Search results for: acetal
#34129264 2021/06/15 To Up
Photo Click Reaction of Acylsilanes with Indoles.Light-mediated coupling of acylsilanes with indoles is reported. This photo click reaction occurs under mild conditions (415 nm) mostly in quantitative yield and provides stable silylated N,O-acetals via light mediated siloxycarbene generation with subsequent indole-N-H insertion. We show that this very efficient and fully atom economic coupling process can be applied to conjugate complex systems, as documented by the clicking of carbohydrates with indole alkaloids. The method is also applicable to the conjugation of polymer chains. The linking acetal moiety can be readily cleaved and it is also shown that wavelength-selective coupling and cleavage with acyl silanes bearing a second photoactive moiety is possible. This is documented by a successful polymerization/depolymerization sequence and by a polymer folding/unfolding process.
Constantin Stuckhardt, Maren Wissing, Armido Studer100 reactions5 reactions20 ml200 Reactions5 reactions1 kit75 reactions100 reactions20000 Units30 Reactions
#34100492 // To Up
Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity.An efficient tandem hydrosilylation of CO2, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C6F5)3, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO2 to CH4, with a turnover frequency of up to 6000 h-1 at room temperature. The catalytic system is robust, and 19â400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent, i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.
Kejian Chang, Iker Del Rosal, Xizhou Zheng, Laurent Maron, Xin Xu
2492 related Products with: Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity.400Tests50 ug 2 Pieces/Box200 Tests100 assays5 mg 96 Tests 100.00 ug
#34094653 2020/11/17 To Up
pH-Controlled Nanoparticle Catalysts for Highly Selective Tandem Henry Reaction from Mixtures.Nature has a remarkable ability to perform selective transformation of complex biological mixtures into desired products using enzymatic catalysts. We report the preparation of nanoparticle catalysts through molecular imprinting within cross-linked micelles. These catalysts were highly selective for their targeted substrates and could selectively hydrolyze less reactive acetals over more reactive ones even under basic conditions. Their catalytic activity and selectivity were tunable through rational postmodification of the active site. These properties enabled the nanoparticle catalysts to produce the desired Î²-nitro alcohol from a four-component acetal mixture in a tandem deprotection/Henry reaction that required incompatible acidic and basic catalysts in the two steps.
Ishani Bose, Yan Zhao
2591 related Products with: pH-Controlled Nanoparticle Catalysts for Highly Selective Tandem Henry Reaction from Mixtures.4 Membranes/Box1.0 mg 1 G2 Pieces/Box200 Reactions100 ml20 ml5 reactions4 Membranes/Box500
#34094328 2020/07/30 To Up
Total synthesis of biseokeaniamides A-C and late-stage electrochemically-enabled peptide analogue synthesis.The first total synthesis of cytotoxic cyanobacterial peptide natural products biseokeaniamides A-C is reported employing a robust solid-phase approach to peptide backbone construction followed by coupling of a key thiazole building block. To rapidly access natural product analogues, we have optimized an operationally simple electrochemical oxidative decarboxylation-nucleophilic addition pathway which exploits the reactivity of native C-terminal peptide carboxylates and abrogates the need for building block syntheses. Electrochemically-generated ,-acetal intermediates are engaged with electron-rich aromatics and organometallic reagents to forge modified amino acids and peptides. The value of this late-stage modification method is highlighted by the expedient and divergent production of bioactive peptide analogues, including compounds which exhibit enhanced cytotoxicity relative to the biseokeaniamide natural products.
Yutong Lin, Lara R Malins
1455 related Products with: Total synthesis of biseokeaniamides A-C and late-stage electrochemically-enabled peptide analogue synthesis.25 Rxns Kit100 Rxns Kit25 Rxns Kit100 Rxns Kit25 g50 ug
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#34080502 2021/06/03 To Up
Denudatine-type diterpenoid alkaloids from an aqueous extract of the lateral root of .Five new denudatine-type diterpenoid alkaloids (1-5), along with the known analogue aconicarmine (), were isolated from an aqueous decoction of the lateral roots of (fu-zi). Their structures were determined by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Compound is the first denudatine-type diterpenoid alcohol iminium alkaloid, which could be partially transformed into the aza acetal form in pyridine-. Compound inhibited mice writhing in an acetic acid-induced writhing assay.
Hui Liu, Shuai Shao, Huan Xia, Yu-Zhuo Wu, Cheng-Gen Zhu, Cheng-Bo Xu, Tian-Tai Zhang, Qing-Lan Guo, Jian-Gong Shi
2008 related Products with: Denudatine-type diterpenoid alkaloids from an aqueous extract of the lateral root of .0.2ml50ul0.1 ml1 mg0.1 mg
#34069653 2021/05/19 To Up
New Cardenolides from Biotransformation of Gitoxigenin by the Endophytic Fungus 1E1BL1: Characterization and Cytotoxic Activities.Microbial biotransformation is an important tool in drug discovery and for metabolism studies. To expand our bioactive natural product library via modification and to identify possible mammalian metabolites, a cytotoxic cardenolide (gitoxigenin) was biotransformed using the endophytic fungus 1E1BL1. Initially, oleandrin was isolated from the dried leaves of L. and subjected to an acid-catalysed hydrolysis to obtain the substrate gitoxigenin (yield; ~25%). After 21 days of incubation, five new cardenolides , , , , and and three previously- identified compounds , and were isolated using chromatographic methods. Structural elucidations were accomplished through 1D/2D NMR, HR-ESI-MS and FT-IR analysis. catalyzed oxygenation, oxidation, epimerization and dimethyl acetal formation reactions on the substrate. Cytotoxicity of the metabolites were evaluated using MTT cell viability method, whereas doxorubicin and oleandrin were used as positive controls. Biotransformation products displayed less cytotoxicity than the substrate. The new metabolite exhibited the highest activity with IC values of 8.25, 1.95 and 3.4 ÂµM against A549, PANC-1 and MIA PaCa-2 cells, respectively, without causing toxicity on healthy cell lines (MRC-5 and HEK-293) up to concentration of 10 ÂµM. Our results suggest that is an effective biocatalyst for modifying cardenolide-type secondary metabolites.
Erdal Bedir, ÃiÄdem Karakoyun, Gamze DoÄan, GÃ¼lten Kuru, Melis KÃ¼Ã§Ã¼ksolak, Hasan YusufoÄlu
1343 related Products with: New Cardenolides from Biotransformation of Gitoxigenin by the Endophytic Fungus 1E1BL1: Characterization and Cytotoxic Activities.100ul 1 kit(s) 25 mg11 kit100 mg2 25 MG200ug
#34067999 2021/05/13 To Up
Crystallization of Long-Spaced Precision Polyacetals III: Polymorphism and Crystallization Kinetics of Even Polyacetals Spaced by 6 to 26 Methylenes.In this paper we extend the study of polymorphism and crystallization kinetics of aliphatic polyacetals to include shorter (PA-6) and longer (PA-26) methylene lengths in a series of even long-spaced systems. On a deep quenching to 0 Â°C, the longest even polyacetals, PA-18 and PA-26, develop mesomorphic-like disordered structures which, on heating, transform progressively to hexagonal, Form I, and Form II crystallites. Shorter polyacetals, such as PA-6 and PA-12 cannot bypass the formation of Form I. In these systems a mixture of this form and disordered structures develops even under fast deep quenching. A prediction from melting points that Form II will not develop in polyacetals with eight or fewer methylene groups between consecutive acetals was further corroborated with data for PA-6. The temperature coefficient of the overall crystallization rate of the two highest temperature polymorphs, Form I and Form II, was analyzed from the differential scanning calorimetry (DSC) peak crystallization times. The crystallization rate of Form II shows a deep inversion at temperatures approaching the polymorphic transition region from above. The new data on PA-26 confirm that at the minimum rate the heat of fusion is so low that crystallization becomes basically extinguished. The rate inversion and dramatic drop in the heat of fusion irrespective of crystallization time are associated with a competition in nucleation between Forms I and II. The latter is due to large differences in nucleation barriers between these two phases. As PA-6 does not develop Form II, the rate data of this polyacetal display a continuous temperature gradient. The data of the extended polyacetal series demonstrate the important role of methylene sequence length on polymorphism and crystallization kinetics.
Stephanie F Marxsen, Manuel HÃ¤uÃler, Stefan Mecking, Rufina G Alamo
1092 related Products with: Crystallization of Long-Spaced Precision Polyacetals III: Polymorphism and Crystallization Kinetics of Even Polyacetals Spaced by 6 to 26 Methylenes.100 mg 1KG1 g1 g500 mg100 mg25 mg 5 G 1 G1000 TESTS/0.65ml 1 G25 mg
#34067793 2021/05/17 To Up
Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides.As an important moiety in natural products, ,-acetal has attracted wide attention in the past few years. An efficient method to construct ,-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding -aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.
Pengcheng Wang, Ruirui Yu, Sajjad Ali, Zhengshen Wang, Zhigang Liu, Jinming Gao, Huaiji Zheng
1297 related Products with: Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides.5mg10 mg100 mg10 mg 5 G2.5 g25 mg100ug 5 G100ug Lyophilized 25 G5 g
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#34064812 2021/05/11 To Up
Preparation of the Key Dolutegravir Intermediate via MgBr-Promoted Cyclization.A novel approach for synthesizing the key dolutegravir intermediate is described via MgBr-promoted intramolecular cyclization. Condensation of commercially available methyl oxalyl chloride and ethyl 3-(,-dimethylamino)acrylate afforded the vinylogous amide in an excellent yield. Subsequent substitution by aminoacetaldehyde dimethyl acetal and methyl bromoacetate gave rise to the expected precursor for cyclization, which was promoted by MgBr to highly selectively convert into pyridinone diester. The key dolutegravir intermediate was finally prepared by the selective hydrolysis of the corresponding diester via LiOH.
Jiahui Kong, Haijian Xia, Renbao He, Hao Chen, Yongping Yu
1160 related Products with: Preparation of the Key Dolutegravir Intermediate via MgBr-Promoted Cyclization.100μg1 kitBox of 10 vials for 500 m1 kit1 vial100μg500 Units200 assays1000pcs100 ug/vial100μl
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