Part 2: Efficient strategies for the construction of variably substituted bicyclo[5.3.1]undecenones (AB-taxane ring systems) and their conversion to tricyclo[9.3.1.0<sup>3,8</sup>]pentadecenones (ABC taxane ring systems) and bicyclo[2.2.2]octanones
作者:Nidia P Villalva-Servín、Alain Laurent、Alex G Fallis
DOI:10.1139/v03-201
日期:2004.2.1
ring-closing metathesis (RCM) afforded the ABC taxane corestructure. Enone accelerated [3,3] sigmatropic rearrangements (Cope rearrangements) generated the bicyclo[2.2.2]octanone nucleus. In the presence of a Lewis acid, the dienophile precursor underwent a tandem reaction via the adduct directly to the bicyclo[2.2.2]octanones. This is the first example of a novel enone accelerated carbocycle Cope rearrangement
The synthesis of the tricyclicABC ring-system of Taxol® (paclitaxel) is described. This direct route involves sequential reactions employing the carbometallation of a propargy] alcohol, followed by a cis-alkene tether controlled stereoselective intramolecular Diets-Alder reaction to generate the AB-ring system and ring closing metathesis (RCM) of the pendant allyl substituents to construct the C ring
A Carbometallation-Intramolecular Cycloaddition Strategy for the AB-Taxane Ring and an Enone Accelerated Cope Rearrangement to Bicyclo[2.2.2]octanones
作者:Pat Forgione、Peter D. Wilson、Glenn P. A. Yap、Alex G. Fallis
DOI:10.1055/s-2000-6291
日期:——
The one pot transformation of the magnesium chelates, derived from alkynyl alcohols, into tetraene-diols for the construction of substituted bicyclo[5.3.1]undecenes is described. This sequence affords a direct route to the AB-taxane ring system via a Lewis acid catalyzed intramolecular Diels-Alder reaction. The cycloaddition gives a single diastereomer due to the preferential formation of the Et2AlCl chelate. This adduct undergoes a facile enone accelerated Cope rearrangement to generate a substituted bicyclo[2.2.2]octanone. This isomerization fails below 110 °C when the ketone is absent.
本研究描述了从炔醇中提取的镁螯合物向四烯二醇的一锅转化过程,以构建取代的双环[5.3.1]十一烯。该序列通过路易斯酸催化的分子内 Diels-Alder 反应提供了通向 AB-三烷环系统的直接途径。由于 Et2AlCl 螯合物的优先形成,该环化反应产生了单一非对映异构体。这种加合物经过简单的烯酮加速科普重排,生成取代的双环[2.2.2]辛酮。当酮不存在时,这种异构化反应在温度低于 110 °C 时会失败。
Synthesis of functionalized ring a building blocks for taxoids
作者:Michael W. Tjepkema、Peter D. Wilson、Timothy Wong、Miguel A. Romero、Hélène Audrain、Alex G. Fallis
DOI:10.1016/0040-4039(95)01244-c
日期:1995.8
The synthesis of a series of oxygenated cyclohexenes 1, 2, 11, 14, 18, and 19 that possess suitable functionality for further elaboration for taxoid synthesis is described. These compounds have been prepared from beta-ionone by a series of oxidative and addition reactions or alternatively by a Lewis acid catalyzed intermolecular Diels-Alder reaction in which the A-ring is constructed directly.
A stereoselective intramolecular Diels–Alder strategy for the tricyclo[9.3.1.03,8]pentadecane core of aromatic C-ring taxanes
作者:David V Smil、Alain Laurent、Nidejda S Spassova、Alex G Fallis
DOI:10.1016/s0040-4039(03)01120-1
日期:2003.6
A stereoselective Lewis acid-catalyzed and chelation controlled intramolecular Diels-Alder entry into the tricyclo[9.3.1.0(3,8)]pentadecane core of aromatic C-ring taxanes is described. The approach affords an efficient, high yield, access to aromatic C-ring taxanes variably functionalized at the C2, C4, C5, and C9 positions. (C) 2003 Elsevier Science Ltd. All rights reserved.