Design, synthesis, and biological evaluation of spiroindolines as novel inducers of oligodendrocyte progenitor cell differentiation—Use of a conformation-based hypothesis to facilitate compound design

Article abstract of DOI:10.1016/j.bmcl.2020.127299

Inducing oligodendrocyte progenitor cell (OPC) differentiation is a novel therapeutic strategy for the treatment of demyelinating diseases such as multiple sclerosis (MS). In the preceding article, we detailed the discovery of compound 1, a potent inducer of OPC differentiation possessing a characteristic spiroindoline structure. Also, we found that N-methylation and des-carbonyl compound 1 (4) led to a loss in potency. Herein, we describe our investigations of a conformation-based hypothesis for OPC differentiation activity based on the preferred conformation of the spiro core, and further structure–activity relationship (SAR) exploration led to the identification of 6-CF₃ derivative 8, which was more potent compared to compound 1.

Full text of DOI:10.1016/j.bmcl.2020.127299

Journal Pre-proofs
Design, synthesis, and biological evaluation of spiroindolines as novel induc‐
ers of oligodendrocyte progenitor cell differentiation—Use of a conformation-
based hypothesis to facilitate compound design
Katsushi Katayama, Tsutomu Nagata, Kouhei Takashima, Ayako Yoshida,
Hiroyuki Okada, Yoshiaki Oyama, Tsuyoshi Muto
PII:
S0960-894X(20)30410-8
DOI:
Reference:
https://doi.org/10.1016/j.bmcl.2020.127299
BMCL 127299
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Bioorganic & Medicinal Chemistry Letters
Received Date:
Revised Date:
Accepted Date:
30 March 2020
24 May 2020
29 May 2020
Please cite this article as: Katayama, K., Nagata, T., Takashima, K., Yoshida, A., Okada, H., Oyama, Y., Muto,
T., Design, synthesis, and biological evaluation of spiroindolines as novel inducers of oligodendrocyte progenitor
cell differentiation—Use of a conformation-based hypothesis to facilitate compound design, Bioorganic &
Medicinal Chemistry Letters (2020), doi: https://doi.org/10.1016/j.bmcl.2020.127299
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Bioorganic & Medicinal Chemistry Letters
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Design, synthesis, and biological evaluation of spiroindolines as novel inducers of
oligodendrocyte progenitor cell differentiation—Use of a conformation-based
hypothesis to facilitate compound design
Katsushi Katayama*,a, Tsutomu Nagataa, Kouhei Takashimaa, Ayako Yoshidab, Hiroyuki Okadaa, Yoshiaki
Oyama, and Tsuyoshi Mutoa
Asubio Pharma Co., Ltd., 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
 Corresponding author. e-mail: katayama.katsushi.ne@daiichisankyo.co.jp
aPresent address: Shinagawa R&D Center, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
bPresent address: Daiichi Sankyo Co., Ltd., 3-5-1 Nihonbashi-honcho, Chuo-ku, Tokyo 103-8426, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Inducing oligodendrocyte progenitor cell (OPC) differentiation is a novel therapeutic strategy for
the treatment of demyelinating diseases such as multiple sclerosis (MS). In the preceding article,
we detailed the discovery of compound 1, a potent inducer of OPC differentiation possessing a
characteristic spiroindoline structure. Also, we found that N-methylation and des-carbonyl
compound 1 (4) led to a loss in potency. Herein, we describe our investigations of a
conformation-based hypothesis for OPC differentiation activity based on the preferred
conformation of the spiro core, and further structure-activity relationship (SAR) exploration led
to the identification of 6-CF3 derivative 8, which was more potent compared to compound 1.
Available online
Keywords:
multiple sclerosis (MS)
myelin
oligodendrocyte progenitor cell (OPC)
spiroindoline
2020 Elsevier Ltd. All rights reserved.
conformational analysis
Multiple sclerosis (MS) is
a
chronic, autoimmune,
We aimed to create a novel MS therapeutic agent that induces
OPC differentiation by evaluating the differentiation-inducing
action (expressed as myelin basic protein expression level) in
OPCs derived from primary rat neonates (hereafter referred to as
rOPC).8 In the preceding article,9 we detailed the synthesis and
structure-activity relationships (SARs) of inducers of OPC
differentiation. These studies led to the discovery of compound 1,
a potent inducer of OPC differentiation with excellent in vitro
and in vivo properties (Fig. 1). Furthermore, we also identified
differences in the activities of this series of compounds (1 [C5-
CF3, N-H, carbonyl], 2 [C5-CF3, N-Me, carbonyl], 3 [C5-CF3, N-
H, des-carbonyl], and 4 [C5-CF3, N-Me, des-carbonyl]). We
suspected that these activity differences arose from the
conformational preferences of the series of compounds reported
previously.10 Herein, we describe the conformational analysis of
this series of compounds to understand the SAR. Furthermore,
the design and synthesis of novel spiroindolines based on a
conformation-based hypothesis and a SAR study of OPC
differentiation activity are described.
inflammatory, and demyelinating disease affecting about 2.5
million people worldwide.1 In particular, MS is the most common
cause of neurological disability among young adults in North
America and Europe.2 Clinically, there are various MS treatment
approaches available that have been shown to decrease the
frequency of relapses and delay disease progression. Examples
include
interferon-β-1b
(IFN-β),
glatiramer
acetate,
mitoxantrone, fingolimod, teriflunomide, dimethyl fumarate,
natalizumab, and ocrelizumab.3 Although effective in reducing
the relapse rate and the formation of new lesions, these drugs
have a limited effect in preventing the progression of disability.4
Most current MS treatments are disease-modifying agents and
treat relapsing-remitting MS (RRMS) and none of the therapies
directly address the neurological deterioration (demyelination
and neuronal death).5 However, promoting oligodendrocyte
progenitor cell (OPC) differentiation, remyelination, and
subsequent functional recovery of the neurons has been proposed
as
a
new direction for MS therapy.6 In particular, the
identification of small molecules that induce the differentiation of
OPCs at sites of demyelinated lesions thereby promoting
endogenous remyelination and/or decreased axonal degeneration
would have a considerable impact on the development of new
and effective treatments for demyelinating diseases such as MS.7
This series of compounds can adopt two chair conformations:
the cis conformation (A: anilino nitrogen is axial) and the trans
conformation (B: anilino nitrogen is equatorial), as shown in Fig.
2.10 Also, that substituent R1 would act as a conformational
"switch" between conformation A and B for this ring system has
been proposed.

O
O
O
O
O
O
O
F3C
H
F3C
O
N
H
N
N
N
H
N
H
N
Me
H
F3C
H
1
2
rOPC EC50 = 0.0032 μM
rOPC EC50 = 0.0093 μM
1
H
Me
F3C
N
H
F3C
N
N
O
N
H
N
H
N
H
F3C
O
Me
3
4
5
rOPC EC50 = 0.24 μM
rOPC EC50 = 7.1 μM
Fig. 4. Single-crystal X-ray structures
of compounds 1 and 5.
Fig. 1. Chemical structure and activity of compounds 1−4.
R2
H
O
H
O
N
H
N
H
R2
group is more sterically demanding than the carbonyl oxygen,
and thus the carbonyl group now prefers to be in proximity to the
Ha axial protons in the trans conformation. Therefore, alkylation
of the indoline nitrogen results in an inversion of the piperidine
chair conformation. Similarly, des-carbonyl compound 4 adopts
the trans conformation B.
H
H
N
H
N
F3C
H
F3C
R1
R1
A (cis)
A'
R1
N
F3C
F3C
H
N
O
O
H
R2
H
H
Furthermore, we confirmed the conformation of compound 1
and N-methyl derivative 511 by single-crystal X-ray analysis as
shown in Fig. 4. The X-ray structures of compounds 1 (CCDC
H
H
H
R2
O
N
H
N
H
N
N
H
H
R1
R1
F3C
R2
H
B (trans)
B'
1993534) and
5 (CCDC 1993532) were suggestive of
Fig. 2. Conformational change of spiroindolines.
predominant cis and trans conformations, respectively, and these
results are consistent with the above NMR structure data.
On the other hand, the situation of compound 3 was different
from that of compounds 1, 2, and 4. Namely, in the nuclear
Overhauser effect spectroscopy (NOESY) spectrum of compound
3, NOE correlations of protons at the α-position to the piperidine
nitrogen (Ha or Hb) with both indoline NH and methylene protons
were observed (Fig. 5). This observation confirms that the
conformation of compound 3 involves both A and B due to
compound 3 being a fast equilibrium between the A and B
conformations.12 This was because there was no steric difference
between methylene and NH and so the energy difference between
By reference to the report,10 we first examined the
conformation of compound 1 and N-methyl derivative 2 as
shown in Fig. 3. The nuclear Overhauser effect (NOE) data
observed between the aniline NH and both the Hb axial and Hd
equatorial protons in compound 1 indicated that the aniline
nitrogen occupies an axial position and predominantly adopts the
cis conformation A. In contrast, the NOE data in compound 2
showed that the aniline nitrogen is in the equatorial position and
adopts the trans conformation B, which is supported by the NOE
correlation observed between the methyl group on the aniline
nitrogen and the axial Hd proton. As in the discussion in the
previous report,10 we suggested that compound 1 exists in the cis
conformer so that the carbonyl group would avoid the Ha axial
protons to minimize 1,3-diaxial interactions found in the trans
conformation (Fig. 3). In the case of compound 2, the methyl
H
H
N
H
R
H
N
H
H
R
N
H
a
a
b
H
H
b
H
N
H
H
F3C
H
H
NOE
d
F3C
c
H
H
H
d
R
A
B
O
N
H
a
R
H
N
H
b
b
H
N
a
R = 4-THP: 3
c
H
H
H
H
A and B is small and there is no dominant conformation.
H
N
H
F3C
O
H
Fig. 5. Conformational analysis of compound 3.
F3C
B
A
R = 4-THP: 1
From the above analysis, the conformations of the
compounds were affected by the substitution pattern of the
indoline part and it could also be expected that the substituent
effect on the benzene ring would be different between the
d
H
c
Me
H
R
N
H
a
O
R
H
N
H
b
b
N
a
c
H
H
H
d
H
H
H
compounds with different conformations. That is, in
a
N
H
F3C
O
Me
comparison between conformation A and conformation B,
although there is no significant difference in the positions of the
nitrogen atom in the piperidine ring and the benzene ring, the
positions and orientations of the aniline nitrogen atom and the
trifluoromethyl substituent on the benzene ring are different.
Therefore, we expected that the N-alkylated compound, in which
the predominant conformation is B, could improve the potency
by shifting the substitution position on the benzene ring from C-5
to C-6, because the C-6 trifluoromethyl substituent in compounds
in the B conformation is in the same orientation as the C-5
substituent in the high-potency compound 1 as shown in Fig. 6.
F3C
B
A
R = 4-THP: 2
c
d
H
H
Me
H
H
R
N
H
b
R
N
H
a
a
N
b
d
c
H
H
H
N
H
F3C
H
Me
H
NOE
F3C
A
B
R = 4-THP: 4
Fig. 3. Conformational analysis of compounds 1, 2, and 4.

Table 1. SAR of the substituents on the aniline group.
H
H
O
Me
H
R
Me
N
H
R
N
H
R
N
H
N
N
N
H
5
H
H
H
H
H
H
6
N
H
N
F3C
H
F3C
H
F3C
H
O
O
R1
5
F3C
O
R = 4-THP: 2
R = 4-THP: 1
EC50 = ? μM
conformation B
EC50 = 0.0093 μM
Compound
R1
rOPC EC50 (μM)
EC50 = 0.0032 μM
conformation A
conformation B
Fig. 6. Design of C-6 trifluoromethyl derivative.
8
0.0019
Me
O
9
0.015
0.70
On the basis of this working hypothesis, we examined the SAR
of 6-trifluoro N-methyl derivatives.
OtBu
O
As expected, the 6-trifluoromethyl substituent derivative (7)
resulted in increased potency (EC50 = 0.0014 μM; Fig. 7). In
addition, to test the hypothesis, the 6-trifluoromethyl substituent
of compound 1 (6) was synthesized, and compound 6 led to a 10-
10
11
N
0.074
OH
fold decrease in the potency compared to compound 1 (EC50
=
0.054 μM). This result supports the working hypothesis that
placing the trifluoromethyl substituent in the appropriate location
increases the activity.13 Moreover, deletion of the carbonyl group
(8) led to the same level of OPC differentiation potency as
compound 7. In sharp contrast to compound 8, des-carbonyl
compound 4, which has a 5-trifluoromethyl substituent, showed a
significant loss of potency (3700-fold), suggesting that
introducing a substituent (CF3) at the appropriate position is
necessary for the high potency. As already shown, des-carbonyl
compound 3 was significantly less potent than compound 1.
Compound 3 was in rapid equilibrium between the two
conformers A and B without taking a predominant conformation,
suggesting that the compound in which the substituent is not
conformed at an appropriate position has less activity and that the
equilibrium state increases the entropy loss for the active
conformation. Taken together, the introduction of a substituent
(CF3) at the appropriate position, and a conformation restriction
to reduce the entropic penalty and adopt a favorable binding
conformation, led to a high potency.14
Since a series of the indolinone derivatives such as compound
7 is fluorescent substance, we were concerned that the indolinone
derivatives might exhibit phototoxicity.15 Therefore, we selected
indoline derivatives which do not show the fluorescent to explore
the SAR. First, we examined the substitution on the aniline group
of des-carbonyl compound 8 (Table 1). Replacement of the
methyl group with a tert-butoxyacetyl (9) or N,N-dimethyl-
acetamide group (10) decreased the activity. Likewise, replacing
12
13
14
0.013
0.060
0.0037
O
O
All the substituents on the aniline group of compounds listed
in Table 1 are larger and bulkier than the methyl group,
suggesting that all compounds would be adopted conformation
B.16 Therefore, these results suggested that the introduction of
more polar groups usually led to decrease the potency
presumably due to the unfavorable interaction with the target
molecule, while a lipophilic substituent, such as a benzyl group
(14), led to a robust potency.
The results of tetrahydropyranylmethyl group modification
are summarized in Table 2. A methoxyethyl group (15) and a
methoxypropyl group (16) demonstrated significantly decreased
potency, suggesting that the position of the oxygen atom is
important
for
the
potency.
Replacement
of
the
tetrahydropyranylmethyl group with a 4-methoxytetrahydro-
pyranylmethyl group (17) resulted in a loss in potency, while
compounds with a 4-hydroxytetrahydropyranylmethyl (18) or
difluorocyclohexylmethyl (19) group retained the potency.
Next, we turned our attention to the 6-position on the indoline
core (Table 3). In contrast to the indolinone derivatives,9
replacing the trifluoromethyl group of compound 8 with a less
lipophilic fluoro group (20) or a chloro group (21) resulted in
only a slight loss in potency (5–10 fold) versus 8.
the methyl group with
a
hydroxyethyl (11) or
tetrahydropyranylmethyl (12) group resulted in a loss in potency
versus compound 8. Moreover, N-acetyl derivative 13 had
decreased potency, while benzyl derivative 14 retained the
potency (EC50 = 0.0037 μM).
O
O
O
H
H
H
Me
O
H
N
H
N
N
H
N-methylation
C=O

N
N
H
H
H
H
H
H
5
H
H
H
H
N
R1
H
H
H
H
H
H
5
5
6
F3C
R2
F3C
conformation A
conformation B
4
EC50 = 7.1 μM
conformation A&B
3
EC50 = 0.24 μM
R1 = CF3, R2 = H; 1 EC50 = 0.0032 μM
R1 = H, R2 = CF3; 6 EC50 = 0.054 μM
N-methylation
x 3700-fold
O
O
O
H
N
H
H
Me
Me
Me
CF3
N
H
N
H
N
N
N
H
H
C=O

5
→
6
H
H
H
H
6
H
O
H
H
H
6
H
F3C
H
H
H
F3C
O
H
5
F3C
conformation B
conformation B
2
conformation B
7
8
EC50 = 0.0014 μM
EC50 = 0.0093 μM
EC50 = 0.0019 μM
Fig. 7. SAR of C-5 and C-6 trifluoromethyl derivatives.

Table 2. SAR of the substituents on the piperidine ring.
Table 3. SAR of the 6-position on the indolinone core.
R2
N
N
N
F3C
N
R3
Me
Me
O
Compound
R2
rOPC EC50 (μM)
Compound
R3
CF3
F
rOPC EC50 (μM)
0.0019
8
8
0.0019
O
O
20
21
0.010
Cl
0.019
15
16
0.25
0.24
Compounds 1−4 were prepared as previously described. 9 The
synthesis of the spiro derivatives 5−21 is described in Scheme 1.
Starting from 2-bromoaniline 22a−22c, the Strecker reaction with
N-benzyl-4-piperidone 23 afforded 24a−24c, respectively. The
indolinone scaffold was then constructed by radical cyclization
with 25a−25c, followed by hydrolysis under acidic conditions.10
Subsequent N-methylation of compound 26a, followed by
conversion of the benzyl group to a tetrahydropyranylmethyl
group afforded 7 (35%) and 7’ (36%). Compound 8 was obtained
from compound 7’ by the reduction of the hydroxyl group using
Et3SiH and TFA. In contrast, conversion of the benzyl group of
O
OMe
17
18
0.054
O
OH
0.0058
O
F
19
0.0047
F
NH
Br
Br
N
(a)
(b)
(c)
N
N
+
N
H
R1
N
H
R1
NH2
R1 = CF3; 22a
R1 = F; 22b
R1 = Cl; 22c
O
R1
CN
R1 = CF3; 24a
R1 = F; 24b
R1 = Cl; 24c
R1 = CF3; 25a
R1 = F; 25b
R1 = Cl; 25c
23
O
O
O
O
OH
O
(d)
(e)
N
N
N
+
N
N
N
N
F3C
F3C
F3C
N
H
R1
(g)
Me
27
Me
Me
7'
R1 = CF3; 26a
R1 = F; 26b
R1 = Cl; 26c
7
(n)
(f) for 8
O
(o)
(p) for 20, 21
O
N
NH
O
N
N
R1
R1
N
Me
R1 = F; 28b
R1 = Cl; 28c
Me
R1 = F; 29b
R1 = Cl; 29c
N
N
R1
N
N
H
Me
F3C
R1 = CF3; 8
R1 = F; 20
R1 = Cl; 21
6
O
(l) for 15-17, 19
(m) for 18
(h)
(k)
R3
NH
27
O
N
N
F3C
(g)
F3C
Me
Me
R3 = methoxyethyl; 15
R3 = methoxypropyl; 16
R3 = 4-methoxytetrahydropyranylmethyl; 17
R3 = 4-hydroxytetrahydropyranylmethyl; 18
R3 = 4,4-difluorocyclohexylmethyl; 19
30
N
N
R2
F3C
R2 = tert-butyl acetate; 9
O
N
(i) for 10
(j) for 11
R2 = N,N-dimethylacetamide; 10
R2 = hydroxyethyl; 11
R2 = tetrahydropyranylmethyl; 12
R2 = acetyl; 13
N
O
R2 = benzyl; 14
F3C
Me
5
Scheme 1. Reagents and conditions: (a) TMSCN, AcOH, rt, 5 h, 51−66%; (b) AIBN, Bu3SnH, toluene, 120 ºC for 15 h, 69−71%; (c) 1 N aq. HCl, 100 ºC, 2 h,
62−86%; (d) MeI, NaH, DMF, 0 ºC, 1.5 h, 76%; (e) 4-formyltetrahydropyran, H2, Pd/C, MeOH, rt, 20 h, 7 (35%), 7’ (36%); (f) Et3SiH, TFA, CH2Cl2, rt, 1 h,
91%; (g) 4-formyltetrahydropyran (for 6) or tetrahydro-4H-pyranone (for 5), H2, Pd/C, MeOH, rt, 3−16 h, 59−72%; (h) Compounds 9, 12, 14: (1) R-Br, NaH,
DMF, 0 ºC to rt, 1 h, 37−79%; (2) NaBH4, MeOH, rt, 1 h, 62−94%; (3) Et3SiH, TFA, CH2Cl2, rt, 1 h, 60−93%. Compound 13: (1) NaBH4, MeOH, rt, 1 h, 94%;
(2) Et3SiH, TFA, CH2Cl2, rt, 1 h, 95%; (3) AcCl, NaH, DMF, 0 ºC to rt, 1 h, 24%; (i) (1) 80% TFA-CH2Cl2, 0 ºC to rt, 2 h, 71%; (2) Me2NH-HCl, HATU,
DIPEA, DMF, 0 ºC to rt, 1 h, 25%; (3) NaBH4, MeOH, rt, 1 h, 90%; (4) Et3SiH, TFA, CH2Cl2, rt, 1 h, 81%; (j) LiAlH4, THF, 0 ºC to rt, 15 h, 87%; (k) H2,
Pd(OH)2/C, MeOH, rt, 2 h, 100%; (l) (1) Compounds 15, 16, 19: R-Br, K2CO3, DMF, 0 ºC to 80 ºC, 2-24 h, 66−85%. Compound 17: 4-methoxyoxane-4-
carbaldehyde, NaBH(OAc)3, AcOH, CH2Cl2, 0 ºC to rt, 2 d, 33%; (2) NaBH4, MeOH, rt, 1 h, 73−90%; (3) Et3SiH, TFA, CH2Cl2, rt, 1 h, 50−93%; (m)
Compound 18: (1) 4-hydroxyoxane-4-carboxylic acid, HATU, DIPEA, DMF, 0 ºC to rt, 16 h, 90% (2) BH3-THF, THF, rt, 17 h, 51%; (n) (1) MeI, NaH, DMF, 0
ºC to rt, 1 h, 86−89%; (2) NaBH4, MeOH, rt, 1 h, 92−94%; (3) Et3SiH, TFA, CH2Cl2, rt, 1 h, 61−69%; (o) Compound 29b: H2, Pd/C, MeOH, rt, 2 h, 75%.
Compound 29c: 1-chloroethyl chloroformate, Et3N, CHCl3, rt to 80 ºC, 1 h, 74%; (p) 4-formyltetrahydropyran, NaBH(OAc)3, AcOH, CH2Cl2, 0 ºC to rt, 10 h,
75−79%.

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compound 26a to a tetrahydropyranylmethyl group led to
compound 6. Likewise, compound 5 was obtained by the
simultaneous deprotection of benzyl group and reductive
amination of compound 27 with tetrahydro-4H-pyranone.
Compounds 9, 12, and 14 were obtained by alkylation of
compound 6 with its corresponding bromide, followed by
reduction of the carbonyl group. Compound 13 was obtained by
reduction of the carbonyl group in compound 6, followed by N-
acetylation. After deprotection of the tert-butyl group in
compound 9 under acidic conditions, followed by amidation with
dimethylamine, reduction of the carbonyl group afforded
compound 10. Compound 11 was obtained by reduction of tert-
butyl ester 9 using LiAlH4. Hydrogenolysis of compound 27 led
to compound 30. Compounds 15, 16, and 19 were obtained by
alkylation of compound 30 with its corresponding bromide,
followed by reduction of the carbonyl group. Compound 17 was
obtained by reductive amination of compound 30 with 4-
methoxyoxane-4-carbaldehyde, followed by reduction of the
carbonyl group. Compound 18 was obtained by amidation of
compound 30 with 4-hydroxyoxane-4-carboxylic acid, followed
by BH3-reduction. The 6-F or Cl substituent derivatives 20 and
21 were synthesized from compounds 26b and 26c in an
analogous manner to that of compound 8.
In conclusion, compound 8, a potent inducer of OPC
differentiation, was discovered by the conformation-based
optimization of compound 1. The main findings of this study are
as follows: (i) By conformation analysis of spiro derivatives, we
propose that the N-alkylated compound, in which the
predominant conformation is B, could improve the potency by
shifting the substitution position on the benzene ring from C-5 to
C-6, and the 6-CF3 substituent derivative (6) resulted in increased
potency (EC50 = 0.0014 μM); (ii) Even in the same conformation,
OPC differentiation potency is changed by 3700-fold due to the
different positions of the substituent (compounds 4 vs. 8). Further
structure optimization and biological evaluations of this series of
compounds will be reported in due course.
5.
6.
7.
8.
9.
10. Sulsky R, Gougoutas JZ, DiMarco J, Biller SA. J. Org. Chem.
1999;64:5504−5510.
11. We tried to acquire the single-crystal X-ray structure of compound
2, which has N-methylation of compound 1, but we were unable to
obtain it. Therefore, we determined the single-crystal X-ray
structure of compound 5 as an analog of 2.
1
12. In a comparison between the H NMR of compound 3 and that of
4, there is no change in the tetrahydropyranyl (THP) group signal,
but there is a broadening of the methylene signal in the piperidine
ring of compound 3 (see supplementary data). This result also
suggests that compound 3 was in rapid equilibrium between the
two conformers A and B without a predominant conformation.
13. In contrast, compound 2 seems to have relatively good activity
despite the CF3 group occupying the wrong position towards good
activity. We consider that there are some possible reasons for this
result. As one possibility, conformation B in compound 2 would
not be adopt typical chair conformation. That is, the actual
conformation could be somewhat distorted due to the influence of
the carbonyl group. Another possibility is that the carbonyl group
of conformation B in compound 2 could be involved in the
interaction with target molecule.
14. Fang Z, Song Y, Zhan P, Zhang Q, Liu X. Future Med. Chem.
2014;6:885−901.
15. Kim WB, Shelley AJ, Novice K, Joo J, Lim HW, Glassman SJ. J.
Am. Acad. Dermatol. 2019;76:1069−1075.
16. From the NOE data of compounds 9 and 11, similar NOE
correlations to that of compound 8 have been observed, indicating
that all the compounds listed in Table 1 predominantly adopt
conformation B.
Declaration of interests
Declaration of Competing Interests
☒ The authors declare that they have no known
competing financial interests or personal
relationships that could have appeared to influence
the work reported in this paper.
The authors declare that they have no competing financial
interests or personal relationships that could influence the work
reported in this paper.
Appendix A.
Supplementa
ry data
Supplementar
y data to this
article can be
found online
at XXXX.
Acknowledg
ments
☐The authors declare the following financial
interests/personal relationships which may be
considered as potential competing interests:
We thank Dr. Masashi Hasegawa for helpful discussions on
medicinal chemistry and manuscript preparation. We would also
like to thank Dr. Makoto Suzuki for assistance with X-ray crystal
analysis.
References and Notes
1.
Friese MA, Schatting B, Fugger L. Nat. Rev. Neurol.
2014;10:225−238.
2.
3.
Dutta R, Trapp BD. Prog. Neurobiol. 2011;93:1−12.
Huned S, Patwa MD. Clin. Ther. 2014;36:1938−1945.

Graphical Abstract
Design, synthesis, and biological evaluation of
spiroindolines as novel inducers of oligodendrocyte
progenitor cell differentiation—Use of a conformation-
based hypothesis to facilitate compound design
Leave this area blank for abstract info.
Katsushi Katayama*,a, Tsutomu Nagataa, Kouhei Takashimaa, Ayako Yoshidab, Hiroyuki Okadaa, Yoshiaki
Oyama, and Tsuyoshi Mutoa
<Previous work>
<This work>
O
O
O
c
d
c
H
H
c
Me
O
H
Me
N
H
N
H
N
H
a
x 3700-fold
x 2200-fold
b
N
a
N
d
d
H
H
5
H
6
b
a
N
b
H
H
F3C
H
H
C5 C6
→
F3C
H
H
H
5
F3C
H
conformation A
1
conformation B
4
conformation B
8
rOPC; EC50 = 0.0032 μM
rOPC; EC50 = 7.1 μM
rOPC; EC50 = 0.0019 μM