Preferred Spatial Arrangement of the Aromatic Side Chains in Linear Oligopeptides Containing Tyrosine

Abstract 1 H‐NMR. studies of the protected linear tetrapeptides CF 3 CO‐Gly‐Gly‐ L ‐Tyr‐ L ‐Ala‐OCH 3 , CF 3 CO‐Gly‐ L ‐Ala‐ L ‐Tyr‐ L ‐Ala‐OCH 3 and CF 3 CO‐Gly‐ L ‐Ala‐ L ‐Tyr‐Gly‐OCH 3 showed that the side chain of the tyrosyl residue was in all three peptides preferentially oriented towards the amino terminus of the peptide chain. This preferred spatial arrangement of the aromatic side chain was manifested in the chemical shifts of the amino acid residue preceding tyrosine and in the vicinal spin‐spin coupling constants 3 J HCαCβH of tyrosine.