(S)-2-((1R,2S)-2-((R)-1-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutyl)cyclopropyl)propanoic Acid has been used in the synthesis of highly conformationally restricted cyclopropane tethers (CPTs) which can control the conformation and improve the cell permeability of cyclic peptides regardless of the amino acid sequence.