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333ChemInform Abstract The thermal cycloaddition of the α-pyrone (I) with the ketal (II) yields the bicyclolactone (III) which is transformed to the amino compounds (IV) and (V). While (IV) directly yields the desired deacetamidocolchiceine (VI), its isomer (V) gives the tropolone (VII). The latter can be converted to (VI) according to a known procedure. (VI), in turn, has already been transformed to colchicine (VIII), a potent mitotic inhibitor. Cycloaddition of (I) with (II) under modest pressure yields the exo-cycloadduct (IX). All attempts to synthesize the compound (X) from this product are unsuccessful.

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