Abstract

Enzyme catalyzed formation of peptide bonds reached practical significance in partial syntheses such as the conversion of pork insulin to human insulin. Catalysis is important also in coupling with active esters. The earlier applied acid-base catalysis was replaced by the use of bifunctional catalysts, 1-hydroxybenzotriazole being an outstanding example: it brought about major improvements in peptide bond formation. Intramolecular catalysis can be discerned in the rapid acylation by certain active esters, e.g., esters of catechol, 4-nitroguaiacol or 8-hydroxyquinoline. The ready formation of symmetrical anhydrides in the reaction of acylamino acids with carbodiimides is best explained by intramolecular catalysis within the O-acylisourea intermediates. Catalysis plays important roles both in introduction and in removal of blocking groups. Preparation of alkyl esters through base-catalyzed transesterification of active aryl esters and the application of this reaction for the anchoring of peptides to polymeric supports are described. Enzyme catalyzed hydrolysis of alkyl esters and hydrolytic fission of the phenylacetyl group from lysine side chains with aid of penicillin amidohydrolase are characteristic examples of the application of catalysis for the removal of blocking groups. Acidolysis of the benzyl groups including the benzyloxcarbonyl group is catalyzed by thioanisole or by 4-methylthiophenol. The catalytic effect of solvents is demonstrated with the cleavage of triphenylmethyl and biphenylyl-isopropyloxycarbonyl groups by 1-hydroxybenzotriazole in trifluoroethanol. The increasing role of catalysis in peptide synthesis and its future application for the solution of fundamental problems, such as amine activation, are discussed.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call