New tri- and tetracyclic diterpenes from Euphorbia villosa

Three new tetracyclic diterpenes were isolated from the chloroform-soluble extract of Euphorbia villosa, together with one new and one known lathyrane diterpene. The structures were elucidated by means of various spectroscopic methods, including HREI-MS, HRFAB-MS, UV, and 1D and 2D NMR techniques. Spectral analyses revealed that two of the tetracyclic compounds contain the rare 5-6-6-4 fused ring system, while the third has a 5-6-7-3 fused diterpene core. Such diterpene skeletons have previously been found only in euphoractines A-E isolated from Euphorbia micractina. As a new structural feature, the diterpene framework described here has a C-2 epimer configuration. The new lathyrane diterpene is a diester of a hitherto unknown polyfunctional parent alcohol.     

Synthesis of novel annulated uracils via domino Knoevenagel-hetero-Diels-Alder reaction in aqueous media

An efficient synthesis of tetracyclic uracil derivatives (polycyclic pyrans) is achieved via domino Knoevenagel-hetero-Diels-Alder reactions of O-propargylated salicylaldehyde derivatives with 1,3-dimethylbarbituric acid in water as solvent in the presence of CuI. The products are formed in good yields.     

Some transformations of 1-(1,2,3,4-tetrahydronaphthylidene)-malononitrile or cyanoacetate

Summary Syntheses of 11-amino-5,6-dihydronaphtho[1,2:4,5]thieno[2,3-d]pyrimidine (8) and its 10-oxide 7 from 2-amino-1-cyano-4,5-dihydronaphtho[2,1-b]thiophene and its derivatives are described. Several open chain tetrahydronaphthylidene derivatives and a substituted pyrimidine derivative9 were also prepared.Dedicated to Professor Dr. K. Gewald on the occasion of his 60th birthday     

(<Emphasis Type="Italic">S</Emphasis>)-(−)-α-Methylbenzylamine as chiral auxiliary in the synthesis of (+)-lortalamine

Abstract  (+)-Lortalamine was synthesised using (S)-(−)-α-methylbenzylamine as a chiral auxiliary. The stereochemistry of an intermediate compound was established on the basis of X-ray crystallography, allowing unambiguous assignment of the absolute configuration. Graphical abstract        

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 .     

Intramolecular Diels–Alder reaction for the synthesis of tetracyclic carbazoles and isocanthines

One pot intramolecular Diels–Alder reaction has been efficiently used as a new route for the synthesis of four tetracyclic carbazoles and four isocanthine analogues where a dialdehyde is utilised as a common intermediate for both the scaffolds. Biological activity was evaluated for some molecules, which demonstrated moderate activity against HeLa cervical cancer cell lines.     

The synthesis of C-13 functionalized pleuromutilins via C-H amidation and subsequent novel rearrangement product

Multi-gram quantities of C-13 functionalized pleuromutilin intermediates were synthesized under mild conditions via C-H amidation chemistry. The initial work was performed using rhodium catalysis. However, the highest yields were achieved using silver catalysis, resulting in stereoselective oxazolidinone formation. The ring closure was performed in the presence of a C-12 vinyl group, which differentiates it from historical methods involving the saturated pleuromutilin skeleton. A highlight of this vinyl template is a unique tetracyclic rearrangement product that can be generated from its treatment with hydrochloric acid and heat.     

Synthesis of new thieno[3,2-b]pyridine derivatives by palladium-catalyzed couplings and intramolecular cyclizations

Two methyl 3-aminothieno[3,2-b]pyridine-2-carboxylates were prepared from 3-fluoro or 3-nitropicolinonitriles and methyl thioglycolate in DMF/KOH(aq). From the unsubstituted precursor in the pyridine ring, di(hetero)arylamines were obtained by C-N Buchwald-Hartwig coupling with bromonitrobenzenes and with 2-bromopyridine. In the latter case a tetracyclic compound was formed by intramolecular cyclization. Using a brominated derivative in the pyridine ring as a coupling component, it was possible to synthesize C-C (Suzuki and Sonogashira) and C-N (Buchwald-Hartwig) coupling products and a tetracyclic compound obtained by bifunctionalization of the thienopyridine system.     

Stirring-controlled mono or double aminocarbonylation of 1,3-bis(2-iodoaryl)propan-2-amines

A palladium-catalyzed highly selective mono or double aminocarbonylation of 1,3-bis(2-iodoaryl)propan-2-amines under balloon pressure of CO has been developed. Tetracyclic isoquinolino[2,3-b]isoquinolinones were obtained through double aminocarbonylation when the reaction was stirred overnight, as most of organic reactions being operated. We accidentally found that monocarbonylated isoquinolinone products could be formed in good selectivity and chemical yield just without stirring the reaction mixture. The low concentration of CO in the still solution may account for the selectivity.     

Synthesis of Novel Rigid Analogs of Tryptamine as Potential Serotonin Ligands through Pd(0)-Catalyzed Diaryl Coupling Reactions

A series of novel tetracyclic 6-thia-5a-aza-acephenanthrylene derivatives 7 were synthesized by rigidization of the arylsulfonyl/carbonyl/methyl moiety through C7 of indole, which was achieved under Heck conditions. The strategy of altering the palladium–bromine exchange site produced target products.