The chemistry of glucal halohydrins: The effect of the halide on epoxide formation
作者:Cecilia H. Marzabadi、Christopher D. Spilling、Lisa M. Tyler
DOI:10.1016/s0040-4020(01)81332-6
日期:1994.1
Chlorohydrins, bromohydrins, and iodohydrins, formed by hydroxyhalogenation of tri-O-methyl glucal, undergo base induced cyclization to give glucal epoxides. The mechanism of the cyclization reaction was probed using 1H NMR and deuterium incorporation studies. Cyclization and in situ trapping with Cs2CO3 in MeOD gave deuterated methyl 3,4,6-tri-O-methyl-α-D-mannoside and methyl 3,4,6-tri-O-methyl-β-D-glucoside
由三-O-甲基葡糖基的羟基卤化作用形成的氯醇,溴代醇和碘代醇经碱诱导的环化反应生成葡糖基环氧化物。使用1 H NMR和氘掺入研究探索了环化反应的机理。Cs 2 CO 3的环化和原位捕集在MeOD中得到氘化的甲基3,4,6-三-O-甲基-α-D-甘露糖苷和甲基3,4,6-三-O-甲基-β-D-葡萄糖苷和不饱和醛。这些研究导致环氧化物形成的优化的立体选择性。葡萄糖溴醇与NaH或LiHMDS在THF中于5°C反应,生成β-环氧化物,甘露糖碘醇与KH和18-crown-6在甲苯中,于-70°C反应,生成α-环氧化物。通过与苯硫醇钠反应打开环氧化物,得到苯基3,4,6-三-O-甲基-1-硫代-α-D-甘露吡喃糖苷(单一异构体)和苯基3,4,6-三-O-苯基甲基-1-硫代-β-D-吡喃葡萄糖苷(18:1)。