A series of SPM VIII analogs were synthesized to investigate the effect of the amino acid moiety on the antitumor activity. The L-threonine analog and the glycylglycine analog of SPM VIII showed much higher cytotoxity to P388 murine leukemia cells (IC 50 5.8 nM and 0.11 nM, respectively) than SPM VIII (IC 50 25 nM). However, replacement of the glycine moiety with other amino acids greatly reduced the antitumor activity against COL-1 human ...
