A. Gopalsamy et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2431–2434
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Table 2
B-Raf kinase activity of thienopyrimidines and cyano thienopyridines
O
O
O
O
N
O
CF3
CF3
CF3
CF3
CF3
NH
S
NH
S
NH
S
NH
N
NH
S
NC
NC
N
N
R
R
R
R
R
N
N
N
N
N
Scaffold B
Scaffold C
Scaffold D
Lead Scaffold
2a: R = 3-pyridyl
2 : R = 4-pyridyl
Scaffold A
11a: R = 3-pyridyl
11b: R = 4-pyridyl
13a: R = 3-pyridyl
13b: R = 4-pyridyl
15a: R = 3-pyridyl
15b: R = 4-pyridyl
7a: R = 3-pyridyl
7b: R = 4-pyridyl
a
Scaffold
Lead
Class
Examples
IC50
(lM)
Pyrazolo[1,5-a]pyrimidine
Thieno[3,2-d]pyrimidine
Thieno[2,3-d]pyrimidine
Cyanothieno[3,2-b]pyridine
Cyanothieno[2,3-b]pyridine
2a
2
7a
7b
11a
11b
13a
13b
15a
15b
>10
0.032 0.009
>10
0.54 0.156
1.11 0.22
0.08 0.018
>10
Scaffold A
Scaffold B
Scaffold C
Scaffold D
5.94 0.87
>10
>10
a
Values are means of two or more experiments.
inhibitor binding at the emission and excitation wavelengths of
465 nm and 295 nm, respectively.
In summary, we have successfully employed a scaffold hopping
strategy starting from the pyrazolopyrimidine scaffold identified as
a B-Raf inhibitor from HTS. The alternate thieno[2,3-d]pyrimidine
scaffold showed good cellular potency and excellent selectivity
over a number of kinases, providing a novel lead for further
exploration.
Acknowledgments
The authors thank Dr. John Ellingboe for his support of this
work. We also thank Dr. Girija Krishnamurthy for KD determina-
tions and the Wyeth Chemical Technologies group for analytical
data.
References and notes
Figure 3. Binding models of compounds 2b, 7b and 11b. The carbon atoms of
compounds 2b, 7b and 11b are colored as green, cyan and magenta, respectively.
The predicted H-bonds were indicated by yellow dotted lines.
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Table 3
Cell growth inhibition data
a
Tumor cell lines
Compound 11b IC50
(
lM)
A375 (B-Raf mutant)
LoVo (K-ras mutant)
HT29 (B-Raf mutant)
CaCo-2 (wild type)
0.23 0.12
0.3 0.035
0.15 0.082
1.1 0.44
WM-266-4 (B-Raf mutant)
3.1 0.53
a
Values are means of two or more experiments.
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l
pound 11b exhibited a single digit nanomolar KD from the changes
in the endogenous tryptophan fluorescence of the enzyme upon