Cyclic α,β-Tetrapeptoids: Sequence-Dependent Cyclization and Conformational Preference

The presence of at least one N-C alpha branched side chain is crucial for successful cyclization of alpha,beta-tetrapeptoids. The ctct amide sequence revealed in the crystal structure of the 14-membered cyclotetrapeptoid 8 is also the most populated conformation in solution and is reminiscent of the predominant amide arrangement of the 12-membered cyclic tetrapeptides (CTPs).