Garrett E C, Serianni A S
Department of Chemistry and Biochemistry, University of Notre Dame, Indiana 46556.
Carbohydr Res. 1990 Oct 10;206(2):183-91. doi: 10.1016/0008-6215(90)80059-c.
Ab initio molecular orbital calculations were performed on 2-deoxy-beta-D-glycero-tetrofuranose (1) using the 6-31G* basis set to evaluate the effect of ring conformation on the molecular parameters (bond lengths, angles, and torsions). Geometric optimizations were conducted on the planar and ten envelope conformers of 1, and these data were compared to those obtained from previous calculations using the STO-3G and 3-21G basis sets. Conformational energy profiles derived from 3-21G and 6-31G* data were found to be qualitatively comparable. The effect of furanose ring conformation on key bond lengths (e.g., C-H, C-O), bond angles (e.g., COC), and bond torsions (e.g., the exoanomeric C-1-O-1 torsion) was examined, and a qualitative agreement was observed between the 3-21G and 6-31G* analyses. The results indicate that, for semi-quantitative ab initio studies of intact carbohydrates, the 3-21G basis set is sufficient, and that the STO-3G basis set should not be employed unless crude structural approximations are desired. The observed concerted behavior of C-O bond lengths in the vicinity of the anomeric carbon of the aldofuranose ring has suggested a possible role of C-1-O-1 bond orientation in affecting the mechanism of glycoside bond hydrolysis.
使用6-31G基组对2-脱氧-β-D-甘油四呋喃糖（1）进行了从头算分子轨道计算，以评估环构象对分子参数（键长、键角和扭转角）的影响。对1的平面构象和十种信封式构象进行了几何优化，并将这些数据与之前使用STO-3G和3-21G基组获得的计算数据进行了比较。发现从3-21G和6-31G数据得出的构象能量分布在定性上具有可比性。研究了呋喃糖环构象对关键键长（如C-H、C-O）、键角（如COC）和键扭转角（如异头碳C-1-O-1扭转角）的影响，并且在3-21G和6-31G*分析之间观察到了定性的一致性。结果表明，对于完整碳水化合物的半定量从头算研究而言，3-21G基组就足够了，并且除非需要粗略的结构近似，否则不应使用STO-3G基组。在醛糖呋喃糖环的异头碳附近观察到的C-O键长的协同行为表明，C-1-O-1键的取向可能在影响糖苷键水解机制中发挥作用。
