Ring fusion strategy for the synthesis of anthra[2,3-d]oxazole-2-thione-5,10-dione homologues as DNA topoisomerase inhibitors and as antitumor agents

The efficient synthesis and ring fusion into anthra[2,3-d]oxazole-2-thione-5,10-diones were developed. Four compounds were selected by NCI and three compounds for topoisomerase I-mediated DNA relaxation.