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Selective Removal of the o ‐Nitrophenylsulfenyl Protecting Group in Peptide Synthesis
Author(s) -
TunKyi Aung
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610318
Subject(s) - chemistry , reagent , peptide synthesis , dimethylformamide , protecting group , methylene , peptide , side chain , methanol , indole test , tryptophan , acetic acid , amino acid , organic chemistry , medicinal chemistry , biochemistry , alkyl , solvent , polymer
2‐Thiopyridone (2‐mercaptopyridine, 1 ) was found to be a very suitable reagent for removing the N α ‐o‐nitrophenylsulfenyl (NPS‐) group in both conventional and solid‐support peptide synthesis. A 3‐ to 5‐molar excess of the reagent together with an equivalent amount of glacial acetic acid in methanol, dimethylformamide, or methylene chloride produces the soluble, stable mixed disulfide, 2‐nitrophenyl 2‐pyridyl disulfide ( 2 ), and the N α ‐deprotected amino‐acid or peptide. The yields are quantitative in less than 5 min if all educts are dissolved, in about 20 to 30 min in solid‐support synthesis. No modifications of either the indole side‐chain of tryptophan or of a series of side‐chain protecting groups, in particular of the t ‐butyl type, are produced. No adverse side‐reactions (insoluble disulfides) were observed. The procedure is illustrated with a series of amino‐acid derivatives and with the solid‐support synthesis of [5‐leucine]‐enkephalin.