Cross-linking of amino acids by formaldehyde. ¹³C N.M.R. spectra of model compounds

Abstract

The use of ¹³C N.M.R. for the identification of the site of cross- linking of amino acids by formaldehyde has been evaluated by use of model compounds, such as 2,4-dimethylphenol for tyrosine. The ¹³C chemical shifts of the formaldehyde-derived methylene carbons occur within the range 50-60 p.p.m. downfield from Me₄Si. Estimated shifts in lysine-lysine and tyrosine-glutamine cross-linked systems fall just outside this region. The ¹³C spectra of a number of related phenols, amines and protected amino acids are also reported.