Total Synthesis of the Alkaloid, (±)-Hasubanonine

(±)-Hasubanonine was synthesized through 16-oxo-hasubanonine (63) as a relay substance starting from the keto-lactam (41). The keto-lactam (41) was derived to the keto-O-acetyl-phenol A (49) which was oxidized to the axial-acetoxy-ketone (50). Bromination of (50) followed by the rearrangement reaction with sodium acetate gave the enol-acetate (51) which was converted to the bromo-enolmethyl-ether (56) via the diosphenol (54) and the bromo-diketone (55). The compound (56) was derived to the β-diketone (57) which was methylated to give (±)-16-oxo-hasubanonine (59) and (±)-aknadilactam (61). On the other hand, hasubanonine was oxidized to 16-oxo-hasubanonine (63) which was put back to hasubanonine by lithium aluminum hydride reduction followed by manganese dioxide oxidation.