Substituted phenyl as a steroid A-ring mimetic: Providing agonist activity to a class of arylsulfonamide nonsteroidal glucocorticoid ligands

Article abstract of DOI:10.1016/j.bmcl.2013.10.047

A class of arylsulfonamide glucocorticoid receptor agonists that contains a substituted phenyl group as a steroid A-ring mimetic is reported. The structural design and SAR that provide the functional switching of a GR antagonist to an agonist is described. A combination of specific hydrogen bonding and lipophilic elements on the A-ring moiety is required to achieve potent GR agonist activity. This study culminated in the identification of compound 23 as a potent GR agonist with selectivity over the PR and MR nuclear hormone receptors.

Full text of DOI:10.1016/j.bmcl.2013.10.047

Bioorganic & Medicinal Chemistry Letters 23 (2013) 6645–6649
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Substituted phenyl as a steroid A-ring mimetic: Providing agonist
activity to a class of arylsulfonamide nonsteroidal glucocorticoid
ligands
a
a
a
a
Darren DiSalvo a, , Daniel Kuzmich , Jörg Bentzien , John Regan , Alison Kukulka ,
⇑
Tazmeen Fadra-Khan a, Richard Nelson a, Christian Harcken a, David Thomson a, Gerald Nabozny b
a Department of Medicinal Chemistry, Boehringer Ingelheim Pharmaceuticals Inc., 900 Ridgebury Road, PO Box 368, Ridgefield, CT 06877-0368, USA
b Department of Inflammation & Immunology, Boehringer Ingelheim Pharmaceuticals Inc., 900 Ridgebury Road, PO Box 368, Ridgefield, CT 06877-0368, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A class of arylsulfonamide glucocorticoid receptor agonists that contains a substituted phenyl group as a
steroid A-ring mimetic is reported. The structural design and SAR that provide the functional switching of
a GR antagonist to an agonist is described. A combination of specific hydrogen bonding and lipophilic ele-
ments on the A-ring moiety is required to achieve potent GR agonist activity. This study culminated in the
identification of compound 23 as a potent GR agonist with selectivity over the PR and MR nuclear hor-
mone receptors.
Received 12 August 2013
Revised 22 October 2013
Accepted 23 October 2013
Available online 31 October 2013
Keywords:
Glucocorticoids
Ó 2013 Elsevier Ltd. All rights reserved.
Glucocorticoid receptor
Nuclear hormone receptor
Mineralocorticoid receptor
Progesterone receptor
Glucocorticoid receptor agonist
Arylsulfonamide
Synthetic glucocorticoids such as dexamethasone and predniso-
lone (Fig. 1) are modulators of the glucocorticoid receptor (GR) and
among the most effective agents for the treatment of acute and
chronic inflammatory diseases. Their therapeutic application cov-
ers a broad range of disorders such as rheumatoid arthritis, asthma,
inflammatory bowel disease and chronic obstructive pulmonary
disease.1–3 Despite their clinical efficacy, treatment with acute high
and chronic low doses are limited due to a number of severe and
sometimes irreversible side effects.4
provided modest GR binding potency (e.g. compound 1 GR IC50 =
40 nM) but lacked the desired agonist activity.9 Previous publica-
tions on GR agonists from our laboratories have shown that
OH
OH
OH
OH
O
O
HO
HO
H
H
With regard to the functional activity of GR, transrepression is
considered to be the key mechanism for beneficial anti-inflamma-
tory activity while transactivation is believed to mediate the mech-
anisms responsible for many of the glucocorticoid-induced side
effects.5–9 The goal of our non-steroidal glucocorticoid mimetic
program has been to provide a potent GR agonist that differenti-
ates between these two functional pathways.
F
H
H
H
O
O
Dexamethasone
Prednisolone
Figure 1. Examples of synthetic glucocorticoids.
Previously we reported a class of a-methyltryptamine sulfona-
N
H
N
mides as exemplified by compound 1 (Fig. 2).10 This compound
was identified in a high-throughput chemistry effort where the ini-
tial SAR focused mainly on the arylsulfonamide portion of the li-
gand that was amenable to rapid synthesis. These analogues
O
F
O
O
HO CF3
S
N
H
A-ring mimeꢀc
1
2
⇑
Corresponding author. Tel.: +1 203 791 6629; fax: +1 203 791 6072.
E-mail address: darren.disalvo@boehringer-ingelheim.com (D. DiSalvo).
Figure 2. Compound 1 (partial antagonist) and 2 (full agonist).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.10.047

6646
D. DiSalvo et al. / Bioorg. Med. Chem. Lett. 23 (2013) 6645–6649
Table 1
SAR of substituted aryl groups as A-ring mimetics
O
O
R
S
N
H
Compound
R
GR IC50 (nM)
83
PR IC50 (nM)
4200
MR IC50 (nM)
700
IL-6 IC50 (nM)
>10,000
IL-6 % efficacy
0
3
4
5
23
5500
3400
400
>10,000
>10,000
0
0
230
1100
6
7
8
110
10
>10000
2000
>10000
350
>10,000
>10,000
>10,000
0
19
0
160
8200
2400
9
25
>10000
320
>10,000
0
10
11
11
48
7400
3400
360
400
>10,000
>10,000
36
0
F
F
Cl
12
10
1200
150
>10,000
0
Cl
13
14
10
78
1500
720
190
400
>10,000
>10,000
0
0
specific and, at times, seemingly minor substitution changes can
have significant effects on functional activity despite similar GR
binding affinities.11–13 The effect that these function-regulating
pharmacophores (FRPs) have on the resultant GR-ligand complex
might be as drastic as inducing a conformational change similar
to that caused by mifepristone, or as subtle as modulating the acid-
ity of a hydrogen bond donor of the ligand.11
eling studies and examination of the SAR, we hypothesized that the
indole of 1 was likely filling the role of the steroid A-ring. To pro-
vide agonist activity to this new series, we envisioned replacing the
indole of compound 1 with a phenyl ring and applying a similar
strategy as was described for 2.14
As a starting point, replacement of the indole of compound 1
with an unsubstituted phenyl group resulted in an analogue (not
In particular, we have described the use of a substituted phenyl
A-ring mimetic as exemplified by compound 2 (Fig. 2).12a The SAR
of the phenyl group revealed that moieties providing both a lipo-
philic and a hydrogen bond interaction with the protein were re-
quired in order to achieve potent agonist activity. Similar SAR
utilizing a cyano group as a replacement for the A-ring carbonyl
has been reported for other nuclear hormone receptors as in the
progesterone12b and androgen12c,d receptors. Based on initial mod-
shown) with no activity up to a concentration of 10 lM in our
GR binding assay.15 The optimization of substitution on the phenyl
ring began by identifying appropriate lipophilic groups to ensure
optimal space filling prior to the incorporation of a hydrogen bond-
ing component. This work was conducted utilizing an N-
group on the sulfonamide core which had previously been
described to be a potent alternative to the N- -methyl substituent
shown in compound 1.10 As shown in Table 1, mono-methyl
a-ethyl
a

D. DiSalvo et al. / Bioorg. Med. Chem. Lett. 23 (2013) 6645–6649
6647
Table 3
Receptor activity; evaluation of a lipophilic requirement for agonist activity
O
O
R
S
N
H
Compound
R
GR
IC50
(nM)
PR
IC50
(nM)
MR
IC50
(nM)
IL-6
IC50
(nM)
IL-6 %
efficacy
HO
HO
20
21
22
23
120
6400
2800
2500
620
5200
1000
2300
270
>2000
>2000
>2000
22
0
27
23
2
0
HO
HO
0
77
Figure 3. Overlay of the docking pose of compound 16 (orange) with the X-ray
complex structure of GR/LBD and dexamethasone (rose).17 Docking was performed
using Glide18 and the picture was generated with MOE.19 Dotted lines represent
hydrogen bonds.
accompanied by weak GR agonist activity as indicated by the IL-
6 efficacy.
substitution at both the ortho and meta positions (e.g., compounds
3 and 4) was preferred over para substitution. Interestingly for
these compounds, a small increase in lipophilicity, as exemplified
by the addition of a single methyl group, provided a significant in-
crease in binding activity for compound 4 (GR IC50 = 23 nM) over
the unsubstituted phenyl analogue. Despite this increase in
binding potency, mono-methyl substitution was not sufficient for
agonist activity as determined by the IL-6 assay.16 For
dimethyl-substitution, combining methyl groups in the 2,3-, 2,5-,
and 3,5-positions (analogs 7, 9, 10) resulted in binding activity of
<25 nM while 2,6- and 2,4-dimethyl analogues 6 and 8 were less
active. For compound 10, potent GR binding potency was also
To further examine 3,5-substitution, compounds 11 and 12
were prepared. Comparing the data of the di-chloro compound
12 with that of 10 suggested that changing the electronic nature
of the phenyl ring in the absence of other substitution has little
effect on binding activity, and that the role of the 3,5-dichloro
substituents might simply be providing lipophilic interactions with
the receptor. The potency of the 2,3-dimethyl analogue 7 led us to
envision fusing a second ring at this position. This was accom-
plished with the 1-napthyl analogue 13, which resulted in equal
GR potency as the corresponding dimethyl analogue 7. As expected
from the methyl SAR, extending the phenyl in the direction of the
para position, as in the 2-napthyl analogue 14, resulted in a loss in
Table 2
SAR of aryl groups containing a hydrogen bonding element as A-ring mimetics
O
O
R
S
N
H
Compound
R
GR IC50 (nM)
62
PR IC50 (nM)
2100
MR IC50 (nM)
330
IL-6 IC50 (nM)
>2000
IL-6 % efficacy
0
O
15
HO
16
17
18
5
250
12
860
240
1400
480
15
81
0
O
>10,000
3500
>2000
89
HO
HO
58
19
3
210
110
23
80

6648
D. DiSalvo et al. / Bioorg. Med. Chem. Lett. 23 (2013) 6645–6649
To further understand the essential components required for
agonist activity, the importance of the lipophilic substitution on
the A-ring mimetic was evaluated by systematically removing
the methyl groups in the presence of the 4-hydroxyl group. This
SAR was examined with the (S)-enantiomer, as shown in Table 3.
A chiral preference for substitution at this position has been previ-
ously reported.10 As seen in the results shown in Table 3, the
hydrogen bond interaction provided by the hydroxyl in compound
20 was not sufficient to provide agonist activity in the absence of
lipophilic groups on the phenyl ring. Interestingly, the deletion of
a single methyl group from racemic analogue 16 to provide com-
pounds 21 and 22 (single enantiomers) rendered them inactive
with respect to agonist activity, despite modest GR binding po-
tency. Comparing data for the racemate 16 with the chiral com-
pound 23, we find no significant enhancement of IL-6 agonist
activity. Examining the binding potencies for the various nuclear
receptors shows that exceptional GR activity is displayed for 23
and selectivity for GR is maintained with 310-fold selectivity over
PR and a 135-fold selectivity over MR.
N
S
Cl
S
O
O
O
O
a, b
NH2
+
OH
26
d
24
25
O
O
H
O
c
S
N
H
23
27
Scheme 1. Synthesis. Reagents and conditions: (a) Pyr, CH2Cl2, rt; (b) KOH, Et2O,
63%; (c) 4-bromo-2,3-dimethylanisole, Mg, CuI, THF, 53%; (d) BBR3, CH2Cl2, 39%.
The synthesis of compound 23 is described in Scheme 1. Central
to the synthesis was the preparation of the aziridine sulfonamide
26, which was synthesized from the readily available amino alco-
hol 24 and two equivalents of the aryl sulfonylchloride 25 in the
presence of pyridine followed by treatment with 2 N KOH.21 Next,
the aziridine 26 was reacted with 4-bromo-2,3-dimethylanisole in
the presence of magnesium and copper iodide at 85 °C in a micro-
wave reactor to provide 27 which was subsequently demethylated
using boron tribromide to afford 23.
In conclusion, we have described a new class of nonsteroidal GR
agonists. Through incorporation of substituted phenyl A-ring
mimetics, we have identified specific function regulating pharma-
cophores that provide potent GR agonist activity to a unique struc-
tural class. This SAR has confirmed the importance of both a
lipophilic and a hydrogen bonding component which work syner-
gistically to provide agonist activity. In particular, identification of
2,3-dimethyl substitution as requisite lipophilic components in
combination with a 4-hydroxyl group as the hydrogen bonding
element has provided compounds with potent GR agonist activity
as exemplified by compound 23 which displayed potency and effi-
cacy against GR as well as selectivity over PR and MR. The synthe-
sis of this class of compounds via a key aziridine intermediate
allowed for rapid access to chiral material and provided for a point
of diversification to gain access to a broad range of structural
variants.
GR binding activity. With respect to nuclear receptor selectivity,
cross reactivity with the mineralocorticoid receptor (MR) and pro-
gesterone receptor (PR) were monitored to evaluate the potential
for off-target pharmacology. It should be noted that each improve-
ment in GR binding was generally accompanied by increases in MR
binding, with the exception of compound 6 which is selective over
both the PR and MR.
To assess whether the R group of analogues in Table 1 could
potentially fill space similar to that occupied by the A-ring of dexa-
methasone when bound to GR, a select group of substituted phenyl
analogues were docked into the GR ligand binding domain (GR-
LBD) using the GR-LBD/dexamethasone X-ray co-crystal struc-
ture.17 Docking of these compounds did suggest that these phenyl
groups can be overlaid with the A-ring of dexamethasone. Figure 3
shows the docking pose of compound 16 ((S)-enantiomer) in the
GR-LBD X-ray co-crystal structure of dexamethasone. The 2,4,6-tri-
methylphenyl moiety of the sulfonamide group extends into an
area typically occupied by the steroid D-ring while the sulfon-
amide replaces the function of the C-11 hydroxyl by engaging
N564. The para-position of the phenyl group which occupies the
A-ring pocket was identified as a position where a hydrogen bond
acceptor could be within binding distance of residues R611/Q570.
These results suggested that a hydrogen bonding element could be
combined with optimal lipophilic substitution as an A-ring mi-
metic. To this end, methoxy and hydroxyl groups were incorpo-
rated into the 4-position of compounds 7, 10 and 13 to provide
the analogues shown in Table 2. The hydroxyl group in combina-
tion with specific lipophilic substitution has been reported to be
an effective FRP, demonstrating efficacious agonist activity in a
non-steroidal glucocorticoid A-ring mimetic.20 A clear preference
for 4-hydroxyl substitution as compared to the corresponding 4-
methoxy derivative was apparent as shown by the potent GR bind-
ing affinities (IC50 <15 nM) of compounds 16, 18 and 19. More
importantly, the addition of a hydrogen bond interaction provided
modest to very potent agonist activity. Although not clearly appar-
ent by the GR binding IC50 alone, the 2,3-dimethyl substitution ap-
peared to be preferred over the 3,5-dimethyl pattern based on GR
agonist data (16: IL-6 IC50 = 15 nM, 81% maximal efficacy vs. 18:
IL-6 IC50 = 89 nM, 58% maximal efficacy). The corresponding 1-
napthyl analogue 19 also displayed binding potency and agonist
activity similar to 16. It is interesting to note that for each of these
examples the addition of the hydroxyl group is essential for potent
agonist activity despite having little to no effect on GR binding
affinity, suggesting the importance of this hydrogen bonding inter-
action as an essential component in function regulation.
References and notes
1. Evans, R. M. Science 1988, 240, 889.
2. Beato, M.; Herrlich, P.; Schutz, G. Cell 1995, 83, 851.
3. Lowenberg, M.; Stahn, C.; Hommes, D. W.; Buttgereit, F. Steroids 2008, 73, 1025.
4. Schacke, H.; Docke, W. D.; Asadullah, K. Pharmacol. Ther. 2002, 96, 23.
5. Eggert, M.; Schulz, M.; Neeck, G. J. Steroid Biochem. Mol. Biol. 2001, 77, 185.
6. Belvisi, M. G.; Thomas, J. B.; Wicks, S.; Foster, M. L. Pulm. Pharmacol. Ther. 2001,
14, 221.
7. Belvisi, M. G.; Wicks, S.; Battram, C. H.; Bottoms, S. E. W.; Redford, J. E.;
Woodman, P.; Brown, T. J.; Webber, S. E.; Foster, M. L. J. Immunol. 1975, 2001,
166.
8. Zhou, J.; Cidlowski, J. A. Steroids 2005, 70, 407.
9. De Bosscher, K.; Van Craenenbroek, K.; Meijer, O. C.; Haegeman, G. Eur. J. Pharm.
2008, 583, 290.
10. (a) Marshall, D. R.; Rodriguez, G.; Nelson, R.; Thomson, D. Abstracts of Papers,
227th ACS National Meeting, Anaheim, CA, United States, March 28-April 1,
2004, MEDI-226.; (b) Marshall, D. R.; Rodriguez, G.; Thomson, D. S.; Nelson, R.;
Capolina, A. Bioorg. Med. Chem. Lett. 2007, 17, 315.
11. Betageri, R.; Zhang, Y.; Zindell, R.; Kuzmich, D.; Kirrane, T. M.; Bentzien, J.;
Cardozo, M.; Capolino, A. J.; Fadra, T. N.; Nelson, R.; Paw, Z.; Shih, C. K.; Shih, D.
T.; Reilly, P.; Zuvela-Jelaska, L.; Nabozny, G.; Thomson, D. Bioorg. Med. Chem.
Lett. 2005, 15, 4761.
12. (a) Kuzmich, D.; Kirrane, T.; Proudfoot, J.; Bekkali, Y.; Zindell, R.; Beck, L.;
Nelson, R.; Shih, C. K.; Kukulka, A. J.; Paw, Z.; Reilly, P.; Deleon, R.; Cardozo, M.;
Nabozny, G.; Thomson, D. Bioorg. Med. Chem. Lett. 2007, 17, 5025; (b) Zhang, P.;

D. DiSalvo et al. / Bioorg. Med. Chem. Lett. 23 (2013) 6645–6649
6649
Terefenko, E.; Kern, J.; Fensome, A.; Trybulski, E.; Unwalla, R.; Wrobel, J.;
Lockhead, S.; Zhu, Y.; Cohen, J.; LaCava, M.; Winneker, R. C.; Zhang, Z. Bioorg.
Med. Chem. 2007, 15, 6556; (c) Li, J. J.; Iula, D. M.; Nguyen, M. N.; Hu, L.-Y.;
Dettling, D.; Johnson, T. R.; Du, D. Y.; Shanmugasundaram, V.; Van Camp, J. A.;
Wang, Z.; Harter, W. G.; Yue, W.-S.; Boys, M. L.; Wade, K. J.; Drummond, E. M.;
Samas, B. M.; Lefker, B. A.; Hoge, G. S.; Lovdahl, M. J.; Asbill, J.; Carroll, M.;
Meade, M. A.; Ciotti, S. M.; Krieger-Burke, T. J. Med. Chem. 2008, 51, 7010; (d)
Ostrowski, J.; Kuhns, J. E.; Lupisella, J. A.; Manfredi, M. C.; Beehler, B. C.;
Krystek, S. R., Jr.; Bi, Y.; Sun, C.; Seethala, R.; Golla, R.; Sleph, P. G.; Fura, A.; An,
Y.; Kish, K. F.; Sack, J. S.; Mookhtiar, K. A.; Grover, G. J.; Hamann, L. G.
Endocrinology 2007, 148, 4.
in lysates of baculovirus-infected insect cells, between a test compound and a
fluorescently labeled receptor ligand, or probe. IC50 values were determined by
fitting the fluorescence polarization signal data to
a 4-parameter logistic
equation. All IC50 values shown represent the mean of at least two independent
determinations. Repeated testing of reference compounds in these assays
demonstrate typical IC50 standard deviations of 20–40% about the mean.
16. In the IL-6 functional assay, potency and% efficacy (percent of the maximal
response observed for dexamethasone) are reported. Human foreskin
fibroblasts are stimulated with 1 ng/mL recombinant human IL-1 in the
presence of test compound. After 24 h, the degree of GR agonist activity
(transrepression) is determined by measuring IL-6 in the tissue culture media
and calculating EC50 values. Top concentration in the assay was 2 mM.
17. Bledsoe, R. K.; Montana, V. G.; Stanley, T. B.; Delves, D. J.; Apolito, C. J.; McKee,
D. D.; Consler, T. G.; Parks, D. J.; Stewart, E. L.; Willson, T. M.; Lambert, M. H.;
Moore, J. T.; Pearce, K. H.; Xu, E. H. Cell 2002, 110, 93.
13. Regan, J.; Lee, T. W.; Zindell, R. M.; Bekkali, Y.; Bentzien, J.; Gilmore, T.;
Hammach, A.; Kirrane, T. M.; Kulkulka, A. J.; Kuzmich, D.; Nelson, R. M.;
Proudfoot, J. R.; Ralph, M.; Pelletier, J.; Souza, D.; Zuvela-Jelaska, L.; Nabozny,
G.; Thomson, D. S. J. Med. Chem. 2006, 49, 7887.
14. This work was previously disclosed in part: DiSalvo, D.; Kuzmich, D.; Betageri,
R.; Bentzien, J.; Kukulka, A.; Marshall, D. R.; Nabozny, G. H.; Nelson, R.;
Thomson, D. S. Abstract of Papers, 235th ACS National Meeting of the American
Chemical Society, New Orleans, LA; American Chemical Society: Washington,
DC, 2008; Abstract MEDI-322.
18. Glide, version 5.8, Schrödinger LLC., New York, NY, 2012.
19. Molecular Operating Environment (MOE), 2012.10; Chemical ComputingGroup
Inc., 1010 Sherbrooke St. West, Suite #910, Montreal, H3A 2R7, QC, Canada,
2012.
20. Roach, S. L.; Higuchi, R. I.; Hudson, A. R.; Adams, M. E.; Syka, P. M.; Mais, D. E.;
Miner, J. N.; Marschke, K. B.; Zhi, L. Bioorg. Med. Chem. 2011, 21, 168.
21. McCoull, W.; Davis, F. A. Synthesis 2000, 10, 1347.
15. GR, PR and MR binding assays were performed in a fluorescence polarization
format that measures competition for binding to the nuclear receptor, present