Discovery of β-benzamido hydroxamic acids as potent, selective, and orally bioavailable TACE inhibitors

Article abstract of DOI:10.1016/j.bmcl.2007.10.093

β-Benzamido hydroxamic acids were discovered as potent TACE inhibitors. A computer model was constructed to help understanding the binding activities and guiding SAR study. SAR optimization led to the discovery of compound 30 which met all in vitro and in

Full text of DOI:10.1016/j.bmcl.2007.10.093

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 241–246
Discovery of b-benzamido hydroxamic acids as potent,
selective, and orally bioavailable TACE inhibitors
James J.-W. Duan,* Lihua Chen, Zhonghui Lu, Chu-Biao Xue, Rui-Qin Liu,
Maryanne B. Covington, Mingxin Qian, Zelda R. Wasserman, Krishna Vaddi,
David D. Christ, James M. Trzaskos, Robert C. Newton and Carl P. Decicco
Research and Development, Bristol-Myers Squibb Company, Princeton, NJ 08543-4000, USA
Received 25 September 2007; revised 23 October 2007; accepted 25 October 2007
Available online 30 October 2007
Abstract—b-Benzamido hydroxamic acids were discovered as potent TACE inhibitors. A computer model was constructed to help
understanding the binding activities and guiding SAR study. SAR optimization led to the discovery of compound 30 which met all
in vitro and in vivo criteria for the program and was selected for further evaluation.
ꢀ 2007 Elsevier Ltd. All rights reserved.
TACE (TNF-a converting enzyme) is a zinc metallopro-
tease that is primarily responsible for the release of sol-
uble TNF-a (tumor necrosis factor-a).1 Because TNF-a
is involved in many inflammatory and immunological
pathways2 and anti-TNF biologics are broadly used to
treat diseases such as rheumatoid arthritis, Crohn’s dis-
ease, and psoriasis,3 many organizations have attempted
to develop small molecule TACE inhibitors to suppress
TNF-a activity.4
O
Gly130
Leu129
N
Glu
O
O
N
H
O
H
H
N
N
O
N
H
O
O
N
H
O
Zn
His
1
His
His
S1' site
We previously disclosed a potent and selective cyclic
succinate inhibitor 1 (Fig. 1).5 Unfortunately, com-
pound 1 was not suitable for development because the
4-(2-methylquinolin-4-ylmethoxy)aniline moiety was
positive in a bacterial reverse mutation (Ames) assay.
Computer modeling suggested that the hydroxamic acid
group of 1 binds in a manner similar to that observed
for previous TACE inhibitors, that is, chelation to cata-
lytic zinc and hydrogen bonding to Gly130 and the cat-
alytic glutamic acid residue. The central amide carbonyl
group appears to engage in hydrogen bonding with
Leu129 and Gly130. The 4-(2-methylquinolin-4-ylmeth-
oxy)phenyl group, which was found to impart selectivity
and improve cellular activity,6 is directed into the S10
pocket as expected. To exploit this binding mode, we
examined the possibility of reversing the central amide
N
H
O
N
HO
O
HN
O
2
Figure 1. Cyclic succinate 1 and b-benzamido hydroxamic acid 2.
moiety to give a series of b-benzamido hydroxamic acids
2. By virtue of this amide reversal, we eliminated the ani-
line moiety and hence addressed the mutagenicity issue.
Computer modeling suggested that 2 could be superim-
posed with 1 and maintains the aforementioned binding
mode of 1. Since the piperidine core in 1 is not involved
in any critical interactions and is mostly solvent exposed
in the model, we proceeded to test the b-benzamido
hydroxamic acid concept with the readily accessible car-
bocyclic templates.
Keyword: TACE inhibitor.
*
Corresponding author. Tel.: +1 609 252 4199; e-mail:
james.duan@bms.com
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.10.093

242
J. J.-W. Duan et al. / Bioorg. Med. Chem. Lett. 18 (2008) 241–246
Scheme 1 outlines the general synthesis of the newly pro-
posed b-benzamido hydroxamic acids. The common 4-
(2-methylquinolin-4-ylmethoxy)phenyl P10 group was
introduced using benzoic acid 5 or benzoyl chloride 6,
which was prepared from methyl 4-hydroxybenzoate
(3) and 4-chloromethyl-2-methylquinoline (4). Potas-
sium carbonate-mediated coupling of 3 and 4 in the
presence of Bu4NI proceeded in near quantitative yield.
Subsequent saponification gave acid 5, which was con-
verted to 6 using thionyl chloride. Coupling of 6 with
b-aminoester 7 was effected using NaHCO3 in biphasic
H2O–CH2Cl2 solvent mixture. Alternatively, compound
7 was coupled with acid 5 using BOP reagent. Finally es-
ter 8 was reacted with excess hydroxylamine hydrochlo-
ride (10–20 equiv) using either NaOH or NaOMe to give
hydroxamic acid 2.
sation of b-ketoester 9a–d7 with (R)-a-methylbenzyl-
amine afforded an enamine intermediate. Ytterbium
triflate was found to accelerate the reaction and prevent
formation of an amide byproduct, derived from nucleo-
philic attack of (R)-a-methylbenzylamine to the ester
group. Following a literature procedure,8 the enamine
was reduced with sodium triacetoxyborohydride in ace-
tic acid and acetonitrile at 0 ꢁC to give 10a–d, which was
debenzylated to provide two piperidine (11a and 11b)
and two tetrahydropyran analogues (11c and 11d). The
enantiomeric excess (ee) ranged from 40 to 67%. After
conversion to intermediate 8 (Scheme 1), the enantio-
meric excess was enriched to >95% either via recrystalli-
zation (8a and 8c) or chiral HPLC separation (8b and
8d). For the two piperidine isomers 8a and 8b, the Boc
group was removed under acidic conditions (HCl or
CF3CO2H) and the nitrogen further functionalized be-
fore conversion to hydroxamic acids.
Carbocyclic analogues of 2 were synthesized from the
corresponding commercially available b-amino acid or
ester derivatives. Heterocyclic b-amino acids were not
commercially available. Most of them were prepared
following a sequence summarized in Scheme 2. Conden-
An alternative route was developed to prepare tetrahy-
dropyran analogue 11e (Scheme 3). 3-Buten-1-ol (12)
was treated with NaH and sodium iodoacetate followed
by iodomethane to give a methyl ester, which was re-
duced with DIBAL to give aldehyde 13. Condensation
with N-benzylhydroxylamine yielded a nitrone, which,
when heated in toluene at 60 ꢁC, underwent intramolec-
ular [3+2]-dipolar cycloaddition with the terminal olefin,
to provide the desired cis-fused-bicyclo[4.3.0]-intermedi-
ate 14 in 50–60% yield along with a bridged-bicy-
clo[4.2.1]-byproduct 15 (10%). Treatment of 14 with
H2 and Pd(OH)2/C effected cleavage of the N–O bond
and removal of the benzyl group. The amino group
was protected with (Boc)2O to give 16. The primary
alcohol was oxidized and esterified to give 11e after re-
moval of the Boc group. The two enantiomers were re-
solved by chiral HPLC after conversion to
intermediate 8.
N
OH
N
a,b
O
+
Cl
MeO2C
R
3
4
5 (R=OH)
6 (R=Cl)
c
O
N
O
d or e
R'O2C
R'O2C
HN
NH2
8
7 (R'=Me or Et)
O
N
H
N
Replacing the piperidine moiety in 1 (Fig. 1) with a
cyclohexane and reversal of the central amide resulted
in a b-benzamido hydroxamic acid 17 (Table 1). We
were delighted to find that 17, as a racemic mixture,
was slightly more potent than 1, with an IC50 of 2 nM
in a porcine TACE (pTACE) assay.9,10 The cyclopen-
O
f
HO
O
HN
2
O
Scheme 1. Reagents and conditions: (a) K2CO3, Bu4NI, CH3CN,
80 ꢁC (99%); (b) LiOH, H2O, THF, MeOH (96%); (c) SOCl2, CH2Cl2,
at reflux (100%); (d) 5, BOP, i-Pr2NEt, DMF; (e) 6, NaHCO3, CH2Cl2,
H2O; (f) NH2OHÆHCl, KOH or NaOMe, MeOH.
O
O
OH
O
a,b
c,d
+
CHO
g-i
12
NBn
O
14
13
a,b
c
O
NBn
15
MeO2C
MeO2C
MeO2C
HN
10a-d
Ph
NH2
11a-d
O
e,f
9a-d
O
O
Boc
N
HO
O
MeO2C
11e
NBoc
O
NH2
NHBoc
16
EtO2C
EtO2C
MeO2C
MeO2C
11a
NH2
11b
40% ee
NH2
11d
65% ee
NH2
11c
60% ee
NH2
Scheme 3. Reagents and conditions: (a) NaH, ICH2CO2Na, DMF,
then MeI (84%); (b) DIBAL, CH2Cl2, ꢀ78 ꢁC (73%); (c) BnNHOH,
MgSO4, Et2O; (d) toluene, 60 ꢁC (50–60% yield of 14); (e) H2,
Pd(OH)2/C, HCl, MeOH; (f) (Boc)2O, Et3N, MeOH, CH2Cl2 (52% for
67% ee
Scheme 2. Reagents and conditions: (a) (R)-a-methylbenzylamine,
Yb(OTf)3, benzene, at reflux; (b) NaBH(OAc)3, AcOH, CH3CN, 0 ꢁC;
(c) H2, Pd(OH)2/C, HCl, EtOH.
2
steps); (g) RuCl3, NaIO4, CH3CN, CCl4, H2O (100%); (h)
TMSCHN2, MeOH, benzene (95%); (i) CF3CO2H, CH2Cl2 (95%).

J. J.-W. Duan et al. / Bioorg. Med. Chem. Lett. 18 (2008) 241–246
Table 1. In vitro potency in pTACE and WB LPS/TNF-aa
243
N
H
A
1
O
N
1
HO
2
2
O
HN
O
HN
O
21 (1
S,2R)
A
pTACE
b
IC50 (nM)
WB LPS/TNF-a
IC50 (nM)
c
1
17
—
6
20
trans-Cyclohexane
trans-Cyclopentane
cis-Cyclohexane
2
>3000
>3000
890
18
19
20
21
22
23
30
2
cis-Cyclopentane
(1S,2R)-Cyclopentane
(1R,2S)-Cyclopentane
–CH2CH2–
2
662
475
1
200
1
—
2860
a All compounds were selective over MMP-1 (>4900 nM), -2
(>3300 nM), and -9 (>2100 nM).
b pTACE IC50 values were from a single determination.
c Inhibition of TNF-a release from WB was determined with three
donors.
Figure 2. Computer model of hydroxamic acid 23 in TACE. Com-
pound 23 is shown in light green except for oxygens (red) and nitrogens
(blue). Hydrogens on the inhibitor are not shown for clarity except for
the four hydrogens on the b-alanine backbone (white). The surface
representation of TACE (yellow) is truncated to expose backbone
atoms of Leu129 and Gly130, catalytic zinc (orange), and three
imidazole side chains of histidines ligating to the zinc. The Leu129 and
Gly130 are shown in white and the imidazoles in green except for
nitrogens (blue) and oxygens (red).
tane counterpart 18 (racemic) was also active for
pTACE, albeit approximately 15-fold less potent than
17. The two cis analogues (19 and 20) were unexpectedly
potent, both were 2 nM inhibitors. The two enantiomers
of 20 were synthesized individually from the homochiral
amino acids and the (1S,2R)-enantiomer 21 was found
to be 200-fold more potent than the antipode 22. Inter-
estingly, the cyclic template is not required. A simple b-
alanine analogue 23 was equally potent, with an IC50 of
1 nM. Also noteworthy here is that compounds 17–23
maintained similar selectivity profile to compound 1
against three related matrix metalloproteinases (MMP-
reasons for the loss of cellular activity are unclear.
One possible factor is its high molecular flexibility,
which can adversely affect cell membrane permeation
rate11 and hence its ability to inhibit intracellular TACE
activity.12 Although not a direct measurement, com-
pound 23 was found to have low permeation rate in
Caco-2 cells (Papp of 0.4 · 10ꢀ6 cm/s). Cyclic analogues
19 and 20, with reduced number of rotatable bonds
and hence reduced molecular flexibility, were found to
have higher Caco-2 permeation rates (3.4 · 10ꢀ6 and
9.0 · 10ꢀ6 cm/s, respectively). Both compounds exhib-
ited improved activity in the WB assay (890 and
662 nM). For reasons not understood, the two trans
analogues 17 and 18 were inactive in the WB assay.
1 >4900 nM, MMP-2 >3300 nM, and MMP-9
>2100 nM), suggesting that these benzamido derivatives
adopt a similar binding mode to succinate 1.
A computer model of 23 in the active site of TACE was
constructed to help understanding the aforementioned
activities (Fig. 2). In this model, the b-alanine backbone
adopts
a U-shaped conformation to engage the
hydroxamic acid group in chelation with the catalytic
zinc and to project the 4-(2-methylquinolin-4-ylmeth-
oxy)phenyl group into the S10 pocket. The central amide
carbonyl appears to be within hydrogen bonding dis-
tance with Leu129 and Gly130 residues of the b-strand
above the catalytic site. The pro-R hydrogen on the a-
carbon of the alanine seems to be in tight contact with
the protein, whereas the pro-S hydrogen and the two
hydrogens on the b-carbon are oriented toward the sol-
vent exposed area of the active site. This model explains
why both cis and trans isomers are active and predicts
that the (1S,2R) enantiomer of the cis-pair (confirmed
with 21) and the (1S,2S) enantiomer of the trans-pair
are responsible for activity.
The effect of heterocyclic constraint to the b-alanine
backbone was evaluated next. Of the three piperidine
isomers studied, the unsubstituted analogues 24–2613
showed promising WB potency (Table 2). The WB po-
tency for each isomer can be improved by derivatization
of the piperidine nitrogen. For example, introducing t-
butyl and 2-(N,N-dimethylamino)ethyl groups to 26 im-
proved WB potency to 44 and 55 nM, respectively (27
and 28). Unfortunately, functional groups beneficial to
WBA potency often resulted in reduced permeability
and erosion of oral bioavailability. After extensive
SAR efforts, we were unable to identify a piperidine lead
that had potent WB activity (<200 nM) and adequate
oral exposure in rodent.
Despite its binding affinity, compound 23 was a weak
inhibitor of TNF-a production in LPS-stimulated whole
blood assay (WB IC50 2860 nM, Table 1). The exact

244
J. J.-W. Duan et al. / Bioorg. Med. Chem. Lett. 18 (2008) 241–246
Table 2. In vitro potency in pTACE, WB LPS/TNF-a, and permeation
rate in Caco-2 cells
transposition of the ether oxygen, was 30-fold less
potent. The location of the ether oxygen also impacted
Caco-2 permeability. The 2-acid 29 was not permeable
in Caco-2 assay, whereas the 3-acid 30 was most perme-
able with a Papp value of 2.3 · 10ꢀ6 cm/s.
N
H
A
O
N
HO
O
HN
Further testing revealed that 30 was a highly potent
inhibitor of pTACE with a Ki of 0.15 nM (Table 2). It
was also selective for pTACE relative to 16 other metal-
loproteases (Table 3). The selectivity was extraordinarily
high (>2000-fold) against MMP-1, -2, -8, -9, -13, -14,
-15, and -16 ADAMTS-4 and -5,14 and ADAM-9 and
-10. Although Ki values for the four remaining MMPs
(MMP-3, -7, -10, and -12) were under 100 nM, com-
pound 30 still maintained respectable selectivity for
pTACE.
O
A
pTACE
a
IC50 (nM)
WB LPS/
TNF-a
IC50 (nM)
Caco-2c
b
H
N
24
25
26
27
28
29
30
31
24
620
393
187
44
0.2
NH
NH
The unbound fractions of 30 in rat, dog, and human ser-
um were 3.8, 17.0, and 7.5%, respectively, with albumin
the major component responsible for the serum bind-
ing.15 CYP 3A4 was the major isozyme responsible for
oxidative metabolism of 30 in vitro, but was not inhib-
ited by 30 to a significant extent at concentrations of
20 lM. In rats and dogs, the major metabolites of 30
were the glucuronide of the parent compound on the
hydroxamic acid moiety and carboxylic acid derivative
of the hydroxamic acid. 30 was also screened at 1 lM
and 10 lM concentrations in an extensive array of as-
says including receptor binding, ion channel effects, reg-
ulatory sites, and enzymes (Nova Screen), and showed
no significant activity in any assay at either of the con-
centrations tested. Finally, 30 was not mutagenic in a
bacterial reverse mutation (Ames) assay.
<1
—
1
0.2
0.6
0.1
0.06
2.3
0.4
N-t-Bu
2
NMe2
N
2
55
O
3
4114
130
290
Compound 30 was tested in a mouse model of endotox-
emia.10 When dosed orally as a 0.5% citric acid and 0.2%
Tween 80 water solution at doses of 0.3, 1.0, 3.0, 10, and
30 mg/kg, compound 30 inhibited LPS-induced TNF-a
production in a dose dependent manner with an ED50
of 2.2 mg/kg. Compound 30 was also tested in a similar
model in rat, and was found to suppress TNF-a produc-
tion with an oral ED50 of 3.0 mg/kg.
O
<1 (Ki = 0.15)
O
<1
To assess its pharmacokinetic profile, 30 was adminis-
tered intravenously and orally to Sprague–Dawley rats
and Beagle dogs, and the plasma samples were analyzed
by LC-MS-MS.10,16 In rats, 30 had a modest clearance
rate of 0.7 L/h/kg and a short half-life (1.4 h, Table 4).
The volume of distribution at steady state was 0.4
L/kg, suggesting limited distribution and tissue binding.
It was rapidly absorbed after oral administration. The
oral bioavailability in rats was 58%. More significantly,
high blood exposure (AUC) was achieved after oral
administration (65 lMÆh at 40 mg/kg dose). Following
iv administration in dogs, 30 had a larger volume of dis-
a pTACE IC50 values were from a single determination.
b Inhibition of TNF-a release from WB was determined with three
donors.
c Caco-2 permeation rates were determined as n of 3 and are reported
as Papp value in ·10ꢀ6 cm/s.
Tetrahydropyran rings were also well tolerated as evi-
denced by the potent pTACE activity (29–31, Table 2).
In the WB assay, 30 was most potent with an IC50 of
130 nM. In contrast, 29, which differs from 30 only by
Table 3. pTACE selectivity of 30 against related metalloproteases
Enzyme
MMP-1
>30,000
MMP-2
>30,000
MMP-3
427
MMP-7
200
MMP-8
5500
MMP-9
>14,000
MMP-10
320
MMP-12
93
Selectivity (fold)
Enzyme
Selectivity (fold)
MMP-13
>30,000
MMP-14
>30,000
MMP-15
>40,000
MMP-16
>30,000
ADAMTS-4
20,000
ADAMTS-5
2267
ADAM-9
>30,000
ADAM-10
>50,000

J. J.-W. Duan et al. / Bioorg. Med. Chem. Lett. 18 (2008) 241–246
245
Table 4. Pharmacokinetic profile of 30
Dose (mg/kg)
t1/2 (h)
Cl (L/h/kg)
Vss (L/kg)
AUC (lMÆh)
F%
Tmax (h)
Rata,b
Dogc,d
2 (iv)
1.4
—
0.7
—
0.4
—
5.7
65
—
58
—
96
—
40 (po)
2 (iv)
8 (po)
0.4
—
1.6
—
1.7
—
1.6
—
2.7
11
0.2
a Determination of 3 for each dosing group.
b Dosed as a mono-trifluoroacetate salt in 50 mM citrate buffer.
c Determination of 2 for each dosing group.
d Dosed as a mono-trifluoroacetate salt in a saline solution.
tribution at steady state (Vss, 1.6 L/kg), more than twice
the total body water of 0.6 L/kg, indicating that 30 has
extensive tissue distribution and binding in dogs. The
difference of Vss between the rat and dog may be attrib-
uted in part to the approximate 4-fold difference of the
unbound fraction in serum between the two species. Fol-
lowing oral administration, 30 was rapidly and com-
pletely absorbed in dogs with peak concentration
achieved within 1 h and oral bioavailability of 96%. A
high oral AUC number was also achieved in dogs
(11 lMÆh after 8 mg/kg dose).
References and notes
1. (a) Moss, M. L.; White, J. M.; Lambert, M. H.; Andrews,
R. C. Drug Discov. Today 2001, 6, 417; (b) Black, R. A.
Int. J. Biochem. Cell Biol. 2002, 34, 1.
2. (a) Newton, R. C.; Decicco, C. P. J. Med. Chem. 1999, 42,
2295; (b) Feldmann, M.; Brennan, F. M.; Williams, R. O.;
Cope, A. P.; Gibbons, D. L.; Katsikis, P. D.; Maini, R. N.
Prog. Growth Factor Res. 1992, 4, 247; (c) Van Assche, G.;
Rutgeerts, P. Exp. Opin. Invest. Drugs 2000, 9, 103; (d)
Kristensen, M.; Chu, C. Q.; Eedy, D. J.; Feldmann, M.;
Brennan, F. M.; Breathnach, S. M. Clin. Exp. Immunol.
1993, 94, 354.
3. (a) Moreland, L. W.; Baumgartner, S. W.; Schiff, M. H.;
Tindall, E. A.; Fleischmann, R. M.; Weaver, A. L.;
Ettlinger, R. E.; Cohen, S.; Koopman, W. J.; Mohler, K.;
Widmer, M. B.; Blosch, C. M. N. Eng. J. Med. 1997, 337,
141; (b) Lipsky, P. E.; van der Heijde, D. M. F. M. E.; St.
Clair, W.; Furst, D. E.; Breedveld, F. C.; Kalden, J. R.;
Smolen, J. S.; Weisman, M.; Emery, P.; Feldmann, M.;
Harriman, G. R.; Maini, R. N. N. Eng. J. Med. 2000, 343,
1594.
4. For a recent review of TACE inhibitors, see Le, G. T.;
Abbenante, G. Curr. Med. Chem. 2005, 12, 2963.
5. (a) Xue, C.-B.; He, X.; Roderick, J. J.; Corbett, R. L.;
Duan, J. J.-W.; Liu, R.-Q.; Covington, M. B.; Newton,
R. C.; Magolda, R. L.; Wexler, R. R.; Decicco, C. P.
Bioorg. Med. Chem. Lett. 2003, 13, 4293; (b) Xue, C.-B.;
He, X.; Roderick, J. J.; Corbett, R. L.; Duan, J. J.-W.;
Liu, R.-Q.; Covington, M. B.; Qian, M.; Ribadeneira,
M.; Vaddi, K.; Christ, D. D.; Newton, R. C.; Wexler,
R. R.; Decicco, C. P. Bioorg. Med. Chem. Lett. 2003,
13, 4299.
In summary, a series of b-benzamido hydroxamic acid
TACE inhibitors was discovered. The TACE selectivity
was addressed from onset by exploiting interactions of
4-(2-methylquinolin-4-ylmethoxy)phenyl group with
the TACE S10 specificity pocket. SAR work to address
the cellular activity and oral bioavailability issues was
guided by a computer-generated binding model and cen-
tered on constrained b-alanine analogues. Compound 30
emerged as an advanced lead with potent enzyme and
cellular activity, good to excellent selectivity, potent oral
efficacy in LPS-challenged mice and rats, and high oral
bioavailability in rat and dog. The overall profile of 30
makes it a highly valuable molecule to evaluate in pre-
clinical models and to assess the benefits associated with
chronic inhibition of TACE as well as potential side
effects.17
The discovery of the simple alanine lead 24 and con-
struction of binding model in TACE (Fig. 1) has not
only led to the discovery of 30, but also uncovered
additional opportunities to constrain the b-alanine
moiety to further improve in vitro and in vivo proper-
ties. Results from those approaches will be reported in
the future.18,19
6. (a) Duan, J. J.-W.; Chen, L.; Wasserman, Z. R.; Lu, Z.;
Liu, R.-Q.; Covington, M. B.; Qian, M.; Hardman, K. D.;
Magolda, R. L.; Newton, R. C.; Christ, D. D.; Wexler, R.
R.; Decicco, C. P. J. Med. Chem. 2002, 45, 4954; (b)
Wasserman, Z. R.; Duan, J. J.-W.; Voss, M. E.; Xue, C.-
B.; Cherney, R. J.; Nelson, D. J.; Hardman, K. D.;
Decicco, C. P. Chem. Biol. 2003, 10, 215.
7. Compound 9a was prepared from methyl 4-oxo-3-
piperidinecarboxylate using Boc2O, i-Pr2NEt, and
CH2Cl2. Compound 9b was prepared from 1-benzyl-3-
oxo-4-piperidinecarboxylate hydrochloride using H2,
Pd(OH)2/C, Boc2O, Et3N, and EtOH. Compound 9c
was synthesized from 4-tetrahydropyranone using
LiHMDS, NCCO2Me, and HMPA in THF at ꢀ78 ꢁC.
Compound 9d was prepared following a known proce-
dure Moody, C. J.; Taylor, R. J. J. Chem. Soc. Perkin
Trans. I 1989, 721.
Acknowledgments
The authors thank Robert E. Waltermire for providing
4-chloromethyl-2-methylquinoline (4), John V. Giann-
aras and Sherrill A. Nurnberg for assistance in enzy-
matic and cell assays, Robert J. Collins for LPS study
in animals, Bernice Brogdon, Bing Lu, Hang Zheng,
and Jingtao Wu for assistance in pharmacokinetic stud-
ies, Maria Ribadeneira for Caco-2 study, and Al Mical
for chiral HPLC separation of intermediate 8. The
authors also thank Gregory R. Ott for critical review
of this manuscript.
8. Cimarelli, C.; Palmieri, G. J. Org. Chem. 1996, 61, 5557.
9. The inhibitory activity was evaluated using porcine TACE
as a result of its availability and homology to human
TACE.

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J. J.-W. Duan et al. / Bioorg. Med. Chem. Lett. 18 (2008) 241–246
10. For details of pTACE and WB LPS/TNF-a assays,
MMPs, LPS-mouse TNFa, and dog pharmacokinetic
studies, see Xue, C.-B.; Voss, M. E.; Nelson, D. J.; Duan,
J. J.-W.; Cherney, R. J.; Jacobson, I. C.; He, X.; Roderick,
J.; Chen, L.; Corbett, R. L.; Wang, L.; Meyer, D. T.;
Kennedy, K.; DeGrado, W. F.; Hardman, K. D.; Teleha,
C. A.; Jaffee, B. D.; Liu, R.-Q.; Copeland, R. A.;
Covington, M. B.; Christ, D. D.; Trzaskos, J. M.; Newton,
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