prises condensing an L- aspartic acid derivative represented by the general Formula II: A-( JHC 0 OH v (L) wherein A is a protected amino group and B is a protected carboxyl group with a compound represented by the general Formula HI: as defined above, to produce a dipeptide ester derivative represented by the general Formula IV: B 0001?. z 2):: A-bH00NHiiH-O00R (L) wherein each of A, B, R R and n