We designed and synthesized several brefeldin A (BFA) analogs. These compounds were evaluated for the ability to induce differentiation and apoptosis in human colonic carcinoma cell line HCT116. Diacetyl BFA (2a), 4-acetyl BFA (2b), 7-acetyl BFA (2c), and 10,11-epoxy BFA (3b) were active but tetrahydro BFA (3a) and other analogs could not induce the malignant cells to differentiate. The results suggested that the moiety from 1- to 4-position in BFA as well as its conformational rigidity is essential for its biological activity. (C) 1997, Elsevier Science Ltd.