Table 3.

Regioselectivity of peptide halogenation derived from ¹H‐NMR data. Strict C6‐selectivity is achieved for bulkier residues next to the Trp moiety.

Regioisomers/%[a]

Substrate	Sequence	C5/%	C6/%
25	H‐d‐Trp‐Gly‐Gly‐Gly‐NH2	24	76
29	H‐d‐Trp‐Val‐Gly‐Gly‐NH2	not found	100
30	H‐d‐Trp‐Ser‐Gly‐Gly‐NH2	7	93
34	H‐d‐Trp‐Phe‐Gly‐Gly‐NH2	not found	100

[a] Percentages refer to ratio of isomer signals calculated from integrals of the NMR signals.