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101.
N. P. Artemova L. E. Nikitina D. A. Yushkov O. G. Shigabutdinova V. V. Plemenkov V. V. Klochkov B. I. Khairutdinov 《Chemistry of Natural Compounds》2005,41(1):45-47
The optimal method for isolating the sesquiterpene lactone britanin from the aerial part of Inula britannica L. (Asteraceae) was developed. Britanin was functionalized by reacting it with methyl mercaptoacetate.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 37–38, January–February, 2005. 相似文献
102.
First Atroposelective Total Synthesis of Enantiomerically Pure Ancistrocladidine and Ancistrotectorine 下载免费PDF全文
Prof. Dr. Gerhard Bringmann Dr. Narasimhulu Manchala Dr. Tobias Büttner Dr. Barbara Hertlein‐Amslinger Raina Seupel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9792-9796
The first regio‐ and stereoselective total synthesis of the axially chiral 7,3′‐coupled naphthylisoquinoline alkaloids ancistrocladidine ( 1 ) and ancistrotectorine ( 2 ) has been described. Both possess a 7,3′‐coupled axis, which before now, was difficult to attain synthetically. Moreover, target 2 has a sensitive relative cis‐array of the two methyl groups at C1 and C3 in the tetrahydroisoquinoline part. The key step in the chosen strategy was the construction of the biaryl axis in accordance with the “lactone method”: the two molecular halves, which were activated in an “inverse‐halogenated” form, were prefixed by an ester bridge, followed by intramolecular coupling, and atroposelective cleavage of the lactone auxiliary bridge delivered the desired biaryl scaffold. 相似文献
103.
Dr. Madhu Sudan Manna Rahul Sarkar Prof. Dr. Santanu Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14912-14919
An enantioselective formal C(sp2)?H vinylation of prochiral 2,2‐disubstituted cyclopentene‐1,3‐dione is presented. This vinylative desymmetrization is realized by using a two‐step procedure that consists of a catalytic enantioselective vinylogous Michael addition of deconjugated butenolides to cyclopentene‐1,3‐dione and a base‐mediated decarboxylation. The overall process utilizes deconjugated butenolides as the source of the highly substituted vinyl unit. Five‐membered carbocycles containing a remote all‐carbon quaternary stereogenic center are obtained in good yields and with good to high enantioselectivities. 相似文献
104.
Tiago A. Fernandes Adelino M. Galvão Ana M. Botelho do Rego M. Fernanda N. N. Carvalho 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3316-3323
The number of CuCl units per camphor ligand in [{CuCl}2L]n was extended to three or four in [{CuCl}3L]n ( 2 ) or [{CuCl}4L]n ( 1 ). The Hartree‐Fock ab initio calculations support the polymeric structure of 1 and 2 that catalyze the cyclization of 4‐pentyn‐1‐oic acid ( A ) forming 5‐methylenedihydrofuran‐2(3H)‐one ( B ) and/or 2‐methyl‐5‐oxotetrahydrofuran‐2‐ylpent‐4‐ynoate ( C ). The catalytic activity of 1 , 2 and other polynuclear Cu(I) complexes ( 3–5 ) was evaluated under solvent free conditions and/or solution. In the absence of solvent, catalyst 2 displays the highest activity and selectivity (75.8/23.1, C to B ratio, at 5.4% loading) while 4 reaches the highest level of A → B conversion (97.5 %) in solution. Selected reactions were followed by NMR and the kinetic constants calculated. A mechanism is proposed based on the equations used for the calculations. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3316–3323 相似文献
105.
Cooperative Activation with Chiral Nucleophilic Catalysts and N‐Haloimides: Enantioselective Iodolactonization of 4‐Arylmethyl‐4‐pentenoic Acids 下载免费PDF全文
Dr. Hidefumi Nakatsuji Yasuhiro Sawamura Prof. Dr. Akira Sakakura Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2014,53(27):6974-6977
Chiral triaryl phosphates promote the enantioselective iodolactonization of 4‐substituted 4‐pentenoic acids to give the corresponding iodolactones in high yields with high enantioselectivity. N‐Chlorophthalimide (NCP) is employed as a Lewis acidic activator and oxidant of I2 for the present iodolactonization. In combination with 1.5 equivalents of NCP, only 0.5 equivalents of I2 are sufficient to generate the iodinating reagent. 相似文献
106.
Ag(I) and Au(I) efficiently catalyze the cycloisomerization of terminal alkynoic acids into methylene seven-membered ring lactones. Depending on the metal, divergent reaction pathways were found for non terminal alkynoic acids. While Ag(I) led to lactones, Au(I) led to 2H-chromenes coming from the hydroarylation of the alkyne. 相似文献
107.
《Angewandte Chemie (International ed. in English)》2017,56(15):4201-4205
A carbene‐catalyzed intermolecular C−N bond formation, which initiates a highly selective cascade reaction for the synthesis of pyrrolidine fused β‐lactones, is disclosed. The nitrogen‐containing bicyclic β‐lactone products are obtained with good yields and excellent stereoselectivities. Synthetic transformations of the reaction products into useful functional molecules, such as amino catalysts, can be efficiently realized under mild reaction conditions. Mechanistically, this study provides insights into modulating the reactivities of heteroatoms, such as nitrogen atoms, in challenging carbene‐catalyzed asymmetric carbon–heteroatom bond‐forming reactions. 相似文献
108.
Dr. Haruhisa Kikuchi Takehiro Nishimura Dr. Eunsang Kwon Junya Kawai Prof. Dr. Yoshiteru Oshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15819-15825
Many natural terpenoid alkaloid conjugates show biological activity because their structures contain both sp3‐rich terpenoid scaffolds and nitrogen‐containing alkaloid scaffolds. However, their biosynthesis utilizes a limited set of compounds as sources of the terpenoid moiety. The production of terpenoid alkaloids containing various types of terpenoid moiety may provide useful, chemically diverse compound libraries for drug discovery. Herein, we report the construction of a library of terpenoid alkaloid‐like compounds based on Lewis‐acid‐catalyzed transannulation of humulene diepoxide and subsequent sequential olefin metathesis. Cheminformatic analysis quantitatively showed that the synthesized terpenoid alkaloid‐like compound library has a high level of three‐dimensional‐shape diversity. Extensive pharmacological screening of the library has led to the identification of promising compounds for the development of antihypolipidemic drugs. Therefore, the synthesis of terpenoid alkaloid‐like compound libraries based on humulene is well suited to drug discovery. Synthesis of terpenoid alkaloid‐like compounds based on several natural terpenoids is an effective strategy for producing chemically diverse libraries. 相似文献
109.
Zhi‐Qin Liang Zhong‐Hua Gao Wen‐Qiang Jia Prof. Dr. Song Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1868-1872
Bifunctional N‐heterocyclic carbenes with a free hydroxy group are demonstrated as efficient catalysts for the [3+4] annulation of enals with aurones to give the corresponding benzofuran‐fused ε‐lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Control experiments reveal that the [3+4] cycloadducts are kinetically favored and could be transformed to the thermodynamically favored [3+2] cycloadducts with a non‐bifunctional NHC catalyst. 相似文献
110.
Alessia Petti Matthew C. Leech Anthony D. Garcia Iain C. A. Goodall Adrian P. Dobbs Kevin Lam 《Angewandte Chemie (International ed. in English)》2019,58(45):16115-16118
A new electrochemical methodology has been developed for the generation of oxycarbonyl radicals under mild and green conditions from readily available hemioxalate salts. Mono‐ and multi‐functionalised γ‐butyrolactones were synthesised through exo‐cyclisation of these oxycarbonyl radicals with an alkene, followed by the sp3–sp3 capture of the newly formed carbon‐centred radical. The synthesis of functionalised valerolactone derivatives was also achieved, demonstrating the versatility of the newly developed methodology. This represents a viable synthetic route towards pharmaceutically important fragments and further demonstrates the practicality of electrosynthesis as a green and economical method to activate small organic molecules. 相似文献