R. Grigg et al. / Tetrahedron Letters 43 (2002) 2605–2608
2607
mM for 8 and 14 mM for 9, thus, having the potential
to act as antineoplastic agents. Recent synthetic work
9
by Danishefsky has identified more active unnatural
analogues. The synthesis of such analogues, together
10
with the natural products, is currently attracting
much attention.
Acknowledgements
We thank Leeds University for support.
References
1
. (a) Ali Dondas, H.; Duraisingham, J.; Grigg, R.;
MacLachlan, W. S.; MacPherson, D. T.; Thornton-Pett,
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Figure 3. X-Ray crystal structures of both stereoisomers of
product 7.
1998, 39, 435–438; (f) Grigg, R.; Sridharan, V.; York,
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Further studies are currently ongoing to determine
the diversity of functionality within the dipole that is
tolerated in the cascade. Although the bimetallic cas-
cade is demonstrated for imines of a-amino esters it
is potentially applicable to the substantial range of
(
i) Grigg, R.; Sridharan, V.; Suganthan, S.; Bridge, A.
W. Tetrahedron 1995, 51, 295–306 and earlier papers.
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3. Hinman, R. L.; Bauman, C. P. J. Org. Chem. 1964, 29,
aminomethyl
substrates
exemplified
in
our
7
publications.
2431.
In conclusion, this bimetallic catalytic cascade offers
access to novel spiro-oxindole analogues, the reaction
proceeding with good to excellent stereoselectivity.
The spiro-oxindole moiety is the core structure in a
number of natural products, which offer potentially
valuable medicinal properties. Typical examples are
the Spirotryprostatins A 8 and B 9, which were
recently isolated from the fermentation broth of
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try 1995, 32, 5817.
6. Grigg, R.; Koppen, I.; Large, S.; unpublished results.
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patanagul, S. Tetrahedron 1989, 45, 1723–1746.
8
Aspergillus fumigatus.
These spiro-oxindole alkaloids inhibit the cell cycle in
the G2/M phase of tsFT210 cells with IC s of 197.5
8. (a) Usui, T.; Kondoh, M.; Cui, C.-B.; Mayumi, T.;
5
0