Synthesis and Highly Selective Bromination of Azacalix[4]pyrimidine Macrocycles
作者:Li-Xia Wang、De-Xian Wang、Zhi-Tang Huang、Mei-Xiang Wang
DOI:10.1021/jo902245q
日期:2010.2.5
A number of N-substituted azacalix[4]pyrimidines were synthesized by two methods. While straightforward condensation reaction between 4,6-dichloropyrimidine and 4,6-bis(alkylamino)-pyrimidines gave identically N-substituted azacalix[4]pyrimidines in low yields, a general and moderate-to-high yielding 1 + 3 macrocyclic fragment coupling reaction afforded azacalix[4]pyrimidines that contained either the same or different N-substituents. Upon treatment with N-bromosuccinimide (NBS) Under controlled conditions, methylazacalix[4]pyrimidine was selectively brominated at lower rim to produce mono-, di-, and tribrominated azacalix[4]pyrimidines in good yields. While azacalix[4]pyrimidine derivatives adopted 1,3-alternate conformation in the solid state, the synthesized macrocycles were fluxional In solution, and the interconversion of various conformational structures was rapid relative to the NMR time scale.
Synthesis, Resolution, Structure, and Racemization of Inherently Chiral 1,3-Alternate Azacalix[4]pyrimidines: Quantification of Conformation Mobility
作者:Jiang-Tao Li、Li-Xia Wang、De-Xian Wang、Liang Zhao、Mei-Xiang Wang
DOI:10.1021/jo500054v
日期:2014.3.7
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