Orally active isoxazoline glycoprotein IIb/IIIa antagonists with extended duration of action

Article abstract of DOI:10.1021/jm980348t

Modification of the α-carbamate substituent of isoxazoline GPIIb/IIIa (α(IIb)β₃) antagonist DMP 754 (7) led to a series of α-sulfonamide and α-sulfamide diaminopropionate isoxazolinylacetamides which were found to be potent inhibitors of in vitro platelet aggregation. Aryl- and heteroaryl-α- sulfonamide groups, in conjunction with (5R)-isoxazoline (2S)- diaminopropionate stereochemistry, were found to impact a pronounced duration of antiplatelet effect in dogs, potentially due to high affinity for unactivated platelets. Isoxazolylsulfonamide 34b (DMP 802), a highly selective GPIIb/IIIa antagonist, demonstrated a prolonged duration of action after iv and po dosing and high affinity for resting and activated platelets. The prolonged antiplatelet profile of DMP 802 in dogs and the high affinity of DMP 802 for human platelets may be predictive of clinical utility as a once-daily antiplatelet agent.

Full text of DOI:10.1021/jm980348t

1178
J . Med. Chem. 1999, 42, 1178-1192
Or a lly Active Isoxa zolin e Glycop r otein IIb/IIIa An ta gon ists w ith Exten d ed
Du r a tion of Action
Richard E. Olson,* Thais M. Sielecki,* J ohn Wityak, Donald J . Pinto, Douglas G. Batt, William E. Frietze,
J ie Liu, A. Ewa Tobin, Michael J . Orwat, Susan V. Di Meo, Gregory C. Houghton, George K. Lalka,
Shaker A. Mousa, Adrienne L. Racanelli, Elizabeth A. Hausner, Ram P. Kapil, Shelley R. Rabel,
Martin J . Thoolen, Thomas M. Reilly, Paul S. Anderson, and Ruth R. Wexler
The DuPont Merck Pharmaceutical Company, P.O. Box 80500, Wilmington, Delaware 19880-0500
Received J une 8, 1998
Modification of the R-carbamate substituent of isoxazoline GPIIb/IIIa (RIIbâ3) antagonist DMP
754 (7) led to a series of R-sulfonamide and R-sulfamide diaminopropionate isoxazolinylaceta-
mides which were found to be potent inhibitors of in vitro platelet aggregation. Aryl- and
heteroaryl-R-sulfonamide groups, in conjunction with (5R)-isoxazoline (2S)-diaminopropionate
stereochemistry, were found to impart a pronounced duration of antiplatelet effect in dogs,
potentially due to high affinity for unactivated platelets. Isoxazolylsulfonamide 34b (DMP 802),
a highly selective GPIIb/IIIa antagonist, demonstrated a prolonged duration of action after iv
and po dosing and high affinity for resting and activated platelets. The prolonged antiplatelet
profile of DMP 802 in dogs and the high affinity of DMP 802 for human platelets may be
predictive of clinical utility as a once-daily antiplatelet agent.
In tr od u ction
els.8 Several orally active nonpeptide GPIIb/IIIa an-
tagonists (Figure 1) are in advanced stages of clinical
evaluation.9-15 Results from clinical trials of GPIIb/IIIa
antagonists suggest that substantial inhibition of plate-
let aggregation may be achieved without unduly com-
promising hemostasis and that GPIIb/IIIa blockade may
lower the risk of thrombotic events in the context of
unstable angina and following coronary angioplasty.16-18
We recently reported that isoxazolinylacetamides of
â-alanine are highly effective frameworks for the display
of the basic and acidic functionality requisite to high
GPIIb/IIIa affinity19 and that the R-carbamate diami-
nopropionate 1 (DMP 754)20-22 provides high oral
potency and prolonged antiplatelet effects in dogs as
compared to the R-unsubstituted analogue 2 (XR300).19
The use of N-R-substituted diaminopropionates in other
Arterial occlusive disorders remain a major cause of
morbidity and mortality despite significant advances in
their diagnosis and treatment. Occlusion of arteries can
occur in association with atherosclerotic processes or as
a result of vessel wall insult caused by invasive coronary
intervention.1 Arterial thrombosis is largely platelet-
mediated and is dependent upon platelet adhesion,
activation, and aggregation. Antiplatelet agents such as
aspirin and ticlopidine, which predominantly target
platelet activation pathways, have found widespread use
in the treatment and prevention of arterial thrombosis.
However, because of the variety of means through which
platelets can be activated, the interruption of any single
platelet agonistic pathway leads to limited efficacy.2
Independent of the means by which platelets become
activated, the final and obligatory step in the formation
of platelet aggregates involves the cross-linking of
platelets by plasma fibrinogen or other matrix proteins.
This process is mediated primarily by the platelet
fibrinogen receptor, glycoprotein IIb/IIIa (GPIIb/IIIa,
R
IIbâ3), which becomes competent to bind fibrinogen
upon platelet activation.3 Proposals regarding the mech-
anism by which fibrinogen interacts with GPIIb/IIIa
have implicated the RGD sequences located in the
R-chain4 and residues 401-411 in the γ-chain.5 Small
molecules designed as mimetics of the Arg-Gly-Asp
sequence present in the fibrinogen R-chain have proven
to be potent and specific antagonists of the fibrinogen-
GPIIb/IIIa interaction in vitro. Such agents feature
appropriately oriented Arg-guanidine mimics and car-
boxylate groups appended to a variety of peptidic and
nonpeptidic core structures.6,7 Peptide and peptidomi-
metic antagonists of GPIIb/IIIa have been shown to
effectively block in vitro or ex vivo platelet aggregation
as well as arterial thrombosis in various animal mod-
series of GPIIb/IIIa antagonists has been recently
reported.23-31 The use of R-sulfonamide substituents in
GPIIb/IIIa antagonists containing piperidine Arg re-
placements has led to antiplatelet agents with extended
(g8 h) duration of action.26-29 In other GPIIb/IIIa
10.1021/jm980348t CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/12/1999

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1179
Sch em e 1. Preparation of Sulfonamide and Sulfamide
Diaminopropionatesa
a
Reagents: (a) RSO2Cl, Et3N, CH2Cl2; (b) TFA, CH2Cl2; (c)
RR′NSO2Cl, Et3N, CH2Cl2.
or Audrieth and Sveda.33 Methyl N2-sulfonyl- (6) and
N2-(aminosulfonyl)-2,3-diaminopropionates (7) were pre-
pared from methyl N3-(tert-butyloxycarbonyl)-2,3-di-
aminopropionate (5)24 and the appropriate sulfonyl or
sulfamoyl chlorides, as shown in Scheme 1.
Isoxa zolin yla ceta m id es a n d Ela bor a tion of F i-
n a l P r od u cts. Coupling of Boc-amidine isoxazoliny-
lacetic acids 4 and various methyl diaminopropionates
provided the desired isoxazolinylacetamides 8 and 9,
which upon deprotection gave the free amidine carboxy-
lates 12a -14a , 16a , 18a , 19a , 21a -28a , and 31a -
44a 34 (Scheme 2).20 Alternatively, the desired sulfona-
mides and sulfamides could be obtained by derivatization
of the free amine of Boc-amidine ester 10 with appropri-
ate sulfonyl and sulfamoyl chlorides. The methyl ester
derivative of Boc-amidine 10 was prepared as previously
described.20 Coupling of the tert-butyl ester of N2-Cbz-
diaminopropionate35 with the protected isoxazolinyl
acetate 4 using TBTU provided the tert-butyl ester of
10. The presence of the tert-butyl ester allowed the
simultaneous deprotection of the amidine and ester
groups at the end of the synthesis. Analogous use of the
scalemic nitrile acids 3, followed by a Pinner amidine
synthesis, allowed access to the individual isoxazoline
diaminopropionate diastereomers (Scheme 3).
Selective methylation of the sulfonamide nitrogen of
nitrile ester 11 was carried out under Mitsunobu
conditions, as shown in Scheme 4, which provided a
route to the N-methylated sulfonamide 29b. Coupling
of methyl N2-(m-tolylsulfonamido)diaminopropionate
with 3-(4-N-Bocamidinophenyl)isoxazolyl-5-acetic acid,20
deprotection of the amidine, and saponification provided
the isoxazole analogue 30 (Scheme 5). Separation of the
isoxazoline C5 diastereomers of the final products using
chiral chromatography20 provided an alternative means
of obtaining the individual isomers. The stereochemical
assignment was confirmed in the case of 34b (DMP 802)
by X-ray crystallographic analysis.
F igu r e 1. Representative oral nonpeptide GPIIb/IIIa antago-
nists in clinical development.
antagonists featuring heterocyclic amidines as Arg
mimics, prolonged plasma levels of active species were
not demonstrated.31 In our search for GPIIb/IIIa an-
tagonists with the potential for use in chronic therapy,
we have sought agents with pharmacologic profiles
consistent with once-daily administration. Following
oral administration to dogs and rhesus monkeys, 1 was
found to provide >60-90% inhibition of platelet ag-
gregation for 12 h. Minimal antiplatelet effect remained
at 24 h in these species. In the baboon, substantial
antiplatelet inhibition was extended to g24 h.20-22
Because of uncertainty over the predictability of the
various animal species with respect to clinical pharma-
codynamics, our efforts to identify GPIIb/IIIa antago-
nists showing extended duration of action continued.
This report describes further investigations into the
effect of R-substitution on the duration of antiplatelet
activity and the identification of 34b (DMP 802), a
potent, orally active isoxazolinyl diaminopropionate
bearing an R-heterocyclic sulfonamide substituent which
demonstrates 24-h duration of action in dogs.
Resu lts a n d Discu ssion
Ch em istr y
The sulfonamides 12-39 and sulfamides 40-44 were
assessed for their ability to inhibit ADP-stimulated
platelet aggregation in platelet-rich plasma (PRP).36
R-Sulfonamide and R-sulfamide functionality at the
carboxy-terminus was found to provide GPIIb/IIIa an-
tagonists with submicromolar in vitro potency; the
majority of the compounds in this series showed IC50’s
in this assay e100 nM. As shown by the entries in
Tables 1-3, substituents with a variety of steric and
electronic properties were tolerated at the R-position.
As demonstrated by the activities of 29b and 20b ,
Syn th esis of Isoxa zolin yla cetic Acid s. (R,S)-(4-
Cyanophenyl)isoxazolinylacetic acid (3), the correspond-
ing (R)- and (S)-enantiomers, and the (R,S)-(4-N-Boc-
amidinophenyl)isoxazolinylacetic acid (4) were synthe-
sized as described previously.19,20
N2-Su lfon yld ia m in op r op ion a t e
Der iva t ives.
Alkyl-, aryl-, and heteroarylsulfonyl chlorides were
available from commercial sources or were prepared
using literature methods. Sulfamoyl chlorides were
prepared using the methods of Kloek and Leschinsky32

1180 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Olson et al.
Sch em e 2. Synthesis of (R,S)-Isoxazolinyl Diaminopropionate Acetamidesa
a
Reagents: (a) 6 or 7, TBTU, Et3N; (b) TFA, CH2Cl2; (c) LiOH or 6 N HCl; (d) RSO2Cl or RR′NSO2Cl, Et3N, CH2Cl2.
Sch em e 3. Chiral Synthesis of Isoxazolinyl Diaminopropionate Acetamidesa
a
Reagents: (a) 6 or 7, TBTU, Et3N, DMF; (b) HCl (anhydrous), MeOH, 0 °C, then NH3 or (NH4)2CO3 or NH4OAc, MeOH, rt; (c) LiOH,
6 N HCl, or rabbit liver esterase.
Sch em e 4. Synthesis of N-Methylsulfonamide 29ba
a
Reagents: (a) DEAD/Ph3P/MeOH (1:1:1), THF; (b) HCl (anhydrous), MeOH, 0 °C, then NH3, MeOH, rt; (c) LiOH.
Sch em e 5. Synthesis of Isoxazolyl Diaminopropionate Acetamide 30a
a
Reagents: (a) methyl N2-(m-tolylsulfonamido)diaminopropionate, TBTU, Et3N, DMF; (b) TFA-CH2Cl2 (1:1), rt; (c) LiOH, H2O-
MeOH.
N-methylation of the sulfonamide caused a loss of
potency, as observed in the previously reported R-car-
bamate series.20
activity comparable to that of DMP 802 and 34d ,
whereas the (S),(R)-diastereomer 34e was significantly
less potent. This pattern of activity in the PRP assay
was previously noted for the diastereomers of DMP
754.20 New R-substituents were generally tested as (S)-
diaminopropionate isoxazoline C5 diastereomeric mix-
tures.
With respect to the structure of the R-substituent, the
potent inhibition of platelet function observed in the
PRP assay across this series did not allow the develop-
ment of definitive structure-activity relationships. With
the objective of identifying compounds with extended
duration of action, we distinguished the potent IIb/IIIa
antagonists of the present study by assessing their in
The effect of stereochemistry at the isoxazolinyl C5
center on in vitro activity (PRP assay) was studied. In
the case of the m-tolylsulfonamides, the (R)- and (S)-
C5 diastereomers 20b,c, as well as the planar isoxazole
30, showed similar activity. In the case of the hetero-
cyclic sulfonamide 34, the effect of the diaminopropi-
onate stereochemistry was also investigated. With the
(R)-isoxazoline isomers 34b (DMP 802) and 34d , both
diaminopropionate configurations gave highly active
GPIIb/IIIa antagonists. In the (S)-isoxazoline series, the
(S)-diaminopropionate isomer 34c demonstrated PRP

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1181
Ta ble 1. In Vitro Potencies of Sulfonamides 12-30
Prolonged in vivo duration was often associated with
ortho substitution, as seen with the o-methyl- (16a ),
o-bromo- (18a ), and o-phenyl- (19a ) phenylsulfonamides
and the quinolinylsulfonamide 39a (Table 4). The an-
tiplatelet activity of o-tolylsulfonamide 16a was followed
for several days; significant inhibition of ex vivo ag-
gregation was still present at 96 h (Figure 2). Ortho
substitution, however, was not essential to prolonged
antiplatelet action, as demonstrated by thiazolylsul-
fonamide (37a ).
As previously discussed, the isoxazoline C5 configu-
ration did not appear to strongly influence the in vitro
activity (PRP); however, the stereochemistry at this
center was found to affect duration of action in vivo. In
the (S)-diaminopropionate m-tolylsulfonamide series,
the (5R)-isoxazoline isomer 20b showed 94% inhibition
of ex vivo platelet aggregation at 5 h, while the (5S)-
isomer 20c demonstrated 64% inhibition at the same
time point. Interestingly, the planar isoxazole analogue
30, while essentially equipotent in the PRP aggregation
assay, provided only 19% ex vivo antiplatelet activity
at 5 h (Figure 3). The effects of both isoxazoline and
diaminopropionate stereochemistry were studied among
the isomers of the dimethylisoxazolesulfonamide (DMP
802) series (34b-34e). The (5R)-isoxazoline (2S)-diami-
nopropionate diastereomer proved superior in terms of
in vivo profile (Figure 4) although the (5S),(2S)- (34c)
and (5R),(2R)- (34d ) isomers had comparable in vitro
activity.
As shown by the in vitro data discussed above, the
PRP assay did not distinguish the compounds in the
present series from R-carbamates such as 1 (DMP
754).20 The limitations of PRP aggregation assays
include a sensitivity limited by the concentration of
GPIIb/IIIa receptors in the assay mixture (∼20-40
nM),27 as well as the inability to distinguish the effects
of protein binding from inherent GPIIb/IIIa affinity.
Recently, certain GPIIb/IIIa antagonists having diami-
nopropionate carboxy-termini have been shown to pos-
sess considerable affinity for the unactivated platelet
GPIIb/IIIa receptor, a further property not assessed by
the PRP assay.20-22,27,37 Affinity for unactivated GPIIb/
IIIa receptors and resting platelets has been proposed
as a mechanism to decrease clearance and prolong
antiplatelet effects of GPIIb/IIIa antagonists.27,38,39 Analo-
gous target-mediated clearance of ACE inhibitors from
plasma40 and of benzodiazepines from cerebrospinal
fluid41 has been reported. The inhibition of aggregation
in platelet-rich dog plasma, as well as the dissociation
constants for activated and unactivated dog platelets,
was measured for the stereoisomers of 34 (Table 5) (see
Experimental Section). Significantly, 34b (DMP 802),
the (5R)-isoxazoline (2S)-diaminopropionate isomer,
showed the highest affinity for unactivated dog platelets
and the longest duration of action in dogs. DMP 802
also demonstrated higher affinity for dog platelets than
the free acid of 1 (DMP 754).
a
Inhibition of ADP-induced platelet aggregation was deter-
b
mined in three donors. See ref 36 for protocol. IC50 determined
for free acid of DMP 754.21 c See refs 42 and 43. Determined for
d
HCl salt. e Result of one determination.
vivo profile in dogs. Selected compounds having an IC50
less than approximately 100 nM in the PRP assay were
assessed for their ability to inhibit ex vivo platelet
aggregation in dogs after administration of an iv bolus
dose of 0.025 mg/kg (Table 4). Using this protocol, the
reference R-carbamate 1 (DMP 754), as the free acid,20
completely inhibited ex vivo aggregation at 1 h (>99%)
and showed approximately 40% inhibition at 5 h. The
antiplatelet activity at the 5 h time point proved useful
in differentiating the compounds of the present study.
Thus, R-n-alkylsulfonamides 12a and 13a 20 and the
isobutylsulfamide 41a were found to have in vivo
duration in dogs comparable to that of the free acid of
1 (Table 4). However, the R-aryl-, heteroaryl-, and
benzylsulfonamides showed enhanced antiplatelet ef-
fects at 5 h postdose. In some cases, complete inhibition
of ex vivo platelet aggregation was present for g24 h.
Selected sulfonamides demonstrating persistent an-
tiplatelet activity after iv dosing were compared for
antiplatelet effects in dogs after oral doses of 0.1 mg/kg
as the (5R),(2S)-isomers. Prolonged antiplatelet activity
was shown by the arylsulfonamides 16b , 18b, and
20b42,43 and by the isoxazolylsulfonamide 34b (DMP
802) (Table 6). Improved potency and prolonged dura-

1182 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Ta ble 2. In Vitro Potencies of Heterocyclic Sulfonamides 31-39
Olson et al.
a
,bSee corresponding footnotes for Table 1.
tion of action with respect to DMP 754 were observed
in dogs, particularly with sulfonamides 16b, 20b, and
DMP 802. However, the >96-h duration of antiplatelet
activity of 16b was deemed undesirable. In reviewing
the physical properties of the orally active analogues
20b and DMP 802, the solubility of DMP 802, a
crystalline mesylate salt, was found to be 18 mg/mL at
pH 1.7 and 0.82 mg/mL at pH 5-7, which was consid-
ered sufficient for consistent oral dosing.
affinity (Kd) of DMP 802 for resting human platelets44
was found to be higher (0.57 nM) and the Koff longer
(32 min) than those of the free acid of DMP 75422
(2.5 nM and 7 min, respectively), potentially predictive
of a prolonged antiplatelet effect in vivo. In dogs,
DMP 802 demonstrated a long duration of ex vivo anti-
platelet effect after oral doses of 0.05 and 0.10 mg/kg
(Table 6, Figure 5) with significant antiplatelet activity
still present at 24 h. The bioavailability of DMP 802 in
dogs after doses of 0.025 mg/kg iv and 0.1 mg/kg po was
found to be 14.9% with a terminal half-life after oral
dosing of 13-17 h.44 Clearance was dose-dependent,
Further characterization of 34b (DMP 802) revealed
a high selectivity for the GPIIb/IIIa receptor over the
R4â1, R5â1, and Rvâ3 integrins in vitro (Table 7). The

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1183
Ta ble 3. In Vitro Potencies of Sulfamides 41-45
used as purchased from commercial sources unless otherwise
stated. The yields quoted in this paper were isolated yields.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(3,5-d im eth yl-4-isoxa zolyl)-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (34a ). This compound
was synthesized in an analogous manner to that used for 25b
in Xue et al.:20 1H NMR (300 MHz, DMSO-d6) δ 9.72 (bs, 2H),
9.29 (bs, 2H), 8.25 (bm, 1H), 8.16 (m, 1H), 7.87 (s, 4H), 5.03
(m, 1H), 3.78 (bs, 1H), 3.6-3.1 (m, 4H) 2.55 (s, 3H), 2.34 (s,
3H), 2.62-2.38 (m, 2H); HRMS (FAB) m/z 493.1487 [(M + H)+
calcd for C20H25N6O7S1 493.1505]; 96.2% purity by HPLC.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a cet yl]a m in o]-N-[(3,5-d im et h yl-4-isoxa zol-
yl)su lfon yl]-L-a la n in e Meth a n esu lfon a te (34b). To a solu-
tion of methyl N3-Boc-(S)-2,3-diaminopropionate (5) (22.05 g,
101 mmol) in CH2Cl2 (300 mL) at 0 °C was added 3,5-
dimethylisoxazole-4-sulfonyl chloride (20.0 g, 102 mmol). A
solution of Et3N (16.2 mL, 116 mmol) in CH2Cl2 (50 mL) was
added over 30 min and the resulting mixture allowed to warm
to room temperature overnight (18 h). The mixture was
washed with 0.1 M HCl, saturated NaHCO3, and brine, dried
(MgSO4), filtered, and concentrated in vacuo. Purification
using flash chromatography (0-8% MeOH-CHCl3) gave 31.56
g (83%) of the desired sulfonamide as a viscous oil: 1H NMR
(300 MHz, CDCl3) δ 6.14 (bs, 1H), 5.04 (m, 1H), 3.97 (bs, 1H),
3.66 (s, 3H), 3.50 (m, 2H), 3.15 (bq, J ) 7.3 Hz, 1H), 2.62 (s,
3H), 2.42 (s, 3H), 1.43 (s, 9H).
Methyl N2-(3,5-dimethylisoxazol-4-ylsulfonyl)-N3-Boc-(S)-
2,3-diaminopropionate (31.56 g, 83.62 mmol) in 4 M HCl/
dioxane (100 mL, 400 mmol) was stirred at room temperature
for 4 h and then concentrated in vacuo to an oil. Trituration
with ether (3 × 10 mL) followed by drying under vacuum
afforded 28.24 g of the desired amine, still containing 30 mol
% residual dioxane (75% yield): 1H NMR (300 MHz, CDCl3) δ
8.23 (bs, 3H), 8.05 (bs, 1H), 4.47 (bs, 1H), 3.64 (m, 2H), 3.50
(m, 2H), 3.58 (s, 3H), 3.13 (m, 1H), 2.61 (s, 3H), 2.43 (s, 3H).
a,b
See corresponding footnotes for Table 1.
increasing from 0.55 to 4.5 mL/min/kg, after iv doses of
0.025 and 0.4 mg/kg, respectively, while the apparent
volume of distribution at steady state increased from
0.8 to 4.2 L/kg over the same dose range. This nonlinear
pharmacokinetic profile44 may reflect a role for platelet-
mediated clearance at low plasma concentrations.
Con clu sion s
Modification of the R-carbamate substituent of the
isoxazoline GPIIb/IIIa antagonist 1 (DMP 754) led to a
series of R-sulfonamide and R-sulfamide diaminopropi-
onate derivatives, which were examined for their in vitro
potency and duration of ex vivo antiplatelet activity in
dogs. Most compounds showed high potency in the
platelet aggregation assay, demonstrating a wide toler-
ance for diverse steric and electronic substituent prop-
erties at the R-position for the GPIIb/IIIa receptor.
However, considerable differences with respect to in vivo
duration of antiplatelet action in dogs were observed.
In the case of the stereoisomers of 34, potent and long
duration antiplatelet effects after iv dosing were found
in the (5R)-isoxazoline (2S)-diaminopropionate isomer
34b (DMP 802), which demonstrated the highest affinity
for unactivated platelets. DMP 802 was also found to
provide prolonged antiplatelet activity after oral ad-
ministration in dogs. The prolonged antiplatelet profile
in dogs and the high affinity of DMP 802 for human
platelets may be predictive of clinical utility as a long-
acting antiplatelet agent. DMP 802 has been selected
for clinical evaluation as an oral GPIIb/IIIa antagonist
for the treatment and prevention of arterial thrombosis.
To a suspension of 3-(4-cyanophenyl)isoxazolin-5(R)-ylacetic
acid (20.72 g, 90.0 mmol) and methyl N2-(3,5-dimethylisoxazol-
4-ylsulfonyl)-(S)-2,3-diaminopropionate hydrochloride (28.24 g,
70% purity, 63.0 mmol) in DMF (200 mL) was added TBTU
(28.90 g, 90 mmol). The mixture was cooled to 0 °C, Et3N (31.4
mL, 225 mmol) was added dropwise, and the resulting mixture
was allowed to warm to room temperature overnight (18 h).
Upon dilution with EtOAc (500 mL) the organic layer was
extracted with H2O (4 × 200 mL), saturated NaHCO3 (100
mL), and saturated NaCl (100 mL), dried (MgSO4), and
filtered. Concentration in vacuo afforded 25.06 g (81%) of the
desired amide: 1H NMR (300 MHz, DMSO-d6) δ 8.77 (bs, 1H),
8.22 (t, J ) 5.9 Hz, 1H), 5.02 (m, 1H), 3.98 (t, J ) 7.0 Hz, 1H),
3.55 (dd, J ) 17.2, 10.6 Hz, 1H), 3.48 (s, 3H), 3.42 (m, 1H),
3.16 (m, 2H), 2.54 (s, 3H, partially coincident with m, 1H and
DMSO-d5), 2.37 (dd, J ) 14.6, 7.0 Hz, 1H), 2.33 (s, 3H).
Into a solution of methyl N2-(3,5-dimethylisoxazol-4-ylsul-
fonyl)-N3-[3-(4-cyanophenyl)isoxazolin-5(R)-ylacetyl]-(S)-2,3-di-
aminopropionate (25.06 g, 51.17 mmol) in MeOH (anhydrous,
750 mL) at 0 °C was bubbled HCl gas for 3 h. The resulting
solution was allowed to warm to room temperature overnight
(18 h), after which the solvent was evaporated in vacuo. The
oily residue was triturated with ether (3 × 100 mL) and the
resulting solid placed under vacuum until constant weight was
achieved. The crude imidate was then dissolved in MeOH (1
L) and ammonium acetate (20.0 g, 259 mmol) added. The
resulting mixture was stirred at room temperature for 18 h
and then concentrated in vacuo. The residue was then crystal-
lized from EtOH, giving 21.75 g of crude amidine. A portion
of this material (8.5 g) was purified using flash chromatogra-
phy (20% MeOH-EtOAc) to give 3.77 g (33%) of pure (by
analytical HPLC) amidine: 1H NMR (300 MHz, DMSO-d6) δ
8.26 (m, 1H), 7.86 (m, 4H), 5.01 (m, 1H), 3.96 (t, J ) 6.6 Hz,
1H), 3.56 (dd, J ) 17.2, 10.6 Hz, 1H), 3.48 (s, 3H, coincident
with m, 1H), 3.18 (m, 2H), 2.53 (s, 3H, partially coincident
with m, 1H and DMSO-d5), 2.54 (s, 3H), 2.36 (dd, J ) 14.6,
7.0 Hz, 1H), 2.32 (s, 3H), 1.74 (s, 3H).
Exp er im en ta l Section
Gen er a l Exp er im en ta l. Melting points were determined
on an Electrothermal melting point apparatus and are uncor-
rected. Unless otherwise stated, preparative HPLC separations
were accomplished on a Vydac C18 column operated at room
temperature and eluted at a 10 mL/min flow rate, using a
linear gradient of 100% H2O containing 0.05% TFA-20% H2O/
MeCN containing 0.05% TFA over 50 min, with UV detection
at 254 nm. 1H and 13C NMR data were obtained using a Varian
Unity 300, Unity 400, or VXR400 spectrometer and were
referenced to TMS or residual HOD. Mass spectral data were
obtained on either VG 70-VSE (FAB, high-res FAB, high-res
DCI) or Finnigan MAT 8230 (DCI) mass spectrometers.
Combustion analyses were performed by Quantitative Tech-
nologies, Inc., Bound Brook, NJ . Solvents and reagents were

1184 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Olson et al.
Ta ble 4. Ex Vivo Inhibition of Platelet Aggregation in Dogs after iv Dosing
a
b
n ) 2. Tested at 0.05 mg/kg.
To a solution of methyl N2-(3,5-dimethylisoxazol-4-ylsulfo-
nyl)-N3-[3-(4-amidinophenyl)isoxazolin-5(R)-ylacetyl]-(S)-2,3-
diaminopropionate HOAc salt (3.77 g, 6.65 mmol) in 0.1 N
Hepes buffer (pH 7, 140 mL, 48 mmol) was added rabbit liver
esterase (3.6 M crystalline suspension in ammonium sulfate,
3500 units; Sigma). The resulting solution was incubated at
37 °C. After 3 days, an additional 2000 units of esterase was
added and the pH was adjusted from 5.2 to 7.2, causing a
substantial amount of zwitterion to precipitate. After 2 ad-
ditional days the precipitate was collected by filtration, washed
with cold H2O (50 mL), and dried under vacuum until constant
weight was achieved to yield 1.850 g of pure zwitterion. Protein
was removed from the filtrate by ultra filtration (Amicon YM-
10 membrane), and the filtrate was then concentrated in vacuo
and lyophilized. Purification using a reverse-phase silica
column (5 × 9.5 cm in H2O; crude product loaded as an
aqueous solution followed by elution with H2O (1000 mL) and
by 500 mL each of 20%, 30%, and 40% CH3CN-H2O). Frac-

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1185
F igu r e 4. Inhibition of ADP (100 µM)-mediated ex vivo
platelet aggregation in the canine dosed intravenously (bolus)
with 0.020 mg/kg stereoisomers of 34 (n ) 2).
F igu r e 2. Inhibition of ADP (100 µM)-mediated ex vivo
platelet aggregation in the canine dosed intravenously (bolus)
with 0.025 mg/kg 16a (n ) 2).
proton not observed); [R]25D ) -51.48° (c ) 0.338, MeOH); MS
(ESI) m/z 493 [(M + H)+, 100]. Anal. (C20H24N5O7S‚CH3SO3H)
C, H, N, S.
(S)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a cet yl]a m in o]-N-[(3,5-d im et h yl-4-isoxa zol-
yl)su lfon yl]-L-a la n in e Meth a n esu lfon a te (34c). This com-
pound was synthesized in an analogous manner to that used
for 34b: 1H NMR (300 MHz, DMSO-d6) δ 13.05 (bs, 1H), 9.44
(bs, 2H), 9.18 (bs, 2H), 8.59 (d, J ) 9.9 Hz, 1H), 8.24 (t, J )
5.9 Hz, 1H), 7.92-7.85 (m, 4H), 5.04-4.98 (m, 1H), 3.94-3.86
(m, 1H), 3.54 (dd, J ) 17.2, 10.6 Hz, 1H), 3.39-3.29 (m, 2H),
3.29-3.20 (m, 2H), 2.54 (s, 3H), 2.41 (dd, J ) 13.9, 7.3 Hz,
1H), 2.35 (s, 3H), 2.34 (s, 3H); [R]25 ) +37.57° (c ) 0.338,
D
MeOH); MS (ESI) m/z 515 [(M+Na)+, 100], 493 [(M + H)+,
60]. Anal. (C20H24N5O7S‚CH3SO3H‚H2O) C, H, N, S.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a cet yl]a m in o]-N-[(3,5-d im et h yl-4-isoxa zol-
yl)su lfon yl]-D-a la n in e Meth a n esu lfon a te (34d ). This com-
pound was synthesized in an analogous manner to that used
for 34b: 1H NMR (300 MHz, DMSO-d6) δ 9.44 (bs, 2H), 9.17
(bs, 2H), 8.59 (d, J ) 9.5 Hz, 1H), 8.23 (t, J ) 5.5 Hz, 1H),
7.92-7.86 (m, 4H), 5.04-4.98 (m, 1H), 3.92-3.88 (m, 1H), 3.54
(dd, J ) 17.2, 10.6 Hz, 1H), 3.38-3.30 (m, 2H), 3.29-3.29 (m,
2H), 2.54 (s, 3H), 2.41 (dd, J ) 14.3, 7.7 Hz, 1H), 2.34 (s, 3H),
F igu r e 3. Inhibition of ADP (100 µM)-mediated ex vivo
platelet aggregation in the canine dosed intravenously (bolus)
with 0.025 mg/kg 20b,c and 30 (n ) 2).
2.34 (s, 3H) (carboxylic acid proton not observed); [R]25
)
D
-42.77° (c ) 0.346, MeOH); MS (ESI) m/z 515 [(M+Na)+, 100],
493 [(M + H)+, 55]. Anal. (C20H24N5O7S‚CH3SO3H) C, H, N,
S.
tions containing the desired product were pooled, acetonitrile
was removed, and the aqueous solution was lyophilized to yield
an additional 900 mg of pure zwitterion to afford a combined
yield of 2.75 g (82%). To a solution of the zwitterion (2.75 g,
5.43 mmol) in 50% CH3CN-H2O (135 mL) was added meth-
anesulfonic acid (0.57 g, 5.97 mmol). The reaction mixture was
stirred at room temperature for 1 h, resulting in a clear
solution. Solvent was removed in vacuo and the residue placed
under vacuum for several hours. The crude mesylate was
dissolved in hot acetone and H2O until the solution was clear
(120 mL total volume). After hot filtration the solution was
allowed to cool to room temperature and then refrigerated for
24 h. A white precipitate was filtered and dried under vacuum,
affording 1.72 g (52%): 1H NMR (300 MHz, DMSO-d6) δ 9.43
(bs, 2H), 9.17 (bs, 2H), 8.60 (d, J ) 9.5 Hz, 1H), 8.27 (t, J )
5.8 Hz, 1H), 7.92-7.85 (m, 4H), 5.06-5.00 (m, 1H), 3.95-3.87
(m, 1H), 3.57 (dd, J ) 17.2, 10.6 Hz, 1H), 3.51-3.44 (m, 1H),
3.22 (dd, J ) 17.6, 7.7 Hz, 1H), 3.14-3.05 (m, 1H), 2.60-2.55
(m, 1H, coincident with 2.55 (s, 3H)), 2.41-2.35 (m, 1H,
coincident with 2.35 (s, 3H)), 2.34 (s, 3H) (carboxylic acid
(S)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a cet yl]a m in o]-N-[(3,5-d im et h yl-4-isoxa zol-
yl)su lfon yl]-D-a la n in e Meth a n esu lfon a te (34e). This com-
pound was synthesized in an analogous manner to that used
for 34b: 1H NMR (300 MHz, DMSO-d6) δ 9.44 (bs, 2H), 9.18
(bs, 2H), 8.59 (d, J ) 9.9 Hz, 1H), 8.27 (t, J ) 5.9 Hz, 1H),
7.92-7.85 (m, 4H), 5.08-4.98 (m, 1H), 3.93-3.89 (m, 1H), 3.56
(dd, J ) 17.6, 10.6 Hz, 1H), 3.51-3.45 (m, 1H), 3.22 (dd, J )
17.6, 7.7 Hz, 1H), 3.13-3.06 (m, 1H), 2.60-2.54 (m, 1H,
coincident with 2.54 (s, 3H)), 2.41-2.34 (m, 1H, coincident with
2.34 (s, 6H)) (carboxylic acid proton not observed); [R]25
)
D
+48.82° (c ) 0.340, MeOH); MS (ESI) m/z 515 [(M+Na)+, 100],
493 [(M + H)+, 50]. Anal. (C20H24N5O7S‚CH3SO3H) C, H, N,
S.
ter t-Bu tyl 3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d i-
h yd r o-5-isoxa zolyl]a cetyl]a m in o]-L-a la n in e (10). The in-
termediate tert-butyl 3-[[[3-[4-(aminoiminomethyl)phenyl]-4,5-
dihydro-5-isoxazolyl]acetyl]amino]-N-[(phenylmethoxy)carbonyl]-
L-alanine was prepared by the coupling reaction (TBTU) of 4
with tert-butyl N-[(phenylmethoxy)carbonyl]-L-alanine45 in an

1186 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Ta ble 5. Dog Platelet Affinities of Isoxazolyl Sulfonamides 34
Olson et al.
a
b
See corresponding footnote for Table 1. See ref 21b.
Ta ble 6. Inhibition of Platelet Aggregation in Dogs after Oral Dosing of 16b, 18b, 20b, and 34b
a
b
n ) 3.20 Inhibition measured at 2 h. c n ) 2.
Ta ble 7. Selectivity of 34b (DMP 802) for GPIIb/IIIa44
and purified by flash chromatography (10% MeOH/CH2Cl2) to
provide 10 as a glass in 64% yield: 1H NMR (300 MHz, CDCl3)
δ 7.88 (d, J ) 8.0 Hz, 2H), 7.69 (d, J ) 8.0 Hz, 2H), 6.43 (bt,
J ) 7.0 Hz, 1H), 5.12 (m, 1H), 3.66 (m, 1H), 3.54 (m, 1H), 3.47
(m, 1H), 3.29 (m, 1H), 3.29 (m, 1H), 3.19 (m, 1H), 2.71 (m,
1H), 2.58 (m, 1H), 1.65 (bs, 2H), 1.56 (s, 9H), 1.48 (s, 9H); MS
(ESI) m/z 490.3 [(M + H)+, 100].
Integrin
Method
% Inhibition/IC50
GPIIb/IIIa PRP
0.029 ( 0.0042 µM
0.012 ( 0.003 µM
GPIIb/IIIa gel-purified platelet-Fg
binding
GPIIb/IIIa ELISA
0.00021 ( 0.00005 µM
>10 µM
Rvâ3
ELISA
Rvâ5
SK-BR-3 cell-Vn-mediated <15% @10 µM
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxazolyl]acetyl]am in o]-N-(pr opylsu lfon yl)-L-alan in e Tr i-
flu or oa ceta te (12a ). This compound was synthesized in an
analogous manner to that used for 34a : 1H NMR (500 MHz,
DMSO-d6) δ 9.45 (s, 1H), 9.34 (s, 1H), 8.23-8.21 (m, 1H), 7.92-
7.86 (m, 4H), 5.07-5.02 (m, 1H), 3.96 (m, 1H), 3.56 (dd, J )
17.2, 10.2 Hz, 1H, partially coincident with m, 1H), 3.28-3.15
(m, partially coincident with H2O, 2H), 3.01-2.94 (m, 2H), 2.61
(dd, J ) 14.6, 6.6 Hz, 1H), 2.46 (dd, J ) 14.6, 7.7 Hz, 1H,
partially coincident with solvent), 1.75-1.65 (m, 2H), 0.95 (t,
J ) 7.7 Hz, 3H) (amidine protons not observed); MS (ESI) m/z
440 [(M + H)+, 100]. Anal. (C18H25N5O6S‚1.3CF3CO2H) C, H,
N.
adhesion
R4â1
R5â1
J urkat-Fn CS-1 adhesion
ELISA
>100 µM
<5% @10 µM
analogous manner to that used for 34b to yield the desired
compound in 75% yield as a colorless glass: 1H NMR (300
MHz, CDCl3) δ 7.85 (d, J ) 8.0 Hz, 2H), 7.63 (d, J ) 8.0, 2H),
7.33 (m, 5H), 6.43 (m, 1H), 5.76 (bt, J ) 8.0 Hz, 1H), 5.08 (s,
2H), 5.05 (m, 1H), 4.35 (m, 1H), 3.65 (m, 2H), 3.45 (m, 1H),
3.10 (m, 1H), 2.65 (m, 1H), 2.48 (m, 1H), 1.56 (s, 9H), 1.47 (s,
9H); MS (ESI) m/z 624 [M + H)+, 100].
tert-Butyl 3-[[[3-[4-(aminoiminomethyl)phenyl]-4,5-dihydro-
5-isoxazolyl]acetyl]amino]-L-alanine (10) was prepared from
tert-butyl 3-[[[3-[4-(aminoiminomethyl)phenyl]-4,5-dihydro-5-
isoxazolyl]acetyl]amino]-N-[(phenylmethoxy)carbonyl]-L-ala-
nine by catalytic reduction (10% Pd/C, EtOH, H2, 1 atm, 18 h)
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(p h en ylm eth yl)su lfon yl]-L-
a la n in e Tr iflu or oa ceta te (14a ). This compound was syn-

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1187
(S)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[(2-m eth ylph en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (16c). This compound was syn-
thesized in an analogous manner to that used for 34b. The
ester was hydrolyzed and product purified following the
procedure for 22 in Xue et al.:20 1HNMR (300 MHz, DMSO-
d6) δ 11.2 (s, 1H), 9.50 (bs, 2H), 9.20 (bs, 2H), 7.80 (s, 4H),
7.75 (d, J ) 8.0 Hz, 1H), 7.45-7.41 (m, 2H), 7.36-7.28 (m,
2H), 4.98-4.92 (m, 1H), 3.80 (dq, J ) 7.9, 16 Hz, 1H), 3.55-
3.38 (m, 2H), 3.15-3.00 (m, 2H), 2.51 (s, 3H), 2.48-2.42 (m,
1H), 2.25-2.18 (m, 1H); MS (ESI) m/z 488 [(M + H)+, 100];
HRMS (FAB) m/z 488.1613 [(M + H)+ calcd for C22H25N5O6S
488.1604]. Chiral HPLC analysis (SFC, Chiralcel OD; 0.46 ×
25 cm; 30 °C; 2.0 mL/min flow rate; 0.1% TFA, 22% MeOH,
78% CO2; 280 nM; 150 atm) showed >99% de with respect to
the (S,S)-diastereomer and >98% chemical purity.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[[2-(tr iflu or om eth yl)ph en yl]-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (17b). This compound
was synthesized in an analogous manner to that used for
34a : 1H NMR (300 MHz, D2O) δ 7.95 (m, 1H), 7.79 (m, 1H),
7.62 (m, 6H), 4.94 (m, 1H), 3.98-3.87 (m, 1H), 3.55-3.34 (m,
2H), 3.29-3.04 (m, 2H), 2.48-2.25 (m, 2H) (amidine protons,
carboxylic acid proton, amide proton, and sulfonamide proton
not observed); MS (ESI) m/z 542 [(M + H)+, 100]. Anal.
(C22H22F3N5O6S‚1.3CF3CO2H‚0.4H2O) C, H, N.
F igu r e 5. Inhibition of ADP (100 µM)-mediated ex vivo
platelet aggregation in the canine dosed orally with 34b (n )
2).
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-[(2-b r om op h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (18a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (300 MHz, DMSO-d6) δ 9.39 (bs, 2H), 9.13 (bs, 2H), 8.22
(m, 2H), 8.0 (dd, J ) 1.8 Hz, 1H), 7.88 (s, 4H), 7.83 (m, 1H),
7.53 (m, 2H), 4.99 (m,1H), 3.99 (m, 1H), 3.5 (m, 2H), 3.2 (m,
2H), 2.45 (m, 2H); HRMS (FAB) m/z 552.0552 [(M + H)+ calcd
for C21H23N5O6S1Br1 552.0552]. Anal. (C21H22BrN5O6S‚1.6CF3-
CO2H) C, H, N.
thesized in an analogous manner to that used for 34a . The
ester was cleaved using the LiOH protocol described in the
preparation of 22 in Xue et al.:20 1H NMR (300 MHz, DMSO-
d6) δ 9.39 (s, 2H), 9.21 (s, 2H), 8.16 (q, J ) 5.5 Hz, 1H), 7.86
(d, J ) 2.2 Hz, 4H), 7.58 (m, 1H), 7.35-7.40 (m, 5H), 5.04 (m,
1H), 4.36 (s, 2H), 4.01 (q, J ) 5.5 Hz, 1H), 3.60-3.47 (m, 2H),
3.27-3.19 (m, 2H), 2.61 (dd, J ) 6.6, 14.6 Hz, 1H), 2.42-2.48
(m, 1H); MS (ESI) m/z 488 [(M + H)+, 100]. Anal. (C22H25N5O6S‚
1.7CF3CO2H) C, H, N.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a ce t yl]a m in o]-N -(p h e n ylsu lfon yl)-L-a la -
n in e Tr iflu or oa ceta te (15b). This compound was synthe-
sized in an analogous manner to that used for 34b. The ester
was hydrolyzed and product purified following the procedure
for 22 in Xue et al.:20 1H NMR (300 MHz, DMSO-d6) δ 9.39 (s,
2H), 9.23 (s, 2H), 8.44 (d, J ) 9.5 Hz, 1H), 8.23 (t, J ) 5.8 Hz,
1H), 7.88 (s, 4H), 7.76 (dd, J ) 1.5, 8.1 Hz, 2H), 7.54-7.66 (m,
3H), 5.0 (m, 1H), 3.99 (q, J ) 7 Hz, 1H), 3.56 (dd, J ) 10.4,
17.2 Hz, 1H), 3.39 (dd, 1H), 3.33-3.1 (m, 2H), 2.57-2.48 (m,
1H, coincident with DMSO-d6), 2.35 (dd, J ) 7.3, 14.5 Hz, 1H);
MS (ESI) m/z 474 [(M + H)+, 100]. Anal. (C21H23N5O6S‚0.5CF3-
CO2H) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(2-m eth ylp h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (16a ). The title compound was
prepared and purified following the general method outlined
for 34a : 1H NMR (300 MHz, DMSO-d6) δ 9.48 (bs, 2H), 9.04
(bs, 2H), 7.91-7.8 (d, J ) 8.0 Hz, 1H), 7.69-7.60 (m, 2H),
7.48-7.18 (m, 5H), 6.50-6.31 (m, 1H), 5.10 (m, 1H), 4.05-
3.97 (m, 1H), 3.66-3.52 (m, 1H), 3.40-3.30 (m, 1H), 3.01-
2.98 (dd, J ) 7.9, 16 Hz, 1H), 2.79 (m, 1H), 2.65-2.50 (m, 4H)
(amidine protons and carboxylic acid proton not observed); MS
(ESI) m/z 488 [(M + H)+, 100]; HRMS (FAB) m/z 488.1603 [(M
+ H)+ calcd for C22H25N5O6S 488.1604]. Anal. (C22H25N5O6S‚
1.1CF3CO2H) C, H, N.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[(2-m eth ylph en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (16b). This compound was syn-
thesized in an analogous manner to that used for 34b. The
ester was hydrolyzed and product purified following the
procedure for 22 in Xue et al.:20 1HNMR (300 MHz, DMSO-
d6) δ 11.3 (s, 1H), 9.45 (bs, 2H), 9.17 (bs, 2H), 7.87 (s, 4H),
7.84-7.81 (d, J ) 7.8 Hz, 1H), 7.54 (m, 2H), 7.51-7.40 (m,
2H), 5.06-4.97 (m, 1H), 3.93-3.85 (m, 1H), 3.60-3.19 (m, 4H),
2.61-2.58 (m overlap, 4H), 2.45-2.41(m, 1H); MS (ESI) m/z
488 [(M + H)+, 100]; HRMS (FAB) m/z 488.1588 [(M + H)+
calcd for C22H25N5O6S 488.1604].
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxa zolyl]a cetyl]a m in o]-N-[(2-br om op h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (18b). This compound was syn-
thesized in an analogous manner to that used for 34b. The
ester was hydrolyzed and product purified following the
procedure for 22 in Xue et al.:20 1H NMR (300 MHz, DMSO-
d6) δ 9.39 (bs, 2H), 9.13 (bs, 2H), 8.21 (m, 2H), 8.0 (dd, J )
2.2, 1.8 Hz, 1H), 7.88 (s, 4H), 7.85 (m, 1H), 7.53 (m, 2H), 5.01
(m, 1H), 3.99 (m, 1H), 3.5 (m, 2H), 3.2 (m, 2H), 2.45 (m, 2H);
HRMS (FAB) m/z 552.0534 [(M + H)+ calcd for C21H23N5O6S1-
Br1 552.0552]. Anal. (C21H22BrN5O6S‚1.7CF3CO2H) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-([1,1′-bip h en yl]-2-ylsu lfon yl)-
L-a la n in e Tr iflu or oa ceta te (19a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (300 MHz, DMSO-d6) δ 9.40 (bs, 2H), 9.20 (bs, 2H), 8.15
(m, 1H), 8.0 (d, J ) 7.0 Hz, 1H), 7.87 (s, 4H), 7.63 (m, 3H),
7.39 (s, 5H), 7.3 (d, J ) 7.3 Hz, 1H), 4.99 (m, 1H), 3.79 (m,
1H), 3.5 (m, 2H), 3.2 (m, 2H), 2.45 (m, 2H); HRMS (FAB) m/z
550.1753 [(M + H)+ calcd for C27H28N5O6S1 550.1760]. Anal.
(C27H27N5O6S‚1.2CF3CO2H) C, H, N.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[(3-m eth ylph en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (20b). This compound was syn-
thesized in an analogous manner to that used for 34b. The
ester was hydrolyzed following the procedure for 22 in Xue et
al.:20 1H NMR (300 MHz, DMSO-d6) δ 9.35 (bs, 2H), 9.28 (bs,
2H), 8.14 (m, 1H), 8.00 (bs, 1H), 7.87 (m, 4H), 7.60 (m, 2H),
7.42 (m, 2H), 4.94 (m, 1H), 3.82 (m, 1H), 3.54 (m, 1H), 3.40
(m, overlaps with H2O peak, 1H), 3.20 (m, 1H), 3.15 (m, 1H),
2.58 (m, 1H), 2.37 (s, 3H), 2.33 (m, 1H) (carboxylic acid proton
not observed); HRMS (FAB) m/z 488.1605 [(M + H)+ calcd for
C22H26N5O6S 488.1604]. Anal. (C22H25N5O6S‚CF3CO2H) C, H,
N, S. Chiral HPLC analysis (SFC, Chiralcel OD; 0.46 × 25
cm; 30 °C; 2.0 mL/min flow rate; 0.1% TFA, 22% MeOH, 78%
CO2; 280 nM; 150 atm) showed >99% de with respect to the
(S,S)-diastereomer and >98% chemical purity.

1188 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Olson et al.
(S)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[(3-m eth ylph en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (20c). This compound was syn-
thesized in an analogous manner to that used for 34b. The
ester was hydrolyzed following the procedure for 22 in Xue et
al.:20 1H NMR (300 MHz, DMSO-d6) δ 12.81 (s, 1H), 9.36 (bs,
2H), 9.14 (bs, 2H), 8.12 (m, 1H), 7.86 (m, 4H), 7.60 (m, 2H),
7.42 (m, 2H), 4.94 (m, 1H), 3.82 (m, 1H), 3.52 (m,, 1H), 3.30
(m, overlaps with H2O, 1H), 3.20 (m, 2H), 2.73 (m, 1H), 2.37
(s, 3H), 2.33 (m, 1H) (sulfonamide proton not observed); MS
(ESI) m/z 488 [(M + H)+, 100]; HRMS (FAB) m/z 488.1603 [(M
+ H)+ calcd for C22H26N5O6S 488.1604]; 99.3% pure by HPLC.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-[[3-(tr iflu or om eth yl)ph en yl]-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (21a ). This compound
was synthesized in an analogous manner to that used for 34a .
The ester was cleaved using the LiOH protocol described in
the preparation of 22 in Xue et al.:20 1H NMR (400 MHz, D2O)
δ 7.97 (s, 1H), 7.88 (d, J ) 8.1 Hz, 1H), 7.78 (d, J ) 7.7 Hz,
1H), 7.69-7.55 (m, 5H), 4.95-4.90 (m, 1H), 3.87-3.80 (m, 1H),
3.52-3.33 (m, 2H), 3.22-3.06 (m, 2H), 2.41-2.29 (m, 2H)
(amidine protons, amide proton, sulfonamide proton, and
carboxylic acid proton not observed); MS (ESI) m/z 542 [(M +
H)+, 100]. Anal. (C22H22F3N5O6S‚1.5CF3CO2H) C, H, N.
NMR (300 MHz, DMSO-d6) δ 9.38 (bs, 2H), 9.09 (bs, 2H), 8.36
(m, 1H), 8.18 (m, 1H), 7.88 (s, 4H), 7.78 (m, 2H), 7.7 (m, 2H),
5.02 (m, 1H), 3.93 (m, 1H), 3.7-3.0 (m, 4H), 2.6-2.3 (m, 2H);
HRMS (ESI) m/z 552.0537 [(M + H)+ calcd for C21H23BrN5-
SO6 552.0552]. Anal. (C21H22BrN5SO6‚2.0CF3CO2H) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-(1-n a p h th a len ylsu lfon yl)-L-
a la n in e Tr iflu or oa ceta te (27a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (300 MHz, DMSO-d6) δ 9.42-9.26 (bs, 1H), 8.63 (d, J )
8.4 Hz, 1H), 8.22-8.14 (m, 2H), 8.07-7.99 (m, 2H), 7.88-7.84
(m, 4H), 7.73-7.59 (m, 3H), 4.95-4.87 (m, 1H), 3.78-3.69 (m,
1H), 3.54-3.08 (m, partially coincident with H2O, 3H), 3.60-
3.48 (m, 1H), 2.46-2.12 (m, 2H) (amidine protons not ob-
served); MS (ESI) m/z 524 [(M + H)+, 100]. Anal. Calcd for
C
25H25N5O6S‚CF3CO2H: C, 50.86; H, 4.11; N, 10.98. Found:
C, 50.55; H, 4.54; N, 11.36.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-(2-n a p h th a len ylsu lfon yl)-L-
a la n in e Tr iflu or oa ceta te (28a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (500 MHz, CD3OD) δ 8.43 (s, 1H), 8.01 (m, 2H), 7.95 (m,
3H), 7.90-7.82 (m, 3H), 7.65-7.58 (m, 2H), 5.11 (m, 1H), 3.85-
3.81 (m, 1H), 3.68-3.53 (m, 2H), 3.43 (m, 1H), 3.32 (m, 1H),
2.69 (m, 1H), 2.48 (m, 1H) (amidine protons, amide proton,
sulfonamide proton, and carboxylic acid proton not observed);
MS (ESI) m/z 524 [(M + H)+, 100]. Anal. (C25H25N5O6S‚1.6CF3-
CO2H) C, H, N.
(R)-3-[[[3-[4-(Am in oim in om eth yl)p h en yl]-4,5-d ih yd r o-
5-isoxazolyl]acetyl]am in o]-N-m eth yl-N-[(3-m eth ylph en yl)-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (29b). To an ice-cold
(0 °C) dry THF (5 mL) solution of nitrile 11 (0.82 g, 1.69 mmol)
were added sequentially diethylacetylene dicarboxylate (0.35
g, 2.03 mmol), triphenylphosphine (0.53 g, 2.03 mmol), and
dry MeOH (0.07 g, 2.03 mmol). The reaction mixture was
stirred at this temperature for 2 h at which point another
equivalent of DEAD, triphenylphosphine, and MeOH were
added. The reaction was then allowed to warm to room
temperature and stirred for 18 h. Evaporation of the solvents
afforded a crude mixture which was subjected to silica gel
column chromatography (ethyl acetate:hexane, 7:3) to afford
desired product (0.45 g, 53%): mp 148-149 °C; 1H NMR (300
MHz, CDCl3) δ 7.60 (d, J ) 7.9 Hz, 3H), 7.46 (m, 1H), 7.41 (d,
J ) 8.2 Hz, 2H), 6.07 (m, 1H), 5.21 (m, 1H), 4.80 (dd, J ) 4.8,
10.6 Hz, 1H), 3.81 (m, 1H), 3.56 (s, 3H), 3.43 (m, 2H), 3.25
(dd, J ) 7.40, 17.4 Hz, 1H), 2.80 (m, 1H), 2.77 (m 3H), 2.56
(dd, J ) 7.7, 15.1 Hz, 1H), 2.44 (s, 3H); IR (KBr) cm-1 3340,
2224, 1726, 1644, 1610, 1596, 1534, 14440, 1402, 1366, 1300,
1284, 1212, 1144, 1012, 934, 918, 896, 844, 812, 690, 586; MS
(ESI) m/z 499 [(M + H)+, 48]; HRMS (FAB) m/z 499.1649 [(M
+ H)+ calcd for C24H27N4O6S 499.1651].
The benzonitrile (0.45 g, 0.90 mmol) obtained above was
then subjected to the Pinner amidine reaction sequence
described previously to obtain crude amidine which was
saponified with LiOH (0.08 g, 1.80 mmol) in THF/H2O (4:1) (5
mL) to afford crude product which was purified via reverse-
phase HPLC (gradient flow acetonitrile:H2O containing 0.05%
TFA). Lyophilization afforded 29b as colorless crystals (0.12
g, 26%): 1H NMR (300 MHz, DMSO-d6) δ 11.2 (s, 1H), 9.5 (bs,
2H), 9.1 (bs, 2H), 7.98-7.90 (dd, J ) 2.4, 8 Hz, 2H), 7.88-
7.82 (dd, J ) 2.4, 8.0 Hz, 2H), 7.64 (m, 2H), 7.41 (d, J ) 8.0
Hz, 2H), 5.15 (m, 1H), 4.81 (m, 1H), 3.70-3.59 (m, 3H), 3.44-
3.38 (m, 1H), 2.84 (s, rotomer,3H), 2.79-2.70 (dd, J ) 8.0, 16.0
Hz, 1H), 2.58-2.45 (m, 1H), 2.43 (s, 3H); MS (ESI) m/z 502
[(M + H)+, 100]; HRMS (FAB) m/z 502.1912 [(M + H)+ calcd
for C23H27N5O6S 502.1917]. Anal. Calcd for C23H27N5O6S‚CF3-
CO2H: C,48.78; H, 4.58; N, 11.38; F, 9.26. Found: C, 48.35;
H, 4.73; N, 11.6; F, 9.82.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-[(3-b r om op h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (22a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (300 MHz, DMSO-d6) δ 9.38 (bs, 2H), 9.1 (bs, 2H), 8.43
(m, 1H), 8.22 (m, 1H), 7.91 (s, 1H), 7.88 (s, 4H), 7.83 (m, 1H),
7.77 (d, J ) 8 Hz, 1H), 7.53 (m, 1H), 5.0 (m, 1H), 3.95 (m, 1H),
3.6-3.0 (m, 4H), 2.6-2.3 (m, 2H); HRMS (ESI) m/z 552.0544
[(M + H)+ calcd for C21H23BrN5SO6 552.0552]. Anal. (C21H22
BrN5SO6‚1.6CF3CO2H) C, H, N.
-
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(4-m eth ylp h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (23a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (300 MHz, DMSO-d6) δ 9.39 (bs, 2H), 9.15 (bs, 2H), 8.19-
8.08 (m, 2H), 7.97 (d, J ) 1.5 Hz, 4H), 7.66 (d, J ) 8.1, 2H),
7.35 (dd, J ) 8.1, 3.7 Hz, 2H), 5.02-4.92 (m, 1H), 3.91-3.83
(m, 1H), 3.60-3.48 (m, 1H), 3.32-3.04 (m, coincident with
H2O, 4H), 2.56-2.45 (m, coincident with solvent, 1H), 2.39-
2.27 (m, 4H); MS (ESI) m/z 488 [(M + H)+, 100]. Anal.
(C22H25N5O6S‚1.5CF3CO2H) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[[4-(tr iflu or om eth yl)p h en yl]-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (24a ). This compound
was synthesized in an analogous manner to that used for
34a : 1H NMR (400 MHz, DMSO-d6) δ 9.6-9.4 (bs, 2H), 9.26
(s, 2H), 8.08-8.05 (m, 1H), 7.96 (AB quartet, ∆ ) 23.2 Hz, J
) 7.6 Hz, 4H), 7.86-7.84 (m, 4H), 5.01-4.96 (m, 1H), 3.80-
3.78 (m, 1H), 3.56-3.48 (m, 2H), 3.42-3.12 (m, partially
coincident with H2O, 3H), 2.54 (dd, J ) 14.4, 6.1 Hz, 1H), 2.40-
2.31 (m, 1H); HRMS (ESI) m/z 542.1313 [(M + H)+ calcd for
C
22H22F3N5O6S 542.1321].
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(4-p r op ylp h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (25a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H
NMR (500 MHz, DMSO-d6) δ 12.9-12.5 (bs, 1H), 9.31 (s, 2H),
9.22 (s, 2H), 8.05 (dt, J ) 15.7, 5.7 Hz, 1H), 7.86 (d, J ) 2.0
Hz, 4H), 7.67 (dd, J ) 8.2, 1.4 Hz, 2H), 7.35 (dd, J ) 8.2, 4.1
Hz, 2H), 5.00-4.94 (m, 1H), 3.78 (s, 1H), 3.56-3.49 (m, 2H),
3.41-3.36 (m, 0.5H), 3.23-3.16 (m, partially coincident with
H2O, 2H), 3.12-3.07 (m, 0.5H), 2.60 (q, J ) 7.8 Hz, 2H), 2.55-
2.47 (m, partially coincident with solvent), 2.38-2.30 (m, 1H),
1.63-1.54 (m, 2H), 0.87 (dt, J ) 7.3, 3.8 Hz, 3H); MS (ESI)
m/z 516 [(M + H)+, 100]. Anal. (C24H29N5O6S‚1.4CF3CO2H) C,
H, N.
3-[[[3-[4-(Am in oim in om e t h yl)p h e n yl]-5-isoxa zolyl]-
acetyl]am in o]-N-[(3-m eth ylph en yl)su lfon yl]-L-alan in e Tr i-
flu or oa ceta te (30). This compound was synthesized in an
analogous fashion to compound 55 in Xue et al.:20 1H NMR
(300 MHz, DMSO-d6) δ 9.37 (bs, 2H), 9.29 (bs, 2H), 8.42 (m,
1H), 8.1 (d, J ) 8.8 Hz, 2H), 8.05 (m, 1H), 7.92 (d, J ) 8.4 Hz,
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-[(4-b r om op h en yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (26a ). This compound was syn-
thesized in an analogous manner to that used for 34a : 1H

Orally Active Isoxazoline GPIIb/ IIIa Antagonists
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1189
2H), 7.59 (m, 2H), 7.42 (m, 2H), 6.99 (s, 1H), 3.85 (m, 1H), 3.7
(ABquart, ∆ ) 16.5, 23.4 Hz, 2H), 3.16 (d, J ) 4.8 Hz, 2H),
2.37 (s, 3H); HRMS (FAB) m/z 486.1436 [(M + H)+ calcd for
22H24N5O6S 486.1447]. Anal. (C22H23N5O6S‚1.2CF3CO2H) C,
H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
2H), 7.88-7.81 (m, 5H), 5.05 (m, 1H), 4.38 (m, 1H), 3.59-3.39
(m, 2H), 3.24-3.09 (m, 2H), 2.54-2.43 (m, 1H), 2.37-2.31 (m,
1H); HRMS (FAB) m/z (532.1080) [(M + H)+ calcd for
21H22N7S2O6 532.1073]. Anal. (C21H21N7S2O6‚1.7CF3CO2H) C,
H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
C
C
isoxa zolyl]a cetyl]a m in o]-N-[(1-m eth yl-1H-im id a zol-4-yl)-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (31a ). This compound
was synthesized in an analogous fashion to compound 34a :
1H NMR (300 MHz, DMSO-d6) δ 9.8 (bs, 2H), 9.33 (bs, 2H),
8.08 (dt, J ) 16.8, 5.7 Hz, 1H), 7.86/7.85 (2s, 4H), 7.77 (s, 1H),
7.73 (s, 1H), 7.35 (m, 1H), 5.01 (m, 1H), 3.77 (m, 1H), 3.68/
3.67 (2s, 3H), 3.6-3.2 (m, 4H), 2.55 (m, 1H), 2.41 (m, 1H);
HRMS (FAB) m/z 478.1503 [(M + H)+ calcd for C19H24N7O6S1
478.1509]; >99% purity by HPLC.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[(1-p h en yl-1H-p yr a zol-4-yl)-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (32a ). This compound
was synthesized in an analogous fashion to compound 34a :
1H NMR (300 MHz, CD3OD) δ 8.69 (s, 1H), 8.24 (m, 1H), 8.31
(m, 1H), 7.93-7.76 (m, 7H), 7.49 (t, J ) 7.3 Hz, 2H), 7.37 (t,
J ) 7.3 Hz, 1H), 5.11 (m, 1H), 4.17 (m, 1H), 3.77-3.44 (m,
2H), 3.47-3.24 (m, 2H), 2.70 (m, 1H), 2.49 (dd, J ) 7.7, 14.3
Hz, 1H) (amidine protons not observed); HRMS (FAB) m/z
540.1649 [(M + H)+ calcd for C24H25N7O6S 540.1665]. HPLC
analysis (Vydac C18; 0.46 × 25 cm; ambient temperature; 1.0
mL/min flow rate; gradient of 0.05% TFA, 90% H2O, 10% CH3-
CN to 0.05% TFA, 10% H2O, 90% CH3CN over 20 min; 254
nM) showed >99% chemical purity.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxazolyl]acetyl]am in o]-N-[(5-m eth yl-2-fu r an yl)su lfon yl]-
L-a la n in e Tr iflu or oa ceta te (33a ). This compound was syn-
thesized in an analogous fashion to compound 34a : 1H NMR
(300 MHz, CD3OD) δ 8.41 (m, 1H), 8.32 (m, 1H), 7.93 (dd, J )
1.1, 8.8 Hz, 2H), 7.83 (dd, J ) 1.8, 6.6 Hz, 2H), 6.88 (d, J )
3.3 Hz, 1H), 6.14 (m, 1H), 5.10 (m, 1H), 4.15 (m, 1H), 3.77-
3.40 (m, 2H), 3.36-3.12 (m, 2H), 2.70 (m, 1H), 2.51 (m, 1H),
2.32 (s, 3H) (amidine protons and carboxylic acid proton not
observed). Anal. (C20H23N5SO7‚2.0CF3CO2H) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a ce t yl]a m in o]-N -(2-t h ie n ylsu lfon yl)-L-a la -
n in e Tr iflu or oa ceta te (35a ). This compound was synthe-
sized in an analogous manner to that used for 34a : 1H NMR
(400 MHz, DMSO-d6) δ 7.85-7.77 (m, 5H), 7.61 (bs, 1H), 7.57
(d, J ) 1.0 Hz, 1H), 7.12 (dd, J ) 4.9, 3.9 Hz, 1H), 5.04-4.96
(m, 1H), 3.54-3.15 (m, 6H), 2.65-2.53 (m, 1H), 2.46-2.41 (m,
partially coincident with solvent, 1H) (amidine protons and
carboxylic acid not observed); MS (ESI) m/z 480 [(M + H)+,
100]. Anal. (C19H21N5O6S2‚0.7CF3CO2H‚1.6H2O) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-[(2,4-d im et h yl-5-t h ia zolyl)-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (36a ). This compound
was synthesized in an analogous fashion to compound 34a :
1H NMR (300 MHz, DMSO-d6) δ 9.48 (bs, 2H), 9.34 (bs, 2H),
8.46 (bs, 1H), 8.18 (m, 1H), 7.88 (s, 4H), 5.01 (m, 1H), 3.89
(bs, 1H), 3.6-3.0 (m, 4H), 2.61/2.60 (2s, 3H), 2.48 (s, 3H), 2.64-
2.37 (m, 2H); HRMS (FAB) m/z 509.1265 [(M + H)+ calcd for
isoxa zolyl]a cetyl]a m in o]-N-(8-qu in olin ylsu lfon yl)-L-a la -
n in e Tr iflu or oa ceta te (39a ). This compound was synthe-
sized in an analogous fashion to compound 34a : 1H NMR (400
MHz, CD3OD) δ 9.03 (m, 1H), 8.42 (m, 1H), 8.36 (dd, J ) 1.2,
7.1 Hz, 1H), 8.19 (dd, J ) 1.2, 8.3 Hz, 1H), 7.95 (m, 2H), 7.84
(m, 2H), 7.69 (dt, J ) 7.3, 0.7 Hz, 1H), 7.63 (m, 1H), 5.13 (m,
1H), 4.41 (m, 1H), 3.70-3.53 (m, 2.5H), 3.38-3.29 (m, 0.5H),
2.75-2.69 (m, 1H), 2.54-2.48 (m, 1H) (amidine protons, amide
proton, sulfonamide proton, and carboxylic acid proton not
observed); HRMS (FAB) m/z 525.1556 [(M + H)+ calcd for
C24H25N6O6S 525.1572]. Anal. (C24H24N6O6S‚3CF3CO2H‚1.1H2O)
C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[[(2-m eth yleth yl)a m in o]su l-
fon yl]-L-a la n in e Tr iflu or oceta te (40a ). Following the pro-
cedure of Kloek and Leschinsky,32 nitromethane (80 mL) was
stirred and treated with concentrated sulfuric acid (12.5 mL)
and then with 30% fuming sulfuric acid (12.5 mL). The
resulting solution was stirred on ice until below room tem-
perature; then isopropyl isocyanate (25 mL, 250 mmol) was
added over 15 min. The mixture was stirred for 5 min, heated
to reflux for 35 min, and then cooled to room temperature.
After stirring for several hours, the precipitate was collected
by filtration, washed with H2O, and dried to provide isopro-
pylsulfamic acid (6.08 g, 17%) as a sticky white solid: 1H NMR
(300 MHz, DMSO-d6) δ 9.60 (bs, 2H), 3.48 (septet, J ) 7.0 Hz,
1H), 1.24 (d, J ) 7.0 Hz, 6H).
Without further purification, a mixture of this material (4.88
g, 35 mmol) in benzene (70 mL) was treated with phosphorus
pentachloride (7.70 g, 37 mmol), and the mixure was heated
at reflux for 60 min. After cooling and concentration, the
residue was purified by distillation to provide isopropylsul-
famyl chloride (1.21 g, 22%) as a colorless liquid: bp 59-60
°C (0.33 Torr); 1H NMR (300 MHz, CDCl3) δ 5.53 (bs, 1H), 3.90
(septet, J ) 7.0 Hz, 1H), 1.36 (d, J ) 7.0 Hz, 6H); (lit. bp 59-
61 °C (0.25-0.3 Torr).46
This intermediate was elaborated to 40a following the
procedure for 44a : 1H NMR (300 MHz, DMSO-d6) δ 9.49 (bs,
2H), 9.24 (bs, 2H), 8.19 (m, 1H), 7.89 (m, 4H), 7.12 (bt, J )
8.0 Hz, 1H), 6.83 (m, 1H), 5.04 (m, 1H), 3.81 (m, 1H), 3.7-3.2
(m, 6H), 2.60 (m, 1H), 2.45 (m, 1H), 1.08 (m, 6H); MS (ESI)
m/z 455.2 [(M + H)+, 100]. Anal. (C18H26N6O6S‚1.8TFA‚1.2H2O)
C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxazolyl]acetyl]am in o]-N-[[(2-m eth ylpr opyl)am in o]su l-
fon yl]-L-a la n in e Tr iflu or oa ceta te (41a ). Following the
procedure of Audrieth and Sveda,33 a solution of isobutylamine
(29.8 mL, 300 mmol) in CH2Cl2 (250 mL) was cooled to -10
°C. Chlorosulfonic acid (6.65 mL, 100 mmol) was added over
30 min, at a rate to keep the temperature below 10 °C. The
mixture was then warmed to room temperature and concen-
trated. The residue was slurried in a small amount of H2O,
filtered, rinsed with ether, and dried to provide the isobuty-
lamine salt of isobutylsulfamic acid (26.3 g) as a sticky white
solid. This material was stirred in benzene (200 mL), treated
with phosphorus pentachloride (20.8 g, 100 mmol), and heated
at reflux for 2 h. The mixture was cooled and concentrated,
and the residue was taken up in CH2Cl2 and filtered. The
filtrate was concentrated and purified by vacuum distillation
to provide isobutylsulfamyl chloride (8.68 g, 51%) as a colorless
C
20H25N6O6S2 509.1277]. Anal. (C20H24N6O6S2‚1.4CF3CO2H) C,
H, N.
N-[[2-(Acetylam in o)-5-th iazolyl]su lfon yl]-3-[[[3-[4-(am i-
n oim in om eth yl)p h en yl]-4,5-d ih yd r o-5-isoxa zolyl]a cetyl]-
a m in o]-L-a la n in e Tr iflu or oa ceta te (37a ). This compound
was synthesized in an analogous fashion to compound 34a :
1H NMR (300 MHz, DMSO-d6) δ 12.5 (bs, 1H), 9.51 (bs, 2H),
9.36 (bs, 2H), 8.20 (m, 2H), 7.88 (s, 4H), 5.0 (m, 1H), 3.84 (bs,
1H), 3.57-3.07 (m, 4H), 2.44 (s, 3H), 2.56-2.35 (m, 2H), 2.15
(s, 3H); HRMS (FAB) m/z 552.1339 [(M + H)+ calcd for
1
liquid: bp 77-85 °C (0.3 Torr); H NMR (300 MHz, CDCl3) δ
5.87 (bs, 1H), 3.14 (t, J ) 7.0 Hz, 2H), 1.95 (m, J ) 7.0 Hz,
C
21H26N7O7S2 552.1335]; 97.8% purity by HPLC.
1H), 1.02 (d, J ) 7.0 Hz, 6H).
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-(2,1,3-b en zot h ia d ia zol-4-yl-
su lfon yl)-L-a la n in e Tr iflu or oa ceta te (38a ). This compound
was synthesized in an analogous fashion to compound 34a :
1H NMR (300 MHz, DMSO-d6) δ 9.38 (s, 2H), 9.05 (s, 2H), 8.36
(dd, J ) 2.6, 9.2 Hz, 1H), 8.31-8.25 (m, 1H), 8.20-8.12 (m,
A solution of 5 (421 mg, 1.93 mmol) in CH2Cl2 (12 mL) was
stirred on ice and treated with triethylamine (0.40 mL, 2.89
mmol) and isobutylsulfamyl chloride (397 mg, 2.31 mmol). The
mixture was warmed to room temperature, stirred for 14.5 h,
and then concentrated. The residue was purified by flash

1190 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 7
Olson et al.
chromatography (chloroform:2-propanol, 95:5) to provide the
intermediate (632 mg, 93%) as a white solid: mp 122-124 °C;
1H NMR (300 MHz, CDCl3) δ 5.43 (bd, J ) 8.0 Hz, 1H), 4.95
(bt, J ) 8.0 Hz, 1H), 4.48 (bt, J ) 6.0 Hz, 1H), 4.11 (m, 1H),
3.80 (s, 3H), 3.55 (m, 2H), 2.87 (m, J ) 6.5 Hz, 2H), 1.79 (m,
J ) 6.5 Hz, 1H), 1.43 (s, 9H), 0.93 (d, J ) 6.5 Hz, 6H); MS
(NH3-CI) m/z 371 [(M + NH4)+, 7), 354 [(M + H)+, 16), 298
fon yl]-L-a la n in e Tr iflu or oa ceta te (43a ). The sulfamyl chlo-
ride was prepared as in 44a : 1H NMR (300 MHz, CDCl3) δ
7.4-7.1 (m, 5H), 5.58 (bs, 1H), 3.58 (q, J ) 7.5 Hz, 2H), 2.97
(t, J ) 7.5 Hz, 2H). The sulfamoyl chloride was further
elaborated as in 44a to give 43a : 1H NMR (300 MHz, DMSO-
d6) δ 9.40 (bs, 2H), 9.20 (bs, 2H), 8.15 (bq, J ) 8.0 Hz, 1H),
7.88 (s, 4H), 7.3-7.15 (m, 6H), 7.05 (bs, 1H), 5.03 (m, 1H),
3.85 (m, 1H), 3.54 (m, 1H), 3.5-3.2 (m, 2H), 3.20 (m, 1H), 3.04
(m, 2H), 2.74 (m, 2H), 2.59 (m, 1H), 2.42 (m, 1H); MS (ESI)
m/z 517.2 [(M + H)+, 100]. Anal. (C24H28N6O6S‚1.1TFA) C, H,
N.
Bin d in g Assa y. Serial dilutions of experimental compounds
were made in platelet buffer containing NaCl (140 mM), KCl
(2.5 mM), MgCl2 (1 mM), HEPES (50 mM), glucose (5.5 mM),
and BSA (1 mg/mL). Compounds were incubated in the
presence of 3 nM [3H]DMP 728 containing epinephrine-
thrombin-arachadonic acid-collagen platelet activation mix
or [3H]SA202 with 2.5 × 105 platelets in platelet buffer having
a total volume of 150 µL/well in a 96-well polypropylene plate.
Following 30 min of incubation at 37 °C, reaction mixtures
were harvested onto poly(ethylenimine) (PEI)-soaked GF/B
unifilters using a Packard harvester. Filters were rinsed twice
with ice-cold PBS and placed in a drying oven at 37 °C for 15
min. Subsequently, 40 µL of Packard Microscint Cocktail was
added to each filter well, and the plates were sealed and
counted in a Packard Topcount. IC50 values were calculated
using the Michaelis-Menton equation.
[100]; [R]25 ) +24.52° (c ) 0.416, CHCl3).
D
The material was further elaborated to 41a as in 34a : 1H
NMR (300 MHz, DMSO-d6) δ 10.46 (bs, 2H), 9.26 (bs, 2H), 7.99
(bs, 1H), 7.83 (m, 4H), 6.94 (bs, 1H), 6.49 (bs, 1H), 5.00 (m,
1H), 3.7-3.1 (m, 6H), 2.65 (2m, 3H), 2.43 (m, 1H), 1.67 (m,
1H), 0.85 (d, J ) 6.5 Hz, 6H); MS (ESI) m/z 469.2 [(M + H)+,
100]. Anal. (C19H28N6O6S‚1.25TFA‚1.5H2O) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cet yl]a m in o]-N-[[(4-m et h ylp h en yl)a m in o]-
su lfon yl]-L-a la n in e Tr iflu or oa ceta te (44a ). Following the
procedure of Audrieth and Sveda,34 a solution of p-toluidine
(39.45 g, 368 mmol) in chloroform (250 mL) was cooled to -5
°C and treated dropwise over 1.5 h with chlorosulfonic acid
(8.1 mL, 122 mmol). The mixture was warmed to room
temperature, stirred for 20 min, and then filtered, and the solid
was washed with CH2Cl2 and dried. The residue was dissolved
in a solution of sodium carbonate (19.4 g, 183 mmol) in H2O
(600 mL), and the resulting mixture was extracted twice with
ether. The aqueous phase was concentrated, and the solid
residue was extracted with boiling ethanol (500 mL). The
filtrate was concentrated to about 200 mL, cooled, and filtered
to provide sodium 4-methylphenylsulfamate (13.49 g, 53%) as
white plates: 1H NMR (300 MHz, DMSO-d6) δ 7.64 (s, 1H),
6.95 (d, J ) 8.0 Hz, 2H), 6.88 (d, J ) 8.0 Hz, 2H), 2.17 (s, 3H).
This salt (4.18 g, 20 mmol) was treated with phosphorus
pentachloride (4.17 g, 20 mmol) in benzene (65 mL) at reflux
for 24 h. The mixture was filtered, and the filtrate was
concentrated to provide 4-methylphenylsulfamyl chloride (4.0
g, 98%) as a brown liquid, used without further purification:
1H NMR (300 MHz, CDCl3) δ 7.40 (bs, 1H), 7.25 (s, 4H), 2.39
(s, 3H).
A solution of 10 (Re ) tBu) (130 mg, 266 µmol) in CH2Cl2 (3
mL) was cooled on ice and treated with triethylamine (46 µL,
332 µmol) and 4-methylphenylsulfamyl chloride (66 mg, 319
µmol). The mixture was stirred at room temperature for 24 h
and then was concentrated. The residue was purified by flash
chromatography (CH2Cl2:EtOAc, 2:8) to provide the intermedi-
ate (68 mg, 39%) as a glass: 1H NMR (300 MHz, CDCl3) δ
7.75 (m, 2H), 7.51 (t, J ) 8.0 Hz, 2H), 7.08 (s, 4H), 6.67 (m,
1H), 5.90 (bs, 1H), 5.11 (m, 1H), 4.07 (m, 1H), 3.66 (m, 1H),
3.5-3.3 (m, 2H), 3.04 (m, 1H), 2.60 (m, 1H), 2.47 (m, 1H), 2.26
(s, 3H), 1.80 (m, 2H), 1.56 (s, 9H), 1.37 (s, 9H); MS (ESI) m/z
659.3 [(M + H)+, 100].
Ack n ow led gm en t. We would like to express our
thanks to J an Hytrek, Dave Meloni, Todd W. Leathers,
and Gregory Hillyer for technical assistance; Alfred J .
Mical and Andrew M. Blum for performing analytical
and preparative chiral HPLC separations; Will Marshall
(DuPont Central Research and Development) and Harry
Li for providing the crystal structure of DMP 802;
Gregory A. Nemeth and Ernest M. Schubert for as-
sistance in acquiring NMR data; Karl F. Blom, Carl
Schwarz, Michael J . Haas, and Robert F. Carney for
providing low- and high-resolution mass spectral data.
We would also like to express our thanks to Mark S.
Forsythe, J effery M. Bozarth, Randine L. Dowling,
Debra A. Munzer, Sandra K. Flint, Lori L. Foster, Karen
L. Schlingmann, Tracy A. Bozarth, Todd C. Mod-
zelewski, Eric J . Wexler, and William Lorelli for techni-
cal assistance in performing the antiplatelet efficacy,
specificity, and in vivo studies.
Refer en ces
The intermediate (66 mg, 100 µmol) in CH2Cl2 (3 mL) was
treated with trifluoroacetic acid (2 mL) and stirred at room
temperature for 4 h. The solution was diluted with ether, and
the resulting precipitate was collected by filtration and dried
to provide 44a : 1H NMR (300 MHz, DMSO-d6) δ 9.60 (bs, 1H),
9.40 (bs, 2H), 9.20 (bs, 2H), 7.97 (bt, J ) 7.0 Hz, 1H), 7.90 (s,
4H), 7.77 (m, 1H), 7.05 (m, 4H), 4.94 (m, 1H), 3.90 (m, 1H),
3.52 (m, 1H), 3.25 (bt, J ) 7.0 Hz, 1H), 3.10 (m, 1H), 2.5-2.2
(m, 3H), 2.20 (2s, 3H); MS (ESI) m/z 503.2 [(M + H)+, 100].
Anal. (C22H26N6O6S‚1.2TFA) C, H, N.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[[m eth yl(p h en ylm eth yl)a m i-
n o]su lfon yl]-L-a la n in e Tr iflu or oa ceta te (42a ). The sul-
famyl chloride was prepared as in example 44a : 1H NMR (300
MHz, CDCl3) δ 7.4-7.3 (m, 5H), 4.38 (bs, 2H), 2.85 (s, 3H).
This sulfamyl chloride was elaborated to 42a following the
procedure outlined for 44a : 1H NMR (300 MHz, DMSO-d6) δ
13.05 (bs, 1H), 9.38 (bs, 2H), 9.27 (bs, 2H), 8.25 (m, 1H), 7.87
(s, 4H), 7.79 (bt, J ) 9.0 Hz, 1H), 7.33 (m, 5H), 5.05 (m, 1H),
4.19 (s, 2H), 3.95 (bm, 1H), 3.56 (m, 1H), 3.4-3.2 (m, 2H), 2.62
(m, 1H), 2.55 (s, 3H), 2.45 (m, 1H); MS (ESI) m/z 517.2 [(M +
H)+, 100]. Anal. (C24H28N6O6S‚TFA‚1.2H2O) C, H, N, S.
3-[[[3-[4-(Am in oim in om et h yl)p h en yl]-4,5-d ih yd r o-5-
isoxa zolyl]a cetyl]a m in o]-N-[[(2-p h en yleth yl)a m in o]su l-
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