A Simple Synthesis of Amphimedine

The marine alkaloid amphimedine has been synthesized by a short sequence of reactions commencing from the known indenopyridinedione (2). Reaction with 4-pyridyllithium, followed by hydrazoic acid treatment, gave 5-(4-pyridyl)-3,6-phenanthrolin-4(3H)-one (12) which was converted into the chlorophenanthroline. The methyl-substituted fluorosulfonate salt of this compound was specifically oxidized by alkaline ferricyanide. Conversion of the pyridone into the nitrile gave the precursor which was cyclized to amphimedine by polyphosphoric acid.

Depsidone synthesis. XXIII. The oxidation of 2,2'-dihydroxy-4,4'-dimethoxy-6,6'-dimethylbenzophenone

Oxidation of 2,2'-dihydroxy-4,4'-dimethoxy-6,6'-dimethylbenzophenone (1) with alkaline ferricyanide gave the expected 4',6-dimethoxy-4,6'-dimethylspiro[benzofuran-2(3H),1'-cyclohexa-3',5'-diene]-2',3(2H)-dione (2) as well as 2'-hydroxy-6-methoxy-4,5'-dimethylspiro[benzofuran-2(3H),1'-cyclopent-4'-ene]-3(2H),3'-dione (3). The structure of compound (3) was deduced from its spectroscopic properties and was confirmed by X-ray diffraction.