通过2-甲基-2,4-己二酸甲酯的环氧化或通过Darzens缩合制备几种二环氧己酸和环氧己酸。它们的1 H-和13 C-NMR。光谱被测量并分配。将这些数据与抗生素合霉素(1)和普拉霉素A(2)的光谱进行比较,可以确定这些抗生素的侧链中的相对构型。发现它们对氦霉素(1)为(14 R *,16 S *,17 R *,18 S *)对于普拉霉素A(2为(14 R *,16 S *,17 Z))。)。
The addition of nucleophiles like lithium ester enolates 6 to oxiranecarbaldimines 1 leads to new oxiranyl-functionalised β-lactams 7 in excellent enantio- and diastereoselectivity. A simple one-pot procedure affords β-lactams (azetidin-2-ones) with three or four neighbouring stereogenic centres and unlike preference. Products resulting fromoxirane ring-opening reactions were not observed. An enantiomerically
Enantioselective organocatalytic epoxidation using hypervalent iodine reagents
作者:Sandra Lee、David W.C. MacMillan
DOI:10.1016/j.tet.2006.07.055
日期:2006.12
A rare example of a hypervalentiodine reagent participating in a 1,4-heteroconjugate addition reaction is reported for the organocatalytic, asymmetric epoxidation of α,β-unsaturated aldehydes using imidazolidinone catalyst 1. Development of an ‘internal syringe pump’ effect via the slow release of iodosobenzene from an iminoiodinane source provides high levels of reaction efficiency and enantiomeric
据报道,使用咪唑烷酮催化剂1可以使α,β-不饱和醛发生有机催化,不对称环氧化,这是参与1,4-杂合物加成反应的高价碘试剂的一个罕见例子。通过从亚碘碘烷源缓慢释放碘代苯来开发“内部注射泵”效应,可在缺电子烯烃的不对称环氧化中提供高水平的反应效率和对映体控制。进行了15 N NMR研究,以阐明在原型氧化剂存在下导致催化剂耗竭的反应途径。这些NMR研究也为亚氨基碘烷作为内部缓释氧化剂的应用提供了机理基础,以规避这些催化剂的消耗途径。
Proposal for structure revision of pinofuranoxin A through total syntheses of stereoisomers
The relative configuration of the epoxide functionality in pinofuranoxin A (1), α-alkylidene-β-hydroxy-γ-methyl-γ-butyrolactone with trans-epoxy side chain isolated by Evidente et al. in 2021, was revised by DFT-based spectral reinvestigations and stereo-controlled synthesis. The present investigation demonstrates the difficulty of the configurational elucidation of the stereogenic centers on the conformationally
Evidente 等人分离出具有反式环氧侧链的呋喃呋喃辛 A ( 1 )、α-亚烷基-β-羟基-γ-甲基-γ-丁内酯中环氧化物官能团的相对构型。 2021年,通过基于DFT的光谱重新研究和立体控制合成进行了修订。目前的研究表明,构象灵活的无环侧链上的立体中心的构型阐明很困难。 Sharpless 的对映选择性环氧化和二羟基化在构型的重新研究中非常有效。由于我们的合成使所有非对映体可用,这些在下一步的结构-生物活性关系研究中将非常有效。 图解摘要
Asymmetric epoxidation of α,β-unsaturated aldehydes catalyzed by a spiro-pyrrolidine-derived organocatalyst
The asymmetric epoxidation of alpha,beta-unsaturated aldehydes, catalyzed by a spiro-pyrrolidine (SPD)-derived organocatalyst, has been accomplished with good diastereoselectivities (up to dr >20:1) and with high to excellent enantioselectivities (up to 99% ee). (C) 2016 Elsevier Ltd. All rights reserved.
Ley, Steven V.; Cox, Liam R.; Meek, Graham, Journal of the Chemical Society. Perkin transactions I, 1997, # 22, p. 3299 - 3313
作者:Ley, Steven V.、Cox, Liam R.、Meek, Graham、Metten, Karl-Heinz、Pique, Carmen、Worrall, Julia M.