Recommanded Product: 87694-50-6On May 6, 1998 ,《γ-Peptides forming more stable secondary structures than α-peptides. Synthesis and helical NMR-solution structure of the γ-hexapeptide analog of H-(Val-Ala-Leu)2-OH》 appeared in Helvetica Chimica Acta. The author of the article were Hintermann, Tobias; Gademann, Karl; Jaun, Bernhard; Seebach, Dieter. The article conveys some information:
For a comparison with the corresponding α- and β-hexapeptides H-(Val-Ala-Leu)2-OH (A) and H-(β-HVal-β-HAla-β-HLeu)2-OH (B), the corresponding γ-hexapeptide (I), built from the homochirally similar (S)-4-aminobutanoate, (R)-4-amino-5-methylhexanoate, and (R)-4-amino-6-methylheptanoate, was prepared The precursors were obtained either by double Arndt-Eistert homologation of protected Boc-Val-OH, Boc-Ala-OH, and Boc-Leu-OH, or by the superior route involving olefination/hydrogenation of the corresponding aldehydes, Boc-valinal, Boc-alaninal, and Boc-leucinal. Conventional peptide coupling (EDC/HOBt) furnished I through the intermediate γ-di- and γ-tripeptide. NMR measurements in (D5)pyridine and CD3OH solution (COSY, TOCSY, HSQC, HMBC, ROESY) reveal that I adopts a right-handed helical structure [(P)-2.61 helix of ∼5-Å pitch, containing 14-membered H-bonded rings] which is to be compared with the left-handed helix of β-peptide B [(M)-31 helix of 5-Å pitch, 14-membered H-bonded rings] and with the familiar right-handed, so-called α-helix of α-peptides [(P)-3.61 helix of 5.4-Å pitch, 13-membered rings]. Like the helix sense, the helix dipole reverses when going from α-(N→C) to β-(C→N) to γ-peptides (N→C). The surprising difference between the natural α-, and the analogous β- and γ-peptides is that the helix stability increases upon homologation of the residues. In the part of experimental materials, we found many familiar compounds, such as (S)-N-Methyl-N-methoxy-2-(tert-butoxycarbonylamino)-4-methylpentanamide(cas: 87694-50-6Recommanded Product: 87694-50-6)
(S)-N-Methyl-N-methoxy-2-(tert-butoxycarbonylamino)-4-methylpentanamide(cas: 87694-50-6) belongs to amides. Because of the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N–C dipole. The presence of a C=O dipole and, to a lesser extent a N–C dipole, allows amides to act as H-bond acceptors.Recommanded Product: 87694-50-6 In primary and secondary amides, the presence of N–H dipoles allows amides to function as H-bond donors as well.
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics