Nin-Cyclohexyloxycarbonyl Group as a New Protecting Group for Tryptophan.

Abstract Several new protecting groups were introduced at the Nin-position of tryptophan, and their reactivities were examined under the conditions used for peptide synthesis by Boc-strategy. Among them, the cyclohexyloxycarbonyl (Hoc) group was found to be the most suitable in terms of stability during elongation of the peptide chain and removability at the final HF reaction without resorting to the use of thiols.