N. Tibrewal, G. I. Elliott / Bioorg. Med. Chem. Lett. 21 (2011) 517–519
519
with two-carbon linker showed almost negligible inhibition. The
formylated derivative, compound 12, unexpectedly did not show
any improvement in activity. There was a similar observed trend
of weak inhibition for both the compounds 17a and 17b.
5:1 asp to cmpd
1:1 asp to cmpd
In conclusion, several structurally similar hadacidin analogues
were tested for possible inhibition of adenylosuccinate synthetase.
The introduction of methyl substituent at the
a-carbon reduced
the ability of the compound to inhibit the enzyme by 50% when
tested at aspartate to substrate of 5:1. Since this was a racemic
compound, the possibility exists that one isomer may be active.
Addition of more bulky groups on the
a-carbon further reduced
a
2
the activity. By increasing the carbon chain length between the ter-
minal ends of the N-hydroxy and carboxylic acid resulted in nearly
complete loss of activity. None of the analogues tested for activity
against adenylosuccinate synthetase showed activity better than
hadacidin. We are currently working on the synthesis of optically
pure 6a to further evaluate the active site and to provide com-
pounds with better activity.
Figure 3. Inhibition of AdSS by hadacidin analogues with varying carbon linker
between N-hydroxy and carboxylic acid. aN-hydroxy glycine.
active components (GDP, GTP, and ASMP) of the mixture at
266 nm. The amount of adenylosuccinate monophosphate formed
was quantified by the integration of peak areas over three runs.
At 10 mM hadacidin completely inhibited the enzyme (Fig. 2).
However, by adjusting the ratio of aspartate to hadacidin to 5:1,
the inhibition dropped to 80%. We tested all final compounds at
both concentrations. Compound 6a, having a methyl group at the
Acknowledgements
This work was supported by the American Cancer Society (IRG
85-001-22). The authors are grateful to Mike Rosenbach and
Dennis Carson of the University of California, San Diego Moores
Cancer Center for providing the enzyme and very helpful
discussions.
a
-carbon demonstrated approximately 50% reduced ability to inhi-
bit the enzyme when asp:6a was 5:1. The inhibition improved to
90% when equimolar concentrations of aspartate and compound
6a were tested.
Supplementary data
Addition of more bulky groups on the a-carbon (6b–d) resulted
in nearly complete loss of activity at 5:1 ratio of aspartate:test
compound. When the concentration of the test compound was in-
creased to 1:1 some inhibition was observed, albeit very low.
Supplementary data associated with this article can be found, in
When the
a-chain went from ethyl to propyl, the expected loss
of activity was observed. But when the diastereomers of isobutyl
6d were tested, some activity against the enzyme was retained.
Furthermore, compounds 6e and 6f with polar carboxylic
References and notes
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