1390
Z. Zhao et al. / Bioorg. Med. Chem. Lett. 17 (2007) 1386–1391
Cl
O
Cl
Cl
O
O
O
HN
O
NBS/cat. Bz2O2
23
CCl4, 90 oC, 4 hrs
PS-DIEA/DCM
rt, 1 h
NH2
O
22
24
O
Cl
O
Cl
NH
26
O
O
O
O
N
H
N
HN
HO
DMF/K2CO3/ca. KI
50 oC overnight
Br
O
O
then LCMS purification
2
25
Scheme 4. Synthesis of CPPHA 2.11
3. Lindsley, C. W.; Wisnoski, D. D.; Duggan, M. E.; Leister,
W. H.; Huff, J. R.; Williams, D. L., Jr.; O’Brien, J. A.;
Lemaire, W.; Sur, C.; Pettibone, D.; Kinney, G.; Burno,
M. J. Med. Chem. 2004, 47, 5825.
4. Kinney, G. G.; O’Brien, J. A.; Lemaire, W.; Burno, M.;
Bickel, D. J.; Clements, M. K.; Wisnoski, D. D.; Lindsley,
C. W.; Tiller, P. R.; Smith, S.; Jacobson, M. A.; Sur, C.;
Duggan, M. E.; Pettibone, D. J.; Williams, D. W., Jr.
J. Pharmacol. Exp. Therapeut. 2005, 313, 199.
5. (a) Williams, D. L., Jr.; Lindsley, C. W. Curr. Topics Med.
Chem. 2005, 5, 825; (b) Lindsley, C. W.; Shipe, W. D.;
Wolkenberg, S. E.; Theberge, C. R.; Williams, D. L., Jr.;
Sur, C.; Kinney, G. G. Curr. Topics Med. Chem. 2006, 8,
771, and references therein; (c) Lindsley, C. W.; Wolken-
berg, S. E.; Shipe, W.; Williams, D. L., Jr. Curr. Opin.
Drug Disc. Dev 2005, 8, 449.
DHPG-induced phosphorylation of the NR1 (Ser 897)
subunit of NMDA receptors.7
In summary, we have disclosed the synthesis and SAR
of the mGluR5 positive allosteric modulator CPPHA,
2, with a unique allosteric binding site, distinct from that
of MPEP, DFB, and CDPPB. SAR was flat and devel-
oping SAR was virtually impossible through traditional
medicinal chemistry strategies. Even with an iterative
analog library synthesis approach, only 4.5% of 985 ana-
logs based on screening leads 4 and 5 possessed mGluR5
PAM activity below 5 lM. In general PAMs have
proved far more challenging to develop robust, tractable
SAR for standard GPCR agonists/antagonists. Despite
these challenges, CPPHA has become an important tool
to probe the pharmacology of mGluR5, and demon-
strated that different PAMs can differentially modulate
coupling of a single receptor to different signaling
pathways.
6. Zhang, Y.; Rodriguez, A. L.; Conn, P. J. J. Pharmacol.
Exp. Therapeut. 2005, 315, 1212.
7. Liu, F.; Zhang, G.; Hornby, G.; Vasylyev, D.; Bowlby,
M.; Park, K.; Gilbert, A.; Marquis, K.; Andree, T. H. Eur.
J. Pharmacol. 2006, 536, 262.
8. EC50 of potentiation and fold potentiation were deter-
mined from concentration–response curves of test com-
pound at a single, low (EC20) concentration of agonist.
Fluo-4 (calcium sensitive dye) was loaded into CHO cells
expressing human or rat mGluR5. These cells were then
pretreated with a range of concentrations of test com-
pound, and finally challenged with an approximate EC20
concentration of agonist (in this case, 300 nM glutamate).
The inflection point of the concentration–response curve
of the test compound was taken as the EC50 for poten-
tiation, and the ratio of the maximum agonist response (at
the agonist EC20) in the presence of test compound versus
the response to the same concentration of agonist in the
absence of test compound is taken as the fold potentiation.
Ref. 2 provides additional experimental details and a curve
(Fig. 2) showing how EC50 and fold potentiation are
determined. The referenced figure provides an illustration
of the variability for each data point. Variability of EC50
for potentiation (ranging from 9.4% to 32.8%), is detailed
in Table of Ref. 2. Note that Figure 3 in the present
paper represents the effect of several fixed concentrations
of test compound on the agonist concentration–response
curve.
Acknowledgments
The authors wish to thank Dr. Sandor Varga for exten-
sive NMR work to confirm the structural assignments of
the analogs represented by general structure 9, 11, 13,
and 14, and Dr. Charles W. Ross III for obtaining
HRMS data.
References and notes
1. O’Brien, J. A.; Lemaire, W.; Chen, T.-B.; Chang, R. L. S.;
Jacobson, M. A.; Ha, S.; Lindsley, C. W.; Sur, C.;
Pettibone, D. J.; Conn, P. J.; Williams, D. L., Jr. Mol.
Pharmacol. 2003, 64, 731.
2. O’Brien, J. A.; Lemaire, W.; Wittmann, M.; Jacobson, M.
A.; Ha, S. N.; Wisnoski, D. D.; Lindsley, C. W.;
Schaffhauser, H. J.; Sur, C.; Duggan, M. E.; Pettibone,
D. J.; Conn, J.; Williams, D. L. J. Pharmacol. Exp.
Therapeut. 2004, 309, 568.