Novel A-Ring Modified Camptothecins as Topoisomerase I Inhibitors.

Abstract A camptothecin derivative has been prepared wherein the A-ring is fused to an oxazole ring. The compound was prepared via a Friedlander condensation involving benzoxazole 8 and tricyclic ketone 9 . This derivative displays potent topoisomerase I inhibition (IC 50 150 nM) when assayed in the ‘cleavable complex’ assay.