Total synthesis of the natural carbazoles glycozolicine, mukoline, and mukolidine, starting from 4,5-dimethyleneoxazolidin-2-ones

A novel and efficient synthesis of naturally occurring 1-methoxycarbazoles glycozolicine, mukolidine, and mukoline is developed by applying a regioselective Diels-Alder reaction of a 4,5-dimethyleneoxazolidin-2-one with acrolein. The cycloadduct is transformed to the corresponding functionalized diarylamine. The key palladium-catalyzed cyclization/deformylation cascade reaction of the latter leads to glycozolicine in high overall yield. Oxidation of the C6 methyl group provides the 6-formylcarbazole mukolidine, which is reduced to the respective natural alcohol mukoline.