Synthesis of pyrrolidine homoazasugars and 3,4-dihydroxy-5-hydroxymethylprolines using aldol additions of metalated bislactim ethers to 2,4-O-ethylidene-d-erythroses
作者:Olga Blanco、Cristina Pato、María Ruiz、Vicente Ojea
DOI:10.1039/b902366f
日期:——
syn-stereoselectivity of the aldol addition to β-protected 2,4-O-ethylidene-erythroses. In the addition to the “unprotected” 2,4-O-ethylidene-erythrose, the preference for chair-shaped transition structures in which the erythrose moiety is involved in a six-membered chelate ring is consistent with the experimentally observed syn,anti-stereochemical outcome. The preparative utility of the aldol-based approach was demonstrated
通过将金属化的双内酯醚向2,4- O-亚乙基-的非对映选择性醛醇加成反应,描述了合成2,5-二脱氧-2,5-亚氨基己糖醇和2,5-二脱氧-2,5-亚氨基糖酸的策略。D-赤藓糖和分子内N-烷基化是关键步骤。改变赤藓酸酯的金属片段的性质和赤藓糖部分的β-烷氧基保护基,以调节在添加羟醛中的不对称诱导的水平和方向。借助密度泛函理论计算(B3LYP / cc-pVDZ-PP),合理化了由锡(II)介导的醛醇缩合反应形成的对比立体化学结果。DFT计算表明,允许形成稳定的氢键的船形过渡结构可以解释除了β-保护的2,4 - O-亚乙基-赤藓糖外,羟醛的不寻常的反,顺-立体选择性。除了“未保护的” 2,4- O-亚乙基-赤藓糖,优先选择椅子形状的过渡结构,其中赤藓糖部分参与六元螯合环,这与实验观察到的顺式,抗立体化学结果一致。通过在简明路线中合成糖苷酶抑制剂的应用证明了基于醛醇缩合的方法的制备效用。2,5-二脱氧-2