NEW MATERIAL:A compound of formula I [R , R are H, lower alkyl, lower alkenyl; A, B are D- or L-basic aminoacid; C is alpha-aminoacid, beta-alanine, alpha- aminobutyric acid; D is -OR (R is H, lower alkyl), -E-OR (E is neutral to acidic aminoacid; R is H, lower alkyl); where the case is excluded where all of the aminoacid constituents are L-aminoacid of formula II (R is residual group, after the group of formula III is removed from the structural formula of aminoacids). EXAMPLE:CH3Tyr-Gly-Gly-Phe-Leu-Arg-CH3Arg-D-Ala-OH. USE:Analgesic. PREPARATION:For example, Z-CH3Arg(Tos)OH is used as a starting substance and converted into Boc-CH3Tyr(Cl2Bzl)-Gly-Gly-PHe-Leu-Arg(Tos)-CH2Arg(Tos)- D-Ala-OBu. Then, the product is allowed to react with HF.