Discovery of cyclic sulfonamide derivatives as potent inhibitors of SARS-CoV-2

Article abstract of DOI:10.1016/j.bmcl.2020.127667

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) continues to spread worldwide, with 25 million confirmed cases and 800 thousand deaths. Effective treatments to target SARS-CoV-2 are urgently needed. In the present study, we have identified a

Full text of DOI:10.1016/j.bmcl.2020.127667

Journal Pre-proofs
Discovery of Cyclic Sulfonamide derivatives as Potent Inhibitors of SARS-
CoV-2
Young Sup Shin, Jun Young Lee, Soojin Noh, Yoonna Kwak, Sangeun Jeon,
Sunoh Kwon, Young-hee Jin, Min Seong Jang, Seungtaek Kim, Jong Hwan
Song, Hyoung Rae Kim, Chul Min Park
PII:
S0960-894X(20)30778-2
DOI:
Reference:
https://doi.org/10.1016/j.bmcl.2020.127667
BMCL 127667
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date:
Revised Date:
Accepted Date:
7 September 2020
29 October 2020
30 October 2020
Please cite this article as: Sup Shin, Y., Young Lee, J., Noh, S., Kwak, Y., Jeon, S., Kwon, S., Jin, Y-h., Seong
Jang, M., Kim, S., Hwan Song, J., Rae Kim, H., Min Park, C., Discovery of Cyclic Sulfonamide derivatives as
Potent Inhibitors of SARS-CoV-2, Bioorganic & Medicinal Chemistry Letters (2020), doi: https://doi.org/
10.1016/j.bmcl.2020.127667
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version
will undergo additional copyediting, typesetting and review before it is published in its final form, but we are
providing this version to give early visibility of the article. Please note that, during the production process, errors
may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier Ltd.

Discovery of Cyclic Sulfonamide derivatives as Potent Inhibitors of SARS-CoV-2
Young Sup Shin,a Jun Young Lee,a Soojin Noh,a Yoonna Kwak,a Sangeun Jeon,b Sunoh
Kwon,c Young-hee Jin,d Min Seong Jang,e Seungtaek Kim,b Jong Hwan Song,a Hyoung Rae
Kim,a Chul Min Parka,*
aCenter for Convergent Research of Emerging Virus Infection (CEVI), Korea Research
Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon 34114, South Korea
bZoonotic Virus Laboratory, Institut Pasteur Korea, Seongnam-si, Gyeonggi-do 13488, South
Korea
cHerbal Medicine Research Division, Korea Institute of Oriental Medicine, Daejeon 34054,
South Korea
dKM Application Center, Korea Institute of Oriental Medicine, Dong-gu, Daegu 41062, South
Korea
eDepartment of Non-Clinical Studies, Korea Institute of Toxicology, Yuseong-gu, Daejeon
34114, South Korea
Abstract: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) continues to
spread worldwide, with 25 million confirmed cases and 800 thousand deaths. Effective
treatments to target SARS-CoV-2 are urgently needed. In the present study, we have identified
a class of cyclic sulfonamide derivatives as novel SARS-CoV-2 inhibitors. Compound 13c of
the synthesized compounds exhibited robust inhibitory activity (IC50 = 0.88 M) against
SARS-CoV-2 without cytotoxicity (CC50 > 25 M), with a selectivity index (SI) of 30.7. In
addition, compound 13c exhibited high oral bioavailability (77%) and metabolic stability with
good safety profiles in hERG and cytotoxicity studies. The present study identified that cyclic
sulfonamide derivatives are a promising new template for the development of anti-SARS-CoV-
2 agents.

In December 2019, the novel coronavirus was first reported in Wuhan Province, China.1 The
infection has since spread worldwide, with 25 million confirmed cases and 800 thousand deaths
as of 31 August 2020.2 The new virus, derived from zoonotic transmission, was named by the
International Committee on Taxonomy of Viruses (ICTV) as Severe Acute Respiratory
Syndrome Coronavirus-2 (SARS-CoV-2).3 It is a positive-sense single-stranded RNA virus
(ssRNA) that is contagious in humans and other mammals.3,4 SARS-CoV-2 shares 82% of its
genome with SARS-CoV.5 Although many studies are ongoing, no effective vaccine or
treatment for SARS-CoV-2 infection has yet been developed.6 The U.S. Food and Drug
Administration (FDA) approved emergency use of remdesivir, a nucleotide analogue prodrug,
in patients hospitalized with severe disease.7 However, this intravenous antiviral drug did not
improve overall survival rates, but it did decrease recovery time in surviving patients.6 More
effective approaches to treatment are urgently needed.
We attempted to find biologically active compounds in the library8 of the Korea Chemical
Bank (KCB) using the Institut Pasteur Korea (IPK) high content screening (HCS) platform.
Cyclic sulfonamide compound 1 (Fig. 1) was identified as a hit, and exhibited anti-SARS-CoV-
2 activity (IC50 = 15.3 M). Cyclic sulfonamide derivatives are known to have various
pharmacological activities such as analgesic9, anti-inflammatory10, herbicidal11, and
antidiabetic12 effects. Here, the present study reported the synthesis and biological effects of
cyclic sulfonamide derivatives.
OH
O
N
S
F
O
O
O
NH
F
1
IC50 : 15.3 M
CC50 : > 25 M
SI : 1.6
Figure 1. Anti-SARS-CoV-2 compound 1 identified from the KCB library screen.
A series of cyclic sulfonamide derivatives were synthesized as shown in Scheme 1. Saccharin
was treated with -bromo ketone and triethylamine to yield the alkylated product 2. A Gabriel–
Colman rearrangement of 2 with sodium ethoxide afforded intermediate 3, which was reacted

with -chloro amide and -bromo ketone (or benzyl bromide) under basic conditions using
sodium hydride to yield 4 and 5, respectively. To synthesize a one-carbon homologation
compound, 3 was treated with ClCH2CH2CONH-p-CF3-Ph and sodium hydride. However,
elimination of the alkyl chloride substrate yielded an undesired product, CH=CHCONH-p-
CF3-Ph. Alternatively, we designed to synthesize ,-unsaturated amide 8. Alkenoic acid ester
6 was prepared by reaction of compound 3 and ethyl propiolate with DABCO as a catalyst.
Hydrolysis of 6 with lithium hydroxide afforded carboxylic acid 7. Amide coupling of 7 with
3-(trifluoromethoxy)aniline, EDCI, and DMAP yielded amide 8. To synthesize 7-fluorinated
cyclic sulfonamide (Scheme 2), sulfonyl chloride 9 was used as a starting material. Amination
of 9 with aqueous ammonium hydroxide yielded sulfonamide 10. Oxidation of 10 with
potassium permanganate afforded compound 11. Cyclization of 11 with sulfuric acid yielded
fluorinated saccharin 12. Compound 13 was prepared as shown in Scheme 2. 13c was treated
with amine groups to yield N-substituted product 14.
Biological activities of the synthesized cyclic sulfonamide derivatives were evaluated in Vero
cells to test both anti-SARS-CoV-2 activity and cytotoxicity by cellular phenotypic screening
method13 as shown in Table 1 and 2. Chloroquine and remdesivir were used as reference
compounds.
O
O
O
X
a
N
NH
X = phenyl, i-propyl
Y = phenyl, alkyl
S
S
O
O
O
O
saccharin
2
Cl
F
R =
or
O
b
OH
O
OH
O
OH
O
X
Cl
N
S
X
c
e
N
NH
O
O
S
F
S
O
NH
Y
O
O
O
O
CO2Et
4
3
6
d
f
OH
O
Cl
F
OH
O
R
OH
O
N
Cl
F
X
S
g
O
O
N
N
O
S
S
O
O
O
O
HN
COOH
OCF3
5
8
7

Scheme 1. Synthesis of cyclic sulfonamide derivatives. Reagents and conditions: (a)
BrCH2COX (X = phenyl groups, i-propyl), Et3N, DMF, rt, 9 h (b) 21% NaOEt, EtOH, 60 oC,
0.5 h (c) ClCH2CONHY (Y = phenyl, alkyl groups), NaH, DMF, rt, 3 h (d) BrCH2COPh-3-Cl-
4-F or BrCH2Ph, NaH, DMF, rt, 3 h (e) ethyl propiolate, DABCO, DCM, 60 oC, 3.5 h (f) LiOH,
THF/MeOH/H2O, rt, 5 h (g) 3-(trifluoromethoxy)aniline, EDCI, DMAP, DCM, rt, 9 h.
O
CH3
CH3
a
b
OH
O
S
O
S
O
O
S
F
F
Cl
NH2
F
O
NH2
O
9
10
11
c
OH
O
Cl
O
N
X = 3-Cl
3-OCF3
4-CF3
F
S
F
d, e, f
NH
O
O
O
O
S
NH
F
O
X
13
12
OH
O
OH O
Cl
F
Cl
F
N
N
F
S
Y
S
O
O
g
O
O
O
NH
O
NH
Y = methylamine
1-methylpiperazine
CF3
CF3
13c
14
Scheme 2. Synthesis of cyclic 7-substituted sulfonamide derivatives. Reagents and conditions:
(a) aq. NH4OH, 100 oC, 1 h (b) KMnO4, 5% aq. NaOH, 120 oC, 5 h (c) sulfuric acid, rt, 1.5 h
o
(d) BrCH2COPh-3-Cl-4-F, Et3N, DMF, rt, 9 h (e) 21% NaOEt, EtOH, 60 C, 0.5 h (f)
ClCH2CONHPhX (X = 3-Cl, 3-OCF3, 4-CF3), NaH, DMF, rt, 3 h (g) methylamine or 1-
methylpiperazine, K2CO3, DMSO, 80 oC, 9 h.

We began structure activity relationship (SAR) studies of 1 with varying substituents of the
phenyl group at the 2 position, having fixed with a 4-fluoro-substituted benzoyl group at the 3
position (Table 1). Unsubstituent (4a) and 2-chloro (4b) compounds showed no inhibitory
effect. 3-Trifluoromethoxy (4c) and 4-trifluoromethyl (4d) at the 2 position improved anti-
SARS-CoV-2 activities (IC50 = 8.90 and 5.30 M, respectively). 4c and 4d exhibited better
activity than compound 1 and similar activity to remdesivir and chloroquine (IC50 = 7.01 and
8.00 M, respectively).
Table 1. Anti-SARS-CoV-2 activity and cytotoxicity of cyclic sulfonamide derivatives
OH
O
OH
O
3
R1
3
R1
2 N
S
2N
O
R3
O
O
O
S
NH
R2
O
4
5
a
b
IC50
CC50
Entry
Cpd
R1
4-F-Ph
4-F-Ph
4-F-Ph
4-F-Ph
4-F-Ph
Ph
Ph
Ph
3-F-Ph
3-CN-Ph
3-Cl-Ph
R2
R3
SI
(M)
15.3
>25
>25
8.90
5.30
11.50
>25
(M)
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
3-F-Ph
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1.6
1.0
1.0
2.7
4.7
2.1
1.0
1.0
2.3
1.6
2.1
2.8
2.9
1.6
2.0
1.9
3.2
1.5
5.8
11.
1
Ph
2-Cl-Ph
3-CF3O-Ph
4-CF3-Ph
3-CF3O-Ph
ethyl
cyclohexyl
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
>25
10.10
14.30
11.90
9.20
3-Cl-4-F-Ph 3-CF3O-Ph
4-Cl-Ph
4-CN-Ph
4-OMe-Ph
i-propyl
3-F-Ph
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
4-CF3-Ph
8.50
14.30
11.60
10.80
7.00
10.70
4.10
3-CN-Ph
3-Cl-Ph
4-CF3-Ph
4-CF3-Ph
20
4s
3-Cl-4-F-Ph 4-CF3-Ph
2.50
>25
21
22
4t
4u
4-Cl-Ph
4-CN-Ph
4-CF3-Ph
4-CF3-Ph
-
-
4.00
9.30
>25
>25
6.0
1.4

23
24
25
26
27
28
29
4v
4w
5a
5b
5c
4-OMe-Ph
i-propyl
Ph
3-CN-Ph
4-CN-Ph
4-CF3-Ph
4-CF3-Ph
-
-
8.60
7.30
>25
>25
>25
8.00
7.01
>25
>25
>25
>25
>25
>25
>25
2.5
3.0
1.0
1.0
1.0
3.1
3.6
-
-
-
PhCH2
3-Cl-4-F-PhCOCH2
3-Cl-4-F-PhCOCH2
chloroquine
remdesivir
a,b
IC50 and CC50 were derived from the results of at least two independent experiments in
Vero cells.
c SI (selectivity index) = CC50/IC50 for inhibiting SARS-CoV-2 infection.
Further optimizations of the 2 position were conducted with an unsubstituted benzoyl group
(4e) at the 3-position, as 4e and 4c had similar anti-SARS-CoV-2 effects (IC50 = 11.5 and 8.9
μM, respectively). Aliphatic amide derivatives (4f and 4g) were detrimental for anti-SARS-
CoV-2 activities. Benzyl (5a) and phenylacetyl groups (5b and 5c) at the 2 position had no
anti-SARS-CoV-2 activities.
Subsequently, substituents at the 3 position (4h–4o) were optimized in the compound
containing 3-CF3O-phenyl acetamide (4c) at the 2 position. 3-Fluoro (4h) and 3-chloro (4j)
showed no significant difference in antiviral activity (IC50 = 10.10 and 11.90 μM, respectively).
The activity of an electron donating group, 4-methoxy compound 4n, also did not improve anti-
SARS-CoV-2 activity (IC50 = 11.60 M). Compound 4o, substituted with an isopropyl, alkyl
group instead of phenyl, had similar activity (IC50 = 10.80 M). 3-Cyano (4i) and 4-cyano (4m)
substituents decreased activity (IC50 = 14.30 M), compared with 4c. 3-Chloro-4-fluoro (4k)
and 4-chloro (4l) exhibited marginally improved antiviral activities (IC50 = 9.20 and 8.50,
respectively). Next, substituent effects at the 3 position with 4-CF3-aryl at the 2 position were
investigated (4p–4w). Compounds with 4-CF3 at the 2 position were generally more active than
compounds with 3-OCF3 at the 2 position. 3-Fluoro (4p), 3-cyano (4q), 4-cyano (4u), 4-
methoxy (4v), and isopropyl (4w) compounds, maintaining 4-CF3 at the 2 position, also
displayed moderate antiviral activities (IC50 = 7.00–10.70 μM). 3-Chloro (4r), 3-chloro-4-
fluoro (4s), and 4-chloro (4t) had good antiviral activities (IC50 = 4.10, 2.50, and 4.00 M,
respectively). Compound 4s was identified as a potent inhibitor of SARS-CoV-2.

Table 2. Anti-SARS-CoV-2 activity and cytotoxicity of further modified cyclic sulfonamide
derivatives
OH
O
Cl
F
N
7
X
S
R
O
O
a
b
IC50
CC50
Entry
Cpd
X
R
SI
(M)
2.50
>25
6.60
2.20
3.10
0.88
13.80
14.00
(M)
>25
>25
>25
>25
>25
>25
>25
>25
1
2
3
4
5
6
7
8
4s
7
8
13a
13b
13c
14a
14b
H
H
H
F
F
F
-CH2CONH-4-CF3-Ph
-CH=CHCOOH
-CH=CHCONH-3-CF3O-Ph
-CH2CONH-3-Cl-Ph
-CH2CONH-3-CF3O-Ph
-CH2CONH-4-CF3-Ph
-CH2CONH-4-CF3-Ph
11.1
1.0
3.6
12.1
8.9
30.7
1.3
NHMe
1-methyl-piperazine -CH2CONH-4-CF3-Ph
1.6
a,b
IC50 and CC50 were derived from the results of at least two independent experiments in
Vero cells.
c SI (selectivity index) = CC50/IC50 for inhibiting SARS-CoV-2 infection.
We conducted further modifications to increase activity (Table 2). Carboxylic acid 7 exhibited
no antiviral effect. Substitution of ,-unsaturated amide 8 for acetamide slightly decreased
antiviral activity (IC50 = 6.60 M). Interestingly, 7-fluorinated cyclic sulfonamide (13a-c)
improved antiviral activity (0.88–3.10 μM). Compound 13c showed the most potent inhibitory
activity against SARS-CoV-2 (IC50 = 0.88 M) without cytotoxicity, having a selectivity index
of 30.7. The 7-N-substituted products 14a and 14b had decreased antiviral activity (IC50 =
13.80 and 14.00 M, respectively), compared with the 7-fluorinated compounds (13a-c).
Compound 13c, found to be a potential anti-SARS-CoV-2 agent, was evaluated for its
metabolic stability, human ether a-go-go (hERG) binding, cytotoxicity, and in vivo PK profile
(Table 3). 13c exhibited good microsomal stability in human and dog, low binding with hERG,
and no cytotoxicity toward Vero, HFL-1, L929, NIH 3T3, and CHO-K1 cell lines. Moreover,
an in vivo PK study of 13c identified good bioavailability of 77% in rats by intravenous (IV)
and oral (PO) routes at 5 and 10 mg/kg, respectively.

Table 3. hERG, microsomal stability (MS), cytotoxicity, and PK profile of 13c
hERG
Compound inhibition %
MSa
Cytotoxicity (μM)b
PKc in rats
at 10 μM
Vero: 42.1
Cmax = 14.33 g/mL
T1/2 = 18.5 h
HFL-1: 44.2
L929: 31.4
93% (human)
61% (monkey)
13c
< 1%
CL = 0.04 L/h/kg
F = 77%
NIH 3T3: 68.0
CHO-K1: 10.6
a % original compound remained after 30 min incubation.
b Cell information. Vero: African green monkey kidney cell line, HFL-1: human embryonic
lung cell line, L929: NCTC clone 929, mouse fibroblast cell line, NIH 3T3: mouse embryonic
fibroblast cell line, CHO-K1: Chinese hamster ovary cell line.
c Rats (n = 3) were dosed at IV 5 mg/kg and PO 10 mg/kg.
In conclusion, we identified a novel class of cyclic sulfonamide derivatives as SARS-CoV-2
inhibitors using SAR optimization, viral inhibitory assays, cytotoxicity assays, and PK studies.
Compound 13c is a potent SARS-CoV-2 inhibitor (IC50 = 0.88 M), has no cytotoxicity, and
has a selectivity index of 30.7. Further evaluation of compound 13c was conducted to
determine the PK profile of cyclic sulfonamide. Compound 13c showed good oral
bioavailability of 77%, metabolic stability, low binding with hERG, and no cytotoxicity. This
study identified that cyclic sulfonamide derivatives are a promising new template for the
development of SARS-CoV-2 inhibitors.
Acknowledgements
The chemical library used in this study was kindly provided by Korea Chemical Bank
(http://www.chembank.org/) of Korea Research Institute of Chemical Technology. This
research was supported through the National Research Foundation of Korea (NRF)

(2020M3E9A1041758) and National Research Council of Science & Technology (NST) (No.
CRC-16-01-KRICT) funded by the ministry of Science and ICT (MSIP).
Reference
1. Zhou P, Yang X-L, Wang X-G, et al. Nature. 2020;579:270.
2. World Health Organization (WHO). Weekly Epidemiological Update, 31 August 2020;
https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200831-
weekly-epi-update-3.pdf?sfvrsn=d7032a2a_4 [online].
3. Yang P, Wang X. Cell Mol Immunol. 2020;17:555.
4. Akhtar MJ. Bioorg Chem. 2020;101:104027.
5. Chan JF, Kok K-H, Zhu Z, et al. Emerg Microbes Infect. 2020;9:221.
6. Baden LR, Rubin EJ. N Engl J Med. 2020;382:1851.
7. U.S. Food & Drug Administration, Coronavirus (COVID-19) Update: FDA Issues
Emergency Use Authorization for Potential COVID-19 Treatment, FDA News Release,
May 1, 2020; https://www.fda.gov/news-events/press-announcements/coronavirus-
covid-19-update-fda-issues-emergency-use-authorization-potential-covid-19-
treatment [online].
8. Lee JY, Shin YS, Lee J, et al. Bioorg Med Chem Lett. 2020;30:127472.
9. Ukrainets IV, Petrushova LA, Sidorenko LV, et al. Sci Pharm. 2016;84:497.
10. Gannarapu MR, Vasamsetti SB, Punna N, et al. Eur J Med Chem. 2014;75:143.
11. Lei K, Hua X-W, Tao Y-Y, et al. Bioorg Med Chem. 2016;24:92.
12. Kim SH, Ramu R, Kwon SW, et al. Bioorg Med Chem Lett. 2010;20:1065.
13. Jeon S, Ko M, Lee J, et al. Antimicrob Agents Chemother 2020;64:e00819.

OH
O
N
S
F
O
O
O
NH
F
1
IC50 : 15.3 M
CC50 : > 25 M
SI : 1.6
Figure 1. Anti-SARS-CoV-2 compound 1 identified from the KCB library screen.

O
O
O
X
a
N
NH
X = phenyl, i-propyl
Y = phenyl, alkyl
S
S
O
O
O
O
saccharin
2
Cl
F
R =
or
O
b
OH
O
OH
O
OH
O
X
Cl
N
S
X
c
e
N
NH
O
O
S
F
S
O
NH
Y
O
O
O
O
CO2Et
4
3
6
d
f
OH
O
Cl
F
OH
O
R
OH
O
N
Cl
F
X
S
g
O
O
N
N
O
S
S
O
O
O
O
HN
COOH
OCF3
5
8
7
Scheme 1. Synthesis of cyclic sulfonamide derivatives. Reagents and conditions: (a)
BrCH2COX (X = phenyl groups, i-propyl), Et3N, DMF, rt, 9 h (b) 21% NaOEt, EtOH, 60 oC,
0.5 h (c) ClCH2CONHY (Y = phenyl, alkyl groups), NaH, DMF, rt, 3 h (d) BrCH2COPh-3-Cl-
4-F or BrCH2Ph, NaH, DMF, rt, 3 h (e) ethyl propiolate, DABCO, DCM, 60 oC, 3.5 h (f) LiOH,
THF/MeOH/H2O, rt, 5 h (g) 3-(trifluoromethoxy)aniline, EDCI, DMAP, DCM, rt, 9 h.

O
CH3
CH3
a
b
OH
O
S
O
S
O
O
S
F
F
Cl
NH2
F
O
NH2
O
9
10
11
c
OH
O
Cl
O
N
X = 3-Cl
3-OCF3
4-CF3
F
S
F
d, e, f
NH
O
O
O
O
S
NH
F
O
X
13
12
OH
O
OH O
Cl
F
Cl
F
N
N
F
S
Y
S
O
O
g
O
O
O
NH
O
NH
Y = methylamine
1-methylpiperazine
CF3
CF3
13c
14
Scheme 2. Synthesis of cyclic 7-substituted sulfonamide derivatives. Reagents and conditions:
(a) aq. NH4OH, 100 oC, 1 h (b) KMnO4, 5% aq. NaOH, 120 oC, 5 h (c) sulfuric acid, rt, 1.5 h
o
(d) BrCH2COPh-3-Cl-4-F, Et3N, DMF, rt, 9 h (e) 21% NaOEt, EtOH, 60 C, 0.5 h (f)
ClCH2CONHPhX (X = 3-Cl, 3-OCF3, 4-CF3), NaH, DMF, rt, 3 h (g) methylamine or 1-
methylpiperazine, K2CO3, DMSO, 80 oC, 9 h.
Table 1. Anti-SARS-CoV-2 activity and cytotoxicity of cyclic sulfonamide derivatives
OH
O
OH
O
3
R1
3
R1
2 N
S
2N
O
R3
O
O
O
S
NH
R2
O
4
5

a
b
IC50
CC50
Entry
Cpd
R1
4-F-Ph
4-F-Ph
4-F-Ph
4-F-Ph
4-F-Ph
Ph
Ph
Ph
3-F-Ph
3-CN-Ph
3-Cl-Ph
R2
R3
SI
(M)
15.3
>25
>25
8.90
5.30
11.50
>25
(M)
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
>25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
3-F-Ph
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1.6
1.0
1.0
2.7
4.7
2.1
1.0
1.0
2.3
1.6
2.1
2.8
2.9
1.6
2.0
1.9
3.2
1.5
5.8
11.
1
Ph
2-Cl-Ph
3-CF3O-Ph
4-CF3-Ph
3-CF3O-Ph
ethyl
cyclohexyl
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
>25
10.10
14.30
11.90
9.20
3-Cl-4-F-Ph 3-CF3O-Ph
4-Cl-Ph
4-CN-Ph
4-OMe-Ph
i-propyl
3-F-Ph
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
3-CF3O-Ph
4-CF3-Ph
8.50
14.30
11.60
10.80
7.00
10.70
4.10
3-CN-Ph
3-Cl-Ph
4-CF3-Ph
4-CF3-Ph
20
4s
3-Cl-4-F-Ph 4-CF3-Ph
2.50
>25
21
22
23
24
25
26
27
28
4t
4u
4v
4w
5a
4-Cl-Ph
4-CN-Ph
4-OMe-Ph
i-propyl
Ph
4-CF3-Ph
4-CF3-Ph
4-CF3-Ph
4-CF3-Ph
-
-
-
-
4.00
9.30
8.60
7.30
>25
>25
>25
8.00
7.01
>25
>25
>25
>25
>25
>25
>25
>25
>25
6.0
1.4
2.5
3.0
1.0
1.0
1.0
3.1
3.6
-
-
-
PhCH2
3-Cl-4-F-PhCOCH2
3-Cl-4-F-PhCOCH2
5b
5c
3-CN-Ph
4-CN-Ph
chloroquine
remdesivir
29
a,b
IC50 and CC50 were derived from the results of at least two independent experiments in
Vero cells.
c SI (selectivity index) = CC50/IC50 for inhibiting SARS-CoV-2 infection.
Table 2. Anti-SARS-CoV-2 activity and cytotoxicity of further modified cyclic sulfonamide
derivatives
OH
O
Cl
F
N
7
X
S
R
O
O
a
b
IC50
CC50
Entry
Cpd
X
R
SI
(M)
2.50
>25
6.60
2.20
(M)
>25
>25
>25
>25
1
2
3
4
4s
7
8
H
H
H
F
-CH2CONH-4-CF3-Ph
-CH=CHCOOH
-CH=CHCONH-3-CF3O-Ph
-CH2CONH-3-Cl-Ph
11.1
1.0
3.6
13a
12.1

5
6
7
8
13b
13c
14a
14b
F
F
-CH2CONH-3-CF3O-Ph
-CH2CONH-4-CF3-Ph
-CH2CONH-4-CF3-Ph
3.10
0.88
13.80
14.00
>25
>25
>25
>25
8.9
30.7
1.3
NHMe
1-methyl-piperazine -CH2CONH-4-CF3-Ph
1.6
a,b
IC50 and CC50 were derived from the results of at least two independent experiments in
Vero cells.
c SI (selectivity index) = CC50/IC50 for inhibiting SARS-CoV-2 infection.
Table 3. hERG, microsomal stability (MS), cytotoxicity, and PK profile of 13c
hERG
Compound inhibition %
MSa
Cytotoxicity (μM)b
PKc in rats
at 10 μM
Vero: 42.1
Cmax = 14.33 g/mL
T1/2 = 18.5 h
HFL-1: 44.2
L929: 31.4
93% (human)
61% (monkey)
13c
< 1%
CL = 0.04 L/h/kg
F = 77%
NIH 3T3: 68.0
CHO-K1: 10.6
a % original compound remained after 30 min incubation.

b Cell information. Vero: African green monkey kidney cell line, HFL-1: human embryonic
lung cell line, L929: NCTC clone 929, mouse fibroblast cell line, NIH 3T3: mouse embryonic
fibroblast cell line, CHO-K1: Chinese hamster ovary cell line.
c Rats (n = 3) were dosed at IV 5 mg/kg and PO 10 mg/kg.
OH
O
Cl
F
N
F
S
O
O
O
NH
13c
CF3
IC50 : 0.88 M
CC50 : > 25 M
SI : 30.7