Design and synthesis of benzoazepinone-derived cyclic malonamides and aminoamides as potent γ-secretase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2007.04.102

We report the synthesis of benzoazepine-derived cyclic malonamides (2) and aminoamides (3) as γ-secretase inhibitors for the potential treatment of Alzheimer's disease. The in vitro structure-activity relationships of 2 and 3 along with dog pharmacokineti

Full text of DOI:10.1016/j.bmcl.2007.04.102

Bioorganic & Medicinal Chemistry Letters 17 (2007) 3910–3915
Design and synthesis of benzoazepinone-derived cyclic
malonamides and aminoamides as potent c-secretase inhibitors
Michael G. Yang,* Jian-Liang Shi, Dilip P. Modi, Jennifer Wells, Brian M. Cochran,
Mark A. Wolf, Lorin A. Thompson, Mercy M. Ramanjulu, Arthur H. Roach,
Robert Zaczek, David W. Robertson, Ruth R. Wexler and Richard E. Olson
Bristol-Myers Squibb Co., Research and Development, 5 Research Parkway, Wallingford, CT 06492, USA
Received 15 March 2007; revised 25 April 2007; accepted 30 April 2007
Available online 3 May 2007
Abstract—We report the synthesis of benzoazepine-derived cyclic malonamides (2) and aminoamides (3) as c-secretase inhibitors for
the potential treatment of Alzheimer’s disease. The in vitro structure–activity relationships of 2 and 3 along with dog pharmacoki-
netic results are described.
Ó 2007 Elsevier Ltd. All rights reserved.
Alzheimer’s disease (AD) is the most common form of
dementia and affects 7–10% of those over 65 years of
age and up to 40% of those over age 80.1 The progres-
sive cognitive impairment and memory loss in AD is
accompanied pathologically by an accumulation in
brain of plaques consisting of 40–42-amino acid b-amy-
loid peptides (Ab), and neurofibrillary tangles made up
of hyperphosphorylated tau.2 Considerable evidence
points to a causative role for Ab in AD, and numerous
strategies for reducing the production and accumulation
of Ab are under investigation.3 Ab peptides are gener-
ated by the cleavage of membrane-bound b-amyloid
precursor protein (APP) by the sequential action of
b-secretase (BACE), an aspartyl protease, and c-secre-
tase, a heteromeric complex consisting of presenilin,
Aph-1, Pen-2, and nicastrin, in which presenilin appears
to be the catalytic component.4,5 Although APP pro-
cessing produces more Ab40 than Ab42, Ab42 is most
closely associated with AD pathogenesis.6 Inhibition
of c-secretase reduces production of all forms of Ab,
and represents a potential strategy for therapeutic
intervention in AD.7
namide 1, many benzodiazepine-derived c-secretase
inhibitors in the literature contain one or more chiral
centers in the side chain.9 In an ongoing study of the
structure–activity relationships (SAR) of succinamides
related to 1, we questioned whether it would be possible
to eliminate the a- and b-stereocenters by making gem-
disubstituted analogs 2 and 3 while maintaining the de-
sired c-secretase activity (Fig. 1). In this strategy, the R0
and R of malonamides 2 and aminoamides 3 could re-
place the n-propyl (R0) and i-butyl (R) groups of 1
and the terminal amide bonds of 2 and 3 could function
as H-bond acceptor/donors, mimicking the primary
amide (see Fig. 1).10 Herein we report the syntheses of
2 and 3 and their c-secretase inhibitory activities.
Amino-benzoazepinones 4 and 5 (Fig. 2) have been used
in the synthesis of c-secretase inhibitors and their syn-
thesis has been reported.11 The synthesis of trifluorom-
ethylphenyl-benzodiazepinone 6 is shown in Scheme 1.
Deacylation of phenyl acetamide 712 with 1N HCl in
EtOH gave aniline 8. Benzotriazole 913 was then coupled
to aniline 8 and the resulting product 10 was cyclized to
benzodiazepinone 11 using NH4OH/MeOH. Methyla-
tion of 11, followed by resolution using preparative chi-
ral HPLC, gave the desired single isomer 12, which was
treated with HBr gas in DMF to provide the amine 6.
The absolute configuration of 6 was confirmed by a re-
lated crystal structure (vide infra).
Previously we reported that succinamide 1 potently
inhibits c-secretase activity in APP-transfected Chinese
hamster ovary (CHO) cells (IC50 = 13 nM).8 Like succi-
Keywords: Gamma-secretase; Benzoazepinone; Inhibitors.
*
A general synthetic scheme for the preparation of cyclic
malonamides (2a) is shown in Scheme 2. Dialkylation of
Corresponding author. Tel.: +1 609 252 3234; e-mail: michael.yang@
bms.com
0960-894X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.04.102

M. G. Yang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3910–3915
3911
H-acceptor/donor
Me
O
O
O
N
H-acceptor/donor
R'
N
H
N
H
N
R
R
Me
H2N
O
O
O
2
N
malonamides
R'
N
H
N
H-acceptor/donor
Me
R
O
O
N
H
N
1
R'
N
succinamide
H
N
R
R
O
3
aminoamides
Figure 1. Proposed synthetic targets.
Me
O
Me
N
O
Me
N
O
H2N
N
H2N
N
H2N
N
4
5
6
CF3
Figure 2. Amino-benzoazepinones.
O
NHCbz
HO
N
N
N
N
O
NHAc O
N
NH2
O
N
c
a
NH
O
9
NH
b
Cbz
10
45% two
steps
CF3
60%
CF3
CF3
Me
7
8
Me
O
H
O
O
N
N
N
d,e
76% and 45%
f
CbzHN
CbzHN
H2N
HBr
N
N
N
75%
11
12
6
CF3
CF3
CF3
Scheme 1. Reagents: (a) HC1, EtOH; (b) (COC1)2, NMM; (c) NH4OH, MeOH; (d) NaH, Mel, DMF; (e) chiral separation using a CHIRALCEL
AD column with 100% acetonitrile; (f) HBr gas, DMF.
malonate 1314 with 1,4-dibromobutane gave cyclic
dicarboxylate 14 in 65% yield. Upon removing the
tert-butyl group, the resulting acid was coupled to
amines and saponified to provide carboxylic acids 16,
which were coupled to aminobenzodiazepinone 6 to give
the desired amides (2a).

3912
M. G. Yang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3910–3915
O
O
O
O
a
b,c
d
O
O
O
OEt
RHN
OEt
O
OEt
O
13
14
15
Me
Me
O
O
O
O
N
N
O
e
RHN
N
H
H2N
+
RHN
OH
N
N
16
6
2a
CF3
CF3
Scheme 2. Reagents: (a) NaH, l,4-dibromobutane, DMF; (b) TFA, CH2C12; (c) RNH2, DIEA, HATU, DMF; (d) LiOH, THF, H2O; (e) DIEA,
HATU, DMF.
Me
OH
O
O
Me
OH
H
N
a
b
H2N
OH
+
Me
OMe
OMe
Me
67%
74%
O
O
O
17
18
19
Me
Me
O
N
Me
OH
O
Me
OH
O
N
H
H
N
c
N
H2N
N
Me
Me
OH
N
H
+
65%
N
O
O
20
6
3k
CF3
Scheme 3. Reagents: (a) DIEA, HATU, DMF; (b) LiOH, THF, H2O; (c) DIEA, HATU, DMF.
CF3
The synthesis of aminoamides 3 is straightforward and
is exemplified with hydroxyl analog 3k (Scheme 3).
Commercially available amine 17 and acid 18 were used
for the initial coupling reaction to yield intermediate 19.
Saponification of 19, followed by the coupling reaction
with benzodiazepinone 6, gave the final product 3k in
32% overall yield. X-ray crystallographic analysis of
3k confirmed the stereocenter of the benzodiazepinone
to be (S) (Fig. 3).
Inhibitors 2 and 3 were initially screened for their ability
to displace a radiolabeled c-secretase inhibitor (3H-1)
from membranes derived from THP-1 cells,15 then eval-
uated in APP-transfected CHO cells for their ability to
block Ab production.16 Binding Ki and cellular IC50 val-
ues for malonamide-derived inhibitors are presented in
Table 1. Examination of the data reveals the following
SAR trends: (I) branched lipophilic side chains (R0),
such as i-Bu, were optimal for c-secretase inhibition
Me
Me
O
Me
O
O
N
N
N
HN
HN
HN
R1
R2
R3
=
=
=
N
N
CF3

M. G. Yang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3910–3915
3913
Figure 3. Crystal structure of compound 3k.
Table 1. Binding Ki and APP IC50 of malonamidesa
O
O
R'
N
H
X
R
R
b
Compound
R
X
R/R
Bindingb (APP IC50
)
2b
2c
2d
2e
2f
Et
R1
R1
R1
R1
R1
R2
R3
R1
R2
R3
Et/Et
Et/Et
1000 nM (NT)
227 nM (NT)
n-Pr
n-Pr
n-Bu
i-Bu
i-Bu
i-Bu
i-Bu
i-Bu
i-Bu
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C5H10
c-C5H10
c-C5H10
15 nM (82 nM)
11 nM (20 nM)
3.5 nM (21 nM)
1.2 nM (28 nM)
1.4 nM (5.8 nM)
6.2 nM (19.5 nM)
2.0 nM (12.5 nM)
3.0 nM (26.1 nM)
2g
2h
2i
2j
2k
a Binding Ki and APP IC50 are 2.6 and 13 nM, respectively, for compound 1.
b Data are reported as means of three determinations. See Ref. 8 for assay protocol.
(e.g., 2f vs 2e and 2d); (II) cyclic malonamides were more
potent than their corresponding acyclic analogs (e.g., 2c
vs 2d); among the cyclic inhibitors, there was no differ-
ence in affinity between five- and six-membered cyclic
compounds; and (III) the incorporation of different ben-
zoazepinones (R1–R3) had minimal impact on the bind-
ing activity, but in some cases cellular potency could be
modestly improved with the bisbenzoazepinone (R3)
group (e.g., 2h vs. 2g).
Binding affinities and cellular IC50 values of amino-
amide-derived inhibitors are presented in Table 2. The
lipophilic side chain R0 was essential for c-secretase inhi-
bition. As noted in the malonamide series, there was no
significant difference in affinity between five- and six-
membered ring analogs (e.g., 3c vs. 3d). In addition,
we observed that the incorporation of a hydroxy moiety
in R0 was well tolerated by the enzyme. The (S)-hydro-
xyl diastereoisomer 3n exhibited superior potency

3914
M. G. Yang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3910–3915
Table 2. Binding Ki and APP IC50 of aminoamidesa
O
H
N
R'
X
R
R
O
b
Compound
R0
X
R/R
Bindingb (APP IC50
)
3a
3b
3c
3d
3e
3f
Thiophene-CH2
c-C5H9-CH2CH2
3,5-Difluorophenyl-CH2
3,5-Difluorophenyl-CH2
i-Bu-CH2
R1
R1
R1
R1
R2
R3
R2
R3
R2
R3
R2
R3
R3
R2
R2
R2
R3
c-C5H10
c-C5H10
c-C5H10
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
c-C4H8
41 nM (19 nM)
36 nM (NT)
9.9 nM (96 nM)
13.5 nM (115 nM)
4.9 nM (14 nM)
4.0 nM (15 nM)
2.2 nM (13 nM)
1.3 nM (21 nM)
1.1 nM (6.7 nM)
3.9 nM (15 nM)
2.1 nM (6.1 nM)
0.9 nM (4.2 nM)
22 nM (280 nM)
3.1 nM (11 nM)
111 nM (280 nM)
93 nM (NT)
i-Bu-CH2
3g
3h
3i
c-C5H9-CH2CH2
c-C5H9-CH2CH2
(S)-i-Pr-CH(OH)
(S)-I-Pr-CH(OH)
(S)-i-Bu-CH(OH)
(S)-i-Bu-CH(OH)
i-Bu-CF2
3j
3k
3l
3m
3n
3o
3p
3q
(S)-c-C6H11CH(OH)
(R)-c-C6H11-CH(OH)
c-C6Hn-C(O)
(S)-c-C6H11-CR(OK)
0.9 nM (3.6 nM)
a Binding Ki and APP IC50 are 2.6 and 13 nM, respectively, for compound 1.
b Data are reported as means of three determinations. See Ref. 8 for assay protocol.
(binding Ki = 3.1 nM), as compared to either the (R)-
isomer 3o (binding Ki = 111 nM) or ketone 3p (binding
Ki = 93 nM). Similarly, the gem-difluoro analog 3m
was approximately 25-fold less active as compared to
the parent hydroxyl analog 3l.
ability to block c-secretase-mediated Notch signaling.
The potency of 3k for inhibition of Notch signaling
(IC50 = 9.8 nM)10 was similar to that observed for inhi-
bition of Ab production (IC50 = 6.1 nM).
In summary, we have found that benzoazepinone-
derived cyclic malonamides and aminoamides are potent
inhibitors of c-secretase, as demonstrated by inhibition
of cellular Ab production and low-nanomolar binding
to presenilin. SAR studies indicated that a cyclic moiety
was preferred at the R position; cyclopentyl and cyclo-
hexyl-derived inhibitors exhibited similar inhibitory
activity. The introduction of a hydroxyl moiety in the
aminoamide side chain improved both binding and cel-
lular activity. Aminoamide 3k has fewer stereocenters
than succinamide 1 and exhibits similar potency against
cellular Ab production. As shown from preliminary
in vivo results, compound 3k has an attractive overall
PK profile in dog. Further studies are needed to assess
the effects of 3k on Ab levels in the central nervous
system.
Representative compounds from Tables 1 and 2 were
tested in the beagle dog for pharmacokinetic (PK) prop-
erties and the resulting in vivo data are summarized in
Table 3. Compounds were dosed in a single animal (cas-
sette format) with up to nine other compounds. The
doses were kept low (0.25 mg/kg iv and 0.5 mg/kg po)
to help minimize potential compound interactions. All
compounds exhibit good oral bioavailability and a mod-
erate (or long) half-life. Compound 3k was noteworthy
in giving plasma levels of 2975 nM (bioavailabil-
ity = 84%) in this study.
Notch-1 is a cell surface receptor important in cell fate
decisions.17 Previous studies have reported that c-secre-
tase inhibitors block Notch-1 signaling and impair
Notch function.18 Therefore, we tested aminoamide 3k
in NIH 3T3 cells using murine Notch DE to assess its
Acknowledgments
Table 3. Pharmacokinetics of selective compounds
The authors thank Cindy Rominger and David Romin-
ger for help with binding and cellular assays, and Dr.
Percy Carter for helpful suggestions with the
manuscript.
Parameter
2f
2h
3e
3h
3k
3f
po Dose (m pk)
Fu (%, dog)
Cl (l/h/kg)
Vss (V kg)
t1/2 (h)
0.5
0.4
1.3
3.1
5.3
84
0.5
0.1
0.5
2.1
4.6
184
47
0.5
0.5
0.2
1.9
13.2
567
61
0.5
0.2
0.3
2.9
13.4
365
71
0.5
1.7
0.5
0.5
0.2
0.9
5.3
172
23
0.04
0.2
6.5
References and notes
Cmax (nM)
F (%)
2975
84
42
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