Total synthesis of the proposed structure for pochonicine and determination of its absolute configuration

Pochonicine is a polyhydroxylated pyrrolizidine alkaloid with a powerful inhibitory activity against β-N-acetylglucosaminidases. The proposed structure for pochonicine and the three diastereomers concerning its C-1 and/or C-3 positions were synthesized from N-acetyl-d-glucosamine through construction of the pyrrolizidine skeleton by two intramolecular amino cyclizations as key steps. This synthetic study not only revised the structure of the natural product to the corresponding 1,3-di-epi-form but also determined the absolute configuration as 1R, 3S, 5R, 6R, 7S, 7aR.