کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5270138 | 1385408 | 2014 | 4 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Estimation of the 2.05 helix type iâi hydrogen bond energy at Aibâ-Oxa motif: an isodesmic approach
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
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چکیده انگلیسی
Bending at the valence angle N-Cα-Câ² (Ï) is a known control feature for attenuating the stability of the rare intramolecular iâi hydrogen bonded pseudo five-membered ring C5 structures, the so called 2.05 helices, at Aib. The competitive 310-helical structures still predominate over the C5 structures at Aib for most values of Ï. However at Aibâ, a mimic of Aib where the carbonyl O of Aib is replaced with an imidate N (in 5,6-dihydro-4H-1,3-oxazine = Oxa), in the peptidomimic Piv-Pro-Aibâ-Oxa (1), the C5i structure is persistent in both crystals and in solution. Here we show that the iâi hydrogen bond energy is a more determinant control for the relative stability of the C5 structure and estimate its value to be 18.5 ± 0.7 kJ/mol at Aibâ in 1, through the computational isodesmic reaction approach, using two independent sets of theoretical isodesmic reactions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tetrahedron Letters - Volume 55, Issue 23, 4 June 2014, Pages 3418-3421
Journal: Tetrahedron Letters - Volume 55, Issue 23, 4 June 2014, Pages 3418-3421
نویسندگان
Ravula Thirupathi, Erode N. Prabhakaran,