A novel polypeptide is defined by the below shown formula and is useful as an analgesic. ##STR1## wherein R.sup.1 and R.sup.2 may be the same or different and each represents a hydrogen atom or a lower alkyl or lower alkenyl group, A represents a D-amino acid, Gly or Sar provided that when the D-amino acid is D-Cys, it is bonded with L-Cys or D-Cys in position 5 through a S--S bond to effect intramolecular ring closure, B represents L-Phe or D-Phe in which the benzene ring may be substituted or an .alpha.-N-alkyl derivative thereof, C represents an L-amino acid, D-Cys or an .alpha.-N-alkyl derivative thereof, D and E each represent an L- or D-basic amino acid or an .alpha.-N-alkyl derivative thereof, F represents a group of the formula --OR.sup.3 (in which R.sup.3 is H or a lower alkyl group), a group of the formula: ##STR2## (in which R.sup.4 and R.sup.5 are the same or different and each represents H or a lower alkyl group), a group of the formula: --G--OR.sup.6 (in which G is an L- or D-amino acid or Gly or an .alpha.-N-alkyl derivative thereof and R.sup.6 represents H or a lower alkyl group), a group of the formula: ##STR3## (in which G is as defined above and R.sup.7 and R.sup.8 may be the same or different and each represents H or a lower alkyl group), a group of the formula: --G--L--Arg--OR.sup.9 or --G--D--Arg--OR.sup.9 (in which G is as defined above and R.sup.9 represents H or a lower alkyl group or a group of the formula: ##STR4## (in which G is as defined above and R.sup.10 and R.sup.11 may be the same or different and each represents H or a lower alkyl group), a group of the formula: --G--J--OR.sup.12 in which G is defined as above, J is a neutral amono acid group or an acidic amino acid group and R.sup.12 is hydrogen or a lower alkyl group; or a group of the formula: --G--Arg--M--OR.sup.13 in which M is D-amino acid group and R.sup.13 is hydrogen or a lower alkyl group, provided that all of the amino acids constituting the polypeptide of the above formula do not represent at the same time an L-amino acid of the general formula: ##STR5## (in which R represents a group corresponding to a structural formula of an amino acid deprived of a group of the formula: ##STR6## or pharmacologically acceptable salts of them.
下面所示的公式定义了一种新型
多肽,并且可用作镇痛剂。其中R.sup.1和R.sup.2可以相同也可以不同,并且每个表示
氢原子或较低的烷基或较低的
烯基基团,A表示D-
氨基酸,Gly或Sar,但当D-
氨基酸为D-Cys时,它通过S-S键与L-Cys或D-Cys在5号位结合以形成分子内环闭合,B表示L-Phe或D-Phe,其中
苯环可以被取代或其α-N-烷基衍
生物,C表示L-
氨基酸,D-Cys或其α-N-烷基衍
生物,D和E分别表示L-或D-碱性
氨基酸或其α-N-烷基衍
生物,F表示以下公式的基团:--OR.sup.3(其中R.sup.3为H或较低的烷基基团),以下公式的基团:##
STR2##(其中R.sup.4和R.sup.5相同或不同,每个表示H或较低的烷基基团),以下公式的基团:--G--OR.sup.6(其中G是L-或D-
氨基酸或Gly或其α-N-烷基衍
生物,R.sup.6表示H或较低的烷基基团),以下公式的基团:##
STR3##(其中G如上所定义,R.sup.7和R.sup.8可以相同也可以不同,每个表示H或较低的烷基基团),以下公式的基团:--G--L--Arg--OR.sup.9或--G--D--Arg--OR.sup.9(其中G如上所定义,R.sup.9表示H或较低的烷基基团或以下公式的基团:##
STR4##(其中G如上所定义,R.sup.10和R.sup.11可以相同也可以不同,每个表示H或较低的烷基基团),以下公式的基团:--G--J--OR.sup.12(其中G如上所定义,J是中性
氨基酸基团或酸性
氨基酸基团,R.sup.12是
氢或较低的烷基基团),或以下公式的基团:--G--Arg--M--OR.sup.13(其中M是D-
氨基酸基团,R.sup.13是
氢或较低的烷基基团),前提是上述公式的所有
氨基酸不同时代表去除了一个公式的基团:##
STR6##的
氨基酸的L-
氨基酸,或其药理学上可接受的盐。