Pluth Michael D, Bergman Robert G, Raymond Kenneth N
Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
J Org Chem. 2008 Sep 19;73(18):7132-6. doi: 10.1021/jo800991g. Epub 2008 Aug 8.
The hydrophobic interior cavity of a self-assembled supramolecular assembly exploits the hydrophobic effect for the encapsulation of tertiary amides. Variable-temperature (1)H NMR experiments reveal that the free energy barrier for rotation around the C-N amide bond is lowered by up to 3.6 kcal/mol upon encapsulation. The hydrophobic cavity of the assembly is able to stabilize the less polar transition state of the amide rotation process. Carbon-13 labeling studies showed that the (13)C NMR chemical shift of the carbonyl resonance increases with temperature for the encapsulated amides, which suggests that the assembly is able to favor a twisted form of the amide.
自组装超分子聚集体的疏水内部空腔利用疏水效应来包封叔酰胺。变温（1）H NMR实验表明，包封后围绕C-N酰胺键旋转的自由能垒降低了高达3.6 kcal/mol。聚集体的疏水空腔能够稳定酰胺旋转过程中极性较小的过渡态。碳-13标记研究表明，对于被包封的酰胺，羰基共振的（13）C NMR化学位移随温度升高，这表明聚集体能够促进酰胺的扭曲形式。
