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)].
The non-steroidal androgen-receptor antagonists WS9761 A (1,6,10-trihydroxy-2,8,10-trimethylanthrone) and WS9761 B (1,6,10-trihydroxy-2-hydroxymethyl-8,10-dimethylanthrone) were synthesized for the first time in racemic form by using Diels-Alder methodology followed by regioselective Grignard addition.