Hodges Jonathan A, Raines Ronald T
Departments of Chemistry and Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Org Lett. 2006 Oct 12;8(21):4695-7. doi: 10.1021/ol061569t.
[structure: see text] The trans/cis ratio of the amide bond in N-formylproline phenylesters correlates with electron withdrawal by a para substituent. The slope of the Hammett plot (rho = 0.26) is indicative of a substantial effect. This effect arises from a favorable n --> pi interaction between the amide oxygen and ester carbonyl. In a polypeptide chain, an analogous interaction can stabilize the conformation of trans peptide bonds, alpha-helices, and polyproline type-II helices.
[结构：见正文] N-甲酰基脯氨酸苯酯中酰胺键的反式/顺式比率与对位取代基的吸电子作用相关。哈米特图的斜率（ρ = 0.26）表明存在显著影响。这种影响源于酰胺氧与酯羰基之间有利的n→π相互作用。在多肽链中，类似的相互作用可以稳定反式肽键、α-螺旋和聚脯氨酸II型螺旋的构象。
