Lamba D, Segre A L, Glover S, Mackie W, Sheldrick B, Pérez S
Istituto di Strutturistica Chimica Girodano Giacomello, Roma, Italy.
Carbohydr Res. 1990 Dec 15;208:215-30. doi: 10.1016/0008-6215(90)80101-8.
The crystal structure of neocarrabiose monohydrate, 3-O-(3,6-anhydro-alpha-D-galactopyranosyl)-beta-D-galactopyranose (C12H20O10.H2O) belongs to the monoclinic space group P2(1), and has a unit cell of dimensions a = 6.351(1), b = 7.675(2), c = 15.096(8) A, and beta = 91.11(1) degree. The reducing unit is in the 4C1 conformation, the non-reducing residue is 1C4, with the 3,6-anhydro bridge in an E conformation, and HO-6 is in a gauche-trans conformation. The orientation about the (1----3) linkage is defined by phi = 94.5 degrees and psi = 141.9 degrees. There is an intramolecular hydrogen bond (O-5'...O-2 = 2.777A). The conformation of the pyranose rings in solution, derived from 3JH.H values, were not significantly different from those in the crystal, but the 3,6-anhydro bridge assumed a half-chair conformation. All these features have been rationalised through molecular modelling and computation of potential energy surfaces.
新卡拉比糖一水合物（3 - O - (3,6 - 脱水 - α - D - 吡喃半乳糖基)-β - D - 吡喃半乳糖，C12H20O10·H2O）的晶体结构属于单斜空间群P2(1)，其晶胞参数为a = 6.351(1) Å，b = 7.675(2) Å，c = 15.096(8) Å，β = 91.11(1)°。还原单元呈4C1构象，非还原残基为1C4构象，3,6 - 脱水桥呈E构象，HO - 6呈反式构象。(1→3)键的取向由φ = 94.5°和ψ = 141.9°确定。存在分子内氢键（O - 5'...O - 2 = 2.777 Å）。由3JH.H值推导得出的溶液中吡喃糖环的构象与晶体中的构象无显著差异，但3,6 - 脱水桥呈半椅式构象。所有这些特征已通过分子建模和势能面计算得到合理解释。
