Miles D W, Townsend L B, Miles D L, Eyring H
Proc Natl Acad Sci U S A. 1979 Feb;76(2):553-6. doi: 10.1073/pnas.76.2.553.
The solution conformations of 2-substituted derivatives of 1-(beta-D-ribofuranosyl)benzimidazole have been determined by circular dichroism spectroscopy in aqueous solutions. It is shown that analogs with methyl, amino, or methylamino substituents at position 2 of the benzimidazole ring (position 8 of the purine ring) have predominantly anti conformations, whereas analogs with chloro, aza, methoxy, or methylmercapto substituents have predominantly syn conformations. The preferred solution conformations of the benzimidazole nucleosides and analogous purine nucleosides are compared. The results demonstrate that the replacement of nitrogen by carbon at position 3 of the purine ring of purine (beta) nucleosides leads to important conformational consequences, which are strengthened or neutralized by substituents at position 8 of the purine ring.
通过圆二色光谱法在水溶液中测定了1-(β-D-呋喃核糖基)苯并咪唑的2-取代衍生物的溶液构象。结果表明，在苯并咪唑环的2位（嘌呤环的8位）带有甲基、氨基或甲氨基取代基的类似物主要具有反式构象，而带有氯、氮杂、甲氧基或甲硫基取代基的类似物主要具有顺式构象。比较了苯并咪唑核苷和类似嘌呤核苷的优选溶液构象。结果表明，嘌呤（β）核苷嘌呤环3位的氮被碳取代会导致重要的构象变化，嘌呤环8位的取代基会增强或抵消这种变化。
