Cycloacylation of chloro-substituted hydroquinone dimethyl ethers with dichloromaleic anhydride

Preparative Synthesis of Spinochrome D, a Pigment of Different Sea Urchin Species

A simple and effective synthesis of spinochrome D (1) (2,3,5,6,8-pentahydroxy-1,4-naphthoquinone), a pigment of different sea urchin species, has been developed starting from 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (13), easily available by cycloacylation of 1,4-dimethoxybenzene (11) with dichloromaleic anhydride (12). Bromination of 13 with either bromine or dioxane dibromide to 6-bromo-2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (21), followed by nucleophilic substitution of the halogen atoms by methoxy groups in 21 and hydrolysis of trimethyl ether 10 produce the target compound in overall yield from 62 to 65%.