Fmoc-Tyr(PO3H2)-OH is an Fmoc protected tyrosine derivative that is potentially useful for proteomics studies and solid phase peptide synthesis techniques. Tyrosine is a very important amino acid - one of the few amino acids which is phosphorylated to vary the physical properties of the peptides, and is a precursor for the formation of iodinated thyroid hormones. The Fmoc group is typically removed with a base such as pyridine - an orthogonal de-protection strategy to the acid labilie Boc group.