Fmoc-S-Trityl-L-penicillamine

CAS 201531-88-6

Two methyl groups beside sulfur distinguish penicillamine from cysteine and can change the environment around a peptide disulfide. Fmoc-Pen(Trt)-OH delivers that residue with temporary protection on nitrogen and sulfur. The masks can be removed while the two methyl groups remain as part of the peptide. A study of selected substitutions in RgIA analogues specifically used this building block, providing a documented example of controlled peptide design. Any measured activity belongs to the finished analogue, not the protected reagent. The position of substitution also matters, so one favorable comparison cannot establish a rule for every cysteine site. This chemistry turns a small steric edit into a precise experiment about a larger molecular scaffold and its resulting behavior. Residue stereochemistry also distinguishes this material from other penicillamine derivatives.