S-Phenylacetamidomethyl (Phacm): An Orthogonal Cysteine Protecting Group for Boc and Fmoc Solid-Phase Peptide Synthesis Strategies.

The reliability of the S-phenylacetamidomethyl-L-cysteine Cys(Phacm), a versatile derivative compatible with both Boc and Fmoc protection schemes, has been examined for solid-phase peptide synthesis. The Phacm group has the same properties as acetamidomethyl (Acm) and in addition is cleaved by the action of the enzyme penicillin amidohydrolase. Thus, Phacm is orthogonal with the common cysteine-protecting groups, such as 4-methylbenzyl (p-MeBzl), trityl (Trt) and fluorenylmethyl (Fm).