The identification of 8,9-dimethoxy-5-(2-aminoalkoxy-pyridin-3-yl)-benzo[c][2,7]naphthyridin-4-ylamines as potent inhibitors of 3-phosphoinositide-dependent kinase-1 (PDK-1)

Article abstract of DOI:10.1016/j.ejmech.2009.12.036

A series of 8,9-dimethoxy-5-(2-aminoalkoxy-pyridin-3-yl)-benzo[c][2,7]naphthyridin-4-ylamine-based inhibitors of 3-phosphoinositide-dependent kinase-1 (PDK-1) has been identified. Several examples appear to be potent and relatively selective inhibitors of PDK-1 over the related AGC kinases PKA, PKB/AKT, and p70S6K. The introduction of a stereochemical center beside the amino substituent on the aminoalkoxy-side chain had little effect upon the inhibitory activity against these enzymes, and X-ray crystallographic analyses of a representative pair of enantiomeric inhibitors bound to the active site of PDK-1 revealed comparable binding modes for each enantiomer.

Full text of DOI:10.1016/j.ejmech.2009.12.036

European Journal of Medicinal Chemistry 45 (2010) 1379–1386
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
The identification of 8,9-dimethoxy-5-(2-aminoalkoxy-pyridin-3-yl)-
benzo[c][2,7]naphthyridin-4-ylamines as potent inhibitors
of 3-phosphoinositide-dependent kinase-1 (PDK-1)
,
a
a
a
a
Thomas Nittoli a , Russell G. Dushin , Charles Ingalls , Katherine Cheung , M. Brawner Floyd ,
Heidi Fraser a, Andrea Olland a, Yongbo Hu a, George Grosu a, Xin Han b, Kim Arndt b, Bing Guo b,
Allan Wissner a
*
a Chemical Sciences, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965, USA
b Discovery Oncology, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 8,9-dimethoxy-5-(2-aminoalkoxy-pyridin-3-yl)-benzo[c][2,7]naphthyridin-4-ylamine-based
inhibitors of 3-phosphoinositide-dependent kinase-1 (PDK-1) has been identified. Several examples
appear to be potent and relatively selective inhibitors of PDK-1 over the related AGC kinases PKA, PKB/
AKT, and p70S6K. The introduction of a stereochemical center beside the amino substituent on the
aminoalkoxy-side chain had little effect upon the inhibitory activity against these enzymes, and X-ray
crystallographic analyses of a representative pair of enantiomeric inhibitors bound to the active site of
PDK-1 revealed comparable binding modes for each enantiomer.
Received 14 October 2009
Received in revised form
14 December 2009
Accepted 16 December 2009
Available online 28 December 2009
Keywords:
Ó 2009 Elsevier Masson SAS. All rights reserved.
3-phosphoinositide-dependent kinase-1
Cancer
Inhibitor
X-ray
1. Introduction
dibenzo[c,f][2,7]-naphthyridine derivative 1 (Fig. 1) as a relatively
potent PDK-1 inhibitor (IC50 ¼ 60 nM) [13]. An X-ray crystal struc-
Phosphoinositide-dependent kinase-1 (PDK-1), a 63 kDa serine/
threonine kinase, is a major player in the PI3-kinase signaling
pathway that regulates gene expression, cell cycle, growth, and
proliferation [1–8]. PDK-1 has been termed the ‘‘master kinase’’
because it phosphorylates highly conserved serine or threonine
residues in the T-loop (or activation loop) of numerous AGC kinases,
including PKB/AKT, PKC, p70S6K, SGK, and PDK-1 itself [9].
Although the precise regulatory mechanisms vary, in the case of
PKB/AKT, activation by PDK-1 is critically dependent upon prior PI3
kinase activation and the presence of phosphatidylinositol-(3,4,5)-
triphosphate (PIP3). A significant proportion (40–50%) of all tumors
involve mutations in PIP3-3-phosphatase (PTEN) [10–12], which
results in elevated levels of PIP3 and enhanced activation of PKB/
AKT, p70S6K, and SGK; inhibitors of PDK-1 could potentially
provide valuable therapeutic agents for the treatment of cancer.
In our initial efforts to identify inhibitors of PDK-1, high-
throughput screening (HTS) was used to discover the tetracyclic
ture of 1 complexed to PDK-1 revealed key hydrogen bonding
interactions between the N8 nitrogen in 1 and the backbone NH of
Ala162, and between the C6-amino group in 1 and the backbone
carbonyl oxygen of Ser160. An additional hydrogen-bonding
interaction was noted between the N5 nitrogen in 1 and the side
chain hydroxyl group of Thr222. Subsequent to this work, we
reported that the truncated 2-heteroaryl-substituted 8,9-dialkoxy-
benzo[c][2,7]naphthyridines [14], exemplified by the imidazole-
substituted derivative 2 (IC50 ¼ 70 nM) and the pyridyl-substituted
derivative 3 (IC50 ¼ 35 nM), were also potent inhibitors of PDK-1. An
X-ray crystal structure of compound 2 bound to PDK-1 revealed, in
addition to all the interactions observed between 1 and PDK-1, that
this compound formed a hydrogen-bonding interaction between
N3 of the imidazole headpiece and the Lys111
PDK-1. This conserved catalytic lysine residue mediates the binding
of the -phosphate of ATP and facilitates the phosphate transfer to
3-amino group in
a
the protein substrate [15]. This additional hydrogen bonding
interaction was predicted on the basis of molecular modeling and
was also thought to be relevant in binding of the compounds
containing the 5-imidazolyl and 3-pyridyl-headpiece substituents,
of which several examples were presented. We noted that an
* Corresponding author. Tel.: þ1 845 602 5762; fax: þ1 845 602 5561.
E-mail address: nittoli@hotmail.com (T. Nittoli).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.12.036

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T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
cyclization which, after removal of the Boc protecting group with
N
NH2
N
acid, furnished the inhibitors 9a–s.
N
N5
N
N3
N
N
C6
NH2
C4
NH2
O
O
O
O
O
O
NH2
3. Results and discussion
O
N N8
N
NN6
As noted above, previous work disclosed by the Abbott group
coupled with our molecular modeling studies on this series of
inhibitors suggested that we could establish additional beneficial
hydrogen bonding interactions by incorporating an aminoalkoxy
substituent at the 5-position of the pyridyl headpiece. We antici-
pated that this type of modification would result in enhanced
potency. Indeed, the compounds prepared in this study each
showed potent PDK-1 inhibitory activity (IC50 < 22 nM). Within
this series, the SAR observed for the R1 substituents was relatively
flat (Table 1). For example, a compound with a small R1 group (9a,
R1]H, IC50 ¼ 5 nM) showed about the same activity as a compound
1
2
3
Fig. 1. PDK-1 inhibitors from our previously reported studies (1 IC50 ¼ 60 nM,
2 IC50 ¼ 70 nM, 3 IC50 ¼ 35 nM).
analogous interaction involving a pyridyl-substituent and the
conserved lysine residue was reported to occur with a series of PKB/
AKT inhibitors containing a 5-aminoalkoxy-3-pyridyl group placed
upon a different kinase-active core structure [16]. The PKB/AKT
inhibitors possessed additional beneficial interactions between the
protonated amino-group on the aminoalkoxy-substituent and
conserved asparagine and aspartate residues normally involved in
magnesium chelation. Having established the hydrogen bonding
interaction between our pyridyl- and imidazolyl-nitrogens and the
conserved lysine residue, we next explored the effect of incorpo-
rating various aminoalkoxy-substituents onto the 5-position of
a 3-pyridyl headpiece installed on the novel 8,9-dimethoxy-ben-
zo[c][2,7]naphthyridine core. Herein are reported the results of
those efforts.
having
a
much larger substituent (9r, R1]CH2-3,4-Cl2–Ph,
IC50 ¼ 6 nM). In addition, for the inhibitors that are enantiomeric
pairs (9b vs. 9c, 9d vs. 9e, 9f vs. 9g, 9h vs. 9i, 9j vs. 9k, 9l vs. 9m, and
9n vs. 9o), the difference in potency between enantiomers was
minimal with the largest difference observed between 9j and 9k,
having IC50s of 3 and 15 nM, respectively. In contrast, some
members of this series of PDK-1 inhibitors did display a measure of
selectivity for PDK-1 relative to some of the other AGC kinases such
as PKA, PKB/AKT, and p70S6K. The largest selectivities were
observed for compounds 9b, 9c, 9e and 9s over PKB/AKT, a kinase
that acts downstream of PDK-1 and which is also a valid target for
cancer therapy [17–22] (AKT/PDK-1 ¼119, 144, 159, and 194,
respectively). Compared to PKB/AKT, the compounds were less
selective for PKA, a ubiquitous kinase that performs numerous
useful functions [23–25], or p70S6K, another multifunctional
kinase [26–29].
In order to derive further insights into the SAR, we obtained the
X-ray crystal structures for one pair of entantiomers, 9h [30] (PDK-1
IC50 ¼ 8 nM) and 9i [31] (PDK-1 IC50 ¼ 17 nM), bound to the cata-
lytic domain of PDK-1. For both enantiomers 9h and 9i, the inter-
actions made by the tricyclic core to PDK-1 were analogous to those
found for 1 and 2 (Fig. 2). Notably, the interactions between the
ligand and the hinge region of PDK-1 were mediated by hydrogen
2. Synthesis
The intermediates 6a–s were prepared either by performing
a Mitsunobu reaction between the Boc-protected aminoalcohols
4a, d–i, k–s and methyl-5-hydroxy nicotinate, 5 or by alkylation of
5 with the mesylates derived from the aminoalcohols (4b,c,j)
(Scheme 1). The key step in the synthesis, as we have shown
previously [14], is the condensation of the functionalized alkoxy-
nicotinates 6a–c, e–s or the acyl imidazole derivative 6d with 6,7-
dimethoxy-4-methyl-3-cyanoquinoline 7 to yield the intermediate
ketones 8. Without purification, these ketones were heated in
acetic acid in the presence of ammonium acetate to promote
O
O
CN
H3CO2C
OH
7
NHBoc
R1
5
N
N
O
N
R1
f
a or b, c
OH
NHBoc
R2
4a-s
6a-c, e-s, R2=CO2CH3
d, e
6d, R2=COimidazole
NHBoc
R1
NH2
O
O
N
N
R1
O
N
g, h
O
O
CN
O
O
NH2
N
N
8
9a-s
Scheme 1. Reagents and conditions: a) DEAD, PPh3, THF; b) MsCl, TEA; c) CsCO3, DMF; d) NaOH, THF; e) CDI, THF; f) LiHMDS, THF, ꢀ78–0 ꢁC; g) NH4OAc, DMF, 100 ꢁC; h) HCl, THF,
60 ꢁC.

T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
1381
Table 1
,b
Inhibition of PDK-1 with Naphthyridines.a
NH2
O
N
R1
N
O
O
NH2
N
.
Compound #
R/S
R1
IC50 (nM) PDK-1
IC50 (nM) PKA
IC50 (nM) AKT
IC50 (nM) p70S6K
PKA/PDK1
AKT/PDK1
p70S6K/PDK1
9a
9b
9c
9d
9e
9f
9g
9h
9i
9j
9k
9l
9m
9n
9o
9p
9q
9r
9s
–
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
S
S
S
H
Me
Me
Et
Et
i -Bu
i -Bu
CH2Ph
5
6
3
6
3
14
18
8
17
3
15
13
21
6
15
8
66
123
86
59
45
113
385
77
<31
32
36
68
142
54
120
79
18
41
138
402
712
377
422
318
905
1395
261
259
183
251
209
889
302
1324
793
78
80
235
97
216
72
219
443
107
88
13
21
33
11
23
8
21
10
<2
11
2
5
7
10
8
10
2
80
119
144
77
159
65
78
33
15
61
17
16
43
55
88
99
10
72
16
39
37
39
36
16
25
13
5
CH2Ph
CH2-4-F–Ph
CH2-4-F–Ph
CH2-3-CF3–Ph
CH2-3-CF3–Ph
CH2-3-indolyl
CH2-3-indolyl
CH2-2-Cl–Ph
CH2-3-Cl–Ph
CH2-3,4-Cl2–Ph
CH2-4-pyridyl
21
93
7
6
182
763
77
254
106
76
14
37
14
17
13
10
3
8
6
9
433
1750
19
343
7
15
194
38
a
See reference [4] for assay procedure.
100 uM ATP used in all assays.
b
bonds between the N6 nitrogen to the NH of Ala162 and the C4
amino group in 9h or 9i to the backbone carbonyl oxygen of Ser160.
An additional hydrogen–bond interaction was also present
between the N3 nitrogen in 9h or 9i and the side chain hydroxyl of
Thr222. The pyridyl headpiece of 9h or 9i interacts with Lys111
through a hydrogen bond in a similar fashion to our observation
earlier for the imidazole headpiece of 2 on the 8,9-dialkoxy-ben-
zo[c][2,7]naphthyridine core.
side chain of 9h with the Asn210 and Asp223 residues of PDK-1,
completely analogous to those observed by the Abbott group with
their inhibitors of PKB/AKT [16]. Similar interactions were observed
for 9i with the Asn210 and Glu209 residues of PDK-1. An overlay of
crystal structures obtained for 9h and 9i complexed to PDK-1 is
shown in Fig. 3 where it is apparent that the amino groups of 9h
and 9i make an electrostatic interaction with Asp223 and Glu209,
respectively. In both structures the benzyl-side chains are oriented
in a very similar manner even though they are derived from
different enantiomers. Apparently, the degree to which the
Significantly, we observed new hydrogen bonding and electro-
static interactions between the protonated primary amine of the
Fig. 2. X-ray crystallographic structures of 9h (yellow) and 9i (green) complexed with PDK-1. Comparable interactions made by the tricyclic core and the pyridyl headpiece were
similar to those observed for 1 and 2. (For interpretation of the reference to colour in this figure legend, the reader is referred to the web version of this article.)

1382
T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
compounds 1 and 2, and that these two compounds each establish
additional beneficial polar interactions with the protein through
hydrogen-bonding and ionic interactions involving the amino-
alkoxy-substituent.
5. Experimental section
5.1. Biological assays
The details of the PDK-1 assay procedures have been published
previously [13] using 100 uM ATP. The ‘‘Z0-LYTE’’ kinase assays for
PKA, PKB/AKT, and p70S6K were performed according to the
manufacturer’s protocols (Invitrogen Cat#: PV3174, PV3179, and
PV3180) using 100 uM ATP.
5.2. X-ray crystallography
An N-terminally truncated version of PDK-1 was purified and
crystallized with ATP as previously described [32]. Crystals were
harvested and transferred to a fresh drop of soaking solution con-
taining 3 M ammonium sulfate, 0.5 M NaCl, 0.1 M Tris–HCl pH 7.0,
10 mM Mg sulfate, 5% DMSO and 0.3 mM inhibitor. Crystals were
soaked for approximately one week then briefly transferred into
a solution of 25% glycerol and 75% soaking solution before being
flash cooled in a nitrogen stream at 100 K. Diffraction data were
recorded in house with a Saturn92 CCD mounted on an FR-E CuKa
rotating anode X-ray source (Rigaku, Japan). Intensities were inte-
grated and scaled using HKL2000 [33]. The structures were phased
by molecular replacement with the CCP4 suite of software [34]. The
search model used was based on a previously determined structure
of PDK-1 in complex with ATP. Refinement and model building
were performed in iterative cycles using the programs REfmac5
(CCP4 1994) and COOT [35]. See Table 2 for refinement statistics.
Fig. 3. An overlay of X-ray crystallographic structures 9h (tan ligand, protein in yellow)
and 9i (green ligand, protein in cyan) complexed with PDK-1 showing the interactions
of the aminoalkoxy side-chains with the protein. The amino-group on this side chain in
either enantiomer interacts with Asn210 and a carboxylate residue; 9h with Asp223
and 9i with Glu209. (For interpretation of the reference to colour in this figure legend,
the reader is referred to the web version of this article.)
Table 2
Statistics from crystallographic analysis of PDK-1 with inhibitors.
9h
9i
Space group
P3221
P3221
Unit cell (Å)
123.37, 123.37, 47.27
50 ꢀ 2.4 (2.49 ꢀ 2.40)
172,842
16,389
99.9 (100.0)
10.1 (70.0)
122.87, 122.87, 47.16
50 ꢀ 2.2 (2.28 ꢀ 2.20)
215,428
Resolution (Å) (last shell)
Total Observations
Unique Observations
Completeness (%)
20,849
99.5 (96.6)
17.1 (57.6)
13.7 (2.8)
a
Rsym
5.3. Chemistry
I/
sI
26.3 (3.8)
1H NMR spectra were determined with a Bruker DRX400 spec-
trometer at 400 MHz. Chemical shifts, d, are in parts per million
Refinement
Resolution (Å)
Rwork/Rfreeb (%)
RMSdc bonds (Å)
RMSdc angles (ꢁ)
20 ꢀ 2.4
24.5/28.2
0.007
20 ꢀ 2.2
23.8/27.8
0.007
relative to the internal standard tetramethylsilane. Electrospray
(ES) mass spectra were recorded in positive mode on a Micromass
Platform spectrometer. High-resolution mass spectra (HRMS) were
obtained on a Finnigan MAT-90 or on a Bruker 9.4T FTMS spec-
trometer. Chromatographic purifications were by flash chroma-
tography using EMD 0.04–0.06 mm silica gel. The following
describes the syntheses and spectral data of non-commercial or
non-published compounds.
1.03
0.964
a
Rsym
¼
S
jI ꢀ <I>j/I, where I is the observed intensity, <I> is the average
intensity of multiple observations of symmetry- related reflections.
b
Rwork
¼
S
kFobsj ꢀ jFcalcj/ jFobsj, Rfree is equivalent to Rwork, but calculated for
S
a randomly chosen 5% of reflections omitted from the refinement process.
c
RMSd is the root mean square deviation from ideal geometry.
interactions of each enantiomer contribute to compound binding is
comparable since the difference in potency in inhibiting PDK-1 is
minimal (IC50 ¼ 8 vs. 17 nM for 9h vs. 9i, respectively). We believe
that these new interactions contribute to the superior potency of
either enantiomer relative to the more simple derivatives 1 and 2.
5.3.1. Methyl 5-{[(2S)-2-[(tert-butoxycarbonyl)amino]-3-(2-
chlorophenyl)propyl]oxy}nicotinate (6p)
To a solution of tert-butyl [(1S)-1-(2-chlorobenzyl)-2-hydrox-
yethyl]carbamate (4.01 g, 14.0 mmol), triphenylphosphine (4.42 g,
14.0 mmol), and 5-hydroxynicotinic acid methyl ester (2.12 g,
14.0 mmol) in anhydrous THF (60 mL) was added DEAD (2.65 mL,
16.9 mmol) in anhydrous THF (12 mL) over a 10 min period. The
solution was stirred at room temperature for 3 h then concentrated
in vacuo. The residue was dissolved in Et2O and stirred for 1 h then
filtered. The filtrate was washed with 3 ꢂ 200 mL 0.5 N NaOH and
the organic layer dried over MgSO4 and concentrated in vacuo. The
residue was purified by silica gel chromatography using a gradient
elution of 10–50% EtOAc/Hexanes to give methyl 5-{[(2S)-2-[(tert-
butoxycarbonyl)amino]-3-(2- chlorophenyl)propyl]oxy}nicotinate
4. Conclusions
We have described in this report our efforts to identify addi-
tional potent PDK-1 inhibitors by expanding upon our previously
reported series of 2-heteroaryl-substituted 8,9-dialkoxy-ben-
zo[c][2,7]naphthyridines. The introduction of aminoalkoxy-
substituents onto the 5-position of the 3-pyridyl headpieces
present on the benzo[c][2,7]naphthyridine scaffold has resulted in
significant increases in PDK-1 inhibitory potency. X-Ray crystallo-
graphic analysis of a PDK-1 complexed with the enantiomers 9h
and 9i has revealed that these inhibitors bind to the ATP site of PDK-
1 in a manner that is completely analogous to that observed for
(1.8 g, 56%). 1H NMR (400 MHz, DMSO-d6)
d 8.70 (d, 1H), 8.52 (d,
1H), 7.78 (m, 1H), 7.40 (m, 1H), 7.35 (m, 1H), 7.25 (m, 2H), 7.02 (d,
1H), 4.13 (s, 2H), 3.89 (s, 3H), 3.09 (m, 1H), 2.80 (s, 1H), 1.28 (s, 9H),
1.07 (s, 1H); MS 421.2 [M þ H].

T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
1383
The following compounds were made using the above
procedure:
5.3.12. Methyl-5-{[(2R)-2-[(tert-butoxycarbonyl)amino]-3-(1H-
indol-3-yl)propyl]oxy}nicotinate (6o)
1H NMR (400 MHz, DMSO-d6)
d
10.82 (s,1H), 8.98 (s, 1H), 8.68 (s,
5.3.2. Methyl 5-{2-[(tert-butoxycarbonyl)amino]ethoxy}nicotinate
1H), 8.51 (d, 1H), 7.72 (m, 1H), 7.56 (d, 1H), 7.33 (d, 1H), 7.15 (s, 1H),
7.01 (m, 2H), 4.07 (m, 3H), 3.88 (s, 3H), 2.94 (m, 2H), 1.36 (s, 9H). MS
(ESI) m/z 426.4.
(6a) WYE-120860
1H NMR (400 MHz, CDCl3)
d 8.81 (d, 1H), 8.47 (d, 1H), 7.76 (m,
1H), 5.01 (bs, 1H), 4.11 (t, 2H), 3.95 (s, 3H), 3.58 (m, 2), 1.45 (s, 9). MS
(ESI) m/z 297.2.
5.3.13. Methyl-5-{[(2S)-2-[(tert-butoxycarbonyl)amino]-3-(3-
chlorophenyl)propyl]oxy}nicotinate (6q)
5.3.3. Methyl 5-({(2R)-2-[(tert-butoxycarbonyl)amino]-
1H NMR (400 MHz, DMSO-d6)
d 8.70 (d, 1H), 8.54 (d, 1H), 7.77
butyl}oxy)nicotinate (6e)
(m, 1H), 7.26 (m, 4H), 7.03 (d, 1H), 4.10 (m, 2H), 3.99 (m, 1H), 3.89 (s,
3H), 2.93 (m, 1H), 2.74 (m, 1H), 1.30 (s, 9H). MS (ESI) m/z 421.1.
1H NMR (400 MHz, DMSO-d6)
d
8.68 (d, 1H), 8.52 (d, 1H), 7.76
(m, 1H), 6.68 (d, 1H), 4.03 (m, 2H), 3.89 (s, 3H), 3.66 (m, 1H),1.59 (m,
1H), 1.46 (m, 1H), 1.37 (s, 9), 0.88 (t, 3H). MS (ESI) m/z 325.2.
5.3.14. Methyl-5-{[(2S)-2-[(tert-butoxycarbonyl)amino]-3-(3,4-
dichlorophenyl)propyl]oxy}nicotinate (6r)
5.3.4. Methyl 5-({(2R)-2-[(tert-butoxycarbonyl)amino]-4-
1H NMR (400 MHz, DMSO-d6)
d 8.70 (s,1H), 8.54 (d,1H), 7.77 (m,
methylpentyl}oxy)nicotinate (6f)
1H), 7.53 (m, 2H), 7.24 (d, 1H), 7.02 (d, 1H), 4.10 (m, 2H), 3.99
(m, 1H), 3.89 (s, 3H), 2.94 (m, 1H), 2.72 (m, 1H), 1.29 (s, 9H). MS (ESI)
m/z 455.
1H NMR (400 MHz, MeOH-d4)
d 8.78 (d, 1H), 8.43 (d, 1H), 7.86 (s,
1H), 5.47 (m,1H), 4.25 (m, 2H), 4.06 (m,1H), 3.97 (s, 3H),1.72 (m,1H),
1.54 (m,1H),1.44 (s, 9H),1.34 (m,1H), 0.96 (t, 6H). MS (ESI) m/z 353.3.
5.3.15. Methyl 5-({(2S)-2-[(tert-butoxycarbonyl)amino]-3-pyridin-
5.3.5. Methyl 5-({(2S)-2-[(tert-butoxycarbonyl)amino]-4-
4-ylpropyl}oxy)nicotinate (6s)
methylpentyl}oxy)nicotinate (6g)
1H NMR (400 MHz, DMSO-d6)
d 8.70 (s, 1H), 8.54 (d, 1H), 8.46 (d,
1H NMR (400 MHz, MeOH-d4)
d
8.78 (d, 1H), 8.43 (d, 1H), 7.86 (s,
2H), 7.78 (m, 1H), 7.26 (d, 2H), 7.06 (d, 1H), 4.11 (m, 2H), 4.06 (m,
1H), 3.89 (s, 3H), 2.94 (m,1H), 2.78 (m,1H),1.29 (s, 9H). MS (ESI) m/z
388.2.
1H), 5.47 (m, 1H), 4.25 (m, 2H), 4.06 (m, 1H), 3.97 (s, 3H), 1.72 (m,
1H), 1.54 (m, 1H), 1.44 (s, 9H), 1.34 (m, 1H), 0.96 (t, 6H). MS (ESI) m/z
353.3.
5.3.16. tert-Butyl [(1S)-1-({[5-(1H-imidazol-1-ylcarbonyl)pyridin-
3-yl]oxy}methyl)propyl]carbamate (6d)
5.3.6. Methyl-5-({(2S)-2-[(tert-butoxycarbonyl)amino]-3-
phenylpropyl}oxy)nicotinate (6h)
To a solution of Boc-S-2-aminobutanol (8.05 g, 42.5 mmol), tri-
phenylphosphine (33.5 g, 127.6 mmol), and 5-hydroxynicotinic acid
methyl ester (6.51 g, 42.5 mmol) in anhydrous THF (200 mL) was
added DEAD (20.1 mL, 127.6 mmol). The solution was stirred at room
temperature for 16 h then concentrated in vacuo. The crude residue
was dissolved in EtOAc then washed with a cold aqueous NaOH
solution (0.5 N). The organic layer was then concentrated and dis-
solved in 200 mL of THF. The solution was then treated with aqueous
NaOH solution (3 N, 150 mL) and stirred for 17 h. The mixture was
concentrated in vacuo until only the aqueous layer remained. The
aqueous layer was extracted with DCM then acidified until the pH
was w3 with concentrated HCl and the resulting white solid was
collected by filtration to give 5-(({(2S)-2-[(tert-butoxycarbonyl)-
amino]butyl)oxy)nicotinic acid (5.74 g, 44% yield) as a white solid. 1H
1H NMR (400 MHz, DMSO-d6)
d 8.69 (d, 1H), 8.52 (d, 1H), 7.75
(m, 1H), 7.24 (m, 5H), 7.01 (d, 1H), 4.07 (m, 2H), 3.98 (m, 1H), 3.89 (s,
3H), 2.89 (m, 1H), 2.76 (m, 1H), 1.31 (s, 9H). MS (ESI) m/z 387.1.
5.3.7. Methyl 5-({(2R)-2-[(tert-butoxycarbonyl)amino]-3-
phenylpropyl}oxy)nicotinate (6i)
1H NMR (400 MHz, DMSO-d6)
d 8.70 (s, 1H), 8.53 (d,1H), 7.76 (m,
1H), 7.24 (m, 5H), 7.02 (d, 1H), 4.07 (m, 2H), 3.99 (m, 1H), 3.89 (s,
3H), 2.89 (m, 1H), 2.77 (m, 1H), 1.32 (s, 9H). MS (ESI) m/z 387.3.
5.3.8. Methyl-5-{[(2R)-2-[(tert-butoxycarbonyl)amino]-3-(4-
fluorophenyl)propyl]oxy}nicotinate (6k)
1H NMR (400 MHz, DMSO-d6)
d 8.70 (d, 1H), 8.53 (d, 1H), 7.76
(m, 1H), 7.26 (m, 2H), 7.10 (m, 2H), 7.00 (d, 1H), 4.07 (m, 2H), 3.96
(m, 1H), 3.89 (s, 3H), 2.89 (m, 1H), 2.73 (m, 1H), 1.30 (s, 9H). MS (ESI)
m/z 405.3.
NMR (400 MHz, CDCl3) d 13.44 (s, 1H), 8.66 (d, 1H), 8.48 (d, 1H), 7.73
(m, 1H), 6.83 (d, 1H), 4.02 (d, 2H), 3.67 (m, 1H), 1.59 (m, 1H), 1.48 (m,
1H), 1.37 (s, 9H), 0.88 (t, 3H). MS (ESI) m/z 309.2.
To
a stirred solution of 5-({(2S)-2-[(tert-butoxycarbonyl)-
5.3.9. Methyl-5-({(2S)-2-[(tert-butoxycarbonyl)amino]-3-[3-
amino]butyl}oxy)nicotinic acid (560 mg, 1.80 mmol) in anhy-
drous THF (9 mL) was added 1,10-carbonyldiimidazole (585 mg,
3.60 mmol). The reaction was stirred for 21 h and then diluted
with EtOAc. The mixture was washed with water and brine,
then dried over anhydrous MgSO4 and concentrated in vacuo to
give tert-butyl [(1S)-1-(({[5-(1H-imidazol-1-ylcarbonyl)pyridin-
3- yl]oxy)methyl)propyl]carbamate (650 mg, 100% yield) as
(trifluoromethyl)phenyl]propyl}oxy)nicotinate (6l)
1H NMR (400 MHz, DMSO-d6)
d 8.70 (d, 1H), 8.54 (d, 1H), 7.78
(m, 1H), 7.55 (m, 3H), 7.05 (d, 2H), 4.12 (m, 2H), 4.03 (m, 1H), 3.90 (s,
3H), 3.04 (m, 1H), 2.82 (m, 1H), 1.26 (s, 9H). MS (ESI) m/z 455.3.
5.3.10. Methyl-5-({(2R)-2-[(tert-butoxycarbonyl)amino]-3-[3-
(trifluoromethyl)phenyl]propyl}oxy)nicotinate (6m)
a white semi-solid. 1H NMR (400 MHz, CDCl3)
d 8.6 (m, 2H), 8.1
1H NMR (400 MHz, DMSO-d6)
d
8.70 (d, 1H), 8.54 (d, 1H), 7.78
(m, 1H), 7.62 (m, 1H), 7.56 (m, 1H), 7.22 (m, 1H), 4.68 (m, 1H), 4.12
(m, 2H), 3.91 (bs, 1H), 1.77 (m, 1H), 1.63 (m, 1H), 1.45 (s, 9H), 1.02
(t, 3H). MS (ESI) m/z 361.3.
(m, 1H), 7.55 (m, 3H), 7.05 (d, 2H), 4.12 (m, 2H), 4.03 (m, 1H), 3.89 (s,
3H), 3.04 (m, 1H), 2.82 (m, 1H), 1.27 (s, 9H). MS (ESI) m/z 455.3.
5.3.11. Methyl 5-{[(2S)-2-[(tert-butoxycarbonyl)amino]-3-(1H-
5.3.17. Methyl-5-{[(2S)-2-[(tert-butoxycarbonyl)amino]-3-(4-
fluorophenyl)propyl]oxy}nicotinate (6j)
To a stirred solution of tert-butyl{(1S)-2-hydroxy-1-[3-(tri-
fluoromethyl)benzyl]ethyl}carbamate (1.00 g, 3.13 mmol) in anhy-
drous DCM was added triethylamine (0.65 mL, 4.70 mmol) followed
by dropwise addition of methanesulfonyl chloride (0.26 mL,
indol-3-yl)propyl]oxy}nicotinate (6n)
1H NMR (400 MHz, DMSO-d6)
d
10.82 (s, 1H), 8.98 (s,1H), 8.67 (s,
1H), 8.53 (d, 1H), 7.72 (m, 1H), 7.56 (d, 1H), 7.33 (d, 1H), 7.15 (s, 1H),
7.01 (m, 2H), 4.07 (m, 3H), 3.88 (s, 3H), 2.94 (m, 2H), 1.36 (s, 9H). MS
(ESI) m/z 426.3.

1384
T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
3.29 mmol). The reaction was stirred 30 min and concentrated in
vacuo. The residue was dissolved in EtOAc (150 mL) and washed
with water, saturated aqueous NaHCO3, brine (100 mL of each), and
then dried over Na2SO4. The organic layer was passed through a pad
of silica gel with EtOAc and concentrated in vacuo. To a stirred
solution of the residue and 5-hydroxynicotinic acid methyl ester
(479 mg, 3.13 mmol) in anhydrous DMF (10 mL) was added Cs2CO3
(2.04 g, 6.26 mmol) and heated to 60 ꢁC for 18 h. The mixture was
concentrated in vacuo and the residue was dissolved in Et2O
(200 mL), washed with 0.1 N NaOH (150 mL), dried over Na2SO4, and
purified by silica gel chromatography using a gradient elution of 20–
100% EtOAc/Hexanes to give methyl 5-(({(2S)-2-[(tert-butox-
ycarbonyl)amino]-3-[3-tri-
5.3.21. 2-[5-(2-Aminoethoxy)pyridin-3-yl]-8,9-dimethoxybenzo[c]-
2,7-naphthyridin-4-amine (9a)
1H NMR (400 MHz, DMSO-d6)
d 9.61 (s, 1H), 9.24 (s, 1H), 8.48 (m,
1H), 8.42(s,1H), 8.22 (m, 2H), 8.11 (bs, 2H), 7.58 (s,1H), 4.49 (t, 2), 4.09
(s, 3), 4.00 (s, 3H), 3.33 (m, 2H). HRMS: calcd for C21H21N5O3 þ Hþ,
392.17172; found (ESI-FTMS, [M þ H]1þ), 392.17316.
5.3.22. 2-(5-{[(2S)-2-Aminopropyl]oxy}pyridin-3-yl)-8,9-
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9b)
1H NMR (DMSO-d6)
d 9.47 (s, 1H), 9.18 (d,1H), 8.38 (m, 2H), 8.17 (s,
2H), 7.50 (s,1H), 7.37 (bs, 2H), 4.07 (s, 3H), 3.97 (s, 3H), 3.94 (m, 2H), 3.25
(m, 1H), 1.82 (bs, 2H), 1.11 (d, 3H). HRMS: calcd for C22H23N5O3 þ Hþ,
406.18737; found (ESI-FTMS, [M þ H]1þ), 406.18804.
fluoromethyl)phenyl]propyl}oxy)nicotinate (0.34 mg, 24%).1H NMR
(400 MHz, DMSO-d6)
d
8.69 (d, 1H), 8.53 (d, 1H), 7.76 (m, 1H), 7.26
5.3.23. 2-(5-{[(2R)-2-Aminopropyl]oxy}pyridin-3-yl)-8,9-
(m, 2H), 7.10 (m, 2H), 7.00 (d, 1H), 4.07 (m, 2H), 3.96 (m, 1H), 3.89 (s,
3H), 2.89 (m, 1H), 2.73 (m, 1H), 1.30 (s, 9H). MS (ESI) m/z 405.2.
The following compounds were made using the above
procedure:
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9c)
1H NMR (DMSO-d6)
d 9.47 (s, 1H), 9.18 (d, 1H), 8.38 (m, 2H), 8.17 (s,
2H), 7.50 (s,1H), 7.37 (bs, 2H), 4.07 (s, 3H), 3.97 (s, 3H), 3.94 (m, 2H), 3.25
(m, 1H), 1.82 (bs, 2H), 1.11 (d, 3H). HRMS: calcd for C22H23N5O3 þ Hþ,
406.18737; found (ESI-FTMS, [M þ H]1þ), 406.18805.
5.3.18. 2-(5-{[(2S)-2-Aminopropyl]oxy}pyridin-3-yl)-8,9-
dimethoxybenzo[c]-2,7- naphthyridin-4-amine (6b)
5.3.24. 2-(5-{[(2S)-2-Aminobutyl]oxy}pyridin-3-yl)-8,9-
1H NMR (DMSO-d6)
d
8.83 (d, 1H), 8.47 (d,1H), 7.75 (m, 1H), 4.75
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9d)
(bs, 1H), 4.09 (m, 1H), 4.01 (d, 2H), 3.95 (s, 3H), 1.44 (s, 9H), 1.31 (d,
1H NMR (400 MHz, DMSO-d6)
d 9.61 (s, 1H), 9.25 (s, 1H), 8.49 (m,
3H). MS (ESI) m/z 406.3.
1H), 8.42 (s, 1H), 8.23 (m, 2H), 8.14 (bs, 2H), 7.57 (s, 1H), 4.41 (m,
1H), 4.24 (m, 1H), 4.09 (s, 3H), 4.00 (s, 3H), 3.54 (bs, 1H), 1.75 (m,
2H), 1.03 (t, 3H). HRMS: calcd for C23H25N5O3 þ Hþ, 420.20302;
found (ESI-FTMS, [M þ H]1þ), 420.20377.
5.3.19. 2-(5-{[(2R)-2-Aminopropyl]oxy}pyridin-3-yl)-8,9-
dimethoxybenzo[c]-2,7- naphthyridin-4-amine (6c)
1H NMR (DMSO-d6)
d 8.83 (d, 1H), 8.47 (d, 1H), 7.75 (m, 1H), 4.75
(bs, 1H), 4.09 (m, 1H), 4.01 (d, 2H), 3.95 (s, 3H), 1.44 (s, 9H), 1.31 (d,
5.3.25. 2-(5-{[(2R)-2-Aminobutyl]oxy}pyridin-3-yl)-8,9-
3H). MS (ESI) m/z 406.3.
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9e)
1H NMR (400 MHz, DMSO-d6)
d 9.61 (s, 1H), 9.25 (s, 1H), 8.49 (m,
5.3.20. 2-(5-{[(2S)-2-Amino-3-(3,4-
dichlorophenyl)propyl]oxy}pyridin-3-yl)-8,9- dimethoxybenzo[c]-
2,7-naphthyridin-4-amine (9r)
1H), 8.42 (s, 1H), 8.23 (m, 2H), 8.14 (bs, 2H), 7.57 (s, 1H), 4.41 (m,
1H), 4.24 (m, 1H), 4.09 (s, 3), 4.00 (s, 3H), 3.54 (bs, 1H), 1.75 (m, 2H),
1.03 (t, 3H). HRMS: calcd for C23H25N5O3 þ Hþ, 420.20302; found
(ESI-FTMS, [M þ H]1þ), 420.2031.
To
a stirred solution of methyl-5-{[(2S)-2-[(tert-butoxy-
carbonyl)amino]-3-(3,4-dichlorophenyl)propyl]oxy}nicotinate (0.50 g,
1.10 mmol) and 6,7-dimethoxy-4-methyl-quinoline-3-carbonitrile
(0.25 g, 1.10 mmol) in anhydrous THF (5 mL) at ꢀ78 ꢁC was
added dropwise LiHMDS (3.52 mL, 1.0 M solution in THF,
3.52 mmol). The reaction was stirred at ꢀ78 ꢁC for 1 h, slowly
warmed to room temperature over 2 h, then stirred an addi-
tional 30 min and quenched by addition of crushed dry ice and
water. The mixture was extracted with 3 ꢂ150 mL EtOAc, dried
over Na2SO4, and concentrated in vacuo. The residue was
further dried by concentrating in vacuo with toluene.
5.3.26. 2-(5-{[(2S)-2-Amino-4-methylpentyl]oxy}pyridin-3-yl)-
8,9-dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9f)
1H NMR (400 MHz, DMSO-d6)
d 9.90 (s, 1H), 9.30 (s, 1H), 8.64 (s,
1H), 8.54 (s, 1H), 8.47 (m, 2H), 8.32 (s, 1H), 7.70 (s, 1H), 4.56 (m, 2H),
4.40 (m, 2H), 4.14 (s, 3H), 4.01 (s, 3H), 3.62 (m, 2H),1.83 (m,1H),1.62
(m, 2H), 0.95 (d, 6H). HRMS: calcd for C25H29N5O3 þ Hþ,
448.23432; found (ESI-FTMS, [M þ H]1þ), 448.23354.
5.3.27. 2-(5-{[(2R)-2-Amino-4-methylpentyl]oxy}pyridin-3-yl)-
The residue was dissolved in 20 mL of anhydrous DMF and
sublimed NH4OAc (1.70 g, 22.0 mmol) was added and the reaction
mixture was heated at 100 ꢁC for 2 h. The DMF was then removed by
concentrating invacuo and 15 mL of2 N HCl in40 ml ofTHFwasadded.
The reaction was stirred at 60 ꢁC for 6 h, concentrated in vacuo to
removed the bulk amount of THF, cooled and poured into 10 N NaOH.
This aqueous solution was extracted with 3 ꢂ 150 mL EtOAc, the
pooled extracts were dried over anhydrous Na2SO4, filtered, and
concentrated in vacuo. The residue was purified by silica gel chroma-
tography using 90:10:1 DCM/MeOH/Et3N to give 2-(5-{[(2S)-2-Amino-
8,9-dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9g)
1H NMR (400 MHz, DMSO-d6)
d 9.90 (s, 1H), 9.30 (s, 1H), 8.64 (s,
1H), 8.54 (s, 1H), 8.47 (m, 2H), 8.32 (s, 1H), 7.70 (s, 1H), 4.56 (m, 2H),
4.40 (m, 2H), 4.14 (s, 3H), 4.01 (s, 3H), 3.62 (m, 2H),1.83 (m,1H),1.62
(m, 2H), 0.95 (d, 6H). HRMS: calcd for C25H29N5O3 þ Hþ,
448.23432; found (ESI-FTMS, [M þ H]1þ), 448.23614.
5.3.28. 2-(5-{[(2S)-2-Amino-3-phenylpropyl]oxy}pyridin-3-yl)-
8,9-dimethoxybenzo[c]-2,7- naphthyridin-4-amine (9h)
1H NMR (400 MHz, DMSO-d6)
d 9.48 (s, 1H), 9.19 (s, 1H), 8.37 (m,
3-(3,4-dichlorophenyl)propyl]oxy}pyridin-3-yl)-8,9-
ybenzo[c]-2,7-naphthyridin-4-amine (280 mg, 46% for 3 steps). 1H
NMR (400 MHz, DMSO-d6) 9.47 (s, 1H), 9.19 (d, 1H), 8.37 (s, 2H), 8.17
dimethox-
2H), 8.18 (m, 2H), 7.51 (s, 1H), 7.36 (bs, 2H), 7.29 (m, 4H), 7.21 (m,
2H), 4.08 (s, 3H), 4.00 (m, 2H), 3.98 (s, 3H), 2.90 (m, 1H), 2.66 (m,
1H). HRMS: calcd for C28H27N5O3 þ Hþ, 482.21867; found (ESI,
[M þ H]þ Obs’d), 482.2186.
d
(m, 2H), 7.58 (d,1H), 7.56 (s,1H), 7.54 (s,1H), 7.51 (s, 2H), 7.36 (bs, 2H),
7.30 (d,1H), 7.28 (d,1H), 4.08 (s, 3H), 4.02 (m, 2H), 3.98 (s, 3H), 2.92 (m,
1H), 2.67 (m, 1H). HRMS: calcd for C28H25Cl2N5O3 þ Hþ, 550.14072;
found (ESI-FTMS, [M þ H]1þ), 550.14001.
5.3.29. 2-(5-{[(2R)-2-Amino-3-phenylpropyl]oxy}pyridin-3-yl)-
8,9-dimethoxybenzo[c]-2,7- naphthyridin-4-amine (9i)
The following compounds were made using the above
procedure:
1H NMR (400 MHz, DMSO-d6)
d
9.48 (s, 1H), 9.19 (s, 1H), 8.38 (m,
2H), 8.18 (m, 2H), 7.51 (s, 1H), 7.36 (bs, 2H), 7.30 (m, 4H), 7.22 (m,

T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
1385
2H), 4.08 (s, 3H), 4.03 (m, 2H), 3.97 (s, 3H), 2.93 (m, 1H), 2.73 (m,
1H). HRMS: calcd for C28H27N5O3 þ Hþ, 482.21867; found (ESI-
FTMS, [M þ H]1þ), 482.22024.
HRMS: calcd for C28H26ClN5O3 þ Hþ, 516.17969; found (ESI-
FTMS, [M þ H]1þ), 516.1801.
5.3.37. 2-(5-{[(2S)-2-Amino-3-(3-chlorophenyl)propyl]oxy}pyridin-
5.3.30. 2-(5-{[(2S)-2-Amino-3-(4-
3-yl)-8,9- dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9q)
fluorophenyl)propyl]oxy}pyridin-3-yl)-8,9- dimethoxybenzo[c]-2,7-
naphthyridin-4-amine (9j)
1H NMR (400 MHz, DMSO-d6)
d 9.49 (s, 1H), 9.25 (s, 1H), 8.42 (s,
1H), 8.37 (s, 1H), 8.18 (m, 2H), 7.52 (s, 1H), 7.46 (s, 1H), 7.35 (m, 4H),
4.32 (m, 1H), 4.14 (m, 1H), 4.08 (s, 3H), 3.98 (s, 3H), 3.90 (m, 2H),
3.07 (d, 2H). HRMS: calcd for C28H26ClN5O3 þ Hþ, 516.17969; found
(ESI-FTMS, [M þ H]1þ), 516.1806.
1H NMR (400 MHz, DMSO-d6)
d 9.47 (s, 1H), 9.18 (d, 1H), 8.37 (m,
2H), 8.17 (m, 2H), 7.51 (s, 1H), 7.36 (bs, 2H), 7.31 (m, 2H), 7.12 (m,
2H), 4.08 (s, 3H), 3.99 (m, 2H), 3.97 (s, 3H), 2.89 (m, 1H), 2.65 (m,
1H). HRMS: calcd for C28H26FN5O3 þ Hþ, 500.20924; found (ESI-
FTMS, [M þ H]1þ), 500.20938.
5.3.38. 2-(5-{[(2S)-2-Amino-3-pyridin-4-ylpropyl]oxy}pyridin-3-
yl)-8,9- dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9s)
5.3.31. 2-(5-{[(2R)-2-Amino-3-(4-
1H NMR (400 MHz, DMSO-d6)
d 9.64 (s, 1H), 9.26 (s, 1H), 8.72 (d,
fluorophenyl)propyl]oxy}pyridin-3-yl)-8,9- dimethoxybenzo[c]-2,7-
naphthyridin-4-amine*HCl (9k)
2H), 8.49 (d, 1H), 8.43 (s, 1H), 8.38 (bs, 2H), 8.25 (s, 1H), 8.18 (s, 1H),
7.68 (d, 2H), 7.59 (s, 1H), 4.38 (m, 1H), 4.21 (m, 1H), 4.11 (s, 3H),
4.08 (m, 3H), 4.01 (s, 3H), 3.22 (d, 2H). HRMS: calcd for
C27H26N6O3 þ Hþ, 483.21391; found (ESI-FTMS, [M þ H]1þ),
483.21474.
1H NMR (400 MHz, DMSO-d6)
d 9.52 (s, 1H), 9.25 (d, 1H), 8.44
(m, 2H), 8.38 (s, 1H), 8.24 (bs, 2H), 8.18 (m, 1H), 7.53 (s, 1H), 7.44
(bs, 1H), 7.38 (m, 2H), 7.20 (m, 2H), 4.31 (m, 1H), 4.13 (m, 1H), 4.08
(s, 3H), 3.98 (s, 3H), 3.06 (d, 2H). HRMS: calcd for
C28H26FN5O3 þ Hþ, 500.20924; found (ESI-FTMS, [M þ H]1þ),
500.20747.
Acknowledgments
The authors wish to thank Drs. Tarek Mansour and Robert
Abraham for their support and encouragement provided during the
course of this work. We also would like to thank the members of
the Wyeth Chemical Technologies group for analytical and spectral
determinations.
5.3.32. 2-[5-({(2S)-2-Amino-3-[3-
(trifluoromethyl)phenyl]propyl}oxy)pyridin-3-yl]-8,9-
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9l)
1H NMR (400 MHz, CDCl3)
d 9.21 (s, 1H), 8.96 (s, 1H), 8.40 (s,
1H), 8.01 (s, 2H), 7.78 (s, 1H), 7.58 (s, 1H), 7.53 (m, 2H), 7.46
(m, 2H), 5.49 (bs, 2H), 4.17 (s, 3H), 4.10 (s, 3H), 4.03 (m, 2H), 3.56
(m, 1H), 3.08 (m, 1H), 2.83 (m, 1H). HRMS: calcd for
C29H26F3N5O3 þ Hþ, 550.20605; found (ESI-FTMS, [M þ H]1þ),
550.20615.
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5.3.33. 2-[5-({(2R)-2-Amino-3-[3-
(trifluoromethyl)phenyl]propyl}oxy)pyridin-3-yl]-8,9-
dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9m)
1H NMR (400 MHz, DMSO-d6)
d 9.48 (s, 1H), 9.02 (d, 1H), 8.38 (d,
1H), 8.36 (s, 1H), 8.18 (s, 2H), 7.58 (m, 5H), 7.36 (s, 1H), 4.08 (s, 3H),
4.04 (m, 2H), 4.03 (m, 2H), 3.98 (s, 3H), 3.04 (m, 1H), 2.80 (m, 1H).
HRMS: calcd for C29H26F3N5O3 þ Hþ, 550.20605; found (ESI-FTMS,
[M þ H]1þ), 550.20631.
5.3.34. 2-(5-{[(2S)-2-Amino-3-(1H-indol-3-yl)propyl]oxy}pyridin-
3-yl)-8,9- dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9n)
1H NMR (400 MHz, DMSO-d6)
d 10.95 (bs, 1H), 9.47 (s,1H), 9.18 (d,
1H), 8.37 (d, 2H), 8.18 (s, 2H), 7.57 (d,1H), 7.51 (s,1H), 7.37 (bs, 2H), 7.34
(d, 1H), 7.21 (d, 1H), 7.05 (t, 1H), 6.94 (t, 1H), 4.07 (s, 3H), 4.03 (m, 2H),
3.98 (s, 3H), 3.41 (m, 1H), 3.01 (m, 1H), 2.80 (m, 1H). HRMS: calcd for
C30H28N6O3 þ Hþ, 521.22957; found (ESI-FTMS, [M þ H]1þ),
521.22985.
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5.3.35. 2-(5-{[(2R)-2-Amino-3-(1H-indol-3-yl)propyl]oxy}pyridin-
3-yl)-8,9- dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9o)
1H NMR (400 MHz, DMSO-d6)
d 10.92 (bs, 1H), 9.47 (s, 1H), 9.20
(s, 1H), 8.37 (m, 2H), 8.18 (s, 2H), 7.60 (d, 1H), 7.51 (s, 1H), 7.35 (m,
3H), 7.24 (s, 1H), 7.07 (t, 1H), 6.96 (t, 1H), 4.11 (m, 2H), 4.07 (s, 3H),
3.96 (s, 3H), 3.57 (m,1H), 3.07 (m,1H), 2.92 (m,1H). HRMS: calcd for
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521.22842.
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5.3.36. 2-(5-{[(2S)-2-Amino-3-(2-chlorophenyl)propyl]oxy}pyridin-
3-yl)-8,9- dimethoxybenzo[c]-2,7-naphthyridin-4-amine (9p)
1H NMR (400 MHz, DMSO-d6)
d 9.48 (s, 1H), 9.23 (s, 1H), 8.37 (m,
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2H), 8.17 (s, 2H), 7.48 (m, 4H), 7.33 (m, 4H), 4.22 (m, 1H), 4.11 (m,
2H), 4.08 (s, 3H), 3.98 (s, 3H), 3.70 (m,1H), 3.18 (m,1H), 3.02 (m,1H).

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T. Nittoli et al. / European Journal of Medicinal Chemistry 45 (2010) 1379–1386
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[30] PDB code: 3ion.
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