A Convenient Synthesis of a Selective Gelatinase Inhibitor as an Antimetastatic Agent

Article abstract of DOI:10.1021/jo049857v

Compound 1, 2-(4-phenoxyphenylsulfonylmethyl)thiirane, is a potent and selective inhibitor for human gelatinases (J. Am. Chem. Soc. 2000, 122, 6799-6800), enzymes implicated in a number of diseases, including cancer. This compound is showing excellent pro

Full text of DOI:10.1021/jo049857v

SCHEME 1
A Con ven ien t Syn th esis of a Selective
Gela tin a se In h ibitor a s a n An tim eta sta tic
Agen t
In Taek Lim, Stephen Brown, and Shahriar Mobashery*
Department of Chemistry and Biochemistry, University of
Notre Dame, Notre Dame, Indiana 46556
mobashery@nd.edu
at the root of some of the difficulties that these MMP
inhibitors have suffered in clinical trials recently.4
We described recently a mechanism-based inhibitor
that was high selectivity for gelatinase inhibition.5
Compound 1 is the prototype of this type of inhibitor. The
biphenyl moiety fits in the deep hydrophobic pocket in
the active sites of gelatinases, and the inhibitor interacts
with the active site zinc ion through the thiirane moiety.
This interaction activates the thiirane for nucleophilic
attack by the active site glutamate in these enzymes,
resulting in species 2, which is the irreversibly inhibited
enzyme.5,6 The mode of inhibition is at the root of the
selectivity seen with the inhibitor for gelatinases, as
described in detail earlier.5
Received J anuary 25, 2004
Abstr a ct: Compound 1, 2-(4-phenoxyphenylsulfonylmeth-
yl)thiirane, is a potent and selective inhibitor for human
gelatinases (J . Am. Chem. Soc. 2000, 122, 6799-6800),
enzymes implicated in a number of diseases, including
cancer. This compound is showing excellent promise in
animal trials in a number of disease models. Large quanti-
ties of this compound were necessary for these studies. A
convenient four-step synthetic route for compound 1 is
described herein. The synthesis is amenable to scale-up to
tens of grams and gives an overall yield of 57% for this
important compound.
The extracellular matrix (ECM) is the environment
that surrounds cells. The health of ECM is critical for
the well-being of the organism in normal physiological
processes. Matrix metalloproteinases (MMPs) constitute
a family of 27 enzymes that have the ability to alter the
ECM by their functions.1 The various functions of MMPs
have not been elucidated, which is an area of active
current research. The functions of these enzymes are
strictly regulated under normal physiological processes.
When the cellular regulation is lost, the levels of activities
of these enzymes are elevated, an event that causes a
number of pathological conditions that include cancer
growth, tumor metastasis and angiogenesis, arthritis,
connective tissue diseases, inflammation, and cardiovas-
cular, neurological, and autoimmune diseases.2
Two of the MMPs, MMP-2 and MMP-9, also known as
gelatinases A and B, have been implicated in a number
of these pathological conditions. They have been the
targets of many inhibitor design programs.3 Unfortu-
nately, the known inhibitors for these enzymes are
generally broad-spectrum in that they also inhibit other
classes of MMPs. This broad breadth of activity may be
Whereas virtually all MMP inhibitors have been
designed as zinc ion chelators, the principles behind the
design of inhibitor 1 and its unique mechanism of action
were points of departure. Furthermore, selectivity in
targeting gelatinases provided a unique opportunity in
exploring the roles of gelatinases in disease processes.
This inhibitor is currently undergoing trials in several
animal models for diseases involving excessive gelatinase
activities, including models for cancer metastasis. These
studies necessitated the development of a new high-
yielding synthetic route for compound 1 that was ame-
nable to scales in quantities of tens of grams, which is
the subject of the present report.
The previous synthesis started from the commercially
available p-phenoxyphenol (3) to give the thiol derivative
4 (Scheme 1). This transformation took place in three
steps, with one step requiring heating at 260 °C, as
described by Newman and Karnes for a related system.7
Oxidation of 5 to 6 required 7 days and proceeded in
(1) Massova, I.; Kotra, L. P.; Fridman, R.; Mobashery, S. Matrix
Metalloproteases: Structures, Evolution and Diversification. FASEB
J . 1998, 12, 1075-1095.
(2) Forget, M.-A.; Desrosier, R. R.; Be´liveau, R. Can. J . Physiol.
Pharmacol. 1999, 77, 465-480. Nelson, A. R.; Fingleton, B.; Rothen-
berg, M. L.; Matrisian, L. M. J . Clin. Oncol. 2000, 18, 1135-1149.
Hanahan, D.; Weinberg, R. A. Cell 2000, 100, 57-70. Chambers, A.
F.; Groom, A. C.; MacDonald, I. C. Nature Rev. 2002, 2, 563-572.
Kerbel, R.; Folkman, J . Nature Rev. 2002, 2, 727-739. Fidler, I. J .
Nature Rev. 2002, 3, 1-6. Bergers, G.; Benjamin, L. E. Fidler, I. J .
Nature Rev. 2003, 3, 401-410. Steeg, P. S. Nature Med. 2003, 9, 822-
823. Van’t Veer, L.; Weigelt, B. Nature Med. 2003, 9, 999-1000.
(3) Cristofanilli, M.; Charnsangavej, C.; Hortobagyi, G. N. Nature
Rev. 2002, 1, 415-426. Buolamwini, J . K. Curr. Opin. Chem. Biol.
1999, 3, 500-509. Whittaker, M.; Floyd, C. D.; Brown, P.; Gearing, A.
J . H. Chem. Rev. 1999, 99, 2735-2776. Skiles, J . W.; Gonnella, N. C.;
J eng, A. Y. Curr. Med. Chem. 2001, 8, 425-474. Lee, M.; Fridman,
R.; Mobashery, S. Chem. Soc. Rev. 2004, in press.
(4) Overall, C. M.; Lo´pez-Ot´ın, C. Nature Rev. Cancer 2002, 2, 657-
672. Egeblad, M.; Werb, Z. Nature Rev. Cancer 2002, 2, 161-174.
Coussens, L. M.; Fingleton, B.; Matrisian, L. M. Science 2002, 295,
2387-2392.
(5) Brown, S.; Bernardo, M.; Li, Z. H., Kotra, L. P.; Tanaka, Y.;
Fridman, R.; Mobashery, S. J . Am. Chem. Soc. 2000, 122, 6799-6800.
(6) Kleifeld, O.; Kotra, L. P.; Gervasi, D. C.; Brown, S.; Bernardo,
M. M.; Fridman, R.; Mobashery, S.; Sagi, I. J . Biol. Chem. 2001, 276,
17125-17131.
(7) Newman M. S.; Karnes H. A. J . Org. Chem. 1966, 31, 3980-
3984.
10.1021/jo049857v CCC: $27.50 © 2004 American Chemical Society
Published on Web 04/16/2004
3572
J . Org. Chem. 2004, 69, 3572-3573

was poured portionwise into a cooled solution of epichlorohydrin
(68 g, 740 mmol) in dichloromethane (700 mL). The mixture was
stirred at room temperature for 1 h after the last portion of
epichlorohydrin was added. The mixture was partitioned be-
tween dichloromethane and an aqueous saturated solution of
sodium potassium tartrate (2 × 500 mL), and the organic layer
was washed with water (2 × 500 mL), dried (MgSO4), and
filtered through Celite. The solvent was evaporated under
reduced pressure, and the residue was purified by column
chromatography (hexane/EtOAc ) 6:1-3:1) to afford 8 (101 g,
93%): 1H NMR (500 MHz, CDCl3) δ 7.4 (m, 2H), 7.4 (m, 2H),
7.2 (m, 1H), 7.1 (m, 2H), 7.0 (m, 2H), 3.9 (m, 1H, CHOH), 3.7
(m, 2H, CH2Cl), 3.1 (ddd, J ) 44.5, 14.0 Hz, 5.5 Hz, 2H,
SCH2CH), 2.7 (d, J ) 5.0 Hz, 1H, OH); 13C NMR (125 MHz,
CDCl3) δ 157.4, 156.7, 133.4, 130.1, 128.0, 124.0, 119.5, 119.6,
69.6, 48.2, 39.9; HRMS calcd for C15H15ClO2S (M+) 294.0481,
found 294.0461.
2-(4-P h en oxyp h en ylsu lfa n ylm et h yl)oxir a n e (9). To a
solution of compound 8 (55 g, 187 mmol) in anhydrous p-dioxane
(250 mL) was added sodium hydroxide (28 g, 700 mmol). The
reaction mixture was stirred at room temperature for 1 h, and
a catalytic amount of sodium hydride (0.1 g, 4 mmol) was added.
The reaction mixture was stirred at room temperature overnight
and then was filtered through Celite. The filtrate was concen-
trated under reduced pressure, yielding the title compound (40.6
g, 84%) as an oil: 1H NMR (500 MHz, CDCl3) δ 7.5 (m, 2H), 7.4
(m, 2H), 7.2 (m, 1H), 7.0 (m, 2H), 6.9 (m, 2H), 3.2 (m, 1H), 3.1
(dd, J ) 14.0, 4.0 Hz, 1H), 2.9 (ddd, J ) 14.0, 6.0, 1.5 Hz, 1H),
2.8 (m, 1H), 2.5 (m, 1H); 13C NMR (125 MHz, CDCl3) δ 157.2,
156.8, 133.7, 130.0, 128.7, 123.9, 119.5, 119.4, 51.3, 47.6, 38.2;
HRMS calcd for C15H14O2S (M+) 258.0715, found 258.0739.
2-(4-P h en oxyp h en ylsu lfon ylm et h yl)oxir a n e (6). To a
solution of compound 9 (35 g, 135 mmol) in dichloromethane (650
mL) was added a solution of m-chloroperoxybenzoic acid (62.8
g, 77%, 280 mmol) in dichloromethane (350 mL) at 0 °C. The
reaction mixture was stirred at 0 °C for 3 h and was then
warmed to room temperature overnight. The suspension was
filtered, and the filtrate was washed with aqueous sodium
thiosulfate (2 × 600 mL, 10% w/v), followed by aqueous sodium
bicarbonate (2 × 500 mL, 5% w/v), followed by brine (500 mL).
The organic layer was dried over magnesium sulfate and was
concentrated. The product was purified by silica gel chromatog-
raphy (hexane/EtOAc ) 3:1-3:2) to yield the title compound as
an oil (35.9 g, 92%). The 1H and 13C NMR spectra and mass
spectrum were identical to the reported values.5
SCHEME 2
modest yield. The oxirane to thiirane conversion with
ammonium thiocyanate (6 to 1) gave a poor yield of only
14%. The synthesis was accomplished in 5% overall yield.
The approach was useful in preparing research quantities
of the desired inhibitor for in vitro studies, but it clearly
was not amenable to large-scale preparation needed for
animal studies.
The new synthesis commences from the commercially
available 4-bromophenyl phenyl ether (7). The lithium
salt of p-phenoxythiophenol was generated in situ from
7 by the use of metallic magnesium and sulfur in the
presence of lithium aluminum hydride, which was in turn
allowed to react with epichlorohydrin to give the key
intermediate, 1-chloro-3-(4-phenoxy-phenylsulfanyl)pro-
pan-2-ol (8). This one-pot reaction obviated the need for
handling of thiol 4, which is both noxious and prone to
air oxidation. The formation of epoxide 9 from derivative
8 under basic condition proceeded well in good yield.
Subsequently, the sulfide was oxidized by the reaction
of m-CPBA to give 6 in 92% yield. The exchange of the
oxygen in the oxirane 6 with a sulfur to give the desired
thiirane 1 with the use of thiourea gave 80% yield.
The number of steps in the synthesis of 1 was reduced
to four, and the overall total yield was increased from
5% in the previous synthesis to 57% by the approach
depicted in Scheme 2. On somewhat less tangible issues,
the reagents in this synthetic sequence were cheaper and
the reactions required shorter durations. The present
synthesis is practical and can be carried out in substan-
tially larger scale. This synthesis has made the animal
studies possible.
2-(4-P h en oxyp h en ylsu lfon ylm eth yl)th iir a n e (1). To a
solution of compound 6 (21 g, 72 mmol) in anhydrous methanol
(700 mL) was added thiourea (12 g, 158 mmol). The reaction
mixture was stirred at room temperature for 24 h. The solvent
was removed under reduced pressure. The residue was parti-
tioned between ethyl acetate (600 mL) and water (400 mL), the
organic layer was washed with brine (400 mL) and dried
(MgSO4), and the suspension was filtered. The solvent was
evaporated from the filtrate, and the residue was purified by
column chromatography (hexane/EtOAc ) 3:1-2:1). The desired
product was crystallized as white needles from ethyl acetate/
hexane (17.8 g, 80%). The 1H and 13C NMR spectra and mass
spectrum were identical to the reported values.5
Exp er im en ta l Section
1-Ch lor o-3-(4-p h en oxyp h en ylsu lfa n yl)p r op a n -2-ol (8).
The procedure was adapted from that reported by Szajnman et
al.8 Metallic magnesium (9.0 g, 370 mmol) was added to a
solution of 4-bromophenyl phenyl ether (92.6 g, 372 mmol) in
anhydrous THF (500 mL) with vigorous stirring at room tem-
perature. The reaction mixture was refluxed under argon until
the metal was dissolved. The solution was cooled to 0 °C, and
sulfur (12.6 g, 393 mmol) was added. The mixture was stirred
at room temperature for 4 h, at which time lithium aluminum
hydride (4 g) was added portionwise to the solution at 0 °C. The
solution was allowed to warm to room temperature, and the
mixture was stirred for 2 h, followed by quenching by the
addition of ethyl acetate (4.4 mL, 45 mmol) at 0 °C. The mixture
Ack n ow led gm en t. This work was supported by the
National Institutes of Health.
Su p p or tin g In for m a tion Ava ila ble: NMR spectra for the
synthetic molecules. This material is available free of charge
via the Internet at http://pubs.acs.org.
(8) Szajnman, S. H.; Yan, W.; Bailey, B. N.; Docampo, R.; Elhalem,
E.; Rodriguez, J . B. J . Med. Chem. 2000, 43, 1826-1840.
J O049857V
J . Org. Chem, Vol. 69, No. 10, 2004 3573