α-alkyl-α-amino-β-sulphone hydroxamates as potent MMP inhibitors that spare MMP-1

Article abstract of DOI:10.1016/S0960-894X(01)00557-1

A series of α-alkyl-α-amino-β-sulphone hydroxamates was prepared and evaluated for potency versus MMP-2 and MMP-13, and for selectivity versus MMP-1. Low nanomolar potency was obtained with selectivity versus MMP-1 ranging from >10 to >1000. Selected comp

Full text of DOI:10.1016/S0960-894X(01)00557-1

Bioorganic & Medicinal Chemistry Letters 11 (2001) 2723–2725
ꢀ-Alkyl-ꢀ-amino-ꢁ-sulphone Hydroxamates as Potent MMP
Inhibitors that Spare MMP-1
Daniel P. Becker,a,* Gary DeCrescenzo,b John Freskos,b Daniel P. Getman,b
b
Susan L. Hockerman,a Madeleine Li,a PramodMehta, Grace E. Munieb
andCraig Swearingen b
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
Received8 December 2000; accepted3 August 2001
Abstract—A series of a-alkyl-a-amino-b-sulphone hydroxamates was prepared and evaluated for potency versus MMP-2 and
MMP-13, andfor selectivity versus MMP-1. Low nanomolar potency was obtainedwith selectivity versus MMP-1 ranging from
>10 to >1000. Selectedcompounds were orally bioavailable. # 2001 Elsevier Science Ltd. All rights reserved.
In our previous letter, we described a series of a-amino-
b-sulphone hydroxamates that are potent inhibitors of
MMP-13, which spare MMP-1.1 OverexpressedMMPs
play a crucial role in tumor growth andmetastasis in
cancer, andin the destruction of articular cartilage in
osteoarthritis (OA) andrheumatoidarthritis (RA).
Hence, the inhibition of the relevant MMP enzymes
may prove to be clinically effective in halting the
advance of these diseases.2 The gelatinases A andB
(MMP-2 andMMP-9) have been implicatedin tumor
progression,3 andMMP-13 has been implicatedin the
destruction of articular cartilage in arthritis.4 Herein, we
report the preparation andpreliminary SAR of a series
of a-amino-a-alkyl-b-sulphones that are highly selective
in sparing MMP-1, basedon the hypothesis that the
musculoskeletal side effect observed clinically with the
broad-spectrum inhibitor marimastat5 is due to potent
inhibition of MMP-1. Alkyl substituents alpha to the
hydroxamate were employed to modulate pharmacoki-
netic properties including absorption and half-life, as
0
well as physicochemical properties, while the P1 sub-
stituent was variedto optimize potency andselectivity.
The targeted a-methyl-a-amino diphenyl ether hydrox-
amates of type 5 were preparedstarting with a halide
displacement of chloroacetone (1) with 4-phenoxy-
thiophenol6 to afford 2 (Scheme 1). Strecker synthesis
then gave the nitrile 3, which was hydrolyzed to the
Scheme 1.
*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)00557-1

2724
D. P. Becker et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2723–2725
carboxylic acid. Oxidation of the sulfide after protection
of the amino group as the acetamide, and subsequent
deprotection, then gave the amino acid 4. Functionali-
zation of the amino group was accomplishedby alkyla-
tion, acylation or reductive amination as required, and
standard EDC coupling with hydroxylamine afforded
the diphenyl ether sulphone hydroxamates 5.
with methylene diiodide gave iodomethyl azlactone 13,
and displacement of the iodide with 4-phenoxy-
thiophenol andsubsequent oxaidtion with
chloroperbenzoic acidgave the sulphone
meta-
14. The
oxazolone was then hydrolyzed and the resulting car-
boxylic acidcoupledwith TMS-protectedhyrdoxyl-
amine to afford 15 (R2=H). Alternatively, the
oxazolone ring was opened directly with hydroxylamine
to afford the benzamide hydroxamate (R2=Bz).
The diaryl thioether 7 was preparedcommencing with
the reaction of chloroacetone (1) with 4-fluoro-
thiophenol (R=F). Strecker synthesis gave nitrile 3
(R=F), which was hydrolyzed and protected as the
acetamide (Scheme 2). Oxidation then afforded the cor-
responding 4-fluorophenylsulphone, and nucleophilic
aromatic substitution with thiophenol gave carboxylic
acid 6. Acetamide hydrolysis preceded amino function-
alization with the appropriate R2 reagent, andEDC
coupling afforded the hydroxamates 7.
Table 1 summarizes the potency versus MMP-2, MMP-
13, andMMP-1 for compounds of generic structures 5,
7, and 15. The diaryl ethers (X=O) were an order of
magnitude more potent than the corresponding thio-
ethers (X=S), although occasionally the thioethers were
notedto be somewhat more selective in sparing MMP-1
(5b vs 7b). Amides of the a-amino group (5a, 5j, 7a, and
15a) were significantly less potent for both MMP-2 and
MMP-13, whereas simple alkyl andaralkyl amines were
potent for both of these enzymes. Disubstitution on the
amine ledto a loss of potency ( 5c). The a-phenyl amine
15b was potent for MMP-13 andMMP-2, but was also
somewhat more potent for MMP-1. Almost all com-
pounds exhibited excellent selectivity versus MMP-1, in
several cases exceeding 1000ꢀ for the ratio of IC50
values (MMP-1/MMP-2 andMMP-1/MMP-13), in
contrast to the broad-spectrum inhibitors CGS 27023A
andmarimastat.
As illustratedin Scheme 3, a-pyrrolidine-b-sulphones
were preparedfrom racemic N-Cbz-proline methyl ester
(8). Alkylation of 8 with methylene diiodide7 gave the a-
iodomethyl derivative, which was used to alkylate 4-
phenoxythiophenol. The resulting aryl sulfide was oxi-
dized to furnish sulphone 9. The Cbz protecting group
was removedby hydrogenolysis, exposing the amine
which was functionalizedby alkylation with propargyl
bromide. Saponification of the methyl ester and
coupling with hydroxylamine then afforded the
hydroxamate 10 (R2=propargyl).
Table 2 shows the enzyme potency of proline-derived
analogue 10. Since the racemate 10 was foundto be
quite potent, the material was resolvedinto its enantio-
mers via chiral chromatography.9 The first eluter,
hydroxamate 10a, was foundto be the more potent
enantiomer (eutomer) by at least two orders of
The a-phenyl-a-amino derivative 15 (Scheme 4) was
preparedfrom d,l-phenylglycine (11) by benzoylation and
treatment with acetic anhydride to give the 2-phenyl-
oxazolone 128 (Scheme 4). Alkylation of this azlactone
Scheme 2.
Scheme 3.
Scheme 4.

D. P. Becker et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2723–2725
Table 1. IC50 (nM)10 values for a-alkyl-a-amino-b-sulphone hydroxamates
2725
1
CompdR
R2
R3
X
MMP-13
MMP-2
MMP-1
MMP-1/13
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
7a
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Ph
Ac
H
CH3
H
H
CH3
H
H
H
H
H
H
H
O
O
O
O
O
O
O
O
O
O
S
41.5
0.2
24.0
1.6
0.3
2.4
1.1
1.4
40.0
0.6
5.0
1.3
0.2
1.3
0.5
0.4
0.2
80
540
3.2
184
0.2
4.6
0.75
>10,000
170
>10,000
1600
1200
2400
2350
>10,000
700
>10,000
>10,000
4400
>10,000
130
>240
850
>416
1000
4000
1000
2136
7143
1167
>62
>17
1833
>62
325
CH2CH3
CH2Ph
CH2CH2Ph
3,4-Methylenedioxybenzyl
2-Naphthylmethyl
Propargyl
Pyrrolidineacetyl
0.6
160
580
2.4
161
0.4
5.1
Ac
H
Benzoyl
H
H
H
H
H
7b
15a
15b
CGS 27023A
Marimastat
S
O
O
Ph
34.3
2.9
6.7
1.4
2.0
Table 2. IC50 (nM)10 values for a-pyrrolidine-b-sulphone hydrox-
amates
compounds in animal models of cancer and arthritis will
be disclosed in due course.
References and Notes
1. Becker, D. P.; Barta, T. E.; Bedell, L.; DeCrescenzo, G.;
Freskos, J.; Getman, D. P.; Hockerman, S. L.; Li, M.; Mehta,
P.; Mischke, B.; Munie, G. E.; Swearingen, C.; Villamil, C. I.
Bioorg. Med. Chem. Lett. 2001, 11, 2719.
2. Cawston, T. E. Pharmacol. Ther. 1996, 70, 163.
3. Nelson, A. R.; Gingleton, B.; Rothenberg, M. L.; Matri-
sian, L. M. J. Clin. Oncol. 2000, 18, 1135.
2
CompdR
MMP-13 MMP-2 MMP-1 MMP-1/13
10 (racemic)
Propargyl
10a (eutomer) Propargyl
10b (distomer) Propargyl
1.3
<0.1
60.0
0.2
<0.1
19.3 >10,000
400
300
308
>3000
>167
4. Freemont, A. J.; Byers, R. J.; Taiwo, Y. O.; Hoyland, J. A.
Ann. Rheum. Dis. 1999, 58, 357.
5. 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.
6. 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.
magnitude against both MMP-13 and MMP-2 as com-
paredto the less potent enantiomer (idstomer) 10b.
Compound 10a was also highly selective in sparing
MMP-1 (3000ꢀ).
Selectedanalogues were dosedorally in rats at 20 mpk
to assess absorption by measuring Cmax, andthe con-
centration remaining at 6 h was usedas an initial rough
indicator of the half-life. The a-methyl-a-amino analo-
gue 5b showeda high Cmax of 6.43 mg/mL, somewhat
greater than the corresponding thioether 7b (Cmax=1.54
mg/mL). N-Ethyl and N-benzyl analogues 5d and 5e
were moderately well absorbed (Cmax=0.561 and0.216
mg/mL, respectively), and N-propargyl amine 5i exhib-
iteda Cmax of 1.37 mg/mL. The propargyl substituent
was selectedfor inclusion with the expectation of
increasing the oral exposure, basedon in-house experi-
ence. However, all of the compounds tested were less
than 15 ng/mL in plasma at the 6 h time point.
7. Chan, C. O.; Cooksey, C. J.; Crich, D. J. Chem. Soc., Per-
kin Trans. 1 1992, 7, 777.
8. Obrecht, D.; Spiegler, C.; Schoenholzer, P.; Mueller, K.;
Heimgartner, H.; Stierli, F. Helv. Chim. Acta 1992, 75, 1666.
9. The resolution of 30 was accomplishedusing a Chiralpak
AD column (4.6 mmꢀ25 cm) at a flow rate of 1.0 mL/min
eluting with a mobile phase of 35:65 ethanol/heptane with
0.2% trifluoroacetic acid. Tony Yan is gratefully acknowl-
edged for performing the chiral separation.
10. Inhibitors were assayedagainst purifiedhMMP-13,
hMMP-1 andhMMP-2 using an enzyme assay basedon clea-
vage of the fluorogenic peptide MCA-Pro-Leu-Gly-Leu-Dpa-
Ala-Arg-NH2. This is similar to conditions described by
Knight, C. G. et al. FEBS Lett. 1992, 296, 263, except that
0.02% final concentration of 2-mercaptoethanol was usedin
the MMP-13 andMMP-1 assays. All basic compounds were
tested as their hydrochloride salts except for 10a and 10b,
which were testedas the trifluoroacetate salts.
In summary, we have described a promising series of a-
alkyl-a-amino-b-sulphone hydroxamates that are potent
inhibitors of both MMP-2 andMMP-13, andthat spare
MMP-1. Several analogues showedgoodabsorption
when administered orally in the rat. The efficacy of these