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1.
The pivotal stereogenic centers of the asymmetric cycle D of (+)-harringtonolide were installed by functionalization of an enantiomerically pure IMDA cycloadduct, constructed from the chiral pool. The chiral 1,3-dioxane template used to direct the IMDA reaction was unraveled in an acidic medium, through spectacular hydrolysis of the acetal and concomitant lactone ring contraction. The central cyclohexene was selectively epoxidized either on the β- or on the α-side depending on the substitution pattern. The reactivity of several epoxide intermediates was challenged toward the construction of the oxygenated bridges of harringtonolide. We found one of them suitable for an access to another natural product, tetrodecamycin, which shares a similar substitution pattern as harringtonolide. Alternatively, functionalization led to set up key-stereocenters, en route to the asymmetric total synthesis of harringtonolide. The reactivity of the epoxide intermediates gave helpful insight for future work on this total synthesis. 相似文献
2.
In model studies towards the synthesis of harringtonolide, the construction of the tropone moiety via arene cyclopropanation was investigated. The installation of the lactone ring was accomplished by way of a Diels-Alder cycloaddition of various indenones and a-pyones. The incorporation of the key bridge methyl group and subsequent control of its stereochemistry is also outlined. 相似文献
3.
Dr. Zhiqiang Ma Dr. Ruining Li Zhen Zhang Cheng Tao Dr. Bin Cheng Dr. Yun Li Dr. Huifei Wang Prof. Dr. Hongbin Zhai 《Angewandte Chemie (International ed. in English)》2016,55(38):11638-11641
Described herein is the first asymmetric total synthesis of (+)‐harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels–Alder reaction and a rhodium‐complex‐catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation. 相似文献
4.
A tandem carbonyl ylide/1,3-dipolar cycloaddition cascade of α-diazo indole-2,3-dione with several different dipolarophiles was investigated. The intermolecular Rh(II)-catalyzed reaction occurs efficiently and affords dipolar cycloadducts in high yields. The analogous intramolecular reaction also takes place and gives an azapolycyclic product derived from trapping of the carbonyl ylide dipole with a tethered alkene. The power of the intramolecular cascade sequence is that it rapidly assembles polycyclic ring systems containing both multiple stereocenters and adjacent quaternary carbon centers in a single step in high yield. This cascade reaction was successfully utilized in a model study directed toward the total synthesis of mersicarpine. 相似文献
5.
Naoe S Suzuki Y Hirano K Inaba Y Oishi S Fujii N Ohno H 《The Journal of organic chemistry》2012,77(11):4907-4916
The gold-catalyzed cascade intermolecular addition-intramolecular carbocyclization reaction of dialkynylbenzenes was developed. In this reaction, regioselective addition of an external nucleophile toward the terminal alkyne and subsequent 6-endo-dig cyclization proceeded to give the 1,3-disubstituted naphthalenes in good yields. The direct synthesis of disubstituted chrysenes via a gold-catalyzed addition and double cyclization cascade using a triyne-type substrate was also achieved. 相似文献
6.
Matsuura BS Condie AG McBee IA Buff RC Karahalis GJ Stephenson CR 《Organic letters》2011,13(23):6320-6323
An intramolecular cyclization cascade reaction has been developed utilizing a high valent palladium intermediate that generates a carbon-carbon and carbon-oxygen bond in a single transformation. This method provides rapid access to highly functionalized tricyclic scaffolds, including spirocyclic cyclohexadienones. Good yields and mild conditions are reported with high tolerance toward oxygen and water. 相似文献
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An efficient palladium-catalyzed intramolecular carbopalladation/cyclization cascade toward tetra- and pentacyclic N-fused heterocycles has been developed. This transformation proceeds via the palladium-catalyzed coupling of aryl halides with internal propargylic esters or ethers followed by the 5-endo-dig cyclization leading to polycyclic pyrroloheterocycles in moderate to excellent yields. 相似文献
10.
A novel cascade reaction has been developed for the rapid construction of heterocyclic rings. The cyclization is thermally induced and does not involve the use of metal ions. This highly efficient construction of furans has been developed during studies directed toward the synthesis of the antibiotic lactonamycin 1. 相似文献
11.
Alexander V. Aksenov Nikita K. Kirilov Nicolai A. Aksenov Dmitrii A. Aksenov Elena A. Sorokina Carolyn Lower Michael Rubin 《Molecules (Basel, Switzerland)》2021,26(18)
Nitroalkanes activated with polyphosphoric acid could serve as efficient electrophiles in reactions with amines and hydrazines, enabling various cascade transformations toward heterocyclic systems. This strategy was developed for an innovative synthetic protocol employing simultaneous or sequential annulation of two different heterocyclic cores, affording [1,2,4]triazolo[4,3-a]quinolines with 1,3,4-oxadiazole substituents. 相似文献
12.
A stereoselective construction of the ABC-ring system of fusidane triterpenes via intermolecular/transannular Michael reaction cascade is described. The substrate, a ten-membered carbocyclic ketone, has been successfully prepared by the Cr-mediated intramolecular alkenylation of the corresponding acyclic compound. The array of functionalities in the product stereoselectively obtained by the cascade reaction is useful for further structural modifications directed toward the total synthesis of fusidane and other triterpenes, and designed molecules intended for studying structure–activity relationships. 相似文献
13.
Zhang X Song X Li H Zhang S Chen X Yu X Wang W 《Angewandte Chemie (International ed. in English)》2012,51(29):7282-7286
A matter of protection: The outcome of a divergent organocatalytic aza-Michael/aldol cascade process toward quinolines and 1,4-dihydroquinolines depends on the choice of the N-protecting group (see scheme; TEA = triethylamine, TMS = trimethylsilyl). Use of an electron-donating sulfonyl group results in an unanticipated aza-Michael/aldol/aromatization cascade to give polysubstituted quinolines (right). In contrast, chiral 1,4-dihydroquinolines are obtained with an electron-withdrawing sulfonyl group (left). 相似文献
14.
李柳 孙仕勇 吕瑞 GOLUBEV Yevgeny Aleksandrovich 王可 董发勤 段涛 KOTOVA Olga Borisovna KOTOVA Elena Leonidovna 《高等学校化学学报》2021,42(3):803-810
以铁氨基黏土(FeAC)为载体, 通过共价交联固定葡萄糖氧化酶(GOx), 构筑了铁氨基黏土-葡萄糖氧化酶纳米复合催化剂(FeAC-GOx). 利用FeAC的过氧化物酶活性, 与GOx结合进行级联反应, 可催化葡萄糖转化为过氧化氢并产生显色反应; 采用扫描电子显微镜(SEM)、 X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)对FeAC-GOx进行了形貌和结构表征, 并评价了其酶动力学参数、 催化稳定性和重复使用性等. 结果表明, GOx的固定化率可达到76.4%, 所构筑的纳米结构酶复合体系具有高效的级联催化能力. 与天然酶体系相比, FeAC-GOx具有更优异的温度和pH耐受性, 且在重复使用6次后, 酶催化活性无明显降低. 该体系不仅为新型葡萄糖传感器的开发奠定了基础, 还为多酶级联纳米结构酶的构筑提供了新思路. 相似文献
15.
[reaction: see text] A synthetic approach toward the immunosuppressants SNF3345 C and SNF4435 D featuring a tandem Stille coupling/electrocyclization cascade is described. 相似文献
16.
Christos Economou Justin P. Romaire Tony Z. Scott Brendan T. Parr Seth B. Herzon 《Tetrahedron》2018,74(26):3188-3197
We recently reported a convergent strategy to access the polycyclic guanidinium alkaloid (+)-batzelladine B via an aldol addition–retro-aldol–aza-Michael addition cascade. Here we describe the application of this approach toward the total syntheses of (+)-batzelladine E, (?)-dehydrobatzelladine C, and (+)-batzelladine K. The identification of suitable methods to functionalize a common tropane core by electrophilic alkynylation and nucleophilic 1,2-addition were essential to generalizing this approach. We provide evidence for the intermediacy of an acylallene species in the cascade reaction. 相似文献
17.
The scope of the 2-azadiene intramolecular Diels-Alder cyclization, previously employed for synthesis of the Daphniphyllum alkaloids, has been further investigated. Through a series of 1,5-diol cyclization precursors the substitution pattern of both the dienophile and the 2-azadiene were examined. From these studies it was shown that the cascade reaction is tolerant toward a variety of alkyl-substituted dienophiles. However, it was also demonstrated that this reaction is very sensitive to the substitution pattern of the 2-azadiene. Alterations made to the structure of the 2-azadiene cause either competing side reactions or complete failure of the reaction cascade. 相似文献
18.
Ziyan Zhang Prof. Vladimir Gevorgyan 《Angewandte Chemie (International ed. in English)》2023,62(47):e202311848
Palladium hydrides are traditionally employed in hydrofunctionalization (i.e. monofunctionalization) of conjugated dienes and enynes, owning to its facile protic hydropalladation of electron-rich (or neutral) unsaturated bonds. Herein, we report a mild PdH-catalyzed difunctionalization of conjugated dienes and enynes. This protocol is enabled by the chemoselectivity switch of the initial hydropalladation step achieved by visible light enhancement of hydricity of PdH species. This method allows for cascade annulation of dienes and enynes with various easily available and abundant substrates, such as acrylic acids, acrylic amides, and Baylis–Hillman adducts, toward a wide range of alkenyl or alkynyl lactones, lactams, and tetrahydrofurans. This protocol also provides an easy access to complex spiro-fused tricyclic frameworks. 相似文献
19.
Noah Z. Burns 《Tetrahedron》2009,65(33):6600-7556
A full account of synthetic efforts toward the indeno-tetrahydropyridine core of haouamine A is presented. Initial failed strategies led to the unexpected discovery of a mild abnormal Chichibabin pyridine synthesis and provided knowledge and inspiration for the development of a cascade annulation that has enabled rapid and scalable access to the core in either racemic or enantiopure form. 相似文献
20.
[reaction: see text]. The reactivity of acetylenic omega-ketoesters toward tetra-n-butylammonium fluoride and potassium tert-butoxide was studied. These cascade reactions proceeded smoothly and afforded either electrophilic allene derivatives or highly functionalized oxetane derivatives in moderate to high yields. 相似文献