Figure 5.

In situ capping of chain ends in the ZIP step. (a) When the CuAAC reaction is carried out on the pre-ZIP intermediate in the presence of an excess of 4-tert-butylbenzyl azide, a single major product is obtained. An antiparallel arrangement of the backbones in the duplex is shown, but the parallel product is also possible (see below). R = 3,5-di-tert-butylphenyl. (b) The effect of the concentration of the capping agent on the product distribution. The lines are the theoretical relationships obtained if the product ratio is directly proportional to the ratio of the concentration of the capping agent and the effective molarity for the intramolecular reaction leading to macrocylization (purple) or to zipping up the duplex (orange).³⁷