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J. Witherington et al. / Bioorg. Med. Chem. Lett. 16 (2006) 2256–2259
CO2Me
Cl
O2N
O2N
O
18
c
a, b
N
NH
16
19
17
H
H
O2N
N
N
d-f
O
O
O
N
N
CO2Me
CO2R
20, R = Me
10, R = H
Scheme 1. Reagents: (a) mCPBA, THF, 25 °C (58%); (b) i—Ac2O, reflux; ii—HCl, reflux, (80%); (c) Cs2CO3, DMF, 25 °C (90%); (d) 10% Pd/C,
EtOH, H2 (1 atm), 25 °C (50%); (e) o-tolyl isocyanate, DCM, 25 °C (80%); (f) 0.5 N aq LiOH, THF, 25 °C (100%).
3. Elices, M. J. Curr. Opin. Anti-inflam. Immunomod. Inves-
tig. Drugs 1999, 1, 14.
4. (a) Gearing, A. J. H.; Newman, W. Immunol. Today 1993,
14, 506; (b) Helmer, M. E. Annu. Rev. Immunol. 1990, 8,
365.
5. (a) Lin, K.-C.; Ateeq, H. S.; Hsiung, S. H.; Chong, L. T.;
Zimmerman, C. N.; Castro, A.; Lee, W.-C.; Hammond,
C. E.; Kalkunte, S.; Chen, L.-L.; Pepinsky, R. B.; Leone,
D. R.; Sprague, A. G.; Abraham, W. M.; Gill, A.; Lobb,
R. A.; Adams, S. P. J. Med. Chem. 1999, 42, 920; (b) Lin,
K.-C.; Castro, A. C. Curr. Opin. Chem. Biol. 1998, 2, 453.
6. Seiffge, D. J. Rheumatol. 1996, 23, 2086.
displayed excellent inhibitory potency and introduction
of a methoxy group into the B-ring gave further
enhancement in potency (cf. 10 and 11). The increased
potency observed for the pyridone 10 relative to the
amide 7 is also noteworthy, suggesting that the carbonyl
of the pyridone may be held in its bioactive conforma-
tion. Although the meta isomer 12 displays comparable
potency to the para isomer 10, in general the position
and length of the linker is critical for optimal potency
(cf. 10 and 13, 14 and 15).
7. (a) Tubridy, N.; Behan, P. O.; Caplildeo, R.; Chaudhuri,
A.; Forbes, R.; Hawkins, C. P.; Hughes, R. A. C.; Palace,
J.; Sharrack, B.; Swingler, R.; Young, C.; Mosley, I. F.;
MacManus, D. G.; Donoghue, S.; Miller, D. H. Neurology
1999, 53, 466; (b) Keszthelyi, E.; Karlik, S.; Hyduk, S.;
Rice, A.; Gordon, G.; Yednock, T.; Horner, H. Neurology
1996, 47, 1053.
8. Podolsky, D. K.; Lobb, R.; King, N.; Benjamin, C. D.;
Pepinsky, B.; Sehgal, P.; deBaumont, M. J. Clin. Invest.
1993, 92, 972.
Cross screening of 10 against a range of integrin recep-
tors indicated excellent selectivity (Table 3). Additional-
ly, cross screening of 10 against a diverse panel of 50
receptors and ion channels13 indicated 615% inhibition
at 1 lM (data not shown).
The pyridone analogues were prepared via a short con-
cise synthesis14 starting with the oxidation of the known
pyridine 1615 with m-chloroperoxybenzoic acid which
afforded the corresponding pyridine N-oxide. Treatment
of the N-oxide with acetic anhydride at reflux afforded,
after hydrolysis, the corresponding pyridone 17. Selec-
tive N-alkylation of 17 with the chloride 1816 in the pres-
ence of caesium carbonate afforded the ester 19.
Hydrogenation of the nitro group afforded the corre-
sponding aniline, which was treated with o-tolyl isocya-
nate to afford the urea 20. Hydrolysis with lithium
hydroxide provided the desired analogue 10 in good
overall yield (Scheme 1).
9. Cannella, B.; Gaupp, S.; Tilton, R. G.; Raine, C. S.
J. Neurosci. Res. 2003, 71, 407.
10. A Jurkat J6 Scintillation Proximity Assay was used to
investigate the interaction of the integrin VLA-4 (Very
Late Antigen-4; a4b1; CD49d, CD29) expressed on the
Jurkat J6 cell membrane with test compounds. J6 cells (1
million cells/well) were allowed to coat wheat germ
agglutinin-coated SPA beads (Amersham, 1 mg/well) in
assay buffer containing 50 mM HEPES, 100 mM NaCl
and 1 mM MnCl2 (pH with 4 M NaOH to 7.5). Tritiated
3H Standard Compound A (1–3 nM final assay concen-
tration) and test compounds were dissolved in an appro-
priate solvent and diluted in assay buffer. Data are
presented as means of pKi. Standard compound A is
(2S)-3-[4-({[4-(aminocarbonyl)-1-piperidinyl]carbonyl}oxy)-
phenyl]-2-[((2S)-4-methyl-2-{[2-(2-methylphenoxy)ace-
tyl]amino}pentanoyl)amino] propanoic acid potassium
salt which is described in patent application WO 00/
37444. Compounds were assayed in duplicate, a four-
parameter curve fit being applied. The equilibrium disso-
ciation constant for each compound was calculated
according to the method of Cheng and Prusoff (Biochem.
Pharmacol. 1973, 22, 3099).
In summary, molecular overlay studies of our initial
leads with known VLA-4 antagonists have led to
hypothesis of a novel pharmacophore. Subsequent
design and synthesis of analogues exploiting this
hypothesis has afforded a novel series of potent and
selective VLA-4 antagonists.
References and notes
11. Astles, P. C.; Clark, D. E.; Collis, A. J.; Cox, P. J.;
Eastwood, P. J.; Harris, N. V.; Lai, J. Y. Q.; Morley, A.
D.; Porter, B. WO 992306.
1. Helmer, M. E.; Elices, M. J.; Parker, C.; Takada, Y.
Immunol. Rev. 1990, 114, 45.
2. Springer, T. A. Cell 1994, 76, 301.