From: Daniel Trachsel (Daniel_Trachsel$##$gmx.ch)
Date: Wed Feb 23 2000 - 09:48:35 EST
We wish to synthesize demecolcine, starting from colchicine.
theoretically,a deacylation and then monomethylation would yield the
needed compound.
There are several experiments in Helv. Chim. Acta 1954 to methylate
directly the colchicine (which is an acetamide) without any or only little
success. Then, there are reactions to produce the unacylated amine in very
good yields. But how to monomethylate it under very mild conditions? The
methoxy-group on the tropone-ring is very unstable against acids and/or
bases. To formylate the amine (with ethylformate) and then reduce to the
corresponding methylamine would give a lot of byproducts (colchicine itself with
NaBH4 gave a reduction on the carbonyl-group on the tropone-ring). To
protect the oxo-group of the tropone-ring (to prevent from reduction or even
1,4-Additions) as an cyclic acetal(ethylenedioxy), catalyzed with TsOH in benzene
afforded some other products (maybe the TsOH did demethylate on the
tropone-ring).
If someone has an idea for this synthesis, please send it to:
Thanks and greetings daniel.
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