Facile Ring Transformation from Gluconolactone to Cyclitol Derivative via Spiro Sugar Ortho Ester
作者:Hiro Ohtake、Shiro Ikegami
DOI:10.1021/ol9913035
日期:2000.2.1
derivative 8 which is a versatile synthon for the synthesis of valiolamine and its related compounds is described. Key steps in this preparation are a novel enol ether formation from spiro sugar orthoesters with AlMe3 and an intramolecular Aldol condensation of alkyl enol ethers catalyzed by ZnCl2 in THF-H2O. With these reactions, gluconolactone derivative 1 was efficiently converted into 8 in short
lactones via spiro sugar ortho esters is described. The key steps are the novel enol ether formation from sugar ortho esters with AlMe3 and the efficient intramolecular aldol cyclization of alkyl enol ethers with ZnCl2 in THF/H2O. Firstly, the spiro sugar ortho esters 3a–c were prepared from the benzyl protected sugar lactones 1a–c and 2,2-dimethylpropanediol (2). These ortho esters were efficiently converted
描述了经由螺糖原酸酯由糖内酯制备环糖醇衍生物。的关键步骤是从糖原酸酯的新颖烯醇醚地层与阿尔梅3和烷基烯醇醚与氯化锌的有效分子内醛醇环化2在THF H / 2 O.首先,螺糖原酸酯图3a - Ç是从制备苄基保护的糖内酯1a – c和2,2-二甲基丙二醇(2)。通过在CH 2 Cl 2中处理AlMe 3,这些原酸酯被有效地转化为烯醇醚5a – c。。该反应的起始步骤是伴随着甲基阴离子插入而进行的吡喃环裂解,第二步骤是由AlMe 3的路易斯酸度引起的二恶烷开环。生成的烷基烯醇醚用DMSO / Ac 2 O处理,并且形成的酮化合物通过ZnCl 2催化的Aldol在THF / H 2 O中环化而转化为碳糖9a - c。总产量9a,9b,基于内酯1a – c的9c和9c分别为64%,64%和54%。