This stereo-controlled synthesis of the title alkaloids provides the first total synthesis of the naturally occurring homoerythrinan alkaloids. The key step of our synthesis of the homoerythrinan ring system lies in [2+2]. photocycloaddition of a benzaepino-pyrrolinedione to an activated butadiene followed by the anionic 1,3-rearrangement of the resulting vinyl-oxy-cyclobutane. Starting from safrole, the 2,8-dioxo-Δ^<1(6)>-homoerythrinan derivative 45 was synthesized in 22 steps through the cyclohomo-erythrinan derivative 35 utilizing the above 1,3-anionic rearrangement, 1,2-carbonyl transposition via phenylselenenylation and decarbomethoxylation reaction by group IIa metal halide-DMSO. The compound 45 was stereoselectively reduced to 3β-alcohol 48 by Bu_4NBH_4 and to 3α-alcohol 49 by NaBH_4-CeCl_3. Methylation and AlH_3 reduction of 50 gave (±)-schelhammericine 1. Similarly methylation and reduction of 51 gave (±)-epischelhammericine 2.
