PURPOSE: To provide a novel compd. comprising a phosphoric ester having a pyrimidine ring and being useful as an effective component of a medicine for treating and preventing a recognizing function disease and emotional disorder, especially, an Alzheimer's disease, depression or the like.

CONSTITUTION: A novel phosphoric ester or phosphonic ester useful for treating and preventing a recognizing function disease, depression or the like is represented by formula I [wherein R is 1-6C alkyl; R1 is 1-6C alkyl or alkoxy; R2 is H, 1-6C alkyl, alkoxy, 3-7C cycloalkyl or the like; R3 is (substd.) 1-6C alkyl, (substd.) 1-6C alkoxy or H; R4 is halogen, 1-4C alkyl or alkoxy; and X is O or S], e.g. O-(6-methoxy-2-t-butyl-pyrimidin-4-yl)-O-methyl- thiomethanephosphonic diester. The compd. is obtained by reacting halogenated phosphonoyl or phosphoryl represented by formula II (wherein Hal is halogen) with 4-hydorxypyrimidine represented by formula III.