Vuorinen T, Serianni A S
Laboratory of Wood Chemistry, Helsinki University of Technology, Finland.
Carbohydr Res. 1991 Jan 15;209:13-31. doi: 10.1016/0008-6215(91)80142-a.
The pentuloses D-erythro-2-pentulose (1) and D-threo-2-pentulose (2) and their 1-13C- and 2-13C-substituted derivatives were prepared by hydrogenating the corresponding isotopically normal and 13C-substituted D-pentos-2-uloses with a Pd-carbon catalyst. The threo isomer and its labeled derivatives were alternatively prepared from isotopically normal and 13C-substituted D-xyloses with immobilized D-xylose (D-glucose) isomerase (E.C.5.3.1.5). The equilibrium compositions of 1 and 2 (furanose anomers and acyclic keto forms) in 2H2O were determined from 13C-n.m.r. spectra (75 MHz) of the 2-13C-labeled derivatives. The conformational properties of the cyclic and acyclic forms in 2H2O were assessed with the use of 1H-1H, 13C-1H, and 13C-13C spin-coupling constants obtained from 1H-n.m.r. (620 MHz) and 13C-n.m.r. (75 MHz) spectra. Compared with the structurally related aldotetrofuranoses the 2-pentulofuranoses more strongly prefer conformations in which the anomeric hydroxyl group is oriented quasi-axially. The strongly dipolarized carbonyl group in the acyclic keto forms of 1 and 2 appears to stabilize chain conformations having O-1 and O-3 eclipsed with the carbonyl oxygen.
通过用钯 - 碳催化剂氢化相应的同位素正常和13C取代的D - 戊糖 - 2 - 酮糖，制备了戊糖D - 赤藓糖 - 2 - 戊酮糖（1）和D - 苏阿糖 - 2 - 戊酮糖（2）及其1 - 13C和2 - 13C取代的衍生物。苏阿糖异构体及其标记的衍生物也可由同位素正常和13C取代的D - 木糖与固定化的D - 木糖（D - 葡萄糖）异构酶（E.C.5.3.1.5）制备。由2 - 13C标记的衍生物的13C - 核磁共振谱（75 MHz）测定了2H2O中1和2（呋喃糖异头物和无环酮形式）的平衡组成。利用从1H - 核磁共振（620 MHz）和13C - 核磁共振（75 MHz）谱获得的1H - 1H、13C - 1H和13C - 13C自旋耦合常数，评估了2H2O中环状和无环形式的构象性质。与结构相关的醛糖四氢呋喃糖相比，2 - 戊酮糖呋喃糖更强烈地倾向于异头羟基准轴向取向的构象。1和2的无环酮形式中强偶极的羰基似乎稳定了O - 1和O - 3与羰基氧重叠的链构象。
