Iterative Synthesis of Deoxypropionate Units: The Inductor Effect in Acyclic Conformation Design

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• 作者：Stephen Hanessian ; Navjot Chahal ; Simon Giroux
• 刊名：Journal of Organic Chemistry
• 出版年：2006
• 出版时间：September 15, 2006
• 年：2006
• 卷：71
• 期：19
• 页码：7403 - 7411
• 全文大小：334K
• 年卷期：v.71,no.19(September 15, 2006)
• ISSN：1520-6904

文摘

Conjugate addition of lithium dimethylcuprate to acyclic ,-unsaturated esters of varying lengths bearingterminal alkyl or phenyl groups leads to a preponderance of syn 1,3-adducts when one methyl is alreadypresent. Conversion to enoates, and iteration of cuprate additions also favors syn adducts to give contiguousdeoxypropionate units in a growing chain. The effect of end-group variation (Me, i-Pr, phenyl, tert-butyl) in conjunction with the nature of the ester group (Me, tert-butyl, etc.) on the diastereoselectivityof syn and anti products was studied. The results are rationalized in terms of inductor effects related tothe minimization of the 1,5-pentane interactions in energetically favored folded conformations andcorroborated by homodecoupling NMR studies.