NEW MATERIAL:The pyrimidine derivative of formula I [X and Y are H or group of formula II (R, R', R" and R''' are alkyl, aryl, etc.: W and W' are hetero atom or hetero atom group; V and V' are heterocyclic ring, etc.; K and K' are 0W10; l, l', m, m', n, and n' are 0W6)].

EXAMPLE: 1-(α-Acetoxyfurfuryl)-5-fluorouracil.

USE: Carcinostatic agent. The characteristic feature of the compound is the introduction of a group which can be coordinated with a polar group or metal, e.g. hetero atom, hetero atom group, hetero-cyclic ring, double bond, etc., or introduction of a crosslinkable aliphatic hydrocarbon group. It has high affinity to the cancerous tissue and low toxicity.

PROCESS: The objective compound is prepared by reacting the chloride of formula III with 5-fluorouracil (pref. 1-acetyl-5-fluorouracil or 1-alkoxycarbonyl-5-fluorouracil).