Anomerization of Methyl Glycosides by Acid-Catalysed Methanolysis: Trapping of Intermediates
作者:Per J. Garegg、Karl-Jonas Johansson、Peter Konradsson、Bengt Lindberg
DOI:10.1080/07328309908543976
日期:1999.1.1
4-di-O-methyl-D-arabino-hexitol, indicating alternative reaction pathways, involving either exo or endo C-O cleavage. The aldofuranosides, when necessary methylated on O-5 in order to avoid formation of pyranosides, gave 1-O-methylalditols, indicating protonation of the ring oxygen, followed by endo C-O cleavage. The methyl 2-deoxy-5-O-methyl-α-D-arabino-hexofuranosides, however, gave a mixture of the 1,5-di-O
摘要通过4-甲基吗啉硼烷还原,可以捕集某些甲基糖苷在酸催化的异构化过程中产生的中间体氧碳鎓离子或其他中间体。如所预期的,在甲基4-O-甲基-α-D-吡喃葡萄糖苷的异构化反应中形成的糖基离子中间体仅提供了α-和β-D-吡喃葡萄糖苷的混合物,因为该反应与α-D-吡喃葡萄糖苷的降解相比是缓慢的。还原剂。更具反应性的甲基2-脱氧-4-O-甲基-α-D-阿拉伯糖醇己吡喃糖苷得到两种还原产物,分别是1,5-脱水-2-脱氧-4-O-甲基-D-阿拉伯糖醇己糖醇和2-deoxy-1,4-di-O-methyl-D-arabino-hexitol,表明其他反应途径,涉及外切或内切CO裂解。为了避免形成吡喃糖苷,必要时在O-5上甲基化了呋喃糖苷,生成了1-O-甲基醛糖醇,指示环氧的质子化,然后发生内切CO裂解。然而,甲基2-脱氧-5-O-甲基-α-D-阿拉伯糖基-呋喃糖苷产生了1,5-二-O ...的混合物。