Addition of bromine to glycals using quaternary ammonium tribromides as bromine donors is realized with higher stereoselectivities (α-1,2-trans configurated products) compared to bromination with molecular bromine. The reaction is neither sensitive to the solvent nor to the nature of the protecting groups (acetyl, benzoyl, benzyl) of the glycals and very slightly affected by the orientation of the substituents of the different glycals. Some of the α-1, 2-trans dibromo adducts have been isolated in 60-75% yields and transformed into the corresponding α-1,2-trans-2-bromo-2-deoxyglycopyranosyl fluorides.
与使用分子
溴进行
溴化相比,使用季
铵三
溴化物作为
溴给体将
溴加到糖醛中具有更高的立体选择性(δ-1,2-反式构型产物)。该反应对溶剂和糖醛保护基(
乙酰基、
苯甲酰基、
苄基)的性质都不敏感,受不同糖醛取代基方向的影响也很小。一些δ-1,2-反式二
溴加合物的分离率为 60-75%,并可转化为相应的δ-1,2-反式-2-
溴-2-
脱氧吡喃糖基
氟化物。