3750
Acid Stability of Several Benzylic Protecting Groups Used in Solid-Phase Pep tide Synthesis. Rearrangement of 0-Benzyltyrosine to 3-Benzyltyrosine' Bruce W. Erickson and R. B. Memifield" Contribution f r o m The Rockefeller University, New York, New York Received November 28, 1972
10021.
The acid stabilities of ten amino acid derivatives bearing benzylic side-chain protecting groups were determined quantitatively by ion-exchange chromatography. The apparent first-order rate constants for loss of the benzylic groups were measured in 50 : 50 (v/v) trifluoroacetic acid-dichloromethane at 20'. The derivatives and sec-l) follow in order of increasing stability : 0-benzyl-L-tyrosine(636) < "-benzyltheir rate constants ( k , oxycarbonyl-L-lysine (396)
