Ramberg-Baecklund Rearrangement Approaches to the Synthesis of Natural Bibenzyls

The Ramberg-Baecklund rearrangement has been successfully utilized to convert readily available α-and α‘-hydrogen bearing substituted dibenzyl sulfones into corresponding stilbene derivatives, which is conveniently followed by hydrogenation in the presence of 10% Pd/C to afford the natural bibenzyls.     

Stereoselective Synthesis of Piperamide Alkaloids by Modified Ramberg-Bcklund Reaction

A convenient and rapid approach for the synthesis of piperamide alkaloids la ~ h by the recently developed one-flask Ramberg-Backlund reaction was described. The synthesis of 1e was reported for the first time.     

Synthesis of gibbilimbols B and D by a modified Ramberg-Bcklund reaction

Gibbilimbols B and D were synthesized from the facile rearrangement of sulfone in the presence of dibromodifluoromethane and alumina-supported KOH in dichloromethane,followed by refluxing the rearrangement products in conc.HCl and methanol and then treating with thiophenol in the presence of AIBN.     

Synthesis of the integrastatin nucleus using the Ramberg-Bäcklund reaction

[reaction: see text] The first synthesis of the tetracyclic nucleus of the Integrastatins, natural products that have been shown to selectively inhibit HIV-1 integrase, is reported. Key steps of this synthesis involve a novel cis-selective Ramberg-B?cklund reaction and an unusual Lewis acid-promoted cyclization step.     

Ramberg-Bcklund反应在构筑碳碳双键中的应用

碳碳双键是有机化学中最基本的官能团之一 ,在众多构筑碳碳双键的方法中Ramberg B cklund反应占有很重要的地位 .该方法的关键步骤是α 卤代砜在碱性条件下 ,发生 1,3 消除反应 ,得到环状砜 ,然后重排失去SO2 形成双键 ,这样形成的双键位置确定 ,即具有良好的区域选择性 ,并且在不同的反应条件下可得到不同构型的产物 ,因而在有机合成中有很好的应用前景 .对Ramberg B cklund反应进行了较为详细的综述 ,并对我们实验室所进行的反应条件的改进和优化以及目前的研究进展作了总结 .     

Ramberg-Bcklund反应在功能有机分子合成中的应用

碳碳双键广泛地存在于功能有机分子中,其构筑在合成化学中具有极其重要的意义.Ramberg-B?cklund反应是构筑碳碳双键的重要方法之一,其关键步骤是砜在碱性条件下进行1,3-消除,得到环状砜,然后重排除去SO2形成双键.该方法具有良好的立体选择性,底物在不同的反应条件下得到不同构型的产物,因而可以应用于合成许多功能有机分子,具有很好的应用前景.结合自己的研究工作对Ramberg-B?cklund反应在功能有机分子合成中的应用进行了较为系统的总结,也对Ramberg-B?cklund反应的拓展进行了简要介绍.     

Unexpected Z-stereoselectivity in the Ramberg-Bäcklund reaction of diarylsulfones leading to cis-stilbenes: the effect of aryl substituents and application in the synthesis of the integrastatin nucleus

With certain substituent patterns, benzyl benzyl sulfone systems have been found to give unexpectedly high Z-stereoselectivity (up to E:Z = 1:16) in the Meyers variant of the Ramberg-B?cklund reaction. A range of sulfones, bearing various aryl substituents, were explored to rationalize this unprecedented selectivity for Z-stilbene systems. This high level of double bond stereocontrol has also been utilized in the synthesis of integrastatin nucleus, the core of two highly bioactive anti-HIV compounds.     

A Ramberg-Bäcklund route to the stilbenoid anti-cancer agents combretastatin A-4 and DMU-212

A concise route to combretastatin A-4, a potent inhibitor of tubulin polymerisation, using a Ramberg-B?cklund reaction to form the key (Z)-stilbene unit has been developed; this Ramberg-B?cklund approach has also been extended to prepare the (E)-stilbene DMU-212, which also possesses interesting growth inhibitory properties.     

Efficient synthesis of exo-olefinated deoxoartemisinin derivatives by Ramberg-Bäcklund rearrangement

10-exo-Bromoalkylidene- and benzylidenedeoxoartemisinins were synthesized from corresponding 10-alkanesulfonyldihydroartemisinin and 10-phenylmethanesulfonyldihydroartemisinin using a highly efficient, mild, and simple Ramberg-B?cklund rearrangement.     

Synthesis of cyclic olefins via Mitsunobu C-alkylation followed by Ramberg-Bäcklund ring contraction

Cyclic olefins were prepared via a novel synthetic approach that involves the formation of two CC bonds in a potentially stereoselective fashion. The first bond is formed by employing a Mitsunobu dehydrative C-alkylation; the second CC bond involves a ring contraction via Ramberg-Bäcklund rearrangement.     

Total Synthesis of the Natural Product-Pinosylvin and its Analog

Polyhydroxy stilbenes were proved to have many biological activitiesl'2. 'We havereported the total synthesis of tWo natural products-resveratrol (3,5,4'-tTihydroxylstilbene) and isorhapontigenin 3'4 which were first found in a traditional Chinese herb,G.Parvghlium by M. Lins et al. Herein,we want to present the total synthesis of anothernatural hydroxyl stilbene, pinosylvin (3,5-dihydroxy stilbene,10) isolated from this plantand its analog (3,5,3',5'-tetfahydroxy stilbene,9 ). In the synth…     

Convergent C-glycolipid synthesis via the Ramberg-Bäcklund reaction: active antiproliferative glycolipids

[formula: see text] A novel methodology has been developed, employing the Ramberg-B?cklund rearrangement and ionic hydrogenation to synthesize C-glycosides with high stereoselectivity at the anomeric center. The C-glycolipid 14b exhibits antiproliferative properties similar to those of O-glycoside analogue 14a.     

Studies on the Synthesis of Pyridine Analogs of the Natural Product3,5,4''''-Trimethoxystilbene

3,5,4'-Trimethoxystilbene is the methoxy precursor of a natural product 3,5,4'-trihydro- xystilbene (resveratrol)1 , which was reported to have many biological activities2. 3,5,4'-trimethoxystilbene itself is also a natural product2. We have synthesized 3,5,4'-trimethoxystilbene. In the screening of its anti-tumor activity using three different human cancer cell lines, 3,5,4'-trimethoxystilbene was found to have an IC50 5.91 mol/L for KB, 5.82 mol/L for A2780, 7.08 mol/L for HCT-8, respe…     

Base Promoted Rearrangement of Carbonate Esters Derived from Aldehyde Cyanohydrins: Application to the Synthesis of α-Keto Esters

Acylation of the cyanohydrin derivative (2) of representative aldehydes with ethyl chloroformate, followed by treatment of the corresponding mixed carbonate esters (3) with lithium hexamethyldisilazide, afforded the cyanohydrin derivative (4) of α-keto esters. Cleavage of the latter (4) with 2,6-lutidine in the presence of silver nitrate led to the procurement of α-keto esters in >50% overall yield.     

Studies on Atropo-Enantioselective Synthesis of the Natural Chiral Axial Biaryls

Ary-aryl bond formation plays an important role in modern organic synthesis. These bonds are very often occurred in natural products such as alkaloids as well as in numerous biologically active parts of pharmaceutical and agrochemical specialties. In addition, they are also the scaffolds of some of the most efficient and selective ligands for asymmetric catalysts, especially when atropisomery is possible. In this report, we report the structure and the enantioselective synthesis of some natura…     

Decarboxylative Cyclization of Allylic Cyclic Carbamates: Mechanism Studies and Applications to the Synthesis of Natural Products

The mechanism of decarboxylative cyclization of allylic cyclic carbamates 1 leading to 2-substituted △~3-piperidines and-pyrrolidines, as well as its applications to the total synthesis of (--)codonopsine, are described.     

New Routes to the Synthesis of Mes

New　Routes　to　the　Synthesis　of　Mes...     

New Approaches to the Synthesis of 2,2′: 6′,2″-Terpyridine and Some of Its Derivatives

A new two-step procedure has been developed for the synthesis of 2,2′: 6′,2″-terpyridine and 4′-methylsulfanyl-2,2′: 6′,2″-terpyridine in more than 70% yield on the basis of Potts’ condensation. Efficient methods have been proposed for purification of all condensation products.     

The Dimroth Rearrangement in the Synthesis of Condensed Pyrimidines – Structural Analogs of Antiviral Compounds

Chemistry of Heterocyclic Compounds - The review discusses the use of the Dimroth rearrangement in the synthesis of condensed pyrimidines which are key structural fragments of antiviral agents. The...