Novel 3 ',6 '-Anhydro And N12,N13-Bridged Glycosylated Fluoroindolo[2,3-A]Carbazoles As Topoisomerase I Inhibitors. Fluorine As A Leaving Group From Sp(3) Carbon

Both 6'- and 4'-fluoro-glycosylated indolo[2,3-a]carbazoles are substrates for base-induced loss of fluorine as a leaving group from sp(3) carbon. In the case of alpha-N-glycosylated substrate 3, loss of fluorine from the V-position leads to 3,6-anhydroglucose analogue 1. A novel N12,N13-bridged sugar analogue 2 results from loss of 4'-fluorine from beta-N-glycosylated analogue 4. Both analogues 1 and 2 display topo I inhibitory potencies similar to camptothecin.