Synthesis of N-succinimidyl 4-guanidinomethyl-3-[*I]iodobenzoate: a radio-iodination agent for labeling internalizing proteins and peptides

Nat Protoc. 2007;2(2):282-6. doi: 10.1038/nprot.2007.20.


This protocol describes a detailed procedure for the synthesis of N-succinimidyl 4-guanidinomethyl-3-[*I]iodobenzoate ([*I]SGMIB), an agent useful in the radio-iodination of proteins, including monoclonal Abs, and peptides that undergo internalization after receptor or antigen binding. In this procedure, the tin precursor N-succinimidyl 4-[N1,N2-bis(tert-butyloxycarbonyl)guanidinomethyl]-3-(trimethylstannyl)benzoate (Boc-SGMTB, 3) was first radio-iodinated to [*I]Boc-SGMIB, a derivative of [*I]SGMIB with the guanidine function protected with Boc groups. Treatment of [*I]Boc-SGMIB with trifluoroacetic acid delivered the final product. The total time for the synthesis and purification of [*I]Boc-SGMIB and its subsequent de-protection is approximately 140 min.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Benzoates / chemical synthesis*
  • Benzoates / isolation & purification*
  • Chromatography, High Pressure Liquid
  • Guanidine / analogs & derivatives*
  • Guanidine / chemical synthesis
  • Guanidine / isolation & purification
  • Molecular Structure
  • Proteins / analysis*
  • Staining and Labeling / methods*


  • Benzoates
  • N-succinimidyl 4-guanidinomethyl-3-iodobenzoate
  • Proteins
  • Guanidine