776
P. J. Murray et al. / Bioorg. Med. Chem. Lett. 11 (2001) 773±776
Table 1. Antiprotozoal activities of apicidin 1aa and analogues 20±22
Parasite
ED50 (mg mLÀ1 b
)
3a
20
21
22
Plasmodium falciparum
Leishmania donovani
Trypanosoma cruzi
0.22Æ0.03
Tc
>1.0
>3 0
>3 0
>1.0
>3 0
>3 0
>1.0
>3 0
>3 0
Tc
Trypanosoma brucei
Cytotoxicity against KB cells
1.90Æ0.54
1.97Æ0.13
11.10Æ6.97
12.97Æ3.93
0.2Æ0.3
134.8Æ0.62
194.2Æ39.6
170.8Æ1.06
aApicidin 1a was obtained by Dr. Paul Stead from cultures of Fusarium pallidoroseum ATCC 7432 within our Biological Chemistry and Biopro-
cessing Unit.
bValues are the meanÆSEM (95%) of a representative experiment for triplicate points at each drug concentration in a three fold dilution series.
cToxicity to both mouse macrophage host cells and intracellular parasites prevented determination of antiprotozoal activity.
sickness. In addition, whilst apicidin showed clear signs
of cellular toxicity in the assays at the higher doses,
these eects were much less marked for the synthetic
mimetics. The results from a preliminary cytotoxicity
assay16 (Table 1) appear to con®rm these observations.
The toxicity of the reduced analogues 20±22, towards
KB cells, (a human nasopharyngeal epithelial cell line)
was observed to be in the order of 1000-fold lower than
the natural product.
Beppu, T. J. Biol. Chem. 1993, 268, 22429. (b) Taunton, J.; Col-
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Schmatz, D. M.; Fischer, M. H.; Wyvratt, M. J.; Meinke, P. T.
Tetrahedron Lett. 2000, 41, 7837. (b) Meinke, P. T.; Colletti, S. L.;
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Clegg, W.; Elsegood, M. R. J. J. Am. Chem. Soc., submitted
for publication.
These encouraging preliminary results suggest that the
methodology revealed above has the potential to pro-
vide apicidin analogues possessing antiparasitic activity
with an improved mammalian toxicity pro®le. Further
studies, utilising
a
solid-phase cyclitive cleavage
approach,17 are currently underway to prepare addi-
tional analogues which incorporate both alternative
amino acids and variations in the key non-proteinogenic
residue Aoda. These results will be the subject of a
future publication.
8. Macromodel 5.5 run on a Silicon Graphics, Indigo 2;
Amber force ®eld, GB/SA (water) solvation; Monte Carlo
conformational search.
Acknowledgements
9. In the transition state model 5 (Fig. 2), the bond forming
between the ammonium nitrogen and the carboxyl carbon was
®xed at 1.8Æ0 A (force constant=900). All other parameters
were free to optimise. The benzotriazole and phenylsulfonyl
groups were included as indicated.
10. (a) Bowman, W. R.; Coghlan, D. R. Tetrahedron 1997, 53,
15787. (b) Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetra-
hedron Lett. 1995, 36, 6373.
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Soc., Chem. Commun. 1993, 778. (b) Nash, I. A.; Bycroft,
B. W.; Chan, W. C. Tetrahedron Lett. 1996, 37, 2625.
12. Crystallographic data for 12 is deposited with the Cam-
bridge Crystallographic Data Centre (Supplementary Publica-
tion No.: CCDC 119472) and can be obtained, free of charge,
on application to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK, by fax: +44-1223-336033 or e-mail: deposit@
ccdc.cam.ac.uk
13. Garner, P.; Park, J. M. Org. Synth. 1992, 70, 18.
14. Kay, C.; Murray, P. J.; Sandow, L.; Holmes, A. B. Tetra-
hedron Lett. 1997, 38, 6941.
15. (a) Basco, L. K.; Marquet, F.; Makler, M. M.; Le Bras, J.
Expt. Parasitol. 1995, 80, 260. (b) Croft, S. L.; Snowdon, D.;
Yardley, V. J. Antimicrob. Chemother. 1996, 38, 1041.
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The authors are grateful to Glaxo Wellcome for a
Postgraduate Studentship (to KNK and FB) and an
Industrial Trainee Placement (to ST). One of us (WC)
thanks the EPSRC for an equipment grant. This inves-
tigation received support from the UNDP/World Bank/
WHO Special Programme for Research and Training in
Tropical Diseases (SLC). The authors are indebted to
the following colleagues for their technical assistance: to
Ian Davidson, Keith Brinded and Tony Cook for mass
specta, to Sean Lynn for help with X-ray crystal-
lography data, and to Claudia Weiss, Vanessa Yardley
and Howard Kendrick at LSHTM for biological assays.
References and Notes
1. (a) Singh, S. B.; Zink, D. L.; Polishook, J. D.; Dom-
browski, A. W.; Darkin-Rattray, S. J.; Schmatz, D. M.;
Goetz, M. A. Tetrahedron Lett. 1996, 37, 8077. (b) Darkin-
Rattray, S. J.; Gurnett, A. M.; Myers, R. W.; Dulski, P. M.;
Crumley, T. M.; Allocco, J. J.; Cannova, C.; Meinke, P. T.;
Colletti, S. L.; Bednarek, M. A.; Singh, S. B.; Goetz, M. A.;
Dombrowski, A. W.; Polishook, J. D.; Schmatz, D. M. Proc.
Natl. Acad. Sci. U.S.A. 1996, 93, 13143.
17. Berst, F.; Holmes, A. B.; Ladlow, M.; Murray, P. J. Tet-
rahedron Lett. 2000, 41, 6649.
2. (a) Kijima, M.; Yoshida, M.; Sugita, K.; Horinouchi, S.;