Short and regiospecific synthesis of echinamine A--the pigment of sea urchin Scaphechinus mirabilis.

New convenient two-step synthesis of natural pigment echinamine A by the condensation of 2,3-dichloro-6-ethyl-7-hydroxy-1,4-naphthoquinone with sodium nitrite and subsequent reduction of intermediate 7-ethyl-2,5,6,8-tetrahydroxy-3-nitro-1,4-naphthoquinone has been developed.