I have an L-cysteine amino acid attached to a silane by thiolate. As it is know that FITC attaches to the amine group by thio urea bond . How can I attach FITC to the free amine group present in amino acid .
In principle it should work with two equivalents FITC and four equivalents DIPEA in DMF (stirring over night). But if you intend to make a peptide at the free acid group of the cysteine you must take into account the Edman degradation which leads to scission of FITC thiourea derivatized terminal amino acids from peptides. In this case you must first react the amino group with a linker like 6-amino capronic acid. If you want to make non-peptide chemistry at the acid group of the cysteine the direct derivatization of the amino group - which you planned - is appropriate.
