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The aspartimide problem in Fmoc‐based SPPS. Part I
Author(s) -
Mergler M.,
Dick F.,
Sax B.,
Weiler P.,
Vorherr T.
Publication year - 2003
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.430
Subject(s) - chemistry , residue (chemistry) , cleavage (geology) , orthoester , side chain , stereochemistry , peptide , alanine , combinatorial chemistry , amino acid , organic chemistry , biochemistry , polymer , geotechnical engineering , fracture (geology) , engineering
A variety of Asp β‐carboxy protecting groups, Hmb backbone protection and a range of Fmoc cleavage protocols have been employed in syntheses of the model hexapeptide H‐VKDGYI‐OH to investigate the aspartimide problem in more detail. The extent of formation of aspartimide and aspartimide‐related by‐products was determined by RP‐HPLC. This study included three new Fmoc‐Asp‐OH derivatives: the β‐(4‐pyridyl‐diphenylmethyl) and β‐(9‐phenyl‐fluoren‐9‐yl) esters and also the orthoester Fmoc‐β‐(4‐methyl‐2,6,7‐trioxabicyclo[2.2.2]‐oct‐1‐yl)‐alanine. 3‐Methylpent‐3‐yl protection of the Asp side chain resulted in significant improvements with respect to aspartimide formation. Complete suppression was achieved using the combination OtBu side chain protection and Hmb backbone protection for the preceding Gly residue. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.