Solvent Effect Observed in Nucleophilic Substitution of 4′-(Benzoyloxy)cordycepin with AlMe<sub>3</sub>: Stereochemical Evidence for S<sub>N</sub>i Mechanism
作者:Yutaka Kubota、Mayumi Kunikata、Kazuhiro Haraguchi、Hiromichi Tanaka
DOI:10.1021/jo900289h
日期:2009.5.1
Nucleophilic substitution between the 4′-benzoyloxy derivative of cordycepin (3′-deoxyadenosine) and AlMe3 proceeds mostly with retention of configuration at the 4′-position: the 4′-benzoyloxy substrate having the β-d-configuration (8a) gave the 4′-methylated β-d-nucleoside (9a) with a high diastereomeric excess, while the substrate 8b having the opposite 4′-configuration gave the corresponding α-l-isomer
虫草素(3'-脱氧腺苷)的4'-苯甲酰氧基衍生物和AlMe 3之间的亲核取代主要是保留了4'-位置的构型:具有β- d-构型(8a)的4'-苯甲酰氧基底物具有高的非对映异构体过量的4'-甲基化的β- d-核苷(9a),而具有相反的4'-构型的底物8b给出了具有相对较低的立体选择性的相应的α- 1-异构体(9b)。对此反应提出了S N i机理(从8到9)。溶剂的极性对立体选择性有重要影响,尤其是对于9b的形成。