[Synthesis of a fragment of the active center of the streptococcal proteinase (EC 3.4.22.10), IX].

The synthesis of the protected pentapeptide tert-butyloxycarbonly-Gln-Ile-Met-Lys(X)-Gly-p-nitrobenzylester (X = benzyloxycarbonyl, 3-chlor-benzyloxycarbonyl) which is part of the carboxylend of a partial sequence of the active center of the streptococcal proteinase is described. Side reactions are observed if the tert-butyloxycarbonyl-protective group is cleaved by trifluoroacetic acid, not with HC1/dioxane. Obviously the presence of methionine is responsible for the formation of by products. Formation of methioninesulfoxide of tert-butylsulfoniummethionine could not be proved. tert-butyloxycarbonyl-Gln-1-hydroxybenzotriazolylester was obtained in a crystalline state from the reaction of tert-butyloxycarbonyl-Gln, dicyclohexylcarbodiimid and 1-hydroxybenzotriazol.