Design, synthesis, and biological evaluation of C7-functionalized DMXAA derivatives as potential human-STING agonists

Article abstract of DOI:10.1039/c8ob01798k

STING, a central protein in the innate immune response to cytosolic DNA, has emerged as a hot target for the development of vaccine-adjuvants and anticancer drugs. The discovery of potent human-STING (hSTING) agonist is expected to revolutionize the current cancer immunotherapy. Inspired by the X-ray crystal structure of DMXAA (5,6-dimethylxanthenone-4-acetic acid) and hSTING^G230I complex, we designed various DMXAA derivatives that contain a hydrogen bonding donor/acceptor or a halide at the C7 position. While 7-bromo- and 7-hydroxyl-DMXAA showed notable binding to mouse-STING (mSTING), our newly synthesized C7-functionalized DMXAA derivatives did not bind to hSTING. Nevertheless, our newly developed synthetic protocol for the C7-functionalization of DMXAA would be applicable to access other C7-substituted DMXAA analogues as potential hSTING agonists.

Full text of DOI:10.1039/c8ob01798k

View Article Online
View Journal
Organic &
Biomolecular
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Hwang, T.
Kang, J. Lee, B. Choi and S. Han, Org. Biomol. Chem., 2018, DOI: 10.1039/C8OB01798K.
This is an Accepted Manuscript, which has been through the
Volume 14 Number
1 7 January 2016 Pages 1–372
Royal Society of Chemistry peer review process and has been
accepted for publication.
Organic &
Biomolecular
Chemistry
www.rsc.org/obc
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-0520
COMMUNICATION
Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
benzene
rsc.li/obc

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 1 of 6
View Article Online
DOI: 10.1039/C8OB01798K
Journal Name
ARTICLE
Design, synthesis, and biological evaluation of C7-functionalized
DMXAA derivatives as potential human-STING agonists
Received 00th January 20xx,
Accepted 00th January 20xx
Jihyun Hwang,a,† Taeho Kang,a,† Janghyun Lee,a Byong-Seok Choi, ,a and Sunkyu Han
* *
,a,b
DOI: 10.1039/x0xx00000x
STING, a central protein in the innate immune response to cytosolic DNA, has emerged as a hot target for the
development of vaccine-adjuvants and anticancer drugs. The discovery of potent human-STING (hSTING) agonist is
expected to revolutionize the current cancer immunotherapy. Inspired by the X-ray crystal structure of DMXAA (5,6-
dimethylxanthenone-4-acetic acid) and hSTINGG230I complex, we designed various DMXAA derivatives that contain a
hydrogen bonding donor/acceptor or a halide at the C7 position. While 7-bromo- and 7-hydroxyl-DMXAA showed notable
binding to mouse-STING (mSTING), our newly synthesized C7-functionalized DMXAA derivatives did not bind to hSTING.
Nevertheless, our newly developed synthetic protocol for the C7-functionalization of DMXAA would be applicable to
www.rsc.org/
access
other
C7-substituted
DMXAA
analogues
as
potential
hSTING
agonists.
various pathways including the modulation of T-cells.
STING has emerged as promising target for the
1. Introduction
a
development of novel immunization, autoinflammation, and
cancer therapeutics.7 Especially, the development of STING
agonist which can recruit T-cells at the site of tumors is
expected to greatly improve the efficacy of antibody-based
checkpoint inhibitors such as KeytrudaⓇ and OpdivoⓇ. DMXAA
1.1. STING and DMXAA
STING (stimulator of interferon genes) is a key protein of
the innate immune system and the body’s first line of defense
against pathogenic invasions of bacteria and viruses.1 STING
controls the transcription of type 1 interferons (IFNs) and pro-
inflammatory cytokines upon binding to cyclic dinucleotides
(CDNs). 2 Aberrant localization of DNA in the cytosol by
pathogen-derived DNA, by self-DNA that has leaked from the
nucleus of the host cell as a consequence of DNA damage, or
by mitochondrial DNA (mtDNA) infiltrated due to
mitochondrial stress induces the production of cyclic GMP-
(1, Vadimezan) was firstly synthesized by Denny and coworkers
as a potent antitumor agent.8 Baguley and Ching showed that
the antivascular action of DMXAA results from its immune
modulation via the induction of cytokines in mouse models.9 A
cocktail treatment comprising DMXAA, paclitaxel, and
carboplatin passed the phase II clinical trial against non-small-
cell lung cancer but failed in the subsequent human phase III
trials.10 In 2012, the research team led by Vogel discovered
that expression of IFN-β in response to DMXAA in murine
3
AMP (cGAMP) by cyclic GMP-AMP synthase (cGAS).
Alternatively, gram-negative and gram positive bacteria have
also been reported to secrete CDNs. CDN then binds to STING
and induces an “open” to “closed” conformational change.4
This structural change of STING serves as a signal to complex it
with TANK-binding kinase 1 (TBK1) and IκB kinase (IKK) and
relocate them to perinuclear regions of the cell.5 These kinases
phosphorylate the transcription factors interferon regulatory
macrophages requires STING, indicating that DMXAA targets
11
the mouse-STING (mSTING) pathway.
In their
contemporaneous studies, the Fitzgerald research team12 and
the Mitchison group13 reported that DMXAA binds to mSTING
but does not bind to human-STING (hSTING) despite their
sequence identity (68% amino acid identity and 81% similarity)
and structural similarity.
factor
3 (IRF3) and nuclear factor-κB (NF-κB) for their
activation.6 The incitement of IRF3 and NF-κB triggers the
induction of cytokines and proteins, such as the type I
interferons (IFNs), which initiate anti-pathogen activity via
Atomic-level understanding of the interaction between
DMXAA and hSTING became available by elegant structural,
biophysical, and cellular essay studies reported by Patel and
coworkers.4,14 The Patel research team identified three point
substitutions (S162A, G230I, and Q266I) of hSTING which
synergistically rendered the mutated hSTING highly sensitive
to DMXAA (Figures 1A). Notably, the substituted I266, together
with I165, L170, and I235 side chains, formed a nonpolar
pocket that maximizes the hydrophobic interaction with the
aromatic methyl groups of DMXAA consistent with its highest
binding affinity (Figure 1B). The crystal structure of DMXAA
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 2 of 6
View Article Online
DOI: 10.1039/C8OB01798K
Journal Name
ARTICLE
bound to hSTINGG230I revealed hydrogen bonding (salt-bridge) between
Figure 1. Patel’s Xꢀray crystal structures of DMXAA bound to mutated hSTING. (A) The 2.37
Å
crystal structure of DMXAA bound to
hSTINGS162A/G230I/Q266I. (B) Crystal structure representation of DMXAA bound to hSTINGS162A/G230I/Q266I with an emphasis on hydrophobic
interactions around DMXAA. (C) The 2.51
bonding as dotted line.
Å
crystal structure of DMXAA bound to hSTINGG230I with representation of hydrogen
the carboxylic acid moiety of DMXAA and the guanidino group
In 1989, Denny and coworkers reported the synthesis and
of R238. It also disclosed additional hydrogen bonding structure-activity relationship studies of monosubstituted
between the ketone moiety of DMXAA and the hydroxyl xanthenone-4-acetic acids (XAA) against the colon 38 tumor in
groups of T267 and S162 (Fig. 1C).
vivo.15 They synthesized various monosubstituted XAA derivatives
including 7-substituted XAAs. A synthetic route for 7-Me-XAA (8) is
1.2. Design of C7-functionalized DMXAAs as potential STING presented in Scheme 1A. Firstly, Iodide 5 and sodium phenolate 6
agonists
The seminal report by Patel and coworkers14 provided insight to
were coupled by copper catalyzed cross coupling reaction to
produce 7. The resulting 7 was heated in aqueous sulfuric acid to
yield 7-Me-XAA (8) by Friedel−Crafts acylation-type reaction. Other
7-substituted-XAAs (9−12) could be accessed using analogous
synthetic procedures (Scheme 1B). Importantly, 7-Me-XAA, along
with 8-Me-XAA, was active in stimulating human leukocytes to
produce IL-6 and IL-8 and for inhibition of tube formation by
ECV304 human endothelial-like cells. On the other hand, 5- and 6-
Me-XAAs were the most active compounds in murine cell systems
hinting at a substitution site dependent species specificity of
XAA.16,17
design novel DMXAA derivatives with potentially higher affinity to
hSTING. In fact, the Patel research team concluded their report14 by
suggesting the synthesis of DMXAA analogues with polar groups at
C1/C2 and C7 for presumed intermolecular hydrogen bondings with
hSTING, respectively. Our group’s interest in developing hSTING
agonists prompted us to devise DMXAA derivatives with hydrogen
bonding donor/acceptor at the C7 position (Figure 2). We
envisioned that the hydroxyl group attached at C7 via a proper
methylene-based linker would hydrogen bond with the primary
amide group of Q266 in hSTING. Notably, our preliminary virtual
docking studies indicated that DMXAA derivatives 2, 3, and 4
complexed to hSTING are 0.47, 0.14, and 0.84 kcal/mol more stable
than DMXAA-hSTING complex, respectively. The docking model of 4
to hSTING predicted hydrogen bondings of the hydroxyl group of
the ligand with Q266, R169, and R232 of hSTING (Figure 2).
A. Representative synthetic route to 7-Me-XAA
Me
COONa
O
COONa
8
1
CuCl
TDAꢀ1
aq.
H2SO4
Me
Me
7
2
3
5
I
+
O
6
O
NaO
dioxane
reflux
91%
80 °C
87%
4
5
NaOOC
CO2H
6
7
8
COONa
B. Representative previously synthesized C7-substituted XAA
O
R = OMe,
R = Cl,
9
R
7
10
O
O
11
12
R = NO2,
R = OH,
O
4
HO
Me
HO
Me
5
4
CO2H
O
O
Me
OH
O
O
Me
6
3
Scheme 1. Denny’s synthesis of C7-monosubstituted XAA
2
7
7
n
1
8
derivatives.
1
DMXAA (
)
2, n=0
3, n=1
4, n=2
H-Bondings
of interest
1.4. Previous synthesis of C7-substituted DMXAA derivatives
The synthetic protocol developed for the synthesis of DMXAA8
could be applied to the synthesis of 7-Me-DMXAA by Xie et al
(Scheme 2A).18 Cross-coupling between the sodium salt of 2-iodo-
3,4,5-trimethylbenzoic acid (13) and sodiumphenolate 6 followed
by an acid mediated cyclization produced 7-Me-DMXAA (15). As an
effort to streamline the synthesis of DMXAA (1), Yang and Denny
Figure 2. Design of DMXAA derivatives with hydrogen bonding
donor/acceptor at the C7 position based on the docking model of 4 to
hSTING.
1.3. Previous synthesis of C7-monosubstituted XAA derivatives
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 2
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 3 of 6
View Article Online
DOI: 10.1039/C8OB01798K
Journal Name
ARTICLE
devised a synthetic strategy which utilized 7-bromo-DMXAA (20) as
a direct precursor to DMXAA (Scheme 2B).19 3,4-Dimethylbenzoic
acid (16) could be converted to dibromo compound 17 upon
treatment with NBS under acidic conditions. They found that the
bromo group at the meta position of the carboxylic acid moiety in
17 activated the bromo group at the ortho position to allow a
regioselective cross-coupling with 2-hydroxyphenylacetic acid (18)
to yield diacid derivative 19 in 68% yield. Subsequent
cyclodehydration of diacid 19 afforded 7-bromo-DMXAA (20).
the presence of N-iodosuccinimide and trifluoroacetic acid to
produce C7-iodinated derivative 24 in 97% yield. Hydrolysis of the
methylester moiety of 24 provided 7-iodo-DMXAA (25).20
With a robust access to 7-iodo-DMXAA derivative 24 in hand,
we next investigated the C7 hydroxylation. Initial evaluations of a
palladium
catalyzed
hydroxylation
of
24 were
not
successful.21 Successful hydroxylation of xanthone-based iodide 24
was achieved when a combination of Cu(acac)2 and N,N′-bis(4-
hydroxyl-2,6-dimethylphenyl)oxalamide (BHMPO),
a
catalytic
system reported by Ma and coworkers,22 was applied. Under these
reaction conditions, the desired 7-hydroxy-DMXAA (2) was obtained
in 62% yield. It is notable that the methylester moiety underwent a
concomitant hydrolysis during this transformation.
A. Synthesis of 7-Me-DMXAA
Me
COONa
O
Me
I
13
COONa
O
8
1
We envisioned that a substitution of the C7-iodide to the vinyl
group in 24 would enable a synthetic access to both alcohols 3 and
CuCl
TDAꢀ1
aq.
H2SO4
Me
Me
Me
Me
7
2
3
Me
6
+
NaO
O
DMSO
85 °C
73%
90 °C
88%
5
4
4
with one and two methylene linkers, respectively. This
Me
NaOOC
Me
CO2H
substitution was attained by Suzuki–Miyaura cross coupling
reaction. Treatment of aryliodide 24 with Buchwald’s third
generation XPhos-based palladacycle precatalyst and vinylboronic
acid pinacol ester under basic conditions resulted in the formation
of vinyl derivative 26. With vinyl derivative 26 in hand, we firstly
explored its transformation to 4. A hydroboration reaction of 26
with BH3·THF followed by an oxidative work-up afforded primary
alcohol derivative 27 in 41% yield. A hydrolysis of the methylester
moiety of 27 yielded 7-(2-hydroxyethyl)-DMXAA (4) in 90% yield.
Upon testing various oxidative cleavage reactions of vinyl
derivative 26, we discovered that 26 was most efficiently converted
to aldehyde 28 in the presence of ruthenium trichloride catalyst and
[bis(acetoxy)iodo]benzene oxidant in a CH2Cl2/water two phase
system. 23 Hydrolysis of the methylester moiety of aldehyde
derivative 28 produced 7-formyl-DMXAA (29). We envisaged that
the hydrogen bond accepting ability of the aldehyde functionality in
29 would provide an interesting additional entry with respect to our
initial design principle of STING agonists. Finally, reduction of the
aldehyde moiety in 28 afforded benzyl alcohol derivative 30.
Hydrolysis of 30 yielded 7-hydroxymethyl-DMXAA (3) in 78% yield.
14
15
6
COONa
B. Synthesis of 7-Br-DMXAA
CO2H
Br
CO2H
Br
NBS
+
HO
Me
Me
H2SO4
20 °C
80%
Me
16
Me
17
CO2H
18
dioxane
85 °C
68%
CuCl
TDAꢀ1
O
CO2H
Br
Br
aq. H2SO4
Me
O
Me
O
80 °C
95%
Me
Me
CO2H
CO2H
19
20
Scheme 2. Synthesis of 7-substituted DMXAA
2. Results and Discussion
2.1 Synthesis of C7-functionalized DMXAA derivatives
Based on our aforementioned rational design, we set out to
synthesize C7-functionalized DMXAA analogues 2−4. Previous
syntheses of various C7-substituted XAA were possible due to the
commercial availability of the trisubstituted benzene derivative
(Scheme 1). However, limited commercial availability of the
pentasubstituted benzene derivatives necessary for the synthesis of
C7-functionalized DMXAAs by Denny’s method prompted us to
devise a novel synthetic strategy. For an efficient access to various
C7-functionalized target DMXAA derivatives, we devised a divergent
synthetic strategy that utilizes a commercially available DMXAA
itself. Our synthesis of the designed DMXAA derivatives
commenced with the methyl ester formation of the carboxylic acid
moiety of DMXAA (1) to make the handling of downstream
compounds easier (Scheme 3). We subsequently installed the
synthetic handle at the C7 position of methylester derivative 21 by
an electrophilic aromatic halogenation of the xanthone framework.
Treatment of 21 with molecular bromine and aluminium trichloride
provided the C7-brominated derivative 22 in 58% yield along with
C2,C7-dibrominated compound 23 in 4% yield. Hydrolysis of
brominated methylester derivative 22 under basic condition yielded
7-bromo-DMXAA (20) in 75% yield. More efficient and selective C7-
monohalogenation of xanthone derivative 21 was accomplished in
2.2 Biological evaluations of our C7-functionalized DMXAA
derivatives
Our synthetic campaign provided us not only with the target
DMXAA analogues 2–4 but also with various synthetic precursors
and their derivatives (Scheme 1). With an access to assorted C7-
functionalized DMXAA derivatives, we firstly tested their binding to
mSTING by thermal shift assay using differential scanning
fluorimetry (DSF).24 We immediately noticed that the presence of
free carboxylic acid moiety in DMXAA derivatives was crucial for the
interaction with mSTING. The thermal shift data identified 7-bromo-
DMXAA (20) and 7-hydroxy-DMXAA (2) to show the strongest
ligand-mSTING interaction among tested DMXAA derivatives. The
observed Kd of 7-bromo-DMXAA (20) was 149 µM (Observed Kd of
DMXAA from this experiment: 83.4 µM) and that of 7-hydroxy-
DMXAA (2) was 522 µM. The ligand-mSTING binding affinity
strongly depended on the C7 substituent in the order of Br > OH >
CH2OH >> CH2CH2OH ~ I ~ CHO. The highest affinity between 7-
bromo-DMXAA (20) and mSTING might be due to
a strong
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 4 of 6
View Article Online
DOI: 10.1039/C8OB01798K
Journal Name
ARTICLE
hydrophobic interaction between the bromine atom and the surrounding I165, I266, L170, and I235 residues.
O
O
O
O
O
HO
Me
HO
MeO
HO
Me
5
MeO
Me
MeO
Me
HO
Me
g
c
4
O
Me
Br
O
O
Me
O
Me
O
O
Me
O
O
Me
6
3
90%
41%
2
7
OH
OH
1
8
O
20
O
26
DMXAA (1)
27
4
h
a
88%
53%
c
f
85%
75%
O
O
O
O
O
MeO
Me
Me
MeO
Me
MeO
Me
MeO
Me
d
i
O
Me
O
Me
O
Me
I
O
Me
O
Me
OH
57%
97%
O
7
2
Br
b
O
22
O
21
O
24
O
28
H
O
30
58%
c
e
c
c
62%
68%
78%
Me
+
76%
O
O
O
O
O
MeO
Br
Me
Me
HO
Me
HO
Me
HO
O
Me
Br
O
Me
I
O
Me
OH
O
Me
O
O
Me
OH
O
O
23
O
O
O
H
25
2
29
3
4%
Scheme 3. Synthesis of various C7ꢀfunctionalized DMXAA derivatives. Reagents and conditions: (a) EDC, HOBt, DIPEA, MeOH, DMF, CH2Cl2,
23 °C. (b) Br2, AlCl3, CS2, 23 °C. (c) NaOH, H2O, MeOH, 50 °C. (d) NIS, TFA, CH2Cl2, 23 °C. (e) Cu(acac)2, N,N'ꢀbis(4ꢀhydroxyꢀ2,6ꢀ
dimethylphenyl)oxalamide, KOH, 1,4ꢀdioxane, H2O, 80 °C. (f) Pd XPhos G3, 4,4,5,5ꢀtetramethylꢀ2ꢀvinylꢀ1,3,2ꢀdioxaborolane, Na2CO3, 1,4ꢀ
dioxane, H2O, 90 °C. (g) BH3—THF, THF, 23 °C; H2O2, NaOH, H2O, 23 °C. (h) RuCl3, PhI(OAc)2, CH2Cl2, H2O, 23 °C. (i) NaBH4, MeOH, 23 °C.
We then tested the interaction between our newly synthesized
DMXAA derivatives and hSTING using DSF based thermal shift essay.
We conducted our studies using three different natural variants of
hSTING, namely, hSTINGR232, hSTINGHAQ, and hSTINGH232 (Figure 3D).
Notably, we could not observe any interaction between our C7-
functionalized DMXAA derivatives and hSTING. We reasoned that
the lack of thermal shift might be due to either no binding of the
ligand or binding but no change in the conformation of hSTING. We,
therefore, conducted an ITC (isothermal titration calorimetry)
experiment using select DMXAA derivatives (2, 3, 4 and 20) and
hSTINGs (hSTINGHAQ and hSTINGH232). The ITC experiment did not
reveal any specific binding between these ligands and hSTING. Our
studies revealed that the introduction of a hydrogen bonding
donor/acceptor or a halide at the C7 position of DMXAA did not
improve the binding to hSTING. It is important to note that our
design of C7-functionalized DMXAA was based on the co-crystal
structure of DMXAA and “mutated” hSTING. We reason that the
subtle structural discrepancy between “natural” and “mutated”
hSTINGs might have contributed to the lack of interactions between
our C7-functionalized DMXAA analogues and hSTING.25
Figure 3. Thermal shift assay data of STING + C7ꢀfunctionalized
3. Conclusions
DMXAA derivative complexes. (A) DSF data of mSTING + C7ꢀ
functionalized DMXAA derivative complexes. (RFU: Relative
Fluorescence Unit) (B) ∆Tm of mSTING + C7ꢀfunctionalized DMXAA
derivative complexes. (C) DSF data of hSTING + C7ꢀfunctionalized
DMXAA derivative complexes. (D) ∆Tm of hSTING + C7ꢀfunctionalized
We rationally designed, synthesized, and tested the
biological activity of various C7-functionalized DMXAA
derivatives based on the x-ray crystal structure of DMXAA
bound to hSTINGG230I. While 7-bromo-DMXAA (20) and 7-
DMXAA derivative complexes. (R232: hSTINGR232, HAQ: hSTINGHAQ
,
hydroxy-DMXAA (2) showed notable binding to mSTING, none
H232: hSTINGH232
)
of our newly synthesized C7-functionalized DMXAA derivatives
showed any affinity to hSTING. Our studies demonstrated that
the introduction of a hydroxyl group appended at the C7-
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 4
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 5 of 6
View Article Online
DOI: 10.1039/C8OB01798K
Journal Name
ARTICLE
position of DMXAA by linkers of different length fell short to
induce a substantial hydrogen bonding with the side chain of
Q266 residue in hSTING to restore the binding of the ligand to
the protein. Our data illustrates the challenge in establishing
the strongly angle-dependent hydrogen bonding in protein-
ligand interactions even with co-crystal structures available.26
Nevertheless, our findings provide a basis for the selective C7-
functionalization of DMXAA and would be applicable to access
other C7-substituted DMXAA analogues.
Conflicts of interest
10
For a review on DMXAA’s clinical trials, see: A. D. F. Adli, R.
Jahanban-Esfahlan, K. Seidi, S. Samandari-Rad, N. Zarghami,
Chem. Biol. Drug. Des., 2018, 91, 996.
D. Prantner, D. J. Perkins, W. Lai, M. S. Williams, S. Sharma, K. A.
Fitzgerald, S. N. Vogel, J. Biol. Chem., 2012, 287, 39776.
J. Conlon, D. L. Burdette, S. Sharma, N. Bhat, M. Thompson, Z.
Jiang, V. A. K. Rathinam, B. Monks, T. Jin, T. S. Xiao, S. N. Vogel,
R. E. Vance, K. A. Fitzgerald, J. Immunol., 2013, 190, 5216.
S. Kim, L. Li, Z. Maliga, Q. Yin, H. Wu, T. M. Mitchison, ACS
Chem. Biol., 2013, 8, 1396.
There are no conflicts to declare.
11
12
Acknowledgements
The authors are grateful for the financial support provided by
the
National
Research
Foundation
of
Korea
(2018R1A2B6004479).
13
14
P. Gao, T. Zillinger, W. Wang, M. Ascano, P. Dai, G. Hartmann, T.
Tuschi, L. Deng, W. Barchet, D. J. Patel, Patel, Cell Rep., 2014, 8,
1668.
G. W. Rewcastle, G. J. Atwell, B. C. Baguley, S. B. Calveley, W. A.
Denny, J. Med. Chem., 1989, 32, 793.
S. M. Tijono, K. Guo, K. Henare, B. D. Palmer, S.-C. S. Wang, S. M.
Albelda, L.-M. Ching, Br. J. Cancer, 2013, 108, 1306.
S.-T. Woon, C. B. Reddy, C. J. Drummond, M. A. Schooltink, B. C.
Notes and references
15
16
17
Baguley, C. Kieda, L.-M. Ching, Oncol. Res., 2005, 15, 351.
18
19
20
G. Xie, B. Yang, W. Li, J. Zhou, L. Huang, 2008, CN 101279967.
S. Yang, W. A. Denny, Tetrahedron Lett., 2009, 50, 3945.
M. R. Schrimpf, K. B. Sippy, J. Ji, T. Li, J. M. Frost, C. A. Briggs, W.
H. Bunnelle, US Patent 2005/0234031 A1.
S. Enthaler, A. Company, Chem. Soc. Rev., 2011, 40, 4912.
S. Xia, L. Gan, K. Wang, Z. Li, D. Ma, J. Am. Chem. Soc., 2016,
138, 13493.
21
22
1
H. Ishikawa, G. N. Barber, Nature, 2008, 455, 674.
2
23
24
(a) H. Ishikawa, Z. Ma, G. N. Barber, Nature, 2009, 461, 788. (b)
D. L. Burdette, K. M. Monroe, K. Troha, J. S. Iwig, B. Eckert, M.
Hyodo, Y. Hayakawa, R. E. Vance, Nature, 2011, 478, 515.
(a) J. Ahn, G. N. Barber, Curr. Opin. Immunol, 2014, 31, 121. (b)
A. P. West, W. Khoury-Hanold, M. Staron, M. C. Tal, C. M.
Pineda, S. M. Lang, M. Bestwick, B. A. Duguay, N. Raimundo, D.
A. MacDuff, S. M. Kaech, J. R. Smiley, R. E. Means, A. Iwasaki, G.
S. Shadel, Nature, 2015, 520, 553.
C. Mi, L. Li, X. Meng, R. Yang, X. Liao, Tetrahedron, 2016, 72,
6705.
(a) F. H. Niesen, H. Berglund, M. Vedadi, Nature Prot., 2007, 2,
2212. (b) M. Vivoli, H. R. Novak, J. A. Littlechild, N. J. Harmer, J.
Vis. Exp., 2014, 91, e51809.
G. Yi, V. P. Brendel, C. Shu, P. Li, S. Palanathan, C. C. Kao, Plos
One, 2013, 8, e77846.
3
25
26
We thank the reviewers for constructive comments.
4
5
P. Gao, M. Ascano, T. Zillinger, W. Wang, P. Dai, A. A. Serganov,
B. L. Gaffney, S. Shuman, R. A. Jones, L. Deng, G. Hartmann, W.
Barchet, T. Tuschl, D. J. Patel, Cell, 2013, 154, 748.
T. Saitoh, N. Fujita, T. Hayashi, K. Takahara, T. Satoh, H. Lee, K.
Matsunaga, S. Kageyama, H. Omori, T. Noda, N. Yamamoto, T.
Kawai, K. Ishii, O. Takeuchi, T. Yoshimori, S. Akira, Proc. Natl
Acad. Sci. USA, 2009, 106, 20842.
6
H. Konno, K. Konno, G. N. Barber, Cell, 2013, 155, 688.
7
S. M. Haag, M. F. Gulen, L. Reymond, A. Gibelin, L. Abrami, A.
Decout, M. Heymann, F. G. van der Goot, G. Turcatti, R.
Behrendt, A. Ablasser, Nature, 2018, 559, 269.
G. W. Rewcastle, G. J. Atwell, L. Zhuang, B. C. Baguley, W. A.
Denny, J. Med. Chem., 1991, 34, 217.
8
9
B. C. Baguley, L.-M. Ching, Int. J. Radiation Oncology Biol. Phys.,
2002, 54, 1503.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Organic & Biomolecular Chemistry
Page 6 of 6
View Article Online
DOI: 10.1039/C8OB01798K