Barili P L, Berti G, Catelani G, D'Andrea F, Miarelli L
Dipartimento di Chimica Bioorganica, Universitá di Pisa, Italy.
Carbohydr Res. 1995 Sep 8;274:197-208. doi: 10.1016/0008-6215(95)00125-d.
3,4-O-Isopropylidene-D-lyxo-hexopyranosid-2-ulose derivatives, obtained by oxidation of 3,4,6-protected D-galactopyranosides, can be alkylated in their anionic 2,6-pyranose forms to produce bis-glycosides containing the 2,5-dioxabicyclo[2.2.2]octane ring system. The 1-benzyl-2-methyl bis-glycoside 4b, when subjected to catalytic hydrogenolysis, produces the methyl D-lyxo-hexopyranos-2-uloside 10, existing as an 8:2 mixture of 1,5-pyranose anomers 9. Computational and NMR evidence is presented in favour of the hypothesis that the major anomer has the alpha configuration. Reduction of 9/10 with NaBH4 gives methyl 3,4-O-isopropylidene-beta-D-tagatopyranoside, that can be hydrolyzed to D-tagatose. A simple synthesis of 1,5-anhydro-D-tagatose, starting from 1,5-anhydro-D-galactitol, is also presented. All new compounds were fully characterized by elemental analysis and by 1H and 13C NMR spectroscopy.
通过氧化3,4,6-保护的D-吡喃半乳糖苷得到的3,4-O-异亚丙基-D-来苏-己吡喃糖苷-2-酮衍生物，可以以其阴离子2,6-吡喃糖形式进行烷基化反应，生成含有2,5-二氧杂双环[2.2.2]辛烷环系的双糖苷。1-苄基-2-甲基双糖苷4b在进行催化氢解时，生成甲基D-来苏-己吡喃糖-2-酮苷10，其以1,5-吡喃糖端基异构体9的8:2混合物形式存在。提供了计算和核磁共振证据，支持主要端基异构体具有α构型这一假说。用硼氢化钠还原9/10得到甲基3,4-O-异亚丙基-β-D-塔格吡喃糖苷，其可水解为D-塔格糖。还介绍了一种从1,5-脱水-D-半乳糖醇出发合成1,5-脱水-D-塔格糖的简便方法。所有新化合物均通过元素分析以及1H和13C核磁共振光谱进行了全面表征。
