Colouring Matters of Australian Plants. I. The Structure of Droserone

Abstract

Droserone, one of the pigments occurring in Drosera whittakeri, is proved to be 3,s-d'ihydroxy-2-methyl-1,4-naphthoquinone by a five step synthesis from the known 5-methoxy-1-tetralone. From an intermediate product, 2-hydroxy-5-methoxy-1,4-naphthoquinone, the droserone isomer 2,5-dihydroxy-3-methyl-1,4-naphtl1oquinone and 2-hydroxyjuglone are also obtained. The latter compound is significant in the chemistry of the natural pigment juglone. 4n interpretation is given for some orientation effects observed in the nucleophilic substitution of certain naphthoquinones.