The structures and absolute configurations of the enantiomers (3aR,8aR)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.33-hydrate, C32H30N2O3·0.33H2O, (Ia), and (3aS,8aS)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.39-hydrate, C32H30N2O3·0.39H2O, (Ib), have been elucidated unambiguously using the complementary power of single-crystal X-ray diffraction (XRD) and vibrational circular dichroism (VCD). The enantiomers crystallize in the Sohncke space groupP21212 and pack as dimers stabilized by two symmetric hydrogen bonds involving one amide group each of the cyclic urea moiety. This double interaction is capped by a water molecule that partially occupies a site lying on the twofold axis and forms an uncommon hydrogen bond between the two monomers. A comparison between the solid-state VCD characterizations and the Bayesian statistics on Bijvoet differences determined from the XRD measurements reveals a tendency towards the correct determination of the absolute configuration by this latter method.
(3aR,8aR)-2,2-二甲基-4,4,8,8-四苯基-4,5,6,7,8,8a-六氢-3aH-1,3-二恶茂并[4,5-e][1,3]二氮杂卓-6-酮 0.33-水合物 C32H30N2O3-0.33H2O, (Ia), and (3aS,8aS)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.39-hydrate, C32H30N2O3·0.我们利用单晶 X 射线衍射 (XRD) 和振动圆二色性 (VCD) 的互补性,明确地阐明了 C32H30N2O3-0.39H2O 的对映体 (Ib)。对映体在索恩克空间群(Sohncke space groupP21212)中结晶,并以二聚体形式包装,由环状脲分子中各涉及一个酰胺基的两个对称氢键所稳定。水分子部分占据了位于两倍轴上的一个位置,并在两个单体之间形成了一个不常见的氢键,从而将这种双重作用封闭起来。固态 VCD 表征与通过 XRD 测量确定的 Bijvoet 差异贝叶斯统计之间的比较表明,后一种方法倾向于正确确定绝对构型。