HOBt·DCHA-Mediated Synthesis of Sterically Hindered Peptides employing Fmoc-Amino Acid Chlorides in Both Solution-Phase and Solid Phase Methods

The synthesis of peptides employing Fmoc-amino acid chlorides in presence of HOBt·DCHA salt in solution as well as by the solid-phase methods is described. The coupling was found to be complete in 30 min and free from racemization. The synthesis of β-casomorphin by solid-phase protocol employing Fmoc-amino acid chloride/HOBt·DCHA in DMF–CH2Cl2 has also been outlined. The final peptide was obtained in 80% yield and was fully characterized