STRUCTURE CORRECTION AND SYNTHESIS OF SUBSPINOSIN

Subspinosin isolated from the root of Damnacanthus subspinosus Hand-Mazz (Rubiaceae) and deduced as 3-ethoxymethyl-2-hydroxy-1-methoxyan-thraquinone 1 by Li et al in 1981, should be corrected as 2-ethoxymethyl-3-hydroxy-1-methoxyanthraquinone 5 by comparison with the synthetic compound. Since 5 is already known as damnacanthol-ω-ethyl ether, the name "Subspinosin" for 1 (not yet a natural isolate) should be abandoned in order to acknowledge this priority, and, what is more, to avoid confusionThe anthraquinones 1 and 5 were synthesized by condensation of phthalic anhydride with 3-methylcatechol or 2-methylresorcinol in fused AICl₃/NaCl (5:1), followed sequentially by selective acetylation, methylation, bromination and condensation with sodium ethoxide.