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1.
Han Wang Renyang Xu Shuobin Liang Fuxiang Ran Lihe Zhang Yongmin Zhang Demin Zhou Sulong Xiao 《中国化学快报》2020,31(2):333-336
The acetyl ester plays an important role for protection of the hydroxyl groups in carbohydrates synthesis.In the present study,we described an efficient deprotection of acetyl group of pentacyclic triterpenoid by using methanolic ammonia in THF solution.Good selectivity for cleaving gal-C2-OAc group of 3β-hydroxy-olean-12-en-28-oic acid 28-N-2,3,4,6-tetra-O-acetyl-β-D-galactopyranoside(3) was achieved in the presence of methanolic ammonia within 4 h at low temperature(-60℃) in a yield of 56%.The reaction disclosed here provides a new method for the synthesis of C2 selective modified carbohydrates,which is more useful than conventional synthesis procedure that usually requires many steps including temporary regioselective protection and deprotection.When the reaction temperature was increased from -60℃ to room temperature,the cleavage of the other three acetyl groups of galactose in an order of C4-OAc>C3-OAc>C6-OAc was observed.Based on this study,a plausible route for the deacetylation reaction has been proposed. 相似文献
2.
An intermolecular two C? C bond formation procedure for the synthesis of carbocycles mediated by hypervalent iodine(III) reagents was developed. This metal free protocol provided a new approach for the synthesis of useful substituted 1‐amino‐2‐naphthoic acid derivatives via benzannulation reactions. Various N‐unsubstituted and N‐alkyl substituted aromatic enamines with terminal alkynes and non‐terminal alkynes can be converted into corresponding 1‐amino‐2‐naphthoic acid derivatives under mild reaction conditions. When meta‐substituted phenyl enamines were employed in the reaction, two cyclization paths were detected in the reaction and ortho‐cyclization products were the only or major products. Good functional group tolerance, readily available material and high atom utilization efficiency make this method a potential procedure which may find broad application in organic synthesis. 相似文献
3.
Total synthesis of (+/-)-taiwaniaquinol B via a domino intramolecular friedel-crafts acylation/carbonyl alpha-tert-alkylation reaction 总被引:1,自引:0,他引:1
The first synthesis of taiwaniaquinol B, a 6-nor-5(6-->7)abeoabietane-type diterpenoid exhibiting the uncommon fused 6-5-6 tricyclic carbon skeleton, was accomplished in 15 steps. A Lewis acid-promoted tandem intramolecular Friedel-Crafts/carbonyl alpha-tert-alkylation reaction was exploited as the core strategy for the synthesis of the sterically congested 1-indanone-containing tricyclic structure. This multiple carbon-carbon bond forming reaction exploits the unique reactivity of Meldrum's acid. The facile precursor synthesis makes this a useful methodology for the expedient modification and assembly of sterically congested 1-indanone-containing ring systems. 相似文献
4.
[reaction: see text] The design and synthesis of a new core structure, a ring-oxygenated variant of 2-carboxy-6-hydroxyoctahydroindole (Choi) from D-glucose, is reported. Choi, a rigid bicyclic unnatural amino acid, is the core structure of about 15 aeruginosins natural compounds. These compounds are thrombin, trypsin, and factor VIIa inhibitors and Choi is important for their biological activity. The ring-oxygenated variant of 2-carboxy-6-hydroxyoctahydroindole can potentially be used as a surrogate of Choi in the design and synthesis of aeruginosin-based thrombin inhibitors. 相似文献
5.
Selenium‐Catalyzed C(sp3)H Acyloxylation: Application in the Expedient Synthesis of Isobenzofuranones
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Felix Krätzschmar Martin Kaßel Daniel Delony Dr. Alexander Breder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7030-7034
Oxidative Se‐catalyzed C(sp3)?H bond acyloxylation has been used to construct a diverse array of isobenzofuranones from simple ortho‐allyl benzoic acid derivatives. The synthetic procedure employs mild reaction conditions and gives high chemoselectivity enabled by an inexpensive organodiselane catalyst. The presented approach offers a new synthetic pathway toward the core structures of phthalide natural products. 相似文献
6.
Shengming Ma Bukuo Ni Shaohui Lin Zhiqiang Liang 《Journal of organometallic chemistry》2005,690(23):5389-5395
Double or triple intramolecular Suzuki coupling reaction has been developed for the efficient synthesis of tri- or tetracyclic products with a benzene core in good yields. The reaction was realized via a one-pot procedure combining the hydroboration of the CC bond in the starting aryl halides and the intramolecular Suzuki coupling. 相似文献
7.
An efficient and novel synthesis of 6,9-disubstituted purin-8-ones has been developed. Starting from dichloropyrimidin-5-ylcarbamate, CuCl/amino acid catalyzed coupling/cyclization reaction with amines was achieved to afford 9-substituted 6-chloropurin-8-ones. Then a microwave-assisted amination procedure was carried out for the synthesis of 6,9-disubstituted purin-8-ones in moderate to good yields. 相似文献
8.
《Comptes Rendus Chimie》2015,18(5):558-563
In this paper, the reaction of indole with electron-deficient alkenes in aqueous media is reported. This procedure allows the synthesis of bis(indole) derivatives in good to high yields at 90 °C under silent and ultrasound irradiation conditions. Short reaction times and high yields of desired products are the main advantages of the presented procedure. This reaction catalyzed by 12-tungstophosphoric acid is operationally simple and considers environmental aspects by avoiding toxic catalysts and solvents. 相似文献
9.
Cuzzupe AN Hutton CA Lilly MJ Mann RK McRae KJ Zammit SC Rizzacasa MA 《The Journal of organic chemistry》2001,66(7):2382-2393
The total synthesis of the epidermal growth factor inhibitor reveromycin B (2) in 25 linear steps from chiral methylene pyran 13 is described. The key steps involved an inverse electron demand hetero-Diels-Alder reaction between dienophile 13 and diene 12 to construct the 6,6-spiroketal 11 which upon oxidation with dimethyldioxirane and acid catalyzed rearrangement gave the 5,6-spiroketal aldehyde 9. Lithium acetylide addition followed by oxidation/reduction and protective group manipulation provided the reveromycin B spiroketal core 8 which was converted into the reveromycin A (1) derivative 6 in order to confirm the stereochemistry of the spiroketal segment. Introduction of the C1-C10 side chain began with sequential Wittig reactions to form the C8-C9 and C7-C6 bonds, and a tin mediated asymmetric aldol reaction installed the C4 and C5 stereocenters. The final key steps to the target molecule 2 involved a Stille coupling to introduce the C21-C22 bond, succinoylation, selective deprotection, oxidation, and Wittig condensation to form the final C2-C3 bond. Deprotection was effected by TBAF in DMF to afford reveromycin B (2) in 72% yield. 相似文献
10.
Seiichi Nakamura 《Tetrahedron》2005,61(47):11078-11106
A total synthesis of zaragozic acid C by a convergent strategy is described in which the key features include (1) the simultaneous creation of the C4 and C5 quaternary stereogenic centers by a Sn(OTf)2-promoted aldol coupling reaction between an α-keto ester and a silyl ketene thioacetal derived from l- and d-tartaric acids, respectively, (2) the direct introduction of lithium acetylide as the C1 side chain equivalent onto the fully functionalized aldehyde, and (3) construction of the bicyclic core structure by acid-catalyzed internal ketalization under kinetically controlled conditions. 相似文献
11.
We utilized the glycosyl acceptor tagging method with ionic liquid support for synthesis of the core segment of Clostridium botulinum C2 toxin ligand through a divergent synthetic strategy without chromatographic purification.The total yield was 57.1% and the reaction was completed in 10 h.The efficient ionic liquid supported glycosylation and purification procedure was applied for the synthesis of branched glucosamine-containing oligosaccharides for the first time,which expanded the scope of ionic liquid supported synthesis of biologically important oligosaccharides. 相似文献
12.
Luke A. Adams 《Tetrahedron letters》2004,45(23):4489-4493
A versatile synthesis of the bicyclo[2.2.2]diazaoctane core structure of asperparaline, brevianamide, paraherquamide, and stephacidin natural products is demonstrated. This convergent synthesis relies on an intramolecular hetero Diels-Alder reaction to construct the key tetracycle from a diketopiperazine derived azadiene; which in turn was formed from prolinamide and a pyruvic acid derivative. The stereochemical outcome of the Diels-Alder reaction was found to favor the brevianamide stereochemistry. 相似文献
13.
A new domino process of three-component Povarov reaction and aerobic dehydrogenation was developed toward the synthesis of polysubstituted quinolines. 2,4-Disubstituted-8-nitroquinolines, which are important precursors for the synthesis of antimalarial primaquine drug-like molecules, were prepared conveniently by this method in moderate to good yields. Brönsted acid (HClO4)-modified montmorillonite was found to be a crucial catalyst in promoting the procedure. 相似文献
14.
A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity. 相似文献
15.
采用水热法制备了新型H6P2W9Mo9O62.24H2O催化剂,并用UV-Vis、FT-IR和TG-DTA等测试技术对催化剂进行了表征。以微波促进30%过氧化氢氧化环己酮制备己二酸合成反应为探针,考察了催化剂的催化性能。通过正交实验探讨了几种因素对反应的影响,确定了优化工艺条件为:n(环己酮)∶n(过氧化氢)∶n(草酸)∶n(催化剂)=100∶400∶1.25∶0.25,反应温度100℃,微波辐射功率400 W,反应时间3.5 h,己二酸产品的收率达87.33%,纯度可达99.7%。反应结束后,将反应后含催化剂的溶液浓缩至一定浓度,催化产率降低,重复使用5次收率降低为45.89%。 相似文献
16.
AbstractAn efficient, green procedure for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) and α-amidoalkyl-β-naphthol’s using biodegradable polymeric catalyst chitosan-SO3H (CTSA), is operationally easy to prepare by mixing chitosan and chlorosulfonic acid. This catalyst displays excellent catalytic activity and reusable for five subsequent reactions without significant loss of catalytic activity. This protocol proceeds with short reaction times, at mild temperatures, in a solvent-free reaction, and generally with high yields. We present herein a practical, efficient and simple procedure with a broad substrate scope that allows access to two different reactions 1H-pyrazole-5-ol and α-amidoalkyl-β-naphthol’s core unit. 相似文献
17.
Aldoximes were converted in high yields by N-Chlorosuccinimide into hydroxamic acid chlorides, and corresponding nitrile oxides generated by addition of triethylamine at 40°–50° underwent 1,3-dipolar polar addition to alkenes, giving 2-isoxazolines. The whole procedure could be performed as a one-pot reaction. Oximes with other functions, sensitive to free chlorine could be converted selectively into hydroxamic acid chlorides by this procedure. Isopropylidene glyceraldoxime was added to acrolein diethylacetal thus affording an entrance to carbohydrate synthesis but the stereospecificity of the reaction is low. 2:3, 5:6-Di-O-isopropylidene-D-mannose oxime was converted to the N-hydroximinolactone by treatment with NCS and base. 相似文献
18.
A one-step procedure was developed for the synthesis of new 6-fluoro-7-(isoxazolidin-2-yl)-4-oxo-1,4-dihydroquinolines. The procedure is based on the 1,3-dipolar cycloaddition of the azomethine oxide and 1,1-disubstituted alkenes, which are generated in situ from 6-fluoro-7-hydroxylamino-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and CH-active compounds (dialkyl malonates, ethyl acetoacetate), respectively, in the presence of formaldehyde at 100—120 °C. 相似文献
19.
An efficient and eco-friendly procedure for the synthesis of 2-amino-5-oxo-4-aryl-4H,5H-pyrano[3,2-c]chromene-3-carboxamide has been developed through a one-pot three-component condensation of 4-hydroxycoumarin with aldehydes and cyanoacetamide, in the presence of catalytic amount of polystyrene-supported p-toluenesulfonic acid (PS-PTSA) as a highly active and reusable heterogeneous acid catalyst in EtOH at 80?°C conditions. This new procedure offers several advantages such as shorter reaction times, excellent yields, a wide range of functional group tolerance, easy experimental work-up procedure, operationally simple under metal-free reaction conditions and C-C/C-O bond formation. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields. 相似文献
20.
High Loading Pt Core/Carbon Shell Derived from Platinum‐Aniline Complex for Direct Methanol Fuel Cell Application
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《Electroanalysis》2018,30(8):1604-1609
A novel approach to high loaded Pt core/carbon shell catalyst synthesis from a Pt‐aniline complex was reported. The Pt‐aniline complex was successfully synthesized by irradiating an ultrasound to the hexachloro platinic acid and aniline monomer mixture. The highly viscous nature of aniline leads to reproducible hexagonal plate like Pt‐aniline complex crystals. The chemical composition of the Pt‐aniline complex was identified as [PtCl2(C6H5NH2)2] with the help of NMR, XPS, HR ESI‐MS, and TGA analyses. Furthermore, the Pt‐aniline hexagonal plates were sintered at various temperatures like 400 °C, 500 °C, and 700 °C for an hour. This formed the highly dispersed carbon covered Pt nano particles with loading of 80.1 wt %, 81.3 wt %, and 83.4 wt % for HP‐4, HP‐5, and HP‐7, respectively. After supporting it on Vulcan XC‐72, Pt core/carbon shell pyrolyzed at a low temperature showed excellent performance in methanol oxidation reaction. In addition, Pt core/carbon shell prepared at a high temperature revealed excellent tolerance to methanol. 相似文献