The achiral tetrapeptide monohydrate N‐(benzyloxycarbonyl)glycyl‐α‐aminoisobutyrylglycyl‐α‐aminoisobutyric acid monohydrate, Z–Gly–Aib–Gly–Aib–OH·H₂O (Z is benzyloxycarbonyl, Aib is α‐aminoisobutyric acid and Gly is glycine) or C₂₀H₂₈N₄O₇·H₂O, exhibits two conformations related by the symmetry operation of an inversion centre. It adopts only one of two possible intramolecular hydrogen bonds in a type I (and I′) β‐turn and forms a maximum of intermolecular hydrogen bonds partly mediated by water. The space group, the molecular structure and the crystal packing differ from two already described (Gly–Aib)₂ peptides which vary only in the protecting groups. This structure confirms the high structural flexibility of Gly–Aib peptides and points to a strong relationship between intermolecular hydrogen bonding and crystal quality and size.

中文翻译：

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去除 C 端保护基会增大晶体尺寸：Z-(Gly-Aib)2-OH·H2O

非手性四肽一水合物N-（苄氧羰基）甘氨酰-α-氨基异丁酰甘氨酰-α-氨基异丁酸一水合物，Z-Gly-Aib-Gly-Aib-OH·H ₂ O（Z是苄氧羰基，Aib 是 α-氨基异丁酸，Gly 是甘氨酸）或C ₂₀ H ₂₈ N ₄ O ₇ ·H ₂ O，表现出两种与反转中心对称操作相关的构象。它仅采用 I 型（和 I'）β-转角中两种可能的分子内氢键中的一种，并形成最大的分子间氢键，部分由水介导。空间群、分子结构和晶体堆积不同于已经描述的两个 (Gly-Aib) ₂仅在保护基团中变化的肽。这种结构证实了 Gly-Aib 肽的高度结构灵活性，并指出分子间氢键与晶体质量和大小之间的密切关系。