Model studies have been carried out in which the Kaiser-DeGrado procedure for solid-phase synthesis has been combined with the use of reactants with a latent activation feature as a potential route to peptide active esters. The rates of reaction of the 4-(methylthio)phenyl ester of L-phenylalanine (1a) with itself, as well as those of a close analogue with tert-butyloxycarbonylglycine bound to a benzophenone oxime functionalized polystyrene resin have been measured in the presence of varying concentrations of the aminolysis catalyst, acetic acid. These studies indicate that under appropriate conditions, it is possible to generate the 4-(methylthio)phenyl esters of suitable peptides, synthesized by solid-phase methods on the oxime-functionalized resin. These peptide esters can then be oxidized to the more strongly electrophilic sulfone derivatives. The preparations of the 4-(me-thylsulfonyl)phenyl esters of N-tert-butyloxycarbonylglycyl-L-phenylalanine and N-carbobenzyloxy-O-carbo-benzyloxy-L-tyrosylglycylglycyl-L-phenylalanine are described as examples of the use of this method of preparing peptide active esters.
ASJC Scopus subject areas
- Organic Chemistry