The molecular and crystal structure of the Aib (α-aminoisobutyric acid)-containing oligopeptide, Boc–(l-Leu–Aib2)2–OBzl, are determined by X-ray diffraction analysis. The hexapeptide crystallizes in the space group P21, with a=19.912(2), b=16.098(1), c=14.710(2) Å, β=96.81(1)°, and Z=4. The unit cell contains two independent molecules (molecules A and B) in the asymmetric unit. The dihedral angles (φ and ψ) of the peptide back bone show that molecule A folds into a right-handed helix and molecule B folds into a left-handed helix. Both the molecules adopt a 310-helical conformation stabilized by four 4→1 intramolecular hydrogen bonds. The right- and left-handed helical molecules are arranged alternately, in head-to-tail fashion to make columns along the [101] direction. These columns are packed closely in the pseudo-hexagonal arrangement.
含Aib(α-
氨基
异丁酸)寡肽Boc–(l-Leu–Aib2)2–OBzl的分子和晶体结构通过X射线衍射分析确定。六肽在空间群P21中结晶,a=19.912(2),b=16.098(1),c=14.710(2) Å,β=96.81(1)°,Z=4。在非对称单元中,晶胞包含两个独立分子(分子A和分子B)。肽主链的双面角(φ和ψ)表明分子A折叠成右旋螺旋,分子B折叠成左旋螺旋。两个分子都采用310螺旋构象,由四个4→1分子内氢键稳定。右旋和左旋螺旋分子以头对尾的方式交替排列,沿[101]方向形成柱状结构。这些柱状结构以伪六边形排列紧密堆积。