AbstractCarbohydrate‐based vinyl acetals (5‐hex‐enopyranosides) undergo reductive rearrangement with triisobutylaluminum (TIBAL) to afford highly functionalized cyclohexanes in which both the aglycon and anomeric stereochemistry are retained. Here, we report the first application of this process to the rearrangement of hex‐5‐enopyranosides of sucrose in which the interglycosidic oxygen atom of the vinyl acetal system links the anomeric centers of both monosaccharide units. The sucrose‐derived 5‐hex‐enopyranoside 1 undergoes smooth reductive rearrangement with TIBAL to afford the (1 → 2′) ether‐linked pseudo‐disaccharide 2 in 34% yield. The rearrangement is accompanied by some loss of stereochemical integrity at C‐2′ due to a competitive exo‐cleavage of the interglycosidic (O‐C2′) bond, hence diastereomers at C‐2′ are also obtained in 12% yield. The 4‐O‐allyl‐protected sucrose‐5‐ene 3 is similarly transformed into the corresponding (1 → 2′) ether‐linked pseudo‐disaccharide 4, illustrating the compatibility of the allyl group with the TIBAL reaction conditions.magnified image
摘要基于碳水化合物的乙烯基缩醛(5-己烯吡喃糖苷)与三异丁基铝(TIBAL)发生还原重排反应,可得到高度官能化的环己烷,其中的苷元和异构体的立体化学结构均得以保留。在这里,我们首次报告了将这一工艺应用于蔗糖六-5-烯吡喃糖苷重排的情况,其中乙烯基缩醛体系的糖苷间氧原子连接了两个单糖单元的异构中心。蔗糖衍生的 5-hex-enopyranoside 1 与 TIBAL 顺利发生还原重排,得到(1 → 2′)醚键假双糖 2,产率为 34%。由于糖苷键(O-C2′)的竞争性外切,重排伴随着 C-2′ 处立体化学完整性的损失,因此也得到了 C-2′ 处的非对映异构体,产率为 12%。4-O 烯丙基保护的蔗糖-5-烯 3 同样转化为相应的(1 → 2′)醚键假双糖 4,这说明了烯丙基与 TIBAL 反应条件的兼容性。