Ten derivatives (3-12) of marine alkaloid lamellarin D (1) were synthesized and evaluated for cytotoxicity against a HeLa cell line in an effort to examine their structure-activity relationships. It appeared that the hydroxyl groups at positions C-8 and C-20 of 1 were important structural requirements for cytotoxic activity, while the hydroxyl group at C-14 and the two methoxy groups at C-13 and C-21 were not necessary for the activity.