Synthesis and activity of quinolinylmethyl P1′ α-sulfone piperidine hydroxamate inhibitors of TACE

Article abstract of DOI:10.1016/j.bmcl.2009.05.020

A series of α-sulfone piperidine hydroxamate TACE inhibitors 11a-n bearing a quinolinyl methyl P1′ group was prepared, and their activity was compared to analogous α- and β-sulfone piperidine hydroxamates with a butynyloxy P1′ group. The quinolinyl methyl

Full text of DOI:10.1016/j.bmcl.2009.05.020

Bioorganic & Medicinal Chemistry Letters 19 (2009) 3445–3448
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and activity of quinolinylmethyl P10
a-sulfone piperidine
hydroxamate inhibitors of TACE
b
b
a
a
c
Chunchun Zhang a, , Frank Lovering , Mark Behnke , Arie Zask , Vincent Sandanayaka , Linhong Sun ,
*
Yi Zhu c, Weixin Xu c, Yuhua Zhang c, Jeremy I. Levin a
a Chemical and Screening Science, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965, USA
b Chemical and Screening Science, Wyeth Research, 200 Cambridge Park Drive, Cambridge, MA 02140, USA
c Department of Inflammation, Wyeth Research, 200 Cambridge Park Drive, Cambridge, MA 02140, USA
a r t i c l e i n f o
a b s t r a c t
-sulfone piperidine hydroxamate TACE inhibitors 11a–n bearing a quinolinyl methyl P10
- and b-sulfone piperidine hydroxa-
Article history:
A series of
group was prepared, and their activity was compared to analogous
mates with a butynyloxy P10 group. The quinolinyl methyl P10 group affords increased inhibitory enzyme
a
Received 8 April 2009
Revised 5 May 2009
Accepted 6 May 2009
Available online 9 May 2009
a
activity relative to the corresponding butynyloxy P10 analogs in the
a-sulfone piperidine hydroxamate
series, and greater selectivity than the corresponding butynyloxy P10 analogs in the b-sulfone piperidine
hydroxamate series.
Keywords:
Ó 2009 Elsevier Ltd. All rights reserved.
a-Sulfone piperidine hydroxamate
TACE inhibitors
MMP selectivity
Tumor necrosis factor-
a
(TNF-a) is a pro-inflammatory cytokine
2 also possesses reasonable cellular activity, as measured by its
that has been demonstrated to play a pivotal role in a variety of
inflammatory diseases including rheumatoid arthritis (RA).1 The
clinical success of biologic anti-TNF therapies including EnbrelÒ,2
HumiraÒ, and RemicadeÒ,3 administered via injection or infusion
ability to inhibit LPS-induced TNF production in Raw cells with
an IC50 of 490 nM. In comparison,
a-sulfone hydroxamates 1 are
less selective and generally have inferior cellular activity relative
to the corresponding b-sulfone analogs.6b Thus, compound 1
(R = Ac) shows less than 5-fold selectivity over MMP-13 and has
moderate TACE enzyme activity with an IC50 of 47 nM.6c
to treat RA via modulation of TNF-
a
levels, has validated TNF-
a
as a target for pharmaceutical intervention. TNF-
a
converting
enzyme (TACE) is a membrane bound zinc proteinase and is the
O
O
O
O
O
primary enzyme responsible for the cleavage of membrane bound
O
a to afford soluble TNF-a
.4 The potential for the development
S
O
S
O
TNF-
of orally active, small molecule inhibitors of TACE that modulate
levels of soluble TNF- to provide an alternative treatment for
HOHN
HOHN
a
N
N
R
RA and other inflammatory diseases has made the design of drugs
2
1
R
for this target the focus of intense interest.5
We have previously discovered that both
a- and b-sulfone
Despite their reasonable enzyme and cellular activity, even the
best - and b-sulfone hydroxamates 1 and 2 show only moderate
activity in human whole blood (HWB). In addition, this class of
compounds demonstrates generally poor pharmacokinetic proper-
ties, making it difficult to achieve and sustain plasma levels above
piperidine hydroxamate scaffolds, 1 and 2, can provide potent
TACE inhibitors, particularly when a butynyloxyphenyl P10 moiety
is attached.6,7 Inhibitors bearing the butynyloxyl group can provide
excellent cellular activity and selectivity for TACE, depending on
the scaffold used.8 The b-sulfone piperdine hydroxamates, 2, are
a
the HWB IC50. Optimization of the piperidine
a-sulfone hydroxa-
generally more potent than a-sulfone piperdine hydroxamates, 1,
mates has so far focused on varying the substituent on the piperi-
dine nitrogen in an effort to further increase activity and
selectivity, while keeping the P10 butynyloxyl group constant.6b
In light of the fact that the quinolinylmethyl ether P10 moiety has
been shown to provide very active and extremely selective TACE
inhibitors,9 we have explored the impact of this group on the
in both the TACE enzyme and cellular assays. For example, 2
(R = Ac) is a 2 nM inhibitor of TACE enzyme, with greater than
75-fold selectivity over MMP-1, -2, -9, -13, and -14.6a Compound
* Corresponding author. Fax: +1 8456025561.
E-mail address: zhangc9@wyeth.com (C. Zhang).
a-sulfone hydroxamate scaffold.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.05.020

3446
C. Zhang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3445–3448
EtO
O
O
EtO
O
O
O
S
Deprotonation of 4 with lithium diisopropylamide, followed by
O
OBn
quenching with 4-(benzyloxy)benzene-1-sulfonyl fluoride, gives
EtO
O
a
-sulfonyl ester 5 in good yield (71%).10 Cleavage of
a
b
the desired
N
H
3
N
N
the benzyl ether of 5 under transfer hydrogenation conditions to
provide phenol 6, and subsequent alkylation with 4-(chloro-
methyl)-2-methylquinoline then affords quinolinylmethyl ether
7. Removal of the N-Boc protecting group from the piperidine with
trifluoroacetic acid then gives the secondary amine 8 and allows
the introduction of a variety of functionality on the piperidine
nitrogen via alkylation, acylation, and sulfonylation, affording 9.
Hydrolysis of the ester of 9 with lithium hydroxide to provide car-
boxylic acid 10, followed by hydroxamate formation under peptide
coupling conditions gives final products 11a–n.
Boc
Boc
5
4
O
O
O
O
S
O
O
S
OH
EtO
EtO
EtO
c
d
N
N
N
N
Boc
Boc
7
6
O
O
S
O
O
O
O
O
O
S
EtO
The 14 analogs bearing the quinolinyl methyl ether P10 group,
11a–n, were all evaluated for in vitro enzyme activity in a FRET
assay using the catalytic domain of TACE, and next profiled for
selectivity against MMP-2 and MMP-13 (Table 1).11 These MMPs
were chosen for profiling because in our MMP/TACE programs, his-
torically, they have been the most challenging for achieving sub-
stantial selectivity.6a,12
f
e
N
H
N
R
8
9
N
O
O
O
O
O
S
O
S
O
HO
HO
N
H
h
g
Of all of these analogs, the least active inhibitors of TACE
enzyme are the NH-piperidine 11a and the N-dichlorobenzyl deriv-
ative 11l with IC50s of 33 nM and 65 nM, respectively. The amides
11b–11f, carbamate 11g, and ureas 11h–i are all extremely active
enzyme inhibitors with IC50s of 3 nM or less, despite the wide size
range of the substituents on the piperidine nitrogen of these com-
pounds. The sulfonamides 11m and 11n show a greater depen-
dence on steric bulk, with the smaller methyl sulfonamide 11m
being 10-fold more active than the bulkier isopropyl sulfonamide
11n. Methylation of the piperidine nitrogen of 11a produces a
3-fold improvement in enzyme activity for 11j (IC50 = 11 nM).
The 4-picolyl derivative 11k is essentially equipotent to 11j, indi-
cating a tolerance for a basic moiety at this position.
N
R
N
R
N
N
11a-n
10
Scheme 1. Reagents and conditions: (a) (Boc)2O, THF, rt, 95%; (b)LDA/ꢀ78 °C;
4-(benzyloxy)benzene-1-sulfonylfluoride; (c) 10% Pd/C, ammonium formate, MeOH;
(d) Cs2CO3/DMF, 4-(chloromethyl)-2-methylquinoline; (e) TFA, 93%; (f) RCOCl or
RSO2Cl or RNCO, TEA, DMAP, CH2Cl2, rt, 12 h, 85–95%; (g) LiOH, THF/MeOH/H2O
(3:2:2); (h) NH2OH, HOBT, 1-ethyl-3-(30-dimethylaminopropyl)carbodiimide, DMF,
81%.
The synthetic route to the desired targets is illustrated in
Scheme 1. Thus, protection of ethyl piperidine-4-carboxylate, 3,
with di-tert-butyl-dicarbonate affords the N-Boc derivative 4.
Table 1
IC50s of quinolinylmethyl
a-sulfone piperidine hydroxamic acid
O
O
O
O
O
O
O
O
O
S
O
S
O
S
O
HO
HO
HO
N
H
N
H
N
H
N
N
N
R
N
R
R
11a-n
1a-e
2a-d
Compound
R
TACE (nM)
MMP-2 (nM)
>15,000
MMP-13 (nM)
Raw Cells (nM)
334
HWB (
lM)
11a
1a
2a
11b
11c
1b
H
H
H
CHO
Ac
33
201
1
2
1
47
2
2
1
73
1
8624
4019
1900
440
1336
136
155
415
204
105
59
349
1110
284
135
835
57
2.4
1590
1401
6958
68
385
1.3
1.5
Ac
Ac
2b
341
1241
516
490
>1000
>1000
8.7
14
28
11d
11e
1c
COiPr
COPh
COPh
COPh
CO-4-Py
Boc
Boc
Boc
CONHEt
CONEt2
Me
2c
62
1093
2674
400
230
>1000
2.5
1.9
>50
11f
11g
1d
2
<1
134
2
2
3
11
9
65
149
1.2
10
2d
620
240
>1000
125
378
14
11h
11i
11j
11k
11l
1e
3614
96
15,099
855
2.5
>50
2.4
11
1451
266
80
72
393
926
CH2-4-Py
CH2Ph-3,4-Cl
CH2Ph-3,4-Cl
SO2Me
145
>1000
>50
11m
11n
1743
2140
345
>1000
2.8
14
SO2iPr

C. Zhang et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3445–3448
3447
Figure 1. Compound 11c docked to 2FVS. The zinc atom is colored in light blue.
Figure 2. Compounds 1b (green) and 2b (gray) docked to 2i47. The zinc atom is
colored in light blue.
The selectivity of the quinolinyl methyl P10 analogs 11a–h, 11j,
11m, and 11n for TACE is greater than 90-fold over MMP-2 and
MMP-13, and can exceed 1000-fold. Compounds 11a and 11b were
also screened against MMP-9, and were found to be very selective
against this enzyme with IC50s of >12,000 nM. Diethyl urea 11i is
the most active of the quinoline derivatives against MMP-2 and
MMP-13 with IC50s of less than 100 nM against both, more than
10-fold more active against these two MMPs than the analogous
ethyl urea analog 11h. The N-picolyl analog 11k is only moderately
active against MMP-2 and MMP-13, but loses selectivity due to its
modest TACE activity (IC50 = 9 nM), while the 3,4-dichlorobenzyl
compound 11l is essentially equipotent against all three enzymes.
The structural basis for these differing selectivity profiles is
unclear.
cell IC50 below 100 nM. Several other analogs, 11a, 11c, 11f, 11h,
11j, 11k, and 11m, have sub-micromolar cell IC50s. There is no
correlation between enzyme IC50 and cell activity, as several com-
pounds with very potent activity in the TACE enzyme assay have
IC50s greater than one micromolar in Raw cells. Activity in human
whole blood tracks reasonably well with Raw cell activity for the
quinolinyl methyl analogs, but none of the analogs tested has
sub-micromolar HWB IC50s. Only in the case of the N-acetyl analog
11c does HWB activity improve for the quinolinyl methyl P10 com-
pound, relative to the corresponding b-sulfone hydroxamate, 2b,
bearing a butynyloxy P10 group.
Finally, in vivo activity was demonstrated for compound 11f,
with a HWB IC50 of 1.9 lM. This a-sulfone piperidine hydroxamate
provided 68% inhibition of LPS-stimulated TNF production after an
For five of the
a-sulfone piperidine hydroxamates bearing the
oral dose of 25 mg/kg dose in a mouse model.11
quinolinyl methyl P10 group, 11a, 11c, 11e, 11g, and 11l, a direct
comparator with a butynyl P10 group was prepared.6c In addition,
three direct comparators, again with butynyl P10 groups, in the
b-sulfone piperidine hydroxamate series have previously been dis-
In summary, we have prepared a series of a-sulfone piperidine
hydroxamate TACE inhibitors bearing a quinolinyl methyl P10
group. These compounds have been shown to be extremely potent
inhibitors of TACE enzyme and, depending on the substituent on
the piperidine nitrogen, can provide excellent selectivity over
MMP-2 and MMP-13. The quinolinyl methyl P10 group affords
increased inhibitory enzyme activity relative to the corresponding
closed.6 The butynyloxy P10 derivatives in the
a-sulfone piperidine
hydroxamate series, 1a–e, are each substantially less active against
TACE enzyme and more active against MMP-13 than their quinoli-
nyl methyl P10 counterparts, with none of these analogs affording
even 10-fold TACE selectivity. In contrast, all of the b-sulfone
piperidine hydroxamate compounds, 2a–2d, are equipotent to
the corresponding quinolinyl analogs 11c and 11e, respectively.
However, although the unsubstituted piperidine analog 2a is great-
er than 1000-fold selective for TACE over MMP-2 and MMP-13,
none of 2b–2d has a level of selectivity approaching that provided
by the quinolinyl methyl P10 moiety.
butynyloxy P10 analogs in the
a-sulfone piperidine hydroxamate
series, and greater selectivity than the corresponding butynyloxy
P10 analogs of the b-sulfone piperidine hydroxamate series.
Although all of the compounds disclosed suffer from moderate
activity in human whole blood, oral activity has been shown in a
mouse model of TNF production for compound 11f, indicating that
this series may provide useful leads for potent, selective and
in vivo active inhibitors of TACE.
In an effort to elucidate the binding modes of these compounds,
11c, 1b, and 2b were docked to TACE.13 As there are conforma-
tional changes upon introduction of the quinolinomethyl tail14
two different PDBs were used for developing models for the dock-
ing evaluations. The PDB 2FV5 contains a pyrrolidinone hydroxa-
mate with the quinolinomethyl tail and was used for docking
11c (Fig. 1). The PDB 2i47 has a b-sulfone hydroxamate with a
butynyloxy P10 group as a ligand and was therefore used for dock-
ing 1b and 2b (Fig. 2). While compound 2b is more potent than 1b
in the TACE FRET assay, the reason for this increased activity is not
clear from the docking studies. Replacement of the butynyloxy P10
moiety of 1b with a quinolinylmethyl tail to give compound 11c
provides increased van der Waals contacts, as well as a hydrogen
bond to Ser141. The increased potency of 11c is likely due to these
additional interactions.
Acknowledgments
We would like to thank the Discovery Analytical Chemistry
group for spectral data of all compounds in this Letter, Junqing
Cui for LPS data, and Dennis Powell and James Clark for their sup-
port of this work.
References and notes
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