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441.
The acid-catalyzed reaction of 1,2-anhydro-3,4,6-tri-O-benzyl-α-d-glucopyranose (7) as glycosyl donor with bis-trimethylsilyl sulfide as acceptor affords the α-thiol. Hence, this sterically hindered S-nucleophile as acceptor should provide with O-glycosyl trichloroacetimidates as glycosyl donors that have nonparticipating groups at C-2, glycosylthiols with the thiol group in axial position. This was confirmed for various donors (4, 16-19) with the exception of the corresponding mannosyl donor (20). However, powerful participating groups at C-2 of the donor (23-28) governed the anomeric selectivity. 相似文献
442.
Treatment of 1,6-anhydrosugars with commercially available bis(trimethylsilyl) sulfide in the presence of trimethylsilyl triflate led to the formation of α-glycosyl thiols. All the reactions were highly stereoselective and afforded the α-glycosyl thiols in good to excellent yields. By this procedure, a variety of 1,6-anhydrosugars, differing in their sugar units, glycosidic linkages, and protecting group pattern, were converted smoothly into the corresponding α-glycosyl thiols, which could be of great utility in thioglycoside chemistry. It is noteworthy that 1,6-anhydrosugars carrying the 2-O-acyl group and 1,6-anhydrosugar-containing oligosaccharides could also be ring-opened stereospecifically under the same conditions to give rise to the corresponding 1-thiosugars in high yields. Thus, a very concise and efficient access to α-glycosyl thiols of great value was established. 相似文献
443.
Kahaly S Yadav SK Wang WM Sengupta S Sheng ZM Das A Kaw PK Kumar GR 《Physical review letters》2008,101(14):145001
We demonstrate near-100% light absorption and increased x-ray emission from dense plasmas created on solid surfaces with a periodic sub-lambda structure. The efficacy of the structure-induced surface plasmon resonance, responsible for enhanced absorption, is directly tested at the highest intensities to date (3 x 10{15} W cm{-2}) via systematic, correlated measurements of absorption and x-ray emission. An analytical grating model as well as 2D particle-in-cell simulations conclusively explain our observations. Our study offers a definite, quantitative way forward for optimizing and understanding the absorption process. 相似文献
444.
Sunil Dattatray Chakave Shrikant Shete Dr. Sandeep Reddy Kandukuri Dr. Mark Montgomery Dr. Bhanu N. Manjunath Dr. Ravindra Punjaji Sonawane 《European journal of organic chemistry》2023,26(5):e202201205
The first total synthesis of des-hydroxy triticone A and B was achieved in 12 steps. The highly chemoselective, base mediated iodolactamization of olefins with N-OMe amide motif is a key highlight of the synthesis. 相似文献
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Patil Amod S. Mundada Anand B. Shravane Ravindra S. Mundada Pooja A. Surana Sanjay J. 《平面色谱法杂志一现代薄层色谱法》2023,36(1):89-97
JPC – Journal of Planar Chromatography – Modern TLC - Two new, simple, fast, and sensitive methods, normal- and reversed-phase high-performance thin-layer chromatography (NP-HPTLC and... 相似文献
448.
Dr. Asfandyar Sikandar Dr. Alexander Popoff Dr. Ravindra P. Jumde Dr. Attila Mándi Dr. Amninder Kaur Dr. Walid A. M. Elgaher Dr. Lara Rosenberger Dr. Stephan Hüttel Dr. Rolf Jansen Dr. Maja Hunter Prof. Dr. Jesko Köhnke Prof. Dr. Anna K. H. Hirsch Prof. Dr. Tibor Kurtán Prof. Dr. Rolf Müller 《Angewandte Chemie (International ed. in English)》2023,62(40):e202306437
Even with the aid of the available methods, the configurational assignment of natural products can be a challenging task that is prone to errors, and it sometimes needs to be corrected after total synthesis or single-crystal X-ray diffraction (XRD) analysis. Herein, the absolute configuration of amidochelocardin is revised using a combination of XRD, NMR spectroscopy, experimental ECD spectra, and time-dependent density-functional theory (TDDFT)-ECD calculations. As amidochelocardin was obtained via biosynthetic engineering of chelocardin, we propose the same absolute configuration for chelocardin based on the similar biosynthetic origins of the two compounds and result of TDDFT-ECD calculations. The evaluation of spectral data of two closely related analogues, 6-desmethyl-chelocardin and its semisynthetic derivative 1 , also supports this conclusion. 相似文献
449.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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