Methyl 2,6-anhydro-3,4-O-isopropylidene-α- and -β-D-talopyranosides are formed when 1,6-anhydro-3,4-O-isopropylidene-2-O-methylsulphonyl-β-D-galactopyranose is heated in methanol containing potassium fluoride dihydrate. The reaction apparently proceeds via an intramolecular displacement, for the isomeric 1,6-anhydro-3,4-O-isopropylidene-2-O-methylsulphonyl-β-D-talopyranose is unreactive in displacement reactions. The utility of potassium fluoride in methanol as a non-nucleophilic base is discussed.
在含有二
水氟化
钾的
甲醇中加热 1,6-脱
水-3,4-O-异亚丙基-2-O-甲基磺酰基-δ²-D-
吡喃半
乳糖,会生成甲基 2,6-脱
水-3,4-O-异亚丙基-δ±-和-δ²-D-
吡喃半
乳糖苷。反应显然是通过分子内置换进行的,因为异构的 1,6-脱
水-3,4-O-异亚丙基-2-O-甲基磺酰基-δ-D-
吡喃半
乳糖在置换反应中没有反应。讨论了
甲醇中的
氟化
钾作为非亲核碱的用途。