Tetrapeptides and pentapeptides, their preparation and compositions

Abstract

Tetrapeptides and pentapeptides of the formula: ##STR1## wherein R represents hydrogen or a fatty acid residue, R.sub.1 represents hydroxy, amino, alkoxy of 1 to 4 carbon atoms, optionally substituted by phenyl or nitrophenyl, one of R.sub.2 and R.sub.4 represents hydrogen, carboxy, carbamoyl, alkoxycarbonyl of 2 to 5 carbon atoms, optionally substituted by phenyl or nitrophenyl, or a N-carbonylglycine or N-carbonyl-D-alanine radical optionally esterified by alkyl of 1 to 4 carbon atoms (which is optionally substituted by phenyl or nitrophenyl) and the other symbol represents hydrogen, carboxy, carbamoyl, or alkoxycarbonyl fof 2 to 5 carbon atoms, optionally substituted by phenyl or nitrophenyl, and R.sub.3 represents hydrogen, a fatty acid residue or a glycyl or D-alanyl moiety in which the amine group is optionally substituted by a fatty acid residue, it being understood that R.sub.2 and R.sub.4 cannot simutaneously represent hydrogen, that at least one of R.sub.2, R.sub.3 and R.sub.4 represents a glycyl or D-alanyl moiety, that at least one of R and R.sub.3 represents or contains a fatty acid residue, and that the alanine moiety is in the L form, the glutamic acid moiety or its derivatives are in the D form, the lysine moiety or its derivatives, when one of the symbols R.sub.2 and R.sub.4 represents a hydrogen atom, are in the L form, and the 2,6-diaminopimelic acid moiety or fits derivatives, when R.sub.2 and R.sub.4 represent a carboxy, carbamoyl or alkoxycarbonyl radical, are in the D,D L,L,D,D/L,L (racemic) or D,L (meso) form, and salts thereof possess immunostimulant activity.