Division of Organic Chemistry, National Chemical Laboratory, Dr Homi Bhabha Road, Pune 411008, India.
Org Lett. 2010 Dec 3;12(23):5390-3. doi: 10.1021/ol1021993. Epub 2010 Nov 4.
4S-Aminoproline polypeptide 2 forms unusual β-structure in trifluoroethanol that switches to the polyproline II (PPII) form in aqueous medium, while 4R-aminoproline peptide 1 retains PPII form in both solvents. This first instance of a polyproline derivative showing a β-structure is attributed to competitive pH-dependent (4-NH(3)(+)/NH(2)) stereoelectronic effect (4R vs 4S) and the overriding importance of stereospecific intra/intermolecular H-bonding in (2,4)-cis-4S-aminoproline in contrast to (2,4)-trans-4R-aminoproline oligomers.
4S-氨基脯氨酸多肽 2 在三氟乙醇中形成不寻常的β-结构，在水介质中转变为聚脯氨酸 II（PPII）形式，而 4R-氨基脯氨酸肽 1 在两种溶剂中均保持 PPII 形式。这是首例显示β-结构的聚脯氨酸衍生物，归因于竞争的 pH 依赖性（4-NH3(+)/NH2）立体电子效应（4R 与 4S）和（2,4）-顺式-4S-氨基脯氨酸中立体特异性的分子内/分子间氢键的重要性（2,4）-反式-4R-氨基脯氨酸低聚物。
