Excess mixed anhydride peptide synthesis with histidine derivatives

Abstract

Abstract The coupling of histidine derivatives by the excess mixed anhydride method was investigated with respect to the yield, the racemization, and the formation of by‐products. The tert ‐butyloxycarbonyl‐ (Boc‐), isobutyloxycarbonyl‐ ( i ‐Boc‐), benzyloxycarbonyl‐ (Z‐), and p ‐toluenesulfonyl‐(Tos‐) groups were found to be suitable for protection of the imidazole nucleus. A new way of selective removal of the N im ‐Tos group, with pyridine hydrochloride, is described.