Peptide Synthesis Using the Pyrrole Ring as an Amino Protecting Group
The utility of a pyrrole ring as an amino protecting group for amino acids in peptide synthesis has been studied.The N-termini of various amino acids (1) were protected with a pyrrole ring by treatment with 2,5-dimethoxytetrahydrofuran (10) to give 2-substituted 2-(1-pyrrolyl)acetic acids (11).The peptide bond between (11) and amino acid methyl ester (2) was formed using N,N'-dicyclohexylcarbodiimide, and the pyrrole ring was cleaved by ozonolysis and hydrolysis without the cleavage of a peptide bond to give the corresponding dipeptide compounds (26) in good yields.
Peptide Decomposition in the Neutral pH Region via the Formation of Diketopiperazines
In the neutral pH region, the decomposition of the tripeptides Leu-Gly-Gly and Gly-Leu-Gly at 130 deg C and the hexapeptide Phe-Gly-Leu-Gly-Val-Gly at 100 deg C has been found to involve the formation of diketopiperazines from the N-terminal position of the peptides.