Design, synthesis, and biological evaluation of novel spin-labeled derivatives of podophyllotoxin as potential antineoplastic agents. Part XII

Five novel nitroxyl spin-labeled ester derivatives of podophyllotoxin (11a-11e) have been prepared and their structural information on these nitroxyl spin-labeled ester derivatives of podophyllotoxin (11a-11e) using (HNMR)-H-1 spectroscopy was efficiently obtained by application of the in situ reduction of representative nitroxyl spin-labeled ester derivative of podophyllotoxin 11e with phenylhydrazine for the preparation of N-hydroxylamine 12 in the NMR tube. These novel derivatives were further evaluated for their in vitro cytotoxic activity against five neoplastic cell lines (K562, HL-60, SPCA-1, Lewis, and L-1210) using MTT assay. Most of the target compounds (except for all these compounds against SPCA-1) exhibited more pronounced cytotoxicity against several neoplastic cell lines than that of the prototypical inhibitor etoposide.