Formation and synthesis of 3'-t-butyltyrosine

During acidolysis by TFA of the t-butyl protecting group from Z-Tyr(But) or from Ser (But) in the presence of tyrosine, C-t-butylation occurred in the aromatic nucleus in Z-Tyr or tyrosine, respectively, to an extent of 0.5-1.0%. CF3COOBut formed during the acidolysis slowly C-t-butylates tyrosine. Tyr(3'But) is formed. The synthesis of Tyr (3'But) . HCl is described.