Synthesis and evaluation of novel heterocyclic MMP inhibitors

Article abstract of DOI:10.1016/j.bmcl.2007.10.020

A variety of novel heterocyclic compounds were synthesized and evaluated for MMP inhibition. Broad spectrum inhibition of MMPs 1, 2, 9, and 12 was found with pyridinone-based compounds while N-heterocyclic triazoles and tetrazoles were largely ineffective. A highly selective tetrazole inhibitor for MMP-2 was discovered.

Full text of DOI:10.1016/j.bmcl.2007.10.020

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 17 (2007) 6864–6870
Synthesis and evaluation of novel heterocyclic MMP inhibitors
Ryuji Hayashi, Xiaomin Jin and Gregory R. Cook*
Center for Protease Research, Department of Chemistry and Molecular Biology,
North Dakota State University, Fargo, ND 58105, USA
Received 13 August 2007; revised 2 October 2007; accepted 5 October 2007
Available online 17 October 2007
Abstract—A variety of novel heterocyclic compounds were synthesized and evaluated for MMP inhibition. Broad spectrum inhibi-
tion of MMPs 1, 2, 9, and 12 was found with pyridinone-based compounds while N-heterocyclic triazoles and tetrazoles were largely
ineffective. A highly selective tetrazole inhibitor for MMP-2 was discovered.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Extracellular proteolysis plays a key role in many bio-
logical processes. Angiogenesis, wound healing, inflam-
matory reactions, management of the blood–brain
barrier, general maintenance of joints, organ develop-
ment, ovulation, fetus implantation in the uterus,
embryogenesis, and many others all depend on enzymes
which remodel connective tissues in the extracellular
matrix. A family of enzymes known as the matrix
metalloproteinases (MMPs) are, at least in part, respon-
sible for these functions. The important role of MMPs in
extracellular degradation has been clearly demonstrated
in many diseases including arthritis, multiple sclerosis,
osteoporosis, Alzheimer’s disease, cancer growth and
metastasis, and periodontal disease.1 For example,
MMPs mediate extracellular matrix and basement-
membrane degradation during the early stages of tumor
growth particularly the gelatinases.2 Abnormal levels of
MMPs are observed for patients of these diseases and
thus inhibition of MMPs offers a potential for new ther-
apeutics. There are more than 24 known MMPs. The
MMP family of enzymes is structurally related with a
zinc-containing catalytic site. There are metalloprotein-
ases that utilize a zinc (II) metal for catalysis of the pro-
teolysis, and therefore, zinc binding groups (ZBGs) are
crucial for designing MMP inhibitors (MMPIs). As a
consequence, there has been a great deal of effort in re-
cent years to design and prepare inhibitors of MMPs,
mostly targeted at the prime side of the active site, which
contains a hydrophobic S10 pocket (Fig. 1a). Key to the
activity of almost all MMPIs is the functional group
that binds the zinc atom in the sctive site and the P10
substituent.3,4 To date, the only medically approved
MMPI is a tetracycline derivative with lM range inhibi-
tions used in the treatment of periodontal disease. In the
last few decades, hydroxamate-based MMPIs have been
mainly studied and fair amount of structure–activity
data is available on these compounds. Many small mol-
ecule MMPIs with hydroxamic acid as a ZBG have
shown outstanding inhibition in preclinical tests. More-
over, MMPIs with other ZBGS, such as thiols, carbox-
ylates, mercaptoalcohols,1e and dithiols, have shown
good inhibition in vitro.5 However, clinical tests for
these compounds have been disappointing. Some of
the reasons for this include low oral availability, poor
in vivo stability, pharmacokinetic problems,6 and unde-
sirable side effects associated with hydroxamates. There-
fore, the discovery of new MMPIs with better properties
and non-toxic ZBGs is critical. Recent reports demon-
strate a continued optimism that MMPI therapy might
be beneficial.7–9 Thus, we have been focused on the
development of MMPIs with non-hydroxamate ZBGs,
better drug-like properties, and efficient and economical
a
b
His
Zn
His
His
O
O
N
P1'
H
O
Keywords: Matrix metalloproteinase inhibitors; Pyridinones;
bis-Heterocycles.
Fig. 1. (a) MMP-2 catalytic domain.11 (b) Hypothetical binding of
pyridinone-based MPIs.
*
Corresponding author; e-mail: Gregory.Cook@ndsu.edu
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.10.020

R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
6865
synthetic routes.10 Herein, we disclose the synthesis of
novel heterocyclic MMPIs and results of their biological
examination.
Since sulfides are known to be good ZBGs for MMPs,
pyridylthiol-based MMPIs12 (4) were synthesized and
tested (Table 2). Compared to pyridinone-based
MMPIs, the pyridylthiols proved to be generally worse
for inhibition of MMPs. The only exception was ob-
served in 4–25 and 4–26, which inihibited MMP-2 over
MMP-1, MMP-9, or MMP-12.
Recently, Cohen reported the investigation of pyridi-
none-based ZBGs for MMP inhibition and these poten-
tially have better drug-like properties for MMPIs.11
Based partly on this work and work ongoing in our
laboratories, we envisioned that a strongly basic pyrid-
inone carbonyl oxygen might efficiently coordinate to
the catalytic Zn(II) in the active site of MMPs and
the ester substituent could play the role of a hydro-
As histidine imidazoles serve as ligands for the catalytic
zinc in the active site of MMPs, this heterocycle should
be ideal for binding the catalytic Zn. We envisioned the
readily accessible triazole to be similar. Oxazoline hetero-
cycles are also well known as ligands for Lewis acids13 and
we have previously utilized them for MMP inhibition.10
We hypothesized the combination of oxazoline and tria-
zole would be useful for chelating to Zn(II). Thus, oxaz-
olinyl triazole compounds were prepared (Scheme 1).
Their synthesis started from trimethylsilyl propiolic acid
(5). Peptide coupling with the aid of N-hydroxy-
succinimide and DCC was followed by dehydration
facilitated by methanesulfonyl chloride to form trimethyl-
silanylethynyl oxazoline (8). Removal of the silyl protect-
ing group with tetrabutylammonium fluoride was
followed by copper-catalyzed [3+2] cycloaddition14 to af-
ford the desired triazole (12). Results of the biological as-
say are presented in Table 3. To our disappointment, these
compounds were largely ineffective for inhibition of all
four MMPs tested. Only the cinnamyl derivative (12–7)
showed any activity at all with modest inhibition of
MMP-2 and slightly improved inhibition of MMP-12.
0
phobic P1 .
In order to provide proof of principle for our proposed
pyridinone ester-based MMPIs, we0prepared a library of
pyridinones containing different P1 substituents. One of
the important challenges of drug synthesis is how eco-
nomical and simple the synthesis of the target molecule
is. All of our novel pyridinone-ester MMPIs were pre-
pared in one step from commercially available 1. The
results of the biological screening of pyridinone-ester
structures for MMP antagonist activity are summarized
in Table 1.
In general, most pyridinone-based MMPIs showed bet-
ter inhibition for MMP-1 over MMP-2, MMP-9, or
MMP-12. Alkyl R-groups (3–1, 3–2, 3–5) provided good
inhibition (25–32 lM) for MMP-1. In the case of aro-
matic R-groups, simple benzyl R-group (3–6) inhibits
MMP-1 (30 lM). Longer alkyl chains with aromatic
R-group showed diminished inhibitions for MMP-1
(3–7, 3–13, 3–14, 3–30). Electron-rich benzyl R-groups
(3–8, 3–11, 3–12) were also found to be less effective.
Interestingly, placing –CF3 in either the p- or m-position
(3–9 and 3–10) resulted in selective inhibition of MMP-
1. These benzyl R-groups with electron-withdrawing
substitutions showed better inhibition (28 and 24 lM)
over electron-rich benzyl R-groups for MMP-1. Since
3–11 and 3–12 showed good inhibition towards MMP-
1, fluorinated benzyl R-groups were tested. Fluorine
substitution on the o-position (3–15) showed moderate
inhibition for MMPs. Fluorine substitution on both
m- (3–16) and p-positions (3–17) showed good inhibition
for MMP-1 (28, 23 lM). We also tested other fluori-
nated compounds and in particular, 3–21 displayed the
best inhibition toward MMP-1 among all of inhibitors
tested (13 lM). Compound 3–23 also showed good inhi-
bition towards MMP-1 (19 lM). In addition, we tested
other halogen substituted aromatic rings. Chlorinated
groups performed similar to fluorinated compounds
with the o-substituted compound (3–24) less effective.
Chlorine substitution on both m- (3–25) and p-positions
(3–25) afforded good inhibition for MMP-1 (21, 26 lM).
In contrast, the o-brominated benzyl group (3–27)
showed increased inhibition over the m-substituted ana-
log (3–28) for MMP-1 (19, 22 lM). Larger aromatic
R-groups (3–31, 3–32, 3–33) resulted in diminished
inhibition for MMPs. Notably, 3–34 showed good inhi-
bition for MMP-1 (42 lM) and MMP-2 (33 lM). Addi-
tionally, heteroaromatic rings were also tested (3–36, 3–
37, 3–38) and they showed moderate inhibitions for
MMP-1.
We also synthesized and tested tetrazole templates as
well. Using [2+3] cycloaddition mediated by Zn(II), tet-
razoles were prepared in high yields (Scheme 2). Since it
has been shown that bidentate ligands have much better
inhibitory potency than monodentate ligands, an addi-
tional potentially chelating heterocycle was incorpo-
rated into the design. We synthesized furanyl,
thiophenyl, and pyridyl substituted tetrazoles (15 and
18). However, these compounds were completely ineffec-
tive. Interestingly, compound 18a, which possesses a
long flexible substituent, showed selective inhibition
for MMP-2 (32 lM).
We next investigated MMPIs with potentially larger six-
membered ring chelation as illustrated by 19a (Scheme
3). Pyridylmethyl tetrazoles 21 were prepared from
cyanomethyl pyridine (19) in a rapid two-step sequence
of [3+2] cycloaddition followed by alkylation. The bio-
logical assay results are summarized in Table 4. Unfor-
tunately compounds 21–1 through
4 showed no
inhibition of MMPs. Interestingly the unsubstituted pyr-
idylmethyl tetrazole 20 afforded complete selectivity for
MMP-2 with a good level of inhibition.
In conclusion, we have prepared and evaluated novel het-
erocyclic MMPIs with good levels of inhibitory activity
with non-hydroxamate ZBGs. Pyridinone esters afforded
broad spectrum low micro molar inhibition of MMPs 1, 2,
9, and 12. These compounds are advantageous as they are
small and readily accessible in one synthetic step from
commercially available materials. We have also synthe-
sized and tested a variety of chelating bis-heterocycles

6866
R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
Table 1. Inhibition of MMPs with pyridinone-based inhibitors
DBU, NaI(5 mol%)
CH3CN, rt, 16 h
Method 1
Br
2a
or
R
OH
O
+
HO
N
O
N
R
DCC, DMAP (5 mol%)
H
HO
2b
R
O
O
1
3
CH2Cl2, -40 ºC to rt, 16 h
Method 2
Entry
Product
R
% Yield
IC50a (lM)
MMP-9
MMP-1
MMP-2
MMP-12
1
2
3–1
3–2
Isopropyl
Cyclobutyl
64b
76b
71
31
25
37
50
32
30
47
65
28
24
69
99
59
67
64
28
23
35
70
41
16
30
19
51
25
26
19
22
81
86
115
75
128
42
68
56
39
46
50
67
66
67
62
69
68
94
69
81
68
na
101
88
100
127
94
76
50
3
67
51
67
71
71
69
68
69
82
64
69
105
79
82
68
16
65
60
100
20
31
56
63
68
46
47
44
31
105
70
111
97
105
99
118
65
62
76
68
3
3–3
3–4
CH2CHC(CH3)2
CH2CCCH3
Cyclohexyl
72
70
4
56
5
3–5
3–6
64b
76
101
65
6
Benzyl
7
3–7
3–8
(CH2)2C6H5
4-Me-Benzyl
3-CF3-Benzyl
3-CF3-Benzyl
3-OMe-Benzyl
4-OMe-Benzyl
(CH2)2OC6H4
(CH2)4OC6H4
2-F-Benzyl
74b
35
69
73
8
9
3–9
73
51
na
112
70
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
3–10
3–11
3–12
3–13
3–14
3–15
3–16
3–17
3–18
3–19
3–20
3–21
3–22
3–23
3–24
3–25
3–26
3–27
3–28
3–29
3–30
3–31
3–32
3–33
3–34
3–35
3–36
3–37
3–38
3–39
60
60
110
na
90
35b
65b
41
71
70
3-F-Benzyl
4-F-Benzyl
59
66
71
66
2,6-F-Benzyl
2,5-F-Benzyl
3,5-F-Benzyl
2,4,6-F-Benzyl
2,4,5-F-Benzyl
CH2C6F5
59
19
60
85
71
33
67
69
81
67
68
59
67
114
73
109
103
114
na
na
70
67
90
66
70
69
67
13
39
86
40c
70
64
69
2-Cl-Benzyl
3-Cl-Benzyl
4-Cl-Benzyl
2-Br-Benzyl
3-Br-Benzyl
4-Br-Benzyl
Cinnamyl
38
47
5
69
46c
47
57
68
38
40
107
90
71
36
1-Napthalyl
2-Napthalyl
Piperonyl
109
125
107
33
42
60d
50
3-Ph-Benzyl
3-OPh-Benzyl
2-Thiophenyl
3-Thiophenyl
2-Furyl
78d
52d
65d
62d
49
na
73
65
111
103
(CH2)4CH3
a na, not active (IC50 > 150 nM).
b Method 1 under 70 ꢁC.
c Alkyl-Cl was used.
d Method 2.
possessing triazole and tetrazole functionality with some
displaying highly selective MMP inhibition.
broad band proton decoupling. Chemical shifts are re-
ported in relative to TMS and coupling constants in
Hz. Melting points were determined without correction.
Reactions were carried out under an inert atmosphere of
nitrogen or argon. Solvents were dried using a nitrogen
pressurized alumina column system from Solvtek.
General experimental procedure.15 Thin layer chroma-
tography (TLC) was performed on silica gel What-
man-60F glass plates, and components were visualized
by illumination with UV light or by staining with potas-
sium permanganate solution. Chromatography was per-
formed using silica E. Merck silica gel 60 (230–400
mesh). NMR spectra were recorded in CDCl3 on a Var-
ian Inova 500 MHz, 400 MHz, or Varian Mercury
300 MHz spectrometer. 13C NMR was recorded using
General procedure of biological assay. The compounds
were tested for inhibition on MMP-1, MMP-2, MMP-
9, and MMP-1216 by using the fluorogenic MMP
substrate 7-(methoxycoumarin-4-yl)acetyl-Pro-Leu-
Gly-Leu(N-3-[2,4-dinitrophenyl]-L-2,3-diamino-propio-

R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
Table 2. Inhibition of MMP’s with pyridithiol-based inhibitors
6867
Lawson's reagent
THF
O
O
O
N
H
R
HS
N
R
O
O
4
3
a
Entry
Product
R
% Yield
IC50 (lM)
MMP-1
MMP-2
MMP-9
MMP-12
1
2
4–1
4–2
Isopropyl
50
60
52
56
47
60
32
43
11
46
30
30
33
20
58
32
30
27
20
16
10
51
59
65
30
45
44
35
60
121
135
102
101
120
95
na
na
73
132
137
91
146
na
Cyclobutyl
Cyclohexyl
Benzyl
3
4–3
4–4
87
82
4
85
88
5
4–5
4–6
(CH2)2C6H5
(CH2)3C6H5
3-Me-Benzyl
4-Me-Benzyl
3-CF3-Benzyl
4-CF3-Benzyl
119
100
7
107
112
7
117
85
6
7
4–7
4–8
na
na
70
81
8
98
119
126
141
93
9
4–9
134
na
110
125
90
134
94
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
4–10
4–11
4–12
4–13
4–14
4–15
4–16
4–17
4–18
4–19
4–20
4–21
4–22
4–23
4–24
4–25
4–26
4–27
4–28
4–29
3-OMe-Benzyl
4-OMe-Benzyl
(CH2)4OC6H5
3-F-Benzyl
86
78
96
108
138
119
120
92
91
63
95
83
78
124
108
66
107
120
101
140
105
100
112
na
151
112
127
17
4-F-Benzyl
2,6-F-Benzyl
2,5-F-Benzyl
2,4,5-F-Benzyl
CH2C6F6
114
124
78
79
90
106
81
70
96
4-Cl-Benzyl
2-Br-Benzyl
1-Napthalyl
2-Napthalyl
4-Ph-Benzyl
3-Ph-Benzyl
3-OPh-Benzyl
4-OPh-Benzyl
3-Thiophenyl
(CH)5CH3
126
na
115
na
108
98
na
99
na
na
100
110
42
119
150
50
101
135
52
119
75
78
46
93
75
71
114
108
115
110
90
109
93
77
85
109
105
a na, not active (IC50 > 150 lM).
O
37 ꢁC for 30 min prior to start of experiment. To the
mixture of MMP and the test compound was added
the substrate (final concentration 7 lM) in Hepes buffer
(50 mM, 5 mM CaCl2, 0.05% w/w Brij-35 at pH 7.5) and
incubated for 30 min. After incubation fluorescence
intensity measurements were taken by a Molecular De-
vices Gemini EM microplate reader (Sunnyvale, CA),
excitation at 328 nm was used, and the time course of
emission at 393 nm was monitored for 45 min at 50-s
intervals.
HO
NH2
N-hydroxysuccinimide
TMS
COOH
+
N
H
DCC, THF
(84%)
TMS
OH
5
6
7
O
O
N
TBAF
MsCl, Et3N
1,2-dichloroethane
TMS
H
THF/H2O
(96%)
N
8
9
(64%)
N
O
O
N
N
N
N
9
NaN3
R
Br
R N3
N
his
his
DMSO
N
P1'
Cu
tBuOH/H2O
N
Zn
R
10
11
12
12a
his
General procedure for synthesis of pyridinone-based
MMPIs.
Scheme 1. Synthesis of oxazolinyl triazoles and their hypothetical
binding to MMPs (12a).
Method 1. DBU (2.4 mmol) was added to a solution of
2-hydroxy-6-picolinic acid (2.0 mmol) and bromide
(2.2 mmol) in CH3CN (10 mL). The mixture was stirred
overnight at the appropriate temperature. When the
reaction mixture was completed (monitored by TLC)
the mixture was quenched by addition of water
(20 mL) and extracted with CH2Cl2 (2· 20 mL). The
combined organic layers were dried over Na2SO4. Re-
moval of the solvent and purification by flash silica gel
chromatography (Hexane–EtOAc 3:7) afforded the de-
sired pyridinones.
nyl)-Ala-Arg-NH2 (Biomol International, Plymouth
Meeting, PA), in wellplate experiments with the catalytic
domains (Biomol International, Plymouth Meeting, PA)
in 384-well format. The catalytic domains of MMPs
(MMP-1, final concentration 85 nM; MMP-2, final con-
centration 24 nM; MMP-9, final concentration 18 nM;
MMP-12, final concentration, 84 nM) and various con-
centrations (150 lM to 1.2 lM using 1:2 dilutions) of
the test compounds were pre-mixed and incubated at

6868
R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
Table 3. Inhibition of MMPs with oxazolinyl triazoles based inhibitors
Entry
Product
R
% Yield
IC50a (l/M)
MMP-9
MMP-1
MMP-2
MMP-12
1
2
3
4
5
6
7
12–1
12–2
12–3
12–4
12–5
12–6
12–7
cyclohexene
hexyl
heptyl
42
34
35
48
41
33
42
na
na
na
na
na
na
na
na
na
na
na
na
na
149
na
na
na
na
na
na
na
na
na
na
na
na
na
61
benzyl
(CH2)2C6H5
(CH2)3C6H5
cinnamyl
a na, not active (IC50 > 150 lM).
with CH2Cl2 (2·20 mL). The combined organic layers
were dried over Na2SO4. Removal of the solvent and
purification by flash silica gel chromatography (Hex-
ane–EtOAc 3:7) afforded the desired pyridinones.
NaN3
ZnBr2
X
N
N
X
N
R = H, hexyl, heptyl,
benzyl, ethylphenyl,
propylphenyl, cinammyl
RBr
N
N
N
X
N
Et3N
DMSO
N
Water
Reflux
N
H
13
X=O or S
14
15
R
Not active
General procedure for synthesis of thiopyridine-based
MMPIs. A mixture of 3 (1.0 mmol) and Lawson’s
reagent (0.6 mmol) was stirred at room temperature in
THF (5 mL) overnight. Upon completion of reaction,
the mixture was quenched with water (10 mL) and
extracted with CH2Cl2 (2·10 mL). The combined organic
layers were dried over Na2SO4. Removal of the solvent
and purification by flash silica gel chromatography (Hex-
ane–EtOAc 8:2) afforded the desired thiopyridines.
NaN3
ZnBr2
N
N
R = H, hexyl, heptyl,
benzyl, ethylphenyl,
propylphenyl cinammyl
N
N
RBr
N
N
N
N
N
Et3N
DMSO
N
Water
Reflux
N
R
N
17
18
16
H
Not active
IC50 (μ
M)
N
N
O
MMP-1: na
MMP-2: 32
MMP-9: na
MMP-12: 126
N
N
N
N
H
18a
Scheme 2. Synthesis of furanyl-, thiophenyl-, and pyridyl-substituted
tetrazoles.
General for the synthesis of triazoles. Alkyne (10.0 mmol)
was added dropwise to the solution of organic azide
(10.0 mmol) in t-BuOH/H2O (3:1, 15 mL). Copper metal
was added and the mixture was stirred overnight at
40 ꢁC. Once the reaction was complete, it was quenched
with water (30 mL), extracted with EtOAc (2·30 mL)
and dried over Na2SO4. Removal of the solvent and
purification by flash silica gel chromatography (Hex-
ane–EtOAc 1:1) afforded the desired triazoles.
NaN3
N
N
ZnBr2
RBr
N
N
N
C
N
N
N
N
N
Et3N
DMSO
N
NH
Water
Reflux
R
19
20
21
N
N
N
N
P1'
N
his
his
Zn
19a
his
Synthesis of compound 7. To a solution of 3-(trimethyl-
silyl) propynoic acid (5.0 mmol) in 25 mL of THF, N-
hydrosuccinimide (6.0 mmol and DCC (6.0 mmol) were
added sequentially. After 2.5 h of stirring at room tem-
perature, hydroxylamine (5.0 mmol) was added via a
syringe. Stirring was maintained for additional 10 h un-
til completion of the reaction. The precipitation was
filtered, and the filtrate was evaporated at reduced pres-
sure. The residue was taken up in EtOAc and was
washed with saturated NaCl solution. The aqueous
phase was extracted with EtOAc twice, the combined
organic extracts were dried over Na2SO4 and the solvent
Scheme 3. Synthesis of pyridylmethyl tetrazoles and its hypothetical
binding to MMPs (19a).
Method 2. Alcohol (2.0 mmol) was added to the solution
of 2-hydroxy-6-picolinic acid (2.0 mmol), DCC
(2.0 mmol), and DMAP (0.2 mmol) in CH2Cl2 (10 mL)
at ꢀ40 ꢁC. The mixture was allowed to warm to room
temperature and stirred overnight. When the reaction
was completed (monitored by TLC) the mixture was
quenched by addition of water (20 mL) and extracted
Table 4. Inhibition of MMPs with pyridylmethyl tetrazoles
Entry
Product
R
% Yield
IC50a (lM)
MMP-1
MMP-2
MMP-9
MMP-12
1
2
3
4
5
20
H
Benzyl
86
48
35
38
12
na
na
na
na
na
48
na
na
na
na
na
na
na
na
na
na
na
na
na
na
21–1
21–2
21–3
21–4
(CH2)2C6H5
(CH2)3C6H5
Cinnamyl
a na, not active (IC50 > 150 lM).

R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
6869
removed under reduced pressure. Flash silica gel chro-
matography afforded the product as white solid.
Francisco (supported by NIH P41 RR-01081). We are
grateful to Thane Underdahl and John R. Smith who
obtained IC50 values for our compounds.
Synthesis of compound 8. To a stirred solution of the
ynamide 7 (3.5 mmol), triethylamine (17.3 mmol) and
DMAP (0.10 mmol) in 1,2-dichloroethane (20 mL) was
added methanesulfonyl chloride (5.2 mmol). The result-
ing mixture was heated to reflux until the disappearance
of the starting amide was noted. After cooling, the sol-
vent and the excess triethylamine were evaporated at
reduce pressure. The residue was purified by flash silica
gel chromatography with hexane/ethyl acetate as eluent.
References and notes
´
´
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Synthesis of compound 9. To a stirred solution of 8
(2.05 mmol) in 5 ml of THF was added sequentially a
solution of tetrabutylammonium fluoride in THF
(0.05 mmol) and 0.05-ml distilled water were added.
After 30 min, the reaction mixture was diluted with
20 mL of dichloromethane and washed with 20 mL of
a saturated NaCl solution. The aqueous phase, after
separation, was washed with dichloromethane. The
combined organic extracts were dried over Na2SO4
and the residue was purified by flash silica gel
chromatography.
General procedure for tetrazoles synthesis. A mixture of
nitrile (5.0 mmol), sodium azide (5.5 mmol), zinc bro-
mide (5.0 mmol), and water was refluxed overnight with
vigorous stirring. HCl (9.0 mL, 3N) and ethyl acetate
(25 mL) were added and the mixture was stirred until
no solid was present and the aqueous layer had a pH
of 1. The organic layer was separated and the aqueous
layer extracted with 2·25 mL of ethyl acetate. The com-
bined organic layers were dried over Na2SO4, filtered,
and evaporated. 50 mL of 0.25N NaOH was added
and the mixture was stirred for 30 min until the original
precipitate was dissolved and a suspension of zinc
hydroxide was formed. The suspension was filtered
and the solid washed with 5 mL of 1N NaOH. To the
filtrate was added 10 mL of 3N HCl with vigorous stir-
ring until pH of 3. The precipitate was filtered, collected,
and dried in the oven.
2. (a) Sternlicht, M. D.; Lochter, A.; Sympson, C. J.; Huey,
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a simple sulfonamide
carboxylate bound to the zinc and S10 pocket, see:
Pavlovsky, A. G.; Williams, M. G.; Ye, Q.-Z.; Ortwine,
D. F.; Purchase, C. F., II; White, A. D.; Dhanaraj, V.;
Roth, B. D.; Johnson, L. L.; Hupe, D.; Humblet, C.;
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General procedure for alkyl substitution17 A solution of
tetrazole (0.71 mmol) in DMSO was added dropwise
into a suspension of NaH (0.71 mmol) in THF
(10 mL) under nitrogen at room temperature. After
15 min alkyl bromide (1.06 mmol) was added via a syr-
inge. After 5 h, the reaction mixture was quenched with
water and extracted by ethyl acetate twice. The organic
phase was washed by water and brine and dried over
Na2SO4. The solvent was removed under reduced pres-
sure. The product was isolated purified by flash silica
gel chromatography.
4. For recent studies of other potential MMPI ZBG’s with
model zinc complexes, see: (a) Puerta, D. T.; Lewis, J. A.;
Cohen, S. M. J. Am. Chem. Soc. 2004.
5. Wu, Z.; Walsh, C. J. Am. Chem. Soc. 1996, 118, 1785.
6. (a) Brown, P. D. APMIS 1999, 107, 174; (b) Coussens, L.
M.; Fingleton, B.; Matrisian, L. M. Science 2002, 295,
2387.
7. Bramhall, S. R.; Hallissey, M. T.; Whiting, J.; Scholefield,
J.; Tierney, G.; Stuart, R. C.; Hawkins, R. E.; McCulloch,
P.; Maughan, T.; Brown, P. D.; Baillet, M.; Fielding, J. W.
L. Br. J. Cancer 2002, 1864.
8. Bramhall, S. R.; Rosemurgy, A.; Brown, P. D.; Bowry, C.;
Buckels, J. A. C.; Lambiase, L.; Langleben, A.; Shparber,
M.; Clark, J.; Kaywin, P.; Lutzsky, J.; Benedetto, P.;
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Harris, J.; Mani, S.; Van Echo, D.; Dutta, S.; Culliney, B.;
Zaknoen, S.; Cohn, A.; Byrne, P.; Waterhouse, D.;
Brookes, D.; Garewel, H.; Staddon, A.; Cynwyd, B.;
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Acknowledgments
We are grateful to the National Institutes of Health
(NCRR-P20-RR15566) for support of this work. The
molecular graphics image in Figure 1a was produced
using the UCSF Chimera package from the Computer
Graphics Laboratory, University of California, San

6870
R. Hayashi et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6864–6870
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15. All compounds demonstrated adequate spectral properties
consistent with their assigned structure and purity.
16. These four were chosen to represent the majority of the
MMPs. For a discussion of the similarity of MMP binding
sites, see: Lukacova, V.; Zhang, Y.; Mackov, M.; Baricic,
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