Design and structure-activity relationships of potent and selective inhibitors of blood coagulation factor Xa

Article abstract of DOI:10.1021/jm990040h

The discovery of a series of non-peptide factor Xa (FXa) inhibitors incorporating 3-(s)-amino-2-pyrrolidinone as a central template is described. After identifying compound 4, improvements in in vitro potency involved modifications of the liphophilic group and optimizing the angle of presentation of the amidine group to the S1 pocket of FXa. These studies ultimately led to compound RPR120844, a potent inhibitor of FXa (K₁ = 7 nM) which shows selectivity for FXa over trypsin, thrombin, and several fibrinolytic serine proteinases. RPR120844 is an effective anticoagulant in both the rat model of FeCl₂-induced carotid artery thrombosis and the rabbit model of jugular vein thrombus formation.

Full text of DOI:10.1021/jm990040h

J . Med. Chem. 1999, 42, 3557-3571
3557
Design a n d Str u ctu r e-Activity Rela tion sh ip s of P oten t a n d Selective In h ibitor s
of Blood Coa gu la tion F a ctor Xa
William R. Ewing,*,† Michael R. Becker,*,† Vincent E. Manetta,† Roderick S. Davis,† Henry W. Pauls,†
Helen Mason,†, Yong Mi Choi-Sledeski,† Daniel Green,†,| Don Cha,† Alfred P. Spada,† Daniel L. Cheney,‡,
J onathan S. Mason,‡, Sebastien Maignan,∇ J ean-Pierre Guilloteau,∇ Karen Brown,§ Dennis Colussi,§
Ross Bentley,§ J eff Bostwick,§ Charles J . Kasiewski,§ Suzanne R. Morgan,§ Robert J . Leadley,§
Christopher T. Dunwiddie,§,X Mark H. Perrone,§ and Valeria Chu§
Departments of Cardiovascular Drug Discovery and New Leads Generation, Rhoˆne-Poulenc Rorer, 500 Arcola Road,
Collegeville, Pennsylvania 19426-0107
Received J anuary 25, 1999
The discovery of a series of non-peptide factor Xa (FXa) inhibitors incorporating 3-(S)-amino-
2-pyrrolidinone as a central template is described. After identifying compound 4, improvements
in in vitro potency involved modifications of the liphophilic group and optimizing the angle of
presentation of the amidine group to the S1 pocket of FXa. These studies ultimately led to
compound RPR120844, a potent inhibitor of FXa (Ki ) 7 nM) which shows selectivity for FXa
over trypsin, thrombin, and several fibrinolytic serine proteinases. RPR120844 is an effective
anticoagulant in both the rat model of FeCl2-induced carotid artery thrombosis and the rabbit
model of jugular vein thrombus formation.
In tr od u ction
formed by the residues Phe174, Tyr99, and Trp215. This
pocket is more aromatic in nature than the correspond-
ing region in thrombin which contains the residues
Leu99 and Ile174. Another recognition element, located
in the back of the aryl binding pocket, has been termed
the “cation hole”.6 The carbonyl functions of Glu97 and
Lys96, together with a structural water molecule, form
the “cation hole”, which can bind basically charged
groups. The S2 site of FXa is small compared to the
same region in thrombin. Recently, the crystal struc-
tures of two non-peptide inhibitors, Daiichi’s DX-9065a6
and Banyu’s FX-2212,7 bound to the active site of FXa
have been reported.
Initiation of the blood coagulation cascade by activa-
tion of either the intrinsic or extrinsic pathway ulti-
mately leads to the conversion of the zymogen factor X
to its activated form, factor Xa (FXa). Once produced,
FXa in the presence of factor Va and calcium ions on a
phospholipid membrane forms the prothrombinase com-
plex. The prothrombinase complex converts prothrom-
bin to thrombin 300 000-fold more efficiently than FXa
alone.1 Once generated, thrombin converts fibrinogen
to fibrin leading to clot formation.1 The efficiency with
which the prothrombinase complex produces thrombin
suggests that the inhibition of FXa would represent an
effective approach to controlling thrombin levels.2 Cur-
rent antithrombotic therapies have limitations such as
the need for clinical monitoring, failure to inhibit
thrombin generation at the site of thrombus formation,
and lack of effectiveness for inactivating clot-bound
thrombin.3 Further studies have suggested that inhibi-
tors of FXa may have a reduced effect on abnormal
bleeding when compared to direct or indirect inhibitors
of thrombin.4 Inhibition of FXa may offer a safety
advantage over currently available antithrombotic
agents.4
Our design of FXa inhibitors focused on developing
molecules with subunits that interacted with the lipo-
philic S4 pocket and the S1 specificity pocket of FXa.
These two subunits were to be presented via a central
scaffold meeting the distance requirements needed for
interaction with S1 and S4. The P1 group was chosen
based on literature precedent which demonstrated that
generally m-benzamidines have higher affinity for FXa
than p-benzamidines.8 For the P4 group, naphthalene
was chosen as modeling studies suggested this group
could fill the highly aromatic S4 pocket. The first
scaffold identified that accommodated these two groups
was 1,3-disubstituted indole 1. Compound 1 was found
to be a modest inhibitor of FXa (Ki ) 0.9 µM) with
selectivity over thrombin and trypsin. Several attempts
to improve on the activity of indole 1 by introducing
H-bonding groups to potentially interact with Gly216
or Gly218 of the â-sheet or by replacing the naphthalene
with other lipophilic groups were not successful. A
search for alternative scaffolds, which possessed better
solubility, synthetic flexibility, and the possibility of
interacting with the â-sheet, led to the identification of
a novel series of FXa inhibitors, incorporating 3-(S)-
amino-2-pyrrolidinone as the central scaffold.
FXa belongs to the trypsin class of serine proteinases.
The X-ray crystal structure of human des(1-45) FXa
was solved by Tulinsky and co-workers.5 The S1 speci-
ficity pocket of FXa is homologous to that found for
thrombin. The aryl binding pocket or S4 of FXa is
§ Department of Cardiovascular Biology.
∇ Department of Crystallography and X-ray Analysis.
† Department of Medicinal Chemistry.
‡ Department of Molecular Modeling.
| Current address: Wyeth-Ayerst Research, 145 King of Prussia Rd,
Radnor, PA 19087.
Current address: Bristol Myers Squibb, Rte 206 and Province Line
Rd, Lawrenceville, NJ 08648.
X Current address: Lilly Research Laboratory, Lilly Co. Center,
Indianapolis, IN 46285.
10.1021/jm990040h CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/21/1999

3558 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ta ble 1. Central Scaffolds
Ewing et al.
Sch em e 1. Synthesis of Heteroaryl Nitrilesa
a
(a) NaBH4, THF; (b) Pd(PPh3)4, Zn(CN)2, DMF; (c) CBr4, PPh3.
chlorides were obtained from the bromide or stannane
intermediate using butyllithium followed by a sulfur
dioxide quench and subsequent reaction with sulfuryl
chloride.
The heteroaryl amidines (Table 6) were prepared from
their respective heteroaryl nitrile methyl halides B as
illustrated in Scheme 1. Thiophene-3-carboxaldehyde
serves as an illustrative example in its conversion to
the 4-(bromomethyl)thiophene-2-carbonitrile. A three-
step procedure involves reduction of the aldehyde,
cyanation via a palladium-mediated cross-coupling with
zinc cyanide15 to generate nitrile intermediate A, and
conversion of the alcohol to the methyl bromide (CBr4/
PPh3).
The synthesis of target compounds proceeded via a
modular approach. Boc-3-(S)-aminopyrrolidin-2-one (C,
n ) 1), exemplified in Scheme 2, was readily obtained
by cyclization of commercially available N-R-Boc-L-2,4-
diaminobutyric acid. N-Alkylation of the lactam ring
nitrogen (NaH or NaHMDS) with the requisite het-
eroaryl halide electrophiles provided intermediates D
and allowed for incorporation of the various P1 units.16
A typical reaction sequence involves deprotection (HCl/
EtOAc or TFA/CH2Cl2), sulfonylation, and imidate
formation under Pinner conditions17 (HCl/EtOH) fol-
lowed by ammonolysis (NH3/MeOH). Amidine formation
could also be achieved using an alternate method via a
thioamide intermediate (H2S/MeI/NH4OAc).18 Addition-
ally, prior to nitrile conversion, the sulfonamide nitrogen
of intermediates E could be alkylated with various
electrophiles (E f F ) (Table 5).
Ch em istr y
The enantiomerically pure 3-amino lactam scaffolds
(Table 1) were prepared from either direct methods or
known literature procedures.9 Both enantiomers of the
3-amino-2-pyrrolidinone and 4-amino-2-pyrrolidinone
were originally derived from the appropriately protected
aspartic acid derivatives. As an example, the template
used for compound 3 was prepared from N-Boc-L-Asp-
(O-t-Bu)-OH. The R-acid functionality was reduced to
the alcohol via its isobutyl mixed anhydride and then
oxidized under Swern conditions to the aldehyde.10
Under reductive amination conditions,11 Boc-L-Asp-(O-
t-Bu)-H was condensed with m-cyanobenzylamine hy-
drochloride12 to give the secondary amine. The product
was then cyclized to Boc-4-(S)-amino-2-pyrrolidinone
under acidic conditions. The other scaffolds were easily
obtained by a combination of similar techniques or from
commercial sources.
The various sulfonyl chlorides used to prepare com-
pounds listed in Tables 2 and 3 were synthesized from
arylsulfonic acids or via a lithiation/sulfonation proce-
dure13 from the corresponding aryl bromide or arylstan-
nane precursors.9b Several of the naphthalene-derived
sulfonic acids were converted directly to their sulfonyl
chlorides using phosphorus oxychloride or thionyl chlo-
ride.14 Many of the naphthyl and biphenyl/biarylsulfonyl
Resu lts a n d Discu ssion
Figure 1 shows inhibitor 1 docked in the active site
of FXa. In this model, the scaffold lies near the â-sheet
but does not appear to have interactions in this region.
Additionally from this model, the phenyl ring of the
indole does not have contacts with the active site. We
began to search for monocyclic templates to replace
indole with functional groups which could potentially
form H-bonds with the â-sheet of FXa. Table 1 shows a
scan of templates which contain H-bond donor and
acceptor groups (sulfonamides and carbonyl groups).
Replacement of indole with a pyrrolidine, 2, results in
a 10-fold loss (comparison of Ki’s) in FXa activity. To
remove the basic center from compound 2, two pyrro-
lidinone regioisomers 3 and 4 were synthesized. Sul-
fonamide 3, derived from 4-(S)-amino-2-pyrrolidinone,
was 10-fold less potent than indole 1. The 3-(S)-amino-
2-pyrrolidinone 4 resulted in an improvement in potency
(Ki ) 0.23 µM) relative to the indole 1. Comparing the
activity of the two pyrrolidinones suggests that the
location of the ring carbonyl plays an important role in
activity. Analogues containing lactams of other ring
sizes, compounds 6-8, were also investigated. None of
these had better activity than the five-membered ring

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3559
Sch em e 2. Synthesis of Final Compoundsa
a
(a) NaH, THF:DMF (10:1), 0 °C; (b) HCl, EtOAc; (c) ArSO2Cl, Et3N, CH2Cl2; (d) K2CO3, DMF, R-Br; (e) HCl, EtOH; (f) NH3, MeOH.
F igu r e 1. Binding model of indole 1 (left) in the FXa active site compared with pyrrolidinone 4 (right) in the FXa active site.
FXa coordinates5 available on the Brookhaven database: 1HCG.
analogue. Additionally, the pyrrolidinone was compared
to glycine 5. While the potency of these two derivatives
is similar, the glycine analogue lacked selectivity for
FXa over thrombin and trypsin.
The docked structure, Figure 1, also suggests that the
naphthalene group does not completely fill the aryl
binding pocket. Initial SAR studies focused on substi-
tuted naphthalenes or biaryl ring systems. Table 2
depicts several attempts to improve the potency of
compound 4 with substituted naphthalene groups. A
preference for the 2-naphthalene moiety was established
by the relative loss in potency observed for the 1-naph-
thalene 9. Compounds 10-19 were synthesized to probe
the effect of increasing the size of the naphthalene group
in the aryl binding pocket. The methyl derivative 10 was
found to be 2-fold more potent than the parent com-
pound 4. Incorporating a methoxy group showed a
preference for the 7-position over the 6-position. The
7-methoxy 12 exhibited a 5-fold improvement in potency
(Ki ) 0.047 µM) relative to compound 4, maintaining
selectivity over thrombin and trypsin. The correspond-
ing 6-methoxy analogue was 20-fold less active than
compound 12. Increasing the length of the alkoxy group
by one carbon, compound 14, resulted in a considerable
loss in potency. Compounds 15 and 16 show the effect
on activity of substituting the 6- and 7-positions with
chlorine. In contrast to the methoxy substitutions, both
chloro compounds were found to be essentially equipo-
tent. Several polar groups were also examined on the
naphthalene ring. The 7-hydroxyl analogue 17 was 10-
fold less active than compound 12. The 7-aniline 18
retained good activity for FXa with a Ki ) 0.12 µM,
One of the shortcomings reported for some direct
inhibitors of thrombin is the lack of selectivity against
serine proteinases involved in fibrinolysis.19 Inhibition
of the fibrinolytic enzymes (plasmin and tPA) and
activated protein C (aPC) has been identified as a
potential liability resulting in the compromise of hemo-
stasis. To further assess the 3-amino-2-pyrrolidinones
as FXa inhibitors, compound 4 was assayed against
several serine proteinases. Pyrrolidinone 4 was found
to display selectivity for FXa over thrombin (Ki > 4 000
nM), trypsin (Ki ) 2 900 nM), aPC (Ki ) 7 000 nM),
plasmin (Ki ) 4 700 nM), and tPA (Ki > 10 000 nM).
With the potency and selectivity profile observed for
compound 4, further optimization studies were under-
taken.
Figure 1 shows the proposed binding model of com-
pound 4 docked into the active site of FXa.5 In this
model, the pyrrolidinone carbonyl oxygen is within
H-bonding distance of the Gly218 NH. The orientation
of the sulfonamide oxygens suggests that they are
pointing away from the â-sheet and facing out toward
the solvent. A primary role of the sulfonamide linkage
may be to direct the naphthalene group into the aryl
binding pocket.

3560 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ta ble 2. Naphthalene Optimization
Ewing et al.
Ta ble 3. Biaryl Ring System Optimization
Ta ble 4. Effect of Stereochemistry on Activity
whereas the methylanilino 19 resulted in a drop in FXa
potency of Ki ) 0.25 µM.
Another approach to improving the potency of com-
pound 4 involves replacement of naphthalene with
biphenyl ring systems (Table 3). Compounds 20 and 21
were prepared to find the preferred location of the
second phenyl ring. Of the two regioisomers, the 1,4-
biphenyl analogue 21 exhibited better activity. Substi-
tution of the distal ring with either methyl (22) or
methoxy (23 and 24) offered only modest potency
enhancements, with compound 23 exhibiting a Ki ) 0.10
µM for FXa. Linking the two aryl groups with either a
carbon (25) or oxygen (26) did not lead to improved FXa
activity. From the SAR studies shown in Tables 2 and
3, the 7-methoxynaphthalene analogue 12 was identi-
fied as the lead structure for further optimization.
Compound 12 has selectivity for FXa over thrombin (Ki
> 1 400 nM), trypsin (Ki ) 853 nM), aPC (Ki ) 1 200
nM), plasmin (Ki ) 4 700 nM), and tPA (Ki > 10 000
nM).
mide nitrogen was alkylated with a methyl group, a
clear stereochemical preference for FXa activity was
observed. Methylation of the (S)-isomer 28 increased
FXa potency 2-fold, whereas methylation of the (R)-
isomer 29 resulted in a 10-fold loss in potency. From
these results, the (S)-isomer was chosen for further
optimization studies.
During the course of our research effort, the relation-
ship between the stereochemistry of the 3-amino-2-
pyrrolidinone scaffold and FXa activity was investigated
(Table 4). When the sulfonamide nitrogen is unsubsti-
tuted, both the (S)- and (R)-3-amino-2-pyrrolidinones 12
and 27 were equipotent. However, when the sulfona-
A series of N-alkylated analogues was prepared based
on the results found for methylsulfonamide 28 (Table
5). This region was probed with small aromatic and
alkyl groups. A set of aryl rings was examined, com-
pounds 31-35, which contained neutral H-bond-donat-
ing or H-bond-accepting groups. The most potent from

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3561
Ta ble 6. Heterocyclic Amidines
Ta ble 5. N-Alkylation of the 3-Sulfonamide Group
this set was compound 32 containing a 3-thiophene
moiety. Amide and carboxylic acid derivatives were also
investigated (compounds 36-38). The acetamide 37 had
a Ki ) 0.025 µM. No analogue was found which
improved on in vitro potency over the N-methyl deriva-
tive 28. The role of small groups such as methyl and
acetamide or small heterocycles is most likely confor-
mational, stabilizing the bound conformation of the
inhibitor rather than forming additional interactions
with the FXa active site.
In an effort to optimize the amidine interaction with
Asp189 in the S1 pocket, the angle of presentation of
the P1 group was varied between 120° and 180° using
the heterocyclic amidines as shown in Table 6.20 The
angles listed represent the calculated angle between the
amidine carbon and the benzylic carbon of the side
chain.21 Placing the amidine group in the para position,
39, resulted in a 20-fold loss in FXa activity. Compounds
40-42 contain thiophene amidine regioisomers. The
calculated angle shows that compound 41 is more “para-
like”, while 40 and 42 are closer to “meta”. Compound
40 (Ki ) 0.011 µM) had the best activity, a 4-fold
improvement over the m-benzamidine 12. The calcu-
lated angle between the methylene bearing the side
chain and the amidine carbon for compounds 40 and
42 is similar. Despite this, the activity for these two
analogues differs by nearly 1 order of magnitude. One
possible explanation for the enhanced activity seen for
compound 40 is favorable van der Waals contacts
between the sulfur atom and Val213 side chain in the
S1 pocket. Other heteroaryl amidines were also ex-
plored. Attempts to form complementary hydrogen
bonds near Asp189 were probed using pyridine and
furan rings (43-45). Again factors other than angle play
a role in activity for these heterocycles as furan 45
offered no improvement in FXa potency.
From the SAR investigated, several structural modi-
fications were found which enhanced FXa activity. The
indole scaffold was replaced by a 3-(S)-sulfonamido-2-
pyrrolidinone resulting in a more potent FXa inhibitor
with good selectivity. The 7-methoxynaphthalene group
was found to bind optimally in the S4 binding pocket.
N-Methylation of the sulfonamide nitrogen improved
potency for analogues containing the (S)-enantiomer of
the scaffold. Finally, FXa activity was further enhanced
by replacing the m-benzamidine with an appropriately
substituted thiophene amidine. Combination of the
optimal groups from the inhibitor design process de-
scribed above resulted in RPR120844 (Table 7). RPR-
120844 is a potent inhibitor of FXa (Ki ) 0.007 µM).
Additionally, RPR120844 is selective for FXa over
thrombin and trypsin and displays high selectivity for
FXa versus plasmin, tPA, and aPC.
Inhibitor RPR120844 was docked into the FXa active
site as shown in Figure 2. The proposed binding models
for inhibitors 4 and RPR120844 are quite similar. The
P1 amidine group forms twin-twin hydrogen bonds
with the Asp189 side chain carboxyl group and one
additional hydrogen bond with the Gly218 oxygen. The
pyrrolidinone carbonyl oxygen and one of the two
sulfonamide oxygens form weak hydrogen bonds with

3562 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ta ble 7. Activity and Selectivity of RPR120844
Ewing et al.
dose, peak plasma levels of 2.4 µM were obtained.
RPR120844 was also tested orally in rats. At a dose of
50 mg/kg, inhibitor RPR120844 obtained plasma levels
of 500 and 260 nM, respectively.
Con clu sion
The 3-(S)-amino-2-pyrrolidinone scaffold has been
identified for the design of noncovalent inhibitors of
FXa. The 2-pyrrolidinone scaffold supported a number
of structural modifications to the P1 and P4 groups
while maintaining activity for FXa. These inhibitors also
displayed good selectivity for FXa over related serine
proteinases. RPR120844, resulting from this research,
was effective in both rat and rabbit models of throm-
bosis. Further optimization studies with this scaffold
are under investigation in these laboratories.
the Gly218 NH. The remaining oxygen of the sulfona-
mide group as well as the sulfonamide methyl group
are oriented away from the protein surface. Although
the pyrrolidinone ring lies directly over Gly216, hydrogen-
bonding contacts with this residue are not formed. The
naphthyl group lies deep within the S4 binding pocket
with the methoxy group oriented favorably toward the
face of Trp215 side chain.
Exp er im en ta l Section
En zym e Assa ys. Human FXa, thrombin, and activated
protein C (aPC) were obtained from Enzyme Research Labo-
ratories, Inc. (South Bend, IN). Bovine trypsin was obtained
from Sigma Chemical Co. (St. Louis, MO). Plasmin was
purchased from Pharmacia Hepar (Franklin, OH). Tissue-
plasminogen activator (tPA; Actives) was obtained from Ge-
nentech (San Francisco, CA). The chromogenic substrates used
were Spectrozyme fXa (American Diagonostica Inc., Green-
wich, CT) for FXa; Pefachrome TH (Centerchem, Inc., Stam-
ford, CT) for thrombin; S-2765 (Diapharma Group Inc.,
Franklin, OH) for trypsin; Pefachrome-tPA (Centerchem Inc.)
for tPA. The chromogenic substrate S-2366 (Diapharma Group
Inc.) was used for assay of both plasmin and aPC.
FXa, thrombin, and plasmin were assayed in a buffer
containing 0.05 M Tris, 0.15 M NaCl, 0.1% PEG-8000, pH 7.5.
Trypsin and aPC were assayed in the aforementioned buffer
with addition of 0.02 M CaCl2. tPA was assayed in the first
buffer, but the PEG-8000 was replaced with 0.1% (w/v) BSA
(bovine serum albumin; Sigma).
The final substrate concentrations in the reactions were 200,
50, 250, and 500 µM for Spectrozyme fXa, Pefachrome TH,
S-2765, and Pefachrome-tPA, respectively. The final concen-
trations of S-2366 for the plasmin and aPC assays were 300
and 500 µM, respectively. All enzyme assays were carried out
at room temperature in 96-well microtiter plates with a final
enzyme concentration of 1 nM. Compound dilutions were
added to the wells containing buffer and enzyme and prein-
cubated for 30 min. The enzyme reactions were initiated by
the addition of substrate, and the color developed from the
release of p-nitroanilide from each chromogenic substrate was
monitored continuously for 5 min at 405 nm on a Thermomax
microtiter plate reader (Molecular Devices, Sunnyvale, CA).
Under the experimental conditions, less than 10% of the
substrate was consumed in all assays. The initial velocities
measured were used to determine the amount of inhibitor
required to diminish 50% of the control velocity, which was
defined as IC50 of the inhibitor. Assuming the kinetic mech-
anisms were all competitive, the apparent Ki values were then
calculated according to the Cheng-Prusoff equation: Ki )
IC50/1 + [S]/Km.
Coa gu la tion Assa y. Activated partial thromboplastin time
(APTT) was measured with a MLA Electra 800 automatic
coagulation timer (Orthodiagnostics, NJ ). Citrated human
(George King Biomedical Inc., Overland Park, KS), dog
(mongrel; Covance Research Product, Alice, TX), and rat
(Sprague-Dawley; Charles River) plasma were used in the
assays. One hundred microliters of freshly thawed plasma was
mixed with 100 µL of compound dilutions followed by auto-
matic addition of 100 µL of actin-activated cephaloplastin
reagent (Dade, Miami, FL) and 100 µL of 0.035 M calcium
chloride to start the clot formation. Anticoagulant activity of
a compound was evaluated with the concentration required
for doubling the plasma clotting time.
RPR120844 was cocrystallized with trypsin (Figure
3) and confirmed several of the observations found from
the modeling study with FXa. Trypsin has been used
as a surrogate for FXa to determine binding conforma-
tions.22 The inhibitor is tightly bound in the P1 pocket
forming a salt bridge between the amidine group and
Asp189 carboxylate group. The amidine also forms
H-bonds with Gly219 carbonyl oxygen atom, Ser190
hydroxyl oxygen, and a water molecule. The sulfur atom
makes a van der Waals contact with the Val213 side
chain in the P1 pocket. The carbonyl oxygen of the
pyrrolidinone ring is oriented toward Gly219 but lies 3
Å away and does not appear to form a strong H-bond.
One of the sulfonamide oxygens is pointing toward
Ser217 but also does not H-bond to this residue. The
7-methoxynaphthalene is in the lipophilic pocket with
the methoxy group pointing toward Trp215. The greater
potency of RPR120844 for FXa over trypsin can be
explained by a better fit of the methoxynaphthalene
group in the aryl binding pocket of FXa as compared
with the same domain in trypsin. In FXa, the methox-
ynaphthalene can π-stack with the Phe174 and Try99,
whereas in trypsin the group is near Ile174 and Leu99.
RPR120844 was found to double-activate partial
thromboplastin time (APTT) in vitro at concentrations
of 1.45, 1.48, and 0.74 µM in plasma obtained from
humans, dogs, and rats, respectively. Antithrombotic
efficacy of intravenously administered RPR120844 was
assessed in arterial (rat) and venous (rabbit) thrombosis
models. At 0.1 and 0.3 mg/kg iv bolus administration,
RPR120844 maximally increased APTT 1.7- and 2.4-
fold above control values, respectively. When adminis-
tered iv to rats, RPR120844 (3 mg/kg iv bolus + 300
µg/kg/min constant infusion) increased time to occlusion
from 18 to 60 min in a rat model of FeCl2-induced
carotid artery thrombosis.23 In this study, thrombus
mass was reduced from 5.5 mg (vehicle) to 1.4 mg. In a
rabbit model of venous thrombosis, RPR120844, dose-
dependently inhibited jugular vein thrombus forma-
tion.24 At a dose of 100 µg/kg/min, RPR120844 decreased
thrombus mass from 42 mg (vehicle) to 12 mg. At this

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3563
F igu r e 2. Proposed binding model of RPR120844 in the FXa active site. FXa coordinates5 available on the Brookhaven
database: 1HCG.
F igu r e 3. X-ray of the RPR120844/trypsin complex at 1.9 Å.
Molecu la r Mod elin g. The inhibitor RPR120844 was flex-
ibly docked into the FXa active site using an automated
protocol developed in-house.20 In this method, lower-energy
conformations of the ligand are generated on the fly using a
modifed version of a rule-based method implemented in Chem-
X. Using ChemDBS-3D with in-house customization, an at-
tempt is made to fit each conformation in turn onto a
predefined, minimal pharmacophore model using a steric shell
of the active site as an added constraint. Matching conforma-
tions are then passed to the program DISCOVER for optimiza-
tion in a partially relaxed active site model using the CFF97
force field. The resulting docked complexes are scored on the
basis of total force field energy. This method has been validated
against several known protein/ligand systems, having repro-
duced the correct bound conformation of the ligand within 0.7
Å rms.20
vine pancreatic trypsin (Sigma T8003) was solubilized in 1 mM
CaCl2, 60 mM benzamidine, 50 mM Mes-NaOH (pH 6.0) buffer
to a final concentration of 30 mg/mL. The hanging drops
crystallization method was used at 19 °C. Single crystals were
obtained with ammonium sulfate (1.4-1.8 M), pH 6.0, in the
“open” form (P212121, a ) 63.6 Å, b ) 63.7 Å, c ) 68.9 Å) for
which the binding site is free of any contact with crystal-
lographic symmetry-related molecules.
RPR120844 is scarcely soluble in water or ammonium
sulfate solution, but it was still possible to prepare a 100 µM
solution in 2.5 M ammonium sulfate, 50 mM Mes-NaOH, pH
6.0. The crystals were soaked in 50 µL of this solution for a
couple of days to allow proper exchange of the benzamidine
by the “low”-affinity inhibitor RPR120844.
Data collection an d pr ocessin g: The crystal was mounted
in a glass capillary and exposed to X-ray radiation at room
temperature on a FR591 rotating anode generator (Nonius,
The Netherlands) equipped with a DIP2020K image plate
Tr yp sin /In h ibitor RP R120844 Cr ysta l Str u ctu r e De-
ter m in a tion . Cr ysta lliza tion a n d in h ibitor soa k in g: Bo-

3564 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ewing et al.
detector (Mac Science, J apan). Data images were processed
using DENZO and SCALEPACK (Otwinowski & Minor, 1997),
and structure refinement was performed using X-PLOR
(Bru¨nger, 1992). The trypsin structure used as a starting point
is the uncomplexed 1.55 Å form (2ptn Protein Data Bank
entry) (Walter et al., 1982).
Ch em istr y. All starting materials, reagents, and solvents
were used as received from commercial sources except for
N-bromosuccinimide which was recrystallized from water and
dried under vacuum. In general, reactions were performed
under an inert atmosphere such as nitrogen or argon. Workup
means drying over sodium or magnesium sulfate, filtering, and
concentrating in vacuo. Flash column chromatography of
intermediates was performed using 230-400 mesh silica gel
60 (E. Merck). Proton NMRs were recorded on a Bruker ARX
300 MHz or ACF 300 spectrometer, and mass spectra were
obtained using a Varian VG-70SE spectrometer. Elemental
analyses were performed by Quantitative Technologies of
Whitehorse, NJ .
Final products were generally purified by preparative
reverse-phase HPLC. Purification was performed on a Rainin
SD-1 Dynamax system with a 2-in. C-18 reverse-phase Dy-
namax 60 Å column using a gradient of about 5-30% aceto-
nitrile/0.1% TFA water to 70-100% acetonitrile/0.1% TFA
water over a 20-40-min period at a flow rate of 40-50 mL/
min. Fractions containing the desired material were concen-
trated and lyophilized to obtain the final products as white
solids.
P r ep a r a tion of [1-(3-Cya n oben zyl)-2-oxop yr r olid in -4-
(S)-yl]ca r ba m ic Acid ter t-Bu tyl Ester (ben zon itr ile p r e-
cu r sor to com p ou n d 3). Boc-L-Asp(O-t-Bu)-OH (18.7 g, 64.8
mmol) is dissolved in 65 mL of THF and cooled to -10 °C.
The solution is treated with N-methylmorpholine (7.48 mL,
68.0 mmol) and stirred for 5 min. To the solution is added
dropwise isobutyl chloroformate (8.82 mL, 68.0 mmol). After
the addition is completed, the solution is stirred for 30 min
and then filtered through a pad of Celite. The collected solution
is cooled to -10 °C. To the solution is added sodium borohy-
dride (3.80 g, 100 mmol) predissolved in 100 mL of water. The
solution is stirred at 0 °C for 1 h and then at room temperature
for 1 h. The solution is poured into a separatory funnel and
diluted with 800 mL of EtOAc. The organic layer is washed
with 1 N HCl solution, water, saturated NaHCO3 solution, and
saturated NaCl solution. The organic layer is dried over
MgSO4, filtered, and concentrated. The residue is purified by
column chromatography (20% EtOAc/hexanes to 33% EtOAc/
hexanes), and the alcohol (12.2 g, 44.3 mmol) is isolated as an
oil: 1H NMR (CDCl3) δ 5.26 (bs, 1H), 3.98 (m, 1H), 3.68 (bs,
2H), 2.82 (bs, 1H), 2.54 (m, 2H), 1.45 (bs, 18H).
of sodium cyanoborohydride (1.43 g, 22.8 mmol). The mixture
is stirred overnight. After this time, the mixture is filtered
through a pad of Celite, washed with MeOH, and concentrated
in vacuo. The residue is diluted with EtOAc and 20 mL of 1 N
NaOH, 100 mL of water is added, and the layers are separated.
The aqueous layer is washed with EtOAc (2×). The combined
organic layers are washed with water and saturated NaCl. The
organic layer is dried over MgSO4, filtered, and concentrated.
The residue is purified by column chromatography (20%
EtOAc/hexanes to 40% EtOAc/hexanes), and the secondary
amine product (4.60 g, 11.8 mmol) is obtained as an oil: 1H
NMR (CDCl3) δ 7.67 (s, 1H), 7.56 (m, 2H), 7.40 (m, 1H), 5.14
(bs, 1H), 4.05 (m, 1H), 3.86 (m, 2H), 2.72 (m, 2H), 2.47 (m,
2H), 1.62 (bs, 1H), 1.42 (bs, 18H).
To a solution of the secondary amine (9.55 g, 24.5 mmol) in
220 mL of toluene is added 24 mL of HOAc. The resulting
mixture is heated at reflux for 1.5 h, then cooled, and
concentrated in vacuo. The residue is purified by column
chromatography (30% EtOAc/CH2Cl2 to 50% EtOAc/CH2Cl2),
and the [1-(3-cyanobenzyl)-2-oxopyrrolidin-4-(S)-yl]carbamic
acid tert-butyl ester (6.30 g, 20.0 mmol) is obtained as a white
solid: 1H NMR (CDCl3) δ 7.59 (m, 1H), 7.51 (m, 1H), 7.46 (m,
2H), 4.92 (bs, 1H), 4.49 (s, 2H), 4.27 (m, 1H), 3.60 (dd, 1H),
3.17 (dd, 1H), 2.82 (dd, 1H), 2.35 (dd, 1H), 1.43 (s, 9H).
Gen er a l P r oced u r es for th e P r ep a r a tion of Cen tr a l
Sca ffold s (Ta ble 1) a s Boc-P r otected 3-Am in o La cta m
Rin g System s (in ter m ed ia tes C a n d D). Boc-3-(S)-Am i-
n oa zetid in -2-on e (C, n ) 0; tem p la te for com p ou n d 6).
To a solution of Boc-L-serine (10.3 g, 50 mmol) in 75 mL of
H2O:t-BuOH (2:1) are added methoxyamine hydrochloride (23
g, 75 mmol) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiim-
ide hydrochloride (9.6 g, 50 mmol). After 2 h, the solution is
saturated with NaCl and extracted with EtOAc. The organic
layer is dried over MgSO4, filtered, and concentrated. The
resulting crude amide is dissolved in 50 mL of pyridine and
cooled to 0 °C. To the solution is added methanesulfonyl
chloride (7.44 g, 65 mmol). After 1 h, the solution is poured
into 100 mL of cold 1 N HCl and diluted with EtOAc. The
layers are separated, and the organic layer is washed with 1
N HCl, saturated NaHCO3, and saturated NaCl. The organic
layer is dried over MgSO4, filtered, and concentrated.
The crude mesylate intermediate is dissolved in 50 mL of
acetone and added dropwise to a solution of K2CO3 (20.7 g,
150 mmol) in 900 mL of acetone at reflux. After 1 h, the
solution is cooled to room temperature. The solution is filtered
through Celite and then washed with 1 N HCl, saturated
NaHCO3, and saturated NaCl. The organic layer is dried over
MgSO4, filtered, and concentrated. The resulting solid is
dissolved in 20 mL of THF and added dropwise to an ammonia
solution containing sodium (2.6 g, 113 mmol) at -78 °C. After
the blue color has dissipated, the solution is stirred for an
additional 10 min. To the reaction mixture is added NH4Cl
(13.4 g, 250 mmol), and the solution is allowed to warm to
room temperature. The solution is filtered and concentrated.
The residue is recrystallized from EtOAc to give the Boc-3-
(S)-aminoazetidin-2-one (2 g, 11 mmol) as a white solid: 1H
NMR (acetone-d6) δ 6.96 (bs, 1H), 6.63 (bs, 12H), 4.81 (bs, 1H),
3.40 (m, 1H), 3.21 (m, 1H),1.40 (s, 9H).
To a solution of oxalyl chloride (6.63 mL, 76 mmol) in 110
mL of CH2Cl2 at -65 °C is added a solution of methyl sulfoxide
(12.4 mL g, 175 mmol) in 25 mL of CH2Cl2 dropwise over 20
min. The alcohol intermediate (12.2 g, 44.3 mmol) in 50 mL of
CH2Cl2 is added dropwise to the mixture over 20 min. The
reaction mixture is stirred at -65 °C for 15 min; then
triethylamine (40.5 mL, 290 mmol) in 110 mL of CH2Cl2 is
added over 20 min. The reaction mixture is stirred at -70 °C
for 40 min. The solution is poured into 400 mL of Et2O and
150 mL of 0.5 N KHSO4 solution. The resulting mixture is
poured into a separatory funnel, and the layers are separated.
The organic layer is washed with 150 mL of 0.5 N KHSO4
solution (2×), then concentrated to one-half volume, diluted
with Et2O, and washed again with water and saturated NaCl.
The organic layer is dried over MgSO4, filtered, and concen-
trated. The crude aldehyde (12.5 g) is used in the next step
without purification: 1H NMR (CDCl3) δ 9.63 (s, 1H), 5.60 (bs,
1H), 4.32 (m, 1H), 2.92 (dd, 1H), 2.74 (dd, 1H), 1.46 (s, 9H),
1.44 (s, 9H).
Boc-3-(S)-Am in op yr r olid in -2-on e (C, n ) 1; tem p la te
for com p ou n d s 4, 9-26, 28, 30-45, a n d RP R120844). To
a solution of N-R-Boc-L-2,4-diaminobutyric acid (25 g, 115
mmol), Et3N (35 g, 344 mmol), and hydroxybenzotriazole (19.3
g, 143 mmol) in 0.5 L of THF is added 1-(3-dimethylamino-
propyl)-3-ethylcarbodiimide hydrochloride (27.4 g, 143 mmol).
The solution is heated to 60 °C over 15 min. A white precipitate
forms, and the solution is kept at 60 °C for 4 h. After this time,
the solution is filtered and concentrated in vacuo. The crude
product is purified by column chromatography (1% MeOH/CH2-
Cl2 to 3% MeOH/CH2Cl2) to afford Boc-3-(S)-aminopyrrolidin-
2-one (19.6 g, 98 mmol) as a white solid: 1H NMR (CDCl3) δ
6.17 (bs, 1H), 5.08 (bs, 1H), 4.12 (m, 1H), 3.33 (m, 2H), 2.65
(m, 1H), 2.00 (m, 1H), 1.42 (s, 9H).
To a solution of Boc-L-Asp(O-t-Bu)-H (6.25 g) dissolved in
50 mL of methanol over 4 Å molecular sieves are added
m-cyanobenzylamine hydrochloride12 (8.5 g, 50.4 mmol) and
NMM (5.6 mL, 50.4 mmol). The solution is stirred for 40 min.
After this time, a solution of zinc chloride (1.55 g, 11.4 mmol)
in 25 mL of MeOH is added followed by portionwise addition
[1-(3-Cya n ob en zyl)-2-oxop ip er id in -3-(S)-yl]ca r b a m ic
Acid ter t-Bu tyl Ester (D, n ) 2; tem p la te for com p ou n d

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3565
7). A mixture of N-R-Boc-L-ornithine (1.5 g, 6.45 mmol) and
3-cyanobenzaldehyde (0.42 g, 3.23 mmol) is suspended in 20
mL of MeOH. A solution of anhydrous zinc chloride (0.24 g,
1.79 mmol) and sodium cyanoborohydride (0.22 g, 3.5 mmol)
in 5 mL of MeOH is added. The mixture is stirred for 16 h at
room temperature. After this time, 20 mL of 1 N NaOH is
added. The solution is concentrated, and the residue is
partitioned between EtOAc and water. The organic layer is
washed with saturated NaCl. The organic layer is dried over
MgSO4, filtered, and concentrated to give N-R-Boc-N-δ-(3-
cyanobenzyl)-L-ornithine.
A portion of the crude residue (0.75 g, 2.16 mmol), BOP
reagent (1.05 g, 2.38 mmol), and potassium hydrogen carbon-
ate (1.08 g, 10.8 mmol) are dissolved in 20 mL of DMF. The
reaction mixture is stirred for 16 h and then diluted with 300
mL of EtOAc. The organic layer is washed with 1 N HCl, 10%
Na2CO3, and saturated NaCl. The organic layer is dried over
MgSO4, filtered, and concentrated. The residue is purified by
column chromatography (15% EtOAc/CH2Cl2 to 35% EtOAc/
CH2Cl2) to give the [1-(3-cyanobenzyl)-2-oxopiperidin-3-(S)-yl]-
carbamic acid tert-butyl ester (0.26 g, 0.76 mmol) as a solid:
1H NMR (CDCl3) δ 7.49 (m, 4H), 5.50 (bs, 1H), 4.59 (s, 2H),
4.08 (m, 1H), 3.21 (m, 2H), 2.48 (m, 1H), 1.89 (m, 2H), 1.62
(m, 1H), 1.45 (s, 9H).
Boc-3-(S)-Am in o-E-ca p r ola cta m (C, n ) 3; tem p la te for
com p ou n d 8). l-(-)-R-Amino-ꢀ-caprolactam (5 g, 39 mmol)
and Et3N (4.9 g, 49 mmol) are dissolved in 100 mL of CH2Cl2.
To the solution is added Boc anhydride (8.5 g, 39 mmol) and
(dimethylamino)pyridine (0.1 g). The reaction mixture is
stirred for 16 h at room temperature. After this time, the
solution is washed with 1 N HCl, 10% Na2CO3, and saturated
NaCl. The organic layer is dried over MgSO4, filtered, and
concentrated to give Boc-3-(S)-amino-ꢀ-caprolactam (6.23 g, 27
mmol) as a solid: 1H NMR (CDCl3) δ 6.15 (bs, 1H), 5.90 (bs,
1H), 4.24 (m, 1H), 3.21 (m, 2H), 2.05 (m, 2H), 1.79 (m, 2H),
1.45 (m, 11H).
Gen er a l P r oced u r e for th e Syn th esis of Ar ylsu lfon yl
Ch lor id es fr om Ar ylsu lfon ic Acid s. 7-Meth oxyn a p h th a -
len e-2-su lfon yl Ch lor id e. To a suspension of 7-hydrox-
ynaphthalene-2-sulfonic acid, sodium salt (15.0 g, 60.9 mmol)
in 150 mL of 2:1 H2O/ethanol is added solid NaOH (2.68 g,
67.0 mmol) at room temperature. The mixture is stirred until
a homogeneous solution forms, and dimethyl sulfate (6.34 mL,
67.0 mmol) is then added. A precipitate eventually forms, and
the mixture is stirred over a period of 16 h. The crude mixture
is concentrated in vacuo, and the residue is stirred in 100 mL
of absolute EtOH as a slurry for 2 h. The precipitate is filtered
and dried. The solid is heated at reflux in 100 mL of 95% EtOH
for 2 h, allowed to cool to room temperature, filtered, and dried
to give 12.6 g of crude 7-methoxynaphthalene-2-sulfonic acid,
sodium salt. A mixture of the sulfonic acid, sodium salt (12.6
g, 48.6 mmol) in 20 mL of phosphorus oxychloride and
phosphorus pentachloride (13.2 g, 63.2 mmol) is heated slowly
to 60 °C until a homogeneous solution forms and then is heated
at 120 °C for 4 h. The resulting mixture is cooled in an ice
bath, and a mixture of ice/ice water is added slowly with
stirring. The mixture is diluted with water and extracted with
CHCl3 (2 × 100 mL). The combined organic layers are washed
successively with water, saturated NaHCO3 solution, and
saturated NaCl. The organic phase is dried over anhydrous
MgSO4, filtered, and concentrated to give 10.0 g of a crude
oil. The crude product is purified by column chromatography
(5% EtOAc/hexanes to 30% EtOAc/hexanes) to afford 7-meth-
oxynaphthalene-2-sulfonyl chloride (3.80 g, 14.8 mmol) as a
white crystalline solid: 1H NMR (CDCl3) δ 8.49 (d, 1H), 7.96
(d, 1H), 7.85 (d, 2H), 7.39 (dd, 1H), 7.29 (d, 1H), 3.99 (s, 3H);
EI MS [M]+ ) 256.
solution is allowed to warm to ambient temperature and
stirred for 3 h. At this time, a solution of 4-iodobromobenzene
(5.6 g, 19.8 mmol) and tetrakis(triphenylphospine)palladium-
(0) (1.1 g, 1 mmol) in 30 mL of THF is added. The reaction
mixture is stirred for 16 h, and then the solution is poured
into 100 mL of H2O. The solution is diluted with EtOAc, and
the organic layer is washed with 2 N NH4OH, H2O, and
saturated NaCl. The organic layer is dried over MgSO4,
filtered, and concentrated. The crude product is purified by
column chromatography (10% CH2Cl2/hexanes to 20% CH2Cl2/
hexanes) to give 4-(2-methoxyphenyl)bromobenzene as a crys-
talline solid: 1H NMR (CDCl3) δ 7.62 (d, 2H), 7.51 (d, 2H),
7.38 (m, 2H), 7.08 (m, 2H), 3.85 (s, 3H).
To a solution of 4-(2-methoxyphenyl)bromobenzene (0.82 g,
3.2 mmol) in 15 mL of THF at -78 °C is added n-butyllithium
(2.0 mL of a 1.6 M solution in hexanes, 3.2 mmol). After 30
min, the solution is transferred via cannula to a flask contain-
ing 10 mL of SO2 in 40 mL of Et2O at -78 °C. The solution is
stirred at -78 °C for 30 min and then at ambient temperature
for 2 h. After this time, the solution is concentrated. The
residue is dissolved in 20 mL of hexanes. The solution is cooled
to 0 °C, and sulfuryl chloride (3.2 mL of a 1 M solution in CH2-
Cl2) is added. The solution is stirred for 1 h. After this time,
the solution is concentrated. The crude product is purified by
column chromatography (2% EtOAc/hexanes) to afford 2′-
methoxybiphenyl-4-sulfonyl chloride (0.34 g, 2.6 mmol) as an
oil: 1H NMR (CDCl3) δ 8.07 (d, 2H), 7.81 (d, 2H), 7.44 (m, 2H),
7.02 (m, 2H), 3.88 (s, 3H).
7-Meth yln a p h th a len e-2-su lfon yl Ch lor id e. To a solution
of 7-methoxy-2-naphthol (5.00 g, 28.7 mmol) in 150 mL CH2-
Cl2 at 0 °C are added Et3N (5.95 g, 58.8 mmol), trifluo-
romethanesulfonic anhydride (10.1 g, 35.6 mmol), and DMAP
(0.36 g, 2.94 mmol). The brown solution is stirred for 1 h at 0
°C and then concentrated in vacuo to remove most of the CH2-
Cl2. The residue is diluted with EtOAc and washed with 1 N
aqueous HCl, water, 10% Na2CO3 solution, and saturated NaCl
solution. The organic layer is dried over MgSO4, filtered, and
concentrated to provide crude material which is purified by
column chromatography (2% EtOAc/hexanes to 10% EtOAc/
hexanes) to give 2-methoxy-7-(trifluoromethylsulfonyl)naph-
1
thalene (8.44 g, 27.5 mmol) as an oil. H NMR (CDCl3) δ 7.90
(d, 1H), 7.78 (d, 1H), 7.65 (d, 1H), 7.22 (m, 2H), 7.15 (d, 1H),
3.95 (s, 3H).
2-Methoxy-7-(trifluoromethylsulfonyl)naphthalene (10.0 g,
32.6 mmol) is dissolved in 300 mL of DMF and treated with
lithium chloride (7.20 g, 170 mmol) and tetramethyltin (12.4
g, 69.3 mmol). Bis(triphenylphosphine)palladium(II) chloride
(1.44 g, 2.00 mmol) is added, and the resulting heterogeneous
mixture is heated at 80 °C for 18 h. The reaction mixture is
cooled to room temperature, filtered through a Celite pad, and
washed with EtOAc. The filtrate is washed with water, and
the layers are separated. The aqueous layer is extracted twice
with EtOAc, and the combined organic layers are washed with
water and saturated NaCl solution. The organic layer is dried
over MgSO4, filtered, and concentrated to give crude material
which is purified by column chromatography (2% EtOAc/
hexanes to 5% EtOAc/hexanes) to yield 2-methoxy-7-methyl-
naphthalene (5.34 g, 31.0 mmol) as a solid: 1H NMR (CDCl3)
δ 7.69 (m, 2H), 7.52 (s, 1H), 7.19 (d, 1H), 7.10 (m, 2H), 3.93 (s,
3H), 2.50 (s, 3H).
A suspension of 2-methoxy-7-methylnaphthalene (5.30 g,
30.8 mmol) in 90 mL of 48% aqueous HBr is heated at reflux
for a period of 2 h. The resulting mixture is allowed to cool to
room temperature, diluted with water, and partially neutral-
ized with saturated NaHCO3 solution. The aqueous mixture
is extracted with EtOAc twice, and the combined organic layers
are washed with water, saturated NaHCO3 solution, and
saturated NaCl solution. The organic phase is dried over
MgSO4, filtered, and concentrated to provide crude material
which is purified by column chromatography (5% EtOAc/
hexanes to 20% EtOAc/hexanes) to afford 7-methyl-2-naphthol
(3.05 g, 19.3 mmol) as a solid: 1H NMR (CDCl3) δ 7.69 (m,
2H), 7.47 (s, 1H), 7.18 (m, 1H), 7.03 (m, 2H), 5.01 (m, 1H),
2.50 (s, 3H).
Gen er a l P r oced u r e for th e Syn th esis of Ar ylsu lfon yl
Ch lor id es fr om Ar yl Br om id es a n d Ar ylsta n n a n es. 2′-
Meth oxybip h en yl-4-su lfon yl Ch lor id e. To a solution of
2-bromoanisole (3.5 g, 18.7 mmol) in 40 mL of THF at -78 °C
is added n-butyllithium (11.7 mL of a 1.6 M solution in THF,
18.7 mmol). The solution is stirred for 15 min after which ZnCl2
(20 mL of a 1 M solution in Et2O, 20 mmol) is added. The

3566 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ewing et al.
7-Methyl-2-naphthol (3.05 g, 19.3 mmol) is converted to
7-methyl-2-(trifluoromethylsulfonyl)naphthalene using Tf2O
and DMAP as described above. The crude product is purified
by column chromatography (2% EtOAc/hexanes to 10% EtOAc/
hexanes) to give an oil (4.74 g, 16.3 mmol): 1H NMR (CDCl3)
δ 7.89 (d, 1H), 7.80 (d, 1H), 7.69 (m, 2H), 7.40 (m, 1H), 7.30
(m, 1H), 2.59 (s, 3H).
2-carbonitrile (14 g, 69 mmol) as a white solid: 1H NMR
(CDCl3) δ 7.62 (s, 1H), 7.49 (s, 1H), 4.42 (s, 2H).
5-(Br om om eth yl)th ioph en e-2-car bon itr ile. Prepared from
5-bromothiophene-2-carboxaldehyde: 1H NMR (CDCl3) δ 7.49
(d, 1H), 7.09 (d, 1H), 4.66 (s, 2H).
5-(Br om om eth yl)th ioph en e-3-car bon itr ile. Prepared from
4-bromothiophene-2-carboxaldehyde: 1H NMR (CDCl3) δ 7.91
(d, 1H), 7.27 (d, 1H), 4.65 (s, 2H).
7-Methyl-2-(trifluoromethylsulfonyl)naphthalene (1.50 g,
5.17 mmol) is dissolved in 30 mL of p-dioxane and treated with
lithium chloride (0.66 g, 15.5 mmol) and hexamethylditin (1.86
g, 5.68 mmol). Bis(triphenylphosphine)palladium(II) chloride
(0.30 g, 0.26 mmol) is added, and the resulting heterogeneous
mixture is heated at reflux for 1 h. The reaction mixture is
cooled to room temperature, diluted with 10% NH4OH solution
and CH2Cl2, and stirred for 45 min. The layers are separated,
and the aqueous layer is extracted twice with CH2Cl2. The
combined organic layers are washed with saturated NaCl
solution. The organic layer is dried over MgSO4, filtered, and
concentrated to give crude material which is purified by
column chromatography (2% EtOAc/hexanes to 5% EtOAc/
hexanes) to yield 7-methyl-2-(trimethylstannyl)naphthalene
(0.60 g, 1.97 mmol) as an oil: 1H NMR (CDCl3) δ 7.90 (s, 1H),
7.75 (d, 1H), 7.70 (d, 1H), 7.60 (s, 1H), 7.51 (d, 1H), 7.30 (d,
1H), 2.54 (s, 3H), 0.34 (m, 9H).
2-Cya n o-4-(br om om eth yl)p yr id in e. A solution of 2-cy-
ano-4-[{(tert-butyldimethylsilyl)oxy}methyl]pyridine25 (10.1 g,
40.5 mmol) in 200 mL of anhydrous MeOH is stirred over 12
g of Dowex-50W-H+ ion-exchange resin (prewashed with
MeOH) for a period of 18 h. After this time, the mixture is
filtered and washed with MeOH twice. The combined filtrates
are concentrated in vacuo. The crude residue is purified by
column chromatography (50% EtOAc/hexanes) to afford 2-cy-
ano-4-(hydroxymethyl)pyridine (4.82 g, 35.9 mmol) as an oil:
1H NMR (CDCl3) δ 8.70 (m, 1H), 7.75 (s, 1H), 7.55 (d, 1H),
4.87 (d, 2H), 2.31 (bs, 1H).
Bromine (6.88 g, 43.1 mmol) is added dropwise to a solution
of triphenylphosphine (11.3 g, 43.1 mmol) in 280 mL of CH2-
Cl2 at 0 °C. The mixture is stirred for 30 min at 0 °C. At this
time, 2-cyano-4-(hydroxymethyl)pyridine (4.82 g, 35.9 mmol)
is added, and the resulting mixture is stirred for 2 h at room
temperature. The reaction mixture is diluted with CH2Cl2 and
washed with water (2×) and saturated NaCl solution. The
organic layer is dried with MgSO4, filtered, and concentrated.
The crude product is purified by column chromatography
eluting (20% EtOAc/hexanes to 30% EtOAc/hexanes) to give
the 2-cyano-4-(bromomethyl)pyridine (6.40 g, 32.5 mmol) as
an oil: 1H NMR (CDCl3) δ 8.75 (d, 1H), 7.79 (s, 1H), 7.60 (d,
1H), 4.49 (s, 2H).
4-(Br om om eth yl)fu r a n -2-ca r bon itr ile. A solution of fu-
ran-3-ylmethanol (9.68 g, 98.7 mmol) in THF (150 mL) at -78
°C is treated with n-butyllithium (65 mL of 1.6 M solution)
for 1 h followed by s-butyllithium (86 mL of 1.3 M solution)
for 4 h. A solution of iodine (29 g, 114 mmol) in THF (250 mL)
is added, and the solution is slowly warmed to room temper-
ature. After stirring overnight, the reaction mixture is diluted
with Et2O, washed with brine, dried (MgSO4), and concen-
trated. The crude residue is purified by column chromatogra-
phy (30% EtOAc/hexanes) to give (5-iodofuran-3-yl)methanol
as a dark red oil (13.7 g, 61.2 mmol) contaminated with furan-
3-ylmethanol.
7-Methyl-2-(trimethylstannyl)naphthalene is converted to
7-methylnaphthalene-2-sulfonyl chloride as described above.
The crude product is purified by column chromatography (10%
EtOAc/hexanes to 20% EtOAc/hexanes) to give a solid: 1H
NMR (CDCl3) δ 8.51 (s, 1H), 8.01 (d, 1H), 7.92 dd, 1H), 7.89
(d, 1H), 7.80 (s, 1H), 7.58 (d, 1H), 2.58 (s, 3H).
Gen er a l P r oced u r es for th e Syn th esis of Heter oa r yl
Nitr iles (in ter m ed ia tes B). 4-(Br om om eth yl)th iop h en e-
2-ca r bon itr ile. To a solution of thiophene-3-carboxaldehyde
(36 g, 321 mmol) in 80 mL of CCl4 and 60 mL of H2O is added
2.5 mL of concentrated H2SO4 in 160 mL of acetic acid. To the
resulting solution are added HIO3 (14 g, 80 mmol) and I2 (38
g, 150 mmol). The solution is refluxed for 6 h. After this time,
the reaction is cooled to ambient temperature, and 200 mL of
CHCl3 is added. The layers are separated, and the aqueous
layer is extracted with CHCl3. The organic layers are combined
and washed with 0.5 M Na2S2O3, saturated NaHCO3, and
saturated NaCl. The organic layer is dried over MgSO4,
filtered, and concentrated. The crude product is purified by
column chromatography (2% EtOAc/hexanes to 5% EtOAc/
hexanes) to afford 5-iodothiophene-3-carboxaldehyde (20 g, 84
mmol) as a white solid: 1H NMR (CDCl3) δ 9.78 (s, 1H), 8.10
(s, 1H), 7.69 (s, 1H).
The crude material is converted to 4-(bromomethyl)furan-
2-carbonitrile as described above: 1H NMR (CDCl3) δ 7.59 (s,
1H), 7.12 (s, 1H), 4.30 (s, 2H); EI MS M+ ) 185/187.
To a solution of 5-iodothiophene-3-carboxaldehyde (42 g, 176
mmol) in 800 mL of THF is added NaBH4 (7 g, 185 mmol).
After 1 h, the reaction is quenched by the addition of 100 mL
of saturated NH4Cl. The resulting solution is diluted with 1 L
of EtOAc, and the layers are separated. The organic layer is
washed with H2O and saturated NaCl. The organic layer is
dried over MgSO4, filtered, and concentrated. (5-Iodothiophene-
3-yl)methanol (42 g, 176 mmol) is obtained as an oil: 1H NMR
(CDCl3) δ 7.18 (s, 2H), 4.63 (s, 2H), 1.92 (bs, 1H).
To a solution of (5-iodothiophene-3-yl)methanol (42 g, 176
mmol) in 150 mL of DMF are added zinc cyanide (Zn(CN)2)
(12.4 g, 106 mmol) and Pd(PPh3)4 (8.13 g, 7.04 mmol). The
solution is heated to 80 °C. After 6 h, the solution is diluted
with 3 L of EtOAc. The resulting solution is washed with 1 N
NH4OH, H2O, and saturated NaCl. The organic layer is dried
over MgSO4, filtered, and concentrated. The crude product is
purified by column chromatography (20% EtOAc/hexanes to
30% EtOAc/hexanes) to give 4-(hydroxymethyl)thiophene-2-
carbonitrile (10 g, 72 mmol) as a clear oil: 1H NMR (CDCl3) δ
7.59 (s, 1H), 7.46 (s, 1H), 4.67 (s, 2H), 2.42 (bs, 1H).
5-(Br om om eth yl)fu r a n -2-ca r bon itr ile. 5-(Hydroxymeth-
yl)furan-2-carbonitrile26 (1.12 g, 9.1 mmol) is dissolved in THF
(75 mL), treated with triphenylphosphine (2.9 g, 11.06 mmol)
and carbon tetrabromide (3.78 g, 11.4 mmol), and stirred at
room temperature for 18 h. Standard workup yields 5-(bro-
momethyl)furan-2-carbonitrile (1.45 g, 7.8 mmol) as an oil: 1H
NMR (CDCl3) δ 7.04 (d, 2H), 6.50 (d, 1H), 4.43 (s, 2H).
Gen er a l P r oced u r e for N-Alk yla tion of Boc-P r otected
3-Am in o La cta m Rin g System s (in ter m ed ia tes D). [1-(3-
Cyan oben zyl)-2-oxopyr r olidin -3-(S)-yl]car bam ic Acid ter t-
Bu tyl Ester (D, n ) 1). To a solution of Boc-3-(S)-aminopy-
rrolidin-2-one (C, n ) 1) (9 g, 45 mmol) and R-bromo-m-toluyl
nitrile (9.3 g, 47 mmol) in 225 mL of THF/DMF (10:1) at 0 °C
is added a 60% mineral oil dispersion of sodium hydride (1.8
g, 46 mmol). The reaction mixture is stirred at 0 °C for 0.5 h
and then allowed to warm to ambient temperature. After 3 h,
the reaction mixture is quenched by the addition of saturated
NH4Cl and diluted with EtOAc. The layers are separated, and
the organic layer is washed with 1 N HCl, H2O, and saturated
NaCl. The organic layer is dried over MgSO4, filtered, and
concentrated. The crude product is purified by column chro-
matography (20% EtOAc/hexanes to 40% EtOAc/hexanes) to
afford [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl]carbamic acid
tert-butyl ester (12.7 g, 40 mmol) as a white solid: 1H NMR
(CDCl3) δ 7.55 (m, 4H), 5.18 (bs, 1H), 4.47 (AB, 2H), 4.18 (dd,
1H), 3.21 (m, 2H), 2.60 (m, 1H), 1.42 (s, 9H).
To a solution of 4-(hydroxymethyl)thiophene-2-carbonitrile
(10 g, 72 mmol) in 360 mL of THF are added triphenylphos-
phine (18.3 g, 76 mmol) and CBr4 (25 g, 76 mmol). After 3 h,
the solution is filtered and concentrated. The crude product
is purified by column chromatography (5% EtOAc/hexanes to
10% EtOAc/hexanes) to afford the 4-(bromomethyl)thiophene-

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3567
[1-(3-Cyan oben zyl)-2-oxoazetidin -3-(S)-yl]car bam ic Acid
ter t-Bu tyl Ester (D, n ) 0). Prepared from Boc-3-(S)-
aminoazetidin-2-one (C, n ) 0): 1H NMR (CDCl3) δ 7.59 (m,
2H), 7.41 (m, 2H), 5.18 (bs, 1H), 4.72 (m, 1H), 4.41 (AB, 2H),
3.41 (m, 1H), 3.23 (m, 1H), 1.41 (s, 9H).
1H), 7.94 (m, 4H), 7.51 (m, 6H), 6.10 (s, 1H), 4.47 (AB, 2H),
3.56 (m, 1H), 3.20 (m, 2H), 2.52 (m, 1H), 1.83 (m, 3H).
Na p h t h a len e-2-su lfon ic Acid [1-(3-Cya n ob en zyl)-2-
oxoa zep a n -3-(S)-yl]a m id e (E, n ) 3). Prepared from [1-(3-
cyanobenzyl)-2-oxoazepan-3-(S)-yl]carbamic acid tert-butyl es-
ter (D, n ) 3): 1H NMR (CDCl3) δ 8.44 (s, 1H), 7.95 (m, 3H),
7.83 (d, 1H), 7.64 (m, 2H), 7.46 (d, 1H), 7.29 (s, 1H), 7.04 (m,
1H), 6.93 (d, 1H), 6.40 (d, 1H), 4.78 (AB, 1H), 4.10 (AB, 1H),
4.03 (m, 1H), 3.18 (dd, 1H), 3.00 (dd, 1H), 2.18 (m, 1H), 1.93
(m, 1H), 1.67 (m, 3H), 1.20 (m, 1H).
[1-(3-Cyan oben zyl)-2-oxoazepan -3-(S)-yl]car bam ic Acid
ter t-Bu tyl Ester . (D, n ) 3). Boc-3-(S)-amino-ꢀ-caprolactam
(C, n ) 3) (1.07 g, 4.7 mmol) is dissolved in 45 mL of THF
and cooled to 0 °C. To the solution is added a 1 M solution of
lithium hexamethyldisilyl azide (4.7 mL, 4.7 mmol) in THF.
The mixture is stirred for 30 min at 0 °C. To the resulting
solution is added R-bromo-m-toluyl nitrile (0.9 g, 4.7 mmol).
The reaction mixture is stirred for 4 h. The solution is diluted
with 100 mL of EtOAc and washed with 1 N HCl, 10% Na2-
CO3, and saturated NaCl. The organic layer is dried over
MgSO4, filtered, and concentrated. The residue is purified by
column chromatography (20% EtOAc/CH2Cl2) to give [1-(3-
cyanobenzyl)-2-oxoazepan-3-(S)-yl]carbamic acid tert-butyl es-
ter (1.05 g, 3.1 mmol) as a solid: 1H NMR (CDCl3) δ 7.45 (m,
4H), 5.95 (d, 1H), 4.85 (AB, 1H), 4.35 (AB, 1H), 4.40 (m, 1H),
3.48 (m, 1H), 3.15 (dd, 1H), 2.05 (m, 1H), 1.90 (m, 1H), 1.70
(m, 2H), 1.49 (m, 1H), 1.45 (s, 9H), 1.20 (m, 1H).
Gen er a l P r oced u r es for th e N-Alk yla tion of 3-Su lfon a -
m id o La cta m Rin g System s (in ter m ed ia tes F ). 7-Meth -
oxyn a p h th a len e-2-su lfon ic Acid [1-(3-Cya n oben zyl)-2-
oxop yr r olid in -3-(S)-yl]m eth yla m id e (F , n ) 1; N-m eth yl
su lfon a m id e p r ecu r sor to com p ou n d 28). 7-Methoxynaph-
thalene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-
(S)-yl]amide (0.34 g, 0.76 mmol) is dissolved in 7 mL of THF
and cooled to 0 °C. Sodium hydride (30 mg of a 60% dispersion
in mineral oil, 0.76 mmol) is added, and the solution is stirred
for 20 min. To the mixture is added methyl iodide (0.32 g, 2.27
mmol). The cooling bath is removed, and the solution is stirred
at room temperature for 2 h. The solution is poured into a
separatory funnel and diluted with 100 mL of EtOAc. The
organic layer is washed with 1 N HCl, dried over MgSO4, and
concentrated. The residue is purified by column chromatog-
raphy (10% EtOAc/CH2Cl2) to give 7-methoxynaphthalene-2-
sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl]-
methylamide (0.25 g, 0.54 mmol) as a white foam: 1H NMR
(CDCl3) δ 8.44 (d, 1H), 7.92 (d, 1H), 7.82 (m, 2H), 7.61 (m,
1H), 7.47 (m, 3H), 7.28 (m, 2H), 4.97 (m, 1H), 4.53 (AB, 1H),
4.39 (AB, 1H), 3.96 (s, 3H), 3.13 (m, 2H), 2.83 (s, 3H), 2.37 (m,
1H), 2.06 (m, 1H).
7-Meth oxyn aph th alen e-2-su lfon ic Acid [1-(3-Cyan oben -
zyl)-2-oxop yr r olid in -3-(S )-yl](t h iop h e n e -3-ylm e t h yl)-
a m id e (F , n ) 1; p r ecu r sor to com p ou n d 32). To a solution
of 7-methoxynaphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-
2-oxopyrrolidin-3-(S)-yl]amide (0.19 g, 0.44 mmol) in 20 mL
of acetone are added K2CO3 (0.12 g, 0.88 mmol) and thiophen-
3-ylmethyl bromide27 (0.30 g, 1.68 mmol). The resulting
mixture is stirred for 48 h, then diluted with CH2Cl2, and
washed with saturated NaHCO3, H2O, and saturated NaCl.
The organic layer is dried over MgSO4, filtered, and concen-
trated. The crude product is triturated with hexane/ether to
give 7-methoxynaphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-
2-oxopyrrolidin-3-(S)-yl](thiophene-3-ylmethyl)amide and used
without further purification: 1H NMR (CDCl3) δ 8.45 (s, 1H),
7.94 (AB, 2H), 7.80 (d, 1H), 7.06 (d, 1H), 7.40-7.65 (m, 2H),
7.18-7.32 (m, 4H), 7.05-7.13 (m, 2H), 4.4-4.6 (m, 3H), 4.38
(AB, 2H), 3.93 (s, 3H), 3.07 (m, 2H), 2.27 (m, 1H), 1.99 (m,
1H); FAB MS [M + H]+ ) 532.
Gen er a l P r oced u r es for th e Syn th esis of 3-Su lfon a -
m id o La cta m Rin g System s (in ter m ed ia tes E). Na p h -
th a len e-2-su lfon ic Acid [1-(3-Cya n oben zyl)-2-oxop yr r o-
lid in -3-(S)-yl]a m id e (E, n ) 1). To a solution of [1-(3-
cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl]carbamic acid tert-butyl
ester (D, n ) 1) (9.1 g, 29 mmol) in 150 mL of EtOAc at 0 °C
is bubbled HCl gas for 10 min. After this time, the solution is
stirred at room temperature for 4 h. The solution is then
concentrated in vacuo and dried to give 3-(3-(S)-amino-2-
oxopyrrolidin-1-ylmethyl)benzonitrile hydrochloride (7.3 g, 29
mmol) as a white solid: 1H NMR (DMSO-d6) δ 8.71 (bs, 3H),
7.85 (m, 2H), 7.70 (m, 2H), 4.58 (AB, 2H), 4.13 (m, 1H), 3.32
(m, 2H), 2.44 (m, 1H), 2.18 (m, 1H).
3-(3-(S)-Amino-2-oxopyrrolidin-1-ylmethyl)benzonitrile hy-
drochloride (0.4 g, 1.6 mmol) is suspended in 10 mL of CH2-
Cl2. To the solution is added triethylamine (0.49 g, 4.8 mmol)
followed by 2-naphthalenesulfonyl chloride (0.4 g, 1.8 mmol).
After stirring for 2 h, the solution is diluted with CH2Cl2. The
solution is washed with 1 N HCl, 10% Na2CO3, and saturated
NaCl. The organic layer is dried over MgSO4, filtered, and
concentrated. The residue is triturated with Et2O to give
naphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-
3-(S)-yl]amide (0.46 g, 1.13 mmol) as a solid: 1H NMR (DMSO-
d6) δ 8.56 (d, 1H), 8.32 (d, 1H), 8.20 (m, 3H), 8.09 (m, 1H),
7.93 (d, 1H), 7.74 (m, 3H), 7.48 (d, 2H), 4.38 (AB, 2H), 4.17
(m, 1H), 3.05 (m, 2H), 2.02 (m, 1H), 1.57 (m, 1H).
Na p h th a len e-2-su lfon ic Acid [1-(3-Cya n oben zyl)-2-ox-
op yr r olid in -4-(S)-yl]a m id e (su lfon a m id e p r ecu r sor to
com p ou n d 3). Prepared from [1-(3-cyanobenzyl)-2-oxopyrro-
lidin-4-(S)-yl]carbamic acid tert-butyl ester: 1H NMR (CDCl3)
δ 8.47 (s, 1H), 7.95 (m, 4H), 7.68 (m, 2H), 7.46 (m, 4H), 5.00
(m, 1H), 4.53 (d, 1H), 4.46 (d, 1H), 4.36 (d, 1H), 3.68 (dd, 1H),
3.36 (dd, 1H), 3.07 (dd, 1H), 2.58 (dd, 1H).
7-Meth oxyn aph th alen e-2-su lfon ic Acid [1-(3-Cyan oben -
zyl)-2-oxop yr r olid in -3-(S )-yl](N -t er t -b u t yloxyca r b on -
ylp yr a zol-3-ylm et h yl)a m id e (F , n ) 1; p r ecu r sor t o
com p ou n d 35). 3-Methylpyrazole (2.04 g, 2.49 mmol) is
dissolved in 25 mL acetonitrile under nitrogen, cooled in a ice
bath, and treated with BOC anhydride (6.5 g, 2.98 mmol)
followed by DMAP (0.303 g, 2.48 mmol). The reaction is
warmed to room temperature over about 2 h and diluted with
ethyl acetate. The organic solution is washed with 1 N HCl,
saturated NaHCO3, and saturated NaCl solution, dried over
Na2SO4, filtered, and concentrated to obtain N-tert-butyloxy-
Na p h t h a len e-2-su lfon ic Acid [1-(3-Cya n ob en zyl)-2-
oxoa zetid in -3-(S)-yl]a m id e (E, n ) 0). Prepared from [1-(3-
cyanobenzyl)-2-oxoazetidin-3-(S)-yl]carbamic acid tert-butyl
ester (D, n ) 0): 1H NMR (CDCl3) δ 8.42 (s, 1H), 7.95 (m,
2H), 7.90 (d, 1H), 7.83 (d, 1H), 7.60 (m, 3H), 7.46 (m, 3H), 5.81
(d, 1H), 4.57 (m, 1H), 4.46 (AB, 2H), 3.41 (dd, 1H), 3.17 (dd,
1H).
carbonyl-3-methylpyrazole (2.5 g, 13.7 mmol): EI MS [M]+
182.
)
A portion of this material (1 g, 5.8 mmol) is dissolved in
CCl4 (20 mL), treated with N-bromosuccinimide (1.47 g, 8.26
mmol) and benzoyl peroxide (0.2 g, 0.83 mmol), and heated to
reflux. After 4 h, the solution is diluted with EtOAc washed
with saturated NaHCO3, dried over Na2SO4, and concentrated.
The residue is purified by column chromatography (10%
EtOAc/hexanes) to yield N-tert-butyloxycarbonylpyrazol-3-
ylmethyl bromide (0.74 g, 2.85 mmol): EI MS [M]+ ) 259/261.
Na p h th a len e-2-su lfon ic Acid [1-(3-Cya n oben zyl)-2-ox-
op ip er id in -3-(S)-yl]a m id e (E, n ) 2). [1-(3-Cyanobenzyl)-
2-oxopiperidin-3-(S)-yl]carbamic acid tert-butyl ester (D, n )
2) (0.25 g, 0.76 mmol) is dissolved in 5 mL of CH2Cl2. To the
solution is added 1 mL of trifluoroacetic acid. The mixture is
stirred for 3 h at room temperature and then concentrated.
The residue is reconcentrated from toluene to give 3-(3-amino-
2-oxopiperidin-1-ylmethyl)benzonitrile trifluoroacetate (0.23 g,
0.76 mmol) as a solid. The crude product is then sulfonylated
as above to give naphthalene-2-sulfonic acid [1-(3-cyanoben-
zyl)-2-oxopiperidin-3-(S)-yl]amide: 1H NMR (CDCl3) δ 8.49 (s,
7-Meth oxyn a ph th a len e-2-su lfon ic a cid [1-(3-cya n oben -
zyl)-2-oxop yr r olid in -3-(S )-yl](N -t er t -b u t yloxyca r b on -
ylp yr a zol-3-ylm eth yl)a m id e is p r ep a r ed a s d escr ibed

3568 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ewing et al.
a bove u sin g N-ter t-bu tyloxyca r bon ylp yr a zol-3-ylm eth yl
br om id e: 1H NMR (CDCl3) δ 8.50 (s, 1H), 7.90-8.02 (m, 3H),
7.79 (d, 1H), 7.46-1.60 (m, 4H), 7.30 (dd, 1H), 7.27 (s, 1H),
6.50 (d, 1H), 4.62 (t, 1H), 4.47 (AB, 2H), 4.45 (AB, 2H), 3.94
(s, 3H), 3.24 (m, 1H), 3.14 (m, 1H), 2.26 (m, 2H), 1.63 (s, 9H);
FAB MS [M + H]+ ) 616.
2-[{1-(3-Cyan oben zyl)-2-oxopyr r olidin -3-(S)-yl}-7-m eth -
oxyn a p h th a len -2-ylsu lfon yla m in o]-N-a cetic Acid (F , n )
1; p r ecu r sor to com p ou n d 36). Prepared from 2-[{1-(3-
cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-7-methoxynaphthalen-
2-ylsulfonylamino]-N-acetic acid tert-butyl ester using tert-
butyl bromoacetate: 1H NMR (CDCl3) δ 8.41 (s, 2H), 7.81 (m,
3H), 7.50 (m, 1H), 7.44 (m, 3H), 7.22 (m, 2H), 4.61 (t, 1H),
4.42 (AB, 2H), 3.90 (s, 3H), 3.74 (AB, 1H), 3.20 (m, 2H), 2.58
(m, 1H), 2.41 (m, 1H), 1.42 (s, 9H).
2-[{1-(3-Cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-7-methoxy-
naphthalen-2-ylsulfonylamino]-N-acetic acid tert-butyl ester is
dissolved in 25 mL of a 5:1 mixture of CH2Cl2/trifluoroacetic
acid. After 3 h, the solution is concentrated in vacuo to give
2-[{1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-7-methoxynaph-
thalen-2-ylsulfonylamino]-N-acetic acid as a white foam: 1H
NMR (CDCl3) δ 9.45 (bs, 1H), 8.41 (s, 2H), 7.91 (d, 1H), 7.80
(d, 1H), 7.71 (m, 1H), 7.62 (m, 1H), 7.59 (m, 3H), 7.20 (m, 1H),
4.81 (t, 1H), 4.50 (AB, 2H), 3.90 (s, 3H), 3.89 (AB, 2H), 3.28
(m, 2H), 2.41 (m, 1H), 2.16 (m, 1H).
3-[{1-(3-Cyan oben zyl)-2-oxopyr r olidin -3-(S)-yl}-7-m eth -
oxyn a p h th a len -2-ylsu lfon yla m in o]p r op ion a m id e (F , n )
1; p r ecu r sor to com p ou n d 38). To a solution of 7-methox-
ynaphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrroli-
din-3-(S)-yl]amide (0.82 g, 1.9 mmol) in 10 mL of DMF are
added K2CO3 (0.52 g, 3.8 mmol) and tert-butyl acrylate (0.48
g, 3.8 mmol). The solution is heated at 60 °C and stirred for
24 h. After this time, the solution is cooled to room temperature
and diluted with EtOAc. The solution is washed with 1 N HCl
and saturated NaCl. The organic layer is dried over MgSO4,
filtered, and concentrated to afford 3-[{1-(3-cyanobenzyl)-2-
oxopyrrolidin-3-(S)-yl}-7-methoxynaphthalen-2-ylsulfonylamino]-
N-propionic acid tert-butyl ester (0.64 g, 1.1 mmol) as a white
foam: 1H NMR (CDCl3) δ 8.41 (s, 1H), 7.89 (m, 2H), 7.80 (m,
1H), 7.56 (m, 4H), 7.23 (m, 2H), 4.71 (t, 1H), 4.50 (AB, 2H),
3.92 (s, 3H), 3.63 (m, 4H), 3.37 (m, 1H), 3.36 (m, 4H), 2.78 (m,
2H), 2.41 (m, 1H), 2.20 (m, 1H) 1.42 (s, 9H).
3-[{1-(3-Cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-7-methoxy-
naphthalen-2-ylsulfonylamino]-N-propionic acid tert-butyl es-
ter is dissolved in 25 mL of a 5:1 mixture of CH2Cl2/
trifluoroacetic acid. After 3 h, the solution is concentrated in
vacuo to give 3-[{1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-
7-methoxynaphthalen-2-ylsulfonylamino]-N-propionic acid as
a white foam: 1H NMR (CDCl3) δ 8.41 (s, 1H), 7.89 (d, 1H),
7.80 (m, 2H), 7.56 (m, 4H), 7.22 (m, 2H), 4.74 (t, 1H), 4.50 (AB,
2H), 3.92 (s, 3H), 3.56 (m, 1H), 3.37 (m, 1H), 3.22 (m, 2H),
2.89 (m, 2H), 2.39 (m, 2H), 2.10 (m, 1H).
To a solution of 3-[{1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-
yl}-7-methoxynaphthalen-2-ylsulfonylamino]-N-propionic acid
(0.51 g, 1.0 mmol) and Et3N (0.12 g, 1.2 mmol) in 10 mL of
THF at -20 °C is added ethyl chloroformate (0.11 g, 1.0 mmol).
The solution is stirred for 15 min. After this time, 14.8 N
ammonium hydroxide (0.1 mL, 1.5 mmol) is added. The
solution is allowed to warm to room temperature, and the
reaction is stirred for 16 h. After this time, the solution is
diluted with EtOAc. The organic layer is washed with 1 N HCl,
10% Na2CO3, and saturated NaCl. The organic layer is dried
over MgSO4, filtered, and concentrated to afford 3-[{1-(3-
cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}-7-methoxynaphthalen-
2-ylsulfonylamino]propionamide (0.39 g, 0.77 mmol) as a white
foam: 1H NMR (CDCl3) δ 8.41 (s, 1H), 7.85 (m, 2H), 7.50 (m,
4H), 7.26 (m, 3H), 5.94 (bs, 1H), 5.34 (bs, 1H), 4.75 (t, 1H),
4.45 (AB, 2H), 3.92 (s, 3H), 3.51 (m, 1H), 3.40 (m, 1H), 3.19
(m, 2H), 2.78 (m, 2H), 2.32 (m, 1H), 2.09 (m, 1H).
[1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl]amide (0.46 g, 1.13
mmol) is dissolved in 50 mL of ethanol. The solution is cooled
to 0 °C, and HCl gas is bubbled through the solution for 10
min. The ice bath is removed, and the reaction mixture is
stirred at room temperature for 6 h. After this time, the
solution is concentrated. The residue is dissolved in 50 mL of
methanol. The solution is cooled to 0 °C, and ammonia gas is
bubbled through the solution for 10 min. The reaction mixture
is stirred for 24 h. After this time, the solution is concentrated.
The crude residue is purified by RP-HPLC eluting in a gradient
of 10% CH3CN/H2O (0.1% TFA) to 60% CH3CN/H2O (0.1%
TFA). The appropriate fractions are lyophilized to give naph-
thalene-2-sulfonic acid {1-[3-(aminoiminomethyl)benzyl]-2-ox-
opyrrolidin-3-(S)-yl}amide trifluoroacetate (4) (0.33 g, 0.61
mmol) as an amorphous solid: 1H NMR (DMSO-d6) δ 9.30 (bs,
2H), 9.14 (bs, 2H), 8.50 (s, 1H), 8.28 (d, 1H), 8.13 (m, 3H), 8.04
(d, 1H), 7.91 (d, 1H), 7.80 (m, 3H), 7.62 (d, 2H), 4.42 (AB, 2H),
4.18 (m, 1H), 3.10 (m, 2H), 2.00 (m, 1H), 1.57 (m, 1H); FAB
MS [M + H]+ ) 423. Anal. (C22H22N4O3S‚TFA‚1.5H2O) C, H,
N.
Na p h th a len e-1-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr iflu or oa c-
eta te (9). Anal. (C22H22N4O3S‚TFA‚H2O) C, H, N.
7-Meth yln a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (10). The imidate intermediate is formed in a
2:1 EtOH/CH2Cl2 solvent mixture. Anal. (C23H24N4O3S‚TFA‚
1.7H2O) C, H, N.
7-Eth yln a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (11). Anal. (C24H26N4O3S‚TFA‚1.6H2O) C, H,
N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e
1
Tr iflu or oa ceta te (12). H NMR (DMSO-d6) δ 9.41 (bs, 2H),
9.29 (bs, 2H), 8.33 (d, 1H), 8.19 (d, 1H), 7.96 (d, 1H), 7.87 (d,
1H), 7.68 (dd, 1H), 7.64 (m, 1H), 7.50 (m, 4H), 7.27 (dd, 1H),
4.36 (AB, 2H), 4.16 (dd, 1H), 3.48 (s, 3H), 3.04 (m, 2H), 1.93
(m, 1H), 1.59 (m, 1H); FAB MS [M + H]+ ) 453. Anal.
(C23H24N4O4S‚TFA‚1.7H2O) C, H, N.
6-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e
Tr iflu or oa ceta te (13). Anal. (C23H24N4O4S‚TFA‚2.5H2O) C,
H, N.
7-Eth oxyn a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim -
in om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (14). Anal. (C24H26N4O4S‚TFA‚1.9H2O) C, H,
N.
7-Ch lor on a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (15). ESI HMRS [M + H]+ calcd for C22H21
-
ClN4O3S 457.1101, found 457.1104; RP-HPLC analysis (C18,
20-min linear gradient; elution 10-100% CH3CN/0.1% TFA
H2O; flow rate 1.0 mL/min) indicated that the product was
95.0A%.
6-Ch lor on a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (16). Anal. (C22H21ClN4O3S‚TFA‚1.35H2O) C,
H, N.
7-H yd r oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e
Tr iflu or oa ceta te (17). Prepared from 7-benzyloxynaphtha-
lene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-
yl]amide. Anal. (C22H22N4O4S‚TFA‚2.6H2O) C, H, N.
7-Am in on a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim i-
n om eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Bistr i-
flu or oacetate (18). Prepared from N-Cbz-7-aminonaphthalene-
2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl]amide.
Anal. (C22H23N5O3S‚2TFA‚0.8H2O) C, H, N.
7-(Met h yla m in o)n a p h t h a len e-2-su lfon ic Acid {1-[3-
(Am in oim in om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}-
a m id e Bist r iflu or oa cet a t e (19). Prepared from N-Cbz-7-
methylaminonaphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-
Gen er a l P r oced u r e for th e P r ep a r a tion of Heter oa r yl
Am id in es (com p ou n d s 3, 4, 6-29, 30-34, 36-42, 44-45,
a n d RP R120844). Na p h th a len e-2-su lfon ic Acid {1-[3-
(Am in oim in om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}-
a m id e Tr iflu or oa ceta te (4). Naphthalene-2-sulfonic acid

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3569
2-oxopyrrolidin-3-(S)-yl]amide. Anal. (C24H24N4O3S‚TFA‚
1.25H2O) C, H, N.
Bip h en yl-3-su lfon ic Acid {1-[3-(Am in oim in om eth yl)-
ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr iflu or oa ceta te
(20). Anal. (C24H24N4O3S‚TFA‚1.25H2O) C, H, N.
Bip h en yl-4-su lfon ic Acid {1-[3-(Am in oim in om eth yl)-
ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr iflu or oa ceta te
(21). Anal. (C24H24N4O3S‚TFA‚0.25H2O) C, H, N.
[{1-[3-Am in oim in om et h yl)b en zyl]-2-oxop yr r old in -3-
(S )-y l}(7-m e t h o x y n a p h t h a le n -2-y ls u lfo n y l)a m in o ]-
a cetic Acid Tr iflu or oa ceta te (36). Anal. (C25H26N4O6S‚TFA‚
2.0H2O) C, H, N.
3-[{1-[3-(Am in oim in om eth yl)ben zyl]-2-oxop yr r olid in -
3-(S)-yl}(7-m eth oxyn a p h th a len -2-ylsu lfon yl)a m in o]a ce-
ta m id e Tr iflu or oa ceta te (37). Anal. (C25H27N5O5S‚1.5TFA)
C, H, N.
3-[{1-[3-(Am in oim in om eth yl)ben zyl]-2-oxop yr r olid in -
3-(S)-yl}(7-m eth oxyn a p h th a len -2-ylsu lfon yl)a m in o]p r o-
p ion a m id e Tr iflu or oa ceta te (38). Prepared from 3-[{1-(3-
cyanobenzyl)-2-oxopyrrolidin-3-(S)-yl}(7-methoxynaphthalen-
2-ylsulfonyl)amino]propionamide. Anal. (C26H29N5O5S‚TFA‚
2.25H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[4-(Am i-
n oim in om eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e
Tr iflu or oa ceta te (39). Anal. (C23H24N4O4S‚TFA‚1.2H2O) C,
H, N.
3′-Met h ylb ip h en yl-4-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (22). Anal. (C25H26N4O3S‚TFA‚2.0H2O) C, H,
N.
3′-Meth oxybip h en yl-4-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (23). Anal. (C25H26N4O4S‚TFA‚H2O) C, H, N.
2′-Meth oxybip h en yl-4-su lfon ic Acid {1-[3-(Am in oim i-
n om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr i-
flu or oa ceta te (24). Anal. (C25H26N4O4S‚2.0TFA‚0.5NH4Cl) C,
H, N.
Ben zylb en zen e-4-su lfon ic Acid {1-[3-(Am in oim in o-
m eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr iflu o-
r oa ceta te (25). Anal. (C25H26N4O3S‚TFA‚1.75H2O) C, H, N.
P h en oxyben zen e-4-su lfon ic Acid {1-[3-(Am in oim in o-
m eth yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}a m id e Tr iflu o-
r oa ceta te (26). Anal. (C24H24N4O4S‚TFA‚0.5H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n o i m i n o m e t h y l)b e n z y l]-2-o x o p y r r o li d i n -3-(R )-y l}-
am ide Tr iflu or oacetate (27). Prepared from 7-methoxynaph-
thalene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrrolidin-3-
(R)-yl]amide which is derived from [1-(3-cyanobenzyl)-2-
oxopyrrolidin-3-(R)-yl]carbamic acid tert-butyl ester according
to the above procedures. The [1-(3-cyanobenzyl)-2-oxopyrroli-
din-3-(R)-yl]carbamic acid tert-butyl ester is obtained from Boc-
D-Asp(OH)-OBn in a manner analogous to procedure for the
preparation of [1-(3-cyanobenzyl)-2-oxopyrrolidin-4-(S)-yl]car-
bamic acid tert-butyl ester. Spectroscopic data is identical to
that reported for compound 12. Anal. (C23H24N4O4S‚TFA‚H2O)
C, H, N.
4-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxopyr r olidin -1-ylm eth yl]th ioph en e-2-car boxam idin e Tr i-
flu or oa ceta te (40). Anal. (C21H22N4O4S2‚2.5TFA‚H2O) C, H,
N.
5-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxopyr r olidin -1-ylm eth yl]th ioph en e-2-car boxam idin e Tr i-
flu or oa ceta te (41). ESI HMRS [M +H]+ calcd for C21H22N4O4S2
459.1160, found 459.1174; RP-HPLC analysis (C18, 20-min
linear gradient; elution 10-100% CH3CN/0.1% TFA H2O; flow
rate 1.0 mL/min) indicated that the product was >95A%.
5-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxopyr r olidin -1-ylm eth yl]th ioph en e-3-car boxam idin e Tr i-
flu or oa ceta te (42). Anal. (C21H22N4O4S‚1.5TFA‚1.0H2O) C,
H, N.
4-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxop yr r olid in -1-ylm et h yl]fu r a n -2-ca r b oxa m id in e Tr i-
flu or oa ceta te (44). Anal. (C21H22N4O5S‚TFA‚0.35H2O) C, H,
N.
5-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxop yr r olid in -1-ylm et h yl]fu r a n -2-ca r b oxa m id in e Tr i-
flu or oa ceta te (45). Anal. (C21H22N4O5S‚TFA‚1.5H2O) C, H,
N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om et h yl)b en zyl]-2-oxop yr r olid in -3-(S)-yl}m et h -
4-{3-(S)-[(7-Met h oxyn a p h t h a len -2-ylsu lfon yl)m et h yl-
amino]-2-oxopyrrolidin-1-ylmethyl}thiophene-2-carboxami-
1
yla m id e Tr iflu or oa ceta te (28). H NMR (DMSO-d6) δ 9.28
(bs, 2H), 9.07 (bs, 2H), 8.38 (s, 1H), 8.01 (d, 1H), 7.93 (s, 1H),
7.68 (m, 2H), 7.54 (m, 4H), 7.33 (d, 1H), 4.90 (m, 1H), 4.40
(AB, 2H), 3.88 (s, 3H), 3.12 (m, 2H), 2.66 (s, 3H), 1.98 (m, 1H),
1.75 (m, 1H); FAB MS [M + H]+ ) 467. Anal. (C24H26N4O4S‚
TFA‚2.5H2O) C, H, N.
1
d in e Tr iflu or oa ceta te (RP R120844). H NMR (DMSO-d6)
δ 9.24 (bs, 2H), 8.97 (bs, 2H), 8.39 (s,1H), 8.02 (d,1H), 7.95 (d,
1H), 7.91 (s, 1H), 7.80 (s, 1H), 7.68 (dd, 1H), 7.55 (s, 1H), 7.32
(dd, 1H), 4.86 (t, 1H), 4.37 (AB, 2H), 3.87 (s, 3H), 3.46 (m, 1H),
3.14 (m, 1H), 2.46 (s, 3H), 1.95 (m, 1H), 1.74 (m, 1H); FAB
MS [M + H]+ ) 473. Anal. (C22H24N4O4S2‚TFA‚1.5H2O) C, H,
N.
Na p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxop yr r olid in -4-(S)-yl}a m id e Tr iflu or oa c-
eta te (3). 1H NMR (CD3CN) δ 10.05 (bs, 4H), 8.45 (s, 1H),
8.12 (m, 1H), 8.00 (m, 1H), 7.93 (m, 1H), 8.05 (m, 2H), 7.78
(m, 3H), 7.55 (m, 1H), 6.18 (m, 1H), 2.32 (m, 2H), 1.91 (m,
1H); FAB MS [M + H]+ ) 423. Anal. (C22H22N4O3S‚1.5TFA)
C, H, N.
Na p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxoa zetid in -3-(S)-yl}a m id e Tr iflu or oa ceta te
(6). 1H NMR (DMSO-d6) δ 9.28 (bs, 2H), 8.98 (bs, 2H), 8.84
(m, 1H), 8.47 (m, 1H), 8.12 (m, 2H), 8.02 (m, 1H), 7.83 (m,
1H), 7.65 (m, 3H), 7.581 (m, 3H), 4.75 (m, 1H), 4.28 (AB, 2H),
3.28 (m, 1H), 2.87 (m, 1H); FAB MS [M + H]+ ) 409; RP-
HPLC analysis (C18, 20-min linear gradient; elution 10-100%
CH3CN/0.1% TFA H2O; flow rate 1.0 mL/min) indicated that
the product was 98.5A%.
Na p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxop ip er id in -3-(S)-yl}a m id e Tr iflu or oa ce-
ta te (7). 1H NMR (DMSO-d6) δ 9.29 (bs, 2H), 9.19 (bs, 2H),
8.48 (s, 1H), 8.04 (m, 4H), 7.90 (d, 1H), 7.60 (m, 6H), 4.48 (s,
2H), 3.95 (m, 1H), 3.18 (s, 2H), 1.86 (m, 1H), 1.69 (m, 3H);
FAB MS [M + H]+ ) 437. Anal. (C23H24N4O3S‚TFA‚H2O) C,
H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om et h yl)b en zyl]-2-oxop yr r olid in -3-(R)-yl}m et h -
yla m id e Tr iflu or oa ceta te (29). Prepared from 7-methox-
ynaphthalene-2-sulfonic acid [1-(3-cyanobenzyl)-2-oxopyrroli-
din-3-(R)-yl]amide according to the above procedures. Spec-
troscopic data is identical to that reported for compound 28.
Anal. (C24H26N4O4S‚TFA‚2.0H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om e t h yl)b e n zyl]-2-oxop yr r olid in -3-(S )-yl}e t h -
yla m id e Tr iflu or oa ceta te (30). Anal. (C25H28N4O4S‚TFA‚
1.75H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n o i m i n o m e t h y l)b e n z y l]-2-o x o p y r r o li d i n -3-(S )-y l}-
ben zyla m id e Tr iflu or oa cet a t e (31). Anal. (C30H30N4O4S‚
TFA‚2.5H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n o i m i n o m e t h y l)b e n z y l]-2-o x o p y r r o li d i n -3-(S )-y l}-
(th iop h en e-3-ylm eth yl)a m id e Tr iflu or oa ceta te (32). Anal.
(C28H28N4O4S2‚TFA‚H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n o i m i n o m e t h y l)b e n z y l]-2-o x o p y r r o li d i n -3-(S )-y l}-
(th iop h en e-2-ylm eth yl)a m id e Tr iflu or oa ceta te (33). Anal.
(C28H28N4O4S2‚TFA‚2.0H2O) C, H, N.
7-Met h oxyn a p h t h a len e-2-su lfon ic Acid {1-[3-(Am i-
n oim in om eth yl)ben zyl]-2-oxopyr r olidin -3-(S)-yl}(pyr idin -
2-ylm eth yl)am ide Tr iflu or oacetate (34). Anal. (C29H29N5O4S‚
TFA‚0.35H2O) C, H, N.
Na p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxoa zep a n -3-(S)-yl}a m id e Tr iflu or oa ceta te

3570 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Ewing et al.
(8). 1H NMR (DMSO-d6) δ 9.22 (bs, 2H), 9.06 (bs, 2H), 8.40 (s,
1H), 8.05 (m, 3H), 7.85 (m, 2H), 7.63 (m, 2H), 7.48 (m, 1H),
7.15 (m, 1H), 7.02 (m, 1H), 4.70 (d, 1H), 4.22 (m, 1H), 4.18 (d,
1H), 3.40 (m, 1H), 3.10 (m, 1H), 1.72 (m, 2H), 1.48 (m, 3H),
1.17 (m, 1H); FAB MS [M + H]+ ) 423. Anal. (C24H26N4O3S‚
TFA‚1.25H2O) C, H, N.
amine hydrochloride:12 1H NMR (DMSO-d6) δ 9.26 (s, 2H), 9.08
(s, 2H), 8.50 (t, 1H), 8.42 (s, 1H), 8.12 (m, 3H), 8.03 (d, 1H),
7.81 (d, 1H), 7.56 (m, 4H), 7.46 (m, 2H), 4.26 (d, 2H), 3.52 (d,
2H); FAB MS [M + H]+ ) 397. Anal. (C20H20N4O3S‚TFA) C,
H, N.
Na p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]p yr r olid in -3-(S)-yl}a m id e Bistr iflu or oa ceta te
(2). Prepared from naphthalene-2-sulfonic acid [1-(3-cyanoben-
zyl)pyrrolidin-3-(S)-yl]amide which is obtained from 3-(S)-
aminopyrrolidine by selective Boc protection,28 sulfonylation
with 2-naphthalenesulfonyl chloride, Boc deprotection, and
alkylation with R-bromo-m-toluyl nitrile: 1H NMR (DMSO-
d6) δ 9.32 (bs, 4H), 8.45 (s, 1H), 8.14 (m, 2H), 8.05 (d, 1H),
7.72 (m, 8H), 4.35 (s, 2H), 3.85 (m, 1H), 3.25 (m, 4H), 1.95 (m,
2H); FAB MS [M + H]+ ) 409. Anal. (C22H24N4O2S‚2.0TFA‚
1.25H2O) C, H, N.
Refer en ces
(1) Colman, R. W.; Marder, V. J .; Salzman, E. W.; Hirsh, J . Plasma
coagulation factors. In Hemostasis and Thrombosis Basic Prin-
ciples and Clinical Practice, 3rd ed.; J . B. Lippincott: Philadel-
phia, 1994; pp 3-18.
(2) (a) Harker, L. A.; Maraganore, J . M.; Hirch, J . Novel antithrom-
botic agents. In Hemostasis and Thrombosis Basic Principles and
Clinical Practice, 3rd ed.; J . B. Lippincott: Philadelphia, 1994;
pp 1638-60. (b) Winstetter, U.; Huber, K.; Gulba, D. C. New
Antithrombotic Agents: an overview. Fibrinolysis Proteolysis
1997, 11, 85-6.
(3) Kaiser, B.; Hauptmann, J . Factor Xa inhibitors as novel anti-
thrombotic agents: facts and perspectives. Cardiovasc. Drug
Rev. 1994, 12, 225-36.
(4) Harker, L. A.; Hanson, S. R.; Kelly, A. B. Antithrombotic benefits
and hemorrhagic risks of direct thrombin antagonists. Thromb.
Haemost. 1995, 74, 464-72.
(5) Padmanabhan, K.; Padmanabhan, K. P.; Tulinsky, A.; Park, C.
H.; Bode, W.; Huber, R.; Blankenship, D. T.; Cardin, A. D.; Kisiel,
W. Structure of human Des(1-45) factor Xa at 2.2 Å resolution.
J . Mol. Biol. 1993, 232, 947-66.
(6) Brandstetter, H.; Kuhne, A.; Bode, W.; Huber, R.; von der Sall,
W.; Wirthensohn, K.; Engh, R. A. X-ray structure of active site-
inhibited clotting factor Xa. J . Biol. Chem. 1996, 271, 29988-
92.
(7) Kamata, K.; Kawamoto, H.; Honma, T.; Iwama, T.; Kim, S. H.
Structural basis for chemical inhibition of human blood coagula-
tion factorXa. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 6630-5.
(8) (a) Sturzebecher, J .; Markwardt, F.; Walsmann, P. Synthetic
inhibitors of serine proteinases XIV. Inhibition of factor Xa by
derivatives of benzamidine. Thromb. Res. 1976, 9, 637-46. (b)
Walsmann, P. Inhibition of serine proteinases by benzamidine
derivatives. Acta Biol. Med. Germ. 1977, 36, 1931-7. (c) Stur-
zebecher, J .; Sturzebecher, U.; Vieweg, H.; Wagner, G.; Haupt-
mann, J .; Markwardt, F. Synthetic inhibitors of bovine factor
Xa and thrombin comparison of their anticoagulant efficiency.
Thromb. Res. 1989, 54, 245-52.
(9) (a) US5,612,353. (b) WO9640679. (c) Floyd, D. M.; Fritz, A. W.;
Pluscec, J .; Weaver, E.; Cimarusti, C. M. Monobactams. Prepa-
ration of (S)-3-amino-2-oxoazetidine-1-sulfonic acids from L-
amino-hydroxy acids via their hydroxamic esters. J . Org. Chem.
1982, 47, 5160-7.
Alter n a te Con ver sion of Heter oa r yl Nitr iles to Het-
er oa r yl Am id in es (com p ou n d s 35, 43, 1, a n d 5). 7-Meth -
oxyn a p h th a len e-2-su lfon ic Acid {1-[3-(Am in oim in om eth -
yl)ben zyl]-2-oxop yr r olid in -3-(S)-yl}(p yr a zol-3-ylm eth yl)-
a m id e Hyd r och lor id e (35). Hydrogen sulfide gas is bubbled
for 5 min through a solution of 7-methoxy-2-naphthalene-
sulfonic acid {1-[3-cyanobenzyl]-2-oxo-3-(S)-pyrrolidin-3-yl}-
(pyrazol-3-ylmethyl)amide (0.37 g, 0.6 mmol) in 10 mL of a
10:1 mixture of pyridine/triethylamine. After the pale green
solution is stirred for a period of 18 h, the reaction mixture is
concentrated in vacuo. The residue is diluted in acetone and
concentrated to give the crude thioamide. To a solution of
thioamide in 20 mL of acetone is added methyl iodide (2 mL,
32 mmol). The resulting mixture is heated at reflux for 2 h,
allowed to cool to room temperature, and concentrated in vacuo
to provide the crude thioimidate hydroiodide. To a solution of
thioimidate hydroiodide in 20 mL of MeOH is added am-
monium acetate (0.24 g, 3.17 mmol). The resulting mixture is
heated at reflux for 3 h and then allowed to cool to room
temperature. The resulting mixture is concentrated in vacuo,
and the crude product is converted to the hydrochloride salt
with methanolic HCl then purified by RP-HPLC eluting with
a gradient of 5% CH3CN/H2O to 50% CH3CN/H2O; the ap-
propriate product fractions are lyophilized to provide the
7-methoxynaphthalene-2-sulfonic acid {1-[3-(aminoimino-
methyl)benzyl]-2-oxopyrrolidin-3-(S)-yl}(pyrazol-3-ylmethyl)amide
hydrochloride (0.045 g, 0.08 mmol) as an amorphous white
solid: 1H NMR (DMSO-d6) δ 9.35 (bs, 2H), 9.07 (bs, 2H), 8.46
(s, 1H), 8.03 (d, 1H), 7.98 (d, 1H), 7.72 (d, 1H), 7.58 (d, 1H),
7.55-7.64 (m, 5H), 7.36 (dd, 1H), 6.12 (s, 1H), 4.80 (t, 1H),
4.40 (two AB, 4H), 3.90 (s, 3H), 3.14 (m, 1H), 3.03 (m, 1H),
2.12 (m, 1H), 1.69 (m, 1H); FAB MS [M + H]+ ) 533. Anal.
(C27H28N6O4S‚HCl‚1.6H2O) C, H, N.
(10) Krysan, D. J .; Haight, A. R.; Lallaman, J . E.; Langridge, D. C.;
Menzia, J . A.; Narayanan, B. A.; Pariza, R. J .; Reno, D. S.;
Rockway, T. W.; Stuk, T. L.; Tien, J . H. An improved preparation
of (S)-(Boc)-cyclohexylalaninal. The Moffat-Swern oxidation of
amino alcohols. Org. Prep. Proc. 1993, 25, 437-43.
(11) Kim, S.; Oh, C. H.; Ko, J . S.; Ahn, K. H.; Kim, Y. J . Zinc-modified
cyanoborohydride as a selective reducing agent. J . Org. Chem.
1985, 50, 1927-32.
(12) Blazevic, N.; Kolbah, D.; Berlin, B.; Sunjic, V.; Kajfez, F.
Hexamethylenetetramine, A versatile reagent in organic syn-
thesis. Synthesis 1979, 161-76.
(13) Hamada, T.; Osamu, Y. An improved synthesis of arylsulfonyl
chlorides from aryl halides. Synthesis 1986, 852-4.
(14) Carried out modifying the procedures described in (a) U.S. Patent
5,371,091. (b) DE Patent 41,21,947.
4-[3-(S)-(7-Met h oxyn a p h t h a len -2-ylsu lfon yla m in o)-2-
oxopyr r olidin -1-ylm eth yl]p yr id in e-2-ca r boxa m idin e Tr i-
flu or oa ceta te (43). Prepared from 7-methoxynaphthalene-
2-sulfonic acid [1-(2-cyanopyridin-4-ylmethyl)-2-oxopyrrolidin-
3-(S)-yl]amide. Anal. (C22H23N5O4S‚TFA‚1.5H2O) C, H, N.
1-[3-(Am in oim in om eth yl)ben zyl]-3-(2-â-n aph th yleth yl)-
in d ole Tr iflu or oa ceta te (1). Prepared from 1-(3-cyanoben-
zyl)-3-(2-â-naphthylethyl)indole which is obtained from indole-
3-carboxaldehyde by alkylating with R-bromo-m-toluyl nitrile,
aldehyde homologation with (naphthalen-2-ylmethyl)phospho-
nic acid diethyl ester cf. Nagarathnam,29 followed by olefin
reduction under hydrogenation conditions: 1H NMR (DMSO-
d6) δ 9.32 (bs, 2H), 9.10 (bs, 2H), 7.84 (m, 4H), 7.75 (s, 1H),
7.64 (m, 2H), 7.42 (m, 5H), 7.28 (s, 1H), 7.22 (d, 1H), 7.10 (m,
1H), 7.02 (m, 1H), 5.40 (s, 2H), 3.11 (bs, 4H); FAB MS [M +
H]+ ) 404; RP-HPLC analysis (C18, 30-min linear gradient;
elution 10-100% CH3CN/0.1% TFA H2O; flow rate 1.0 mL/
min) indicated that the product was 97.9A%.
N-[3-(Am in oim in om eth yl)ben zyl]-2-(n a p h th a len -2-yl-
su lfon yla m in o)a ceta m id e Tr iflu or oa ceta te (5). Prepared
from N-(3-cyanobenzyl)-2-(naphthalen-2-ylsulfonylamino)ac-
etamide which is obtained from glycine methyl ester hydro-
chloride by sulfonylation with 2-naphthalenesulfonyl chloride,
ester hydrolysis, and amide formation with m-cyanobenzyl-
(15) Tschaen, D. M.; Desmond, R.; King, A. O.; Fortin, M. C.; Pipik,
B.; Verhoevan, T. R. An improved procedure for aromatic
cyanation. Synth. Commun. 1994, 24, 887-90.
(16) Thorsett, E. D.; Harris E. E.; Aster, S. D.; Peterson, E. R.;
Snyder, J . P.; Springer, J . P.; Hirshfield, J .; Tristram, E. W.;
Patchett, A. A.; Ulm, E. H.; Vassil, T. C. Conformationally
restricted inhibitors of angiotensin converting enzyme: synthesis
and computations. J . Med. Chem. 1986, 29, 251-60.
(17) Pinner, A. In Die Imidoaether und ihre derivate; Oppenhiem:
Berlin, 1892; pp 1-85.
(18) Pfeiffer, C.; Voigt, B.; Wagner, G.; Synthese von N-(tosyl-alanyl)-
und N-(tosyl-aminocapronyl)amidinophenylalainamiden ais stark
wirksame thrombin inhibioren. Pharmazie 1984, 39, 315-7.
(19) Callas, D.; Fareed, J . Comparative pharmacology of site directed
antithrombin agents. Implication in drug development. Thromb.
Haemost. 1995, 74, 473-81.
(20) (a) Ewing, W. R.; Becker, M. B.; Manetta, V.; Davis, R.; Pauls,
H.; Mason, H.; Spada, S.; Chemey, D.; Mason, J .; Brown, K.;
Bentley, R.; Dunwiddie, C.; Leadley, R.; Chu, V. 214th ACS
Symposium, Sept 7-11, 1997, Las Vegas, NV; MEDI 50. (b)
Cheney, D. L.; Mason, J . S. A new method for fast flexible
docking and receptor mapping. IBC 5th Annual Rational Drug

Design and SAR of Inhibitors of FXa
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18 3571
Design Symposium, Dec 16-17, 1996, San Diego, CA. (c) Cheney,
D. L.; Barton, J . N.; Mason, J . S.; Morize, I. Flexible docking
protocols for structure-based drug design. Lecture at the ACS
Sympsium on De Novo Drug Design, Aug 25-29, 1996, Orlando,
FL.
inhibitor of coagulation factor Xa, inhibits venous thrombus
formation in the rabbit. Thromb. Hemost. 1999, 81, 157-60.
(25) Hardi, A. E.; Leclerc, G. A Convenient Synthesis of cis-4-
(Sulfomethyl)-piperidine-2-carboxylic Acid: NMR Assignment.
J . Heterocycl. Chem. 1993, 30, 631-5.
(21) Obtained at B3LYP/G-31G** using J aguar v3.5.
(22) Stubbs, M. T.; Huber, R.; Bode, W. Crystal structures of factor
Xa specific inhibitors in complex with trypsin: Structural
grounds for inhibition of factor Xa and selectivity against
thrombin. FEBS Lett. 1995, 375, 103-7. (b) Renatus, M.; Bode,
W.; Huber, H.; Sturzebecher, J .; Stubbs, M. Structural and
functional analyses of benzamidine-based inhibitors in complex
with trypsin: Implications for the inhibition of factor Xa, tPA,
and urokinase. J . Med. Chem. 1998, 41, 5445-6.
(26) Floyd, A. J .; Kinsman, R. G.; Roshan-Ali, Y.; Brown, D. W. Direct
cyanation of the furan nucleus by chlorosulphonyl isocyanate.
Tetrahedron 1983, 39, 3881-5.
(27) Moustrou, C.; Samat, A.; Guglielmetti, R.; Dubest, R.; Garnier,
F. 142. Syntheisis of thiophene-substituted spiropyrans and
spirooxazines, precursors of photochromic polymers. Helv. Chem.
Acta 1995, 78, 1887-93.
(28) Prugh, J . D.; Birchenough, L. A.; Egbertson, M. S. A simple
method of protecting a secondary amine with tert-butyloxycar-
bonyl (BOC) in the presence of a primary amine. Synth.
Commun. 1992, 22, 2357-60.
(29) Nagarathnam, D. A facile synthesis of 3-substituted indoles. J .
Heterocycl. Chem. 1992, 29, 953-8.
(23) Kurz, K. D.; Main, B. W.; Sandusky, G. E. Rat model of arterial
thrombosis induced by ferric chloride. Thromb. Res. 1990, 60,
269-80.
(24) Bostwick, J . S.; Bentley, R.; Morgan, S.; Brown, K.; Chu, V.;
Ewing, W. R.; Spada, A. P.; Pauls, H. W.; Perrone, M. H.;
Dunwiddie, C. T.; Leadley, R. J . RPR120844, a novel, specific
J M990040H