Synthesis and SAR of thiazolylmethylphenyl glucoside as novel C -aryl glucoside SGLT2 inhibitors

Article abstract of DOI:10.1021/ml100256c

Novel C-aryl glucoside SGLT2 inhibitors containing the thiazole motif were designed and synthesized for biological evaluation. Among the compounds assayed, thiazole containing furanyl moiety 14v and thiophenyl moiety 14y demonstrated the best in vitro inh

Full text of DOI:10.1021/ml100256c

pubs.acs.org/acsmedchemlett
Synthesis and SAR of Thiazolylmethylphenyl Glucoside
as Novel C-Aryl Glucoside SGLT2 Inhibitors
Kwang-Seop Song, Suk Ho Lee, Min Ju Kim, Hee Jeong Seo, Junwon Lee, Sung-Han Lee,
Myung Eun Jung, Eun-Jung Son, MinWoo Lee, Jeongmin Kim, and Jinhwa Lee*
Green Cross Corporation Research Center, 303 Bojeong-Dong, Giheung-Gu, Yongin, Gyeonggi-Do, 446-770, Republic of Korea
ABSTRACT Novel C-aryl glucoside SGLT2 inhibitors containing the thiazole motif
were designed and synthesized for biological evaluation. Among the compounds
assayed, thiazole containing furanyl moiety 14v and thiophenyl moiety 14y
demonstrated the best in vitro inhibitory activity against SGLT2 in this series to
date (IC50 = 0.720 nM for 14v and IC50 = 0.772 nM for 14y). Both of these
compounds have been further evaluated on a urinary glucose excretion test and
the urine volumes excreted.
KEYWORDS Thiazole, SAR, SGLT2, glucoside, diabetes
iabetes has become an increasing concern world-
wide. In 2010, approximately 285 million people
around the world will have diabetes, corresponding
line, the structure of dapagliflozin (1) was modified into 5,
bearing a thiazole ring at the distal ring position as shown in
Figure 1. Herein, we report the synthesis and structure-
activity relationship (SAR) evaluation of thiazolylmethylphe-
nyl glucoside congeners.
Preparation of the thiazole compound is described in
Scheme 1. Thus, previously reported carboxylic acid 614,15
was coupled with 2-amino-1-(furan-2-yl)ethanone hydro-
chloride in the presence of EDCI, HOBt, and NMM to provide
the corresponding amide 7 in 82% yield. Amide 7 smoothly
underwent thionation and subsequent cyclization by the action
of Lawesson reagent in refluxing THF to lead to thiazole 8.
Finally, total removal of benzyl protection was affected with
TMSI at mild heating for 15 h to produce the target com-
pound 14v in 73% yield.
The cell-based SGLT2 AMG (methyl-R-D-glucopyranoside)
inhibition assay was performed to evaluate the inhibitory
effects of all prepared compounds on hSGLT2 activities.18,19
Exploration of the SAR began by replacing the phenyl moiety
at the distal ring position of dapagliflozin 1 with the 2-thi-
azolyl moiety. Table 1 shows the structure-activity relation-
ship upon alteration of the substituent at the distal thiazole
ring employing only the β-anomer. Initially, ethyl on the C-5
thiazole ring showed decent activity (14a, IC50=16.7 nM).
However, as the number of carbons increases, the inhibitory
activity against hSGLT2 fluctuates. For example, a 7-fold drop
in activity is observed by varying the length of the alkyl chain
from ethyl (14a, IC50=16.7 nM) to n-butyl (14b, IC50=119 nM),
whereas a 9-fold increase in activity is observed from n-butyl
(14b, IC50 = 119 nM) to n-pentyl (14c, IC50 = 13.3 nM).
Additional 3-fold increase in activity is observed from n-pentyl
(14c) to n-hexyl (14d, IC50 = 5.0 nM). A branched alkyl
D
to 6.4% of the world's adult population, with a prediction
that by 2030 the number of people with diabetes will have
grown to 438 million.1 Type 2 diabetes is the most common
disorder of glucose homeostasis, accounting for nearly 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 Naþ down a concentra-
tion gradient.3 It is estimated that 90% of renal glucose
reabsorption is facilitated by SGLT2.4 SGLT2 inhibitors have
attracted considerable attention because there is need for
novel antidiabetic agents with a unique mode of action to
compensate for existing therapies and avert potential side
effects.5
Bristol-Myers Squibb and Johnson & Johnson have identi-
fied, respectively, dapagliflozin 1 and canagliflozin 2, potent,
selective SGLT2 inhibitors for the treatment of type 2
diabetes.6-9 At present, dapagliflozin is the most advanced
SGLT2 inhibitor in clinical trials (Phase 3), and canagliflozin is
the second most advanced clinical candidate. In addition,
Boehringer Ingelheim, Lexicon, Astellas, and Pfizer are
reported to be in various phases of clinical trials.10-13
We have explored metabolically more stable C-glucosides
bearing a heteroaromatic ring in order to develop novel
SGLT2 targeting antidiabetic agents since C-glucosides are
more stable than O-glucoside derivatives. We envisioned
that replacement of the distal ring or proximal ring of
dapagliflozin 1 with a heterocyclic ring might improve the
physicochemical properties while maintaining a similar level
of antidiabetic activity, thereby providing a high possibility
for clinical development.14-17 For instance, C log P values of
this series of compounds would routinely show 2.7-3.0,
while that of dapagliflozin (1) is shown to be 3.4. Along this
Received Date: October 25, 2010
Accepted Date: December 7, 2010
Published on Web Date: December 13, 2010
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Figure 1. Exploration of C-glucoside bearing thiazole at the distal ring.
Scheme 1
group at the position appears to decrease activity (14f, IC50
51.4 nM), whereas the conjugated alkenyl group exemplified
in 14g restores inhibitory activity against hSGLT2 (IC50
=
IC50 = 3.13 nM; 14ab, IC50 = 14.0 nM) than furan 14v or
thiophene 14y, likelysuggesting that increased polarity is not
favorable in the region. This phenomenon is unequivocally
observed in carboxylic acid 14ad, which is completely devoid
of any activity against hSGLT2 (IC50>10,000 nM).
=
4.69 nM). Carbocycle at the position also appears to be
tolerant (14i, IC50=9.71 nM). Alkoxy groups on the thiazole
were also explored. These alkoxides (14k-14n) appear to
be tolerated across the board (IC50 = 8.2 nM-19.6 nM).
Meanwhile, isosteric replacement of alkoxy groups with
alkylthio groups for this region appears to diminish inhib-
itoryactivity in approximately 3-fold, primarily implying that
the bulky sulfur atom is less favored at this location. Re-
placement of this moiety with phenyl group 14s improved
the inhibitory activity against hSGLT2 (IC50 = 13.3 nM).
Interestingly, the somewhat big biphenyl group 14u showed
good inhibitory activity (IC50=9.31 nM). Meanwhile, substitu-
tion of phenyl with 2-furyl (14v) or 3-thiophenyl (14y) drama-
tically improved the inhibitory activity against hSGLT2 (14v,
IC50=0.720 nM vs 14y, IC50=0.772 nM). Substituted thiophene
14z decreases activity 10-fold. However, thiazole 14aa and
thiadiazole 14ab demonstrated lower in vitro activity (14aa,
It was encouraging to note that considerable inhibitory
activity against hSGLT2 was already evident in compounds
14v and 14y. At this juncture, we proceeded to explore the
C-4 region of the proximal phenyl ring by using 5-(furan-
2-yl)thiazolyl and 5-(thiophen-3-yl)thiazolyl as lead scaffolds.
The inhibitory activity data is shown in Table 2. The small
methyl group (15a and 15b) or other halogen atoms (15c-
15f) appear to maintain a similar level of activity, albeit in
slightly decreased potency. On the contrary, hydrogen 15i,
cyano 15j, 15k, or cyclopropyl 15l demonstrated a loss of
activity in an order of magnitude, suggesting that merely
small lipophilic groups are favored at the C-4 position of the
proximal phenyl ring.
Next, an isomeric thiazole series of compounds was explored
by using 2-furanyl and 3-thiophenyl as lead scaffolds
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Table 1. In Vitro Screening Data for hSGLT2 Inhibitory Activity
a These data were obtained by single determinations. b The IC50 value was obtained by in-house multiple determinations. c Compound 14s had been
disclosed in WO2005012326.22
(16a-16d, Table 3). This series exhibited a slight decrease in
inhibitory activities against hSGLT2 compared with that of
the previous thiazole series. For instance, 2-(furan-2-yl)thi-
azol-5-yl 16a (IC50=1.42 nM) showed a 2-fold decrease in
activity than the counterpart 14v (IC50 = 0.720 nM). As a
more clear demonstration, two pairs of examples are pre-
elevation in glucose disposal relative to that of vehicle
controls. However, a single oral dose of thiazole 14v (1 mg/
kg or 10 mg/kg) increased urinary glucose excretion in
normal SD rats, resulting in 230-fold (1 mg/kg) or 700-fold
(10 mg/kg) elevation in glucose disposal relative to that of
vehicle controls. Urine volumes excreted in normal SD rats
are also shown in Figure 2. Dapagliflozin 1 (1 mg/kg) caused
increased urine volume over that of the vehicle by 5.7-fold,
while thiazole 14y (1 mg/kg or 10 mg/kg) increased urine
volume by 2.5-fold (1 mg/kg) or by 4.2-fold, respectively.
Thiazole 14v increased urine volume to a lesser degree at a
dose of 10 mg/kg (3.7-fold increase).
sented, including furans 14w (IC50=1.57 nM), 16b (IC50
=
4.47 nM), and thiophenes 14x (IC50=1.14 nM) and 16c (IC50=
2.79 nM), demonstrating close to a 3-fold decrease of activity,
respectively.
Selected promising compounds (14v and 14y) were tested
on animal models for in vivo efficacy. Urinary glucose
excretion was evaluated in normal SD rats. As shown in
Figure 2, a single oral dose of thiazole 14y (1 mg/kg or 10 mg/
kg) increased urinary glucose excretion in normal SD rats,
resulting in 160-fold (1 mg/kg) or 730-fold (10 mg/kg)
In order to further evaluate this series, the PK properties of
14y and 14v were measured in male SD rats. After oral
administration of 5 mg/kg of 14y to rats, a Cmax of 1.54 μg/
mL was obtained at 0.38 h. The elimination half-life of 14y
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Table 2. In Vitro Inhibitory Activity against hSGLT2
a These data were obtained by single determinations.
Table 3. In Vitro Inhibitory Activity against hSGLT2
a These data were obtained by single determinations.
following oral administration was 2.51 h. Compound 14y
showed moderate oral bioavailability (F=15%). Furanyl
compound 14v also demonstrated PK profiles similar to
those of compound 14y, showing slightly better oral bioavail-
ability (F=20.6%). For comparison, in-house oral adminis-
tration of 5 mg/kg of dapagliflozin 1 to rats showed a Cmax of
2.50 μg/mL at 0.67 h. The elimination half-life of 1 following
oral administration was 4.01 h. Dapagliflozin 1 showed
superior oral bioavailability (F=88%). Therefore, it is con-
cluded that the decreased in vivo efficacy of the current
SGLT2 inhibitors 14v and 14y, compared with that of dapa-
gliflozin 1, should be attributed to the 1.5-fold lower in vitro
potencies as well as their unfavorable PK properties.
In summary, the potential of metabolically more stable
C-glucosides bearing a thiazole ring as antidiabetic agents
was exploited. Among the compounds tested, thiazole contain-
ing furanyl moiety 14v or thiophenyl moiety 14y showed the
best in vitro inhibitory activity against hSGLT2 in this series to
date (IC50 = 0.720 nM for 14v; IC50 = 0.772 nM for 14y).
These compounds demonstrated reasonable glucose excretion
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Figure 2. Effects of dapagliflozin, compound 14y and 14v on urine glucose excretion and urine volume in normal Spraue-Dawley rats. All
results are expressed as means ( SEM. The statistical analysis was performed by one-way ANOVA followed by Dunnett's posthoc test. *P <
0.05 vs vehicle. **P < 0.01 vs vehicle.
and glucosuria in normal SD rats along with moderate PK
profiles. Further work concerning optimization of SGLT2
inhibitors suitable for development is ongoing on the basis
of this series.
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SUPPORTING INFORMATION AVAILABLE Experimental
details. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
(7)
Corresponding Author: *Tel: þ82 31 260 9892. Fax: þ82 31
260 9020. E-mail: jinhwalee@greencross.com.
ACKNOWLEDGMENT We appreciate Dr. Eun Chul Huh for his
leadership and support as CTO, Green Cross Corporation (GCC).
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