Regiospecificity in the reaction of 2,3-dichloronaphthazarins with azide anions. Synthesis of echinamine A—a metabolite produced by the sea urchin Scaphechinus mirabilis

It was found that 6-hydroxy- and 6-alkoxy-2,3-dichloronaphthazarins react smoothly with sodium azide in methanol to produce the corresponding 2-azido derivatives as single regioisomers. We have explored the utility of this reaction for the synthesis of echinamine A (3-amino-7-ethyl-2,5,6,8-tetrahydroxy-1,4-naphthoquinone)—the first marine aminated hydroxynaphthazarin, a metabolite of the sea urchin Scaphechinus mirabilis (Agassiz).