This requires a solid phase peptide synthesis-compatible, and methyliminodiacetic acid (MIDA), a boron protecting group, orthogonal amino acid in 5 steps.[12] As a final step, enantioselective oxidation at the tryptathionine linkage was achieved using a bulky organic oxidizing agent and an optimized solvent system to afford the desired the bio-reactive (R)-enantiomer sulfoxide, completing the total synthesis.