1486
J. Wityak et al. / Bioorg. Med. Chem. Lett. 14 (2004) 1483–1486
and benzodioxanyl replacements (13 and 14) lowered
affinity. The N-methyl amides (10 and 11) being 2 atom
linkers could also be less potent due to size limitations
imposed by this terminal aromatic pocket. Cell pene-
tration is required for MEK inhibition and thus charged
compounds display poor AP-1 transcription inhibition.
With the replacement of a vinylogous cyanamide group
of U0126 with a benzene ring, we have increased both
chemical stability and potency. Some of the compounds
described in Tables 1 and 2 have been found to be stable
in aqueous buffer at pH=1 whereas U0126 is not. Further
work will be aimed at replacing the remaining cyanamide
moiety. The in vitro results translated into in vivo anti-
inflammatory activity seen in the TPA mediated ear
edema mouse model.
Scheme 2.
References and notes
1. Cato, A.; Wade, E. BioEssays 1996, 18, 371.
2. (a) Gehring, U. Biochem. Sci. 1987, 12, 399. (b) Fuller,
P. J. FASEB J. 1991, 5, 3092. (c) Mangelsdorf, D. J.;
Thummer, C.; Beato, M.; Herrlich, P.; Schutz, G.; Umesono,
K.; Blumberg, B.; Kastner, P.; Mark, M.; Chambon, P.;
Evans, R. M. Cell 1995, 83, 835.
3. Avery, M. A.; Woolfrey, J. R. In Burger’s Medicinal
Chemistry and Drug Discovery, 5th ed.; Wolf, M. E., Ed.;
John Wiley and Sons, Inc.: New York, 1997; p 286.
4. Duncia, J. V.et al. Bioorg. Med. Chem. Lett. 1998, 8, 2839.
5. Herrlich, P.; Ponta, H. Trends Endocrinol. Metab. 1994, 5,
341.
6. Favata, M. F., et al. J. Biol. Chem. 1998, 273, 18623.
7. MEK inhibition in Ras & Raf transformed cells: Dudley,
D. T.; Pang, L.; Decker, S. J.; Bridges, A. J.; Saltiel, A. R.
Proc. Natl. Acad. Sci. 1995, 92, 7686.
8. MEK inhibition in colon tumors: Sebolt-Leopold, J. S.;
Dudley, D. T.; Herrera, R.; Van Becelaere, K.; Wiland,
A.; Gowan, R. C.; Tecle, H.; Barrett, S. D.; Bridges, A.;
Przybranowski, S.; Leopold, W. R.; Saltiel, A. R. Nature
Medicine 1999, 5, 810.
9. MEK inhibition in tumor cell lines: Berger, D.; Dutia, M.;
Powell, D.; Wu, B.; Wissner, A.; Boschelli, D. H.; Floyd,
M. B.; Zhang, N.; Torres, N.; Levin, J.; Du, X.; Wojcie-
chowicz, D.; Discafani, C.; Kohler, C.; Kim, S. C.; Feld-
berg, L. R.; Collins, K.; Mallon, R. Bioorg. Med. Chem.
Lett. 2003, 13, 3031 and references therein.
10. The compounds in this letter were screened using a
constitutively active form of MEK: Mansour, S. J.; Mat-
ten, W. T.; Hermann, A. S.; Candia, J. M.; Rong, S.;
Fukasawa, K.; Vande Woude, G. F.; Ahn, N. G. Science
1994, 265, 966.
Scheme 3. Dianion chemistry. (a) LDA, 0 ꢂC to 25 ꢂC, benzene, 80%;
(b) 2 equiv n-BuLi, ꢀ70 ꢂC, THF, 4-pyridinecarboxaldehyde, 54%; (c)
2-aminothiophenol, Et3N, THF, 25 ꢂC, 62%.
In an attempt to replace the sulfur atom of SH053 with
a carbon, we initially tried to add benzyl Grignard to
phenylmalononitrile (Scheme 2). Even with 7 equiv of
Grignard reagent, starting material phenylmalononitrile
was obtained unchanged. This meant that the mal-
ononitrile anion protects both nitriles from nucleophilic
attack.
Using this ‘anionic protection’ we found that we could
generate a dianion of phenylmalononitrile (Scheme 3)
and quench it with a wide variety of aldehydes and
ketones. Subsequent reaction with aryl thiols led to a
library of CH(OH) and CR(OH) linker analogues,
which are summarized in Table 2. Thus, Cava cyanation
leads to malononitrile 62 (Scheme 3). Deprotonation of
the malononitrile proton followed by halogen–metal
exchange at ꢀ70 ꢂC with two equivalents of n-BuLi
yields dianion 63 as an orange slurry. Immediate
quenching with, for example, 4-pyridine-carbox-
aldehyde yields 64. Vinylogous cyanamide formation
yields compound 41. The dianion forming reaction was
scaled up to 0.15 moles for the synthesis of 41.
11. The compounds in this letter were assayed for potency
against AP-1 transcription activity in COS-7 cells as
delineated in reference 6.
12. Copeland, R. A. Enzymes: A Practical Introduction to
Structure, Mechanism and Data Analysis; VCH/Wiley:
New York, 1996; pp 187–223.
13. For MKK3 and MKK4, coupled assays were used as
described in reference 6.
14. TPA treatment activates the Ras pathway; the TPA ear
edema assay was performed as described in: Jaffee, B. D.,
et al. Biochemical and Biophysical Research Communi-
cations 2000, 268, 647.
3. Conclusion
We found that one of the vinylogous cyanamides of
U0126 could be effectively replaced by a benzene ring,
leading to the discovery of SH053. Attachment of an
additional phenyl ring with a para-H-bonding sub-
stituent increases the potency by 1 order of magnitude
over that of SH053. The binding pocket for this addi-
tional aromatic ring is limited in size, since naphthalene
15. Davis, W. A.; Cava, M. P. J. Org. Chem. 1983, 48, 2774.