Synthesis of peptides containing C -terminal methyl esters using trityl side-chain anchoring: Application to the synthesis of a-factor and a-factor analogs

A new cysteine anchoring method was developed for the synthesis of peptides containing C-terminal cysteine methyl esters. This method consists of attachment of Fmoc-Cys-OCH₃ to either 2-ClTrt-Cl or Trt-Cl resins (via the side-chain thiol) followed by preparation of the desired peptide using Fmoc-based SPPS. We applied this method to the synthesis of the mating pheromone a-factor and a 5-FAM labeled a-factor analog. The peptides were obtained with high yield and purity and were shown to be bioactive in a growth arrest assay.