Acid-labile handles for Fmoc solid-phase synthesis of peptide N-alkylamides

Michael F. Songster, Josef Vágner, George Barany

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


By analogy to established methodology for the preparation of C-terminal peptide amides by 9-fluorenylmethyl-oxycarbonyl (Fmoc) chemistry, in conjunction with the acidolyzable 5-(4-Fmoc-aminomethyl-3,5-dimethoxyphenoxy)valeric acid (PAL, 1) handle, the present paper reports on 5-(4-(N-Fmoc-N-alkyl)aminomethyl-3,5-dimethoxyphenoxy)valeric acid [(R)PAL, 2] handles that can be used for synthesis of peptide N-alkylamides. The key step in the preparation of these handles was the NaBH3CN-mediated reductive amination (60 to 85% yields; R=CH3, CH3CH2, C6H5CH2CH2, 4-NO2C6H5) of 5-(4-formyl-3,5-dimethoxyphenoxy)valeric acid (4), an aldehyde precursor to PAL. The (R)PAL handles (2a and b) were applied to the preparation of LHRH analogues. After anchoring of handles to PEG-PS supports, peptide chain assemblies were carried out, and treatments with TFA-thioanisolephenol-1,2-ethanedithiol (87:5:5:3) for 90 min at 25 °C, followed by aqueous workups, provided the expected products in excellent yields and purities as supported by HPLC and mass spectrometric characterization.

Original languageEnglish (US)
Pages (from-to)265-270
Number of pages6
JournalLetters in Peptide Science
Issue number5
StatePublished - Jan 1996


  • Acidolyzable anchors
  • LHRH analogues
  • Reductive amination
  • Tris(alkoxybenzyl) N-alkylamides [(R)PAL]


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