Semisynthesis of DB-67 and other silatecans from camptothecin by thiol-promoted addition of silyl radicals Original Research Article

Thiol- or acid-promoted additions of silyl radicals to camptothecin are reported. At 105 °C, mixtures of 7-silyl (favored) and 12-silyl camptothecins are formed alongside substantial amounts of recovered camptothecin. At 160 °C, 12-silyl isomers are formed preferentially, but the total mass balance is substantially reduced. The silyl radical addition is featured in short semi-syntheses of DB-67 (7-tert-butyldimethylsilyl-10-hydroxy camptothecin) from both camptothecin and 10-hydroxycamptothecin.