Catelani G, D'Andrea F, Puccioni L
Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Italy.
Carbohydr Res. 2000 Feb 25;324(3):204-9. doi: 10.1016/s0008-6215(99)00295-5.
The reactivity order of O-deisopropylidenation of the three isopropylidene protecting groups of 2',6'-di-O-benzyl-2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal (2) with various reagents was established. The 5,6-acetal group was, although to a limited extent, more reactive as compared with the 3',4' group, while the 2,3-O-isopropylidene group was definitely less reactive. Conditions were determined for the direct preparation of the 5,6,3',4'-tetraol 5 (60% aqueous acetic acid, room temperature, 48 h, 73% yield) and the 5,6-diol 4 (propylene glycol and p-toluenesulphonic acid in dichloromethane, 46% yield). The diacetonated derivative 3, formally arising from a selective 3',4'-O-deisopropylidenation, was obtained in high yield (90%) through a selective acetonation with 2-methoxypropene of the tetraol 5.
确定了2',6'-二-O-苄基-2,3:5,6:3',4'-三-O-异亚丙基乳糖二甲基缩醛（2）的三个异亚丙基保护基团进行O-去亚异丙基化反应与各种试剂的反应活性顺序。5,6-缩醛基团与3',4'基团相比，虽然反应活性有限，但反应活性更高，而2,3-O-异亚丙基基团的反应活性肯定更低。确定了直接制备5,6,3',4'-四醇5（60%的乙酸水溶液，室温，48小时，产率73%）和5,6-二醇4（二氯甲烷中的丙二醇和对甲苯磺酸，产率46%）的条件。通过用2-甲氧基丙烯对四醇5进行选择性缩酮化反应，以高产率（90%）获得了正式由选择性3',4'-O-去亚异丙基化产生的二缩酮衍生物3。
