Synthesis of Highly Oxygenated Anthraquinones from Chamaecrista greggii

Abstract

Four isomeric anthraquinones (2)–(5) have been synthesized for the first time, by cycloaddition involving the new dienes (8) and (9). Their spectroscopic properties have been compared together and with data for two natural anthraquinones reported from Chamaecrista greggii. The assigned structure (2) was thereby supported for one of the natural isomers. The other isomer, previously formulated as (3), did not correspond to any of the synthesized compounds [(2)–(5)].