Lesarri Alberto, Pinacho Ruth, Enríquez Lourdes, Rubio José E, Jaraíz Martín, Abad José L, Gigosos Marco A
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid, Spain.
Departamento de Electrónica, Escuela de Ingeniería de Telecomunicaciones, Universidad de Valladolid, 47011 Valladolid, Spain.
Phys Chem Chem Phys. 2017 Jul 21;19(27):17553-17559. doi: 10.1039/c7cp01432e. Epub 2017 May 5.
Sparteine is a quinolizidine alkaloid used as a chiral auxiliary in asymmetric synthesis. We examine whether hydration by a single molecule can flip sparteine from the most stable trans conformation to the bidentate cis arrangement observed in catalytic complexation to a metal center. Sparteine and the sparteine-water dimer were generated in a supersonic jet expansion with HO and HO, and characterized by broadband chirped-pulse microwave spectroscopy. Even though the bidentate water dimer was predicted with larger binding energy, a single isomer was observed for the monohydrated cluster, with sparteine retaining the trans conformation observed for the free molecule. The absence of the bidentate dimer is attributed to the kinetic control of cluster formation, favoring the pre-expansion most abundant monomer. The structural properties of the O-HN hydrogen bond in the dimer are compared with those of complexes of other secondary and tertiary amines.
鹰爪豆碱是一种喹诺里西啶生物碱，用作不对称合成中的手性助剂。我们研究单个水分子的水合作用是否能使鹰爪豆碱从最稳定的反式构象转变为在与金属中心催化络合时观察到的双齿顺式排列。鹰爪豆碱和鹰爪豆碱 - 水二聚体通过与HO和HO在超声速喷射膨胀中产生，并通过宽带啁啾脉冲微波光谱进行表征。尽管预测双齿水二聚体具有更大的结合能，但对于一水合簇观察到单一异构体，鹰爪豆碱保留了在游离分子中观察到的反式构象。双齿二聚体的不存在归因于簇形成的动力学控制，有利于预膨胀时最丰富的单体。将二聚体中O - HN氢键的结构性质与其他仲胺和叔胺配合物的结构性质进行了比较。
