Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitors VI. A series of new derivatives containing N,S- and N,SO2-spiro acetal scaffolds

Article abstract of DOI:10.1248/cpb.55.317

In the course of development of factor Xa (FXa) inhibitors, we have found unique compounds containing an N,O- and an N,N-spiro acetal structure. It appeared that the difference in overall conformation due to the N,X-spiro acetal structure might be importa

Full text of DOI:10.1248/cpb.55.317

February 2007
Chem. Pharm. Bull. 55(2) 317—323 (2007)
317
Synthesis and Evaluation of 1-Arylsulfonyl-3-piperazinone Derivatives as
Factor Xa Inhibitors1—6) VI. A Series of New Derivatives Containing
N,S- and N,SO2-Spiro Acetal Scaffolds
Fumihiko SAITOH,* Hidemitsu NISHIDA, Takafumi MUKAIHIRA, Naoto KOSUGA, Munetaka OHKOUCHI,
Tomokazu MATSUSUE, Ikuya SHIROMIZU, Yoshitaka HOSAKA, Miwa MATSUMOTO, and Ichiro YAMAMOTO
Pharmaceutical Research Center, Mochida Pharmaceutical Co., Ltd.; 722 Jimba-aza-uenohara, Gotemba, Shizuoka
412–8524, Japan. Received October 26, 2006; accepted November 20, 2006; published online November 24, 2006
In the course of development of factor Xa (FXa) inhibitors, we have found unique compounds containing an
N,O- and an N,N-spiro acetal structure. It appeared that the difference in overall conformation due to the N,X-
spiro acetal structure might be important for FXa inhibitory activity. Therefore, other N,X-spiro acetal struc-
tures, an N,S- and an N,SO2-spiro acetal, were developed as analogues of the N,X-spiro acetal structure. Com-
pound 7b (N,S-spiro acetal structure) was found to have the strongest activity in these series of N,X-spiro acetal
compounds, which had ever been synthesized.4,5)
Key words factor Xa inhibitor; structure–activity relationship; N,S-spiro acetal; N,SO2-spiro acetal; intramolecular cyclization
Factor Xa (FXa), a trypsin-like serine protease, occupies a quite different from the N,O- and N,N-spiro acetal structures
central position in the blood coagulation cascade in linking (as calculated by MOPAC PM3).38)
the intrinsic and extrinsic mechanisms. FXa is known to acti-
Therefore, these N,S- and N,SO2-spiro acetal structures,
vate prothrombin to thrombin. Thrombin has several proco- which can be prepared by changing the central atom to sul-
agulant functions, including the activation of platelets, feed- fur, would have the potential for increasing inhibitory activ-
back activation of other coagulation factors, and conversion ity of FXa.
of fibrinogen to insoluble fibrin clots.7—11) Comparison of
In this paper, we discuss the synthesis and structure–activ-
hirudin12—16) (a thrombin inhibitor) and tick anticoagulant ity relationships of compounds containing the N,S-spiro
peptide17—22) (a FXa inhibitor) suggests that inhibition of acetal, which is spiro[5H-thiazolo[3,2-a]pyradine-2(3H)-
FXa may result in less risk of bleeding, leading to a more fa- piperidin]-5-one scaffold, and containing the N,SO2-spiro
vorable safety/efficacy ratio.23—27)
acetal, which is spiro[5H-thiazolo[3,2-a]pyradine-2(3H)-
Direct inhibition of FXa has therefore emerged as an at- piperidin]-5-one 1,1-dioxide scaffold, as analogues to the
tractive strategy for the discovery of novel antithrombotic central part of the compound.
agents.28—34) Fondaparinux (Arixtra®),35—37) which was ap-
proved as the first selective FXa inhibitor in 2002, has been Chemistry
proven to be clinically useful. However, because fonda-
First, the amino-thiol 4, an acyclic precursor, was prepared
parinux is a penta-saccharide limited to subcutaneous admin- as shown in Chart 1.
istration, novel orally administratable FXa inhibitors have
The carboxylic acid 1, which had been reported,39) was
been desired. However, no approved orally administratable converted to the corresponding amide 2 with ethyl chlorofor-
FXa inhibitor is available in the world.
In previous papers,4,5) we reported that spiro[5H-oxa-
Table 1. Cyclic N,O- and N,N-Spiro Acetal vs. Cyclic N,S- and N,SO2-
zolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one (N,O-spiro ac-
etal) derivatives and their nitrogen analogues, which were
spiro[imidazo[1,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5(1H)-one
(N,N-spiro acetal) derivertives, were found to be potent in-
hibitors of FXa.
Spiro Acetal
With change of the central atom from oxygen to nitrogen,
the inhibitory activity of FXa tended to increase. This im-
provement of activity might be based on the slight difference
in the conformation between the N,O- and the N,N-spiro ac-
etal structures.
X
O
N(R)
S
SO2
Bond length C2-X (Å)
Bond length X-C8a (Å)
Bong angle C2-X-C8 (°)
1.44
1.43
111.7
1.50
1.50
110.3
1.85
1.87
94.7
1.87
1.91
93.7
Calculated by MOPAC PM3.
As shown in Table 1, the N,S- and N,SO2-spiro acetals are
Chart 1. Synthesis of the Amino-Thiol 4 as an Acyclic Precursor
∗ To whom correspondence should be addressed. e-mail: fsaitoh@mochida.co.jp
© 2007 Pharmaceutical Society of Japan

318
Vol. 55, No. 2
Chart 2. Synthesis of the Key Tricyclic Intermediates 6a—c and the N,S-Spiro Acetal Compounds 7a—c
Chart 3. Synthesis of the N,SO2-Spiro Acetal Compounds 10a—c
mate and 6.5 N ammonia–ethanol. The Boc group in amide 2 the desired compounds 7a—c by deprotection reaction of the
was deprotected, and a benzyl moiety was introduced to ob- N-benzyl moiety with a-chloroethyl chloroformate and by
tain the N-benzyl amide 3. The amide moiety of 3 was re- the pyridine coupling reaction, as shown in Chart 2.
duced to an aminomethyl moiety with lithium aluminum hy-
Meanwhile, the N,SO2-spiro acetal compounds 10a—c
dride, and the p-methoxybenzyl moiety of the thioether in the were converted from the key tricyclic compounds 6a—c as
compound was deprotected with trifluoromethansulfonic acid shown in Chart 3.
and trifluoroacetic acid40) to obtain the amino-thiol 4 in good
yield.
Compounds 8a—c, which were derived from the key tri-
cyclic compounds 6a—c by deprotection reaction of the N-
Second, the key tricyclic compound 6a, which was an N,S- benzyl group and by inducing the Boc group on the piperi-
spiro acetal scaffold, was prepared by an intramolecular cy- dine ring, were oxidized with m-chloroperoxybenzoic acid to
clization reaction, as shown in Chart 2.
obtain the N,SO2-spiro acetal compounds 9a—c, respectively.
The Boc group in compounds 9a—c was removed in tri-
The amino-thiol 4 was coupled with the keto-ester 5a41,42)
under slightly acidic conditions to obtain the key tricyclic fluoroacetic acid, and pyridine coupling reaction was carried
compound 6a in a fashion similar to the method described in out to obtain compounds 10a—c, respectively.
previous papers.4,5)
The other key tricyclic compounds 6b and 6c were ob- Results and Discussion
tained with the amino-thiol 4 and the other keto-ester 5b4) or
The FXa inhibitory activities of new compounds with the
N,S- and the N,SO2-spiro acetal structure synthesized in the
the aldehyde-ester 5c2) instead of the keto-ester 5a.
To synthesize compound 6b, which has the acetoxymethyl present investigation were measured using the same method
moiety as a side chain, reaction for amide formation was car- as described in previous papers.4,5) Results were summarized
ried out by adding p-toluene sulfonic acid, and toluene fol- in Table 2.
lowing the first N,S-sipro acetal formation step. Compound
6c was obtained in toluene–H2O in the presence of p-toluene acetal compounds 7a and 10a, with methoxymethyl moiety
sulfonic acid. as a side chain, had high activity (IC50; 7a: 1.3 nM, 10a: 2.3
These key tricyclic compounds 6a—c were converted to nM). These activities were almost equivalent compared with
As might have been expected, the N,S- and the N,SO2-spiro

February 2007
319
Table 2. Comparison of FXa Inhibitory Activity of Cyclic N,S- and
N,SO2-Spiro Acetal Compounds
Compound
X
R
IC50 (nM)
7a
10a
11
12
13
7b
10b
14
15
16
S
SO2
NH
NMe
O
CH2OMe
CH2OMe
CH2OMe
CH2OMe
CH2OMe
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
H
1.3
2.3
1.55)
1.65)
5.04)
1.2
S
SO2
NH
NMe
O
1.9
2.45)
1.75)
5.04)
1.5
Fig. 1. Overall conformations of N,S- or N,SO2-acetal scaffolds are better
than N,N- or N,O-acetal scaffolds for binding in S1 and S4 pockets of FXa.
7c
S
10c
17
18
SO2
NH
NMe
O
H
H
H
H
3.0
cupy S2/S3 regions where the tricyclic scaffold located.
In contrast, the N,O- or N,N- acetal scaffolds, without a
side chain, might be slightly smaller for that steric occupa-
tion43) and they might have less suitable overall conforma-
tions for binding with FXa active site. Hence the N,O- or
5.75)
18.25)
17.25)
19
N,N-acetal compounds 11 and 12,5) and were superior to N,N-acetal scaffolds would generally need a side chain (R: in
N,O-acetal compound 13.4)
Compound 7b and 10b, which had hydroxymethyl moiety maintain the FXa inhibitory activity.
Fig. 1) like the methoxymethyl or hydroxymethyl moieties to
as a side chain, also inhibited activity of FXa (IC50; 7b: 1.2
In conclusion, we have reported novel active FXa in-
nM, 10b: 1.9 nM). These compounds also had approximately hibitors which have N,S- and N,SO2-spiro acetal structures as
equivalent activity compared to corresponding N,N-acetal analogues of N,O- and N,N-spiro acetals and demonstrated
compounds 14 and 15,5) and had slightly higher activity than that both compounds with and without side chains have high
corresponding N,O-acetal compound 16.4)
FXa inhibitory activity.
In addition, compound 7c and 10c, in which a substituent
Further investigations regarding other N,X-spiro acetal
was changed to a proton from the methoxymethyl or the hy- parts are going in our laboratory and results will be pub-
droxymethyl moiety as a side chain, had high activities (IC50; lished in due course.
7c: 1.5 nM, 10c: 3.0 nM). Although corresponding N,O- or
Experimental
N,N-acetal compounds 17—19 tended to reduce their activ-
Melting points (mp) were determined by using METTLER FP82 hotstage
ity,5) compounds 7c and 10c could maintain high activity.
melting point apparatus and were uncorrected. Nuclear magnetic resonance
Based on these results, we have thought that the features
of N,S- and N,SO2-spiro acetal scaffolds were as below.
First, sulfur atom is larger than nitrogen or oxygen atom
and thus both C–S(O2) bond length must be longer than C–O
or C–N bond. In addition, the bond angles of C2–S(O2)–C8a
(NMR) spectra were taken with JEOL JNM-EX270 FT-NMR or JEOL JNM-
LA300 in CDCl3, dimethyl sulfoxide-d6 (DMSO-d6) using tetramethylsilane
as the internal reference. Mass spectra (MS) were obtained using BRUKER
Auto FLEX TOF/TOF or Waters FranctionLynx® MS System (LC/ESI-MS).
Infrared absorption spectra (IR) were run using HORIBA FT-720 FT-IR.
Measurement of Factor Xa Inhibition Enzyme solution was mixed
must be smaller than C2–N–C8a or C2–O–C8a angles as men- with a test compound dissolved at various concentrations in dimethyl sulfox-
ide (DMSO). Synthetic substrate was added and incubated in a 20 mM
Tris–HCl buffer (pH 7.5) containing 0.13 M NaCl at 37 °C. The absorbance
at 405 nm was measured continuously. Enzyme and substrate were used as
follows: human factor Xa (Enzyme Research Laboratories, Inc., 0.019 U/ml)
and S-2222 (Chromogenix AB, 0.4 mM). To calculate the inhibitory activity
of the test compound, the initial reaction velocity was compared with the
value for a control containing no test compound. The inhibitory activity of a
test compound was expressed as IC50.
tioned in Table 1. Therefore, conformations of the N,S- and
the N,SO2-acetal scaffolds could be slightly changed and the
overall conformations of these compounds could be more ad-
vantageous for inhibiting the FXa active site.
As shown in Fig. 1, it is essential for FXa inhibitory activ-
ity that the pyridine ring on the compound is located in the
S4 pocket and that the naphthyl ring enters into the S1
pocket. In addition, the halogen-p interaction between the
chlorine atom on the naphthyl ring of the compound and
phenyl ring on Tyr228, which exists in the bottom of S1
pocket, is important for this activity. The tricyclic scaffold
including N,X-acetal structures (XꢁO, N, or S(O2)) plays a
role of a linker which connects pyridine ring and naphthyl
ring being suitable position. In particular, the N,S- and
N,SO2-acetal scaffolds could fit the above pharmacophore.
Second, one of the reasons why compounds 7c and 10c,
without a side chain, also had high activity might be that not
only overall conformations of N,S- and N,SO2-acetal scaf-
4-Carbamoyl-4-[[(4-methoxyphenyl)methyl]thio]piperidine-1-car-
boxylic Acid tert-butyl Ester (2) To the solution of compound 1,39) (2.8 g)
in CHCl3 (50 ml) were added Et3N (1.23 ml) and ethyl chloroformate
(0.77 ml) at 0 °C. The reaction mixture was stirred for 30 min at 0 °C. Then
6.5 N NH3–EtOH (5.6 ml) was added into the reaction mixture and the reac-
tion mixture was stirred for 30 min at room temperature. To the reaction
mixture was added water at 0 °C and the reaction mixture was extracted with
CH2Cl2. The organic solvent was washed with 1 N HCl, water, saturated
NaHCO3 aqueous solution, and brine, respectively and dried with anhydrous
Na2SO4. The solvent was removed under reduced pressure and the resulting
residue was purified by silica gel flash column chromatography (eluant:
Hex/AcOEtꢁ1/1) to afford compound 2 (2.12 g, 76% yield) as a colorless
amorphous solid.
1H-NMR (270 MHz, DMSO-d6, 100 °C) d: 7.23—7.14 (2H, m), 6.95 (2H,
folds could be more suitable, but also they could widely oc- br s), 6.88—6.78 (2H, m), 3.73 (3H, s), 3.69 (2H, s), 3.52—3.39 (2H, m),

320
Vol. 55, No. 2
3.34—3.22 (2H, m), 2.12—1.99 (2H, m), 1.75—1.62 (2H, m), 1.40 (9H, s).
1.80 (2H, m), 1.70—1.40 (2H, m). 13C-NMR (75 MHz, CDCl3) d: 162.85,
4-[[(4-Methoxyphenyl)methyl]thio]-1-(phenymethyl)piperidine-4-car- 138.06, 135.69, 135.49, 133.01, 130.84, 130.47, 129.05, 129.02 (3C),
boxamide (3) [Step 1]: To the compound 2 (2.47 g) was added 10% 128.98, 128.23 (2C), 127.11, 126.84, 123.55, 74.99, 71.68, 62.86, 59.67,
HCl–MeOH (40 ml) and the reaction mixture was stirred at room tempera- 56.81, 56.67, 52.30, 51.01, 50.72, 47.80, 38.50, 36.28. IR (KBr) cmꢃ1
ture overnight. Additionally, 10% HCl–MeOH (20 ml) was added to the re- 1664, 1452, 1410, 1350, 1165, 1119, 1078, 729, 692.
:
action mixture and the reaction mixture was stirred at 30 °C for 2 h. The re-
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(methoxymethyl)-
action mixture was concentrated in vacuo. To the resulting residue was 1ꢀ-(4-pyridinyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-
washed with Et2O and the supernatant was decanted. The remaining Et2O one (7a) [Step 1]: To the solution of compound 6a (0.45 g) in 1,2-
was removed under reduced pressure to afford the deprotected compound— dichloroethane (9 ml), were added 1,8-bis(dimethylamino)naphthalene
hydrochloric acid salt (1.87 g, 91% yield) as a colorless amorphous solid.
(0.033 g) and a-chloroethyl chloroformate (0.21 ml) at 0 °C. The reaction
1H-NMR (300 MHz, DMSO-d6, 100 °C) d: 8.91 (2H, m), 7.25—7.15 (2H, mixture was stirred at room temperature for 30 min then was refluxed for
m), 7.14 (1H, br s), 6.88—6.82 (2H, m), 3.75 (3H, s), 3.71 (2H, s), 3.22— 1 h. It was concentrated in vacuo. To the resulting residue was added MeOH
3.12 (2H, m), 3.03—2.88 (2H, m), 2.39—2.27 (2H, m), 2.07—1.05 (2H, m).
(9 ml) and the mixture was refluxed for 30 min. After cooling, the reaction
[Step 2]: The deprotected compound (1.8 g) which was afforded in Step 1, mixture was concentrated in vacuo. To the resulting residue was added Et2O
was dissolved in N,N-dimethylformamide (80 ml). To the reaction mixture for precipitation. The supernatant was decanted. Then the above washing
were added K2CO3 (1.96 g) and benzyl bromide (0.74 ml) at 0 °C. The reac-
tion mixture was stirred at room temperature overnight. The reaction mix- precipitate was dissolved in water and the aqueous solution was made basic
ture was concentrated in vacuo to approximately 20 ml volume and 1 N HCl
to pH 9—10 with saturated NaHCO3 aqueous solution. The aqueous solu-
was carried out several times, the precipitate was collected by filtration. The
was added to the concentrated mixture. Then this mixture was washed with tion was extracted with CH2Cl2 and the organic layer was washed with brine
AcOEt for removing excess benzyl bromide and the water layer was adjusted and was dried with anhydrous Na2SO4. The solvent was removed under re-
to pH 10 with 1 N NaOH and with saturated NaHCO3 aqueous solution. The
duced pressure and the resulting residue was purified by amino-silica gel
water layer was extracted with AcOEt and the organic layer was washed with column chromatography (Fuji Silysia Chemical Ltd., Chromatorex NH®,
water, brine and was dried with anhydrous Na2SO4. The solvent was re- eluant: Hex/CH2Cl2ꢁ1/1—0/100) to afford deprotected compound (0.34 g,
moved under reduced pressure and the resulting residue was purified by sil- 90% yield) as a colorless amorphous solid.
ica gel flash column chromatography (eluant: CH2Cl2/MeOHꢁ98/2—95/
5—90/10) to afford compound 3 (1.74 g, 83% yield) as a colorless amor-
phous solid.
1H-NMR (300 MHz, CDCl3) d: 8.38—8.33 (1H, m), 8.00—7.90 (3H, m),
7.79 (1H, dd, Jꢁ1.8, 8.6 Hz), 7.61 (1H, dd, Jꢁ2.2, 8.6 Hz), 4.70 (1H, d, Jꢁ
12.3 Hz), 4.41 (1H, d, Jꢁ12.1 Hz), 4.34 (1H, d, Jꢁ17.1 Hz), 3.89 (1H, d, Jꢁ
1H-NMR (300 MHz, CDCl3) d: 7.34—7.17 (7H, m), 6.86—6.79 (2H, m), 9.0 Hz), 3.46 (3H, s), 3.35 (1H, d, Jꢁ17.1 Hz), 3.13 (1H, d, Jꢁ12.3 Hz),
6.38 (1H, br s), 5.34 (1H, br s), 3.79 (3H, s), 3.66 (2H, s), 3.51 (2H, s),
2.67—2.45 (4H, m), 2.32—2.19 (2H, m), 1.90—1.78 (2H, m).
3.00—2.58 (4H, m), 2.58 (1H, d, Jꢁ12.1 Hz), 1.90—1.74 (2H, m), 1.60—
1.40 (2H, m).
4-Aminomethyl-1-(phenylmethyl)piperidine-4-thiol bis(trifluorometh-
[Step 2]: To a solution of the deprotected compound (50 mg) which was
anesulfonate) (4) [Step 1]: To a suspension of LiAlH4 (0.88 g) in Et2O afforded in Step 1 in EtOH (0.8 ml) were added 4-chloropyridine hydrochlo-
(15 ml) was dropwised the suspension of compound 3 (1.23 g) in Et2O
(18 ml) at 0 °C. The reaction mixture was stirred at room temperature for
ride (23 mg) and i-Pr2NEt (88 ml). The mixture was stirred at 150—160 °C
in a sealed tube for 4 h then it was concentrated in vacuo. The resulting
15 min and then was refluxed 3.5 h. After cooling the reaction mixture, water residue was purified by amino-silica gel column chromatography (Fuji
(0.9 ml), 1 N NaOH (0.9 ml), and water (2.7 ml) were added to the reaction
Silysia Chemical Ltd., Chromatorex NH®, eluant: Hex/CH2Cl2ꢁ1/1—
mixture at 0 °C for quenching. Additionally, Et2O was added to the mixture CH2Cl2–CH2Cl2/MeOHꢁ99/1) then was re-purified by silica gel column
and stirred at room temperature for 30 min. Then insoluble matter was re- chromatography (eluant: CH2Cl2–CH2Cl2/MeOHꢁ99/1—98/2) to afford
moved by Celite® filtration and was washed with THF and Et2O. The filtrate compound 7a (14 mg, 24% yield) as a colorless amorphous solid.
was concentrated in vacuo to afford amino-compound (1.12 g, 95% yield) as
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C27H3035ClN4O4S2:
573.1397. Found: 573.1426. H-NMR (300 MHz, CDCl3) d: 8.37 (1H, s),
1
a colorless amorphous solid.
1H-NMR (300 MHz, CDCl3) d: 7.34—7.20 (7H, m), 6.87—6.80 (2H, m), 8.24 (2H, d, Jꢁ6.2 Hz), 7.80 (1H, dd, Jꢁ1.5, 8.6 Hz), 7.62 (1H, dd, Jꢁ2.0,
3.79 (3H, s), 3.54 (2H, s), 3.54 (2H, s), 2.68—2.48 (4H, m), 2.65 (2H, s), 8.6 Hz), 6.59 (2H, d, Jꢁ6.2 Hz), 4.72 (1H, d, Jꢁ12.5 Hz), 4.43 (1H, d,
1.79—1.55 (4H, m).
[Step 2]: The amino-compound (0.69 g) which was afforded in Step 1,
Jꢁ12.3 Hz), 4.36 (1H, d, Jꢁ17.1 Hz), 3.91 (1H, d, Jꢁ8.8 Hz), 3.75—3.43
(2H, m), 3,59 (1H, d, Jꢁ8.8 Hz), 3.47 (3H, s), 3.38 (1H, d, Jꢁ17.1 Hz), 3.22
was dissolved in trifluoroacetic acid (10 ml). To the reaction mixture were (1H, d, Jꢁ12.5 Hz), 3.15—2.90 (2H, m), 2.61 (1H, d, Jꢁ12.3 Hz), 2.05—
added anisole (0.69 ml) and trifluoromethansulfonic acid (6.9 ml) at 0 °C.
The reaction mixture was stirred at 0 °C for 40 min. Then to the reaction
mixture was added Et2O for precipitating compound 4. The supernatant was
1.90 (2H, m), 1.75—1.50 (2H, m). 13C-NMR (75 MHz, CDCl3) d: 162.97,
154.35, 150.31 (2C), 135.72, 135.60, 133.01, 130.85, 130.47, 129.13,
129.05, 129.03, 126.84, 123.53, 108.63 (2C), 74.98, 72.20, 59.70, 56.83,
decanted and The remaining Et2O was removed under reduced pressure to 56.74, 52.04, 47.90, 45.63, 43.90, 37.45, 35.24. IR (film) cmꢃ1: 1662, 1597,
afford the compound 4 (0.89 g, 86% yield) as a colorless amorphous solid.
1462, 1412, 1348, 1240, 1165, 970, 692.
8a-(Acetoxymethyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]tetrahydro-
1H-NMR (300 MHz, CDCl3) d: 7.35—7.20 (5H, m), 7.17 (2H, br s), 3.55
(2H, s), 2.75—2.65 (2H, m), 2.72 (2H, s), 2.52—2.40 (2H, m), 1.76—1.58 1ꢀ-(phenylmethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-
(4H, m).
5-one (6b) To the solution of compound 4 (5.0 g) and compound 5b (4.1 g)
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(methoxymethyl)- in EtOH (50 ml) was added sodium acetate (1.5 g). The reaction mixture was
1ꢀ-(phenylmethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]- refluxed for 4 h. Then the reaction mixture was concentrated in vacuo. The
5-one (6a) The solution of compound 4 (0.79 g) and compound 5a (0.61 g)
resulting mixture was dissolved in toluene (500 ml) and TsOH–H2O (20 mg)
in EtOH (12 ml) was refluxed for 1 h. Then sodium acetate (0.12 g) was was added into the solution. The reaction mixture was refluxed for 1 h. After
added into the reaction mixture and the reaction mixture was refluxed for an- cooling, to the reaction mixture was added water and the mixture was ex-
other hour. The reaction mixture was poured into a sealed tube and toluene tracted with AcOEt. The organic layer was washed with brine and was dried
(11 ml) was additionally added to the reaction mixture. It was stirred at with anhydrous Na2SO4. The solvent was removed under reduced pressure
150—160 °C for 2.5 h. After cooling, the reaction mixture was concentrated
and the resulting residue was purified by silica gel flash column chromatog-
in vacuo and the resulting residue was purified by silica gel flash column raphy (eluant: Hex/AcOEtꢁ70/30—50/50—30/70) to afford compound 6b
chromatography (eluant: CH2Cl2/MeOHꢁ99.5/0.5—99/1—98.5/1.5—98/2) (4.0 g, 70% yield) as a colorless amorphous solid.
to afford compound 6a (0.70 g, 72% yield) as a pale yellow amorphous
solid.
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C30H3335ClN3O5S2:
614.1550. Found: 614.1580. 1H-NMR (300 MHz, CDCl3) d: 8.37—8.33
(1H, m), 7.98—7.90 (3H, m), 7.77 (1H, dd, Jꢁ1.8, 8.8 Hz), 7.61 (1H, dd,
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C29H3335ClN3O4S2: 586.1601.
Found: 586.1572. 1H-NMR (300 MHz, CDCl3) d: 8.17—8.12 (1H, m), Jꢁ2.2, 8.8 Hz), 7.3—7.18 (5H, m), 4.70 (1H, d, Jꢁ12.5 Hz), 4.46—4.25
8.00—7.87 (3H, m), 7.78 (1H, dd, Jꢁ1.8, 8.8 Hz), 7.60 (1H, dd, Jꢁ2.0, 8.8 (4H, m), 3.44 (2H, s), 3.36 (1H, d, Jꢁ17.1 Hz), 3.16 (1H, d, Jꢁ12.5 Hz),
Hz), 7.32—7.18 (5H, m), 4.68 (1H, d, Jꢁ12.1 Hz), 4.39 (1H, d, Jꢁ12.1 Hz),
4.32 (1H, d, Jꢁ17.1 Hz), 3.88 (1H, d, Jꢁ9.0 Hz), 3.54 (1H, d, Jꢁ9.0 Hz),
2.71 (1H, d, Jꢁ12.5 Hz), 2.70—2.50 (2H, m), 2.10 (3H, s), 2.28—2.03 (2H,
m), 1.97—1.80 (2H, m), 1.70—1.58 (1H, m), 1.57—1.45 (1H, m). 13C-
3.45 (3H, s), 3.45 (2H, s), 3.34 (1H, d, Jꢁ17.1 Hz), 3.13 (1H, d, Jꢁ12.1 Hz), NMR (75 MHz, CDCl3) d: 169.98, 162.64, 137.96, 135.73, 135.59, 132.86,
2.72—2.47 (2H, m), 2.56 (1H, d, Jꢁ12.1 Hz), 2.30—2.05 (2H, m), 1.98— 130.83, 130.43, 129.14, 129.11, 129.07, 129.00 (2C), 128.25 (2C), 127.14,

February 2007
321
126.85, 123.50, 70.62, 65.96, 62.85, 57.44, 56.36, 52.35, 51.54, 50.76, After cooling, the reaction mixture was concentrated in vacuo. To the result-
47.69, 38.67, 36.40, 20.74. IR (KBr) cmꢃ1: 1747, 1668, 1454, 1408, 1225,
1165, 1078, 694.
ing residue was added Et2O for precipitation. The precipitate was collected
by filtration and the filtrate was dissolved in saturated NaHCO3 aqueous so-
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(hydroxymethyl)- lution. The aqueous solution was extracted with AcOEt and the organic layer
1ꢀ-(4-pyridinyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-
one (7b) [Step 1]: To the solution of compound 6b (4.0 g) in CH2Cl2
was washed with water and brine and then was dried with anhydrous
Na2SO4. The solvent was removed under reduced pressure and the resulting
(80 ml), were added 1,8-bis(dimethylamino)naphthalene (0.28 g) and a- residue was purified by amino-silica gel column chromatography (Fuji
chloroethyl chloroformate (1.78 ml) at 0 °C. The reaction mixture was Silysia Chemical Ltd., Chromatorex NH®, eluant: Hex/AcOEtꢁ1/1—
stirred at room temperature for 2 h. The reaction mixture was concentrated AcOEt–AcOEt/MeOHꢁ90/10) to afford the deprotected compound (3.9 g,
in vacuo. MeOH (80 ml) was added to the resulting residue and the reaction
mixture was refluxed for 1 h. After cooling, the reaction mixture was con-
centrated in vacuo. To the resulting residue was added Et2O for precipita- m), 7.78 (1H, dd, Jꢁ2.0, 8.6 Hz), 7.61 (1H, dd, Jꢁ2.0, 8.6 Hz), 5.08 (1H, dd,
tion. The supernatant was decanted. Then the above washing was carried out Jꢁ4.3, 10.2 Hz), 4.43 (1H, d, Jꢁ12.2 Hz), 4.32 (1H, d, Jꢁ16.8 Hz), 4.32—
quant.) as a pale red amorphous solid.
1H-NMR (270 MHz, CDCl3) d: 8.35 (1H, d, Jꢁ2.0 Hz), 8.99—8.91 (3H,
several times, the precipitate was dissolved in EtOH (40 ml) and 1 N NaOH
4.22 (1H, m), 3.34 (1H, d, Jꢁ16.7 Hz), 3.12 (1H, d, Jꢁ12.2 Hz), 3.05—2.85
(40 ml). While stirring the above solution, the precipitate was appeared. The (2H, m), 2.80—2.65 (2H, m), 2.58 (1H, dd, Jꢁ10.2, 12.2 Hz), 1.90—1.35
precipitate was collected by filtration to afford deprotected compound (2.7 g, (4H, m).
86% yield) as a pale yellow amorphous solid.
[Step 2]: To a solution of the deprotected compound (1.0 g) which was af-
1H-NMR (270 MHz, DMSO-d6) d: 8.59 (1H, s), 8.35—8.13 (3H, m), 7.89 forded in Step 1 in EtOH (20 ml) were added 4-chloropyridine hydrochloride
(1H, dd, Jꢁ2.0, 8.9 Hz), 7.74 (1H, dd, Jꢁ2.3, 8.9 Hz), 5.50 (1H, br s), 4.50
(1H, d, Jꢁ11.9 Hz), 4.15 (1H, d, Jꢁ12.2 Hz), 3.99 (1H, d, Jꢁ16.2 Hz), 3.77
(1H, dd, Jꢁ4.3, 10.6 Hz), 3.67—3.45 (2H, m), 3.13 (1H, d, Jꢁ12.2 Hz),
(0.5 g) and i-Pr2NEt (1.9 ml). The mixture was stirred at 140—160 °C in a
sealed tube for 3 h then it was concentrated in vacuo. The resulting residue
was purified by amino-silica gel column chromatography (Fuji Silysia
3.00—2.30 (4H, m), 2.85 (1H, d, Jꢁ11.9 Hz), 1.80—1.60 (2H, m), 1.55— Chemical Ltd., Chromatorex NH®, eluant: Hex/AcOEtꢁ1/2—AcOEt–
1.28 (2H, m).
AcOEt/MeOHꢁ95/5) to afford compound 7c (163 mg, 14% yield) as a col-
[Step 2]: To a solution of the deprotected compound (0.43 g) which was orless amorphous solid.
afforded in Step 1 in EtOH (20 ml) were added 4-chloropyridine hydrochlo-
ride (0.20 g) and i-Pr2NEt (0.78 ml). The mixture was stirred at 140—160 °C
in a sealed tube for 9 h then it was concentrated in vacuo. The resulting
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C25H2635ClN4O3S2:
529.1135. Found: 529.1110. H-NMR (300 MHz, CDCl3) d: 8.36 (1H, s),
8.26 (2H, d, Jꢁ5.9 Hz), 8.02—7.90 (3H, m), 7.84—7.75 (1H, m), 7.67—
1
residue was purified by amino-silica gel column chromatography (Fuji 7.58 (1H, m), 6.62 (2H, d, Jꢁ5.9 Hz), 5.20—5.10 (1H, m), 4.48 (1H, d, Jꢁ
Silysia Chemical Ltd., Chromatorex NH®, eluant: AcOEt–AcOEt/MeOHꢁ 12.3 Hz), 4.40—4.25 (2H, m), 3.80—3.55 (2H, m), 3.38 (1H, d, Jꢁ16.9 Hz),
90/10) to afford compound 7b (58 mg, 12% yield) as a colorless amorphous
3.18 (1H, d, Jꢁ12.3 Hz), 3.15—2.97 (2H, m), 2.67—2.55 (1H, m), 2.05—
1.90 (2H, m), 1.87—1.60 (2H, m). 13C-NMR (75 MHz, CDCl3) d: 162.33,
solid.
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C26H2835ClN4O4S2: 154.31, 150.30 (2C), 135.68, 135.58, 132.84, 130.79, 130.39, 129.11 (2C),
559.1240. Found: 559.1218. 1H-NMR (300 MHz, CDCl3) d: 8.40—8.39 129.02, 126.80, 123.46, 108.63 (2C), 59.62, 57.66, 55.90, 49.60, 47.93,
(1H, m), 8.28—8.22 (2H, m), 8.00—7.93 (3H, m), 7.80 (1H, dd, Jꢁ1.8, 8.6 45.27, 44.24, 37.38, 35.46. IR (film) cmꢃ1: 1664, 1597, 1421, 1348, 1163,
Hz), 7.63 (1H, dd, Jꢁ2.0, 9.0 Hz), 6.66—6.58 (2H, m), 4.74 (1H, d, Jꢁ 694.
12.5 Hz), 4.48—4.33 (2H, m), 4.17 (1H, d, Jꢁ11.2 Hz), 3.80 (1H, d, Jꢁ
11.2 Hz), 3.78—3.66 (1H, m), 3.64—3.54 (1H, m), 3.43 (1H, d, Jꢁ16.9 Hz),
3.24 (1H, d, Jꢁ12.5 Hz), 3.18—2.97 (2H, m), 2.71 (1H, d, Jꢁ12.7 Hz),
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]-
tetrahydro-8a-(methoxymethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-
2(3H),4ꢀ-piperidin]-5-one (8a)The deprotected compound (100 mg), which
2.05—1.94 (2H, m), 1.85—1.45 (2H, m). 13C-NMR (75 MHz, CDCl3) d: was obtained in the synthesis of compound 7a; Step 1, was dissolved in
162.70, 154.33, 149.98 (2C), 135.71, 135.63, 133.11, 130.80, 130.43, CH2Cl2 (2 ml). To this solution was added di-t-butyl dicarbonate (44.1 mg)
129.16, 129.10, 128.94, 126.84, 123.32, 108.61 (2C), 74.07, 65.82, 57.39, at 0 °C. The reaction mixture was stirred at room temperature overnight.
56.65, 50.67, 47.85, 45.61, 43.94, 37.65, 35.51. IR (film) cmꢃ1: 1657, 1599, Then it was concentrated in vacuo and the resulting mixture was purified by
1462, 1346, 1165, 692.
silica gel flash column chromatography (eluant: CH2Cl2–CH2Cl2/MeOHꢁ
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-1ꢀ-(phenylmethyl)- 98/2) to afford compound 8a (107 mg, 89% yield) as a colorless amorphous
spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one (6c) To the
suspension of compound 4 (5.0 g) and compound 5c (3.45 g) in toluene (500
solid.
ESI-MS m/z (MꢂH): 596 (MꢂꢂH), 496 (MꢂꢃBocꢂH). H-NMR (300
1
ml) was added sodium acetate (1.53 g). Water (5 ml) was added into the mix- MHz, CDCl3) d: 8.38—8.33 (1H, m), 8.00—7.91 (3H, m), 7.79 (1H, dd, Jꢁ
ture. The reaction mixture was stirred at room temperature for 1 h then was 1.7, 8.8 Hz), 7.61 (1H, dd, Jꢁ2.0, 8.8 Hz), 4.67 (1H, d, Jꢁ12.3 Hz), 4.45—
refluxed for 2 h. Then the reaction mixture was concentrated in vacuo. To the 4.30 (2H, m), 3.95—3.68 (3H, m), 3.57 (1H, d, Jꢁ8.4 Hz), 3.46 (3H, s),
resulting mixture was added water and the mixture was extracted with 3.35 (1H, d, Jꢁ17.0 Hz), 3.17 (1H, d, Jꢁ12.3 Hz), 3.10—2.83 (2H, m), 2.57
AcOEt. The organic layer was washed with saturated NaHCO3 aqueous so-
(1H, d, Jꢁ11.9 Hz), 1.87—1.75 (2H, m), 1.68—1.35 (2H, m), 1.41 (9H, s).
lution, brine, and was dried with anhydrous Na2SO4. The solvent was re- 13C-NMR (75 MHz, CDCl3) d: 162.92, 154.46, 135.72, 135.56, 132.97,
moved under reduced pressure and Et2O was added to the resulting residue 130.84, 130.48, 129.11, 129.04 (2C), 126.84, 123.51, 79.94, 74.98, 72.02,
for crystallization. The precipitate was collected by filtration to afford com- 59.69, 57.06, 56.87, 51.02, 47.85, 42.88, 40.97, 38.13, 36.00, 28.36 (3C). IR
pound 6c (4.7 g, 93% yield) as colorless crystals.
(KBr) cmꢃ1: 1689, 1672, 1412, 1350, 1240, 1167, 1078, 692.
mp 170.5—171.8 °C. MALDI-TOF-HR-MS m/z (MꢂH): Calcd for
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]-
tetrahydro-8a-(methoxymethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-
C27H2935ClN3O3S2: 542.1339. Found: 542.1389. 1H-NMR (300 MHz,
CDCl3) d: 8.37—8.32 (1H, m), 8.00—7.90 (3H, m), 7.77 (1H, dd, Jꢁ1.8, 2(3H),4ꢀ-piperidin]-5-one 1,1-dioxide (9a) To the solution of compound
8.8 Hz), 7.60 (1H, dd, Jꢁ2.0, 9.0 Hz), 7.35—7.20 (5H, m), 5.06 (1H, dd, 8a (95 mg) in CH2Cl2 (9.5 ml), was added m-chloroperoxybenzoic acid
Jꢁ4.2, 10.3 Hz), 4.40 (1H, d, Jꢁ12.3 Hz), 4.37—4.20 (2H, m), 3.47 (2H, s), (77 mg) at 0 °C. The reaction mixture was stirred at 0 °C for 50 min and then
3.33 (1H, d, Jꢁ16.3 Hz), 3.13 (1H, d, Jꢁ12.3 Hz), 2.75—2.50 (2H, m), 2.57 at room temperature for 30 min. To the reaction mixture was added saturated
(1H, dd, Jꢁ10.3, 12.3 Hz), 2.30—2.10 (2H, m), 2.00—1.50 (4H, m). 13C- NaHCO3 aqueous solution and the mixture was extracted with CH2Cl2. The
NMR (75 MHz, CDCl3) d: 162.23, 138.01, 135.70, 135.55, 132.87, 130.82, organic layer was washed with brine and was dried with anhydrous Na2SO4.
130.43, 129.13, 129.09, 129.03 (3C), 128.27 (2C), 127.15, 126.84, 123.54, The solvent was removed under reduced pressure and the resulting residue
62.89, 59.45, 57.72, 55.87, 51.99, 51.15, 49.70, 47.90, 38.41, 36.54. IR
was purified by amino-silica gel flash column chromatography (Fuji Silysia
(KBr) cmꢃ1: 1662, 1421, 1350, 1271, 1165, 970, 694.
Chemical Ltd., Chromatorex NH®, eluant: Hex/AcOEtꢁ1/1—1/2—AcOEt)
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-1ꢀ-(4-pyridinyl)- to afford compound 9a (78 mg, 78% yield) as a pale yellow amorphous
spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one (7c) [Step
1]: To the solution of compound 6c (4.7 g) in CH2Cl2 (50 ml), were added
1,8-bis(dimethylamino)naphthalene (0.37 g) and a-chloroethyl chlorofor- 8.35 (1H, d, Jꢁ1.8 Hz), 8.00—7.92 (3H, m), 7.78 (1H, dd, Jꢁ1.8, 8.8 Hz),
mate (2.4 ml) at 0 °C. The reaction mixture was stirred at room temperature 7.62 (1H, dd, Jꢁ1.8, 8.8 Hz), 4.83 (1H, d, Jꢁ13.0 Hz), 4.39 (1H, d, Jꢁ
solid.
ESI-MS m/z (MꢂH): 528 (MꢂꢃBocꢂH). 1H-NMR (300 MHz, CDCl3) d:
for 2 h. The reaction mixture was concentrated in vacuo and MeOH (70 ml)
was added to the resulting residue and the mixture was refluxed for 4 h.
17.1 Hz), 4.26 (1H, d, Jꢁ12.7 Hz), 4.04 (1H, d, Jꢁ10.5 Hz), 3.94 (1H, d, Jꢁ
10.5 Hz), 3.82—3.63 (2H, m), 3.42 (3H, s), 3.37 (1H, d, Jꢁ17.1 Hz), 3.35—

322
Vol. 55, No. 2
3.15 (3H, m), 2.89 (1H, d, Jꢁ12.7 Hz), 2.13—2.00 (1H, m), 1.93—1.30 (eluant: Hex/AcOEtꢁ3/1—1/1) to afford compound 9b (1.8 g, 83% yield) as
(3H, m), 1.42 (9H, s). 13C-NMR (75 MHz, CDCl3) d: 163.32, 154.24, a colorless amorphous solid.
135.84, 135.80, 132.36, 130.88, 130.46, 129.26, 129.24 (2C), 126.88,
ESI-MS m/z (MꢂH): 514 (MꢂꢃBocꢂH). 1H-NMR (300 MHz, CDCl3) d:
123.40, 80.32, 75.82, 71.74, 60.70, 59.62, 48.90, 48.55, 45.56, 40.79, 40.41, 8.40—8.36 (1H, m), 8.00—7.92 (3H, m), 7.79 (1H, dd, Jꢁ1.7, 8.6 Hz), 7.62
30.22, 29.21, 28.33 (3C). IR (KBr) cmꢃ1: 1685, 1408, 1352, 1246, 1167,
1136, 1080, 696.
(1H, dd, Jꢁ2.0, 8.6 Hz), 4.95 (1H, d, Jꢁ13.4 Hz), 4.56 (1H, dd, Jꢁ1.7,
12.8 Hz), 4.41 (1H, d, Jꢁ17.2 Hz), 4.30—4.05 (2H, m), 3.82—3.65 (2H, m),
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(methoxymethyl)- 3.40 (1H, d, Jꢁ17.2 Hz), 3.32—3.15 (2H, m), 3.21 (1H, d, Jꢁ13.4 Hz),
1ꢀ-(4-pyridinyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5- 2.98—2.88 (1H, m), 2.84 (1H, d, Jꢁ12.8 Hz), 2.13—2.01 (1H, m), 1.92—
one 1,1-dioxide (10a) [Step 1]: To the compound 9a (220 mg) were added 1.65 (2H, m), 1.50—1.30 (1H, m), 1.42 (9H, s). 13C-NMR (75 MHz, CDCl3)
trifluoroacetic acid (2.2 ml) and anisole (1 drop) at 0 °C. The reaction mix- d: 163.22, 154.18, 135.84, 135.79, 132.54, 130.92, 130.47, 129.30, 129.25,
ture was stirred at room temperature for 10 min. To the reaction mixture 129.23, 126.89, 123.33, 80.46, 76.65, 61.92, 61.87, 48.54, 47.74, 44.84,
were added 1 N NaOH and saturated NaHCO3 aqueous solution for adjusting
40.63, 40.40, 29.46, 28.72, 28.32 (3C). IR (KBr) cmꢃ1: 3404, 1672, 1414,
to more than pH 10 and the mixture was extracted with CH2Cl2. The organic 1350, 1304, 1248, 1169, 1134, 696.
layer was washed with brine and was dried with anhydrous Na2SO4. The sol-
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(hydroxymethyl)-
vent was removed under reduced pressure and the resulting residue was puri- 1ꢀ-(4-pyridinyl)-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-
fied by silica gel flash column chromatography (eluant: CH2Cl2–CH2Cl2/ one 1,1-dioxide (10b) [Step 1]: To the solution of compound 9b (1.85 g)
MeOHꢁ97/3—95/5) to afford the deprotected compound (176 mg, 95%
in CH2Cl2 (50 ml), were added trifluoroacetic acid (3.4 g) and anisole
(32.6 mg) at 0 °C. The reaction mixture was stirred at room temperature for
yield) as a colorless amorphous solid.
1H-NMR (300 MHz, CDCl3) d: 8.38—8.35 (1H, m), 8.00—7.90 (3H, m), 3 h. To the reaction mixture was added Et2O and the resulting precipitate
7.78 (1H, dd, Jꢁ1.8, 8.6 Hz), 7.62 (1H, dd, Jꢁ2.0, 8.6 Hz), 4.91 (1H, d, Jꢁ was collected by filtration to afford deprotected compound (1.9 g, quant.) as
13.2 Hz), 4.38 (1H, d, Jꢁ17.1 Hz), 4.28 (1H, dd, Jꢁ1.7, 12.7 Hz), 4.01 (1H,
d, Jꢁ10.5 Hz), 3.92 (1H, d, Jꢁ10.5 Hz), 3.42 (3H, s), 3.37 (1H, d, Jꢁ17.1
Hz), 3.26 (1H, d, Jꢁ13.2 Hz), 3.13—2.97 (2H, m), 2.88 (1H, d, Jꢁ12.7 Hz), br s), 8.35—8.15 (3H, m), 7.92 (1H, dd, Jꢁ1.8, 8.8 Hz), 7.76 (1H, dd, Jꢁ
2.81—2.63 (2H, m), 2.08—1.96 (1H, m), 1.88—1.71 (2H, m), 1.40—1.28 2.0, 8.8 Hz), 4.94 (1H, d, Jꢁ13.9 Hz), 4.09 (1H, d, Jꢁ12.3 Hz), 4.01 (1H, d,
a colorless amorphous solid.
1H-NMR (300 MHz, DMSO-d6) d: 8.83 (1H, br s), 8.63 (1H, s), 8.53 (1H,
(1H, m).
Jꢁ16.5 Hz), 3.96 (1H, d, Jꢁ11.9 Hz), 3.85 (1H, d, Jꢁ11.9 Hz), 3.74 (1H, d,
[Step 2]: To the solution of the deprotected compound (72 mg) which was Jꢁ16.5 Hz), 3.40—3.00 (5H, m), 3.22 (1H, d, Jꢁ12.3 Hz), 2.10—1.83 (3H,
afforded in Step 1 in EtOH (1.4 ml) were added 4-chloropyridine hydrochlo- m), 1.77—1.62 (1H, m).
ride (31 mg) and i-Pr2NEt (120 ml). The mixture was stirred at 150—160 °C
in a sealed tube for 5 h then it was concentrated in vacuo. The resulting
[Step 2]: To the solution of the deprotected compound (50 mg) which was
afforded in Step 1 in EtOH (3.0 ml) were added 4-chloropyridine hydrochlo-
residue was purified by amino-silica gel column chromatography (Fuji ride (17.9 mg) and i-Pr2NEt (51.4 mg). The mixture was stirred at 150—
Silysia Chemical Ltd., Chromatorex NH®, eluant: CH2Cl2/MeOHꢁ99/1) 160 °C in a sealed tube for 4 h. After cooling, water was added into the reac-
and then was re-purified by silica gel flash column chromatography (eluant: tion mixture and then the mixture was extracted with CH2Cl2. The organic
CH2Cl2/MeOHꢁ50/1—30/1—25/1) to afford compound 10a (10.4 mg, 13%
layer was washed with brine and was dried with anhydrous Na2SO4. The sol-
vent was removed under reduced pressure. The resulting residue was puri-
yield) as a colorless amorphous solid.
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C27H3035ClN4O6S2: fied by preparative TLC (CH2Cl2/MeOHꢁ4/1) to afford compound 10b
1
605.1295. Found: 605.1252. H-NMR (300 MHz, CDCl3) d: 8.36 (1H, s),
8.27 (2H, d, Jꢁ5.1 Hz), 8.02—7.90 (3H, m), 7.78 (1H, d, Jꢁ8.8 Hz), 7.63
(1H, d, Jꢁ8.8 Hz), 6.61 (2H, d, Jꢁ5.1 Hz), 4.85 (1H, d, Jꢁ13.0 Hz), 4.40
(1H, d, Jꢁ16.5 Hz), 4.24 (1H, d, Jꢁ12.8 Hz), 4.07 (1H, d, Jꢁ10.5 Hz), 3.96
(4.8 mg, 10% yield) as a colorless amorphous solid.
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C26H2835ClN4O6S2:
1
591.1139. Found: 591.1100. H-NMR (300 MHz, CDCl3) d: 8.39 (1H, s),
8.27 (2H, d, Jꢁ5.5 Hz), 8.05—7.92 (3H, m), 7.80 (1H, d, Jꢁ8.6 Hz), 7.63
(1H, d, Jꢁ10.5 Hz), 3.73—3.52 (2H, m), 3.50—3.17 (4H, m), 3.44 (3H, s), (1H, d, Jꢁ8.6 Hz), 6.61 (2H, d, Jꢁ5.5 Hz), 4.97 (1H, d, Jꢁ13.8 Hz), 4.54
2.94 (1H, d, Jꢁ13.0 Hz), 2.30—2.15 (1H, m), 2.08—1.80 (2H, m), 1.75— (1H, d, Jꢁ13.0 Hz), 4.42 (1H, d, Jꢁ17.2 Hz), 4.27 (1H, d, Jꢁ12.7 Hz), 4.16
1.44 (1H, m). 13C-NMR (75 MHz, CDCl3) d: 163.39, 153.84, 150.51 (2C),
(1H, d, Jꢁ12.7 Hz), 3.75—3.55 (2H, m), 3.43 (1H, d, Jꢁ17.2 Hz), 3.38—
135.83 (2C), 132.41, 130.89, 130.46, 129.27, 129.24 (2C), 126.87, 123.38, 3.23 (2H, m), 3.28 (1H, d, Jꢁ13.8 Hz), 2.90 (1H, d, Jꢁ13.0 Hz), 2.35—1.67
108.69 (2C), 75.94, 71.93, 60.41, 59.64, 49.19, 48.59, 45.53, 43.58, 43.45,
(4H, m). 13C-NMR (75 MHz, CDCl3) d: 163.32, 153.84, 150.38 (2C),
29.65, 28.41 IR (film) cmꢃ1 : 1678, 1599, 1402, 1350, 1167, 1130, 733, 696, 141.49, 135.85, 132.59, 130.92, 130.47, 129.30, 129.27 (2C), 126.89,
594. 123.34, 108.72 (2C), 76.84, 62.02, 61.53, 48.58, 48.02, 44.88, 43.53, 43.19,
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]- 28.91, 27.94. IR (film) cmꢃ1: 1670, 1600, 1456, 1338, 1167, 1128, 696.
tetrahydro-8a-(hydroxymethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-
2(3H),4ꢀ-piperidin]-5-one (8b) The deprotected compound (2.0 g), which
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]-
tetrahydro-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one
was obtained in the synthesis of compound 7b; Step 1, was dissolved in (8c) The deprotected compound (2.0 g), which was obtained in the synthe-
CH2Cl2 (50 ml). To this solution was added di-t-butyl dicarbonate (0.91 g) at sis of compound 7c; Step 1, was dissolved in CH2Cl2 (50 ml). To this solu-
0 °C. The reaction mixture was stirred at room temperature overnight. Then tion was added di-t-butyl dicarbonate (1.0 g) at 0 °C. The reaction mixture
it was concentrated in vacuo and the resulting mixture was purified by silica was stirred at room temperature for 2 h. To the reaction mixture was added
gel column chromatography (eluant: Hex/AcOEtꢁ1/1) to afford compound n-hexane for precipitation. The precipitate was collected by filtration to af-
8b (2.5 g, quant.) as a pale yellow amorphous solid.
ford compound 8c (2.3 g, 94% yield) as colorless crystals.
ESI-MS m/z (MꢂH): 582 (MꢂꢂH), 482 (MꢂꢃBocꢂH). 1H-NMR
mp 212.9—214.2 °C. ESI-MS m/z (MꢂH): 552 (MꢂꢂH), 452 (Mꢂꢃ
1
(300 MHz, CDCl3) d: 8.37—8.33 (1H, m), 8.00—7.90 (3H, m), 7.78 (1H, BocꢂH). H-NMR (300 MHz, CDCl3) d: 8.35 (1H, d, Jꢁ2.0 Hz), 8.00—
dd, Jꢁ1.8, 8.6 Hz), 7.61 (1H, dd, Jꢁ2.2, 8.6 Hz), 4.69 (1H, d, Jꢁ12.5 Hz),
7.90 (3H, m), 7.78 (1H, dd, Jꢁ2.0, 8.8 Hz), 7.61 (1H, dd, Jꢁ2.2, 8.8 Hz),
4.46—4.32 (2H, m), 4.20—4.08 (1H, m), 3.95—3.65 (3H, m), 3.39 (1H, d, 5.11 (1H, dd, Jꢁ4.0, 10.3 Hz), 4.43 (1H, d, Jꢁ12.3 Hz), 4.33 (1H, d, Jꢁ
Jꢁ16.9 Hz), 3.20 (1H, d, Jꢁ12.5 Hz), 3.10—2.85 (2H, m), 2.78—2.65 (1H, 16.7 Hz), 4.33—4.25 (1H, m), 4.00—3.70 (2H, m), 3.35 (1H, d, Jꢁ16.7 Hz),
m), 2.66 (1H, d, Jꢁ12.3 Hz), 1.88—1.77 (2H, m), 1.63—1.30 (2H, m), 1.42 3.14 (1H, d, Jꢁ12.3 Hz), 3.05—2.92 (2H, m), 2.59 (1H, dd, Jꢁ10.1, 12.3
(9H, s). 13C-NMR (75 MHz, CDCl3) d: 162.75, 154.47, 135.74, 135.60,
Hz), 1.85—1.75 (2H, m), 1.70—1.35 (2H, m), 1.43 (9H, s). 13C-NMR (75
133.00, 130.86, 130.47, 129.12 (2C), 128.98, 126.86, 123.37, 80.01, 73.88, MHz, CDCl3) d: 162.34, 154.47, 135.73, 135.60, 132.85, 130.83, 130.44,
65.77, 57.60, 56.79, 50.68, 47.84, 42.93, 41.08, 38.27, 36.17, 28.36 (3C). IR 129.15, 129.12, 129.07, 126.85, 123.51, 80.00, 59.56, 57.85, 56.14, 49.69,
(KBr) cmꢃ1: 3420, 1685, 1666, 1415, 1350, 1242, 1165, 1078, 692.
47.94, 42.58, 41.51, 38.06, 36.16, 28.37 (3C). IR (KBr) cmꢃ1: 1691, 1662,
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]- 1419, 1342, 1244, 1165, 962, 694.
tetrahydro-8a-(hydroxymethyl)-spiro[5H-thiazolo[3,2-a]pyrazine-
2(3H),4ꢀ-piperidin]-5-one 1,1-dioxide (9b) To the solution of compound
1ꢀ-(tert-Butoxycarbonyl)-7-[(6-chloro-2-naphthalenyl)sulfonyl]-
tetrahydro-spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one
8b (2.1 g) in 1,2-dichloroethane (210 ml), was added m-chloroperoxybenzoic 1,1-dioxide (9c) To the solution of compound 8c (100 mg) in CH2Cl2
acid (1.7 g) at 0 °C. The reaction mixture was stirred at room temperature for (10 ml), was added m-chloroperoxybenzoic acid (65.6 mg) at 0 °C. The reac-
1 h and then at 65 °C for another hour. After cooling, silica gel was added tion mixture was stirred at 0 °C for 30 min and then at room temperature for
into the reaction mixture. This suspension was concentrated in vacuo for re- 30 min. To the reaction mixture was additionally added m-chloroperoxyben-
moving solvent and then silica gel column chromatography was carried out zoic acid (65.6 mg) and the reaction mixture was stirred at room temperature

February 2007
323
for 3 h. To the reaction mixture was added saturated NaHCO3 aqueous solu-
tion and the mixture was extracted with CH2Cl2. The organic layer was
washed with brine and was dried with anhydrous Na2SO4. The solvent was
removed under reduced pressure and the resulting residue was purified by
amino-silica gel column chromatography (Fuji Silysia Chemical Ltd., Chro-
matorex NH®, eluant: Hex/AcOEtꢁ1/1) to afford compound 9c (82.2 mg,
78% yield) as colorless crystals.
Y., Matsumoto M., Ohnishi S., Chem. Pharm. Bull., 54, 1535—1544
(2006).
6) Hosaka Y., Matsumoto M., Shinozaki M., Ohno T., Yatagai Y., Kamiya
M., Kurokawa M., Nishida H., Matsusue T., Mizuguchi K., Ishi H.,
Eur. J. Pharmacol., 529, 164—171 (2006).
7) Davie E. W., Fujikawa K., Kisiel W., Biochemistry, 30, 10363—10370
(1991).
8) Mann K. G., Nesheim M. E., Church W. R., Haley P., Krishnaswamy
S., Blood, 76, 1—16 (1990).
mp 247.0—248.1 °C. ESI-MS m/z (MꢂH): 484 (MꢂꢃBocꢂH). 1H-NMR
(300 MHz, CDCl3) d: 8.40—8.33 (1H, m), 8.00—7.92 (3H, m), 7.78 (1H,
dd, Jꢁ1.8, 8.8 Hz), 7.63 (1H, dd, Jꢁ2.0, 8.8 Hz), 4.66—4.56 (1H, m), 4.60
(1H, d, Jꢁ13.0 Hz), 4.50—4.40 (1H, m), 4.39 (1H, d, Jꢁ17.1 Hz), 3.83—
9) Rosenberg J. S., Beeler D. L., Rosenberg R. D., J. Biol. Chem., 250,
1607—1617 (1995).
3.65 (2H, m), 3.37 (1H, d, Jꢁ17.1 Hz), 3.37—3.23 (2H, m), 3.21 (1H, d, Jꢁ 10) Harker L. A., Hanson S. R., Kelly A. B., Thromb. Haemost., 78, 736—
13.0 Hz), 2.92 (1H, dd, Jꢁ10.1, 12.7 Hz), 2.17—2.04 (1H, m), 2.00—1.87
741 (1997).
(1H, m), 1.78—1.66 (1H, m), 1.63—1.35 (1H, m), 1.44 (9H, s). 13C-NMR 11) Elodi S., Varadi K., Thromb. Res., 15, 617—629 (1979).
(75 MHz, CDCl3) d: 162.70, 154.19, 135.90, 135.87, 132.45, 130.88, 12) Markwardt F., Nowak G., Sturzebecher J., Vogel G., Thromb. Res., 52,
130.43, 129.38, 129.30 (2C), 126.90, 123.40, 80.48, 69.06, 60.02, 49.97,
393—400 (1988).
48.51, 42.48, 40.56, 40.21, 29.69, 29.08, 28.34 (3C). IR (KBr) cmꢃ1: 1693, 13) Heras M., Chesbro J. H., Penny W. J., Bailey K. R., Badimon L.,
1658, 1439, 1415, 1350, 1246, 1165, 1132, 970, 698. Fuster V., Circulation, 79, 657—665 (1989).
7-[(6-Chloro-2-naphthalenyl)sulfonyl]tetrahydro-1ꢀ-(4-pyridinyl)- 14) Markwardt F., Thromb. Haemost., 66, 141—152 (1991).
spiro[5H-thiazolo[3,2-a]pyrazine-2(3H),4ꢀ-piperidin]-5-one 1,1-dioxide 15) Markwardt F., Thromb. Res., 74, 1—23 (1994).
(10c) [Step 1]: To the solution of compound 9c (73 mg) in CH2Cl2 (4 ml), 16) Kaplan K. L., Francis C. W., Semin. Hematol., 39, 187—196 (2002).
were added trifluoroacetic acid (0.2 ml) and anisole (1 drop) at 0 °C. The re- 17) Waxman L., Smith D. E., Arcuri K. E., Vlasuk G. P., Science, 248,
action mixture was stirred at room temperature overnight. The reaction mix-
ture was concentrated in vacuo and Et2O was added into the resulting 18) Jordan S. P., Waxman L., Smith D. E., Vlasuk G. P., Biochemisyry, 29,
residue for precipitation of deprotected compound. The precipitate was col- 11095—11100 (1990).
lected by filtration to afford deprotected compound (70.5 mg, 94% yield) as 19) Neper M. P., Waxman L., Smith D. E., Schulman C. A., Sardana M.,
593—596 (1990).
a colorless amorphous solid.
Ellis R. W., Schaffer L. W., Siegel P. K. S., Vlasuk G. P., J. Biol.
Chem., 265, 17746—17752 (1990).
20) Schaffer L. W., Davidson J. T., Vlasuk G. P., Siegl P. K. S., Circulation,
84, 1741—1748 (1991).
21) Dunwiddie C. T., Neeper M. P., Nutt E. M., Waxman L., Smith D. E.,
Hofmann K. J., Lumma P. K., Garsky V. M., Vlasuk G. P., Bio-
chemisyry, 31, 12126—12131 (1992).
1H-NMR (270 MHz, DMSO-d6) d: 8.65 (1H, s), 8.56 (2H, br s), 8.32—
8.16 (3H, m), 7.96 (1H, dd, Jꢁ2.0, 8.9 Hz), 7.76 (1H, dd, Jꢁ2.3, 8.9 Hz),
4.93 (1H, dd, Jꢁ4.9, 9.2 Hz), 4.72 (1H, d, Jꢁ13.2 Hz), 4.40—4.23 (1H, m),
4.03 (1H, d, Jꢁ16.5 Hz), 3.68 (1H, d, Jꢁ16.5 Hz), 3.50—3.00 (6H, m),
2.15—1.85 (3H, m), 1.80—1.65 (1H, m).
[Step 2]: The deprotected compound, which was afforded in Step 1, was
neutralized with saturated NaHCO3 aqueous solution and the basic suspen-
22) Vlasuk G. P., Thromb. Haemost., 70, 212—216 (1993).
sion was ordinarily worked up. to afford the salt free substrate. To the solu- 23) Ragosta M., Gimple L. W., Gertz D., Dunwiddie C. T., Vlasuk G. P.,
tion of the salt free substrate (50 mg) in EtOH (3 ml), was added 4-chloropy-
ridine (120 mg). The mixture was stirred at 130 °C for 2 h and at 150 °C for
Haber H. L., Powers E. R., Roberts W. C., Sarembock I. J.,
Circulation, 89, 1262—1271 (1994).
2 h. After cooling, saturated NaHCO3 aqueous solution was added into the 24) Fevig J. M., Wexler R. R., Ann. Rep. Med. Chem., 34, 81—100 (1999).
reaction mixture and then the mixture was extracted with CH2Cl2. The or- 25) Sanderson P. E. J., Med. Res. Rev., 19, 179—197 (1999).
ganic layer was washed with brine and was dried with anhydrous Na2SO4. 26) Hauptmann J., Sturzebecher J., Thromb. Res., 93, 203—241 (1999).
The solvent was removed under reduced pressure. The resulting residue was 27) Weitz J. I., Hirsh J., Chest, 119, 95S—107S (2001).
purified purified by silica gel column chromatography (CH2Cl2/MeOHꢁ 28) Eisenberg P. R., Siegel J. E., Abendschein D. R., Miletich J. P., J. Clin.
90/10) to afford compound 10c (13.2 mg, 23% yield) as a colorless amor-
Invest., 91, 1877—1883 (1993).
phous solid.
29) Kaiser B., Hauptmann J., Cardiovasc. Drug Rev., 12, 225—236
MALDI-TOF-HR-MS m/z (MꢂH): Calcd for C25H2635ClN4O5S2:
(1994).
1
561.1033. Found: 561.0994. H-NMR (300 MHz, DMSO-d6) d: 8.66 (1H, 30) Prager N. A., Abendschein D. R., McKenzie C. R., Eisenberg P. R.,
s), 8.35—8.08 (5H, m), 8.00—7.90 (1H, m), 7.80—7.70 (1H, m), 6.84 (2H,
Circulation, 92, 962—967 (1995).
d, Jꢁ5.7 Hz), 4.95—4.83 (1H, m), 4.64 (1H, d, Jꢁ13.2 Hz), 4.35—4.20 31) Wong P. C., Crain E. J., Jr., Nguan O., Watson C. A., Racanelli A.,
(1H, m), 4.03 (1H, d, Jꢁ16.5 Hz), 3.71 (1H, d, Jꢁ16.5 Hz), 3.70—3.10 (6H,
m), 2.00—1.70 (3H, m), 1.65—1.50 (1H, m). 13C-NMR (75 MHz, DMSO-
d6) d: 162.59, 153.66, 149.31 (2C), 135.50, 133.95, 132.75, 131.70, 130.40,
Thromb. Res., 83, 117—126 (1996).
32) Herault J. P., Bernat A., Pflieger A. M., Lormeau J. C., Herbert J. M., J.
Pharmacol. Exp. Ther., 283, 16—22 (1997).
129.27, 129.09, 128.31, 126.63, 123.99, 108.48 (2C), 68.86, 59.49, 48.69, 33) Scarborough R. M., J. Enzym. Inhib., 14, 15—25 (1998).
48.19, 42.51, 42.48, 41.43, 27.47, 27.33. IR (KBr) cmꢃ1 : 1664, 1601, 1448, 34) Kunitada S., Therap. Res., 19, 7—12 (1998).
1346, 1163, 1132, 758, 698, 596.
35) Petitou M., Duchaussoy P., Jaurand G., Gourvenec F., Lederman I.,
Strassel J.-M., Bârzu T., Crépon B., Hérault J.-P., Lormeau J.-C.,
Bernat A., Herbert J.-M., J. Med. Chem., 40, 1600—1607 (1997).
References and Notes
1) Part 1: Nishida H., Miyazaki Y., Kitamura Y., Ohashi M., Matsusue T., 36) Boneu B., Necciari J., Cariou R., Sie P., Gabaig A. M., Kieffer G.,
Okamoto A., Hosaka Y., Ohnishi S., Mochizuki H., Chem. Pharm.
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Dickinson J., Lamond G., Moelker H., Mant T., Magnani H., Thromb.
Haemost., 74, 1468—1473 (1995).
2) Part 2: Nishida H., Miyazaki Y., Mukaihira T., Saitoh F., Fukui M., 37) Vuillemenot A., Schiele F., Meneveau N., Claudel S., Donat F., Fonte-
Harada K., Itoh M., Muraoka A., Matsusue T., Okamoto A., Hosaka
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1187—1194 (2002).
cave S., Cariou R., Samama M. M., Bassand J. P., Thromb. Haemost.,
81, 214—220 (1999).
38) MOPAC PM3 calculation was used in SYBYL7.1 (Tripos Inc.).
39) Warshawsky A. M., Flynn G. A., WO 9404531 (1994).
3) Part 3: Nishida H., Miyazaki Y., Mukaihira T., Shimada H., Suzuki K.,
Saitoh F., Mizuno M., Matsusue T., Okamoto A., Hosaka Y., Matsu- 40) Fujii N., Yajima H., Chem. Pharm. Bull., 23, 1596—1603 (1975).
moto M., Ohnishi S., Mochizuki H., Chem. Pharm. Bull., 52, 459— 41) Nishida H., Mukaihira T., WO 2002053568 (2002).
462 (2004).
42) Nishida H., Saitoh F., Harada K., Shiromizu I., WO 2001002397
(2001).
4) Part 4: Nishida H., Mukaihira T., Saitoh F., Harada K., Fukui M., Ma-
tsusue T., Okamoto A., Hosaka Y., Matsumoto M., Shiromizu I., 43) It has been unclear that compound 18 reduced FXa inhibitory activity
Ohnishi S., Mochizuki H., Chem. Pharm. Bull., 52, 406—412 (2004).
5) Part 5: Saitoh F., Mukaihira T., Nishida H., Satoh T., Okano A., Yu-
miya Y., Ohkouchi M., Johka R., Matsusue T., Shiromizu I., Hosaka
(IC50; 18.2 nM). The overall conformation of compound 18 might be
changed by both N-mathylation and without a side chain.