scispace - formally typeset
Search or ask a question
Author

Mohamed Brakta

Bio: Mohamed Brakta is an academic researcher from Claude Bernard University Lyon 1. The author has contributed to research in topics: Mass spectrometry & Dissociation (chemistry). The author has an hindex of 7, co-authored 11 publications receiving 194 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the utility of 1 H, 13 C, and nuclear Overhauser enhancement spectrometries for assignment of C-glycopyranosides and Cglycofuranosides to α or β series has been assessed.
Abstract: The utility of 1 H, 13 C, and nuclear Overhauser enhancement spectrometries for assignment of C-glycopyranosides and C-glycofuranosides to α or β another series has been assessed. Specifically examined were 1 H- 1 H coupling constants J 1',2' and J 4',5' , 1 H chemical shifts δ H1' , 13 C chemical shifts δ C1' and δ C5' , 1 H- 13 C coupling constants J C1',H1' , and nuclear Overhauser effects (NOE) observed upon irradiation of H1', H4', and H5'. While all of these data have been used for assignment of anomeric configuration of C-glycosides, this study demonstrates that the NOE obtained by irradiation of H1' is uniquely reliable

33 citations

Journal ArticleDOI
TL;DR: In this paper, the pyrazolo[1, 5a]-1, 3, 5-triazine aglycon system has been prepared by palladium-mediated coupling of 8-iodopyrazolo and the furanoid glycal 1, 4-anhydro-2-deoxy-3-O[(1, 1 dimethylethyl)diphenylsilyl]-D-erythro-pent-1-enitol.
Abstract: C-Nucleosides of the pyrazolo[1, 5-a]-1, 3, 5-triazine aglycon system have been prepared by palladium-mediated coupling of 8-iodopyrazolo[1, 5-a]-1, 3, 5-triazines. 4-(N, N-Diisobutyloxycarbonyl)amino-8-iodopyrazolo[1, 5-a]-1, 3, 5-triazine and the furanoid glycal 1, 4-anhydro-2-deoxy-3-O[(1, 1 dimethylethyl)diphenylsilyl]-D-erythro-pent-1-enitol coupled in the presence of catalytic palladium(0) to yield, after desilylation of the intermediate silyl enol ether, a C-glycoside analog of adenosine.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the mass-analysed ion kinetic energy (MIKE) and collision-activated dissociation (CAD) MIKE spectra of selected positive ions can be used as fingerprints of the α- or β-anomers.
Abstract: Positive-ion fast atom bombardment mass spectrometry appears to be a useful method for the differentiation of anomeric C-glycosides. The mass-analysed ion kinetic energy (MIKE) and collision-activated dissociation (CAD) MIKE spectra of selected positive ions can be used as fingerprints of the α- or β-anomers. The main fragmentation routes and particularly the formation of the [M − H]+ ion and the [M + H − PhCH2OH]+ ion were traced for each anomer.

14 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: The collective studies suggest that stereochemical control of the C-glycosides is dependent on the substrate and catalysts combination, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.
Abstract: A Ni-catalyzed Negishi cross-coupling approach to C-glycosides is described with an emphasis on C-aryl glycosides. The combination of NiCl2/PyBox in N,N'-dimethylimidazolidinone (DMI) enabled the synthesis of C-alkyl glycosides under mild reaction conditions. Moderate yields and beta-selectivities were obtained for C-glucosides, and good yields and high alpha-selectivities were the norm for C-mannosides. For C-aryl glycosides, reactions employing Ni(COD)2/(t)Bu-Terpy in N,N-dimethylformamide (DMF) were typically high yielding and provided C-glucosides with high beta-selectivities (1:>10 alpha:beta) and C-mannosides in moderate alpha-selectivities (3:1 alpha:beta); alpha-C-aryl glycosides could be obtained by the combination of Ni(COD)2/PyBox in DMF (>20:1 alpha:beta). The collective studies suggest that stereochemical control of the C-glycosides is dependent on the substrate and catalysts combination. The Negishi protocol displays excellent functional group tolerance, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.

203 citations

Book ChapterDOI
TL;DR: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position as discussed by the authors.
Abstract: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.

146 citations

Journal ArticleDOI
TL;DR: A review of recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals can be found in this paper.

121 citations