Stereocontrolled Diels−Alder Cycloadditions of Sugar-Derived Dihydropyranones with Dienes
作者:Christian A. Iriarte Capaccio、Oscar Varela
DOI:10.1021/jo020309w
日期:2002.11.1
dihydropyranone. The influence of other catalysts (BF(3) or iodine) employed for the glycosylation on the optical purity of the dihydropyranone was studied. Enantiomerically pure dihydropyranones 8b and 9c were obtained using chiral alcohols ((R)- and (S)-2-octanol, respectively) as glycosylating agents. Compounds 8a,b and 9a,c proved to be reactive dienophiles in thermal and Lewis acid-promoted Diels-Alder
类似于其D-木糖类似物4的2-乙酰氧基-3,4-二-O-乙酰基-D-阿拉伯糖醛(6)通过氯化锡(IV)促进的糖基化反应与苯甲醇反应生成旋光性(S )-2-苄氧基-2H-吡喃-3(6H)-一(8a)。L-阿拉伯衍生物(5)得到9a,8a的二氢吡喃酮对映体。这些结果表明起始糖醛中C-4立体中心的构型定义了所得二氢吡喃酮中新手性中心的构型。研究了用于糖基化的其他催化剂(BF(3)或碘)对二氢吡喃酮的光学纯度的影响。使用手性醇(分别为(R)-和(S)-2-辛醇)作为糖基化剂获得对映体纯的二氢吡喃酮8b和9c。化合物8a,b和9a,c在热反应和路易斯酸促进的Diels-Alder反应中被证明是反应性亲二烯体。向β-吡喃酮8a,b中添加2,3-二甲基丁二烯,环戊二烯和1,3-环己二烯产生相应的主要产物加合物10a,b,12a,b和16a,b。从α-吡喃酮9a,c合成对映体环加合物。主要产物是通过在C-