Synthesis and Fucosidase Inhibitory Study of Unnatural Pyrrolidine Alkaloid 4-epi-(+)-Codonopsinine

The total synthesis of enantiopure 4-epi-(+)-codonopsinine was achieved in 10 steps starting from d-ribose as a chiral building block. The key step involved a highly stereoselective nucleophilic addition of a Grignard reagent to a protected ribosylamine. Synthesis of the N-desmethyl derivative and its p-tolyl analogue was also accomplished, and the compounds were assayed against α-fucosidase.