Z. Kazimierczuk et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1197–1200
1199
allows generation of the adamantyl cation without pro-
tonation, or with only partial protonation of the exo-
cyclic amino group. The introduction of the bulky
adamantyl residue depends strongly on the steric effects.
For instance, we were unable to introduce the ada-
mantyl group using the acid reaction conditions (with
either orthophosporic acid or trifluoroacetic acid) if
there was a methyl group or halogen atom at the ortho
position relative to the exocyclic amino group. Because
of the relatively good solubility of the respective het-
erocyclic bases in aqueous medium, the use of an excess
of heterocycles allowed purification of the products
without column chromatography in most cases.15
sides of the pyridine ring. The other is the presence of
two nitrogen atoms, which are capable of forming
hydrogen bonds in the interconnecting o-aminopyridine
bridge. Rentgenostructural study on 2-adamantyl-
amino-6-methylpyridine 2e is in progress (Maurin and
Kazimierczuk, in preparation).
Genetically modified cells producing mediators of the
immune system (cytokines, interleukines and TNF-a)
show promise as ‘vaccines’ used to stimulate antitumor
response in new, experimental forms of cancer ther-
apy.20 We hope that some of the adamantane deriva-
tives described above, especially 2e, might be good
candidates for adjuvant drugs used to potentiate anti-
tumor efficacy of such therapeutic strategies.
Biological Evaluation
The ability of the (1-adamantyl)aminopyrimidines and
(1-adamantyl)aminopyridines described above to stimu-
late TNF-a production was studied in cultures of B78-
H1 murine melanoma cells that had been transduced
with the gene for human TNF-a (clone 9, hereafter
named B78/TNF/9).18 This cell line secretes TNF-a at a
constant rate, and by this reason appears useful for
testing the effect of various chemicals on TNF-a pro-
duction. TNF-a in 24 h cultures of these cells was
assayed using enzyme-linked immunosorbent assay
(ELISA).
Acknowledgements
This study was supported by grant no. 1 M19/W2/2000
from the Medical University of Warsaw and by the
Foundation for the Development of Diagnostic and
Therapy in Warsaw, Poland.
References and Notes
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14. Kazimierczuk, Z.; Orzeszko, A.; Sikorska, A. In Perspec-
All the adamantane derivatives tested significantly
enhanced TNF-a production in B78/TNF/9 cells at
concentrations of 10 mM (Fig. 1). The results obtained
reveal certain relationships between chemical structure
and biological activity of the adamantane derivative
series. First, the adamantylamino group appears practi-
cally a ‘must’ for biological activity in the system
employed. The mother compound (2-amino-6-methyl-
pyridine) of the most active derivative 2e showed only
about 10% enhancement of TNF-a production, also
amantadine (1-aminoadamantane) was inactive in the
tests used. Introduction of the adamantylamino residue
at position 4 in the pyrimidine ring, or either at position
3 or 4 of the pyridine ring was much less effective in
terms of enhancement of the TNF-a production by the
respective derivatives than the corresponding 2-ada-
mantylaminated compounds. The presence of the ada-
mantylamino group at position 2 and of the methyl
group at either the 6 position of the pyridine nucleus, or
at position 4 in pyrimidines provided the three most
potent derivatives 1b, 2f and 2e (Fig. 1). Of note, these
latter compounds showed a detectable enhancement of
TNF-a production already at 10 nM concentration.19
Introduction of an extra methyl group or chlorine atom
at the heterocyclic ring (e.g., see 2a and 2f) resulted in
no significant change in TNF-a secretion activity;
instead, most such derivatives showed an increased
cytotoxicity (data not shown).
ˆ
tives in Nucleoside and Nucleic Acid Chemistry; Kisakurek, M.
V., Rosemeyer, H., Eds., Wiley-VCH: Weinheim, Germany,
2000.
15. Typical procedure for the synthesis of (1-adamantyl)-
aminopyrimidines or -pyridines. A solution of aminohetero-
cyclic base (11 mmol) and 1-adamantanol (10 mmol) in
trifluoroacetic acid (10 mL) was stirred under reflux for 5 h.
The reaction mixture was poured into ice-cooled water
(50 mL) and brought to pH 7 with concd aq NH3 solution.
Structural similarities among the most active com-
pounds allow speculation that there are two characteristic
features that may both be important for their biological
activity. One is the presence of two hydrophobic groups,
the adamantyl one and the methyl one, on the opposite
Kazimierczuk, Zygmunt
