Xanthocyclines: 5-oxaanthracyclines (7,8,9,10-tetrahydrobenzo[b]xanthen-12-one)

Abstract
The anthracycline antibiotics daunorubicin and adriamycin are potent antitumor agents. It has recently been suggested that 5-oxaanthracycline analogs of these compounds might show reduced cardiotoxicity, a property that limits the clinical use of the anthracyclines. In this paper we describe the condensation–cyclization reactions of 2-methylchromone-3-carboxylate with cyclohexanones, a reaction that leads ultimately to the xanthocycline skeleton.