The kinetics of methylation of methyl 5-deoxy-α-D-xylofuranoside (1), methyl 5-deoxy-β-D-xylofuranoside (2) and their partly methylated derivatives with methyl iodide in the presence of sodium hydroxide in acetonitrile was studied. The reaction rate was independent of the base concentration during the first half-time only and the methylation proceeded as a first-order reaction. The rate constants of all side and consecutive reactions were calculated and the influence of both polar and steric effect is discussed. The methylation of 1 was highly regioselective giving almost exclusively 5-deoxy-2-O-methyl-α-D-xylofuranoside.
研究了在乙腈中,钠氢氧化物存在下,甲基碘对甲基5-去氧-α-D-木糖呋喃苷(1)、甲基5-去氧-β-D-木糖呋喃苷(2)及其部分甲基化衍生物的甲基化动力学。反应速率仅在前半个时间内与碱浓度无关,甲基化过程是一级反应。计算了所有副反应和连续反应的速率常数,并讨论了极性和立体效应的影响。1的甲基化高度选择性,几乎只产生5-去氧-2-O-甲基-α-D-木糖呋喃苷。