Alkylation of lithium dienediolates of butenoic acids. Regioselectivity effects of structure and leaving group of the alkylating agent
作者:Maria J. Aurell、Salvador Gil、Ramon Mestres、Margarita Parra、Lilian Parra
DOI:10.1016/s0040-4020(98)00149-5
日期:1998.4
Regioselectivity of alkylation of but-2-enoic acids 1 and 2 by alkyl halides strongly depends on the reactivity of the electrophile. High α selectivity results for saturated alkyl halides, whereas poor α-selectivity is obtained for highly reactive allyl and benzyl halides. For reactive alkylating halides selectivity is partly governed by the ion pairing aggregates of the dienediolates. Lithium bromide
Allylic alcohols were readily converted into allylic iodides by hydrogen iodide generated in situ from chlorotrimethylsilane/sodium iodide and water, or alcohols, under mild conditions. Displacement of allylic alcohols containing a terminal double bond gave allylic iodides accompanied by allylic rearrangement. This procedure has successfully been extended to a one-pot synthesis of homoallylic alcohols by carrying out successive Barbier type reactions.
An enantioselectivetotalsynthesis of (+)-anthecularin, an antiplasmodial and antitrypanosomal sesquiterpene lactone, has been achieved in 3.9% overall yield through 18 steps from a known dibromo alcohol. The key features of the synthesis include an intramolecular Claisen-type cyclization of a formyl-protected hydroxyl lactone to construct a bicyclic intermediate with a quaternary stereogenic center
Highly Enantioselective Copper-Catalyzed Alkylation of β-Ketoesters and Subsequent Cyclization to Spirolactones/Bi-spirolactones
作者:Qing-Hai Deng、Hubert Wadepohl、Lutz H. Gade
DOI:10.1021/ja211859w
日期:2012.2.15
Cu-catalyzed enantioselective alkylation of β-ketoesters using alcohols for in situ preparation of alkylating reagents is reported. A number of functionalized β-ketoesters containing a quaternary carbon stereocenter are obtained with up to 99% ee. The alkylation products derived from 2-substituted allylic alcohols or their corresponding iodides can then be converted to spirolactones, bi-spirolactones
报道了使用醇对 β-酮酯进行 Cu 催化的对映选择性烷基化,用于原位制备烷基化试剂。获得了许多含有季碳立体中心的官能化 β-酮酯,ee 高达 99%。然后可以将衍生自 2-取代烯丙醇或其相应碘化物的烷基化产物转化为螺内酯、双螺内酯和相关的手性目标产物。
Enantioselective Total Synthesis of Brevetoxin A: Unified Strategy for the B, E, G, and J Subunits
作者:Michael T. Crimmins、J. Michael Ellis、Kyle A. Emmitte、Pamela A. Haile、Patrick J. McDougall、Jonathan D. Parrish、J. Lucas Zuccarello
DOI:10.1002/chem.200900776
日期:2009.9.14
oxacycles, as well as 22 tetrahedral stereocenters. Herein, we describe a unified approach to the B, E, G, and J rings based upon a ring‐closing metathesis strategy from the corresponding dienes. The enolate technologies developed in our laboratory allowed access to the precursor acyclic dienes for the B, E, and G medium‐ring ethers. The strategies developed for the syntheses of these four monocycles
Brevetoxin A 是一种十环梯形毒素,具有 5、6、7、8 和 9 元氧杂环,以及 22 个四面体立体中心。在此,我们描述了基于来自相应二烯的闭环复分解策略的 B、E、G 和 J 环的统一方法。我们实验室开发的烯醇技术允许获得 B、E 和 G 中环醚的前体无环二烯。为合成这四个单环而开发的策略最终提供了数克数量的每个环,支持我们为完成短毒素 A 的收敛合成所做的努力。