Synthesis of glycosylthiols and reactivity studies

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.     

Synthesis of α-glycosyl thiols by stereospecific ring-opening of 1,6-anhydrosugars

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.     

Near-complete absorption of intense, ultrashort laser light by sub-lambda gratings

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.     

Total Synthesis of (E/Z) des-Hydroxy Triticone A and B

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.     

Normal- and reversed-phase high-performance thin-layer chromatography methods for the simultaneous determination of remogliflozin etabonate and metformin hydrochloride antidiabetic drugs in bulk and tablet formulation

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...     

Revision of the Absolute Configurations of Chelocardin and Amidochelocardin

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.     

ChemInform Abstract: Theoretical Study of Structural and Vibrational Properties of Al3N3, Ga3N3, and In3N3.

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