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M. Urbano et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5470–5474
heterocycles with basic lone pares at the ring d are detrimental to
the potency. In agreement with the SAR trend within the furan
derivatives, the methylated phenyl analog 48 was 32-fold less po-
tent than the corresponding homolog 47, supporting the hypothe-
sis that a methyl group in the ring d ortho to the biaryl C–C bond is
detrimental to the activity.
The most active compounds 19 and 47 were selected for func-
tional assays at S1P1–3,5 subtypes (Table 2). Notably, both com-
pounds displayed an exquisite selectivity for the S1P4 receptor
versus the other receptor family subtypes.
References and notes
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In summary, a systematic SAR analysis was carried out on re-
gion B of the original hit 1a and its analog 1b. Structural modifica-
tions of the central ring d showed that electronic effects are
fundamental for the activity, and revealed that a methyl substitu-
tion ortho to the C–C biaryl bond has a negative impact on the
activity, perhaps by forcing the biaryl system into an anti-coplanar
conformation. Interestingly, both thiophene and phenyl rings were
found to be bioisosteres of the furan moiety, thus expanding the
molecular diversity within the hit-derived molecules and including
new chemotypes which may address potential metabolic/toxicity
issues. Remarkably, compounds 19 (CYM50333) and 47
(CYM50367), as novel highly selective S1P4 antagonists with low
nanomolar activity, represent valuable small molecule tools to
investigate the biological and pharmacological role of the target
receptor in megakaryocyte differentiation and fundamental im-
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(A, B, C),17 additional studies are currently ongoing in our research
group to improve the physicochemical properties and further in-
crease the S1P4 antagonist potency, while preserving the S1P1–3,5
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20. The activity was measured by using Tango™ EDG6-bla U2OS cells which
contain the human Endothelial Differentiation Gene 6 linked to a GAL4-VP16
transcription factor via a TEV protease site. The cells also express a beta-
arrestin/TEV protease fusion protein and a beta-lactamase (BLA) reporter gene
under the control of a UAS response element. BLA expression is monitored by
Acknowledgments
This work was supported by the National Institute of Health
Molecular Library Probe Production Center grant U54 MH084512
(ER, HR), and by AI074564 (Michael Oldstone, PI). We thank Mark
Southern for data management with Pub Chem.
measuring fluorescence resonance energy transfer (FRET) of
fluorogenic, cell-permeable BLA substrate.
a cleavable,
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