Polypeptides. Part XIV. The synthesis of some oligopeptides containing lysine and glutamic acid residues

Abstract

Several oligopeptides of the general formula A-Ly[graphic omitted].(or [graphic omitted]lu).Gly_n.[graphic omitted]lu.(or [graphic omitted]ys).Gly_n.OB have been synthesised; their projected use for polymerisation experiments and for “doubling” imposes limitations on the protecting groups which can be used, since these must be selectively removable. In two cases, it was not found possible to remove an N-formyl group without breaking peptide linkages, while in these and a further case, selective removal of other protecting groups was prevented by the great lability of side-chain benzyl ester groups towards alkali. Finally, four protected oligopeptides of the required type were synthesised, using benzyloxycarbonyl for α-N-protection, t-butyl ester for ω-C-protection, and trifluoroacetyl and methyl ester for the protection of lysine and glutamic acid side-chains, respectively. Three of these were converted into side-chain protected peptides suitable for polymerisation and into the free peptides, and two of them, by a “doubling” procedure into the octa- and dodeca-peptides.