1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose (2), 1,2-O-isopropylidene-α-D-xylofuranose (3), 2,4-O-ethylidene-D-erythritol (4) and 1,3-O-ethylidene-D-threitol (5) were alkylated with racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) using boron trifluoride diethyl etherate as a catalyst. The desired mono- or disubstituted polyfluoroalkyl derivatives 6-11 were isolated only in low to medium yields. The fluoroalkylation was accompanied with disproportional distributions of the protecting acetal/ketal groups and polymerization of saccharides. Therefore the stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose (14) and 1,2-O-isopropylidene-α-D-glucofuranose (15) in the presence of a catalytic amount of boron trifluoride diethyl etherate was investigated in various solvents. A mechanism explaining the effect of the catalyst has been proposed.
1,2-异丙基亚甲基-3-甲氧基-α-D-木糖呋喃糖(2),1,2-异丙基-α-D-木糖呋喃糖(3),2,4-乙基亚甲基-D-赤霉醇(4)和1,3-乙基亚甲基-D-甘露醇(5)被使用三氟化硼乙醚酸酯作为催化剂与外消旋(2,2,3,3,4,4,5,5,6,6,7,7,7-十三氟庚基)环氧丙烷(1)发生烷基化反应。所得的单取代或双取代的多氟烷基衍生物6-11只以低至中等收率分离。氟烷基化反应伴随着保护缩醛/缩酮基团的不均匀分布和糖苷的聚合。因此,在各种溶剂中研究了3,4,5,5-乙酰基-1,2-异丙基-α-D-木糖呋喃糖(14)和1,2-异丙基-α-D-葡萄糖呋喃糖(15)在存在少量三氟化硼乙醚酸酯的情况下的稳定性。提出了解释催化剂作用的机制。