A Modified Synthesis of α-N-carbobenzoxy-L-lysine and the preparation and analysis of mixtures of ε-N-methyllysines

Abstract

α-N-Carbobenzoxy-L-lysine has been obtained in 37% yield by carbobenzoxylation of L-lysine in 25% excess benzaldehyde followed by passage of the solution through a cupric carbonate – alumina column. Reaction of the product in aqueous solution with diazomethane, followed by deprotection, gave a mixture of ε-N-methyllysine (MML), ε-N,ε-N-dimethyllysine (DML), and ε-N,ε-N,ε-N-trimethyllysine suitable as a standard for chromatographic purposes. It has been demonstrated that when a mixture of MML and DML emerges as one peak when chromatographed with an amino acid analyzer, the relative concentrations of the two amino acids in the mixture can be established from the 570/440 nm absorbance ratio.