Synthesis of desaza analogues of annomontine and canthin-4-one alkaloids.

1-Acetylcarbazoles are readily converted to 3-desazacanthin-4-ones upon treatment with Bredereck's reagent, but in contrast to canthin-4-ones, these do not undergo ring transformation reactions with guanidine. Only after N-protection (methyl or 2-(trimethylsilyl)ethoxymethyl group), 2-desaza analogues of the alkaloid annomontine are accessible via the enaminoketones obtained by condensation with Bredereck's reagent. One of the annomontine analogues is an inhibitor of the Plasmodium falciparum CDC-like kinases (CLK) and shows antimalarial activity.