NEW MATERIAL:The stilbene derivative of formula I (R1 and R2 are H, lower or medium alkyl or cycloalkyl, at least one of R1 and R2 is not H; R3 and R4 are H, methyl or trifluoromethyl; R5 is OH, lower alkoxy or -NR6R7; R6 and R7 are H or lower alyl).

USE: It has the activity to morphologically and functionally promote the differentiation of cancer cell, especially leukemia cell, and is useful as a drug.

PREPARATION: The objective compound of formula I can be prepared by reacting the compound of formula II with the compound of formula III [X is group of formula IV (Y is anion of organic or inorganic acid) or dialkoxyphosphinylalkyl group of formula V (R is lower alkyl)], and if necessary, converting the carboxylic acid ester of formula -COR5 to carboxylic acid or acid amide.