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We report herein the first systematic crystal structural investigation of azaproline incorporated in homo‐ and heterochiral diprolyl peptides. The X‐ray crystallography data of peptides 1–5 illustrates that stereodynamic nitrogen in azaproline adopted the stereochemistry of neighbouring proline residue without depending on its position in the peptide sequence. Natural bond orbital analysis of crystal structures indicates OazPro−C′Pro of peptides 4 and 5 participating in n→π* interaction with stabilization energy about 1.21–1.33 kcal/mol. Density functional theory calculations suggested that the endo‐proline ring puckering favoured over exo‐conformation by 6.72–7.64 kcal/mol. NBO and DFT data reveals that the n→π* interactions and proline ring puckering stabilize azaproline chirality with the neighbouring proline stereochemistry. The CD, solvent titration, variable‐temperature and 2D NMR experimental results further supported the crystal structures conformation.

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