Naturally occurring quinones. Part XXVI. A synthesis of tetrangulol (1,8-dihydroxy-3-methylbenz[a]anthracene-7,12-quinone)

Abstract

Hydroxybenz[a]anthracene-7,12-quinones can be prepared from 2-chloro-1,4-naphthoquinones by decarboxylative alkylation at C-3 with β-(3-acetoxyphenyl)propionic acids followed by treatment with sodium carbonate, which results in hydrolysis, cyclisation, and dehydrogenation. In this way tetrangulol and its 3,8-dihydroxy-1-methyl isomer were obtained from 5-acetoxy-3-[β-(3-acetoxy-5-methylphenyl)ethyl]-2-chloro-4-naphthoquinone.