PURPOSE: To obtain a new compound which is useful as a carcinostatic agent of high activity caused by the metabolism in living bodies by reaction of 3'- amino-2',3'-dideoxycytidine with N-substituted-L-phenylalanine derivative.

CONSTITUTION: A new compound: 2',3'-dideoxy-3'-N-substituted-L-phenyl- alanylamidocytidine of the formula I (R is amino-protecting group), which is useful as a prodrug from which 3'-amino-2',3'-dideoxycytidine is cut out by chymotrypsin to develop excellent carcinostatic action which is more powerful than the direct action of the cytidine. The compound is obtained by reaction of 3'-amino-2',3'-dideoxycytidine of the formula II with N-substituted L- phenylalanine derivative of the formula III (R1 is pentachlorophenyl, p- nitrophenyl, N-hydroxysuccinic imide).