Exploration of SAR regarding glucose moiety in novel C-aryl glucoside inhibitors of SGLT2

Article abstract of DOI:10.1016/j.bmcl.2010.11.115

In order to investigate SAR regarding glucose moiety in novel C-aryl glucoside SGLT2 inhibitors containing a thiazole motif, a series of chemical modifications on glucose was conducted to explore potential utility as a suitable replacement of glucose per

Full text of DOI:10.1016/j.bmcl.2010.11.115

Bioorganic & Medicinal Chemistry Letters 21 (2011) 742–746
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Exploration of SAR regarding glucose moiety in novel C-aryl glucoside
inhibitors of SGLT2
⇑
Eun-Jung Park, Younggyu Kong, Jun Sung Lee, Sung-Han Lee, Jinhwa Lee
Green Cross Corporation, Research Center, 303 Bojeong-Dong, Giheung-Gu, Yongin, Gyeonggi-Do 446-770, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
In order to investigate SAR regarding glucose moiety in novel C-aryl glucoside SGLT2 inhibitors contain-
ing a thiazole motif, a series of chemical modifications on glucose was conducted to explore potential
utility as a suitable replacement of glucose per se. Among the compounds prepared, deshydroxy 29
(IC50 = 7.01 nM) demonstrated the best in vitro inhibitory activity against SGLT2 in this series to date.
But, none of the compounds were better than the parent molecule 5 (IC50 = 1.75 nM).
Ó 2010 Elsevier Ltd. All rights reserved.
Received 8 October 2010
Revised 20 November 2010
Accepted 24 November 2010
Available online 3 December 2010
Keywords:
SGLT
Dapagliflozin
Thiazole
Glucose
Diabetes
Diabetes has become an increasing concern to the world’s pop-
ulation. In 2010, approximately 285 million people around the
world will have diabetes, corresponding to 6.4% of the world’s
adult population, with a prediction that the number of people with
diabetes will have grown to 438 million by 2030.1 Type 2 diabetes
is the most common disorder of glucose homeostasis, accounting
for approximately 90–95% of all cases of diabetes.2
Sodium-dependent glucose cotransporters (SGLTs) couple the
transport of glucose against a concentration gradient with the
simultaneous transport of Na+ down a concentration gradient.3 It
is estimated that 90% of renal glucose reabsorption is facilitated
by SGLT2.4
Bristol-Myers Squibb has identified dapagliflozin 1, a potent,
selective SGLT2 inhibitor for the treatment of type 2 diabetes.5–7
At present, dapagliflozin 1 is the most advanced SGLT2 inhibitor
in clinical trials.8 On the other hand, Johnson & Johnson (2), Lexicon
(3), and Pfizer (4) are reported to be in various phase of clinical tri-
als (Fig. 1).9
In the previous study, C-glucosides bearing a heterocycle ring
were exploited in order to develop novel SGLT2 targeting antidia-
betic agents, since we envisioned that replacement of the distal or
proximal ring of dapagliflozin 1 with a heterocyclic ring might
improve the overall physicochemical properties of SGLT2 inhibi-
tors.10 Based on the structure of dapagliflozin, the distal ring was
modified into thiazole. A series of lead optimization efforts led to
the discovery of thiazole 5 bearing a furanyl moiety as shown in
Figure 2.11 In the present study, a variety of modifications, espe-
cially C-6 position on glucose (as shown in 6) were conducted to
establish SAR on carbohydrate pharmacophore based on structure
of potent thiazole 5.12 Along this line, we report the synthesis and
biological evaluation of thiazolylmethylphenyl glucoside congen-
ers herein.
Preparation of the thiazole compound is described in Scheme 1.
Thus, previously reported carboxylic acid 710a,b was coupled with
2-amino-1-(furan-2-yl)ethanone hydrochloride in the presence of
EDCI (1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide), HOBt
(1-hydroxybenzotriazole), and NMM (4-methylmorpholine) to
provide the corresponding amide 9 in 82% yield. Amide 9 smoothly
underwent requisite cyclization by the action of Lawesson’s reagent
in refluxing THF (tetrahydrofuran) to result in thiazole 10. Total
removal of benzyl protections was accomplished with BCl3 at 0 °C
to produce a target compound 5 in 70% yield (Scheme 1).
As shown in Scheme 2, functionalization was initiated with
alcohol 11, which was prepared from 10 via a selective debenzyla-
tion.13 Oxidation of the alcohol 11 to aldehyde 12 was achieved
through Dess–Martin periodinane.14 Aldehyde 12 turned out to
be a versatile intermediate. This aldehyde was treated with DAST
(diethylaminosulfur trifluoride)15 to provide the corresponding
difluoromethyl 13. Aldehyde 12 was also treated with a Grignard
reagent to provide the corresponding alcohols (14–16). Alterna-
tively, aldehyde 12 was further oxidized to acid 17 by use of
sodium chlorite and monobasic potassium phosphate in aqueous
t-BuOH. Acid 17 was transformed into ester 18 by trimethylsilyl-
diazomethane. Ester 18 was then treated with excess Grignard
reagent to tertiary alcohol 19. Ester 18 also smoothly underwent
⇑
Corresponding author. Tel.: +82 31 260 9892; fax: +82 31 260 9020.
E-mail address: jinhwalee@greencross.com (J. Lee).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.11.115

E.-J. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 742–746
Cl OEt Me
743
O
O
F
S
HO
HO
HO
HO
OH
OH
OH
OH
1, dapagliflozin
2, canagliflozin
Cl
OEt
Cl
OEt
O
MeO
HO
O
O
HO
HO
OH
OH
4, Pfizer's
OH
OH
3, Lexicon's
Figure 1. Structures of C-aryl glucoside SGLT2 inhibitors.
Cl
OEt
Cl
N
O
O
S
HO
HO
HO
O
HO
OH
OH
O
5
OH
1, dapagliflozin
OH
Cl
N
R
O
S
HO
OH
OH
6
Figure 2. Exploration of C-6 position of glucose moiety in novel C-glucoside bearing thiazole 5.
Cl
Cl
O
O
O
CO2H
O
a
O
BnO
BnO
H2N
HCl
BnO
BnO
N
H
+
O
OBn
O
OBn
OBn
OBn
7
8
9
Cl
Cl
N
N
O
O
b
c
70%
S
S
BnO
BnO
HO
HO
O
O
82%, 2steps
OBn
OH
OBn
OH
10
5
Scheme 1. Reagents and conditions: (a) EDCI, HOBt, NMM, DMF, rt; (b) Lawesson’s reagent, THF, 85 °C; (c) BCl3(1 M in CH2Cl2), CH2Cl2, 0 °C.
Kulinkovich cyclopropanation to generate the corresponding
cyclopropanol 20.16 Finally, deprotection of benzyl groups was
accomplished with BCl3 at 0 °C to produce the corresponding target
compounds as previously described.
respectively. Also iodide 24, which was prepared by treatment of
tosylate 21 with NaI, was reduced to 29 by action of hydrogen in
the presence of catalytic Raney-Nickel.17
The cell-based SGLT2 AMG (Methyl-a-D-glucopyranoside) inhi-
Alternatively, free alcohol form 5 was utilized to provide vari-
ous glucose analogs as shown in Scheme 3. Thus, 5 was selectively
tosylated with tosyl chloride in the presence of 2,6-lutidine to pro-
duce tosylate 21. Diverse nucleophiles were used to generate the
glucose analogs as shown in Scheme 3. For example, compounds
containing 1,2,4-triazole (26) or tetrazole (27, 28) were obtained
by treating tosylate 21 with 1,2,4-triazole or tetrazole in the pres-
ence of a suitable base such as cesium carbonate or triethylamine,
bition assay was performed to evaluate the inhibitory effects of all
prepared compounds on hSGLT2 activities.18,19 Exploration of the
SAR began by removing C-6 hydroxyl group at the glucose of
4-chloro-3-((5-(furan-2-yl)thiazol-2-yl)methyl)phenyl 5. Table 1
shows the structure–activity relationship upon alteration of the
C-6 substituent at the glucose employing only the b-anomer. For
instance, deshydroxy 29 showed fourfold decrease of inhibitory
activity (29, IC50 = 7.01 nM), compared with parent 5 (IC50
=

744
E.-J. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 742–746
O
A
BnO
BnO
OBn
OBn
10
a, b
Cl
N
89%, 2 steps
A =
S
O
O
A
HO
BnO
OBn
OBn
11
c
61%
F
R1
O
A
O
A
O
A
O
F
e
HO
BnO
d
60-75%
41%
BnO
OBn
BnO
OBn
OBn
OBn
12
OBn
13
OBn
14 R1=Me
f
15 R1=vinyl
16 R1=allyl
84%
HO2C
BnO
O
A
OBn
OBn
17
g
32%
Me Me
MeO2C
BnO
O
A
O
A
O
A
OBn
HO
BnO
HO
BnO
h
55%
i
56%
OBn
OBn
OBn
18
OBn
20
OBn
19
Scheme 2. Reagents and conditions: (a) TMSOTf, Ac2O, CH2Cl2, À55 °C, 1 h; (b) NaOMe, MeOH, rt, 2 h; (c) Dess–Martin Periodinane, CH2Cl2, rt, 2 h; (d) DAST, CH2Cl2, À78 °C to
rt, 15 h; (e) R1MgBr, THF, 0 °C, 3 h; (f) KH2PO4, NaClO2, 2-methyl-2-butene, aq t-BuOH, rt, 15 h; (g) TMSCH2N2, CH2Cl2, 0 °C to rt, 15 h; (h) MeMgCl, THF, 0 °C, 3 h; (i) EtMgCl,
Ti(Oi-Pr)4, THF, 0 °C, 3 h.
1.75 nM). Addition of an extra methyl group at C-6 glucose deteri-
orated activity by 8- to 14-fold, dependent on the stereochemistry
at C-6 on glucose (32a, IC50 = 13.5 nM; 32b, IC50 = 23.8 nM). This
effect was also observed as the vinyl group was introduced at the
position as exemplified in 33a and 33b (33a, IC50 = 54.9 nM; 33b,
IC50 = 54.8 nM). This adverse steric effect became even more
evident as gem-dimethyl group was introduced at the position as
exemplified in 36 (36, IC50 = 89.5 nM). Cyclopropyl group, which
is rigid and compact, demonstrates twofold increase of inhibitory
activity against hSGLT2 (37, IC50 = 48.9 nM), but it is still threefold
activities against hSGLT2 compared with the parent compound 5.
For instance, methyl ether 22 (IC50 = 23.5 nM) showed 13-fold
decrease in activity than the parent 5 (IC50 = 1.75 nM). Ethyl ether
39 even further reduced inhibitory activity against hSGLT2 (39,
IC50 = 68.7 nM). Thioethers appear to be slightly more active than
the ether counterparts as exemplified in 25 and 41 (25,
IC50 = 18.6 nM; 41, IC50 = 31.9 nM). However, oxidation of methyl
thioether 25 to sulfone 30 demonstrated significant loss of activity
such as two orders of magnitude (30, IC50 = 1450 nM), implying
that sulfonyl functionality in the region is not tolerated. Addition-
ally, substitution with triazole (26), tetrazole (27, 28) was per-
formed. These analogs showed moderate inhibitory activity
against hSGLT2, but none improved potency relative to the simple
glucose 5. Among the azole compounds, tetrazoles proved to be
more potent than triazole as shown in Table 1, implying that an ex-
tra nitrogen in tetrazole ring might be involved in shaping mole-
cule more compact, thereby improving inhibitory activity.
less active than monosubstituted compound 32a (32a, IC50
=
13.5 nM), likely suggesting that increased steric crowdedness is
not favorable in the region. Carbonyl groups on the glucose were
also explored. Ester 35 showed 30-fold decrease in inhibitory activ-
ity against hSGLT2 (35: IC50 = 59.1 nM), likewise ketone 38 showed
even 60-fold decrease in activity, implying that sp2 character at
this particular position is not that favorable. Fluorides appear to
be tolerated to some degree and demonstrate remote possibility
for replacement of the hydroxyl group (IC50 = 10.6 nM for monoflu-
oride 23 and IC50 = 9.55 nM for difluoride 31).
Overall, modifications of the C-6 on glucose appear to weaken
in vitro inhibitory activity against hSGLT2 perhaps for unfavorable
steric environments at the glucose ring position.
Next, a series of simple alkylated compounds was explored
(22, 39, 40, Table 1). This series exhibited decrease in inhibitory
In summary, a variety of modifications at the C-6 position on
glucose was conducted in the present study to establish SAR on

E.-J. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 742–746
745
O
A
HO
HO
OH
OH
a
5
O
A
O
A
MeO
HO
F
OH
HO
OH
OH
c
OH
b
22
23
O
A
TsO
HO
OH
OH
21
g
e
d
O
A
O
A
MeS
HO
I
f
OH
HO
OH
24
OH
i
OH
h
25
O
A
N
O
A
N
N
N
N
N
HO
OH
N
HO
OH
OH
Cl
26
OH
O
27
+
Me
HO
O
A
A
O
A
N
N
N
MeO2S
HO
N
OH
29
HO
OH
OH
OH
OH
OH
30
28
N
A =
S
O
Scheme 3. Reagents and conditions: (a) TsCl, 2,6-lutidine, rt, 15 h, 78%; (b) NaOMe, MeOH, rt, 15 h, 36%; (c) KF, 1,2-ethanediol, 100 °C, 20 h, 11%; (d) NaI, 2-butanone, 80 °C,
2 h, 48%; (e) NaSMe, DMF, rt, 4 h, 45%; (f) 1,2,4-triazole, Cs2CO3, DMF, rt, 3 d, 14%; (g) tetrazole, Et3N, DMF, 80 °C, 3 days, 24%; (h) H2, cat. Raney-Nickel, Et2NH, MeOH, rt, 1 d,
31%; (i) mCPBA, CH2Cl2, 0 °C, 1 h, 66%.
Table 1
In vitro inhibitory activity against hSGLT2
Cl
N
R
O
S
O
HO
OH
OH
Compound
R
hSGLT2 IC50 (nm)
Compound
R
hSGLT2 IC50 (nm)
10.6
1 Dapagliflozin
—
0.49 0.04
23
F
Me
F
29
7.01
31
9.55
F
5
1.75
13.5
22
39
23.5
68.7
HO
HO
HO
O
32a
O
S
HO
S
32b
33a
23.8
54.9
40
25
30.9
18.6
O
HO
HO
33b
34
54.8
20.8
41
30
31.9
O
S
O
Me
1450
HO
(continued on next page)

746
E.-J. Park et al. / Bioorg. Med. Chem. Lett. 21 (2011) 742–746
Table 1 (continued)
Compound
R
hSGLT2 IC50 (nm)
89.5
Compound
R
hSGLT2 IC50 (nm)
156
O
S
36
HO
21
O
N
N
37
35
38
48.9
59.1
110
26
28
27
471
68.9
106
HO
O
N
O
O
N
N
N
N
N
N
N
N
Chem. 2010, 53, 6355; (b) Lexicon Pharmaceuticals, www.clinicaltrials.gov,
2009, NCT00962065.; (c) Mascitti, V. Presented at the 240th American
Chemical Society National Meeting and Exposition, Boston, MA, August 2010;
CARB 90.
carbohydrate pharmacophore based on structure of potent thiazole
5. Among the compounds tested, deshydroxy 29 or difluoride 31
appear to be tolerated at this position to a degree, but none im-
proved potency against hSGLT2.
10. (a) Lee, J.; Lee, S.-H.; Seo, H. J.; Son, E.-J.; Lee, S. H.; Jung, M. E.; Lee, M.; Han, H.-
K.; Kim, J.; Kang, J.; Lee, J. Bioorg. Med. Chem. 2010, 18, 2178; (b) Kim, M. J.; Lee,
J.; Kang, S. Y.; Lee, S.-H.; Son, E.-J.; Jung, M. E.; Lee, S. H.; Song, K.-S.; Lee, M.;
Han, H.-K.; Kim, J.; Lee, J. Bioorg. Med. Chem. Lett. 2010, 20, 3420; (c) Kang, S. Y.;
Song, K.-S.; Lee, J.; Lee, S.-H.; Lee, J. Bioorg. Med. Chem. 2010, 18, 6069; (d) Lee,
J.; Kim, J. Y.; Choi, J.; Lee, S.-H.; Kim, J.; Lee, J. Bioorg. Med. Chem. Lett. 2010, 20,
7046.
11. Song, K.-S.; Lee, S. H.; Kim, M.; Seo, H.; Lee, J.; Lee, S.-H.; Jung, M. E.; Son, E. J.;
Lee, M.; Kim, J.; Lee, J. ACS Med. Chem. Lett. doi:10.1021/ml100256c.
12. Modifications at other positions on glucose including C-2, C-3, C-4, and C-5
appear to devastate in vitro inhibitory activity against hSGLT2. See: (a)
Washbrun, W. N. Exp. Opin. Ther. Patents 2009, 19, 1485; (b) Honda, T.; Oguchi,
M.; Yoshida, M.; Okuyama, R.; Ogata, T. Abe, M.; Ueda, K.; Ohsumi, J.; Izumi, M.
Patent EP2048105; 2009.
Acknowledgments
We are grateful to Dr. Jeongmin Kim (Green Cross Corporation)
for his counsel on small molecule projects. Dr. Kwang-Seop Song
and Mr. Suk Ho Lee are appreciated for their previous contributions
to the thiazole series. We also appreciate Dr. Eun Chul Huh for his
leadership and valuable advice as CTO at Green Cross Corporation.
Supplementary data
13. Kobertz, W. R.; Bertozzi, C. R.; Bednarski, M. D. J. Org. Chem. 1996, 61, 1894.
14. Dess, D. B.; Martin, J. C. J. Org. Chem. 1983, 48, 4155.
15. Walba, D. M.; Razavi, H. A.; Clark, N. A. J. Am. Chem. Soc. 1988, 110, 8686.
16. (a) Wolan, A.; Six, Y. Tetrahedron 2010, 66, 3097; (b) Lee, J.; Kang, C. H.; Kim, H.;
Cha, J. K. J. Am. Chem. Soc. 1996, 118, 291.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.11.115.
17. Hanessian, S.; Simard, B. D.; Simard, D. Tetrahedron 2009, 65, 6656.
18. For cloning and cell line construction for human SGLT2, human SGLT2
(hSGLT2) gene was amplified by PCR from cDNA-Human Adult Normal
Tissue Kidney (Invitrogen, Carlsbad, CA). The hSGLT2 sequence was cloned
into pcDNA3.1(+) for mammalian expression and were stably transfected into
chinese hamster ovary (CHO) cells. SGLT2-expressing clones were selected
based on resistance to G418 antibiotic (GeneticinÒ, Invitrogen, Carlsbad, CA)
References and notes
1. International Diabetes Federation Diabetes Atlas, 4th ed.; International Diabetes
Federation: Montreal, Canada, 2009.
2. Dwarakanathan, A. J. Insur. Med. 2006, 38, 20.
3. Mackenzie, B.; Loo, D. D. J. Biol. Chem. 1996, 20, 32678.
4. Moe, O. W.; Berry, C. A.; Rector, F. C. In The Kidney; Brenner, B. M., Rector, F. C.,
Eds., 5th ed.; WB Saunders Co.: Philadelphia, 2000; p 375.
5. Ellsworth, B. A.; Meng, W.; Patel, M.; Girotra, R. N.; Wu, G.; Sher, P.; Hagan, D.;
Obermeier, M.; Humphreys, W. G.; Robertson, J. G.; Wang, A.; Han, S.; Waldron,
T.; Morgan, N. N.; Whaley, J. M.; Washburn, W. N. Bioorg. Med. Chem. Lett. 2008,
18, 4770.
6. Meng, W.; Ellsworth, B. A.; Nirschl, A. A.; McCann, P. J.; Patel, M.; Girotra, R. N.;
Wu, G.; Sher, P. M.; Morrison, E. P.; Biller, A. A.; Zahler, R.; Deshpande, P. P.;
Pullockaran, A.; Hagan, D. L.; Morgan, N.; Taylor, J. R.; Obermeier, M. T.;
Humphreys, W. G.; Khanna, A.; Discenza, L.; Robertson, J. G.; Wang, A.; Han, S.;
Wetterau, J. R.; Janovitz, E. B.; Flint, O. P.; Whaley, J. M.; Washburn, W. N. J. Med.
Chem. 2008, 51, 1145.
and activity in the 14C- -glucopyranoside (14C-AMG) uptake assay.
a-methyl-D
19. For sodium-dependent glucose transport assay, cells expressing hSGLT2 were
seeded into a 96-well culture plate at a density of 5 Â 104 cells/well in RPMI
medium 1640 containing 10% fetal bovine serum. The cells were used 1 day
after plating. They were incubated in pretreatment buffer (10 mM HEPES,
5 mM Tris, 140 mM choline chloride, 2 mM KCl, 1 mM CaCl2, and 1 mM MgCl2,
pH 7.4) at 37 °C for 10 min. They were then incubated in uptake buffer (10 mM
HEPES, 5 mM Tris, 140 mM NaCl, 2 mM KCl, 1 mM CaCl2, 1 mM MgCl2, and
1 mM 14C-nonlabeled AMG pH 7.4) containing 14C-labeled (8
lM) and inhibitor
or dimethyl sulfoxide (DMSO) vehicle at 37 °C for 2 h. Cells were washed twice
with washing buffer (pretreatment buffer containing 10 mM AMG at room
temperature) and then the radioactivity was measured using
a liquid
scintillation counter. IC50 was determined by nonlinear regression analysis
7. Washburn, W. N. J. Med. Chem. 2009, 52, 1785.
using GraphPad PRISM.20,21
8. According to a report from Business Wire on June 26, 2010, dapagliflozin as add
on therapy to insulin demonstrated improved glycemic control in patients with
type 2 diabetes inadequately controlled with insulin.
9. (a) Nomura, S.; Sakamaki, S.; Hongu, M.; Kawanshi, E.; Koga, Y.; Sakamoto, T.;
Yamamoto, Y.; Ueta, K.; Kimata, H.; Nakayama, K.; Tsuda-Tsukimoto, M. J. Med.
20. Han, S.; Hagan, D. L.; Taylor, J. R.; Xin, L.; Meng, W.; Biller, S. A.; Wetterau, J. R.;
Washburn, W. N.; Whaley, J. M. Diabetes 2008, 57, 1723.
21. Katsuno, K.; Fujimori, Y.; Takemura, Y.; Hiratochi, M.; Itoh, F.; Komatsu, Y.;
Fujikura, H.; Isaji, M. J. Pharmacol. Exp. Ther. 2007, 320, 323.