Syntheses of Erythrinan Alkaloids : (±)-Coccolinine, (±)-Isococculidine, (±)-Coccuvinine, and (±)-Cocculidine

抄録

Total syntheses of 'abnormal-type' erythrinan alkaloids, (±)-coccolinine (1), (±)-isococculidine (2), (±)-coccuvinine (3) and (±)-cocculidine (4), are described. Mondon's glyoxylic ester synthesis was successfully applied in these syntheses. The key intermediate, 16-ethoxycarbamido-2, 15-dimethoxyerythrinan-7, 8-dione (7), was obtained by condensation of 3-ethoxycarbamido-4-methoxyphenylethylamine (5) with ethyl 4-methoxycyclohexanone-2-glyoxylate (6), followed by treatment with phosphoric acid. The ethoxycarbamido group at the C₁₆ position was effectively employed as a regiospecific para-directing group in the isoquinoline ring closure.