ChemInform Abstract: Hydroxymethylation of Protoberberine Alkaloids by Photoinduced SET. The Total Synthesis of (.+-.)-Solidaline

The direct insertion of a hydroxymethyl group at position C-8 in a protoberberinium ion by photoaddition of methanol was approached via two mechanistic pathways: acetone-sensitized and single-electron transfer. The latter produces 8-hydroxymethylberbines in good yields after reduction. By combining this photochemical reaction with the oxidation of the photoproduct, syntheses of (±)-solidaline and its C-13 epimer from palmatine chloride were accomplished for the first time. On the other hand, insertion of a hydroxymethyl group at position 14 of the berberine skeleton in order to open a synthetic pathway for zijinlongine proved unsuccessful.