Simple preparative synthesis of spinochrome E, a pigment from sea urchins of the genus Echinothrix

摘要

A preparative synthesis of spinochrome E (2,3,5,6,7,8-hexahydroxy-1,4- naphthoquinone, 1), a metabolite of sea urchins of the genus Echinothrix, is proposed starting from 2,3-dichloro-6,7-diethoxynaphthazarine (4) with simultaneous substitution of the Cl atoms by hydroxyl- and nitro-groups, reduction of the latter, and subsequent removal of alkoxy groups and hydrolysis of the amine in the resulting 3-amino-2-hydroxy-6,7-diethoxynaphthazarine (6).