Synthesis and biological evaluation of bicyclo[3.3.0] octane derivatives as dipeptidyl peptidase 4 inhibitors for the treatment of type 2 diabetes

Article abstract of DOI:10.1016/j.bmcl.2010.04.138

A series of novel bicyclo[3.3.0]octane derivatives have been synthesized and found to be dipeptidyl peptidase 4 (DPP-4) inhibitors. Compounds 10a and 10b demonstrate good efficacies in oral glucose tolerance tests.

Full text of DOI:10.1016/j.bmcl.2010.04.138

Bioorganic & Medicinal Chemistry Letters 20 (2010) 3521–3525
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological evaluation of bicyclo[3.3.0] octane derivatives
as dipeptidyl peptidase 4 inhibitors for the treatment of type 2 diabetes
a
a
a
a
a
a
Tang Peng Cho a, , Lin Zhi Gang , Yang Fang Long , Wang Yang , Wang Qian , Zhang Lei , Luo Jing Jing ,
*
Feng Ying b, Yan Pang Ke a,b, Leng Ying b, Feng Jun a
a Shanghai Hengrui Pharmaceuticals Co., Ltd, 279 Wenjing Road, Shanghai 200245, China
b State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel bicyclo[3.3.0]octane derivatives have been synthesized and found to be dipeptidyl pep-
tidase 4 (DPP-4) inhibitors. Compounds 10a and 10b demonstrate good efficacies in oral glucose toler-
ance tests.
Received 22 February 2010
Revised 30 March 2010
Accepted 28 April 2010
Available online 18 May 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Bicyclo[3.3.0]octane derivatives
Dipeptidyl peptidase 4
Inhibitors
Oral glucose tolerance tests
Type 2 diabetes
Type 2 diabetes mellitus (T2DM) is the most common form of
the diabetes disease, accounting for about 90–95% of all diagnosed
North American cases of diabetes.1 T2DM may be effectively trea-
ted by agents that induce the biosynthesis and secretion of insulin
during periods of hyperglycemia. Two endogenous peptides that
stimulate glucose-dependent insulin secretion are the incretin hor-
mones glucagon-like peptide 1 (GLP-1) and glucose-dependent
insulinotropic polypeptide (GIP).2 Continuous infusion of GLP-1
in patients with type 2 diabetes has resulted in the lowering of
plasma glucose.3,4 However, active GLP-1 is rapidly converted to
inactive GLP-1 by the serine protease dipeptidyl peptidase 4
(DPP-4),5 thus limiting its therapeutic practicality. A straightfor-
ward solution is to inhibit DPP-4 to increase the level of endoge-
nous intact GLP-1. Much attention has been paid to DPP-4
inhibitors as effective medicaments for the treatment of T2DM.
Various classes of structurally different DPP-4 inhibitors have been
reported.6–8 Sitagliptin (JanuviaÒ, MK-0431),9 Vildagliptin (Gla-
vusÒ, LAF-237)10 and Saxagliptin (Onglyza™, BMS-477118)11,12
were approved for the treatment of T2DM (Fig. 1).
According to the retrosynthetic analysis, the derivatives 1 can be
prepared from carbonyl compounds 2 and amine 3 as shown in
Figure 1.
As shown in Scheme 1, cis-bicyclo[3.3.0]octane-3,7-dione (4)14
was mono-protected with ethylene glycol in the presence of
catalytic amount of p-TsOH to afford acetal 5. Stereoselective reduc-
tion of monoketone 5 with NaBH4 gave 5b-hydroxy isomer 6 and
5a-hydroxy isomer 7 in a 90:10 ratio. A higher diastereoselectivity
(6:7 = 99:1) could be achieved when bulky LiAlH(O-t-Bu)3 was
employed.15 The key intermediate 6 was alkylated to ethers
8b–c and reacted with various carbamic acid chlorides or acid anhy-
drides to give derivatives 8d–i. Deprotection and followed by
reductive amination of these compounds afforded the desired
bicyclo[3.3.0]octane derivatives 10a–i as their hydrochloride
salts.16
Stereoisomers of compound 10b were prepared in order to probe
the SAR as related to stereochemistry. The 5b-secondary alcohol 6
was efficiently converted to 5a-hydroxy isomer 7 through a Mitsun-
obu reaction. The synthesis of desired compound 13 was accom-
plished in three steps from 7 following the same synthetic route
for 10b (Scheme 2). To synthesize stereoisomer 18, the monoketone
12 was reduced to 2b-hydroxy isomer 14, which was mesylated and
Continued SAR studies of Vildagliptin and Saxagliptin in our
laboratory led to the discovery of difluorocyclobutyl pyrrolidine-
2-carbonitrile compound.13 Retaining this pyrrolidine-2-carboni-
trile fragment, a series of novel bicyclo[3.3.0]octane derivatives
was designed, synthesized and evaluated as DPP-4 inhibitors.
inverted to 2a-azide 15 with NaN3. Subsequent hydrogenation of 15
followed by alkylation with (S)-1-(2-chloroacetyl)pyrrolidine-2-
carbonitrile (17)17 under KI catalyzed conditions afforded the iso-
mer 18 (Scheme 3). Under the similar conditions, compound 21
was prepared from compound 9a (Scheme 4).
* Corresponding author. Tel.: +86 21 54752877; fax: +86 21 54759072.
E-mail address: tangpc@shhrp.com (T.P. Cho).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.04.138

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T. P. Cho et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3521–3525
F
F
F
HO
NH2
O
HO
N
N
N
H
N
N
CN
O
H2N
N
N
CN
O
CF3
Vildagliptin
LAF-237
Saxagliptin
BMS-477118
Sitagliptin
MK-0431
.
HCl
N
O
HN
R3
2
CN
O
1
3
N
+
H
H
H2N
TFA
H
H
CN
O
4
6
.
R1
R2
R1 R2
1
3
2
Figure 1. Structures of selected DPP-4 inhibitors and bicyclo[3.3.0]octane derivatives.
h
O
O
O
O
O
O
O
O
a
f or g
c
b
H
H
H
H
H
H
H
H
H
H
O
O
OR
OR
8b-i
OH
4
5
6
9b-9i
d,e
c
.
HCl
O
H
N
N
O
O
O
CN
d,e
H
H
H
H
H
H
OH
OH
OR
9a
7
10a-10i
e, R = CON(C2H5)2
a, R = H
b, R = Me
c, R = Et
f, R = CONHCH(CH3)2
g, R = CONHC(CH3)3
h, R = CONHC6H6
i, R = COCH3
d, R = CON(CH3)2
Scheme 1. Reagents and conditions: (a) HOCH2CH2OH, p-TsOH (Cat.), benzene, reflux, 56%; (b) LiAlH(O-t-Bu)3, rt, 92%; (c) oxalic acid, ethyl acetate/water, 75%; (d) (S)-1-(2-
aminoacetyl)pyrrolidine-2-carbonitrile TFA salt (3), NaBH(OAc)3, Et3N, rt 30–50%; (e) 0.5 N hydrochloric acid ether solution, 40–80%; (f) 50% NaH, RI, THF, rt, 88–95%; (g)
carbamic acid chloride or acetic anhydride, DMAP, reflux, 67–88%; (h) triphosgene, RNH2, toluene, reflux, 56%.
.
H
HCl
N
N
O
O
O
O
O
O
O
O
CN
a,b
d
c
e
H
H
H
H
H
H
H
H
H
H
OH
O
O
OH
O
7
6
12
13
11
Scheme 2. Reagents and conditions: (a) benzoic acid, DEAD, Ph3P, Et2O, rt, 50%; (b) KOH, CH3OH, 93%; (c) 50% NaH, CH3I, THF, rt; (d) oxalic acid, ethyl acetate/water; (e) (S)-1-
(2-aminoacetyl)pyrrolidine-2-carbonitrile TFA salt (3), NaBH(OAc)3, Et3N, then 0.5 N HCl/Et2O, rt 33%.

T. P. Cho et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3521–3525
3523
.
HCl
N
H
O
N
OH
O
N3
NH2
O
CN
a
b,c
d
e
H
H
H
H
H
H
H
H
H
H
N
O
Cl
O
O
O
O
17
CN
15
16
14
12
18
Scheme 3. Reagents and conditions: (a) NaBH4, rt; (b) MsCl, Et3N, CH2Cl2; (c) NaN3, DMF, 65 °C,57%; (d) H2, 10%Pd/C, CH3OH; (e) (S)-1-(2-chloroacetyl)pyrrolidine-2-
carbonitrile (17), K2CO3, KI, CH2Cl2, then HCl/Et2O, 31%.
.
HCl
H
N
O
O
NH2
N
O
CN
a
b,c,d,e
f
H
H
H
H
H
H
H
H
OH
O
O
20
O
9a
19
21
Scheme 4. Reagents and conditions: (a) 50% NaH, CH3I, THF, rt; (b) NaBH4, rt; (c) MsCl, Et3N, CH2Cl2; (d) NaN3, DMF, 65 °C; (e) H2, 10%Pd/C, CH3OH, 92%; (f) (S)-1-(2-
chloroacetyl)pyrrolidine-2-carbonitrile (17), K2CO3, KI, CH2Cl2, then HCl/Et2O, 28%.
Table 1
Potency and selectivities of bicyclo[3.3.0]octane derivatives
.
HCl
N
HN
R3
CN
O
H
H
R1 R2
R1
R2
R3
IC50
(lM)
SRc
a,b
Compd
DPP-4
DPP-8
DPP-9
(DPP-8 IC50/DPP-4 IC50)
10a
10b
10c
10d
10e
10f
10g
10h
10i
13
OH
OMe
OEt
OCON(CH3)2
OCON(C2H5)2
OCONHCH(CH3)2
OCONHC(CH3)3
OCONHC6H6
OCOCH3
H
H
H
H
H
H
H
H
H
H(
H(
H(
H(
H(
H(
H(
H(
H(
a
a
a
a
a
a
a
a
a
)
)
)
)
)
)
)
)
)
0.012
0.008
0.059
0.065
0.080
0.204
0.326
0.121
0.032
0.027
0.027
0.047
7.93
3.57
3.74
8.42
12.74
ND
ND
ND
1.43
ND
0.235
0.023
3.22
0.43
1.40
6.86
7.75
ND
ND
ND
1.38
ND
0.037
0.037
661
446
64
130
159
—
—
—
45
—
11
0.5
H
OMe
OMe
H
H(b)
H(b)
H(a)
18
21
H
OMe
ND: not determined.
a
Average values (at least two experiments).
b
c
In vitro activities of LAF-2377: DPP-4 IC50 = 0.009
lM, DPP-8 IC50 = 3.82
l
M, DPP-9 IC50 = 0.23
l
M, SR = 424.
Selectivity ratio(SR) = DPP-8 IC50/DPP-4 IC50
.
As shown in Table 1, these compounds were evaluated in vitro
potency nor enhanced selectivity against DPP-8 and DPP-9. Substi-
tution with carbamates or carbonates (10d–i) gave less active com-
pounds. Increasing the steric bulk at 5b position reduced the
potency. Of all of stereoisomers of 10b, compound 10b was the
most potent and selective DPP-4 inhibitor.
for their inhibitions of DPP-4, DPP-8 and DPP-9.18 The selectivity of
DPP-4 against DPP-8 and DPP-9 is critical as the inhibition of these
two enzymes may be associated with profound toxicities.19 Com-
pound 10a (5b-OH) was found to be a potent and selective inhibi-
tor (IC50 0.012
methyl group (10b, 5b-OCH3) displayed slightly improvement in
DPP-4 inhibitory potency (IC50 0.008 M) but not in selectivity
(SR 446). Ethyl analog 10c neither improved DPP-4 inhibitory
l
M, selectivity ratio: SR 661). Introduction of
Therefore, compounds 10a and 10b were chosen for in vivo
evaluation by assessing for their ability to improve glucose toler-
ance in lean mice (ICR mice) and type 2 diabetic mice (KKAy
mice).20 Administration of 10a or 10b with different doses (0.3,
l

3524
T. P. Cho et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3521–3525
120
100
80
60
40
20
0
Control
30
25
20
15
10
5
Control
10a-3mg/kg
LAF237-10mg/kg
10a-3mg/kg
LAF237-10mg/kg
*
**
***
**
-30
0
30
60
90
120
Time (min)
Control
25
20
15
10
5
120
100
80
60
40
20
0
Control
10b-3mg/kg
10b-10mg/kg
LAF237-10mg/kg
10b-3mg/kg
10b-10mg/kg
LAF237-10mg/kg
*
*
*
**
-30
0
30
60
90
120
Time (min)
Figure 2. Glucose responses (A, C) and AUC0–120min change rate (B, D) during an oral glucose tolerance test (OGTT) in KKAy mice following treatment with 10a or 10b. Data
** ***
*
are represented as Mean SEM (n = 5). P <0.05, P <0.01,
P <0.001 versus control.
3. Nauck, M. A.; Wollschläger, D.; Werner, J.; Holst, J. J.; Ørskov, C.; Creutzfeldt,
W.; Willms, B. Diabetologia 1996, 39, 1546.
4. Nauck, M. A. Acta Diabetol. 1998(3), :117.
5. Sebokova, E.; Christ, A. D.; Boehringer, M.; Mizrahi, J. Curr. Top. Med. Chem.
2007, 7, 547.
6. Rasmussen, H. B.; Branner, S.; Wiberg, F. C.; Wagtmann, N. Nat. Struct. Biol.
2003, 10, 19.
7. Longenecker, K. L.; Stewart, K. D.; Madar, D. J.; Jakob, C. G.; Fry, E. H.; Wilk, S.;
Lin, C. W.; Ballaron, S. J.; Stashko, M. A.; Lubben, T. H.; Yong, H.; Pireh, D.; Pei,
Z.; Basha, F.; Wiedeman, P. E.; von Geldern, T. W.; Trevillyan, J. M.; Stoll, V. S.
Biochemistry 2006, 45, 7474.
8. Qiao, L.; Baumann, C. A.; Crysler, C. S.; Ninan, N. S.; Abad, M. C.; Spurlino, J. C.;
DesJarlais, R. L.; Kervinen, J.; Neeper, M. P.; Bayoumy, S. S.; Williams, R.;
Deckman, I. C.; Dasgupta, M.; Reed, R. L.; Huebert, N. D.; Tomczuk, B. E.;
Moriarty, K. J. Bioorg. Med. Chem. Lett. 2006, 16, 123.
1, 3 and 10 mg/kg) to ICR mice 0.5 h before an oral glucose chal-
lenge produced a significant decrease in glucose excursion, which
suggested the improvement of glucose tolerance (data not shown).
Moreover, the same results were observed on KKAy mice. After
glucose load, the blood glucose level of KKAy mice increased signif-
icantly. Administration of 3 mg/kg 10a 0.5 h before glucose chal-
lenge reduced the AUC0–120min value of blood glucose by 61.9%,
while LAF237 need 10 mg/kg to show comparable effect with the
decrease rate of 52.2%. Compound 10b also induced a significant
decrease in AUC0–120min values by 45.7% and 47.1% at the dose of
3 and 10 mg/kg (Fig. 2).
In conclusion, a series of novel bicyclo[3.3.0]octane derivatives
was synthesized and found to have inhibitory activities against
DPP-4 and selectivities over DPP-8 and DPP-9. Compounds 10a
and 10b showed good in vitro activities and moderate selectivities
and demonstrated beneficial effects on oral glucose tolerance. Fur-
ther studies are underway to optimize this class of compounds for
the treatment of T2DM.
9. Kim, D.; Wang, L.; Beconi, M.; Eiermann, G. J.; Fisher, M. H.; He, H.; Hickey, G. J.;
Kowalchick, J. E.; Leiting, B.; Lyons, K.; Marsilio, F.; McCann, M. E.; Patel, R. A.;
Petrov, A.; Scapin, G.; Patel, S. B.; Roy, R. S.; Wu, J. K.; Wyvratt, M. J.; Zhang, B.
B.; Zhu, L.; Thornberry, N. A.; Weber, A. E. J. Med. Chem. 2005, 48, 141.
10. Villhauer, E. B.; Brinkman, J. A.; Naderi, G. B.; Burkey, B. F.; Dunning, B. E.;
Prasad, K.; Mangold, B. L.; Russell, M. E.; Hughes, T. E. J. Med. Chem. 2003, 46,
2774.
11. Augeri, D. J.; Robl, J. A.; Betebenner, D. A.; Magnin, D. R.; Khanna, A.; Robertson,
J. G.; Wang, A.; Simpkins, L. M.; Taunk, P.; Huang, Q.; Han, S.-P.; Abboa-Offei, B.;
Cap, M.; Xin, L.; Tao, L.; Tozzo, E.; Welzel, G. E.; Egan, D. M.; Marcinkeviciene, J.;
Chang, S. Y.; Biller, S. A.; Kirby, M. S.; Parker, R. A.; Hamann, L. G. J. Med. Chem.
2005, 48, 5025.
Acknowledgements
12. Peters, J.-U. Curr. Top. Med. Chem. 2007, 7, 579.
The authors would like to thank Mr. Sun Piao Yang for his vision
and support in new drug discovery in China, and Mr. Wu Qian and
Li Chun Fa of Analytical Chemistry Group of Shanghai Hengrui
Pharmaceuticals Co., Ltd for 1H NMR and Mass Spectroscopy
services.
13. Tang, P. C.; Lin, Z. G.; Wang, Y.; Yang, F. L.; Wang, Q.; Fu, J. H.; Zhang, L.; Gong,
A. S.; Luo, J. J.; Dai, J.; She, G. H.; Si, D. D.; Feng, J. Chin. Chem. Lett. 2009, 21,
253.
14. Bertz, S. H.; Cook, J. M.; Gawish, A.; Weiss, U. Org. Synth. 1990, Coll. Vol. 7, 50.
15. The stereoisomeric ratio was determined by gas chromatography (GC) analysis.
16. All new compounds were characterized by 1H NMR and MS prior to biological
evaluation. Preparation of compound 10a is described herein. A stirred solution
of (S)-1-(2-aminoacetyl)-pyrrolidine-2-carbonitrile trifluoroacetic acid salt (3)
(3.6 mmol) in 50 mL methanol was added with triethylamine (10.7 mmol), 5b-
hydroxy-hexahydro-pentalen-2-one (9a) (0.5 g, 3.6 mmol) and sodium
triacetoxy borohydride (14.3 mmol). The reaction mixture was stirred
overnight at room temperature until the start material disappeared as
monitored by TLC. The mixture was poured into saturated sodium carbonate
References and notes
1. Zimmet, P.; Alberti, K. G. M. M.; Shaw, J. Nature 2001, 414, 782.
2. Gautier, J. F.; Fetita, S.; Sobngwi, E.; Salaün-Martin, C. Diabetes Metab. 2005, 31,
233.

T. P. Cho et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3521–3525
3525
solution (20 mL) and extracted with ethyl acetate (3 Â 80 mL). The combined
organic extracts were washed with saturated sodium chloride aqueous solution,
dried over anhydrous sodium sulfate, filtered and concentrated under reduced
pressure, the residue is purified by column chromatography to give (S)-1-[2-(5b-
hydroxyl-octahydro -pentalen-2-ylamino)acetyl] pyrrolidine-2-carbonitrile
(10a) (200 mg, yield 20.4%) as a white powder. Compound 10a (192 mg,
0.686 mmol) was suspended in 10 mL ether. The mixture was added with a
solution of 0.5 N hydrochloric acid in ether in an ice-water bath. The resulting
solid was concentrated to give compound 10a hydrochloride salt (80 mg, white
powder, yield 40%). Compound 10a: 1H NMR (400 MHZ, CDCl3) d (ppm) 4.49(m,
1H), 3.98(m, 1H), 3.36(m, 2H), 3.20(m, 1H), 3.07(s, 1H), 2.99(m, 1H), 2.77(m, 2H),
1.98(m, 5H), 1.79(m, 2H), 1.31(m, 3H), 1.05(m, 2H). MS m/z (ESI): 278.2 [M+1]+.
Compound 10b: 1H NMR (400 MHZ, CDCl3) d (ppm) 4.79(m, 1H), 3.82(m, 2H),
3.67(m, 2H), 3.48(m, 1H), 3.26(s, 3H), 2.40(m, 2H), 2.36–1.98(m, 6H), 1.85(m,
3H), 1.62(m, 2H), 1.53–1.14(m, 2H). MS m/z (ESI): 292.7 [M+1]+.
19. Lankas, G. R.; Leiting, B.; Roy, S. R.; Eiermann, G. J.; Beconi, M. G.; Biftu, T.; Chan,
C.-C.; Edmondson, S.; Feeney, W. P.; He, H.; Ippolito, D. E.; Kim, D.; Lyons, K. A.;
Ok, H. O.; Patel, R. A.; Petrov, A. N.; Pryor, K. A.; Qian, X.; Reigle, L.; Woods, A.;
Wu, J. K.; Zaller, D.; Zhang, X.; Zhu, L.; Weber, A. E.; Thornberry, N. A. Diabetes
2005, 54, 2988.
20. Oral Glucose tolerance test on ICR and KKAy mice: KKAy and ICR mice were
purchased from Shanghai Laboratory Animal Center, Chinese Academy of
Sciences (Shanghai, China). The mice were provided with a normal diet and
water ad libitum. The KKAy mice were housed individually. All the animals were
kept under conventional conditions of controlled temperature, humidity, and
lighting. All procedures were approved by the Animal Care and Use committee,
Shanghai Institute of Materia Medica, Chinese Academy of Sciences. The effects
of 10a and 10b on blood glucose after an oral glucose challenge were observed on
ICR and KKAy mice. Indicated dose of 10a, 10b, LAF237 or vehicle (distilled
water) was orally administered to 6 h fasting ICR or KKAy mice 0.5 h prior to oral
glucose load (2.5 g/kg). Blood glucose values were measured with ONE TOUCH
BASIC Plus blood glucose meter (LIFESCAN Inc., USA) at 0, 30, 60, 120 min after
the glucose load. The area under the concentration–time curve from 0 to 120 min
(AUC0–120min) of blood glucose after challenge was calculated by the trapezoidal
rule. All date were expressed as the mean SEM. The statistical analysis between
two groups was performed using an unpaired Student’s t test. P <0.05 was
considered to be statistically significance.
17. Villhauer, E. B.; Brinkman, J. A.; Naderi, G. B.; Dunning, B. E.; Mangold, B. L.; Mone,
M. D.; Russell, M. E.; Weldon, S. C.; Hughes, T. E. J. Med. Chem. 2002, 45,
2362.
18. IC50 values for DPP-4, DPP-8 and DPP-9 were obtained by chemical
Luminescent assay using Glo™ Protease Assay Kit (cat. G 8350). For assay
conditions, see: Deng, B. C. (Tang, P. C.); Yang, F. L.; Fan, J.; Feng, H.; Wang, Y.;
Yang, T. CN101468988A.