Experiments Directed Towards the Synthesis of Anthracyclinones. X. A Synthesis of (±)-4-Demethoxydaunomycinone

Abstract

The acetal methyl 2-(3-dimethoxymethyl-4-hydroxy-1-methoxy-9,10-dioxo- 9,10-dihydroanthracen-2-yl)acetate (2), a versatile intermediate prepared earlier from quinizarin (1), has been converted into (±)-4- demethoxydaunomycinone (5) in 43% yield (on a small scale) from the acetal (2) and in 29% overall yield from quinizarin. The structure of (±)-9α-acetyl-6,9-dihydroxy-7α,11-dimethoxy-5,7,8,9,10,12-hexahydronaphthacene-5,12-dione (6), an intermediate in the sequence, has been confirmed by X-ray studies.