Synthesis of quinone and xanthone analogs of rhein

A new strategy based on carbonylation of aryl triflates has been developed to prepare 7-methyl rhein from emodin and new xanthone analogs of rhein. Th is approach avoids the oxidation step of methyl derivatives with toxic chro mium salts. Although possessing the same structural arrangement of phenol a nd carboxylic acid functions as found in rhein, these new xanthone derivati ves have no activity against IL-1. Thus, the quinone moiety of rhein appear s to be essential for activity. (C) 2001 Elsevier Science Ltd. All rights r eserved.