Discovery of (1 S,2 R,3 R)-2,3-dimethyl-2-phenyl-1- sulfamidocyclopropanecarboxylates: Novel and highly selective aggrecanase inhibitors

Article abstract of DOI:10.1021/jm101609j

Aggrecanases, particularly aggrecanase-1 (ADAMTS-4) and aggrecanase-2 (ADAMTS-5), are believed to be key enzymes involved in the articular cartilage breakdown that leads to osteoarthritis. Thus, aggrecanases are considered to be viable drug targets for the treatment of this debilitating disease. A series of (1S,2R,3R)-2,3-dimethyl-2-phenyl-1-sulfamidocyclopropanecarboxylates was discovered to be potent, highly selective, and orally bioavailable aggrecanase inhibitors. These compounds have unique P1′ groups comprising novel piperidine- or piperazine-based heterocycles that are connected to a cyclopropane amino acid scaffold via a sulfamido linkage. These P1′ groups are quite effective in imparting selectivity over other MMPs, and this selectivity was further increased by incorporation of a methyl substituent in the 2-position of the cyclopropane ring. In contrast to classical hydroxamate-based inhibitors that tend to lack metabolic stability, our aggrecanase inhibitors bear a carboxylate zinc-binding group and have good oral bioavailability. Lead compound 13b, characterized by the novel P1′ portion of 1,2,3,4-tetrahydropyrido[3′,4′:4,5]imidazo[1,2-a]pyridine ring, is a potent and selective aggrecanse inhibitor with excellent pharmacokinetic profiles.

Full text of DOI:10.1021/jm101609j

ARTICLE
pubs.acs.org/jmc
Discovery of (1S,2R,3R)-2,3-Dimethyl-2-phenyl-1-
sulfamidocyclopropanecarboxylates: Novel and Highly Selective
Aggrecanase Inhibitors
Makoto Shiozaki,*,† Katsuya Maeda,† Tomoya Miura,† Masayuki Kotoku,† Takayuki Yamasaki,†
Isamu Matsuda,† Kenta Aoki,† Katsutaka Yasue,† Hiroto Imai,† Minoru Ubukata,† Akira Suma,†
Masahiro Yokota,† Takahiro Hotta,† Masahiro Tanaka,† Yasunori Hase,† Julia Haas,‡ Andrew M. Fryer,‡
Ellen R. Laird,‡ Nicole M. Littmann,‡ Steven W. Andrews,‡ John A. Josey,‡ Takayuki Mimura,§
Yuichi Shinozaki,§ Hiromi Yoshiuchi,§ and Takashi Inaba*,†
†Chemical Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., 1-1 Murasaki-cho, Takatsuki, Osaka
569-1125, Japan
‡Array BioPharma Inc., 3200 Walnut Street, Boulder, Colorado 80301, United States
§Biological Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., 1-1 Murasaki-cho,
Takatsuki, Osaka 569-1125, Japan
S Supporting Information
b
ABSTRACT:
Aggrecanases, particularly aggrecanase-1 (ADAMTS-4) and aggrecanase-2 (ADAMTS-5), are believed to be key enzymes involved
in the articular cartilage breakdown that leads to osteoarthritis. Thus, aggrecanases are considered to be viable drug targets for the
treatment of this debilitating disease. A series of (1S,2R,3R)-2,3-dimethyl-2-phenyl-1-sulfamidocyclopropanecarboxylates was
discovered to be potent, highly selective, and orally bioavailable aggrecanase inhibitors. These compounds have unique P10 groups
comprising novel piperidine- or piperazine-based heterocycles that are connected to a cyclopropane amino acid scaffold via a
sulfamido linkage. These P10 groups are quite effective in imparting selectivity over other MMPs, and this selectivity was further
increased by incorporation of a methyl substituent in the 2-position of the cyclopropane ring. In contrast to classical hydroxamate-
based inhibitors that tend to lack metabolic stability, our aggrecanase inhibitors bear a carboxylate zinc-binding group and have good
oral bioavailability. Lead compound 13b, characterized by the novel P10 portion of 1,2,3,4-tetrahydropyrido[30,40:4,5]imidazo[1,2-a]-
pyridine ring, is a potent and selective aggrecanse inhibitor with excellent pharmacokinetic profiles.
’ INTRODUCTION
therapeutic agents for the treatment of cartilage degradation are
of great interest. In 1999, two zinc metalloproteases, aggreca-
nase-1 (ADAMTS-4) and aggrecanase-2 (ADAMTS-5), were
identified as the major enzymes responsible for aggrecan cleavage
at the Glu373-Ala374 site.2 These proteases cleave aggrecan at this
site 1000-fold more efficiently than any other matrix metallo-
proteases (MMPs). This finding drew a great deal of interest
Osteoarthritis (OA) is a debilitating disease caused by break-
down of aggrecan and collagen in the articular cartilage, which
leads to chronic joint pain and reduced physical function of a
large population in the elderly.1 Current therapeutic options such
as treatment with NSAIDs and intra-articular injections of
hyaluronic acid only offer temporary symptomatic relief such
as pain reduction but rarely halt the progression of the disease.
Since OA affects millions of people all over the world and its
incidence is increasing with the aging of the population, new
Received: December 20, 2010
Published: March 21, 2011
r
2011 American Chemical Society
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MMP inhibitors arose from lack of selectivity. Hence, we under-
took the optimization of compound 6 in order to identify highly
selective aggrecanase inhibitors, especially inhibitors of aggreca-
nase-2.
MMP-14 has been implicated as a possible cause of side effects
based on knockout mouse studies.14 Because the inhibitory
activity of 6 against MMP-14 was twice as strong as that against
aggrecanase-2, an MMP-14 assay was newly employed in addi-
tion to the original selectivity assay system which also in-
cluded MMP-1 and tumor necrosis factor R-converting enzyme
(TACE).15 The earlier gene knockout studies indicated that
inhibition of aggrecanase-2 is more important in mice, and thus,
the inhibition of aggrecanase-1 was expected to cause no severe
side effects based on the phenotype of aggrecanase-1 knockout
mice,6 and its inhibition may even exert some positive effects
in vivo. Therefore, in this study we followed only aggrecanase-2
inhibitory activity and did not routinely monitor aggrecanase-1
inhibitory activity.
’ RESULTS AND DISCUSSION
Initial SAR Exploration of Close Sulfonamide-Based Ana-
logues of Compound 6. Zinc metalloproteases including
MMPs contain highly conserved structural features within the
catalytic domain, with the exception of the loop region which
forms part of the S10 pocket of each enzyme and imparts
substrate specificity. Therefore, generating P10 moieties that
specifically interact with the S10 pocket of each target MMP
may be a key for the development of more selective inhibitors.16
We therefore initiated an exploration of inhibitor binding to the
S10 pocket starting from compound 6, whose sulfonyl moiety is
accommodated in the S10 pocket of aggrecanase-2.12b First, we
examined the effects of substitutions on the two consecutive
pyrazole and thiophene rings (Table 1). The compounds were
tested in vitro on human recombinant aggrecanase-2, MMPs, and
TACE, which used a fluorogenic peptide as the substrate.
Introduction of an additional methyl group on the thiophene
ring resulted in complete loss of potency (7a), while replacement
of the terminal chlorine atom with a methoxy or a methyl group
led to a slight reduction of selectivity over MMP-14 (7b, 7c).
Although these minor modifications on the present ring system
had virtually no beneficial effect on aggrecanase-2 selectivity over
MMP-14, relatively high selectivity over MMP-1 was observed
for 7d,12b a phenyl analogue of compound 6. This analogue
became the focus of additional efforts to impart selectivity over
MMP-14.
Figure 1. Examples of ADAMTS-5 inhibitors.
because the aggrecan fragments generated from cleavage at this
site are found in the synovial fluid of OA patients, which suggests
that aggrecanases play a pivotal role in the pathological catabo-
lism of aggrecan.3 In osteoarthritic cartilage, degradation of
aggrecan is initially observed and is followed by substantial and
irreversible collagen breakdown, which leads to structural da-
mage of the joints.4 Thus, blockade of aggrecanases is currently
expected to prevent aggrecan degradation and could eventually
protect the joints of OA patients.5 Of the two enzymes, aggre-
canase-2 was demonstrated to play a pivotal role in the cleavage
of mouse cartilage based on studies using knockout animals,6 and
there have been several reports that suggest that either enzyme
could be a major player in the destruction of the cartilage of OA
patients.7 Initially, several general aggrecanase inhibitors as
represented by DuPont’s hydroxamate-based compound 18a
were reported (Figure 1).9 The inhibitory activity of compound
1 against each aggrecanase was also reported.8b Subsequently, the
knockout mouse studies6 inspired the design of aggrecanase-2
inhibitors.10 In particular, Wyeth reported a variety of aggreca-
nase-2 inhibitors exemplified by 2. Most recently, Cappelli and
co-workers reported aggrecanase inhibitors such as 3 that
showed submicromolar IC50 values for both aggrecanase-1
and -2.11 Similarly, Pfizer’s MMP-13 inhibitor (4)9e showed
strong aggrecanse inhibitory activity, while Wyeth’s carboxy-
late-based compound (5)9g selectively inhibited aggrecanases.
Recently we have reported aggrecanase-2 inhibitors such as 6
that bear a carboxylate zinc-binding group.12 While 6 was the
most potent compound of these non-hydroxamate inhibitors
against aggrecanase-1 and -2, it also inhibited other MMPs such
as MMP-3, MMP-9, MMP-13, and MMP-14 in a broad-range
selectivity panel. It is widely believed that a variety of unaccep-
table adverse events, such as musculoskeletal syndrome,13 that
have been clinically observed with the use of broad spectrum
Discovery of Tricyclic Sulfonamides as P10 Groups. Among
the close analogues of 6 listed in Table 1, only 7a showed a
significant reduction of aggrecanase-2 potency. We considered
that the introduction of the methyl group forces the linked
heterocycle of 7a to lose coplanarity, a distortion of the geometry
that causes steric congestion in the aggrecanase-2 S10 pocket and
leads to the observed loss of potency. On the basis of this
hypothesis, we synthesized 8aꢀc as analogues of 7d which bear
flat tricyclic structures as the P10 moiety (Table 2). Analogues
8aꢀc retained good aggrecanase-2 potency, and moreover, 8c
showed good selectivity over MMP-1. Unfortunately the selec-
tivity over MMP-14 was still unsatisfactory (Table 2). Com-
pounds 8d and 8e were subsequently synthesized to evaluate the
effect of the terminal chlorine atom, but these compounds
offered no improvement in selectivity over MMP-14.
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Table 1. SAR of Sulfonamide-Based P10 Portion of Close Analogues of 6f
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13. f nd: not determined.
Discovery and Initial Exploration of Sulfamide-Based P10
Groups. We next evaluated sulfamides as bioisosteric replace-
ments of the sulfonamide group to introduce greater synthetic
versatility.17 We initially synthesized 9a and 9b, and although
these compounds showed reduced aggrecanase-2 potency
compared to the sulfonamide series, their selectivities over
MMP-14, MMP-1, and TACE were comparable to that of the
most selective sulfonamide 8c. These results prompted us to
modify the piperazine ring of 9a. Substitution of a methyl group
as in 9c and 9d provided a 2-fold increase in aggrecanase-2
inhibitory activity and a surprising 10-fold increase in selectivity
with respect to MMP-14. These results were in contrast to the
loss of potency in compound 7a, which also has a methyl
substituent at the corresponding location of the P10 site but
showed no aggrecanase-2 inhibition. Maity et al. have recently
reported a crystal structure of a 2-substituted-1-phenylpiper-
azine derivative.18 They reported that in similar systems the
piperazine ring was coplanar with the phenyl ring, and this
coplanar conformation forced the alkyl substituent at the
2-position of the piperazine into the axial orientation. On the
basis of this observation, we postulated that the phenylpiper-
azine moieties of 9c and 9d adopt a similar coplanar conforma-
tion so that they can fit in the S10 pocket of aggrecanase-2
without the steric congestion of 7a and thus retain their good
inhibitory activity. To explain the improved selectivity of the
sulfamides, we compared the binding of 9c and 9d in the crystal
structures of aggrecanase-219 and MMP-14.20 These two pro-
tein X-ray structures were superimposed by aligning the CR
atoms, and 9c and 9d were docked manually into the resulting
protein structures with the carboxylate acting as a zinc-binding
group and the phenylpiperazine moiety positioned in the S10
pocket. As seen in Figure 2, the most striking difference
between aggrecanase-2 and MMP-14 is the chemical environ-
ment around the piperazine ring of the inhibitors: the backbone
carbonyl of Pro259 comes too close to the methyl substituent of
9c and 9d in the S10 pocket of MMP-14, while the correspond-
ing amino acid of aggrecanase-2, Ser441, projects away from the
methyl substituent (Figure 2a and Figure 2b). Thus, the
available space near the piperazine ring in the S10 pocket of
aggrecanase-2 could account for the aggrecanase-2 selectivity
found in 9c and 9d. Recently, Wei et al. have reported a similar
modulation of selectivity in their MMP-12 inhibitor program.21
This approach of introducing differences in the S10 pocket
that are more subtle than simply changing the depth repre-
sents a novel and attractive strategy for obtaining highly select-
ive MMP inhibitors. To exploit this approach further, we prepared
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Table 2. SAR of the P10 Portion Comprising Novel Tricyclic Heteroaromatics
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13.
Figure 2. Compounds (a) 9c and (b) 9d harbored in the catalytic pockets of aggrecanase-2 and MMP-14. The compounds are depicted in white.
Aggrecanase-2 is depicted in green. MMP-14 is depicted in pink, and zinc ion is portrayed as a yellow sphere. The backbone carbonyl of Pro259 (pink
arrow) comes too close to the methyl substituent (white dashed circle) of 9c and 9d in the S10 pocket of MMP-14, while the corresponding amino acid of
aggrecanase-2, Ser441 (green arrow), projects away from the methyl substituent.
an additional small set of substituted piperazines including a 3-ethyl
analogue (9e), a3,3-dimethylanalogue(9f), anda 3-hydroxymethyl
analogue (9g) (Table 3). Unfortunately, these compounds
showed neither increased aggrecanase-2 potency nor improved
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Table 3. SAR of the P10 Portion Comprising 4-Chlorophenylpiperazines and 4-Chlorophenylpiperidine Sulfamidesf
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13. f nd: not determined.
selectivity. Therefore, we concluded that this region of the S10
pocket is too small to accommodate substituents larger than methyl.
As no further improvement in selectivity was achieved by mod-
ification of the piperazine ring, we next focused on the distal benzene
portion starting from 9c. Although simple replacement of the terminal
chlorine atom with a smaller fluorine atom (10a) or a larger
cyclopropane ring (10b) resulted in reduction of potency, substitu-
tion of phenyl with a five-membered heterocycle (10cꢀf) gave some
encouraging results. Most notably, 10d was not only as potent as 9c
but also showed a significantly higher selectivity over MMP-14 (200-
fold). This compound also did not inhibit MMP-1 or TACE
at >10 μM.
Discovery of Tricyclic Sulfamide P10 Groups. In the afore-
mentioned SAR investigations of the sulfonamide series, aggre-
canase-2 inhibitory activity was significantly improved by
incorporating tricycle-based P10 groups represented by the 4H-
thieno[3,2-b]indole-2-yl core of compound 8c. These findings
encouraged us to prepare compounds that possess P10 groups
comprising tricyclic sulfamides as homologues of 9a and 9b
(Table 5). Unfortunately, we found no significant improvements
in aggrecanase-2 inhibitory activity or selectivity against MMP-
14 in the initial small set of tricyclic sulfamides with a fused-
piperazine core (11a,b,d), a fused-piperidine core (11c), and a
fused-pyrrolidine core (11e). Thus, we next investigated the
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Table 4. SAR of the P10 Portion Comprising (R)-4-Substituted 3-Methylpiperazinesf
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13. f nd: not determined.
effect of substituents on the terminal ring starting from 11b,
which has a chlorine atom at the 8-position (Table 6). Deletion
of the chlorine atom of 11b resulted in a slight reduction of
aggrecanase-2 potency (12a), while 12b, possessing a fluorine
atom at this position, retained both the potency against aggre-
canase-2 and good selectivity over MMP-14. The regioisomer
12c, having a fluorine atom at the 7-position, was a nonselective
compound with reduced aggrecanase-2 inhibition and increased
MMP-14 inhibition compared to the 8-F isomer 12b. According
to our previous SAR investigation,12b 6- and 9-substituted
regioisomers were unlikely to show good potency. Therefore,
only the 8-position of the tricyclic structure was further investi-
gated, and small substituents such as cyano, methyl, and methoxy
Figure 3. Compound 12b (in white) is harbored in the catalytic pockets
groups were introduced at this position (12d, 12e, and 12f,
of aggrecanase-2 and MMP-14. Aggrecanase-2 is depicted in green.
respectively). As listed in Table 6, these compounds are more
MMP-14 is depicted in pink, and the zinc ion is portrayed as a yellow
than 10-fold less potent than 12b against aggrecanase-2. Thus,
sphere. The backbone carbonyl of Pro259 (pink arrow) comes too close
to the basic nitrogen atom (white dashed circle) of 12b in the S10 pocket
of MMP-14, while the corresponding amino acid of aggrecanase-2,
Ser441 (green arrow), projects away from the nitrogen atom.
the presence of a halogen atom at the 8-position of the tricyclic
system appears to be important to boost aggrecanase-2 inhibi-
tion. As expected, the other heterotricycles 12gꢀi with a fluorine
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Table 5. Initial SAR of the P10 Portion Comprised of Heterotricycle-Based Sulfamides
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13.
atom at the corresponding position in 12b were as potent as 12b,
supporting the importance of a halogen atom at this position. As
for the selectivity over MMP-14, positioning a basic nitrogen
atom in the middle of the P10 portion appeared to be a key to
reducing MMP-14 inhibition: the IC50 values of the two basic
imidazole analogues 12b and 12g are much higher than those of
the less basic pyrazole and pyrrole counterparts 12h and 12i. On
the basis of the docking studies depicted in Figure 3, perhaps the
presence of a basic nitrogen atom in the middle of the P10 portion
of the inhibitor causes electrostatic repulsion with the backbone
carbonyl oxygen of Pro259 in MMP-14, resulting in reduced
MMP-14 potency. In aggrecanase-2, the corresponding amino
acid Ser441 located in this position appears to cause no such
Figure 4. Compound 13a (in white) in the catalytic pockets of
aggrecanase-2 and MMP-14. Aggrecanase-2 is depicted in green.
repulsion so that all of these compounds showed similar poten-
cies against aggrecanase-2.
MMP-14 is depicted in pink, and the zinc ion is portrayed as a yellow
Effects of Substitutions on the Cyclopropane Ring. In our
sphere. The 2-methyl substituent on the cyclopropane ring of 13a
earlier paper, we reported 2-methyl-2-phenylcyclopropane as an
comes too close to Phe198 (pink arrow) of MMP-14, causing a steric
attractive scaffold although its aggrecanase-2 inhibitory activity
was slightly weaker than the corresponding 3-methyl derivatives.12b
To determine whether there are any combined effects of 2-methyl
repulsion. Meanwhile, the corresponding residue of aggrecanase-2 is
Thr378 (green arrow), which allows enough space to accommodate
the 2-methyl group.
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Table 6. Effects of Substitutions on the Terminal Ring of P10 Portion of Heterotricycle-Based Sulfamides
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13.
and 3-methyl substituents on the cyclopropane ring, 13a and 13b
were synthesized as 2,3-dimethyl analogues of 12b and 12g, res-
pectively. Fortunately, significant improvement of aggrecanase-2
selectivity over MMP-14 was observed and these compounds displayed
IC50 values of >10 μM against all other zinc metalloproteases in
Table 7, including MMP-14, MMP-1, and TACE. The aggrecanase-2
inhibitory activity of 13a and 13b exceeded that of 12b and 12g,
respectively, and a more than 10-fold improvement of selectivity
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Table 7. SAR of the P10 Portion of 1-Amino-2,3-dimethyl-2-phenylcycloprapanecarboxylates
a See Experimental Section for assay protocols. The IC50 values are the average of at least two determinations with a standard deviation of <30%.
b Reference compound 1 gave mean ((SEM) IC50 = 12 ((0.60) nM, n = 30. c Reference compound 1 gave IC50 > 10 μM, n = 18. d Reference compound
1 gave IC50 > 10 μM, n = 16. e Reference compound 1 gave mean ((SEM) IC50 = 430 ((43) nM, n = 13.
over MMP-14 was finally achieved. This improvement in selec-
tivity could also be rationalized by means of the docking model as
shown in Figure 4. The newly introduced 2-methyl substituent
on the cyclopropane ring comes too close to Phe198 of MMP-14,
causing a steric repulsion. Meanwhile, the corresponding residue
of aggrecanase-2 is Thr378, which allows enough space to
accommodate the 2-methyl group. Interestingly, this strong
substitution effect on the selectivity was also seen in other P10
analogues: introduction of a methyl group in the 2-position of
10c, 10d, and 12h afforded 13d, 13e, and 13c, respectively, with
a great improvement of aggrecanase-2 selectivity over MMP-14.
Pharmacokinetic (PK) and Selectivity Profiles of Repre-
sentative Compounds. To assess the PK profile of this series of
compounds, we focused on several of the compounds 13 listed in
Table 7. SpragueꢀDawley rats were used in these experiments,
and each compound (10 mg/kg) was administered as a solution
in Solutol/ethanol/H2O = 4:1:5. As shown in Table 8, 13b
aggrecanase selectivity over six other members of the Zn
metalloproteases (MMP-1, MMP-3, MMP-9, MMP-13, MMP-
14, and TACE, Table 9).
Chemistry. Sulfonamide-based aggrecanase-2 inhibitors
(Tables 1 and 2) were synthesized as shown in Scheme 1. Amine
1412b was coupled with an appropriate sulfonyl chloride such as
16aꢀc and 21, and subsequent acidic cleavage of the t-Bu ester
gave the targeted compounds 7aꢀc and 8a. 16aꢀc were
synthesized from 15aꢀc,22 using the procedure described for
preparation of 6 and 7d.12b 21 was synthesized by the following
steps: coupling of 17 with 2-amino-4-chloropyridine, regioselec-
tive bromination of the resultant 18 followed by saponification to
19, condensation of 19 with ethyl thioglycolate, subsequent
saponification to 20, and decarboxylation in the presence of
copper catalyst followed by chlorosulfonylation. In contrast,
tricyclic P10 portions of 8bꢀe were constructed after sulfonam-
ide bond formation since no examples of chlorosulfonylation of
these tricycles were known. Thus, 22 and 24, obtained by a
coupling reaction of 14 with the corresponding sulfonyl chloride,
were first coupled with appropriate arylmetal species to give 23
and 25aꢀc, respectively. The tricyclic systems were constructed
showed the best oral bioavailability with an AUC of 421.0 μM h
3
and having a low clearance of 0.06 μM h. All the compounds
3
showed no CYP inhibition up to 50 μM (3A4, 2C9, 2D6, 1A2,
2A6, and 2C19). Most strikingly, 13b showed excellent
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Table 8. Pharmacokinetics Data for Selected Aggrecanase-2 Inhibitors
compd
iva (mg/kg)
Vdss(L/kg)
CL((L/h)/kg)
pob(mg/kg)
T1/2(h)
Cmax(μM)
AUC(μM h)
F (%)
3
13a
13b
13d
13e
1
1
1
1
0.70
0.25
2.6
0.60
0.06
0.29
0.70
10
10
10
10
2.0
4.0
4.5
1.9
17.4
54.1
15.9
4.9
76.9
421.0
88.4
196
103
119
64
1.9
17.8
a Administered intravenously at 1 mg per 0.5 mL/kg in a solution of Solutol/ethanol/H2O = 4:1:5. b Administered orally by gavage at 10 mg per 5 mL/kg
in a solution of Solutol/ethanol/H2O = 4:1:5.
Table 9. Selectivity Profiles of Compounds 6 and 13b
Scheme 1a
IC50 (μM)a
aggrecanase
MMP
compd
1
2
1
3
9
13
14
TACE
6
0.0040 0.0074 0.18 0.068 0.058 0.0034 0.0039 4.0
0.023 0.0084 >10 9.6 >10 >10 >10 >10
13b
a See Experimental Section for assay protocols. The IC50 values are the
average of at least two determinations with a standard deviation of <30%.
via active nitrene intermediates generated by reduction of 23 and
25aꢀc with P(OEt)3. The final acidic ester cleavage of the thus
obtained products gave 8bꢀe. There have been few reports of
syntheses of these kinds of highly constrained heterocycles, and
we found this reductive cyclization through the nitrene inter-
mediate to be one of the best options to synthesize such complex
molecules of biological interest.23
The sulfamide-based compounds listed in Tables 3 and 4 were
synthesized as described in our previous work:12b coupling
reaction of 26 with appropriate amines24 and subsequent depro-
tection gave targeted compounds 9aꢀg and 10aꢀf. The novel
amines for the synthesis of 9g and 10bꢀf were prepared as
shown in Scheme 2. N-Arylation of 2725 with aryl bromides was
performed by applying a typical Buchwald protocol to obtain
28aꢀc. 28c was further transformed to 28d by bromination and
subsequent Suzuki-coupling. As for isoxazole-substituted piper-
azines, 3-bromoisoxazole 31aꢀc were initially prepared by 1,3-
dipolar cycloaddition of 29a or 29b with 1,1-dibromoformaldoxime
and by fluorination of known ketone 30,26 respectively. Thus
obtained 31aꢀc were methylated to form quaternary salts by
the action of MeOTf to increase their electrophilicity.27 They
were subsequently coupled with 27b followed by a reductive
demethylation28 to obtain 32a, 32b, and 32d. 32b was further
transformed to 32c via hydrolysis, oxidation and fluorination.
Deprotection of the thus obtained Boc-protected amines
with HCl then afforded 33aꢀf, which were ready for coupling
with 26.
The compounds listed in Tables 5 and 6 were synthesized in
an analogous manner. The amines for the synthesis of 11a, 11b,
12aꢀf, and 12i were prepared following known procedures,29
while the amines for 11cꢀe, 12g, and 12h were prepared as
shown in Scheme 3. The most challenging step in the synthesis of
these novel tricyclic amines, including 38a, 38b, 43, 46, and 51,
was thought to be the construction of the aromatic bicycle;
therefore, we planned to prepare the aromatic part prior to the
cyclization step that would lead to the aliphatic amine moieties.
The imidazo[1,2-a]pyridine core for 38 was constructed by the
reaction of 34 and 3-bromo-2-oxopentanedioic acid dimethyl
a Reagents and conditions: (a) (i) ArSO2Cl, pyridine; (ii) HCl/1,4-
dioxane; (b) (i) 2-bromothiophene or 2-bromo-3-methylthiophene,
Cu2O, salicylaldoxime, Cs2CO3, DMA, 150 °C; (ii) ClSO3H, 70 °C; (c)
(i) 2-amino-4-chloropyridine, DME; (ii) EtOH, 80 °C; (d) (i) NBS,
CH3CN; (ii) CaCO3, H2O/CH3CN, 100 °C; (e) (i) ethyl thioglycolate,
NaO-t-Bu, EtOH, 100 °C; (ii) 4 M NaOH, 100 °C; (f) (i) Cu2O,
quinoline, 200 °C; (ii) ClSO3H, 80 °C; (g) 5-chloro-2-trimethylstan-
nanylpyridine, PdClBn(PPh3)2, toluene, 120 °C; (h) 2-(4- or 5- halo-2-
nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, PdCl2-
(dppf) CH2Cl2, 2 M Na2CO3, DME, 100 °C; (i) (i) P(OEt)3,
3
mesitylene, 150 °C; (ii) HCl/1,4-dioxane.
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ARTICLE
Scheme 2a
Figure 5. X-ray structure of (1S,2R,3R)-1-tert-butoxycarbonylamino-
2,3-dimethyl-2-phenylcyclopropanecarboxylic acid quinidine salt 57.
Atomic ellipsoids are drawn at the 50% probability level, and the Flack
parameter is refined to ꢀ0.2(5). CCDC 810738 contains the supple-
mentary crystallographic data for 57 (available free of charge at The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif).
reduced to an amine with phosphine, and protected with Boc2O
to give 42. The THP group in 42 was deprotected in hot AcOH,
and the resultant hydroxyl group was replaced with a bromine
atom. The final pyrrolidine ring formation by the action of NaH
and successive Boc deprotection gave 43. Contrary to other
tricycles, the aromatic bicyclic portion of 46 did not have to be
constructed because commercially available 44 proved to be a
good source of this ring system. Reaction of 44 with tert-butyl
2,2-dioxo[1,2,3]oxathiazolidine-3-carboxylate31and subsequent
acidic Boc deprotection followed by treatment with K2CO3 gave
intermediate 45. Finally, this compound was reduced by BH3
3
a Reagents and conditions: (a) (i) R1R2NH nHCl, NMM, 1,4-dioxane,
3
THF complex to obtain the desired amine 46. The pyrazolo[1,5-a]-
pyridine core of 51 was constructed via 1,3-dipolar cyclo-
addition32 of 1-aminopyridinium mesitylenesulfonate 4733 and
4-(tetrahydropyran-2-yloxy)but-2-ynal.34 Condensation of the
thus obtained 48 with nitromethane followed by LAH reduction
gave 49, which was then converted to 50 by Boc protection and
selective THP deprotection. Cyclization of 50 to 51 was con-
ducted via replacement of the hydroxyl group with bromine and
successive Boc deprotection. Herein, we have synthesized novel
and unique heterocycles as depicted in Scheme 3. These hetero-
cycles and their synthetic procedures are potentially useful for the
discovery of other pharmacologically relevant molecules includ-
ing metalloprotease inhibitors.23
The (1S,2R,3R)-1-amino-2,3-dimethyl-2-phenylcyclopropa-
necarboxylic acid core skeleton was prepared as described in
our previous reports.12b,35 Trans addition of freshly prepared
methanesulfenyl chloride to cis-2-phenyl-2-butene 52 and sub-
sequent treatment of the adduct with dimethyl malonate gave a
mixture of rac-53 and rac-54. The mixture of these compounds
was converted to rac-55 via sulfonium salt formation and
subsequent cyclization under basic conditions.36 Selective hydro-
lysis of the less hindered ester of rac-55 and successive Curtius
rearrangement yielded rac-56, which was ready for chiral
100 °C; (ii) HCl/1,4-dioxane or TBAF, THF then HCl/1,4-dioxane;
(b) ArBr, NaO-t-Bu, Pd(OAc)2, P(t-Bu)3, toluene, 110 °C; (c) (i) n-
Bu4N Br3, CHCl3; (ii) cyclopropylboronic acid, Pd(OAc)2, PCy3,
3
K3PO4, toluene/H2O, 110 °C; (d) 1,1-dibromoformaldoxime, KHCO3,
CH2Cl2, 40 °C; (e) bis(2-methoxyethyl)aminosulfur trifluoride,
CH2Cl2, 45 °C; (f) (i) MeOTf, 80 °C; (ii) 27b, methanol; (iii) Ph3P,
DMF, 130 °C; (g) (i) 1 M NaOH, ethanol, 80 °C; (ii) DessꢀMartin
periodinane, CH2Cl2; (iii) bis(2-methoxyethyl)aminosulfur trifluoride,
CH2Cl2; (h) HCl/1,4-dioxane.
ester. Thus, the obtained 35 was reduced with excess DIBAL-H
to diol 36, which was directly transformed to 37 by DPPA
treatment. Fortunately, compound 37, obtained by these simple
reactions, had a masked nucleophilic nitrogen atom as well as a
phosphate leaving group and was ready to cyclize to the
piperidine. As expected, reduction of 37 with PPh3 gave the
desired 38 in good yield. Reaction of 34a with 2-chloro-3-
oxosuccinic acid diethyl ester gave the imidazo[1,2-a]pyridine
core for 43. One of the two ester groups of the resultant diester
39 was selectively reduced in a chelation-controlled manner to an
aldehyde,30 which was further reduced with NaBH4 to obtain 40.
After THP protection of 40, the other ester group was reduced by
LAH to give 41, converted to an azide by DPPA treatment,
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Scheme 3a
a Reagents and conditions: (a) (i) R1R2NH nHCl, NMM, 1,4-dioxane, 100 °C; (ii) HCl/1,4-dioxane; (b) 3-bromo-2-oxopentanedioic acid dimethyl
3
ester, ethanol, 100 °C; (c) DIBAL-H, CH2Cl2, 0 °C; (d) DPPA, DBU, THF; (e) (i) PPh3, THF/H2O, 60 °C; (ii) Boc2O, DMAP; (iii) HCl/1,4-dioxane;
(f) 2-chloro-3-oxosuccinic acid diethyl ester, ethanol, 100 °C; (g) (i) DIBAL-H, toluene/THF, ꢀ78 °C; (ii) NaBH4, methanol; (h) (i) dihydropyrane,
In(OTf)3, CHCl3, 80 °C; (ii) LAH, Et2O, 0 °C; (i) (i) DPPA, DBU, THF; (ii) PPh3, H2O, 60 °C; (iii) Boc2O, DMAP; (j) (i) AcOH, H2O, 100 °C; (ii)
CBr4, PPh3, CH2Cl2; (iii) NaH, DMSO, 90 °C; (iv) HCl/1,4-dioxane; (k) (i) 3-tert-butoxycarbonyl-2,2-dioxo[1,2,3]oxathiazolidine, NaH, DMF; (ii)
TFA, CHCl3; (iii) K2CO3, THF/methanol; (l) BH3 THF, THF, 60 °C; (m) 4-(tetrahydropyran-2-yloxy)but-2-ynal, K2CO3, DMF; (n) (i) CH3NO2,
3
AcOꢀNþH4, 100 °C; (ii) LAH, THF; (o) (i) Boc2O, THF; (ii) 1 M HCl, 1,4-dioxane; (p) (i) CBr4, PPh3, CH2Cl2; (ii) NaH, DMF; (iii) HCl/1,4-
dioxane.
Scheme 4a
determined as (1S,2R,3R) by its X-ray crystallographic analysis, as
shown in Figure 5. 57 was converted to sulfamide precursor 58 in
thesamewaydescribedinourearlierpaper.12b Treatment of 58 with
appropriate amines prepared above and subsequent acidic tert-butyl
ester deprotection provided 13aꢀe (Scheme 4).
’ CONCLUSION
Given that broad-spectrum MMP inhibitors have shown
serious side effects in clinical trials owing to their lack of
specificity, the focus of our aggrecanase inhibitor program has
been to develop inhibitors with high selectivity. During the
course of our SAR investigation, we discovered that modulation
of the P10 moiety was quite effective in increasing the selectivity
for aggrecanase vs other closely related zinc metalloproteases. On
the basis of this concept, we have synthesized several novel
sulfamide-based compounds and achieved a dramatic enhance-
ment in selectivity. The selectivity was further increased by
a Reagents and conditions: (a) (i) (MeS)2, SO2Cl2, toluene, ꢀ10 °C;
introduction of a methyl group at the 2-position of the cyclo-
(ii) 52, ꢀ40 °C; (iii) dimethyl malonate, NaO-t-Bu, DME; (b) (i)
propane ring. Lead compound 13b had an IC50 of 8.4 nM for
(MeO)2SO2, 1,4-dioxane, 50 °C; (ii) NaOMe, methanol, 70 °C; (c) (i)
aggrecanase-2 and >1000-fold selectivity over the other six zinc
metalloproteases tested. Generally, these compounds showed
4 M NaOH, THF/methanol; (ii) DPPA, t-BuOH, Et3N, toluene, 100
°C; (d) (i) 4 M NaOH, THF/methanol, 90 °C; (ii) quinidine, acetone;
good pharmacokinetic properties, as represented by the data for
compound 13b, and exhibited neither CYP inhibition (IC50 > 50
μM against 3A4, 2C9, 2D6, 1A2, 2A6, and 2C19) nor hERG
potassium ion channel activity (5.4% inhibition at 30 μM) in the
patch clamp assay. Recently, Agg-523, Wyeth’s aggrecanase
inhibitor, has entered into clinical trials aiming to become the
first disease modifying osteoarthritis drug (DMORD).37
Although its efficacy data are currently unavailable, selective
aggrecanase inhibitors, including our compounds such as 13b,
(e) (i) 10% KHSO4; (ii) (t-BuO)2CHNMe2, toluene, 100 °C; (iii) p-
TsOH H2O, methanol; (iv) ClSO2NCO, 2-chloroethanol, NMM,
3
CH3CN, 50 °C; (f) (i) R1R2NH nHCl, NMM, 1,4-dioxane, 100 °C; (ii)
3
HCl/1,4-dioxane.
resolution after hydrolysis of another ester group. Among several
conditions we examined, recrystallization of the quinidine salt from
acetone was finally found to be the best combination to obtain 57 in
enantiomerically pure form. The absolute stereochemistry of 57 was
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Journal of Medicinal Chemistry
ARTICLE
have great potential to become DMORDs without the side
effects seen previously with nonselective MMP inhibitors.
mp 202ꢀ206 °C; [R]20 þ100.00° (c 0.14, methanol); 1H NMR
D
(400 MHz, methanol-d4) δ 1.37 (d, J = 6.5 Hz, 3H), 2.14 (s, 3H),
2.16ꢀ2.24 (m, 1H), 2.94 (d, J = 10.2 Hz, 1H), 7.08 (d, J = 4.2 Hz, 1H),
7.16ꢀ7.30 (m, 5H), 7.48 (dd, J = 4.2, 0.9 Hz, 1H), 7.51 (s, 1H), 7.99
’ EXPERIMENTAL SECTION
(br s, 1H). Anal. (C19H19N3O4S2 0.5H2O) calcd C 53.50%, H 4.73%, N
3
9.85%; found C 53.85%, H 4.72%, N 9.86%.
Chemistry. Unless otherwise specified, materials were purchased
from commercial suppliers or prepared using procedures reported
elsewhere. Melting points were obtained with a Yanagimoto micromelt-
ing point apparatus or a Stanford Research Systems MPA100 and were
uncorrected. Combustion analyses were performed with a Perkin-Elmer
2400 series II CHNS/O analyzer, and all values were within (0.4% of
the calculated values. Mass spectra were recorded on an Agilent
Technologies 1100 series LC/MS (ESI) spectrometer. 1H NMR spectra
were recorded on a JEOL JNM-A300W, Bruker DPX300, Bruker
ARX400, or Varian MERCURYplus-AS400 spectrometer in a solution
of CDCl3, methanol-d4, or DMSO-d6 using tetramethylsilane as the
internal standard. Chemical shifts are expressed as δ (ppm) values for
protons relative to the internal standard. Standard abbreviations indicat-
ing multiplicity were used as follows: s = singlet, br s = broad singlet, d =
doublet, dd = double doublet, ddd = double double doublet, dt = double
triplet, dq = double quartet, t = triplet, q = quartet, and m = multiplet. All
compounds gave spectra consistent with their assigned structures.
Optical rotation was measured at 20 °C with a Rudolph Research
Analytical AUTOPOL V spectrometer. Single-crystal X-ray analysis was
performed with Rigaku R-AXIS RAPID analysis system. The purity of all
of the tested compounds was determined by combustion analyses and
was g95%.
(1S,2R,3R)-1-(6-Chlorothieno[30,20:4,5]imidazo[1,2-a]py-
ridine-2-sulfonylamino)-2-methyl-3-phenylcyclopropane-
carboxylic Acid (8a). 8a was prepared by coupling of 14 with 21
following the procedures described for 7a. The crude product was
purified by trituration with methanol/H2O to yield 8a as a white solid
(57% yield): mp 243ꢀ248 °C; [R]20 þ52.67° (c 0.21, methanol);
D
1H NMR (400 MHz, DMSO-d6) δ 1.26 (d, J = 6.6 Hz, 3H), 2.00 (dq,
J = 10.3, 6.5 Hz, 1H), 2.80 (d, J = 10.1 Hz, 1H), 7.12ꢀ7.30 (m, 5H), 7.81
(s, 1H), 7.89 (s, 1H), 9.02 (d, J = 7.5 Hz, 1H), 9.15 (br s, 1H), 12.22
(br s, 1H). Anal. (C20H16ClN3O4S2 H2O) calcd C 50.05%, H 3.78%, N
3
8.75%; found C 50.20%, H 3.59%, N 8.66%.
5-(4-Chloropyrazol-1-yl)-4-methylthiophene-2-sulfonyl
Chloride (16a). A mixture of 15a (500 mg, 3.24 mmol), 2-bromo-
3-methylthiophene (689 mg, 3.89 mmol), Cu2O (46 mg, 0.324 mmol),
salicylaldoxime (178 mg, 1.30 mmol), and Cs2CO3 (2.11 g, 6.48 mmol)
in N,N-dimethylacetamide (5.0 mL) was heated at 150 °C under an
argon atmosphere. After 12 h, the reaction mixture was diluted with H2O
and extracted with EtOAc. The organic layer was dried over Na2SO4,
concentrated in vacuo, and the residue was purified by flash chroma-
tography (n-hexane/EtOAc 8:1) to afford 4-chloro-1-(3-methylthio-
phen-2-yl)pyrazole as a yellow oil (211 mg, 33% yield). To this product,
HSO3Cl (0.8 mL, 12 mmol) was added, and the mixture was heated at
70 °C for 8 h under argon. After cooling to room temperature, the
reaction mixture was poured into iceꢀwater and the resulting precipitate
was collected by filtration to give 16a as a brown solid (214 mg, 68%
yield). 1H NMR (400 MHz, CDCl3) δ 2.40 (s, 3H), 7.62 (s, 1H), 7.70
(s, 1H), 7.82 (s, 1H).
5-(4-Methoxypyrazol-1-yl)thiophene-2-sulfonyl Chloride
(16b). 16b was prepared by coupling of 2-bromothiophene with
4-methoxypyrazole 15b and subsequent sulfonylation following the
procedures described for 16a. Pale yellow solid (53% yield); 1H NMR
(400 MHz, CDCl3) δ 3.83 (s, 3H), 6.87 (d, J = 4.4 Hz, 1H), 7.48 (s, 1H),
7.51 (s, 1H), 7.74 (d, J = 4.4 Hz, 1H).
5-(4-Methylpyrazol-1-yl)thiophene-2-sulfonyl Chloride
(16c). 16c was prepared by coupling of 2-bromothiophene with
4-methylpyrazole 15c and subsequent sulfonylation following the
procedures described for 16a. Pale yellow solid (13% yield); 1H NMR
(300 MHz, DMSO-d6) δ 2.07 (s, 3H), 6.95 (d, J = 3.8 Hz, 1H), 6.99 (d,
J = 3.8 Hz, 1H), 7.49 (s, 1H), 8.14 (s, 1H).
7-Chloro-2-dichloromethylimidazo[1,2-a]pyridine (18). A
solution of 1,1,3-trichloropropan-2-one 17 (15.1 g, 93.4 mmol) in 1,
2-dimethoxyethane (20 mL) was added dropwise to a stirred suspension of
2-amino-4-chloropyridine (8.00 g, 62.3 mmol) in 1,2-dimethoxyethane
(80 mL) at 0 °C. The suspension soon turned into a clear solution, and a
white precipitate was formed after stirring for 12 h at room temperature.
The white solid was collected by filtration and successively heated in
ethanol (60 mL) at 80 °C for 4 h. After removal of the solvent under
reduced pressure, the mixture was poured into a saturated solution of
NaHCO3 at 0 °C and extracted with chloroform. The organic layer was
dried over Na2SO4 and concentrated. The resultant crude product was
purified by trituration with diethyl ether to give 18 as a pale yellow solid
(8.22 g, 56% yield). 1H NMR (400 MHz, DMSO-d6) δ 7.06 (dd, J = 7.3,
2.2 Hz, 1H), 7.58 (s, 1H), 7.78 (d, J = 2.2 Hz, 1H), 8.18 (s, 1H), 8.59 (d,
J = 7.3 Hz, 1H).
(1S,2R,3R)-1-[5-(4-Chloropyrazol-1-yl)-4-methylthiophene-
2-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (7a). To a stirred solution of (1S,2R,3R)-1-amino-
2-methyl-3-phenylcyclopropanecarboxylic acid tert-butyl ester 1412b
(47 mg, 0.19 mmol) in pyridine (0.5 mL) was added 16a (56 mg, 0.19
mmol) portionwise at 0 °C. The mixture was stirred at room tempera-
ture for 12 h and was then poured into iceꢀwater, and the product was
extracted with EtOAc. The organic layer was washed with 0.5 M HCl, 5%
solution of NaHCO3, and brine, dried over MgSO4, and evaporated
under reduced pressure. The residue was purified by flash chromatog-
raphy (n-hexane/EtOAc 4:1) to give the tert-butyl ester of 7a (46 mg,
48% yield), which was successively treated with 4 M HCl in 1,4-dioxane
(1 mL) at room temperature for 12 h. After the solvent was removed in
vacuo, the crude product was purified by trituration with methanol/H2O
to yield 7a as a white solid (36 mg, 83% yield): mp 177ꢀ181 °C; [R]20
D
þ104.74° (c 0.19, methanol); 1H NMR (400 MHz, DMSO-d6) δ 1.27
(d, J = 6.8 Hz, 3H), 1.97 (dq, J = 10.4, 6.8 Hz, 1H), 2.25 (s, 3H), 2.79 (d,
J = 10.4 Hz, 1H), 7.16ꢀ7.22 (m, 3H), 7.24ꢀ7.29 (m, 2H), 7.43 (s, 1H),
7.94 (d, J = 0.7 Hz, 1H), 8.53 (d, J = 0.5 Hz, 1H), 9.08 (br s, 1H), 12.35
(br s, 1H). Anal. (C19H18ClN3O4S2 0.5H2O) calcd C 49.51%, H 4.15%,
3
N 9.11%; found C 49.49%, H 4.26%, N 9.14%.
(1S,2R,3R)-1-[5-(4-Methoxypyrazol-1-yl)thiophene-2-
sulfonylamino]-2-methyl-3-phenylcyclopropanecarboxylic
Acid (7b). 7b was prepared by coupling of 14 with 16b following the
procedures described for 7a. The crude product was purified by
trituration with methanol/H2O to yield 7b as a white solid (41% yield):
1
mp 84ꢀ88 °C; [R]20 þ79.23° (c 0.13, methanol); H NMR (300
D
MHz, methanol-d4) δ 1.38 (d, J = 6.8 Hz, 3H), 2.15ꢀ2.25 (m, 1H), 2.93
(d, J = 10.5 Hz, 1H), 3.81 (s, 3H), 7.05(d, J = 4.1 Hz, 1H), 7.20ꢀ7.24
(m, 5H), 7.47ꢀ7.49 (m, 2H), 7.97 (d, J = 0.8 Hz, 1H). Anal.
(C19H19N3O5S2 0.5H2O) calcd C 51.57%, H 4.56%, N 9.50%; found
3
C 51.67%, H 4.66%, N 9.53%.
(1S,2R,3R)-2-Methyl-1-[5-(4-methylpyrazol-1-yl)thiophene-
2-sulfonylamino]-3-phenylcyclopropanecarboxylic Acid
(7c). 7c was prepared by coupling of 14 with 16c following the
procedures described for 7a. The crude product was purified by
trituration with methanol/H2O to yield 7c as a white solid (34% yield):
3-Bromo-7-chloroimidazo[1,2-a]pyridine-2-carbaldehyde
(19). To a suspension of 18 (8.22 g, 34.9 mmol) in acetonitrile (80 mL)
was added N-bromosuccinimide (8.06 g, 45.3 mmol) at room tempera-
ture, and the mixture was stirred for 4 h under an argon atmosphere.
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CaCO3 (10.4 g, 104 mmol) and H2O (40 mL) were added to the
mixture, and the mixture was heated at 100 °C for 4 h. After cooling to
room temperature, the reaction mixture was poured into a saturated
solution of NaHCO3 at 0 °C and extracted with chloroform. The organic
layer was dried over Na2SO4 and concentrated, affording a crude
product, which was purified by flash chromatography (CHCl3/EtOAc
25:1) to afford 19 as a pale yellow solid (7.69 g, 85% yield). 1H NMR
(400 MHz, CDCl3) δ 7.04 (dd, J = 7.4, 2.1 Hz, 1H), 7.71 (dd, J = 2.1,
0.9 Hz, 1H), 8.16 (dd, J = 7.4, 0.9 Hz, 1H), 10.18 (s, 1H).
6-Chlorothieno[30,20:4,5]imidazo[1,2-a]pyridine-2-carboxylic
Acid (20). Ethyl thioglycolate (4.3 mL, 39.2 mmol) was added
dropwise to a solution of NaO-t-Bu (3.77 g, 39.2 mmol) in ethanol
(40 mL), and the mixture was stirred at room temperature for 0.5 h. To
this reaction mixture was added a solution of 19 (4.85 g, 18.7 mmol) in
ethanol (70 mL). The mixture was heated at 100 °C for 2 h and further
heated at this temperature for 1 h after addition of 4 M NaOH (10 mL).
After cooling to room temperature, the mixture was concentrated under
reduced pressure and neutralized with 2 M HCl at 0 °C to afford a pale
yellow solid. The crude product was purified by trituration with ethanol
to give 20 as a pale yellow solid (1.33 g, 28% yield). 1H NMR (400 MHz,
DMSO-d6) δ 7.13 (dd, J = 7.3, 2.2 Hz, 1H), 7.88 (dd, J = 2.2, 0.7 Hz, 1H),
7.95 (s, 1H), 8.97 (dd, J = 7.3, 0.7 Hz, 1H), 13.43 (br s, 1H).
(1S,2R,3R)-1-[5-(4-Chloro-2-nitrophenyl)thiophene-2-sul-
fonylamino]-2-methyl-3-phenylcyclopropanecarboxylic
Acid tert-Butyl Ester (25a). A mixture of 24 (5.57 g, 11.8 mmol),
2-(4-chloro-2-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(3.68 g, 13.0 mmol), and PdCl2(dppf) CH2Cl2 (963 mg, 1.18 mmol) in
3
2 M Na2CO3/1,2-dimethoxyethane (70 mL, 2:5) was heated at 100 °C
under an argon atmosphere. After 12 h, the reaction mixture was diluted
with H2O and EtOAc. The resultant precipitate was removed by
filtration, and the organic layer of the filtrate was separated, washed
with brine, dried over Na2SO4, and concentrated. The crude product
was purified by flash chromatography (n-hexane/EtOAc 5:1) to afford
25a as a brown solid (3.52 g, 54% yield). 1H NMR (400 MHz, DMSO-
d6) δ 1.02 (s, 9H), 1.31 (d, J = 7.0 Hz, 3H), 1.96ꢀ2.05 (m, 1H), 2.83 (d,
J = 10.7 Hz, 1H), 7.17ꢀ7.24 (m, 4H), 7.25ꢀ7.31 (m, 2H), 7.57 (d,
J = 3.9 Hz, 1H), 7.69 (d, J = 8.6 Hz, 1H), 7.87 (dd, J = 8.6, 2.3 Hz, 1H),
8.23 (d, J = 2.3 Hz, 1H), 9.14 (br s, 1H).
(1S,2R,3R)-1-[5-(4-Fluoro-2-nitrophenyl)thiophene-2-sul-
fonylamino]-2-methyl-3-phenylcyclopropanecarboxylic
Acid tert-Butyl Ester (25b). 25b was prepared by coupling of 24 with
2-(4-fluoro-2-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane fol-
lowing the procedures described for 25a. Brown solid (78% yield).
1H NMR (400 MHz, DMSO-d6) δ 1.03 (s, 9H), 1.31 (d, J = 6.7 Hz, 3H),
1.95ꢀ2.02 (m, 1H), 2.82 (d, J = 11.6 Hz, 1H), 7.16ꢀ7.24 (m, 4H),
7.25ꢀ7.32 (m, 2H), 7.51ꢀ7.57 (m, 1H), 7.66ꢀ7.75 (m, 2H), 8.08 (dd,
J = 8.2, 2.4 Hz, 1H), 9.12 (br s, 1H).
6-Chlorothieno[30,20:4,5]imidazo[1,2-a]pyridine-2-sulfonyl
Chloride (21). A mixture of 20 (411 mg, 1.63 mmol) and Cu2O
(23 mg, 0.16 mmol) in quinoline (4.1 mL) was heated at 200 °C under
an argon atmosphere for 1 h. After the mixture was cooled to room
temperature, the crude product was purified by flash chromatography
(n-hexane/EtOAc 5:1) to give 6-chlorothieno[30,20:4,5]imidazo[1,
2-a]pyridine as a brown solid (241 mg, 71% yield). To this brown solid,
ClSO3H (0.5 mL, 7.5 mmol) was added and the mixture was heated at
80 °C for 5 h under an argon atmosphere. After cooling to room
temperature, the reaction mixture was poured into iceꢀwater and the
resulting precipitate was collected by filtration to give 21 as a pale yellow
(1S,2R,3R)-1-[5-(5-Fluoro-2-nitrophenyl)thiophene-2-sul-
fonylamino]-2-methyl-3-phenylcyclopropanecarboxylic
Acid tert-Butyl Ester (25c). 25c was prepared by coupling of 24 with
2-(5-fluoro-2-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane fol-
lowing the procedures described for 25a. Brown solid (83% yield).
1H NMR (400 MHz, DMSO-d6) δ 1.04 (s, 9H), 1.31 (d, J = 6.7 Hz, 3H),
1.95ꢀ2.01 (m, 1H), 2.82 (d, J = 10.4 Hz, 1H), 7.16ꢀ7.32 (m, 6H),
7.53ꢀ7.62 (m, 3H), 8.14 (dd, J = 8.8, 4.9 Hz, 1H), 9.13 (br s, 1H).
(1S,2R,3R)-1-(7-Chlorothieno[30,20:3,4]pyrazolo[1,5-a]py-
ridine-2-sulfonylamino)-2-methyl-3-phenylcyclopropane-
carboxylic Acid (8b). To a solution of 23 (200 mg, 0.364 mmol) in
mesitylene (4.0 mL) was added P(OEt)3 (362 mg, 2.18 mmol), and the
mixture was heated at 150 °C under argon. After 8 h, the reaction
mixture was concentrated and the residue was purified by preparative
TLC (n-hexane/EtOAc 2:1) to afford tert-butyl ester of 8b as a brown oil
(22.6 mg, 12% yield), which was successively treated with 4 M HCl in
1,4-dioxane (0.5 mL) at room temperature for 12 h. After the solvent was
removed in vacuo, the crude product was purified by trituration with
methanol/H2O to give 8b as a pale yellow solid (8.2 mg, 40% yield): mp
220ꢀ226 °C; [R]20D þ82.50° (c 0.20, methanol); 1H NMR (400 MHz,
CDCl3) δ 1.46 (d, J = 6.6 Hz, 3H), 1.82ꢀ1.87 (m, 1H), 3.09 (d, J = 10.1
Hz, 1H), 6.31 (br s, 1H), 7.14ꢀ7.23 (m, 6H), 7.56 (d, J = 9.7 Hz, 1H),
1
solid (279 mg, 79% yield). H NMR (300 MHz, CDCl3) δ 7.00 (dd,
J = 7.2, 2.2 Hz, 1H), 7.78 (d, J = 2.2 Hz, 1H), 8.13 (d, J = 7.2 Hz, 1H),
8.18 (s, 1H).
(1S,2R,3R)-1-(5-Chloro-4-nitrothiophene-2-sulfonylamino)-
2-methyl-3-phenylcyclopropanecarboxylic Acid tert-Butyl
Ester (22). 22 was prepared by coupling of 14 with 5-chloro-4-
nitrothiophene-2-sulfonyl chloride following the procedures described
for 7a, but in this case the final acidic hydrolysis was not conducted. Pale
yellow solid (50% yield); 1H NMR (400 MHz, CDCl3) δ 1.00 (s, 9H),
1.45 (d, J = 6.8 Hz, 3H), 2.40 (dq, J = 10.8, 6.8 Hz, 1H), 3.09 (d, J = 10.8
Hz, 1H), 6.03 (br s, 1H), 7.16ꢀ7.34 (m, 5H), 8.03 (s, 1H).
(1S,2R,3R)-1-[5-(5-Chloropyridin-2-yl)-4-nitrothiophene-
2-sulfonylamino]-2-methyl-3-phenylcyclopropanecarboxylic
Acid tert-Butyl Ester (23). A mixture of 22 (352 mg, 0.745 mmol),
5-chloro-2-trimethylstannanylpyridine (300 mg, 0.745 mmol), and
PdClBn(PPh3)2 (56 mg, 0.075 mmol) in toluene (7.0 mL) was heated
at 120 °C under argon. After 12 h, the reaction mixture was concentrated
and purified by flash chromatography (n-hexane/EtOAc 8:1) to afford
23 as a yellow oil (206 mg, 50% yield). 1H NMR (400 MHz, CDCl3) δ
1.01 (s, 9H), 1.46 (d, J = 6.6 Hz, 3H), 2.41 (dq, J = 10.6, 6.6 Hz, 1H),
3.09 (d, J = 10.6 Hz, 1H), 6.05 (br s, 1H), 7.19ꢀ7.32 (m, 5H),
7.77ꢀ7.78 (m, 2H), 8.08 (s, 1H), 8.60ꢀ8.61 (m, 1H).
7.76 (s, 1H), 8.58 (s, 1H). Anal. (C20H16ClN3O4S2 0.5H2O) calcd C
3
51.00%, H 3.64%, N 8.92%; found C 51.12%, H 3.83%, N 8.95%.
(1S,2R,3R)-1-(6-Chloro-4H-thieno[3,2-b]indole-2-sulfonyl-
amino)-2-methyl-3-phenylcyclopropanecarboxylic Acid
(8c). 8c was prepared from 25a following the procedures described
for 8b. The crude product was purified by trituration with methanol/
H2O to yield 8c as a pale yellow solid (22% yield): mp 136ꢀ140 °C;
1
[R]20 þ118.18° (c 0.33, THF); H NMR (300 MHz, DMSO-d6) δ
D
1.26 (d, J = 6.4 Hz, 3H), 1.98 (dq, J = 10.4, 6.6 Hz, 1H), 2.78 (d, J = 10.5
Hz, 1H), 7.10ꢀ7.30 (m, 6H), 7.59 (s, 1H), 7.68 (s, 1H), 7.92 (d, J = 8.3
Hz, 1H), 9.02 (s, 1H), 11.72 (s, 1H), 12.23 (s, 1H). Anal.
(C21H17ClN2O4S2) calcd C 54.72%, H 3.72%, N 6.08%; found C
54.63%, H 3.80%, N 6.16%.
(1S,2R,3R)-1-(5-Bromothiophene-2-sulfonylamino)-
2-methyl-3-phenylcyclopropanecarboxylic Acid tert-Butyl
Ester (24). 24 was prepared by coupling of 14 with 5-bromothio-
phene-2-sulfonyl chloride following the procedures described for 7a, but
in this case the final acidic hydrolysis was not conducted. White solid
(69% yield); 1H NMR (400 MHz, DMSO-d6) δ 1.00 (s, 9H), 1.32 (d,
J = 6.7 Hz, 3H), 2.00ꢀ2.09 (m, 1H), 2.81 (d, J = 10.4 Hz, 1H),
7.18ꢀ7.24 (m, 3H), 7.26ꢀ7.30 (m, 2H), 7.31 (d, J = 3.9 Hz, 1H), 7.40
(d, J = 3.9 Hz, 1H), 9.12 (br s, 1H).
(1S,2R,3R)-1-(6-Fluoro-4H-thieno[3,2-b]indole-2-sulfonyl-
amino)-2-methyl-3-phenylcyclopropanecarboxylic Acid
(8d). 8d was prepared from 25b following the procedures described for
8b. The crude product was purified by trituration with methanol/H2O
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Journal of Medicinal Chemistry
ARTICLE
to yield 8d as a pale yellow solid (57% yield): mp 229ꢀ233 °C; [R]20
(1S,2R,3R)-1-[(S)-4-(4-Chlorophenyl)-3-methylpiperazine-
1-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (9d). 9d was prepared by coupling of 26 with (S)-1-(4-
chlorophenyl)-2-methylpiperazine24a following the procedures de-
scribed for 9a. The crude product was purified by trituration with
DMSO/H2O to yield 9d as a white solid (75% yield): mp 124ꢀ128 °C;
[R]20D þ41.42° (c 0.45, methanol); 1H NMR (400 MHz, DMSO-d6) δ
0.97 (d, J = 6.5 Hz, 3H), 1.26 (d, J = 6.7 Hz, 3H), 2.01 (dq, J = 10.3, 6.8
Hz, 1H), 2.77ꢀ2.86 (m, 1H), 2.91 (d, J = 10.4 Hz, 1H), 2.95ꢀ3.04 (m,
2H), 3.32ꢀ3.41 (m, 3H), 4.06ꢀ4.14 (m, 1H), 6.90ꢀ6.98 (m, 2H),
D
þ130.80° (c 0.10, methanol); 1H NMR (400 MHz, DMSO-d6) δ 1.25
(d, J = 6.7 Hz, 3H), 1.97 (dd, J = 10.2, 6.7 Hz, 1H), 2.77 (d,
J = 10.2 Hz, 1H), 6.96ꢀ7.03 (m, 1H), 7.14ꢀ7.21 (m, 3H), 7.22ꢀ7.28
(m, 2H), 7.30ꢀ7.35 (m, 1H), 7.65 (s, 1H), 7.88ꢀ7.93 (m, 1H), 8.97
(br s, 1H), 11.68 (br s, 1H), 12.22 (br s, 1H). Anal. (C21H17FN2O4S2)
calcd C 56.74%, H 3.85%, N 6.30%; found C 56.95%, H 4.09%, N 6.26%.
(1S,2R,3R)-1-(7-Fluoro-4H-thieno[3,2-b]indole-2-sulfo-
nylamino)-2-methyl-3-phenylcyclopropanecarboxylic Acid
(8e). 8e was prepared from 25c following the procedures described
for 8b. The crude product was purified by trituration with methanol/
H2O to yield 8e as a pale yellow solid (12% yield): mp 129ꢀ131 °C;
[R]20D þ124.6° (c 0.13, methanol); 1H NMR (400 MHz, DMSO-d6) δ
1.25 (d, J = 6.7 Hz, 3H), 1.97 (dq, J = 10.2, 6.7 Hz, 1H), 2.78 (d, J = 10.2
Hz, 1H), 7.11ꢀ7.22 (m, 4H), 7.22ꢀ7.29 (m, 2H), 7.49ꢀ7.56 (m, 1H),
7.65 (s, 1H), 7.71ꢀ7.78 (m, 1H), 9.01 (br s, 1H), 11.65 (br s, 1H), 12.22
7.15ꢀ7.30 (m, 7H), 8.35 (s, 1H). Anal. (C22H26ClN3O4S 0.75
3
DMSO) calcd C 54.01%, H 5.88%, N 8.04%; found C 53.73%, H
5.82%, N 7.99%.
Mixture of (1S,2R,3R)-1-[(R)-4-(4-Chlorophenyl)-3-ethyl-
piperazine-1-sulfonylamino]-2-methyl-3-phenylcyclopro-
panecarboxylic Acid Hydrochloride and (1S,2R,3R)-1-[(S)-
4-(4-Chlorophenyl)-3-ethylpiperazine-1-sulfonylamino]-2-
methyl-3-phenylcyclopropanecarboxylic Acid Hydrochlor-
ide (9e). 9e was prepared by coupling of 26 with 1-(4-chlorophenyl)-2-
ethylpiperazine24b following the procedures described for 9a. The crude
product was purified by trituration with DMSO/EtOAc to yield 9e as a
white solid (74% yield); 1H NMR (300 MHz, DMSO-d6) δ 0.70ꢀ0.91
(m, 3H), 1.21ꢀ1.33 (m, 3H), 1.52ꢀ1.73 (m, 1H), 1.94ꢀ2.14 (m, 1H),
2.67ꢀ3.06 (m, 5H), 3.31ꢀ3.68 (m, 3H), 3.76ꢀ3.94 (m, 1H),
6.83ꢀ6.99 (m, 2H), 7.12ꢀ7.34 (m, 7H), 8.35 (s, 1H), 11.88ꢀ12.55
(m, 1H). Anal. (C23H28ClN3O4S HCl 0.30DMSO) calcd C 52.70%, H
(br s, 1H). Anal. (C21H17FN2O4S2 0.5H2O) calcd C 55.62%, H 4.00%,
3
N 6.18%; found C 55.69%, H 4.06%, 6.20%.
(1S,2R,3R)-1-[4-(4-Chlorophenyl)piperazine-1-sulfonyl-
amino]-2-methyl-3-phenylcyclopropanecarboxylic Acid Hy-
drochloride (9a). To a solution of 2612b (127 mg, 0.32 mmol) in 1,4-
dioxane (2.5 mL) were added N-methylmorpholine (0.14 mL, 1.27
mmol) and 1-(4-chlorophenyl)piperazine (62 mg, 0.32 mmol) obtained
by neutralization of its dihydrochloride. After being stirred at 100 °C
under argon atmosphere, the reaction mixture was diluted with saturated
aqueous solution of NH4Cl and extracted with EtOAc. The organic layer
was washed with brine, dried over MgSO4, and concentrated. The
residue was purified by flash chromatography (n-hexane/EtOAc 5:1) to
afford tert-butyl ester of 9a (101 mg, 70% yield), which was successively
treated with 4 M HCl in 1,4-dioxane (2.0 mL) at room temperature for
12 h. After the solvent was removed in vacuo, the crude product was
purified by trituration with EtOAc to yield 9a as a white solid (60 mg,
56% yield): mp 107ꢀ110 °C; [R]20D þ70.43° (c 0.14, methanol); 1H
NMR (400 MHz, DMSO-d6) δ 1.25 (d, J = 6.7 Hz, 3H), 2.00 (dq, J =
10.4, 6.7 Hz, 1H), 2.86 (d, J = 10.4 Hz, 1H), 3.18 (br s, 8H), 6.97 (d, J =
3
3
5.77%, N 7.81%; found C 52.52%, H 5.47%, N 7.52%.
(1S,2R,3R)-1-[4-(4-Chlorophenyl)-3,3-dimethylpiperazine-
1-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (9f). 9f was prepared by coupling of 26 with 1-(4-
chlorophenyl)-2,2-dimethylpiperazine following the procedures de-
scribed for 9a. The crude product was purified by trituration with
methanol/H2O to yield 9f as a white solid (72% yield): mp 131 °C;
[R]20D þ74.33° (c 0.55, methanol); 1H NMR (400 MHz, DMSO-d6) δ
0.96 (s, 3H), 0.98 (s, 3H), 1.27 (d, J = 6.5 Hz, 3H), 2.02 (br s, 1H), 2.78
(br s, 1H), 2.97 (s, 2H), 3.06 (br s, 2H), 3.15 (br s, 2H), 7.07ꢀ7.18
9.3 Hz, 2H), 7.12ꢀ7.31 (m, 7H), 8.34 (s, 1H). Anal. (C21H24ClN3O4S
3
(m, 3H), 7.22 (br s, 4H), 7.28ꢀ7.31 (m, 2H). Anal. (C23H28ClN3O4S
HCl calcd C 51.86%, H 5.18%, N 8.64%; found C 51.68%, H 5.23%,
N 8.72%.
3
0.75H2O) calcd C 56.20%, H 6.05%, N 8.55%; found C 56.13%,
H 6.02%, N 8.30%.
(1S,2R,3R)-1-[4-(4-Chlorophenyl)-1,2,3,6-tetrahydropyri-
dine-1-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (9b). 9b was prepared by coupling of 26 with 4-(4-
chlorophenyl)-1,2,3,6-tetrahydropyridine following the procedures de-
scribed for 9a. The crude product was purified by trituration with
methanol/H2O to yield 9b as a pale yellow solid (15% yield): mp 94 °C;
[R]20D þ45.64° (c 0.11, methanol); 1H NMR (400 MHz, DMSO-d6)
δ 1.26 (d, J = 6.8 Hz, 3H), 2.02 (dq, J = 10.1, 6.8 Hz, 1H), 2.51ꢀ2.58
(m, 2H), 2.88 (d, J = 10.1 Hz, 1H), 3.29ꢀ3.37 (m, 2H), 3.80 (d,
J = 3.4 Hz, 2H), 6.24 (t, J = 3.4 Hz, 1H), 7.15ꢀ7.29 (m, 5H), 7.40 (d,
J = 11.0 Hz, 2H), 7.46 (d, J = 11.0 Hz, 2H), 8.31 (s, 1H), 12.36 (br s, 1H).
Mixture of (1S,2R,3R)-1-[(R)-4-(4-Chlorophenyl)-3-hydro-
xymethylpiperazine-1-sulfonylamino]-2-methyl-3-phenyl-
cyclopropanecarboxylic Acid and (1S,2R,3R)-1-[(S)-4-(4-
Chlorophenyl)-3-hydroxymethylpiperazine-1-sulfonyl-
amino]-2-methyl-3-phenylcyclopropanecarboxylic Acid
(9g). To a solution of 26 (71 mg, 0.181 mmol) in 1,4-dioxane
(3.0 mL) were added N-methylmorpholine (0.022 mL, 0.200 mmol)
and 33a (vide infra, 84 mg, 0.181 mmol). After being stirred at 100 °C
under an argon atmosphere for 12 h, the reaction mixture was diluted
with a saturated solution of NH4Cl, extracted with EtOAc, washed with
brine, dried over MgSO4, and concentrated. The residue was purified by
flash chromatography (n-hexane/EtOAc 5:1) to give the coupling
product as a yellow oil (46 mg, 33% yield). To the solution of this
compound in THF (1.0 mL) was added 1 M TBAF in THF (0.10 mL) at
room temperature, and the mixture was stirred for 0.5 h. The solvent was
removed in vacuo and the residue was purified by preparative TLC
(CHCl3/methanol 20:1) to afford the corresponding alcohol (30 mg,
94% yield), which was successively treated with 4 M HCl in 1,4-dioxane
(2 mL) at room temperature for 12 h. After concentration in vacuo, the
crude product was purified by trituration with DMSO/H2O to yield 9g
as a pale yellow solid (19 mg, 71% yield). 1H NMR (400 MHz, DMSO-d6)
δ 1.20ꢀ1.28 (m, 3H), 1.88ꢀ2.05 (m, 1H), 2.66ꢀ3.79 (m, 10H), 6.90
(dd, J = 9.3, 2.8 Hz, 2H), 7.11ꢀ7.28 (m, 7H), 8.13 (br s, 1H). Anal.
Anal. (C22H23ClN2O4S 0.25H2O) calcd C 58.53%, H 5.25%, N 6.21%;
3
found C 58.70%, H 5.27%, N 6.18%.
(1S,2R,3R)-1-[(R)-4-(4-Chlorophenyl)-3-methylpiperazine-
1-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (9c). 9c was prepared by coupling of 26 with (R)-1-(4-
chlorophenyl)-2-methylpiperazine24a following the procedures de-
scribed for 9a. The crude product was purified by trituration with 1,
4-dioxane/H2O to yield 9c as a white solid (70% yield): mp 115ꢀ120 °C;
[R]20D þ66.70° (c 0.40, methanol); 1H NMR (400 MHz, DMSO-d6) δ
0.92 (d, J = 6.4 Hz, 3H), 1.28 (d, J = 6.6 Hz, 3H), 2.09 (dq, J = 10.5, 6.7
Hz, 1H), 2.74ꢀ2.82 (m, 1H), 2.86 (d, J = 10.4 Hz, 1H), 2.93ꢀ3.04 (m,
2H), 3.32ꢀ3.39 (m, 2H), 3.49ꢀ3.55 (m, 1H), 4.09 (d, J = 6.6 Hz, 1H),
6.91 (d, J = 8.8 Hz, 2H), 7.15ꢀ7.30 (m, 7H), 8.33 (s, 1H). Anal.
(C22H26ClN3O4S 0.75 1,4-dioxane) calcd C 56.65%, H 6.09%, N
(C23H28ClN3O4S DMSO) calcd C 53.22%, H 5.63%, N 8.10%; found
3
3
7.93%; found C 56.47%, H 5.74%, N 7.72%.
C 52.86%, H 5.90%, N 7.70%.
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Journal of Medicinal Chemistry
ARTICLE
(1S,2R,3R)-1-[(R)-4-(4-Fluorophenyl)-3-methylpiperazine-
1-sulfonylamino]-2-methyl-3-phenylcyclopropanecar-
boxylic Acid (10a). 10a was prepared by coupling of 26 with (R)-
1-(4-fluorophenyl)-2-methylpiperazine24b following the procedures de-
scribed for 9a. The crude product was purified by trituration with
(d, J = 10.4 Hz, 1H), 3.00 (dd, J = 11.8, 3.4 Hz, 1H), 3.11ꢀ3.20 (m, 1H),
3.39ꢀ3.46 (m, 1H), 3.46ꢀ3.52 (m, 1H), 3.59ꢀ3.67 (m, 1H),
3.88ꢀ3.96 (m, 1H), 6.43 (s, 1H), 7.01ꢀ7.19 (m, 5H). Anal.
(C21H26F2N4O5S 0.25H2O) calcd C 51.58%, H 5.46%, N 11.46%;
3
found C 51.40%, H 5.57%, 11.43%.
CHCl3/methanol to yield 10a as a white solid (58% yield): mp
(1S,2R,3R)-1-[(R)-4-(5-Methoxymethylisoxazol-3-yl)-3-
methylpiperazine-1-sulfonylamino]-2-methyl-3-phenylcy-
clopropanecarboxylic Acid (10f). 10f was prepared by coupling of
26 with 33d (vide infra) following the procedures described for 9a. The
crude product was purified by trituration with methanol/H2O to yield
1
218ꢀ222 °C; [R]20 þ174.38° (c 0.16, THF); H NMR (400 MHz,
D
DMSO-d6) δ 0.87 (d, J = 6.3 Hz, 3H), 1.28 (d, J = 6.7 Hz, 3H),
1.86ꢀ1.98 (m, 1H), 2.52ꢀ2.62 (m, 1H), 2.91ꢀ3.00 (m, 2H),
3.12ꢀ3.20 (m, 2H), 3.22ꢀ3.28 (m, 1H), 3.45ꢀ3.53 (m, 1H),
3.84ꢀ3.91 (m, 1H), 6.89ꢀ6.95 (m, 2H), 7.01ꢀ7.11 (m, 3H), 7.16
(t, J = 7.4 Hz, 2H), 7.25 (d, J = 7.9 Hz, 2H), 7.45 (br s, 1H). Anal.
10f as a pale yellow solid (67% yield): mp 71 °C; [R]20 þ61.70°
D
(c 0.47, methanol); 1H NMR (400 MHz, methanol-d4) δ 1.18 (d, J = 6.6
Hz, 3H), 1.37 (d, J = 6.8 Hz, 3H), 2.24 (dq, J = 10.4, 6.8 Hz, 1H), 2.86
(td, J = 12.0, 3.6 Hz, 1H), 2.96 (d, J = 10.4 Hz, 1H), 3.09 (dd, J = 11.7, 3.3
Hz, 1H), 3.23 (td, J = 12.5, 3.3 Hz, 1H), 3.38 (s, 3H), 3.47 (d, J = 12.6
Hz, 1H), 3.57 (dt, J = 11.7, 2.0 Hz, 1H), 3.67ꢀ3.74 (m, 1H), 3.93ꢀ4.00
(m, 1H), 4.41 (s, 2H), 6.17 (s, 1H), 7.15ꢀ7.20 (m, 1H), 7.21ꢀ7.29 (m,
(C22H26FN3O4S 0.75CHCl3) calcd C 56.21%, H 5.55%, N 8.64%;
3
found C 56.33%, H 5.49%, 8.80%.
(1S,2R,3R)-1-[(R)-4-(4-Cyclopropylphenyl)-3-methylpiper-
azine-1-sulfonylamino]-2-methyl-3-phenylcyclopropane-
carboxylic Acid Hydrochloride (10b). 10b was prepared by
coupling of 26 with 33c (vide infra) following the procedures described
for 9a. The crude product was purified by trituration with DMSO/
EtOAc to yield 10b as a pale yellow solid (49% yield): mp 141 °C;
[R]20D þ50.89° (c 0.45, methanol); 1H NMR (400 MHz, methanol-d4)
δ 0.75 (dt, J = 6.5, 4.6 Hz, 2H), 1.03ꢀ1.09 (m, 2H), 1.12 (d, J = 6.5 Hz,
3H), 1.40 (d, J = 6.8 Hz, 3H), 1.96ꢀ2.04 (m, 1H), 2.24 (dq, J = 10.6, 6.8
Hz, 1H), 3.03 (d, J = 10.4 Hz, 1H), 3.21 (dd, J = 13.6, 10.7 Hz, 1H),
3.43ꢀ3.52 (m, 1H), 3.71ꢀ3.78 (m, 2H), 3.94ꢀ4.04 (m, 2H), 4.08 (d,
J = 13.8 Hz, 1H), 7.17ꢀ7.23 (m, 1H), 7.24ꢀ7.33 (m, 6H), 7.48ꢀ7.53
(m, 2H). Anal. (C25H31N3O4S HCl 1.1DMSO) calcd C 55.18%,
4H). Anal. (C21H28N4O6S 0.5H2O) calcd C 53.26%, H 6.17%, N
3
11.83%; found C 53.04%, H 6.13%, N 11.66%.
1-(tert-Butoxycarbonyl)-3-(tert-butyldiphenylsilanyloxy-
methyl)-4-(4-chlorophenyl)piperazine (28a). A mixture of
27a25 (227 mg, 0.50 mmol), 1-bromo-4-chlorobenzene (115 mg, 0.60
mmol), NaO-t-Bu (67 mg, 0.70 mmol), Pd(OAc)2 (2.2 mg, 0.013
mmol), and P(t-Bu)3 (8.1 mg, 0.040 mmol) in toluene (3.0 mL) was
heated at 110 °C under argon. After 12 h, the reaction mixture was
diluted with H2O and then extracted with EtOAc. The organic layer was
separated, washed with brine, dried over MgSO4, and concentrated. The
crude product was purified by flash chromatography (n-hexane/EtOAc
9:1) to give 28a as a yellow oil (152 mg, 54% yield). 1H NMR (400 MHz,
DMSO-d6) δ 0.94 (s, 9H), 1.40 (s, 9H), 2.88ꢀ3.28 (m, 4H), 3.37ꢀ3.41
(m, 1H), 3.65ꢀ3.92 (m, 3H), 4.26 (d, J = 13.0 Hz, 1H), 6.62ꢀ6.84
(m, 2H), 7.05ꢀ7.17 (m, 2H), 7.35ꢀ7.50 (m, 6H), 7.52ꢀ7.60 (m, 4H).
(R)-1-(tert-Butoxycarbonyl)-4-(5-cyanothiophen-2-yl)-3-
methylpiperazine (28b). 28b was prepared by coupling of 27b with
5-bromothiophene-2-carbonitrile following the procedures described
for 28a. Pale yellow oil (21% yield); 1H NMR (400 MHz, DMSO-d6) δ
1.05 (d, J = 6.5 Hz, 3H), 1.41 (s, 9H), 2.86ꢀ3.22 (m, 3H), 3.31ꢀ3.36
(m, 1H), 3.72ꢀ4.05 (m, 3H), 6.19 (d, J = 4.2 Hz, 1H), 7.61 (d, J = 4.2
Hz, 1H).
3
3
H 6.57%, N 7.10%; found C 54.86%, H 6.27%, N 7.42%.
(1S,2R,3R)-1-[(R)-4-(5-Cyanothiophen-2-yl)-3-methylpi-
perazine-1-sulfonylamino]-2-methyl-3-phenylcyclopropa-
necarboxylic Acid (10c). 10c was prepared by coupling of 26 with
33b (vide infra) following the procedures described for 9a. The crude
product was purified by trituration with methanol/H2O to yield 10c as a
pale yellow solid (74% yield): mp 104 °C; [R]20 þ75.35° (c 0.99,
D
methanol); 1H NMR (400 MHz, DMSO-d6) δ 1.11 (d, J = 6.7 Hz, 3H),
1.27 (d, J = 6.7 Hz, 3H), 2.08 (dq, J = 10.4, 6.7 Hz, 1H), 2.70ꢀ2.84 (m,
2H), 2.99 (d, J = 12.5 Hz, 1H), 3.16ꢀ3.22 (m, 1H), 3.38ꢀ3.47 (m, 2H),
3.59 (d, J = 10.9 Hz, 1H), 3.95ꢀ4.02 (m, 1H), 6.20 (d, J = 4.4 Hz, 1H),
7.11ꢀ7.29 (m, 5H), 7.61 (d, J = 4.4 Hz, 1H), 8.38 (br s, 1H). Anal.
(C21H24N4O4S2 methanol) calcd C 53.64%, H 5.73%, N 11.37%;
(R)-1-(tert-Butoxycarbonyl)-3-methyl-4-phenylpiperazine
(28c). 28c was prepared by coupling of 27b with bromobenzene
following the procedures described for 28a. Pale yellow oil (73% yield);
1H NMR (400 MHz, CDCl3) δ 0.99 (d, J = 6.3 Hz, 3H), 1.49 (s, 9H),
3.02ꢀ3.29 (m, 3H), 3.38 (dd, J = 13.0, 3.6 Hz, 1H), 3.73 (ddd, J = 13.0,
3.6, 1.5 Hz, 1H), 3.77ꢀ3.85 (m, 1H), 3.85ꢀ4.16 (m, 1H), 6.84ꢀ6.94
(m, 3H), 7.22ꢀ7.30 (m, 2H).
3
found C 53.40%, H 5.55%, 11.10%.
(1S,2R,3R)-1-[(R)-4-(5-Difluoromethylisoxazol-3-yl)-3-methy-
lpiperazine-1-sulfonylamino]-2-methyl-3-phenylcyclopro-
panecarboxylic Acid (10d). 10d was prepared by coupling of 26
with 33e (vide infra) following the procedures described for 9a. The
crude product was purified by trituration with methanol/H2O to yield
10d as a pale yellow solid (68% yield): mp 99 °C; [R]20D þ49.51° (c 1.0,
methanol); 1H NMR (400 MHz, CDCl3) δ 1.21 (d, J = 6.6 Hz, 3H), 1.35
(d, J = 6.8 Hz, 3H), 2.30 (dq, J = 10.6, 6.8 Hz, 1H), 2.90 (td, J = 11.9, 3.5
Hz, 1H), 3.07 (d, J = 10.4 Hz, 1H), 3.12 (dd, J = 11.9, 3.5 Hz, 1H), 3.28
(td, J = 12.4, 3.4 Hz, 1H), 3.49 (d, J = 12.6 Hz, 1H), 3.58 (d, J = 11.9 Hz,
1H), 3.70 (d, J = 11.9 Hz, 1H), 3.89ꢀ3.97 (m, 1H), 5.76 (br s, 1H), 6.20
(s, 1H), 6.59 (t, J = 53.8 Hz, 1H), 7.18ꢀ7.31 (m, 5H). Anal.
(R)-1-(tert-Butoxycarbonyl)-4-(4-cyclopropylphenyl)-3-
methylpiperazine (28d). To a solution of 28c (900 mg, 3.25 mmol)
in CHCl3 (45 mL) was added tetrabutylammonium tribromide (1.57 g,
3.25 mmol) at 0 °C. After being stirred for 0.5 h at room temperature,
the reaction mixture was diluted with a saturated solution of NaHCO3,
extracted with CHCl3, and dried over MgSO4. The organic layer
was concentrated in vacuo, and the crude product was purified by
flash chromatography (n-hexane/EtOAc 10:1) to afford (R)-1-(4-
bromophenyl)-4-(tert-butoxycarbonyl)-2-methylpiperazine as a yellow
oil (790 mg, 68% yield). To the solution of this product in toluene/H2O
(10.5 mL, 20:1) were added cyclopropylboronic acid (229 mg, 2.66
mmol), K3PO4 (1.65 g, 7.77 mmol), Pd(OAc)2 (25 mg, 0.111 mmol),
and tricyclohexylphosphine (62 mg, 0.222 mmol). After heating at
110 °C for 4 h, the reaction mixture was diluted with H2O and then
extracted with EtOAc. The organic layer was dried over MgSO4 and
concentrated under reduced pressure, and the residue was purified by
flash chromatography (n-hexane/EtOAc 10:1) to give 28d as a yellow oil
(647 mg, 92% yield). 1H NMR (400 MHz,, CDCl3) δ 0.59ꢀ0.64
(C20H24F2N4O5S 1.2H2O) calcd C 48.81%, H 5.41%, N 11.39%; found
3
C 48.54%, H 5.10%, N 11.17%.
(1S,2R,3R)-1-{(R)-4-[5-(1,1-Difluoroethyl)isoxazol-3-yl]-3-
methylpiperazine-1-sulfonylamino}-2-methyl-3-phenylcy-
clopropanecarboxylic Acid (10e). 10e was prepared by coupling
of 26 with 33f (vide infra) following the procedures described for 9a.
The crude product was purified by trituration with methanol/H2O to
yield 10e as a pale yellow solid (54% yield): mp 85ꢀ90 °C; [R]20
D
þ47.73° (c 0.22, methanol); 1H NMR (400 MHz, methanol-d4) δ 1.11
(d, J = 6.6 Hz, 3H), 1.28 (d, J = 6.8 Hz, 3H), 1.86 (t, J = 18.6 Hz, 3H),
2.15 (dq, J = 10.5, 6.7 Hz, 1H), 2.77 (td, J = 11.9, 3.5 Hz, 1H), 2.88
2854
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Journal of Medicinal Chemistry
ARTICLE
(m, 2H), 0.86ꢀ0.91 (m, 2H), 0.95 (d, J = 6.3 Hz, 3H), 1.48 (s, 9H),
1.79ꢀ1.87 (m, 1H), 2.98ꢀ3.10 (m, 2H), 3.19ꢀ3.37 (m, 1H),
3.37ꢀ3.48 (m, 1H), 3.54ꢀ3.70 (m, 2H), 3.70ꢀ3.99 (m, 1H), 6.83 (d,
J = 8.7 Hz, 2H), 6.99 (d, J = 8.7 Hz, 2H).
crude product was purified by flash chromatography (n-hexane/EtOAc
4:1) to give 32c as a pale yellow oil (58 mg, 73% yield). 1H NMR (400
MHz, CDCl3) δ 1.17 (d, J = 6.6 Hz, 3H), 1.48 (s, 9H), 2.87ꢀ3.27
(m, 3H), 3.33ꢀ3.47 (m, 1H), 3.76ꢀ4.26 (m, 3H), 6.19 (s, 1H), 6.60 (t,
J = 53.8 Hz, 1H).
3-Bromo-5-methoxymethylisoxazole (31a). To a mixture of
29a (1 mL, 11.8 mmol) and 1,1-dibromoformaldoxime (2.00 g, 9.86
mmol) in CH2Cl2 (20 mL) was added KHCO3 (2.96 g, 29.6 mmol) at
0 °C. After being stirred at 40 °C for 4 h, the reaction mixture was diluted
with H2O and extracted with CHCl3. The organic layer was dried over
MgSO4 and concentrated under reduced pressure. The thus obtained
residue was purified by flash chromatography (n-hexane/EtOAc 20:1)
to give 31a as a yellow oil (1.59 g, 84% yield based on 1,1-
dibromoformaldoxime). 1H NMR (400 MHz, CDCl3) δ 3.45 (s, 3H),
4.55 (d, J = 0.7 Hz, 2H), 6.35 (t, J = 0.7 Hz, 1H).
5-Benzoyloxymethyl-3-bromoisoxazol (31b). 31b was pre-
pared from 29b following the procedures described for 31a. Yellow oil
(83% yield based on 1,1-dibromoformaldoxime); 1H NMR (400 MHz,
CDCl3) δ 5.43 (s, 2H), 6.48 (s, 1H), 7.47 (t, J = 7.4 Hz, 2H), 7.61 (t,
J = 7.4 Hz, 1H), 8.06 (d, J = 7.4 Hz, 2H).
(R)-1-(tert-Butoxycarbonyl)-4-[5-(1,1-difluoroethyl)isoxazol-
3-yl]-3-methylpiperazine (32d). 32d was prepared from 31c
following the procedures described for 32a. Pale yellow oil (4% yield);
1H NMR (400 MHz, CDCl3) δ 1.17 (d, J = 6.8 Hz, 3H), 1.47 (s, 9H),
1.97 (t, J = 18.5 Hz, 3H), 2.84ꢀ3.28 (m, 3H), 3.32ꢀ3.45 (m, 1H),
3.74ꢀ4.27 (m, 3H), 6.11 (s, 1H).
2-(tert-Butyldiphenylsilanyloxymethyl)-1-(4-chlorophenyl)
piperazine (33a). 28a (152 mg, 0.269 mmol) was treated with 4 M
HCl in 1,4-dioxane (3 mL) at room temperature for 12 h. After removal
of the solvent in vacuo, the mixture was diluted with EtOAc, washed with
saturated solution of NaHCO3, dried over MgSO4, and concentrated
under reduced pressure. The crude product was purified by flash
chromatography (CHCl3/methanol 10:1) to give 33a as a yellow oil
1
(70 mg, 56% yield). H NMR (400 MHz, DMSO-d6) δ 0.93 (s, 9H),
2.59ꢀ2.69 (m, 1H), 2.73ꢀ2.84 (m, 2H), 2.92 (d, J = 11.6 Hz, 1H), 3.16
(d, J = 10.7 Hz, 1H), 3.24 (d, J = 11.6 Hz, 1H), 3.47 (dd, J = 9.5, 4.9 Hz,
1H), 3.77ꢀ3.85 (m, 1H), 4.00 (t, J = 9.5 Hz, 1H), 6.69 (d, J = 9.0 Hz,
2H), 7.06 (d, J = 9.0 Hz, 2H), 7.36ꢀ7.50 (m, 6H), 7.52ꢀ7.61 (m, 4H).
5-((R)-2-Methylpiperazin-1-yl)thiophene-2-carbonitrile
(33b). 33b was prepared from 28b following the procedures described
for 33a. Pale yellow oil (99% yield); 1H NMR (400 MHz, DMSO-d6) δ
1.16 (d, J = 6.6 Hz, 3H), 2.60ꢀ2.70 (m, 1H), 2.74 (d, J = 12.5 Hz, 1H),
2.84 (dd, J = 12.5, 3.6 Hz, 1H), 2.92 (d, J = 11.9 Hz, 1H), 3.04 (td,
J = 11.9, 3.6 Hz, 1H), 3.13ꢀ3.21 (m, 1H), 3.65ꢀ3.74 (m, 1H), 6.13 (d,
J = 4.4 Hz, 1H), 7.58 (d, J = 4.4 Hz, 1H).
(R)-1-(4-Cyclopropylphenyl)-2-methylpiperazine (33c).
33c was prepared from 28d following the procedures described for
33a. Pale yellow oil (90% yield); 1H NMR (400 MHz, CDCl3) δ
0.55ꢀ0.68 (m, 2H), 0.82ꢀ0.93 (m, 2H), 0.98 (d, J = 6.5 Hz, 3H),
1.78ꢀ1.90 (m, 1H), 2.72ꢀ2.86 (m, 1H), 2.89ꢀ3.18 (m, 5H),
3.49ꢀ3.63 (m, 1H), 6.86 (d, J = 6.5 Hz, 2H), 6.99 (d, J = 6.6 Hz, 2H).
(R)-1-(5-Methoxymethylisoxazol-3-yl)-2-methylpiperazine
(33d). 33d was prepared from 32a following the procedures described
for 33a. Pale yellow oil (89% yield); 1H NMR (400 MHz, CDCl3) δ 1.24
(d, J = 6.8 Hz, 3H), 2.79ꢀ2.92 (m, 2H), 2.98ꢀ3.20 (m, 3H), 3.31ꢀ3.39
(m, 1H), 3.43 (s, 3H), 3.68ꢀ3.79 (m, 1H), 4.42 (s, 2H), 5.87 (s, 1H).
(R)-1-(5-Difluoromethylisoxazol-3-yl)-2-methylpiperazine
(33e). 33e was prepared from 32c following the procedures described
for 33a. Pale yellow oil (88% yield); 1H NMR (400 MHz, CDCl3) δ 1.26
(d, J = 6.6 Hz, 3H), 2.82ꢀ2.92 (m, 2H), 2.98ꢀ3.12 (m, 2H), 3.13ꢀ3.23
(m, 1H), 3.31ꢀ3.40 (m, 1H), 3.70ꢀ3.79 (m, 1H), 6.18 (s, 1H), 6.60 (t,
J = 53.8 Hz, 1H).
3-Bromo-5-(1,1-difluoroethyl)isoxazole (31c). To a solution
of 30 (500 mg, 2.63 mmol) in CH2Cl2 (5 mL) was added bis(2-
methoxyethyl)aminosulfur trifluoride (2.43 mL, 13.2 mmol) at 0 °C.
After being stirred at 45 °C for 4 h, the reaction mixture was poured into
1 M NaOH at 0 °C and extracted with CHCl3. The organic layer was
dried over MgSO4 and concentrated under reduced pressure. The thus
obtained residue was purified by flash chromatography (n-hexane) to
give 31c as a pale yellow oil (211 mg, 38% yield). 1H NMR (400 MHz,
CDCl3) δ 2.02 (td, J = 18.5, 1.1 Hz, 3H), 6.58 (t, J = 1.1 Hz, 1H).
(R)-1-(tert-Butoxycarbonyl)-4-(5-methoxymethylisoxa-
zol-3-yl)-3-methylpiperazine (32a). A mixture of 31a (1.45 g, 7.55
mmol) and MeOTf (0.897 mL, 7.93 mmol) was heated at 80 °C for 1 h.
The resulting methylisoxazolium salt was dissolved in methanol (25 mL)
and treated with 27b (3.18 g, 15.9 mmol) at room temperature for 1 h.
After concentration, the residue was treated with PPh3 (2.97 g, 11.3
mmol) in DMF (20 mL) at 130 °C for 12 h. The reaction mixture was
poured into a saturated aqueous solution of NaHCO3 at 0 °C and
extracted with EtOAc. The organic layer was dried over MgSO4 and
concentrated. The thus obtained residue was purified by flash chroma-
tography (n-hexane/EtOAc 9:1) to give 32a as a pale yellow oil (507 mg,
22% yield). 1H NMR (400 MHz, CDCl3) δ 1.15 (d, J = 6.6 Hz, 3H), 1.48
(s, 9H), 2.91ꢀ3.23 (m, 3H), 3.34ꢀ3.45 (m, 1H), 3.43 (s, 3H),
3.76ꢀ4.24 (m, 3H), 4.42 (s, 2H), 5.88 (s, 1H).
(R)-1-(tert-Butoxycarbonyl)-4-(5-benzoyloxymethylisoxa-
zol-3-yl)-3-methylpiperazine (32b). 32b was prepared from 31b
following the procedures described for 32a. Pale yellow oil (26% yield);
1H NMR (400 MHz, CDCl3) δ 1.16 (d, J = 6.6 Hz, 3H), 1.47 (s, 9H),
2.85ꢀ3.25 (m, 3H), 3.33ꢀ3.45 (m, 1H), 3.78ꢀ4.23 (m, 3H), 5.31 (s,
2H), 5.99 (s, 1H), 7.45 (t, J = 7.4 Hz, 2H), 7.59 (t, J = 7.4 Hz, 1H), 8.06
(d, J = 7.4 Hz, 2H).
(R)-1-[5-(1,1-Difluoroethyl)isoxazol-3-yl]-2-methylpipera-
zine (33f). 33f was prepared from 32d following the procedures
1
described for 33a. Pale yellow oil (74% yield); H NMR (400 MHz,
(R)-1-(tert-Butoxycarbonyl)-4-(5-difluoromethylisoxazol-
3-yl)-3-methylpiperazine (32c). To a solution of 32b (100 mg,
0.249 mmol) in ethanol (1 mL) was added 1 M NaOH (0.55 mL), and
the mixture was heated at 80 °C for 1 h. After neutralization with 1 M
HCl, the mixture was extracted with EtOAc and dried over MgSO4. The
organic layer was concentrated under reduced pressure, and the
resultant alcohol was oxidized by DessꢀMartin periodinane (116 mg,
0.274 mmol) in CH2Cl2 (1.5 mL) at room temperature for 1 h. The
mixture was diluted with saturated NaHCO3 and extracted with EtOAc.
The organic layer was dried over MgSO4 and concentrated to give the
corresponding aldehyde. The product was dissolved in CH2Cl2 (1 mL)
and treated with bis(2-methoxyethyl)aminosulfur trifluoride (0.087 mL,
0.479 mmol) at room temperature for 1.5 h. The reaction mixture was
poured into saturated NaHCO3 at 0 °C and extracted with CHCl3. The
organic layer was dried over MgSO4 and evaporated. The thus obtained
DMSO-d6) δ 1.13 (d, J = 6.6 Hz, 3H), 2.00 (t, J = 19.2 Hz, 3H), 2.62 (td,
J = 12.1, 3.6 Hz, 1H), 2.70 (d, J = 12.1 Hz, 1H), 2.80ꢀ2.91 (m, 2H), 2.98
(td, J = 12.1, 3.6 Hz, 1H), 3.24ꢀ3.31 (m, 1H), 3.69ꢀ3.77 (m, 1H), 6.77
(s, 1H).
(1S,2R,3R)-1-(8-Chloro-1,2,3,4-tetrahydropyrazino[1,2-a]
indole-2-sulfonylamino)-2-methyl-3-phenylcyclopropane-
carboxylic Acid (11a). 11a was prepared by coupling of 26 with
8-chloro-1,2,3,4-tetrahydropyrazino[1,2-a]indole29a following the pro-
cedures described for 9a. The product was purified by trituration with
methanol/H2O to yield 11a as a pale yellow solid (20% yield): mp
145 °C; [R]20D þ65.14° (c 0.21, THF); 1H NMR (400 MHz, DMSO-
d6) δ 1.25 (d, J = 6.6 Hz, 3H), 2.03 (dq, J = 10.4, 6.8 Hz, 1H), 2.90 (d,
J = 10.4 Hz, 1H), 3.70 (t, J = 5.4 Hz, 2H), 4.15 (t, J = 5.5 Hz, 2H), 4.54
(s, 2H), 6.32 (s, 1H), 7.11 (dd, J = 8.6, 2.2 Hz, 1H), 7.15ꢀ7.26 (m, 5H),
2855
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Journal of Medicinal Chemistry
ARTICLE
7.41 (d, J = 8.6 Hz, 1H), 7.55 (d, J = 2.2 Hz, 1H), 8.59 (br s, 1H). Anal.
HCl 0.5H2O) calcd C 53.44%, H 5.13%, N 11.87%; found C 53.62%, H
5.34%, N 11.67%.
3
(C22H22ClN3O4S 0.5H2O) calcd C 56.35%, H 4.94%, N 8.96%; found
3
C 56.05%, H 5.04%, N 8.86%.
(1S,2R,3R)-1-(8-Fluoro-1,2,3,4-tetrahydropyrazino[1,2-a]-
benzimidazole-2-sulfonylamino)-2-methyl-3-phenylcyclo-
propanecarboxylic Acid Hydrochloride (12b). 12b was pre-
pared by coupling of 26 with 8-fluoro-1,2,3,4-tetrahydropyrazino[1,2-
a]benzimidazole29b following the procedures described for 9a. The
product was purified by trituration with EtOAc to yield 12b as a white
solid (67% yield): mp 190ꢀ193 °C; [R]20D þ73.33° (c 0.18, methanol);
1H NMR (400 MHz, DMSO-d6) δ 1.27 (d, J = 6.8 Hz, 3H), 2.02ꢀ2.11
(m, 1H), 2.95 (d, J = 10.4 Hz, 1H), 3.82ꢀ3.89 (m, 2H), 4.37 (t, J = 5.2
Hz, 2H), 4.78 (s, 2H), 7.16ꢀ7.30 (m, 5H), 7.36 (td, J = 9.4, 2.4 Hz, 1H),
7.65 (dd, J = 9.2, 2.3 Hz, 1H), 7.81 (dd, J = 8.9, 4.5 Hz, 1H), 8.90 (s, 1H).
(1S,2R,3R)-1-(8-Chloro-1,2,3,4-tetrahydropyrazino[1,2-a]
benzimidazole-2-sulfonylamino)-2-methyl-3-phenylcyclo-
propanecarboxylic Acid Hydrochloride (11b). 11b was pre-
pared by coupling of 26 with 8-chloro-1,2,3,4-tetrahydropyrazino[1,2-
a]benzimidazole29b following the procedures described for 9a. The
product was purified by trituration with EtOAc/DMSO to yield 11b as a
white solid (38% yield): mp 188 °C; [R]20 þ76.31° (c 0.13,
D
1
methanol); H NMR (400 MHz, DMSO-d6) δ 1.25 (d, J = 6.7 Hz,
3H), 2.04 (dq, J = 10.4, 6.7 Hz, 1H), 2.93 (d, J = 10.4 Hz, 1H),
3.77ꢀ3.85 (m, 2H), 4.27ꢀ4.34 (m, 2H), 4.70 (br s, 2H), 7.13ꢀ7.21 (m,
3H), 7.21ꢀ7.33 (m, 2H), 7.42 (dd, J = 8.8, 1.9 Hz, 1H), 7.71 (d, J = 8.8
Anal. (C21H21FN4O4S HCl) calcd C 52.45%, H 4.61%, N 11.65%;
3
Hz, 1H), 7.80 (d, J = 1.9 Hz, 1H), 8.83 (br s, 1H). Anal. (C21H21ClN4O4S
found C 52.21%, H 4.71%, N 11.58%.
3
HCl 0.75DMSO) calcd C 48.60%, H 4.80%, N 10.07%; found C
(1S,2R,3R)-1-(7-Fluoro-1,2,3,4-tetrahydropyrazino[1,2-a]-
benzimidazole-2-sulfonylamino)-2-methyl-3-phenylcyclo-
propanecarboxylic Acid Hydrochloride (12c). 12c was pre-
pared by coupling of 26 with 7-fluoro-1,2,3,4-tetrahydropyrazino[1,2-
a]benzimidazole29b following the procedures described for 9a. The
product was purified by trituration with EtOAc to yield 12c as a white
solid (62% yield): mp 170 °C; [R]20D þ68.89° (c 0.18, methanol); 1H
NMR (400 MHz, DMSO-d6) δ 1.27 (d, J = 6.6 Hz, 3H), 2.02ꢀ2.11 (m,
1H), 2.95 (d, J = 10.4 Hz, 1H), 3.82ꢀ3.88 (m, 2H), 4.30ꢀ4.34 (m, 2H),
4.76 (s, 2H), 7.18ꢀ7.35 (m, 6H), 7.73 (dd, J = 8.8, 2.4 Hz, 1H), 7.79 (dd,
J = 8.9, 4.5 Hz, 1H), 8.90 (s, 1H). Anal. (C21H21FN4O4S HCl H2O)
3
48.43%, H 5.02%, N 10.18%.
(1S,2R,3R)-1-(8-Chloro-1,2,3,4-tetrahydropyrido[30,40:4,5]
imidazo[1,2-a]pyridine-2-sulfonylamino)-2-methyl-3-phe-
nylcyclopropanecarboxylic Acid (11c). 11c was prepared by
coupling of 26 with 38a (vide infra) following the procedures
described for 9a. The product was purified by trituration with
methanol/H2O to yield 11c as a white solid (59% yield): mp
1
193ꢀ197 °C; [R]20 þ57.32° (c 0.41, methanol); H NMR (400
D
MHz, DMSO-d6) δ 1.26 (d, J = 6.6 Hz, 3H), 2.02 (dq, J = 10.4, 6.6 Hz,
1H), 2.88 (d, J = 10.4 Hz, 1H), 2.96 (t, J = 5.4 Hz, 2H), 3.56ꢀ3.69 (m,
2H), 4.37 (s, 2H), 7.00 (dd, J = 7.3, 2.0 Hz, 1H), 7.16ꢀ7.28 (m, 5H),
7.68 (d, J = 2.2 Hz, 1H), 8.32 (d, J = 7.3 Hz, 1H), 8.42 (s, 1H), 12.37
(br s, 1H). Anal. (C21H21ClN4O4S) calcd C 54.72%, H 4.59%, N
12.15%; found C 54.40%, H 4.62%, N 12.22%.
3
3
calcd C 50.55%, H 4.85%, N 11.23%; found C 50.69%, H 5.22%, N
10.89%.
(1S,2R,3R)-1-(8-Cyano-1,2,3,4-tetrahydropyrazino[1,2-a]-
benzimidazole-2-sulfonylamino)-2-methyl-3-phenylcyclo-
propanecarboxylic Acid Hydrochloride (12d). 12d was pre-
pared by coupling of 26 with 1,2,3,4-tetrahydropyrazino[1,2-a]-
benzimidazole-8-carbonitrile29b following the procedures described for
9a. The product was purified by trituration with EtOAc/methanol to
yield 12d as a white solid (41% yield): mp 151 °C; [R]20D þ62.22° (c
0.18, methanol); 1H NMR (300 MHz, DMSO-d6) δ 1.26 (d, J = 6.4 Hz,
3H), 2.05 (dq, J = 10.5, 6.8 Hz, 1H), 2.93 (d, J = 10.2 Hz, 1H),
3.79ꢀ3.86 (m, 2H), 4.30 (t, J = 5.3 Hz, 2H), 4.65 (s, 2H), 7.16ꢀ7.31 (m,
5H), 7.66 (dd, J = 8.5, 1.3 Hz, 1H), 7.75 (d, J = 8.3 Hz, 1H), 8.16 (d, J =
0.8 Hz, 1H), 8.78 (s, 1H). Anal. (C22H21N5O4S HCl 0.75methanol)
(1S,2R,3R)-1-(2-Chloro-5,6,7,8-tetrahydrothieno[30,20:4,5]
pyrrolo[1,2-a]pyrazine-7-sulfonylamino)-2-methyl-3-phe-
nylcyclopropanecarboxylic Acid (11d). 11d was prepared by
coupling of 26 with 46 (vide infra) following the procedures described
for 9a. The product was purified by trituration with methanol/H2O to
yield 11d as a white solid (75% yield): mp 95 °C; [R]20 þ65.88°
D
(c 0.17, THF); 1H NMR (300 MHz, DMSO-d6) δ 1.25 (d, J = 6.8 Hz,
3H), 2.02 (dq, J = 10.5, 6.8 Hz, 1H), 2.89 (d, J = 10.2 Hz, 1H), 3.63 (t, J =
5.5 Hz, 2H), 4.01 (t, J = 5.5 Hz, 2H), 4.41 (s, 2H), 6.20 (s, 1H), 7.10 (s,
1H), 7.15ꢀ7.28 (m, 6H), 8.57 (br s, 1H). Anal. (C20H20ClN3O4S2)
calcd C 51.55%, H 4.33%, N 9.02%; found C 51.50%, H 4.63%, N 8.80%.
(1S,2R,3R)-1-(6-Chloro-2,3-dihydro-1H-pyrrolo[30,40:4,5]
imidazo[1,2-a]pyridine-2-sulfonylamino)-2-methyl-3-phe-
nylcyclopropanecarboxylic Acid Hydrochloride (11e). 11e
was prepared by coupling of 26 with 43 (vide infra) following the
procedures described for 9a. The product was purified by trituration
with EtOAc/methanol to yield 11e as a white solid (22% yield): mp
176ꢀ181 °C; [R]20D þ65.33° (c 0.15, methanol); 1H NMR (400 MHz,
DMSO-d6) δ 1.28 (d, J = 6.6 Hz, 3H), 2.03ꢀ2.13 (m, 1H), 2.89 (d,
J = 10.1 Hz, 1H), 4.49ꢀ4.63 (m, 2H), 4.67ꢀ4.79 (m, 2H), 7.16ꢀ7.23
(m, 4H), 7.23ꢀ7.29 (m, 2H), 7.85 (d, J = 1.5 Hz, 1H), 8.55 (s, 1H), 8.61
(d, J = 7.3 Hz, 1H). Anal. (C20H19ClN4O4S HCl 1.25methanol) calcd
3
3
calcd C 53.37%, H 4.92%, N 13.68%; found C 53.34%, H 4.63%, N
13.53%.
(1S,2R,3R)-2-Methyl-1-(8-methyl-1,2,3,4-tetrahydro-
pyrazino[1,2-a]benzimidazole-2-sulfonylamino)-3-phenyl-
cyclopropanecarboxylic Acid (12e). 12e was prepared by cou-
pling of 26 with 8-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]benzi-
midazole29b following the procedures described for 9a. The product
was purified by trituration with DMSO/H2O to yield 12e as a white solid
(63% yield): mp 185ꢀ189 °C; [R]20D þ55.26° (c 0.19, methanol); 1H
NMR (400 MHz, DMSO-d6) δ 1.28 (d, J = 6.5 Hz, 3H), 2.02ꢀ2.12 (m,
1H), 2.49 (s, 3H), 2.95 (d, J = 10.4 Hz, 1H), 3.86 (t, J = 5.3 Hz, 2H),
4.34ꢀ4.39 (m, 2H), 4.80 (s, 2H), 7.16ꢀ7.37 (m, 6H), 7.61 (s, 1H), 7.70
3
3
C 48.76%, H 4.81%, N 10.70%; found C 48.79%, H 4.77%, N 10.45%.
(1S,2R,3R)-2-Methyl-3-phenyl-1-(1,2,3,4-tetrahydropyrazino-
[1,2-a]benzimidazole-2-sulfonylamino)cyclopropane-
carboxylic Acid Hydrochloride (12a). 12a was prepared by
coupling of 26 with 1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole29b
following the procedure described for 9a. The product was purified by
trituration with EtOAc to yield 12a as a white solid (43% yield): mp
182ꢀ186 °C; [R]20D þ64.22° (c 0.18, methanol); 1H NMR (400 MHz,
DMSO-d6) δ 1.28 (d, J = 6.6 Hz, 3H), 2.08 (dq, J = 10.5, 6.7 Hz, 1H),
2.96 (d, J = 10.4 Hz, 1H), 3.88 (t, J = 5.5 Hz, 2H), 4.36ꢀ4.46 (m, 2H),
4.84 (s, 2H), 7.17ꢀ7.23 (m, 3H), 7.24ꢀ7.30 (m, 2H), 7.51ꢀ7.56
(d, J = 8.1 Hz, 1H), 8.94 (s, 1H). Anal. (C22H24N4O4S 1.25DMSO)
3
calcd C 54.67%, H 5.90%, N 10.41%; found C 54.23%, H 6.03%, N
10.34%.
(1S,2R,3R)-1-(8-Methoxy-1,2,3,4-tetrahydropyrazino[1,2-
a]benzimidazole-2-sulfonylamino)-2-methyl-3-phenylcy-
clopropanecarboxylic Acid Hydrochloride (12f). 12f was pre-
pared by coupling of 26 with 8-methoxy-1,2,3,4-tetrahydropyrazino[1,2-
a]benzimidazole29b following the procedures described for 9a. The
product was purified by trituration with EtOAc to yield 12f as a white
solid (79% yield): mp 170 °C; [R]20 þ66.67° (c 0.18, methanol);
D
1H NMR (400 MHz, DMSO-d6) δ 1.28 (d, J = 6.6 Hz, 3H), 2.02ꢀ2.11
(m, 2H), 7.80ꢀ7.87 (m, 2H), 8.95 (s, 1H). Anal. (C21H22N4O4S
(m, 1H), 2.95 (d, J = 9.9 Hz, 1H), 3.82ꢀ3.86 (m, 2H), 3.85 (s, 3H),
3
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ARTICLE
4.32ꢀ4.38 (m, 2H), 4.78 (s, 2H), 7.13 (d, J = 8.4 Hz, 1H), 7.17ꢀ7.22
(m, 3H), 7.24ꢀ7.31 (m, 3H), 7.68ꢀ7.73 (m, 1H), 8.91 (s, 1H). Anal.
(C22H24N4O5S HCl H2O) calcd C 51.71%, H 5.33%, N 10.96%;
methanol 9:1) to give 36a as a pale yellow oil (2.84 g, 76% yield). 1H
NMR (400 MHz, DMSO-d6) δ 3.12 (t, J = 6.2 Hz, 2H), 3.63 (dt, J = 6.2,
5.2 Hz, 2H), 4.55 (d, J = 5.6 Hz, 2H), 4.81 (t, J = 5.2 Hz, 1H), 4.97 (t, J =
5.6 Hz, 1H), 6.93 (dd, J = 7.3, 2.2 Hz, 1H), 7.60 (dd, J = 2.2, 0.7 Hz, 1H),
8.42 (dd, J = 7.3, 0.7 Hz, 1H).
2-(7-Fluoro-2-hydroxymethylimidazo[1,2-a]pyridin-3-yl)
ethanol (36b). 36b was prepared from 35b following the procedures
described for 36a. Yellow oil (76% yield); 1H NMR (400 MHz, DMSO-
d6) δ 3.11 (t, J = 6.4 Hz, 2H), 3.58ꢀ3.66 (m, 2H), 4.53 (d, J = 5.6 Hz,
2H), 4.80 (t, J = 5.6 Hz, 1H), 4.92 (t, J = 5.6 Hz, 1H), 6.86ꢀ6.97 (m,
1H), 7.22ꢀ7.33 (m, 1H), 8.39ꢀ8.48 (m, 1H).
3
3
found C 51.43%, H 5.50%, N 10.65%.
(1S,2R,3R)-1-(8-Fluoro-1,2,3,4-tetrahydropyrido[30,40:4,5]
imidazo[1,2-a]pyridine-2-sulfonylamino)-2-methyl-3-phe-
nylcyclopropanecarboxylic Acid (12g). 12g was prepared by
coupling of 26 with 38b (vide infra) following the procedures described
for 9a. The product was purified by trituration with methanol/H2O to
yield 12g as a white solid (65% yield): mp 212ꢀ214 °C; [R]20D þ58.53°
1
(c 0.095, methanol); H NMR (300 MHz, methanol-d4) δ 1.36 (d,
J = 6.8 Hz, 3H), 2.21 (dq, J = 10.5, 6.8 Hz, 1H), 3.02ꢀ3.13 (m, 3H), 3.86
(t, J = 5.8 Hz, 2H), 4.62ꢀ4.67 (m, 2H), 7.14ꢀ7.28 (m, 4H), 7.47 (td,
J = 7.5, 2.4 Hz, 1H), 7.50ꢀ7.59 (m, 1H), 7.59ꢀ7.67 (m, 1H), 7.76 (dd,
J = 8.1, 2.4 Hz, 1H), 8.70 (dd, J = 7.3, 5.1 Hz, 1H). Anal.
(C21H21FN4O4S) calcd C 56.75%, H 4.76%, N 12.61%; found C
56.41%, H 4.82%, N 12.46%.
(1S,2R,3R)-1-(7-Fluoro-1,2,3,4-tetrahydropyrido[3040:3,4]
pyrazolo[1,5-a]pyridine-2-sulfonylamino)-2-methyl-3-phe-
nylcyclopropanecarboxylic Acid (12h). 12h was prepared
by coupling of 26 with 7-fluoro-1,2,3,4-tetrahydropyrido[3040:3,4]-
pyrazolo[1,5-a]pyridine 51 following the procedures described for 9a.
The product was purified by trituration with methanol/H2O to yield
12h as a white solid (49% yield): mp 205ꢀ209 °C; [R]20D þ101.88°
(c 0.16, THF); 1H NMR (400 MHz, DMSO-d6) δ 1.25 (d, J = 6.8 Hz,
3H), 2.03 (dq, J = 10.3, 6.7 Hz, 1H), 2.84 (t, J = 5.7 Hz, 2H), 2.90 (d,
J = 10.4 Hz, 1H), 3.52 (q, J = 5.4 Hz, 2H), 4.43 (s, 2H), 7.16ꢀ7.32 (m,
6H), 7.65 (dd, J = 9.8, 5.8 Hz, 1H), 8.43 (s, 1H), 8.89 (dd, J = 5.0, 2.1 Hz,
1H), 12.34 (br s, 1H). Anal. (C21H21FN4O4S) calcd C 56.75%, H
4.76%, N 12.61%; found C 56.74%, H 4.90%, N 12.41%.
(1S,2R,3R)-1-(7-Fluoro-1,2,3,4-tetrahydro-9H-pyrido[3,4-
b]indole-2-sulfonylamino)-2-methyl-3-phenylcyclopropa-
necarboxylic Acid (12i). 12i was prepared by coupling of 26 with
7-fluoro-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole29c following the
procedure described for 9a. The product was purified by trituration
with methanol/H2O to yield 12i as a white solid (18% yield): mp
150ꢀ152 °C; [R]20D þ73.64° (c 0.22, methanol); 1H NMR (400 MHz,
DMSO-d6) δ 1.26 (d, J = 6.6 Hz, 3H), 1.98ꢀ2.08 (m, 1H), 2.72ꢀ2.78
(m, 2H), 2.89 (d, J = 10.4 Hz, 1H), 3.49 (t, J = 5.6 Hz, 2H), 4.35 (s, 2H),
6.79ꢀ6.84 (m, 1H), 7.10 (dd, J = 10.1, 2.2 Hz, 1H), 7.15ꢀ7.28 (m, 5H),
7.37 (dd, J = 8.6, 5.5 Hz, 1H), 8.38 (br s, 1H), 10.96 (s, 1H), 12.37 (br s,
Phosphoric Acid 2-(2-Azidomethyl-7-chloroimidazo[1,2-
a]pyridin-3-yl)ethyl Ester Diphenyl Ester (37a). To a mixture of
36a (500 mg, 2.21 mmol) and DBU (739 mg, 4.86 mmol) in THF
(5.0 mL) was added DPPA (1.34 g, 4.86 mmol) at 0 °C. After being
stirred at room temperature for 1 h, the mixture was diluted with EtOAc
and washed with H2O. The organic layer was dried over MgSO4 and
concentrated. The thus obtained crude product was purified by flash
chromatography (n-hexane/EtOAc 2:1) to give 37a as a yellow oil (851
mg, 80% yield). 1H NMR (400 MHz, CDCl3) δ 3.33 (t, J = 6.5 Hz, 2H),
4.39ꢀ4.47 (m, 4H), 6.71 (dd, J = 7.3, 2.0 Hz, 1H), 7.10 (d, J = 7.9 Hz,
4H), 7.15ꢀ7.42 (m, 6H), 7.54 (d, J = 2.0 Hz, 1H), 7.90 (d, J = 7.3 Hz,
1H).
Phosphoric Acid 2-(2-Azidomethyl-7-fluoroimidazo[1,2-
a]pyridin-3-yl)ethyl Ester Diphenyl Ester (37b). 37b was pre-
pared from 36b following the procedures described for 37a. Yellow oil
(70% yield); 1H NMR (400 MHz, CDCl3) δ 3.33 (t, J = 6.5 Hz, 2H),
4.36ꢀ4.50 (m, 4H), 6.59ꢀ6.66 (m, 1H), 7.07ꢀ7.22 (m, 6H),
7.24ꢀ7.37 (m, 5H), 7.92ꢀ7.99 (m, 1H).
8-Chloro-1,2,3,4-tetrahydropyrido[30,40:4,5]imidazo[1,2-a]
pyridine (38a). A mixture of 37a (850 mg, 1.76 mmol) and PPh3 (600
mg, 2.29 mmol) in THF/H2O = 10:1 (11 mL) was heated at 60 °C for 4
h. After the mixture was cooled to room temperature, Boc2O (768 mg,
3.52 mmol) and DMAP (22 mg, 0.176 mmol) were added to the
mixture, which was then stirred at room temperature for 12 h. The
mixture was diluted with EtOAc, washed with brine, and dried over
MgSO4. After concentration, the residue was purified by flash chroma-
tography (n-hexane/EtOAc 1:1) to give the corresponding tricycle (352
mg, 65% yield) as a white solid, which was successively treated with 4 M
HCl in 1,4-dioxane (4.0 mL) at room temperature for 12 h. The solvent
was removed in vacuo, and the crude product was neutralized with NaO-
t-Bu (219 mg, 2.28 mmol) in THF (4.0 mL). After filtration of the
resultant precipitates, the filtrate was concentrated to give 38a as a white
solid (234 mg, 99% yield). 1H NMR (400 MHz, DMSO-d6) δ 2.91 (br s,
2H), 3.24 (br s, 2H), 4.01 (br s, 2H), 7.00 (dd, J = 7.3, 2.0 Hz, 1H), 7.66
(d, J = 2.0 Hz, 1H), 8.34 (d, J = 7.3 Hz, 1H).
8-Fluoro-1,2,3,4-tetrahydropyrido[30,40:4,5]imidazo[1,2-a]
pyridine (38b). 38b was prepared from 37b following the procedure
described for 38a. Pale yellow solid (70% yield); 1H NMR (400 MHz,
DMSO-d6) δ 2.73 (t, J = 5.6 Hz, 2H), 3.05 (t, J = 5.6 Hz, 2H), 3.80 (br s,
2H), 6.89ꢀ6.97 (m, 1H), 7.27ꢀ7.34 (m, 1H), 8.26ꢀ8.32 (m, 1H).
7-Chloroimidazo[1,2-a]pyridine-2,3-dicarboxylic Acid Di-
ethyl Ester (39). A mixture of 34a (1.15 g, 8.98 mmol) and 2-chloro-3-
oxosuccinic acid diethyl ester (1.00 g, 4.49 mmol) in ethanol (10 mL)
was heated at 100 °C for 12 h. After concentration, the crude product
was purified by flash chromatography (n-hexane/EtOAc 20:1) to give 39
as a white solid (982 mg, 74% yield based on 2-chloro-3-oxosuccinic acid
diethyl ester). 1H NMR (400 MHz, CDCl3) δ 1.40 (t, J = 7.2 Hz, 3H),
1.44 (t, J = 7.2 Hz, 3H), 4.43 (q, J = 6.5 Hz, 2H), 4.48 (q, J = 6.5 Hz, 2H),
7.08 (dd, J = 7.5, 2.2 Hz, 1H), 7.75 (dd, J = 2.2, 0.9 Hz, 1H), 9.21 (dd,
J = 7.5, 0.9 Hz, 1H).
1H). Anal. (C22H22FN3O4S 0.25H2O) calcd C 58.98%, H 5.06%, N
3
9.38%; found C 58.76%, H 5.24%, N 9.21%.
7-Chloro-3-methoxycarbonylmethylimidazo[1,2-a]pyridine-
2-carboxylic Acid Methyl Ester (35a). A mixture of 34a (11.0 g,
85.6 mmol) and 3-bromo-2-oxopentanedioic acid dimethyl ester (30.3
g, 120 mmol) in ethanol (200 mL) was heated at 100 °C for 12 h. After
concentration, the crude product was purified by flash chromatography
(CHCl3/methanol 20:1) to give 35a as a yellow oil (11.8 g, 49% yield).
1H NMR (400 MHz, CDCl3) δ 3.73 (s, 3H), 3.99 (s, 3H), 4.45 (s, 2H),
6.92 (dd, J = 7.5, 2.1 Hz, 1H), 7.68 (dd, J = 2.1, 0.9 Hz, 1H), 7.96 (dd,
J = 7.5, 0.9 Hz, 1H).
7-Fluoro-3-methoxycarbonylmethylimidazo[1,2-a]pyridine-
2-carboxylic Acid Methyl Ester (35b). 35b was prepared from 34b
following the procedure described for 35a. Yellow oil (39% yield). 1H
NMR (400 MHz, CDCl3) δ 3.73 (s, 3H), 3.99 (s, 3H), 4.45 (s, 2H),
6.80ꢀ6.86 (m, 1H), 7.27ꢀ7.33 (m, 1H), 7.98ꢀ8.04 (m, 1H).
2-(7-Chloro-2-hydroxymethylimidazo[1,2-a]pyridin-3-yl)
ethanol (36a). To a solution of 35a (4.66 g, 16.5 mmol) in CH2Cl2
(100 mL) was added 1 M DIBAL-H in CH2Cl2 (99 mL, 99 mmol)
dropwise at 0 °C. After being stirred for 2 h, the mixture was diluted with
a saturated solution of Rochelle’s salt and extracted with CHCl3. The
organic layer was dried over MgSO4 and concentrated. The thus
obtained crude product was purified by flash chromatography (CHCl3/
7-Chloro-2-hydroxymethylimidazo[1,2-a]pyridine-3-car-
boxylic Acid Ethyl Ester (40). To a solution of 39 (980 mg, 3.30
mmol) in THF (10 mL) was added 1 M DIBAL-H in toluene (4.0 mL,
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ARTICLE
4.0 mmol) dropwise at ꢀ78 °C. After being stirred for 2 h, the mixture
was diluted with saturated solution of Rochelle’s salt and extracted with
CHCl3. The organic layer was dried over MgSO4 and concentrated. The
resultant aldehyde was treated with NaBH4 (62 mg, 1.63 mmol) in
methanol (8.2 mL) at room temperature. After being stirred for 2 h, the
reaction was neutralized with 2 M H2SO4 and extracted with CHCl3.
The organic layer was dried over MgSO4 and concentrated. The thus
obtained crude product was purified by trituration with n-hexane/
(35 mg, 0.364 mmol). After filtration of the resultant precipitate, the
filtrate was concentrated to give 43 as a white solid (32 mg, 90% yield).
1H NMR (400 MHz, CDCl3) δ 4.21 (t, J = 2.6 Hz, 2H), 4.32 (t, J = 2.6
Hz, 2H), 6.81 (dd, J = 7.2, 2.1 Hz, 1H), 7.59 (dd, J = 2.1, 0.7 Hz, 1H),
7.77 (dd, J = 7.2, 0.7 Hz, 1H).
2-Chloro-5,6,7,8-tetrahydrothieno[30,20:4,5]pyrrolo[1,2-
a]pyrazine-5-one (45). To a solution of 44 (800 mg, 3.48 mmol) in
DMF (8.0 mL) was added 60% NaH (153 mg, 3.83 mmol) at 0 °C. After
the mixture was stirred at the same temperature for 15 min, 3-tert-
butoxycarbonyl-2,2-dioxo[1,2,3]oxathiazolidine31 (894 mg, 4.00 mmol)
was added to the mixture, which was then stirred at room temperature
for 12 h. The mixture was diluted with EtOAc, washed with saturated
solution of NaHCO3, and dried over MgSO4. After concentration, the
residue was diluted with CHCl3 (14 mL) and treated with TFA (4.0 mL)
at room temperature for 2 h. The mixture was concentrated, and the
residue was again diluted with THF/methanol (1:1, 54 mL) and treated
with K2CO3 (3.00 g, 21.7 mmol) at room temperature for 12 h. The
mixture was diluted with EtOAc, washed with 5% solution of KHSO4,
and dried over MgSO4. After concentration, the crude product was
purified by trituration with n-hexane to give 45 as a white solid (630 mg,
80% yield). 1H NMR (300 MHz, DMSO-d6) δ 3.52ꢀ3.61 (m, 2H), 4.17
(t, J = 5.8 Hz, 2H), 6.85 (s, 1H), 7.20 (s, 1H), 7.90 (br s, 1H).
2-Chloro-5,6,7,8-tetrahydrothieno[30,20:4,5]pyrrolo[1,2-a]
pyrazine (46). To a solution of 45 (630 mg, 2.78 mmol) in THF
1
EtOAc to give 40 as a white solid (786 mg, 94% yield). H NMR
(300 MHz, CDCl3) δ 1.45 (t, J = 7.2 Hz, 3H), 4.45 (q, J = 7.2 Hz, 2H),
5.05 (s, 2H), 7.03 (dd, J = 7.5, 1.9 Hz, 1H), 7.69 (d, J = 1.9 Hz, 1H), 9.22
(d, J = 7.5 Hz, 1H).
[7-Chloro-2-(tetrahydropyran-2-yloxymethyl)imidazo[1,2-a]
pyridin-3-yl]methanol (41). A mixture of 40 (786 mg, 3.09 mmol),
dihydropyrane (1.41 mL, 15.5 mmol), and In(OTf)3 (84 mg, 0.15
mmol) in CHCl3 (8.0 mL) was heated at 80 °C for 12 h. After the solvent
was removed in vacuo, the residue was purified by flash chromatography
(n-hexane/EtOAc 3:1) to give the corresponding THP-protected ether
as a pale yellow solid (868 mg, 83% yield), which was further dissolved in
Et2O (9.0 mL) and transferred to a suspension of LiAlH4 (97 mg, 2.56
mmol) in Et2O (4.0 mL) dropwise at 0 °C. After the mixture was stirred
for 1 h, the reaction was quenched by an addition of 15% NaOH
(0.10 mL) and H2O (0.40 mL), and the resultant precipitate was
removed by filtration. The filtrate was concentrated, and the residue
was purified by flash chromatography (CHCl3/methanol 20:1) to give
41 as a white solid (632 mg, 83% yield). 1H NMR (400 MHz, DMSO-d6)
δ 1.40ꢀ1.76 (m, 6H), 3.44ꢀ3.54 (m, 1H), 3.78ꢀ3.87 (m, 1H), 4.56 (d,
J = 11.9 Hz, 1H), 4.71ꢀ4.74 (m, 1H), 4.74 (d, J = 11.9 Hz, 1H), 4.84 (d,
J = 5.3 Hz, 2H), 5.21 (t, J = 5.3 Hz, 1H), 7.04 (dd, J = 7.3, 2.2 Hz, 1H),
7.70 (dd, J = 2.2, 0.6 Hz, 1H), 8.41 (dd, J = 7.3, 0.6 Hz, 1H).
3-tert-Butoxycarbonylaminomethyl-7-chloro-2-(tetrahydro-
pyran-2-yloxymethyl)imidazo[1,2-a]pyridine (42). To a solution
of 41 (632 mg, 2.12 mmol) in THF (6.3 mL) were added DPPA (762 mg,
2.77 mmol) and DBU (422 mg, 2.77 mmol) at 0 °C. After the mixture was
stirred at room temperature for 12 h, PPh3 (838 mg, 3.20 mmol) and H2O
(1.1 mL) were added to the mixture, which was then heated at 60 °C for4 h.
Boc2O (929 mg, 4.26 mmol) and DMAP (13 mg, 0.106 mmol) were added
to this solution, and the mixture was stirred at room temperature for 12 h.
The mixture was diluted with H2O and extracted with CHCl3. The organic
layer was dried over MgSO4 and concentrated. The thus obtained crude
product was purified by flash chromatography (n-hexane/EtOAc 1:1) to
give 42 as a white solid (498 mg, 59% yield). 1H NMR (400 MHz, CDCl3)
δ 1.44 (s, 9H), 1.51ꢀ1.89 (m, 6H), 3.52ꢀ3.61 (m, 1H), 3.85ꢀ3.94 (m,
1H), 4.65ꢀ4.73 (m, 3H), 4.73 (d, J = 12.4 Hz, 1H), 4.94 (d, J = 12.4 Hz,
1H), 5.17 (br s, 1H), 6.81 (dd, J = 7.3, 2.0 Hz, 1H), 7.55 (d, J = 2.0 Hz, 1H),
8.35 (d, J = 7.3 Hz, 1H).
6-Chloro-2,3-dihydro-1H-pyrrolo[30,40:4,5]imidazo[1,2-a]
pyridine (43). A solution of 42 (498 mg, 1.26 mmol) in AcOH/H2O
(1:1, 5.0 mL) was heated at 100 °C for 1 h. The mixture was neutralized
with 4 M NaOH and triturated by addition of n-hexane/EtOAc to afford
the corresponding alcohol as a white solid (282 mg, 72% yield). To a
solution of this compound in CH2Cl2 (2.8 mL), CBr4 (360 mg, 1.09
mmol) and PPh3 (286 mg, 1.09 mmol) were added. The mixture was
stirred at room temperature for 1 h. After concentration, the residue was
purified by flash chromatography (CHCl3/EtOAc 2:1) to give the
corresponding bromide (275 mg, 81% yield), which was further treated
with 60% NaH (44 mg, 1.10 mmol) in DMSO (34 mL) at 90 °C for 10
min. The mixture was diluted with iceꢀwater and extracted with EtOAc.
The organic layer was dried over MgSO4 and concentrated. The thus
obtained residue was purified by preparative TLC (CHCl3/EtOAc 1:1)
to give the cyclized product as a white solid (54 mg, 25% yield). This
product was treated with 4 M HCl in 1,4-dioxane (1.0 mL) at room
temperature for 12 h. The solvent was removed in vacuo, and the crude
product was diluted by THF (3.0 mL) and neutralized with NaO-t-Bu
(6.3 mL) was added 1 M BH3 THF (22.2 mL, 22.2 mmol). After being
3
stirred at 60 °C for 3 h, the mixture was poured into a saturated solution
of NaHCO3 at 0 °C and extracted with EtOAc. The organic layer was
washed with brine, dried over MgSO4, and concentrated. The thus
obtained crude product was purified by flash chromatography (CHCl3/
methanol 10:1) to give 46 as a white solid (37 mg, 6.3% yield). 1H NMR
(400 MHz, DMSO-d6) δ 3.09 (t, J = 5.7 Hz, 2H), 3.80 (t, J = 5.7 Hz, 2H),
3.90 (d, J = 0.7 Hz, 2H), 5.99 (t, J = 0.7 Hz, 1H), 7.05 (s, 1H).
6-Fluoro-2-(tetrahydropyran-2-yloxymethyl)pyrazolo[1,5-a]
pyridine-3-carbaldehyde (48). To a solution of 4733 (50 g, 160 mmol)
in DMF (500 mL) were added 4-(tetrahydropyran-2-yloxy)but-2-ynal34
(40.4 g, 240 mmol) and K2CO3 (28.8 g, 208 mmol) at 0 °C. After being
stirred at room temperature for 12 h, the mixture was poured into iceꢀwater
and extracted with EtOAc. The organic layer was dried over MgSO4 and
concentrated. The thus obtained residue was purified by flash chromatog-
raphy (n-hexane/EtOAc 5:1) to give 48 as a yellow solid (5.59 g, 13% yield).
1H NMR (400 MHz, CDCl3) δ 1.50ꢀ1.90 (m, 6H), 3.56ꢀ3.64 (m, 1H),
3.87ꢀ3.95 (m, 1H), 4.83 (t, J = 3.3 Hz, 1H), 4.91 (d, J = 12.6 Hz, 1H), 5.18
(d,J= 12.6 Hz, 1H), 7.40ꢀ7.46 (m, 1H), 8.32 (ddd, J=9.7, 5.6, 0.7Hz, 1H),
8.46 (ddd, J = 3.7, 2.3, 0.7 Hz, 1H), 10.25 (s, 1H).
2-[6-Fluoro-2-(tetrahydropyran-2-yloxymethyl)pyrazolo-
[1,5-a]pyridin-3-yl]ethylamine (49). A mixture of 48 (5.50 g, 19.8
mmol) and ammonium acetate (762 mg, 9.89 mmol) in CH3NO2
(44 mL) was heated at 100 °C for 2 h. The mixture was diluted with a
saturated aqueous solution of NaHCO3 and extracted with EtOAc. The
organic layer was dried over MgSO4 and concentrated. The thus
obtained residue was purified by flash chromatography (CHCl3/EtOAc
10:1) to give the corresponding nitroolefin as a yellow solid (4.55 g, 72%
yield). A solution of this compound in THF (140 mL) was added to a
suspension of LiAlH4 (2.69 g, 70.8 mmol) in THF (50 mL) dropwise at
0 °C. After being stirred at room temperature for 4 h, the mixture was
diluted with a saturated solution of Rochelle’s salt and extracted with
EtOAc. The organic layer was dried over MgSO4 and concentrated to
give 49 as a yellow oil (4.12 g, 99% yield). 1H NMR (400 MHz, CDCl3)
δ 1.47ꢀ1.90 (m, 6H), 2.87ꢀ3.00 (m, 4H), 3.52ꢀ3.64 (m, 1H),
3.89ꢀ4.00 (m, 1H), 4.66 (d, J = 11.7 Hz, 1H), 4.78 (t, J = 3.4 Hz,
1H), 4.96 (d, J = 11.7 Hz, 1H), 6.97ꢀ7.06 (m, 1H), 7.42ꢀ7.47 (m, 1H),
8.34 (ddd, J = 4.3, 2.2, 0.8 Hz, 1H).
3-(2-tert-Butoxycarbonylaminoethyl)-6-fluoro-2-hydro-
xymethylpyrazolo[1,5-a]pyridine (50). To a solution of 49
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Journal of Medicinal Chemistry
ARTICLE
(4.12 g, 14.0 mmol) in THF (60 mL) was added Boc2O (3.71 g, 17.0
mmol), and the mixture was stirred at room temperature for 12 h. The
mixture was diluted with a saturated solution of NaHCO3 and
extracted with EtOAc. The organic layer was dried over MgSO4 and
concentrated. The thus obtained residue was purified by flash
chromatography (n-hexane/EtOAc 3:1) to give the corresponding
Boc-protected amine (1.82 g, 33% yield). The product was further
treated with 1 M HCl (18 mL) in 1,4-dioxane (36 mL) at room
temperature for 2 h. After neutralization with 1 M NaOH, the mixture
was extracted with EtOAc. The organic layer was washed with brine,
dried over MgSO4, and concentrated. The thus obtained residue was
purified by flash chromatography (n-hexane/EtOAc 1:1) to give 50 as
a yellow oil (1.07 g, 75% yield). 1H NMR (400 MHz, CDCl3) δ 1.39
(s, 9H), 2.95 (t, J = 6.7 Hz, 2H), 3.29ꢀ3.39 (m, 2H), 4.84 (s, 2H), 4.97
(br s, 1H), 6.99ꢀ7.07 (m, 1H), 7.42 (dd, J = 9.5, 5.5 Hz, 1H), 8.30 (dd,
J = 4.3, 2.1 Hz, 1H).
temperature. After being stirred at 70 °C for 2 h, the mixture was
concentrated under reduced pressure and the residue was triturated in
H2O to give rac-55 as a pale yellow solid (134 g, 93% yield). 1H NMR
(300 MHz, CDCl3) δ 1.26 (d, J = 6.5 Hz, 3H), 1.35 (s, 3H), 2.10 (q, J =
6.5 Hz, 1H), 3.57 (s, 3H), 3.83 (s, 3H), 7.13ꢀ7.38 (m, 5H).
(1R*,2S*,3S*)-Methyl 1-(tert-Butoxycarbonylamino)-2,3-
dimethyl-2-phenylcyclopropanecarboxylate (rac-56). To a
solution of rac-55 (7.35 g, 28.0 mmol) in THF/methanol (1:1,
76 mL) was added 4 M NaOH (16.8 mL, 67.2 mmol) at room
temperature. After being stirred for 12 h, the mixture was diluted with
H2O and washed with diisopropyl ether. The aqueous layer was acidified
with 4 M HCl and extracted with EtOAc twice. The combined organic
layers were dried over MgSO4 and concentration in vacuo. To a mixture
of the thus obtained residue and Et3N (5.4 mL, 38.7 mmol) in t-BuOH
(77 mL) was added a solution of diphenylphosphorylazide (6.8 mL, 31.6
mmol) in toluene (23 mL) dropwise at 100 °C. After being stirred at the
same temperature for 12 h, the reaction mixture was concentrated and
purified by flash chromatography (n-hexane/EtOAc 4:1) to afford rac-
56 as a yellow oil (5.21 g, 58% yield). 1H NMR (300 MHz, CDCl3) δ
1.37 (d, J = 6.0 Hz, 3H), 1.50 (s, 9H), 1.59ꢀ1.68 (m, 1H), 2.35 (s, 3H),
3.49 (s, 3H), 5.25 (br s, 1H), 7.08ꢀ7.33 (m, 5H).
7-Fluoro-1,2,3,4-tetrahydropyrido[3040:3,4]pyrazolo[1,5-
a]pyridine (51). A mixture of 50 (1.07 g, 3.46 mmol), CBr4 (1.72 g,
5.19 mmol), and PPh3 (1.18 g, 4.50 mmol) in CH2Cl2 (20 mL) was
stirred at room temperature for 0.5 h. The mixture was diluted with a
saturated solution of NaHCO3 and extracted with CHCl3. The organic
layer was dried over MgSO4 and concentrated. The thus obtained
residue was purified by flash chromatography (n-hexane/EtOAc 4:1) to
give the corresponding bromide (1.12 g, 87% yield). To a solution of this
product in DMF (22 mL) was added 60% NaH (177 mg, 4.43 mmol).
After the mixture was stirred at room temperature for 12 h, the reaction
was quenched by an addition of H2O and extracted with EtOAc. The
organic layer was dried over MgSO4 and concentrated. The thus
obtained residue was purified by flash chromatography (n-hexane/
EtOAc 6:1) to give the cyclized product as a white solid (673 mg,
78% yield). To a solution of this compound in 1,4-dioxane (14 mL) was
added 4 M HCl in 1,4-dioxane (14 mL). After being stirred at room
temperature for 12 h, the mixture was concentrated in vacuo, neutralized
with saturated aqueous solution of NaHCO3, and extracted with EtOAc.
The organic layer was dried over MgSO4 and concentrated to give 51 as
a yellow solid (437 mg, 99% yield). 1H NMR (400 MHz, CDCl3) δ 2.76
(t, J = 5.8 Hz, 2H), 3.18 (t, J = 5.8 Hz, 2H), 4.14 (s, 2H), 6.97ꢀ7.04 (m,
1H), 7.32 (dd, J = 9.7, 5.5 Hz, 1H), 8.31 (ddd, J = 4.4, 2.2, 0.7 Hz, 1H).
Mixture of Dimethyl 2-((2R*,3R*)-3-(Methylthio)-3-phe-
nylbutan-2-yl)malonate (rac-53) and Dimethyl 2-((2R*,3R*)-
3-(Methylthio)-2-phenylbutan-2-yl)malonate (rac-54). To a
solution of dimethyl disulfide (36.4 g, 0.387 mol) in toluene (350 mL)
was added sulfuric chloride (31.1 mL, 0.387 mol) dropwise at ꢀ10 °C,
and the mixture was stirred at the same temperature for 5 min. A solution
of 52 (102 g, 0.773 mol) in toluene (102 mL) was successively added to
the mixture at ꢀ40 °C. After being stirred at the same temperature for 1
h, the mixture was concentrated. The thus obtained residual oil in DME
(770 mL) was added to a solution of sodiodimethyl malonate prepared
from dimethyl malonate (337 g, 2.55 mol) and NaO-t-Bu (223 g, 2.32
mol) in DME (1.55 L). After the mixture was stirred at room
temperature for 12 h, the reaction was neutralized with 4 M HCl and
extracted with EtOAc. The organic layer was washed with brine, dried
over MgSO4, and concentrated to give a mixture of rac-53 and rac-54 as a
yellow oil (214 g, 89% yield). 1H NMR (300 MHz, CDCl3) δ 1.08ꢀ1.14
(m, 3H), 1.64ꢀ1.74 (m, 3H), 2.00ꢀ2.08 (m, 3H), 3.39ꢀ3.68 (m, 7H),
3.72ꢀ3.77 (m, 1H), 7.11ꢀ7.38 (m, 3H), 7.40ꢀ7.57 (m, 2H).
Quinidine Salt of (1S,2R,3R)-1-(tert-Butoxycarbonylamino)-
2,3-dimethyl-2-phenylcyclopropanecarboxylic Acid (57). A
mixture of rac-56 (5.21 g, 16.3 mmol) and 4 M NaOH (16.3 mL, 65.2
mmol) in THF/methanol (1:1, 66 mL) was stirred at 90 °C for 12 h. The
reaction mixture was acidified with a saturated solution of KHSO4 and
extracted with EtOAc. The organic layer was dried over MgSO4 and
concentrated. The residue was treated with quinidine (5.29 g, 16.3
mmol) in acetone (63 mL) and the resultant precipitates were collected
by filtration to give 57 as fine crystals (3.73 g, 36% yield). Their quality
was good enough, and they were directly used for a single crystal X-ray
diffraction analysis: mp 236ꢀ238 °C; 1H NMR (400 MHz, DMSO-d6)
δ 1.08 (d, J = 5.1 Hz, 1H), 1.33ꢀ1.53 (m, 17H), 1.69 (s, 1H), 1.90 (dd, J
= 13.1, 8.3 Hz, 1H), 2.00 (d, J = 4.2 Hz, 1H), 2.19 (q, J = 8.3 Hz, 1H),
2.44ꢀ2.74 (m, 3H), 2.95ꢀ3.07 (m, 2H), 3.90 (s, 3H), 5.02ꢀ5.12 (m,
2H), 5.28 (d, J = 6.8 Hz, 1H), 5.62 (br s, 1H), 6.04ꢀ6.14 (m, 1H),
7.10ꢀ7.16 (m, 1H), 7.20ꢀ7.30 (m, 4H), 7.38 (dd, J = 9.0, 2.9 Hz, 1H),
7.45 (d, J = 2.9 Hz, 1H), 7.49 (d, J = 4.4 Hz, 1H), 7.54 (br s, 1H), 7.92
(d, J = 9.0 Hz, 1H), 8.68 (d, J = 4.4 Hz, 1H). Anal. (C37H47N3O6
0.25H2O) calcd C 70.06%, H 7.55%, N 6.62%; found 70.16%, H 7.37%,
N 6.79%.
3
(1S,2R,3R)-tert-Butyl 2,3-Dimethyl-1-(2-oxooxazolidine-3-
sulfonamido)-2-phenylcyclopropanecarboxylate (58). To a
suspension of 57 (3.73 g, 5.92 mmol) in EtOAc (50 mL) was added 10%
KHSO4 until the mixture turned into a clear solution. The organic layer
was separated, dried over MgSO4, and concentrated under reduced
pressure. To a solution of the thus obtained residue in toluene (8.9 mL)
was added N,N-dimethylformamide di-tert-butyl acetal (5.69 mL, 23.7
mmol) dropwise at 100 °C and stirred for 2 h. The mixture was diluted
with 5% aqueous NaHCO3 solution and extracted with n-hexane/
EtOAc (2:1). The organic layer was washed with brine, dried over
MgSO4, and concentrated to give the corresponding t-Bu ester. To a
solution of this ester in methanol (11 mL) was added p-TsOH H2O
3
(2.25 g, 11.8 mmol), and the mixture was stirred at room temperature for
12 h. After neutralization with 4 M NaOH, the mixture was concentrated
under reduced pressure and extracted with EtOAc. The organic layer was
washed with brine, dried over MgSO4, and concentrated to afford the
corresponding amine as a yellow oil (1.30 g, 84% yield). This product
was then dissolved in acetonitrile (7.0 mL), and the resultant solution
was added to a mixture of chlorosulfonyl isocyanate (0.476 mL, 5.47
mmol), 2-chloroethanol (0.400 mL, 5.96 mmol), and N-methylmorpho-
line (2.19 mL, 19.9 mmol) in acetonitrile (7.0 mL). After being stirred at
50 °C for 2 h, the mixture was acidified with 2 M HCl and extracted with
EtOAc. The organic layer was washed with brine, dried over MgSO4, and
(2R*,3R*)-Dimethyl 2,3-Dimethyl-2-phenylcyclopropane-
1,1-dicarboxylate (rac-55). To a mixture of rac-53 and rac-54
(214 g, 0.689 mol) in 1,4-dioxane (214 mL) was added dimethyl sulfate
(78.4 mL, 0.827 mol), and the mixture was stirred at 50 °C for 12 h. After
the mixture was cooled to room temperature, the precipitates were
triturated with EtOAc to give a mixture of the corresponding sulfonium
salt (239 g, 79% yield). To a solution of this salt in methanol (1.1 L)
was added 28% NaOMe in methanol (123 mL) dropwise at room
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Journal of Medicinal Chemistry
ARTICLE
concentrated. The thus obtained crude product was purified by flash
chromatography (n-hexane/EtOAc 4:1) to give 58 as a pale yellow oil
(1.77 g, 87% yield). 1H NMR (400 MHz, CDCl3) δ 1.06 (s, 9H), 1.49
(d, J = 6.8 Hz, 3H), 1.54 (s, 3H), 2.23 (q, J = 6.8 Hz, 1H), 3.92ꢀ4.02 (m,
1H), 4.15ꢀ4.24 (m, 1H), 4.32ꢀ4.46 (m, 2H), 6.27 (br s, 1H),
7.10ꢀ7.17 (m, 2H), 7.19ꢀ7.33 (m, 3H).
trituration with methanol/H2O to yield 13e as a pale yellow solid
(71% yield): mp 174ꢀ180 °C; [R]20D þ10.1° (c 0.93, methanol); 1H
NMR (400 MHz, CDCl3) δ 1.23 (d, J = 6.6 Hz, 3H), 1.43 (d, J = 6.8
Hz, 3H), 1.51 (s, 3H), 2.26 (q, J = 6.7 Hz, 1H), 2.91 (td, J = 11.9, 3.3
Hz, 1H), 3.16 (dd, J = 11.9, 3.3 Hz, 1H), 3.25 (td, J = 12.4, 3.2 Hz, 1H),
3.48 (d, J = 12.6 Hz, 1H), 3.58 (d, J = 11.9 Hz, 1H), 3.75 (d, J = 11.9
Hz, 1H), 3.87ꢀ3.95 (m, 1H), 6.18 (br s, 1H), 6.21 (s, 1H), 6.58 (t, J =
53.8 Hz, 1H), 7.06 (d, J = 7.1 Hz, 2H), 7.16ꢀ7.27 (m, 3H). Anal.
(1S,2R,3R)-2,3-Dimethyl-1-(8-fluoro-1,2,3,4-tetrahydro-
pyrazino[1,2-a]benzimidazole-2-sulfonylamino)-2-phenyl-
cyclopropanecarboxylic Acid (13a). 13a was prepared by cou-
pling of 58 with 8-fluoro-1,2,3,4-tetrahydropyrazino[1,2-a]benzimida-
zole29b following the procedures described for 9a. The crude product
was purified by trituration with methanol/H2O to yield 13a as a white
(C21H26F2N4O5S 0.75H2O) calcd C 50.64%, H 5.57%, N 11.25%; found C
3
50.97%, H 5.46%, N 11.13%.
Binding Model. Molecular modeling and visualization were per-
formed using Insight II/Discover software (Accelrys, Inc.). Crystal
structures of aggrecanase-2 and MMP-14 were both available in the
Protein Data Bank (PDB codes 2RJQ and 1BQQ, respectively), and
their structural information was used to generate the binding models for
the inhibitors. Each compound was manually docked into aggrecanase or
MMP-14 so that the sulfonylamino portion of the compound was placed
in the S10 pocket of enzymes while the carboxylate oxygens bound the
zinc atom in a bidentate fashion.
solid (41% yield): mp 202ꢀ207 °C; [R]20 þ27.85° (c 0.53,
D
1
methanol); H NMR (400 MHz, DMSO-d6) δ 1.35 (d, J = 6.8 Hz,
3H), 1.37 (s, 3H), 1.96 (q, J = 6.8 Hz, 1H), 3.73ꢀ3.86 (m, 2H), 4.22 (t,
J = 5.3 Hz, 2H), 4.57 (d, J = 16.8 Hz, 1H), 4.62 (d, J = 16.8 Hz, 1H),
7.08ꢀ7.19 (m, 4H), 7.22ꢀ7.29 (m, 2H), 7.40 (dd, J = 9.8, 2.3 Hz, 1H),
7.53 (dd, J = 8.8, 4.6 Hz, 1H), 8.80 (s, 1H), 12.37 (br s, 1H). Anal.
(C22H23FN4O4S) calcd C 57.63%, H 5.06%, N 12.22%; found C
57.55%, H 5.14%, N 12.18%.
Biological Assays. Recombinant human enzymes of MMP-1,
MMP-3, MMP-9, MMP-13, and TACE were purchased from R&D
Systems. Recombinant human enzymes of MMP-14 and aggrecanases
(ADAMTS-4, ADAMTS-5) were purchased from Calbiochem and
ImmunoDiagnostics, respectively. MMP-1 and MMP-14 assays were
performed by incubating 10 μM fluorogenic substrate MOCAc-Lys-Pro-
Leu-Gly-Leu-A2pr(Dnp)-Ala-Arg-NH2 (Peptide Institute) with 20 ng/
mL rh-MMP-1 or rh-MMP-14 along with various concentrations of
inhibitor in the buffer (100 mM Tris-HCl, pH 7.5, 150 mM NaCl,
10 mM CaCl2, and 0.05% Brij-35). MMP-3 assay was performed by
incubating 10 μM fluorogenic substrate MOCAc-Arg-Pro-Lys-Pro-Val-
Glu-Nva-Trp-Arg-Lys(Dnp)-NH2 (Peptide Institute) with 40 ng/mL
rh-MMP-3 along with various concentrations of inhibitor in the buffer
(100 mM Tris-HCl, pH 7.5, 150 mM NaCl, 10 mM CaCl2, and 0.05%
Brij-35). MMP-9 assay was performed by incubating 10 μM fluorogenic
substrate MOCAc-Pro-Leu-Gly-Leu-A2pr(Dnp)-Ala-Arg-NH2 (Peptide
Institute) with 4 ng/mL rh-MMP-9 along with various concentrations
of inhibitor in the buffer (100 mM Tris-HCl, pH 7.5, 150 mM NaCl,
10 mM CaCl2, and 0.05% Brij-35). MMP-13 assay was performed by
incubating 5 μM fluorogenic substrate 7-MCA-Pro-CHA-Gly-NVal-
His-Ala-DPA (Enzyme Systems Products) with 40 ng/mL rh-MMP-
13 along with various concentrations of inhibitor in the buffer
(100 mM Tris-HCl, pH 7.5, 150 mM NaCl, 10 mM CaCl2, and
0.05% Brij-35). TACE assay was performed by incubating 10 μM
fluorogenic substrate MCA-Pro-Leu-Ala-Gln-Ala-Val-Dpa-Arg-Ser-
Ser-Ser-Arg-NH2 (Calbiochem) with 80 ng/mL rh-TACE along with
various concentrations of inhibitor in the buffer (100 mM Tris-HCl,
pH 7.5, 150 mM NaCl, 10 mM CaCl2, and 0.05% Brij-35). Aggreca-
nase assay was performed by incubating 120 μM fluorogenic substrate
Abz-Thr-Glu-Gly-Glu-Ala-Arg-Gly-Ser-Val-Ile-Dap(Dnp)-Lys-Lys-
NH2 (AnaSpec) with 1 μg/mL rh-aggrecanase-1 (ADAMTS-4) or rh-
aggrecanase-2 (ADAMTS-5) along with various concentrations of
inhibitor in the buffer (50 mM Tris-HCl, pH 7.5, 100 mM NaCl, and
10 mM CaCl2). Each enzyme was pretreated with inhibitor at 25 °C for
15 min, and the enzymatic reaction was initiated by an addition of the
(1S,2R,3R)-2.3-Dimethyl-1-(8-fluoro-1,2,3,4-tetrahydro-
pyrido[30,40:4,5]imidazo[1,2-a]pyridine-2-sulfonylamino)-2-
phenylcyclopropanecarboxylic Acid (13b). 13b was prepared
by coupling of 58 with 38b following the procedures described for 9a.
The crude product was purified by trituration with methanol/H2O to
yield 13b as a white solid (76% yield): mp 189ꢀ193 °C; [R]20D þ41.29°
(c 0.42, CHCl3); 1H NMR (400 MHz, DMSO-d6) δ 1.34 (d, J = 6.6 Hz,
3H), 1.35 (s, 3H), 1.92 (q, J = 6.8 Hz, 1H), 2.95 (t, J = 5.0 Hz, 2H),
3.56ꢀ3.69 (m, 2H), 4.33 (d, J = 15.2 Hz, 1H), 4.40 (d, J = 15.2 Hz, 1H),
6.99 (td, J = 7.6, 2.6 Hz, 1H), 7.09ꢀ7.20 (m, 3H), 7.24ꢀ7.30 (m, 2H),
7.38 (dd, J = 10.1, 2.4 Hz, 1H), 8.35 (t, J = 6.5 Hz, 1H), 8.46 (br s, 1H),
12.21 (br s, 1H). Anal. (C22H23FN4O4S 0.5H2O) calcd C 56.52%, H
3
5.17%, N 11.98%; found C 56.38%, H 5.31%, N 11.86%.
(1S,2R,3R)-2,3-Dimethyl-1-(7-fluoro-1,2,3,4-tetrahydro-
pyrido[30,40:3,4]pyrazolo[1,5-a]pyridine-2-sulfonylamino)-
2-phenylcyclopropanecarboxylic Acid (13c). 13c was prepared
by coupling of 58 with 51 following the procedure described for 9a. The
crude product was purified by trituration with methanol/H2O to yield
13c as a white solid (84% yield): mp 194ꢀ200 °C; [R]20D þ37.0° (c 1.1,
1
methanol); H NMR (400 MHz, DMSO-d6) δ 1.26 (s, 3H), 1.30 (d,
J = 6.6 Hz, 3H), 1.98 (q, J = 6.6 Hz, 1H), 2.75ꢀ2.83 (m, 2H), 3.33ꢀ3.46
(m, 1H), 3.69ꢀ3.78 (m, 1H), 4.49 (d, J = 15.0 Hz, 1H), 4.61 (d, J = 15.0
Hz, 1H), 7.00ꢀ7.12 (m, 3H), 7.12ꢀ7.20 (m, 2H), 7.23ꢀ7.32 (m, 1H),
7.59ꢀ7.66 (m, 1H), 8.84ꢀ8.91 (m, 1H). Anal. (C22H23FN4O4S
3
0.5H2O) calcd C 56.52%, H 5.17%, N 11.98%; found C 56.59%, H
5.13%, N 12.12%.
(1S,2R,3R)-1-[(R)-4-(5-Cyanothiophen-2-yl)-3-methylpi-
perazine-1-sulfonylamino]-2,3-dimethyl-2-phenylcyclopro-
panecarboxylic Acid (13d). 13d was prepared by coupling of 58
with 33b following the procedures described for 9a. The crude product
was purified by trituration with chloroform to yield 13d as a pale yellow
solid (93% yield): mp 128ꢀ132 °C; [R]20D þ34.6° (c 1.0, methanol);
1H NMR (400 MHz, DMSO-d6) δ 1.12 (d, J = 6.5 Hz, 3H), 1.35 (d,
J = 6.7 Hz, 3H), 1.38 (s, 3H), 1.97 (q, J = 6.8 Hz, 1H), 2.78 (td, J = 11.7,
3.1 Hz, 1H), 2.99ꢀ3.05 (m, 1H), 3.18 (td, J = 12.1, 3.6 Hz, 1H),
3.38ꢀ3.47 (m, 2H), 3.68 (d, J = 11.8 Hz, 1H), 3.95ꢀ4.02 (m, 1H), 6.20
(d, J = 4.4 Hz, 1H), 7.12ꢀ7.20 (m, 3H), 7.23ꢀ7.29 (m, 2H), 7.61 (d, J =
substrate at 37 °C. The increase in fluorescence (λex = 325 nm, λem
=
405 nm) due to cleavage of the substrate was monitored with a BMG
FLUOstar fluorescence plate reader after 150 and 60 min for aggreca-
nases and the others, respectively. IC50 of each inhibitor was calculated
with Excel software, using three points in the central linear range of
fluorescence inhibition.
4.4 Hz, 1H), 8.53 (br s, 1H), 12.41 (br s, 1H). Anal. (C22H26N4O4S2
1.25CHCl3) calcd C 51.81%, H 5.10%, N 10.40%; found C 51.62%, H
5.41%, N 10.60%.
3
In Vivo Pharmacokinetics. The pharmacokinetic profile was
investigated in SD rats following a single dose given intravenously (iv)
and orally (po). Two rats were treated with the compound. Blood
samples of each rat were collected at 0.08, 0.17, 0.25, 0.50, 1, 2, 4, 8, 24 h
(1S,2R,3R)-1-[(R)-4-(5-Difluoromethylisoxazol-3-yl)-3-methyl-
piperazine-1-sulfonylamino]-2,3-dimethyl-2-phenylcyclopropa-
necarboxylic Acid (13e). 13e was prepared by coupling of 58 with 33e
following the procedures described for 9a. The crude product was purified by
2860
dx.doi.org/10.1021/jm101609j |J. Med. Chem. 2011, 54, 2839–2863

Journal of Medicinal Chemistry
ARTICLE
following oral dosing (10 mg/kg) and at 0.50, 1, 2, 4, 8, 24 h following iv
dosing (1 mg/kg). Samples were centrifuged at 10 000 rpm for 5 min
and the plasma collected and stored at ꢀ20 °C until analysis. Samples
were analyzed by LCꢀMS/MS technique. The pharmacokinetic para-
meters were derived by noncompartmental analysis.
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data for com-
b
pound 57. This material is available free of charge via the Internet
at http://pubs.acs.org.
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’ AUTHOR INFORMATION
Corresponding Author
*For M.S.: phone, (þ) 81-72-681-9700; fax, (þ) 81-72-681-
9725; e-mail, makoto.shiozaki@jt.com. For T.I.: phone, (þ) 81-
72-681-9700; fax, (þ) 81-72-681-9725; e-mail, takashi.inaba@jt.
com.
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’ ACKNOWLEDGMENT
We thank Yasushi Ono and Kenji Fukuda for analytical
support. We thank Tamotsu Negoro for PK data. We also thank
Dr. Jun-ichi Haruta and Dr. Hiromasa Hashimoto for support.
’ ABBREVIATIONS USED
OA, osteoarthritis; ADAMTS-4, a disintegrin and metallopro-
tease with thrombospondin motifs-4; ADAMTS-5, a disintegrin
and metalloprotease with thrombospondin motifs-5; PK, phar-
macokinetic; MMP, matrix metalloprotease; TACE, tumor ne-
crosis factor R-converting enzyme; SAR, structureꢀactivity
relationship; CYP, cytochrome P450; DMORD, disease modify-
ing osteoarthritis drug
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’ NOTE ADDED AFTER ASAP PUBLICATION
After this paper was published online March 21, 2011,
a misspelling was corrected in the author list for author
Takayuki Yamasaki. The revised version was published
March 23, 2011.
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dx.doi.org/10.1021/jm101609j |J. Med. Chem. 2011, 54, 2839–2863