Figure 3.
(a) X-ray crystal structures of Br-Nph-Ns1npe-dma, 3, and 4a. All hydrogen atoms except for the s1npe side chain methines have been omitted for clarity. The black dashed line indicates a side chain – side chain C ••• C distance. (b) The main chain atoms of the X-ray crystal structure of 4a illustrate the reverse turn and the green arrow depicts an n→π*C=O interaction. The black dashed line indicates a main chain Cα•••Cα distance. (c) A displaced aromatic-aromatic stacking interaction was detected between the side chains of residues 1 and 4 in the X-ray crystal structure of 4a. Only the side chain and nitrogen atoms are shown. The black dashed line indicates the centroid to centroid distance between the two aryl rings.