macrocycles, and three pairs of conformationally stable P and M enantiomers with >99.5% ee were obtained from the resolution of racemic samples by chiral HPLC. Absolute configurations were determined by X-ray crystallography and were correlated with their CD spectra. The rate constants for racemization of macrocycles were measured, and enthalpies (ΔH⧧) and entropies (ΔS⧧) of activation were determined by the
报道了固有手性的1,3-交替的氮杂杯[4]
嘧啶大环的合成,拆分,结构和外消旋化。用
NBS,
NCS和
NFSI对单卤素取代的azacalix [4]
嘧啶进行位点选择性卤化,产生了许多下边缘二卤代的1,3-交替azacalix [4] pyrimidines。带有两个近端取代基的1,3-交替的氮杂杯[4]
嘧啶为
AABB型和ABCC型固有手性大环,并通过消旋样品的拆分得到三对构象稳定的P和M对映体,其ee均> 99.5%。手性HPLC。绝对构型是通过X射线晶体学测定的,并与它们的CD光谱相关。测量了大环外消旋化的速率常数,并计算了焓(Δħ ⧧)和熵(Δ小号⧧活化的)由艾林情节方法测定。本研究表明,在下部边缘,两个大于范德华半径r w = 1.75Å(例如
氯)和r w = 1.47Å(例如
氟)的近端取代基的组合是该化合物的最低空间要求。分离和分离1,3-交替氮杂杂杯[4]
嘧啶的构象稳定的固有手性对映