M. Kameda et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5124–5127
5127
Table 2
3. Tatemoto, K.; Mann, M. J.; Shimizu, M. Proc. Natl. Acad. Sci. U.S.A. 1992, 89.
SAR of compound 2i–oa
4. Stanley, B. G.; Leibowitz, S. F. Proc. Natl. Acad. Sci. U.S.A. 1985, 82, 3940.
5. Stanley, B. G.; Magdalin, W.; Seirafi, A.; Nguyen, M. M.; Leibowitz, S. F. Peptides
1992, 13, 581.
6. Walker, P.; Grouzmann, E.; Burnier, M.; Waeber, B. Trends Pharmacol. Sci. 1991,
12, 111.
X
N
7. Kalra, S. P.; Fuentes, M.; Fournier, A.; Parker, S. L.; Crowley, W. R. Endocrinology
1992, 130, 3323.
8. Cougnon, N.; Hudspith, M. J.; Munglani, R. Exp. Opin. Invest. Drugs 1997, 6, 759.
9. Blomqvist, A. G.; Herzog, H. Trends Neurosci. 1997, 20, 294.
10. Eva, C.; Serra, M.; Mele, P.; Panzica, G.; Oberto, A. Front. Neuroendocrinol. 2006,
27, 308.
11. For recent reviews: (a) Ishihara, A.; Moriya, M.; MacNeil, D. J.; Fukami, T.;
Kanatani, A. Exp. Opin. Therap. Patents 2006, 16, 1701; (b) MacNeil, D. J. Curr.
Top. Med. Chem. 2007, 7, 1721.
S
N
Y
N
N
R1
H
N
R2
12. Halldin, C.; Gulyás, B.; Langer, O.; Farde, L. Q. J. Nucl. Med. 2001, 45, 139.
13. Waterhouse, R. N. Mol. Imaging Biol. 2003, 5, 376.
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Pharm. Des. 2004, 10, 1493.
15. For tritium-labeled NPY Y1 antagonists for in vitro studies of this receptor, see:
(a) Keller, M.; Pop, N.; Hutzler, C.; Beck-Sickinger, A. G.; Bernhardt, G.;
Buschauer, A. J. Med. Chem. 2008, 51, 8166; (b) Entzeroth, M.; Braunger, H.;
Eberlein, W.; Engel, W.; Rudolf, K.; Wienen, W.; Wieland, H. A.; Willim, K. D.;
Doods, H. N. Eur. J. Pharmacol. 1995, 278, 239; For fluorescent NPY Y1
antagonist, see: (c) Schneider, E.; Keller, M.; Brennauer, A.; Hoefelschweiger, B.
K.; Gross, D.; Wolfbeis, O. S.; Bernhardt, G.; Buschauer, A. ChemBioChem 2007,
16, 1981.
b
c
Compound
X
Y
R1
CH3
CH2CH3
R2
Y1 binding IC50 (nM)
Log D7.4
2i
2j
O
O
O
O
O
O
O
O
O
O
S
S
S
CH3
CH3
0.69
0.39
0.46
0.27
0.56
0.20
0.13
2.8
3.1
3.5
2.9
2.3
2.7
3.2
2k
2l
2m
2n
2o
R1 = R2 = (CH2)4
CH3
CH2F
CH3
CH3
CH3
CH2F
CH2F
S
CH2CH3
a
Values represent the mean for n P 2 experiments.
[
125I]PYY binding assay using CHO (NFAT-bla) cell membranes expressing
b
16. (a) Kameda, M.; Kobayashi, K.; Ito, H.; Miyazoe, H.; Tsujino, T.; Nakama, C.;
Kawamoto, H.; Ando, M.; Ito, S.; Suzuki, T.; Kanno, T.; Tanaka, T.; Tahara, Y.;
Tani, T.; Tanaka, S.; Tokita, S.; Sato, N. Bioorg. Med. Chem. Lett. 2009, 19, 4325;
see also: (b) Kanatani, A.; Hata, M.; Mashiko, S.; Ishihara, A.; Okamoto, O.;
Haga, Y.; Ohe, T.; Kanno, T.; Murai, N.; Ishii, Y.; Fukuroda, T.; Fukami, T.; Ihara,
M. Mol. Pharmacol. 2001, 59, 501; (c) Fukami, T.; Mase, T.; Tsuchiya, Y.;
Kanatani, A.; Fukuroda, T. PCT Int. Appl. WO 9734873.
human recombinant Y1 receptors.
c
Octanol–water distribution coefficient at pH 7.4; see Ref. 20.
ing with an IC50 of 0.13 nM and applicable lipophilicity with a
log D7.4 value of 3.2. Overall, compounds 2n and 2o appeared to
be the best candidates in this series for PET tracers. Compounds
2n and 2o showed good selectivity over other NPY receptor sub-
17. For [18F]-labeling of the 2-position of pyridine rings, see: Dolci, L.; Dolle,
F.; Jubeau, S.; Vaufrey, F.; Crouzel, C. J. Label. Compd. Radiopharm. 1999,
42, 975.
types (Y2, Y4, Y5; IC50 > 10 l
M).22 In addition, 2n and 2o have
18. For the preparation of 4,5,6,7-tetrahydrobenzoxazole-2-thiol for compound 2k,
see: Bobosik, V.; Piklerova, A.; Martvon, A. Collect. Czech. Chem. Commun. 1983,
48, 3421. 4,5-Dimethyloxazole-2-thiol for 2a–i and 5-ethyl-4-methyloxazole-
2-thiol for 2j were prepared in a similar manner. 4,5-Dimethylthiazole-2-thiol
for 2l is commercially available (Wako Pure Chemical Industries, Ltd).
low or negligible human P-gp susceptibility (the transcellular
transport ratios (B-to-A/A-to-B) for 2n and 2o are 1.8 and 1.4 for
human P-gp, respectively).23
Insummary, a seriesof 2,4-diaminopyridineswassynthesizedand
evaluated for the development of novel NPY Y1 PET tracers. Our SAR
studies were focused on increasing the Y1 affinity of lead compound
2a while maintaining reasonable lipophilicity, and resulted in the
identification of the potent and selective compounds 2n and 2o as
promising candidates for Y1 PET tracers. Further evaluation and
in vivo studies with radiolabeled compounds are ongoing.
19. Inhibitory effects of compounds on
[
125I]PYY binding to membranes
minor
overexpressing human NPY Y1 receptors were examined using
a
modification of the method described in Ref. 16b. In brief, the membranes
were incubated in 0.2 ml of 20 mM HEPES buffer (pH 7.4), containing 0.1%
bacitracin, 1 mM phenylmethylsulfonyl fluoride (PMSF), 0.5% BSA and Hank’s
balanced salt solution (HBSS) in the presence of various concentrations of the
test compound with [125I]PYY (25 pM) at 25 °C for 120 min. Following three
washes, the membrane-bound radioactivity was measured using a TopCountTM
microplate scintillation counter (Packard, Meriden, CT). Non-specific binding
was determined in the presence of an excess amount of cold porcine PYY
(1 lM).
Acknowledgment
20. Dohta, Y.; Yamashita, T.; Horiike, S.; Nakamura, T.; Fukami, T. Anal. Chem. 2007,
79, 8312.
21. For [11C]-labeling of the 2-position of pyridine rings, see: (a) Bourdier, T.;
Huiban, M.; Huet, A.; Sobrio, F.; Fouquet, E.; Perrio, C.; Barre, L. Synthesis 2008,
6, 978; (b) Huang, Y.; Narendran, R.; Bischoff, F.; Guo, N.; Zhu, Z.; Bae, S.;
Lesage, A. S.; Laruelle, M. J. Med. Chem. 2005, 48, 5096.
The authors thank Hiroaki Suwa for measurement of log D7.4
values.
References and notes
22. Kanatani, A.; Ishihara, A.; Iwaasa, H.; Nakamura, K.; Okamoto, O.; Hidaka, M.;
Ito, J.; Fukuroda, T.; MacNeil, D. J.; Van der Ploeg, L. H. T.; Ishii, Y.; Okabe, T.;
Fukami, T.; Ihara, M. Biochem. Biophys. Res. Commun. 2000, 272, 169.
23. For the experimental details for the determination of the transcellular
transport ratio see: Yamazaki, M.; Neway, W. E.; Ohe, T.; Chen, I.; Rowe, J. F.;
Hochman, J. H.; Chiba, M.; Lin, J. H. J. Pharmacol. Exp. Ther. 2001, 296, 723.
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