Identification of a novel fluoropyrrole derivative as a potassium-competitive acid blocker with long duration of action

Article abstract of DOI:10.1016/j.bmc.2017.04.014

With the aim to find a novel long-lasting potassium-competitive acid blocker (P-CAB) that would perfectly overcome the limitations of proton pump inhibitors (PPIs), we tried various approaches based on pyrrole derivative 1b as a lead compound. As part of

Full text of DOI:10.1016/j.bmc.2017.04.014

Accepted Manuscript
Identification of a novel fluoropyrrole derivative as a potassium-competitive
acid blocker with long duration of action
Haruyuki Nishida, Yasuyoshi Arikawa, Keizo Hirase, Toshihiro Imaeda,
Nobuhiro Inatomi, Yasunobu Hori, Jun Matsukawa, Yasushi Fujioka, Teruki
Hamada, Motoo Iida, Mitsuyoshi Nishitani, Akio Imanishi, Hideo Fukui, Fumio
Itoh, Masahiro Kajino
PII:
S0968-0896(17)30497-2
DOI:
http://dx.doi.org/10.1016/j.bmc.2017.04.014
BMC 13684
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
11 March 2017
9 April 2017
11 April 2017
Please cite this article as: Nishida, H., Arikawa, Y., Hirase, K., Imaeda, T., Inatomi, N., Hori, Y., Matsukawa, J.,
Fujioka, Y., Hamada, T., Iida, M., Nishitani, M., Imanishi, A., Fukui, H., Itoh, F., Kajino, M., Identification of a
novel fluoropyrrole derivative as a potassium-competitive acid blocker with long duration of action, Bioorganic &
Medicinal Chemistry (2017), doi: http://dx.doi.org/10.1016/j.bmc.2017.04.014
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Identification of a novel fluoropyrrole derivative as a potassium-competitive acid blocker with
long duration of action
Haruyuki Nishida*, Yasuyoshi Arikawa, Keizo Hirase, Toshihiro Imaeda, Nobuhiro Inatomi,
Yasunobu Hori, Jun Matsukawa, Yasushi Fujioka, Teruki Hamada, Motoo Iida, Mitsuyoshi Nishitani,
Akio Imanishi, Hideo Fukui, Fumio Itoh, and Masahiro Kajino
Pharmaceutical Research Division: Takeda Pharmaceutical Company, Ltd., 26-1, Muraokahigashi
2-chome, Fujisawa, Kanagawa 251-8555, Japan
*To whom correspondence should be addressed. Phone: +81 466-32-1239. Fax: +81 466-29-4536.
E-mail: haruyuki.nishida@takeda.com
Present address: 2-26-1, Muraokahigashi, Fujisawa, Kanagawa 251-8555, Japan
Keywords: H+,K+-ATPase; potassium-competitive acid blocker; fluoropyrrole; low lipophilicity;
long duration of action
Abbreviations: absorption, distribution, metabolism, excretion, and toxicity (ADME-Tox), hepatic
cytochrome P450 2C19 (CYP2C19), hepatic cytochrome P450 3A4 (CYP3A4), differential scanning
calorimetry (DSC), Diisobutylaluminium hydride (DIBAL-H), 1,2-dimethoxyethane (DME),
N,N-dimethylformamide (DMF), drug metabolism and pharmacokinetics (DMPK), half-maximal
inhibitory concentration (IC50), high-performance liquid chromatography (HPLC), high-resolution
mass spectrometry (HRMS), human ether-a-go-go-related gene (hERG), intravenous injection (iv),
ligand-lipophilicity efficiency (LLE), liquid chromatography with tandem mass spectrometry
(LC/MS/MS), lithium diisopropylamide (LDA), melting point (mp), methoxy (MeO), molecular
sieves 4 angstrom (MS4Å), N-chlorosuccinimide (NCS), N-methylmorpholine N-oxide (NMO),
parallel artificial membrane permeability assay (PAMPA), per os (po), potassium-competitive acid
blocker (P-CAB), proton pump inhibitor (PPI), pyridyl (Py), relative light units (RLU), room
temperature
(rt),
structure-activity
relationship
(SAR),
tetrahydrofuran
(THF),
thermogravimetry-differential thermal analysis (TG-DTA), thin-layer chromatography (TLC),
p-toluenesulfonyl chloride (TsCl), tetrapropylammonium perruthenate (TPAP)
Abstract
With the aim to find a novel long-lasting potassium-competitive acid blocker (P-CAB) that would
perfectly overcome the limitations of proton pump inhibitors (PPIs), we tried various approaches
based on pyrrole derivative 1b as a lead compound. As part of a comprehensive approach to
1

identification of a new drug, we explored excellent compounds that have low lipophilicity by
introducing a polar hetero-aromatic group at position 5 of the pyrrole ring. Among the compounds
synthesized, fluoropyrrole derivative 37c, which has a 2-F-3-Py group at the fifth position, lower
pKa, and much lower Clog P and log D values than 1b dose, showed potent gastric-acid suppressive
action resulting from gastric H+,K+-ATPase inhibition in animal models. Its maximum intragastric
pH elevation effect was strong in rats, and its duration of action was much longer than that of either
lansoprazole or lead compound 1b in dogs. Therefore, compound 37c can be considered a promising
new P-CAB with long duration of action.
1. Introduction
Gastric H+,K+-ATPase is the key enzyme at the final step of gastric acid secretion. Proton pump
inhibitors (PPIs) such as lansoprazole, omeprazole, rabeprazole, and pantoprazole inhibit gastric
H+,K+-ATPase by covalently binding to its sulfhydryl group, resulting in the inhibition of gastric
acid secretion.1–5 PPIs are widely used in the treatment of acid-related diseases such as
gastroesophageal reflux disease, and peptic ulcer disease,6–8 and in combination with antibiotics to
eradicate Helicobacter pylori.9 Although PPIs are now the mainstay of therapy for acid-related
diseases, there are several limitations in terms of acid lability, delayed onset of action, variation of
efficacy among patients (largely because of CYP2C19 metabolism), and insufficient inhibition of
nocturnal acid breakthrough.10–14
For improved intragastric pH control, several strategies other than PPIs have been explored.
Potassium-competitive acid blocker (P-CAB)-type inhibitors of H+,K+-ATPase hold promise for
better treatment of acid-related diseases. P-CABs, as the name suggests, inhibit H+,K+-ATPase
activity in gastric parietal cells reversibly and in a potassium-competitive manner.15
Several pharmaceutical companies have attempted to develop P-CABs (Figure 1).
2

Figure 1. Structures of several reported potassium-competitive acid blockers.
These compounds were found to show a rapid onset of inhibition of acid secretion on the basis of
rapid attainment of their peak plasma concentration in clinical studies. Moreover, the full effect was
observed after the first dose. Among these compounds, revaprazan is used clinically only in South
Korea and India.16,17 Vonoprazan fumarate (TAK-438) was recently approved in Japan for the
treatment of gastric ulcer, duodenal ulcer, erosive esophagitis, prevention of low-dose aspirin- or
non-steroidal anti-inflammatory drug-induced ulcer recurrence, and as an adjunctive therapy for
Helicobacter pylori eradication.17,18 Other P-CABs are not used clinically because of their
insufficient efficacy and/or hepatic toxicity.19–24
In our previous paper,25 we have reported novel pyrrole compound 1b and its derivatives as P-CABs
(Figure 2), which showed not only potent and selective H+,K+-ATPase inhibitory activity in vitro but
also potent inhibitory action on histamine-stimulated gastric acid secretion in rats and Heidenhain
pouch dogs. Moreover, the duration of action of compound 1b in Heidenhain pouch dog was
obviously longer than that of lansoprazole.25
These results encouraged us to continue the optimization to identify a new type of P-CAB with
longer duration of action in humans, while compound 1b needed considerable improvement in
various ADME-Tox parameters such as cytotoxicity and hERG-inhibitory activity.
Through the extensive data analysis of our pyrrole derivatives including the novel approach to
evaluation of the structure–toxicity relations, a relatively strong correlation between the actual
measured log D value at pH 7.4 and in vitro cytotoxicity was observed. In addition, a slight
3

correlation between the measured log D value and hERG inhibition was estimated.
Consequently, we advanced a hypothesis that pyrroles with lowered log D have excellent
ADME-Tox parameters. Moreover, such pyrroles may stay longer in the stomach in terms of the
decline of membrane permeability in an acidic environment in addition to the physicochemical acid
resistance.
Subsequently, we carried out further optimization of compound 1b, which led to identification of
TAK-438, which showed excellent activities in rats and Heidenhain pouch dogs.26,27 In the study
where TAK-438 was found, we initially focused on replacing the phenyl (Ph) group at the first
position of the pyrrole ring through docking analysis in an H+,K+-ATPase homology model, and
identified the 3-pyridyl (3-Py) group as the best substituent, which yielded potent activity, low
lipophilicity, and preferable properties, mainly because of ligand-lipophilicity efficiency (LLE =
pIC50 − log D).28
Apart from that optimization effort, we tried exploring highly safe compounds with longer duration
of action by introducing a polar hetero-aromatic group at position 5 of the pyrrole ring based on the
hypothesis about our pyrroles (Figure 2), and succeeded only in identifying a novel fluoropyrrole
derivative after further optimizations.
Herein we report identification of a novel fluoropyrrole derivative as a P-CAB with long duration of
action.
Figure 2. Another approach to identification of a novel pyrrole derivative as a P-CAB with better
safety and a longer-lasting effect.
4

2. Chemistry
The synthesis of initial-stage key compounds containing polar hetero-aromatic groups at position 5,
e.g., 3a–e was mainly accomplished by starting from two previously reported bromo-pyrrole
intermediates 2 and 5 as shown in Scheme 1.25,28
Scheme 1. Reagents and conditions: (a) (1) Ar-B(OH)2, Pd(PPh3)4, Na2CO3, DME, H2O, 90 C; (2) 4
mol/L HCl/EtOAc, MeOH, 70 C; (b) Ar-B(O-iPr)2, Pd(PPh3)4, Na2CO3, DME, H2O, 105 C; (c)
Zn(CN)2, Pd(PPh3)4, DMF, 120 C; (d) 4 mol/L HCl/EtOAc, EtOH, room temperature (rt), or 4
mol/L HCl/EtOAc, MeOH, EtOAc, rt; (e) NaH, Ph-SO2Cl, THF, rt; (f) 2-F-3-Py-B(OH)3, Pd(PPh3)4,
NaHCO3, DME, H2O, 80 C; (g) (1) 40% MeNH2 in MeOH, MeOH, rt; (2) NaBH4, rt; (3) fumaric
acid, EtOH.
Compounds 3a and 3b were synthesized from 2 via the Suzuki-Miyaura coupling reaction using
corresponding boronic acid followed by treatment with a strong acid. Sulfonylation of 5 under basic
conditions yielded sulfonyl pyrrole 6; then, we used the Suzuki-Miyaura coupling reaction with
2-F-3-Py boronic acid, which afforded compound 7, which was then converted by reductive
amination to compound 3c containing an N-methyl methanamine moiety.
2-Cl-3-Py derivative 4d, which was isolated before deprotection, was transformed into 2-CN-3-Py
derivative 4e by Pd-catalyzed cyanation. Thus obtained compounds 4d and 4e were finally
deprotected by treatment with hydrogen chloride to produce compounds 3d and 3e, respectively, as
hydrochlorides (Scheme 1).
The synthesis of hetero-aryl and aryl derivatives at the fifth position, e.g., 2-Py compound 17a and
substituted phenyl compounds 17b-f was conducted as shown in Scheme 2.
5

Scheme 2. Reagents and conditions: (a) (1) Br2, Et2O, rt, or Br2, Et2O, CHCl3, rt, or CuBr2, AcOEt,
refluxed temperature; (2) ethyl cyanoacetate, K2CO3, 4045 C, then rt, acetone; (b) HCl(g), THF, rt,
or 4 mol/L HCl/EtOAc, rt; (c) (1) ethyl cyanoacetate, K2CO3, acetone, 45 C; (2) 4 mol/L
HCl/EtOAc, 60 C; (3) 4 mol/L HCl/EtOAc, EtOAc; (d) H2, 10% Pd–C, EtOH, 50 C or rt; (e) 1.5
mol/L DIBAL-H in toluene, THF, 50 C; (f) TPAP, NMO, MS4Å, MeCN, rt; (g) NaH, THF,
15-crown-5, Ph-SO2Cl, rt; (h) NaH, DMF, TsCl, rt; (i) 1.5 mol/L DIBAL-H in toluene, THF, 78 C;
(j) TPAP, MNO, MS4Å, MeCN, rt; (k) 40% MeNH2 in MeOH, MeOH, NaBH4, rt, or methylamine
hydrochloride, NaBH3CN, THF, rt.
Each pyrrole-3-carboxylic acid ester 11 was synthesized from the corresponding α-bromo derivatives,
which are commercially available 8a or were prepared via bromination of acetophenone derivatives
8b–f. Condensation of α-bromo derivatives of 8b–f with ethyl cyanoacetate yielded corresponding
intermediates 9b–f, which were cyclized under acidic conditions to obtain 10b–f, followed by
dehalogenation to produce pyrrole-3-carboxylic acid esters 11b–f. As for compound 8a, it was also
converted to cyclized compound 10a without intermediate isolation by a similar method, followed
by dehalogenation by a similar method to obtain 11a.
6

Reduction of the ester group of 11a with diisobutylaluminum hydride (DIBAL-H) gave alcohol 12,
which was followed by oxidation with tetra-n-propylammonium perruthenate and
N-methylmorpholine-N-oxide to obtain formyl pyrrole 13. The latter was then sulfonylated by means
of benzene sulfonyl chloride in the presence of a base to produce sulfonyl derivative 16a.
Sulfonylation of 11b–f was performed in a manner similar to the above-mentioned method to obtain
the corresponding sulfonyl derivatives 14, which were converted to formyl compounds 16 via
alcohol 15 using a procedure similar to the method for transformation of 11a into 13.
Subsequent transformation of formyl derivatives 16 into methylaminomethyl derivatives 17 was also
conducted in a manner similar to the above-mentioned procedure (Scheme 2).
Conversion of the aryl sulfonyl group at the first position including the hetero-aromatic group was
achieved via 5-(2-fluoropyridin-3-yl) -1H-pyrrole intermediates 20 starting from compound 18,
which was reported in our previous paper,28 or via another similar intermediate 23 starting from
compound 7. Their synthesis methods are shown in Scheme 3.
Scheme 3. Reagents and conditions: (a) NaH, 15-crown-5, R-SO2Cl, THF, rt; (b) 2-F-3-Py-B(OH)2,
Pd(PPh3)4, Na2CO3, DME, H2O, 105 C; (c) 8 mol/L NaOH, THF, MeOH, rt; (d) NaH, 15-crown-5,
R-SO2Cl, THF, 0 C, then rt; (e) 8 mol/L NaOH, THF, MeOH, rt; (f) NaH, THF, 15-crown-5,
R-SO2Cl, rt; (g) 4 mol/L HCl/EtOAc, EtOH, rt or (1) 4 mol/L HCl/EtOAc, MeOH, EtOAc, rt; (2)
NaHCO3, H2O; (3) fumaric acid, MeOH or EtOH, EtOAc. (h) (1) 40% MeNH2 in MeOH, MeOH, rt;
(2) NaBH4, rt; (3) fumaric acid, MeOH, EtOAc.
As for sulfonylation of 18, 21, and 22, addition of 15-crown-5 under basic conditions was essential
or effective for this reaction in many cases. In particular, the reaction did not proceed without
15-crown-5 in the case of a highly polar sulfonyl chloride with low reactivity and/or low stability in
7

a reaction mixture. It is presumed that 15-crown-5 largely enhanced the reactivity of the pyrrole
anion by keeping the sodium ion in the molecule and by reducing the influence on the pyrrole anion.
The reaction of coupling of 19 with 2-F-3-Py boronic acid and subsequent N-Boc deprotection of 20
were conducted using an approach similar to the above-mentioned method.
Desulfonylation reaction of compound 7 with a strong alkali afforded key intermediate 22, which
was sulfonylated in a manner similar to the procedure mentioned before to obtain 23, followed by
introduction of an N-methyl methanamine moiety by a method similar to the procedure for
transformation of 7 into 3 to produce target compounds 24 (Scheme 3).
The synthesis of various pyridyl derivatives substituted at position 5 and introduction of a methyl
and halogen group at position 4 were achieved by starting from intermediate 19h, commercially
available 27, and intermediate 22, respectively. Their synthesis methods are shown in Scheme 4.
Scheme 4. Reagents and conditions: (a) ArB(OH)2, Na2CO3, Pd(PPh3)4, DME, H2O, 105 C; (b)
3-Me-2-(SnBu3)Py, Pd(PPh3)4, toluene, 120 C; (c) Zn(CN)2, Pd(PPh3)4, DMF, 120 C; (d) (1) 4
mol/L HCl/EtOAc, MeOH, EtOAc, rt or 70 C; (2) NaHCO3, H2O; (3) fumaric acid, MeOH or EtOH,
EtOAc; (e) (1) 3-F-4-Py-B(OH)2, Pd(PPh3)4, NaHCO3, DME, H2O, 80 C; (2) 4 mol/L HCl/EtOAc,
MeOH, 70 C; (3) NaHCO3, H2O; (4) fumaric acid, MeOH, EtOAc; (f) (1) LDA, THF, 78 °C; (2)
2-F-Py, THF, 78 °C; (3) propionaldehyde, THF, 78 °C; (g) SO3-Py, Et3N, DMSO, rt; (h) Br2, 25%
8

HBr, AcOH, rt; (i) ethyl cyanoacetate, iPr2NEt, THF, rt; (j) 4 mol/L HCl/EtOAc, EtOAc, rt; (k) H2,
10% Pd–C, Et3N, EtOH, 60 C; (l) 1.5 mol/L DIBAL-H in toluene, THF, 78 C, then 0 C; (m)
TPAP, NMO, MS4Å, MeCN, rt; (n) 1-fluoro-2,6-dichloropyridinium triflate, THF, MeCN, rt (R =
F); (o) NCS, DMF, 80 °C (R = Cl); (p) NaH, THF, 15-crown-5, 3-Py-SO2Cl, rt; (q) (1) 40% MeNH2
in MeOH, MeOH, THF, rt; (2) NaBH4, rt; (3) fumaric acid, EtOH, EtOAc; or (1) methylamine
hydrochloride, NaBH(OAc)3, MeOH, rt; (2) fumaric acid, MeOH, EtOAc, or fumaric acid, EtOH,
EtOAc.
Conversion of the bromine group of 19h to various pyridyl groups via the Suzuki-Miyaura coupling
reaction or Migita-Kosugi-Stille coupling reaction gave 25, which was then subjected to a
deprotection reaction to obtain compounds 26 in a manner similar to the above-mentioned
procedure.
Reaction of 27 with LDA followed by a reaction of nucleophilic addition to propionaldehyde yielded
secondary alcohol 28, which was converted via an oxidation reaction with a pyridine-sulfur trioxide
complex to ketone derivative 29 followed by bromination to produce α-bromo derivative 30.
Condensation of compound 30 with ethyl cyanoacetate in the presence of N,
N-diisopropylethylamine afforded intermediate 31, which was cyclized under acidic conditions to
obtain 32 followed by dehalogenation to produce pyrrole-3-carboxylic acid ester 33. Subsequent
reduction of 33 and oxidation of 34 to obtain 35a were conducted by a method similar to the
procedure described above.
Chlorination of 22 with NCS gave 35b, and fluorination of 22 was performed by means of
1-fluoro-2,6-dichloropyridinium triflate to obtain 35c.
Subsequent sulfonylation of 35 in the presence of 15-crown-5 and reductive amination of 36 to
produce compounds 37 were performed in a manner similar to the method described above (Scheme
4).
Intermediates 2, 5, and 18 were prepared by a method similar to a previously reported procedure.25,28
As for compounds 1a–c described above, they were prepared in a manner similar to a previously
reported method.25
3. Results and discussion
The compounds synthesized were evaluated for their Clog P values, log D values at pH 7.4, and
H+,K+-ATPase-inhibitory activities at pH 6.5 according to their IC50 values (in vitro), and some of
the compounds were analyzed for their inhibitory effects on histamine-induced gastric acid secretion
in anesthetized rats (in vivo), effects on ATP content (cytotoxicity) and hERG-inhibitory activity. We
also calculated their values of LLE (= pIC50  log D), which is a parameter for estimating their
drug-likeness based on their linking potency and lipophilicity,29 to facilitate the selection of better
9

compounds.
An in vivo assay was carried out by intravenous administration of the compound at 1 mg/kg, and the
total acid output for 3 h after histamine injection was compared to that obtained after administration
of vehicle. The log D values were measured at pH 7.4 with relative retention time to standard
compounds in HPLC analysis.30 The results are shown in Tables 1, 3 and 4.
First, we examined the effects of replacement of the phenyl group with highly polar heteroaromatic
groups at the fifth position (R1) of the pyrrole ring to assess the possibility of favorable drug-like
profiles, and the results are summarized in Table 1.
5-Pyrimidyl compound 3a, 3-pyridyl compound 3b and 2-pyridyl compound 17a all showed a more
dramatic reduction in log D values than expected from their Clog P values, although their in vitro
activities were considerably reduced as compared to original phenyl compound 1c. As we expected,
their ADME-Tox parameters in vitro were noticeably improved. Especially, 3-pyridyl compound 3b
had a relatively large LLE value (6.81), and actually showed good ADME-Tox parameters such as
metabolic stability, solubility, CYP inhibition, cytotoxicity, and hERG inhibition (Table 1, some data
not shown). These results prompted us to continue further modification of 3-pyridyl compound 3b,
although the basicity of pyridine at position 5 was assumed to be not beneficial for relevant activities
judging by the results of both previous docking analysis in an H+,K+-ATPase model and actual in
vivo activity on this compound (4% inhibition at 1mg/kg, iv).
To estimate the priority of further modifications of 3b, the influence of some substituent groups on
activities and ADME-Tox parameters was studied on the basis of compound 1a. 2-Me-Ph derivative
17b, 2-CF3-Ph derivative 17c, and 2-F-Ph derivative 17d, all of which have some kind of substituent
at the ortho-position of the phenyl group at position 5 of the pyrrole ring, all showed enhanced in
vivo activities: inhibition by 92%, 86% and 91% at 1mg/kg, iv, respectively. Although ADME-Tox
parameters of 2-Me-Ph derivative 17b and 2-CF3-Ph derivative 17c were worse, e.g., in terms of
CYP3A4 inhibition and cytotoxicity, 2-F-Ph derivative 17d showed relatively good parameters
(Table 1, some data not shown). Moreover, its log D value (1.56) was much lower than that of
original Ph compound 1a (log D = 1.84) contrary to our expectations. On the other hand, 3-F-Ph
derivative 17e (log D = 1.98) and 4-F-Ph derivative 17f (log D = 2.05) had greater log D values than
1a did, reflecting the increased Clog P values caused by lipophilicity of the fluorine atom. pKa
values of 17d, 17e, 17f, and 1a were 9.48, 9.31, 9.40, and 9.49, respectively, and there were no
significant differences among these four compounds. Although we cannot offer a conclusive
explanation for such unique behavior of the log D value at present, it may be caused by the presence
of an oxygen atom close to a fluorine.31 Steric conformations among these pyrrole compounds were
almost comparable in single-crystal structures including non-fluorinated compound 1a (Figure 3),
but the shortest distance between oxygen atoms and the fluorine atom in each single-crystal structure
was 4.34 Å in ortho compound 17d, 5.53 Å in meta compound 17e, and 5.80 Å in para compound
10

17f. In addition, the shortest distance between a fluorine and the center of benzene ring of the tosyl
group was 4.02 Å in ortho compound 17d, 6.06 Å in meta compound 17e, and 7.26 Å in para
compound 17f.
To determine the behavior in an aqueous solution, several NMR analyses in D2O and DMSO-d6 were
conducted (Table 2). Because in D2O, there were few significant differences in chemical shifts in the
benzene ring of the tosyl group and methylaminomethyl group among the compounds, it was
presumed that they indicated a high potential for almost the same conformation even in an aqueous
solution regardless of whether fluorine is actually presemt at any position. Nevertheless, the
chemical shifts of 13C-NMR in the tosyl group were almost comparable among four compounds, but
1
the chemical shifts of H-NMR in the tosyl group of ortho compound 17d were slightly shifted
downfield as compared to the other compounds (Table 2). This downfield shift of the proton signals
seems to be caused by the influence of the interaction with the fluorine group of 17d because the
distance between the fluorine atom and each benzene ring proton of the tosyl group was significantly
shorter than that in 17e and 17f. Judging by this measurable fluorine effect, it is possible that such a
fluorine group polarizes the neighboring oxygen atoms, and this change leads to stronger hydrogen
bonds between the oxygen atoms and neighboring water molecules in addition to increasing overall
polarity of the molecule.
Moreover, ortho compound 17d showed a much smaller difference in the chemical shift during
19F-NMR analysis between the DMSO-d6 solution and D2O solution as compared to the other
compounds (Table 2). This result suggests that a stronger intramolecular interaction of fluorine may
form in the case of ortho compound 17d.
In terms of their overall inhibitory activities in vivo including DMPK properties, ortho compound
17d (IC50 = 34 nM, 91% inhibition at 1mg/kg, iv) showed excellent inhibition as compared to meta
compound 17e (IC50 = 19 nM, 77% inhibition at 1mg/kg, iv) or para compound 17f (IC50 = 90 nM,
86% inhibition at 1mg/kg, iv).
With these observations in mind, we designed several 2-(electron-withdrawing substituent)-3-Py
derivatives including a hybrid compound with the 2-F-3-Py group. Exceeding our expectations, each
of the three synthesized compounds (3c, 3d, and 3e) had both a low log D value and strong
gastric-acid suppressive activity in rats. Their in vivo potency was even stronger than that of lead
compound 1b. 2-CN-3-Py derivative 3e had relatively weak in vitro activity (IC50 = 120 nM) but
showed strong in vivo action and an excellent profiles of ADME-Tox parameters.
In contrast, 2-F-3-Py derivative 3c and 2-Cl-3-Py derivative 3d showed strong activities not only in
vivo but also in vitro (IC50=26 and 43 nM, respectively). Nevertheless, their hERG-inhibitory
activities were slightly out of the acceptable range for their preferable ADME-Tox profiles.
It seems to be difficult to discuss the relative superiority of the three compounds including their
actual potency at this stage of the lead optimization study, but the direction of compound design
11

based on our hypothesis was assumed to be basically appropriate because their LLE values increased.
Among the three compounds that showed stronger in vivo action than 1a did (95% inhibition),
2-F-3-Py derivative 3c had the highest LLE value (7.68), accompanied by high potency (IC50 = 26
nM) and low log D value (0.09).
Table 1 Effects of substituents at position 5 (R1) on activities and properties of pyrrole compounds
Compound. R1
X
Clog P log D
In vitro
LLE
In vivo
ATP content hERG
H+,K+-ATPase
Acid secretion
at 100 M
% inhibition
inhibitory activities
in rats (1 mg/kg,
(%control)
at 10 M
FCS (-)
NTb
(IC50, nM)
46
iv, % inhibition)
1a
Ph
Me
MeO
H
4.21
3.88
3.71
1.42
2.36
2.57
4.41
5.15
4.39
4.39
4.39
2.56
2.88
2.17
1.83
1.54
1.44
–0.4
0.08
0.28
2.12
1.94
1.56
1.98
2.05
–0.09
–0.1
–0.32
5.51
5.98
6.59
6.79
6.81
6.64
5.09
5.12
5.91
5.74
5.00
7.68
7.47
7.24
66
95
96
NTb
4
NTb
92
86
91
77
86
99
99
99
(38.6)a
(22.1)a
(53.8)a
97.5
1b
Ph
30
89.1
87.5
24.2
43.3
48.0
NTb
1c
Ph
9.4
410
130
120
62
3a
5-Pyrimidyl
3-Py
H
3b
H
95
17a
17b
17c
17d
17e
17f
3c
2-Py
H
91.2
2-Me-Ph
2-CF3-Ph
2-F-Ph
3-F-Ph
4-F-Ph
2-F-3-Py
2-Cl-3-Py
2-CN-3-Py
Me
Me
Me
Me
Me
H
(0.3)a
(0.5)a
(8)a
88
NTb
NTb
34
19
(0.6)a
(0.4)a
59.9
NTb
NTb
90
26
57.0
40.9
32.9
3d
H
43
76.3
3e
H
120
82.1
a ATP content at 30 μM (% control)
b Not tested
Figure 3. Superposition of single-crystal structures obtained by X-ray structural analysis for 1a,
2-F-Ph (ortho) compound 17d, 3-F-Ph (meta) compound 17e, and 4-F-Ph (para) compound 17f.
12

Table 2 NMR analysis of pyrrole compounds regarding the effect of fluorine substitution at position
5
Compound
Y
17d
17e
17f
1a
2-F
3-F
4-F
H
1H-NMR
(600MHz,
D2O)
13C-NMR
(151MHz,
D2O)
1H-NMR
(600MHz,
D2O)
13C-NMR
(151MHz,
D2O)
1H-NMR
(600MHz,
D2O)
13C-NMR
(151MHz,
D2O)
1H-NMR
(600MHz,
D2O)
13C-NMR
(151MHz,
D2O)
δ (ppm)
δ (ppm)
132.22
119.89
119.99
127.68
135.90
129.65
132.80
149.80
23.49
δ (ppm):
δ (ppm)
138.42
119.08
119.87
127.99
136.00
129.65
132.68
149.74
23.47
δ (ppm)
δ (ppm)
138.74
118.72
119.73
127.56
136.10
129.62
132.66
149.65
23.47
δ (ppm)
δ (ppm)
139.92
118.69
119.96
127.68
136.14
129.58
132.65
149.58
23.46
2
3
6.446
7.775
6.397
7.736
6.353
7.722
6.362
7.722
4
5
9
10, 14
11, 13
12
15
16
17
18
19
20
21
22
23
24
7.321
7.318
7.305
7.290
7.280
7.280
7.284
7.284
2.388
2.371
6.943
2.371
2.371
120.71
163.33
117.87
134.62
126.58
135.88
47.00
134.81
120.22
164.40
118.53
132.24
129.45
46.98
128.99
135.52
117.34
165.74
117.34
135.52
47.04
133.00
133.43
130.53
131.79
130.53
133.43
47.02
7.170
7.090
7.201
7.380
7.475
7.380
7.201
4.119
7.152
7.522
7.185
7.075
4.131
7.208
7.361
7.011
4.118
7.090
7.170
4.115
2.686
34.35
2.672
34.31
2.677
34.32
2.675
34.31
19F-NMR
(376MHz,
D2O)
19F-NMR
Differencea
(ppm)
19F-NMR
(376MHz,
D2O)
19F-NMR
Differencea
(ppm)
19F-NMR
(376MHz,
D2O)
19F-NMR
Differencea
(ppm)
19F-NMR
(376MHz,
D2O)
19F-NMR
Differencea
(ppm)
δ (ppm)
δ (ppm)
δ (ppm)
–114.016
δ (ppm)
25
–113.970
0.289
–115.577
1.309
1.887
a Difference in the chemical shift between D2O and DMSO-d6 solutions
Second, we evaluated the effects of position 1 (R2) with regard to a series of 2-F-3-Py derivatives at
position 5 (R1) and the results are shown in Table 3.
Replacement of the phenyl group with the 3-F-Ph group (compound 24a) yielded similar activities,
but in the case of replacement with 3-MeO-Ph (compound 24b), a slight reduction of in vivo activity
was observed. On the other hand, 3-CN-Ph derivative 24c retained strong in vivo activity in spite of
the reduced in vitro activity. Thus, 3-(polar substituent)-Ph derivatives almost maintained strong
activities. Nonetheless, obvious signs of improvement of hERG-inhibitory activities were not
observed. 3-Thienyl derivative 24d and 2-thienyl derivative 24e also retained almost equal in vitro
13

and in vivo activities as compared to 3c in spite of a big reduction in the log D value. Their LLE
values were high, more than 8, but their hERG inhibition was not improved. Both 3-furyl derivative
24f and 2-furyl derivative 24g showed a greater reduction in log D values than did thienyl
derivatives, but their in vivo activities were reduced to 82% and 74%, respectively, and the
hERG-inhibitory activities were not improved either.
Both 3-pyridyl derivative 24h and 2-pyridyl derivative 24i showed remarkably reduced in vitro
activities, but 3-Py derivative 24h exerted strong inhibitory action in vivo (96% inhibition), despite
its quite low log D value, and showed excellent ADME-Tox parameters including hERG-inhibitory
activity in association with its high LLE value (7.53). Therefore, we selected compound 24h as a
lead compound for further optimization (Table 3).
Table 3 Effects of substituents at the first position (R2) on activities and properties of pyrrole
compounds
Compound. R1
R2
Clog P log D
In vitro
LLE
In vivo
ATP content hERG
H+,K+-ATPase
Acid secretion
at 100 M
% inhibition
inhibitory activities
in rats (1 mg/kg,
(%control)
at 10 M
FCS (-)
NTb
(IC50, nM)
55
iv, % inhibition)
1a
Ph
Ph
Ph
4-Me-Ph
4-MeO-Ph
Ph
4.21
3.88
3.71
2.56
2.71
2.72
2.00
2.28
2.28
1.74
1.74
1.21
1.21
1.83
5.43
5.98
6.59
7.68
7.25
7.45
7.41
8.32
8.18
8.35
8.38
7.53
6.97
66
95
96
99
99
92
99
98
96
82
74
96
81
(38.6)a
(22.1)a
(53.8)a
59.9
1b
1.54
30
89.1
87.5
57.0
56.2
72.8
46.7
60.0
63.0
59.3
49.1
4.4
1c
1.44
9.4
26
3c
2-F-3-Py Ph
–0.09
0.23
24a
24b
24c
24d
24e
24f
24g
24h
24i
2-F-3-Py 3-F-Ph
2-F-3-Py 3-MeO-Ph
2-F-3-Py 3-CN-Ph
2-F-3-Py 3-thienyl
2-F-3-Py 2-thienyl
2-F-3-Py 3-furyl
2-F-3-Py 2-furyl
2-F-3-Py 3-Py
33
65.9
0.10
28
30.6
–0.36
–0.83
–0.69
–1.31
–1.15
–0.85
0.05
89
46.7
32
64.0
32
74.9
92
77.4
59
68.7
210
120
85.7
2-F-3-Py 2-Py
78.6
NTb
a ATP content at 30 μM (% control)
b Not tested
Lastly, we analyzed several analogs of compound 24h in detail to understand not only the SAR but
also the relation of structure with ADME-Tox parameters, and the results are summarized in Table
4.
Introduction of a methoxy group at position 6 of the 3-pyridyl group in the R2 moiety yielded
~5-fold more potent in vitro activity (compound 24j, IC50 = 40 nM) as compared to original
compound 24h. Compound 24j also had a 97% inhibitory activity in vivo, but its cytotoxicity (effect
14

on ATP content) was assumed to be slightly out of range for the preferable ADME-Tox profiles for
an ideal long-lasting P-CAB.
Replacement of the 2-F-3-Py group at position 5 (R1) of the pyrrole ring by a 2-Cl-3-Py group
showed enhanced in vitro activity (compound 26a, IC50 = 120 nM). In addition, this replacement
maintained excellent ADME-Tox parameters, while the in vivo activity decreased slightly to 92%.
In the case of replacement with the 2-CN-3-Py group (compound 26b), it yieded a lower log D value
and greatly reduced activities not only in vivo but also in vitro.
To determine the influence of basicity at position 5, two ortho-methylated 3-pyridyl derivatives, 26c
and 26d, were studied next. Consequently, in vitro activity of each compound was almost identical to
that of 24h, but in vivo activity of each compound was greatly reduced. Basicity of pyridine at the
fifth position of the pyrrole ring seemed to be unfavorable for in vivo activities judging by the data
on a comparison of 2-Me-Ph compound 17b (IC50 = 62 nM, 92% inhibition at 1mg/kg, iv) with
2-F-Ph compound 17d (IC50 = 34 nM, 91% inhibition at 1mg/kg, iv). Replacement with other types
of ortho-substituted pyridyl groups, such as 3-Me-2-Py (compound 26e) or 3-F-4-Py (compound
26f), did not produce sufficient enhancement of activities.
Compound 37a with a methyl group at position 4 of the pyrrole ring (R3) retained in vitro activity
(IC50 = 220 nM) almost equal to that of 24h, but showed slightly decreased in vivo activity (93%
inhibition at 1mg/kg, iv).
Compound 37b with a chlorine atom at position 4 of the pyrrole ring (R3) possessed increased in
vitro activity (IC50 = 99 nM), and retained almost equal in vivo activity (95% inhibition at 1mg/kg,
iv) as compared to 24h.
By contrast, compound 37c having a fluorine atom at position 4 of the pyrrole ring (R3) exerted more
potent activities both in vitro and in vivo (IC50 = 49 nM, 98% inhibition at 1mg/kg, iv). Moreover,
compound 37c showed an excellent ADME-Tox profile, especially low cytotoxicity (100.2% ATP
content at 100 µM).
Compounds with a substituent at the second position of the pyrrole ring were not studied because an
obvious reduction of in vivo activity was observed in our previous study.25
15

Table 4 Effects of substituents (R1, R2, and R3) on activities and properties of pyrrole compounds
Compound R1
R2
R3
Clog P log D
In vitro
LLE
In vivo
ATP content hERG
H+,K+-ATPase
Acid secretion
at 100 M
% inhibition
inhibition
(IC50, nM)
30
in rats (1 mg/kg,
(%control)
at 10 M
FCS (-)
89.1
4.4
iv, % inhibition)
1b
Ph
4-MeO-Ph
H
H
H
H
H
H
H
H
H
Me
Cl
F
3.88
1.21
1.97
1.53
0.81
1.18
1.18
1.39
1.21
1.36
1.77
1.45
1.54
–0.85
0.24
–0.5
–1.29
0.06
–0.51
0.53
–0.34
–0.4
0.48
0.04
5.98
7.53
7.16
7.42
7.57
6.54
7.15
5.36
6.88
7.07
6.52
7.27
95
96
97
92
48
–41
–54
5
(22.1)a
85.7
47.6
82.9
85.3
107.2
86.0
88.7
78.8
47.1
64.5
100.2
24h
24j
26a
26b
26c
26d
26e
26f
37a
37b
37c
2-F-3-Py 3-Py
2-F-3-Py 6-MeO-3-Py
2-Cl-3-Py 3-Py
2-CN-3-Py 3-Py
2-Me-3-Py 3-Py
4-Me-3-Py 3-Py
3-Me-2-Py 3-Py
3-F-4-Py 3-Py
2-F-3-Py 3-Py
2-F-3-Py 3-Py
2-F-3-Py 3-Py
210
40
33.1
10.6
1.9
120
530
250
NTb
230
8.3
NTb
1300
290
48
93
95
98
18.8
30.3
41.3
39.8
220
99
49
a ATP content at 30 M (% control)
b Not tested
Because compounds 3e, 24h and 37c showed superior ADME-Tox properties in addition to
promising activities, we studied the effects of compounds 3e, 24h, and 37c and lansoprazole on the
pH of a gastric perfusate during histamine stimulation in anesthetized rats (Figure 4).
The pH value of saline under these experimental conditions was 6.0 to 6.3. Intravenous infusion of
histamine 2HCl at 8 mg/kg/h stimulated gastric acid secretion and decreased pH of the gastric
perfusate to ~2. Lansoprazole, which is one of typical PPIs, resulted in a rapid increase of perfusate
pH but not up to 5 after administration of a 3 mg/kg dose, and the perfusate pH gradually decreased
thereafter even at such a high dose (Figure 4A).
On the other hand, intravenous administration of compounds 3e, 24h, and 37c clearly increased pH
of the gastric perfusate at a low dose of 1 mg/kg or less.
Compound 3e increased perfusate pH value (>5) within 2 h after the administration at 1 mg/kg, but
the perfusate pH gradually decreased thereafter (Figure 4B).
Compound 24h also increased pH of the gastric perfusate, and pH reached ~5 at a dose of 1 mg/kg.
Moreover it took 150–180 min for the pH of the perfusate to reach its peak value after administration
of this compound (Figure 4C).
In contrast, intravenous administration of 37c at 0.7 mg/kg caused a relatively rapid increase in pH
of the gastric perfusate, to approximately 6, and the effect was sustained for more than 5 h after
administration (Figure 4D).
According to these results, compound 37c, which showed the longest duration of action in rats, was
16

selected for further analysis.
Figure 4. Effects of intravenous administration of lansoprazole (A) and compounds 3e (B), 24h (C),
and 37c (D) on pH of a gastric perfusate under conditions of histamine stimulation in anesthetized
rats. Each data point represents mean ± SE from three or four rats.
We evaluated the effect of oral administration of compound 37c in rats and dogs (Figures 5 and 6).
As shown in Figure 5, compound 37c attenuated histamine-stimulated acid secretion in anesthetized
rats in a dose-dependent manner. In addition, it caused complete inhibition at a dose of 4 mg/kg,
probably because acid activation is not required for compound 37c to exert its acid-suppressive
effect in contrast to PPIs.
17

Figure 5. Effects of oral administration of compound 37c on histamine-stimulated acid secretion in
anesthetized rats. Each column represents the mean ± SE from six rats. Statistical significance of the
difference was determined by the one-tailed Shirley-Williams test; *p < 0.025 compared to vehicle.
Compound 37c completely inhibited histamine-stimulated gastric acid secretion in Heidenhain
pouch dogs after oral administration at a dose of 0.8 mg/kg. Its duration of action was much longer
than that of lansoprazole at 3 mg/kg, per os (po). Moreover, its effect was clearly longer as compared
to that of lead compound 1b at 1 mg/kg, po, which was reported in our previous paper,25 and
well-pronounced suppression of acid secretion was observed even 48 h after the administration
(Figure 6).
18

Figure 6. Effects of oral administration of compound 37c (A), lansoprazole (B), or lead compound
1b (C)25 on histamine-stimulated acid secretion in Heidenhain pouch dogs. Each data point
represents mean ± SE from three or four dogs.
Compound 37c was designed to have moderate basicity in addition to weak lipophilic properties
(Clog P = 1.45); the log D value was 0.04 at pH 7.4, and pKa of the side chain amino group portion
was 8.54. Therefore, compound 37c mostly dissociates in vivo, while showing excellent membrane
penetration at pH 7.4, which is similar to blood pH. The lowered pKa value of compound 37c caused
by introduction of the fluorine atom at position 4 of the pyrrole ring may have contributed to the
excellent membrane penetration at pH 7.4 [256 Pe (nm/sec) in parallel artificial membrane
permeability assay (PAMPA)] (Table 5).
In contrast, a pronounced decline in membrane penetration was observed at lower pH, even in a
slightly acidic environment, e.g., at pH 5.0, because of a further increase in the proportion of its
dissociated molecules, accompanied by a decrease in lipophilicity [47 Pe (nm/sec) at pH 5.0 in
PAMPA] (Table 5). Based on these physicochemical properties, compound 37c is considered to have
rapid onset and long duration of action after single administration because of moving rapidly into the
acidic secretory canaliculi and remaining there for a long period. Therefore, compound 37c was
19

assumed to exert stronger and longer-lasting action than lead compound 1b dose.
Table 5 Physicochemical properties and biological activities of hit compounds 1b and 37c
Compound
Clog P
log D
pKa
In vitro
In vivo
PAMPAa
PAMPAa
at pH 7.4
H+,K+-ATPase inhibition
Acid secretion
in rats (1 mg/kg,
iv, % inhibition)
95
pH 7.4
pH 5.0
(IC50, nM)
Pe (nm/sec)
Pe (nm/sec)
1b
3.88
1.45
1.54
9.48
8.54
30
49
246
256
198
47
37c
0.04a
98
a Parallel artificial membrane permeability assay
These results indicate that the pharmacological effect of 37c is superior to that of lansoprazole. This
compound also showed good acid resistance and limited susceptibility to CYP polymorphism (data
not shown) unlike lansoprazole. Furthermore, the overall DMPK and safety profiles of 37c were
much better than those of the lead compound 1b. Additionally, compound 37c was expected to have
longer duration of action in humans as compared to TAK-438 according to its physicochemical
properties.
On the basis of these findings, compound 37c, which has physicochemical properties different from
those of TAK-438, e.g., in terms of lipophilicity and basicity, may be a promising alternative as a
P-CAB, if the need arises.
4. Conclusion
We synthesized novel pyrrole derivatives with low lipophilicity in accordance with our hypothesis
on the basis of lead compound 1b and evaluated their potency as P-CABs and their safety profiles.
Our initial aim to greatly reduce log D values implied introduction of polar hetero-aromatic groups
at the fifth position of the pyrrole ring. We found that substituted 3-pyridyl groups with lower
basicity possess favorable properties. Eventually, our experiments revealed that the combination of
the replacement with a 2-F-3-Py group at position 5, replacement with a 3-Py group at positions 1,
and introduction of a fluorine atom at position 4 of the pyrrole ring is the most suitable for both
potent activities with longer duration of action and low lipophilicity with effective improvement of
ADME-Tox parameters.
Thus, the identified compound 37c shows potent H+,K+-ATPase-inhibitory activity in vitro, and
potent and long-lasting inhibitory activities on histamine-induced gastric acid secretion in rats and
Heidenhain pouch dogs.
We succeeded in identifying a new P-CAB with long duration of action as a possible alternative to
TAK-438, if the need arises.
20

5. Experimental section
Experimental procedures and characterization data for all synthetic intermediates are reported in
Supplementary data.
5.1. General
Commercial reagents and solvents were used without additional purification. The pKa values were
measured by pH-metric assays using a Sirius T3 system (Sirius Analytical Ltd., UK). The assay
measures the concentration of H+ ions in solution between pH 2 and 12 using a pH electrode
(Ag/AgCl). Melting points were determined on a Yanagimoto micro melting point apparatus or
Büche B-545 or by differential scanning calorimetry (DSC) or TG-DTA analyses. DSC analyses
were performed using a DSC1 system (Mettler Toledo, Switzerland). The thermograms were
obtained at a temperature of 25–300 °C and a heating rate of 5 °C/min under nitrogen gas at a flow
rate of 40 mL/min. The powders (~1 mg) were weighed in an aluminum pan, crimped, and then
placed in the thermal analysis chamber. TG-DTA analyses were conducted by from Sumika
Chemical Analysis Service, Ltd. Nuclear magnetic resonance (1H-NMR, 13C-NMR and 19F-NMR)
spectra were recorded on a Varian Gemini-200, a Varian Mercury-300, a Bruker AV-300M, a Bruker
AV-400 or a Bruker AV- 600 spectrometer. Chemical shifts are given in  values (ppm) using
tetramethylsilane or sodium 3-(trimethylsilyl)-1-propane-1,1,2,2,3,3-d6-sulfonate as an internal
1
standard for H and 13C-NMR, with sodium trifluoroacetate as the internal standard for 19F-NMR
(76.53 ppm). Coupling constants are reported in hertz (Hz). Spectral splitting patterns were
designated as follows: s, singlet; br, broad; d, doublet; t, triplet; q, quartet; and m, multiplet.
High-resolution mass spectrometry (HRMS) experiments were carried out by Sumika Chemical
Analysis Service, Ltd. All mass spectrometry (MS) experiments were conducted using electrospray
ionization (ESI) in positive or negative ion mode. Elemental analyses were performed by Takeda
Analytical Laboratories, Ltd., or Sumika Chemical Analysis Service, Ltd. Thin-layer
chromatography (TLC) analyses were carried out on Merck Kieselgel 60 F254 plates or Fuji Silysia
Chemical, Ltd., Chromatorex NH-TLC plates. Silica gel column chromatography was run by means
of Merck 0.0630.200 mm silica gel 60, Fuji Silysia Chemical Ltd. 100200 mesh Chromatorex NH
silica DM1020 or Purif-Pack (SI 60 μM or NH 60 μM, Fuji Silysia Chemical Ltd.).
5.2. N-Methyl-1-[1-(phenylsulfonyl)-5-(pyrimidin-5-yl)-1H-pyrrol-3-yl]methanamine hydrochloride
(3a)
A mixture of tert-butyl {[5-bromo-1-(phenylsulfonyl)-1H-pyrrol-3-yl]methyl}methylcarbamate 2
(170 mg, 0.40 mmol), pyrimidin-5-ylboronic acid (123 mg, 0.99 mmol), Na2CO3 (147 mg, 1.39
mmol) and tetrakis(triphenylphosphine)palladium (46 mg, 0.040 mmol) in DME (10 mL) and H2O
(5 mL) was stirred at 90 C for 3 h under Ar atmosphere. After cooling to room temperature, the
21

mixture was poured into H2O, and extracted with EtOAc. The extract was washed with brine, dried
over anhydrous MgSO4, and concentrated under reduced pressure. The residue was purified by silica
gel column chromatography (n-hexane/EtOAc = 4/11/3), and the resulting oil was dissolved in
MeOH (20 mL), and then 4 mol/L HCl/EtOAc (2 mL) was added. The mixture was stirred at 70 C
for 30 min, and concentrated under reduced pressure. The residue was suspended in EtOAc and
1
collected by filtration to obtain 3a (42.0 mg, 29%) as a colorless solid: mp 179 C; H-NMR
(DMSO-d6)  2.50 (3H, m), 4.00 (2H, t, J = 5.8 Hz), 6.71 (1H, d, J = 1.8 Hz), 7.447.47 (2H, m),
7.557.60 (2H, m), 7.737.78 (1H, m), 7.89 (1H, d, J = 1.8 Hz), 8.62 (2H, s), 9.18 (2H, br), 9.23
(1H, s); HRMS (ESI) calcd for C16H16N4O2S (M+H)+ m/z 329.1067, found m/z 329.1026.
5.3. N-Methyl-1-[1-(phenylsulfonyl)-5-(pyridin-3-yl)-1H-pyrrol-3-yl]methanamine dihydrochloride
(3b)
Compound 3b was prepared from 2 in a manner similar to that described for compound 3a. A
1
colorless solid (49%): mp 187 C; H-NMR (DMSO-d6)  2.47 (3H, t, J = 5.5 Hz), 3.98 (2H, t, J =
5.5 Hz), 6.72 (1H, d, J = 1.8 Hz), 7.457.58 (4H, m), 7.707.76 (2H, m), 7.88 (1H, d, J = 1.3 Hz),
7.957.98 (1H, m), 8.53 (1H, d, J = 1.8 Hz), 8.76 (1H, dd, J=1.3, 5.3 Hz), 9.34 (2H, br), 1H not
detected; HRMS (ESI) calcd for C17H17N3O2S (M+H)+ m/z 328.1114, found m/z 328.1085.
5.4. 1-[5-(2-Fluoropyridin-3-yl)-1-(phenylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine fumarate
(3c)
To a stirred mixture of 5-(2-Fluoropyridin-3-yl)-1-(phenylsulfonyl)-1H-pyrrole-3-carbaldehyde 7
(160 mg, 0.48 mmol) and 40% methanol solution of methylamine (188 mg, 2.42 mmol) in MeOH
(16 mL) was added sodium borohydride (55 mg, 1.45 mmol) at room temperature under N2
atmosphere, and the mixture was stirred at room temperature for 30 min, quenched with a solution of
NaHCO3, and then extracted with EtOAc. The extract was washed with brine, dried over anhydrous
MgSO4, and concentrated under reduced pressure. The residue was purified by basic silica gel
column chromatography (EtOAc/MeOH = 99/1), and then crystalized from a solution of fumaric
acid (57 mg, 0.4911 mmol) in EtOH (5 mL). The obtained crystals were collected by filtration and
1
rinsed with EtOH to produce 3c (92 mg, 41%) as colorless crystals: mp 191192 C; H-NMR
(DMSO-d6)  2.39 (3H, s), 3.79 (2H, s), 6.48 (2H, s), 6.51 (1H, d, J = 1.5 Hz), 7.387.42 (1H, m),
7.467.49 (2H, m), 7.547.60 (2H, m), 7.677.77 (3H, m), 8.308.33 (1H, m), 3H not detected;
Anal. Calcd for C21H20FN3O6S: C, 54.66; H, 4.37; N, 9.11. Found: C, 54.57; H, 4.31; N, 9.02.
5.5.
1-[5-(2-Chloropyridin-3-yl)-1-(phenylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
hydrochloride (3d)
To a solution of compound 4d (259 mg, 0.56 mmol) in EtOH (2 mL) was added 4 mol/L HCl/EtOAc
22

(2 mL), and the mixture was stirred at room temperature for 2 h, concentrated under reduced
pressure, and then recrystallized from EtOH to produce compound 3d (124 mg, 56%) as colorless
1
crystals: mp 215216 C; H-NMR (DMSO-d6)  2.51 (3H, s), 4.00 (2H, s), 6.576.61 (1H, m),
7.467.52 (3H, m), 7.577.62 (3H, m), 7.747.83 (2H, m), 8.498.51 (1H, m), 9.049.23 (2H, m);
Anal. Calcd for C17H17 Cl2N3O2S: C, 51.26; H, 4.30; N, 10.55. Found: C, 51.28; H, 4.23; N, 10.56.
5.6.
3-{4-[(Methylamino)methyl]-1-(phenylsulfonyl)-1H-pyrrol-2-yl}pyridine-2-carbonitrile
hydrochloride (3e)
To a solution of compound 4e (250 mg, 0.55 mmol) in EtOAc (5mL) and MeOH (3 mL) was added
4 mol/L HCl/EtOAc (3 mL), and the mixture was stirred at room temperature for 4h, concentrated
under reduced pressure, and then recrystallized from EtOH to produce compound 3e (127 mg, 59%)
1
as colorless crystals: mp 240250 C (decomposition); H-NMR (DMSO-d6)  2.49 (3H, s), 4.03
(2H, s), 6.80 (1H, d, J = 1.8 Hz), 7.457.48 (2H, m), 7.567.61 (2H, m), 7.757.94 (4H, m),
8.818.83 (1H, m), 9.21 (2H, brs); Anal. Calcd for C18H17 ClN4O2S: C, 55.59; H, 4.41; N, 14.41.
Found: C, 55.46; H, 4.31; N, 14.32.
5.7. N-Methyl-1-[1-(phenylsulfonyl)-5-(pyridin-2-yl)-1H-pyrrol-3-yl]methanamine oxalate (17a)
To a solution of 16a (78 mg, 0.25 mmol) in MeOH (10 mL) was added 40% methylamine methanol
solution (100 mg, 1.28 mmol) at room temperature. After stirred for 10 min, sodium borohydride (29
mg, 0.77 mmol) was added at room temperature, and the reaction mixture was stirred for 1 h and
then quenched with 1 mol/L HCl (20 mL). After stirred for 10 min, the mixture was basified with a
solution of NaHCO3 and extracted with EtOAc. The extract was washed with brine, dried over
anhydrous MgSO4, and concentrated under reduced pressure. The residue was purified by basic
silica gel column chromatography (EtOAc/MeOH = 1/07/3) and dissolved in EtOAc (10 mL).
Oxalic acid (50 mg) was added, and the mixture was stirred for 15 min. The resulting crystals were
1
collected by filtration to obtain 17a (47 mg, 45%) as colorless crystals: mp 146148 C; H-NMR
(DMSO-d6)  2.55 (3H, s), 4.02 (2H, s), 6.70 (1H, d, J = 1.8 Hz), 7.337.38 (1H, m), 7.517.54 (1H,
m), 7.637.68 (2H, m), 7.747.91 (5H, m), 8.448.46 (1H, m), 3H not detected; HRMS (ESI) calcd
for C17H17N3O2S (M+H)+ m/z 328.1114, found m/z 328.1085.
5.8.
N-Methyl-1-{5-(2-methylphenyl)-1-[(4-methylphenyl)sulfonyl]-1H-pyrrol-3-yl}methanamine
hydrochloride (17b)
To a solution of 16b (0.46 g, 1.36 mmol) in THF was added methylamine hydrochloride (1.11 g,
13.6 mmol) and sodium cyano borohydride (0.26 g, 4.14 mmol), and the mixture was stirred at room
temperature for 20 h and then concentrated under reduced pressure. A solution of NaHCO3 was
added, and then the mixture was extracted with EtOAc. The extract was washed with brine, dried
23

over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by silica gel
column chromatography (EtOAc/MeOH = 1/05/1) and dissolved in EtOAc (5 mL). 4 mol/L
HCl/EtOAc (2 mL) was added, and the mixture was concentrated in vacuo. The residue was
crystalized from n-hexane/EtOAc to produce 17b (0.37 g, 70%) as colorless cryatals: mp 192193
C; 1H-NMR (DMSO-d6)  1.79 (3H, s), 2.38 (3H, s), 3.32 (3H, s), 4.00 (2H, s), 6.34 (1H, d, J = 1.8
Hz), 6.84 (1H, d, J = 6.2 Hz), 7.117.21 (2H, m), 7.257.36 (6H, m), 7.72 (1H, s), 9.02 (1H, br);
Anal. Calcd for C20H23ClN2O2S: C, 61.45; H, 5.93; N, 7.17. Found: C, 61.23; H, 5.96; N, 7.22.
5.9.
N-Methyl-1-{1-[(4-methylphenyl)sulfonyl]-5-[2-(trifluoromethyl)phenyl]-1H-pyrrol-3-yl}methanami
ne hydrochloride (17c)
Compound 17c was prepared from compound 16c using a similar procedure as for the preparation of
1
compound 17b. White crystals (35%): mp 195196 C; H-NMR (DMSO-d6)  2.39 (3H, s), 2.50
(3H, s), 3.32 (2H, s), 6.43 (1H, s), 7.12 (1H, d, J = 6.8 Hz), 7.37 (4H, s), 7.637.79 (4H, m), 8.92
(2H, br); Anal. Calcd for C20H20ClF3N2O2S: C, 53.99; H, 4.53; N, 6.30. Found: C, 53.91; H, 4.55; N,
6.24.
5.10.
1-{5-(2-fluorophenyl)-1-[(4-methylphenyl)sulfonyl]-1H-pyrrol-3-yl}-N-methylmethanamine
hydrochloride (17d)
Compound 17d was prepared from compound 16d using a similar procedure as for the preparation
of compound 17b. White crystals (76%): mp 172 C; 1H-NMR (DMSO-d6)  2.37 (3H, s), 3.32 (3H,
s), 3.97 (2H, s), 6.48 (1H, d, J = 1.8 Hz), 7.027.08 (1H, m), 7.187.34 (6H, m), 7.477.55 (1H, m),
7.74 (1H, d, J = 1.8 Hz), 9.01 (2H, brs); Anal. Calcd for C19H20ClFN2O2S: C, 57.79; H, 5.10; N, 7.09.
Found: C, 57.57; H, 5.21; N, 6.79.
5.11.
1-{5-(3-Fluorophenyl)-1-[(4-methylphenyl)sulfonyl]-1H-pyrrol-3-yl}-N-methylmethanamine
hydrochloride (17e)
Compound 17e was prepared from compound 16e using a similar procedure as for the preparation of
1
compound 17b. White crystals (69%): mp 164165 C; H-NMR (DMSO-d6)  2.36 (3H, s), 3.32
(3H, s), 3.98 (2H, s), 6.48 (1H, d, J = 1.8 Hz), 6.947.00 (2H, m), 7.257.45 (6H, m), 7.73 (1H, d, J
= 1.8 Hz), 8.94 (2H, brs); Anal. Calcd for C19H20ClFN2O2S: C, 57.79; H, 5.10; N, 7.09. Found: C,
57.82; H, 5.20; N, 6.87.
5.12.
1-{5-(4-Fluorophenyl)-1-[(4-methylphenyl)sulfonyl]-1H-pyrrol-3-yl}-N-methylmethanamine
hydrochloride (17f)
Compound 17f was prepared from compound 16f using a similar procedure as for the preparation of
24

compound 17b. White crystals (71%): mp 224 C; 1H-NMR (DMSO-d6)  2.36 (3H, s), 2.51 (3H, s),
3.97 (2H, s), 6.43 (1H, d, J = 1.8 Hz), 7.167.36 (8H, m), 7.71 (1H,s), 9.05 (1H, brs), 1H not
detected; Anal. Calcd for C19H20ClFN2O2S: C, 57.79; H, 5.10; N, 7.09. Found: C, 57.57; H, 5.09; N,
6.97.
5.13.
1-{1-[(3-Fluorophenyl)sulfonyl]-5-(2-fluoropyridin-3-yl)-1H-pyrrol-3-yl}-N-methylmethanamine
hydrochloride (24a)
Compound 24a was prepared from 20a using a similar procedure as for the preparation of compound
1
3d from 4d. Colorless crystals (54%): mp 211212 C; H-NMR (DMSO-d6)  2.51 (3H, s), 3.99
(2H, s), 6.67 (1H, d, J = 1.8 Hz), 7.337.36 (2H, m), 7.417.46 (1H, m), 7.657.76 (3H, m), 7.87
(1H, d, J = 1.8 Hz), 8.348.36 (1H, m), 9.18 (2H, brs); Anal. Calcd for C17H16ClF2N3O2S: C, 51.07;
H, 4.03; N, 10.51. Found: C, 51.01; H, 4.04; N, 10.46.
5.14.
1-{5-(2-Fluoropyridin-3-yl)-1-[(3-methoxyphenyl)sulfonyl]-1H-pyrrol-3-yl}-N-methylmethanamine
fumarate (24b)
To a solution of compound 20b (303 mg, 0.637 mmol) in EtOAc (1 mL) and MeOH (1 mL) was
added dropwise 4 mol/L HCl/EtOAc (3 mL), and the mixture was stirred at room temperature for 2 h.
The reaction was quenched by a solution of NaHCO3, and the resulting mixture was extracted with
EtOAc. The extract was washed with brine, dried over anhydrous Na2SO4, and concentrated under
reduced pressure. The residue was purified by basic silica gel column chromatography
(n-hexane/EtOAc = 1/11/9), and then dissolved in EtOAc (2 mL). A solution of fumaric acid (46
mg) in MeOH (2 mL) was added to the solution, and then the mixture was concentrated under
reduced pressure. The residue was recrystallized from EtOH/H2O (9/1) to produce 24b (138 mg,
44%) as colorless crystals: mp 177 C; 1H-NMR (DMSO-d6)  2.40 (3H, s), 3.75 (3H, s), 3.82 (2H,
s), 6.47 (2H, s), 6.53 (1H, d, J = 1.5 Hz), 6.866.88 (1H, m), 7.057.08 (1H, m), 7.277.31 (1H, m),
7.387.51 (2H, m), 7.697.75 (2H, m), 8.318.32 (1H, m), 3H not detected; Anal. Calcd for
C22H22FN3O7S: C, 53.76; H, 4.51; N, 8.55. Found: C, 53.61; H, 4.53; N, 8.58.
5.15.
3-({2-(2-Fluoropyridin-3-yl)-4-[(methylamino)methyl]-1H-pyrrol-1-yl}sulfonyl)benzonitrile
fumarate (24c)
Compound 24c was prepared from 20c using a similar procedure as for the preparation of compound
24b from 20b. Colorless crystals (44%): mp 149 C; 1H-NMR (DMSO-d6)  2.40 (3H, s), 3.82 (2H,
s), 6.47 (2H, s), 6.57 (1H, d, J = 1.8 Hz), 7.397.44 (1H, m), 7.717.81 (4H, m), 7.957.96 (1H, m),
8.218.24 (1H, m), 8.328.34 (1H, m), 3H not detected; Anal. Calcd for C22H19FN4O6S: C, 54.32; H,
25

3.94; N, 11.52. Found: C, 54.25; H, 4.01; N, 11.52.
5.16. 1-[5-(2-Fluoropyridin-3-yl)-1-(thiophen-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (24d)
Compound 24d was prepared from 20d using a similar procedure as for the preparation of
1
compound 24b from 20b. Colorless crystals (63%): mp 173175 C; H-NMR (DMSO-d6)  2.41
(3H, s), 3.81 (2H, s), 6.48 (2H, s), 6.53 (1H, d, J = 1.8 Hz), 7.087.10 (1H, m), 7.387.42 (1H, m),
7.647.79 (3H, m), 8.088.10 (1H, m), 8.308.32 (1H, m), 3H not detected; Anal. Calcd for
C19H18FN3O6S2: C, 48.81; H, 3.88; N, 8.99. Found: C, 48.87; H, 3.90; N, 8.95.
5.17. 1-[5-(2-Fluoropyridin-3-yl)-1-(thiophen-2-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (24e)
Compound 24e was prepared from 23e using a similar procedure as for the preparation of compound
1
3c from 7. Colorless crystals (75%): mp 204 C; H-NMR (DMSO-d6)  2.40 (3H, s), 3.80 (2H, s),
6.48 (2H, s), 6.55 (1H, d, J = 1.5 Hz), 7.18 (1H, dd, J = 4.9 Hz, 4.2 Hz), 7.407.45 (1H, m), 7.47
(1H, dd, J = 4.0 Hz, 1.3 Hz), 7.62 (1H, d, J = 1.5 Hz), 7.757.82 (1H, m), 8.11 (1H, dd, J = 5.1 Hz,
1.3 Hz), 8.318.33 (1H, m), 3H not detected; Anal. Calcd for C19H18FN3O6S2: C, 48.81; H, 3.88; N,
8.99. Found: C, 48.88; H, 4.09; N, 9.06.
5.18.
1-[5-(2-Fluoropyridin-3-yl)-1-(furan-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
hydrochloride (24f)
To a solution of compound 20f (253 mg, 0.581 mmol) in EtOAc (3 mL) and iPrOH (2 mL) was
added dropwise 4 mol/L HCl/EtOAc (6 mL), and the mixture was stirred at room temperature for 2.5
h, and then concentrated in vacuo. The residue was recrystallized from EtOAc/EtOH (1/1) to obtain
24f (134 mg, 62%) as colorless crystals: mp 205 C; 1H-NMR (DMSO-d6)  2.53 (3H, s), 4.00 (2H,
s), 6.636.67 (2H, m), 7.43 (1H, ddd, J=7.1 Hz, 5.0 Hz, 1.9 Hz), 7.75 (1H, d, J = 1.9 Hz), 7.80 (1H,
ddd, J = 9.6 Hz, 7.5 Hz, 1.9 Hz), 7.94 (1H, t, J = 1.9 Hz), 8.278.30 (1H, m), 8.318.37 (1H, m),
9.03 (2H, brs); Anal. Calcd for C15H15ClFN3O3S: C, 48.45; H, 4.07; N, 11.30. Found: C, 48.48; H,
4.04; N, 11.34.
5.19.
1-[5-(2-Fluoropyridin-3-yl)-1-(furan-2-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (24g)
Compound 24g was prepared from 23g using a similar procedure as for the preparation of compound
1
3c from 7. Colorless crystals (66%): mp 197 C; H-NMR (DMSO-d6)  2.41 (3H, s), 3.81 (2H, s),
6.48 (2H, s), 6.58 (1H, d, J = 1.9 Hz), 6.72 (1H, dd, J = 3.7 Hz, 1.8 Hz), 7.10 (1H, dd, J = 3.7 Hz,
0.8 Hz), 7.407.44 (1H, m), 7.57 (1H, d, J = 1.8 Hz), 7.787.84 (1H, m), 8.07 (1H, dd, J = 1.8 Hz,
26

0.8 Hz), 8.308.33 (1H, m), 3H not detected; Anal. Calcd for C19H18FN3O7S: C, 50.55; H, 4.02; N,
9.31. Found: C, 50.65; H, 4.15; N, 9.48.
5.20.
1-[5-(2-Fluoropyridin-3-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (24h)
Compound 24h was prepared from 20h using a similar procedure as for the preparation of
1
compound 24b from 20b. Colorless crystals (29%): mp 183184 C; H-NMR (DMSO-d6)  2.39
(3H, s), 3.78 (2H, s), 6.48 (2H, s), 6.56 (1H, d, J = 1.8 Hz), 7.407.44 (1H, m), 7.617.65 (1H, m),
7.727.79 (2H, m), 7.897.93 (1H, m), 8.328.34 (1H, m), 8.62 (1H, d, J = 1.8 Hz), 8.888.90 (1H,
m), 3H not detected; Anal. Calcd for C20H19FN4O6S: C, 51.94; H, 4.14; N, 12.12. Found: C, 51.92;
H, 4.23; N, 12.04.
5.21.
1-[5-(2-Fluoropyridin-3-yl)-1-(pyridin-2-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
hydrochloride (24i)
Compound 24i was prepared from 20i using a similar procedure as for the preparation of compound
3d from 4d. Colorless crystals (15%): mp 198 C; 1H-NMR (DMSO-d6)  2.53 (3H, s), 3.34 (2H, s),
6.64 (1H, d, J = 1.3 Hz), 7.38 (1H, ddd, J = 7.2 Hz, 5.0 Hz, 1.9 Hz), 7.617.88 (4H, m), 8.10 (1H, dt,
J = 7.8 Hz, 1.7 Hz), 8.248.38 (1H, m), 8.71 (1H, dt, J = 3.9 Hz, 0.8 Hz), 8.93 (2H, brs); HRMS
(ESI) calcd for C16H15FN4O2S (M+H)+ m/z 347.0973, found m/z 347.0936.
5.22.
1-{5-(2-fluoropyridin-3-yl)-1-[(6-methoxypyridin-3-yl)sulfonyl]-1H-pyrrol-3-yl}-N-methylmethanam
ine hydrochloride (24j)
Compound 24j was prepared from 20j using a similar procedure as for the preparation of compound
1
3d from 4d. Colorless crystals (29%): mp 223225 °C; H-NMR (DMSO-d6)  2.52 (3H, s), 3.94
(3H, s), 3.99 (2H, s), 6.65 (1H, d, J = 1.8 Hz), 6.997.02 (1H, m), 7.427.47 (1H, m), 7.737.80 (2H,
m), 7.84 (1H, d, J = 1.8 Hz), 8.278.28 (1H, m), 8.348.36 (1H, m), 9.10 (2H, brs). Anal. Calcd for
C17H18ClFN4O3S: C, 49.45; H, 4.39; N, 13.57. Found: C, 49.16; H, 4.42; N, 13.44.
5.23.
1-[5-(2-Chloropyridin-3-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (26a)
To a solution of compound 25a (280 mg, 0.605 mmol) in MeOH (10 mL) was added dropwise 4
mol/L HCl/EtOAc (2 mL), and the mixture was stirred at 70 C for 30 min, and then concentrated in
vacuo. A solution of NaHCO3 was added to the residue and the mixture was extracted with EtOAc.
The extract was washed with brine, dried over anhydrous MgSO4, and concentrated under reduced
pressure. The residue was dissolved in EtOAc (10 mL), and a solution of fumaric acid (116 mg, 1.0
27

mmol) in MeOH (3 mL) was added dropwise to the solution. The resulting crystals were collected
by filtration and rinsed with EtOAc to obtain 26a (197 mg, 68%) as colorless crystals: mp 170174
1
C; H-NMR (DMSO-d6)  2.40 (3H, s), 3.81 (2H, s), 6.49 (2H, s), 6.52 (1H, d, J = 1.9 Hz),
7.477.52 (1H, m), 7.617.73 (3H, m), 7.907.94 (1H, m), 8.50 (1H, dd, J = 4.9 Hz, 1.9 Hz),
8.638.64 (1H, m), 8.90 (1H, dd, J = 4.5 Hz, 1.5 Hz), 3H not detected. Anal. Calcd for
C20H19ClN4O6S: C, 50.16; H, 4.00; N, 11.70. Found: C, 49.98; H, 4.06; N, 11.63.
5.24. 3-{4-[(Methylamino)methyl]-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-2-yl}pyridine-2-carbonitrile
fumarate (26b)
Compound 26b was prepared from 25b using a similar procedure as for the preparation of
1
compound 24b from 20b. Colorless crystals (39%): mp 204205 C; H-NMR (DMSO-d6)  2.39
(3H, s), 3.83 (2H, s), 6.48 (2H, s), 6.74 (1H, d, J = 1.8 Hz), 7.607.65 (1H, m), 7.787.83 (2H, m),
7.887.95 (2H, m), 8.588.59 (1H, m), 8.808.82 (1H, m), 8.898.91 (1H, m), 3H not detected.
Anal. Calcd for C21H19N5O6S: C, 53.73; H, 4.08; N, 14.92. Found: C, 53.54; H, 4.03; N, 14.92.
5.25.
N-Methyl-1-[5-(2-methylpyridin-3-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]methanamine
fumarate (26c)
Compound 26c was prepared from 25c using a similar procedure as for the preparation of compound
24b from 20b. Colorless crystals (32%): mp 203204 °C; 1H-NMR (DMSO-d6)  2.00 (3H, s), 2.43
(3H, s), 3.83 (2H, s), 6.42 (1H, s), 6.47 (2H, s), 7.207.24 (1H, m), 7.287.31 (1H, m), 7.597.63
(1H, m), 7.70 (1H, s), 7.807.84 (1H, m), 8.498.51 (2H, m), 8.888.90 (1H, m), 3H not detected.
Anal. Calcd for C21H22N4O6S: C, 55.01; H, 4.84; N, 12.22. Found: C, 54.94; H, 4.90; N, 12.25.
5.26.
N-Methyl-1-[5-(4-methylpyridin-3-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]methanamine
fumarate (26d)
Compound 26d was prepared from 25d using a similar procedure as for the preparation of
compound 24b from 20b. Colorless crystals (48%): mp 184 °C; 1H-NMR (DMSO-d6)  1.89 (3H, s),
2.43 (3H, s), 3.84 (2H, s), 6.45 (1H, d, J = 1.9 Hz), 6.48 (2H, s), 7.29 (1H, d, J = 4.9 Hz),
7.607.65 (1H, m), 7.73 (1H, d, J = 1.9 Hz), 7.817.85 (1H, m), 7.98 (1H, s), 8.47 (1H, d, J = 4.9
Hz), 8.51 (1H, d, J = 1.9 Hz), 8.90 (1H, dd, J = 4.9 Hz, 1.5 Hz), 3H not detected. Anal. Calcd for
C21H22N4O6S: C, 55.01; H, 4.84; N, 12.22. Found: C, 54.73; H, 4.79; N, 12.16.
5.27.
N-Methyl-1-[5-(3-methylpyridin-2-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]methanamine
fumarate (26e)
Compound 26e was prepared from 25e using a similar procedure as for the preparation of compound
24b from 20b. Colorless crystals (53%): mp 185186 °C; 1H-NMR (DMSO-d6)  2.18 (3H, s), 2.44
28

(3H, s), 3.86 (2H, s), 6.46 (2H, s), 6.52 (1H, d, J = 1.8 Hz), 7.327.36 (1H, m), 7.667.74 (3H, m),
8.178.21 (1H, m), 8.288.30 (1H, m), 8.878.90 (2H, m), 3H not detected; Anal. Calcd for
C21H22N4O6S: C, 55.01; H, 4.84; N, 12.22. Found: C, 54.95; H, 4.82; N, 12.24.
5.28.
1-[5-(3-Fluoropyridin-4-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (26f)
A degassed mixture of compound 19h (215 mg, 0.50 mmol), (3-fluoropyridin-4-yl)boronic acid (120
mg, 0.76 mmol), tetrakis(triphenylphosphine)palladium (87 mg, 0.075 mmol) and NaHCO3 (126 mg,
1.50 mmol) in DME (8 mL) and water (2 mL) was stirred at 80 C for 6 h. After cooling to room
temperature, the reaction mixture was diluted with a solution of NaHCO3, and extracted with EtOAc.
The extract was washed with brine, dried over anhydrous MgSO4, and concentrated under reduced
pressure. The residue was purified by basic silica gel column chromatography (n-hexane/EtOAc =
1/1), and then the obtained a pale yellow oil (60 mg) was dissolved in MeOH (5 mL). 4 mol/L
HCl/EtOAc (1.5 mL) was added to the solution, and the mixture was stirred at 70 C for 30 min, and
then concentrated in vacuo. A solution of NaHCO3 was added to the residue and the mixture was
extracted with EtOAc. The extract was washed with brine, dried over anhydrous MgSO4, and
concentrated under reduced pressure. The residue was dissolved in EtOAc (5 mL), and a solution of
fumaric acid (19 mg, 0.164 mmol) in MeOH (1 mL) was added to the solution. The resulting crystals
were collected by filtration and rinsed with EtOAc to obtain 26f (45 mg, 19%) as colorless crystals:
mp 201 °C; 1H-NMR (DMSO-d6)  2.37 (3H, s), 3.78 (2H, s), 6.49 (2H, s), 6.64 (1H, d, J = 1.5 Hz),
7.307.33 (1H, m), 7.627.66 (1H, m), 7.77 (1H, d, J = 1.5 Hz), 7.947.98 (1H, m), 8.498.51 (1H,
m), 8.64 (1H, d, J = 1.5 Hz), 8.69 (1H, d, J = 2.3 Hz), 8.90 (1H, dd, J = 4.9 Hz, 1.5 Hz), 3H not
detected. Anal. Calcd for C20H19FN4O6S: C, 51.94; H, 4.14; N, 12.12. Found: C, 51.73; H, 4.13; N,
12.15.
5.29.
1-[5-(2-Fluoropyridin-3-yl)-4-methyl-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-
methylmethanamine fumarate (37a)
Compound 37a was prepared from 36a using a similar procedure as for the preparation of compound
3c from 7. Colorless crystals (32%): mp 173175 °C; 1H-NMR (DMSO-d6)  1.76 (3H, s), 2.42 (3H,
s), 3.75 (2H, s), 6.50 (2H, s), 7.427.46 (1H, m), 7.597.75 (3H, m), 7.847.88 (1H, m), 8.338.35
(1H, m), 8.568.57 (1H, m), 8.868.88 (1H, m), 3H not detected; Anal. Calcd for C21H21FN4O6S: C,
52.94; H, 4.44; N, 11.76. Found: C, 52.66; H, 4.42; N, 11.76.
5.30.
1-[4-chloro-5-(2-fluoropyridin-3-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine
fumarate (37b)
29