The 1,4-anhydro-5-deoxy-6-thio-D-ribo-hexofuranitol (1) was prepared from 1,2-O-isopropylidene-α-D-glucose in 10 steps. In a key step treatment of the 1,2-O-isopropylidenehexofuranose derivative with BF3/Et3SiH effected deacetonization and reductive deoxygenation at carbon 1. Pulse radiolysis experiments with 6-thiohexofuranitol 1 and its disulfide derivative demonstrated formation of the ribosyl-based carbon-centered radical upon generation of 6-thiyl radical in basic medium. The proposed [1,5]-hydrogen shift abstraction with generation of the C3 radical mimics the initial substrate reaction of RNRs. The reversible H-atom transfer has been quantified and was correlated with the computed rate constants for the internal H atom abstraction from C1, C2, C3 and C4 by the thiyl radical. The energy barrier for the H3 and H4 abstractions were calculated to be most favorable with the corresponding barriers of 11.1 and 11.2 kcal/mol, respectively.
1,4-脱
水-5-脱氧-6-
硫代-D-
核糖-己呋醇(
1)是由1,2-
O-异丙基苄基-α-
D-葡萄糖经过10个步骤制备而成。在关键步骤中,使用BF
3/Et
3SiH处理1,2-
O-异丙基己呋醇衍
生物,使碳1上的乙酰基脱除并还原脱氧化。使用6-
硫代己呋醇
1及其二
硫代衍
生物进行脉冲辐解实验,证明在碱性介质中生成6-
硫基自由基时,会形成基于
核糖的碳中心自由基。所提出的[1,5]-氢迁移抽象与C3自由基的生成类似于RNRs的初始底物反应。可逆的氢原子转移已被量化,并与通过
硫基自由基从C1、C2、C3和C4进行内部氢原子抽象的计算速率常数相关联。对于H3和H4的抽象,能量壁垒被计算为最有利的,分别为11.1和11.2 kcal/mol。