The development of new carboxylic acid-based MMP inhibitors derived from a cyclohexylglycine scaffold

Article abstract of DOI:10.1016/S0960-894X(01)00371-7

A series of carboxylic acids was prepared based on cyclohexylglycine scaffolds and tested for potency as matrix metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for five enzymes within the MMP family, and a number of inhibitors such as compound 18 display low nanomolar potency for MMP-2 and MMP-13, while selectively sparing MMP-1 and MMP-7.

Full text of DOI:10.1016/S0960-894X(01)00371-7

Bioorganic & Medicinal Chemistry Letters 11 (2001) 1975–1979
The Development of New Carboxylic Acid-Based MMP
Inhibitors Derived from a Cyclohexylglycine Scaffold
Joshua S. Tullis,a,*,y Matthew J. Laufersweiler,a John C. VanRens,a Michael G. Natchus,a,y
Roger G. Bookland,a Neil G. Almstead,a,{ Stanislaw Pikul,a,x Biswanath De,a
Lily C. Hsieh,a Michael J. Janusz,a Todd M. Branch,a Sean X. Peng,a Yingkun Y. Jin,a
Tomas Hudlickyb and Kofi Oppongb
aProcter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
bDepartment of Chemistry, University of Florida, Gainesville, FL 32611, USA
Received 18 January 2001; accepted 8 May 2001
Abstract—Aseries of carboxylic acids was prepared based on cyclohexylglycine scaffolds and tested for potency as matrix
metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for five enzymes within the MMP family, and a
number of inhibitors such as compound 18 display low nanomolar potency for MMP-2 and MMP-13, while selectively sparing
MMP-1 and MMP-7. # 2001 Elsevier Science Ltd. All rights reserved.
Introduction
Recently, significant interest has been directed toward
selective MMPIs that contain a carboxylic acid moiety
as a zinc binding element and this effort is benchmarked
by BAY-129566 and disclosures by Warner–Lambert6
and Shionogi (Fig. 1).7 Both series of compounds con-
tain a biaryl moiety that inserts into the P10 pocket of
MMP enzymes and effectively selects against shallow
pocket enzymes such as MMP-1 and -7.
It has long been postulated that the aberrant over-
expression of matrix metalloproteinase enzymes
(MMPs) may play a pivotal role in the progression of
many pathological disease states where tissue turnover
plays a key role.1 These include osteoarthritis,2 cancer,3
congestive heart failure,4 and others. Thus, considerable
interest has been directed toward the direct inhibition of
the MMPs. The majority of inhibitor scaffolds that have
been disclosed contain a hydroxamic acid moiety which
contributes key binding interactions to the active site
zinc atom. The progression of these compounds in clin-
ical trials has been hampered, however, by the emer-
gence of musculoskeletal syndrome (MSS). Following a
widespread hypothesis that this may be the result of
broad spectrum inhibition of the MMP family, a wave
of disclosures then followed which described the devel-
opment of selective hydroxamate MMPIs which typi-
cally spared MMP-1 and MMP-7.5
Figure 1. Other carboxylic acid based MMP-inhibitors.
We sought to design and target carboxylic acid inhibi-
tors that would specifically allow interactions with the
S2 pocket of the enzyme and minimize the high protein
binding issues reported for BAY-129566.2 We were
encouraged upon the realization of very potent piper-
idinyl glycine-based inhibitors,8 and chose to follow this
lead with some substituted cyclohexylglycine analogues
which we have previously shown to be synthetically
accessible.9 Herein, we communicate the synthesis and
*Corresponding author. E-mail: jtullis@nutecsciences.com
yCurrent address: NuTec Sciences, 1201 W. Peachtree St., Suite 800,
Atlanta, GA 30309, USA.
{Current address: PTC Therapeutics, 100 Corporate Ct., South Plain-
field, NJ 07080, USA.
xCurrent address: Avalon Pharmaceuticals, 19 Firstfield Rd., Gai-
thersburg, MD 20878, USA.
0960-894X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00371-7

1976
J. S. Tullis et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1975–1979
biological data for a series of novel 1,3- and 1,4-cyclo-
hexylglycine-based inhibitors which exhibit selective
inhibition of MMP-2 and MMP-13 while sparing
MMP-1 and MMP-7.
followed by sulfonamide formation14 provided ketone
8. Ketone derivatization followed by ester hydrolysis
yielded the desired carboxylic acid inhibitors 9.
Ketones 3 and 8 were most easily functionalized via
standard ketal formation conditions or by reductive
amination with primary amines, which gave ꢀ2:1 mix-
tures of diastereomers that were typically carried for-
ward without separation. Reductive amination (RNH2,
NaCNBH3, NaOAc, AcOH, MeOH, rt) of 3 and 8 with
benzylamine, methylamine, aniline, and ethanolamine,
provided access to various secondary amines. Acylation
or sulfonylation of the secondary amines was accom-
plished with acetyl chloride, mesityl chloride, and
methoxyethyl chloroformate (+Et3N, CH2Cl2, rt).
Oxime 28 was formed by addition of MeONH3Cl
(+NaOAc, dioxane/MeOH/H2O, rt) to 8. Ketals 12
and 21 were formed from 1,3-propane diol and ethylene
Chemistry
We recently described an application of the Kazmaier–
Claisen rearrangement reaction, which provided an
enantio- and stereoselective method for the synthesis of
4-hydroxy-cyclohexylglycines and alanines.9 We have
also been able to construct the 4-substituted cyclohexyl
glycines in six steps from 4-hydroxyphenyl glycine 1
(Scheme 1), which is commercially available in either
enantiomeric form as well as in racemic form.10 Glycine
1 was efficiently hydrogenated in the presence of Raney
nickel and subsequent sulfonylation and Williams
esterification gave 2 as a 2:1 mixture of unassigned cis
and trans isomers. The methoxybiphenylsulfonyl group
was used as the P10 substituent of choice based on ear-
lier data acquired with a related, propargyl glycine
scaffold.11 The alcohol moiety in 2 proved to be inert to
Mitsunobu displacement, mesylate formation and
alkylation; however, oxidation with Jones’ reagent pro-
vided ketone 3, which could be further functionalized
via ketal formation and reductive amination type
events. Saponification of the methyl ester with LiOH
then revealed the desired carboxylic acid inhibitors.
.
glycol, respectively, and either BF3 Et2O or PTSA.
Results and Discussion
All compounds were tested as diastereomeric mixtures
for the inhibition of various MMP enzymes and plasma
protein binding. The data are summarized in Table 1.
Both 1,4- and 1,3-substituted cyclohexyl glycines
demonstrated similar selectivity profiles, which seemed
to vary only slightly from one analogue to another.
Extremely potent binding was observed with MMP-2
and MMP-13 whereas MMP-1 and MMP-7 were spared
by roughly three orders of magnitude. Stromelysin
(MMP-3) was inhibited with moderate potency.
The related 3-substituted cyclohexyl glycines were pre-
pared via Michael reaction with glycine imine 6 to give 7
(Scheme 2) as an inseparable mixture of two diaster-
eomers. Therefore, the data reported herein were gath-
ered with racemates which were often mixtures of
diastereomers; however, Corey and co-workers have
reported the enantioselective (200:1) and diastereo-
selective (25:1) Michael addition of 2-cyclohexenone to
tert-butylglycinate benzophenone imine under chiral
phase transfer catalysis (PTC) conditions,12 which may
provide a solution to this diastereomer issue in future
work. Cleavage of the imine in 7 with citric acid13
The absolute potencies of the inhibitors varied some-
what depending upon the nature of the substituent. This
is consistent with binding interactions that were docu-
mented for a related set of piperidinyl glycines.8 Amore
pronounced substituent effect was noted in the binding
characteristics of the molecules with serum albumen.
We hoped to target delivery of the molecules to the
synovial fluid and anticipated that we could not tolerate
protein binding >95%. There were isolated examples of
Scheme 2. Reagents and conditions: (a) benzophenone imine, CH2Cl2,
rt, 4 h, quant; (b) LDA, CuI, THF, À78 ꢁC, 45 min; then a,b-unsat-
urated ketone, À78 ꢁC!rt, 18 h (e.g., 2-cyclohexen-1-one, 85%; 3-
methyl-2-cyclohexen-1-one, 35%); (c) citric acid, H2O, THF, rt, 5 h;
(d) 40-methoxy-4-biphenylsulfonyl chloride, NaHCO3, dioxane/H2O
(1:1), rt, 18 h, 85% (two steps); (e) ketone derivatization conditions
(see text); (f) LiOH, H2O/MeOH/THF (1:2:4), rt, 18–48 h.
Scheme 1. Reagents and conditions: (a) Raney Ni, H2 (100 psi), 3 N
NaOH, H2O, 80 ꢁC,
nylsulfonyl chloride, dioxane/H2O; (c) MeOH, SOCl2, 65% (three
steps); (d) Jones’ reagent, acetone, 95%; (e) ketone derivatization
conditions (see text); (f) LiOH, H2O/MeOH/THF (1:2:4), rt, 18–48 h.
3
days; (b) NaHCO3, 40-methoxy-4-biphe-

J. S. Tullis et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1975–1979
1977
Table 1. MMP enzyme inhibition and plasma protein binding data for 1,4-cyclohexylglycine and 1,3-cyclohexylglycine derivatives
Compound
General structure
Q
IC50 (nM)a
MMP-3
Protein
binding (%)
MMP-1
MMP-2
MMP-7
MMP-13
10
11
4
4
–H
¼O
4350
8950
8
47
2150
4700
15,147
>10,000
43
200
99.7
—
12
13
14
15
16
17
18
19
4
4
4
4
4
4
4
4
4999
4183
9829
8270
6728
284
7
5
2320
520
600
1340
783
26
24,061
9128
36
17
22
26
21
0.8
1
96.5
94.2
97.7
99.3
87.8
98.5
99.0
90.1
14
12
7
7069
20498
>10,000
845
0.6
1
4785
22,927
98
3307
41
5660
>10,000
64
20
21
9
9
–OH
5370
3780
13
9
1610
630
7960
54
13
—
>10,000
98.9
22
23
24
25
26
27
9
9
9
9
9
9
2190
7960
7910
5350
4660
4730
5
15
12
6
250
860
500
210
560
230
5470
>10,000
4450
8
67
32
16
29
11
99.8
—
99.4
—
6340
17
8
>10,000
>10,000
99.4
97.6

1978
J. S. Tullis et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1975–1979
Table 1 (continued)
Compound
General structure
Q
IC50 (nM)a
Protein
binding (%)
MMP-1
4130
MMP-2
9
MMP-3
1250
MMP-7
MMP-13
21
28
29
30
9
9
9
>10,000
99.7
—
4110
5960
3
320
410
5150
8540
7
10
11
97.6
aAll in vitro inhibition assays were performed as described previously;11 standard deviations for enzyme assays were typically ꢂ30% of the mean or
less.
Table 2. Comparison of MMP-13 inhibition and plasma protein
binding data for cis versus trans cyclohexylglycine derivatives
and MMP-13 while sparing MMP-1 and MMP-7. Based
on the overall profile described so far, this novel series
bears the potential of producing multiple orally active
as well as selective MMP inhibitors. We hope to report
some of these promising data in the future.
Compd Configuration
Structure
MMP-13 Protein
IC50 (nM) binding (%)
100
37
84.0
99.2
31
32
cis
trans
References and Notes
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21
83.1
95.5
33
34
cis
trans
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36
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including 13, 16, and 19, but we observed significant
variabilities between isolated diasteromers as noted in
Table 2. Despite the promising profiles of some inhibi-
tors including 31, 33, and 34, none of the compounds in
this series has shown in vivo activity in the rat iodoace-
tate model of osteoarthritis. We are continuing to opti-
mize characteristics of the carboxylate inhibitors to
provide in vivo activity.
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Almstead, N. G.; De, B.; Natchus, M. G.; Hsieh, L. C.;
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Y. O.; Mieling. G. E. Bioorg. Med. Chem. Lett., 2001, sub-
mitted for publication.
Conclusion
We have reported a novel series of substituted cyclo-
hexylglycine carboxylic acid MMP inhibitors. These
inhibitors were highly selective inhibitors of MMP-2

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