α-Amino-β-sulphone hydroxamates as potent MMP-13 inhibitors that spare MMP-1

Article abstract of DOI:10.1016/S0960-894X(01)00556-X

A series of α-amino-β-sulphone hydroxamates was prepared and evaluated for potency versus MMP-13 and selectivity versus MMP-1. Various substituents were employed on the α-amino group (P₁ position), as well as different groups attached to the su

Full text of DOI:10.1016/S0960-894X(01)00556-X

Bioorganic & Medicinal Chemistry Letters 11 (2001) 2719–2722
ꢀ-Amino-ꢁ-sulphone Hydroxamates as Potent MMP-13
Inhibitors that Spare MMP-1
Daniel P. Becker,a,* Thomas E. Barta,a Louis Bedell,a Gary DeCrescenzo,b
John Freskos,b Daniel P. Getman,b Susan L. Hockerman,a Madeleine Li,a
Pramod Mehta,b Brent Mischke,b Grace E. Munie,b Craig Swearingenb
and Clara I. Villamila
aDepartments of Medicinal Chemistry and Inflammation-Oncology, Pharmacia Research & Development, 4901 Searle Parkway,
Skokie, IL 60077, USA
bDepartments of Medicinal Chemistry and Inflammation-Oncology, Pharmacia Research & Development,
700 Chesterfield Village Parkway, St. Louis, MO 63198, USA
Received 8 December 2000; accepted 3 August 2001
Abstract—A series of a-amino-b-sulphone hydroxamates was prepared and evaluated for potency versus MMP-13 and selectivity
versus MMP-1. Various substituents were employed on the a-amino group (P1 position), as well as different groups attached to the
0
sulphone group extending into P1 . Low nanomolar potency was obtained for MMP-13 with selectivity versus MMP-1 of >1000ꢀ
for a number of analogues. # 2001 Elsevier Science Ltd. All rights reserved.
Matrix metalloproteinase (MMP) enzymes1,2 are endo-
peptidases that mediate the breakdown of structural
proteins of the extracellular matrix and are involved in
many normal physiological processes such as the remo-
deling of connective tissues and basement membranes.3
The activity of these enzymes is closely controlled
through expression as a latent proform that requires
prior activation for activity, and also through direct
inhibition by tissue inhibitors of metalloproteinases
(TIMPs). Elevated levels of MMPs are associated with
certain pathologies including osteoarthritis (OA) and
rheumatoid arthritis (RA). Recently, Freemont et al.4
reported the use of in situ zymography to localize type
II collagen degrading activity in osteoarthritic human
articular cartilage, and in situ hybridization to localize
MMP-13 mRNA. Significantly, they found that MMP-
13 mRNA expression co-distributed with type II col-
lagenase activity in articular chondrocytes, and that
MMP-13 was upregulated in articular osteoarthritic
cartilage but not in cartilage from normals. Thus, inhi-
bition of the relevant collagenase enzymes, particularly
MMP-13, may prove to be clinically effective in halting
the advance of OA and RA.5 Roche collagenase
inhibitor Ro 32-35556 inhibits collagenases 1, 2, and 3
(MMP-1, MMP-8, and MMP-13, respectively) and pre-
vents cartilage breakdown both in vitro and in vivo. For
the treatment of arthritis we targeted inhibitors of
MMP-13 that spare interstitial collagenase (MMP-1) in
order to avoid the musculoskeletal side effect observed
clinically with the broad-spectrum inhibitor marima-
stat.7 The hypothesis8 that sparing MMP-1 will elim-
inate the fibroplasia seen with broad-spectrum
inhibitors is still speculative. We wish to report pre-
liminary SAR of a series of potent a-amino-b-sul-
phone9,10 hydroxamate MMP-13 inhibitors that are
selective in sparing MMP-1.
Racemic a-amino compounds bearing methoxyphenyl
sulphones and phenoxyphenyl sulphone moieties were
prepared as shown in Scheme 1. The Michael acceptor
methyl-2-acetamidoacrylate (1) was reacted with 4-
methoxythiophenol (XR1=OMe) or 4-phenoxy-
thiophenol, which was prepared via Newman rearr-
angement11 from 4-phenoxyphenol as we reported
previously for our g-sulphone thiol series of MMP
inhibitors.12 Oxone1 treatment of the crude thioether
afforded the sulphone 2 in excellent yield from the
acrylate. Vigorous hydrolysis of 2 with concentrated
hydrochloric acid in glacial acetic acid afforded the free
amino acid, which was re-esterified with thionyl chloride
*Corresponding author. Fax: +1-847-982-4714; e-mail: daniel.p.
becker@pharmacia.com
0960-894X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00556-X

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D. P. Becker et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2719–2722
Scheme 1.
in methanol. Derivitization with the appropriate R2
reagent and direct conversion of the methyl ester to the
hydroxamate with aqueous hydroxylamine in methanol/
tetrahydrofuran afforded the hydroxamic acid 3.
which was oxidized directly with Oxone1 to afford 9
with (R)-stereochemistry. Nucleophilic aromatic dis-
placement of the aryl fluoride with thiophenol followed
by acidic deprotection of the BOC group and acylation
afforded the functionalized carboxylic acid, which was
converted to hydroxamate 10 via coupling with
THPONH2 and deprotection.
Racemic compounds bearing the phenylthiophenyl sul-
phone moiety were prepared as illustrated in Scheme 2.
4-Fluorothiophenol was added in a conjugate fashion to
methyl-2-acetamidoacrylate (1), and treatment of the
crude thioether with Oxone1 gave the sulphone 4.
Controlled hydrolysis of the methyl ester gave the car-
boxylic acid with the acetamide intact. Nucleophilic
aromatic displacement of the fluoride proceeded cleanly
on the carboxylate salt to afford 5, whereas attempts to
perform the fluoride displacement directly on ester 4 did
not afford the desired product due to competing beta-
elimination. Hydrolysis of the acetamide 5 followed by
derivitization with the appropriate R2 reagent gave car-
boxylic acid 6. The hydroxamic acid 7 was then pre-
pared by employing the standard EDC/HOBT coupling
with tetrahydropyranyl hydroxylamine followed by
deprotection under acidic conditions.
Chiral a-amino b-phenoxyphenyl sulphones were pre-
pared by sodium thiolate displacement14 of the tosy-
late15 of Cbz-l-serine methyl ester (11) to afford 12 after
oxidation with Oxone1. Hydrogenolysis, acylation and
conversion of the methyl ester of 12 to the hydroxamate
with hydroxylamine afforded compounds of type 13
with (R)-stereochemistry (Scheme 4). It may be noted
that Schemes 3 and 4 are complementary with respect to
amine protecting groups and also with respect to the
state of the carboxylate. Specifically, the nucleophilic
aromatic fluoride displacement accomplished on free
carboxylic acid 9 was not viable on the corresponding
Cbz-protected methyl ester prepared by the general
method of Scheme 4 due to beta-elimination.
Chiral (R)-a-amino-b-phenylthiophenyl sulphones were
synthesized from N-BOC-l-serine-b-lactone, which was
prepared from BOC-l-serine by the procedure of
Vederas13 (Scheme 3). Nucleophilic ring-opening of 8
with sodium 4-fluorothiophenoxide gave the sulphide,
Chiral (R)-a-amino b-phenoxyphenyl sulphones were
prepared with minor modifications of the above proce-
dures according to Scheme 5. Commercially available
(S)-BOC-N-methyl-serine (14) was esterified with
methyl iodide, then treated with 4-phenoxythiophenol
Scheme 2.
Scheme 3.
Scheme 4.

D. P. Becker et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2719–2722
2721
Scheme 5.
under Mitsunobu conditions. Oxidation of the resulting
sulphide with tetra-N-butylammonium Oxone1 gave
sulphone 15. Removal of the tert-butylcarbamate pro-
tecting group under acidic conditions was followed by
functionalization with the appropriate R2 reagent. The
methyl ester was converted directly to the hydroxamate
16 by treating with aqueous hydroxylamine, albeit in
lower yields as expected, due to the increased steric
hindrance in the a-position of the ester.
position appended to the a-amino group. The Cbz-gly-
cine group was selected to probe for an additional
binding region to enhance potency. Incorporation of the
phenylthiophenyl moiety (XR2=SPh) afforded a mod-
est increase in potency (17 vs 21) and very high levels of
selectivity (21–25). The Cbz-glycine moiety again affor-
ded a large jump in potency for MMP-13, which trans-
lated to exceptional selectivity (>12,000ꢀ) versus
(XR1=OPh, 26–28) led to compounds of excellent
potency for MMP-13 but which had somewhat lower
selectivity than the phenylthiophenyl compounds versus
MMP-1.
0
MMP-1. Utilization of the diaryl ether in P1
We elected initially to examine racemic a-amino-b-sul-
phones in order to explore potency for MMP-13 and
selectivity versus MMP-01 (Table 1). A 4-methoxyphenyl
sulphone moiety in P1 (XR2=OMe) afforded lower
potency and selectivity16ꢁ18 with the notable exception
of compound 20 bearing a Cbz-glycine moiety in the P1
Table 2 shows the enzyme results of chiral (R)-a-amino-
b-sulphones derived from l-serine. Direct comparison
of the single enantiomers and racemates of N-acetyl (30
vs 21) and N-Cbz (31 vs 22) showed an increase in
potency expected for the eutomers, and an accompany-
ing (apparent) increase in selectivity. Comparison of
BOC derivatives 29 and 32 reveal again the order of
magnitude increase in potency of the diphenyl ether
versus the diaryl thioether (X=O vs X=S), although
the thioethers are more selective. Hydrophilic groups
including isonicotinyl (33) were incorporated into R2 to
increase water solubility, and the unsubstituted analo-
gue 34 (R2 and R3=H) was also prepared. Bulky
groups (such as dimethoxybenzoyl in compound 34)
were introduced to increase the half-life of these com-
pounds by adding steric hindrance to block the meta-
bolism of the hydroxamate moiety. This was the reason
for preparation of the disubstituted compounds 36–39
(R3=CH3). These compounds exhibited sub-nanomolar
potency for MMP-13 and good selectivity versus MMP-
1. The acetyl analogue 36 showed unexpected potency
versus MMP-1.
Table 1. IC50 (nM)19 values for racemic a-amino-b-sulphone
hydroxamates
Compd
XR1
R2
MMP-13
MMP-1
MMP-1/13
17
18
19
20
21
22
23
24
25
26
27
28
OMe
OMe
OMe
OMe
SPh
SPh
SPh
SPh
SPh
Ac
BOC
H
CbzGly
Ac
Cbz
Tos
H
CbzGly
Ac
Cbz
Tos
15
15
15
300
1500
250
40
20
100
17
>40
<1.0
5.9
3.7
0.4
24
0.8
1.1
1.1
0.6
>10,000
>10,000
600
>10,000
>10,000
770
>1700
>2700
1500
420
>12,000
700
OPh
OPh
OPh
1400
400
1300
670
Table 2. IC50 (nM)19 values for (R)-a-amino-b-sulphone hydroxamates
Compd
X
R2
R3
MMP-13
MMP-1
MMP-1/13
29
30
31
32
33
34
35
36
37
38
39
SBOC
SAc
SCbz
O
O
O
O
O
O
O
H
H
H
4.0
2.9
0.4
>10,000
3400
20,000
500
>2500
10,000
8000
0.3
0.8
0.4
0.4
0.2
0.3
2.0
BOC
Isonicotinyl
2,6-Dimethoxybenzoyl
H
H
H
CH3
CH3
CH3
CH3
CH3
1600
1100
870
1100
450
5300
130
2400
900
350
440
90
1600
258
475
H
Ac
BOC
4-Pyridineacetyl
Benzyl
O
0.2

2722
D. P. Becker et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2719–2722
Selected analogues were dosed orally in rats at 20 mpk
to assess absorption by measuring Cmax, and the con-
centration remaining at 6 h was used as an initial rough
indicator of the half-life. N-Methyl derivative 35
showed a high Cmax of 6.66 mg/mL, with 0.049 mg/mL
remaining at 6 h, and acetyl analogue 36 exhibited a
Cmax of 2.45 mg/mL (0.060 mg/mL at 6 h). Pyridineacetyl
analogue 38 had a somewhat lower Cmax of 0.71 mg/mL,
but was not detected at 6 h. These analogues exhibited
higher Cmax values than compounds 32, 33, and 34,
which exhibited Cmax values of <0.2 mg/mL.
7. Wojtowicz-Praga, S.; Torri, J.; Johnson, M.; Steen, V.;
Marshall, J.; Ness, E.; Dickson, R.; Sale, M.; Rasmussen,
H. S.; Chiodo, R. A.; Hawkins, M. J. Clin. Oncol. 1998, 16,
2150.
8. Freskos, J. N.; McDonald, J. J.; Mischke, B. B.; Mullins,
P. B.; Shieh, H.-S.; Stegeman, R. A.; Stevens, A. M. Bioorg.
Med. Chem. Lett. 1999, 9, 1757.
9. Burns et al. reported a series of b-substituted-b-sulphone
hydroxamates which are both MMP and phosphodiesterase
inhibitors: Burns, C. J.; Groneberg, R. D.; Salvino, J. M.;
McGeehan, G.; Condon, S. M.; Morris, R.; Morrissette, M.;
Mathew, R.; Darnbrough, S.; Neuenschwander, K.; Scotese,
A.; Djuric, S. W.; Ullrich, J.; Labaudiniere, R. Angew. Chem.
Int. Ed. 1998, 37, 2848.
10. Roche workers have disclosed development compound RS
130830 which is a b-sulphone hydroxamate: Lollini, L.; Haller,
J.; Eugui, E. M.; American College of Rheumatology 61st
National Scientific Meeting; Washington, DC, Nov 8–12,
1997; Poster No. 341.
11. (a) Newman, M. S.; Karnas, H. J. Org. Chem. 1966, 31,
3980. (b) Newman, M. S.; Hetzel, F. W. Org. Synth. VI 1988,
824.
12. Freskos, J. N.; Mischke, B. V.; DeCrescenzo, G. A.;
Heintz, R.; Getman, D. P.; Howard, S. C.; Kishore, N. N.;
McDonald, J. J.; Munie, G. E.; Rangwala, S.; Swearingen,
C. A.; Voliva, C.; Welsch, D. J. Bioorg. Med. Chem. Lett.
1999, 9, 943.
In summary, we have described a promising series of a-
amino-b-sulphone hydroxamates that are potent inhibi-
tors of MMP-13 that spare MMP-1. Potency and selec-
0
tivity were modulated by varying the P1 moiety (XR1),
and a wide variety of substituents are tolerated in the P1
(solvent exposed) a-amino position of MMP-13. This
position was utilized to modulate solubility and phar-
macokinetic parameters. Compounds 35 and 36 showed
good absorption when administered orally in the rat.
The activity of these MMP-1 sparing b-sulphone
hydroxamates in animal models of arthritis and cancer
will be disclosed in due course.
13. (a) Arnold, L. D.; Kalantar, T. H.; Vederas, J. C. J. Am.
Chem. Soc. 1985, 107, 7105. (b) Pansare, S. V.; Huyer, G.;
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contained 0.02% 2-mercaptoethanol (Sigma). All basic com-
pounds were tested as their hydrochloride salts.