Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... The crucial E-ring of camptothecin has been modified to afford the homologous β-hydroxylactone derivative BN 80245. This compound, which is more stable than camptothecin, remains a potent inhibitor of both cell growth and topoisomerase I. ... The crucial E-ring of camptothecin ...