图1. (a) exo-NB-COOH、(b) endo-NB-COOH、(c) exo-NB-CH2OH和(d) endo-NB-CH2OH的化学结构及计算机模拟能量最低构象(碳原子:灰色;氢原子:紫色;氧原子:红色)
Fig.1. The chemical structures of (a) exo-NB-COOH, (b) endo-NB-COOH, (c) exo-NB-CH2OH, and (d) endo-NB-CH2OH, and their calculated conformations with minimum energy (the gray, purple, and red balls stand for the C, H, and O atoms, respectively)