丙氨酰胺基硫脲及其阴离子配合物的手性传递

Chirality Transfer in Alanine Based N-amidothioureas and Their Anion Complexes

通过改变丙氨酸N端的取代基,设计合成了2种基于丙氨酸残基的酰胺基硫脲衍生物.通过X-射线单晶衍射、核磁共振波谱、吸收光谱和圆二色(CD)光谱等方法研究了2种不同取代基对硫脲分子自身及其阴离子络合物的氢键网络的影响以及由此引起的手性传递能力的不同.实验表明,当丙氨酸N端取代基为N,N-二甲基甘氨酸残基时,其羰基氧能与硫脲基团中的NH以分子内十元环氢键结合,分子呈折叠构象,实现了手性从丙氨酸残基到苯基硫脲基团的传递.阴离子加入后,该分子的硫脲基团与阴离子以双重氢键结合,分子原有的氢键网络发生改变,羰基氧与酰胺氮氢(NH)之间七元环氢键的存在将手性更多的限制于丙氨酸残基部分,手性传递至阴离子结合部位的效率极低.而N端被二甲基取代的硫脲衍生物由于分子内不同的氢键网络而表现出不同的手性传递能力:结合阴离子前,分子本身不具有折叠构象而无手性传递发生,结合阴离子后,新的氢键网络诱导了手性信号的长程传递.

Two different N-amidothioureas bearing substituents at the N terminus of alanine residue were synthesized.The influence of the substituents on the hydrogen bonding networks and chirality transfer in both the N-amidothioureas and their anion binding complexes were also investigated by single-crystal X-ray diffraction,NMR,UV-Vis,and circular dichroism（CD）.Our study reveals that the hydrogen bonding between the oxygen atom of the substituent at the N terminus and the thiourea NH makes the molecule fold and promotes chirality transfer from the alanine residue to the thiourea moiety.Similar influence of the substituents is also observed in the thioureas anion binding complexes.The hydrogen bonding formed between the oxygen atom of the substituent and the amido NH limits the chirality transfer to the anion binding moiety,while the molecule with the dimethyl substituent at the N terminus has different chirality transfer ability due to different hydrogen bonding network.