NEW MATERIAL:The compound of formula IWIV or its salt.

USE: Hapten for the preparation of antibody for immunoglobulin therapy and an antigen composition for E.coli vaccine.

PREPARATION: The peptide of formula IWIV can be produced e.g. by (1) bonding a C-terminal amino acid to a chloromethylated styrene-divinylbenzene copolymer resin, (2) coupling the resin successively with amino acids having protected amino group according to the amino acid sequence of the objective peptide in the presence of a condensation agent, (3) removing the amino-protecting group, (4) repeating the steps (2) and (3) to obtain a peptide resin and (5) separating peptide from the resin and eliminating protective groups from all functional groups.