Bioinspired Syntheses of the Pyridoacridine Marine Alkaloids Demethyldeoxyamphimedine, Deoxyamphimedine, and Amphimedine

Efficient bioinspired syntheses of the biologically active pyridoacridine marine alkaloids demethyldeoxyamphimedine, deoxyamphimedine, and amphimedine are reported. Reaction of styelsamine D, prepared via an optimized route starting from Boc-dopamine, with paraformaldehyde afforded demethyldeoxyamphimedine and deoxyamphimedine. Oxidation of the latter using either K₃[Fe­(CN)₆] or DMSO/conc. HCl gave amphimedine in 8 steps from tryptamine with an overall yield of 14%. The versatility of the method was demonstrated by the synthesis of non-natural ethyl and benzyl congeners of deoxyamphimedine and amphimedine

Biomimetic Synthesis of Thiaplidiaquinones A and B

A biomimetic synthesis of the biologically active ascidian metabolites thiaplidiaquinones A and B is described. Reaction of geranylbenzoquinone with Et₃N in CH₂Cl₂ yielded two isomeric quinones, comprising the benzo­[<i>c</i>]­chromene-7,10-dione core of the natural products. Subsequent reaction with hypotaurine yielded the title compounds and their dioxothiazino regioisomers