Substituents at Cγ of proline are valuable probes to tune the trans/cis ratio of Xaa–Pro bonds. We investigated the effect of Cγ-substituents on the reactivity and stereoselectivity of the peptidic catalyst H-dPro-Pro-Glu-NH2. Derivatives that bear electron-withdrawing and -donating substituents (OH, F, N3, and SMe) at Cγ of the middle Pro-residue were examined. The results show that substituents at a 4R-configured Cγ hardly affect the stereoselectivity of the peptidic catalyst whereas substituents at a 4S-configured Cγ can be used to tune and improve the catalytic performance.
脯氨酸Cγ位置的取代基是调节Xaa-Pro键的反式/顺式比例的有价值的探针。我们研究了Cγ取代基对肽催化剂H-dPro-Pro-Glu-NH2的反应性和立体选择性的影响。我们检查了在中间脯氨酸残基的Cγ位置带有电子吸引和给予取代基(OH,F,N3和SMe)的衍生物。结果表明,4R构型的Cγ位置的取代基几乎不影响肽催化剂的立体选择性,而4S构型的Cγ位置的取代基可以用来调节和改善催化性能。