New derivatives of spicamycin modified at the fatty acid moieties of t
he molecule were synthesized and their structure-activity relationship
s were examined. The antitumor activity was greatly influenced by modi
fication of the fatty acid moieties to tetradecadienoyl or dodecadieno
yl analogues exhibiting better antitumor activity against COL-1 human
colon cancer xenograft than SPM VIII.