Discovery of a tetrahydropyrimidin-2(1 H)-one derivative (TAK-442) as a potent, selective, and orally active factor Xa inhibitor

Article abstract of DOI:10.1021/jm901699j

Coagulation enzyme factor Xa (FXa) is a particularly promising target for the development of new anticoagulant agents. We previously reported the imidazo[1,5-c]imidazol-3-one derivative 1 as a potent and orally active FXa inhibitor. However, it was found that 1 predominantly undergoes hydrolysis upon incubation with human liver microsomes, and the human specific metabolic pathway made it difficult to predict the human pharmacokinetics. To address this issue, our synthetic efforts were focused on modification of the imidazo[1,5-c] imidazol-3-one moiety of the active metabolite 3a, derived from 1, which resulted in the discovery of the tetrahydropyrimidin-2(1H)-one derivative 5k as a highly potent and selective FXa inhibitor. Compound 5k showed no detectable amide bond cleavage in human liver microsomes, exhibited a good pharmacokinetic profile in monkeys, and had a potent antithrombotic efficacy in a rabbit model without prolongation of bleeding time. Compound 5k is currently under clinical development with the code name TAK-442.

Full text of DOI:10.1021/jm901699j

J. Med. Chem. 2010, 53, 3517–3531 3517
DOI: 10.1021/jm901699j
Discovery of a Tetrahydropyrimidin-2(1H)-one Derivative (TAK-442) as a Potent, Selective, and
Orally Active Factor Xa Inhibitor
Takuya Fujimoto,† Yasuhiro Imaeda,† Noriko Konishi,† Katsuhiko Hiroe,† Masaki Kawamura,† Garret P. Textor,‡
Kathleen Aertgeerts,‡ and Keiji Kubo*,†
†Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd., 2-17-85, Jusohomachi, Yodogawa-ku, Osaka 532-8686, Japan, and
‡Takeda San Diego, Inc., 10410 Science Center Drive, San Diego, California, 92121
Received November 17, 2009
Coagulation enzyme factor Xa (FXa) is a particularly promising target for the development of new
anticoagulant agents. We previously reported the imidazo[1,5-c]imidazol-3-one derivative 1 as a potent
and orally active FXa inhibitor. However, it was found that 1 predominantly undergoes hydrolysis upon
incubation with human liver microsomes, and the human specific metabolic pathway made it difficult to
predict the human pharmacokinetics. To address this issue, our synthetic efforts were focused on
modification of the imidazo[1,5-c]imidazol-3-one moiety of the active metabolite 3a, derived from 1,
which resulted in the discovery of the tetrahydropyrimidin-2(1H)-one derivative 5k as a highly potent
and selective FXa inhibitor. Compound 5k showed no detectable amide bond cleavage in human liver
microsomes, exhibited a good pharmacokinetic profile in monkeys, and had a potent antithrombotic
efficacy in a rabbit model without prolongation of bleeding time. Compound 5k is currently under
clinical development with the code name TAK-442.
Introduction
FXa byhighlyselectiveinhibitorseffectively inhibitsa burst of
thrombin generation and prevents both venous and arterial
thrombosis in animals, without a significant increase in
bleeding.6 Hence, selective FXa inhibitors have been sought
as new safe and efficacious anticoagulants,7 and indeed, a
wide variety of novel and selective FXa inhibitors have been
reported.8 Rivaroxaban9 was approved for the prevention of
venous thromboembolism in both the E.U. and Canada in
2008, and several orally active FXa inhibitors such as Apix-
aban,10 Eribaxaban,11 and Edoxaban12 have been advancing
in late clinical stages.
We previously reported on the discovery of the imidazo[1,5-c]-
imidazol-3-one derivative 1 as a potent and orally active
FXa inhibitor.13 Compound 1 exhibited potent inhibitory
activity against human FXa (IC50 = 4.8 nM) and potent
anticoagulant activity (PT2 = 1.0 μM, the concentration of
compound required to double the clotting time in a human
prothrombin time (PT) assay) with a favorable pharmaco-
kinetic profile in monkeys (bioavailability: BA = 46%).
However, during the course of our preclinical development
program of 1, it was found that the metabolic hydrolysis of
1 was observed on incubating with human liver micro-
somes (HLM) (Table 1). In a metabolic study of 1 using
HLM in the absence of NADPH, the carboxylic acid 2, which
mightbe liberatedbyhydrolyticmetabolismof1, wasdetected
in23.3%yieldin addition tothe parent compound1 (Table1).
On the other hand, in the case of incubation with monkey
liver microsomes, intact 1 remained with no detectable
amount of 2 (Table 1). The fact that the stability toward
metabolic hydrolysis depended on the species made human
pharmacokinetics difficult to be predicted. To minimize the
influence of the human specific metabolic pathway on the
pharmacokinetics, we focusedour researchonidentifying new
Thrombotic disease, such as deep vein thrombosis, pul-
monary embolism, acute myocardial infarction, unstable
angina, and ischemic stroke is a major cause of morbidity
and mortality in developed countries.1 Anticoagulant therapy
with heparins, low molecular weight heparins (LMWH),2 and
warfarin3 has been widely used for the treatment and preven-
tion of thrombotic diseases. Warfarin is the only oral anti-
coagulant available for long-term use, but has several draw-
backs including a narrow therapeutic window, large inter- and
intrapatient variability, drug-drug interactions, food effects,
slow onset and offset of action, and the requirement of
frequent coagulation monitoring. Therefore, there is a sig-
nificant unmet medical need for oral anticoagulants with a
superior safety for chronic usage.4 Factor Xa (FXaa) is a
trypsin-like serine protease that is located at the convergence
of the intrinsic and extrinsic pathways of the coagulation
cascade and plays a pivotal role in blood coagulation.5 FXa
forms a prothrombinase complex with factor Va and calcium
ion on a phospholipid surface, generating thrombin via
proteolysis of prothrombin. Thrombin causes fibrin forma-
tion, activates platelets, and provides positive feedback to
the coagulation cascade, resulting in thrombus formation.
Extensive preclinical studies have shown that inactivation of
*Corresponding author. Tel: þ81-6-6300-6280. Fax: þ81-6-6300-
6206; e-mail: Kubo_Keiji@takeda.co.jp.
a Abbreviations: FXa, factor Xa; HLM, human liver microsomes;
LMWH, low molecular weight heparins; PT, prothrombin time; BA,
bioavailability; NADPH, nicotinamide adenine dinucleotide phosphate;
CYP, cytochrome P450; WSC, 1-[3-(dimethylamino)propyl]-3-ethylcar-
bodiimide hydrochloride; HOBt, 1-hydroxybenzotriazole hydrate; CDI,
1,10-carbonyldiimidazole; DBU, 1,8-diazabicyclo[5.4.0]-7-undecene;
t-PA, tissue plasminogen activator.
r
2010 American Chemical Society
Published on Web 03/31/2010
pubs.acs.org/jmc

3518 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
Table 1. Hydrolytic Conversion of 1 to 2 in Human or Monkey Liver Microsomes
liver microsomes
% of 1 remaining
% yield of 2
human
monkey
70.5
99.9
23.3
0.0
Table 2. In Vitro Activities and Metabolic Stabilities for Compounds 1, 3a, 3b and 4
metabolic stability, NADPH (-)
human FXa
IC50 (nM)a
compd
R1
R2
PT2 (μM)b
(% yield of acid)c, human/monkey
1
H
H
4.8 (4.6-5.1)
2.1 (1.9-2.2)
21 (17-25)
1.0
23.3/0.0
4.4/0.0
0.6/0.0
10.6/0.0
3a
3b
4
(S)-OH
(R)-OH
H
H
0.92
1.9
H
OH
8.0 (7.5-8.6)
0.83
a Inhibitory activity against human FXa. Data are from duplicate experiments. IC50 values and 95% confidence limits are calculated from the
concentration-response curves generated by logistic regression and shown in parentheses. b PT2 is defined as the concentration of compound required to
double the time to clot formation in the PT (prothrombin time) assay. PT2 values shown are the mean of duplicate measurements. c Metabolic stability is expressed
as the percent yield of the corresponding acid liberated after incubation with human or monkey liver microsomes in the absence of NADPH at 37 °C for 2 h.
FXa inhibitors with improved stability toward hydrolysis in
HLM.
aromatic rings of Tyr99, Phe174, and Trp215 in the S4 site of
FXa.14 The imidazoimidazolone moiety in 3a seemed to be
replaceable with other bicyclic or monocyclic heterocycles
that can form hydrophobic interactions with the S4 site. Thus,
our synthetic efforts were focused on optimization of the
imidazoimidazolone moiey in 3a to improve the stability
toward hydrolytic metabolism in HLM without the loss of
FXa inhibitory activity. In this report, we describe the dis-
covery of a highly potent and orally active FXa inhibitor 5k
(TAK-442)16 as a clinical candidate with improved metabolic
stability in HLM.
In the course of metabolic studies on 1, the R-hydroxy
derivatives 3a and 3b, and the hydroxymethyl derivative 4
were identified as active metabolites after oral administration
in rats or monkeys.14 Their FXa inhibitory activities (IC50=
2.1, 21, and 8.0 nM for 3a, 3b, and 4, respectively) and anti-
coagulant activities (PT2=0.92, 1.9, and 0.83 μM for 3a, 3b,
and 4, respectively) are shown in Table 2. A significantly
improved stability toward hydrolysis in HLM was observed
for 3a and 3b (4.4% and 0.6% yield of the corresponding acid,
respectively) compared to the parent compound 1 (23.3%
yield of 2). This result indicated that the hydroxy groups at the
R-position of the amide carbonyl group in 3a and 3b might
prevent the close approach of a nucleophile to the amide
carbonyl group by serving as a substantial blocking substitu-
ent.15 Thus, we thought that the R-hydroxy groups of 3a and
3b might be the key substituent for the improvement of
stability toward hydrolysis. Hydroxymethyl derivative 4 was
also more stable toward hydrolysis in HLM (10.6% yield of 2)
than the parent compound 1. Since the introduction of a
hydroxymethyl group into the imidazoimidazolone moiety,
distant from the amide bond, led to improved stability of4, we
postulated that the imidazoimidazolone moiety might be
involved in substrate recognition of hydrolytic enzymes.
Therefore, we thought that modification of the imidazoimi-
dazolone moiety in 3a, the eutomer of the R-hydroxy deriva-
tives, could also improve the stability toward hydrolysis.
Meanwhile, our binding model for 3a in FXa revealed that
the imidazoimidazolone moiety in 3a formed no obvious
hydrogen bond but the hydrophobic interactions with the
Chemistry
The synthesis of compounds 5a-p is outlined in Scheme 1.
Compounds 5a-p were prepared by the condensation of
carboxylic acid 614 with piperidine derivatives 7a-p using
1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochlor-
ide (WSC) and 1-hydroxybenzotriazole hydrate (HOBt), with-
out deterioration of enantiomeric purity. Piperidines 7a-i and
7k-p were synthesized via deprotection of protected piperi-
dines 8a-iand 8k-punder the appropriate conditions, while 7j
was commercially available.
The piperidine derivatives bearing a bicyclic heterocycle
8a-d were synthesized as shown in Scheme 2. The reductive
amination of aldehyde 9 with 4-amino-1-benzylpiperidine 10
followed by cyclization using 1,10-carbonyldiimidazole (CDI)
and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) gave 8a. The
isoindolin-1-one derivative 8b was synthesized by condensa-
tion of isobenzofuran-1(3H)-one 11 with 10. Reductive ami-
nation of commercially available aldehydes 12a and 12b with
10 gave amines 13a and 13b, respectively. Trifluoroacetic acid

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3519
Results and Discussion
Scheme 1. Synthesis of Compounds 5a-pa
The compoundsthus synthesized were evaluated for theirin
vitro inhibitoryactivityagainst human FXa, expressed as IC50
values, and for their activity in the prolongation of human PT,
expressed as PT2. To estimate their stability toward metabolic
hydrolysis, the yield of acid 6 was determined after incubation
with human or monkey liver microsomes in the absence of
NADPH at 37 °C for 2 h. The oxidative metabolic stability
of compounds was determined after incubation with human
or monkey liver microsomes in the presence of NADPH at
37 °C for 20 min, and is expressed as the percent elimination.
The log D values were determined at pH 7.4 by the reported
method.17
Replacement of the imidazoimidazolone moiety in 3a with
the other heterocycles resulted in improved hydrolytic stabi-
lity in HLM, and no detectable amount of the carboxylic acid
6 was observed after incubation with HLM in the absence of
NADPH, except 5i (Tables 3-5). Minor structural changes,
such as changing one nitrogen atom to a carbon atom and
removing one methyl group from 3a, made a remarkable
change in stability. These observations indicated that the
imidazoimidazolone moiety in 3a might be specifically recog-
nized by the metabolizing enzyme(s). In contrast, log D values
seemed not to affect the stability toward hydrolysis in HLM,
at least for log D values in the range 1.56-2.60.
a Reagents and conditions: (a) Pd(OH)2/C, H2, MeOH, room temp.,
67%-quant.; (b) Pd/C, HCO2NH4, MeOH, reflux, 90%-quant.;
(c) Pd/C, H2, MeOH, room temp., quant.; (d) 6, WSC, HOBt, DMF,
room temp., 9-54%.
Scheme 2. Synthesis of Piperidine Derivatives 8a-da
The in vitro activities of compounds 5a-d bearing various
bicyclic rings in place of the imidazoimidazolone ring of 3a
were investigated, and the results are shown in Table 3.
Pyrrolo[1,2-c]imidazol-3-one derivative 5a was evaluated to
examine the effect of the nitrogen atom at the 6-position of
the imidazoimidazolone ring in 3a on potent FXa inhi-
bitory activity. Compound 5a (IC50 = 1.7 nM) was found
to exhibit comparable FXa inhibitory activity to that of 3a
(IC50=2.1 nM). Replacement of the pyrrole ring in 5a with a
phenyl ring resulted in 5b (IC50 = 2.3 nM) that has an
equipotent FXa inhibitory activity to 5a. These results sup-
ported our hypothesis that the imidazole ring in 3a was not
essential for potent FXa inhibitory activity and could be
replaced. The saturated bicyclic analogues 5c and 5d (IC50=
24, 51 nM, respectively) showed more than 10ꢀ lower FXa
inhibitory activities compared to the aromatized analogue 5a.
These bicyclic imidazolones 5a-d have less potent anti-
coagulant activity than 3a.
Furthermore, compounds 5a-d showed poor stability
toward oxidative metabolism in human or monkey liver
microsomes compared to 3a (Table 3). Since this metabolic
instability seemed to be derived from the bicyclic imidazolone
moieties, we decided to remove the methylimidazole part in
3a. As can be seen from Table 3, imidazolidinone analogue 5e
exhibited improved stability toward oxidative metabolism
and moderateFXa inhibitory activitywith excellent resistance
against metabolic hydrolysis. Interestingly, imidazolidinone
derivative 5e has more potent anticoagulant activity (PT2=
1.1μM) than5a-d (PT2=1.7-2.7μM) in spite of its moderate
FXa inhibitory activity (IC50 = 23 nM). These results sug-
gested that improvement in the anticoagulant activity of 5e
might be attributed to its lower lipophilicity (log D=1.73 and
2.16-2.60 for 5e and 5a-d, respectively). It has been reported
that high lipophilicity is likely to result in high plasma protein
binding; therefore, the FXa inhibitory activities of the less
lipophilic compounds are more effectively translated into in
vitro anticoagulant activities.18 Thus, we chose to investigate
the monocyclic analogue of 5e to enhance the FXa inhibitory
a Reagents and conditions: (a) (1) 4-amino-1-benzylpiperidine 10,
NaBH(OAc)3, AcOH, CH2Cl2, 0 °C to room temp., (2) CDI, DBU,
CH3CN, reflux, 29% for two steps; (b) 10, neat, 200 °C, 49%; (c) 10,
NaBH3CN, AcOH, MeOH, room temp., 86-89%; (d) (1) TFA,
CH2Cl2, room temp., (2) CDI, DBU, CH3CN, room temp., 88-89%
for two steps.
mediated removal of the Boc group in 13a and 13b, followed
by cyclization using CDI, afforded 8c and 8d, respectively.
The synthesis of piperidines having a varied monocyclic ring is
depicted in Scheme 3. Reductive amination of the commercially
available piperidone 14 with amines 15a and 15b provided
compounds 16a and 16b, respectively. Cleavage of the Boc group
in 16a and 16b, using4MHClinEtOAc, followedbycyclization
using CDI and DBU, afforded 8e and 8k, respectively. Oxazoli-
dinone 8g and oxazinanone 8l were prepared by a similar method
using 17a and 17b as the amines for the reductive amination.
Acylation of the secondary amino group in 18a with chloroacetyl
chloride and subsequent intramolecular cyclization using
sodium hydride gave the morpholinone 8m. The piperidine
derivatives 8h, 8i, 8n, and 8p were prepared by acylation or
sulfonylation of the primary amino group of piperidine 10 with
the corresponding acid chlorides in the presence of pyridine,
followed by intramolecular alkylation in the presence of a base.
Scheme 4 illustrates the synthesis of the imidazolone ana-
logue 8f and the tetrahydropyrazinone analogue 8o. Nucleo-
philic addition of 2-aminoacetaldehyde dimethyl acetal to
isocyanate 19 gave 20, which was subsequently treated with
aqueous HCl afforded 8f. Boc-protected hydrazine 21, which
was synthesized from 14 and tert-butyl carbazate by reductive
amination, was converted into 22 by alkylation and acyla-
tion, and successive removal of the Boc group in 22 furnished
8o. Compound 23 was synthesized by condensation of 2
with piperidine 7k using WSC and HOBt, as shown in Scheme 5.

3520 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
Scheme 3. Synthesis of Piperidines Bearing a Monocyclic Ring 8e, 8g-i, 8k-n and 8pa
a Reagents and conditions: (a) NaBH(OAc)3, AcOH, 1,2-dichloroethane, 0 °C to room temp., quant.; (b) 4 M HCl/EtOAc, EtOAc, room temp.,
85-91%; (c) CDI, DBU, CH3CN, room temp., 83%-quant.; (d) (1) chloroacetyl chloride, Et3N, THF, 0 °C, (2) NaH, DMF, 0 °C to room temp., and
then 80 °C, 44% for two steps; (e) (1) pyridine, CH2Cl2, 0 °C to room temp., (2) NaH, THF, room temp., and then reflux, 33-80% for two steps.
Scheme 4. Synthesis of Piperidines Bearing a Monocyclic Ring 8f and 8oa
a Reagents and conditions: (a) H2NCH2CH(OMe)2, CH3CN, room temp., quant.; (b) aq. HCl, MeOH-H2O, room temp., 90%. (c) H2NNHBoc,
NaBH3CN, AcOH, MeOH, 0 °C to room temp., quant.; (d) (1) Br(CH2)3COCl, Et3N, THF, 0 °C, (2) NaH, THF, room temp., quant. for two steps; (e)
TFA, CH2Cl2, room temp., quant.
Scheme 5. Synthesis of Compound 23a
(IC50=14 nM, PT2 =0.97 μM) exhibited comparable FXa
inhibitory and anticoagulant activities to 5e (IC50=23 nM,
PT2 =1.1 μM), while the FXa inhibitory activities of cyclic
sulfonamide analogue 5i (IC50 = 198 nM) and pyrroridine
analogue 5j (IC50 = 147 nM) were significantly decreased.
These results indicated that the carbonyl group in the terminal
ring is important for FXa inhibitory activity by bringing the
a Reagents and conditions: (a) WSC, HOBt, Et3N, DMF, room
temp., 76%.
terminal ring into a perpendicular arrangement to the inner
piperidine ring to make a favorable hydrophobic interaction
with the S4 site.
and anticoagulant activities while maintaining good meta-
bolic stability.
To increase the FXa inhibitory and anticoagulant activities,
we investigated six- and seven-membered heterocycles bearing
a carbonyl group, which were designed to increase hydro-
phobic interactions with the S4 site by ring expansion
(Table 5). Among the compounds synthesized, tetrahydro-
pyrimidinone 5k and morpholinone 5m displayed the most
potent FXa inhibitory and anticoagulant activities (IC50=3.5
and 3.6 nM, PT2=0.58 and 0.74 μM, respectively). One atom
The assay results for five-membered monocyclic analogues
5f-j are shown in Table 4. Introduction of a double bond into
the dihydroimidazolone ring in 5e resulted in a slight decrease
in FXa inhibitory activity (5f, IC50=46 nM). Replacement of
a nitrogen atom in 5e with an oxygen atom also slightly
reduced the activity (5g, IC50 = 60 nM). Pyrrolidinone 5h

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3521
Table 3. In Vitro Activities for Compounds 3a and 5a-e
a,b,c Refers to Table 2. d Metabolic stability is expressed as the percent elimination of compounds after incubation with human or monkey liver
microsomes in the presence of NADPH at 37 °C for 20 min. e Measured at pH 7.4.
exchange in the tetrahydropyrimidinone ring in 5k has an
apparent effect on activity. For example, 1,3-oxazinanone 5l,
piperidinone 5n, and tetrahydropyridazinone 5o showed de-
further evaluation. To estimate their oral bioavailability in
monkeys, cassette dosing experiments were performed on 5k
and 5m, and their pharmacokinetic parameters are shown in
Table 7. Tetrahydropyrimidinone derivative 5k showed better
oral bioavailability and longer duration at a dose of 1 mg/kg
creased FXa inhibitory and anticoagulant activities (IC50
=
20, 9.1, and 49 nM, PT2=1.1, 0.81, and 2.5 μM, respectively).
Extension of the ring size also resulted in reduced activities
(5p, IC50=28 nM, PT2=1.5 μM). These results suggested that
among the five- to seven-membered rings a six-membered ring
might be the most favorable size for hydrophobic interactions
with the aromatic rings in the S4 site.
(AUC=760 ng h/mL, BA=52.5%, MRTpo=6.96 h) than 5m
3
(AUC=335 ng h/mL, BA=33.2%, MRTpo=5.58 h). The
3
better stability of 5k toward oxidative metabolism in monkey
liver microsomes compared to 5m is reflected in its better
pharmacokinetic profile in monkey. Futhermore, 5k showed
better metabolic stability toward oxidative metabolism in
HLM than in monkey liver microsomes. Therefore, we chose
5k as a clinical candidate, which is expected to avoid the
potential concern of metabolic hydrolysis in humans and to
exhibit a favorable pharmacokinetic profile in humans com-
parable to that found in monkeys.
Regarding the stability toward oxidative metabolism, the
monocyclic derivatives 5e-g and 5k-m showed improved
stability in HLM and monkey liver microsomes relative to
bicyclic derivatives 3a and 5a-d. Introduction of a hetero-
atom into the rings seems to increase the stability, and the
compounds with lower log D values tended to be more stable.
To confirm the impact of the presence of the hydroxy group
in5k onstability towardhydrolysis inHLM, the stability of 23
without the hydroxy group was examined (Table 6). Com-
pound 23 was less stable compared to5k, and this result shows
that the hydroxy group at the R-position of the amide
carbonyl is also important for suppression of metabolic
hydrolysis in HLM. In addition, the hydroxy group of 5k
also had an incremental effect on FXa inhibitory activity, as
observed for 3a vs 1 (IC50=3.5, 11, 2.1, and 4.8 nM for 5k, 23,
3a, and 1, respectively), which was explained by the X-ray
structural analysis described below.
Since selectivity over other trypsin-like proteases is an
important consideration for the development of FXa inhi-
bitors,19 the selectivity profile of 5k was evaluated against
other human serine proteases such as thrombin, factor IXa,
kallikrein, t-PA, trypsin, activated protein C, and plasmin
(Table 8). Compound 5k displayed good selectivity for FXa
over these serine proteases (more than 500-fold).
Finally, the in vivoantithrombotic efficacy of compound5k
was evaluated in a rabbit venous thrombosis model.20 It was
found that compound 5k at 50 and 100 μg/kg, i.v. (given as a
bolus [1/2 of total dose] followed by a constant infusion for
1 h) significantly inhibited venous thrombus formation by
50% and 81%, respectively, and did not affect the bleeding
Considering their excellent anticoagulant activity and good
metabolic stability in HLM, 5k and 5m were selected for

3522 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Table 4. In Vitro Activities for Compounds 5e-j
Fujimoto et al.
a,b,c,d,e Refers to Table 2 and Table 3.
time even at a higher dose of 500 μg/kg, i.v. Detailed
pharmacological evaluation of 5k will be reported in due
course.
bond with the Gln192 main chain nitrogen. Overall, com-
pound 5k fits into the FXa active site in a highly complemen-
tary manner.
On the basis of its potent inhibitory activity against FXa,
potent anticoagulant activity, improved stability toward meta-
bolic hydrolysis in HLM, good selectivity over other human
serine proteases, favorable pharmacokinetic profile in mon-
keys, and in vivo antithrombotic efficacy without prolonga-
tion of bleeding time in rabbit model, compound 5k was
selected as a development candidate and is currently under-
going phase II clinical trials.
Conclusion
To address the vulnerability of our FXa inhibitor 1 toward
metabolic hydrolysis in HLM, chemical modification of the
imidazoimidazolone moiety in active metabolite 3a, which
showed improved stability toward hydrolysis, was conducted.
Replacement of the imidazoimidazolone ring in 3a with other
bicyclic and monocyclic rings resulted in the discovery of
tetrahydropyrimidinone derivative 5k as a potent and selec-
tive FXa inhibitor. Compound 5k showed no detectable
formation of carboxylic acid 6 in HLM and exhibited a
favorable pharmacokinetic profile in monkeys and potent
antithrombotic efficacy in a rabbit model without prolonga-
tion of bleeding time. Compound 5k was selected and is under
clinical trials.
X-ray Crystallography of Compound 5k
The X-ray structure of compound 5k in complex with
human FXa was obtained at a very high resolution of
˚
1.45 A (Figure 1). The 6-chloronaphthyl group occupies the
S1 substrate binding site and points into the site where it
makes a hydrophobic interaction with the aromatic ring of
Tyr228. A hydrogen-bonding interaction between the oxygen
atom of the amide carbonyl in 5k and the backbone amide
nitrogen of Gly219 is observed. The hydroxy group at the
R-position of the amide carbonyl forms a hydrogen bond with
the nitrogen atom of the main chain Gly216. This hydrogen-
bonding interaction could account for the increase in FXa
inhibitory activity of 5k compared to compound 23. The
tetrahydropyrimidinone moiety is located in the S4 site mak-
ing hydrophobic interactions with the aromatic rings of
Tyr99, Phe174, and Trp215. The carbonyl oxygen of the
tetrahydropyrimidinone moiety makes a water-mediated
interaction with the backbone carbonyl oxygen of Lys96,
and brings it into a perpendicular arrangement to the inner
piperidine ring. The sulfone oxygen is involved in a hydrogen
Experimental Section
Melting points were determined with a Yanagimoto melting
point apparatus or a Buchi meltingpointapparatusB-545 andare
€
uncorrected. 1H NMR spectra were obtained at 200 or 300 MHz
on a Varian Gemini-200 or a Varian Ultra-300 spectrometer.
Chemical shifts are given in δ values (ppm) using tetramethyl-
silaneas the internal standard. Peak multiplicitiesare expressed as
follows. Abbreviations are used as follows: s, singlet; d, doublet; t,
triplet; q, quartet; dd, doublet of doublet; brs, broad singlet; m,
multiplet. Specific rotations were measured with a JASCO DIP-
370 or a JASCO P-1030 digital polarimeter. Elemental analyses
were carried out by Takeda Analytical Laboratories Ltd. Reac-
tions were followed by TLC on Silica gel 60 F 254 precoated TLC
plates (E. Merck) or NH TLC plates (Fuji Silysia Chemical Ltd.).

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3523
Table 5. In Vitro Activities for Compounds 5k-p
a,b,c,d,e Refers to Table 2 and Table 3.
Table 6. Effect of the Hydroxy Group in 5k on Activity and Hydrolytic Stability in HLM
metabolic stability, NADPH (-)
human FXa
IC50 (nM)a
human PT
PT2 (μM)b
compd
R
(% yield of acid)c, human/monkey
5k
23
OH
H
3.5 (3.3-3.7)
11 (10-12)
0.58
1.4
0.0/0.0
4.6/0.0
a,b,c Refers to Table 2.
Table 7. Pharmacokinetic Profiles in Monkeys for 5k and 5m (Cassette Dosing, n = 3)
0.1 mg/kg, i.v.
1.0 mg/kg, p.o.
compd
Vd(ss) (mL/kg)
CLtotal (mL/h/kg)
AUCpo (ng h/mL)
MRTpo (h)
BA(%)
3
5k
5m
579 ( 174
687 ( 18
708 ( 289
1001 ( 215
760 ( 220
335 ( 42.2
6.96 ( 1.21
5.58 ( 1.12
52.5 ( 19.1
33.2 ( 6.6
Chromatographic separations were carried out on silica gel 60
(0.063-0.200 or 0.040-0.063 mm, E. Merck) or basic silica gel
(Chromatorex NH, 100-200 mesh, Fuji Silysia Chemical Ltd.)
using the indicated eluents. Yields are unoptimized. Chemical
intermediates were characterized by 1H NMR. The purities of all
compounds tested in biological systems were assessed as being
>95% using analytical HPLC. The HPLC analyses were per-
formed using a Shimadzu UFLC instrument. Elution was done
with a gradient of 5-90% solvent B in solvent A (solvent A was
0.1% TFA in water, and solvent B was 0.1% TFA in acetonitrile)
through a L-column 2 ODS (3.0 ꢀ 50 mm, 2 μm) column at 1.2
mL min-1. Area % purity was measured at 254 nm.
1-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)tetrahydropyrimidin-2(1H)-one (5k).
To a solution of 6 (0.53 g, 1.70 mmol), 7k (0.31 g, 1.70 mmol),
and HOBt (0.26 g, 1.70 mmol) in DMF (10 mL) was added WSC

3524 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
Table 8. Inhibitory Activity of Compound 5k for Human FXa, Thrombin, Factor IXa, Kallikrein, t-PA, Trypsin, Activated Protein C, and Plasmin
IC50 values (nM)a
enzymes
FXa
enzymes
IC50 values (nM)a
2.2 (2.0-2.4)
1200 (1100-1300)
4500 (3700-5400)
12000 (11000-13000)
t-PA
Trypsin
44 000 (38 000-52000)
>60 000
>60 000
Thrombin
Factor IXa
Kallikrein
Activated protein C
Plasmin
>60 000
a Data were from duplicate experiments. The 95% confidence intervals are shown in parentheses. See Experimental Section.
Figure 1. X-ray structure of compound 5k (white carbons) in complex with human FXa. The amino acids (blue carbons, yellow text) and binding
sites (white text) are indicated. The hydrogen bonds are shown as yellow dotted lines, where water molecules are shown as red cross marks.
(0.32 g, 1.70 mmol). The mixture was stirred at room tempera-
ture for 15 h and concentrated in vacuo. The residue was
partitioned between CH2Cl2 and an aqueous solution of
NaHCO3. The organic layer was separated, washed with water,
5% aqueous solution of citric acid, and brine, dried over
anhydrous Na2SO4, and concentrated in vacuo. The residue
was purified by silica gel column chromatography (EtOAc to
EtOAc/MeOH = 10:1). The product was recrystallized from
EtOAc to give 5k (0.12 g, 15%) as colorless crystals, mp
4.68-4.76 (1H, m), 5.00-5.08 (1H, m), 7.46-7.61 (4H, m), 7.86
(1H, d, J=7.4 Hz), 7.95-7.98 (4H, m), 8.52 (1H, s). Anal. Calcd
for C26H25ClN2O5S H2O: C, 58.81; H, 5.12; N, 5.28. Found: C,
3
58.74; H, 5.17; N, 5.24. [R]25D þ18.6 (c 0.25, CHCl3).
(7aS)-2-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hy-
droxypropanoyl}piperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]imid-
azol-3-one (5c). Compound 5c was prepared in a manner similar
to that described for 5k in 39% yield as a colorless powder, mp
154-155 °C. 1H NMR (200 MHz, CDCl3) δ: 1.18-1.39 (1H, m),
1.49-1.65 (2H, m), 1.78-2.02 (5H, m), 2.63-2.81 (1H, m),
3.00-3.17 (3H, m), 3.39-3.54 (3H, m), 3.59-3.85 (3H, m),
3.88-4.15 (2H, m), 4.55-4.70 (1H, m), 4.90-5.05 (1H, m), 7.59
(1H, dd, J=2.2, 8.8 Hz), 7.94 (3H, s), 7.96 (1H, d, J=8.8 Hz),
8.52 (1H, s). Anal. Calcd for C24H28ClN3O5S: C, 56.97; H,
1
173-174 °C. H NMR (300 MHz, CDCl3) δ: 1.57-1.78 (4H,
m), 1.90-1.93 (2H, m), 2.70-2.76 (1H, m), 3.11-3.20 (3H, m),
3.27-3.30 (2H, m), 3.40-3.48 (2H, m), 3.78-3.90 (1H, m),
3.94-3.99 (1H, m), 4.56-4.66 (3H, m), 4.97-5.03 (1H, m), 7.59
(1H, dd, J=1.8, 8.7 Hz), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal.
Calcd for C22H26ClN3O5S: C, 55.05; H, 5.46; N, 8.75. Found:
C, 54.96; H, 5.57; N, 8.80. [R]25D þ21.6 (c 1.0875, CHCl3).
2-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)-1,2-dihydro-3H-pyrrolo[1,2-c]imid-
azol-3-one (5a). Compound 5a was prepared in a manner similar
to that described for 5k in 48% yield as a colorless powder, mp
195-196 °C. 1H NMR (300 MHz, CDCl3) δ: 1.60-1.90 (2H, m),
1.90-2.09 (2H, m), 2.66-2.95 (1H, m), 3.11-3.36 (1H, m),
3.38-3.54 (2H, m), 3.62-3.86 (1H, m), 3.98-4.17 (1H, m),
4.20-4.36 (3H, m), 4.61-4.79 (1H, m), 4.93-5.15 (1H, m), 6.06
(1H, d, J=1.7 Hz), 6.39 (1H, t, J=3.1 Hz), 7.05-7.16 (1H, m),
7.60 (1H, dd, J=2.1, 8.7 Hz), 7.87-8.04 (4H, m), 8.52 (1H, s).
Anal. Calcd for C24H24ClN3O5S: C, 57.42; H, 4.82; N, 8.37.
Found: C, 57.41; H, 4.79; N, 8.44. [R]25D þ20.8 (c 0.25, CHCl3).
2-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)isoindolin-1-one (5b). Compound 5b
was prepared in a manner similar to that described for 5k in
25% yield as a colorless powder, mp 200-201 °C. 1H NMR (300
MHz, CDCl3) δ: 1.68-1.87 (3H, m), 1.88-2.05 (2H, m),
2.77-2.90 (1H, m), 3.22-3.35 (1H, m), 3.44-3.51 (2H, m),
4.05-4.10 (1H, m), 4.33-4.36 (2H, m), 4.52-4.60 (1H, m),
5.58; N, 8.30. Found: C, 56.91; H, 5.55; N, 8.43. [R]25 -45.1
D
(c 0.25, MeOH).
(7aR)-2-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hy-
droxypropanoyl}piperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]imid-
azol-3-one (5d). Compound 5d was prepared in a manner similar
to that described for 5k in 52% yield as a colorless powder, mp
166-167 °C. 1H NMR (300 MHz, CDCl3) δ: 1.22-1.38 (1H, m),
1.48-1.62 (2H, m), 1.71-1.99 (5H, m), 2.66-2.80 (1H, m),
3.03-3.24 (3H, m), 3.36-3.52 (3H, m), 3.61-3.69 (2H, m),
3.72-3.86 (1H, m), 3.96-4.11 (2H, m), 4.61-4.65 (1H, m),
4.95-5.05 (1H, m), 7.59 (1H, dd, J=2.4, 8.4 Hz), 7.94 (3H, s),
7.96 (1H, d, J = 8.4 Hz), 8.52 (1H, s). Anal. Calcd for
C24H28ClN3O5S: C, 56.97; H, 5.58; N, 8.30. Found: C, 56.94;
H, 5.54; N, 8.45. [R]25D þ48.3 (c 0.25, MeOH).
1-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)imidazolidin-2-one (5e). Compound 5e
was prepared in a manner similar to that described for 5k in 46%
1
yield as a colorless powder, mp 170-171 °C. H NMR (300
MHz, CDCl3) δ: 1.55-1.64 (2H, m), 1.77-1.85 (2H, m),
2.66-2.77 (1H, m), 3.11-3.24 (1H, m), 3.37-3.45 (6H, m),
3.75-3.88 (1H, m), 3.97-4.02 (2H, m), 4.40 (1H, s), 4.61-4.66

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3525
(1H, m), 4.98-5.03 (1H, m), 7.59 (1H, dd, J = 2.3, 8.7 Hz),
7.94-7.97 (4H, m), 8.51 (1H, s). Anal. Calcd for
C21H24ClN3O5S: C, 54.13; H, 5.19; N, 9.02. Found: C, 54.06;
H, 5.16; N, 8.95. [R]25D þ7.3 (c 0.25, MeOH).
4-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)morpholin-3-one (5m). Compound 5m
was prepared in a manner similar to that described for 5k in 42%
1
yield as a colorless amorphous powder. H NMR (300 MHz,
1-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)-1,3-dihydro-2H-imidazol-2-one (5f).
Compound 5f was prepared in a manner similar to that de-
scribed for 5k in 10% yield as a colorless amorphous powder. 1H
NMR (300 MHz, CDCl3) δ: 1.62-1.78 (2H, m), 2.05-2.34 (4H,
m), 2.69-2.85 (1H, m), 3.16-3.30 (1H, m), 3.42-3.56 (2H, m),
4.09-4.14 (1H, m), 4.20-4.28 (1H, m), 4.63-4.70 (1H, m),
5.00-5.06 (1H, m), 6.22 (1H, dd, J=3.0, 12.4 Hz), 6.29-6.30
(1H, m), 7.60 (1H, dd, J=1.9, 8.7 Hz), 7.95-7.98 (4H, m), 8.51
CDCl3) δ: 1.60-1.82 (4H, m), 2.69-2.83 (1H, m), 3.15-3.29
(3H, m), 3.41-3.48 (2H, m), 3.67-3.90 (3H, m), 4.02-4.05 (1H,
m), 4.20 (2H, s), 4.62-4.80 (2H, m), 5.02 (1H, m), 7.58-7.61
(1H, m), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal. Calcd for
C22H25ClN2O6S 0.5H2O: C, 53.93; H, 5.35; N, 5.72. Found:
3
C, 53.82; H, 5.22; N, 5.52. [R]25D þ11.9 (c 0.25, MeOH).
10-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxypro-
panoyl}-1,40-bipiperidin-2-one (5n). Compound 5n was prepared
in a manner similar to that described for 5k in 54% yield as a
1
(1H, s). Anal. Calcd for C21H22ClN3O5S 0.5H2O: C, 53.33; H,
colorless amorphous powder. H NMR (300 MHz, CDCl3) δ:
3
4.90; N, 8.88. Found: C, 53.56; H, 4.97; N, 8.62. [R]25D þ8.9 (c
1.62-1.79 (9H, m), 2.41-2.45 (2H, m), 2.68-2.82 (1H, m),
3.14-3.26 (3H, m), 3.40-3.48 (2H, m), 3.97-4.01 (1H, m),
4.60-4.68 (1H, m), 4.80-4.84 (1H, m), 4.96-5.04 (1H, m), 7.59
(1H, dd, J=2.1, 8.7 Hz), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal.
0.25, MeOH).
3-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)-1,3-oxazolidin-2-one (5g). Compound
5g was prepared in a manner similar to that described for 5k in
41% yield as a colorless amorphous powder. 1H NMR (300
MHz, CDCl3) δ: 1.52-1.95 (4H, m), 2.67-2.82 (1H, m),
3.13-3.26 (1H, m), 3.41-3.56 (4H, m), 3.68-3.84 (1H, m),
3.95-4.03 (2H, m), 4.36 (2H, t, J=8.0 Hz), 4.62-4.67 (1H, m),
4.96-5.06 (1H, m), 7.60 (1H, dd, J=2.1, 8.9 Hz), 7.91-7.97 (4H,
Calcd for C23H27ClN2O5S 0.2CH2Cl2: C, 54.21; H, 5.77; N,
3
5.45. Found: C, 54.44; H, 5.56; N, 5.17. [R]25 þ7.7 (c 0.25,
D
MeOH).
2-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)tetrahydropyridazin-3(2H)-one (5o).
Compound 5o was prepared in a manner similar to that des-
cribed for 5k in 9% yield as a colorless amorphous powder. 1H
NMR (200 MHz, CDCl3) δ: 1.63-2.07 (6H, m), 2.42-3.24 (6H,
m), 3.26-4.04 (5H, m), 4.50-4.76 (2H, m), 5.01 (1H, s),
7.59 (1H, dd, J=2.0, 8.8 Hz), 7.86-8.05 (4H, m), 8.52 (1H, d,
J=3.0 Hz). Anal. Calcd for C22H26ClN3O5S: C, 55.05; H, 5.46;
N, 8.75. Found: C, 54.91; H, 5.28; N, 8.45. [R]25D þ9.2 (c 0.25,
MeOH).
m), 8.51 (1H, s). Anal. Calcd for C21H23ClN2O6S 0.5H2O:
3
C, 52.99; H, 5.08; N, 5.89. Found: C, 52.91; H, 5.06; N, 5.91.
[R]25D þ5.5 (c 0.25, MeOH).
1-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)pyrrolidin-2-one (5h). Compound 5h
was prepared in a manner similar to that described for 5k in
41% yield as a colorless amorphous powder. 1H NMR (300
MHz, CDCl3) δ: 1.62-1.87 (3H, m), 2.01-2.08 (3H, m),
2.39-2.44 (2H, m), 2.66-2.81 (1H, m), 3.13-3.48 (5H, m),
3.75-4.24 (3H, m), 4.61-4.65 (1H, m), 5.02-5.03 (1H, m), 7.59
(1H, dd, J=2.1, 8.7 Hz), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal.
1-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)azepan-2-one (5p). Compound 5p was
prepared in a manner similar to that described for 5k in 27%
1
yield as a colorless powder, mp 152-153 °C. H NMR (300
Calcd for C22H25ClN2O5S 0.5H2O: C, 55.75; H, 5.53; N,
MHz, CDCl3) δ: 1.50-1.71 (10H, m), 2.55-2.57 (2H, m),
2.67-2.81 (1H, m), 3.12-3.24 (3H, m), 3.39-3.46 (2H, m),
3.71-3.87 (1H, m), 3.95-4.00 (1H, m), 4.58-4.66 (1H,
m), 4.75-4.83 (1H, m), 5.02 (1H, m), 7.59 (1H, dd, J = 2.3,
8.7 Hz), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal. Calcd for
C24H29ClN2O5S: C, 58.47; H, 5.93; N, 5.68. Found: C, 58.24;
H, 5.75; N, 5.56. [R]25D þ6.5 (c 0.25, MeOH).
3
5.91. Found: C, 55.63; H, 5.74; N, 5.71. [R]25 þ7.1 (c 0.25,
D
MeOH).
(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-1-[4-(1,1-dioxido-
isothiazolidin-2-yl)piperidin-1-yl]-1-oxopropan-2-ol (5i). Com-
pound 5i was prepared in a manner similar to that described
for 5k in 51% yield as a colorless amorphous powder. 1H NMR
(300 MHz, CDCl3) δ: 1.63-1.84 (2H, m), 1.97-2.08 (2H, m),
2.32-2.42 (2H, m), 2.72-2.94 (1H, m), 3.14-3.30 (5H, m),
3.40-3.46 (2H, m), 3.64-3.81 (2H, m), 3.93-4.02 (1H, m),
4.46-4.58 (1H, m), 4.97-5.02 (1H, m), 7.60 (1H, dd, J=2.1,
8.9 Hz), 7.94-7.97 (4H, m), 8.51 (1H, s). Anal. Calcd for
C21H25ClN2O6S2: C, 50.34; H, 5.03; N, 5.59. Found: C, 50.02;
H, 5.04; N, 5.42. [R]25D þ2.7 (c 0.25, MeOH).
2-(Piperidin-4-yl)-1,2-dihydro-3H-pyrrolo[1,2-c]imidazol-
3-one (7a). A mixture of 8a (0.90 g, 3.0 mmol) and Pd(OH)2
(50% wet, 0.20 g) and MeOH (50 mL) was stirred at room
temperature under H2 atmosphere (1 atm) for 15 h, followed by
filtration through on a pad on Celite, and the filtrate was
concentrated in vacuo to afford the desired compound 7a
(0.41 g, 67%) as a yellow powder. 1H NMR (300 MHz, CDCl3)
δ: 1.59-1.85 (4H, m), 2.67-2.80 (2H, m), 3.14-3.21 (2H, m),
4.04-4.15 (1H, m), 4.30 (2H, m), 6.03-6.05 (1H, m), 6.35-6.38
(1H, m), 7.09-7.11 (1H, m).
(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-1-oxo-1-[4-(pyrrolidin-
1-yl)piperidin-1-yl]propan-2-ol (5j). Compound 5j was prepared
in a manner similar to that described for 5k in 51% yield as a
1
colorless amorphous powder. H NMR (300 MHz, CDCl3) δ:
(7aS)-2-(Piperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]imidazol-
3-one (7c). Compound 7c was prepared in a manner similar to
that described for 7a in 74% yield as a colorless powder. H
1.46-2.05 (8H, m), 2.25-2.31 (1H, m), 2.57(4H, brs), 2.84-3.44
(4H, m), 3.82-3.89 (2H, m), 4.23-4.39 (1H, m), 4.99-5.05 (1H,
m), 7.58 (1H, dd, J=1.9, 8.7 Hz), 7.91-7.97 (4H, m), 8.52 (1H,
1
NMR (300 MHz, CDCl3) δ: 1.27-1.37 (1H, m), 1.53-1.99 (5H,
m), 2.67-2.78 (4H, m), 3.01-3.24 (4H, m), 3.49-3.69 (3H, m),
3.80-3.91 (1H, m).
s). Anal. Calcd for C22H27ClN2O4S 0.5H2O: C, 57.44; H, 6.14;
3
N, 6.09. Found: C, 57.35; H, 6.09; N, 5.94. [R]25D þ3.0 (c 0.25,
MeOH).
(7aR)-2-(Piperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]imidazol-
3-one (7d). Compound 7d was prepared in a manner similar to
that described for 7a in 93% yield as a colorless powder. H
3-(1-{(2S)-3-[(6-Chloronaphthalen-2-yl)sulfonyl]-2-hydroxy-
propanoyl}piperidin-4-yl)-1,3-oxazinan-2-one (5l). Compound 5l
was prepared in a manner similar to that described for 5k in 41%
1
NMR (300 MHz, CDCl3) δ: 1.23-1.37 (1H, m), 1.48-1.98 (5H,
m), 2.67-2.78 (4H, m), 3.00-3.23 (4H, m), 3.49-3.70 (3H, m),
3.80-3.91 (1H, m).
1
yield as a colorless amorphous powder. H NMR (300 MHz,
CDCl3) δ: 1.65-2.08 (6H, m), 2.66-2.80 (1H, m), 3.17-3.25
(3H, m), 3.40-3.48 (2H, m), 3.68-3.84 (1H, m), 4.00-4.04 (1H,
m), 4.25 (2H, t, J=5.2 Hz), 4.38-4.45 (1H, m), 4.62-4.70 (1H,
m), 4.95-5.05 (1H, m), 7.59 (1H, dd, J=2.1, 8.7 Hz), 7.94-7.97
4-(1,1-Dioxidoisothiazolidin-2-yl)piperidine (7i). Compound
7i was prepared in a manner similar to that described for 7a in
quantitative yield as a colorless powder. H NMR (300 MHz,
1
(4H, m), 8.51 (1H, s). Anal. Calcd for C22H25ClN2O6S 0.5H2O:
CDCl3) δ: 1.59-1.92 (6H, m), 2.28-2.39 (2H, m), 2.70 (2H, dt,
J=2.3, 12.1 Hz), 3.11-3.16 (3H, m), 3.30 (2H, t, J=6.8 Hz),
3.49-3.60 (1H, m).
3
C, 53.93; H, 5.35; N, 5.72. Found: C, 54.23; H, 5.36; N, 5.50.
[R]25D þ9.6 (c 0.25, MeOH).

3526 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
1-(Piperidin-4-yl)azepan-2-one (7p). Compound 7p was pre-
pared in a manner similar to that described for 7a in quanti-
tative yield as a brown oil. 1H NMR (300 MHz, CDCl3) δ:
1.46-1.69 (11H, m), 2.52-2.56 (2H, m), 2.71 (2H, dt, J=2.9,
11.9 Hz), 3.09-3.13 (2H, m), 3.28-3.31 (2H, m), 4.53-4.63
(1H, m).
2-(Piperidin-4-yl)isoindolin-1-one (7b). A mixture of 8b (1.90
g, 6.20 mmol), 10% Pd/C (50% wet, 0.20 g) and ammonium
formate (2.50 g, 39.6 mmol), and MeOH (50 mL) was refluxed
for 3 h. After cooling to room temperature, the mixture was
filtered, and the filtrate was concentrated in vacuo to give 7b
(1.40 g, quant.) as a colorless powder. 1H NMR (300 MHz,
CDCl3) δ: 1.88-2.15 (4H, m), 2.85-3.01 (2H, m), 3.42 (2H, d,
J=12.6 Hz), 4.41 (2H, s), 4.42-4.56 (1H, m), 7.43-7.60 (3H, m),
7.81-7.90 (1H, m).
2-(1-Benzylpiperidin-4-yl)-1,2-dihydro-3H-pyrrolo[1,2-c]imid-
azol-3-one (8a). NaBH(OAc)3 (12.7 g, 60 mmol) was added
portionwise to a solution of 4-amino-1-benzylpiperidine 10
(5.71 g, 30 mmol), pyrrole-2-carbaldehyde 9 (2.85 g, 30 mmol),
and AcOH (1.80 g, 30 mmol) in CH2Cl2 (250 mL) at 0 °C. After
stirring at room temperature for 15 h, the mixture was basified
with 1 M NaOH solution and an aqueous solution of K2CO3.
The organic layer was separated, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was dissolved in aceto-
nitrile (150 mL), and to the mixture was added CDI (5.84 g,
36 mmol) and DBU (4.57 g, 30 mmol). After refluxing for 15 h,
the mixture was cooled to room temperature and concentrated
in vacuo. The residue was partitioned between water and
CH2Cl2, and the organic layer was separated, dried over anhy-
drous Na2SO4, and concentrated in vacuo. The residue was
purified by silica gel column chromatography (EtOAc) to give
1-(Piperidin-4-yl)pyrrolidin-2-one (7h). Compound 7h was
prepared in a manner similar to that described for 7b in
quantitative yield as a pale yellow oil. 1H NMR (300 MHz,
CDCl3) δ: 1.52-1.68 (4H, m), 1.95-2.05 (2H, m), 2.40 (2H, t,
J=8.1 Hz), 2.67-2.76 (2H, m), 3.12 (2H, d, J=12.0 Hz), 3.36
(2H, t, J=6.9 Hz), 4.01-4.12 (1H, m).
1
8a (2.54 g, 29%) as a colorless powder. H NMR (300 MHz,
CDCl3) δ: 1.68-1.89 (4H, m), 2.08-2.24 (2H, m), 2.99 (2H, d,
J=11.7 Hz), 3.53 (2H, s), 3.93-4.10 (1H, m), 4.29 (2H, s), 6.03
(1H, d, J=1.5 Hz), 6.36 (1H, t, J=3.0 Hz), 7.09 (1H, d, J=2.3
Hz), 7.17-7.40 (5H, m).
1,40-Bipiperidin-2-one (7n). Compound 7n was prepared in a
manner similar to that described for 7b in 90% yield as a
2-(1-Benzylpiperidin-4-yl)isoindolin-1-one (8b). A mixture of
isobenzofuran-1(3H)-one 11 (7.68 g, 57.2 mmol) and 10 (10.9 g,
57.2 mmol) was stirred at 200 °C for 3 days. After cooling to
room temperature, the mixture was partitioned between EtOAc
and a saturated aqueous solution of NaHCO3. The separated
organic layer was washed with brine, dried over anhydrous
Na2SO4, and concentrated in vacuo. The residue was purified
by silica gel column chromatography (EtOAc) to give 8b (8.60 g,
1
colorless powder. H NMR (300 MHz, CDCl3) δ: 1.57-1.83
(8H, m), 2.41 (2H, t, J=6.4 Hz), 2.69-2.87 (2H, m), 3.15-3.27
(4H, m), 4.56-4.69 (1H, m).
1-(Piperidin-4-yl)imidazolidin-2-one (7e). A mixture of 8e
(0.50 g, 1.6 mmol) and 10% Pd/C (50% wet, 0.10 g), and MeOH
(15 mL) was stirred at room temperature under H2 atmosphere
(1 atm) for 15 h, followed by filtration through a pad of Celite.
The filtrate was concentrated in vacuo to afford 7e (0.32 g,
quant.) as a gray powder. 1H NMR (300 MHz, CDCl3) δ:
1.50-1.73 (4H, m), 2.66-2.75 (2H, m), 3.13 (2H, d, J=12.0
Hz), 3.33-3.47 (4H, m), 3.76-3.87 (1H, m).
1-(Piperidin-4-yl)-1,3-dihydro-2H-imidazol-2-one (7f). Com-
pound 7f was prepared in a manner similar to that described
for 7e in quantitative yield as a colorless powder. 1H NMR (300
MHz, CDCl3) δ: 2.03-2.07 (2H, m), 2.32-2.46 (4H, m),
2.97-3.07 (2H, m), 3.53-3.57 (2H, m), 4.09-4.17 (1H, m),
6.31 (1H, d, J=3.0 Hz), 6.37 (1H, d, J=2.6 Hz).
1
49%) as a colorless powder. H NMR (300 MHz, CDCl3) δ:
1.81-1.92 (4H, m), 2.12-2.23 (2H, m), 2.99 (2H, d, J=12.0 Hz),
3.54 (2H, s), 4.25-4.36 (3H, m), 7.23-7.40 (5H, m), 7.43-7.57
(3H, m), 7.85 (1H, d, J=8.4 Hz).
tert-Butyl (2S)-2-{[(1-Benzylpiperidin-4-yl)amino]methyl}-
pyrrolidine-1-carboxylate (13a). NaBH3CN (0.38 g, 6.00 mmol)
was added to a solution of tert-butyl (2S)-2-formylpyrrolidine-
1-carboxylate 12a (1.00 g, 5.00 mmol) and 10 (0.95 g, 5.00 mmol)
in MeOH (45 mL) and AcOH (5 mL), and the mixture was
stirred at room temperature overnight, followed by basifying
with a saturated aqueous solution of K2CO3. After removal of
the solvents in vacuo, the mixture was extracted with CH2Cl2.
The organic layer was washed with brine, dried over anhydrous
MgSO4, and concentrated in vacuo. The residue was purified by
basic silica gel column chromatography (hexane/EtOAc=4:1 to
EtOAc) to give 13a (1.60 g, 86%) as a pale yellow oil. 1H NMR
(300 MHz, CDCl3) δ: 1.30-1.43 (2H, m), 1.46 (9H, s),
1.78-1.89 (6H, m), 1.96-2.05 (2H, m), 2.38-2.55 (2H, m),
2.78-2.88 (3H, m), 3.25-3.35 (2H, m), 3.48 (2H, s), 3.75-3.90
(1H, m), 7.22-7.31 (5H, m).
tert-Butyl (2R)-2-{[(1-Benzylpiperidin-4-yl)amino]methyl}-
pyrrolidine-1-carboxylate (13b). Compound 13b was prepared
in a manner similar to that described for 13a using 12b in 89% yield
as a colorless oil. 1H NMR (300 MHz, CDCl3) δ: 1.28-1.43 (2H,
m), 1.46 (9H, s), 1.79-1.89 (6H, m), 1.96-2.05 (2H, m), 2.40-2.55
(2H, m), 2.80-2.85 (3H, m), 3.30-3.40 (2H, m), 3.49 (2H, s),
3.75-3.90 (1H, m), 7.21-7.32 (5H, m).
(7aS)-2-(1-Benzylpiperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]-
imidazol-3-one (8c). TFA (10 mL) was added to a solution of 13a
(1.50 g, 4.00 mmol) in CH2Cl2 (20 mL) at room temperature.
After stirring at room temperature overnight, the mixture was
basified with 1 M NaOH solution. The separated organic
layer was washed with brine, dried over anhydrous MgSO4,
and concentrated in vacuo. The residue and DBU (1.22 g,
8.00 mmol) were dissolved in THF (50 mL), and to the solution
was added CDI (0.78 g, 4.8 mmol) at room temperature. After
stirring at room temperature overnight, the solvent was re-
moved in vacuo. The residue was diluted with EtOAc, washed
with water and brine, dried over anhydrous MgSO4, and con-
centrated in vacuo. The residue was purified by basic silica
gel column chromatography (hexane/EtOAc=1:4) to give 8c
3-(Piperidin-4-yl)-1,3-oxazolidin-2-one (7g). Compound 7g
was prepared in a manner similar to that described for 7e in
quantitative yield as a colorless powder. H NMR (300 MHz,
1
CDCl3) δ: 1.51-1.65 (2H, m), 1.76-1.81 (2H, m), 2.70 (2H, dt,
J=2.4, 12.3 Hz), 3.15 (2H, d, J=12.7 Hz), 3.54 (2H, t, J=8.1
Hz), 3.73-3.86 (1H, m), 4.30-4.36 (2H, m).
1-(Piperidin-4-yl)tetrahydropyrimidin-2(1H)-one (7k). Com-
pound 7k was prepared in a manner similar to that described
for 7e in quantitative yield as a colorless powder. 1H NMR (300
MHz, CDCl3) δ: 1.71-1.95 (6H, m), 2.58-2.88 (4H, m),
3.20-3.40 (6H, m), 4.32-4.40 (1H, m).
3-(Piperidin-4-yl)-1,3-oxazinan-2-one (7l). Compound 7l was
prepared in a manner similar to that described for 7e in
quantitative yield as a colorless powder. H NMR (300 MHz,
1
CDCl3) δ: 1.55-1.78 (4H, m), 1.95-2.10 (2H, m), 2.72 (2H, dt,
J=2.7, 12.1 Hz), 3.15 (2H, dd, J=2.0, 10.0 Hz), 3.26 (2H, t, J=
6.1 Hz), 4.13-4.33 (3H, m).
4-(Piperidin-4-yl)morpholin-3-one (7m). Compound 7m was
prepared in a manner similar to that described for 7e in
quantitative yield as a pale yellow oil. 1H NMR (300 MHz,
CDCl3) δ: 1.54-1.69 (5H, m), 2.75 (2H, dt, J=3.0, 11.3 Hz),
3.13-3.17 (2H, m), 3.31 (2H, t, J=5.1 Hz), 3.88 (2H, t, J=5.1
Hz), 4.19 (2H, s), 4.52-4.63 (1H, m).
2-(Piperidin-4-yl)tetrahydropyridazin-3(2H)-one (7o). Com-
pound 7o was prepared in a manner similar to that described
for 7e in quantitative yield as a colorless powder. 1H NMR (300
MHz, CDCl3) δ: 1.54-1.66 (2H, m), 1.71-1.87 (2H, m),
1.90-2.02 (2H, m), 2.47 (2H, t, J=7.3 Hz), 2.70 (2H, dt, J=
2.7, 12.7 Hz), 3.00 (2H, t, J = 6.7 Hz), 3.06-3.22 (2H, m),
4.37-4.53 (1H, m).

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3527
(1.06 g, 89%) as a colorless powder. 1H NMR (300 MHz,
CDCl3) δ: 1.21-1.35 (1H, m), 1.57-1.96 (7H, m), 2.01-2.11
(2H, m), 2.92 (2H, d, J=11.1 Hz), 2.99-3.07 (1H, m), 3.18-3.21
(1H, m), 3.46-3.52 (3H, m), 3.56-3.69 (2H, m), 3.72-3.83 (1H,
m), 7.20-7.36 (5H, m).
concentrated in vacuo. The residue was partitioned between
EtOAc and water. The organic layer was separated, washed with
5% aqueous solution of citric acid and brine, and concentrated in
vacuo. The residue was recrystallized from EtOAc-MeOH to
afford 8k (5.95 g, 87%) as a colorless powder. 1H NMR (300 MHz,
CDCl3) δ: 1.54-1.71 (4H, m), 1.86-1.93 (2H, m), 2.83-2.92
(2H, m), 3.13 (2H, t, J=5.6 Hz), 3.24-3.29 (2H, m), 4.28 (2H,
brs), 4.45-4.56 (1H, m), 4.71 (1H, brs), 5.12 (2H, s), 7.31-7.37
(5H, m).
(7aR)-2-(1-Benzylpiperidin-4-yl)hexahydro-3H-pyrrolo[1,2-c]-
imidazol-3-one (8d). Compound 8d was prepared in a manner
similar to that described for 8c using 13b in place of 13a in 88%
1
yield as a colorless powder. H NMR (300 MHz, CDCl3) δ:
1.21-1.35 (1H, m), 1.58-1.98 (7H, m), 2.03-2.11 (2H, m), 2.93
(2H, d, J=11.1 Hz), 2.99-3.08 (1H, m), 3.18-3.21 (1H, m),
3.43-3.54 (3H, m), 3.59-3.69 (2H, m), 3.75-3.84 (1H, m),
7.22-7.37 (5H, m).
Benzyl 4-[(2-Hydroxyethyl)amino]piperidine-1-carboxylate (18a).
A mixture of benzyl 4-oxopiperidine-1-carboxylate 14 (7.00 g, 30.0
mmol), 2-aminoethanol 17a (2.80 g, 46.0 mmol), and AcOH
(2.70 g, 46.0 mmol) in 1,2-dichloroethane (150 mL) and MeOH
(10 mL) was stirred at room temperature for 3 h, and to the mixture
was added portionwise NaBH(OAc)3 (12.7 g, 46.0 mmol). After
stirring at room temperature for 15 h, the mixture was basified to
pH 12 with 1 M NaOH solution. The separated organic layer was
dried over anhydrous Na2SO4 and concentrated in vacuo to give
18a (9.00 g, quant.) as a colorless oil. 1H NMR (300 MHz, CDCl3)
δ: 1.21-1.33 (2H, m), 1.86-1.97 (4H, m), 2.58-2.67 (1H, m),
2.78-2.92 (4H, m), 3.63 (2H, t, J=5.2Hz), 4.10(2H, brs), 5.12(2H,
s), 7.29-7.36 (5H, m).
Benzyl 4-[(3-Hydroxypropyl)amino]piperidine-1-carboxylate
(18b). A mixture of benzyl 4-oxopiperidine-1-carboxylate 14
(12.7 g, 54.0 mmol), 3-aminopropanol 17b (4.50 g, 60.0 mmol),
and AcOH (3.60 g, 60.0 mmol) in 1,2-dichloroethane (350 mL)
was stirred at room temperature for 2 h. To the mixture was
added portionwise NaBH(OAc)3 (23.1 g, 109 mmol), and the
mixture was stirred at room temperature for 15 h. The mixture
was basified with 2 M NaOH solution and an aqueous solution
of K2CO3. The organic layer was separated, dried over anhy-
drous Na2SO4, and concentrated in vacuo to give 18b (16.8 g,
quant.) as a colorless oil. 1H NMR (300 MHz, CDCl3) δ:
1.13-1.36 (2H, m), 1.63-1.75 (2H, m), 1.89 (2H, d, J=11.7
Hz), 2.56-2.70 (1H, m), 2.87-2.99 (4H, m), 3.76-3.86 (2H, m),
3.93-4.24 (2H, m), 5.12 (2H, s), 7.27-7.44 (5H, m).
Benzyl 4-({2-[(tert-Butoxycarbonyl)amino]ethyl}amino)piper-
idine-1-carboxylate (16a). To a mixture of benzyl 4-oxopiper-
idine-1-carboxylate 14 (12.4 g, 53.0 mmol), tert-butyl(2-amino-
ethyl)carbamate 15a (8.50 g, 53.0 mmol), and AcOH (3.18 g,
53.0 mmol) in 1,2-dichloroethane (350 mL) was added portion-
wise NaBH(OAc)3 (28.1 g, 133 mmol) at 0 °C. After stirring at
room temperature for 15 h, the mixture was basified with 1 M
NaOH solution. The separated organic layer was dried over
anhydrous Na2SO4, and concentrated in vacuo to give 16a
(20.0 g, quant.) as a colorless oil. 1H NMR (300 MHz, CDCl3)
δ: 1.09-1.41 (2H, m), 1.44 (9H, s), 1.74-1.94 (2H, m),
2.47-2.69 (1H, m), 2.70-2.81 (2H, m), 2.81-2.98 (2H, m),
3.20 (2H, q, J=5.8 Hz), 3.97-4.22 (2H, m), 4.89 (1H, brs), 5.12
(2H, s), 7.27-7.41 (5H, m).
Benzyl 4-({3-[(tert-Butoxycarbonyl)amino]propyl}amino)piper-
idine-1-carboxylate (16b). Compound 16b was prepared in a
manner similar to that described for 16a using 15b in quantita-
1
tive yield as a pale yellow oil. H NMR (300 MHz, CDCl3) δ:
1.25-1.33 (3H, m), 1.43 (9H, s), 1.59-1.68 (2H, m), 1.83-1.87
(2H, m), 2.57-2.64 (1H, m), 2.69 (2H, t, J=6.6 Hz), 2.87-2.95
(2H, m), 3.17-3.23 (2H, m), 4.07-4.10 (2H, m), 5.09 (1H, brs),
5.12 (2H, s), 7.30-7.36 (5H, m).
Benzyl 4-(2-Oxoimidazolidin-1-yl)piperidine-1-carboxylate (8e).
To a solution of 16a (2.00 g, 5.30 mmol) in EtOAc (5 mL) was
added 4 M HCl/EtOAc (30 mL). The mixture was stirred at room
temperature for 5 h. The resulting precipitate was collected by
filtration and washed with EtOAc to give benzyl 4-[(2-amino-
ethyl)amino]piperidine-1-carboxylate dihydrochloride (1.58 g,
Benzyl 4-(2-Oxo-1,3-oxazinan-3-yl)piperidine-1-carboxylate
(8l). To a solution of 18b (15.9 g, 54.4 mmol) and DBU (0.83
g, 5.50 mmol) in THF (400 mL) was added CDI (8.82 g,
54.4 mmol) at room temperature. The mixture was stirred at
room temperature for 15 h and refluxed for 15 h. After removal
of the solvent in vacuo, the residue was partitioned between
EtOAc and water. The organic layer was separated, washed with
water, 5% aqueous solution of citric acid, and brine, and
concentrated in vacuo to give 8l (17.5 g, quant.) as a colorless
1
85%) as a beige powder. H NMR (300 MHz, DMSO-d6) δ:
1.39-1.63 (2H, m), 2.05 (2H, d, J=11.1 Hz), 2.66-3.01 (2H, m),
3.20 (4H, s), 3.25-3.42 (1H, m). 4.08 (2H, d, J=13.6Hz), 5.09(2H,
s), 7.23-7.47 (5H, m). To a solution of benzyl 4-[(2-amino-
ethyl)amino]piperidine-1-carboxylate dihydrochloride (1.55 g,
4.40 mmol) and DBU (1.48 g, 9.70 mmol) in acetonitrile
(100 mL) was added CDI (0.79 g, 4.90 mmol). The mixture was
stirred at room temperature for 15 h and concentrated in vacuo.
The residue was partitioned between water and EtOAc. The
organic layer was separated, washed with water and a 5% solution
of citric acid, dried over anhydrous Na2SO4, and concentrated in
vacuo to give 8e (1.20 g, 90%) as a colorless powder. 1HNMR(300
MHz, CDCl3) δ: 1.42-1.64 (2H, m), 1.64-1.82 (2H, m),
2.69-3.01 (2H, m), 3.28-3.49 (4H, m), 3.75-4.01 (1H, m),
4.18-4.41 (3H, m), 5.13 (2H, s), 7.29-7.42 (5H, m).
1
powder. H NMR (300 MHz, CDCl3) δ: 1.48-1.81 (4H, m),
1.94-2.10 (2H, m), 2.75-2.99 (2H, m), 3.19 (2H, t, J=6.2 Hz),
4.18-4.46 (5H, m), 5.12 (2H, s), 7.28-7.41 (5H, m).
Benzyl 4-(2-Oxo-1,3-oxazolidin-3-yl)piperidine-1-carboxylate
(8g). Compound 8g was prepared in a manner similar to that
described for 8l using 18a in 83% yield as a colorless powder. 1H
NMR (300 MHz, CDCl3) δ: 1.49-1.68 (2H, m), 1.66-1.81
(2H, m), 2.86 (2H, d, J = 9.0 Hz), 3.49 (2H, t, J = 7.8 Hz),
3.83-3.94 (1H, m), 4.20-4.36 (4H, m), 5.13 (2H, s), 7.29-7.40
(5H, m).
Benzyl 4-(3-Oxomorpholin-4-yl)piperidine-1-carboxylate (8m).
To a solution of 18a (7.50 g, 27.0 mmol) and Et3N (4.10 mL,
29.0 mmol) in THF (70 mL) was added dropwise chloroacetyl
chloride (2.2 mL, 28.0 mmol) at 0 °C, and the mixture was stirred
at 0 °C for 2 h. After the solvent was removed in vacuo, the
residue was diluted with water, and the mixture was extracted
with EtOAc. The extract was washed with a 5% aqueous
solution of citric acid and brine, dried over anhydrous Na2SO4,
and the solvent removed in vacuo. The residue was dissolved in
DMF (60 mL) and cooled to 0 °C, and then NaH (60% in
mineral oil; 1.20 g, 30.0 mmol) was added to the mixture. The
mixture was stirred at 0 °C for 1 h, at room temperature for 1 h,
and at 80 °C for 15 h. After removal of the solvent in vacuo, the
residue was diluted with water, acidified with 1 N HCl solution,
and extracted with EtOAc. The extract was washed with water
Benzyl 4-(2-Oxotetrahydropyrimidin-1(2H)-yl)piperidine-1-
carboxylate (8k). To a solution of 16b (9.50 g, 24.3 mmol) in
EtOAc (10 mL) was added 4 M HCl/EtOAc (20 mL) at 0 °C.
After stirring at room temperature for 5 h, the resulting pre-
cipitate was collected by filtration to give benzyl 4-[(3-amino-
propyl)amino]piperidine-1-carboxylate dihydrochloride (8.00
1
g, 91%) as a colorless powder. H NMR (300 MHz, DMSO-
d6) δ: 1.46-1.57 (2H, m), 1.96-2.07 (4H, m), 2.91-3.21 (8H, m),
4.08-4.10 (2H, m), 5.09 (2H, s), 7.32-7.41 (5H, m), 8.09 (2H,
brs), 9.33 (2H, brs). To a solution of benzyl 4-[(3-amino-
propyl)amino]piperidine-1-carboxylate dihydrochloride (7.85 g,
21.5 mmol) and DBU (7.00 g, 47.4 mmol) in acetonitrile
(250 mL) was added CDI (3.84 g, 23.7 mmol) at room temperature.
The mixture was stirred at room temperature for 15 h and

3528 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
and brine and dried over anhydrous Na2SO4, and the solvent
was removed in vacuo. The residue was purified by silica gel
column chromatography (hexane/EtOAc = 1:2 to EtOAc) to
available benzyl 4-isocyanatotetrahydro-1(2H)-pyridinecarboxy-
late 19 (0.88 g, 2.40 mmol) in acetonitrile (15 mL), and the mixture
was stirred at room temperature for 2 h. After removal of the
solvent in vacuo, the residue was diluted with 0.1 M HCl solution
and extracted with EtOAc. The extract was washed with brine,
dried over anhydrous Na2SO4, and concentrated in vacuo to give
20 (1.24 g, quant.) as a colorless oil. 1H NMR (300 MHz, CDCl3)
δ: 1.29 (2H, m), 1.91-1.96 (2H, m), 2.90-2.99 (2H, m), 3.30 (2H,
t, J=5.7 Hz), 3.40 (6H, s), 3.72-3.79 (1H, m), 4.09 (2H, m), 4.35
(1H, t, J=5.1 Hz), 4.57-4.61 (2H, m), 5.12 (2H, s), 7.31-7.36
(5H, m).
Benzyl 4-(2-Oxo-2,3-dihydro-1H-imidazol-1-yl)piperidine-1-
carboxylate (8f). One M HCl solution (5 mL) was added to a
solution of 20 (0.37 g, 1.23 mmol) in water (5 mL) and MeOH
(10 mL), and the mixture was stirred at room temperature for
3 days. After removal of the solvents in vacuo, the residue was
dissolved in water and extracted with EtOAc. The extract was
washed with water and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo to give 8f (0.27 g, 90%) as a colorless
powder. 1H NMR (300 MHz, CDCl3) δ: 1.63 (2H, m),
1.92-1.96 (2H, m), 2.88-2.96 (2H, m), 4.09-4.22 (1H, m),
4.34 (2H, brs), 5.14 (2H, s), 6.19 (1H, t, J=2.4 Hz), 6.30 (1H, t,
J=2.6 Hz), 7.26-7.38 (5H, m), 9.66 (1H, brs).
1
give 8m (3.80 g, 44%) as a colorless oil. H NMR (300 MHz,
CDCl3) δ: 1.56-1.69 (4H, m), 2.85-2.93 (2H, m), 3.24 (2H, t,
J=5.1 Hz), 3.87 (2H, t, J=5.1 Hz), 4.19 (2H, s), 4.31 (2H, brs),
4.60-4.71 (1H, m), 5.13 (2H, s), 7.29-7.37 (5H, m).
1-(1-Benzylpiperidin-4-yl)pyrrolidin-2-one (8h). To a solution
of 10 (3.81 g, 20.0 mmol) and pyridine (2.37 g, 30.0 mmol) in
CH2Cl2 (50 mL) was added dropwise 4-bromobutanoyl chloride
(2.42 mL, 21.0 mmol) at 0 °C. The mixture was stirred at 0 °C for
2 h and at room temperature for 15 h. An aqueous solution of
K2CO3 was added, and the organic layer was separated, dried
over anhydrous Na2SO4, and concentrated in vacuo. The resi-
due was dissolved in THF (20 mL), and this solution was added
dropwise to a suspension of NaH (60% in mineral oil, 1.60 g,
42.0 mmol) in THF (30 mL). After stirring at room temperature
for 1 h and at reflux for 15 h, the mixture was allowed to cool to
room temperature. An aqueous solution of K2CO3 was added
and extracted with EtOAc. The extract was dried over anhy-
drous Na2SO4 and concentrated in vacuo. The residue was
purified by basic silica gel column chromatography (EtOAc/
1
MeOH=10:1) to give 8h (1.72 g, 33%) as an orange oil. H
NMR (300 MHz, CDCl3) δ: 1.61-1.79 (4H, m), 1.94-2.13 (4H,
m), 2.38 (2H, t, J=8.1 Hz), 2.94 (2H, d, J=9.9 Hz), 3.35 (2H, t,
J=6.9 Hz), 3.50 (2H, s), 3.93-4.13 (1H, m), 7.20-7.35 (5H, m).
1-Benzyl-4-(1,1-dioxidoisothiazolidin-2-yl)piperidine (8i). Com-
pound 8i was prepared in a manner similar to that described for
8h using 3-chloropropane-1-sulfonyl chloride in 63% yield as a pale
yellow powder. 1H NMR (300 MHz, CDCl3) δ:1.75-1.88 (4H, m),
2.03-2.12 (2H, m), 2.28-2.38 (2H, m), 2.91-2.95 (2H, m), 3.13
(2H, t, J=7.6 Hz), 3.28 (2H, t, J=6.6 Hz), 3.42-3.49 (1H, m), 3.49
(2H, s), 7.25-7.34 (5H, m).
Benzyl 4-[2-(tert-Butoxycarbonyl)hydrazino]piperidine-1-car-
boxylate (21). To a solution of 14 (9.87 g, 42.3 mmol), tert-butyl
carbazate (14.7 g, 42.3 mmol), and AcOH (2.42 mL, 42.3 mmol)
in MeOH (150 mL) was added NaBH3CN (5.33 g, 84.8 mmol)
portionwise at 0 °C. The mixture was stirred at room tempera-
ture for 15 h and concentrated in vacuo. The residue was basified
with 1 M NaOH solution and extracted with CH2Cl2. The
extract was dried over anhydrous Na2SO4 and concentrated in
vacuo to give 21 (15.0 g, quant.) as colorless crystals. 1H NMR
(300 MHz, CDCl3) δ: 1.21-1.41 (2H, m), 1.46 (9H, s),
1.73-1.86 (2H, m), 2.84-3.10 (3H, m), 3.96 (1H, brs),
3.99-4.17 (2H, m), 5.12 (2H, s), 6.04 (1H, brs), 7.28-7.41
(5H, m).
tert-Butyl 2-{1-[(Benzyloxy)carbonyl]piperidin-4-yl}-3-oxo-
tetrahydropyridazine-1(2H)-carboxylate (22). To a solution of
21 (1.05 g, 3.00 mmol) and Et3N (0.46 mL, 3.30 mmol) in THF
(30 mL) was added dropwise 4-bromobutyryl chloride (0.35 mL,
3.00 mmol) at 0 °C. The mixture was stirred at 0 °C for 1 h and
concentrated in vacuo. The residue was diluted with EtOAc,
washed with water and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was dissolved in THF
(30 mL), and NaH (60% in mineral oil, 0.18 g, 4.50 mmol) was
added. The mixture was stirred at room temperature for 15 h
and concentrated in vacuo. The residue was diluted with EtOAc,
washed with water and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo to give 22 (1.28 g, quant.) as a yellow
amorphous powder. 1H NMR (300 MHz, CDCl3) δ: 1.47
(9H, s), 1.54-2.51 (8H, m), 2.75-3.04 (3H, m), 4.09-4.54
(4H, m), 5.06-5.18 (2H, m), 7.28-7.44 (5H, m).
Benzyl 4-(6-Oxotetrahydropyridazin-1(2H)-yl)piperidine-1-
carboxylate (8o). A solution of 22 (0.84 g, 2.60 mmol) and
TFA (1.0 mL) in CH2Cl2 (1.5 mL) was stirred at room tempera-
ture and concentrated in vacuo. The residue was basified with an
aqueous solution of NaHCO3 and extracted with CH2Cl2. The
extract was dried over anhydrous Na2SO4 and concentrated in
vacuo to give 8o (1.28 g, quant.) as a colorless powder. 1H NMR
(300 MHz, CDCl3) δ: 1.50-1.65 (2H, m), 1.68-1.86 (2H, m),
1.90-2.01 (2H, m), 2.47 (2H, t, J=7.3 Hz), 2.74-2.94 (2H, m),
2.95-3.03 (2H, m), 3.62 (1H, t, J=7.7 Hz), 4.17-4.36 (2H, m),
4.47-4.58 (1H, m), 5.12 (2H, d, J=4.6 Hz), 7.28-7.42 (5H, m).
1-(1-{3-[(6-Chloronaphthalen-2-yl)sulfonyl]propanoyl}piper-
idin-4-yl)tetrahydropyrimidin-2(1H)-one (23). To a solution of 2
(299 mg, 1.00 mmol), 7k (183 mg, 1.50 mmol), and HOBt (230
mg, 1.50 mmol) in DMF (10 mL) were added WSC (288 mg, 1.50
mmol) and Et3N (417 μL, 3.00 mmol). The mixture was stirred
at room temperature for 15 h and concentrated in vacuo. The
residue was diluted with an aqueous solution of NaHCO3 and
10-Benzyl-1,40-bipiperidin-2-one (8n). Compound 8n was pre-
pared in a manner similar to that described for 8h using
5-bromopentanoyl chloride in 80% yield as a colorless powder.
1H NMR (400 MHz, CDCl3) δ: 1.51-1.65 (2H, m), 1.64-1.83
(6H, m), 2.05-2.20 (2H, m), 2.39 (2H, t, J=6.2 Hz), 2.93 (2H,
dd, J=2.2 and 9.5 Hz), 3.19 (2H, t, J=5.6 Hz), 3.50 (2H, s),
4.45-4.64 (1H, m), 7.15-7.42 (5H, m).
1-(1-Benzylpiperidin-4-yl)azepan-2-one (8p). A solution of
6-bromohexanoyl chloride (5.61 g, 26.2 mmol) in THF
(20 mL) was added dropwise to a solution of 4-amino-1-
benzylpiperidine 10 (5.00 g, 26.2 mmol) and Et3N (3.65 mL,
26.2 mmol) in THF (200 mL) at 0 °C. The mixture was stirred
at room temperature for 5 h, and the mixture was partitioned
between with EtOAc and water. The organic layer was sepa-
rated, washed with brine, dried over anhydrous Na2SO4, and
concentrated in vacuo, giving N-(1-benzylpiperidin-4-yl)-6-bromo-
1
hexanamide (8.75 g, 91%) as a white powder. H NMR (300
MHz, CDCl3) δ: 1.36-1.52 (4H, m), 1.59-1.70 (2H, m),
1.82-1.93 (4H, m), 2.06-2.20 (4 H, m), 2.81 (2H, d, J=11.7
Hz), 3.38-3.44 (2H, m), 3.49 (2H, s), 3.70-3.88 (1H, m), 5.30
(1H, d, J=7.8 Hz), 7.14-7.38 (5H, m). To a solution of N-(1-
benzylpiperidin-4-yl)-6-bromohexanamide (3.00 g, 8.17 mmol)
in DMF (150 mL) was added NaH (60% in mineral oil, 359 mg,
8.98 mmol) at 0 °C, and the mixture was stirred at 80 °C for 15 h.
After cooling to room temperature, the solvent was removed in
vacuo. The residue was diluted with water and extracted with
EtOAc. The combined organic layer was washed with water and
brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residue was purified by basic silica gel column
chromatography (hexane/EtOAc=10:1 to 1:2) to give 8p (1.43
g, 61%) as a colorless oil. 1H NMR (300 MHz, CDCl3) δ:
1.51-1.76 (10H, m), 2.06-2.14 (2H, m), 2.48-2.57 (2H, m),
2.86-2.99 (2H, m), 3.25-3.35 (2H, m), 3.49 (2H, s), 4.39-4.63
(1H, m), 7.17-7.39 (5H, m).
Benzyl 4-({[(2,2-Dimethoxyethyl)amino]carbonyl}amino)piper-
idine-1-carboxylate (20). 2-Aminoacetaldehydedimethylacetal
(0.36 g, 3.40 mmol) was added to a solution of commercially

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9 3529
extracted with CH2Cl2. The extract was dried over anhydrous
Na2SO4 and concentrated in vacuo. The residue was purified by
basic silica gel column chromatography (EtOAc to EtOAc/
MeOH=10:1) to give 23 (353 mg, 76%) as a colorless amor-
phous powder. 1H NMR (300 MHz, CDCl3) δ: 1.41-1.80 (4H,
m), 1.83-2.00 (2H, m), 2.49-2.67 (1H, m), 2.76-2.97 (2H, m),
3.04-3.19 (3H, m), 3.22-3.35 (2H, m), 3.42-3.66 (2H, m),
3.80-3.96 (1H, m), 4.45-4.71 (3H, m), 7.60 (1H, dd, J=1.9, 8.9
Hz), 7.84-8.02 (4H, m), 8.48 (1H, s). Anal. Calcd for
C22H26ClN3O4S: C, 56.95; H, 5.65; N, 9.06. Found: C, 56.65;
H, 5.61; N, 9.00.
In Vitro Assays for the Inhibition of Human FXa. Human
factor Xa (0.3 U/mL) was obtained from Roche Diagnostics.
Chromogenic substrate, S-2765 (Chromogenix-Instrumenta-
tion Laboratory) was used for the measurement of the inhibition
of FXa. Anti-FXa activity was assayed in a buffer containing
50 mM Tris-HCl, 145 mM NaCl and 2 mM CaCl2 at pH 8.3.
Enzymatic assays were carried out in 96-well microtiter plates.
An initial stock solution of test compound at 10 mM was
prepared in DMSO, and subsequently diluted with DMSO.
Five microliters of compound dilutions (final concentration:
0.2 nM-0.6 μM, 2 nM-6 μM, or 2 nM-60 μM) and 10 μL of
enzyme solution were added to the well containing 225 μL
of buffer, and preincubated. The enzymatic reactions were
initiated with the addition of 10 μL of 3 mM substrate and the
mixture was incubated for 10 min at 37 °C. The reaction was
terminated with the addition of 25 μL of 50% acetic acid. The
color development from the release of p-nitroanilide from each
chromogenic substrate was measured at 405 nm on a microtiter
plate reader (Multiskan Ascent, Dainippon Pharmaceuticals,
Japan). Each absorbance [T] was calculated by subtracting the
absorbance measured without the substrate. The control [C] was
performed using DMSO solution in place of test compound.
Inhibitory effect (%) was calculated according to the eq (1 -
[T]/[C]) ꢀ 100. IC50 values (and 95% confidence limits) were
calculated from the concentration-response curves generated
by logistic regression using the SAS system.
In Vitro PT Assays. The assay of plasma clotting time was
performed using an automatic coagulometer (STA Compact,
Diagnostica Stago). PT was measured with PT reagent (Roche
Diagnostics). An initial stock solution of test compound at
10 mM was prepared in DMSO, and subsequently diluted with
DMSO. Compound dilutions of 1.5 μL were added to 48.5 μL of
human normal plasma (fresh human plasma: FFP, Sekisui
Chemical Co.), and the mixture was preincubated at 37 °C for
4 min (DMSO derived from test compound solution did not
exceed a plasma concentration of 3% v/v). Coagulation was
initiated with the addition of 100 μL of PT reagent, and
coagulation time was measured. Coagulation time was deter-
mined on plasma containing three or four different concentra-
tions of test compound. Coagulation time prolonging ratio (%)
was calculated based on coagulation time when DMSO was
added instead of test compound. The plasma clotting time
doubling concentration (PT2) was calculated from the regres-
sion line based on the method of least-squares.
Enzyme Affinity Assays. Following enzymes and chromo-
genic substrates were used in this study: human FXa (Roche
Diagnostics), human thrombin and human activated protein C
(Sigma Chemical), human factor IXa (MP Biomedicals), human
kallikrein (Calbiochem), human recombinant tissue plasmino-
gen activator (t-PA) (Kyowa Hakko Kogyo), human trypsin
(Athens Research and Technology), human plasmin (Enzyme
Research Laboratories), S-2222, S-2288, S-2302 and S-2366
(Chromogenix-Instrumentation Laboratory), and Spectrozyme
FIXa (American Diagnostica). All other reagents were of the
highest grade commercially available. Tris-HCl buffer solution
(Tris-HCl, 50 mmol/L; NaCl, 145 mmol/L; CaCl2, 2 mmol/L;
pH 8.3) (215 μL) and drugs (5 μL) dissolved in DMSO were
preincubated at 37 °C for 10 min, and were mixed with enzyme
solution (10 μL). A reaction was started with the addition of
chromogenic substrate (20 μL). Optical density (O. D.) at
405 nm was then continuously measured by microplate reader
for 5 min (plasmin, t-PA, activated protein C) or 10 min (FXa,
thrombin, FIXa, kallikrein, trypsin). The following chromo-
genic substrate for each serine protease was used: S-2222 (0.40
mmol/L) for FXa (0.012 unit/mL), S-2366 (0.24 mmol/L) for
thrombin (0.050 unit/mL), Spectrozyme FIXa (0.40 mmol/L)
for factor IXa (2.0 μg/mL), S-2302 (0.24 mmol/L) for kallikrein
(0.20 μg/mL), S-2288 (0.48 mmol/L) for t-PA (4000 unit/mL),
S-2222 (0.18 mmol/L) for trypsin (0.020 μg/mL), S-2366 (0.48
mmol/L) for activated protein C (0.12 μg/mL) and S-2366 (0.48
mmol/L) for plasmin (0.4 μg/mL). Data were expressed as
mean ( SEM. IC50 values (and 95% confidence limits) were
calculated as described above.
Metabolic Stability Assay in the Absence of NADPH. Human
and monkey hepatic microsomes were purchased from Xenotech,
LLC (Lenexa, KS). An incubation mixture with a final volume
of 0.1 mL consisted of microsomal protein in 50 mmol/L
KH2PO4-K2HPO4 phosphate buffer (pH 7.4) and 10 μmol/L test
compound in DMSO. The concentration of hepatic microsomal
protein was 4 mg/mL. The reaction mixture was incubated at 37 °C
for 120 min. The reaction was terminated by the addition of 0.1 mL
of acetonitrile to reaction mixture. All incubations were made in
duplicate. The hydrolytic metabolite produced in the reaction
mixture was measured by HPLC system equipped with a UV
detector.
Metabolic Stability Assay in the Presence of NADPH. Human
hepatic microsomes were purchased from Xenotech, LLC
(Lenexa, KS). An incubation mixture with a final volume of
0.1 mL consisted of microsomal protein in 50 mmol/L
KH2PO4-K2HPO4 phosphate buffer (pH 7.4) and 1 μmol/L
test compound in DMSO. The concentration of hepatic micro-
somal protein was 0.2 mg/mL. An NADPH-generating system
containing 50 mmol/L MgCl2, 50 mmol/L glucose-6-phosphate,
5 mmol/L β-NADPþ and 15 unit/mL glucose-6-phosphate
dehydrogenase was prepared and added to the incubation
mixture with a 10% volume of the reaction mixture. After the
addition of the NADPH-generating system, the mixture was
incubated at 37 °C for 0 and 20 min. The reaction was termi-
nated by the addition of acetonitrile equivalent to the volume of
the reaction mixture. All incubations were made in duplicate.
Test compound in the reaction mixture was measured by HPLC
system equipped with a UV detector. For metabolic stability
determinations, chromatograms were analyzed for parent com-
pound disappearance from the reaction mixtures.
Cassette Dosing in Cynomolgus Monkeys. All experiments
were conducted in accordance with the regulations of Animal
Care and Use Committee of the Takeda Chemical Industries
Ltd. Test compounds were administered as a cassette dosing to
cynomolgus monkeys. After oral and intravenous administra-
tion, blood samples were collected. The blood samples were
centrifuged to obtain the plasma fraction. The plasma samples
were deproteinized with acetonitrile containing an internal
standard. After centrifugation, the supernatant was diluted with
0.01 mol/L ammonium acetate and centrifuged again. The
compound concentrations in the supernatant were measured
by LC/MS/MS.
Factor Xa þ Compound 5k Crystal Structure Determination.
The cDNA encoding human factor Xa was obtained by PCR
from a human liver cDNA library and cloned into a modified
pBastbacHTb vector (Invitrogen). The final construct contains
a baculovirus gp67 signal peptide followed by a His10 tag, a
TEV cleavage site and the coding sequence corresponding
to residues 127-475 of factor Xa. The expressed glycosylated
enzyme was isolated from the cell culture medium by diafiltration
using crossflow ultrafiltration followed by passage over a nickel
chelate resin (binding buffer: 25 mM Tris [pH 7.9], 200 mM
NaCl). After removal of the His10-tag, the protein was activated
using snake venom (Enzyme Research, Russels Viper Venom,
RVV-X). The activated protein was deglycosylated (BioLabs,

3530 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 9
Fujimoto et al.
PNGase F, #P0704L) and then further purified over a MonoS
column (25 mM MES pH 6.5) followed by a S-200 column
(25 mM Tris pH 7.6, 200 mM NaCl) to remove inactive and
glycosylated species of the protease. The protein was incubated
with 1 mM of compound 5k for 30 min and concentrated to a
final concentration of 15 mg/mL. Crystals were obtained at
20 °C using Syrrx’s automated Nanovolume Crystallization
technology.21 The reservoir solution was 25% PEG 3350, 0.1 M
Tris pH 8.5. Crystals appeared within 3 days and grew to a
maximum size within 7-10 days. X-ray diffraction data were
collected at Advanced Light Source (ALS) beamline 5.0.3, and
processed using the program HKL2000.22 The crystals dif-
orally active, specific inhibitor of factor Xa, inhibits thrombosis without
affecting bleeding time in rats. Thromb. Haemostasis 1995, 74, 635–
639. (c) Perzborn, E.; Strassburger, J.; Wilmen, A.; Pohlmann, J.;
Roehrig, S.; Schlemmer, K.-H.; Straub, A. In vitro and in vivo studies
of the novel antithrombotic agent BAY 59-7939 an oral, direct factor
Xa inhibitor. J. Thromb. Haemostasis 2005, 3, 514–521. (d) Kubitza,
D.; Becka, M.; Voith, B.; Zuehlsdorf, M.; Wensing, G. Safety, pharma-
codynamics, and pharmacokinetics of single doses of BAY 59-7939,
an Oral, direct factor Xa inhibitor. Clin. Pharmacol. Ther. 2005, 78,
412–421. (e) Wong, P. C.; Pinto, D. J. P.; Knabb, R. M. Nonpeptide
factor Xa inhibitors: DPC423, a highly potent and orally bioavailable
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˚
fracted to 1.45 A resolution and belong to the P212121 space
group with one molecule in the asymmetric unit and unit cell
˚
˚
˚
parameters of a =49.0 A; b =70.3 A; and C =78.5 A. The
structure was determined by molecular replacement using
MOLREP, utilizing the published coordinates of factor Xa
with accession code 1FJS.23,24 Subsequent structure refine-
ment and model building were performed utilizing REFMAC
and XtalView.23,25 The final refined crystallographic statistics
for the cocrystal structure with compound 5k are R=19.4%
(Rfree, 21.2%), with root-mean-square deviations (rmsd) for
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current and future use of novel anticoagulants. Thromb. Res. 2008, 123,
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˚
bond lengths of 0.007 A, and for bond angles of 1.15°.
Compound 5k was bound into the active site and clearly
visible in the electron density maps.
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and treatment of thromboembolic diseases. Expert Opin. Investig.
Drugs 2006, 15, 843–855. (b) Casimiro-Garcia, A.; Dudley, D. A.;
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the discovery of Factor Xa inhibitors. Expert Opin. Ther. Patents
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J. Z.; Bauer, M. S.; Goldman, E. A.; Probst, G. D.; Song, Y.; Su, T.; Fan,
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R. M.; Zhu, B. Discovery of betrixaban (PRT054021), N-(5-chloropyri-
din-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxy-
benzamide, a highly potent, selective, and orally efficacious factor Xa
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7-Fluoroindazoles as potent and selective inhibitors of factor Xa.
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Klei, H. E.; Kish, K.; Liu, E. C. K.; Hartl, K. S.; Seiler, S. M.; Chang, M.;
Huang, C.; Youssef, S.; Steinbacher, T. E.; Schumacher, W. A.; Grazier,
N.; Pudzianowski, A.; Apedo, A.; Discenza, L.; Yanchunas, J.; Stein, J.;
P., D.; Atwal, K. S. Design, structure-activity relationships, X-ray
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potent and orally available factor Xa inhibitors. J. Med. Chem.
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Burns-Kurtis, C. L.; Campbell, M.; Chaudry, L.; Chung, C.; Convery,
M. A.; Hamblin, J. N.; Johnstone, L.; Kelly, H. A.; Kleanthous, S.;
Patikis, A.; Patel, C.; Pateman, A. J.; Senger, S.; Shah, G. P.; Toomey,
J. R.; Watson, N. S.; Weston, H. E.; Whitworth, C.; Young, R. J.; Zhou,
P. Factor Xa inhibitors: S1 binding interactions of a series of N-{(3S)-
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sulfonamides. J. Med. Chem. 2007, 50, 1546–1557. (h) Quan, M. L.;
Lam, P. Y. S.; Han, Q.; Pinto, D. J. P.; He, M. Y.; Li, R.; Ellis, C. D.;
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1-(30-aminobenzisoxazol-50-yl)-3-trifluoromethyl-N-[2-fluoro-4-[(20-
dimethylaminomethyl)imidazol-1-yl]phenyl]-1H-pyrazole-5-carboxy-
amide hydrochloride (Razaxaban), a highly potent, selective, and orally
bioavailable factor Xa inhibitor. J. Med. Chem. 2005, 48, 1729–1744.
(i) Koshio, H.; Hirayama, F.; Ishihara, T.; Shiraki, R.; Shigenaga, T.;
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tives as factor Xa inhibitors. Bioorg. Med. Chem. 2005, 13, 1305–
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Acknowledgment. The authors thank Dr. Shuji Kitamura
for helpful discussions; Dr. Teruaki Okuda, Shinichi Niwa,
and Yoko Hara for measuring metabolic stabilities of the
compounds highlighted in Table 1-6; the DMPK group at
Takeda Pharmaceutical Company for the monkey cassette
dosing experiments in Table 7 and measuring log D values for
the compounds highlighted in Tables 3-6; Craig Behnke,
Bi-Ching Sang, Shant Salakian, Jason Yano, Kumar
Saikatendu and Gyorgy Snell for molecular biology, protein
expression, crystallization and X-ray data collection support
highlighted in Figure 1.
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