作者:Toshio Itahara
DOI:10.1039/a708866c
日期:——
A relationship between the chemical shifts of adenine and xanthine ring protons of 7-[ω-(6-aminopurin-9-yl)alkyl]-1,3-dimethylxanthines (1) and the number of carbons (n = 2–10) in their polymethylene chains has been compared with that of 1-[ω-(6-aminopurin-9-yl)alkyl]-3,7-dimethylxanthines (2) in the buffer solutions at pD 7.0, 1.0 and 13.0 and in organic solvents. The relationship of 1 is clearly distinct from that of 2. The concentration dependence and the effects of temperature on the chemical shifts of 1 and 2 have also been investigated. While the upfield shifts of the ring protons of 1 and 2 in the buffer solutions at pD 7.0 and 13.0 are explained in terms of stacking interactions between adenine and xanthine rings, the results in the buffer solution at pD 1.0 may be due to cation–π interactions. On the basis of these data, it can be assumed that the stacking interactions do not only consist of interactions between adenine and xanthine rings.
比较了 7-[ω-(6-氨基嘌呤-9-基)烷基]-1,3-二甲基黄嘌呤(1)与 1-[ω-(6-氨基嘌呤-9-基)烷基]-3,7-二甲基黄嘌呤(2)在 pD 7.0、1.0 和 13.0 的缓冲溶液中以及在有机溶剂中的腺嘌呤环和黄嘌呤环质子的化学位移与其聚亚甲基链中碳原子数(n = 2-10)之间的关系。此外,还研究了浓度依赖性和温度对 1 和 2 化学位移的影响。在 pD 值为 7.0 和 13.0 的缓冲溶液中,1 和 2 的环质子的上场移位可以用腺嘌呤环和黄嘌呤环之间的堆叠相互作用来解释,而在 pD 值为 1.0 的缓冲溶液中的结果则可能是阳离子-π 相互作用所致。根据这些数据可以推测,堆积相互作用不仅包括腺嘌呤环和黄嘌呤环之间的相互作用。