). The combined ether extracts were dried (MgSO4) and
concentrated in vacuo. The crude product was purified by silica
gel flash column chromatography (0-100% EtOAc/hexane) to
provide the product (2.30 g, 47%) as a tan solid. 1H NMR (400
MHz, CDCl3) δ 7.42 - 7.30 (m, 5H), 6.64 (d, J = 11.0 Hz, 1H),
Benzyl (S)-3-(1-(tert-butoxy)-2-methoxy-2-oxoethyl)-2-
methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-
carboxylate (40a). To a solution of benzyl 3-(1-hydroxy-2-
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Page 13 of 17
Journal of Medicinal Chemistry
methoxy-2-oxoethyl)-2-methyl-4-(p-tolyl)-7,8-dihydro-1,6- (0.14 g, 0.131 mmol, 0.1 equiv) in MeOH (12 mL) was stirred
1
2
3
4
5
6
7
8
naphthyridine-6(5H)-carboxylate (S2) (0.10 g, 0.217 mmol, 1
equiv) in DCM (3 mL) was added tert-butyl acetate (2.05 mL,
15.2 mmol, 70 equiv) followed by 70% HClO4 (0.056 mL,
0.651 mmol, 3 equiv). The flask was sealed and stirred at room
temperature for 2.5 h. The reaction was quenched with
saturated aqueous NaHCO3 (gas evolution observed). The
organic phase was dried (Na2SO4) and concentrated in vacuo.
The crude product was purified by silica gel flash column
chromatography (0-30% EtOAc/hexanes) to provide the
under a balloon of hydrogen for 2 h. The reaction was then
filtered through Celite eluting with MeOH. The filtrate was
concentrated in vacuo to provide the HCl salt of the product
(0.56 g, 86%) as a white solid. LCMS (ESI, M+1): 457.35.
6-((Benzyloxy)carbonyl)-2-methyl-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridine-3-carboxylic acid (S1).
A
mixture of 6-benzyl 3-methyl 2-methyl-4-(p-tolyl)-7,8-
dihydro-1,6-naphthyridine-3,6(5H)-dicarboxylate (37a) (0.48
g, 1.12 mmol, 1 equiv) and lithium chloride (0.48 g, 11.19
mmol, 10 equiv) in 2,6-lutadine (10 mL) and DMSO (10 mL)
was stirred at 130 °C for 2 h. The mixture was allowed to cool
to ambient temperature, diluted with water, and washed with
EtOAc. The aqueous phase was made acidic with 1 N HCl and
extracted with EtOAc (x2) and DCM (x1). The combined
organic extracts were dried (Na2SO4) and concentrated in vacuo
to provide the product (74 mg, 15%) as an amber oil. 1H NMR
(400 MHz, CDCl3) δ 7.33 (br. s., 4H), 7.24 (d, J = 7.8 Hz, 3H),
7.13 (d, J = 7.6 Hz, 2H), 5.11 (s, 2H), 4.36 (s, 2H), 3.78 (t, J =
5.6 Hz, 2H), 3.30 (br. s., 2H), 2.80 (br. s., 3H), 2.38 (s, 3H);
LCMS (ESI, M+1): 417.4.
9
1
product (82 mg, 72%) as a colorless oil. H NMR (400 MHz,
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CDCl3) δ 7.01-7.78 (m, 9H), 5.13 (s, 2H), 4.97 (s, 1H), 4.29-
4.32 (m, 1H), 4.05-4.10 (m, 1H), 3.78-3.81 (m, 2H), 3.71 (s,
3H), 3.06 (bs, 2H), 2.64 (s, 3H), 2.45 (s, 3H) 0.99 (s, 9H).
LCMS (ESI, M+1): 517.4.
Benzyl (R)-3-((S)-1-(tert-butoxy)-2-methoxy-2-oxoethyl)-
4-(8-fluoro-5-methylchroman-6-yl)-2-methyl-7,8-dihydro-
1,6-naphthyridine-6(5H)-carboxylate (40b). To a solution of
(R)-benzyl
4-(8-fluoro-5-methylchroman-6-yl)-3-((S)-1-
hydroxy-2-methoxy-2-oxoethyl)-2-methyl-7,8-dihydro-1,6-
naphthyridine-6(5H)-carboxylate (S6) (0.91 g, 1.71 mmol, 1
equiv) in DCM (10 ml) and tert-butyl acetate (16 ml) was added
70% perchloric acid (0.44 mL, 5.12 mmol, 3 equiv). After 1 h,
the reaction is a white slurry so chloroform (10 mL) was added.
Reaction is now a homogenous solution. After stirring 2 h
more, the reaction was diluted with DCM and washed with
saturated aqueous sodium bicarbonate, water, and brine. The
organic layer was dried (Na2SO4) and concentrated in vacuo.
The crude product was purified by flash column silica gel
chromatography (0-100% EtOAc/hex) to provide the product
(0.49 g, 49%) as an off white solid. Starting alcohol was also
recovered (0.31 g, 34%). 1H NMR (400 MHz, CDCl3) δ 7.41 -
7.29 (m, 5H), 6.59 (d, J = 11.0 Hz, 1H), 5.12 (br. s., 2H), 4.93
(s, 1H), 4.34 - 4.24 (m, J = 4.8 Hz, 2H), 4.05 (br. s., 2H), 3.86
(dt, J = 13.3, 5.9 Hz, 1H), 3.72 (dd, J = 11.3, 4.5 Hz, 1H), 3.61
(s, 3H), 3.10 - 2.96 (m, 2H), 2.69 (s, 3H), 2.14 (br. s., 2H), 1.86
- 1.67 (m, 3H), 1.55 (s, 3H), 1.11 (s, 9H); 19F NMR (376 MHz,
CDCl3) δ -140.06 (br. s., 1F); LCMS (ESI, M+1): 591.45.
Benzyl 3-(1-hydroxy-2-methoxy-2-oxoethyl)-2-methyl-4-
(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-carboxylate
(S2). A solution of benzyl 3-(2-methoxy-2-oxoacetyl)-2-
methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-
carboxylate (39a) (2.53 g, 5.52 mmol, 1 equiv) and R-5,5-
diphenyl-2-methyl-3,4-propano-1,3,2-oxazaborlidine (2.21 mL
of a 1 M solution in toluene, 2.21 mmol, 0.4 equiv) in toluene
(100 mL) was cooled to -35 °C. Catecholborane (1.65 mL of a
50% weight solution in toluene, 7.73 mmol, 1.5 equiv) was
added dropwise and the solution stirred at -35 °C for 30 min
then at -15 °C for 2 h. The reaction was diluted with EtOAc and
stirred vigorously with saturated aqueous Na2CO3 for 1 h. The
organic phase was washed with saturated aqueous Na2CO3 (x2),
dried (Na2SO4), and concentrated in vacuo. The crude product
was purified by silica gel flash column chromatography (0-
100% EtOAc/hexane) to provide the product (1.29 g, 50%) as a
white foam. 1H NMR (400 MHz, CDCl3) δ 7.20-7.49 (m, 7H),
7.08 (t, J = 8.7 Hz, 2H), 5.11 (d, J = 15.7 Hz, 3H), 4.22 (br. s.,
2H), 3.67-3.89 (m, 5H), 3.14 (d, J = 2.5 Hz, 1H), 2.99-3.11 (m,
2H), 2.55 (s, 3H), 2.43 (s, 3H). LCMS (ESI, M+1): 461.0.
Methyl 2-(tert-Butoxy)-2-(2-methyl-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetate (41a).
To a
solution of benzyl 3-(1-(tert-butoxy)-2-methoxy-2-oxoethyl)-
2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-
carboxylate (40a) (0.100 g, 0.194 mmol, 1 equiv) in DCM (2
mL) and methanol (2 mL) was added 10% Pd/C (10 mg, 0.0097
mol, 0.05 equiv) followed by 12 M HCl (0.024 mL, 0.290
mmol, 1 equiv). The mixture was shaken on a Parr shaker under
H2 (50 psi) for 3 h. Celite was added and the mixture was
filtered through Celite eluting with methanol. The filtrate was
concentrated in vacuo. The crude product was triturated with
Et2O and the solids were collected by filtration to provide the
product as the presumed HCl salt (0.066 g, 74%) as a white
solid. 1H NMR (400 MHz, CD3OD) δ 7.44 (t, J = 8.4 Hz, 2H),
7.24 (dd, J = 6.9, 18.3 Hz, 2H), 5.08 (s, 1H), 4.10-4.26 (m, 1H),
3.70-3.85 (m, 4H), 3.57-3.70 (m, 2H), 3.21-3.31 (m, 2H), 2.66
(s, 3H), 2.47 (s, 3H), 0.99 (s, 9H). LCMS (ESI, M+1): 383.1.
(S)-2-(tert-butoxy)-2-(2-methyl-4-(p-tolyl)-5,6,7,8-
tetrahydro-1,6-naphthyridin-3-yl)acetic acid (S3). To a
solution of (S)-2-(6-((benzyloxy)carbonyl)-2-methyl-4-(p-
tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)-2-(tert-
butoxy)acetic acid (12) (0.34 g, 0.668 mmol, 1 equiv) in MeOH
(5 mL) was added 10% Pd/C (7 mg, 0.67 mmol, 0.1 equiv). The
reaction was stirred under a balloon of hydrogen for 2 h. The
mixture was then filtered through a pad of Celite eluting with
MeOH and the filtrate was concentrated in vacuo to provide the
product (0.21 g, 85%) as an off white glass. LCMS (ESI, M+1)
369.4.
tert-Butyl
2-((8-fluoro-5-methylchroman-6-
yl)methylene)-3-oxobutanoate (S4). A solution of 8-fluoro-5-
methylchromane-6-carbaldehyde (34) (4.0 g, 21.3 mmol, 1
equiv), tert-butyl acetoacetate (4.2 mL, 25.5 mmol, 1.2 equiv),
and piperidinium acetate (0.31 g, 0.257 mmol, 0.1 equiv) in
benzene (53 mL) was refluxed for 18 h with a Dean-Stark trap.
More tert-butyl acetoacetate (4.2 mL, 25.5 mmol, 1.2 equiv)
and piperidinium acetate (0.31 g, 0.257 mmol, 0.1 equiv) were
added. After heating at reflux for another 24 h, the reaction was
allowed to cool to ambient temperature and concentrated in
Methyl
(S)-2-(tert-butoxy)-2-((R)-4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-
naphthyridin-3-yl)acetate (41b). A solution of benzyl (R)-3-
((S)-1-(tert-butoxy)-2-methoxy-2-oxoethyl)-4-(8-fluoro-5-
methylchroman-6-yl)-2-methyl-7,8-dihydro-1,6-
naphthyridine-6(5H)-carboxylate (40b) (0.77 g, 1.31 mmol, 1
equiv), 1 M HCl (2.1 mL, 2.10 mmol, 1.6 equiv), and 10% Pd/C
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vacuo. Crude product was purified by silica gel flash column solution of Cu(acac)2 (0.24 g, 0.90 mmol, 0.03 equiv) and
1
2
3
4
5
6
7
8
chromatography (0-20% EtOAc/hexane and 20-100%
DCM/hexane) to provide the major geometric isomer (2.28 g,
32%) as a yellow solid and the minor geometric isomer (0.70 g,
10%) as a yellow oil. Major isomer: 1H NMR (400 MHz,
CDCl3) δ 7.72 (s, 1H), 7.11 (d, J = 11.8 Hz, 1H), 4.28 - 4.21
(m, 2H), 2.70 (t, J = 6.7 Hz, 2H), 2.41 (s, 3H), 2.19 (s, 3H), 2.13
- 2.07 (m, 2H), 1.50 (s, 9H). Minor isomer: 1H NMR (500
MHz, CDCl3) δ 7.77 (s, 1H), 6.85 (d, J = 11.7 Hz, 1H), 4.28 -
4.22 (m, 2H), 2.71 (t, J = 6.5 Hz, 2H), 2.28 (s, 3H), 2.21 (s,3H),
2.13 - 2.08 (m, 2H), 1.56 (s, 9H).
phenyl hydrazine (6 drops) in DCM (60 mL) was heated to
reflux to produce a dark blue solution. Styrene (3.4 mL, 30
mmol, 1 equiv) was added. Ethyl diazoacetate (4.7 mL, 45
mmol, 1.5 equiv) was then added by syringe pump over 40 min.
After 5 h, the reaction was allowed to cool to ambient
temperature and washed with saturated aqueous sodium
bicarbonate and brine. The DCM layer was dried (Na2SO4) and
concentrated in vacuo. NMR of the crude product indicated
~2:1 anti:syn cyclopropanation. The crude product was purified
by silica gel flash chromatography (0-10% ether/hexane) to
provide the product as a colorless oil (0.88 g, 15%). 1H NMR
(500 MHz, CDCl3) δ 7.35 - 7.16 (m, 5H), 3.89 (q, J = 7.1 Hz,
2H), 2.70 - 2.51 (m, 1H), 2.10 (ddd, J = 9.3, 7.8, 5.6 Hz, 1H),
1.81 - 1.69 (m, 1H), 1.34 - 1.31 (m, 1H), 0.99 (t, J = 1.0 Hz,
3H), 0.99 (t, J = 7.1 Hz, 3H).
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33
34
35
36
37
38
39
40
41
42
43
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48
49
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60
6-((Benzyloxy)carbonyl)-4-(8-fluoro-5-methylchroman-
6-yl)-2-methyl-5,6,7,8-tetrahydro-1,6-naphthyridine-3-
carboxylic acid (S5). An orange solution of 6-benzyl 3-tert-
butyl
4-(8-fluoro-5-methylchroman-6-yl)-2-methyl-7,8-
dihydro-1,6-naphthyridine-3,6(5H)-dicarboxylate (37b) (2.3 g,
4.21 mmol, 1 equiv) in TFA (21 mL) was stirred for 18 h. The
solution was concentrated in vacuo and triturated with ether to
provide the putative TFA salt of the product (2.42 g, 95%) as a
tan solid. LCMS (ESI, M+1): 491.35.
Syn (2-phenylcyclopropyl)methanol (S8). To a solution of
S7 (0.88 g, 4.63 mmol, 1 equiv) in THF (23 mL) was added
LiBH4 (4.6 mL of a 2 M solution in THF, 9.25 mmol, 2 equiv)
followed by methanol (0.37 mL, 9.25 mmol, 2 equiv). Gas
o
evolution. The reaction was heated to 60 C for 1 h. Upon
Benzyl (R)-4-(8-fluoro-5-methylchroman-6-yl)-3-((S)-1-
hydroxy-2-methoxy-2-oxoethyl)-2-methyl-7,8-dihydro-1,6-
naphthyridine-6(5H)-carboxylate (S6). To a solution of
benzyl 4-(8-fluoro-5-methylchroman-6-yl)-3-(2-methoxy-2-
oxoacetyl)-2-methyl-7,8-dihydro-1,6-naphthyridine-6(5H)-
carboxylate (39b) (2.50 g, 4.69 mmol, 1 equiv) and (R)-1-
methyl-3,3-diphenylhexahydropyrrolo[1,2-
cooling to ambient temperature, the reaction was diluted with
ether and washed with 1 N HCl and brine. The ether layer was
dried (Na2SO4) and concentrated in vacuo to provide the
product (0.32 g, 47%) as a colorless oil. 1H NMR (400 MHz,
CDCl3) δ 7.33 - 7.18 (m, 5H), 3.50 (dd, J = 11.8, 6.3 Hz, 1H),
3.29 (dd, J = 11.5, 8.5 Hz, 1H), 2.37 - 2.26 (m, 1H), 1.56 -1.47
(m, 1H), 1.11 - 1.03 (m, 1H), 0.90 (q, J = 5.6 Hz, 1H).
c][1,3,2]oxazaborole (1.88 mL of a 1 M solution in toluene,
o
1.88 mmol, 0.4 equiv) in toluene (45 mL) at -30 C (IPA/dry
Syn 2-phenylcyclopropanecarbaldehyde (S9).
To a
ice) was added catecholborane (3.15 mL of a 50% solution in
toluene, 6.57 mmol, 1.4 equiv). The reaction was placed in a
freezer (-15 to -20 oC) for 4 d. The reaction was quenched with
saturated aqueous sodium carbonate. EtOAc was added and the
mixture was allowed to warm to ambient temperature. After
stirring vigorously for 1 h, the emulsion was filtered through
Celite. The organic layer was separated and stirred vigorously
with saturated aqueous sodium carbonate for 1 h. The organic
layer was separated and then again stirred vigorously with
saturated aqueous sodium carbonate for 1 h. The organic layer
was seperated and washed with brine, dried (Na2SO4), and
concentrated in vacuo. The crude product as ~1:1 mixture of
atropisomers was carefully purified by silica gel flash
chromatography (5% TFE/DCM) to provide the product the
desired product as the lower Rf spot and the undesired
atropisomer as the higher Rf spot. The desired atropisomer was
isolated (1.12 g, 45%) as a white solid. The undesired
atropisomer/diastereomer was also isolated (1.22 g, 49%) as a
solution of S8 (0.32 g, 2.16 mmol, 1 equiv) in DCM (11 mL)
was added Dess-Martin periodinane (1.28 g, 3.02 mmol, 1.4
equiv). After 1 h, the reaction was diluted with ether and
washed with saturated aqueous sodium bicarbonate and brine.
The organic layer was dried (MgSO4) and concentrated in
vacuo. The crude product was purified by silica gel flash
chromatography (0-30% ethyl acetate/hexane) to provide the
product as a yellow oil (0.15 g, 48%). 1H NMR (500 MHz,
CDCl3) δ 8.70 (d, J = 6.6 Hz, 1H), 7.36 - 7.26 (m, 5H), 2.89 -
2.82 (m, 1H), 2.20 - 2.13 (m, 1H), 1.91 (dt, J = 7.3, 5.3 Hz, 1H),
1.65 - 1.60 (m, 1H).
ASSOCIATED CONTENT
Supporting Information. Methods for binding assay, cell assay,
cytoxicity assay, in vitro metabolic stability assay, in vivo
pharmacokinetic study, crystallography, and modeling. Accession
Codes. The coordinates of the crystal structure of 24 bound with
integrase CCD (PDB ID 6NCJ) have been deposited in the Protein
Data Bank (www.pdb.org). Authors will release the atomic
coordinates and experimental data upon article publication.
Molecular Formula Strings available.
1
white solid. H NMR (400 MHz, CDCl3) δ 7.40 - 7.30 (m, 5H),
6.62 (d, J = 10.8 Hz, 1H), 5.16 - 5.07 (m, J = 17.3 Hz, 2H), 5.00
(d, J = 2.3 Hz, 1H), 4.27 (t, J = 4.3 Hz, 2H), 4.19 - 4.03 (m, 2H),
3.93 - 3.84 (m, 1H), 3.73 (s, 3H), 3.10 - 3.00 (m, 3H), 2.68 (br.
s., 1H), 2.52 (s, 3H), 2.11 (br. s., 2H), 1.84 (br. s., 1H), 1.72 (br.
s., 1H); 19F NMR (376 MHz, CDCl3) δ -139.11 (d, J = 12.1 Hz,
1F); LCMS (ESI, M+1): 535.35. Other atropisomer: 1H NMR
(400 MHz, CDCl3) δ 7.40 - 7.30 (m, 5H), 6.64 (d, J = 11.0 Hz,
1H), 5.12 (d, J = 9.3 Hz, 2H), 4.97 (d, J = 2.5 Hz, 1H), 4.27 (t,
J = 5.0 Hz, 2H), 4.21 - 4.02 (m, 2H), 3.93 - 3.83 (m, 1H), 3.75
(s, 3H), 3.17 (d, J = 2.5 Hz, 1H), 3.05 (br. s., 2H), 2.70 (br. s.,
1H), 2.50 (s, 3H), 2.11 (br. s., 2H), 1.89 - 1.73 (m, 3H), 1.59 (s,
3H); LCMS (ESI, M+1): 535.35.
AUTHOR INFORMATION
Corresponding Author
* Email: kevin.m.peese@viivhealthcare.com.
Author Contributions
The manuscript was written through contributions of all authors.
All authors have given approval to the final version of the
manuscript.
ACKNOWLEDGMENT
Ethyl (syn)-2-phenyl-cyclopropanecarboxylate (S7).
Following the procedure in J. Med. Chem. 2009, 52, 1885. A
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Journal of Medicinal Chemistry
resistance profile. Antimicrob. Agents Chemother. 2016, 60, 7086–
7097.
(13) Christ, F.; Debyser, Z. The LEDGF/p75 integrase interaction,
a novel target for anti-HIV therapy. Virology 2013, 435, 102–109.
(14) Demeulemeester, J.; Chaltin, P.; Marchand, A.; De Maeyer, M.;
Debyser, Z.; Christ, F. LEDGINs, non-catalytic site inhibitors of HIV-
1 integrase: a patent review (2006-2014). Exp. Opin. Ther. Patents
2014, 24, 609-632.
(15) Le Rouzic, E.; Bonnard, D.; Chasset, S.; Bruneau, J.-M.;
Chevreuil, F.; Le Strat, F.; Nguyen, J.; Beauvoir, R.; Amadori, C.;
Brias, J.; Vomscheid1, S.; Eiler, S.; Lévy, N.; Delelis, O.; Deprez, E.;
Saïb, A.; Zamborlini, A.; Emiliani, S.; Ruff, M.; Ledoussal, B.;
Moreau, F.; Benarous, R. Dual inhibition of HIV-1 replication by
integrase-LEDGF allosteric inhibitors is predominant at the post-
integration stage. Retrovirology 2013, 10, 144.
(16) Feng, L.; Larue, R. C.; Slaughter, A.; Kessl, J. J.; Kvaratskhelia,
M. HIV-1 integrase multimerization as a therapeutic target. Curr. Top.
Microbiol. Immunol. 2015, 389, 93–119.
Wade Blair is acknowledged for helpful discussion regarding
biology and mechanism of action. David Langley, Prasanna Siva,
Eric Arnault, and Eugene Stewart are acknowledged for helpful
discussions regarding molecular modeling. Mian Gao is
acknowledged for protein expression efforts. The Bristol-Myers
Squibb Department of Chemical Synthesis is acknowledged for
synthetic support.
1
2
3
4
5
6
7
8
ABBREVIATIONS
ALLINI, allosteric integrase inhibitor; CAN, ceric ammonium
nitrate; CBS, Corey–Bakshi–Shibata; Cbz, benzyl carbamate;
CCD, catalytic core domain; CL, clearance; CYP, cytochrome
9
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12
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24
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37
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39
40
41
42
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44
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49
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P450;
DNA,
deoxyribonucleic
acid;
HIV,
Human
Immunodeficiency Virus; IN, integrase; INLAI, IN-LEDGF/p75
inhibitor; INSTI, integrase strand transfer inhibitors; IV,
intravenous; LEDGF, lens epithelium-derived growth factor;
LEDGIN,
LEDGF
inhibitor;
LiHMDS,
lithium
(17) Bonnard, D.; Le Rouzic, E.; Eiler, S.; Amadori, C.; Orlov, I.;
Bruneau, J.-M.; Brias, J.; Barbion, J.; Chevreuil, F.; Spehner, D.;
Chasset, S.; Ledoussal, B.; Moreau, F.; Saïb, A.; Klaholz, B. P.;
Emiliani, S.; Ruff, M.; Zamborlini, A.; Benarous, R. Structure-
function analyses unravel distinct effects of allosteric inhibitors of
HIV-1 integrase on viral maturation and integration. J. Biol. Chem.
2018, 293, 6172–6186.
bis(trimethylsilyl)amide; NCINI, non-catalytic site integrase
inhibitor; PO, oral; SAR, structure activity relationship; Vss, steady
state volume of distribution; WHO, World Health Organization
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