Synthesis and reactivity of enediyne–nucleobase hybrids: effect of intramolecular π-stacking
作者:Snigdha Roy、Subhendu Sekhar Bag、Amit Basak
DOI:10.1016/j.tet.2012.07.093
日期:2012.10
been synthesized to explore the effect of π-stacking interaction in accelerating the rate of Bergmancyclization (BC). Chemical reactivity study, both experimental and computations demonstrated the important role that aromatic π-stacking interactions between the appended nucleobases within an enediyne frame play in lowering the activationbarrier of Bergmancyclization.
Conformationally Gated Fragmentations and Rearrangements Promoted by Interception of the Bergman Cyclization through Intramolecular H-Abstraction: A Possible Mechanism of Auto-Resistance to Natural Enediyne Antibiotics?
作者:Abdulkader Baroudi、Justin Mauldin、Igor V. Alabugin
DOI:10.1021/ja905100u
日期:2010.1.27
six-membered TS and transforms the p-benzyne into a new more stable radical. Depending on the substitution pattern and reaction conditions, this radical follows four alternative paths: (a) abstraction of an external hydrogen atom, (b) O-neophyl rearrangement which transposes O- and C-atoms of the substituent, (c) fragmentation of the O-C bond in the acetal ring, or (d) fragmentation with elimination of the appended
在配备有缩醛环的烯二炔中,可以在伯格曼环化之后进行各种断裂和重排,模拟 esperamicine 和 calchiamicine 家族的天然烯二炔抗生素的碳水化合物部分。在所有这些过程的第一步中,分子内 H 原子提取通过六元 TS 有效拦截伯格曼环化的对苄产物,并将对苄转化为新的更稳定的自由基。根据取代模式和反应条件,该自由基遵循四种替代路径:(a) 外部氢原子的提取,(b) O-neophy 重排,其置换取代基的 O-和 C-原子,(c)缩醛环中的 OC 键,或 (d) 断裂并整体消除附加的缩醛部分。进行了不同浓度的外部 H 原子供体(1,4-环己二烯)的实验,以进一步了解分子间 H 抽象和碎片之间的竞争。gem-二甲基取代的烯二炔中的 Thorpe-Ingold 效应将碎裂效率提高到了即使大量过量的外部 H 原子供体也无法阻止的程度。这些过程使人们深入了解了 esperamicin A(1)
Reaction of ene-bis(phosphinylallenes): [2+2] versus [4+2] cycloaddition
作者:Shinji Kitagaki、Yuki Okumura、Chisato Mukai
DOI:10.1016/j.tet.2006.08.083
日期:2006.10
Reaction of ene-bis(phosphinylallenes), derived from ene-bis(propargyl alcohols) and chlorodiphenylphosphine, was investigated. Benzene-bridged bis(phosphinylallenes) exclusively gave intramolecular [2+2] cycloadducts in the presence of dimethyl fumarate in sharp contrast to the reaction of benzene-bridged bis(sulfinylallenes), which gave the corresponding [4+2] cycloadducts. On the other hand, substituted ethylene- or five-membered heterocycle-bridged bis(phosphinylallenes) provided [4+2] cycloadducts. Reaction of benzene-bridged diallene bearing both a sulfinyl group and a phosphinyl group on the two allenyl groups was also described. (c) 2006 Elsevier Ltd. All rights reserved.
Activation of Macrocyclic Enediynes by Transannular Cyclization
作者:Amit Basak、Sandip Kumar Roy、Subrata Mandal
DOI:10.1002/anie.200460831
日期:2005.1
Visible light-promoted radical cyclization of silicon-tethered alkyl iodide and phenyl alkyne. An efficient approach to synthesize benzosilolines
作者:Xinglong Lin、Zubao Gan、Ji Lu、Zhishan Su、Changwei Hu、Yuebao Zhang、Ya Wu、Lu Gao、Zhenlei Song
DOI:10.1039/c6cc00635c
日期:——
An efficient approach to synthesize benzosiloline has been developed by a visible light-promoted radical cyclization of silicon-tethered alkyl iodide and phenyl alkyne. The nature of the terminal substituent of alkyne...