Experiments Directed Towards the Synthesis of Anthracyclinones. XXX. Formation and Use of an Anthraquinone Formyl Ester

Abstract

Methods for the preparation of methyl 3-formyl-1,4-dimethoxy-9,10-dioxo-9,10-dihydroanthracene-2-acetate (1) from quinizarin (8) have been investigated. Reaction of the ester (1) with either a titanium enolate of acetone or with acetone trimethylsilyl enol ether and titanium tetrachloride gave the aldol (29) which was then converted into the pentacyclic lactone mixture (41) and (42). While hydrolysis of (41) and (42) with base for long periods (>30 min) gave α,β -unsaturated ketones , brief (2 min) treatment gave the dimethyl ether (5) of the 4-deoxyanthracyclinone (6) corresponding to the antitumour anthracycline 14A10.