title: Comparison of methods for the Fmoc solid-phase synthesis and cleavage of a peptide containing both tryptophan and arginine.
abstract: A major side reaction which can occur during the synthesis of Trp-containing peptides is modification of the Trp indole by reactive carbonium ion species released during acidolytic cleavage. [Asn2,Trp4]Dynorphin A-(1-13), a sequence which is very susceptible to Trp modification, was chosen as a model peptide to compare the effectiveness of various methods proposed to minimize Trp modification during Fmoc solid-phase synthesis. The peptide was synthesized with the side chain of Trp unprotected and cleaved by Reagent K [82.5% trifluoroacetic acid (TFA)/5% phenol/5% water/5% thioanisole/2.5% ethanedithiol (EDT)] [King, D.S. et al. (1990) Int. J. Peptide Protein Res. 36, 255-266], Reagent R [90% TFA/5% thioanisole/3% EDT/2% anisole] [Albericio, F. et al. (1990) J. Org. Chem. 55, 3730-3743], TFA containing 20% EDT and 4% water [Riniker, B. & Hartmann, A. (1990) in Peptides: Chemistry, Structure, and Biology (Rivier, J.E. & Marshall, G.R., eds.), pp. 950-952, Escom, Leiden], and TFA containing trialkylsilane, MeOH, and ethylmethyl sulfide [Chan, W.C. & Bycroft, B.W. (1992) in Peptides: Chemistry, Structure, and Biology, Op. cit., pp. 613-614]. Cleavage with Reagent K, Reagent R and TFA containing 20% EDT and 4% water yielded similar results; in addition to the desired peptide, the crude product contained 22-30% of a side product which appeared to result from Trp modification by a Pmc group. Cleavage with the trialkylsilane-containing mixture gave the lowest recovery of the desired peptide and the highest levels of Pmc-containing peptides.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Oregon State University, College of Pharmacy, Corvallis.
authors.forename: H
authors.initials: H
authors.lastname: Choi
authors.forename: J V
authors.initials: JV
authors.lastname: Aldrich
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D004399:Dynorphins / Q000138:chemical synthesis* / Q000737:chemistry; D005069:Evaluation Studies as Topic; D005449:Fluorenes; D007202:Indicators and Reagents; D008722:Methods; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis* / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry
chemical_list: D005449:Fluorenes; D007202:Indicators and Reagents; D010446:Peptide Fragments; D010455:Peptides; C083166:dynorphin A (1-13), Asn(2)-Trp(4)-; D004399:Dynorphins; D014364:Tryptophan; D001120:Arginine